Trend of heat flow in france: relation with deep structures

NASA Astrophysics Data System (ADS)

Vasseur, Guy; Nouri, Yamina; Groupe Fluxchaf

1980-06-01

The trend of heat flow over France is discussed using both direct measurements at equilibrium in boreholes and file data. The two types of data are found to be in agreement. They exhibit high heat flow values over the Massif Central and the Vosges. An E-W cross section across the Massif Central allows us to observe the relationship between the high heat flow values, the thinning of the crust and the uprising of the asthenosphere deduced from seismic and gravity measurements. High heat flow values could be explained using a cinematic model where upward convection occurs in the upper mantle for a period of 40 m.y. with a vertical velocity reaching 5 mm/y.

Interpretation of lunar heat flow data. [for estimating bulk uranium abundance

NASA Technical Reports Server (NTRS)

Conel, J. E.; Morton, J. B.

1975-01-01

Lunar heat flow observations at the Apollo 15 and 17 sites can be interpreted to imply bulk U concentrations for the moon of 5 to 8 times those of normal chondrites and 2 to 4 times terrestrial values inferred from the earth's heat flow and the assumption of thermal steady state between surface heat flow and heat production. A simple model of nearsurface structure that takes into account the large difference in (highly insulating) regolith thickness between mare and highland provinces is considered. This model predicts atypically high local values of heat flow near the margins of mare regions - possibly a factor of 10 or so higher than the global average. A test of the proposed model using multifrequency microwave techniques appears possible wherein heat flow traverse measurements are made across mare-highland contacts. The theoretical considerations discussed here urge caution in attributing global significance to point heat-flow measurements on the moon.

Heat exchanger with oscillating flow

NASA Technical Reports Server (NTRS)

Scotti, Stephen J. (Inventor); Blosser, Max L. (Inventor); Camarda, Charles J. (Inventor)

1992-01-01

Various heat exchange apparatuses are described in which an oscillating flow of primary coolant is used to dissipate an incident heat flux. The oscillating flow may be imparted by a reciprocating piston, a double action twin reciprocating piston, fluidic oscillators, or electromagnetic pumps. The oscillating fluid flows through at least one conduit in either an open loop or a closed loop. A secondary flow of coolant may be used to flow over the outer walls of at least one conduit to remove heat transferred from the primary coolant to the walls of the conduit.

Heat exchanger with oscillating flow

NASA Technical Reports Server (NTRS)

Scotti, Stephen J. (Inventor); Blosser, Max L. (Inventor); Camarda, Charles J. (Inventor)

1993-01-01

Various heat exchange apparatuses are described in which an oscillating flow of primary coolant is used to dissipate an incident heat flux. The oscillating flow may be imparted by a reciprocating piston, a double action twin reciprocating piston, fluidic oscillators or electromagnetic pumps. The oscillating fluid flows through at least one conduit in either an open loop or a closed loop. A secondary flow of coolant may be used to flow over the outer walls of at least one conduit to remove heat transferred from the primary coolant to the walls of the conduit.

Colorado Heat Flow Data from IHFC

DOE Data Explorer

Richard E. Zehner

2012-02-01

This layer contains the heat flow sites and data of the State of Colorado compiled from the International Heat Flow Commission (IHFC) of the International Association of Seismology and Physics of the Earth's Interior (IASPEI) global heat flow database (www.heatflow.und.edu/index2.html). The data include different items: Item number, descriptive code, name of site, latitude and longitude, elevation, depth interval, number of temperature data, temperature gradient, number of conductivity measurement, average conductivity, number of heat generation measurements, average heat production, heat flow, number of individual sites, references, and date of publication.

Condensation heat transfer and flow friction in silicon microchannels

NASA Astrophysics Data System (ADS)

Wu, Huiying; Wu, Xinyu; Qu, Jian; Yu, Mengmeng

2008-11-01

An experimental investigation was performed on heat transfer and flow friction characteristics during steam condensation flow in silicon microchannels. Three sets of trapezoidal silicon microchannels, with hydraulic diameters of 77.5 µm, 93.0 µm and 128.5 µm respectively, were tested under different flow and cooling conditions. It was found that both the condensation heat transfer Nusselt number (Nu) and the condensation two-phase frictional multiplier (phi2Lo) were dependent on the steam Reynolds number (Rev), condensation number (Co) and dimensionless hydraulic diameter (Dh/L). With the increase in the steam Reynolds number, condensation number and dimensionless hydraulic diameter, the condensation Nusselt number increased. However, different variations were observed for the condensation two-phase frictional multiplier. With the increase in the steam Reynolds number and dimensionless hydraulic diameter, the condensation two-phase frictional multiplier decreased, while with the increase in the condensation number, the condensation two-phase frictional multiplier increased. Based on the experimental results, dimensionless correlations for condensation heat transfer and flow friction in silicon microchannels were proposed for the first time. These correlations can be used to determine the condensation heat transfer coefficient and pressure drop in silicon microchannels if the steam mass flow rate, cooling rate and geometric parameters are fixed. It was also found that the condensation heat transfer and flow friction have relations to the injection flow (a transition flow pattern from the annular flow to the slug/bubbly flow), and with injection flow moving toward the outlet, both the condensation heat transfer coefficient and the condensation two-phase frictional multiplier increased.

Triaxial thermopile array geo-heat-flow sensor

DOEpatents

Carrigan, C.R.; Hardee, H.C.; Reynolds, G.D.; Steinfort, T.D.

1990-01-01

A triaxial thermopile array geothermal heat flow sensor is designed to measure heat flow in three dimensions in a reconstituted or unperturbed subsurface regime. Heat flow can be measured in conductive or permeable convective media. The sensor may be encased in protective pvc tubing and includes a plurality of thermistors and an array of heat flow transducers produce voltage proportional to heat flux along the subsurface regime and permit direct measurement of heat flow in the subsurface regime. The presence of the thermistor array permits a comparison to be made between the heat flow estimates obtained from the transducers and heat flow calculated using temperature differences and Fourier's Law. The device is extremely sensitive with an accuracy of less than 0.1 Heat Flow Units (HFU) and may be used for long term readings. 6 figs.

Triaxial thermopile array geo-heat-flow sensor

DOEpatents

Carrigan, Charles R.; Hardee, Harry C.; Reynolds, Gerald D.; Steinfort, Terry D.

1992-01-01

A triaxial thermopile array geothermal heat flow sensor is designed to measure heat flow in three dimensions in a reconstituted or unperturbed subsurface regime. Heat flow can be measured in conductive or permeable convective media. The sensor may be encased in protective pvc tubing and includes a plurality of thermistors and an array of heat flow transducers arranged in a vertical string. The transducers produce voltage proportional to heat flux along the subsurface regime and permit direct measurement of heat flow in the subsurface regime. The presence of the thermistor array permits a comparison to be made between the heat flow estimates obtained from the transducers and heat flow calculated using temperature differences and Fourier's Law. The device is extremely sensitive with an accuracy of less than 0.1 Heat Flow Units (HFU) and may be used for long term readings.

Vapor Flow Patterns During a Start-Up Transient in Heat Pipes

NASA Technical Reports Server (NTRS)

Issacci, F.; Ghoniem, N, M.; Catton, I.

1996-01-01

The vapor flow patterns in heat pipes are examined during the start-up transient phase. The vapor core is modelled as a channel flow using a two dimensional compressible flow model. A nonlinear filtering technique is used as a post process to eliminate the non-physical oscillations of the flow variables. For high-input heat flux, multiple shock reflections are observed in the evaporation region. The reflections cause a reverse flow in the evaporation and circulations in the adiabatic region. Furthermore, each shock reflection causes a significant increase in the local pressure and a large pressure drop along the heat pipe.

Effect of the load size on the efficiency of microwave heating under stop flow and continuous flow conditions.

PubMed

Patil, Narendra G; Rebrov, Evgeny V; Eränen, Kari; Benaskar, Faysal; Meuldijk, Jan; Mikkola, Jyri-Pekka; Hessel, Volker; Hulshof, Lumbertus A; Murzin, Dmitry Yu; Schouten, Jaap C

2012-01-01

A novel heating efficiency analysis of the microwave heated stop-flow (i.e. stagnant liquid) and continuous-flow reactors has been presented. The thermal losses to the surrounding air by natural convection have been taken into account for heating efficiency calculation of the microwave heating process. The effect of the load diameter in the range of 4-29 mm on the heating efficiency of ethylene glycol was studied in a single mode microwave cavity under continuous flow and stop-flow conditions. The variation of the microwave absorbing properties of the load with temperature was estimated. Under stop-flow conditions, the heating efficiency depends on the load diameter. The highest heating efficiency has been observed at the load diameter close to the half wavelength of the electromagnetic field in the corresponding medium. Under continuous-flow conditions, the heating efficiency increased linearly. However, microwave leakage above the propagation diameter restricted further experimentation at higher load diameters. Contrary to the stop-flow conditions, the load temperature did not raise monotonously from the inlet to outlet under continuous-flow conditions. This was due to the combined effect of lagging convective heat fluxes in comparison to volumetric heating. This severely disturbs the uniformity of the electromagnetic field in the axial direction and creates areas of high and low field intensity along the load Length decreasing the heating efficiency as compared to stop-flow conditions.

Temperature-gated thermal rectifier for active heat flow control.

PubMed

Zhu, Jia; Hippalgaonkar, Kedar; Shen, Sheng; Wang, Kevin; Abate, Yohannes; Lee, Sangwook; Wu, Junqiao; Yin, Xiaobo; Majumdar, Arun; Zhang, Xiang

2014-08-13

Active heat flow control is essential for broad applications of heating, cooling, and energy conversion. Like electronic devices developed for the control of electric power, it is very desirable to develop advanced all-thermal solid-state devices that actively control heat flow without consuming other forms of energy. Here we demonstrate temperature-gated thermal rectification using vanadium dioxide beams in which the environmental temperature actively modulates asymmetric heat flow. In this three terminal device, there are two switchable states, which can be regulated by global heating. In the "Rectifier" state, we observe up to 28% thermal rectification. In the "Resistor" state, the thermal rectification is significantly suppressed (<1%). To the best of our knowledge, this is the first demonstration of solid-state active-thermal devices with a large rectification in the Rectifier state. This temperature-gated rectifier can have substantial implications ranging from autonomous thermal management of heating and cooling systems to efficient thermal energy conversion and storage.

Heat-flow studies in the northwest geysers geothermal field, California

USGS Publications Warehouse

Williams, Colin F.; Galanis, S. Peter; Moses, Thomas H.; Grubb, Frederick V.; ,

1993-01-01

Temperature and thermal conductivity data were acquired from 3 idle production wells in the Northwest Geysers. Heat-flow profiles derived from data recorded in the caprock which overlies the steam reservoir reveal a decrease of heat flow with depth in 2 of the 3 wells. These observations contradict the generally accepted theory that conductive heat flow is constant with depth within The Geysers caprock. There are several possible explanations for this, but the available data suggest that these profiles reflect a local recession or cooling of the reservoir top within the past 5000 to 10000 years.

Critical heat flux in subcooled flow boiling

NASA Astrophysics Data System (ADS)

Hall, David Douglas

The critical heat flux (CHF) phenomenon was investigated for water flow in tubes with particular emphasis on the development of methods for predicting CHF in the subcooled flow boiling regime. The Purdue University Boiling and Two-Phase Flow Laboratory (PU-BTPFL) CHF database for water flow in a uniformly heated tube was compiled from the world literature dating back to 1949 and represents the largest CHF database ever assembled with 32,544 data points from over 100 sources. The superiority of this database was proven via a detailed examination of previous databases. The PU-BTPFL CHF database is an invaluable tool for the development of CHF correlations and mechanistic models that are superior to existing ones developed with smaller, less comprehensive CHF databases. In response to the many inaccurate and inordinately complex correlations, two nondimensional, subcooled CHF correlations were formulated, containing only five adjustable constants and whose unique functional forms were determined without using a statistical analysis but rather using the parametric trends observed in less than 10% of the subcooled CHF data. The correlation based on inlet conditions (diameter, heated length, mass velocity, pressure, inlet quality) was by far the most accurate of all known subcooled CHF correlations, having mean absolute and root-mean-square (RMS) errors of 10.3% and 14.3%, respectively. The outlet (local) conditions correlation was the most accurate correlation based on local CHF conditions (diameter, mass velocity, pressure, outlet quality) and may be used with a nonuniform axial heat flux. Both correlations proved more accurate than a recent CHF look-up table commonly employed in nuclear reactor thermal hydraulic computer codes. An interfacial lift-off, subcooled CHF model was developed from a consideration of the instability of the vapor-liquid interface and the fraction of heat required for liquid-vapor conversion as opposed to that for bulk liquid heating. Severe

Present-day heat flow model of Mars

PubMed Central

Parro, Laura M.; Jiménez-Díaz, Alberto; Mansilla, Federico; Ruiz, Javier

2017-01-01

Until the acquisition of in-situ measurements, the study of the present-day heat flow of Mars must rely on indirect methods, mainly based on the relation between the thermal state of the lithosphere and its mechanical strength, or on theoretical models of internal evolution. Here, we present a first-order global model for the present-day surface heat flow for Mars, based on the radiogenic heat production of the crust and mantle, on scaling of heat flow variations arising from crustal thickness and topography variations, and on the heat flow derived from the effective elastic thickness of the lithosphere beneath the North Polar Region. Our preferred model finds heat flows varying between 14 and 25 mW m−2, with an average value of 19 mW m−2. Similar results (although about ten percent higher) are obtained if we use heat flow based on the lithospheric strength of the South Polar Region. Moreover, expressing our results in terms of the Urey ratio (the ratio between total internal heat production and total heat loss through the surface), we estimate values close to 0.7–0.75, which indicates a moderate contribution of secular cooling to the heat flow of Mars (consistent with the low heat flow values deduced from lithosphere strength), unless heat-producing elements abundances for Mars are subchondritic. PMID:28367996

Controlling heat and particle currents in nanodevices by quantum observation

NASA Astrophysics Data System (ADS)

Biele, Robert; Rodríguez-Rosario, César A.; Frauenheim, Thomas; Rubio, Angel

2017-07-01

We demonstrate that in a standard thermo-electric nanodevice the current and heat flows are not only dictated by the temperature and potential gradient, but also by the external action of a local quantum observer that controls the coherence of the device. Depending on how and where the observation takes place, the direction of heat and particle currents can be independently controlled. In fact, we show that the current and heat flow in a quantum material can go against the natural temperature and voltage gradients. Dynamical quantum observation offers new possibilities for the control of quantum transport far beyond classical thermal reservoirs. Through the concept of local projections, we illustrate how we can create and directionality control the injection of currents (electronic and heat) in nanodevices. This scheme provides novel strategies to construct quantum devices with application in thermoelectrics, spintronic injection, phononics, and sensing among others. In particular, highly efficient and selective spin injection might be achieved by local spin projection techniques.

Oscillatory/Chaotic Thermocapillary Flow Induced by Radiant Heating

NASA Technical Reports Server (NTRS)

DeWitt, Kenneth J.

1998-01-01

There is a continuing need to understand the fluid physics occurring under low gravity conditions in processes such as crystal growth, materials processing, and the movement of bubbles or droplets. The fluid flow in such situations is often caused by a gradient in interfacial tension. If a temperature gradient is created due to a heat source, the resulting flow is called thermocapillary flow, a special case of Marangoni Convection. In this study, an experimental investigation was conducted using silicone oil in cylindrical containers with a laser heat source at the free surface. It was desired to determine the conditions under which steady, axisymmetrical thermocapillary flow becomes unstable and oscillatory three-dimensional flow states develop. The critical Marangoni number for each observed oscillatory state was measured as a function of the container aspect ratio and the dynamic Bond number, a measure of buoyant force versus ii thermocapillary force. Various oscillatory modes were observed during three- dimensional convection, and chaotic flow was reached in one test condition. The critical Marangoni numbers are compared with those measured in previous studies, and the power spectra and phase trajectories of the instantaneous surface temperature distributions are used to characterize the routes of transitions to the chaotic flow state. Results show that only superharmonic modes appear in the routes to chaos while infinite number of subharmonic modes occur in flow transitions for pure Rayleigh convection.

Heat flow and subsurface temperature as evidence for basin-scale ground-water flow, North Slope of Alaska

USGS Publications Warehouse

Deming, D.; Sass, J.H.; Lachenbruch, A.H.; De Rito, R. F.

1992-01-01

Several high-resolution temperature logs were made in each of 21 drillholes and a total of 601 thermal conductivity measurements were made on drill cuttings and cores. Near-surface heat flow (??20%) is inversely correlated with elevation and ranges from a low of 27 mW/m2 in the foothills of the Brooks Range in the south, to a high of 90 mW/m2 near the north coast. Subsurface temperatures and thermal gradients estimated from corrected BHTs are similarly much higher on the coastal plain than in the foothills province to the south. Significant east-west variation in heat flow and subsurface temperature is also observed; higher heat flow and temperature coincide with higher basement topography. The observed thermal pattern is consistent with forced convection by a topographically driven ground-water flow system. Average ground-water (Darcy) velocity in the postulated flow system is estimated to be of the order of 0.1 m/yr; the effective basin-scale permeability is estimated to be of the order of 10-14 m2. -from Authors

Determination of the Io heat flow. 1: Eclipse observations

NASA Technical Reports Server (NTRS)

Sinton, W. M.; Kaminski, C.

1983-01-01

The thermal emission from Io during eclipse by Jupiter yields data from which the total thermal flux from the volcanoes on the satellite surface can be estimated. Thermal infrared observations in spectral bands between 3.5 and 30 microns of five Io eclipse reappearances and one eclipse disappearance are reported and discussed. The thermal emission of the volcanoes which occurs almost all of the time was determined from the Io heat flux data. The thermal observations of Io are discussed with respect to previous thermophysical theories.

Lunar heat-flow experiment

NASA Technical Reports Server (NTRS)

Langseth, M. G.

1977-01-01

The principal components of the experiment were probes, each with twelve thermometers of exceptional accuracy and stability, that recorded temperature variations at the surface and in the regolith down to 2.5 m. The Apollo 15 experiment and the Apollo 17 probes recorded lunar surface and subsurface temperatures. These data provided a unique and valuable history of the interaction of solar energy with lunar surface and the effects of heat flowing from the deep interior out through the surface of the moon. The interpretation of these data resulted in a clearer definition of the thermal and mechanical properties of the upper two meters of lunar regolith, direct measurements of the gradient in mean temperature due to heat flow from the interior and a determination of the heat flow at the Apollo 15 and Apollo 17 sites.

Convective heat flow probe

DOEpatents

Dunn, J.C.; Hardee, H.C.; Striker, R.P.

1984-01-09

A convective heat flow probe device is provided which measures heat flow and fluid flow magnitude in the formation surrounding a borehole. The probe comprises an elongate housing adapted to be lowered down into the borehole; a plurality of heaters extending along the probe for heating the formation surrounding the borehole; a plurality of temperature sensors arranged around the periphery of the probe for measuring the temperature of the surrounding formation after heating thereof by the heater elements. The temperature sensors and heater elements are mounted in a plurality of separate heater pads which are supported by the housing and which are adapted to be radially expanded into firm engagement with the walls of the borehole. The heat supplied by the heater elements and the temperatures measured by the temperature sensors are monitored and used in providing the desired measurements. The outer peripheral surfaces of the heater pads are configured as segments of a cylinder and form a full cylinder when taken together. A plurality of temperature sensors are located on each pad so as to extend along the length and across the width thereof, with a heating element being located in each pad beneath the temperature sensors. An expansion mechanism driven by a clamping motor provides expansion and retraction of the heater pads and expandable packet-type seals are provided along the probe above and below the heater pads.

Convective heat flow probe

DOEpatents

Dunn, James C.; Hardee, Harry C.; Striker, Richard P.

1985-01-01

A convective heat flow probe device is provided which measures heat flow and fluid flow magnitude in the formation surrounding a borehole. The probe comprises an elongate housing adapted to be lowered down into the borehole; a plurality of heaters extending along the probe for heating the formation surrounding the borehole; a plurality of temperature sensors arranged around the periphery of the probe for measuring the temperature of the surrounding formation after heating thereof by the heater elements. The temperature sensors and heater elements are mounted in a plurality of separate heater pads which are supported by the housing and which are adapted to be radially expanded into firm engagement with the walls of the borehole. The heat supplied by the heater elements and the temperatures measured by the temperature sensors are monitored and used in providing the desired measurements. The outer peripheral surfaces of the heater pads are configured as segments of a cylinder and form a full cylinder when taken together. A plurality of temperature sensors are located on each pad so as to extend along the length and across the width thereof, with a heating element being located in each pad beneath the temperature sensors. An expansion mechanism driven by a clamping motor provides expansion and retraction of the heater pads and expandable packer-type seals are provided along the probe above and below the heater pads.

Topographically driven groundwater flow and the San Andreas heat flow paradox revisited

USGS Publications Warehouse

Saffer, D.M.; Bekins, B.A.; Hickman, S.

2003-01-01

Evidence for a weak San Andreas Fault includes (1) borehole heat flow measurements that show no evidence for a frictionally generated heat flow anomaly and (2) the inferred orientation of ??1 nearly perpendicular to the fault trace. Interpretations of the stress orientation data remain controversial, at least in close proximity to the fault, leading some researchers to hypothesize that the San Andreas Fault is, in fact, strong and that its thermal signature may be removed or redistributed by topographically driven groundwater flow in areas of rugged topography, such as typify the San Andreas Fault system. To evaluate this scenario, we use a steady state, two-dimensional model of coupled heat and fluid flow within cross sections oriented perpendicular to the fault and to the primary regional topography. Our results show that existing heat flow data near Parkfield, California, do not readily discriminate between the expected thermal signature of a strong fault and that of a weak fault. In contrast, for a wide range of groundwater flow scenarios in the Mojave Desert, models that include frictional heat generation along a strong fault are inconsistent with existing heat flow data, suggesting that the San Andreas Fault at this location is indeed weak. In both areas, comparison of modeling results and heat flow data suggest that advective redistribution of heat is minimal. The robust results for the Mojave region demonstrate that topographically driven groundwater flow, at least in two dimensions, is inadequate to obscure the frictionally generated heat flow anomaly from a strong fault. However, our results do not preclude the possibility of transient advective heat transport associated with earthquakes.

Radial flow heat exchanger

DOEpatents

Valenzuela, Javier

2001-01-01

A radial flow heat exchanger (20) having a plurality of first passages (24) for transporting a first fluid (25) and a plurality of second passages (26) for transporting a second fluid (27). The first and second passages are arranged in stacked, alternating relationship, are separated from one another by relatively thin plates (30) and (32), and surround a central axis (22). The thickness of the first and second passages are selected so that the first and second fluids, respectively, are transported with laminar flow through the passages. To enhance thermal energy transfer between first and second passages, the latter are arranged so each first passage is in thermal communication with an associated second passage along substantially its entire length, and vice versa with respect to the second passages. The heat exchangers may be stacked to achieve a modular heat exchange assembly (300). Certain heat exchangers in the assembly may be designed slightly differently than other heat exchangers to address changes in fluid properties during transport through the heat exchanger, so as to enhance overall thermal effectiveness of the assembly.

Heat flow from Io /JI/

NASA Technical Reports Server (NTRS)

Matson, D. L.; Ransford, G. A.; Johnson, T. V.

1981-01-01

The existing ground-based measurements of Io's thermal emission at infrared wavelengths of 8.4, 10.6, and 21 microns have been reexamined. Present in these data is the signature of hot spots, presumably similar to the hot spots seen by the IRIS experiment on Voyager. It is possible to extract from these data the total amount of power radiated. Since the hot spots are believed to be a result of deep-seated activity in Io and since the remainder of Io's surface is an extraordinarily poor thermal conductor, the power radiated by the hot spots is essentially the total heat flow. The analysis yields a heat flow of 2 + or - 1 W/sq m. This value is tremendously large in comparison to the average heat flow of the earth (0.06 W/sq m) and the moon (0.02 W/sq m), but is characteristic of active geothermal areas on the earth. A heat flow this large requires that the interior of Io be at least partially molten on a global scale.

First heat flow density determinations from Southeastern Zaïre (Central Africa)

NASA Astrophysics Data System (ADS)

Sebagenzi, M. N.; Vasseur, G.; Louis, P.

1993-05-01

First heat flow density determinations from southeastern Zaïre are presented. Sites are located in the late Proterozoic metasedimentary cover of the Pan-African belt (600 Ma.). For each individual boreholes, heat flow ranges between 48 and 72 mWm -2. The average value of 62 mW m -2 for the sites is similar to that of 66 mW m -2 observed in Zambia. Both values are higher than what is expected for Pan-African terranes. These heat flow determinations in Shaba province of southeastern Zaïre, together with gravity and seismological observations, support the hypothesis of lithospheric thinning for this area. As already suggested for Zambia, this lithospheric thinning may be associated with a southwestern extension of the East African Rift System from Tanganyika across the central African plateau.

Lunar ash flow with heat transfer.

NASA Technical Reports Server (NTRS)

Pai, S. I.; Hsieh, T.; O'Keefe, J. A.

1972-01-01

The most important heat-transfer process in the ash flow under consideration is heat convection. Besides the four important nondimensional parameters of isothermal ash flow (Pai et al., 1972), we have three additional important nondimensional parameters: the ratio of the specific heat of the gas, the ratio of the specific heat of the solid particles to that of gas, and the Prandtl number. We reexamine the one dimensional steady ash flow discussed by Pai et al. (1972) by including the effects of heat transfer. Numerical results for the pressure, temperature, density of the gas, velocities of gas and solid particles, and volume fraction of solid particles as function of altitude for various values of the Jeffreys number, initial velocity ratio, and two different gas species (steam and hydrogen) are presented.

Heat-flow equation motivated by the ideal-gas shock wave.

PubMed

Holian, Brad Lee; Mareschal, Michel

2010-08-01

We present an equation for the heat-flux vector that goes beyond Fourier's Law of heat conduction, in order to model shockwave propagation in gases. Our approach is motivated by the observation of a disequilibrium among the three components of temperature, namely, the difference between the temperature component in the direction of a planar shock wave, versus those in the transverse directions. This difference is most prominent near the shock front. We test our heat-flow equation for the case of strong shock waves in the ideal gas, which has been studied in the past and compared to Navier-Stokes solutions. The new heat-flow treatment improves the agreement with nonequilibrium molecular-dynamics simulations of hard spheres under strong shockwave conditions.

Heat flow from the Liberian Precambrian Shield

NASA Astrophysics Data System (ADS)

Sass, J. H.; Behrendt, J. C.

1980-06-01

Uncorrected heat flow in iron formation rocks from three areas within the Liberian part of the West African Shield ranges from 50 to more than 80 mW m-2. When corrections are applied for topography and refraction, the range of heat flow is narrowed to between 38 and 42 mW m-2. In comparison with heat flows from other parts of the West African Craton, these values are consistent with preliminary results from Ghana (42±8 mW m-2) and Nigeria (38±2 mW m-2) but are somewhat higher than values from Niger (20 mW m-2) and neighboring Sierra Leone (26 mW m-2). The Liberian values are significantly lower than the heat flow offshore in the equatorial Atlantic Ocean (58±8 m W m-2), suggesting large lateral temperature gradients within the lithosphere near the coast. Values of heat production from outcrops of crystalline basement rocks near the holes are between 2 and 2.3 /μW m-3. A heat-flow/heat-production relation cannot be established because of the small range of values; however, assuming a `characteristic depth' of 8 km (similar to the North American Craton) the reduced heat flow of from 20 to 25 mW m-2 is consistent with that from other Precambrian shields.

Gas Flow and Ion Transfer in Heated ESI Capillary Interfaces

NASA Astrophysics Data System (ADS)

Bernier, Laurent; Pinfold, Harry; Pauly, Matthias; Rauschenbach, Stephan; Reiss, Julius

2018-02-01

Transfer capillaries are the preferred means to transport ions, generated by electrospray ionization, from ambient conditions to vacuum. During the transfer of ions through the narrow, long tubes into vacuum, substantial losses are typical. However, recently it was demonstrated that these losses can be avoided altogether. To understand the experimental observation and provide a general model for the ion transport, here, we investigate the ion transport through capillaries by numerical simulation of interacting ions. The simulation encompasses all relevant factors, such as space charge, diffusion, gas flow, and heating. Special attention is paid to the influence of the gas flow on the transmission and especially the change imposed by heating. The gas flow is modeled by a one-dimensional gas dynamics description. A large number of ions are treated as point particles in this gas flow. This allows to investigate the influence of the capillary heating on the gas flow and by this on the ion transport. The results are compared with experimental findings. [Figure not available: see fulltext.

Joule heating effects on electroosmotic flow in insulator-based dielectrophoresis.

PubMed

Sridharan, Sriram; Zhu, Junjie; Hu, Guoqing; Xuan, Xiangchun

2011-09-01

Insulator-based dielectrophoresis (iDEP) is an emerging technology that has been successfully used to manipulate a variety of particles in microfluidic devices. However, due to the locally amplified electric field around the in-channel insulator, Joule heating often becomes an unavoidable issue that may disturb the electroosmotic flow and affect the particle motion. This work presents the first experimental study of Joule heating effects on electroosmotic flow in a typical iDEP device, e.g., a constriction microchannel, under DC-biased AC voltages. A numerical model is also developed to simulate the observed flow pattern by solving the coupled electric, energy, and fluid equations in a simplified two-dimensional geometry. It is observed that depending on the magnitude of the DC voltage, a pair of counter-rotating fluid circulations can occur at either the downstream end alone or each end of the channel constriction. Moreover, the pair at the downstream end appears larger in size than that at the upstream end due to DC electroosmotic flow. These fluid circulations, which are reasonably simulated by the numerical model, form as a result of the action of the electric field on Joule heating-induced fluid inhomogeneities in the constriction region. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Heat flow from the Liberian precambrian shield

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

Sass, J.H.; Behrendt, J.C.

1980-06-10

Uncorrected heat flow in iron formation rocks from three areas within the Liberian part of the West African Shield ranges from 50 to more than 80 mW m/sup -2/. When corrections are applied for topography and refraction, the range of heat flow is narrowed to between 38 and 42 mW m/sup -2/. In comparison with heat flows from other parts of the West African Craton, these values are consistent with preliminary results from Ghana (42 +- 8 mW m/sup -2/) and Nigeria (38 +- 2 mW /sup -2/) but are somewhat higher than values from Niger (20 mW m/sup -2/)more » and neighboring Sierra Leone (26 mW m/sup -2/). The Liberian values are significantly lower than the heat flow offshore in the equatorial Atlantic Ocean (58 +- 8 mW m/sup -2/), suggesting large lateral temperature gradients within the lithosphere near the coast. Values of heat production from outcrops of crystalline basement rocks near the holes are between 2 and 2.3 ..mu..W m/sup -3/. A heat-flow/heat-production relation cannot be established because of the small range of values; however, assuming a 'characteristic depth' of 8 km (similar to the North American Craton) the reduced heat flow of from 20 to 25 mW m/sup -2/ is consistent with that from other Precambrian shields.« less

Systematic Heat Flow Measurements Across the Wagner Basin, Northern Gulf of California

NASA Astrophysics Data System (ADS)

Neumann, F.; Negrete-Aranda, R.; Harris, R. N.; Contreras, J.; Sclater, J. G.; Gonzalez-Fernandez, A.

2017-12-01

A primary control on the geodynamics of rifting is the thermal regime. To better understand the geodynamics of rifting in the northern Gulf of California we systematically measured heat-flow across the Wagner Basin, a tectonically active basin that lies near the southern terminus of the Cerro Prieto fault. Seismic reflection profiles show sediment in excess of 5 s two-way travel time, implying a sediment thickness of > 7 km. The heat flow profile is 40 km long, has a nominal measurement spacing of 1 km, and is collocated with a seismic reflection profile. Heat flow measurements were made with a 6.5-m violin-bow probe. Most measurements are of good quality in that the probe fully penetrated sediments and measurements were stable enough to invert for heat flow and thermal properties. We have estimated corrections for environmental perturbations due to changes in bottom water temperature and sedimentation. The mean and standard deviation of heat flow across the western, central, and eastern parts of the basin are 220±60, 99±14, 1058±519 mW m-2, respectively. Corrections for sedimentation would increase measured heat flow across the central part of basin by 40 to 60%. We interpret the relatively high heat flow and large variability on the western and eastern flanks in terms of upward fluid flow at depth below the seafloor, whereas the lower and more consistent values across the central part of the basin are suggestive of conductive heat transfer. Based on an observed fault depth of 1.75 km we estimated the maximum Darcy velocities through the western and eastern flanks as 3 and 10 cm yr-1, respectively. Heat flow across the central basin is consistent with gabbroic underplating at a depth of 15 km and suggests that continental rupture here has not gone to completion.

Two-phase gas-liquid flow characteristics inside a plate heat exchanger

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

Nilpueng, Kitti; Wongwises, Somchai

In the present study, the air-water two-phase flow characteristics including flow pattern and pressure drop inside a plate heat exchanger are experimentally investigated. A plate heat exchanger with single pass under the condition of counter flow is operated for the experiment. Three stainless steel commercial plates with a corrugated sinusoidal shape of unsymmetrical chevron angles of 55 and 10 are utilized for the pressure drop measurement. A transparent plate having the same configuration as the stainless steel plates is cast and used as a cover plate in order to observe the flow pattern inside the plate heat exchanger. The air-watermore » mixture flow which is used as a cold stream is tested in vertical downward and upward flow. The results from the present experiment show that the annular-liquid bridge flow pattern appeared in both upward and downward flows. However, the bubbly flow pattern and the slug flow pattern are only found in upward flow and downward flow, respectively. The variation of the water and air velocity has a significant effect on the two-phase pressure drop. Based on the present data, a two-phase multiplier correlation is proposed for practical application. (author)« less

Numerical simulation of turbulent flow and heat transfer though sinusoidal ducts

NASA Astrophysics Data System (ADS)

Abroshan, Hamid

2018-02-01

Turbulent forced convection heat transfer in corrugated plate surfaces was studied by means of CFD. Flow through corrugated plates, which are sets of sinusoidal ducts, was analyzed for different inlet flow angles (0° to 50°), aspect ratios (0.1 to 10), Reynolds numbers (2000 to 40,000) and Prantdel numbers (0.7 to 5). Heat transfer is affected significantly by variation of aspect ratio. A maximum heat transfer coefficient is observed at a particular aspect ratio although the aspect ratio has a minor effect on friction factor. Enlarging inlet flow angle also leads to a higher heat transfer coefficient and pressure loss in aspect ratios close to unity. Dependency of Nusselt and friction factor on the angle and aspect ratio was interpreted by means of appearance of secondary motions and coexistence of laminar and turbulent flow in a cross section. Comparing the results with experimental data shows a maximum 12.8% difference. By evaluating the results, some correlations were proposed to calculate Nusselt number and friction factor for entrance and fully developed regions. A corrugated plate with an aspect ratio equal to 1.125 and an inlet flow angle equal to 50° gives the best heat transfer and pressure drop characteristics.

Exhaust bypass flow control for exhaust heat recovery

DOEpatents

Reynolds, Michael G.

2015-09-22

An exhaust system for an engine comprises an exhaust heat recovery apparatus configured to receive exhaust gas from the engine and comprises a first flow passage in fluid communication with the exhaust gas and a second flow passage in fluid communication with the exhaust gas. A heat exchanger/energy recovery unit is disposed in the second flow passage and has a working fluid circulating therethrough for exchange of heat from the exhaust gas to the working fluid. A control valve is disposed downstream of the first and the second flow passages in a low temperature region of the exhaust heat recovery apparatus to direct exhaust gas through the first flow passage or the second flow passage.

A New Determination of Io's Heat Flow Using Diurnal Heat Balance Constraints

NASA Technical Reports Server (NTRS)

Spencer, J. R.; Rathbun, J. A.; McEwen, A. S.; Pearl, J. C.; Bastos, A.; Andrade, J.; Correia, M.; Barros, S.

2002-01-01

We use heat balance arguments to obtain a new estimate of Io's heat flow that does not depend on assumptions about the temperatures of its thermal anomalies. Our estimated heat flow is somewhat less than 2.2 +/- 0.9 W/sq m. Additional information is contained in the original extended abstract.

Viscosity induced non-uniform flow in laminar flow heat exchangers

NASA Astrophysics Data System (ADS)

Putnam, G. R.; Rohsenow, W. M.

1985-05-01

Laminar flow heat exchangers which cool oil in noninterconnected parallel passages can experience nonuniform flows and a reduction in the effective heat exchanger coefficient in a range of Reynolds number which varies with tube length and diameter, tube wall temperature and fluid inlet temperature. The method of predicting the reduction in effective heat transfer coefficient and the range of Reynolds number over which these instabilities exist is presented for a particular oil, Mobil aviation oil 120. Included, also, is the prediction of the effect of radial viscosity variation on the constant property magnitudes of friction and heat transfer coefficient.

New Marine Heat Flow measurements at the Costa Rica Rift, Panama Basin

NASA Astrophysics Data System (ADS)

Harris, R. N.; Kolandaivelu, K. P.; Gregory, E. P. M.; Alshafai, R.; Lowell, R. P.; Hobbs, R. W.

2016-12-01

We report new heat flow measurements collected along the southern flank of the Costa Rica ridge. This ridge flank has been the site of numerous seismic, heat flow, and ocean drilling experiments and has become an important type location for investigations of off-axis hydrothermal processes. These data were collected as part of an interdisciplinary NERC and NSF-funded collaboration entitled: Oceanographic and Seismic Characterization of heat dissipation and alteration by hydrothermal fluids at an Axial Ridge (OSCAR), to better understand links between crustal evolution, hydrothermal heat loss and the impact of this heat loss and fluid mass discharge on deep ocean circulation. The heat flow measurements are collocated with a newly acquired high-resolution seismic profile collected using a GI-gun source to image the sedimentary and upper crustal section. The profile is tied to ODP Hole 504B and provides robust estimates of the sediment thickness as well as its internal structure. In total five heat flow stations consisting of 67 new heat flow measurements were made, spanning crustal ages between 1.3 and 5.4 Myr. The full spreading rate of 66 mm/yr gives rise to abyssal hill basement relief between 500 and 250 m. Sediment cover is relatively incomplete in this region and varies between 0 and 290 m. The majority of heat flow values fall below half-space cooling models indicating that significant amounts of heat are removed by hydrothermal circulation. Low heat flow values are observed in sediment ponds between abyssal hill relief and high values are generally associated with ridge-ward dipping faults bounding abyssal hills. These faults are likely high permeability pathways where heated fluids are discharging, providing an example where large-scale faulting and block rotation plays a major role in ventilated ridge flank fluid circulation. The heat flow fraction (qobs/qpred) varies between varies between 0.01 and 4.1 and has a mean of 0.3 indicating that on average 70

Heat flow in relation to hydrothermal activity in the southern Black Rock Desert, Nevada

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

Sass, J.H.; Zoback, M.L.; Galanis, S.P. Jr.

1979-01-01

As part of an investigation of the Gerlach NE KGRA (Known Geothermal Resource Area) a number of heat-flow measurements were made in playa sediments of the southern Black Rock Desert, northwestern Nevada. These data together with additional previously unpublished heat-flow values reveal a complex pattern of heat flow with values ranging between 1.0 to 5.0 HFU (40 to 100 mWm/sup -2/) outside of the hot springs area. The mean heat flow for the 13 reported sites in the southern Black Rock Desert is 1.8 +- 0.15 HFU (75 +- 6 mWm/sup -2/). The complexity of the pattern of heat flowmore » is believed to arise from hydrothermal circulation supporting the numerous hot springs throughout the region. The fact that the lowest observed heat flow occurs in the deepest part of the basin strongly suggests that fluid movement within the basin represents part of the recharge for the hydrothermal system. A thermal balance for the system incorporating both anomalous conductive heat loss and convective heat loss from the spring systems indicate a total energy loss of about 8.0 Mcal/sec or 34 megawatts over an estimated 1000 km/sup 2/ region. Consideration of this additional heat loss yields a mean regional heat flow of 2.5 + HFU (100 + mWm/sup -2/) and warrants inclusion of this region in the Battle Mountain heat-flow high (Lachenbruch and Sass, 1977, 1978).« less

Study of flow control by localized volume heating in hypersonic boundary layers

NASA Astrophysics Data System (ADS)

Keller, M. A.; Kloker, M. J.; Kirilovskiy, S. V.; Polivanov, P. A.; Sidorenko, A. A.; Maslov, A. A.

2014-12-01

Boundary-layer flow control is a prerequisite for a safe and efficient operation of future hypersonic transport systems. Here, the influence of an electric discharge—modeled by a heat-source term in the energy equation—on laminar boundary-layer flows over a flat plate with zero pressure gradient at Mach 3, 5, and 7 is investigated numerically. The aim was to appraise the potential of electro-gasdynamic devices for an application as turbulence generators in the super- and hypersonic flow regime. The results with localized heat-source elements in boundary layers are compared to cases with roughness elements serving as classical passive trips. The numerical simulations are performed using the commercial code ANSYS FLUENT (by ITAM) and the high-order finite-difference DNS code NS3D (by IAG), the latter allowing for the detailed analysis of laminar flow instability. For the investigated setups with steady heating, transition to turbulence is not observed, due to the Reynolds-number lowering effect of heating.

Thaw flow control for liquid heat transport systems

DOEpatents

Kirpich, Aaron S.

1989-01-01

In a liquid metal heat transport system including a source of thaw heat for use in a space reactor power system, the thaw flow throttle or control comprises a fluid passage having forward and reverse flow sections and a partition having a plurality of bleed holes therein to enable fluid flow between the forward and reverse sections. The flow throttle is positioned in the system relatively far from the source of thaw heat.

Natural convection flows and associated heat transfer processes in room fires

NASA Astrophysics Data System (ADS)

Sargent, William Stapf

This report presents the results of experimental investigations of natural convection flows and associated heat transfer processes produced by small fires in rooms with a single door or window opening. Calculation procedures have been developed to model the major aspects of these flows.Two distinct sets of experiments were undertaken.First, in a roughly 1/4 scale facility, a slightly dense solution of brine was allowed to flow into a tank of fresh water. The resulting density difference produced a flow which simulated a very small fire in a room with adiabatic walls. Second, in an approximately 1/2 scale test room, a nearly stoichioinetric mixture of air and natural gas was burned at floor level to model moderate strength fires. In this latter facility, we directly measured the heat conducted through the walls, in addition to determining the gas temperature and composition throughout the room.These two facilities complemented each other. The former offered good flow visualization and allowed us to observe the basic flow phenomena in the absence of heat transfer effects. On the other hand, the latter, which involved relatively larger fires, was a more realistic simulation of an actual room fire, and allowed us to calculate the convective heat transfer to the ceiling and walls. In addition, the stronger sources present in these 1/2 scale tests produced significant secondary flows. These secondary flows along with heat transfer effects act to modify the gas temperature or density profiles within the room from those observed in the 1/4 scale experiments.Several calculation procedures have been developed, based on the far field properties of plumes when the density differences are small (the Boussinesq approximation). The simple point source plume solution is used along with hydraulic analysis of flow through an orifice to estimate the temperatures of the hot ceiling layer gas and of the cooler floor zone fluid, as well as the height of the interface between them. A

The stress heat-flow paradox and thermal results from Cajon Pass

USGS Publications Warehouse

Lachenbruch, A.H.; Sass, J.H.

1988-01-01

Conventional friction models predict a substantial thermal anomaly associated with active traces of strike-slip faults, but no such anomaly is observed from over 100 heat-flow determinations along 1000 km of the San Andreas fault. The Cajon Pass well is being drilled to bring deep heat-flow and stress data to bear on this paradox. Preliminary stress results from Cajon Pass and a new interpretation of regional data by Mark D. Zoback and colleagues suggests that the maximum compressive stress near the fault is almost normal to the trace, and hence the resolved shear stress is low and the fault, weak. The heat-flow data show large variability with depth, probably from three-dimensional structure, and an overall decrease from over 90 mW/m2 in the upper kilometer to less than 80 mW/m2 in the lower 300 m with no evidence of advective heat transfer. -from Authors

Internal (Annular) and Compressible External (Flat Plate) Turbulent Flow Heat Transfer Correlations.

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

Dechant, Lawrence; Smith, Justin

Here we provide a discussion regarding the applicability of a family of traditional heat transfer correlation based models for several (unit level) heat transfer problems associated with flight heat transfer estimates and internal flow heat transfer associated with an experimental simulation design (Dobranich 2014). Variability between semi-empirical free-flight models suggests relative differences for heat transfer coefficients on the order of 10%, while the internal annular flow behavior is larger with differences on the order of 20%. We emphasize that these expressions are strictly valid only for the geometries they have been derived for e.g. the fully developed annular flow ormore » simple external flow problems. Though, the application of flat plate skin friction estimate to cylindrical bodies is a traditional procedure to estimate skin friction and heat transfer, an over-prediction bias is often observed using these approximations for missile type bodies. As a correction for this over-estimate trend, we discuss a simple scaling reduction factor for flat plate turbulent skin friction and heat transfer solutions (correlations) applied to blunt bodies of revolution at zero angle of attack. The method estimates the ratio between axisymmetric and 2-d stagnation point heat transfer skin friction and Stanton number solution expressions for sub-turbulent Reynolds numbers %3C1x10 4 . This factor is assumed to also directly influence the flat plate results applied to the cylindrical portion of the flow and the flat plate correlations are modified by« less

The Role of Nonlocal Heat Flow in Hohlraums

NASA Astrophysics Data System (ADS)

Town, R. P. J.; Short, R. W.; Verdon, C. P.; Afeyan, B. B.; Glenzer, S. H.; Suter, L. J.

1997-11-01

Glenzer,(Submitted to Physical Review Letters.)* using the Thomson scattering technique, has measured the time evolution of the electron temperature in scale-1 hohlraums. The measured peak electron temperature was 5 keV. Lasnex simulations, using a flux-limited Spitzer heat diffusion model with the standard sharp-cutoff flux limiter of 0.05, gave a peak electron temperature of only 3 keV. Good agreement between simulation and experiment was found when Lasnex simulations employed a time-varying flux limiter, which had a value of 0.01 when the main drive came on. The need to severly inhibit heat transport over the entire volume of hot plasma at late time suggests that nonlocal heat flow could be important in explaining these experimental observations. In this presentation we will report on Fokker--Planck calculations of idealized hohlraums and compare them to standard hydrodynamic calculations using flux-limited Spitzer heat flow. This work was supported by the U.S. Department of Energy Office of Inertial Confinement Fusion under Cooperative Agreement No. DE-FC03-92SF19460. Also, work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract W-7405-ENG-48.

Heat transfer in melt ponds with convection and radiative heating: observationally-inspired modelling

NASA Astrophysics Data System (ADS)

Wells, A.; Langton, T.; Rees Jones, D. W.; Moon, W.; Kim, J. H.; Wilkinson, J.

2016-12-01

Melt ponds have key impacts on the evolution of Arctic sea ice and summer ice melt. Small changes to the energy budget can have significant consequences, with a net heat-flux perturbation of only a few Watts per square metre sufficient to explain the thinning of sea ice over recent decades. Whilst parameterisations of melt-pond thermodynamics often assume that pond temperatures remain close to the freezing point, recent in-situ observations show more complex thermal structure with significant diurnal and synoptic variability. We here consider the energy budget of melt ponds and explore the role of internal convective heat transfer in determining the thermal structure within the pond in relatively calm conditions with low winds. We quantify the energy fluxes and temperature variability using two-dimensional direct numerical simulations of convective turbulence within a melt pond, driven by internal radiative heating and surface fluxes. Our results show that the convective flow dynamics are modulated by changes to the incoming radiative flux and sensible heat flux at the pond surface. The evolving pond surface temperature controls the outgoing longwave emissions from the pond. Hence the convective flow modifies the net energy balance of a melt pond, modulating the relative fractions of the incoming heat flux that is re-emitted to the atmosphere or transferred downward into the sea ice to drive melt.

Thermocapillary flow contribution to dropwise condensation heat transfer

NASA Astrophysics Data System (ADS)

Phadnis, Akshay; Rykaczewski, Konrad

2017-11-01

With recent developments of durable hydrophobic materials potentially enabling industrial applications of dropwise condensation, accurate modeling of heat transfer during this phase change process is becoming increasingly important. Classical steady state models of dropwise condensation are based on the integration of heat transfer through individual droplets over the entire drop size distribution. These models consider only the conduction heat transfer inside the droplets. However, simple scaling arguments suggest that thermocapillary flows might exist in such droplets. In this work, we used Finite Element heat transfer model to quantify the effect of Marangoni flow on dropwise condensation heat transfer of liquids with a wide range of surface tensions ranging from water to pentane. We confirmed that the Marangoni flow is present for a wide range of droplet sizes, but only has quantifiable effects on heat transfer in drops larger than 10 µm. By integrating the single drop heat transfer simulation results with drop size distribution for the cases considered, we demonstrated that Marangoni flow contributes a 10-30% increase in the overall heat transfer coefficient over conduction only model.

Restoration of the Apollo Heat Flow Experiments Metadata

NASA Technical Reports Server (NTRS)

Nagihara, S.; Stephens, M. K.; Taylor, P. T.; Williams, D. R.; Hills, H. K.; Nakamura, Y.

2015-01-01

Geothermal heat flow probes were deployed on the Apollo 15 and 17 missions as part of the Apollo Lunar Surface Experiments Package (ALSEP). At each landing site, the astronauts drilled 2 holes, 10-m apart, and installed a probe in each. The holes were 1- and 1.5-m deep at the Apollo 15 site and 2.5-m deep at the Apollo 17 sites. The probes monitored surface temperature and subsurface temperatures at different depths. At the Apollo 15 site, the monitoring continued from July 1971 to January 1977. At the Apollo 17 site, it did from December 1972 to September 1977. Based on the observations made through December 1974, Marcus Langseth, the principal investigator of the heat flow experiments (HFE), determined the thermal conductivity of the lunar regolith by mathematically modeling how the seasonal temperature fluctuation propagated down through the regolith. He also determined the temperature unaffected by diurnal and seasonal thermal waves of the regolith at different depths, which yielded the geothermal gradient. By multiplying the thermal gradient and the thermal conductivity, Langseth obtained the endogenic heat flow of the Moon as 21 mW/m(exp 2) at Site 15 and 16 mW/m(exp 2) at Site 17.

Combining IRIS/Hinode Observations and Modeling: a Pathfinder for Coronal Heating

NASA Astrophysics Data System (ADS)

Antolin, P.; Okamoto, J.; De Pontieu, B.

2015-12-01

The combination of imaging and spectroscopic instruments with multiple temperature diagnostics at high spatial, temporal and spectral resolution can allow to recover the 3D plasma flow and thermodynamic evolution associated with specific coronal heating mechanisms. Although very hard considering the complexity of the solar atmosphere, this approach is becoming possible now through combination of instruments such as IRIS and Hinode, and with proper guiding from advanced numerical simulations and forward modeling. In this talk I will review recent examples of this approach, focusing on a particular, recently published, case study, that serves as a pathfinder in the search for the dominant coronal heating mechanism. In this case, resonant absorption, a long hypothesised wave-related energy conversion mechanism is spotted in action for the first time, and is characterised by a peculiar 3D motion of the plasma. With the help of 3D MHD numerical simulations and forward modeling the observational signatures of resonant absorption are characterised, matching very well the observational results. The process through which this mechanism can lead to observed significant heating in the solar corona is further identified: the resonant flow becomes turbulent following dynamic instabilities and heats the plasma. I will show how this resonance + instability process is expected in different scenarios of the solar atmosphere (the corona, prominences and spicules) and can potentially explain several observed features that remain so far unexplained.

Heat Flow and Gas Hydrates on the Continental Margin of India: Building on Results from NGHP Expedition 01

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

Trehu, Anne; Kannberg, Peter

2011-06-30

The Indian National Gas Hydrate Program (NGHP) Expedition 01 presented the unique opportunity to constrain regional heat flow derived from seismic observations by using drilling data in three regions on the continental margin of India. The seismic bottom simulating reflection (BSR) is a well-documented feature in hydrate bearing sediments, and can serve as a proxy for apparent heat flow if data are available to estimate acoustic velocity and density in water and sediments, thermal conductivity, and seafloor temperature. Direct observations of temperature at depth and physical properties of the sediment obtained from drilling can be used to calibrate the seismicmore » observations, decreasing the uncertainty of the seismically-derived estimates. Anomalies in apparent heat flow can result from a variety of sources, including sedimentation, erosion, topographic refraction and fluid flow. We constructed apparent heat flow maps for portions of the Krishna-Godavari (K-G) basin, the Mahanadi basin, and the Andaman basin and modeled anomalies using 1-D conductive thermal models. Apparent heat flow values in the Krishna-Godavari (K-G) basin and Mahanadi basin are generally 0.035 to 0.055 watts per square meter (W/m2). The borehole data show an increase in apparent heat flow as water depth increases from 900 to 1500 m. In the SW part of the seismic grid, 1D modeling of the effect of sedimentation on heat flow shows that ~50% of the observed increase in apparent heat flow with increasing water depth can be attributed to trapping of sediments behind a "toe-thrust" ridge that is forming along the seaward edge of a thick, rapidly accumulating deltaic sediment pile. The remainder of the anomaly can be explained either by a decrease in thermal conductivity of the sediments filling the slope basin or by lateral advection of heat through fluid flow along stratigraphic horizons within the basin and through flexural faults in the crest of the anticline. Such flow probably plays a

Heat Flow and Gas Hydrates on the Continental Margin of India: Building on Results from NGHP Expedition 01

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

Anne Trehu; Peter Kannberg

2011-06-30

The Indian National Gas Hydrate Program (NGHP) Expedition 01 presented the unique opportunity to constrain regional heat flow derived from seismic observations by using drilling data in three regions on the continental margin of India. The seismic bottom simulating reflection (BSR) is a well-documented feature in hydrate bearing sediments, and can serve as a proxy for apparent heat flow if data are available to estimate acoustic velocity and density in water and sediments, thermal conductivity, and seafloor temperature. Direct observations of temperature at depth and physical properties of the sediment obtained from drilling can be used to calibrate the seismicmore » observations, decreasing the uncertainty of the seismically-derived estimates. Anomalies in apparent heat flow can result from a variety of sources, including sedimentation, erosion, topographic refraction and fluid flow. We constructed apparent heat flow maps for portions of the Krishna-Godavari (K-G) basin, the Mahanadi basin, and the Andaman basin and modeled anomalies using 1-D conductive thermal models. Apparent heat flow values in the Krishna-Godavari (K-G) basin and Mahanadi basin are generally 0.035 to 0.055 watts per square meter (W/m{sup 2}). The borehole data show an increase in apparent heat flow as water depth increases from 900 to 1500 m. In the SW part of the seismic grid, 1D modeling of the effect of sedimentation on heat flow shows that {approx}50% of the observed increase in apparent heat flow with increasing water depth can be attributed to trapping of sediments behind a 'toe-thrust' ridge that is forming along the seaward edge of a thick, rapidly accumulating deltaic sediment pile. The remainder of the anomaly can be explained either by a decrease in thermal conductivity of the sediments filling the slope basin or by lateral advection of heat through fluid flow along stratigraphic horizons within the basin and through flexural faults in the crest of the anticline. Such flow

Visualization and flow boiling heat transfer of hydrocarbons in a horizontal tube

NASA Astrophysics Data System (ADS)

Yang, Zhuqiang; Bi, Qincheng; Guo, Yong; Liu, Zhaohui; Yan, Jianguo

2013-07-01

Visualizations of a specific hydrocarbon fuel in a horizontal tube with 2.0 mm inside diameter were investigated. The experiments were conducted at mass velocity of 213.4, 426.5 and 640.2 kg/ (m2ṡs), diabatic lengths of 140, 240 and 420 mm under the pressure from 2.0-2.7 MPa. In the sub-pressure conditions, bubbly, intermittent, stratified-wave, churn and annular flow patterns were observed. The frictional pressure drops were also measured to distinguish the patterns. The development of flow patterns and frictional pressure drop were positively related to the mass velocity and the heat flux. However, the diabatic length of the tube takes an important part in the process. The residence time of the fluid does not only affect the transition of the patterns but influence the composition of the fuel manifested by the fuel color and carbon deposit. The special observational phenomenon was obtained for the supercritical pressure fluid. The flow in the tube became fuzzier and pressure drop changed sharply near the pseudocritical point. The flow boiling heat transfer characteristics of the hydrocarbons were also discussed respectively. The curve of critical heat flux about onset of nucleate boiling was plotted with different mass velocities and diabatic tube lengths. And heat transfer characteristics of supercritical fuel were proved to be better than that in subcritical conditions.

Impact of wall hydrophobicity on condensation flow and heat transfer in silicon microchannels

NASA Astrophysics Data System (ADS)

Fang, Chen; Steinbrenner, Julie E.; Wang, Fu-Min; Goodson, Kenneth E.

2010-04-01

While microchannel condensation has been the subject of several recent studies, the critical impact of wall hydrophobicity on the microchannel condensation flow has received very little attention. The paper experimentally studies steam condensation in a silicon microchannel 286 µm in hydraulic diameter with three different wall hydrophobicities. It is found that the channel surface wettability has a significant impact on the flow pattern, pressure drop and heat transfer characteristic. Spatial flow pattern transition is observed in both hydrophobic and hydrophilic channels. In the hydrophobic channel, the transition from dropwise/slugwise flow to plug flow is induced by the slug instability. In the hydrophilic channel, the flow transition is characterized by the periodic bubble detachment, a process in which pressure evolution is found important. Local temperature measurement is conducted and heat flux distribution in the microchannel is reconstructed. For the same inlet vapor flux and temperature, the hydrophobic microchannel yields higher heat transfer rate and pressure drop compared to the hydrophilic channel. The difference is attributed to the distinction in flow pattern and heat transfer mechanism dictated by the channel hydrophobicity. This study highlights the importance of the channel hydrophobicity control for the optimization of the microchannel condenser.

Three-phase flow? Consider helical-coil heat exchangers

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

Haraburda, S.S.

1995-07-01

In recent years, chemical process plants are increasingly encountering processes that require heat exchange in three-phase fluids. A typical application, for example, is heating liquids containing solid catalyst particles and non-condensable gases. Heat exchangers designed for three-phase flow generally have tubes with large diameters (typically greater than two inches), because solids can build-up inside the tube and lead to plugging. At the same time, in order to keep heat-transfer coefficients high, the velocity of the process fluid within the tube should also be high. As a result, heat exchangers for three-phase flow may require less than five tubes -- eachmore » having a required linear length that could exceed several hundred feet. Given these limitations, it is obvious that a basic shell-and-tube heat exchanger is not the most practical solution for this purpose. An alternative for three-phase flow is a helical-coil heat exchanger. The helical-coil units offer a number of advantages, including perpendicular, counter-current flow and flexible overall dimensions for the exchanger itself. The paper presents equations for: calculating the tube-side heat-transfer coefficient; calculating the shell-side heat-transfer coefficient; calculating the heat-exchanger size; calculating the tube-side pressure drop; and calculating shell-side pressure-drop.« less

Heat Flow and Hydrothermal Circulation of the Lucky Strike Segment, Mid Atlantic Ridge

NASA Astrophysics Data System (ADS)

Bonneville, A.; Escartin, J.; Lucazeau, F.; Cannat, M.; Gouze, P.; von Herzen, R. P.; Adam, C.; Le Bars, M.; Monoury, E.; Vidal, V.

2003-12-01

In June 2003, expedition Luckyflux aboard the R/V Poseidon conducted a heat flow survey of a zone centred on the Lucky Strike segment of the Mid Atlantic ridge south of the Azores between ˜35° N and 39° N. Using a 5 m-long lance with 7 outrigger thermal probes, about 150 successful thermal gradient measurements were obtained, 140 of these with in-situ thermal conductivity. Measurements were made at ˜1 mile intervals along several profiles, where adequately sedimented sites were identified using 6-channel and 3.5 kHz seismic data from the previous Sudazores'98 cruise. We conducted heat flow measurements in two areas: a near axis region within the V-shaped ridge of overthickened crust that emanated from the Azores hotspot between ˜14 and 4 Ma, and an off-axis region East of the V-shaped ridge. The off-axis region is characterized by an homogeneous sediment cover, 300-400 m thick, and crustal ages varying between ˜6 and >10 Ma. Long wavelength (tens of km) low heat flow anomalies can be identified but the mean of 160 mWm-2 is comparable to the conductive heat flow expected for a crust of that age. Along two 80-km profiles perpendicular to the ridge, we observed coherent but different patterns. On the first profile, low heat flow values of 20-50 mWm-2 are observed at the base of the V-shaped ridge. These values are 100 mWm-2 below the profile average, showing that hydrothermal circulations can also affect oceanic crust beneath a thick and relatively impermeable sediment cover. On the other profile, heat flow generally decreases from west to east. On both profiles, higher than average values of heat flow are also present, associated on one of them with a nearly outcropping basement elevation. These contrasting overall heat flow patterns in similar geological context indicate that the likely pattern of hydrothermal circulations is mainly 3D, and not driven only by the presence of basement outcrops. In the near-axis region, where the tectonic structure is more

Understanding heat and fluid flow in linear GTA welds

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

Zacharia, T.; David, S.A.; Vitek, J.M.

1992-01-01

A transient heat flow and fluid flow model was used to predict the development of gas tungsten arc (GTA) weld pools in 1.5 mm thick AISI 304 SS. The welding parameters were chosen so as to correspond to an earlier experimental study which produced high-resolution surface temperature maps. The motivation of the present study was to verify the predictive capability of the computational model. Comparison of the numerical predictions and experimental observations indicate good agreement.

Understanding heat and fluid flow in linear GTA welds

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

Zacharia, T.; David, S.A.; Vitek, J.M.

1992-12-31

A transient heat flow and fluid flow model was used to predict the development of gas tungsten arc (GTA) weld pools in 1.5 mm thick AISI 304 SS. The welding parameters were chosen so as to correspond to an earlier experimental study which produced high-resolution surface temperature maps. The motivation of the present study was to verify the predictive capability of the computational model. Comparison of the numerical predictions and experimental observations indicate good agreement.

A review of the heat flow data of NE Morocco

NASA Astrophysics Data System (ADS)

Chiozzi, Paolo; Barkaoui, Alae-Eddine; Rimi, Abdelkrim; Verdoya, Massimo; Zarhloule, Yassine

2016-04-01

The Atlas chain is characterised by a SW-NE trending volcanic belt roughly extending from the Atlantic to the Mediterranean Sea and showing activity that spans in age mainly from Middle Miocene to Quaternary (14.6-0.3 Ma). The geochemical features of volcanism are mostly intraplate and alkaline with the exception of the northeastern termination of the belt where calc-alkaline series crop out. Lithospheric thermal and density models so far proposed, constrained by heat flow, gravity anomalies, geoid, and topography data, show that the Atlas chain is not supported isostatically by a thickened crust and a thin, hot and low-density lithosphere explains the high topography. One of the possible explanations for lithospheric mantle thinning, possibly in relation with the observed alkaline volcanism, is thermal erosion produced by either small-scale convection or activation of a small mantle plume, forming part of a hot and deep mantle reservoir system extending from the Canary Islands. This paper focuses on the several geothermal data available in the northeastern sector of the volcanic belt. The occurrence of an extensive, often artesian, carbonatic reservoir hosting moderately hot groundwater might boost the temperature gradient in the overlying impermeable cover, and consequently mask the deep thermal regime. We therefore revised the available dataset and investigated the contribution of advection. Temperature data available from water and oil wells were reprocessed and analysed in combination with thermal conductivity measurements on a wide set of lithotypes. Data were filtered according to rigid selection criteria, and, in the deeper boreholes, the heat flow was inferred by taking into account the porosity variation with depth and the temperature effect on the matrix and pore-filling fluid conductivity. Moreover, the possible effect of advection was evaluated with simple analytical models which envisage the carbonatic layers as confined aquifers heated by the

Flow and heat transfer enhancement in tube heat exchangers

NASA Astrophysics Data System (ADS)

Sayed Ahmed, Sayed Ahmed E.; Mesalhy, Osama M.; Abdelatief, Mohamed A.

2015-11-01

The performance of heat exchangers can be improved to perform a certain heat-transfer duty by heat transfer enhancement techniques. Enhancement techniques can be divided into two categories: passive and active. Active methods require external power, such as electric or acoustic field, mechanical devices, or surface vibration, whereas passive methods do not require external power but make use of a special surface geometry or fluid additive which cause heat transfer enhancement. The majority of commercially interesting enhancement techniques are passive ones. This paper presents a review of published works on the characteristics of heat transfer and flow in finned tube heat exchangers of the existing patterns. The review considers plain, louvered, slit, wavy, annular, longitudinal, and serrated fins. This review can be indicated by the status of the research in this area which is important. The comparison of finned tubes heat exchangers shows that those with slit, plain, and wavy finned tubes have the highest values of area goodness factor while the heat exchanger with annular fin shows the lowest. A better heat transfer coefficient ha is found for a heat exchanger with louvered finned and thus should be regarded as the most efficient one, at fixed pumping power per heat transfer area. This study points out that although numerous studies have been conducted on the characteristics of flow and heat transfer in round, elliptical, and flat tubes, studies on some types of streamlined-tubes shapes are limited, especially on wing-shaped tubes (Sayed Ahmed et al. in Heat Mass Transf 50: 1091-1102, 2014; in Heat Mass Transf 51: 1001-1016, 2015). It is recommended that further detailed studies via numerical simulations and/or experimental investigations should be carried out, in the future, to put further insight to these fin designs.

Simulation of Stagnation Region Heating in Hypersonic Flow on Tetrahedral Grids

NASA Technical Reports Server (NTRS)

Gnoffo, Peter A.

2007-01-01

Hypersonic flow simulations using the node based, unstructured grid code FUN3D are presented. Applications include simple (cylinder) and complex (towed ballute) configurations. Emphasis throughout is on computation of stagnation region heating in hypersonic flow on tetrahedral grids. Hypersonic flow over a cylinder provides a simple test problem for exposing any flaws in a simulation algorithm with regard to its ability to compute accurate heating on such grids. Such flaws predominantly derive from the quality of the captured shock. The importance of pure tetrahedral formulations are discussed. Algorithm adjustments for the baseline Roe / Symmetric, Total-Variation-Diminishing (STVD) formulation to deal with simulation accuracy are presented. Formulations of surface normal gradients to compute heating and diffusion to the surface as needed for a radiative equilibrium wall boundary condition and finite catalytic wall boundary in the node-based unstructured environment are developed. A satisfactory resolution of the heating problem on tetrahedral grids is not realized here; however, a definition of a test problem, and discussion of observed algorithm behaviors to date are presented in order to promote further research on this important problem.

Slip-Flow and Heat Transfer of a Non-Newtonian Nanofluid in a Microtube

PubMed Central

Niu, Jun; Fu, Ceji; Tan, Wenchang

2012-01-01

The slip-flow and heat transfer of a non-Newtonian nanofluid in a microtube is theoretically studied. The power-law rheology is adopted to describe the non-Newtonian characteristics of the flow, in which the fluid consistency coefficient and the flow behavior index depend on the nanoparticle volume fraction. The velocity profile, volumetric flow rate and local Nusselt number are calculated for different values of nanoparticle volume fraction and slip length. The results show that the influence of nanoparticle volume fraction on the flow of the nanofluid depends on the pressure gradient, which is quite different from that of the Newtonian nanofluid. Increase of the nanoparticle volume fraction has the effect to impede the flow at a small pressure gradient, but it changes to facilitate the flow when the pressure gradient is large enough. This remarkable phenomenon is observed when the tube radius shrinks to micrometer scale. On the other hand, we find that increase of the slip length always results in larger flow rate of the nanofluid. Furthermore, the heat transfer rate of the nanofluid in the microtube can be enhanced due to the non-Newtonian rheology and slip boundary effects. The thermally fully developed heat transfer rate under constant wall temperature and constant heat flux boundary conditions is also compared. PMID:22615961

Numerical analysis of the heat transfer and fluid flow in the butt-fusion welding process

NASA Astrophysics Data System (ADS)

Yoo, Jae Hyun; Choi, Sunwoong; Nam, Jaewook; Ahn, Kyung Hyun; Oh, Ju Seok

2017-02-01

Butt-fusion welding is an effective process for welding polymeric pipes. The process can be simplified into two stages. In heat soak stage, the pipe is heated using a hot plate contacted with one end of the pipe. In jointing stage, a pair of heated pipes is compressed against one another so that the melt regions become welded. In previous works, the jointing stage that is highly related to the welding quality was neglected. However, in this study, a finite element simulation is conducted including the jointing stage. The heat and momentum transfer are considered altogether. A new numerical scheme to describe the melt flow and pipe deformation for the butt-fusion welding process is introduced. High density polyethylene (HDPE) is used for the material. Flow via thermal expansion of the heat soak stage, and squeezing and fountain flow of the jointing stage are well reproduced. It is also observed that curling beads are formed and encounter the pipe body. The unique contribution of this study is its capability of directly observing the flow behaviors that occur during the jointing stage and relating them to welding quality.

Heat flow from eastern Panama and northwestern Colombia

USGS Publications Warehouse

Sass, J.H.; Munroe, R.J.; Moses, T.H.

1974-01-01

Heat flows were determined at 12 sites in four distinct areas between longitude 77?? and 80??W in eastern Panama and northwestern Colombia. Evidently, most of the region is underlain by mafic oceanic crust so that the crustal radiogenic component of heat flow is very small (??? 0.1 ??cal cm-2 sec-1). Low heat-flow values (??? 0.7 ??cal cm-2 sec-1) in northwestern Colombia may reflect thermal transients associated with shallow subduction. The normal values (??? 1) at about 78??W are consistent with the mean heat flow from the western Caribbean and the Gulf of Mexico. At 80??W, a fairly high value of 1.8 may define the easterly limit of thermal transients due to Cenozoic volcanic activity in Central America. ?? 1974.

Birch's Crustal Heat Production-Heat Flow Law: Key to Quantifying Mantle Heat Flow as a function of time

NASA Astrophysics Data System (ADS)

Blackwell, D. D.; Thakur, M.

2007-12-01

Birch (1968) first showed the linear correlation of surface heat flow and radioactive heat production (Qs = Qo + bAs ) in granites in New England, USA and discussed implications to the vertical scale of radioactive heat generation in the crust. Subsequently similar relationships have been found worldwide and numerous papers written describing more details and expanding the implications of Birch's Law. The results are a powerful contribution from heat flow research to the understanding of the lithosphere and its evolution. Models are both well constrained experimentally and simple in implications. However, there still exist thermal models of the crust and lithosphere that do not have the same firm foundation and involve unnecessary ad hoc assumptions. A main point of confusion has been that the several of the original relationships were so low in error as to be considered by some to be "fortuitous". Interestingly a "similar" relationship has been proposed based on regional scale averaging of Qs -As data. A second point of confusion is that one admissible crustal radioactivity distribution model (the constant heat generation to depth b) has been criticized as unrealistic for a number of reasons, including the effect of erosion. However, it is appropriate to refer to the Qs -As relationship as a law because in fact the relationship holds as long as the vertical distribution is "geologically realistic." as will be demonstrated in this paper. All geologic and geophysical models of the continental crust imply decreasing heat production as a function of depth (i.e. the seismic layering for example) except in very special cases. This general decrease with depth is the only condition required for the existence of a "linear" Qs -As relationship. A comparison of all the Qs -As relationships proposed for terrains not affected by thermal events over the last 150 to 200 Ma shows a remarkably uniformity in slope (10 ± 3 km) and intercept value (30 ± 5 mWm-2 ). Therefore these

Heat Flow, Regional Geophysics and Lithosphere Structure In The Czech Republic

NASA Astrophysics Data System (ADS)

Safanda, J.; Cermak, V.; Kresl, M.; Dedecek, P.

Paper summarises and critically revises heat flow data that have been collected in the Czech Republic to date. The regional heat flow density map was prepared in view of all existing heat flow data completed with the similar in the surrounding countries and taking into consideration also temperature measurements in deep boreholes. Crustal temperature profiles were calculated by using the available geological information, results of deep seismic sounding and the laboratory data on radiogenic heat produc- tion and thermal conductivity. Special attention was paid to numerous temperature logs in two sedimentary basins, namely in the Cheb and Ostrava-Karvina coal basins, for which detailed heat flow patterns were proposed. Relationships between heat flow distribution and the crustal/lithosphere evolution, between heat flow and the heat pro- duction of the crustal rocks, heat flow and crustal thickness and the steady-state vs. transient heat transport are discussed.

Investigation on heat transfer characteristics and flow performance of Methane at supercritical pressures

NASA Astrophysics Data System (ADS)

Xian, Hong Wei; Oumer, A. N.; Basrawi, F.; Mamat, Rizalman; Abdullah, A. A.

2018-04-01

The aim of this study is to investigate the heat transfer and flow characteristic of cryogenic methane in regenerative cooling system at supercritical pressures. The thermo-physical properties of supercritical methane were obtained from the National institute of Standards and Technology (NIST) webbook. The numerical model was developed based on the assumptions of steady, turbulent and Newtonian flow. For mesh independence test and model validation, the simulation results were compared with published experimental results. The effect of four different performance parameter ranges namely inlet pressure (5 to 8 MPa), inlet temperature (120 to 150 K), heat flux (2 to 5 MW/m2) and mass flux (7000 to 15000 kg/m2s) on heat transfer and flow performances were investigated. It was found that the simulation results showed good agreement with experimental data with maximum deviation of 10 % which indicates the validity of the developed model. At low inlet temperature, the change of specific heat capacity at near-wall region along the tube length was not significant while the pressure drop registered was high. However, significant variation was observed for the case of higher inlet temperature. It was also observed that the heat transfer performance and pressure drop penalty increased when the mass flux was increased. Regarding the effect of inlet pressure, the heat transfer performance and pressure drop results decreased when the inlet pressure is increased.

Heat flow vs. atmospheric greenhouse on early Mars

NASA Technical Reports Server (NTRS)

Fanale, F. P.; Postawko, S. E.

1991-01-01

Researchers derived a quantitative relationship between the effectiveness of an atmospheric greenhouse and internal heat flow in producing the morphological differences between earlier and later Martian terrains. The derivation is based on relationships previously derived by other researchers. The reasoning may be stated as follows: the CO2 mean residence time in the Martian atmosphere is almost certainly much shorter than the total time span over which early climate differences are thought to have been sustained. Therefore, recycling of previously degassed CO2 quickly becomes more important than the ongoing supply of juvenile CO2. If so, then the atmospheric CO2 pressure, and thereby the surface temperature, may be approximated mathematically as a function of the total degassed CO2 in the atmosphere plus buried material and the ratio of the atmospheric and regolith mean residence times. The latter ratio can also be expressed as a function of heat flow. Hence, it follows that the surface temperature may be expressed as a function of heat flow and the total amount of available CO2. However, the depth to the water table can simultaneously be expressed as a function of heat flow and the surface temperature (the boundary condition). Therefore, for any given values of total available CO2 and regolith conductivity, there exist coupled independent equations which relate heat flow, surface temperature, and the depth to the water table. This means we can now derive simultaneous values of surface temperature and the depth of the water table for any value of the heat flow. The derived relationship is used to evaluate the relative importance of the atmospheric greenhouse effect and the internal regolith thermal gradient in producing morphological changes for any value of the heat flow, and to assess the absolute importance of each of the values of the heat flow which are thought to be reasonable on independent geophysical grounds.

Boundary layer transition observations on a body of revolution with surface heating and cooling in water

NASA Astrophysics Data System (ADS)

Arakeri, V. H.

1980-04-01

Boundary layer flow visualization in water with surface heat transfer was carried out on a body of revolution which had the predicted possibility of laminar separation under isothermal conditions. Flow visualization was by in-line holographic technique. Boundary layer stabilization, including elimination of laminar separation, was observed to take place on surface heating. Conversely, boundary layer destabilization was observed on surface cooling. These findings are consistent with the theoretical predictions of Wazzan et al. (1970).

Pluto's Polygonal Terrain Places Lower Limit on Planetary Heat Flow

NASA Astrophysics Data System (ADS)

Trowbridge, A.; Steckloff, J. K.; Melosh, H., IV; Freed, A. M.

2015-12-01

During its recent flyby of Pluto, New Horizons imaged an icy plains region (Sputnik Planum) whose surface is divided into polygonal blocks, ca. 20-30 km across, bordered by what appear to be shallow troughs. The lack of craters within these plains suggests they are relatively young, implying that the underlying material is recently active. The scale of these features argues against an origin by cooling and contraction. Here we investigate the alternative scenario that they are the surface manifestation of shallow convection in a thick layer of nitrogen ice. Typical Rayleigh-Bernard convective cells are approximately three times wider than the depth of the convecting layer, implying a layer depth of ca. 7-10 km. Our convection hypothesis requires that the Rayleigh number exceed a minimum of about 1000 in the nitrogen ice layer. We coupled a parameterized convection model with a temperature dependent rheology of nitrogen ice (Yamashita, 2008), finding a Rayleigh number 1500 to 7500 times critical for a plausible range of heat flows for Pluto's interior. The computed range of heat flow (3.5-5.2 mW/m2) is consistent with the radiogenic heat generated by a carbonaceous chondrite (CC) core implied by Pluto's bulk density. The minimum heat flow at the critical Rayleigh number is 0.13 mW/m2. Our model implies a core temperature of 44 K in the interior of the convecting layer. This is very close to the exothermic β-α phase transition in nitrogen ice at 35.6 K (for pure N2 ice; dissolved CO can increase this, depending on its concentration), suggesting that the warm cores of the rising convective cells may be β phase, whereas the cooler sinking limbs may be α phase. This transition may thus be observable due to the large difference in their spectral signature. Further applying our model to Pluto's putative water ice mantle, the heat flow from CC is consistent with convection in Pluto's mantle and the activity observed on its surface.

Advective and Conductive Heat Flow Budget Across the Wagner Basin, Northern Gulf of California

NASA Astrophysics Data System (ADS)

Neumann, F.; Negrete-Aranda, R.; Contreras, J.; Müller, C.; Hutnak, M.; Gonzalez-Fernandez, A.; Harris, R. N.; Sclater, J. G.

2015-12-01

In May 2015, we conducted a cruise across the northern Gulf of California, an area of continental rift basin formation and rapid deposition of sediments. The cruise was undertaken aboard the R/V Alpha Helix; our goal was to study variation in superficial conductive heat flow, lateral changes in the shallow thermal conductivity structure, and advective transport of heat across the Wagner basin. We used a Fielax heat flow probe with 22 thermistors that can penetrate up to 6 m into the sediment cover. The resulting data set includes 53 new heat flow measurements collected along three profiles. The longest profile (42 km) contains 30 measurements spaced 1-2 km apart. The western part of the Wagner basin (hanging wall block) exhibit low to normal conductive heat flow whereas the eastern part of the basin (foot wall block) heat flow is high to very high (up to 2500 mWm-2). Two other short profiles (12 km long each) focused on resolving an extremely high heat flow anomaly up to 15 Wm-2 located near the intersection between the Wagner bounding fault system and the Cerro Prieto fault. We hypothesize that the contrasting heat flow values observed across the Wagner basin are due to horizontal water circulation through sand layers and fault pathways of high permeability. Circulation appears to be from west (recharge zone) to east (discharge zone). Additionally, our results reveal strong vertical advection of heat due to dehydration reactions and compaction of fine grained sediments.

Experimental investigation of heat transfer and flow pattern from heated horizontal rectangular fin array under natural convection

NASA Astrophysics Data System (ADS)

Taji, S. G.; Parishwad, G. V.; Sane, N. K.

2014-07-01

This paper presents results of the experimental study conducted on heated horizontal rectangular fin array under natural convection. The temperature mapping and the prediction of the flow patterns over the fin array with variable fin spacing is carried out. Dimensionless fin spacing to height (S/H) ratio is varied from 0.05 to 0.3 and length to height ratio (L/H) = 5 is kept constant. The heater input to the fin array assembly is varied from 25 to 100 W. The single chimney flow pattern is observed from 8 to 12 mm fin spacing. The end flow is choked below 6 mm fin spacing. The single chimney flow pattern changes to sliding or end flow choking at 6 mm fin spacing. The average heat transfer coefficient (ha) is very small (2.52-5.78 W/m2 K) at 100 W for S = 5-12 mm. The ha is very small (1.12-1.8 W/m2 K) at 100 W for 2-4 mm fin spacing due to choked fin array end condition. The end flow is not sufficient to reach up to central portion of fin array and in the middle portion there is an unsteady down and up flow pattern resulting in sliding chimney. The central bottom portion of fin array channel does not contribute much in heat dissipation for S = 2-4 mm. The ha has significantly improved at higher spacing as compared to lower spacing region. The single chimney flow pattern is preferred from heat transfer point of view. The optimum spacing is confirmed in the range of 8-10 mm. The average heat transfer results are compared with previous literature and showed similar trend and satisfactory agreement. An empirical equation has been proposed to correlate the average Nusselt number as a function of Grashof number and fin spacing to height ratio. The average error for this equation is -0.32 %.

Analysis of flow in an observation well intersecting a single fracture

USGS Publications Warehouse

Lapcevic, P.A.; Novakowski, K.S.; Paillet, Frederick L.

1993-01-01

A semi-analytical model is developed to determine transmissivity and storativity from the interpretation of transient flow in an observation well due to pumping in a source well where the two wells are connected by a single fracture. Flow rate can be determined using a heat-pulse flowmeter located above the intersection of the fracture in the observation well. The results of a field experiment were interpreted using the new model and compared with drawdown data from the same test. Good agreement between the transmissivity estimates was observed whereas estimates of storativity were found to be better determined from the analysis of flow rate. ?? 1993.

Magnetohydrodynamic flow and heat transfer around a heated cylinder of arbitrary conductivity

NASA Astrophysics Data System (ADS)

Tassone, A.; Nobili, M.; Caruso, G.

2017-11-01

The interaction of the liquid metal with the plasma confinement magnetic field constitutes a challenge for the design of fusion reactor blankets, due to the arise of MHD effects: increased pressure drops, heat transfer suppression, etc. To overcome these issues, a dielectric fluid can be employed as coolant for the breeding zone. A typical configuration involves pipes transverse to the liquid metal flow direction. This numerical study is conducted to assess the influence of pipe conductivity on the MHD flow and heat transfer. The CFD code ANSYS CFX was employed for this purpose. The fluid is assumed to be bounded by rectangular walls with non-uniform thickness and subject to a skewed magnetic field with the main component aligned with the cylinder axis. The simulations were restricted to Re = (20; 40) and M = (10; 50). Three different scenarios for the obstacle were considered: perfectly insulating, finite conductivity and perfectly conducting. The electrical conductivity was found to affect the channel pressure penalty due to the obstacle insertion only for M = 10 and just for the two limiting cases. A general increment of the heat transfer with M was found due to the tendency of the magnetic field to equalize the flow rate between the sub-channels individuated by the pipe. The best results were obtained with the insulating pipe, due to the reduced electromagnetic drag. The generation of counter-rotating vortices close to the lateral duct walls was observed for M = 50 and perfectly conducting pipe as a result of the modified currents distribution.

Conjugate Heat Transfer Study in Hypersonic Flows

NASA Astrophysics Data System (ADS)

Sahoo, Niranjan; Kulkarni, Vinayak; Peetala, Ravi Kumar

2018-04-01

Coupled and decoupled conjugate heat transfer (CHT) studies are carried out to imitate experimental studies for heat transfer measurement in hypersonic flow regime. The finite volume based solvers are used for analyzing the heat interaction between fluid and solid domains. Temperature and surface heat flux signals are predicted by both coupled and decoupled CHT analysis techniques for hypersonic Mach numbers. These two methodologies are also used to study the effect of different wall materials on surface parameters. Effectiveness of these CHT solvers has been verified for the inverse problem of wall heat flux recovery using various techniques reported in the literature. Both coupled and decoupled CHT techniques are seen to be equally useful for prediction of local temperature and heat flux signals prior to the experiments in hypersonic flows.

Self-sustained flow oscillations and heat transfer in radial flow through co-rotating parallel disks

NASA Astrophysics Data System (ADS)

Mochizuki, S.; Inoue, T.

1990-03-01

An experimental study was conducted to determine the fluid flow and heat transfer characteristics in a passage formed by two parallel rotating disks. The local heat transfer coefficients along the disk radius were measured in detail and the flow patterns between the two rotating disks were visualized by using paraffin mist and a laser-light sheet. It was disclosed that: (1) the self-sustained laminar flow separation which is characteristic of the stationary disks still exists even when the disks are set in motion, giving significant influence to the heat transfer; (2) for small source flow Reynolds number, Re, and large rotational Reynolds number, Re(omega), rotating stall dominates the heat transfer; and (3) heat transfer for steady laminar flow occurs only when Re is less than 1200 and Re(omega) is less than 20.

Heat flow measurements on the southeast coast of Australia

USGS Publications Warehouse

Hyndman, R.D.; Jaeger, J.C.; Sass, J.H.

1969-01-01

Three boreholes have been drilled for the Australian National University near the southeast coast of New South Wales, Australia. The heat flows found are 1.1, 1.0, and 1.3 ??cal/cm2sec. The errors resulting from the proximity of the sea and a lake, surface temperature change, conductivity structure and water flow have been examined. The radioactive heat production in some of the intrusive rocks of the area have also been measured. The heat flows are much lower than the values of about 2.0 found elsewhere in south eastern Australia. The lower values appear to be part of a distinct heat flow province in eastern Australia. ?? 1969.

The augmentation of heat transfer in a pipe flow using a swirling perforated twisted (SPT) tape insert

NASA Astrophysics Data System (ADS)

Ahmad, Shahrokh; Oishe, Sadia Noon; Rahman, Md. Lutfor

2017-12-01

The purpose of this research work is to increase the heat transfer coefficient by operating the heat exchangers at smaller revolution per minute. This signifies an achievement of reduction of pressure drop corresponding to less operating cost. This study has used two types of SPT tape insert to observe the various heat transfer coefficient, heat transfer rate and heat transfer augmentation efficiency. One tape was fully twisted and another tape was partially twisted. The shape of the SPT tape creates turbulence effect. The turbulence flow (swirl flow) generated by SPT tape promotes greater mixing and high heat transfer coefficients. An arrangement scheme has been developed for the experimental investigation. For remarking the rate of change of heat transfer, temperature has been measured numerically through the temperature sensors with various flow rates and RPM. The volume flow rate was varied from 10.3448276 LPM to 21.045574 LPM and the rotation of the perforated twisted tape was varied from 50 RPM to 400 RPM. Finally the research study demonstrates the effectiveness of the results of the proposed approaches. It is observed that the suggested method of heat transfer augmentations is much more effective than existing methods, since it results in an increase in heat transfer area and also an increase in the heat transfer coefficient and reduction of cost in the industrial sectors.

Frictional strength and heat flow of southern San Andreas Fault

NASA Astrophysics Data System (ADS)

Zhu, P. P.

2016-01-01

Frictional strength and heat flow of faults are two related subjects in geophysics and seismology. To date, the investigation on regional frictional strength and heat flow still stays at the stage of qualitative estimation. This paper is concentrated on the regional frictional strength and heat flow of the southern San Andreas Fault (SAF). Based on the in situ borehole measured stress data, using the method of 3D dynamic faulting analysis, we quantitatively determine the regional normal stress, shear stress, and friction coefficient at various seismogenic depths. These new data indicate that the southern SAF is a weak fault within the depth of 15 km. As depth increases, all the regional normal and shear stresses and friction coefficient increase. The former two increase faster than the latter. Regional shear stress increment per kilometer equals 5.75 ± 0.05 MPa/km for depth ≤15 km; regional normal stress increment per kilometer is equal to 25.3 ± 0.1 MPa/km for depth ≤15 km. As depth increases, regional friction coefficient increment per kilometer decreases rapidly from 0.08 to 0.01/km at depths less than ~3 km. As depth increases from ~3 to ~5 km, it is 0.01/km and then from ~5 to 15 km, and it is 0.002/km. Previously, frictional strength could be qualitatively determined by heat flow measurements. It is difficult to obtain the quantitative heat flow data for the SAF because the measured heat flow data exhibit large scatter. However, our quantitative results of frictional strength can be employed to investigate the heat flow in the southern SAF. We use a physical quantity P f to describe heat flow. It represents the dissipative friction heat power per unit area generated by the relative motion of two tectonic plates accommodated by off-fault deformation. P f is called "fault friction heat." On the basis of our determined frictional strength data, utilizing the method of 3D dynamic faulting analysis, we quantitatively determine the regional long-term fault

Anomalous heat flow belt along the continental margin of Brazil

NASA Astrophysics Data System (ADS)

Hamza, Valiya M.; Vieira, Fabio P.; Silva, Raquel T. A.

2018-01-01

A comprehensive analysis of thermal gradient and heat flow data was carried out for sedimentary basins situated in the continental margin of Brazil (CMB). The results point to the existence of a narrow belt within CMB, where temperature gradients are higher than 30 °C/km and the heat flow is in excess of 70 mW/m2. This anomalous geothermal belt is confined between zones of relatively low to normal heat flow in the adjacent continental and oceanic regions. The width of the belt is somewhat variable, but most of it falls within the range of 100-300 km. The spatial extent is relatively large in the southern (in the basins of Pelotas, Santos and Campos) and northern (in the basins of Potiguar and Ceará) parts, when compared with those in the central parts (in the basins of South Bahia, Sergipe and Alagoas). The characteristics of heat flow anomalies appear to be compatible with those produced by thermal sources at depths in the lower crust. Hence, magma emplacement at the transition zone between lower crust and upper mantle is considered the likely mechanism producing such anomalies. Seismicity within the belt is relatively weak, with focal depths less than 10 km for most of the events. Such observations imply that "tectonic bonding" between continental and oceanic segments, at the transition zone of CMB, is relatively weak. Hence, it is proposed that passive margins like CMB be considered as constituting a type of plate boundary that is aseismic at sub-crustal levels, but allows for escape of significant amounts of earth's internal heat at shallow depths.

A heat-flow reconnaissance of southeastern Alaska.

USGS Publications Warehouse

Sass, J.H.; Lawver, L.A.; Munroe, R.J.

1985-01-01

Heat flow was measured at nine sites in crystalline and sedimentary rocks of SE Alaska. Seven of the sites, located between 115 and 155 km landward of the Queen Charlotte-Fairweather transform fault, have heat flows significantly higher than the mean in the coastal provinces between Cape Mendocino and the Queen Charlotte Islands, and lower than the mean for 81 values within 100 km of the San Andreas transform fault, even further S. There is no evidence for heat sources that might be associated with late Cainozoic thermal events.-P.Br.

A note on drillhole depths required for reliable heat flow determinations

USGS Publications Warehouse

Chapman, D.S.; Howell, J.; Sass, J.H.

1984-01-01

In general, there is a limiting depth in a drillhole above which the reliability of a single determination of heat flow decreases rapidly with decreasing depth and below which the statistical uncertainty of a heat flow determination does not change perceptibly with increasing depth. This feature has been established empirically for a test case comprising a group of twelve heat flow sites in the Republic of Zambia. The technique consists of constructing heat flow versus depth curves for individual sites by progressively discarding data from the lower part of the hole and recomputing heat flow from the remaining data. For the Zambian test case, the curves converge towards a uniform value of 67 ?? 3 mW m-2 when all available data are used, but values of heat flow calculated for shallow(< 100 m) parts of the same holes range from 45 to 95 mW m-2. The heat flow versus depth curves are enclosed by a perturbation envelope which has an amplitude of 40 mW m-2 at the surface and decreases linearly to the noise level at 190 m. For the test region of Zambia a depth of 170 m is needed to guarantee a heat flow measurement within ?? 10% of the background regional value. It is reasonable to expect that this depth will be shallower in some regions and deeper in others. Features of heat flow perturbation envelopes can be used as quantitative reliability indices for heat flow studies. ?? 1984.

Analysis of Heat Transfers inside Counterflow Plate Heat Exchanger Augmented by an Auxiliary Fluid Flow

PubMed Central

Khaled, A.-R. A.

2014-01-01

Enhancement of heat transfers in counterflow plate heat exchanger due to presence of an intermediate auxiliary fluid flow is investigated. The intermediate auxiliary channel is supported by transverse conducting pins. The momentum and energy equations for the primary fluids are solved numerically and validated against a derived approximate analytical solution. A parametric study including the effect of the various plate heat exchanger, and auxiliary channel dimensionless parameters is conducted. Different enhancement performance indicators are computed. The various trends of parameters that can better enhance heat transfer rates above those for the conventional plate heat exchanger are identified. Large enhancement factors are obtained under fully developed flow conditions. The maximum enhancement factors can be increased by above 8.0- and 5.0-fold for the step and exponential distributions of the pins, respectively. Finally, counterflow plate heat exchangers with auxiliary fluid flows are recommended over the typical ones if these flows can be provided with the least cost. PMID:24719572

Analysis of heat transfers inside counterflow plate heat exchanger augmented by an auxiliary fluid flow.

PubMed

Khaled, A-R A

2014-01-01

Enhancement of heat transfers in counterflow plate heat exchanger due to presence of an intermediate auxiliary fluid flow is investigated. The intermediate auxiliary channel is supported by transverse conducting pins. The momentum and energy equations for the primary fluids are solved numerically and validated against a derived approximate analytical solution. A parametric study including the effect of the various plate heat exchanger, and auxiliary channel dimensionless parameters is conducted. Different enhancement performance indicators are computed. The various trends of parameters that can better enhance heat transfer rates above those for the conventional plate heat exchanger are identified. Large enhancement factors are obtained under fully developed flow conditions. The maximum enhancement factors can be increased by above 8.0- and 5.0-fold for the step and exponential distributions of the pins, respectively. Finally, counterflow plate heat exchangers with auxiliary fluid flows are recommended over the typical ones if these flows can be provided with the least cost.

Reversing Flows and Heat Spike: Caused by Solar g-Modes?

NASA Technical Reports Server (NTRS)

Mayr, Hans G.; Wolff, Charles L.

2003-01-01

The Quasi Biennial Oscillation in the Earth s upper atmosphere has an analog deep inside the Sun. As on Earth, the flow is east or west, it is at low latitude, and it reverses direction in a roughly periodic manner. The period in the solar case is 1.3 years. It was detected using solar oscillations similar to the way earthquakes are used to study the Earth's interior. But its cause was not known. We showed that global oscillations (g-modes) can supply enough angular momentum to drive zonal flows with the observed reversal period. This required a calculation of wave dissipation rates inside each flow and in the turbulent layer that separates any two flows of opposite sign. Heat that this process leaves behind causes a thermal spike inside the Sun at the same depth. This may explain an anomaly in observed sound speed that has had no sure explanation.

Visualization of various working fluids flow regimes in gravity heat pipe

NASA Astrophysics Data System (ADS)

Nemec, Patrik

Heat pipe is device working with phase changes of working fluid inside hermetically closed pipe at specific pressure. The phase changes of working fluid from fluid to vapour and vice versa help heat pipe to transport high heat flux. Amount of heat flux transferred by heat pipe, of course depends on kind of working fluid. The article deal about visualization of various working fluids flow regimes in glass gravity heat pipe by high speed camera and processes casing inside during heat pipe operation. Experiment working fluid flow visualization is performed with two glass heat pipes with different inner diameter (13 mm and 22 mm) filled with water, ethanol and fluorinert FC 72. The working fluid flow visualization explains the phenomena as a working fluid boiling, nucleation of bubbles, and vapour condensation on the wall, vapour and condensate flow interaction, flow down condensate film thickness on the wall occurred during the heat pipe operation.

Relationships between heat flow, thermal and pressure fields in the Gulf of Mexico

NASA Astrophysics Data System (ADS)

Husson, L.; Henry, P.; Le Pichon, X.

2004-12-01

The thermal field of the Gulf of Mexico (GoM) is restored from a comprehensive temperature-depth database. A striking feature is the systematic sharp gradient increase between 2500 and 4000 m. The analysis of the pressure (fracturation tests and mud weights) indicates a systematic correlation between the pressure and temperature fields, as well as with the thickness of Plio-Pleistocene sedimentary layer, and is interpreted as the fact of cooling from fluid flow in the upper, almost hydrostatically pressured layer. The Nusselt number, that we characterize by the ratio between the near high-P gradient over low-P gradient varies spatially and is correlated to the structural pattern of the GoM; this observation outlines the complex relationships between heat and fluid flows, structure and sedimentation. The deep thermal signal is restored in terms of gradient and heat flow density from a statistical analysis of the thermal data combined to the thermal modelling of about 175 wells. At a regional scale, although the sedimentary cover is warmer in Texas than in Louisiana in terms of temperature, the steady state basal heat flow is higher in Louisiana. In addition, beneath the Corsair Fault, which lay offshore parallel to the Texan coast, the high heat flow suggests a zone of Tertiary lithospheric thinning.

Flow regimes and mechanistic modeling of critical heat flux under subcooled flow boiling conditions

NASA Astrophysics Data System (ADS)

Le Corre, Jean-Marie

Thermal performance of heat flux controlled boiling heat exchangers are usually limited by the Critical Heat Flux (CHF) above which the heat transfer degrades quickly, possibly leading to heater overheating and destruction. In an effort to better understand the phenomena, a literature review of CHF experimental visualizations under subcooled flow boiling conditions was performed and systematically analyzed. Three major types of CHF flow regimes were identified (bubbly, vapor clot and slug flow regime) and a CHF flow regime map was developed, based on a dimensional analysis of the phenomena and available data. It was found that for similar geometric characteristics and pressure, a Weber number (We)/thermodynamic quality (x) map can be used to predict the CHF flow regime. Based on the experimental observations and the review of the available CHF mechanistic models under subcooled flow boiling conditions, hypothetical CHF mechanisms were selected for each CHF flow regime, all based on a concept of wall dry spot overheating, rewetting prevention and subsequent dry spot spreading. It is postulated that a high local wall superheat occurs locally in a dry area of the heated wall, due to a cyclical event inherent to the considered CHF two-phase flow regime, preventing rewetting (Leidenfrost effect). The selected modeling concept has the potential to span the CHF conditions from highly subcooled bubbly flow to early stage of annular flow. A numerical model using a two-dimensional transient thermal analysis of the heater undergoing nucleation was developed to mechanistically predict CHF in the case of a bubbly flow regime. In this type of CHF two-phase flow regime, the high local wall superheat occurs underneath a nucleating bubble at the time of bubble departure. The model simulates the spatial and temporal heater temperature variations during nucleation at the wall, accounting for the stochastic nature of the boiling phenomena. The model has also the potential to evaluate

Basic data for some recent Australian heat-flow measurements

USGS Publications Warehouse

Munroe, Robert J.; Sass, J.H.; Milburn, G.T.; Jaeger, J.C.; Tammemagi, H.Y.

1975-01-01

This report has been compiled to provide background information and detailed temperature and thermal conductivity data for the heat-flow values reported in Sass, Jaeger, and Munroe (in press). The data were collected as part of a joint heat-flow study by the Australian National University (ANU) and the U.S. Geological Survey (USGS) under the direction of J. C. Jaeger (ANU) and J. H. Sass (USGS). The format is similar to that used for basic data from United States heat-flow determinations (Sass and Munroe, 1974). Each section contains a state map showing the geographic distribution of heat-flow data followed by tables which list individual temperatures, thermal conductivities, and radiogenic heat production values. A companion volume (Bunker and others, 1975) gives details of the heat-production measurements together with individual radioelement concentrations. Localities are arranged in alphabetical order within each state. The methods and techniques of measurements have been described by Sass and others (1971a, b). Unusual methods or procedures which differ markedly from these techniques are noted and described in the comments sections of the tables.

Submarine hydrogeology of the Hawaiian archipelagic apron: 2. Numerical simulations of coupled heat transport and fluid flow

NASA Astrophysics Data System (ADS)

Harris, Robert N.; Garven, Grant; Georgen, Jennifer; McNutt, Marcia K.; Christiansen, Lizet; von Herzen, Richard P.

2000-09-01

We perform numerical simulations of buoyancy-driven, pore fluid flow in the Hawaiian archipelagic apron and underlying oceanic crust in order to determine the extent to which heat redistributed by such flow might cause conductive heat flow measurements to underrepresent the true mantle heat flux. We also seek an understanding of undulations observed in finely spaced heat flow measurements acquired north of Oahu and Maro Reef with wavelengths of 10 to 100 km and amplitudes of 2 to 7 mW m-2. We find that pore fluid flow can impart significant perturbations to seafloor heat flow from the value expected assuming a constant mantle flux. In the simplest scenario, moat-wide circulation driven by bathymetric relief associated with the volcanic edifice recharges a fluid system over the moat and discharges the geothermally heated water through the volcanic edifice. The existing heat flow data are unable to confirm the existence of such a flow regime, in that it produces prominent heat flow anomalies only on the steep flanks of the volcano where heat flow probes cannot penetrate. However, this flow system does not significantly mask the mantle flux for reasonable permeabilities and flow rates. Another numerical simulation in which the upper oceanic basement acts as a aquifer for a flow loop recharged at basement outcrops on the flexural arch and discharged within a permeable volcanic edifice is capable of almost uniformly depressing conductive heat flow across the entire moat by ˜15%. Large heat flow anomalies (>20 mW m-2) are located over the recharge and discharge zones but are beyond the area sampled by our data. Presumably finely spaced heat flow measurements over the flexural arch could test for the existence of the predicted recharge zone. We demonstrate that the prominent, shorter-wave undulations in heat flow across the Oahu and Maro Reef moats are too large to be explained solely by relief in the upper oceanic basement. More likely, shallower large-scale turbidites

Turbulent Heat Transfer in Curved Pipe Flow

NASA Astrophysics Data System (ADS)

Kang, Changwoo; Yang, Kyung-Soo

2013-11-01

In the present investigation, turbulent heat transfer in fully-developed curved pipe flow with axially uniform wall heat flux has been numerically studied. The Reynolds numbers under consideration are Reτ = 210 (DNS) and 1,000 (LES) based on the mean friction velocity and the pipe radius, and the Prandtl number (Pr) is 0.71. For Reτ = 210 , the pipe curvature (κ) was fixed as 1/18.2, whereas three cases of κ (0.01, 0.05, 0.1) were computed in the case of Reτ = 1,000. The mean velocity, turbulent intensities and heat transfer rates obtained from the present calculations are in good agreement with the previous numerical and experimental results. To elucidate the secondary flow structures due to the pipe curvature, the mean quantities and rms fluctuations of the flow and temperature fields are presented on the pipe cross-sections, and compared with those of the straight pipe flow. To study turbulence structures and their influence on turbulent heat transfer, turbulence statistics including but not limited to skewness and flatness of velocity fluctuations, cross-correlation coefficients, an Octant analysis, and turbulence budgets are presented and discussed. Based on our results, we attempt to clarify the effects of Reynolds number and the pipe curvature on turbulent heat transfer. This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology (2010-0008457).

Heat and mass transfer and hydrodynamics in swirling flows (review)

NASA Astrophysics Data System (ADS)

Leont'ev, A. I.; Kuzma-Kichta, Yu. A.; Popov, I. A.

2017-02-01

Research results of Russian and foreign scientists of heat and mass transfer in whirling flows, swirling effect, superficial vortex generators, thermodynamics and hydrodynamics at micro- and nanoscales, burning at swirl of the flow, and technologies and apparatuses with the use of whirling currents for industry and power generation were presented and discussed at the "Heat and Mass Transfer in Whirling Currents" 5th International Conference. The choice of rational forms of the equipment flow parts when using whirling and swirling flows to increase efficiency of the heat-power equipment and of flow regimes and burning on the basis of deep study of the flow and heat transfer local parameters was set as the main research prospect. In this regard, there is noticeable progress in research methods of whirling and swirling flows. The number of computational treatments of swirling flows' local parameters has been increased. Development and advancement of the up to date computing models and national productivity software are very important for this process. All experimental works are carried out with up to date research methods of the local thermoshydraulic parameters, which enable one to reveal physical mechanisms of processes: PIV and LIV visualization techniques, high-speed and infrared photography, high speed registration of parameters of high-speed processes, etc. There is a problem of improvement of researchers' professional skills in the field of fluid mechanics to set adequately mathematics and physics problems of aerohydrodynamics for whirling and swirling flows and numerical and pilot investigations. It has been pointed out that issues of improvement of the cooling system and thermal protection effectiveness of heat-power and heat-transfer equipment units are still actual. It can be solved successfully using whirling and swirling flows as simple low power consumption exposing on the flow method and heat transfer augmentation.

Conjugate Compressible Fluid Flow and Heat Transfer in Ducts

NASA Technical Reports Server (NTRS)

Cross, M. F.

2011-01-01

A computational approach to modeling transient, compressible fluid flow with heat transfer in long, narrow ducts is presented. The primary application of the model is for analyzing fluid flow and heat transfer in solid propellant rocket motor nozzle joints during motor start-up, but the approach is relevant to a wide range of analyses involving rapid pressurization and filling of ducts. Fluid flow is modeled through solution of the spatially one-dimensional, transient Euler equations. Source terms are included in the governing equations to account for the effects of wall friction and heat transfer. The equation solver is fully-implicit, thus providing greater flexibility than an explicit solver. This approach allows for resolution of pressure wave effects on the flow as well as for fast calculation of the steady-state solution when a quasi-steady approach is sufficient. Solution of the one-dimensional Euler equations with source terms significantly reduces computational run times compared to general purpose computational fluid dynamics packages solving the Navier-Stokes equations with resolved boundary layers. In addition, conjugate heat transfer is more readily implemented using the approach described in this paper than with most general purpose computational fluid dynamics packages. The compressible flow code has been integrated with a transient heat transfer solver to analyze heat transfer between the fluid and surrounding structure. Conjugate fluid flow and heat transfer solutions are presented. The author is unaware of any previous work available in the open literature which uses the same approach described in this paper.

The effect of heating direction on flow boiling heat transfer of R134a in micro-channels

NASA Astrophysics Data System (ADS)

Xu, Mingchen; Jia, Li; Dang, Chao; Peng, Qi

2017-04-01

This paper presents effects of heating directions on heat transfer performance of R134a flow boiling in micro- channel heat sink. The heat sink has 30 parallel rectangular channels with cross-sectional dimensions of 500μm width 500μm depth and 30mm length. The experimental operation condition ranges of the heat flux and the mass flux were 13.48 to 82.25 W/cm2 and 373.3 to 1244.4 kg/m2s respectively. The vapor quality ranged from 0.07 to 0.93. The heat transfer coefficients of top heating and bottom heating both were up to 25 kW/m2 K. Two dominate transfer mechanisms of nucleate boiling and convection boiling were observed according to boiling curves. The experimental results indicated that the heat transfer coefficient of bottom heating was 13.9% higher than top heating in low heat flux, while in high heat flux, the heat transfer coefficient of bottom heating was 9.9%.higher than the top heating, because bubbles were harder to divorce the heating wall. And a modified correlation was provided to predict heat transfer of top heating.

Molecular dynamics study of solid-liquid heat transfer and passive liquid flow

NASA Astrophysics Data System (ADS)

Yesudasan Daisy, Sumith

equilibrium canonical ensemble (NVT) is simulated using thermostat algorithms. For research in heat transfer involving solid liquid interaction, we need to perform non equilibrium MD (NEMD) simulations. In such NEMD simulations, the methods used for simulating heating from a surface is very important and must capture proper physics and thermodynamic properties. Development of MD simulation techniques to simulate solid-liquid heating and the study of fundamental mechanism of passive flow is the main focus of this thesis. An accurate surface-heating algorithm was developed for water which can now allow the study of a whole new set of fundamental heat transfer problems at the nanoscale like surface heating/cooling of droplets, thin-films, etc. The developed algorithm is implemented in the in-house developed C++ MD code. A direct two dimensional local pressure estimation algorithm is also formulated and implemented in the code. With this algorithm, local pressure of argon and platinum interaction is studied. Also, the surface tension of platinum-argon (solid-liquid) was estimated directly from the MD simulations for the first time. Contact angle estimation studies of water on platinum, and argon on platinum were also performed. A thin film of argon is kept above platinum plate and heated in the middle region, leading to the evaporation and pressure reduction thus creating a strong passive flow in the near surface region. This observed passive liquid flow is characterized by estimating the pressure, density, velocity and surface tension using Eulerian mapping method. Using these simulation, we have demonstrated the fundamental nature and origin of surface-driven passive flow. Heat flux removed from the surface is also estimated from the results, which shows a significant improvement can be achieved in thermal management of electronic devices by taking advantage of surface-driven strong passive liquid flow. Further, the local pressure of water on silicon di-oxide surface is

A novel compact heat exchanger using gap flow mechanism.

PubMed

Liang, J S; Zhang, Y; Wang, D Z; Luo, T P; Ren, T Q

2015-02-01

A novel, compact gap-flow heat exchanger (GFHE) using heat-transfer fluid (HTF) was developed in this paper. The detail design of the GFHE coaxial structure which forms the annular gap passage for HTF is presented. Computational fluid dynamics simulations were introduced into the design to determine the impacts of the gap width and the HTF flow rate on the GFHE performance. A comparative study on the GFHE heating rate, with the gap widths ranged from 0.1 to 1.0 mm and the HTF flow rates ranged from 100 to 500 ml/min, was carried out. Results show that a narrower gap passage and a higher HTF flow rate can yield a higher average heating rate in GFHE. However, considering the compromise between the GFHE heating rate and the HTF pressure drop along the gap, a 0.4 mm gap width is preferred. A testing loop was also set up to experimentally evaluate the GFHE capability. The testing results show that, by using 0.4 mm gap width and 500 ml/min HTF flow rate, the maximum heating rate in the working chamber of the as-made GFHE can reach 18 °C/min, and the average temperature change rates in the heating and cooling processes of the thermal cycle test were recorded as 6.5 and 5.4 °C/min, respectively. These temperature change rates can well satisfy the standard of IEC 60068-2-14:2009 and show that the GFHE developed in this work has sufficient heat exchange capacity and can be used as an ideal compact heat exchanger in small volume desktop thermal fatigue test apparatus.

Flow-dependent vascular heat transfer during microwave thermal ablation.

PubMed

Chiang, Jason; Hynes, Kieran; Brace, Christopher L

2012-01-01

Microwave tumor ablation is an attractive option for thermal ablation because of its inherent benefits over radiofrequency ablation (RFA) in the treatment of solid tumors such as hepatocellular carcinoma (HCC). Microwave energy heats tissue to higher temperatures and at a faster rate than RFA, creating larger, more homogenous ablation zones. In this study, we investigate microwave heating near large vasculature using coupled fluid-flow and thermal analysis. Low-flow conditions are predicted to be more likely to cause cytotoxic heating and, therefore, vessel thrombosis and endothelial damage of downstream tissues. Such conditions may be more prevalent in patient with severe cirrhosis or compromised blood flow. High-flow conditions create the more familiar heat-sink effect that can protect perivascular tissues from the intended thermal damage. These results may help guide placement and use of microwave ablation technologies in future studies.

Heat flow and near-surface radioactivity in the Australian continental crust

USGS Publications Warehouse

Sass, J.H.; Jaeger, J.C.; Munroe, Robert J.

1976-01-01

Heat-flow data have been obtained at 44 sites in various parts of Australia. These include seven sites from the old (~ 2500 m.y.) Precambrian shield of Western Australia, seventeen from the younger (~ 600- 2000 m.y.) Precambrian rocks of South Australia, the Northern Territory, and Queensland, and twenty within the eastern Paleozoic and younger rocks. Thirty of the sites are located where no previous heat-flow data existed, and the remainder provide significant extensions or refinements of areas previously studied. Where the holes studied penetrated the crystalline basement rocks, or where the latter rocks were exposed within a few kilometers of the holes, the upper crustal radiogenic heat production has been estimated based on gamma-ray spectrometric determinations of U, Th, and K abundances. Three heat-flow provinces are recognized in Australia based on the linear relation (q = q* + DA0 ) between heat flow q and surface radioactivity A0. New data from the Western Australian shield support earlier studies showing that heat flow is low to normal with values ranging from 0.7 to 1.2 hfu and with the majority of values less than 1.0 hfu, and the parameters q* = 0.63 hfu and 0 = 4.5 km determined previously were confirmed. Heat flow in the Proterozoic shield of central Australia is quite variable, with values ranging between about l and 3 hfu. This variability is attributed mainly to variations in near-surface crustal radioactivity. The parameters of the heat-flow line are q* = 0.64 hfu and 0 = 11.1 km and moderately high temperatures are predicted for the lower crust and upper mantle. Previous suggestions of a band of l ow- to - normal heat flow near the coast in eastern Australia were confirmed in some areas, but the zone is interrupted in at least one region (the Sydney Basin), where heat flow is about 2.0 hfu over a large area. The reduced heat flow, q*, in the Paleozoic intrusive rocks of eastern Australia varies from about 0.8 to 2.0 hfu . This variability might

Study of the heat-transfer crisis on heat-release surfaces of annular channels with swirl and transit flows

NASA Astrophysics Data System (ADS)

Boltenko, E. A.

2016-10-01

The results of the experimental study of the heat-transfer crisis on heat-release surfaces of annular channels with swirl and transit flow are presented. The experiments were carried out using electric heated annular channels with one and (or) two heat-release surfaces. For the organization of transit flow on a convex heat-release surface, four longitudinal ribs were installed uniformly at its perimeter. Swirl flow was realized using a capillary wound tightly (without gaps) on the ribs. The ratio between swirl and transit flows in the annular gap was varied by applying longitudinal ribs of different height. The experiments were carried out using a closed-type circulatory system. The experimental data were obtained in a wide range of regime parameters. Both water heated to the temperature less than the saturation temperature and water-steam mixture were fed at the inlet of the channels. For the measurement of the temperature of the heat-release surfaces, chromel-copel thermocouples were used. It was shown that the presence of swirl flow on a convex heatrelease surface led to a significant decrease in critical heat flows (CHF) compared to a smooth surface. To increase CHF, it was proposed to use the interaction of swirl flows of the heat carrier. The second swirl flow was transit flow, i.e., swirl flow with the step equal to infinity. It was shown that CHF values for a channel with swirl and transit flow in all the studied range of regime parameters was higher than CHF values for both a smooth annular channel and a channel with swirl. The empirical ratios describing the dependence of CHF on convex and concave heat-release surfaces of annular channels with swirl and transit flow on the geometrical characteristics of channels and the regime parameters were obtained. The experiments were carried out at the pressure p = 3.0-16.0 MPa and the mass velocity ρw = 250-3000 kg/(m2s).

A Prototype Flux-Plate Heat-Flow Sensor for Venus Surface Heat-Flow Determinations

NASA Technical Reports Server (NTRS)

Morgan, Paul; Reyes, Celso; Smrekar, Suzanne E.

2005-01-01

Venus is the most Earth-like planet in the Solar System in terms of size, and the densities of the two planets are almost identical when selfcompression of the two planets is taken into account. Venus is the closest planet to Earth, and the simplest interpretation of their similar densities is that their bulk compositions are almost identical. Models of the thermal evolution of Venus predict interior temperatures very similar to those indicated for the regions of Earth subject to solid-state convection, but even global analyses of the coarse Pioneer Venus elevation data suggest Venus does not lose heat by the same primary heat loss mechanism as Earth, i.e., seafloor spreading. The comparative paucity of impact craters on Venus has been interpreted as evidence for relatively recent resurfacing of the planet associated with widespread volcanic and tectonic activity. The difference in the gross tectonic styles of Venus and Earth, and the origins of some of the enigmatic volcano-tectonic features on Venus, such as the coronae, appear to be intrinsically related to Venus heat loss mechanism(s). An important parameter in understanding Venus geological evolution, therefore, is its present surface heat flow. Before the complications of survival in the hostile Venus surface environment were tackled, a prototype fluxplate heat-flow sensor was built and tested for use under synthetic stable terrestrial surface conditions. The design parameters for this prototype were that it should operate on a conforming (sand) surface, with a small, self-contained power and recording system, capable of operating without servicing for at least several days. The precision and accuracy of the system should be < 5 mW/sq m. Additional information is included in the original extended abstract.

Experimental Study of the Relation Between Heat Transfer and Flow Behavior in a Single Microtube

NASA Astrophysics Data System (ADS)

Huang, Shih-Che; Kawanami, Osamu; Kawakami, Kazunari; Honda, Itsuro; Kawashima, Yousuke; Ohta, Haruhiko

2008-09-01

The flow boiling heat transfer in microchannels have become important issue because it is extremely high-performance heat exchanger for electronic devices. For a detailed study on flow boiling heat transfer in a microtube, we have used a transparent heated microtube, which is coated with a thin gold film on its inner wall. The gold film is used as a resistance thermometer to directly evaluate the inner wall temperature averaged over the entire temperature measurement length. At the same time, the transparency of the film enables the observation of fluid behavior. Flow boiling experiments have been carried out using the microtube under the following conditions; mass velocity of 105 kg/m2 s, tube diameter of 1 mm, heat flux in the range of 10 380 kW/m2 s, and the test fluid used is ionized water. Under low heat flux conditions, the fluctuations in the inner wall temperature and mass velocity are closely related; the frequency of these fluctuations is the same. However, the fluctuations in the inner wall temperature and heat transfer coefficient are found to be independent of the fluctuation in the mass velocity under high heat flux conditions.

Numerical prediction of turbulent oscillating flow and associated heat transfer

NASA Technical Reports Server (NTRS)

Koehler, W. J.; Patankar, S. V.; Ibele, W. E.

1991-01-01

A crucial point for further development of engines is the optimization of its heat exchangers which operate under oscillatory flow conditions. It has been found that the most important thermodynamic uncertainties in the Stirling engine designs for space power are in the heat transfer between gas and metal in all engine components and in the pressure drop across the heat exchanger components. So far, performance codes cannot predict the power output of a Stirling engine reasonably enough if used for a wide variety of engines. Thus, there is a strong need for better performance codes. However, a performance code is not concerned with the details of the flow. This information must be provided externally. While analytical relationships exist for laminar oscillating flow, there has been hardly any information about transitional and turbulent oscillating flow, which could be introduced into the performance codes. In 1986, a survey by Seume and Simon revealed that most Stirling engine heat exchangers operate in the transitional and turbulent regime. Consequently, research has since focused on the unresolved issue of transitional and turbulent oscillating flow and heat transfer. Since 1988, the University of Minnesota oscillating flow facility has obtained experimental data about transitional and turbulent oscillating flow. However, since the experiments in this field are extremely difficult, lengthy, and expensive, it is advantageous to numerically simulate the flow and heat transfer accurately from first principles. Work done at the University of Minnesota on the development of such a numerical simulation is summarized.

View of equipment used for Heat Flow and Convection Experiment

NASA Image and Video Library

1972-12-17

AS17-162-24063 (7-19 Dec. 1972) --- A close-up view of the equipment used for the Heat Flow and Convection Experiment, an engineering and operational test and demonstration carried out aboard the Apollo 17 command module during the final lunar landing mission in NASA's Apollo program. Three test cells were used in the demonstration for measuring and observing fluid flow behavior in the absence of gravity in space flight. Data obtained from such demonstrations will be valuable in the design of future science experiments and for manufacturing processes in space.

Numerical and Experimental Approaches Toward Understanding Lava Flow Heat Transfer

NASA Astrophysics Data System (ADS)

Rumpf, M.; Fagents, S. A.; Hamilton, C.; Crawford, I. A.

2013-12-01

We have performed numerical modeling and experimental studies to quantify the heat transfer from a lava flow into an underlying particulate substrate. This project was initially motivated by a desire to understand the transfer of heat from a lava flow into the lunar regolith. Ancient regolith deposits that have been protected by a lava flow may contain ancient solar wind, solar flare, and galactic cosmic ray products that can give insight into the history of our solar system, provided the records were not heated and destroyed by the overlying lava flow. In addition, lava-substrate interaction is an important aspect of lava fluid dynamics that requires consideration in lava emplacement models Our numerical model determines the depth to which the heat pulse will penetrate beneath a lava flow into the underlying substrate. Rigorous treatment of the temperature dependence of lava and substrate thermal conductivity and specific heat capacity, density, and latent heat release are imperative to an accurate model. Experiments were conducted to verify the numerical model. Experimental containers with interior dimensions of 20 x 20 x 25 cm were constructed from 1 inch thick calcium silicate sheeting. For initial experiments, boxes were packed with lunar regolith simulant (GSC-1) to a depth of 15 cm with thermocouples embedded at regular intervals. Basalt collected at Kilauea Volcano, HI, was melted in a gas forge and poured directly onto the simulant. Initial lava temperatures ranged from ~1200 to 1300 °C. The system was allowed to cool while internal temperatures were monitored by a thermocouple array and external temperatures were monitored by a Forward Looking Infrared (FLIR) video camera. Numerical simulations of the experiments elucidate the details of lava latent heat release and constrain the temperature-dependence of the thermal conductivity of the particulate substrate. The temperature-dependence of thermal conductivity of particulate material is not well known

In situ determination of heat flow in unconsolidated sediments

USGS Publications Warehouse

Sass, J.H.; Kennelly, J.P.; Wendt, W.E.; Moses, T.H.; Ziagos, J.P.

1979-01-01

Subsurface thermal measurements are the most effective, least ambiguous tools for identifying and delineating possible geothernml resources. Measurements of thermal gradient in the upper few tens of meters generally are sufficient to outline the major anomalies, but it is always desirable to combine these gradients with reliable estimates of thermal conductivity to provide data on the energy flux and to constrain models for the heat sources responsible for the observed, near-surface thermal anomalies. The major problems associated with heat-flow measurements in the geothermal exploration mode are concerned with the economics of casing and/or grouting holes, the repeated site visits necessary to obtain equilibrium temperature values, the possible legal liability associated with the disturbance of underground aquifers, the surface hazards presented by pipes protruding from the ground, and the security problems associated with leaving cased holes open for periods of weeks to months. We have developed a technique which provides reliable 'real-time' determinations of temperature, thermal conductivity, and hence, of heat flow during the drilling operation in unconsolidated sediments. A combined temperature, gradient, and thermal conductivity experiment can be carried out, by driving a thin probe through the bit about 1.5 meters into the formation in the time that would otherwise be required for a coring trip. Two or three such experiments over the depth range of, say, 50 to 150 meters provide a high-quality heat-flow determination at costs comparable to those associated with a standard cased 'gradient hole' to comparable depths. The hole can be backfilled and abandoned upon cessation of drilling, thereby eliminating the need for casing, grouting, or repeated site visits.

Heat-transfer measurements of the 1983 Kilauea lava flow

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

Hardee, H.C.

1983-10-07

Convective heat flow measurements of a basaltic lava flow were made during the 1983 eruption of Kilauea volcano in Hawaii. Eight field measurements of induced natural convection were made, giving heat flux values that ranged from 1.78 to 8.09 kilowatts per square meter at lava temperatures of 1088 and 1128 degrees Celsius, respectively. These field measurements of convective heat flux at subliquidus temperatures agree with previous laboratory measurements in furnace-melted samples of molten lava, and are useful for predicting heat transfer in magma bodies and for estimating heat extraction rates for magma energy.

Heat transfer measurements of the 1983 kilauea lava flow.

PubMed

Hardee, H C

1983-10-07

Convective heat flow measurements of a basaltic lava flow were made during the 1983 eruption of Kilauea volcano in Hawaii. Eight field measurements of induced natural convection were made, giving heat flux values that ranged from 1.78 to 8.09 kilowatts per square meter at lava temperatures of 1088 and 1128 degrees Celsius, respectively. These field measurements of convective heat flux at subliquidus temperatures agree with previous laboratory measurements in furnace-melted samples of molten lava, and are useful for predicting heat transfer in magma bodies and for estimating heat extraction rates for magma energy.

Rapid heat-flowing surveying of geothermal areas, utilizing individual snowfalls as calorimeters

USGS Publications Warehouse

White, Donald E.

1969-01-01

Local differences in rate of heat transfer in vapor and by conduction through the ground in hot spring areas are difficult and time-consuming to measure quantitatively. Individual heavy snowfalls provide a rapid low-cost means of measuring total heat flow from such ground. After a favorable snowfall (heavy, brief duration, little wind, air temperature near 0°C), contacts between snow-covered and snow-free ground are mapped on a suitable base. Each mapped contact, as time elapses after a specific snowfall, is a heat-flow contour representing a decreasing rate of flow. Calibration of each mapped contact or snow line is made possible by the fact that snow remains on insulated surfaces (such as the boardwalks of Yellowstone's thermal areas) long after it has melted on adjacent warm ground. Heat-flow contours mapped to date range from 450 to 5500 μcal/cm2 sec, or 300 to 3700 times the world average of conductive heat flow. The very high rates of heat flow (2000 to > 10,000 μcal/cm2 sec) are probably too high, and the lower heat flows determinable by the method (2 sec) may be too low. Values indicated by the method are, however, probably within a factor of 2 of the total conductive and convective heat flow. Thermal anomalies from infrared imagery are similar in shape to heat-flow contours of a test area near Old Faithful geyser. Snowfall calorimetry provides a rapid means for evaluating the imagery and computer-derived products of the infrared data in terms of heat flow.

Systematic heat flow measurements across the Wagner Basin, northern Gulf of California

NASA Astrophysics Data System (ADS)

Neumann, Florian; Negrete-Aranda, Raquel; Harris, Robert N.; Contreras, Juan; Sclater, John G.; González-Fernández, Antonio

2017-12-01

A primary control on the geodynamics of rifting is the thermal regime. To better understand the geodynamics of rifting in the northern Gulf of California we systematically measured heat-flow across the Wagner Basin, a tectonically active basin that lies near the southern terminus of the Cerro Prieto fault. The heat flow profile is 40 km long, has a nominal measurement spacing of ∼1 km, and is collocated with a seismic reflection profile. Heat flow measurements were made with a 6.5-m violin-bow probe. Although heat flow data were collected in shallow water, where there are significant temporal variations in bottom water temperature, we use CTD data collected over many years to correct our measurements to yield accurate values of heat flow. After correction for bottom water temperature, the mean and standard deviation of heat flow across the western, central, and eastern parts of the basin are 220 ± 60, 99 ± 14, 889 ± 419 mW m-2, respectively. Corrections for sedimentation would increase measured heat flow across the central part of basin by 40 to 60%. We interpret the relatively high heat flow and large variability on the western and eastern flanks in terms of upward fluid flow at depth below the seafloor, whereas the lower and more consistent values across the central part of the basin are suggestive of conductive heat transfer. Moreover, heat flow across the central basin is consistent with gabbroic underplating at a depth of 15 km and suggests that continental rupture here has not gone to completion.

Method for identifying anomalous terrestrial heat flows

DOEpatents

Del Grande, Nancy Kerr

1977-01-25

A method for locating and mapping the magnitude and extent of terrestrial heat-flow anomalies from 5 to 50 times average with a tenfold improved sensitivity over orthodox applications of aerial temperature-sensing surveys as used for geothermal reconnaissance. The method remotely senses surface temperature anomalies such as occur from geothermal resources or oxidizing ore bodies by: measuring the spectral, spatial, statistical, thermal, and temporal features characterizing infrared radiation emitted by natural terrestrial surfaces; deriving from these measurements the true surface temperature with uncertainties as small as 0.05 to 0.5 K; removing effects related to natural temperature variations of topographic, hydrologic, or meteoric origin, the surface composition, detector noise, and atmospheric conditions; factoring out the ambient normal-surface temperature for non-thermally enhanced areas surveyed under otherwise identical environmental conditions; distinguishing significant residual temperature enhancements characteristic of anomalous heat flows and mapping the extent and magnitude of anomalous heat flows where they occur.

Observations of the effect of wind on the cooling of active lava flows

USGS Publications Warehouse

Keszthelyi, L.; Harris, A.J.L.; Dehn, J.

2003-01-01

We present the first direct observations of the cooling of active lava flows by the wind. We confirm that atmospheric convective cooling processes (i.e., the wind) dominate heat loss over the lifetime of a typical pahochoe lava flow. In fact, the heat extracted by convection is greater than predicted, especially at wind speeds less than 5 m/s and surface temperatures less than 400??C. We currently estimate that the atmospheric heat transfer coefficient is about 45-50 W m-2 K-1 for a 10 m/s wind and a surface temperature ???500??C. Further field experiments and theoretical studies should expand these results to a broader range of surface temperatures and wind speeds.

Sensor fault detection and isolation via high-gain observers: application to a double-pipe heat exchanger.

PubMed

Escobar, R F; Astorga-Zaragoza, C M; Téllez-Anguiano, A C; Juárez-Romero, D; Hernández, J A; Guerrero-Ramírez, G V

2011-07-01

This paper deals with fault detection and isolation (FDI) in sensors applied to a concentric-pipe counter-flow heat exchanger. The proposed FDI is based on the analytical redundancy implementing nonlinear high-gain observers which are used to generate residuals when a sensor fault is presented (as software sensors). By evaluating the generated residual, it is possible to switch between the sensor and the observer when a failure is detected. Experiments in a heat exchanger pilot validate the effectiveness of the approach. The FDI technique is easy to implement allowing the industries to have an excellent alternative tool to keep their heat transfer process under supervision. The main contribution of this work is based on a dynamic model with heat transfer coefficients which depend on temperature and flow used to estimate the output temperatures of a heat exchanger. This model provides a satisfactory approximation of the states of the heat exchanger in order to allow its implementation in a FDI system used to perform supervision tasks. Copyright © 2011 ISA. Published by Elsevier Ltd. All rights reserved.

Observations and Numerical Models of Solar Coronal Heating Associated with Spicules

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

Pontieu, B. De; Martinez-Sykora, J.; Moortel, I. De

Spicules have been proposed as significant contributors to the mass and energy balance of the corona. While previous observations have provided a glimpse of short-lived transient brightenings in the corona that are associated with spicules, these observations have been contested and are the subject of a vigorous debate both on the modeling and the observational side. Therefore, it remains unclear whether plasma is heated to coronal temperatures in association with spicules. We use high-resolution observations of the chromosphere and transition region (TR) with the Interface Region Imaging Spectrograph and of the corona with the Atmospheric Imaging Assembly on board themore » Solar Dynamics Observatory to show evidence of the formation of coronal structures associated with spicular mass ejections and heating of plasma to TR and coronal temperatures. Our observations suggest that a significant fraction of the highly dynamic loop fan environment associated with plage regions may be the result of the formation of such new coronal strands, a process that previously had been interpreted as the propagation of transient propagating coronal disturbances. Our observations are supported by 2.5D radiative MHD simulations that show heating to coronal temperatures in association with spicules. Our results suggest that heating and strong flows play an important role in maintaining the substructure of loop fans, in addition to the waves that permeate this low coronal environment.« less

Heat transfer in thin, compact heat exchangers with circular, rectangular, or pin-fin flow passages

NASA Technical Reports Server (NTRS)

Olson, D. A.

1992-01-01

Heat transfer and pressure drop have been measured of three thin, compact heat exchangers in helium gas at 3.5 MPa and higher, with Reynolds numbers of 450 to 36,000. The flow geometries for the three heat exchanger specimens were: circular tube, rectangular channel, and staggered pin fin with tapered pins. The specimens were heated radiatively at heat fluxes up to 77 W/sq cm. Correlations were developed for the isothermal friction factor as a function of Reynolds number, and for the Nusselt number as a function of Reynolds number and the ratio of wall temperature to fluid temperature. The specimen with the pin fin internal geometry had significantly better heat transfer than the other specimens, but it also had higher pressure drop. For certain conditions of helium flow and heating, the temperature more than doubled from the inlet to the outlet of the specimens, producing large changes in gas velocity, density, viscosity, and thermal conductivity. These changes in properties did not affect the correlations for friction factor and Nusselt number in turbulent flow.

Post-Dryout Heat Transfer to a Refrigerant Flowing in Horizontal Evaporator Tubes

NASA Astrophysics Data System (ADS)

Mori, Hideo; Yoshida, Suguru; Kakimoto, Yasushi; Ohishi, Katsumi; Fukuda, Kenichi

Studies of the post-dryout heat transfer were made based on the experimental data for HFC-134a flowing in horizontal smooth and spiral1y grooved (micro-fin) tubes and the characteristics of the post-dryout heat transfer were c1arified. The heat transfer coefficient at medium and high mass flow rates in the smooth tube was lower than the single-phase heat transfer coefficient of the superheated vapor flow, of which mass flow rate was given on the assumption that the flow was in a thermodynamic equilibrium. A prediction method of post-dryout heat transfer coefficient was developed to reproduce the measurement satisfactorily for the smooth tube. The post dryout heat transfer in the micro-fin tube can be regarded approximately as a superheated vapor single-phase heat transfer.

Pressure Gradient Effects on Hypersonic Cavity Flow Heating

NASA Technical Reports Server (NTRS)

Everhart, Joel L.; Alter, Stephen J.; Merski, N. Ronald; Wood, William A.; Prabhu, Ramadas K.

2006-01-01

The effect of a pressure gradient on the local heating disturbance of rectangular cavities tested at hypersonic freestream conditions has been globally assessed using the two-color phosphor thermography method. These experiments were conducted in the Langley 31-Inch Mach 10 Tunnel and were initiated in support of the Space Shuttle Return-To-Flight Program. Two blunted-nose test surface geometries were developed, including an expansion plate test surface with nearly constant negative pressure gradient and a flat plate surface with nearly zero pressure gradient. The test surface designs and flow characterizations were performed using two-dimensional laminar computational methods, while the experimental boundary layer state conditions were inferred using the measured heating distributions. Three-dimensional computational predictions of the entire model geometry were used as a check on the design process. Both open-flow and closed-flow cavities were tested on each test surface. The cavity design parameters and the test condition matrix were established using the computational predictions. Preliminary conclusions based on an analysis of only the cavity centerline data indicate that the presence of the pressure gradient did not alter the open cavity heating for laminar-entry/laminar-exit flows, but did raise the average floor heating for closed cavities. The results of these risk-reduction studies will be used to formulate a heating assessment of potential damage scenarios occurring during future Space Shuttle flights.

Pressure Gradient Effects on Hypersonic Cavity Flow Heating

NASA Technical Reports Server (NTRS)

Everhart, Joel L.; Alter, Stephen J.; Merski, N. Ronald; Wood, William A.; Prabhu, Ramdas K.

2007-01-01

The effect of a pressure gradient on the local heating disturbance of rectangular cavities tested at hypersonic freestream conditions has been globally assessed using the two-color phosphor thermography method. These experiments were conducted in the Langley 31-Inch Mach 10 Tunnel and were initiated in support of the Space Shuttle Return-To-Flight Program. Two blunted-nose test surface geometries were developed, including an expansion plate test surface with nearly constant negative pressure gradient and a flat plate surface with nearly zero pressure gradient. The test surface designs and flow characterizations were performed using two-dimensional laminar computational methods, while the experimental boundary layer state conditions were inferred using the measured heating distributions. Three-dimensional computational predictions of the entire model geometry were used as a check on the design process. Both open-flow and closed-flow cavities were tested on each test surface. The cavity design parameters and the test condition matrix were established using the computational predictions. Preliminary conclusions based on an analysis of only the cavity centerline data indicate that the presence of the pressure gradient did not alter the open cavity heating for laminar-entry/laminar-exit flows, but did raise the average floor heating for closed cavities. The results of these risk-reduction studies will be used to formulate a heating assessment of potential damage scenarios occurring during future Space Shuttle flights.

Radiative Heat Loss Measurements During Microgravity Droplet Combustion in a Slow Convective Flow

NASA Technical Reports Server (NTRS)

Hicks, Michael C.; Kaib, Nathan; Easton, John; Nayagam, Vedha; Williams, Forman A.

2003-01-01

Radiative heat loss from burning droplets in a slow convective flow under microgravity conditions is measured using a broad-band (0.6 to 40 microns) radiometer. In addition, backlit images of the droplet as well as color images of the flame were obtained using CCD cameras to estimate the burning rates and the flame dimensions, respectively. Tests were carried out in air at atmospheric pressure using n-heptane and methanol fuels with imposed forced flow velocities varied from 0 to 10 centimeters per second and initial droplet diameters varied from 1 to 3 millimeters. Slow convective flows were generated using three different experimental configurations in three different facilities in preparation for the proposed International Space Station droplet experiments. In the 2.2 Second Drop-Tower Facility a droplet supported on the leading edge of a quartz fiber is placed within a flow tunnel supplied by compressed air. In the Zero-Gravity Facility (five-second drop tower) a tethered droplet is translated in a quiescent ambient atmosphere to establish a uniform flow field around the droplet. In the KC 135 aircraft an electric fan was used to draw a uniform flow past a tethered droplet. Experimental results show that the burn rate increases and the overall flame size decreases with increases in forced-flow velocities over the range of flow velocities and droplet sizes tested. The total radiative heat loss rate, Q(sub r), decreases as the imposed flow velocity increases with the spherically symmetric combustion having the highest values. These observations are in contrast to the trends observed for gas-jet flames in microgravity, but consistent with the observations during flame spread over solid fuels where the burning rate is coupled to the forced flow as here.

Heat flow and hydrocarbon generation in the Transylvanian basin, Romania

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

Cranganu, C.; Deming, D.

1996-10-01

The Transylvanian basin in central Romania is a Neogene depression superimposed on the Cretaceous nappe system of the Carpathian Mountains. The basin contains the main gas reserves of Romania, and is one of the most important gas-producing areas of continental Europe; since 1902, gas has been produced from more than 60 fields. Surface heat flow in the Transylvanian basin as estimated in other studies ranges from 26 to 58 mW/m{sup 2}, with a mean value of 38 mW/m{sup 2}, relatively low compared to surrounding areas. The effect of sedimentation on heat flow and temperature in the Transylvanian basin was estimatedmore » with a numerical model that solved the heat equation in one dimension. Because both sediment thickness and heat flow vary widely throughout the Transylvanian basin, a wide range of model variables were used to bracket the range of possibilities. Three different burial histories were considered (thin, average, and thick), along with three different values of background heat flow (low, average, and high). Altogether, nine different model permutations were studied. Modeling results show that average heat flow in the Transylvanian basin was depressed approximately 16% during rapid Miocene sedimentation, whereas present-day heat flow remains depressed, on average, about 17% below equilibrium values. We estimated source rock maturation and the timing of hydrocarbon generation by applying Lopatin`s method. Potential source rocks in the Transylvanian basin are Oligocene-Miocene, Cretaceous, and Jurassic black shales. Results show that potential source rocks entered the oil window no earlier than approximately 13 Ma, at depths of between 4200 and 8800 m. Most simulations encompassing a realistic range of sediment thicknesses and background heat flows show that potential source rocks presently are in the oil window; however, no oil has ever been discovered or produced in the Transylvanian basin.« less

Two-dimensional heat flow apparatus

NASA Astrophysics Data System (ADS)

McDougall, Patrick; Ayars, Eric

2014-06-01

We have created an apparatus to quantitatively measure two-dimensional heat flow in a metal plate using a grid of temperature sensors read by a microcontroller. Real-time temperature data are collected from the microcontroller by a computer for comparison with a computational model of the heat equation. The microcontroller-based sensor array allows previously unavailable levels of precision at very low cost, and the combination of measurement and modeling makes for an excellent apparatus for the advanced undergraduate laboratory course.

Heat transfer and flow characteristics on a gas turbine shroud.

PubMed

Obata, M; Kumada, M; Ijichi, N

2001-05-01

The work described in this paper is an experimental investigation of the heat transfer from the main flow to a turbine shroud surface, which may be applicable to ceramic gas turbines. Three kinds of turbine shrouds are considered with a flat surface, a taper surface and a spiral groove surface opposite to the blades in an axial flow turbine of actual turbo-charger. Heat transfer measurements were performed for the experimental conditions of a uniform heat flux or a uniform wall temperature. The effects of the inlet flow angle, rotational speed, and tip clearance on the heat transfer coefficient were clarified under on- and off-design flow conditions. The mean heat transfer coefficient was correlated to the blade Reynolds number and tip clearance, and compared with an experimental correlation and measurements of a flat surface. A comparison was also made for the measurement of static pressure distributions.

Heat transfer, pressure drop and flow patterns during flow boiling of R407C in a horizontal microfin tube

NASA Astrophysics Data System (ADS)

Rollmann, P.; Spindler, K.; Müller-Steinhagen, H.

2011-08-01

The heat transfer, pressure drop and flow patterns during flow boiling of R407C in a horizontal microfin tube have been investigated. The microfin tube is made of copper with a total fin number of 55 and a helix angle of 15°. The fin height is 0.24 mm and the inner tube diameter at fin root is 8.95 mm. The test tube is 1 m long. It is heated electrically. The experiments have been performed at saturation temperatures between -30°C and +10°C. The mass flux was varied between 25 and 300 kg/m2/s, the heat flux from 20,000 W/m2 down to 1,000 W/m2. The vapour quality was kept constant at 0.1, 0.3, 0.5, 0.7 at the inlet and 0.8, 1.0 at the outlet, respectively. The measured heat transfer coefficient is compared with the correlations of Cavallini et al., Shah as well as Zhang et al. Cavallini's correlation contains seven experimental constants. After fitting these constants to our measured values, the correlation achieves good agreement. The measured pressure drop is compared to the correlations of Pierre, Kuo and Wang as well as Müller-Steinhagen and Heck. The best agreement is achieved with the correlation of Kuo and Wang. Almost all values are calculated within an accuracy of ±30%. The flow regimes were observed. It is shown, that changes in the flow regime affect the heat transfer coefficient significantly.

Wellbore heat flow from the Toa Baja scientific drillhole, Puerto Rico

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

Anderson, R.N.; Larue, D.K.

1991-03-01

Heat flow values, determined from temperature logs and estimates of thermal conductivity from geophysical logs range from 23 to 37 mW/m{sup 2} from 800 to 2,500 m depth in the Toa Baja scientific drillhole on the north, central coast of Puerto Rico. Near the target seismic reflector at the base of the well, an active hydrothermal system was encountered in which heat flow of up to 90 mW/m{sup 2} was found in a mineralized zone beneath a volcanic sill or flow. The heat flow then dropped to 50 mW/m{sub 2} beneath this subhorizontal flow zone. The mining of heat frommore » downdip is proposed to account for this thermal anomaly, as well as the scatter in the heat flow determined from the few other wells drilled into Puerto Rico. The time-temperature history of the well indicates that Eocene volcaniclastics of the lower 2 km were deposited into a geothermal gradient of 60C/km north of an active arc (heat flow estimated to have been 120-180 mW/m{sup 2}). Uplift, erosion and cooling occurred between 40 and 30 Ma. Reburial and deposition of Oligocene-Miocene Limestones produced the present-day geothermal gradient of 15C/km (heat flow of 30-50 mW/m{sup 2}). Based upon comparisons with slab cooling models, the crustal thickness beneath Puerto Rico is estimated to be closer to continental then oceanic.« less

Mixed convection and heat generation/absorption aspects in MHD flow of tangent-hyperbolic nanoliquid with Newtonian heat/mass transfer

NASA Astrophysics Data System (ADS)

Qayyum, Sajid; Hayat, Tasawar; Shehzad, Sabir Ali; Alsaedi, Ahmed

2018-03-01

This article concentrates on the magnetohydrodynamic (MHD) stagnation point flow of tangent hyperbolic nanofluid in the presence of buoyancy forces. Flow analysis caused due to stretching surface. Characteristics of heat transfer are examined under the influence of thermal radiation and heat generation/absorption. Newtonian conditions for heat and mass transfer are employed. Nanofluid model includes Brownian motion and thermophoresis. The governing nonlinear partial differential systems of the problem are transformed into a systems of nonlinear ordinary differential equations through appropriate variables. Impact of embedded parameters on the velocity, temperature and nanoparticle concentration fields are presented graphically. Numerical computations are made to obtain the values of skin friction coefficient, local Nusselt and Sherwood numbers. It is concluded that velocity field enhances in the frame of mixed convection parameter while reverse situation is observed due to power law index. Effect of Brownian motion parameter on the temperature and heat transfer rate is quite reverse. Moreover impact of solutal conjugate parameter on the concentration and local Sherwood number is quite similar.

Heat transfer and flow friction correlations for perforated plate matrix heat exchangers

NASA Astrophysics Data System (ADS)

Ratna Raju, L.; Kumar, S. Sunil; Chowdhury, K.; Nandi, T. K.

2017-02-01

Perforated plate matrix heat exchangers (MHE) are constructed of high conductivity perforated plates stacked alternately with low conductivity spacers. They are being increasingly used in many cryogenic applications including Claude cycle or Reversed Brayton cycle cryo-refrigerators and liquefiers. Design of high NTU (number of (heat) transfer unit) cryogenic MHEs requires accurate heat transfer coefficient and flow friction factor. Thermo-hydraulic behaviour of perforated plates strongly depends on the geometrical parameters. Existing correlations, however, are mostly expressed as functions of Reynolds number only. This causes, for a given configuration, significant variations in coefficients from one correlation to the other. In this paper we present heat transfer and flow friction correlations as functions of all geometrical and other controlling variables. A FluentTM based numerical model has been developed for heat transfer and pressure drop studies over a stack of alternately arranged perforated plates and spacers. The model is validated with the data from literature. Generalized correlations are obtained through regression analysis over a large number of computed data.

Long-lasting Science Returns from the Apollo Heat Flow Experiments

NASA Astrophysics Data System (ADS)

Nagihara, S.; Taylor, P. T.; Williams, D. R.; Zacny, K.; Hedlund, M.; Nakamura, Y.

2012-12-01

The Apollo astronauts deployed geothermal heat flow instruments at landing sites 15 and 17 as part of the Apollo Lunar Surface Experiments Packages (ALSEP) in July 1971 and December 1972, respectively. These instruments continuously transmitted data to the Earth until September 1977. Four decades later, the data from the two Apollo sites remain the only set of in-situ heat flow measurements obtained on an extra-terrestrial body. Researchers continue to extract additional knowledge from this dataset by utilizing new analytical techniques and by synthesizing it with data from more recent lunar orbital missions such as the Lunar Reconnaissance Orbiter. In addition, lessons learned from the Apollo experiments help contemporary researchers in designing heat flow instruments for future missions to the Moon and other planetary bodies. For example, the data from both Apollo sites showed gradual warming trends in the subsurface from 1971 to 1977. The cause of this warming has been debated in recent years. It may have resulted from fluctuation in insolation associated with the 18.6-year-cycle precession of the Moon, or sudden changes in surface thermal environment/properties resulting from the installation of the instruments and the astronauts' activities. These types of re-analyses of the Apollo data have lead a panel of scientists to recommend that a heat flow probe carried on a future lunar mission reach 3 m into the subsurface, ~0.6 m deeper than the depths reached by the Apollo 17 experiment. This presentation describes the authors' current efforts for (1) restoring a part of the Apollo heat flow data that were left unprocessed by the original investigators and (2) designing a compact heat flow instrument for future robotic missions to the Moon. First, at the conclusion of the ALSEP program in 1977, heat flow data obtained at the two Apollo sites after December 1974 were left unprocessed and not properly archived through NASA. In the following decades, heat flow data

Long-Lasting Science Returns from the Apollo Heat Flow Experiments

NASA Technical Reports Server (NTRS)

Nagihara, S.; Taylor, P. T.; Williams, D. R.; Zacny, K.; Hedlund, M.; Nakamura, Y.

2012-01-01

The Apollo astronauts deployed geothermal heat flow instruments at landing sites 15 and 17 as part of the Apollo Lunar Surface Experiments Packages (ALSEP) in July 1971 and December 1972, respectively. These instruments continuously transmitted data to the Earth until September 1977. Four decades later, the data from the two Apollo sites remain the only set of in-situ heat flow measurements obtained on an extra-terrestrial body. Researchers continue to extract additional knowledge from this dataset by utilizing new analytical techniques and by synthesizing it with data from more recent lunar orbital missions such as the Lunar Reconnaissance Orbiter. In addition, lessons learned from the Apollo experiments help contemporary researchers in designing heat flow instruments for future missions to the Moon and other planetary bodies. For example, the data from both Apollo sites showed gradual warming trends in the subsurface from 1971 to 1977. The cause of this warming has been debated in recent years. It may have resulted from fluctuation in insolation associated with the 18.6-year-cycle precession of the Moon, or sudden changes in surface thermal environment/properties resulting from the installation of the instruments and the astronauts' activities. These types of reanalyses of the Apollo data have lead a panel of scientists to recommend that a heat flow probe carried on a future lunar mission reach 3 m into the subsurface, approx 0.6 m deeper than the depths reached by the Apollo 17 experiment. This presentation describes the authors current efforts for (1) restoring a part of the Apollo heat flow data that were left unprocessed by the original investigators and (2) designing a compact heat flow instrument for future robotic missions to the Moon. First, at the conclusion of the ALSEP program in 1977, heat flow data obtained at the two Apollo sites after December 1974 were left unprocessed and not properly archived through NASA. In the following decades, heat flow

MHD heat flux mitigation in hypersonic flow around a blunt body with ablating surface

NASA Astrophysics Data System (ADS)

Bityurin, V. A.; Bocharov, A. N.

2018-07-01

One of the possible applications of magnetohydrodynamic flow control is considered. Namely, the surface heat flux mitigation by means of magnetohydrodynamic (MHD) interaction in hypersonic flow around a blunt body. The 2D computational model realizes a coupled solution of chemically non-equilibrium ionized airflow in magnetic field. Heat- and mass-transfer due to the ablation of materials from the body surface is taken into account. Two cases of free-stream flow conditions are considered: moderate free-stream velocity (7500 m s‑1) case and high free-stream velocity (11 000 m s‑1) case. It is shown that the first flow case results in moderate ionization in the shock layer, while the second flow case results in high ionization. In the first case, the Hall effect is significant, and effective electrical conductivity in the shock layer is rather low. In the second case, the Hall effect reduces, and effective conductivity is high. Even if the Hall effect is strong, as in the first case, intensive MHD deceleration of the flow behind the shock is provided due to the presence of insulating boundaries, the bow shock front and non-conductive wall of the blunt body. In the second case, high effective conductivity provides a high intensity of MHD flow deceleration. In both cases, a strong effect of MHD interaction on the flow structure is observed. As a consequence, a noticeable reduction of the surface heat flux is revealed for reasonable values of magnetic induction. The new treatment of mechanism for the surface heat flux reduction is proposed, which is different from commonly used one assuming that MHD interaction increases the bow shock stand-off distance, and, consequently results in a decrease of the mean temperature drop across the shock layer. The new effect of ‘saturation of heat flux’ is discussed.

Volcanic eruptions on Io: Heat flow, resurfacing, and lava composition

NASA Astrophysics Data System (ADS)

Blaney, Diana L.; Johnson, Torrence V.; Matson, Dennis L.; Veeder, Glenn J.

1995-01-01

We model an infrared outburst on Io as being due to a large, erupting lava flow which increased its area at a rate of 1.5 x 105/sq m and cooled from 1225 to 555 K over the 2.583-hr period of observation. The inferred effusion rate of 3 x 105 cu m/sec for this eruption is very high, but is not unprece- dented on the Earth and is similar to the high eruption rates suggested for early lunar volcanism. Eruptions occur approxi- mately 6% of the time on Io. These eruptions provide ample resurfacing to explain Io's lack of impact craters. We suggest that the large total radiometric heat flow, 1014 W, and the size and temperature distribution of the thermal anomalies (McEwen et al. 1992; Veeder et al. 1994) can be accounted for by a series of silicate lava flows in various stages of cooling. We propose that the whole suite of Io's currently observed thermal anomalies was produced by multiple, high-eruptive-rate silicate flows within the past century.

Volcanic eruptions on Io: Heat flow, resurfacing, and lava composition

NASA Technical Reports Server (NTRS)

Blaney, Diana L.; Johnson, Torrence V.; Matson, Dennis L.; Veeder, Glenn J.

1995-01-01

We model an infrared outburst on Io as being due to a large, erupting lava flow which increased its area at a rate of 1.5 x 10(exp 5)/sq m and cooled from 1225 to 555 K over the 2.583-hr period of observation. The inferred effusion rate of 3 x 10(exp 5) cu m/sec for this eruption is very high, but is not unprece- dented on the Earth and is similar to the high eruption rates suggested for early lunar volcanism. Eruptions occur approxi- mately 6% of the time on Io. These eruptions provide ample resurfacing to explain Io's lack of impact craters. We suggest that the large total radiometric heat flow, 10(exp 14) W, and the size and temperature distribution of the thermal anomalies (McEwen et al. 1992; Veeder et al. 1994) can be accounted for by a series of silicate lava flows in various stages of cooling. We propose that the whole suite of Io's currently observed thermal anomalies was produced by multiple, high-eruptive-rate silicate flows within the past century.

Cryogenic fluid flow instabilities in heat exchangers

NASA Technical Reports Server (NTRS)

Fleming, R. B.; Staub, F. W.

1969-01-01

Analytical and experimental investigation determines the nature of oscillations and instabilities that occur in the flow of two-phase cryogenic fluids at both subcritical and supercritical pressures in heat exchangers. Test results with varying system parameters suggest certain design approaches with regard to heat exchanger geometry.

The heat flow study in the Tertiary Basin of Vietnam offshore

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

Huyen, T.

1994-07-01

In Vietnam, study of heat flow has paralleled petroleum exploration activities. For a long time there had only been results on temperature gradients in the Tertiary basin. Recently, with its participation in CCOP's project on the establishment of heat flow regional maps (1992-1993) and the government's mineral resources program (1993-1995) (Coded KT-01-18), Vietnam Petroleum Institute's group on heat flow obtained results on heat flow. A heat flow study in the oil basinal area in Vietnam has been conducted using data from 76 exploratory wells. Thermal conductivity of 427 cores was measured using the quick thermal conductivity meter (QTM) within temperaturemore » gradients of wells calculated from well log data and from testing data. The average heat flow of sedimentary basins in Vietnam follows: Hanoi graben, 125 Q (mW/m2); north Gulf of Tonkin, 87 Q (mW/m2); south Gulf of Tonkin, 119 Q (mW/m2); Danang Graben, 89 Q (mW/m2); northeast-south Conson, 88 Q (mW/m2); southwest-south Conson, 85 Q (mW/m2); Mekong Basin, 64 Q (mW/m2).« less

Study on Gas-liquid Falling Film Flow in Internal Heat Integrated Distillation Column

NASA Astrophysics Data System (ADS)

Liu, Chong

2017-10-01

Gas-liquid internally heat integrated distillation column falling film flow with nonlinear characteristics, study on gas liquid falling film flow regulation control law, can reduce emissions of the distillation column, and it can improve the quality of products. According to the distribution of gas-liquid mass balance internally heat integrated distillation column independent region, distribution model of heat transfer coefficient of building internal heat integrated distillation tower is obtained liquid distillation falling film flow in the saturated vapour pressure of liquid water balance, using heat transfer equation and energy equation to balance the relationship between the circulating iterative gas-liquid falling film flow area, flow parameter information, at a given temperature, pressure conditions, gas-liquid flow falling film theory makes the optimal parameters to achieve the best fitting value with the measured values. The results show that the geometric gas-liquid internally heat integrated distillation column falling film flow heat exchange area and import column thermostat, the average temperature has significant. The positive correlation between the heat exchanger tube entrance due to temperature difference between inside and outside, the heat flux is larger, with the increase of internal heat integrated distillation column temperature, the slope decreases its temperature rise, which accurately describes the internal gas-liquid heat integrated distillation tower falling film flow regularity, take appropriate measures to promote the enhancement of heat transfer. It can enhance the overall efficiency of the heat exchanger.

Observing the Roots of Coronal Heating - in the Chromosphere

NASA Astrophysics Data System (ADS)

McIntosh, S. W.; de Pontieu, B.; Hansteen, V. H.; Schrjver, K.

2009-12-01

I will discuss recent results using Hinode/SOT-EIS-XRT, SOHO/SUMER, CRISP (at the Swedish Solar Telescope) and TRACE that provide a direct connection between coronal dynamics and those of the lower atmosphere. We use chromospheric measurements (H-alpha and Ca II 8542 spectral imaging, and Ca II H images), as well as UV spectra (EIS and SUMER), and EUV/X-ray images (XRT and TRACE) to show that faint, high-speed upflows at velocities of 50-100 km/s across a wide range of temperatures from chromospheric (10,000 K), through lower and upper transition region (0.1 to 0.7 MK) and coronal temperatures (2 MK) are associated with significant mass-loading of the corona with hot plasma. Our observations are incompatible with current models in which coronal heating occurs as a result of nanoflares at coronal heights. Instead we suggest that a significant fraction of heating of plasma to coronal temperatures may occur at chromospheric heights in association with jets driven from below (the recently discovered type II spicules). Illustrating the mass and energy transport between the chromosphere, transition region and corona, as deduced from Hinode observations. Convective flows and oscillations in the convection zone and photosphere of the Sun buffet the magnetic field of the Sun. This leads to at least two different kinds of jets in the chromosphere: Type I, and II spicules. Type II spicules drive matter upward violently and likely form when magnetic field reconnects because of stresses introduced by convective flows. A significant fraction of the plasma in type II spicules is heated to coronal temperatures (>1MK), providing the corona with hot plasma. The correlation between the chromospheric and coronal parts of the spicules depends greatly on the viewing angle between the line-of-sight and the direction of the upward flows. Order of magnitude estimates indicate that the mass supplied by type II spicules plays a significant role in supplying the corona with hot plasma.

A study of the flow boiling heat transfer in a minichannel for a heated wall with surface texture produced by vibration-assisted laser machining

NASA Astrophysics Data System (ADS)

Piasecka, Magdalena; Strąk, Kinga; Maciejewska, Beata; Grabas, Bogusław

2016-09-01

The paper presents results concerning flow boiling heat transfer in a vertical minichannel with a depth of 1.7 mm and a width of 16 mm. The element responsible for heating FC-72, which flowed laminarly in the minichannel, was a plate with an enhanced surface. Two types of surface textures were considered. Both were produced by vibration-assisted laser machining. Infrared thermography was used to record changes in the temperature on the outer smooth side of the plate. Two-phase flow patterns were observed through a glass pane. The main aim of the study was to analyze how the two types of surface textures affect the heat transfer coefficient. A two-dimensional heat transfer approach was proposed to determine the local values of the heat transfer coefficient. The inverse problem for the heated wall was solved using a semi-analytical method based on the Trefftz functions. The results are presented as relationships between the heat transfer coefficient and the distance along the minichannel length and as boiling curves. The experimental data obtained for the two types of enhanced heated surfaces was compared with the results recorded for the smooth heated surface. The highest local values of the heat transfer coefficient were reported in the saturated boiling region for the plate with the type 1 texture produced by vibration-assisted laser machining.

Thermal heat-balance mode flow-to-frequency converter

NASA Astrophysics Data System (ADS)

Pawlowski, Eligiusz

2016-11-01

This paper presents new type of thermal flow converter with the pulse frequency output. The integrating properties of the temperature sensor have been used, which allowed for realization of pulse frequency modulator with thermal feedback loop, stabilizing temperature of sensor placed in the flowing medium. The system assures balancing of heat amount supplied in impulses to the sensor and heat given up by the sensor in a continuous way to the flowing medium. Therefore the frequency of output impulses is proportional to the heat transfer coefficient from sensor to environment. According to the King's law, the frequency of those impulses is a function of medium flow velocity around the sensor. The special feature of presented solution is total integration of thermal sensor with the measurement signal conditioning system. Sensor and conditioning system are not the separate elements of the measurement circuit, but constitute a whole in form of thermal heat-balance mode flow-to-frequency converter. The advantage of such system is easiness of converting the frequency signal to the digital form, without using any additional analogue-to-digital converters. The frequency signal from the converter may be directly connected to the microprocessor input, which with use of standard built-in counters may convert the frequency into numerical value of high precision. Moreover, the frequency signal has higher resistance to interference than the voltage signal and may be transmitted to remote locations without the information loss.

Experimental study on heat transfer to supercritical water flowing through tubes

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

Zhao, M.; Gu, H.; Cheng, X.

2012-07-01

A test facility named SWAMUP (Supercritical Water Multi-Purpose Loop) has been constructed in Shanghai Jiao Tong Univ. to investigate heat transfer and pressure drop through tubes and rod bundles. SWAMUP is a closed loop with operating pressure up to 30 MPa, outlet-water temperature up to 550 deg. C, and mass flow rate up to 5 t/h. In this paper, experimental study has been carried out on heat transfer of supercritical water flowing vertically through tubes (ID=7.6 and 10 mm). A large number of test points in tubes has been obtained with a wide range of heat flux (200-1500 kw/m{sup 2})more » and mass flux (450-2000 kg/m{sup 2}s). Test results showed that heat transfer deterioration (HTD) caused by buoyancy effect only appears in upward flow and HTD caused by acceleration effect appears both in upward flow and downward flow. The heat transfer coefficients (HTC) produced in tube tests were compared with existing heat transfer correlations. (authors)« less

Experimental and Numerical Analysis of Air Flow, Heat Transfer and Thermal Comfort in Buildings with Different Heating Systems

NASA Astrophysics Data System (ADS)

Sabanskis, A.; Virbulis, J.

2016-04-01

Monitoring of temperature, humidity and air flow velocity is performed in 5 experimental buildings with the inner size of 3×3×3 m3 located in Riga, Latvia. The buildings are equipped with different heating systems, such as an air-air heat pump, air-water heat pump, capillary heating mat on the ceiling and electric heater. Numerical simulation of air flow and heat transfer by convection, conduction and radiation is carried out using OpenFOAM software and compared with experimental data. Results are analysed regarding the temperature and air flow distribution as well as thermal comfort.

Heat Transfer Characteristics of Mixed Electroosmotic and Pressure Driven Micro-Flows

NASA Astrophysics Data System (ADS)

Horiuchi, Keisuke; Dutta, Prashanta

We analyze heat transfer characteristics of steady electroosmotic flows with an arbitrary pressure gradient in two-dimensional straight microchannels considering the effects of Joule heating in electroosmotic pumping. Both the temperature distribution and local Nusselt number are mathematically derived in this study. The thermal analysis takes into consideration of the interaction among advective, diffusive, and Joule heating terms to obtain the thermally developing behavior. Unlike macro-scale pipes, axial conduction in micro-scale cannot be negligible, and the governing energy equation is not separable. Thus, a method that considers an extended Graetz problem is introduced. Analytical results show that the Nusselt number of pure electrooosmotic flow is higher than that of plane Poiseulle flow. Moreover, when the electroosmotic flow and pressure driven flow coexist, it is found that adverse pressure gradient to the electroosmotic flow makes the thermal entrance length smaller and the heat transfer ability stronger than pure electroosmotic flow case.

Two-phase flow patterns of a top heat mode closed loop oscillating heat pipe with check valves (THMCLOHP/CV)

NASA Astrophysics Data System (ADS)

Thongdaeng, S.; Bubphachot, B.; Rittidech, S.

2016-11-01

This research is aimed at studying the two-phase flow pattern of a top heat mode closed loop oscillating heat pipe with check valves. The working fluids used are ethanol and R141b and R11 coolants with a filling ratio of 50% of the total volume. It is found that the maximum heat flux occurs for the R11 coolant used as the working fluid in the case with the inner diameter of 1.8 mm, inclination angle of -90°, evaporator temperature of 125°C, and evaporator length of 50 mm. The internal flow patterns are found to be slug flow/disperse bubble flow/annular flow, slug flow/disperse bubble flow/churn flow, slug flow/bubble flow/annular flow, slug flow/disperse bubble flow, bubble flow/annular flow, and slug flow/annular flow.

Global Atmospheric Heat Distributions Observed from Space

NASA Technical Reports Server (NTRS)

Lin, Bing; Fan, Tai-Fang

2009-01-01

This study focuses on the observations of global atmospheric heat distributions using satellite measurements. Major heat components such as radiation energy, latent heat and sensible heat are considered. The uncertainties and error sources are assessed. Results show that the atmospheric heat is basically balanced, and the observed patterns of radiation and latent heat from precipitation are clearly related to general circulation.

Heat transfer from cylinders in subsonic slip flows

NASA Technical Reports Server (NTRS)

Nagabushana, K. A.; Stainback, P. C.

1992-01-01

The heat transfer in heated wires was measured using a constant temperature anemometer over a Mach number range from 0.05 to 0.4 and pressures from 0.5 to 8.0 atmospheres. The total temperature ranged from 80 to 120 F and the wire diameters were 0.00015, 0.00032, and 0.00050 inch. The heat transfer data is presented in the form of a corrected Nusselt number. Based on suggested criteria, much of the data was obtained in the slip flow regime. Therefore, the data is compared with data having comparable flow conditions. The possible application of the heat transfer data to hot wire anemometry is discussed. To this end, the sensitivity of the wires to velocity, density, and total temperature is computed and compared using two different types of correlations.

Bottom-simulating reflector variability at the Costa Rica subduction zone and corresponding heat flow model

NASA Astrophysics Data System (ADS)

Cavanaugh, S.; Bangs, N. L.; Hornbach, M. J.; McIntosh, K. D.

2011-12-01

We use 3D seismic reflection data acquired in April - May 2011 by the R/V Marcus G. Langseth to extract heat flow information using the bottom-simulating reflector across the Costa Rica convergent margin. These data are part of the CRISP Project, which will image the Middle America subduction zone in 3D. The survey was conducted in an area approximately 55 x 11 km, to the northwest of the Osa Peninsula, Costa Rica. For the analysis presented here, 3D seismic data were processed with Paradigm Focus software through post-stack time migration. The bottom-simulating reflector (BSR)-a reverse polarity reflection indicating the base of the gas hydrate phase boundary-is imaged very clearly in two regions within the slope-cover sediments in the accretionary prism. In deep water environments, the BSR acts as a temperature gauge revealing subsurface temperatures across the margin. We predict BSR depth using a true 3D diffusive heat flow model combined with IODP drilling data and compare results with actual BSR depth observations to determine anomalies in heat flow. Uniform heat flow in the region should result in a deepening BSR downslope toward the trench, however our initial results indicate the BSR shoals near the trench to its shallowest level below sea floor of approximately 96 m below the sea floor, suggesting elevated heat flow towards the toe. Landward, the BSR deepens to about 333 m below the sea floor indicating lower heat flow. Both BSR segments display a trend of deepening landward from the trench, however the depth below the sea floor is greater overall for the landward segment than the segment near the toe. We suggest two regimes with differing heat flow exist across the margin that likely represent two separate fluid flow regimes - one from recently accreted sediments near the prism toe and the other through the older materials making up the prism.

Coherent flow structures and heat transfer in a duct with electromagnetic forcing

NASA Astrophysics Data System (ADS)

Himo, Rawad; Habchi, Charbel

2018-04-01

Coherent vortices are generated electromagnetically in a square duct flow. The vortices are induced by a Lorentz force applied in a small section near the entrance of the duct. The flow structure complexity increases with the electromagnetic forcing since the primary vortices propagating along the duct detach to generate secondary smaller streamwise vortices and hairpin-like structures. The Reynolds number based on the mean flow velocity and hydraulic diameter is 500, and five cases were studied by varying the electromagnetic forcing. Even though this Reynolds number is relatively low, a periodic sequence of hairpin-like structure flow was observed for the high forcing cases. This mechanism enhances the mixing process between the different flow regions resulting in an increase in the thermal performances which reaches 66% relative to the duct flow without forcing. In addition to the flow complexity, lower forcing cases remained steady, unlike high Lorentz forces that induced periodic instabilities with a Strouhal number around 0.59 for the transient eddies. The effect of the flow structure on the heat transfer is analyzed qualitatively and quantitatively using numerical simulations based on the finite volume method. Moreover, proper orthogonal decomposition (POD) analysis was performed on the flow structures to evaluate the most energetic modes contributing in the flow. It is found from the POD analysis that the primary streamwise vortices and hairpin legs are the flow structures that are the most contributing to the heat transfer process.

Turbulence modeling and surface heat transfer in a stagnation flow region

NASA Technical Reports Server (NTRS)

Wang, C. R.; Yeh, F. C.

1987-01-01

Analysis for the turbulent flow field and the effect of freestream turbulence on the surface heat transfer rate of a stagnation flow is presented. The emphasis is on modeling and its augmentation of surface heat transfer rate. The flow field considered is the region near the forward stagnation point of a circular cylinder in a uniform turbulent mean flow.

Heat flow in eastern Egypt - The thermal signature of a continental breakup

NASA Technical Reports Server (NTRS)

Morgan, P.; Boulos, F. K.; Hennin, S. F.; El-Sherif, A. A.; El-Sayed, A. A.

1985-01-01

Data on the heat flow in eastern Egypt were collected to provide information related to the mode and the mechanism of the Red Sea opening. The data indicate a general increase in heat flow towards the Red Sea (75-100 mW/sq m in a zone within 40 km of the coast compared with 35-55 mW/sq m inland). Moderately high heat flow (about 70 mW/sq m) was found for the Gulf of Suez. Heat production data indicate that the coastal thermal anomaly is not primarily related to crustal radiogenic heat production. Possible causes of the anomaly (one of which could be a high mantle heat flow causing a lithospheric thinning centered beneath the Red Sea) are discussed.

Abnormal high surface heat flow caused by the Emeishan mantle plume

NASA Astrophysics Data System (ADS)

Jiang, Qiang; Qiu, Nansheng; Zhu, Chuanqing

2016-04-01

It is commonly believed that increase of heat flow caused by a mantle plume is small and transient. Seafloor heat flow data near the Hawaiian hotspot and the Iceland are comparable to that for oceanic lithosphere elsewhere. Numerical modeling of the thermal effect of the Parana large igneous province shows that the added heat flow at the surface caused by the magmatic underplating is less than 5mW/m2. However, the thermal effect of Emeishan mantle plume (EMP) may cause the surface hear-flow abnormally high. The Middle-Late Emeishan mantle plume is located in the western Yangtze Craton. The Sichuan basin, to the northeast of the EMP, is a superimposed basin composed of Paleozoic marine carbonate rocks and Mesozoic-Cenozoic terrestrial clastic rocks. The vitrinite reflectance (Ro) data as a paleogeothermal indicator records an apparent change of thermal regime of the Sichuan basin. The Ro profiles from boreholes and outcrops which are close to the center of the basalt province exhibit a 'dog-leg' style at the unconformity between the Middle and Upper Permian, and they show significantly higher gradients in the lower subsection (pre-Middle Permian) than the Upper subsection (Upper Permian to Mesozoic). Thermal history inversion based on these Ro data shows that the lower subsection experienced a heat flow peak much higher than that of the upper subsection. The abnormal heat flow in the Sichuan basin is consistent with the EMP in temporal and spatial distribution. The high-temperature magmas from deep mantle brought heat to the base of the lithosphere, and then large amount of heat was conducted upwards, resulting in the abnormal high surface heat flow.

Internal flow patterns on heat transfer characteristics of a closed-loop oscillating heat-pipe with check valves using ethanol and a silver nano-ethanol mixture

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

Bhuwakietkumjohn, N.; Rittidech, S.

The aim of this research was to investigate the internal flow patterns and heat transfer characteristics of a closed-loop oscillating heat-pipe with check valves (CLOHP/CV). The ratio of number of check valves to meandering turns was 0.2. Ethanol and a silver nano-ethanol mixture were used as working fluids with a filling ratio of 50% by total volume of tube. The CLOHP/CV was made of a glass tube with an inside diameter of 2.4 mm. The evaporator section was 50 mm and 100 mm in length and there were 10 meandering turns. An inclination angle of 90 from horizontal axis wasmore » established. The evaporator section was heated by an electric heater and the condenser section was cooled by distilled water. Temperature at the evaporator section was controlled at 85 C, 105 C and 125 C. The inlet and outlet temperatures were measured. A digital camera and video camera were used to observe the flow patterns at the evaporator. The silver nano-ethanol mixture gave higher heat flux than ethanol. When the temperature at the evaporator section was increased from 85 C to 105 C and 125 C. It was found that, the flow patterns occurred as annular flow + slug flow, slug flow + bubble flow and dispersed bubble flow + bubble flow respectively. The main regime of each flow pattern can be determined from the flow pattern map ethanol and a silver nano-ethanol mixture. Each of the two working fluids gave corresponding flow patterns. (author)« less

Heat flow in the flanks of the Oceanographer-Hayes segment of the Mid-Atlantic Ridge

NASA Astrophysics Data System (ADS)

Le Gal, V.; Lucazeau, F.; Cannat, M.; Battani, A.; Poort, J.; Guichet, X.; Monnin, C.; Fontaine, F. J.; Leroy, S. D.

2016-12-01

It is currently estimated that a third of the oceanic heat loss is due to fluid circulation in the oceanic crust. Besides high and low temperature fluid discharge at ridge axis, off-axis low temperature fluid circulations can affect large volumes of the oceanic crust. Long term investigations of the Eastern Juan de Fuca ridge flank (Hutnak et al.2006) have established a circulation pattern where hydrothermal discharge and recharge occur at basement outcrops and where sediment is mostly impermeable. Here, we present results from the recent Oceanograflu cruise (2013), on the Oceanographer-Hayes segment ridge flanks of the Mid-Atlantic ridge in crust 5 and 12 myrs in age. On both flanks, we obtained 185 temperature gradients and conductivities in-situ, 30 Küllenberg cores (3 to 5 meters long) coupled with temperature gradients in-situ and conductivity measurements onboard. These data are interpreted in terms of heat flow values and are generally lower than the conductive cooling model. Several temperature-depth profiles don't show linear gradients, but rather sigmoid shapes or inverse gradients suggesting superficial circulations through the first meters of sediments. The corresponding heat flow pattern is not similar to the one observed at Juan de Fuca. No systematic links have been observed between basement outcrops and lower or higher heat flow which would point to discharge or recharge sites. Instead, the pattern recalls studies in the North Pond area (Langseth et al.1992), with a clear predominance of low heat flow values over the site. We propose that the North Pond circulation model is applicable to large portions of slow-spreading ridge flanks such as the Atlantic. In this model, seawater cools the uppermost crust below sediments in basins that are typically tens of kms wide, reducing the surface heat flow under cooling model values. Based on subsidence rates, these shallow hydrothermal circulations have a minor impact on the cooling of the diverging plates.

Experimental determination of heat transfer in a Poiseuille-Rayleigh-Bénard flow

NASA Astrophysics Data System (ADS)

Taher, R.; Abid, C.

2018-05-01

This paper deals with an experimental study of heat transfer in a Poiseuille-Rayleigh-Bénard flow. This situation corresponds to a mixed convection phenomenon in a horizontal rectangular channel uniformly heated from below. Flow visualisation and temperature measurements were achieved in order to describe the flow regimes and heat transfer behaviour. The classical measurement techniques such employing thermocouples give local measurement on one hand and on other hand they often disturb the flow. As the flow is three-dimensional, these techniques are not efficient. In order to not disturb the flow, a non-intrusive method is used for thermal measurement. The Planar laser Induced Fluorescence (PLIF) was implemented to determine thermal fields in the fluid. Experiments conducted for various Reynolds and Rayleigh numbers allow to determine the heat transfer and thus to propose correlation for Nusselt number for a mixed convection flow in Poiseuille-Rayleigh-Bénard configuration. First a description of the use of this technique in water flow is presented and then the obtained results for various Reynolds and Rayleigh numbers allow to propose a correlation for the Nusselt number for such configuration of mixed convection. The comparison between the obtained heat transfer and the pure forced convection one confirms the well-known result that the convective heat transfer is greatly enhanced in mixed convection. Indeed, secondary flow induced by buoyant forces contributes to the refreshment of thermal boundary layers and so acts like mixers, which significantly enhances heat transfer.

A laser-induced heat flux technique for convective heat transfer measurements in high speed flows

NASA Technical Reports Server (NTRS)

Porro, A. R.; Keith, T. G., Jr.; Hingst, W. R.

1991-01-01

A technique is developed to measure the local convective heat transfer coefficient on a model surface in a supersonic flow field. The technique uses a laser to apply a discrete local heat flux at the model test surface, and an infrared camera system determines the local temperature distribution due to the heating. From this temperature distribution and an analysis of the heating process, a local convective heat transfer coefficient is determined. The technique was used to measure the local surface convective heat transfer coefficient distribution on a flat plate at nominal Mach numbers of 2.5, 3.0, 3.5, and 4.0. The flat plate boundary layer initially was laminar and became transitional in the measurement region. The experimentally determined convective heat transfer coefficients were generally higher than the theoretical predictions for flat plate laminar boundary layers. However, the results indicate that this nonintrusive optical measurement technique has the potential to measure surface convective heat transfer coefficients in high speed flow fields.

Effect of velocity boundary conditions on the heat transfer and flow topology in two-dimensional Rayleigh-Bénard convection.

PubMed

van der Poel, Erwin P; Ostilla-Mónico, Rodolfo; Verzicco, Roberto; Lohse, Detlef

2014-07-01

The effect of various velocity boundary condition is studied in two-dimensional Rayleigh-Bénard convection. Combinations of no-slip, stress-free, and periodic boundary conditions are used on both the sidewalls and the horizontal plates. For the studied Rayleigh numbers Ra between 10(8) and 10(11) the heat transport is lower for Γ=0.33 than for Γ=1 in case of no-slip sidewalls. This is, surprisingly, the opposite for stress-free sidewalls, where the heat transport increases for a lower aspect ratio. In wider cells the aspect-ratio dependence is observed to disappear for Ra ≥ 10(10). Two distinct flow types with very different dynamics can be seen, mostly dependent on the plate velocity boundary condition, namely roll-like flow and zonal flow, which have a substantial effect on the dynamics and heat transport in the system. The predominantly horizontal zonal flow suppresses heat flux and is observed for stress-free and asymmetric plates. Low aspect-ratio periodic sidewall simulations with a no-slip boundary condition on the plates also exhibit zonal flow. In all the other cases, the flow is roll like. In two-dimensional Rayleigh-Bénard convection, the velocity boundary conditions thus have large implications on both roll-like and zonal flow that have to be taken into consideration before the boundary conditions are imposed.

Analysis of counter flow of corona wind for heat transfer enhancement

NASA Astrophysics Data System (ADS)

Shin, Dong Ho; Baek, Soo Hong; Ko, Han Seo

2018-03-01

A heat sink for cooling devices using the counter flow of a corona wind was developed in this study. Detailed information about the numerical investigations of forced convection using the corona wind was presented. The fins of the heat sink using the counter flow of a corona wind were also investigated. The corona wind generator with a wire-to-plate electrode arrangement was used for generating the counter flow to the fin. The compact and simple geometric characteristics of the corona wind generator facilitate the application of the heat sink using the counter flow, demonstrating the heat sink is effective for cooling electronic devices. Parametric studies were performed to analyze the effect of the counter flow on the fins. Also, the velocity and temperature were measured experimentally for the test mock-up of the heat sink with the corona wind generator to verify the numerical results. From a numerical study, the type of fin and its optimal height, length, and pitch were suggested for various heat fluxes. In addition, the correlations to calculate the mass of the developed heat sink and its cooling performance in terms of the heat transfer coefficient were derived. Finally, the cooling efficiencies corresponding to the mass, applied power, total size, and noise of the devices were compared with the existing commercial central processing unit (CPU) cooling devices with rotor fans. As a result, it was confirmed that the heat sink using the counter flow of the corona wind showed appropriate efficiencies for cooling electronic devices, and is a suitable replacement for the existing cooling device for high power electronics.

Heat flow anomalies on the Western Mediterranean margins: first results from the WestMedFlux-2016 cruise

NASA Astrophysics Data System (ADS)

Poort, Jeffrey; Lucazeau, Francis; Le Gal, Virginie; Rabineau, Marina; Dal Cin, Michela; Bouzid, Abderrezak; Palomino, Desirée; Leroux, Estelle; Akhmanov, Grigory; Battani, Anne; Bachir, Roza Si; Khlystov, Oleg; Koptev, Aleksandre

2017-04-01

continent, both strongly reduced and elevated heat flow are observed and suggest other heat sink and sources. We will discuss on the different processes that might have affected the surface heat flow (e.g., bottom water currents, slope instabilities and focused fluid migrations) and try to link the large scale heat flow patterns with crustal nature, structuring of the margins and mantle dynamics.

Heat flow, deep formation temperature and thermal structure of the Tarim Basin, northwest China

NASA Astrophysics Data System (ADS)

Liu, Shaowen; Lei, Xiao; Feng, Changge; Li, Xianglan

2016-04-01

depth are the favorable conditions for hydrocarbon generation and preservation. As far as heat budget of the Tarim Basin is concerned, the radiogenic heat from the sedimentary cover accounts only for 20 percent of the surface heat flow (~9 mW/m2), while the mantle heat flow is estimated to be low as 6~15 mW/m2; this indicates the dominant contribution of crustal radiogenic heat to the observed heat flow. Any variations in surface heat flow for the Tarim Basin can be due only to changes in crustal heat production. Thermal contrast between the Tarim Basin and Tibet Plateau, represented by a difference in surface heat flow and deep crustal temperature, is remarkable. This inherited thermal contrast can be traced as far as before the India-Asia collision. Moreover, the lithosphere beneath the Tarim Basin is sufficiently strong to resist the gravitational potential energy difference and tectonic forces from Tibet. The observed thermal and rheological contrast accounts for the differential Cenozoic deformation in the Tarim Basin and adjacent areas.

Heat-flow measurements at shot points along the 1978 Saudi Arabia seismic deep-refraction line; Part II, Discussion and interpretation

USGS Publications Warehouse

Gettings, M.E.

1982-01-01

The heat-flow profile across the Arabian Shield from Ar Riyad to Ad Darb and across the Red Sea is examined for compatibility with the lithospheric structure of the area as deduced from geologic and other geophysical data. Broad continental uplift associated with Red Sea rifting is symmetric about the Red Sea axis, and geologic and geochronologic evidence indicate that uplift has occurred mainly in the interval 25-13 Ma (mega-annum) ago. Thermal-profile changes in the upper mantle resulting from an influx of hot material associated with rifting yield the correct order of magnitude of uplift, and this mechanism is suggested as the explanation for the regional doming. A lithospheric section, constructed from seismic refraction, gravity, and regional geologic data, provides the framework for construction of thermal models. Thermal gradient measurements were made in drill holes at five shot points. Geotherms for the Shield, which assume a radiogenic heat-source distribution that decreases exponentially with depth, yield temperatures of about 450?C at a depth of 40 km (base of the crust) for shot points 2 (Sabhah) and 3. The geotherm for shot point 4 (near Bishah) yields a distinctly higher temperature (about 580?C) for the same depth. Static models used to model the heat flow in the oceanic crust of the Red Sea shelf and coastal plain either yield too small a heat flow to match the observed heat flow or give lithosphere thicknesses that are so thin as to be improbable. Dynamic (solid-state accretion) models, which account for mantle flow at the base of the lithosphere, adequately match the observed heat-flow values. In the deep-water trough of the Red Sea, which is presently undergoing active sea-floor spreading, classical models of heat flow for a moving slab with accretion at the spreading center are adequate to explain the average heat-flow level. At shot point 5 (Ad Darb), the anomalous heat flow of 2 HFU (heat-flow units) can be explained in terms of a Shield

Hot springs, geochemistry, and regional heat flow of northcentral Mexico

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

Swanberg, C.A.; Marvin, P.R.; Salazar S., L.

1981-10-01

To date we have found, sampled and performed chemical analyses on 21 hot springs (T > 30/sup 0/C), 4 hot wells (T > 30/sup 0/C) and 15 warm springs (T = 25 to 30/sup 0/C) from the states of Chihuahua, Coahuila and Sonora, Mexico. Also in order to establish background chemistry, an additional 250 cold wells and springs (T = 12 to 25/sup 0/C) were sampled and analyzed and several hundred water analyses from the several thousand provided by various Mexican agencies were included. The technique of silica geothermometry was used to estimate the regional heat flow of northcentral Mexico.more » Both the traditional heat flow and the silica heat flow values are generally high and show considerable scatter as is typical of areas having Tertiary and Quaternary volcanic and tectonic activity. Specific areas of high heat flow (> 2.5 HFU) include the Presidio and Los Muertos Bolsons, the Cuidad Chihuahua-Chuatemoc area, the Delicias area, and the area south of the San Bernardino Bolson of southeast Arizona. Areas of lower heat flow (2.0 to 2.5 HFU) include the Jimenez-Camargo region and the area between the Los Muertos and Presidio Bolsons.« less

DSMC simulation of rarefied gas flows under cooling conditions using a new iterative wall heat flux specifying technique

NASA Astrophysics Data System (ADS)

Akhlaghi, H.; Roohi, E.; Myong, R. S.

2012-11-01

Micro/nano geometries with specified wall heat flux are widely encountered in electronic cooling and micro-/nano-fluidic sensors. We introduce a new technique to impose the desired (positive/negative) wall heat flux boundary condition in the DSMC simulations. This technique is based on an iterative progress on the wall temperature magnitude. It is found that the proposed iterative technique has a good numerical performance and could implement both positive and negative values of wall heat flux rates accurately. Using present technique, rarefied gas flow through micro-/nanochannels under specified wall heat flux conditions is simulated and unique behaviors are observed in case of channels with cooling walls. For example, contrary to the heating process, it is observed that cooling of micro/nanochannel walls would result in small variations in the density field. Upstream thermal creep effects in the cooling process decrease the velocity slip despite of the Knudsen number increase along the channel. Similarly, cooling process decreases the curvature of the pressure distribution below the linear incompressible distribution. Our results indicate that flow cooling increases the mass flow rate through the channel, and vice versa.

Attachment-Line Heating in a Compressible Flow

NASA Astrophysics Data System (ADS)

Reed, Helen; Saric, William

2011-11-01

The attachment-line boundary layer on a swept wing can be subject to either an instability or contamination by wing-root turbulence. A model of the attachment-line boundary layer is first developed including compressibility and wall heating in a Falkner-Skan-Cooke class of 3-D boundary layers with Hartree parameter of 1.0. For cases otherwise subcritical to either contamination or instability, the destabilizing effect of leading-edge heating under a variety of sweep angles and flight conditions is demonstrated. The results correlate with the attachment-line Reynolds number. Because the required heating levels are reasonable and achievable to trip the flow over the wing to turbulent, one possible application of this work is in the establishing of a baseline turbulent flow (on demand) for the calibration of a laminar-flow-control health monitoring system. *Portion based on work under Framework Agreement between Airbus Americas and NIA, and opinions, findings, conclusions do not necessarily reflect views of Airbus or NIA. Support from AFOSR/NASA National Center for Hypersonic Research in Laminar-Turbulent Transition through Grant FA9550-09-1-0341 gratefully acknowledged.

Utility of bromide and heat tracers for aquifer characterization affected by highly transient flow conditions

NASA Astrophysics Data System (ADS)

Ma, Rui; Zheng, Chunmiao; Zachara, John M.; Tonkin, Matthew

2012-08-01

A tracer test using both bromide and heat tracers conducted at the Integrated Field Research Challenge site in Hanford 300 Area (300A), Washington, provided an instrument for evaluating the utility of bromide and heat tracers for aquifer characterization. The bromide tracer data were critical to improving the calibration of the flow model complicated by the highly dynamic nature of the flow field. However, most bromide concentrations were obtained from fully screened observation wells, lacking depth-specific resolution for vertical characterization. On the other hand, depth-specific temperature data were relatively simple and inexpensive to acquire. However, temperature-driven fluid density effects influenced heat plume movement. Moreover, the temperature data contained "noise" caused by heating during fluid injection and sampling events. Using the hydraulic conductivity distribution obtained from the calibration of the bromide transport model, the temperature depth profiles and arrival times of temperature peaks simulated by the heat transport model were in reasonable agreement with observations. This suggested that heat can be used as a cost-effective proxy for solute tracers for calibration of the hydraulic conductivity distribution, especially in the vertical direction. However, a heat tracer test must be carefully designed and executed to minimize fluid density effects and sources of noise in temperature data. A sensitivity analysis also revealed that heat transport was most sensitive to hydraulic conductivity and porosity, less sensitive to thermal distribution factor, and least sensitive to thermal dispersion and heat conduction. This indicated that the hydraulic conductivity remains the primary calibration parameter for heat transport.

A Study of Heat Transfer and Flow Characteristics of Rising Taylor Bubbles

NASA Technical Reports Server (NTRS)

Scammell, Alexander David

2016-01-01

Practical application of flow boiling to ground- and space-based thermal management systems hinges on the ability to predict the systems heat removal capabilities under expected operating conditions. Research in this field has shown that the heat transfer coefficient within two-phase heat exchangers can be largely dependent on the experienced flow regime. This finding has inspired an effort to develop mechanistic heat transfer models for each flow pattern which are likely to outperform traditional empirical correlations. As a contribution to the effort, this work aimed to identify the heat transfer mechanisms for the slug flow regime through analysis of individual Taylor bubbles.An experimental apparatus was developed to inject single vapor Taylor bubbles into co-currently flowing liquid HFE 7100. The heat transfer was measured as the bubble rose through a 6 mm inner diameter heated tube using an infrared thermography technique. High-speed flow visualization was obtained and the bubble film thickness measured in an adiabatic section. Experiments were conducted at various liquid mass fluxes (43-200 kgm2s) and gravity levels (0.01g-1.8g) to characterize the effect of bubble drift velocityon the heat transfer mechanisms. Variable gravity testing was conducted during a NASA parabolic flight campaign.Results from the experiments showed that the drift velocity strongly affects the hydrodynamics and heat transfer of single elongated bubbles. At low gravity levels, bubbles exhibited shapes characteristic of capillary flows and the heat transfer enhancement due to the bubble was dominated by conduction through the thin film. At moderate to high gravity, traditional Taylor bubbles provided small values of enhancement within the film, but large peaks in the wake heat transfer occurred due to turbulent vortices induced by the film plunging into the trailing liquid slug. Characteristics of the wake heat transfer profiles were analyzed and related to the predicted velocity field

Observations of single-pass ion cyclotron heating in a trans-sonic flowing plasma

NASA Astrophysics Data System (ADS)

Bering, E. A.; Díaz, F. R. Chang; Squire, J. P.; Glover, T. W.; Carter, M. D.; McCaskill, G. E.; Longmier, B. W.; Brukardt, M. S.; Chancery, W. J.; Jacobson, V. T.

2010-04-01

The VAriable Specific Impulse Magnetoplasma Rocket (VASIMR®) is a high power electric spacecraft propulsion system, capable of Isp/thrust modulation at constant power [F. R. Chang Díaz et al., Proceedings of the 39th AIAA Aerospace Sciences Meeting and Exhibit, Reno, NV, 8-11 Jan. 2001]. The VASIMR® uses a helicon discharge to generate plasma. This plasma is energized by an rf booster stage that uses left hand polarized slow mode waves launched from the high field side of the ion cyclotron resonance. In the experiments reported in this paper, the booster uses 2-4 MHz waves with up to 50 kW of power. This process is similar to the ion cyclotron heating (ICH) in tokamaks, but in the VASIMR® the ions only pass through the resonance region once. The rapid absorption of ion cyclotron waves has been predicted in recent theoretical studies. These theoretical predictions have been supported with several independent measurements in this paper. The single-pass ICH produced a substantial increase in ion velocity. Pitch angle distribution studies showed that this increase took place in the resonance region where the ion cyclotron frequency was roughly equal to the frequency on the injected rf waves. Downstream of the resonance region the perpendicular velocity boost should be converted to axial flow velocity through the conservation of the first adiabatic invariant as the magnetic field decreases in the exhaust region of the VASIMR®. This paper will review all of the single-pass ICH ion acceleration data obtained using deuterium in the first VASIMR® physics demonstrator machine, the VX-50. During these experiments, the available power to the helicon ionization stage increased from 3 to 20+ kW. The increased plasma density produced increased plasma loading of the ICH coupler. Starting with an initial demonstration of single-pass ion cyclotron acceleration, the experiments demonstrate significant improvements in coupler efficiency and in ion heating efficiency. In

Heat flow calorimeter. [measures output of Ni-Cd batteries

NASA Technical Reports Server (NTRS)

Fletcher, J. C.; Johnston, W. V. (Inventor)

1974-01-01

Heat flow calorimeter devices are used to measure heat liberated from or absorbed by an object. This device is capable of measuring the thermal output of sealed nickel-cadmium batteries or cells during charge-discharge cycles. An elongated metal heat conducting rod is coupled between the calorimeter vessel and a heat sink, thus providing the only heat exchange path from the calorimeter vessel itself.

Heat flow and energetics of the San Andreas fault zone.

USGS Publications Warehouse

Lachenbruch, A.H.; Sass, J.H.

1980-01-01

Approximately 100 heat flow measurements in the San Andreas fault zone indicate 1) there is no evidence for local frictional heating of the main fault trace at any latitude over a 1000-km length from Cape Mendocino to San Bernardino, 2) average heat flow is high (ca.2 HFU, ca.80 mW m-2) throughout the 550-km segment of the Coast Ranges that encloses the San Andreas fault zone in central California; this broad anomaly falls off rapidly toward the Great Valley to the east, and over a 200-km distance toward the Mendocino Triple Junction to the northwest. As others have pointed out, a local conductive heat flow anomaly would be detectable unless the frictional resistance allocated to heat production on the main trace were less than 100 bars. Frictional work allocated to surface energy of new fractures is probably unimportant, and hydrologic convection is not likely to invalidate the conduction assumption, since the heat discharge by thermal springs near the fault is negligible. -Authors

Thermally determining flow and/or heat load distribution in parallel paths

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

Chainer, Timothy J.; Iyengar, Madhusudan K.; Parida, Pritish R.

A method including obtaining calibration data for at least one sub-component in a heat transfer assembly, wherein the calibration data comprises at least one indication of coolant flow rate through the sub-component for a given surface temperature delta of the sub-component and a given heat load into said sub-component, determining a measured heat load into the sub-component, determining a measured surface temperature delta of the sub-component, and determining a coolant flow distribution in a first flow path comprising the sub-component from the calibration data according to the measured heat load and the measured surface temperature delta of the sub-component.

Thermally determining flow and/or heat load distribution in parallel paths

DOEpatents

Chainer, Timothy J.; Iyengar, Madhusudan K.; Parida, Pritish R.

2016-12-13

A method including obtaining calibration data for at least one sub-component in a heat transfer assembly, wherein the calibration data comprises at least one indication of coolant flow rate through the sub-component for a given surface temperature delta of the sub-component and a given heat load into said sub-component, determining a measured heat load into the sub-component, determining a measured surface temperature delta of the sub-component, and determining a coolant flow distribution in a first flow path comprising the sub-component from the calibration data according to the measured heat load and the measured surface temperature delta of the sub-component.

Ongoing hydrothermal heat loss from the 1912 ash-flow sheet, Valley of Ten Thousand Smokes, Alaska

USGS Publications Warehouse

Hogeweg, N.; Keith, T.E.C.; Colvard, E.M.; Ingebritsen, S.E.

2005-01-01

The June 1912 eruption of Novarupta filled nearby glacial valleys on the Alaska Peninsula with ash-flow tuff (ignimbrite), and post-eruption observations of thousands of steaming fumaroles led to the name 'Valley of Ten Thousand Smokes' (VTTS). By the late 1980s most fumarolic activity had ceased, but the discovery of thermal springs in mid-valley in 1987 suggested continued cooling of the ash-flow sheet. Data collected at the mid-valley springs between 1987 and 2001 show a statistically significant correlation between maximum observed chloride (Cl) concentration and temperature. These data also show a statistically significant decline in the maximum Cl concentration. The observed variation in stream chemistry across the sheet strongly implies that most solutes, including Cl, originate within the area of the VTTS occupied by the 1912 deposits. Numerous measurements of Cl flux in the Ukak River just below the ash-flow sheet suggest an ongoing heat loss of ???250 MW. This represents one of the largest hydrothermal heat discharges in North America. Other hydrothermal discharges of comparable magnitude are related to heat obtained from silicic magma bodies at depth, and are quasi-steady on a multidecadal time scale. However, the VTTS hydrothermal flux is not obviously related to a magma body and is clearly declining. Available data provide reasonable boundary and initial conditions for simple transient modeling. Both an analytical, conduction-only model and a numerical model predict large rates of heat loss from the sheet 90 years after deposition.

Precursory signals of the 2014-15 Fogo eruption (Cape Verde) detected by surface CO2 emission and heat flow observations

NASA Astrophysics Data System (ADS)

Pérez, Nemesio M.; Dionis, Samara; Fernandes, Paulo; Barrancos, José; Rodríguez, Fátima; Bandomo, Zuleyka; Hernández, Pedro A.; Melián, Gladys V.; Silva, Sónia; Padilla, Germán; Padrón, Eleazar; Cabral, Jeremias; Calvo, David; Asensio-Ramos, María; Pereira, José Manuel; Gonçalves, António A.; Barros, Inocencio; Semedo, Helio

2015-04-01

2010, the diffuse CO2 emission rate was 219 ± 36 t d-1 (Dionis et al., 2015). The second anomalous period started on March 2014, eight months before the 2014-15 Fogo eruption onset, and reached a relatively high value of 337 ± 119 t d-1 on August 30, 2014. It was likely caused by rising of magmatic gases from a second magma intrusion which ended on an eruption. Heat flow temporal evolution during the observation period also shows a quasi-continuous increase before the eruption onset, with the maximum observed heat flow (16.4 ± 3.4 MW) on March 2014. These geochemical and geophysical evidences are clearly precursory signals of the 2014-15 Fogo eruption. Dawson, G.B. (1964), N Z J Geol Geophys 7:155-171; Dionis S. et al. (2015), Bull. Volcanol., in press

Thermal effects of groundwater flow through subarctic fens: A case study based on field observations and numerical modeling

DOE PAGES

Sjöberg, Ylva; Coon, Ethan; K. Sannel, A. Britta; ...

2016-02-04

Modeling and observation of ground temperature dynamics are the main tools for understanding current permafrost thermal regimes and projecting future thaw. Until recently, most studies on permafrost have focused on vertical ground heat fluxes. Groundwater can transport heat in both lateral and vertical directions but its influence on ground temperatures at local scales in permafrost environments is not well understood. In this paper, we combine field observations from a subarctic fen in the sporadic permafrost zone with numerical simulations of coupled water and thermal fluxes. At the Tavvavuoma study site in northern Sweden, ground temperature profiles and groundwater levels weremore » observed in boreholes. These observations were used to set up one- and two-dimensional simulations down to 2 m depth across a gradient of permafrost conditions within and surrounding the fen. Two-dimensional scenarios representing the fen under various hydraulic gradients were developed to quantify the influence of groundwater flow on ground temperature. Our observations suggest that lateral groundwater flow significantly affects ground temperatures. This is corroborated by modeling results that show seasonal ground ice melts 1 month earlier when a lateral groundwater flux is present. Further, although the thermal regime may be dominated by vertically conducted heat fluxes during most of the year, isolated high groundwater flow rate events such as the spring freshet are potentially important for ground temperatures. Finally, as sporadic permafrost environments often contain substantial portions of unfrozen ground with active groundwater flow paths, knowledge of this heat transport mechanism is important for understanding permafrost dynamics in these environments.« less

Flow and heat transfer in a curved channel

NASA Technical Reports Server (NTRS)

Brinich, P. F.; Graham, R. W.

1977-01-01

Flow and heat transfer in a curved channel of aspect ratio 6 and inner- to outer-wall radius ratio 0.96 were studied. Secondary currents and large longitudinal vortices were found. The heat-transfer rates of the outer and inner walls were independently controlled to maintain a constant wall temperature. Heating the inner wall increased the pressure drop along the channel length, whereas heating the outer wall had little effect. Outer-wall heat transfer was as much as 40 percent greater than the straight-channel correlation, and inner-wall heat transfer was 22 percent greater than the straight-channel correlation.

Three-dimensional numerical study of heat transfer enhancement in separated flows

NASA Astrophysics Data System (ADS)

Kumar, Saurav; Vengadesan, S.

2017-11-01

The flow separation appears in a wide range of heat transfer applications and causes poor heat transfer performance. It motivates the study of heat transfer enhancement in laminar as well as turbulent flows over a backward facing step by means of an adiabatic fin mounted on the top wall. Recently, we have studied steady, 2-D numerical simulations in laminar flow and investigated the effect of fin length, location, and orientation. It revealed that the addition of fin causes enhancement of heat transfer and it is very effective to control the flow and thermal behavior. The fin is most effective and sensitive when it is placed exactly above the step. A slight displacement of the fin in upstream of the step causes the complete change of flow and thermal behavior. Based on the obtained 2-D results it is interesting to investigate the side wall effect in three-dimensional simulations. The comparison of two-dimensional and three-dimensional numerical simulations with the available experimental results will be presented. Special attention has to be given to capture unsteadiness in the flow and thermal field.

A review of surface heat-flow data of the northern Middle Atlas (Morocco)

NASA Astrophysics Data System (ADS)

Chiozzi, Paolo; Barkaoui, Alae-Eddine; Rimi, Abdelkrim; Verdoya, Massimo; Zarhloule, Yassine

2017-12-01

We revised thermal data available from water and oil wells in the northern sector of the Middle Atlas region. To avoid biased estimation of surface heat flow caused by advection likely occurring in shallow aquifers, temperature measurements in water boreholes were carefully inspected and selected. The heat flow in the oil wells was inferred by taking into account the porosity variation with depth, the temperature effect on thermal conductivity of the matrix and the pore fluid, together with the contribution of the radiogenic heat production. Moreover, the possible bias in heat flow caused by convection occurring in confined carbonate aquifers was evaluated. The results of heat flow slightly modify the picture reported in previous investigations. The heat flow value over the investigated region is rather uniform (about 80 mW m-2) and is similar in oil wells and in water boreholes. Geothermal calculations indicate that such a surface heat flow is compatible with a ∼70 km thick thermal lithosphere and normal thermal conditions in the asthenospheric mantle.

Impact basin relaxation on Rhea and Iapetus and relation to past heat flow

NASA Astrophysics Data System (ADS)

White, Oliver L.; Schenk, Paul M.; Dombard, Andrew J.

2013-04-01

Evidence for relaxation of impact crater topography has been observed on many icy satellites, including those of Saturn, and the magnitude of relaxation can be related to past heat flow (e.g. Moore, J.M., Schenk, P.M., Bruesch, L.S., Asphaug, E., McKinnon, W.B. [2004]. Icarus 171, 421-443; Dombard, A.J., McKinnon, W.B. [2006]. J. Geophys. Res. 111, E01001. http://dx.doi.org/10.1029/2005JE002445). We use new global digital elevation models of the surfaces of Rhea and Iapetus generated from Cassini data to obtain crater depth/diameter data for both satellites and topographic profiles of large basins on each. In addition to the factor of three lower amplitude of global topography on Rhea compared to Iapetus, we show that basins on Iapetus >100 km in diameter show little relaxation compared to similar sized basins on Rhea. Because of the similar gravities of Rhea and Iapetus, we show that Iapetus basin morphologies can be used to represent the initial, unrelaxed morphologies of the Rhea basins, and we use topographic profiles taken across selected basins to model heat flow on both satellites. We find that Iapetus has only experienced radiogenic heat flow since formation, whereas Rhea must have experienced heat flow reaching a few tens of mW m-2, although this heat flow need only be sustained for as little as several million years in order to achieve the observed relaxation magnitudes. Rhea experienced a different thermal history from Iapetus, which we consider to be primarily related to their different formation mechanisms and locations within the saturnian system. A recent model for the formation of Saturn's mid-sized icy satellites interior to and including Rhea (Charnoz, S. et al. [2011]. Icarus 216, 535-550) describes how Rhea's orbit would have expanded outwards after its accretion from a giant primordial ring, which would have instigated early heating through rapid despinning and tidal interaction with Saturn and other satellites. Rhea's basins would therefore be

Enhanced two phase flow in heat transfer systems

DOEpatents

Tegrotenhuis, Ward E; Humble, Paul H; Lavender, Curt A; Caldwell, Dustin D

2013-12-03

A family of structures and designs for use in devices such as heat exchangers so as to allow for enhanced performance in heat exchangers smaller and lighter weight than other existing devices. These structures provide flow paths for liquid and vapor and are generally open. In some embodiments of the invention, these structures can also provide secondary heat transfer as well. In an evaporate heat exchanger, the inclusion of these structures and devices enhance the heat transfer coefficient of the evaporation phase change process with comparable or lower pressure drop.

Flow reversal and thermal limit in a heated rectangular channel

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

Cheng, L.Y.; Tichler, P.R.; Yang, B.W.

The thermal limit in a vertical rectangular channel was determined in a series of experiments whereby the internal coolant underwent a change in flow direction from forced downflow to upward natural circulation. The tests were designed to simulate the flow reversal transient in the High Flux Beam Reactor. A number of parameters were varied in the flow reversal experiments to examine their effects on the thermal limit. Among the parameters varied were the rate of flow coastdown, inlet subcooling, water level in the upper plenum, bypass ratio (ratio of initial flow through the heated section to initial flow through themore » bypass orifice), and single- verses double-sided heating.« less

Utility of Bromide and Heat Tracers for Aquifer Characterization Affected by Highly Transient Flow Conditions

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

Ma, Rui; Zheng, Chunmiao; Zachara, John M.

A tracer test using both bromide and heat tracers conducted at the Integrated Field Research Challenge site in Hanford 300 Area (300A), Washington, provided an instrument for evaluating the utility of bromide and heat tracers for aquifer characterization. The bromide tracer data were critical to improving the calibration of the flow model complicated by the highly dynamic nature of the flow field. However, most bromide concentrations were obtained from fully screened observation wells, lacking depth-specific resolution for vertical characterization. On the other hand, depth-specific temperature data were relatively simple and inexpensive to acquire. However, temperature-driven fluid density effects influenced heatmore » plume movement. Moreover, the temperature data contained “noise” caused by heating during fluid injection and sampling events. Using the hydraulic conductivity distribution obtained from the calibration of the bromide transport model, the temperature depth profiles and arrival times of temperature peaks simulated by the heat transport model were in reasonable agreement with observations. This suggested that heat can be used as a cost-effective proxy for solute tracers for calibration of the hydraulic conductivity distribution, especially in the vertical direction. However, a heat tracer test must be carefully designed and executed to minimize fluid density effects and sources of noise in temperature data. A sensitivity analysis also revealed that heat transport was most sensitive to hydraulic conductivity and porosity, less sensitive to thermal distribution factor, and least sensitive to thermal dispersion and heat conduction. This indicated that the hydraulic conductivity remains the primary calibration parameter for heat transport.« less

Impact of different thickness of the smooth heated surface on flow boiling heat transfer

NASA Astrophysics Data System (ADS)

Strąk, Kinga; Piasecka, Magdalena

2018-06-01

This paper presents a comparison of the performance of three smooth heated surfaces with different thicknesses. Analysis was carried out on an experimental setup for flow boiling heat transfer. The most important element of the setup was the test section with a rectangular minichannel, 1.7 mm deep, 16 mm wide and 180 mm long, oriented vertically. The heated element for the FC-72 Fluorinert flowing in the minichannel was designated as a Haynes-230 alloy plate (0.10 mm and 0.45 mm thick) or a Hastelloy X alloy plate (0.65 mm thick). Infrared thermography was used to measure the temperature of the outer plate surface. The local values of the heat transfer coefficient for stationary state conditions were calculated using a simple one-dimensional method. The experimental results were presented as the relationship between the heat transfer coefficients in the subcooled boiling region and the distance along the minichannel length and boiling curves. The highest local heat transfer coefficients were recorded for the surface of 0.10 mm thick heated plate at the outlet and 0.45 mm thick plate at the minichannel inlet. All boiling curves were typical in shape.

Experimental Study of Subcooled Flow Boiling Heat Transfer on a Smooth Surface in Short-Term Microgravity

NASA Astrophysics Data System (ADS)

Zhang, Yonghai; Liu, Bin; Zhao, Jianfu; Deng, Yueping; Wei, Jinjia

2018-06-01

The flow boiling heat transfer characteristics of subcooled air-dissolved FC-72 on a smooth surface (chip S) were studied in microgravity by utilizing the drop tower facility in Beijing. The heater, with dimensions of 40 × 10 × 0.5 mm3 (length × width × thickness), was combined with two silicon chips with the dimensions of 20 × 10 × 0.5 mm3. High-speed visualization was used to supplement observation in the heat transfer and vapor-liquid two-phase flow characteristics. In the low and moderate heat fluxes region, the flow boiling of chip S at inlet velocity V = 0.5 m/s shows almost the same regulations as that in pool boiling. All the wall temperatures at different positions along the heater in microgravity are slightly lower than that in normal gravity, which indicates slight heat transfer enhancement. However, in the high heat flux region, the pool boiling of chip S shows much evident deterioration of heat transfer compared with that of flow boiling in microgravity. Moreover, the bubbles of flow boiling in microgravity become larger than that in normal gravity due to the lack of buoyancy Although the difference of the void fraction in x-y plain becomes larger with increasing heat flux under different gravity levels, it shows nearly no effect on heat transfer performance except for critical heat flux (CHF). Once the void fraction in y-z plain at the end of the heater equals 1, the vapor blanket will be formed quickly and transmit from downstream to upstream along the heater, and CHF occurs. Thus, the height of channel is an important parameter to determine CHF in microgravity at a fixed velocity. The flow boiling of chip S at inlet velocity V = 0.5 m/s shows higher CHF than that of pool boiling because of the inertia force, and the CHF under microgravity is about 78-92% of that in normal gravity.

Noxious heat and scratching decrease histamine-induced itch and skin blood flow.

PubMed

Yosipovitch, Gil; Fast, Katharine; Bernhard, Jeffrey D

2005-12-01

The aim of this study was to assess the effect of thermal stimuli or distal scratching on skin blood flow and histamine-induced itch in healthy volunteers. Twenty-one healthy volunteers participated in the study. Baseline measurements of skin blood flow were obtained on the flexor aspect of the forearm. These measurements were compared with skin blood flow after various stimuli: heating the skin, cooling the skin, noxious cold 2 degrees C, noxious heat 49 degrees C, and scratching via a brush with controlled pressure. Afterwards histamine iontophoresis was performed and skin blood flow and itch intensity were measured immediately after the above-mentioned stimuli. Scratching reduced mean histamine-induced skin blood flow and itch intensity. Noxious heat pain increased basal skin blood flow but reduced histamine-induced maximal skin blood flow and itch intensity. Cold pain and cooling reduced itch intensity, but neither affected histamine-induced skin blood flow. Sub-noxious warming the skin did not affect the skin blood flow or itch intensity. These findings suggest that heat pain and scratching may inhibit itch through a neurogenic mechanism that also affects skin blood flow.

A high performance cocurrent-flow heat pipe for heat recovery applications

NASA Technical Reports Server (NTRS)

Saaski, E. W.; Hartl, J. C.

1980-01-01

By the introduction of a plate-and-tube separator assembly into a heat pipe vapor core, it has been demonstrated that axial transport capacity in reflux mode can be improved by up to a factor of 10. This improvement is largely the result of eliminating the countercurrent shear that commonly limits reflux heat pipe axial capacity. With benzene, axial heat fluxes up to 1800 W/sq cm were obtained in the temperature range 40 to 80 C, while heat flux densities up to 3000 W/sq cm were obtained with R-11 over the temperature range 40 to 80 C. These very high axial capacities compare favorably with liquid metal limits; the sonic limit for liquid sodium, for example, is 3000 W/sq cm at 657 C. Computational models developed for these cocurrent flow heat pipes agreed with experimental data within + or - 25%.

Heat Flow Contours and Well Data Around the Milford FORGE Site

DOE Data Explorer

Joe Moore

2016-03-09

This submission contains a shapefile of heat flow contour lines around the FORGE site located in Milford, Utah. The model was interpolated from data points in the Milford_wells shapefile. This heat flow model was interpolated from 66 data points using the kriging method in Geostatistical Analyst tool of ArcGIS. The resulting model was smoothed 100%. The well dataset contains 59 wells from various sources, with lat/long coordinates, temperature, quality, basement depth, and heat flow. This data was used to make models of the specific characteristics.

Simulation of Rocket-Grade Kerosene Flowing in an Electrically Heated Experimental Apparatus

DTIC Science & Technology

2015-07-01

Technical Paper 3. DATES COVERED (From - To) July 2015-July 2015 4. TITLE AND SUBTITLE Simulation of Rocket Kerosene Flowing in an Electrically Heated...rocket-grade kerosene (RP-2) flowing in an electrically heated tube is simulated. The model and boundary conditions are selected so as to simulate an...and Astronautics 1 Simulation of Rocket-Grade Kerosene Flowing in an Electrically Heated Experimental Apparatus Ananda Himansu1 and Matthew C

Lunar Global Heat Flow: Predictions and Constraints

NASA Astrophysics Data System (ADS)

Siegler, M.; Williams, J. P.; Paige, D. A.; Feng, J.

2017-12-01

The global thermal state of the Moon provides fundamental information on its bulk composition and interior evolution. The Moon is known to have a highly asymmetric surface composition [e.g. Lawrence et al., 2003] and crustal thickness [Wieczorek et al.,2012], which is suspected to result from interior asymmetries [Wieczorek and Phillips, 2000; Laneuville et al., 2013]. This is likely to cause a highly asymmetric surface heat flux, both past and present. Our understanding the thermal evolution and composition of the bulk moon therefore requires a global picture of the present lunar thermal state, well beyond our two-point Apollo era measurement. As on the on the Earth, heat flow measurements need to be taken in carefully selected locations to truly characterize the state of the planet's interior. Future surface heat flux and seismic observations will be affected by the presence of interior temperature and crustal radiogenic anomalies, so placement of such instruments is critically important for understanding the lunar interior. The unfortunate coincidence that Apollo geophysical measurements lie areas within or directly abutting the highly radiogenic, anomalously thin-crusted Procellarum region highlights the importance of location for in situ geophysical study [e.g. Siegler and Smrekar, 2014]. Here we present the results of new models of global lunar geothermal heat flux. We synthesize data from several recent missions to constrain lunar crustal composition, thickness and density to provide global predictions of the surface heat flux of the Moon. We also discuss implications from new surface heat flux constraints from the LRO Diviner Lunar Radiometer Experiment and Chang'E 2 Microwave Radiometer. We will identify areas with the highest uncertainty to provide insight on the placement of future landed geophysical missions, such as the proposed Lunar Geophysical Network, to better aim our future exploration of the Moon.

Analysis of Heat Transfer Phenomenon in Magnetohydrodynamic Casson Fluid Flow Through Cattaneo-Christov Heat Diffusion Theory

NASA Astrophysics Data System (ADS)

Ramesh, G. K.; Gireesha, B. J.; Shehzad, S. A.; Abbasi, F. M.

2017-07-01

Heat transport phenomenon of two-dimensional magnetohydrodynamic Casson fluid flow by employing Cattaneo-Christov heat diffusion theory is described in this work. The term of heat absorption/generation is incorporated in the mathematical modeling of present flow problem. The governing mathematical expressions are solved for velocity and temperature profiles using RKF 45 method along with shooting technique. The importance of arising nonlinear quantities namely velocity, temperature, skin-friction and temperature gradient are elaborated via plots. It is explored that the Casson parameter retarded the liquid velocity while it enhances the fluid temperature. Further, we noted that temperature and thickness of temperature boundary layer are weaker in case of Cattaneo-Christov heat diffusion model when matched with the profiles obtained for Fourier’s theory of heat flux.

Control of reactor coolant flow path during reactor decay heat removal

DOEpatents

Hunsbedt, Anstein N.

1988-01-01

An improved reactor vessel auxiliary cooling system for a sodium cooled nuclear reactor is disclosed. The sodium cooled nuclear reactor is of the type having a reactor vessel liner separating the reactor hot pool on the upstream side of an intermediate heat exchanger and the reactor cold pool on the downstream side of the intermediate heat exchanger. The improvement includes a flow path across the reactor vessel liner flow gap which dissipates core heat across the reactor vessel and containment vessel responsive to a casualty including the loss of normal heat removal paths and associated shutdown of the main coolant liquid sodium pumps. In normal operation, the reactor vessel cold pool is inlet to the suction side of coolant liquid sodium pumps, these pumps being of the electromagnetic variety. The pumps discharge through the core into the reactor hot pool and then through an intermediate heat exchanger where the heat generated in the reactor core is discharged. Upon outlet from the heat exchanger, the sodium is returned to the reactor cold pool. The improvement includes placing a jet pump across the reactor vessel liner flow gap, pumping a small flow of liquid sodium from the lower pressure cold pool into the hot pool. The jet pump has a small high pressure driving stream diverted from the high pressure side of the reactor pumps. During normal operation, the jet pumps supplement the normal reactor pressure differential from the lower pressure cold pool to the hot pool. Upon the occurrence of a casualty involving loss of coolant pump pressure, and immediate cooling circuit is established by the back flow of sodium through the jet pumps from the reactor vessel hot pool to the reactor vessel cold pool. The cooling circuit includes flow into the reactor vessel liner flow gap immediate the reactor vessel wall and containment vessel where optimum and immediate discharge of residual reactor heat occurs.

A survey of oscillating flow in Stirling engine heat exchangers

NASA Technical Reports Server (NTRS)

Simon, Terrence W.; Seume, Jorge R.

1988-01-01

Similarity parameters for characterizing the effect of flow oscillation on wall shear stress, viscous dissipation, pressure drop and heat transfer rates are proposed. They are based on physical agruments and are derived by normalizing the governing equations. The literature on oscillating duct flows, regenerator and porous media flows is surveyed. The operating characteristics of the heat exchanger of eleven Stirling engines are discribed in terms of the similarity parameters. Previous experimental and analytical results are discussed in terms of these parameters and used to estimate the nature of the oscillating flow under engine operating conditions. The operating points for many of the modern Stirling engines are in or near the laminar to turbulent transition region. In several engines, working fluid does not pass entirely through heat exchangers during a cycle. Questions that need to be addressed by further research are identified.

­­MMS Observations of a Hot Flow Anomaly in the Magnetosheath

NASA Astrophysics Data System (ADS)

Zhang, H.; Le, G.; Sibeck, D. G.

2017-12-01

Hot flow anomalies (HFAs) are events observed near planetary bow shocks that are characterized by greatly heated solar wind plasmas and substantial flow deflection. HFAs are universal phenomena that have been observed near the bow shock of Earth, Venus, Mars, and Saturn. The dynamic pressure inside HFAs is lower than the ambient solar wind due to the density depletion and flow deflection. The passage of HFAs will therefore result in local negative pressure impulses, which lead to a local sunward expansion of the magnetopause. NASA's MMS mission produce unprecedented high resolution data, which enable the observations of HFA structures in great details. We report MMS observations of an HFA in the post-noon magnetosheath which lasted 25 minutes. Sunward and dawnward plasma flow was observed in the core of the HFA, which is in the opposite direction of the plasma flow in the ambient magnetosheath. The plasma density in the HFA was about one order of magnitude lower than that in the ambient magnetosheath. Two magnetopause crossings were observed inside the HFA. Boundary normal analysis shows the normal direction of the magnetopause was along the GSE Y direction, indicating a strongly deformed magnetopause. The first in, first out crossing sequence of the magnetopause by multiple spacecraft also indicates that the two magnetopause crossings were due to a bulged-out magnetopause rather than the back and forth motion of the magnetopause.

The Mystery of Io's Warm Polar Regions: Implications for Heat Flow

NASA Technical Reports Server (NTRS)

Matson, D. L.; Veeder, G. J.; Johnson, T. V.; Blaney, D. L.; Davies, A. G.

2002-01-01

Unexpectedly warm polar temperatures further support the idea that Io is covered virtually everywhere by cooling lava flows. This implies a new heat flow component. Io's heat flow remains constrained between a lower bound of (approximately) 2.5 W m(exp -2) and an upper bound of (approximately) 13 W m(exp -2). Additional information is contained in the original extended abstract.

Enhanced heat transfer characteristics of viscous liquid flows in a chevron plate heat exchanger

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

Muley, A.; Manglik, R.M.; Metwally, H.M.

1999-11-01

Thermal processing and manufacturing in the chemical, foods, pharmaceutical, hygiene products, and biochemical industries invariably involve heating and cooling of highly viscous fluid media. These fluids tend to flow in the low Reynolds number regime, inherently have relatively low heat transfer coefficients, and are often temperature sensitive and prone to thermal degradation in the presence of large temperature differences. In recent times, plate heat exchangers (PHEs) have found increasing usage in such applications, primarily due to their features that promote enhanced heat transfer, and provide for the flexibility in altering their unit thermal size with ease, close approach temperature operation,more » and mitigation of thermal degradation of the process fluid. Here, steady-state heat transfer and pressure drop data for single-phase viscous fluid flows (2 {le} Re {le} 400) in a single-pass U-type counterflow plate heat exchanger (PHE) with chevron plates are presented. With vegetable oil as test fluid (130 {lt} Pr {lt} 290), three different plate arrangements are employed: two symmetric ({beta} = 30 deg/30 deg and 60 deg/60 deg) and one mixed ({beta} = 30 deg/60 deg). The effects of chevron angle {beta}, corrugation aspect ratio {gamma}, and flow conditions (Re, Pr, {mu}/{mu}{sub w}) on Nu and f characteristics of the PHE are delineated. The results show a rather complex influence of plate surface corrugations on the enhanced thermal-hydraulic behavior. Relative to the performance of equivalent flat-plate packs, chevron plates sustain up to 2.9 times higher heat transfer rates on a fixed geometry and constant pumping power basis, and require up to 48% less surface area for the fixed heat load and pressure drop constraint.« less

Condensation and single-phase heat transfer coefficient and flow regime visualization in microchannel tubes for HFC-134A

NASA Astrophysics Data System (ADS)

Wang, Wei-Wen William

This dissertation is to document experimental, local condensation and single-phase heat transfer and flow data of the minute diameter, microchannel tube and to develop correlation methods for optimizing the design of horizontal-microchannel condensers. It is essential to collect local data as the condensation progresses through several different flow patterns, since as more liquid is formed, the mechanism conducting heat transfer and flow is also changing. Therefore, the identification of the flow pattern is as important as the thermal and dynamic data. The experimental results were compared with correlation and flow regime maps from literature. The experiment using refrigerant HFC-134a in flat, multi-port aluminum tubing with 1.46mm hydraulic diameter was conducted. The characteristic of single-phase friction can be described with the analytical solution of square channel. The Gnielinski correlation provided good prediction of single-phase turbulent flow heat transfer. Higher mass fluxes and qualities resulted in increased condensation heat transfer and were more effective in the shear-dominated annular flow. The effect of temperature gradient from wall to refrigerant attributed profoundly in the gravity-dominated wavy/slug flow. Two correlation based on different flow mechanisms were developed for specified flow regimes. Finally, an asymptotic correlation was successfully proposed to account for the entire data regardless of flow patterns. Data taken from experiment and observations obtained from flow visualization, resulted in a better understanding of the physics in microchannel condensation, optimized designs in the microchannel condensers are now possible.

Heat flow and thermal history of the Anadarko basin, Oklahoma

USGS Publications Warehouse

Carter, L.S.; Kelley, S.A.; Blackwell, D.D.; Naeser, N.D.

1998-01-01

New heat-flow values for seven sites in the Anadarko basin, Oklahoma, were determined using high-precision temperature logs and thermal conductivity measurements from nearly 300 core plugs. Three of the sites are on the northern shelf, three sites are in the deep basin, and one site is in the frontal fault zone of the northern Wichita Mountains. The heat flow decreased from 55 to 64 mW/m2 in the north, and from 39 to 54 mW/m2 in the south, due to a decrease in heat generation in the underlying basement rock toward the south. Lateral lithologic changes in the basin, combined with the change in heat flow across the basin, resulted in an unusual pattern of thermal maturity. The vitrinite reflectance values of the Upper Devonian-Lower Mississippian Woodford formation are highest 30-40 km north-northwest of the deepest part of the basin. The offset in highest reflectance values is due to the contrast in thermal conductivity between the Pennsylvanian "granite wash" section adjacent to the Wichita uplift and the Pennsylvanian shale section to the north. The geothermal gradient in the low-conductivity shale section is elevated relative to the geothermal gradient in the high-conductivity "granite wash" section, thus displacing the highest temperatures to the north of the deepest part of the basin. Apatite fission-track, vitrinite reflectance, and heat-flow data were used to constrain regional aspects of the burial history of the Anadarko basin. By combining these data sets, we infer that at least 1.5 km of denudation has occurred at two sites in the deep Anadarko basin since the early to middle Cenozoic (40 ?? 10 m.y.). The timing of the onset of denudation in the southern Anadarko basin coincides with the period of late Eocene erosion observed in the southern Rocky Mountains and in the northern Great Plains. Burial history models for two wells from the deep Anadarko basin predict that shales of the Woodford formation passed through the hydrocarbon maturity window by the

Cryogenic two-phase flow during chilldown: Flow transition and nucleate boiling heat transfer

NASA Astrophysics Data System (ADS)

Jackson, Jelliffe Kevin

The recent interest in space exploration has placed a renewed focus on rocket propulsion technology. Cryogenic propellants are the preferred fuel for rocket propulsion since they are more energetic and environmentally friendly compared with other storable fuels. Voracious evaporation occurs while transferring these fluids through a pipeline that is initially in thermal equilibrium with the environment. This phenomenon is referred to as line chilldown. Large temperature differences, rapid transients, pressure fluctuations and the transition from the film boiling to the nucleate boiling regime characterize the chilldown process. Although the existence of the chilldown phenomenon has been known for decades, the process is not well understood. Attempts have been made to model the chilldown process; however the results have been fair at best. A major shortcoming of these models is the use of correlations that were developed for steady, non-cryogenic flows. The development of reliable correlations for cryogenic chilldown has been hindered by the lack of experimental data. An experimental facility was constructed that allows the flow structure, the temperature history and the pressure history to be recorded during the line chilldown process. The temperature history is then utilized in conjunction with an inverse heat conduction procedure that was developed, which allows the unsteady heat transfer coefficient on the interior of the pipe wall to be extracted. This database is used to evaluate present predictive models and correlations for flow regime transition and nucleate boiling heat transfer. It is found that by calibrating the transition between the stratified-wavy and the intermittent/annular regimes of the Taitel and Dukler flow regime map, satisfactory predictions are obtained. It is also found that by utilizing a simple model that includes the effect of flow structure and incorporating the enhancement provided by the local heat flux, significant improvement in the

The combined effects of longitudinal heat conduction, flow nonuniformity and temperature nonuniformity in crossflow plate-fin heat exchangers

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

Ranganayakulu, C.; Seetharamu, K.N.

An analysis of a crossflow plate-fin compact heat exchanger, accounting for the combined effects of two-dimensional longitudinal heat conduction through the exchanger wall and nonuniform inlet fluid flow and temperature distribution is carried out using a finite element method. A mathematical equation is developed to generate different types of fluid flow/temperature maldistribution models considering the possible deviations in fluid flow. Using these models, the exchanger effectiveness and its deterioration due to the combined effects of longitudinal heat conduction, flow nonuniformity and temperature nonuniformity are calculated for various design and operating conditions of the exchanger. It was found that the performancemore » variations are quite significant in some typical applications.« less

Is Earth-based scaling a valid procedure for calculating heat flows for Mars?

NASA Astrophysics Data System (ADS)

Ruiz, Javier; Williams, Jean-Pierre; Dohm, James M.; Fernández, Carlos; López, Valle

2013-09-01

Heat flow is a very important parameter for constraining the thermal evolution of a planetary body. Several procedures for calculating heat flows for Mars from geophysical or geological proxies have been used, which are valid for the time when the structures used as indicators were formed. The more common procedures are based on estimates of lithospheric strength (the effective elastic thickness of the lithosphere or the depth to the brittle-ductile transition). On the other hand, several works by Kargel and co-workers have estimated martian heat flows from scaling the present-day terrestrial heat flow to Mars, but the so-obtained values are much higher than those deduced from lithospheric strength. In order to explain the discrepancy, a recent paper by Rodriguez et al. (Rodriguez, J.A.P., Kargel, J.S., Tanaka, K.L., Crown, D.A., Berman, D.C., Fairén, A.G., Baker, V.R., Furfaro, R., Candelaria, P., Sasaki, S. [2011]. Icarus 213, 150-194) criticized the heat flow calculations for ancient Mars presented by Ruiz et al. (Ruiz, J., Williams, J.-P., Dohm, J.M., Fernández, C., López, V. [2009]. Icarus 207, 631-637) and other studies calculating ancient martian heat flows from lithospheric strength estimates, and casted doubts on the validity of the results obtained by these works. Here however we demonstrate that the discrepancy is due to computational and conceptual errors made by Kargel and co-workers, and we conclude that the scaling from terrestrial heat flow values is not a valid procedure for estimating reliable heat flows for Mars.

Active heat pulse sensing of 3-D-flow fields in streambeds

NASA Astrophysics Data System (ADS)

Banks, Eddie W.; Shanafield, Margaret A.; Noorduijn, Saskia; McCallum, James; Lewandowski, Jörg; Batelaan, Okke

2018-03-01

Profiles of temperature time series are commonly used to determine hyporheic flow patterns and hydraulic dynamics in the streambed sediments. Although hyporheic flows are 3-D, past research has focused on determining the magnitude of the vertical flow component and how this varies spatially. This study used a portable 56-sensor, 3-D temperature array with three heat pulse sources to measure the flow direction and magnitude up to 200 mm below the water-sediment interface. Short, 1 min heat pulses were injected at one of the three heat sources and the temperature response was monitored over a period of 30 min. Breakthrough curves from each of the sensors were analysed using a heat transport equation. Parameter estimation and uncertainty analysis was undertaken using the differential evolution adaptive metropolis (DREAM) algorithm, an adaption of the Markov chain Monte Carlo method, to estimate the flux and its orientation. Measurements were conducted in the field and in a sand tank under an extensive range of controlled hydraulic conditions to validate the method. The use of short-duration heat pulses provided a rapid, accurate assessment technique for determining dynamic and multi-directional flow patterns in the hyporheic zone and is a basis for improved understanding of biogeochemical processes at the water-streambed interface.

Understanding heat and groundwater flow through continental flood basalt provinces: insights gained from alternative models of permeability/depth relationships for the Columbia Plateau, USA

USGS Publications Warehouse

Burns, Erick R.; Williams, Colin F.; Ingebritsen, Steven E.; Voss, Clifford I.; Spane, Frank A.; DeAngelo, Jacob

2015-01-01

Heat-flow mapping of the western USA has identified an apparent low-heat-flow anomaly coincident with the Columbia Plateau Regional Aquifer System, a thick sequence of basalt aquifers within the Columbia River Basalt Group (CRBG). A heat and mass transport model (SUTRA) was used to evaluate the potential impact of groundwater flow on heat flow along two different regional groundwater flow paths. Limited in situ permeability (k) data from the CRBG are compatible with a steep permeability decrease (approximately 3.5 orders of magnitude) at 600–900 m depth and approximately 40°C. Numerical simulations incorporating this permeability decrease demonstrate that regional groundwater flow can explain lower-than-expected heat flow in these highly anisotropic (kx/kz ~ 104) continental flood basalts. Simulation results indicate that the abrupt reduction in permeability at approximately 600 m depth results in an equivalently abrupt transition from a shallow region where heat flow is affected by groundwater flow to a deeper region of conduction-dominated heat flow. Most existing heat-flow measurements within the CRBG are from shallower than 600 m depth or near regional groundwater discharge zones, so that heat-flow maps generated using these data are likely influenced by groundwater flow. Substantial k decreases at similar temperatures have also been observed in the volcanic rocks of the adjacent Cascade Range volcanic arc and at Kilauea Volcano, Hawaii, where they result from low-temperature hydrothermal alteration.

Relaxed impact craters on Ganymede: Regional variation and high heat flows

NASA Astrophysics Data System (ADS)

Singer, Kelsi N.; Bland, Michael T.; Schenk, Paul M.; McKinnon, William B.

2018-05-01

Viscously relaxed craters provide a window into the thermal history of Ganymede, a satellite with copious geologic signs of past high heat flows. Here we present measurements of relaxed craters in four regions for which suitable imaging exists: near Anshar Sulcus, Tiamat Sulcus, northern Marius Regio, and Ganymede's south pole. We describe a technique to measure apparent depth, or depth of the crater with respect to the surrounding terrain elevation. Measured relaxation states are compared with results from finite element modeling to constrain heat flow scenarios [see companion paper: Bland et al. (2017)]. The presence of numerous, substantially relaxed craters indicates high heat flows-in excess of 30-40 mW m-2 over 2 Gyr, with many small (<10 km in diameter) relaxed craters indicating even higher heat flows. Crater relaxation states are bimodal for some equatorial regions but not in the region studied near the south pole, which suggests regional variations in Ganymede's thermal history.

Assessment of Aerothermal Heating Augmentation Attributed to Surface Catalysis in High Enthalpy Shock Tunnel Flows

NASA Astrophysics Data System (ADS)

MacLean, M.; Holden, M.

2009-01-01

The effect of gas/surface interaction in making CFD predictions of convective heating has been considered with application to ground tests performed in high enthalpy shock tunnels where additional heating augmentation attributable to surface recombination has been observed for nitrogen, air and carbon dioxide flows. For test articles constructed of stainless steel and aluminum, measurements have been made with several types of heat transfer instrumentation including thin- film, calorimeter, and coaxial thermocouple sensors. These experiments have been modeled by computations made with the high quality, chemically reacting, Navier- Stokes solver, DPLR and the heating results compared. Some typical cases considered include results on an axisymmetric sphere-cone, axisymmetric spherical capsule, spherical capsule at angle of attack, and two- dimensional cylinder. In nitrogen flows, cases considered show a recombination probability on the order of 10-3, which agrees with published data. In many cases in air and CO2, measurements exceeding the predicted level of convective heating have been observed which are consistent with approximately complete recombination (to O2/N2 or CO2) on the surface of the model (sometimes called a super-catalytic wall). It has been recognized that the conclusion that this behavior is tied to an excessively high degree of catalytic efficiency is dependent on the current understanding of the freestream and shock-layer state of the gas.

Wall Area of Influence and Growing Wall Heat Transfer due to Sliding Bubbles in Subcooled Boiling Flow

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

Yoo, Junsoo; Estrada-Perez, Carlos E.; Hassan, Yassin A.

A variety of dynamical features of sliding bubbles and their impact on wall heat transfer were observed at subcooled flow boiling conditions in a vertical square test channel. Among the wide range of parameters observed, we particularly focus in this paper on (i) the sliding bubbles’ effect on wall heat transfer (supplemantry discussion to the authors’ previous work in Yoo et al. (2016a,b)) and (ii) the wall area influenced by sliding bubbles in subcooled boiling flow. At first, this study reveals that the degree of wall heat transfer improvement due to sliding bubbles depended less on the wall superheat conditionmore » as the mass flux increased. Also, the sliding bubble trajectory was found to be one of the critical factors in order to properly describe the wall heat transfer associated with sliding bubbles. In particular, the wall area influenced by sliding bubbles depended strongly on both sliding bubble trajectory and sliding bubble size; the sliding bubble trajectory was also observed to be closely related to the sliding bubble size. Importantly, these results indicate the limitation of current approach in CFD analyses especially for the wall area of bubble influence. In addition, the analyses on the temporal fraction of bubbles’ residence (FR) along the heated wall show that the sliding bubbles typically travel through narrow path with high frequency while the opposite was observed downstream. That is, both FR and sliding bubble trajectory depended substantially on the distance from nucleation site, which is expected to be similar for the quenching heat transfer mode induced by sliding bubbles.« less

MHD boundary layer slip flow and heat transfer of ferrofluid along a stretching cylinder with prescribed heat flux.

PubMed

Qasim, Muhammad; Khan, Zafar Hayat; Khan, Waqar Ahmad; Ali Shah, Inayat

2014-01-01

This study investigates the magnetohydrodynamic (MHD) flow of ferrofluid along a stretching cylinder. The velocity slip and prescribed surface heat flux boundary conditions are employed on the cylinder surface. Water as conventional base fluid containing nanoparticles of magnetite (Fe3O4) is used. Comparison between magnetic (Fe3O4) and non-magnetic (Al2O3) nanoparticles is also made. The governing non-linear partial differential equations are reduced to non-linear ordinary differential equations and then solved numerically using shooting method. Present results are compared with the available data in the limiting cases. The present results are found to be in an excellent agreement. It is observed that with an increase in the magnetic field strength, the percent difference in the heat transfer rate of magnetic nanoparticles with Al2O3 decreases. Surface shear stress and the heat transfer rate at the surface increase as the curvature parameter increases, i.e curvature helps to enhance the heat transfer.

Study of Periodical Flow Heat Transfer in an Internal Combustion Engine

NASA Astrophysics Data System (ADS)

Luo, Xi

In-cylinder heat transfer is one of the most critical physical behaviors which has a direct influence on engine out emission and thermal efficiency for IC engine. In-cylinder wall temperature has to be precisely controlled to achieve high efficiency and low emission. However, this cannot be done without knowing gas-to-wall heat flux. This study reports on the development of a technique suitable for engine in-cylinder surface temperature measurement, as the traditional method is "hard to reach." A laser induced phosphorescence technique was used to study in-cylinder wall temperature effects on engine out unburned hydrocarbons during the engine transitional period (warm up). A linear correlation was found between the cylinder wall surface temperature and the unburned hydrocarbons at mediate and high charge densities. At low charge density, no clear correlation was observed because of miss-fire events. A new auto background correction infrared (IR) diagnostic was developed to measure the instantaneous in-cylinder surface temperature at 0.1 CAD resolution. A numerical mechanism was designed to suppress relatively low-frequency background noise and provide an accurate in-cylinder surface temperature measurements with an error of less than 1.4% inside the IC engine. In addition, a proposed optical coating reduced time delay errors by 50% compared to more conventional thermocouple techniques. A new cycle-averaged Res number was developed for an IC engine to capture the characteristics of engine flow. Comparison and scaling between different engine flow parameters are available by matching the averaged Res number. From experimental results, the engine flow motion was classified as intermittently turbulent, and it is different from the original fully developed turbulent assumption, which has previously been used in almost all engine simulations. The intermittent turbulence could have a great impact on engine heat transfer because of the transitional turbulence effect

Observational Signatures of Coronal Heating Mechanisms

NASA Astrophysics Data System (ADS)

Judge, Philip

1998-11-01

Many mechanisms for heating the corona have been proposed since the problem was identified by Edlen more than 50 years ago. Identifying those that are important is a challenging problem that has so far not been resolved. One thing is clear: based upon a variety of observations, the corona is heated by conversion of magnetic flux into thermal energy. The flux emerges from sub-photospheric layers and is buffeted by photospheric dynamics. The ``coronal heating problem'' is to identify how, given the high conductivities of coronal plasma, the magnetic energy is dissipated. After reviewing some basic observational facts and placing the corona into appropriate physical regimes, I will focus on two pieces of information recently obtained from spacecraft. In one, I will discuss the interpretation of line profiles from the UVCS instrument on the SOHO spacecraft, presented by Kohl and colleagues. These observations indicate the presence of asymmetric particle distribution functions low in the solar wind, so I will discuss implications for heating mechanisms for plasma on these ``open'' field lines, in terms of ion cyclotron resonant heating by high frequency Alfven waves. In the other, I will try to review evidence for the ``nano-flare'' heating mechanism proposed by Parker to explain the heating of plasma along closed field lines, such as are present in active regions, based upon data from the SOHO and TRACE spacecraft. Parker's picture is one of slow field line ``braiding'', driven by random footpoint motions, with sudden energy release at critical energies. An attempt will be made to relate these different mechanisms by looking for the source of the high frequency waves implied by the UVCS observations.

Study on Fins' Effect of Boiling Flow in Millimeter Channel Heat Exchanger

NASA Astrophysics Data System (ADS)

Watanabe, Satoshi

2005-11-01

Recently, a lot of researches about compact heat exchangers with mini-channels have been carried out with the hope of obtaining a high-efficiency heat transfer, due to the higher ratio of surface area than existing heat exchangers. However, there are many uncertain phenomena in fields such as boiling flow in mini-channels. Thus, in order to understand the boiling flow in mini-channels to design high-efficiency heat exchangers, this work focused on the visualization measurement of boiling flow in a millimeter channel. A transparent acrylic channel (heat exchanger form), high-speed camera (2000 fps at 1024 x 1024 pixels), and halogen lamp (backup light) were used as the visualization system. The channel's depth is 2 mm, width is 30 mm, and length is 400 mm. In preparation for commercial use, two types of channels were experimented on: a fins type and a normal slit type (without fins). The fins are circular cylindrical obstacles (diameter is 5 mm) to promote heat transfer, set in a triangular array (distance between each center point is 10 mm). Especially in this work, boiling flow and heat transfer promotion in the millimeter channel heat exchanger with fins was evaluated using a high-speed camera.

Heat Flow Budget of the Gulf of California Rift: Preliminary Results of a High Resolution Survey Across the Wagner Basin

NASA Astrophysics Data System (ADS)

Negrete-Aranda, R.; Neumann, F.; Harris, R. N.; Contreras, J.; Gonzalez-Fernandez, A.; Sclater, J. G.

2016-12-01

The thermal regime exerts a primary control on rift dynamics and mode of extension for continental lithosphere. We present three heat-flow profiles across the southern terminus of the Cerro Prieto fault, in the northern Gulf of California. The longest profile is 42 km and has a measurement spacing of 1 km that spans the hanging-wall block (Wagner basin) and the footwall block of that fault. Measurements were taken with a 6.5 m long Fielax, violin-bow probe. Most measurements are of good quality, i.e., the probe fully penetrated sediments and measurements were stable enough to perform reliable inversion for heat flow and thermal properties. However, it was necessary to perform numerous corrections due to environmental phenomena related the copious sedimentation in the area, and seasonal changes in water temperature. Our measurements indicate the total throughput across the central rift and its east shoulder is 15 KW/m per meter of rift length. More important, heat flow values cluster in three distinct spatial groups: (i) heat flow in the well sedimented depocenter of the Wagner basin is approximately 200 mW/m2; (ii) the footwall block heat-flow is approximately 400 mW/m2; and (iii) heat flow across the fault zone is very high, up to 5,000 mW/m2. Our interpretation is that the former value represents the background conductive heat flow in the rift whereas heat flow across the fault represents advective heat transport by hydrothermal fluids. The high heat flow in the footwall block of the Cerro Prieto fault might be result of both conductive and advective heat transfer by fluid seepage from the basin. These data provide evidence that fluids from deep magma bodies transported along faults assist rifting in the northern Gulf of California. We are exploring how fluids may play a role in weakening the lithosphere and help localizing/delocalizing strain along major transforms and numerous normal faults observed in the area.

Inclusion of heat transfer computations for particle laden flows

NASA Astrophysics Data System (ADS)

Feng, Zhi-Gang; Michaelides, Efstathios E.

2008-04-01

A newly developed direct numerical simulation method has been used to study the dynamics of nonisothermal cylindrical particles in particulate flows. The momentum and energy transfer equations are solved to compute the effects of heat transfer in the sedimentation of particles. Among the effects examined is the drag force on nonisothermal particles, which we found strongly depends on the Reynolds and Grashof numbers. It was observed that heat advection between hotter particles and fluid causes the drag coefficient of particles to significantly increase at relatively low Reynolds numbers. For Grashof number of 100, the drag enhancement effect diminishes when the Reynolds number exceeds 50. On the contrary, heat advection with colder particles reduces the drag coefficient for low and medium Reynolds number (Re<50) for Grashof number of -100. We used this numerical method to study the problem of a pair of hot particles settling in a container at different Grashof numbers. In isothermal cases, such a pair of particles would undergo the well-known drafting-kissing-tumbling (DKT) motion. However, it was observed that the buoyancy currents induced by the hotter particles reverse the DKT motion of the particles or suppress it altogether. Finally, the sedimentation of a circular cluster of 172 particles in an enclosure at two different Grashof numbers was studied and the main features of the results are presented.

Does attenuated skin blood flow lower sweat rate and the critical environmental limit for heat balance during severe heat exposure?

PubMed

Cramer, Matthew N; Gagnon, Daniel; Crandall, Craig G; Jay, Ollie

2017-02-01

What is the central question of this study? Does attenuated skin blood flow diminish sweating and reduce the critical environmental limit for heat balance, which indicates maximal heat loss potential, during severe heat stress? What is the main finding and its importance? Isosmotic hypovolaemia attenuated skin blood flow by ∼20% but did not result in different sweating rates, mean skin temperatures or critical environmental limits for heat balance compared with control and volume-infusion treatments, suggesting that the lower levels of skin blood flow commonly observed in aged and diseased populations may not diminish maximal whole-body heat dissipation. Attenuated skin blood flow (SkBF) is often assumed to impair core temperature (T c ) regulation. Profound pharmacologically induced reductions in SkBF (∼85%) lead to impaired sweating, but whether the smaller attenuations in SkBF (∼20%) more often associated with ageing and certain diseases lead to decrements in sweating and maximal heat loss potential is unknown. Seven healthy men (28 ± 4 years old) completed a 30 min equilibration period at 41°C and a vapour pressure (P a ) of 2.57 kPa followed by incremental steps in P a of 0.17 kPa every 6 min to 5.95 kPa. Differences in heat loss potential were assessed by identifying the critical vapour pressure (P crit ) at which an upward inflection in T c occurred. The following three separate treatments elicited changes in plasma volume to achieve three distinct levels of SkBF: control (CON); diuretic-induced isosmotic dehydration to lower SkBF (DEH); and continuous saline infusion to maintain SkBF (SAL). The T c , mean skin temperature (T sk ), heart rate, mean laser-Doppler flux (forearm and thigh; LDF mean ), mean local sweat rate (forearm and thigh; LSR mean ) and metabolic rate were measured. In DEH, a 14.2 ± 5.7% lower plasma volume resulted in a ∼20% lower LDF mean in perfusion units (PU) (DEH, 139 ± 23 PU; CON, 176 ± 22 PU; and SAL

In-situ shear stress indicator using heated strain gages at the flow boundary

NASA Astrophysics Data System (ADS)

Yeh, Chi-An; Yang, Fuling

2011-11-01

This work borrows the concept of hot-wire anemometry and sketch a technique that uses local heat transfer to infer the flow field and the corresponding stress. Conventional strain gages were mounted at the flow solid boundary as the heat source and acrylic boundary was chosen for its low thermal conductivity ensuring heat accumulation when a gage is energized. The gage would now work in slightly overheated state and its self-heating leads to an additional thermal strain. When exposed to a flow field, heat is brought away by local forced convection, resulting in deviations in gage signal from that developed in quiescent liquid. We have developed a facility to achieve synchronous gage measurements at different locations on a solid boundary. Three steady flow motions were considered: circular Couette flow, rectilinear uniform flow, and rectilinear oscillating flow. Preliminary tests show the gage reading does respond to the imposed flow through thermal effects and greater deviation was measured in flows of higher shear strain rates. The correlation between the gage signals and the imposed flow field is further examined by theoretical analysis. We also introduced a second solid boundary to the vicinity of the gage in the two rectilinear flows. The gage readings demonstrate rises in its magnitudes indicating wall amplification effect on the local shear strain, agreeing to the drag augmentation by a second solid boundary reported in many multiphase flow literatures.

Stirling Engine With Radial Flow Heat Exchangers

NASA Technical Reports Server (NTRS)

Vitale, N.; Yarr, George

1993-01-01

Conflict between thermodynamical and structural requirements resolved. In Stirling engine of new cylindrical configuration, regenerator and acceptor and rejector heat exchangers channel flow of working gas in radial direction. Isotherms in regenerator ideally concentric cylinders, and gradient of temperature across regenerator radial rather than axial. Acceptor and rejector heat exchangers located radially inward and outward of regenerator, respectively. Enables substantial increase in power of engine without corresponding increase in diameter of pressure vessel.

Heat transfer in turbulent magneto-fluid-mechanic pipe flow

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

Andelman, M.P.

1975-12-01

The ability to predict heat transfer in Magneto-Fluid-Mechanic flow is of importance in light of the development of MHD generators and the proposed development of thermonuclear reactors. In both cases heat transfer from (or to) a conducting fluid in the presence of a magnetic field plays an important part in the overall economics of the system. A semi-empirical analytical method is given for obtaining heat transfer coefficients in turbulent liquid metal pipe flow in the presence of a magnetic field aligned to the flow. The analysis was based on the Lykoudis turbulent transport model with the influence of a longitudinalmore » magnetic field included. The results are shown to be in agreement with available experimental values. Experimental velocity profiles in mercury for pipe flow in a transverse magnetic field were made at a Reynolds number of 315,000; for Hartmann numbers of 0, 92, 184, 369, and 1198; and at orientations of 0 degrees, 45 degrees, and 90 degrees from the magnetic field. These results provide a basis for the determination of the effect of a transverse magnetic field on turbulent diffusivities.« less

Computer code for predicting coolant flow and heat transfer in turbomachinery

NASA Technical Reports Server (NTRS)

Meitner, Peter L.

1990-01-01

A computer code was developed to analyze any turbomachinery coolant flow path geometry that consist of a single flow passage with a unique inlet and exit. Flow can be bled off for tip-cap impingement cooling, and a flow bypass can be specified in which coolant flow is taken off at one point in the flow channel and reintroduced at a point farther downstream in the same channel. The user may either choose the coolant flow rate or let the program determine the flow rate from specified inlet and exit conditions. The computer code integrates the 1-D momentum and energy equations along a defined flow path and calculates the coolant's flow rate, temperature, pressure, and velocity and the heat transfer coefficients along the passage. The equations account for area change, mass addition or subtraction, pumping, friction, and heat transfer.

Crustal heat production and estimate of terrestrial heat flow in central East Antarctica, with implications for thermal input to the East Antarctic ice sheet

NASA Astrophysics Data System (ADS)

Goodge, John W.

2018-02-01

Terrestrial heat flow is a critical first-order factor governing the thermal condition and, therefore, mechanical stability of Antarctic ice sheets, yet heat flow across Antarctica is poorly known. Previous estimates of terrestrial heat flow in East Antarctica come from inversion of seismic and magnetic geophysical data, by modeling temperature profiles in ice boreholes, and by calculation from heat production values reported for exposed bedrock. Although accurate estimates of surface heat flow are important as an input parameter for ice-sheet growth and stability models, there are no direct measurements of terrestrial heat flow in East Antarctica coupled to either subglacial sediment or bedrock. As has been done with bedrock exposed along coastal margins and in rare inland outcrops, valuable estimates of heat flow in central East Antarctica can be extrapolated from heat production determined by the geochemical composition of glacial rock clasts eroded from the continental interior. In this study, U, Th, and K concentrations in a suite of Proterozoic (1.2-2.0 Ga) granitoids sourced within the Byrd and Nimrod glacial drainages of central East Antarctica indicate average upper crustal heat production (Ho) of about 2.6 ± 1.9 µW m-3. Assuming typical mantle and lower crustal heat flux for stable continental shields, and a length scale for the distribution of heat production in the upper crust, the heat production values determined for individual samples yield estimates of surface heat flow (qo) ranging from 33 to 84 mW m-2 and an average of 48.0 ± 13.6 mW m-2. Estimates of heat production obtained for this suite of glacially sourced granitoids therefore indicate that the interior of the East Antarctic ice sheet is underlain in part by Proterozoic continental lithosphere with an average surface heat flow, providing constraints on both geodynamic history and ice-sheet stability. The ages and geothermal characteristics of the granites indicate that crust in central

Large-Eddy Simulation of Flow and Pollutant Transport in Urban Street Canyons with Ground Heating

NASA Astrophysics Data System (ADS)

Li, Xian-Xiang; Britter, Rex E.; Koh, Tieh Yong; Norford, Leslie K.; Liu, Chun-Ho; Entekhabi, Dara; Leung, Dennis Y. C.

2010-11-01

Our study employed large-eddy simulation (LES) based on a one-equation subgrid-scale model to investigate the flow field and pollutant dispersion characteristics inside urban street canyons. Unstable thermal stratification was produced by heating the ground of the street canyon. Using the Boussinesq approximation, thermal buoyancy forces were taken into account in both the Navier-Stokes equations and the transport equation for subgrid-scale turbulent kinetic energy (TKE). The LESs were validated against experimental data obtained in wind-tunnel studies before the model was applied to study the detailed turbulence, temperature, and pollutant dispersion characteristics in the street canyon of aspect ratio 1. The effects of different Richardson numbers ( Ri) were investigated. The ground heating significantly enhanced mean flow, turbulence, and pollutant flux inside the street canyon, but weakened the shear at the roof level. The mean flow was observed to be no longer isolated from the free stream and fresh air could be entrained into the street canyon at the roof-level leeward corner. Weighed against higher temperature, the ground heating facilitated pollutant removal from the street canyon.

Oscillating flow loss test results in Stirling engine heat exchangers

NASA Technical Reports Server (NTRS)

Koester, G.; Howell, S.; Wood, G.; Miller, E.; Gedeon, D.

1990-01-01

The results are presented for a test program designed to generate a database of oscillating flow loss information that is applicable to Stirling engine heat exchangers. The tests were performed on heater/cooler tubes of various lengths and entrance/exit configurations, on stacked and sintered screen regenerators of various wire diameters and on Brunswick and Metex random fiber regenerators. The test results were performed over a range of oscillating flow parameters consistent with Stirling engine heat exchanger experience. The tests were performed on the Sunpower oscillating flow loss rig which is based on a variable stroke and variable frequency linear drive motor. In general, the results are presented by comparing the measured oscillating flow losses to the calculated flow losses. The calculated losses are based on the cycle integration of steady flow friction factors and entrance/exit loss coefficients.

Effect of jet-mainstream velocity ratio on flow characteristics and heat transfer enhancement of jet on flat plate flow

NASA Astrophysics Data System (ADS)

Puzu, N.; Prasertsan, S.; Nuntadusit, C.

2017-09-01

The aim of this research was to study the effect of jet-mainstream velocity ratio on flow and heat transfer characteristics of jet on flat plate flow. The jet from pipe nozzle with inner diameter of D=14 mm was injected perpendicularly to mainstream on flat plate. The flat plate was blown by mainstream with uniform velocity profile at 10 m/s. The velocity ratio (jet to mainstream velociy) was varied at VR=0.25 and 3.5 by adjusting velocity of jet flow. For heat transfer measurement, a thin foil technique was used to evaluate the heat transfer coefficient by measuring temperature distributions on heat transfer surface with constant heat flux by using infrared camera. Flow characteristics were simulated by using a computational fluid dynamics (CFD) with commercial software ANSYS Fluent (Ver.15.0). The results showed that the enhancement of heat transfer along downstream direction for the case of VR=0.25 was from the effect of jet stream whereas for the case of VR=3.5 was from the effect of mainstream.

Void fraction distribution in a heated rod bundle under flow stagnation conditions

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

Herrero, V.A.; Guido-Lavalle, G.; Clausse, A.

1995-09-01

An experimental study was performed to determine the axial void fraction distribution along a heated rod bundle under flow stagnation conditions. The development of the flow pattern was investigated for different heat flow rates. It was found that in general the void fraction is overestimated by the Zuber & Findlay model while the Chexal-Lellouche correlation produces a better prediction.

A mechanistic model of heat transfer for gas-liquid flow in vertical wellbore annuli.

PubMed

Yin, Bang-Tang; Li, Xiang-Fang; Liu, Gang

2018-01-01

The most prominent aspect of multiphase flow is the variation in the physical distribution of the phases in the flow conduit known as the flow pattern. Several different flow patterns can exist under different flow conditions which have significant effects on liquid holdup, pressure gradient and heat transfer. Gas-liquid two-phase flow in an annulus can be found in a variety of practical situations. In high rate oil and gas production, it may be beneficial to flow fluids vertically through the annulus configuration between well tubing and casing. The flow patterns in annuli are different from pipe flow. There are both casing and tubing liquid films in slug flow and annular flow in the annulus. Multiphase heat transfer depends on the hydrodynamic behavior of the flow. There are very limited research results that can be found in the open literature for multiphase heat transfer in wellbore annuli. A mechanistic model of multiphase heat transfer is developed for different flow patterns of upward gas-liquid flow in vertical annuli. The required local flow parameters are predicted by use of the hydraulic model of steady-state multiphase flow in wellbore annuli recently developed by Yin et al. The modified heat-transfer model for single gas or liquid flow is verified by comparison with Manabe's experimental results. For different flow patterns, it is compared with modified unified Zhang et al. model based on representative diameters.

Flow and Heat Transfer in a Newtonian Nanoliquid due to a Curved Stretching Sheet

NASA Astrophysics Data System (ADS)

Siddheshwar, Pradeep Ganapathi; Nerolu, Meenakshi; Pažanin, Igor

2017-08-01

Flow of a Newtonian nanoliquid due to a curved stretching sheet and heat transfer in it is studied. The governing nonlinear partial differential equations are reduced to nonlinear ordinary differential equations with variable coefficients by using a similarity transformation. The flow characteristics are studied using plots of flow velocity components and the skin-friction coefficient as a function of suction-injection parameter, curvature, and volume fraction. Prescribed surface temperature and prescribed surface heat flux are considered for studying the temperature distribution in the flow. The thermophysical properties of 20 nanoliquids are considered in the investigation by modeling them through the use of phenomenological laws and mixture theory. The results of the corresponding problem involving a plane stretching sheet is obtained as a particular case of those obtained in the present paper. Skin friction coefficient and Nusselt number are evaluated and it is observed that skin friction coefficient decreases with concentration of nanoparticles in the absence as well as presence of suction where as Nusselt number increases with increase in concentration of nanoparticles in a dilute range.

Heat flow and geothermal potential of the East Mesa KGRA, Imperial Valley, California

NASA Technical Reports Server (NTRS)

Swanberg, C. A.

1974-01-01

The East Mesa KGRA (Known Geothermal Resource Area) is located in the southeast part of the Imperial Valley, California, and is roughly 150 kilometers square in areal extent. A new heat flow technique which utilizes temperature gradient measurements across best clays is presented and shown to be as accurate as conventional methods for the present study area. Utilizing the best clay gradient technique, over 70 heat flow determinations have been completed within and around the East Mesa KGRA. Background heat flow values range from 1.4 to 2.4 hfu (1 hfu = .000001 cal. per square centimeter-second) and are typical of those throughout the Basin and Range province. Heat flow values for the northwest lobe of the KGRA (Mesa anomaly) are as high as 7.9 hfu, with the highest values located near gravity and seismic noise maxima and electrical resistivity minima. An excellent correlation exists between heat flow contours and faults defined by remote sensing and microearthquake monitoring.

Incorporation of Condensation Heat Transfer in a Flow Network Code

NASA Technical Reports Server (NTRS)

Anthony, Miranda; Majumdar, Alok; McConnaughey, Paul K. (Technical Monitor)

2001-01-01

In this paper we have investigated the condensation of water vapor in a short tube. A numerical model of condensation heat transfer was incorporated in a flow network code. The flow network code that we have used in this paper is Generalized Fluid System Simulation Program (GFSSP). GFSSP is a finite volume based flow network code. Four different condensation models were presented in the paper. Soliman's correlation has been found to be the most stable in low flow rates which is of particular interest in this application. Another highlight of this investigation is conjugate or coupled heat transfer between solid or fluid. This work was done in support of NASA's International Space Station program.

Periodic unsteady effects on turbulent boundary layer transport and heat transfer: An experimental investigation in a cylinder-wall junction flow

NASA Astrophysics Data System (ADS)

Xie, Qi

Heat transfer in a turbulent boundary layer downstream of junction with a cylinder has many engineering applications including controlling heat transfer to the endwall in gas turbine passages and cooling of protruding electronic chips. The main objective of this research is to study the fundamental process of heat transport and wall heat transfer in a turbulent three-dimensional flow superimposed with local large-scale periodic unsteadiness generated by vortex shedding from the cylinder. Direct measurements of the Reynolds heat fluxes (/line{utheta},\\ /line{vtheta}\\ and\\ /line{wtheta}) and time-resolved wall heat transfer rate will provide insight into unsteady flow behavior and data for advanced turbulence models for numerical simulation of complex engineering flows. Experiments were conducted in an open-circuit, low-speed wind tunnel. Reynolds stresses and heat fluxes were obtained from turbulent heat-flux probes which consisted of two hot wires, arranged in an X-wire configuration, and a cold wire located in front of the X-wire. Thin-film surface heat flux sensors were designed for measuring time-resolved wall heat flux. A reference probe and conditional-sampling technique connected the flow field dynamics to wall heat transfer. An event detecting and ensemble-averaging method was developed to separate effects of unsteadiness from those of background turbulence. Results indicate that unsteadiness affects both heat transport and wall heat transfer. The flow behind the cylinder can be characterized by three regions: (1) Wake region, where unsteadiness is observed to have modest effect; (2) Unsteady region, where the strongest unsteadiness effect is found; (3) Outer region, where the flow approaches the two-dimensional boundary-layer behavior. Vortex shedding from both sides of the cylinder contributes to mixing enhancement in the wake region. Unsteadiness contributes up to 51% of vertical and 59% of spanwise turbulent heat fluxes in the unsteady region. The

Heat flow diagnostics for helicon plasmas.

PubMed

Berisford, Daniel F; Bengtson, Roger D; Raja, Laxminarayan L; Cassady, Leonard D; Chancery, William J

2008-10-01

We present experimental studies of power balance in an argon helicon discharge. An infrared camera measures the heating of the dielectric tube containing a helicon discharge based on measurement of temperature profiles of the tube surface before and after a rf pulse. Using this diagnostic, we have measured surface heating trends at a variety of operating conditions on two helicon systems: the 10 kW VASIMR VX-50 experiment and the University of Texas at Austin 1 kW helicon experiment. Power losses downstream from the antenna are measured using thermocouples and probes. The heating of the dielectric tube increases with decreasing magnetic fields, higher gas flow rates, and higher molecular mass of the gas. These preliminary results suggest that cross-field particle diffusion contributes a significant proportion of the energy flux to the wall.

Analytical skin friction and heat transfer formula for compressible internal flows

NASA Technical Reports Server (NTRS)

Dechant, Lawrence J.; Tattar, Marc J.

1994-01-01

An analytic, closed-form friction formula for turbulent, internal, compressible, fully developed flow was derived by extending the incompressible law-of-the-wall relation to compressible cases. The model is capable of analyzing heat transfer as a function of constant surface temperatures and surface roughness as well as analyzing adiabatic conditions. The formula reduces to Prandtl's law of friction for adiabatic, smooth, axisymmetric flow. In addition, the formula reduces to the Colebrook equation for incompressible, adiabatic, axisymmetric flow with various roughnesses. Comparisons with available experiments show that the model averages roughly 12.5 percent error for adiabatic flow and 18.5 percent error for flow involving heat transfer.

Evaluation of correlations of flow boiling heat transfer of R22 in horizontal channels.

PubMed

Zhou, Zhanru; Fang, Xiande; Li, Dingkun

2013-01-01

The calculation of two-phase flow boiling heat transfer of R22 in channels is required in a variety of applications, such as chemical process cooling systems, refrigeration, and air conditioning. A number of correlations for flow boiling heat transfer in channels have been proposed. This work evaluates the existing correlations for flow boiling heat transfer coefficient with 1669 experimental data points of flow boiling heat transfer of R22 collected from 18 published papers. The top two correlations for R22 are those of Liu and Winterton (1991) and Fang (2013), with the mean absolute deviation of 32.7% and 32.8%, respectively. More studies should be carried out to develop better ones. Effects of channel dimension and vapor quality on heat transfer are analyzed, and the results provide valuable information for further research in the correlation of two-phase flow boiling heat transfer of R22 in channels.

Effect of Cattaneo-Christov heat flux on Jeffrey fluid flow with variable thermal conductivity

NASA Astrophysics Data System (ADS)

Hayat, Tasawar; Javed, Mehwish; Imtiaz, Maria; Alsaedi, Ahmed

2018-03-01

This paper presents the study of Jeffrey fluid flow by a rotating disk with variable thickness. Energy equation is constructed by using Cattaneo-Christov heat flux model with variable thermal conductivity. A system of equations governing the model is obtained by applying boundary layer approximation. Resulting nonlinear partial differential system is transformed to ordinary differential system. Homotopy concept leads to the convergent solutions development. Graphical analysis for velocities and temperature is made to examine the influence of different involved parameters. Thermal relaxation time parameter signifies that temperature for Fourier's heat law is more than Cattaneo-Christov heat flux. A constitutional analysis is made for skin friction coefficient and heat transfer rate. Effects of Prandtl number on temperature distribution and heat transfer rate are scrutinized. It is observed that larger Reynolds number gives illustrious temperature distribution.

Heat transfer and oil flow studies on a single-stage-to-orbit control-configured winged entry vehicle

NASA Technical Reports Server (NTRS)

Helms, V. T., III; Bradley, P. F.

1984-01-01

Results are presented for oil flow and phase change paint heat transfer tests conducted on a 0.006 scale model of a proposed single stage to orbit control configured vehicle. The data were taken at angles of attack up to 40 deg at a free stream Mach number of 10 for Reynolds numbers based on model length of 0.5 x 10 to the 6th power, 1.0 x 10 to the 6th power and 2.0 x 10 to the 6th power. The magnitude and distribution of heating are characterized in terms of angle of attack and Reynolds number aided by an analysis of the flow data which are used to suggest the presence of various three dimensional flow structures that produce the observed heating patterns. Of particular interest are streak heating patterns that result in high localized heat transfer rates on the wing windward surface at low to moderate angles of attack. These streaks are caused by the bow-shock/wing-shock interaction and formation of the wing-shock. Embedded vorticity was found to be associated with these interactions.

Heating and dynamics of two flare loop systems observed by AIA and EIS

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

Li, Y.; Ding, M. D.; Qiu, J., E-mail: yingli@nju.edu.cn

2014-02-01

We investigate heating and evolution of flare loops in a C4.7 two-ribbon flare on 2011 February 13. From Solar Dynamics Observatory/Atmospheric Imaging Assembly (AIA) imaging observations, we can identify two sets of loops. Hinode/EUV Imaging Spectrometer (EIS) spectroscopic observations reveal blueshifts at the feet of both sets of loops. The evolution and dynamics of the two sets are quite different. The first set of loops exhibits blueshifts for about 25 minutes followed by redshifts, while the second set shows stronger blueshifts, which are maintained for about one hour. The UV 1600 observation by AIA also shows that the feet ofmore » the second set of loops brighten twice. These suggest that continuous heating may be present in the second set of loops. We use spatially resolved UV light curves to infer heating rates in the few tens of individual loops comprising the two loop systems. With these heating rates, we then compute plasma evolution in these loops with the 'enthalpy-based thermal evolution of loops' model. The results show that, for the first set of loops, the synthetic EUV light curves from the model compare favorably with the observed light curves in six AIA channels and eight EIS spectral lines, and the computed mean enthalpy flow velocities also agree with the Doppler shift measurements by EIS. For the second set of loops modeled with twice-heating, there are some discrepancies between modeled and observed EUV light curves in low-temperature bands, and the model does not fully produce the prolonged blueshift signatures as observed. We discuss possible causes for the discrepancies.« less

Modeling studies for a Mars penetrator heat flow measurement

NASA Technical Reports Server (NTRS)

Keihm, S. J.; Langseth, M. G.

1976-01-01

There were, two different design concepts considered for the purpose of measuring heat flow as part of a Mars penetrator mission. The first of the tentative designs utilizes temperature sensors emplaced along the trailing umbilicus at regularly spaced intervals, no greater than 1m, which is thermally coupled to the adjacent regolith radiatively and possibly convectively or conductively. The second of the heat flow designs considered requires the radial deployment of two or more low thermal mass temperature sensors outward from the penetrator body over a vertical (depth) range on the order of 1m.

Observational Signatures of Coronal Heating

NASA Astrophysics Data System (ADS)

Dahlburg, R. B.; Einaudi, G.; Ugarte-Urra, I.; Warren, H. P.; Rappazzo, A. F.; Velli, M.; Taylor, B.

2016-12-01

Recent research on observational signatures of turbulent heating of a coronal loop will be discussed. The evolution of the loop is is studied by means of numericalsimulations of the fully compressible three-dimensionalmagnetohydrodynamic equations using the HYPERION code. HYPERION calculates the full energy cycle involving footpoint convection, magnetic reconnection,nonlinear thermal conduction and optically thin radiation.The footpoints of the loop magnetic field are convected by random photospheric motions. As a consequence the magnetic field in the loop is energized and develops turbulent nonlinear dynamics characterized by the continuous formation and dissipation of field-aligned current sheets: energy is deposited at small scales where heating occurs. Dissipation is non-uniformly distributed so that only a fraction of thecoronal mass and volume gets heated at any time. Temperature and density are highly structured at scales which, in the solar corona, remain observationally unresolved: the plasma of the simulated loop is multi-thermal, where highly dynamical hotter and cooler plasma strands arescattered throughout the loop at sub-observational scales. Typical simulated coronal loops are 50000 km length and have axial magnetic field intensities ranging from 0.01 to 0.04 Tesla.To connect these simulations to observations the computed numberdensities and temperatures are used to synthesize the intensities expected inemission lines typically observed with the Extreme ultraviolet Imaging Spectrometer(EIS) on Hinode. These intensities are then employed to compute differentialemission measure distributions, which are found to be very similar to those derivedfrom observations of solar active regions.

Unsteady Magnetized Flow and Heat Transfer of a Viscoelastic fluid over a Stretching Surface

NASA Astrophysics Data System (ADS)

Ghosh, Sushil Kumar

2017-12-01

This paper is to study the flow of heated ferro-fluid over a stretching sheet under the influence of magnetic field. The fluid considered in the present investigation is a mixture of blood as well as fluid-dispersed magnetic nano particles and under this context blood is found to be the appropriate choice of viscoelastic, Walter's B fluid. The objective of the present work is to study the effect of various parameters found in the mathematical analysis. Taking into account the blood has zero electrical conductivity, magnetization effect has been considered in the governing equation of the present study with the use of ferro-fluid dynamics principle. By introducing appropriate non-dimensional variables into the governing equations of unsteady two-dimensional flow of viscoelastic fluid with heat transfer are converted to a set of ordinary differential equations with appropriate boundary conditions. Newton's linearization technique has been employed for the solution of non-linear ordinary differential equations. Important results found in the present investigation are the substantial influence of ferro-magnetic parameter, Prandlt number and the parameter associated with the thermal conductivity on the flow and heat transfer. It is observed that the presence of magnetic dipole essentially reduces the flow velocity in the vertical direction and that helps to damage the cancer cells in the tumor region.

Heat Flow Measurement and Analysis of Thermal Vacuum Insulation

NASA Astrophysics Data System (ADS)

Laa, C.; Hirschl, C.; Stipsitz, J.

2008-03-01

A new kind of calorimeter has been developed at Austrian Aerospace to measure specific material parameters needed for the analysis of thermal vacuum insulation. A detailed description of the measuring device and the measurement results will be given in this paper. This calorimeter facility allows to measure the heat flow through the insulation under vacuum conditions in a wide temperature range from liquid nitrogen to ambient. Both boundary temperatures can be chosen within this range. Furthermore the insulation can be characterized at high vacuum or under degraded vacuum, the latter is simulated by using helium or nitrogen gas. The mechanisms of heat transfer have been investigated, namely infrared radiation between the reflective layers of the insulation and conduction through the interleaving spacer material. A mathematical description of the heat flow through the insulation has been derived. Based on this, the heat flow for a typical insulation material has been calculated by finite element analysis by use of the sotware tool Ansys®. Such a transient calculation is needed to determine the time to reach thermal equilibrium, which is mandatory for a proper interpretation and evaluation of the measurement. The new insulation measurement results combined with the proposed type of analysis can be applied to better understand the thermal behavior of any kind of cryogenic system.

Evaluation of Correlations of Flow Boiling Heat Transfer of R22 in Horizontal Channels

PubMed Central

Fang, Xiande; Li, Dingkun

2013-01-01

The calculation of two-phase flow boiling heat transfer of R22 in channels is required in a variety of applications, such as chemical process cooling systems, refrigeration, and air conditioning. A number of correlations for flow boiling heat transfer in channels have been proposed. This work evaluates the existing correlations for flow boiling heat transfer coefficient with 1669 experimental data points of flow boiling heat transfer of R22 collected from 18 published papers. The top two correlations for R22 are those of Liu and Winterton (1991) and Fang (2013), with the mean absolute deviation of 32.7% and 32.8%, respectively. More studies should be carried out to develop better ones. Effects of channel dimension and vapor quality on heat transfer are analyzed, and the results provide valuable information for further research in the correlation of two-phase flow boiling heat transfer of R22 in channels. PMID:23956695

Characteristics of turbulence transport for momentum and heat in particle-laden turbulent vertical channel flows

NASA Astrophysics Data System (ADS)

Liu, Caixi; Tang, Shuai; Shen, Lian; Dong, Yuhong

2017-10-01

The dynamic and thermal performance of particle-laden turbulent flow is investigated via direction numerical simulation combined with the Lagrangian point-particle tracking under the condition of two-way coupling, with a focus on the contributions of particle feedback effect to momentum and heat transfer of turbulence. We take into account the effects of particles on flow drag and Nusselt number and explore the possibility of drag reduction in conjunction with heat transfer enhancement in particle-laden turbulent flows. The effects of particles on momentum and heat transfer are analyzed, and the possibility of drag reduction in conjunction with heat transfer enhancement for the prototypical case of particle-laden turbulent channel flows is addressed. We present results of turbulence modification and heat transfer in turbulent particle-laden channel flow, which shows the heat transfer reduction when large inertial particles with low specific heat capacity are added to the flow. However, we also found an enhancement of the heat transfer and a small reduction of the flow drag when particles with high specific heat capacity are involved. The present results show that particles, which are active agents, interact not only with the velocity field, but also the temperature field and can cause a dissimilarity in momentum and heat transport. This demonstrates that the possibility to increase heat transfer and suppress friction drag can be achieved with addition of particles with different thermal properties.

Temperature and blood flow distribution in the human leg during passive heat stress

PubMed Central

Chiesa, Scott T.; Trangmar, Steven J.

2016-01-01

The influence of temperature on the hemodynamic adjustments to direct passive heat stress within the leg's major arterial and venous vessels and compartments remains unclear. Fifteen healthy young males were tested during exposure to either passive whole body heat stress to levels approaching thermal tolerance [core temperature (Tc) + 2°C; study 1; n = 8] or single leg heat stress (Tc + 0°C; study 2; n = 7). Whole body heat stress increased perfusion and decreased oscillatory shear index in relation to the rise in leg temperature (Tleg) in all three major arteries supplying the leg, plateauing in the common and superficial femoral arteries before reaching severe heat stress levels. Isolated leg heat stress increased arterial blood flows and shear patterns to a level similar to that obtained during moderate core hyperthermia (Tc + 1°C). Despite modest increases in great saphenous venous (GSV) blood flow (0.2 l/min), the deep venous system accounted for the majority of returning flow (common femoral vein 0.7 l/min) during intense to severe levels of heat stress. Rapid cooling of a single leg during severe whole body heat stress resulted in an equivalent blood flow reduction in the major artery supplying the thigh deep tissues only, suggesting central temperature-sensitive mechanisms contribute to skin blood flow alone. These findings further our knowledge of leg hemodynamic responses during direct heat stress and provide evidence of potentially beneficial vascular alterations during isolated limb heat stress that are equivalent to those experienced during exposure to moderate levels of whole body hyperthermia. PMID:26823344

Numerical simulation of heat transfer in blood flow altered by electroosmosis through tapered micro-vessels.

PubMed

Prakash, J; Ramesh, K; Tripathi, D; Kumar, R

2018-07-01

A numerical simulation is presented to study the heat and flow characteristics of blood flow altered by electroosmosis through the tapered micro-vessels. Blood is assumed as non-Newtonian (micropolar) nanofluids. The flow regime is considered as asymmetric diverging (tapered) microchannel for more realistic micro-vessels which is produced by choosing the peristaltic wave train on the walls to have different amplitudes and phase. The Rosseland approximation is employed to model the radiation heat transfer and temperatures of the walls are presumed constants. The mathematical formulation of the present problem is simplified under the long-wavelength, low-Reynolds number and Debye-Hückel linearization approximations. The influence of various dominant physical parameters are discussed for axial velocity, microrotation distribution, thermal temperature distribution and nanoparticle volume fraction field. However, our foremost emphasis is to determine the effects of thermal radiation and coupling number on the axial velocity and microrotation distribution beneath electroosmotic environment. This analysis places a significant observation on the thermal radiation and coupling number which plays an influential role in hearten fluid velocity. This study is encouraged by exploring the nanofluid-dynamics in peristaltic transport as symbolized by heat transport in biological flows and also in novel pharmacodynamics pumps and gastro-intestinal motility enhancement. Copyright © 2018 Elsevier Inc. All rights reserved.

Analytical modeling for heat transfer in sheared flows of nanofluids.

PubMed

Ferrari, Claudio; Kaoui, Badr; L'vov, Victor S; Procaccia, Itamar; Rudenko, Oleksii; ten Thije Boonkkamp, J H M; Toschi, Federico

2012-07-01

We developed a model for the enhancement of the heat flux by spherical and elongated nanoparticles in sheared laminar flows of nanofluids. Besides the heat flux carried by the nanoparticles, the model accounts for the contribution of their rotation to the heat flux inside and outside the particles. The rotation of the nanoparticles has a twofold effect: it induces a fluid advection around the particle and it strongly influences the statistical distribution of particle orientations. These dynamical effects, which were not included in existing thermal models, are responsible for changing the thermal properties of flowing fluids as compared to quiescent fluids. The proposed model is strongly supported by extensive numerical simulations, demonstrating a potential increase of the heat flux far beyond the Maxwell-Garnett limit for the spherical nanoparticles. The road ahead, which should lead toward robust predictive models of heat flux enhancement, is discussed.

Topology optimization of natural convection: Flow in a differentially heated cavity

NASA Astrophysics Data System (ADS)

Saglietti, Clio; Schlatter, Philipp; Berggren, Martin; Henningson, Dan

2017-11-01

The goal of the present work is to develop methods for optimization of the design of natural convection cooled heat sinks, using resolved simulation of both fluid flow and heat transfer. We rely on mathematical programming techniques combined with direct numerical simulations in order to iteratively update the topology of a solid structure towards optimality, i.e. until the design yielding the best performance is found, while satisfying a specific set of constraints. The investigated test case is a two-dimensional differentially heated cavity, in which the two vertical walls are held at different temperatures. The buoyancy force induces a swirling convective flow around a solid structure, whose topology is optimized to maximize the heat flux through the cavity. We rely on the spectral-element code Nek5000 to compute a high-order accurate solution of the natural convection flow arising from the conjugate heat transfer in the cavity. The laminar, steady-state solution of the problem is evaluated with a time-marching scheme that has an increased convergence rate; the actual iterative optimization is obtained using a steepest-decent algorithm, and the gradients are conveniently computed using the continuous adjoint equations for convective heat transfer.

Analytical and numerical study on cooling flow field designs performance of PEM fuel cell with variable heat flux

NASA Astrophysics Data System (ADS)

Afshari, Ebrahim; Ziaei-Rad, Masoud; Jahantigh, Nabi

2016-06-01

In PEM fuel cells, during electrochemical generation of electricity more than half of the chemical energy of hydrogen is converted to heat. This heat of reactions, if not exhausted properly, would impair the performance and durability of the cell. In general, large scale PEM fuel cells are cooled by liquid water that circulates through coolant flow channels formed in bipolar plates or in dedicated cooling plates. In this paper, a numerical method has been presented to study cooling and temperature distribution of a polymer membrane fuel cell stack. The heat flux on the cooling plate is variable. A three-dimensional model of fluid flow and heat transfer in cooling plates with 15 cm × 15 cm square area is considered and the performances of four different coolant flow field designs, parallel field and serpentine fields are compared in terms of maximum surface temperature, temperature uniformity and pressure drop characteristics. By comparing the results in two cases, the constant and variable heat flux, it is observed that applying constant heat flux instead of variable heat flux which is actually occurring in the fuel cells is not an accurate assumption. The numerical results indicated that the straight flow field model has temperature uniformity index and almost the same temperature difference with the serpentine models, while its pressure drop is less than all of the serpentine models. Another important advantage of this model is the much easier design and building than the spiral models.

Regional Heat Flow Map and the Continental Thermal Isostasy Understanding of México

NASA Astrophysics Data System (ADS)

Espinoza-Ojeda, O. M.; Harris, R. N.

2014-12-01

The first heat flow values made in Mexico were reported by Von Herzen [Science, 1963] for the marine environment and Smith [EPSL, 1974] for the continent. Since that time the number of measurements has increased greatly but are mostly from oil and gas exploration and in and around geothermal areas. We have compiled published values of conductive heat flow for Mexico and the Gulf of California to generate a new regional heat flow map consisting of 261 values. In addition to those original values, published heat flow sources include, Lee and Henyey [JGR, 1975], Lawver and Williams [JGR, 1979] Smith et al. [JGR, 1979], Lachenbruch et al. [JGR, 1985], and Ziagos et al. [JGR, 1985]. Although the geographic distribution is uneven, heat flow data are present in each of the eight main tectonic provinces. Our new compilation indicates relatively high regional heat flow averages in the Gulf Extensional Province (n=114, 92±22 mW/m2) and Mexican Basin and Range (n=21, 82±20 mW/m2) and are consistent with geologic estimates of extension. Lower regional averages are found in the Baja California Microplate (n=91, 75±19 mW/m2), the Sierra Madre Occidental (n=9, 75±12 mW/m2), the Sierra Madre Oriental (n=4, 68±15 mW/m2) and Mesa Central (n=X 77±23 mW/m2). In contrast low and variable heat flow value characterize the forearc region of the Middle America Trench (n=6, 35±16 mW/m2). A higher mean heat flow is associated with the Trans-Mexican Volcanic Belt (n=6, 78±26 mW/m2). Continental elevation results from a combination of buoyancy (i.e. compositional and thermal) and geodynamic forces. We combine these regional heat flow values with estimates of crustal thickness and density for each tectonic province and compute the thermal and compositional buoyancy following the approach of Hasterok and Chapman [JGR, 2007a,b]. We find that within uncertainties most provinces lie near the theoretical isostatic relationship with the exception of the Mesa Central and Sierra Madre del Sur

Heat transfer simulation of unsteady swirling flow in a vortex tube

NASA Astrophysics Data System (ADS)

Veretennikov, S. V.; Piralishvili, Sh A.; Evdokimov, O. A.; Guryanov, A. I.

2018-03-01

Effectiveness of not-adiabatic vortex tube application in the cooling systems of gas turbine blades depends on characteristics of swirling flows formed in the energy separation chamber. An analysis of the flow structure in the vortex tube channels has shown a presence of a complex three-dimensional spiral vortex, formed under relatively high turbulence intensity and vortex core precession. This indicates the presence of a significant unsteady flow in the energy separation chamber of the vortex tube that has a great influence on convective heat transfer of the swirling flow to the inner surface of tube. The paper contains the results of investigation of gas dynamics and heat transfer in the vortex tube taking into account the flow unsteadiness.

Experimental investigation on the heat transfer characteristics and flow pattern in vertical narrow channels heated from one side

NASA Astrophysics Data System (ADS)

Huang, Lihao; Li, Gang; Tao, Leren

2016-07-01

Experimental investigation for the flow boiling of water in a vertical rectangular channel was conducted to reveal the boiling heat transfer mechanism and flow patterns map aspects. The onset of nucleate boiling went upward with the increasing of the working fluid mass flow rate or the decreasing of the inlet working fluid temperature. As the vapour quality was increased, the local heat transfer coefficient increased first, then decreased, followed by various flow patterns. The test data from other researchers had a similar pattern transition for the bubble-slug flow and the slug-annular flow. Flow pattern transition model analysis was performed to make the comparison with current test data. The slug-annular and churn-annular transition models showed a close trend with current data except that the vapor phase superficial velocity of flow pattern transition was much higher than that of experimental data.

Heat flow diagnostics for helicon plasmas

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

Berisford, Daniel F.; Bengtson, Roger D.; Raja, Laxminarayan L.

2008-10-15

We present experimental studies of power balance in an argon helicon discharge. An infrared camera measures the heating of the dielectric tube containing a helicon discharge based on measurement of temperature profiles of the tube surface before and after a rf pulse. Using this diagnostic, we have measured surface heating trends at a variety of operating conditions on two helicon systems: the 10 kW VASIMR VX-50 experiment and the University of Texas at Austin 1 kW helicon experiment. Power losses downstream from the antenna are measured using thermocouples and probes. The heating of the dielectric tube increases with decreasing magneticmore » fields, higher gas flow rates, and higher molecular mass of the gas. These preliminary results suggest that cross-field particle diffusion contributes a significant proportion of the energy flux to the wall.« less

Physics of microstructures enhancement of thin film evaporation heat transfer in microchannels flow boiling

PubMed Central

Bigham, Sajjad; Fazeli, Abdolreza; Moghaddam, Saeed

2017-01-01

Performance enhancement of the two-phase flow boiling heat transfer process in microchannels through implementation of surface micro- and nanostructures has gained substantial interest in recent years. However, the reported results range widely from a decline to improvements in performance depending on the test conditions and fluid properties, without a consensus on the physical mechanisms responsible for the observed behavior. This gap in knowledge stems from a lack of understanding of the physics of surface structures interactions with microscale heat and mass transfer events involved in the microchannel flow boiling process. Here, using a novel measurement technique, the heat and mass transfer process is analyzed within surface structures with unprecedented detail. The local heat flux and dryout time scale are measured as the liquid wicks through surface structures and evaporates. The physics governing heat transfer enhancement on textured surfaces is explained by a deterministic model that involves three key parameters: the drying time scale of the liquid film wicking into the surface structures (τd), the heating length scale of the liquid film (δH) and the area fraction of the evaporating liquid film (Ar). It is shown that the model accurately predicts the optimum spacing between surface structures (i.e. pillars fabricated on the microchannel wall) in boiling of two fluids FC-72 and water with fundamentally different wicking characteristics. PMID:28303952

Effect of thermal interface on heat flow in carbon nanofiber composites.

PubMed

Gardea, F; Naraghi, M; Lagoudas, D

2014-01-22

The thermal transport process in carbon nanofiber (CNF)/epoxy composites is addressed through combined micromechanics and finite element modeling, guided by experiments. The heat exchange between CNF constituents and matrix is studied by explicitly accounting for interface thermal resistance between the CNFs and the epoxy matrix. The effects of nanofiber orientation and discontinuity on heat flow and thermal conductivity of nanocomposites are investigated through simulation of the laser flash experiment technique and Fourier's model of heat conduction. Our results indicate that when continuous CNFs are misoriented with respect to the average temperature gradient, the presence of interfacial resistance does not affect the thermal conductivity of the nanocomposites, as most of the heat flow will be through CNFs; however, interface thermal resistance can significantly alter the patterns of heat flow within the nanocomposite. It was found that very high interface resistance leads to heat entrapment at the interface near to the heat source, which can promote interface thermal degradation. The magnitude of heat entrapment, quantified via the peak transient temperature rise at the interface, in the case of high thermal resistance interfaces becomes an order of magnitude more intense as compared to the case of low thermal resistance interfaces. Moreover, high interface thermal resistance in the case of discontinuous fibers leads to a nearly complete thermal isolation of the fibers from the matrix, which will marginalize the contribution of the CNF thermal conductivity to the heat transfer in the composite.

Transient heat transfer to a forced flow of supercritical helium at 4.2 K

NASA Astrophysics Data System (ADS)

Bloem, W. B.

The transient heat transfer coefficient of supercritical helium flowing through a rectangular copper tube with a hydraulic diameter of 5 mm has been measured. The conditions of the flow were: inlet bulk temperature of the fluid was 4.2 K pressures from 3 to 10 bar and Reynolds numbers between 1.5 × 10 4 and 2 × 10 5. The tube was heated on four sides with heat fluxes up to 9800 W m -2. From the experiments it followed that during the first tens of milliseconds the heat transfer is determined by the heat conduction in the boundary layer of the supercritical helium flow. The heat transfer coefficient can be described by h = 0.5(Π λ p C p/t) 1/2. Although the helium properties λ p and Cp are a strong function of pressure and temperature, it was remarkable that the temperature increase during a heat pulse was almost the same at different flow pressures. After analysing the data an empirical relation, h =b ṁ0.75 (t t/t) case1/n, was derived, which predicts the heat transfer coefficient at a given mass flow, ṁ, to within 10% during 0.1 s. The constants b, n and tt are related to the mass flow, ṁ, and the pressure of the fluid.

Plasma Heating and Flow in an Auroral Arc

NASA Technical Reports Server (NTRS)

Moore, T. E.; Chandler, M. O.; Pollock, C. J.; Reasoner, D. L.; Arnoldy, R. L.; Austin, B.; Kintner, P. M.; Bonnell, J.

1996-01-01

We report direct observations of the three-dimensional velocity distribution of selected topside ionospheric ion species in an auroral context between 500 and 550 km altitude. We find heating transverse to the local magnetic field in the core plasma, with significant heating of 0(+), He(+), and H(+), as well as tail heating events that occur independently of the core heating. The 0(+) velocity distribution departs from bi-Maxwellian, at one point exhibiting an apparent ring-like shape. However, these observations are shown to be aliased within the auroral arc by temporal variations that arc not well-resolved by the core plasma instrument. The dc electric field measurements reveal superthermal plasma drifts that are consistent with passage of the payload through a series of vortex structures or a larger scale circularly polarized hydromagnetic wave structure within the auroral arc. The dc electric field also shows that impulsive solitary structures, with a frequency spectrum in the ion cyclotron frequency range, occur in close correlation with the tail heating events. The drift and core heating observations lend support to the idea that core ion heating is driven at low altitudes by rapid convective motions imposed by the magnetosphere. Plasma wave emissions at ion frequencies and parallel heating of the low-energy electron plasma are observed in conjunction with this auroral form; however, the conditions are much more complex than those typically invoked in previous theoretical treatments of superthermal frictional heating. The observed ion heating within the arc clearly exceeds that expected from frictional heating for the light ion species H(+) and He(+), and the core distributions also contain hot transverse tails, indicating an anomalous transverse heat source.

Entropy generation of nanofluid flow in a microchannel heat sink

NASA Astrophysics Data System (ADS)

Manay, Eyuphan; Akyürek, Eda Feyza; Sahin, Bayram

2018-06-01

Present study aims to investigate the effects of the presence of nano sized TiO2 particles in the base fluid on entropy generation rate in a microchannel heat sink. Pure water was chosen as base fluid, and TiO2 particles were suspended into the pure water in five different particle volume fractions of 0.25%, 0.5%, 1.0%, 1.5% and 2.0%. Under laminar, steady state flow and constant heat flux boundary conditions, thermal, frictional, total entropy generation rates and entropy generation number ratios of nanofluids were experimentally analyzed in microchannel flow for different channel heights of 200 μm, 300 μm, 400 μm and 500 μm. It was observed that frictional and total entropy generation rates increased as thermal entropy generation rate were decreasing with an increase in particle volume fraction. In microchannel flows, thermal entropy generation could be neglected due to its too low rate smaller than 1.10e-07 in total entropy generation. Higher channel heights caused higher thermal entropy generation rates, and increasing channel height yielded an increase from 30% to 52% in thermal entropy generation. When channel height decreased, an increase of 66%-98% in frictional entropy generation was obtained. Adding TiO2 nanoparticles into the base fluid caused thermal entropy generation to decrease about 1.8%-32.4%, frictional entropy generation to increase about 3.3%-21.6%.

A comparative study on heat and mass transfer of the Blasius and Falkner-Skan flow of a bio-convective Casson fluid past a wedge

NASA Astrophysics Data System (ADS)

Raju, C. S. K.; Sandeep, N.

2016-11-01

Nowadays, many theoretical models are available for analyzing the heat and mass transfer of flows through different geometries. Nevertheless, it is challenging for researchers to choose among these models, the most suitable for a particular geometry. In addition to this, the extrinsic magnetic field is capable to set the thermal and physical properties of magnetic fluids and regulate the flow and heat transfer characteristics. The strength of the applied magnetic field affects the thermal conductivity of the fluids and makes it anisotropic. With this incentive, we attempt to study the thermophoresis and Brownian motion effects on the magnetohydrodynamic radiative Casson fluid flow over a wedge filled with gyrotactic microorganisms by considering the Blasius and Falkner-Skan models. Numerical solutions are offered graphically as well as in tabular form with the aid of Runge-Kutta and Newton's methods. Results for Blasius and Falkner-Skan flow cases are exhibited through plots for the parameters of concern. For real life applications, we also calculated the heat and mass transfer rates. It is observed that thermal and concentration boundary layers are not uniform for Falkner-Skan and Blasius flow cases. It is also observed that the heat and mass transfer rate is high in Falkner-Skan flow when compared with Blasius flow.

Heat flow, heat production, and crustal temperatures in the Archaean Bundelkhand craton, north-central India: Implications for thermal regime beneath the Indian shield

NASA Astrophysics Data System (ADS)

Podugu, Nagaraju; Ray, Labani; Singh, S. P.; Roy, Sukanta

2017-07-01

Heat flow and heat production data sets constrain the crustal thermal structure in the 2.5-3.5 Ga Bundelkhand craton, the oldest cratonic core in northern Indian shield, for the first time and allow comparisons with the southern Indian shield. Temperature measurements carried out in 10 boreholes at five sites in the craton, combined with systematic thermal conductivity measurements on major rock types, yield low heat flow in the range of 32-41 mW m-2, which is distinct from the generally high heat flow reported from other parts of the northern Indian shield. Radioelemental measurements on 243 samples of drill cores and outcrops reveal both large variability and high average heat production for the Neo-Archaean to Palaeo-Proterozoic granites (4.0 ± 2.1 (SD) μW m-3) relative to the Meso-Archaean tonalite-trondhjemite-granodiorite (TTG) gneisses (2.0 ± 1.0 (SD) μW m-3). On the basis of new heat flow and heat production data sets combined with available geological and geophysical information, a set of steady state, heat flow-crustal heat production models representative of varying crustal scenarios in the craton are envisaged. Mantle heat flow and Moho temperatures are found to be in the range of 12-22 mW m-2 and 290-420°C, respectively, not much different from those reported for the similar age Dharwar craton in southern India. This study reveals similar mantle thermal regimes across the northern and southern parts of the Indian shield, in spite of varying surface heat flow regimes, implying that much of the intraprovince and interprovince variations in the Indian shield are explained by variations in upper crustal heat production.

Heat flow, seismic cut-off depth and thermal modeling of the Fennoscandian Shield

NASA Astrophysics Data System (ADS)

Veikkolainen, Toni; Kukkonen, Ilmo T.; Tiira, Timo

2017-12-01

Being far from plate boundaries but covered with seismograph networks, the Fennoscandian Shield features an ideal test laboratory for studies of intraplate seismicity. For this purpose, this study applies 4190 earthquake events from years 2000-2015 with magnitudes ranging from 0.10 to 5.22 in Finnish and Swedish national catalogues. In addition, 223 heat flow determinations from both countries and their immediate vicinity were used to analyse the potential correlation of earthquake focal depths and the spatially interpolated heat flow field. Separate subset analyses were performed for five areas of notable seismic activity: the southern Gulf of Bothnia coast of Sweden (area 1), the northern Gulf of Bothnia coast of Sweden (area 2), the Swedish Norrbotten and western Finnish Lapland (area 3), the Kuusamo region of Finland (area 4) and the southernmost Sweden (area 5). In total, our subsets incorporated 3619 earthquake events. No obvious relation of heat flow and focal depth exists, implying that variations of heat flow are primarily caused by shallow lying heat producing units instead of deeper sources. This allows for construction of generic geotherms for the range of representative palaeoclimatically corrected (steady-state) surface heat flow values (40-60 mW m-2). The 1-D geotherms constructed for a three-layer crust and lithospheric upper mantle are based on mantle heat flow constrained with the aid of mantle xenolith thermobarometry (9-15 mW m-2), upper crustal heat production values (3.3-1.1 μWm-3) and the brittle-ductile transition temperature (350 °C) assigned to the cut-off depth of seismicity (28 ± 4 km). For the middle and lower crust heat production values of 0.6 and 0.2 μWm-3 were assigned, respectively. The models suggest a Moho temperature range of 460-500 °C.

Darcy-Forchheimer flow with Cattaneo-Christov heat flux and homogeneous-heterogeneous reactions

PubMed Central

Hayat, Tasawar; Haider, Farwa; Alsaedi, Ahmed

2017-01-01

Here Darcy-Forchheimer flow of viscoelastic fluids has been analyzed in the presence of Cattaneo-Christov heat flux and homogeneous-heterogeneous reactions. Results for two viscoelastic fluids are obtained and compared. A linear stretching surface has been used to generate the flow. Flow in porous media is characterized by considering the Darcy-Forchheimer model. Modified version of Fourier's law through Cattaneo-Christov heat flux is employed. Equal diffusion coefficients are employed for both reactants and auto catalyst. Optimal homotopy scheme is employed for solutions development of nonlinear problems. Solutions expressions of velocity, temperature and concentration fields are provided. Skin friction coefficient and heat transfer rate are computed and analyzed. Here the temperature and thermal boundary layer thickness are lower for Cattaneo-Christov heat flux model in comparison to classical Fourier's law of heat conduction. Moreover, the homogeneous and heterogeneous reactions parameters have opposite behaviors for concentration field. PMID:28380014

A study of leeside flow field heat transfer on Shuttle Orbiter configuration

NASA Technical Reports Server (NTRS)

Baranowski, L. C.; Kipp, H. W.

1984-01-01

A coupled inviscid and viscous theoretical solution of the flow about the entire configuration is the desirable and comprehensive approach to defining thermal environments about the space shuttle orbiter. Simplified methods for predicting entry heating on leeside surfaces of the orbiter are considered. Wind tunnel heat transfer and oil flow data at Mach 6 and 10 and Reynolds numbers ranging from 500,000 to 73 million were used to develop correlations for the wing upper surface and the top surface of the fuselage. These correlations were extrapolated to flight Reynolds number and compared with heating data obtained during the shuttle STS-2 reentry. Efforts directed toward the wing leeside surface resulted in an approach which generally agreed with the flight data. Heating predictions for the upper fuselage were less successful due to the extreme complexity of local flow interactions and the associated heating environment.

Heat flow in eastern Egypt - The thermal signature of a continental breakup

NASA Technical Reports Server (NTRS)

Morgan, P.; Boulos, F. K.; Hennin, S. F.; El-Sherif, A. A.; El-Sayed, A. A.

1985-01-01

It is noted that the Red Sea is a modern example of continental fragmentation and incipient ocean formation. A consistent pattern of high heat flow in the Red Sea margins and coastal zone, including Precambrian terrane up to at least 30 km from the Red Sea, has emerged from the existing data. It is noted that this pattern has important implications for the mode and mechanism of Red Sea opening. High heat flow in the Red Sea shelf requires either a high extension of the crust in this zone (probably with major basic magmatic activity) or young oceanic crust beneath this zone. High heat flow in the coastal thermal anomaly zone may be caused by lateral conduction from the offshore lithosphere and/or from high mantle heat flow. It is suggested that new oceanic crust and highly extended continental crust would be essentially indistinguishable with the available data in the Red Sea margins, and are for many purposes essentially identical.

Heat flow and thermal processes in the Jornada delMuerto, New Mexico

NASA Technical Reports Server (NTRS)

Reiter, M.

1985-01-01

Most heat flow data in rifts are uncertain largely because of hydrologic disturbances in regions of extensive fracturing. Estimates of heat flow in deep petroleum tests within a large basin of the Rio Grande rift, which has suffered little syn-rift fracturing, may begin to provide clearer insight into the relationships between high heat flow and crustal thinning processes. The Jornada del Muerto is a large basin located in the Rio Grande rift of south central New Mexico. The region of interest within the Jornada del Muerto is centered about 30 km east of the town of Truth or Consequences, and is approximately 60 km north-south by 30 km east-west. High heat flows are estimated for the region. Values increase from about 90 mWm(-2) in the northern part of the study area to about 125 mWm(-2) in the southern part. These high heat flows are rather enigmatic because in the immediate vicinities of the sites there is little evidence of Cenozoic volcanism or syn-rift extensional tectonics. It is suggested that the geothermal anomaly in the southern Jornada del Muerto (approx. 125 to approx. 95 mWm(-2) results from some type of mass movement-heat transfer mechanism operating in the crust just below the elastic layer. This conclusion is consistent with the geologic and geophysical data which describe a thin crust, apparently devoid of features indicative of extensional-tectonics in the upper part of the lastic crust.

Temperature and blood flow distribution in the human leg during passive heat stress.

PubMed

Chiesa, Scott T; Trangmar, Steven J; González-Alonso, José

2016-05-01

The influence of temperature on the hemodynamic adjustments to direct passive heat stress within the leg's major arterial and venous vessels and compartments remains unclear. Fifteen healthy young males were tested during exposure to either passive whole body heat stress to levels approaching thermal tolerance [core temperature (Tc) + 2°C; study 1; n = 8] or single leg heat stress (Tc + 0°C; study 2; n = 7). Whole body heat stress increased perfusion and decreased oscillatory shear index in relation to the rise in leg temperature (Tleg) in all three major arteries supplying the leg, plateauing in the common and superficial femoral arteries before reaching severe heat stress levels. Isolated leg heat stress increased arterial blood flows and shear patterns to a level similar to that obtained during moderate core hyperthermia (Tc + 1°C). Despite modest increases in great saphenous venous (GSV) blood flow (0.2 l/min), the deep venous system accounted for the majority of returning flow (common femoral vein 0.7 l/min) during intense to severe levels of heat stress. Rapid cooling of a single leg during severe whole body heat stress resulted in an equivalent blood flow reduction in the major artery supplying the thigh deep tissues only, suggesting central temperature-sensitive mechanisms contribute to skin blood flow alone. These findings further our knowledge of leg hemodynamic responses during direct heat stress and provide evidence of potentially beneficial vascular alterations during isolated limb heat stress that are equivalent to those experienced during exposure to moderate levels of whole body hyperthermia. Copyright © 2016 the American Physiological Society.

Heat transfer and pressure drop characteristics of the tube bank fin heat exchanger with fin punched with flow redistributors and curved triangular vortex generators

NASA Astrophysics Data System (ADS)

Liu, Song; Jin, Hua; Song, KeWei; Wang, LiangChen; Wu, Xiang; Wang, LiangBi

2017-10-01

The heat transfer performance of the tube bank fin heat exchanger is limited by the air-side thermal resistance. Thus, enhancing the air-side heat transfer is an effective method to improve the performance of the heat exchanger. A new fin pattern with flow redistributors and curved triangular vortex generators is experimentally studied in this paper. The effects of the flow redistributors located in front of the tube stagnation point and the curved vortex generators located around the tube on the characteristics of heat transfer and pressure drop are discussed in detail. A performance comparison is also carried out between the fins with and without flow redistributors. The experimental results show that the flow redistributors stamped out from the fin in front of the tube stagnation points can decrease the friction factor at the cost of decreasing the heat transfer performance. Whether the combination of the flow redistributors and the curved vortex generators will present a better heat transfer performance depends on the size of the curved vortex generators. As for the studied two sizes of vortex generators, the heat transfer performance is promoted by the flow redistributors for the fin with larger size of vortex generators and the performance is suppressed by the flow redistributors for the fin with smaller vortex generators.

Surface heat flow and CO2 emissions within the Ohaaki hydrothermal field, Taupo Volcanic Zone, New Zealand

USGS Publications Warehouse

Rissmann, C.; Christenson, B.; Werner, C.; Leybourne, M.; Cole, J.; Gravley, D.

2012-01-01

Carbon dioxide emissions and heat flow have been determined from the Ohaaki hydrothermal field, Taupo Volcanic Zone (TVZ), New Zealand following 20a of production (116MW e). Soil CO2 degassing was quantified with 2663 CO2 flux measurements using the accumulation chamber method, and 2563 soil temperatures were measured and converted to equivalent heat flow (Wm -2) using published soil temperature heat flow functions. Both CO2 flux and heat flow were analysed statistically and then modelled using 500 sequential Gaussian simulations. Forty subsoil CO 2 gas samples were also analysed for stable C isotopes. Following 20a of production, current CO2 emissions equated to 111??6.7T/d. Observed heat flow was 70??6.4MW, compared with a pre-production value of 122MW. This 52MW reduction in surface heat flow is due to production-induced drying up of all alkali-Cl outflows (61.5MW) and steam-heated pools (8.6MW) within the Ohaaki West thermal area (OHW). The drying up of all alkali-Cl outflows at Ohaaki means that the soil zone is now the major natural pathway of heat release from the high-temperature reservoir. On the other hand, a net gain in thermal ground heat flow of 18MW (from 25MW to 43.3??5MW) at OHW is associated with permeability increases resulting from surface unit fracturing by production-induced ground subsidence. The Ohaaki East (OHE) thermal area showed no change in distribution of shallow and deep soil temperature contours despite 20a of production, with an observed heat flow of 26.7??3MW and a CO 2 emission rate of 39??3T/d. The negligible change in the thermal status of the OHE thermal area is attributed to the low permeability of the reservoir beneath this area, which has limited production (mass extraction) and sheltered the area from the pressure decline within the main reservoir. Chemistry suggests that although alkali-Cl outflows once contributed significantly to the natural surface heat flow (~50%) they contributed little (<1%) to pre-production CO 2

A Dual-Plane PIV Study of Turbulent Heat Transfer Flows

NASA Technical Reports Server (NTRS)

Wernet, Mark P.; Wroblewski, Adam C.; Locke, Randy J.

2016-01-01

Thin film cooling is a widely used technique in turbomachinery and rocket propulsion applications, where cool injection air protects a surface from hot combustion gases. The injected air typically has a different velocity and temperature from the free stream combustion flow, yielding a flow field with high turbulence and large temperature differences. These thin film cooling flows provide a good test case for evaluating computational model prediction capabilities. The goal of this work is to provide a database of flow field measurements for validating computational flow prediction models applied to turbulent heat transfer flows. In this work we describe the application of a Dual-Plane Particle Image Velocimetry (PIV) technique in a thin film cooling wind tunnel facility where the injection air stream velocity and temperatures are varied in order to provide benchmark turbulent heat transfer flow field measurements. The Dual-Plane PIV data collected include all three components of velocity and all three components of vorticity, spanning the width of the tunnel at multiple axial measurement planes.

Experimental investigation of heat transfer and fluid flow behaviour in multiple square perforated twisted tape with square wing inserts heat exchanger tube

NASA Astrophysics Data System (ADS)

Suri, Amar Raj Singh; Kumar, Anil; Maithani, Rajesh

2018-06-01

The present work deals with experimental investigation of heat transfer and fluid flow characteristics of multiple square perforated twisted tape with wing inserts in a heat exchanger tube. The range of selected geometrical parameters are, perforation width ratio (a/WT) of 0.083-0.333, twist ratio (TL/WT) of 2.0-3.5, wing depth ratio (Wd/WT) of 0.042-0.167 and number of twisted tapes (TP) of 4. The Reynolds number (Ren) selected for experimentation ranges from 5000 to 27,000. The maximum heat transfer and friction factor enhancement was found to be 6.96 and 8.34 times that of plane tube, respectively. The maximum heat transfer enhancement is observed at a a/WT of 0.250, TL/WT of 2.5, and Wd/WT of 0.167.

Experimental investigation of heat transfer and fluid flow behaviour in multiple square perforated twisted tape with square wing inserts heat exchanger tube

NASA Astrophysics Data System (ADS)

Suri, Amar Raj Singh; Kumar, Anil; Maithani, Rajesh

2018-01-01

The present work deals with experimental investigation of heat transfer and fluid flow characteristics of multiple square perforated twisted tape with wing inserts in a heat exchanger tube. The range of selected geometrical parameters are, perforation width ratio (a/WT) of 0.083-0.333, twist ratio (TL/WT) of 2.0-3.5, wing depth ratio (Wd/WT) of 0.042-0.167 and number of twisted tapes (TP) of 4. The Reynolds number (Ren) selected for experimentation ranges from 5000 to 27,000. The maximum heat transfer and friction factor enhancement was found to be 6.96 and 8.34 times that of plane tube, respectively. The maximum heat transfer enhancement is observed at a a/WT of 0.250, TL/WT of 2.5, and Wd/WT of 0.167.

Relaxed impact craters on Ganymede: Regional variation and high heat flows

USGS Publications Warehouse

Singer, Kelsi N.; Bland, Michael T.; Schenk, Paul M.; McKinnon, William B.

2018-01-01

Viscously relaxed craters provide a window into the thermal history of Ganymede, a satellite with copious geologic signs of past high heat flows. Here we present measurements of relaxed craters in four regions for which suitable imaging exists: near Anshar Sulcus, Tiamat Sulcus, northern Marius Regio, and Ganymede's south pole. We describe a technique to measure apparent depth, or depth of the crater with respect to the surrounding terrain elevation. Measured relaxation states are compared with results from finite element modeling to constrain heat flow scenarios [see companion paper: Bland et al. (2017)]. The presence of numerous, substantially relaxed craters indicates high heat flows—in excess of 30–40 mW m−2 over 2 Gyr, with many small (<10 km in diameter) relaxed craters indicating even higher heat flows. Crater relaxation states are bimodal for some equatorial regions but not in the region studied near the south pole, which suggests regional variations in Ganymede's thermal history.

Chaotic advection and heat transfer in two similar 2-D periodic flows and in their corresponding 3-D periodic flows

NASA Astrophysics Data System (ADS)

Vinsard, G.; Dufour, S.; Saatdjian, E.; Mota, J. P. B.

2016-03-01

Chaotic advection can effectively enhance the heat transfer rate between a boundary and fluids with high Prandtl number. These fluids are usually highly viscous and thus turbulent agitation is not a viable solution since the energy required to mix the fluid would be prohibitive. Here, we analyze previously obtained results on chaotic advection and heat transfer in two similar 2-D periodic flows and on their corresponding 3-D periodic flows when an axial velocity component is superposed. The two flows studied are the flow between eccentric rotating cylinders and the flow between confocal ellipses. For both of these flows the analysis is simplified because the Stokes equations can be solved analytically to obtain a closed form solution. For both 2-D periodic flows, we show that chaotic heat transfer is enhanced by the displacement of the saddle point location during one period. Furthermore, the enhancement by chaotic advection in the elliptical geometry is approximately double that obtained in the cylindrical geometry because there are two saddle points instead of one. We also explain why, for high eccentricity ratios, there is no heat transfer enhancement in the cylindrical geometry. When an axial velocity component is added to both of these flows so that they become 3-D, previous work has shown that there is an optimum modulation frequency for which chaotic advection and heat transfer enhancement is a maximum. Here we show that the optimum modulation frequency can be derived from results without an axial flow. We also explain by physical arguments other previously unanswered questions in the published data.

Observations and Modeling of Transition Region and Coronal Heating Associated with Spicules

NASA Astrophysics Data System (ADS)

De Pontieu, B.; Martinez-Sykora, J.; De Moortel, I.; Chintzoglou, G.; McIntosh, S. W.

2017-12-01

Spicules have been proposed as significant contributorsto the coronal energy and mass balance. While previous observationshave provided a glimpse of short-lived transient brightenings in thecorona that are associated with spicules, these observations have beencontested and are the subject of a vigorous debate both on the modelingand the observational side so that it remains unclear whether plasmais heated to coronal temperatures in association with spicules. We use high-resolution observations of the chromosphere and transition region with the Interface Region Imaging Spectrograph (IRIS) and ofthe corona with the Atmospheric Imaging Assembly (AIA) onboard theSolar Dynamics Observatory (SDO) to show evidence of the formation of coronal structures as a result of spicular mass ejections andheating of plasma to transition region and coronaltemperatures. Our observations suggest that a significant fraction of the highly dynamic loop fan environment associated with plage regions may be the result of the formation of such new coronal strands, a process that previously had been interpreted as the propagation of transient propagating coronal disturbances (PCD)s. Our observationsare supported by 2.5D radiative MHD simulations that show heating tocoronal temperatures in association with spicules. Our results suggest that heating and strong flows play an important role in maintaining the substructure of loop fans, in addition to the waves that permeate this low coronal environment. Our models also matches observations ofTR counterparts of spicules and provides an elegant explanation forthe high apparent speeds of these "network jets".

Compact, Deep-Penetrating Geothermal Heat Flow Instrumentation for Lunar Landers

NASA Technical Reports Server (NTRS)

Nagihara, S.; Zacny, K.; Hedlund, M.; Taylor, P. T.

2012-01-01

Geothermal heat flow is obtained as a product of the two separate measurements of geothermal gradient in, and thermal conductivity of, the vertical soi/rock/regolith interval penetrated by the instrument. Heat flow measurements are a high priority for the geophysical network missions to the Moon recommended by the latest Decadal Survey [I] and previously the International Lunar Network [2]. The two lunar-landing missions planned later this decade by JAXA [3] and ESA [4] also consider geothermal measurements a priority.

Flow-Boiling Critical Heat Flux Experiments Performed in Reduced Gravity

NASA Technical Reports Server (NTRS)

Hasan, Mohammad M.; Mudawar, Issam

2005-01-01

Poor understanding of flow boiling in microgravity has recently emerged as a key obstacle to the development of many types of power generation and advanced life support systems intended for space exploration. The critical heat flux (CHF) is perhaps the most important thermal design parameter for boiling systems involving both heatflux-controlled devices and intense heat removal. Exceeding the CHF limit can lead to permanent damage, including physical burnout of the heat-dissipating device. The importance of the CHF limit creates an urgent need to develop predictive design tools to ensure both the safe and reliable operation of a two-phase thermal management system under the reduced-gravity (like that on the Moon and Mars) and microgravity environments of space. At present, very limited information is available on flow-boiling heat transfer and the CHF under these conditions.

Heat flux and plasma flow in the far scrape-off layer of the inboard poloidal field null configuration in QUEST

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

Onchi, T.; Zushi, H.; Hanada, K.

2015-08-15

Heat flux and plasma flow in the scrape-off layer (SOL) are examined for the inboard poloidal field null (IPN) configuration of the spherical tokamak QUEST. In the plasma current (I{sub p}) ramp-up phase, high heat flux (>1 MW/m{sup 2}) and supersonic flow (Mach number M > 1) are found to be present simultaneously in the far-SOL. The heat flux is generated by energetic electrons excursed from the last closed flux surface. Supersonic flows in the poloidal and toroidal directions are correlated with each other. In the quasi-steady state, sawtooth-like oscillation of I{sub p} at 20 Hz is observed. Heat flux and subsonic plasma flowmore » in the far-SOL are modified corresponding to the I{sub p}-oscillation. The heat flow caused by motion of energetic electrons and the bulk-particle transport to the far-SOL is enhanced during the low-I{sub p} phase. Modification of plasma flow in the far SOL occurs earlier than the I{sub p} crash. The M–I{sub p} curve has a limit-cycle characteristic with sawtooth-like oscillation. Such a core–SOL relationship indicates that the far-SOL flow plays an important role in sustaining the oscillation of I{sub p} in the IPN configuration.« less

Nanoflare vs Footpoint Heating : Observational Signatures

NASA Technical Reports Server (NTRS)

Winebarger, Amy; Alexander, Caroline; Lionello, Roberto; Linker, Jon; Mikic, Zoran; Downs, Cooper

2015-01-01

Time lag analysis shows very long time lags between all channel pairs. Impulsive heating cannot address these long time lags. 3D Simulations of footpoint heating shows a similar pattern of time lags (magnitude and distribution) to observations. Time lags and relative peak intensities may be able to differentiate between TNE and impulsive heating solutions. Adding a high temperature channel (like XRT Be-­thin) may improve diagnostics.

Transition to turbulence and noise radiation in heated coaxial jet flows

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

Gloor, Michael, E-mail: gloor@ifd.mavt.ethz.ch; Bühler, Stefan; Kleiser, Leonhard

2016-04-15

Laminar-turbulent transition and noise radiation of a parametrized set of subsonic coaxial jet flows with a hot primary (core) stream are investigated numerically by Large-Eddy Simulation (LES) and direct noise computation. This study extends our previous research on local linear stability of heated coaxial jet flows by analyzing the nonlinear evolution of initially laminar flows disturbed by a superposition of small-amplitude unstable eigenmodes. First, a baseline configuration is studied to shed light on the flow dynamics of coaxial jet flows. Subsequently, LESs are performed for a range of Mach and Reynolds numbers to systematically analyze the influences of the temperaturemore » and the velocity ratios between the primary and the secondary (bypass) stream. The results provide a basis for a detailed analysis of fundamental flow-acoustic phenomena in the considered heated coaxial jet flows. Increasing the primary-jet temperature leads to an increase of fluctuation levels and to an amplification of far-field noise, especially at low frequencies. Strong mixing between the cold bypass stream and the hot primary stream as well as the intermittent character of the flow field at the end of the potential core lead to a pronounced noise radiation at an aft angle of approximately 35{sup ∘}. The velocity ratio strongly affects the shear-layer development and therefore also the noise generation mechanisms. Increasing the secondary-stream velocity amplifies the dominance of outer shear-layer perturbations while the disturbance growth rates in the inner shear layer decrease. Already for r{sub mic} > 40R{sub 1}, where r{sub mic} is the distance from the end of the potential core and R{sub 1} is the core-jet radius, a perfect 1/r{sub mic} decay of the sound pressure amplitudes is observed. The potential-core length increases for higher secondary-stream velocities which leads to a shift of the center of the dominant acoustic radiation in the downstream direction.« less

Re-evaluation of heat flow data near Parkfield, CA: Evidence for a weak San Andreas Fault

USGS Publications Warehouse

Fulton, P.M.; Saffer, D.M.; Harris, Reid N.; Bekins, B.A.

2004-01-01

Improved interpretations of the strength of the San Andreas Fault near Parkfield, CA based on thermal data require quantification of processes causing significant scatter and uncertainty in existing heat flow data. These effects include topographic refraction, heat advection by topographically-driven groundwater flow, and uncertainty in thermal conductivity. Here, we re-evaluate the heat flow data in this area by correcting for full 3-D terrain effects. We then investigate the potential role of groundwater flow in redistributing fault-generated heat, using numerical models of coupled heat and fluid flow for a wide range of hydrologic scenarios. We find that a large degree of the scatter in the data can be accounted for by 3-D terrain effects, and that for plausible groundwater flow scenarios frictional heat generated along a strong fault is unlikely to be redistributed by topographically-driven groundwater flow in a manner consistent with the 3-D corrected data. Copyright 2004 by the American Geophysical Union.

Numberical Solution to Transient Heat Flow Problems

ERIC Educational Resources Information Center

Kobiske, Ronald A.; Hock, Jeffrey L.

1973-01-01

Discusses the reduction of the one- and three-dimensional diffusion equation to the difference equation and its stability, convergence, and heat-flow applications under different boundary conditions. Indicates the usefulness of this presentation for beginning students of physics and engineering as well as college teachers. (CC)

FOXSI-2 Observations and Coronal Heating

NASA Astrophysics Data System (ADS)

Christe, S.; Glesener, L.; Krucker, S.; Ramsey, B.; Ishikawa, S. N.; Buitrago Casas, J. C.; Takahashi, T.; Foster, N.

2015-12-01

Energy release and particle acceleration on the Sun is a frequent occurrence associated with a number of different solar phenomenon including but not limited to solar flares, coronal mass ejections and nanoflares. The exact mechanism through which particles are accelerated and energy is released is still not well understood. This issue is related to the unsolved coronal heating problem, the mystery of the heating mechanism for the million degree solar corona. One prevalent theory posits the existence of a multitude of small flares, dubbed nanoflares. Recent observations of active region AR11890 by IRIS (Testa et al. 2014) are consistent with numerical simulations of heating by impulsive beams of nonthermal electrons, suggesting that nanoflares may be similar to large flares in that they accelerate particles. Furthermore, observations by the EUNIS sounding rocket (Brosius et al. 2014) of faint Fe XIX (592.2 Angstrom) emission in an active region is indicative of plasma at temperatures of at least 8.9 MK providing further evidence of nanoflare heating. One of the best ways to gain insight into accelerated particles on the Sun and the presence of hot plasma is by observing the Sun in hard X-rays (HXR). We present on observations taken during the second successful flight of the Focusing Optics X-ray Solar Imager (FOXSI-2). FOXSI flew on December 11, 2014 with upgraded optics as well as new CdTe strip detectors. FOXSI-2 observed thermal emission (4-15 keV) from at least three active regions (AR#12234, AR#12233, AR#12235) and observed regions of the Sun without active regions. We present on using FOXSI observations to test the presence of hot temperatures in and outside of active regions.

A Numerical Method for Incompressible Flow with Heat Transfer

NASA Technical Reports Server (NTRS)

Sa, Jong-Youb; Kwak, Dochan

1997-01-01

A numerical method for the convective heat transfer problem is developed for low speed flow at mild temperatures. A simplified energy equation is added to the incompressible Navier-Stokes formulation by using Boussinesq approximation to account for the buoyancy force. A pseudocompressibility method is used to solve the resulting set of equations for steady-state solutions in conjunction with an approximate factorization scheme. A Neumann-type pressure boundary condition is devised to account for the interaction between pressure and temperature terms, especially near a heated or cooled solid boundary. It is shown that the present method is capable of predicting the temperature field in an incompressible flow.

Unidirectional spin-wave heat conveyer.

PubMed

An, T; Vasyuchka, V I; Uchida, K; Chumak, A V; Yamaguchi, K; Harii, K; Ohe, J; Jungfleisch, M B; Kajiwara, Y; Adachi, H; Hillebrands, B; Maekawa, S; Saitoh, E

2013-06-01

When energy is introduced into a region of matter, it heats up and the local temperature increases. This energy spontaneously diffuses away from the heated region. In general, heat should flow from warmer to cooler regions and it is not possible to externally change the direction of heat conduction. Here we show a magnetically controllable heat flow caused by a spin-wave current. The direction of the flow can be switched by applying a magnetic field. When microwave energy is applied to a region of ferrimagnetic Y3Fe5O12, an end of the magnet far from this region is found to be heated in a controlled manner and a negative temperature gradient towards it is formed. This is due to unidirectional energy transfer by the excitation of spin-wave modes without time-reversal symmetry and to the conversion of spin waves into heat. When a Y3Fe5O12 film with low damping coefficients is used, spin waves are observed to emit heat at the sample end up to 10 mm away from the excitation source. The magnetically controlled remote heating we observe is directly applicable to the fabrication of a heat-flow controller.

Heat transfer in nonequilibrium boundary layer flow over a partly catalytic wall

NASA Astrophysics Data System (ADS)

Wang, Zhi-Hui

2016-11-01

Surface catalysis has a huge influence on the aeroheating performance of hypersonic vehicles. For the reentry flow problem of a traditional blunt vehicle, it is reasonable to assume a frozen boundary layer surrounding the vehicles' nose, and the catalytic heating can be decoupled with the heat conduction. However, when considering a hypersonic cruise vehicle flying in the medium-density near space, the boundary layer flow around its sharp leading-edge is likely to be nonequilibrium rather than frozen due to rarefied gas effects. As a result, there will be a competition between the heat conduction and the catalytic heating. In this paper, the theoretical modeling and the direct simulation Monte Carlo (DSMC) method are employed to study the corresponding rarefied nonequilibrium flow and heat transfer phenomena near the leading edge of the near space hypersonic vehicles. It is found that even under identical rarefication degree, the nonequilibrium degree of the flow and the corresponding heat transfer performance of the sharp leading edges could be different from that of the big blunt noses. A generalized model is preliminarily proposed to describe and to evaluate the competitive effects between the homogeneous recombination of atoms inside the nonequilibrium boundary layer and the heterogeneous recombination of atoms on the catalytic wall surface. The introduced nonequilibrium criterion and the analytical formula are validated and calibrated by the DSMC results, and the physical mechanism is discussed.

Evolution of Heat Flow with Age on the Southern Flank of the Costa Rica Rift

NASA Astrophysics Data System (ADS)

Kolandaivelu, K. P.; Harris, R. N.; Lowell, R. P.; Wilson, D. J.; Hobbs, R. W.

2017-12-01

Analysis of 67 new conductive heat flow measurements at five sites ranging between ≈ 1.6 and 5.7 Ma on the southern flank of the Costa Rica Rift yields insight into factors that influence hydrothermal circulation in young oceanic crust. The heat flow measurements were collocated with a high-resolution multi-channel seismic line, extending from the ridge axis to ODP hole 504B. The mean conductive heat flow, qobs, 80 mWm-2, is ≈ 25% of the mean lithospheric heat flux, qth, predicted by half-space conductive cooling model. The ratio qobs/qth varies significantly from site to site indicating that advective heat loss may be influenced by the presence of high-angle, ridge-ward dipping normal faults, surface topography, and sediment thickness, which vary significantly along the profile. The 1.6 Ma heat flow site, which is located between two outcrops separated by 2 km and has thin sediment cover, yields qobs/qth » 0.08. The advective heat loss indicates a mass flux of 3 x 10-5 kgm-2s-1 and upper crustal permeabilities of 4 x 10-11 and 3 x 10-9 m2 for 1000 m and 100 m aquifer thicknesses, respectively. At the 2.6 Ma site with 75 m sediment cover, qobs/qth » 0.18 and heat flow is uniformly low, except for one high value near a fault. At the 3.5 Ma site, qobs/qth » 0.15. The heat flow deficit results from outcrop to outcrop flow, but subcritical cellular convection driven by local basement topography produces small heat flow highs and lows superimposed on the overall trend. At the 4.5 Ma site, qobs/qth » 0.06. The heat flow distribution indicates that discharge occurs through a large, thinly-sedimented topographical high, where estimated mass flux is 3 x 10-5 kgm-2s-1. At the oldest site of 5.7 Ma, qobs/qth » 1, but some heat flow values greater than qth occur near sparsely-sedimented basement outcrops, suggesting redistribution of heat by subsurface convection controlled by basement topography, similar to ODP Hole 504B. That qobs/qth » 1 at a much younger age than

Heat transfer and pressure drop for air flow through enhanced passages

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

Obot, N.T.; Esen, E.B.

1992-06-01

An extensive experimental investigation was carried out to determine the pressure drop and heat transfer characteristics for laminar, transitional and turbulent flow of air through a smooth passage and twenty-three enhanced passages. The internal surfaces of all enhanced passages had spirally shaped geometries; these included fluted, finned/ribbed and indented surfaces. The Reynolds number (Re) was varied between 400 and 50000. The effect of heat transfer (wall cooling or fluid heating) on pressure drop is most significant within the transition region; the recorded pressure drop with heat transfer is much higher than that without heat transfer. The magnitude of this effectmore » depends markedly on the average surface temperature and, to a lesser extent, on the geometric characteristics of the enhanced surfaces. When the pressure drop data are reduced as values of the Fanning friction factor(f), the results are about the same with and without heat transfer for turbulent flow, with moderate differences in the laminar and transition regions.« less

Lattice Boltzmann simulations of heat transfer in fully developed periodic incompressible flows

NASA Astrophysics Data System (ADS)

Wang, Zimeng; Shang, Helen; Zhang, Junfeng

2017-06-01

Flow and heat transfer in periodic structures are of great interest for many applications. In this paper, we carefully examine the periodic features of fully developed periodic incompressible thermal flows, and incorporate them in the lattice Boltzmann method (LBM) for flow and heat transfer simulations. Two numerical approaches, the distribution modification (DM) approach and the source term (ST) approach, are proposed; and they can both be used for periodic thermal flows with constant wall temperature (CWT) and surface heat flux boundary conditions. However, the DM approach might be more efficient, especially for CWT systems since the ST approach requires calculations of the streamwise temperature gradient at all lattice nodes. Several example simulations are conducted, including flows through flat and wavy channels and flows through a square array with circular cylinders. Results are compared to analytical solutions, previous studies, and our own LBM calculations using different simulation techniques (i.e., the one-module simulation vs. the two-module simulation, and the DM approach vs. the ST approach) with good agreement. These simple, however, representative simulations demonstrate the accuracy and usefulness of our proposed LBM methods for future thermal periodic flow simulations.

Numerical Study of Laminar Flow and Convective Heat Transfer Utilizing Nanofluids in Equilateral Triangular Ducts with Constant Heat Flux

PubMed Central

Ting, Hsien-Hung; Hou, Shuhn-Shyurng

2016-01-01

This study numerically investigates heat transfer augmentation using water-based Al2O3 and CuO nanofluids flowing in a triangular cross-sectional duct under constant heat flux in laminar flow conditions. The Al2O3/water nanofluids with different volume fractions (0.1%, 0.5%, 1%, 1.5%, and 2%) and CuO/water nanofluids with various volume fractions (0.05%, 0.16%, 0.36%, 0.5%, and 0.8%) are employed, and Reynolds numbers in the range of 700 to 1900 in a laminar flow are considered. The heat transfer rate becomes more remarkable when employing nanofluids. As compared with pure water, at a Peclet number of 7000, a 35% enhancement in the convective heat transfer coefficient, is obtained for an Al2O3/water nanofluid with 2% particle volume fraction; at the same Peclet number, a 41% enhancement in the convective heat transfer coefficient is achieved for a CuO/water nanofluid with 0.8% particle volume concentration. Heat transfer enhancement increases with increases in particle volume concentration and Peclet number. Moreover, the numerical results are found to be in good agreement with published experimental data. PMID:28773698

Slip effect on stagnation point flow past a stretching surface with the presence of heat generation/absorption and Newtonian heating

NASA Astrophysics Data System (ADS)

Mohamed, Muhammad Khairul Anuar; Noar, Nor Aida Zuraimi Md; Ismail, Zulkhibri; Kasim, Abdul Rahman Mohd; Sarif, Norhafizah Md; Salleh, Mohd Zuki; Ishak, Anuar

2017-08-01

Present study solved numerically the velocity slip effect on stagnation point flow past a stretching surface with the presence of heat generation/absorption and Newtonian heating. The governing equations which in the form of partial differential equations are transformed to ordinary differential equations before being solved numerically using the Runge-Kutta-Fehlberg method in MAPLE. The numerical solution is obtained for the surface temperature, heat transfer coefficient, reduced skin friction coefficient as well as the temperature and velocity profiles. The flow features and the heat transfer characteristic for the pertinent parameter such as Prandtl number, stretching parameter, heat generation/absorption parameter, velocity slip parameter and conjugate parameter are analyzed and discussed.

Heat Transfer Computations of Internal Duct Flows With Combined Hydraulic and Thermal Developing Length

NASA Technical Reports Server (NTRS)

Wang, C. R.; Towne, C. E.; Hippensteele, S. A.; Poinsatte, P. E.

1997-01-01

This study investigated the Navier-Stokes computations of the surface heat transfer coefficients of a transition duct flow. A transition duct from an axisymmetric cross section to a non-axisymmetric cross section, is usually used to connect the turbine exit to the nozzle. As the gas turbine inlet temperature increases, the transition duct is subjected to the high temperature at the gas turbine exit. The transition duct flow has combined development of hydraulic and thermal entry length. The design of the transition duct required accurate surface heat transfer coefficients. The Navier-Stokes computational method could be used to predict the surface heat transfer coefficients of a transition duct flow. The Proteus three-dimensional Navier-Stokes numerical computational code was used in this study. The code was first studied for the computations of the turbulent developing flow properties within a circular duct and a square duct. The code was then used to compute the turbulent flow properties of a transition duct flow. The computational results of the surface pressure, the skin friction factor, and the surface heat transfer coefficient were described and compared with their values obtained from theoretical analyses or experiments. The comparison showed that the Navier-Stokes computation could predict approximately the surface heat transfer coefficients of a transition duct flow.

Heat-flow properties of systems with alternate masses or alternate on-site potentials.

PubMed

Pereira, Emmanuel; Santana, Leonardo M; Ávila, Ricardo

2011-07-01

We address a central issue of phononics: the search of properties or mechanisms to manage the heat flow in reliable materials. We analytically study standard and simple systems modeling the heat flow in solids, namely, the harmonic, self-consistent harmonic and also anharmonic chains of oscillators, and we show an interesting insulating effect: While in the homogeneous models the heat flow decays as the inverse of the particle mass, in the chain with alternate masses it decays as the inverse of the square of the mass difference, that is, it decays essentially as the mass ratio (between the smaller and the larger one) for a large mass difference. A similar effect holds if we alternate on-site potentials instead of particle masses. The existence of such behavior in these different systems, including anharmonic models, indicates that it is a ubiquitous phenomenon with applications in the heat flow control.

New computer program solves wide variety of heat flow problems

NASA Technical Reports Server (NTRS)

Almond, J. C.

1966-01-01

Boeing Engineering Thermal Analyzer /BETA/ computer program uses numerical methods to provide accurate heat transfer solutions to a wide variety of heat flow problems. The program solves steady-state and transient problems in almost any situation that can be represented by a resistance-capacitance network.

Two-dimensional heat flow analysis applied to heat sterilization of ponderosa pine and Douglas-fir square timbers

Treesearch

William T. Simpson

2004-01-01

Equations for a two-dimensional finite difference heat flow analysis were developed and applied to ponderosa pine and Douglas-fir square timbers to calculate the time required to heat the center of the squares to target temperature. The squares were solid piled, which made their surfaces inaccessible to the heating air, and thus surface temperatures failed to attain...

Comparison of visualized turbine endwall secondary flows and measured heat transfer patterns

NASA Technical Reports Server (NTRS)

Gaugler, R. E.; Russell, L. M.

1983-01-01

Various flow visualization techniques were used to define the secondary flows near the endwall in a large heat transfer data. A comparison of the visualized flow patterns and the measured Stanton number distribution was made for cases where the inlet Reynolds number and exit Mach number were matched. Flows were visualized by using neutrally buoyant helium-filled soap bubbles, by using smoke from oil soaked cigars, and by a few techniques using permanent marker pen ink dots and synthetic wintergreen oil. Details of the horseshoe vortex and secondary flows can be directly compared with heat transfer distribution. Near the cascade entrance there is an obvious correlation between the two sets of data, but well into the passage the effect of secondary flow is not as obvious.

Teflon probing for the flow characterization of arc-heated wind tunnel facilities

NASA Astrophysics Data System (ADS)

Gulli, Stefano; Ground, Cody; Crisanti, Matthew; Maddalena, Luca

2014-02-01

The experimental flow characterization of the arc-heated wind tunnel of the University of Texas at Arlington is investigated in this work using ablative Teflon probes in combination with total pressure measurements. A parallel analytical work, focused on the dimensional analysis of the ablation process, has been conducted with the purpose of improving existing semi-empirical correlations for the heat blockage due to the mass injection inside the boundary layer. A control volume analysis at the receding surface of the specimens is used to calculate the wall heat transfer for a non-ablating probe by including the blockage effect. The new correlations, obtained for the convective blockage, show an improvement of the correlation coefficient of 110 % with respect to those available in literature, once a new blowing parameter containing the stagnation pressure is introduced. A correlation developed by NASA during the Round-Robin program, which relates the Teflon mass loss rate to the total pressure and cold-wall heat flux measured experimentally, is also used to predict the wall heat transfer referred to the ablation temperature of Teflon. For both approaches, a simplified stagnation point convective heat transfer equation allows the average stagnation enthalpy to be calculated. Several locations downstream of the nozzle exit have been surveyed, and selected points of the facility's performance map have been used for the experimental campaign. The results show that both approaches provide similar results in terms of stagnation heat flux and enthalpy prediction with uncertainties comparable to those provided by standard intrusive heat flux probes ( δ q max < 25 %). The analysis of the Teflon's ablated surface does not reveal significant flow non-uniformities, and a 1.14 heat flux enhancement factor due to the shock-shock interaction is detectable at x = 3.5 in. from the nozzle exit plane. The results show the use of ablative probes for the flow characterization of arc

Conductive heat transfer from an isothermal magma chamber and its application to the measured heat flow distribution from mount hood, Oregon

USGS Publications Warehouse

Nathenson, Menuel; Tilling, Robert I.; ,

1993-01-01

A steady-state solution for heat transfer from an isothermal, spherical magma chamber, with an imposed regional geothermal gradient far from the chamber, is developed. The extensive published heat-flow data set for Mount Hood, Oregon, is dominated by conductive heat transfer in the deeper parts of most drill holes and provides an ideal application of such a model. Magma-chamber volumes or depths needed to match the distribution of heat-flow data are larger or shallower than those inferred from geologic evidence.

Development of a radiative heating facility for studying flow and heat transfer in hydrocarbon-cooled structures

NASA Astrophysics Data System (ADS)

Dong, Da; Lu, Yang; Yuan, Yueming; Fan, Xuejun

2018-06-01

An experimental facility was designed to simulate the heat exchange between the hot gas and the fuel-cooled wall in a scramjet combustor. Thermal radiation from an electrically heated graphite plate is employed to unilaterally heat up a multi-channeled cooling plate. A maximum heat flux of over 0.8 MW/m2 was achieved for an effective heating area up to 1000 mm × 40 mm. Precise control of the back pressure of a coolant (up to 5 MPa) in a unique way was also demonstrated. With this facility, studies of flow and heat transfer in hydrocarbon-cooled structures can be performed under a well-controlled manner.

Temperature and flow fields in samples heated in monoellipsoidal mirror furnaces

NASA Astrophysics Data System (ADS)

Rivas, D.; Haya, R.

The temperature field in samples heated in monoellipsoidal mirror furnaces will be analyzed. The radiation heat exchange between the sample and the mirror is formulated analytically, taking into account multiple reflections at the mirror. It will be shown that the effect of these multiple reflections in the heating process is quite important, and, as a consequence, the effect of the mirror reflectance in the temperature field is quite strong. The conduction-radiation model will be used to simulate the heating process in the floating-zone technique in microgravity conditions; important parameters like the Marangoni number (that drives the thermocapillary flow in the melt), and the temperature gradient at the melt-crystal interface will be estimated. The model will be validated comparing with experimental data. The case of samples mounted in a wall-free configuration (as in the MAXUS-4 programme) will be also considered. Application to the case of compound samples (graphite-silicon-graphite) will be made; the melting of the silicon part and the surface temperature distribution in the melt will be analyzed. Of special interest is the temperature difference between the two graphite rods that hold the silicon part, since it drives the thermocapillary flow in the melt. This thermocapillary flow will be studied, after coupling the previous model with the convective effects. The possibility of counterbalancing this flow by the controlled vibration of the graphite rods will be studied as well. Numerical results show that suppressing the thermocapillary flow can be accomplished quite effectively.

Heat fluxes across the Antarctic Circumpolar Current

NASA Astrophysics Data System (ADS)

Ferrari, Ramiro; Provost, Christine; Hyang Park, Young; Sennéchael, Nathalie; Garric, Gilles; Bourdallé-Badie, Romain

2014-05-01

Determining the processes responsible for the Southern Ocean heat balance is fundamental to our understanding of the weather and climate systems. Therefore, in the last decades, various studies aimed at analyzing the major mechanisms of the oceanic poleward heat flux in this region. Previous works stipulated that the cross-stream heat flux due to the mesoscale transient eddies was responsible for the total meridional heat transport across the Antarctic Circumpolar Current (ACC). Several numerical modelling and current meters data studies have recently challenged this idea. These showed that the heat flux due to the mean flow in the southern part of the Antarctic Circumpolar Current could be larger than the eddy heat flux contribution by two orders of magnitude. Eddy heat flux and heat flux by the mean flow distributions of were examined in Drake Passage using in situ measurements collected during the DRAKE 2006-9 project (from January 2006 to March 2009), available observations from the historical DRAKE 79 experiment and high resolution model outputs (ORCA 12, MERCATOR). The Drake Passage estimations provided a limited view of heat transport in the Southern Ocean. The small spatial scales shown by the model derived heat flux by the mean flow indicate that circumpolar extrapolations from a single point observation are perilous. The importance of the heat flux due by the mean flow should be further investigated using other in situ observations and numerical model outputs. Similar situation has been observed, with important implication for heat flux due to the mean flow, in other topographically constricted regions with strong flow across prominent submarine ridges (choke points). We have estimated the heat flux due to the mean flow revisiting other ACC mooring sites where in situ time series are available, e.g. south of Australia (Tasmania) (Phillips and Rintoul, 2000), southeast of New Zealand (Campbell Plateau) (Bryden and Heath, 1985). Heat fluxes due to the mean

Heat transfer in laminar flow along circular rods in infinite square arrays

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

Kim, J.H.; Li, W.H.

1988-02-01

The need to understand heat transfer characteristics over rods or tube bundles often arises in the design of compact heat exchangers and safety analysis of nuclear reactors. In particular, the fuel bundles of typical light water nuclear reactors are composed of a large number of circular rods arranged in square array pattern. The purpose of the present study is to analyze heat transfer characteristics of flow in such a multirod geometric configuration. The analysis given here will follow as closely as possible the method of Sparrow et al. who analyzed a similar problem for circular cylinders arranged in an equilateralmore » triangular array. The following major assumptions are made in the present analysis: (1) Flow is fully developed laminar flow paralleled to the axis of rods. (2) The axial profile of the surface heat flux to the fluid is uniform.(3) Thermodynamic properties are assumed constant.« less

Thermographic observation of heat transport in solid foams

NASA Astrophysics Data System (ADS)

Netzelmann, U.; Abuhamad, M.; Walle, G.

2005-06-01

Heat transport in solid foams was studied by flash lamp heated dynamic thermography. For polyurethane foams, a movement of the peak temperature from the heated surface into the depth could be observed. This could be modelled by assuming a Beer optical absorber with non-adiabatic boundary. For large open pores, individual temperature-time curves were observed in the thermographic image. There is evidence for non-conductive heat transfer in the bulk of mixed-cell foams. In SiSiC ceramic foams, indications for sub-surface defects were detected.

Study of Cold Heat Energy Release Characteristics of Flowing Ice Water Slurry in a Pipe

NASA Astrophysics Data System (ADS)

Inaba, Hideo; Horibe, Akihiko; Ozaki, Koichi; Yokota, Maki

This paper has dealt with melting heat transfer characteristics of ice water slurry in an inside tube of horizontal double tube heat exchanger in which a hot water circulated in an annular gap between the inside and outside tubes. Two kinds of heat exchangers were used; one is made of acrylic resin tube for flow visualization and the other is made of stainless steel tube for melting heat transfer measurement. The result of flow visualization revealed that ice particles flowed along the top of inside tube in the ranges of small ice packing factor and low ice water slurry velocity, while ice particles diffused into the whole of tube and flowed like a plug built up by ice particles for large ice packing factor and high velocity. Moreover, it was found that the flowing ice plug was separated into numbers of small ice clusters by melting phenomenon. Experiments of melting heat transfer were carried out under some parameters of ice packing factor, ice water slurry flow rate and hot water temperature. Consequently, the correlation equation of melting heat transfer was derived as a function of those experimental parameters.

Test of a new heat-flow equation for dense-fluid shock waves.

PubMed

Holian, Brad Lee; Mareschal, Michel; Ravelo, Ramon

2010-09-21

Using a recently proposed equation for the heat-flux vector that goes beyond Fourier's Law of heat conduction, we model shockwave propagation in the dense Lennard-Jones fluid. Disequilibrium among the three components of temperature, namely, the difference between the kinetic temperature in the direction of a planar shock wave and those in the transverse directions, particularly in the region near the shock front, gives rise to a new transport (equilibration) mechanism not seen in usual one-dimensional heat-flow situations. The modification of the heat-flow equation was tested earlier for the case of strong shock waves in the ideal gas, which had been studied in the past and compared to Navier-Stokes-Fourier solutions. Now, the Lennard-Jones fluid, whose equation of state and transport properties have been determined from independent calculations, allows us to study the case where potential, as well as kinetic contributions are important. The new heat-flow treatment improves the agreement with nonequilibrium molecular-dynamics simulations under strong shock wave conditions, compared to Navier-Stokes.

Oscillatory/chaotic thermocapillary flow induced by radiant heating

NASA Technical Reports Server (NTRS)

Hsieh, Kwang-Chung; Thompson, Robert L.; Vanzandt, David; Dewitt, Kenneth; Nash, Jon

1994-01-01

The objective of this paper is to conduct ground-based experiments to measure the onset conditions of oscillatory Marangoni flow in laser-heated silicone oil in a cylindrical container. For a single fluid, experimental data are presented using the aspect ratio and the dynamic Bond number. It is found that for a fixed aspect ratio, there seems to be an asymptotic limit of the dynamic Bond number beyond which no onset of flow oscillation could occur. Experimental results also suggested that there could be a lower limit of the aspect ratio below which there is no onset of oscillatory flow.

Enhancement of convective heat transfer in internal flows using an electrically-induced corona jet

NASA Astrophysics Data System (ADS)

Baghaei Lakeh, Reza

The enhancement of heat transfer by active and passive methods has been the subject of many academic and industrial research studies. Internal flows play a major role in many applications and different methods have been utilized to augment the heat transfer to internal flows. Secondary flows consume part of the kinetic energy of the flow and disturb the boundary layer. Inducing secondary flows is known as mechanism for heat transfer enhancement. Secondary flows may be generated by corona discharge and ion-driven flows. When a high electric potential is applied to a conductor, a high electric field will be generated. The high electric field may exceed the partial break-down of the neutral molecules of surrounding gas (air) and generate a low-temperature plasma in the vicinity of the conductor. The generated plasma acts as a source of ions that accelerate under the influence of the electric field and escape beyond the plasma region and move toward the grounded electrode. The accelerating ions collide with neutral particles of the surrounding gas and impose a dragging effect which is interpreted as a body-force to the air particles. The shape and configuration of the emitting and receiving electrodes has a significant impact on the distribution of the electric body-force and the resulting electrically-induced flow field. It turned out that the certain configurations of longitudinal electrodes may cause a jet-like secondary flow field on the cross section of the flow passage in internal flows. The impingement effect of the corona jet on the walls of the channel disturbs the boundary layer, enhances the convective heat transfer, and generates targeted cooling along the centerline of the jet. The results of the current study show that the concentric configuration of a suspended wire-electrode in a circular tube leads to a hydrostatic condition and do not develop any electrically-induced secondary flow; however, the eccentric wire-electrode configuration generates a

Numerical evaluation of laminar heat transfer enhancement in nanofluid flow in coiled square tubes

PubMed Central

2011-01-01

Convective heat transfer can be enhanced by changing flow geometry and/or by enhancing thermal conductivity of the fluid. This study proposes simultaneous passive heat transfer enhancement by combining the geometry effect utilizing nanofluids inflow in coils. The two nanofluid suspensions examined in this study are: water-Al2O3 and water-CuO. The flow behavior and heat transfer performance of these nanofluid suspensions in various configurations of coiled square tubes, e.g., conical spiral, in-plane spiral, and helical spiral, are investigated and compared with those for water flowing in a straight tube. Laminar flow of a Newtonian nanofluid in coils made of square cross section tubes is simulated using computational fluid dynamics (CFD)approach, where the nanofluid properties are treated as functions of particle volumetric concentration and temperature. The results indicate that addition of small amounts of nanoparticles up to 1% improves significantly the heat transfer performance; however, further addition tends to deteriorate heat transfer performance. PMID:21711901

Comparison of visualized turbine endwall secondary flows and measured heat transfer patterns

NASA Technical Reports Server (NTRS)

Gaugler, R. E.; Russell, L. M.

1984-01-01

Various flow visualization techniques were used to define the seondary flows near the endwall in a large heat transfer data. A comparison of the visualized flow patterns and the measured Stanton number distribution was made for cases where the inlet Reynolds number and exit Mach number were matched. Flows were visualized by using neutrally buoyant helium-filled soap bubbles, by using smoke from oil soaked cigars, and by a few techniques using permanent marker pen ink dots and synthetic wintergreen oil. Details of the horseshoe vortex and secondary flows can be directly compared with heat transfer distribution. Near the cascade entrance there is an obvious correlation between the two sets of data, but well into the passage the effect of secondary flow is not as obvious. Previously announced in STAR as N83-14435

Minimal vascular flows cause strong heat sink effects in hepatic radiofrequency ablation ex vivo.

PubMed

Lehmann, Kai S; Poch, Franz G M; Rieder, Christian; Schenk, Andrea; Stroux, Andrea; Frericks, Bernd B; Gemeinhardt, Ole; Holmer, Christoph; Kreis, Martin E; Ritz, Jörg P; Zurbuchen, Urte

2016-08-01

The present paper aims to assess the lower threshold of vascular flow rate on the heat sink effect in bipolar radiofrequency ablation (RFA) ex vivo. Glass tubes (vessels) of 3.4 mm inner diameter were introduced in parallel to bipolar RFA applicators into porcine liver ex vivo. Vessels were perfused with flow rates of 0 to 1,500 ml/min. RFA (30 W power, 15 kJ energy input) was carried out at room temperature and 37°C. Heat sink effects were assessed in RFA cross sections by the decrease in ablation radius, area and by a high-resolution sector planimetry. Flow rates of 1 ml/min already caused a significant cooling effect (P ≤ 0.001). The heat sink effect reached a maximum at 10 ml/min (18.4 mm/s) and remained stable for flow rates up to 1,500 ml/min. Minimal vascular flows of ≥1 ml/min cause a significant heat sink effect in hepatic RFA ex vivo. A lower limit for volumetric flow rate was not found. The maximum of the heat sink effect was reached at a flow rate of 10 ml/min and remained stable for flow rates up to 1,500 ml/min. Hepatic inflow occlusion should be considered in RFA close to hepatic vessels. © 2016 Japanese Society of Hepato-Biliary-Pancreatic Surgery.

3-Dimensional numerical study of cooling performance of a heat sink with air-water flow through mini-channel

NASA Astrophysics Data System (ADS)

Majumder, Sambit; Majumder, Abhik; Bhaumik, Swapan

2016-07-01

The present microelectronics market demands devices with high power dissipation capabilities having enhanced cooling per unit area. The drive for miniaturizing the devices to even micro level dimensions is shooting up the applied heat flux on such devices, resulting in complexity in heat transfer and cooling management. In this paper, a method of CPU processor cooling is introduced where active and passive cooling techniques are incorporated simultaneously. A heat sink consisting of fins is designed, where water flows internally through the mini-channel fins and air flows externally. Three dimensional numerical simulations are performed for large set of Reynolds number in laminar region using finite volume method for both developing flows. The dimensions of mini-channel fins are varied for several aspect ratios such as 1, 1.33, 2 and 4. Constant temperature (T) boundary condition is applied at heat sink base. Channel fluid temperature, pressure drop are analyzed to obtain best cooling option in the present study. It has been observed that as the aspect ratio of the channel decreases Nusselt number decreases while pressure drop increases. However, Nusselt number increases with increase in Reynolds number.

Heat Generation in Axial and Centrifugal Flow Left Ventricular Assist Devices.

PubMed

Yost, Gardner; Joseph, Christine Rachel; Royston, Thomas; Tatooles, Antone; Bhat, Geetha

Despite increasing use of left ventricular assist devices (LVADs) as a surgical treatment for advanced heart failure in an era of improved outcomes with LVAD support, the mechanical interactions between these pumps and the cardiovascular system are not completely understood. We utilized an in vitro mock circulatory loop to analyze the heat production incurred by operation of an axial flow and centrifugal flow LVAD. A HeartMate II and a HeartWare HVAD were connected to an abbreviated flow loop and were implanted in a viscoelastic gel. Temperature was measured at the surface of each LVAD. Device speed and fluid viscosity were altered and, in the HeartMate II, as artificial thrombi were attached to the inflow stator, impeller, and outflow stator. The surface temperatures of both LVADs increased in all trials and reached a plateau within 80 minutes of flow initiation. Rate of heat generation and maximum system temperature were greater when speed was increased, when viscosity was increased, and when artificial thrombi were attached to the HeartMate II impeller. Normal operation of these two widely utilized LVADs results in appreciable heat generation in vitro. Increased pump loading resulted in more rapid heat generation, which was particularly severe when a large thrombus was attached to the impeller of the HeartMate II. While heat accumulation in vivo is likely minimized by greater dissipation in the blood and soft tissues, focal temperature gains with the pump housing of these two devices during long-term operation may have negative hematological consequences.

The effects of orbital and climatic variations on Martian surface heat flow

NASA Technical Reports Server (NTRS)

Mellon, Michael T.; Jakosky, Bruce M.

1993-01-01

Large changes in the orbital elements of Mars on timescales of 10(exp 4) to 10(exp 6) years will cause widely varying climate, specifically surface temperatures, as a result of varying insolation. These surface temperature oscillations will produce subsurface thermal gradients which contribute to the total surface heat flux. We investigate the thermal behavior of the Martian regolith on orbital timescales and show that this climatological surface heat flux is spatially variable and contributes significantly to the total surface heat flux at many locations. We model the thermal behavior of the Martian regolith by calculating the mean annual surface temperatures for each epoch (spaced 1000 years apart to resolve orbital variations) for the past 200,000 years at a chosen location on the surface. These temperatures are used as a boundary condition for the deeper regolith and subsurface temperature oscillation are then computed. The surface climatological heat flux due to past climate changes can then be found from the temperature gradient between the surface and about 150 m depth (a fraction of the thermal skin depth on these timescales). This method provides a fairly accurate determination of the climatological heat flow component at a point; however, this method is computationally time consuming and cannot be applied to all points on the globe. To map the spatial variations in the surface heat flow we recognize that the subsurface temperature structure will be largely dominated by the most recent surface temperature oscillations. In fact, the climate component of the surface heat flow will be approximately proportional to the magnitude of the most recent surface temperature change. By calculating surface temperatures at all points globally for the present epoch and an appropriate past epoch, and combining these results with a series of more precise calculations described above, we estimate the global distribution of climatological surface heat flow.

NEW MODEL AND MEASUREMENT PRINCIPLE OF FLOWING AND HEAT TRANSFER CHARACTERISTICS OF REGENERATOR

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

Chen, Y. Y.; Graduate University of the Chinese Academy of Sciences, Beijing, 100049; Luo, E. C.

2008-03-16

Regenerators play key role in oscillating-flow cryocoolers or thermoacoustic heat engine systems. However, their flowing and heat transfer mechanism is still not well understood. The complexities of the oscillating flow regenerator make traditional method of heat transfer research become difficult or helpless. In this paper, a model for porous media regenerator was given based on the linear thermoacoustic theory. Then the correlations for characteristic parameters were obtained by deducing universal expressions for thermoacoustic viscous function F{sub v} and thermal function F{sub T}. A simple acoustical method and experimental system to get F{sub v} and F{sub T} via measurements of isothermalmore » regenerators were presented. Some measurements of packed stainless screen regenerators were performed, and preliminary experimental results for flow and convective coefficients were derived, which showing flowing friction factor is approximately within 132/Re to 173/Re.« less

Augmentation of heat and mass transfer in laminar flow of suspensions: A correlation of data

NASA Astrophysics Data System (ADS)

Ahuja, Avtar S.

1980-01-01

The experimental data from literature on the augmentation of heat and gas transport in the laminar flow of suspensions of polystyrene spheres have been correlated on common coordinates. The correlation includes the influences of particle size, tube diameter and length, shear rate of flow, transport properties of diffusing species (heat or gas) in suspending liquids, and of the particle interactions on the augmentation of heat or gas transfer in flowing suspensions.

The contribution of skin blood flow in warming the skin after the application of local heat; the duality of the Pennes heat equation.

PubMed

Petrofsky, Jerrold; Paluso, Dominic; Anderson, Devyn; Swan, Kristin; Yim, Jong Eun; Murugesan, Vengatesh; Chindam, Tirupathi; Goraksh, Neha; Alshammari, Faris; Lee, Haneul; Trivedi, Moxi; Hudlikar, Akshay N; Katrak, Vahishta

2011-04-01

As predicted by the Pennes equation, skin blood flow is a major contributor to the removal of heat from an external heat source. This protects the skin from erythema and burns. But, for a person in a thermally neutral room, the skin is normally much cooler than arterial blood. Therefore, if skin blood flow (BF) increases, it should initially warm the skin paradoxically. To examine this phenomenon, 10 young male and female subjects participated in a series of experiments to examine the contribution of skin blood flow in the initial warming the skin after the application of local heat. Heat flow was measured by the use of a thermode above the brachioradialis muscle. The thermode was warmed by constant temperature water at 44°C entering the thermode at a water flow rate of 100 cm(3)/min. Skin temperature was measured by a thermistor and blood flow in the underlying skin was measured by a laser Doppler imager in single point mode. The results of the experiments showed that, when skin temperature is cool (31-32°C), the number of calories being transferred to the skin from the thermode cannot account for the rise in skin temperature alone. A significant portion of the rise in skin temperature is due to the warm arterialized blood traversing the skin from the core areas of the body. However, as skin temperature approaches central core temperature, it becomes less of a heat source and more of a heat sync such that when skin temperature is at or above core temperature, the blood flow to the skin, as predicted by Pennes, becomes a heat sync pulling heat from the thermode. Copyright © 2010 IPEM. Published by Elsevier Ltd. All rights reserved.

Observations in Nonurban Heat Islands.

NASA Astrophysics Data System (ADS)

Hogan, A. W.; Ferrick, M. G.

1998-02-01

The urban heat island is a well-known and well-described temperature anomaly, but other types of heat islands are also infrequently reported. A 10 km × 30 km data field containing more than 100 individual winter morning air temperature measurement points was examined for areas characteristically warmer than surrounding areas. The very small `downtown' of Hanover, New Hampshire, was found to be 1°-2°C warmer than nearby open areas at the same elevation. The same technique was applied to examine the morning air temperature within a nearby hamlet consisting of about 60 wooden buildings within an area less than 0.3 km2. The bulk of observations and observations stratified by snow and sky cover showed no systematic difference between hamlet air temperatures and those obtained in surrounding terrain. Morning air temperatures along a freezing river were measured and found to be systematically warmer than nearby air temperatures for several days, until a significant snowfall diminished the ice growth rate. A thorough examination of temperature profiles near the river showed that the increase in air temperature beneath the overnight inversion during this freezing period was proportional to the heat release resulting from river ice growth.

Analysis of the Hydrodynamics and Heat Transfer Aspects of Microgravity Two-Phase Flows

NASA Technical Reports Server (NTRS)

Rezkallah, Kamiel S.

1996-01-01

Experimental results for void fractions, flow regimes, and heat transfer rates in two-phase, liquid-gas flows are summarized in this paper. The data was collected on-board NASA's KC-135 reduced gravity aircraft in a 9.525 mm circular tube (i.d.), uniformly heated at the outer surface. Water and air flows were examined as well as three glycerol/water solutions and air. Results are reported for the water-air data.

Effect of heat transfer on rotating electroosmotic flow through a micro-vessel: haemodynamical applications

NASA Astrophysics Data System (ADS)

Sinha, A.; Mondal, A.; Shit, G. C.; Kundu, P. K.

2016-08-01

This paper theoretically analyzes the heat transfer characteristics associated with electroosmotic flow of blood through a micro-vessel having permeable walls. The analysis is based on the Debye-Hückel approximation for charge distributions and the Navier-Stokes equations are assumed to represent the flow field in a rotating system. The velocity slip condition at the vessel walls is taken into account. The essential features of the rotating electroosmotic flow of blood and associated heat transfer characteristics through a micro-vessel are clearly highlighted by the variation in the non-dimensional flow velocity, volumetric flow rate and non-dimensional temperature profiles. Moreover, the effect of Joule heating parameter and Prandtl number on the thermal transport characteristics are discussed thoroughly. The study reveals that the flow of blood is appreciably influenced by the elctroosmotic parameter as well as rotating Reynolds number.

A laser-induced heat flux technique for convective heat transfer measurements in high speed flows

NASA Technical Reports Server (NTRS)

Porro, A. R.; Keith, T. G., Jr.; Hingst, W. R.

1991-01-01

A technique is developed to measure the local convective heat transfer coefficient on a model surface in a supersonic flow field. The technique uses a laser to apply a discrete local heat flux at the model test surface, and an infrared camera system determines the local temperature distribution due to the heating. From this temperature distribution and an analysis of the heating process, a local convective heat transfer coefficient is determined. The technique was used to measure the local surface convective heat transfer coefficient distribution on a flat plate at nominal Mach numbers of 2.5, 3.0, 3.5, and 4.0. The flat plate boundary layer initially was laminar and became transitional in the measurement region. The experimentally determined convective heat transfer coefficients were generally higher than the theoretical predictions for flat plate laminar boundary layers. However, the results indicate that this nonintrusive optical measurement technique has the potential to measure surface convective heat transfer coefficients in high-speed flowfields.

Complex fluid flow and heat transfer analysis inside a calandria based reactor using CFD technique

NASA Astrophysics Data System (ADS)

Kulkarni, P. S.

2017-04-01

Series of numerical experiments have been carried out on a calandria based reactor for optimizing the design to increase the overall heat transfer efficiency by using Computational Fluid Dynamic (CFD) technique. Fluid flow and heat transfer inside the calandria is governed by many geometric and flow parameters like orientation of inlet, inlet mass flow rate, fuel channel configuration (in-line, staggered, etc.,), location of inlet and outlet, etc.,. It was well established that heat transfer is more wherever forced convection dominates but for geometries like calandria it is very difficult to achieve forced convection flow everywhere, intern it strongly depends on the direction of inlet jet. In the present paper the initial design was optimized with respect to inlet jet angle, the optimized design has been numerically tested for different heat load mass flow conditions. To further increase the heat removal capacity of a calandria, further numerical studies has been carried out for different inlet geometry. In all the analysis same overall geometry size and same number of tubes has been considered. The work gives good insight into the fluid flow and heat transfer inside the calandria and offer a guideline for optimizing the design and/or capacity enhancement of a present design.

Subsurface temperatures and surface heat flow in the Michigan Basin and their relationships to regional subsurface fluid movement

USGS Publications Warehouse

Vugrinovich, R.

1989-01-01

Linear regression of 405 bottomhole temperature (BHT) measurements vs. associated depths from Michigan's Lower Peninsula results in the following equation relating BHT and depth: BHT(??C) = 14.5 + 0.0192 ?? depth(m) Temperature residuals, defined as (BHT measured)-(BHT calculated), were determined for each of the 405 BHT's. Areas of positive temperature residuals correspond to areas of regional groundwater discharge (determined from maps of equipotential surface) while areas of negative temperature residuals correspond to areas of regional groundwater recharge. These relationships are observed in the principal aquifers in rocks of Devonian and Ordovician age and in a portion of the principal aquifer in rocks of Silurian age. There is a similar correspondence between high surface heat flow (determined using the silica geothermometer) and regional groundwater discharge areas and low surface heat flow and regional groundwater recharge areas. Post-Jurassic depositional and tectonic histories suggest that the observed coupling of subsurface temperature and groundwater flow systems may have persisted since Jurassic time. Thus the higher subsurface palaeotemperatures (and palaeogeothermal gradients) indicated by recent studies most likely pre-date the Jurassic. ?? 1989.

Characterization of Preferential Flow Path in Fractured Rock Using Heat-pulse Flowmeter

NASA Astrophysics Data System (ADS)

Lee, Tsai-Ping; Lin, Ming-Hsuan; Chuang, Po-Yu; Chia, Yeeping

2015-04-01

Rigorous thinking on how to dispose radioactive wastes safely is essential to mankind and living environment. The concepts of multiple barriers and deep geologic disposal remain the preferred option to retard the radionuclide migration in most countries. However, the investigation of preferential groundwater flow path in a fractured rock is a challenge to the characterization of potential disposal site. Heat-pulse flowmeter is a developing logging tool for measuring the vertical flow velocity in a borehole under a constant pumping or injection rate and provides a promising direct measurement method for determining the vertical distribution of hydraulic conductivity of formation. As heat-pulse flowmeter is a potential technique to measure low-velocity borehole flow, we adopted it to test the feasibility of detecting permeable fractures. Besides, a new magnetic tracer made by nano-iron particles is developed to identify the possible flow path precisely and to verify the permeable section detected by the heat-pulse flowmeter. The magnetic tracer was received by a magnet array and can also be detected by a sensor of electric conductivity. The test site is located in the Heshe of Taiwan. Eight wells were established in a fractured sandy siltstone for characterizing the fracture network. The test wells are 25 to 45 m depth and opened ranging from 15 to 45 m. Prior to the heat-pulse flowmeter measurement, we also performed surface geological investigation, pumping test, geophysical logging, and salt tracer test. Field measurements using heat-pulse flowmeter were then conducted at a constant pumping rate. The measurement interval is 50 to 100 cm in depth but improved to 25 cm near the relatively permeable zone. Based on the results of heat-pulse flowmeter, several permeable sections were identified. The magnetic tracer tests were then conducted to verify the potential preferential flow pathway between adjacent wells. Test results indicated that water flow in borehole is

Heat Transfer to Longitudinal Laminar Flow Between Cylinders

NASA Technical Reports Server (NTRS)

Sparrow, Ephraim M.; Loeffler, Albert L. Jr.; Hubbard, H. A.

1960-01-01

Consideration is given to the fully developed heat transfer characteristics for longitudinal laminar flow between cylinders arranged in an equilateral triangular array. The analysis is carried out for the condition of uniform heat transfer per unit length. Solutions are obtained for the temperature distribution, and from these, Nusselt numbers are derived for a wide range of spacing-to-diameter ratios. It is found that as the spacing ratio increases, so also does the wall-to-bulk temperature difference for a fixed heat transfer per unit length. Corresponding to a uniform surface temperature around the circumference of a cylinder, the circumferential variation of the local heat flux is computed. For spacing ratios of 1.5 - 2.0 and greater, uniform peripheral wall temperature and uniform peripheral heat flux are simultaneously achieved. A simplified analysis which neglects circumferential variations is also carried out, and the results are compared with those from the more exact formulation.

Investigation of Impact Jets Flow in Heat Sink Device of Closed-Circuit Cooling Systems

NASA Astrophysics Data System (ADS)

Tokarev, D. A.; Yenivatov, V. V.; Sokolov, S. S.; Erofeev, V. L.

2018-03-01

The flow simulations of impact jets in the heat sink device of the closed-circuit cooling systems are presented. The analysis of the rate of fluid flow in the heat sink device with the jet supply coolant is given.

Heat flow and thermotectonic problems of the central Ventura Basin, southern California

USGS Publications Warehouse

De Rito, R. F.; Lachenbruch, A.H.; Moses, T.H.; Munroe, R.J.

1989-01-01

The Ventura Basin, southern California, is located near the Big Bend area of the San Andreas fault system, within the Transverse Ranges physiographic province. Negative curvature of the Ventura Avenue temperature profiles may be explained by an increase in thermal conductivity associated with tectonic compaction of the underlying Pliocene clastic sequence. Basinwide, heat flow averages about 48 mW/m2, a value which is low relative to most of southern California. As heat flow does not vary systematically to the maximum measured depth of about 4 km, this anomly is not easily explained in terms of hydrologic effects or recent uplift and erosion. However, a diminution of heat flow is an expectable consequence of the accumulation of cold sediments (up to 12 km) since Eocene time. -from Authors

Heat flow and continental breakup: The Gulf of Elat (Aqaba)

NASA Technical Reports Server (NTRS)

Ben-Avraham, Z.; Vonherzen, R. P.

1985-01-01

Heat flow measurements were made in the major basins of the Gulf of Elat (Aqaba), northern Red Sea. The gulf is located at the southern portion of the Dead Sea rift which is a transform plate boundary. Gradient measurements at each site were made with a probe which allows multiple penetration of the bottom during a single deployment of the instrument. Thermal conductivity was determined by needle probe measurements on sedimentary cores. The mean heat flux, about 80 mWm(-2), is significantly above the continental mean, and probably also above that from the adjacent Sinai and Arabian continental blocks. The heat flow appears to increase from north to south. Such an increase may be related to the more advanced rifting stage of the Red Sea immediately to the south, which presently includes creation of an oceanic crust. This trend also corresponds to the general trend of the deep crustal structure in the gulf. Evidence from various geophysical fields suggest a gradual thinning of the crust towards the direction of the Red Sea where a normal oceanic crust exists. The heat flow data, together with other geophysical data, indicate a propagation of mature rifting activity from the Red Sea into the Gulf of Elat. This process is acting simultaneously with the transform motion along the Dead Sea rift.

Passive flow heat exchanger simulation for power generation from solar pond using thermoelectric generators

NASA Astrophysics Data System (ADS)

Baharin, Nuraida'Aadilia; Arzami, Amir Afiq; Singh, Baljit; Remeli, Muhammad Fairuz; Tan, Lippong; Oberoi, Amandeep

2017-04-01

In this study, a thermoelectric generator heat exchanger system was designed and simulated for electricity generation from solar pond. A thermoelectric generator heat exchanger was studied by using Computational Fluid Dynamics to simulate flow and heat transfer. A thermoelectric generator heat exchanger designed for passive in-pond flow used in solar pond for electrical power generation. A simple analysis simulation was developed to obtain the amount of electricity generated at different conditions for hot temperatures of a solar pond at different flow rates. Results indicated that the system is capable of producing electricity. This study and design provides an alternative way to generate electricity from solar pond in tropical countries like Malaysia for possible renewable energy applications.

Observing changes in atmospheric heat content

NASA Astrophysics Data System (ADS)

Balcerak, Ernie

2011-10-01