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1

Simulation and Analysis of Influence Factors on Performance of Vertical Ground Heat Exchanger for Ground Coupled Heat Pump  

Microsoft Academic Search

A numerical heat transfer model of vertical ground heat exchanger was developed based on finite volume method, and the influence factors on performance of ground heat exchanger was investigated. Simulation results indicate that higher conductivity of pipe material is more benefit to enhance the performance of ground heat exchanger. The heat transfer of ground heat exchanger increases with the augment

Tian Bai; Jian-Li Zhang; Mao-Yu Zheng

2010-01-01

2

NUMERICAL STUDY OF HEAT TRANSFER OF A SINGLE U-TUBE IN VERTICAL GROUND-COUPLED HEAT PUMP SYSTEMS  

Microsoft Academic Search

The heat transfer rate of a single U-tube ground heat exchanger was studied numerically. First, a 3D 60-m full scale computational model of a working single U-tube ground heat exchanger was built and numerical simulation was performed. The simulation was validated by comparing numerically calculated results with experimental results. After that, two models are built to compute the heat extraction

C F Ma; Y T Wu

3

Ground-coupled heat pump applications and case studies  

SciTech Connect

The paper presents an overview of group loops for space-conditioning heat pumps, hot water, ice machines, and water-cooled refrigeration in residential and commercial applications. In Louisiana, a chain of hamburger drive-in's uses total ground-coupling in its stores. A grocery store has ground-coupling for all heat pumps and refrigeration. Desuperheaters provide 80% of the hot water for a coin laundry in the same building. A comparison of energy costs in a bank with a ground-coupled heat pump to a similar bank building with air-conditioning and gas for heat revealed a 22% reduction in utility costs for the ground-coupled building. In a retrofit application of ground-coupled heat pumps to replace air-conditioning and electric heat, energy consumption was reduced by 67%, and peak kilowatt demand was reduced by 50%.

Braud, H.J. (Louisiana State Univ., Baton Rouge (United States))

1992-04-01

4

A Reference Model for Ground Coupled Heat Transfer  

Microsoft Academic Search

A recently completed extension to IEA BESTEST includes further work on tests suitable for the validation of ground coupled heat transfer modules within building energy simulation software. The model described here forms part of this work. A finite difference model was prepared and applied to ground coupled heat transfer in the environs of a building for a range of geometries

Michael Crowley

2009-01-01

5

Ground-coupled heat pump applications and case studies  

Microsoft Academic Search

The paper presents an overview of group loops for space-conditioning heat pumps, hot water, ice machines, and water-cooled refrigeration in residential and commercial applications. In Louisiana, a chain of hamburger drive-in's uses total ground-coupling in its stores. A grocery store has ground-coupling for all heat pumps and refrigeration. Desuperheaters provide 80% of the hot water for a coin laundry in

Braud

1992-01-01

6

Cooperative heat transfer and ground coupled storage system  

DOEpatents

A cooperative heat transfer and ground coupled storage system wherein collected solar heat energy is ground stored and permitted to radiate into the adjacent ground for storage therein over an extended period of time when such heat energy is seasonally maximally available. Thereafter, when said heat energy is seasonally minimally available and has propagated through the adjacent ground a substantial distance, the stored heat energy may be retrieved by a circumferentially arranged heat transfer means having a high rate of heat transfer.

Metz, Philip D. (Rocky Point, NY)

1982-01-01

7

International Energy Agency BESTEST for Ground Coupled Heat Transfer  

Microsoft Academic Search

The objective of this project is to assess the accuracy of building energy analysis tools that have incorporated detailed models for predicting ground-coupled heat transfer related to floor slab and basement constructions. An executive summary is to be found in the main report.

Joel Neymark; Ron Judkoff; Michael Crowley

2008-01-01

8

Ground-Coupled Heat Pump Applications and Case Studies  

E-print Network

The paper presents an overview of ground loops for space-conditioning heat pumps, hot water, ice machines, and water-cooled refrigeration in residential and commercial applications. In Louisiana, a chain of hamburger drive-ins uses total ground-coupling...

Braud, H. J.

1989-01-01

9

A simplified methodology for sizing ground coupled heat pump heat exchangers in cooling dominated climates  

E-print Network

A SIMPLIFIED METHODOLOGY FOR SIZING GROUND COUPLED HEAT PUMP HEAT EXCHANGERS IN COOLING DOMINATED CLIMATES A Thesis by JOSE ANTONIO GONZALEZ Submitted to the Office of Graduate Studies of Texas ARM University in partial fulfillment... of the requirements for the degree of MASTER OF SCIENCE August 1993 Major Subject: Mechanical Engineering A SIMPLIFIED METHODOLOGY FOR SIZING GROUND COUPLED HEAT PUMP HEAT EXCHANGERS IN COOLING DOMINATED CLIMATES A Thesis by JOSE ANTONIO GONZALEZ Approved...

Gonzalez, Jose Antonio

1993-01-01

10

Model for Ground-Coupled Heat and Moisture Transfer from Buildings  

SciTech Connect

An important factor in soil heat transfer that is often over looked is the effect of moisture, which can vary the effective thermal conductivity by a factor of ten. The objective of this research was to investigate the ground-coupled heat and moisture transfer from buildings, and to develop results and tools to improve energy simulation of ground-coupled heat transfer.

Deru, M.

2003-06-01

11

Horizontal Ground Heat Exchanger Design for Ground-Coupled Heat Pumps  

Microsoft Academic Search

Ground-source heat pump (GSHP) is used as an all in clusive term for a variety of systems that use the ground, ground water and surfa ce water as a heat source and sink. There are several examples of various types of GSHPs which ar e subdivided into ground-coupled heat pumps (GCHPs), ground water heat pumps (GWHPs) and surfac e water

S. A. M. Said; M. A. Habib; E. M. A. Mokheimer; N. Al-Shayea; M. Sharqawi

12

Performance monitoring of ground-coupled solar-assisted heat pump systems  

SciTech Connect

Three Okalhoma Gas and Electric Company demonstration houses in Perkins, Oklahoma, and the HVAC and data acquisition systems are described. The project involves comparison of the performance of a ground-coupled, solar-assisted heat pump system with that of a ground coupled heat pump system without solar assist, and with a conventional air source heat pump system. Details of the data acquisition and processing system are given. Problems encountered and anticipated are discussed.

Parker, J.D.; Frierson, B.

1981-02-01

13

The use of ground-coupled tanks in solar-assisted heat-pump systems  

Microsoft Academic Search

A research program at Brookhaven National Laboratory (BNL) has studied ground coupling, i.e., the use of the earth as a heat source\\/sink or storage element, for solar-assisted heat-pump systems. As part of this research program, four buried tank experiments were operated between December 1978 and March 1981 in order to determine the feasibility of ground-coupled tanks in these systems. Heat

P. D. Metz

1982-01-01

14

Ground-Coupled Heating-Cooling Systems in Urban Areas: How Sustainable Are They?  

ERIC Educational Resources Information Center

Ground-coupled heating-cooling systems (GCHCSs) exchange heat between the built environment and the subsurface using pipework buried in trenches or boreholes. If heat pumps in GCHCSs are powered by "green electricity," they offer genuine carbon-free heating-cooling; for this reason, there has been a surge in the technology in recent years.…

Younger, Paul L.

2008-01-01

15

Whole-Building Energy Simulation with a Three-Dimensional Ground-Coupled Heat Transfer Model: Preprint  

Microsoft Academic Search

A three-dimensional, finite-element, heat-transfer computer program was developed to study ground-coupled heat transfer from buildings. It was used in conjunction with the SUNREL whole-building energy simulation program to analyze ground-coupled heat transfer from buildings, and the results were compared with the simple ground-coupled heat transfer models used in whole-building energy simulation programs. The detailed model provides another method of testing

M. Deru; R. Judkoff; J. Neymark

2002-01-01

16

Efficiency improvement of a ground coupled heat pump system from energy management  

E-print Network

to improve the efficiency of a ground coupled heat pump air conditioning system by adapting its produced thermal energy to the actual thermal demand. For this purpose, an air conditioning system composed and heating systems [1e3]. In this context, the development of air conditioning (HVAC) systems should

Fernández de Córdoba, Pedro

17

Local\\/global analysis applications to ground-coupled heat transfer  

Microsoft Academic Search

In this paper, a new local\\/global analysis technique is developed to solve multi-dimensional ground-coupled heat transfer problems. In particular, the novel method is applied in this paper to determine foundation heat transfer for buildings with slab-on-grade floors. It is found that analytical solutions can be used successfully to capture thermal bridging effect when integrated in the developed local\\/global analysis technique.

Adnan Al-Anzi; Moncef Krarti

2003-01-01

18

Comparative evaluation of ground-coupled heat pumps that use solar energy  

NASA Astrophysics Data System (ADS)

A study of combined building space conditioning systems using both solar energy and heat pumps was conducted for the US Department of Energy (DOE). Several of these systems used the ground as a source or storage element for thermal energy, in order to reduce or eliminate the need for backup energy. The results obtained for these systems in the United States are summarized and the relationship of ground-coupling to the overall US solar-assisted heat-pump program is described.

Andrews, J. W.; Catan, M. A.

1985-03-01

19

Experimental analysis of direct-expansion ground-coupled heat pump systems  

SciTech Connect

Direct-expansion ground-coil-coupled (DXGC) heat pump systems have certain energy efficiency advantages over conventional ground-coupled heat pump (GCHP) systems. Principal among these advantages are that the secondary heat transfer fluid heat exchanger and circulating pump are eliminated. While the DXGC concept can produce higher efficiencies, it also produces more system design and environmental problems (e.g., compressor starting, oil return, possible ground pollution, and more refrigerant charging). Furthermore, general design guidelines for DXGC systems are not well documented. A two-pronged approach was adopted for this study: (1) a literature survey, and (2) a laboratory study of a DXGC heat pump system with R-22 as the refrigerant, for both heating and cooling mode tests done in parallel and series tube connections. The results of each task are described in this paper. A set of general design guidelines was derived from the test results and is also presented. 12 refs., 11 figs., 1 tab.

Mei, V.C.; Baxter, V.D.

1991-09-01

20

Experimental investigation and theoretical model of heat transfer of saturated soil around coaxial ground coupled heat exchanger  

Microsoft Academic Search

This study is performed to investigate the thermal performance of saturated soil around coaxial ground coupled heat exchanger (GCHE). Based on artificial glass micro-balls as porous medium, heat-transfer experiments are conducted. Then a theoretical model with Darcy’s natural convection is developed and some numerical solutions are obtained using Keller-Shooting method. There is a better coincidence between theoretical and experimental results,

Jun Zhao; Huajun Wang; Xinguo Li; Chuanshan Dai

2008-01-01

21

Vertical Concentric Tube Ground Couoled Heat Exchangers V. C. Mei and S. K. Fischer*  

E-print Network

, and * the ground is saturated with moisture a short distance below the surface and provides a good heat transfer#12;Vertical Concentric Tube Ground Couoled Heat Exchangers V. C. Mei and S. K. Fischer* Abstract An experimental and analytical project to study the design of vertical, concentric-tube ground-coupled heat

Oak Ridge National Laboratory

22

Field Performance of a Ground-Coupled Heat Pump in Abilene, Texas  

E-print Network

the experimental GCHP, the equipment used to monitor it, and the experimental uncertainties. This will be followed by a discussion of the start-up characteristics of GCHPs. Third, the success of the GCHP in achieving improved thermal performance is assessed... is that the soil temperature is favorable to the air temperature for either rejecting or extracting heat. This argument has its origins in the Carnot cycle, which assumes heat exchange processes with infinitesimal temperature differences. In reality, however...

Dobson, M.; O'Neal, D. L.; Aldred, W.; Margo, R.

1994-01-01

23

Solar/performance goals for solar and ground-coupled heat pump systems  

SciTech Connect

Cost goals for combined solar/heat pump systems are developed. Three methods of analysis are used: simple payback, positive cash flow, and life cycle costing. The goals are parameterized on system energy efficiency, with the air-to-air heat pump as the conventional system which is used as a basis for comparison. Cost goals for nine systems are determined in three generic climates.

Andrews, J.W.

1980-09-01

24

A two-region simulation model of vertical U-tube ground heat exchanger and its experimental verification  

Microsoft Academic Search

Heat transfer around vertical ground heat exchanger (GHE) is a common problem for the design and simulation of ground coupled heat pump (GCHP). In this paper, an updated two-region vertical U-tube GHE analytical model, which is fit for system dynamic simulation of GCHP, is proposed and developed. It divides the heat transfer region of GHE into two parts at the

Weibo Yang; Mingheng Shi; Guangyuan Liu; Zhenqian Chen

2009-01-01

25

Mitigation potential of horizontal ground coupled heat pumps for current and future climatic conditions: UK environmental modelling and monitoring studies  

NASA Astrophysics Data System (ADS)

An increased uptake of alternative low or non-CO2 emitting energy sources is one of the key priorities for policy makers to mitigate the effects of environmental change. Relatively little work has been undertaken on the mitigation potential of Ground Coupled Heat Pumps (GCHPs) despite the fact that a GCHP could significantly reduce CO2 emissions from heating systems. It is predicted that under climate change the most probable scenario is for UK temperatures to increase and for winter rainfall to become more abundant; the latter is likely to cause a general rise in groundwater levels. Summer rainfall may reduce considerably, while vegetation type and density may change. Furthermore, recent studies underline the likelihood of an increase in the number of heat waves. Under such a scenario, GCHPs will increasingly be used for cooling as well as heating. These factors will affect long-term performance of horizontal GCHP systems and hence their economic viability and mitigation potential during their life span ( 50 years). The seasonal temperature differences encountered in soil are harnessed by GCHPs to provide heating in the winter and cooling in the summer. The performance of a GCHP system will depend on technical factors (heat exchanger (HE) type, length, depth, and spacing of pipes), but also it will be determined to a large extent by interactions between the below-ground parts of the system and the environment (atmospheric conditions, vegetation and soil characteristics). Depending on the balance between extraction and rejection of heat from and to the ground, the soil temperature in the neighbourhood of the HE may fall or rise. The GROMIT project (GROund coupled heat pumps MITigation potential), funded by the Natural Environment Research Council (UK), is a multi-disciplinary research project, in collaboration with EarthEnergy Ltd., which aims to quantify the CO2 mitigation potential of horizontal GCHPs. It considers changing environmental conditions and combines model predictions of soil moisture content and soil temperature with measurements at different GCHP locations over the UK. The combined effect of environment dynamics and horizontal GCHP technical properties on long-term GCHP performance will be assessed using a detailed land surface model (JULES: Joint UK Land Environment Simulator, Meteorological Office, UK) with additional equations embedded describing the interaction between GCHP heat exchangers and the surrounding soil. However, a number of key soil physical processes are currently not incorporated in JULES, such as groundwater flow, which, especially in lowland areas, can have an important effect on the heat flow between soil and HE. Furthermore, the interaction between HE and soil may also cause soil vapour and moisture fluxes. These will affect soil thermal conductivity and hence heat flow between the HE and the surrounding soil, which will in turn influence system performance. The project will address these issues. We propose to drive an improved version of JULES (with equations to simulate GCHP exchange embedded), with long-term gridded (1 km) atmospheric, soil and vegetation data (reflecting current and future environmental conditions) to reliably assess the mitigation potential of GCHPs over the entire domain of the UK, where uptake of GCHPs has been low traditionally. In this way we can identify areas that are most suitable for the installation of GCHPs. Only then recommendations can be made to local and regional governments, for example, on how to improve the mitigation potential in less suitable areas by adjusting GCHP configurations or design.

García González, Raquel; Verhoef, Anne; Vidale, Pier Luigi; Gan, Guohui; Wu, Yupeng; Hughes, Andrew; Mansour, Majdi; Blyth, Eleanor; Finch, Jon; Main, Bruce

2010-05-01

26

A Simplified Procedure for Sizing Vertical Ground Coupled Heat Pump Heat Exchangers for Residences in Texas  

E-print Network

Hourly Weather Data Generator for Driving Energy Simulation and Equipment Design Software for Buildings", Proceedings for the Conference on Building Simulation, Sophia, Antipolis, Nice, France. 9. EPRI, Electrical Power Research Institute., 1989...

O'Neal, D. L.; Gonzalez, J. A.; Aldred, W.

1994-01-01

27

Development and Application of a Ground-Coupled Heat Pump Simulation Model for Residential Code-Compliance Simulation in Texas  

E-print Network

) model for residential systems to be used with the DOE-2.1e simulation program. To accomplish this, this study investigated closed-loop ground heat exchanger (GHX) models, including horizontal, surface water, and vertical GHX models. This study selected...

Do, Sung Lok

2014-04-18

28

EnergyPlus vs DOE-2: The Effect of Ground Coupling on Heating and Cooling Energy Consumption of a Slab-On-Grade Code House in a Cold Climate  

E-print Network

ABSTRACT For low-rise buildings, the heat loss through the ground coupled floor is a significant load component. Studies showed that the current simulation tools give dissimilar results for the ground coupled heat transfer (GCHT) in slab...) model in DOE-2.1e, Winkelmann?s model in EnergyPlus and EnergyPlus with its GCHT calculator utility, Slab. INTRODUCTION Ground-coupled heat transfer (GCHT) through concrete floor slabs is a significant component of the total load for heating...

Andolsun, S.; Culp, C.; Haberl, J.

29

Experimental analysis and mathematical modeling of a direct-expansion ground-coupled heat-pump system  

Microsoft Academic Search

The author the author investigates a direct expansion heat pump system that is uniquely coupled to the earth through a heat transfer concentrator (GLHXC, Ground Loop Heat Exchanger Concentrator). A description of the system and its instrumentation with a presentation of performance results for winter and summer operation are included. The results are compared to experimental data obtained from four

Safemazandarani

1989-01-01

30

An experimental study of heating performance and seasonal modeling of vertical U-tube ground coupled heat pumps  

E-print Network

the unit from the ground coil, referred to herein as EWT (Entering Water Temperature). Soil thermal conductivity values vary greatly across the state of Texas, causing concern about GCHP performance in locations with poor soil thermal properties... enthalpy, ia, from the same data. From this analysis, it was determined that the same phenomena that caused performance degradation in ASHP's (refrigerant dynamics and the thermal capacitance of the coil) existed in GCHP's. As with ASHP's, the GCHP...

Margo, Randal E.

2012-06-07

31

The Numerical Simulation and Experiment Study on the Coupled Thermal Conduction and Groundwater Advection Heat Transfer Process under the Intermittent Operation of the Ground-Coupled Heat Pump System  

Microsoft Academic Search

The three-dimension coupled thermal conduction and groundwater advection unsteady state heat transfer model in this paper is developed according to the heat-transfer process between the vertical U tube underground and its ambient soil. The feasibility of this model is verified by intermittent experiment of ground source heat pump in winter. In the model, boundary layer is replaced by velocity equation

Sufen Li; Yan Shang

2010-01-01

32

Geothermal Energy Utilization via Effective Design of Ground-Coupled  

E-print Network

Geothermal Energy Utilization via Effective Design of Ground-Coupled Heat Exchange System Charlie and condensers, piping systems · Research subjects ­ 3D developing turbulent flows ­ Heat transfer in near Efficiency (Data Center Thermal Management and Air Flow) ­ Waste Heat Recovery in Industrial Processes

Tennessee, University of

33

Vertical eddy heat fluxes from model simulations  

NASA Technical Reports Server (NTRS)

Vertical eddy fluxes of heat are calculated from simulations with a variety of climate models, ranging from three-dimensional GCMs to a one-dimensional radiative-convective model. The models' total eddy flux in the lower troposphere is found to agree well with Hantel's analysis from observations, but in the mid and upper troposphere the models' values are systematically 30 percent to 50 percent smaller than Hantel's. The models nevertheless give very good results for the global temperature profile, and the reason for the discrepancy is unclear. The model results show that the manner in which the vertical eddy flux is carried is very sensitive to the parameterization of moist convection. When a moist adiabatic adjustment scheme with a critical value for the relative humidity of 100 percent is used, the vertical transports by large-scale eddies and small-scale convection on a global basis are equal: but when a penetrative convection scheme is used, the large-scale flux on a global basis is only about one-fifth to one-fourth the small-scale flux. Comparison of the model results with observations indicates that the results with the latter scheme are more realistic. However, even in this case, in mid and high latitudes the large and small-scale vertical eddy fluxes of heat are comparable in magnitude above the planetary boundary layer.

Stone, Peter H.; Yao, Mao-Sung

1991-01-01

34

Field and Laboratory Study of a Ground-Coupled Water Source Heat Pump with an Integral Enthalpy Exchange System for Classrooms  

E-print Network

water-source heat pump, coupled with a geothermal water loop and incorporating a forced fresh-air enthalpy exchange system was installed in a typical middle school classroom in Oak Ridge, Tennessee. This project is a joint effort among Oak Ridge School...

Domitrovic, R.; Hayzen, G. J.; Johnson, W. S.; Chen, F. C.

2002-01-01

35

The vertical structure of ocean heat transport G. Boccaletti,1  

E-print Network

global ocean heat transport can be deduced from estimates of air-sea fluxes [Trenberth and Caron, 2001The vertical structure of ocean heat transport G. Boccaletti,1 R. Ferrari,1 A. Adcroft,2 D is through its poleward heat transport: about 1.5 PW or more than 30% of that accomplished by the ocean

Marshall, John

36

Heat capacity of vertical ground heat exchangers with single U-tube in stallation in the function of time  

Microsoft Academic Search

O ne of the major problems of ensuring optimal working of ground source heat pump systems is a heat transfer around vertical ground heat exchanger. The working of vertical U-tube can be understood as a heat exchanger between the ground and the heat carrying medium. In our case this heat carrying medium is fluid, which transfers the extracted heat from

LÁSZLÓ GARBAI; SZABOLCS MÉHES

37

Heat transfer analysis of boreholes in vertical ground heat exchangers  

Microsoft Academic Search

A ground heat exchanger (GHE) is devised for extraction or injection of thermal energy from\\/into the ground. Bearing strong impact on GHE performance, the borehole thermal resistance is defined by the thermal properties of the construction materials and the arrangement of flow channels of the GHEs. Taking the fluid axial convective heat transfer and thermal “short-circuiting” among U-tube legs into

Heyi Zeng; Nairen Diao; Zhaohong Fang

2003-01-01

38

Natural convective heat transfer in water enclosed between pairs of differentially heated vertical plates  

Microsoft Academic Search

This paper presents the results of an experimental study of buoyancy-driven convective heat transfer between three parallel\\u000a vertical plates, symmetrically spaced with water as the intervening medium. The centre plate was electrically heated, while\\u000a the other side plates were water-cooled forming two successive parallel vertical channels of dimensions 20 cm × 3.5 cm × 35 cm\\u000a (length W, gap L, height H) each. Top, bottom and sides

Asish Mitra; Tapas Kumar Dutta; Dibyendu Narayan Ghosh

2008-01-01

39

Improvement in Modeling of Heat Transfer in Vertical Ground Heat Exchangers  

Microsoft Academic Search

The heat transfer model of vertical ground heat exchangers for ground-source heat pump systems is discussed. An explicit solution of a finite line-source model has been derived to better describe temperature response of boreholes for long time steps, which can be easily incorporated into computer programs for thermal analysis of ground heat exchangers. A quasi-three-dimensional model is also presented for

N. R. Diao; H. Y. Zeng; Z. H. Fang

2004-01-01

40

Development of convective heat transfer near suddenly heated, vertically aligned horizontal wires  

Microsoft Academic Search

Experiments have been performed which describe the transient development of natural convective flow from both a single and two vertically aligned horizontal cylindrical heat sources. The temperature of the wire heat sources was monitored with a resistance bridge arrangement while the development of the flow field was observed optically with a Mach-Zehnder interferometer. Results for the single wire show that

J. R. Jr. Parsons; M. L. Jr. Arey

1987-01-01

41

Heat-transfer mechanism of liquid film flow in a vertical, finely grooved heating surface  

SciTech Connect

The heating surface structure characteristic of a vertical tube is emphasized in order to obtain nucleate boiling stability in the liquid film and to avoid the splitting of the liquid film into rivulets. Horizontally, vertically, and obliquely grooved surfaces were used in this paper with a constant liquid flow rate and isothermal surface conditions. The overall, as well as local, heat-transfer coefficients, the heat-transfer mechanisms, the flow characteristics, and the dry-out have been observed and measured. A comparison with pool boiling data is made. Useful findings were obtained from the above experimental analysis.

Ouchi, M.; Izumi, M.; Yamakawa, N. (Faculty of Engineering, Iwate Univ. (JP)); Takamori, Y. (Shoa Cabot Co., Ltd. (JP)); Takeyama, T. (Faculty of Engineering, Tohoku Univ. (JP))

1991-01-01

42

Development of spiral heat source model for novel pile ground heat exchangers  

Microsoft Academic Search

The extensive application of ground coupled heat pump system (GCHP) is restricted by the installation cost of conventional borehole ground heat exchangers (GHE), which is not only expensive but also requires additional ground area. The idea of combining the GHE with building foundation piles, i.e., the “energy pile,” has arisen in recent years. The novel pile GHEs consisting of vertical

Yi Man; Hongxing Yang; Nairen Diao; Ping Cui; Lin Lu; Zhaohong Fang

2011-01-01

43

Spray cooling heat-transfer with subcooled trichlorotrifluoroethane (Freon-113) for vertical constant heat flux surfaces  

SciTech Connect

Experiments were done using subcooled Freon-113 sprayed vertically downward. Local and average heat transfers were investigated fro Freon-113 sprays with 40 C subcooling, droplet sizes 200-1250{mu}m, and droplet breakup velocities 5-29 m/s. Full-cone type nozzles were used to generate the spray. Test assemblies consisted of 1 to 6 7.62 cm vertical constant heat flux surfaces parallel with each other and aligned horizontally. Distance between heated surfaces was varied from 6.35 to 76.2 mm. Steady state heat fluxes as high as 13 W/cm{sup 2} were achieved. Dependence on the surface distance from axial centerline of the spray was found. For surfaces sufficiently removed from centerline, local and average heat transfers were identical and correlated by a power relation of the form seen for normal-impact sprays which involves the Weber number, a nondimensionalized temperature difference, and a mass flux parameter. For surfaces closer to centerline, the local heat transfer depended on vertical location on the surface while the average heat transfer was described by a semi-log correlation involving the same parameters. The heat transfer was independent of the distance (gap) between the heated surfaces for the gaps investigated.

Kendall, C.M. [Lawrence Livermore National Lab., CA (United States); Holman, J.P. [Southern Methodist Univ., Dallas, TX (United States). Dept. of Mechanical Engineering

1996-06-06

44

Flow regimes and heat transfer in vertical narrow annuli  

SciTech Connect

In shell side boiling heat exchangers narrow crevices that are formed between the tubes and the tube support structure provide areas for local thermal-hydraulic conditions which differ significantly from bulk fluid conditions. Understanding of the processes of boiling and dryout in flow restricted crevices can help in designing of tube support geometries to minimize the likelihood of tube support plate and tube corrosion observed in commercial power plant steam generators. This paper describes a one dimensional thermal-hydraulic model of a vertical crevice between a tube and a support plate with cylindrical holes. The annulus formed by the support plate hole and an eccentrically located tube has been represented by vertical strips. The formation, growth and collapse of a steam bubble in each strip has been determined. Based on the bubble history, and flow regimes characterized by ``isolated`` bubbles, ``coalesced`` bubbles and liquid deficient regions have been defined.

Ulke, A.; Goldberg, I.

1993-11-01

45

Natural convection in symmetrically heated vertical parallel plates with discrete heat sources  

SciTech Connect

Laminar air natural convection in a symmetrically heated vertical channel with uniform flush-mounted discrete heat sources has been experimentally investigated. The effects of heated strips location and of their number are pointed out in terms of the maximum wall temperatures. A flow visualization in the entrance region of the channel was carried out and air temperatures and velocities in two cross sections have been measured. Dimensionless local heat transfer coefficients have been evaluated and monomial correlations among relevant parameters have bee derived in the local Rayleigh number range 10--10{sup 6}. Channel Nusselt number has been correlated in a polynomial form in terms of channel Rayleigh number.

Manca, O. [Seconda Univ. degli studi di Napoli, Aversa (Italy). Dipt. di Ingegneria Aerospaziale; Nardini, S.; Naso, V. [Univ. degli studi Federico II, Napoli (Italy)

1996-12-31

46

Numerical characterization of heat transfer in closed-loop vertical ground heat exchanger  

Microsoft Academic Search

A series of numerical analyses has been performed on the characteristics of heat transfer in a closed-loop vertical ground heat exchanger (U-loop). A 2-D finite element analysis was conducted to evaluate the temperature distribution over the cross section of the U-loop system involving high-density polyethylene (HDPE) pipe\\/grout\\/soil to compare the sectional efficiency between the conventional U-loop and a new latticed

Chulho Lee; Hujeong Gil; Hangseok Choi; Shin-Hyung Kang

2010-01-01

47

Combined heat and mass transfer in a uniformly heated vertical tube with water film cooling  

Microsoft Academic Search

A computational study is reported of buoyancy-influenced forced upward turbulent flow of air and water vapour in the range of Reynolds number from 4600 to 13?800 within a long uniformly heated vertical tube in the presence of a falling film of water on the inside wall. Procedures have been successfully developed which enable this complex problem to be simulated using

S. He; P. An; J. Li; J. D. Jackson

1998-01-01

48

Vertical Dependence of the Viscous Heating in Accretion Disks  

NASA Astrophysics Data System (ADS)

This paper treats the problem of how viscous heating in accretion disks changes in the vertical direction. It is assumed that the disk is isothermal and that the turbulence is homogeneous in the horizontal-plane. The model of turbulence applied is a three-equation model by Yoshizawa (1992, Phys. Rev. A46, 3292), an extension of the so-called K--varepsilon model, which is well known in engineering fields. It gives a set of differential equations which describe the vertical dependences of the turbulent kinetic energy (K), the dissipation rate (varepsilon ), and the density variance (K_d). It turns out that the turbulent kinetic energy (per unit mass) and the so-called alpha -value generally increases from the equator toward the surface by turbulent diffusion. This is consistent with our previous results obtained by a different method. Near to the surface, however, the values of K and varepsilon may decrease outwards, if model constants representing the effects of the compressibility of turbulence are estimated to be large. Physical explanations of the results are briefly presented.

Nakao, Yasushi; Kato, Shoji

1995-08-01

49

Forced convection heat transfer of saturated liquid hydrogen in vertically-mounted heated pipes  

NASA Astrophysics Data System (ADS)

Heat transfer from the inner side of vertically-mounted heated pipes to forced flow of saturated liquid hydrogen was measured with a quasi-steady increase of a heat generation rate for wide ranges of flow rate and saturated pressure. The tube heaters have lengths L of 100 mm and 167 mm with the diameter D of 4 mm and lengths of 150 mm and 250 mm with the diameter of 6 mm. The heat fluxes at departure from nucleate boiling (DNB) were higher for higher flow velocity, lower pressures and shorter L/D. The effect of L/D on the DNB heat flux was clarified. It is confirmed that our DNB correlation can describe the experimental data.

Tatsumoto, Hideki; Shirai, Yasuyuki; Shiotsu, Masahiro; Hata, Koichi; Naruo, Yoshihiro; Kobayasi, Hiroaki; Inatani, Yoshifumi

2014-01-01

50

Fluid Flow and Heat Transfer of Natural Convection around Heated Vertical Cylinders  

NASA Astrophysics Data System (ADS)

Natural convective flows of water induced around heated vertical cylinders have been investigated experimentally. Special interests were paid to the influences of cylinder diameter on the turbulent transition and also on the local heat transfer characteristics of the cylinders. The diameters of the cylinders were varied systematically from 10 to 165mm. Visualizations of the flows around the cylinder and of the surface temperatures of the heated cylinders have been carried out to determine the onset of turbulent transition. The result showed that the onset of turbulent transition shifts toward downstream with decreasing the cylinder diameters, when, in particular, the diameters are smaller than 60mm. Moreover, the local heat transfer coefficients of the cylinder show marked increase in the both regions of laminar and turbulent flows with decreasing the diameters.

Kimura, Fumiyoshi; Tachibana, Tatsuo; Kitamura, Kenzo; Hosokawa, Tsutomu

51

The conjugate conduction–natural convection heat transfer along a thin vertical plate with non-uniform internal heat generation  

Microsoft Academic Search

The steady state heat transfer characteristics of a thin vertical strip with internal heat generation is studied in this work. The nondimensional temperature distribution in the strip is obtained as a function of the following parameters: (a) the intensity and distribution of the internal heat sources, (b) the aspect ratio of the strip, (c) the longitudinal heat conductance of the

F Méndez; C Treviño

2000-01-01

52

Heat transfer augmentation of mixed convection through vortex shedding from an inclined plate in a vertical channel containing heated blocks  

SciTech Connect

A numerical analysis is made of the unsteady flow and heat transfer characteristics of mixed convection in a vertical block-heated channel with and without installing an inclined plate above an upstream block. Parameter studies including the inclined plate angle, Reynolds number (ranging from 260 to 530), and Grashof number (in the range of 0--3,200,000) on heat transfer performance have been explored in detail. The results show that the installation of an inclined plate in the vertical block-heated channel can effectively augment the blocks` heat transfer performance in the channel. This can be applied to heat exchangers.

Wu, H.W.; Perng, S.W. [National Cheng Kung Univ., Tainan (Taiwan, Province of China). Dept. of Naval Architecture and Marine Engineering

1998-02-06

53

Critical heat flux prediction for water boiling in vertical tubes of a steam generator  

Microsoft Academic Search

This paper presents a methodology for the prediction of the critical heat flux (CHF) for the boiling of water in vertical tubes operating under typical conditions found in steam generators. At the furnace, the water flows through long vertical tubes under an axially non-uniform heat flux and with relatively low mass fluxes. This fact causes that the recent theories and

L. A. Payan-Rodriguez; A. Gallegos-Muñoz; G. L. Porras-Loaiza; M. Picon-Nuñez

2005-01-01

54

Heat exchanger sizing for vertical closed-loop ground-source heat pumps  

SciTech Connect

A building energy simulation program has been used in conjunction with a ground heat exchanger sizing algorithm to develop general guidelines on how to size vertical ground heat exchangers for closed-loop ground-source heat pump systems in large buildings. The analysis considered three commercial building types of varying size with different internal loads and heat pump efficiencies. Each building variation was simulated in seven cities, three in the US and four in Canada. The ground heat exchanger sizing algorithm has been previously validated against actual system data. The analysis results showed a strong correlation between heat exchanger length required and annual energy rejected to the ground, if the building was cooling-dominated, or annual energy extracted from the ground, if the building was heating-dominated. The resulting sizing guidelines recommend hour-by-hour energy analysis to determine the energy extracted from and rejected to the building water loop. Using this information the designer will have available easy-to-use, accurate sizing guidelines that should result in more economical installations than those based on previous ``rule of thumb`` guidelines.

Cane, R.L.D.; Clemes, S.B.; Morrison, A. [Caneta Research, Inc., Mississauga, Ontario (Canada); Hughes, P.J. [Oak Ridge National Lab., TN (United States)

1995-12-31

55

New analytical solution for sizing vertical borehole ground heat exchangers in environments with significant groundwater flow: Parameter estimation from thermal response test data  

Microsoft Academic Search

Accurate prediction of transient subsurface heat transfer is important in sizing ground heat exchangers in ground coupled heat pump systems. This article examines three analytical solutions for the heat transfer characteristics around closed-loop borehole heat exchangers in significant groundwater flow. The first solution is the so-called moving line source solution, the second is based on the groundwater g-function, and the

Andrew Chiasson; Amanda O’Connell

2011-01-01

56

The Design of Ground-Coupled Heat Pump Systems  

E-print Network

.S. Prlnting Office, Washlngton, DC 20402). Salomone. L. A. (1983a). Procedures used to predict the thermal behavior of soils. 1983 International Conference on Earth Sheltered Buildings Proceedings, Sydney, Australia. Salomone, L. A,, and Kovacs, W. D...

Parker, J. D.

1985-01-01

57

Efficient Energy Supply from Ground Coupled Heat Transfer Source  

Microsoft Academic Search

\\u000a The increasing demands of Energy for industrial production and urban facilities, asks for new strategies for Energy sources.\\u000a In recent years an important problem is to have some energy storage, energy production and energy consumption which fulfill\\u000a some environment friendly expectations. Much more attention has been recently devoted to renewable energies [1]. Among them\\u000a energy production from geothermal sources has

Maurizio Carlini; Sonia Castellucci

2010-01-01

58

Comparison of DOE-2.1E with Energyplus and TRNSYS for Ground Coupled Residential Buildings in Hot anf Humid Climates Stage 2  

E-print Network

and results of the comparative studies on the basement heat transfer models of the same programs. Introduction Foundation heat transfer is a significant load component for low-rise residential buildings. For a contemporary code or above code house, ground...-coupled heat losses may account for 30%–50% of the total heat loss [1]. Comparative studies on ground coupled heat transfer models of current simulation tools showed a high degree of variation for basements and slab-on-grade floors. For an uninsulated slab...

Andolsun, S.; Culp, C.

2011-01-01

59

Pulse-Heated Vertical Electron Cyclotron Emission Diagnostic  

NASA Astrophysics Data System (ADS)

Determination of plasma parameters in tokamak experiments is of primary importance for learning to control and optimize fusion plasmas. Electron cyclotron emission (ECE) diagnostics play an important role in these experiments and are planned for future test reactors, since they require only simple collecting optics in the harsh reactor environment. A novel diagnostic system, which extracts information about plasma parameters by examining the ECE resulting from a perturbation of the plasma, was examined and applied on the PBX-M tokamak. This diagnostic uses a brief pulse of power from the lower hybrid current drive system to create a population of superthermal electrons. These electrons evolve according to the Fokker-Planck equation, which involves dependences on the magnetic field pitch, ion charge state, background density, and electric field. Coincident with the evolution of the electrons is the evolution of their ECE radiation. The diagnostic exploits the fact that the temporal changes in the radiation are dependent upon those parameters which affect the electrons. The analysis method, which compares measured experimental signal with simulated radiation (as functions of frequency and time) and determines most probable plasma parameter values, was computationally tested for effectiveness and robustness. The method was extended to include determination of parameters of the lower hybrid current drive power deposition. A measurement system, based on a grating polychromator, was assembled, tested, and calibrated, and pulse-heated vertical ECE data were collected from the PBX-M tokamak. A proof-of-principle test of the diagnostic yielded positive results, resulting in information about the lower hybrid current drive deposition location.

Voss, Keith Edward

1995-01-01

60

Bond Graph Model of a Vertical U-Tube Steam Condenser Coupled with a Heat Exchanger  

E-print Network

Bond Graph Model of a Vertical U-Tube Steam Condenser Coupled with a Heat Exchanger K. Medjaher1+ A and thus the bottom well acts as a heat exchanger. The storage of hydraulic and thermal energies steam condenser; Heat exchanger; Bond graph 1. Introduction Modern process engineering plants

Paris-Sud XI, Université de

61

The effects of the vertical location of a heat source in a UFAD system  

Microsoft Academic Search

An Under Floor Air Distribution (UFAD) system with a heat source positioned at different heights is studied experimentally and theoretically. In the experiment, a plume and a fountain represent a heat source and a cooling vent separately. The cooling vent is located on the floor and the heat source is placed at different vertical positions in the room. Two-layer temperature

Qing A. Liu; Paul F. Linden

2003-01-01

62

Gas heat transfer in a heated vertical channel under deteriorated turbulent heat transfer regime  

E-print Network

Passive cooling via natural circulation of gas after a loss of coolant (LOCA) accident is one of the major goals of the Gas-cooled Fast Reactor (GFR). Due to its high surface heat flux and low coolant velocities under ...

Lee, Jeongik

2007-01-01

63

Augmentation of condensation heat transfer with electrohydrodynamics on vertical enhanced tubes  

E-print Network

from the surface can be realized. The liquid film thickness is reduced and as a result the condensation heat transfer coefficient is increased. A vertical single tube condenser (I m long) is used to investigate the electrohydrodynamically enhanced...

Motte, Edouard

1994-01-01

64

Mixed convective heat transfer between a series of vertical parallel plates with planar heat sources  

SciTech Connect

Laminar mixed convection between a series of vertical parallel plates with planar heat sources has been studied numerically. A finite volume based method employing the SIMPLER algorithm was used for the numerical calculations. The numerical model was validated by comparing the numerical predictions with the experimentally measured values of streamwise velocities (Baek et al. 1990) for a single channel. Independent parameters that varied in this study include the buoyancy parameter (Gr/Re), the ratio of the wall conductivity to the fluid conductivity (K), and the ratio of the plate thickness to the channel width (W/B). The velocity profiles within the channel skewed substantially to the hot wall as profiles within the channel skewed substantially to the hot wall as Gr/Re increased and K decreased. The thermal conductivity ratio, K, and buoyancy parameter, Gr/Re, had a significant impact on local friction factor distribution. There was also a significant difference between the hot and cold surface heat fluxes at low values of K, while the heat flux distribution on both surfaces was essentially identical for K = 100. The effect of the exposed surface at the top of the plates was to reduce the wall temperatures near the vicinity of the plate tip, although heat was not removed out of the plate top nearly as effectively as at the plate bottom. An extended wake developed beyond the plate top for asymmetric heating cases, which included recirculation zones as far as 10 to 2 channel widths from the exit. A correlation relating maximum hot surface temperatures with the independent parameters was developed.

Watson, J.C.; Anand, N.K.; Fletcher, L.S. [Texas A and M Univ., College Station, TX (United States). Dept. of Mechanical Engineering

1995-12-31

65

Comparison of DOE-2.1E with Energyplus and TRNSYS for Ground Coupled Residential Buildings in Hot anf Humid Climates Stage 1  

E-print Network

ESL-TR-11-12-08 COMPARISON OF DOE-2.1E WITH ENERGYPLUS AND TRNSYS FOR GROUND COUPLED RESIDENTIAL BUILDINGS IN HOT AND HUMID CLIMATES STAGE 1 “Literature Survey on Slab-on-grade Heat Transfer Models of DOE-2, EnergyPlus and TRNSYS... in DOE-2, EnergyPlus and TRNSYS programs. 2. Introduction Foundation heat transfer is a significant load component for low-rise residential buildings. For a contemporary code or above code house, ground-coupled heat losses may account for 30...

Andolsun, S.; Culp, C.

2011-01-01

66

Natural convection heat transfer from a long heated vertical cylinder to an adjacent air gap of concentric and eccentric conditions  

Microsoft Academic Search

In this work, the natural convection heat transfer from a long vertical electrically heated cylinder to an adjacent air gap\\u000a is experimentally studied. The aspect and diameter ratios of the cylinder are 55.56 and 6.33, respectively. The experimental\\u000a measurements were obtained for a concentric condition and six eccentricities from 0.1 to 0.92 at five different heat fluxes.\\u000a The surface temperature

R. Hosseini; A. Rezania; M. Alipour; L. A. Rosendahl

2011-01-01

67

Method and apparatus for determining vertical heat flux of geothermal field  

DOEpatents

A method and apparatus for determining vertical heat flux of a geothermal field, and mapping the entire field, is based upon an elongated heat-flux transducer (10) comprised of a length of tubing (12) of relatively low thermal conductivity with a thermopile (20) inside for measuring the thermal gradient between the ends of the transducer after it has been positioned in a borehole for a period sufficient for the tube to reach thermal equilibrium. The transducer is thermally coupled to the surrounding earth by a fluid annulus, preferably water or mud. A second transducer comprised of a length of tubing of relatively high thermal conductivity is used for a second thermal gradient measurement. The ratio of the first measurement to the second is then used to determine the earth's thermal conductivity, k.sub..infin., from a precalculated graph, and using the value of thermal conductivity thus determined, then determining the vertical earth temperature gradient, b, from predetermined steady state heat balance equations which relate the undisturbed vertical earth temperature distributions at some distance from the borehole and earth thermal conductivity to the temperature gradients in the transducers and their thermal conductivity. The product of the earth's thermal conductivity, k.sub..infin., and the earth's undisturbed vertical temperature gradient, b, then determines the earth's vertical heat flux. The process can be repeated many times for boreholes of a geothermal field to map vertical heat flux.

Poppendiek, Heinz F. (LaJolla, CA)

1982-01-01

68

Numerical investigation on thermal performance of vertical U buried pipe heat exchanger with intermittent operation  

Microsoft Academic Search

The effect of intermittent operation on the heat transfer performance of vertical U buried pipe heat exchangers is studied by method of numerical simulation and analytical solution. The calculation area is divided into two parts by the boundary of the borehole wall. For the area in the borehole, the calculation method is steady analytical solution, and for the soil area,

Yuan Yanping; Cao Xiaoling; Lei Bo; Yang Conghui

2010-01-01

69

Numerical simulation for thermal response test performance in closed-loop vertical ground heat exchanger  

Microsoft Academic Search

In this study, a series of numerical analyses was performed in order to evaluate the performance of full-scale closed-loop vertical ground heat exchangers constructed in Wonju, South Korea. The circulating HDPE pipe, borehole and surrounding ground formation were modeled using FLUENT, a finite-volume method (FVM) program, for analyzing the heat transfer process of the ground heat exchanger system. Two user-defined

Jong Min Choi; Chulho Lee; Shin-Hyung Kang; Hangseok Choi

2011-01-01

70

Heat flow experiment. [direct measurement of vertical flow of heat through lunar soil in Apollo 17 lunar landing site area  

NASA Technical Reports Server (NTRS)

The heat flow experiment conducted during the Apollo 17 flight in the Taurus-Littrow area of the moon is discussed. The concept of the experiment is based on the direct measurement of the vertical flow of heat through the regolith. The measurement is made far enough below the surface so that the time-varying heat flow resulting from the very large diurnal variations of the surface temperature is small as compared with the flow from the interior. The equipment used for the experiment is described and illustrated. Graphs are developed to present the results of heat flow and surface temperature measurements.

Langseth, M. G., Jr.; Keihm, S. J.; Chute, J. L., Jr.

1973-01-01

71

Heat transfer coefficient determination for flow boiling in vertical and horizontal minichannels  

NASA Astrophysics Data System (ADS)

The paper presents the results of boiling heat transfer research during FC-72 laminar flow along a minichannel of 1 mm depth, positioned vertically and horizontally, with an enhanced heating surface. One glass pane allows to determine the temperature of the heating wall by liquid crystal thermography. Calculations are aimed at the evaluation of one- and two-dimensional heat transfer approaches to determine the local heat transfer coefficient. In the one-dimensional approach only the direction of the flow in the channel is considered. In the two-dimensional approach the inverse problem in the heating wall and the direct problem in the glass barrier were solved by the finite element method with Trefftz functions as shape functions (FEMT). The developed flow boiling area was studied. Heat transfer coefficient values obtained for the horizontal minichannel were higher than those obtained for the vertical one. When the heat flux supplied to heating wall grows, the share of gas-phase increases leading to the heat transfer coefficient decreases. The same courses of the experiment were observed for the two applied methods, but the results obtained in the one-dimensional approach are considerably higher than in the two-dimensional one. One-dimensional approach seems to be less sensitive to measurement errors.

Piasecka, Magdalena; Maciejewska, Beata

2014-03-01

72

Convection Heat and Mass Transfer in an Electrical Conducting Power Law Flow over a Heated Vertical Porous Plate  

Microsoft Academic Search

This paper investigates convection heat and mass transfer flow in an electrically conducting power law fluid past a vertical porous plate in presence of a transverse magnetic field, thermal radiation, and thermal diffusion. The non–linear partial differential equations governing the flow are transformed into ordinary differential equations using the usual similarity method and the resulting similarity equations are solved numerically

B. I. Olajuwon

2010-01-01

73

Experimental study of natural convective heat transfer in a vertical hexagonal sub channel  

SciTech Connect

The development of new practices in nuclear reactor safety aspects and optimization of recent nuclear reactors, including the APWR and the PHWR reactors, needs a knowledge on natural convective heat transfer within sub-channels formed among several nuclear fuel rods or heat exchanger tubes. Unfortunately, the currently available empirical correlation equations for such heat transfer modes are limited and researches on convective heat transfer within a bundle of vertical cylinders (especially within the natural convection modes) are scarcely done. Although boundary layers around the heat exchanger cylinders or fuel rods may be dominated by their entry regions, most of available convection correlation equations are for fully developed boundary layers. Recently, an experimental study on natural convective heat transfer in a subchannel formed by several heated parallel cylinders that arranged in a hexagonal configuration has been being done. The study seeks for a new convection correlation for the natural convective heat transfer in the sub-channel formed among the hexagonal vertical cylinders. A new convective heat transfer correlation equation has been obtained from the study and compared to several similar equations in literatures.

Tandian, Nathanael P.; Umar, Efrizon; Hardianto, Toto; Febriyanto, Catur [Faculty of Mechanical and Aerospace Engineering, Institut Teknologi Bandung, Jl. Ganesa 10, Bandung 40132 (Indonesia); Nuclear Technology Center for Materials and Radiometry, National Nuclear Energy Agency, Bandung (Indonesia); Faculty of Mechanical and Aerospace Engineering, Institut Teknologi Bandung, Jl. Ganesa 10, Bandung 40132 (Indonesia); Nuclear Energy Regulation Agency, Jakarta (Indonesia)

2012-06-06

74

Experimental study of natural convective heat transfer in a vertical hexagonal sub channel  

NASA Astrophysics Data System (ADS)

The development of new practices in nuclear reactor safety aspects and optimization of recent nuclear reactors, including the APWR and the PHWR reactors, needs a knowledge on natural convective heat transfer within sub-channels formed among several nuclear fuel rods or heat exchanger tubes. Unfortunately, the currently available empirical correlation equations for such heat transfer modes are limited and researches on convective heat transfer within a bundle of vertical cylinders (especially within the natural convection modes) are scarcely done. Although boundary layers around the heat exchanger cylinders or fuel rods may be dominated by their entry regions, most of available convection correlation equations are for fully developed boundary layers. Recently, an experimental study on natural convective heat transfer in a subchannel formed by several heated parallel cylinders that arranged in a hexagonal configuration has been being done. The study seeks for a new convection correlation for the natural convective heat transfer in the sub-channel formed among the hexagonal vertical cylinders. A new convective heat transfer correlation equation has been obtained from the study and compared to several similar equations in literatures.

Tandian, Nathanael P.; Umar, Efrizon; Hardianto, Toto; Febriyanto, Catur

2012-06-01

75

Heat transfer enhancement in a vertical annulus by electrophoretic forces acting on a dielectric liquid  

Microsoft Academic Search

In the presence of a sharp HV electrode, free charge can build up in a single-phase liquid by ion injection at the metal\\/liquid interface. Electrophoretic forces acting on ions can generate strong convective motion, thus augmenting the heat transfer rate.In a vertical annular duct, uniformly heated on the outer wall, a dielectric liquid is weakly forced to flow upward. Sharp

Walter Grassi; Daniele Testi; Mario Saputelli

2005-01-01

76

The transfer of heat and mass to a vertical plate under frosting conditions  

E-print Network

THE TRAESFPIR OF HEAT . 'ND NASH 10 A VERTICAL PLATE UNDER FROSTING CONDITIONS A Thesis Louis Joseph Poth, Jr. Submitted to the Graduate School of the Agricultural and Nechanioal College of Texas in partial fulfili ment of the requirements... of the Husselt-Grashof correlation for heat transfer. coefficient of saturation temper ture and concen- tration gradient correlation, for small temper- ature difference. ooefficient of frost specific gravity-thermal oonductivity correlation. coefficient...

Poth, Louis Joseph

1960-01-01

77

Development of supercritical water heat-transfer correlation for vertical bare tubes  

Microsoft Academic Search

This paper presents an analysis of heat-transfer to supercritical water in bare vertical tubes. A large set of experimental data, obtained in Russia, was analyzed and a new heat-transfer correlation for supercritical water was developed. This experimental dataset was obtained within conditions similar to those in supercritical water-cooled nuclear reactor (SCWR) concepts.The experimental dataset was obtained in supercritical water flowing

Sarah Mokry; Igor Pioro; Amjad Farah; Krysten King; Sahil Gupta; Wargha Peiman; Pavel Kirillov

2011-01-01

78

Applicability of Related Data, Algorithms, and Models to the Simulation of Ground-Coupled Residential Hot Water Piping in California  

E-print Network

preliminary model for ground heat transfer that includes thein Modeling of Heat Transfer in Vertical Ground HeatHeat transfer algorithms and models devised for generalized, hot water distribution system, ground-

Warner, J.L.

2009-01-01

79

Heat-transfer characteristics of climbing film evaporation in a vertical tube  

SciTech Connect

Heat-transfer characteristics of climbing film evaporation were experimentally investigated on a vertical climbing film evaporator heated by tube-outside hot water. The experimental setup was designed for determining the effect of the height of feed water inside a vertical tube and the range of temperature difference on local heat transfer coefficient inside a vertical tube (h{sub i}). In this setup, the height of feed water was successfully controlled and the polypropylene shell effectively impedes the heat loss to the ground. The results indicated that a reduction in the height of feed water contributed to a significant increase in h{sub i} if no dry patches around the wall of the heated tube appeared inside the tube. The height ratio of feed water R{sub h} = 0.3 was proposed as the optimal one as dry patches destroyed the continuous climbing film when R{sub h} is under 0.3. It was found that the minimum temperature difference driving climbing film evaporation is suggested as 5 C due to a sharp reduction in h{sub i} for temperature difference below 5 C. The experiment also showed that h{sub i} increased with an increase in temperature difference, which proved the superiority of climbing film evaporation in utilizing low-grade surplus heating source due to its wide range of driving temperature difference. The experimental results were compared with the previous literature and demonstrated a satisfactory agreement. (author)

Yang, Luopeng; Chen, Xue; Shen, Shengqiang [Key Laboratory of Ocean Energy Utilization and Energy Conservation of Ministry of Education, School of Energy and Power Engineering, Dalian University of Technology, Dalian 116024 (China)

2010-09-15

80

Critical heat flux of water in vertical round tubes at low pressure and low flow conditions  

Microsoft Academic Search

An experimental study on critical heat flux (CHF) has been performed for water flow in vertical round tubes under low pressure and low flow (LPLF) conditions to provide a systematic data base and to investigate parametric trends. Totally 513 experimental data have been obtained with Inconel-625 tube test sections in the following conditions: diameter of 6, 8, 10 and 12

Hong Chae Kim; Won-Pil Baek; Soon Heung Chang

2000-01-01

81

An analysis of the performance of a vertically oriented, gas loaded, variable conductance heat pipe  

Microsoft Academic Search

An analysis of steady state operation of a vertically oriented, variable conductance heat pipe is presented. The effects of binary mass diffusion, axial pipe wall conduction, and gravitational effects, caused by the difference in molecular weight of the non-condensible gas and the working fluid are incorporated. Analytical expressions for the conservation of mass, momentum, and energy are combined along with

G. A. Glover Sr.

1986-01-01

82

Inaccuracies in soil heat flux measurement and modeling: a matter of vertical and temporal resolution?  

Microsoft Academic Search

We here demonstrate with a conceptual model of the land-atmosphere interaction and a high vertical resolution Soil Vegetation Atmosphere Transfer model that the high daily frequencies of incoming radiation play a fundamental role in the soil heat flux signal. These high frequencies remain concentrated in a very shallow layer at the surface of about 1cm, which precludes the use of

P. Gentine; D. Entekhabi

2010-01-01

83

Heat transfer analysis in a two-side heated smooth square vertical channel with adverse and favorable mixed convection  

SciTech Connect

Experimental heat transfer measurements and analysis for mixed convection in a vertical square channel are presented. The flow direction is changed with respect to the earth's gravity field by selectively opening and closing the flow control valves. Desired flow directions are selected such that buoyancy assists or opposes the bulk flow direction pressure gradient. The heating condition is asymmetric. Most previous experiments used symmetrically heated circular tubes. Present configuration shows significant increase in the Nusselt number in both assisted and opposed flow conditions. In general, opposed flow shows higher heat transfer coefficients. Unlike symmetric heating conditions, Nusselt number ratio is observed to be increasing with increasing Gr/Re or Gr/Re{sup 2} ratios for both assisted and opposed flow conditions.

Dutta, S.; Zhang, X.; Khan, J.A.; Bell, D.

1997-07-01

84

Heat transfer in vertical Bridgman growth of oxides - Effects of conduction, convection, and internal radiation  

NASA Technical Reports Server (NTRS)

In the present investigation of crystalline phase internal radiation and heat conduction during the vertical Bridgman growth of a YAG-like oxide crystal, where transport through the melt is dominated by convection and conduction, heat is also noted to be conducted through ampoule walls via natural convection and enclosure radiation. The results of a quasi-steady-state axisymmetric Galerkin FEM indicate that heat transfer through the system is powerfully affected by the optical absorption coefficient of the crystal. The coupling of internal radiation through the crystal with conduction through the ampoule walls promotes melt/crystal interface shapes that are highly reflected near the ampoule wall.

Brandon, S.; Derby, J. J.

1992-01-01

85

Experimental research on heat transfer of natural convection in vertical rectangular channels with large aspect ratio  

SciTech Connect

This work presents the experimental research on the steady laminar natural convection heat transfer of air in three vertical thin rectangular channels with different gap clearance. The much higher ratio of width to gap clearance (60-24) and the ratio of length to gap clearance (800-320) make the rectangular channels similar with the coolant flow passage in plate type fuel reactors. The vertical rectangular channels were composed of two stainless steal plates and were heated by electrical heating rods. The wall temperatures were detected with the K-type thermocouples which were inserted into the blind holes drilled in the steal plates. Also the air temperatures at the inlet and outlet of the channel were detected. The wall heat fluxes added to the air flow were calculated by the Fourier heat conduction law. The heat transfer characteristics were analyzed, and the average Nusselt numbers in all the three channels could be well correlated with the Rayleigh number or the modified Rayleigh number in a uniform correlation. Furthermore, the maximum wall temperatures were investigated, which is a key parameter for the fuel's integrity during some accidents. It was found that even the wall heat flux was up to 1500 W/m{sup 2}, the maximum wall temperature was lower than 350 C. All this work is valuable for the plate type reactor's design and safety analysis. (author)

Lu, Qing; Qiu, Suizheng; Su, Guanghui [State Key Laboratory of Multi Phase Flow in Power Engineering, Xi'an JIaotong University, Xi'an, Shaanxi 710049 (China); School of Nuclear Science and Technology, Xi'an Jiaotong University, Xi'an, Shaanxi 710049 (China); Tian, Wenxi; Ye, Zhonghao [School of Nuclear Science and Technology, Xi'an Jiaotong University, Xi'an, Shaanxi 710049 (China)

2010-01-15

86

Modeling of Vertical Ground Loop Heat Exchangers with Variable Convective Resistance and Thermal Mass of the Fluid  

E-print Network

simulate the heat transfer of ground loop heat exchanger in any time scale, it could not model varyingModeling of Vertical Ground Loop Heat Exchangers with Variable Convective Resistance and Thermal-term behavior of ground loop heat exchangers (GLHE) is critical to the design and energy analysis of ground

87

Natural convection heat transfer from a long heated vertical cylinder to an adjacent air gap of concentric and eccentric conditions  

NASA Astrophysics Data System (ADS)

In this work, the natural convection heat transfer from a long vertical electrically heated cylinder to an adjacent air gap is experimentally studied. The aspect and diameter ratios of the cylinder are 55.56 and 6.33, respectively. The experimental measurements were obtained for a concentric condition and six eccentricities from 0.1 to 0.92 at five different heat fluxes. The surface temperature of the heated rod is measured at different heights, and the Nusselt number is calculated at the temperature measurement locations. A correlation is suggested to determine the Nusselt number based on the variation of the eccentric ratio values. The experimental results show a good agreement with other studies.

Hosseini, R.; Rezania, A.; Alipour, M.; Rosendahl, L. A.

2012-01-01

88

Experimental investigation of the local heat transfer in a vertical gas-liquid slug unit  

NASA Astrophysics Data System (ADS)

Heat transfer mechanism in two-phase flows and particularly in vertical slug flow is of high interest both for basic hydrodynamic research and for industrial applications. Two-phase slug flow is highly complicated and only a limited number of heat transfer studies have been carried out. The flow field around a single Taylor bubble propagating in a vertical pipe can be subdivided into three distinct hydrodynamic regions: the gas bubble surrounded by a thin liquid film, a highly turbulent liquid wake in the vicinity of the bubble bottom, and the far wake region. Experimental and theoretical works were presented during the last decades investigating the hydrodynamic parameters in each region. Due to the complexity and intermittent nature of slug flow the existing data on the heat transfer in slug flow is limited to a narrow range of operational conditions. To improve the understanding of the heat transfer mechanism in slug flow a new experimental setup was constructed. A part of the vertical pipe wall was replaced by a thin metal foil heated by electrical current. An IR video camera was used to determine the temporal variation of the instantaneous temperature field along the foil at two locations: at the thermal entrance region and at the upper part of the foil where thermal boundary is thicker. The video camera was synchronized with a sensor that determined the instantaneous location of the Taylor bubble. The results of the instantaneous heat transfer measurements along the liquid film and in the wake of the Taylor bubble can be correlated with the detailed velocity measurements carried out in the same facility (Shemer et al. 2007)[1]. The effect of the local hydrodynamic parameters on the heat transfer coefficient in each region is examined.

Babin, Valery; Shemer, Lev; Barnea, Dvora

2012-03-01

89

Fundamental Study of Local Heat Transfer in Forced Convective Boiling of Ammonia on Vertical Flat Plate  

NASA Astrophysics Data System (ADS)

In the present study, the fundamental experiments that investigate characteristics of local heat transfer in forced convective boiling on vertical flat plate with 2-mm channel height are taken to realize plate type compact evaporator for OTEC or STEC. The experiments are performed with ammonia as the working fluid. The experiments are also carried out with the following test conditions; saturated pressure = 0.7, 0.8, 0.9 MPa, mass flux = 7.5, 10, 15 kg/(m2•s), heat flux = 15, 20, 25 kW/m2 and inlet quality = 0.1 ~ 0.4 [-]. The result shows that the wall superheated temperature of forced convective boiling is lower than that of pool boiling. And the heat transfer coefficient increases with an increase in quality and the decrease in the local heat flux and saturated pressure for prescribed experimental conditions. However, local heat transfer coefficients are not affected by mass fluxes in the prescribed experimental conditions. An empirical correlation that can predict the local heat transfer coefficient on vertical flat plate within experimental conditions is also proposed.

Kim, Jeong-Hun; Arima, Hirofumi; Ikegami, Yasuyuki

90

Inaccuracies in soil heat flux measurement and modeling: a matter of vertical and temporal resolution?  

NASA Astrophysics Data System (ADS)

We here demonstrate with a conceptual model of the land-atmosphere interaction and a high vertical resolution Soil Vegetation Atmosphere Transfer model that the high daily frequencies of incoming radiation play a fundamental role in the soil heat flux signal. These high frequencies remain concentrated in a very shallow layer at the surface of about 1cm, which precludes the use of deeper measurement to accurately describe the surface soil heat flux signal. Current measurement techniques lead to important errors in the surface energy budget. In addition the currently-used calorimetric method is demonstrated to be unable to characterize the variability, magnitude and phase in the surface soil heat flux. In consequence, these results call for a higher-resolution sampling of soil heat flux, both in time and vertically near the surface, in order to accurately quantify the surface soil heat flux and to account for its rapid variations, especially in cloudy situations. In addition those results demonstrate the need for high vertical and temporal resolution in the modeling of the soil surface in order to describe the diurnal course of the surface soil heat flux. Coarser resolutions are shown to miss most of the soil heat flux signal since it acts as a high-pass filter of incoming radiation. Finally this works points out important limitations of the assimilation of infrared surface temperature because of the rapid fluctuations in solar radiation (weather noise). Comparison of the soil heat flux at different depth obtained with SVAT (continuous line) and conceptual land-atmosphere model (dashed line) over 135 days of data from the SUDMED project. The conceptual model captures the emergent behavior of the soil heat flux response. Soil heat flux at the surface is mostly influenced by high frequencies, whereas the high-frequency component of the signal has almost disappeared at typical soil heat flux measurement depth (2.5 or 5cm). This shows the limitation of current soil heat flux methodology since they do not capture most of the surface signal and cannot therefore close the surface energy partitioning.

Gentine, P.; Entekhabi, D.

2010-12-01

91

Two-Gradient Convection in a Vertical Slot with Maxwell-Cattaneo Heat Conduction  

SciTech Connect

We study the effect of the Maxwell-Cattaneo law of heat conduction (MCHC) on the 1D flow in a vertical slot subject to both vertical and horizontal temperature gradients. The gravitational acceleration is allowed to oscillate, which provides an opportunity to investigate the quantitative contribution of thermal inertia as epitomized by MCHC. The addition of the time derivative in MCHC increases the order of the system. We use a spectral expansion with Rayleigh's beam functions as the basis set, which is especially suited to fourth order boundary value problems (BVP). We show that the time derivative (relaxation of the thermal flux) has a dissipative nature and leads to the appearance of purely real negative eigenvalues. Yet it also increases the absolute value of the imaginary part and decreases the absolute value of the real part of the complex eigenvalues. Thus, the system has a somewhat more oscillatory behavior than the one based on Fourier's heat conduction law (FHC)

Papanicolaou, N. C. [Department of Computer Science, University of Nicosia, P.O. Box 24005, 1700 Nicosia (Cyprus); Christov, C. I. [Department of Mathematics, University of Louisiana at Lafayette, LA 70504-1010 (United States); Jordan, P. M. [Entropy Reversal Consultants (L.L.C), P. O. Box 691, Abita Springs, LA 70420 (United States); Code 7181, Naval Research Lab., Stennis Space Ctr., MS 39529 (United States)

2009-10-29

92

Explicit Solutions of a Gravity-Induced Film Flow along a Convectively Heated Vertical Wall  

PubMed Central

The gravity-driven film flow has been analyzed along a vertical wall subjected to a convective boundary condition. The Boussinesq approximation is applied to simplify the buoyancy term, and similarity transformations are used on the mathematical model of the problem under consideration, to obtain a set of coupled ordinary differential equations. Then the reduced equations are solved explicitly by using homotopy analysis method (HAM). The resulting solutions are investigated for heat transfer effects on velocity and temperature profiles. PMID:24453862

Raees, Ammarah

2013-01-01

93

Explicit solutions of a gravity-induced film flow along a convectively heated vertical wall.  

PubMed

The gravity-driven film flow has been analyzed along a vertical wall subjected to a convective boundary condition. The Boussinesq approximation is applied to simplify the buoyancy term, and similarity transformations are used on the mathematical model of the problem under consideration, to obtain a set of coupled ordinary differential equations. Then the reduced equations are solved explicitly by using homotopy analysis method (HAM). The resulting solutions are investigated for heat transfer effects on velocity and temperature profiles. PMID:24453862

Raees, Ammarah; Xu, Hang

2013-01-01

94

Transient natural convection along vertical cylinder with Heat and Mass transfer  

NASA Astrophysics Data System (ADS)

A numerical solution for the transient natural convection flow over a vertical cylinder under the combined buoyancy effect of heat and mass transfer is presented. The velocity, temperature and concentration profiles, local and average skin-friction, Nusselt number and Sherwood number are shown graphically. It is observed that time taken to reach steady state increases with Schmidt number and decreases as combined buoyancy ratio parameter N increases. Stability and convergence of the finite difference scheme are established.

Ganesan, P.; Rani, H. P.

95

Vortex ring head-on collision with a heated vertical plate  

NASA Astrophysics Data System (ADS)

We report experimental results of the normal impact of a vortex ring in air on a vertical heated plate at constant temperature. We address the case in which the natural convection boundary layer is laminar and the vortex ring is stable. Vortex rings are created by pushing air through a circular exit orifice of a cavity, using a piston-cylinder system. The impinging vortex ring perturbs both the thermal and dynamical boundary layers where we measure the total heat flux exchanged by the heated plate and visualize the vortex motion during the impact. This unsteady impingement process is investigated for different vortex sizes and self-induced velocities, characterized by the Reynolds number of the ring. As a result, a localized heat transfer enhancement is originated by the ring impingement, which increases with the Reynolds number.

Arévalo, G.; Hernández, R. H.; Nicot, C.; Plaza, F.

2007-08-01

96

Vertically integrated sensible-heat budgets for stable nocturnal boundary layers  

NASA Astrophysics Data System (ADS)

The stable nocturnal boundary layer is commonly viewed or modelled as a balance between the temperature tendency (cooling) and vertical heat-flux divergence. Sometimes the radiative-flux divergence is also included. This perspective has dictated the design of field experiments for investigating stable nocturnal boundary layers.Tower-based micrometeorological data from three field campaigns are analysed to evaluate the vertically integrated sensible-heat budget for nocturnal stable conditions. Our analysis indicates frequent occurrence of large imbalance between the temperature tendency and vertical heat-flux divergence terms. The values of the radiative-flux divergence are generally too small and sometimes of the wrong sign to explain the residual. An analysis of random flux errors and uncertainties in the tendency term indicate that such errors cannot explain large imbalances, suggesting the importance of advection of temperature or possibly the divergence of mesoscale fluxes. The implied role of advection is consistent with circumstantial evidence. Even weak surface heterogeneity can create significant horizontal gradients in stable boundary layers. However, it is shown that existing field data and observational strategy do not allow adequate evaluation of advection and mesoscale flux divergence terms.

Nakamura, Reina; Mahrt, L.

2006-01-01

97

Experimental study on condensation heat transfer of steam on vertical titanium plates with different surface energies  

SciTech Connect

Visual experiments were employed to investigate heat transfer characteristics of steam on vertical titanium plates with/without surface modifications for different surface energies. Stable dropwise condensation and filmwise condensation were achieved on two surface modification titanium plates, respectively. Dropwise and rivulet filmwise co-existing condensation form of steam was observed on unmodified titanium surfaces. With increase in the surface subcooling, the ratio of area ({eta}) covered by drops decreased and departure diameter of droplets increased, resulting in a decrease in condensation heat transfer coefficient. Condensation heat transfer coefficient decreased sharply with the values of {eta} decreasing when the fraction of the surface area covered by drops was greater than that covered by rivulets. Otherwise, the value of {eta} had little effect on the heat transfer performance. Based on the experimental phenomena observed, the heat flux through the surface was proposed to express as the sum of the heat flux through the dropwise region and rivulet filmwise region. The heat flux through the whole surface was the weighted mean value of the two regions mentioned above. The model presented explains the gradual change of heat transfer coefficient for transition condensation with the ratio of area covered by drops. The simulation results agreed well with the present experimental data when the subcooling temperature is lower than 10 C. (author)

Baojin, Qi; Li, Zhang; Hong, Xu; Yan, Sun [State-Key Laboratory of Chemical Engineering, School of Mechanical and Power Engineering, East China University of Science and Technology, Shanghai 200237 (China)

2011-01-15

98

Applicability of Related Data, Algorithms, and Models to the Simulation of Ground-Coupled Residential Hot Water Piping in California  

SciTech Connect

Residential water heating is an important consideration in California?s building energy efficiency standard. Explicit treatment of ground-coupled hot water piping is one of several planned improvements to the standard. The properties of water, piping, insulation, backfill materials, concrete slabs, and soil, their interactions, and their variations with temperature and over time are important considerations in the required supporting analysis. Heat transfer algorithms and models devised for generalized, hot water distribution system, ground-source heat pump and ground heat exchanger, nuclear waste repository, buried oil pipeline, and underground electricity transmission cable applications can be adapted to the simulation of under-slab water piping. A numerical model that permits detailed examination of and broad variations in many inputs while employing a technique to conserve computer run time is recommended.

Warner, J.L.; Lutz, J.D.

2006-01-01

99

Experimental study of mixed convection heat transfer in vertical helically coiled tube heat exchangers  

SciTech Connect

In this study the mixed convection heat transfer in a coil-in-shell heat exchanger for various Reynolds numbers, various tube-to-coil diameter ratios and different dimensionless coil pitch was experimentally investigated. The experiments were conducted for both laminar and turbulent flow inside coil. Effects of coil pitch and tube diameters on shell-side heat transfer coefficient of the heat exchanger were studied. Different characteristic lengths were used in various Nusselt number calculations to determine which length best fits the data and several equations were proposed. The particular difference in this study in comparison with the other similar studies was the boundary conditions for the helical coils. The results indicate that the equivalent diameter of shell is the best characteristic length. (author)

Ghorbani, N. [School of Mechanical Engineering, University of Leeds, Leeds, England (United Kingdom); Taherian, H. [Department of Engineering Technology and Industrial Distribution, Texas A and M University, College Station, TX (United States); Gorji, M. [Department of Mechanical Engineering, Babol Noushirvani University of Technology, Babol (Iran); Mirgolbabaei, H. [Department of Mechanical Engineering, Islamic Azad University, Jouybar branch, Jouybar (Iran)

2010-10-15

100

Vibration Characteristics of a Vertical Round Tube According to Heat Transfer Regimes  

SciTech Connect

This paper presents the results of an experimental work on the effects of boiling heat transfer regimes on the flow-induced vibration (FIV). The experiment has been performed using an electrically heated vertical round tube through which water flows at atmospheric pressure. Vibration characteristics of the heated tube are changed significantly by heat transfer regimes and flow patterns. For single-phase liquid convection, the rod vibrations are negligible. However, on the beginning of subcooled nucleate boiling at tube exit, vibration level becomes very large. As bubble departure occurs at the nucleation site of heated surface, the vibration decreases to saturated boiling region where thermal equilibrium quality becomes 0.0 at tube exit. In saturated boiling region, vibration amplitude increases with exit quality up to a certain maximum value due to the reinforced turbulence then decreases. At liquid film dryout condition, vibration could be regarded as negligible, however, these results cannot be extended to DNB-type CHF mechanism. Frequency analysis results of vibration signals suggested that excitation sources be different with heat transfer regimes. This study would contribute to improve the understanding of the relationship between boiling heat transfer and FIV. (authors)

Yong Ho Lee; Soon Heung Chang [Korea Advanced Institute of Science and Technology, 373-1, Guseung-dong, Yuseong-ku, Daejeon, 305-701 (Korea, Republic of); Won-Pil Baek [Korea Atomic Energy Research Institute, 150, Dukjin-Dong, Yusong-Gu, Taejon 305-353 (Korea, Republic of)

2002-07-01

101

Conjugate Effects on Steady Laminar Natural Convection Heat Transfer in Vertical Eccentric Annuli  

NASA Astrophysics Data System (ADS)

Combined conduction-free convection heat transfer in vertical eccentric annuli is numerically investigated using finite-difference technique. Numerical results are presented for a fluid of Prandtl number 0.7 in an annulus of radius ratio 0.5 and dimensionless eccentricity 0.5. The conjugation effect on the induced flow rate and the total heat absorbed in the annulus is presented for the case of one wall being isothermally heated while the other wall is kept at inlet fluid temperature. The conjugate effects are controlled by solid-fluid conductivity ratio, cylinder walls thickness and dimensionless channel height (i.e. Grashof number). Solid-fluid conductivity ratio is varied over a range that covers practical cases with commonly encountered inner and outer walls thickness. Values of conductivity ratio over which conjugate effect can be neglected have been obtained.

El-Shaarawi, Maged A. I.; Mokheimer, Esmail M. A.; Jamal, Ahmad

2005-12-01

102

Natural Convection Condensation Heat Transfer of Carbon Dioxide on a Vertical Surface in the Subcritical Region  

NASA Astrophysics Data System (ADS)

As pressure increases and approaches the critical pressure, density difference between liquid and vapor becomes small, latent heat of condensation approaches zero and other physical properties show remarkably different behaviors from those at lower pressure. Therefore it is expected that condensation heat transfer near the critical pressure differs from that at lower pressure. An experimental study of natural convection condensation on a vertical cylinder surface was carried out using Carbon Dioxide as a working fluid in the pressure range of 5.0 to 7.1 MPa. Filmwise condensation was observed, and heat transfer coefficients were obtained from measuring condensate volume and compared with Nusselt's theory and with experimental results under usual pressure conditions.

Ishihara, Isao; Matsumoto, Ryosuke; Ebihara, Tsutomu; Maegoya, Akira

103

Natural convection in a vertical heated tube attached to a thermally insulated chimney of a different diameter  

Microsoft Academic Search

Natural convection is often a convenient and inexpensive mode of heat transfer. It is commonly employed in the cooling of electronic equipment and many other applications. Since the initial work by Bodoia and Osterle (1962) on finite difference solutions of natural convection between vertical isothermal plates, many other researchers have studied natural convection in vertical channels. Specifically Davis and Perona

Y. Asako; H. Nakamura; M. Faghri

1990-01-01

104

Natural convection heat transfer of nanofluids along a vertical plate embedded in porous medium  

PubMed Central

The unsteady natural convection heat transfer of nanofluid along a vertical plate embedded in porous medium is investigated. The Darcy-Forchheimer model is used to formulate the problem. Thermal conductivity and viscosity models based on a wide range of experimental data of nanofluids and incorporating the velocity-slip effect of the nanoparticle with respect to the base fluid, i.e., Brownian diffusion is used. The effective thermal conductivity of nanofluid in porous media is calculated using copper powder as porous media. The nonlinear governing equations are solved using an unconditionally stable implicit finite difference scheme. In this study, six different types of nanofluids have been compared with respect to the heat transfer enhancement, and the effects of particle concentration, particle size, temperature of the plate, and porosity of the medium on the heat transfer enhancement and skin friction coefficient have been studied in detail. It is found that heat transfer rate increases with the increase in particle concentration up to an optimal level, but on the further increase in particle concentration, the heat transfer rate decreases. For a particular value of particle concentration, small-sized particles enhance the heat transfer rates. On the other hand, skin friction coefficients always increase with the increase in particle concentration and decrease in nanoparticle size. PMID:23391481

2013-01-01

105

A vertical resonance heating model for X- or peanut-shaped galactic bulges  

NASA Astrophysics Data System (ADS)

We explore a second-order Hamiltonian vertical resonance model for X-shaped or peanut-shaped galactic bulges. The X- or peanut-shape is caused by the 2:1 vertical Lindblad resonance with the bar, with two vertical oscillation periods per orbital period in the bar frame. We examine N-body simulations and find that due to the bar slowing down and disc thickening during bar buckling, the resonance and associated peanut-shape moves outward. The peanut-shape is consistent with the location of the 2:1 vertical resonance, independent of whether the bar buckled or not. We estimate the resonance width from the potential m = 4 Fourier component and find that the resonance is narrow, affecting orbits over a narrow range in the angular momentum distribution, dL/L ˜ 0.05. As the resonance moves outward, stars originally in the mid-plane are forced out of the mid-plane and into orbits just within the resonance separatrix. The height of the separatrix orbits, estimated from the Hamiltonian model, is approximately consistent with the peanut-shape height. The peanut- or X-shape is comprised of stars in the vicinity of the resonance separatrix. The velocity distributions from the simulations illustrate that low-inclination orbits are depleted within resonance. Within resonance, the vertical velocity distribution is broad, consistent with resonant heating caused by the passage of the resonance through the disc. In the Milky Way bulge, we relate the azimuthally averaged mid-plane mass density near the vertical resonance to the rotation curve and bar pattern speed. At an estimated vertical resonance galactocentric radius of ˜1.3 kpc, we confirm a mid-plane density of ˜5 × 108 M? kpc-3, consistent with recently estimated mass distributions. We find that the rotation curve, bar pattern speed, 2:1 vertical resonance location, X-shaped tips and mid-plane mass density, are all self-consistent in the Milky Way galaxy bulge.

Quillen, Alice C.; Minchev, Ivan; Sharma, Sanjib; Qin, Yu-Jing; Di Matteo, Paola

2014-01-01

106

Comparison of DOE-2.1E with Energyplus and TRNSYS for Ground Coupled Residential Buildings in Hot anf Humid Climates Stage 4  

E-print Network

Qsoil/slab heat transfer between the soil and the slab Qfm(s) monthly average floor heat flux(es) Tam(s) monthly average outside air temperature(s) Tg(s) monthly average deep ground temperature(s) calculated by DOE-2 using Kasuda approach [21] Tslab... sealed boxes in four U.S. climates. 2. INTRODUCTION Ground coupled heat transfer (GCHT) through concrete floor slabs can be a significant component of the total load for heating or cooling in low-rise residential buildings. For a contemporary code...

Andolsun, S.; Culp, C.

2012-01-01

107

Modeling Vertical Structure and Heat Transport within the Oceans of Ice-covered Worlds (Invited)  

NASA Astrophysics Data System (ADS)

Indirect observational evidence provides a strong case for liquid oceans beneath the icy crust of Europa and several other frozen moons in the outer solar system. However, little is known about the fluid circulation within these exotic oceans. As a first step toward understanding circulations driven by buoyancy (rather than mechanical forcing from tides), one must understand the typical vertical structure of temperature, salinity, and thus density within the ocean. Following a common approach from terrestrial oceanography, I have built a "single column convection model" for icy world oceans, which describes the density structure of the ocean as a function of depth only: horizontal variations are ignored. On Earth, this approach is of limited utility, because of the strong influence of horizontal wind-driven currents and sea-surface temperature gradients set in concert with the overlying atmosphere. Neither of these confounding issues is present in an icy world's ocean. In the model, mixing of fluid properties via overturning convection is modeled as a strong diffusive process which only acts when the ocean is vertically unstable. "Double diffusive" processes (salt fingering and diffusive layering) are included: these are mixing processes resulting from the unequal molecular diffusivities of heat and salt. Other important processes, such as heating on adiabatic compression, and freshwater fluxes from melting overlying ice, are also included. As a simple test case, I considered an ocean of Europa-like depth (~100 km) and gravity, heated from the seafloor. To simplify matters, I specified an equation of state appropriate to terrestrial seawater, and a simple isothermal ocean as an initial condition. As expected, convection gradually penetrates upward, warming the ocean to an adiabatic, unstratified equilibrium density profile on a timescale of 50 kyr if 4.5 TW of heat are emitted by the silicate interior; the same result is achieved in proportionally more/less time for weaker/stronger internal heating. Unlike Earth's oceans, I predict that since icy worlds' oceans are heated from below, they will generally be unstratified, with constant potential density from top to bottom. There will be no pycnocline as on Earth, so global ocean currents supported by large-scale density gradients seem unlikely. However, icy world oceans may be "weird" in ways which are unheard-of in terrestrial oceanography The density of sulfate brine has a very different equation of state than chloride brines: does this affect the vertical structure? If the ocean water is very pure, cold water can be less dense than warm. Can this lead to periodic catastrophic overturning, as proposed by other authors? These and other questions are currently being investigated using the single-column convection model as a primary tool.

Goodman, J. C.

2010-12-01

108

Unsteady natural convective flow past a moving vertical cylinder with heat and mass transfer  

NASA Astrophysics Data System (ADS)

Transient natural convection boundary layer flow of an incompressible viscous fluid past an impulsively moving semi- infinite vertical cylinder is considered. The temperature and concentration of the cylinder surface are taken to be uniform. The unsteady, nonlinear and coupled governing equations of the flow are solved using an implicit finite difference scheme. The finite difference scheme is unconditionally stable and accurate. Numerical results are presented with various sets of parameters for both air and water. Transient effects of velocity, temperature and concentration profiles are analyzed. Local and average skin friction, rates of heat and mass transfer are shown graphically.

Ganesan, P.; Loganathan, P.

109

An Algorithm to Estimate the Heating Budget from Vertical Hydrometeor Profiles.  

NASA Astrophysics Data System (ADS)

A simple algorithm to estimate the latent heating of cloud systems from their vertical hydrometer profiles is proposed. The derivation as well as the validation of the algorithm is based on output generated by a non-hydrostatic cloud model with parameterized microphysical processes. Mature and decaying stages of a GATE squall-type convective system have been tested. The algorithm-derived heating budget is in reasonable agreement with the budget predicted by the cloud model. The input to the proposed algorithm can be obtained from either a rain retrieval technique based on information from multichannel passive microwave signals or a kinematic cloud model based on information from Doppler radar wind fields and radar reflectivity patterns. Such an application would have significant implications for spaceborne remote sensing and the large-scale weather prediction data assimilation problem.

Tao, Wei-Kuo; Simpson, Joanne; Lang, Stephen; McCumber, Michael; Adler, Robert; Penc, Richard

1990-12-01

110

Effect of oxygen on flame heat flux in horizontal and vertical orientations  

Microsoft Academic Search

A systematic empirical and analytical study was conducted to directly\\u000d\\u000a\\u0009quantify the effect of enhanced ambient oxygen concentration on flame\\u000d\\u000a\\u0009heat flux at bench scale and its ability to represent large-scale\\u000d\\u000a\\u0009flame heat flux of well-ventilated fires. The Advanced Flammability\\u000d\\u000a\\u0009Measurements Apparatus was used to conduct bench scale horizontal\\u000d\\u000a\\u0009and single wall vertical orientation experiments for black polymethylmethacrylate,\\u000d\\u000a\\u0009propylene gas

Patricia A. Beaulieu; Nicholas A. Dembsey

2008-01-01

111

Boiling heat transfer in a vertical microchannel: Local estimation during flow boiling with a non intrusive method  

E-print Network

Boiling heat transfer in a vertical microchannel: Local estimation during flow boiling with a non densities. Indeed, microchannels are already attrac- tive in many domains such as: electronics cooling removal, and they have large heat dissipa- tion capabilities. Moreover, microchannels can be used

112

A boundary layer analysis for entrance region heat transfer in vertical microchannels within the slip flow regime  

Microsoft Academic Search

A boundary layer integral analysis has been executed to investigate the heat transfer characteristics of natural convection gas flows in symmetrically heated vertical microchannels, under the conditions of large channel aspect ratios, in the slip flow regime. It has been revealed that for low values of Rayleigh number, the entrance region length is only a small fraction of the total

Suman Chakraborty; S. K. Som; Rahul

2008-01-01

113

Three-dimensional numerical study of natural convection in vertical cylinders partially heated from the side  

NASA Astrophysics Data System (ADS)

Three-dimensional steady and oscillatory flows are simulated in a vertical cylinder partially heated from the side. The vertical wall is heated in a zone at midheight and is insulated above and below this middle zone, while both ends of the cylinder are cooled. The cylinder aspect ratio (A=height/radius) ranges from 2 to 8, whereas a fixed Prandtl number, Pr =0.021, is considered as well as a fixed length of the heated zone, equal to the cylinder radius. Three-dimensional steady and unsteady simulations as well as mode decomposition techniques and energy transfer analyses are used to characterize the flows and their transitions. The flows that develop from the steady toroidal pattern beyond the first instability threshold break the axisymmetry. At small A (2?A?2.5), the flow corresponds to a two-roll rotating pattern, which is triggered by a k =2 azimuthal mode as a result of a hydrodynamic instability. At large A (3?A?8), the flow is steady and corresponds to a main one-roll pattern in the upper part of the cylinder. The flow is triggered by a k =1 mode as a result of buoyancy effects affecting this unstably stratified upper part (Rayleigh-Bénard instability), but shear effects are involved in the instability for the smaller values of A. These steady flows then transit at a higher threshold to a standing-wave oscillatory one-roll pattern associated with the breaking of symmetry of the previous steady pattern. For intermediate values of A (2.7?A?2.9), the transition is toward an oscillatory pattern, but hysteresis phenomena with multiplicity of steady and oscillatory states have been found. Comparisons with experiments performed at aspect ratios A =4 and 8 are then considered and discussed.

Ma, D. J.; Henry, D.; Ben Hadid, H.

2005-12-01

114

The study and development of the empirical correlations equation of natural convection heat transfer on vertical rectangular sub-channels  

NASA Astrophysics Data System (ADS)

This study focused on natural convection heat transfer using a vertical rectangular sub-channel and water as the coolant fluid. To conduct this study has been made pipe heaters are equipped with thermocouples. Each heater is equipped with five thermocouples along the heating pipes. The diameter of each heater is 2.54 cm and 45 cm in length. The distance between the central heating and the pitch is 29.5 cm. Test equipment is equipped with a primary cooling system, a secondary cooling system and a heat exchanger. The purpose of this study is to obtain new empirical correlations equations of the vertical rectangular sub-channel, especially for the natural convection heat transfer within a bundle of vertical cylinders rectangular arrangement sub-channels. The empirical correlation equation can support the thermo-hydraulic analysis of research nuclear reactors that utilize cylindrical fuel rods, and also can be used in designing of baffle-free vertical shell and tube heat exchangers. The results of this study that the empirical correlation equations of natural convection heat transfer coefficients with rectangular arrangement is Nu = 6.3357 (Ra.Dh/x)0.0740.

Kamajaya, Ketut; Umar, Efrizon; Sudjatmi, K. S.

2012-06-01

115

Finite element analysis of natural heat transfer from an isothermal array of cylinders in presence of vertical oscillations  

NASA Astrophysics Data System (ADS)

A numerical simulation is performed to study the effects of vertical vibrations on natural convection heat transfer in an array of isothermal circular cylinders. Governing equations consist of continuity, momentum and energy equations were solved numerically by finite element method and Arbitrary Lagrangian-Eulerian kinematics description. The results showed that vertical oscillations of cylinders do not necessarily results in increment of average Nusselt number of each cylinder.

Shokouhmand, H.; Abadi, S. M. A. Noori Rahim

2010-10-01

116

Unsteady free convection on a vertical cylinder with variable heat and mass flux  

NASA Astrophysics Data System (ADS)

The unsteady natural convection boundary layer flow over a semi-infinite vertical cylinder is considered with combined buoyancy force effects, for the situation in which the surface temperature T'w(x) and C'w(x) are subjected to the power-law surface heat and mass flux as K(T'/r) = -axn and D(C'/r) = -bxm. The governing equations are solved by an implicit finite difference scheme of Crank-Nicolson method. Numerical results are obtained for different values of Prandtl number, Schmidt number `n' and `m'. The velocity, temperature and concentration profiles, local and average skin-friction, Nusselt and Sherwood numbers are shown graphically. The local Nusselt and Sherwood number of the present study are compared with the available result and a good agreement is found to exist.

Ganesan, P.; Rani, H. P.

117

Exact Solution Of MHD Mixed Convection Periodic Flow In A Rotating Vertical Channel With Heat Radiation  

NASA Astrophysics Data System (ADS)

Magnetohydrodynamic (MHD) mixed convection flow of a viscous, incompressible and electrically conducting fluid in a vertical channel is analyzed analytically. A magnetic field of uniform strength is applied perpendicular to the planes of the channel walls. The fluid is acted upon by a periodic variation of the pressure gradient in the vertically upward direction. The temperature of one of the plates is non-uniform and the temperature difference of the walls of the channel is high enough to induce heat transfer due to radiation. The fluid and the channel rotate in unison with an angular velocity about the axis normal to the plates of the channel. An exact analytical solution of the problem is obtained. Two cases of small and large rotation have been considered to assess the effects of different parameters involved in the flow problem. The velocity field, the amplitude and the phase angle of the shear stress are shown graphically and discussed in detail. During analysis it is found that the flow problem studied by Makinde and Mhone (2005) is incorrect physically and mathematically

Singh, K. D.

2013-08-01

118

Unsteady natural convection on an evenly heated vertical plate for Prandtl number Pr< 1.  

PubMed

The transient behavior of the natural convection boundary-layer flow adjacent to a vertical plate heated with a uniform flux in a quiescent homogeneous ambient fluid with Prandtl number Pr<1 is investigated by scaling analysis and direct numerical simulation (DNS). The flow is characterized by a startup stage, a short transitional stage and a steady state. The flow is parametrized by the thermal and velocity boundary-layer thickness scales, the vertical velocity scale, the time scale for the boundary layer to reach the steady state and the plate temperature scale. Scaling analysis is used to obtain laws relating these quantities to the flow governing parameters, the Rayleigh number Ra, the Prandtl number, and the Boussinesq number Bo=RaPr which is a much more important control parameter than Ra for small Pr fluids. A series of DNS with selected values of Ra and Pr in the ranges of 10(6)< or =R< or =10(10) and 0.01< or =Pr < or =0.5 are used to validate the scaling laws and obtain scaling constants. PMID:16486061

Lin, Wenxian; Armfield, S W

2005-12-01

119

Sensitivity of shortwave radiative flux density, forcing, and heating rates to the aerosol vertical profile  

SciTech Connect

The effect of the aerosol vertical distribution on the solar radiation profiles, for idealized and measured profiles of optical properties (extinction and single-scattering albedo (SSA)) during the May 2003 Atmospheric Radiation Measurement (ARM) Aerosol Intensive Observation Period (AIOP), has been investigated using the Rapid Radiative Transfer Model Shortwave (RRTM_SW) code. Calculated profiles of down-welling and up-welling solar fluxes during the AIOP have been compared with the data measured by up- and down-looking solar broadband radiometers aboard a profiling research aircraft. The measured profiles of aerosol extinction, SSA, and water vapor obtained from the same aircraft that carried the radiometers served as the inputs for the model calculations. It is noteworthy that for this study, the uplooking radiometers were mounted on a stabilized platform that kept the radiometers parallel with respect to the earth’s horizontal plane. The results indicate that the shape of the aerosol extinction profiles has very little impact on direct radiative forcings at the top of atmosphere and surface in a cloud-free sky. However, as long as the aerosol is not purely scattering, the shape of the extinction profiles is important for forcing profiles. Identical extinction profiles with different absorption profiles drastically influence the forcing and heating rate profiles. Using aircraft data from 19 AIOP profiles over the Southern Great Plains (SGP), we are able to achieve broadband down-welling solar flux closure within 0.8% (bias difference) or 1.8% (rms difference), well within the expected measurement uncertainty of 1 to 3%. The poorer agreement in up-welling flux (bias -3.7%, rms 10%) is attributed to the use of inaccurate surface albedo data. The sensitivity tests reveal the important role accurate, vertically resolved aerosol extinction data plays in tightening flux closure. This study also suggests that in the presence of a strongly absorbing substance, aircraft flux measurements from a stabilized platform have the potential to determine heating rate profiles. These measurement-based heating rate profiles provide useful data for heating rate closure studies and indirect estimates of single scattering albedo assumed in radiative transfer calculations.

Guan, Hong; Schmid, Beat; Bucholtz, Anthony; Bergstrom, Robert

2010-03-31

120

Investigation on the heat transfer characteristics during flow boiling of liquefied natural gas in a vertical micro-fin tube  

NASA Astrophysics Data System (ADS)

This paper presents an experimental investigation on the heat transfer characteristics of liquefied natural gas flow boiling in a vertical micro-fin tube. The effect of heat flux, mass flux and inlet pressure on the flow boiling heat transfer coefficients was analyzed. The Kim, Koyama, and two kinds of Wellsandt correlations with different Ftp coefficients were used to predict the flow boiling heat transfer coefficients. The predicted results showed that the Koyama correlation was the most accurate over the range of experimental conditions.

Xu, Bin; Shi, Yumei; Chen, Dongsheng

2014-03-01

121

Buoyancy-driven flows of a radiatively participating fluid in a vertical cylinder heated from below  

NASA Astrophysics Data System (ADS)

The effect of radiative energy transport on the onset and evolution of natural convective flows is studied in a Rayleigh-Benard system. Steady, axisymmetric flows of a radiatively participating fluid contained in a rigid-walled, vertical cylinder which is heated on the base, cooled on top, and insulated on the side wall are calculated by using the Galerkin FEM. Bifurcation analysis techniques are used to investigate the changes in the flow structure due to internal radiation. The results of this two-parameter study - where the Rayleigh number, Ra and optical thickness, tau, are varied - apply to fluids ranging from opaque to nearly transparent with respect to IR radiation. For any nonopaque fluid, internal radiation eliminates the static state that without radiation, exists for all values of the Rayleigh number. This heat transfer mechanism also destroys a symmetry of the system that relates clockwise and counterclockwise flows. The connectivity between characteristic flow families and the range of Ra where families are stable are found to depend greatly on tau. Results demonstrate the inadequacy of characterizing the behavior of this system using simple notions of radiative transfer in optically thick or thin media; the nonlinear interaction of radiation and flow are far more complicated than these asymptotic limits would imply.

Salinger, A. G.; Brandon, S.; Aris, R.; Derby, J. J.

1993-08-01

122

Ability of the direct wave of radar ground-coupled antenna for NDT of concrete structures  

Microsoft Academic Search

The research work presented in this paper aims at evaluating the potential of the direct wave of radar ground-coupled antennas for the on site physical characterization of concrete. According to studies highlighting the ability of radar reflected waves to characterize concrete, the potential of the direct wave is studied by systematic comparison of direct and reflected wave attenuations. Among the

Z. M. Sbartaï; S. Laurens; J.-P. Balayssac; G. Arliguie; G. Ballivy

2006-01-01

123

Effect of Pressure Stress Work and Viscous Dissipation in Natural Convection Flow along a Vertical Flat Plate with Heat Conduction  

Microsoft Academic Search

In this paper, the effect of viscous dissipation and pressure stress work on free convection flow along a vertical flat plate has been investigated. Heat conduction due to wall thickness b is considered in this investigation. With a goal to attain similarity solutions of the problem posed, the developed equations are made dimensionless by using suitable transformations. The non-dimensional equations

M. A. Alim

2008-01-01

124

A general correlation for saturated two-phase flow boiling heat transfer inside horizontal and vertical tubes  

Microsoft Academic Search

A simple correlation was developed earlier by Kandlikar (1983) for predicting saturated flow boiling heat transfer coefficients inside horizontal and vertical tubes. It was based on a model utilizing the contributions due to nucleate boiling and convective mechanisms. It incorporated a fluid-dependent parameter F{sub fl} in the nucleate boiling term. The predictive ability of the correlation for different refrigerants was

S. G. Kandlikar

1990-01-01

125

UNSTEADY HYDROMAGNETIC FREE CONVECTION FLOW OF A DISSIPATIVE AND RADIATING FLUID PAST A VERTICAL PLATE WITH CONSTANT HEAT FLUX  

Microsoft Academic Search

The effect of thermal radiation absorption on an unsteady free convective flow past a vertical plate is studied in the presence of a magnetic field and constant wall heat flux. Boundary layer equations are derived, and the resulting approximate nonlinear ordinary differential equations are solved analytically using asymptotic technique. A parametric study of all parameters involved is conducted, and a

A. Ogulu; O. D. Makinde

2008-01-01

126

Unsteady Heat and Mass Transfer MHD Flow of a Chemically Reacting Fluid Past an Impulsively Started Vertical Plate with Radiation  

NASA Astrophysics Data System (ADS)

The object of this study is to investigate thermal radiation in an unsteady fl ow of a viscous incompressible chemically reacting hydromagnetic fluid past an impulsively started vertical plate with heat and mass transfer. The fluid is a gray, absorbing-emitting, and nonscattering medium, and the Rosseland approximation is used to describe the radiative heat flux in the energy equation. The governing equations are solved using an implicit finite difference scheme of the Crank-Nicolson type. Numerical results for the transient velocity, temperature, concentration, local as well as average skin frictions, and the rate of heat and mass transfer are shown graphically.

Reddy, M. Gnaneswara

2014-09-01

127

Rayleigh-Benard Convection in a Vertical Cylinder Heated from Below with a Nonuniform Temperature  

NASA Astrophysics Data System (ADS)

Rayleigh-Benard convection in a vertical cylinder heated from below with a uniform bottom wall temperature has been studied extensively. At low aspect ratios, the flow starts as an axisymmetric pattern and gradually becomes non-axisymmetric when the Rayleigh number is increased. For aspect ratios around and greater than unity, the first stable flow pattern is a non-axisymmetric mode at all Rayleigh numbers beyond the first critical value. Almost all of the studies of natural convection flow in a cylinder have been concerned with a uniform bottom wall temperature. Even with this simple boundary condition, the flow is very complex, with a number of bifurcations in the Rayleigh number aspect ratio space. However, no previous studies have investigated what would happen if the bottom wall has a radially nonuniform temperature distribution. In this work, we have numerically studied the transitions in natural convection in a cylinder where the bottom wall has a parabolic temperature distribution and the side walls are perfectly conducting. The flow fields at two different nonuniformity factors and several Rayleigh numbers have been computed with a finite volume method.

Luo, Gang; Vanka, Pratap

2001-11-01

128

Unsteady Convection Flow and Heat Transfer over a Vertical Stretching Surface  

PubMed Central

This paper investigates the effect of thermal radiation on unsteady convection flow and heat transfer over a vertical permeable stretching surface in porous medium, where the effects of temperature dependent viscosity and thermal conductivity are also considered. By using a similarity transformation, the governing time-dependent boundary layer equations for momentum and thermal energy are first transformed into coupled, non-linear ordinary differential equations with variable coefficients. Numerical solutions to these equations subject to appropriate boundary conditions are obtained by the numerical shooting technique with fourth-fifth order Runge-Kutta scheme. Numerical results show that as viscosity variation parameter increases both the absolute value of the surface friction coefficient and the absolute value of the surface temperature gradient increase whereas the temperature decreases slightly. With the increase of viscosity variation parameter, the velocity decreases near the sheet surface but increases far away from the surface of the sheet in the boundary layer. The increase in permeability parameter leads to the decrease in both the temperature and the absolute value of the surface friction coefficient, and the increase in both the velocity and the absolute value of the surface temperature gradient. PMID:25264737

Cai, Wenli; Su, Ning; Liu, Xiangdong

2014-01-01

129

High Rayleigh number convection in rectangular enclosures with differentially heated vertical walls and aspect ratios between zero and unity  

NASA Technical Reports Server (NTRS)

High Rayleigh number convection in a rectangular cavity with insulated horizontal surfaces and differentially heated vertical walls was analyzed for an arbitrary aspect ratio smaller than or equal to unity. Unlike previous analytical studies, a systematic method of solution based on linearization technique and analytical iteration procedure was developed to obtain approximate closed-form solutions for a wide range of aspect ratios. The predicted velocity and temperature fields are shown to be in excellent agreement with available experimental and numerical data.

Kassemi, Siavash A.

1988-01-01

130

Analysis of the performance of a vertically oriented, gas-loaded, variable-conductance heat pipe. Master's thesis  

Microsoft Academic Search

An analysis of steady-state operation of a vertically oriented, variable-conductance heat pipe is presented. The effects of binary mass diffusion, axial pipe wall conduction, and gravitational effects, caused by the difference in molecular weight of the non-condensible gas and the working fluid are incorporated. Analytical expressions for the conservation of mass, momentum, and energy are combined along with equations of

Glover

1986-01-01

131

Forced convection heat transfer from a wire inserted into a vertically-mounted pipe to liquid hydrogen flowing upward  

NASA Astrophysics Data System (ADS)

Forced convection heat transfer from a PtCo wire with a length of 120 mm and a diameter of 1.2 mm that was inserted into a vertically-mounted pipe with a diameter of 8.0 mm to liquid hydrogen flowing upward was measured with a quasi-steady increase of a heat generation rate for wide ranges of flow rate under saturated conditions. The pressures were varied from 0.4 MPa to 1.1 MPa. The non-boiling heat transfer characteristic agrees with that predicted by Dittus-Boelter correlation. The critical heat fluxes are higher for higher flow rates and lower pressures. Effect of Weber number on the CHF was clarified and a CHF correlation that can describe the experimental data is derived based on our correlation for a pipe.

Tatsumoto, H.; Shirai, Y.; Shiotsu, M.; Naruo, Y.; Kobayashi, H.; Inatani, Y.

2014-12-01

132

Numerical modeling of a 2K J-T heat exchanger used in Fermilab Vertical Test Stand VTS-1  

SciTech Connect

Fermilab Vertical Test Stand-1 (VTS-1) is in operation since 2007 for testing the superconducting RF cavities at 2 K. This test stand has single layer coiled finned tubes heat exchanger before J-T valve. A finite difference based thermal model has been developed in Engineering Equation Solver (EES) to study its thermal performance during filling and refilling to maintain the constant liquid level of test stand. The model is also useful to predict its performance under other various operating conditions and will be useful to design the similar kind of heat exchanger for future needs. Present paper discusses the different operational modes of this heat exchanger and its thermal characteristics under these operational modes. Results of this model have also been compared with the experimental data gathered from the VTS-1 heat exchanger and they are in good agreement with the present model.

Gupta, Prabhat Kumar [Raja Ramanna Centre for Advanced Technology (RRCAT), Indore (MP), India; Rabehl, Roger [FNAL

2014-07-01

133

Unsteady free convection flow near an infinite vertical plate with prescribed surface heat flux and skin friction  

NASA Astrophysics Data System (ADS)

The unsteady free convection flow of an incompressible viscous fluid over an infinite vertical plate, under prescribed forms of the surface shear and heat flux, is numerically studied. The governing partial differential equations are transformed in a non-dimensional system of nonlinear ordinary differential equations, whose solutions are obtained by means of the Bulirsch-Stoer method. The influence of pertinent parameters on the dimensionless velocity and temperature fields is graphically underlined. The friction parameter ? and the heat flux coefficient q have a meaningful influence especially on the velocity.

Sohail, A.; Samiulhaq; Vieru, D.

2014-02-01

134

Explicit formulas for laminar natural convection heat transfer along vertical cylinders with power-law wall temperature distribution  

NASA Astrophysics Data System (ADS)

Natural convection heat transfer coefficients for vertical cylinders with variable surface temperature distribution must be found by complex numerical integration of the corresponding system of governing differential equations. Its evaluation for practical heat transfer calculations is always based on more or less complex correlations fitted to numerical or experimental results. This paper presents alternative approximate formulas for the calculation of the local Nusselt number and heat transfer coefficient and for laminar natural convection around vertical cylinders with power-law wall temperature distribution. These formulae have been derived from the integration of the energy and momentum equations, following the integral method and assuming some simplifying hypothesis, and then, finally fitted to numerical results in order to improve their accuracy. The formula obtained, with only two fitted coefficients, is able to predict the corresponding Nusselt number with a maximum error of 7% over a very wide range of Prandtl numbers (0.1-100) and curvatures, from slender vertical cylinders and needles to the flat plate case, and for the power-law exponents of practical interest.

Muñoz-Cobo, José; Corberán, José; Chiva, Sergio

2002-06-01

135

MHD Free Convective Boundary Layer Flow of a Nanofluid past a Flat Vertical Plate with Newtonian Heating Boundary Condition  

PubMed Central

Steady two dimensional MHD laminar free convective boundary layer flows of an electrically conducting Newtonian nanofluid over a solid stationary vertical plate in a quiescent fluid taking into account the Newtonian heating boundary condition is investigated numerically. A magnetic field can be used to control the motion of an electrically conducting fluid in micro/nano scale systems used for transportation of fluid. The transport equations along with the boundary conditions are first converted into dimensionless form and then using linear group of transformations, the similarity governing equations are developed. The transformed equations are solved numerically using the Runge-Kutta-Fehlberg fourth-fifth order method with shooting technique. The effects of different controlling parameters, namely, Lewis number, Prandtl number, buoyancy ratio, thermophoresis, Brownian motion, magnetic field and Newtonian heating on the flow and heat transfer are investigated. The numerical results for the dimensionless axial velocity, temperature and nanoparticle volume fraction as well as the reduced Nusselt and Sherwood number have been presented graphically and discussed. It is found that the rate of heat and mass transfer increase as Newtonian heating parameter increases. The dimensionless velocity and temperature distributions increase with the increase of Newtonian heating parameter. The results of the reduced heat transfer rate is compared for convective heating boundary condition and found an excellent agreement. PMID:23166688

Uddin, Mohammed J.; Khan, Waqar A.; Ismail, Ahmed I.

2012-01-01

136

A complete conjugate conduction convection and radiation problem for a heated block in a vertical differentially heated square enclosure  

Microsoft Academic Search

The complete conjugate heat conduction, convection and radiation problem for a heated block in a differentially heated square\\u000a enclosure is solved by an operator-splitting pseudo-time-stepping finite element method. The main feature of the solution\\u000a procedure is that the multi-phases are treated as a single computational domain with unknown interfacial boundary conditions.\\u000a The temperature distribution in the heated block and in

Y. Liu; N. Phan-Thien

1999-01-01

137

Experimental investigation of free-convection heat transfer in vertical tube at large Grashof numbers / E. R. G. Eckert, A. J. Diaguila  

NASA Technical Reports Server (NTRS)

Local free-convection heat-transfer coefficients and temperature fields in the turbulent flow range were obtained within a vertical, stationary tube closed at the boom, heated along its walls, and having a length-to-diameter ratio of 5. Convective heat-transfer coefficients were correlated by the general relations for free-convection heat transfer. These coefficients, converted to dimensionless Nusselt numbers were 35 percent below known relations for vertical flat plates. Air temperature measurements within the tube indicated a thin boundary layer along the heated wall surface and unstable conditions in the air flow.

Eckert, E R G; Diaguila, A J

1952-01-01

138

A Review of Ground Coupled Heat Pump Models Used in Whole-Building Computer Simulation Programs  

E-print Network

are the most common: the g-function model developed by Eskilson (Eskilson, 1987) and the other is the duct storage (DST) model developed by Hellstr?m (Hellstr?m, 1989). Table 4. Brief development history for the numerical solutions Year Numerical... configurations have to be pre-computed and stored as a massive database (Yang et al., 2010). In addition, the g-function model developed by Eskilson does not explain the thermal resistance effects of the borehole elements, such as the pipe wall, the grout...

Do, S. L.; Haberl, J. S.

139

Numerical modelling the unsteady process of closed rectangular area radiant heating in conjugate formulation with accounting energy distribution along horizontal and vertical enclosure structures  

NASA Astrophysics Data System (ADS)

Mathematical modelling of unsteady convective-conductive heat exchange in premises, heated by infrared radiant heater is passed. Heat flux density from infrared radiant heater was calculated accounting energy distribution along horizontal and vertical building envelope. Comparison between zonal method and Lambert's law radiant energy distribution was done.

Nee, A. E.

2014-08-01

140

Experimental investigation on heat transfer and frictional characteristics of vertical upward rifled tube in supercritical CFB boiler  

SciTech Connect

Water wall design is a key issue for supercritical Circulating Fluidized Bed (CFB) boiler. On account of the good heat transfer performance, rifled tube is applied in the water wall design of a 600 MW supercritical CFB boiler in China. In order to investigate the heat transfer and frictional characteristics of the rifled tube with vertical upward flow, an in-depth experiment was conducted in the range of pressure from 12 to 30 MPa, mass flux from 230 to 1200 kg/(m{sup 2} s), and inner wall heat flux from 130 to 720 kW/m{sup 2}. The wall temperature distribution and pressure drop in the rifled tube were obtained in the experiment. The normal, enhanced and deteriorated heat transfer characteristics were also captured. In this paper, the effects of pressure, inner wall heat flux and mass flux on heat transfer characteristics are analyzed, the heat transfer mechanism and the frictional resistance performance are discussed, and the corresponding empirical correlations are presented. The experimental results show that the rifled tube can effectively prevent the occurrence of departure from nucleate boiling (DNB) and keep the tube wall temperature in a permissible range under the operating condition of supercritical CFB boiler. (author)

Yang, Dong; Pan, Jie; Zhu, Xiaojing; Bi, Qincheng; Chen, Tingkuan [State Key Laboratory of Multiphase Flow in Power Engineering, Xi'an Jiaotong University, Xi'an 710049 (China); Zhou, Chenn Q. [Department of Mechanical Engineering, Purdue University Calumet, Hammond, IN 46323 (United States)

2011-02-15

141

Numerical simulation of laminar natural convection in a laterally heated vertical cylindrical enclosure: application to crystal growth  

NASA Astrophysics Data System (ADS)

Laminar natural convection has been studied in a laterally heated vertical cylindrical enclosure with a free insulated surface and a centrally located constant temperature wall at the top. These conditions are a simplification of the conditions existing in a Czochralski crystal pulling system. The laminar, axisymmetric flow of a Newtonian, constant physical properties fluid under Boussinesq’s approximation has been considered. Governing equations in primitive variable form are solved numerically by control volume method. SIMPLE algorithm due to Patankar has been used for the numerical simulation. The effects of the constant wall heat flux boundary condition at the side wall have been investigated whereas the bottom wall is considered to be insulated. Streamlines and isotherms are presented for various Rayleigh numbers and Prandtl numbers. Heat flux vectors through the melt are plotted for selected cases. The axial velocity and temperature variations at different horizontal sections of the crucible have been presented graphically to explain the transport processes inside the crucible. It has been observed that in case of low Pr and high Ra, flow separation occurs at the vertical wall of the crucible which leads to an oscillatory flow as Ra increases. The investigation has been extended to the oscillatory regime of flow in the zone of supercritical Rayleigh numbers and some unsteady results are also presented. Finally a heat transfer correlation has been developed for steady-state case.

Roy, Subhransu; Roy, Abhra; Arora, R. C.

2006-01-01

142

The vertical structure of diabatic heating associated with the Madden-Julian oscillation simulated by the Goddard Laboratory for Atmospheres climate model  

NASA Technical Reports Server (NTRS)

The diabatic heating structure of the nine-layer Goddard Laboratory for Atmospheres model of the Madden-Julian oscillation (MJO) is illustrated with composite charts made for those times when this low-frequency mode reaches its maximum and minimum amplitudes. These composite charts compare the vertically integrated diabatic heating with potential functions, the vertical distribution of diabatic heating with the east-west mass flux function in the tropics, and the vertical profiles of diabatic heating at the centers of maximum and minimum MJO amplitude. Three interesting features of the model MJO's diabatic heating are revealed: (1) the maximum heating rate of this low-frequency mode is located over the Asian monsoon region and its amplitude is about a half of the maximum value of the seasonal mean heating rate in this region, (2) the vertical diabatic heating rate profile has a maximum at 500 mbar and resembles the seasonal mean total heating profile, and (3) the total diabatic heating is for the most part composed of the latent heat released by cumulus convection.

Chen, Tsing-Chang; Yen, Ming-Cheng; Pfaendtner, James; Sud, Y. C.

1993-01-01

143

Ocean Turbulence. Paper 2; One-Point Closure Model Momentum, Heat and Salt Vertical Diffusivities in the Presence of Shear  

NASA Technical Reports Server (NTRS)

We develop and test a 1-point closure turbulence model with the following features: 1) we include the salinity field and derive the expression for the vertical turbulent diffusivities of momentum K(sub m) , heat K(sub h) and salt K(sub s) as a function of two stability parameters: the Richardson number R(sub i) (stratification vs. shear) and the Turner number R(sub rho) (salinity gradient vs. temperature gradient). 2) to describe turbulent mixing below the mixed layer (ML), all previous models have adopted three adjustable "background diffusivities" for momentum, heat and salt. We propose a model that avoids such adjustable diffusivities. We assume that below the ML, the three diffusivities have the same functional dependence on R( sub i) and R(sub rho) as derived from the turbulence model. However, in order to compute R(sub i) below the ML, we use data of vertical shear due to wave-breaking.measured by Gargett et al. The procedure frees the model from adjustable background diffusivities and indeed we employ the same model throughout the entire vertical extent of the ocean. 3) in the local model, the turbulent diffusivities K(sub m,h,s) are given as analytical functions of R(sub i) and R(sub rho). 5) the model is used in an O-GCM and several results are presented to exhibit the effect of double diffusion processes. 6) the code is available upon request.

Canuto, V. M.; Howard, A.; Cheng, Y.; Dubovikov, M. S.

1999-01-01

144

LDA measurements and numerical simulation of the induced flow through a rectangular chamber containing a vertical cylindrical heat source  

NASA Astrophysics Data System (ADS)

Experimental (LDA) and computational (CFD) investigations of steady, laminar natural convection in a horizontally vented chamber containing a vertical heated cylinder at the center are reported. The heated cylinder was located on the lower adiabatic wall of the chamber and was 2/3 the height of the chamber. The cylinder surfaces were maintained at a constant temperature. The chamber inlet and outlet were located at the bottom and top of facing vertical walls, respectively. In this study, experiments were conducted using laser-Doppler anemometry (LDA) with a two-component Ar-Ion laser connected to two burst spectrum analyzers (BSA). Velocity profiles (of both vertical and horizontal velocity components) were measured at the inlet, outlet and at other locations inside the chamber. For the numerical simulation (3-D, steady-state, laminar) the governing equations were solved using the computational fluid dynamics code PHOENICS. Comparison of the experimental data with computational results showed satisfactory agreement and the importance that LDA measurements have in verifying CFD simulations.

Baskaya, S.; Gilchrist, A.; Fraser, Simon M.

1993-08-01

145

Predicting the fluid temperature at the exit of the vertical ground heat exchangers  

Microsoft Academic Search

The energy analysis of ground source heat pump systems is based on the instantaneous fluid temperature at the ground heat exchanger outlet. This temperature defines the ground source heat pump coefficient of performance (COP) and hence the electricity consumption required in order to fulfill the energy demands of the building. The aim of this work is to present a model

?. Michopoulos; ?. ?yriakis

2009-01-01

146

Effects of wetted walls on laminar natural convection between vertical parallel plates with asymmetric heating  

Microsoft Academic Search

A numerical analysis is carried out to investigate the effect of latent heat transfer, in association with the evaporation or condensation of the water vapor on the wetted channel walls which are under asymmetric heating, on the natural convection heat transfer. Major nondimensional groups identified are GrT, GrM, Pr and Sc. Results for Nusselt and Sherwood numbers are specifically presented

W. M. Yan; Y. L. Tsay; T. F. Lin

1990-01-01

147

Long-term model-based performance of ground heat exchangers  

Microsoft Academic Search

Ground-coupled heat pumps are highly efficient HVAC systems that provide heating and cooling for buildings. The high initial cost of drilling boreholes is one of the primary reasons that limit the widespread application of a ground-coupled heat pump. It is very important to develop numerical models that are capable of predicting and evaluating the performance of the ground heat exchanger

Wei Ruan; William Travis Horton

2011-01-01

148

Evaporation heat transfer and friction characteristics of R-134a flowing downward in a vertical corrugated tube  

SciTech Connect

Differently from most previous studies, the heat transfer and friction characteristics of the pure refrigerant HFC-134a during evaporation inside a vertical corrugated tube are experimentally investigated. The double tube test sections are 0.5 m long with refrigerant flowing in the inner tube and heating water flowing in the annulus. The inner tubes are one smooth tube and two corrugated tubes, which are constructed from smooth copper tube of 8.7 mm inner diameter. The test runs are performed at evaporating temperatures of 10, 15, and 20 C, heat fluxes of 20, 25, and 30 kW/m{sup 2}, and mass fluxes of 200, 300, and 400 kg/m{sup 2} s. The quality of the refrigerant in the test section is calculated using the temperature and pressure obtained from the experiment. The pressure drop across the test section is measured directly by a differential pressure transducer. The effects of heat flux, mass flux, and evaporation temperature on the heat transfer coefficient and two-phase friction factor are also discussed. It is found that the percentage increases of the heat transfer coefficient and the two-phase friction factor of the corrugated tubes compared with those of the smooth tube are approximately 0-10% and 70-140%, respectively. (author)

Aroonrat, Kanit; Wongwises, Somchai [Fluid Mechanics, Thermal Engineering and Multiphase Flow Research Lab. (FUTURE), Department of Mechanical Engineering, King Mongkut's University of Technology Thonburi, Bangmod, Bangkok 10140 (Thailand)

2011-01-15

149

Flow and heat transfer characteristics of laminar mixed convection of water with sub-millimeter bubbles in a vertical channel  

NASA Astrophysics Data System (ADS)

Laminar mixed-convection heat transfer is widely seen in compact heat exchangers. Injection of sub-millimeter bubbles is considered as one of the efficient techniques for enhancing laminar mixed-convection heat transfer for liquids. However, the effects of sub-millimeter-bubble injection on the laminar mixed-convection heat transfer are poorly understood. In this study, we experimentally investigate flow and heat transfer characteristics of the laminar mixed-convection of water with sub-millimeter bubbles in a vertical channel. The thermocouples and a PTV (Particle Tracking Velocimetry) technique are used for the temperature and velocity measurements, respectively. Tap water is used for working fluid and hydrogen bubbles generated by electrolysis of water are used as the sub-millimeter bubbles. The Reynolds number of the main flow ranges from 100 to 150. Our results show that the ratio of the heat transfer coefficient with sub-millimeter-bubble injection to that without injection decreases as the Reynolds number increases. It is found from the liquid velocity measurements that this decrease is mainly due to a decrease in the "bubble advection effect".

Kitagawa, A.; Kimura, K.; Endo, H.; Hagiwara, Y.

2009-02-01

150

Natural convection along a heated vertical plate immersed in a nonlinearly stratified medium: application to liquefied gas storage  

NASA Astrophysics Data System (ADS)

We consider free convection driven by a heated vertical plate immersed in a nonlinearly stratified medium. The plate supplies a uniform horizontal heat flux to a fluid, the bulk of which has a stable stratification, characterized by a non-uniform vertical temperature gradient. This gradient is assumed to have a typical length scale of variation, denoted Z0, while 0, and the physical properties of the medium.We then apply the new theory to the natural convection affecting the vapour phase in a liquefied pure gas tank (e.g. the cryogenic storage of hydrogen). It is assumed that the cylindrical storage tank is subject to a constant uniform heat flux on its lateral and top walls. We are interested in the vapour motion above a residual layer of liquid in equilibrium with the vapour. High-precision axisymmetric numerical computations show that the flow remains steady for a large range of parameters, and that a bulk stratification characterized by a quadratic temperature profile is undoubtedly present. The application of the theory permits a comparison of the numerical and analytic results, showing that the theory satisfactorily predicts the primary dynamical and thermal properties of the storage tank.

Forestier, M.; Haldenwang, P.

151

Impact of black carbon aerosol over Italian basin valleys: high resolution measurements along vertical profiles, radiative forcing and heating rate  

NASA Astrophysics Data System (ADS)

This study presents the first measured high resolution vertical profiles of black carbon and calculation of aerosol radiative forcing and atmospheric heating rates in the lower troposphere, over Italy and Europe. The calculation is based on vertical profiles of black carbon, aerosol number size distribution and chemical composition measured over three Italian basin valleys (Po Valley, Terni Valley and Passiria Valley) by means of a tethered balloon equipped with a micro-Aethalometer, an optical particle counter (OPC), a cascade impactor and a meteorological station. Experimental measurements allowed first the calculation of the aerosol optical properties. In this respect, the aerosol refractive index was calculated along height using the effective medium approximation applied to aerosol chemical composition; Mie calculations were performed on the base of the OPC number-size distribution which was corrected for the ambient aerosol refractive index. The obtained vertical profiles of aerosol optical properties were validated with AERONET data and were used as input to the radiative transfer model libRadtran. Vertical profiles of direct aerosol radiative forcing, atmospheric absorption and heating rate were calculated. Reported results evidenced common behaviours along height over the investigated basin valleys (an orographic feature present elsewhere in Europe): at the mixing height a marked a concentration drop of both BC (range: -48.4 ± 5.3% to -69.1 ± 5.5%) and particle number concentration (range: -23.9 ± 4.3% to -46.5 ± 7.3%) was evidenced. More in details, the percentage decrease of BC along height was higher than that measured for aerosol and thus, the BC content of the aerosol decreased along height; correspondingly the Single Scattering Albedo increased along height (range: +4.9 ± 2.2% to +7.4 ± 1.0%). Therefore, the highest atmospheric absorption was observed below the mixing height (range: +0.5 ± 0.1 W m-2 to +2.5 ± 0.2 W m-2) with the associated heating rate characterized by a vertical negative gradient (range: -0.5 K day-1 km-1 to -6.8 K day-1 km-1). As a result, the Black Carbon loaded below the mixing height potentially weakens the ground-based thermal inversions (common over basin valleys) thus promoting an increase of the atmospheric dispersal conditions.

Ferrero, L.; Castelli, M.; Ferrini, B. S.; Moscatelli, M.; Perrone, M. G.; Sangiorgi, G.; Rovelli, G.; D'Angelo, L.; Moroni, B.; Scardazza, F.; Mocnik, G.; Bolzacchini, E.; Petitta, M.; Cappelletti, D.

2014-01-01

152

Theoretical analysis of film condensation heat transfer inside vertical mini triangular channels  

Microsoft Academic Search

An analytical model is presented for predicting film condensation of vapor flowing inside a vertical mini triangular channel. The concurrent liquid–vapor two-phase flow field is divided into three zones: the thin liquid film flow on the sidewall, the condensate flow in the corners, and the vapor core flow in the center. The model takes into account the effects of capillary

T. S. Zhao; Q. Liao

2002-01-01

153

Modeling Vertical Structure and Heat Transport within the Oceans of Ice-covered Worlds (Invited)  

Microsoft Academic Search

Indirect observational evidence provides a strong case for liquid oceans beneath the icy crust of Europa and several other frozen moons in the outer solar system. However, little is known about the fluid circulation within these exotic oceans. As a first step toward understanding circulations driven by buoyancy (rather than mechanical forcing from tides), one must understand the typical vertical

J. C. Goodman

2010-01-01

154

Dufour effect on unsteady natural convection flow past an infinite vertical plate with constant heat and mass fluxes  

NASA Astrophysics Data System (ADS)

In this paper, Dufour effect on unsteady natural convection flow near an infinite vertical plate with constant heat and mass fluxes has been investigated analytically. The resulting system of coupled linear partial differential equations is solved using the Laplace transform technique. Closed form analytical solutions are obtained for the velocity, temperature and concentration fields, skin-friction, Nusselt and Sherwood numbers. The effect of Dufour number on the velocity and temperature fields, skin-friction and Nusselt number have been discussed through graphs and tables. The study revealed that the Dufour number has significant influence on the velocity and temperature fields.

Tippa, Sowmya; Narahari, M.; Pendyala, Rajashekhar

2014-10-01

155

Stability of a vertical liquid film with consideration of the marangoni effect and heat exchange with the environment  

NASA Astrophysics Data System (ADS)

The stability of a free vertical liquid film under the combined action of gravity and thermocapillary forces has been studied. An exact solution of the Navier-Stokes and thermal conductivity equations is obtained for the case of plane steady flow with constant film thickness. It is shown that if the free surfaces of the film are perfectly heat insulated, the liquid flow rate through the cross section of the layer is zero. It is found that to close the model with consideration of the heat exchange with the environment, it is necessary to specify the liquid flow rate and the derivative of the temperature with respect to the longitudinal coordinate or the flow rate and the film thickness. The stability of the solution with constant film thickness at small wave numbers is studied. A solution of the spectral problem for perturbations in the form of damped oscillations is obtained.

Burmistrova, O. A.

2014-05-01

156

Multiple states, stability and bifurcations of natural convection in a rectangular cavity with partially heated vertical walls  

NASA Astrophysics Data System (ADS)

The multiplicity, stability and bifurcations of low-Prandtl-number steady natural convection in a two-dimensional rectangular cavity with partially and symmetrically heated vertical walls are studied numerically. The problem represents a simple model of a set-up in which the height of the heating element is less than the height of the molten zone. The calculations are carried out by the global spectral Galerkin method. Linear stability analysis with respect to two-dimensional perturbations, a weakly nonlinear approximation of slightly supercritical states and the arclength path-continuation technique are implemented. The symmetry-breaking and Hopf bifurcations of the flow are studied for aspect ratio (height/length) varying from 1 to 6. It is found that, with increasing Grashof number, the flow undergoes a series of turning-point bifurcations. Folding of the solution branches leads to a multiplicity of steady (and, possibly, oscillatory) states that sometimes reaches more than a dozen distinct steady solutions. The stability of each branch is studied separately. Stability and bifurcation diagrams, patterns of steady and oscillatory flows, and patterns of the most dangerous perturbations are reported. Separated stable steady-state branches are found at certain values of the governing parameters. The appearance of the complicated multiplicity is explained by the development of the stably and unstably stratified regions, where the damping and the Rayleigh Bénard instability mechanisms compete with the primary buoyancy force localized near the heated parts of the vertical boundaries. The study is carried out for a low-Prandtl-number fluid with Pr {=} 0.021. It is shown that the observed phenomena also occur at larger Prandtl numbers, which is illustrated for Pr {=} 10. Similar three-dimensional instabilities that occur in a cylinder with a partially heated sidewall are discussed.

Erenburg, V.; Gelfgat, A. Yu.; Kit, E.; Bar-Yoseph, P. Z.; Solan, A.

2003-10-01

157

Chaotic dynamics of a convection roll in a highly confined, vertical, differentially heated fluid layer  

NASA Astrophysics Data System (ADS)

Direct numerical simulation is used to study the air flow between two vertical plates maintained at different temperatures. The periodic dimensions of the plates are small so as to accommodate only one flow structure, which consists of a convection roll with oblique vorticity braids. At lower Rayleigh numbers, the roll and the braids grow and shrink alternatively following a cyclical process. As the Rayleigh number is increased, the flow becomes temporally chaotic through a period-doubling cascade. Windows corresponding to multiperiodic regimes and interior crises are observed. As the Rayleigh number is further increased, the structure intermittently switches between two vertical positions, which is seen to correspond to an "attractor-merging" crisis. The chaotic flow dynamics are characterized and the corresponding physical mechanisms are identified. We show that some of the flow key features, such as the chaotic oscillation and intermittency, can be captured by a low-order model.

Gao, Zhenlan; Podvin, Berengere; Sergent, Anne; Xin, Shihe

2015-01-01

158

Geothermal Studies of the Outokumpu Deep Drill Hole, Finland: Vertical variation in heat flow and palaeoclimatic implications  

NASA Astrophysics Data System (ADS)

Detailed geothermal studies of deep drill holes provide insights to heat transfer processes in the crust, and allow separation of different factors involved, such as palaeoclimatic and structural conductive effects as well as advective fluid flow effects. We present high resolution geothermal results of the 2,516 m deep Outokumpu Deep Drill Hole in eastern Finland drilled in 2004-2005 into a Palaeoproterozoic formation with metasedimentary rocks, ophiolite-derived altered ultramafic rocks and pegmatitic granite. The down-hole temperatures have been logged five times after end of drilling and extend to day 948 after drilling. The hole is completely cored (79% core coverage) and thermal conductivity measurements were done at 1 m intervals. The geothermal results on temperature gradient, thermal conductivity and heat flow density yield an exceptionally detailed data set and indicate a significant vertical variation in gradient and heat flow density. Heat flow density increases from about 28-32 mW m-2 in the uppermost 1000 m to 40-45 mW m-2 at depths exceeding 2000 m. The estimated undisturbed surface heat flow value is 42 mWm-2. We present results on forward and inverse transient conductive models which suggest that the vertical variation in heat flow can mostly be attributed to a palaeoclimatic effect due to ground surface temperature (GST) variations during the last 100,000 years. The modelling suggests that the average GST was about -3…-4°C during the Weichselian glaciation. Holocene GST values are within ±2 degree from the present average GST in Outokumpu (5°C). The topographic hydraulic heads and hydraulic conductivity of crystalline rocks are low which suggests that advective heat transfer in the formation is not significant. The slow replacement of fresh flushing water by saline formation fluids is observed in the hole, but it does not generate significant thermal disturbances in the logs. On the other hand, free sluggish thermal convection is present in the large diameter (22 cm) borehole, and temperature variations in the range of few mK to 0.01 K occur over times of minutes to tens of minutes. Theory suggests that convection cells are about as tall as the drill hole diameter, and thus the free convection is expected to generate only local thermal 'noise'not affecting the general geothermal results. Reference: Physics of the Earth and Planetary Interiors 188 (2011) 9-25 (doi:10.1016/j.pepi.2011.06.002)

Kukkonen, I. T.; Rath, V.; Kivekäs, L.; Šafanda, J.; ?ermak, V.

2012-04-01

159

The flow structure under mixed convection in a uniformly heated vertical pipe  

E-print Network

For decay heat removal systems in the conceptual Gas-cooled Fast Reactor (GFR) currently under development, passive emergency cooling using natural circulation of a gas at an elevated pressure is being considered. Since ...

Lee, Jeongik

2005-01-01

160

Numerical modelling of temperature fields in the flow boiling liquid through a vertical minichannel with an enhanced heating surface  

NASA Astrophysics Data System (ADS)

The paper presents results of heat transfer research on flow boiling in a rectangular minichannel positioned vertically, with an enhanced surface. One of the channel walls was made of thin foil powered by direct current. This foil is enhanced on the side contacting fluid in the minichannel. It is possible to observe both surfaces of the minichannel through two openings covered with glass panes. One allows detecting temperature of the plain side of the foil by liquid crystal thermography. The opposite surface of the minichannel (from the enhanced side of the foil) can be observed through the other glass pane. The observations of the flow structures allowed to calculate the void fraction for some cross-sections of selected two phase flow images. In mathematical modelling of the considered process stationary heat transfer in a glass pane, heating foil and boiling liquid can be described with Laplace equation, Poisson equation and energy equation, respectively. For completeness of the model a corresponding system of boundary conditions was given. The two-dimensional temperature fields of glass pane, heating foil and fluid was computed with the Trefftz method. The equalizing calculus used to smooth the measured data has reduced errors.

Ho?ejowska, Sylwia; Piasecka, Magdalena

2014-03-01

161

Interaction of surface radiation with conjugate mixed convection from a vertical channel with multiple discrete heat sources  

NASA Astrophysics Data System (ADS)

Important results of a numerical study performed on combined conduction-mixed convection-surface radiation from a vertical channel equipped with three identical flush-mounted discrete heat sources in its left wall are provided here. The channel has walls of identical height with the spacing varied by varying its aspect ratio (AR). The cooling medium is air that is considered to be radiatively transparent. The heat generated in the channel gets conducted along its walls before getting dissipated by mixed convection and radiation. The governing equations for fluid flow and heat transfer are considered without boundary layer approximations and are transformed into vorticity-stream function form and are later normalized. The resulting equations are solved, along with relevant boundary conditions, making use of the finite volume method. The computer code written for the purpose is validated both for fluid flow and heat transfer results with those available in the literature. Detailed parametric studies have been performed and the effects of modified Richardson number, surface emissivity, thermal conductivity and AR on various pertinent results have been looked into. The significance of radiation in various regimes of mixed convection has been elucidated. The relative contributions of mixed convection and radiation in carrying the mandated cooling load have been thoroughly explored.

Londhe, Shrikant D.; Gururaja Rao, C.

2014-09-01

162

Magnetohydrodynamic peristaltic flow of a hyperbolic tangent fluid in a vertical asymmetric channel with heat transfer  

NASA Astrophysics Data System (ADS)

In the present paper we discuss the magnetohydrodynamic (MHD) peristaltic flow of a hyperbolic tangent fluid model in a vertical asymmetric channel under a zero Reynolds number and long wavelength approximation. Exact solution of the temperature equation in the absence of dissipation term has been computed and the analytical expression for stream function and axial pressure gradient are established. The flow is analyzed in a wave frame of reference moving with the velocity of wave. The expression for pressure rise has been computed numerically. The physical features of pertinent parameters are analyzed by plotting graphs and discussed in detail.

Nadeem, Sohail; Akram, Safia

2011-04-01

163

A susceptor with a ?-shaped slot in a vertical MOCVD reactor by induction heating  

NASA Astrophysics Data System (ADS)

By using the numerical simulation for the temperature field in the metal organic vapor deposition (MOCVD) reactor by induction heating, it is found that the temperature distribution in the conventional cylinder-shaped susceptor is nonuniform due to the skin effect of the induced current, which makes the temperature distribution of the wafer nonuniform. Therefore, a novel susceptor with a ?-shaped slot is proposed. This slot changes the mode and the rate of the heat transfer in the susceptor, which improves the uniformity of the temperature distribution in the wafer. By using the finite element method (FEM), the susceptor with this structure for heating a wafer of four inches in diameter is optimized. It is observed that the optimized susceptor with the ?-shaped slot makes the uniformity of the temperature distribution in the wafer improve by more than 85%, and a good uniformity of temperature distributions is kept under different wafer temperatures, which may be beneficial to the film growth.

Zhiming, Li; Hailing, Li; Xiaobing, Gan; Haiying, Jiang; Jinping, Li; Xiaoqian, Fu; Yanbin, Han; Yingjie, Xia; Jianqin, Yin; Yimei, Huang; Shigang, Hu

2014-09-01

164

Model Relating Heat-Flow Values near, and Vertical Velocities of Mass Transport beneath, Oceanic Rises  

Microsoft Academic Search

The heat transport equation along the stagnation point streamline is solved by the method of matched asymptotic expansions as a first approximation of the temperature distribution directly beneath an oceanic rise. Far below the ocean bottom the temperature T(Z, ) is given by the temperature calculated for adiabatic (upward) displacement. In a narrow region near the surface, the thermal boundary

Thomas C. Hanks

1971-01-01

165

Effects of nanoparticle migration on hydromagnetic mixed convection of alumina/water nanofluid in vertical channels with asymmetric heating  

NASA Astrophysics Data System (ADS)

The effects of nanoparticle migration on mixed convection of alumina/water nanofluid inside a vertical channel in the presence of a uniform magnetic field have been investigated theoretically. Walls are subjected to different heat fluxes; q lw ' ' for the left wall and q rw ' ' for the right wall, and nanoparticles are assumed to have a slip velocity relative to the base fluid induced by the Brownian motion and thermophoresis. Considering hydrodynamically and thermally fully developed flow, the governing equations including continuity, momentum, and energy equations have been reduced to two-point ordinary boundary value differential equations and they have been solved numerically. It is shown that nanoparticles eject themselves from the heated walls, construct a depleted region, and accumulate in the core region, but they are more likely to accumulate toward the wall with the lower heat flux. In addition, inclusion of nanoparticles in the presence of a magnetic field has a negative effect on the performance.

Malvandi, A.; Ganji, D. D.

2015-02-01

166

Nonsimilar hydromagnetic simultaneous heat and mass transfer by mixed convection from a vertical plate embedded in a uniform porous medium  

SciTech Connect

Simultaneous heat and mass transfer from different geometries embedded in porous media has many engineering and geophysical applications, such as migration of water in geothermal reservoirs, underground spreading of chemical wastes and other pollutants, thermal insulation, enhanced oil recovery, packed-bed catalytic reactors, cooling of nuclear reactors, grain storage, and evaporative cooling and solidification. This work considers steady, laminar, hydromagnetic simultaneous heat and mass transfer by mixed convection flow over a permeable vertical plate immersed in a uniform porous medium for the cases of power law variations of both the wall temperature and concentration and the wall heat flux and mass flux. Appropriate transformations are employed to transform the governing differential equations to a nonsimilar form. The transformed equations are solved numerically by an accurate, implicit, iterative, finite difference method. The obtained results are validated by favorable comparisons with previously published work on special cases of the problem. A parametric study illustrating the influence of all involved parameters on the local Nusselt and Sherwood numbers is conducted. The results of this parametric study are shown graphically, and the physical aspects of the problem are discussed.

Chamkha, A.J.; Khaled, A.R.A. [Kuwait Univ., Safat (Kuwait). Dept. of Mechanical and Industrial Engineering

1999-08-27

167

Epitaxial growth of thick 4H?SiC layers in a vertical radiant-heating reactor  

NASA Astrophysics Data System (ADS)

A vertical radiant-heating reactor has been developed for thick silicon carbide (SiC) epitaxial growth, in which the susceptor and substrates are heated by radiation from the hot wall. The benefit of the heating and sample-holding method is demonstrated by improvements in the curvature of crystal bending and FWHM of X-ray ?-rocking curves followed by epitaxial growth. The typical growth rate is 13-16 ?m/h at 1530-1550°C at the susceptor top under reduced pressure as low as 50-70 mbar. Low background doping at low 10 13 cm -3 ( Nd- Na) was achieved, and some of the 4H-SiC epilayers exhibited a high resistivity. We also succeeded in growing a 4H-SiC epilayer over 240 ?m-thick with minimal surface roughness. Little sign of impurities was observed by low-temperature photoluminescence (LTPL), and no impurities (Al, B, Ti, V and Cr) exceeding 1×10 14 cm -3 were found by secondary ion mass spectroscopy (SIMS) for a 150 ?m-thick 4H-SiC epilayer. Thickness and doping uniformity along the gas flow of ˜5% and ˜11%, respectively, were obtained for 2-in substrates. Molten KOH etching analysis revealed that some of the micropipes were dissociated into closed core screw dislocations during epitaxial growth. The electrical performance of high-voltage devices was also demonstrated.

Tsuchida, H.; Kamata, I.; Jikimoto, T.; Izumi, K.

2002-04-01

168

Magnetohydrodynamic non-Darcy mixed convection heat transfer from a vertical heated plate embedded in a porous medium with variable porosity  

NASA Astrophysics Data System (ADS)

A numerical model is developed to study magnetohydrodynamics (MHD) mixed convection from a heated vertical plate embedded in a Newtonian fluid saturated sparsely packed porous medium by considering the variation of permeability, porosity and thermal conductivity. The boundary layer flow in the porous medium is governed by Forchheimer-Brinkman extended Darcy model. The conservation equations that govern the problem are reduced to a system of non-linear ordinary differential equations by using similarity transformations. Because of non-linearity, the governing equations are solved numerically. The effects of magnetic field on velocity and temperature distributions are studied in detail by considering uniform permeability (UP) and variable permeability (VP) of the porous medium and the results are discussed graphically. Besides, skin friction and Nusselt number are also computed for various physical parameters governing the problem under consideration. It is found that the inertial parameter has a significant influence in increasing the flow field and the rate of heat transfer for variable permeability case. The important finding of the present work is that the magnetic field has considerable effects on the boundary layer velocity and on the rate of heat transfer for variable permeability of the porous medium. Further, the results obtained under the limiting conditions were found to be in good agreement with the existing ones.

Pal, Dulal

2010-12-01

169

Numerical study of natural convection in a cylindrical cavity bounded by a partially-heated vertical wall  

NASA Astrophysics Data System (ADS)

Natural convection in a cylindrical cavity is numerically investigated. The cavity is bounded by a vertical cylindrical wall with aspect ratio 10 (= height/radius), and in its central region a heat source with height equal to the diameter is located. The numerical method used is an explicit finite difference scheme with a fourth-order accuracy for the non-linear convective terms. In the range of small Rayleigh numbers Ra and fixed Prandtl number Pr = 0.72 for air, a steady-state flow consists of three convection cells corresponding to the thermal boundary condition imposed at the vertical wall. At the critical value of Ra estimated as about 6.9 × 10 3, the flow is changed from a steady-state to an oscillatory state. In the range of large Ra, it can be observed that the oscillatory convection exhibits a 2 n-bifurcations process: simply periodic ? doubly periodic ? quadruply periodic ? eight-fold periodic and non-periodic motions with intermittent noise.

Sakata, Mitsuo

1996-09-01

170

association of companies and the Edison Electric Institute (1953). Their final report cites investigations from 1945 through 1953 and includes correlated information on coil data, heat  

E-print Network

, and the significantly higher ground heat transfer in the cooling mode leads to the conclusion that the ground heat of electricity has increased, interest has again been focused on the ground-coupled heat pump system. Metz (1979) reports on ground-coupled heat pump research at Brookhaven National Laboratory including the testing

Oak Ridge National Laboratory

171

Study of dynamic structure and heat and mass transfer of a vertical ceramic tiles dryer using CFD simulations  

NASA Astrophysics Data System (ADS)

In this study, we developed a two-dimensional Computational Fluid Dynamics (CFD) model to simulate dynamic structure and heat and mass transfer of a vertical ceramic tiles dryer (EVA 702). The carrier's motion imposed the choice of a dynamic mesh based on two methods: "spring based smoothing" and "local remeshing". The dryer airflow is considered as turbulent ( Re = 1.09 × 105 at the dryer inlet), therefore the Re-Normalization Group model with Enhanced Wall Treatment was used as a turbulence model. The resolution of the governing equation was performed with Fluent 6.3 whose capacities do not allow the direct resolution of drying problems. Thus, a user defined scalar equation was inserted in the CFD code to model moisture content diffusion into tiles. User-defined functions were implemented to define carriers' motion, thermo-physical properties… etc. We adopted also a "two-step" simulation method: in the first step, we follow the heat transfer coefficient evolution (Hc). In the second step, we determine the mass transfer coefficient (Hm) and the features fields of drying air and ceramic tiles. The found results in mixed convection mode (Fr = 5.39 at the dryer inlet) were used to describe dynamic and thermal fields of airflow and heat and mass transfer close to the ceramic tiles. The response of ceramic tiles to heat and mass transfer was studied based on Biot numbers. The evolutions of averages temperature and moisture content of ceramic tiles were analyzed. Lastly, comparison between experimental and numerical results showed a good agreement.

Kriaa, Wassim; Bejaoui, Salma; Mhiri, Hatem; Le Palec, Georges; Bournot, Philippe

2014-02-01

172

A Vertical Resonance Heating Model for X- or Peanut-Shaped Galactic Bulges  

E-print Network

We explore a second order Hamiltonian vertical resonance model for X-shaped galactic bulges. We examine N-body simulations and find that due to the bar slowing down and disk thickening during bar buckling, the resonance and associated peanut-shape moves outward. The peanut-shape is consistent with the location of the resonance, independent of whether the bar buckled or not. We estimate the resonance width from the potential m=4 Fourier component and find that the resonance is narrow, affecting orbits in angular momentum over a range dL/L ~ 0.05. As the resonance moves outward, stars originally in the mid plane are forced out of the mid plane and into orbits just within the resonance separatrix. The height of these orbits, estimated from the Hamiltonian model, is consistent with the peanut-shape height. The X-shape is comprised of stars in these orbits as they are the only ones that would support the peanut-shape in the drifting system. The resonance condition in the Milky Way bulge relates the mid-plane mass ...

Quillen, Alice C; Sharma, Sanjib; Di Matteo, Paola

2013-01-01

173

Ocean Turbulence. Paper 3; Two-Point Closure Model Momentum, Heat and Salt Vertical Diffusivities in the Presence of Shear  

NASA Technical Reports Server (NTRS)

In papers 1 and 2 we have presented the results of the most updated 1-point closure model for the turbulent vertical diffusivities of momentum, heat and salt, K(sub m,h,s). In this paper, we derive the analytic expressions for K(sub m,h,s) using a new 2-point closure model that has recently been developed and successfully tested against some approx. 80 turbulence statistics for different flows. The new model has no free parameters. The expressions for K(sub m, h. s) are analytical functions of two stability parameters: the Turner number R(sub rho) (salinity gradient/temperature gradient) and the Richardson number R(sub i) (temperature gradient/shear). The turbulent kinetic energy K and its rate of dissipation may be taken local or non-local (K-epsilon model). Contrary to all previous models that to describe turbulent mixing below the mixed layer (ML) have adopted three adjustable "background diffusivities" for momentum. heat and salt, we propose a model that avoids such adjustable diffusivities. We assume that below the ML, K(sub m,h,s) have the same functional dependence on R(sub i) and R(sub rho) derived from the turbulence model. However, in order to compute R(sub i) below the ML, we use data of vertical shear due to wave-breaking measured by Gargett et al. (1981). The procedure frees the model from adjustable background diffusivities and indeed we use the same model throughout the entire vertical extent of the ocean. Using the new K(sub m,h, s), we run an O-GCM and present a variety of results that we compare with Levitus and the KPP model. Since the traditional 1-point (used in papers 1 and 2) and the new 2-point closure models used here represent different modeling philosophies and procedures, testing them in an O-GCM is indispensable. The basic motivation is to show that the new 2-point closure model gives results that are overall superior to the 1-point closure in spite of the fact that the latter rely on several adjustable parameters while the new 2-point closure has none. After the extensive comparisons presented in papers 1 and 2, we conclude that the new model presented here is overall superior for it not only is parameter free but also 2 because is part of a more general turbulence model that has been previously successfully tested on a wide variety of other types of turbulent flows.

Canuto, V. M.; Dubovikov, M. S.; Howard, A.; Cheng, Y.

1999-01-01

174

Part 2: Computational simulation of flow through a vertical slurry heat exchanger  

SciTech Connect

An effort was made to model the slurry flow computationally through the heat exchanger in Part 1. For that aim FLOW-3D a commercially available fluid mechanics and heat transfer finite difference code was used. The code was run on the Cray Y-MP 2/216, a two-processor supercomputer with 16 megawords (128 MB) of central memory and a 32 megaword I/O subsystem. At the time the simulation model was being formulated on the FLOW-3D the authors of the code were not aware that the code had been used for a similar purpose and were interested in finding out its capabilities. The modeling approach used three simulation strategies beginning with a single fluid model using properties of water and simulating 683 particles introduced at the inlet to the heat exchanger and were tracked towards the outlet. These particles were neutrally buoyant and had zero volume and mass. These were fluid particles that were tracked through the flow geometry. A recent addition to the model was the possibility that particles have their own inertia term. Each particle has its own independent velocity and satisfies the equation of motion as well. In this second simulation the particles were given a density similar to glass of 2.5 g/cm{sup 3} and a volume of 0.00818 cm{sup 3} which is the volume of a single spherical particle 250 {micro}m in diameter. Two different viscous drag coefficients were specified as a function of the relative velocity locally between the fluid and the particle. Also a coefficient of restitution of one (specular reflections) between particles was assigned. The last method used was with the help of a drift flux model. These models usually work well if the relative velocities are not too large between the two-phases. The best options chosen for that model is the two incompressible fluid model with different densities. No diffusion coefficients were given for each fluid so that the flow code simulates two immiscible materials. In all these models a k-{var{underscore}epsilon} turbulent flow model is used because of the expected Reynolds numbers of the flow. It was found from the limited testing on these models that the particle model with different fluid and particle densities is the most realistic and can be enhanced by increasing the number of particles allowed by the code to make the simulation more realistic. This is based in part on the comparative results between the computer simulations and the results from part 1 which indicated that with increased particle density and flow rate the particle density distribution at the entrance region of the heat exchanger becomes more uniform. The drift flux model took a much longer computing time and still did not converge to a steady state solution. It is concluded then that for a slurry flow with significant different phase density variations that a two-fluid model would be more appropriate for predicting the bulk flow in 3D geometries.

Moujaes, S.F.; Francis, J.J.; Nassersharif, B.

1999-07-01

175

Numerical investigation of heat and mass transfer during vertical Bridgman crystal growth under rotational vibrations  

NASA Astrophysics Data System (ADS)

The paper deals with the numerical investigation of convective flows and heat and mass transfer in the directional solidification of binary melts in the presence of rotational vibrations of finite amplitude and frequency. The study is performed in the framework of the Boussinesq approximation and unsteady axisymmetric approach, taking into account the existence of the two-phase zone. The simulation is conducted for binary melt with low phase change temperature (succinonitrile with ethanol), using ANSYS Fluent package which realizes the finite volume method. The data on the temporal evolution of velocity, temperature and solute concentration fields in the melt and on the solute distribution in the grown crystal with and without vibrations are obtained. It is demonstrated that the vibrations make strong stabilizing effect; they reduce the radial segregation and prevent the pit formation and solidification front breakdown, which leads to a substantial increase of grown crystal homogeneity.

Lyubimova, T. P.; Parshakova, Ya. N.

2014-01-01

176

Experimental and numerical study of convection heat transfer of CO 2 at super-critical pressures during cooling in small vertical tube  

Microsoft Academic Search

Convection heat transfer of CO2 at super-critical pressures during cooling in a vertical small tube with inner diameter of 2.00mm was investigated experimentally and numerically. The local heat transfer coefficients were determined through a combination of experimental measurements and numerical simulations. This study investigated the effects of pressure, cooling water mass flow rate, CO2 mass flow rate, CO2 inlet temperature,

Pei-Xue Jiang; Chen-Ru Zhao; Run-Fu Shi; Yang Chen; Walter Ambrosini

2009-01-01

177

On MHD boundary-layer flow and mass transfer past a vertical plate in a porous medium with constant heat flux  

Microsoft Academic Search

Purpose – The hydromagnetic mixed convection flow of an incompressible viscous electrically conducting fluid and mass transfer over a vertical porous plate with constant heat flux embedded in a porous medium is investigated. Design\\/methodology\\/approach – Using the Boussinesq and boundary-layer approximations, the fluid equations for momentum, energy balance and concentration governing the problem are formulated. These equations are solved numerically

O. D. Makinde

2009-01-01

178

Effect of Heat Spreader Location on Lasing Property of End-pumped Vertical-external-cavity Surface-emitting Lasers (VECSELs)  

Microsoft Academic Search

We analyzed the effect of heat-spreader location on lasing properties of newly devised end-pumped vertical-external-cavity surface-emitting lasers in terms of the dissimilar behavior of pump beam redirection scheme and thermal lens effect

Jun-Youn Kim; Junho Lee; Gi Bum Kim; Soohaeng Cho; Jaeryung Yoo; Ki-Sung Kim; Seong-Jin Lim; Sang-Moon Lee; Sung-Min Hwang; Taek Kim

2006-01-01

179

Characterizing fractured rock aquifers using heated Distributed Fiber-Optic Temperature Sensing to determine borehole vertical flow  

NASA Astrophysics Data System (ADS)

In highly heterogeneous media, fracture network connectivity and hydraulic properties can be estimated using methods such as packer- or cross-borehole pumping-tests. Typically, measurements of hydraulic head or vertical flow in such tests are made either at a single location over time, or at a series of depths by installing a number of packers or raising or lowering a probe. We show how this often encountered monitoring problem, with current solutions sacrificing either one of temporal or spatial information, can be addressed using Distributed Temperature Sensing (DTS). Here, we electrically heat the conductive cladding materials of cables deployed in boreholes to determine the vertical flow profile. We present results from heated fiber optic cables deployed in three boreholes in a fractured rock aquifer at the much studied experimental site near Ploemeur, France, allowing detailed comparisons with alternative methods (e.g. Le Borgne et al., 2007). When submerged in water and electrically heated, the cable very rapidly reaches a steady state temperature (less than 60 seconds). The steady state temperature of the heated cable, measured using the DTS method, is then a function of the velocity of the fluid in the borehole. We find that such cables are sensitive to a wide range of fluid velocities, and thus suitable for measuring both ambient and pumped flow profiles at the Ploemeur site. The cables are then used to monitor the flow profiles during all possible configurations of: ambient flow, cross-borehole- (pumping one borehole, and observing in another), and dipole-tests (pumping one borehole, re-injection in another). Such flow data acquired using DTS may then be used for tomographic flow inversions, for instance using the approach developed by Klepikova et al., (submitted). Using the heated fiber optic method, we are able to observe the flow response during such tests in high spatial detail, and are also able to capture temporal flow dynamics occurring at the start of both the pumping and recovery phase of cross-borehole- and dipole- tests. In addition, the clear advantage of this is that by deploying a single fiber optic cable in multiple boreholes at a site, the flow profiles in all boreholes can be simultaneously measured, allowing many different pumping experiments to be conducted and monitored in a time efficient manner. Klepikova M. V., Le Borgne T., Bour O., and J-R.de Dreuzy, Inverse modelling of flow tomography experiments in fractured media, submitted to Water Resources Research. Le Borgne T., Bour O., Riley M. S., Gouze P., Pezard P.A., Belghoul A., Lods G., Le Provost R., Greswell R. B., Ellis P.A., Isakov E., and B. J. Last, Comparison of alternative methodologies for identifying and characterizing preferential flow paths in heterogeneous aquifers. Journal of Hydrology 2007, 345, 134-148.

Read, T. O.; Bour, O.; Selker, J. S.; Le Borgne, T.; Bense, V.; Hochreutener, R.; Lavenant, N.

2013-12-01

180

Experimental study on boiling heat transfer and two-phase frictional pressure drop characteristics of glycol-water solution in a vertical porous surface tube  

NASA Astrophysics Data System (ADS)

Although much research has been conducted on investigating the flow boiling heat transfer of low saturation temperature refrigerants, there are few experimental data and theory about the flow boiling heat transfer of high saturation temperature organic mixture which exists widely in the petrochemical industry. To investigate the characteristics of flow boiling heat transfer of high saturation temperature organic mixture, experiments of glycol-water solution flow boiling in a vertical porous surface tube and a vertical smooth tube are conducted. Test tubes are uniformly heated by electrical current with a heated length of 2,000 mm. The mass flux in the experiment ranges from 500 to 1,500t?h-1 and the heat flux on test tubes ranges from 10 to 40 kW?m-2. The flow boiling heat transfer coefficients and two-phase frictional pressure drops of the two types of tubes are obtained and compared. The results indicate that: the flow boiling heat transfer coefficient in the porous surface tube is 3.8˜5.7 times of that in smooth tube and the pressure drop of the porous surface tube is 0.99˜1.007 times of that in the smooth tube. The physical mechanisms of the enhanced heat transfer characteristics of flow boiling in the porous surface tube are analyzed. By the regression analysis of the experimental data, correlations predicting the flow boiling heat transfer coefficient and pressure drop of glycol-water solution within the error range of ±20% are established. The experimental results can be used to guide the design of heat exchange equipment using the porous surface tube as heat transfer elements under these test conditions.

Qiao, Shouxu; Wang, Haijun; Gu, Hongfang; Luo, Yushan; Zhang, Lei; Xiong, Wei

2013-07-01

181

Onset of unsteady axi-symmetric laminar natural convection in a vertical cylindrical enclosure heated at the wall  

NASA Astrophysics Data System (ADS)

In the present study laminar transition to oscillatory convection of fluids having different Prandtl numbers in a laterally heated vertical cylindrical enclosure for different aspect ratios (melt height to crucible radius) of 2-4 is investigated numerically for 0.01 ? Pr ? 10. Numerical solution to two-dimensional axisymmetric transient Navier Stokes equations and energy equation were solved by finite volume method using SIMPLE algorithm. Numerical results illustrate that there exists a critical Rayleigh number for each Prandtl number beyond which sustained laminar oscillatory flow sets in. The oscillatory regime was characterised by the oscillation of the average kinetic energy and average thermal energy of the melt. For a given aspect ratio, critical Rayleigh number increases with Pr upto 1 and then flattens. It was observed that for low Prandtl number fluids, Pr < 1.0, critical Rayleigh number is found to increase with increase in aspect ratio while for high Prandtl number fluids, Pr ? 1.0, it is found to decrease with increase in aspect ratio. The influence of aspect ratio on the transient behaviour of the melt volume below and above the critical Rayleigh number was studied.

Kumar, Amitesh; Vegad, Mitesh; Roy, Subhransu

2010-04-01

182

Heat Transfer Mechanism of a Vertical Wall Inside a Two-Phase Closed Thermosiphon Evaporator and Its Estimation  

NASA Astrophysics Data System (ADS)

The inside heat transfer coefficient, overall heat transfer coefficient, and heat flow rate at the heating section of the thermosiphon were determined for each heating method. In order to observe the heat transfer mechanism in the evaporator, a thermosiphon unit made of glass was assembled and conducted separately. The results of these experiments with these two units are summarized as follows. (1) Nucleate boiling due to the internal heat transfer mechanism improves the heat transfer characteristics of the thermosiphon unit. Under the specific heating conditions with dropwise condensation, there are two types of heat transfer mechanism occur in the evaporator accompanying nucleate boiling, i. e. latent heat transfer and sensible heat transfer. (2) In the case of latent heat transfer, the inside heat transfer coefficient has an upper limit which can be used as a criterion to determine the type of internal heat transfer mechanism.

O-Uchi, Masaki; Hirose, Koichi; Saito, Futami

183

Heat flux measurement from vertical temperature profile and thermal infrared imagery in low-flux fumarolic zones  

NASA Astrophysics Data System (ADS)

Hydrothermal systems are associated to most of the dormant volcanoes. Heat is transported by steam from the hot magma body in the connected porosity and the fissures of the rock to the surface. If the flux is low enough (<500 W/m²), the steam mainly condensates in the soil close to surface, and a significant proportion of the heat is transported to the surface by conduction, producing a gradient of temperature and a thermal anomaly detectable at the surface. Detecting and monitoring these fluxes is crucial for hazard management, since it reflects the state of the magma body in depth. In order to quantify this flux two methods are considered. First, a vertical profile of temperature is measured by a series of thermocouples, and the conducted flux is estimated thanks to the Fourier law. Secondly, a more recent method uses the thermal infrared imagery to monitor the surface temperature anomaly (STA) between the studied zone and an equivalent zone not affected by the geothermal flux. The heat flux from the soil to the atmosphere is computed as the sum of (1) the radiative flux, (2) the sensible flux and (3) the residual steam flux. These two methods are complementary and have an equivalent uncertainty of approximately 20%, which would allow to track the major changes in the hydrothermal system. However, the surface and sub-surface temperatures are strongly influenced by the climate. For instance, it has been widely demonstrated that the surface temperature dramatically decreases after a rainfall. In order to estimate the reliability of the measurements, a numerical model simulating the evolution of the subsurface temperature in low flux fumarolic zone has been built. In depth, the heat can be transported either by conduction, or by the rising steam, or by condensed water. In surface, both the radiative flux and the sensible flux (convection of the atmosphere) are taken into account. This model allows to estimate the changes of temperature due to a variation of solar illumination, wind, or rainfalls. It has been successfully tested during 5 months with a permanent station built on the Ty fault on La Soufrière volcano (Guadeloupe, Lesser Antilles). Results show that the diurnal cycle has a significant influence on the temperature up to ca. 30 cm depth, hindering the use of the thermal gradient in this zone, while the STA has a negligible variation. Rain has a more dramatic influence: the surface temperature and the STA are significantly affected, even for small rains. The model shows that the drop of temperature and the affected thickness are mainly controlled by the amount of rain, while the relaxation time is primarily a function of the heat flux. These results have strong implications in the interpretation and the reliability of the temperature surveys, and could be used to correct them from the climate fluctuations.

Gaudin, Damien; Finizola, Anthony; Beauducel, François; Brothelande, Elodie; Allemand, Pascal; Delacourt, Christophe; Delcher, Eric; Peltier, Aline

2014-05-01

184

Vortex ring head-on collision with a heated vertical plate G. Arvalo and R. H. Hernndeza  

E-print Network

measurement of the global heat flux released by the heated surface to the fluid. We focus particularly measure the total heat flux exchanged by the heated plate and visualize the vortex motion during transfer enhancement is given in a significant mean heat flux increase, but a detailed scenario

Paris-Sud XI, Université de

185

Impact of black carbon aerosol over Italian basin valleys: high-resolution measurements along vertical profiles, radiative forcing and heating rate  

NASA Astrophysics Data System (ADS)

A systematic study of black carbon (BC) vertical profiles measured at high-resolution over three Italian basin valleys (Terni Valley, Po Valley and Passiria Valley) is presented. BC vertical profiles are scarcely available in literature. The campaign lasted 45 days and resulted in 120 measured vertical profiles. Besides the BC mass concentration, measurements along the vertical profiles also included aerosol size distributions in the optical particle counter range, chemical analysis of filter samples and a full set of meteorological parameters. Using the collected experimental data, we performed calculations of aerosol optical properties along the vertical profiles. The results, validated with AERONET data, were used as inputs to a radiative transfer model (libRadtran). The latter allowed an estimation of vertical profiles of the aerosol direct radiative effect, the atmospheric absorption and the heating rate in the lower troposphere. The present measurements revealed some common behaviors over the studied basin valleys. Specifically, at the mixing height, marked concentration drops of both BC (range: from -48.4 ± 5.3 to -69.1 ± 5.5%) and aerosols (range: from -23.9 ± 4.3 to -46.5 ± 7.3%) were found. The measured percentage decrease of BC was higher than that of aerosols: therefore, the BC aerosol fraction decreased upwards. Correspondingly, both the absorption and scattering coefficients decreased strongly across the mixing layer (range: from -47.6 ± 2.5 to -71.3 ± 3.0% and from -23.5 ± 0.8 to -61.2 ± 3.1%, respectively) resulting in a single-scattering albedo increase along height (range: from +4.9 ± 2.2 to +7.4 ± 1.0%). This behavior influenced the vertical distribution of the aerosol direct radiative effect and of the heating rate. In this respect, the highest atmospheric absorption of radiation was predicted below the mixing height (~ 2-3 times larger than above it) resulting in a heating rate characterized by a vertical negative gradient (range: from -2.6 ± 0.2 to -8.3 ± 1.2 K day-1 km-1). In conclusion, the present results suggest that the BC below the mixing height has the potential to promote a negative feedback on the atmospheric stability over basin valleys, weakening the ground-based thermal inversions and increasing the dispersal conditions.

Ferrero, L.; Castelli, M.; Ferrini, B. S.; Moscatelli, M.; Perrone, M. G.; Sangiorgi, G.; D'Angelo, L.; Rovelli, G.; Moroni, B.; Scardazza, F.; Mo?nik, G.; Bolzacchini, E.; Petitta, M.; Cappelletti, D.

2014-09-01

186

Survey of advanced-heat-pump developments for space conditioning  

SciTech Connect

A survey of heat pump projects with special emphasis on those supported by DOE, EPRI, and the Gas Research Institute is presented. Some historical notes on heat pump development are discussed. Market and equipment trends, well water and ground-coupled heat pumps, heat-actuated heat pump development, and international interest in heat pumps are also discussed. 30 references.

Fairchild, P.D.

1981-01-01

187

Comparative study of water boiling in a vertical tube under temperature-controlled or heat-flux-controlled boundary conditions. [LMFBR  

Microsoft Academic Search

The Simulant Boiling Flow Visualization (SBFV) loop is an experimental facility where natural-convection boiling of water was accomplished in a transparent vertical tube by using hot glycerine; thus, direct observation was possible. As a result, heating was obtained through a temperature-controlled rather than a power-controlled boundary condition. To compare the SBFV data with previous experiments using a stainless steel test

Carbajo

1983-01-01

188

A rigorous bound on the vertical transport of heat in Rayleigh-Bénard convection at infinite Prandtl number with mixed thermal boundary conditions  

NASA Astrophysics Data System (ADS)

A rigorous upper bound on the Nusselt number is derived for infinite Prandtl number Rayleigh-Bénard convection for a fluid constrained between no-slip, mixed thermal vertical boundaries. The result suggests that the thermal boundary condition does not affect the qualitative nature of the heat transport. The bound is obtained with the use of a nonlinear, stably stratified background temperature profile in the bulk, notwithstanding the lack of boundary control of the temperature due to the Robin boundary conditions.

Whitehead, Jared P.; Wittenberg, Ralf W.

2014-09-01

189

The Influence of the Wall Surface Heating Conditions on Velocity Profiles of the Natural Convection in a Vertical Channel of Electronic Equipment  

NASA Astrophysics Data System (ADS)

Natural convective flow field and cooling capability in compact electronic equipment have been investigated. Temperature and velocity measurements were carried out using a channel model of electronic equipment. The channel model having a vertical duct with rectangular section was used as experimental model. The channel model has two copper walls simulating the printed circuit boards and two transparent acrylic walls simulating the case walls. The clearance between the copper walls and the wall surface heating conditions were taken as parameters of channel model. The clearance between the copper walls was varied from 5mm to 15 mm. The experiments were conducted at three different thermal conditions: symmetric heating, asymmetric heating and one-sided heating. Velocity profiles of natural cooling flow in the channel were quantitatively measured using a particle image velocimetry (PIV). From the results, it is clarified that the changes in the velocity profiles strongly depend on the thermal conditions.

Nishino, Yasushi; Imai, Ryoji; Ishizuka, Masaru; Nakagawa, Shinji

190

Nonlinear Radiation Heat Transfer Effects in the Natural Convective Boundary Layer Flow of Nanofluid Past a Vertical Plate: A Numerical Study  

PubMed Central

The problem of natural convective boundary layer flow of nanofluid past a vertical plate is discussed in the presence of nonlinear radiative heat flux. The effects of magnetic field, Joule heating and viscous dissipation are also taken into consideration. The governing partial differential equations are transformed into a system of coupled nonlinear ordinary differential equations via similarity transformations and then solved numerically using the Runge–Kutta fourth-fifth order method with shooting technique. The results reveal an existence of point of inflection for the temperature distribution for sufficiently large wall to ambient temperature ratio. Temperature and thermal boundary layer thickness increase as Brownian motion and thermophoretic effects intensify. Moreover temperature increases and heat transfer from the plate decreases with an increase in the radiation parameter. PMID:25251242

Mustafa, Meraj; Mushtaq, Ammar; Hayat, Tasawar; Ahmad, Bashir

2014-01-01

191

Vertical Profiles of Latent Heat Release over the Global Tropics using TRMM Rainfall Products from December 1997 to November 2002  

NASA Technical Reports Server (NTRS)

NASA Tropical Rainfall Measuring Mission (TRMM) precipitation radar (PR) derived rainfall information will be used to estimate the four-dimensional structure of global monthly latent heating and rainfall profiles over the global tropics from December 1997 to November 2000. Rainfall, latent heating and radar reflectivity structures between El Nino (DJF 1997-98) and La Nina (DJF 1998-99) will be examined and compared. The seasonal variation of heating over various geographic locations (i.e., oceanic vs continental, Indian ocean vs west Pacific, Africa vs. S. America ) will also be analyzed. In addition, the relationship between rainfall, latent heating (maximum heating level), radar reflectivity and SST is examined and will be presented in the meeting. The impact of random error and bias in stratiform percentage estimates from PR on latent heating profiles is studied and will also be presented in the meeting. The Goddard Cumulus Ensemble Model is being used to simulate various mesoscale convective systems that developed in different geographic locations. Specifically, the model estimated rainfall, radar reflectivity and latent heating profiles will be compared to observational data collected from TRMM field campaigns over the South China Sea in 1998 (SCSMEX), Brazil in 1999 (TRMM-LBA), and the central Pacific in 1999 (KWAJEX). Sounding diagnosed heating budgets and radar reflectivity from these experiments can provide the means to validate (heating product) as well as improve the GCE model. Review of other latent heating algorithms will be discussed in the workshop.

Tao, W.-K.; Lang, S.; Simpson, J.; Meneghini, R.; Halverson, J.; Johnson, R.; Adler, R.

2003-01-01

192

Numerical simulation and experimental analysis of heat transfer through the neck tube into vertical cryogenic insulated cylinders  

NASA Astrophysics Data System (ADS)

The neck tube is an important support structure in cryogenic insulated cylinders. The heat flux from the outside environment through the neck tube into the cryogenic liquid occupies a great proportion of the total heat leak and can be more than half of the total heat loads. In this paper, conjugate convective-conductive heat transfer model between wall and the cold vapor in conditions of natural discharge is numerically investigated. Also a liquid nitrogen boil-off method was adopted in experiments to validate the result of numerical simulation. Experimental results indicate more favorable agreement with conjugate heat transfer (CHT) model compared with simple solid heat conduction (SSHC) model by ANSYS software. And the convection between the wall and vapor is also calculated. The research and results can provide reference in design for neck tube of the cryogenic cylinder.

Li, Yang; Wang, Caili; Wang, Rongshun

2011-07-01

193

Natural convection liquid immersion cooling of high density columns of discrete heat sources in a vertical channel  

Microsoft Academic Search

Natural convection liquid cooling of simulated electronic components in a vertical channel was investigated. The test surface consisted of three columns of fifteen flush mounted foil heaters. The channel was formed by placing a smooth movable shrouding wall parallel to the test surface. The experimental procedure called for temperature measurements and flow visualization at various power levels and channel spacings.

Alfred O. Gaiser

1989-01-01

194

Free convection about a vertical flat plate embedded in a porous medium with application to heat transfer from a dike  

Microsoft Academic Search

An analysis is made for steady free convection about a vertical flat plate embedded in a saturated porous medium at high Rayleigh numbers. Within the framework of boundary layer approximations, similarity solutions are obtained for a class of problems where wall temperature varies as xlambda, i.e., a power function of distance from the origin where wall temperature begins to deviate

Ping Cheng; W. J. Minkowycz

1977-01-01

195

Vertical Profiles of Latent Heat Release over the Global Tropics using TRMM rainfall products from December 1997 to November 2001  

NASA Technical Reports Server (NTRS)

NASA Tropical Rainfall Measuring Mission (TRMM) precipitation radar (PR) derived rainfall information will be used to estimate the four-dimensional structure of global monthly latent heating and rainfall profiles over the global tropics from December 1997 to November 2001. Rainfall, latent heating and radar reflectivity structures between El Nino (DE 1997-98) and La Nina (DJF 1998-99) will be examined and compared. The seasonal variation of heating over various geographic locations (i.e., oceanic vs continental, Indian ocean vs. west Pacific, Africa vs. S. America) will also be analyzed. In addition, the relationship between rainfall, latent heating (maximum heating level), radar reflectivity and SST is examined and will be presented in the meeting. The impact of random error and bias in strtaiform percentage estimates from PR on latent heating profiles is studied and will also be presented in the meeting. The Goddard Cumulus Ensemble Model is being used to simulate various mesoscale convective systems that developed in different geographic locations. Specifically, the model estimated rainfall, radar reflectivity and latent heating profiles will be compared to observational data collected from TRMM field campaigns over the South China Sea in 1998 (SCSMEX), Brazil in 1999 (TRMM-LBA), and the central Pacific in 1999 (KWAJEX). Sounding diagnosed heating budgets and radar reflectivity from these experiments can provide the means to validate (heating product) as well as improve the GCE model.

Tao, W.-K.; Lang, S.; Simpson, J.; Meneghini, R.; Halverson, J.; Johnson, R.; Adler, R.

2002-01-01

196

Vertical Profiles of Latent Heat Release over the Global Tropics Using TRMM Rainfall Products from December 1997 to November 2002  

NASA Technical Reports Server (NTRS)

NASA Tropical Rainfall Measuring Mission (TRMM) precipitation radar (PR) derived rainfall information will be used to estimate the four-dimensional structure of global monthly latent heating and rainfall profiles over the global tropics from December 1997 to November 2000. Rainfall, latent heating and radar reflectivity structures between El Nino (DJF 1997-98) and La Nina (DJF 1998-99) will be examined and compared. The seasonal variation of heating over various geographic locations (i.e., oceanic vs continental, Indian ocean vs west Pacific, Africa vs S. America) will also be analyzed. In addition, the relationship between rainfall, latent heating (maximum heating level), radar reflectivity and SST is examined and will be presented in the meeting. The impact of random error and bias in straitform percentage estimates from PR on latent heating profiles is studied and will also be presented in the meeting. The Goddard Cumulus Ensemble Model is being used to simulate various mesoscale convective systems that developed in different geographic locations. Specifically, the model estimated rainfall, radar reflectivity and latent heating profiles will be compared to observational data collected from TRMM field campaigns over the South China Sea in 1998 (SCSMXX), Brazil in 1999 (TRMM- LBA), and the central Pacific in 1999 (KWAJEX). Sounding diagnosed heating budgets and radar reflectivity from these experiments can provide the means to validate (heating product) as well as improve the GCE model.

Tao, W.-K.

2003-01-01

197

Experimental and analytical evaluation of a ground-coupled refrigerator-freezer  

SciTech Connect

In response to efforts to reduce refrigerator-freezer energy consumption, several design options based on using a ground-source heat exchanger as a means of rejecting heat from the cabinet and condenser were investigated for improving the energy efficiency of a 15.5 ft{sup 3} (440 L) domestic refrigerator-freezer. The options included (1) a cooling circuit throughout the cabinet to reduce the cabinet heat gain, (2) a liquid-cooled condenser and smaller compressor, and (3) a secondary cooling circuit in the fresh food section during winter operation. An additional option, increasing the cabinet volume by reducing the insulation thickness, was also investigated as a means of reducing costs. This was accomplished by using the cooling circuit to maintain the same cabinet heat gain as for the original baseline cabinet rather than reduce energy consumption. The modeled results for all the options show that the energy consumption could be reduced by 24.0% with a cabinet cooling circuit, 40.4% with the addition of a liquid-cooled condenser and smaller compressor, and 51.1% from utilizing a fresh food cooling circuit during winter operation. Modeling simulations also show that the cabinet volume could be increased by 2.4 ft{sup 3} (70 L), a 15.3% increase, by utilizing the cabinet cooling circuit to reduce the insulation thickness rather than reduce energy consumption. These improvements do not account for the pumping power required for circulating the coolant. In addition to the modeling exercise, a laboratory prototype was fabricated and tested to experimentally verify the energy consumption of a unit with a cabinet cooling circuit. The resulting energy consumption was 1.35 kWh/d, a substantial energy-efficiency improvement of 24.0% compared to the 1997 model baseline unit (1.78 kWh/d). Abbreviated test results with the addition of a liquid-cooled condenser and smaller compressor show a savings of 39.9% (1.07 kWh/d).

Vineyard, E.A. [Vineyard Associates, Knoxville, TN (United States); Horvay, J.B. [Horvay Associates, Isle of Palms, SC (United States); Schulak, E.R. [Edward Schulak Equities, Inc., Birmingham, MI (United States)

1998-12-31

198

Mass transfer effects on the unsteady mhd radiative- convective flow of a micropolar fluid past a vertical porous plate with variable heat and mass fluxes  

NASA Astrophysics Data System (ADS)

The problem of unsteady two-dimensional laminar flow of a viscous incompressible micropolar fluid past a vertical porous plate in the presence of a transverse magnetic field and thermal radiation with variable heat and mass fluxes is considered. The free stream velocity is subjected to exponentially increasing or decreasing small perturbations. A uniform magnetic field acts perpendicularly to a porous surface where a micropolar fluid is absorbed with a suction velocity varying with time. The Rosseland approximation is used to describe radiative heat transfer in the limit of optically thick fluids. The effects of the flow parameters and thermophysical properties on the velocity and temperature fields across the boundary layer are investigated. The effects of various parameters on the velocity, microrotation velocity, temperature, and concentration profiles are given graphically, and the values of the skin friction and couple stress coefficients are presented.

Reddy, M. Gnaneswara

2013-03-01

199

The Effects of Thermal Radiation and Heat Source on an Unsteady MHD Free Convection Flow Past an Infinite Vertical Plate with Thermal Diffusion and Diffusion Thermo  

NASA Astrophysics Data System (ADS)

In this paper, we investigate the effects of thermal radiation and heat source on an unsteady magnetohydrodynamic free convection flow past an infinite vertical plate in a porous medium in presence of thermal diffusion and diffusion thermo. The dimensionless governing equations are solved numerically using finite element method. The numerical results for some special cases were compared with Shanker et al. and were found to be in good agreement. Graphical results for velocity, temperature and concentration profiles based on the numerical solutions are presented and discussed within the boundary layer. And also the skin-friction at the plate due to velocity field, rate of heat transfer due to temperature field and mass transfer due to concentration field are obtained in non-dimensional form. The effects of the different physical flow parameters on these respective flow fields are discussed through graphs and results are physically interpreted.

Raju, R. S.; Sudhakar, K.; Rangamma, M.

2013-04-01

200

Combined effect of buoyancy force and Navier slip on MHD flow of a nanofluid over a convectively heated vertical porous plate.  

PubMed

We examine the effect of magnetic field on boundary layer flow of an incompressible electrically conducting water-based nanofluids past a convectively heated vertical porous plate with Navier slip boundary condition. A suitable similarity transformation is employed to reduce the governing partial differential equations into nonlinear ordinary differential equations, which are solved numerically by employing fourth-order Runge-Kutta with a shooting technique. Three different water-based nanofluids containing copper (Cu), aluminium oxide (Al2O3), and titanium dioxide (TiO2) are taken into consideration. Graphical results are presented and discussed quantitatively with respect to the influence of pertinent parameters, such as solid volume fraction of nanoparticles (?), magnetic field parameter (Ha), buoyancy effect (Gr), Eckert number (Ec), suction/injection parameter (f w ), Biot number (Bi), and slip parameter ( ? ), on the dimensionless velocity, temperature, skin friction coefficient, and heat transfer rate. PMID:24222749

Mutuku-Njane, Winifred Nduku; Makinde, Oluwole Daniel

2013-01-01

201

Current status of ground source heat pumps and underground thermal energy storage in Europe  

Microsoft Academic Search

Geothermal Heat Pumps, or Ground Coupled Heat Pumps (GCHP), are systems combining a heat pump with a ground heat exchanger (closed loop systems), or fed by ground water from a well (open loop systems). They use the earth as a heat source when operating in heating mode, with a fluid (usually water or a water–antifreeze mixture) as the medium that

Burkhard Sanner; Constantine Karytsas; Dimitrios Mendrinos; Ladislaus Rybach

2003-01-01

202

Hydrodynamics and heat transfer of a water flow with supercritical parameters in a vertical assembly of fuel elements  

NASA Astrophysics Data System (ADS)

Water flow in a hexahedral seven-rod fuel assembly at supercritical pressure has been modeled. Consideration has been given to nonstationary regimes of this flow in the case of a stepwise increase in the heat flux on the fuelelement surface and of a drop in the flow rate of the coolant at entry. Numerical investigation of the processes of hydrodynamics and heat transfer was based on the RNG k-? turbulence model; equations of state of the IF-97 formulation were used. Hydrodynamic and thermal characteristics of the coolant flow in the indicated assembly have been obtained as a result of the modeling.

Avramenko, A. A.; Kondrat?eva, E. A.; Kovetskaya, M. M.; Tyrinov, A. I.

2013-07-01

203

Velocity and temperature distribution of air in the boundary layer of a vertical plate for free-convective heat transfer  

E-print Network

. , and Klebanoff, Theory and A lication of Hot-Wire in the, lnvestigation~our~uent ~gers. Nrcrwt w:Iyt, Tpn. 16. Hutchison, J. P. , "The Design, Construction, and Instrumentation of a Chamber to Study Heat, Mass, and Momentum Transfer from Humid Air to Metal...

Jullienne, Jean Maxime Jose

1962-01-01

204

Fabrication of monoblock high heat flux components for ITER divertor upper vertical target using hot isostatic pressing diffusion welding  

Microsoft Academic Search

The monoblock concept is one of the most promising design concepts for high heat flux (HHF) components to be used in international thermonuclear reactor (ITER) divertor area. The fabrication of monoblocks is difficult due to the thermal expansion mismatch between copper alloy and tungsten. To overcome this problem, a Cu-OFHC compliant layer is used. A hot isostatic pressing diffusion welding

E Rigal; P Bucci; G Le Marois

2000-01-01

205

Natural convection of water-fine particle suspension in a rectangular cell heated and cooled from opposing vertical walls  

SciTech Connect

Experiments of a natural convection of a water-fine particle suspension in a rectangular cell which was headed from a vertical wall and cooled from the opposing vertical wall were carried out. The suspension was a mixture of micro beads and water. Two kinds of particles were used. One was the micro beads made of soda glass of which specific gravity was 2.5. Mean diameter of the particle was 5.85{micro}m and standard deviation was 2.65{micro}m. It was considered that this particle size distribution was wide relatively. The other was micro beads made of SiO{sub 2} of which specific gravity was 2.15. Mean diameter of the particles was 2.97{micro}m and the standard deviation was 0.033{micro}m. This particle size distribution was considered to be narrow relatively. In the case of the suspension with particles whose size distribution is wide, many layers separated by almost-horizontal sharp interfaces were observed. In the beginning many layers appeared, and each interface of the layers fell gradually with a constant velocity, and finally all layers vanished. In the case of the suspension with the particles whose size distribution is narrow many layers were not formed but three layers were. The location of the interface was measured by video camera and at that time the temperature distribution in the vertical direction along the centerline of the test cell was measured. Furthermore the mean diameter and concentration of beads in each layer of the suspension were measured. In the above measurements the following results were obtained. The falling velocity of the interface becomes smaller as the initial concentration of particles becomes larger and the lower interface has the larger falling velocity. Each layer has a circular flow and each flow in a layer does not go into neighboring layers. The concentration of particles in each layer is almost uniform and the lower layer has the larger concentration and the larger mean diameter of particles. When the particle size distribution is narrow, the number of formed layers is depressed.

Okada, Masashi; Kang, Chaedong; Oyama, Kazuya; Yano, Satoshi

1999-07-01

206

Performance of heat charge\\/discharge of magnesium nitrate hexahydrate and magnesium chloride hexahydrate mixture to a single vertical tube for a latent heat storage system  

Microsoft Academic Search

The authors focused on a mixture of magnesium nitrate hexahydrate as a base material and magnesium chloride hexahydrate as an additive to store and utilize urban waste heat from emerged co-generation systems, typically available at temperatures of 60–90 °C. The second paper revealed that this mixture has good thermal characteristics as a PCM for latent thermal energy storage. In this

K Nagano; K Ogawa; T Mochida; K Hayashi; H Ogoshi

2004-01-01

207

New CHF correlation scheme proposed for vertical rectangular channels heated from both sides in nuclear research reactors  

Microsoft Academic Search

In this study, an investigation was carried out to identify the important parameters affecting critical heat flux (CHF) in rectangular channels, focusing on the effects of flow direction, channel inlet subcooling from 1 to 213 K, the channel outlet condition extending from subcooling of 0-74 K to quality of 0-1.0, pressure of 0.1 to 4 MPa, water mass flux of

Y. Sudo; M. Kaminaga

1993-01-01

208

Fast Simulation of a Vertical U-Tube Ground Heat Exchanger by Using a One-Dimensional Transient Numerical Model  

Microsoft Academic Search

An explicit one-dimensional transient numerical model has been built for a single-borehole ground heat exchanger, and two computing algorithms are given. The outlet temperature of the U-tube and the soil temperature can be predicted by using arbitrary time-varying load or inlet temperatures as inputs. This numerical model has been compared with analytical models and validated by using test data of

H. Su; Q. Li; X.-H. Li; Y. Zhang; Y.-T. Kang; Z.-H. Si; X.-G. Shi

2011-01-01

209

Study of instabilities and quasi-two-dimensional turbulence in volumetrically heated magnetohydrodynamic flows in a vertical rectangular duct  

NASA Astrophysics Data System (ADS)

We consider magnetohydrodynamic (MHD) rectangular duct flows with volumetric heating. The flows are upward, subject to a strong transverse magnetic field perpendicular to the temperature gradient, such that the flow dynamics is quasi-two-dimensional. The internal volumetric heating imitates conditions of a blanket of a fusion power reactor, where a buoyancy-driven flow is imposed on the forced flow. Studies of this mixed-convection flow include analysis for the basic flow, linear stability analysis and Direct Numerical Simulation (DNS)-type computations. The parameter range covers the Hartmann number (Ha) up to 500, the Reynolds number (Re) from 1000 to 10 000, and the Grashof number (Gr) from 105 to 5 × 108. The linear stability analysis predicts two primary instability modes: (i) bulk instability associated with the inflection point in the velocity profile near the "hot" wall and (ii) side-wall boundary layer instability. A mixed instability mode is also possible. An equation for the critical Hartmann number has been obtained as a function of Re and Gr. Effects of Ha, Re, and Gr on turbulent flows are addressed via nonlinear computations that demonstrate two characteristic turbulence regimes. In the "weak" turbulence regime, the induced vortices are localized near the inflection point of the basic velocity profile, while the boundary layer at the wall parallel to the magnetic field is slightly disturbed. In the "strong" turbulence regime, the bulk vortices interact with the boundary layer causing its destabilization and formation of secondary vortices that may travel across the flow, even reaching the opposite wall. In this regime, the key phenomena are vortex-wall and various vortex-vortex interactions. Flow and magnetic field effects on heat transfer are also analyzed.

Vetcha, N.; Smolentsev, S.; Abdou, M.; Moreau, R.

2013-02-01

210

Vertical profiles and storage fluxes of CO2, heat and water in a tropical rainforest at Pasoh, Peninsular Malaysia  

NASA Astrophysics Data System (ADS)

Ambient CO2 concentration, air temperature and relative humidity were measured intermittently for a 3-year period from the floor to the canopy top of a tropical rainforest in Pasoh, Peninsular Malaysia. Mean diurnal CO2 storage flux (Sc; ?mol m-2 s-1) and sensible and latent heat storage fluxes (Qa and Qw; W m-2) ranged from -12.7 to 3.2 ?mol m-2 s-1, -15 to 27 W m-2 and -10 to 20 W m-2, respectively. Small differences in diurnal changes were observed in Sc and Qa between the driest and wettest periods. Compared with the ranges of mean diurnal CO2 eddy flux (-14.7 to 4.9 ?mol m-2 s-1), sensible eddy flux (-12 to 169 W m-2) and latent eddy flux (0 to 250 W m-2), the contribution of CO2 storage flux was especially large. Comparison with summertime data from a temperate Japanese cypress forest suggested a higher contribution of Sc in the tropical rainforest, probably mainly due to the difference in nighttime friction velocity at the sites. On the other hand, differences in Qa and Qw were smaller than the difference in Sc, probably because of the smaller nighttime sinks/sources of heat and water vapour.

Ohkubo, Shinjiro; Kosugi, Yoshiko; Takanashi, Satoru; Matsuo, Naoko; Tani, Makoto; Nik, Abdul Rahim

2008-09-01

211

Heat-transfer characteristics of an earth-probe model for a ground-source heat pump (experiments on forced-convection-boiling heat transfer in a vertical double tube: The case of small flow rates)  

Microsoft Academic Search

An experimental investigation was conducted to determine the heat-transfer characteristics of HCFC-22 for a two-phase double tube connected to a heat pump. This study focused on the forced-convection-boiling heat transfer at small flow rates in a double tube. It was clarified that the quality at the dryout point increases as mass velocity increases, and that the heat-transfer coefficient of two-phase

Junji Nishioka; Hiromu Sugiyama; Takakage Arai

1994-01-01

212

Analysis of hyperbolic signatures from small discontinuities using an UWB ground-coupled radar: FDTD simulations and field experiments  

NASA Astrophysics Data System (ADS)

Ground penetrating radar (GPR) is a well-known non-destructive technique based on electromagnetic wave propagation that is able to detect by reflection or scattering of waves dielectric discontinuities in the underground. Our application is mainly concerned with civil engineering to perform supervision, inventory, and soil characterization. Because the air-coupled radar suffers from a significant reflection at the ground interface that reduces energy transfer of electromagnetic radiation in the sub-surface and penetration depth, we have developed an ultra-wide band (UWB) ground-coupled radar made of a pair of partially shielded compact planar bowtie slot antennas. As the antenna dimension (36*23 cm2) is close to the A4 sheet size, the maturity of the microstrip technology has allowed to design a particular geometry on the FR4 substrate (h=1.5 mm) which is able to operate at frequencies from 460 MHz to beyond 4 GHz in air. Contrary to a commercial GPR where details on antenna design are not available, it appears here possible to know and control the radiation characteristics and develop full-wave FDTD modeling that can represent field experiments for comparisons and analyses. The objective of this work is to improve, by means of a parametric study, the knowledge of physical phenomena involved in dielectric polarization when waves interact with buried discontinuities and particularly cracks, pipes, delaminations that can be distinguished by their shape, size, dielectric contrast with the surrounding medium, orientation relative to the electric field… Thus, we have first characterized by FDTD modeling and field measurements in a wet sand the radar link in two perpendicular polarizations (parallel and mirror) in the presence of a common soil (epsilon'=5.5, sigma=0.01 S/m) considering variable offsets. Afterwards, we have studied and analyzed the hyperbola signatures generated by the presence of buried canonical objects (pipes, strips) with several dielectric properties (dielectric and conductive) in a wet sand with a small lateral dimension (less than 20 mm) in both polarizations. Comparisons with FDTD simulations including the detailed structure of the antennas appear promising as they have allowed to interpret the measurements and take advantage of signal polarization to extract information associated with the discontinuities. After cluster removal using classical data processing (SVD, median value substraction…), the analytical model based on the ray theory and including the antenna size has allowed to first analyze the hyperbola responses. This study is supposed to prepare the development of data processing associated with B-scans to extract quantitative information from the electromagnetic probing of the subsurface in a very large frequency band.

Sagnard, Florence; Tebchrany, Elias; Baltazart, Vincent

2013-04-01

213

Thermal conductivity of cementitious grouts for geothermal heat pumps. Progress report FY 1997  

SciTech Connect

Grout is used to seal the annulus between the borehole and heat exchanger loops in vertical geothermal (ground coupled, ground source, GeoExchange) heat pump systems. The grout provides a heat transfer medium between the heat exchanger and surrounding formation, controls groundwater movement and prevents contamination of water supply. Enhanced heat pump coefficient of performance (COP) and reduced up-front loop installation costs can be achieved through optimization of the grout thermal conductivity. The objective of the work reported was to characterize thermal conductivity and other pertinent properties of conventional and filled cementitious grouts. Cost analysis and calculations of the reduction in heat exchanger length that could be achieved with such grouts were performed by the University of Alabama. Two strategies to enhance the thermal conductivity of cementitious grouts were used simultaneously. The first of these was to incorporate high thermal conductivity filler in the grout formulations. Based on previous tests (Allan and Kavanaugh, in preparation), silica sand was selected as a suitable filler. The second strategy was to reduce the water content of the grout mix. By lowering the water/cement ratio, the porosity of the hardened grout is decreased. This results in higher thermal conductivity. Lowering the water/cement ratio also improves such properties as permeability, strength, and durability. The addition of a liquid superplasticizer (high range water reducer) to the grout mixes enabled reduction of water/cement ratio while retaining pumpability. Superplasticizers are commonly used in the concrete and grouting industry to improve rheological properties.

Allan, M.L.

1997-11-01

214

The Maximum Drop-Height of a Droplet in a Vertical Countercurrent Water-Air Heat and Moisture Exchange Tower Attached to a Main Fan Diffuser in a Coal Mine  

NASA Astrophysics Data System (ADS)

A vertical countercurrent water-air heat and moisture exchange tower attached to a main fan diffuser is designed. To reduce water loss blown away by the airflow from the exchange tower, the forces acting on droplets are analysed. Droplet motion may be classified under four conditions: (1) downward initial acceleration; (2) upward initial acceleration; (3) droplet blown away by airflow; (4) droplet suspension. With droplet break-up neglected, a general equation for the maximum droplet drop-height is presented and numerical calculations are performed. Equations for the maximum drop-height under Conditions 3 and 4 are deduced, and the equation for Condition 3 is applied to an engineering case study. The effect of air velocity on the maximum drop-height is more significant than that of other factors. The conclusions provide a novel approach to optimizing the design of vertical countercurrent water-air heat and moisture exchange towers attached to main fan diffusers.

Chen, S.; Cui, H.; Wang, H.; Zhao, J.

2014-10-01

215

Analysis of solar aided heat pump systems with seasonal thermal energy storage in surface tanks  

Microsoft Academic Search

Annual periodic performance of a solar assisted ground-coupled heat pump space heating system with seasonal energy storage in a hemispherical surface tank is investigated using analytical and computational methods. The system investigated employs solar energy collection and dumping into a seasonal surface tank throughout the whole year with extraction of thermal energy from the tank for space heating during the

R. Yumruta?; M. Ünsal

2000-01-01

216

Validity ranges of three analytical solutions to heat transfer in the vicinity of single boreholes  

Microsoft Academic Search

In ground-coupled heat pump systems, accurate prediction of transient ground heat transfer is important to establish the required borehole length and to determine precisely the resulting fluid temperature. Three analytical solutions to transient heat transfer in the vicinity of geothermal boreholes are presented. These solutions are referred to as the infinite line source (ILS), the infinite cylindrical source (ICS) and

Mikael Philippe; Michel Bernier; Dominique Marchio

2009-01-01

217

THE EFFECT OF THERMAL RADIATION ON THE HEAT AND MASS TRANSFER FLOW OF A VARIABLE VISCOSITY FLUID PAST A VERTICAL POROUS PLATE PERMEATED BY A TRANSVERSE MAGNETIC FIELD  

Microsoft Academic Search

The effect of temperature-dependent viscosity on free convective flow past a vertical porous plate is studied in the presence of a magnetic field, thermal radiation, and a first-order homogeneous chemical reaction. Boundary layer equations are derived and the resulting approximate nonlinear ordinary differential equations are solved numerically by the shooting method. A parametric study of all parameters involved is conducted,

O. D. Makinde; A. Ogulu

2008-01-01

218

Numerical analysis and experimental validation of heat transfer in ground heat exchangers in alternative operation modes  

Microsoft Academic Search

A finite element numerical model has been developed for the simulation of the ground heat exchangers (GHEs) in alternative operation modes over a short time period for ground-coupled heat pump applications. Comparisons between the numerical and analytical results show that the finite line-source model is not capable of modeling the GHEs within a few hours because of the line-source assumption.

P. Cui; H. Yang; Z. Fang

2008-01-01

219

Numerical analysis of thermal response tests with a groundwater flow and heat transfer model  

Microsoft Academic Search

The Kelvin line-source equation, used to analyze thermal response tests, describes conductive heat transfer in a homogeneous medium with a constant temperature at infinite boundaries. The equation is based on assumptions that are valid for most ground-coupled heat pump environments with the exception of geological settings where there is significant groundwater flow, heterogeneous distribution of subsurface properties, a high geothermal

J. Raymond; R. Therrien; L. Gosselin; R. Lefebvre

2011-01-01

220

A Lagrangian investigation of vertical turbulent heat fluxes in the upper ocean during Tropical Ocean–Global Atmosphere\\/Coupled Ocean-Atmosphere Response Experiment (TOGA-COARE)  

Microsoft Academic Search

We investigated the diurnal cycle of the near-surface ocean temperatures in the western Pacific Warm Pool, using temperature data from drifters with 20 m thermistor chains, during the Coupled Ocean-Atmosphere Response Experiment (COARE) Intensive Observation Period (December 1992 to February 1993). We estimated turbulent heat fluxes at 20 m as a residual in the hourly heat budget along each drifter

Yves du Penhoat; Gilles Reverdin; Guy Caniaux

2002-01-01

221

Natural convection immersion cooling of an array of vertically oriented heated protrusions in an enclosure filled with a dielectric liquid: Effects of enclosure width, Prandtl number and component orientation  

NASA Astrophysics Data System (ADS)

The natural convection heat transfer characteristics of a 3 x 3 array of vertically oriented heated protrusions, immersed in a dielectric liquid, were investigated. Aluminum blocks, 24 x 8 x 6 mm, were used to simulate 20 pin dual in-line packages. Surface temperature measurements of the components were made by imbedding copper-constantan thermocouples below the surface of each component face. A constant heat flux was provided to each component using an Inconel foil heating element. Power supplied to each component varied from 0.115 to 2.90 W. The aluminum blocks were mounted on a plexiglass substrate to form a 3 x 3 array of simulated electronic components. The circuit board containing the components was placed in a rectangular, plexiglass enclosure with inner dimensions: L = 203.2 mm H = 152.0 mm W = 82.6 mm, and a wall thickness of 25.4 mm. The upper boundary was maintained at 10 C, while all other exterior surfaces were insulated. The chamber width, measured from the surface of the circuit board to the opposite, inner wall of the enclosure, was varied from 42 to 7 mm by inserting plexiglass spacers into the enclosure. Two dielectric liquids, FC-75 and FC-43, were used as working fluids. Nondimensional data from this study was combined with the data obtained for a horizontal component orientation, to develop an empirical correlation which predicts the Nusselt number as a function of Rayleigh number, Prandtl number, component orientation, and chamber width.

Matthews, Scott T.

1991-12-01

222

Rate of heat recovery from a hot-water store: Influence of the aspect ratio of a vertical-axis open-ended cylinder beneath a submerged heat-exchanger  

Microsoft Academic Search

A coiled finned-pipe heat-exchanger was employed to extract heat rapidly, from a 90-litre hot-water charged tank; the water being initially at a temperature of approximately 80°C. Free-convective buoyancy movements of the water around the outside of this coiled pipe (immersed in the store) occur as a result of initially-cold water (at 20°C) being forced internally through the heat-exchanger's pipe. The

R. Mote; S. D. Probert; D. Nevrala

1992-01-01

223

AN ANALYTICAL SOLUTION OF THE TEMPERATURE RESPONSE IN GROUND HEAT EXCHANGERS WITH GROUNDWATER ADVECTION  

Microsoft Academic Search

A ground heat exchanger is devised for extraction or injection of thermal energy from\\/into the ground. In order to investigate the impact of groundwater advection on the performance of geothermal heat exchangers in ground-coupled heat pump systems, a governing equation of conduction-advection is established, and an analytical solution is obtained for a line heat source in an infinite porous medium

Dengchao Su; Nairen Diao

224

Heat transfer to and from a reversible thermosiphon placed in porous media  

NASA Astrophysics Data System (ADS)

The primary focus of this work is an assessment of heat transfer to and from a reversible thermosiphon imbedded in porous media. The interest in this study is the improvement of underground thermal energy storage (UTES) system performance with an innovative ground coupling using an array of reversible (pump-assisted) thermosiphons for air conditioning or space cooling applications. The dominant mechanisms, including the potential for heat transfer enhancement due to natural convection, of seasonal storage of "cold" in water-saturated porous media is evaluated experimentally and numerically. Winter and summer modes of operation are studied. A set of 6 experiments are reported that describe the heat transfer in both fine and coarse sand in a 0.32 cubic meter circular tank, saturated with water, under freezing (due to heat extraction) and thawing (due to heat injection) conditions, driven by the heat transfer to or from the vertical thermosiphon in the center of the tank. It was found that moderate to strong natural convection was induced at Rayleigh numbers of 30 or higher. Also, near water freezing temperatures (0°C-10°C), due to higher viscosity of water at lower temperatures, almost no natural convection was observed. A commercial heat transfer code, ANSYS FLUENT, was used to simulate both the heating and cooling conditions, including liquid/solid phase change. The numerical simulations of heat extraction from different permeability and temperature water-saturated porous media showed that enhancement to heat transfer by convection becomes significant only under conditions where the Rayleigh number is in the range of 100 or above. Those conditions would be found only for heat storage applications with higher temperatures of water (thus, its lower viscosity) and large temperature gradients at the beginning of heat injection (or removal) into (from) soil. For "cold" storage applications, the contribution of natural convection to heat transfer in water-saturated soils would be negligible. Thus, the dominant heat transfer mechanism for air conditioning applications of UTES can be assumed to be conduction. An evaluation of the potential for heat transfer enhancement in air-saturated media is also reported. It was found that natural convection in soils with high permeability and air saturations near 1 becomes more important as temperatures drop significantly below freezing.

Kekelia, Bidzina

225

Downflow dryout in a heated ribbed vertical annulus with a cosine power profile (Results from test series ECS-2, WSR, and ECS-2cE)  

SciTech Connect

Experiments designed to investigate surface dryout in a heated, ribbed annulus test section simulating one of the annular coolant channels of a Savannah River Plant production reactor Mark 22 fuel assembly have been conducted at the Idaho National Engineering Laboratory. The inner surface of the annulus was constructed of aluminum and was electrically heated to provide an axial cosine power profile and a flat azimuthal power shape. Data presented in this report are from the ECS-2, WSR, and ECS-2cE series of tests. These experiments were conducted to examine the onset of wall thermal excursion for a range of flow, inlet fluid temperature, and annulus outlet pressure. Hydraulic boundary conditions on the test section represent flowrates (0.1--1.4 1/s), inlet fluid temperatures (293--345 K), and outlet pressures (-18--139.7 cm of water relative to the bottom of the heated length (61--200 cm of water relative to the bottom of the lower plenum)) expected to occur during the Emergency Coolant System (ECS) phase of postulated Loss-of-Coolant Accident in a production reactor. The onset of thermal excursion based on the present data is consistent with data gathered in test rigs with flat axial power profiles. The data indicate that wall dryout is primarily a function of liquid superficial velocity. Air entrainment rate was observed to be a strong function of the boundary conditions (primarily flowrate and liquid temperature), but had a minor effect on the power at the onset of thermal excursion for the range of conditions examined. 14 refs., 33 figs., 13 tabs.

Larson, T.K.; Anderson, J.L.; Condie, K.G.

1990-12-01

226

Hybrid Heat Pumps Using Selective Water Sorbents (SWS)  

SciTech Connect

The development of the ground-coupled and air-coupled Heating Ventilation and Air-Conditioning (HVAC) system is essential in meeting the goals of Zero Energy Houses (ZEH), a viable concept vigorously pursued under DOE sponsorship. ORNL has a large Habitat for Humanity complex in Lenoir City where modem buildings technology is incorporated on a continual basis. This house of the future is planned for lower and middle income families in the 21st century. The work undertaken in this CRADA is an integral part of meeting DOE's objectives in the Building America program. SWS technology is a prime candidate for reducing the footprint, cost and improve the performance of ground-coupled heat pumps. The efficacy of this technique to exchange energy with the ground is a topic of immense interest to DOE, builders and HVAC equipment manufacturers. If successful, the SWS concept will become part of a packaged ZEH kit for affordable and high-end houses. Lennox Industries entered into a CRADA with Oak Ridge National Laboratory in November 2004. Lennox, Inc. agreed to explore ways of using Selective Water Sorbent materials to boost the efficiency of air-coupled heat pumps whereas ORNL concentrated on ground-coupled applications. Lennox supplied ORNL with heat exchangers and heat pump equipment for use at ORNL's Habitat for Humanity site in Lenoir City, Tennessee. Lennox is focused upon air-coupled applications of SWS materials at the Product Development and Research Center in Carrollton, TX.

Ally, M.R.

2006-11-30

227

Mixed convection flow in narrow vertical ducts  

Microsoft Academic Search

The mixed convection flow in a vertical duct is analysed under the assumption that e, the ratio of the duct width to the length over which the wall is heated, is small. It is assumed that a fully developed Poiseuille flow has already been set up in the duct before heat from the wall causes this to be changed by

T. Mahmood; J. H. Merkin

1989-01-01

228

Optimizing three-frequency Na, Fe, and He lidars for measurements of wind, temperature, and species density and the vertical fluxes of heat and constituents.  

PubMed

The measurement accuracies of three-frequency resonance fluorescence Doppler lidars are limited by photon noise and uncertainties in the laser frequency and line width. We analyze the performance of Na, Fe, and He lidars using a new technique, which incorporates precise information about the absorption spectrum of the species and the pulse spectrum of the lasers. We derive the measurement errors associated with photon noise, laser frequency errors, and laser line width errors. Optimizing the lidar design, based upon the measurement requirements, can improve system performance by reducing the required integration times, enabling measurements to be made in less time or at higher altitudes where the densities and signal levels are smaller. The optimum frequency shift for observing heat and constituent transport velocities is 689 MHz (580 MHz) at night (day) for Na lidars and 774 MHz (597 MHz) for Fe lidars. The optimum frequency shift for observing winds, temperature, and He densities is 3.66 GHz (3.16 GHz) at night (day) for He lidars. PMID:25089967

Gardner, Chester S; Vargas, Fabio A

2014-07-01

229

Operation Characteristics of Heat Pump Systems with Ground Heat Exchangers  

Microsoft Academic Search

This paper examines the merits of heating systems with a vapor compressor heat pump unit for small residential homes. In this case, the ground is assumed to serve as the low heat source, and the ground heat exchanger may be horizontal or vertical in form. A mathematical model for all vapor compressor heat pump (VCHP)-ground heat exchanger (GHE) systems is

Ma?gorzata Hanuszkiewicz-Drapa?a; Jan Sk?adzie?

2012-01-01

230

Heat and mass transfer for Soret and Dufour’s effect on mixed convection boundary layer flow over a stretching vertical surface in a porous medium filled with a viscoelastic fluid  

NASA Astrophysics Data System (ADS)

A mathematical model is analyzed in order to study the heat and mass transfer characteristics in mixed convection boundary layer flow about a linearly stretching vertical surface in a porous medium filled with a viscoelastic fluid, by taking into account the diffusion-thermo (Dufour) and thermal-diffusion (Soret) effects. The governing partial differential equations are transformed into a set of coupled ordinary differential equations, which are solved analytically using the homotopy analysis method (HAM) to determine the convergent series expressions of velocity, temperature and concentration. The physical interpretation to these expressions is assigned through graphs and a table for the wall shear stress f(0), Nusselt number -?'(0) and Sherwood number -?'(0). Results showed that the fields were influenced appreciably by the effects of the governing parameters: mixed convection parameter ?, Lewis number Le, Prandtl number Pr, viscoelastic parameter K, concentration buoyancy parameter N, porosity parameter ?, Dufour number Df and Soret number Sr. It was evident that for some kind of mixtures such as the light and medium molecular weight, the Soret and Dufour's effects should be considered as well.

Hayat, T.; Mustafa, M.; Pop, I.

2010-05-01

231

Vertical axis wind turbines  

Microsoft Academic Search

A vertical wind turbine having vertical blades, each blade being connected intermediate its ends by a hinge to a support arm having a hub that enables the blades to rotate around a vertical axis, a tie wire connected to the blade at positions spaced along the blade from the hinge, said tie wire engaging a spring-loaded pulley disposed inwardly of

P. E. Delgado; B. A. Holmes

1981-01-01

232

Vertical Map Storage.  

ERIC Educational Resources Information Center

Discusses the superiority of vertical filing of maps in compressor-style vertical units over horizontal filing in drawers, emphasizing such factors as physical protection of the collection, ease of filing and retrieval, and efficient use of space. Disadvantages of vertical filing are also reviewed. (Author/JL)

Perry, Joanne M.

1982-01-01

233

Vertical axis wind turbines  

DOEpatents

A vertical axis wind turbine is described. The wind turbine can include a top ring, a middle ring and a lower ring, wherein a plurality of vertical airfoils are disposed between the rings. For example, three vertical airfoils can be attached between the upper ring and the middle ring. In addition, three more vertical airfoils can be attached between the lower ring and the middle ring. When wind contacts the vertically arranged airfoils the rings begin to spin. By connecting the rings to a center pole which spins an alternator, electricity can be generated from wind.

Krivcov, Vladimir (Miass, RU); Krivospitski, Vladimir (Miass, RU); Maksimov, Vasili (Miass, RU); Halstead, Richard (Rohnert Park, CA); Grahov, Jurij (Miass, RU)

2011-03-08

234

Local\\/global analysis of transient heat transfer from building foundations  

Microsoft Academic Search

In this paper, a novel local\\/global (L–G) analysis technique is developed to solve transient ground-coupled heat transfer problems. The presented (L–G) analysis approach combines analytical and numerical techniques to obtain solutions of building foundation heat transfer problems with significant localized thermal bridges. Even though simplified analytical solutions generally fail to account for thermal bridging in building foundations, they can be

Adnan Al-Anzi; Moncef Krarti

2004-01-01

235

A simple method for estimating transient heat transfer in slab-on-ground floors  

Microsoft Academic Search

The problem of calculating transient heat transfer in concrete floor slabs is complicated due to ground coupling, which can require the numerical solution of two or three-dimensional transient conduction equations. This paper presents a simplified method for calculating transient slab-on-ground heat transfer that can be incorporated within hourly simulation programs. The method assumes that there are two primary one-dimensional paths

Zhipeng Zhong; James E. Braun

2007-01-01

236

Vertical axis wind turbines  

Microsoft Academic Search

A vertical axis wind turbine comprises one or more aerofoil section blades attached to a support structure. The blade has at least one part thereof which is acted on by centrifugal forces as the blade rotates with the support structure and thereby caused to increase its angle of inclination to the vertical axis when the speed of rotation increases beyond

Musgrove

1978-01-01

237

Vertical two chamber reaction furnace  

DOEpatents

A vertical two chamber reaction furnace is disclosed. The furnace comprises a lower chamber having an independently operable first heating means for heating the lower chamber and a gas inlet means for admitting a gas to create an ambient atmosphere, and an upper chamber disposed above the lower chamber and having an independently operable second heating means for heating the upper chamber. Disposed between the lower chamber and the upper chamber is a vapor permeable diffusion partition. The upper chamber has a conveyor means for conveying a reactant there through. Of particular importance is the thallinating of long-length thallium-barium-calcium copper oxide (TBCCO) or barium-calcium-copper oxide (BCCO) precursor tapes or wires conveyed through the upper chamber to thereby effectuate the deposition of vaporized thallium (being so vaporized as the first reactant in the lower chamber at a temperature between about 700 and 800 C) on TBCCO or BCCO tape or wire (the second reactant) at its simultaneous annealing temperature in the upper chamber of about 800 to 950 C to thereby replace thallium oxide lost from TBCCO tape or wire because of the high annealing temperature or to deposit thallium on BCCO tape or wire. Continuously moving the tape or wire provides a single-step process that effectuates production of long-length TBCCO superconducting product. 2 figs.

Blaugher, R.D.

1999-03-16

238

Industrial Heat Recovery - 1982  

E-print Network

,dedlJe regarding the principle;' of two Dhase flow with simultaneous heat absorption. Still, much research is needed in order to provide a simple and reliable method for the designer to avoid circula tion-related problems. Literature abounds with statements... like: "Vertical, natural circulation boilers are intrinsically mbre reliable than horizontal, forced circula tion boilers.",4 and " it will be seen that horizontal tubes have much lower heat fluxes at burnout than do vertical ones, though...

Csathy, D.

1982-01-01

239

Vertical optical floating zone furnace: Principles of irradiation profile formation  

Microsoft Academic Search

The light distribution within the vertical double-ellipsoid mirror furnace applied for floating zone crystal growth with optical heating is studied. During the last few years, this setup was intensively applied for crystal growth of intermetallic and oxide materials due to its advantages for radiation focussing, which is superior in some key features compared to other commercial horizontal and vertical optical

D. Souptel; W. Löser; G. Behr

2007-01-01

240

Methods of testing parameterizations: Vertical ocean mixing  

NASA Technical Reports Server (NTRS)

The ocean's velocity field is characterized by an exceptional variety of scales. While the small-scale oceanic turbulence responsible for the vertical mixing in the ocean is of scales a few centimeters and smaller, the oceanic general circulation is characterized by horizontal scales of thousands of kilometers. In oceanic general circulation models that are typically run today, the vertical structure of the ocean is represented by a few tens of discrete grid points. Such models cannot explicitly model the small-scale mixing processes, and must, therefore, find ways to parameterize them in terms of the larger-scale fields. Finding a parameterization that is both reliable and plausible to use in ocean models is not a simple task. Vertical mixing in the ocean is the combined result of many complex processes, and, in fact, mixing is one of the less known and less understood aspects of the oceanic circulation. In present models of the oceanic circulation, the many complex processes responsible for vertical mixing are often parameterized in an oversimplified manner. Yet, finding an adequate parameterization of vertical ocean mixing is crucial to the successful application of ocean models to climate studies. The results of general circulation models for quantities that are of particular interest to climate studies, such as the meridional heat flux carried by the ocean, are quite sensitive to the strength of the vertical mixing. We try to examine the difficulties in choosing an appropriate vertical mixing parameterization, and the methods that are available for validating different parameterizations by comparing model results to oceanographic data. First, some of the physical processes responsible for vertically mixing the ocean are briefly mentioned, and some possible approaches to the parameterization of these processes in oceanographic general circulation models are described in the following section. We then discuss the role of the vertical mixing in the physics of the large-scale ocean circulation, and examine methods of validating mixing parameterizations using large-scale ocean models.

Tziperman, Eli

1992-01-01

241

Development of a theoretical model for predicting the thermal performance characteristics of a vertical pin-fin array heat sink under combined forced and natural convection with impinging flow  

Microsoft Academic Search

A comprehensive theoretical and experimental study was carried out on the thermal performance of a pin-fin heat sink. A theoretical model was formulated that has the capability of predicting the influence of various geometrical, thermal, and flow parameters on the effective thermal resistance of the heat sink. An experimental technique was developed for measuring the thermal performance of the heat

C. J. Kobus; T. Oshio

2005-01-01

242

Geothermal direct-heat utilization assistance. Quarterly project progress report, October--December 1993  

SciTech Connect

This report consists of brief summaries of the activities of the Geo-Heat Center during the report period. Technical assistance was given to requests from 20 states in the following applications: space and district heating; geothermal heat pumps; greenhouses; aquaculture; industrial plants; electric power; resource/well; equipment; and resort/spa. Research and development activities progressed on (1) compilation of data on low-temperature resources and (2) evaluation of groundwater vs. ground-coupled heat pumps. Also summarized are technology transfer activities and geothermal progress monitoring activities.

Not Available

1993-12-31

243

Micromachined electrostatic vertical actuator  

DOEpatents

A micromachined vertical actuator utilizing a levitational force, such as in electrostatic comb drives, provides vertical actuation that is relatively linear in actuation for control, and can be readily combined with parallel plate capacitive position sensing for position control. The micromachined electrostatic vertical actuator provides accurate movement in the sub-micron to micron ranges which is desirable in the phase modulation instrument, such as optical phase shifting. For example, compact, inexpensive, and position controllable micromirrors utilizing an electrostatic vertical actuator can replace the large, expensive, and difficult-to-maintain piezoelectric actuators. A thirty pound piezoelectric actuator with corner cube reflectors, as utilized in a phase shifting diffraction interferometer can be replaced with a micromirror and a lens. For any very precise and small amplitudes of motion` micromachined electrostatic actuation may be used because it is the most compact in size, with low power consumption and has more straightforward sensing and control options.

Lee, Abraham P. (Walnut Creek, CA); Sommargren, Gary E. (Santa Cruz, CA); McConaghy, Charles F. (Livermore, CA); Krulevitch, Peter A. (Pleasanton, CA)

1999-10-19

244

Vertical comb array microactuators  

Microsoft Academic Search

A vertical actuator fabricated using a trench-refilled-with-polysilicon (TRiPs) process technology and employing an array of vertical oriented comb electrodes is presented. This actuator structure provides a linear drive to deflection characteristic and a large throw capability which are key features in many sensors, actuators and micromechanisms. The actuation principle and relevant theory is developed, including FastCap simulations for theoretical verification.

Arjun Selvakumar; Khalil Najafi

2003-01-01

245

Transition in Convective Flows Heated Internally  

Microsoft Academic Search

We consider an incompressible viscous flow in a vertical chan- nel under the influence of a vertical pressure gradient with a ho- mogeneously distributed heat source. There are several ways in which such a heat source may be produced. Heat released in chemical reactions taking place in the fluid, by currents through electrically conducting fluid solutions ~Wilkie and Fisher @1#!

Masato Nagata; Sotos Generalis

2002-01-01

246

Heat transfer system  

DOEpatents

A heat transfer system for a nuclear reactor. Heat transfer is accomplished within a sealed vapor chamber which is substantially evacuated prior to use. A heat transfer medium, which is liquid at the design operating temperatures, transfers heat from tubes interposed in the reactor primary loop to spaced tubes connected to a steam line for power generation purposes. Heat transfer is accomplished by a two-phase liquid-vapor-liquid process as used in heat pipes. Condensible gases are removed from the vapor chamber through a vertical extension in open communication with the chamber interior.

McGuire, Joseph C. (Richland, WA)

1982-01-01

247

Heat transfer system  

DOEpatents

A heat transfer system for a nuclear reactor is described. Heat transfer is accomplished within a sealed vapor chamber which is substantially evacuated prior to use. A heat transfer medium, which is liquid at the design operating temperatures, transfers heat from tubes interposed in the reactor primary loop to spaced tubes connected to a steam line for power generation purposes. Heat transfer is accomplished by a two-phase liquid-vapor-liquid process as used in heat pipes. Condensible gases are removed from the vapor chamber through a vertical extension in open communication with the chamber interior.

Not Available

1980-03-07

248

Implementation of a building foundation heat transfer model in EnergyPlus  

Microsoft Academic Search

In this article, a two-dimensional transient ground-coupled numerical model for slab-on-grade foundation is developed and integrated into EnergyPlus. A verification analysis is first presented to ensure that the developed building foundation heat transfer module is properly implemented within EnergyPlus. Then, predictions from the developed model are compared with those obtained from a simplified building foundation model currently used in EnergyPlus.

Moncef Krarti; Pyeongchan Ihm

2009-01-01

249

Vertical axis wind turbines  

SciTech Connect

A vertical wind turbine having vertical blades, each blade being connected intermediate its ends by a hinge to a support arm having a hub that enables the blades to rotate around a vertical axis, a tie wire connected to the blade at positions spaced along the blade from the hinge, said tie wire engaging a spring-loaded pulley disposed inwardly of the blades, the arrangement being such that when the angle of inclination of the blades to the vertical axis alters under the action of centrifugal force the tie wire exerts a force on the pulley opposing the spring force whereby as the turbine speeds up the blades will remain at a predetermined angle of inclination until the force exerted by the wire exceeds the force of the spring. One end of the tie wire can be connected to a position on one blade and connected to another position on another blade so that all of the blades adopt the same angle of inclination to the vertical axis.

Delgado, P.E.; Holmes, B.A.

1981-06-23

250

Vertical emitting aperture nanoantennas.  

PubMed

Herein we propose, theoretically investigate, and numerically demonstrate a compact design for a vertical emitter at a wavelength of 1.5 ?m based on nanophotonic aperture antennas coupled to a dielectric waveguide. The structure utilizes a plasmonic antenna placed above a Si3N4 waveguide with a ground plane for breaking the up-down symmetry and increasing the emission efficiency. Three-dimensional (3-D) finite-difference time-domain (FDTD) simulations reveal that up to 60% vertical emission efficiency is possible in a structure only four wavelengths long with a 3 dB bandwidth of over 300 nm. PMID:22555702

Yaacobi, Ami; Timurdogan, Erman; Watts, Michael R

2012-05-01

251

Fast reactor power plant design having heat pipe heat exchanger  

Microsoft Academic Search

The invention relates to a pool-type fission reactor power plant design having a reactor vessel containing a primary coolant (such as liquid sodium), and a steam expansion device powered by a pressurized water\\/steam coolant system. Heat pipe means are disposed between the primary and water coolants to complete the heat transfer therebetween. The heat pipes are vertically oriented, penetrating the

Paul R. Huebotter; George A. McLennan

1985-01-01

252

Fast reactor power plant design having heat pipe heat exchanger  

Microsoft Academic Search

The invention relates to a pool-type fission reactor power plant design having a reactor vessel containing a primary coolant (such as liquid sodium), and a steam expansion device powered by a pressurized water\\/steam coolant system. Heat pipe means are disposed between the primary and water coolants to complete the heat transfer therebetween. The heat pipes are vertically oriented, penetrating the

P. R. Huebotter; G. A. McLennan

1984-01-01

253

Aiding Vertical Guidance Understanding  

NASA Technical Reports Server (NTRS)

A two-part study was conducted to evaluate modern flight deck automation and interfaces. In the first part, a survey was performed to validate the existence of automation surprises with current pilots. Results indicated that pilots were often surprised by the behavior of the automation. There were several surprises that were reported more frequently than others. An experimental study was then performed to evaluate (1) the reduction of automation surprises through training specifically for the vertical guidance logic, and (2) a new display that describes the flight guidance in terms of aircraft behaviors instead of control modes. The study was performed in a simulator that was used to run a complete flight with actual airline pilots. Three groups were used to evaluate the guidance display and training. In the training, condition, participants went through a training program for vertical guidance before flying the simulation. In the display condition, participants ran through the same training program and then flew the experimental scenario with the new Guidance-Flight Mode Annunciator (G-FMA). Results showed improved pilot performance when given training specifically for the vertical guidance logic and greater improvements when given the training and the new G-FMA. Using actual behavior of the avionics to design pilot training and FMA is feasible, and when the automated vertical guidance mode of the Flight Management System is engaged, the display of the guidance mode and targets yields improved pilot performance.

Feary, Michael; McCrobie, Daniel; Alkin, Martin; Sherry, Lance; Polson, Peter; Palmer, Everett; McQuinn, Noreen

1998-01-01

254

Construction & Therapy Vertical Integration  

E-print Network

Construction & Therapy Vertical Integration Pilot Project Collaboration Partners Department to work with a local population to realize direct construction. Titled Construction & Therapy the studio will be documented and developed as a therapeutic exercise. The production of the welcome building will be delivered

Strathclyde, University of

255

A Hydrodynamical Model for Calculating the Vertical Temperature Profile in Lakes During Cooling  

Microsoft Academic Search

A one-dimensional hydrodynamical model is used for simulating the vertical temperature profile in a lake during cooling conditions. The vertical mixing rate is calculated by solving the equations for turbulent kinetic energy, k, and dissipation of energy, E. The heat exchange between the water and atmos- phere consists of the radiation fluxes, sensible and latent heat flux. Tempera- ture measurements

Jorgen Sahlberg

1983-01-01

256

Vertical velocity-CCN correlations  

NASA Astrophysics Data System (ADS)

The realization that smaller cloud droplets evaporate more readily (Xue and Feingold 2006; Jiang et al. 2002) gives rise to an anti-indirect aerosol effect (IAE); less cloudiness with pollution. The greater latent heat exchange of the greater evaporation in more polluted clouds adds TKE and buoyancy gradients that can enhance vertical velocity (W), mixing and entrainment (Zhao and Austin 2005). Stronger W can increase horizontal motions, which can further enhance droplet evaporation, which further enhances latent heat exchange and vertical motions, thus, positive feedback. This could also include latent heat released during condensation (Lee and Feingold 2010), which is more rapid for the greater surface areas of the smaller more numerous droplets. These theories imply a positive relationship between within-cloud W variations; i.e., standard deviation of W (?w) and CCN concentration (NCCN) rather than W and NCCN. This implies greater turbulence in polluted clouds, which could possibly counteract the reduction of cloudiness of anti-IAE. During two stratus cloud projects, 50 cloud penetrations in 9 MASE flights and 34 cloud penetrations in 13 POST flights, within-cloud ?w-NCCN showed correlation coefficients (R) of 0.50 and 0.39. Panel a shows similar within-cloud ?w-NCCN R in all altitude bands for 17 RICO flights in small cumulus clouds. R for W-NCCN showed similar values but only at low altitudes. Out-of-cloud ?w-NCCN showed similar high values except at the highest altitudes. Within-cloud ?w showed higher R than within-cloud W with droplet concentrations (Nc), especially at higher altitudes. Panel b for 13 ICE-T cumulus cloud flights in the same location as RICO but during the opposite season, however, showed ?w and W uncorrelated with NCCN at all altitudes; and W and ?w correlated with Nc only at the highest altitudes. On the other hand, out-of-cloud ?w was correlated with NCCN at all altitudes with R similar to the corresponding R of the other projects. Overall these results are consistent with the theories noted above. Supported by NSF AGS-1035230 and DOE SC0009162. Jiang, H., G. Feingold, and W.R. Cotton, 2002: J. Geophys. Res, 107, D24, 4813. Lee, S.-S., and G. Feingold, 2010: Geophys. Res. Lett., 37, L23806. Xue, H., and G. Feingold, 2006: J. Atmos. Sci., 63, 1605-1622. Zhao, M., and P.H. Austin, 2005: J. Atmos. Sci., 62, 1291-1310. Fig. Correlation coefficients (R) between mean and standard deviations of vertical velocity (W; ?w within and outside of clouds) with CCN concentrations at 1% supersaturation (N1%) measured below the clouds and with droplet concentrations (Nc) within various altitude bands.

Hudson, J. G.; Noble, S. R.

2013-12-01

257

Vortex Formation in Vertically Stratified Protoplanetary Disks  

NASA Astrophysics Data System (ADS)

A central problem of planet formation is how to form large planetesimals in a turbulent protoplanetary disk. Recent work suggests that MRI turbulence would excite such large velocities that the planetesimals would collisionally fragment rather than grow. The structure of chondritic meteorites indicates a gentle nebular environment where chondrules are sorted by size and cemented together rapidly. Although it is well established that anticyclones can concentrate particles that are weakly coupled to the gas in protoplanetary disks, the conditions required for the formation and long-time stability of anticyclones in a vertically stratified disk are still highly uncertain. Fully three dimensional fluid dynamic simulations of protoplanetary disks are computationally expensive when one requires a computational domain that is large compared to the vertical scale height of the disk. An alternative simulation approach is to use potential temperature as the vertical coordinate so that the equations of motion resemble the shallow water equations (Dowling et al. 1998). We have therefore modified a multilayer shallow water simulation code to model the formation of vortices in a vertically stratified protoplanetary disk with a radial entropy gradient. Vertical stratification of the disk is modeled by using multiple layers, where each layer has a different constant value of the entropy. By forcing a slope in the interfaces between the layers, we impose a radial entropy gradient in the disk. Radiative heating and cooling causes vertical mass exchange between adjacent constant entropy layers according to a Newton cooling formula. We find that the formation of anticyclones is robust, and that these vortices actively excite density waves, which in turn, transport angular momentum through the disk. Our simulations therefore yield new insights on how the dusty dead zones of protoplanetary disks can transport angular momentum through the disk by purely hydrodynamic processes. Support from NASA’s Origins of Solar Systems program is gratefully acknowledged.

Stewart, Glen R.

2013-10-01

258

Wood burning space heating stove  

Microsoft Academic Search

The design of a space heating wood burning stove, formed as a rectangular fire box, having a plurality of horizontal flue ducts leading to a flue manifold, adapted to generate substantial vertical convection currents of air, and further including vertical fins to enhance said convection currents, and further including a plurality of draft valves in substantial alignment with respective ones

Bane

1981-01-01

259

Advanced heat pump research and development  

NASA Astrophysics Data System (ADS)

The Office of Building Energy Research and Development of the U.S. Department of Energy (DOE), has been funding R&D in advanced heat pumps and appliances since 1976. Much of that research has been managed for DOE by the Oak Ridge National Laboratory (ORNL). The objective of the Building Equipment Research (BER) program at ORNL has been to generate new concepts and develop a technology base for improving the energy efficiency and load characteristics of energy conversion equipment used in residential and commercial buildings. The research being pursued to achieve these objectives falls under three general areas: thermally activated heat pumps (TAHP), refrigeration systems, and building equipment systems. The TAHP work is concentrated on three technologies: (1) absorption heat pumps; (2) Stirling engine-driven heat pumps; and (3) internal combustion (IC) engine-driven heat pumps. Major project areas in refrigeration systems research include electric heat pumps, ground-coupled heat pumps, and refigerant mixtures. In the building equipment systems areas, project areas include advanced distribution systems, advanced insulation for appliances, and commercial building equipment.

Kuliasha, M. A.

260

Vertical Motion Simulator  

NSDL National Science Digital Library

The Vertical Motion Simulator (VMS), at the NASA Ames Research Center, is an advanced flight simulation facility. This Web site provides thorough descriptions of all of the VMS systems. The VMS is a full immersion environment, complete with customizable cockpit, controls, and instrumentation to give the appearance of any aerospace vehicle. One of its most intriguing characteristics is "out-the-window graphics." This allows the pilot to see computer generated imagery of real locations, so virtually everything is identical to the actual flying experience. Even aircraft that are still in the design stage can be simulated on the VMS.

261

'Endurance' Untouched (vertical)  

NASA Technical Reports Server (NTRS)

This navigation camera mosaic, created from images taken by NASA's Mars Exploration Rover Opportunity on sols 115 and 116 (May 21 and 22, 2004) provides a dramatic view of 'Endurance Crater.' The rover engineering team carefully plotted the safest path into the football field-sized crater, eventually easing the rover down the slopes around sol 130 (June 12, 2004). To the upper left of the crater sits the rover's protective heatshield, which sheltered Opportunity as it passed through the martian atmosphere. The 360-degree view is presented in a vertical projection, with geometric and radiometric seam correction.

2004-01-01

262

Vertical slender jets  

NASA Technical Reports Server (NTRS)

The shape of a vertical slender jet of fluid falling steadily under the force of gravity is studied. The problem is formulated as a nonlinear free boundary-value problem for the potential. Surface tension effects are neglected. The use of perturbation expansions results in a system of equations that can be solved by an efficient numerical procedure. Computations were made for jets issuing from orifices in various shapes including an ellipse, a rectangle, and an equilateral triangle. Computational results are presented illustrating the propagation of discontinuities and the formation of thin sheets of fluid.

Geer, J. F.; Strikwerda, J. C.

1980-01-01

263

ON-LINE TOOLS FOR PROPER VERTICAL POSITIONING OF VERTICAL SAMPLING INTERVALS DURING SITE ASSESSMENT  

EPA Science Inventory

This presentation presents on-line tools for proper vertical positioning of vertical sampling intervals during site assessment. Proper vertical sample interval selection is critical for generate data on the vertical distribution of contamination. Without vertical delineation, th...

264

Vertical allometry: fact or fiction?  

PubMed

In pharmacokinetics, vertical allometry is referred to the clearance of a drug when the predicted human clearance is substantially higher than the observed human clearance. Vertical allometry was initially reported for diazepam based on a 33-fold higher human predicted clearance than the observed human clearance. In recent years, it has been found that many other drugs besides diazepam, can be classified as drugs which exhibit vertical allometry. Over the years, many questions regarding vertical allometry have been raised. For example, (1) How to define and identify the vertical allometry? (2) How much difference should be between predicted and observed human clearance values before a drug could be declared 'a drug which follows vertical allometry'? (3) If somehow one can identify vertical allometry from animal data, how this information can be used for reasonably accurate prediction of clearance in humans? This report attempts to answer the aforementioned questions. The concept of vertical allometry at this time remains complex and obscure but with more extensive works one can have better understanding of 'vertical allometry'. PMID:24534003

Mahmood, Iftekhar; Boxenbaum, Harold

2014-04-01

265

Natural convection on a vertical stretching cylinder  

NASA Astrophysics Data System (ADS)

The flow and natural (or mixed) convection due to a vertical stretching cylinder is studied. Using similarity transforms, the Navier-Stokes and energy equations reduce to a set of nonlinear ordinary differential equations. Asymptotic analysis for large Reynolds numbers shows the relation between axisymmetric flow and two-dimensional flow. Due to the algebraic decay of the similarity functions, numerical integration is performed using a compressed coordinate. The axial velocity is composed of forced convection due to stretching and natural convection from the heated cylinder. The heat transfer increases with both the Reynolds number and the Prandtl number. The result is also a rare similarity solution of the free convection and Navier-Stokes equations.

Wang, C. Y.

2012-03-01

266

Heat-pipe Earth.  

PubMed

The heat transport and lithospheric dynamics of early Earth are currently explained by plate tectonic and vertical tectonic models, but these do not offer a global synthesis consistent with the geologic record. Here we use numerical simulations and comparison with the geologic record to explore a heat-pipe model in which volcanism dominates surface heat transport. These simulations indicate that a cold and thick lithosphere developed as a result of frequent volcanic eruptions that advected surface materials downwards. Declining heat sources over time led to an abrupt transition to plate tectonics. Consistent with model predictions, the geologic record shows rapid volcanic resurfacing, contractional deformation, a low geothermal gradient across the bulk of the lithosphere and a rapid decrease in heat-pipe volcanism after initiation of plate tectonics. The heat-pipe Earth model therefore offers a coherent geodynamic framework in which to explore the evolution of our planet before the onset of plate tectonics. PMID:24067709

Moore, William B; Webb, A Alexander G

2013-09-26

267

Quantification of vertical Transport in high Alpine Terrain  

Microsoft Academic Search

The effect of thermally induced flow systems on air pollutants was investigated in mountainous terrain. During summer fair weather conditions thermally driven flow systems develop in mountainous terrain and lead to meso-scale export of heat, momentum and trace gases from the atmospheric boundary layer to the lower free troposphere (mountain venting). The research projects VOTALP (Vertical transport of ozone above

S. Henne; M. Furger; S. Nyeki; A. S. H. Prevot

2003-01-01

268

A parametric model of vertical eddy fluxes in the atmosphere  

Microsoft Academic Search

A scheme for the representation of the vertical eddy fluxes of heat, momentum and water vapour in a forecast model is presented. An important feature of the scheme is the dependence of the diffusion coefficients on the static stability of the atmosphere. Two tests are presented, using the scheme in a one-dimensional model: the simulation of the diurnal cycle, and

Jean-François Louis

1979-01-01

269

Vertically reciprocating auger  

NASA Technical Reports Server (NTRS)

The mathematical model and test results developed for the Vertically Reciprocating Auger (VRA) are summarized. The VRA is a device capable of transporting cuttings that result from below surface drilling. It was developed chiefly for the lunar surface, where conventional fluid flushing while drilling would not be practical. The VRA uses only reciprocating motion and transports material through reflections with the surface above. Particles are reflected forward and land ahead of radially placed fences, which prevent the particles from rolling back down the auger. Three input wave forms are considered to drive the auger. A modified sawtooth wave form was chosen for testing, over a modified square wave or sine wave, due to its simplicity and effectiveness. The three-dimensional mathematical model predicted a sand throughput rate of 0.2667 pounds/stroke, while the actual test setup transported 0.075 pounds/stroke. Based on this result, a correction factor of 0.281 is suggested for a modified sawtooth input.

Etheridge, Mark; Morgan, Scott; Fain, Robert; Pearson, Jonathan; Weldi, Kevin; Woodrough, Stephen B., Jr.

1988-01-01

270

The Gains from Vertical Scaling  

ERIC Educational Resources Information Center

It is often assumed that a vertical scale is necessary when value-added models depend upon the gain scores of students across two or more points in time. This article examines the conditions under which the scale transformations associated with the vertical scaling process would be expected to have a significant impact on normative interpretations…

Briggs, Derek C.; Domingue, Ben

2013-01-01

271

Measuring Growth with Vertical Scales  

ERIC Educational Resources Information Center

A vertical score scale is needed to measure growth across multiple tests in terms of absolute changes in magnitude. Since the warrant for subsequent growth interpretations depends upon the assumption that the scale has interval properties, the validation of a vertical scale would seem to require methods for distinguishing interval scales from…

Briggs, Derek C.

2013-01-01

272

Vertical axis wind turbine motor  

Microsoft Academic Search

A wind power conversion turbine motor has a body supported to rotate about a vertical axis and carrying a plurality of substantially upright vanes substantially spaced from the vertical axis and circumferentially spaced from one another so that wind thrusting propulsively against outer sides of the vanes can move across the space circumscribed by the vanes and thrust propulsively against

Rumsey

1977-01-01

273

Modeling Verticality Estimation During Locomotion  

E-print Network

for gravitational vertical estimation is introduced including an inclinometer combined with an imu, as proposed´eal, Qc, Canada 3 Laboratoire de Physiologie de la Perception et de l'Action, Coll`ege de France, Paris, France Abstract Estimation of the gravitational vertical is a fundamental problem faced by locomoting

Hayward, Vincent

274

A Simple Model of Climatological Rainfall and Vertical Motion Patterns over the Tropical Oceans  

E-print Network

A simple model is developed that predicts climatological rainfall, vertical motion, and diabatic heating profiles over the tropical oceans given the sea surface temperature (SST), using statistical relationships deduced ...

Back, Larissa E.

275

Atmospheric Environment 38 (2004) 48054813 Vertical profiles of particulate matter size distributions during  

E-print Network

is overwhelmingly dominated by fine particles (o1 mm in aerodynamic diameter). The vertical profiles reveal for winter home heating represents a very significant source of elevated PM concentrations. The physico

McKendry, Ian

276

Transition from film boiling to nucleate boiling in forced convection vertical flow  

E-print Network

The mechanism of collapse of forced cnnvection annular vertical flow film boiling, with liquid core, is investigated using liquid nitrogen at low pressures. The report includes the effect of heat flux from the buss bar. ...

Iloeje, Onwuamaeze C.

1972-01-01

277

Dynamics of vertical mixing in a shallow lake with submersed macrophytes  

Microsoft Academic Search

A model for vertical turbulent diffusion and stratification in a shallow lake with submersed macrophytes is formulated on the basis of a one-dimensional equation for production, transport, and dissipation of turbulent kinetic energy, coupled with a vertical heat transfer equation. Numerical solutions of the coupled equations allow simulation of the hourly variation of water temperature profiles in a shallow lake

William R. Herb; Heinz G. Stefan

2005-01-01

278

A new contribution to the finite line-source model for geothermal boreholes  

Microsoft Academic Search

Heat transfer around vertical ground heat exchangers is a common problem for the design and simulation of ground-coupled heat pump (GCHP) systems. Most models are based on step response of the heat transfer rate, and the superposition principle allows the final solution to be in the form of the convolution of these contributions. The step response is thus a very

Louis Lamarche; Benoit Beauchamp

2007-01-01

279

Heat exchanger with auxiliary cooling system  

DOEpatents

A heat exchanger with an auxiliary cooling system capable of cooling a nuclear reactor should the normal cooling mechanism become inoperable. A cooling coil is disposed around vertical heat transfer tubes that carry secondary coolant therethrough and is located in a downward flow of primary coolant that passes in heat transfer relationship with both the cooling coil and the vertical heat transfer tubes. A third coolant is pumped through the cooling coil which absorbs heat from the primary coolant which increases the downward flow of the primary coolant thereby increasing the natural circulation of the primary coolant through the nuclear reactor.

Coleman, John H. (Salem Township, Westmoreland County, PA)

1980-01-01

280

Heat pipe array heat exchanger  

DOEpatents

A heat pipe arrangement for exchanging heat between two different temperature fluids. The heat pipe arrangement is in a ounterflow relationship to increase the efficiency of the coupling of the heat from a heat source to a heat sink.

Reimann, Robert C. (Lafayette, NY)

1987-08-25

281

Measured Local Heat Transport in Turbulent Rayleigh-Benard Convection X.-D. Shang,1  

E-print Network

September 2002; published 20 February 2003) Local convective heat flux in turbulent thermal convection filled with water. It is found that fluctuations of the vertical heat flux are highly intermittent heat is trans- ported vertically through a convection cell [1­3]. A large number of global heat

Tong, Penger

282

SchoolFEFLOW Exercise Heat extraction  

E-print Network

projection #12;Summer SchoolHeat extraction from sloped aquifer 5 Flow Problem - Material parameters · Global the flux: q = 0.15 m/d Pumping (heat extraction) from aquifer and re-injection (of cooled waterSummer SchoolFEFLOW® Exercise Heat extraction from a sloped sandstone aquifer Vertical cross

Kornhuber, Ralf

283

Vertically Aligned Nanocomposite Thin Films  

E-print Network

Vertically aligned nanocomposite (VAN) thin films have recently stimulated significant research interest to achieve better material functionality or multifunctionalities. In VAN thin films, both phases grow epitaxially in parallel on given...

Bi, Zhenxing

2012-07-16

284

Vertically scanned laser sheet microscopy  

NASA Astrophysics Data System (ADS)

Laser sheet microscopy is a widely used imaging technique for imaging the three-dimensional distribution of a fluorescence signal in fixed tissue or small organisms. In laser sheet microscopy, the stripe artifacts caused by high absorption or high scattering structures are very common, greatly affecting image quality. To solve this problem, we report here a two-step procedure which consists of continuously acquiring laser sheet images while vertically displacing the sample, and then using the variational stationary noise remover (VSNR) method to further reduce the remaining stripes. Images from a cleared murine colon acquired with a vertical scan are compared with common stitching procedures demonstrating that vertically scanned light sheet microscopy greatly improves the performance of current light sheet microscopy approaches without the need for complex changes to the imaging setup and allows imaging of elongated samples, extending the field of view in the vertical direction.

Dong, Di; Arranz, Alicia; Zhu, Shouping; Yang, Yujie; Shi, Liangliang; Wang, Jun; Shen, Chen; Tian, Jie; Ripoll, Jorge

2014-10-01

285

Vertical axis wind turbine airfoil  

DOEpatents

A vertical axis wind turbine airfoil is described. The wind turbine airfoil can include a leading edge, a trailing edge, an upper curved surface, a lower curved surface, and a centerline running between the upper surface and the lower surface and from the leading edge to the trailing edge. The airfoil can be configured so that the distance between the centerline and the upper surface is the same as the distance between the centerline and the lower surface at all points along the length of the airfoil. A plurality of such airfoils can be included in a vertical axis wind turbine. These airfoils can be vertically disposed and can rotate about a vertical axis.

Krivcov, Vladimir; Krivospitski, Vladimir; Maksimov, Vasili; Halstead, Richard; Grahov, Jurij Vasiljevich

2012-12-18

286

Research and Development on Heat Pumps for Space Conditioning Applications: Proceedings of the DOE/ORNL Heat Pump Conference  

NASA Astrophysics Data System (ADS)

This conference was planned to provide information on current activities in the US Department of Energy (DOE) and Oak Ridge National Laboratory (ORNL) Building Equipment Research (BER) Program. It was primarily for the benefit of HVAC equipment manufacturers and other interested parties, including utilities, independent research and development organizations, universities, other government groups, and research funding and management organizations. The technical presentations were grouped into two principal subject areas: electric systems and thermally activated systems. Electric-system topics included field performance studies, laboratory experiments on cycling performance, analytical estimates of the benefits of variable capacity and zone control, nonazeotropic refrigerant mixtures, ground-coupled systems, and an analysis of Stirling-cycle heat pumps. In the area of thermally activated heat pumps, presentations centered on the development of absorption systems, Stirling-engine-driven systems, and a linear, free-piston IC-engine compressor. Separate abstracts have been prepared for 27 presentations for inclusion in the Energy Data Base.

Jacobs, V. A.; Powell, R. H., Jr.

1985-08-01

287

Ground-Source Heat Pumps Applied to Commercial Buildings  

SciTech Connect

Ground-source heat pumps can provide an energy-efficient, cost-effective way to heat and cool commercial facilities. While ground-source heat pumps are well established in the residential sector, their application in larger, commercial-style, facilities is lagging, in part because of a lack of experience with the technology by those in decision-making positions. Through the use of a ground-coupling system, a conventional water-source heat pump design is transformed to a unique means of utilizing thermodynamic properties of earth and groundwater for efficient operation throughout the year in most climates. In essence, the ground (or groundwater) serves as a heat source during winter operation and a heat sink for summer cooling. Many varieties in design are available, so the technology can be adapted to almost any site. Ground-source heat pump systems can be used widely in commercial-building applications and, with proper installation, offer great potential for the commercial sector, where increased efficiency and reduced heating and cooling costs are important. Ground-source heat pump systems require less refrigerant than conventional air-source heat pumps or air-conditioning systems, with the exception of direct-expansion-type ground-source heat pump systems. This chapter provides information and procedures that an energy manager can use to evaluate most ground-source heat pump applications. Ground-source heat pump operation, system types, design variations, energy savings, and other benefits are explained. Guidelines are provided for appropriate application and installation. Two case studies are presented to give the reader a sense of the actual costs and energy savings. A list of manufacturers and references for further reading are included for prospective users who have specific or highly technical questions not fully addressed in this chapter. Sample case spreadsheets are provided in Appendix A. Additional appendixes provide other information on the ground-source heat pump technology.

Parker, Steven A.; Hadley, Donald L.

2006-12-31

288

Natural convection of two staggered cylinders for various prandtl numbers and vertical and horizontal pitches  

NASA Astrophysics Data System (ADS)

Natural convection heat transfer phenomena of two staggered cylinders were investigated for laminar flows. Numerical simulations were carried out to examine the effect of varying the Prandtl number and the vertical and horizontal pitch-to-diameter ratios for a Rayleigh number of 1.5 × 108 using FLUENT. This study focused on phenomena related to very small vertical pitch. The heat transfer rates of the upper cylinders were influenced by plumes from the lower cylinders, exhibiting preheating, velocity, sweep, and side flow effects. The heat transfer rates of the lower cylinders were not affected by the upper cylinders at moderate vertical pitches. However, when the vertical pitch was very small, they were affected by stagnant flow, sweep, and side flow effects.

Heo, Jeong-Hwan; Chung, Bum-Jin

2014-06-01

289

Vertically transmitted symbiont reduces host fitness along temperature gradient.  

PubMed

Parasites with exclusive vertical transmission from host parent to offspring are an evolutionary puzzle. With parasite fitness entirely linked to host reproduction, any fitness cost for infected hosts risks their selective elimination. Environmental conditions likely influence parasite impact and thereby the success of purely vertical transmission strategies. We tested for temperature-dependent virulence of Caedibacter taeniospiralis, a vertically transmitted bacterial symbiont of the protozoan Paramecium tetraurelia. We compared growth of infected and cured host populations at five temperatures (16–32 °C). Infection reduced host density at all temperatures, with a peak of ?30% at 28 °C. These patterns were largely consistent across five infected Paramecium strains. Similar to Wolbachia symbionts, C. taeniospiralis may compensate fitness costs by conferring to the host a ‘killer trait’, targeting uninfected competitors. Considerable loss of infection at 32 °C suggests that killer efficacy is not universal and that limited heat tolerance restricts the conditions for persistence of C. taeniospiralis. PMID:24779056

Dusi, E; Krenek, S; Schrallhammer, M; Sachse, R; Rauch, G; Kaltz, O; Berendonk, T U

2014-04-01

290

Convective flows in enclosures with vertical temperature or concentration gradients  

NASA Technical Reports Server (NTRS)

The transport process in the fluid phase during the growth of a crystal has a profound influence on the structure and quality of the solid phase. In vertical growth techniques the fluid phase is often subjected to vertical temperature and concentration gradients. The main objective is to obtain more experimental data on convective flows in enclosures with vertical temperature or concentration gradients. Among actual crystal systems the parameters vary widely. The parametric ranges studied for mass transfer are mainly dictated by the electrochemical system employed to impose concentration gradients. Temperature or concentration difference are maintained between two horizontal end walls. The other walls are kept insulated. Experimental measurements and observations were made of the heat transfer or mass transfer, flow patterns, and the mean and fluctuating temperature distribution. The method used to visualize the flow pattern in the thermal cases is an electrochemical pH-indicator method. Laser shadowgraphs are employed to visualize flow patterns in the solutal cases.

Wang, L. W.; Chai, A. T.; Sun, D. J.

1988-01-01

291

Vertical optical floating zone furnace: Principles of irradiation profile formation  

NASA Astrophysics Data System (ADS)

The light distribution within the vertical double-ellipsoid mirror furnace applied for floating zone crystal growth with optical heating is studied. During the last few years, this setup was intensively applied for crystal growth of intermetallic and oxide materials due to its advantages for radiation focussing, which is superior in some key features compared to other commercial horizontal and vertical optical floating zone facilities. A point source model was used as a light source to reveal basic principles of the irradiation profile formation, which can strongly affect the melt flows, as well as the curvature and stability of crystallization front. Effects of the lamp displacement along the vertical optical axis with respect to the focal point of the lower elliptical mirror and the effect of mirror apertures were studied as the prime factors, which determine the light profile on the crystal. The efficiency of the light focusing in the presented optical configuration is discussed.

Souptel, D.; Löser, W.; Behr, G.

2007-03-01

292

Wood burning space heating stove  

SciTech Connect

The design of a space heating wood burning stove, formed as a rectangular fire box, having a plurality of horizontal flue ducts leading to a flue manifold, adapted to generate substantial vertical convection currents of air, and further including vertical fins to enhance said convection currents, and further including a plurality of draft valves in substantial alignment with respective ones of said flue ducts for efficient burning of wood within said fire box is presented. Assembly of the fire box of the stove is completed under stressed conditions to prevent warping of the fire box panels from heating and cooling cycles.

Bane, J.H.

1981-08-04

293

Vertical structure of recent Arctic warming.  

PubMed

Near-surface warming in the Arctic has been almost twice as large as the global average over recent decades-a phenomenon that is known as the 'Arctic amplification'. The underlying causes of this temperature amplification remain uncertain. The reduction in snow and ice cover that has occurred over recent decades may have played a role. Climate model experiments indicate that when global temperature rises, Arctic snow and ice cover retreats, causing excessive polar warming. Reduction of the snow and ice cover causes albedo changes, and increased refreezing of sea ice during the cold season and decreases in sea-ice thickness both increase heat flux from the ocean to the atmosphere. Changes in oceanic and atmospheric circulation, as well as cloud cover, have also been proposed to cause Arctic temperature amplification. Here we examine the vertical structure of temperature change in the Arctic during the late twentieth century using reanalysis data. We find evidence for temperature amplification well above the surface. Snow and ice feedbacks cannot be the main cause of the warming aloft during the greater part of the year, because these feedbacks are expected to primarily affect temperatures in the lowermost part of the atmosphere, resulting in a pattern of warming that we only observe in spring. A significant proportion of the observed temperature amplification must therefore be explained by mechanisms that induce warming above the lowermost part of the atmosphere. We regress the Arctic temperature field on the atmospheric energy transport into the Arctic and find that, in the summer half-year, a significant proportion of the vertical structure of warming can be explained by changes in this variable. We conclude that changes in atmospheric heat transport may be an important cause of the recent Arctic temperature amplification. PMID:18172495

Graversen, Rune G; Mauritsen, Thorsten; Tjernström, Michael; Källén, Erland; Svensson, Gunilla

2008-01-01

294

Vertical saccades in dyslexic children.  

PubMed

Vertical saccades have never been studied in dyslexic children. We examined vertical visually guided saccades in fifty-six dyslexic children (mean age: 10.5±2.56 years old) and fifty-six age matched non dyslexic children (mean age: 10.3±1.74 years old). Binocular eye movements were recorded using an infrared video-oculography system (mobileEBT®, e(ye)BRAIN). Dyslexic children showed significantly longer latency than the non dyslexic group, also the occurrence of anticipatory and express saccades was more important in dyslexic than in non dyslexic children. The gain and the mean velocity values were significantly smaller in dyslexic than in non dyslexic children. Finally, the up-down asymmetry reported in normal population for the gain and the velocity of vertical saccades was observed in dyslexic children and interestingly, dyslexic children also reported an up-down asymmetry for the mean latency. Taken together all these findings suggested impairment in cortical areas responsible of vertical saccades performance and also at peripheral level of the extra-ocular oblique muscles; moreover, a visuo-attentionnal bias could explain the up-down asymmetry reported for the vertical saccade triggering. PMID:25151607

Tiadi, Aimé; Seassau, Magali; Bui-Quoc, Emmanuel; Gerard, Christophe-Loïc; Bucci, Maria Pia

2014-11-01

295

Transient or steady-state? Using vertical temperature profiles to quantify groundwater-surface water exchange  

Microsoft Academic Search

Heat is recognized as a natural tracer to identify the exchange of water between the groundwater and surface water compartment. One-dimensional (1D) heat transport models have the ability to obtain quantitative estimates of vertical fluxes through the sediment matrix. Input to these models can come from temperatures observed in the surface water and in the bed material of rivers and

Christian Anibas; Jan H. Fleckenstein; Nina Volze; Kerst Buis; Ronny Verhoeven; Patrick Meire; Okke Batelaan

2009-01-01

296

Cooling of a vertical cylinder by natural convection: An undergraduate experiment  

NASA Astrophysics Data System (ADS)

The transient cooling of a vertical cylinder by natural convection is studied in a computerized undergraduate laboratory experiment. The dependence of the heat transfer coefficient on temperature is determined using simple data fitting algorithms. The results of the experiment clearly show that the natural convection heat transfer coefficient is proportional to ?T1/4, in agreement with previously published values.

Spuller, J. E.; Cobb, R. W.

1993-06-01

297

Effects of nozzle and grid acceleration of corona wind on cooling of a vertical flat plate  

Microsoft Academic Search

Several experiments were conducted to determine the effect of nozzle and grid acceleration of a corona wind on the free convection heat transfer rate of a vertically mounted heated flat plate. The plate was maintained at ground potential and was suspended in a Mach-Zehnder interferometer. A positively charged stretched wire emitter and 19 point emitter were used. Baseline tests were

M. E. Stefkovich

1983-01-01

298

Neglected locked vertical patellar dislocation.  

PubMed

Patellar dislocations occurring about the vertical and horizontal axis are rare and irreducible. The neglected patellar dislocation is still rarer. We describe the clinical presentation and management of a case of neglected vertical patellar dislocation in a 6 year-old boy who sustained an external rotational strain with a laterally directed force to his knee. Initially the diagnosis was missed and 2 months later open reduction was done. The increased tension generated by the rotation of the lateral extensor retinaculum kept the patella locked in the lateral gutter even with the knee in full extension. Traumatic patellar dislocation with rotation around a vertical axis has been described earlier, but no such neglected case has been reported to the best of our knowledge. PMID:23162154

Gupta, Rakesh Kumar; Gupta, Vinay; Sangwan, Sukhbir Singh; Kamboj, Pradeep

2012-09-01

299

Vertical and Interfacial Transport in Wetlands (Invited)  

NASA Astrophysics Data System (ADS)

The objective of this work is to understand the fluxes connecting the water column, substrate, and atmosphere in wetland environments. To do this, analytical, numerical, and laboratory models have been used to quantify the hydrodynamic contributions to vertical fluxes. A key question is whether the hydrodynamic transport can be modeled as a diffusivity, and, if so, what the vertical structure of this diffusivity is. This question will be addressed in a number of flow types and for a number of fluxes. The fluxes of interest are heat, sediment, dissolved gases (such as methane and oxygen) and other dissolved solutes (such as nutrients and pollutants). The flows of interest include: unidirectional current, reversing flow (under waves, seiches, and tides), wind-sheared surface flows, and thermal convection. Rain and bioturbation can be important, but are not considered in the modeling work discussed herein. Specifically, we will present results on gas transport at wind-sheared free surface, sediment transport in unidirectional flow, and heat transfer in an oscillating flow cause by a seiche. All three of these will be used to consider the question of appropriate analytical models for vertical transport. The analytic models considered here are all 1D models that assume homogeneity in the horizontal plane. The numerical models use finite element methods and resolve the flow around individual vegetation stems in an idealized geometry. Laboratory models discussed herein also use an idealized geometry. Vegetation is represented by an array of cylinders, whose geometry is modeled after Scirpus spp. wetlands in Northern California. The laboratory model is constructed in a way that allows optical access to the flow, even in dense vegetation and far from boundaries. This is accomplished by using fluoropolymer plastics to construct vegetation models. The optical access allows us to employ particle image velocimetry (PIV) and planar laser induced fluorescence (PLIF) to measure the velocity and scalar fields, respectively. To study sediment transport, an additional step is needed. Idealized sediment grains are manufactured, again using fluoropolymers. This allows the sediment and fluid phase to be resolved simultaneously, and the velocities of each to be determined independently of the other. The use of fluoropolymers means that the laboratory imaging techniques do not suffer from blockage during laser light delivery or during image capture by digital cameras. Cameras are paired and run in stereoscopic mode to allow three-dimensional velocities to be determined. This is important given the 3D nature of flow through vegetation. Current results from ongoing laboratory, field, and modeling efforts will be discussed, as well as the upcoming steps.

Variano, E. A.

2010-12-01

300

Measurements of vertical bar Vcb vertical bar and vertical bar Vub vertical bar at BaBar  

SciTech Connect

We report results from the BABAR Collaboration on the semileptonic B decays, highlighting the measurements of the magnitude of the Cabibbo-Kobayashi-Maskawa matrix elements Vub and Vcb. We describe the techniques used to obtain the matrix element |Vcb| using the measurement of the inclusive B {yields} Xclv process and a large sample of exclusive B {yields} D*lv decays. The vertical bar Vub vertical bar matrix elements has been measured studying different kinematic variables of the B {yields} Xulv process, and also with the exclusive reconstruction of B {yields} {pi}({rho})lv decays.

Rotondo, M. [Dipartimento di Fisica Galileo Galilei, Via Marzolo 8, Padova 35131 (Italy)

2005-10-12

301

Waves, circulation and vertical dependence  

NASA Astrophysics Data System (ADS)

Longuet-Higgins and Stewart (J Fluid Mech 13:481-504, 1962; Deep-Sea Res 11:529-562, 1964) and later Phillips (1977) introduced the problem of waves incident on a beach, from deep to shallow water. From the wave energy equation and the vertically integrated continuity equation, they inferred velocities to be Stokes drift plus a return current so that the vertical integral of the combined velocities was nil. As a consequence, it can be shown that velocities of the order of Stokes drift rendered the advective term in the momentum equation negligible resulting in a simple balance between the horizontal gradients of the vertically integrated elevation and wave radiation stress terms; the latter was first derived by Longuet-Higgins and Stewart. Mellor (J Phys Oceanogr 33:1978-1989, 2003a), noting that vertically integrated continuity and momentum equations were not able to deal with three-dimensional numerical or analytical ocean models, derived a vertically dependent theory of wave-circulation interaction. It has since been partially revised and the revisions are reviewed here. The theory is comprised of the conventional, three-dimensional, continuity and momentum equations plus a vertically distributed, wave radiation stress term. When applied to the problem of waves incident on a beach with essentially zero turbulence momentum mixing, velocities are very large and the simple balance between elevation and radiation stress gradients no longer prevails. However, when turbulence mixing is reinstated, the vertically dependent radiation stresses produce vertical velocity gradients which then produce turbulent mixing; as a consequence, velocities are reduced, but are still larger by an order of magnitude compared to Stokes drift. Nevertheless, the velocity reduction is sufficient so that elevation set-down obtained from a balance between elevation gradient and radiation stress gradients is nearly coincident with that obtained by the aforementioned papers. This paper includes four appendices. The first appendix demonstrates the numerical process by which Stokes drift is excluded from the turbulence stress parameterization in the momentum equation. A second appendix determines a bottom slope criterion for the application of linear wave relations to the derivation of the wave radiation stress. The third appendix explores the possibility of generalizing results by non-dimensionalization. The final appendix applies the basic theory to a problem introduced by Bennis and Ardhuin (J Phys Oceanogr 41:2008-2012, 2011).

Mellor, George

2013-04-01

302

Convection in vertical Bridgman configurations  

NASA Technical Reports Server (NTRS)

We are interested in tracing the convective profiles of vertical Bridgman growth in two configurations, the pure Rayleigh convective mode and the combined Rayleigh-Marangoni mode. In order to do so, we conducted a numerical investigation that involved a finite volume calculation. The governing equations were integrated about a cell volume, using the Gauss Theorem and the volume variables like temperature and velocity were related to the surface variables. In order to solve for the pressure field, we employed the continuity equation and the residuals resulted in a Poisson equation. Results and comments for the Rayleigh and Marangoni problems in a vertical cylinder or Bridgman configuration are given.

Narayanan, Ranga

1991-01-01

303

Vertical motion simulator familiarization guide  

NASA Technical Reports Server (NTRS)

The Vertical Motion Simulator Familiarization Guide provides a synoptic description of the Vertical Motion Simulator (VMS) and descriptions of the various simulation components and systems. The intended audience is the community of scientists and engineers who employ the VMS for research and development. The concept of a research simulator system is introduced and the building block nature of the VMS is emphasized. Individual sections describe all the hardware elements in terms of general properties and capabilities. Also included are an example of a typical VMS simulation which graphically illustrates the composition of the system and shows the signal flow among the elements and a glossary of specialized terms, abbreviations, and acronyms.

Danek, George L.

1993-01-01

304

The Effect of Vertical Shear on Tropical Cyclone Intensity Change  

Microsoft Academic Search

The effect of vertical shear on tropical cyclone intensity change is usually explained in terms of `ventilation' where heat and moisture at upper levels are advected away from the low-level circulation, which inhibits development. A simple two-layer diagnostic balance model is used to provide an alternate explanation of the effect of shear. When the upper-layer wind in the vortex environment

Mark Demaria

1996-01-01

305

On the Vertical Thermal Structure of Pluto's Atmosphere  

Microsoft Academic Search

A radiative-conductive model for the vertical thermal structure of Pluto's atmosphere is developed with a non-LTE treatment of solar heating in the CH_4 3.3 mum and 2.3 mum bands, non-LTE radiative exchange and cooling in the CH_4 7.6 mum band, and LTE cooling by CO rotational line emission. The model includes the effects of opacity and vibrational energy transfer in

Darrell F. Strobel; Xun Zhu; Michael E. Summers; Michael H. Stevens

1996-01-01

306

On the Vertical Thermal Structure of Pluto's Atmosphere  

Microsoft Academic Search

A radiative–conductive model for the vertical thermal structure of Pluto's atmosphere is developed with a non-LTE treatment of solar heating in the CH43.3 ?m and 2.3 ?m bands, non-LTE radiative exchange and cooling in the CH47.6 ?m band, and LTE cooling by CO rotational line emission. The model includes the effects of opacity and vibrational energy transfer in the CH4molecule.

Darrell F. Strobel; Xun Zhu; Michael E. Summers; Michael H. Stevens

1996-01-01

307

Vertical feed stick wood fuel burning furnace system  

DOEpatents

A stove or furnace for efficient combustion of wood fuel includes a vertical feed combustion chamber (15) for receiving and supporting wood fuel in a vertical attitude or stack. A major upper portion of the combustion chamber column comprises a water jacket (14) for coupling to a source of water or heat transfer fluid for convection circulation of the fluid. The locus (31) of wood fuel combustion is thereby confined to the refractory base of the combustion chamber. A flue gas propagation delay channel (34) extending laterally from the base of the chamber affords delayed travel time in a high temperature refractory environment sufficient to assure substantially complete combustion of the gaseous products of wood burning with forced air prior to extraction of heat in heat exchanger (16). Induced draft draws the fuel gas and air mixture laterally through the combustion chamber and refractory high temperature zone to the heat exchanger and flue. Also included are active sources of forced air and induced draft, multiple circuit couplings for the recovered heat, and construction features in the refractory material substructure and metal component superstructure.

Hill, Richard C. (Orono, ME)

1982-01-01

308

Heat transfer analysis of ground heat exchangers with inclined boreholes  

Microsoft Academic Search

Consisting of closed-loop of pipes buried in boreholes, ground heat exchangers (GHEs) are devised for extraction or injection of thermal energy from\\/into the ground. Evolved from the vertical borehole systems, the configuration of inclined boreholes is considered in order to reduce the land plots required to install the GHEs in densely populated areas. A transient three-dimensional heat conduction model has

Ping Cui; Hongxing Yang; Zhaohong Fang

2006-01-01

309

Heating stove  

SciTech Connect

A heating stove has a fire box composed of first and second pluralities of parallel aligned connected vertically oriented curved open-ended conduits. The lower extremities of the conduits of said first and second pluralities being aligned for contacting a common planar surface to support the stove, with the fire box further being formed by generally planar front and back plates, of substantially the same size and shape, with the front plate having an inlet port therethrough and the back plate having an exhaust port therein. The conduit central portions are largely within the stove fire box. A baffle within the fire box promotes three-pass flow of hot air across the conduit surfaces within the fire box. The first and second pluralities of curved conduits are opposed and in interdigitated engagement. Curved strips separate the curved conduits and thus facilitate stove construction with the conduits in interdigitated engagement. A closing mechanism for the stove door operates with caming action to assure that the door, when closed, is tightly fastened so that the hot coals cannot escape. In another embodiment, the fire box is cylindrical , formed by two curved side plates and two generally planar end plates, and the curved conduits pass through the fire box.

Darnell, E.

1980-10-28

310

Vertical Instability at IPNS RCS.  

SciTech Connect

The rapid cycling synchrotron (RCS) of the intense pulsed neutron source (IPNS) at ANL accelerates > 3.0 times 10{sup 12} protons from 50 MeV to 450 MeV with 30-Hz repetition frequency. During the acceleration cycle, the rf frequency varies from 2.21 MHz to 5.14 MHz. Presently, the beam current is limited by a vertical instability. By analyzing turn-by-turn beam position monitor (BPM) data, large- amplitude mode 0 and mode 1 vertical beam centroid oscillations were observed in the later part of the acceleration cycle. The oscillations start in the tail of the bunch, build up, and remain localized in the tail half of the bunch. This vertical instability was compared with a head-tail instability that was intentionally induced in the RCS by adjusting the trim sextupoles. It appears that our vertical instability is not a classical head-tail instability [1]. More data analysis and experiments were performed to characterize the instability.

Wang, S.; Brumwell, F. R.; Dooling, J. C.; Harkay, K. C.; Kustom, R.; McMichael, G. E.; Middendorf, M. E.; Nassiri, A.; Accelerator Systems Division (APS)

2008-01-01

311

Vertical capacitive SiBARs  

Microsoft Academic Search

This work introduces high frequency, vertical silicon bulk acoustic resonators (SiBAR). A combination of the new resonator structures with much larger transduction area and the HARPSS fabrication process is used to demonstrate high frequency capacitive resonators with significantly lower impedances compared to the previous capacitive resonators. Impedances as low as a few kilo-Ohms and quality factors in the range of

Siavash Pourkamali; Gavin K. Ho; Farrokh Ayazi

2005-01-01

312

Long wavelength vertical cavity lasers  

Microsoft Academic Search

The need for low cost, high speed telecommunication sources demands the maturation of long wavelength vertical cavity lasers (VCLs). Both long haul fiber optic systems and gigabit ethernet links are potential markets for 1.3 and 1.55 micron VCLs. This past year has seen much progress to this end, but the emerging technology has yet to be determined. This paper overviews

K. A. Blacka; P. Abraham; A. Keating; Y. J. Chiu; E. L. Hu; J. E. Bowers

1999-01-01

313

Vertical Sextants give Good Sights  

NASA Astrophysics Data System (ADS)

Many texts stress the need for marine sextants to be held precisely vertical at the instant that the altitude of a heavenly body is measured. Several authors lay particular emphasis on the technique of the instrument in a small arc about the horizontal axis to obtain a good sight. Nobody, to the author's knowledge, however, has attempted to quantify the errors involved, so as to compare them with other errors inherent in determining celestial position lines. This paper sets out to address these issues and to pose the question: what level of accuracy of vertical alignment can reasonably be expected during marine sextant work at sea ?When a heavenly body is brought to tangency with the visible horizon it is particularly important to ensure that the sextant is held in a truly vertical position. To this end the instrument is rocked gently about the horizontal so that the image of the body describes a small arc in the observer's field of vision. As Bruce Bauer points out, tangency with the horizon must be achieved during the process of rocking and not a second or so after rocking has been discontinued. The altitude is recorded for the instant that the body kisses the visible horizon at the lowest point of the rocking arc, as in Fig. 2. The only other visual clue as to whether the sextant is vertical is provided by the right angle made by the vertical edge of the horizon glass mirror with the horizon. There may also be some input from the observer's sense of balance and his hand orientation.

Dixon, Mark

314

Fast reactor power plant design having heat pipe heat exchanger  

DOEpatents

The invention relates to a pool-type fission reactor power plant design having a reactor vessel containing a primary coolant (such as liquid sodium), and a steam expansion device powered by a pressurized water/steam coolant system. Heat pipe means are disposed between the primary and water coolants to complete the heat transfer therebetween. The heat pipes are vertically oriented, penetrating the reactor deck and being directly submerged in the primary coolant. A U-tube or line passes through each heat pipe, extended over most of the length of the heat pipe and having its walls spaced from but closely proximate to and generally facing the surrounding walls of the heat pipe. The water/steam coolant loop includes each U-tube and the steam expansion device. A heat transfer medium (such as mercury) fills each of the heat pipes. The thermal energy from the primary coolant is transferred to the water coolant by isothermal evaporation-condensation of the heat transfer medium between the heat pipe and U-tube walls, the heat transfer medium moving within the heat pipe primarily transversely between these walls.

Huebotter, P.R.; McLennan, G.A.

1984-08-30

315

Fast reactor power plant design having heat pipe heat exchanger  

DOEpatents

The invention relates to a pool-type fission reactor power plant design having a reactor vessel containing a primary coolant (such as liquid sodium), and a steam expansion device powered by a pressurized water/steam coolant system. Heat pipe means are disposed between the primary and water coolants to complete the heat transfer therebetween. The heat pipes are vertically oriented, penetrating the reactor deck and being directly submerged in the primary coolant. A U-tube or line passes through each heat pipe, extended over most of the length of the heat pipe and having its walls spaced from but closely proximate to and generally facing the surrounding walls of the heat pipe. The water/steam coolant loop includes each U-tube and the steam expansion device. A heat transfer medium (such as mercury) fills each of the heat pipes. The thermal energy from the primary coolant is transferred to the water coolant by isothermal evaporation-condensation of the heat transfer medium between the heat pipe and U-tube walls, the heat transfer medium moving within the heat pipe primarily transversely between these walls.

Huebotter, Paul R. (Western Springs, IL); McLennan, George A. (Downers Grove, IL)

1985-01-01

316

Film boiling on the inside of vertical tubes with upward flow of the fluid at low qualities  

E-print Network

Flow regimes, local heat transfer coefficients, and temperature distributions along the wall have been studied for film boiling inside a vertical tube with upward flow of a saturated liquid. The area of interest has been ...

Dougall, R. S.

1963-01-01

317

Wood burning stove heat exchanger  

SciTech Connect

A wood burning stove includes a water circulating grate within the stove fire chamber which includes horizontally extending, vertically spaced, first and second tubular manifolds. Fuel supporting pipes, including bottom portions which define a ''V'', physically and fluidly interconnect the manifolds. An inlet pipe extends throughout the majority of the length of the bottom manifold, and the top manifold is connected-through a container having a larger cross-sectional area than the cross-sectional area of the manifold-to an outlet. The inlet to and outlet from the manifold are connected up to a hydronic space heating system. The container supports a heat exchanger comprising a finned copper tube, so that the heat exchanger extends generally horizontally and within the first manifold. The heat exchanger is connected up to a domestic hot water supply. The container also supports one or more electric resistance heating coils, which heat liquid within the container in emergency situations.

Manno, J. T.

1985-08-13

318

Kinematic Fitting of Detached Vertices  

SciTech Connect

The eg3 experiment at the Jefferson Lab CLAS detector aims to determine the existence of the $\\Xi_{5}$ pentaquarks and investigate the excited $\\Xi$ states. Specifically, the exotic $\\Xi_{5}^{--}$ pentaquark will be sought by first reconstructing the $\\Xi^{-}$ particle through its weak decays, $\\Xi^{-}\\to\\pi^{-}\\Lambda$ and $\\Lambda\\to\\pi^{-}$. A kinematic fitting routine was developed to reconstruct the detached vertices of these decays, where confidence level cuts on the fits are used to remove background events. Prior to fitting these decays, the exclusive reaction $\\gamma D\\rightarrow pp\\pi^{-}$ was studied in order to correct the track measurements and covariance matrices of the charged particles. The $\\Lambda\\rightarrow p\\pi^{-}$ and $\\Xi^{-}\\to\\pi^{-}\\Lambda$ decays were then investigated to demonstrate that the kinematic fitting routine reconstructs the decaying particles and their detached vertices correctly.

Paul Mattione

2007-05-01

319

Vertically Integrated Circuits at Fermilab  

SciTech Connect

The exploration of the vertically integrated circuits, also commonly known as 3D-IC technology, for applications in radiation detection started at Fermilab in 2006. This paper examines the opportunities that vertical integration offers by looking at various 3D designs that have been completed by Fermilab. The emphasis is on opportunities that are presented by through silicon vias (TSV), wafer and circuit thinning and finally fusion bonding techniques to replace conventional bump bonding. Early work by Fermilab has led to an international consortium for the development of 3D-IC circuits for High Energy Physics. The consortium has submitted over 25 different designs for the Fermilab organized MPW run organized for the first time.

Deptuch, Grzegorz; Demarteau, Marcel; Hoff, James; Lipton, Ronald; Shenai, Alpana; Trimpl, Marcel; Yarema, Raymond; Zimmerman, Tom; /Fermilab

2009-01-01

320

Vertically Integrated Circuits at Fermilab  

SciTech Connect

The exploration of vertically integrated circuits, also commonly known as 3D-IC technology, for applications in radiation detection started at Fermilab in 2006. This paper examines the opportunities that vertical integration offers by looking at various 3D designs that have been completed by Fermilab. The emphasis is on opportunities that are presented by through silicon vias (TSV), wafer and circuit thinning, and finally fusion bonding techniques to replace conventional bump bonding. Early work by Fermilab has led to an international consortium for the development of 3D-IC circuits for High Energy Physics. For the first time, Fermilab has organized a 3D MPW run, to which more than 25 different designs have been submitted by the consortium.

Deptuch, Grzegorz; Demarteau, Marcel; Hoff, James; Lipton, Ronald; Shenai, Alpana; Trimpl, Marcel; Yarema, Raymond; Zimmerman, Tom; /Fermilab

2010-01-01

321

Vertical combustor for refuse combustion  

Microsoft Academic Search

A vertical combustor for refuse-particle combustion was analyzed for waste-to-energy recovery. A one-dimensional model was constructed that consisted of fuel particles, inert solid particles, and the gaseous mixture. The gaseous mixture was divided further into six chemical species that are involved in combustion at temperatures below about 2000°F. It was concluded that such combustors may be viable in the United

Chung

1981-01-01

322

Vertical Structure of the Atmosphere  

NSDL National Science Digital Library

Earth is surrounded by a protective atmosphere, composed of nitrogen, oxygen, and argon, and trace amounts of other gases, that protects Earth's surface from damaging solar radiation and plays a major role in water and energy transport. This interactive feature shows the vertical structure of the atmosphere. Viewers can see the regions of the atmosphere, some of the objects (natural and man-made) found at various altitudes, as well as the variations in air temperature and pressure with altitude.

323

Vertical Height of the Atmosphere  

NSDL National Science Digital Library

This is a lesson about the vertical dimension of the atmosphere and includes four activities. Activity 1 Introduces concepts related to distance, including length and height and units of measurement. Students are asked to make comparisons of distances. In activity 2, students learn about the vertical profile of the atmosphere. They work with a graph and plot the heights of objects and the layers of the atmosphere: troposphere, stratosphere, mesosphere, thermosphere, and exosphere. In activity 3, students learn about other forms of visual displays using satellite imagery. They compare images of the same weather feature, a hurricane, using two different images from MODIS and CALIPSO. One image is looking down on the hurricane from space, the other looks through the hurricane to display a profile of the hurricane. Activity 4 reinforces the concept of the vertical nature of the atmosphere. Students will take a CALIPSO satellite image that shows a profile of the atmosphere and use this information to plot mountains and clouds on their own graph of the atmosphere. The recommended order for the activities is to complete the first two activities on day one, and the second two activities on day two. Each day will require approximately 1 to 1.5 hours.

324

Vertical Integration and Technology: Theory and Evidence  

E-print Network

We study the determinants of vertical integration. We first derive a number of predictions regarding the relationship between technology intensity and vertical integration from a simple incomplete contracts model. Then, ...

Acemoglu, Daron

325

An Experimental Study of Upward and Downward Flow of Supercritical Carbon Dioxide in a Straight Pipe Heat Exchanger with Constant Wall Heat Flux  

E-print Network

An experimental analysis was conducted on a single circular tube heat exchanger using supercritical carbon dioxide as the working fluid. The heat exchanger was operated in two different orientations: vertically upward and downward. The experimental...

Umrigar, Eric Dara

2014-05-01

326

Vertical feed stick wood fuel burning furnace system  

DOEpatents

A new and improved stove or furnace for efficient combustion of wood fuel including a vertical feed combustion chamber for receiving and supporting wood fuel in a vertical attitude or stack, a major upper portion of the combustion chamber column comprising a water jacket for coupling to a source of water or heat transfer fluid and for convection circulation of the fluid for confining the locus of wood fuel combustion to the bottom of the vertical gravity feed combustion chamber. A flue gas propagation delay channel extending from the laterally directed draft outlet affords delayed travel time in a high temperature environment to assure substantially complete combustion of the gaseous products of wood burning with forced air as an actively induced draft draws the fuel gas and air mixture laterally through the combustion and high temperature zone. Active sources of forced air and induced draft are included, multiple use and circuit couplings for the recovered heat, and construction features in the refractory material substructure and metal component superstructure.

Hill, Richard C. (Orono, ME)

1984-01-01

327

Vertical feed stick wood fuel burning furnace system  

SciTech Connect

A new and improved stove or furnace for efficient combustion of wood fuel including a vertical feed combustion chamber for receiving and supporting wood fuel in a vertical attitude or stack, a major upper portion of the combustion chamber column comprising a water jacket for coupling to a source of water or heat transfer fluid and for convection circulation of the fluid for confining the locus of wood fuel combustion to the bottom of the vertical gravity feed combustion chamber. A flue gas propagation delay channel extending from the laterally directed draft outlet affords delayed travel time in a high temperature environment to assure substantially complete combustion of the gaseous products of wood burning with forced air as an actively induced draft draws the fuel gas and air mixture laterally through the combustion and high temperature zone. Active sources of forced air and induced draft are included multiple use and circuit couplings for the recovered heat, and construction features in the refractory material substructure and metal component superstructure.

Hill, R.C.

1984-09-25

328

Twins Vertices in Hypergraphs Raoul Medina1  

E-print Network

Twins Vertices in Hypergraphs Raoul Medina1 and Caroline Noyer and Olivier Raynaud2 Research Report;Abstract Twin vertices in graphs correspond to vertices sharing the same neighbor- hood. We propose an extension to hypergraphs of the concept of twin ver- tices. For this we give two characterizations of twin

Boyer, Edmond

329

7, 22492274, 2007 Vertical ozone over  

E-print Network

ACPD 7, 2249­2274, 2007 Vertical ozone over Eastern Mediterranean and Central Europe P. D a Creative Commons License. Atmospheric Chemistry and Physics Discussions Vertical ozone measurements (kalabokas pavlos@yahoo.gr) 2249 #12;ACPD 7, 2249­2274, 2007 Vertical ozone over Eastern Mediterranean

Boyer, Edmond

330

?Vertical Sextants give Good Sights?  

NASA Astrophysics Data System (ADS)

Mark Dixon suggests (Forum, Vol. 50, 137) that nobody thus far has attempted to quantify the errors from tilt that arise while observing with the marine sextant. The issue in fact, with the related problem of what exactly is the axis about which the sextant is rotated whilst being (to define the vertical), was the subject of a lively controversy in the first two volumes of this Journal some fifty years ago. Since the consensus of opinion seems to have been that the maximum error does not necessarily occur at 45 degrees, whereas Dixon's table suggests that it does, some reiteration of the arguments may be in order.

Richey, Michael

331

Neighbourly polytopes with few vertices  

SciTech Connect

A family of neighbourly polytopes in R{sup 2d} with N=2d+4 vertices is constructed. All polytopes in the family have a planar Gale diagram of a special type, namely, with exactly d+3 black points in convex position. These Gale diagrams are parametrized by 3-trees (trees with a certain additional structure). For all polytopes in the family, the number of faces of dimension m containing a given vertex A depends only on d and m. Bibliography: 7 titles.

Devyatov, Rostislav A [M. V. Lomonosov Moscow State University, Faculty of Mechanics and Mathematics, Moscow (Russian Federation)

2011-10-31

332

ATLAS LTCS Vertically Challenged System Lessons Learned  

NASA Technical Reports Server (NTRS)

Re-planning of LTCS TVAC testing and supporting RTA (Receiver Telescope Assembly) Test Plan and Procedure document preparation. The Laser Thermal Control System (LTCS) is designed to maintain the lasers onboard Advanced Topographic Laser Altimeter System (ATLAS) at their operational temperatures. In order to verify the functionality of the LTCS, a thermal balance test of the thermal hardware was performed. During the first cold start of the LTCS, the Loop Heat Pipe (LHP) was unable to control the laser mass simulators temperature. The control heaters were fully on and the loop temperature remained well below the desired setpoint. Thermal analysis of the loop did not show these results. This unpredicted behavior of the LTCS was brought up to a panel of LHP experts. Based on the testing and a review of all the data, there were multiple diagnostic performed in order to narrow down the cause. The prevailing theory is that gravity is causing oscillating flow within the loop, which artificially increased the control power needs. This resulted in a replan of the LTCS test flow and the addition of a GSE heater to allow vertical operation.

Patel, Deepak; Garrison, Matt; Ku, Jentung

2014-01-01

333

Laser tracking for vertical control  

NASA Technical Reports Server (NTRS)

The Global Laser Tracking Network has provided LAGEOS ranging data of high accuracy since the first MERIT campaign in late 1983 and we can now resolve centimeter-level three dimensional positions of participating observatories at monthly intervals. In this analysis, the station height estimates have been considered separately from the horizontal components, and can be determined by the strongest stations with a formal standard error of 2 mm using eight years of continuous observations. The rate of change in the vertical can be resolved to a few mm/year, which is at the expected level of several geophysical effects. In comparing the behavior of the stations to that predicted by recent models of post-glacial rebound, we find no correlation in this very small effect. Particular attention must be applied to data and survey quality control when measuring the vertical component, and the survey observations are critical components of the geodynamic results. Seasonal patterns are observed in the heights of most stations, and the possibility of secular motion at the level of several millimeters per year cannot be excluded. Any such motion must be considered in the interpretation of horizontal inter-site measurements, and can help to identify mechanisms which can cause variations which occur linearly with time, seasonally, or abruptly.

Dunn, Peter; Torrence, Mark; Pavlis, Erricos; Kolenkiewicz, Ron; Smith, David

1993-01-01

334

A visualization comparison of convective flow boiling heat transfer augmentation devices  

E-print Network

The qualitative effects of inset-table heat transfer phics. augmentation devices on vertical in-tube convective flow boiling flow regimes, transition mechanisms, and heat transfer are presented in this study. Three twisted tapes with twist ratios...

Lundy, Brian Franklin

2012-06-07

335

Heat pumps  

NSDL National Science Digital Library

What electric heating system is the most efficient in moderate climates? This reading, part of a series about the future of energy, introduces students to the modern heat pump. Students read about the efficiency of heat pumps and the three types currently being used in homes. A simple explanation of how a heat pump works is offered. Copyright 2005 Eisenhower National Clearinghouse

Iowa Public Television. Explore More Project

2004-01-01

336

Heat waves  

Microsoft Academic Search

The concept of transmission of heat by waves is reviewed and interpreted. The notion of an effective thermal conductivity, an effective heat capacity, and relaxation functions for heat and energy is introduced along lines used recently to describe the elastic response of viscous liquids. An annotated bibliography of the literature on heat waves, from the beginning until now, gives a

D. D. Joseph; Luigi Preziosi

1989-01-01

337

Heat pump  

SciTech Connect

A heat pump is disclosed that is, driven by a free piston engine, wherein a refrigeration type of heat transfer unit is used and no externally energized electric motors are required but could be used, if desired. The engine is larger in horsepower than would be required for driving the compressor of the unit only, as it also provides power for driving one or more gas driven or other motors for forcing air through heat exchangers. This arrangement requires substantially less total energy than a unit requiring external electrical energy for operating portions of the heat pumps in that the extra heat in the exhaust from the larger horsepower engine is utilized in a heat exchanger to supply extra heat to the space being heated by the heat pump's primary heat supplier.

Braun, A.

1981-10-06

338

MHD mixed convection from a vertical plate embedded in a porous medium with a convective boundary condition  

Microsoft Academic Search

A numerical approach has been used to study the heat and mass transfer from a vertical plate embedded in a porous medium experiencing a first-order chemical reaction and exposed to a transverse magnetic field. Instead of the commonly used conditions of constant surface temperature or constant heat flux, a convective boundary condition is employed which makes this study unique and

O. D. Makinde; A. Aziz

2010-01-01

339

On the Vertical Structuring of Gigantic Jets  

NASA Astrophysics Data System (ADS)

Gigantic Jets (GJs) are large-scale electrical discharges between the thundercloud tops and the lower ionosphere. It is estimated that an individual GJ can contribute as much as cloud-to-ground lightning in discharging a thunderstorm system, transferring hundreds of coulombs from thundercloud to the ionosphere [Cummer et al., Nat. Geosci., 2, 617-620, 2009]. GJs are initiated deep inside the thundercloud as intracloud lightning discharges. Owing to a charge imbalance, meaning the upper charge center is depleted with respect to the midlevel charge center, the upward-directed lightning leaders manage to escape through the thundercloud top to form GJs [Krehbiel et al., Nat. Geosci., 1, 233-237, 2008]. As a GJ leader crosses the stratosphere its streamer zone becomes longer and longer, due to the dynamics of streamer growth in a medium with exponentially-decreasing air density, such as in the Earth's atmosphere [Raizer et al., GRL, 33, L23801, 2006]. The speed at which a leader propagates is limited by the air heating of every newly formed leader section, rate of which is slower at upper altitudes in the Earth's atmosphere [da Silva and Pasko, GRL, 39, L13805, 2012]. Despite the expected deceleration of an upward-directed leader, GJs are observed to accelerate as they approach the ionosphere. To address this issue, we propose a simple time-dynamic model for GJ propagation that simulates the upward propagation of a leader discharge accounting for the effects of the expansion of its streamer zone. We propose that the GJ acceleration is a consequence of its vertical structuring and, therefore, can be used to trace the transition altitude between the leader and streamer zone sections of GJs [da Silva and Pasko, GRL, 40, 12, 3315-3319, 2013]. Leaders and streamers are very different electrical discharges in terms of the degree of ionization, temperature, and composition of the plasma inside their channels. A correct description of the vertical structuring of GJs is of fundamental importance for evaluation of their effects in the stratosphere and mesosphere.

Da Silva, C.; Pasko, V. P.

2013-12-01

340

Vertical combustor for refuse combustion  

SciTech Connect

A vertical combustor for refuse-particle combustion was analyzed for waste-to-energy recovery. A one-dimensional model was constructed that consisted of fuel particles, inert solid particles, and the gaseous mixture. The gaseous mixture was divided further into six chemical species that are involved in combustion at temperatures below about 2000/sup 0/F. It was concluded that such combustors may be viable in the United States since US refuse contains large amounts of volatile matter. Combustion of the relatively small char, however, may not be cost-effective in the present combustor where the fuel residence time is on the order of 2 s for a combustor height of 20 to 30 ft. A computer solution was designed to optimize a given combustor system. A simplified version of the solution was programmed for a TI-59 programmable hand calculator for field use.

Chung, P.M.

1981-06-01

341

Heating Structures Derived from Satellite  

NASA Technical Reports Server (NTRS)

Rainfall is a key link in the hydrologic cycle and is a primary heat source for the atmosphere. The vertical distribution of latent-heat release, which is accompanied by rainfall, modulates the large-scale circulations of the tropics and in turn can impact midlatitude weather. This latent heat release is a consequence of phase changes between vapor, liquid, and solid water. The Tropical Rainfall Measuring Mission (TRMM), a joint U.S./Japan space project, was launched in November 1997. It provides an accurate measurement of rainfall over the global tropics which can be used to estimate the four-dimensional structure of latent heating over the global tropics. The distributions of rainfall and inferred heating can be used to advance our understanding of the global energy and water cycle. This paper describes several different algorithms for estimating latent heating using TRMM observations. The strengths and weaknesses of each algorithm as well as the heating products are also discussed. The validation of heating products will be exhibited. Finally, the application of this heating information to global circulation and climate models is presented.

Tao, W.-K.; Adler, R.; Haddad, Z.; Hou, A.; Kakar, R.; Krishnamurti, T. N.; Kummerow, C.; Lang, S.; Meneghini, R.; Olson, W.

2004-01-01

342

MHD MIXED-CONVECTION INTERACTION WITH THERMAL RADIATION AND nTH ORDER CHEMICAL REACTION PAST A VERTICAL POROUS PLATE EMBEDDED IN A POROUS MEDIUM  

Microsoft Academic Search

This article investigates the hydromagnetic mixed convection heat and mass transfer flow of an incompressible Boussinesq fluid past a vertical porous plate with constant heat flux in the presence of radiative heat transfer in an optically thin environment, viscous dissipation, and an nth order homogeneous chemical reaction between the fluid and the diffusing species. The dimensionless governing equations for this

O. D. Makinde

2010-01-01

343

Monolithic vertical combdrive actuators for adaptive optics  

Microsoft Academic Search

High aspect ratio vertical combdrive actuators are demonstrated which advance the capabilities and applications of SOI-MEMS by adding additional independent degrees of freedom of operation: both upward and downward vertical pistoning motion as well as bi-directional pure rotation. The methodology for the first time enables monolithic fabrication of isolated vertical combdrive sets in the SOI device layer, with combfinger self-alignment

Veliko MilanoviC; Sunghoon Kwon; L. P. Lee

2002-01-01

344

Monitoring soil water content by vertical temperature variations.  

PubMed

The availability of high sensitivity temperature sensors (0.001 K sensitivity platinum resistors), which can be positioned at intervals of a few centimeters along a vertical profile in the unsaturated zone, allows short-term in situ determinations-one day or even less-of the thermal diffusivity. The development of high data storage capabilities also makes this possible over long periods and the relative variations in thermal diffusivity allow the monitoring of the variations in water content. The processing of temperature measurements recorded at different depths is achieved by solving the heat equation, using the finite elements method, with both conductive and convective heat transfers. A first set of measurements has allowed this approach to be validated. Water content variations derived from thermal diffusivity values are in excellent agreement with TDR measurements carried out on the experimental site at Boissy-le-Châtel (Seine et Marne, France). PMID:23834312

Bechkit, Mohamed Amine; Flageul, Sébastien; Guerin, Roger; Tabbagh, Alain

2014-01-01

345

Remote observation of ocean colour for prediction of upper ocean heating rates  

Microsoft Academic Search

The magnitude and variability in the vertical distribution of solar heating of the ocean is controlled by the concentration of pigments imaged by the Coastal Zone Colour Scanner. The vertical heating profile influences the thermal structure and dynamics of the upper ocean on time-scales from the diurnal to the climatic, and can potentially be predicted from estimation of attenuance from

Marlon R. Lewis; Trevor C. Platt

1987-01-01

346

Analysis of tropical radiative heating profiles: A comparison of models and observations  

Microsoft Academic Search

The vertical distribution of radiative heating in the atmosphere is an important driver of atmospheric circulation. Evaluation of model simulations of the Earth's radiation budget typically focus only on performance at the top of the atmosphere or at the surface. In this study, we compare the vertical distribution of cloud properties and radiative heating rates calculated from observations at the

Sally A. McFarlane; James H. Mather; Thomas P. Ackerman

2007-01-01

347

Effects of dynamical heat fluxes on model climate sensitivity  

Microsoft Academic Search

The effect of the meridional and vertical dynamic heat fluxes on climate sensitivity is investigated using an annual mean coupled high and low latitude radiative-dynamical model of the northern hemisphere. The model was constructed by incorporating a meridonal (atmosphere and ocean) dynamical heat flux parameterization into a two-zone (flow latitude 0°-30°N and high latitude 30°-90°N) version of the vertical radiative-convective

Wei-Chyung Wang; Gyula Molnar; Todd P. Mitchell; Peter H. Stone

1984-01-01

348

Effects of Dynamical Heat Fluxes on Model Climate Sensitivity  

Microsoft Academic Search

The effect of the meridional and vertical dynamical heat fluxes on climate sensitivity is investigated using an annual mean coupled high and low latitude radiative-dynamical model of the northern hemisphere. The model was constructed by incorporating a meridional (atmosphere and ocean) dynamical heat flux parameterization into a two-zone (low latitude 0ø-30øN and high latitude 30ø-90øN) version of the vertical radiative-convective

Wei-Chyung Wang; Gyula Molnar; Todd P. Mitchell; Peter H. Stone

1984-01-01

349

Heating Safety  

MedlinePLUS

... from heating equipment, such as the furnace, fireplace, wood stove, or portable heater. • Only use heating equipment ... into the room and burn only dry, seasoned wood. Allow ashes to cool before disposing in a ...

350

Heat emergencies  

MedlinePLUS

... can lead to heat exhaustion and then heatstroke. Heat stroke occurs when the body is no longer able to regulate the temperature, and it keeps rising. Heatstroke can cause shock, brain damage, organ failure, and even death. The ...

351

Vertical Diffusivities of Active and Passive Tracers  

NASA Technical Reports Server (NTRS)

The climate models that include a carbon-cycle need the vertical diffusivity of a passive tracer. Since an expression for the latter is not available, it has been common practice to identify it with that of salt. The identification is questionable since T, S are active, not passive tracers. We present the first derivation of the diffusivity of a passive tracer in terms of Ri (Richardson number) and Rq (density ratio, ratio of salinity over temperature z-gradients). The following results have emerged: (a) The passive tracer diffusivity is an algebraic function of Ri, Rq. (b) In doubly stable regimes (DS, partial derivative of T with respect to z > 0, partial derivative of S with respect to z < 0), the passive scalar diffusivity is nearly the same as that of salt/heat for any values of Rq < 0 and Ri > 0. (c) In DC regimes (diffusive convection, partial derivative of T with respect to z < 0, partial derivative of S with respect to z < 0, Rq > 1), the passive scalar diffusivity is larger than that of salt. At Ri = O(1), it can be more than twice as large. (d) In SF regimes (salt fingers, partial derivative of T with respect to z > 0, partial derivative of S with respect to z > 0, Rq < 1), the passive scalar diffusivity is smaller than that of salt. At Ri = O(1), it can be less than half of it. (e) The passive tracer diffusivity predicted at the location of NATRE (North Atlantic Tracer Release Experiment) is discussed. (f) Perhaps the most relevant conclusion is that the common identification of the tracer diffusivity with that of salt is valid only in DS regimes. In the Southern Ocean, where there is the largest CO2 absorption, the dominant regime is diffusive convection discussed in (c) above.

Canuto, V. M.; Cheng, Y.; Howard, A. M.

2010-01-01

352

On the Measurement of the Thermal Resistance of Vertical-External-Cavity Surface-Emitting Lasers (VECSELs)  

Microsoft Academic Search

Heat management is a key concern in the development of vertical-external-cavity surface-emitting lasers. Especially, high power systems are mainly limited by their heat transfer capabilities. A commonly used quantitative measure for the heat flow in such systems is the thermal resistance. So far, the thermal resistance is usually determined by evaluating the shift rates of the emission spectrum induced by

Bernd Heinen; Fan Zhang; Mino Sparenberg; Bernardette Kunert; Martin Koch; Wolfgang Stolz

2012-01-01

353

Natural convection of ferrofluids in partially heated square enclosures  

NASA Astrophysics Data System (ADS)

In this study, natural convection of ferrofluid in a partially heated square cavity is numerically investigated. The heater is located to the left vertical wall and the right vertical wall is kept at constant temperature lower than that of the heater. Other walls of the square enclosure are assumed to be adiabatic. Finite element method is utilized to solve the governing equations. The influence of the Rayleigh number (104?Ra?5×105), heater location (0.25H?yh?0.75H), strength of the magnetic dipole (0???2), horizontal and vertical location of the magnetic dipole (-2H?a?-0.5H, 0.2H?b?0.8H) on the fluid flow and heat transfer characteristics are investigated. It is observed that different velocity components within the square cavity are sensitive to the magnetic dipole source strength and its position. The length and size of the recirculation zones adjacent to the heater can be controlled with magnetic dipole strength. Averaged heat transfer increases with decreasing values of horizontal position of the magnetic dipole source. Averaged heat transfer value increases from middle towards both ends of the vertical wall when the vertical location of the dipole source is varied. When the heater location is changed, a symmetrical behavior in the averaged heat transfer plot is observed and the minimum value of the averaged heat transfer is attained when the heater is located at the mid of vertical wall.

Selimefendigil, Fatih; Öztop, Hakan F.; Al-Salem, Khaled

2014-12-01

354

Analysis and optimization of a natural draft heat sink system  

Microsoft Academic Search

An analytical solution for a system consisting of a vertical, parallel-plate, isothermal heat sink, and a chimney is presented. The result is applied to problems in which the size of the overall system is constrained. A ridge of maximum total heat transfer is observed with respect to the plate spacing and heat-sink height. The ridge suggests that heat-sink height may

Timothy S. Fisher; Kenneth E. Torrance; Kamal K. Sikka

1997-01-01

355

Energy, Exergy and Uncertainty Analyses of the Thermal Response Test for a Ground Heat Exchanger  

E-print Network

1 Energy, Exergy and Uncertainty Analyses of the Thermal Response Test for a Ground Heat Exchanger response test of a ground heat exchanger. In this study, a vertical U-shaped ground heat exchanger with 80 of the ground heat exchanger. The thermal response test was carried out four times at different thermal loads

Al-Shayea, Naser Abdul-Rahman

356

Sensible and latent heating of the atmosphere as inferred from DST-6 data  

NASA Technical Reports Server (NTRS)

The average distribution of convective latent heating, boundary layer sensible heat flux, and vertical velocity are determined for the winter 1976 DST period from GLAS model diagnostics. Key features are the regions of intense latent heating over Brazil, Central Africa, and Indonesia; and the regions of strong sensible heating due to air mass modification over the North Atlantic and North Pacific Oceans.

Herman, G. F.; Schubert, S. D.; Johnson, W. T.

1979-01-01

357

Heat transfer in microwave heating  

NASA Astrophysics Data System (ADS)

Heat transfer is considered as one of the most critical issues for design and implement of large-scale microwave heating systems, in which improvement of the microwave absorption of materials and suppression of uneven temperature distribution are the two main objectives. The present work focuses on the analysis of heat transfer in microwave heating for achieving highly efficient microwave assisted steelmaking through the investigations on the following aspects: (1) characterization of microwave dissipation using the derived equations, (2) quantification of magnetic loss, (3) determination of microwave absorption properties of materials, (4) modeling of microwave propagation, (5) simulation of heat transfer, and (6) improvement of microwave absorption and heating uniformity. Microwave heating is attributed to the heat generation in materials, which depends on the microwave dissipation. To theoretically characterize microwave heating, simplified equations for determining the transverse electromagnetic mode (TEM) power penetration depth, microwave field attenuation length, and half-power depth of microwaves in materials having both magnetic and dielectric responses were derived. It was followed by developing a simplified equation for quantifying magnetic loss in materials under microwave irradiation to demonstrate the importance of magnetic loss in microwave heating. The permittivity and permeability measurements of various materials, namely, hematite, magnetite concentrate, wüstite, and coal were performed. Microwave loss calculations for these materials were carried out. It is suggested that magnetic loss can play a major role in the heating of magnetic dielectrics. Microwave propagation in various media was predicted using the finite-difference time-domain method. For lossy magnetic dielectrics, the dissipation of microwaves in the medium is ascribed to the decay of both electric and magnetic fields. The heat transfer process in microwave heating of magnetite, which is a typical magnetic dielectric, was simulated by using an explicit finite-difference approach. It is demonstrated that the heat generation due to microwave irradiation dominates the initial temperature rise in the heating and the heat radiation heavily affects the temperature distribution, giving rise to a hot spot in the predicted temperature profile. Microwave heating at 915 MHz exhibits better heating homogeneity than that at 2450 MHz due to larger microwave penetration depth. To minimize/avoid temperature nonuniformity during microwave heating the optimization of object dimension should be considered. The calculated reflection loss over the temperature range of heating is found to be useful for obtaining a rapid optimization of absorber dimension, which increases microwave absorption and achieves relatively uniform heating. To further improve the heating effectiveness, a function for evaluating absorber impedance matching in microwave heating was proposed. It is found that the maximum absorption is associated with perfect impedance matching, which can be achieved by either selecting a reasonable sample dimension or modifying the microwave parameters of the sample.

Peng, Zhiwei

358

INVESTIGATING THERMODYNAMICS OF VERTICAL ATMOSPHERIC ENERGY TRANSPORT  

E-print Network

INVESTIGATING THERMODYNAMICS OF VERTICAL ATMOSPHERIC ENERGY TRANSPORT Wei Wu and Yangang Liu National Laboratory P.O. Box, Upton, NY www.bnl.gov ABSTRACT Thermodynamics of vertical atmospheric energy. Potential thermodynamic constraint(s) for the Earth's climate system are also explored from these simple

359

Downstream Competition, Foreclosure, and Vertical Integration  

E-print Network

Downstream Competition, Foreclosure, and Vertical Integration Gilles Chemla ¤ July 8, 2002 and Management Strategy 12, 2 (2003) 261-289." #12;Downstream Competition, Forclosure, and Vertical Integration Abstract This paper analyzes the impact of competition among downstream ¯rms on an upstream ¯rm's payo

Paris-Sud XI, Université de

360

Evolution of Mutualistic Symbiosis without Vertical Transmission  

Microsoft Academic Search

Mutualistic symbioses are considered to evolve from parasitic relationships. Vertical transmission, defined as the direct transfer of infection from a parent organism to its progeny, has been suggested as a key factor causing reduction of symbiont virulence and evolution of mutualism. On the other hand, there are several mutualistic associations without vertical transmission, such as those between plants and mycorrhizal

Motomi Genkai-Kato; Norio Yamamura

1999-01-01

361

Silicon Micromachined Vertical Structures for Nanoparticle Separation  

Microsoft Academic Search

In this thesis we described a new approach to design, fabricate, package and test three silicon based porous vertical structures for nanoparticle separations. These vertical structures stand in between two microfluidic channels. In these walls nano channels that connect the two adjacent microchannels are embedded. Fluid and small particles can penetrate the walls through the embedded nano channels while particles

C. Shen

2011-01-01

362

Heat Pipes  

NASA Technical Reports Server (NTRS)

Phoenix Refrigeration Systems, Inc.'s heat pipe addition to the Phoenix 2000, a supermarket rooftop refrigeration/air conditioning system, resulted from the company's participation in a field test of heat pipes. Originally developed by NASA to control temperatures in space electronic systems, the heat pipe is a simple, effective, heat transfer system. It has been used successfully in candy storage facilities where it has provided significant energy savings. Additional data is expected to fully quantify the impact of the heat pipes on supermarket air conditioning systems.

1991-01-01

363

Origami Multistabilty: From Single Vertices to Metasheets  

E-print Network

We explore the surprisingly rich energy landscape of origami-like folding planar structures. We show that the configuration space of rigid-paneled degree-4 vertices, the simplest building blocks of such systems, consists of at least two distinct branches meeting at the flat state. This suggests that generic vertices are at least bistable, but we find that the nonlinear nature of these branches allows for vertices with as many as five distinct stable states. In vertices with collinear folds and/or symmetry, more branches emerge leading to up to six stable states. Finally, we introduce a procedure to tile arbitrary 4-vertices while preserving their stable states, thus allowing the design and creation of multistable origami metasheets.

Scott Waitukaitis; Rémi Menaut; Bryan Gin-ge Chen; Martin van Hecke

2014-09-09

364

Dust vertical profile impact on global radiative forcing estimation using a coupled chemical-transport-radiative-transfer model  

NASA Astrophysics Data System (ADS)

Atmospheric mineral dust particles exert significant direct radiative forcings and are important drivers of climate and climate change. We used the GEOS-Chem global three-dimensional chemical transport model (CTM) coupled with the Fu-Liou-Gu (FLG) radiative transfer model (RTM) to investigate the dust radiative forcing and heating rate based on different vertical profiles for April 2006. We attempt to actually quantify the sensitivities of radiative forcing to dust vertical profiles, especially the discrepancies between using realistic and climatological vertical profiles. In these calculations, dust emissions were constrained by observations of aerosol optical depth (AOD). The coupled calculations utilizing a more realistic dust vertical profile simulated by GEOS-Chem minimize the physical inconsistencies between 3-D CTM aerosol fields and the RTM. The use of GEOS-Chem simulated vertical profile of dust extinction, as opposed to the FLG prescribed vertical profile, leads to greater and more spatially heterogeneous changes in the estimated radiative forcing and heating rate produced by dust. Both changes can be attributed to a different vertical structure between dust and non-dust source regions. Values of the dust vertically resolved AOD per grid level (VRAOD) are much larger in the middle troposphere, though smaller at the surface when the GEOS-Chem simulated vertical profile is used, which leads to a much stronger heating rate in the middle troposphere. Compared to the FLG vertical profile, the use of GEOS-Chem vertical profile reduces the solar radiative forcing at the top of atmosphere (TOA) by approximately 0.2-0.25 W m-2 over the African and Asian dust source regions. While the Infrared (IR) radiative forcing decreases 0.2 W m-2 over African dust belt, it increases 0.06 W m-2 over the Asian dust belt when the GEOS-Chem vertical profile is used. Differences in the solar radiative forcing at the surface between the use of the GEOS-Chem and FLG vertical profiles are most significant over the Gobi desert with a value of about 1.1 W m-2. The radiative forcing effect of dust particles is more pronounced at the surface over the Sahara and Gobi deserts by using FLG vertical profile, while it is less significant over the downwind area of Eastern Asia.

Zhang, L.; Li, Q. B.; Gu, Y.; Liou, K. N.; Meland, B.

2013-07-01

365

Advanced Si solid phase crystallization for vertical channel in vertical NANDs  

SciTech Connect

The advanced solid phase crystallization (SPC) method using the SiGe/Si bi-layer structure is proposed to obtain high-mobility poly-Si thin-film transistors in next generation vertical NAND (VNAND) devices. During the SPC process, the top SiGe thin film acts as a selective nucleation layer to induce surface nucleation and equiaxial microstructure. Subsequently, this SiGe thin film microstructure is propagated to the underlying Si thin film by epitaxy-like growth. The initial nucleation at the SiGe surface was clearly observed by in situ transmission electron microscopy (TEM) when heating up to 600?°C. The equiaxial microstructures of both SiGe nucleation and Si channel layers were shown in the crystallized bi-layer plan-view TEM measurements. Based on these experimental results, the large-grained and less-defective Si microstructure is expected to form near the channel region of each VNAND cell transistor, which may improve the electrical characteristics.

Lee, Sangsoo [Department of Materials Science and Engineering and Inter-university Semiconductor Research Center, Seoul National University, Seoul 151-742 (Korea, Republic of); Son, Yong-Hoon [Department of Materials Science and Engineering and Inter-university Semiconductor Research Center, Seoul National University, Seoul 151-742 (Korea, Republic of); Semiconductor R and D Center, Samsung Electronics Co., Ltd., Hwasung 445-701 (Korea, Republic of); Hwang, Kihyun; Shin, Yoo Gyun [Semiconductor R and D Center, Samsung Electronics Co., Ltd., Hwasung 445-701 (Korea, Republic of); Yoon, Euijoon, E-mail: eyoon@snu.ac.kr [Department of Materials Science and Engineering and Inter-university Semiconductor Research Center, Seoul National University, Seoul 151-742 (Korea, Republic of); Energy Semiconductor Research Center, Advanced Institutes of Convergence Technology, Seoul National University, Suwon 443-270 (Korea, Republic of)

2014-07-01

366

Zonal and Vertical Structure of the Madden-Julian Oscillation.  

NASA Astrophysics Data System (ADS)

A statistical study of the three-dimensional structure of the Madden-Julian oscillation (MJO) is carried out by projecting dynamical fields from reanalysis and radiosonde data onto space-time filtered outgoing longwave radiation (OLR) data. MJO convection is generally preceded by low-level convergence and upward motion in the lower troposphere, while subsidence, cooling, and drying prevail aloft. This leads to moistening of the boundary layer and the development of shallow convection, followed by a gradual and then more rapid lofting of moisture into the middle troposphere at the onset of deep convection. After the passage of the heaviest rainfall, a westerly wind burst region is accompanied by stratiform precipitation, where lower tropospheric subsidence and drying coincide with continuing upper tropospheric upward motion. The evolution of the heating field leads to a temperature structure that favors the growth of the MJO. The analysis also reveals distinct differences in the vertical structure of the MJO as it evolves, presumably reflecting changes in its vertical heating profile, phase speed, or the basic-state circulation that the MJO propagates through.The dynamical structure and the evolution of cloud morphology within the MJO compares favorably in many respects with other propagating convectively coupled equatorial waves. One implication is that the larger convective envelopes within the Tropics tend to be composed of more shallow convection along their leading edges, a combination of deep convection and stratiform rainfall in their centers, and then a preponderance of stratiform rainfall along their trailing edges, regardless of scale or propagation direction. While this may ultimately be the factor that governs the dynamical similarities across the various wave types, it raises questions about how the smaller-scale, higher-frequency disturbances making up the MJO conspire to produce its heating and dynamical structures. This suggests that the observed cloud morphology is dictated by fundamental interactions with the large-scale circulation.

Kiladis, George N.; Straub, Katherine H.; Haertel, Patrick T.

2005-08-01

367

Surface tension profiles in vertical soap films  

NASA Astrophysics Data System (ADS)

Surface tension profiles in vertical soap films are experimentally investigated. Measurements are performed by introducing deformable elastic objets in the films. The shape adopted by those objects once set in the film is related to the surface tension value at a given vertical position by numerically solving the adapted elasticity equations. We show that the observed dependency of the surface tension versus the vertical position is predicted by simple modeling that takes into account the mechanical equilibrium of the films coupled to previous thickness measurements.

Adami, N.; Caps, H.

2015-01-01

368

Design and analysis of a 5-MW vertical-fluted-tube condenser for geothermal applications  

SciTech Connect

The design and analysis of an industtial-sized vertical-fluted-tube condenser. The condenser is used to condense superheated isobutane vapor discharged from a power turbine in a geothermal test facility operated for the US Department of Energy. The 5-MW condenser has 1150 coolant tubes in a four-pass configuration with a total heat transfer area of 725 m/sup 2/ (7800 ft/sup 2/). The unit is being tested at the Geothermal Components Test Facility in the Imperial Valley of East Mesa, California. The condenser design is based on previous experimental research work done at the Oak Ridge National Laboratory on condensing refrigerants on a wide variety of single vertical tubes. Condensing film coefficients obtained on the high-performance vertical fluted tubes in condensing refrigerants are as much as seven times greater than those obtained with vertical smooth tubes that have the same diameter and length. The overall heat transfer performance expected from the fluted tube condenser is four to five times the heat transfer obtained from the identical units employing smooth tubes. Fluted tube condensers also have other direct applications in the Ocean Thermal Energy Conversion (OTEC) program in condensing ammonia, in the petroleum industry in condensing light hydrocarbons, and in the air conditioning and refrigeration industry in condensing fluorocarbon vapors.

Llewellyn, G.H.

1982-03-01

369

Heat Transfer  

NSDL National Science Digital Library

Students explore heat transfer and energy efficiency using the context of energy efficient houses. They gain a solid understanding of the three types of heat transfer: radiation, convection and conduction, which are explained in detail and related to the real world. They learn about the many ways solar energy is used as a renewable energy source to reduce the emission of greenhouse gasses and operating costs. Students also explore ways in which a device can capitalize on the methods of heat transfer to produce a beneficial result. They are given the tools to calculate the heat transferred between a system and its surroundings.

Integrated Teaching and Learning Program,

370

Subsurface imaging with reverse vertical seismic profiles  

E-print Network

This thesis presents imaging results from a 3D reverse vertical seismic profile (RVSP) dataset measured at a hydrocarbon bearing pinnacle reef in northern Michigan. The study presented many challenges in seismic data ...

Krasovec, Mary L. (Mary Lee), 1972-

2001-01-01

371

Stability of Granular Materials under Vertical Vibrations  

E-print Network

The influence of periodic vibrations on the granular flow of materials is of great interests to scientists and engineers due to both theoretical and practical reasons. In this paper, the stability of a vertically vibrated ...

Deng, Rensheng

372

Continuous Growth of Vertically Aligned Carbon Nanotubes  

E-print Network

Vertically aligned carbon nanotubes (VACNTs), sometimes called forests or carpets, are a promising material due to their unique physical and scale-dependent physical properties [1-3]. Continuous production of VACNTs is ...

Guzman de Villoria, R.

373

Vertical Axis Wind Turbine Foundation parameter study  

SciTech Connect

The dynamic failure criterion governing the dimensions of prototype Vertical Axis Wind Turbine Foundations is treated as a variable parameter. The resulting change in foundation dimensions and costs is examined.

Lodde, P.F.

1980-07-01

374

Vertical Glider Robots for Subsea Equipment Delivery  

E-print Network

We have developed an underwater vehicle that offers significant performance improvements over existing sub sea elevators. Our Vertical Glider Robot falls under its own weight to a precise location on the seafloor, employing ...

Reed, Brooks L.

2011-01-01

375

Vertical axis wind turbine foundation parameter study  

NASA Astrophysics Data System (ADS)

The foundation/anchor requirements for the Vertical Axis Wind Turbine are identified. Information is supplied concerning the selection, design, and cost estimates for the geologic conditions which may be encountered at potential wind turbine sites.

Ludde, P. F.

1980-07-01

376

Vertical Discretization in Tidal Flow Simulations  

NASA Astrophysics Data System (ADS)

We propose an empirical law for vertical nodal placement in tidal simulations that depends on a single parameter p. The influence of dimensionless numbers on the optimal value of p is analysed through a series of numerical experiments for an individual vertical and a single value of p is found to be adequate for all cases. The proposed law can lead to gains in accuracy of over two orders of magnitude relative to a uniform grid and compares favourably with non-uniform grids previously used in the literature. In practical applications the most effective use of this law may require each vertical to have a different number of nodes. Criteria for the distribution of the total number of nodes among different verticals are also proposed, based on the concept of equalizing errors across the domain. The usefulness of the overall approach is demonstrated through a two-dimensional laterally averaged application to a synthetic estuary.

Fortunato, André B.; Baptista, António M.

1996-05-01

377

Vertical Motions of Oceanic Volcanoes  

NASA Astrophysics Data System (ADS)

Oceanic volcanoes offer abundant evidence of changes in their elevations through time. Their large-scale motions begin with a period of rapid subsidence lasting hundreds of thousands of years caused by isostatic compensation of the added mass of the volcano on the ocean lithosphere. The response is within thousands of years and lasts as long as the active volcano keeps adding mass on the ocean floor. Downward flexure caused by volcanic loading creates troughs around the growing volcanoes that eventually fill with sediment. Seismic surveys show that the overall depression of the old ocean floor beneath Hawaiian volcanoes such as Mauna Loa is about 10 km. This gross subsidence means that the drowned shorelines only record a small part of the total subsidence the islands experienced. In Hawaii, this history is recorded by long-term tide-gauge data, the depth in drill holes of subaerial lava flows and soil horizons, former shorelines presently located below sea level. Offshore Hawaii, a series of at least 7 drowned reefs and terraces record subsidence of about 1325 m during the last half million years. Older sequences of drowned reefs and terraces define the early rapid phase of subsidence of Maui, Molokai, Lanai, Oahu, Kauai, and Niihau. Volcanic islands, such as Maui, tip down toward the next younger volcano as it begins rapid growth and subsidence. Such tipping results in drowned reefs on Haleakala as deep as 2400 m where they are tipped towards Hawaii. Flat-topped volcanoes on submarine rift zones also record this tipping towards the next younger volcano. This early rapid subsidence phase is followed by a period of slow subsidence lasting for millions of years caused by thermal contraction of the aging ocean lithosphere beneath the volcano. The well-known evolution along the Hawaiian chain from high to low volcanic island, to coral island, and to guyot is due to this process. This history of rapid and then slow subsidence is interrupted by a period of minor uplift lasting a few hundred thousand years as the island migrates over a broad flexural arch related to isostatic compensation of a nearby active volcano. The arch is located about 190±30 km away from the center of volcanic activity and is also related to the rejuvenated volcanic stage on the islands. Reefs on Oahu that are uplifted several tens of m above sea level are the primary evidence for uplift as the islands over-ride the flexural arch. At the other end of the movement spectrum, both in terms of magnitude and length of response, are the rapid uplift and subsidence that occurs as magma is accumulated within or erupted from active submarine volcanoes. These changes are measured in days to years and are of cm to m variation; they are measured using leveling surveys, tiltmeters, EDM and GPS above sea level and pressure gauges and tiltmeters below sea level. Other acoustic techniques to measure such vertical movement are under development. Elsewhere, evidence for subsidence of volcanoes is also widespread, ranging from shallow water carbonates on drowned Cretaceous guyots, to mapped shoreline features, to the presence of subaerially-erupted (degassed) lavas on now submerged volcanoes. Evidence for uplift is more limited, but includes makatea islands with uplifted coral reefs surrounding low volcanic islands. These are formed due to flexural uplift associated with isostatic loading of nearby islands or seamounts. In sum, oceanic volcanoes display a long history of subsidence, rapid at first and then slow, sometimes punctuated by brief periods of uplift due to lithospheric loading by subsequently formed nearby volcanoes.

Clague, D. A.; Moore, J. G.

2006-12-01

378

Wake interference for a heated oscillating cylinder  

NASA Technical Reports Server (NTRS)

Penney and Jefferson (1966) have studied heat transfer from an oscillating, horizontal wire. The present investigation has the objective to determine the governing parameters which indicate when interaction between an oscillating circular cylinder and its wake will reduce the apparent heat transfer coefficient in quasi-steady conditions, taking into account, if possible, also the determination of the approximate magnitude of the reduction. A definition is provided of a nondimensional vertical mass flux, representing the induced flow due to heating of the stagnant fluid. It is hypothesized that the flux is related to a natural convection parameter which describes the heating of the wake. For oscillation of a circular cylinder in air under the conditions studied, it is found that the application of a cross-flow correlation in a quasi-steady, transient analysis predicts heat transfer parameters in close agreement with experiment over a certain range, provided interaction with the heated wake is avoided.

Mceligot, D. M.; Smith, S. B.; Verity, R. L.

1982-01-01

379

Effect of vertical motion on current meters  

USGS Publications Warehouse

The effect of vertical motion on the performance of current meters at various stream velocities was evaluated to determine whether accurate discharge measurements can be made from a bobbing boat. Three types of current meters--Ott, Price, and vane types--were tested under conditions simulating a bobbing boat. A known frequency and amplitude of vertical motion were imparted to the current meter, and the related effect on the measured stream velocity was determined. One test of the Price meter was made under actual conditions, using a boat and standard measuring gear. The results of the test under actual conditions verified those obtained by simulating the vertical movements of a boat. The tests show that for stream velocities below 2.5 feet per second the accuracy of all three meters is significantly affected when the meters are subjected to certain conditions of vertical motion that can occur during actual field operations. Both the rate of vertical motion and the frequency of vertical oscillation affect the registration of the meter. The results of these tests, presented in the form of graphs and tables, can be used as a guide to determine whether wind and stream flow are within an acceptable range for a reliable discharge measurement from a boat.

Kallio, Nicholas A.

1966-01-01

380

Phase change heat transfer during melting and resolidification of melt around cylindrical heat source(s)\\/sink(s)  

Microsoft Academic Search

Melting and resolidification of a phase change material around two cylindrical heat exchangers spaced vertically have been investigated experimentally. Experiments have been performed to examine the effects of the cylinder surface temperatures on heat transfer during the melting and freezing cycle. The processes have been clarified on the basis of observations of timewise variations in the solid\\/liquid interface and of

K. Sasaguchi; R. Viskanta

1989-01-01

381

Mean Vertical Velocities Measured by Indian MST Radar and Comparison with Indirectly Computed Values.  

NASA Astrophysics Data System (ADS)

Mean vertical velocities and their variations observed with Indian mesosphere-stratosphere-troposphere (MST) radar located at Gadanki (13.5°N, 79.2°E), a tropical station in India, are presented. In this study, a comparison has been made between Indian MST radar-measured vertical velocities and those computed by radiosonde data using kinematic and adiabatic methods. From this study, it is observed that the signs of vertical motion estimated by the kinematic method agree well with MST-radar values, although the magnitudes differ, except in a small region where radar vertical velocity changes in sign from negative to positive in the lower troposphere during monsoon months. This upward motion in this season is attributed to horizontal convergence due to change in wind direction that is not observed in radiosonde data when averaged, because of poor height resolution of the radiosonde (500 m or more varying with height) as compared with the radar range resolution (150 m). Profiles of vertical velocities computed using the kinematic method tend to approach the shape of radar vertical velocity profiles as the separation of the radiosonde network decreases. The vertical velocities computed using the adiabatic method are found to be small and are attributed to a small tilt in isentropic surfaces caused by small latitudinal temperature gradients commonly observed in the Tropics; they also may be partly due to neglect of diabatic heating. The bias between radar and radiosonde vertical velocities tends to decrease when the time used for averaging of MST radar data is approximately 6 h (before and after 3-h average).

Jagannadha Rao, V. V. M.; Narayana Rao, D.; Venkat Ratnam, M.; Mohan, K.; Vijaya Bhaskar Rao, S.

2003-04-01

382

Horizontal Cross Bracing Detail, Vertical Cross Bracing Detail, Horizontal Cross ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

Horizontal Cross Bracing Detail, Vertical Cross Bracing Detail, Horizontal Cross Bracing Detail, Vertical Cross Bracing-End Detail - Cumberland Covered Bridge, Spanning Mississinewa River, Matthews, Grant County, IN

383

WHICH HYDRAULIC MODEL TO USE IN VERTICAL FLOW CONSTRUCTED WETLANDS?  

E-print Network

WHICH HYDRAULIC MODEL TO USE IN VERTICAL FLOW CONSTRUCTED WETLANDS? Ania Morvannoua , Nicolas-equilibrium model, preferential flow path, vertical flow constructed wetlands INTRODUCTION Constructed wetlands (CWs

Paris-Sud XI, Université de

384

Nanofluid impingement jet heat transfer  

PubMed Central

Experimental investigation to study the heat transfer between a vertical round alumina-water nanofluid jet and a horizontal circular round surface is carried out. Different jet flow rates, jet nozzle diameters, various circular disk diameters and three nanoparticles concentrations (0, 6.6 and 10%, respectively) are used. The experimental results indicate that using nanofluid as a heat transfer carrier can enhance the heat transfer process. For the same Reynolds number, the experimental data show an increase in the Nusselt numbers as the nanoparticle concentration increases. Size of heating disk diameters shows reverse effect on heat transfer. It is also found that presenting the data in terms of Reynolds number at impingement jet diameter can take into account on both effects of jet heights and nozzle diameter. Presenting the data in terms of Peclet numbers, at fixed impingement nozzle diameter, makes the data less sensitive to the percentage change of the nanoparticle concentrations. Finally, general heat transfer correlation is obtained verses Peclet numbers using nanoparticle concentrations and the nozzle diameter ratio as parameters. PMID:22340669

2012-01-01

385

Heat collector  

DOEpatents

A heat collector and method suitable for efficiently and cheaply collecting solar and other thermal energy are provided. The collector employs a heat pipe in a gravity-assist mode and is not evacuated. The collector has many advantages, some of which include ease of assembly, reduced structural stresses on the heat pipe enclosure, and a low total materials cost requirement. Natural convective forces drive the collector, which after startup operates entirely passively due in part to differences in molecular weights of gaseous components within the collector.

Merrigan, M.A.

1981-06-29

386

Heat collector  

DOEpatents

A heat collector and method suitable for efficiently and cheaply collecting solar and other thermal energy are provided. The collector employs a heat pipe in a gravity-assist mode and is not evacuated. The collector has many advantages, some of which include ease of assembly, reduced structural stresses on the heat pipe enclosure, and a low total materials cost requirement. Natural convective forces drive the collector, which after startup operates entirely passively due in part to differences in molecular weights of gaseous components within the collector.

Merrigan, Michael A. (Santa Cruz, NM)

1984-01-01

387

Vertical mixing at intermediate depths in the Arctic boundary current  

NASA Astrophysics Data System (ADS)

Microstructure and hydrographic observations, during September 2007 in the boundary current on the East Siberian continental slope, document upper ocean stratification and along-stream water mass changes. A thin warm surface layer overrides a shallow halocline characterized by a ~40-m thick temperature minimum layer beginning at ~30 m depth. Below the halocline, well-defined thermohaline diffusive staircases extended downwards to warm Atlantic Water intrusions found at 200-800 m depth. Observed turbulent eddy kinetic energy dissipations are extremely low ($\\epsilon$ < 10-6 W m-3), such that double diffusive convection dominates the vertical mixing in the upper-ocean. The diffusive convection heat fluxes F H dc ~1 W m-2, are an order of magnitude too small to account for the observed along-stream cooling of the boundary current. Our results implicate circulation patterns and the influence of shelf waters in the evolution of the boundary current waters.

Lenn, Y. D.; Wiles, P. J.; Torres-Valdes, S.; Abrahamsen, E. P.; Rippeth, T. P.; Simpson, J. H.; Bacon, S.; Laxon, S. W.; Polyakov, I.; Ivanov, V.; Kirillov, S.

2009-03-01

388

A correction method for heated length effect in critical heat flux prediction  

Microsoft Academic Search

A new correction method is developed for the effect of the length-to-diameter (L\\/D) ratio on critical heat flux (CHF) by applying artificial neural networks and conventional regression techniques to the KAIST CHF data base for water flow in uniformly-heated, vertical round tubes. It consists of two parts: (a) a threshold L\\/D over which the length effect becomes negligible; and (b)

Yong Ho Lee; Won-Pil Baek; Soon Heung Chang

2000-01-01

389

Fully Coupled 3-D Conjugate Heat Transfer Algorithm for Borehole Heat Exchanger Performance Prediction  

Microsoft Academic Search

Quantitative three-dimensional prediction of the thermal performance of a vertical borehole heat exchanger (BHE) in a ground-source heat pump installation is sought. As BHE installation exhibits exceptionally disparate characteristic length scales, an alternative formation-fluid-thermal fully coupled algorithm is derived to quickly predict the 3-D temperature distributions. The time scale of the steady prediction is of order minutes. This simulation capability

Allen J. Baker; Cheng-Xian Lin; Joe A. Orzechowski; Cormack Gordon

2011-01-01

390

Vertical mixing due to double diffusion in the tropical western Pacific  

NASA Astrophysics Data System (ADS)

study calculates the vertical diffusivity and the fluxes of heat, salt, and buoyancy due to turbulence and double diffusion based on a 14 day time series of observations of the dissipation rates of turbulent kinetic energy and thermal variance at 0°N, 156°E from 25 October to 18 November 2012. Salt fingering dominates shear-driven turbulence below 100 m. The estimated flux and associated vertical diffusivity due to double diffusion are approximately 1 order of magnitude higher for temperature and density and 2 orders of magnitude higher for salinity compared to values calculated from a turbulence model. Under weak turbulence conditions, the turbulence model significantly underestimates the magnitude of the vertical buoyancy flux with the flux having the wrong sign. Under these conditions, fluxes induced by double-diffusive mixing need to be considered.

Lee, Chorong; Chang, Kyung-Il; Lee, Jae Hak; Richards, Kelvin J.

2014-11-01

391

hal-00162166,version1-12Jul2007 A numerical study of heat island flows in an open domain  

E-print Network

hal-00162166,version1-12Jul2007 A numerical study of heat island flows in an open domain heat island [2, 3]. Heat island fluid flows occur in open configurations, which require, from. A thermal stratification is applied in the vertical direction and the flow circulation is induced by a heat

Paris-Sud XI, Université de

392

Temporal variability of vertical export flux at the DYFAMED time-series station (Northwestern Mediterranean Sea)  

NASA Astrophysics Data System (ADS)

The temporal evolution of the vertical export flux at the DYFAMED time-series station (Ligurian Sea) over the last 20 years reveals a strong interannual variability. Winter convection allows particulate (and dissolved) matter to be vertically exported (“flush-down” effect). The efficiency of this process determines also the concentration of nutrients brought to surface waters and, therefore, the intensity of the subsequent phytoplankton bloom. The sequence “convection-bloom” is the main driving force of vertical export flux in this region. The present work attempts to better identify the parameters that control vertical export flux dynamics by observing a 20 year time-series in relation with the temporal variability of mixed layer depth and surface primary production. The consequences of a more stratified water column in the future on biological productivity and vertical export flux are pointed out. In winter, the cooling of surface water, combined with evaporation, increases its density and determines the vertical convection. This allows for a rapid downward transfer of dissolved and particulate matter, yielding high vertical export flux. This “flush-down effect” results from a combination of convection and gravitational flux, since the diving of dense surface waters breaks the stratification of the water column and carries all material (particulate + dissolved) accumulated in the surface layer to depth. The rapid downward transfer of dissolved and particulate matter by this “flush-down effect” yields high vertical export fluxes. The magnitude of these fluxes may vary according to the amount of atmospheric material accumulated in surface waters during the preceding stratified period. In the present data set, highest vertical export fluxes were observed in 1999, 2003 and 2004. In those years, the MLD was greater (Fig. 2), suggesting a causal relationship between the efficiency of vertical mixing and the subsequent vertical export flux. In spring, nutrients brought to surface waters by the vertical mixing trigger phytoplankton blooms, which generate new material for the vertical transfer of dissolved and particulate matter. Maximum Chl-a occurs shortly after the MLD maximum. Ga?i? et al. (2002) observed a marked seasonal variability of POC fluxes in the Adriatic Sea. Spring maxima are associated with phytoplankton blooms. In spite of interannual variations in the intensity of the phytoplankton blooms, their seasonal distribution and biomass abundance are reproducible (Marty et al., 2002), with maximum values of carbon assimilation in March and April (Marty and Chiavérini, 2002; Fig. 2). Indeed, high vertical export fluxes were observed within the present dataset in spring, as a result of biological productivity (e.g. 2000). In summer and fall, the heating of the sea surface results in a stratified water column with a shallow ML which is rapidly exhausted of nutrients. During such oligotrophic conditions (June to November), the concentrations of biogenic matter in the photic layer are minimal. Therefore, owing to insignificant transfer of POC, atmospherically-transported individual particles presumably do not sink (or sink with negligible sinking velocity), according to Stokesian settling calculations (Stokes, 1901). In the absence of packaging into large biogenic material (adsorption onto phytoplanktonic debris or incorporation into fecal pellets), atmospheric particles thus accumulate in the surface ML. In addition, dissolved atmospheric matter (e.g., from atmospheric wet deposition) is not removed from surface waters via its assimilation by phytoplankton, and it accumulates in the surface ML (e.g. dissolved organic matter (DOM); (Copin-Montégut and Avril, 1993)). Consequently, the lowest vertical export fluxes are observed during this period of the year. For example, years 2003 and 2004 exhibited minimal vertical export fluxes during summer and fall (Fig. 2). However, summer 2002 was unusual, with relatively a high vertical export flux. This resulted from the combination of particularly strong summer

Heimbürger, Lars-Eric; Lavigne, Héloïse; Migon, Christophe; D'Ortenzio, Fabrizio; Estournel, Claude; Coppola, Laurent; Miquel, Juan-Carlos

2013-12-01

393

Corrosive resistant heat exchanger  

DOEpatents

A corrosive and errosive resistant heat exchanger which recovers heat from a contaminated heat stream. The heat exchanger utilizes a boundary layer of innocuous gas, which is continuously replenished, to protect the heat exchanger surface from the hot contaminated gas. The innocuous gas is conveyed through ducts or perforations in the heat exchanger wall. Heat from the heat stream is transferred by radiation to the heat exchanger wall. Heat is removed from the outer heat exchanger wall by a heat recovery medium.

Richlen, Scott L. (Annandale, VA)

1989-01-01

394

Heat transfer from a rod bundle under natural circulation conditions  

Microsoft Academic Search

A rectangular natural circulation loop with heat exchangers in the vertical legs was used to obtain heat transfer and fluid friction data from a tube bundle under natural circulation conditions. A 21 rod bundle arranged in a square array with a pitch-to-diameter ratio of 1.33 was used as the test heat exchanger. Deionized water at atmospheric pressure was used as

K. P. Hallinan; R. Viskanta

1986-01-01

395

Heat transfer from a turbulent swirling inverse diffusion flame to a flat surface  

Microsoft Academic Search

The heat transfer characteristics of a turbulent and swirling inverse diffusion flame (IDF) impinging vertically normal to a flat surface were investigated experimentally. The heat flux was measured by a heat flux sensor, Vatell HFM-6D\\/H. The effects of Reynolds number, overall equivalence ratio, nozzle-to-surface distance H and swirl number on the heat flux distributions were examined. The comparison of heat

H. S. Zhen; C. W. Leung; C. S. Cheung

2009-01-01

396

Extreme Heat  

MedlinePLUS

... its limits. In extreme heat and high humidity, evaporation is slowed and the body must work extra ... the body by increasing the perspiration rate of evaporation. Eat well-balanced, light, and regular meals. Avoid ...

397

Heating stove  

SciTech Connect

This stove invention relates to wood and coal burning stoves employed for heating. More effective draft control and heat transfer is achieved by a stove employing straight and serpentine flues, a control rod to coordinate movement of a baffle and damper for defining passageways to the flues, and a channel for apportioning air above and below the fuel and into first and second combustion chambers.

Johnson, V.

1982-03-23

398

Nation's tallest VAWT (Vertical Axis Wind Turbine) turning out the watts. [Vertical Axis Wind Turbine  

Microsoft Academic Search

This article describes the development of the tallest and most powerful windmill of its kind in the U.S. Known as a Vertical Axis Wind Turbine (VAWT), the machine is meant for testing new concepts in vertical axis turbine design. As part of its overall testing program, the turbine will supply electricity to automated water pumps used in irrigation research at

1988-01-01

399

Vertical seismic profiling on the sea shelf  

NASA Astrophysics Data System (ADS)

Results of a numerical experiment on vertical seismic profiling of the sea bottom on the shelf are presented. The results are obtained by analyzing the acoustic fields in the shelf area with the use of both hydroacoustic and seismic bottom sources of radiation. The influence of both transmission depth and source type on the efficiency of seismic wave excitation in the bottom is investigated. The formation of the vertical wave hodographs and its dependence on the acoustic parameters and structure of the bottom in the oceanic shelf region is analyzed. A high sensitivity of the vertical wave hodographs to variations in the parameters of the bottom medium is revealed. For the layered bottom model, the possibility of estimating the positions of layer boundaries in depth and the velocities of waves within the layers is demonstrated.

Zaslavski?, Yu. M.; Kerzhakov, B. V.; Kulinich, V. V.

2008-05-01

400

Vertical vibration analysis for elevator compensating sheave  

NASA Astrophysics Data System (ADS)

Most elevators applied to tall buildings include compensating ropes to satisfy the balanced rope tension between the car and the counter weight. The compensating ropes receive tension by the compensating sheave, which is installed at the bottom space of the elevator shaft. The compensating sheave is only suspended by the compensating ropes, therefore, the sheave can move vertically while the car is traveling. This paper shows the elevator dynamic model to evaluate the vertical motion of the compensating sheave. Especially, behavior in emergency cases, such as brake activation and buffer strike, was investigated to evaluate the maximum upward motion of the sheave. The simulation results were validated by experiments and the most influenced factor for the sheave vertical motion was clarified.

Watanabe, Seiji; Okawa, Takeya; Nakazawa, Daisuke; Fukui, Daiki

2013-07-01

401

Vertical Velocity Measurements in Warm Stratiform Clouds  

NASA Astrophysics Data System (ADS)

Measurements of vertical air motion in warm boundary layer clouds are key for quantitatively describing cloud-scale turbulence and for improving our understanding of cloud and drizzle microphysical processes. Recently, a new technique that produces seamless measurements of vertical air velocity in the cloud and sub-cloud layers for both drizzling and non-drizzling stratocumulus clouds has been developed. The technique combines radar Doppler spectra-based retrievals of vertical air motion in cloud and light drizzle conditions with a novel neural network analysis during heavily drizzling periods. Observations from Doppler lidars are used to characterize sub-cloud velocities and to evaluate the performance of the technique near the cloud base. The technique is applied to several cases of stratiform clouds observed by the ARM Mobile Facility during the Two-Column Aerosol Project (TCAP) campaign in Cape Cod. The observations clearly illustrate coupling of the sub-cloud and cloud layer turbulent structures.

Luke, E. P.; Kollias, P.

2013-12-01

402

Experimental investigation on the heat transfer of an impinging inverse diffusion flame  

Microsoft Academic Search

This paper presents the results of an experimental study on the heat transfer characteristics of an inverse diffusion flame (IDF) impinging vertically upwards on a horizontal copper plate. The IDF burner used in the experiment has a central air jet surrounded circumferentially by 12 outer fuel jets. The heat flux at the stagnation point and the radial distribution of heat

T. K. Ng; C. W. Leung; C. S. Cheung

2007-01-01

403

Gravitational effects on the operation of a variable conductive heat pipe  

Microsoft Academic Search

A variable conductance heat pipe, measuring 2.5 centimeters in diameter and 152 centimeters in length, was built. The heat pipe was operated in both the conventional and variable conductance modes to obtain experimental data concerning performance characteristics. The input electrical power was varied from 20 to 50 watts with the heat pipe placed in both the horizontal and vertical positions.

R. S. Owendoff

1977-01-01

404

On the measurement of vertical velocity by MST radar  

NASA Technical Reports Server (NTRS)

An overview is presented of the measurement of atmospheric vertical motion utilizing the MST radar technique. Vertical motion in the atmosphere is briefly discussed as a function of scale. Vertical velocity measurement by MST radars is then considered from within the context of the expected magnitudes to be observed. Examples are drawn from published vertical velocity observations.

Gage, K. S.

1983-01-01

405

Combined high density solar panels and vertical wind turbines  

Microsoft Academic Search

The combined high density solar panels and vertical wind turbines consist of multiple solar panels with closely spaced solar cells on both sides which are supported by an open framework and vertical posts. The adoption of an elevated, rooftop solar panel array, supported by vertical posts makes the basic structure attractive for the inclusion of multiple vertical wind turbines, as

1978-01-01

406

European Vertical Datum: Unification within Geopotential Space  

NASA Astrophysics Data System (ADS)

Various local vertical datums, as realised for particular countries or even regions, are in use around the world. These datums were typically established from sea level observations at single or multiple tide gauges. The fundamental geodetic parameter, W0, which represents the geopotential value at the geoid surface, can be used to unify vertical datums within geopotential space. This requires geodetic coordinates of points at mean sea level (MSL), a high resolution geopotential model and an accurate mean dynamic topography (MDT) model. In this study, the UK, German and French datums are unified within geopotential space. The tide gauge time series and co-located GPS provide the tools to connect mean sea level to the Earth's centre of mass. A mean dynamic topography model enables the reduction of MSL to the geoid surface. Referencing the geodetic coordinates of the geoid to an Earth's gravity field model yields a geopotential value which corresponds to the geoid at the TG sites which can then be used to connect the vertical datums in different regions. This study also illustrates the improvement of EGM2008 compared with EGM96 and demonstrates the influence of omission error on our work. Furthermore, to connect regional vertical datums to a world height system, W0 is estimated globally from an altimetry-based global MSL model, a global MDT and EGM2008. Our results show that, at current accuracy of GPS and TG observations and processing strategies, unification of vertical datums is mainly influenced by the accuracy of the geopotential model and MDT. Keywords: Geopotential, EGM2008, vertical datum, MDT

Dayoub, Nadim; Moore, Philip; Edwards, Stuart; Penna, Nigel

2010-05-01

407

Modular Heat Exchanger With Integral Heat Pipe  

NASA Technical Reports Server (NTRS)

Modular heat exchanger with integral heat pipe transports heat from source to Stirling engine. Alternative to heat exchangers depending on integrities of thousands of brazed joints, contains only 40 brazed tubes.

Schreiber, Jeffrey G.

1992-01-01

408

Photochemistry and vertical mixing. [in Uranus atmosphere  

NASA Technical Reports Server (NTRS)

Earth-based observations relevant to the question of photochemistry and vertical mixing are discussed. Phytolysis of methane, the only known photochemically active volatile in the Uranian atmosphere, produces heavier hydrocarbons, the most abundant of which are ethane, acetylene, and the polyacetylenes. Unlike Jupiter and Saturn, these hydrocarbon products condense at the low temperatures prevalent in the middle atmosphere. Contrary to the pre-Voyager notion that the atmosphere of Uranus is remarkable clear, it is found that the aerosols are widely and extensively distributed. Despite its photodestruction, methane remains stable in the Uranian atmosphere. The vertical mixing on Uranus is found to be the least efficient of any of the planetary atmospheres.

Atreya, S. K.; Sandel, B. R.; Romani, P. N.

1991-01-01

409

Vertical Component of Satellite Navigation Systems  

NASA Astrophysics Data System (ADS)

The altitude is one of four coordinates of the user's position obtained from Satellite Navigation System (SNS) measurements. The distributions (in per cent) of VDOP coefficient value for different constellations of three SNS - GPS, GLONASS and Galileo - for different masking elevation angles for different user's latitudes are presented in the paper. The results of the measurements of GPS position and vertical accuracy in mode "3D" and position accuracy in mode "2D" for different GPS receivers and different receiver's antenna heights are demonstrated also. Additionally the use of vertical component of SNS in maritime navigation like the determination highly accurate sea-floor depths is presented.

Januszewski, Jacek

2010-01-01

410

Transient non-equilibrium two-phase flow: reflooding of a vertical flow channel  

Microsoft Academic Search

Reflooding of a hot vertical tube was investigated in connection with the analysis of the loss-of-coolant accidents in light water reactors. A 3.66 m long, 14.3 mm ID thin-walled Inconel tube was initially heated to a high temperature and reflooded by injection of water from bottom at a constant rate. In addition to wall temperature, fluid carryover and pressure drop

Kawaji

1984-01-01

411

Dynamics of a vertically falling film in the presence of a first-order chemical reaction  

Microsoft Academic Search

The evolution of a vertically falling film in the presence of a simple first-order (exothermic or endothermic) chemical reaction is considered. The heat of reaction sets up surface tension gradients that induce thermocapillary stresses on the free-surface, thus affecting the evolution of the film. By using a long-wave expansion of the equations of motion and associated boundary conditions, we derive

Philip M. J. Trevelyan; Serafim Kalliadasis; John H. Merkin; Stephen K. Scott

2002-01-01

412

Multichip vertical-external-cavity surface-emitting lasers: a coherent power scaling scheme.  

PubMed

We propose an efficient coherent power scaling scheme, the multichip vertical-external-cavity surface-emitting laser (VECSEL), in which the waste heat generated in the active region is distributed on multi-VECSEL chips such that the pump level at the thermal rollover is significantly increased. The advantages of this laser are discussed, and the development and demonstration of a two-chip VECSEL operating around 970 nm with over 19 W of output power is presented. PMID:17130920

Fan, Li; Fallahi, Mahmoud; Hader, Jörg; Zakharian, Aramais R; Moloney, Jerome V; Murray, James T; Bedford, Robert; Stolz, Wolfgang; Koch, Stephan W

2006-12-15

413

Measurements of turbulent natural convection flow over a vertical backward-facing step  

SciTech Connect

Measurements of turbulent natural convection boundary-layer air flow over a two dimensional, vertical backward-facing step are reported. The upstream and downstream walls of the step were heated to a constant and uniform temperature, while the step is kept adiabatic. The experiment was carried out for a step height of 22 mm and a temperature difference {Delta}T = 30 C between the heated walls and the ambient air. Laser-Doppler velocimeter and cold wire anemometer were used, respectively, to measure simultaneously the mean turbulent velocity and temperature distributions and their turbulent fluctuations. Measurements of the mean velocities and temperature distributions along with the distributions for turbulent intensities, turbulent heat fluxes, and Reynolds stress are presented at various axial locations upstream and downstream of the step. These detailed measurements can serve as benchmark data for testing the accuracy of turbulence models in predicting numerically the flow and heat transfer characteristics in this geometry and flow conditions.

Abu-Mulaweh, H.I.; Armaly, B.F.; Chen, T.S. [Univ. of Missouri, Rolla, MO (United States)

1996-12-31

414

Effects of viscous dissipation on MHD natural convection flow along a vertical wavy surface  

NASA Astrophysics Data System (ADS)

An analysis is presented to investigate the influences of viscous dissipation on MHD natural convection flow along a uniformly heated vertical wavy surface. The governing equations are transformed into dimensionless non-similar equations using a set of suitable transformations and solved numerically by the implicit finite difference method known as the Keller box scheme. Numerical results for the velocity profiles, temperature profiles, skin friction coefficient, and the rate of heat transfers are shown graphically and in tabular form for different values of the selective set of parameters.

Kabir, Kazi H.; Alim, Md A.; Andallah, Laek S.

2013-06-01

415

On the measurement of the thermal impedance in vertical-external-cavity surface-emitting lasers  

NASA Astrophysics Data System (ADS)

A detailed and systematic analysis of the loss mechanisms in vertical-external-cavity surface-emitting lasers is presented with the goal to correctly determine the amount of pump power that is converted to heat. With this input, the accuracy of a recently proposed method for measuring the thermal impedance based on roll-over characteristics is shown to be very high for devices with and without dielectric coating. Potential errors arising from non-heating losses can be determined by performing experiments with different out-coupling mirrors.

Hader, J.; Wang, T.-L.; Moloney, J. V.; Heinen, B.; Koch, M.; Koch, S. W.; Kunert, B.; Stolz, W.

2013-04-01

416

Vertical InGaN light-emitting diodes with a sapphire-face-up structure.  

PubMed

Vertical GaN-based light-emitting diodes (LEDs) were fabricated with a Si substrate using the wafer-bonding technique. Lapping and dry-etching processes were performed for thinning the sapphire substrate instead of removing this substrate using the laser lift-off technique and the thinning process associated with the wafer-bonding technique to feature LEDs with a sapphire-face-up structure and vertical conduction property. Compared with conventional lateral GaN/sapphire-based LEDs, GaN/Si-based vertical LEDs exhibit higher light output power and less power degradation at a high driving current, which could be attributed to the fact that vertical LEDs behave in a manner similar to flip-chip GaN/sapphire LEDs with excellent heat conduction. In addition, with an injection current of 350 mA, the output power (or forward voltage) of fabricated vertical LEDs can be enhanced (or reduced) by a magnitude of 60% (or 5%) compared with conventional GaN/sapphire-based LEDs. PMID:22379672

Yang, Y C; Sheu, Jinn-Kong; Lee, Ming-Lun; Tu, Shang-Ju; Huang, Feng-Wen; Lai, Wei-Chih; Hon, Schang Jing; Ko, Tsun Kai

2012-01-01

417

Estimation of the vertical velocities associated with coastal upwelling using models and observations  

NASA Astrophysics Data System (ADS)

Apart from some exceptions (e.g. certain convection movements, small scale turbulence, or surface gravity wave), vertical velocities in the ocean are generally too weak to be measured. In particular, that is the case of the vertical movements associated to the coastal upwelling dynamics. This prevents any accurate assessment of the vertical fluxes (mass, heat, oxygen and carbon) which are of particular importance when it comes to quantify the nutrient enrichment. As a result, questions related to the source, position, and debit of a coastal upwelling are still largely opened. In a first part, we analyze the vertical velocity field in a series of models of increasing complexity : from Ekman theory (unstratified theory in which the upwelling structure is controlled by the interaction of the surface and bottom boundary layers) to the primitive equation of a realistic simulation of the Senegalese coastal upwelling (ROMS). Then in the second part, we present preliminary results from the Upsen cruise (9-18 march 2012) in which we will seek to measure horizontal flows associated with the South Senegal upwelling in order to estimate the corresponding vertical velocities.

Estrade, P.

2012-04-01

418

Heat Pipes  

NASA Technical Reports Server (NTRS)

Bobs Candies, Inc. produces some 24 million pounds of candy a year, much of it 'Christmas candy.' To meet Christmas demand, it must produce year-round. Thousands of cases of candy must be stored a good part of the year in two huge warehouses. The candy is very sensitive to temperature. The warehouses must be maintained at temperatures of 78-80 degrees Fahrenheit with relative humidities of 38- 42 percent. Such precise climate control of enormous buildings can be very expensive. In 1985, energy costs for the single warehouse ran to more than $57,000 for the year. NASA and the Florida Solar Energy Center (FSEC) were adapting heat pipe technology to control humidity in building environments. The heat pipes handle the jobs of precooling and reheating without using energy. The company contacted a FSEC systems engineer and from that contact eventually emerged a cooperative test project to install a heat pipe system at Bobs' warehouses, operate it for a period of time to determine accurately the cost benefits, and gather data applicable to development of future heat pipe systems. Installation was completed in mid-1987 and data collection is still in progress. In 1989, total energy cost for two warehouses, with the heat pipes complementing the air conditioning system was $28,706, and that figures out to a cost reduction.

1990-01-01

419

ABSORPTION HEAT PUMP IN THE DISTRICT HEATING  

E-print Network

#12;ABSORPTION HEAT PUMP IN THE DISTRICT HEATING PLANT Dr.sc.ing. Agnese Lickrastina M.Sc. Normunds European Heat Pump Summit 2013, Nuremberg, 15-16.10.2013 · Riga District Heating company · Operation of the DH plant Imanta · Selection of the heat pump/chiller · Operation of the heat pump/chiller · Summary

Oak Ridge National Laboratory

420

Extension of Phoenix/City of Colorado Springs solar assisted heat pump project. Final report  

SciTech Connect

Ground coupled heat pump systems employing commercially available equipment have been installed and tested in three different climatic regions of the US in residential, commercial, and industrial building applications. These systems were automatically controlled to respond to load requirements and provided space heating, space cooling, and domestic water heating. Results of the key technical and economic tradeoff work are presented. Component and configuration options are screened and a final cost effective design is justified. Final system design specifications are given. A complete preliminary design of a natural gas fired heat pump is reported, including a performance analysis. The market side economics of the system is examined, including load and system performance, system and utility energy cost summaries, and an economic analysis for new and retrofit systems. The impact of electric and gas utility interfaces with the system is discussed. The status of the natural gas and electric power utilities systems in the Colorado Springs area are assessed. Some options for commercializing the system are discussed. (LEW)

Not Available

1981-07-31

421

Growth of vertically aligned multiwall carbon nanotubes columns  

NASA Astrophysics Data System (ADS)

Capability of patterning carbon nanotubes (CNTs) growth is of tantamount importance for a number of applications ranging from thermal to electronic. This article reports on the columnar growth of vertically aligned multiwall carbon nanotubes (VA-MWCNTs) on patterned Silicon (Si) surface. We have developed procedures based on negative as well as positive masking approaches which allows the growth of predetermined MWCNTs patterns. We describe in detail the process steps leading to Si surface patterning. As quoted above, patterns are exploited to grow VA-MWCNTs. We have focused in particular on the growth of CNT pillars by chemical vapor despoition (CVD) technique at 850°C with camphor and ferrocene as carbon precursors and catalyst respectively. Field emission scanning electron microscopy (FESEM) is employed at low magnification to verify the correct patterning, and at high magnification to examine the surface morphology of CNTs pillars. The pillars are up to 2 mm high, their height being tailored through the deposition time. The diameter of each MWCNT is in the range 30-70 nm and the length is up to few hundred micrometers. The small CNT pillars produced, have several electrical and thermal applications. For instance they can be very useful for heat transfer systems as the lower thermal conductivity of fluids can be improved by the inclusion of nanotubes thanks to their peculiar 1-dimensional heat transfer characteristics.

Shahzad, M. I.; Giorcelli, M.; Perrone, D.; Virga, A.; Shahzad, N.; Jagdale, P.; Cocuzza, M.; Tagliaferro, A.

2013-06-01

422

Development and Application of the Delta-DM Method for Computing Shortwave Radiative Fluxes in a Vertically Inhomogeneous Atmosphere  

Microsoft Academic Search

This study describes the development and application of the Delta-DM method for computing shortwave radiative fluxes planetary albedo and heating rates in vertically inhomogeneous atmospheres. Delta-DM was designed to minimize computer time requirements, furnish accurate flux estimates and permit a wide range of shortwave radiative transfer problems to be studied. Phase function approximation is variable and there is no restriction

Allan M. Sawchuk

1983-01-01

423

Condensation of pure steam and steam-air mixture with surface waves of condensate film on a vertical wall  

Microsoft Academic Search

A series of experiments has been conducted to investigate the effect of wavy interface on film condensation with and without a noncondensable gas present on a vertical wall. Concurrently, the instantaneous film thickness was measured. Overall heat transfer coefficients across the condensate film and the diffusion layer formed by a noncondensable gas were obtained in various parameters such as air-mass

S. K. Park; M. H. Kim; K. J. Yoo

1996-01-01

424

Mixed convection flow of couple stress fluid between parallel vertical plates with Hall and Ion-slip effects  

Microsoft Academic Search

An analysis is presented to investigate the Hall and Ion-slip effects on fully developed electrically conducting couple stress fluid flow between vertical parallel plates in the presence of a temperature dependent heat source. The governing non-linear partial differential equations are transformed into a system of ordinary differential equations using similarity transformations and then solved using homotopy analysis method (HAM). The

D. Srinivasacharya; K. Kaladhar

425

Vertical Transmission of Babesia microti, United States  

PubMed Central

Babesiosis is usually acquired from a tick bite or through a blood transfusion. We report a case of babesiosis in an infant for whom vertical transmission was suggested by evidence of Babesia spp. antibodies in the heel-stick blood sample and confirmed by detection of Babesia spp. DNA in placenta tissue. PMID:22840424

Purtill, Kerry; Wong, Susan J.; Munoz, Jose; Teal, Allen; Madison-Antenucci, Susan; Horowitz, Harold W.; Aguero-Rosenfeld, Maria E.; Moore, Julie M.; Abramowsky, Carlos; Wormser, Gary P.

2012-01-01

426

Dynamic alongwind fatigue of slender vertical structures  

Microsoft Academic Search

The wind-excited vibrations of structures induce fluctuating stresses around mean deformation states that lead to fatigue damage accumulation and can determine structural failure without exceeding design wind actions. This paper proposes a mathematical model aimed at deriving a histogram of the stress cycles, the accumulated damage and the fatigue life of slender vertical structures (e.g. towers, chimneys, poles and masts)

Maria Pia Repetto; Giovanni Solari

2001-01-01

427

Dynamic crosswind fatigue of slender vertical structures  

Microsoft Academic Search

Wind-excited vibrations of slender structures can induce fatigue damage and cause structural failure without exceeding ultimate limit state. Unfortunately, the growing importance of this problem is coupled with an evident lack of simple calculation criteria. This paper proposes a mathematical method for evaluating the crosswind fatigue of slender vertical structures, which represents the dual formulation of a parallel method that

Maria Pia Repetto; Giovanni Solari

2002-01-01

428

Vertical root fractures and their management  

PubMed Central

Vertical root fractures associated with endodontically treated teeth and less commonly in vital teeth represent one of the most difficult clinical problems to diagnose and treat. In as much as there are no specific symptoms, diagnosis can be difficult. Clinical detection of this condition by endodontists is becoming more frequent, where as it is rather underestimated by the general practitioners. Since, vertical root fractures almost exclusively involve endodontically treated teeth; it often becomes difficult to differentiate a tooth with this condition from an endodontically failed one or one with concomitant periodontal involvement. Also, a tooth diagnosed for vertical root fracture is usually extracted, though attempts to reunite fractured root have been done in various studies with varying success rates. Early detection of a fractured root and extraction of the tooth maintain the integrity of alveolar bone for placement of an implant. Cone beam computed tomography has been shown to be very accurate in this regard. This article focuses on the diagnostic and treatment strategies, and discusses about predisposing factors which can be useful in the prevention of vertical root fractures. PMID:24778502

Khasnis, Sandhya Anand; Kidiyoor, Krishnamurthy Haridas; Patil, Anand Basavaraj; Kenganal, Smita Basavaraj

2014-01-01

429

Locating vertical well casings with a magnetometer  

SciTech Connect

Prior theoretical results to describe the magnetic field caused by a vertical steel well casing are confirmed by field tests. A proton magnetometer was used to survey a gridded area about a known well casing. The measured magnetic fields are plotted in isometric views to show the steel well casing with and without interfering magnetic fields.

Laine, E.F.; Lytle, R.J.

1982-03-30

430

Food Supply Chains with Vertical Integration  

E-print Network

Food Supply Chains with Vertical Integration SOM 822 Research Paper Diogo Souza-Monteiro Dep. of Resource Economics 05/10/2004 #12;Introduction Food Supply chains are becoming increasingly complex in different tiers of food chains. Barkena and Drabenstott (1995) claim that contracts are quickly taking

Nagurney, Anna

431

Vertical occupational mobility and its measurement  

Microsoft Academic Search

This paper describes a number of alternative approaches to devising a vertical occupational scale and compares the outcomes of different scales on calculations of occupational mobility. The paper describes the conceptual issues relevant to calculating occupational mobility and documents the measurement error embedded in the choice of measure, as applied to different data sets. The ranking schemes used include SOC

Shirley Dex; Joanne Lindley; Kelly Ward

2007-01-01

432

On the Design of Vertical Hydraulic Fractures  

Microsoft Academic Search

Some of the assumptions involved in designing vertical hydraulic fractures should be critically examined as to their validity. This is done on the basis of a new width equation and a numerical design procedure. It is found that some of the assumptions related to the fluid mechanics of the problem greatly affect the computed results and therefore deserve special attention.

Abbas Daneshy

1973-01-01

433

A Simple Vertical Slab Gel Electrophoresis Apparatus.  

ERIC Educational Resources Information Center

Describes an inexpensive, easily constructed, and safe vertical slab gel kit used routinely for sodium dodecyl sulphate-polyacrylamide gel electrophoresis research and student experiments. Five kits are run from a single transformer. Because toxic solutions are used, students are given plastic gloves and closely supervised during laboratory…

Carter, J. B.; And Others

1983-01-01

434

Surgical correction of primary cutis vertices gyrata.  

PubMed

Primary cutis vertices gyrata is a rare condition of the scalp characterized by the formation of furrows and folds resembling the convolutions of the brain. A review of the English literature did not reveal any surgically treated cases. The authors report three cases treated by simple excision of the deepest furrows with a satisfactory result. PMID:12461454

Al-Malaq, Ali; Hashem, Fuad K; Helmi, Ayman; Al-Qattan, Mohammed M

2002-12-01

435

Viewing Vertical Objects with an Overhead Projector.  

ERIC Educational Resources Information Center

Discusses the use of an overhead projector for the deflection of a vertical image to a screen. Describes three demonstrations: magnetizing of a steel ball bearing and paper clip; convection currents of a hot liquid within a cold liquid; and oscillation of concentrated salt solution into fresh water. (YP)

Wild, R. L.

1988-01-01

436

Vertical axis wind turbine development: Executive summary  

Microsoft Academic Search

Information is presented concerning (1) the numerical solution of the aerodynamics of cross-flow wind turbines; (2) boundary layer considerations for a vertical axis wind turbine (VAWT); (3) VAWT outdoor test model; (4) low solidity blade tests; (5) high solidity blade design; (6) cost analysis of the VAWT test model; (7) structural parametric analysis of VAWT blades; and (8) cost study

R. E. Walters; J. B. Fanucci; P. W. Hill; P. G. Migliore

1979-01-01

437

Vertical distribution of natural radionuclides in soils  

NASA Astrophysics Data System (ADS)

Low-level alpha spectrometry techniques using semiconductor detectors (PIPS) and liquid scintillation counters (LKB Quantulus 1220™) were used in order to determine the activity concentration of 238U, 232Th, 234U, 230Th, 226Ra, and 210Pb in soil samples. The soils were collected from an old disused uranium mine located in southwest Spain. The soils were selected with different levels of influence from the installation, in such a way that they had different levels of radioactive contamination. The vertical profiles in the soils (down to 40 cm depth) were studied in order to evaluate the vertical distribution of the natural radionuclides. The possible contamination of subsurface waters depends strongly on vertical migration, and the transfer to plants (herbs, shrubs, and trees) also will depend on the distribution of the radionuclides in the root zone. The study of the activity ratios between radionuclides belonging to the same series allowed us to assess the differing behaviour of the radionuclides involved. The vertical profiles for these radionuclides were different at each sampling point, showing the local impact of the installation. However, the profiles per point were similar for the long-lived radionuclides of the 238TJ series (238U, 234U, 230Th, and 226Ra). Also, a major disequilibrium was observed between 210Pb and 226Ra in the surface layer, due to 222Rn emanation and subsequent surface deposition of 210Pb.

Blanco Rodríguez, P.; Tomé, F. Vera; Lozano, J. C.

2012-04-01

438

FUNDAMENTOS TEÓRICOS DE LA INTEGRACIÓN VERTICAL 1  

Microsoft Academic Search

In order to analyze the concept of the vertical integration of companies and the possible effect s on the final prices and the power of market, this article leads from an approach of which it is the company and the relationships that occur internally and externally considering the approach which is different from the neoclassic conventional model. The n, the

José Vicente Cadavid Herrera; John Jairo; García Rendón; Gustavo Adolfo; López Álvarez

439

Vertical File Usage: A Comparative Study.  

ERIC Educational Resources Information Center

Since recorded usage of vertical files in a university library does not always indicate actual needs of patrons, a study was conducted on the use of a collection of 20,000 pamphlets over a three-year period (1972-75). Data were collected from circulation records and from a questionnaire circulated with each pamphlet. Three subject areas had the…

Wells, Dorothy P.

440

Vertical distribution of Pahang River plume  

NASA Astrophysics Data System (ADS)

Large rivers transported high amount of discharge towards the sea and induced the river plume formation. The contents of the plume consist of suspended solids, nutrients, pollutants and other particles. Productivity at estuary depends on the organic and nutrient contents from the river discharge. Due to many possible factors, the dispersal of the plume shows spatial variation horizontally and vertically. The monsoonal wind is a factor that effecting plume vertical profile pattern. This study determines the vertical distribution pattern of the plumeat Pahang River through field observation. Several water parameters were measured during cruises conducted at respective monsoon. Data collected includes depth, chlorophyll-a, salinity, temperature and suspended particulate matter. Depth at Pahang's offshore usually does not reached more than 15 m depth because of the shallow continental shelf at South China Sea. The plume has higher concentration at the mouth of the river which causes the area to be less saline and it decreases as the station furthers from the river. Chlorophyll-a is distributed mainly at the surface level where the area is warmer and received freshwater runoff. Suspended particulate matter shows downward distribution from the front of the estuary towards deep water column depth (10 m). Temperature pattern shows warmer surface layer with depth less than 5 m while deeper water column has lower temperature. Vertical profile pattern of Pahang River plume generally shows slight difference between each monsoon by referring to particular parameter.

Taher, T. M.; Lihan, T.; Mustapha, M. A.

2013-11-01

441

Vertically aligned biaxially textured molybdenum thin films  

SciTech Connect

Vertically aligned, biaxially textured molybdenum nanorods were deposited using dc magnetron sputtering with glancing flux incidence (alpha = 85 degrees with respect to the substrate normal) and a two-step substrate-rotation mode. These nanorods were identified with a body-centered cubic crystal structure. The formation of a vertically aligned biaxial texture with a [110] out-of-plane orientation was combined with a [-110] in-plane orientation. The kinetics of the growth process was found to be highly sensitive to an optimum rest time of 35 seconds for the two-step substrate rotation mode. At all other rest times, the nanorods possessed two separate biaxial textures each tilted toward one flux direction. While the in-plane texture for the vertical nanorods maintains maximum flux capture area, inclined Mo nanorods deposited at alpha = 85 degrees without substrate rotation display a [-1-1-4] in-plane texture that does not comply with the maximum flux capture area argument. Finally, an in situ capping film was deposited with normal flux incidence over the biaxially textured vertical nanorods resulting in a thin film over the porous nanorods. This capping film possessed the same biaxial texture as the nanorods and could serve as an effective substrate for the epitaxial growth of other functional materials.

Krishnan, Rahul [Department of Materials Science and Engineering, Rensselaer Polytechnic Institute, Troy, New York 12180 (United States); Riley, Michael [Department of Chemical and Biological Engineering, Rensselaer Polytechnic Institute, Troy, New York 12180 (United States); Lee, Sabrina [US Army Armament Research, Development and Engineering Center, Benet Labs, Watervliet, New York 12189 (United States); Lu, Toh-Ming [Department of Physics, Applied Physics and Astronomy, Rensselaer Polytechnic Institute, Troy, New York 12180 (United States)

2011-09-15

442

Vertical leaf pressure filter LVAzh 225  

Microsoft Academic Search

A new vertical lead pressure filter LVAzh 225 has been developed with an arrangement for hydraulic coke removal. Industrial trials of the filter, however, showed the service life of the rubber seals of the butterfly valves to be short, so that butterfly valves were replaced by shut-off valves with a pneumatic drive. The prototype of the LVAzh 225 leaf filter

V. I. Fomichev; V. P. Abramov; Y. V. Gutin

1984-01-01

443

Vertical Integration in Building Automation Systems  

Microsoft Academic Search

Building automation systems (BAS) are widely deployed in modern buildings. They are typically engineered adhering to the classical, hierarchical 3-layer model, which has served well in the past but is reaching its limits in complex BAS. The move to more integrated building services also requires tighter integration of the mostly heterogeneous technologies. Vertical integration promises seamless communication from the individual

Stefan Soucek; Dietmar Loy

2007-01-01

444

A vertical MRAM free of write disturbance  

Microsoft Academic Search

Write disturbance in the cross-point addressing scheme employed in most of today's magnetoresistive random access memories (MRAM) designs presents practical limitations in memory element down-size scaling. In this paper, we present a new vertical MRAM design that is free of write disturbance. Its performance is analyzed via micromagnetic modeling. A memory element in this design is of an annular shape

Xiaochun Zhu; Jian-Gang Zhu

2003-01-01

445

Silicon Vertically Integrated Nanowire Field Effect Transistors  

E-print Network

of the threshold voltage is commonly observed due to the presence of surface and interface charge-trapping states. Herein we demonstrate the direct vertical integration of Si nanowire arrays into surrounding gate field challenging issues such as short-channel effects (SCEs), scaling of gate oxide thickness, and increasing power

Yang, Peidong

446

Vertical Acoustic Arrays in the Deep Ocean  

NASA Astrophysics Data System (ADS)

The R/P FLIP has made possible the deployments of vertical arrays to study sound propagation and ambient noise in the deep ocean in ways never before possible from existing research vessels. Long vertical arrays can be deployed without the flow noise contamination from platform motion, long a bane for making such studies. The vertical stability of FLIP combined with the deep mooring capability developed by Earl D. Bronson made it possible to deploy multi-element arrays beginning with a versatile 20 element array with variable spacing developed by Bill Whitney in Fred Spiess's group. The 20 element array consisted of bungee mounted hydrophones in metal cages at either uniform spacing or variable spacing to meet directivity or other requirements. It was assembled on station in the vertical and deployed to the desired depths for the elements. Gerald Morris at MPL conducted ambient noise studies using variable spacing of the elements to below the critical depth as well as in the water column above. Vic Anderson used it for his DIMUS processing system for detecting low level signals masked by ambient noise. As a 500 meter array, I used it for a series of CONTRACK (Continuous Tracking of signals at long range) experiments to resolve multipaths so they wouldn't interfere with one another. The VEKA vertical array developed by Rick Swenson of NORDA was deployed in very deep (below 3300 m) water by Dan Ramsdale of NORDA using the winch and double lay armored cable on FLIP, the same cable system for the MPL 20 element array. In my group Bruce Williams designed a rapidly deployable array to study vertical anisotropy of ambient noise as a function of range from near shore shipping via downslope conversion in a series of 48 hours FLIP stations 350, 1000 and 1500 miles from the Pacific coast. A short 120 element array, 1000 meters long, was built by John Hildebrands's group for a test of matched field processing and the SLICE experiment in acoustic tomography research of Peter Worcester and Walter Munk in 1987. Later a different 200 element array over 3000 meters long was also built by John Hildebrand's group for deloyment in the VAST experiment in 1987. This array included acoustic navigation to measure element location for several different experiments including matched field processing at 1000 km, normal mode studies and down-slope conversion of shipping noise and by Stan Flatte of UCSC for looking at long range barotropic wave reflections from Alaska. In a separate talk, Gerald D'Spain will discuss a trifar (3D) vertical array developed at MPL.

Fisher, F.

2002-12-01

447

Thermal entrance length in falling liquid film heat transfer  

SciTech Connect

Subcooled and evaporating falling liquid films are frequently encountered in the process industry, desalination, and nuclear reactor safety. Thermal entrance lengths in a subcooled falling liquid film were studied experimentally on a vertical cylindrical heater preceded by an adiabatic section. A wavy-laminar flow regime close to the transition to turbulent flow was achieved. Water at atmospheric pressure was used as the test fluid. Heating surface temperatures were measured at eight axial locations along the flow direction and the local heat transfer coefficients were obtained as functions of heat flux and mass flow rate. Heat transfer coefficients were observed decreasing along the heater and reaching a minimum. The influences of the Reynolds number and heat flux on the thermal entrance length at low heat fluxes were weak. Both the Reynolds number and the heat flux strongly influenced the thermal entrance length at relatively high heat fluxes.

Ulucakli, E. [Lafayette Coll., Easton, PA (United States). Dept. of Mechanical Engineering

1996-06-01

448

Computation of vertical profiles of longwave radiative cooling over the equatorial Pacific  

NASA Technical Reports Server (NTRS)

An important quantity whose magnitude has not been throughly examined is the vertical distribution of heating in the Tropics. The details of the vertical distribution of heating have a significant impact on a number of phenomena, including the 30-60 day oscillation, sometimes known as the intraseasonal oscillation. Prior attempts to establish the structure of the heating relied on limited field data or assimilated data, coupled with climatological radiative heating parameters. The availability of high quality global-scale datasets has made it possible to make more accurate calculations than were possible a few years ago. An important component of the apparent heat budget is the longwave radiative cooling, which in this paper is found by using the ECMWF/WCRP/TOGA Archive 2 and ISCCP C1 datasets, together with a well-established parameterization scheme. A method is developed that can be used to estimate the vertical structure of cloud amounts based on top-of-atmosphere cloud observations, and the results are used with a wide-band longwave parameterization to produce longwave cooling rates over the tropical Pacific Ocean. Outgoing longwave radiation is calculated and compared the ERBE results. The calculated values are generally higher than those from ERBE, though the spatial distributions are similar. Some significant problems exist with the ECMWF upper-tropospheric water vapor amounts, which could imply uncertainties of 0.5 C/day in the calculated cooling rates. This is comparable to the differences associated with the minimum or random overlap assumptions used to generate cloud profiles.

Ramsey, Perry G.; Vincent, Dayton G.

1995-01-01

449

Long-term evolution of anthropogenic heat fluxes into a subsurface urban heat island.  

PubMed

Anthropogenic alterations in urban areas influence the thermal environment causing elevated atmospheric and subsurface temperatures. The subsurface urban heat island effect is observed in several cities. Often shallow urban aquifers exist with thermal anomalies that spread laterally and vertically, resulting in the long-term accumulation of heat. In this study, we develop an analytical heat flux model to investigate possible drivers such as increased ground surface temperatures (GSTs) at artificial surfaces and heat losses from basements of buildings, sewage systems, subsurface district heating networks, and reinjection of thermal wastewater. By modeling the anthropogenic heat flux into the subsurface of the city of Karlsruhe, Germany, in 1977 and 2011, we evaluate long-term trends in the heat flux processes. It revealed that elevated GST and heat loss from basements are dominant factors in the heat anomalies. The average total urban heat flux into the shallow aquifer in Karlsruhe was found to be ?759 ± 89 mW/m(2) in 1977 and 828 ± 143 mW/m(2) in 2011, which represents an annual energy gain of around 1.0 × 10(15) J. However, the amount of thermal energy originating from the individual heat flux processes has changed significantly over the past three decades. PMID:23895264

Menberg, Kathrin; Blum, Philipp; Schaffitel, Axel; Bayer, Peter

2013-09-01

450

Latent Heating from TRMM Satellite Measurements  

NASA Technical Reports Server (NTRS)

Rainfall production is a fundamental process within the Earth;s hydrological cycle because it represents both a principal forcing term in surface water budgets, and its energetics corollary, latent heating, is the principal source of atmospheric diabatic heating. Latent heat release itself is a consequence of phase changes between the vapor, liquid, and frozen states of water. The properties of the vertical distribution of latent heat release modulate large-scale meridional and zonal circulations with the Tropics - as well as modify the energetic efficiencies of mid-latitude weather systems. This paper highlights the retrieval of observatory, which was launched in November 1997 as a joint American-Japanese space endeavor. Since then, TRMM measurements have been providing an accurate four-dimensional amount of rainfall over the global Tropics and sub-tropics - information which can be used to estimate the spacetime structure of latent heating across the Earth's low latitudes. A set of algorithm methodologies has and continues to be developed to estimate latent heating based on rain rate profile retrievals obtained from TRMM measurements. These algorithms are briefly described followed by a discussion of the foremost latent heating products that can be generate from them. The investigation then provides an overview of how TRMM-derived latent heating information is currently being used in conjunction with global weather and climate models, concluding with remarks intended to stimulate further research on latent heating retrieval from satellites.

Tao, W.-K.; Smith, E.; Olson, W.

2005-01-01

451

Hypersonic shock tunnel heat transfer tests of the Space Shuttle SILTS pod configuration  

NASA Technical Reports Server (NTRS)

Heat transfer measurements have been made on a 0.0175-scale NASA Space Shuttle orbiter model having a simulated SILTS (Shuttle Infrared Leeside Temperature Sensor) pod on top of the vertical tail. Heat transfer distributions were measured both on the pod and on the vertical tail. The test program covered Mach numbers of 8, 11 and 16 in air, at Reynolds numbers from 100,000 to 18 million, based on model length. The angle of attack ranged from 30 deg to 40 deg at sideslip angles from -2 to +2 deg. Data were obtained with 92 thin film assistance thermometers located on the SILTS pod and on the upper 30 percent of the vertical tail. Heat transfer rates measured on the vertical tail show good agreement with flight data obtained from missions STS-1, -2 and -3. The variation of heat transfer to the pod with Reynolds number, Mach number and angle of attack is discussed.

Wittliff, C. E.

1983-01-01

452

Entirely passive heat-pipe apparatus capable of operating against gravity  

DOEpatents

The disclosure is directed to an entirely passive heat pipe apparatus capable of operating against gravity for vertical distances in the order of 3 to 7 and more. A return conduit into which an inert gas is introduced is used to lower the specific density of the working fluid so that it may be returned a greater vertical distance from condenser to evaporator.

Koenig, D.R.

1981-02-11

453

The vertical-mill stage : design of a vertical movement stage for surface machining  

E-print Network

To allow the widespread use of three dimensional patterns on walls, the manufacturing cost must be reduced. The goal of this project is to design a machine for vertical axis movement which can be measured and controlled. ...

Herrera, Juan, Jr

2007-01-01

454

Effect of gravity on vertical eye position.  

PubMed

There is growing evidence that gravity markedly influences vertical eye position and movements. A new model for the organization of brainstem upgaze pathways is presented in this review. The crossing ventral tegmental tract (CVTT) could be the efferent tract of an "antigravitational" pathway terminating at the elevator muscle motoneurons in the third nerve nuclei and comprising, upstream, the superior vestibular nucleus and y-group, the flocculus, and the otoliths. This pathway functions in parallel to the medial longitudinal fasciculus pathways, which control vertical eye movements made to compensate for all vertical head movements and may also comprise the "gravitational" vestibular pathways, involved in the central reflection of the gravity effect. The CVTT could provide the upgaze system with the supplement of tonic activity required to counteract the gravity effect expressed in the gravitational pathway, being permanently modulated according to the static positions of the head (i.e., the instantaneous gravity vector) between a maximal activity in the upright position and a minimal activity in horizontal positions. Different types of arguments support this new model. The permanent influence of gravity on vertical eye position is strongly suggested by the vertical slow phases and nystagmus observed after rapid changes in hypo- or hypergravity. The chin-beating nystagmus, existing in normal subjects with their head in the upside-down position, suggests that gravity is not compensated for in the downgaze system. Upbeat nystagmus due to brainstem lesions, most likely affecting the CVTT circuitry, is improved when the head is in the horizontal position, suggesting that this circuitry is involved in the counteraction of gravity between the upright and horizontal positions of the head. In downbeat nystagmus due to floccular damage, in which a permanent hyperexcitation of the CVTT could exist, a marked influence of static positions of the head is also observed. Finally, the strongest argument supporting a marked role of gravity in vertical eye position is that the eye movement alterations observed in the main, typical physiological and pathological conditions are precisely those that would be expected from a direct effect of gravity on the eyeballs, with, moreover, no single alternative interpretation existing so far that could account for all these different types of findings. PMID:19645894

Pierrot-Deseilligny, C

2009-05-01

455

Habitat Demonstration Unit (HDU) Vertical Cylinder Habitat  

NASA Technical Reports Server (NTRS)

NASA's Constellation Architecture Team defined an outpost scenario optimized for intensive mobility that uses small, highly mobile pressurized rovers supported by portable habitat modules that can be carried between locations of interest on the lunar surface. A compact vertical cylinder characterizes the habitat concept, where the large diameter maximizes usable flat floor area optimized for a gravity environment and allows for efficient internal layout. The module was sized to fit into payload fairings for the Constellation Ares V launch vehicle, and optimized for surface transport carried by the All-Terrain Hex-Limbed Extra-Terrestrial Explorer (ATHLETE) mobility system. Launch and other loads are carried through the barrel to a top and bottom truss that interfaces with a structural support unit (SSU). The SSU contains self-leveling feet and docking interfaces for Tri-ATHLETE grasping and heavy lift. A pressurized module needed to be created that was appropriate for the lunar environment, could be easily relocated to new locations, and could be docked together in multiples for expanding pressurized volume in a lunar outpost. It was determined that horizontally oriented pressure vessels did not optimize floor area, which takes advantage of the gravity vector for full use. Hybrid hard-inflatable habitats added an unproven degree of complexity that may eventually be worked out. Other versions of vertically oriented pressure vessels were either too big, bulky, or did not optimize floor area. The purpose of the HDU vertical habitat module is to provide pressurized units that can be docked together in a modular way for lunar outpost pressurized volume expansion, and allow for other vehicles, rovers, and modules to be attached to the outpost to allow for IVA (intra-vehicular activity) transfer between them. The module is a vertically oriented cylinder with a large radius to allow for maximal floor area and use of volume. The modular, 5- m-diameter HDU vertical habitat module consists of a 2-m-high barrel with 0.6-mhigh end domes forming the 56-cubicmeter pressure vessel, and a 19-squaremeter floor area. The module has up to four docking ports located orthogonally from each other around the perimeter, and up to one docking port each on the top or bottom end domes. In addition, the module has mounting trusses top and bottom for equipment, and to allow docking with the ATHLETE mobility system. Novel or unique features of the HDU vertical habitat module include the nodelike function with multiple pressure hatches for docking with other versions of itself and other modules and vehicles; the capacity to be carried by an ATHLETE mobility system; and the ability to attach inflatable 'attic' domes to the top for additional pressurized volume.

Howe, Alan; Kennedy, Kriss J.; Gill, Tracy R.; Tri, Terry O.; Toups, Larry; Howard, Robert I.; Spexarth, Gary R.; Cavanaugh, Stephen; Langford, William M.; Dorsey, John T.

2014-01-01

456

Modeling the ascent of sounding balloons: derivation of the vertical air motion  

NASA Astrophysics Data System (ADS)

A new model to describe the ascent of sounding balloons in the troposphere and lower stratosphere (up to ~30-35 km altitude) is presented. Contrary to previous models, detailed account is taken of both the variation of the drag coefficient with altitude and the heat imbalance between the balloon and the atmosphere. To compensate for the lack of data on the drag coefficient of sounding balloons, a reference curve for the relationship between drag coefficient and Reynolds number is derived from a dataset of flights launched during the Lindenberg Upper Air Methods Intercomparisons (LUAMI) campaign. The transfer of heat from the surrounding air into the balloon is accounted for by solving the radial heat diffusion equation inside the balloon. The potential applications of the model include the forecast of the trajectory of sounding balloons, which can be used to increase the accuracy of the match technique, and the derivation of the air vertical velocity. The latter is obtained by subtracting the ascent rate of the balloon in still air calculated by the model from the actual ascent rate. This technique is shown to provide an approximation for the vertical air motion with an uncertainty error of 0.5 m s-1 in the troposphere and 0.2 m s-1 in the stratosphere. An example of extraction of the air vertical velocity is provided in this paper. We show that the air vertical velocities derived from the balloon soundings in this paper are in general agreement with small-scale atmospheric velocity fluctuations related to gravity waves, mechanical turbulence, or other small-scale air motions measured during the SUCCESS campaign (Subsonic Aircraft: Contrail and Cloud Effects Special Study) in the orographically unperturbed mid-latitude middle troposphere.

Gallice, A.; Wienhold, F. G.; Hoyle, C. R.; Immler, F.; Peter, T.

2011-06-01

457

Heat transfer coefficients of dilute flowing gas-solids suspensions  

NASA Technical Reports Server (NTRS)

Heat transfer coefficients of air-glass, argon-glass, and argon-aluminum suspensions were measured in horizontal and vertical tubes. The glass, 21.6 and 36.0 micron diameter particles, was suspended at gas Reynolds numbers between 11,000 and 21,000 and loading ratios between 0 and 2.5. The presence of particles generally reduced the heat transfer coefficient. The circulation of aluminum powder in the 0.870 inch diameter closed loop system produced tenacious deposits on protuberances into the stream. In the vertical test section, the Nusselt number reduction was attributed to viscous sublayer thickening; in the horizontal test section to particle deposition.

Kane, R. S.; Pfeffer, R.

1973-01-01

458

Ultimately short ballistic vertical graphene Josephson junctions  

PubMed Central

Much efforts have been made for the realization of hybrid Josephson junctions incorporating various materials for the fundamental studies of exotic physical phenomena as well as the applications to superconducting quantum devices. Nonetheless, the efforts have been hindered by the diffusive nature of the conducting channels and interfaces. To overcome the obstacles, we vertically sandwiched a cleaved graphene monoatomic layer as the normal-conducting spacer between superconducting electrodes. The atomically thin single-crystalline graphene layer serves as an ultimately short conducting channel, with highly transparent interfaces with superconductors. In particular, we show the strong Josephson coupling reaching the theoretical limit, the convex-shaped temperature dependence of the Josephson critical current and the exceptionally skewed phase dependence of the Josephson current; all demonstrate the bona fide short and ballistic Josephson nature. This vertical stacking scheme for extremely thin transparent spacers would open a new pathway for exploring the exotic coherence phenomena occurring on an atomic scale. PMID:25635386

Lee, Gil-Ho; Kim, Sol; Jhi, Seung-Hoon; Lee, Hu-Jong

2015-01-01

459

Lunar vertical-shaft mining system  

NASA Technical Reports Server (NTRS)

This report proposes a method that will allow lunar vertical-shaft mining. Lunar mining allows the exploitation of mineral resources imbedded within the surface. The proposed lunar vertical-shaft mining system is comprised of five subsystems: structure, materials handling, drilling, mining, and planning. The structure provides support for the exploration and mining equipment in the lunar environment. The materials handling subsystem moves mined material outside the structure and mining and drilling equipment inside the structure. The drilling process bores into the surface for the purpose of collecting soil samples, inserting transducer probes, or locating ore deposits. Once the ore deposits are discovered and pinpointed, mining operations bring the ore to the surface. The final subsystem is planning, which involves the construction of the mining structure.

Introne, Steven D. (editor); Krause, Roy; Williams, Erik; Baskette, Keith; Martich, Frederick; Weaver, Brad; Meve, Jeff; Alexander, Kyle; Dailey, Ron; White, Matt

1994-01-01

460

Coupled Resonator Vertical Cavity Laser Diode  

SciTech Connect

We report the operation of an electrically injected monolithic coupled resonator vertical cavity laser which consists of an active cavity containing In{sub x}Ga{sub 1{minus}x}As quantum wells optically coupled to a passive GaAs cavity. This device demonstrates novel modulation characteristics arising from dynamic changes in the coupling between the active and passive cavities. A composite mode theory is used to model the output modulation of the coupled resonator vertical cavity laser. It is shown that the laser intensity can be modulated by either forward or reverse biasing the passive cavity. Under forward biasing, the modulation is due to carrier induced changes in the refractive index, while for reverse bias operation the modulation is caused by field dependent cavity enhanced absorption.

CHOQUETTE, KENT D.; CHOW, WENG W.; FISCHER, ARTHUR J.; GEIB, KENT M.; HOU, HONG Q.

1999-09-16

461

Heat pipe system  

Microsoft Academic Search

A heat pipe diode device for transferring heat from a heat source component to a heat sink wall is described. It contains a heat pipe body member attached to the best source; the heat source having a wall forming at least a portion of the normal evaporator section of the heat pipe diode; a working fluid within the body member;

H. L. Kroebig; F. J. Riha

1974-01-01

462

Waste heat recovery using heat pipe heat exchanger for heating automobile using exhaust gas  

Microsoft Academic Search

The feasibility of using heat pipe heat exchangers for heating applying automotive exhaust gas is studied and the calculation method is developed. Practical heat pipe heat exchanger is set up for heating HS663, a large bus. Simple experiments are carried out to examine the performance of the heat exchanger. It is shown that the experimental results, which indicate the benefit

Feng Yang; Xiugan Yuan; Guiping Lin

2003-01-01

463

Present day vertical deformation in New Zealand  

NASA Astrophysics Data System (ADS)

New Zealand is tectonically very active. It lies along the oblique convergent plate boundary between the Pacific and Australian plate. In the North Island active tectonics is dominated by westward subduction of the Pacific Plate beneath the eastern North Island at the Hikurangi Trench, strike-slip faulting in the upper plate, and back-arc rifting in the central North Island. A series of very large strike-slip faults run through the South Island (Marlborough Fault System and the Alpine Fault) connecting with the Puysegur subduction zone in the south. The present day uplift rates are evaluated by analyzing data from continuous GPS stations in New Zealand. The up to 20 years of continuous GPS gives us a snapshot into the deformation rate. The average velocity is corrected for significant coseismic offsets, but the data can also be influenced by postseismic deformation, slow slip events along the Hikurangi subduction zone, volcanic deformation, as well as none tectonic local affects such as water extraction. We evaluate the interseismic vertical rate. We exclude data significantly affected by postseismic deformation from recent earthquakes and provide vertical rates both with and without correcting for slow slip events. Outside the Taupo rift zone the vertical rates are range from -6 to +6 mm/yr with uplift observed across the Alpine fault, few mm/yr uplift around the Raukumara Peninsula, northeast North Island, and subsidence along the southeast North Island, reflecting variation in plate locking. We compare the present day vertical deformation to the long-term motion along the coast determined primarily from 125,000 years old marine geological markers. The largest proportion of the New Zealand coastline (45%) is undergoing long-term tectonic uplift. Small stretches of the coastline (15%) are undergoing long-term subsidence. Areas farthest from the plate boundary (northern North Island and southeastern South Island) are assessed to be tectonically stable, in agreement with the continuous GPS data.

Hreinsdóttir, Sigrún; Wallace, Laura; Litchfield, Nicola; D'Anastasio, Elisabetta; Denys, Paul; Pearson, Christopher

2014-05-01

464

Electrically floating, near vertical incidence, skywave antenna  

SciTech Connect

An Electrically Floating, Near Vertical Incidence, Skywave (NVIS) Antenna comprising an antenna element, a floating ground element, and a grounding element. At least part of said floating ground element is positioned between said antenna element and said grounding element. The antenna is separated from the floating ground element and the grounding element by one or more electrical insulators. The floating ground element is separated from said antenna and said grounding element by one or more electrical insulators.

Anderson, Allen A.; Kaser, Timothy G.; Tremblay, Paul A.; Mays, Belva L.

2014-07-08

465

Spirit 360-Degree View, Sol 388 (vertical)  

NASA Technical Reports Server (NTRS)

NASA's Mars Exploration Rover Spirit used its navigation camera to take the images combined into this 360-degree view of the rover's surroundings on Spirit's 388th martian day, or sol (Feb. 4, 2005). Spirit had driven about 13 meters (43 feet) uphill toward 'Cumberland Ridge' on this sol. This location is catalogued as Spirit's Site 102, Position 513. The view is presented in a vertical projection with geometric and brightness seam correction.

2005-01-01

466

Engineering high-performance vertical cavity lasers  

SciTech Connect

The cw and high-speed performance of vertical cavity surface emitting laser diodes (VCSELs) are affected by both electrical and optical issues arising from the geometry and fabrication of these devices. Structures with low resistance semiconductor mirrors and Al-oxide confinement layers address these issues and have produced record performance including 50% power conversion efficiency and modulation bandwidths up to 20 GHz at small bias currents.

Lear, K.L.; Hou, H.Q.; Hietala, V.M.; Choquette, K.D.; Schneider, R.P. Jr.

1996-12-31

467

Method to Compute the Vertical Deflection Components  

Microsoft Academic Search

\\u000a To make a more exact mathematical model of the global atmosphere circulation and to improve the weather forecast one needs\\u000a to take into account the Vertical Deflection Components (VDCs). The required accuracy for these tasks is 1–2?? now and 0.4–1.0?? in future. The VDCs were calculated by integration of the free air gravity anomalies (taken from the Internet site of

E. A. Boyarsky; L. V. Afanasieva; V. N. Koneshov

468

Record Drive Day, Opportunity Sol 383 (vertical)  

NASA Technical Reports Server (NTRS)

NASA's Mars Exploration Rover Opportunity set a one-day distance record for martian driving on the rover's 383rd martian day, or sol, which began on Feb. 19, 2005. Opportunity rolled 177.5 meters (582 feet) across the plain of Meridiani on that sol. It used its navigation camera after the drive to take the images that are combined into this mosaic view. The view is presented here in a vertical projection with geometric seam correction.

2005-01-01

469

Vertical leaf pressure filter LVAzh 225  

SciTech Connect

A new vertical lead pressure filter LVAzh 225 has been developed with an arrangement for hydraulic coke removal. Industrial trials of the filter, however, showed the service life of the rubber seals of the butterfly valves to be short, so that butterfly valves were replaced by shut-off valves with a pneumatic drive. The prototype of the LVAzh 225 leaf filter has been recommended for series production.

Fomichev, V.I.; Abramov, V.P.; Gutin, Y.V.

1984-01-01

470

Geothermal heating  

SciTech Connect

The aim of the study is to demonstrate the viability of geothermal heating projects in energy and economic terms and to provide nomograms from which an initial estimate may be made without having to use data-processing facilities. The effect of flow rate and temperature of the geothermal water on drilling and on the network, and the effect of climate on the type of housing are considered.

Aureille, M.

1982-01-01

471

The vertical distribution of tropospheric ammonia  

NASA Technical Reports Server (NTRS)

A one-dimensional tropospheric photochemical model is used to simulate measured profiles of NH3 obtained with the Infrared Heterodyne Radiometer. The relative roles of homogeneous loss, heterogeneous loss, and vertical eddy transport are discussed in terms of selecting parameters which best fit the measurements. The best fit was obtained for a vertical eddy diffusion coefficient of 200,000/sq cm per sec or greater (corresponding to a characteristic vertical transport time in excess of about 35 days), and a characteristic heterogeneous loss time in excess of 10 days. The characteristic homogeneous chemical loss time was found to be about 40 days at the surface and decreased to about 180 days at 10 km, and not very sensitive to model chemical perturbations. Increased ground-level concentrations of NH3 to about 10 ppb, compared to background surface concentrations of about 1 ppb, were measured several weeks after application of ammonium nitrate fertilizer. This suggests that the volatilization of ammonium nitrate fertilizer is rapid, and an important source of NH3. Because of the characteristic times for the loss mechanisms, synoptic time-scale phenomena may play an important role in determining the tropospheric distribution of NH3 concentrations.

Levine, J. S.; Hoell, J. M.; Augustsson, T. R.

1980-01-01

472

Magnetic induced heating for ferritic metal annealing  

SciTech Connect

A method is described for annealing the wall of a nuclear reactor vessel, including, positioning an electromagnet within a vertically positioned nuclear reactor vessel by lowering the electromagnet into the vessel, supplying power to the electromagnet to generate substantially uniform heat in the vessel wall, maintaining the power to the electromagnet for a predetermined length of time which will anneal the vessel wall, and removing the electromagnet.

De Witt, G.L.; Huber, D.J.

1987-03-24