Fractal-Like Materials Design with Optimized Radiative Properties for High-Efficiency Solar Energy Conversion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ho, Clifford K.; Ortega, Jesus D.; Christian, Joshua Mark

Novel designs to increase light trapping and thermal efficiency of concentrating solar receivers at multiple length scales have been conceived, designed, and tested. The fractal-like geometries and features are introduced at both macro (meters) and meso (millimeters to centimeters) scales. Advantages include increased solar absorptance, reduced thermal emittance, and increased thermal efficiency. Radial and linear structures at the meso (tube shape and geometry) and macro (total receiver geometry and configuration) scales redirect reflected solar radiation toward the interior of the receiver for increased absorptance. Hotter regions within the interior of the receiver can reduce thermal emittance due to reduced localmore » view factors to the environment, and higher concentration ratios can be employed with similar surface irradiances to reduce the effective optical aperture, footprint, and thermal losses. Coupled optical/fluid/thermal models have been developed to evaluate the performance of these designs relative to conventional designs. Modeling results showed that fractal-like structures and geometries can increase the effective solar absorptance by 5 – 20% and the thermal efficiency by several percentage points at both the meso and macro scales, depending on factors such as intrinsic absorptance. Meso-scale prototypes were fabricated using additive manufacturing techniques, and a macro-scale bladed receiver design was fabricated using Inconel 625 tubes. On-sun tests were performed using the solar furnace and solar tower at the National Solar Thermal Test facility. The test results demonstrated enhanced solar absorptance and thermal efficiency of the fractal-like designs.« less

Novel high refractive index, thermally conductive additives for high brightness white LEDs

NASA Astrophysics Data System (ADS)

Hutchison, Richard Stephen

In prior works the inclusion of nanoparticle fillers has typically been shown to increase the thermal conductivity or refractive index of polymer nanocomposites separately. High refractive index zirconia nanoparticles have already proved their merit in increasing the optical efficiency of encapsulated light emitting diodes. However, the thermal properties of zirconia-silicone nanocomposites have yet to be investigated. While phosphor-converted light emitting diodes are at the forefront of solid-state lighting technologies for producing white light, they are plagued by efficiency losses due to excessive heating at the semiconductor die and in and around the phosphor particles, as well as photon scattering losses in the phosphor layer. It would then be of great interest if the high refractive index nanoparticles were found to both be capable of increasing the refractive index, thus reducing the optical scattering, and also the thermal conductivity, channeling more heat away from the LED die and phosphors, mitigating efficiency losses from heat. Thermal conductance measurements on unfilled and nanoparticle loaded silicone samples were conducted to quantify the effect of the zirconia nanoparticle loading on silicone nanocomposite thermal conductivity. An increase in thermal conductivity from 0.27 W/mK to 0.49 W/mK from base silicone to silicone with 33.5 wt% zirconia nanoparticles was observed. This trend closely mirrored a basic rule of mixtures prediction, implying a further enhancement in thermal conductivity could be achieved at higher nanoparticle loadings. The optical properties of transparency and light extraction efficiency of these composites were also investigated. While overall the zirconia nanocomposite showed good transparency, there was a slight decrease at the shorter wavelengths with increasing zirconia content. For longer wavelength LEDs, such as green or red, this might not matter, but phosphor-converted white LEDs use a blue LED as the photon source making this decrease in transparency important to note. This decrease in transparency may be partially or wholly why a decrease in light extraction efficiency is observed at the 33.5 wt% zirconia loading fraction used for the LED samples. Preliminary aging studies under full and enhanced power conditions were conducted over 500 and 1000 hours to observe any changes in the spectral output power and phosphor conversion efficiency of the LEDs due to inclusion of the zirconia nanoparticles. It was found that the nanoparticles have no negative effect on the aging properties but also show no enhancement in relative output power over a preliminary aging study. However, their inclusion did result in increased phosphor conversion efficiency over the use of an unfilled silicone. This increase was seen as around a 10% or greater enhancement for the nanocomposite over that for the base Sylgard silicone. These experiments were originally conducted on the commercially available methylated Sylgard 184 silicone and then again on a higher refractive index methyl-phenyl silicone from Momentive. While some of the results from the Momentive silicone were perplexing, it was seen that, even without the inclusion of nanoparticles, the Momentive silicone had a higher refractive index, better aging properties, and a higher phosphor conversion efficiency over 500 hours under enhanced power conditions, warranting further studies into methyl-phenyl silicone nanocomposites.

Experimental and numerical investigations of heat transfer and thermal efficiency of an infrared gas stove

NASA Astrophysics Data System (ADS)

Charoenlerdchanya, A.; Rattanadecho, P.; Keangin, P.

2018-01-01

An infrared gas stove is a low-pressure gas stove type and it has higher thermal efficiency than the other domestic cooking stoves. This study considers the computationally determine water and air temperature distributions, water and air velocity distributions and thermal efficiency of the infrared gas stove. The goal of this work is to investigate the effect of various pot diameters i.e. 220 mm, 240 mm and 260 mm on the water and air temperature distributions, water and air velocity distributions and thermal efficiency of the infrared gas stove. The time-dependent heat transfer equation involving diffusion and convection coupled with the time-dependent fluid dynamic equation is implemented and is solved by using the finite element method (FEM). The computer simulation study is validated with an experimental study, which is use standard experiment by LPG test for low-pressure gas stove in households (TIS No. 2312-2549). The findings revealed that the water and air temperature distributions increase with greater heating time, which varies with the three different pot diameters (220 mm, 240 mm and 260 mm). Similarly, the greater heating time, the water and air velocity distributions increase that vary by pot diameters (220, 240 and 260 mm). The maximum water temperature in the case of pot diameter of 220 mm is higher than the maximum water velocity in the case of pot diameters of 240 mm and 260 mm, respectively. However, the maximum air temperature in the case of pot diameter of 260 mm is higher than the maximum water velocity in the case of pot diameters of 240 mm and 220 mm, respectively. The obtained results may provide a basis for improving the energy efficiency of infrared gas stoves and other equipment, including helping to reduce energy consumption.

885-nm Pumped Ceramic Nd:YAG Master Oscillator Power Amplifier Laser System

NASA Technical Reports Server (NTRS)

Yu, Anthony

2012-01-01

The performance of a traditional diode pumped solid-state laser that is typically pumped with 808-nm laser diode array (LDA) and crystalline Nd:YAG was improved by using 885-nm LDAs and ceramic Nd:YAG. The advantage is lower quantum defect, which will improve the thermal loading on laser gain medium, resulting in a higher-performance laser. The use of ceramic Nd:YAG allows a higher Nd dopant level that will make up the lower absorption at the 885-nm wavelength on Nd:YAG. When compared to traditional 808-nm pump, 885-nm diodes will have 30% less thermal load (or wasted heat) and will thus see a similar percentage improvement in the overall laser efficiency. In order to provide a more efficient laser system for future flight missions that require the use of low-repetition- rate (1% Nd. To make certain that the absorption at 885 nm is on the same par as the 808-nm diode, the Nd:YAG material needs to be doped with higher concentration of Nd. Ceramic Nd:YAG is the only material that can be tailored to specific needs.

MATLAB Simulation of Photovoltaic and Photovoltaic/Thermal Systems Performance

NASA Astrophysics Data System (ADS)

Nasir, Farah H. M.; Husaini, Yusnira

2018-03-01

The efficiency of the photovoltaic reduces when the photovoltaic cell temperature increased due to solar irradiance. One solution is come up with the cooling system photovoltaic system. This combination is forming the photovoltaic-thermal (PV/T) system. Not only will it generate electricity also heat at the same time. The aim of this research is to focus on the modeling and simulation of photovoltaic (PV) and photovoltaic-thermal (PV/T) electrical performance by using single-diode equivalent circuit model. Both PV and PV/T models are developed in Matlab/Simulink. By providing the cooling system in PV/T, the efficiency of the system can be increased by decreasing the PV cell temperature. The maximum thermal, electrical and total efficiency values of PV/T in the present research are 35.18%, 15.56% and 50.74% at solar irradiance of 400 W/m2, mass flow rate of 0.05kgs-1 and inlet temperature of 25 °C respectively has been obtained. The photovoltaic-thermal shows that the higher efficiency performance compared to the photovoltaic system.

Power Electronics Thermal Management Research: Annual Progress Report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Moreno, Gilberto

The objective for this project is to develop thermal management strategies to enable efficient and high-temperature wide-bandgap (WBG)-based power electronic systems (e.g., emerging inverter and DC-DC converter). Reliable WBG devices are capable of operating at elevated temperatures (≥ 175 °Celsius). However, packaging WBG devices within an automotive inverter and operating them at higher junction temperatures will expose other system components (e.g., capacitors and electrical boards) to temperatures that may exceed their safe operating limits. This creates challenges for thermal management and reliability. In this project, system-level thermal analyses are conducted to determine the effect of elevated device temperatures on invertermore » components. Thermal modeling work is then conducted to evaluate various thermal management strategies that will enable the use of highly efficient WBG devices with automotive power electronic systems.« less

Integration Research on Gas Turbine and Tunnel Kiln Combined System

NASA Astrophysics Data System (ADS)

Shi, Hefei; Ma, Liangdong; Liu, Mingsheng

2018-04-01

Through the integrated modeling of gas turbine and tunnel kiln combined system, a thermodynamic calculation method of combined system is put forward, and the combined system operation parameters are obtained. By this method, the optimization of the combined system is analyzed and the optimal configuration of the gas turbine is calculated. At the same time, the thermal efficiency of the combined system is analyzed, and the heat distribution and thermal efficiency of the system before and after the improvement are explained. Taking the 1500 kg/h ceramic production as an example, pointed out that if the tunnel kiln has a gas turbine with a power of 342 kw. The amount of electricity of the combined system that produced per unit volume of the fuel which consumes more than it used to will be 7.19 kwh, the system thermal efficiency will reach 57.49%, which higher than the individual gas turbine’s cycle thermal efficiency 20% at least.

The effect of filler parameters on the healing of thermal conductivity and mechanical properties of a thermal interface material based on a self-healable organic-inorganic polymer matrix

NASA Astrophysics Data System (ADS)

Zhong, Nan; Garcia, Santiago J.; van der Zwaag, Sybrand

2016-08-01

Thermal interface materials (TIMs) are widely used in all kinds of electronic devices to handle the heat dissipation and the mechanical anchoring of the heat producing component. The aging of TIMs may lead to delamination and internal crack formation causing a loss of heat transfer and mechanical integrity both leading to premature device failure. In the present work, a novel TIM system based on a self-healing organic-inorganic polymer matrix filled with spherical glass beads is presented which is capable of healing both the thermal conductivity and the mechanical properties upon thermal activation. The effect of particle volume concentration (PVC) and particle size on tensile strength and thermal conductivity healing behavior is investigated. The results show that a higher PVC increases the mechanical property but decreases mechanical healing. For the same PVC, bigger particles lead to lower mechanical properties but higher thermal conductivities and higher mechanical healing efficiencies.

Photon energy upconversion through thermal radiation with the power efficiency reaching 16%.

PubMed

Wang, Junxin; Ming, Tian; Jin, Zhao; Wang, Jianfang; Sun, Ling-Dong; Yan, Chun-Hua

2014-11-28

The efficiency of many solar energy conversion technologies is limited by their poor response to low-energy solar photons. One way for overcoming this limitation is to develop materials and methods that can efficiently convert low-energy photons into high-energy ones. Here we show that thermal radiation is an attractive route for photon energy upconversion, with efficiencies higher than those of state-of-the-art energy transfer upconversion under continuous wave laser excitation. A maximal power upconversion efficiency of 16% is achieved on Yb(3+)-doped ZrO2. By examining various oxide samples doped with lanthanide or transition metal ions, we draw guidelines that materials with high melting points, low thermal conductivities and strong absorption to infrared light deliver high upconversion efficiencies. The feasibility of our upconversion approach is further demonstrated under concentrated sunlight excitation and continuous wave 976-nm laser excitation, where the upconverted white light is absorbed by Si solar cells to generate electricity and drive optical and electrical devices.

Rapid charging of thermal energy storage materials through plasmonic heating.

PubMed

Wang, Zhongyong; Tao, Peng; Liu, Yang; Xu, Hao; Ye, Qinxian; Hu, Hang; Song, Chengyi; Chen, Zhaoping; Shang, Wen; Deng, Tao

2014-09-01

Direct collection, conversion and storage of solar radiation as thermal energy are crucial to the efficient utilization of renewable solar energy and the reduction of global carbon footprint. This work reports a facile approach for rapid and efficient charging of thermal energy storage materials by the instant and intense photothermal effect of uniformly distributed plasmonic nanoparticles. Upon illumination with both green laser light and sunlight, the prepared plasmonic nanocomposites with volumetric ppm level of filler concentration demonstrated a faster heating rate, a higher heating temperature and a larger heating area than the conventional thermal diffusion based approach. With controlled dispersion, we further demonstrated that the light-to-heat conversion and thermal storage properties of the plasmonic nanocomposites can be fine-tuned by engineering the composition of the nanocomposites.

Rapid Charging of Thermal Energy Storage Materials through Plasmonic Heating

PubMed Central

Wang, Zhongyong; Tao, Peng; Liu, Yang; Xu, Hao; Ye, Qinxian; Hu, Hang; Song, Chengyi; Chen, Zhaoping; Shang, Wen; Deng, Tao

2014-01-01

Direct collection, conversion and storage of solar radiation as thermal energy are crucial to the efficient utilization of renewable solar energy and the reduction of global carbon footprint. This work reports a facile approach for rapid and efficient charging of thermal energy storage materials by the instant and intense photothermal effect of uniformly distributed plasmonic nanoparticles. Upon illumination with both green laser light and sunlight, the prepared plasmonic nanocomposites with volumetric ppm level of filler concentration demonstrated a faster heating rate, a higher heating temperature and a larger heating area than the conventional thermal diffusion based approach. With controlled dispersion, we further demonstrated that the light-to-heat conversion and thermal storage properties of the plasmonic nanocomposites can be fine-tuned by engineering the composition of the nanocomposites. PMID:25175717

Removal of PCDD/Fs, PCP and mercury from sediments: Thermal oxidation versus pyrolysis.

PubMed

Chang, Moo-Been; Hsu, Yen-Chen; Chang, Shu-Hao

2018-05-07

A continuous pilot-scale system (CPS) equipped with effective air pollution control devices (APCDs) is used for remediating the sediments contaminated with PCDD/Fs, PCP and Hg simultaneously. The removal efficiencies of these three pollutants in sediments collected from seawater pond and river, respectively, are evaluated via thermal treatment processes. PAHs and CBz formed during thermal oxidation and pyrolysis are also analyzed for better understanding the behaviors of chlorinated organic compounds. Experimental results indicate that low-molecular-weight PAHs are closely related to the formation of CBz, PCDD/Fs, and CPs, while low chlorinated PCDD/Fs and CBz are predominant in flue gas with thermal oxidation. However, the PM concentration is higher in thermal oxidation than pyrolysis due to the higher air flow rate of thermal oxidation. It may bring more particles out of the furnace and have a greater potential to form PCDD/Fs within APCDs. Besides, the high air flow also dilutes the Hg vapor in flue gas and would require more energy to condense and collect Hg with the quench tower. Furthermore, for removal of total amount of PCDD/Fs, pyrolysis is better than thermal oxidation. Thus, pyrolysis is more suitable for remediating the contaminated sediment. The removal efficiencies of PCDD/Fs, PCP and Hg in sediments achieved with pyrolysis increase with increasing operating temperature and retention time in CPS. Overall, the residual concentrations of PCDD/Fs and PCP in river sediment are higher than that in seawater-pond sediment since significant formation of tar is observed due to higher organic matter content in river sediment. Copyright © 2018 Elsevier Ltd. All rights reserved.

Steam gasification of acid-hydrolysis biomass CAHR for clean syngas production.

PubMed

Chen, Guanyi; Yao, Jingang; Yang, Huijun; Yan, Beibei; Chen, Hong

2015-03-01

Main characteristics of gaseous product from steam gasification of acid-hydrolysis biomass CAHR have been investigated experimentally. The comparison in terms of evolution of syngas flow rate, syngas quality and apparent thermal efficiency was made between steam gasification and pyrolysis in the lab-scale apparatus. The aim of this study was to determine the effects of temperature and steam to CAHR ratio on gas quality, syngas yield and energy conversion. The results showed that syngas and energy yield were better with gasification compared to pyrolysis under identical thermal conditions. Both high gasification temperature and introduction of proper steam led to higher gas quality, higher syngas yield and higher energy conversion efficiency. However, excessive steam reduced hydrogen yield and energy conversion efficiency. The optimal value of S/B was found to be 3.3. The maximum value of energy ratio was 0.855 at 800°C with the optimal S/B value. Copyright © 2014 Elsevier Ltd. All rights reserved.

Low-Thermal-Conductivity Pyrochlore Oxide Materials Developed for Advanced Thermal Barrier Coatings

NASA Technical Reports Server (NTRS)

Bansal, Narottam P.; Zhu, Dong-Ming

2005-01-01

When turbine engines operate at higher temperatures, they consume less fuel, have higher efficiencies, and have lower emissions. The upper-use temperatures of the base materials (superalloys, silicon-based ceramics, etc.) used for the hot-section components of turbine engines are limited by the physical, mechanical, and corrosion characteristics of these materials. Thermal barrier coatings (TBCs) are applied as thin layers on the surfaces of these materials to further increase the operating temperatures. The current state-of-the-art TBC material in commercial use is partially yttria-stabilized zirconia (YSZ), which is applied on engine components by plasma spraying or by electron-beam physical vapor deposition. At temperatures higher than 1000 C, YSZ layers are prone to sintering, which increases thermal conductivity and makes them less effective. The sintered and densified coatings can also reduce thermal stress and strain tolerance, which can reduce the coating s durability significantly. Alternate TBC materials with lower thermal conductivity and better sintering resistance are needed to further increase the operating temperature of turbine engines.

Advanced Passivation Technology and Loss Factor Minimization for High Efficiency Solar Cells.

PubMed

Park, Cheolmin; Balaji, Nagarajan; Jung, Sungwook; Choi, Jaewoo; Ju, Minkyu; Lee, Seunghwan; Kim, Jungmo; Bong, Sungjae; Chung, Sungyoun; Lee, Youn-Jung; Yi, Junsin

2015-10-01

High-efficiency Si solar cells have attracted great attention from researchers, scientists, photovoltaic (PV) industry engineers for the past few decades. With thin wafers, surface passivation becomes necessary to increase the solar cells efficiency by overcoming several induced effects due to associated crystal defects and impurities of c-Si. This paper discusses suitable passivation schemes and optimization techniques to achieve high efficiency at low cost. SiNx film was optimized with higher transmittance and reduced recombination for using as an effective antireflection and passivation layer to attain higher solar cell efficiencies. The higher band gap increased the transmittance with reduced defect states that persisted at 1.68 and 1.80 eV in SiNx films. The thermal stability of SiN (Si-rich)/SiN (N-rich) stacks was also studied. Si-rich SiN with a refractive index of 2.7 was used as a passivation layer and N-rich SiN with a refractive index of 2.1 was used for thermal stability. An implied Voc of 720 mV with a stable lifetime of 1.5 ms was obtained for the stack layer after firing. Si-N and Si-H bonding concentration was analyzed by FTIR for the correlation of thermally stable passivation mechanism. The passivation property of spin coated Al2O3 films was also investigated. An effective surface recombination velocity of 55 cm/s with a high density of negative fixed charges (Qf) on the order of 9 x 10(11) cm(-2) was detected in Al2O3 films.

Thermophotonics for ultra-high efficiency visible LEDs

NASA Astrophysics Data System (ADS)

Ram, Rajeev J.

2017-02-01

The wall-plug efficiency of modern light-emitting diodes (LEDs) has far surpassed all other forms of lighting and is expected to improve further as the lifetime cost of a luminaire is today dominated by the cost of energy. The drive towards higher efficiency inevitably opens the question about the limits of future enhancement. Here, we investigate thermoelectric pumping as a means for improving efficiency in wide-bandgap GaN based LEDs. A forward biased diode can work as a heat pump, which pumps lattice heat into the electrons injected into the active region via the Peltier effect. We experimentally demonstrate a thermally enhanced 450 nm GaN LED, in which nearly fourfold light output power is achieved at 615 K (compared to 295 K room temperature operation), with virtually no reduction in the wall-plug efficiency at bias V < ℏω/q. This result suggests the possibility of removing bulky heat sinks in high power LED products. A review of recent high-efficiency GaN LEDs suggests that Peltier thermal pumping plays a more important role in a wide range of modern LED structures that previously thought - opening a path to even higher efficiencies and lower lifetime costs for future lighting.

Cold climate specialization: adaptive covariation between metabolic rate and thermoregulation in pregnant vipers.

PubMed

Lourdais, Olivier; Guillon, Michaël; Denardo, Dale; Blouin-Demers, Gabriel

2013-07-02

We compared thermoregulatory strategies during pregnancy in two congeneric viperid snakes (Vipera berus and Vipera aspis) with parapatric geographic ranges. V. berus is a boreal specialist with the largest known distribution among terrestrial snakes while V. aspis is a south-European species. Despite contrasted climatic affinities, the two species displayed identical thermal preferences (Tset) in a laboratory thermal gradient. Under identical natural conditions, however, V. berus was capable of maintaining Tset for longer periods, especially when the weather was constraining. Consistent with the metabolic cold adaptation hypothesis, V. berus displayed higher standard metabolic rate at all temperatures considered. We used the thermal dependence of metabolic rate to calculate daily metabolic profiles from body temperature under natural conditions. The boreal specialist experienced higher daily metabolic rate and minimized gestation duration chiefly because of differences in the metabolic reaction norms, but also superior thermoregulatory efficiency. Under cold climates, thermal constraints should make precise thermoregulation costly. However, a shift in the metabolic reaction norm may compensate for thermal constraints and modify the cost-benefit balance of thermoregulation. Covariation between metabolic rate and thermoregulation efficiency is likely an important adaptation to cold climates. Copyright © 2013 Elsevier Inc. All rights reserved.

Optimization of the Army’s Fast Neutron Moderator for Radiography

DTIC Science & Technology

2013-02-26

thermal neutron flux from a commercially available high-energy D-T neutron generator. This paper details the steps taken to increase exposure rates...experiment was to have increased thermal neutron flux rates and shorter exposure times than previously achieved. Additional technology developments...This reduced the thermalizing efficiency of the moderator at higher energies, resulted in a large loss of neutron flux at the image plane, and

Efficient 2-μm Tm:YAP Q-switched and CW lasers

NASA Astrophysics Data System (ADS)

Hays, A. D.; Cole, Brian; King, Vernon; Goldberg, Lew

2018-02-01

Highly efficient, diode pumped Tm:YAP lasers generating emission in the 1.85-1.94 μm range are demonstrated and characterized. Laser optical efficiencies of 51% and 45%, and electrical efficiencies of 31% and 25% are achieved under CW and Q-switched operation, respectively. Laser performance was characterized for maximum average powers up to 20W with various cavity configurations, all using an intra-cavity lens to compensate for thermal lensing in the Tm:YAP crystal. Q-switched lasers incorportating a Cr:ZnS saturable absorber (SA), resonant mechanical mirror scanner, or acousto-optic modulator were characterized. To enable higher average output powers, measurements of the thermal lens were conducted for the Tm:YAP crystal as a function of pump power and were compared to values predicted by a finiteelement- analysis (FEA) thermal-optical model of the Tm:YAP crystal. A resonator model is developed to incorporate this calculated thermal lens and its effect on laser performance. This paper will address approaches for improving the performance of Tm:YAP lasers, and means for achieving increased average output powers while maintaining high optical efficiency for both SA and mechanical Q-switching.

High-performance noncontact thermal diode via asymmetric nanostructures

NASA Astrophysics Data System (ADS)

Shen, Jiadong; Liu, Xianglei; He, Huan; Wu, Weitao; Liu, Baoan

2018-05-01

Electric diodes, though laying the foundation of modern electronics and information processing industries, suffer from ineffectiveness and even failure at high temperatures. Thermal diodes are promising alternatives to relieve above limitations, but usually possess low rectification ratios, and how to obtain a high-performance thermal rectification effect is still an open question. This paper proposes an efficient contactless thermal diode based on the near-field thermal radiation of asymmetric doped silicon nanostructures. The rectification ratio computed via exact scattering theories is demonstrated to be as high as 10 at a nanoscale gap distance and period, outperforming the counterpart flat-plate diode by more than one order of magnitude. This extraordinary performance mainly lies in the higher forward and lower reverse radiative heat flux within the low frequency band compared with the counterpart flat-plate diode, which is caused by a lower loss and smaller cut-off wavevector of nanostructures for the forward and reversed scheme, respectively. This work opens new routes to realize high performance thermal diodes, and may have wide applications in efficient thermal computing, thermal information processing, and thermal management.

SparkJet Efficiency

NASA Technical Reports Server (NTRS)

Golbabaei-Asl, Mona; Knight, Doyle; Anderson, Kellie; Wilkinson, Stephen

2013-01-01

A novel method for determining the thermal efficiency of the SparkJet is proposed. A SparkJet is attached to the end of a pendulum. The motion of the pendulum subsequent to a single spark discharge is measured using a laser displacement sensor. The measured displacement vs time is compared with the predictions of a theoretical perfect gas model to estimate the fraction of the spark discharge energy which results in heating the gas (i.e., increasing the translational-rotational temperature). The results from multiple runs for different capacitances of c = 3, 5, 10, 20, and 40 micro-F show that the thermal efficiency decreases with higher capacitive discharges.

Thermodynamic analysis of performance improvement by reheat on the CO2 transcritical power cycle

NASA Astrophysics Data System (ADS)

Tuo, Hanfei

2012-06-01

The CO2 transcritical rankine power cycle has been widely investigated recently, because of its better temperature glide matching between sensible heat source and working fluid in vapor generator, and its desirable qualities, such as moderate critical point, little environment impact and low cost. A reheat CO2 transcritical power cycle with two stage expansion is presented to improve baseline cycle performance in this paper. Energy and exergy analysis are carried out to investigate effects of important parameters on cycle performance. The main results show that reheat cycle performance is sensitive to the variation of medium pressures and the optimum medium pressures exist for maximizing work output and thermal efficiency, respectively. Reheat cycle is compared to baseline cycle under the same conditions. More significant improvements by reheat are obtained at lower turbine inlet temperatures and larger high cycle pressure. Work output improvement is much higher than thermal efficiency improvement, because extra waste heat is required to reheat CO2. Based on second law analysis, exergy efficiency of reheat cycle is also higher than that of baseline cycle, because more useful work is converted from waste heat. Reheat with two stage expansion has great potential to improve thermal efficiency and especially net work output of a CO2 transcritical power cycle using a low-grade heat source.

Multiphysics Computational Analysis of a Solid-Core Nuclear Thermal Engine Thrust Chamber

NASA Technical Reports Server (NTRS)

Wang, Ten-See; Canabal, Francisco; Cheng, Gary; Chen, Yen-Sen

2007-01-01

The objective of this effort is to develop an efficient and accurate computational heat transfer methodology to predict thermal, fluid, and hydrogen environments for a hypothetical solid-core, nuclear thermal engine - the Small Engine. In addition, the effects of power profile and hydrogen conversion on heat transfer efficiency and thrust performance were also investigated. The computational methodology is based on an unstructured-grid, pressure-based, all speeds, chemically reacting, computational fluid dynamics platform, while formulations of conjugate heat transfer were implemented to describe the heat transfer from solid to hydrogen inside the solid-core reactor. The computational domain covers the entire thrust chamber so that the afore-mentioned heat transfer effects impact the thrust performance directly. The result shows that the computed core-exit gas temperature, specific impulse, and core pressure drop agree well with those of design data for the Small Engine. Finite-rate chemistry is very important in predicting the proper energy balance as naturally occurring hydrogen decomposition is endothermic. Locally strong hydrogen conversion associated with centralized power profile gives poor heat transfer efficiency and lower thrust performance. On the other hand, uniform hydrogen conversion associated with a more uniform radial power profile achieves higher heat transfer efficiency, and higher thrust performance.

Enhancing low-grade thermal energy recovery in a thermally regenerative ammonia battery using elevated temperatures.

PubMed

Zhang, Fang; LaBarge, Nicole; Yang, Wulin; Liu, Jia; Logan, Bruce E

2015-03-01

A thermally regenerative ammonia battery (TRAB) is a new approach for converting low-grade thermal energy into electricity by using an ammonia electrolyte and copper electrodes. TRAB operation at 72 °C produced a power density of 236 ± 8 Wm(-2), with a linear decrease in power to 95 ± 5 Wm(-2) at 23 °C. The improved power at higher temperatures was due to reduced electrode overpotentials and more favorable thermodynamics for the anode reaction (copper oxidation). The energy density varied with temperature and discharge rates, with a maximum of 650 Wh m(-3) at a discharge energy efficiency of 54% and a temperature of 37 °C. The energy efficiency calculated with chemical process simulation software indicated a Carnot-based efficiency of up to 13% and an overall thermal energy recovery of 0.5%. It should be possible to substantially improve these energy recoveries through optimization of electrolyte concentrations and by using improved ion-selective membranes and energy recovery systems such as heat exchangers. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Coupled optical-thermal-fluid and structural analyses of novel light-trapping tubular panels for concentrating solar power receivers

NASA Astrophysics Data System (ADS)

Ortega, Jesus D.; Christian, Joshua M.; Yellowhair, Julius E.; Ho, Clifford K.

2015-09-01

Traditional tubular receivers used in concentrating solar power are formed using tubes connected to manifolds to form panels; which in turn are arranged in cylindrical or rectangular shapes. Previous and current tubular receivers, such as the ones used in Solar One, Solar Two, and most recently the Ivanpah solar plants, have used a black paint coating to increase the solar absorptance of the receiver. However, these coatings degrade over time and must be reapplied, increasing the receiver maintenance cost. This paper presents the thermal efficiency evaluation of novel receiver tubular panels that have a higher effective solar absorptance due to a light-trapping effect created by arranging the tubes in each panel into unique geometric configurations. Similarly, the impact of the incidence angle on the effective solar absorptance and thermal efficiency is evaluated. The overarching goal of this work is to achieve effective solar absorptances of ~90% and thermal efficiencies above 85% without using an absorptance coating. Several panel geometries were initially proposed and were down-selected based on structural analyses considering the thermal and pressure loading requirements of molten salt and supercritical carbon-dioxide receivers. The effective solar absorptance of the chosen tube geometries and panel configurations were evaluated using the ray-tracing modeling capabilities of SolTrace. The thermal efficiency was then evaluated by coupling computational fluid dynamics with the ray-tracing results using ANSYS Fluent. Compared to the base case analysis (flat tubular panel), the novel tubular panels have shown an increase in effective solar absorptance and thermal efficiency by several percentage points.

Reliability and Heat Transfer Performance of a Miniature High-Temperature Thermosyphon-Based Thermal Valve

DOE Office of Scientific and Technical Information (OSTI.GOV)

Alleman, Jeffrey L; Olsen, Michele L; Glatzmaier, Gregory C

Latent heat thermal energy storage systems have the advantages of near isothermal heat release and high energy density compared to sensible heat, generally resulting in higher power block efficiencies. Until now, there has been no highly effective and reliable method to passively extract that stored latent energy. Most modern attempts rely on external power supplied to a pump to move viscous heat transfer fluids from the phase change material (PCM) to the power block. In this work, the problem of latent heat dispatchability has been addressed with a redesigned thermosyphon geometry that can act as a 'thermal valve' capable ofmore » passively and efficiently controlling the release of heat from a thermal reservoir. A bench-scale prototype with a stainless steel casing and sodium working fluid was designed and tested to be reliable for more than fifty 'on/off' cycles at an operating temperature of 600 degrees C. The measured thermal resistances in the 'on' and 'off' states were 0.0395 K/W and 11.0 K/W respectively. This device demonstrated efficient, fast, reliable, and passive heat extraction from a PCM and may have application to other fields and industries using thermal processing.« less

AISI/DOE Technology Roadmap Program: Development of Cost-effective, Energy-efficient Steel Framing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nader R. Elhajj

2003-01-06

Steel members in wall construction form a thermal bridge that interrupts the insulation layer of a wall. This causes higher rate of heat transfer by conduction through the wall framing than through other parts of the wall. One method to reduce the thermal bridging effect is to provide a break, such as insulating sheathing. A thermally efficient slit-web and stud was developed in this program to mitigate the conductivity of steel. The thermal performance of the slit-web stud was evaluated at Oak Ridge National Laboratory using hotbox testing. The thermal test results showed that the prototype slit-web stud performed 17%more » better than the solid-web stud, using R-13 fiber glass batts with exterior OSB sheathing and interior drywall. The structural behavior of this slit-web stud was evaluated in axial, bending, shear, shearwall, and stub-column tests. Test results indicated that the slitweb stud performed similarly or better than the solid-web stud in most structural performance characteristics investigated. Thus, the prototype slit-web stud has been shown to be thermally efficient, economiexecy viable, structurally sound, easily manufactured and usable in a range of residential installations.« less

Improving methane production from digested manure biofibers by mechanical and thermal alkaline pretreatment.

PubMed

Tsapekos, P; Kougias, Panagiotis G; Frison, A; Raga, R; Angelidaki, I

2016-09-01

Animal manure digestion is associated with limited methane production, due to the high content in fibers, which are hardly degradable lignocellulosic compounds. In this study, different mechanical and thermal alkaline pretreatment methods were applied to partially degradable fibers, separated from the effluent stream of biogas reactors. Batch and continuous experiments were conducted to evaluate the efficiency of these pretreatments. In batch experiments, the mechanical pretreatment improved the degradability up to 45%. Even higher efficiency was shown by applying thermal alkaline pretreatments, enhancing fibers degradability by more than 4-fold. In continuous experiments, the thermal alkaline pretreatment, using 6% NaOH at 55°C was proven to be the most efficient pretreatment method as the methane production was increased by 26%. The findings demonstrated that the methane production of the biogas plants can be increased by further exploiting the fraction of the digested manure fibers which are discarded in the post-storage tank. Copyright © 2016 Elsevier Ltd. All rights reserved.

Effect of Material Composition and Environmental Condition on Thermal Characteristics of Conductive Asphalt Concrete.

PubMed

Pan, Pan; Wu, Shaopeng; Hu, Xiaodi; Liu, Gang; Li, Bo

2017-02-23

Conductive asphalt concrete with high thermal conductivity has been proposed to improve the solar energy collection and snow melting efficiencies of asphalt solar collector (ASC). This paper aims to provide some insight into choosing the basic materials for preparation of conductive asphalt concrete, as well as determining the evolution of thermal characteristics affected by environmental factors. The thermal properties of conductive asphalt concrete were studied by the Thermal Constants Analyzer. Experimental results showed that aggregate and conductive filler have a significant effect on the thermal properties of asphalt concrete, while the effect of asphalt binder was not evident due to its low proportion. Utilization of mineral aggregate and conductive filler with higher thermal conductivity is an efficient method to prepare conductive asphalt concrete. Moreover, change in thermal properties of asphalt concrete under different temperature and moisture conditions should be taken into account to determine the actual thermal properties of asphalt concrete. There was no noticeable difference in thermal properties of asphalt concrete before and after aging. Furthermore, freezing-thawing cycles strongly affect the thermal properties of conductive asphalt concrete, due to volume expansion and bonding degradation.

Effect of Material Composition and Environmental Condition on Thermal Characteristics of Conductive Asphalt Concrete

PubMed Central

Pan, Pan; Wu, Shaopeng; Hu, Xiaodi; Liu, Gang; Li, Bo

2017-01-01

Conductive asphalt concrete with high thermal conductivity has been proposed to improve the solar energy collection and snow melting efficiencies of asphalt solar collector (ASC). This paper aims to provide some insight into choosing the basic materials for preparation of conductive asphalt concrete, as well as determining the evolution of thermal characteristics affected by environmental factors. The thermal properties of conductive asphalt concrete were studied by the Thermal Constants Analyzer. Experimental results showed that aggregate and conductive filler have a significant effect on the thermal properties of asphalt concrete, while the effect of asphalt binder was not evident due to its low proportion. Utilization of mineral aggregate and conductive filler with higher thermal conductivity is an efficient method to prepare conductive asphalt concrete. Moreover, change in thermal properties of asphalt concrete under different temperature and moisture conditions should be taken into account to determine the actual thermal properties of asphalt concrete. There was no noticeable difference in thermal properties of asphalt concrete before and after aging. Furthermore, freezing–thawing cycles strongly affect the thermal properties of conductive asphalt concrete, due to volume expansion and bonding degradation. PMID:28772580

Performance Evaluation of Dual-axis Tracking System of Parabolic Trough Solar Collector

NASA Astrophysics Data System (ADS)

Ullah, Fahim; Min, Kang

2018-01-01

A parabolic trough solar collector with the concentration ratio of 24 was developed in the College of Engineering; Nanjing Agricultural University, China with the using of the TracePro software an optical model built. Effects of single-axis and dual-axis tracking modes, azimuth and elevating angle tracking errors on the optical performance were investigated and the thermal performance of the solar collector was experimentally measured. The results showed that the optical efficiency of the dual-axis tracking was 0.813% and its year average value was 14.3% and 40.9% higher than that of the eat-west tracking mode and north-south tracking mode respectively. Further, form the results of the experiment, it was concluded that the optical efficiency was affected significantly by the elevation angle tracking errors which should be kept below 0.6o. High optical efficiency could be attained by using dual-tracking mode even though the tracking precision of one axis was degraded. The real-time instantaneous thermal efficiency of the collector reached to 0.775%. In addition, the linearity of the normalized efficiency was favorable. The curve of the calculated thermal efficiency agreed well with the normalized instantaneous efficiency curve derived from the experimental data and the maximum difference between them was 10.3%. This type of solar collector should be applied in middle-scale thermal collection systems.

Research and application of high performance GPES rigid foam composite plastic insulation boards

NASA Astrophysics Data System (ADS)

sun, Hongming; xu, Hongsheng; Han, Feifei

2017-09-01

A new type of heat insulation board named GPES was prepared by several polymers and modified nano-graphite particles, injecting high-pressure supercritical CO2. Compared with the traditional thermal insulation material, GPES insulation board has higher roundness bubble and thinner bubble wall. Repeatability and reproducibility tests show that melting knot, dimensional stability, strength and other physical properties are significantly better than traditional organic heat insulation materials. Especially the lower and more stable thermal conductivity of GPES can significantly reduce thermal insulation layer thickness. Obviously GPES is the best choice of insulation materials with the implement of 75% and higher energy efficiency standard.

Technical assessment of discarded tires gasification as alternative technology for electricity generation.

PubMed

Machin, Einara Blanco; Pedroso, Daniel Travieso; de Carvalho, João Andrade

2017-10-01

Concern about contamination associated with the disposal of tires has led to the search for technologies to reuse discarded tires, which include the use of Tire Derived Fuel (TDF) as fuel in advanced thermal-conversion processes, this allows the energy use of these wastes at affordable costs and reduces the environmental impact on scrap tires disposal. A theoretical assessment of the technical viability of TDF gasification for electric and thermal power generation, from the producer gas combustion in an internal combustion engine and in a gas turbine, was performed. The combustion of producer gas derived from the gasification of TDF in an internal combustion engine driving a generator (ICE-G) appears as the more efficient route for electricity generation when compared with the efficiency obtained with the use of gas turbine (GT-G). A higher global efficiency, considering the electric and thermal generation efficiency can be expected with the use of TDF producer gas in GT-G, where is expected an overall efficiency of 77.49%. The assessment shows that is possible produces up to 7.67MJ and 10.62MJ of electric and thermal energy per kilogram of TDF gasified using an ICE-G and up to 6.06MJ and 13.03MJ of electric and thermal energy respectively per kilogram of gasified TDF using a GT-G. Copyright © 2017 Elsevier Ltd. All rights reserved.

Thermal modeling of high efficiency AMTEC cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ivanenok, J.F. III; Sievers, R.K.; Crowley, C.J.

1995-12-31

Remotely condensed Alkali Metal Thermal to Electric Conversion (AMTEC) cells achieve high efficiency by thermally isolating the hot {beta} Alumina Solid Electrolyte (BASE) tube from the cold condensing region. In order to design high efficiency AMTEC cells the designer must understand the heat losses associated with the AMTEC process. The major parasitic heat losses are due to conduction and radiation, and significant coupling of the two mechanisms occurs. This paper describes an effort to characterize the thermal aspects of the model PL-6 AMTEC cell and apply this understanding to the design of a higher efficiency AMTEC cell, model PL-8. Twomore » parallel analyses were used to model the thermal characteristics of PL-6. The first was a lumped node model using the classical electric circuit analogy and the second was a detailed finite-difference model. The lumped node model provides high speed and reasonable accuracy, and the detailed finite-difference model provides a more accurate, as well as visual, description of the cell temperature profiles. The results of the two methods are compared to the as-measured PL-6 data. PL-6 was the first cell to use a micromachined condenser to lower the radiation losses to the condenser, and it achieved a conversion efficiency of 15% (3 W output/20 W Input) at a temperature of 1050 K.« less

Facile fabrication of multilayer separators for lithium-ion battery via multilayer coextrusion and thermal induced phase separation

NASA Astrophysics Data System (ADS)

Li, Yajie; Pu, Hongting

2018-04-01

Polypropylene (PP)/polyethylene (PE) multilayer separators with cellular-like submicron pore structure for lithium-ion battery are efficiently fabricated by the combination of multilayer coextrusion (MC) and thermal induced phase separation (TIPS). The as-prepared separators, referred to as MC-TIPS PP/PE, not only show efficacious thermal shutdown function and wider shutdown temperature window, but also exhibit higher thermal stability than the commercial separator with trilayer construction of PP and PE (Celgard® 2325). The dimensional shrinkage of MC-TIPS PP/PE can be negligible until 160 °C. In addition, compared to the commercial separator, MC-TIPS PP/PE exhibits higher porosity and electrolyte uptake, leading to higher ionic conductivity and better battery performances. The above-mentioned fascinating characteristics with the convenient preparation process make MC-TIPS PP/PE a promising candidate for the application as high performance lithium-ion battery separators.

Thermal conductivity characteristics of dewatered sewage sludge by thermal hydrolysis reaction.

PubMed

Song, Hyoung Woon; Park, Keum Joo; Han, Seong Kuk; Jung, Hee Suk

2014-12-01

The purpose of this study is to quantify the thermal conductivity of sewage sludge related to reaction temperature for the optimal design of a thermal hydrolysis reactor. We continuously quantified the thermal conductivity of dewatered sludge related to the reaction temperature. As the reaction temperature increased, the dewatered sludge is thermally liquefied under high temperature and pressure by the thermal hydrolysis reaction. Therefore, the bound water in the sludge cells comes out as free water, which changes the dewatered sludge from a solid phase to slurry in a liquid phase. As a result, the thermal conductivity of the sludge was more than 2.64 times lower than that of the water at 20. However, above 200, it became 0.704 W/m* degrees C, which is about 4% higher than that of water. As a result, the change in physical properties due to thermal hydrolysis appears to be an important factor for heat transfer efficiency. Implications: The thermal conductivity of dewatered sludge is an important factor the optimal design of a thermal hydrolysis reactor. The dewatered sludge is thermally liquefied under high temperature and pressure by the thermal hydrolysis reaction. The liquid phase slurry has a higher thermal conductivity than pure water.

Thermal barrier coatings application in diesel engines

NASA Technical Reports Server (NTRS)

Fairbanks, J. W.

1995-01-01

Commercial use of thermal barrier coatings in diesel engines began in the mid 70's by Dr,. Ingard Kvernes at the Central Institute for Industrial Research in Oslo, Norway. Dr. Kvernes attributed attack on diesel engine valves and piston crowns encountered in marine diesel engines in Norwegian ships as hot-corrosion attributed to a reduced quality of residual fuel. His solution was to coat these components to reduce metal temperature below the threshold of aggressive hot-corrosion and also to provide protection. The Department of Energy has supported thermal barrier coating development for diesel engine applications. In the Clean Diesel - 50 Percent Efficient (CD-50) engine for the year 2000, thermal barrier coatings will be used on piston crowns and possibly other components. The primary purpose of the thermal barrier coatings will be to reduce thermal fatigue as the engine peak cylinder pressure will nearly be doubled. As the coatings result in higher available energy in the exhaust gas, efficiency gains are achieved through use of this energy by turbochargers, turbocompounding or thermoelectric generators.

High-performance flat-panel solar thermoelectric generators with high thermal concentration

NASA Astrophysics Data System (ADS)

Kraemer, Daniel; Poudel, Bed; Feng, Hsien-Ping; Caylor, J. Christopher; Yu, Bo; Yan, Xiao; Ma, Yi; Wang, Xiaowei; Wang, Dezhi; Muto, Andrew; McEnaney, Kenneth; Chiesa, Matteo; Ren, Zhifeng; Chen, Gang

2011-07-01

The conversion of sunlight into electricity has been dominated by photovoltaic and solar thermal power generation. Photovoltaic cells are deployed widely, mostly as flat panels, whereas solar thermal electricity generation relying on optical concentrators and mechanical heat engines is only seen in large-scale power plants. Here we demonstrate a promising flat-panel solar thermal to electric power conversion technology based on the Seebeck effect and high thermal concentration, thus enabling wider applications. The developed solar thermoelectric generators (STEGs) achieved a peak efficiency of 4.6% under AM1.5G (1 kW m-2) conditions. The efficiency is 7-8 times higher than the previously reported best value for a flat-panel STEG, and is enabled by the use of high-performance nanostructured thermoelectric materials and spectrally-selective solar absorbers in an innovative design that exploits high thermal concentration in an evacuated environment. Our work opens up a promising new approach which has the potential to achieve cost-effective conversion of solar energy into electricity.

Metamaterial Receivers for High Efficiency Concentrated Solar Energy Conversion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yellowhair, Julius E.; Kwon, Hoyeong; Alu, Andrea

Operation of concentrated solar power receivers at higher temperatures (>700°C) would enable supercritical carbon dioxide (sCO 2) power cycles for improved power cycle efficiencies (>50%) and cost-effective solar thermal power. Unfortunately, radiative losses at higher temperatures in conventional receivers can negatively impact the system efficiency gains. One approach to improve receiver thermal efficiency is to utilize selective coatings that enhance absorption across the visible solar spectrum while minimizing emission in the infrared to reduce radiative losses. Existing coatings, however, tend to degrade rapidly at elevated temperatures. In this report, we report on the initial designs and fabrication of spectrally selectivemore » metamaterial-based absorbers for high-temperature, high-thermal flux environments important for solarized sCO 2 power cycles. Metamaterials are structured media whose optical properties are determined by sub-wavelength structural features instead of bulk material properties, providing unique solutions by decoupling the optical absorption spectrum from thermal stability requirements. The key enabling innovative concept proposed is the use of structured surfaces with spectral responses that can be tailored to optimize the absorption and retention of solar energy for a given temperature range. In this initial study through the Academic Alliance partnership with University of Texas at Austin, we use Tungsten for its stability in expected harsh environments, compatibility with microfabrication techniques, and required optical performance. Our goal is to tailor the optical properties for high (near unity) absorptivity across the majority of the solar spectrum and over a broad range of incidence angles, and at the same time achieve negligible absorptivity in the near infrared to optimize the energy absorbed and retained. To this goal, we apply the recently developed concept of plasmonic Brewster angle to suitably designed nanostructured Tungsten surfaces. We predict that this will improve the receiver thermal efficiencies by at least 10% over current solar receivers.« less

Geometrical effects on the concentrated behavior of heat flux in metamaterials thermal harvesting devices

NASA Astrophysics Data System (ADS)

Xu, Guoqiang; Zhang, Haochun; Xie, Ming; Jin, Yan

2017-10-01

Thermal harvesting devices based on transformation optics, which can manipulate the heat flux concentration significantly through rational arrangements of the conductivities, have attracted considerable interest owing to several great potential applications of the technique for high-efficiency thermal conversion and collection. However, quantitative studies on the geometrical effects, particularly wedge angles, on the harvesting behaviors are rare. In this paper, we adopt wedge structure-based thermal harvesting schemes, and focus on the effects of the geometrical parameters including the radii ratios and wedge angles on the harvesting performance. The temperature deformations at the boundaries of the compressional region and temperature gradients for the different schemes with varying design parameters are investigated. Moreover, a concept for temperature stabilization was derived to evaluate the fluctuation in the energy distributions. In addition, the effects of interface thermal resistances have been investigated. Considering the changes in the radii ratios and wedge angles, we proposed a modification of the harvesting efficiency to quantitatively assess the concentration performance, which was verified through random tests and previously fabricated devices. In general, this study indicates that a smaller radii ratio contributes to a better harvesting behavior, but causes larger perturbations in the thermal profiles owing to a larger heat loss. We also find that a smaller wedge angle is beneficial to ensuring a higher concentration efficiency with less energy perturbations. These findings can be used to guide the improvement of a thermal concentrator with a high efficiency in reference to its potential applications as novel heat storage, thermal sensors, solar cells, and thermoelectric devices.

Oligoyne Molecular Junctions for Efficient Room Temperature Thermoelectric Power Generation.

PubMed

Sadeghi, Hatef; Sangtarash, Sara; Lambert, Colin J

2015-11-11

Understanding phonon transport at a molecular scale is fundamental to the development of high-performance thermoelectric materials for the conversion of waste heat into electricity. We have studied phonon and electron transport in alkane and oligoyne chains of various lengths and find that, due to the more rigid nature of the latter, the phonon thermal conductances of oligoynes are counterintuitively lower than that of the corresponding alkanes. The thermal conductance of oligoynes decreases monotonically with increasing length, whereas the thermal conductance of alkanes initially increases with length and then decreases. This difference in behavior arises from phonon filtering by the gold electrodes and disappears when higher-Debye-frequency electrodes are used. Consequently a molecule that better transmits higher-frequency phonon modes, combined with a low-Debye-frequency electrode that filters high-energy phonons is a viable strategy for suppressing phonon transmission through the molecular junctions. The low thermal conductance of oligoynes, combined with their higher thermopower and higher electrical conductance lead to a maximum thermoelectric figure of merit of ZT = 1.4, which is several orders of magnitude higher than that of alkanes.

Thermal barrier coatings (TBC's) for high heat flux thrust chambers

NASA Astrophysics Data System (ADS)

Bradley, Christopher M.

The last 30 years materials engineers have been under continual pressure to develop materials with a greater temperature potential or to produce configurations that can be effectively cooled or otherwise protected at elevated temperature conditions. Turbines and thrust chambers produce some of the harshest service conditions for materials which lead to the challenges engineers face in order to increase the efficiencies of current technologies due to the energy crisis that the world is facing. The key tasks for the future of gas turbines are to increase overall efficiencies to meet energy demands of a growing world population and reduce the harmful emissions to protect the environment. Airfoils or blades tend to be the limiting factor when it comes to the performance of the turbine because of their complex design making them difficult to cool as well as limitations of their thermal properties. Key tasks for space transportation it to lower costs while increasing operational efficiency and reliability of our space launchers. The important factor to take into consideration is the rocket nozzle design. The design of the rocket nozzle or thrust chamber has to take into account many constraints including external loads, heat transfer, transients, and the fluid dynamics of expanded hot gases. Turbine engines can have increased efficiencies if the inlet temperature for combustion is higher, increased compressor capacity and lighter weight materials. In order to push for higher temperatures, engineers need to come up with a way to compensate for increased temperatures because material systems that are being used are either at or near their useful properties limit. Before thermal barrier coatings were applied to hot-section components, material alloy systems were able to withstand the service conditions necessary. But, with the increased demand for performance, higher temperatures and pressures have become too much for those alloy systems. Controlled chemistry of hot-section components has become critical, but at the same time the service conditions have put our best alloy systems to their limits. As a result, implementation of cooling holes and thermal barrier coatings are new advances in hot-section technologies now looked at for modifications to reach higher temperature applications. Current thermal barrier coatings used in today's turbine applications is known as 8%yttria-stabilized zirconia (YSZ) and there are no coatings for current thrust chambers. Current research is looking at the applicability of 8%yttria-stabilized hafnia (YSH) for turbine applications and the implementation of 8%YSZ onto thrust chambers. This study intends to determine if the use of thermal barrier coatings are applicable for high heat flux thrust chambers using industrial YSZ will be advantageous for improvements in efficiency, thrust and longer service life by allowing the thrust chambers to be used more than once.

A 3D graphene interface (Si-doped) of Ag matrix with excellent electronic transmission and thermal conductivity via nano-assembly modification

NASA Astrophysics Data System (ADS)

Ye, Xianzhu; Li, Ming; Zhang, Yafei

2018-04-01

The wide development of electronic materials requires higher load capacity and high temperature resistance. In this study, a novel architecture was fabricated consisting of a 3D reduced graphene oxide (rGO)-Si interface using a simple nano-assembly sintering to achieve high current capacity and excellent thermal features. Via the analysis of catalytic oxidation for methanol, the loading catalytic activity of nano-Ag still remained to a certain extent for the composite with 0.8 vol.% rGO. The final Ag-rGO composite apparently possesses a higher initial oxidation temperature and lower rate of oxidation for internal passing and shielding, and the thermal conductivity is significantly enhanced from 344 to 407 W m‑1 K‑1. Importantly, with a 3D synergistic transportation network, the resistivity of the Ag-rGO composite is much lower than pure Ag, and with a longer conductive time under a stress condition of current density of 6.0  ×  104 A cm‑2. Thermal-electronic features demonstrate that the dispersed graphene interface can efficiently suppress the primary failure pathways (high temperature) in Ag matrix and make it uniquely efficient for the advancement of microscale and thermal-management electronics.

Influence of Nano-Fluid and Receiver Modification in Solar Parabolic Trough Collector Performance

NASA Astrophysics Data System (ADS)

Dharani Kumar, M.; Yuvaraj, G.; Balaji, D.; Pravinraj, R.; shanmugasundaram, Prabhu

2018-02-01

Utilization of natural renewal sources in India is very high over the past decades. Solar power is a prime source of energy available plenty in the world. In this work solar energy is modified into thermal energy by using copper absorber tube with fins. Due to low heat transfer coefficient results leading to higher thermal losses and lower thermal efficiency. In order to increase the heat transfer coefficient copper receiver tube with fins is used and as well as solid has higher thermal conductivity compare to fluid (Tio2) nano fluid is used to improve the heat transfer rate. The analyses have been carried out and take the account of parameters such as solar radiation with time variation, mass flow rate of water, temperatures.

Correlation between Thermodynamic Efficiency and Ecological Cyclicity for Thermodynamic Power Cycles

PubMed Central

Layton, Astrid; Reap, John; Bras, Bert; Weissburg, Marc

2012-01-01

A sustainable global community requires the successful integration of environment and engineering. In the public and private sectors, designing cyclical (“closed loop”) resource networks increasingly appears as a strategy employed to improve resource efficiency and reduce environmental impacts. Patterning industrial networks on ecological ones has been shown to provide significant improvements at multiple levels. Here, we apply the biological metric cyclicity to 28 familiar thermodynamic power cycles of increasing complexity. These cycles, composed of turbines and the like, are scientifically very different from natural ecosystems. Despite this difference, the application results in a positive correlation between the maximum thermal efficiency and the cyclic structure of the cycles. The immediate impact of these findings results in a simple method for comparing cycles to one another, higher cyclicity values pointing to those cycles which have the potential for a higher maximum thermal efficiency. Such a strong correlation has the promise of impacting both natural ecology and engineering thermodynamics and provides a clear motivation to look for more fundamental scientific connections between natural and engineered systems. PMID:23251638

Enhanced interfacial thermal transport in pnictogen tellurides metallized with a lead-free solder alloy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Devender,; Ramanath, Ganpati, E-mail: Ramanath@rpi.edu; Lofgreen, Kelly

2015-11-15

Controlling thermal transport across metal–thermoelectric interfaces is essential for realizing high efficiency solid-state refrigeration and waste-heat harvesting power generation devices. Here, the authors report that pnictogen chalcogenides metallized with bilayers of Sn{sub 96.5}Ag{sub 3}Cu{sub 0.5} solder and Ni barrier exhibit tenfold higher interfacial thermal conductance Γ{sub c} than that obtained with In/Ni bilayer metallization. X-ray diffraction and x-ray spectroscopy indicate that reduced interdiffusion and diminution of interfacial SnTe formation due to Ni layer correlates with the higher Γ{sub c}. Finite element modeling of thermoelectric coolers metallized with Sn{sub 96.5}Ag{sub 3}Cu{sub 0.5}/Ni bilayers presages a temperature drop ΔT ∼ 22 K that is 40%more » higher than that obtained with In/Ni metallization. Our results underscore the importance of controlling chemical intermixing at solder–metal–thermoelectric interfaces to increase the effective figure of merit, and hence, the thermoelectric cooling efficiency. These findings should facilitate the design and development of lead-free metallization for pnictogen chalcogenide-based thermoelectrics.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Van Blarigan, P.

A hydrogen fueled engine is being developed specifically for the auxiliary power unit (APU) in a series type hybrid vehicle. Hydrogen is different from other internal combustion (IC) engine fuels, and hybrid vehicle IC engine requirements are different from those of other IC vehicle engines. Together these differences will allow a new engine design based on first principles that will maximize thermal efficiency while minimizing principal emissions. The experimental program is proceeding in four steps: (1) Demonstration of the emissions and the indicated thermal efficiency capability of a standard CLR research engine modified for higher compression ratios and hydrogen fueledmore » operation. (2) Design and test a new combustion chamber geometry for an existing single cylinder research engine, in an attempt to improve on the baseline indicated thermal efficiency of the CLR engine. (3) Design and build, in conjunction with an industrial collaborator, a new full scale research engine designed to maximize brake thermal efficiency. Include a full complement of combustion diagnostics. (4) Incorporate all of the knowledge thus obtained in the design and fabrication, by an industrial collaborator, of the hydrogen fueled engine for the hybrid vehicle power train illustrator. Results of the CLR baseline engine testing are presented, as well as preliminary data from the new combustion chamber engine. The CLR data confirm the low NOx produced by lean operation. The preliminary indicated thermal efficiency data from the new combustion chamber design engine show an improvement relative to the CLR engine. Comparison with previous high compression engine results shows reasonable agreement.« less

SS-mPEG chemical modification of recombinant phospholipase C for enhanced thermal stability and catalytic efficiency.

PubMed

Fang, Xian; Wang, Xueting; Li, Guiling; Zeng, Jun; Li, Jian; Liu, Jingwen

2018-05-01

PEGylation is one of the most promising and extensively studied strategies for improving the properties of proteins as well as enzymic physical and thermal stability. Phospholipase C, hydrolyzing the phospholipids offers tremendous applications in diverse fields. However, the poor thermal stability and higher cost of production have restricted its industrial application. This study focused on improving the stabilization of recombinant PLC by chemical modification with methoxypolyethylene glycol-Succinimidyl Succinate (SS-mPEG, MW 5000). PLC gene from isolate Bacillus cereus HSL3 was fused with SUMO, a novel small ubiquitin-related modifier expression vector and over expressed in Escherichia coli. The soluble fraction of SUMO-PLC reached 80% of the total recombinant protein. The enzyme exhibited maximum catalytic activity at 80 °C and was relatively thermostable at 40-70 °C. It showed extensive substrate specificity pattern and marked activity toward phosphatidylcholine, which made it a typical non-specific PLC for industrial purpose. SS-mPEG-PLC complex exhibited an enhanced thermal stability at 70-80 °C and the catalytic efficiency (K cat /K m ) had increased by 3.03 folds compared with free PLC. CD spectrum of SS-mPEG-PLC indicated a possible enzyme aggregation after chemical modification, which contributed to the higher thermostability of SS-mPEG-PLC. The increase of antiparallel β sheets in secondary structure also made it more stable than parallel β sheets. The presence of SS-mPEG chains on the enzyme molecule surface somewhat changed the binding rate of the substrates, leading to a significant improvement in catalytic efficiency. This study provided an insight into the addition of SS-mPEG for enhancing the industrial applications of phospholipase C at higher temperature. Copyright © 2018 Elsevier B.V. All rights reserved.

Introduction of Nano-seconds Pulsed Discharge Plasma and its Applications

NASA Astrophysics Data System (ADS)

Namihira, Takao; Wang, Douyan; Matsumoto, Takao; Okada, Sho; Akiyama, Hidenori

During the decades, the developments of high power semiconductor switch, magnetic core and etc have allowed us to manufacture the pulsed power source having higher energy transfer efficiency. As the results, the pulsed discharge has been recognized as one of the promised non-thermal plasma to practical use. In this paper, a generation process, electron energy, impedance and a temperature of the pulsed discharge plasma would be explained. In addition, a nano-seconds pulsed discharge plasma would be introduced as the non-thermal plasma processing giving us the highest energy efficiency and be demonstrated it.

Influence of Temperature on CaO-MgO-Al2O3-SiO2 (CMAS) Corrosion on Thermal Barrier Coatings

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Honglong; Zhang, Xingxing; Agubra, Victor

2015-10-23

Higher operating temperature improves the energy efficiency in gas turbine engines and thermal barrier coatings are applied to protect the blades from high temperature and dust corrosion. Dust composed by CaO-MgO-Al2O3-SiO2 (CMAS) can melt and react with pyrochlore zirconates thermal barrier materials and degrade the performance or cause failure of the coatings. This paper discusses the relationship of the reaction product and corrosion temperature.

Effect of solvent and subsequent thermal annealing on the performance of phenylenevinylene copolymer: PCBM solar cells.

PubMed

Sharma, G D; Suresh, P; Sharma, S S; Vijay, Y K; Mikroyannidis, John A

2010-02-01

The morphology of the photoactive layer used in the bulk heterojunction photovoltaic devices is crucial for efficient charge generation and their collection at the electrodes. We investigated the solvent vapor annealing and thermal annealing effect of an alternating phenylenevinylene copolymer P:PCBM blend on its morphology and optical properties. The UV-visible absorption spectroscopy shows that both solvent and thermal annealing can result in self-assembling of copolymer P to form an ordered structure, leading to enhanced absorption in the red region and hole transport enhancement. By combining the solvent and thermal annealing of the devices, the power conversion efficiency is improved. This feature was attributed to the fact that the PCBM molecules begin to diffuse into aggregates and together with the ordered copolymer P phase form bicontinuous pathways in the entire layer for efficient charge separation and transport. Furthermore, the measured photocurrent also suggests that the space charges no longer limit the values of the short circuit current (J(sc)) and fill factor (FF) for solvent-treated and thermally annealed devices. These results indicate that the higher J(sc) and PCE for the solvent-treated and thermally annealed devices can be attributed to the phase separation of active layers, which leads to a balanced carrier mobility. The overall PCE of the device based on the combination of solvent annealing and thermal annealing is about 3.7 %.

Thermal Management and Reliability of Power Electronics and Electric Machines

DOE Office of Scientific and Technical Information (OSTI.GOV)

Narumanchi, Sreekant

2016-09-19

Increasing the number of electric-drive vehicles (EDVs) on America's roads has been identified as a strategy with near-term potential for dramatically decreasing the nation's dependence on oil - by the U.S. Department of Energy, the federal cross-agency EV-Everywhere Challenge, and the automotive industry. Mass-market deployment will rely on meeting aggressive technical targets, including improved efficiency and reduced size, weight, and cost. Many of these advances will depend on optimization of thermal management. Effective thermal management is critical to improving the performance and ensuring the reliability of EDVs. Efficient heat removal makes higher power densities and lower operating temperatures possible, andmore » in turn enables cost and size reductions. The National Renewable Energy Laboratory (NREL), along with DOE and industry partners is working to develop cost-effective thermal management solutions to increase device and component power densities. In this presentation, the activities in recent years related to thermal management and reliability of automotive power electronics and electric machines are presented.« less

Low Conductivity Thermal Barrier Coatings

NASA Technical Reports Server (NTRS)

Zhu, Dong-Ming

2005-01-01

Thermal barrier coatings will be more aggressively designed to protect gas turbine engine hot-section components in order to meet future engine higher fuel efficiency and lower emission goals. In this presentation, thermal barrier coating development considerations and requirements will be discussed. An experimental approach is established to monitor in real time the thermal conductivity of the coating systems subjected to high-heat-flux, steady-state and cyclic temperature gradients. Advanced low conductivity thermal barrier coatings have also been developed using a multi-component defect clustering approach, and shown to have improved thermal stability. The durability and erosion resistance of low conductivity thermal barrier coatings have been improved utilizing advanced coating architecture design, composition optimization, in conjunction with more sophisticated modeling and design tools.

Zirconia and Pyrochlore Oxides for Thermal Barrier Coatings in Gas Turbine Engines

NASA Astrophysics Data System (ADS)

Fergus, Jeffrey W.

2014-06-01

One of the important applications of yttria-stabilized zirconia (YSZ) is as a thermal barrier coating for gas turbine engines. While YSZ performs well in this function, the need for increased operating temperatures to achieve higher energy conversion efficiencies, requires the development of improved materials. To meet this challenge, some rare-earth zirconates that form the cubic fluorite-derived pyrochlore structure are being developed for use in thermal barrier coatings due to their low thermal conductivity, excellent chemical stability, and other suitable properties. In this paper, the thermal conductivities of current and prospective oxides for use in thermal barrier coatings are reviewed. The factors affecting the variations and differences in the thermal conductivities and the degradation behaviors of these materials are discussed.

Recent Developments in Niobium Containing Austenitic Stainless Steels for Thermal Power Plants

NASA Astrophysics Data System (ADS)

de Oliveira, Mariana Perez; Zhang, Wei; Yu, Hongyao; Bao, Hansheng; Xie, Xishan

The challenge of growing continuously in a sustainable way is the main driver to improve efficiency in the use of natural resources. The increasing demand for energy has made thermal power based countries to set audacious programs to increase efficiency of thermal power generation. In China, coal-burning accounts nowadays for approximately 65% of the total primary energy supply being responsible for around 25% of the countries' CO2 emission, this coal-based energy supply scenario is believed to continue until 2020. Therefore, the country has invested strongly in the last years in the construction of more efficient power plants. To attend higher operating temperatures and steam pressures, the application of higher performance materials is mandatory, presenting improved mechanical resistance — to stand the higher pressures applied — and having sufficient high temperature and corrosion resistance with the best cost-benefit relation possible. The present work addresses some research developments made in niobium containing austenitic stainless steels for super heaters and re-heater tubes in the past years as a joint effort between industry and academia to understand mechanisms and optimize the steel chemical composition, improving its performance. Niobium role has been studied in detail in heat resistant stainless steels TP347H, Super 304 and HR3C, a summary of such studies is presented in this paper. Niobium improves high temperature properties as it precipitates as nano-size MX and NbCrN, well dispersed in the matrix, hindering dislocation movement, increasing precipitation strengthening and creep resistance.

75 FR 10873 - Energy Conservation Program: Energy Conservation Standards for Small Electric Motors

Federal Register 2010, 2011, 2012, 2013, 2014

2010-03-09

... design option to be technologically feasible if it is in use by the respective industry or if research.... Baseline Motor Performance 3. Higher Efficiency Motor Designs a. Electrical Steel b. Thermal Analysis c... a variety of provisions designed to improve energy efficiency. Part A of Title III (42 U.S.C. 6291...

Thermal biology in two syntopic lizards, Phymaturus extrilidus and Liolaemus parvus, in the Puna region of Argentina.

PubMed

Gómez Alés, Rodrigo; Acosta, Juan Carlos; Laspiur, Alejandro

2017-08-01

Body temperature is the most important ecophysiological variable affecting reptiles' life history. Moreover, thermoregulation in ectotherms implies a struggle to reach preferred temperatures in natural conditions due to the influence of biotic and abiotic factors. Our objective was to evaluate and compare the thermal biology of two syntopic species, Phymaturus extrilidus and Liolaemus parvus, in the Puna region of San Juan, Argentina. We determined body temperature (T b ), micro-environmental temperatures (T a and T s ) and operative temperatures (T e ) in the field. In the laboratory, we measured preferred temperatures (T pref ) and calculated the index of thermoregulatory efficiency (E). Neither body temperatures in the field nor preferred temperatures varied between seasons and sexes. Body temperatures were lower than preferred temperatures for both species. Nevertheless, regardless of the low thermal offer available in habitat, both species did achieve body temperatures higher than operative temperatures during activity. Thermoregulatory effectiveness was moderate in P. extrilidus (E=0.65), while L. parvus presented greater thermoregulatory efficiency (E=0.78). We conclude that under the rigorous climate conditions of the Puna, Phymaturus extrilidus and Liolaemus parvus are able to actively and efficiently thermoregulate, maintaining body temperatures close to the preferred and higher than those of its habitat. Differences in thermal characteristics between Phymaturus extrilidus and Liolaemus parvus are a consequence of differential limitations imposed on each species by the environment and of forces inherent to their life histories. Copyright © 2017 Elsevier Ltd. All rights reserved.

High-performance flat-panel solar thermoelectric generators with high thermal concentration.

PubMed

Kraemer, Daniel; Poudel, Bed; Feng, Hsien-Ping; Caylor, J Christopher; Yu, Bo; Yan, Xiao; Ma, Yi; Wang, Xiaowei; Wang, Dezhi; Muto, Andrew; McEnaney, Kenneth; Chiesa, Matteo; Ren, Zhifeng; Chen, Gang

2011-05-01

The conversion of sunlight into electricity has been dominated by photovoltaic and solar thermal power generation. Photovoltaic cells are deployed widely, mostly as flat panels, whereas solar thermal electricity generation relying on optical concentrators and mechanical heat engines is only seen in large-scale power plants. Here we demonstrate a promising flat-panel solar thermal to electric power conversion technology based on the Seebeck effect and high thermal concentration, thus enabling wider applications. The developed solar thermoelectric generators (STEGs) achieved a peak efficiency of 4.6% under AM1.5G (1 kW m(-2)) conditions. The efficiency is 7-8 times higher than the previously reported best value for a flat-panel STEG, and is enabled by the use of high-performance nanostructured thermoelectric materials and spectrally-selective solar absorbers in an innovative design that exploits high thermal concentration in an evacuated environment. Our work opens up a promising new approach which has the potential to achieve cost-effective conversion of solar energy into electricity. © 2011 Macmillan Publishers Limited. All rights reserved

Navy Expeditionary Technology Transition Program (NETTP)

DTIC Science & Technology

2012-03-02

water vapor from feed air using a zeolite membrane •Temperature/Humidity levels can be met in warm, humid climates without reheating •Allows higher...UNCLASSIFIED, Distribution Unlimited Modular Thermal Hub •Small, efficient absorption cooling •Energy source: Combustion, low- grade waste heat, solar... thermal energy •Reversible operation enables space cooling and heating, and water heating •Modular cooling and heating unit •Monolithic packaging offers

Field testing of aquifer thermal energy storage

NASA Astrophysics Data System (ADS)

Kannberg, L. D.; Allen, R. D.

1984-03-01

Results of field and laboratory studies of aquifer thermal energy storage (ATES) indicate both the problems and promise of the concept. Geohydrothermal modeling and field testing demonstrated the ability to recover substantial quantities of aquifer stored energy. However, the local hydrologic conditions play an important role in determining the recovery temperature and storage efficiency. Geochemistry is also an important factor, particularly for higher temperature ATES systems.

Model Comparison for Electron Thermal Transport

NASA Astrophysics Data System (ADS)

Moses, Gregory; Chenhall, Jeffrey; Cao, Duc; Delettrez, Jacques

2015-11-01

Four electron thermal transport models are compared for their ability to accurately and efficiently model non-local behavior in ICF simulations. Goncharov's transport model has accurately predicted shock timing in implosion simulations but is computationally slow and limited to 1D. The iSNB (implicit Schurtz Nicolai Busquet electron thermal transport method of Cao et al. uses multigroup diffusion to speed up the calculation. Chenhall has expanded upon the iSNB diffusion model to a higher order simplified P3 approximation and a Monte Carlo transport model, to bridge the gap between the iSNB and Goncharov models while maintaining computational efficiency. Comparisons of the above models for several test problems will be presented. This work was supported by Sandia National Laboratory - Albuquerque and the University of Rochester Laboratory for Laser Energetics.

Multiphase Nanocrystalline Ceramic Concept for Nuclear Fuel

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mecartnery, Martha; Graeve, Olivia; Patel, Maulik

2017-05-25

The goal of this research is to help develop new fuels for higher efficiency, longer lifetimes (higher burn-up) and increased accident tolerance in future nuclear reactors. Multiphase nanocrystalline ceramics will be used in the design of simulated advanced inert matrix nuclear fuel to provide for enhanced plasticity, better radiation tolerance, and improved thermal conductivity

Steam reforming of n-hexane on pellet and monolithic catalyst beds. A comparative study on improvements due to heat transfer

NASA Technical Reports Server (NTRS)

1981-01-01

Monolithic catalysts with higher available active surface areas and better thermal conductivity than conventional pellets beds, making possible the steam reforming of fuels heavier than naphtha, were examined. Performance comparisons were made between conventional pellet beds and honeycomb monolith catalysts using n-hexane as the fuel. Metal-supported monoliths were examined. These offer higher structural stability and higher thermal conductivity than ceramic supports. Data from two metal monoliths of different nickel catalyst loadings were compared to pellets under the same operating conditions. Improved heat transfer and better conversion efficiencies were obtained with the monolith having higher catalyst loading. Surface-gas interaction was observed throughout the length of the monoliths.

In-depth investigation of spin-on doped solar cells with thermally grown oxide passivation

NASA Astrophysics Data System (ADS)

Ahmad, Samir Mahmmod; Cheow, Siu Leong; Ludin, Norasikin A.; Sopian, K.; Zaidi, Saleem H.

Solar cell industrial manufacturing, based largely on proven semiconductor processing technologies supported by significant advancements in automation, has reached a plateau in terms of cost and efficiency. However, solar cell manufacturing cost (dollar/watt) is still substantially higher than fossil fuels. The route to lowering cost may not lie with continuing automation and economies of scale. Alternate fabrication processes with lower cost and environmental-sustainability coupled with self-reliance, simplicity, and affordability may lead to price compatibility with carbon-based fuels. In this paper, a custom-designed formulation of phosphoric acid has been investigated, for n-type doping in p-type substrates, as a function of concentration and drive-in temperature. For post-diffusion surface passivation and anti-reflection, thermally-grown oxide films in 50-150-nm thickness were grown. These fabrication methods facilitate process simplicity, reduced costs, and environmental sustainability by elimination of poisonous chemicals and toxic gases (POCl3, SiH4, NH3). Simultaneous fire-through contact formation process based on screen-printed front surface Ag and back surface through thermally grown oxide films was optimized as a function of the peak temperature in conveyor belt furnace. Highest efficiency solar cells fabricated exhibited efficiency of ∼13%. Analysis of results based on internal quantum efficiency and minority carried measurements reveals three contributing factors: high front surface recombination, low minority carrier lifetime, and higher reflection. Solar cell simulations based on PC1D showed that, with improved passivation, lower reflection, and high lifetimes, efficiency can be enhanced to match with commercially-produced PECVD SiN-coated solar cells.

Columnar-Structured Mg-Al-Spinel Thermal Barrier Coatings (TBCs) by Suspension Plasma Spraying (SPS)

NASA Astrophysics Data System (ADS)

Schlegel, N.; Ebert, S.; Mauer, G.; Vaßen, R.

2015-01-01

The suspension plasma spraying (SPS) process has been developed to permit the feeding of sub-micrometer-sized powder into the plasma plume. In contrast to electron beam-physical vapor deposition and plasma spray-physical vapor deposition, SPS enables the cost-efficient deposition of columnar-structured coatings. Due to their strain tolerance, these coatings play an important role in the field of thermal barrier coatings (TBCs). In addition to the cost-efficient process, attention was turned to the TBC material. Nowadays, yttria partially stabilized zirconia (YSZ) is used as standard TBC material. However, its long-term application at temperatures higher than 1200 °C is problematic. At these high temperatures, phase transitions and sintering effects lead to the degradation of the TBC system. To overcome those deficits of YSZ, Mg-Al-spinel was chosen as TBC material. Even though it has a lower melting point (~2135 °C) and a higher thermal conductivity (~2.5 W/m/K) than YSZ, Mg-Al-spinel provides phase stability at high temperatures in contrast to YSZ. The Mg-Al-spinel deposition by SPS resulted in columnar-structured coatings, which have been tested for their thermal cycling lifetime. Furthermore, the influence of substrate cooling during the spraying process on thermal cycling behavior, phase composition, and stoichiometry of the Mg-Al-spinel has been investigated.

The World Bank’s Clean Technology Fund (CTF)

DTIC Science & Technology

2008-11-24

economies such as China and India. The incremental carbon dioxide (CO2) emissions from China and India alone have accounted for an estimated 62% of new...gas reductions. Carbon dioxide emissions from power plants are directly proportional to efficiency, so a plant going with an 18% absolute increase in...efficiency would produce 18% less carbon dioxide . These are the higher heating value (HHV) thermal efficiency rates, not be confused with lower heating

Thermal desorption of PCB-contaminated soil with sodium hydroxide.

PubMed

Liu, Jie; Qi, Zhifu; Zhao, Zhonghua; Li, Xiaodong; Buekens, Alfons; Yan, Jianhua; Ni, Mingjiang

2015-12-01

The thermal desorption was combined with sodium hydroxide to remediate polychlorinated biphenyl (PCB)-contaminated soil. The experiments were conducted at different temperatures ranging from 300 to 600 °C with three NaOH contents of 0.1, 0.5, and 1 %. The results showed that thermal desorption was effective for PCB removal, destruction, and detoxication, and the presence of NaOH enhanced the process by significant dechlorination. After treatment with 0.1 % NaOH, the removal efficiency (RE) increased from 84.8 % at 300 °C to 98.0 % at 600 °C, corresponding to 72.7 and 91.7 % of destruction efficiency (DE). With 1 % NaOH content treated at 600 °C, the RE and DE were 99.0 and 93.6 %, respectively. The effect of NaOH content on PCB removal was significant, especially at lower temperature, yet it weakened under higher temperature. The interaction between NaOH content and temperature influenced the PCB composition. The higher temperature with the help of NaOH effectively increased the RE and DE of 12 dioxin-like PCBs (based on WHO-TEQ).

Metallic phase change material thermal storage for Dish Stirling

DOE PAGES

Andraka, C. E.; Kruizenga, A. M.; Hernandez-Sanchez, B. A.; ...

2015-06-05

Dish-Stirling systems provide high-efficiency solar-only electrical generation and currently hold the world record at 31.25%. This high efficiency results in a system with a high possibility of meeting the DOE SunShot goal of $0.06/kWh. However, current dish-Stirling systems do not incorporate thermal storage. For the next generation of non-intermittent and cost-competitive solar power plants, we propose adding a thermal energy storage system that combines latent (phase-change) energy transport and latent energy storage in order to match the isothermal input requirements of Stirling engines while also maximizing the exergetic efficiency of the entire system. This paper reports current findings in themore » area of selection, synthesis and evaluation of a suitable high performance metallic phase change material (PCM) as well as potential interactions with containment alloy materials. The metallic PCM's, while more expensive than salts, have been identified as having substantial performance advantages primarily due to high thermal conductivity, leading to high exergetic efficiency. Systems modeling has indicated, based on high dish Stirling system performance, an allowable cost of the PCM storage system that is substantially higher than SunShot goals for storage cost on tower systems. Several PCM's are identified with suitable melting temperature, cost, and performance.« less

STEP wastewater treatment: a solar thermal electrochemical process for pollutant oxidation.

PubMed

Wang, Baohui; Wu, Hongjun; Zhang, Guoxue; Licht, Stuart

2012-10-01

A solar thermal electrochemical production (STEP) pathway was established to utilize solar energy to drive useful chemical processes. In this paper, we use experimental chemistry for efficient STEP wastewater treatment, and suggest a theory based on the decreasing stability of organic pollutants (hydrocarbon oxidation potentials) with increasing temperature. Exemplified by the solar thermal electrochemical oxidation of phenol, the fundamental model and experimental system components of this process outline a general method for the oxidation of environmentally stable organic pollutants into carbon dioxide, which is easily removed. Using thermodynamic calculations we show a sharply decreasing phenol oxidation potential with increasing temperature. The experimental results demonstrate that this increased temperature can be supplied by solar thermal heating. In combination this drives electrochemical phenol removal with enhanced oxidation efficiency through (i) a thermodynamically driven decrease in the energy needed to fuel the process and (ii) improved kinetics to sustain high rates of phenol oxidation at low electrochemical overpotential. The STEP wastewater treatment process is synergistic in that it is performed with higher efficiency than either electrochemical or photovoltaic conversion process acting alone. STEP is a green, efficient, safe, and sustainable process for organic wastewater treatment driven solely by solar energy. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Utilizing Radioisotope Power System Waste Heat for Spacecraft Thermal Management

NASA Technical Reports Server (NTRS)

Pantano, David R.; Dottore, Frank; Geng, Steven M.; Schrieber, Jeffrey G.; Tobery, E. Wayne; Palko, Joseph L.

2005-01-01

One of the advantages of using a Radioisotope Power System (RPS) for deep space or planetary surface missions is the readily available waste heat, which can be used to maintain electronic components within a controlled temperature range, to warm propulsion tanks and mobility actuators, and to gasify liquid propellants. Previous missions using Radioisotope Thermoelectric Generators (RTGs) dissipated a very large quantity of waste heat due to the relatively low efficiency of the thermoelectric conversion technology. The next generation RPSs, such as the 110-watt Stirling Radioisotope Generator (SRG110) will have much higher conversion efficiencies than their predecessors and therefore may require alternate approaches to transferring waste heat to the spacecraft. RTGs, with efficiencies of approx. 6 to 7% and 200 C housing surface temperatures, would need to use large and heavy radiator heat exchangers to transfer the waste heat to the internal spacecraft components. At the same time, sensitive spacecraft instruments must be shielded from the thermal radiation by using the heat exchangers or additional shields. The SRG110, with an efficiency around 22% and 50 C nominal housing surface temperature, can use the available waste heat more efficiently by more direct heat transfer methods such as heat pipes, thermal straps, or fluid loops. The lower temperatures allow the SRG110 much more flexibility to the spacecraft designers in configuring the generator without concern of overheating nearby scientific instruments, thereby eliminating the need for thermal shields. This paper will investigate using a high efficiency SRG110 for spacecraft thermal management and outline potential methods in several conceptual missions (Lunar Rover, Mars Rover, and Titan Lander) to illustrate the advantages with regard to ease of assembly, less complex interfaces, and overall mass savings.

Efficiency of depleted UO2 based semiconductor neutron detectors in direct and indirect configuration—A GEANT4 simulation study

NASA Astrophysics Data System (ADS)

Parida, M. K.; Prabakar, K.; Sundari, S. T.

2018-03-01

In the present work, Monte Carlo simulations using GEANT4 are carried out to estimate the efficiency of semiconductor neutron detectors with depleted UO2 (DUO2) as converter material, in both planar (direct and indirect) and 3D geometry (cylindrical perforation and trenches structure) configurations. The simulations were conducted for neutrons of variable energy viz., thermal (25 meV) and fast (1 to 10 MeV) that were incident on varying thicknesses (0.25 μm to 1000 μm), diameters (1 μm to 9 μm) and widths (1 μm to 9 μm) along with depths (50 μm to 275 μm) of DUO2 for planar, cylindrical perforated and trench structures, respectively. In the case of direct planar detectors, efficiency was found to increase with the thickness of DUO2 and the rate at which efficiency increased was found to follow the macroscopic fission cross section at the corresponding neutron energy. In the case of indirect planar detector, efficiency was lower as compared to direct configuration and was found to saturate beyond a thickness of ~3 μm. This saturation is explained on the basis of mean free path of neutrons in the DUO2 material. For the 3D perforated silicon detectors of cylindrical (trench) geometry, backfilled with DUO2, the efficiency for detection of thermal neutrons ~25 meV and fast neutrons ~ typical energy of 10 MeV was found to be ~0.0159% (~0.0177%) and ~0.0088% (0.0098%), respectively. These efficiency values were two (one) order values higher than planar indirect detector for thermal (fast) neutrons. Histogram plots were also obtained from the GEANT4 simulations to monitor the energy distribution of fission products in planar (direct and indirect) and 3D geometry (cylindrical and trench) configurations. These plots revealed that, for all the detector configurations, the energy deposited by the fission products are higher as compared to the typical gamma ray background. Thus, for detectors with DUO2 as converter material, higher values of low level discriminator (LLD) can be set, so as to achieve good background discrimination.

The use of salinity contrast for density difference compensation to improve the thermal recovery efficiency in high-temperature aquifer thermal energy storage systems

NASA Astrophysics Data System (ADS)

van Lopik, Jan H.; Hartog, Niels; Zaadnoordijk, Willem Jan

2016-08-01

The efficiency of heat recovery in high-temperature (>60 °C) aquifer thermal energy storage (HT-ATES) systems is limited due to the buoyancy of the injected hot water. This study investigates the potential to improve the efficiency through compensation of the density difference by increased salinity of the injected hot water for a single injection-recovery well scheme. The proposed method was tested through numerical modeling with SEAWATv4, considering seasonal HT-ATES with four consecutive injection-storage-recovery cycles. Recovery efficiencies for the consecutive cycles were investigated for six cases with three simulated scenarios: (a) regular HT-ATES, (b) HT-ATES with density difference compensation using saline water, and (c) theoretical regular HT-ATES without free thermal convection. For the reference case, in which 80 °C water was injected into a high-permeability aquifer, regular HT-ATES had an efficiency of 0.40 after four consecutive recovery cycles. The density difference compensation method resulted in an efficiency of 0.69, approximating the theoretical case (0.76). Sensitivity analysis showed that the net efficiency increase by using the density difference compensation method instead of regular HT-ATES is greater for higher aquifer hydraulic conductivity, larger temperature difference between injection water and ambient groundwater, smaller injection volume, and larger aquifer thickness. This means that density difference compensation allows the application of HT-ATES in thicker, more permeable aquifers and with larger temperatures than would be considered for regular HT-ATES systems.

Efficiently-cooled plasmonic amorphous silicon solar cells integrated with a nano-coated heat-pipe plate

PubMed Central

Zhang, Yinan; Du, Yanping; Shum, Clifford; Cai, Boyuan; Le, Nam Cao Hoai; Chen, Xi; Duck, Benjamin; Fell, Christopher; Zhu, Yonggang; Gu, Min

2016-01-01

Solar photovoltaics (PV) are emerging as a major alternative energy source. The cost of PV electricity depends on the efficiency of conversion of light to electricity. Despite of steady growth in the efficiency for several decades, little has been achieved to reduce the impact of real-world operating temperatures on this efficiency. Here we demonstrate a highly efficient cooling solution to the recently emerging high performance plasmonic solar cell technology by integrating an advanced nano-coated heat-pipe plate. This thermal cooling technology, efficient for both summer and winter time, demonstrates the heat transportation capability up to ten times higher than those of the metal plate and the conventional wickless heat-pipe plates. The reduction in temperature rise of the plasmonic solar cells operating under one sun condition can be as high as 46%, leading to an approximate 56% recovery in efficiency, which dramatically increases the energy yield of the plasmonic solar cells. This newly-developed, thermally-managed plasmonic solar cell device significantly extends the application scope of PV for highly efficient solar energy conversion. PMID:27113558

Efficiently-cooled plasmonic amorphous silicon solar cells integrated with a nano-coated heat-pipe plate.

PubMed

Zhang, Yinan; Du, Yanping; Shum, Clifford; Cai, Boyuan; Le, Nam Cao Hoai; Chen, Xi; Duck, Benjamin; Fell, Christopher; Zhu, Yonggang; Gu, Min

2016-04-26

Solar photovoltaics (PV) are emerging as a major alternative energy source. The cost of PV electricity depends on the efficiency of conversion of light to electricity. Despite of steady growth in the efficiency for several decades, little has been achieved to reduce the impact of real-world operating temperatures on this efficiency. Here we demonstrate a highly efficient cooling solution to the recently emerging high performance plasmonic solar cell technology by integrating an advanced nano-coated heat-pipe plate. This thermal cooling technology, efficient for both summer and winter time, demonstrates the heat transportation capability up to ten times higher than those of the metal plate and the conventional wickless heat-pipe plates. The reduction in temperature rise of the plasmonic solar cells operating under one sun condition can be as high as 46%, leading to an approximate 56% recovery in efficiency, which dramatically increases the energy yield of the plasmonic solar cells. This newly-developed, thermally-managed plasmonic solar cell device significantly extends the application scope of PV for highly efficient solar energy conversion.

Efficiently-cooled plasmonic amorphous silicon solar cells integrated with a nano-coated heat-pipe plate

NASA Astrophysics Data System (ADS)

Zhang, Yinan; Du, Yanping; Shum, Clifford; Cai, Boyuan; Le, Nam Cao Hoai; Chen, Xi; Duck, Benjamin; Fell, Christopher; Zhu, Yonggang; Gu, Min

2016-04-01

Solar photovoltaics (PV) are emerging as a major alternative energy source. The cost of PV electricity depends on the efficiency of conversion of light to electricity. Despite of steady growth in the efficiency for several decades, little has been achieved to reduce the impact of real-world operating temperatures on this efficiency. Here we demonstrate a highly efficient cooling solution to the recently emerging high performance plasmonic solar cell technology by integrating an advanced nano-coated heat-pipe plate. This thermal cooling technology, efficient for both summer and winter time, demonstrates the heat transportation capability up to ten times higher than those of the metal plate and the conventional wickless heat-pipe plates. The reduction in temperature rise of the plasmonic solar cells operating under one sun condition can be as high as 46%, leading to an approximate 56% recovery in efficiency, which dramatically increases the energy yield of the plasmonic solar cells. This newly-developed, thermally-managed plasmonic solar cell device significantly extends the application scope of PV for highly efficient solar energy conversion.

Heat transfer and thermal management of electric vehicle batteries with phase change materials

NASA Astrophysics Data System (ADS)

Ramandi, M. Y.; Dincer, I.; Naterer, G. F.

2011-07-01

This paper examines a passive thermal management system for electric vehicle batteries, consisting of encapsulated phase change material (PCM) which melts during a process to absorb the heat generated by a battery. A new configuration for the thermal management system, using double series PCM shells, is analyzed with finite volume simulations. A combination of computational fluid dynamics (CFD) and second law analysis is used to evaluate and compare the new system against the single PCM shells. Using a finite volume method, heat transfer in the battery pack is examined and the results are used to analyse the exergy losses. The simulations provide design guidelines for the thermal management system to minimize the size and cost of the system. The thermal conductivity and melting temperature are studied as two important parameters in the configuration of the shells. Heat transfer from the surroundings to the PCM shell in a non-insulated case is found to be infeasible. For a single PCM system, the exergy efficiency is below 50%. For the second case for other combinations, the exergy efficiencies ranged from 30-40%. The second shell content did not have significant influence on the exergy efficiencies. The double PCM shell system showed higher exergy efficiencies than the single PCM shell system (except a case for type PCM-1). With respect to the reference environment, it is found that in all cases the exergy efficiencies decreased, when the dead-state temperatures rises, and the destroyed exergy content increases gradually. For the double shell systems for all dead-state temperatures, the efficiencies were very similar. Except for a dead-state temperature of 302 K, with the other temperatures, the exergy efficiencies for different combinations are well over 50%. The range of exergy efficiencies vary widely between 15 and 85% for a single shell system, and between 30-80% for double shell systems.

Solid-State Additive Manufacturing for Heat Exchangers

NASA Astrophysics Data System (ADS)

Norfolk, Mark; Johnson, Hilary

2015-03-01

Energy densities in devices are increasing across many industries including power generation, high power electronics, manufacturing, and automotive. Increasingly, there is a need for very high efficiency thermal management devices that can pull heat out of a small area at higher and higher rates. Metal additive manufacturing (AM) technologies have the promise of creating parts with complex internal geometries required for integral thermal management. However, this goal has not been met due to constraints in fusion-based metal 3D printers. This work presents a new strategy for metal AM of heat exchangers using an ultrasonic sheet lamination approach.

Low lattice thermal conductivity of stanene

NASA Astrophysics Data System (ADS)

Peng, Bo; Zhang, Hao; Shao, Hezhu; Xu, Yuchen; Zhang, Xiangchao; Zhu, Heyuan

2016-02-01

A fundamental understanding of phonon transport in stanene is crucial to predict the thermal performance in potential stanene-based devices. By combining first-principle calculation and phonon Boltzmann transport equation, we obtain the lattice thermal conductivity of stanene. A much lower thermal conductivity (11.6 W/mK) is observed in stanene, which indicates higher thermoelectric efficiency over other 2D materials. The contributions of acoustic and optical phonons to the lattice thermal conductivity are evaluated. Detailed analysis of phase space for three-phonon processes shows that phonon scattering channels LA + LA/TA/ZA ↔ TA/ZA are restricted, leading to the dominant contributions of high-group-velocity LA phonons to the thermal conductivity. The size dependence of thermal conductivity is investigated as well for the purpose of the design of thermoelectric nanostructures.

Zirconia and Pyrochlore Oxides for Thermal Barrier Coatings in Gas Turbine Engines

DOE PAGES

Fergus, Jeffrey W.

2014-04-12

One of the important applications of yttria stabilized zirconia is as a thermal barrier coating for gas turbine engines. While yttria stabilized zirconia performs well in this function, the need for increased operating temperatures to achieve higher energy conversion efficiencies, requires the development of improved materials. To meet this challenge, some rare-earth zirconates that form the cubic fluorite derived pyrochlore structure are being developed for use in thermal barrier coatings due to their low thermal conductivity, excellent chemical stability and other suitable properties. In this paper, the thermal conductivities of current and prospective oxides for use in thermal barrier coatingsmore » are reviewed. The factors affecting the variations and differences in the thermal conductivities and the degradation behaviors of these materials are discussed.« less

Development of a Solar Cell Back Sheet with Excellent UV Durability and Thermal Conductivity.

PubMed

Kang, Seong-Hwan; Choi, Jaeho; Lee, Sung-Ho; Song, Young-Hoon; Park, Jong-Se; Jung, In-Sung; Jung, Jin-Su; Kim, Chong-Yeal; Yang, O-Bong

2018-09-01

The back sheet is one of the most important materials in photovoltaic (PV) modules. It plays an important role in protecting the solar cell from the environment by preventing moisture penetration. In the back sheet, the outermost layer is composed of a polyester (PET) film to protect the PV module from moisture, and the opposite layer is composed of a TiO2 + PE material. Nowadays, PV modules are installed in the desert. Therefore, methods to improve the power generation efficiency of PV modules need to be investigated as the efficiency is affected by temperature resulting from the heat radiation effect. Using a back sheet with a high thermal conductivity, the module output efficiency can be increased as heat is efficiently dissipated. In this study, a thermally conductive film was fabricated by mixing a reference film (TiO2 + PE) and a non-metallic material, MgO, with high thermal conductivity. UV irradiation tests of the film were conducted. The thermally conductive film (TiO2 + PE + MgO) showed higher conductivity than a reference film. No visible cracks and low yellowing degree were found in thermally conductive film, confirming its excellent UV durability characteristics. The sample film was bonded to a PET layer, and a back sheet was fabricated. The yellowing of the back sheet was also analyzed after UV irradiation. In addition, mini modules with four solar cell were fabricated using the developed back sheet, and a comparative outdoor test was conducted. The results showed that power generation improved by 1.38%.

Techno-economic analysis of supercritical carbon dioxide power blocks

NASA Astrophysics Data System (ADS)

Meybodi, Mehdi Aghaei; Beath, Andrew; Gwynn-Jones, Stephen; Veeraragavan, Anand; Gurgenci, Hal; Hooman, Kamel

2017-06-01

Developing highly efficient power blocks holds the key to enhancing the cost competitiveness of Concentration Solar Thermal (CST) technologies. Supercritical CO2 (sCO2) Brayton cycles have proved promising in providing equivalent or higher cycle efficiency than supercritical or superheated steam cycles at temperatures and scales relevant for Australian CST applications. In this study, a techno-economic methodology is developed using a stochastic approach to determine the ranges for the cost and performance of different components of central receiver power plants utilizing sCO2 power blocks that are necessary to meet the Australian Solar Thermal Initiative (ASTRI) final LCOE target of 12 c/kWh.

Combustion characteristics of an SI engine fueled with biogas fuel

NASA Astrophysics Data System (ADS)

Chen, Lei; Long, Wuqiang; Song, Peng

2017-04-01

An experimental research of the effect of H2 substitution and CO2 dilution on CH4 combustion has been carried out on a spark ignition engine. The results show that H2 addition could improve BMEP, thermal efficiency, CO and THC emissions. NOX emissions increased for higher low heating value (LHV) of H2 than CH4. CO2 dilution could effective reduce NOX emission of H2-CH4 combustion. Although engine performance, thermal efficiency and exhaust get unacceptable under high fuel dilution ratio (F.D.R.) conditions, it could be solved by decreasing F.D.R. and/or increasing hydrogen substitution ratio (H.S.R.).

Conjugate heat transfer investigation on the cooling performance of air cooled turbine blade with thermal barrier coating

NASA Astrophysics Data System (ADS)

Ji, Yongbin; Ma, Chao; Ge, Bing; Zang, Shusheng

2016-08-01

A hot wind tunnel of annular cascade test rig is established for measuring temperature distribution on a real gas turbine blade surface with infrared camera. Besides, conjugate heat transfer numerical simulation is performed to obtain cooling efficiency distribution on both blade substrate surface and coating surface for comparison. The effect of thermal barrier coating on the overall cooling performance for blades is compared under varied mass flow rate of coolant, and spatial difference is also discussed. Results indicate that the cooling efficiency in the leading edge and trailing edge areas of the blade is the lowest. The cooling performance is not only influenced by the internal cooling structures layout inside the blade but also by the flow condition of the mainstream in the external cascade path. Thermal barrier effects of the coating vary at different regions of the blade surface, where higher internal cooling performance exists, more effective the thermal barrier will be, which means the thermal protection effect of coatings is remarkable in these regions. At the designed mass flow ratio condition, the cooling efficiency on the pressure side varies by 0.13 for the coating surface and substrate surface, while this value is 0.09 on the suction side.

Analysis and optimization of hybrid electric vehicle thermal management systems

NASA Astrophysics Data System (ADS)

Hamut, H. S.; Dincer, I.; Naterer, G. F.

2014-02-01

In this study, the thermal management system of a hybrid electric vehicle is optimized using single and multi-objective evolutionary algorithms in order to maximize the exergy efficiency and minimize the cost and environmental impact of the system. The objective functions are defined and decision variables, along with their respective system constraints, are selected for the analysis. In the multi-objective optimization, a Pareto frontier is obtained and a single desirable optimal solution is selected based on LINMAP decision-making process. The corresponding solutions are compared against the exergetic, exergoeconomic and exergoenvironmental single objective optimization results. The results show that the exergy efficiency, total cost rate and environmental impact rate for the baseline system are determined to be 0.29, ¢28 h-1 and 77.3 mPts h-1 respectively. Moreover, based on the exergoeconomic optimization, 14% higher exergy efficiency and 5% lower cost can be achieved, compared to baseline parameters at an expense of a 14% increase in the environmental impact. Based on the exergoenvironmental optimization, a 13% higher exergy efficiency and 5% lower environmental impact can be achieved at the expense of a 27% increase in the total cost.

Carbon nanotube-copper exhibiting metal-like thermal conductivity and silicon-like thermal expansion for efficient cooling of electronics.

PubMed

Subramaniam, Chandramouli; Yasuda, Yuzuri; Takeya, Satoshi; Ata, Seisuke; Nishizawa, Ayumi; Futaba, Don; Yamada, Takeo; Hata, Kenji

2014-03-07

Increasing functional complexity and dimensional compactness of electronic devices have led to progressively higher power dissipation, mainly in the form of heat. Overheating of semiconductor-based electronics has been the primary reason for their failure. Such failures originate at the interface of the heat sink (commonly Cu and Al) and the substrate (silicon) due to the large mismatch in thermal expansion coefficients (∼300%) of metals and silicon. Therefore, the effective cooling of such electronics demands a material with both high thermal conductivity and a similar coefficient of thermal expansion (CTE) to silicon. Addressing this demand, we have developed a carbon nanotube-copper (CNT-Cu) composite with high metallic thermal conductivity (395 W m(-1) K(-1)) and a low, silicon-like CTE (5.0 ppm K(-1)). The thermal conductivity was identical to that of Cu (400 W m(-1) K(-1)) and higher than those of most metals (Ti, Al, Au). Importantly, the CTE mismatch between CNT-Cu and silicon was only ∼10%, meaning an excellent compatibility. The seamless integration of CNTs and Cu was achieved through a unique two-stage electrodeposition approach to create an extensive and continuous interface between the Cu and CNTs. This allowed for thermal contributions from both Cu and CNTs, resulting in high thermal conductivity. Simultaneously, the high volume fraction of CNTs balanced the thermal expansion of Cu, accounting for the low CTE of the CNT-Cu composite. The experimental observations were in good quantitative concurrence with the theoretically described 'matrix-bubble' model. Further, we demonstrated identical in-situ thermal strain behaviour of the CNT-Cu composite to Si-based dielectrics, thereby generating the least interfacial thermal strain. This unique combination of properties places CNT-Cu as an isolated spot in an Ashby map of thermal conductivity and CTE. Finally, the CNT-Cu composite exhibited the greatest stability to temperature as indicated by its low thermal distortion parameter (TDP). Thus, this material presents a viable and efficient alternative to existing materials for thermal management in electronics.

Multiphysics Modeling of a Single Channel in a Nuclear Thermal Propulsion Grooved Ring Fuel Element

NASA Technical Reports Server (NTRS)

Kim, Tony; Emrich, William J., Jr.; Barkett, Laura A.; Mathias, Adam D.; Cassibry, Jason T.

2013-01-01

In the past, fuel rods have been used in nuclear propulsion applications. A new fuel element concept that reduces weight and increases efficiency uses a stack of grooved discs. Each fuel element is a flat disc with a hole on the interior and grooves across the top. Many grooved ring fuel elements for use in nuclear thermal propulsion systems have been modeled, and a single flow channel for each design has been analyzed. For increased efficiency, a fuel element with a higher surface-area-to-volume ratio is ideal. When grooves are shallower, i.e., they have a lower surface area, the results show that the exit temperature is higher. By coupling the physics of turbulence with those of heat transfer, the effects on the cooler gas flowing through the grooves of the thermally excited solid can be predicted. Parametric studies were done to show how a pressure drop across the axial length of the channels will affect the exit temperatures of the gas. Geometric optimization was done to show the behaviors that result from the manipulation of various parameters. Temperature profiles of the solid and gas showed that more structural optimization is needed to produce the desired results. Keywords: Nuclear Thermal Propulsion, Fuel Element, Heat Transfer, Computational Fluid Dynamics, Coupled Physics Computations, Finite Element Analysis

Nano-based PCMs for building energy efficiency

DOE Office of Scientific and Technical Information (OSTI.GOV)

Biswas, Kaushik

Thermal storage using phase change materials (PCMs) is seen as a viable method for improving the energy efficiency of buildings. PCMs have been used in building applications in various forms PCM slurries in heat exchangers, macro- or microencapsulated PCMs in building envelopes, bulk PCM for modulating photovoltaic temperatures, etc. In the last decade a new class of PCMs, called nano-enhanced PCM (or nanoPCM), has been extensively investigated with the goal of improving the heat transfer and thermal storage properties of PCMs. NanoPCMs can primarily be categorized as nano-encapsulated PCMs and nanoparticle-PCM composites. The former are nano-sized capsules in which themore » PCM forms the core and is surrounded by a high-conductivity membrane or shell. The latter consist of PCM supported within nanostructures or nanoparticles dispersed in PCMs. This article reviews the current state of nanoPCM synthesis and characterization of their heat transfer and thermal storage properties. Further, a critical review of nanoPCM applications and their potential energy benefits is performed. Nano-enhanced PCMs exhibit higher thermal conductivities than regular PCM. However, whether the higher conductivity is desirable in all applications and if the property enhancements are worth the cost and effort needed to create nanoPCMs are questions that still need to be answered.« less

Effects of 946-nm thermal shift and broadening on Nd3+:YAG laser performance

NASA Astrophysics Data System (ADS)

Seyed Ebrahim, Pourmand; Ghasem, Rezaei

2015-12-01

Spectroscopic properties of flashlamp pumped Nd3+:YAG laser are studied as a function of temperature in a range from -30 °C to 60 °C. The spectral width and shift of quasi three-level 946.0-nm inter-Stark emission within the respective intermanifold transitions of 4F3/2 → 4I9/2 are investigated. The 946.0-nm line shifts toward the shorter wavelength and broadens. In addition, the threshold power and slope efficiency of the 946.0-nm laser line are quantified with temperature. The lower the temperature, the lower the threshold power is and the higher the slope efficiency of the 946.0-nm laser line is, thus the higher the laser output is. This phenomenon is attributed to the ion-phonon interaction and the thermal population in the ground state. Project supported by Estahban Branch, Islamic Azad University.

High-performance thermoelectric nanocomposites from nanocrystal building blocks

PubMed Central

Ibáñez, Maria; Luo, Zhishan; Genç, Aziz; Piveteau, Laura; Ortega, Silvia; Cadavid, Doris; Dobrozhan, Oleksandr; Liu, Yu; Nachtegaal, Maarten; Zebarjadi, Mona; Arbiol, Jordi; Kovalenko, Maksym V.; Cabot, Andreu

2016-01-01

The efficient conversion between thermal and electrical energy by means of durable, silent and scalable solid-state thermoelectric devices has been a long standing goal. While nanocrystalline materials have already led to substantially higher thermoelectric efficiencies, further improvements are expected to arise from precise chemical engineering of nanoscale building blocks and interfaces. Here we present a simple and versatile bottom–up strategy based on the assembly of colloidal nanocrystals to produce consolidated yet nanostructured thermoelectric materials. In the case study on the PbS–Ag system, Ag nanodomains not only contribute to block phonon propagation, but also provide electrons to the PbS host semiconductor and reduce the PbS intergrain energy barriers for charge transport. Thus, PbS–Ag nanocomposites exhibit reduced thermal conductivities and higher charge carrier concentrations and mobilities than PbS nanomaterial. Such improvements of the material transport properties provide thermoelectric figures of merit up to 1.7 at 850 K. PMID:26948987

High-performance thermoelectric nanocomposites from nanocrystal building blocks.

PubMed

Ibáñez, Maria; Luo, Zhishan; Genç, Aziz; Piveteau, Laura; Ortega, Silvia; Cadavid, Doris; Dobrozhan, Oleksandr; Liu, Yu; Nachtegaal, Maarten; Zebarjadi, Mona; Arbiol, Jordi; Kovalenko, Maksym V; Cabot, Andreu

2016-03-07

The efficient conversion between thermal and electrical energy by means of durable, silent and scalable solid-state thermoelectric devices has been a long standing goal. While nanocrystalline materials have already led to substantially higher thermoelectric efficiencies, further improvements are expected to arise from precise chemical engineering of nanoscale building blocks and interfaces. Here we present a simple and versatile bottom-up strategy based on the assembly of colloidal nanocrystals to produce consolidated yet nanostructured thermoelectric materials. In the case study on the PbS-Ag system, Ag nanodomains not only contribute to block phonon propagation, but also provide electrons to the PbS host semiconductor and reduce the PbS intergrain energy barriers for charge transport. Thus, PbS-Ag nanocomposites exhibit reduced thermal conductivities and higher charge carrier concentrations and mobilities than PbS nanomaterial. Such improvements of the material transport properties provide thermoelectric figures of merit up to 1.7 at 850 K.

Evaluation of annual efficiencies of high temperature central receiver concentrated solar power plants with thermal energy storage.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ehrhart, Brian David; Gill, David Dennis

The current study has examined four cases of a central receiver concentrated solar power plant with thermal energy storage using the DELSOL and SOLERGY computer codes. The current state-of-the-art base case was compared with a theoretical high temperature case which was based on the scaling of some input parameters and the estimation of other parameters based on performance targets from the Department of Energy SunShot Initiative. This comparison was done for both current and high temperature cases in two configurations: a surround field with an external cylindrical receiver and a north field with a single cavity receiver. There is amore » fairly dramatic difference between the design point and annual average performance, especially in the solar field and receiver subsystems, and also in energy losses due to the thermal energy storage being full to capacity. Additionally, there are relatively small differences (<2%) in annual average efficiencies between the Base and High Temperature cases, despite an increase in thermal to electric conversion efficiency of over 8%. This is due the increased thermal losses at higher temperature and operational losses due to subsystem start-up and shut-down. Thermal energy storage can mitigate some of these losses by utilizing larger thermal energy storage to ensure that the electric power production system does not need to stop and re-start as often, but solar energy is inherently transient. Economic and cost considerations were not considered here, but will have a significant impact on solar thermal electric power production strategy and sizing.« less

Thermal management of LEDs: package to system

NASA Astrophysics Data System (ADS)

Arik, Mehmet; Becker, Charles A.; Weaver, Stanton E.; Petroski, James

2004-01-01

Light emitting diodes, LEDs, historically have been used for indicators and produced low amounts of heat. The introduction of high brightness LEDs with white light and monochromatic colors have led to a movement towards general illumination. The increased electrical currents used to drive the LEDs have focused more attention on the thermal paths in the developments of LED power packaging. The luminous efficiency of LEDs is soon expected to reach over 80 lumens/W, this is approximately 6 times the efficiency of a conventional incandescent tungsten bulb. Thermal management for the solid-state lighting applications is a key design parameter for both package and system level. Package and system level thermal management is discussed in separate sections. Effect of chip packages on junction to board thermal resistance was compared for both SiC and Sapphire chips. The higher thermal conductivity of the SiC chip provided about 2 times better thermal performance than the latter, while the under-filled Sapphire chip package can only catch the SiC chip performance. Later, system level thermal management was studied based on established numerical models for a conceptual solid-state lighting system. A conceptual LED illumination system was chosen and CFD models were created to determine the availability and limitations of passive air-cooling.

Hybrid photovoltaic/thermal (PV/T) solar systems simulation with Simulink/Matlab

DOE Office of Scientific and Technical Information (OSTI.GOV)

da Silva, R.M.; Fernandes, J.L.M.

The purpose of this work consists in thermodynamic modeling of hybrid photovoltaic-thermal (PV/T) solar systems, pursuing a modular strategy approach provided by Simulink/Matlab. PV/T solar systems are a recently emerging solar technology that allows for the simultaneous conversion of solar energy into both electricity and heat. This type of technology present some interesting advantages over the conventional ''side-by-side'' thermal and PV solar systems, such as higher combined electrical/thermal energy outputs per unit area, and a more uniform and aesthetical pleasant roof area. Despite the fact that early research on PV/T systems can be traced back to the seventies, only recentlymore » it has gained a renewed impetus. In this work, parametric studies and annual transient simulations of PV/T systems are undertaken in Simulink/Matlab. The obtained results show an average annual solar fraction of 67%, and a global overall efficiency of 24% (i.e. 15% thermal and 9% electrical), for a typical four-person single-family residence in Lisbon, with p-Si cells, and a collector area of 6 m{sup 2}. A sensitivity analysis performed on the PV/T collector suggests that the most important variable that should be addressed to improve thermal performance is the photovoltaic (PV) module emittance. Based on those results, some additional improvements are proposed, such as the use of vacuum, or a noble gas at low-pressure, to allow for the removal of PV cells encapsulation without air oxidation and degradation, and thus reducing the PV module emittance. Preliminary results show that this option allows for an 8% increase on optical thermal efficiency, and a substantial reduction of thermal losses, suggesting the possibility of working at higher fluid temperatures. The higher working temperatures negative effect in electrical efficiency was negligible, due to compensation by improved optical properties. The simulation results are compared with experimental data obtained from other authors and perform reasonably well. The Simulink modeling platform has been mainly used worldwide on simulation of control systems, digital signal processing and electric circuits, but there are very few examples of application to solar energy systems modeling. This work uses the modular environment of Simulink/Matlab to model individual PV/T system components, and to assemble the entire installation layout. The results show that the modular approach strategy provided by Matlab/Simulink environment is applicable to solar systems modeling, providing good code scalability, faster developing time, and simpler integration with external computational tools, when compared with traditional imperative-oriented programming languages. (author)« less

Activation of the surface dark-layer to enhance upconversion in a thermal field

NASA Astrophysics Data System (ADS)

Zhou, Jiajia; Wen, Shihui; Liao, Jiayan; Clarke, Christian; Tawfik, Sherif Abdulkader; Ren, Wei; Mi, Chao; Wang, Fan; Jin, Dayong

2018-03-01

Thermal quenching, in which light emission experiences a loss with increasing temperature, broadly limits luminescent efficiency at higher temperature in optical materials, such as lighting phosphors1-3 and fluorescent probes4-6. Thermal quenching is commonly caused by the increased activity of phonons that leverages the non-radiative relaxation pathways. Here, we report a kind of heat-favourable phonons existing at the surface of lanthanide-doped upconversion nanomaterials to combat thermal quenching. It favours energy transfer from sensitizers to activators to pump up the intermediate excited-state upconversion process. We identify that the oxygen moiety chelating Yb3+ ions, [Yb...O], is the key underpinning this enhancement. We demonstrate an approximately 2,000-fold enhancement in blue emission for 9.7 nm Yb3+-Tm3+ co-doped nanoparticles at 453 K. This strategy not only provides a powerful solution to illuminate the dark layer of ultra-small upconversion nanoparticles, but also suggests a new pathway to build high-efficiency upconversion systems.

Analytical analysis of solar thermal collector with glass and Fresnel lens glazing

NASA Astrophysics Data System (ADS)

Zulkifle, Idris; Ruslan, Mohd Hafidz Hj; Othman, Mohd Yusof Hj; Ibarahim, Zahari

2018-04-01

Solar thermal collector is a system that converts solar radiation to heat. The heat will raise the temperature higher than the ambient temperature. Absorber and glazing are two important components in order to increase the temperature of the collector. The thermal absorber will release heat by convection and as radiation to the surrounding. These losses will be reduced by glazing. Other than that, glazing is beneficial for protecting the collector from dust and water. This study discusses about modelling of solar thermal collector effects of different mass flow rates with different glazing for V-groove flat plate solar collectors. The glazing used was the glass and linear Fresnel lens. Concentration ratio in this modelling was 1.3 for 0.1m solar collector thickness. Results show that solar collectors with linear Fresnel lens has the highest efficiency value of 71.18% compared to solar collectors with glass which has efficiency 54.10% with same operation conditions.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Narumanchi, Sreekant

Increasing the number of electric-drive vehicles (EDVs) on America's roads has been identified as a strategy with near-term potential for dramatically decreasing the nation's dependence on oil - by the U.S. Department of Energy, the federal cross-agency EV-Everywhere Challenge, and the automotive industry. Mass-market deployment will rely on meeting aggressive technical targets, including improved efficiency and reduced size, weight, and cost. Many of these advances will depend on optimization of thermal management. Effective thermal management is critical to improving the performance and ensuring the reliability of EDVs. Efficient heat removal makes higher power densities and lower operating temperatures possible, andmore » in turn enables cost and size reductions. The National Renewable Energy Laboratory (NREL), along with DOE and industry partners is working to develop cost-effective thermal management solutions to increase device and component power densities. In this presentation, the activities in recent years related to thermal management and reliability of automotive power electronics and electric machines are presented.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Narumanchi, Sreekant

Increasing the number of electric-drive vehicles (EDVs) on America's roads has been identified as a strategy with near-term potential for dramatically decreasing the nation's dependence on oil -- by the U.S. Department of Energy, the federal cross-agency EV-Everywhere Challenge, and the automotive industry. Mass-market deployment will rely on meeting aggressive technical targets, including improved efficiency and reduced size, weight, and cost. Many of these advances will depend on optimization of thermal management. Effective thermal management is critical to improving the performance and ensuring the reliability of EDVs. Efficient heat removal makes higher power densities and lower operating temperatures possible, andmore » in turn enables cost and size reductions. The National Renewable Energy Laboratory (NREL), along with DOE and industry partners is working to develop cost-effective thermal management solutions to increase device and component power densities. In this presentation, the activities in recent years related to thermal management and reliability of automotive power electronics and electric machines will be presented.« less

Practical considerations for solar energy thermally enhanced photo-luminescence (TEPL) (Conference Presentation)

NASA Astrophysics Data System (ADS)

Kruger, Nimrod; Manor, Assaf; Kurtulik, Matej; Sabapathy, Tamilarasan; Rotschild, Carmel

2017-04-01

While single-junction photovoltaics (PV's) are considered limited in conversion efficiency according to the Shockley-Queisser limit, concepts such as solar thermo-photovoltaics aim to harness lost heat and overcome this barrier. We claim the novel concept of Thermally Enhanced Photoluminescence (TEPL) as an easier route to achieve this goal. Here we present a practical TEPL device where a thermally insulated photo-luminescent (PL) absorber, acts as a mediator between a photovoltaic cell and the sun. This high temperature absorber emits blue-shifted PL at constant flux, then coupled to a high band gap PV cell. This scheme promotes PV conversion efficiencies, under ideal conditions, higher than 62% at temperatures lower than 1300K. Moreover, for a PV and absorber band-gaps of 1.45eV (GaAs PV's) and 1.1eV respectively, under practical conditions, solar concentration of 1000 suns, and moderate thermal insulation; the conversion efficiencies potentially exceed 46%. Some of these practical conditions belong to the realm of optical design; including high photon recycling (PR) and absorber external quantum efficiency (EQE). High EQE values, a product of the internal QE of the active PL materials and the extraction efficiency of each photon (determined by the absorber geometry and interfaces), have successfully been reached by experts in laser cooling technology. PR is the part of emitted low energy photons (in relation to the PV band-gap) that are reabsorbed and consequently reemitted with above band-gap energies. PV back-reflector reflectivity, also successfully achieved by those who design the cutting edge high efficiency PV cells, plays a major role here.

Low lattice thermal conductivity of stanene

PubMed Central

Peng, Bo; Zhang, Hao; Shao, Hezhu; Xu, Yuchen; Zhang, Xiangchao; Zhu, Heyuan

2016-01-01

A fundamental understanding of phonon transport in stanene is crucial to predict the thermal performance in potential stanene-based devices. By combining first-principle calculation and phonon Boltzmann transport equation, we obtain the lattice thermal conductivity of stanene. A much lower thermal conductivity (11.6 W/mK) is observed in stanene, which indicates higher thermoelectric efficiency over other 2D materials. The contributions of acoustic and optical phonons to the lattice thermal conductivity are evaluated. Detailed analysis of phase space for three-phonon processes shows that phonon scattering channels LA + LA/TA/ZA ↔ TA/ZA are restricted, leading to the dominant contributions of high-group-velocity LA phonons to the thermal conductivity. The size dependence of thermal conductivity is investigated as well for the purpose of the design of thermoelectric nanostructures. PMID:26838731

Mathematical modeling of the gas and powder flow in the (HVOF) systems to optimize their coatings quality

NASA Technical Reports Server (NTRS)

Tawfik, Hazem H.

1996-01-01

Thermally sprayed coatings have been extensively used to enhance materials properties and provide surface protection against their working environments in a number of industrial applications. Thermal barrier coatings (TBC) are used to reduce the thermal conductivity of aerospace turbine blades and improve the turbine overall thermal efficiency. TBC allows higher gas operating temperatures and lower blade material temperatures due to the thermal insulation provided by these ceramic coatings. In the automotive industry, coatings are currently applied to a number of moving parts that are subjected to friction and wear inside the engine such as pistons, cylinder liners, valves and crankshafts to enhance their wear resistance and prolong their useful operation and lifetime.

Highly Efficient Nd:yag Lasers for Free-space Optical Communications

NASA Technical Reports Server (NTRS)

Sipes, D. L., Jr.

1985-01-01

A highly efficient Nd:YAG laser end-pumped by semiconductor lasers as a possible free-space optical communications source is discussed. Because this concept affords high pumping densities, a long absorption length, and excellent mode-matching characteristics, it is estimated that electrical-to-optical efficiencies greater than 5% could be achieved. Several engineering aspects such as resonator size and configuration, pump collecting optics, and thermal effects are also discussed. Finally, possible methods for combining laser-diode pumps to achieve higher output powers are illustrated.

Absorber for solar power.

PubMed

Powell, W R

1974-10-01

A simple, economical absorber utilizing a new principle of operation to achieve very low reradiation losses while generating temperatures limited by material properties of quartz is described. Its performance is analyzed and indicates approximately 90% thermal efficiency and 73% conversion efficiency for an earth based unit with moderately concentrated (~tenfold) sunlight incident. It is consequently compatible with the most economic of concentrator mirrors (stamped) or mirrors deployable in space. Space applications are particularly attractive, as temperatures significantly below 300 K are possible and permit even higher conversion efficiency.

Homojunction silicon solar cells doping by ion implantation

NASA Astrophysics Data System (ADS)

Milési, Frédéric; Coig, Marianne; Lerat, Jean-François; Desrues, Thibaut; Le Perchec, Jérôme; Lanterne, Adeline; Lachal, Laurent; Mazen, Frédéric

2017-10-01

Production costs and energy efficiency are the main priorities for the photovoltaic (PV) industry (COP21 conclusions). To lower costs and increase efficiency, we are proposing to reduce the number of processing steps involved in the manufacture of N-type Passivated Rear Totally Diffused (PERT) silicon solar cells. Replacing the conventional thermal diffusion doping steps by ion implantation followed by thermal annealing allows reducing the number of steps from 7 to 3 while maintaining similar efficiency. This alternative approach was investigated in the present work. Beamline and plasma immersion ion implantation (BLII and PIII) methods were used to insert n-(phosphorus) and p-type (boron) dopants into the Si substrate. With higher throughput and lower costs, PIII is a better candidate for the photovoltaic industry, compared to BL. However, the optimization of the plasma conditions is demanding and more complex than the beamline approach. Subsequent annealing was performed on selected samples to activate the dopants on both sides of the solar cell. Two annealing methods were investigated: soak and spike thermal annealing. Best performing solar cells, showing a PV efficiency of about 20%, was obtained using spike annealing with adapted ion implantation conditions.

A geothermal AMTEC system

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schuller, M.J.; LeMire, R.A.; Horner-Richardson, K.

1995-12-31

The Phillips Laboratory Power and Thermal Management Division (PL/VTP), with the support of ORION International Technologies, is investigating new methods of advanced thermal to electric power conversion for space and terrestrial applications. The alkali metal thermal-to-electric converter (AMTEC), manufactured primarily by Advanced Modular Power Systems (AMPS) of Ann Arbor, MI, has reached a level of technological maturity which would allow its use in a constant, unattended thermal source, such as a geothermal field. Approximately 95,000 square miles in the western United States has hot dry rock with thermal gradients of 60 C/km and higher. Several places in the United Statesmore » and the world have thermal gradients of 500 C/km. Such heat sources represent an excellent thermal source for a system of modular power units using AMTEC devices to convert the heat to electricity. AMTEC cells using sodium as a working fluid require heat input at temperatures between 500 and 1,000 C to generate power. The present state of the art is capable of 15% efficiency with 800 C heat input and has demonstrated 18% efficiency for single cells. This paper discusses the basics of AMTEC operation, current drilling technology as a cost driver, design of modular AMTEC power units, heat rejection technologies, materials considerations, and estimates of power production from a geothermal AMTEC concept.« less

The rise of non-imaging optics for rooftop solar collectors

NASA Astrophysics Data System (ADS)

Rosengarten, Gary; Stanley, Cameron; Ferrari, Dave; Blakers, Andrew; Ratcliff, Tom

2016-09-01

In this paper we explore the use of non-imaging optics for rooftop solar concentrators. Specifically, we focus on compound parabolic concentrators (CPCs), which form an ideal shape for cylindrical thermal absorbers, and for linear PV cells (allowing the use of more expensive but more efficient cells). Rooftops are ideal surfaces for solar collectors as they face the sky and are generally free, unused space. Concentrating solar radiation adds thermodynamic value to thermal collectors (allowing the attainment of higher temperature) and can add efficiency to PV electricity generation. CPCs allow that concentration over the day without the need for tracking. Hence they have become ubiquitous in applications requiring low concentration.

Advanced DC/DC Converters Towards Higher Volumetric Efficiencies For Space Applications

NASA Technical Reports Server (NTRS)

Shaw, Harry; Shue, Jack; Liu, David; Wang, Bright; Plante, Jeanette

2005-01-01

A new emphasis on planetary exploration by NASA drives the need for small, high power DC/DC converters which are functionally modular. NASA GSFC and other government space organizations are supporting technology development in the DC/DC converter area to both meet new needs and to promote more sources of supply. New technologies which enable miniaturization such as embedded passive technologies and thermal management using high thermal conductivity materials are features of the new designs. Construction of some simple DC/DC converter core circuits using embedded components was found to be successful for increasing volumetric efficiency to 37 W/inch. The embedded passives were also able to perform satisfactorily in this application in cryogenic temperatures.

Thermodynamic analysis of the efficiency of high-temperature steam electrolysis system for hydrogen production

NASA Astrophysics Data System (ADS)

Mingyi, Liu; Bo, Yu; Jingming, Xu; Jing, Chen

High-temperature steam electrolysis (HTSE), a reversible process of solid oxide fuel cell (SOFC) in principle, is a promising method for highly efficient large-scale hydrogen production. In our study, the overall efficiency of the HTSE system was calculated through electrochemical and thermodynamic analysis. A thermodynamic model in regards to the efficiency of the HTSE system was established and the quantitative effects of three key parameters, electrical efficiency (η el), electrolysis efficiency (η es), and thermal efficiency (η th) on the overall efficiency (η overall) of the HTSE system were investigated. Results showed that the contribution of η el, η es, η th to the overall efficiency were about 70%, 22%, and 8%, respectively. As temperatures increased from 500 °C to 1000 °C, the effect of η el on η overall decreased gradually and the η es effect remained almost constant, while the η th effect increased gradually. The overall efficiency of the high-temperature gas-cooled reactor (HTGR) coupled with the HTSE system under different conditions was also calculated. With the increase of electrical, electrolysis, and thermal efficiency, the overall efficiencies were anticipated to increase from 33% to a maximum of 59% at 1000 °C, which is over two times higher than that of the conventional alkaline water electrolysis.

Utilization of Indonesia's Hot Spring Sources for Electricity using Kalina Cycle and Organic Rankine Cycle

NASA Astrophysics Data System (ADS)

Prabumukti, Grano; Purwanto; Widodo, Wahyu

2018-02-01

Indonesia posses 40% of the world's geothermal energy sources. The existence of hydrothermal sources is usually characterized by their surface manifestations such as hot springs, geysers and fumarole. Hot spring has a potential to be used as a heat source to generate electricity especially in a rural and isolated area. Hot springs can be converted into electricity by binary thermodynamic cycles such as Kalina cycle and ORC. The aim of this study is to obtain the best performances of cycle configuration and the potential power capacity. Simulation is conducted using UNISIM software with working fluid and its operating condition as the decision variables. The simulation result shows that R1234yf and propene with simple ORC as desired working fluid and cycle configuration. It reaches a maximum thermal efficiency up to 9.6% with a specific turbine inlet pressure. Higher temperature heat source will result a higher thermal efficiency‥ Cycle thermal efficiency varies from 4.7% to 9.6% depends on source of hot spring temperature. Power capacity that can be generated using Indonesia's hot spring is ranged from 2 kWe to 61.2 kWe. The highest capacity located in Kawah Sirung and the least located in Kaendi.

Sub-100 nm Gold Nanomatryoshkas Improve Photo-thermal Therapy Efficacy in Large and Highly Aggressive Triple Negative Breast Tumors

PubMed Central

Bishnoi, Sandra; Urban, Alexander; Charron, Heather; Mitchell, Tamika; Shea, Martin; Nanda, Sarmistha; Schiff, Rachel; Halas, Naomi; Joshi, Amit

2014-01-01

There is an unmet need for efficient near-infrared photothermal transducers for the treatment of highly aggressive cancers and large tumors where the penetration of light can be substantially reduced, and the intra-tumoral nanoparticle transport is restricted due to the presence of hypoxic or nectrotic regions. We report the performance advantages obtained by sub 100 nm gold nanomatryushkas, comprising of concentric gold-silica-gold layers compared to conventional ~150 nm silica core gold nanoshells for photothermal therapy of triple negative breast cancer. We demonstrate that a 33% reduction in silica-core-gold-shell nanoparticle size, while retaining near-infrared plasmon resonance, and keeping the nanoparticle surface charge constant, results in a four to five fold tumor accumulation of nanoparticles following equal dose of injected gold for both sizes. The survival time of mice bearing large (>1000 mm3) and highly aggressive triple negative breast tumors is doubled for the nanomatryushka treatment group under identical photo-thermal therapy conditions. The higher absorption cross-section of a nanomatryoshka results in a higher efficiency of photonic to thermal energy conversion and coupled with 4-5X accumulation within large tumors results in superior therapy efficacy. PMID:25051221

Do gravid female Anolis nebulosus thermoregulate differently than males and non-gravid females?

PubMed

Woolrich-Piña, Guillermo A; Smith, Geoffrey R; Lemos-Espinal, Julio A; Ramírez-Silva, Juan Pablo

2015-08-01

In lizards, the role of gravid oviparous females in controlling the temperature experienced by developing embryos prior to oviposition has been rarely examined. In particular, relatively little is known about the effect of gravidity on the thermal ecology of female Anolis lizards. Here we examine the thermal ecology of Anolis nebulosus from Nayarit, Mexico, with a particular goal of comparing the thermal ecology of gravid females to that of non-gravid females and males. The thermal efficiency (E) of gravid female A. nebulosus (E=0.782) was higher than in males (E=0.464), and to a lesser extent, non-gravid females (E=0.637), despite no significant differences observed in body, air, operative, or set point temperatures among males, gravid females, and non-gravid females. Gravid females had smaller differences between body temperatures and set point temperatures (db), but did not differ in the difference between operative temperature and set point temperature (de). Gravid females used sun-shade and shaded microhabitats proportionately more than males and non-gravid females, and rarely used sunny microhabitats. Our results suggest that gravid A. nebulosus are using a different and more efficient thermoregulatory strategy than other adults in the population. Such efficient thermoregulation is possibly related to females attempting to provide a thermal environment that is conducive to the development of embryos in eggs prior to oviposition. Copyright © 2015 Elsevier Ltd. All rights reserved.

Design study on the efficiency of the thermal scheme of power unit of thermal power plants in hot climates

NASA Astrophysics Data System (ADS)

Sedlov, A.; Dorokhov, Y.; Rybakov, B.; Nenashev, A.

2017-11-01

At the stage of pre-proposals unit of the thermal power plants for regions with a hot climate requires a design study on the efficiency of possible options for the structure of the thermal circuit and a set of key parameters. In this paper, the thermal circuit of the condensing unit powerfully 350 MW. The main feature of the external conditions of thermal power plants in hot climates is the elevated temperature of cooling water of the turbine condensers. For example, in the Persian Gulf region as the cooling water is sea water. In the hot season of the year weighted average sea water temperature of 30.9 °C and during the cold season to 22.8 °C. From the turbine part of the steam is supplied to the distillation-desalination plant. In the hot season of the year heat scheme with pressure fresh pair of 23.54 MPa, temperature 570/560 °C and feed pump with electric drive (EDP) is characterized by a efficiency net of 0.25% higher than thermal schem with feed turbine pump (TDP). However, the supplied power unit with PED is less by 11.6 MW. Calculations of thermal schemes in all seasons of the year allowed us to determine the difference in the profit margin of units of the TDP and EDP. During the year the unit with the TDP provides the ability to obtain the profit margin by 1.55 million dollars more than the unit EDP. When using on the market subsidized price of electricity (Iran) marginal profit of a unit with TDP more at 7.25 million dollars.

Impact of initial biodegradability on sludge anaerobic digestion enhancement by thermal pretreatment.

PubMed

Carrère, Hélène; Bougrier, Claire; Castets, Delphine; Delgenès, Jean Philippe

2008-11-01

Thermal treatments with temperature ranging from 60 to 210 degrees C were applied to 6 waste-activated sludge samples originating from high or medium load, extended aeration wastewater treatment processes that treated different wastewaters (urban, urban and industrial or slaughterhouse). COD sludge solubilisation was linearly correlated with the treatment temperature on the whole temperature range and independently of the sludge samples. Sludge batch mesophilic biodegradability increased with treatment temperature up to 190 degrees C. In this temperature range, biodegradability enhancement or methane production increase by thermal hydrolysis was shown to be a function of sludge COD solubilisation but also of sludge initial biodegradability. The lower the initial biodegradability means the higher efficiency of thermal treatment.

Ultrasound and microwave assisted synthesis of isoindolo-1,2-diazine: a comparative study.

PubMed

Bejan, Vasilichia; Mantu, Dorina; Mangalagiu, Ionel I

2012-09-01

A comparative study, ultrasound (US) versus microwave (MW) versus conventional thermal heating (TH), for synthesis of isoindolo-1,2-diazine is described. The reaction pathway is fast, efficient and straight applicable, involving a Huisgen [3+2] dipolar cycloaddition of cycloimmonium ylides to 1,4-naphthoquinone. A feasible reaction mechanism for the obtaining of the fully aromatized tetra- and penta- cyclic isoindolo-1,2-diazine is presented. Under US irradiation the yields are much higher (sometimes substantially, by almost double), the reaction time decreases substantially, the reaction conditions are milder. The use of a generator with a higher nominal power induces higher yields and short reaction times. Overall the use of US it proved to be more efficient than MW or TH. A feasible explication for US efficiency is presented. Copyright © 2012 Elsevier B.V. All rights reserved.

Design of Particle-Based Thermal Energy Storage for a Concentrating Solar Power System

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ma, Zhiwen; Zhang, Ruichong; Sawaged, Fadi

Solid particles can operate at higher temperature than current molten salt or oil, and they can be a heat-transfer and storage medium in a concentrating solar power (CSP) system. By using inexpensive solid particles and containment material for thermal energy storage (TES), the particle-TES cost can be significantly lower than other TES methods such as a nitrate-salt system. The particle-TES system can hold hot particles at more than 800 degrees C with high thermal performance. The high particle temperatures increase the temperature difference between the hot and cold particles, and they improve the TES capacity. The particle-based CSP system ismore » able to support high-efficiency power generation, such as the supercritical carbon-dioxide Brayton power cycle, to achieve >50% thermal-electric conversion efficiency. This paper describes a solid particle-TES system that integrates into a CSP plant. The hot particles discharge to a heat exchanger to drive the power cycle. The returning cold particles circulate through a particle receiver to absorb solar heat and charge the TES. This paper shows the design of a particle-TES system including containment silos, foundation, silo insulation, and particle materials. The analysis provides results for four TES capacities and two silo configurations. The design analysis indicates that the system can achieve high thermal efficiency, storage effectiveness (i.e., percentage usage of the hot particles), and exergetic efficiency. An insulation method for the hot silo was considered. The particle-TES system can achieve high performance and low cost, and it holds potential for next-generation CSP technology.« less

Hybrid Pressure Retarded Osmosis-Membrane Distillation System for Power Generation from Low-Grade Heat: Thermodynamic Analysis and Energy Efficiency

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lin, SH; Yip, NY; Cath, TY

2014-05-06

We present a novel hybrid membrane system that operates as a heat engine capable of utilizing low-grade thermal energy, which is not readily recoverable with existing technologies. The closed-loop system combines membrane distillation (MD), which generates concentrated and pure water streams by thermal separation, and pressure retarded osmosis (PRO), which converts the energy of mixing to electricity by a hydro-turbine. The PRO-MD system was modeled by coupling the mass and energy flows between the thermal separation (MD) and power generation (PRO) stages for heat source temperatures ranging from 40 to 80 degrees C and working concentrations of 1.0, 2.0, andmore » 4.0 mol/kg NaCl. The factors controlling the energy efficiency of the heat engine were evaluated for both limited and unlimited mass and heat transfer kinetics in the thermal separation stage. In both cases, the relative flow rate between the MD permeate (distillate) and feed streams is identified as an important operation parameter. There is an optimal relative flow rate that maximizes the overall energy efficiency of the PRO-MD system for given working temperatures and concentration. In the case of unlimited mass and heat transfer kinetics, the energy efficiency of the system can be analytically determined based on thermodynamics. Our assessment indicates that the hybrid PRO-MD system can theoretically achieve an energy efficiency of 9.8% (81.6% of the Carnot efficiency) with hot and cold working temperatures of 60 and 20 degrees C, respectively, and a working solution of 1.0 M NaCl. When mass and heat transfer kinetics are limited, conditions that more closely represent actual operations, the practical energy efficiency will be lower than the theoretically achievable efficiency. In such practical operations, utilizing a higher working concentration will yield greater energy efficiency. Overall, our study demonstrates the theoretical viability of the PRO-MD system and identifies the key factors for performance optimization.« less

Hybrid pressure retarded osmosis-membrane distillation system for power generation from low-grade heat: thermodynamic analysis and energy efficiency.

PubMed

Lin, Shihong; Yip, Ngai Yin; Cath, Tzahi Y; Osuji, Chinedum O; Elimelech, Menachem

2014-05-06

We present a novel hybrid membrane system that operates as a heat engine capable of utilizing low-grade thermal energy, which is not readily recoverable with existing technologies. The closed-loop system combines membrane distillation (MD), which generates concentrated and pure water streams by thermal separation, and pressure retarded osmosis (PRO), which converts the energy of mixing to electricity by a hydro-turbine. The PRO-MD system was modeled by coupling the mass and energy flows between the thermal separation (MD) and power generation (PRO) stages for heat source temperatures ranging from 40 to 80 °C and working concentrations of 1.0, 2.0, and 4.0 mol/kg NaCl. The factors controlling the energy efficiency of the heat engine were evaluated for both limited and unlimited mass and heat transfer kinetics in the thermal separation stage. In both cases, the relative flow rate between the MD permeate (distillate) and feed streams is identified as an important operation parameter. There is an optimal relative flow rate that maximizes the overall energy efficiency of the PRO-MD system for given working temperatures and concentration. In the case of unlimited mass and heat transfer kinetics, the energy efficiency of the system can be analytically determined based on thermodynamics. Our assessment indicates that the hybrid PRO-MD system can theoretically achieve an energy efficiency of 9.8% (81.6% of the Carnot efficiency) with hot and cold working temperatures of 60 and 20 °C, respectively, and a working solution of 1.0 M NaCl. When mass and heat transfer kinetics are limited, conditions that more closely represent actual operations, the practical energy efficiency will be lower than the theoretically achievable efficiency. In such practical operations, utilizing a higher working concentration will yield greater energy efficiency. Overall, our study demonstrates the theoretical viability of the PRO-MD system and identifies the key factors for performance optimization.

Magnetic record associated with tree ring density: Possible climate proxy

PubMed Central

Kletetschka, Gunther; Pruner, Petr; Venhodova, Daniela; Kadlec, Jaroslav

2007-01-01

A magnetic signature of tree rings was tested as a potential paleo-climatic indicator. We examined wood from sequoia tree, located in Mountain Home State Forest, California, whose tree ring record spans over the period 600 – 1700 A.D. We measured low and high-field magnetic susceptibility, the natural remanent magnetization (NRM), saturation isothermal remanent magnetization (SIRM), and stability against thermal and alternating field (AF) demagnetization. Magnetic investigation of the 200 mm long sequoia material suggests that magnetic efficiency of natural remanence may be a sensitive paleoclimate indicator because it is substantially higher (in average >1%) during the Medieval Warm Epoch (700–1300 A.D.) than during the Little Ice Age (1300–1850 A.D.) where it is <1%. Diamagnetic behavior has been noted to be prevalent in regions with higher tree ring density. The mineralogical nature of the remanence carrier was not directly detected but maghemite is suggested due to low coercivity and absence of Verwey transition. Tree ring density, along with the wood's magnetic remanence efficiency, records the Little Ice Age (LIA) well documented in Europe. Such a record suggests that the European LIA was a global phenomenon. Magnetic analysis of the thermal stability reveals the blocking temperatures near 200 degree C. This phenomenon suggests that the remanent component in this tree may be thermal in origin and was controlled by local thermal condition. PMID:17381844

Immobilization on graphene oxide improves the thermal stability and bioconversion efficiency of D-psicose 3-epimerase for rare sugar production.

PubMed

Dedania, Samir R; Patel, Manisha J; Patel, Dijit M; Akhani, Rekha C; Patel, Darshan H

2017-12-01

D-Psicose (D-ribo-2-hexulose or D-allulose), an epimer of D-fructose is considered as a rare low-calorie sugar displaying important physiological functions. Enzymatic production using ketose 3-epimerases is the feasible process for the production of D-Psicose. However, major drawbacks in application of ketose 3-epimerases are bioconversion efficiency and reusability of the enzyme. We have attempted immobilization of ketose 3-epimerases from Agrobacterium tumefaciens (agtu) D-psicose 3-epimerase (DPEase) on graphene oxide. Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and Thermo gravimetric analysis (TGA) showed that the enzyme was successfully immobilized on the graphene oxide. Graphene oxide immobilized agtu-DPEase (GO-agtu-DPEase) shows pH optima at 7.5 and 60°C as higher working temperature. Significant improvement in thermal stability was observed which showed half-life of 720min at 60°C whereas Agrobacterium tumefaciens (agtu) DPEase displayed 3.99min. At equilibrium, 40:60 (D-psicose: D-fructose) the bioconversion efficiency was accounted for Graphene oxide immobilized DPEase which is higher than the agtu-DPEase. Graphene oxide immobilized DPEase showed bioconversion efficiency up to 10 cycles of reusability. Copyright © 2017 Elsevier Inc. All rights reserved.

Energy Advantages for Green Schools

ERIC Educational Resources Information Center

Griffin, J. Tim

2012-01-01

Because of many advantages associated with central utility systems, school campuses, from large universities to elementary schools, have used district energy for decades. District energy facilities enable thermal and electric utilities to be generated with greater efficiency and higher system reliability, while requiring fewer maintenance and…

Towards AlN optical cladding layers for thermal management in hybrid lasers

NASA Astrophysics Data System (ADS)

Mathews, Ian; Lei, Shenghui; Nolan, Kevin; Levaufre, Guillaume; Shen, Alexandre; Duan, Guang-Hua; Corbett, Brian; Enright, Ryan

2015-06-01

Aluminium Nitride (AlN) is proposed as a dual function optical cladding and thermal spreading layer for hybrid ridge lasers, replacing current benzocyclobutene (BCB) encapsulation. A high thermal conductivity material placed in intimate contact with the Multi-Quantum Well active region of the laser allows rapid heat removal at source but places a number of constraints on material selection. AlN is considered the most suitable due to its high thermal conductivity when deposited at low deposition temperatures, similar co-efficient of thermal expansion to InP, its suitable refractive index and its dielectric nature. We have previously simulated the possible reduction in the thermal resistance of a hybrid ridge laser by replacing the BCB cladding material with a material of higher thermal conductivity of up to 319 W/mK. Towards this goal, we demonstrate AlN thin-films deposited by reactive DC magnetron sputtering on InP.

Preliminary assessment of a potassium-steam-gas vapor cycle for better fuel economy and reduced thermal pollution

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fraas, A.P.

1971-08-01

The facts of fuel supply limitations, environmental quality demands, and spiraling electric generating costs strongly favor development of electric power plants that simultaneously run at higher efficiency, i.e., higher temperature, use to advantage clean fuels, and have as low a capital cost as possible. Both fuel supply and thermal pollution considerations that are becoming progressively more important strongly favor the development of a higher temperature, and more efficient, thermodynamic cycle for electric power plants. About 200,000 hr of operation of boiling potassium systems, including over 15,000 hr of potassium vapor turbine operation under the space power plant program, suggest thatmore » a potassium vapor topping cycle with a turbine inlet temperature of approximately 1500/sup 0/F merits consideration. A design study has been carried out to indicate the size, cost, and development problems of the new types of equipment required. The results indicate that a potassium vapor cycle superimposed on a conventional 1050/sup 0/F steam cycle would give an overall thermal efficiency of about 54% as compared to only 40% from a conventional steam cycle. Thus the proposed system would have a fuel consumption only 75% and a heat rejection rate only 50% that of a conventional plant. The system requires clean fuel, and takes advantage of the present trend toward eliminating SO/sub 2/, NO/sub x/ and ash emissions. Surprisingly, at first sight, the assessment at this stage shows that the capital cost may be less than that of a conventional plant. The main reason for this is use of pressurized combustion, which leads to a much smaller combustor, and thin tube walls to contain potassium at about the same pressure.« less

New configurations of a heat recovery absorption heat pump integrated with a natural gas boiler for boiler efficiency improvement

DOE Office of Scientific and Technical Information (OSTI.GOV)

Qu, Ming; Abdelaziz, Omar; Yin, Hongxi

2014-11-01

Conventional natural gas-fired boilers exhaust flue gas direct to the atmosphere at 150 200 C, which, at such temperatures, contains large amount of energy and results in relatively low thermal efficiency ranging from 70% to 80%. Although condensing boilers for recovering the heat in the flue gas have been developed over the past 40 years, their present market share is still less than 25%. The major reason for this relatively slow acceptance is the limited improvement in the thermal efficiency of condensing boilers. In the condensing boiler, the temperature of the hot water return at the range of 50 60more » C, which is used to cool the flue gas, is very close to the dew point of the water vapor in the flue gas. Therefore, the latent heat, the majority of the waste heat in the flue gas, which is contained in the water vapor, cannot be recovered. This paper presents a new approach to improve boiler thermal efficiency by integrating absorption heat pumps with natural gas boilers for waste heat recovery (HRAHP). Three configurations of HRAHPs are introduced and discussed. The three configurations are modeled in detail to illustrate the significant thermal efficiency improvement they attain. Further, for conceptual proof and validation, an existing hot water-driven absorption chiller is operated as a heat pump at operating conditions similar to one of the devised configurations. An overall system performance and economic analysis are provided for decision-making and as evidence of the potential benefits. These three configurations of HRAHP provide a pathway to achieving realistic high-efficiency natural gas boilers for applications with process fluid return temperatures higher than or close to the dew point of the water vapor in the flue gas.« less

Improving the sludge disintegration efficiency of sonication by combining with alkalization and thermal pre-treatment methods.

PubMed

Şahinkaya, S; Sevimli, M F; Aygün, A

2012-01-01

One of the most serious problems encountered in biological wastewater treatment processes is the production of waste activated sludge (WAS). Sonication, which is an energy-intensive process, is the most powerful sludge pre-treatment method. Due to lack of information about the combined pre-treatment methods of sonication, the combined pre-treatment methods were investigated and it was aimed to improve the disintegration efficiency of sonication by combining sonication with alkalization and thermal pre-treatment methods in this study. The process performances were evaluated based on the quantities of increases in soluble chemical oxygen demand (COD), protein and carbohydrate. The releases of soluble COD, carbohydrate and protein by the combined methods were higher than those by sonication, alkalization and thermal pre-treatment alone. Degrees of sludge disintegration in various options of sonication were in the following descending order: sono-alkalization > sono-thermal pre-treatment > sonication. Therefore, it was determined that combining sonication with alkalization significantly improved the sludge disintegration and decreased the required energy to reach the same yield by sonication. In addition, effects on sludge settleability and dewaterability and kinetic mathematical modelling of pre-treatment performances of these methods were investigated. It was proven that the proposed model accurately predicted the efficiencies of ultrasonic pre-treatment methods.

Prolonging thermal barrier coated specimen life by thermal cycle management

NASA Technical Reports Server (NTRS)

Hendricks, R. C.; Mcdonald, G.; Poolos, N. P.

1981-01-01

Thermal barrier coatings applied to the heated side of engine components such as seals, combustor, and blades of a gas turbine offer a potential increase in efficiency through the use of higher gas temperatures or less cooling air or benefits arising from extended component life by reducing component metal temperatures. The considered investigation has the objective to show that while a thermal barrier coated (TBC) specimen can be brought to a fixed temperature using various fuel-air ratio (F/A) values, lower calculated stresses are associated with lower (F/A) values. This implies that control of (F/A) values (i.e., rates of heat input) during the starting transient and to a lesser extent during shutdown and operation, offers a potential method of improving TBC lifetime through thermal cycle management.

Distribution and removal of organochlorine pesticides in waste clay bricks from an abandoned manufacturing plant using low-temperature thermal desorption technology.

PubMed

Cong, Xin; Li, Fasheng; Kelly, Ryan M; Xue, Nandong

2018-04-01

The distribution of pollutants in waste clay bricks from an organochlorine pesticide-contaminated site was investigated, and removal of the pollutants using a thermal desorption technology was studied. The results showed that the contents of HCHs in both the surface and the inner layer of the bricks were slightly higher than those of DDTs. The total pore volume of the bricks was 37.7 to 41.6% with an increase from external to internal surfaces. The removal efficiency by thermal treatment was within 62 to 83% for HCHs and DDTs in bricks when the temperature was raised from 200 to 250 °C after 1 h. HCHs were more easily removed than DDTs with a higher temperature. Either intraparticle or surface diffusion controls the desorption processes of pollutants in bricks. It was feasible to use the polluted bricks after removal of the pollutants by low-temperature thermal desorption technology.

Cycling Performance of a Columnar-Structured Complex Perovskite in a Temperature Gradient Test

NASA Astrophysics Data System (ADS)

Schlegel, N.; Sebold, D.; Sohn, Y. J.; Mauer, G.; Vaßen, R.

2015-10-01

To increase the efficiency of turbines for the power generation and the aircraft industry, advanced thermal barrier coatings (TBCs) are required. They need to be long-term stable at temperatures higher than 1200 °C. Nowadays, yttria partially stabilized zirconia (YSZ) is applied as standard TBC material. But its long-term application at temperatures higher than 1200 °C leads to detrimental phase changes and sintering effects. Therefore, new materials have to be investigated, for example, complex perovskites. They provide high melting points, high thermal expansion coefficients and thermal conductivities of approx. 2.0 W/(m K). In this work, the complex perovskite La(Al1/4Mg1/2Ta1/4)O3 (LAMT) was investigated. It was deposited by the suspension plasma spraying (SPS) process, resulting in a columnar microstructure of the coating. The coatings were tested in thermal cycling gradient tests and they show excellent results, even though some phase decomposition was found.

Multilayer Thermal Barrier Coating (TBC) Architectures Utilizing Rare Earth Doped YSZ and Rare Earth Pyrochlores

NASA Technical Reports Server (NTRS)

Schmitt, Michael P.; Rai, Amarendra K.; Bhattacharya, Rabi; Zhu, Dongming; Wolfe, Douglas E.

2014-01-01

To allow for increased gas turbine efficiencies, new insulating thermal barrier coatings (TBCs) must be developed to protect the underlying metallic components from higher operating temperatures. This work focused on using rare earth doped (Yb and Gd) yttria stabilized zirconia (t' Low-k) and Gd2Zr2O7 pyrochlores (GZO) combined with novel nanolayered and thick layered microstructures to enable operation beyond the 1200 C stability limit of current 7 wt% yttria stabilized zirconia (7YSZ) coatings. It was observed that the layered system can reduce the thermal conductivity by approximately 45 percent with respect to YSZ after 20 hr of testing at 1316 C. The erosion rate of GZO is shown to be an order to magnitude higher than YSZ and t' Low-k, but this can be reduced by almost 57 percent when utilizing a nanolayered structure. Lastly, the thermal instability of the layered system is investigated and thought is given to optimization of layer thickness.

Utilizing Radioisotope Power System Waste Heat for Spacecraft Thermal Management

NASA Technical Reports Server (NTRS)

Pantano, David R.; Dottore, Frank; Tobery, E. Wayne; Geng, Steven M.; Schreiber, Jeffrey G.; Palko, Joseph L.

2005-01-01

An advantage of using a Radioisotope Power System (RPS) for deep space or planetary surface missions is the readily available waste heat, which can be used for a number of beneficial purposes including: maintaining electronic components within a controlled temperature range, warming propulsion tanks and mobility actuators, and maintaining liquid propellants above their freezing temperature. Previous missions using Radioisotope Thermoelectric Generators (RTGs) dissipated large quantities of waste heat due to the low efficiency of the thermoelectric conversion technology. The next generation RPSs, such as the 110-Watt Stirling Radioisotope Generator (SRG110) will have higher conversion efficiencies, thereby rejecting less waste heat at a lower temperature and may require alternate approaches to transferring waste heat to the spacecraft. RTGs, with efficiencies of 6 to 7 percent, reject their waste heat at the relatively high heat rejection temperature of 200 C. This is an advantage when rejecting heat to space; however, transferring heat to the internal spacecraft components requires a large and heavy radiator heat exchanger. At the same time, sensitive spacecraft instruments must be shielded from the thermal radiation of the RTG. The SRG110, with an efficiency around 22 percent and 50 C nominal housing surface temperature, can readily transfer the available waste heat directly via heat pipes, thermal straps, or fluid loops. The lower temperatures associated with the SRG110 avoid the chances of overheating other scientific components, eliminating the need for thermal shields. This provides the spacecraft designers more flexibility when locating the generator for a specific mission. A common misconception with high-efficiency systems is that there is not enough waste heat for spacecraft thermal management. This paper will dispel this misconception and investigate the use of a high-efficiency SRG110 for spacecraft thermal management and outline potential methods of waste heat utilization in several conceptual missions (Lunar Rover, Mars Rover, and Titan Lander). The advantages associated with the SRG110 as they relate to ease of assembly, less complex interfaces, and overall mass savings for a spacecraft will be highlighted.

A novel electroluminescent PPV copolymer and silsesquioxane nanocomposite film for the preparation of efficient PLED devices.

PubMed

Venegoni, Ivan; Carniato, Fabio; Olivero, Francesco; Bisio, Chiara; Pira, Nello Li; Lambertini, Vito Guido; Marchese, Leonardo

2012-11-02

Polymer light-emitting diodes (PLEDs) have attracted growing interest in recent years for their potential use in displays and lighting fields. Nevertheless, PLED devices have some disadvantages in terms of low optoelectronic efficiency, high cost, short lifetimes and low thermal stability, which limit their final applications. Huge efforts have been made recently to improve the performances of these devices. The addition of inorganic or hybrid organic-inorganic nanoparticles to the light-emitting polymers, for example, allows their thermal stability and electroluminescent efficiency to be increased. Following this approach, novel PLED devices based on composite films of PPV-derivative copolymer (commercial name Super Yellow, SY) and octaisobutil POSS, were developed in this study. The device containing Super Yellow loaded with 1 wt% of POSS showed higher efficiency (ca. +30%) and improved lifetime in comparison to PLED prepared with the pure electroluminescent polymer. The PLED devices developed in this study are suitable candidates for automotive dashboards and, in general, for lighting applications.

Hot leptogenesis from thermal Dark Matter

DOE PAGES

Bernal, Nicolas; Fong, Chee Sheng

2017-10-26

In this work, we investigate a scenario in which heavy Majorana Right-Handed Neutrinos (RHNs) are in thermal equilibrium with a dark sector with temperature higher than the Standard Model (SM) thermal bath. Specifically, we consider the scenario in which thermal Dark Matter (DM) abundance is fixed from the freeze-out of DM annihilations into RHNs. Due to the inert nature of the RHNs, we show that it is possible for the two sectors to remain thermally decoupled by having more than two generations of the RHNs. The hotter temperature implies higher abundances of DM and RHNs with the following consequences. Formore » leptogenesis, an enhancement in efficiency up to a factor of 51.6 can be obtained, though a resonant enhancement of CP violation is still required due to an upper mass bound of about 4 TeV for the RHNs. For the DM, an enhanced annihilation cross section up to a factor of 51.6 is required to obtain the correct DM abundance. This scenario can be probed via indirect detection of DM annihilating into RHNs, which then decay into hν, Zν and W ± ℓ ∓ with an enhanced annihilation cross section above the typical thermal value.« less

Higher Temperature Thermal Barrier Coatings with the Combined Use of Yttrium Aluminum Garnet and the Solution Precursor Plasma Spray Process

NASA Astrophysics Data System (ADS)

Gell, Maurice; Wang, Jiwen; Kumar, Rishi; Roth, Jeffery; Jiang, Chen; Jordan, Eric H.

2018-04-01

Gas-turbine engines are widely used in transportation, energy and defense industries. The increasing demand for more efficient gas turbines requires higher turbine operating temperatures. For more than 40 years, yttria-stabilized zirconia (YSZ) has been the dominant thermal barrier coating (TBC) due to its outstanding material properties. However, the practical use of YSZ-based TBCs is limited to approximately 1200 °C. Developing new, higher temperature TBCs has proven challenging to satisfy the multiple property requirements of a durable TBC. In this study, an advanced TBC has been developed by using the solution precursor plasma spray (SPPS) process that generates unique engineered microstructures with the higher temperature yttrium aluminum garnet (YAG) to produce a TBC that can meet and exceed the major performance standards of state-of-the-art air plasma sprayed YSZ, including: phase stability, sintering resistance, CMAS resistance, thermal cycle durability, thermal conductivity and erosion resistance. The temperature improvement for hot section gas turbine materials (superalloys & TBCs) has been at the rate of about 50 °C per decade over the last 50 years. In contrast, SPPS YAG TBCs offer the near-term potential of a > 200 °C improvement in temperature capability.

Design and Performance Optimizations of Advanced Erosion-Resistant Low Conductivity Thermal Barrier Coatings for Rotorcraft Engines

NASA Technical Reports Server (NTRS)

Zhu, Dongming; Miller, Robert A.; Kuczmarski, Maria A.

2012-01-01

Thermal barrier coatings will be more aggressively designed to protect gas turbine engine hot-section components in order to meet future rotorcraft engine higher fuel efficiency and lower emission goals. For thermal barrier coatings designed for rotorcraft turbine airfoil applications, further improved erosion and impact resistance are crucial for engine performance and durability, because the rotorcraft are often operated in the most severe sand erosive environments. Advanced low thermal conductivity and erosion-resistant thermal barrier coatings are being developed, with the current emphasis being placed on thermal barrier coating toughness improvements using multicomponent alloying and processing optimization approaches. The performance of the advanced thermal barrier coatings has been evaluated in a high temperature erosion burner rig and a laser heat-flux rig to simulate engine erosion and thermal gradient environments. The results have shown that the coating composition and architecture optimizations can effectively improve the erosion and impact resistance of the coating systems, while maintaining low thermal conductivity and cyclic oxidation durability

Evaluation of Emerging Technologies on a 1.6 L Turbocharged GDI Engine

EPA Science Inventory

Low-pressure loop exhaust gas recirculation (LPL- EGR) combined with a higher compression ratio is a technology package that has been the focus of significant research to increase engine thermal efficiency of downsized, turbocharged GDI engines. Research shows that the addition ...

Sourcing of Steam and Electricity for Carbon Capture Retrofits.

PubMed

Supekar, Sarang D; Skerlos, Steven J

2017-11-07

This paper compares different steam and electricity sources for carbon capture and sequestration (CCS) retrofits of pulverized coal (PC) and natural gas combined cycle (NGCC) power plants. Analytical expressions for the thermal efficiency of these power plants are derived under 16 different CCS retrofit scenarios for the purpose of illustrating their environmental and economic characteristics. The scenarios emerge from combinations of steam and electricity sources, fuel used in each source, steam generation equipment and process details, and the extent of CO 2 capture. Comparing these scenarios reveals distinct trade-offs between thermal efficiency, net power output, levelized cost, profit, and net CO 2 reduction. Despite causing the highest loss in useful power output, bleeding steam and extracting electric power from the main power plant to meet the CCS plant's electricity and steam demand maximizes plant efficiency and profit while minimizing emissions and levelized cost when wholesale electricity prices are below 4.5 and 5.2 US¢/kWh for PC-CCS and NGCC-CCS plants, respectively. At prices higher than these higher profits for operating CCS retrofits can be obtained by meeting 100% of the CCS plant's electric power demand using an auxiliary natural gas turbine-based combined heat and power plant.

A three-dimensional architecture of vertically aligned multilayer graphene facilitates heat dissipation across joint solid surfaces

NASA Astrophysics Data System (ADS)

Liang, Qizhen; Yao, Xuxia; Wang, Wei; Wong, C. P.

2012-02-01

Low operation temperature and efficient heat dissipation are important for device life and speed in current electronic and photonic technologies. Being ultra-high thermally conductive, graphene is a promising material candidate for heat dissipation improvement in devices. In the application, graphene is expected to be vertically stacked between contact solid surfaces in order to facilitate efficient heat dissipation and reduced interfacial thermal resistance across contact solid surfaces. However, as an ultra-thin membrane-like material, graphene is susceptible to Van der Waals forces and usually tends to be recumbent on substrates. Thereby, direct growth of vertically aligned free-standing graphene on solid substrates in large scale is difficult and rarely available in current studies, bringing significant barriers in graphene's application as thermal conductive media between joint solid surfaces. In this work, a three-dimensional vertically aligned multi-layer graphene architecture is constructed between contacted Silicon/Silicon surfaces with pure Indium as a metallic medium. Significantly higher equivalent thermal conductivity and lower contact thermal resistance of vertically aligned multilayer graphene are obtained, compared with those of their recumbent counterpart. This finding provides knowledge of vertically aligned graphene architectures, which may not only facilitate current demanding thermal management but also promote graphene's widespread applications such as electrodes for energy storage devices, polymeric anisotropic conductive adhesives, etc.

Experimental Study on the Thermal Start-Up Performance of the Graphene/Water Nanofluid-Enhanced Solar Gravity Heat Pipe.

PubMed

Zhao, Shanguo; Xu, Guoying; Wang, Ning; Zhang, Xiaosong

2018-01-28

The solar gravity heat pipe has been widely used for solar thermal water heating because of its high efficient heat transfer and thermal diode characteristics. Operated on fluctuant and low intensity solar radiation conditions, a solar gravity heat pipe may frequently start up. This severely affects its solar collection performance. To enhance the thermal performance of the solar gravity heat pipe, this study proposes using graphene/water nanofluid as the working fluid instead of deionized water. The stability of the prepared graphene/water nanofluid added with PVP was firstly investigated to obtain the optimum mass ratios of the added dispersant. Thermophysical properties-including the thermal conductivity and viscosity-of nanofluid with various graphene nanoplatelets (GNPs) concentrations were measured at different temperatures for further analysis. Furthermore, based on the operational evaluation on a single heat pipe's start-up process, the performance of nanofluid-enhanced solar gravity heat pipes using different concentrations of GNPs were compared by using water heating experiments. Results indicated that the use of 0.05 wt % graphene/water nanofluid instead of water could achieve a 15.1% and 10.7% reduction in start-up time under 30 and 60 W input heating conditions, respectively. Consequently, a higher thermal efficiency for solar collection could be expected.

Experimental Study on the Thermal Start-Up Performance of the Graphene/Water Nanofluid-Enhanced Solar Gravity Heat Pipe

PubMed Central

Zhao, Shanguo; Xu, Guoying; Wang, Ning; Zhang, Xiaosong

2018-01-01

The solar gravity heat pipe has been widely used for solar thermal water heating because of its high efficient heat transfer and thermal diode characteristics. Operated on fluctuant and low intensity solar radiation conditions, a solar gravity heat pipe may frequently start up. This severely affects its solar collection performance. To enhance the thermal performance of the solar gravity heat pipe, this study proposes using graphene/water nanofluid as the working fluid instead of deionized water. The stability of the prepared graphene/water nanofluid added with PVP was firstly investigated to obtain the optimum mass ratios of the added dispersant. Thermophysical properties—including the thermal conductivity and viscosity—of nanofluid with various graphene nanoplatelets (GNPs) concentrations were measured at different temperatures for further analysis. Furthermore, based on the operational evaluation on a single heat pipe’s start-up process, the performance of nanofluid-enhanced solar gravity heat pipes using different concentrations of GNPs were compared by using water heating experiments. Results indicated that the use of 0.05 wt % graphene/water nanofluid instead of water could achieve a 15.1% and 10.7% reduction in start-up time under 30 and 60 W input heating conditions, respectively. Consequently, a higher thermal efficiency for solar collection could be expected. PMID:29382094

Efficiency of SparkJet

NASA Technical Reports Server (NTRS)

Golbabaei-Asl, M.; Knight, D.; Wilkinson, S.

2013-01-01

The thermal efficiency of a SparkJet is evaluated by measuring the impulse response of a pendulum subject to a single spark discharge. The SparkJet is attached to the end of a pendulum. A laser displacement sensor is used to measure the displacement of the pendulum upon discharge. The pendulum motion is a function of the fraction of the discharge energy that is channeled into the heating of the gas (i.e., increasing the translational-rotational temperature). A theoretical perfect gas model is used to estimate the portion of the energy from the heated gas that results in equivalent pendulum displacement as in the experiment. The earlier results from multiple runs for different capacitances of C = 3, 5, 10, 20, and 40(micro)F demonstrate that the thermal efficiency decreases with higher capacitive discharges.1 In the current paper, results from additional run cases have been included and confirm the previous results

Study on convection improvement of standard vacuum tube

NASA Astrophysics Data System (ADS)

He, J. H.; Du, W. P.; Qi, R. R.; He, J. X.

2017-11-01

For the standard all-glass vacuum tube collector, enhancing the vacuum tube axial natural convection can improve its thermal efficiency. According to the study of the standard all-glass vacuum tube, three kinds of guide plates which can inhibit the radial convection and increase axial natural convection are designed, and theory model is established. Experiments were carried out on vacuum tubes with three types of baffles and standard vacuum tubes without the improvement. The results show that T-type guide plate is better than that of Y-type guide plate on restraining convection and increasing axial radial convection effect, Y type is better than that of flat plate type, all guide plates are better than no change; the thermal efficiency of the tube was 2.6% higher than that of the unmodified standard vacuum tube. The efficiency of the system in the experiment can be increased by 3.1%.

[Trigger factor dependent refolding of bacterial luciferases in Escherichia coli cells: kinetics, efficiency and effect of the bichaperone system, DnaKJE-ClpB].

PubMed

Mel'kina, O E; Gorianin, I I; Manukhov, I V; Zavil'gel'skiĭ, G B

2013-01-01

Here were determined the basic parameters of the Tigger Factor (TF) -dependent refolding of thermal inactivated bacterial luciferases. The TF-dependent refolding is less efficient and requires more time than DnaKJE-dependent refolding. The increase in the intracellular concentration of TF leads to an apparent decrease in the level of the thermal inactivated bacterial luciferase refolding. For thermolabile luciferases, the level of TF-dependent refolding is significantly higher, than for thermostable luciferases: 30-40%--for the thermolabile Aliivibrio fischeri and Photobacterium leiognathi luciferases, and 10 and 0.5% for the thermostable Vibrio harveyi and Photorhabdus luminescens luciferases, respectively. The negative effect of the ClpB protein on the TF-dependent refolding was shown: in Escherichia coli clpB::kan TF-dependent refolding is more efficient than in the E. coli clpB+.

Yb:YAG ceramic-based laser driver for Inertial Fusion Energy (IFE)

NASA Astrophysics Data System (ADS)

Vetrovec, John; Copeland, Drew A.; Litt, Amardeep S.

2016-03-01

We report on a new class of laser amplifiers for inertial confinement fusion (ICF) drivers based on a Yb:YAG ceramic disk in an edge-pumped configuration and cooled by a high-velocity gas flow. The Yb lasant offers very high efficiency and low waste heat. The ceramic host material has a thermal conductivity nearly 15-times higher than the traditionally used glass and it is producible in sizes suitable for a typical 10- to 20-kJ driver beam line. The combination of high lasant efficiency, low waste heat, edge-pumping, and excellent thermal conductivity of the host, enable operation at 10 to 20 Hz at over 20% wall plug efficiency while being comparably smaller and less costly than recently considered face-pumped alternative drivers using Nd:glass, Yb:S-FAP, and cryogenic Yb:YAG. Scalability of the laser driver over a broad range of sizes is presented.

Heterogeneously-integrated VCSEL using high-contrast grating on silicon

NASA Astrophysics Data System (ADS)

Ferrara, James; Zhu, Li; Yang, Weijian; Qiao, Pengfei; Chang-Hasnain, Connie J.

2015-02-01

We present a unique heterogeneous integration approach for VCSELs on silicon using eutectic bonding. An electrically pumped III-V - silicon heterogeneous VCSEL is demonstrated using a high-contrast grating (HCG) reflector on silicon. CW output power >1.5 mW, thermal resistance of 1.46 K/mW, and 5 Gb/s direct modulation is demonstrated. We also explore the possibility of an all-HCG VCSEL structure that would benefit from stronger thermal performance, larger tuning efficiency, and higher direct modulation speeds.

Determination of thermal contact conductance in vacuum-bagged thermoplastic prepreg stacks using infrared thermography

NASA Astrophysics Data System (ADS)

Baumard, Théo; De Almeida, Olivier; Menary, Gary; Le Maoult, Yannick; Schmidt, Fabrice; Bikard, Jérôme

2016-10-01

The infrared heating of a vacuum-bagged, thermoplastic prepreg stack of glass/PA66 was studied to investigate the influence of vacuum level on thermal contact resistance between plies. A higher vacuum level was shown experimentally to decrease the transverse heat transfer efficiency, indicating that considering only the effect of heat conduction at the plies interfaces is not sufficient to predict the temperature distribution. An inverse analysis was used to retrieve the contact resistance coefficients as a function of vacuum pressure.

Ontogenetic shifts in thermal tolerance, selected body temperature and thermal dependence of food assimilation and locomotor performance in a lacertid lizard, Eremias brenchleyi.

PubMed

Xu, Xue-Feng; Ji, Xiang

2006-01-01

We used Eremias brenchleyi as a model animal to examine differences in thermal tolerance, selected body temperature, and the thermal dependence of food assimilation and locomotor performance between juvenile and adult lizards. Adults selected higher body temperatures (33.5 vs. 31.7 degrees C) and were able to tolerate a wider range of body temperatures (3.4-43.6 vs. 5.1-40.8 degrees C) than juveniles. Within the body temperature range of 26-38 degrees C, adults overall ate more than juveniles, and food passage rate was faster in adults than juveniles. Apparent digestive coefficient (ADC) and assimilation efficiency (AE) varied among temperature treatments but no clear temperature associated patterns could be discerned for these two variables. At each test temperature ADC and AE were both higher in adults than in juveniles. Sprint speed increased with increase in body temperature at lower body temperatures, but decreased at higher body temperatures. At each test temperature adults ran faster than did juveniles, and the range of body temperatures where lizards maintained 90% of maximum speed differed between adults (27-34 degrees C) and juveniles (29-37 degrees C). Optimal temperatures and thermal sensitivities differed between food assimilation and sprint speed. Our results not only show strong patterns of ontogenetic variation in thermal tolerance, selected body temperature and thermal dependence of food assimilation and locomotor performance in E. brenchleyi, but also add support for the multiple optima hypothesis for the thermal dependence of behavioral and physiological variables in reptiles.

Methods of reducing energy consumption of the oxidant supply system for MHD/steam power plants

NASA Technical Reports Server (NTRS)

Juhasz, A. J.

1983-01-01

An in-depth study was conducted to identify possible improvements to the oxidant supply system for combined cycle MHD power plants which would lead to higher thermal efficiency and reduction in the cost of electricity, COE. Results showed that the oxidant system energy consumption could be minimized when the process was designed to deliver a product O2 concentration of 70 mole percent. The study also led to the development of a new air separation process, referred to as liquid pumping and internal compression. MHD system performance calculations show that the new process would permit an increase in plant thermal efficiency of 0.6 percent while allowing more favorable tradeoffs between magnetic energy and oxidant system capacity requirements.

Methods of reducing energy consumption of the oxidant supply system for MHD/steam power plants

NASA Technical Reports Server (NTRS)

Juhasz, A. J.

1983-01-01

An in-depth study was conducted to identify possible improvements to the oxidant supply system for combined cycle MHD power plants which would lead to higher thermal efficiency and reduction in the cost of electricity, COE. Results showed that the oxidant system energy consumption could be minimized when the process was designed to deliver a product O2 concentration of 70 mole percent. The study also led to the development of a new air separation process, referred to as 'liquid pumping and internal compression'. MHD system performance calculations show that the new process would permit an increase in plant thermal efficiency of 0.6 percent while allowing more favorable tradeoffs between magnetic energy and oxidant system capacity requirements.

Alternate aircraft fuels: Prospects and operational implications

NASA Technical Reports Server (NTRS)

Witcofski, R. D.

1977-01-01

The potential use of coal-derived aviation fuels was assessed. The studies addressed the prices and thermal efficiencies associated with the production of coal-derived aviation kerosene, liquid methane and liquid hydrogen and the air terminal requirements and subsonic transport performance when utilizing liquid hydrogen. The fuel production studies indicated that liquid methane can be produced at a lower price and with a higher thermal efficiency than aviation kerosene or liquid hydrogen. Ground facilities of liquefaction, storage, distribution and refueling of liquid hydrogen fueled aircraft at airports appear technically feasibile. The aircraft studies indicate modest onboard energy savings for hydrogen compared to conventional fuels. Liquid hydrogen was found to be superior to both aviation kerosene and liquid methane from the standpoint of aircraft engine emissions.

Improvements in the efficiency of turboexpanders in cryogenic applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Agahi, R.R.; Lin, M.C.; Ershaghi, B.

1996-12-31

Process designers have utilized turboexpanders in cryogenic processes because of their higher thermal efficiencies when compared with conventional refrigeration cycles. Process design and equipment performance have improved substantially through the utilization of modern technologies. Turboexpander manufacturers have also adopted Computational Fluid Dynamic Software, Computer Numerical Control Technology and Holography Techniques to further improve an already impressive turboexpander efficiency performance. In this paper, the authors explain the design process of the turboexpander utilizing modern technology. Two cases of turboexpanders processing helium (4.35{degrees}K) and hydrogen (56{degrees}K) will be presented.

New Molecular Design Concurrently Providing Superior Pure Blue, Thermally Activated Delayed Fluorescence and Optical Out-Coupling Efficiencies.

PubMed

Rajamalli, P; Senthilkumar, N; Huang, P-Y; Ren-Wu, C-C; Lin, H-W; Cheng, C-H

2017-08-16

Simultaneous enhancement of out-coupling efficiency, internal quantum efficiency, and color purity in thermally activated delayed fluorescence (TADF) emitters is highly desired for the practical application of these materials. We designed and synthesized two isomeric TADF emitters, 2DPyM-mDTC and 3DPyM-pDTC, based on di(pyridinyl)methanone (DPyM) cores as the new electron-accepting units and di(tert-butyl)carbazole (DTC) as the electron-donating units. 3DPyM-pDTC, which is structurally nearly planar with a very small ΔE ST , shows higher color purity, horizontal ratio, and quantum yield than 2DPyM-mDTC, which has a more flexible structure. An electroluminescence device based on 3DPyM-pDTC as the dopant emitter can reach an extremely high external quantum efficiency of 31.9% with a pure blue emission. This work also demonstrates a way to design materials with a high portion of horizontal molecular orientation to realize a highly efficient pure-blue device based on TADF emitters.

Utilization of waste heat from aluminium electrolytic cell

NASA Astrophysics Data System (ADS)

Nosek, Radovan; Gavlas, Stanislav; Lenhard, Richard; Malcho, Milan; Sedlak, Veroslav; Teie, Sebastian

2017-12-01

During the aluminium production, 50% of the supplied energy is consumed by the chemical process, and 50% of the supplied energy is lost in form of heat. Heat losses are necessary to maintain a frozen side ledge to protect the side walls, so extra heat has to be wasted. In order to increase the energy efficiency of the process, it is necessary to significantly lower the heat losses dissipated by the furnace's external surface. Goodtech Recovery Technology (GRT) has developed a technology based on the use of heat pipes for utilization energy from the waste heat produced in the electrolytic process. Construction of condenser plays important role for efficient operation of energy systems. The condensation part of the heat pipe is situated on top of the heating zone. The thermal oil is used as cooling medium in the condenser. This paper analyses the effect of different operation condition of thermal oil to thermal performance. From the collected results it is obvious that the larger mass flow and higher temperature cause better thermal performance and lower pressure drop.

Thermal Aggregation of Calcium-Fortified Skim Milk Enhances Probiotic Protection during Convective Droplet Drying.

PubMed

Wang, Juan; Huang, Song; Fu, Nan; Jeantet, Romain; Chen, Xiao Dong

2016-08-03

Probiotic bacteria have been reported to confer benefits on hosts when delivered in an adequate dose. Spray-drying is expected to produce dried and microencapsulated probiotic products due to its low production cost and high energy efficiency. The bottleneck in probiotic application addresses the thermal and dehydration-related inactivation of bacteria during process. A protective drying matrix was designed by modifying skim milk with the principle of calcium-induced protein thermal aggregation. The well-defined single-droplet drying technique was used to monitor the droplet-particle conversion and the protective effect of this modified Ca-aggregated milk on Lactobacillus rhamnosus GG. The Ca-aggregated milk exhibited a higher drying efficiency and superior protection on L. rhamnosus GG during thermal convective drying. The mechanism was explained by the aggregation in milk, causing the lower binding of water in the serum phase and, conversely, local concentrated milk aggregates involved in bacteria entrapment in the course of drying. This work may open new avenues for the development of probiotic products with high bacterial viability and calcium enrichment.

Membrane-based osmotic heat engine with organic solvent for enhanced power generation from low-grade heat.

PubMed

Shaulsky, Evyatar; Boo, Chanhee; Lin, Shihong; Elimelech, Menachem

2015-05-05

We present a hybrid osmotic heat engine (OHE) system that uses draw solutions with an organic solvent for enhanced thermal separation efficiency. The hybrid OHE system produces sustainable energy by combining pressure-retarded osmosis (PRO) as a power generation stage and membrane distillation (MD) utilizing low-grade heat as a separation stage. While previous OHE systems employed aqueous electrolyte draw solutions, using methanol as a solvent is advantageous because methanol is highly volatile and has a lower heat capacity and enthalpy of vaporization than water. Hence, the thermal separation efficiency of a draw solution with methanol would be higher than that of an aqueous draw solution. In this study, we evaluated the performance of LiCl-methanol as a potential draw solution for a PRO-MD hybrid OHE system. The membrane transport properties as well as performance with LiCl-methanol draw solution were evaluated using thin-film composite (TFC) PRO membranes and compared to the results obtained with a LiCl-water draw solution. Experimental PRO methanol flux and maximum projected power density of 47.1 L m(-2) h(-1) and 72.1 W m(-2), respectively, were achieved with a 3 M LiCl-methanol draw solution. The overall efficiency of the hybrid OHE system was modeled by coupling the mass and energy flows between the thermal separation (MD) and power generation (PRO) stages under conditions with and without heat recovery. The modeling results demonstrate higher OHE energy efficiency with the LiCl-methanol draw solution compared to that with the LiCl-water draw solution under practical operating conditions (i.e., heat recovery<90%). We discuss the implications of the results for converting low-grade heat to power.

Membrane-Based Osmotic Heat Engine with Organic Solvent for Enhanced Power Generation from Low-Grade Heat

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shaulsky, E; Boo, C; Lin, SH

We present a hybrid osmotic heat engine (OHE) system that uses draw solutions with an organic solvent for enhanced thermal separation efficiency. The hybrid OHE system produces sustainable energy by combining pressure-retarded osmosis (PRO) as a power generation stage and membrane distillation (MD) utilizing low-grade heat as a separation stage. While previous OHE systems employed aqueous electrolyte draw solutions, using methanol as a solvent is advantageous because methanol is highly volatile and has a lower heat capacity and enthalpy of vaporization than water. Hence, the thermal separation efficiency of a draw solution with methanol would be higher than that ofmore » an aqueous draw solution. In this study, we evaluated the performance of LiCl-methanol as a potential draw solution for a PRO-MD hybrid OHE system. The membrane transport properties as well as performance with LiCl methanol draw solution were evaluated using thin-film composite (TFC) PRO membranes and compared to the results obtained with a LiCl water draw solution. Experimental PRO methanol flux and maximum projected power density of 47.1 L m(-2) h(-1) and 72.1 W m(-2), respectively, were achieved with a 3 M LiCl-methanol draw solution. The overall efficiency of the hybrid OHE system was modeled by coupling the mass and energy flows between the thermal separation (MD) and power generation (PRO) stages under conditions with and without heat recovery. The modeling results demonstrate higher ORE energy efficiency with the LiCl methanol draw solution compared to that with the LiCl water draw solution under practical operating conditions (i.e., heat recovery <90%). We discuss the implications of the results for converting low-grade heat to power.« less

Side Chain Engineering on Medium Bandgap Copolymers to Suppress Triplet Formation for High-Efficiency Polymer Solar Cells.

PubMed

Xue, Lingwei; Yang, Yankang; Xu, Jianqiu; Zhang, Chunfeng; Bin, Haijun; Zhang, Zhi-Guo; Qiu, Beibei; Li, Xiaojun; Sun, Chenkai; Gao, Liang; Yao, Jia; Chen, Xiaofeng; Yang, Yunxu; Xiao, Min; Li, Yongfang

2017-10-01

Suppression of carrier recombination is critically important in realizing high-efficiency polymer solar cells. Herein, it is demonstrated difluoro-substitution of thiophene conjugated side chain on donor polymer can suppress triplet formation for reducing carrier recombination. A new medium bandgap 2D-conjugated D-A copolymer J91 is designed and synthesized with bi(alkyl-difluorothienyl)-benzodithiophene as donor unit and fluorobenzotriazole as acceptor unit, for taking the advantages of the synergistic fluorination on the backbone and thiophene side chain. J91 demonstrates enhanced absorption, low-lying highest occupied molecular orbital energy level, and higher hole mobility, in comparison with its control polymer J52 without fluorination on the thiophene side chains. The transient absorption spectra indicate that J91 can suppress the triplet formation in its blend film with n-type organic semiconductor acceptor m-ITIC (3,9-bis(2-methylene-(3-(1,1-dicyanomethylene)-indanone)-5,5,11,11-tetrakis(3-hexylphenyl)-dithieno[2,3-d:2,3'-d']-s-indaceno[1,2-b:5,6-b']-dithiophene). With these favorable properties, a higher power conversion efficiency of 11.63% with high V OC of 0.984 V and high J SC of 18.03 mA cm -2 is obtained for the polymer solar cells based on J91/m-ITIC with thermal annealing. The improved photovoltaic performance by thermal annealing is explained from the morphology change upon thermal annealing as revealed by photoinduced force microscopy. The results indicate that side chain engineering can provide a new solution to suppress carrier recombination toward high efficiency, thus deserves further attention. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Multi-stage fuel cell system method and apparatus

DOEpatents

George, Thomas J.; Smith, William C.

2000-01-01

A high efficiency, multi-stage fuel cell system method and apparatus is provided. The fuel cell system is comprised of multiple fuel cell stages, whereby the temperatures of the fuel and oxidant gas streams and the percentage of fuel consumed in each stage are controlled to optimize fuel cell system efficiency. The stages are connected in a serial, flow-through arrangement such that the oxidant gas and fuel gas flowing through an upstream stage is conducted directly into the next adjacent downstream stage. The fuel cell stages are further arranged such that unspent fuel and oxidant laden gases too hot to continue within an upstream stage because of material constraints are conducted into a subsequent downstream stage which comprises a similar cell configuration, however, which is constructed from materials having a higher heat tolerance and designed to meet higher thermal demands. In addition, fuel is underutilized in each stage, resulting in a higher overall fuel cell system efficiency.

Study, optimization, and design of a laser heat engine. [for satellite applications

NASA Technical Reports Server (NTRS)

Taussig, R. T.; Cassady, P. E.; Zumdieck, J. F.

1978-01-01

Laser heat engine concepts, proposed for satellite applications, are analyzed to determine which engine concept best meets the requirements of high efficiency (50 percent or better), continuous operation in space using near-term technology. The analysis of laser heat engines includes the thermodynamic cycles, engine design, laser power sources, collector/concentrator optics, receiving windows, absorbers, working fluids, electricity generation, and heat rejection. Specific engine concepts, optimized according to thermal efficiency, are rated by their technological availability and scaling to higher powers. A near-term experimental demonstration of the laser heat engine concept appears feasible utilizing an Otto cycle powered by CO2 laser radiation coupled into the engine through a diamond window. Higher cycle temperatures, higher efficiencies, and scalability to larger sizes appear to be achievable from a laser heat engine design based on the Brayton cycle and powered by a CO laser.

Thermal effects in the Input Optics of the Enhanced Laser Interferometer Gravitational-Wave Observatory interferometers.

PubMed

Dooley, Katherine L; Arain, Muzammil A; Feldbaum, David; Frolov, Valery V; Heintze, Matthew; Hoak, Daniel; Khazanov, Efim A; Lucianetti, Antonio; Martin, Rodica M; Mueller, Guido; Palashov, Oleg; Quetschke, Volker; Reitze, David H; Savage, R L; Tanner, D B; Williams, Luke F; Wu, Wan

2012-03-01

We present the design and performance of the LIGO Input Optics subsystem as implemented for the sixth science run of the LIGO interferometers. The Initial LIGO Input Optics experienced thermal side effects when operating with 7 W input power. We designed, built, and implemented improved versions of the Input Optics for Enhanced LIGO, an incremental upgrade to the Initial LIGO interferometers, designed to run with 30 W input power. At four times the power of Initial LIGO, the Enhanced LIGO Input Optics demonstrated improved performance including better optical isolation, less thermal drift, minimal thermal lensing, and higher optical efficiency. The success of the Input Optics design fosters confidence for its ability to perform well in Advanced LIGO.

Can storage reduce electricity consumption? A general equation for the grid-wide efficiency impact of using cooling thermal energy storage for load shifting

NASA Astrophysics Data System (ADS)

Deetjen, Thomas A.; Reimers, Andrew S.; Webber, Michael E.

2018-02-01

This study estimates changes in grid-wide, energy consumption caused by load shifting via cooling thermal energy storage (CTES) in the building sector. It develops a general equation for relating generator fleet fuel consumption to building cooling demand as a function of ambient temperature, relative humidity, transmission and distribution current, and baseline power plant efficiency. The results present a graphical sensitivity analysis that can be used to estimate how shifting load from cooling demand to cooling storage could affect overall, grid-wide, energy consumption. In particular, because power plants, air conditioners and transmission systems all have higher efficiencies at cooler ambient temperatures, it is possible to identify operating conditions such that CTES increases system efficiency rather than decreasing it as is typical for conventional storage approaches. A case study of the Dallas-Fort Worth metro area in Texas, USA shows that using CTES to shift daytime cooling load to nighttime cooling storage can reduce annual, system-wide, primary fuel consumption by 17.6 MWh for each MWh of installed CTES capacity. The study concludes that, under the right circumstances, cooling thermal energy storage can reduce grid-wide energy consumption, challenging the perception of energy storage as a net energy consumer.

Experimental study on flat plate air solar collector using a thin sand layer

NASA Astrophysics Data System (ADS)

Lati, Moukhtar; Boughali, Slimane; Bouguettaia, Hamza; Mennouche, Djamel; Bechki, Djamel

2016-07-01

A flat plate air solar collector was constructed in the laboratory of New and Renewable Energy in Arid Zones LENREZA, Ouargla University-South East Algeria. The absorber of the flat plate air solar collector was laminated with a thin layer of local sand. This acted as a thermal storage system (packed bed) with a collecting area of 2.15 m2 (0.86 m × 2.5 m). It was noticed that the solar heater integrated with the thermal storage material delivered comparatively higher temperatures; thus, giving a better efficiency than the air heater without the thermal storage system.

A thermoacoustic-Stirling heat engine: detailed study

PubMed

Backhaus; Swift

2000-06-01

A new type of thermoacoustic engine based on traveling waves and ideally reversible heat transfer is described. Measurements and analysis of its performance are presented. This new engine outperforms previous thermoacoustic engines, which are based on standing waves and intrinsically irreversible heat transfer, by more than 50%. At its most efficient operating point, it delivers 710 W of acoustic power to its resonator with a thermal efficiency of 0.30, corresponding to 41% of the Carnot efficiency. At its most powerful operating point, it delivers 890 W to its resonator with a thermal efficiency of 0.22. The efficiency of this engine can be degraded by two types of acoustic streaming. These are suppressed by appropriate tapering of crucial surfaces in the engine and by using additional nonlinearity to induce an opposing time-averaged pressure difference. Data are presented which show the nearly complete elimination of the streaming convective heat loads. Analysis of these and other irreversibilities show which components of the engine require further research to achieve higher efficiency. Additionally, these data show that the dynamics and acoustic power flows are well understood, but the details of the streaming suppression and associated heat convection are only qualitatively understood.

A soil-column gas chromatography (SCGC) approach to explore the thermal desorption behavior of hydrocarbons from soils.

PubMed

Yu, Ying; Liu, Liang; Shao, Ziying; Ju, Tianyu; Sun, Bing; Benadda, Belkacem

2016-01-01

A soil-column gas chromatography approach was developed to simulate the mass transfer process of hydrocarbons between gas and soil during thermally enhanced soil vapor extraction (T-SVE). Four kinds of hydrocarbons-methylbenzene, n-hexane, n-decane, and n-tetradecane-were flowed by nitrogen gas. The retention factor k' and the tailing factor T f were calculated to reflect the desorption velocities of fast and slow desorption fractions, respectively. The results clearly indicated two different mechanisms on the thermal desorption behaviors of fast and slow desorption fractions. The desorption velocity of fast desorption fraction was an exponential function of the reciprocal of soil absolute temperature and inversely correlated with hydrocarbon's boiling point, whereas the desorption velocity of slow desorption fraction was an inverse proportional function of soil absolute temperature, and inversely proportional to the log K OW value of the hydrocarbons. The higher activation energy of adsorption was found on loamy soil with higher organic content. The increase of carrier gas flow rate led to a reduction in the apparent activation energy of adsorption of slow desorption fraction, and thus desorption efficiency was significantly enhanced. The obtained results are of practical interest for the design of high-efficiency T-SVE system and may be used to predict the remediation time.

Detailed performance analysis of the A.A.D. - concept B

NASA Technical Reports Server (NTRS)

Sekar, R.; Tozzi, L.

1983-01-01

New concepts for engine performance improvement are seen through the adoption of heat regeneration techniques; advanced methods to enhance the combustion; and higher efficiency air handling machinery, such as the positive displacement helical screw expander and compressor. Each of these concepts plays a particular role in engine performance improvement. First regeneration has a great potential for achieving higher engine thermal efficiency through the recovery of waste energy. Although the concept itself is not new (this technique is used in the gas turbine), the application to reciprocating internal combustion engines is quite unusual and presents conceptual difficulties. The second important area is better control of the combustion process in terms of heat transfer characteristics, combustion products, and heat release rate. The third area for performance improvement is in the adoption of high efficiency air handling machinery. In particular, positive displacement helical expander and compressor exhibit an extremely high efficiency over a wide range of operating conditions.

Versatile benzimidazole/triphenylamine hybrids: efficient nondoped deep-blue electroluminescence and good host materials for phosphorescent emitters.

PubMed

Gong, Shaolong; Zhao, Yongbiao; Wang, Meng; Yang, Chuluo; Zhong, Cheng; Qin, Jingui; Ma, Dongge

2010-09-03

Two new bipolar compounds, N,N,N',N'-tetraphenyl-5'-(1-phenyl-1H-benzimidazol-2-yl)-1,1':3',1''-terphenyl-4,4''-diamine (1) and N,N,N',N'-tetraphenyl-5'-(1-phenyl-1H-benzimidazol-2-yl)-1,1':3',1''-terphenyl-3,3''-diamine (2), were synthesized and characterized, and their thermal, photophysical, and electrochemical properties were investigated. Compounds 1 and 2 possess good thermal stability with high glass-transition temperatures of 109-129 degrees C and thermal decomposition temperatures of 501-531 degrees C. The fluorescence quantum yield of 1 (0.52) is higher than that of 2 (0.16), which could be attributed to greater pi conjugation between the donor and acceptor moieties. A nondoped deep-blue fluorescent organic light-emitting diode (OLED) using 1 as the blue emitter displays high performance, with a maximum current efficiency of 2.2 cd A(-1) and a maximum external efficiency of 2.9 % at the CIE coordinates of (0.17, 0.07) that are very close to the National Television System Committee's blue standard (0.15, 0.07). Electrophosphorescent devices using the two compounds as host materials for green and red phosphor emitters show high efficiencies. The best performance of a green phosphorescent device was achieved using 2 as the host, with a maximum current efficiency of 64.3 cd A(-1) and a maximum power efficiency of 68.3 lm W(-1); whereas the best performance of a red phosphorescent device was achieved using 1 as the host, with a maximum current efficiency of 11.5 cd A(-1), and a maximum power efficiency of 9.8 lm W(-1). The relationship between the molecular structures and optoelectronic properties are discussed.

On-sun testing of an advanced falling particle receiver system

NASA Astrophysics Data System (ADS)

Ho, Clifford K.; Christian, Joshua M.; Yellowhair, Julius; Siegel, Nathan; Jeter, Sheldon; Golob, Matthew; Abdel-Khalik, Said I.; Nguyen, Clayton; Al-Ansary, Hany

2016-05-01

A 1 MWth high-temperature falling particle receiver was constructed and tested at the National Solar Thermal Test Facility at Sandia National Laboratories. The continuously recirculating system included a particle elevator, top and bottom hoppers, and a cavity receiver that comprised a staggered array of porous chevron-shaped mesh structures that slowed the particle flow through the concentrated solar flux. Initial tests were performed with a peak irradiance of ~300 kW/m2 and a particle mass flow rate of 3.3 kg/s. Peak particle temperatures reached over 700 °C near the center of the receiver, but the particle temperature increase near the sides was lower due to a non-uniform irradiance distribution. At a particle inlet temperature of ~440 °C, the particle temperature increase was 27 °C per meter of drop length, and the thermal efficiency was ~60% for an average irradiance of 110 kW/m2. At an average irradiance of 211 kW/m2, the particle temperature increase was 57.1 °C per meter of drop length, and the thermal efficiency was ~65%. Tests with higher irradiances are being performed and are expected to yield greater particle temperature increases and efficiencies.

Fiber-Based, Double-Sided, Reduced Graphene Oxide Films for Efficient Solar Vapor Generation.

PubMed

Guo, Ankang; Ming, Xin; Fu, Yang; Wang, Gang; Wang, Xianbao

2017-09-06

Solar vapor generation is a promising and whole new branch of photothermal conversion for harvesting solar energy. Various materials and devices for solar thermal conversion were successively produced and reported for higher solar energy utilization in the past few years. Herein, a compact device of reduced graphene oxides (rGO) and paper fibers was designed and assembled for efficient solar steam generation under light illumination, and it consists of water supply pipelines (WSP), a thermal insulator (TI) and a double-sided absorbing film (DSF). Heat localization is enabled by the black DSF due to its broad absorption of sunlight. More importantly, the heat transfer, from the hot DSF to the cold base fluid (water), was suppressed by TI with a low thermal conductivity. Meanwhile, bulk water was continuously transported to the DSF by WSP through TI, which was driven by the surface energy and surface tension based on the capillary effect. The effects of reduction degrees of rGO on the photothermal conversion were explored, and the evaporation efficiency reached 89.2% under one sun with 60 mg rGO. This new microdevice provided a basic technical support for distillation, desalination, sewage treatment, and related technologies.

Biodiesel from lemon and lemon grass oil and its effect on engine performance and exhaust emission

NASA Astrophysics Data System (ADS)

Dhivagar, R.; Sundararaj, S.; Vignesh, V. R.

2018-03-01

In the present scenario many developing countries are depending on oil producing nations for their fuel resources. Due to demand and scarcity of the fuel, there has been a huge increase in fuel prices. The vehicular population is also continuously increasing and becoming a great menace to peoples. This paper aims to provide an alternate solution for petroleum based fuels. It suggests that biodiesel produced from lemon and lemon grass oil can be used as an alternative fuel. This work investigates the thermal performance of four stroke diesel engine using blends of biodiesel and diesel as a fuel. Performance parameters like brake thermal efficiency, mechanical efficiency and specific fuel consumption were measured at different loads for diesel and various combination of biofuel (L10, L20, and L30). The maximum brake thermal efficiency obtained is about 26.12%for L20 which is slightly higher than that of diesel (24.91%). Engine experimental results showed that exhaust emissions including CO2 and HC were reduced by 6% and 5% for L20 mixture of biodiesel whereas CO emission was as same as diesel. However, there was increase in NOxby 26% to the diesel fuel.

[Municipal biowaste thermal-hydrolysis and ASBR anaerobic digestion].

PubMed

Hou, Hua-hua; Wang, Wei; Hu, Song; Xu, Yi-xian

2010-02-01

Thermal-hydrolysis can remarkably improve the solid organics dissolving efficiency of urban biomass waste, and anaerobic sequencing batch reactor (ASBR) was used to improve the efficiency of urban biomass waste anaerobic digestion. The optimum thermal-hydrolysis temperature and holding time was 175 degrees C and 60 min, the volatile suspended solid (VSS) dissolving ratio of kitchen waste, fruit-and-vegetable waste and sludge were 31.3%, 31.9% and 49.7%, respectively. Two ASBR and one continuous-flow stirred tank reactor (CSTR) were started at hydraulic retention time (HRT) = 20 d, COD organic loading rate (OLR) = 3.2-3.6 kg/(m3 x d). The biogas production volumes were 5656 mL/d(A1), 6335 mL/d(A2) and 3 103 mL/d(CSTR), respectively; VSS degradation ratios were 45.3% (A1), 50.87% (A2), 20.81% (CSTR), and the total COD (TCOD) removal rates were 88.1% (A1), 90% (A2), 72.6% (CSTR). In ASBR, organic solid and anaerobic microorganism were remained in the reactor during settling period. When HRT was 20 d, the solid retention time (SRT) was over 130 d, which made ASBR higher efficiency than CSTR.

A theoretical prediction of super high-performance thermoelectric materials based on MoS2/WS2 hybrid nanoribbons

NASA Astrophysics Data System (ADS)

Zhang, Zhongwei; Xie, Yuee; Peng, Qing; Chen, Yuanping

2016-02-01

Modern society is hungry for electrical power. To improve the efficiency of energy harvesting from heat, extensive efforts seek high-performance thermoelectric materials that possess large differences between electronic and thermal conductance. Here we report a super high-performance material of consisting of MoS2/WS2 hybrid nanoribbons discovered from a theoretical investigation using nonequilibrium Green’s function methods combined with first-principles calculations and molecular dynamics simulations. The hybrid nanoribbons show higher efficiency of energy conversion than the MoS2 and WS2 nanoribbons due to the fact that the MoS2/WS2 interface reduces lattice thermal conductivity more than the electron transport. By tuning the number of the MoS2/WS2 interfaces, a figure of merit ZT as high as 5.5 is achieved at a temperature of 600 K. Our results imply that the MoS2/WS2 hybrid nanoribbons have promising applications in thermal energy harvesting.

A theoretical prediction of super high-performance thermoelectric materials based on MoS2/WS2 hybrid nanoribbons

PubMed Central

Zhang, Zhongwei; Xie, Yuee; Peng, Qing; Chen, Yuanping

2016-01-01

Modern society is hungry for electrical power. To improve the efficiency of energy harvesting from heat, extensive efforts seek high-performance thermoelectric materials that possess large differences between electronic and thermal conductance. Here we report a super high-performance material of consisting of MoS2/WS2 hybrid nanoribbons discovered from a theoretical investigation using nonequilibrium Green’s function methods combined with first-principles calculations and molecular dynamics simulations. The hybrid nanoribbons show higher efficiency of energy conversion than the MoS2 and WS2 nanoribbons due to the fact that the MoS2/WS2 interface reduces lattice thermal conductivity more than the electron transport. By tuning the number of the MoS2/WS2 interfaces, a figure of merit ZT as high as 5.5 is achieved at a temperature of 600 K. Our results imply that the MoS2/WS2 hybrid nanoribbons have promising applications in thermal energy harvesting. PMID:26884123

Supercritical CO2 Power Cycles: Design Considerations for Concentrating Solar Power

DOE Office of Scientific and Technical Information (OSTI.GOV)

Neises, Ty; Turchi, Craig

2014-09-01

A comparison of three supercritical CO2 Brayton cycles: the simple cycle, recompression cycle and partial-cooling cycle indicates the partial-cooling cycle is favored for use in concentrating solar power (CSP) systems. Although it displays slightly lower cycle efficiency versus the recompression cycle, the partial-cooling cycle is estimated to have lower total recuperator size, as well as a lower maximum s-CO2 temperature in the high-temperature recuperator. Both of these effects reduce recuperator cost. Furthermore, the partial-cooling cycle provides a larger temperature differential across the turbine, which translates into a smaller, more cost-effective thermal energy storage system. The temperature drop across the turbinemore » (and by extension, across a thermal storage system) for the partial-cooling cycle is estimated to be 23% to 35% larger compared to the recompression cycle of equal recuperator conductance between 5 and 15 MW/K. This reduces the size and cost of the thermal storage system. Simulations by NREL and Abengoa Solar indicate the partial-cooling cycle results in a lower LCOE compared with the recompression cycle, despite the former's slightly lower cycle efficiency. Advantages of the recompression cycle include higher thermal efficiency and potential for a smaller precooler. The overall impact favors the use of a partial-cooling cycle for CSP compared to the more commonly analyzed recompression cycle.« less

7 CFR 3300.13 - Determination of the efficiency of the thermal appliances as installed in the insulated body.

Code of Federal Regulations, 2011 CFR

2011-01-01

... 7 Agriculture 15 2011-01-01 2011-01-01 false Determination of the efficiency of the thermal... Determination of the efficiency of the thermal appliances as installed in the insulated body. In determining the efficiency of a thermal appliance with respect to maintaining a prescribed temperature inside the body, the...

A comparative study of p(+)n and n(+)p InP solar cells made by a closed ampoule diffusion

NASA Technical Reports Server (NTRS)

Faur, M.; Faur, M.; Flood, D. J.; Weinberg, I.; Brinker, D. J.; Goradia, C.; Fatemi, N.; Goradia, M.; Thesling, W.

1991-01-01

The purpose was to demonstrate the possibility of fabricating thermally diffused p(+)n InP solar cells having high open-circuit voltage without sacrificing the short circuit current. The p(+)n junctions were formed by closed-ampoule diffusion of Cd through a 3 to 5 nm thick anodic or chemical phosphorus-rich oxide cap layer grown on n-InP:S Czochralski LEC grown substrates. For solar cells made by thermal diffusion the p(+)n configuration is expected to have a higher efficiency than the n(+)p configuration. It is predicted that the AM0, BOL efficiencies approaching 19 percent should be readily achieved providing that good ohmic front contacts could be realized on the p(+) emitters of thickness lower than 1 micron.

Thermal buffering performance of composite phase change materials applied in low-temperature protective garments

NASA Astrophysics Data System (ADS)

Yang, Kai; Jiao, Mingli; Yu, Yuanyuan; Zhu, Xueying; Liu, Rangtong; Cao, Jian

2017-07-01

Phase change material (PCM) is increasingly being applied in the manufacturing of functional thermo-regulated textiles and garments. This paper investigated the thermal buffering performance of different composite PCMs which are suitable for the application in functional low-temperature protective garments. First, according to the criteria selecting PCM for functional textiles/garments, three kinds of pure PCM were selected as samples, which were n-hexadecane, n-octadecane and n-eicosane. To get the adjustable phase change temperature range and higher phase change enthalpy, three kinds of composite PCM were prepared using the above pure PCM. To evaluate the thermal buffering performance of different composite PCM samples, the simulated low-temperature experiments were performed in the climate chamber, and the skin temperature variation curves in three different low temperature conditions were obtained. Finally composite PCM samples’ thermal buffering time, thermal buffering capacity and thermal buffering efficiency were calculated. Results show that the comprehensive thermal buffering performance of n-octadecane and n-eicosane composite PCM is the best.

High thermal conductivity in electrostatically engineered amorphous polymers

PubMed Central

Shanker, Apoorv; Li, Chen; Kim, Gun-Ho; Gidley, David; Pipe, Kevin P.; Kim, Jinsang

2017-01-01

High thermal conductivity is critical for many applications of polymers (for example, packaging of light-emitting diodes), in which heat must be dissipated efficiently to maintain the functionality and reliability of a system. Whereas uniaxially extended chain morphology has been shown to significantly enhance thermal conductivity in individual polymer chains and fibers, bulk polymers with coiled and entangled chains have low thermal conductivities (0.1 to 0.4 W m−1 K−1). We demonstrate that systematic ionization of a weak anionic polyelectrolyte, polyacrylic acid (PAA), resulting in extended and stiffened polymer chains with superior packing, can significantly enhance its thermal conductivity. Cross-plane thermal conductivity in spin-cast amorphous films steadily grows with PAA degree of ionization, reaching up to ~1.2 W m−1 K−1, which is on par with that of glass and about six times higher than that of most amorphous polymers, suggesting a new unexplored molecular engineering strategy to achieve high thermal conductivities in amorphous bulk polymers. PMID:28782022

Adapted diffusion processes for effective forging dies

NASA Astrophysics Data System (ADS)

Paschke, H.; Nienhaus, A.; Brunotte, K.; Petersen, T.; Siegmund, M.; Lippold, L.; Weber, M.; Mejauschek, M.; Landgraf, P.; Braeuer, G.; Behrens, B.-A.; Lampke, T.

2018-05-01

Hot forging is an effective production method producing safety relevant parts with excellent mechanical properties. The economic efficiency directly depends on the occurring wear of the tools, which limits service lifetime. Several approaches of the presenting research group aim at minimizing the wear caused by interacting mechanical and thermal loads by using enhanced nitriding technology. Thus, by modifying the surface zone layer it is possible to create a resistance against thermal softening provoking plastic deformation and pronounced abrasive wear. As a disadvantage, intensely nitrided surfaces may possibly include the risk of increased crack sensitivity and therefore feature the chipping of material at the treated surface. Recent projects (evaluated in several industrial applications) show the high technological potential of adapted treatments: A first approach evaluated localized treatments by preventing areas from nitrogen diffusion with applied pastes or other coverages. Now, further ideas are to use this principle to structure the surface with differently designed patterns generating smaller ductile zones beneath nitrided ones. The selection of suitable designs is subject to certain geo-metrical requirements though. The intention of this approach is to prevent the formation and propagation of cracks under thermal shock conditions. Analytical characterization methods for crack sensitivity of surface zone layers and an accurate system of testing rigs for thermal shock conditions verified the treatment concepts. Additionally, serial forging tests using adapted testing geometries and finally, tests in the industrial production field were performed. Besides stabilizing the service lifetime and decreasing specific wear mechanisms caused by thermal influences, the crack behavior was influenced positively. This leads to a higher efficiency of the industrial production process and enables higher output in forging campaigns of industrial partners.

Desorption of isopropyl alcohol from adsorbent with non-thermal plasma.

PubMed

Shiau, Chen Han; Pan, Kuan Lun; Yu, Sheng Jen; Yan, Shaw Yi; Chang, Moo Been

2017-09-01

Effective desorption of isopropyl alcohol (IPA) from adsorbents with non-thermal plasma is developed. In this system, IPA is effectively adsorbed with activated carbon while dielectric barrier discharge is applied to replace the conventional thermal desorption process to achieve good desorption efficiency, making the treatment equipment smaller in size. Various adsorbents including molecular sieves and activated carbon are evaluated for IPA adsorption capacity. The results indicate that BAC has the highest IPA adsorption capacity (280.31 mg IPA/g) under the operating conditions of room temperature, IPA of 400 ppm, and residence time of 0.283 s among 5 adsorbents tested. For the plasma desorption process, the IPA selectivity of 89% is achieved with BAC as N 2 is used as desorbing gas. In addition, as air or O 2 is used as desorbing gas, the IPA desorption concentration is reduced, because air and O 2 plasmas generate active species to oxidize IPA to form acetone, CO 2 , and even CO. Furthermore, the results of the durability test indicate that the amount of IPA desorbed increases with increasing desorption times and plasma desorption process has a higher energy efficiency if compared with thermal desorption. Overall, this study indicates that non-thermal plasma is a viable process for removing VOCs to regenerate adsorbent.

Study on finned pipe performance as a ground heat exchanger

NASA Astrophysics Data System (ADS)

Lin, Qinglong; Ma, Jinghui; Shi, Lei

2017-08-01

The GHEs (ground heat exchangers) is an important element that determines the thermal efficiency of the entire ground-source heat-pump system. The aim of the present study is to clarify thermal performance of a new type GHE pipe, which consists straight fins of uniform cross sectional area. In this paper, GHE model is introduced and an analytical model of new type GHE pipe is developed. The heat exchange rate of BHEs utilizing finned pips is 40.42 W/m, which is 16.3% higher than normal BHEs, based on simulation analyses.

Silicon Germanium Quantum Well Thermoelectrics

NASA Astrophysics Data System (ADS)

Davidson, Anthony Lee, III

Today's growing energy demands require new technologies to provide high efficiency clean energy. Thermoelectrics that convert heat to electrical energy directly can provide a method for the automobile industry to recover waste heat to power vehicle electronics, hence improving fuel economy. If large enough efficiencies can be obtained then the internal combustion engine could even be replaced. Exhaust temperature for automotive application range from 400 to 800 K. In this temperature range the current state of the art materials are bulk Si1-xGex alloys. By alternating layers of Si and Si1-xGex alloy device performance may be enhanced through quantum well effects and variations in material thermal properties. In this study, superlattices designed for in-plane operation with varying period and crystallinity are examined to determine the effect on electrical and thermal properties. In-plane electrical resistivity of these materials was found to be below the bulk material at a similar doping at room temperature, confirming the role of quantum wells in electron transport. As period is reduced in the structures boundary scattering limits electron propagation leading to increased resistivity. The Seebeck coefficient measured at room temperature is higher than the bulk material, additionally lending proof to the effects of quantum wells. When examining cross-plane operation the low doping in the Si layers of the device produce high resistivity resulting from boundary scattering. Thermal conductivity was measured from 77 K up to 674 K and shows little variation due to periodicity and temperature, however an order of magnitude reduction over bulk Si1-xGex is shown in all samples. A model is developed that suggests a combination of phonon dispersion effects and strong boundary scattering. Further study of the phonon dispersion effects was achieved through the examination of the heat capacity by combining thermal diffusivity with thermal conductivity. All superlattices show a reduction in heat capacity when compared to Si, suggesting the importance of phonon dispersion effects due to the periodicity. The Debye model does not provide agreement with this result due to the inadequate treatment of optical phonons. Overall the results show that the design of the superlattice structures results in a thermoelectric that has improved efficiency at room temperature to the state of the art materials with the promise of increased efficiency at higher temperatures.

Thermal behaviour of ESP ash from municipal solid waste incinerators.

PubMed

Yang, Y; Xiao, Y; Wilson, N; Voncken, J H L

2009-07-15

Stricter environmental regulations demand safer treatment and disposal of incinerator fly ashes. So far no sound technology or a process is available for a sustainable and ecological treatment of the waste incineration ashes, and only partial treatment is practised for temporary and short-term solutions. New processes and technology need to be developed for comprehensive utilization and detoxification of the municipal solid waste (MSW) incinerator residues. To explore the efficiency of thermal stabilisation and controlled vitrification, the thermal behaviour of electrostatic precipitator (ESP) ash was investigated under controlled conditions. The reaction stages are identified with the initial moisture removal, volatilization, melting and slag formation. At the temperature higher than 1100 degrees C, the ESP ashes have a quicker weight loss, and the total weight loss reaches up to 52%, higher than the boiler ash. At 1400 degrees C a salt layer and a homogeneous glassy slag were formed. The effect of thermal treatment on the leaching characteristics of various elements in the ESP ash was evaluated with the availability-leaching test. The leaching values of the vitrified slag are significantly lowered than that of the original ash.

Reduced temperature hydrolysis at 134 °C before thermophilic anaerobic digestion of waste activated sludge at increasing organic load.

PubMed

Gianico, A; Braguglia, C M; Cesarini, R; Mininni, G

2013-09-01

The performance of thermophilic digestion of waste activated sludge, either untreated or thermal pretreated, was evaluated through semi-continuous tests carried out at organic loading rates in the range of 1-3.7 kg VS/m(3)d. Although the thermal pretreatment at T=134 °C proved to be effective in solubilizing organic matter, no significant gain in organics degradation was observed. However, the digestion of pretreated sludge showed significant soluble COD removal (more than 55%) whereas no removal occurred in control reactors. The lower the initial sludge biodegradability, the higher the efficiency of thermal pretreated digestion was observed, in particular as regards higher biogas and methane production rates with respect to the parallel untreated sludge digestion. Heat balance of the combined thermal hydrolysis/thermophilic digestion process, applied on full-scale scenarios, showed positive values for direct combustion of methane. In case of combined heat and power generation, attractive electric energy recoveries were obtained, with a positive heat balance at high load. Copyright © 2013. Published by Elsevier Ltd.

Cryogenic vacuumm RF feedthrough device

DOEpatents

Wu, Genfa [Yorktown, VA; Phillips, Harry Lawrence [Hayes, VA

2008-12-30

A cryogenic vacuum rf feedthrough device comprising: 1) a probe for insertion into a particle beam; 2) a coaxial cable comprising an inner conductor and an outer conductor, a dielectric/insulating layer surrounding the inner conductor, the latter being connected to the probe for the transmission of higher mode rf energy from the probe; and 3) a high thermal conductivity stub attached to the coaxial dielectric about and in thermal contact with the inner conductor which high thermal conductivity stub transmits heat generated in the vicinity of the probe efficiently and radially from the area of the probe and inner conductor all while maintaining useful rf transmission line characteristics between the inner and outer coaxial conductors.

Damage Accumulation and Failure of Plasma-Sprayed Thermal Barrier Coatings under Thermal Gradient Cyclic Conditions

NASA Technical Reports Server (NTRS)

Zhu, Dongming; Choi, Sung R.; Ghosn, Louis J.; Miller, rober A.

2005-01-01

Thermal barrier coatings will be more aggressively designed to protect gas turbine engine hot-section components in order to meet future engine higher fuel efficiency and lower emission goals. A fundamental understanding of the sintering and thermal cycling induced delamination of thermal barrier coating systems under engine-like heat flux conditions will potentially help to improve the coating temperature capability. In this study, a test approach is established to emphasize the real-time monitoring and assessment of the coating thermal conductivity, which can initially increase under the steady-state high temperature thermal gradient test due to coating sintering, and later decrease under the thermal gradient cyclic test due to coating cracking and delamination. Thermal conductivity prediction models have been established for a ZrO2-(7- 8wt%)Y2O3 model coating system in terms of heat flux, time, and testing temperatures. The coating delamination accumulation is then assessed based on the observed thermal conductivity response under the combined steady-state and cyclic thermal gradient tests. The coating thermal gradient cycling associated delaminations and failure mechanisms under simulated engine heat-flux conditions will be discussed in conjunction with the coating sintering and fracture testing results.

Improving efficiency of polystyrene concrete production with composite binders

NASA Astrophysics Data System (ADS)

Lesovik, R. V.; Ageeva, M. S.; Lesovik, G. A.; Sopin, D. M.; Kazlitina, O. V.; Mitrokhina, A. A.

2018-03-01

According to leading marketing researchers, the construction market in Russia and CIS will continue growing at a rapid rate; this applies not only to a large-scale major construction, but to a construction of single-family houses and small-scale industrial facilities as well. Due to this, there are increased requirements for heat insulation of the building enclosures and a significant demand for efficient walling materials with high thermal performance. All these developments led to higher requirements imposed on the equipment that produces such materials.

L-Nitroargininium picrate

NASA Astrophysics Data System (ADS)

Apreyan, R. A.; Fleck, M.; Atanesyan, A. K.; Sukiasyan, R. P.; Petrosyan, A. M.

2015-12-01

L-Nitroargininium picrate has been obtained from an aqueous solution containing equimolar quantities of L-nitroarginine and picric acid by slow evaporation. Single crystal was grown by evaporation method. Crystal structure was determined at room temperature. The salt crystallizes in monoclinic crystal system (space group P21). Vibrational spectra and thermal properties were studied. Second harmonic generation efficiency measured by powder method is found to be four times higher than in L-nitroarginine, which in turn is ten times more efficient than KDP (KH2PO4).

Experimental investigation of a nanofluid absorber employed in a low-profile, concentrated solar thermal collector

NASA Astrophysics Data System (ADS)

Li, Qiyuan; Zheng, Cheng; Mesgari, Sara; Hewakuruppu, Yasitha L.; Hjerrild, Natasha; Crisostomo, Felipe; Morrison, Karl; Woffenden, Albert; Rosengarten, Gary; Scott, Jason A.; Taylor, Robert A.

2015-12-01

Recent studies [1-3] have demonstrated that nanotechnology, in the form of nanoparticles suspended in water and organic liquids, can be employed to enhance solar collection via direct volumetric absorbers. However, current nanofluid solar collector experimental studies are either relevant to low-temperature flat plate solar collectors (<100 °C) [4] or higher temperature (>100 °C) indoor laboratory-scale concentrating solar collectors [1, 5]. Moreover, many of these studies involve in thermal properties of nanofluid (such as thermal conductivity) enhancement in solar collectors by using conventional selective coated steel/copper tube receivers [6], and no full-scale concentrating collector has been tested at outdoor condition by employing nanofluid absorber [2, 6]. Thus, there is a need of experimental researches to evaluate the exact performance of full-scale concentrating solar collector by employing nanofluids absorber at outdoor condition. As reported previously [7-9], a low profile (<10 cm height) solar thermal concentrating collector was designed and analysed which can potentially supply thermal energy in the 100-250 °C range (an application currently met by gas and electricity). The present study focuses on the design and experimental investigation of a nanofluid absorber employed in this newly designed collector. The nanofluid absorber consists of glass tubes used to contain chemically functionalized multi-walled carbon nanotubes (MWCNTs) dispersed in DI water. MWCNTs (average diameter of 6-13 nm and average length of 2.5-20 μm) were functionalized by potassium persulfate as an oxidant. The nanofluids were prepared with a MCWNT concentration of 50 +/- 0.1 mg/L to form a balance between solar absorption depth and viscosity (e.g. pumping power). Moreover, experimentally comparison of the thermal efficiency between two receivers (a black chrome-coated copper tube versus a MWCNT nanofluid contained within a glass tubetube) is investigated. Thermal experimentation reveals that while the collector efficiency reduced from 73% to 54% when operating temperature increased from ambient to 80 °C by employing a MWCNT nanofluid receiver, the efficiency decreased from 85% to 68% with same operating temperature range by employing black chrome-coated copper tube receiver. This difference can mainly be explained by the reflection optical loss off and higher thermal emission heat loss the front surface of the glass tube, yielding a 90% of transmittance to the MWCNT fluid and a 0.9 emissivity of glass pipe. Overall, an experimental investigation of the performance of a low profile solar collector with a direct volumetric absorber and conventional surface absorber is presented. In order to bring nanotechnology into industrial and commercial heating applications,

Quantum thermal diode based on two interacting spinlike systems under different excitations.

PubMed

Ordonez-Miranda, Jose; Ezzahri, Younès; Joulain, Karl

2017-02-01

We demonstrate that two interacting spinlike systems characterized by different excitation frequencies and coupled to a thermal bath each, can be used as a quantum thermal diode capable of efficiently rectifying the heat current. This is done by deriving analytical expressions for both the heat current and rectification factor of the diode, based on the solution of a master equation for the density matrix. Higher rectification factors are obtained for lower heat currents, whose magnitude takes their maximum values for a given interaction coupling proportional to the temperature of the hotter thermal bath. It is shown that the rectification ability of the diode increases with the excitation frequencies difference, which drives the asymmetry of the heat current, when the temperatures of the thermal baths are inverted. Furthermore, explicit conditions for the optimization of the rectification factor and heat current are explicitly found.

Pressure-assisted thermal sterilization of soup

NASA Astrophysics Data System (ADS)

Shibeshi, Kidane; Farid, Mohammed M.

2010-12-01

The overall efficiency of an existing scale-up pressure-assisted thermal sterilization (PATS) unit was investigated with regards to inactivation of Geobacillus stearothermophilus spores suspended in pumpkin soup. The PATS unit is a double pipe heat exchanger in which the soup is pumped into its inner high pressure tube and constrained by two high pressure valves, while steam is continuously passed through the annular region to heat the content. The technology is based on pressure generation by thermal expansion of the liquid in an enclosure. In this work, the addition of an air line to push the treated liquid food out of the existing PATS unit has improved the overall quality of the treated samples, as evidenced by achieving higher log reduction of the spores. Compared with thermal processing, the application of PATS shows the potential for lowering the thermal treatment temperature, offering improved food quality.

Development and Life Prediction of Erosion Resistant Turbine Low Conductivity Thermal Barrier Coatings

NASA Technical Reports Server (NTRS)

Zhu, Dongming; Miller, Robert A.; Kuczmarski, Maria A.

2010-01-01

Future rotorcraft propulsion systems are required to operate under highly-loaded conditions and in harsh sand erosion environments, thereby imposing significant material design and durability issues. The incorporation of advanced thermal barrier coatings (TBC) in high pressure turbine systems enables engine designs with higher inlet temperatures, thus improving the engine efficiency, power density and reliability. The impact and erosion resistance of turbine thermal barrier coating systems are crucial to the turbine coating technology application, because a robust turbine blade TBC system is a prerequisite for fully utilizing the potential coating technology benefit in the rotorcraft propulsion. This paper describes the turbine blade TBC development in addressing the coating impact and erosion resistance. Advanced thermal barrier coating systems with improved performance have also been validated in laboratory simulated engine erosion and/or thermal gradient environments. A preliminary life prediction modeling approach to emphasize the turbine blade coating erosion is also presented.

A 1 kW-class multi-stage heat-driven thermoacoustic cryocooler system operating at liquefied natural gas temperature range

NASA Astrophysics Data System (ADS)

Zhang, L. M.; Hu, J. Y.; Wu, Z. H.; Luo, E. C.; Xu, J. Y.; Bi, T. J.

2015-07-01

This article introduces a multi-stage heat-driven thermoacoustic cryocooler capable of reaching cooling capacity about 1 kW at liquefied natural gas temperature range without any moving mechanical parts. The cooling system consists of an acoustically resonant double-acing traveling wave thermoacoustic heat engine and three identical pulse tube coolers. Unlike other traditional traveling wave thermoacoustic heat engines, the acoustically resonant double-acting thermoacoustic heat engine is a closed-loop configuration consists of three identical thermoacoustic conversion units. Each pulse tube cooler is bypass driven by one thermoacoustic heat engine unit. The device is acoustically completely symmetric and therefore "self-matching" for efficient traveling-wave thermoacoustic conversion. In the experiments, with 7 MPa helium gas as working gas, when the heating temperature reaches 918 K, total cooling capacity of 0.88 kW at 110 K is obtained with a resonant frequency of about 55 Hz. When the heating temperature is 903 K, a maximum total cooling capacity at 130 K of 1.20 kW is achieved, with a thermal-to-cold exergy efficiency of 8%. Compared to previously developed heat-driven thermoacoustic cryocoolers, this device has higher thermal efficiency and higher power density. It shows a good prospect of application in the field of natural gas liquefaction and recondensation.

Novel thermal efficiency-based model for determination of thermal conductivity of membrane distillation membranes

DOE PAGES

Vanneste, Johan; Bush, John A.; Hickenbottom, Kerri L.; ...

2017-11-21

Development and selection of membranes for membrane distillation (MD) could be accelerated if all performance-determining characteristics of the membrane could be obtained during MD operation without the need to recur to specialized or cumbersome porosity or thermal conductivity measurement techniques. By redefining the thermal efficiency, the Schofield method could be adapted to describe the flux without prior knowledge of membrane porosity, thickness, or thermal conductivity. A total of 17 commercially available membranes were analyzed in terms of flux and thermal efficiency to assess their suitability for application in MD. The thermal-efficiency based model described the flux with an average %RMSEmore » of 4.5%, which was in the same range as the standard deviation on the measured flux. The redefinition of the thermal efficiency also enabled MD to be used as a novel thermal conductivity measurement device for thin porous hydrophobic films that cannot be measured with the conventional laser flash diffusivity technique.« less

Novel thermal efficiency-based model for determination of thermal conductivity of membrane distillation membranes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vanneste, Johan; Bush, John A.; Hickenbottom, Kerri L.

Development and selection of membranes for membrane distillation (MD) could be accelerated if all performance-determining characteristics of the membrane could be obtained during MD operation without the need to recur to specialized or cumbersome porosity or thermal conductivity measurement techniques. By redefining the thermal efficiency, the Schofield method could be adapted to describe the flux without prior knowledge of membrane porosity, thickness, or thermal conductivity. A total of 17 commercially available membranes were analyzed in terms of flux and thermal efficiency to assess their suitability for application in MD. The thermal-efficiency based model described the flux with an average %RMSEmore » of 4.5%, which was in the same range as the standard deviation on the measured flux. The redefinition of the thermal efficiency also enabled MD to be used as a novel thermal conductivity measurement device for thin porous hydrophobic films that cannot be measured with the conventional laser flash diffusivity technique.« less

Unconventional Three-Armed Luminogens Exhibiting Both Aggregation-Induced Emission and Thermally Activated Delayed Fluorescence Resulting in High-Performing Solution-Processed Organic Light-Emitting Diodes.

PubMed

Park, Seo Yeon; Choi, Suna; Park, Gi Eun; Kim, Hyung Jong; Lee, Chiho; Moon, Ji Su; Kim, Si Woo; Park, Sungnam; Kwon, Jang Hyuk; Cho, Min Ju; Choi, Dong Hoon

2018-05-02

In this work, three-armed luminogens IAcTr-out and IAcTr-in were synthesized and used as emitters bearing triazine and indenoacridine moieties in thermally activated delayed fluorescence organic light-emitting diodes (OLEDs). These molecules could form a uniform thin film via the solution process and also allowed the subsequent deposition of an electron transporting layer either by vacuum deposition or by an all-solution coating method. Intriguingly, the new luminogens displayed aggregation-induced emission (AIE), which is a unique photophysical phenomenon. As a nondoped emitting layer (EML), IAcTr-in showed external quantum efficiencies (EQEs) of 11.8% for the hybrid-solution processed OLED and 10.9% for the all-solution processed OLED with a low efficiency roll-off. This was evident by the higher photoluminescence quantum yield and higher rate constant of reverse intersystem crossing of IAcTr-in, as compared to IAcTr-out. These AIE luminogens were used as dopants and mixed with the well-known host material 1,3-bis( N-carbazolyl)benzene (mCP) to produce a high-efficiency OLED with a two-component EML. The maximum EQE of 17.5% was obtained when using EML with IAcTr-out doping (25 wt %) into mCP, and the OLED with EML bearing IAcTr-in and mCP showed a higher maximum EQE of 18.4% as in the case of the nondoped EML-based device.

Efficient up-conversion in Yb:Er:NaT(XO4)2 thermal nanoprobes. Imaging of their distribution in a perfused mouse

PubMed Central

Serrano, María Dolores; Han, Xiumei; Cascales, Concepción; Cantero, Marta; Montoliu, Lluís; Arza, Elvira; Caiolfa, Valeria R.; Zamai, Moreno

2017-01-01

Yb and Er codoped NaT(XO4)2 (T = Y, La, Gd, Lu and X = Mo, W) disordered oxides show a green (Er3+ related) up-conversion (UC) efficiency comparable to that of Yb:Er:β-NaYF4 compound and unless 3 times larger UC ratiometric thermal sensitivity. The similar UC efficiency of Yb:Er doped NaT(XO4)2 and β-NaYF4 compounds allowed testing equal subcutaneous depths of ex-vivo chicken tissue in both cases. This extraordinary behavior for NaT(XO4)2 oxides with large cutoff phonon energy (ħω≈ 920 cm-1) is ascribed to 4F9/2 electron population recycling to higher energy 4G11/2 level by a phonon assisted transition. Crystalline nanoparticles of Yb:Er:NaLu(MoO4)2 have been synthesized by sol-gel with sizes most commonly in the 50–80 nm range, showing a relatively small reduction of the UC efficiency with regards to bulk materials. Fluorescence lifetime and multiphoton imaging microscopies show that these nanoparticles can be efficiently distributed to all body organs of a perfused mouse. PMID:28542327

Concept for power scaling second harmonic generation using a cascade of nonlinear crystals.

PubMed

Hansen, A K; Tawfieq, M; Jensen, O B; Andersen, P E; Sumpf, B; Erbert, G; Petersen, P M

2015-06-15

Within the field of high-power second harmonic generation (SHG), power scaling is often hindered by adverse crystal effects such as thermal dephasing arising from the second harmonic (SH) light, which imposes limits on the power that can be generated in many crystals. Here we demonstrate a concept for efficient power scaling of single-pass SHG beyond such limits using a cascade of nonlinear crystals, in which the first crystal is chosen for high nonlinear efficiency and the subsequent crystal(s) are chosen for power handling ability. Using this highly efficient single-pass concept, we generate 3.7 W of continuous-wave diffraction-limited (M(2)=1.25) light at 532 nm from 9.5 W of non-diffraction-limited (M(2)=7.7) light from a tapered laser diode, while avoiding significant thermal effects. Besides constituting the highest SH power yet achieved using a laser diode, this demonstrates that the concept successfully combines the high efficiency of the first stage with the good power handling properties of the subsequent stages. The concept is generally applicable and can be expanded with more stages to obtain even higher efficiency, and extends also to other combinations of nonlinear media suitable for other wavelengths.

Geothermal area detection using Landsat ETM+ thermal infrared data and its mechanistic analysis—A case study in Tengchong, China

NASA Astrophysics Data System (ADS)

Qin, Qiming; Zhang, Ning; Nan, Peng; Chai, Leilei

2011-08-01

Thermal infrared (TIR) remote sensing is an important technique in the exploration of geothermal resources. In this study, a geothermal survey is conducted in Tengchong area of Yunnan province in China using TIR data from Landsat-7 Enhanced Thematic Mapper Plus (ETM+) sensor. Based on radiometric calibration, atmospheric correction and emissivity calculation, a simple but efficient single channel algorithm with acceptable precision is applied to retrieve the land surface temperature (LST) of study area. The LST anomalous areas with temperature about 4-10 K higher than background area are discovered. Four geothermal areas are identified with the discussion of geothermal mechanism and the further analysis of regional geologic structure. The research reveals that the distribution of geothermal areas is consistent with the fault development in study area. Magmatism contributes abundant thermal source to study area and the faults provide thermal channels for heat transfer from interior earth to land surface and facilitate the present of geothermal anomalies. Finally, we conclude that TIR remote sensing is a cost-effective technique to detect LST anomalies. Combining TIR remote sensing with geological analysis and the understanding of geothermal mechanism is an accurate and efficient approach to geothermal area detection.

Advanced Low Conductivity Thermal Barrier Coatings: Performance and Future Directions (Invited paper)

NASA Technical Reports Server (NTRS)

Zhu, Dongming; Miller, Robert A.

2008-01-01

Thermal barrier coatings will be more aggressively designed to protect gas turbine engine hot-section components in order to meet future engine higher fuel efficiency and lower emission goals. In this presentation, thermal barrier coating development considerations and performance will be emphasized. Advanced thermal barrier coatings have been developed using a multi-component defect clustering approach, and shown to have improved thermal stability and lower conductivity. The coating systems have been demonstrated for high temperature combustor applications. For thermal barrier coatings designed for turbine airfoil applications, further improved erosion and impact resistance are crucial for engine performance and durability. Erosion resistant thermal barrier coatings are being developed, with a current emphasis on the toughness improvements using a combined rare earth- and transition metal-oxide doping approach. The performance of the toughened thermal barrier coatings has been evaluated in burner rig and laser heat-flux rig simulated engine erosion and thermal gradient environments. The results have shown that the coating composition optimizations can effectively improve the erosion and impact resistance of the coating systems, while maintaining low thermal conductivity and cyclic durability. The erosion, impact and high heat-flux damage mechanisms of the thermal barrier coatings will also be described.

Advanced Low Conductivity Thermal Barrier Coatings: Performance and Future Directions

NASA Technical Reports Server (NTRS)

Zhu, Dongming; Miller, Robert A.

2008-01-01

Thermal barrier coatings will be more aggressively designed to protect gas turbine engine hot-section components in order to meet future engine higher fuel efficiency and lower emission goals. In this presentation, thermal barrier coating development considerations and performance will be emphasized. Advanced thermal barrier coatings have been developed using a multi-component defect clustering approach, and shown to have improved thermal stability and lower conductivity. The coating systems have been demonstrated for high temperature combustor applications. For thermal barrier coatings designed for turbine airfoil applications, further improved erosion and impact resistance are crucial for engine performance and durability. Erosion resistant thermal barrier coatings are being developed, with a current emphasis on the toughness improvements using a combined rare earth- and transition metal-oxide doping approach. The performance of the toughened thermal barrier coatings has been evaluated in burner rig and laser heat-flux rig simulated engine erosion and thermal gradient environments. The results have shown that the coating composition optimizations can effectively improve the erosion and impact resistance of the coating systems, while maintaining low thermal conductivity and cyclic durability. The erosion, impact and high heat-flux damage mechanisms of the thermal barrier coatings will also be described.

Spectrum-splitting hybrid CSP-CPV solar energy system with standalone and parabolic trough plant retrofit applications

NASA Astrophysics Data System (ADS)

Orosz, Matthew; Zweibaum, Nicolas; Lance, Tamir; Ruiz, Maritza; Morad, Ratson

2016-05-01

Sunlight to electricity efficiencies of Parabolic Trough Collector (PTC) plants are typically on the order of 15%, while commercial solar Photovoltaic (PV) technologies routinely achieve efficiencies of greater than 20%, albeit with much higher conversion efficiencies of photons at the band gap. Hybridizing concentrating solar power and photovoltaic technologies can lead to higher aggregate efficiencies due to the matching of photons to the appropriate converter based on wavelength. This can be accomplished through spectral filtering whereby photons unusable or poorly utilitized by PV (IR and UV) are passed through to a heat collection element, while useful photons (VIS) are reflected onto a concentrating PV (CPV) receiver. The mechanical design and experimental validation of spectral splitting optics is described in conjunction with system level modeling and economic analysis. The implications of this architecture include higher efficiency, lower cost hybrid CSP-PV power systems, as well as the potential to retrofit existing PTC plants to boost their output by ~ 10% at a projected investment cost of less than 1 per additional net Watt and an IRR of 18%, while preserving the dispatchability of the CSP plant's thermal energy storage.

Efficiency of the energy transfer in the FMO complex using hierarchical equations on Graphics Processing Units

NASA Astrophysics Data System (ADS)

Kramer, Tobias; Kreisbeck, Christoph; Rodriguez, Mirta; Hein, Birgit

2011-03-01

We study the efficiency of the energy transfer in the Fenna-Matthews-Olson complex solving the non-Markovian hierarchical equations (HE) proposed by Ishizaki and Fleming in 2009, which include properly the reorganization process. We compare it to the Markovian approach and find that the Markovian dynamics overestimates the thermalization rate, yielding higher efficiencies than the HE. Using the high-performance of graphics processing units (GPU) we cover a large range of reorganization energies and temperatures and find that initial quantum beatings are important for the energy distribution, but of limited influence to the efficiency. Our efficient GPU implementation of the HE allows us to calculate nonlinear spectra of the FMO complex. References see www.quantumdynamics.de

Seasonal shifts in the thermal biology of the lizard Liolaemus tandiliensis (Squamata, Liolaemidae).

PubMed

Stellatelli, Oscar Aníbal; Villalba, Agustina; Block, Carolina; Vega, Laura Estela; Dajil, Juan Esteban; Cruz, Félix Benjamín

2018-04-01

Small lizards can accommodate to constraints imposed by temporal changes in ambient temperature through a combination of adaptive evolution and behavioral and physiological plasticity. Thermal physiology plasticity may compensate for climate variation and favor performance while minimizing behavioral costs in sub-optimal conditions. The Tandilia's lizard, Liolaemus tandiliensis, occurs in an isolated mountain range of the Argentinean temperate Pampas. In this study, we compared the thermal biology of L. tandiliensis between late spring (December) and mid-summer (February). The habitats' thermal quality was lower in late spring than in mid-summer. The lizard's field-body temperature (Tb) was 2-3 °C higher than the operative temperature (Te). Overall, the mean preferred temperature (Tsel) was 37.4 °C [preferred range (Tset): 36.2-38.7 °C], and was similar to other Liolaemus species. The Tset and Tsel of females in late spring were 1.8 °C lower than in mid-summer. In the case of males, the Tsel did not vary among seasons, while the Tset had a difference of 2.5 °C between seasons. Adults were moderate thermoregulators, but females were more efficient only in late spring (E males = 0.69; E females = 0.58), compared to mid-summer (E males = 0.68; E females = 0.50). Juveniles did not show temporal differences in temperature preferences and had a relatively higher efficiency in late spring (E = 0.38) compared to mid-summer (E = 0.28). An increased proportion of juveniles and adults shifted their Tb near to the Tset in late spring respect to mid-summer. The adults also matched their preferred temperatures to their current body temperature. These results suggest that seasonal shifts in the thermoregulatory parameters of L. tandiliensis may improve their thermoregulatory efficiency. Although temporal variation in ambient temperatures might influence the thermal biology of the studied lizards, other factors such as changes in the reproductive status may have also interfered. Copyright © 2018 Elsevier Ltd. All rights reserved.

Analysis and experimental investigation of ceramic powder coating on aluminium piston

NASA Astrophysics Data System (ADS)

Pal, S.; Deore, A.; Choudhary, A.; Madhwani, V.; Vijapuri, D.

2017-11-01

Energy conservation and efficiency have always been the quest of engineers concerned with internal combustion engines. The diesel engine generally offers better fuel economy than its counterpart petrol engine. Even the diesel engine rejects about two thirds of the heat energy of the fuel, one-third to the coolant, and one third to the exhaust, leaving only about one-third as useful power output. Theoretically if the heat rejected could be reduced, then the thermal efficiency would be improved, at least up to the limit set by the second law of thermodynamics. Low Heat Rejection engines aim to do this by reducing the heat lost to the coolant. Thermal Barrier Coatings (TBCs) in diesel engines lead to advantages including higher power density, fuel efficiency, and multifuel capacity due to higher combustion chamber temperature. Using TBC can increase engine power by 8%, decrease the specific fuel consumption by 15-20% and increase the exhaust gas temperature by 200K. Although several systems have been used as TBC for different purposes, yttria stabilized zirconia with 7-8 wt.% yttria has received the most attention. Several factors playing important role in TBC life include thermal conductivity, thermo chemical stability at the service temperature, high thermo mechanical stability to the maximum service temperature and thermal expansion coefficient (TEC). This work mainly concentrates on the behaviour of three TBC powders under the same diesel engine conditions. This work finds out the best powder among yttria, alumina and zirconia to be used as a piston coating material i.e., the one resulting in lowest heat flux and low side skirt and bottom temperature has been chosen for the coating purpose. This work then analyses the coated sample for its surface properties such as hardness, roughness, corrosion resistance and microstructural study. This work aims at making it easier for the manufacturers choose the coating material for engine coating purposes and surface properties for operating them in their service period.

Improved heating efficiency with High-Intensity Focused Ultrasound using a new ultrasound source excitation.

PubMed

Bigelow, Timothy A

2009-01-01

High-Intensity Focused Ultrasound (HIFU) is quickly becoming one of the best methods to thermally ablate tissue noninvasively. Unlike RF or Laser ablation, the tissue can be destroyed without inserting any probes into the body minimizing the risk of secondary complications such as infections. In this study, the heating efficiency of HIFU sources is improved by altering the excitation of the ultrasound source to take advantage of nonlinear propagation. For ultrasound, the phase velocity of the ultrasound wave depends on the amplitude of the wave resulting in the generation of higher harmonics. These higher harmonics are more efficiently converted into heat in the body due to the frequency dependence of the ultrasound absorption in tissue. In our study, the generation of the higher harmonics by nonlinear propagation is enhanced by transmitting an ultrasound wave with both the fundamental and a higher harmonic component included. Computer simulations demonstrated up to a 300% increase in temperature increase compared to transmitting at only the fundamental for the same acoustic power transmitted by the source.

Highly Efficient Near Infrared Photothermal Conversion Properties of Reduced Tungsten Oxide/Polyurethane Nanocomposites

PubMed Central

Chala, Tolesa Fita; Wu, Chang-Mou; Chou, Min-Hui; Gebeyehu, Molla Bahiru; Cheng, Kuo-Bing

2017-01-01

In this work, novel WO3-x/polyurethane (PU) nanocomposites were prepared by ball milling followed by stirring using a planetary mixer/de-aerator. The effects of phase transformation (WO3 → WO2.8 → WO2.72) and different weight fractions of tungsten oxide on the optical performance, photothermal conversion, and thermal properties of the prepared nanocomposites were examined. It was found that the nanocomposites exhibited strong photoabsorption in the entire near-infrared (NIR) region of 780–2500 nm and excellent photothermal conversion properties. This is because the particle size of WO3-x was greatly reduced by ball milling and they were well-dispersed in the polyurethane matrix. The higher concentration of oxygen vacancies in WO3-x contribute to the efficient absorption of NIR light and its conversion into thermal energy. In particular, WO2.72/PU nanocomposites showed strong NIR light absorption of ca. 92%, high photothermal conversion, and better thermal conductivity and absorptivity than other WO3/PU nanocomposites. Furthermore, when the nanocomposite with 7 wt % concentration of WO2.72 nanoparticles was irradiated with infrared light, the temperature of the nanocomposite increased rapidly and stabilized at 120 °C after 5 min. This temperature is 52 °C higher than that achieved by pure PU. These nanocomposites are suitable functional materials for solar collectors, smart coatings, and energy-saving applications. PMID:28737689

Thermal behaviors of Ni-MH batteries using a novel impedance spectroscopy

NASA Astrophysics Data System (ADS)

Xiao, Pu; Gao, Wenying; Qiu, Xinping; Zhu, Wentao; Sun, Jie; Chen, Liquan

In this paper, a novel impedance spectroscopy was used to describe the thermal behaviors of Ni-MH batteries. The impedance functions were derived similarly to electric impedance functions. The square of current was treated as a current equivalent and heat-flow as a voltage equivalent. The impedance spectra of batteries during charge showed that the combination of hydrogen and oxygen increased rapidly when charge rate was higher than 0.5 C. Thermal runaway might happen when battery was charged at temperature above 348 K even at a low charge rate. The cycling test showed that the charge efficiency of battery was the highest after cycling at high-rate for 10-100 cycles and decreased after more cycles. Different batteries showed different thermal behaviors which may be caused by the different structures of batteries.

Tuning conductivity in boron nanowire by edge geometry

NASA Astrophysics Data System (ADS)

Bhuyan, Prabal Dev; Gupta, Sanjeev K.; Sonvane, Yogesh; Gajjar, P. N.

2018-04-01

In present study, we have investigated electronic and temperature dependent transport properties of carbyne like linear chain and ribbon like zigzag structures of Boron (B) nanowire. The linear chain structure showed higher electric and thermal conductivity, as it is sp-hybridized, than its counterpart ribbon (R) structure. However the conductivity of ribbon structure increases with increases in width due to edge geometry effect. The ribbon (3R) structure showed high electric and thermal conductivity of 8.0×1019 1/Ω m s and 0.59×1015 W/ m K respectively. Interestingly we have observed that B linear chain showed higher thermal conductivity of 0.23×1015 W/ m K than its ribbon R and 2R structure above 600K. Because of high Seebeck co-efficient of boron chain and ribbon (R) structures at low temperature, they could find applications in thermoelectric sensors. Our results show that tuning conductivity property of boron nanowire could be of great interest in research for future electric connector in nanodevices.

The equivalence of minimum entropy production and maximum thermal efficiency in endoreversible heat engines.

PubMed

Haseli, Y

2016-05-01

The objective of this study is to investigate the thermal efficiency and power production of typical models of endoreversible heat engines at the regime of minimum entropy generation rate. The study considers the Curzon-Ahlborn engine, the Novikov's engine, and the Carnot vapor cycle. The operational regimes at maximum thermal efficiency, maximum power output and minimum entropy production rate are compared for each of these engines. The results reveal that in an endoreversible heat engine, a reduction in entropy production corresponds to an increase in thermal efficiency. The three criteria of minimum entropy production, the maximum thermal efficiency, and the maximum power may become equivalent at the condition of fixed heat input.

Novel Molten Salts Thermal Energy Storage for Concentrating Solar Power Generation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Reddy, Ramana G.

2013-10-23

The explicit UA program objective is to develop low melting point (LMP) molten salt thermal energy storage media with high thermal energy storage density for sensible heat storage systems. The novel Low Melting Point (LMP) molten salts are targeted to have the following characteristics: 1. Lower melting point (MP) compared to current salts (<222ºC) 2. Higher energy density compared to current salts (>300 MJ/m3) 3. Lower power generation cost compared to current salt In terms of lower power costs, the program target the DOE's Solar Energy Technologies Program year 2020 goal to create systems that have the potential to reducemore » the cost of Thermal Energy Storage (TES) to less than $15/kWh-th and achieve round trip efficiencies greater than 93%. The project has completed the experimental investigations to determine the thermo-physical, long term thermal stability properties of the LMP molten salts and also corrosion studies of stainless steel in the candidate LMP molten salts. Heat transfer and fluid dynamics modeling have been conducted to identify heat transfer geometry and relative costs for TES systems that would utilize the primary LMP molten salt candidates. The project also proposes heat transfer geometry with relevant modifications to suit the usage of our molten salts as thermal energy storage and heat transfer fluids. The essential properties of the down-selected novel LMP molten salts to be considered for thermal storage in solar energy applications were experimentally determined, including melting point, heat capacity, thermal stability, density, viscosity, thermal conductivity, vapor pressure, and corrosion resistance of SS 316. The thermodynamic modeling was conducted to determine potential high temperature stable molten salt mixtures that have thermal stability up to 1000 °C. The thermo-physical properties of select potential high temperature stable (HMP) molten salt mixtures were also experimentally determined. All the salt mixtures align with the go/no-go goals stipulated by the DOE for this project. Energy densities of all salt mixtures were higher than that of the current solar salt. The salt mixtures costs have been estimated and TES system costs for a 2 tank, direct approach have been estimated for each of these materials. All estimated costs are significantly below the baseline system that used solar salt. These lower melt point salts offer significantly higher energy density per volume than solar salt – and therefore attractively smaller inventory and equipment costs. Moreover, a new TES system geometry has been recommended A variety of approaches were evaluated to use the low melting point molten salt. Two novel changes are recommended that 1) use the salt as a HTF through the solar trough field, and 2) use the salt to not only create steam but also to preheat the condensed feedwater for Rankine cycle. The two changes enable the powerblock to operate at 500°C, rather than the current 400°C obtainable using oil as the HTF. Secondly, the use of salt to preheat the feedwater eliminates the need to extract steam from the low pressure turbine for that purpose. Together, these changes result in a dramatic 63% reduction required for 6 hour salt inventory, a 72% reduction in storage volume, and a 24% reduction in steam flow rate in the power block. Round trip efficiency for the Case 5 - 2 tank “direct” system is estimated at >97%, with only small losses from time under storage and heat exchange, and meeting RFP goals. This attractive efficiency is available because the major heat loss experienced in a 2 tank “indirect” system - losses by transferring the thermal energy from oil HTF to the salt storage material and back to oil to run the steam generator at night - is not present for the 2 tank direct system. The higher heat capacity values for both LMP and HMP systems enable larger storage capacities for concentrating solar power.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Zhi-jie; Dai, Le-yang; Yang, De-zheng

Highlights: • A novel and high efficiency synthesizing AlN powders method combining mechanical ball milling and DBDP has been developed. • The particle size, the crystallite size, the lattice distortion, the morphology of Al{sub 2}O{sub 3} powders, and the AlN conversion rate are investigated and compared under the ball milled Al{sub 2}O{sub 3} powders with DBDP and without DBDP. • The ball milled Al{sub 2}O{sub 3} powders with DBDP have small spherical structure morphology with very fine particles size and high specific surface area, which result in a higher chemical efficiency and a higher AlN conversion rate at lower thermalmore » temperature. - Abstract: In this paper, aluminum nitride (AlN) powers have been produced with a novel and high efficiency method by thermal annealing at 1100–1600 °C of alumina (Al{sub 2}O{sub 3}) powders which were previously ball milled for various time up to 40 h with and without the assistant of dielectric barrier discharge plasma (DBDP). The ball milled Al{sub 2}O{sub 3} powders with DBDP and without DBDP and the corresponding synthesized AlN powers are characterized by X-ray diffraction, scanning electron microscope, and transmission electron microscopy. From the characteristics of the ball milled Al{sub 2}O{sub 3} powders with DBDP and without DBDP, it can be seen that the ball milled Al{sub 2}O{sub 3} powders with DBDP have small spherical structure morphology with very fine particles size and high specific surface area, which result in a higher chemical efficiency and a higher AlN conversion rate at lower thermal temperature. Meanwhile, the synthesized AlN powders can be known as hexagonal AlN with fine crystal morphology and irregular lump-like structure, and have uniform distribution with the average particle size of about between 500 nm and 1000 nm. This provides an important method for fabricating ultra fine powders and synthesizing nitrogen compounds.« less

Prediction of the Thermal Conductivity of Refrigerants by Computational Methods and Artificial Neural Network.

PubMed

Ghaderi, Forouzan; Ghaderi, Amir H; Ghaderi, Noushin; Najafi, Bijan

2017-01-01

Background: The thermal conductivity of fluids can be calculated by several computational methods. However, these methods are reliable only at the confined levels of density, and there is no specific computational method for calculating thermal conductivity in the wide ranges of density. Methods: In this paper, two methods, an Artificial Neural Network (ANN) approach and a computational method established upon the Rainwater-Friend theory, were used to predict the value of thermal conductivity in all ranges of density. The thermal conductivity of six refrigerants, R12, R14, R32, R115, R143, and R152 was predicted by these methods and the effectiveness of models was specified and compared. Results: The results show that the computational method is a usable method for predicting thermal conductivity at low levels of density. However, the efficiency of this model is considerably reduced in the mid-range of density. It means that this model cannot be used at density levels which are higher than 6. On the other hand, the ANN approach is a reliable method for thermal conductivity prediction in all ranges of density. The best accuracy of ANN is achieved when the number of units is increased in the hidden layer. Conclusion: The results of the computational method indicate that the regular dependence between thermal conductivity and density at higher densities is eliminated. It can develop a nonlinear problem. Therefore, analytical approaches are not able to predict thermal conductivity in wide ranges of density. Instead, a nonlinear approach such as, ANN is a valuable method for this purpose.

Prediction of the Thermal Conductivity of Refrigerants by Computational Methods and Artificial Neural Network

PubMed Central

Ghaderi, Forouzan; Ghaderi, Amir H.; Ghaderi, Noushin; Najafi, Bijan

2017-01-01

Background: The thermal conductivity of fluids can be calculated by several computational methods. However, these methods are reliable only at the confined levels of density, and there is no specific computational method for calculating thermal conductivity in the wide ranges of density. Methods: In this paper, two methods, an Artificial Neural Network (ANN) approach and a computational method established upon the Rainwater-Friend theory, were used to predict the value of thermal conductivity in all ranges of density. The thermal conductivity of six refrigerants, R12, R14, R32, R115, R143, and R152 was predicted by these methods and the effectiveness of models was specified and compared. Results: The results show that the computational method is a usable method for predicting thermal conductivity at low levels of density. However, the efficiency of this model is considerably reduced in the mid-range of density. It means that this model cannot be used at density levels which are higher than 6. On the other hand, the ANN approach is a reliable method for thermal conductivity prediction in all ranges of density. The best accuracy of ANN is achieved when the number of units is increased in the hidden layer. Conclusion: The results of the computational method indicate that the regular dependence between thermal conductivity and density at higher densities is eliminated. It can develop a nonlinear problem. Therefore, analytical approaches are not able to predict thermal conductivity in wide ranges of density. Instead, a nonlinear approach such as, ANN is a valuable method for this purpose. PMID:29188217

Efficient Solar-Thermal Energy Harvest Driven by Interfacial Plasmonic Heating-Assisted Evaporation.

PubMed

Chang, Chao; Yang, Chao; Liu, Yanming; Tao, Peng; Song, Chengyi; Shang, Wen; Wu, Jianbo; Deng, Tao

2016-09-07

The plasmonic heating effect of noble nanoparticles has recently received tremendous attention for various important applications. Herein, we report the utilization of interfacial plasmonic heating-assisted evaporation for efficient and facile solar-thermal energy harvest. An airlaid paper-supported gold nanoparticle thin film was placed at the thermal energy conversion region within a sealed chamber to convert solar energy into thermal energy. The generated thermal energy instantly vaporizes the water underneath into hot vapors that quickly diffuse to the thermal energy release region of the chamber to condense into liquids and release the collected thermal energy. The condensed water automatically flows back to the thermal energy conversion region under the capillary force from the hydrophilic copper mesh. Such an approach simultaneously realizes efficient solar-to-thermal energy conversion and rapid transportation of converted thermal energy to target application terminals. Compared to conventional external photothermal conversion design, the solar-thermal harvesting device driven by the internal plasmonic heating effect has reduced the overall thermal resistance by more than 50% and has demonstrated more than 25% improvement of solar water heating efficiency.

Solution-processed MoS(x) as an efficient anode buffer layer in organic solar cells.

PubMed

Li, Xiaodong; Zhang, Wenjun; Wu, Yulei; Min, Chao; Fang, Junfeng

2013-09-25

We reported a facile solution-processed method to fabricate a MoSx anode buffer layer through thermal decomposition of (NH4)2MoS4. Organic solar cells (OSCs) based on in situ growth MoSx as the anode buffer layer showed impressive improvements, and the power conversion efficiency was higher than that of conventional PEDOT:PSS-based device. The MoSx films obtained at different temperatures and the corresponding device performance were systematically studied. The results indicated that both MoS3 and MoS2 were beneficial to the device performance. MoS3 could result in higher Voc, while MoS2 could lead to higher Jsc. Our results proved that, apart from MoO3, molybdenum sulfides and Mo(4+) were also promising candidates for the anode buffer materials in OSCs.

Reduction of CO2 to C1 products and fuel

USGS Publications Warehouse

Mill, T.; Ross, D.

2002-01-01

Photochemical semiconductor processes readily reduced CO2 to a broad range of C1 products. However the intrinsic and solar efficiencies for the processes were low. Improved quantum efficiencies could be realized utilizing quantum-sized particles, but at the expense of using less of the visible solar spectrum. Conversely, semiconductors with small bandgaps used more of the visible solar spectrum at the expense of quantum efficiency. Thermal reduction of CO2 with Fe(II) was thermodynamically favored for forming many kinds of organic compounds and occurred readily with olivine and other Fe(II) minerals above 200??C to form higher alkanes and alkenes. No added hydrogen was required.

Dimensionless figure of merit and its efficiency estimation for transient response of thermoelectric module based on impedance spectroscopy

NASA Astrophysics Data System (ADS)

Otsuka, Mioko; Hasegawa, Yasuhiro; Arisaka, Taichi; Shinozaki, Ryo; Morita, Hiroyuki

2017-11-01

The dimensionless figure of merit and its efficiency for the transient response of a Π-shaped thermoelectric module are estimated according to the theory of impedance spectroscopy. The effective dimensionless figure of merit is described as a function of the product of the characteristic time to reduce the temperature and the representative angular frequency of the module, which is expressed by the thermal diffusivity and the length of the elements used. The characteristic time required for achieving a higher dimensionless figure of merit and efficiency is derived quantitatively for the transient response using the properties of a commercial thermoelectric module.

Modeling Pumped Thermal Energy Storage with Waste Heat Harvesting

NASA Astrophysics Data System (ADS)

Abarr, Miles L. Lindsey

This work introduces a new concept for a utility scale combined energy storage and generation system. The proposed design utilizes a pumped thermal energy storage (PTES) system, which also utilizes waste heat leaving a natural gas peaker plant. This system creates a low cost utility-scale energy storage system by leveraging this dual-functionality. This dissertation first presents a review of previous work in PTES as well as the details of the proposed integrated bottoming and energy storage system. A time-domain system model was developed in Mathworks R2016a Simscape and Simulink software to analyze this system. Validation of both the fluid state model and the thermal energy storage model are provided. The experimental results showed the average error in cumulative fluid energy between simulation and measurement was +/- 0.3% per hour. Comparison to a Finite Element Analysis (FEA) model showed <1% error for bottoming mode heat transfer. The system model was used to conduct sensitivity analysis, baseline performance, and levelized cost of energy of a recently proposed Pumped Thermal Energy Storage and Bottoming System (Bot-PTES) that uses ammonia as the working fluid. This analysis focused on the effects of hot thermal storage utilization, system pressure, and evaporator/condenser size on the system performance. This work presents the estimated performance for a proposed baseline Bot-PTES. Results of this analysis showed that all selected parameters had significant effects on efficiency, with the evaporator/condenser size having the largest effect over the selected ranges. Results for the baseline case showed stand-alone energy storage efficiencies between 51 and 66% for varying power levels and charge states, and a stand-alone bottoming efficiency of 24%. The resulting efficiencies for this case were low compared to competing technologies; however, the dual-functionality of the Bot-PTES enables it to have higher capacity factor, leading to 91-197/MWh levelized cost of energy compared to 262-284/MWh for batteries and $172-254/MWh for Compressed Air Energy Storage.

A new phosphine oxide host based on ortho-disubstituted dibenzofuran for efficient electrophosphorescence: towards high triplet state excited levels and excellent thermal, morphological and efficiency stability.

PubMed

Han, Chunmiao; Xie, Guohua; Li, Jing; Zhang, Zhensong; Xu, Hui; Deng, Zhaopeng; Zhao, Yi; Yan, Pengfei; Liu, Shiyong

2011-08-01

An efficient host for blue and green electrophosphorescence, 4,6-bis(diphenylphosphoryl)dibenzofuran (o-DBFDPO), with the structure of a short-axis-substituted dibenzofuran was designed and synthesised. It appears that the greater density of the diphenylphosphine oxide (DPPO) moieties in the short-axis substitution configuration effectively restrains the intermolecular interactions, because only very weak π-π stacking interactions could be observed, with a centroid-to-centroid distance of 3.960 Å. The improved thermal stability of o-DBFDPO was corroborated by its very high glass transition temperature (T(g)) of 191 °C, which is the result of the symmetric disubstitution structure. Photophysical investigation showed o-DBFDPO to be superior to the monosubstituted derivative, with a longer lifetime (1.95 ns) and a higher photoluminescent quantum efficiency (61 %). The lower first singlet state excited level (3.63 eV) of o-DBFDPO demonstrates the stronger polarisation effect attributable to the greater number of DPPO moieties. Simultaneously, an extremely high first triplet state excited level (T(1)) of 3.16 eV is observed, demonstrating the tiny influence of short-axis substitution on T(1). The improved carrier injection ability, which contributed to low driving voltages of blue- and green-emitting phosphorescent organic light-emitting diodes (PHOLEDs), was further confirmed by Gaussian calculation. Furthermore, the better thermal and morphological properties of o-DBFDPO and the matched frontier molecular orbital (FMO) levels in the devices significantly reduced efficiency roll-offs. Efficient blue and green electrophosphorescence based on the o-DBFDPO host was demonstrated. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Pyrolytic graphite collector development program

NASA Technical Reports Server (NTRS)

Wilkins, W. J.

1982-01-01

Pyrolytic graphite promises to have significant advantages as a material for multistage depressed collector electrodes. Among these advantages are lighter weight, improved mechanical stiffness under shock and vibration, reduced secondary electron back-streaming for higher efficiency, and reduced outgassing at higher operating temperatures. The essential properties of pyrolytic graphite and the necessary design criteria are discussed. This includes the study of suitable electrode geometries and methods of attachment to other metal and ceramic collector components consistent with typical electrical, thermal, and mechanical requirements.

Humidifier for fuel cell using high conductivity carbon foam

DOEpatents

Klett, James W.; Stinton, David P.

2006-12-12

A method and apparatus of supplying humid air to a fuel cell is disclosed. The extremely high thermal conductivity of some graphite foams lends itself to enhance significantly the ability to humidify supply air for a fuel cell. By utilizing a high conductivity pitch-derived graphite foam, thermal conductivity being as high as 187 W/m.dot.K, the heat from the heat source is more efficiently transferred to the water for evaporation, thus the system does not cool significantly due to the evaporation of the water and, consequently, the air reaches a higher humidity ratio.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Davlin, Thomas

The overall deliverable from the project is the design, construction and commissioning of a detention facility heating and cooling system that minimizes ownership costs and maximizes efficiency (and therefore minimizes environmental impact). The primary deliverables were the proof of concept for the application of geothermal systems for an institutional facility and the ongoing, quarterly system operating data downloads to the Department of Energy . The primary advantage of geothermal based heat pump systems is the higher efficiency of the system compared to a conventional chiller, boiler, cooling tower based system. The higher efficiency results in a smaller environmental foot printmore » and lower energy costs for the detention facility owner, Lancaster County. The higher efficiency for building cooling is primarily due to a more constant compressor condensing temperature with the geothermal well field acting as a thermal “sink” (in place of the conventional system’s cooling tower). In the heating mode, Ground Couple Heat Pump (GCHP) systems benefits from the advantage of a heat pump Coefficient of Performance (COP) of approximately 3.6, significantly better than a conventional gas boiler. The geothermal well field acting as a thermal “source” allows the heat pumps to operate efficiently in the heating mode regardless of ambient temperatures. The well field is partially located in a wetland with a high water table so, over time, the project will be able to identify the thermal loading characteristics of a well field located in a high water table location. The project demonstrated how a large geothermal well field can be installed in a wetland area in an economical and environmentally sound manner. Finally, the SW 40th Street Thermal Energy Plant project demonstrates the benefits of providing domestic hot water energy, as well as space heating, to help balance well filed thermal loading in a cooling dominated application. During the period of August 2012 thru March 2014, with the detention facility occupied for the final seven months, the well field supply water temperatures to the heat pumps dropped to a minimum of 39°F and reached a maximum temperature of 68 °F while providing 15,819 MMBtu of cooling energy and 27,467 MMBtu of heating energy. During this period the peak recorded system cooling load was 610 tons and the peak heating load was 8.4 MMBtu. The DEC is currently evaluating the most beneficial electric rate for plant operations. Total project cost of $16.9 million was approximately $3.2 million less than the estimate provided in the grant application. The reduction in project costs were primarily due to favorable construction material prices as well as strong competition in the local construction contractor market. The DEC plant reached the substantial completion milestone in December 2011 and began providing thermal service to the detention facility in January 2012 when the building’s HVAC system was ready to accept heating service. The plant reached commercial operating status on August 1, 2012. However, due to construction delays, the detention facility was not occupied until September of 2013. The detention facility construction delays also impacted the installation and commissioning of the project’s dedicated domestic hot water heat pump. Final coordination with the detention facility’s building management system vendor to establish network links for the exchange of date is currently being completed. This will allow the development of control sequences for the optimal operation of the domestic hot water system.« less

Molecular engineered conjugated polymer with high thermal conductivity

PubMed Central

Song, Bai; Lee, Elizabeth M. Y.; Gleason, Karen K.

2018-01-01

Traditional polymers are both electrically and thermally insulating. The development of electrically conductive polymers has led to novel applications such as flexible displays, solar cells, and wearable biosensors. As in the case of electrically conductive polymers, the development of polymers with high thermal conductivity would open up a range of applications in next-generation electronic, optoelectronic, and energy devices. Current research has so far been limited to engineering polymers either by strong intramolecular interactions, which enable efficient phonon transport along the polymer chains, or by strong intermolecular interactions, which enable efficient phonon transport between the polymer chains. However, it has not been possible until now to engineer both interactions simultaneously. We report the first realization of high thermal conductivity in the thin film of a conjugated polymer, poly(3-hexylthiophene), via bottom-up oxidative chemical vapor deposition (oCVD), taking advantage of both strong C=C covalent bonding along the extended polymer chain and strong π-π stacking noncovalent interactions between chains. We confirm the presence of both types of interactions by systematic structural characterization, achieving a near–room temperature thermal conductivity of 2.2 W/m·K, which is 10 times higher than that of conventional polymers. With the solvent-free oCVD technique, it is now possible to grow polymer films conformally on a variety of substrates as lightweight, flexible heat conductors that are also electrically insulating and resistant to corrosion. PMID:29670943

Path integrals with higher order actions: Application to realistic chemical systems

NASA Astrophysics Data System (ADS)

Lindoy, Lachlan P.; Huang, Gavin S.; Jordan, Meredith J. T.

2018-02-01

Quantum thermodynamic parameters can be determined using path integral Monte Carlo (PIMC) simulations. These simulations, however, become computationally demanding as the quantum nature of the system increases, although their efficiency can be improved by using higher order approximations to the thermal density matrix, specifically the action. Here we compare the standard, primitive approximation to the action (PA) and three higher order approximations, the Takahashi-Imada action (TIA), the Suzuki-Chin action (SCA) and the Chin action (CA). The resulting PIMC methods are applied to two realistic potential energy surfaces, for H2O and HCN-HNC, both of which are spectroscopically accurate and contain three-body interactions. We further numerically optimise, for each potential, the SCA parameter and the two free parameters in the CA, obtaining more significant improvements in efficiency than seen previously in the literature. For both H2O and HCN-HNC, accounting for all required potential and force evaluations, the optimised CA formalism is approximately twice as efficient as the TIA formalism and approximately an order of magnitude more efficient than the PA. The optimised SCA formalism shows similar efficiency gains to the CA for HCN-HNC but has similar efficiency to the TIA for H2O at low temperature. In H2O and HCN-HNC systems, the optimal value of the a1 CA parameter is approximately 1/3 , corresponding to an equal weighting of all force terms in the thermal density matrix, and similar to previous studies, the optimal α parameter in the SCA was ˜0.31. Importantly, poor choice of parameter significantly degrades the performance of the SCA and CA methods. In particular, for the CA, setting a1 = 0 is not efficient: the reduction in convergence efficiency is not offset by the lower number of force evaluations. We also find that the harmonic approximation to the CA parameters, whilst providing a fourth order approximation to the action, is not optimal for these realistic potentials: numerical optimisation leads to better approximate cancellation of the fifth order terms, with deviation between the harmonic and numerically optimised parameters more marked in the more quantum H2O system. This suggests that numerically optimising the CA or SCA parameters, which can be done at high temperature, will be important in fully realising the efficiency gains of these formalisms for realistic potentials.

Thermal considerations in the cryogenic regime for the BNL double ridge higher order mode waveguide

DOE PAGES

Ravikumar, Dhananjay K.; Than, Yatming; Xu, Wencan; ...

2017-09-06

Brookhaven National Laboratory (BNL) has proposed to build an electron ion collider (EIC) as an upgrade to the existing Relativistic Heavy Ion Collider (RHIC). One part of the new design is to use superconducting radio frequency (SRF) cavities for acceleration, which sit in a bath of superfluid helium at a temperature of 2 K. SRF cavities designed for the BNL EIC create a standing electromagnetic wave, oscillating at a fundamental frequency of 647 MHz. Interaction of the charged particle beam with the EM field in the cavity creates higher order modes (HOM) of oscillation which have adverse effects on themore » beam when allowed to propagate down the beam tube. HOM waveguides are thus designed to remove this excess energy which is then damped at room temperature. Thus, these waveguides provide a direct thermal link between room temperature and the superconducting cavities adding a static thermal load. The EM wave propagating through the warmer sections of the waveguide creates an additional dynamic thermal load. This study calculates these thermal loads, concluding that the dynamic load is small in comparison to the static load. Temperature distributions are mapped on the waveguide and the number of heat intercepts required to efficiently manage thermal loads have been determined. Additonally, a thermal radiation study has been performed and it is found that this contribution is around three orders of magnitude smaller than the static conduction and dynamic loads.« less

Thermal considerations in the cryogenic regime for the BNL double ridge higher order mode waveguide

NASA Astrophysics Data System (ADS)

Ravikumar, Dhananjay K.; Than, Yatming; Xu, Wencan; Longtin, Jon

2017-09-01

Brookhaven National Laboratory (BNL) has proposed to build an electron ion collider (EIC) as an upgrade to the existing Relativistic Heavy Ion Collider (RHIC). A part of the new design is to use superconducting radio frequency (SRF) cavities for acceleration, which sit in a bath of superfluid helium at a temperature of 2 K. SRF cavities designed for the BNL EIC create a standing electromagnetic wave, oscillating at a fundamental frequency of 647 MHz. Interaction of the charged particle beam with the EM field in the cavity creates higher order modes (HOM) of oscillation which have adverse effects on the beam when allowed to propagate down the beam tube. HOM waveguides are thus designed to remove this excess energy which is then damped at room temperature. As a result, these waveguides provide a direct thermal link between room temperature and the superconducting cavities adding a static thermal load. The EM wave propagating through the warmer sections of the waveguide creates an additional dynamic thermal load. This study calculates these thermal loads, concluding that the dynamic load is small in comparison to the static load. Temperature distributions are mapped on the waveguide and the number of heat intercepts required to efficiently manage thermal loads have been determined. In addition, a thermal radiation study has been performed and it is found that this contribution is around three orders of magnitude smaller than the static conduction and dynamic loads.

Thermal considerations in the cryogenic regime for the BNL double ridge higher order mode waveguide

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ravikumar, Dhananjay K.; Than, Yatming; Xu, Wencan

Brookhaven National Laboratory (BNL) has proposed to build an electron ion collider (EIC) as an upgrade to the existing Relativistic Heavy Ion Collider (RHIC). One part of the new design is to use superconducting radio frequency (SRF) cavities for acceleration, which sit in a bath of superfluid helium at a temperature of 2 K. SRF cavities designed for the BNL EIC create a standing electromagnetic wave, oscillating at a fundamental frequency of 647 MHz. Interaction of the charged particle beam with the EM field in the cavity creates higher order modes (HOM) of oscillation which have adverse effects on themore » beam when allowed to propagate down the beam tube. HOM waveguides are thus designed to remove this excess energy which is then damped at room temperature. Thus, these waveguides provide a direct thermal link between room temperature and the superconducting cavities adding a static thermal load. The EM wave propagating through the warmer sections of the waveguide creates an additional dynamic thermal load. This study calculates these thermal loads, concluding that the dynamic load is small in comparison to the static load. Temperature distributions are mapped on the waveguide and the number of heat intercepts required to efficiently manage thermal loads have been determined. Additonally, a thermal radiation study has been performed and it is found that this contribution is around three orders of magnitude smaller than the static conduction and dynamic loads.« less

ICF target 2D modeling using Monte Carlo SNB electron thermal transport in DRACO

NASA Astrophysics Data System (ADS)

Chenhall, Jeffrey; Cao, Duc; Moses, Gregory

2016-10-01

The iSNB (implicit Schurtz Nicolai Busquet multigroup diffusion electron thermal transport method is adapted into a Monte Carlo (MC) transport method to better model angular and long mean free path non-local effects. The MC model was first implemented in the 1D LILAC code to verify consistency with the iSNB model. Implementation of the MC SNB model in the 2D DRACO code enables higher fidelity non-local thermal transport modeling in 2D implosions such as polar drive experiments on NIF. The final step is to optimize the MC model by hybridizing it with a MC version of the iSNB diffusion method. The hybrid method will combine the efficiency of a diffusion method in intermediate mean free path regions with the accuracy of a transport method in long mean free path regions allowing for improved computational efficiency while maintaining accuracy. Work to date on the method will be presented. This work was supported by Sandia National Laboratories and the Univ. of Rochester Laboratory for Laser Energetics.

Multi-sensor fusion of Landsat 8 thermal infrared (TIR) and panchromatic (PAN) images.

PubMed

Jung, Hyung-Sup; Park, Sung-Whan

2014-12-18

Data fusion is defined as the combination of data from multiple sensors such that the resulting information is better than would be possible when the sensors are used individually. The multi-sensor fusion of panchromatic (PAN) and thermal infrared (TIR) images is a good example of this data fusion. While a PAN image has higher spatial resolution, a TIR one has lower spatial resolution. In this study, we have proposed an efficient method to fuse Landsat 8 PAN and TIR images using an optimal scaling factor in order to control the trade-off between the spatial details and the thermal information. We have compared the fused images created from different scaling factors and then tested the performance of the proposed method at urban and rural test areas. The test results show that the proposed method merges the spatial resolution of PAN image and the temperature information of TIR image efficiently. The proposed method may be applied to detect lava flows of volcanic activity, radioactive exposure of nuclear power plants, and surface temperature change with respect to land-use change.

Review of Computational Stirling Analysis Methods

NASA Technical Reports Server (NTRS)

Dyson, Rodger W.; Wilson, Scott D.; Tew, Roy C.

2004-01-01

Nuclear thermal to electric power conversion carries the promise of longer duration missions and higher scientific data transmission rates back to Earth for both Mars rovers and deep space missions. A free-piston Stirling convertor is a candidate technology that is considered an efficient and reliable power conversion device for such purposes. While already very efficient, it is believed that better Stirling engines can be developed if the losses inherent its current designs could be better understood. However, they are difficult to instrument and so efforts are underway to simulate a complete Stirling engine numerically. This has only recently been attempted and a review of the methods leading up to and including such computational analysis is presented. And finally it is proposed that the quality and depth of Stirling loss understanding may be improved by utilizing the higher fidelity and efficiency of recently developed numerical methods. One such method, the Ultra HI-Fl technique is presented in detail.

Fuel Cell Auxiliary Power Study Volume 1: RASER Task Order 5

NASA Technical Reports Server (NTRS)

Mak, Audie; Meier, John

2007-01-01

This study evaluated the feasibility of a hybrid solid oxide fuel cell (SOFC) auxiliary power unit (APU) and the impact in a 90-passenger More-Electric Regional Jet application. The study established realistic hybrid SOFC APU system weight and system efficiencies, and evaluated the impact on the aircraft total weight, fuel burn, and emissions from the main engine and the APU during cruise, landing and take-off (LTO) cycle, and at the gate. Although the SOFC APU may be heavier than the current conventional APU, its weight disadvantage can be offset by fuel savings in the higher SOFC APU system efficiencies against the main engine bleed and extraction during cruise. The higher SOFC APU system efficiency compared to the conventional APU on the ground can also provide considerable fuel saving and emissions reduction, particularly at the gate, but is limited by the fuel cell stack thermal fatigue characteristic.

Recycled Thermal Energy from High Power Light Emitting Diode Light Source.

PubMed

Ji, Jae-Hoon; Jo, GaeHun; Ha, Jae-Geun; Koo, Sang-Mo; Kamiko, Masao; Hong, JunHee; Koh, Jung-Hyuk

2018-09-01

In this research, the recycled electrical energy from wasted thermal energy in high power Light Emitting Diode (LED) system will be investigated. The luminous efficiency of lights has been improved in recent years by employing the high power LED system, therefore energy efficiency was improved compared with that of typical lighting sources. To increase energy efficiency of high power LED system further, wasted thermal energy should be re-considered. Therefore, wasted thermal energy was collected and re-used them as electrical energy. The increased electrical efficiency of high power LED devices was accomplished by considering the recycled heat energy, which is wasted thermal energy from the LED. In this work, increased electrical efficiency will be considered and investigated by employing the high power LED system, which has high thermal loss during the operating time. For this research, well designed thermoelement with heat radiation system was employed to enhance the collecting thermal energy from the LED system, and then convert it as recycled electrical energy.

Ultrahigh lattice thermal conductivity in topological semimetal TaN caused by a large acoustic-optical gap.

PubMed

Guo, San-Dong; Liu, Bang-Gui

2018-03-14

Topological semimetals may have potential applications such as in topological qubits, spintronics and quantum computations. Efficient heat dissipation is a key factor for the reliability and stability of topological semimetal-based nano-electronics devices, which is closely related to high thermal conductivity. In this work, the elastic properties and lattice thermal conductivity of TaN are investigated using first-principles calculations and the linearized phonon Boltzmann equation within the single-mode relaxation time approximation. According to the calculated bulk modulus, shear modulus and C 44 , TaN can be regarded as a potential incompressible and hard material. The room-temperature lattice thermal conductivity is predicted to be 838.62 [Formula: see text] along the a axis and 1080.40 [Formula: see text] along the c axis, showing very strong anisotropy. It is found that the lattice thermal conductivity of TaN is several tens of times higher than other topological semimetals, such as TaAs, MoP and ZrTe, which is due to the very longer phonon lifetimes for TaN than other topological semimetals. The very different atomic masses of Ta and N atoms lead to a very large acoustic-optical band gap, and then prohibit the scattering between acoustic and optical phonon modes, which gives rise to very long phonon lifetimes. Calculated results show that isotope scattering has little effect on lattice thermal conductivity, and that phonons with mean free paths larger than 20 (80) [Formula: see text] along the c direction at 300 K have little contribution to the total lattice thermal conductivity. This work implies that TaN-based nano-electronics devices may be more stable and reliable due to efficient heat dissipation, and motivates further experimental works to study lattice thermal conductivity of TaN.

Ultrahigh lattice thermal conductivity in topological semimetal TaN caused by a large acoustic-optical gap

NASA Astrophysics Data System (ADS)

Guo, San-Dong; Liu, Bang-Gui

2018-03-01

Topological semimetals may have potential applications such as in topological qubits, spintronics and quantum computations. Efficient heat dissipation is a key factor for the reliability and stability of topological semimetal-based nano-electronics devices, which is closely related to high thermal conductivity. In this work, the elastic properties and lattice thermal conductivity of TaN are investigated using first-principles calculations and the linearized phonon Boltzmann equation within the single-mode relaxation time approximation. According to the calculated bulk modulus, shear modulus and C 44, TaN can be regarded as a potential incompressible and hard material. The room-temperature lattice thermal conductivity is predicted to be 838.62 W~m-1~K^{-1} along the a axis and 1080.40 W~m-1~K^{-1} along the c axis, showing very strong anisotropy. It is found that the lattice thermal conductivity of TaN is several tens of times higher than other topological semimetals, such as TaAs, MoP and ZrTe, which is due to the very longer phonon lifetimes for TaN than other topological semimetals. The very different atomic masses of Ta and N atoms lead to a very large acoustic-optical band gap, and then prohibit the scattering between acoustic and optical phonon modes, which gives rise to very long phonon lifetimes. Calculated results show that isotope scattering has little effect on lattice thermal conductivity, and that phonons with mean free paths larger than 20 (80) μm along the c direction at 300 K have little contribution to the total lattice thermal conductivity. This work implies that TaN-based nano-electronics devices may be more stable and reliable due to efficient heat dissipation, and motivates further experimental works to study lattice thermal conductivity of TaN.

885-nm laser diode array pumped ceramic Nd:YAG master oscillator power amplifier system

NASA Astrophysics Data System (ADS)

Yu, Anthony W.; Li, Steven X.; Stephen, Mark A.; Seas, Antonios; Troupaki, Elisavet; Vasilyev, Aleksey; Conley, Heather; Filemyr, Tim; Kirchner, Cynthia; Rosanova, Alberto

2010-04-01

The objective of this effort is to develop more reliable, higher efficiency diode pumped Nd:YAG laser systems for space applications by leveraging technology investments from the DoD and other commercial industries. Our goal is to design, build, test and demonstrate the effectiveness of combining 885 nm laser pump diodes and the use of ceramic Nd:YAG for future flight missions. The significant reduction in thermal loading on the gain medium by the use of 885 nm pump lasers will improve system efficiency.

Thermal management and design for optical refrigeration

NASA Astrophysics Data System (ADS)

Symonds, G.; Farfan, B. G.; Ghasemkhani, M. R.; Albrecht, A. R.; Sheik-Bahae, M.; Epstein, R. I.

2016-03-01

We present our recent work in developing a robust and versatile optical refrigerator. This work focuses on minimizing parasitic energy losses through efficient design and material optimization. The cooler's thermal linkage system and housing are studied using thermal analysis software to minimize thermal gradients through the device. Due to the extreme temperature differences within the device, material selection and characterization are key to constructing an efficient device. We describe the design constraints and material selections necessary for thermally efficient and durable optical refrigeration.

Hierarchical Graphene Foam for Efficient Omnidirectional Solar-Thermal Energy Conversion.

PubMed

Ren, Huaying; Tang, Miao; Guan, Baolu; Wang, Kexin; Yang, Jiawei; Wang, Feifan; Wang, Mingzhan; Shan, Jingyuan; Chen, Zhaolong; Wei, Di; Peng, Hailin; Liu, Zhongfan

2017-10-01

Efficient solar-thermal energy conversion is essential for the harvesting and transformation of abundant solar energy, leading to the exploration and design of efficient solar-thermal materials. Carbon-based materials, especially graphene, have the advantages of broadband absorption and excellent photothermal properties, and hold promise for solar-thermal energy conversion. However, to date, graphene-based solar-thermal materials with superior omnidirectional light harvesting performances remain elusive. Herein, hierarchical graphene foam (h-G foam) with continuous porosity grown via plasma-enhanced chemical vapor deposition is reported, showing dramatic enhancement of broadband and omnidirectional absorption of sunlight, which thereby can enable a considerable elevation of temperature. Used as a heating material, the external solar-thermal energy conversion efficiency of the h-G foam impressively reaches up to ≈93.4%, and the solar-vapor conversion efficiency exceeds 90% for seawater desalination with high endurance. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Ultrasonic and Thermal Pretreatments on Anaerobic Digestion of Petrochemical Sludge: Dewaterability and Degradation of PAHs

PubMed Central

Zhou, Jun; Xu, Weizhong; Wong, Jonathan W. C.; Yong, Xiaoyu; Yan, Binghua; Zhang, Xueying; Jia, Honghua

2015-01-01

Effects of different pretreatment methods on sludge dewaterability and polycyclic aromatic hydrocarbons (PAHs) degradation during petrochemical sludge anaerobic digestion were studied. Results showed that the total biogas production volume in the thermal pretreatment system was 4 and 5 times higher than that in the ultrasound pretreatment and in the control system, and the corresponding volatile solid removal efficiencies reached 28%, 15%, and 8%. Phenanthrene, paranaphthalene, fluoranthene, benzofluoranthene, and benzopyrene removal rates reached 43.3%, 55.5%, 30.6%, 42.9%, and 41.7%, respectively, in the thermal pretreatment system, which were much higher than those in the ultrasound pretreatment and in the control system. Moreover, capillary suction time (CST) of sludge increased after pretreatment, and then reduced after 20 days of anaerobic digestion, indicating that sludge dewaterability was greatly improved after anaerobic digestion. The decrease of protein and polysaccharide in the sludge could improve sludge dewaterability during petrochemical sludge anaerobic digestion. This study suggested that thermal pretreatment might be a promising enhancement method for petrochemical sludge solubilization, thus contributing to degradation of the PAHs, biogas production, and improvement of dewaterability during petrochemical sludge anaerobic digestion. PMID:26327510

Core-Sheath Paraffin-Wax-Loaded Nanofibers by Electrospinning for Heat Storage.

PubMed

Lu, Yuan; Xiao, Xiudi; Zhan, Yongjun; Huan, Changmeng; Qi, Shuai; Cheng, Haoliang; Xu, Gang

2018-04-18

Paraffin wax (PW) is widely used for smart thermoregulation materials due to its good thermal performance. However, the leakage and low thermal conductivity of PW hinder its application in the heat storage field. Accordingly, developing effective methods to address these issues is of great importance. In this study, we explored a facile approach to obtain PW-loaded core-sheath structured flexible nanofibers films via coaxial electrospinning technique. The PW as the core layer was successfully encapsulated by the sheath-layer poly(methyl methacrylate). The diameter of the fiber core increased from 395 to 848 nm as the core solution speed rate increased from 0.1 to 0.5 mL/h. In addition, it can be seen that higher core solution speed rate could lead to higher PW encapsulation efficiency according to the transmission electron microscopy results. The core-sheath nanofiber films, moreover, possessed the highest latent heat of 58.25 J/g and solidifying enthalpy of -56.49 J/g. In addition, we found that after 200 thermal cycles, there was little change in latent heat, which demonstrated that it is beneficial for the PW-loaded core-sheath structure to overcome the leakage issue and enhance thermal stability properties for the thermoregulation film.

Theoretical Analysis of Two Novel Hybrid Thermoelectric-Photovoltaic Systems Based on Cu₂ZnSnS₄ Solar Cells.

PubMed

Lorenzi, Bruno; Contento, Gaetano; Sabatelli, Vincenzo; Rizzo, Antonella; Narducci, Dario

2017-03-01

The development and commercialization of Photovoltaic (PV) cells with good cost-efficiency trade-off not using critical raw materials (CRMs) is one of the strategies chosen by the European Community (EC) to address the Energy Roadmap 2050. In this context Cu2ZnSnS4 (CZTS) solar cells are attracting a major interest since they have the potential to combine low price with relatively high conversion efficiencies. Although a ≈9% lab scale efficiency has already been reported for CZTS this technology is still far from being competitive in terms of cost per peak-power (€/Wp) with other common materials. One possible near-future solution to increase the CZTS competiveness comes from thermoelectrics. Actually it has already been shown that Hybrid Thermoelectric-Photovoltaic Systems (HTEPVs) based on CIGS, another kesterite very similar to CZTS, can lead to a significant efficiency improvement. However it has been also clarified how the optimal hybridization strategy cannot come from the simple coupling of solar cells with commercial TEGs, but special layouts have to be implemented. Furthermore, since solar cell performances are well known to decrease with temperature, thermal decoupling strategies of the PV and TEG sections have to be taken. To address these issues, we developed a model for two different HTEPV solutions, both coupled with CZTS solar cells. In the first case we considered a Thermally-Coupled HTEPV device (TC-HTEPV) in which the TEG is placed underneath the solar cell and in thermal contact with it. The second system consists instead of an Optically-Coupled but thermally decoupled device (OC-HTEPV) in which part of the solar spectrum is focused by a non-imaging optical concentrator on the TEG hot side. For both solutions the model returns conversion efficiencies higher than that of the CZTS solar cell alone. Specifically, increases of ≈30% are predicted for both kind of systems considered.

Advanced Natural Gas Reciprocating Engines(s)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zurlo, James

The ARES program was initiated in 2001 to improve the overall brake thermal efficiency of stationary, natural gas, reciprocating engines. The ARES program is a joint award that is shared by Dresser, Inc., Caterpillar and Cummins. The ARES program was divided into three phases; ARES I (achieve 44% BTE), ARES II (achieve 47% BTE) and ARES III (achieve 50% BTE). Dresser, Inc. completed ARES I in March 2005 which resulted in the commercialization of the APG1000 product line. ARES II activities were completed in September 2010 and the technology developed is currently being integrated into products. ARES III activities beganmore » in October 2010. The ARES program goal is to improve the efficiency of natural gas reciprocating engines. The ARES project is structured in three phases with higher efficiency goals in each phase. The ARES objectives are as follows: 1. Achieve 44% (ARES I), 47% (ARES II), and 50% brake thermal efficiency (BTE) as a final ARES III objective 2. Achieve 0.1 g/bhp-hr NOx emissions (with after-treatment) 3. Reduce the cost of the produced electricity by 10% 4. Improve or maintain reliability, durability and maintenance costs« less

The effect of travel speed on thermal response in CO2 laser welding of small electronic components

NASA Astrophysics Data System (ADS)

Gianoulakis, S. E.; Burchett, S. N.; Fuerschbach, P. W.; Knorovsky, G. A.

A comprehensive three-dimensional numerical investigation of the effect of beat source travel speed on temperatures and resulting thermal stresses was performed for CO2-laser welding. The test specimen was a small thermal battery header containing several stress-sensitive glass-to-metal seals surrounding the electrical connections and a temperature sensitive ignitor located under the header near the center. Predictions of the thermal stresses and temperatures in the battery header were made for several travel speeds of the laser. The travel speeds examined ranged from 10mm/sec to 50mm/sec. The results indicate that faster weld speeds result in lower temperatures and stresses for the same size weld. This is because the higher speed welds are more efficient, requiring less energy to produce a given weld. Less energy absorbed by the workpiece results in lower temperatures, which results in lower stresses.

Non-thermal dielectric barrier discharge plasma induces angiogenesis through reactive oxygen species.

PubMed

Arjunan, Krishna P; Clyne, Alisa Morss

2011-01-01

Vascularization plays a key role in processes such as wound healing and tissue engineering. Non-thermal plasma, which primarily produces reactive oxygen species (ROS), recently emerged as an efficient tool in medical applications. Liquids and endothelial cells were treated with a non-thermal dielectric barrier discharge plasma. Plasma treatment of phosphate buffered saline (PBS) and serum-free medium increased ROS concentration in a dose-dependent manner, with a higher concentration in serum-free medium. ROS concentration in cells peaked 1 hour after treatment. 4.2 J/cm(2) increased cell proliferation, 2D and 3D migration, as well as tube formation. A fibroblast growth factor-2 (FGF-2) neutralizing antibody and ROS scavengers for hydrogen peroxide and hydroxyl radicals abrogated these angiogenic effects. Non-thermal plasma may be a potential tool for applying ROS in precise doses to enhance vascularization.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Miller, L. B.; Donohoe, S. P.; Jones, M. H.

This article reports on the testing and comparison of a prototype hydrogen fuel cell light tower (H2LT) and a conventional diesel-powered metal halide light trailer for use in road maintenance and construction activities. The prototype was originally outfitted with plasma lights and then with light-emitting diode (LED) luminaires. Light output and distribution, lighting energy efficiency (i.e., efficacy), power source thermal efficiency, and fuel costs are compared. The metal halide luminaires have 2.2 and 3.1 times more light output than the plasma and LED luminaires, respectively, but they require more power/lumen to provide that output. The LED luminaires have 1.6 timesmore » better light efficacy than either the metal halide or plasma luminaires. The light uniformity ratios produced by the plasma and LED towers are acceptable. The fuel cell thermal efficiency at the power required to operate the plasma lights is 48%, significantly higher than the diesel generator efficiency of 23% when operating the metal halide lights. Due to the increased efficiency of the fuel cell and the LED lighting, the fuel cost per lumen-hour of the H2LT is 62% of the metal halide diesel light tower assuming a kilogram of hydrogen is twice the cost of a gallon of diesel fuel.« less

10 CFR 429.43 - Commercial heating, ventilating, air conditioning (HVAC) equipment.

Code of Federal Regulations, 2012 CFR

2012-01-01

... seasonal energy efficiency ratio (SEER in British thermal units per Watt-hour (Btu/Wh)), the heating...) Package terminal air conditioners: The energy efficiency ratio (EER in British thermal units per Watt-hour... package vertical air conditioner: The energy efficiency ratio (EER in British thermal units per Watt-hour...

10 CFR 429.43 - Commercial heating, ventilating, air conditioning (HVAC) equipment.

Code of Federal Regulations, 2013 CFR

2013-01-01

... seasonal energy efficiency ratio (SEER in British thermal units per Watt-hour (Btu/Wh)), the heating...) Package terminal air conditioners: The energy efficiency ratio (EER in British thermal units per Watt-hour... package vertical air conditioner: The energy efficiency ratio (EER in British thermal units per Watt-hour...

High-power, continuous-wave, second-harmonic generation at 532 nm in periodically poled KTiOPO(4).

PubMed

Samanta, G K; Kumar, S Chaitanya; Mathew, M; Canalias, C; Pasiskevicius, V; Laurell, F; Ebrahim-Zadeh, M

2008-12-15

We report efficient generation of high-power, cw, single-frequency radiation in the green in a simple, compact configuration based on single-pass, second-harmonic generation of a cw ytterbium fiber laser at 1064 nm in periodically poled KTiOPO(4). Using a crystal containing a 17 mm single grating with period of 9.01 microm, we generate 6.2 W of cw radiation at 532 nm for a fundamental power of 29.75 W at a single-pass conversion efficiency of 20.8%. Over the entire range of pump powers, the generated green output is single frequency with a linewidth of 8.5 MHz and has a TEM(00) spatial profile with M(2)<1.34. The demonstrated green power can be further improved by proper thermal management of crystal heating effects at higher pump powers and also by optimized design of the grating period to include thermal issues.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ghosh, B.B.

The object of the study reported in this paper was to investigate the possibility of using the blend of kerosene with petrol in a gasoline engines, without much losses in performance. The authors carried out experiments on a four-stroke cycle Briggs and Stratton S. I. Engine using five blends of kerosene with petrol at a compression ratios 5.3 and 7.47 to 1 with and without surge chambers, at a constant engine speed of 1500 rev/min with the following conclusions: 1. At part-load and the lower compression ratio the brake thermal efficiency is improved with percentage increase of kerosene but atmore » the higher compression ratio it is improved only upto 50% kerosene blend with petrol. 2. The knock-free maximum bhp is reduced with (a) the percentage increase of kerosene, (b) the increase of compression ratio. 3. Use of a surge chamber increase the knock-free maximum bhp, and reduces the brake thermal efficiency.« less

Binary PVA bio-nanocomposites containing cellulose nanocrystals extracted from different natural sources: part I.

PubMed

Fortunati, E; Puglia, D; Luzi, F; Santulli, C; Kenny, J M; Torre, L

2013-09-12

PVA bio-nanocomposites reinforced with cellulose nanocrystals (CNC) extracted from commercial microcrystalline cellulose (MCC) and from two types of natural fibres, Phormium tenax and Flax of the Belinka variety, were produced by solvent casting in water. Morphological, thermal, mechanical and transparency properties were studied while the respective efficiency of the extraction process of CNC from the three sources was evaluated. The effect of CNC types and content on PVA properties and water absorption capacity were also evaluated. Natural fibres offered higher levels of extraction efficiency when compared with MCC hydrolysis yield. Thermal analysis proved that CNC promotes the crystallization of the PVA matrix, while improving its plastic response. It was also clarified that all PVA/CNC systems remain transparent due to CNC dispersion at the nanoscale, while being all saturated after the first 18-24h of water absorption. Copyright © 2013 Elsevier Ltd. All rights reserved.

Geographic variation and acclimation effects on thermoregulation behavior in the widespread lizard Liolaemus pictus.

PubMed

Artacho, Paulina; Saravia, Julia; Perret, Samuel; Bartheld, José Luis; Le Galliard, Jean-François

2017-01-01

Populations at the warm range margins of the species distribution may be at the greatest risks of extinction from global warming unless they can tolerate extreme environmental conditions. Yet, some studies suggest that the thermal behavior of some lizard species is evolutionarily rigid. During two successive years, we compared the thermal biology of two populations of Liolaemus pictus living at the northern (warmer) and one population living at the southern (colder) range limits, thus spanning an 800km latitudinal distance. Populations at the two range margins belong to two deeply divergent evolutionary clades. We quantified field body temperatures (T b ), laboratory preferred body temperatures (PBT), and used operative temperature data (T e ) to calculate the effectiveness of thermoregulation (E). During one year in all populations, we further exposed half of the lizards to a cold or a hot acclimation treatment to test for plasticity in the thermal behavior. The environment at the southern range limit was characterized by cooler weather and lower T e . Despite that, females had higher T b and both males and females had higher PBT in the southernmost population (or clade) than in the northernmost populations. Acclimation to cold conditions led to higher PBT in all populations suggesting that plastic responses to thermal conditions, instead of evolutionary history, may contribute to geographic variation. Lizards regulated moderately well their body temperature (E≈0.7): they avoided warm microhabitats in the northern range but capitalized on warm microhabitats in the southern range. We review literature data to show that Liolaemus species increase their thermoregulation efficiency in thermally challenging environments. Altogether, this indicates that habitats of low thermal quality generally select against thermoconformity in these lizards. Copyright © 2016 Elsevier Ltd. All rights reserved.

5-HMF and carbohydrates content in stingless bee honey by CE before and after thermal treatment.

PubMed

Biluca, Fabíola C; Della Betta, Fabiana; de Oliveira, Gabriela Pirassol; Pereira, Lais Morilla; Gonzaga, Luciano Valdemiro; Costa, Ana Carolina Oliveira; Fett, Roseane

2014-09-15

This study aimed to assess 5-hydroximethylfurfural and carbohydrates (fructose, glucose, and sucrose) in 13 stingless bee honey samples before and after thermal treatment using a capillary electrophoresis method. The methods were validated for the parameters of linearity, matrix effects, precision, and accuracy. A factorial design was implemented to determine optimal thermal treatment conditions and then verify the postprocedural 5-HMF formation, but once 5-HMF were

Metal-wool heat shields for space shuttle. [design, fabrication, and attachment to structure

NASA Technical Reports Server (NTRS)

Miller, R. C.; Clure, J. L.

1974-01-01

The packaging of metal wool for reusable thermal heat shields applied to aerodynamic and other surfaces for the space shuttle was analyzed and designed, and samples were fabricated and experimentally studied. Parametric trends were prepared for selected configurations. An all-metal thermally efficient, reliable, reusable and producible heat shield system was designed and structurally tested for use on spacecraft aerodynamic surfaces where temperatures do not exceed 810 K. Stainless steel sheet, primarily for structure and secondarily in the transverse plane for thermal expansion, was shown to accommodate thermal expansion in all directions when restrained at the edges and heated to 1360 K. Aerodynamic loads of 0.35 x 1000,000 newtons/sq meter, and higher, may be easily accepted by structures of this design. Seven all-metal thermal protection specimens, 12.7 cm square and 2.5 cm thick were fabricated and are being experimentally evaluated at simulated shuttle entry conditions in an arc jet facility.

Efficient Reformulation of HOTFGM: Heat Conduction with Variable Thermal Conductivity

NASA Technical Reports Server (NTRS)

Zhong, Yi; Pindera, Marek-Jerzy; Arnold, Steven M. (Technical Monitor)

2002-01-01

Functionally graded materials (FGMs) have become one of the major research topics in the mechanics of materials community during the past fifteen years. FGMs are heterogeneous materials, characterized by spatially variable microstructure, and thus spatially variable macroscopic properties, introduced to enhance material or structural performance. The spatially variable material properties make FGMs challenging to analyze. The review of the various techniques employed to analyze the thermodynamical response of FGMs reveals two distinct and fundamentally different computational strategies, called uncoupled macromechanical and coupled micromechanical approaches by some investigators. The uncoupled macromechanical approaches ignore the effect of microstructural gradation by employing specific spatial variations of material properties, which are either assumed or obtained by local homogenization, thereby resulting in erroneous results under certain circumstances. In contrast, the coupled approaches explicitly account for the micro-macrostructural interaction, albeit at a significantly higher computational cost. The higher-order theory for functionally graded materials (HOTFGM) developed by Aboudi et al. is representative of the coupled approach. However, despite its demonstrated utility in applications where micro-macrostructural coupling effects are important, the theory's full potential is yet to be realized because the original formulation of HOTFGM is computationally intensive. This, in turn, limits the size of problems that can be solved due to the large number of equations required to mimic realistic material microstructures. Therefore, a basis for an efficient reformulation of HOTFGM, referred to as user-friendly formulation, is developed herein, and subsequently employed in the construction of the efficient reformulation using the local/global conductivity matrix approach. In order to extend HOTFGM's range of applicability, spatially variable thermal conductivity capability at the local level is incorporated into the efficient reformulation. Analytical solutions to validate both the user-friendly and efficient reformulations am also developed. Volume discretization sensitivity and validation studies, as well as a practical application of the developed efficient reformulation are subsequently carried out. The presented results illustrate the accuracy and implementability of both the user-friendly formulation and the efficient reformulation of HOTFGM.

Controllable Thermal Rectification Realized in Binary Phase Change Composites

PubMed Central

Chen, Renjie; Cui, Yalong; Tian, He; Yao, Ruimin; Liu, Zhenpu; Shu, Yi; Li, Cheng; Yang, Yi; Ren, Tianling; Zhang, Gang; Zou, Ruqiang

2015-01-01

Phase transition is a natural phenomenon happened around our daily life, represented by the process from ice to water. While melting and solidifying at a certain temperature, a high heat of fusion is accompanied, classified as the latent heat. Phase change material (PCM) has been widely applied to store and release large amount of energy attributed to the distinctive thermal behavior. Here, with the help of nanoporous materials, we introduce a general strategy to achieve the binary eicosane/PEG4000 stuffed reduced graphene oxide aerogels, which has two ends with different melting points. It's successfully demonstrated this binary PCM composites exhibits thermal rectification characteristic. Partial phase transitions within porous networks instantaneously result in one end of the thermal conductivity saltation at a critical temperature, and therefore switch on or off the thermal rectification with the coefficient up to 1.23. This value can be further raised by adjusting the loading content of PCM. The uniqueness of this device lies in its performance as a normal thermal conductor at low temperature, only exhibiting rectification phenomenon when temperature is higher than a critical value. The stated technology has broad applications for thermal energy control in macroscopic scale such as energy-efficiency building or nanodevice thermal management. PMID:25748640

Controllable Thermal Rectification Realized in Binary Phase Change Composites

NASA Astrophysics Data System (ADS)

Chen, Renjie; Cui, Yalong; Tian, He; Yao, Ruimin; Liu, Zhenpu; Shu, Yi; Li, Cheng; Yang, Yi; Ren, Tianling; Zhang, Gang; Zou, Ruqiang

2015-03-01

Phase transition is a natural phenomenon happened around our daily life, represented by the process from ice to water. While melting and solidifying at a certain temperature, a high heat of fusion is accompanied, classified as the latent heat. Phase change material (PCM) has been widely applied to store and release large amount of energy attributed to the distinctive thermal behavior. Here, with the help of nanoporous materials, we introduce a general strategy to achieve the binary eicosane/PEG4000 stuffed reduced graphene oxide aerogels, which has two ends with different melting points. It's successfully demonstrated this binary PCM composites exhibits thermal rectification characteristic. Partial phase transitions within porous networks instantaneously result in one end of the thermal conductivity saltation at a critical temperature, and therefore switch on or off the thermal rectification with the coefficient up to 1.23. This value can be further raised by adjusting the loading content of PCM. The uniqueness of this device lies in its performance as a normal thermal conductor at low temperature, only exhibiting rectification phenomenon when temperature is higher than a critical value. The stated technology has broad applications for thermal energy control in macroscopic scale such as energy-efficiency building or nanodevice thermal management.

Ejector gas cooling. Phase 1. Final report, 1 April 1987-30 April 1988

DOE Office of Scientific and Technical Information (OSTI.GOV)

MacCracken, C.D.; Silvetti, B.M.; Hrbek, R.

1988-11-01

Closed-circuit ejector cooling systems have never in the past achieved acceptable operating efficiencies in their vapor-compression cycle using standard refrigerants. Despite their long history, relative simplicity, quietness, rugged design, low maintenance and low cost, they could not compete with electric-motor-driven compressors. Phase I is an assessment of two immiscible fluids in an ejector cooling system with different latent heat capacity and molecular weights intended to require less heat in the boiler producing the propellant and taking more heat out in the evaporator cooling fluid. Actual tests corrected to standard conditions and neglecting thermal losses showed 0.5 closed-cycle thermal COP (excludingmore » stack losses), higher than ever previously achieved but below original expectations. Computer programs developed indicate higher COP values are attainable along with competitive first costs.« less

Department of Defense Space Science and Technology Strategy 2015

DTIC Science & Technology

2015-01-01

solar cells at 34% efficiency enabling higher power spacecraft capability. These solar cells developed by the Air Force Research Laboratory (AFRL...Reduce size, weight, power , cost, and improve thermal management for SATCOM terminals  Support intelligence surveillance and reconnaissance (ISR...Improve understanding and awareness of the Earth-to-Sun environment  Improve space environment forecast capabilities and tools to predict operational

Design and evaluation of a high temperature/pressure supercritical carbon dioxide direct tubular receiver for concentrating solar power applications

NASA Astrophysics Data System (ADS)

Ortega, Jesus Daniel

This work focuses on the development of a solar power thermal receiver for a supercritical-carbon dioxide (sCO2), Brayton power-cycle to produce ~1 MWe. Closed-loop sCO2 Brayton cycles are being evaluated in combination with concentrating solar power to provide higher thermal-to-electric conversion efficiencies relative to conventional steam Rankine cycles. High temperatures (923--973 K) and pressures (20--25 MPa) are required in the solar receiver to achieve thermal efficiencies of ~50%, making concentrating solar power (CSP) technologies a competitive alternative to current power generation methods. In this study, the CSP receiver is required to achieve an outlet temperature of 923 K at 25 MPa or 973 K at 20 MPa to meet the operating needs. To obtain compatible receiver tube material, an extensive material review was performed based the ASME Boiler and Pressure Vessel Code, ASME B31.1 and ASME B313.3 codes respectively. Subsequently, a thermal-structural model was developed using a commercial computational fluid (CFD) dynamics and structural mechanics software for designing and analyzing the tubular receiver that could provide the heat input for a ~2 MWth plant. These results were used to perform an analytical cumulative damage creep-fatigue analysis to estimate the work-life of the tubes. In sequence, an optical-thermal-fluid model was developed to evaluate the resulting thermal efficiency of the tubular receiver from the NSTTF heliostat field. The ray-tracing tool SolTrace was used to obtain the heat-flux distribution on the surfaces of the receiver. The K-ω SST turbulence model and P-1 radiation model used in Fluent were coupled with SolTrace to provide the heat flux distribution on the receiver surface. The creep-fatigue analysis displays the damage accumulated due to the cycling and the permanent deformation of the tubes. Nonetheless, they are able to support the required lifetime. The receiver surface temperatures were found to be within the safe operational limit while exhibiting a receiver thermal efficiency of ~85%. Future work includes the completion of a cyclic loading analysis to be performed using the Larson-Miller creep model in nCode Design Life to corroborate the structural integrity of the receiver over the desired lifetime of ~10,000 cycles.

Surface properties and graphitization of polyacrylonitrile based fiber electrodes affecting the negative half-cell reaction in vanadium redox flow batteries

NASA Astrophysics Data System (ADS)

Langner, J.; Bruns, M.; Dixon, D.; Nefedov, A.; Wöll, Ch.; Scheiba, F.; Ehrenberg, H.; Roth, C.; Melke, J.

2016-07-01

Carbon felt electrodes for vanadium redox flow batteries are obtained by the graphitization of polyacrylonitrile based felts at different temperatures. Subsequently, the surface of the felts is modified via thermal oxidation at various temperatures. A single-cell experiment shows that the voltage efficiency is increased by this treatment. Electrode potentials measured with reference electrode setup show that this voltage efficiency increase is caused mainly by a reduction of the overpotential of the negative half-cell reaction. Consequently, this reaction is investigated further by cyclic voltammetry and the electrode activity is correlated with structural and surface chemical properties of the carbon fibers. By Raman, X-ray photoelectron and near edge X-ray absorption fine structure spectroscopy the role of edge sites and oxygen containing functional groups (OCFs) for the electrochemical activity are elucidated. A significant activity increase is observed in correlation with these two characteristics. The amount of OCFs is correlated with structural defects (e.g. edge sites) of the carbon fibers and therefore decreases with an increasing graphitization degree. Thus, for the same thermal oxidation temperature carbon fibers graphitized at a lower temperature show higher activities than those graphitized at a higher temperature.

Design and experimental investigations on six-stroke SI engine using acetylene with water injection.

PubMed

Gupta, Keshav; Suthar, Kishanlal; Jain, Sheetal Kumar; Agarwal, Ghanshyam Das; Nayyar, Ashish

2018-06-02

In the present study, a four-stroke cycle gasoline engine is redesigned and converted into a six-stroke cycle engine and experimental study has been conducted using gasoline and acetylene as fuel with water injection at the end of the recompression stroke. Acetylene has been used as an alternative fuel along with gasoline and performance of the six-stroke spark ignition (SI) engine with these two fuels has been studied separately and compared. Brake power and thermal efficiency are found to be 5.18 and 1.55% higher with acetylene as compared to gasoline in the six-stroke engine. However, thermal efficiency is found to be 45% higher with acetylene in the six-stroke engine as compared to four-stroke SI engine. The CO and HC emissions were found to be reduced by 13.33 and 0.67% respectively with acetylene as compared to gasoline due to better combustion of acetylene. The NO x emission was reduced by 5.65% with acetylene due to lower peak temperature by water injection. The experimental results showed better engine performance and emissions with acetylene as fuel in the six-stroke engine.

Treatment of high salinity brines by direct contact membrane distillation: Effect of membrane characteristics and salinity.

PubMed

Li, Jianfeng; Guan, Yunshan; Cheng, Fangqin; Liu, Yu

2015-12-01

Direct contact membrane distillation (DCMD) is one of the attractive technologies for high salinity brine treatment. In this study, four polytetrafluoroethylene (PTFE) membranes were examined in treating highly concentrated salt solutions. Results showed that non-supported membranes generally have a higher overall mass transfer coefficient but porosity seems to be the most important parameter controlling membrane flux and thermal efficiency. Supported membranes with large thickness had relatively higher thermal efficiency than small thickness. This can be attributed to their reduced heat loss through heat condition. In addition, KCl, NaCl and MgCl2 solutions showed distinct trends over flux decline at high salt concentrations (⩾2.0M). The difference in flux was largely due to the discrepancy in water activities of these solutions (KCl>NaCl>MgCl2). However, the effect of viscosity on permeate flux could not be neglected for MgCl2 at high salt concentrations as the suddenly increased viscosity could lead to serious temperature polarization. This study indicates that membrane distillation is a promising technology for high salinity brine treatment. Copyright © 2014 Elsevier Ltd. All rights reserved.

Innovative ammonia stripping with an electrolyzed water system as pretreatment of thermally hydrolyzed wasted sludge for anaerobic digestion.

PubMed

Park, Seyong; Kim, Moonil

2015-01-01

In this study, the anaerobic digestion of thermally hydrolyzed wasted sludge (THWS) with a high concentration of ammonia was carried out through combining with an ammonia stripping and an electrolyzed water system (EWS). The EWS produced acidic water (pH 2-3) at the anode and alkaline water (pH 11-12) at the cathode with an electro-diaphragm between the electrodes that could be applied to ammonia stripping. The ammonia stripping efficiency was strongly dependent on the pH and aeration rate, and the ammonium ion removal rate followed pseudo-first-order kinetics. From the BMP test, the methane yield of THWS after ammonia stripping using the EWS was 2.8 times higher than that of the control process (raw THWS without ammonia stripping). Furthermore, both methane yield and ammonium removal efficiency were higher in this study than in previous studies. Since ammonia stripping with the EWS does not require any chemicals for pH control, no precipitated sludge is produced and anaerobic microorganisms are not inhibited by cations. Therefore, ammonia stripping using the EWS could be an effective method for digestion of wastewater with a high concentration of ammonium nitrogen.

Permeability enhancement by shock cooling

NASA Astrophysics Data System (ADS)

Griffiths, Luke; Heap, Michael; Reuschlé, Thierry; Baud, Patrick; Schmittbuhl, Jean

2015-04-01

The permeability of an efficient reservoir, e.g. a geothermal reservoir, should be sufficient to permit the circulation of fluids. Generally speaking, permeability decreases over the life cycle of the geothermal system. As a result, is usually necessary to artificially maintain and enhance the natural permeability of these systems. One of the methods of enhancement -- studied here -- is thermal stimulation (injecting cold water at low pressure). This goal of this method is to encourage new thermal cracks within the reservoir host rocks, thereby increasing reservoir permeability. To investigate the development of thermal microcracking in the laboratory we selected two granites: a fine-grained (Garibaldi Grey granite, grain size = 0.5 mm) and a course-grained granite (Lanhelin granite, grain size = 2 mm). Both granites have an initial porosity of about 1%. Our samples were heated to a range of temperatures (100-1000 °C) and were either cooled slowly (1 °C/min) or shock cooled (100 °C/s). A systematic microstructural (2D crack area density, using standard stereological techniques, and 3D BET specific surface area measurements) and rock physical property (porosity, P-wave velocity, uniaxial compressive strength, and permeability) analysis was undertaken to understand the influence of slow and shock cooling on our reservoir granites. Microstructurally, we observe that the 2D crack surface area per unit volume and the specific surface area increase as a result of thermal stressing, and, for the same maximum temperature, crack surface area is higher in the shock cooled samples. This observation is echoed by our rock physical property measurements: we see greater changes for the shock cooled samples. We can conclude that shock cooling is an extremely efficient method of generating thermal microcracks and modifying rock physical properties. Our study highlights that thermal treatments are likely to be an efficient method for the "matrix" permeability enhancement of granitic geothermal reservoirs.

'Squeezing' near-field thermal emission for ultra-efficient high-power thermophotovoltaic conversion.

PubMed

Karalis, Aristeidis; Joannopoulos, J D

2016-07-01

We numerically demonstrate near-field planar ThermoPhotoVoltaic systems with very high efficiency and output power, at large vacuum gaps. Example performances include: at 1200 °K emitter temperature, output power density 2 W/cm(2) with ~47% efficiency at 300 nm vacuum gap; at 2100 °K, 24 W/cm(2) with ~57% efficiency at 200 nm gap; and, at 3000 °K, 115 W/cm(2) with ~61% efficiency at 140 nm gap. Key to this striking performance is a novel photonic design forcing the emitter and cell single modes to cros resonantly couple and impedance-match just above the semiconductor bandgap, creating there a 'squeezed' narrowband near-field emission spectrum. Specifically, we employ surface-plasmon-polariton thermal emitters and silver-backed semiconductor-thin-film photovoltaic cells. The emitter planar plasmonic nature allows for high-power and stable high-temperature operation. Our simulations include modeling of free-carrier absorption in both cell electrodes and temperature dependence of the emitter properties. At high temperatures, the efficiency enhancement via resonant mode cross-coupling and matching can be extended to even higher power, by appropriately patterning the silver back electrode to enforce also an absorber effective surface-plasmon-polariton mode. Our proposed designs can therefore lead the way for mass-producible and low-cost ThermoPhotoVoltaic micro-generators and solar cells.

‘Squeezing’ near-field thermal emission for ultra-efficient high-power thermophotovoltaic conversion

PubMed Central

Karalis, Aristeidis; Joannopoulos, J. D.

2016-01-01

We numerically demonstrate near-field planar ThermoPhotoVoltaic systems with very high efficiency and output power, at large vacuum gaps. Example performances include: at 1200 °K emitter temperature, output power density 2 W/cm2 with ~47% efficiency at 300 nm vacuum gap; at 2100 °K, 24 W/cm2 with ~57% efficiency at 200 nm gap; and, at 3000 °K, 115 W/cm2 with ~61% efficiency at 140 nm gap. Key to this striking performance is a novel photonic design forcing the emitter and cell single modes to cros resonantly couple and impedance-match just above the semiconductor bandgap, creating there a ‘squeezed’ narrowband near-field emission spectrum. Specifically, we employ surface-plasmon-polariton thermal emitters and silver-backed semiconductor-thin-film photovoltaic cells. The emitter planar plasmonic nature allows for high-power and stable high-temperature operation. Our simulations include modeling of free-carrier absorption in both cell electrodes and temperature dependence of the emitter properties. At high temperatures, the efficiency enhancement via resonant mode cross-coupling and matching can be extended to even higher power, by appropriately patterning the silver back electrode to enforce also an absorber effective surface-plasmon-polariton mode. Our proposed designs can therefore lead the way for mass-producible and low-cost ThermoPhotoVoltaic micro-generators and solar cells. PMID:27363522

808nm high-power high-efficiency GaAsP/GaInP laser bars

NASA Astrophysics Data System (ADS)

Wang, Ye; Yang, Ye; Qin, Li; Wang, Chao; Yao, Di; Liu, Yun; Wang, Lijun

2008-11-01

808nm high power diode lasers, which is rapidly maturing technology technically and commercially since the introduction in 1999 of complete kilowatt-scale diode laser systems, have important applications in the fields of industry and pumping solid-state lasers (DPSSL). High power and high power conversion efficiency are extremely important in diode lasers, and they could lead to new applications where space, weight and electrical power are critical. High efficiency devices generate less waste heat, which means less strain on the cooling system and more tolerance to thermal conductivity variation, a lower junction temperature and longer lifetimes. Diode lasers with Al-free materials have superior power conversion efficiency compared with conventional AlGaAs/GaAs devices because of their lower differential series resistance and higher thermal conductivity. 808nm GaAsP/GaInP broad-waveguide emitting diode laser bars with 1mm cavity length have been fabricated. The peak power can reach to 100.9W at 106.5A at quasicontinuous wave operation (200μs, 1000Hz). The maximum power conversion efficiency is 57.38%. Based on these high power laser bars, we fabricate a 1x3 arrays, the maximum power is 64.3W in continuous wave mode when the current is 25.0A. And the threshold current is 5.9A, the slope efficiency is 3.37 W/A.

Ideal cycle analysis of a regenerative pulse detonation engine for power production

NASA Astrophysics Data System (ADS)

Bellini, Rafaela

Over the last few decades, considerable research has been focused on pulse detonation engines (PDEs) as a promising replacement for existing propulsion systems with potential applications in aircraft ranging from the subsonic to the lower hypersonic regimes. On the other hand, very little attention has been given to applying detonation for electric power production. One method for assessing the performance of a PDE is through thermodynamic cycle analysis. Earlier works have adopted a thermodynamic cycle for the PDE that was based on the assumption that the detonation process could be approximated by a constant volume process, called the Humphrey cycle. The Fickett-Jacob cycle, which uses the one--dimensional Chapman--Jouguet (CJ) theory of detonation, has also been used to model the PDE cycle. However, an ideal PDE cycle must include a detonation based compression and heat release processes with a finite chemical reaction rate that is accounted for in the Zeldovich -- von Neumann -- Doring model of detonation where the shock is considered a discontinuous jump and is followed by a finite exothermic reaction zone. This work presents a thermodynamic cycle analysis for an ideal PDE cycle for power production. A code has been written that takes only one input value, namely the heat of reaction of a fuel-oxidizer mixture, based on which the program computes all the points on the ZND cycle (both p--v and T--s plots), including the von Neumann spike and the CJ point along with all the non-dimensionalized state properties at each point. In addition, the program computes the points on the Humphrey and Brayton cycles for the same input value. Thus, the thermal efficiencies of the various cycles can be calculated and compared. The heat release of combustion is presented in a generic form to make the program usable with a wide variety of fuels and oxidizers and also allows for its use in a system for the real time monitoring and control of a PDE in which the heat of reaction can be obtained as a function of fuel-oxidizer ratio. The Humphrey and ZND cycles are studied in comparison with the Brayton cycle for different fuel-air mixtures such as methane, propane and hydrogen. The validity and limitations of the ZND and Humphrey cycles related to the detonation process are discussed and the criteria for the selection of the best model for the PDE cycle are explained. It is seen that the ZND cycle is a more appropriate representation of the PDE cycle. Next, the thermal and electrical power generation efficiencies for the PDE are compared with those of the deflagration based Brayton cycle. While the Brayton cycle shows an efficiency of 0 at a compressor pressure ratio of 1, the thermal efficiency for the ZND cycle starts out at 42% for hydrogen--air and then climbs to a peak of 66% at a compression ratio of 7 before falling slowly for higher compression ratios. The Brayton cycle efficiency rises above the PDEs for compression ratios above 23. This finding supports the theoretical advantage of PDEs over the gas turbines because PDEs only require a fan or only a few compressor stages, thereby eliminating the need for heavy compressor machinery, making the PDEs less complex and therefore more cost effective than other engines. Lastly, a regeneration study is presented to analyze how the use of exhaust gases can improve the performance of the system. The thermal efficiencies for the regenerative ZND cycle are compared with the efficiencies for the non--regenerative cycle. For a hydrogen--air mixture the thermal efficiency increases from 52%, for a cycle without regeneration, to 78%, for the regenerative cycle. The efficiency is compared with the Carnot efficiency of 84% which is the maximum possible theoretical efficiency of the cycle. When compared to the Brayton cycle thermal efficiencies, the regenerative cycle shows efficiencies that are always higher for the pressure ratio studied of 5 ≤ pic ≤ 25, where pi c the compressor pressure ratio of the cycle. This observation strengthens the idea of using regeneration on PDEs.

Current Issues in Human Spacecraft Thermal Control Technology

NASA Technical Reports Server (NTRS)

Ungar, Eugene K.

2008-01-01

Efficient thermal management of Earth-orbiting human spacecraft, lunar transit spacecraft and landers, as well as a lunar habitat will require advanced thermal technology. These future spacecraft will require more sophisticated thermal control systems that can dissipate or reject greater heat loads at higher input heat fluxes while using fewer of the limited spacecraft mass, volume and power resources. The thermal control designs also must accommodate the harsh environments associated with these missions including dust and high sink temperatures. The lunar environment presents several challenges to the design and operation of active thermal control systems. During the Apollo program, landings were located and timed to occur at lunar twilight, resulting in a benign thermal environment. The long duration polar lunar bases that are foreseen in 15 years will see extremely cold thermal environments. Long sojourns remote from low-Earth orbit will require lightweight, but robust and reliable systems. Innovative thermal management components and systems are needed to accomplish the rejection of heat from lunar bases. Advances are required in the general areas of radiators, thermal control loops and equipment. Radiators on the Moon's poles must operate and survive in very cold environments. Also, the dusty environment of an active lunar base may require dust mitigation and removal techniques to maintain radiator performance over the long term.

Design of a high temperature subsurface thermal energy storage system

NASA Astrophysics Data System (ADS)

Zheng, Qi

Solar thermal energy is taking up increasing proportions of future power generation worldwide. Thermal energy storage technology is a key method for compensating for the inherent intermittency of solar resources and solving the time mismatch between solar energy supply and electricity demand. However, there is currently no cost-effective high-capacity compact storage technology available (Bakker et al., 2008). The goal of this work is to propose a high temperature subsurface thermal energy storage (HSTES) technology and demonstrate its potential energy storage capability by developing a solar-HSTES-electricity generation system. In this work, main elements of the proposed system and their related state-of-art technologies are reviewed. A conceptual model is built to illustrate the concept, design, operating procedure and application of such a system. A numerical base model is built within the TOUGH2-EOS1 multiphase flow simulator for the evaluation of system performance. Additional models are constructed and simulations are done to identify the effect of different operational and geological influential factors on the system performance. Our work shows that when the base model is run with ten years operation of alternate injection and production processes - each for a month - with a thermal power input of 10.85 MW, about 83% of the injected thermal energy could be recovered within each working cycle from a stabilized HSTES system. After the final conversion into electrical energy, a relative (compared with the direct use of hot water) electricity generation efficiency of 73% is obtained. In a typical daily storage scenario, the simulated thermal storage efficiency could exceed 78% and the relative electricity generation efficiency is over 66% in the long run. In a seasonal storage scenario, these two efficiencies reach 69% and 53% respectively by the end of the simulation period of 10 years. Additional simulations reveal a thinner storage aquifer with a higher horizontal-to-vertical permeability ratio is favored by the storage system. A basin-shape reservoir is more favored than a flat reservoir, while a flat reservoir is better than a dome-shape reservoir. The effect of aquifer stratification is variable: it depends on the relative position of the well screen and the impermeable lenses within the reservoir. From the operational aspect, the well screen position is crucial and properly shortening the screen length can help heat recovery. The proportion of the injection/storage/recovery processes within a cycle, rather than their exact lengths, affects the storage efficiency. Reservoir preheating helps improve the energy storage efficiency for the first several cycles. However, it does not contribute much to the system performance in the long run. Simulations also indicate that buoyancy effect is of significant importance in heat distribution and the plume migration. Reducing the gravity override effect of the heat plume could be an important consideration in efficiency optimization.

Beneficiation of Turkish lignites by thermal treatment and magnetic separation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Onal, G.; Renda, D.; Mustafaev, I.

1999-07-01

In this paper, the improvement of Turkish lignites by semi-coking and REMS magnetic separation, in two stages, is discussed. The oxidation and decomposition of pyrite through the thermal treatment result in the formation of iron oxide and pyrrhotite on the surface. In addition to pyrite, part of the organic sulfur is also removed. After thermal treatment of lignites at temperatures ranging from 370 to 650 C, the application of REMS magnetic separator produces a product higher in calorific value and lower in sulfur content. The product can be utilized after briquetting. The volatile gases can also be used after sulfurmore » removal. This process appears to be feasible as a clean coal manufacture from the point of energy efficiency. A short economic analysis is also presented.« less

Performance Improvement of Energy Storage System with nano-additivesin HTF

NASA Astrophysics Data System (ADS)

Beemkumar, N.; Karthikeyan, A.; Saravanakumar, B.; Jayaprabakar, J.

2017-05-01

This paper is intended to improve the heat transfer rate of thermal energy storage system with copper oxide (CuO) as nano-additivesin heat transfer fluid (HTF) by varying encapsulation materials. The experimentation is done with different encapsulating materials like copper, brass and aluminium. The results are analysed for their thermal performance characteristics during charging and discharging processes. D-Sorbitol and therminol-66 with CuO is used as PCM and HTF respectively. A comparison was made between the different encapsulations and it was found that copper encapsulation has higher efficient, storing and recovering energy. However, its high thermal conductivity promotes larger heat losses and its cost is also high on other side. So the economical use of encapsulation material is aluminium compared to other two materials.

10 CFR 429.43 - Commercial heating, ventilating, air conditioning (HVAC) equipment.

Code of Federal Regulations, 2014 CFR

2014-01-01

... conditioners: The energy efficiency ratio (EER in British thermal units per Watt-hour (Btu/Wh)), the cooling...) Package terminal heat pumps: The energy efficiency ratio (EER in British thermal units per Watt-hour (Btu...: The energy efficiency ratio (EER in British thermal units per Watt-hour (Btu/Wh)) and the cooling...

Influence of interconnection on the long-term reliability of UV LED packages

NASA Astrophysics Data System (ADS)

Nieland, S.; Mitrenga, D.; Karolewski, D.; Brodersen, O.; Ortlepp, T.

2017-02-01

High power LEDs have conquered the mass market in recent years. Besides the main development focus to achieve higher productivity in the field of visible semiconductor LED processing, the wavelength range is further enhanced by active research and development in the direction of UVA / UVB / UVC. UVB and UVC LEDs are new and promising due to their numerous advantages. UV LEDs emit in a near range of one single emission peak with a width (FWHM) below 15 nm compared to conventional mercury discharge lamps and xenon sources, which show broad spectrums with many emission peaks over a wide range of wavelengths. Furthermore, the UV LED size is in the range of a few hundred microns and offers a high potential of significant system miniaturization. Of course, LED efficiency, lifetime and output power have to be increased [1]. Lifetime limiting issues of UVB/UVC-LED are the very high thermal stress in the chip resulting from the higher forward voltages (6-10 V @ 350 mA), the lower external quantum efficiency, below 10 % (most of the power disappears as heat), and the thermal resistance Rth of conventional LED packages being not able to dissipate these large amounts of heat for spreading. Beside the circuit boards and submounts which should have maximum thermal conductivity, the dimension of contacts as well as the interconnection of UV LED to the submount/package determinates the resolvable amount of heat [2]. In the paper different innovative interconnection techniques for UVC-LED systems will be discussed focused on the optimization of thermal conductivity in consideration of the assembly costs. Results on thermal simulation for the optimal contact dimensions and interconnections will be given. In addition, these theoretical results will be compared with results on electrical characterization as well as IR investigations on real UV LED packages in order to give recommendations for optimal UV LED assembly.

Measuring and analyzing thermal deformations of the primary reflector of the Tianma radio telescope

NASA Astrophysics Data System (ADS)

Dong, Jian; Fu, Li; Liu, Qinghui; Shen, Zhiqiang

2018-06-01

The primary reflector of the Tianma Radio Telescope (TMRT) distorts due to the varying thermal conditions, which dramatically reduces the aperture efficiency of Q-band observations. To evaluate and overcome the thermal effects, a thermal deformations measurement system has been established based on the extended Out-of-Focus holography (e-OOF). The thermal deformations can be measured in approximately 20 min with an illumination-weighted surface root mean square (RMS) accuracy of approximately 50 μm. We have measured the thermal deformations when the backup and front structure were heated by the sun respectively, and used the active surface system to correct the thermal deformations immediately to confirm the measurements. The thermal deformations when the backup structure is heated are larger than those when the front structure is heated. The values of half power beam width (HPBW) are related to the illumination-weighted surface RMS, and can be used to check the thermal deformations. When the backup structure is heated, the aperture efficiencies can remain above 90% of the maximum efficiency at 40 GHz for approximately two hours after one adjustment. While the front structure is heated, the aperture efficiencies can remain above 90% of the maximum efficiency at 40 GHz, and above 95% after one adjustment in approximately three hours.

Determination of thermal physical properties of alkali fluoride/carbonate eutectic molten salt

NASA Astrophysics Data System (ADS)

An, Xue-Hui; Cheng, Jin-Hui; Su, Tao; Zhang, Peng

2017-06-01

Molten salts used in high temperatures are more and more interested in the CSP for higher energy conversion efficiency. Thermal physical properties are the basic engineering data of thermal hydraulic calculation and safety analysis. Therefore, the thermophysical performances involving density, specific heat capacity, viscosity and thermal conductivity of FLiNaK, (LiNaK)2CO3 and LiF(NaK)2CO3 molten salts are experimentally determined and through comparison the general rules can be summarized. Density measurement was performed on the basis of Archimedes theory; specific heat capacity was measured using the DSC technique; viscosity was tested based on the rotating method; and the thermal conductivity was gained by laser flash method with combination of the density, specific heat capacity and thermal diffusivity through a formula. Finally, the energy storage capacity and figures of merit are calculated to evaluate their feasibility as TES and HFT media. The results show that FLiNaK has the largest energy storage capacity and best heat transfer performance, LiF(NaK)2CO3 is secondary, and (LiNaK)2CO3 has the smallest.

Microstructural Analysis and Transport Properties of Thermally Sprayed Multiple-Layer Ceramic Coatings

NASA Astrophysics Data System (ADS)

Wang, Hsin; Muralidharan, Govindarajan; Leonard, Donovan N.; Haynes, J. Allen; Porter, Wallace D.; England, Roger D.; Hays, Michael; Dwivedi, Gopal; Sampath, Sanjay

2018-02-01

Multilayer, graded ceramic/metal coatings were prepared by an air plasma spray method on Ti-6Al-4V, 4140 steel and graphite substrates. The coatings were designed to provide thermal barriers for diesel engine pistons to operate at higher temperatures with improved thermal efficiency and cleaner emissions. A systematic, progressive variation in the mixture of yttria-stabilized zirconia and bondcoat alloys (NiCoCrAlYHfSi) was designed to provide better thermal expansion match with the substrate and to improve thermal shock resistance and cycle life. Heat transfer through the layers was evaluated by a flash diffusivity technique based on a model of one-dimensional heat flow. The aging effect of the as-sprayed coatings was captured during diffusivity measurements, which included one heating and cooling cycle. The hysteresis of thermal diffusivity due to aging was not observed after 100-h annealing at 800 °C. The measurements of coatings on substrate and freestanding coatings allowed the influence of interface resistance to be evaluated. The microstructure of the multilayer coating was examined using scanning electron microscope and electron probe microanalysis.

Transferring of components and energy output in industrial sewage sludge disposal by thermal pretreatment and two-phase anaerobic process.

PubMed

Yang, Xiaoyi; Wang, Xin; Wang, Lei

2010-04-01

For a better sewage sludge disposal and more efficient energy reclamation, transforming of components and energy in sludge by thermal and WAO pretreatment followed by two-phase anaerobic UASB process were studied in the pilot scale. Biogas outputs and the qualities and quantities of the effluent and solid residue were compared with a traditional anaerobic sludge digestion. Sludge components, including carbon, nitrogen, phosphorus, sulphur, were observed and mass balances were discussed throughout the process. The input and output energy balance was also studied. Results showed different trait to compare with biogas outputs in terms of COD added and raw sludge added. Pretreatment improved the transformation of carbon substances into biogas production with higher carbon removal and higher VSS removal. Comparing the energy obtained from biogas production with energy inputs required for pretreatment, energy output in the whole process decreased with higher pretreatment temperature. Copyright 2009 Elsevier Ltd. All rights reserved.

Development of a higher-efficiency tubular cavity receiver for direct steam generation on a dish concentrator

NASA Astrophysics Data System (ADS)

Pye, John; Hughes, Graham; Abbasi, Ehsan; Asselineau, Charles-Alexis; Burgess, Greg; Coventry, Joe; Logie, Will; Venn, Felix; Zapata, José

2016-05-01

An integrated model for an axisymmetric helical-coil tubular cavity receiver is presented, incorporating optical ray-tracing for incident solar flux, radiosity analysis for thermal emissions, computational fluid dynamics for external convection, and a one-dimensional hydrodynamic model for internal flow-boiling of water. A receiver efficiency of 98.7% is calculated, for an inlet/outlet temperature range of 60-500 °C, which is the ratio of fluid heating to receiver incident irradiance. The high-efficiency design makes effective use of non-uniform flux in its non-isothermal layout, matching lower temperature regions to areas of lower flux. Full-scale testing of the design will occur in late 2015.

Thermal Propulsion Capture System Heat Exchanger Design

NASA Technical Reports Server (NTRS)

Richard, Evan M.

2016-01-01

One of the biggest challenges of manned spaceflight beyond low earth orbit and the moon is harmful radiation that astronauts would be exposed to on their long journey to Mars and further destinations. Using nuclear energy has the potential to be a more effective means of propulsion compared to traditional chemical engines (higher specific impulse). An upper stage nuclear engine would allow astronauts to reach their destination faster and more fuel efficiently. Testing these engines poses engineering challenges due to the need to totally capture the engine exhaust. The Thermal Propulsion Capture System is a concept for cost effectively and safely testing Nuclear Thermal Engines. Nominally, hydrogen exhausted from the engine is not radioactive, but is treated as such in case of fuel element failure. The Thermal Propulsion Capture System involves injecting liquid oxygen to convert the hydrogen exhaust into steam. The steam is then cooled and condensed into liquid water to allow for storage. The Thermal Propulsion Capture System concept for ground testing of a nuclear powered engine involves capturing the engine exhaust to be cooled and condensed before being stored. The hydrogen exhaust is injected with liquid oxygen and burned to form steam. That steam must be cooled to saturation temperatures before being condensed into liquid water. A crossflow heat exchanger using water as a working fluid will be designed to accomplish this goal. Design a cross flow heat exchanger for the Thermal Propulsion Capture System testing which: Eliminates the need for water injection cooling, Cools steam from 5800 F to saturation temperature, and Is efficient and minimizes water requirement.

Coupled Chiral Structure in Graphene-Based Film for Ultrahigh Thermal Conductivity in Both In-Plane and Through-Plane Directions.

PubMed

Meng, Xin; Pan, Hui; Zhu, Chengling; Chen, Zhixin; Lu, Tao; Xu, Da; Li, Yao; Zhu, Shenmin

2018-06-21

The development of high-performance thermal management materials to dissipate excessive heat both in plane and through plane is of special interest to maintain efficient operation and prolong the life of electronic devices. Herein, we designed and constructed a graphene-based composite film, which contains chiral liquid crystals (cellulose nanocrystals, CNCs) inside graphene oxide (GO). The composite film was prepared by annealing and compacting of self-assembled GO-CNC, which contains chiral smectic liquid crystal structures. The helical arranged nanorods of carbonized CNC act as in-plane connections, which bridge neighboring graphene sheets. More interestingly, the chiral structures also act as through-plane connections, which bridge the upper and lower graphene layers. As a result, the graphene-based composite film shows extraordinary thermal conductivity, in both in-plane (1820.4 W m -1 K -1 ) and through-plane (4.596 W m -1 K -1 ) directions. As a thermal management material, the heat dissipation and transportation behaviors of the composite film were investigated using a self-heating system and the results showed that the real-time temperature of the heater covered with the film was 44.5 °C lower than a naked heater. The prepared film shows a much higher efficiency of heat transportation than the commonly used thermal conductive Cu foil. Additionally, this graphene-based composite film exhibits excellent mechanical strength of 31.6 MPa and an electrical conductivity of 667.4 S cm -1 . The strategy reported here may open a new avenue to the development of high-performance thermal management films.

Investigating the origin of efficiency droop by profiling the temperature across the multi-quantum well of an operating light-emitting diode

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jung, Euihan; Hwang, Gwangseok; Chung, Jaehun

2015-01-26

Performance degradation resulting from efficiency droop during high-power operation is a critical problem in the development of high-efficiency light-emitting diodes (LEDs). In order to resolve the efficiency droop and increase the external quantum efficiency of LEDs, the droop's origin should be identified first. To experimentally investigate the cause of efficiency droop, we used null-point scanning thermal microscopy to quantitatively profile the temperature distribution on the cross section of the epi-layers of an operating GaN-based vertical LED with nanoscale spatial resolution at four different current densities. The movement of temperature peak towards the p-GaN side as the current density increases suggestsmore » that more heat is generated by leakage current than by Auger recombination. We therefore suspect that at higher current densities, current leakage becomes the dominant cause of the droop problem.« less

Impact of Reflow on the Output Characteristics of Piezoelectric Microelectromechanical System Devices

NASA Astrophysics Data System (ADS)

Nogami, Hirofumi; Kobayashi, Takeshi; Okada, Hironao; Masuda, Takashi; Maeda, Ryutaro; Itoh, Toshihiro

2012-09-01

An animal health monitoring system and a wireless sensor node aimed at preventing the spread of animal-transmitted diseases and improving pastoral efficiency which are especially suitable for chickens, were developed. The sensor node uses a piezoelectric microelectromechanical system (MEMS) device and an event-driven system that is activated by the movements of a chicken. The piezoelectric MEMS device has two functions: a) it measures the activity of a chicken and b) switches the micro-control unit (MCU) of the wireless sensor node from the sleep mode. The piezoelectric MEMS device is required to produce high output voltages when the chicken moves. However, after the piezoelectric MEMS device was reflowed to the wireless sensor node, the output voltages of the piezoelectric MEMS device decreased. The main reason for this might be the loss of residual polarization, which is affected by the thermal load during the reflow process. After the reflow process, we were not able to apply a voltage to the piezoelectric MEMS device; thus, the piezoelectric output voltage was not increased by repoling the piezoelectric MEMS device. To address the thermal load of the reflow process, we established a thermal poling treatment, which achieves a higher temperature than the reflow process. We found that on increasing the thermal poling temperature, the piezoelectric output voltages did not decreased low significantly. Thus, we considered that a thermal poling temperature higher than that of the reflow process prevents the piezoelectric output voltage reduction caused by the thermal load.

7 CFR 3300.13 - Determination of the efficiency of the thermal appliances as installed in the insulated body.

Code of Federal Regulations, 2010 CFR

2010-01-01

... appliances as installed in the insulated body. 3300.13 Section 3300.13 Agriculture Regulations of the... Determination of the efficiency of the thermal appliances as installed in the insulated body. In determining the efficiency of a thermal appliance with respect to maintaining a prescribed temperature inside the body, the...

Carbon-carbon cylinder block

NASA Technical Reports Server (NTRS)

Ransone, Philip O. (Inventor)

1995-01-01

A lightweight cylinder block composed of carbon-carbon is disclosed. The use of carbon-carbon over conventional materials, such as cast iron or aluminum, reduces the weight of the cylinder block and improves thermal efficiency of the internal combustion reciprocating engine. Due to the negligible coefficient of thermal expansion and unique strength at elevated temperatures of carbon-carbon, the piston-to-cylinder wall clearance can be small, especially when the carbon-carbon cylinder block is used in conjunction with a carbon-carbon piston. Use of the carbon-carbon cylinder has the effect of reducing the weight of other reciprocating engine components allowing the piston to run at higher speeds and improving specific engine performance.

Preparation of stationary phases for reversed-phase high-performance liquid chromatography using thermal treatments at high temperature.

PubMed

Vigna, Camila R M; Bottoli, Carla B G; Collins, Kenneth E; Collins, Carol H

2007-07-13

Batches of poly(methyloctylsiloxane) (PMOS)-loaded silica were prepared by deposition from a solution of PMOS into the pores of HPLC silica. Portions of PMOS-loaded silica were subjected to a thermal treatment at 100 degrees C for 24h (condition 1) in a tube furnace under a nitrogen atmosphere. After that, the material was heated for 4h at higher temperatures (150-400 degrees C) (condition 2). Heating at higher temperatures produces polymer bilayers. Non-immobilized and thermally treated stationary phases were characterized by percent carbon, (29)Si cross-polarization magic angle spinning nuclear magnetic resonance spectroscopy and reversed-phase chromatographic performance. The results show that thermal treatment between 150 and 300 degrees C accelerates the immobilization process, possibly due to some bond breaking of the polysiloxane, with formation of strong linkages to the surface of the support, resulting in more complete coverage of the silica. The chromatographic results show an improvement of efficiency with the increase of the temperature of condition 2 up to 300 degrees C and an increase in the resolution of the components, mainly for the phase heated at 300 degrees C. Such results demonstrate that a two-step thermal treatment (100 degrees C then 150-300 degrees C) produces stationary phases with good properties for use in reversed-phase high-performance liquid chromatography.

Advanced Seal Sessions I and II

NASA Technical Reports Server (NTRS)

Steinetz, Bruce M.; Dunlap, Patrick H.; Sarawate, Neelesh

2013-01-01

As aircraft operators continue to seek higher fuel efficiency, lower emissions, and longer on-wing performance, turbine engine designers are scrutinizing all components for areas of improvement. To achieve overall goals, turbine pressure ratios and by-pass ratios continue to climb. Also, designers are seeking to minimize parasitic and cooling flows to extract the most useful work out of the flow stream, placing a renewed interest on seal technology and secondary flow path management. In the area of future manned spacecraft, advancements are being examined for both habitat seals and re-entry thermal protection system thermal barrierseals. For long duration space craft, designers are continuing to look for savings in parasitic losses to reduce the amount of cabin re-supply air that needs to be brought along. This is placing greater demands on seal designs and materials to exhibit low leakage and be resistant to space environments. For future missions to and from distant planets, the re-entry heating will be higher than for low-earth orbit or lunar return motivating advanced thermal barrier development. This presentation will provide an overview of the seal challenges and opportunities in these diverse areas.

Parametric Weight Comparison of Current and Proposed Thermal Protection System (TPS) Concepts

NASA Technical Reports Server (NTRS)

Myers, David E.; Martin, Carl J.; Blosser, Max L.

1999-01-01

A parametric weight assessment of advanced metallic panel, ceramic blanket, and ceramic tile thermal protection systems (TPS) was conducted using an implicit, one-dimensional (1 -D) thermal finite element sizing code. This sizing code contained models to ac- count for coatings, fasteners, adhesives, and strain isolation pads. Atmospheric entry heating profiles for two vehicles, the Access to Space (ATS) rocket-powered single-stage-to-orbit (SSTO) vehicle and a proposed Reusable Launch Vehicle (RLV), were used to ensure that the trends were not unique to a particular trajectory. Eight TPS concepts were compared for a range of applied heat loads and substructural heat capacities to identify general trends. This study found the blanket TPS concepts have the lightest weights over the majority of their applicable ranges, and current technology ceramic tiles and metallic TPS concepts have similar weights. A proposed, state-of-the-art metallic system which uses a higher temperature alloy and efficient multilayer insulation was predicted to be significantly lighter than the ceramic tile systems and approaches blanket TPS weights for higher integrated heat loads.

Anisotropic, lightweight, strong, and super thermally insulating nanowood with naturally aligned nanocellulose

PubMed Central

Li, Tian; Song, Jianwei; Zhao, Xinpeng; Yang, Zhi; Pastel, Glenn; Xu, Shaomao; Jia, Chao; Dai, Jiaqi; Chen, Chaoji; Gong, Amy; Jiang, Feng; Yao, Yonggang; Fan, Tianzhu; Yang, Bao; Wågberg, Lars; Yang, Ronggui; Hu, Liangbing

2018-01-01

There has been a growing interest in thermal management materials due to the prevailing energy challenges and unfulfilled needs for thermal insulation applications. We demonstrate the exceptional thermal management capabilities of a large-scale, hierarchal alignment of cellulose nanofibrils directly fabricated from wood, hereafter referred to as nanowood. Nanowood exhibits anisotropic thermal properties with an extremely low thermal conductivity of 0.03 W/m·K in the transverse direction (perpendicular to the nanofibrils) and approximately two times higher thermal conductivity of 0.06 W/m·K in the axial direction due to the hierarchically aligned nanofibrils within the highly porous backbone. The anisotropy of the thermal conductivity enables efficient thermal dissipation along the axial direction, thereby preventing local overheating on the illuminated side while yielding improved thermal insulation along the backside that cannot be obtained with isotropic thermal insulators. The nanowood also shows a low emissivity of <5% over the solar spectrum with the ability to effectively reflect solar thermal energy. Moreover, the nanowood is lightweight yet strong, owing to the effective bonding between the aligned cellulose nanofibrils with a high compressive strength of 13 MPa in the axial direction and 20 MPa in the transverse direction at 75% strain, which exceeds other thermal insulation materials, such as silica and polymer aerogels, Styrofoam, and wool. The excellent thermal management, abundance, biodegradability, high mechanical strength, low mass density, and manufacturing scalability of the nanowood make this material highly attractive for practical thermal insulation applications. PMID:29536048

Anisotropic Thermal Diffusivities of Plasma-Sprayed Thermal Barrier Coatings

NASA Astrophysics Data System (ADS)

Akoshima, Megumi; Takahashi, Satoru

2017-09-01

Thermal barrier coatings (TBCs) are used to shield the blades of gas turbines from heat and wear. There is a pressing need to evaluate the thermal conductivity of TBCs in the thermal design of advanced gas turbines with high energy efficiency. These TBCs consist of a ceramic-based top coat and a bond coat on a superalloy substrate. Usually, the focus is on the thermal conductivity in the thickness direction of the TBC because heat tends to diffuse from the surface of the top coat to the substrate. However, the in-plane thermal conductivity is also important in the thermal design of gas turbines because the temperature distribution within the turbine cannot be ignored. Accordingly, a method is developed in this study for measuring the in-plane thermal diffusivity of the top coat. Yttria-stabilized zirconia top coats are prepared by thermal spraying under different conditions. The in-plane and cross-plane thermal diffusivities of the top coats are measured by the flash method to investigate the anisotropy of thermal conduction in a TBC. It is found that the in-plane thermal diffusivity is higher than the cross-plane one for each top coat and that the top coats have significantly anisotropic thermal diffusivity. The cross-sectional and in-plane microstructures of the top coats are observed, from which their porosities are evaluated. The thermal diffusivity and its anisotropy are discussed in detail in relation to microstructure and porosity.

Quantum engine efficiency bound beyond the second law of thermodynamics.

PubMed

Niedenzu, Wolfgang; Mukherjee, Victor; Ghosh, Arnab; Kofman, Abraham G; Kurizki, Gershon

2018-01-11

According to the second law, the efficiency of cyclic heat engines is limited by the Carnot bound that is attained by engines that operate between two thermal baths under the reversibility condition whereby the total entropy does not increase. Quantum engines operating between a thermal and a squeezed-thermal bath have been shown to surpass this bound. Yet, their maximum efficiency cannot be determined by the reversibility condition, which may yield an unachievable efficiency bound above unity. Here we identify the fraction of the exchanged energy between a quantum system and a bath that necessarily causes an entropy change and derive an inequality for this change. This inequality reveals an efficiency bound for quantum engines energised by a non-thermal bath. This bound does not imply reversibility, unless the two baths are thermal. It cannot be solely deduced from the laws of thermodynamics.

Energy Efficiency of Low-Temperature Deaeration of Makeup Water for a District Heating System

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sharapov, V. I., E-mail: vlad-sharapov2008@yandex.ru; Kudryavtseva, E. V.

2016-07-15

It is shown that the temperature of makeup water in district heating systems has a strong effect on the energy efficiency of turbines of thermal power plants. A low-temperature deaeration process that considerably improves the energy efficiency of thermal power plants is developed. The desorbing agent is the gas supplied to the burners of the boiler. The energy efficiency of the process for a typical unit of thermal power plant is assessed.

Dust as a Working Fluid for Heat Transfer Project

NASA Technical Reports Server (NTRS)

Mantovani, James G.

2015-01-01

The project known as "Dust as a Working Fluid" demonstrates the feasibility of a dust-based system for transferring heat radiatively into space for those space applications requiring higher efficiency, lower mass, and the need to operate in extreme vacuum and thermal environments - including operating in low or zero gravity conditions in which the dust can be conveyed much more easily than on Earth.

Effect of powder compaction on radiation-thermal synthesis of lithium-titanium ferrites

NASA Astrophysics Data System (ADS)

Surzhikov, A. P.; Lysenko, E. N.; Vlasov, V. A.; Malyshev, A. V.; Korobeynikov, M. V.; Mikhailenko, M. A.

2017-01-01

Effect of powder compaction on the efficiency of thermal and radiation-thermal synthesis of lithium-substituted ferrites was investigated by X-Ray diffraction and specific magnetization analysis. It was shown that the radiation-thermal heating of compacted powder reagents mixture leads to an increase in efficiency of lithium-titanium ferrites synthesis.

Nucleated casting for the production of large superalloy ingots

NASA Astrophysics Data System (ADS)

Carter, William T.; Jones, Robin M. Forbes

2005-04-01

The gas turbine industry is continuously driven to achieve higher thermodynamic efficiency, higher electrical output, and higher reliability through turbine design improvements. The specific component of interest in this article is the turbine wheel, which is the rotating hub on which turbine blades are mounted. The wheel is mechanically loaded by both axial and centrifugal forces and thermally loaded by heat that is conducted from the turbine blades. Currently, the turbine wheel is forged from an ingot that is triple-melted, but nucleated casting is under development as a long-term option. This article describes the investigation into nucleated casting technology for future turbine wheel production.

Electric Motor Thermal Management R&D. Annual Report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bennion, Kevin

With the push to reduce component volumes, lower costs, and reduce weight without sacrificing performance or reliability, the challenges associated with thermal management increase for power electronics and electric motors. Thermal management for electric motors will become more important as the automotive industry continues the transition to more electrically dominant vehicle propulsion systems. The transition to more electrically dominant propulsion systems leads to higher-power duty cycles for electric drive systems. Thermal constraints place significant limitations on how electric motors ultimately perform, and as thermal management improves, there will be a direct trade-off between motor performance, efficiency, cost, and the sizingmore » of electric motors to operate within the thermal constraints. The goal of this research project is to support broad industry demand for data, analysis methods, and experimental techniques to improve and better understand motor thermal management. Work in FY15 focused on two areas related to motor thermal management: passive thermal performance and active convective cooling. Passive thermal performance emphasized the thermal impact of materials and thermal interfaces among materials within an assembled motor. The research tasks supported the publication of test methods and data for thermal contact resistances and direction-dependent thermal conductivity within an electric motor. Active convective cooling focused on measuring convective heat-transfer coefficients using automatic transmission fluid (ATF). Data for average convective heat transfer coefficients for direct impingement of ATF jets was published. Also, experimental hardware for mapping local-scale and stator-scale convective heat transfer coefficients for ATF jet impingement were developed.« less

Water nucleation in helium, methane, and argon: A molecular dynamics study

NASA Astrophysics Data System (ADS)

Dumitrescu, Lucia R.; Huinink, Henk; Smeulders, David M. J.; Dam, Jacques A. M.; Gaastra-Nedea, Silvia V.

2018-05-01

Nucleation of highly supersaturated water vapor in helium, methane, and argon carrier gases at 350 K was investigated using molecular dynamics simulations. Nucleation rates obtained from the mean first passage time (MFPT) method are typically one order of magnitude lower than those from the Yasuoka and Matsumoto method, which can be attributed to the overestimation of the critical cluster size in the MFPT method. It was found that faster nucleation will occur in carrier gases that have better thermalization properties such that latent heat is removed more efficiently. These thermalization properties are shown to be strongly dependent on the molecular mass and Lennard-Jones (LJ) parameters. By varying the molecular mass, for unaltered LJ parameters, it was found that a heavier carrier gas removes less heat although it has a higher collision rate with water than a lighter carrier. Thus, it was shown that a clear distinction between water vapor-carrier gas collisions and water cluster-carrier gas collisions is indispensable for understanding the effect of collision rates on thermalization. It was also found that higher concentration of carrier gas leads to higher nucleation rate. The nucleation rates increased by a factor of 1.3 for a doubled concentration and by almost a factor of two for a tripled concentration.

Thermal strategies and energetics in two sympatric colubrid snakes with contrasted exposure.

PubMed

Lelièvre, Hervé; Le Hénanff, Maxime; Blouin-Demers, Gabriel; Naulleau, Guy; Lourdais, Olivier

2010-03-01

The thermoregulatory strategy of reptiles should be optimal if ecological costs (predation risk and time devoted to thermoregulation) are minimized while physiological benefits (performance efficiency and energy gain) are maximized. However, depending on the exact shape of the cost and benefit curves, different thermoregulatory optima may exist, even between sympatric species. We studied thermoregulation in two coexisting colubrid snakes, the European whipsnake (Hierophis viridiflavus, Lacépède 1789) and the Aesculapian snake (Zamenis longissimus, Laurenti 1768) that diverge markedly in their exposure, but otherwise share major ecological and morphological traits. The exposed species (H. viridiflavus) selected higher body temperatures (approximately 30 degrees C) than the secretive species (Z. longissimus, approximately 25 degrees C) both in a laboratory thermal gradient and in the field. Moreover, this difference in body temperature was maintained under thermophilic physiological states such as digestion and molting. Physiological and locomotory performances were optimized at higher temperatures in H. viridiflavus compared to Z. longissimus, as predicted by the thermal coadaptation hypothesis. Metabolic and energetic measurements indicated that energy requirements are at least twice higher in H. viridiflavus than in Z. longissimus. The contrasted sets of coadapted traits between H. viridiflavus and Z. longissimus appear to be adaptive correlates of their exposure strategies.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Moto, Kenta; Sadoh, Taizoh; Miyao, Masanobu, E-mail: miyao@ed.kyushu-u.ac.jp

Crystalline GeSn-on-insulator structures with high Sn concentration (>8%), which exceeds thermal equilibrium solid-solubility (∼2%) of Sn in Ge, are essential to achieve high-speed thin film transistors and high-efficiency optical devices. We investigate non-thermal equilibrium growth of Ge{sub 1−x}Sn{sub x} (0 ≤ x ≤ 0.2) on quartz substrates by using pulsed laser annealing (PLA). The window of laser fluence enabling complete crystallization without film ablation is drastically expanded (∼5 times) by Sn doping above 5% into Ge. Substitutional Sn concentration in grown layers is found to be increased with decreasing irradiation pulse number. This phenomenon can be explained on the basis of significant thermal non-equilibriummore » growth achieved by higher cooling rate after PLA with a lower pulse number. As a result, GeSn crystals with substitutional Sn concentration of ∼12% are realized at pulse irradiation of single shot for the samples with the initial Sn concentration of 15%. Raman spectroscopy and electron microscopy measurements reveal the high quality of the grown layer. This technique will be useful to fabricate high-speed thin film transistors and high-efficiency optical devices on insulating substrates.« less

Quantity, Quality, and Availability of Waste Heat from United States Thermal Power Generation.

PubMed

Gingerich, Daniel B; Mauter, Meagan S

2015-07-21

Secondary application of unconverted heat produced during electric power generation has the potential to improve the life-cycle fuel efficiency of the electric power industry and the sectors it serves. This work quantifies the residual heat (also known as waste heat) generated by U.S. thermal power plants and assesses the intermittency and transport issues that must be considered when planning to utilize this heat. Combining Energy Information Administration plant-level data with literature-reported process efficiency data, we develop estimates of the unconverted heat flux from individual U.S. thermal power plants in 2012. Together these power plants discharged an estimated 18.9 billion GJ(th) of residual heat in 2012, 4% of which was discharged at temperatures greater than 90 °C. We also characterize the temperature, spatial distribution, and temporal availability of this residual heat at the plant level and model the implications for the technical and economic feasibility of its end use. Increased implementation of flue gas desulfurization technologies at coal-fired facilities and the higher quality heat generated in the exhaust of natural gas fuel cycles are expected to increase the availability of residual heat generated by 10.6% in 2040.

Nanostructured porous Si optical biosensors: effect of thermal oxidation on their performance and properties.

PubMed

Shtenberg, Giorgi; Massad-Ivanir, Naama; Fruk, Ljiljana; Segal, Ester

2014-09-24

The influence of thermal oxidation conditions on the performance of porous Si optical biosensors used for label-free and real-time monitoring of enzymatic activity is studied. We compare three oxidation temperatures (400, 600, and 800 °C) and their effect on the enzyme immobilization efficiency and the intrinsic stability of the resulting oxidized porous Si (PSiO2), Fabry-Pérot thin films. Importantly, we show that the thermal oxidation profoundly affects the biosensing performance in terms of greater optical sensitivity, by monitoring the catalytic activity of horseradish peroxidase and trypsin-immobilized PSiO2. Despite the significant decrease in porous volume and specific surface area (confirmed by nitrogen gas adsorption-desorption studies) with elevating the oxidation temperature, higher content and surface coverage of the immobilized enzymes is attained. This in turn leads to greater optical stability and sensitivity of PSiO2 nanostructures. Specifically, films produced at 800 °C exhibit stable optical readout in aqueous buffers combined with superior biosensing performance. Thus, by proper control of the oxide layer formation, we can eliminate the aging effect, thus achieving efficient immobilization of different biomolecules, optical signal stability, and sensitivity.

Upgrading producer gas quality from rubber wood gasification in a radio frequency tar thermocatalytic treatment reactor.

PubMed

Anis, Samsudin; Zainal, Z A

2013-12-01

This study focused on improving the producer gas quality using radio frequency (RF) tar thermocatalytic treatment reactor. The producer gas containing tar, particles and water was directly passed at a particular flow rate into the RF reactor at various temperatures for catalytic and thermal treatments. Thermal treatment generates higher heating value of 5.76 MJ Nm(-3) at 1200°C. Catalytic treatments using both dolomite and Y-zeolite provide high tar and particles conversion efficiencies of about 97% on average. The result also showed that light poly-aromatic hydrocarbons especially naphthalene and aromatic compounds particularly benzene and toluene were still found even at higher reaction temperatures. Low energy intensive RF tar thermocatalytic treatment was found to be effective for upgrading the producer gas quality to meet the end user requirements and increasing its energy content. Copyright © 2013 Elsevier Ltd. All rights reserved.

Liquid crystalline perylene diimide outperforming nonliquid crystalline counterpart: higher power conversion efficiencies (PCEs) in bulk heterojunction (BHJ) cells and higher electron mobility in space charge limited current (SCLC) devices.

PubMed

Zhang, Youdi; Wang, Helin; Xiao, Yi; Wang, Ligang; Shi, Dequan; Cheng, Chuanhui

2013-11-13

In this work, we propose the application of liquid crystalline acceptors as a potential means to improve the performances of bulk heterojunction (BHJ) organic solar cells. LC-1, a structurally-simple perylene diimide (PDI), has been adopted as a model for thorough investigation. It exhibits a broad temperature range of liquid crystalline (LC) phase from 41 °C to 158 °C, and its LC properties have been characterized by differental scanning calorimetry (DSC), polarization optical microscopy (POM), and X-ray diffraction (XRD). The BHJ devices, using P3HT:LC-1 (1:2) as an organic photovoltaic active layer undergoing thermal annealing at 120 °C, shows an optimized efficiency of 0.94 %. By contrast, the devices based on PDI-1, a nonliquid crystalline PDI counterpart, only obtain a much lower efficiency of 0.22%. Atomic force microscopy (AFM) images confirm that the active layers composed of P3HT:LC-1 have smooth and ordered morphology. In space charge limited current (SCLC) devices fabricated via a spin-coating technique, LC-1 shows the intrinsic electron mobility of 2.85 × 10(-4) cm(2)/(V s) (at 0.3 MV/cm) which is almost 5 times that of PDI-1 (5.83 × 10(-5) cm(2)/(V s)) under the same conditions for thermal annealing at 120 °C.

Evaluation of Metal Halide, Plasma, and LED Lighting Technologies for a Hydrogen Fuel Cell Mobile Light (H 2 LT)

DOE PAGES

Miller, L. B.; Donohoe, S. P.; Jones, M. H.; ...

2015-04-22

This article reports on the testing and comparison of a prototype hydrogen fuel cell light tower (H2LT) and a conventional diesel-powered metal halide light trailer for use in road maintenance and construction activities. The prototype was originally outfitted with plasma lights and then with light-emitting diode (LED) luminaires. Light output and distribution, lighting energy efficiency (i.e., efficacy), power source thermal efficiency, and fuel costs are compared. The metal halide luminaires have 2.2 and 3.1 times more light output than the plasma and LED luminaires, respectively, but they require more power/lumen to provide that output. The LED luminaires have 1.6 timesmore » better light efficacy than either the metal halide or plasma luminaires. The light uniformity ratios produced by the plasma and LED towers are acceptable. The fuel cell thermal efficiency at the power required to operate the plasma lights is 48%, significantly higher than the diesel generator efficiency of 23% when operating the metal halide lights. Due to the increased efficiency of the fuel cell and the LED lighting, the fuel cost per lumen-hour of the H2LT is 62% of the metal halide diesel light tower assuming a kilogram of hydrogen is twice the cost of a gallon of diesel fuel.« less

Lightweight, Mesoporous, and Highly Absorptive All-Nanofiber Aerogel for Efficient Solar Steam Generation.

PubMed

Jiang, Feng; Liu, He; Li, Yiju; Kuang, Yudi; Xu, Xu; Chen, Chaoji; Huang, Hao; Jia, Chao; Zhao, Xinpeng; Hitz, Emily; Zhou, Yubing; Yang, Ronggui; Cui, Lifeng; Hu, Liangbing

2018-01-10

The global fresh water shortage has driven enormous endeavors in seawater desalination and wastewater purification; among these, solar steam generation is effective in extracting fresh water by efficient utilization of naturally abundant solar energy. For solar steam generation, the primary focus is to design new materials that are biodegradable, sustainable, of low cost, and have high solar steam generation efficiency. Here, we designed a bilayer aerogel structure employing naturally abundant cellulose nanofibrils (CNFs) as basic building blocks to achieve sustainability and biodegradability as well as employing a carbon nanotube (CNT) layer for efficient solar utilization with over 97.5% of light absorbance from 300 to 1200 nm wavelength. The ultralow density (0.0096 g/cm 3 ) of the aerogel ensures that minimal material is required, reducing the production cost while at the same time satisfying the water transport and thermal-insulation requirements due to its highly porous structure (99.4% porosity). Owing to its rationally designed structure and thermal-regulation performance, the bilayer CNF-CNT aerogel exhibits a high solar-energy conversion efficiency of 76.3% and 1.11 kg m -2 h -1 at 1 kW m -2 (1 Sun) solar irradiation, comparable or even higher than most of the reported solar steam generation devices. Therefore, the all-nanofiber aerogel presents a new route for designing biodegradable, sustainable, and scalable solar steam generation devices with superb performance.

Hybrid transport and diffusion modeling using electron thermal transport Monte Carlo SNB in DRACO

NASA Astrophysics Data System (ADS)

Chenhall, Jeffrey; Moses, Gregory

2017-10-01

The iSNB (implicit Schurtz Nicolai Busquet) multigroup diffusion electron thermal transport method is adapted into an Electron Thermal Transport Monte Carlo (ETTMC) transport method to better model angular and long mean free path non-local effects. Previously, the ETTMC model had been implemented in the 2D DRACO multiphysics code and found to produce consistent results with the iSNB method. Current work is focused on a hybridization of the computationally slower but higher fidelity ETTMC transport method with the computationally faster iSNB diffusion method in order to maximize computational efficiency. Furthermore, effects on the energy distribution of the heat flux divergence are studied. Work to date on the hybrid method will be presented. This work was supported by Sandia National Laboratories and the Univ. of Rochester Laboratory for Laser Energetics.

Reassessing the Efficiency Penalty from Carbon Capture in Coal-Fired Power Plants.

PubMed

Supekar, Sarang D; Skerlos, Steven J

2015-10-20

This paper examines thermal efficiency penalties and greenhouse gas as well as other pollutant emissions associated with pulverized coal (PC) power plants equipped with postcombustion CO2 capture for carbon sequestration. We find that, depending on the source of heat used to meet the steam requirements in the capture unit, retrofitting a PC power plant that maintains its gross power output (compared to a PC power plant without a capture unit) can cause a drop in plant thermal efficiency of 11.3-22.9%-points. This estimate for efficiency penalty is significantly higher than literature values and corresponds to an increase of about 5.3-7.7 US¢/kWh in the levelized cost of electricity (COE) over the 8.4 US¢/kWh COE value for PC plants without CO2 capture. The results follow from the inclusion of mass and energy feedbacks in PC power plants with CO2 capture into previous analyses, as well as including potential quality considerations for safe and reliable transportation and sequestration of CO2. We conclude that PC power plants with CO2 capture are likely to remain less competitive than natural gas combined cycle (without CO2 capture) and on-shore wind power plants, both from a levelized and marginal COE point of view.

Thermal conductivity from hierarchical heat sinks using carbon nanotubes and graphene nanosheets.

PubMed

Hsieh, Chien-Te; Lee, Cheng-En; Chen, Yu-Fu; Chang, Jeng-Kuei; Teng, Hsi-sheng

2015-11-28

The in-plane (kip) and through-plane (ktp) thermal conductivities of heat sinks using carbon nanotubes (CNTs), graphene nanosheets (GNs), and CNT/GN composites are extracted from two experimental setups within the 323-373 K temperature range. Hierarchical three-dimensional CNT/GN frameworks display higher kip and ktp values, as compared to the CNT- and GN-based heat sinks. The kip and ktp values of the CNT/GN-based heat sink reach as high as 1991 and 76 W m(-1) K(-1) at 323 K, respectively. This improved thermal conductivity is attributed to the fact that the hierarchical heat sink offers a stereo thermal conductive network that combines point, line, and plane contact, leading to better heat transport. Furthermore, the compression treatment provided an efficient route to increase both kip and ktp values. This result reveals that the hierarchical carbon structures become denser, inducing more thermal conductive area and less thermal resistivity, i.e., a reduced possibility of phonon-boundary scattering. The correlation between thermal and electrical conductivity (ε) can be well described by two empirical equations: kip = 567 ln(ε) + 1120 and ktp = 20.6 ln(ε) + 36.1. The experimental results are obtained within the temperature range of 323-373 K, suitably complementing the thermal management of chips for consumer electronics.

Cashew gum and inulin: New alternative for ginger essential oil microencapsulation.

PubMed

Fernandes, Regiane Victória de Barros; Botrel, Diego Alvarenga; Silva, Eric Keven; Borges, Soraia Vilela; Oliveira, Cassiano Rodrigues de; Yoshida, Maria Irene; Feitosa, Judith Pessoa de Andrade; de Paula, Regina Célia Monteiro

2016-11-20

This study aimed to evaluate the effect of partial replacement of cashew gum by inulin used as wall materials, on the characteristics of ginger essential oil microencapsulated by spray drying with ultrasound assisted emulsions. The characterization of particles was evaluated as encapsulation efficiency and particle size. In addition, the properties of the microcapsules were studied through FTIR analysis, adsorption isotherms, thermal gravimetric analysis, X-ray and scanning electron microscopy. It was found that the solubility of the treatments was affected by the composition of the wall material and reached higher values (89.80%) when higher inulin concentrations were applied. The encapsulation efficiency (15.8%) was lower at the highest inulin concentration. The particles presented amorphous characteristics and treatment with cashew gum as encapsulant exhibited the highest water absorption at high water activity. The cashew gum and inulin matrix (3:1(w/w) ratio) showed the best characteristics regarding the encapsulation efficiency and morphology, showing no cracks in the structure. Copyright © 2016 Elsevier Ltd. All rights reserved.

How to Overcome Numerical Challenges to Modeling Stirling Engines

NASA Technical Reports Server (NTRS)

Dyson, Rodger W.; Wilson, Scott D.; Tew, Roy C.

2004-01-01

Nuclear thermal to electric power conversion carries the promise of longer duration missions and higher scientific data transmission rates back to Earth for a range of missions, including both Mars rovers and deep space missions. A free-piston Stirling convertor is a candidate technology that is considered an efficient and reliable power conversion device for such purposes. While already very efficient, it is believed that better Stirling engines can be developed if the losses inherent in current designs could be better understood. However, they are difficult to instrument and so efforts are underway to simulate a complete Stirling engine numerically. This has only recently been attempted and a review of the methods leading up to and including such computational analysis is presented. And finally it is proposed that the quality and depth of Stirling loss understanding may be improved by utilizing the higher fidelity and efficiency of recently developed numerical methods. One such method, the Ultra HI-FI technique is presented in detail.

Thermal conductivity engineering in width-modulated silicon nanowires and thermoelectric efficiency enhancement

NASA Astrophysics Data System (ADS)

Zianni, Xanthippi

2018-03-01

Width-modulated nanowires have been proposed as efficient thermoelectric materials. Here, the electron and phonon transport properties and the thermoelectric efficiency are discussed for dimensions above the quantum confinement regime. The thermal conductivity decreases dramatically in the presence of thin constrictions due to their ballistic thermal resistance. It shows a scaling behavior upon the width-modulation rate that allows for thermal conductivity engineering. The electron conductivity also decreases due to enhanced boundary scattering by the constrictions. The effect of boundary scattering is weaker for electrons than for phonons and the overall thermoelectric efficiency is enhanced. A ZT enhancement by a factor of 20-30 is predicted for width-modulated nanowires compared to bulk silicon. Our findings indicate that width-modulated nanostructures are promising for developing silicon nanostructures with high thermoelectric efficiency.

Modulation of digestive physiology and biochemistry in Mytilus californianus in response to feeding level acclimation and microhabitat

PubMed Central

Sung, Aaron; Garcia, Nathan S.; Gracey, Andrew Y.; German, Donovan P.

2016-01-01

ABSTRACT The intertidal mussel Mytilus californianus is a critical foundation species that is exposed to fluctuations in the environment along tidal- and wave-exposure gradients. We investigated feeding and digestion in mussels under laboratory conditions and across environmental gradients in the field. We assessed whether mussels adopt a rate-maximization (higher ingestion and lower assimilation) or a yield-maximization acquisition (lower ingestion and higher assimilation) strategy under laboratory conditions by measuring feeding physiology and digestive enzyme activities. We used digestive enzyme activity to define resource acquisition strategies in laboratory studies, then measured digestive enzyme activities in three microhabitats at the extreme ends of the tidal- and wave-exposure gradients within a stretch of shore (<20 m) projected sea-ward. Our laboratory results indicated that mussels benefit from a high assimilation efficiency when food concentration is low and have a low assimilation efficiency when food concentration is high. Additionally, enzyme activities of carbohydrases amylase, laminarinase and cellulase were elevated when food concentration was high. The protease trypsin, however, did not increase with increasing food concentration. In field conditions, low-shore mussels surprisingly did not have high enzyme activities. Rather, high-shore mussels exhibited higher cellulase activities than low-shore mussels. Similarly, trypsin activity in the high-shore-wave-sheltered microhabitat was higher than that in high-shore-wave-exposed. As expected, mussels experienced increasing thermal stress as a function of reduced submergence from low to high shore and shelter from wave-splash. Our findings suggest that mussels compensate for limited feeding opportunities and thermal stress by modulating digestive enzyme activities. PMID:27402963

Influences of calcium oxide content in marine fuel oil on emission characteristics of marine furnaces under varying humidity and temperature of the inlet air.

PubMed

Lin, Cherng-Yuan; Chen, Wei-Cheng

2004-01-01

A marine furnace made of stainless steel. combined with an automatic small-size oil-fired burner, was used to experimentally investigate the influences of calcium oxide content in fuel oil on the combustion and emission characteristics under varying temperatures and humidity of the inlet air. Marine fuel oil generally contains various extents of metallic oxides such as CaO, Fe2O3, V2O5, etc which might affect its burning properties. In this study, an air-conditioner was used to adjust the humidity and temperatures of the inlet air to preset values prior to entering the burner. The adjusted inlet air atomized the marine diesel oil A containing a calcium oxide compound, to form a heterogeneous reactant mixture. The reactant mixture was thereafter ignited by a high-voltage electrode in the burner and burned within the marine furnace. The probes of a gas analyzer, H2S analyzer and a K-type thermocouple were inserted into the radial positions of the furnace through the eight rectangular slots which were cut in the upper side of the furnace. The experimental results showed that an increase of either humidity or temperature of the inlet air caused the promotion of the reaction rate of the fuel. The existence of calcium oxide compound in the diesel fuel also facilitated the oxidation reaction in the combustion chamber. The addition of CaO in the diesel fuel under the conditions of higher temperature or higher relative humidity of the inlet air produced the following: higher concentrations of CO2, SO2, and H2S emissions, an increased burning efficiency, a lowered O2 level, production of excess air and NOx emissions as well as a lower thermal loss and a lower burning gas temperature, as compared with the conditions of a lower temperature or a lower humidity of the inlet air. In addition, the burning of diesel fuel with added CaO compound caused a large variation in the burning efficiency, thermal loss, plus CO2, O2, and excess air emissions between the conditions of higher temperature/higher humidity and lower temperature/lower humidity inlet air compared with no CaO addition in the fuel. Moreover, the burning efficiency and the concentrations of excess air and O2 emissions increased, while the thermal loss, burning gas temperature and H2S, SO2, NOx, and CO2 emissions decreased with the increase of the axial distance from the measured location to the burner nozzle.

Efficient thermal diode with ballistic spacer

NASA Astrophysics Data System (ADS)

Chen, Shunda; Donadio, Davide; Benenti, Giuliano; Casati, Giulio

2018-03-01

Thermal rectification is of importance not only for fundamental physics, but also for potential applications in thermal manipulations and thermal management. However, thermal rectification effect usually decays rapidly with system size. Here, we show that a mass-graded system, with two diffusive leads separated by a ballistic spacer, can exhibit large thermal rectification effect, with the rectification factor independent of system size. The underlying mechanism is explained in terms of the effective size-independent thermal gradient and the match or mismatch of the phonon bands. We also show the robustness of the thermal diode upon variation of the model's parameters. Our finding suggests a promising way for designing realistic efficient thermal diodes.

Ultra-High Temperature Thermal Barrier Coatings

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jordan, Eric; Gell, Maurice; Wang, Jiwen

In this project, HiFunda LLC worked with the University of Connecticut (UConn) to demonstrate an attractive option for thermal barrier coatings (TBCs), namely yttrium aluminum garnet (YAG), which was well known to have proven thermal stability and excellent high-temperature mechanical properties. YAG and other higher temperature TBCs have not been used to date because they exhibit inadequate durability, resulting from (a) poor erosion resistance and (b) greater thermal expansion mismatch strains compared to 7YSZ. UConn had previously demonstrated that the solution precursor plasma spray (SPPS) process could produce a durable 7YSZ TBC resulting from a highly strain tolerant microstructure, consistingmore » of through-coating-thickness vertical cracks. HiFunda/UConn reasoned at the start of Phase I that such a strain-tolerant microstructure could produce durable, higher temperature TBCs. The Phase I work demonstrated the feasibility of that concept and of SPPS YAG TBCs. The Phase II work demonstrated that SPPS YAG coating possessed the necessary range of properties to be a viable high temperature TBC, including cyclic durability and reduced elevated temperature thermal conductivity. The SPPS YAG TBCs were shown to have the potential to be used at temperatures 200°C higher than APS YSZ, based on thermal stability, sinter resistance, and CMAS resistance. The overall technical objectives of this Phase 2A project were to further improve the commercial viability of SPPS by improving their performance capabilities and manufacturing economics. The improved performance capability was to be achieved through: (1) further reductions in thermal conductivity, which allows higher gas temperatures and/or thinner coatings to achieve similar gas temperatures; and (2) improved resistance to calcium magnesium alumnoslicate (CMAS) attack of the TBCs, which can yield improved lifetimes. The improved thermal conductivity and CMAs resistance was to be accomplished through compositional and microstructural optimization. Finally, the key metrics to improve the process economics were increased deposition rate and efficiency. In addition to these technical objectives, there were commercialization objectives of getting key commercialization partners to evaluate and qualify the SPPS YAG technology independently so that the technology readiness level (TRL) of the technology could be sufficiently advanced to facilitate Phase III strategic partnerships, leading to eventual commercialization consistent with the overall objectives of the DOE SBIR/STTR program. All the Phase 2A goals were successfully achieved.« less

Battery cell thermal-conductive coating increases efficiency

NASA Technical Reports Server (NTRS)

Doyle, H. M.

1973-01-01

Thin coating of high-temperature epoxy resin provides necessary electrical insulation, as well as good thermal conductivity between battery cells. Insulation increases efficiency of nickel-cadmium battery, as it would any multicell battery assembly in which cell-to-cell thermal balance is critical.

Comparative study for "36 V" vehicle applications: advantages of lead-acid batteries

NASA Astrophysics Data System (ADS)

Lailler, Patrick; Sarrau, Jean-François; Sarrazin, Christian

From thermal engine equipped vehicles to completely electric ones, evolution of light weight vehicles in the future will take several steps in so far as there is no adequate battery or fuel cell presently available to power these vehicles for "on the road" driving. On the other hand, for city driving, vehicles can be improved a lot in terms of fuel efficiency as well as air pollution, if partly or totally electric propulsion can be developed, manufactured and marketed for appropriate applications. The 36-42 V battery is part of this orientation towards improving the efficiency of thermal vehicles in city driving, while keeping adequate autonomy on the roads. Actually, in city traffic, thermal engines are idle most of the time and stop periods represent a large part of the time spent "driving", using up fuel and polluting air for no use at all. The idea of stopping the engine during these periods, if appropriately managed, might potentially lead to a large improvement in fuel economy as well as air pollution reduction. The association of a higher voltage battery to an alternator-starter device in thermal vehicles, seems to be an interesting way towards that end. In this paper, we are presenting our results of a study we have just completed in relationship with RENAULT & VALEO, supported by the French Ministry of Industry, concerning a comparative evaluation of different automobile energy storage systems, and the definition of specifications as the final step of this study. The main conclusion is that lead-acid will still remain dominant in this role, since its operational cost versus efficiency is by far the lowest of every battery presently considered, more particularly in the less expensive car segments.

Influence of geologic layering on heat transport and storage in an aquifer thermal energy storage system

NASA Astrophysics Data System (ADS)

Bridger, D. W.; Allen, D. M.

2014-01-01

A modeling study was carried out to evaluate the influence of aquifer heterogeneity, as represented by geologic layering, on heat transport and storage in an aquifer thermal energy storage (ATES) system in Agassiz, British Columbia, Canada. Two 3D heat transport models were developed and calibrated using the flow and heat transport code FEFLOW including: a "non-layered" model domain with homogeneous hydraulic and thermal properties; and, a "layered" model domain with variable hydraulic and thermal properties assigned to discrete geological units to represent aquifer heterogeneity. The base model (non-layered) shows limited sensitivity for the ranges of all thermal and hydraulic properties expected at the site; the model is most sensitive to vertical anisotropy and hydraulic gradient. Simulated and observed temperatures within the wells reflect a combination of screen placement and layering, with inconsistencies largely explained by the lateral continuity of high permeability layers represented in the model. Simulation of heat injection, storage and recovery show preferential transport along high permeability layers, resulting in longitudinal plume distortion, and overall higher short-term storage efficiencies.

A Novel Approach to Thermal Design of Solar Modules: Selective-Spectral and Radiative Cooling

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sun, Xingshu; Dubey, Rajiv; Chattopadhyay, Shashwata

2016-11-21

For commercial solar modules, up to 80% of the incoming sunlight may be dissipated as heat, potentially raising the temperature 20-30 degrees C higher than the ambient. In the long run, extreme self-heating may erode efficiency and shorten lifetime, thereby, dramatically reducing the total energy output by almost ~10% Therefore, it is critically important to develop effective and practical cooling methods to combat PV self-heating. In this paper, we explore two fundamental sources of PV self-heating, namely, sub-bandgap absorption and imperfect thermal radiation. The analysis suggests that we redesign the optical and thermal properties of the solar module to eliminatemore » the parasitic absorption (selective-spectral cooling) and enhance the thermal emission to the cold cosmos (radiative cooling). The proposed technique should cool the module by ~10 degrees C, to be reflected in significant long-term energy gain (~ 3% to 8% over 25 years) for PV systems under different climatic conditions.« less

Laser Glass Frit Sealing for Encapsulation of Vacuum Insulation Glasses

NASA Astrophysics Data System (ADS)

Kind, H.; Gehlen, E.; Aden, M.; Olowinsky, A.; Gillner, A.

Laser glass frit sealing is a joining method predestined in electronics for the sealing of engineered materials housings in dimensions of some 1 mm2 to several 10 mm2. The application field ranges from encapsulation of display panels to sensor housings. Laser glass frit sealing enables a hermetical closure excluding humidity and gas penetration. But the seam quality is also interesting for other applications requiring a hermetical sealing. One application is the encapsulation of vacuum insulation glass. The gap between two panes must be evacuated for reducing the thermal conductivity. Only an efficient encapsulating technique ensures durable tight joints of two panes for years. Laser glass frit sealing is an alternative joining method even though the material properties of soda lime glass like sensitivity to thermal stresses are much higher as known from engineered materials. An adapted thermal management of the process is necessary to prevent the thermal stresses within the pane to achieve crack free and tight glass frit seams.

Performance analysis and optimization of power plants with gas turbines

NASA Astrophysics Data System (ADS)

Besharati-Givi, Maryam

The gas turbine is one of the most important applications for power generation. The purpose of this research is performance analysis and optimization of power plants by using different design systems at different operation conditions. In this research, accurate efficiency calculation and finding optimum values of efficiency for design of chiller inlet cooling and blade cooled gas turbine are investigated. This research shows how it is possible to find the optimum design for different operation conditions, like ambient temperature, relative humidity, turbine inlet temperature, and compressor pressure ratio. The simulated designs include the chiller, with varied COP and fogging cooling for a compressor. In addition, the overall thermal efficiency is improved by adding some design systems like reheat and regenerative heating. The other goal of this research focuses on the blade-cooled gas turbine for higher turbine inlet temperature, and consequently, higher efficiency. New film cooling equations, along with changing film cooling effectiveness for optimum cooling air requirement at the first-stage blades, and an internal and trailing edge cooling for the second stage, are innovated for optimal efficiency calculation. This research sets the groundwork for using the optimum value of efficiency calculation, while using inlet cooling and blade cooling designs. In the final step, the designed systems in the gas cycles are combined with a steam cycle for performance improvement.

Experimental study of airflow characteristics of stratum ventilation in a multi-occupant room with comparison to mixing ventilation and displacement ventilation.

PubMed

Cheng, Y; Lin, Z

2015-12-01

The motivation of this study is stimulated by a lack of knowledge about the difference of airflow characteristics between a novel air distribution method [i.e., stratum ventilation (SV)] and conventional air distribution methods [i.e., mixing ventilation (MV) and displacement ventilation (DV)]. Detailed air velocity and temperature measurements were conducted in the occupied zone of a classroom with dimensions of 8.8 m (L) × 6.1 m (W) × 2.4 m (H). Turbulence intensity and power spectrum of velocity fluctuation were calculated using the measured data. Thermal comfort and cooling efficiency were also compared. The results show that in the occupied zone, the airflow characteristics among MV, DV, and SV are different. The turbulent airflow fluctuation is enhanced in this classroom with multiple thermal manikins due to thermal buoyancy and airflow mixing effect. Thermal comfort evaluations indicate that in comparison with MV and DV, a higher supply air temperature should be adopted for SV to achieve general thermal comfort with low draft risk. Comparison of the mean air temperatures in the occupied zone reveals that SV is of highest cooling efficiency, followed by DV and then MV. This study reports the unique profiles of flow, temperature, turbulence intensity, and power spectrum of stratum ventilation, which can have a number of implications for both knowledge and understanding of the flow characteristics in a stratum-ventilated room. With respect to the former, it expounds the fundamental characteristics of this air distribution method; and with respect to the latter, it reveals the mechanism of thermal comfort and energy saving under stratum ventilation. © 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Thermoregulation and microhabitat choice in the polymorphic asp viper (Vipera aspis).

PubMed

Muri, Daniele; Schuerch, Johan; Trim, Naïke; Golay, Joaquim; Baillifard, Alexandre; El Taher, Athimed; Dubey, Sylvain

2015-10-01

In ectotherms, thermoregulation strongly depends on environmental conditions, as well as on intrinsic factors, such as skin colour. Indeed, due to its physical properties, melanin pigments allow melanistic morphs to benefit of a more efficient thermoregulation compared to non-melanistic ones. Despite thermal benefits of melanism have often been highlighted under experimental conditions, such field data remain scarce. In this study, we investigated the influence of colouration on body temperature and microhabitat choice in a montane population of colour polymorphic asp viper (Vipera aspis) characterized by a strong presence of melanism (64%). Results highlighted a difference in internal body temperature, but only within gravid females, with melanistic individuals having higher body temperatures compared to non-melanistic ones. No differences were found when considering both sexes. We also showed that melanistic and non-melanistic vipers were found in different microhabitat types, i.e. melanistic snakes used areas marked by a scarcer sun exposure and by higher vegetation cover compared to non-melanistic ones. This result has important implications. Indeed, besides providing a possible explanation for the lack of difference in body temperature (except for gravid females), it confirms that melanistic individuals can potentially use their efficient thermoregulation in order to inhabit less exposed and thermally unfavourable microhabitats. Copyright © 2015 Elsevier Ltd. All rights reserved.

New latent heat storage system with nanoparticles for thermal management of electric vehicles

NASA Astrophysics Data System (ADS)

Javani, N.; Dincer, I.; Naterer, G. F.

2014-12-01

In this paper, a new passive thermal management system for electric vehicles is developed. A latent heat thermal energy storage with nanoparticles is designed and optimized. A genetic algorithm method is employed to minimize the length of the heat exchanger tubes. The results show that even the optimum length of a shell and tube heat exchanger becomes too large to be employed in a vehicle. This is mainly due to the very low thermal conductivity of phase change material (PCM) which fills the shell side of the heat exchanger. A carbon nanotube (CNT) and PCM mixture is then studied where the probability of nanotubes in a series configuration is defined as a deterministic design parameter. Various heat transfer rates, ranging from 300 W to 600 W, are utilized to optimize battery cooling options in the heat exchanger. The optimization results show that smaller tube diameters minimize the heat exchanger length. Furthermore, finned tubes lead to a higher heat exchanger length due to more heat transfer resistance. By increasing the CNT concentration, the optimum length of the heat exchanger decreases and makes the improved thermal management system a more efficient and competitive with air and liquid thermal management systems.

One-dimensional thermal evolution calculation based on a mixing length theory: Application to Saturnian icy satellites

NASA Astrophysics Data System (ADS)

Kamata, S.

2017-12-01

Solid-state thermal convection plays a major role in the thermal evolution of solid planetary bodies. Solving the equation system for thermal evolution considering convection requires 2-D or 3-D modeling, resulting in large calculation costs. A 1-D calculation scheme based on mixing length theory (MLT) requires a much lower calculation cost and is suitable for parameter studies. A major concern for the MLT scheme is its accuracy due to a lack of detailed comparisons with higher dimensional schemes. In this study, I quantify its accuracy via comparisons of thermal profiles obtained by 1-D MLT and 3-D numerical schemes. To improve the accuracy, I propose a new definition of the mixing length (l), which is a parameter controlling the efficiency of heat transportation due to convection. Adopting this new definition of l, I investigate the thermal evolution of Dione and Enceladus under a wide variety of parameter conditions. Calculation results indicate that each satellite requires several tens of GW of heat to possess a 30-km-thick global subsurface ocean. Dynamical tides may be able to account for such an amount of heat, though their ices need to be highly viscous.

Microstructural Analysis and Transport Properties of Thermally Sprayed Multiple-Layer Ceramic Coatings

DOE PAGES

Wang, Hsin; Muralidharan, Govindarajan; Leonard, Donovan N.; ...

2018-01-04

In this paper, multilayer, graded ceramic/metal coatings were prepared by an air plasma spray method on Ti-6Al-4V, 4140 steel and graphite substrates. The coatings were designed to provide thermal barriers for diesel engine pistons to operate at higher temperatures with improved thermal efficiency and cleaner emissions. A systematic, progressive variation in the mixture of yttria-stabilized zirconia and bondcoat alloys (NiCoCrAlYHfSi) was designed to provide better thermal expansion match with the substrate and to improve thermal shock resistance and cycle life. Heat transfer through the layers was evaluated by a flash diffusivity technique based on a model of one-dimensional heat flow.more » The aging effect of the as-sprayed coatings was captured during diffusivity measurements, which included one heating and cooling cycle. The hysteresis of thermal diffusivity due to aging was not observed after 100-h annealing at 800 °C. The measurements of coatings on substrate and freestanding coatings allowed the influence of interface resistance to be evaluated. Finally, the microstructure of the multilayer coating was examined using scanning electron microscope and electron probe microanalysis.« less

Microstructural Analysis and Transport Properties of Thermally Sprayed Multiple-Layer Ceramic Coatings

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Hsin; Muralidharan, Govindarajan; Leonard, Donovan N.

In this paper, multilayer, graded ceramic/metal coatings were prepared by an air plasma spray method on Ti-6Al-4V, 4140 steel and graphite substrates. The coatings were designed to provide thermal barriers for diesel engine pistons to operate at higher temperatures with improved thermal efficiency and cleaner emissions. A systematic, progressive variation in the mixture of yttria-stabilized zirconia and bondcoat alloys (NiCoCrAlYHfSi) was designed to provide better thermal expansion match with the substrate and to improve thermal shock resistance and cycle life. Heat transfer through the layers was evaluated by a flash diffusivity technique based on a model of one-dimensional heat flow.more » The aging effect of the as-sprayed coatings was captured during diffusivity measurements, which included one heating and cooling cycle. The hysteresis of thermal diffusivity due to aging was not observed after 100-h annealing at 800 °C. The measurements of coatings on substrate and freestanding coatings allowed the influence of interface resistance to be evaluated. Finally, the microstructure of the multilayer coating was examined using scanning electron microscope and electron probe microanalysis.« less

Thin and Flexible Fe-Si-B/Ni-Cu-P Metallic Glass Multilayer Composites for Efficient Electromagnetic Interference Shielding.

PubMed

Zhang, Jijun; Li, Jiawei; Tan, Guoguo; Hu, Renchao; Wang, Junqiang; Chang, Chuntao; Wang, Xinmin

2017-12-06

Thin and flexible materials that can provide efficient electromagnetic interference (EMI) shielding are urgently needed, especially if they can be easily processed and withstand harsh environments. Herein, layer-structured Fe-Si-B/Ni-Cu-P metallic glass composites have been developed by simple electroless plating Ni-Cu-P coating on commercial Fe-Si-B metallic glasses. The 0.1 mm-thick composite shows EMI shielding effectiveness of 40 dB over the X-band frequency range, which is higher than those of traditional metals, metal oxides, and their polymer composites of larger thickness. Most of the applied electromagnetic waves are proved to be absorbed rather than bounced back. This performance originates from the combination of a superior soft magnetic property, excellent electrical conductivity, and multiple internal reflections from multilayer composites. In addition, the flexible composites also exhibit good corrosion resistance, high thermal stability, and excellent tensile strength, making them suitable for EMI shielding in harsh chemical or thermal environments.

Mathematical modeling of a four-stroke resonant engine for micro and mesoscale applications

NASA Astrophysics Data System (ADS)

Preetham, B. S.; Anderson, M.; Richards, C.

2014-12-01

In order to mitigate frictional and leakage losses in small scale engines, a compliant engine design is proposed in which the piston in cylinder arrangement is replaced by a flexible cavity. A physics-based nonlinear lumped-parameter model is derived to predict the performance of a prototype engine. The model showed that the engine performance depends on input parameters, such as heat input, heat loss, and load on the engine. A sample simulation for a reference engine with octane fuel/air ratio of 0.043 resulted in an indicated thermal efficiency of 41.2%. For a fixed fuel/air ratio, higher output power is obtained for smaller loads and vice-versa. The heat loss from the engine and the work done on the engine during the intake stroke are found to decrease the indicated thermal efficiency. The ratio of friction work to indicated work in the prototype engine is about 8%, which is smaller in comparison to the traditional reciprocating engines.

Research on structural integration of thermodynamic system for double reheat coal-fired unit with CO2 capture

NASA Astrophysics Data System (ADS)

Wang, Lanjing; Shao, Wenjing; Wang, Zhiyue; Fu, Wenfeng; Zhao, Wensheng

2018-02-01

Taking the MEA chemical absorption carbon capture system with 85% of the carbon capture rate of a 660MW ultra-super critical unit as an example,this paper puts forward a new type of turbine which dedicated to supply steam to carbon capture system. The comparison of the thermal systems of the power plant under different steam supply schemes by using the EBSILON indicated optimal extraction scheme for Steam Extraction System in Carbon Capture System. The results show that the cycle heat efficiency of the unit introduced carbon capture turbine system is higher than that of the usual scheme without it. With the introduction of the carbon capture turbine, the scheme which extracted steam from high pressure cylinder’ s steam input point shows the highest cycle thermal efficiency. Its indexes are superior to other scheme, and more suitable for existing coal-fired power plant integrated post combustion carbon dioxide capture system.

Experimental study on drying kinetic of cassava starch in a pneumatic drying system

NASA Astrophysics Data System (ADS)

Suherman, Kumoro, Andri Cahyo; Kusworo, Tutuk Djoko

2015-12-01

The aims of this study are to present the experimental research on the drying of cassava starch in a pneumatic dryer, to describe its drying curves, as well as to calculate its thermal efficiency. The effects of operating conditions, namely the inlet air temperature (60-100 °C) and solid-gas flow rate ratio (Ms/Mg 0.1-0.3) were studied. Heat transfer is accomplished through convection mechanism in a drying chamber based on the principle of direct contact between the heated air and the moist material. During the drying process, intensive heat and mass transfer between the drying air and the cassava starch take place. In order to meet the SNI standards on solid water content, the drying process was done in two cycles. The higher the temperature of the drying air, the lower the water content of the solids exiting the dryer. Thermal efficiency of the 2nd cycle was found to be lower than the 1st cycle.

Vapor phase growth technique of III-V compounds utilizing a preheating step

NASA Technical Reports Server (NTRS)

Olsen, Gregory Hammond (Inventor); Zamerowski, Thomas Joseph (Inventor); Buiocchi, Charles Joseph (Inventor)

1978-01-01

In the vapor phase epitaxy fabrication of semiconductor devices and in particular semiconductor lasers, the deposition body on which a particular layer of the laser is to be grown is preheated to a temperature about 40.degree. to 60.degree. C. lower than the temperature at which deposition occurs. It has been discovered that by preheating at this lower temperature there is reduced thermal decomposition at the deposition surface, especially for semiconductor materials such as indium gallium phosphide and gallium arsenide phosphide. A reduction in thermal decomposition reduces imperfections in the deposition body in the vicinity of the deposition surface, thereby providing a device with higher efficiency and longer lifetime.

Method for Making a Carbon-Carbon Cylinder Block

NASA Technical Reports Server (NTRS)

Ransone, Phillip O. (Inventor)

1997-01-01

A method for making a lightweight cylinder block composed of carbon-carbon is disclosed. The use of carbon-carbon over conventional materials. such as cast iron or aluminum, reduces the weight of the cylinder block and improves thermal efficiency of the internal combustion reciprocating engine. Due to the negligible coefficient of thermal expansion and unique strength at elevated temperatures of carbon-carbon, the piston-to-cylinder wall clearance can be small, especially when the carbon-carbon cylinder block is used in conjunction with a carbon-carbon piston. Use of the carbon-carbon cylinder block has the effect of reducing the weight of other reciprocating engine components allowing the piston to run at higher speeds and improving specific engine performance.

Positive and negative effects of oxygen in thermal annealing of p-type GaN

NASA Astrophysics Data System (ADS)

Wu, L. L.; Zhao, D. G.; Jiang, D. S.; Chen, P.; Le, L. C.; Li, L.; Liu, Z. S.; Zhang, S. M.; Zhu, J. J.; Wang, H.; Zhang, B. S.; Yang, H.

2012-08-01

The effect of oxygen on ambient gas on activating p-GaN by rapid thermal annealing was investigated. When the ratio of N2 to O2 is 4:1, the sample activated after annealing at 750 °C exhibits the best electrical properties with respect to resistivity. It is confirmed that the concentration of hydrogen which passivates Mg acceptors in GaN decreases more efficiently when oxygen is introduced into N2 ambient gas. Although oxygen-involved annealing at higher temperature may further reduce the concentration of hydrogen, the resistivity of p-GaN may increase due to the negative effect caused by too much incorporation of oxygen-related donors.

Integration of Decentralized Thermal Storages Within District Heating (DH) Networks

NASA Astrophysics Data System (ADS)

Schuchardt, Georg K.

2016-12-01

Thermal Storages and Thermal Accumulators are an important component within District Heating (DH) systems, adding flexibility and offering additional business opportunities for these systems. Furthermore, these components have a major impact on the energy and exergy efficiency as well as the heat losses of the heat distribution system. Especially the integration of Thermal Storages within ill-conditioned parts of the overall DH system enhances the efficiency of the heat distribution. Regarding an illustrative and simplified example for a DH system, the interactions of different heat storage concepts (centralized and decentralized) and the heat losses, energy and exergy efficiencies will be examined by considering the thermal state of the heat distribution network.

Innovative and Advanced Coupled Neutron Transport and Thermal Hydraulic Method (Tool) for the Design, Analysis and Optimization of VHTR/NGNP Prismatic Reactors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rahnema, Farzad; Garimeela, Srinivas; Ougouag, Abderrafi

2013-11-29

This project will develop a 3D, advanced coarse mesh transport method (COMET-Hex) for steady- state and transient analyses in advanced very high-temperature reactors (VHTRs). The project will lead to a coupled neutronics and thermal hydraulic (T/H) core simulation tool with fuel depletion capability. The computational tool will be developed in hexagonal geometry, based solely on transport theory without (spatial) homogenization in complicated 3D geometries. In addition to the hexagonal geometry extension, collaborators will concurrently develop three additional capabilities to increase the code’s versatility as an advanced and robust core simulator for VHTRs. First, the project team will develop and implementmore » a depletion method within the core simulator. Second, the team will develop an elementary (proof-of-concept) 1D time-dependent transport method for efficient transient analyses. The third capability will be a thermal hydraulic method coupled to the neutronics transport module for VHTRs. Current advancements in reactor core design are pushing VHTRs toward greater core and fuel heterogeneity to pursue higher burn-ups, efficiently transmute used fuel, maximize energy production, and improve plant economics and safety. As a result, an accurate and efficient neutron transport, with capabilities to treat heterogeneous burnable poison effects, is highly desirable for predicting VHTR neutronics performance. This research project’s primary objective is to advance the state of the art for reactor analysis.« less

Thermal oxidation saves $500,000, lifts capacity, upholds compliance

DOE Office of Scientific and Technical Information (OSTI.GOV)

Harley, C.G.; Nagy, A.J.; Sendecki, M.

1985-12-01

The age and destruction of the heat recovery system dictated the replacement of the original fume incinerator at the Congoleum Resilient Flooring Division Plant in Trenton, NJ. The original unit, installed in 1967, had a conventional air-to-oil heat recovery system. Plant personnel placed high priority on finding a replacement with a higher thermal efficiency while still maintaining environmental integrity. A proprietary software program was used to obtain values for NPV (net pressure value) for several competitive equipment systems. The NPV allows simple comparison of equipment based on data such as purchase pgsrice, cost of installation, operating costs, and maintenance costsmore » for the predicted life span of each unit. Based on NPV analysis, a regenerative thermal oxidation unit was selected. To assure expansion capability, Congoleum opted for a 30,000 scfm system. The regenerative thermal oxidation unit consists of a central combustion chamber with five lobes extending radially outward. Each lobe is packed with ceramic refractory elements (saddles) which serve as heat exchange media. The elements are retained by perforated refractory blocks on the hot combustion chamber side and by a grating on the cold side. Estimated savings from the system, about a half million dollars the first year, are expected to significantly exceed Congoleum's original estimates. About half of the total savings will result from reduced consumption of natural gas since the unit is fueled mainly by the organic material in the process exhaust. The other half of the savings has resulted from improvements in production efficiency and the recycling of waste heat from the thermal oxidizer.« less

Goals of thermionic program for space power

NASA Technical Reports Server (NTRS)

English, R. E.

1981-01-01

The thermionic and Brayton reactor concepts were compared for application to space power. For a turbine inlet temperature of 15000 K the Brayton powerplant weighted 5 to 40% less than the thermionic concept. The out of core concept separates the thermionic converters from their reactor. Technical risks are diminished by: (1) moving the insolator out of the reactor; (2) allowing a higher thermal flux for the thermionic converters than is required of the reactor fuel; and (3) eliminating fuel swelling's threat against lifetime of the thermionic converters. Overall performance can be improved by including power processing in system optimization for design and technology on more efficient, higher temperature power processors. The thermionic reactors will be larger than those for competitive systems with higher conversion efficiency and lower reactor operating temperatures. It is concluded that although the effect of reactor size on shield weight will be modest for unmanned spacecraft, the penalty in shield weight will be large for manned or man-tended spacecraft.

Efficiency and its bounds for thermal engines at maximum power using Newton's law of cooling.

PubMed

Yan, H; Guo, Hao

2012-01-01

We study a thermal engine model for which Newton's cooling law is obeyed during heat transfer processes. The thermal efficiency and its bounds at maximum output power are derived and discussed. This model, though quite simple, can be applied not only to Carnot engines but also to four other types of engines. For the long thermal contact time limit, new bounds, tighter than what were known before, are obtained. In this case, this model can simulate Otto, Joule-Brayton, Diesel, and Atkinson engines. While in the short contact time limit, which corresponds to the Carnot cycle, the same efficiency bounds as that from Esposito et al. [Phys. Rev. Lett. 105, 150603 (2010)] are derived. In both cases, the thermal efficiency decreases as the ratio between the heat capacities of the working medium during heating and cooling stages increases. This might provide instructions for designing real engines. © 2012 American Physical Society

Facile thiol-ene thermal crosslinking reaction facilitated hole-transporting layer for highly efficient and stable perovskite solar cells

DOE PAGES

Li, Zhong'an; Zhu, Zonglong; Chueh, Chu -Chen; ...

2016-08-08

A crosslinked organic hole-transporting layer (HTL) is developed to realize highly efficient and stable perovskite solar cells via a facile thiol-ene thermal reaction. This crosslinked HTL not only facilitates hole extraction from perovskites, but also functions as an effective protective barrier. Lastly, a high-performance (power conversion efficiency: 18.3%) device is demonstrated to show respectable photo and thermal stability without encapsulation.

Integrated photovoltaic-thermal solar energy conversion systems

NASA Technical Reports Server (NTRS)

Samara, G. A.

1975-01-01

A combined photovoltaic/thermal collector has been built and is now being tested. Initial tests have concentrated on evaluating the thermal efficiency of the collector before and after the silicon cells are mounted. With likely improvements in bonding between cells and receiver and in the absorptivity of the cells, thermal efficiencies greater than 50% can be expected for the combined receiver operating at 100 C.

Twisting phonons in complex crystals with quasi-one-dimensional substructures [Twisting Phonons in Higher Manganese Silicides with a Complex Nowotny Chimney Ladder Structure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Abernathy, Douglas L.; Ma, Jie; Yan, Jiaqiang

A variety of crystals contain quasi-one-dimensional substructures, which yield distinctive electronic, spintronic, optical and thermoelectric properties. There is a lack of understanding of the lattice dynamics that influences the properties of such complex crystals. Here we employ inelastic neutron scatting measurements and density functional theory calculations to show that numerous low-energy optical vibrational modes exist in higher manganese silicides, an example of such crystals. These optical modes, including unusually low-frequency twisting motions of the Si ladders inside the Mn chimneys, provide a large phase space for scattering acoustic phonons. A hybrid phonon and diffuson model is proposed to explain themore » low and anisotropic thermal conductivity of higher manganese silicides and to evaluate nanostructuring as an approach to further suppress the thermal conductivity and enhance the thermoelectric energy conversion efficiency. This discovery offers new insights into the structure-property relationships of a broad class of materials with quasi-one-dimensional substructures for various applications.« less

Twisting phonons in complex crystals with quasi-one-dimensional substructures [Twisting Phonons in Higher Manganese Silicides with a Complex Nowotny Chimney Ladder Structure

DOE PAGES

Abernathy, Douglas L.; Ma, Jie; Yan, Jiaqiang; ...

2015-04-15

A variety of crystals contain quasi-one-dimensional substructures, which yield distinctive electronic, spintronic, optical and thermoelectric properties. There is a lack of understanding of the lattice dynamics that influences the properties of such complex crystals. Here we employ inelastic neutron scatting measurements and density functional theory calculations to show that numerous low-energy optical vibrational modes exist in higher manganese silicides, an example of such crystals. These optical modes, including unusually low-frequency twisting motions of the Si ladders inside the Mn chimneys, provide a large phase space for scattering acoustic phonons. A hybrid phonon and diffuson model is proposed to explain themore » low and anisotropic thermal conductivity of higher manganese silicides and to evaluate nanostructuring as an approach to further suppress the thermal conductivity and enhance the thermoelectric energy conversion efficiency. This discovery offers new insights into the structure-property relationships of a broad class of materials with quasi-one-dimensional substructures for various applications.« less

Silicon Nitride Plates for Turbine Blade Application: FEA and NDE Assessment

NASA Technical Reports Server (NTRS)

Abdul-Aziz, Ali; Baaklini, George Y.; Bhatt, Ramakrishna T.

2001-01-01

Engine manufacturers are continually attempting to improve the performance and the overall efficiency of internal combustion engines. The thermal efficiency is typically improved by raising the operating temperature of essential engine components in the combustion area. This reduces the heat loss to a cooling system and allows a greater portion of the heat to be used for propulsion. Further improvements can be achieved by diverting part of the air from the compressor, which would have been used in the combustor for combustion purposes, into the turbine components. Such a process is called active cooling. Increasing the operating temperature, decreasing the cooling air, or both can improve the efficiency of the engine. Furthermore, lightweight, strong, tough hightemperature materials are required to complement efficiency improvement for nextgeneration gas turbine engines that can operate with minimum cooling. Because of their low-density, high-temperature strength, and thermal conductivity, ceramics are being investigated as potential materials for replacing ordinary metals that are currently used for engine hot section components. Ceramic structures can withstand higher operating temperatures and other harsh environmental factors. In addition, their low densities relative to metals helps condense component mass (ref. 1). The objectives of this program at the NASA Glenn Research Center are to develop manufacturing technology, a thermal barrier coating/environmental barrier coating (TBC/EBC), and an analytical modeling capability to predict thermomechanical stresses, and to do minimal burner rig tests of silicon nitride (Si3N4) and SiC/SiC turbine nozzle vanes under simulated engine conditions. Furthermore, and in support of the latter objectives, an optimization exercise using finite element analysis and nondestructive evaluation (NDE) was carried out to characterize and evaluate silicon nitride plates with cooling channels.

Thermal conductivity of zirconia thermal barrier coatings

NASA Technical Reports Server (NTRS)

Dinwiddie, R. B.; Beecher, S. C.; Nagaraj, B. A.; Moore, C. S.

1995-01-01

Thermal barrier coatings (TBC's) applied to the hot gas components of turbine engines lead to enhanced fuel efficiency and component reliability. Understanding the mechanisms which control the thermal transport behavior of the TBC's is of primary importance. Physical vapor description (PVD) and plasma spraying (PS) are the two most commonly used coating techniques. These techniques produce coatings with unique microstructures which control their performance and stability. The PS coatings were applied with either standard power or hollow sphere particles. The hollow sphere particles yielded a lower density and lower thermal conductivity coating. The thermal conductivity of both fully and partially stabilized zirconia, before and after thermal aging, will be compared. The thermal conductivity of the coatings permanently increase upon being exposed to high temperatures. These increases are attributed to microstructural changes within the coatings. Sintering of the as fabricated plasma sprayed lamellar structure is observed by scanning electron microscopy of coatings isothermally heat treated at temperatures greater than 1100 C. During this sintering process the planar porosity between lamella is converted to a series of small spherical pores. The change in pore morphology is the primary reason for the observed increase in thermal conductivity. This increase in thermal conductivity can be modeled using a relationship which depends on both the temperature and time of exposure. Although the PVD coatings are less susceptible to thermal aging effects, preliminary results suggest that they have a higher thermal conductivity than PS coatings, both before and after thermal aging. The increases in thermal conductivity due to thermal aging for partially stabilized plasma sprayed zirconia have been found to be less than for fully stabilized plasma sprayed zirconia coatings. The high temperature thermal diffusivity data indicates that if these coatings reach a temperature above 1100 C during operation, they will begin to lose their effectiveness as a thermal barrier.

Thermal conductivity of zirconia thermal barrier coatings

NASA Technical Reports Server (NTRS)

Dinwiddie, R. B.; Beecher, S. C.; Nagaraj, B. A.; Moore, C. S.

1995-01-01

Thermal barrier coatings (TBC's) applied to the hot gas components of turbine engines lead to enhanced fuel efficiency and component reliability. Understanding the mechanisms which control the thermal transport behavior of the TBC's is of primary importance. Physical vapor deposition (PVD) and plasma spraying (PS) are the two most commonly used coating techniques. These techniques produce coatings with unique microstructures which control their performance and stability. The PS coatings were applied with either standard powder or hollow sphere particles. The hollow sphere particles yielded a lower density and lower thermal conductivity coating. The thermal conductivity of both fully and partially stabilized zirconia, before and after thermal aging, will be compared. The thermal conductivity of the coatings permanently increases upon exposed to high temperatures. These increases are attributed to microstructural changes within the coatings. Sintering of the as-fabricated plasma sprayed lamellar structure is observed by scanning electron microscopy of coatings isothermally heat treated at temperatures greater than 1100 C. During this sintering process the planar porosity between lamella is converted to a series of small spherical pores. The change in pore morphology is the primary reason for the observed increase in thermal conductivity. This increase in thermal conductivity can be modeled using a relationship which depends on both the temperature and time of exposure. Although the PVD coatings are less susceptible to thermal aging effects, preliminary results suggest that they have a higher thermal conductivity than PS coatings, both before and after thermal aging. The increases in thermal conductivity due to thermal aging for partially stabilized plasma sprayed zirconia have been found to be less than for fully stabilized plasma sprayed zirconia coatings. The high temperature thermal diffusivity data indicate that if these coatings reach a temperature above 1100 C during operation, they will begin to lose their effectiveness as a thermal barrier.

Claisen thermally rearranged (CTR) polymers

PubMed Central

Tena, Alberto; Rangou, Sofia; Shishatskiy, Sergey; Filiz, Volkan; Abetz, Volker

2016-01-01

Thermally rearranged (TR) polymers, which are considered the next-generation of membrane materials because of their excellent transport properties and high thermal and chemical stability, are proven to have significant drawbacks because of the high temperature required for the rearrangement and low degree of conversion during this process. We demonstrate that using a [3,3]-sigmatropic rearrangement, the temperature required for the rearrangement of a solid glassy polymer was reduced by 200°C. Conversions of functionalized polyimide to polybenzoxazole of more than 97% were achieved. These highly mechanically stable polymers were almost five times more permeable and had more than two times higher degrees of conversion than the reference polymer treated under the same conditions. Properties of these second-generation TR polymers provide the possibility of preparing efficient polymer membranes in a form of, for example, thin-film composite membranes for various gas and liquid membrane separation applications. PMID:27482538

Claisen thermally rearranged (CTR) polymers.

PubMed

Tena, Alberto; Rangou, Sofia; Shishatskiy, Sergey; Filiz, Volkan; Abetz, Volker

2016-07-01

Thermally rearranged (TR) polymers, which are considered the next-generation of membrane materials because of their excellent transport properties and high thermal and chemical stability, are proven to have significant drawbacks because of the high temperature required for the rearrangement and low degree of conversion during this process. We demonstrate that using a [3,3]-sigmatropic rearrangement, the temperature required for the rearrangement of a solid glassy polymer was reduced by 200°C. Conversions of functionalized polyimide to polybenzoxazole of more than 97% were achieved. These highly mechanically stable polymers were almost five times more permeable and had more than two times higher degrees of conversion than the reference polymer treated under the same conditions. Properties of these second-generation TR polymers provide the possibility of preparing efficient polymer membranes in a form of, for example, thin-film composite membranes for various gas and liquid membrane separation applications.

Thermal Adaptation of Dihydrofolate Reductase from the Moderate Thermophile Geobacillus stearothermophilus

PubMed Central

2014-01-01

The thermal melting temperature of dihydrofolate reductase from Geobacillus stearothermophilus (BsDHFR) is ∼30 °C higher than that of its homologue from the psychrophile Moritella profunda. Additional proline residues in the loop regions of BsDHFR have been proposed to enhance the thermostability of BsDHFR, but site-directed mutagenesis studies reveal that these proline residues contribute only minimally. Instead, the high thermal stability of BsDHFR is partly due to removal of water-accessible thermolabile residues such as glutamine and methionine, which are prone to hydrolysis or oxidation at high temperatures. The extra thermostability of BsDHFR can be obtained by ligand binding, or in the presence of salts or cosolvents such as glycerol and sucrose. The sum of all these incremental factors allows BsDHFR to function efficiently in the natural habitat of G. stearothermophilus, which is characterized by temperatures that can reach 75 °C. PMID:24730604

Photosynthetic response to low sink demand after fruit removal in relation to photoinhibition and photoprotection in peach trees.

PubMed

Duan, Wei; Fan, Pei G; Wang, Li J; Li, Wei D; Yan, Shu T; Li, Shao H

2008-01-01

Diurnal variations in photosynthesis, chlorophyll fluorescence, xanthophyll cycle, antioxidant enzymes and antioxidant metabolism in leaves in response to low sink demand caused by fruit removal (-fruit) were studied in 'Zaojiubao' peach (Prunus persica (L.) Batch) trees during the final stage of rapid fruit growth. Compared with the retained fruit treatment (+fruit), the -fruit treatment resulted in a significantly lower photosynthetic rate, stomatal conductance and transpiration rate, but generally higher internal CO(2) concentration, leaf-to-air vapor pressure difference and leaf temperature. The low photosynthetic rate in the -fruit trees paralleled reductions in maximal efficiency of photosystem II (PSII) photochemistry and carboxylation efficiency. The midday depression in photosynthetic rate in response to low sink demand resulting from fruit removal was mainly caused by non-stomatal limitation. Fruit removal resulted in lower quantum efficiency of PSII as a result of both a decrease in the efficiency of excitation capture by open PSII reaction centers and an increase in closure of PSII reaction centers. Both xanthophyll-dependent thermal dissipation and the antioxidant system were up-regulated providing protection from photo-oxidative damage to leaves during low sink demand. Compared with the leaves of +fruit trees, leaves of -fruit trees had a larger xanthophyll cycle pool size and a higher de-epoxidation state, as well as significantly higher activities of antioxidant enzymes, including superoxide dismutase, ascorbate peroxidase, monodehydroascorbate reductase, dehydroascorbate reductase, glutathione reductase and a higher reduction state of ascorbate and glutathione. However, the -fruit treatment resulted in higher hydrogen peroxide and malondialdehyde concentrations compared with the +fruit treatment, indicating photo-oxidative damage.

Effect of ultrasonication in synthesis of gold nano fluid for thermal applications

NASA Astrophysics Data System (ADS)

Nath, G.; Giri, R.

2018-02-01

Ultrasonically synthesized nanofluids are efficient coolant and heat exchanger material has demonstrated its potential in various fields and thermal engineering. The computation of different acoustical parameter using the ultrasonic velocity data of gold nanofluids are taken in estimation of thermal conductivity. The computational and experimental measured values of thermal conductivity are well agrees. The results execute ultrasonically synthesized gold nanofluids is an economic and efficient technology for explaining the increase of thermal conductivity of nanofluids in suitable optimum conditions.

Temperature, energy metabolism, and adaptive divergence in two oyster subspecies.

PubMed

Li, Ao; Li, Li; Song, Kai; Wang, Wei; Zhang, Guofan

2017-08-01

Comparisons of related species that have diverse spatial distributions provide an efficient way to investigate adaptive evolution in face of increasing global warming. The oyster subjected to high environmental selections is a model species as sessile marine invertebrate. This study aimed to detect the adaptive divergence of energy metabolism in two oyster subspecies from the genus Crassostrea - C. gigas gigas and C. gigas angulata -which are broadly distributed along the northern and southern coasts of China, respectively. We examined the effects of acute thermal stress on energy metabolism in two oyster subspecies after being common gardened for one generation in identical conditions. Thermal responses were assessed by incorporating physiological, molecular, and genomic approaches. Southern oysters exhibited higher fluctuations in metabolic rate, activities of key energetic enzymes, and levels of thermally induced gene expression than northern oysters. For genes involved in energy metabolism, the former displayed higher basal levels of gene expression and a more pronounced downregulation of thermally induced expression, while the later exhibited lower basal levels and a less pronounced downregulation of gene expression. Contrary expression pattern was observed in oxidative stress gene. Besides, energy metabolic tradeoffs were detected in both subspecies. Furthermore, the genetic divergence of a nonsynonymous SNP ( SOD-132 ) and five synonymous SNPs in other genes was identified and validated in these two subspecies, which possibly affects downstream functions and explains the aforementioned phenotypic variations. Our study demonstrates that differentiations in energy metabolism underlie the plasticity of adaptive divergence in two oyster subspecies and suggest C. gigas angulata with moderate phenotypic plasticity has higher adaptive potential to cope with exacerbated global warming.

Optically Transparent Thermally Insulating Silica Aerogels for Solar Thermal Insulation.

PubMed

Günay, A Alperen; Kim, Hannah; Nagarajan, Naveen; Lopez, Mateusz; Kantharaj, Rajath; Alsaati, Albraa; Marconnet, Amy; Lenert, Andrej; Miljkovic, Nenad

2018-04-18

Rooftop solar thermal collectors have the potential to meet residential heating demands if deployed efficiently at low solar irradiance (i.e., 1 sun). The efficiency of solar thermal collectors depends on their ability to absorb incoming solar energy and minimize thermal losses. Most techniques utilize a vacuum gap between the solar absorber and the surroundings to eliminate conduction and convection losses, in combination with surface coatings to minimize reradiation losses. Here, we present an alternative approach that operates at atmospheric pressure with simple, black, absorbing surfaces. Silica based aerogels coated on black surfaces have the potential to act as simple and inexpensive solar thermal collectors because of their high transmission to solar radiation and low transmission to thermal radiation. To demonstrate their heat-trapping properties, we fabricated tetramethyl orthosilicate-based silica aerogels. A hydrophilic aerogel with a thickness of 1 cm exhibited a solar-averaged transmission of 76% and thermally averaged transmission of ≈1% (at 100 °C). To minimize unwanted solar absorption by O-H groups, we functionalized the aerogel to be hydrophobic, resulting in a solar-averaged transmission of 88%. To provide a deeper understanding of the link between aerogel properties and overall efficiency, we developed a coupled radiative-conductive heat transfer model and used it to predict solar thermal performance. Instantaneous solar thermal efficiencies approaching 55% at 1 sun and 80 °C were predicted. This study sheds light on the applicability of silica aerogels on black coatings for solar thermal collectors and offers design priorities for next-generation solar thermal aerogels.

Microcombustor-thermoelectric power generator for 10-50 watt applications

NASA Astrophysics Data System (ADS)

Marshall, Daniel S.; Cho, Steve T.

2010-04-01

Fuel-based portable power systems, including combustion and fuel cell systems, take advantage of the 80x higher energy density of fuel over lithium battery technologies and offer the potential for much higher energy density power sources - especially for long-duration applications, such as unattended sensors. Miniaturization of fuel-based systems poses significant challenges, including processing of fuel in small channels, catalyst poisoning, and coke and soot formation. Recent advances in micro-miniature combustors in the 200Watt thermal range have enabled the development of small power sources that use the chemical energy of heavy fuel to drive thermal-to-electric converters for portable applications. CUBE Technology has developed compact Micro-Furnace combustors that efficiently deliver high-quality heat to optimized thermal-to-electric power converters, such as advanced thermoelectric power modules and Stirling motors, for portable power generation at the 10-50Watt scale. Key innovations include a compact gas-gas recuperator, innovative heavy fuel processing, coke- & soot-free operation, and combustor optimization for low balance-of-plant power use while operating at full throttle. This combustor enables the development of robust, high energy density, miniature power sources for portable applications.

Chapter 11: Concentrating Solar Power

DOE Office of Scientific and Technical Information (OSTI.GOV)

Turchi, Craig S; Stekli, J.; Bueno, P. C.

2017-01-02

This chapter summarizes the applications of the supercritical CO2 (sCO2) Brayton cycle in concentrating solar power (CSP) plants. The design and operation of CSP plants are reviewed to highlight the requirements for the power cycle and attributes that are advantageous for the solar-thermal application. The sCO2 Brayton cycle offers the potential of higher cycle efficiency versus superheated or supercritical steam cycles at temperatures relevant for CSP applications. In addition, Brayton cycle systems using sCO2 are anticipated to have smaller weight and volume, lower thermal mass, and less complex power blocks compared with Rankine cycles due to the higher density ofmore » the fluid and simpler cycle design. The simpler machinery and compact size of the sCO2 process may also reduce the installation, maintenance, and operation cost of the system. Power cycle capacities in the range of 10-150 MWe are anticipated for the CSP application. In this chapter, we explore sCO2 Brayton cycle configurations that have attributes that are desirable from the perspective of a CSP application, such as the ability to accommodate dry cooling and daily cycling, as well as integration with thermal energy storage.« less

Experimental investigations of hybrid PV/Spiral flow thermal collector system performance using Al2O3/water nanofluid

NASA Astrophysics Data System (ADS)

Gangadevi, R.; Vinayagam, B. K.; Senthilraja, S.

2017-05-01

In this paper, the PV/T (Photovoltaic thermal unit) system is investigated experimentally to examine the thermal, electrical and overall efficiency by circulating Al2O3/water nanofluid of 1wt% and 2wt% with an optimum flow rate of 40L/H. The overall efficiency of PVT system is largely influenced by various factors such as heat due to photovoltaic action; energy radiated at the infrared wavelength of the solar spectrum, solar irradiance, mounting structure, tilt angle, wind speed direction, Ambient temperature and panel material composition. However, the major factor is considered in this study to extract the heat generated in the PV panel by using nanofluid as a coolant to increase the overall system efficiency. Therefore, the result shows that by using 2 wt% Al2O3/water nanofluid the electrical efficiency, thermal efficiency and overall efficiency of the PVT system enhanced by 13%, 45%, and 58% respectively compared with water.

Concept Doped-Silicon Thermopile Detectors for Future Planetary Thermal Imaging Instruments

NASA Astrophysics Data System (ADS)

Lakew, Brook; Barrentine, Emily M.; Aslam, Shahid; Brown, Ari D.

2016-10-01

Presently, uncooled thermopiles are the detectors of choice for thermal mapping in the 4.6-100 μm spectral range. Although cooled detectors like Ge or Si thermistor bolometers, and MgB2 or YBCO superconducting bolometers, have much higher sensitivity, the required active or passive cooling mechanisms add prohibitive cost and mass for long duration missions. Other uncooled detectors, likepyroelectrics, require a motor mechanism to chop against a known reference temperature, which adds unnecessary mission risk. Uncooled vanadium oxide or amorphous Si microbolometer arrays with integrated CMOS readout circuits, not only have lower sensitivity, but also have not been proven to be radiation hard >100 krad (Si) total ionizing dose, and barring additional materials and readout development, their performance has reached a plateau.Uncooled and radiation hard thermopiles with D* ~1x109 cm√Hz/W and time constant τ ~100 ms have been integrated into thermal imaging instruments on several past missions and have extensive flight heritage (Mariner, Voyager, Cassini, LRO, MRO). Thermopile arrays are also on the MERTIS instrument payload on-board the soon to be launched BepiColombo Mission.To date, thermopiles used for spaceflight instrumentation have consisted of either hand assembled "one-off" single thermopile pixels or COTS thermopile pixel arrays both using Bi-Sb or Bi-Te thermoelectric materials. For future high performance imagers, thermal detector arrays with higher D*, lower τ, and high efficiency delineated absorbers are desirable. Existing COTS and other flight thermopile designs require highly specialized and nonstandard processing techniques to fabricate both the Bi-Sb or Bi-Te thermocouples and the gold or silver black absorbers, which put limitations on further development.Our detector arrays will have a D* ≥ 3x109 cm√Hz/W and a thermal time constant ≤ 30 ms at 170 K. They will be produced using proven, standard semiconductor and MEMS fabrication techniques, which will enable the future integration of other ancillary structures like high efficiency broadband absorbers, which will result in D* ≥ 5x109 cm√Hz/W.

Energy Engineering Analysis Program. Lighting Survey of Selected Buildings, Pine Bluff Arsenal, Pine Bluff, Arkansas. Volume 2A: Appendices

DTIC Science & Technology

1995-06-01

Energy efficient, 30 and 40 watt ballasts are Rapid Start, thermally protected, automatic resetting. Class P, high or low power factor as required...BALLASTS Energy efficient, 30 ana 40 watt Rapic Start, thermally protected, automatic resetting. Class P. high power factor, CEM, sound rated A. unless...BALLASTS Energy efficient, 40 Watt Rapid Start, thermally protected, automatic resetting, Class P, high power factor, CBM, sound rated A, unless

Thermally regenerative hydrogen/oxygen fuel cell power cycles

NASA Technical Reports Server (NTRS)

Morehouse, J. H.

1986-01-01

Two innovative thermodynamic power cycles are analytically examined for future engineering feasibility. The power cycles use a hydrogen-oxygen fuel cell for electrical energy production and use the thermal dissociation of water for regeneration of the hydrogen and oxygen. The TDS (thermal dissociation system) uses a thermal energy input at over 2000 K to thermally dissociate the water. The other cycle, the HTE (high temperature electrolyzer) system, dissociates the water using an electrolyzer operating at high temperature (1300 K) which receives its electrical energy from the fuel cell. The primary advantages of these cycles is that they are basically a no moving parts system, thus having the potential for long life and high reliability, and they have the potential for high thermal efficiency. Both cycles are shown to be classical heat engines with ideal efficiency close to Carnot cycle efficiency. The feasibility of constructing actual cycles is investigated by examining process irreversibilities and device efficiencies for the two types of cycles. The results show that while the processes and devices of the 2000 K TDS exceed current technology limits, the high temperature electrolyzer system appears to be a state-of-the-art technology development. The requirements for very high electrolyzer and fuel cell efficiencies are seen as determining the feasbility of the HTE system, and these high efficiency devices are currently being developed. It is concluded that a proof-of-concept HTE system experiment can and should be conducted.

Efficient solar-driven synthesis, carbon capture, and desalinization, STEP: solar thermal electrochemical production of fuels, metals, bleach.

PubMed

Licht, S

2011-12-15

STEP (solar thermal electrochemical production) theory is derived and experimentally verified for the electrosynthesis of energetic molecules at solar energy efficiency greater than any photovoltaic conversion efficiency. In STEP the efficient formation of metals, fuels, chlorine, and carbon capture is driven by solar thermal heated endothermic electrolyses of concentrated reactants occuring at a voltage below that of the room temperature energy stored in the products. One example is CO(2) , which is reduced to either fuels or storable carbon at a solar efficiency of over 50% due to a synergy of efficient solar thermal absorption and electrochemical conversion at high temperature and reactant concentration. CO(2) -free production of iron by STEP, from iron ore, occurs via Fe(III) in molten carbonate. Water is efficiently split to hydrogen by molten hydroxide electrolysis, and chlorine, sodium, and magnesium from molten chlorides. A pathway is provided for the STEP decrease of atmospheric carbon dioxide levels to pre-industial age levels in 10 years. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A dual-stage sodium thermal electrochemical converter (Na-TEC)

NASA Astrophysics Data System (ADS)

Limia, Alexander; Ha, Jong Min; Kottke, Peter; Gunawan, Andrey; Fedorov, Andrei G.; Lee, Seung Woo; Yee, Shannon K.

2017-12-01

The sodium thermal electrochemical converter (Na-TEC) is a heat engine that generates electricity through the isothermal expansion of sodium ions. The Na-TEC is a closed system that can theoretically achieve conversion efficiencies above 45% when operating between thermal reservoirs at 1150 K and 550 K. However, thermal designs have confined previous single-stage devices to thermal efficiencies below 20%. To mitigate some of these limitations, we consider dividing the isothermal expansion into two stages; one at the evaporator temperature (1150 K) and another at an intermediate temperature (650 K-1050 K). This dual-stage Na-TEC takes advantage of regeneration and reheating, and could be amenable to better thermal management. Herein, we demonstrate how the dual-stage device can improve the efficiency by up to 8% points over the best performing single-stage device. We also establish an application regime map for the single- and dual-stage Na-TEC in terms of the power density and the total thermal parasitic loss. Generally, a single-stage Na-TEC should be used for applications requiring high power densities, whereas a dual-stage Na-TEC should be used for applications requiring high efficiency.

Study on cold head structure of a 300 Hz thermoacoustically driven pulse tube cryocooler

NASA Astrophysics Data System (ADS)

Yu, G. Y.; Wang, X. T.; Dai, W.; Luo, E. C.

2012-04-01

High reliability, compact size and potentially high thermal efficiency make the high frequency thermoacoustically-driven pulse tube cryocooler quite promising for space use. With continuous efforts, the lowest temperature and the thermal efficiency of the coupled system have been greatly improved. So far, a cold head temperature below 60 K has been achieved on such kind of cryocooler with the operation frequency of around 300 Hz. To further improve the thermal efficiency and expedite its practical application, this work focuses on studying the influence of cold head structure on the system performance. Substantial numerical simulations were firstly carried out, which revealed that the cold head structure would greatly influence the cooling power and the thermal efficiency. To validate the predictions, a lot of experiments have been done. The experiments and calculations are in reasonable agreement. With 500 W heating power input into the engine, a no-load temperature of 63 K and a cooling power of 1.16 W at 80 K have been obtained with parallel-plate cold head, indicating encouraging improvement of the thermal efficiency.

Study of the electrical and thermal performances of photovoltaic thermal collector-compound parabolic concentrated

NASA Astrophysics Data System (ADS)

Jaaz, Ahed Hameed; Sopian, Kamaruzzaman; Gaaz, Tayser Sumer

2018-06-01

The importance of utilizing the solar energy as a very suitable source among multi-source approaches to replace the conventional energy is on the rise in the last four decades. The invention of the photovoltaic module (PV) could be the corner stone in this process. However, the limited amount of energy obtained from PV was and still the main challenge of full utilization of the solar energy. In this paper, the use of the compound parabolic concentrator (CPC) along with the thermal photovoltaic module (PVT) where the cooling process of the CPC is conducted using a novel technique of water jet impingement has applied experimentally and physically tested. The test includes the effect of water jet impingement on the total power, electrical efficiency, thermal efficiency, and total efficiency on CPC-PVT system. The cooling process at the maximum irradiation by water jet impingement resulted in improving the electrical efficiency by 7%, total output power by 31% and the thermal efficiency by 81%. These results outperform the recent highest results recorded by the most recent work.

Effect of temperature on the release of hexadecane from soil by thermal treatment.

PubMed

Merino, Jerónimo; Bucalá, Verónica

2007-05-08

A natural organic soil (2.5% of total organic carbon) was artificially contaminated with hexadecane, and thermally treated under an inert medium up to different final temperatures (150-800 degrees C) for 30 min to simulate ex situ thermal process conditions. The experiments were conducted using a complete organic soil, instead of the clays or isolated soil fractions that are commonly used. Neat and contaminated samples were separately heated to understand the impact of the soil itself and the contaminant in the release of volatiles. The soil quality as well as the quality and amount of volatile compounds generated during the process were monitored. More than 80-88% of the initial hexadecane content in the soil matrix was recovered in liquids traps after the thermal treatment, therefore the contaminant could be recovered for further recycling. The high amount of hexadecane collected without suffering chemical transformations indicated that the main mechanism for the hexadecane removal was evaporation. The analysis of the light gases released from contaminated samples indicated negligible or null hexadecane pyrolysis reaction rates, confirming that the evaporation/desorption of the contaminant are the processes that governed the removal of the contaminant from the soil. For the soil tested, of a relatively low surface area, good removal efficiencies (higher than 99.9%) were detected at about 300 degrees C, being higher temperatures not necessary to significantly improve the contamination removal.

Steam gasification of a thermally pretreated high lignin corn stover simultaneous saccharification and fermentation digester residue

DOE Office of Scientific and Technical Information (OSTI.GOV)

Howe, Daniel T.; Taasevigen, Danny; Garcia-Perez, Manuel

Efficient conversion of all components in lignocellulosic biomass is essential to realizing economic feasibility of biorefineries. However, when utilizing biochemical pathways, lignin cannot be fermented. Furthermore, the high lignin and high ash residue resulting from simultaneous saccharification and fermentation (SSF) reactors is difficult to thermochemically process due to feed line plugging and bed agglomeration. In this study a corn stover SSF digester residue was thermally pretreated at 300°C for 22.5 minutes (min) and then gasified in a bubbling fluidized bed gasifier to study the effect of thermal pretreatment on its processing behavior. Untreated, pelletized SSF residue was gasified at themore » same conditions to establish the baseline processing behavior. Results indicate that the thermal pretreatment process removes a substantial portion of the polar and non-polar extractives, with a resultant increase in the concentration of lignin, cellulose, and ash. Feed line plugging was not observed, although bed agglomeration was occurring at similar rates for both feedstocks, suggesting that overall ash content is the most important factor affecting bed agglomeration. Benzene, phenol, and polyaromatic hydrocarbons in the tar were present at higher concentrations in the treated material, with higher tar loading in the product gas. Total product gas generation is lower for the treated material, although the overall gas composition does not change.« less

Lower-Conductivity Ceramic Materials for Thermal-Barrier Coatings

NASA Technical Reports Server (NTRS)

Bansal, Narottam P.; Zhu, Dongming

2006-01-01

Doped pyrochlore oxides of a type described below are under consideration as alternative materials for high-temperature thermal-barrier coatings (TBCs). In comparison with partially-yttria-stabilized zirconia (YSZ), which is the state-of-the-art TBC material now in commercial use, these doped pyrochlore oxides exhibit lower thermal conductivities, which could be exploited to obtain the following advantages: For a given difference in temperature between an outer coating surface and the coating/substrate interface, the coating could be thinner. Reductions in coating thicknesses could translate to reductions in weight of hot-section components of turbine engines (e.g., combustor liners, blades, and vanes) to which TBCs are typically applied. For a given coating thickness, the difference in temperature between the outer coating surface and the coating/substrate interface could be greater. For turbine engines, this could translate to higher operating temperatures, with consequent increases in efficiency and reductions in polluting emissions. TBCs are needed because the temperatures in some turbine-engine hot sections exceed the maximum temperatures that the substrate materials (superalloys, Si-based ceramics, and others) can withstand. YSZ TBCs are applied to engine components as thin layers by plasma spraying or electron-beam physical vapor deposition. During operation at higher temperatures, YSZ layers undergo sintering, which increases their thermal conductivities and thereby renders them less effective as TBCs. Moreover, the sintered YSZ TBCs are less tolerant of stress and strain and, hence, are less durable.

Process Parameters for Successful Synthesis of Carbon Nanotubes by Chemical Vapor Deposition: Implications for Chemical Mechanisms and Life-cycle Assessment

NASA Astrophysics Data System (ADS)

Xue, Ke

Manufacturing of carbon nanotubes (CNTs) via chemical vapor deposition (CVD) calls for thermal treatment associated with gas-phase rearrangement and catalyst deposition to achieve high cost efficiency and limited influence on environmental impact. Taking advantage of higher degree of structure control and economical efficiency, catalytic chemical vapor deposition (CCVD) has currently become the most prevailing synthesis approach for the synthesis of large-scale pure CNTs in past years. Because the synthesis process of CNTs dominates the potential ecotoxic impacts, materials consumption, energy consumption and greenhouse gas emissions should be further limited to efficiently reduce life cycle ecotoxicity of carbon naotubes. However, efforts to reduce energy and material requirements in synthesis of CNTs by CCVD are hindered by a lack of mechanistic understanding. In this thesis, the effect of operating parameters, especially the temperature, carbon source concentration, and residence time on the synthesis were studied to improve the production efficiency in a different angle. Thus, implications on the choice of operating parameters could be provided to help the synthesis of carbon nanotubes. Here, we investigated the typical operating parameters in conditions that have yielded successful CNT production in the published academic literature of over seventy articles. The data were filtered by quality of the resultant product and deemed either "successful" or "unsuccessful" according to the authors. Furthermore, growth rate data were tabulated and used as performance metric for the process whenever possible. The data provided us an opportunity to prompt possible and common methods for practioners in the synthesis of CNTs and motivate routes to achieve energy and material minimization. The statistical analysis revealed that methane and ethylene often rely on thermal conversion process to form direct carbon precursor; further, methane and ethylene could not be the direct CNT precursors by themselves. Acetylene does not show an additional energy demand or thermal conversion in the synthesis, and it could be the direct CNT precursors by itself; or at least, it would be most easily to get access to carbon nanotube growth while minimizing synthesis temperature. In detail, methane employs more energy demand (Tavg=883°C) than ethylene (Tavg=766°C), which in turn demands more energy than acetylene (Tavg=710°C) to successfully synthesize carbon nanotubes. The distinction in energy demand could be the result of kinetic energy requirements by the thermal conversion process of methane and ethylene to form direct CNT precursors, and methane employs the highest activation demand among three hydrocarbons. Thus, these results support the hypothesis that methane and ethylene could be thermally converted to form acetylene before CNT incorporation. In addition, methane and ethylene show the demand for hydrogen in thermal conversion process before CNT incorporation; whereas, hydrogen does not contribute to the synthesis via acetylene before CNT incorporation, except the reduction of catalyst. At relatively low hydrogen concentration, this work suggests that hydrogen prompts growth of carbon nanotubes via methane and ethylene, probably by reducing the catalysts or participating thermal reactions. In addition, "polymerization-like formation mechanism" could be supported by the higher growth rate of CNTs via ethylene than acetylene. There could be an optimum residence time to maintain a relatively higher growth rate. At too low residence time, carbon source could not be accumulated, causing a waste of material; while too high residence time may cause the limitation of carbon source supplement and accumulation of byproducts. At last, high concentration of carbon source and hydrogen could cause more energy consumption, while it helps to achieve a high growth rate, due to the more presence of direct carbon precursor.

Acceleration efficiency in nonthermal sources and the soft gamma rays from NGC 4151 observed by OSSE and SIGMA

NASA Technical Reports Server (NTRS)

Zdziarski, Andrzej A.; Lightman, Alan P.; Maciolek-Niedzwiecki, Andrzej

1993-01-01

We show that the recent observations of the Seyfert galaxy NGC 4151 in hard X-rays and soft gamma rays by the OSSE and SIGMA detectors on board CGRO and GRANAT, respectively, are well explained by a nonthermal model with acceleration of relativistic electrons at an efficiency of less than 50 percent and with the remaining power dissipated thermally in the source (the standard nonthermal e(+/-) pair model assumed 100 percent efficiency). Such an acceleration efficiency is generally expected on physical grounds. The resulting model unifies previously proposed purely thermal and purely nonthermal models. The pure nonthermal model for NGC 4151 appears to be ruled out. The pure thermal model gives a worse fit to the data than our hybrid nonthermal/thermal model.

Glove thermal insulation: local heat transfer measures and relevance.

PubMed

Sari, Hayet; Gartner, Maurice; Hoeft, Alain; Candas, Victor

2004-09-01

When exposed to cold, the hands need to be protected against heat loss not only in order to reduce thermal discomfort, but also to keep their efficiency. Although gloves are usually the most common protection, their thermal insulation is generally unknown. The aim of this study was to measure the heat losses from a gloved hand with a special interest in local variations. Using a calorimetric hand placed in a cold box, several types of gloves were tested. The results indicated that depending on the glove and on the area covered the heat loss reduction may vary from almost 60% to 90%. When the least efficient pair of gloves was excluded, heat exchange coefficients varied from 1.8 to 4.8 W/m2 per degrees C for the palm and from 4.2 to 6.2 W/m2 per degrees C for the back of the hand. The three medium fingers seemed to be equally treated, with a heat exchange coefficient variation of 6.3-9.0 W/m2 per degrees C. The thumb and the little finger, which require better insulation, exhibited higher local heat transfer coefficients of 8.3-12.7 W/m2 per degrees C. Some practical aspects are evoked.

Including Thermal Fluctuations in Actomyosin Stable States Increases the Predicted Force per Motor and Macroscopic Efficiency in Muscle Modelling

PubMed Central

2016-01-01

Muscle contractions are generated by cyclical interactions of myosin heads with actin filaments to form the actomyosin complex. To simulate actomyosin complex stable states, mathematical models usually define an energy landscape with a corresponding number of wells. The jumps between these wells are defined through rate constants. Almost all previous models assign these wells an infinite sharpness by imposing a relatively simple expression for the detailed balance, i.e., the ratio of the rate constants depends exponentially on the sole myosin elastic energy. Physically, this assumption corresponds to neglecting thermal fluctuations in the actomyosin complex stable states. By comparing three mathematical models, we examine the extent to which this hypothesis affects muscle model predictions at the single cross-bridge, single fiber, and organ levels in a ceteris paribus analysis. We show that including fluctuations in stable states allows the lever arm of the myosin to easily and dynamically explore all possible minima in the energy landscape, generating several backward and forward jumps between states during the lifetime of the actomyosin complex, whereas the infinitely sharp minima case is characterized by fewer jumps between states. Moreover, the analysis predicts that thermal fluctuations enable a more efficient contraction mechanism, in which a higher force is sustained by fewer attached cross-bridges. PMID:27626630

Comparative thermometric properties of bi-functional Er3+-Yb3+ doped rare earth (RE = Y, Gd and La) molybdates

NASA Astrophysics Data System (ADS)

Sinha, Shriya; Mahata, Manoj Kumar; Kumar, Kaushal

2018-02-01

The molybdate compounds as luminescent medium have received great attention of recent research due to their excellent intrinsic optical properties. Therefore, the investigation on the optical thermometry and nanoheating effect in Er3+-Yb3+ doped molybdates of yttrium (EYYMO), gadolinium (EYGMO) and lanthanum (EYLMO) nanophosphors is reported herein. The temperature dependent fluorescence intensity ratio of green (525 and 548 nm) emission bands of Er3+ ions were analyzed within 300-500 K temperature range to determine the thermal behavior. The comparative temperature sensitivity of the materials has been found to depend on the phonon energy of their own. The thermal sensitivity is higher in the materials with low phonon energy. The intensity ratio of the green emission bands has been found to alter with the laser excitation density, which can be used to estimate the induced temperature in the materials. Furthermore, the photothermal conversion efficiency is calculated in the water dispersed samples and the maximum photothermal conversion efficiency of 49.6% is achieved for EYGMO nanophosphor. Comparative experimental results explore unequal thermal sensing and induced optical heating in the three rare earth molybdates. The optical properties of the green emitting molybdates are interesting for temperature sensing and optical heating applications.

Efficiency and its bounds for a quantum Einstein engine at maximum power.

PubMed

Yan, H; Guo, Hao

2012-11-01

We study a quantum thermal engine model for which the heat transfer law is determined by Einstein's theory of radiation. The working substance of the quantum engine is assumed to be a two-level quantum system of which the constituent particles obey Maxwell-Boltzmann (MB), Fermi-Dirac (FD), or Bose-Einstein (BE) distributions, respectively, at equilibrium. The thermal efficiency and its bounds at maximum power of these models are derived and discussed in the long and short thermal contact time limits. The similarity and difference between these models are discussed. We also compare the efficiency bounds of this quantum thermal engine to those of its classical counterpart.

Limits to solar power conversion efficiency with applications to quantum and thermal systems

NASA Technical Reports Server (NTRS)

Byvik, C. E.; Buoncristiani, A. M.; Smith, B. T.

1983-01-01

An analytical framework is presented that permits examination of the limit to the efficiency of various solar power conversion devices. Thermodynamic limits to solar power efficiency are determined for both quantum and thermal systems, and the results are applied to a variety of devices currently considered for use in space systems. The power conversion efficiency for single-threshold energy quantum systems receiving unconcentrated air mass zero solar radiation is limited to 31 percent. This limit applies to photovoltaic cells directly converting solar radiation, or indirectly, as in the case of a thermophotovoltaic system. Photoelectrochemical cells rely on an additional chemical reaction at the semiconductor-electrolyte interface, which introduces additional second-law demands and a reduction of the solar conversion efficiency. Photochemical systems exhibit even lower possible efficiencies because of their relatively narrow absorption bands. Solar-powered thermal engines in contact with an ambient reservoir at 300 K and operating at maximum power have a peak conversion efficiency of 64 percent, and this occurs for a thermal reservoir at a temperature of 2900 K. The power conversion efficiency of a solar-powered liquid metal magnetohydrodydnamic generator, a solar-powered steam turbine electric generator, and an alkali metal thermoelectric converter is discussed.

Radiance limits of ceramic phosphors under high excitation fluxes

NASA Astrophysics Data System (ADS)

Lenef, Alan; Kelso, John; Zheng, Yi; Tchoul, Maxim

2013-09-01

Ceramic phosphors, excited by high radiance pump sources, offer considerable potential for high radiance conversion. Interestingly, thermodynamic arguments suggest that the radiance of the luminescent spot can even exceed that of the incoming light source. In practice, however, thermal quenching and (non-thermal) optical saturation limit the maximum attainable radiance of the luminescent source. We present experimental data for Ce:YAG and Ce:GdYAG ceramics in which these limits have been investigated. High excitation fluxes are achieved using laser pumping. Optical pumping intensities exceeding 100W/mm2 have been shown to produce only modest efficiency depreciation at low overall pump powers because of the short Ce3+ lifetime, although additional limitations exist. When pump powers are higher, heat-transfer bottlenecks within the ceramic and heat-sink interfaces limit maximum pump intensities. We find that surface temperatures of these laser-pumped ceramics can reach well over 150°C, causing thermal-quenching losses. We also find that in some cases, the loss of quantum efficiency with increasing temperature can cause a thermal run-away effect, resulting in a rapid loss in converted light, possibly over-heating the sample or surrounding structures. While one can still obtain radiances on the order of many W/mm2/sr, temperature quenching effects ultimately limit converted light radiance. Finally, we use the diffusion-approximation radiation transport models and rate equation models to simulate some of these nonlinear optical pumping and heating effects in high-scattering ceramics.

Round-the-clock power supply and a sustainable economy via synergistic integration of solar thermal power and hydrogen processes

PubMed Central

Gençer, Emre; Mallapragada, Dharik S.; Maréchal, François; Tawarmalani, Mohit; Agrawal, Rakesh

2015-01-01

We introduce a paradigm—“hydricity”—that involves the coproduction of hydrogen and electricity from solar thermal energy and their judicious use to enable a sustainable economy. We identify and implement synergistic integrations while improving each of the two individual processes. When the proposed integrated process is operated in a standalone, solely power production mode, the resulting solar water power cycle can generate electricity with unprecedented efficiencies of 40–46%. Similarly, in standalone hydrogen mode, pressurized hydrogen is produced at efficiencies approaching ∼50%. In the coproduction mode, the coproduced hydrogen is stored for uninterrupted solar power production. When sunlight is unavailable, we envision that the stored hydrogen is used in a “turbine”-based hydrogen water power (H2WP) cycle with the calculated hydrogen-to-electricity efficiency of 65–70%, which is comparable to the fuel cell efficiencies. The H2WP cycle uses much of the same equipment as the solar water power cycle, reducing capital outlays. The overall sun-to-electricity efficiency of the hydricity process, averaged over a 24-h cycle, is shown to approach ∼35%, which is nearly the efficiency attained by using the best multijunction photovoltaic cells along with batteries. In comparison, our proposed process has the following advantages: (i) It stores energy thermochemically with a two- to threefold higher density, (ii) coproduced hydrogen has alternate uses in transportation/chemical/petrochemical industries, and (iii) unlike batteries, the stored energy does not discharge over time and the storage medium does not degrade with repeated uses. PMID:26668380

Round-the-clock power supply and a sustainable economy via synergistic integration of solar thermal power and hydrogen processes.

PubMed

Gençer, Emre; Mallapragada, Dharik S; Maréchal, François; Tawarmalani, Mohit; Agrawal, Rakesh

2015-12-29

We introduce a paradigm-"hydricity"-that involves the coproduction of hydrogen and electricity from solar thermal energy and their judicious use to enable a sustainable economy. We identify and implement synergistic integrations while improving each of the two individual processes. When the proposed integrated process is operated in a standalone, solely power production mode, the resulting solar water power cycle can generate electricity with unprecedented efficiencies of 40-46%. Similarly, in standalone hydrogen mode, pressurized hydrogen is produced at efficiencies approaching ∼50%. In the coproduction mode, the coproduced hydrogen is stored for uninterrupted solar power production. When sunlight is unavailable, we envision that the stored hydrogen is used in a "turbine"-based hydrogen water power (H2WP) cycle with the calculated hydrogen-to-electricity efficiency of 65-70%, which is comparable to the fuel cell efficiencies. The H2WP cycle uses much of the same equipment as the solar water power cycle, reducing capital outlays. The overall sun-to-electricity efficiency of the hydricity process, averaged over a 24-h cycle, is shown to approach ∼35%, which is nearly the efficiency attained by using the best multijunction photovoltaic cells along with batteries. In comparison, our proposed process has the following advantages: (i) It stores energy thermochemically with a two- to threefold higher density, (ii) coproduced hydrogen has alternate uses in transportation/chemical/petrochemical industries, and (iii) unlike batteries, the stored energy does not discharge over time and the storage medium does not degrade with repeated uses.

Prospects for energy efficiency improvement and reduction of emissions and life cycle costs for natural gas vehicles

NASA Astrophysics Data System (ADS)

Kozlov, A. V.; Terenchenko, A. S.; Luksho, V. A.; Karpukhin, K. E.

2017-01-01

This work is devoted to the experimental investigation of the possibilities to reduce greenhouse gas emissions and to increase energy efficiency of engines that use natural gas as the main fuel and the analysis of economic efficiency of use of dual fuel engines in vehicles compared to conventional diesel. The results of experimental investigation of a 190 kW dual-fuel engine are presented; it is shown that quantitative and qualitative working process control may ensure thermal efficiency at the same level as that of the diesel engine and in certain conditions 5...8% higher. The prospects for reduction of greenhouse gas emissions have been assessed. The technical and economic evaluation of use of dual fuel engines in heavy-duty vehicles has been performed, taking into account the total life cycle. It is shown that it is possible to reduce life cycle costs by two times.

Process Performances of 2 ns Pulsed Discharge Plasma

NASA Astrophysics Data System (ADS)

Matsumoto, Takao; Wang, Douyan; Namihira, Takao; Akiyama, Hidenori

2011-08-01

Pulsed discharge plasmas have been used to treat exhaust gases. Since pulse duration and the rise time of applied voltage to the discharge electrode has a strong influence on the energy efficiency of pollutant removal, the development of a short-pulse generator is of paramount importance for practical applications. In this work, it is demonstrated that the non thermal plasma produced by the 2 ns pulsed discharge has a higher energy efficiency than the 5 ns pulsed discharge plasma for NO removal and ozone generation. Typically, the NO removal efficiency was 1.0 mol kW-1 h-1 for 70% NO removal (initial NO concentration = 200 ppm, gas flow = 10 L/min). Meanwhile, the ozone yield was 500 g kW-1 h-1 for 20 g/m3 ozone concentration in the case of oxygen feeding. These energy efficiencies are the highest in the literature.

Nano-engineered Multiwall Carbon Nanotube-copper Composite Thermal Interface Material for Efficient Heat Conduction

NASA Technical Reports Server (NTRS)

Ngo, Quoc; Cruden, Brett A.; Cassell, Alan M.; Sims, Gerard; Li, Jun; Meyyappa, M.; Yang, Cary Y.

2005-01-01

Efforts in integrated circuit (IC) packaging technologies have recently been focused on management of increasing heat density associated with high frequency and high density circuit designs. While current flip-chip package designs can accommodate relatively high amounts of heat density, new materials need to be developed to manage thermal effects of next-generation integrated circuits. Multiwall carbon nanotubes (MWNT) have been shown to significantly enhance thermal conduction in the axial direction and thus can be considered to be a candidate for future thermal interface materials by facilitating efficient thermal transport. This work focuses on fabrication and characterization of a robust MWNT-copper composite material as an element in IC package designs. We show that using vertically aligned MWNT arrays reduces interfacial thermal resistance by increasing conduction surface area, and furthermore, the embedded copper acts as a lateral heat spreader to efficiently disperse heat, a necessary function for packaging materials. In addition, we demonstrate reusability of the material, and the absence of residue on the contacting material, both novel features of the MWNT-copper composite that are not found in most state-of-the-art thermal interface materials. Electrochemical methods such as metal deposition and etch are discussed for the creation of the MWNT-Cu composite, detailing issues and observations with using such methods. We show that precise engineering of the composite surface affects the ability of this material to act as an efficient thermal interface material. A thermal contact resistance measurement has been designed to obtain a value of thermal contact resistance for a variety of different thermal contact materials.

A role for high frequency superconducting devices in free space power transmission systems

NASA Technical Reports Server (NTRS)

Christian, Jose L., Jr.; Cull, Ronald C.

1988-01-01

Major advances in space power technology are being made in photovoltaic, solar thermal, and nuclear systems. Despite these advances, the power systems required by the energy and power intensive mission of the future will be massive due to the large collecting surfaces, large thermal management systems, and heavy shielding. Reducing this mass on board the space vehicle can result in significant benefits because of the high cost of transporting and moving mass about in space. An approach to this problem is beaming the power from a point where the massiveness of the power plant is not such a major concern. The viability of such an approach was already investigated. Efficient microwave power beam transmission at 2.45 GHz was demonstrated over short range. Higher frequencies are desired for efficient transmission over several hundred or thousand kilometers in space. Superconducting DC-RF conversion as well as RF-DC conversion offers exciting possibilities. Multivoltage power conditioning for multicavity high power RF tubes could be eliminated since only low voltages are required for Josephson junctions. Small, high efficiency receivers may be possible using the reverse Josephson effects. A conceptual receiving antenna design using superconducting devices to determine possible system operating efficiency is assessed. If realized, these preliminary assessments indicate a role for superconducting devices in millimeter and submillimeter free space power transmission systems.

Understanding perovskite formation through the intramolecular exchange method in ambient conditions

NASA Astrophysics Data System (ADS)

Szostak, Rodrigo; Castro, Jhon A. P.; Marques, Adriano S.; Nogueira, Ana F.

2017-04-01

Among the methods to prepare hybrid organic-inorganic perovskite films, the intramolecular exchange method was the first one that made possible to prepare perovskite solar cells with efficiencies higher than 20%. However, perovskite formation by this method is not completely understood, especially in ambient conditions. In this work, perovskite films were prepared by the intramolecular exchange method in ambient conditions. The spin coating speed and the frequency of the MAI solution dripping onto PbI2(DMSO) were varied during the deposition steps. With the combination of these two parameters, a rigid control of the solvent drying was possible. Thus, depending on the chosen conditions, the intermediate MAPb3I8·2DMSO was formed with residual PbI2. Otherwise, direct formation of perovskite film was attained. A mechanism for the direct formation of bulk perovskite was proposed. We also investigated how the posterior thermal annealing affects the crystallinity and defects in perovskite films. With prolonged thermal annealing, the excess of MAI can be avoided, increasing the efficiency and decreasing the hysteresis of the solar cells. The best perovskite solar cell achieved a stabilized power output of 12.9%. The findings of this work pave the way for realizing the fabrication of efficient perovskite solar cells in ambient atmosphere, a very desirable condition for cost-efficient large scale manufacturing of this technology.

Crucial role of molecular planarity on the second order nonlinear optical property of pyridine based chalcone single crystals

NASA Astrophysics Data System (ADS)

Menezes, Anthoni Praveen; Jayarama, A.; Ng, Seik Weng

2015-05-01

An efficient nonlinear optical material 2E-3-(4-bromophenyl)-1-(pyridin-3-yl) prop-2-en-1-one (BPP) was synthesized and single crystals were grown using slow evaporation solution growth technique at room temperature. Grown crystal had prismatic morphology and its structure was confirmed by various spectroscopic studies, elemental analysis, and single crystal X-ray diffraction (XRD) technique. The single crystal XRD of the crystal showed that BPP crystallizes in monoclinic system with noncentrosymmetric space group P21 and the cell parameters are a = 5.6428(7) Å, b = 3.8637(6) Å, c = 26.411(2) Å, β = 97.568(11) deg and v = 575.82(12) Å3. The UV-Visible spectrum reveals that the crystal is optically transparent and has high optical energy band gap of 3.1 eV. The powder second harmonic generation efficiency (SHG) of BPP is 6.8 times that of KDP. From thermal analysis it is found that the crystal melts at 139 °C and decomposes at 264 °C. High optical transparency down to blue region, higher powder SHG efficiency and better thermal stability than that of urea makes this chalcone derivative a promising candidate for SHG applications. Furthermore, effect of molecular planarity on SHG efficiency and role of pyridine ring adjacent to carbonyl group in forming noncentrosymmetric crystal systems of chalcone family is also discussed.

COMPARISON OF THERMAL EFFICIENCIES FOR A MERCURY-STEAM BINARY VAPOR CYCLE AND THE RANKINE CYCLE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Prem, L.L.

1961-05-19

A comparison of the thermal efficiencies of the mercurysteam binary vapor cycle and the Rankine cycle shows that the binary cycle efficiency is greater. A temperatureentropy diagram and a schematic layout of the binary cycle are presented for clarity. (N.W.R.)

General formalism of local thermodynamics with an example: Quantum Otto engine with a spin-1/2 coupled to an arbitrary spin.

PubMed

Altintas, Ferdi; Müstecaplıoğlu, Özgür E

2015-08-01

We investigate a quantum heat engine with a working substance of two particles, one with a spin-1/2 and the other with an arbitrary spin (spin s), coupled by Heisenberg exchange interaction, and subject to an external magnetic field. The engine operates in a quantum Otto cycle. Work harvested in the cycle and its efficiency are calculated using quantum thermodynamical definitions. It is found that the engine has higher efficiencies at higher spins and can harvest work at higher exchange interaction strengths. The role of exchange coupling and spin s on the work output and the thermal efficiency is studied in detail. In addition, the engine operation is analyzed from the perspective of local work and efficiency. We develop a general formalism to explore local thermodynamics applicable to any coupled bipartite system. Our general framework allows for examination of local thermodynamics even when global parameters of the system are varied in thermodynamic cycles. The generalized definitions of local and cooperative work are introduced by using mean field Hamiltonians. The general conditions for which the global work is not equal to the sum of the local works are given in terms of the covariance of the subsystems. Our coupled spin quantum Otto engine is used as an example of the general formalism.

General formalism of local thermodynamics with an example: Quantum Otto engine with a spin-1 /2 coupled to an arbitrary spin

NASA Astrophysics Data System (ADS)

Altintas, Ferdi; Müstecaplıoǧlu, Ã.-zgür E.

2015-08-01

We investigate a quantum heat engine with a working substance of two particles, one with a spin-1 /2 and the other with an arbitrary spin (spin s ), coupled by Heisenberg exchange interaction, and subject to an external magnetic field. The engine operates in a quantum Otto cycle. Work harvested in the cycle and its efficiency are calculated using quantum thermodynamical definitions. It is found that the engine has higher efficiencies at higher spins and can harvest work at higher exchange interaction strengths. The role of exchange coupling and spin s on the work output and the thermal efficiency is studied in detail. In addition, the engine operation is analyzed from the perspective of local work and efficiency. We develop a general formalism to explore local thermodynamics applicable to any coupled bipartite system. Our general framework allows for examination of local thermodynamics even when global parameters of the system are varied in thermodynamic cycles. The generalized definitions of local and cooperative work are introduced by using mean field Hamiltonians. The general conditions for which the global work is not equal to the sum of the local works are given in terms of the covariance of the subsystems. Our coupled spin quantum Otto engine is used as an example of the general formalism.

Thermally efficient and highly scalable In2Se3 nanowire phase change memory

NASA Astrophysics Data System (ADS)

Jin, Bo; Kang, Daegun; Kim, Jungsik; Meyyappan, M.; Lee, Jeong-Soo

2013-04-01

The electrical characteristics of nonvolatile In2Se3 nanowire phase change memory are reported. Size-dependent memory switching behavior was observed in nanowires of varying diameters and the reduction in set/reset threshold voltage was as low as 3.45 V/6.25 V for a 60 nm nanowire, which is promising for highly scalable nanowire memory applications. Also, size-dependent thermal resistance of In2Se3 nanowire memory cells was estimated with values as high as 5.86×1013 and 1.04×106 K/W for a 60 nm nanowire memory cell in amorphous and crystalline phases, respectively. Such high thermal resistances are beneficial for improvement of thermal efficiency and thus reduction in programming power consumption based on Fourier's law. The evaluation of thermal resistance provides an avenue to develop thermally efficient memory cell architecture.

Micro-scale thermal imaging of CO2 absorption in the thermochemical energy storage of Li metal oxides at high temperature

NASA Astrophysics Data System (ADS)

Morikawa, Junko; Takasu, Hiroki; Zamengo, Massimiliano; Kato, Yukitaka

2017-05-01

Li-Metal oxides (typical example: lithium ortho-silicate Li4SiO4) are regarded as a novel solid carbon dioxide CO2 absorbent accompanied by an exothermic reaction. At temperatures above 700°C the sorbent is regenerated with the release of the captured CO2 in an endothermic reaction. As the reaction equilibrium of this reversible chemical reaction is controllable only by the partial pressure of CO2, the system is regarded as a potential candidate for chemical heat storage at high temperatures. In this study, we applied our recent developed mobile type instrumentation of micro-scale infrared thermal imaging system to observe the heat of chemical reaction of Li4SiO4 and CO2 at temperature higher than 600°C or higher. In order to quantify the micro-scale heat transfer and heat exchange in the chemical reaction, the superimpose signal processing system is setup to determine the precise temperature. Under an ambient flow of carbon dioxide, a powder of Li4SiO4 with a diameter 50 micron started to shine caused by an exothermic chemical reaction heat above 600°C. The phenomena was accelerated with increasing temperature up to 700°C. At the same time, the reaction product lithium carbonate (Li2CO3) started to melt with endothermic phase change above 700°C, and these thermal behaviors were captured by the method of thermal imaging. The direct measurement of multiple thermal phenomena at high temperatures is significant to promote an efficient design of chemical heat storage materials. This is the first observation of the exothermic heat of the reaction of Li4SiO4 and CO2 at around 700°C by the thermal imaging method.

Human thermal physiological and psychological responses under different heating environments.

PubMed

Wang, Zhaojun; Ning, Haoran; Ji, Yuchen; Hou, Juan; He, Yanan

2015-08-01

Anecdotal evidence suggests that many residents of severely cold areas of China who use floor heating (FH) systems feel warmer but drier compared to those using radiant heating (RH) systems. However, this phenomenon has not been verified experimentally. In order to validate the empirical hypothesis, and research the differences of human physiological and psychological responses in these two asymmetrical heating environments, an experiment was designed to mimic FH and RH systems. The subjects participating in the experiment were volunteer college-students. During the experiment, the indoor air temperature, air speed, relative humidity, globe temperature, and inner surface temperatures were measured, and subjects' heart rate, blood pressure and skin temperatures were recorded. The subjects were required to fill in questionnaires about their thermal responses during testing. The results showed that the subjects' skin temperatures, heart rate and blood pressure were significantly affected by the type of heating environment. Ankle temperature had greatest impact on overall thermal comfort relative to other body parts, and a slightly cool FH condition was the most pleasurable environment for sedentary subjects. The overall thermal sensation, comfort and acceptability of FH were higher than that of RH. However, the subjects of FH felt drier than that of RH, although the relative humidity in FH environments was higher than that of the RH environment. In future environmental design, the thermal comfort of the ankles should be scrutinized, and a FH cool condition is recommended as the most comfortable thermal environment for office workers. Consequently, large amounts of heating energy could be saved in this area in the winter. The results of this study may lead to more efficient energy use for office or home heating systems. Copyright © 2015 Elsevier Ltd. All rights reserved.

50W CW output power and 12mJ pulses from a quasi-2-level Yb:YAG ceramic rod laser end-pumped at the 969nm zero-phonon line

NASA Astrophysics Data System (ADS)

Fries, Christian; Weitz, Marco; Theobald, Christian; v. Löwis of Menar, Patric; Bartschke, Jürgen; L'huillier, Johannes A.

2015-02-01

With the advent of high power and narrow bandwidth 969 nm pump diodes, direct pumping into the upper laser level of Yb:YAG and hence quasi-2-level lasers became possible. Pumping directly into the emitting level leads to higher quantum efficiency and reduction of non-radiative decay. Consequently, thermal load, thermal lensing and risk of fracture are reduced significantly. Moreover pump saturation and thermal population of uninvolved energy-levels in ground and excited states are benefical for a homogenous distribution of the pump beam as well as the reduction of reabsorption loss compared to 3-level systems, which allows for high-power DPSS lasers. Beside continuous-wave (cw) operation, nanosecond pulses with a repetition rate between 1 and 5 kHz are an attractive alternative to flashlamp-pumped systems (10-100 Hz) in various measurement applications that require higher data acquisition rates because of new faster detectors. Based on measurements of the absorption and a detailed numerical model for pump beam distribution, including beam propagation and saturation factors, power-scaling of a ceramic rod Yb:YAG oscillator was possible. Finally a cw output power of 50 W with 33 % pump efficiency at 1030 nm has been demonstrated (M2 < 1.2). Nanosecond pulses have been produced by cavity-dumping of this system. The cavity-dumped setup allowed for 3-10 ns pulses with a pulse energy of 12.5 mJ at 1 kHz (M2 < 1.1). In order to achieve these results a systematic experimental and numerical investigation on gain dynamics and the identification of different stable operating regimes has been carried out.

Wide-range and fast thermally-tunable silicon photonic microring resonators using the junction field effect.

PubMed

Wang, Xiaoxi; Lentine, Anthony; DeRose, Christopher; Starbuck, Andrew L; Trotter, Douglas; Pomerene, Andrew; Mookherjea, Shayan

2016-10-03

Tunable silicon microring resonators with small, integrated micro-heaters which exhibit a junction field effect were made using a conventional silicon-on-insulator (SOI) photonic foundry fabrication process. The design of the resistive tuning section in the microrings included a "pinched" p-n junction, which limited the current at higher voltages and inhibited damage even when driven by a pre-emphasized voltage waveform. Dual-ring filters were studied for both large (>4.9 THz) and small (850 GHz) free-spectral ranges. Thermal red-shifting was demonstrated with microsecond-scale time constants, e.g., a dual-ring filter was tuned over 25 nm in 0.6 μs 10%-90% transition time, and with efficiency of 3.2 μW/GHz.

Biological evaluation of pearl millet protein: effect of different treatments and storage.

PubMed

Kapoor, R; Kapoor, A C

1990-07-01

Whole grain flour of one variety (HC-4) of pearl millet (Pennisetum americanum L. Leeke) after giving different treatments (defatting, butylated hydroxyanisole, ascorbic acid and thermal) was stored in earthen pots at prevailing room temperature (28-34 degrees C) and relative humidity (70-80%) for 30 days. The flour samples were evaluated for protein quality using rats. Storage of flour for 30 days markedly reduced the protein quality. The values of protein efficiency ratio, true digestibility, biological value, net protein retention and net protein utilisation were significantly (P less than 0.05) higher in fresh and treated flour than untreated flour. Among treated flours, defatted flour showed best growth followed by butylated hydroxyanisole, thermal and ascorbic acid treated flour.

Thermally stable, highly efficient, ultraflexible organic photovoltaics

PubMed Central

Xu, Xiaomin; Fukuda, Kenjiro; Karki, Akchheta; Park, Sungjun; Kimura, Hiroki; Jinno, Hiroaki; Watanabe, Nobuhiro; Yamamoto, Shuhei; Shimomura, Satoru; Kitazawa, Daisuke; Yokota, Tomoyuki; Umezu, Shinjiro; Nguyen, Thuc-Quyen; Someya, Takao

2018-01-01

Flexible photovoltaics with extreme mechanical compliance present appealing possibilities to power Internet of Things (IoT) sensors and wearable electronic devices. Although improvement in thermal stability is essential, simultaneous achievement of high power conversion efficiency (PCE) and thermal stability in flexible organic photovoltaics (OPVs) remains challenging due to the difficulties in maintaining an optimal microstructure of the active layer under thermal stress. The insufficient thermal capability of a plastic substrate and the environmental influences cannot be fully expelled by ultrathin barrier coatings. Here, we have successfully fabricated ultraflexible OPVs with initial efficiencies of up to 10% that can endure temperatures of over 100 °C, maintaining 80% of the initial efficiency under accelerated testing conditions for over 500 hours in air. Particularly, we introduce a low-bandgap poly(benzodithiophene-cothieno[3,4-b]thiophene) (PBDTTT) donor polymer that forms a sturdy microstructure when blended with a fullerene acceptor. We demonstrate a feasible way to adhere ultraflexible OPVs onto textiles through a hot-melt process without causing severe performance degradation. PMID:29666257

Prediction and design of efficient exciplex emitters for high-efficiency, thermally activated delayed-fluorescence organic light-emitting diodes.

PubMed

Liu, Xiao-Ke; Chen, Zhan; Zheng, Cai-Jun; Liu, Chuan-Lin; Lee, Chun-Sing; Li, Fan; Ou, Xue-Mei; Zhang, Xiao-Hong

2015-04-08

High-efficiency, thermally activated delayed-fluorescence organic light-emitting diodes based on exciplex emitters are demonstrated. The best device, based on a TAPC:DPTPCz emitter, shows a high external quantum efficiency of 15.4%. Strategies for predicting and designing efficient exciplex emitters are also provided. This approach allow prediction and design of efficient exciplex emitters for achieving high-efficiency organic light-emitting diodes, for future use in displays and lighting applications. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A hot-electron thermophotonic solar cell demonstrated by thermal up-conversion of sub-bandgap photons

PubMed Central

Farrell, Daniel J.; Sodabanlu, Hassanet; Wang, Yunpeng; Sugiyama, Masakazu; Okada, Yoshitaka

2015-01-01

The direct conversion of solar energy to electricity can be broadly separated into two main categories: photovoltaics and thermal photovoltaics, where the former utilizes gradients in electrical potential and the latter thermal gradients. Conventional thermal photovoltaics has a high theoretical efficiency limit (84%) but in practice cannot be easily miniaturized and is limited by the engineering challenges of sustaining large (>1,000 K) temperature gradients. Here we show a hot-carrier-based thermophotonic solar cell, which combines the compact nature of photovoltaic devices with the potential to reach the high-efficiency regime of thermal photovoltaics. In the device, a thermal gradient of 500 K is established by hot electrons, under Stokes illumination, rather than by raising the temperature of the material itself. Under anti-Stokes (sub-bandgap) illumination we observe a thermal gradient of ∼20 K, which is maintained by steady-state Auger heating of carriers and corresponds to a internal thermal up-conversion efficiency of 30% between the collector and solar cell. PMID:26541415

Effect of solvents on the bulk growth of 4-aminobenzophenone single crystals: A potential material for blue and green lasers

NASA Astrophysics Data System (ADS)

Natarajan, V.; Usharani, S.; Arivanandhan, M.; Anandan, P.; Hayakawa, Y.

2015-06-01

Although 4-aminobenzophenone (4-ABP) is the best derivative of benzophenone with 260 times higher second harmonic generation (SHG) efficiency than potassium dihydrogen phosphate (KDP), growth of high quality bulk crystal still remains a difficult task. In the present work, the effect of solvents on solubility and growth aspects of 4-ABP was investigated to grow inclusion free 4-ABP crystals. The growth processes were discussed based on solute-solvent interaction in two different growth media of ethyl acetate and ethanol. The growth rate and thereby solvent inclusions are relatively higher in ethyl acetate grown crystal than the crystal grown from ethanol. The structural, thermal and optical properties of 4-ABP crystals were studied. The enthalpy of 4-ABP melting process was estimated from differential thermal analysis. The optical transmission study shows that 4-ABP crystals grown from ethanol has high transparency compared to ethyl acetate grown sample due to solvent inclusion in the later crystal.

Parametric Weight Comparison of Advanced Metallic, Ceramic Tile, and Ceramic Blanket Thermal Protection Systems

NASA Technical Reports Server (NTRS)

Myers, David E.; Martin, Carl J.; Blosser, Max L.

2000-01-01

A parametric weight assessment of advanced metallic panel, ceramic blanket, and ceramic tile thermal protection systems (TPS) was conducted using an implicit, one-dimensional (I-D) finite element sizing code. This sizing code contained models to account for coatings fasteners, adhesives, and strain isolation pads. Atmospheric entry heating profiles for two vehicles, the Access to Space (ATS) vehicle and a proposed Reusable Launch Vehicle (RLV), were used to ensure that the trends were not unique to a certain trajectory. Ten TPS concepts were compared for a range of applied heat loads and substructural heat capacities to identify general trends. This study found the blanket TPS concepts have the lightest weights over the majority of their applicable ranges, and current technology ceramic tiles and metallic TPS concepts have similar weights. A proposed, state-of-the-art metallic system which uses a higher temperature alloy and efficient multilayer insulation was predicted to be significantly lighter than the ceramic tile stems and approaches blanket TPS weights for higher integrated heat loads.

ZrO2-modified mesoporous nanocrystalline TiO2-xNx as efficient visible light photocatalysts.

PubMed

Wang, Xinchen; Yu, Jimmy C; Chen, Yilin; Wu, Ling; Fu, Xianzhi

2006-04-01

Mesoporous nanocrystalline TiO2-xNx and TiO2-xNx/ZrO2 visible-light photocatalysts have been prepared by a sol-gel method. The photocatalysts were characterized by XRD, N2 adsorption-desorption, TEM, XPS, UV/Vis, and IR spectroscopy. The photocatalytic activity of the samples was evaluated by the decomposition of ethylene in air under visible light (lambda > 450 nm) illumination. Results revealed that nitrogen was doped into the lattice of TiO2 by the thermal treatment of NH3-adsorbed TiO2 hydrous gels, converting the TiO2 into a visible-light responsive catalyst. The introduction of ZrO2 into TiO2-xNx considerably inhibits the undesirable crystal growth during calcination. Consequently, the ZrO2-modified TiO2-xNx displays higher porosity, higher specific surface area, and an improved thermal stability over the corresponding unmodified TiO2-xNx samples.

Thermal analysis elements of liquefied gas storage tanks

NASA Astrophysics Data System (ADS)

Yanvarev, I. A.; Krupnikov, A. V.

2017-08-01

Tasks of solving energy and resource efficient usage problems, both for oil producing companies and for companies extracting and transporting natural gas, are associated with liquefied petroleum gas technology development. Improving the operation efficiency of liquefied products storages provides for conducting structural, functional, and appropriate thermal analysis of tank parks in the general case as complex dynamic thermal systems.

Work and information from thermal states after subtraction of energy quanta.

PubMed

Hloušek, J; Ježek, M; Filip, R

2017-10-12

Quantum oscillators prepared out of thermal equilibrium can be used to produce work and transmit information. By intensive cooling of a single oscillator, its thermal energy deterministically dissipates to a colder environment, and the oscillator substantially reduces its entropy. This out-of-equilibrium state allows us to obtain work and to carry information. Here, we propose and experimentally demonstrate an advanced approach, conditionally preparing more efficient out-of-equilibrium states only by a weak dissipation, an inefficient quantum measurement of the dissipated thermal energy, and subsequent triggering of that states. Although it conditionally subtracts the energy quanta from the oscillator, average energy grows, and second-order correlation function approaches unity as by coherent external driving. On the other hand, the Fano factor remains constant and the entropy of the subtracted state increases, which raise doubts about a possible application of this approach. To resolve it, we predict and experimentally verify that both available work and transmitted information can be conditionally higher in this case than by arbitrary cooling or adequate thermal heating up to the same average energy. It qualifies the conditional procedure as a useful source for experiments in quantum information and thermodynamics.

Failure Analysis of Multilayered Suspension Plasma-Sprayed Thermal Barrier Coatings for Gas Turbine Applications

NASA Astrophysics Data System (ADS)

Gupta, M.; Markocsan, N.; Rocchio-Heller, R.; Liu, J.; Li, X.-H.; Östergren, L.

2018-02-01

Improvement in the performance of thermal barrier coatings (TBCs) is one of the key objectives for further development of gas turbine applications. The material most commonly used as TBC topcoat is yttria-stabilized zirconia (YSZ). However, the usage of YSZ is limited by the operating temperature range which in turn restricts the engine efficiency. Materials such as pyrochlores, perovskites, rare earth garnets are suitable candidates which could replace YSZ as they exhibit lower thermal conductivity and higher phase stability at elevated temperatures. The objective of this work was to investigate different multilayered TBCs consisting of advanced topcoat materials fabricated by suspension plasma spraying (SPS). The investigated topcoat materials were YSZ, dysprosia-stabilized zirconia, gadolinium zirconate, and ceria-yttria-stabilized zirconia. All topcoats were deposited by TriplexPro-210TM plasma spray gun and radial injection of suspension. Lifetime of these samples was examined by thermal cyclic fatigue and thermal shock testing. Microstructure analysis of as-sprayed and failed specimens was performed with scanning electron microscope. The failure mechanisms in each case have been discussed in this article. The results show that SPS could be a promising route to produce multilayered TBCs for high-temperature applications.

Significant improvement in the interface thermal conductivity of graphene-nanoplatelets/silicone composite

NASA Astrophysics Data System (ADS)

Lv, Jian; Cai, Xiaoming; Ye, Qianxu; Zhang, Hui; Ruan, Zilin; Cai, Jinming

2018-05-01

Heat conducting silica gel sheets with graphene nanoplatelets (GNPs) filler prepared by high pressure homogenization were fabricated. The dispersed GNPs filler in silica gel significantly affects the thermal conductivity of GNPs silica gel sheets (GNPs-SGS). The thermal conductivity of GNPs-SGS with 5 wt% GNPs reaches 0.43 W(m · k)‑1 which increased by 110% and 50% comparing to the pure silica gel sheets (Pure-SGS) and graphite silica gel sheets (GP-SGS) with the same mass fraction. The efficient of heat conduction of heat-sink device which made of GNPs-SGS with 5 wt% is higher than the one which made of Pure-SGS. Besides, The temperature of the thermal plate is 22 °C lower when using 5 wt% GNPs-SGS compared to the bare one measured by thermal management simulator (TMS), proving its good heat radiation ability. FE-SEM was used to observe the fillers and the section of gel sheets, it can be clearly observed the layered and the uniform distribution of GNPs in the matrix. The facile process of high pressure homogenization to exfoliate GNPs is a feasible program for industrial production.

Hybrid solar collector using nonimaging optics and photovoltaic components

NASA Astrophysics Data System (ADS)

Winston, Roland; Yablonovitch, Eli; Jiang, Lun; Widyolar, Bennett K.; Abdelhamid, Mahmoud; Scranton, Gregg; Cygan, David; Kozlov, Alexandr

2015-08-01

The project team of University of California at Merced (UC-M), Gas Technology Institute, and Dr. Eli Yablonovitch of University of California at Berkeley developed a novel hybrid concentrated solar photovoltaic thermal (PV/T) collector using nonimaging optics and world record single-junction Gallium arsenide (GaAs) PV components integrated with particle laden gas as thermal transfer and storage media, to simultaneously generate electricity and high temperature dispatchable heat. The collector transforms a parabolic trough, commonly used in CSP plants, into an integrated spectrum-splitting device. This places a spectrum-sensitive topping element on a secondary reflector that is registered to the thermal collection loop. The secondary reflector transmits higher energy photons for PV topping while diverting the remaining lower energy photons to the thermal media, achieving temperatures of around 400°C even under partial utilization of the solar spectrum. The collector uses the spectral selectivity property of Gallium arsenide (GaAs) cells to maximize the exergy output of the system, resulting in an estimated exergy efficiency of 48%. The thermal media is composed of fine particles of high melting point material in an inert gas that increases heat transfer and effectively stores excess heat in hot particles for later on-demand use.

Low temperature thermoelectric properties of p-type doped single-crystalline SnSe

NASA Astrophysics Data System (ADS)

Wang, Si; Hui, Si; Peng, Kunling; Bailey, Trevor P.; Liu, Wei; Yan, Yonggao; Zhou, Xiaoyuan; Tang, Xinfeng; Uher, Ctirad

2018-04-01

SnSe single crystals have been widely studied lately as a result of their record high ZT and controversial low thermal conductivity. Much research has focused on the high-temperature properties of single crystals and polycrystalline SnSe, but few studies were carried out on the low-temperature properties of doped single-crystalline SnSe. To study the mechanism of the charge carrier and phonon scattering, and to eliminate the ambiguity of the high temperature thermal conductivity measurement, we performed low temperature transport characterization of Na-doped and Ag-doped single-crystalline SnSe by a longitudinal steady-state technique. The electronic transport property measurements suggest that Na is a more efficient p-type dopant in SnSe than Ag. In the thermal conductivity data, we observe pronounced dielectric peak around 10 K with magnitude dependent on the doping level. In the p-type doped samples, we found that our room temperature lattice thermal conductivities (>1.74 W m-1 K-1) are in general higher than those previously reported. Based on these findings, our study implies that the lattice thermal conductivity values of doped and pure single-crystalline SnSe were underestimated.

Flashlamp radiation recycling for enhanced pumping efficiency and reduced thermal load

DOEpatents

Jancaitis, Kenneth S.; Powell, Howard T.

1989-01-01

A method for recycling laser flashlamp radiation in selected wavelength ranges to decrease thermal loading of the solid state laser matrix while substantially maintaining the pumping efficiency of the flashlamp.

Solar selective performance of metal nitride/oxynitride based magnetron sputtered thin film coatings: a comprehensive review

NASA Astrophysics Data System (ADS)

Ibrahim, Khalil; Taha, Hatem; Mahbubur Rahman, M.; Kabir, Humayun; Jiang, Zhong-Tao

2018-03-01

Since solar-thermal collectors are considered to be the most direct way of converting solar energy into usable forms, in the last few years growing attention has been paid to the development of transition metal nitride and metal oxynitride based thin film selective surfaces for solar-thermal collectors, in order to harvest more solar energy. A solar-thermal energy system, generally, shows very high solar absorption of incident solar radiation from the solar-thermal collectors in the visible range (0.3 to 2.5 μm) and extremely low thermal losses through emission (or high reflection) in the infrared region (≥2.5 μm). The efficiency of a solar-thermal energy conversion system can be improved by the use of solar selective surfaces consisting of novel metallic nanoparticles embedded in metal nitride/oxynitride systems. In order to enhance the effectiveness of solar-thermal devices, solar selective surfaces with high thermal stability are a prerequisite. Over the years, substantial efforts have been made in the field of solar selective surfaces to attain higher solar absorptance and lower thermal emittance in high temperature (above 400 °C) applications. In this article, we review the present state-of-the-art transition metal nitride and/or oxynitride based vacuum sputtered nanostructured thin film coatings, with respect to their optical and solar selective surface applications. We have also summarized the solar selectivity data from recently published investigations, including discussion on some potential applications for these materials.

Thermodynamic and design considerations of organic Rankine cycles in combined application with a solar thermal gas turbine

NASA Astrophysics Data System (ADS)

Braun, R.; Kusterer, K.; Sugimoto, T.; Tanimura, K.; Bohn, D.

2013-12-01

Concentrated Solar Power (CSP) technologies are considered to provide a significant contribution for the electric power production in the future. Different kinds of technologies are presently in operation or under development, e.g. parabolic troughs, central receivers, solar dish systems and Fresnel reflectors. This paper takes the focus on central receiver technologies, where the solar radiation is concentrated by a field of heliostats in a receiver on the top of a tall tower. To get this CSP technology ready for the future, the system costs have to reduce significantly. The main cost driver in such kind of CSP technologies are the huge amount of heliostats. To reduce the amount of heliostats, and so the investment costs, the efficiency of the energy conversion cycle becomes an important issue. An increase in the cycle efficiency results in a decrease of the solar heliostat field and thus, in a significant cost reduction. The paper presents the results of a thermodynamic model of an Organic Rankine Cycle (ORC) for combined cycle application together with a solar thermal gas turbine. The gas turbine cycle is modeled with an additional intercooler and recuperator and is based on a typical industrial gas turbine in the 2 MW class. The gas turbine has a two stage radial compressor and a three stage axial turbine. The compressed air is preheated within a solar receiver to 950°C before entering the combustor. A hybrid operation of the gas turbine is considered. In order to achieve a further increase of the overall efficiency, the combined operation of the gas turbine and an Organic Rankine Cycle is considered. Therefore an ORC has been set up, which is thermally connected to the gas turbine cycle at two positions. The ORC can be coupled to the solar-thermal gas turbine cycle at the intercooler and after the recuperator. Thus, waste heat from different cycle positions can be transferred to the ORC for additional production of electricity. Within this investigation different working fluids and ORC conditions have been analyzed in order to evaluate the best configuration. The investigations have been performed by application of improved thermodynamic and process analysis tools, which consider the real gas behavior of the analyzed fluids. The results show that by combined operation of the solar thermal gas turbine and the ORC, the combined cycle efficiency is approximately 4%-points higher than in the solar-thermal gas turbine cycle.

An Efficient Algorithm for Server Thermal Fault Diagnosis Based on Infrared Image

NASA Astrophysics Data System (ADS)

Liu, Hang; Xie, Ting; Ran, Jian; Gao, Shan

2017-10-01

It is essential for a data center to maintain server security and stability. Long-time overload operation or high room temperature may cause service disruption even a server crash, which would result in great economic loss for business. Currently, the methods to avoid server outages are monitoring and forecasting. Thermal camera can provide fine texture information for monitoring and intelligent thermal management in large data center. This paper presents an efficient method for server thermal fault monitoring and diagnosis based on infrared image. Initially thermal distribution of server is standardized and the interest regions of the image are segmented manually. Then the texture feature, Hu moments feature as well as modified entropy feature are extracted from the segmented regions. These characteristics are applied to analyze and classify thermal faults, and then make efficient energy-saving thermal management decisions such as job migration. For the larger feature space, the principal component analysis is employed to reduce the feature dimensions, and guarantee high processing speed without losing the fault feature information. Finally, different feature vectors are taken as input for SVM training, and do the thermal fault diagnosis after getting the optimized SVM classifier. This method supports suggestions for optimizing data center management, it can improve air conditioning efficiency and reduce the energy consumption of the data center. The experimental results show that the maximum detection accuracy is 81.5%.

Thermal Barrier Coatings Resistant to Glassy Deposits

NASA Astrophysics Data System (ADS)

Drexler, Julie Marie

Engineering of alloys has for years allowed aircraft turbine engines to become more efficient and operate at higher temperatures. As advancements in these alloy systems have become more difficult, ceramic thermal barrier coatings (TBCs), often yttria (7 wt %) stabilized zirconia (7YSZ), have been utilized for thermal protection. TBCs have allowed for higher engine operating temperatures and better fuel efficiency but have also created new engineering problems. Specifically, silica based particles such as sand and volcanic ash that enter the engine during operation form glassy deposits on the TBCs. These deposits can cause the current industrial 7YSZ thermal barrier coatings to fail since the glass formed penetrates and chemically interacts with the TBC. When this occurs, coating failure may occur due to a loss of strain tolerance, which can lead to fracture, and phase changes of the TBC material. There have been several approaches used to stop calcium-magnesium aluminio-silcate (CMAS) glasses (molten sand) from destroying the entire TBC, but overall there is still limited knowledge. In this thesis, 7YSZ and new TBC materials will be examined for thermochemical and thermomechanical performance in the presence of molten CMAS and volcanic ash. Two air plasma sprayed TBCs will be shown to be resistant to volcanic ash and CMAS. The first type of coating is a modified 7YSZ coating with 20 mol% Al2O3 and 5 mol% TiO2 in solid solution (YSZ+20Al+5Ti). The second TBC is made of gadolinium zirconate. These novel TBCs impede CMAS and ash penetration by interacting with the molten CMAS or ash and drastically changing the chemistry. The chemically modified CMAS or ash will crystallize into an apatite or anorthite phase, blocking the CMAS or ash from further destroying the coating. A presented mechanism study will show these coatings are effective due to the large amount of solute (Gd, Al) in the zirconia structure, which is the key to creating the crystalline apatite or anorthite phases. In fact, it will be shown that if the industrial standard 7YSZ coatings contained more Y2O3 they would be very effective in stopping CMAS penetration. Lastly, thermal cyclic testing of 7YSZ and YSZ+20Al+5Ti TBCs reveals that partially CMAS-impregnated TBCs can survive mechanically if cycled in thermal gradient while in most isothermal tests they would fail. Since parts in a jet engine are in a thermal gradient, this type of testing should be performed on future CMAS resistant TBCs.

Cap rock efficiency of geothermal systems in fold-and-thrust belts: Evidence from paleo-thermal and structural analyses in Rosario de La Frontera geothermal area (NW Argentina)

NASA Astrophysics Data System (ADS)

Maffucci, R.; Corrado, S.; Aldega, L.; Bigi, S.; Chiodi, A.; Di Paolo, L.; Giordano, G.; Invernizzi, C.

2016-12-01

Cap rock characterization of geothermal systems is often neglected despite fracturing may reduce its efficiency and favours fluid migration. We investigated the siliciclastic cap rock of Rosario de La Frontera geothermal system (NW Argentina) in order to assess its quality as a function of fracture patterns and related thermal alteration. Paleothermal investigations (XRD on fine-grained fraction of sediments, organic matter optical analysis and fluid inclusions on veins) and 1D thermal modelling allowed us to distinguish the thermal fingerprint associated to sedimentary burial from that related to fluid migration. The geothermal system is hosted in a Neogene N-S anticline dissected by high angle NNW- and ENE-striking faults. Its cap rock can be grouped into two quality categories: rocks acting as good insulators, deformed by NNW-SSE and E-W shear fractures, NNE-SSW gypsum- and N-S-striking calcite-filled veins that developed during the initial stage of anticline growth. Maximum paleo-temperatures (< 60 °C) were experienced during deposition to folding phases. rocks acting as bad insulators, deformed by NNW-SSE fault planes and NNW- and WNW-striking sets of fractures associated to late transpressive kinematics. Maximum paleo-temperatures higher than about 115 °C are linked to fluid migration from the reservoir to surface (with a reservoir top at maximum depths of 2.5 km) along fault damage zones. This multi-method approach turned out to be particularly useful to trace the main pathways of hot fluids and can be applied in blind geothermal systems where either subsurface data are scarce or surface thermal anomalies are lacking.

Modeling warming predicts a physiological threshold for the extinction of the living fossil frog Calyptocephalella gayi.

PubMed

Vidal, Marcela A; Novoa-Muñoz, Francisco; Werner, Enrique; Torres, Cristian; Nova, Ricardo

2017-10-01

Global climate change will have a greater impact on ectotherms in tropical and subtropical communities than at higher latitudes, because ambient temperatures are closer to the upper thermal limits of species. Amphibian species are highly dependent on external weather conditions, and the effect of global warming on these has been evaluated recently. The Great Chilean frog (Calyptocephalella gayi) is an endemic, monotypic species and genus whose conservation status is considered Vulnerable because of high extraction pressure for human consumption, lack of regulatory measures and comprehension by its consumers. Their populations have also declined due to the loss and destruction of their habitats. C. gayi has not been considered as an object of physiological study, so this large species is not known as one that can adapt to current environmental changes. In this study we analyze the thermoregulatory capacity and thermal efficiency of C. gayi to determine its potential for climatic adaptation. The results indicate that this species is strictly a thermal-conformer; its thermal efficiency and its ability to withstand high temperatures allow it to sustain itself under a climate change scenario, however, it has thermal constraints that do not allow it to withstand temperatures greater than 30°C. By modeling its ontogenetic conditions mathematically, we project that the larvae are not in danger, although there is a group of around 4% which is very close to 30°C, which is the highest temperature recorded for the species. However, about 40% of subadults and approximately 47% of adult frogs will not survive the change of ~7°C projected for the following 85 years, which will affect future generations. Copyright © 2017 Elsevier Ltd. All rights reserved.

Phase of Photothermal Emission Analysis as a Diagnostic Tool for Thermal Barrier Coatings on Serviceable Engine Components

NASA Astrophysics Data System (ADS)

Kakuda, Tyler

Power generation and aircraft companies are continuously improving the efficiency of gas turbines to meet economic and environmental goals. The trend towards higher efficiency has been achieved in part by raising the operating temperature of engines. At elevated temperatures, engine components are subject to many forms of degradation including oxidation, creep deformation and thermal cycle fatigue. To minimize these harmful effects, ceramic thermal barrier coatings (TBCs) are routinely used to insulate metal components from excessive heat loads. Efforts to make realistic performance assessments of current and candidate coating materials has led to a diverse battery of creative measurement techniques. While it is unrealistic to envision a single measurement that would provide all conceivable information about the TBC, it is arguable that the capability for the single most important measurement is still lacking. A quantitative and nondestructive measurement of the thermal protection offered by a coating is not currently among the measurements one can employ on a serviceable engine part (or even many experimental specimens). In this contribution, phase of photothermal emission analysis (PopTea) is presented as a viable thermal property measurement for serviceable engine components. As it will be shown, PopTea has the versatility to make measurements on gas turbine parts in situ, with the goal of monitoring TBCs over the lifetime of the engine. The main challenges toward this goal are dealing with changes that occur to the TBC during service. Several of the main degradations seen on engine equipment include: aging, surface contamination and infiltration of foreign deposits. Measuring coatings under these conditions, is the impetus of this work. Furthermore, it is demonstrated that PopTea can be used on real engine equipment with measurements made on an actual turbine blade.

Thermochemical valorization and characterization of household biowaste.

PubMed

Vakalis, S; Sotiropoulos, A; Moustakas, K; Malamis, D; Vekkos, K; Baratieri, M

2017-12-01

Valorization of municipal solid waste (MSW), by means of energy and material recovery, is considered to be a crucial step for sustainable waste management. A significant fraction of MSW is comprised from food waste, the treatment of which is still a challenge. Therefore, the conventional disposal of food waste in landfills is being gradually replaced by recycling aerobic treatment, anaerobic digestion and waste-to-energy. In principle, thermal processes like combustion and gasification are preferred for the recovery of energy due to the higher electrical efficiency and the significantly less time required for the process to be completed when compared to biological process, i.e. composting, anaerobic digestion and transesterification. Nonetheless, the high water content and the molecular structure of biowaste are constraining factors in regard to the application of thermal conversion pathways. Investigating alternative solutions for the pre-treatment and more energy efficient handling of this waste fraction may provide pathways for the optimization of the whole process. In this study, by means of utilizing drying/milling as an intermediate step, thermal treatment of household biowaste has become possible. Household biowaste has been thermally processed in a bench scale reactor by means of torrefaction, carbonization and high temperature pyrolysis. According to the operational conditions, fluctuating fractions of biochar, bio-oil (tar) and syngas were recovered. The thermochemical properties of the feedstock and products were analyzed by means of Simultaneous Thermal Analysis (STA), Ultimate and Proximate analysis and Attenuated Total Reflectance (ATR). The analysis of the products shows that torrefaction of dried household biowaste produces an energy dense fuel and high temperature pyrolysis produces a graphite-like material with relatively high yield. Copyright © 2016 Elsevier Ltd. All rights reserved.

Thermal management in MoS2 based integrated device using near-field radiation

NASA Astrophysics Data System (ADS)

Peng, Jiebin; Zhang, Gang; Li, Baowen

2015-09-01

Recently, wafer-scale growth of monolayer MoS2 films with spatial homogeneity is realized on SiO2 substrate. Together with the latest reported high mobility, MoS2 based integrated electronic devices are expected to be fabricated in the near future. Owing to the low lattice thermal conductivity in monolayer MoS2, and the increased transistor density accompanied with the increased power density, heat dissipation will become a crucial issue for these integrated devices. In this letter, using the formalism of fluctuation electrodynamics, we explored the near-field radiative heat transfer from a monolayer MoS2 to graphene. We demonstrate that in resonance, the maximum heat transfer via near-field radiation between MoS2 and graphene can be ten times higher than the in-plane lattice thermal conduction for MoS2 sheet. Therefore, an efficient thermal management strategy for MoS2 integrated device is proposed: Graphene sheet is brought into close proximity, 10-20 nm from MoS2 device; heat energy transfer from MoS2 to graphene via near-field radiation; this amount of heat energy then be conducted to contact due to ultra-high lattice thermal conductivity of graphene. Our work sheds light for developing cooling strategy for nano devices constructing with low thermal conductivity materials.

Gas recirculation flash drying of filtercake as a safe and economic alternative to fluidized bed drying

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kalb, G.W.; Sisti, D.

1996-12-31

Although approximately 50% of the thermal coal dryers in North America have been idled or demolished in the past twelve years, thermal coal dryers are currently operating at the highest yearly evaporative load in their history. This is due to the combination of idling/demolishing the marginally required thermal dryers, and replacing the evaporative capacity with more efficient centrifugal dryers while operating the remaining thermal dryers at significantly higher evaporative loads for a greater number of hours. Although previously unheard of in this industry, many of the remaining thermal coal dryers are operating at and above their design evaporative capacity. Thermalmore » coal dryers are used to meet the common moisture specifications of 6.0% in the United States and 7.5 to 8.0% in Canada and are normally required when (1) the Hardgrove grindability exceeds 90, (2) the preparation plant feed topsize is less than 1 {1/2}-inch and/or (3) for transportation reasons in northern climates. It is anticipated that thermal coal drying will be rejuvenated as a result of (1) addressing inherent moisture in low raw coals, (2) the Australian need to address their 10% moisture bituminous coal shipments, and (3) the increased ash and sulfur liberation with decreasing topsize of preparation plant feeds.« less

Ultra-Thin Monocrystalline Silicon Solar Cell with 12.2% Efficiency Using Silicon-On-Insulator Substrate.

PubMed

Bian, Jian-Tao; Yu, Jian; Duan, Wei-Yuan; Qiu, Yu

2015-04-01

Single side heterojunction silicon solar cells were designed and fabricated using Silicon-On-Insulator (SOI) substrate. The TCAD software was used to simulate the effect of silicon layer thickness, doping concentration and the series resistance. A 10.5 µm thick monocrystalline silicon layer was epitaxially grown on the SOI with boron doping concentration of 2 x 10(16) cm(-3) by thermal CVD. Very high Voc of 678 mV was achieved by applying amorphous silicon heterojunction emitter on the front surface. The single cell efficiency of 12.2% was achieved without any light trapping structures. The rear surface recombination and the series resistance are the main limiting factors for the cell efficiency in addition to the c-Si thickness. By integrating an efficient light trapping scheme and further optimizing fabrication process, higher efficiency of 14.0% is expected for this type of cells. It can be applied to integrated circuits on a monolithic chip to meet the requirements of energy autonomous systems.

A new concept of hybrid photovoltaic thermal (PVT) collector with natural circulation

NASA Astrophysics Data System (ADS)

Lu, Longsheng; Wang, Xiaowu; Wang, Shuai; Liu, Xiaokang

2017-07-01

Hybrid photovoltaic thermal (PVT) technology refers to the integration of a photovoltaic module into a conventional solar thermal collector. Generally, the traditional design of a PVT collector has solar cells fixed on the top surface of an absorber in a flat-plate solar thermal collector. In this work, we presented a new concept of water-based PVT collector in which solar cells were directly placed on the bottom surface of its glass cover. A dynamic numerical model of this new PVT is developed and validated by experimental tests. With numerical analysis, it is found that at same covering factor, the electricity conversion efficiency of solar cells of the new PVT exceed that of the traditional PVT by nearly 10% while its thermal efficiency is approximately 30% lower than that of the traditional PVT. When the covering factor changes from 0.05 to 1, the thermal efficiency of the new PVT drops nearly 70%. The thermal efficiency of both the new PVT and the traditional PVT rise up as the water mass in tank increases. Meanwhile, the final water temperature in tank of the traditional PVT collector declines more than 17 °C, whereas that of the new PVT declines less than 6 °C, when the water mass increases from 100 to 300 kg.

Vibrational quenching of CO2(010) by collisions with O(3P) at thermal energies: A quantum-mechanical study

NASA Astrophysics Data System (ADS)

de Lara-Castells, M. P.; Hernández, Marta I.; Delgado-Barrio, G.; Villarreal, P.; López-Puertas, M.

2006-04-01

The CO2(010)-O(3P) vibrational energy transfer (VET) efficiency is a key input to aeronomical models of the energy budget of the upper atmospheres of Earth, Venus, and Mars. This work addresses the physical mechanisms responsible for the high efficiency of the VET process at the thermal energies existing in the terrestrial upper atmosphere (150 K<=T<=550 K). We present a quantum-mechanical study of the process within a reduced-dimensionality approach. In this model, all the particles remain along a plane and the O(3P) atom collides along the C2v symmetry axis of CO2, which can present bending oscillations around the linear arrangement, while the stretching C-O coordinates are kept fixed at their equilibrium values. Two kinds of scattering calculations are performed on high-quality ab initio potential energy surfaces (PESs). In the first approach, the calculations are carried out separately for each one of the three PESs correlating to O(3P). In the second approach, nonadiabatic effects induced by spin-orbit couplings (SOC) are also accounted for. The results presented here provide an explanation to some of the questions raised by the experiments and aeronomical observations. At thermal energies, nonadiabatic transitions induced by SOC play a key role in causing large VET efficiencies, the process being highly sensitive to the initial fine-structure level of oxygen. At higher energies, the two above-mentioned approaches tend to coincide towards an impulsive Landau-Teller mechanism of the vibrational to translational (V-T) energy transfer.

Isoprene improves photochemical efficiency and enhances heat dissipation in plants at physiological temperatures.

PubMed

Pollastri, Susanna; Tsonev, Tsonko; Loreto, Francesco

2014-04-01

Isoprene-emitting plants are better protected against thermal and oxidative stresses. Isoprene may strengthen membranes avoiding their denaturation and may quench reactive oxygen and nitrogen species, achieving a similar protective effect. The physiological role of isoprene in unstressed plants, up to now, is not understood. It is shown here, by monitoring the non-photochemical quenching (NPQ) of chlorophyll fluorescence of leaves with chemically or genetically altered isoprene biosynthesis, that chloroplasts of isoprene-emitting leaves dissipate less energy as heat than chloroplasts of non-emitting leaves, when exposed to physiologically high temperatures (28-37 °C) that do not impair the photosynthetic apparatus. The effect was especially remarkable at foliar temperatures between 30 °C and 35 °C, at which isoprene emission is maximized and NPQ is quenched by about 20%. Isoprene may also allow better stability of photosynthetic membranes and a more efficient electron transfer through PSII at physiological temperatures, explaining most of the NPQ reduction and the slightly higher photochemical quenching that was also observed in isoprene-emitting leaves. The possibility that isoprene emission helps in removing thermal energy at the thylakoid level is also put forward, although such an effect was calculated to be minimal. These experiments expand current evidence that isoprene is an important trait against thermal and oxidative stresses and also explains why plants invest resources in isoprene under unstressed conditions. By improving PSII efficiency and reducing the need for heat dissipation in photosynthetic membranes, isoprene emitters are best fitted to physiologically high temperatures and will have an evolutionary advantage when adapting to a warming climate.

Isoprene improves photochemical efficiency and enhances heat dissipation in plants at physiological temperatures

PubMed Central

Loreto, Francesco

2014-01-01

Isoprene-emitting plants are better protected against thermal and oxidative stresses. Isoprene may strengthen membranes avoiding their denaturation and may quench reactive oxygen and nitrogen species, achieving a similar protective effect. The physiological role of isoprene in unstressed plants, up to now, is not understood. It is shown here, by monitoring the non-photochemical quenching (NPQ) of chlorophyll fluorescence of leaves with chemically or genetically altered isoprene biosynthesis, that chloroplasts of isoprene-emitting leaves dissipate less energy as heat than chloroplasts of non-emitting leaves, when exposed to physiologically high temperatures (28–37 °C) that do not impair the photosynthetic apparatus. The effect was especially remarkable at foliar temperatures between 30 °C and 35 °C, at which isoprene emission is maximized and NPQ is quenched by about 20%. Isoprene may also allow better stability of photosynthetic membranes and a more efficient electron transfer through PSII at physiological temperatures, explaining most of the NPQ reduction and the slightly higher photochemical quenching that was also observed in isoprene-emitting leaves. The possibility that isoprene emission helps in removing thermal energy at the thylakoid level is also put forward, although such an effect was calculated to be minimal. These experiments expand current evidence that isoprene is an important trait against thermal and oxidative stresses and also explains why plants invest resources in isoprene under unstressed conditions. By improving PSII efficiency and reducing the need for heat dissipation in photosynthetic membranes, isoprene emitters are best fitted to physiologically high temperatures and will have an evolutionary advantage when adapting to a warming climate. PMID:24676032

Modeling of photoluminescence in laser-based lighting systems

NASA Astrophysics Data System (ADS)

Chatzizyrli, Elisavet; Tinne, Nadine; Lachmayer, Roland; Neumann, Jörg; Kracht, Dietmar

2017-12-01

The development of laser-based lighting systems has been the latest step towards a revolution in illumination technology brought about by solid-state lighting. Laser-activated remote phosphor systems produce white light sources with significantly higher luminance than LEDs. The weak point of such systems is often considered to be the conversion element. The high-intensity exciting laser beam in combination with the limited thermal conductivity of ceramic phosphor materials leads to thermal quenching, the phenomenon in which the emission efficiency decreases as temperature rises. For this reason, the aim of the presented study is the modeling of remote phosphor systems in order to investigate their thermal limitations and to calculate the parameters for optimizing the efficiency of such systems. The common approach to simulate remote phosphor systems utilizes a combination of different tools such as ray tracing algorithms and wave optics tools for describing the incident and converted light, whereas the modeling of the conversion process itself, i.e. photoluminescence, in most cases is circumvented by using the absorption and emission spectra of the phosphor material. In this study, we describe the processes involved in luminescence quantum-mechanically using the single-configurational-coordinate diagram as well as the Franck-Condon principle and propose a simulation model that incorporates the temperature dependence of these processes. Following an increasing awareness of climate change and environmental issues, the development of ecologically friendly lighting systems featuring low power consumption and high luminous efficiency is imperative more than ever. The better understanding of laser-based lighting systems is an important step towards that aim as they may improve on LEDs in the near future.

RERTR-8 Irradiation Summary Report

DOE Office of Scientific and Technical Information (OSTI.GOV)

D. M. Perez; M. A. Lillo; G. S. Chang

2011-12-01

The Reduced Enrichment for Research and Test Reactor (RERTR) experiment RERTR-8, was designed to test monolithic mini-fuel plates fabricated via hot isostatic pressing (HIP), the effect of molybdenum (Mo) content on the monolithic fuel behavior, and the efficiency of ternary additions to dispersion fuel particles on the interaction layer behavior at higher burnup. The following report summarizes the life of the RERTR-8 experiment through end of irradiation, including as-run neutronic analysis, thermal analysis and hydraulic testing results.

Three-dimensional Cascaded Lattice Boltzmann Model for Thermal Convective Flows

NASA Astrophysics Data System (ADS)

Hajabdollahi, Farzaneh; Premnath, Kannan

2017-11-01

Fluid motion driven by thermal effects, such as due to buoyancy in differentially heated enclosures arise in several natural and industrial settings, whose understanding can be achieved via numerical simulations. Lattice Boltzmann (LB) methods are efficient kinetic computational approaches for coupled flow physics problems. In this study, we develop three-dimensional (3D) LB models based on central moments and multiple relaxation times for D3Q7 and D3Q15 lattices to solve the energy transport equations in a double distribution function approach. Their collision operators lead to a cascaded structure involving higher order terms resulting in improved stability. This is coupled to a central moment based LB flow solver with source terms. The new 3D cascaded LB models for the convective flows are first validated for natural convection of air driven thermally on two vertically opposite faces in a cubic cavity at different Rayleigh numbers against prior numerical and experimental data, which show good quantitative agreement. Then, the detailed structure of the 3D flow and thermal fields and the heat transfer rates at different Rayleigh numbers are analyzed and interpreted.

ON THE VIGOR OF MANTLE CONVECTION IN SUPER-EARTHS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Miyagoshi, Takehiro; Tachinami, Chihiro; Kameyama, Masanori

2014-01-01

Numerical models are presented to clarify how adiabatic compression affects thermal convection in the mantle of super-Earths ten times the Earth's mass. The viscosity strongly depends on temperature, and the Rayleigh number is much higher than that of the Earth's mantle. The strong effect of adiabatic compression reduces the activity of mantle convection; hot plumes ascending from the bottom of the mantle lose their thermal buoyancy in the middle of the mantle owing to adiabatic decompression, and do not reach the surface. A thick lithosphere, as thick as 0.1 times the depth of the mantle, develops along the surface boundary, and themore » efficiency of convective heat transport measured by the Nusselt number is reduced by a factor of about four compared with the Nusselt number for thermal convection of incompressible fluid. The strong effect of adiabatic decompression is likely to inhibit hot spot volcanism on the surface and is also likely to affect the thermal history of the mantle, and hence, the generation of magnetic field in super-Earths.« less

Optics-based approach to thermal management of photovoltaics: Selective-spectral and radiative cooling

DOE PAGES

Sun, Xingshu; Silverman, Timothy J.; Zhou, Zhiguang; ...

2017-01-20

For commercial one-sun solar modules, up to 80% of the incoming sunlight may be dissipated as heat, potentially raising the temperature 20-30 °C higher than the ambient. In the long term, extreme self-heating erodes efficiency and shortens lifetime, thereby dramatically reducing the total energy output. Therefore, it is critically important to develop effective and practical (and preferably passive) cooling methods to reduce operating temperature of photovoltaic (PV) modules. In this paper, we explore two fundamental (but often overlooked) origins of PV self-heating, namely, sub-bandgap absorption and imperfect thermal radiation. The analysis suggests that we redesign the optical properties of themore » solar module to eliminate parasitic absorption (selective-spectral cooling) and enhance thermal emission (radiative cooling). Comprehensive opto-electro-thermal simulation shows that the proposed techniques would cool one-sun terrestrial solar modules up to 10 °C. As a result, this self-cooling would substantially extend the lifetime for solar modules, with corresponding increase in energy yields and reduced levelized cost of electricity.« less

The possibility of developing hybrid PV/T solar system

NASA Astrophysics Data System (ADS)

Dobrnjac, M.; Zivkovic, P.; Babic, V.

2017-05-01

An alternative and cost-effective solution to developing integrated PV system is to use hybrid photovoltaic/thermal (PV/T) solar system. The temperature of PV modules increases due to the absorbed solar radiation that is not converted into electricity, causing a decrease in their efficiency. In hybrid PV/T solar systems the reduction of PV module temperature can be combined with a useful fluid heating. In this paper we present the possibility of developing a new hybrid PV/T solar system. Hybrid PV/T system can provide electrical and thermal energy, thus achieving a higher energy conversion rate of the absorbed solar radiation. We developed PV/T prototype consisted of commercial PV module and thermal panel with our original solution of aluminium absorber with special geometric shapes. The main advantages of our combined PV/T system are: removing of heat from the PV panel; extending the lifetime of photovoltaic cells; excess of the removing heat from PV part is used to heat the fluid in the thermal part of the panel; the possibility of using on the roof and facade constructions because less weight.

Improvement of anaerobic digestion of sewage sludge in a wastewater treatment plant by means of mechanical and thermal pre-treatments: Performance, energy and economical assessment.

PubMed

Ruffino, Barbara; Campo, Giuseppe; Genon, Giuseppe; Lorenzi, Eugenio; Novarino, Daniel; Scibilia, Gerardo; Zanetti, Mariachiara

2015-01-01

Performances of mechanical and low-temperature (<100°C) thermal pre-treatments were investigated to improve the present efficiency of anaerobic digestion (AD) carried out on waste activated sludge (WAS) in the largest Italian wastewater treatment plant (2,300,000p.e.). Thermal pre-treatments returned disintegration rates of one order of magnitude higher than mechanical ones (about 25% vs. 1.5%). The methane specific production increased by 21% and 31%, with respect to untreated samples, for treatment conditions of respectively 70 and 90°C, 3h. Thermal pre-treatments also decreased WAS viscosity. Preliminary energy and economic assessments demonstrated that a WAS final total solid content of 5% was enough to avoid the employment of auxiliary methane for the pre-treatment at 90°C and the subsequent AD process, provided that all the heat generated was transferred to WAS through heat exchangers. Moreover, the total revenues from sale of the electricity produced from biogas increased by 10% with respect to the present scenario. Copyright © 2014 Elsevier Ltd. All rights reserved.

Apparatus for nuclear transmutation and power production using an intense accelerator-generated thermal neutron flux

DOEpatents

Bowman, C.D.

1992-11-03

Apparatus for nuclear transmutation and power production using an intense accelerator-generated thermal neutron flux. High thermal neutron fluxes generated from the action of a high power proton accelerator on a spallation target allows the efficient burn-up of higher actinide nuclear waste by a two-step process. Additionally, rapid burn-up of fission product waste for nuclides having small thermal neutron cross sections, and the practicality of small material inventories while achieving significant throughput derive from employment of such high fluxes. Several nuclear technology problems are addressed including 1. nuclear energy production without a waste stream requiring storage on a geological timescale, 2. the burn-up of defense and commercial nuclear waste, and 3. the production of defense nuclear material. The apparatus includes an accelerator, a target for neutron production surrounded by a blanket region for transmutation, a turbine for electric power production, and a chemical processing facility. In all applications, the accelerator power may be generated internally from fission and the waste produced thereby is transmuted internally so that waste management might not be required beyond the human lifespan.

Direct fusion of geostationary meteorological satellite visible and infrared images based on thermal physical properties.

PubMed

Han, Lei; Wulie, Buzha; Yang, Yiling; Wang, Hongqing

2015-01-05

This study investigated a novel method of fusing visible (VIS) and infrared (IR) images with the major objective of obtaining higher-resolution IR images. Most existing image fusion methods focus only on visual performance and many fail to consider the thermal physical properties of the IR images, leading to spectral distortion in the fused image. In this study, we use the IR thermal physical property to correct the VIS image directly. Specifically, the Stefan-Boltzmann Law is used as a strong constraint to modulate the VIS image, such that the fused result shows a similar level of regional thermal energy as the original IR image, while preserving the high-resolution structural features from the VIS image. This method is an improvement over our previous study, which required VIS-IR multi-wavelet fusion before the same correction method was applied. The results of experiments show that applying this correction to the VIS image directly without multi-resolution analysis (MRA) processing achieves similar results, but is considerably more computationally efficient, thereby providing a new perspective on VIS and IR image fusion.

Direct Fusion of Geostationary Meteorological Satellite Visible and Infrared Images Based on Thermal Physical Properties

PubMed Central

Han, Lei; Wulie, Buzha; Yang, Yiling; Wang, Hongqing

2015-01-01

This study investigated a novel method of fusing visible (VIS) and infrared (IR) images with the major objective of obtaining higher-resolution IR images. Most existing image fusion methods focus only on visual performance and many fail to consider the thermal physical properties of the IR images, leading to spectral distortion in the fused image. In this study, we use the IR thermal physical property to correct the VIS image directly. Specifically, the Stefan-Boltzmann Law is used as a strong constraint to modulate the VIS image, such that the fused result shows a similar level of regional thermal energy as the original IR image, while preserving the high-resolution structural features from the VIS image. This method is an improvement over our previous study, which required VIS-IR multi-wavelet fusion before the same correction method was applied. The results of experiments show that applying this correction to the VIS image directly without multi-resolution analysis (MRA) processing achieves similar results, but is considerably more computationally efficient, thereby providing a new perspective on VIS and IR image fusion. PMID:25569749

Apparatus for nuclear transmutation and power production using an intense accelerator-generated thermal neutron flux

DOEpatents

Bowman, Charles D.

1992-01-01

Apparatus for nuclear transmutation and power production using an intense accelerator-generated thermal neutron flux. High thermal neutron fluxes generated from the action of a high power proton accelerator on a spallation target allows the efficient burn-up of higher actinide nuclear waste by a two-step process. Additionally, rapid burn-up of fission product waste for nuclides having small thermal neutron cross sections, and the practicality of small material inventories while achieving significant throughput derive from employment of such high fluxes. Several nuclear technology problems are addressed including 1. nuclear energy production without a waste stream requiring storage on a geological timescale, 2. the burn-up of defense and commercial nuclear waste, and 3. the production of defense nuclear material. The apparatus includes an accelerator, a target for neutron production surrounded by a blanket region for transmutation, a turbine for electric power production, and a chemical processing facility. In all applications, the accelerator power may be generated internally from fission and the waste produced thereby is transmuted internally so that waste management might not be required beyond the human lifespan.

Thermal Barrier and Protective Coatings to Improve the Durability of a Combustor Under a Pulse Detonation Engine Environment

NASA Technical Reports Server (NTRS)

Ghosn, Louis J.; Zhu, Dongming

2008-01-01

Pulse detonation engine (PDE) concepts are receiving increasing attention for future aeronautic propulsion applications, due to their potential thermodynamic cycle efficiency and higher thrust to density ratio that lead to the decrease in fuel consumption. But the resulting high gas temperature and pressure fluctuation distributions at high frequency generated with every detonation are viewed to be detrimental to the combustor liner material. Experimental studies on a typical metal combustion material exposed to a laser simulated pulse heating showed extensive surface cracking. Coating of the combustor materials with low thermal conductivity ceramics is shown to protect the metal substrate, reduce the thermal stresses, and hence increase the durability of the PDE combustor liner material. Furthermore, the temperature fluctuation and depth of penetration is observed to decrease with increasing the detonation frequency. A crack propagation rate in the coating is deduced by monitoring the variation of the coating apparent thermal conductivity with time that can be utilized as a health monitoring technique for the coating system under a rapid fluctuating heat flux.

Thermally enhanced photoluminescence for energy harvesting: from fundamentals to engineering optimization

NASA Astrophysics Data System (ADS)

Kruger, N.; Kurtulik, M.; Revivo, N.; Manor, A.; Sabapathy, T.; Rotschild, C.

2018-05-01

The radiance of thermal emission, as described by Planck’s law, depends only on the emissivity and temperature of a body, and increases monotonically with the temperature rise at any emitted wavelength. Non-thermal radiation, such as photoluminescence (PL), is a fundamental light–matter interaction that conventionally involves the absorption of an energetic photon, thermalization, and the emission of a redshifted photon. Such a quantum process is governed by rate conservation, which is contingent on the quantum efficiency. In the past, the role of rate conservation for significant thermal excitation had not been studied. Recently, we presented the theory and an experimental demonstration that showed, in contrast to thermal emission, that the PL rate is conserved when the temperature increases while each photon is blueshifted. A further rise in temperature leads to an abrupt transition to thermal emission where the photon rate increases sharply. We also demonstrated how such thermally enhanced PL (TEPL) generates orders of magnitude more energetic photons than thermal emission at similar temperatures. These findings show that TEPL is an ideal optical heat pump that can harvest thermal losses in photovoltaics with a maximal theoretical efficiency of 70%, and practical concepts potentially reaching 45% efficiency. Here we move the TEPL concept onto the engineering level and present Cr:Nd:YAG as device grade PL material, absorbing solar radiation up to 1 μm wavelength and heated by thermalization of energetic photons. Its blueshifted emission, which can match GaAs cells, is 20% of the absorbed power. Based on a detailed balance simulation, such a material coupled with proper photonic management can reach 34% power conversion efficiency. These results raise confidence in the potential of TEPL becoming a disruptive technology in photovoltaics.

NASA Fixed Wing Project Propulsion Research and Technology Development Activities to Reduce Thrust Specific Energy Consumption

NASA Technical Reports Server (NTRS)

Hathaway, Michael D.; Rosario, Ruben Del; Madavan, Nateri K.

2013-01-01

This paper presents an overview of the propulsion research and technology portfolio of NASA Fundamental Aeronautics Program Fixed Wing Project. The research is aimed at significantly reducing the thrust specific fuel/energy consumption of notional advanced fixed wing aircraft (by 60 percent relative to a baseline Boeing 737-800 aircraft with CFM56-7B engines) in the 2030 to 2035 time frame. The research investments described herein are aimed at improving propulsive efficiency through higher bypass ratio fans, improving thermal efficiency through compact high overall pressure ratio gas generators, and exploring the potential benefits of boundary layer ingestion propulsion and hybrid gas-electric propulsion concepts.

NASA Fixed Wing Project Propulsion Research and Technology Development Activities to Reduce Thrust Specific Energy Consumption

NASA Technical Reports Server (NTRS)

Hathaway, Michael D.; DelRasario, Ruben; Madavan, Nateri K.

2013-01-01

This paper presents an overview of the propulsion research and technology portfolio of NASA Fundamental Aeronautics Program Fixed Wing Project. The research is aimed at significantly reducing the thrust specific fuel/energy consumption of notional advanced fixed wing aircraft (by 60 % relative to a baseline Boeing 737-800 aircraft with CFM56-7B engines) in the 2030-2035 time frame. The research investments described herein are aimed at improving propulsive efficiency through higher bypass ratio fans, improving thermal efficiency through compact high overall pressure ratio gas generators, and exploring the potential benefits of boundary layer ingestion propulsion and hybrid gas-electric propulsion concepts.

Develop and test fuel cell powered on-site integrated total energy systems: Phase 3: Full-scale power plant development

NASA Technical Reports Server (NTRS)

1982-01-01

The development of a commercially viable and cost-effective phospheric acid fuel cell powered on-site integrated energy system (OS/IES) is described. The fuel cell offers energy efficients in the range of 35-40% of the higher heating value of available fuels in the form of electrical energy. In addition, by utilizing the thermal energy generated for heating, ventilating and air-conditioning (HVAC), a fuel cell OS/IES could provide total energy efficiencies in the neighborhood of 80%. Also, the Engelhard fuel cell OS/IES offers the important incentive of replacing imported oil with domestically produced methanol, including coal-derived methanol.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Moreno, Gilbert; Bennion, Kevin

This project will develop thermal management strategies to enable efficient and high-temperature wide-bandgap (WBG)-based power electronic systems (e.g., emerging inverter and DC-DC converter designs). The use of WBG-based devices in automotive power electronics will improve efficiency and increase driving range in electric-drive vehicles; however, the implementation of this technology is limited, in part, due to thermal issues. This project will develop system-level thermal models to determine the thermal limitations of current automotive power modules under elevated device temperature conditions. Additionally, novel cooling concepts and material selection will be evaluated to enable high-temperature silicon and WBG devices in power electronics components.more » WBG devices (silicon carbide [SiC], gallium nitride [GaN]) promise to increase efficiency, but will be driven as hard as possible. This creates challenges for thermal management and reliability.« less

Thermally Activated Delayed Fluorescence in Polymers: A New Route toward Highly Efficient Solution Processable OLEDs.

PubMed

Nikolaenko, Andrey E; Cass, Michael; Bourcet, Florence; Mohamad, David; Roberts, Matthew

2015-11-25

Efficient intermonomer thermally activated delayed fluorescence is demonstrated for the first time, opening a new route to achieving high-efficiency solution processable polymer light-emitting device materials. External quantum efficiency (EQE) of up to 10% is achieved in a simple fully solution-processed device structure, and routes for further EQE improvement identified. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Study on key technologies of optimization of big data for thermal power plant performance

NASA Astrophysics Data System (ADS)

Mao, Mingyang; Xiao, Hong

2018-06-01

Thermal power generation accounts for 70% of China's power generation, the pollutants accounted for 40% of the same kind of emissions, thermal power efficiency optimization needs to monitor and understand the whole process of coal combustion and pollutant migration, power system performance data show explosive growth trend, The purpose is to study the integration of numerical simulation of big data technology, the development of thermal power plant efficiency data optimization platform and nitrogen oxide emission reduction system for the thermal power plant to improve efficiency, energy saving and emission reduction to provide reliable technical support. The method is big data technology represented by "multi-source heterogeneous data integration", "large data distributed storage" and "high-performance real-time and off-line computing", can greatly enhance the energy consumption capacity of thermal power plants and the level of intelligent decision-making, and then use the data mining algorithm to establish the boiler combustion mathematical model, mining power plant boiler efficiency data, combined with numerical simulation technology to find the boiler combustion and pollutant generation rules and combustion parameters of boiler combustion and pollutant generation Influence. The result is to optimize the boiler combustion parameters, which can achieve energy saving.

Sorbent Material Property Requirements for On-Board Hydrogen Storage for Automotive Fuel Cell Systems.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ahluwalia, R. K.; Peng, J-K; Hua, T. Q.

2015-05-25

Material properties required for on-board hydrogen storage in cryogenic sorbents for use with automotive polymer electrolyte membrane (PEM) fuel cell systems are discussed. Models are formulated for physical, thermodynamic and transport properties, and for the dynamics of H-2 refueling and discharge from a sorbent bed. A conceptual storage configuration with in-bed heat exchanger tubes, a Type-3 containment vessel, vacuum insulation and requisite balance-of-plant components is developed to determine the peak excess sorption capacity and differential enthalpy of adsorption for 5.5 wt% system gravimetric capacity and 55% well-to-tank (WTT) efficiency. The analysis also determines the bulk density to which the materialmore » must be compacted for the storage system to reach 40 g.L-1 volumetric capacity. Thermal transport properties and heat transfer enhancement methods are analyzed to estimate the material thermal conductivity needed to achieve 1.5 kg.min(-1) H-2 refueling rate. Operating temperatures and pressures are determined for 55% WTT efficiency and 95% usable H-2. Needs for further improvements in material properties are analyzed that would allow reduction of storage pressure to 50 bar from 100 bar, elevation of storage temperature to 175-200 K from 150 K, and increase of WTT efficiency to 57.5% or higher.« less

Efficient Carbon-Based CsPbBr3 Inorganic Perovskite Solar Cells by Using Cu-Phthalocyanine as Hole Transport Material

NASA Astrophysics Data System (ADS)

Liu, Zhiyong; Sun, Bo; Liu, Xingyue; Han, Jinghui; Ye, Haibo; Shi, Tielin; Tang, Zirong; Liao, Guanglan

2018-06-01

Metal halide perovskite solar cells (PSCs) have attracted extensive research interest for next-generation solution-processed photovoltaic devices because of their high solar-to-electric power conversion efficiency (PCE) and low fabrication cost. Although the world's best PSC successfully achieves a considerable PCE of over 20% within a very limited timeframe after intensive efforts, the stability, high cost, and up-scaling of PSCs still remain issues. Recently, inorganic perovskite material, CsPbBr3, is emerging as a promising photo-sensitizer with excellent durability and thermal stability, but the efficiency is still embarrassing. In this work, we intend to address these issues by exploiting CsPbBr3 as light absorber, accompanied by using Cu-phthalocyanine (CuPc) as hole transport material (HTM) and carbon as counter electrode. The optimal device acquires a decent PCE of 6.21%, over 60% higher than those of the HTM-free devices. The systematic characterization and analysis reveal a more effective charge transfer process and a suppressed charge recombination in PSCs after introducing CuPc as hole transfer layer. More importantly, our devices exhibit an outstanding durability and a promising thermal stability, making it rather meaningful in future fabrication and application of PSCs.[Figure not available: see fulltext.

1800 MHz in vitro exposure device for experimental studies on the effects of mobile communication systems.

PubMed

Ardoino, L; Lopresto, V; Mancini, S; Pinto, R; Lovisolo, G A

2004-01-01

A wire patch cell (WPC) operating at the uplink frequency band of GSM 1800 MHz has been designed for in vitro experiments with the aim of investigating the possible biological effects of electromagnetic radiation associated with cellular phones. The 1800 MHz WPC design is a direct descendant of the original 900 MHz WPC introduced by Laval et al. This system provides a homogeneous specific absorption rate distribution, using four 3.5 cm petri dishes simultaneously. Numerical dosimetry has been performed using a commercial code (CST Microwave Studio), in order to evaluate accurately the efficiency of the structure (in terms of W kg(-1) per 1 W input power) and the distribution in the chosen biological target. The numerical results have been confirmed by experimental measurements performed by measuring thermal increase due to a high power impulse. The efficiency of the structure is 1.25 +/- 25% W kg(-1) per 1 W input power higher than the efficiency of the 900 MHz WPC. A few adjustments have been made in order to use the WPC in a standard incubator and to avoid thermal increases related to the radio frequency exposure. This exposure system has been adopted for the experiments scheduled in the RAMP and GUARD projects (VFPE).

Efficient long-term cryopreservation of pluripotent stem cells at −80 °C

PubMed Central

Yuan, Ye; Yang, Ying; Tian, Yuchen; Park, Jinkyu; Dai, Aihua; Roberts, R. Michael; Liu, Yang; Han, Xu

2016-01-01

Current long term cryopreservation of cell stocks routinely requires the use of liquid nitrogen (LN2), because commonly used cryopreservation media containing cell membrane permeating cryoprotectants are thermally unstable when frozen at higher storage temperatures, e.g. −80 °C. This instability leads to ice recrystallization, causing progressive loss of cell viability over time under the storage conditions provided by most laboratory deep freezers. The dependency on LN2 for cell storage significantly increases operational expense and raises issues related to impaired working efficiency and safety. Here we demonstrate that addition of Ficoll 70 to cryoprotectant solutions significantly improves system thermal stability at the working temperature (~−80 °C) of laboratory deep freezers. Moreover, a medium comprised of Ficoll 70 and dimethyl sulfoxide (DMSO) in presence or absence of fetal bovine serum (FBS) can provide reliable cryopreservation of various kinds of human and porcine pluripotent stem cells at −80 °C for periods that extend up to at least one year, with the post-thaw viability, plating efficiency, and full retention of pluripotent phenotype comparable to that achieved with LN2 storage. These results illustrate the practicability of a promising long-term cryopreservation method that completely eliminates the need for LN2. PMID:27694817

Experimental Investigation on Effect of Fin Shape on the Thermal-Hydraulic Performance of Compact Fin-and-Tube Heat Exchangers

NASA Astrophysics Data System (ADS)

Moorthy, P.; Oumer, A. N.; Ishak, M.

2018-03-01

The aim of this paper is to investigate the effect of fin shapes on the performance of compact finned flat tube heat exchangers. Three types of fin shapes namely plain, wavy, and rectangular grooved fins attached to three by three arrays of flat tube banks were considered. Moreover, the tubes were deployed in in-line and staggered arrangements. In addition to the fin shapes, the air velocity and the tube inclination angles were varied and the thermal-hydraulic performance was analysed. On the other hand, the temperatures at the tube surfaces were kept constant to produce constant heat flux throughout the study. The results showed that as flowrate increases, the heat transfer increases, however, the friction factor decreases. Staggered arrangement produces higher heat transfer and friction factor than inline fin. Moreover, the rectangular fin is the best in terms of high heat transfer however the drawback of high friction factor leads the fin to have the least efficiency of all. On the other hand, plain fin had the least heat transfer performance however the highest efficiency was achieved. Therefore, plain fin should be used when efficiency is prioritized and rectangular fin when high heat transfer is desired.

Improvement of thermal management in the composite Yb:YAG/YAG thin-disk laser

NASA Astrophysics Data System (ADS)

Kuznetsov, I. I.; Mukhin, I. B.; Palashov, O. V.

2016-04-01

To improve the thermal management in the composite Yb:YAG/YAG thin-disk laser a new design of laser head is developed. Thermal-induced phase distortions, small signal gain and lasing in the upgraded laser head are investigated and compared with previously published results. A substantial decrease of the thermal lens optical power and phase aberrations and increase of the laser slope efficiency are observed. A continuous-wave laser with 440 W average power and 44% slope efficiency is constructed.

Experimental and numerical study of two dimensional heat and mass transfer in unsaturated soil with and application to soil thermal energy storage (SBTES) systems

NASA Astrophysics Data System (ADS)

Moradi, A.; Smits, K. M.

2014-12-01

A promising energy storage option to compensate for daily and seasonal energy offsets is to inject and store heat generated from renewable energy sources (e.g. solar energy) in the ground, oftentimes referred to as soil borehole thermal energy storage (SBTES). Nonetheless in SBTES modeling efforts, it is widely recognized that the movement of water vapor is closely coupled to thermal processes. However, their mutual interactions are rarely considered in most soil water modeling efforts or in practical applications. The validation of numerical models that are designed to capture these processes is difficult due to the scarcity of experimental data, limiting the testing and refinement of heat and water transfer theories. A common assumption in most SBTES modeling approaches is to consider the soil as a purely conductive medium with constant hydraulic and thermal properties. However, this simplified approach can be improved upon by better understanding the coupled processes at play. Consequently, developing new modeling techniques along with suitable experimental tools to add more complexity in coupled processes has critical importance in obtaining necessary knowledge in efficient design and implementation of SBTES systems. The goal of this work is to better understand heat and mass transfer processes for SBTES. In this study, we implemented a fully coupled numerical model that solves for heat, liquid water and water vapor flux and allows for non-equilibrium liquid/gas phase change. This model was then used to investigate the influence of different hydraulic and thermal parameterizations on SBTES system efficiency. A two dimensional tank apparatus was used with a series of soil moisture, temperature and soil thermal properties sensors. Four experiments were performed with different test soils. Experimental results provide evidences of thermally induced moisture flow that was also confirmed by numerical results. Numerical results showed that for the test conditions applied here, moisture flow is more influenced by thermal gradients rather than hydraulic gradients. The results also demonstrate that convective fluxes are higher compared to conductive fluxes indicating that moisture flow has more contribution to the overall heat flux than conductive fluxes.

Thermal barrier coatings application in diesel engines

NASA Technical Reports Server (NTRS)

Fairbanks, J. W.

1995-01-01

Commercial use of thermal barrier coatings in diesel engines began in the mid 70's by Dr. Ingard Kvernes at the Central Institute for Industrial Research in Oslo, Norway. Dr. Kvernes attributed attack on diesel engine valves and piston crowns encountered in marine diesel engines in Norwegian ships as hot-corrosion attributed to a reduced quality of residual fuel. His solution was to coat these components to reduce metal temperature below the threshold of aggressive hot-corrosion and also provide protection. Roy Kamo introduced thermal barrier coatings in his 'Adiabatic Diesel Engine' in the late 70's. Kamo's concept was to eliminate the engine block water cooling system and reduce heat losses. Roy reported significant performance improvements in his thermally insulated engine at the SAE Congress in 1982. Kamo's work stimulates major programs with insulated engines, particularly in Europe. Most of the major diesel engine manufacturers conducted some level of test with insulated combustion chamber components. They initially ran into increased fuel consumption. The German engine consortium had Prof. Woschni of the Technical Institute in Munich. Woschni conducted testing with pistons with air gaps to provide the insulation effects. Woschni indicated the hot walls of the insulated engine created a major increase in heat transfer he refers to as 'convection vive.' Woschni's work was a major factor in the abrupt curtailment of insulated diesel engine work in continental Europe. Ricardo in the UK suggested that combustion should be reoptimized for the hot-wall effects of the insulated combustion chamber and showed under a narrow range of conditions fuel economy could be improved. The Department of Energy has supported thermal barrier coating development for diesel engine applications. In the Clean Diesel - 50 Percent Efficient (CD-50) engine for the year 2000, thermal barrier coatings will be used on piston crowns and possibly other components. The primary purpose of the thermal barrier coatings will be to reduce thermal fatigue as the engine peak cylinder pressure will nearly be doubled. As the coatings result in higher available energy in the exhaust gas, efficiency gains are achieved through use of this energy by turbochargers, turbocompounding or thermoelectric generators.

Laccase-Functionalized Graphene Oxide Assemblies as Efficient Nanobiocatalysts for Oxidation Reactions

PubMed Central

Patila, Michaela; Kouloumpis, Antonios; Gournis, Dimitrios; Rudolf, Petra; Stamatis, Haralambos

2016-01-01

Multi-layer graphene oxide-enzyme nanoassemblies were prepared through the multi-point covalent immobilization of laccase from Trametes versicolor (TvL) on functionalized graphene oxide (fGO). The catalytic properties of the fGO-TvL nanoassemblies were found to depend on the number of the graphene oxide-enzyme layers present in the nanostructure. The fGO-TvL nanoassemblies exhibit an enhanced thermal stability at 60 °C, as demonstrated by a 4.7-fold higher activity as compared to the free enzyme. The multi-layer graphene oxide-enzyme nanoassemblies can efficiently catalyze the oxidation of anthracene, as well as the decolorization of an industrial dye, pinacyanol chloride. These materials retained almost completely their decolorization activity after five reaction cycles, proving their potential as efficient nano- biocatalysts for various applications. PMID:26927109

Semiconducting lithium indium diselenide: Charge-carrier properties and the impacts of high flux thermal neutron irradiation

NASA Astrophysics Data System (ADS)

Hamm, Daniel S.; Rust, Mikah; Herrera, Elan H.; Matei, Liviu; Buliga, Vladimir; Groza, Michael; Burger, Arnold; Stowe, Ashley; Preston, Jeff; Lukosi, Eric D.

2018-06-01

This paper reports on the charge carrier properties of several lithium indium diselenide (LISe) semiconductors. It was found that the charge collection efficiency of LISe was improved after high flux thermal neutron irradiation including the presence of a typically unobservable alpha peak from hole-only collection. Charge carrier trap energies of the irradiated sample were measured using photo-induced current transient spectroscopy. Compared to previous studies of this material, no significant differences in trap energies were observed. Through trap-filled limited voltage measurements, neutron irradiation was found to increase the density of trap states within the bulk of the semiconductor, which created a polarization effect under alpha exposure but not neutron exposure. Further, the charge collection efficiency of the irradiated sample was higher (14-15 fC) than that of alpha particles (3-5 fC), indicating that an increase in hole signal contribution resulted from the neutron irradiation. Finally, it was observed that significant charge loss takes place near the point of generation, producing a significant scintillation response and artificially inflating the W-value of all semiconducting LISe crystals.

Investigations on laser hard tissue ablation under various environments

NASA Astrophysics Data System (ADS)

Kang, H. W.; Oh, J.; Welch, A. J.

2008-06-01

The purpose of this study was to investigate the effect of liquid environments upon laser bone ablation. A long-pulsed Er,Cr:YSGG laser was employed to ablate bovine bone tibia at various radiant exposures under dry, wet (using water or perfluorocarbon) and spray environmental conditions. Energy loss by the application of liquid during laser irradiation was evaluated, and ablation performance for all conditions was quantitatively measured by optical coherence tomography (OCT). Microscope images were also used to estimate thermal side effects in tissue after multiple-pulse ablation. Wet using water and spray conditions equally attenuated the 2.79 µm wavelength laser beam. Higher transmission efficiency was obtained utilizing a layer of perfluorocarbon. Dry ablation exhibited severe carbonization due to excessive heat accumulation. Wet condition using water resulted in similar ablation volume to the dry case without carbonization. The perfluorocarbon layer produced the largest ablation volume but some carbonization due to the poor thermal conductivity. Spray induced clean cutting with slightly reduced efficiency. Liquid-assisted ablation provided significant beneficial effects such as augmented material removal and cooling/cleaning effects during laser osteotomy.

Thermal valorization of post-consumer film waste in a bubbling bed gasifier.

PubMed

Martínez-Lera, S; Torrico, J; Pallarés, J; Gil, A

2013-07-01

The use of plastic bags and film packaging is very frequent in manifold sectors and film waste is usually present in different sources of municipal and industrial wastes. A significant part of it is not suitable for mechanical recycling but could be safely transformed into a valuable gas by means of thermal valorization. In this research, the gasification of film wastes has been experimentally investigated through experiments in a fluidized bed reactor of two reference polymers, polyethylene and polypropylene, and actual post-consumer film waste. After a complete experimental characterization of the three materials, several gasification experiments have been performed to analyze the influence of the fuel and of equivalence ratio on gas production and composition, on tar generation and on efficiency. The experiments prove that film waste and analogue polymer derived wastes can be successfully gasified in a fluidized bed reactor, yielding a gas with a higher heating value in a range from 3.6 to 5.6 MJ/m3 and cold gas efficiencies up to 60%. Copyright © 2013 Elsevier Ltd. All rights reserved.

D-A-D-type orange-light emitting thermally activated delayed fluorescence (TADF) materials based on a fluorenone unit: simulation, photoluminescence and electroluminescence studies.

PubMed

Gan, Lin; Li, Xianglong; Cai, Xinyi; Liu, Kunkun; Li, Wei; Su, Shi-Jian

2018-01-01

The design of orange-light emitting, thermally activated, delayed fluorescence (TADF) materials is necessary and important for the development and application of organic light-emitting diodes (OLEDs). Herein, two donor-acceptor-donor (D-A-D)-type orange TADF materials based on fluorenone and acridine, namely 2,7-bis(9,9-dimethylacridin-10(9 H )-yl)-9 H -fluoren-9-one (27DACRFT, 1 ) and 3,6-bis(9,9-dimethylacridin-10(9 H )-yl)-9 H -fluoren-9-one (36DACRFT, 2 ), were successfully synthetized and characterized. The studies on their structure-property relationship show that the different configurations have a serious effect on the photoluminescence and electroluminescence performance according to the change in singlet-triplet splitting energy (Δ E ST ) and excited state geometry. This indicates that a better configuration design can reduce internal conversion and improve triplet exciton utilization of TADF materials. Importantly, OLEDs based on 2 exhibited a maximum external quantum efficiency of 8.9%, which is higher than the theoretical efficiency of the OLEDs based on conventional fluorescent materials.

A self-sustained, complete and miniaturized methanol fuel processor for proton exchange membrane fuel cell

NASA Astrophysics Data System (ADS)

Yang, Mei; Jiao, Fengjun; Li, Shulian; Li, Hengqiang; Chen, Guangwen

2015-08-01

A self-sustained, complete and miniaturized methanol fuel processor has been developed based on modular integration and microreactor technology. The fuel processor is comprised of one methanol oxidative reformer, one methanol combustor and one two-stage CO preferential oxidation unit. Microchannel heat exchanger is employed to recover heat from hot stream, miniaturize system size and thus achieve high energy utilization efficiency. By optimized thermal management and proper operation parameter control, the fuel processor can start up in 10 min at room temperature without external heating. A self-sustained state is achieved with H2 production rate of 0.99 Nm3 h-1 and extremely low CO content below 25 ppm. This amount of H2 is sufficient to supply a 1 kWe proton exchange membrane fuel cell. The corresponding thermal efficiency of whole processor is higher than 86%. The size and weight of the assembled reactors integrated with microchannel heat exchangers are 1.4 L and 5.3 kg, respectively, demonstrating a very compact construction of the fuel processor.

Unravelling the magnetism, high spin polarization and thermoelectric efficiency of ZrFeSi half-Heusler

NASA Astrophysics Data System (ADS)

Yousuf, Saleem; Gupta, D. C.

2018-04-01

We report the systematic investigation of structural properties, occupancy of density of states, nature of bonding and thermoelectric efficiency of half-Heusler ZrFeSi. The band structure analysis predicts the hybridization of Zr-d and Fe-d metal atoms resulting in occupation of density of states above the Fermi level (EF) while Fe-p and Si-p occupy the lower energy states below the EF. Thermoelectric transport coefficients are predicted using the Boltzmann transport theory under constant relaxation approximation, where Seebeck coefficient (S), total thermal conductivity and figure of merit are calculated. The negative value of total S as -14.02 μV/K predicts the material as n-type with thermoelectric figure of merit (zT) of 0.5 at 800 K. The lattice thermal conductivity decreases with increasing temperature with room temperature value of 4.18 W/mK and shows a significant reduction towards higher temperatures. In view of above elements, structural stability, high zT, ZrFeSi alloy have the capabilities to stimulate experimental verification as a promising materials for high temperature power generation and spintronic device fabrications.

Constructing Efficient and Stable Perovskite Solar Cells via Interconnecting Perovskite Grains.

PubMed

Hou, Xian; Huang, Sumei; Ou-Yang, Wei; Pan, Likun; Sun, Zhuo; Chen, Xiaohong

2017-10-11

A high-quality perovskite film with interconnected perovskite grains was obtained by incorporating terephthalic acid (TPA) additive into the perovskite precursor solution. The presence of TPA changed the crystallization kinetics of the perovskite film and promoted lateral growth of grains in the vicinity of crystal boundaries. As a result, sheet-shaped perovskite was formed and covered onto the bottom grains, which made some adjacent grains partly merge together to form grains-interconnected perovskite film. Perovskite solar cells (PSCs) with TPA additive exhibited a power conversion efficiency (PCE) of 18.51% with less hysteresis, which is obviously higher than that of pristine cells (15.53%). PSCs without and with TPA additive retain 18 and 51% of the initial PCE value, respectively, aging for 35 days exposed to relative humidity 30% in air without encapsulation. Furthermore, MAPbI 3 film with TPA additive shows superior thermal stability to the pristine one under 100 °C baking. The results indicate that the presence of TPA in perovskite film can greatly improve the performance of PSCs as well as their moisture resistance and thermal stability.

Improving urban district heating systems and assessing the efficiency of the energy usage therein

NASA Astrophysics Data System (ADS)

Orlov, M. E.; Sharapov, V. I.

2017-11-01

The report describes issues in connection with improving urban district heating systems from combined heat power plants (CHPs), to propose the ways for improving the reliability and the efficiency of the energy usage (often referred to as “energy efficiency”) in such systems. The main direction of such urban district heating systems improvement suggests transition to combined heating systems that include structural elements of both centralized and decentralized systems. Such systems provide the basic part of thermal power via highly efficient methods for extracting thermal power plants turbines steam, while peak loads are covered by decentralized peak thermal power sources to be mounted at consumers’ locations, with the peak sources being also reserve thermal power sources. The methodology was developed for assessing energy efficiency of the combined district heating systems, implemented as a computer software product capable of comparatively calculating saving on reference fuel for the system.

Trade-offs in disease and bleaching susceptibility among two color morphs of the Hawaiian reef coral, Montipora capitata

NASA Astrophysics Data System (ADS)

Shore-Maggio, Amanda; Callahan, Sean M.; Aeby, Greta S.

2018-06-01

Two threats impacting coral reefs are bleaching and disease, and differential susceptibility to both exists among and within coral taxa. Bleaching resistance is commonly linked to the clade of endosymbiotic Symbiodinium, but may come at a cost to other biological traits. Montipora capitata is an Indo-Pacific reef-building coral with two color morphs, red and orange, which harbor different clades of Symbiodinium. We explored whether these color morphs displayed differences in bleaching/disease susceptibility and other biological traits (growth rate, reproductive output, and lipid content). We found a trade-off between disease and bleaching susceptibility. The orange morph had significantly higher disease prevalence, whereas the red morph had significantly higher bleaching prevalence. Thermal stress experiments found that bleaching and loss of photochemical efficiency occurred significantly faster in the red morph, but at normal temperatures, the red morph had a significantly higher growth rate. Higher abundance of the red morph in the field suggests that disease resistance is a more successful strategy in the absence of thermal stress events. The orange morph may better tolerate increases in sea temperatures, but may not persist due to decreased growth rate and increased disease susceptibility. Trade-offs in response to stressors highlight the need to consider local and global threats to coral reefs.

Diamond Thin-Film Thermionic Generator

NASA Astrophysics Data System (ADS)

Clewell, J. M.; Ordonez, C. A.; Perez, J. M.

1997-03-01

Since the eighteen-hundreds scientists have sought to develop the highest thermal efficiency in heat engines such as thermionic generators. Modern research in the emerging diamond film industry has indicated the work functions of diamond thin-films can be much less than one electron volt, compelling fresh investigation into their capacity as thermionic generators and inviting new methodology for determining that efficiency. Our objective is to predict the efficiency of a low-work-function, degenerate semiconductor (diamond film) thermionic generator operated as a heat engine between two constant-temperature thermal reservoirs. Our presentation will focus on a theoretical model which predicts the efficiency of the system by employing a Monte Carlo computational technique from which we report results for the thermal efficiency and the thermionic current densities of diamond thin-films.

Microencapsulation of Garcinia fruit extract by spray drying and its effect on bread quality.

PubMed

Ezhilarasi, Perumal Natarajan; Indrani, Dasappa; Jena, Bhabani Sankar; Anandharamakrishnan, Chinnaswamy

2014-04-01

(-)-Hydroxycitric acid (HCA) is the major acid present in the fruit rinds of certain species of Garcinia. HCA has been reported to have several health benefits. As HCA is highly hygroscopic in nature and thermally sensitive, it is difficult to incorporate in foodstuffs. Hence, Garcinia cowa fruit extract was microencapsulated using three different wall materials such as whey protein isolate (WPI), maltodextrin (MD) and a combination of whey protein isolate and maltodextrin (WPI + MD) by spray drying. Further, these microencapsulated powders were evaluated for their impact on bread quality and HCA retention. Maltodextrin (MD) encapsulates had higher free (86%) and net HCA (90%) recovery. Microencapsulates incorporated breads had enhanced qualitative characteristics and higher HCA content than water extract incorporated bread due to efficient encapsulation during bread baking. Comparatively, bread with MD encapsulates showed softer crumb texture, desirable sensory attributes with considerable volume and higher HCA content. The higher HCA contents of encapsulate incorporated breads were sufficient to claim for functionality of HCA in bread. Comparatively, MD had efficiently encapsulated Garcinia fruit extract during spray drying and bread baking. Spray drying proved to be an excellent encapsulation technique for incorporation into the food system. © 2013 Society of Chemical Industry.

Slotting Fins of Heat Exchangers to Provide Thermal Breaks

NASA Technical Reports Server (NTRS)

Scull, Timothy D.

2003-01-01

Heat exchangers that include slotted fins (in contradistinction to continuous fins) have been invented. The slotting of the fins provides thermal breaks that reduce thermal conduction along flow paths (longitudinal thermal conduction), which reduces heat-transfer efficiency. By increasing the ratio between transverse thermal conduction (the desired heat-transfer conduction) and longitudinal thermal conduction, slotting of the fins can be exploited to (1) increase heat-transfer efficiency (thereby reducing operating cost) for a given heat-exchanger length or to (2) reduce the length (thereby reducing the weight and/or cost) of the heat exchanger needed to obtain a given heat transfer efficiency. By reducing the length of a heat exchanger, one can reduce the pressure drop associated with the flow through it. In a case in which slotting enables the use of fins with thermal conductivity greater than could otherwise be tolerated on the basis of longitudinal thermal conduction, one can exploit the conductivity to make the fins longer (in the transverse direction) than they otherwise could be, thereby making it possible to make a heat exchanger that contains fewer channels and therefore, that weighs less, contains fewer potential leak paths, and can be constructed from fewer parts and, hence, reduced cost.

Investigation of the charge boost technology for the efficiency increase of closed sorption thermal energy storage systems

NASA Astrophysics Data System (ADS)

Rohringer, C.; Engel, G.; Köll, R.; Wagner, W.; van Helden, W.

2017-10-01

The inclusion of solar thermal energy into energy systems requires storage possibilities to overcome the gap between supply and demand. Storage of thermal energy with closed sorption thermal energy systems has the advantage of low thermal losses and high energy density. However, the efficiency of these systems needs yet to be increased to become competitive on the market. In this paper, the so-called “charge boost technology” is developed and tested via experiments as a new concept for the efficiency increase of compact thermal energy storages. The main benefit of the charge boost technology is that it can reach a defined state of charge for sorption thermal energy storages at lower temperature levels than classic pure desorption processes. Experiments are conducted to provide a proof of principle for this concept. The results show that the charge boost technology does function as predicted and is a viable option for further improvement of sorption thermal energy storages. Subsequently, a new process application is developed by the author with strong focus on the utilization of the advantages of the charge boost technology over conventional desorption processes. After completion of the conceptual design, the theoretical calculations are validated via experiments.

Structural Modulation from 1D Chain to 3D Framework: Improved Thermostability, Insensitivity, and Energies of Two Nitrogen-Rich Energetic Coordination Polymers.

PubMed

Guo, Zhaoqi; Wu, Yunlong; Deng, Chongqing; Yang, Guoping; Zhang, Jiangong; Sun, Zhihua; Ma, Haixia; Gao, Chao; An, Zhongwei

2016-11-07

Two new energetic coordination polymers (CPs) [Pb(BT)(H 2 O) 3 ] n (1) and [Pb 3 (DOBT) 3 (H 2 O) 2 ] n ·(4H 2 O) n (2) with 1D and 3D structures were synthesized by employing two rational designed ligands, 1H,1'H-5,5'-bitetrazole (H 2 BT) and 1H,1'H-[5,5'-bitetrazole]-1,1'-diol ligands (DHBT), respectively. Thermal analyses and sensitivity tests show that the 3D architecture reinforces the network of 2 which has higher thermal stability and lower sensitivity than that of 1. Through oxygen-bomb combustion calorimetry the molar enthalpy of formation of 2 is derived to be much higher than that of 1 as well as the reported CPs. Herein, more importantly, the heats of detonation (ΔH det ) were calculated according to the decomposition products of TG-DSC-MS-FTIR simultaneous analyses for the first time. The calculated results show that ΔH det of 2 is 23% higher than that of 1. This research demonstrates that 3D energetic CP with outstanding energetic properties can be obtained through efficient and reasonable design.

Advanced oxidation technology for H2S odor gas using non-thermal plasma

NASA Astrophysics Data System (ADS)

Tao, ZHU; Ruonan, WANG; Wenjing, BIAN; Yang, CHEN; Weidong, JING

2018-05-01

Non-thermal plasma technology is a new type of odor treatment processing. We deal with H2S from waste gas emission using non-thermal plasma generated by dielectric barrier discharge. On the basis of two criteria, removal efficiency and absolute removal amount, we deeply investigate the changes in electrical parameters and process parameters, and the reaction process of the influence of ozone on H2S gas removal. The experimental results show that H2S removal efficiency is proportional to the voltage, frequency, power, residence time and energy efficiency, while it is inversely proportional to the initial concentration of H2S gas, and ozone concentration. This study lays the foundations of non-thermal plasma technology for further commercial application.

Study of the thermal-optics parameters of Nd3+-doped phosphate glass as a function of temperature

NASA Astrophysics Data System (ADS)

Filho, J. C.; Pilla, V.; Messias, D. N.; Lourenço, S. A.; Silva, A. C. A.; Dantas, N. O.; Andrade, A. A.

2017-02-01

The spectroscopic properties of rare earth ions in many different hosts have been investigated, including surveys of Nd3+ in silicate, phosphate, fluorophosphates and fluoride glasses. Some of the thermal-optical properties of materials are influenced by temperature change, such as thermal diffusivity, specific heat and luminescence quantum efficiency. In this work the luminescence quantum efficiency of PANK: Nd3+, as a function of temperature (80- 480 K), was investigated using the normalized lifetime thermal lens technique. This system presents high quantum efficiency at low Nd3+ concentration and at ambient temperature, 100%, which decrease as temperature increase. Below room temperature the effects are not in accord with the maximum value of η, which must be unity.

Transparent layered YAG ceramics with structured Yb doping produced via tape casting

NASA Astrophysics Data System (ADS)

Hostaša, Jan; Piancastelli, Andreana; Toci, Guido; Vannini, Matteo; Biasini, Valentina

2017-03-01

The flexibility of the ceramic production process, in particular in terms of shaping and spatial control of distribution of active ions, is one of the strong points in favor of transparent ceramics. In high power lasers in particular, where thermal management is a critical issue, the finely controlled design of spatial distribution of the doping ions within the laser gain media can reduce undesired thermally induced effects and large temperature gradients, and thus enhance the efficiency and laser beam quality especially under increased thermal load. In the present work transparent structured YAG ceramics with Yb doping were produced by tape casting followed by thermal compression of assembled tapes and sintered under high vacuum. The thermal compression of variously doped tape cast layers is a very promising method because it allows a high precision and good control over dopant distribution in the sintered material. After sintering, the distribution of Yb across the layers was characterized by SEM-EDX and the thickness of Yb diffusion zones between the layers with different Yb content was measured. Optical homogeneity was assessed by means of optical transmittance mapping of the samples and by 2D scanning of laser output. The effect of structured dopant distribution on laser performance was measured in quasi-CW and CW regime with different duty factors. Slope efficiency values higher than 50% were measured both in quasi-CW and in CW lasing conditions. The results are in good agreement with previously calculated predictions, confirming the beneficial effect of structured doping on laser performances and enlightening the impact of the residual scattering losses. Compared to other processing methods, such as the pressing of granulated powders, tape casting followed by thermal compression leads to straight and narrow interfaces between layers with different composition and allows to build structures composed of extremely thin layers with defined dopant content.

Thermal and Electrical Recharging of Sodium/Sulfur Cells

NASA Technical Reports Server (NTRS)

Richter, Robert

1987-01-01

Efficiency as high as 60 percent achieved. Proposed thermal and electrical recharging scheme expected to increase overall energy efficiency of battery of sodium/sulfur cells (beta cells). Takes advantage of peculiarity in chemical kinetics of recharge portion of operating cycle to give thermal assist to electrically driven chemical reactions. Future application include portable power supplies and energy storage in commercial power systems during offpeak periods.

A new laboratory-scale experimental facility for detailed aerothermal characterizations of volumetric absorbers

NASA Astrophysics Data System (ADS)

Gomez-Garcia, Fabrisio; Santiago, Sergio; Luque, Salvador; Romero, Manuel; Gonzalez-Aguilar, Jose

2016-05-01

This paper describes a new modular laboratory-scale experimental facility that was designed to conduct detailed aerothermal characterizations of volumetric absorbers for use in concentrating solar power plants. Absorbers are generally considered to be the element with the highest potential for efficiency gains in solar thermal energy systems. The configu-ration of volumetric absorbers enables concentrated solar radiation to penetrate deep into their solid structure, where it is progressively absorbed, prior to being transferred by convection to a working fluid flowing through the structure. Current design trends towards higher absorber outlet temperatures have led to the use of complex intricate geometries in novel ceramic and metallic elements to maximize the temperature deep inside the structure (thus reducing thermal emission losses at the front surface and increasing efficiency). Although numerical models simulate the conjugate heat transfer mechanisms along volumetric absorbers, they lack, in many cases, the accuracy that is required for precise aerothermal validations. The present work aims to aid this objective by the design, development, commissioning and operation of a new experimental facility which consists of a 7 kWe (1.2 kWth) high flux solar simulator, a radiation homogenizer, inlet and outlet collector modules and a working section that can accommodate volumetric absorbers up to 80 mm × 80 mm in cross-sectional area. Experimental measurements conducted in the facility include absorber solid temperature distributions along its depth, inlet and outlet air temperatures, air mass flow rate and pressure drop, incident radiative heat flux, and overall thermal efficiency. In addition, two windows allow for the direct visualization of the front and rear absorber surfaces, thus enabling full-coverage surface temperature measurements by thermal imaging cameras. This paper presents the results from the aerothermal characterization of a siliconized silicon carbide monolithic honeycomb, conducted at realistic conditions of incident radiative power per unit mass flow rate in order to validate its operation.

Light and Strong Hierarchical Porous SiC Foam for Efficient Electromagnetic Interference Shielding and Thermal Insulation at Elevated Temperatures.

PubMed

Liang, Caiyun; Wang, Zhenfeng; Wu, Lina; Zhang, Xiaochen; Wang, Huan; Wang, Zhijiang

2017-09-06

A novel light but strong SiC foam with hierarchical porous architecture was fabricated by using dough as raw material via carbonization followed by carbothermal reduction with silicon source. A significant synergistic effect is achieved by embedding meso- and nanopores in a microsized porous skeleton, which endows the SiC foam with high-performance electromagnetic interference (EMI) shielding, thermal insulation, and mechanical properties. The microsized skeleton withstands high stress. The meso- and nanosized pores enhance multiple reflection of the incident electromagnetic waves and elongate the path of heat transfer. For the hierarchical porous SiC foam with 72.8% porosity, EMI shielding can be higher than 20 dB, and specific EMI effectiveness exceeds 24.8 dB·cm 3 ·g -1 at a frequency of 11 GHz at 25-600 °C, which is 3 times higher than that of dense SiC ceramic. The thermal conductivity reaches as low as 0.02 W·m -1 ·K -1 , which is comparable to that of aerogel. The compressive strength is as high as 9.8 MPa. Given the chemical and high-temperature stability of SiC, the fabricated SiC foam is a promising candidate for modern aircraft and automobile applications.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Antolovich, S.D.; Saxena, A.; Cullers, C.

One of the ongoing challenges of the aerospace industry is to develop more efficient turbine engines. Greater efficiency entails reduced specific strength and larger temperature gradients, the latter of which means higher operating temperatures and increased thermal conductivity. Continued development of nickel-based superalloys has provided steady increases in engine efficiency and the limits of superalloys have probably not been realized. However, other material systems are under intense investigation for possible use in high temperature engines. Ceramic, intermetallic, and various composite systems are being explored in an effort to exploit the much higher melting temperatures of these systems. NiAl is consideredmore » a potential alternative to conventional superalloys due to its excellent oxidation resistance, low density, and high melting temperature. The fact that NiAl is the most common coating for current superalloy turbine blades is a tribute to its oxidation resistance. Its density is one-third that of typical superalloys and in most temperature ranges its thermal conductivity is twice that of common superalloys. Despite these many advantages, NiAl requires more investigation before it is ready to be used in engines. Binary NiAl in general has poor high-temperature strength and low-temperature ductility. On-going research in alloy design continues to make improvements in the high-temperature strength of NiAl. The factors controlling low temperature ductility have been identified in the last few years. Small, but reproducible ductility can now be achieved at room temperature through careful control of chemical purity and processing. But the mechanisms controlling the transition from brittle to ductile behavior are not fully understood. Research in the area of fatigue deformation can aid the development of the NiAl system in two ways. Fatigue properties must be documented and optimized before NiAl can be applied to engineering systems.« less

Exploring Near-Field Radiative Heat Transfer for Thermo-photovoltaic Applications

NASA Astrophysics Data System (ADS)

Ganjeh, Yashar; Song, Bai; Sadat, Seid; Thompson, Dakotah; Fiorino, Anthony; Reddy, Pramod; Meyhofer, Edgar

2014-03-01

Understanding near-field radiative heat transfer (NFRHT) is critical for developing efficient thermo-photovoltaic devices. Theoretical predictions suggest that when the spatial separation of two parallel planes at different temperatures is less than their Wien's thermal wavelength, thermal transport via radiation can be greatly enhanced. The radiative heat flow across nanoscale gaps is predicted to be orders-of-magnitude higher than that given by Stefan-Boltzmann law, due to contribution of evanescent waves. In order to test these predictions, a novel experimental platform was designed and built enabling parallelization of two planar surfaces (50 μm by 50 μm) with 500 microradian resolution in their relative orientation. This platform was used to probe NFRHT between two planes and also between a plane and a sphere. It was found that, when a 50 μm diameter silica sphere was approximately 20 nm away from a 50 by 50 μm2 silica plane, a significant increase in radiative heat transfer coefficient was observed. This increase is 3 orders of magnitude higher than the value predicted by the blackbody limit. Other setups, including Au spheres and planes, and the plane-plane geometries are currently being investigated. 1) Army Research office (W911NF-12-1-0612), 2) NSF Thermal Transport Prcesses (CBET 1235691), 3) Center for Solar and Thermal Energy conversion, funded by the US Department of Energy, Office of Science, Basic Energy Sciences under award no. DE-SC0000957.

Improved finite element methodology for integrated thermal structural analysis

NASA Technical Reports Server (NTRS)

Dechaumphai, P.; Thornton, E. A.

1982-01-01

An integrated thermal-structural finite element approach for efficient coupling of thermal and structural analysis is presented. New thermal finite elements which yield exact nodal and element temperatures for one dimensional linear steady state heat transfer problems are developed. A nodeless variable formulation is used to establish improved thermal finite elements for one dimensional nonlinear transient and two dimensional linear transient heat transfer problems. The thermal finite elements provide detailed temperature distributions without using additional element nodes and permit a common discretization with lower order congruent structural finite elements. The accuracy of the integrated approach is evaluated by comparisons with analytical solutions and conventional finite element thermal structural analyses for a number of academic and more realistic problems. Results indicate that the approach provides a significant improvement in the accuracy and efficiency of thermal stress analysis for structures with complex temperature distributions.

Vertically Aligned and Interconnected SiC Nanowire Networks Leading to Significantly Enhanced Thermal Conductivity of Polymer Composites.

PubMed

Yao, Yimin; Zhu, Xiaodong; Zeng, Xiaoliang; Sun, Rong; Xu, Jian-Bin; Wong, Ching-Ping

2018-03-21

Efficient heat removal via thermal management materials has become one of the most critical challenges in the development of modern microelectronic devices. However, previously reported polymer composites exhibit limited enhancement of thermal conductivity, even when highly loaded with thermally conductive fillers, because of the lack of efficient heat transfer pathways. Herein, we report vertically aligned and interconnected SiC nanowire (SiCNW) networks as efficient fillers for polymer composites, achieving significantly enhanced thermal conductivity. The SiCNW networks are produced by freeze-casting nanowire aqueous suspensions followed by thermal sintering to consolidate the nanowire junctions, exhibiting a hierarchical architecture in which honeycomb-like SiCNW layers are aligned. The composite obtained by infiltrating SiCNW networks with epoxy resin, at a relatively low SiCNW loading of 2.17 vol %, represents a high through-plane thermal conductivity (1.67 W m -1 K -1 ) compared to the pure matrix, which is equivalent to a significant enhancement of 406.6% per 1 vol % loading. The orderly SiCNW network which can act as a macroscopic expressway for phonon transport is believed to be the main contributor for the excellent thermal performance. This strategy provides insights for the design of high-performance composites with potential to be used in advanced thermal management materials.

Dynamic Geospatial Modeling of the Building Stock to Project Urban Energy Demand.

PubMed

Breunig, Hanna Marie; Huntington, Tyler; Jin, Ling; Robinson, Alastair; Scown, Corinne Donahue

2018-06-26

In the United States, buildings account for more than 40 percent of total energy consumption, and the evolution of the urban form will impact the effectiveness of strategies to reduce energy use and mitigate emissions. This paper presents a broadly applicable approach for modeling future commercial, residential, and industrial floorspace, thermal consumption (heating and cooling), and associated GHG emissions at the tax assessor land parcel level. The approach accounts for changing building standards and retrofitting, climate change, and trends in housing and industry. We demonstrate the automated workflow for California, and project building stock, thermal energy consumption, and associated GHG emissions out to 2050. Our results suggest that if buildings in California have long lifespans, and minimal energy efficiency improvements compared to building codes reflective of 2008, then the state will face a 20% or higher increase in thermal energy consumption by 2050. Baseline annual GHG emissions associated with thermal energy consumption in the modeled building stock in 2016 is 34% below 1990 levels (110 Mt CO2eq/y).While the 2020 targets for the reduction of GHG emissions set by the California Senate Bill 350 have already been met, none of our scenarios achieve >80% reduction from 1990 levels by 2050, despite assuming an 86% reduction in electricity carbon intensity in our "Low Carbon" scenario. The results highlight the challenge California faces in meeting its new energy efficiency targets unless the State's building stock undergoes timely and strategic turnover, paired with deep retrofitting of existing buildings and natural gas equipment.

Efficiency loss of thin film Cu(InxGa1-x)Se(S) solar panels by lamination process

NASA Astrophysics Data System (ADS)

Xu, Li

2017-04-01

Efficiency loss of thin film Cu(InxGa1-x)Se(S) (CIGS) solar panels by lamination process has been compromising the final output power in commercial products of solar modules, but few reports have been published on such issue, as the majority of the investigation is focused on the efficiency at the circuit level, i.e., before lamination process. In this paper, we studied the effect of lamination process to the efficiency loss of thin film CIGS solar panels. It was observed that the fill factor degradation dominated the efficiency loss with the small change of Voc and Jsc. Experiments showed that neither the temperature nor the pressure, nor the two combined in the lamination process is the root cause of the efficiency loss; instead, the ethylene vinyl acetate (EVA) layer as the encapsulation material which directly contacts the solar cell devices was the major factor responsible for the efficiency loss. It was found that the gel content of the cured EVA film after lamination was highly correlated to the efficiency loss. The higher the gel content, the higher the efficiency loss. The mismatch of coefficient of thermal expansion between the EVA film and the CIGS thin film resulted in compressive stress in the device layer after lamination process. The compressive stress is speculated to affect the lattice defects, but need to be confirmed with the measurement of capacitance voltage (CV) and drive level capacitance profiling (DLCP). Three-day sun soak was then carried out and it was observed that the fill factor recovered significantly and so did the efficiency. Experiments also showed that there was no impact of chemical erosion on the front electrode of transparent conductive oxide (TCO) films by chemicals released from the EVA films during lamination.

The effect of diffusion induced lattice stress on the open-circuit voltage in silicon solar cells

NASA Technical Reports Server (NTRS)

Weizer, V. G.; Godlewski, M. P.

1984-01-01

It is demonstrated that diffusion induced stresses in low resistivity silicon solar cells can significantly reduce both the open-circuit voltage and collection efficiency. The degradation mechanism involves stress induced changes in both the minority carrier mobility and the diffusion length. Thermal recovery characteristics indicate that the stresses are relieved at higher temperatures by divacancy flow (silicon self diffusion). The level of residual stress in as-fabricated cells was found to be negligible in the cells tested.

Dielectric compound parabolic concentrating solar collector with frustrated total internal reflection absorber

NASA Astrophysics Data System (ADS)

Hull, J. R.

Since its introduction, the concept of nonimaging solar concentrators, as exemplified by the compound parabolic concentrator (CPC) design, has greatly enhanced the ability to collect solar energy efficiently in thermal and photovoltaic devices. When used as a primary concentrator, a CPC can provide significant concentration without the complication of a tracking mechanism and its associated maintenance problems. When used as a secondary, a CPC provides higher total concentration, or for a fixed concentration, tolerates greater tracking error in the primary.

DUCT RETROFIT STRATEGY TO COMPLEMENT A MODULATING FURNACE.

DOE Office of Scientific and Technical Information (OSTI.GOV)

ANDREWS,J.W.

2002-10-02

Some recent work (Walker 2001, Andrews 2002) has indicated that installing a modulating furnace in a conventional duct system may, in many cases, result in a significant degradation in thermal distribution efficiency. The fundamental mechanism was pointed out nearly two decades ago (Andrews and Krajewski 1985). The problem occurs in duct systems that are less-than-perfectly insulated (e.g., R-4 duct wrap) and are located outside the conditioned space. It stems from the fact that when the airflow rate is reduced, as it will be when the modulating furnace reduces its heat output rate, the supply air will have a longer residencemore » time in the ducts and will therefore lose a greater percentage of its heat by conduction than it did at the higher airflow rate. The impact of duct leakage, on the other hand, is not expected to change very much under furnace modulation. The pressures in the duct system will be reduced when the airflow rate is reduced, thus reducing the leakage per unit time. This is balanced by the fact that the operating time will increase in order to meet the same heating load as with the conventional furnace operating at higher output and airflow rates. The balance would be exact if the exponent in the pressure vs. airflow equation were the same as that in the pressure vs. duct leakage equation. Since the pressure-airflow exponent is usually {approx}0.5 and the pressure-leakage exponent is usually {approx}0.6, the leakage loss as a fraction of the load should be slightly lower for the modulating furnace. The difference, however, is expected to be small, determined as it is by a function with an exponent equal to the difference between the above two exponents, or {approx}0.1. The negative impact of increased thermal conduction losses from the duct system may be partially offset by improved efficiency of the modulating furnace itself. Also, the modulating furnace will cycle on and off less often than a single-capacity model, and this may add a small amount (probably in the range 1%-3%) to the thermal distribution efficiency. Nevertheless, the effect of furnace modulation on thermal distribution efficiency, both as calculated and as measured in the laboratory, is quite significant. Although exact quantification of the impact will depend on factors such as climate and the location of the ducts within the structure, impacts in the 15%-25% range are to be expected for ducts located outside the conditioned space, as most residential duct systems are. This is too large a handicap to ignore.« less

Paracetamol degradation in aqueous solution by non-thermal plasma

NASA Astrophysics Data System (ADS)

Baloul, Yasmine; Aubry, Olivier; Rabat, Hervé; Colas, Cyril; Maunit, Benoît; Hong, Dunpin

2017-08-01

This study deals with paracetamol degradation in water using a non-thermal plasma (NTP) created by a dielectric barrier discharge (DBD). The effects of the NTP operating conditions on the degradation were studied, showing that the treatment efficiency of the process was highly dependent on the electrical parameters and working gas composition in the reactor containing the aqueous solution. A conversion rate higher than 99% was reached with an energy yield of 12 g/kWh. High resolution mass spectrometry (HRMS) measurements showed that the main species produced in water during the process were nitrogen compounds, carboxylic acids and aromatic compounds. Contribution to the topical issue "The 15th International Symposium on High Pressure Low Temperature Plasma Chemistry (HAKONE XV)", edited by Nicolas Gherardi and Tomáš Hoder

Thermal effects on fish ecology

USGS Publications Warehouse

Coutant, Charles C.

1976-01-01

Of all the environmental factors that influence aquatic organisms, temperature is the most all-pervasive. There is always an environmental temperature while other factors may or may not be present to exert their effects. Fish are, for all practical purposes, thermal conformers, or obligate poikilotherms. That is, they are able to exert little significant influence on maintaining a certain body temperature by specialized metabolic or behavioral means. Their body temperature thus fluctuates nearly in concert with the temperature of their aquatic medium (although particularly large, actively-moving fish such as tuna have deep muscle temperatures slightly higher than the water). Intimate contact at the gills of body fluids with the outside water and the high specific heat of water provide a very efficient heat exchanger that insures this near identity of internal and external temperatures.

Perspective on thermal barrier coatings for industrial gas turbine applications

NASA Technical Reports Server (NTRS)

Mutasim, Z. Z.; Hsu, L. L.; Brentnall, W. D.

1995-01-01

Thermal Barrier Coatings (TBC's) have been used in high thrust aircraft engines for many years, and have proved to be very effective in allowing higher turbine inlet temperatures. TBC life requirements for aircraft engines are typically less than those required in industrial gas turbines. The use of TBC's for industrial gas turbines can increase if durability and longer service life can be successfully demonstrated. This paper will describe current and future applications of TBC's in industrial gas turbine engines. Early testing and applications of TBC's will also be reviewed. This paper focuses on the key factors that are expected to influence utilization of TBC's in advanced industrial gas turbine engines. It is anticipated that reliable, durable and high effective coating systems will be produced that will ultimately improve engine efficiency and performance.

Reverberatory screen for a radiant burner

DOEpatents

Gray, Paul E.

1999-01-01

The present invention relates to porous mat gas fired radiant burner panels utilizing improved reverberatory screens. The purpose of these screens is to boost the overall radiant output of the burner relative to a burner using no screen and the same fuel-air flow rates. In one embodiment, the reverberatory screen is fabricated from ceramic composite material, which can withstand higher operating temperatures than its metallic equivalent. In another embodiment the reverberatory screen is corrugated. The corrugations add stiffness which helps to resist creep and thermally induced distortions due to temperature or thermal expansion coefficient differences. As an added benefit, it has been unexpectedly discovered that the corrugations further increase the radiant efficiency of the burner. In a preferred embodiment, the reverberatory screen is both corrugated and made from ceramic composite material.

Advanced solar receivers for space power

NASA Technical Reports Server (NTRS)

Strumpf, H. J.; Coombs, M. G.; Lacy, D. E.

1988-01-01

A study has been conducted to generate and evaluate advanced solar heat receiver concepts suitable for orbital application with Brayton and Stirling engine cycles in the 7-kW size range. The generated receiver designs have thermal storage capability and, when implemented, will be lighter, smaller, and/or more efficient than baseline systems such as the configuration used for the Brayton solar receiver under development by Garrett AiResearch for the NASA Space Station. In addition to the baseline designs, four other receiver concepts were designed and evaluated with respect to Brayton and Stirling engines. These concepts include a higher temperature version of the baseline receiver, a packed bed receiver, a plate-fin receiver, and a heat pipe receiver. The thermal storage for all designs is provided by the melting and freezing of a salt.

Fluidized-bed technology enabling the integration of high temperature solar receiver CSP systems with steam and advanced power cycles

DOE PAGES

Sakadjian, B.; Hu, S.; Maryamchik, M.; ...

2015-06-05

Solar Particle Receivers (SPR) are under development to drive concentrating solar plants (CSP) towards higher operating temperatures to support higher efficiency power conversion cycles. The novel high temperature SPR-based CSP system uses solid particles as the heat transfer medium (HTM) in place of the more conventional fluids such as molten salt or steam used in current state-of-the-art CSP plants. The solar particle receiver (SPR) is designed to heat the HTM to temperatures of 800 °C or higher which is well above the operating temperatures of nitrate-based molten salt thermal energy storage (TES) systems. The solid particles also help overcome somemore » of the other challenges associated with molten salt-based systems such as freezing, instability and degradation. The higher operating temperatures and use of low cost HTM and higher efficiency power cycles are geared towards reducing costs associated with CSP systems. This paper describes the SPR-based CSP system with a focus on the fluidized-bed (FB) heat exchanger and its integration with various power cycles. Furthermore, the SPR technology provides a potential pathway to achieving the levelized cost of electricity (LCOE) target of $0.06/kWh that has been set by the U.S. Department of Energy's SunShot initiative.« less

Fluidized-bed technology enabling the integration of high temperature solar receiver CSP systems with steam and advanced power cycles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sakadjian, B.; Hu, S.; Maryamchik, M.

Solar Particle Receivers (SPR) are under development to drive concentrating solar plants (CSP) towards higher operating temperatures to support higher efficiency power conversion cycles. The novel high temperature SPR-based CSP system uses solid particles as the heat transfer medium (HTM) in place of the more conventional fluids such as molten salt or steam used in current state-of-the-art CSP plants. The solar particle receiver (SPR) is designed to heat the HTM to temperatures of 800 °C or higher which is well above the operating temperatures of nitrate-based molten salt thermal energy storage (TES) systems. The solid particles also help overcome somemore » of the other challenges associated with molten salt-based systems such as freezing, instability and degradation. The higher operating temperatures and use of low cost HTM and higher efficiency power cycles are geared towards reducing costs associated with CSP systems. This paper describes the SPR-based CSP system with a focus on the fluidized-bed (FB) heat exchanger and its integration with various power cycles. Furthermore, the SPR technology provides a potential pathway to achieving the levelized cost of electricity (LCOE) target of $0.06/kWh that has been set by the U.S. Department of Energy's SunShot initiative.« less

Estimation of the temperature spatial variability in confined spaces based on thermal imaging

NASA Astrophysics Data System (ADS)

Augustyn, Grzegorz; Jurasz, Jakub; Jurczyk, Krzysztof; Korbiel, Tomasz; Mikulik, Jerzy; Pawlik, Marcin; Rumin, Rafał

2017-11-01

In developed countries the salaries of office workers are several times higher than the total cost of maintaining and operating the building. Therefore even a small improvement in human work productivity and performance as a result of enhancing the quality of their work environment may lead to a meaningful economic benefits. The air temperature is the most commonly used indicator in assessing the indoor environment quality. What is more, it is well known that thermal comfort has the biggest impact on employees performance and their ability to work efficiently. In majority of office buildings, indoor temperature is managed by heating, ventilation and air conditioning (HVAC) appliances. However the way how they are currently managed and controlled leads to the nonhomogeneous distribution of temperature in certain space. An approach to determining the spatial variability of temperature in confined spaces was introduced based on thermal imaging temperature measurements. The conducted research and obtained results enabled positive verification of the method and creation of surface plot illustrating the temperature variability.