Jackson, J. D.
2012-07-01
Severe deterioration of forced convection heat transfer can be encountered with compressible fluids flowing through strongly heated tubes of relatively small bore as the flow accelerates and turbulence is reduced because of the fluid density falling (as the temperature rises and the pressure falls due to thermal and frictional influence). The model presented here throws new light on how the dependence of density on both temperature and pressure can affect turbulence and heat transfer and it explains why the empirical equations currently available for calculating effectiveness of forced convection heat transfer under conditions of strong non-uniformity of fluid properties sometimes fail to reproduce observed behaviour. It provides a criterion for establishing the conditions under which such deterioration of heat transfer might be encountered and enables heat transfer coefficients to be determined when such deterioration occurs. The analysis presented here is for a gaseous fluid at normal pressure subjected strong non-uniformity of fluid properties by the application of large temperature differences. Thus the model leads to equations which describe deterioration of heat transfer in terms of familiar parameters such as Mach number, Reynolds number and Prandtl number. It is applicable to thermal power plant systems such as rocket engines, gas turbines and high temperature gas-cooled nuclear reactors. However, the ideas involved apply equally well to fluids at supercritical pressure. Impairment of heat transfer under such conditions has become a matter of growing interest with the active consideration now being given to advanced water-cooled nuclear reactors designed to operate at pressures above the critical value. (authors)
Pressure-drop Reduction and Heat-transfer Deterioration of Slush Nitrogen in Square Pipe flow
NASA Astrophysics Data System (ADS)
Ohira, Katsuhide; Nakagomi, Kei; Takahashi, Koichi; Aoki, Itsuo
Pressure drop and heat transfer tests were carried out using slush nitrogen flowing in a horizontal square pipe at flow velocity between 1.0 and 4.9 m/s, with a mass solid fraction between 6 and 26 wt.%, and with heat fluxes of 0, 10 and 20 kW/m2. Pressure drop reduction became apparent at flow velocity of 2.5 m/s and over, with the maximum amount of reduction being 12% in comparison with liquid nitrogen, regardless of heating, while heat transfer deterioration became apparent at flow velocity of 1.0 m/s and over, with the maximum amount of deterioration being 16 and 21% at 10 and 20 kW/m2, respectively.
NASA Astrophysics Data System (ADS)
Ohira, Katsuhide; Kurose, Kizuku; Okuyama, Jun; Saito, Yutaro; Takahashi, Koichi
2017-01-01
Slush fluids such as slush hydrogen and slush nitrogen are characterized by superior properties as functional thermal fluids due to their density and heat of fusion. In addition to allowing efficient hydrogen transport and storage, slush hydrogen can serve as a refrigerant for high-temperature superconducting (HTS) equipment using MgB2, with the potential for synergistic effects. In this study, pressure drop reduction and heat transfer deterioration experiments were performed on slush nitrogen flowing in a horizontal triangular pipe with sides of 20 mm under the conditions of three different cross-sectional orientations. Experimental conditions consisted of flow velocity (0.3-4.2 m/s), solid fraction (0-25 wt.%), and heat flux (0, 10, and 20 kW/m2). Pressure drop reduction became apparent at flow velocities exceeding about 1.3-1.8 m/s, representing a maximum amount of reduction of 16-19% in comparison with liquid nitrogen, regardless of heating. Heat transfer deterioration was seen at flow velocities of over 1.2-1.8 m/s, for a maximum amount of deterioration of 13-16%. The authors of the current study compared the results for pressure drop reduction and heat transfer deterioration in triangular pipe with those obtained previously for circular and square pipes, clarifying differences in flow and heat transfer properties. Also, a correlation equation was obtained between the slush Reynolds number and the pipe friction factor, which is important in the estimation of pressure drop in unheated triangular pipe. Furthermore, a second correlation equation was derived between the modified slush Reynolds number and the pipe friction factor, enabling the integrated prediction of pressure drop in both unheated triangular and circular pipes.
Williams, Brian G.; Schultz, Richard R.; McEligot, Don M.; McCreery, Glenn
2015-08-31
A reference design for the Next Generation Nuclear Plant (NGNP) is to use General Atomics Modular High Temperature Gas-cooled Reactor (MHTGR). For such a configuration in normal operation, the helium coolant flow proceeds from the upper plenum to the lower plenum principally through the core coolant channels and the interstitial gaps (bypass flow) that separate the prismatic blocks from one another. Only the core prismatic blocks have coolant channels. The interstitial gaps are present throughout the core, the inner reflector region, and the out reflector region. The bypass flows in a prismatic gas-cooled reactor (GCR) are of potential concern because they reduce the desired flow rates in the coolant channels and, thereby, can increase outlet gas temperatures and maximum fuel temperatures. Consequently, it is appropriate to account for bypass flows in reactor thermal gas dynamic analyses. The objectives of this project include the following: fundamentally understand bypass flow and heat transfer at scaled, undistorted conditions and with geometry distortions; develop improved estimates of associated loss coefficients, surface friction and heat transfer for systems and network codes; and obtain related data for validation of CFD (computational fluid dynamic) or system (e.g., RELAP5) codes which can be employed in predictions for a GCR for normal power, reduced power, and residual heat removal operations.
Not Available
1980-03-07
A heat transfer system for a nuclear reactor is described. Heat transfer is accomplished within a sealed vapor chamber which is substantially evacuated prior to use. A heat transfer medium, which is liquid at the design operating temperatures, transfers heat from tubes interposed in the reactor primary loop to spaced tubes connected to a steam line for power generation purposes. Heat transfer is accomplished by a two-phase liquid-vapor-liquid process as used in heat pipes. Condensible gases are removed from the vapor chamber through a vertical extension in open communication with the chamber interior.
McGuire, Joseph C.
1982-01-01
A heat transfer system for a nuclear reactor. Heat transfer is accomplished within a sealed vapor chamber which is substantially evacuated prior to use. A heat transfer medium, which is liquid at the design operating temperatures, transfers heat from tubes interposed in the reactor primary loop to spaced tubes connected to a steam line for power generation purposes. Heat transfer is accomplished by a two-phase liquid-vapor-liquid process as used in heat pipes. Condensible gases are removed from the vapor chamber through a vertical extension in open communication with the chamber interior.
NASA Astrophysics Data System (ADS)
Nakayama, W.
Recent publications on enhancement of heat transfer are reviewed, emphasizing the effects of roughness elements, fins, and porous surfaces. Enhancement of forced convective heat transfer on roughened surfaces, performance evaluation of enhanced surfaces, viscous flows in cooled tubes and tubes with swirlers, and active methods of enhancement are addressed. Aspects of pool boiling heat transfer are considered, including nucleate boiling heat transfer on rough surfaces and porous surfaces, and maximum and minimum heat fluxes. Evaporative heat transfer is discussed for thin-film evaporation on structured surfaces and liquid spray cooling of a heated surface. Condensation heat transfer on external surfaces is covered, including filmwise condensation on vertical finned and fluted surfaces and on horizontal tubes. In-tube boiling and condensation are treated, discussing their enhancement by fins and inserts, as well as critical heat flux in coiled, rifled, and corrugated tubes.
Heat transfer in microwave heating
NASA Astrophysics Data System (ADS)
Peng, Zhiwei
Heat transfer is considered as one of the most critical issues for design and implement of large-scale microwave heating systems, in which improvement of the microwave absorption of materials and suppression of uneven temperature distribution are the two main objectives. The present work focuses on the analysis of heat transfer in microwave heating for achieving highly efficient microwave assisted steelmaking through the investigations on the following aspects: (1) characterization of microwave dissipation using the derived equations, (2) quantification of magnetic loss, (3) determination of microwave absorption properties of materials, (4) modeling of microwave propagation, (5) simulation of heat transfer, and (6) improvement of microwave absorption and heating uniformity. Microwave heating is attributed to the heat generation in materials, which depends on the microwave dissipation. To theoretically characterize microwave heating, simplified equations for determining the transverse electromagnetic mode (TEM) power penetration depth, microwave field attenuation length, and half-power depth of microwaves in materials having both magnetic and dielectric responses were derived. It was followed by developing a simplified equation for quantifying magnetic loss in materials under microwave irradiation to demonstrate the importance of magnetic loss in microwave heating. The permittivity and permeability measurements of various materials, namely, hematite, magnetite concentrate, wüstite, and coal were performed. Microwave loss calculations for these materials were carried out. It is suggested that magnetic loss can play a major role in the heating of magnetic dielectrics. Microwave propagation in various media was predicted using the finite-difference time-domain method. For lossy magnetic dielectrics, the dissipation of microwaves in the medium is ascribed to the decay of both electric and magnetic fields. The heat transfer process in microwave heating of magnetite
Heat transfer equipment design
NASA Astrophysics Data System (ADS)
Shah, R. K.; Subbarao, Eleswarapu Chinna; Mashelkar, R. A.
A comprehensive presentation is made of state-of-the-art configurations and design methodologies for heat transfer devices applicable to industrial processes, automotive systems, air conditioning/refrigeration, cryogenics, and petrochemicals refining. Attention is given to topics in heat exchanger mechanical design, single-phase convection processes, thermal design, two-phase exchanger thermal design, heat-transfer augmentation, and rheological effects. Computerized analysis and design methodologies are presented for the range of heat transfer systems, as well as advanced methods for optimization and performance projection.
NASA Technical Reports Server (NTRS)
Burbach, T.
1985-01-01
The heat transfer from hot water to a cold copper pipe in laminar and turbulent flow condition is determined. The mean flow through velocity in the pipe, relative test length and initial temperature in the vessel were varied extensively during tests. Measurements confirm Nusselt's theory for large test lengths in laminar range. A new equation is derived for heat transfer for large starting lengths which agrees satisfactorily with measurements for large starting lengths. Test results are compared with the new Prandtl equation for heat transfer and correlated well. Test material for 200- and to 400-diameter test length is represented at four different vessel temperatures.
NASA Astrophysics Data System (ADS)
Mohseni, Kamran; Young, Patrick
2007-11-01
This presentation presents theoretical and numerical results describing digitized heat transfer (DHT), an active thermal management technique for high-power electronics and integrated micro systems. In digitized heat transfer discrete droplets are employed. The internal flow inside a discrete droplet is dominated by internal circulation imposed by the boundaries. This internal circulation imposes a new timescale for recirculating cold liquid from the middle of the droplet to the boundary. This internal circulation produces periodic oscillation in the overall convective heat transfer rate. Numerical simulations are presented for heat transfer in the droplet for both constant temperature and flux boundary conditions. The effectiveness of DHT for managing both localized temperature spikes and steady state cooling is demonstrated, identifying key parameters for optimization of the DHT method.
NASA Technical Reports Server (NTRS)
Rohde, J. E.
1982-01-01
Objectives and approaches to research in turbine heat transfer are discussed. Generally, improvements in the method of determining the hot gas flow through the turbine passage is one area of concern, as is the cooling air flow inside the airfoil, and the methods of predicting the heat transfer rates on the hot gas side and on the coolant side of the airfoil. More specific areas of research are: (1) local hot gas recovery temperatures along the airfoil surfaces; (2) local airfoil wall temperature; (3) local hot gas side heat transfer coefficients on the airfoil surfaces; (4) local coolant side heat transfer coefficients inside the airfoils; (5) local hot gas flow velocities and secondary flows at real engine conditions; and (6) local delta strain range of the airfoil walls.
Heat transfer fluids containing nanoparticles
Singh, Dileep; Routbort, Jules; Routbort, A.J.; Yu, Wenhua; Timofeeva, Elena; Smith, David S.; France, David M.
2016-05-17
A nanofluid of a base heat transfer fluid and a plurality of ceramic nanoparticles suspended throughout the base heat transfer fluid applicable to commercial and industrial heat transfer applications. The nanofluid is stable, non-reactive and exhibits enhanced heat transfer properties relative to the base heat transfer fluid, with only minimal increases in pumping power required relative to the base heat transfer fluid. In a particular embodiment, the plurality of ceramic nanoparticles comprise silicon carbide and the base heat transfer fluid comprises water and water and ethylene glycol mixtures.
Boehm, R.; Chen, Y.T.; Sathappan, A.K.
1995-10-20
Work continued from last quarter related to studies of heat transfer and fluid flow in porous media. One experiment focused on issues of drying in subresidually-saturated systems. The other experiment deals with studies of flows in a repository-like geometry around a heated horizontal annulus. In the subresidual saturation studies, elevated temperature environments were considered during this quarter. A 1 in. {times} 8 ft long heating tape (heating capabilities of 8.6 W/in{sup 2}) with an on-off type temperature controller has been used to maintain a constant temperature on the aluminum test section (the latter has been described in earlier reports). Nitrogen gas with a flow rate of 1 SLPM was flowed through a glass-bead medium with an isothermal (90{degrees}C) boundary condition. The drying characteristics of this system are reported. In a second experiment, that of flow and heat transfer around a simulated drift, a low, constant heat flux boundary condition on the heater has been used. Two different admitted water quantities, 200 ml and 300 ml, have been used as before. The response of temperatures and relative humidity in the porous medium and annulus are very similar to the results of the high constant heat flux on the case of 300 ml water experiments. This is not the case for the 200 ml water experiment. The low constant heat flux with a small quantity of water is found to have no significant effect on the temperature responses.
Ultrafast radiative heat transfer.
Yu, Renwen; Manjavacas, Alejandro; García de Abajo, F Javier
2017-02-23
Light absorption in conducting materials produces heating of their conduction electrons, followed by relaxation into phonons within picoseconds, and subsequent diffusion into the surrounding media over longer timescales. This conventional picture of optical heating is supplemented by radiative cooling, which typically takes place at an even lower pace, only becoming relevant for structures held in vacuum or under extreme thermal isolation. Here, we reveal an ultrafast radiative cooling regime between neighboring plasmon-supporting graphene nanostructures in which noncontact heat transfer becomes a dominant channel. We predict that more than 50% of the electronic heat energy deposited on a graphene disk can be transferred to a neighboring nanoisland within a femtosecond timescale. This phenomenon is facilitated by the combination of low electronic heat capacity and large plasmonic field concentration in doped graphene. Similar effects should occur in other van der Waals materials, thus opening an unexplored avenue toward efficient heat management.Electron relaxation, which is the dominant release channel of electronic heat in nanostructures, occurs with characteristic times of several picoseconds. Here, the authors predict that an ultrafast (femtosecond) radiative cooling regime takes place in plasmonically active neighboring graphene nanodisks prior to electron relaxation.
Thermal radiation heat transfer.
NASA Technical Reports Server (NTRS)
Siegel, R.; Howell, J. R.
1972-01-01
A comprehensive discussion of heat transfer by thermal radiation is presented, including the radiative behavior of materials, radiation between surfaces, and gas radiation. Among the topics considered are property prediction by electromagnetic theory, the observed properties of solid materials, radiation in the presence of other modes of energy transfer, the equations of transfer for an absorbing-emitting gas, and radiative transfer in scattering and absorbing media. Also considered are radiation exchange between black isothermal surfaces, radiation exchange in enclosures composed of diffuse gray surfaces and in enclosures having some specularly reflecting surfaces, and radiation exchange between nondiffuse nongray surfaces. The use of the Monte Carlo technique in solving radiant-exchange problems and problems of radiative transfer through absorbing-emitting media is explained.
Heat transfer mechanisms in microgravity flow boiling.
Ohta, Haruhiko
2002-10-01
The objective of this paper is to clarify the mechanisms of heat transfer and dryout phenomena in flow boiling under microgravity conditions. Liquid-vapor behavior in annular flow, encountered in the moderate quality region, has extreme significance for practical application in space. To clarify the gravity effect on the heat transfer observed for an upward flow in a tube, the research described here started from the measurement of pressure drop for binary gas-liquid mixture under various gravity conditions. The shear stress acting on the surface of the annular liquid film was correlated by an empirical method. Gravity effects on the heat transfer due to two-phase forced convection were investigated by the analysis of velocity and temperature profiles in the film. The results reproduce well the trends of heat transfer coefficients varying with the gravity level, quality, and mass velocity. Dryout phenomena in the moderate quality region were observed in detail by the introduction of a transparent heated tube. At heat fluxes just lower and higher than CHF value, a transition of the heat transfer coefficient was calculated from oscillating wall temperature, where a series of opposing heat transfer trends--the enhancement due to the quenching of dried areas or evaporation from thin liquid films and the deterioration due to the extension of dry patches--were observed between the passage of disturbance waves. The CHF condition that resulted from the insufficient decrease of wall temperature in the period of enhanced heat transfer was overcome by a temperature increase in the deterioration period. No clear effect of gravity on the mechanisms of dryout was observed within the range of experiments.
ERIC Educational Resources Information Center
Knapp, Henry H., III
This module on heat transfer is one of six in a series intended for use as supplements to currently available materials on solar energy and energy conservation. Together with the recommended texts and references (sources are identified), these modules provide an effective introduction to energy conservation and solar energy technologies. The…
Methane heat transfer investigation
NASA Technical Reports Server (NTRS)
1984-01-01
Future high chamber pressure LOX/hydrocarbon booster engines require copper base alloy main combustion chamber coolant channels similar to the SSME to provide adequate cooling and reusable engine life. Therefore, it is of vital importance to evaluate the heat transfer characteristics and coking thresholds for LNG (94% methane) cooling, with a copper base alloy material adjacent to he fuel coolant. High pressure methane cooling and coking characteristics recently evaluated at Rocketdyne using stainless steel heated tubes at methane bulk temperatures and coolant wall temperatures typical of advanced engine operation except at lower heat fluxes as limited by the tube material. As expected, there was no coking observed. However, coking evaluations need be conducted with a copper base surface exposed to the methane coolant at higher heat fluxes approaching those of future high chamber pressure engines.
Methane heat transfer investigation
NASA Technical Reports Server (NTRS)
Cook, R. T.
1984-01-01
Future high chamber pressure LOX/hydrocarbon booster engines require copper-base alloy main combustion chamber coolant channels similar to the SSME to provide adequate cooling and resuable engine life. Therefore, it is of vital importance to evaluate the heat transfer characteristics and coking thresholds for LNG (94% methane) cooling, with a copper-base alloy material adjacent to the fuel coolant. High-pressure methane cooling and coking characteristics were recently evaluated using stainless-steel heated tubes at methane bulk temperatures and coolant wall temperatures typical of advanced engine operation except at lower heat fluxes as limited by the tube material. As expected, there was no coking observed. However, coking evaluations need be conducted with a copper-base surface exposed to the methane coolant at higher heat fluxes approaching those of future high chamber pressure engines.
Gambill, W.R.; Greene, N.D.
1960-08-30
A method is given for increasing burn-out heat fluxes under nucleate boiling conditions in heat exchanger tubes without incurring an increase in pumping power requirements. This increase is achieved by utilizing a spinning flow having a rotational velocity sufficient to produce a centrifugal acceleration of at least 10,000 g at the tube wall. At this acceleration the heat-transfer rate at burn out is nearly twice the rate which can be achieved in a similar tube utilizing axial flow at the same pumping power. At higher accelerations the improvement over axial flow is greater, and heat fluxes in excess of 50 x 10/sup 6/ Btu/hr/sq ft can be achieved.
Basmajian, V.V.
1986-01-28
This patent describes a heat transfer apparatus which consists of: heat exchanging means for orientation in the earth below ground substantially vertically, having a hollow conduit of length from top to bottom much greater than the span across the hollow conduit orthogonal to its length with a top, bottom and an intermediate portion contiguous and communicating with the top and bottom portions for allowing thermally conductive fluid to flow freely between the top, intermediate and bottom portions for immersion in thermally conductive fluid in the region around the heat exchanging means for increasing the heat flow between the latter and earth when inserted into a substantially vertical borehole in the earth with the top portion above the bottom portion. The heat exchanger consists of heat exchanging conduit means in the intermediate portion for carrying refrigerant. The heat exchanging conduit consisting of tubes of thermally conductive material for carrying the refrigerant and extending along the length of the hollow conduit for a tube length that is less than the length of the hollow conduit. The hollow conduit is formed with port means between the top and the plurality of tubes for allowing the thermally conductive fluid to pass in a flow path embracing the tubes, the bottom portion, an outer channel around the hollow conduit and the port means.
Transferring heat during a bounce
NASA Astrophysics Data System (ADS)
Shiri, Samira; Bird, James
2015-11-01
When a hot liquid drop impacts a cold non-wetting surface, the temperature difference drives heat transfer. If the drop leaves the surface before reaching thermal equilibrium, the amount of heat transfer may depend on the contact time. Past studies exploring finite-time heat exchange with droplets focus on the Leidenfrost condition where heat transfer is regulated by a thin layer of vapor. Here, we present systematic experiments to measure the heat transferred by a bouncing droplet in non-Leidenfrost conditions. We propose a physical model of this heat transfer and compare our model to the experiments.
Heat-Transfer Coupling For Heat Pipes
NASA Technical Reports Server (NTRS)
Nesmith, Bill J.
1991-01-01
Proposed welded heat-transfer coupling joins set of heat pipes to thermoelectric converter. Design avoids difficult brazing operation. Includes pair of mating flanged cups. Upper cup integral part of housing of thermoelectric converter, while lower cup integral part of plate supporting filled heat pipes. Heat pipes prefilled. Heat of welding applied around periphery of coupling, far enough from heat pipes so it would not degrade working fluid or create excessive vapor pressure in the pipes.
Heat transfer in aeropropulsion systems
NASA Astrophysics Data System (ADS)
Simoneau, R. J.
1985-07-01
Aeropropulsion heat transfer is reviewed. A research methodology based on a growing synergism between computations and experiments is examined. The aeropropulsion heat transfer arena is identified as high Reynolds number forced convection in a highly disturbed environment subject to strong gradients, body forces, abrupt geometry changes and high three dimensionality - all in an unsteady flow field. Numerous examples based on heat transfer to the aircraft gas turbine blade are presented to illustrate the types of heat transfer problems which are generic to aeropropulsion systems. The research focus of the near future in aeropropulsion heat transfer is projected.
Heat transfer in aeropropulsion systems
NASA Technical Reports Server (NTRS)
Simoneau, R. J.
1985-01-01
Aeropropulsion heat transfer is reviewed. A research methodology based on a growing synergism between computations and experiments is examined. The aeropropulsion heat transfer arena is identified as high Reynolds number forced convection in a highly disturbed environment subject to strong gradients, body forces, abrupt geometry changes and high three dimensionality - all in an unsteady flow field. Numerous examples based on heat transfer to the aircraft gas turbine blade are presented to illustrate the types of heat transfer problems which are generic to aeropropulsion systems. The research focus of the near future in aeropropulsion heat transfer is projected.
Frank, Jeffrey I.; Rosengart, Axel J.; Kasza, Ken; Yu, Wenhua; Chien, Tai-Hsin; Franklin, Jeff
2006-10-10
Apparatuses, systems, methods, and computer code for, among other things, monitoring the health of samples such as the brain while providing local cooling or heating. A representative device is a heat transfer probe, which includes an inner channel, a tip, a concentric outer channel, a first temperature sensor, and a second temperature sensor. The inner channel is configured to transport working fluid from an inner inlet to an inner outlet. The tip is configured to receive at least a portion of the working fluid from the inner outlet. The concentric outer channel is configured to transport the working fluid from the inner outlet to an outer outlet. The first temperature sensor is coupled to the tip, and the second temperature sensor spaced apart from the first temperature sensor.
NASA Technical Reports Server (NTRS)
Kalkbrenner, R. W. (Inventor)
1974-01-01
A heat transfer device is characterized by an hermetically sealed tubular housing including a tubular shell terminating in spaced end plates, and a tubular mesh wick concentrically arranged and operatively supported within said housing. The invention provides an improved wicking restraint formed as an elongated and radially expanded tubular helix concentrically related to the wick and adapted to be axially foreshortened and radially expanded into engagement with the wick in response to an axially applied compressive load. The wick is continuously supported in a contiguous relationship with the internal surfaces of the shell.
Conduction heat transfer solutions
VanSant, J.H.
1983-08-01
This text is a collection of solutions to a variety of heat conduction problems found in numerous publications, such as textbooks, handbooks, journals, reports, etc. Its purpose is to assemble these solutions into one source that can facilitate the search for a particular problem solution. Generally, it is intended to be a handbook on the subject of heat conduction. There are twelve sections of solutions which correspond with the class of problems found in each. Geometry, state, boundary conditions, and other categories are used to classify the problems. Each problem is concisely described by geometry and condition statements, and many times a descriptive sketch is also included. The introduction presents a synopsis on the theory, differential equations, and boundary conditions for conduction heat transfer. Some discussion is given on the use and interpretation of solutions. Supplementary data such as mathematical functions, convection correlations, and thermal properties are included for aiding the user in computing numerical values from the solutions. 155 figs., 92 refs., 9 tabs.
Conduction heat transfer solutions
VanSant, James H.
1980-03-01
This text is a collection of solutions to a variety of heat conduction problems found in numerous publications, such as textbooks, handbooks, journals, reports, etc. Its purpose is to assemble these solutions into one source that can facilitate the search for a particular problem solution. Generally, it is intended to be a handbook on the subject of heat conduction. This material is useful for engineers, scientists, technologists, and designers of all disciplines, particularly those who design thermal systems or estimate temperatures and heat transfer rates in structures. More than 500 problem solutions and relevant data are tabulated for easy retrieval. There are twelve sections of solutions which correspond with the class of problems found in each. Geometry, state, boundary conditions, and other categories are used to classify the problems. A case number is assigned to each problem for cross-referencing, and also for future reference. Each problem is concisely described by geometry and condition statements, and many times a descriptive sketch is also included. At least one source reference is given so that the user can review the methods used to derive the solutions. Problem solutions are given in the form of equations, graphs, and tables of data, all of which are also identified by problem case numbers and source references.
Hal E. Anderson
1969-01-01
Experimental testing of a mathematical model showed that radiant heat transfer accounted for no more than 40% of total heat flux required to maintain rate of spread. A reasonable prediction of spread was possible by assuming a horizontal convective heat transfer coefficient when certain fuel and flame characteristics were known. Fuel particle size had a linear relation...
Tubing for augmented heat transfer
Yampolsky, J.S.; Pavlics, P.
1983-08-01
The objectives of the program reported were: to determine the heat transfer and friction characteristics on the outside of spiral fluted tubing in single phase flow of water, and to assess the relative cost of a heat exchanger constructed with spiral fluted tubing with one using conventional smooth tubing. An application is examined where an isolation water/water heat exchanger was used to transfer the heat from a gaseous diffusion plant to an external system for energy recovery. (LEW)
Heat transfer and thermal control
NASA Astrophysics Data System (ADS)
Crosbie, A. L.
Radiation heat transfer is considered along with conduction heat transfer, heat pipes, and thermal control. Attention is given to the radiative properties of a painted layer containing nonspherical pigment, bidirectional reflectance measurements of specular and diffuse surfaces with a simple spectrometer, the radiative equilibrium in a general plane-parallel environment, and the application of finite-element techniques to the interaction of conduction and radiation in participating medium, a finite-element approach to combined conductive and radiative heat transfer in a planar medium. Heat transfer in irradiated shallow layers of water, an analytical and experimental investigation of temperature distribution in laser heated gases, numerical methods for the analysis of laser annealing of doped semiconductor wafers, and approximate solutions of transient heat conduction in a finite slab are also examined. Consideration is also given to performance testing of a hydrogen heat pipe, heat pipe performance with gravity assist and liquid overfill, vapor chambers for an atmospheric cloud physics laboratory, a prototype heat pipe radiator for the German Direct Broadcasting TV Satellite, free convection in enclosures exposed to compressive heating, and a thermal analysis of a multipurpose furnace for material processing in space.
Fraas, A.P.; Wislicenus, G.F.
1961-07-11
A heat exchanger is adapted to unifomly cool a spherical surface. Equations for the design of a spherical heat exchanger hav~g tubes with a uniform center-to-center spining are given. The heat exchanger is illustrated in connection with a liquid-fueled reactor.
Advances in enhanced heat transfer: 1987
Jensen, M.K.; Carey, V.P.
1987-01-01
This book contains nine selections. Some of the titles are: High Heat-Flux, Forced-Convection Heat Transfer for Tubes with Twisted-Tape Inserts; Heat Transfer Augmentation by Interrupted Surfaces - Experimental Consideration; Turbulent Flow Heat Transfer from Externally Roughened Tubes in Axial Flow in Concentric Pipe Heat Exchangers; and Heat Transfer Enhancement of Turbulent Flow in Pipes with an Internal Circular Rib.
Sphere Drag and Heat Transfer.
Duan, Zhipeng; He, Boshu; Duan, Yuanyuan
2015-07-20
Modelling fluid flows past a body is a general problem in science and engineering. Historical sphere drag and heat transfer data are critically examined. The appropriate drag coefficient is proposed to replace the inertia type definition proposed by Newton. It is found that the appropriate drag coefficient is a desirable dimensionless parameter to describe fluid flow physical behavior so that fluid flow problems can be solved in the simple and intuitive manner. The appropriate drag coefficient is presented graphically, and appears more general and reasonable to reflect the fluid flow physical behavior than the traditional century old drag coefficient diagram. Here we present drag and heat transfer experimental results which indicate that there exists a relationship in nature between the sphere drag and heat transfer. The role played by the heat flux has similar nature as the drag. The appropriate drag coefficient can be related to the Nusselt number. This finding opens new possibilities in predicting heat transfer characteristics by drag data. As heat transfer for flow over a body is inherently complex, the proposed simple means may provide an insight into the mechanism of heat transfer for flow past a body.
Duan, Zhipeng; He, Boshu; Duan, Yuanyuan
2015-01-01
Modelling fluid flows past a body is a general problem in science and engineering. Historical sphere drag and heat transfer data are critically examined. The appropriate drag coefficient is proposed to replace the inertia type definition proposed by Newton. It is found that the appropriate drag coefficient is a desirable dimensionless parameter to describe fluid flow physical behavior so that fluid flow problems can be solved in the simple and intuitive manner. The appropriate drag coefficient is presented graphically, and appears more general and reasonable to reflect the fluid flow physical behavior than the traditional century old drag coefficient diagram. Here we present drag and heat transfer experimental results which indicate that there exists a relationship in nature between the sphere drag and heat transfer. The role played by the heat flux has similar nature as the drag. The appropriate drag coefficient can be related to the Nusselt number. This finding opens new possibilities in predicting heat transfer characteristics by drag data. As heat transfer for flow over a body is inherently complex, the proposed simple means may provide an insight into the mechanism of heat transfer for flow past a body. PMID:26189698
NASA Technical Reports Server (NTRS)
Widener, Edward L.
1992-01-01
The objective is to introduce some concepts of thermodynamics in existing heat-treating experiments using available items. The specific objectives are to define the thermal properties of materials and to visualize expansivity, conductivity, heat capacity, and the melting point of common metals. The experimental procedures are described.
NASA Technical Reports Server (NTRS)
Friedell, M. V.; Anderson, A. J.
1974-01-01
Thermal switch maintains temperature of planetary lander, within definite range, by transferring heat. Switch produces relatively large stroke and force, uses minimum electrical power, is lightweight, is vapor pressure actuated, and withstands sterilization temperatures without damage.
Heat transfer, diffusion, and evaporation
NASA Technical Reports Server (NTRS)
Nusselt, Wilhelm
1954-01-01
Although it has long been known that the differential equations of the heat-transfer and diffusion processes are identical, application to technical problems has only recently been made. In 1916 it was shown that the speed of oxidation of the carbon in iron ore depends upon the speed with which the oxygen of the combustion air diffuses through the core of gas surrounding the carbon surface. The identity previously referred to was then used to calculate the amount of oxygen diffusing to the carbon surface on the basis of the heat transfer between the gas stream and the carbon surface. Then in 1921, H. Thoma reversed that procedure; he used diffusion experiments to determine heat-transfer coefficients. Recently Lohrisch has extended this work by experiment. A technically very important application of the identity of heat transfer and diffusion is that of the cooling tower, since in this case both processes occur simultaneously.
Heat Transfer Parametric System Identification
1993-06-01
Transfer Parametric System Identification 6. AUTHOR(S Parker, Gregory K. 7. PERFORMING ORGANIZATION NAME(S) AND AOORESS(ES) 8. PERFORMING ORGANIZATION...distribution is unlimited. Heat Transfer Parametric System Identification by Gregory K. Parker Lieutenant, United States Navy BS., DeVry Institute of...Modeling Concept ........ ........... 3 2. Lumped Parameter Approach ...... ......... 4 3. Parametric System Identification ....... 4 B. BASIC MODELING
Heat transfer in damaged material
NASA Astrophysics Data System (ADS)
Kruis, J.
2013-10-01
Fully coupled thermo-mechanical analysis of civil engineering problems is studied. The mechanical analysis is based on damage mechanics which is useful for modeling of behaviour of quasi-brittle materials, especially in tension. The damage is assumed to be isotropic. The heat transfer is assumed in the form of heat conduction governed by the Fourier law and heat radiation governed by the Stefan-Boltzmann law. Fully coupled thermo-mechanical problem is formulated.
Enhanced heat transfer using nanofluids
Choi, Stephen U. S.; Eastman, Jeffrey A.
2001-01-01
This invention is directed to a method of and apparatus for enhancing heat transfer in fluids such as deionized water. ethylene glycol, or oil by dispersing nanocrystalline particles of substances such as copper, copper oxide, aluminum oxide, or the like in the fluids. Nanocrystalline particles are produced and dispersed in the fluid by heating the substance to be dispersed in a vacuum while passing a thin film of the fluid near the heated substance. The fluid is cooled to control its vapor pressure.
Heat transfer from oriented heat exchange areas
NASA Astrophysics Data System (ADS)
Vantuch, Martin; Huzvar, Jozef; Kapjor, Andrej
2014-03-01
This paper deals with the transfer of heat-driven heat transfer surface area in relation to the construction of the criterion equation for "n" horizontal pipe one about another. On the bases of theoretical models have been developed for calculating the thermal performance of natural convection by Churilla and Morgan, for various pipe diameters and temperatures. These models were compared with models created in CFD-Fluent Ansys the same boundary conditions. The aim of the analyse of heat and fluxional pipe fields "n" pipes one about another at natural convection is the creation of criterion equation on the basis of which the heat output of heat transfer from pipe oriented areas one above another with given spacing could be quantified. At presence a sum of criterion equations exists for simple geometrical shapes of individual oriented geometrical areas but the criterion equation which would consider interaction of fluxional field generated by free convection from multiple oriented areas is not mentioned in standardly accessible technical literature and other magazine publications.
Nanofluid impingement jet heat transfer
2012-01-01
Experimental investigation to study the heat transfer between a vertical round alumina-water nanofluid jet and a horizontal circular round surface is carried out. Different jet flow rates, jet nozzle diameters, various circular disk diameters and three nanoparticles concentrations (0, 6.6 and 10%, respectively) are used. The experimental results indicate that using nanofluid as a heat transfer carrier can enhance the heat transfer process. For the same Reynolds number, the experimental data show an increase in the Nusselt numbers as the nanoparticle concentration increases. Size of heating disk diameters shows reverse effect on heat transfer. It is also found that presenting the data in terms of Reynolds number at impingement jet diameter can take into account on both effects of jet heights and nozzle diameter. Presenting the data in terms of Peclet numbers, at fixed impingement nozzle diameter, makes the data less sensitive to the percentage change of the nanoparticle concentrations. Finally, general heat transfer correlation is obtained verses Peclet numbers using nanoparticle concentrations and the nozzle diameter ratio as parameters. PMID:22340669
Measurement of thermoacoustic convection heat transfer phenomenon
NASA Technical Reports Server (NTRS)
Parang, M.; Salah-Eddine, A.
1983-01-01
In this paper the results of an experimental investigation of thermoacoustic convection (TAC) heat transfer phenomenon in both zero-gravity and gravity environment are presented and compared with pure conduction heat transfer. The numerical solutions of the governing equations obtained by others for TAC heat transfer phenomenon are also discussed. The experimental results show that for rapid heating rate at a boundary, the contribution of TAC heat transfer to a gas could be significantly (one order of magnitude) higher than heat transfer rate from pure conduction. The results also show significantly reduced transient time in heat transfer processes involving thermoacoustic convective heat transfer mode in both space and gravity environment.
Investigation of Heat Transfer From
NASA Technical Reports Server (NTRS)
Lewis, James P.; Ruggeri, Robert S.
1956-01-01
The convective heat transfer from the surface of an ellipsoidal forebody of fineness ratio 3 and 20-inch maximum diameter was investigated in clear air for both stationary and rotating operation over a range of conditions including air speeds up to 240 knots, rotational speeds up to 1200 rpm, and angles of attack of 0 deg, 3 deg, and 6 deg. The results are presented in the form of heat-transfer coefficients and the correlation of Nusselt and Reynolds numbers. Both a uniform surface temperature and a uniform input heater density distribution were used. The experimental results agree well with theoretical predictions for uniform surface temperature distribution. Complete agreement was not obtained with uniform input heat density in the laminar-flow region because of conduction effects. No significant effects of rotation were obtained over the range of airstream and rotational speeds investigated. Operation at angle of attack had only minor effects on the local heat transfer. Transition from laminar to turbulent heat transfer occurred over a wide range of Reynolds numbers. The location of transition depended primarily on surface roughness and pressure and temperature gradients. Limited transient heating data indicate that the variation of surface temperature with time followed closely an exponential relation.
NASA Astrophysics Data System (ADS)
Chapman, K.; Ramadhyani, S.; Ramamurthy, H.; Viskanta, R.
1989-03-01
A simple two-dimensional mathematical model was developed to predict the steady state thermal performance and combustion characteristics of a natural gas indirectly fired once-through radiant tube. Different burner geometries were studied and a grid size analysis was performed to determine the optimum grid spacing for each case. The rate of fuel burn-up was correlated using the burner geometry, the equivalence ratio, the fuel firing rate and air preheat temperatures as variables for non-swirling diffusion flames in the radiant tube. The model predictions were also compared with available experimental data for the purpose of validating the model. The transient, zero-dimensional model was used to conduct a detailed parametric study of a directly-fired batch reheating furnace. The parameters that were investigated are the load and refractory emissivities, the air preheat temperature, the heat capacity of the load, and the height of the combustion space. A one-dimensional model of a directly-fired continuous reheating furnace was also developed. A parametric study was completed to examine the effect of the local throughput on the furnace performance.
Short duration heat transfer measurements
NASA Astrophysics Data System (ADS)
Arts, T.; Camci, C.
Shock tunnels, blowdown cascades, and isentropic light piston compression tubes used to study heat transfer and aerodynamic phenomena in turbine components are described. Thin film heat transfer gages, calorimeter gages, and optical measurements methods are presented. Compression tube investigations of convective heat transfer on a flat plate, with and without film cooling; and convective heat transfer on a high pressure rotor blade with and without film cooling are summarized. Results show that along the suction side, laminar to turbulent transition is strongly influenced by the presence of the leading edge cooling holes, even when no coolant flow is ejected. Along the pressure side, the boundary layer behavior is dominated by the free stream pressure gradient rather than by the existence of the cooling holes. Significant coolant temperature effects are also observed. At low blowing rate this effect is mainly observed up to 35 to 40 hole diameters downstream of the suction side ejection rows when the coolant temperature is lowered from wall temperature to half of the mainstream level. At high blowing rate, the influence of the coolant temperature is felt much further downstream.
Host turbine heat transfer overview
NASA Technical Reports Server (NTRS)
Rohde, J. E.
1984-01-01
Improved methods of predicting airfoil local metal temperatures require advances in the understanding of the physics and methods of analytically predicting the following four aerothermal loads: hot gas flow over airfoils, heat transfer rates on the gas-side of airfoils, cooling air flow inside airfoils, and heat transfer rates on the coolant-side of airfoils. A systematic building block research approach is being pursued to investigate these four areas of concern from both the experimental and analytical sides. Experimental approaches being pursued start with fundamental experiments using simple shapes and flat plates in wind tunnels, progress to more realistic cold and hot cascade tests using airfoils, continue to progress in large low-speed rigs and turbines and warm turbines, and finally, combine all the interactive effects in tests using real engines or real engine type turbine rigs. Analytical approaches being pursued also build from relatively simple steady two dimensional inviscid flow and boundary layer heat transfer codes to more advanced steady two and three dimensional viscous flow and heat transfer codes. These advanced codes provide more physics to model better the interactive effects and the true real-engine environment.
Sodium heat transfer system modeling
NASA Astrophysics Data System (ADS)
Baker, A. F.; Fewell, M. E.
1983-11-01
The sodium heat transfer system of the international energy agency (IEA) small solar power systems (SSPS) central receiver system (CRS), which includes the heliostat field, receiver, hot and cold storage vessels, and sodium/water steam generator was modeled. The computer code SOLTES (simulator of large thermal energy systems), was used to model this system. The results from SOLTES are compared to measured data.
Heat transfer in aerospace propulsion
NASA Technical Reports Server (NTRS)
Simoneau, Robert J.; Hendricks, Robert C.; Gladden, Herbert J.
1988-01-01
Presented is an overview of heat transfer related research in support of aerospace propulsion, particularly as seen from the perspective of the NASA Lewis Research Center. Aerospace propulsion is defined to cover the full spectrum from conventional aircraft power plants through the Aerospace Plane to space propulsion. The conventional subsonic/supersonic aircraft arena, whether commercial or military, relies on the turbine engine. A key characteristic of turbine engines is that they involve fundamentally unsteady flows which must be properly treated. Space propulsion is characterized by very demanding performance requirements which frequently push systems to their limits and demand tailored designs. The hypersonic flight propulsion systems are subject to severe heat loads and the engine and airframe are truly one entity. The impact of the special demands of each of these aerospace propulsion systems on heat transfer is explored.
Numerical methods in heat transfer
Lewis, R.W.; Morgan, K.; Schrefler, B.A.
1983-01-01
Topics discussed in this book include modelling the effects of fire, ablation, heat flow in porous rock, thermal stress and dissolving coal. Alternative energy sources such as geothermal reservoirs and solar radiation are also discussed. Includes bibliographies at the end of the papers, a cited author index, and a subject index. Contents, abridged: Exact finite element solutions for linear steady state thermal problems. Steep gradient modelling in diffusion problems. Numerical solution of coupled conduction-convection problems using lumped-parameter methods. The prediction of turbulent heat transfer by the finite element methods. The influence of creep and transformation plasticity in the analysis of stresses due to heat treatment. Heat and moisture movement in wood composite materials during the pressing operation-a simplified model. Index.
Combustion, heat transfer and analysis
Not Available
1986-01-01
This book presents papers on diesel engines combustion. Topics considered include combustion control, high-speed photography, visual studies of diesel combustion, swirl chambers, heat insulated turbochargers, direct injection, autoignition, statistical analysis software, particulate emissions, improvements in exhaust gas emissions and cold startability of diesel engines with new injection-rate-control pumps, jet mixing processes, a thermodynamic simulation model, heat transfer in ceramic combustion chamber walls, temperature distribution in a diesel piston, and the application of a variable swirl device to a two-stroke engine.
Selective tube roughening increases heat transfer capability
NASA Technical Reports Server (NTRS)
Carlson, L. W.
1966-01-01
Selectively roughening inside surfaces of tubes increases the heat transfer capabilities, but minimizes the pressure drop. This technique is used to construct roughened test sections for hydrogen heat transfer studies.
Boiling Heat Transfer to Halogenated Hydrocarbon Refrigerants
NASA Astrophysics Data System (ADS)
Yoshida, Suguru; Fujita, Yasunobu
The current state of knowledge on heat transfer to boiling refrigerants (halogenated hydrocarbons) in a pool and flowing inside a horizontal tube is reviewed with an emphasis on information relevant to the design of refrigerant evaporators, and some recommendations are made for future research. The review covers two-phase flow pattern, heat transfer characteristics, correlation of heat transfer coefficient, influence of oil, heat transfer augmentation, boiling from tube-bundle, influence of return bend, burnout heat flux, film boiling, dryout and post-dryout heat transfer.
Heat exchanger device and method for heat removal or transfer
Koplow, Jeffrey P [San Ramon, CA
2012-07-24
Systems and methods for a forced-convection heat exchanger are provided. In one embodiment, heat is transferred to or from a thermal load in thermal contact with a heat conducting structure, across a narrow air gap, to a rotating heat transfer structure immersed in a surrounding medium such as air.
Heat exchanger device and method for heat removal or transfer
Koplow, Jeffrey P.
2015-12-08
Systems and methods for a forced-convection heat exchanger are provided. In one embodiment, heat is transferred to or from a thermal load in thermal contact with a heat conducting structure, across a narrow air gap, to a rotating heat transfer structure immersed in a surrounding medium such as air.
Heat exchanger device and method for heat removal or transfer
Koplow, Jeffrey P
2013-12-10
Systems and methods for a forced-convection heat exchanger are provided. In one embodiment, heat is transferred to or from a thermal load in thermal contact with a heat conducting structure, across a narrow air gap, to a rotating heat transfer structure immersed in a surrounding medium such as air.
Heat exchanger device and method for heat removal or transfer
Koplow, Jeffrey P
2015-03-24
Systems and methods for a forced-convection heat exchanger are provided. In one embodiment, heat is transferred to or from a thermal load in thermal contact with a heat conducting structure, across a narrow air gap, to a rotating heat transfer structure immersed in a surrounding medium such as air.
Heat Transfer in a Thermoacoustic Process
ERIC Educational Resources Information Center
Beke, Tamas
2012-01-01
Thermoacoustic instability is defined as the excitation of acoustic modes in chambers with heat sources due to the coupling between acoustic perturbations and unsteady heat addition. The major objective of this paper is to achieve accurate theoretical results in a thermoacoustic heat transfer process. We carry out a detailed heat transfer analysis…
Heat Transfer in a Thermoacoustic Process
ERIC Educational Resources Information Center
Beke, Tamas
2012-01-01
Thermoacoustic instability is defined as the excitation of acoustic modes in chambers with heat sources due to the coupling between acoustic perturbations and unsteady heat addition. The major objective of this paper is to achieve accurate theoretical results in a thermoacoustic heat transfer process. We carry out a detailed heat transfer analysis…
Handbook of heat transfer applications (2nd edition)
NASA Astrophysics Data System (ADS)
Rohsenow, W. M.; Hartnett, J. P.; Ganic, E. N.
The applications of heat transfer in engineering problems are considered. Among the applications discussed are: mass transfer cooling; heat exchangers; and heat pipes. Consideration is also given to: heat transfer in nonNewtonian fluids; fluidized and packed beds; thermal energy storage; and heat transfer in solar collectors. Additional topics include: heat transfer in buildings; cooling towers and ponds; and geothermal heat transfer.
High Resolution Convective Heat Transfer Measurements
2001-05-30
ONR Thermal Materials Workshop 2001 1 HIGH RESOLUTION CONVECTIVE HEAT TRANSFER MEASUREMENTS Peter Ireland and Terry Jones R-R UTC in Heat Transfer...temperatures. • Fluid dynamics correct through use of Reynolds number, Mach number and Prandtl number. Mach)Pr,(Re,fNu Dimensionless heat transfer...depends on local h su rf ac e te m p T s gas temperature Tg timestart of test hTc Calibration Test data ONR Thermal Materials Workshop 2001 10 Heat
Heat transfer measurements with TOIRT method
NASA Astrophysics Data System (ADS)
Solnař, S.; Petera, K.; Dostál, M.; Jirout, T.
Temperature Oscillation Infra-Red Thermography (TOIRT) method was used to measure heat transfer coefficients between a at surface and a confined impinging jet generated by an impeller in a difusor and baffled vessel. The TOIRT method is based on measuring a phase-lag between the oscillating heat flux applied to the heat transfer surface and the surface temperature response using a contactless infra-red camera. The phase lag is in a direct relationship with the heat transfer coefficient.
Tunable heat transfer with smart nanofluids.
Bernardin, Michele; Comitani, Federico; Vailati, Alberto
2012-06-01
Strongly thermophilic nanofluids are able to transfer either small or large quantities of heat when subjected to a stable temperature difference. We investigate the bistability diagram of the heat transferred by this class of nanofluids. We show that bistability can be exploited to obtain a controlled switching between a conductive and a convective regime of heat transfer, so as to achieve a controlled modulation of the heat flux.
Heat Transfer in Complex Fluids
Mehrdad Massoudi
2012-01-01
(linear) behavior for a given range of parameters or geometries; there are many empirical or semi-empirical constitutive equations suggested for these fluids. There have also been many non-linear constitutive relations which have been derived based on the techniques of continuum mechanics. The non-linearities oftentimes appear due to higher gradient terms or time derivatives. When thermal and or chemical effects are also important, the (coupled) momentum and energy equations can give rise to a variety of interesting problems, such as instability, for example the phenomenon of double-diffusive convection in a fluid layer. In Conclusion, we have studied the flow of a compressible (density gradient type) non-linear fluid down an inclined plane, subject to radiation boundary condition. The heat transfer is also considered where a source term, similar to the Arrhenius type reaction, is included. The non-dimensional forms of the equations are solved numerically and the competing effects of conduction, dissipation, heat generation and radiation are discussed. It is observed that the velocity increases rapidly in the region near the inclined surface and is slower in the region near the free surface. Since R{sub 7} is a measure of the heat generation due to chemical reaction, when the reaction is frozen (R{sub 7}=0.0) the temperature distributions would depend only on R{sub 1}, and R{sub 2}, representing the effects of the pressure force developed in the material due to the distribution, R{sub 3} and R{sub 4} viscous dissipation, R{sub 5} the normal stress coefficient, R{sub 6} the measure of the emissivity of the particles to the thermal conductivity, etc. When the flow is not frozen (RP{sub 7} > 0) the temperature inside the flow domain is much higher than those at the inclined and free surfaces. As a result, heat is transferred away from the flow toward both the inclined surface and the free surface with a rate that increases as R{sub 7} increases. For a given temperature, an
Industrial furnace with improved heat transfer
Hoetzl, M.; Lingle, T.M.
1992-07-07
This patent describes an industrial furnace for heating work which emits volatiles during heating. It comprises a generally cylindrical, closed end furnace section defining a sealable heat transfer chamber for heating work disposed therein; fan means for directing furnace atmosphere as a swirling wind mass about the interior of the furnace section over a portion thereof; heat means for heating the wind mass within the fan chamber; and an incineration track formed as a circumferentially extending groove about the exterior of the furnace section and in heat transfer relationship with and situated at least to extend about a portion of the fan chamber.
NASA Technical Reports Server (NTRS)
Garg, Vijay K.
2001-01-01
The turbine gas path is a very complex flow field. This is due to a variety of flow and heat transfer phenomena encountered in turbine passages. This manuscript provides an overview of the current work in this field at the NASA Glenn Research Center. Also, based on the author's preference, more emphasis is on the computational work. There is much more experimental work in progress at GRC than that reported here. While much has been achieved, more needs to be done in terms of validating the predictions against experimental data. More experimental data, especially on film cooled and rough turbine blades, are required for code validation. Also, the combined film cooling and internal cooling flow computation for a real blade is yet to be performed. While most computational work to date has assumed steady state conditions, the flow is clearly unsteady due to the presence of wakes. All this points to a long road ahead. However, we are well on course.
Convective Heat Transfer for Ship Propulsion.
1981-04-01
OF RILJORT 6 PelIOO COVERED Convective Heat Transfer for Ship Propulsion . Annual gummary Report / (Sixth Annual Sumary Report) //115 Jan 180-30 Mard...DO* IrCOVE) Sixth Annual Summary Report CONVECTIVE HEAT TRANSFER FOR SHIP PROPULSION By M. A. Habib and D. M. McEligot Aerospace and Mechanical...permitted for any purpose of the United States Government. ._ _ _ _ _ _ I CONVECTIVE HEAT TRANSFER FOR SHIP PROPULSION M. A. Habib* and D. M. McEligot
Heat-transfer data for hydrogen
NASA Technical Reports Server (NTRS)
Mc Carthy, J. R.; Miller, W. S.; Okuda, A. S.; Seader, J. D.
1970-01-01
Information is given regarding experimental heat-transfer data compiled for the turbulent flow of hydrogen within straight, electrically heated, round cross section tubes. Tube materials, test conditions, parameters studied, and generalized conclusions are presented.
NASA Astrophysics Data System (ADS)
Wang, J. G.; Li, H. X.; Guo, B.; Yu, S. Q.; Zhang, Y. Q.; Chen, T. K.
2010-03-01
The heat transfer characteristics of water at supercritical pressures in a vertically-upward internally-ribbed tube are investigated experimentally to investigate the mechanism of abnormal heat transfer of supercritical pressure water in the so-called large specific heat region. One kind optimized internally-ribbed tube is used in this study. The tube is made of SA-213T12 steel with an outer diameter of 31.8 mm and a wall thickness of 6 mm and the mean inside diameter of the tube is measured to be 17.63 mm. According to experimental data, the characteristics and mechanisms of the heat transfer enhancement and also the heat transfer deterioration of supercritical pressure water in the large specific heat region are discussed respectively. The heat transfer enhancement of the supercritical pressure water in the large specific heat region is believed to be a result of combined effect caused by the rapid variations of thermophysical properties of the supercritical pressure water in the large specific heat region, and the same is true of the heat transfer deterioration. The drastic changes in thermophysical properties near the pseudocritical points, especially the sudden rise in the specific heat of water at supercritical pressures, may result in the occurrence of the heat transfer enhancement, while the covering of the heat transfer surface by fluids lighter and hotter than the bulk fluid makes the heat transfer deteriorated eventually and explains how this lighter fluid layer forms. It is also found that the heat transfer deterioration of water at supercritical pressures is similar to the DNB (departure from nucleate boiling) at subcritical pressures in mechanism.
Radiative heat transfer in porous uranium dioxide
Hayes, S.L.
1992-12-01
Due to low thermal conductivity and high emissivity of UO{sub 2}, it has been suggested that radiative heat transfer may play a significant role in heat transfer through pores of UO{sub 2} fuel. This possibility was computationally investigated and contribution of radiative heat transfer within pores to overall heat transport in porous UO{sub 2} quantified. A repeating unit cell was developed to model approximately a porous UO{sub 2} fuel system, and the heat transfer through unit cells representing a wide variety of fuel conditions was calculated using a finite element computer program. Conduction through solid fuel matrix as wekk as pore gas, and radiative exchange at pore surface was incorporated. A variety of pore compositions were investigated: porosity, pore size, shape and orientation, temperature, and temperature gradient. Calculations were made in which pore surface radiation was both modeled and neglected. The difference between yielding the integral contribution of radiative heat transfer mechanism to overall heat transport. Results indicate that radiative component of heat transfer within pores is small for conditions representative of light water reactor fuel, typically less than 1% of total heat transport. It is much larger, however, for conditions present in liquid metal fast breeder reactor fuel; during restructuring of this fuel type early in life, the radiative heat transfer mode was shown to contribute as much as 10-20% of total heat transport in hottest regions of fuel.
Enhancement of Forced Convection Heat Transfer
NASA Astrophysics Data System (ADS)
Tanasawa, Ichiro
There has been strong demand for enhancement techniques of single-phase forced convection heat transfer because of its wide area of application on the one side and because of inferior heat-transfer capability, when compared with phase change heat transfer such as boiling and condensation, on the other side. The enhancement techniques are indispensable when gases are used as heat-transfer media. In this article the basic principles of enhancement of single-phase forced convection heat transfer are described in the first place. Three principal techniques currently employed, i.e.,(a) interrupted fins, (b) twisted tapes, and (c) turbulence promoters, are introduced. Mechanisms of heat-tansfer enhancement and the state-of-the art review on the R&D are presented for these techniques. In addition to these, supplementary remarks are given on techniques utilizing multiphase flow and electrostatic field.
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.
Impingement Heat Transfer of Reciprocating Jet Array
NASA Astrophysics Data System (ADS)
Su, Lo May; Chang, Shyy Woei; Chiou, Shyr Fuu
This paper describes an experimental study of impingement heat transfer of reciprocating jet-array with piston cooling application for marine heavy-duty diesel engine. A selection of heat transfer measurements illustrates the manner by which the individual and interactive influences of reciprocating force and buoyancy on heat transfer for the impinging jet-array. It is demonstrated that the reciprocating force coupled with buoyancy interaction causes considerable heat transfer modifications from the static results. The isolated reciprocating force effect could initially reduce heat transfer to a level about 0.45 of static level with weak reciprocation but recovers when the reciprocating force increases. Heat transfer improvement and impediment could be aided by the location-dependent buoyancy effect in addition to the reciprocating force effect. An empirical heat transfer correlation, which is physically consistent, has been developed to permit the evaluation of the individual and synergistic effects of reciprocating force and buoyancy interaction on local heat transfer of the impinging jet-array.
Fundamental heat transfer experiments of heat pipes for turbine cooling
Yamawaki, S.; Yoshida, T.; Taki, M.; Mimura, F.
1998-07-01
Fundamental heat transfer experiments were carried out for three kinds of heat pipes that may be applied to turbine cooling in future aero-engines. In the turbine cooling system with a heat pipe, heat transfer rate and start-up time of the heat pipe are the most important performance criteria to evaluate and compare with conventional cooling methods. Three heat pipes are considered, called heat pipe A, B, and C, respectively. All heat pipes have a stainless steel shell and nickel sintered powder metal wick. Sodium (Na) was the working fluid for heat pipes A and B; heat pipe C used eutectic sodium-potassium (NaK). Heat pipes B and C included noncondensible gas for rapid start-up. There were fins on the cooling section of heat pipes. In the experiments, an infrared image furnace supplied heat to the heat pipe simulating turbine blade surface conditions. In the results, heat pipe B demonstrated the highest heat flux of 17 to 20 W/cm{sup 2}. The start-up time was about 6 minutes for heat pipe B and about 6 minutes for heat pipe A. Thus, adding noncondensible gas effectively reduced start-up time. Although NaK is a liquid phase at room temperature, the start-up time of heat pipe C (about 7 to 8 minutes) was not shorter than the heat pipe B. The effect of a gravitational force on heat pipe performance was also estimated by inclining the heat pipe at an angle of 90 deg. There was no significant gravitational dependence on heat transport for heat pipes including noncondensible gas.
Phase Change Heat Transfer Device for Process Heat Applications
Piyush Sabharwall; Mike Patterson; Vivek Utgikar; Fred Gunnerson
2010-10-01
The next generation nuclear plant (NGNP) will most likely produce electricity and process heat, with both being considered for hydrogen production. To capture nuclear process heat, and transport it to a distant industrial facility requires a high temperature system of heat exchangers, pumps and/or compressors. The heat transfer system is particularly challenging not only due to the elevated temperatures (up to approx.1300 K) and industrial scale power transport (=50MW), but also due to a potentially large separation distance between the nuclear and industrial plants (100+m) dictated by safety and licensing mandates. The work reported here is the preliminary analysis of two-phase thermosyphon heat transfer performance with alkali metals. A thermosyphon is a thermal device for transporting heat from one point to another with quite extraordinary properties. In contrast to single-phased forced convective heat transfer via ‘pumping a fluid’, a thermosyphon (also called a wickless heat pipe) transfers heat through the vaporization/condensing process. The condensate is further returned to the hot source by gravity, i.e., without any requirement of pumps or compressors. With this mode of heat transfer, the thermosyphon has the capability to transport heat at high rates over appreciable distances, virtually isothermally and without any requirement for external pumping devices. Two-phase heat transfer by a thermosyphon has the advantage of high enthalpy transport that includes the sensible heat of the liquid, the latent heat of vaporization, and vapor superheat. In contrast, single-phase forced convection transports only the sensible heat of the fluid. Additionally, vapor-phase velocities within a thermosyphon are much greater than single-phase liquid velocities within a forced convective loop. Thermosyphon performance can be limited by the sonic limit (choking) of vapor flow and/or by condensate entrainment. Proper thermosyphon requires analysis of both.
"Nanotechnology Enabled Advanced Industrial Heat Transfer Fluids"
Dr. Ganesh Skandan; Dr. Amit Singhal; Mr. Kenneth Eberts; Mr. Damian Sobrevilla; Prof. Jerry Shan; Stephen Tse; Toby Rossmann
2008-06-12
ABSTRACT Nanotechnology Enabled Advanced industrial Heat Transfer Fluids” Improving the efficiency of Industrial Heat Exchangers offers a great opportunity to improve overall process efficiencies in diverse industries such as pharmaceutical, materials manufacturing and food processing. The higher efficiencies can come in part from improved heat transfer during both cooling and heating of the material being processed. Additionally, there is great interest in enhancing the performance and reducing the weight of heat exchangers used in automotives in order to increase fuel efficiency. The goal of the Phase I program was to develop nanoparticle containing heat transfer fluids (e.g., antifreeze, water, silicone and hydrocarbon-based oils) that are used in transportation and in the chemical industry for heating, cooling and recovering waste heat. Much work has been done to date at investigating the potential use of nanoparticle-enhanced thermal fluids to improve heat transfer in heat exchangers. In most cases the effect in a commercial heat transfer fluid has been marginal at best. In the Phase I work, we demonstrated that the thermal conductivity, and hence heat transfer, of a fluid containing nanoparticles can be dramatically increased when subjected to an external influence. The increase in thermal conductivity was significantly larger than what is predicted by commonly used thermal models for two-phase materials. Additionally, the surface of the nanoparticles was engineered so as to have a minimal influence on the viscosity of the fluid. As a result, a nanoparticle-laden fluid was successfully developed that can lead to enhanced heat transfer in both industrial and automotive heat exchangers
Heat transfer coefficient of cryotop during freezing.
Li, W J; Zhou, X L; Wang, H S; Liu, B L; Dai, J J
2013-01-01
Cryotop is an efficient vitrification method for cryopreservation of oocytes. It has been widely used owing to its simple operation and high freezing rate. Recently, the heat transfer performance of cryotop was studied by numerical simulation in several studies. However, the range of heat transfer coefficient in the simulation is uncertain. In this study, the heat transfer coefficient for cryotop during freezing process was analyzed. The cooling rates of 40 percent ethylene glycol (EG) droplet in cryotop during freezing were measured by ultra-fast measurement system and calculated by numerical simulation at different value of heat transfer coefficient. Compared with the results obtained by two methods, the range of the heat transfer coefficient necessary for the numerical simulation of cryotop was determined, which is between 9000 W/(m(2)·K) and 10000 W/(m (2)·K).
Rotary Joint for Heat Transfer
NASA Technical Reports Server (NTRS)
Shauback, R.
1986-01-01
Rotary joint exchanges heat between two heat pipes - one rotating and one stationary. Joint accommodates varying heat loads with little temperature drop across interface. According to concept, heat pipe enters center of disklike stationary section of joint. There, wicks in central artery of heat pipe separate into multiple strands that lead to concentric channels on rotaryinterface side of stationary disk. Thin layer of liquid sodium/potassium alloy carries heat from one member of rotary joint to other. Liquid conducts heat efficiently while permitting relative motion between members. Polypropylene rings contain liquid without interfering with rotation.
Pool Boiling Heat Transfer on structured Surfaces
NASA Astrophysics Data System (ADS)
Addy, J.; Olbricht, M.; Müller, B.; Luke, A.
2016-09-01
The development in the process and energy sector shows the importance of efficient utilization of available resources to improve thermal devices. To achieve this goal, all thermal components have to be optimized continuously. Various applications of multi-phase heat and mass transfer have to be improved. Therefore, the heat transfer and the influence of surface roughness in nucleate boiling with the working fluid propane is experimentally investigated on structured mild steel tubes, because only few data are available in the literature. The mild steel tube is sandblasted to obtain different surface roughness. The measurements are carried out over wide ranges of heat flux and pressure. The experimental results are compared with correlations from literature and the effect of surface roughness on the heat transfer is discussed. It is shown that the heat transfer coefficient increases with increasing surface roughness, heat flux and reduced pressure at nucleate pool boiling.
Forced convective heat transfer in curved diffusers
NASA Technical Reports Server (NTRS)
Rojas, J.; Whitelaw, J. H.; Yianneskis, M.
1987-01-01
Measurements of the velocity characteristics of the flows in two curved diffusers of rectangular cross section with C and S-shaped centerlines are presented and related to measurements of wall heat transfer coefficients along the heated flat walls of the ducts. The velocity results were obtained by laser-Doppler anemometry in a water tunnel and the heat transfer results by liquid crystal thermography in a wind tunnel. The thermographic technique allowed the rapid and inexpensive measurement of wall heat transfer coefficients along flat walls of arbitrary boundary shapes with an accuracy of about 5 percent. The results show that an increase in secondary flow velocities near the heated wall causes an increase in the local wall heat transfer coefficient, and quantify the variation for maximum secondary-flow velocities in a range from 1.5 to 17 percent of the bulk flow velocity.
Periodic Heat Transfer at Small Pressure Fluctuations
NASA Technical Reports Server (NTRS)
Pfriem, H.
1943-01-01
The effect of cyclic gas pressure variations on the periodic heat transfer at a flat wall is theoretically analyzed and the differential equation describing the process and its solution for relatively. Small pressure fluctuations developed, thus explaining the periodic heat cycle between gas and wall surface. The processes for pure harmonic pressure and temperature oscillations, respectively, in the gas space are described by means of a constant heat transfer coefficient and the equally constant phase angle between the appearance of the maximum values of the pressure and heat flow most conveniently expressed mathematically in the form of a complex heat transfer coefficient. Any cyclic pressure oscillations, can be reduced by Fourier analysis to harmonic oscillations, which result in specific, mutual relationships of heat-transfer coefficients and phase angles for the different harmonics.
Heat-transfer coefficients in agitated vessels. Sensible heat models
Kumpinsky, E.
1995-12-01
Transient models for sensible heat were developed to assess the thermal performance of agitated vessels with coils and jackets. Performance is quantified with the computation of heat-transfer coefficients by introducing vessel heating and cooling data into model equations. Of the two model categories studied, differential and macroscopic, the latter is preferred due to mathematical simplicity and lower sensitivity to experimental data variability.
Heat transfer research on enhanced heating surfaces in pool boiling
NASA Astrophysics Data System (ADS)
Kalawa, Wojciech; Wójcik, Tadeusz M.; Piasecka, Magdalena
The paper focuses on the analysis of the enhanced surfaces in such applications as boiling heat transfer. The testing measurement module with enhanced heating surfaces was used for pool boiling research. Pool boiling experiments were conducted with distilled water at atmospheric pressure in the vessel using an enhanced sample as the bottom heating surface. The samples are soldered to a copper heating block of the round cross-section .They were placed: in the fluid (saturation temperature measurement), under the sample for temperature determination. A vessel made of four flat glass panes was used for visualization. The heated surfaces in contact with the fluid differed in roughness were smooth or enhanced. This paper analyzes the effects of the microstructured heated surface on the heat transfer coefficient. The results are presented as relationships between the heat transfer coefficient and the heat flux 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 for the enhanced surfaces.
Fluid flow and heat transfer in polygonal micro heat pipes
NASA Astrophysics Data System (ADS)
Rao, Sai; Wong, Harris
2015-11-01
Micro heat pipes have been used to cool microelectronic devices, but their heat transfer coefficients are low compared with those of conventional heat pipes. We model heat and mass transfer in triangular, square, hexagonal, and rectangular micro heat pipes under small imposed temperature differences. A micro heat pipe is a closed microchannel filled with a wetting liquid and a long vapor bubble. When a temperature difference is applied across a micro heat pipe, the equilibrium vapor pressure at the hot end is higher than that at the cold end, and the difference drives a vapor flow. As the vapor moves, the vapor pressure at the hot end drops below the saturation pressure. This pressure drop induces continuous evaporation from the interface. Two dimensionless numbers emerge from the momentum and energy equations: the heat-pipe number H, and the evaporation exponent S. When H >> 1 and S >> 1, vapor-flow heat transfer dominates and a thermal boundary layer appears at the hot end, the thickness of which scales as L/S, where L is the half-length of the pipe. A similar boundary layer exists at the cold end. Outside the boundary layers, the temperature is uniform. We also find a dimensionless optimal pipe length Sm =Sm(H) for maximum evaporative heat transfer. Thus, our model suggests that micro heat pipes should be designed with H >> 1 and S =Sm. We calculate H and S for four published micro-heat-pipe experiments, and find encouraging support for our design criterion.
Gopinath, A.; Sadhal, S.S.; Jones, P.D.; Seyed-Yagoobi, J.; Woodbury, K.A.
1996-12-31
In the first section on heat transfer in microgravity, the papers cover phase-change phenomena and thermocapillary flows and surface effects. In the second section, several papers cover solution methods for radiative heat transfer while the rest cover heat transfer in low-temperature environments. The last section covers papers containing valuable information for thermal contact conductance of various materials plus papers on inverse problems in heat transfer. Separate abstracts were prepared for most papers in this volume.
Thermographic heat transfer measurements in separated flows
NASA Astrophysics Data System (ADS)
Scherer, V.; Wittig, S.; Bittlinger, G.; Pfeiffer, A.
1993-12-01
A measurement technique to determine the surface heat transfer distribution in complex turbulent flows is described. For this purpose, a constant wall heat flux test surface has been designed. To measure the surface temperature of the test plate, an infrared camera was used. The instrumentation allows the determination of the heat transfer with high accuracy and detailed spatial resolution. In examining combustor-type separated flow, the capabilities of the technique are demonstrated and its accuracy is verified by appropriate conventional techniques.
Heat transfer characteristics of rotating triangular thermosyphon
NASA Astrophysics Data System (ADS)
Ibrahim, E.; Moawed, M.; Berbish, N. S.
2012-09-01
An experimental investigation is carried out to study heat transfer characteristics of a rotating triangular thermosyphon, using R-134a refrigerant as the working fluid. The tested thermosyphon is an equilateral triangular tube made from copper material of 11 mm triangular length, 2 mm thickness, and a total length of 1,500 mm. The length of the evaporator section is 600 mm, adiabatic section is 300 mm, and condenser section is 600 mm. The effects of the rotational speed, filling ratio, and the evaporator heat flux on each of the evaporator heat transfer coefficient, he, condenser heat transfer coefficient, hc, and the overall effective thermal conductance, Ct are studied. Experiments are performed with a vertical position of thermosyphon within heat flux ranges from 11 to 23 W/m2 for the three selected filling ratios of 10, 30 and 50 % of the evaporator section volume. The results indicated that the maximum values of the tested heat transfer parameters of the rotational equilateral triangular thermosyphon are obtained at the filling ratio of 30 %. Also, it is found that the heat transfer coefficient of the condensation is increased with increasing the rotational speed. The tested heat transfer parameters of the thermosyphon are correlated as a function of the evaporator heat flux and angular velocity.
Heat Transfer in Metal Foam Heat Exchangers at High Temperature
NASA Astrophysics Data System (ADS)
Hafeez, Pakeeza
Heat transfer though open-cell metal foam is experimentally studied for heat exchanger and heat shield applications at high temperatures (˜750°C). Nickel foam sheets with pore densities of 10 and 40 pores per linear inch (PPI), have been used to make the heat exchangers and heat shields by using thermal spray coating to deposit an Inconel skin on a foam core. Heat transfer measurements were performed on a test rig capable of generating hot gas up to 1000°C. The heat exchangers were tested by exposing their outer surface to combustion gases at a temperature of 550°C and 750°C while being cooled by air flowing through them at room temperature at velocities up to 5 m/s. The temperature rise of the air, the surface temperature of the heat exchangers and the air temperature inside the heat exchanger were measured. The volumetric heat transfer coefficient and Nusselt number were calculated for different velocities. The heat transfer performance of the 40PPI sample brazed with the foil is found to be the most efficient. Pressure drop measurements were also performed for 10 and 40PPI metal foam. Thermographic measurements were done on 40PPI foam heat exchangers using a high temperature infrared camera. A high power electric heater was used to produce hot air at 300°C that passed over the foam heat exchanger while the cooling air was blown through it. Heat shields were made by depositing porous skins on metal foam and it was observed that a small amount of coolant leaking through the pores notably reduces the heat transfer from the hot gases. An analytical model was developed based assuming local thermal non-equilibrium that accounts for the temperature difference between solid and fluid phase. The experimental results are found to be in good agreement with the predicted values of the model.
Heat Transfer of Nanofluid in a Double Pipe Heat Exchanger.
Aghayari, Reza; Maddah, Heydar; Zarei, Malihe; Dehghani, Mehdi; Kaskari Mahalle, Sahar Ghanbari
2014-01-01
This paper investigates the enhancement of heat transfer coefficient and Nusselt number of a nanofluid containing nanoparticles (γ-AL2O3) with a particle size of 20 nm and volume fraction of 0.1%-0.3% (V/V). Effects of temperature and concentration of nanoparticles on Nusselt number changes and heat transfer coefficient in a double pipe heat exchanger with counter turbulent flow are investigated. Comparison of experimental results with valid theoretical data based on semiempirical equations shows an acceptable agreement. Experimental results show a considerable increase in heat transfer coefficient and Nusselt number up to 19%-24%, respectively. Also, it has been observed that the heat transfer coefficient increases with the operating temperature and concentration of nanoparticles.
Heat Transfer of Nanofluid in a Double Pipe Heat Exchanger
Aghayari, Reza; Maddah, Heydar; Zarei, Malihe; Dehghani, Mehdi; Kaskari Mahalle, Sahar Ghanbari
2014-01-01
This paper investigates the enhancement of heat transfer coefficient and Nusselt number of a nanofluid containing nanoparticles (γ-AL2O3) with a particle size of 20 nm and volume fraction of 0.1%–0.3% (V/V). Effects of temperature and concentration of nanoparticles on Nusselt number changes and heat transfer coefficient in a double pipe heat exchanger with counter turbulent flow are investigated. Comparison of experimental results with valid theoretical data based on semiempirical equations shows an acceptable agreement. Experimental results show a considerable increase in heat transfer coefficient and Nusselt number up to 19%–24%, respectively. Also, it has been observed that the heat transfer coefficient increases with the operating temperature and concentration of nanoparticles. PMID:27433521
Novel Heat Transfer Device Research
2012-04-01
Thermography Comparison of the Qu Tube with the Wicked Heat Pipe .................. 4 3.3 Quantitative Characterization of both Qu Tube and Heat Pipe...the Qu Tube operations in comparison with a wicked water heat pipe using the IR thermography . III. Quantitative characterization of both Qu Tubes...4 Approved for public release; distribution unlimited. Figure 2: X-Ray Images of Copper Heat Pipes 3.2 IR Thermography
Van der Waals Force Assisted Heat Transfer
NASA Astrophysics Data System (ADS)
Sasihithlu, K.; Pendry, J. B.; Craster, R. V.
2017-02-01
Phonons (collective atomic vibrations in solids) are more effective in transporting heat than photons. This is the reason why the conduction mode of heat transport in nonmetals (mediated by phonons) is dominant compared to the radiation mode of heat transport (mediated by photons). However, since phonons are unable to traverse a vacuum gap (unlike photons), it is commonly believed that two bodies separated by a gap cannot exchange heat via phonons. Recently, a mechanism was proposed [J. B. Pendry, K. Sasihithlu, and R. V. Craster, Phys. Rev. B 94, 075414 (2016)] by which phonons can transport heat across a vacuum gap - through the Van der Waals interaction between two bodies with gap less than the wavelength of light. Such heat transfer mechanisms are highly relevant for heating (and cooling) of nanostructures; the heating of the flying heads in magnetic storage disks is a case in point. Here, the theoretical derivation for modelling phonon transmission is revisited and extended to the case of two bodies made of different materials separated by a vacuum gap. Magnitudes of phonon transmission, and hence the heat transfer, for commonly used materials in the micro- and nano-electromechanical industry are calculated and compared with the calculation of conduction heat transfer through air for small gaps as well as the heat transfer calculation due to photon exchange.
Heat transfer and planetary evolution
NASA Astrophysics Data System (ADS)
Tozer, D. C.
1985-06-01
The object of this account is to show how much one can interprete and predict about the present state of material forming planet size objects, despite the fact we do not and could never have the kind of exact or prior knowledge of initial conditions and in situ material behaviour that would make a formal mathematical analysis of the dynamical problems of planetary evolution an efficient or meaningful exercise The interest and usefulness of results obtained within these limitations stem from the highly non linear nature of planetary scale heat transfer problems when posed in any physically plausible form. The non linearity arising from a strongly temperature dependent rheology assumed for in situ planetary material is particularly valuable in deriving results insensitive to such uncertainties. Qualitatively, the thermal evolution of a planet is quite unlike that given by heat conduction calculation below a very superficial layer, and much unnecessary argument and confusion results from a persistent failure to recognise that fact. At depths that are no greater on average than a few tens of kilometres in the case of Earth, the temperature distribution is determined by a convective flow regime inaccessble to the laboratory experimenter and to the numerical methods regularly employed to study convective movement. A central and guiding quantitative result is the creation in homogeneous planet size objects having surface temperatures less than about half the absolute melting temperature of their material, of internal states with horizontally a veraged viscosity values ˜1021 poise. This happens in times short compared with the present Solar System age. The significance of this result for an understanding of such processes and features as isostasy, continental drift, a minimum in seismic S wave velocity in Earth's upper mantle, a uniformity of mantle viscosity values, the survival of liquid planetary cores and the differentiation of terrestrial planet material is examined
Pumped two-phase heat transfer loop
NASA Technical Reports Server (NTRS)
Edelstein, Fred
1988-01-01
A pumped loop two-phase heat transfer system, operating at a nearly constant temperature throughout, includes several independently operating grooved capillary heat exchanger plates supplied with working fluid through independent flow modulation valves connected to a liquid supply line, a vapor line for collecting vapor from the heat exchangers, a condenser between the vapor and the liquid lines, and a fluid circulating pump between the condenser and the heat exchangers.
Pumped two-phase heat transfer loop
NASA Technical Reports Server (NTRS)
Edelstein, Fred (Inventor)
1987-01-01
A pumped loop two-phase heat transfer system, operating at a nearly constant temperature throughout, includes a plurality of independently operating grooved capillary heat exchanger plates supplied with working fluid through independent flow modulation valves connected to a liquid supply line, a vapor line for collecting vapor from the heat exchangers, a condenser between the vapor and the liquid lines, and a fluid circulating pump between the condenser and the heat exchangers.
Conjugate heat transfer characterization in cooling channels
NASA Astrophysics Data System (ADS)
Cukurel, Beni; Arts, Tony; Selcan, Claudio
2012-06-01
Cooling technology of gas turbine blades, primarily ensured via internal forced convection, is aimed towards withdrawing thermal energy from the airfoil. To promote heat exchange, the walls of internal cooling passages are lined with repeated geometrical flow disturbance elements and surface non-uniformities. Raising the heat transfer at the expense of increased pressure loss; the goal is to obtain the highest possible cooling effectiveness at the lowest possible pressure drop penalty. The cooling channel heat transfer problem involves convection in the fluid domain and conduction in the solid. This coupled behavior is known as conjugate heat transfer. This experimental study models the effects of conduction coupling on convective heat transfer by applying iso-heat-flux boundary condition at the external side of a scaled serpentine passage. Investigations involve local temperature measurements performed by Infrared Thermography over flat and ribbed slab configurations. Nusselt number distributions along the wetted surface are obtained by means of heat flux distributions, computed from an energy balance within the metal domain. For the flat plate experiments, the effect of conjugate boundary condition on heat transfer is estimated to be in the order of 3%. In the ribbed channel case, the normalized Nusselt number distributions are compared with the basic flow features. Contrasting the findings with other conjugate and convective iso-heat-flux literature, a high degree of overall correlation is evident.
Passive heat transfer means for nuclear reactors
Burelbach, James P.
1984-01-01
An improved passive cooling arrangement is disclosed for maintaining adjacent or related components of a nuclear reactor within specified temperature differences. Specifically, heat pipes are operatively interposed between the components, with the vaporizing section of the heat pipe proximate the hot component operable to cool it and the primary condensing section of the heat pipe proximate the other and cooler component operable to heat it. Each heat pipe further has a secondary condensing section that is located outwardly beyond the reactor confinement and in a secondary heat sink, such as air ambient the containment, that is cooler than the other reactor component. Means such as shrouding normally isolated the secondary condensing section from effective heat transfer with the heat sink, but a sensor responds to overheat conditions of the reactor to open the shrouding, which thereby increases the cooling capacity of the heat pipe. By having many such heat pipes, an emergency passive cooling system is defined that is operative without electrical power.
Convective Heat Transfer for Ship Propulsion.
1980-01-30
Report Contract No. N00014-75-C-0694 Contract Authority NR-097-395 I0 I CONVECTIVE HEAT TRANSFER FOR SHIP PROPULSION Prepared for Office of Naval...Vj~ / TITE find~&ie S.~ TYPE OF REPOAT-& PERIOD COVERED CovcieHeat Transfer for Ship Propulsion # nna umary /epS’Ptoi ", 1’ . Anua MING 14G RE an...ee Fifth Annual Summary Report CONVECTIVE HEAT TRANSFER FOR SHIP PROPULSION By S. E. Faas and D. M. McEligot Aerospace and Mechanical Engineering
Fundamental phenomena governing heat transfer during rolling
NASA Astrophysics Data System (ADS)
Chen, W. C.; Samarasekera, I. V.; Hawbolt, E. B.
1993-06-01
To quantify the effect of roll chilling on the thermal history of a slab during hot rolling, tests were conducted at the Canada Center for Mineral and Energy Technology (CANMET) and at the University of British Columbia (UBC). In these tests, the surface and the interior temperatures of specimens were recorded during rolling using a data acquisition system. The corresponding heat-transfer coefficients in the roll bite were back-calculated by a trial-and-error method using a heat-transfer model. The heat-transfer coefficient was found to increase along the arc of contact and reach a maximum, followed by a decrease, until the exit of the roll bite. Its value was influenced by rolling parameters, such as percent reduction, rolling speed, rolling temperature, material type, etc. It was shown that the heat-transfer coefficient in the roll gap was strongly dependent on the roll pressure, and the effect of different variables on the interfacial heat-transfer coefficient can be related to their influence on pressure. At low mean roll pressure, such as in the case of rolling plain carbon steels at elevated temperature, the maximum heat-transfer coefficient in the roll bite was in the 25 to 35 kW/m2 °C range. As the roll pressure increased with lower rolling temperature and higher deformation resistance of stainless steel and microalloyed grades, the maximum heat-transfer coefficient reached a value of 620 kW/m2 °C. Obviously, the high pressure improved the contact between the roll and the slab surface, thereby reducing the resistance to heat flow. The mean roll-gap heat-transfer coefficient at the interface was shown to be linearly related to mean roll pressure. This finding is important because it permitted a determination of heat-transfer coefficients applicable to industrial rolling from pilot mill data. Thus, the thermal history of a slab during rough rolling was computed using a model in which the mean heat-transfer coefficient between the roll and the slab was
Bae, Yoon-Yeong; Kim, Hwan-Yeol; Kang, Deog-Ji
2010-11-15
An experiment of heat transfer to CO{sub 2}, which flows upward and downward in a circular tube with an inner diameter of 6.32 mm, was carried out with mass flux of 285-1200 kg/m{sup 2} s and heat flux of 30-170 kW/m{sup 2} at pressures of 7.75 and 8.12 MPa, respectively. The corresponding Reynolds number at the tube test section inlet ranges from 1.8 x 10{sup 4} to 3.8 x 10{sup 5}. The tube inner diameter corresponds to the equivalent hydraulic diameter of the fuel assembly sub-channel, which is being studied at KAERI. Among the tested correlations, the Bishop correlation predicted the experimental data most accurately, but only 66.9% of normal heat transfer data were predicted within {+-}30% error range. The Watts and Chou correlation, which is claimed to be valid for both the normal and deteriorated heat transfer regime, showed unsatisfactory performance. A significant decrease in Nusselt number was observed in the range of 10{sup -6}
Heat transfer enhancement using 2MHz ultrasound.
Bulliard-Sauret, Odin; Ferrouillat, Sebastien; Vignal, Laure; Memponteil, Alain; Gondrexon, Nicolas
2017-11-01
The present work focuses on possible heat transfer enhancement from a heating plate towards tap water in forced convection by means of 2MHz ultrasound. The thermal approach allows to observe the increase of local convective heat transfer coefficients in the presence of ultrasound and to deduce a correlation between ultrasound power and Nusselt number. Heat transfer coefficient under ultrasound remains constant while heat transfer coefficient under silent conditions increases with Reynolds number from 900 up to 5000. Therefore, heat transfer enhancement factor ranges from 25% up to 90% for the same energy conditions (supplied ultrasonic power=110W and supplied thermal power=450W). In the same time cavitational activity due to 2MHz ultrasound emission was characterized from mechanical and chemical viewpoints without significant results. At least, Particle Image Velocimetry (PIV) measurements have been performed in order to investigate hydrodynamic modifications due to the presence of 2MHz ultrasound. It was therefore possible to propose a better understanding of heat transfer enhancement mechanism with high frequency ultrasound. Copyright © 2017 Elsevier B.V. All rights reserved.
Heat transfer behavior of molten nitrate salt
NASA Astrophysics Data System (ADS)
Das, Apurba K.; Clark, Michael M.; Teigen, Bard C.; Fiveland, Woodrow A.; Anderson, Mark H.
2016-05-01
The usage of molten nitrate salt as heat transfer fluid and thermal storage medium decouples the generation of electricity from the variable nature of the solar resource, allowing CSP plants to avoid curtailment and match production with demand. This however brings some unique challenges for the design of the molten salt central receiver (MSCR). An aspect critical to the use of molten nitrate (60wt%/40wt% - NaNO3/KNO3) salt as heat transfer fluid in the MSCR is to understand its heat transfer behavior. Alstom collaborated with the University of Wisconsin to conduct a series of experiments and experimentally determined the heat transfer coefficients of molten nitrate salt up to high Reynolds number (Re > 2.0E5) and heat flux (q″ > 1000 kW/m2), conditions heretofore not reported in the literature. A cartridge heater instrumented with thermocouples was installed inside a stainless steel pipe to form an annular test section. The test section was installed in the molten salt flow loop at the University of Wisconsin facility, and operated over a range of test conditions to determine heat transfer data that covered the expected operating regime of a practical molten salt receiver. Heat transfer data were compared to widely accepted correlations found in heat transfer literature, including that of Gnielinski. At lower Reynolds number conditions, the results from this work concurred with the molten salt heat transfer data reported in literature and followed the aforementioned correlations. However, in the region of interest for practical receiver design, the correlations did not accurately model the experimentally determined heat transfer data. Two major effects were observed: (i) all other factors remaining constant, the Nusselt numbers gradually plateaued at higher Reynolds number; and (ii) at higher Reynolds number a positive interaction of heat flux on Nusselt number was noted. These effects are definitely not modeled by the existing correlations. In this paper a new
Heat Transfer Correlations for compressible flow in Micro Heat Exchangers
NASA Astrophysics Data System (ADS)
Coppola, M. A.; Croce, G.
2016-09-01
The paper discusses the definition of dimensionless parameters useful to define a local correlation for convective heat transfer in compressible, micro scale gaseous flows. A combination of static and stagnation temperatures is chosen, as it allows to weight the temperature change related to the heat transfer and that induced by conversion of internal energy into kinetic one. The correlation offers a purely convective local Nusselt number, i.e. correlating the heat flow rate with the local flow parameters and wall surface temperature. The correlation is validated through a series of numerical computations in both counter-current and co-current micro heat exchanger configurations. The numerical computations take into account rarefaction and conjugate heat transfer effects.
Coolant passage heat transfer with rotation
NASA Technical Reports Server (NTRS)
Rohde, J. E.
1982-01-01
Although the effects of the coriolis and buoyancy forces due to rotation on coolant-side heat transfer are generally not included in the design methods for blades, the influence of these forces could be large. Comparisons of nonrotating heat transfer data and extrapolations of available correlation for the average heat transfer coefficients with radial outflow of cooling air showed that neglecting rotation at gas turbine engine conditions result in variations in the heat transfer coefficient by as much as 45 percent. This, in effect, results in blade metal temperatures running as much as 100 F different from predicted values. This also may explain why rotating blade metal temperatures in engine tests are often higher than expected from results obtained in nonrotating cascade tests.
Cooling Heat Transfer of Supercritical Carbon Dioxide
NASA Astrophysics Data System (ADS)
Dang, Chaobin; Hihara, Eiji
The characteristics of carbon dioxide cooled under supercritical condition were investigated theoretically and experimentally. Based on the results of numerical calculation and experimental measurements described in the 1st report, a new correlation was proposed to predict the heat transfer coefficient, and the Filonenko's equation was found adequate to predict the pressure drop inside as mall seized tube. Those correlations were compared with measurement results and the deviations were found lower than ±20%. Furthermore, a compressor cycle was assembled to investigate the effect of lubricant oil on heat transfer and pressure drop. The oil content in CO2 was set to be about 0.5% during the measurements. This amount of lubricant oil was found affected the heat transfer coefficient significantly, with largest degradation of heat transfer coefficient at the pseudocritical point to nearly 50%. The effect of lubricant oil at small concentration on the pressure drop was found negligible.
Solving nonlinear heat transfer constant area fin problems
NASA Technical Reports Server (NTRS)
1968-01-01
Tables and graphs were compiled for solving nonlinear heat transfer constant area fin problems. The differential equation describing one-dimensional steady-state temperature distribution and heat flow under three modes of heat transfer with heat generation was investigated.
Nanoparticle enhanced ionic liquid heat transfer fluids
Fox, Elise B.; Visser, Ann E.; Bridges, Nicholas J.; Gray, Joshua R.; Garcia-Diaz, Brenda L.
2014-08-12
A heat transfer fluid created from nanoparticles that are dispersed into an ionic liquid is provided. Small volumes of nanoparticles are created from e.g., metals or metal oxides and/or alloys of such materials are dispersed into ionic liquids to create a heat transfer fluid. The nanoparticles can be dispersed directly into the ionic liquid during nanoparticle formation or the nanoparticles can be formed and then, in a subsequent step, dispersed into the ionic liquid using e.g., agitation.
Convective Heat Transfer for Ship Propulsion.
1982-04-01
RD-A124 Wi CONVECTIVE HEAT TRANSFER FOR SHIP PROPULSION (U) ARIZONA 112 UNIV TUCSON ENGINEERING EXPERIMENT STATION PARK ET AL. 01 APR 82 1248-9 N814...395 CONVECTIVE HEAT TRANSFER FOR SHIP PROPULSION Prepared for Office of Naval Research Code 431 Arlington, Virginia Prepared by J. S. Park, M. F...FOR SHIP PROPULSION By J. S. Park, M. F. Taylor and D. M. McEligot Aerospace and Mechanical Engineering Department University of Arizona Tucson
Condensation heat transfer in a microgravity environment
NASA Technical Reports Server (NTRS)
Chow, L. C.; Parish, R. C.
1986-01-01
In the present treatment of the condensation heat transfer process in a microgravity environment, two mechanisms for condensate removal are analyzed in light of two problems: (1) film condensation on a flat, porous plate, with condensate being removed by wall suction; and (2) the analytical prediction of the heat transfer coefficient of condensing annular flows, where the condensate film is driven by vapor shear. Both suction and vapor shear can effectively drain the condensate, ensuring continuous operation in microgravity.
Analytical Prediction of Turbulent Heat Transfer Parameters.
1985-04-01
ofMaterfals (McGraw-Hill, equations show that the resistive bending moment in the New York, 1949), p. 184. cross section is OA . Bejan. J. Heat Transfer...178011981. graphed wavelengths agree with each other and with the ’ OA . Bejan, Lett. Heat Mass Transfer 8, 187 119810. buckling wavelength -’D/2...nicht- tear hslresaemto.wiht oeft ’ zahe Bereich der Fahne (die _Fahnensdule-) elastische Eigen- * schaften besitzt ihnlich jener elastischer Stiibe
Heat transfer coefficient of nanofluids in minichannel heat sink
NASA Astrophysics Data System (ADS)
Utomo, Adi T.; Zavareh, Ashkan I. T.; Poth, Heiko; Wahab, Mohd; Boonie, Mohammad; Robbins, Phillip T.; Pacek, Andrzej W.
2012-09-01
Convective heat transfer in a heat sink consisting of rectangular minichannels and cooled with alumina and titania nanofluids has been investigated experimentally and numerically. Numerical simulations were carried out in a three dimensional domain employing homogeneous mixture model with effective thermo-physical properties of nanofluids. The predictions of base temperature profiles of the heat sink cooled with both water and nanofluids agree well with the experimental data. Experimental and numerical results show that the investigated nanofluids neither exhibits unusual enhancement of heat transfer coefficient nor decreases the heat sink base temperature. Although both nanofluids showed marginal thermal conductivity enhancements, the presence of solid nanoparticles lowers the specific heat capacity of nanofluids offseting the advantage of thermal conductivity enhancement. For all investigated flow rates, the Nusselt number of both nanofluids overlaps with that of water indicating that both nanofluids behave like single-phase fluids.
Examination of Liquid Fluoride Salt Heat Transfer
Yoder Jr, Graydon L
2014-01-01
The need for high efficiency power conversion and energy transport systems is increasing as world energy use continues to increase, petroleum supplies decrease, and global warming concerns become more prevalent. There are few heat transport fluids capable of operating above about 600oC that do not require operation at extremely high pressures. Liquid fluoride salts are an exception to that limitation. Fluoride salts have very high boiling points, can operate at high temperatures and low pressures and have very good heat transfer properties. They have been proposed as coolants for next generation fission reactor systems, as coolants for fusion reactor blankets, and as thermal storage media for solar power systems. In each case, these salts are used to either extract or deliver heat through heat exchange equipment, and in order to design this equipment, liquid salt heat transfer must be predicted. This paper discusses the heat transfer characteristics of liquid fluoride salts. Historically, heat transfer in fluoride salts has been assumed to be consistent with that of conventional fluids (air, water, etc.), and correlations used for predicting heat transfer performance of all fluoride salts have been the same or similar to those used for water conventional fluids an, water, etc). A review of existing liquid salt heat transfer data is presented, summarized, and evaluated on a consistent basis. Less than 10 experimental data sets have been found in the literature, with varying degrees of experimental detail and measured parameters provided. The data has been digitized and a limited database has been assembled and compared to existing heat transfer correlations. Results vary as well, with some data sets following traditional correlations; in others the comparisons are less conclusive. This is especially the case for less common salt/materials combinations, and suggests that additional heat transfer data may be needed when using specific salt eutectics in heat transfer
Heat transfer between fish and ambient water.
Stevens, E D; Sutterlin, A M
1976-08-01
1. The ability of fish gills to transfer heat was measured by applying a heat pulse to blood in the ventral aorta and measuring it before and after passing through the gills of a teleost, Hemitripterus americanus. 2. 80-90% of heat contained in the blood is lost during passage through the gills. 3. The fraction of heat not lost during passage through the gills is due to direct transfer of heat between the afferent and efferent artery within the gill bar. 4. The major fraction of metabolic heat (70 - 90%) is lost through the body wall and fins of the sea raven in sea water at 5 degrees C; the remainder is lost through the gills.
Conjugate Heat Transfer Study in Hypersonic Flows
NASA Astrophysics Data System (ADS)
Sahoo, Niranjan; Kulkarni, Vinayak; Peetala, Ravi Kumar
2017-05-01
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.
Interactive Heat Transfer Simulations for Everyone
ERIC Educational Resources Information Center
Xie, Charles
2012-01-01
Heat transfer is widely taught in secondary Earth science and physics. Researchers have identified many misconceptions related to heat and temperature. These misconceptions primarily stem from hunches developed in everyday life (though the confusions in terminology often worsen them). Interactive computer simulations that visualize thermal energy,…
Interactive Heat Transfer Simulations for Everyone
ERIC Educational Resources Information Center
Xie, Charles
2012-01-01
Heat transfer is widely taught in secondary Earth science and physics. Researchers have identified many misconceptions related to heat and temperature. These misconceptions primarily stem from hunches developed in everyday life (though the confusions in terminology often worsen them). Interactive computer simulations that visualize thermal energy,…
Heat transfer measurements for Stirling machine cylinders
NASA Technical Reports Server (NTRS)
Kornhauser, Alan A.; Kafka, B. C.; Finkbeiner, D. L.; Cantelmi, F. C.
1994-01-01
The primary purpose of this study was to measure the effects of inflow-produced heat turbulence on heat transfer in Stirling machine cylinders. A secondary purpose was to provide new experimental information on heat transfer in gas springs without inflow. The apparatus for the experiment consisted of a varying-volume piston-cylinder space connected to a fixed volume space by an orifice. The orifice size could be varied to adjust the level of inflow-produced turbulence, or the orifice plate could be removed completely so as to merge the two spaces into a single gas spring space. Speed, cycle mean pressure, overall volume ratio, and varying volume space clearance ratio could also be adjusted. Volume, pressure in both spaces, and local heat flux at two locations were measured. The pressure and volume measurements were used to calculate area averaged heat flux, heat transfer hysteresis loss, and other heat transfer-related effects. Experiments in the one space arrangement extended the range of previous gas spring tests to lower volume ratio and higher nondimensional speed. The tests corroborated previous results and showed that analytic models for heat transfer and loss based on volume ratio approaching 1 were valid for volume ratios ranging from 1 to 2, a range covering most gas springs in Stirling machines. Data from experiments in the two space arrangement were first analyzed based on lumping the two spaces together and examining total loss and averaged heat transfer as a function of overall nondimensional parameter. Heat transfer and loss were found to be significantly increased by inflow-produced turbulence. These increases could be modeled by appropriate adjustment of empirical coefficients in an existing semi-analytic model. An attempt was made to use an inverse, parameter optimization procedure to find the heat transfer in each of the two spaces. This procedure was successful in retrieving this information from simulated pressure-volume data with artificially
Uppanisakorn, Supattra; Bhurayanontachai, Rungsun; Boonyarat, Jaruwan; Kaewpradit, Julawan
2017-09-13
This study aims to determine the ability of the National Early Warning Score at ICU discharge (NEWSdc) to predict the development of clinical deterioration within 24h. A prospective observational study was conducted. The NEWS was immediately recorded before discharge (NEWSdc). The development of early clinical deterioration was defined as acute respiratory failure or circulatory shock within 24h of ICU discharge. The discrimination of NEWSdc and the best cut off value of NEWSdc to predict the early clinical deterioration was determined. Data were collected from 440 patients. The incidence of early clinical deterioration after ICU discharge was 14.8%. NEWSdc was an independent predictor for early clinical deterioration after ICU discharge (OR 2.54; 95% CI 1.98-3.26; P<0.001). The AUROC of NEWSdc was 0.92±0.01 (95% CI 0.89-0.94, P<0.001). A NEWSdc>7 showed a sensitivity of 93.6% and a specificity of 82.2% to detect an early clinical deterioration after ICU discharge. Among critically ill patients who were discharged from ICU, a NEWSdc>7 showed the best sensitivity and specificity to detect early clinical deterioration 24h after ICU discharge. Copyright © 2017 The Authors. Published by Elsevier Inc. All rights reserved.
Heat Transfer to Fuel Sprays Injected into Heated Gases
NASA Technical Reports Server (NTRS)
Selden, Robert F; Spencer, Robert C
1938-01-01
This report presents the results of a study made of the influence of several variables on the pressure decrease accompanying injection of a relatively cool liquid into a heated compressed gas. Indirectly, this pressure decrease and the time rate of change of it are indicative of the total heat transferred as well as the rate of heat transfer between the gas and the injected liquid. Air, nitrogen, and carbon dioxide were used as ambient gases; diesel fuel and benzene were the injected liquids. The gas densities and gas-fuel ratios covered approximately the range used in compression-ignition engines. The gas temperatures ranged from 150 degrees c. to 350 degrees c.
Bistable heat transfer in a nanofluid.
Donzelli, Gea; Cerbino, Roberto; Vailati, Alberto
2009-03-13
Heat convection in water can be suppressed by adding a small amount of highly thermophilic nanoparticles. We show that such suppression is not effective when a suspension with uniform concentration of nanoparticles is suddenly heated from below. At Rayleigh numbers smaller than a sample dependent threshold Ra;{*} we observe transient oscillatory convection. Unexpectedly, the duration of convection diverges at Ra;{*}. Above Ra;{*} oscillatory convection becomes permanent and the heat transferred exhibits bistability. Our results are explained only partially and qualitatively by existing theories.
Capillary-Condenser-Pumped Heat-Transfer Loop
NASA Technical Reports Server (NTRS)
Silverstein, Calvin C.
1989-01-01
Heat being transferred supplies operating power. Capillary-condenser-pumped heat-transfer loop similar to heat pipe and to capillary-evaporator-pumped heat-transfer loop in that heat-transfer fluid pumped by evaporation and condensation of fluid at heat source and sink, respectively. Capillary condenser pump combined with capillary evaporator pump to form heat exchanger circulating heat-transfer fluids in both loops. Transport of heat more nearly isothermal. Thermal stress in loop reduced, and less external surface area needed in condenser section for rejection of heat to heat sink.
Capillary-Condenser-Pumped Heat-Transfer Loop
NASA Technical Reports Server (NTRS)
Silverstein, Calvin C.
1989-01-01
Heat being transferred supplies operating power. Capillary-condenser-pumped heat-transfer loop similar to heat pipe and to capillary-evaporator-pumped heat-transfer loop in that heat-transfer fluid pumped by evaporation and condensation of fluid at heat source and sink, respectively. Capillary condenser pump combined with capillary evaporator pump to form heat exchanger circulating heat-transfer fluids in both loops. Transport of heat more nearly isothermal. Thermal stress in loop reduced, and less external surface area needed in condenser section for rejection of heat to heat sink.
The Principles of Turbulent Heat Transfer
NASA Technical Reports Server (NTRS)
Reichardt, H.
1957-01-01
The literature on turbulent heat transfer has in the course of years attained a considerable volume. Since this very complicated problem has not as yet found a complete solution, further studies in this field may be expected. The heat engineer must therefore accomodate himself to a constantly increasing number of theories and formulas. Since the theories generally start from hypothetical assumptions, and since they contain true and false assertions, verified knowledge and pure suppositions often being intermingled in a manner difficult to tell them apart, the specialist had difficulty in forming a correct evaluation of the individual studies. The need therefore arises for a presentation of the problem of turbulent heat transfer which is not initially bound by hypothetical assumptions and in which uninvestigated can be clearly distinguished form each other. Such a presentation will be given in the present treatment. Brief remarks with regard to the development of the theory of local heat transfer are included.
Indirect evaporative coolers with enhanced heat transfer
Kozubal, Eric; Woods, Jason; Judkoff, Ron
2015-09-22
A separator plate assembly for use in an indirect evaporative cooler (IEC) with an air-to-air heat exchanger. The assembly includes a separator plate with a first surface defining a dry channel and a second surface defining a wet channel. The assembly includes heat transfer enhancements provided on the first surface for increasing heat transfer rates. The heat transfer enhancements may include slit fins with bodies extending outward from the first surface of separator plate or may take other forms including vortex generators, offset strip fins, and wavy fins. In slit fin implementations, the separator plate has holes proximate to each of the slit fins, and the separator plate assembly may include a sealing layer applied to the second surface of the separator plate to block air flow through the holes. The sealing layer can be a thickness of adhesive, and a layer of wicking material is applied to the adhesive.
Heat transfer in rocket combustion chambers
NASA Technical Reports Server (NTRS)
Anderson, P.; Cheng, G.; Farmer, R.
1993-01-01
Complexities of liquid rocket engine heat transfer which involve the injector faceplate and film cooled walls are being investigated by computational analysis. A conjugate heat transfer analysis was used to describe localized heating phenomena associated with particular injector configurations and film coolant flows. These components were analyzed, and the analyses verified when appropriate test data were available. The component analyses are being synthesized into an overall flowfield/heat transfer model. A Navier-Stokes flow solver, the FDNS code, was used to make the analyses. Particular attention was given to the representation of the thermodynamic properties of the fluid streams. Unit flow models of specific coaxial injector elements have been developed and are being used to describe the flame structure near the injector faceplate.
A heat transfer model of a horizontal ground heat exchanger
NASA Astrophysics Data System (ADS)
Mironov, R. E.; Shtern, Yu. I.; Shtern, M. Yu.; Rogachev, M. S.
2016-04-01
Ground-source heat pumps are gaining popularity in Eastern Europe, especially those which are using the horizontal ground heat exchanger (GHX). Due to the difficulty of accessing GHX after the installation, materials and the quality of the installation must satisfy the very high requirements. An inaccurate calculation of GHX can be the reason of a scarcity of heat power in a crucial moment. So far, there isn't any appropriate mathematical description of the horizontal GHX which takes into account the mutual influence of GHX pipes on each other. To solve this problem we used the temperature wave approach. As a result, a mathematical model which describes the dependence of the heat transfer rate per unit length of the horizontal GHX pipe on the thermal properties of soil, operating time of GHX and the distance between pipes was obtained. Using this model, heat transfer rates per unit length of a horizontal GHX were plotted as functions of the distance between pipes and operating time. The modeling shows that heat transfer rates decreases rapidly with the distance between pipes lower then 2 meters. After the launch of heat pump, heat power of GHX is reduced during the first 20 - 30 days and get steady after that. The obtained results correlate with experimental data. Therefore the proposed mathematical model can be used to design a horizontal GHX with the optimal characteristics, and predict its capability during operation.
Modeling microscale heat transfer using Calore.
Gallis, Michail A.; Rader, Daniel John; Wong, Chung-Nin Channy; Bainbridge, Bruce L.; Torczynski, John Robert; Piekos, Edward Stanley
2005-09-01
Modeling microscale heat transfer with the computational-heat-transfer code Calore is discussed. Microscale heat transfer problems differ from their macroscopic counterparts in that conductive heat transfer in both solid and gaseous materials may have important noncontinuum effects. In a solid material, three noncontinuum effects are considered: ballistic transport of phonons across a thin film, scattering of phonons from surface roughness at a gas-solid interface, and scattering of phonons from grain boundaries within the solid material. These processes are modeled for polycrystalline silicon, and the thermal-conductivity values predicted by these models are compared to experimental data. In a gaseous material, two noncontinuum effects are considered: ballistic transport of gas molecules across a thin gap and accommodation of gas molecules to solid conditions when reflecting from a solid surface. These processes are modeled for arbitrary gases by allowing the gas and solid temperatures across a gas-solid interface to differ: a finite heat transfer coefficient (contact conductance) is imposed at the gas-solid interface so that the temperature difference is proportional to the normal heat flux. In this approach, the behavior of gas in the bulk is not changed from behavior observed under macroscopic conditions. These models are implemented in Calore as user subroutines. The user subroutines reside within Sandia's Source Forge server, where they undergo version control and regression testing and are available to analysts needing these capabilities. A Calore simulation is presented that exercises these models for a heated microbeam separated from an ambient-temperature substrate by a thin gas-filled gap. Failure to use the noncontinuum heat transfer models for the solid and the gas causes the maximum temperature of the microbeam to be significantly underpredicted.
Simplified models for heat transfer in rooms
NASA Astrophysics Data System (ADS)
Graca, Guilherme C. C. Carrilho Da
Buildings protect their occupants from the outside environment. As a semi-enclosed environment, buildings tend to contain the internally generated heat and air pollutants, as well as the solar and conductive heat gains that can occur in the facade. In the warmer months of the year this generally leads to overheating, creating a need for a cooling system. Ventilation air replaces contaminated air in the building and is often used as the dominant medium for heat transfer between indoor and outdoor environments. The goal of the research presented in this thesis is to develop a better understanding of the important parameters in the performance of ventilation systems and to develop simplified convective heat transfer models. The general approach used in this study seeks to capture the dominant physical processes for these problems with first order accuracy, and develop simple models that show the correct system behavior trends. Dimensional analysis, in conjunction with simple momentum and energy conservation, scaled model experiments and numerical simulations, is used to improve airflow and heat transfer rate predictions in both single and multi room ventilation systems. This study includes the three commonly used room ventilation modes: mixing, displacement and cross-ventilation. A new modeling approach to convective heat transfer between the building and the outside is presented: the concept of equivalent room heat transfer coefficient. The new model quantifies the reduction in heat transfer between ventilation air and internal room surfaces caused by limited thermal capacity and temperature variation of the air for the three modes studied. Particular emphasis is placed on cross-ventilation, and on the development of a simple model to characterize the airflow patterns that occur in this case. The implementation of the models in a building thermal simulation software tool is presented as well as comparisons between model predictions, experimental results and complex
NASA Astrophysics Data System (ADS)
Han, Chang-Liang; Ren, Jing-Jie; Dong, Wen-Ping; Bi, Ming-Shu
2016-09-01
The submerged combustion vaporizer (SCV) is indispensable general equipment for liquefied natural gas (LNG) receiving terminals. In this paper, numerical simulation was conducted to get insight into the flow and heat transfer characteristics of supercritical LNG on the tube-side of SCV. The SST model with enhanced wall treatment method was utilized to handle the coupled wall-to-LNG heat transfer. The thermal-physical properties of LNG under supercritical pressure were used for this study. After the validation of model and method, the effects of mass flux, outer wall temperature and inlet pressure on the heat transfer behaviors were discussed in detail. Then the non-uniformity heat transfer mechanism of supercritical LNG and effect of natural convection due to buoyancy change in the tube was discussed based on the numerical results. Moreover, different flow and heat transfer characteristics inside the bend tube sections were also analyzed. The obtained numerical results showed that the local surface heat transfer coefficient attained its peak value when the bulk LNG temperature approached the so-called pseudo-critical temperature. Higher mass flux could eliminate the heat transfer deteriorations due to the increase of turbulent diffusion. An increase of outer wall temperature had a significant influence on diminishing heat transfer ability of LNG. The maximum surface heat transfer coefficient strongly depended on inlet pressure. Bend tube sections could enhance the heat transfer due to secondary flow phenomenon. Furthermore, based on the current simulation results, a new dimensionless, semi-theoretical empirical correlation was developed for supercritical LNG convective heat transfer in a horizontal serpentine tube. The paper provided the mechanism of heat transfer for the design of high-efficiency SCV.
Characteristics of Transient Boiling Heat Transfer
Liu, Wei; Monde, Masanori; Mitsutake, Y.
2002-07-01
In this paper, one dimensional inverse heat conduction solution is used for a measurement of pool boiling curve. The experiments are performed under atmospheric pressure for copper, brass, carbon steel and gold. Boiling curves, including unsteady transition boiling region, are found can be traced fairly well from a simple experiment system by solving inverse heat conduction solution. Boiling curves for steady heating and transient heating, for heating process and cooling process are compared. Surface behavior around CHF point, transition boiling and film-boiling regions are observed by using a high-speed camera. The results show the practicability of the inverse heat conduction solution in tracing boiling curve and thereby supply us a new way in boiling heat transfer research. (authors)
Heat transfer in suspensions of rigid particles
NASA Astrophysics Data System (ADS)
Brandt, Luca; Niazi Ardekani, Mehdi; Abouali, Omid
2016-11-01
We study the heat transfer in laminar Couette flow of suspensions of rigid neutrally buoyant particles by means of numerical simulations. An Immersed Boundary Method is coupled with a VOF approach to simulate the heat transfer in the fluid and solid phase, enabling us to fully resolve the heat diffusion. First, we consider spherical particles and show that the proposed algorithm is able to reproduce the correlations between heat flux across the channel, the particle volume fraction and the heat diffusivity obtained in laboratory experiments and recently proposed in the literature, results valid in the limit of vanishing inertia. We then investigate the role of inertia on the heat transfer and show an increase of the suspension diffusivity at finite particle Reynolds numbers. Finally, we vary the relativity diffusivity of the fluid and solid phase and investigate its effect on the effective heat flux across the channel. The data are analyzed by considering the ensemble averaged energy equation and decomposing the heat flux in 4 different contributions, related to diffusion in the solid and fluid phase, and the correlations between wall-normal velocity and temperature fluctuations. Results for non-spherical particles will be examined before the meeting. Supported by the European Research Council Grant No. ERC-2013- CoG-616186, TRITOS. The authors acknowledge computer time provided by SNIC (Swedish National Infrastructure for Computing).
Heat transfer in pressurized circulating fluidized beds
Wirth, K.E.
1997-12-31
The wall-to-suspension heat transfer in circulating fluidized beds (CFBs) operated at almost atmospheric pressure depends on the fluid mechanics immediately near the wall and on the thermal properties of the gas used. No influence of the superficial gas velocity adjusted is present. Consequently, the wall-to-suspension heat transfer coefficient in the form of the Nusselt number can be described by the Archimedes number of the gas-solid-system and the pressure drop number. The last number relates the cross-sectional average solids concentration to the solids concentration at minimum fluidization condition. However, with pressurized CFBs an influence of the superficial gas velocity on the wall-to-suspension heat transfer can be observed. Normalizing the superficial gas velocity in the form of the particle Froude number, two cases for the heat transfer in pressurized CFBs can be detected: with small particle Froude numbers (smaller than four) the same flow behavior and consequently the same heat transfer correlation is valid as it is for CFBs operated at almost atmospheric conditions; and with high particle Froude numbers (for example higher than four) the flow behavior immediately near the heat exchanger surface (CFB wall) can change. Instead of curtains of solids falling down with almost atmospheric pressure swirls of gas and solids can occur in the vicinity of the CFB wall when the static pressure is increased. With the change of the flow pattern near the CFB wall, i.e., the heat exchanger surface, a change of the heat transfer coefficient takes place. For the same Archimedes number, i.e., the same gas-solid system, and the same pressure drop number, i.e., the same cross-sectional average solids concentration, the Nusselt number, i.e., the heat transfer coefficient, increases when the flow pattern near the CFB wall changes from the curtain-type flow to that of the swirl-type flow. From experimentally obtained data in a cold running CFB a very simple correlation was
Gas-side heat transfer with rotation
NASA Technical Reports Server (NTRS)
Dring, R. P.
1983-01-01
The primary basis for heat transfer analysis of turbine blades is experimental data obtained in linear cascades. These data have been very valuable in identifying the major heat transfer and fluid flow features of a turbine airfoil. The question of major interest is how well all of these data translate to the rotating turbine blade. It is known from the work of Lokay and Trushin that average heat transfer coefficients on the rotor may be as much as 40 percent above the values measured on the same blades nonrotating. Recent work by Dunn and Holt supports the Russian conclusion. What is lacking is a set of data from a rotating system which is of sufficient detail as to make careful local comparisons between static system in which there is sufficient documentation of the flow field to support the computer analyses being developed today. A second major question is the influence, if any, of the first stator row on the heat transfer of the second stator row after the flow has passed through the rotor. An objective of the present program, is to obtain a detailed set of heat transfer coefficients along the midspan of a blade in a rotating turbine.
Dissociation heat transfer characteristics of methane hydrates
Kamath, V.A.; Holder, G.D.
1987-02-01
Knowledge of the interfacial heat transfer phenomenon during the dissociation of gas hydrates is essential in modeling the hydrate dissociation process. Such knowledge has applications in natural gas processing, storage, or transportation; in the drilling and recovery of oil and gas in the presence of gas hydrates; in the desalination of sea water; and in the production of natural gas from hydrate reservoirs. The process of hydrate dissociation is a unique phenomenon in which gas and water are simultaneously produced at the dissociated hydrate surface and play an important role in the mechanism of heat transfer to hydrates. An earlier study of propane hydrate dissociation showed that hydrate dissociation is a heat-transfer-limited process and somewhat similar to the nucleate boiling of liquids. In the present study, heat transfer limitations for methane hydrate dissociation were studied for two reasons. First, a comparison of the results of this study with propane hydrate was desired. Second, the effect of hydrate structure and gas molecule type on the rate of heat transfer during hydrate dissociation was sought.
Axial flow heat exchanger devices and methods for heat transfer using axial flow devices
Koplow, Jeffrey P.
2016-02-16
Systems and methods described herein are directed to rotary heat exchangers configured to transfer heat to a heat transfer medium flowing in substantially axial direction within the heat exchangers. Exemplary heat exchangers include a heat conducting structure which is configured to be in thermal contact with a thermal load or a thermal sink, and a heat transfer structure rotatably coupled to the heat conducting structure to form a gap region between the heat conducting structure and the heat transfer structure, the heat transfer structure being configured to rotate during operation of the device. In example devices heat may be transferred across the gap region from a heated axial flow of the heat transfer medium to a cool stationary heat conducting structure, or from a heated stationary conducting structure to a cool axial flow of the heat transfer medium.
Electromagnetic Heat Transfer in Artificial Materials
NASA Astrophysics Data System (ADS)
Woods, Lilia; Drosdoff, David; Phan, Anh
2014-03-01
Electromagnetic energy exchange has found promising new opportunities by greatly enhancing the heat transfer between bodies via radiation in the near-field regime. The greatest heat transfer occurs when the bodies support surface plasmons or polaritons that share the same resonant frequency. It has been shown, however, that 2-D materials such as graphene can have their surface plasmons tuned by modifying the chemical potential and temperature. This allows for tuning its resonance with other systems. In this talk, we investigated the electromagnetic radiation in metamaterials characterized by a strong magnetic response. We study theoretically Pendry-like and magnetically active metamaterial/graphene composites. The possibility for enhancing or inhibiting the heat transfer via the graphene properties is investigated.
Condensation heat transfer under a microgravity environment
NASA Technical Reports Server (NTRS)
Chow, L. C.
1986-01-01
A description of the condensation heat transfer process in microgravity is given. A review of the literature is also reported. The most essential element of condensation heat transfer in microgravity is the condensate removal mechanism. Two mechanisms for condensate removal are analyzed by looking into two problems. The first problem is concerned with film condensation on a flat porous plate with the condensate being removed by suction at the wall. The second problem is an analytical prediction of the heat transfer coefficient for condensing annular flows with the condensate film driven by the vapor shear. It is concluded that both suction and vapor shear can effectively drain the condensate to ensure continuous operation of the condensers operated under a microgravity environment. It is recommended that zero-g flight experiments be carried out to verify the prediction made in the present report. The results contained in this report should also aid in the design of future space condensers.
Radiant heat transfer between nongray directional surfaces.
NASA Technical Reports Server (NTRS)
Fischer, W. D.; Hering, R. G.
1972-01-01
Real surface property effects on local and overall heat transfer are studied for a simple system of interacting opaque surfaces. Wavelength, temperature and directional dependence of surface properties is included in the analysis for equal and unequal temperature specularly reflecting surfaces. Tungsten is employed as a representative metal and Roberts' model is used to describe the wavelength and temperature dependence of its optical parameters. The relationships of electromagnetic theory are employed to describe the directional dependence of spectral properties. Numerical results establish that gray direction independent property analysis adequately predicts the general trends of real surface analysis. The results also establish that spectral and temperature dependence of surface properties influences radiant heat transfer to a greater degree than does directional dependence of properties. Property models which adequately account for the nongray character of engineering surfaces while neglecting directional dependence of properties can provide heat transfer results of acceptable engineering accuracy.
Evaporative heat transfer in beds of sensible heat pellets
Arimilli, R.V.; Moy, C.A.
1989-03-01
An experimental study of boiling/evaporative heat transfer from heated spheres in vertical packed beds with downward liquid-vapor flow of Refrigerant-113 was conducted. Surface superheats of 1 to 50{degrees}C, mass flow rates of 1.7 to 5.6 Kg/min, sphere diameters of 1.59 and 2.54 cm, quality (i.e., mass fraction of vapor) of the inlet flow of 0.02 to 1.0, and two surface conditions were considered. Instrumented smooth and rough aluminum spheres were used to measure the heat transfer coefficients under steady state conditions. Heat transfer coefficients were independently determined for each sphere at three values three values of surface superheat. The quantitative results of this extensive experimental study are successfully correlated. The correlation equation for the boiling heat transfer coefficients is presented in terms of a homogeneous model. The correlation may be used in the development of numerical models to simulate the transient thermal performance of packed bed thermal energy storage unit while operating as an evaporator. The boiling of the liquid-vapor flow around the spheres in the packed bed was visually observed with a fiber-optic baroscope and recorded on a videotape. The visualization results showed qualitatively the presence of four distinct flow regimes. One of these occurs under saturated inlet conditions and are referred to as the Low-quality, Medium-quality, and High-quality Regimes. The regimes are discussed in detail in this paper.
Heat transfer mechanisms in pulsating heat-pipes with nanofluid
NASA Astrophysics Data System (ADS)
Gonzalez, Miguel; Kelly, Brian; Hayashi, Yoshikazu; Kim, Yoon Jo
2015-01-01
In this study, the effect of silver nanofluid on a pulsating heat-pipe (PHP) thermal performance was experimentally investigated to figure out how nanofluid works with PHP. A closed loop PHP was built with 3 mm diameter tubes. Thermocouples and pressure transducers were installed for fluid and surface temperature and pressure measurements. The operating temperature of the PHP varied from 30-100 °C, with power rates of 61 W and 119 W. The fill ratio of 30%, 50%, and 70% were tested. The results showed that the evaporator heat transfer performance was degraded by the addition of nanoparticles due to increased viscosity at high power rate, while the positive effects of high thermal conductivity and enhanced nucleate boiling worked better at low power rate. In the condenser section, owing to the relatively high liquid content, nanofluid more effectively improved the heat transfer performance. However, since the PHP performance was dominantly affected by evaporator heat transfer performance, the overall benefit of enhanced condenser section performance was greatly limited. It was also observed that the poor heat transfer performance with nanofluid at the evaporator section led to lower operating pressure of PHP.
Enhancement of pool boiling heat transfer to lithium bromide aqueous solution
NASA Astrophysics Data System (ADS)
Kaji, Masuo; Furukawa, Masahiro; Suyama, Takayuki; Sekoguchi, Kotohiko
1995-04-01
An experimental study on enhancement of nucleate pool boiling heat transfer by placing a sponge metal, which had a three-dimensional mesh structure like sponge, close to a plain smooth heat transfer surface was conducted to improve the heat transfer performance of the high temperature generator of absorption chiller/heaters. Boiling curves of water and lithium bromide aqueous solution of mass concentration of 55 to 58% at the atmospheric pressure were presented. Heat transfer characteristics were improved by two to three times both for water and lithium bromide aqueous solution when the sponge metal was attached with an appropriate clearance. Three kinds of sponge metals were tested for lithium bromide aqueous solution under a reduced pressure (24 kPa). The sponge metal #6, which had the finest mesh among the three sponge metals, brought about excellent results at lower heat fluxes, but it caused deterioration of heat transfer at higher heat fluxes. For the wide range of heat flux (5 x 10(exp 4) approximately 2 x 10(exp 5) W/m(exp 2), it was found that the sponge metal #4 with the middle fineness was the most suitable and the optimal clearance was in the range of 0.1 approximately 0.5 mm. The employment of sponge metals for enhancing boiling heat transfer is practically excellent, since no special manufacturing is required to mount them on the heated surface.
Heat Transfer Measurements of Internally Finned Rotating Heat Pipes.
1983-12-01
Noncondensable Gases, Rotating Heat Pipe , Performance, Helical and Straight Pin, Internal Heat Transfer Coefficient. AS"RACY (40115111111141 WH ide of* 0686...improvement over the smooth condenser. By helically finning the tube wall in addition to increasing the internal area, the counter-clockwise spiral ... spirally -finned condenser then on the straight-finned condenser. Apparently, during fabrication of the helically -finned condenser, a series of
Metallized Gelled Propellant Heat Transfer Tests Analyzed
NASA Technical Reports Server (NTRS)
Palaszewski, Bryan A.
1997-01-01
A series of rocket engine heat transfer experiments using metallized gelled liquid propellants was conducted at the NASA Lewis Research Center. These experiments used a small 20- to 40-lbf thrust engine composed of a modular injector, an igniter, a chamber, and a nozzle. The fuels used were traditional liquid RP-1 and gelled RP-1 with 0-, 5-, and 55-wt % loadings of aluminum particles. Gaseous oxygen was used as the oxidizer. Heat transfer measurements were made with a rocket engine calorimeter chamber and nozzle with a total of 31 cooling channels. Each channel used water flow to carry heat away from the chamber and the attached thermocouples; flow meters allowed heat flux estimates at each of the 31 stations.
Coolant passage heat transfer with rotation
NASA Technical Reports Server (NTRS)
Hajek, T. J.; Wagner, J.; Johnson, B. V.
1986-01-01
In current and advanced gas turbine engines, increased speeds, pressures and temperatures are used to reduce specific fuel consumption and increase thrust/weight ratios. Hence, the turbine airfoils are subjected to increased heat loads escalating the cooling requirements to satisfy life goals. The efficient use of cooling air requires that the details of local geometry and flow conditions be adequately modeled to predict local heat loads and the corresponding heat transfer coefficients. The objective of this program is to develop a heat transfer and pressure drop data base, computational fluid dynamic techniques and correlations for multi-pass rotating coolant passages with and without flow turbulators. The experimental effort is focused on the simulation of configurations and conditions expected in the blades of advanced aircraft high pressure turbines. With the use of this data base, the effects of Coriolis and buoyancy forces on the coolant side flow can be included in the design of turbine blades.
Transfer of radiative heat through clothing ensembles.
Lotens, W A; Pieters, A M
1995-06-01
A mathematical model was designed to calculate the temperature and dry heat transfer in the various layers of a clothing ensemble, and the total heat loss of a human who is irradiated for a certain fraction of his or her area. The clothing ensemble that is irradiated by an external heat source is considered to be composed of underclothing, trapped air, and outer fabric. The model was experimentally tested with heat balance methods, using subjects, varying the activity, wind, and radiation characteristics of the outer garment of two-layer ensembles. In two experiments the subjects could only give off dry heat because they were wrapped in plastic foil. The model appeared to be correct within about 1 degree C (rms error) and 10 Wm-2 (rms error). In a third experiment, sweat evaporation was also taken into account, showing that the resulting physiological heat load of 10 to 30% of the intercepted additional radiation is compensated by additional sweating. The resulting heat strain was rather mild. It is concluded that the mathematical model is a valid tool for the investigation of heat transfer through two-layer ensembles in radiant environments.
Low-temperature heat transfer in nanowires.
Glavin, B A
2001-05-07
A new regime of low-temperature heat transfer in suspended nanowires is predicted. It takes place when (i) only "acoustic" phonon modes of the wire are thermally populated and (ii) phonons are subject to the effective elastic scattering. Qualitatively, the main peculiarities of heat transfer originate due to the appearance of the flexural modes with high density of states in the wire phonon spectrum. They give rise to the T(1/2) temperature dependence of the wire thermal conductance. Experimental situations where the new regime is likely to be detected are discussed.
Convective heat transfer during dendritic growth
NASA Technical Reports Server (NTRS)
Glicksman, M. E.; Huang, S. C.
1979-01-01
Axial growth rate measurements were carried out at 17 levels of supercooling between 0.043 C and 2 C, a temperature range in which convection, instead of diffusion, becomes the controlling mechanism of heat transfer in the dentritic growth process. The growth velocity, normalized to that expected for pure diffusive heat transfer, displays a dependence on orientation. The ratio of the observed growth velocity to that for convection-free growth and the coefficients of supercooling are formulated. The dependence of normalized growth rate in supercooling is described for downward growing dendrites. These experimental correlations can be justified theoretically only to a limited extent.
Splice connector with internal heat transfer jacket
Silva, Frank A.; Mayer, Robert W.
1977-01-01
A heat transfer jacket is placed over the terminal portions of the conductors of a pair of high voltage cables which are connected in a splice connection wherein a housing surrounds the connected conductor portions, the heat transfer jacket extending longitudinally between the confronting ends of a pair of adaptor sleeves placed upon the insulation of the cables to engage and locate the adaptor sleeves relative to one another, and laterally between the conductors and the housing to provide a path of relatively high thermal conductivity between the connected conductor portions and the housing.
Experimental determination of stator endwall heat transfer
NASA Technical Reports Server (NTRS)
Boyle, Robert J.; Russell, Louis M.
1989-01-01
Local Stanton numbers were experimentally determined for the endwall surface of a turbine vane possage. A six vane linear cascade having vanes with an axial chord of 13.81 cm was used. Resutls were obtained for Reynolds numbers based on inlet velocity and axial chord between 75,000 and 495,000. The test section was connected to a low pressure exhaust system. Ambient air was drawn into the test section, inlet velocity was controlled up to a maximum of 59.4 m/sec. The effect of the inlet boundary layer thickness on the endwall heat transfer was determined for a range of test section flow rates. The liquid crystal measurement technique was used to measure heat transfer. Endwall heat transfer was determined by applying electrical power to a foil heater attached to the cascade endwall. The temperature at which the liquid crystal exhibited a specific color was known from a calibration test. Lines showing this specific color were isotherms, and because of uniform heat generation they were also lines of nearly constant heat transfer. Endwall static pressures were measured, along with surveys of total pressure and flow angles at the inlet and exit of the cascade.
Experimental determination of stator endwall heat transfer
NASA Technical Reports Server (NTRS)
Boyle, Robert J.; Russell, Louis M.
1989-01-01
Local Stanton numbers were experimentally determined for the endwall surface of a turbine vane passage. A six vane linear cascade having vanes with an axial chord of 13.81 cm was used. Results were obtained for Reynolds numbers based on inlet velocity and axial chord between 73,000 and 495,000. The test section was connected to a low pressure exhaust system. Ambient air was drawn into the test section, inlet velocity was controlled up to a maximum of 59.4 m/sec. The effect of the inlet boundary layer thickness on the endwall heat transfer was determined for a range of test section flow rates. The liquid crystal measurement technique was used to measure heat transfer. Endwall heat transfer was determined by applying electrical power to a foil heater attached to the cascade endwall. The temperature at which the liquid crystal exhibited a specific color was known from a calibration test. Lines showing this specific color were isotherms, and because of uniform heat generation they were also lines of nearly constant heat transfer. Endwall static pressures were measured, along with surveys of total pressure and flow angles at the inlet and exit of the cascade.
Heat transfer during quenching of gases
NASA Astrophysics Data System (ADS)
Ambraziavichius, A.
Results of theoretical and experimental investigations of gas-side heat transfer of subsonic laminar or turbulent flows of diatomic gases (air or nitrogen) heated to 5000 K in cold-wall pipes are presented. While determining the mixing length, physical parameters which consider local temperatures of the boundary layer were adopted. Thus, the generalized fields of velocities and temperatures in the turbulent region of the boundary layer are identical for both moderate and high gas temperature ranges, and Pr-sub-t may be considered constant and approximately equal to 0.9. The temperature level of gases in turblent flow is shown to insignificantly affect heat transfer equations, provided the physical parameters in the similarity numbers are chosen according to the bulk flow temperature. A calculation technique is developed for heat transfer of dissociated diatomic gases in annular and rectangular channels, in slots, and over bundles of square tubes in cross flow. Also, a relation is shown between the heat transfer coefficient, quenching velocity, and nitrogen oxide concentration in the air exhaust of a nitrogen oxide quenching apparatus.
Microscale surface modifications for heat transfer enhancement.
Bostanci, Huseyin; Singh, Virendra; Kizito, John P; Rini, Daniel P; Seal, Sudipta; Chow, Louis C
2013-10-09
In this experimental study, two surface modification techniques were investigated for their effect on heat transfer enhancement. One of the methods employed the particle (grit) blasting to create microscale indentations, while the other used plasma spray coating to create microscale protrusions on Al 6061 (aluminum alloy 6061) samples. The test surfaces were characterized using scanning electron microscopy (SEM) and confocal scanning laser microscopy. Because of the surface modifications, the actual surface area was increased up to 2.8× compared to the projected base area, and the arithmetic mean roughness value (Ra) was determined to vary from 0.3 μm for the reference smooth surface to 19.5 μm for the modified surfaces. Selected samples with modified surfaces along with the reference smooth surface were then evaluated for their heat transfer performance in spray cooling tests. The cooling system had vapor-atomizing nozzles and used anhydrous ammonia as the coolant in order to achieve heat fluxes up to 500 W/cm(2) representing a thermal management setting for high power systems. Experimental results showed that the microscale surface modifications enhanced heat transfer coefficients up to 76% at 500 W/cm(2) compared to the smooth surface and demonstrated the benefits of these practical surface modification techniques to enhance two-phase heat transfer process.
Natural convective heat transfer from square cylinder
Novomestský, Marcel Smatanová, Helena Kapjor, Andrej
2016-06-30
This article is concerned with natural convective heat transfer from square cylinder mounted on a plane adiabatic base, the cylinders having an exposed cylinder surface according to different horizontal angle. The cylinder receives heat from a radiating heater which results in a buoyant flow. There are many industrial applications, including refrigeration, ventilation and the cooling of electrical components, for which the present study may be applicable.
Experimental Investigations of Heat and Mass Transfer in Microchannel Heat-Transfer Elements
NASA Astrophysics Data System (ADS)
Konovalov, D. A.
2016-05-01
The present work seeks to develop and investigate experimentally microchannel heat-exchange apparatuses of two designs: with porous elements manufactured from titanium and copper, and also based on the matrix of filamentary silicon single crystals under operating conditions with high heat loads, unsteadiness, and nonlinear flow of the coolant. For experimental investigations, the authors have developed and manufactured a unique test bench allowing tests of the developed heat-transfer elements in unsteady operating regimes. The performed experimental investigations have made it possible to obtain criterial dependences of the heat-transfer coefficient on the Reynolds and Prandtl numbers and to refine the values of viscous and inertial coefficients. It has been established that microchannel heat-transfer elements based on silicon single crystals, which make it possible to remove a heat flux above 100 W/cm2, are the most efficient. For porous heat-transfer elements, the best result was attained for wedge-shaped copper samples. According to investigation results, the authors have considered the issues of optimization of thermal and hydraulic characteristics of the heat-transfer elements under study. In the work, the authors have given examples of practical use of the developed heat-transfer elements for cooling systems of radioelectronic equipment.
Heat Transfer and Cooling in Gas Turbines
1985-09-01
pillar -like protrusions. .1-2 The accurate determination of ILet transfer coefficient distributions in these blade passages is vital at the design...verification. The fin analysis had indirectly assumed absence of any contact resistance between the copper endwall and the wood pins, woich could be...thin layer of epoxy (-.005-.006 cm) between the copper pin and the endwalls of less than 1% of the heat transfer surface temperature. The resulting
Self supporting heat transfer element
Story, Grosvenor Cook; Baldonado, Ray Orico
2002-01-01
The present invention provides an improved internal heat exchange element arranged so as to traverse the inside diameter of a container vessel such that it makes good mechanical contact with the interior wall of that vessel. The mechanical element is fabricated from a material having a coefficient of thermal conductivity above about 0.8 W cm.sup.-1.degree. K.sup.-1 and is designed to function as a simple spring member when that member has been cooled to reduce its diameter to just below that of a cylindrical container or vessel into which it is placed and then allowed to warm to room temperature. A particularly important application of this invention is directed to a providing a simple compartmented storage container for accommodating a hydrogen absorbing alloy.
Heat Flux Sensors for Infrared Thermography in Convective Heat Transfer
Carlomagno, Giovanni Maria; de Luca, Luigi; Cardone, Gennaro; Astarita, Tommaso
2014-01-01
This paper reviews the most dependable heat flux sensors, which can be used with InfraRed (IR) thermography to measure convective heat transfer coefficient distributions, and some of their applications performed by the authors' research group at the University of Naples Federico II. After recalling the basic principles that make IR thermography work, the various heat flux sensors to be used with it are presented and discussed, describing their capability to investigate complex thermo-fluid-dynamic flows. Several applications to streams, which range from natural convection to hypersonic flows, are also described. PMID:25386758
Heat flux sensors for infrared thermography in convective heat transfer.
Carlomagno, Giovanni Maria; de Luca, Luigi; Cardone, Gennaro; Astarita, Tommaso
2014-11-07
This paper reviews the most dependable heat flux sensors, which can be used with InfraRed (IR) thermography to measure convective heat transfer coefficient distributions, and some of their applications performed by the authors' research group at the University of Naples Federico II. After recalling the basic principles that make IR thermography work, the various heat flux sensors to be used with it are presented and discussed, describing their capability to investigate complex thermo-fluid-dynamic flows. Several applications to streams, which range from natural convection to hypersonic flows, are also described.
Cooperative heat transfer and ground coupled storage system
Metz, Philip D.
1982-01-01
A cooperative heat transfer and ground coupled storage system wherein collected solar heat energy is ground stored and permitted to radiate into the adjacent ground for storage therein over an extended period of time when such heat energy is seasonally maximally available. Thereafter, when said heat energy is seasonally minimally available and has propagated through the adjacent ground a substantial distance, the stored heat energy may be retrieved by a circumferentially arranged heat transfer means having a high rate of heat transfer.
Cooperative heat transfer and ground coupled storage system
Metz, P.D.
A cooperative heat transfer and ground coupled storage system wherein collected solar heat energy is ground stored and permitted to radiate into the adjacent ground for storage therein over an extended period of time when such heat energy is seasonally maximally available. Thereafter, when said heat energy is seasonally minimally available and has propagated through the adjacent ground a substantial distance, the stored heat energy may be retrieved by a circumferentially arranged heat transfer means having a high rate of heat transfer.
Evaporative Heat Transfer Mechanisms within a Heat Melt Compactor
NASA Technical Reports Server (NTRS)
Golliher, Eric L.; Gotti, Daniel J.; Rymut, Joseph Edward; Nguyen, Brian K; Owens, Jay C.; Pace, Gregory S.; Fisher, John W.; Hong, Andrew E.
2013-01-01
This paper will discuss the status of microgravity analysis and testing for the development of a Heat Melt Compactor (HMC). Since fluids behave completely differently in microgravity, the evaporation process for the HMC is expected to be different than in 1-g. A thermal model is developed to support the design and operation of the HMC. Also, low-gravity aircraft flight data is described to assess the point at which water may be squeezed out of the HMC during microgravity operation. For optimum heat transfer operation of the HMC, the compaction process should stop prior to any water exiting the HMC, but nevertheless seek to compact as much as possible to cause high heat transfer and therefore shorter evaporation times.
Heat transfer variations of bicycle helmets.
Brühwiler, P A; Buyan, M; Huber, R; Bogerd, C P; Sznitman, J; Graf, S F; Rösgen, T
2006-09-01
Bicycle helmets exhibit complex structures so as to combine impact protection with ventilation. A quantitative experimental measure of the state of the art and variations therein is a first step towards establishing principles of bicycle helmet ventilation. A thermal headform mounted in a climate-regulated wind tunnel was used to study the ventilation efficiency of 24 bicycle helmets at two wind speeds. Flow visualization in a water tunnel with a second headform demonstrated the flow patterns involved. The influence of design details such as channel length and vent placement was studied, as well as the impact of hair. Differences in heat transfer among the helmets of up to 30% (scalp) and 10% (face) were observed, with the nude headform showing the highest values. On occasion, a negative role of some vents for forced convection was demonstrated. A weak correlation was found between the projected vent cross-section and heat transfer variations when changing the head tilt angle. A simple analytical model is introduced that facilitates the understanding of forced convection phenomena. A weak correlation between exposed scalp area and heat transfer was deduced. Adding a wig reduces the heat transfer by approximately a factor of 8 in the scalp region and up to one-third for the rest of the head for a selection of the best ventilated helmets. The results suggest that there is significant optimization potential within the basic helmet structure represented in modern bicycle helmets.
Forced Convection Heat Transfer in Circular Pipes
ERIC Educational Resources Information Center
Tosun, Ismail
2007-01-01
One of the pitfalls of engineering education is to lose the physical insight of the problem while tackling the mathematical part. Forced convection heat transfer (the Graetz-Nusselt problem) certainly falls into this category. The equation of energy together with the equation of motion leads to a partial differential equation subject to various…
Heat Transfer and Thermodynamics: a Compilation
NASA Technical Reports Server (NTRS)
1974-01-01
A compilation is presented for the dissemination of information on technological developments which have potential utility outside the aerospace and nuclear communities. Studies include theories and mechanical considerations in the transfer of heat and the thermodynamic properties of matter and the causes and effects of certain interactions.
Computational Aspects of Heat Transfer in Structures
NASA Technical Reports Server (NTRS)
Adelman, H. M. (Compiler)
1982-01-01
Techniques for the computation of heat transfer and associated phenomena in complex structures are examined with an emphasis on reentry flight vehicle structures. Analysis methods, computer programs, thermal analysis of large space structures and high speed vehicles, and the impact of computer systems are addressed.
Forced Convection Heat Transfer in Circular Pipes
ERIC Educational Resources Information Center
Tosun, Ismail
2007-01-01
One of the pitfalls of engineering education is to lose the physical insight of the problem while tackling the mathematical part. Forced convection heat transfer (the Graetz-Nusselt problem) certainly falls into this category. The equation of energy together with the equation of motion leads to a partial differential equation subject to various…
FED. Zoning for TRUMP Heat Transfer Code
Elrod, D.
1987-10-23
FED reduces the effort required to obtain the necessary geometric input for problems which are to be solved using the heat-transfer code, TRUMP. TRUMP calculates transient and steady-state temperature distributions in multidimensional systems. FED can properly zone any body of revolution in one, two, or three dimensions.
Turbine airfoil gas side heat transfer
NASA Technical Reports Server (NTRS)
Turner, E. R.
1984-01-01
Work is currently underway to develop and characterize an analytical approach, based on boundary layer theory, for predicting the effects of leading edge (showerhead) film cooling on downstream gas side heat transfer rates. Parallel to this work, experiments are being conducted to build a relevant data base for present and future methods verification.
Turbulent Heat Transfer in Ribbed Pipe Flow
NASA Astrophysics Data System (ADS)
Kang, Changwoo; Yang, Kyung-Soo
2012-11-01
From the view point of heat transfer control, surface roughness is one of the popular ways adopted for enhancing heat transfer in turbulent pipe flow. Such a surface roughness is often modeled with a rib. In the current investigation, Large Eddy Simulation has been performed for turbulent flow in a pipe with periodically-mounted ribs at Reτ=700, Pr=0.71, and p / k =2, 4, and 8. Here, p and k represent the pitch and rib height, respectively. The rib height is fixed as one tenth of the pipe radius. The profiles of mean velocity components, mean temperature, root-mean-squares (rms) of temperature fluctuation are presented at the selected streamwise locations. In comparison with the smooth-pipe case at the same Re and Pr, the effects of the ribs are clearly identified, leading to overall enhancement of turbulent heat transfer in terms of Nu. The budget of temperature variance is presented in the form of contours. The results of an Octant analysis are also given to elucidate the dominant events. Our LES results shed light on a complete understanding of the heat-transfer mechanisms in turbulent ribbed-pipe flow which has numerous applications in engineering. This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MEST) (No. 2012013019).
Boiling heat transfer characteristics of liquid xenon
NASA Astrophysics Data System (ADS)
Haruyama, T.
2002-05-01
Liquid xenon is one of the excellent media for high-energy particle calorimeter. In order to detect a scintillation light effectively, a large number of photo-multipliers (PMTs) will be immersed in liquid xenon. Many chip-resistors equipped with the PMTs dissipate heat into liquid and possibly generate thermal turbulence, such as bubbles, convection flow under a certain operating condition. There is, however, no heat transfer curve (q-ΔT curve) in the literature. Boiling heat transfer characteristics of liquid xenon were measured at a saturated pressure of 0.1 MPa for the first time by using a small pulse tube refrigerator. The heat transfer surface is a thin platinum wire of 0.1 mm diameter and 25 mm long. The measured results were in good agreement with the calculated values both in natural convection and nucleate boiling condition. The film boiling state was difficult to obtain due to its poor reproducibility, and only one data was obtained. The relationship between the heat flux q and temperature difference ΔT was in good agreement with the Morgan's empirical equation in the natural convection region, and with the Kutateladze's equation in the nucleate boiling region.
Advanced Heat Transfer and Thermal Storage Fluids
Moens, L.; Blake, D.
2005-01-01
The design of the next generation solar parabolic trough systems for power production will require the development of new thermal energy storage options with improved economics or operational characteristics. Current heat-transfer fluids such as VP-1?, which consists of a eutectic mixture of biphenyl and diphenyl oxide, allow a maximum operating temperature of ca. 300 C, a limit above which the vapor pressure would become too high and would require pressure-rated tanks. The use of VP-1? also suffers from a freezing point around 13 C that requires heating during cold periods. One of the goals for future trough systems is the use of heat-transfer fluids that can act as thermal storage media and that allow operating temperatures around 425 C combined with lower limits around 0 C. This paper presents an outline of our latest approach toward the development of such thermal storage fluids.
Heat transfer in a real engine environment
NASA Astrophysics Data System (ADS)
Gladden, Herbert J.
1985-10-01
The hot section facility at the Lewis Research Center was used to demonstrate the capability of instruments to make required measurements of boundary conditions of the flow field and heat transfer processes in the hostile environment of the turbine. The results of thermal scaling tests show that low temperature and pressure rig tests give optimistic estimates of the thermal performance of a cooling design for high pressure and temperature application. The results of measuring heat transfer coefficients on turbine vane airfoils through dynamic data analysis show good comparison with measurements from steady state heat flux gauges. In addition, the data trends are predicted by the STAN5 boundary layer code. However, the magnitude of the experimental data was not predicted by the analysis, particularly in laminar and transitional regions near the leading edge. The infrared photography system was shown capable of providing detailed surface thermal gradients and secondary flow features on a turbine vane and endwell.
Heat transfer in a real engine environment
NASA Technical Reports Server (NTRS)
Gladden, Herbert J.
1985-01-01
The hot section facility at the Lewis Research Center was used to demonstrate the capability of instruments to make required measurements of boundary conditions of the flow field and heat transfer processes in the hostile environment of the turbine. The results of thermal scaling tests show that low temperature and pressure rig tests give optimistic estimates of the thermal performance of a cooling design for high pressure and temperature application. The results of measuring heat transfer coefficients on turbine vane airfoils through dynamic data analysis show good comparison with measurements from steady state heat flux gauges. In addition, the data trends are predicted by the STAN5 boundary layer code. However, the magnitude of the experimental data was not predicted by the analysis, particularly in laminar and transitional regions near the leading edge. The infrared photography system was shown capable of providing detailed surface thermal gradients and secondary flow features on a turbine vane and endwell.
Numerical Modeling of Ablation Heat Transfer
NASA Technical Reports Server (NTRS)
Ewing, Mark E.; Laker, Travis S.; Walker, David T.
2013-01-01
A unique numerical method has been developed for solving one-dimensional ablation heat transfer problems. This paper provides a comprehensive description of the method, along with detailed derivations of the governing equations. This methodology supports solutions for traditional ablation modeling including such effects as heat transfer, material decomposition, pyrolysis gas permeation and heat exchange, and thermochemical surface erosion. The numerical scheme utilizes a control-volume approach with a variable grid to account for surface movement. This method directly supports implementation of nontraditional models such as material swelling and mechanical erosion, extending capabilities for modeling complex ablation phenomena. Verifications of the numerical implementation are provided using analytical solutions, code comparisons, and the method of manufactured solutions. These verifications are used to demonstrate solution accuracy and proper error convergence rates. A simple demonstration of a mechanical erosion (spallation) model is also provided to illustrate the unique capabilities of the method.
Heat transfer in bioengineering and medicine
Chato, J.C.; Diller, T.E.; Diller, K.R.; Roemer, R.B.
1987-01-01
This book contains the following papers: New ideas in heat transfer for agricultural animals; Issues in heat transfer and tumor blood flow in localized hyperthermia treatments of cancer; Ultrasound enhances adriamycin toxicity in vitro; Scanned, focused ultrasound hyperthermia treatment of brain tumors; Mathematical prediction and phantom studies of the clinical target ''hot spot'' using a three applicator phased array system (TRIPAS); Development of an endoscopic RF hyperthermia system for deep tumor therapy; Simultaneous measurement of intrinsic and effective thermal conductivity; Determination of the transport of thermal energy by conduction in perfused tissue; A whole body thermal model of man with a realistic circulatory system; and Canine muscle blood flow changes in response to initial heating rates.
Numerical study of heat transfer characteristics in BOG heat exchanger
NASA Astrophysics Data System (ADS)
Yan, Yan; Pfotenhauer, John M.; Miller, Franklin; Ni, Zhonghua; Zhi, Xiaoqin
2016-12-01
In this study, a numerical study of turbulent flow and the heat transfer process in a boil-off liquefied natural gas (BOG) heat exchanger was performed. Finite volume computational fluid dynamics and the k - ω based shear stress transport model were applied to simulate thermal flow of BOG and ethylene glycol in a full-sized 3D tubular heat exchanger. The simulation model has been validated and compared with the engineering specification data from its supplier. In order to investigate thermal characteristics of the heat exchanger, velocity, temperature, heat flux and thermal response were studied under different mass flowrates in the shell-side. The shell-side flow pattern is mostly determined by viscous forces, which lead to a small velocity and low temperature buffer area in the bottom-right corner of the heat exchanger. Changing the shell-side mass flowrate could result in different distributions of the shell-side flow. However, the distribution in the BOG will remain in a relatively stable pattern. Heat flux increases along with the shell-side mass flowrate, but the increase is not linear. The ratio of increased heat flux to the mass flow interval is superior at lower mass flow conditions, and the threshold mass flow for stable working conditions is defined as greater than 0.41 kg/s.
Analysis of a heat transfer device for measuring film coefficients
NASA Technical Reports Server (NTRS)
Medrow, R. A.; Johnson, R. L.; Loomis, W. R.; Wedeven, L. D.
1975-01-01
A heat transfer device consisting of a heated rotating cylinder in a bath was analyzed for its effectiveness to determine heat transfer coefficient of fluids. A time dependent analysis shows that the performance is insensitive to the value of heat transfer coefficient with the given rig configuration.
Heat transfer in GTA welding arcs
NASA Astrophysics Data System (ADS)
Huft, Nathan J.
Heat transfer characteristics of Gas Tungsten Arc Welding (GTAW) arcs with arc currents of 50 to 125 A and arc lengths of 3 to 11 mm were measured experimentally through wet calorimetry. The data collected were used to calculate how much heat reported to the cathode and anode and how much was lost from the arc column. A Visual Basic for Applications (VBA) macro was written to further analyze the data and account for Joule heating within the electrodes and radiation and convection losses from the arc, providing a detailed account of how heat was generated and dissipated within the system. These values were then used to calculate arc efficiencies, arc column voltages, and anode and cathode fall voltages. Trends were noted for variances in the arc column voltage, power dissipated from the arc column, and the total power dissipated by the system with changing arc length. Trends for variances in the anode and cathode fall voltages, total power dissipated, Joule heating within the torches and electrodes with changing arc current were also noted. In addition, the power distribution between the anode and cathode for each combination of arc length and arc current was examined. Keywords: Gas Tungsten Arc Welding, GTAW, anode fall, cathode fall, heat transfer, wet calorimetry
Heat transfer characteristics for some coolant additives used for water cooled engines
Abou-Ziyan, H.Z.; Helali, A.H.B.
1996-12-31
Engine coolants contain certain additives to prevent engine overheating or coolant freezing in cold environments. Coolants, also, contain corrosion and rust inhibitors, among other additives. As most engines are using engine cooling solutions, it is of interest to evaluate the effect of engine coolants on the boiling heat transfer coefficient. This has its direct impact on radiator size and environment. This paper describes the apparatus and the measurement techniques. Also, it presents the obtained boiling heat transfer results at different parameters. Three types of engine coolants and their mixtures in distilled water are evaluated, under sub-cooled and saturated boiling conditions. A profound effect of the presence of additives in the coolant, on heat transfer, was clear since changes of heat transfer for different coolants were likely to occur. The results showed that up to 180% improvement of boiling heat transfer coefficient is experienced with some types of coolants. However, at certain concentrations other coolants provide deterioration or not enhancement in the boiling heat transfer characteristics. This investigation proved that there are limitations, which are to be taken into consideration, for the composition of engine coolants in different environments. In warm climates, ethylene glycol should be kept at the minimum concentration required for dissolving other components, whereas borax is beneficial to the enhancement of the heat transfer characteristics.
Heterogeneous nanofluids: natural convection heat transfer enhancement
2011-01-01
Convective heat transfer using different nanofluid types is investigated. The domain is differentially heated and nanofluids are treated as heterogeneous mixtures with weak solutal diffusivity and possible Soret separation. Owing to the pronounced Soret effect of these materials in combination with a considerable solutal expansion, the resulting solutal buoyancy forces could be significant and interact with the initial thermal convection. A modified formulation taking into account the thermal conductivity, viscosity versus nanofluids type and concentration and the spatial heterogeneous concentration induced by the Soret effect is presented. The obtained results, by solving numerically the full governing equations, are found to be in good agreement with the developed solution based on the scale analysis approach. The resulting convective flows are found to be dependent on the local particle concentration φ and the corresponding solutal to thermal buoyancy ratio N. The induced nanofluid heterogeneity showed a significant heat transfer modification. The heat transfer in natural convection increases with nanoparticle concentration but remains less than the enhancement previously underlined in forced convection case. PMID:21711755
Unsteady heat transfer during subcooled film boiling
NASA Astrophysics Data System (ADS)
Yagov, V. V.; Zabirov, A. R.; Lexin, M. A.
2015-11-01
Cooling of high-temperature bodies in subcooled liquid is of importance for quenching technologies and also for understanding the processes initiating vapor explosion. An analysis of the available experimental information shows that the mechanisms governing heat transfer in these processes are interpreted ambiguously; a more clear-cut definition of the Leidenfrost temperature notion is required. The results of experimental observations (Hewitt, Kenning, and previous investigations performed by the authors of this article) allow us to draw a conclusion that there exists a special mode of intense heat transfer during film boil- ing of highly subcooled liquid. For revealing regularities and mechanisms governing intense transfer of energy in this process, specialists of Moscow Power Engineering Institute's (MPEI) Department of Engineering Thermal Physics conduct systematic works aimed at investigating the cooling of high-temperature balls made of different metals in water with a temperature ranging from 20 to 100°C. It has been determined that the field of temperatures that takes place in balls with a diameter of more than 30 mm in intense cooling modes loses its spherical symmetry. An approximate procedure for solving the inverse thermal conductivity problem for calculating the heat flux density on the ball surface is developed. During film boiling, in which the ball surface temperature is well above the critical level for water, and in which liquid cannot come in direct contact with the wall, the calculated heat fluxes reach 3-7 MW/m2.
NASA Astrophysics Data System (ADS)
Jiang, Yuguang; Feng, Yu; Zhang, Silong; Qin, Jiang; Bao, Wen
2016-01-01
Hydrocarbon fuel has been widely used in air-breathing scramjets and liquid rocket engines as coolant and propellant. However, possible heat transfer deterioration and threats from local high heat flux area in scramjet make heat transfer enhancement essential. In this work, 2-D steady numerical simulation was carried out to study different schemes of heat transfer enhancement based on a partially filled porous media in a tube. Both boundary and central layouts were analyzed and effects of gradient porous media were also compared. The results show that heat transfer in the transcritical area is enhanced at least 3 times with the current configuration compared to the clear tube. Besides, the proper use of gradient porous media also enhances the heat transfer compared to homogenous porous media, which could help to avoid possible over-temperature in the thermal protection.
Heat Transfer Problems of Mixed Refrigerants
NASA Astrophysics Data System (ADS)
Fujii, Tetsu; Koyama, Shigeru; Goto, Masao; Takamatsu, Hiroshi
From the point of view of the application of non-azeotropic mixed refrigerants to heat pump and refrigeration cycles, literatures on condensation and evaporation are surveyed and future problems to be studied are extracted. All researches on the relevant problems are recently started and still in developing way except for condensation on a single horizontal tube. Particularly, the studies for condensation and evaporation of mixed Freon refrigerant in a horizontal tube, which are the most important in practice, are far backward in comparison with single component refrigerant in every point of heat transfer characteristics, flow pattern and theoretical analysis.
Pool boiling heat transfer of water/ γ-alumina micro-fluids around the horizontal cylinder
NASA Astrophysics Data System (ADS)
Nikkhah, V.; Hormozi, F.
2016-04-01
A set of experiments was performed to quantify the pool boiling heat transfer coefficient of water/ γ-alumina micro-fluids at mass concentration ranged from 0.1 to 0.4 % of micro-particles with mean size of 1-2 μm. To stabilize the prepared micro-fluid, pH control, stirring and adding the SDS as a surfactant were carried out. Also, thermal conductivity of micro-fluids are measured using KD2 decagon pro. Results showed that micro-fluids have relatively higher thermal conductivity rather than the base fluids. According to the results, there are two distinguishable heat transfer regions namely natural convection and nucleate boiling regions. Influence of some operating parameters such as heat flux, mass concentration of micro-particles and surface fouling resistance on the pool boiling heat transfer coefficient were experimentally studied and briefly discussed. Results demonstrated a significant deterioration of heat transfer coefficient of micro-fluids in comparison with the base fluid over the extended time (1000 min of operation) in nucleate boiling region, while in natural convection region, enhancement of heat transfer coefficient is registered. According to the results, heat transfer coefficient is strongly controlled by/ γ-alumina concentration due to the deposition of micro-particles on the heating section. Rectilinear changes of scale formation with time in term of fouling resistance were clearly seen at regions, where natural convection is a dominant heat transfer mechanism and also for higher heat fluxes at nucleate boiling heat transfer region.
Acquisition systems for heat transfer measurement
De Witt, R.J.
1983-01-01
Practical heat transfer data acquisition systems are normally characterized by the need for high-resolution, low-drift, low-speed recording devices. Analog devices such as strip chart or circular recorders and FM analog magnetic tape have excellent resolution and work well when data will be presented in temperature versus time format only and need not be processed further. Digital systems are more complex and require an understanding of the following components: digitizing devices, interface bus types, processor requirements, and software design. This paper discusses all the above components of analog and digital data acquisition, as they are used in current practice. Additional information on thermocouple system analysis will aid the user in developing accurate heat transfer measuring systems.
Coolant passage heat transfer with rotation
NASA Technical Reports Server (NTRS)
Hajek, T. J.; Higgins, A. W.
1985-01-01
The objective is to develop a heat transfer and pressure drop data base, computational fluid dynamic techniques, and correlations for multi-pass rotating coolant passages with and without flow turbulators. The experimental effort is focused on the simulation of configurations and conditions expected in the blades of advanced aircraft high pressure turbines. With the use of this data base, the effects of Coriolis and buoyancy forces on the coolant side flow can be included in the design of turbine blades.
Heat Transfer Characteristics of SHS Reactions
1990-07-01
A+R?0 Qt43 =5 -YA co ,/A FINAL REPORT AD- A225 769-=-_ HEAT TRANSFER CHARACTERISTICS OF SHS REACTIONS K. V. Logan, G. R. Villalobos, J. N. Harris, P...2741 Ta 180.9 3287 5731 Cr 52.0 2130 2945 lNb 95.9 2890 4919 W 183.8 3683 >6000 Mli 54.9 1518 2335 Fe 55.8 1808 3135 Co 58.9 1768 3201 Ni 58.7 1726
Boiling Heat Transfer in Confined Space.
1981-10-01
the problem the following assumptions were made: Cl) The problem is steady state with constant properties for the fluid. (2) The flow is laminar in...T7ax - 1 62 (11) Heat Transfer: Considering the constant properties and neglecting the viscous dissipation, the energy equation of the laminar flow in...evaluated from the assumed local quality and fluid properties using I.J equation (6). Using an assumed local friction factor f , the local pressure gradient
Radiation heat transfer shapefactors for combustion systems
NASA Technical Reports Server (NTRS)
Emery, A. F.; Johansson, O.; Abrous, A.
1987-01-01
The computation of radiation heat transfer through absorbing media is commonly done through the zoning method which relies upon values of the geometric mean transmittance and absorptance. The computation of these values is difficult and expensive, particularly if many spectral bands are used. This paper describes the extension of a scan line algorithm, based upon surface-surface radiation, to the computation of surface-gas and gas-gas radiation transmittances.
Heat Transfer in a Superelliptic Transition Duct
NASA Technical Reports Server (NTRS)
Poinsatte, Philip; Thurman, Douglas; Hippensteele, Steven
2008-01-01
Local heat transfer measurements were experimentally mapped using a transient liquid-crystal heat transfer technique on the surface of a circular-to-rectangular transition duct. The transition duct had a length-to-diameter ratio of 1.5 and an exit-plane aspect ratio of 3. The crosssectional geometry was defined by the equation of a superellipse. The cross-sectional area was the same at the inlet and exit but varied up to 15 percent higher through the transition. The duct was preheated to a uniform temperature (nominally 64 C) before allowing room temperature air to be suddenly drawn through it. As the surface cooled, the resulting isothermal contours on the duct surface were revealed using a surface coating of thermochromic liquid crystals that display distinctive colors at particular temperatures. A video record was made of the surface temperature and time data for all points on the duct surfaces during each test. Using this surface temperature-time data together with the temperature of the air flowing through the model and the initial temperature of the model wall, the heat transfer coefficient was calculated by employing the classic one-dimensional, semi-infinite wall heat transfer conduction model. Test results are reported for inlet diameter-based Reynolds numbers ranging from 0.4x106 to 2.4x106 and two grid-generated freestream turbulence intensities of about 1 percent, which is typical of wind tunnels, and up to 16 percent, which may be more typical of real engine conditions.
Unsteady heat transfer on turbine blades
NASA Technical Reports Server (NTRS)
Cebeci, Tuncer; Simoneau, Robert J.; Platzer, Max F.
1990-01-01
This paper describes a method for calculating heat transfer on turbine blades subjected to passing wakes. It is based on the numerical solution of the boundary-layer equations for laminar, transitional, and turbulent flows with a novel procedure to account for the movement of the stagnation point. Results are presented for a model flow and show that the procedure is numerically sound and produces results that can give good agreement with measurements provided that the turbulence model is adequate.
Low-melting point heat transfer fluid
Cordaro, Joseph Gabriel; Bradshaw, Robert W.
2010-11-09
A low-melting point, heat transfer fluid made of a mixture of five inorganic salts including about 29.1-33.5 mol % LiNO.sub.3, 0-3.9 mol % NaNO.sub.3, 2.4-8.2 mol % KNO.sub.3, 18.6-19.9 mol % NaNO.sub.2, and 40-45.6 mol % KNO.sub.2. These compositions can have liquidus temperatures below 80.degree. C. for some compositions.
Unsteady heat transfer on turbine blades
NASA Technical Reports Server (NTRS)
Cebeci, Tuncer; Simoneau, Robert J.; Platzer, Max F.
1990-01-01
This paper describes a method for calculating heat transfer on turbine blades subjected to passing wakes. It is based on the numerical solution of the boundary-layer equations for laminar, transitional, and turbulent flows with a novel procedure to account for the movement of the stagnation point. Results are presented for a model flow and show that the procedure is numerically sound and produces results that can give good agreement with measurements provided that the turbulence model is adequate.
Thermal Storage and Advanced Heat Transfer Fluids (Fact Sheet)
Not Available
2010-08-01
Fact sheet describing NREL CSP Program capabilities in the area of thermal storage and advanced heat transfer fluids: measuring thermophysical properties, measuring fluid flow and heat transfer, and simulating flow of thermal energy and fluid.
HOST turbine heat transfer subproject overview
NASA Technical Reports Server (NTRS)
Gladden, Herbert J.
1986-01-01
The experimental part of the turbine heat transfer subproject consists of six large experiments, which are highlighted in this overview, and three of somewhat more modest scope. One of the initial efforts was the stator airfoil heat transfer program. The non-film cooled and the showerhead film cooled data have already been reported. The gill region film cooling effort is currently underway. The investigation of secondary flows in a 90 deg curved duct, was completed. The first phase examined flows with a relatively thin inlet boundary layer and low free stream turbulence. The second phase studied a thicker inlet boundary layer and higher free stream turbulence. A comparison of analytical and experimental cross flow velocity vectors is shown for the 60 deg plane. Two experiments were also conducted in the high pressure facility. One examined full coverage film cooled vanes, and the other, advanced instrumentation. The other three large experimental efforts were conducted in a rotation reference frame. An experiment to obtain gas path airfoil heat transfer coefficients in the large, low speed turbine was completed. Single-stage data with both high and low-inlet turbulence were taken. The second phase examined a one and one-half stage turbine and focused on the second vane row. Under phase 3 aerodynamic quantities such as interrow time-averaged and rms values of velocity, flow angle, inlet turbulence, and surface pressure distribution were measured.
Combustion and heat transfer in porous media
Sathe, S.B.; Peck, R.E.; Tong, T.W.
1990-06-01
The objective of the present study is to generate fundamental knowledge about heat transfer and combustion in porous radiant burners (PRBs) in order to improve their performance. A theoretical heat transfer and combustion model is developed to study the characteristics of PRBs. The model accounts for non-local thermal equilibrium between the solid and gas phases. The solid is assumed to absorb, emit and scatter radiant energy. Combustion is modeled as a one-step global reaction. It is revealed that the flame speed inside the porous medium is enhanced compared to the adiabatic flame speeds due to the higher conductivity of the solid compared to the gas as well as due to radiative preheating of the reactants. The effects of the properties of the porous material on the flame speeds, radiative outputs and efficiencies were investigated. To improve the radiative output from the burner, it is desirable that the porous layer has an optical thickness of about ten. The radiative output and the efficiency is higher for lower scattering albedo. The heat transfer coupling between the solid and gas phases should be high enough to ensure local thermal equilibrium, by choosing a fine porous matrix. Higher solid phase conduction enhances the flame speed and the radiative output. Experiments are performed on a ceramic foam to verify the theoretical findings. The existence of the two stability regions was verified experimentally.
Supercritical oxygen heat transfer. [regenerative cooling
NASA Technical Reports Server (NTRS)
Spencer, R. G.; Rousar, D. C.
1977-01-01
Heat transfer to supercritical oxygen was experimentally measured in electrical heated tubes. Experimental data were obtained for pressures ranging from 17 to 34.5 MPa (2460 to 5000 psia), and heat fluxes from 2 to 90 million w/sq cm (1.2 to 55 Btu/(sq in. sec)). Bulk temperatures ranged from 96 to 217 K (173 to 391 R). Experimental data obtained by other investigators were added to this to increase the range of pressure down to 2 MPa (290 psia) and increase the range of bulk temperature up to 566 K (1019 R). From this compilation of experimental data a correlating equation was developed which predicts over 95% of the experimental data within + or - 30%.
Measuring Furnace/Sample Heat-Transfer Coefficients
NASA Technical Reports Server (NTRS)
Rosch, William R.; Fripp, Archibald L., Jr.; Debnam, William J., Jr.; Woodell, Glenn A.
1993-01-01
Complicated, inexact calculations now unnecessary. Device called HTX used to simulate and measure transfer of heat between directional-solidification crystal-growth furnace and ampoule containing sample of crystalline to be grown. Yields measurement data used to calculate heat-transfer coefficients directly, without need for assumptions or prior knowledge of physical properties of furnace, furnace gas, or specimen. Determines not only total heat-transfer coefficients but also coefficients of transfer of heat in different modes.
Heat Transfer in Glass, Aluminum, and Plastic Beverage Bottles
ERIC Educational Resources Information Center
Clark, William M.; Shevlin, Ryan C.; Soffen, Tanya S.
2010-01-01
This paper addresses a controversy regarding the effect of bottle material on the thermal performance of beverage bottles. Experiments and calculations that verify or refute advertising claims and represent an interesting way to teach heat transfer fundamentals are described. Heat transfer coefficients and the resistance to heat transfer offered…
Heat Transfer in Glass, Aluminum, and Plastic Beverage Bottles
ERIC Educational Resources Information Center
Clark, William M.; Shevlin, Ryan C.; Soffen, Tanya S.
2010-01-01
This paper addresses a controversy regarding the effect of bottle material on the thermal performance of beverage bottles. Experiments and calculations that verify or refute advertising claims and represent an interesting way to teach heat transfer fundamentals are described. Heat transfer coefficients and the resistance to heat transfer offered…
Film-Cooling Heat-Transfer Measurements Using Liquid Crystals
NASA Technical Reports Server (NTRS)
Hippensteele, Steven A.
1997-01-01
The following topics are discussed: (1) The Transient Liquid-Crystal Heat-Transfer Technique; (2) 2-D Film-Cooling Heat-Transfer on an AlliedSignal Vane; and (3) Effects of Tab Vortex Generators on Surface Heat Transfer. Downstream of a Jet in Crossflow.
7 CFR 2902.54 - Heat transfer fluids.
Code of Federal Regulations, 2011 CFR
2011-01-01
... 7 Agriculture 15 2011-01-01 2011-01-01 false Heat transfer fluids. 2902.54 Section 2902.54... Items § 2902.54 Heat transfer fluids. (a) Definition. Products with high thermal capacities used to... heat transfer fluids....
7 CFR 3201.54 - Heat transfer fluids.
Code of Federal Regulations, 2012 CFR
2012-01-01
... 7 Agriculture 15 2012-01-01 2012-01-01 false Heat transfer fluids. 3201.54 Section 3201.54... Designated Items § 3201.54 Heat transfer fluids. (a) Definition. Products with high thermal capacities used to facilitate the transfer of heat from one location to another, including coolants or refrigerants...
7 CFR 3201.54 - Heat transfer fluids.
Code of Federal Regulations, 2014 CFR
2014-01-01
... 7 Agriculture 15 2014-01-01 2014-01-01 false Heat transfer fluids. 3201.54 Section 3201.54... Designated Items § 3201.54 Heat transfer fluids. (a) Definition. Products with high thermal capacities used to facilitate the transfer of heat from one location to another, including coolants or refrigerants...
7 CFR 3201.54 - Heat transfer fluids.
Code of Federal Regulations, 2013 CFR
2013-01-01
... 7 Agriculture 15 2013-01-01 2013-01-01 false Heat transfer fluids. 3201.54 Section 3201.54... Designated Items § 3201.54 Heat transfer fluids. (a) Definition. Products with high thermal capacities used to facilitate the transfer of heat from one location to another, including coolants or refrigerants...
An experimental investigation on heat transfer performance of nanofluid pulsating heat pipe
NASA Astrophysics Data System (ADS)
Jia, Hongwei; Jia, Li; Tan, Zetao
2013-10-01
The effect of SiO2 particles on heat transfer performance of a pulsating heat pipe (PHP) was investigated experimentally. DI water was used as the base fluid and contrast medium for the PHP. In order to study and measure the character, there are SiO2/H2O nanofluids with different concentration and applying with various heating powers during the experiment investigation. According to the experimental result, the high fraction of SiO2/H2O will deteriorate the performance of PHP compared with DI water, i.e. the thermal resistance and the temperature of evaporation section increases. It is in contrary in the case of low fraction of SiO2/H2O. Finally, the comparison of the thermal performances between the normal operation system and the static settlement system is given. It is found that both the thermal resistance of nanofluid PHP and the temperature of the evaporation section increase after standing for a period, and it is the same trend for the temperature fluctuation at the identical heating power for PHP.
Low heat transfer oxidizer heat exchanger design and analysis
NASA Technical Reports Server (NTRS)
Kanic, P. G.; Kmiec, T. D.; Peckham, R. J.
1987-01-01
The RL10-IIB engine, a derivative of the RLIO, is capable of multi-mode thrust operation. This engine operates at two low thrust levels: tank head idle (THI), which is approximately 1 to 2 percent of full thrust, and pumped idle (PI), which is 10 percent of full thrust. Operation at THI provides vehicle propellant settling thrust and efficient engine thermal conditioning; PI operation provides vehicle tank pre-pressurization and maneuver thrust for log-g deployment. Stable combustion of the RL10-IIB engine at THI and PI thrust levels can be accomplished by providing gaseous oxygen at the propellant injector. Using gaseous hydrogen from the thrust chamber jacket as an energy source, a heat exchanger can be used to vaporize liquid oxygen without creating flow instability. This report summarizes the design and analysis of a United Aircraft Products (UAP) low-rate heat transfer heat exchanger concept for the RL10-IIB rocket engine. The design represents a second iteration of the RL10-IIB heat exchanger investigation program. The design and analysis of the first heat exchanger effort is presented in more detail in NASA CR-174857. Testing of the previous design is detailed in NASA CR-179487.
Heat Transfer Through Turbulent Friction Layers
NASA Technical Reports Server (NTRS)
Reichardt, H.
1943-01-01
The "general Prandtl number" Pr(exp 1) - A(sub q)/A Pr, aside from the Reynolds number determines the ratio of turbulent to molecular heat transfer, and the temperature distribution in turbulent friction layers. A(sub q) = exchange coefficient for heat; A = exchange coefficient for momentum transfer. A formula is derived from the equation defining the general Prandtl number which describes the temperature as a function of the velocity. For fully developed thermal boundary layers all questions relating to heat transfer to and from incompressible fluids can be treated in a simple manner if the ratio of the turbulent shear stress to the total stress T(sub t)/T in the layers near the wall is known, and if the A(sub q)/A can be regarded as independent of the distance from the wall. The velocity distribution across a flat smooth channel and deep into the laminar sublayer was measured for isothermal flow to establish the shear stress ratio T(sub t)/T and to extend the universal wall friction law. The values of T(sub t)/T which resulted from these measurements can be approximately represented by a linear function of the velocity in the laminar-turbulent transition zone. The effect of the temperature relationship of the material values on the flow near the wall is briefly analyzed. It was found that the velocity at the laminar boundary (in contrast to the thickness of the laminar layer) is approximately independent of the temperature distribution. The temperature gradient at the wall and the distribution of temperature and heat flow in the turbulent friction layers were calculated on the basis of the data under two equations. The derived formulas and the figures reveal the effects of the Prandtl number, the Reynolds number, the exchange quantities and the temperature relationship of the material values.
46 CFR 153.430 - Heat transfer systems; general.
Code of Federal Regulations, 2012 CFR
2012-10-01
... 46 Shipping 5 2012-10-01 2012-10-01 false Heat transfer systems; general. 153.430 Section 153.430... Temperature Control Systems § 153.430 Heat transfer systems; general. Each cargo cooling system required by... separated from all other cooling and heating systems; and (c) Allow manual regulation of the system's heat...
46 CFR 153.430 - Heat transfer systems; general.
Code of Federal Regulations, 2013 CFR
2013-10-01
... 46 Shipping 5 2013-10-01 2013-10-01 false Heat transfer systems; general. 153.430 Section 153.430... Temperature Control Systems § 153.430 Heat transfer systems; general. Each cargo cooling system required by... separated from all other cooling and heating systems; and (c) Allow manual regulation of the system's heat...
46 CFR 153.430 - Heat transfer systems; general.
Code of Federal Regulations, 2014 CFR
2014-10-01
... 46 Shipping 5 2014-10-01 2014-10-01 false Heat transfer systems; general. 153.430 Section 153.430... Temperature Control Systems § 153.430 Heat transfer systems; general. Each cargo cooling system required by... separated from all other cooling and heating systems; and (c) Allow manual regulation of the system's heat...
Enhancement of Pool Boiling Heat Transfer to Lithium Bromide Aqueous Solution
NASA Astrophysics Data System (ADS)
Furukawa, Masahiro; Kaji, Masuo; Suyama, Takayuki; Sekoguchi, Kotohiko
An experimental study on enhancement of nucleate pool boiling heat tranfer by placing a sponge metal close to a plain heated surface was conducted in order to improve the heat transfer performance of the high temperature generator of absorption chiller/heater. The sponge metal has three dimensional porous mesh framework like sponge. Boiling curves of water under the atmospheric pressure were compared with those of lithium bromide aqueous solution of mass concentration 55 to 58%. Heat transfer characteristics were improved by 2 to3 times both for water and lithium bromide aqueous solution when the sponge metal was placed on the heated surface with and without cleareance. Three kinds of sponge metals were used for lithium bromide aqueous solution under the reduced pressure (24 kPa). At lower heat fluxes,#6 sponge metal which has the finest mesh and the lowest porosity shows excellent results. At high heat fluxes, however,it causes deterioration of heat transfer. Over the wide range of heat fluxes,# 4 sponge metal was found to be most suitable and the optimal clearence was determined as 0.5 mm. The sponge metal is of good practical use as a device to enhance the boiling, since no special manufacturing is required for placing it on the heated surface.
Flow drag and heat transfer characteristics of drag-reducing nanofluids with CuO nanoparticles
NASA Astrophysics Data System (ADS)
Wang, Ping-Yang; Wang, Xue-Jiao; Liu, Zhen-Hua
2017-02-01
A new kind of aqueous CuO nanofluid with drag-reducing performance was developed. The new working fluid was an aqueous CTAC (cetyltrimethyl ammonium chloride) solution with CuO nanoparticles added and has both special effects of drag-reducing and heat transfer enhancement. An experiment was carried out to investigate the forced convective flow and heat transfer characteristics of conventional drag reducing fluid (aqueous CTAC solution) and the new drag-reducing nanofluid in a test tube with an inner diameter of 25.6 mm. Results indicated that there were no obvious differences of the drag-reducing characteristics between conventional drag reducing fluid and new drag-reducing nanofluid. However, their heat transfer characteristics were obvious different. The heat transfer characteristics of the new drag-reducing nanofluid significantly depend on the liquid temperature, the nanoparticle concentration and the CTAC concentration. The heat transfer enhancement technology of nanofluid could be applied to solve the problem of heat transfer deterioration for conventional drag-reducing fluids.
Thermochromic liquid crystals in heat transfer research
NASA Astrophysics Data System (ADS)
Stasiek, Jan A.; Kowalewski, Tomasz A.
2002-06-01
In recent years Thermochromic Liquid Crystals (TLC) have been successfully used in non-intrusive heat transfer and fluid mechanics studies. Thin coatings of TLC's at surfaces is utilized to obtain detailed heat transfer data of steady or transient process. Application of TLC tracers allows instantaneous measurement of the temperature and velocity fields for two-dimensional cross-section of flow. Computerized flow visualization techniques allow automatic quantification of temperature of the analyzed surface or the visualized flow cross-section. Here we describe our experience in applying the method to selected problems studied in our laboratory. They include modeling flow configurations in the differentially heated inclined cavity with vertical temperature gradient simulating up-slope flow as well as thermal convection under freezing surface. The main aim of these experimental models is to generate reliable experimental database on velocity and temperature fields for specific flow. The methods are based on computerized true-color analysis of digital images for temperature measurements and modified Particle Image Velocimetry and Thermometry (PIVT) used to obtain the flow field velocity.
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.
[Mechanism of heat transfer in various regions of human body].
Luchakov, Iu I; Nozdrachev, A D
2009-01-01
The processes of heat transfer in a human body were studied with the use of a mathematical model. It has been shown that only conductive or only convective heat transfer may occur in different body areas. The rate of blood-mediated heat transfer in the presence of blood circulation is many times higher than heat transfer due to temperature gradient; therefore, the convective process prevails over the conductive process. The body core contains a variety of blood vessels, and the bulk of blood concentrates there in the norm. Hence, heat transfer in it is mainly convective. In surface tissues, where the rate of blood circulation is lower and the vasculature has certain specific features, heat transfer is mainly conductive. Hence, the core and surface tissues are absolutely different body zones in terms of heat transfer.
Transient heat transfer in superfluid helium
Dresner, L.
1981-01-01
According to the Goerter-Mellink law, the heat flux in superfluid helium is proportional to the cube root of the temperature gradient. If we use this proportionality in place of Fourier's linear law to derive an equation of heat conduction, we obtain a non-linear partial differential equation. Such equations are usually difficult to solve because we cannot superpose solutions to obtain others. In spite of this, the problem of this paper, the constant-flux problem, can be solved because its temperature profiles are self-similar. Self-similarity means that the temperature profile at one time can be obtained from that at a different time by suitable (different) stretching of the distance and temperature axes of the latter profle. The self-similarity of the temperature profiles is connected with the invariance of the non-linear partial differential equation to certain groups of transformations. We reduce the partial differential equation of heat conduction to an ordinary differential equation, the appropriate solution of which we find without extensive computation. The reduction involves the similarity variables ..delta..T/..sqrt..t and z/..sqrt..t, where ..delta..T is the temperature rise at a distance z from the heated face at a time t after the (constant) heating has begun. Use of these variables should, and does, reduce all of the experimental temperature profiles reported by van Sciver to a single, universal curve. We obtain this curve as well by solving the differential equation; agreement is excellent. In fact agreement with all the experimental data reported by van Sciver is excellent, so that the Goerter-Mellink law seems to be a very successful basis for describing transient heat transfer in superfluid helium.
Advances in refrigeration and heat transfer engineering
Bansal, Pradeep; Cremaschi, Prof. Lorenzo
2015-05-13
This special edition of Science and Technology for the Built Environment (STBE) presents selected high quality papers that were presented at the 15th International Refrigeration and Air Conditioning Conference held at Purdue University during July 14-17 2014. All papers went through the additional review before being finally accepted for publication in this special issue of Science and Technology and the Built Environment. Altogether 20 papers made to this special issue that cover a wide range of topics, including advancements in alternative refrigerants, heat exchangers/heat transfer, nano-fluids, systems design and optimization and modeling approaches. Although CO2 may perhaps have been themore » most researched and popular refrigerant in the past decade, R32 is being seriously considered lately as an alternative and environmentally friendly refrigerant for small systems due to its low Global Warming Potential (GWP).« less
Advances in refrigeration and heat transfer engineering
Bansal, Pradeep; Cremaschi, Prof. Lorenzo
2015-05-13
This special edition of Science and Technology for the Built Environment (STBE) presents selected high quality papers that were presented at the 15th International Refrigeration and Air Conditioning Conference held at Purdue University during July 14-17 2014. All papers went through the additional review before being finally accepted for publication in this special issue of Science and Technology and the Built Environment. Altogether 20 papers made to this special issue that cover a wide range of topics, including advancements in alternative refrigerants, heat exchangers/heat transfer, nano-fluids, systems design and optimization and modeling approaches. Although CO_{2} may perhaps have been the most researched and popular refrigerant in the past decade, R32 is being seriously considered lately as an alternative and environmentally friendly refrigerant for small systems due to its low Global Warming Potential (GWP).
Convective heat transfer and infrared thermography.
Carlomagno, Giovanni M; Astarita, Tommaso; Cardone, Gennaro
2002-10-01
Infrared (IR) thermography, because of its two-dimensional and non-intrusive nature, can be exploited in industrial applications as well as in research. This paper deals with measurement of convective heat transfer coefficients (h) in three complex fluid flow configurations that concern the main aspects of both internal and external cooling of turbine engine components: (1) flow in ribbed, or smooth, channels connected by a 180 degrees sharp turn, (2) a jet in cross-flow, and (3) a jet impinging on a wall. The aim of this study was to acquire detailed measurements of h distribution in complex flow configurations related to both internal and external cooling of turbine components. The heated thin foil technique, which involves the detection of surface temperature by means of an IR scanning radiometer, was exploited to measure h. Particle image velocimetry was also used in one of the configurations to precisely determine the velocity field.
Heat Transfer Model for Hot Air Balloons
NASA Astrophysics Data System (ADS)
Llado-Gambin, Adriana
A heat transfer model and analysis for hot air balloons is presented in this work, backed with a flow simulation using SolidWorks. The objective is to understand the major heat losses in the balloon and to identify the parameters that affect most its flight performance. Results show that more than 70% of the heat losses are due to the emitted radiation from the balloon envelope and that convection losses represent around 20% of the total. A simulated heating source is also included in the modeling based on typical thermal input from a balloon propane burner. The burner duty cycle to keep a constant altitude can vary from 10% to 28% depending on the atmospheric conditions, and the ambient temperature is the parameter that most affects the total thermal input needed. The simulation and analysis also predict that the gas temperature inside the balloon decreases at a rate of -0.25 K/s when there is no burner activity, and it increases at a rate of +1 K/s when the balloon pilot operates the burner. The results were compared to actual flight data and they show very good agreement indicating that the major physical processes responsible for balloon performance aloft are accurately captured in the simulation.
Porous media heat transfer for injection molding
Beer, Neil Reginald
2016-05-31
The cooling of injection molded plastic is targeted. Coolant flows into a porous medium disposed within an injection molding component via a porous medium inlet. The porous medium is thermally coupled to a mold cavity configured to receive injected liquid plastic. The porous medium beneficially allows for an increased rate of heat transfer from the injected liquid plastic to the coolant and provides additional structural support over a hollow cooling well. When the temperature of the injected liquid plastic falls below a solidifying temperature threshold, the molded component is ejected and collected.
Heat transfer augmentation in nanofluids via nanofins.
Vadasz, Peter
2011-02-18
Theoretical results derived in this article are combined with experimental data to conclude that, while there is no improvement in the effective thermal conductivity of nanofluids beyond the Maxwell's effective medium theory (J.C. Maxwell, Treatise on Electricity and Magnetism, 1891), there is substantial heat transfer augmentation via nanofins. The latter are formed as attachments on the hot wire surface by yet an unknown mechanism, which could be related to electrophoresis, but there is no conclusive evidence yet to prove this proposed mechanism.
Convective Heat Transfer for Ship Propulsion.
1985-11-29
frpiac i aU cd i INds-- butl .<. Contract No. N00014-75-C-0694; NR-097-395 ! _; "’ ~CONVECTIVE HEAT TRANSFER FOR SHIP PROPULSION -’- Aerospace and...Claaification, CONVECTIVEHET7 TRNSE FOR SHIP PROPULSION (U) ______ 1.PRSONAL AUTHOR(S) McEligot, Donald M., P. 0. Box 4282, Middletown, Rhode Island...cooled -"ireactors using N2 04 compared with atomic2 4- I.- electric stations using sodium. The potential benefits for ship propulsion are obvious
Solar Pond Fluid Dynamics and Heat Transfer
NASA Technical Reports Server (NTRS)
Jones, G. F.
1984-01-01
The primary objective of the solar pond research was to obtain an indepth understanding of solar pond fluid dynamics and heat transfer. The key product was the development of a validated one-dimensional computer model with the capability to accurately predict time-dependent solar pond temperature, salinities, and interface motions. Laboratory scale flow visualization experiments were conducted to better understand layer motion. Two laboratory small-scale ponds and a large-scale outdoor solar pond were designed and built to provide quantitative data. This data provided a basis for validating the model and enhancing the understanding of pond dynamic behavior.
Analysis of radial fin assembly heat transfer with dehumidification
Rosario, L.; Rahman, M.M.
1996-12-31
The aim of this paper is the analysis of heat transfer in a radial fin assembly during the process of dehumidification. An individual finned tube geometry is a reasonable representation of heat exchangers used in air conditioning. The condensation process involves both heat and mass transfer and the cooling takes place by the removal of sensible as well as latent heat. The ratio of sensible to total heat is an important quantity that defines the heat transfer process during a dehumidifier operation. A one-dimensional model for heat transfer in the fin and the heat exchanger block is developed to study the effects of condensation on the fin surface. The combined heat and mass transfer process is modeled by incorporating the ratio of sensible to total heat in the formulation. The augmentation of heat transfer due to fin was established by comparing heat transfer rate with and without fins under the same operating conditions. Numerical calculations were carried out to study the effects of relative humidity and dry bulb temperature of the incoming air, and cold fluid temperature inside the coil on the performance of the heat exchanger. Results were compared to those published for rectangular fin under humid condition showed excellent agreement when the present model was used to compute that limiting condition. It was found that the heat transfer rate increased with increment in both dry bulb temperature and relative humidity of the air. The augmentation factor, however, decreased with increment in relative humidity and the dry bulb temperature.
Thermodynamics of flame impingement heat transfer
NASA Astrophysics Data System (ADS)
Som, S. K.; Agrawal, G. K.; Chakraborty, Suman
2007-08-01
A theoretical model for entropy generation and utilization of work potential (exergy) in flame impingement (both premixed and diffusion) heat transfer has been developed in this article, to offer physical insights on the optimal operational regimes, depicting high values of the surface heat flux with minimal exergy destruction, within the practical constraints. The irreversibility components due to different physical processes have been evaluated from a general entropy transport equation. The velocity, temperature, and species concentration fields required for the solution of entropy transport equation have been determined from the numerical computation of flow-field in the flame. Global two-step chemical kinetics has been considered with methane (CH4) and air as fuel and oxidizer, respectively. The results have been predicted in terms of average nondimensional heat flux, expressed as Nusselt number at the target plate, the irreversibility components, and second law efficiency, as functions of the pertinent input parameters such as the jet Reynolds number and the ratio of plate separation distance to nozzle diameter (H /d). The average Nusselt number has been found to increase with an increase in jet Reynolds number and a decrease in H /d ratio, up to a value of 8. The dominant source of thermodynamic irreversibility in a premixed flame has been attributed to the thermal energy exchange whereas, in a diffusion flame, the same has been attributed to an uncontrolled exchange of electrons accompanying the reactive kinetics. The second law efficiency has been found to increase with an increase in jet Reynolds number and an increase in the H /d ratio, up to a value of 20. Values of the jet Reynolds number greater than 10 000 and H /d ratio in the tune of 15 have been observed to pertain to the regime of optimum flame impingement heat transfer, consistent with the energy and exergy balance constraints.
Fibre optic sensors for heat transfer studies
NASA Astrophysics Data System (ADS)
Sinha, Pranay G.
This thesis describes the design and development of a prototype sensor, based on a miniature optical fiber Fabry-Perot interferometer, for heat transfer studies on model turbomachinery components in transient flow wind tunnels. These sensors overcome a number of difficulties which are often encountered in using conventional electrical thin-film resistance gauges such as in the measurement of rapidly varying heat transfer rates, spatial resolution, electromagnetic interference, calibration and signal processing. The special features of the optical sensor are: (1) short length (less than 5 mm), and therefore embeddable in thin structures of model components; (2) direct measurement of heat flux rates; (3) calorimetric operation with temperature resolution of less than 25 mK over a measurement bandwidth of 100 kHz; (4) capability of measuring heat flux less than 5 kWm(exp -2) with measurement range in excess of 10 MWm(exp -2); (5) temporal response time of less than 10 microseconds; (6) minimal thermal disturbances because models are often made of ceramic materials with thermal properties similar to those of the optical fiber from which sensors are made;(7) possibility of using in models with dissimilar thermal properties to the optical fiber, for example, metals; (8) spatial resolution of less than 5 microns; (9) remote operation; (10) an ability to be multiplexed; and (11) immunity to electromagnetic interference. A detailed discussion of the design considerations for the sensor, system development, evaluation of the sensor performance both in the laboratory and wind tunnel environments is presented in this thesis. The performance of the sensor compared favorably with electrical gauges namely, platinum thin-film resistance thermometers. A 4-sensor multiplexed system has been successfully operated, and is reported in the thesis. A brief discussion is also included to indicate that the same sensor design may be considered for applications in other engineering areas.
Fibre Optic Sensors for Heat Transfer Studies.
NASA Astrophysics Data System (ADS)
Sinha, Pranay G.
Available from UMI in association with The British Library. This thesis describes the design and development of a prototype sensor, based on a miniature optical fibre Fabry-Perot interferometer, for heat transfer studies on model turbomachinery components in transient flow wind tunnels. These sensors overcome a number of difficulties which are often encountered in using conventional electrical thin-film resistance gauges such as in the measurement of rapidly varying heat transfer rates, spatial resolution, electromagnetic interference, calibration and signal processing. The special features of the optical sensor are: (i) short length (<5 mm), and therefore embeddable in thin structures of model components; (ii) direct measurement of heat flux rates; (iii) calorimetric operation with temperature resolution of <25 mK over a measurement bandwidth of 100 kHz: (iv) capability of measuring heat flux <5 kWm^ {-2} with measurement range in excess of 10 MWm^{-2}; (v) temporal response time of <10 mus; (vi) minimal thermal disturbances because models are often made of ceramic materials with thermal properties similar to those of the optical fibre from which sensors are made; (vii) possibility of using in models with dissimilar thermal properties to the optical fibre, for example, metals; (viii) spatial resolution of <5 mu m; (ix) remote operation; (x) an ability to be multiplexed; and (xi) immunity to electromagnetic interference. A detailed discussion of the design considerations for the sensor, system development, evaluation of the sensor performance both in the laboratory and wind tunnel environments is presented in this thesis. The performance of the sensor compared favourably with electrical gauges namely, platinum thin-film resistance thermometers. A 4-sensor multiplexed system has been sucessfully operated, and is reported in the thesis. A brief discussion is also included to indicate that the same sensor design may be considered for applications in other engineering
Nanoscale heat transfer and phase transformation surrounding intensely heated nanoparticles
NASA Astrophysics Data System (ADS)
Sasikumar, Kiran
Over the last decade there has been significant ongoing research to use nanoparticles for hyperthermia-based destruction of cancer cells. In this regard, the investigation of highly non-equilibrium thermal systems created by ultrafast laser excitation is a particularly challenging and important aspect of nanoscale heat transfer. It has been observed experimentally that noble metal nanoparticles, illuminated by radiation at the plasmon resonance wavelength, can act as localized heat sources at nanometer-length scales. Achieving biological response by delivering heat via nanoscale heat sources has also been demonstrated. However, an understanding of the thermal transport at these scales and associated phase transformations is lacking. A striking observation made in several laser-heating experiments is that embedded metal nanoparticles heated to extreme temperatures may even melt without an associated boiling of the surrounding fluid. This unusual phase stability is not well understood and designing experiments to understand the physics of this phenomenon is a challenging task. In this thesis, we will resort to molecular dynamics (MD) simulations, which offer a powerful tool to investigate this phenomenon, without assumptions underlying continuum-level model formulations. We present the results from a series of steady state and transient non-equilibrium MD simulations performed on an intensely heated nanoparticle immersed in a model liquid. For small nanoparticles (1-10 nm in diameter) we observe a stable liquid phase near the nanoparticle surface, which can be at a temperature well above the boiling point. Furthermore, we report the existence of a critical nanoparticle size (4 nm in diameter) below which we do not observe formation of vapor even when local fluid temperatures exceed the critical temperature. Instead, we report the existence of a stable fluid region with a density much larger than that of the vapor phase. We explain this stability in terms of the
Heat Transfer Phenomena in Supercritical Water Nuclear Reactors
Mark H. Anderson; MichaelL. Corradini; Riccardo Bonazza; Jeremy R. Licht
2007-10-03
A supercritical water heat transfer facility has been built at the University of Wisconsin to study heat transfer in ancircular and square annular flow channel. A series of integral heat transfer measurements has been carried out over a wide range of heat flux, mas velocity and bulk water temperatures at a pressure of 25 MPa. The circular annular test section geometry is a 1.07 cm diameter heater rod within a 4.29 diameter flow channel.
Active chimney effect using heated porous layers: optimum heat transfer
NASA Astrophysics Data System (ADS)
Mehiris, Abdelhak; Ameziani, Djamel-Edine; Rahli, Omar; Bouhadef, Khadija; Bennacer, Rachid
2017-05-01
The purpose of the present work is to treat numerically the problem of the steady mixed convection that occurs in a vertical cylinder, opened at both ends and filled with a succession of three fluid saturated porous elements, namely a partially porous duct. The flow conditions fit with the classical Darcy-Brinkman model allowing analysing the flow structure on the overall domain. The induced heat transfer, in terms of local and average Nusselt numbers, is discussed for various controlling parameters as the porous medium permeability, Rayleigh and Reynolds numbers. The efficiency of the considered system is improved by the injection/suction on the porous matrices frontier. The undertaken numerical exploration particularly highlighted two possible types of flows, with and without fluid recirculation, which principally depend on the mixed convection regime. Thus, it is especially shown that recirculation zones appear in some domain areas under specific conditions, obvious by a negative central velocity and a prevalence of the natural convection effects, i.e., turnoff flow swirls. These latter are more accentuated in the areas close to the porous obstacles and for weak permeability. Furthermore, when fluid injection or suction is considered, the heat transfer increases under suction and reduces under injection. Contribution to the topical issue "Materials for Energy Harvesting, Conversion and Storage II (ICOME 2016)", edited by Jean-Michel Nunzi, Rachid Bennacer and Mohammed El Ganaoui
Study and Analysis of Heat Transfer Limitation of Separated Heat Pipe
NASA Astrophysics Data System (ADS)
Mou, Qizheng; Mou, Kai
2002-01-01
satellite and spacecraft. evaporator, heat isolation and condenser along the axial direction. The working fluid absorbs heat and evaporates in evaporator, and then the vapor flows to condenser and gives out heat. The condensed liquid is pumped to evaporator by wick. By the circulation, the heat can by transferred continuously. heat pipe as follow: - Vapor-liquid two phase flow inside pipe; - The manner of latent heat to transfer heat; - Automatic circulation by working fluid flowing - A certain extent of vacuum. and the traditional heat pipe, that is, the vapor fluid and liquid fluid flow along the same direction. So it is obviously that the separated heat pipe has special internal heat transfer characteristic and crisis. This paper has regard for the heat transfer crisis of the separated heat pipe, and meanwhile relevant calculation and analysis have been done. 1. FLOW TYPE OF THE WORKING FLUID IN SEPARATED HEAT PIPE 2. HEAT TRANSFER CRISIS IN THE EVAPORATOR 3. CARRYING PHENOMENON INSIDE SEPARATED HEAT PIPE 4. THE STAGNANT FLOW PHENOMENON AND THE BACKWARD FLOW PHENOMENON IN EVAPORATOR CONCLUSION transfer limitation of location burn-out, and the heat transfer limitation of flow unconventionality in erective pipe. The carrying phenomenon can occurs not only in evaporator but also in condenser of separated heat pipe. It is in the evaporator that should take place the heat transfer limitation of liquid film dry-out at first. Then with the increasing of heat flux, the heat transfer limitation of location burn-out would happen. In order to avoid the heat transfer limitation of flow unconventionality in erective pipe, the length and diameter of the outflow tube and inflow tube must be reasonably calculated to control the flow velocity of the working fluid inside pipe. Key words:Separated Heat PipeHeat Transfer LimitationDry-OutCarryingStagnancy
Nakamura, Masaaki; Chida, Koichi; Inaba, Yohei; Kobayashi, Ryota; Zuguchi, Masayuki
2017-06-26
There are no feasible real-time and direct skin dosimeters for interventional radiology. One would be available if there were x-ray phosphors that had no brightness change caused by x-ray irradiation, but the emission of the Y2O3:Eu, (Y, Gd, Eu)BO3, and YVO4:Eu phosphors investigated in our previous study was reduced by x-ray irradiation. We found that the brightness of those phosphors recovered, and the purpose of this study is to investigate their recovery phenomena. It is expected that more kinds of phosphors could be used in x-ray dosimeters if the brightness changes caused by x-rays are elucidated and prevented. Three kinds of phosphors-Y2O3:Eu, (Y, Gd, Eu)BO3, and YVO4:Eu-were irradiated by x-rays (2 Gy) to reduce their brightness. After the irradiation, brightness changes occurring at room temperature and at 80 °C were investigated. The irradiation reduced the brightness of all the phosphors by 5%-10%, but the brightness of each recovered immediately both at room temperature and at 80 °C. The recovery at 80 °C was faster than that at room temperature, and at both temperatures the recovered brightness remained at 95%-98% of the brightness before the x-ray irradiation. The brightness recovery phenomena of Y2O3:Eu, (Y, Gd, Eu)BO3, and YVO4:Eu phosphors occurring after brightness deterioration due to x-ray irradiation were found to be more significant at 80 °C than at room temperature. More kinds of phosphors could be used in x-ray scintillation dosimeters if the reasons for the brightness changes caused by x-rays were elucidated.
Nucleation and Heat Transfer in Liquid Nitrogen
NASA Astrophysics Data System (ADS)
Roth, Eric Warner
1993-01-01
With the advent of the new high Tc superconductors as well as the increasing use of cryo-cooled conventional electronics, liquid nitrogen will be one of the preferred cryogens used to cool these materials. Consequently, a more thorough understanding of the heat transfer characteristics of liquid nitrogen is required. In these investigations the transient heating characteristics of liquid nitrogen to states of nucleate and film boiling under different liquid flow conditions are examined. Using a metal hot wire/plate technique, it is verified that there is a premature transition to film boiling in the transient case at power levels as much as 30 percent lower than under steady state nucleate boiling conditions. It is also shown that the premature transition can be reduced or eliminated depending on the flow velocity. The second part of this research analyses the nucleation (boiling) process from a dynamical systems point of view. By observing how the boiling system variables evolve and fluctuate over time, it is hoped that physical insight and predictive information can be gained. One goal is to discover some indicator or signature in the data that anticipates the transition from nucleate boiling to film boiling. Some of the important variables that make up the boiling system are the temperature of the heater and the heat flux through the heater surface into the liquid nitrogen. The result, gained by plotting the system's trajectory in the heat flux-temperature plane, is that on average the system follows a counterclockwise trajectory. A physical model is constructed that explains this behavior. Also, as the applied heater power approaches levels at which the transition to film is known to occur, the area per unit time swept out in the heat flux-temperature plane is seen to reach a maximum. This could be of practical interest as the threshold to film boiling can be anticipated and possibly prevented.
Heat Transfer in High Temperature Multilayer Insulation
NASA Technical Reports Server (NTRS)
Daryabeigi, Kamran; Miller, Steve D.; Cunnington, George R.
2007-01-01
High temperature multilayer insulations have been investigated as an effective component of thermal-protection systems for atmospheric re-entry of reusable launch vehicles. Heat transfer in multilayer insulations consisting of thin, gold-coated, ceramic reflective foils and Saffil(TradeMark) fibrous insulation spacers was studied both numerically and experimentally. A finite volume numerical thermal model using combined conduction (gaseous and solid) and radiation in porous media was developed. A two-flux model with anisotropic scattering was used for radiation heat transfer in the fibrous insulation spacers between the reflective foils. The thermal model was validated by comparison with effective thermal conductivity measurements in an apparatus based on ASTM standard C201. Measurements were performed at environmental pressures in the range from 1x10(exp -4) to 760 torr over the temperature range from 300 to 1300 K. Four multilayer samples with nominal densities of 48 kg/cu m were tested. The first sample was 13.3 mm thick and had four evenly spaced reflective foils. The other three samples were 26.6 mm thick and utilized either one, two, or four reflective foils, located near the hot boundary with nominal foil spacing of 1.7 mm. The validated thermal model was then used to study relevant design parameters, such as reflective foil spacing and location in the stack-up and coating of one or both sides of foils.
Micro-grooved heat transfer combustor wall
NASA Technical Reports Server (NTRS)
Ward, Steven D. (Inventor)
1994-01-01
A gas turbine engine hot section combustor liner is provided a non-film cooled portion of a heat transfer wall having a hot surface and a plurality of longitudinally extending micro-grooves disposed in the portion of the wall along the hot surface in a direction parallel to the direction of the hot gas flow. The depth of the micro-grooves is very small and on the order of magnitude of a predetermined laminar sublayer of a turbulent boundary layer. The micro-grooves are sized so as to inhibit heat transfer from the hot gas flow to the hot surface of the wall while reducing NOx emissions of the combustor relative to an otherwise similar combustor having a liner wall portion including film cooling apertures. In one embodiment the micro-grooves are about 0.001 inches deep and have a preferred depth range of from about 0.001 inches to 0.005 inches and which are square, rectangular, or triangular in cross-section and the micro-grooves are spaced about one width apart.
Transient critical heat flux and blowdown heat-transfer studies
Leung, J.C.
1980-05-01
Objective of this study is to give a best-estimate prediction of transient critical heat flux (CHF) during reactor transients and hypothetical accidents. To accomplish this task, a predictional method has been developed. Basically it involves the thermal-hydraulic calculation of the heated core with boundary conditions supplied from experimental measurements. CHF predictions were based on the instantaneous ''local-conditions'' hypothesis, and eight correlations (consisting of round-tube, rod-bundle, and transient correlations) were tested against most recent blowdown heat-transfer test data obtained in major US facilities. The prediction results are summarized in a table in which both CISE and Biasi correlations are found to be capable of predicting the early CHF of approx. 1 s. The Griffith-Zuber correlation is credited for its prediction of the delay CHF that occurs in a more tranquil state with slowly decaying mass velocity. In many instances, the early CHF can be well correlated by the x = 1.0 criterion; this is certainly indicative of an annular-flow dryout-type crisis. The delay CHF occurred at near or above 80% void fraction, and the success of the modified Zuber pool-boiling correlation suggests that this CHF is caused by flooding and pool-boiling type hydrodynamic crisis.
Boiling local heat transfer enhancement in minichannels using nanofluids
NASA Astrophysics Data System (ADS)
Chehade, Ali Ahmad; Gualous, Hasna Louahlia; Le Masson, Stephane; Fardoun, Farouk; Besq, Anthony
2013-03-01
This paper reports an experimental study on nanofluid convective boiling heat transfer in parallel rectangular minichannels of 800 μm hydraulic diameter. Experiments are conducted with pure water and silver nanoparticles suspended in water base fluid. Two small volume fractions of silver nanoparticles suspended in water are tested: 0.000237% and 0.000475%. The experimental results show that the local heat transfer coefficient, local heat flux, and local wall temperature are affected by silver nanoparticle concentration in water base fluid. In addition, different correlations established for boiling flow heat transfer in minichannels or macrochannels are evaluated. It is found that the correlation of Kandlikar and Balasubramanian is the closest to the water boiling heat transfer results. The boiling local heat transfer enhancement by adding silver nanoparticles in base fluid is not uniform along the channel flow. Better performances and highest effect of nanoparticle concentration on the heat transfer are obtained at the minichannels entrance.
Boiling local heat transfer enhancement in minichannels using nanofluids
2013-01-01
This paper reports an experimental study on nanofluid convective boiling heat transfer in parallel rectangular minichannels of 800 μm hydraulic diameter. Experiments are conducted with pure water and silver nanoparticles suspended in water base fluid. Two small volume fractions of silver nanoparticles suspended in water are tested: 0.000237% and 0.000475%. The experimental results show that the local heat transfer coefficient, local heat flux, and local wall temperature are affected by silver nanoparticle concentration in water base fluid. In addition, different correlations established for boiling flow heat transfer in minichannels or macrochannels are evaluated. It is found that the correlation of Kandlikar and Balasubramanian is the closest to the water boiling heat transfer results. The boiling local heat transfer enhancement by adding silver nanoparticles in base fluid is not uniform along the channel flow. Better performances and highest effect of nanoparticle concentration on the heat transfer are obtained at the minichannels entrance. PMID:23506445
Boiling local heat transfer enhancement in minichannels using nanofluids.
Chehade, Ali Ahmad; Gualous, Hasna Louahlia; Le Masson, Stephane; Fardoun, Farouk; Besq, Anthony
2013-03-18
This paper reports an experimental study on nanofluid convective boiling heat transfer in parallel rectangular minichannels of 800 μm hydraulic diameter. Experiments are conducted with pure water and silver nanoparticles suspended in water base fluid. Two small volume fractions of silver nanoparticles suspended in water are tested: 0.000237% and 0.000475%. The experimental results show that the local heat transfer coefficient, local heat flux, and local wall temperature are affected by silver nanoparticle concentration in water base fluid. In addition, different correlations established for boiling flow heat transfer in minichannels or macrochannels are evaluated. It is found that the correlation of Kandlikar and Balasubramanian is the closest to the water boiling heat transfer results. The boiling local heat transfer enhancement by adding silver nanoparticles in base fluid is not uniform along the channel flow. Better performances and highest effect of nanoparticle concentration on the heat transfer are obtained at the minichannels entrance.
Heat transfer assembly for a fluorescent lamp and fixture
Siminovitch, M.J.; Rubenstein, F.M.; Whitman, R.E.
1992-12-29
In a lighting fixture including a lamp and a housing, a heat transfer structure is disclosed for reducing the minimum lamp wall temperature of a fluorescent light bulb. The heat transfer structure, constructed of thermally conductive material, extends from inside the housing to outside the housing, transferring heat energy generated from a fluorescent light bulb to outside the housing where the heat energy is dissipated to the ambient air outside the housing. Also disclosed is a method for reducing minimum lamp wall temperatures. Further disclosed is an improved lighting fixture including a lamp, a housing and the aforementioned heat transfer structure. 11 figs.
Heat transfer assembly for a fluorescent lamp and fixture
Siminovitch, Michael J.; Rubenstein, Francis M.; Whitman, Richard E.
1992-01-01
In a lighting fixture including a lamp and a housing, a heat transfer structure is disclosed for reducing the minimum lamp wall temperature of a fluorescent light bulb. The heat transfer structure, constructed of thermally conductive material, extends from inside the housing to outside the housing, transferring heat energy generated from a fluorescent light bulb to outside the housing where the heat energy is dissipated to the ambient air outside the housing. Also disclosed is a method for reducing minimum lamp wall temperatures. Further disclosed is an improved lighting fixture including a lamp, a housing and the aforementioned heat transfer structure.
Experimental analysis of nanofluid pool boiling heat transfer in copper bead packed porous layers
NASA Astrophysics Data System (ADS)
Chen, Wei; Wang, Ji
2017-03-01
Coupling the nanofluid as working fluid and the copper beads packed porous structure on heating surface were employed to enhance the pool boiling heat transfer by changing the fluid properties with the adjunction of nanoparticles in liquid and altering the heating surface with a bead porous layer. Due to the higher thermal conductivity, the copper beads served as an extended heating surface and the boiling nucleation sites rose, but the flow resistance increased. The CuO-water and SiO2-water nanofluids as well as the pure water were respectively employed as working fluids in the pool boiling experiments. Comparing with the base fluid of water, the higher thermal conductivity and lower surface tension occur in the nanofluids and those favor the boiling heat transfer, but the higher viscosity and density of nanofluids serve as deteriorative factors. So, the concentration region of the nanofluids should be chosen properly. The maximum relative error between the collected experimental data of the pure water on a flat surface and the theoretical prediction of pool boiling using the Rohsenow correlation was less than 12 %. The comparisons of the pool boiling heat transfer characteristics were also conducted between the pure water and the nanofluids respectively on the horizontal flat surface and on the heating surface packed with a copper bead porous layer. Besides, the boiling bubble generation, integration and departure have a great affect on the pool boiling and were recorded with a camera in the bead stacked porous structures at different heat flux.
Convective heat transfer in porous media
NASA Astrophysics Data System (ADS)
Cheng, P.
Recent emerging technologies on the extraction of geothermal energy, the design of insulation systems for energy conservation, the use of aquifers for hot-water storage, the disposal of nuclear wastes in sub-seabeds, the enhanced recovery of oils by thermal methods, and the design of catalyst-bed reactors have demanded an improved understanding of heat transfer mechanisms in fluid-filled porous media. Experiments have been conducted to investigate the onset of free convection in rectangular and cylindrical enclosures filled with porous media and heated from below. The Nusselt numbers determined from these experiments during steady conditions are correlated in terms of the Rayleigh number. The data for free convection in rectangular geometries show considerable scattering among investigators using different porous media and fluids. Recently, some data has been obtained for free convect on in water-filled glass beads adjacent to a heated vertical flat plate, a horizontal cylinder and between vertical concentric cylinders. The data obtained at low Rayleigh numbers is found to be in good agreement with theoretical predictions based on Darcy's law.
Control of Impingement Heat Transfer Using Mist
NASA Astrophysics Data System (ADS)
Kanamori, Azusa; Hiwada, Munehiko; Mimatsu, Junji; Sugimoto, Hiraku; Oyakawa, Kenyuu
Impingement heat transfer from a circular orifice jet by using latent heat of water mists was studied experimentally. The amounts of mists of about Zauter's mean diameter 14 µm were from 60 to 200 g/h within a range where liquid films were not formed on the target plate and mists were added near the orifice edge. Experiments covered Reynolds numbers from 12,500 to 50,000 and a heat flux is 1,400 W/m2. The experimental results indicate that adding mists had little influence on free jet mean velocity profiles and target plate pressure coefficients. On the other hand, mists had a strong influence on temperature and humidity profiles of a free jet and they also influenced Nusselt number distributions on the target plate. Increases of mists and Reynolds number caused increases in Nusselt number on the developed region. In addition, we investigated influence of the way mists were added and these results showed that Nusselt number was influenced not only by the amounts of mists but also by the adding method. Local Nusselt number profiles with mists were closely related to temperature distributions of the free jet at the location corresponding to the target plate.
The heat transfer of cooling fins on moving air
NASA Technical Reports Server (NTRS)
Doetsch, Hans
1935-01-01
The present report is a comparison of the experimentally defined temperature and heat output of cooling fins in the air stream with theory. The agreement is close on the basis of a mean coefficient of heat transfer with respect to the total surface. A relationship is established between the mean coefficient of heat transfer, the dimensions of the fin arrangement, and the air velocity.
Heat transfer from starlings sturnus vulgaris during flight
Ward; Rayner; MOLler; Jackson; Nachtigall; Speakman
1999-06-01
Infrared thermography was used to measure heat transfer by radiation and the surface temperature of starlings (Sturnus vulgaris) (N=4) flying in a wind tunnel at 6-14 m s-1 and at 15-25 degrees C. Heat transfer by forced convection was calculated from bird surface temperature and biophysical modelling of convective heat transfer coefficients. The legs, head and ventral brachial areas (under the wings) were the hottest parts of the bird (mean values 6.8, 6.0 and 5.3 degrees C, respectively, above air temperature). Thermal gradients between the bird surface and the air decreased at higher air temperatures or during slow flight. The legs were trailed in the air stream during slow flight and when air temperature was high; this could increase heat transfer from the legs from 1 to 12 % of heat transfer by convection, radiation and evaporation (overall heat loss). Overall heat loss at a flight speed of 10.2 m s-1 averaged 11. 3 W, of which radiation accounted for 8 % and convection for 81 %. Convection from the ventral brachial areas was the most important route of heat transfer (19 % of overall heat loss). Of the overall heat loss, 55 % occurred by convection and radiation from the wings, although the primaries and secondaries were the coolest parts of the bird (2.2-2.5 degrees C above air temperature). Calculated heat transfer from flying starlings was most sensitive to accurate measurement of air temperature and convective heat transfer coefficients.
46 CFR 153.430 - Heat transfer systems; general.
Code of Federal Regulations, 2011 CFR
2011-10-01
... 46 Shipping 5 2011-10-01 2011-10-01 false Heat transfer systems; general. 153.430 Section 153.430... Temperature Control Systems § 153.430 Heat transfer systems; general. Each cargo cooling system required by... separated from all other cooling and heating systems; and (c) Allow manual regulation of the system's...
46 CFR 153.430 - Heat transfer systems; general.
Code of Federal Regulations, 2010 CFR
2010-10-01
... 46 Shipping 5 2010-10-01 2010-10-01 false Heat transfer systems; general. 153.430 Section 153.430... Temperature Control Systems § 153.430 Heat transfer systems; general. Each cargo cooling system required by... separated from all other cooling and heating systems; and (c) Allow manual regulation of the system's...
NASA Astrophysics Data System (ADS)
Kılıç, Bayram; İpek, Osman
2017-02-01
In this study, heat transfer rate and effectiveness of corrugated plate heat exchangers having different chevron angles were investigated experimentally. Chevron angles of plate heat exchangers are β = 30° and β = 60°. For this purpose, experimentally heating system used plate heat exchanger was designed and constructed. Thermodynamic analysis of corrugated plate heat exchangers having different chevron angles were carried out. The heat transfer rate and effectiveness values are calculated. The experimental results are shown that heat transfer rate and effectiveness values for β = 60° is higher than that of the other. Obtained experimental results were graphically presented.
Numerical evaluation of laminar heat transfer enhancement in nanofluid flow in coiled square tubes.
Sasmito, Agus Pulung; Kurnia, Jundika Candra; Mujumdar, Arun Sadashiv
2011-05-09
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.
Numerical evaluation of laminar heat transfer enhancement in nanofluid flow in coiled square tubes
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
Characteristics of turbulent heat transfer in an annulus at supercritical pressure
NASA Astrophysics Data System (ADS)
Peeters, J. W. R.; Pecnik, R.; Rohde, M.; van der Hagen, T. H. J. J.; Boersma, B. J.
2017-02-01
Heat transfer to fluids at supercritical pressure is different from heat transfer at lower pressures due to strong variations of the thermophysical properties with the temperature. We present and analyze results of direct numerical simulations of heat transfer to turbulent CO2 at 8 MPa in an annulus. Periodic streamwise conditions are imposed so that mean streamwise acceleration due to variations in the density does not occur. The inner wall of the annulus is kept at a temperature of 323 K, while the outer wall is kept at a temperature of 303 K. The pseudocritical temperature Tp c=307.7 K, which is the temperature where the thermophysical properties vary the most, can be found close to the inner wall. This work is a continuation of an earlier study, in which turbulence attenuation due to the variable thermophysical properties of a fluid at supercritical pressure was studied. In the current work, the direct effects of variations in the specific heat capacity, thermal diffusivity, density, and the molecular Prandtl number on heat transfer are investigated using different techniques. Variations in the specific heat capacity cause significant differences between the mean nondimensionalized temperature and enthalpy profiles. Compared to the enthalpy fluctuations, temperature fluctuations are enhanced in regions with low specific heat capacity and diminished in regions with a large specific heat capacity. The thermal diffusivity causes local changes to the mean enthalpy gradient, which in turn affects molecular conduction of thermal energy. The turbulent heat flux is directly affected by the density, but it is also affected by the mean molecular Prandtl number and attenuated or enhanced turbulent motions. In general, enthalpy fluctuations are enhanced in regions with a large mean molecular Prandtl number, which enhances the turbulent heat flux. While analyzing the Nusselt numbers under different conditions it is found that heat transfer deterioration or enhancement can
Modelling heat transfer in heterogeneous media using fractional calculus.
Sierociuk, Dominik; Dzielinski, Andrzej; Sarwas, Grzegorz; Petras, Ivo; Podlubny, Igor; Skovranek, Tomas
2013-05-13
This paper presents the results of modelling the heat transfer process in heterogeneous media with the assumption that part of the heat flux is dispersed in the air around the beam. The heat transfer process in a solid material (beam) can be described by an integer order partial differential equation. However, in heterogeneous media, it can be described by a sub- or hyperdiffusion equation which results in a fractional order partial differential equation. Taking into consideration that part of the heat flux is dispersed into the neighbouring environment we additionally modify the main relation between heat flux and the temperature, and we obtain in this case the heat transfer equation in a new form. This leads to the transfer function that describes the dependency between the heat flux at the beginning of the beam and the temperature at a given distance. This article also presents the experimental results of modelling real plant in the frequency domain based on the obtained transfer function.
Boiling heat transfer of refrigerant R-21 in upward flow in plate-fin heat exchanger
NASA Astrophysics Data System (ADS)
Kuznetsov, V. V.; Shamirzaev, A. S.
2015-11-01
The article presents the results of experimental investigation of boiling heat transfer of refrigerant R-21 in upward flow in a vertical plate-fin heat exchanger with transverse size of the channels that is smaller than the capillary constant. The heat transfer coefficients obtained in ranges of small mass velocities and low heat fluxes, which are typical of the industry, have been poorly studied yet. The characteristic patterns of the upward liquid-vapor flow in the heat exchanger channels and the regions of their existence are detected. The obtained data show a weak dependence of heat transfer coefficient on equilibrium vapor quality, mass flow rate, and heat flux density and do not correspond to calculations by the known heat transfer models. A possible reason for this behavior is a decisive influence of evaporation of thin liquid films on the heat transfer at low heat flux.
Liu, Jiawei; Zhou, Xingqiu; Wu, Jiangdong; Gao, Wen; Qian, Xu
2017-08-28
The temperature is the essential factor that influences the efficiency of anaerobic reactors. During the operation of the anaerobic reactor, the fluctuations of ambient temperature can cause a change in the internal temperature of the reactor. Therefore, insulation and heating measures are often used to maintain anaerobic reactor's internal temperature. In this paper, a simplified heat transfer model was developed to study heat transfer between cylindrical anaerobic reactors and their surroundings. Three cylindrical reactors of different sizes were studied, and the internal relations between ambient temperature, thickness of insulation, and temperature fluctuations of the reactors were obtained at different reactor sizes. The model was calibrated by a sensitivity analysis, and the calibrated model was well able to predict reactor temperature. The Nash-Sutcliffe model efficiency coefficient was used to assess the predictive power of heat transfer models. The Nash coefficients of the three reactors were 0.76, 0.60, and 0.45, respectively. The model can provide reference for the thermal insulation design of cylindrical anaerobic reactors.
Nanofluids for heat transfer: an engineering approach.
Timofeeva, Elena V; Yu, Wenhua; France, David M; Singh, Dileep; Routbort, Jules L
2011-02-28
An overview of systematic studies that address the complexity of nanofluid systems and advance the understanding of nanoscale contributions to viscosity, thermal conductivity, and cooling efficiency of nanofluids is presented. A nanoparticle suspension is considered as a three-phase system including the solid phase (nanoparticles), the liquid phase (fluid media), and the interfacial phase, which contributes significantly to the system properties because of its extremely high surface-to-volume ratio in nanofluids. The systems engineering approach was applied to nanofluid design resulting in a detailed assessment of various parameters in the multivariable nanofluid systems. The relative importance of nanofluid parameters for heat transfer evaluated in this article allows engineering nanofluids with desired set of properties.
Turbine disk cavity aerodynamics and heat transfer
NASA Technical Reports Server (NTRS)
Johnson, B. V.; Daniels, W. A.
1992-01-01
Experiments were conducted to define the nature of the aerodynamics and heat transfer for the flow within the disk cavities and blade attachments of a large-scale model, simulating the Space Shuttle Main Engine (SSME) turbopump drive turbines. These experiments of the aerodynamic driving mechanisms explored the following: (1) flow between the main gas path and the disk cavities; (2) coolant flow injected into the disk cavities; (3) coolant density; (4) leakage flows through the seal between blades; and (5) the role that each of these various flows has in determining the adiabatic recovery temperature at all of the critical locations within the cavities. The model and the test apparatus provide close geometrical and aerodynamic simulation of all the two-stage cavity flow regions for the SSME High Pressure Fuel Turbopump and the ability to simulate the sources and sinks for each cavity flow.
Heat transfer characteristics in film cooling applications
NASA Astrophysics Data System (ADS)
Licu, Dragos Nicolae
1998-11-01
The leading edge region of gas turbine blades and vanes experiences high thermal and mechanical stresses and has to be properly cooled. External cooling of the leading edge region is typically achieved by a film cooling technique. An investigation into the film cooling effectiveness of three different large scale leading edge geometries is presented in this study. One of the geometries investigated represents an original design and is an example of an improved film cooling layout. AD geometries used have four rows of cooling holes placed symmetrically about the geometrical leading edge, but the layout of the cooling holes is different from one leading edge geometry to another. A broad range of variables is considered including mass flow ratio, coolant density, and jet Reynolds number. Film cooling effectiveness measurements were made in a low speed wind tunnel environment using a flame ionization detector technique and the mass/heat transfer analogy. These measurements significantly extend the insight into the effects of hole geometry on the film cooling characteristics of the leading edge of turbine blades and provide new data for design purposes. The effect of geometry is more important for the case of double row injection where spanwise-averaged film cooling effectiveness is improved by the use of compound angle holes. The spanwise-averaged film cooling effectiveness is higher at lower mass flow ratios and decreases typically as the mass flow ratio increases. At higher mass flow ratios, the newly designed leading edge geometry produces higher spanwise-averaged film cooling effectiveness than the other two geometries investigated thus providing the necessary backflow margin at operating conditions more relevant to gas turbine use. For the case of single row injection, the effects of geometry scale reasonably well when the local mass flow ratio is used in the analysis of the spanwise-averaged film cooling effectiveness immediately downstream of the injection holes
Nanofluids for heat transfer : an engineering approach.
Timofeeva, E. V.; Yu, W.; France, D. M.; Singh, D.; Routbort, J. L.
2011-02-28
An overview of systematic studies that address the complexity of nanofluid systems and advance the understanding of nanoscale contributions to viscosity, thermal conductivity, and cooling efficiency of nanofluids is presented. A nanoparticle suspension is considered as a three-phase system including the solid phase (nanoparticles), the liquid phase (fluid media), and the interfacial phase, which contributes significantly to the system properties because of its extremely high surface-to-volume ratio in nanofluids. The systems engineering approach was applied to nanofluid design resulting in a detailed assessment of various parameters in the multivariable nanofluid systems. The relative importance of nanofluid parameters for heat transfer evaluated in this article allows engineering nanofluids with desired set of properties.
Heat and mass transfer in flames
NASA Technical Reports Server (NTRS)
Faeth, G. M.
1986-01-01
Heat- and mass-transfer processes in turbulent diffusion flames are discussed, considering turbulent mixing and the structure of single-phase flames, drop processes in spray flames, and nonluminous and luminous flame radiation. Interactions between turbulence and other phenomena are emphasized, concentrating on past work of the author and his associates. The conserved-scalar formalism, along with the laminar-flamelet approximation, is shown to provide reasonable estimates of the structure of gas flames, with modest levels of empiricism. Extending this approach to spray flames has highlighted the importance of drop/turbulence interactions; e.g., turbulent dispersion of drops, modification of turbulence by drops, etc. Stochastic methods being developed to treat these phenomena are yielding encouraging results.
Heat and mass transfer in flames
NASA Technical Reports Server (NTRS)
Faeth, G. M.
1986-01-01
Heat- and mass-transfer processes in turbulent diffusion flames are discussed, considering turbulent mixing and the structure of single-phase flames, drop processes in spray flames, and nonluminous and luminous flame radiation. Interactions between turbulence and other phenomena are emphasized, concentrating on past work of the author and his associates. The conserved-scalar formalism, along with the laminar-flamelet approximation, is shown to provide reasonable estimates of the structure of gas flames, with modest levels of empiricism. Extending this approach to spray flames has highlighted the importance of drop/turbulence interactions; e.g., turbulent dispersion of drops, modification of turbulence by drops, etc. Stochastic methods being developed to treat these phenomena are yielding encouraging results.
Submersible pumping system with heat transfer mechanism
Hunt, Daniel Francis Alan; Prenger, F. Coyne; Hill, Dallas D; Jankowski, Todd Andrew
2014-04-15
A submersible pumping system for downhole use in extracting fluids containing hydrocarbons from a well. In one embodiment, the pumping system comprises a rotary induction motor, a motor casing, one or more pump stages, and a cooling system. The rotary induction motor rotates a shaft about a longitudinal axis of rotation. The motor casing houses the rotary induction motor such that the rotary induction motor is held in fluid isolation from the fluid being extracted. The pump stages are attached to the shaft outside of the motor casing, and are configured to impart fluid being extracted from the well with an increased pressure. The cooling system is disposed at least partially within the motor casing, and transfers heat generated by operation of the rotary induction motor out of the motor casing.
HEAT TRANSFER AND TRITIUM PRODUCING SYSTEM
Johnson, E.F.
1962-06-01
This invention related to a circulating lithium-containing blanket system in a neution source hav'ing a magnetic field associated therewith. The blanket serves simultaneously and efficiently as a heat transfer mediunm and as a source of tritium. The blanket is composed of a lithium-6-enriched fused salt selected from the group consisting of lithium nitrite, lithium nitrate, a mixture of said salts, a mixture of each of said salts with lithium oxide, and a mixture of said salts with each other and with lithium oxide. The moderator, which is contained within the blanket in a separate conduit, can be water. A stellarator is one of the neutron sources which can be used in this invention. (AEC)
Low-melting point heat transfer fluid
Cordaro, Joseph G [Oakland, CA; Bradshaw, Robert W [Livermore, CA
2011-04-12
A low-melting point, heat transfer fluid comprising a mixture of LiNO.sub.3, NaNO.sub.3, KNO.sub.3, NaNO.sub.2 and KNO.sub.2 salts where the Li, Na and K cations are present in amounts of about 20-33.5 mol % Li, about 18.6-40 mol % Na, and about 40-50.3 mol % K and where the nitrate and nitrite anions are present in amounts of about 36-50 mol % NO.sub.3, and about 50-62.5 mol % NO.sub.2. These compositions can have liquidus temperatures between 70.degree. C. and 80.degree. C. for some compositions.
Analysis of the heat transfer in double and triple concentric tube heat exchangers
NASA Astrophysics Data System (ADS)
Rădulescu, S.; Negoiţă, L. I.; Onuţu, I.
2016-08-01
The tubular heat exchangers (shell and tube heat exchangers and concentric tube heat exchangers) represent an important category of equipment in the petroleum refineries and are used for heating, pre-heating, cooling, condensation and evaporation purposes. The paper presents results of analysis of the heat transfer to cool a petroleum product in two types of concentric tube heat exchangers: double and triple concentric tube heat exchangers. The cooling agent is water. The triple concentric tube heat exchanger is a modified constructive version of double concentric tube heat exchanger by adding an intermediate tube. This intermediate tube improves the heat transfer by increasing the heat area per unit length. The analysis of the heat transfer is made using experimental data obtained during the tests in a double and triple concentric tube heat exchanger. The flow rates of fluids, inlet and outlet temperatures of water and petroleum product are used in determining the performance of both heat exchangers. Principally, for both apparatus are calculated the overall heat transfer coefficients and the heat exchange surfaces. The presented results shows that triple concentric tube heat exchangers provide better heat transfer efficiencies compared to the double concentric tube heat exchangers.
Methods and problems in heat and mass transfer
NASA Astrophysics Data System (ADS)
Kotliar, Iakov Mikhailovich; Sovershennyi, Viacheslav Dmitrievich; Strizhenov, Dmitrii Sergeevich
The book focuses on the mathematical methods used in heat and mass transfer problems. The theory, statement, and solution of some problems of practical importance in heat and mass transfer are presented, and methods are proposed for solving algebraic, transcendental, and differential equations. Examples of exact solutions to heat and mass transfer equations are given. The discussion also covers some aspects of the development of a mathematical model of turbulent flows.
Flow and heat transfer in microchannels using a microcontinuum approach
Jacobi, A.M. )
1989-11-01
Heat and mass transfer in small channels has many important applications. Recent advances in electronic cooling technology have suggested the use of microchannels for cooling electronic components. The purpose of this note is to employ Eringen's theory to predict how heat transfer may be affected as the classical fluid model breaks down. Such predictions hold not only theoretical importance, but may serve useful in modeling heat transfer in microchannel, or arterioles where the theory has been widely applied.
Liquid jet impingement heat transfer with or without boiling
NASA Astrophysics Data System (ADS)
Ma, C. F.; Gan, Y. P.; Tian, Y. C.; Lei, D. H.; Gomi, T.
1993-03-01
The purpose of this paper is to summarize the important studies in the area of impingement heat transfer with or without phase change, with emphasis on the research conducted at Beijing Polytechnic University mainly with circular jets. Heat transfer characteristics of single phase jets are discussed in detail. Comment is presented on boiling heat transfer of impinging jets for steady and transient states. Some special cooling configurations of two-phase jets are also introduced.
Sensitivity Analysis of the Gap Heat Transfer Model in BISON.
Swiler, Laura Painton; Schmidt, Rodney C.; Williamson, Richard; Perez, Danielle
2014-10-01
This report summarizes the result of a NEAMS project focused on sensitivity analysis of the heat transfer model in the gap between the fuel rod and the cladding used in the BISON fuel performance code of Idaho National Laboratory. Using the gap heat transfer models in BISON, the sensitivity of the modeling parameters and the associated responses is investigated. The study results in a quantitative assessment of the role of various parameters in the analysis of gap heat transfer in nuclear fuel.
In - line determination of heat transfer coefficients in a plate heat exchanger
NASA Astrophysics Data System (ADS)
Sotelo, S. Silva; Domínguez, R. J. Romero
This paper shows an in - line determination of heat transfer coefficients in a plate heat exchanger. Water and aqueous working solution of lithium bromide + ethylene glycol are considered. Heat transfer coefficients are calculated for both fluids. "Type T" thermocouples were used for monitoring the wall temperature in a plate heat exchanger, which is one of the main components in an absorption system. Commercial software Agilent HP Vee Pro 7.5 was used for monitoring the temperatures and for the determination of the heat transfer coefficients. There are not previous works for heat transfer coefficients for the working solution used in this work.
High thermal power density heat transfer. [thermionic converters
NASA Technical Reports Server (NTRS)
Morris, J. F. (Inventor)
1980-01-01
Heat from a high temperature heat pipe is transferred through a vacuum or a gap filled with electrically nonconducting gas to a cooler heat pipe. The heat pipe is used to cool the nuclear reactor while the heat pipe is connected thermally and electrically to a thermionic converter. If the receiver requires greater thermal power density, geometries are used with larger heat pipe areas for transmitting and receiving energy than the area for conducting the heat to the thermionic converter. In this way the heat pipe capability for increasing thermal power densities compensates for the comparatively low thermal power densities through the electrically non-conducting gap between the two heat pipes.
Generator-absorber-heat exchange heat transfer apparatus and method and use thereof in a heat pump
Phillips, Benjamin A.; Zawacki, Thomas S.; Marsala, Joseph
1994-11-29
Numerous embodiments and related methods for generator-absorber heat exchange (GAX) are disclosed, particularly for absorption heat pump systems. Such embodiments and related methods use the working solution of the absorption system for the heat transfer medium.
Heat transfer enhancement by application of nano-powder
NASA Astrophysics Data System (ADS)
Mosavian, M. T. Hamed; Heris, S. Zeinali; Etemad, S. Gh.; Esfahany, M. Nasr
2010-09-01
In this investigation, laminar flow heat transfer enhancement in circular tube utilizing different nanofluids including Al2O3 (20 nm), CuO (50 nm), and Cu (25 nm) nanoparticles in water was studied. Constant wall temperature was used as thermal boundary condition. The results indicate enhancement of heat transfer with increasing nanoparticle concentrations, but an optimum concentration for each nanofluid suspension can be found. Based on the experimental results, metallic nanoparticles show better enhancement of heat transfer coefficient in comparison with oxide particles. The promotions of heat transfer due to utilizing nanoparticles are higher than the theoretical correlation prediction.
Nonlinear Transient Problems Using Structure Compatible Heat Transfer Code
NASA Technical Reports Server (NTRS)
Hou, Gene
2000-01-01
The report documents the recent effort to enhance a transient linear heat transfer code so as to solve nonlinear problems. The linear heat transfer code was originally developed by Dr. Kim Bey of NASA Largely and called the Structure-Compatible Heat Transfer (SCHT) code. The report includes four parts. The first part outlines the formulation of the heat transfer problem of concern. The second and the third parts give detailed procedures to construct the nonlinear finite element equations and the required Jacobian matrices for the nonlinear iterative method, Newton-Raphson method. The final part summarizes the results of the numerical experiments on the newly enhanced SCHT code.
Conjugate Heat Transfer in Porous Cavity: ANN approach
NASA Astrophysics Data System (ADS)
Jafer Kazi1, Mohammed; Yunus Khan, T. M.
2017-08-01
Artificial neural network is a technique to predict the outcome of a function depending on various input parameters that could be either or geometric variables. This technique is widely used in many fields to predict an outcome. The current article discusses the usage of artificial neural network to predict conjugate heat transfer behaviour inside the porous cavity. The artificial neural network is run with neurons placed in multiple layers. The heat transfer inside the porous cavity is predicted in terms of Nusselt number which shows the convective heat transfer in relation to its conduction counterpart. The heat transfer prediction is compared with the results obtained by finite element method.
Ethyl alcohol boiling heat transfer on multilayer meshed surfaces
NASA Astrophysics Data System (ADS)
Dåbek, Lidia; Kapjor, Andrej; Orman, Łukasz J.
2016-06-01
The paper presents the problem of heat transfer enhancement with the application of multilayer metal mesh structures during boiling of ethyl alcohol at ambient pressure. The preparation of samples involved sintering fine copper meshes with the copper base in the reduction atmosphere in order to prevent oxidation of the samples. The experiments included testing up to 4 layers of copper meshes. Significant augmentation of boiling heat transfer is possible, however, considerable number of meshes actually hinders heat transfer conditions and leads to the reduction in the heat flux transferred from the heater surface.
Liquid-Infused Smooth Surface for Improved Condensation Heat Transfer.
Tsuchiya, Hirotaka; Tenjimbayashi, Mizuki; Moriya, Takeo; Yoshikawa, Ryohei; Sasaki, Kaichi; Togasawa, Ryo; Yamazaki, Taku; Manabe, Kengo; Shiratori, Seimei
2017-09-12
Control of vapor condensation properties is a promising approach to manage a crucial part of energy infrastructure conditions. Heat transfer by vapor condensation on superhydrophobic coatings has garnered attention, because dropwise condensation on superhydrophobic surfaces with rough structures leads to favorable heat-transfer performance. However, pinned condensed water droplets within the rough structure and a high thermodynamic energy barrier for nucleation of superhydrophobic surfaces limit their heat-transfer increase. Recently, slippery liquid-infused surfaces (SLIPS) have been investigated, because of their high water sliding ability and surface smoothness originating from the liquid layer. However, even on SLIPS, condensed water droplets are eventually pinned to degrade their heat-transfer properties after extended use, because the rough base layer is exposed as infused liquid is lost. Herein, we report a liquid-infused smooth surface named "SPLASH" (surface with π electron interaction liquid adsorption, smoothness, and hydrophobicity) to overcome the problems derived from the rough structures in previous approaches to obtain stable, high heat-transfer performance. The SPLASH displayed a maximum condensation heat-transfer coefficient that was 175% higher than that of an uncoated substrate. The SPLASH also showed higher heat-transfer performance and more stable dropwise condensation than superhydrophobic surfaces and SLIPS from the viewpoints of condensed water droplet mobility and the thermodynamic energy barrier for nucleation. The effects of liquid-infused surface roughness and liquid viscosity on condensation heat transfer were investigated to compare heat-transfer performance. This research will aid industrial applications using vapor condensation.
Heat transfer coefficient in serpentine coolant passage for CCDTL
Leslie, P.; Wood, R.; Sigler, F.; Shapiro, A.; Rendon, A.
1998-12-31
A series of heat transfer experiments were conducted to refine the cooling passage design in the drift tubes of a coupled cavity drift tube linac (CCDTL). The experimental data were then compared to numerical models to derive relationships between heat transfer rates, Reynold`s number, and Prandtl number, over a range of flow rates. Data reduction consisted of axisymmetric finite element modeling where the heat transfer coefficients were modified to match the experimental data. Unfortunately, the derived relationship is valid only for this specific geometry of the test drift tube. Fortunately, the heat transfer rates were much better (approximately 2.5 times) than expected.
Heat Transfer Variation on Protuberances and Surface Roughness Elements
NASA Technical Reports Server (NTRS)
Henry, Robert C.; Hansman, R. John, Jr.; Breuer, Kenneth S.
1995-01-01
In order to determine the effect of surface irregularities on local convective heat transfer, the variation in heat transfer coefficients on small (2-6 mm diam) hemispherical roughness elements on a flat plate has been studied in a wind funnel using IR techniques. Heat transfer enhancement was observed to vary over the roughness elements with the maximum heat transfer on the upstream face. This heat transfer enhancement increased strongly with roughness size and velocity when there was a laminar boundary layer on the plate. For a turbulent boundary layer, the heat transfer enhancement was relatively constant with velocity, but did increase with element size. When multiple roughness elements were studied, no influence of adjacent roughness elements on heat transfer was observed if the roughness separation was greater than approximately one roughness element radius. As roughness separation was reduced, less variation in heat transfer was observed on the downstream elements. Implications of the observed roughness enhanced heat transfer on ice accretion modeling are discussed.
NASA Technical Reports Server (NTRS)
Fink, Richard
2015-01-01
The increasing use of power electronics, such as high-current semiconductor devices and modules, within space vehicles is driving the need to develop specialty thermal management materials in both the packaging of these discrete devices and the packaging of modules consisting of these device arrays. Developed by Applied Nanotech, Inc. (ANI), CarbAl heat transfer material is uniquely characterized by its low density, high thermal diffusivity, and high thermal conductivity. Its coefficient of thermal expansion (CTE) is similar to most power electronic materials, making it an effective base plate substrate for state-of-the-art silicon carbide (SiC) super junction transistors. The material currently is being used to optimize hybrid vehicle inverter packaging. Adapting CarbAl-based substrates to space applications was a major focus of the SBIR project work. In Phase I, ANI completed modeling and experimentation to validate its deployment in a space environment. Key parameters related to cryogenic temperature scaling of CTE, thermal conductivity, and mechanical strength. In Phase II, the company concentrated on improving heat sinks and thermally conductive circuit boards for power electronic applications.
TACO: a finite element heat transfer code
Mason, W.E. Jr.
1980-02-01
TACO is a two-dimensional implicit finite element code for heat transfer analysis. It can perform both linear and nonlinear analyses and can be used to solve either transient or steady state problems. Either plane or axisymmetric geometries can be analyzed. TACO has the capability to handle time or temperature dependent material properties and materials may be either isotropic or orthotropic. A variety of time and temperature dependent loadings and boundary conditions are available including temperature, flux, convection, and radiation boundary conditions and internal heat generation. Additionally, TACO has some specialized features such as internal surface conditions (e.g., contact resistance), bulk nodes, enclosure radiation with view factor calculations, and chemical reactive kinetics. A user subprogram feature allows for any type of functional representation of any independent variable. A bandwidth and profile minimization option is also available in the code. Graphical representation of data generated by TACO is provided by a companion post-processor named POSTACO. The theory on which TACO is based is outlined, the capabilities of the code are explained, the input data required to perform an analysis with TACO are described. Some simple examples are provided to illustrate the use of the code.
Heat transfer characteristics of igniter output plumes
NASA Astrophysics Data System (ADS)
Evans, N. A.; Durand, N. A.
Seven types of pyrotechnic igniters were each mounted at one end of a closed cylindrical bore hole representative of the center hole in a thermal battery. Measurements of local bore wall temperature, T(sub w), using commercially available, fast response (10 microsec) sheathed chromel-constantan thermocouples allowed calculation of local heat transfer rates, q, and wall heat flows, Q. The principal charge constituents of all these igniters were titanium and potassium perchlorate, while three types also contained barium styphnate as an ignition sensitizer. Igniter closure disc materials included glass-ceramic, glass, metal (plain, scored, with and without capture cone), and kapton/RTV. All igniters produced the lowest values of T(sub w) and q at the beginning of the bore, and, except for the igniter with the kapton/RTV closure disc, these quantities increased with distance along the bore. For igniters containing only titanium/potassium perchlorate, the rates of increase of Q along the bore length, compared with those for T(sub w) and q, were generally lower and more variable. The inclusion of barium styphnate produced rates of change in Q that were essentially constant to the end of the bore. The highest overall average wall temperatures were achieved by two igniter types with metal closure discs and no capture cone. No clear correlation was established between peak bore pressure and maximum wall temperature.
Generator-absorber-heat exchange heat transfer apparatus and method and use thereof in a heat pump
Phillips, Benjamin A.; Zawacki, Thomas S.
1996-12-03
Numerous embodiments and related methods for generator-absorber heat exchange (GAX) are disclosed, particularly for absorption heat pump systems. Such embodiments and related methods use the working solution of the absorption system for the heat transfer medium. A combination of weak and rich liquor working solution is used as the heat transfer medium.
Personalized recommendation based on heat bidirectional transfer
NASA Astrophysics Data System (ADS)
Ma, Wenping; Feng, Xiang; Wang, Shanfeng; Gong, Maoguo
2016-02-01
Personalized recommendation has become an increasing popular research topic, which aims to find future likes and interests based on users' past preferences. Traditional recommendation algorithms pay more attention to forecast accuracy by calculating first-order relevance, while ignore the importance of diversity and novelty that provide comfortable experiences for customers. There are some levels of contradictions between these three metrics, so an algorithm based on bidirectional transfer is proposed in this paper to solve this dilemma. In this paper, we agree that an object that is associated with history records or has been purchased by similar users should be introduced to the specified user and recommendation approach based on heat bidirectional transfer is proposed. Compared with the state-of-the-art approaches based on bipartite network, experiments on two benchmark data sets, Movielens and Netflix, demonstrate that our algorithm has better performance on accuracy, diversity and novelty. Moreover, this method does better in exploiting long-tail commodities and cold-start problem.
Heat transfer enhancement -- the maturing of second-generation heat transfer technology
Bergles, A.E.
1997-01-01
This paper is basically the text of the Kern Lecture for 1991 (the 1990 Kern Award). The paper begins with some remarks about Dr. Kern. By way of introduction to heat transfer enhancement, historical notes and the evolution of literature in this area are presented. Comments are made about the increasing practical applications of enhancement technology. Developments in single-phase convection are presented, with particular emphasis on offset strip fins and twisted-tape inserts. Pool boiling and flow boiling (particularly microfin tubes) are then considered in some detail. It is concluded that enhancement represents a powerful technology to improve heat exchanger performance.
The heat transfer coefficients of the heating surface of 300 MWe CFB boiler
NASA Astrophysics Data System (ADS)
Wu, Haibo; Zhang, Man; Lu, Qinggang; Sun, Yunkai
2012-08-01
A study of the heat transfer about the heating surface of three commercial 300 MWe CFB boilers was conducted in this work. The heat transfer coefficients of the platen heating surface, the external heat exchanger (EHE) and cyclone separator were calculated according to the relative operation data at different boiler loads. Moreover, the heat transfer coefficient of the waterwall was calculated by heat balance of the hot circuit of the CFB boiler. With the boiler capacity increasing, the heat transfer coefficients of these heating surface increases, and the heat transfer coefficient of the water wall is higher than that of the platen heating surface. The heat transfer coefficient of the EHE is the highest in high boiler load, the heat transfer coefficient of the cyclone separator is the lowest. Because the fired coal is different from the design coal in No.1 boiler, the ash content of the fired coal is much lower than that of the design coal. The heat transfer coefficients which calculated with the operation data are lower than the previous design value and that is the reason why the bed temperature is rather high during the boiler operation in No.1 boiler.
Banerjee, S.; Hassan, Y.A.
1995-09-01
Condensation in the presence of noncondensible gases plays an important role in the nuclear industry. The RELAP5/MOD3 thermal hydraulic code was used to study the ability of the code to predict this phenomenon. Two separate effects experiments were simulated using this code. These were the Massachusetts Institute of Technology`s (MIT) Pressurizer Experiment, the MIT Single Tube Experiment. A new iterative approach to calculate the interface temperature and the degraded heat transfer coefficient was developed and implemented in the RELAP5/MOD3 thermal hydraulic code. This model employs the heat transfer simultaneously. This model was found to perform much better than the reduction factor approach. The calculations using the new model were found to be in much better agreement with the experimental values.
Heat transfer research on supercritical water flow upward in tube
Li, H. B.; Yang, J.; Gu, H. Y.; Zhao, M.; Lu, D. H.; Zhang, J. M.; Wang, F.; Zhang, Y.
2012-07-01
The experimental research of heat transfer on supercritical water has been carried out on the supercritical water multipurpose test loop with a 7.6 mm upright tube. The experimental data of heat transfer is obtained. The experimental results of thermal-hydraulic parameters on flow and heat transfer of supercritical water show that: Heat transfer enhancement occurs when the fluid temperature reaches pseudo-critical point with low mass flow velocity, and peters out when the mass flow velocity increases. The heat transfer coefficient and Nusselt number decrease with the heat flux or system pressure increases, and increase with the increasing of mass flow velocity. The wall temperature increases when the mass flow velocity decreases or the system pressure increases. (authors)
Study of a high performance evaporative heat transfer surface
NASA Technical Reports Server (NTRS)
Saaski, E. W.; Hamasaki, R. H.
1977-01-01
An evaporative surface is described for heat pipes and other two-phase heat transfer applications that consists of a hybrid composition of V-grooves and capillary wicking. Characteristics of the surface include both a high heat transfer coefficient and high heat flux capability relative to conventional open-faced screw thread surfaces. With a groove density of 12.6 cm/1 and ammonia working fluid, heat transfer coefficients in the range of 1 to 2 W/sq cm have been measured along with maximum heat flux densities in excess of 20 W/sq cm. A peak heat transfer coefficient in excess of 2.3 W/sq cm was measured with a 37.8 cm/1 hybrid surface.
Numerical Heat Transfer Model for a Heat-Barrier-Piston Engine with Hypergolic Combustion.
1986-02-01
MODEL FOR A HEAT-BARRIER-PISTON ENGINE WITH I HYPERGOLIC COMBUSTION David A. Blank, LCD. , USN UNITED STATES NAVAL ACADEMY Annapolis, MD 21402 February...1fflOMG STATEMENT 1 ^ELECTE I MAR 101986 Dub~ -- t I~ NUMERICAL HEAT TRANSFER MODEL FOR A 4 - HEAT-BARRIER-PISTON ENGINE WITH HYPERGOLI C COMBUSTION...COVERED Numerical Heat Transfer Model for a Heat- IIBarrier-Piston Engine with Hypergolic Combustion Progress, 19a2-1986 I. .29AFORMINC, ORG. REPORT
Capillary Pumped Heat Transfer (CHT) Experiment
NASA Technical Reports Server (NTRS)
Hallinan, Kevin P.; Allen, J. S.
1998-01-01
The operation of Capillary Pumped Loops (CPL's) in low gravity has generally been unable to match ground-based performance. The reason for this poorer performance has been elusive. In order to investigate the behavior of a CPL in low-gravity, an idealized, glass CPL experiment was constructed. This experiment, known as the Capillary-driven Heat Transfer (CHT) experiment, was flown on board the Space Shuttle Columbia in July 1997 during the Microgravity Science Laboratory mission. During the conduct of the CHT experiment an unexpected failure mode was observed. This failure mode was a result of liquid collecting and then eventually bridging the vapor return line. With the vapor return line blocked, the condensate was unable to return to the evaporator and dry-out subsequently followed. The mechanism for this collection and bridging has been associated with long wavelength instabilities of the liquid film forming in the vapor return line. Analysis has shown that vapor line blockage in present generation CPL devices is inevitable. Additionally, previous low-gravity CPL tests have reported the presence of relatively low frequency pressure oscillations during erratic system performance. Analysis reveals that these pressure oscillations are in part a result of long wavelength instabilities present in the evaporator pores, which likewise lead to liquid bridging and vapor entrapment in the porous media. Subsequent evaporation to the trapped vapor increases the vapor pressure. Eventually the vapor pressure causes ejection of the bridged liquid. Recoil stresses depress the meniscus, the vapor pressure rapidly increases, and the heated surface cools. The process then repeats with regularity.
Two dimensional finite element heat transfer models for softwood
Hongmei Gu; John F. Hunt
2004-01-01
The anisotropy of wood creates a complex problem for solving heat and mass transfer problems that require analyses be based on fundamental material properties of the wood structure. Most heat transfer models use average thermal properties across either the radial or tangential directions and have not differentiated the effects of cellular alignment, earlywood/latewood...
Improving Heat Transfer Performance of Printed Circuit Boards
NASA Technical Reports Server (NTRS)
Schatzel, Donald V.
2009-01-01
This paper will explore the ability of printed circuit boards laminated with a Carbon Core Laminate to transfer heat vs. standard printed circuit boards that use only thick layers of copper. The paper will compare the differences in heat transfer performance of printed circuit boards with and without CCL.
Improving Heat Transfer Performance of Printed Circuit Boards
NASA Technical Reports Server (NTRS)
Schatzel, Donald V.
2009-01-01
This paper will explore the ability of printed circuit boards laminated with a Carbon Core Laminate to transfer heat vs. standard printed circuit boards that use only thick layers of copper. The paper will compare the differences in heat transfer performance of printed circuit boards with and without CCL.
Mixed convection heat transfer in concave and convex channels
Moukalled, F.; Doughan, A.; Acharya, S.
1997-07-01
Mixed convection heat transfer studies in the literature have been primarily confined to pipe and rectangular channel geometry's. In some applications, however, heat transfer in curved channels may be of interest (e.g., nozzle and diffuser shaped passages in HVAC systems, fume hoods, chimneys, bell-shaped or dome-shaped chemical reactors, etc.). A numerical investigation of laminar mixed convection heat transfer of air in concave and convex channels is presented. Six different channel aspects ratios (R/L = 1.04, 1.25, 2.5, 5, 10, and {infinity}) and five different values of Gr/Re{sup 2} (Gr/Re{sup 2} = 0, 0.1, 1, 3, 5) are considered. Results are displayed in terms of streamline and isotherm plots, velocity and temperature profiles, and local and average Nusselt number estimates. Numerical predictions reveal that compared to straight channels of equal height, concave channels of low aspect ratio have lower heat transfer at relatively low values of Gr/Re{sup 2} and higher heat transfer at high values of Gr/Re{sup 2}. When compared to straight channels of equal heated length, concave channels are always found to have lower heat transfer and for all values of Gr/Re{sup 2}. On the other hand, predictions for convex channels revealed enhancement in heat transfer compared to straight channels of equal height and/or equal heated length for all values of Gr/Re{sup 2}.
Influence of oscillation-induced diffusion on heat transfer in a uniformly heated channel
Siegel, R. )
1987-02-01
The purpose of this note is to show that, for forced convection in slow laminar flow in a channel with uniform heat addition, the effect of flow oscillation will be to reduce the channel heat transfer coefficient. This is becausethe heat addition along the channel wall produces an increasing fluid temperature along the channel length. The flow oscillations interacting with this positive temperature gradient will induce a heat flow back toward the channel inlet. This will tend to inhibit the heat transfer process and will raise the wall temperature required to transfer away a given amount of heating at the channel wall.
Li, Zhi-Hui; Jiang, Pei-Xue; Zhao, Chen-Ru; Zhang, Yu.
2010-11-15
The convection heat transfer characteristics of supercritical CO{sub 2} in a vertical circular tube of 2 mm inner diameter were investigated experimentally for pressures ranging from 78 to 95 bar, inlet temperatures from 25 to 40 C, and inlet Reynolds numbers from 3800 to 20,000. The effects of the heat flux, thermo-physical properties, buoyancy and thermal acceleration on the convection heat transfer were analyzed. The experimental results show that for high inlet Reynolds numbers (e.g. Re = 9000) and high heat fluxes, a significant local deterioration and recovery of the heat transfer was found for upward flows but not for downward flows. Comparison of the experimental data for inlet Reynolds numbers from 3800 to 20,000 with some well-known empirical correlations showed large differences especially when the heat transfer deteriorates and then recovers when the effect of buoyancy is significant. The experimental data was used to develop modified local turbulent Nusselt number correlations for supercritical CO{sub 2} flowing in vertical small circular tubes. (author)
NASA Astrophysics Data System (ADS)
Sarafraz, M. M.; Peyghambarzadeh, S. M.; Alavifazel, S. A.
2012-10-01
Experimental studies on enhancing the pool boiling heat transfer coefficient of binary dilute mixtures of water/glycerol, water/MEG (Mono-ethylene glycol) and water/DEG (di-ethylene glycol) have been carried out. Some particular endothermic chemical reactions related to ammonium salts were used to enhance the pool boiling heat transfer coefficient, simultaneously with occurrence of pool boiling heat transfer. Accordingly, 100 g of Ammonium nitrate, ammonium perborate and Ammonium sulfate were selected to dissolve into mixtures. High and extreme solution enthalpies of each of these ammonium salt powders are employed to reduce the surface temperature around the horizontal cylinder locally. Results demonstrated that presence of ammonium salts into the mixtures deteriorates the surface temperature of cylinder and as the result, higher pool boiling heat transfer coefficient is reported for tested solutions. Results are also reported and compared for different ammonium salts to find the influence of inducing different enthalpies of solution on pool boiling heat transfer coefficient. Obtained results also indicated that presence of endothermic reaction besides the pool boiling heat transfer enhances the heat transfer coefficients in comparison with nucleate pool boiling phenomenon solely.
Boyer, B.D.; Parlatan, Y.; Slovik, G.C.
1995-09-01
RELAP5 MOD3.1.1 is being used to simulate Loss of Coolant Accidents (LOCA) for the Simplified Boiling Water Reactor (SBWR) being proposed by General Electric (GE). One of the major components associated with the SBWR is the Passive Containment Cooling System (PCCS) which provides the long-term heat sink to reject decay heat. The RELAP5 MOD3.1.1 code is being assessed for its ability to represent accurately the PCCS. Data from the Phase 1, Step 1 Heat Transfer Tests performed at Toshiba`s Gravity-Driven Integral Full-Height Test for Passive Heat Removal (GIRAFFE) facility will be used for assessing the ability of RELAP5 to model condensation in the presence of noncondensables. The RELAP5 MOD3.1.1 condensation model uses the University of California at Berkeley (UCB) correlation developed by Vierow and Schrock. The RELAP5 code uses this heat transfer coefficient with the gas velocity effect multiplier being limited to 2. This heat transfer option was used to analyze the condensation heat transfer in the GIRAFFE PCCS heat exchanger tubes in the Phase 1, Step 1 Heat Transfer Tests which were at a pressure of 3 bar and had a range of nitrogen partial pressure fractions from 0.0 to 0.10. The results of a set of RELAP5 calculations at these conditions were compared with the GIRAFFE data. The effects of PCCS cell noding on the heat transfer process were also studied. The UCB correlation, as implemented in RELAP5, predicted the heat transfer to {plus_minus}5% of the data with a three--node model. The three-node model has a large cell in the entrance region which smeared out the entrance effects on the heat transfer, which tend to overpredict the condensation. Hence, the UCB correlation predicts condensation heat transfer correlation implemented in the code must be removed to allow for accurate calculations with smaller cell sizes.
Heat transfer characteristics of a linear solar collector.
Seraphin, B O
1973-02-01
The heat transfer characteristics of a linear solar energy collector are calculated as functions of dimensions, spectral quality of the selective absorber surface, optical flux concentration of the optical configuration, and thermal parameters and flow rate of the heat transfer medium. Carnot efficiency, exit temperature, and an upper limit to the amount of heat extracted are determined for systems in which liquid sodium serves as the heat transfer medium. The performance is evaluated for selective absorber surfaces representing the state of the art as well as for surfaces requiring a more mature thin-film technology.
Simultaneous velocity-surface heat transfer behavior of turbulent spots
NASA Astrophysics Data System (ADS)
Sabatino, D.; Smith, C. R.
2002-06-01
The properties of artificially initiated turbulent spots in a heated laminar boundary layer were investigated in a water channel facility. The instantaneous velocity field and surface heat transfer were determined simultaneously over a temporal sequence using a technique that combines traditional particle image velocimetry and thermochromic liquid crystal temperature measurements. The correlated results indicate that the highest surface heat transfer occurs in the trailing region of the spot where only the near-wall fluid is energetic. The results suggest that the "body" of the spot entrains, and subsequently recirculates, warm surface fluid within the spot, which reduces the effective heat transfer.
Fem Formulation of Coupled Partial Differential Equations for Heat Transfer
NASA Astrophysics Data System (ADS)
Ameer Ahamad, N.; Soudagar, Manzoor Elahi M.; Kamangar, Sarfaraz; Anjum Badruddin, Irfan
2017-08-01
Heat Transfer in any field plays an important role for transfer of energy from one region to another region. The heat transfer in porous medium can be simulated with the help of two partial differential equations. These equations need an alternate and relatively easy method due to complexity of the phenomenon involved. This article is dedicated to discuss the finite element formulation of heat transfer in porous medium in Cartesian coordinates. A triangular element is considered to discretize the governing partial differential equations and matrix equations are developed for 3 nodes of element. Iterative approach is used for the two sets of matrix equations involved representing two partial differential equations.
Quantitative Global Heat Transfer in a Mach-6 Quiet Tunnel
NASA Technical Reports Server (NTRS)
Sullivan, John P.; Schneider, Steven P.; Liu, Tianshu; Rubal, Justin; Ward, Chris; Dussling, Joseph; Rice, Cody; Foley, Ryan; Cai, Zeimin; Wang, Bo; Woodiga, Sudesh
2012-01-01
This project developed quantitative methods for obtaining heat transfer from temperature sensitive paint (TSP) measurements in the Mach-6 quiet tunnel at Purdue, which is a Ludwieg tube with a downstream valve, moderately-short flow duration and low levels of heat transfer. Previous difficulties with inferring heat transfer from TSP in the Mach-6 quiet tunnel were traced to (1) the large transient heat transfer that occurs during the unusually long tunnel startup and shutdown, (2) the non-uniform thickness of the insulating coating, (3) inconsistencies and imperfections in the painting process and (4) the low levels of heat transfer observed on slender models at typical stagnation temperatures near 430K. Repeated measurements were conducted on 7 degree-half-angle sharp circular cones at zero angle of attack in order to evaluate the techniques, isolate the problems and identify solutions. An attempt at developing a two-color TSP method is also summarized.
Experimental study of heat transfer to falling liquid films
NASA Astrophysics Data System (ADS)
Fagerholm, N. E.; Kivioja, K.; Ghazanfari, A. R.; Jaervinen, E.
1985-12-01
This project was initiated in order to obtain more knowledge about thermal design of falling film heat exchangers and to find methods to improve heat transfer in film flow. A short literature survey of film flow characteristics and heat transfer is presented. An experimental apparatus designed and built for studying falling film evaporation is described. The first experiments were made with smooth Cu tube 25/22 mm and refrigerant R114 as evaporating liquid. A significant amount of droplet entrainment was observed during the tests. The measured average heat transfer coefficient varied from 1000 to 1800 W/m K when Re=1300 to 11000 respectively and when the transfer mode is surface evaporation. This could be predicted accurately with the experimental correlation of Chun and Seban. When nucleate boiling is dominant the heat transfer could be predicted well with pool boiling correlation of VDI-84.
A review of NASA combustor and turbine heat transfer research
NASA Technical Reports Server (NTRS)
Rudey, R. A.; Graham, R. W.
1984-01-01
The thermal design of the combustor and turbine of a gas turbine engine poses a number of difficult heat transfer problems. The importance of improved prediction techniques becomes more critical in anticipation of future generations of gas turbine engines which will operate at higher cycle pressure and temperatures. Research which addresses many of the complex heat transfer processes holds promise for yielding significant improvements in prediction of metal temperatures. Such research involves several kinds of program including: (1) basic experiments which delineate the fundamental flow and heat transfer phenomena that occur in the hot sections of the gas turbine but at low enthalpy conditions; (2) analytical modeling of these flow and heat transfer phenomena which results from the physical insights gained in experimental research; and (3) verification of advanced prediction techniques in facilities which operate near the real engine thermodynamic conditions. In this paper, key elements of the NASA program which involves turbine and combustor heat transfer research will be described and discussed.
Heat transfer between elastic solids with randomly rough surfaces.
Volokitin, A I; Lorenz, B; Persson, B N J
2010-01-01
We study the heat transfer between elastic solids with randomly rough surfaces.We include both the heat transfer from the area of real contact, and the heat transfer between the surfaces in the non-contact regions.We apply a recently developed contact mechanics theory, which accounts for the hierarchical nature of the contact between solids with roughness on many different length scales. For elastic contact, at the highest (atomic) resolution the area of real contact typically consists of atomic (nanometer) sized regions, and we discuss the implications of this for the heat transfer. For solids with very smooth surfaces, as is typical in many modern engineering applications, the interfacial separation in the non-contact regions will be very small, and for this case we show the importance of the radiative heat transfer associated with the evanescent electromagnetic waves which exist outside of all bodies.
Heat transfer in a longitudinal glow discharge
NASA Astrophysics Data System (ADS)
Yunusov, R. F.
2017-01-01
This article is devoted to the experimental study of heat transfer in a longitudinal glow discharge. The discharge was ignited in the discharge chamber (DC), consisting of a glass tube 10 mm in diameter and two electrodes. Copper electrodes were placed in the side branches, so that the average distance between them was 9 cm. The discharge pressure was varied in the range of P = (2.5 – 8.5) kPa. The air flow rate was varied from zero to G = 0.06 g / s. Current was varied in the range of I = (30-80) mA. Current-voltage characteristics of the discharge had falling form, and the voltage was varied in the range of U = (1-2) kV. The temperature of neutral particles in the plasma glow discharge was measured by six thermocouples, which were insertedon radius of DC. The aim of the article was to compare achieved experiment data with theoretical studies: recombination and diffusion plasma models.
Dual circuit embossed sheet heat transfer panel
Morgan, G.D.
1984-02-21
A heat transfer panel provides redundant cooling for fusion reactors or the like environment requiring low-mass construction. Redundant cooling is provided by two independent cooling circuits, each circuit consisting of a series of channels joined to inlet and outlet headers. The panel comprises a welded joinder of two full-size and two much smaller partial-size sheets. The first full-size sheet is embossed to form first portions of channels for the first and second circuits, as well as a header for the first circuit. The second full-sized sheet is then laid over and welded to the first full-size sheet. The first and second partial-size sheets are then overlaid on separate portions of the second full-sized sheet, and are welded thereto. The first and second partial-sized sheets are embossed to form inlet and outlet headers, which communicate with channels of the second circuit through apertures formed in the second full-sized sheet. 6 figs.
Dual circuit embossed sheet heat transfer panel
Morgan, Grover D.
1984-01-01
A heat transfer panel provides redundant cooling for fusion reactors or the like environment requiring low-mass construction. Redundant cooling is provided by two independent cooling circuits, each circuit consisting of a series of channels joined to inlet and outlet headers. The panel comprises a welded joinder of two full-size and two much smaller partial-size sheets. The first full-size sheet is embossed to form first portions of channels for the first and second circuits, as well as a header for the first circuit. The second full-sized sheet is then laid over and welded to the first full-size sheet. The first and second partial-size sheets are then overlaid on separate portions of the second full-sized sheet, and are welded thereto. The first and second partial-sized sheets are embossed to form inlet and outlet headers, which communicate with channels of the second circuit through apertures formed in the second full-sized sheet.
Direct contact heat transfer for thermal energy storage
NASA Astrophysics Data System (ADS)
Wright, J. D.
1982-03-01
Direct contact heat exchange offers the potential for increased efficiency and lower heat transfer costs in a variety of thermal energy storage systems. SERI models of direct contact heat transfer based on literature information identified dispersed phase drop size, the mechanism of heat transfer within the drop, and dispersed phase holdup as the parameters controlling direct contact system performance. Tests were defined and equipment constructed to provide independent determination of drop size, heat transfer mechanism, and hold up. Further experiments are needed to conclusively determine whether the salt in a salt hydrate melt acts to block internal circulation. The potential of low temperature oil/salt hydrate latent heat storage systems is being evaluated in the laboratory.
Direct contact heat transfer for thermal energy storage
NASA Astrophysics Data System (ADS)
Wright, J. D.
1980-11-01
Direct contact heat exchange offers the potential for increased efficiency and lower heat transfer costs in a variety of thermal energy storage systems. Models of direct contact heat transfer based on literature information identified dispersed phase drop size, the mechanism of heat transfer within the drop, and dispersed phase holdup as the parameters controlling direct contact system performance. Tests were defined and equipment constructed to provide independent determination of drop size, heat transfer mechanism, and hold up. Experiments with heptane dispersed in water are described. The velocity at which drop formation changes from dropwise to jetting was overpredicted by all literature correlations. Further experiments are needed to conclusively determine whether the salt in a salt hydrate melt acts to block internal circulation. In addition, the potential of low temperature oil/salt hydrate latent heat storage systems is evaluated in the laboratory.
Conjugate heat transfer with the entropic lattice Boltzmann method.
Pareschi, G; Frapolli, N; Chikatamarla, S S; Karlin, I V
2016-07-01
A conjugate heat-transfer model is presented based on the two-population entropic lattice Boltzmann method. The present approach relies on the extension of Grad's boundary conditions to the two-population model for thermal flows, as well as on the appropriate exact conjugate heat-transfer condition imposed at the fluid-solid interface. The simplicity and efficiency of the lattice Boltzmann method (LBM), and in particular of the entropic multirelaxation LBM, are retained in the present approach, thus enabling simulations of turbulent high Reynolds number flows and complex wall boundaries. The model is validated by means of two-dimensional parametric studies of various setups, including pure solid conduction, conjugate heat transfer with a backward-facing step flow, and conjugate heat transfer with the flow past a circular heated cylinder. Further validations are performed in three dimensions for the case of a turbulent flow around a heated mounted cube.
Heat Transfer Analysis of the NAHBE Piston Cap,
1977-09-01
r~~~ U____________ ____s HEAT TRANSFER ANALYSIS :~ OF THE NAHBE PISTON CAP* Engineering and Wea pons Report EW-l1—77...transfer variations in thecap of a nodified piston engine (NN~BE) was made. The objective was to estimatethe regenerative heating effect d~e to the cap...ABSTRACT The piston modification for the NAHBE (Naval Academy Heat Bal ance Engine ) consists of a cap which extends above the standard piston used
Applications of Infrared Thermography in Convective Heat Transfer.
1986-03-01
INFRARED THERMOGRAPHY IN CONVECTIVE HEAT TRANSFER by Timothy M. SpenceVX March 1986 Thesis Advisor: R.H. Nunn Approved for public release...Include Security Classfication) APPLICATIONS OF INFRARED THERMOGRAPHY IN CONVECTIVE HEAT TRANSFER !2 PERSONAL AUTHOR(S) Spence, Timothy M. a TYPE...I18 SUBJECT TERMS (Continue on reverse if necessary and identify by block number) P:ELD GROUP SUB-GROUP Infrared Thermography ; TVC Convective Heat
Laser Measurement Of Convective-Heat-Transfer Coefficient
NASA Technical Reports Server (NTRS)
Porro, A. Robert; Hingst, Warren R.; Chriss, Randall M.; Seablom, Kirk D.; Keith, Theo G., Jr.
1994-01-01
Coefficient of convective transfer of heat at spot on surface of wind-tunnel model computed from measurements acquired by developmental laser-induced-heat-flux technique. Enables non-intrusive measurements of convective-heat-transfer coefficients at many points across surfaces of models in complicated, three-dimensional, high-speed flows. Measurement spot scanned across surface of model. Apparatus includes argon-ion laser, attenuator/beam splitter electronic shutter infrared camera, and subsystem.
Heat transfer from aluminum surfaces to pool boiling He I
Huang, Y.; Van Sciver, S.W.
1996-12-31
Heat transfer measurements between different aluminum surfaces and pool boiling He I at 4.21 K are reported. The samples are contained in a channel configuration similar to what might be found in a large bath cooled superconducting magnet. Results include heat transfer coefficients in the nucleate and film boiling regimes as well as values for the peak nucleate and minimum film boiling heat flux. The effects of sample orientation and surface condition are also studied.
Predicting spacecraft multilayer insulation performance from heat transfer measurements
NASA Technical Reports Server (NTRS)
Stimpson, L. D.; Hagemeyer, W. A.
1974-01-01
Multilayer insulation (MLI) ideally consists of a series of radiation shields with low-conductivity spacers. When MLI blankets were installed on cryogenic tanks or spacecraft, a large discrepancy between the calorimeter measurements and the performance of the installed blankets was discovered. It was found that discontinuities such as exposed edges coupled with high lateral heat transfer created 'heat leaks' which overshadowed the basic heat transfer of the insulation. Approaches leading to improved performance predictions of MLI units are discussed.
Laser Measurement Of Convective-Heat-Transfer Coefficient
NASA Technical Reports Server (NTRS)
Porro, A. Robert; Hingst, Warren R.; Chriss, Randall M.; Seablom, Kirk D.; Keith, Theo G., Jr.
1994-01-01
Coefficient of convective transfer of heat at spot on surface of wind-tunnel model computed from measurements acquired by developmental laser-induced-heat-flux technique. Enables non-intrusive measurements of convective-heat-transfer coefficients at many points across surfaces of models in complicated, three-dimensional, high-speed flows. Measurement spot scanned across surface of model. Apparatus includes argon-ion laser, attenuator/beam splitter electronic shutter infrared camera, and subsystem.
Heat-Transfer Head For Stirling-Cycle Machine
NASA Technical Reports Server (NTRS)
Emigh, Stuart G.; Lehmann, Gregory A.; Noble, Jack E.
1995-01-01
New common heat-transfer head for two cylinders of opposed-cylinder Stirling-cycle machine performs function formerly performed by two heat acceptors-one for each cycle. Simplifies structure of machine and increases efficiency of operation by reducing resistance to flow of working gas and/or increasing transfer of heat to or from working gas during flow between compression and expansion spaces of machine.
Three-Dimensional Modelling of Heat Transfer from Slab Floors
1989-07-01
a general change in heat transfer rate. Effects of thermal diffusivity, and lower boundary condition variation were small (on the order of 10%) for...ground surface conditions, foundation design, and floor shape/size are esseatial elcmnts rf a general change in heat transfer rate. N.Effec es of...11 5 111-12. Change in floor heat loss due to substitution of zero flux lower boundary for fixed temperature lower
Enhanced two phase flow in heat transfer systems
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.
Some observations on the historical development of conduction heat transfer
NASA Astrophysics Data System (ADS)
Cheng, Kwo Chang
An attempt is made to obtain historical perspectives on the development of the mathematical theory of heat conduction considering Newton's law of cooling (1701) and its close connection with Fourier's work from 1807 to 1822 resulting in his epoch-making treatise on "The Analytical Theory of Heat". Fourier was the principal architect of the heat conduction theory. Fourier's work established a new methodology for the formulation and solution of physical problems, based on partial differential equations and marked a major turning point in the history of physics. The developments in the periods 1822 to 1900 and 1900 to 1950 are also briefly reviewed as are the classical (analytical) and numerical methods of solution for heat conduction problems. The analogy in heat, momentum, and mass transfer for transport phenomena is discussed. A list of recent conduction heat transfer books is presented to show the scope of recent developments. Some observations on conduction heat transfer are noted.
Heat transfer to the adsorbent in solar adsorption cooling device
NASA Astrophysics Data System (ADS)
Pilat, Peter; Patsch, Marek; Papucik, Stefan; Vantuch, Martin
2014-08-01
The article deals with design and construction of solar adsorption cooling device and with heat transfer problem in adsorber. The most important part of adsorption cooling system is adsorber/desorber containing adsorbent. Zeolith (adsorbent) type was chosen for its high adsorption capacity, like a coolant was used water. In adsorber/desorber occur, at heating of adsorbent, to heat transfer from heat change medium to the adsorbent. The time required for heating of adsorber filling is very important, because on it depend flexibility of cooling system. Zeolith has a large thermal resistance, therefore it had to be adapted the design and construction of adsorber. As the best shows the tube type of adsorber with double coat construction. By this construction is ensured thin layer of adsorbent and heating is quick in all volume of adsorbent. The process of heat transfer was experimentally measured, but for comparison simulated in ANSYS, too.
Anode heat transfer in a constricted tube arc.
NASA Technical Reports Server (NTRS)
Lukens, L. A.; Incropera, F. P.
1971-01-01
The complex energy exchange mechanisms occurring on the most severely heated component of an arc constrictor, the anode, have been investigated. Measurements performed to determine the anode heat flux for a cascade, atmospheric argon arc of the Maecker type are described. The results are used to check the validity of an existing anode heat transfer model.
Two-Dimensional Heat Transfer in a Heterogeneous Fracture Network
NASA Astrophysics Data System (ADS)
Gisladottir, V. R.; Roubinet, D.; Tartakovsky, D. M.
2015-12-01
Geothermal energy harvesting requires extraction and injection of geothermal fluid. Doing so in an optimal way requires a quantitative understanding of site-specific heat transfer between geothermal fluid and the ambient rock. We develop a heat transfer particle-tracking approach to model that interaction. Fracture-network models of heat transfer in fractured rock explicitly account for the presence of individual fractures, ambient rock matrix, and fracture-matrix interfaces. Computational domains of such models span the meter scale, whereas fracture apertures are on the millimeter scale. The computations needed to model these multi-scale phenomenon can be prohibitively expensive, even for methods using nonuniform meshes. Our approach appreciably decreases the computational costs. Current particle-tracking methods usually assume both infinite matrix and one-dimensional (1D) heat transfer in the matrix blocks. They rely on 1D analytical solutions for heat transfer in a single fracture, which can lead to large predictive errors. Our two-dimensional (2D) heat transfer simulation algorithm is mesh-free and takes into account both longitudinal and transversal heat conduction in the matrix. It uses a probabilistic model to transfer particle to the appropriate neighboring fracture unless it returns to the fracture of origin or remains in the matrix. We use this approach to look at the impact of a fracture-network topology (e.g. the importance of smaller scale fractures), as well as the matrix block distribution on the heat transport in heterogeneous fractured rocks.
Enhanced heat transfer in the entrance region of microchannels
Gui, F.; Scaringe, R.P.
1995-12-31
A detailed heat transfer analysis has been performed on the data from previously-reported experiments (Rahman and Gui 1993) to investigate the characteristics of high-heat-flux (10{sup 6} W/m{sup 2}) microchannel cooling in electronic chips. The use of microchannel directly etched into a silicon wafer has shortened the cooling path and improved the performance by significantly minimizing the thickness of the heat transfer layer. Experimental convective heat transfer coefficients (up to 45 kW/m{sup 2} K) for low temperature single-phase flow was an order of magnitude higher than conventional heat transfer coefficients; and reached the level of two-phase boiling heat transfer. The flow and heat transfer modes and their transitions in the experiments were investigated. The influence of the microchannel passage geometry, fluid property variation, and the fluid flow mode on the local Nusselt number in the entrance region of the microchannel has been analyzed. The analysis indicates that the significant enhancement obtained in microchannel cooling results from four key aspects: a thinner thermal boundary layer, entry effects, the roughness of the channel, and strong pre-existing turbulence at the inlet. The preexisting turbulence delayed the formation of the thermal boundaries, thereby increasing the entry effects on heat transfer. The critical Re shifted from 2,300 to 1,400 in microchannels, possibly due to the wall roughness which does not affect the Re{sub c} otherwise in normal size tubes.
CFD Extraction of Heat Transfer Coefficient in Cryogenic Propellant Tanks
NASA Technical Reports Server (NTRS)
Yang, H. Q.; West, Jeff
2015-01-01
Current reduced-order thermal model for cryogenic propellant tanks is based on correlations built for flat plates collected in the 1950's. The use of these correlations suffers from inaccurate geometry representation; inaccurate gravity orientation; ambiguous length scale; and lack of detailed validation. This study uses first-principles based CFD methodology to compute heat transfer from the tank wall to the cryogenic fluids and extracts and correlates the equivalent heat transfer coefficient to support reduced-order thermal model. The CFD tool was first validated against available experimental data and commonly used correlations for natural convection along a vertically heated wall. Good agreements between the present prediction and experimental data have been found for flows in laminar as well turbulent regimes. The convective heat transfer between the tank wall and cryogenic propellant, and that between the tank wall and ullage gas were then simulated. The results showed that the commonly used heat transfer correlations for either vertical or horizontal plate over-predict heat transfer rate for the cryogenic tank, in some cases by as much as one order of magnitude. A characteristic length scale has been defined that can correlate all heat transfer coefficients for different fill levels into a single curve. This curve can be used for the reduced-order heat transfer model analysis.
Efficient Heat and Mass Transfer Formulations for Oil Shale Retorting
NASA Astrophysics Data System (ADS)
Parker, J. C.; Zhang, F.
2007-12-01
A mathematical model for oil shale retorting is described that considers kerogen pyrolysis, oil coking, residual carbon gasification, carbonate mineral decomposition, water-gas shift, and phase equilibria reaction. Reaction rate temperature-dependence is described by Arrhenius kinetics. Fractured rock is modeled as a bi-continuum consisting of fracture porosity in which advective and dispersive gas and heat transport occur, and rock matrix in which diffusive mass transport and thermal conduction occur. Heat transfer between fracture and matrix regions is modeled either by a partial differential equation for spherical conduction or by a linear first-order heat transfer formulation. Mass transfer is modeled in an analogous manner or assuming local equilibrium. First-order mass and heat transfer coefficients are computed by a theoretical model from fundamental rock matrix properties. The governing equations are solved using a 3-D finite element formulation. Simulations of laboratory retort experiments and hypothetical problems indicated thermal disequilibrium to be the dominant factor controlling retort reactions. Simulation accuracy was unaffected by choice of mass transfer formulation. However, computational effort to explicitly simulate diffusive mass transfer in the rock matrix increased computational effort by more than an order of magnitude compared with first-order mass transfer or equilibrium analyses. A first-order heat transfer approximation of thermal conduction can be used without significant loss of accuracy if the block size and/or heating rate are not too large, as quantified by a proposed dimensionless heating rate.
Analytical approach for the effect of melting heat transfer on nanofluid heat transfer
NASA Astrophysics Data System (ADS)
Sheikholeslami, M.; Nimafar, M.; Ganji, D. D.
2017-09-01
In this article, the impact of melting heat transfer on nanofluid flow in the presence of Lorentz forces is reported. Different shapes of nanoparticles are considered. The impacts of Joule heating, viscous dissipation and thermal radiation are added in the governing equations. The Homotopy Analysis Method (HAM) is selected to solve Ordinary Differential Equations (ODEs). The roles of nanofluid volume fraction, shape of the nanoparticles, Hartmann number, porosity parameter, melting parameter, Eckert number are presented graphically. The results reveal that choosing a platelet shape leads to the maximum Nusselt number. The temperature reduces with the rise of the melting parameter but velocity increases with the increase of the melting parameter. Nu augments with the increase of the Lorentz forces while it reduces with the augment of porosity and melting parameters.
Simulation of Heat Transfer of Heating-System and Water Pipelines Under Northern Conditions
NASA Astrophysics Data System (ADS)
Stepanov, A. V.; Egorova, G. N.
2016-09-01
A mathematical model of joint laying of water pipelines and of city-block heating-system pipelines is considered. The effect of radiation on the process of combined heat transfer in the heat insulation jacket between the construction elements is investigated. The results of mathematical simulation of heat losses with account of the radiant component are given.
NASA Astrophysics Data System (ADS)
Fazeli, Seyyed Abdolreza; Hosseini Hashemi, Seyyed Mohammad; Zirakzadeh, Hootan; Ashjaee, Mehdi
2012-02-01
In this paper, heat transfer characteristics of a miniature heat sink cooled by SiO 2-water nanofluids were investigated both experimentally and numerically. The heat sink was fabricated from aluminum and insulated by plexiglass cover plates. The heat sink consisted of an array of 4 mm diameter circular channels with a length of 40 mm. Tests were performed while inserting a 180 W/cm 2 heat flux to the bottom of heat sink and Reynolds numbers ranged from 400 to 2000. The three-dimensional heat transfer characteristics of the heat sink were analyzed numerically by solving conjugate heat transfer problem of thermally and hydrodynamically developing fluid flow. Experimental results showed that dispersing SiO 2 nanoparticles in water significantly increased the overall heat transfer coefficient while thermal resistance of heat sink was decreased up to 10%. Numerical results revealed that channel diameter, as well as heat sink height and number of channels in a heat sink have significant effects on the maximum temperature of heat sink. Finally, an artificial neural network (ANN) was used to simulate the heat sink performance based on these parameters. It was found that the results of ANN are in excellent agreement with the mathematical simulation and cover a wider range for evaluation of heat sink performance.
Heat Transfer Performances of Pool Boiling on Metal-Graphite Composite Surfaces
NASA Technical Reports Server (NTRS)
Zhang, Nengli; Chao, David F.; Yang, Wen-Jei
2000-01-01
Nucleate boiling, especially near the critical heat flux (CHF), can provide excellent economy along with high efficiency of heat transfer. However, the performance of nucleate boiling may deteriorate in a reduced gravity environment and the nucleate boiling usually has a potentially dangerous characteristic in CHF regime. That is, any slight overload can result in burnout of the boiling surface because the heat transfer will suddenly move into the film-boiling regime. Therefore, enhancement of nucleate boiling heat transfer becomes more important in reduced gravity environments. Enhancing nucleate boiling and critical heat flux can be reached using micro-configured metal-graphite composites as the boiling surface. Thermocapillary force induced by temperature difference between the graphite-fiber tips and the metal matrix, which is independent of gravity, will play an important role in bubble detachment. Thus boiling heat transfer performance does not deteriorate in a reduced-gravity environment. Based on the existing experimental data, and a two-tier theoretical model, correlation formulas are derived for nucleate boiling on the copper-graphite and aluminum-graphite composite surfaces, in both the isolated and coalesced bubble regimes. Experimental studies were performed on nucleate pool boiling of pentane on cooper-graphite (Cu-Gr) and aluminum-graphite (Al-Gr) composite surfaces with various fiber volume concentrations for heat fluxes up to 35 W per square centimeter. It is revealed that a significant enhancement in boiling heat transfer performance on the composite surfaces is achieved, due to the presence of micro-graphite fibers embedded in the matrix. The onset of nucleate boiling (the isolated bubble regime) occurs at wall superheat of about 10 C for the Cu-Gr surface and 15 C for the Al-Gr surface, much lower than their respective pure metal surfaces. Transition from an isolated bubble regime to a coalesced bubble regime in boiling occurs at a superheat of
Heat Transfer Performances of Pool Boiling on Metal-Graphite Composite Surfaces
NASA Technical Reports Server (NTRS)
Zhang, Nengli; Chao, David F.; Yang, Wen-Jei
2000-01-01
Nucleate boiling, especially near the critical heat flux (CHF), can provide excellent economy along with high efficiency of heat transfer. However, the performance of nucleate boiling may deteriorate in a reduced gravity environment and the nucleate boiling usually has a potentially dangerous characteristic in CHF regime. That is, any slight overload can result in burnout of the boiling surface because the heat transfer will suddenly move into the film-boiling regime. Therefore, enhancement of nucleate boiling heat transfer becomes more important in reduced gravity environments. Enhancing nucleate boiling and critical heat flux can be reached using micro-configured metal-graphite composites as the boiling surface. Thermocapillary force induced by temperature difference between the graphite-fiber tips and the metal matrix, which is independent of gravity, will play an important role in bubble detachment. Thus boiling heat transfer performance does not deteriorate in a reduced-gravity environment. Based on the existing experimental data, and a two-tier theoretical model, correlation formulas are derived for nucleate boiling on the copper-graphite and aluminum-graphite composite surfaces, in both the isolated and coalesced bubble regimes. Experimental studies were performed on nucleate pool boiling of pentane on cooper-graphite (Cu-Gr) and aluminum-graphite (Al-Gr) composite surfaces with various fiber volume concentrations for heat fluxes up to 35 W per square centimeter. It is revealed that a significant enhancement in boiling heat transfer performance on the composite surfaces is achieved, due to the presence of micro-graphite fibers embedded in the matrix. The onset of nucleate boiling (the isolated bubble regime) occurs at wall superheat of about 10 C for the Cu-Gr surface and 15 C for the Al-Gr surface, much lower than their respective pure metal surfaces. Transition from an isolated bubble regime to a coalesced bubble regime in boiling occurs at a superheat of
Air-side flow and heat transfer in compact heat exchangers: A discussion of enhancement mechanisms
Jacobi, A.M.; Shah, R.K.
1998-10-01
The behavior of air flows in complex heat exchanger passages is reviewed with a focus on the heat transfer effects of boundary-layer development, turbulence, spanwise and streamwise vortices, and wake management. Each of these flow features is discussed for the plain, wavy, and interrupted passages found in contemporary compact heat exchanger designs. Results from the literature are used to help explain the role of these mechanisms in heat transfer enhancement strategies.
Heat transfer during heat sterilization and cooling processes of canned products
NASA Astrophysics Data System (ADS)
Dincer, I.
In this paper, an analysis of transient heat transfer during heat sterilization and cooling processes of a cylindrical canned product is presented. In the analysis, most practical case including the boundary condition of third kind (i.e., convection boundary condition, leading to 0.1 <= Bi <= 100) was employed. A simple analytical model for determining effective heat transfer coefficients for such products is developed. For the heat sterilization process, heating coefficient is incorporated into heat transfer coefficient model. An experimental study was performed to measure the thermal center temperatures of the short-cylindrical canned products (i.e., Tuna fish) during heat sterilization at the retort medium temperatures of 115∘C and 121∘C, and during cooling process at 16∘C. The effective heat transfer coefficient model used the experimental temperature data. Using these effective heat transfer coefficients the center temperature distributions were calculated and compared with the experimental temperature distributions. Agreement was found considerably high. The results of the present study indicate that the heat-transfer analysis technique and heat-transfer coefficient model are reliable, and can provide accurate results for such problems.
Heat transfer during the boiling of liquids in heat pipe wicks
NASA Technical Reports Server (NTRS)
Gontarev, Yu. K.; Navruzov, Yu. V.; Prisnyakov, V. F.; Serebryanskiy, N.
1987-01-01
Data in the literature on heat transfer in the case of nucleate boiling of various liquids in the wicks of heat pipes are reviewed. It is shown that none of the known analytical relationships can be used to generalize, with sufficient accuracy, the experimental data found in the literature. It is further shown that the exponent of the specific heat flux in the heat transfer law changes as a function of the liquid and wick properties. A relationship is obtained which generalizes experimental data for heat transfer agents of moderate temperatures (water, acetone, ethanol, and R-11 and R-113 coolants) and ammonia.
A one-dimensional heat transfer model for parallel-plate thermoacoustic heat exchangers.
de Jong, J A; Wijnant, Y H; de Boer, A
2014-03-01
A one-dimensional (1D) laminar oscillating flow heat transfer model is derived and applied to parallel-plate thermoacoustic heat exchangers. The model can be used to estimate the heat transfer from the solid wall to the acoustic medium, which is required for the heat input/output of thermoacoustic systems. The model is implementable in existing (quasi-)1D thermoacoustic codes, such as DeltaEC. Examples of generated results show good agreement with literature results. The model allows for arbitrary wave phasing; however, it is shown that the wave phasing does not significantly influence the heat transfer.
Radiative heat transfer in low-dimensional systems -- microscopic mode
NASA Astrophysics Data System (ADS)
Woods, Lilia; Phan, Anh; Drosdoff, David
2013-03-01
Radiative heat transfer between objects can increase dramatically at sub-wavelength scales. Exploring ways to modulate such transport between nano-systems is a key issue from fundamental and applied points of view. We advance the theoretical understanding of radiative heat transfer between nano-objects by introducing a microscopic model, which takes into account the individual atoms and their atomic polarizabilities. This approach is especially useful to investigate nano-objects with various geometries and give a detailed description of the heat transfer distribution. We employ this model to study the heat exchange in graphene nanoribbon/substrate systems. Our results for the distance separations, substrates, and presence of extended or localized defects enable making predictions for tailoring the radiative heat transfer at the nanoscale. Financial support from the Department of Energy under Contract No. DE-FG02-06ER46297 is acknowledged.
Heat transfer and flow characteristics on a gas turbine shroud.
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 For Subcooled Flow Boiling In Hypervapotron Configuration
Chena, Peipei; Wua, Wen; Jonesa, Barclay G.; Newell, Ty A
2006-07-01
This work reports on experimental studies that examine subcooled boiling on the enhanced heat transfer surface of hypervapotron structures. The use of simulant fluid (refrigerant R134a) instead of prototypic water allows examination of a full range of subcooled boiling, including up to critical heat flux (CHF). The experimental results are compared to Bjorge's model and Kandlikar's heat transfer correlation in the subcooled boiling region. It is found that the fully developed boiling curve has a slope of about 2.96 (q{sup {approx}} {delta}{sub sat} {sup 2}.{sup 96}), which shows good agreement with Bjorge's recognition for flat surface channels. In addition, Kandlikar's correlation is also able to predict the heat transfer coefficient for the range from net vapor generation (NVG) to the fully developed boiling region with acceptable accuracy. However, the heat transfer curve shows a significant deviation when subcooled boiling approaches CHF. (authors)
Heat transfer near spacer grids in rod bundles
Yoder, G.L.
1985-01-01
Heat transfer data from several sources have been assembled which show the effect of spacer grids on local heat transfer within a rod bundle. Both single phase (air and steam) data and two phase (steam/water) data show heat transfer augmentation in the grid region. Heat transfer improvement immediately beyond the grid ranges from a few percent to over fifty percent in these experiments, depending on flow conditions. The data are examined using several nondimensional parameters which relate the above effects to known quantities. The relative effect of the grid on local heat transfer is altered by both the Reynolds number and blockage ratio. Twenty to thirty hydraulic diameters are required before the local effect of the grid dissipates. Locally, both the single phase and two phase data show the same trends. Comparison of the single and two phase data also shown some differences. Some film boiling data indicate that an altered heat transfer regime may exist near the grid. High rod heat transfer coefficients at the grid locations indicate either a rewet of the rods or at least a change from film boiling to transition boiling near the spacer. The comparison also indicates that the film boiling data is affected on a global as well as local basis. This is due to the effect of the grid on the liquid distribution.
Boiling and quenching heat transfer advancement by nanoscale surface modification.
Hu, Hong; Xu, Cheng; Zhao, Yang; Ziegler, Kirk J; Chung, J N
2017-07-21
All power production, refrigeration, and advanced electronic systems depend on efficient heat transfer mechanisms for achieving high power density and best system efficiency. Breakthrough advancement in boiling and quenching phase-change heat transfer processes by nanoscale surface texturing can lead to higher energy transfer efficiencies, substantial energy savings, and global reduction in greenhouse gas emissions. This paper reports breakthrough advancements on both fronts of boiling and quenching. The critical heat flux (CHF) in boiling and the Leidenfrost point temperature (LPT) in quenching are the bottlenecks to the heat transfer advancements. As compared to a conventional aluminum surface, the current research reports a substantial enhancement of the CHF by 112% and an increase of the LPT by 40 K using an aluminum surface with anodized aluminum oxide (AAO) nanoporous texture finish. These heat transfer enhancements imply that the power density would increase by more than 100% and the quenching efficiency would be raised by 33%. A theory that links the nucleation potential of the surface to heat transfer rates has been developed and it successfully explains the current finding by revealing that the heat transfer modification and enhancement are mainly attributed to the superhydrophilic surface property and excessive nanoscale nucleation sites created by the nanoporous surface.
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.
Radiation Heat Transfer Procedures for Space-Related Applications
NASA Technical Reports Server (NTRS)
Chai, John C.
2000-01-01
Over the last contract year, a numerical procedure for combined conduction-radiation heat transfer using unstructured grids has been developed. As a result of this research, one paper has been published in the Numerical Heat Transfer Journal. One paper has been accepted for presentation at the International Center for Heat and Mass Transfer's International Symposium on Computational Heat Transfer to be held in Australia next year. A journal paper is under review by my NASA's contact. A conference paper for the ASME National Heat Transfer conference is under preparation. In summary, a total of four (4) papers (two journal and two conference) have been published, accepted or are under preparation. There are two (2) to three (3) more papers to be written for the project. In addition to the above publications, one book chapter, one journal paper and six conference papers have been published as a result of this project. Over the last contract year, the research project resulted in one Ph.D. thesis and partially supported another Ph.D. student. My NASA contact and myself have formulated radiation heat transfer procedures for materials with different indices of refraction and for combined conduction-radiation heat transfer. We are trying to find other applications for the procedures developed under this grant.
Radiative heat transfer in the extreme near field
NASA Astrophysics Data System (ADS)
Kim, Kyeongtae; Song, Bai; Fernández-Hurtado, Víctor; Lee, Woochul; Jeong, Wonho; Cui, Longji; Thompson, Dakotah; Feist, Johannes; Reid, M. T. Homer; García-Vidal, Francisco J.; Cuevas, Juan Carlos; Meyhofer, Edgar; Reddy, Pramod
2015-12-01
Radiative transfer of energy at the nanometre length scale is of great importance to a variety of technologies including heat-assisted magnetic recording, near-field thermophotovoltaics and lithography. Although experimental advances have enabled elucidation of near-field radiative heat transfer in gaps as small as 20-30 nanometres (refs 4, 5, 6), quantitative analysis in the extreme near field (less than 10 nanometres) has been greatly limited by experimental challenges. Moreover, the results of pioneering measurements differed from theoretical predictions by orders of magnitude. Here we use custom-fabricated scanning probes with embedded thermocouples, in conjunction with new microdevices capable of periodic temperature modulation, to measure radiative heat transfer down to gaps as small as two nanometres. For our experiments we deposited suitably chosen metal or dielectric layers on the scanning probes and microdevices, enabling direct study of extreme near-field radiation between silica-silica, silicon nitride-silicon nitride and gold-gold surfaces to reveal marked, gap-size-dependent enhancements of radiative heat transfer. Furthermore, our state-of-the-art calculations of radiative heat transfer, performed within the theoretical framework of fluctuational electrodynamics, are in excellent agreement with our experimental results, providing unambiguous evidence that confirms the validity of this theory for modelling radiative heat transfer in gaps as small as a few nanometres. This work lays the foundations required for the rational design of novel technologies that leverage nanoscale radiative heat transfer.
An analytical and experimental investigation of melting heat transfer
NASA Astrophysics Data System (ADS)
Wen, C.; Sheffield, J. W.; O'dell, M. P.; Leland, J. E.
1988-01-01
A computational model is presented for the prediction of the heat transfer between a heat transfer fluid (HTF) and a phase change material (PCM) of a latent heat storage unit. Two models of flow, hydrodynamically fully developed flow and developing flow, of the HTF were proposed in this study. A two-dimensional enthalpy method was used for the computation of the phase change heat transfer in the PCM. A fully implicit finite difference scheme was utilized for the calculation of convective heat transfer in the HTF. The unknown time dependent boundary condition between the HTF and the PCM was found iteratively. The predictions are substantiated by their excellent agreement with experimental data. Factors which affect the heat transfer rates between the HTF and the PCM were studied numerically for both hydrodynamically fully developed flow and developing flow. It is found that the Nusselt number is significantly increased by the developing temperature profiles. The developing velocity profiles also will increase the Nusselt number. However, the influence on Nusselt number due to the developing temperature profiles. Other factors which affect the Nusselt number are discussed. The heat transfer of this latent heat storage unit was also studied experimentally. The experimental results were compared with the numerical results for P116, a sun wax.
Cryogenic apparatus for study of near-field heat transfer
Kralik, T.; Hanzelka, P.; Musilova, V.; Srnka, A.; Zobac, M.
2011-05-15
For bodies spaced in vacuum at distances shorter than the wavelength of the thermal radiation, radiative heat transfer substantially increases due to the contribution of evanescent electromagnetic waves. Experimental data on heat transfer in near-field regime are scarce. We have designed a cryogenic apparatus for the study of heat transfer over microscopic distances between metallic and non-metallic surfaces. Using a mechanical positioning system, a planeparallel gap between the samples, concentric disks, each 35 mm in diameter, is set and varied from 10{sup 0} to 10{sup 3} {mu}m. The heat transferred from the hot (10 - 100 K) to the cold sample ({approx}5 K) sinks into a liquid helium bath through a thermal resistor, serving as a heat flux meter. Transferred heat power within {approx}2 nW/cm{sup 2} and {approx}30 {mu}W/cm{sup 2} is derived from the temperature drop along the thermal resistor. For tungsten samples, the distance of the near-field effect onset was inversely proportional to temperature and the heat power increase was observed up to three orders of magnitude greater than the power of far-field radiative heat transfer.
Nanoscale heat transfer in the head-disk interface for heat assisted magnetic recording
NASA Astrophysics Data System (ADS)
Wu, Haoyu; Xiong, Shaomin; Canchi, Sripathi; Schreck, Erhard; Bogy, David
2016-02-01
Laser heating has been introduced in heat-assisted magnetic recording in order to reduce the magnetic coercivity and enable data writing. However, the heat flow inside a couple of nanometers head-disk gap is still not well understood. An experimental stage was built for studying heat transfer in the head-disk interface (HDI) and the heat-induced instability of the HDI. A laser heating system is included to produce a heated spot on the disk at the position of the slider. A floating air bearing slider is implemented in the stage for sensing the temperature change of the slider due to the heat transfer from the disk by the use of an embedded contact sensor, and the gap between the two surfaces is controlled by the use of a thermal fly-height control actuator. By using this system, we explore the dependency of the heat transfer on the gap spacing as well as the disk temperature.
Wall-to-suspension heat transfer in circulating fluidized beds
Wirth, K.E.
1995-12-31
The wall-to-suspension heat transfer in circulating fluidized beds depends on the fluid mechanics immediately near the wall and on the thermal properties of the gas used. Experimental investigations of circulating fluidized beds of low dimensionless pressure gradients with different solid particles like bronze, glass and polystyrene at ambient temperatures showed no influence of the conductivity and the heat capacity of the solids on the heat transfer coefficient. Consequently the heat transfer coefficient in the form of the dimensionless Nusselt number can be described by the dimensionless numbers which characterize the gas-solid-flow near the wall. These numbers are the Archimedes number and the pressure drop-number. The last number relates the cross-sectional average solids concentration to the solids concentration at minimum fluidization condition. With the aid of a model of segregated vertical gas-solid flow, the flow pattern in the wall region can be calculated and thus the wall heat transfer which depends only on heat conduction in the gas and on the convective heat transfer by the gas. With elevated suspension temperatures, radiation contributes additionally to the heat transfer. When the solids concentration is low, the effect of the radiation on the heat transfer is high. Increasing solids concentration results in a decrease of the radiation effect due to the wall being shielded from the radiation of the hot particles in the core region by the cold solids clusters moving down the wall. A simple correlation is presented for calculating the wall-to-suspension heat transfer in circulating fluidized beds.
Jackson, J. D.; Jiang, P. X.; Liu, B.
2012-07-01
This paper is concerned with buoyancy-influenced turbulent convective heat transfer in vertical tubes for conditions where the physical properties vary strongly with temperature as in fluids at supercritical pressure in the pseudocritical temperature region. An extended physically-based, semi-empirical model is described which has been developed to account for the extreme non-uniformity of properties which can be present in such fluids and lead to strong influences of buoyancy which cause the mean flow and turbulence fields to be modified in such a manner that has a very profound effect on heat transfer. Data for both upward and downward flow from experiments using carbon dioxide at supercritical pressure (8.80, MPa, p/pc=1.19) in a uniformly heated tube of internal diameter 2 mm and length 290 mm, obtained under conditions of strong non-uniformity of fluid properties, are being correlated and fitted using an approach based on the model. It provides a framework for describing the complex heat transfer behaviour which can be encountered in such experiments by means of an equation of simple form. Buoyancy-induced impairment and enhancement of heat transfer is successfully reproduced by the model. Similar studies are in progress using experimental data for both carbon dioxide and water from other sources. The aim is to obtain an in-depth understanding of the mechanisms by which deterioration of heat transfer might arise in sensitive applications involving supercritical pressure fluids, such as high pressure, water-cooled reactors operating above the critical pressure. (authors)
A Compact Remote Heat Transfer Device for Space Cryocoolers
NASA Astrophysics Data System (ADS)
Yan, T.; Zhao, Y.; Liang, T.
In this paper a compact remote heat transfer device (CRHD) for cryocoolers is proposed. This device is especially attractive in cases where cryocoolers are not easy to set near the heat source, generally the infrared sensor. The CRHD is designed on basis of the concept of loop heat pipes, while the primary evaporator is located near the cryocooler cold head and a simple tube-in-tube secondary evaporator is remotely located and thermally connected with the heat source for cooling. With such a device a cooling power of 1 W is achieved across a heat transfer distance of about 2 m. The major problem of this device is the low heat transfer efficiency (1 W of net cooling power at the cost of about 7 W of cooling power from the cryocooler), and in the future a secondary wicked evaporator will be used instead of the tube-in-tube evaporator in order to improve the efficiency.
A review on boiling heat transfer enhancement with nanofluids
2011-01-01
There has been increasing interest of late in nanofluid boiling and its use in heat transfer enhancement. This article covers recent advances in the last decade by researchers in both pool boiling and convective boiling applications, with nanofluids as the working fluid. The available data in the literature is reviewed in terms of enhancements, and degradations in the nucleate boiling heat transfer and critical heat flux. Conflicting data have been presented in the literature on the effect that nanofluids have on the boiling heat-transfer coefficient; however, almost all researchers have noted an enhancement in the critical heat flux during nanofluid boiling. Several researchers have observed nanoparticle deposition at the heater surface, which they have related back to the critical heat flux enhancement. PMID:21711794
Determination of the heat transfer coefficients in porous media
Kim, L.V.
1994-06-01
The process of transpiration cooling is considered. Methods are suggested for estimating the volumetric coefficient of heat transfer with the use of a two-temperature model and the surface heat transfer coefficient at entry into a porous wall. The development of new technology under conditions of increasing heat loads puts the search for effective methods of heat transfer enhancement in the forefront of theoretical investigations. One of the promising trends in the solution of this problem is the use of porous materials (PM) in the elements of power units. For thermal protection against convective or radiative heat fluxes, the method of transpiration cooling is successfully used. The mechanism operative in the thermal protection involves the injection of a coolant through a porous medium to produce a screen over the contour of a body in a flow for removing heat energy from the skeleton of the porous material.
A review on boiling heat transfer enhancement with nanofluids.
Barber, Jacqueline; Brutin, David; Tadrist, Lounes
2011-04-04
There has been increasing interest of late in nanofluid boiling and its use in heat transfer enhancement. This article covers recent advances in the last decade by researchers in both pool boiling and convective boiling applications, with nanofluids as the working fluid. The available data in the literature is reviewed in terms of enhancements, and degradations in the nucleate boiling heat transfer and critical heat flux. Conflicting data have been presented in the literature on the effect that nanofluids have on the boiling heat-transfer coefficient; however, almost all researchers have noted an enhancement in the critical heat flux during nanofluid boiling. Several researchers have observed nanoparticle deposition at the heater surface, which they have related back to the critical heat flux enhancement.
NASA Astrophysics Data System (ADS)
Hamid, Rohana Abdul; Nazar, Roslinda; Pop, Ioan
2016-11-01
The problem of stagnation-point flow and heat transfer with the effect of the blowing from species transfer over an impermeable shrinking sheet is studied. The governing boundary layer equations are transformed into the ordinary differential equations using the similarity transformations which are then solved numerically using the bvp4c function in Matlab. The focus of this study is the effect of the blowing parameter to the velocity of the flow, the rate of heat transfer and the mass of species transfer over a flat surface of shrinking sheet. From the numerical results, it is found that the blowing parameter substantially affects the flow, heat and mass transfer characteristics.
Heat transfer to liquid and supercritical helium in superconducting rotors
Nakajima, R.; Sato, K.; Miyaike, K.; Kumagai, M. ); Kobayashi, Y. )
1992-12-01
This paper reports on cooling designs of superconducting generator rotors which are quite important for maintaining a stable superconducting state of field windings, and it is essential to comprehend the heat transfer characteristics of helium in rotating fields. Experiments were carried out using a large-scale rotating cryostat with a cold rotor diameter of approximately 800 mm. The heat transfer characteristics of liquid and supercritical helium under conditions of gravitational and centrifugal acceleration fields (maximum: approx. 3000 g at the refrigerant outer side in the rotor) with heat-transfer surfaces horizontal upward facing and perpendicular to such fields, radial and axial channels, and dummy winding cooling surfaces were obtained.
Experiments on heat transfer in a cryogenic engine thrust chamber
NASA Astrophysics Data System (ADS)
Sugathan, N.; Srinivasan, K.; Srinivasa Murthy, S.
1993-04-01
Tests are conducted on a cryogenic engine using liquid oxygen as oxidizer and gaseous hydrogen as fuel with water as a coolant. The coolant flow passage of the thrust chamber is of milled channel configuration. Measured heat transfer results compare well with those predicted by a thermal analysis using the standard Bartz correlation and the Hess and Kunz correlation for hot gas side and coolant side heat transfer coefficients, respectively. This confirms the conclusions of a recent theoretical study by the authors in which a comparison of various heat transfer correlations was made.
Convective heat transfer in buildings: Recent research results
NASA Astrophysics Data System (ADS)
Bauman, F. S.; Gadgil, A.; Kammerud, R. C.; Altmayer, E.; Nansteel, M.
1982-04-01
Small scale water filled enclosures were used to study convective heat transfer in buildings. The convective processes investigated are: (1) natural convective heat transfer between room surfaces and the adjacent air; (2) natural convective heat transfer between adjacent rooms through a doorway or other openings; and (3) forced convection between the building and its external environment (such as, wind driven ventilation through windows, doors, or other openings). Results for surface convection coefficients are compared with existing ASHRAE coorelations and differences of as much as 20% are observed. Numerical simulations of wind driven natural ventilation exhibit good qualitative agreement with published wind tunnel data.
Heat transfer with very high free-stream turbulence and heat transfer with streamwise vortices
NASA Technical Reports Server (NTRS)
Moffat, Robert J.; Maciejewski, Paul; Eaton, John K.; Pauley, Wayne
1987-01-01
Two experimental programs related to augmentation of heat transfer by complex flow characteristics are reviewed. The first program deals with very high turbulence (up to 63 percent) which was shown to result in Stanton numbers as much as five times the expected values. Results from a number of trials show that fixing the free stream velocity, x-Reynolds number, turbulence intensity and integral length scale does not fix the Stanton number. Two such cases were found in which the Stanton number of one was 40 percent larger than the other. Mean velocity and mean temperature profiles are presented, as well as profiles of turbulence intensity within the boundary layer. The second program deals with vortices originating at bluff bodies and traveling downstream embedded in the wall boundary layer. Velocity vector maps from the boundary layers and distributions of Stanton number on the wall are presented for three types of bodies: square, cylindrical and teardrop. The heat transfer and velocity maps do not show evidence of the expected horseshoe vortices but, instead, show a strong common flow up vortex pair. The fluid mechanic mechanism responsible for this secondary flow field has not yet been identified.
Experimental free convection heat transfer from inclined square cylinders
NASA Astrophysics Data System (ADS)
Ali, Mohamed
2016-10-01
Natural convection from axisymmetric objects such as vertical or horizontal cylinders and spheres are two dimensional. However, for inclined circular or noncircular cylinders the flow and heat transfer is three dimensional and hence more complex and needs more attention. This study investigates the steady state mechanism of natural convection from inclined square cylinders in air. Five different cylinders of 1 m length, 8 × 8, 7 × 7, 6 × 6, 4 × 4 and 2.5 × 2.5 cm2 cross sections are used. The cylinders are heated using inserted heating element of 6 mm in diameter. Self-adhesive thermocouples are used at the upper, bottom and at one side of the cylinders for temperature measurement. Three inclination angles to the horizontal 30, 45 and 60o are used for each cylinder with uniform heat flux boundary conditions. For each cylinder, about ten heat fluxes are used to generate the heat transfer data. Local and average heat transfer coefficient is determined for each cylinder at each inclination angle for each uniform heat flux. Laminar and transition to turbulent regimes are obtained and characterized. Local critical axial distance where heat transfer coefficient changes the mode is obtained for each heat flux. Local and averaged Nusselt numbers are correlated with the modified Rayleigh numbers for all angles.
Experimental free convection heat transfer from inclined square cylinders
NASA Astrophysics Data System (ADS)
Ali, Mohamed
2017-05-01
Natural convection from axisymmetric objects such as vertical or horizontal cylinders and spheres are two dimensional. However, for inclined circular or noncircular cylinders the flow and heat transfer is three dimensional and hence more complex and needs more attention. This study investigates the steady state mechanism of natural convection from inclined square cylinders in air. Five different cylinders of 1 m length, 8 × 8, 7 × 7, 6 × 6, 4 × 4 and 2.5 × 2.5 cm2 cross sections are used. The cylinders are heated using inserted heating element of 6 mm in diameter. Self-adhesive thermocouples are used at the upper, bottom and at one side of the cylinders for temperature measurement. Three inclination angles to the horizontal 30, 45 and 60o are used for each cylinder with uniform heat flux boundary conditions. For each cylinder, about ten heat fluxes are used to generate the heat transfer data. Local and average heat transfer coefficient is determined for each cylinder at each inclination angle for each uniform heat flux. Laminar and transition to turbulent regimes are obtained and characterized. Local critical axial distance where heat transfer coefficient changes the mode is obtained for each heat flux. Local and averaged Nusselt numbers are correlated with the modified Rayleigh numbers for all angles.
Analysis of radiative heat transfer impact in cross-flow tube and fin heat exchangers
NASA Astrophysics Data System (ADS)
Hanuszkiewicz-Drapała, Małgorzata; Bury, Tomasz; Widziewicz, Katarzyna
2016-03-01
A cross-flow, tube and fin heat exchanger of the water - air type is the subject of the analysis. The analysis had experimental and computational form and was aimed for evaluation of radiative heat transfer impact on the heat exchanger performance. The main element of the test facility was an enlarged recurrent segment of the heat exchanger under consideration. The main results of measurements are heat transfer rates, as well as temperature distributions on the surface of the first fin obtained by using the infrared camera. The experimental results have been next compared to computational ones coming from a numerical model of the test station. The model has been elaborated using computational fluid dynamics software. The computations have been accomplished for two cases: without radiative heat transfer and taking this phenomenon into account. Evaluation of the radiative heat transfer impact in considered system has been done by comparing all the received results.
Heat transfer through an extended surface containing He II
Van Sciver, S.W.
1999-02-01
A semi-analytic solution for the heat transfer process between a He II pressurized bath and a saturated tube-type heat exchanger is presented. The problem is modeled with an extended surface heat transfer formulation analogous to that in conventional conduction. The process is governed by Kapitza conductance and counterflow within the bulk fluid in the tube. The resulting nonlinear differential equation may be integrated for the special case of constant properties, yielding a simple solution applicable to design and analysis of practical heat exchangers.
A flux correction method for the conjugate heat transfer problem
He, M.; Bishop, P.J.; Minardi, A.; Kassab, A.J.
1995-12-31
A computational method, the flux correction method, is proposed to deal with the conjugate heat transfer problem, which uses a coupled FDM/BEM iteration scheme. The convective heat transfer in the fluid is solved using the BEM. The two solutions are coupled by enforcing continuity of temperature and heat flux at the solid-fluid interfaces. The proposed method is tested using available experimental data. For the considered cases of flow in a parallel plate channel subjected to constant heat flux or constant temperature, good agreements are observed.
Heat transfer characteristics of building walls using phase change material
NASA Astrophysics Data System (ADS)
Irsyad, M.; Pasek, A. D.; Indartono, Y. S.; Pratomo, A. W.
2017-03-01
Minimizing energy consumption in air conditioning system can be done with reducing the cooling load in a room. Heat from solar radiation which passes through the wall increases the cooling load. Utilization of phase change material on walls is expected to decrease the heat rate by storing energy when the phase change process takes place. The stored energy is released when the ambient temperature is low. Temperature differences at noon and evening can be utilized as discharging and charging cycles. This study examines the characteristics of heat transfer in walls using phase change material (PCM) in the form of encapsulation and using the sleeve as well. Heat transfer of bricks containing encapsulated PCM, tested the storage and released the heat on the walls of the building models were evaluated in this study. Experiments of heat transfer on brick consist of time that is needed for heat transfer and thermal conductivity test as well. Experiments were conducted on a wall coated by PCM which was exposed on a day and night cycle to analyze the heat storage and heat release. PCM used in these experiments was coconut oil. The measured parameter is the temperature at some points in the brick, walls and ambient temperature as well. The results showed that the use of encapsulation on an empty brick can increase the time for thermal heat transfer. Thermal conductivity values of a brick containing encapsulated PCM was lower than hollow bricks, where each value was 1.3 W/m.K and 1.6 W/m.K. While the process of heat absorption takes place from 7:00 am to 06:00 pm, and the release of heat runs from 10:00 pm to 7:00 am. The use of this PCM layer can reduce the surface temperature of the walls of an average of 2°C and slows the heat into the room.
Heat transfer intensification by increasing vapor flow rate in flat heat pipes
NASA Astrophysics Data System (ADS)
Sprinceana, Silviu; Mihai, Ioan; Beniuga, Marius; Suciu, Cornel
2015-02-01
Flat heat pipes have various technical applications, one of the most important being the cooling of electronic components[9]. Their continuous development is due to the fact that these devices permit heat transfer without external energetic contribution. The practical exploitation of flat heat pipes however is limited by the fact that dissipated power can only reach a few hundred watts. The present paper aims to advance a new method for the intensification of convective heat transfer. A centrifugal mini impeller, driven by a turntable which incorporates four permanent magnets was designed. These magnets are put in motion by another rotor, which in its turn includes two permanent magnets and is driven by a mini electrical motor. Rotation of the centrifugal blades generates speed and pressure increase of the cooling agent brought to vapor state within the flat micro heat pipe. It's well known that the liquid suffers biphasic transformations during heat transfer inside the heat pipe. Over the hotspot (the heat source being the electronic component) generated at one end of the heat pipe, convective heat transfer occurs, leading to sudden vaporization of the liquid. Pressures generated by newly formed vapors push them towards the opposite end of the flat heat pipe, where a finned mini heat sink is usually placed. The mini-heat exchanger is air-cooled, thus creating a cold spot, where vapors condensate. The proposed method contributes to vapor flow intensification by increasing their transport speed and thus leading to more intense cooling of the heat pipe.
Fourier analysis of conductive heat transfer for glazed roofing materials
NASA Astrophysics Data System (ADS)
Roslan, Nurhana Lyana; Bahaman, Nurfaradila; Almanan, Raja Noorliyana Raja; Ismail, Razidah; Zakaria, Nor Zaini
2014-07-01
For low-rise buildings, roof is the most exposed surface to solar radiation. The main mode of heat transfer from outdoor via the roof is conduction. The rate of heat transfer and the thermal impact is dependent on the thermophysical properties of roofing materials. Thus, it is important to analyze the heat distribution for the various types of roofing materials. The objectives of this paper are to obtain the Fourier series for the conductive heat transfer for two types of glazed roofing materials, namely polycarbonate and polyfilled, and also to determine the relationship between the ambient temperature and the conductive heat transfer for these materials. Ambient and surface temperature data were collected from an empirical field investigation in the campus of Universiti Teknologi MARA Shah Alam. The roofing materials were installed on free-standing structures in natural ventilation. Since the temperature data are generally periodic, Fourier series and numerical harmonic analysis are applied. Based on the 24-point harmonic analysis, the eleventh order harmonics is found to generate an adequate Fourier series expansion for both glazed roofing materials. In addition, there exists a linear relationship between the ambient temperature and the conductive heat transfer for both glazed roofing materials. Based on the gradient of the graphs, lower heat transfer is indicated through polyfilled. Thus polyfilled would have a lower thermal impact compared to polycarbonate.
Turbulent spot flow topology and mechanisms for surface heat transfer
NASA Astrophysics Data System (ADS)
Sabatino, D. R.; Smith, C. R.
The properties of artificially initiated turbulent spots over a heated plate were investigated in a water channel. The instantaneous velocity field and surface Stanton number were simultaneously established using a technique that combines particle image velocimetry and thermochromic liquid crystal thermography. Several characteristics of a spot are found to be similar to those of a turbulent boundary layer. The spacing of the surface heat transfer streak patterns within the middle or of a turbulent spot are comparable to the low-speed streak spacing within a turbulent boundary layer. Additionally, the surface shear stress in the same region of a spot is also found to be comparable to a turbulent boundary layer. However, despite these similarities, the heat transfer within the spot body is found to be markedly less than the heat transfer for a turbulent boundary layer. In fact, the highest surface heat transfer occurs at the trailing or calmed region of a turbulent spot, regardless of maturity. Using a modified set of similarity coordinates, instantaneous two-dimensional streamlines suggest that turbulent spots entrain and subsequently recirculate warm surface fluid, thereby reducing the effective heat transfer within the majority of the spot. It is proposed that energetic vortices next to the wall, near the trailing edge of the spot body, are able to generate the highest surface heat transfer because they have the nearest access to cooler free-stream fluid.
Percolation induced heat transfer in deep unsaturated zones
Lu, N.; LeCain, G.D.
2003-01-01
Subsurface temperature data from a borehole located in a desert wash were measured and used to delineate the conductive and advective heat transfer regimes, and to estimate the percolation quantity associated with the 1997-1998 El Ni??no precipitation. In an arid environment, conductive heat transfer dominates the variation of shallow subsurface temperature most of the time, except during sporadic precipitation periods. The subsurface time-varying temperature due to conductive heat transfer is highly correlated with the surface atmospheric temperature variation, whereas temperature variation due to advective heat transfer is strongly correlated with precipitation events. The advective heat transfer associated with precipitation and infiltration is the focus of this paper. Disruptions of the subsurface conductive temperature regime, associated with the 1997-1998 El Ni??no precipitation, were detected and used to quantify the percolation quantity. Modeling synthesis using a one-dimensional coupled heat and unsaturated flow model indicated that a percolation per unit area of 0.7 to 1.3 m height of water in two weeks during February 1998 was responsible for the observed temperature deviations down to a depth of 35.2 m. The reported study demonstrated quantitatively, for the first time, that the near surface temperature variation due to advective heat transfer can be significant at a depth greater than 10 m in unsaturated soils and can be used to infer the percolation amount in thick unsaturated soils.
Fourier analysis of conductive heat transfer for glazed roofing materials
Roslan, Nurhana Lyana; Bahaman, Nurfaradila; Almanan, Raja Noorliyana Raja; Ismail, Razidah; Zakaria, Nor Zaini
2014-07-10
For low-rise buildings, roof is the most exposed surface to solar radiation. The main mode of heat transfer from outdoor via the roof is conduction. The rate of heat transfer and the thermal impact is dependent on the thermophysical properties of roofing materials. Thus, it is important to analyze the heat distribution for the various types of roofing materials. The objectives of this paper are to obtain the Fourier series for the conductive heat transfer for two types of glazed roofing materials, namely polycarbonate and polyfilled, and also to determine the relationship between the ambient temperature and the conductive heat transfer for these materials. Ambient and surface temperature data were collected from an empirical field investigation in the campus of Universiti Teknologi MARA Shah Alam. The roofing materials were installed on free-standing structures in natural ventilation. Since the temperature data are generally periodic, Fourier series and numerical harmonic analysis are applied. Based on the 24-point harmonic analysis, the eleventh order harmonics is found to generate an adequate Fourier series expansion for both glazed roofing materials. In addition, there exists a linear relationship between the ambient temperature and the conductive heat transfer for both glazed roofing materials. Based on the gradient of the graphs, lower heat transfer is indicated through polyfilled. Thus polyfilled would have a lower thermal impact compared to polycarbonate.
Boiling heat transfer and droplet spreading of nanofluids.
Murshed, S M Sohel; de Castro, C A Nieto
2013-11-01
Nanofluids- a new class of heat transfer fluids have recently been a very attractive area of research due to their fascinating thermophysical properties and numerous potential benefits and applications in many important fields. However, there are many controversies and inconsistencies in reported arguments and experimental results on various thermal characteristics such as effective thermal conductivity, convective heat transfer coefficient and boiling heat transfer rate of nanofluids. As of today, researchers have mostly focused on anomalous thermal conductivity of nanofluids. Although investigations on boiling and droplet spreading are very important for practical application of nanofluids as advanced coolants, considerably fewer efforts have been made on these thermal features of nanofluids. In this paper, recent research and development in boiling heat transfer and droplet spreading of nanofluids are reviewed together with summarizing most related patents on nanofluids published in literature. Review reveals that despite some inconsistent results nanofluids exhibit significantly higher boiling heat transfer performance compared to their base fluids and show great promises to be used as advanced heat transfer fluids in numerous applications. However, there is a clear lack of in-depth understanding of heat transport mechanisms during phase change of nanofluids. It is also found that the nanofluids related patents are limited and among them most of the patents are based on thermal conductivity enhancement and synthesising processes of specific type of nanofluids.
Asymmetric heat transfer from nanoparticles in lipid bilayers
NASA Astrophysics Data System (ADS)
Potdar, Dipti; Sammalkorpi, Maria
2015-12-01
Here, we use molecular dynamics simulations to characterize the heat transfer properties of lipid bilayer - gold nanoparticle systems in which the nanoparticle acts as a heat source. The focus is on dipalmitoylphosphatidylcholine (DPPC) lipid bilayers and thiolated alcohol and alkyl functionalized nanoparticles as prototype hydrophilic and hydrophobic nanoparticles. We find hydrophilic nanoparticles which are partly in contact with the surrounding water environment are more efficient in transferring heat to the system than hydrophobic ones which reside surrounded by the membrane. This is because of the hydrogen bonding capability of the hydroxy pentanethiol and the more efficient heat conductivity through water than the lipid bilayer. Additionally, we find the heat conductance is strongly asymmetric and has a discontinuity between the bilayer leaflets. In total, the findings provide understanding on heat transport from localized heat sources in lipid bilayers and could bear significance, e.g., in engineering and controlling photoactivated triggering of liposomal systems.
Evaporative heat transfer characteristics of industrial safety helmets.
Liu, X; Holmér, I
1995-04-01
Thermal discomfort is one of the major complaints from the wearers of industrial safety helmets. While studies have been reported on dry heat transfer (conduction, convection and radiation) in safety helmets, the investigation of wet heat dissipating (evaporation) properties has not been found in the literature. To evaluate experimentally the evaporative heat transfer characteristics of industrial safety helmets, a method was developed to simulate sweating of a human head on a thermal head manikin, and to use this manikin to assess the wet heat transfer of five industrial safety helmets. A thermal head manikin was covered with a form-fitting cotton stocking to simulate 'skin'. The skin was wetted with distilled water to simulate 'sweating'. A form-fitting perforated polyethylene film was used to cover the wetted stocking to control the skin wettedness at two levels, 0.64 and 1.0. Experiments were conducted in a climatic chamber, under the following conditions: the ambient temperature = head manikin surface temperature = 34 +/- 0.5 degrees C; ambient relative humidity 30% and 60%. Also, the effects of wind and a simulated solar heat load were investigated. The five helmets showed statistically significant difference in evaporative heat transfer under the experimental conditions. Skin wettedness, ambient humidity, wind and solar heat showed significant effects on evaporative heat transfer. These effects were different for the different helmets.
Nanofluid jet impingement heat transfer characteristics in the rectangular mini-fin heat sink
NASA Astrophysics Data System (ADS)
Naphon, Paisarn; Nakharintr, Lursukd
2012-11-01
The nanofluid jet impingement heat transfer characteristics in a rectangular mini-fin heat sink are studied. The heat sink is fabricated from aluminum by a wire electrical discharge machine. The nanofluid is a mixture of deionized water and nanoscale TiO2 particles with a volume nanoparticle concentration of 0.2%. The results obtained for nanofluid jet impingement cooling in the rectangular mini-fin heat sink are compared with those found in the water jet impingement cooling. The effects of the inlet temperature of the nanofluid, its Reynolds number, and the heat flux on the heat transfer characteristics of the rectangular mini-fin heat sink are considered. It is found that the average heat transfer rates for the nanofluid as coolant are higher than those for deionized water.
The Experimental Study on Heat Transfer Characteristics of The External Heat Exchanger
NASA Astrophysics Data System (ADS)
Ji, X. Y.; Lu, X. F.; Yang, L.; Liu, H. Z.
Using the external heat exchanger in large-scale CFB boilers can control combustion and heat transfer separately, make the adjustments of bed temperature and steam temperature convenient. The state of gas-solid two phase flow in the external heat exchanger is bubbling fluidized bed, but differs from the regular one as there is a directional flow in it. Consequently, the temperature distribution changes along the flow direction. In order to study the heat transfer characteristics of the water cooled tubes in the bubbling fluidized bed and ensure the uniformity of heat transfer in the external heat exchanger, a physical model was set up according to the similarity principle and at the geometric ratio of 1∶28 to an external heat exchanger of a 300MW CFB boiler. The model was connected with an electrically heated CFB test-bed which provides the circulating particles. The influencing factors and the distribution rule of the particles' heat transfer coefficient in the external heat exchanger were assessed by measuring the temperature changes of the water in the tubes and different parts of particles flow along the flow direction. At the end, an empirical correlation of particles' heat transfer coefficient in external heat exchanger was given by modifying the Veedendery empirical correlation.
NASA Astrophysics Data System (ADS)
Zverev, V. G.; Goldin, V. D.; Teploukhov, A. V.
2016-04-01
Radiative heating of a metal plate protected by an intumescent coating layer has been studied experimentally and theoretically. Special aspects of physical modeling of intumescent coating heating on a test bench for radiative heating are considered. Heat resistance testing of metal structures is justified. A conjugate mathematical model of radiative-conductive heat transfer in an intumesced material layer is proposed. The experimental and calculation data on the metal plate temperature beneath the coating are shown to agree well.
Heat transfer across the interface between nanoscale solids and gas.
Cheng, Chun; Fan, Wen; Cao, Jinbo; Ryu, Sang-Gil; Ji, Jie; Grigoropoulos, Costas P; Wu, Junqiao
2011-12-27
When solid materials and devices scale down in size, heat transfer from the active region to the gas environment becomes increasingly significant. We show that the heat transfer coefficient across the solid-gas interface behaves very differently when the size of the solid is reduced to the nanoscale, such as that of a single nanowire. Unlike for macroscopic solids, the coefficient is strongly pressure dependent above ∼10 Torr, and at lower pressures it is much higher than predictions of the kinetic gas theory. The heat transfer coefficient was measured between a single, free-standing VO(2) nanowire and surrounding air using laser thermography, where the temperature distribution along the VO(2) nanowire was determined by imaging its domain structure of metal-insulator phase transition. The one-dimensional domain structure along the nanowire results from the balance between heat generation by the focused laser and heat dissipation to the substrate as well as to the surrounding gas, and thus serves as a nanoscale power-meter and thermometer. We quantified the heat loss rate across the nanowire-air interface, and found that it dominates over all other heat dissipation channels for small-diameter nanowires near ambient pressure. As the heat transfer across the solid-gas interface is nearly independent of the chemical identity of the solid, the results reveal a general scaling relationship for gaseous heat dissipation from nanostructures of all solid materials, which is applicable to nanoscale electronic and thermal devices exposed to gaseous environments.
Yang, Dong; Pan, Jie; Zhu, Xiaojing; Bi, Qincheng; Chen, Tingkuan; Zhou, Chenn Q.
2011-02-15
Water wall design is a key issue for supercritical Circulating Fluidized Bed (CFB) boiler. On account of the good heat transfer performance, rifled tube is applied in the water wall design of a 600 MW supercritical CFB boiler in China. In order to investigate the heat transfer and frictional characteristics of the rifled tube with vertical upward flow, an in-depth experiment was conducted in the range of pressure from 12 to 30 MPa, mass flux from 230 to 1200 kg/(m{sup 2} s), and inner wall heat flux from 130 to 720 kW/m{sup 2}. The wall temperature distribution and pressure drop in the rifled tube were obtained in the experiment. The normal, enhanced and deteriorated heat transfer characteristics were also captured. In this paper, the effects of pressure, inner wall heat flux and mass flux on heat transfer characteristics are analyzed, the heat transfer mechanism and the frictional resistance performance are discussed, and the corresponding empirical correlations are presented. The experimental results show that the rifled tube can effectively prevent the occurrence of departure from nucleate boiling (DNB) and keep the tube wall temperature in a permissible range under the operating condition of supercritical CFB boiler. (author)
Boyer, B.D.; Parlatan, Y.; Slovik, G.C.; Rohatgi, U.S.
1995-09-01
RELAP5 MOD3.1.1 is being used to simulate Loss of Coolant Accidents (LOCA) for the Simplified Boiling Water Reactor (SBWR) being proposed by General Electric (GE). One of the major components associated with the SBWR is the Passive Containment Cooling System (PCCS) which provides the long-term heat sink to reject decay heat. The RELAP5 MOD3.1.1 code is being assessed for its ability to represent accurately the PCCS. Data from the Phase 1, Step 1 Heat Transfer Tests performed at Toshiba`s Gravity-Driven Integral Full-Height Test for Passive Heat Removal (GIRAFFE) facility will be used for assessing the ability of RELAP5 to model condensation in the presence of noncondensables. The RELAP5 MOD3.1.1 condensation model uses the University of California at Berkeley (UCB) correlation developed by Vierow and Schrock. The RELAP5 code uses this heat transfer coefficient with the gas velocity effect multiplier being limited to 2. This heat transfer option was used to analyze the condensation heat transfer in the GIRAFFE PCCS heat exchanger tubes in the Phase 1, Step 1 Heat Transfer Tests which were at a pressure of 3 bar and had a range of nitrogen partial pressure fractions from 0.0 to 0.10. The results of a set of RELAP5 calculations al these conditions were compared with the GIRAFFE data. The effects of PCCS cell nodings on the heat transfer process were also studied. The UCB correlation, as implemented in RELAP5, predicted the heat transfer to {+-}5% of the data with a three-node model. The three-node model has a large cell in the entrance region which smeared out the entrance effects on the heat transfer, which tend to overpredict the condensation. Hence, the UCB correlation predicts condensation heat transfer in the presence of noncondensable gases with only a coarse mesh. The cell length term in the condensation heat transfer correlation implemented in the code must be removed to allow for accurate calculations with smaller cell sizes.
Enhancement of laminar convective heat transfer using microparticle suspensions
NASA Astrophysics Data System (ADS)
Zhu, Jiu Yang; Tang, Shiyang; Yi, Pyshar; Baum, Thomas; Khoshmanesh, Khashayar; Ghorbani, Kamran
2017-01-01
This paper investigates the enhancement of convective heat transfer within a sub-millimetre diameter copper tube using Al2O3, Co3O4 and CuO microparticle suspensions. Experiments are conducted at different particle concentrations of 1.0, 2.0 and 5.0 wt% and at various flow rates ranging from 250 to 1000 µl/min. Both experimental measurements and numerical analyses are employed to obtain the convective heat transfer coefficient. The results indicate a significant enhancement in convective heat transfer coefficient due to the implementation of microparticle suspensions. For the case of Al2O3 microparticle suspension with 5.0 wt% concentration, a 20.3 % enhancement in convective heat transfer coefficient is obtained over deionised water. This is comparable to the case of Al2O3 nanofluid at the same concentration. Hence, there is a potential for the microparticle suspensions to be used for cooling of compact integrated systems.
The measurement of capsule heat transfer gaps using neutron radiography.
NASA Technical Reports Server (NTRS)
Thaler, L. A.
1971-01-01
The use of neutron radiographs to determine dimensional changes of heat transfer gaps in cylindrical nuclear fueled capsules is described. A method was developed which involves scanning a very fine grained neutron radiograph negative with a recording microdensitometer. The output of the densitometer is recorded on graph paper and the heat transfer gap is plotted as a well-defined optical density change. Calibration of the recording microdensitometer ratio arms permits measurements to be made of the heat transfer optical density change from the microdensitometer trace. Total heat transfer gaps, measured by this method, agree with the physical measurements within plus or minus 0.005 cm over a range of gaps from 0.061 to 0.178 cm.
Volume-energy parameters for heat transfer to supercritical fluids
NASA Technical Reports Server (NTRS)
Kumakawa, A.; Niino, M.; Hendricks, R. C.; Giarratano, P. J.; Arp, V. D.
1986-01-01
Reduced Nusselt numbers of supercritical fluids from different sources were grouped by several volume-energy parameters. A modified bulk expansion parameter was introduced based on a comparative analysis of data scatter. Heat transfer experiments on liquefied methane were conducted under near-critical conditions in order to confirm the usefulness of the parameters. It was experimentally revealed that heat transfer characteristics of near-critical methane are similar to those of hydrogen. It was shown that the modified bulk expansion parameter and the Gibbs-energy parameter grouped the heat transfer data of hydrogen, oxygen and methane including the present data on near-critical methane. It was also indicated that the effects of surface roughness on heat transfer were very important in grouping the data of high Reynolds numbers.
Surface heat transfer coefficients of pin-finned cylinders
NASA Technical Reports Server (NTRS)
Vanfossen, G. J., Jr.
1975-01-01
An experimental investigation was conducted to measure heat-transfer coefficients for a 15.24-centimeter-diameter cylinder with pin fins on its surface. Pin diameters of 0.3175 and 0.6350 centimeter with staggered pin spacings of 3 and 4 pin diameters and pin lengths of 5, 7, and 9 pin diameters were tested. Flow was normal to the axis of the cylinder, and local heat-transfer coefficients were measured as a function of angle around the circumference of the cylinder. The average heat-transfer coefficient was also computed. Reynolds number based on pin diameter ranged from 3600 to 27,750. The smallest diameter, closest spacing, and largest pin-length-to-diameter ratio gave the highest average effective heat-transfer coefficients.
Heat and Mass Transfer in an L Shaped Porous Medium
NASA Astrophysics Data System (ADS)
Salman Ahmed, N. J.; Azeem; Yunus Khan, T. M.
2017-08-01
This article is an extension to the heat transfer in L-shaped porous medium by including the mass diffusion. The heat and mass transfer in the porous domain is represented by three coupled partial differential equations representing the fluid movement, energy transport and mass transport. The equations are converted into algebraic form of equations by the application of finite element method that can be conveniently solved by matrix method. An iterative approach is adopted to solve the coupled equations by setting suitable convergence criterion. The results are discussed in terms of heat transfer characteristics influenced by physical parameters such as buoyancy ratio, Lewis number, Rayleigh number etc. It is found that these physical parameters have significant effect on heat and mass transfer behavior of L-shaped porous medium.
Prediction of Unshsrouded Rotor Blade Tip Heat Transfer
NASA Technical Reports Server (NTRS)
Ameri, A. A.; Steinthorsson, E.
1994-01-01
The rate of heat transfer on the tip of a turbine rotor blade and on the blade surface in the vicinity of the tip, was successfully predicted. The computations were performed with a multiblock computer code which solves the Reynolds Averaged Navier-Stokes equations using an efficient multigrid method. The case considered for the present calculations was the Space Shuttle Main Engine (SSME) high pressure fuel side turbine. The predictions of the blade tip heat transfer agreed reasonably well with the experimental measurements using the present level of grid refinement. On the tip surface, regions with high rate of heat transfer was found to exist close to the pressure side and suction side edges. Enhancement of the heat transfer was also observed on the blade surface near the tip. Further comparison of the predictions was performed with results obtained from correlations based on fully developed channel flow.
Scalable graphene coatings for enhanced condensation heat transfer.
Preston, Daniel J; Mafra, Daniela L; Miljkovic, Nenad; Kong, Jing; Wang, Evelyn N
2015-05-13
Water vapor condensation is commonly observed in nature and routinely used as an effective means of transferring heat with dropwise condensation on nonwetting surfaces exhibiting heat transfer improvement compared to filmwise condensation on wetting surfaces. However, state-of-the-art techniques to promote dropwise condensation rely on functional hydrophobic coatings that either have challenges with chemical stability or are so thick that any potential heat transfer improvement is negated due to the added thermal resistance of the coating. In this work, we show the effectiveness of ultrathin scalable chemical vapor deposited (CVD) graphene coatings to promote dropwise condensation while offering robust chemical stability and maintaining low thermal resistance. Heat transfer enhancements of 4× were demonstrated compared to filmwise condensation, and the robustness of these CVD coatings was superior to typical hydrophobic monolayer coatings. Our results indicate that graphene is a promising surface coating to promote dropwise condensation of water in industrial conditions with the potential for scalable application via CVD.
The effect of magnetic field on nanofluids heat transfer through a uniformly heated horizontal tube
NASA Astrophysics Data System (ADS)
Hatami, N.; Kazemnejad Banari, A.; Malekzadeh, A.; Pouranfard, A. R.
2017-02-01
In this study, the effects of magnetic field on forced convection heat transfer of Fe3O4-water nanofluid with laminar flow regime in a horizontal pipe under constant heat flux conditions were studied, experimentally. The convective heat transfer of magnetic fluid flow inside the heated pipe with uniform magnetic field was measured. Fe3O4 nanoparticles with diameters less than 100 nm dispersed in water with various volume concentrations are used as the test fluid. The effect of the external magnetic field (Ha = 33.4 ×10-4 to 136.6 ×10-4) and nanoparticle concentrations (φ = 0, 0.1, 0.5, 1%) on heat transfer characteristics were investigated. Results showed that by the presence of a magnetic field, increase in nanoparticle concentration caused reduction of convection heat transfer coefficient. In this condition, heat transfer decreased up to 25%. Where, in the absence of an external magnetic field, adding magnetic nanoparticles increased convection heat transfer more than 60%. It was observed that the Nusselt number decreased by increasing the Hartmann number at a specified concentration of magnetic nanofluids, that reduction about 25% in heat transfer rate could be found.
Heat Transfer of Airfoils and Plates
NASA Technical Reports Server (NTRS)
Seibert, Otto
1943-01-01
The few available test data on the heat dissipation of wholly or partly heated airfoil models are compared with the corresponding data for the flat plate as obtained by an extension of Prandtl's momentum theory, with differentiation between laminar and turbulent boundary layer and transitional region between both, the extent and appearance of which depend upon certain critical factors. The satisfactory agreement obtained justifies far-reaching conclusions in respect to other profile forms and arrangements of heated surface areas. The temperature relationship of the material quantities in its effect on the heat dissipation is discussed as far as is possible at tk.e present state of research, and it is shown that the profile drag of heated wing surfaces can increase or decrease with the temperature increase depending upon the momentarily existent structure of the boundary layer.
Heat Transfer in an L Shaped Porous Medium using FEM
NASA Astrophysics Data System (ADS)
Anjum Badruddin, Irfan; Yunus Khan, T. M.
2017-08-01
Heat transfer in porous medium has been an intense field of study for many years that has tremendously improved our understanding about the heat flow behavior in porous region. Finite element method has been widely acknowledged to be one of the most robust numerical techniques that has proven its capability in handling the tedious and complex set of equations representing various phenomenon. The present research investigates the heat transfer inside a L shaped porous domain having heated from bottom surface and cooled at the top edge. Finite element method is used with the help of triangular element to divide the porous domain into smaller segments. The results are discussed with respect to various physical parameters affecting the heat transfer behaviour.
Mesoscopic near-field radiative heat transfer at low temperatures
NASA Astrophysics Data System (ADS)
Maasilta, Ilari; Geng, Zhuoran; Chaudhuri, Saumyadip; Koppinen, Panu
2015-03-01
Near-field radiative heat transfer has mostly been discussed at room temperatures and/or macroscopic scale geometries. Here, we discuss our recent theoretical and experimental advances in understanding near-field transfer at ultra-low temperatures below 1K. As the thermal wavelengths increase with lowering temperature, we show that with sensitive tunnel junction bolometers it is possible to study near-field transfer up to distances ~ 10 μm currently, even though the power levels are low. In addition, these type of experiments correspond to the extreme near-field limit, as the near-field region starts at ~ mm distances at 0.1 K, and could have theoretical power enhancement factors of the order of 1010. Preliminary results on heat transfer between two parallel metallic wires are presented. We also comment on possible areas were such heat transfer might be relevant, such as densely packed arrays of low-temperature detectors.
NASA Technical Reports Server (NTRS)
Reynolds, W. C.; Kays, W. M.; Kline, S. J.
1958-01-01
Superposition techniques are used to calculate the rate of heat transfer from a flat plate to a turbulent incompressible boundary layer for several cases of variable surface temperature. The predictions of a number of these calculations are compared with experimental heat- transfer rates, and good agreement is obtained. A simple computing procedure for determining the heat-transfer rates from surfaces with arbitrary wall-temperature distributions is presented and illustrated by two examples. The inverse problem of determining the temperature distribution from an arbitrarily prescribed heat flux is also treated, both experimentally and analytically.
Development of heat-transfer circuits in the blast furnace
NASA Astrophysics Data System (ADS)
Spirin, N. A.; Yaroshenko, Yu G.; Lavrov, V. V.
2016-09-01
The development of heat-transfer circuits in the blast furnace as the technologies of blast-furnace smelting are improved are considered. It is shown that there are two zones of intense heat-transfer, and in modern conditions, when different kinds of iron ore are smelted, the use of combined blast with high parameters is a prerequisite for the stability of blastfurnace smelting operation and the smelting efficiency.
Enhanced heat transfer in partially-saturated hydrothermal systems
Bixler, N.E.; Carrigan, C.R.
1986-01-01
The role of capillarity is potentially important for determining heat transfer in hydrothermal regions. Capillarity allows mixing of phases in liquid/vapor systems and results in enhanced two-phase convection. Comparisons involving a numerical model with capillarity and analytical models without indicate that heat transfer can be enhanced by about an order of magnitude. Whether capillarity can be important for a particular hydrothermal region will depend on the nature of mineral precipitation as well as pore and fracture size distributions.
High-Power Liquid-Metal Heat-Transfer Loop
NASA Technical Reports Server (NTRS)
Bhandari, Pradeep; Fujita, Toshio
1991-01-01
Proposed closed-loop system for transfer of thermal power operates at relatively high differential pressure between vapor and liquid phases of liquid-metal working fluid. Resembles "capillary-pumped" liquid-metal heat-transfer loop except electric field across permselective barrier of beta alumina keeps liquid and vapor separate at heat-input end. Increases output thermal power, contains no moving parts, highly reliable and well suited to long-term unattended operation.
Advanced turbine cooling, heat transfer, and aerodynamic studies
Han, Je-Chin; Schobeiri, M.T.
1995-12-31
The contractual work is in three parts: Part I - Effect of rotation on enhanced cooling passage heat transfer, Part II - Effect of Thermal Barrier Coating (TBC) spallation on surface heat transfer, and Part III - Effect of surface roughness and trailing edge ejection on turbine efficiency under unsteady flow conditions. Each section of this paper has been divided into three parts to individually accommodate each part. Part III is further divided into Parts IIIa and IIIb.
Comparison of Methods for Calculating Radiative Heat Transfer
Schock, Alfred; Abbate, M J
2012-01-19
Various approximations for calculating radioactive heat transfer between parallel surfaces are evaluated. This is done by applying the approximations based on total emissivities to a special case of known spectral emissivities, for which exact heat transfer calculations are possible. Comparison of results indicates that the best approximation is obtained by basing the emissivity of the receiving surface primarily on the temperature of the emitter. A specific model is shown to give excellent agreement over a very wide range of values.
Advanced turbine cooling, heat transfer, and aerodynamic studies
Je-Chin Han; Schobeiri, M.T.
1995-10-01
The contractual work is in three parts: Part I - Effect of rotation on enhanced cooling passage heat transfer, Part II - Effect on Thermal Barrier Coating (TBC) spallation on surface heat transfer, and Part III - Effect of surface roughness and trailing edge ejection on turbine efficiency under unsteady flow conditions. Each section of this paper has been divided into three parts to individually accommodate each part. Part III is further divided into Parts IIIa and IIIb.
One dimensional lunar ash flow with and without heat transfer
NASA Technical Reports Server (NTRS)
Pai, S. I.; Hsieh, T.
1971-01-01
The characteristics of lunar ash flow are discussed in terms of the two phase flow theory of a mixture of a gas and small solid particles. A model is developed to present the fundamental equations and boundary conditions. Numerical solutions for special ash flow with and without heat transfer are presented. In the case of lunar ash flow with small initial velocity, the effect of the heat transfer makes the whole layer of ash flow more compacted together than the corresponding isothermal case.
Modeling of radiative - conductive heat transfer in compositing materials
NASA Astrophysics Data System (ADS)
Luchnikov, P. A.; Nefedov, V. I.; Trefilov, N. A.; Dementiev, A. N.; Surzhikov, A. P.
2017-01-01
A layer of composite material is investigated, which is heated one-sidedly with one-dimensional energy transfer accounting for thermal conductivity and radiation. A mathematical model is suggested for non-stationary coefficient thermophysical problem under radiative-conductive heat transfer in a material layer. Temperature dependencies of thermal capacity and thermal conductivity coefficient of composite radio-transparent material have been determined through numerical modeling by solving the coefficient reverse problem of thermal conductivity.
Code for Multiblock CFD and Heat-Transfer Computations
NASA Technical Reports Server (NTRS)
Fabian, John C.; Heidmann, James D.; Lucci, Barbara L.; Ameri, Ali A.; Rigby, David L.; Steinthorsson, Erlendur
2006-01-01
The NASA Glenn Research Center General Multi-Block Navier-Stokes Convective Heat Transfer Code, Glenn-HT, has been used extensively to predict heat transfer and fluid flow for a variety of steady gas turbine engine problems. Recently, the Glenn-HT code has been completely rewritten in Fortran 90/95, a more object-oriented language that allows programmers to create code that is more modular and makes more efficient use of data structures. The new implementation takes full advantage of the capabilities of the Fortran 90/95 programming language. As a result, the Glenn-HT code now provides dynamic memory allocation, modular design, and unsteady flow capability. This allows for the heat-transfer analysis of a full turbine stage. The code has been demonstrated for an unsteady inflow condition, and gridding efforts have been initiated for a full turbine stage unsteady calculation. This analysis will be the first to simultaneously include the effects of rotation, blade interaction, film cooling, and tip clearance with recessed tip on turbine heat transfer and cooling performance. Future plans call for the application of the new Glenn-HT code to a range of gas turbine engine problems of current interest to the heat-transfer community. The new unsteady flow capability will allow researchers to predict the effect of unsteady flow phenomena upon the convective heat transfer of turbine blades and vanes. Work will also continue on the development of conjugate heat-transfer capability in the code, where simultaneous solution of convective and conductive heat-transfer domains is accomplished. Finally, advanced turbulence and fluid flow models and automatic gridding techniques are being developed that will be applied to the Glenn-HT code and solution process.
Heat transfer augmentation of a car radiator using nanofluids
NASA Astrophysics Data System (ADS)
Hussein, Adnan M.; Bakar, R. A.; Kadirgama, K.; Sharma, K. V.
2014-05-01
The car radiator heat transfer enhancement by using TiO2 and SiO2 nanoparticles dispersed in water as a base fluid was studied experimentally. The test rig is setup as a car radiator with tubes and container. The range of Reynolds number and volume fraction are (250-1,750) and (1.0-2.5 %) respectively. Results showed that the heat transfer increases with increasing of nanofluid volume fraction. The experimental data is agreed with other investigator.
Condensation Heat Transfer of Steam on a Single Horizontal Tube.
1983-06-01
thermometers. The inside heat-transfer coefficient was determined using the Sieder - Tate correlation with leading coefficient of 0.029. Initial...measured accurately using quartz crystal thermometers. The inside heat-transfer coefficient was determined using the Sieder -Tate correlation with...ACQUISITION/REDUCTION 34 A. DATA ACQUISITION AND STORAGE 34 3. DATA REDUCTION 34 C. STEPWISE SOLUTION PROCEDURE 35 1 . Program SIEDER 35
Application of ray tracing in radiation heat transfer
NASA Technical Reports Server (NTRS)
Baumeister, Joseph F.
1993-01-01
This collection of presentation figures displays the capabilities of ray tracing for radiation propagation calculations as compared to an analytical approach. The goal is to introduce the terminology and solution process used in ray tracing, and provide insight into radiation heat transfer principles and analysis tools. A thermal analysis working environment is introduced that solves demanding radiation heat transfer problems based on ray tracing. This information may serve as a reference for designing and building ones own analysis environment.
Radiative heat transfer between nanoparticles enhanced by intermediate particle
Wang, Yanhong; Wu, Jingzhi
2016-02-15
Radiative heat transfer between two polar nanostructures at different temperatures can be enhanced by resonant tunneling of surface polaritons. Here we show that the heat transfer between two nanoparticles is strongly varied by the interactions with a third nanoparticle. By controlling the size of the third particle, the time scale of thermalization toward the thermal bath temperature can be modified over 5 orders of magnitude. This effect provides control of temperature distribution in nanoparticle aggregation and facilitates thermal management at nanoscale.
NASA Astrophysics Data System (ADS)
Wang, Yiping; Li, Shuai; Yang, Xue; Deng, Yadong; Su, Chuqi
2016-03-01
For vehicle thermoelectric exhaust energy recovery, the temperature difference between the heat exchanger and the coolant has a strong influence on the electric power generation, and ribs are often employed to enhance the heat transfer of the heat exchanger. However, the introduction of ribs will result in a large unwanted pressure drop in the exhaust system which is unfavorable for the engine's efficiency. Therefore, how to enhance the heat transfer and control the pressure drop in the exhaust system is quite important for thermoelectric generators (TEG). In the current study, a symmetrical arrangement of dimpled surfaces staggered in the upper and lower surfaces of the heat exchanger was proposed to augment heat transfer rates with minimal pressure drop penalties. The turbulent flow characteristics and heat transfer performance of turbulent flow over the dimpled surface in a flat heat exchanger was investigated by numerical simulation and temperature measurements. The heat transfer capacity in terms of Nusselt number and the pressure loss in terms of Fanning friction factors of the exchanger were compared with those of the flat plate. The pressure loss and heat transfer characteristics of dimples with a depth-to-diameter ratio ( h/D) at 0.2 were investigated. Finally, a quite good heat transfer performance with minimal pressure drop heat exchanger in a vehicle TEG was obtained. And based on the area-averaged surface temperature of the heat exchanger and the Seeback effect, the power generation can be improved by about 15% at Re = 25,000 compared to a heat exchanger with a flat surface.
Numerical Modeling of Conjugate Heat Transfer in Fluid Network
NASA Technical Reports Server (NTRS)
Majumdar, Alok
2004-01-01
Fluid network modeling with conjugate heat transfer has many applications in Aerospace engineering. In modeling unsteady flow with heat transfer, it is important to know the variation of wall temperature in time and space to calculate heat transfer between solid to fluid. Since wall temperature is a function of flow, a coupled analysis of temperature of solid and fluid is necessary. In cryogenic applications, modeling of conjugate heat transfer is of great importance to correctly predict boil-off rate in propellant tanks and chill down of transfer lines. In TFAWS 2003, the present author delivered a paper to describe a general-purpose computer program, GFSSP (Generalized Fluid System Simulation Program). GFSSP calculates flow distribution in complex flow circuit for compressible/incompressible, with or without heat transfer or phase change in all real fluids or mixtures. The flow circuit constitutes of fluid nodes and branches. The mass, energy and specie conservation equations are solved at the nodes where as momentum conservation equations are solved at the branches. The proposed paper describes the extension of GFSSP to model conjugate heat transfer. The network also includes solid nodes and conductors in addition to fluid nodes and branches. The energy conservation equations for solid nodes solves to determine the temperatures of the solid nodes simultaneously with all conservation equations governing fluid flow. The numerical scheme accounts for conduction, convection and radiation heat transfer. The paper will also describe the applications of the code to predict chill down of cryogenic transfer line and boil-off rate of cryogenic propellant storage tank.
Numerical Modeling of Conjugate Heat Transfer in Fluid Network
NASA Technical Reports Server (NTRS)
Majumdar, Alok
2004-01-01
Fluid network modeling with conjugate heat transfer has many applications in Aerospace engineering. In modeling unsteady flow with heat transfer, it is important to know the variation of wall temperature in time and space to calculate heat transfer between solid to fluid. Since wall temperature is a function of flow, a coupled analysis of temperature of solid and fluid is necessary. In cryogenic applications, modeling of conjugate heat transfer is of great importance to correctly predict boil-off rate in propellant tanks and chill down of transfer lines. In TFAWS 2003, the present author delivered a paper to describe a general-purpose computer program, GFSSP (Generalized Fluid System Simulation Program). GFSSP calculates flow distribution in complex flow circuit for compressible/incompressible, with or without heat transfer or phase change in all real fluids or mixtures. The flow circuit constitutes of fluid nodes and branches. The mass, energy and specie conservation equations are solved at the nodes where as momentum conservation equations are solved at the branches. The proposed paper describes the extension of GFSSP to model conjugate heat transfer. The network also includes solid nodes and conductors in addition to fluid nodes and branches. The energy conservation equations for solid nodes solves to determine the temperatures of the solid nodes simultaneously with all conservation equations governing fluid flow. The numerical scheme accounts for conduction, convection and radiation heat transfer. The paper will also describe the applications of the code to predict chill down of cryogenic transfer line and boil-off rate of cryogenic propellant storage tank.
Experimental and numerical investigation of HyperVapotron heat transfer
NASA Astrophysics Data System (ADS)
Wang, Weihua; Deng, Haifei; Huang, Shenghong; Chu, Delin; Yang, Bin; Mei, Luoqin; Pan, Baoguo
2014-12-01
The divertor first wall and neutral beam injection (NBI) components of tokamak devices require high heat flux removal up to 20-30 MW m-2 for future fusion reactors. The water cooled HyperVapotron (HV) structure, which relies on internal grooves or fins and boiling heat transfer to maximize the heat transfer capability, is the most promising candidate. The HV devices, that are able to transfer large amounts of heat (1-20 MW m-2) efficiently, have therefore been developed specifically for this application. Until recently, there have been few attempts to observe the detailed bubble characteristics and vortex evolvement of coolant flowing inside their various parts and understand of the internal two-phase complex heat transfer mechanism behind the vapotron effect. This research builds the experimental facilities of HyperVapotron Loop-I (HVL-I) and Pressure Water HyperVapotron Loop-II (PWHL-II) to implement the subcooled boiling principle experiment in terms of typical flow parameters, geometrical parameters of test section and surface heat flux, which are similar to those of the ITER-like first wall and NBI components (EAST and MAST). The multiphase flow and heat transfer phenomena on the surface of grooves and triangular fins when the subcooled water flowed through were observed and measured with the planar laser induced fluorescence (PLIF) and high-speed photography (HSP) techniques. Particle image velocimetry (PIV) was selected to reveal vortex formation, the flow structure that promotes the vapotron effect during subcooled boiling. The coolant flow data for contributing to the understanding of the vapotron phenomenon and the assessment of how the design and operational conditions that might affect the thermal performance of the devices were collected and analysed. The subcooled flow boiling model and methods of HV heat transfer adopted in the considered computational fluid dynamics (CFD) code were evaluated by comparing the calculated wall temperatures with the
Theoretical and Computational Study of Forced-Convection Heat Transfer at Supercritical Pressures
NASA Astrophysics Data System (ADS)
Zhong, Jianguo
In the simulation of turbulent fluid flow and heat transfer at supercritical pressures, substantial difficulties have been encountered in the modeling of turbulence and bounda-ry layer. This is due to significant fluid property variations with respect to the local temperature and pressure, especially in the near-wall region of a heated wall, where large temperature differences occur. The classical turbulence models available in literature were typically developed for constant-property fluids, where an empirical wall function in the high-Re k-epsilon model, and a damping function in the low-Re k-epsilon model were derived based on the constant-property data to solve the boundary layer. As it can be found in the existing literature, large differences have been observed between the experimental and numerical simulation results of the heat transfer coefficient predictions in the en-hanced and deteriorated heat transfer situations for supercritical fluids. In this thesis, a novel near-wall treatment method is proposed to treat large property variations in the thermal and velocity sub-layers. In the near-wall region, the supercritical fluids can be considered thermal-conductive and viscous forces dominated. The thick-ness of the viscous sub-layer (VSL) and the conduction sub-layer (CSL) can be related to the wall shear stress and local Prandtl number information by using computational CFD models, such as that implemented in the NPHASE-CMFD code. The fluids' bulk and wall temperature information has been obtained from the literature review of experi-mental measurements. The wall temperature and heat transfer coefficient calculated from the k-epsilon model with the proposed wall treatment method have been found to be in good agreement with experimental data for both heat transfer enhancement and deterioration cases for two most widely used fluids: CO2 and water. The proposed model has been applied in the reactor-scale thermal-hydraulic analysis of different flow path
Investigation of heat transfer inside a PCM-air heat exchanger: a numerical parametric study
NASA Astrophysics Data System (ADS)
Herbinger, Florent; Bhouri, Maha; Groulx, Dominic
2017-07-01
In this paper, the use of PCMs for thermal storage of energy in HVAC applications was investigated by studying numerically the thermal performance of a PCM-air heat exchanger. The PCM used in this study was dodecanoic acid. A symmetric 3D model, incorporating conductive and convective heat transfer (air only) as well as laminar flow, was created in COMSOL Multiphysics 5.0. Simulations examined the dependence of the heat transfer rate on the temperature and velocity of the incoming air as well as the size of the channels in the heat exchanger. Results indicated that small channels size lead to a higher heat transfer rates. A similar trend was also obtained for high incoming air temperature, whereas the heat transfer rate was less sensitive to the incoming air velocity.
Revealing the complex conduction heat transfer mechanism of nanofluids.
Sergis, A; Hardalupas, Y
2015-12-01
Nanofluids are two-phase mixtures consisting of small percentages of nanoparticles (sub 1-10 %vol) inside a carrier fluid. The typical size of nanoparticles is less than 100 nm. These fluids have been exhibiting experimentally a significant increase of thermal performance compared to the corresponding carrier fluids, which cannot be explained using the classical thermodynamic theory. This study deciphers the thermal heat transfer mechanism for the conductive heat transfer mode via a molecular dynamics simulation code. The current findings are the first of their kind and conflict with the proposed theories for heat transfer propagation through micron-sized slurries and pure matter. The authors provide evidence of a complex new type of heat transfer mechanism, which explains the observed abnormal heat transfer augmentation. The new mechanism appears to unite a number of popular speculations for the thermal heat transfer mechanism employed by nanofluids as predicted by the majority of the researchers of the field into a single one. The constituents of the increased diffusivity of the nanoparticle can be attributed to mismatching of the local temperature profiles between parts of the surface of the solid and the fluid resulting in increased local thermophoretic effects. These effects affect the region surrounding the solid manifesting interfacial layer phenomena (Kapitza resistance). In this region, the activity of the fluid and the interactions between the fluid and the nanoparticle are elevated. Isotropic increased nanoparticle mobility is manifested as enhanced Brownian motion and diffusion effects.
Heat transfer measurements from a smooth NACA 0012 airfoil
NASA Technical Reports Server (NTRS)
Poinsatte, Philip E.; Van Fossen, G. J.; Newton, James E.; De Witt, Kenneth J.
1991-01-01
Local convective heat transfer coefficients were measured from a smooth NACA 0012 airfoil having a chord length of 0.533 m. Flight data were taken for the smooth airfoil at Reynolds numbers based on chord in the range 1.24 to 2.50 million and at various angles of attack up to 4 deg. During these flight tests, the freestream velocity turbulence intensity was found to be very low. Wind tunnel data were acquired in the Reynolds number range 1.20 to 4.52 million and at angles of attack from -4 to +8 deg. The turbulence intensity in the IRT was 0.5-0.7 percent with the cloud-generating sprays off. A direct comparison between the results obtained in flight and in the IRT showed that the higher level of turbulence intensity in the IRT had little effect on the heat transfer for the lower Reynolds numbers but caused a moderate increase in heat transfer at the higher Reynolds numbers. Turning on the cloud-generating spray nozzle atomizing air in the IRT did not alter the heat transfer. The present data were compared with leading-edge cylinder and flat plate heat transfer correlations that are often used to estimate airfoil heat transfer in computer codes.
Heat transfer coefficients for staggered arrays of short pin fins
NASA Technical Reports Server (NTRS)
Vanfossen, G. J.
1981-01-01
Short pin fins are often used to increase that heat transfer to the coolant in the trailing edge of a turbine blade. Due primarily to limits of casting technology, it is not possible to manufacture pins of optimum length for heat transfer purposes in the trailing edge region. In many cases the pins are so short that they actually decrease the total heat transfer surface area compared to a plain wall. A heat transfer data base for these short pins is not available in the literature. Heat transfer coefficients on pin and endwall surfaces were measured for several staggered arrays of short pin fins. The measured Nusselt numbers when plotted versus Reynolds numbers were found to fall on a single curve for all surfaces tested. The heat transfer coefficients for the short pin fins (length to diameter ratios of 1/2 and 2) were found to be about a factor of two lower than data from the literature for longer pin arrays (length to diameter ratios of about 8).
Revealing the complex conduction heat transfer mechanism of nanofluids
NASA Astrophysics Data System (ADS)
Sergis, A.; Hardalupas, Y.
2015-06-01
Nanofluids are two-phase mixtures consisting of small percentages of nanoparticles (sub 1-10 %vol) inside a carrier fluid. The typical size of nanoparticles is less than 100 nm. These fluids have been exhibiting experimentally a significant increase of thermal performance compared to the corresponding carrier fluids, which cannot be explained using the classical thermodynamic theory. This study deciphers the thermal heat transfer mechanism for the conductive heat transfer mode via a molecular dynamics simulation code. The current findings are the first of their kind and conflict with the proposed theories for heat transfer propagation through micron-sized slurries and pure matter. The authors provide evidence of a complex new type of heat transfer mechanism, which explains the observed abnormal heat transfer augmentation. The new mechanism appears to unite a number of popular speculations for the thermal heat transfer mechanism employed by nanofluids as predicted by the majority of the researchers of the field into a single one. The constituents of the increased diffusivity of the nanoparticle can be attributed to mismatching of the local temperature profiles between parts of the surface of the solid and the fluid resulting in increased local thermophoretic effects. These effects affect the region surrounding the solid manifesting interfacial layer phenomena (Kapitza resistance). In this region, the activity of the fluid and the interactions between the fluid and the nanoparticle are elevated. Isotropic increased nanoparticle mobility is manifested as enhanced Brownian motion and diffusion effects
Heat transfer coefficients for staggered arrays of short pin fins
NASA Technical Reports Server (NTRS)
Vanfossen, G. J.
1981-01-01
Short pin fins are often used to increase the heat transfer to the coolant in the trailing edge of a turbine blade. Due primarily to limits of casting technology, it is not possible to manufacture pins of optimum length for heat transfer purposes in the trailing edge region. In many cases the pins are so short that they actually decrease the total heat transfer surface area compared to a plain wall. A heat transfer data base for these short pins is not available in the literature. Heat transfer coefficients on pin and endwall surfaces were measured for several staggered arrays of short pin fins. The measured Nusselt numbers when plotted versus Reynolds numbers were found to fall on a single curve for all surfaces tested. The heat transfer coefficients for the short pin fins (length to diameter ratios of 1/2 and 2) were found to be about a factor of two lower than data from the literature for longer pin arrays (length to diameter ratios of about 8).
Literature survey of heat transfer enhancement techniques in refrigeration applications
Jensen, M.K.; Shome, B.
1994-05-01
A survey has been performed of the technical and patent literature on enhanced heat transfer of refrigerants in pool boiling, forced convection evaporation, and condensation. Extensive bibliographies of the technical literature and patents are given. Many passive and active techniques were examined for pure refrigerants, refrigerant-oil mixtures, and refrigerant mixtures. The citations were categorized according to enhancement technique, heat transfer mode, and tube or shell side focus. The effects of the enhancement techniques relative to smooth and/or pure refrigerants were illustrated through the discussion of selected papers. Patented enhancement techniques also are discussed. Enhanced heat transfer has demonstrated significant improvements in performance in many refrigerant applications. However, refrigerant mixtures and refrigerant-oil mixtures have not been studied extensively; no research has been performed with enhanced refrigerant mixtures with oil. Most studies have been of the parametric type; there has been inadequate examination of the fundamental processes governing enhanced refrigerant heat transfer, but some modeling is being done and correlations developed. It is clear that an enhancement technique must be optimized for the refrigerant and operating condition. Fundamental processes governing the heat transfer must be examined if models for enhancement techniques are to be developed; these models could provide the method to optimize a surface. Refrigerant mixtures, with and without oil present, must be studied with enhancement devices; there is too little known to be able to estimate the effects of mixtures (particularly NARMs) with enhanced heat transfer. Other conclusions and recommendations are offered.
Heat Transfer Modeling for Rigid High-Temperature Fibrous Insulation
NASA Technical Reports Server (NTRS)
Daryabeigi, Kamran; Cunnington, George R.; Knutson, Jeffrey R.
2012-01-01
Combined radiation and conduction heat transfer through a high-temperature, high-porosity, rigid multiple-fiber fibrous insulation was modeled using a thermal model previously used to model heat transfer in flexible single-fiber fibrous insulation. The rigid insulation studied was alumina enhanced thermal barrier (AETB) at densities between 130 and 260 kilograms per cubic meter. The model consists of using the diffusion approximation for radiation heat transfer, a semi-empirical solid conduction model, and a standard gas conduction model. The relevant parameters needed for the heat transfer model were estimated from steady-state thermal measurements in nitrogen gas at various temperatures and environmental pressures. The heat transfer modeling methodology was evaluated by comparison with standard thermal conductivity measurements, and steady-state thermal measurements in helium and carbon dioxide gases. The heat transfer model is applicable over the temperature range of 300 to 1360 K, pressure range of 0.133 to 101.3 x 10(exp 3) Pa, and over the insulation density range of 130 to 260 kilograms per cubic meter in various gaseous environments.
Heat transfer measurements of the 1983 kilauea lava flow.
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
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.
Gondrexon, N; Cheze, L; Jin, Y; Legay, M; Tissot, Q; Hengl, N; Baup, S; Boldo, P; Pignon, F; Talansier, E
2015-07-01
This paper aims to illustrate the interest of ultrasound technology as an efficient technique for both heat and mass transfer intensification. It is demonstrated that the use of ultrasound results in an increase of heat exchanger performances and in a possible fouling monitoring in heat exchangers. Mass transfer intensification was observed in the case of cross-flow ultrafiltration. It is shown that the enhancement of the membrane separation process strongly depends on the physico-chemical properties of the filtered suspensions.
Heat transfer in geometrically similar cylinders
NASA Technical Reports Server (NTRS)
Riekert, P; Held, A
1941-01-01
The power and heat-stress conditions of geometrically similar engines are discussed. The advantages accruing from smaller cylinder dimensions are higher specific horsepower, lower weight per horsepower, lower piston temperature, and less frontal area, with reduced detonation tendency.
Rocket engine heat transfer and material technology for commercial applications
NASA Technical Reports Server (NTRS)
Hiltabiddle, J.; Campbell, J.
1974-01-01
Liquid fueled rocket engine combustion, heat transfer, and material technology have been utilized in the design and development of compact combustion and heat exchange equipment intended for application in the commercial field. An initial application of the concepts to the design of a compact steam generator to be utilized by electrical utilities for the production of peaking power is described.
Rocket engine heat transfer and material technology for commercial applications
NASA Technical Reports Server (NTRS)
Hiltabiddle, J.; Campbell, J.
1974-01-01
Liquid fueled rocket engine combustion, heat transfer, and material technology have been utilized in the design and development of compact combustion and heat exchange equipment intended for application in the commercial field. An initial application of the concepts to the design of a compact steam generator to be utilized by electrical utilities for the production of peaking power is described.
Study on analysis of ionic wind for heat transfer enhancement .
NASA Astrophysics Data System (ADS)
Ko, Han Seo; Shin, Dong Ho
2016-11-01
Local heat transfer technology was investigated using ionic wind generation in this study. Characteristics of ionic wind using wire and plate electrodes were studied by experimental and numerical methods. A particle image velocitimetry (PIV) test was conducted for a study of a boundary layer controlled by the ionic wind on the heated surface in the wind tunnel. It was found that the coulombic force consistently acted on the surface to reduce the effect of the viscous boundary layer. The boundary layer was formed on the heated surface and controlled by the ionic wind regardless of the Reynolds number of the bulk flow. The heat transfer coefficient increased and decreased, 11% and 19% in average on the heated surface by the ionic wind, for the condition of lower (100 200) and higher (2500 3500) Reynolds numbers of the bulk flow, respectively. It was concluded that the ionic wind can be used for enhancing the convection heat transfer rate or insulating the local surface according to its operating condition. The results of the local heat transfer controlled by the ionic wind were applied for the heat exchanger and the performance was confirmed by the experimental and numerical methods.
Heat Transfer from Finned Metal Cylinders in an Air Stream
NASA Technical Reports Server (NTRS)
Biermann, Arnold, E; Pinkel, Benjamin
1935-01-01
This report presents the results of tests made to supply design information for the construction of metal fins for the cooling of heated cylindrical surfaces by an air stream. A method is given for determining fin dimensions for a maximum heat transfer with the expenditure of a given amount of material for a variety of conditions of air flow and metals.
Students' Misconceptions about Heat Transfer Mechanisms and Elementary Kinetic Theory
ERIC Educational Resources Information Center
Pathare, S. R.; Pradhan, H. C.
2010-01-01
Heat and thermodynamics is a conceptually rich area of undergraduate physics. In the Indian context in particular there has been little work done in this area from the point of view of misconceptions. This prompted us to undertake a study in this area. We present a study of students' misconceptions about heat transfer mechanisms, i.e. conduction,…
Instabilities encountered during heat transfer to a supercritical fluid
NASA Technical Reports Server (NTRS)
Cornelius, A. J.
1969-01-01
Investigation was made of the unstable behavior of a heat-transfer loop operating at a supercritical pressure. Natural convection operation of the loop, with observations on acoustic and slow oscillatory behavior, was emphasized during testing. The basic cause of both types of behavior appeared to originate in the heated boundary layer.
Heat transfer model of above and underground insulated piping systems
Kwon, K.C.
1998-07-01
A simplified heat transfer model of above and underground insulated piping systems was developed to perform iterative calculations for fluid temperatures along the entire pipe length. It is applicable to gas, liquid, fluid flow with no phase change. Spreadsheet computer programs of the model have been developed and used extensively to perform the above calculations for thermal resistance, heat loss and core fluid temperature.
Students' Misconceptions about Heat Transfer Mechanisms and Elementary Kinetic Theory
ERIC Educational Resources Information Center
Pathare, S. R.; Pradhan, H. C.
2010-01-01
Heat and thermodynamics is a conceptually rich area of undergraduate physics. In the Indian context in particular there has been little work done in this area from the point of view of misconceptions. This prompted us to undertake a study in this area. We present a study of students' misconceptions about heat transfer mechanisms, i.e. conduction,…
Environmental Heat Transfer to a Microclimate Cooling System During Heat Exposure.
2007-11-02
models, heat transfer measured during future physiological tests can be apportioned between Q^ and Qt^y. Introduction Heat stress and the resultant...is prudent to institute countermeasures to heat stress when work is required in environments where heat dissipation is limited. One countermeasure...19.0 14.2 Min 60 26.2 19.2 21.1 15.0 10 Table 8 - Heat transfer (w) at the calves during whole-body cooling. Time 15°C 20°C 25°C 30°C Min 0 -2.5
Komendantov, A.S.; Kuzma-Kichta, Y.A.; Vasil'eva, L.T.; Ovodkov, A.A. )
1991-01-01
In this paper burnout is investigated in tubes under nonuniform heating on the perimeter. Data on heat transfer and critical heat flux (q{sub chf}) in the case of water were obtained for ranges of mass velocity {rho}w = 200--3000 kg/m{sup 2} s, pressure p = 1--1 MPa, and inlet water temperature T = 25--98{degrees}C. The test section was a horizontal copper tube of 21 mm outer diameter, 8 mm inner diameter with a technically smooth surface and heat transfer-intensifying twisted tape and porous sintered coating. The test section was heated by bombardment with electrons. It is established that a redistribution of heat fluxes and an increase of wall temperature fluctuations occur at burnout. The range of regime parameters to prevent burnout of a heat transfer surface is determined.
Unsteady heat transfer performance of heat pipe with axially swallow-tailed microgrooves
NASA Astrophysics Data System (ADS)
Zhang, R. P.
2017-04-01
A mathematical model is developed for predicting the transient heat transfer and fluid flow of heat pipe with axially swallow-tailed microgrooves. The effects of liquid convective heat transfer in the microgrooves, liquid-vapor interfacial phase-change heat transfer and liquid-vapor interfacial shear stress are accounted for in the present model. The coupled non-linear control equations are solved numerically. Mass flow rate at the interface is obtained from the application of kinetic theory. Time variation of wall temperature is studied from the initial startup to steady state. The numerical results are verified by experiments. Time constants for startup and shutdown operation are defined to determine how fast a heat pipe responds to an applied input heat flux, which slightly decreases with increasing heat load.
A Conceptual Change Model for Teaching Heat Energy, Heat Transfer and Insulation
ERIC Educational Resources Information Center
Lee, C. K.
2014-01-01
This study examines the existing knowledge that pre-service elementary teachers (PSETs) have regarding heat energy, heat transfer and insulation. The PSETs' knowledge of heat energy was initially assessed by using an activity: determining which container would be best to keep hot water warm for the longest period of time. Results showed that PSETs…
Heat Transfer Over the Circumference of a Heated Cylinder in Transverse Flow
NASA Technical Reports Server (NTRS)
Schmidt, Ernst; Wenner, Karl
1943-01-01
A method for recording the local heat-transfer coefficients on bodies in flow was developed. The cylinder surface was kept at constant temperature by the condensation of vapor except for a narrow strip which is heated separately to the same temperature by electricity. The heat-transfer coefficient at each point was determined from the electric heat output and the temperature increase. The distribution of the heat transfer along the circumference of cylinders was recorded over a range of Reynolds numbers of from 5000 to 426,000. The pressure distribution was measured at the same time. At Reynolds numbers up to around 100,000 high maximums of the heat transfer occurred in the forward stagnation point at and on the rear side at 180C, while at around 80 the heat-transfer coefficient on both sides of the cylinder behind the forward stagnation point manifested distinct minimums. Two other maximums occurred at around 115 C behind the forward stagnation point between 170,000 and 426,000. At 426,000 the heat transfer at the location of those maximums was almost twice as great as in the forward stagnation point, and the rear half of the cylinder diffused about 60 percent of the entire heat, The tests are compared with the results of other experimental and theoretical investigations.
Nanoscale Heat Transfer using Phonon Boltzmann Transport Equation
2009-10-01
Fourier diffusive equation ( FDE ). The equation can be derived using a conservation law of energy and Fourier’s linear approximation of heat flux...using a temperature gradient. The FDE is a parabolic equation reflecting a diffusive nature of heat transport. An underlying assumption is that...the heat is effectively transferred between localized regions through sufficient scattering events of phonons within a medium. Therefore, the FDE
Introduction to heat transfer test setup for the SCRAP receiver
NASA Astrophysics Data System (ADS)
Lubkoll, Matti; Harms, Thomas M.; von Backström, Theodor W.
2017-06-01
The Spiky Central Receiver Air Pre-heater (SCRAP) receiver is a novel external tubular metallic central receiver concept. The SCRAP receiver is designed to increase an air-receivers solar-thermal performance. This is aimed to be achieved by enhancing heat transfer to the pressurized air-stream within the absorber assemblies (spikes) by utilizing an internally finned tube geometry. The fin shape is defined to create rectangular ducts as passages for the air flow, therewith a high heat transfer coefficient. The spikes are arranged in such a way that they trap incoming concentrated radiation (reduce reflection losses) and minimize thermal radiation losses from the receiver to ambient. In previous work, the modeling of a SCRAP receiver was discussed on. This included the modeling of the internal air flow and heat transfer within a spike, analysis of the optical characteristics of a SCRAP receiver and the impingement heat transfer capabilities in the spike tip (exposed to the highest flux). Further, analysis of the thermal interaction of spikes with one another and with ambient (convective and radiative heat loss) permitted drawing of first conclusions of the receiver performance potential. To validate the models predicting the pressurized air flow and heat transfer within a spike, an experimental test setup was designed, constructed and built at the heat transfer laboratories at Stellenbosch University. This work introduces the design of the test setup and will discuss preliminary results obtained during its commissioning. From first analysis the predictions made for the pressure drop within the internally finned section appear adequate. The heat transfer behavior will require further detailed analysis to develop sufficient confidence to allow for conclusions. Initial results, however, show good general agreement between measured and simulated data.
NASA Astrophysics Data System (ADS)
Abbasian Arani, Ali Akbar; Aberoumand, Hossein; Jafarimoghaddam, Amin; Aberoumand, Sadegh
2017-09-01
The heat transfer and flow characteristics of Cu-heat transfer oil nanofluid during mixed convection through horizontal annular tubes under uniform heat flux as boundary condition are investigated experimentally. Data were acquired at low Reynolds number ranged from about 26 to 252. The applied nanofluid prepared by Electrical Explosion of Wire technique with no nanoparticles agglomeration during nanofluid preparation process and experiments. Pure heat transfer oil and nanofluids with nanoparticles weight concentrations of 0.12, 0.36 and 0.72% were used as the working fluids. Based on these results, Effects of nanoparticles concentration, heat flux and free convection on the thermal field development are studied under buoyancy assisted flow condition for Grashof number, Richardson number between 2820 and 12,686, and 0.1-10, respectively. Results show that Nusselt number increases with an increase of nanoparticles weight concentrations from 0 to 0.72% under certain Richardson numbers.
Boiling heat transfer in a small horizontal rectangular channel
Tran, T.N.; Wambsganss, M.W.; Jendrzejczyk, J.A.; France, D.M.
1993-08-01
Compact heat exchangers have traditionally found wide application in the transportation industry, where they are used as evaporators and condensers in vapor compression cycles for air conditioning and refrigeration. Such heat exchangers possess numerous attractive features including high thermal effectiveness, small size, low weight, design flexibility, and pure counterflow, and they can accommodate multiple streams. Today, there is a widespread interest in expanding the range of application of compact heat exchangers to include phase-change heat transfer in the process industries, among others. An overall objective of this effort is to provide the basis for establishing design technology in this area. In the present study, small channel flow boiling heat transfer was extended to a rectangular channel (4.06 {times} 1.70 mm) using refrigerant 12 (R-12). As with the circular tube studies, the flow channel wall was electrically heated providing a constant heat flux. Tests were performed over a quality range of 0.15 to 0.80, and large ranges of mass fluxes (50 to 400 kg/m{sup 2}s) and heat flux (4 to 34 kW/m{sup 2}). Heat transfer was measured and results are compared with correlation predictions.
O'Brien, James Edward; Sohal, Manohar Singh; Huff, George Albert
2002-08-01
A combined experimental and numerical investigation is under way to investigate heat transfer enhancement techniques that may be applicable to large-scale air-cooled condensers such as those used in geothermal power applications. The research is focused on whether air-side heat transfer can be improved through the use of finsurface vortex generators (winglets,) while maintaining low heat exchanger pressure drop. A transient heat transfer visualization and measurement technique has been employed in order to obtain detailed distributions of local heat transfer coefficients on model fin surfaces. Pressure drop measurements have also been acquired in a separate multiple-tube row apparatus. In addition, numerical modeling techniques have been developed to allow prediction of local and average heat transfer for these low-Reynolds-number flows with and without winglets. Representative experimental and numerical results presented in this paper reveal quantitative details of local fin-surface heat transfer in the vicinity of a circular tube with a single delta winglet pair downstream of the cylinder. The winglets were triangular (delta) with a 1:2 height/length aspect ratio and a height equal to 90% of the channel height. Overall mean fin-surface Nusselt-number results indicate a significant level of heat transfer enhancement (average enhancement ratio 35%) associated with the deployment of the winglets with oval tubes. Pressure drop measurements have also been obtained for a variety of tube and winglet configurations using a single-channel flow apparatus that includes four tube rows in a staggered array. Comparisons of heat transfer and pressure drop results for the elliptical tube versus a circular tube with and without winglets are provided. Heat transfer and pressure-drop results have been obtained for flow Reynolds numbers based on channel height and mean flow velocity ranging from 700 to 6500.
Rod Bundle Heat Transfer: Steady-State Steam Cooling Experiments
Spring, J.P.; McLaughlin, D.M.
2006-07-01
Through the joint efforts of the Pennsylvania State University and the United States Nuclear Regulatory Commission, an experimental rod bundle heat transfer (RBHT) facility was designed and built. The rod bundle consists of a 7 x 7 square pitch array with spacer grids and geometry similar to that found in a modern pressurized water reactor. From this facility, a series of steady-state steam cooling experiments were performed. The bundle inlet Reynolds number was varied from 1 400 to 30 000 over a pressure range from 1.36 to 4 bars (20 to 60 psia). The bundle inlet steam temperature was controlled to be at saturation for the specified pressure and the fluid exit temperature exceeded 550 deg. C in the highest power tests. One important quantity of interest is the local convective heat transfer coefficient defined in terms of the local bulk mean temperature of the flow, local wall temperature, and heat flux. Steam temperatures were measured at the center of selected subchannels along the length of the bundle by traversing miniaturized thermocouples. Using an analogy between momentum and energy transport, a method was developed for relating the local subchannel centerline temperature measurement to the local bulk mean temperature. Wall temperatures were measured using internal thermocouples strategically placed along the length of each rod and the local wall heat flux was obtained from an inverse conduction program. The local heat transfer coefficient was calculated from the data at each rod thermocouple location. The local heat transfer coefficients calculated for locations where the flow was fully developed were compared against several published correlations. The Weisman and El-Genk correlations were found to agree best with the RBHT steam cooling data, especially over the range of turbulent Reynolds numbers. The effect of spacer grids on the heat transfer enhancement was also determined from instrumentation placed downstream of the spacer grid locations. The local
Sparkes, Louise; Chan, Maggie Mee Kie; Cooper, Simon; Pang, Michelle Tsz Ha; Tiwari, Agnes
2016-09-01
International concerns relating to healthcare professionals' failure to rescue deteriorating patients exist. Web-based training programs have been developed and evaluated in Western settings but further testing is required before application in non-Western countries, as traditional modalities of learning may differ between cultures. We trialed an Australian English language online simulation program for the management of deteriorating patients, Feedback Incorporating Review and Simulation Techniques to Act on Clinical Trends (FIRST(2) ACTWeb), to test cultural acceptability, transferability, and educational impact. The study was designed as a quasi-experimental evaluation of the FIRST(2) ACTWeb program with final year nursing students from a Bachelor of Nursing program at the University of Hong Kong. Participants completed pre-course and post-course tests, three interactive scenarios, and program evaluations. The program was positively evaluated, with significant improvements in knowledge, skills, self-rating of performance, confidence, and competence. Outcomes were comparable to earlier evaluations with Australian students, demonstrating that an interactive simulation-based program of patient deterioration management has cultural and language acceptability and transferability across communities with significant educational impact. © 2016 John Wiley & Sons Australia, Ltd.
Heat transfer to a silicon carbide/water nanofluid.
Yu, W.; France , D. M.; Smith, D. S.; Singh, D.; Timofeeva, E. V.; Routbort, J. L.; Univ. of Illinois at Chicago
2009-07-01
Heat transfer experiments were performed with a water-based nanofluid containing 170-nm silicon carbide particles at a 3.7% volume concentration and having potential commercial viability. Heat transfer coefficients for the nanofluid are presented for Reynolds numbers ranging from 3300 to 13,000 and are compared to the base fluid water on the bases of constant Reynolds number, constant velocity, and constant pumping power. Results were also compared to predictions from standard liquid correlations and a recently altered nanofluid correlation. The slip mechanisms of Brownian diffusion and thermophoresis postulated in the altered correlation were investigated in a series of heating and cooling experiments.
Radiative heat transfer as a Landauer-Büttiker problem
NASA Astrophysics Data System (ADS)
Yap, Han Hoe; Wang, Jian-Sheng
2017-01-01
We study the radiative heat transfer between two semi-infinite half-spaces, bounded by conductive surfaces in contact with vacuum. This setup is interpreted as a four-terminal mesoscopic transport problem. The slabs and interfaces are viewed as bosonic reservoirs, coupled perfectly to a scattering center consisting of the two planes and vacuum. Using Rytov's fluctuational electrodynamics and assuming Kirchhoff's circuital law, we calculate the heat flow in each bath. This allows for explicit evaluation of a conductance matrix, from which one readily verifies Büttiker symmetry. Thus, radiative heat transfer in layered media with conductive interfaces becomes a Landauer-Büttiker transport problem.
Free convective heat transfer to supercritical carbon dioxide
NASA Astrophysics Data System (ADS)
Neumann, R. J.; Hahne, E. W. P.
1980-12-01
Experiments on free convective heat transfer from electrically heated platinum wires and a platinum strip to supercritical carbon dioxide were performed for a wide range of bulk conditions. It is shown that heat transfer can be predicted by a conventional Nusselt-type correlation if the dimensionless numbers are based on integrated thermophysical properties in order to account for large changes in these properties. The anomaly of thermal conductivity has to be considered. Agreement between the experimental results and the correlation is within 10 percent even for very thin wires when for those a correction factor is introduced.
Heat transfer in serpentine passages with turbulence promoters
NASA Technical Reports Server (NTRS)
Boyle, R. J.
1984-01-01
Local heat transfer rates and overall pressure losses were determined for serpentine passages of square cross section. The flow entered an inlet leg, turned 180 deg and then passed through an outlet leg. Results were obtained for a passage with smooth walls for three different bend geometries and the effect of turbulence promoters was investigated. Turbulence promoters between 0.6 and 15% of the passage height were tested. Local heat transfer rates are determined from thermocouple measurements on a thin electrically heated Inconel foil and pressure drop is measured along the flow path.
Turbulent heat transfer prediction method for application to scramjet engines
NASA Technical Reports Server (NTRS)
Pinckney, S. Z.
1974-01-01
An integral method for predicting boundary layer development in turbulent flow regions on two-dimensional or axisymmetric bodies was developed. The method has the capability of approximating nonequilibrium velocity profiles as well as the local surface friction in the presence of a pressure gradient. An approach was developed for the problem of predicting the heat transfer in a turbulent boundary layer in the presence of a high pressure gradient. The solution was derived with particular emphasis on its applicability to supersonic combustion; thus, the effects of real gas flows were included. The resulting integrodifferential boundary layer method permits the estimation of cooling reguirements for scramjet engines. Theoretical heat transfer results are compared with experimental combustor and noncombustor heat transfer data. The heat transfer method was used in the development of engine design concepts which will produce an engine with reduced cooling requirements. The Langley scramjet engine module was designed by utilizing these design concepts and this engine design is discussed along with its corresponding cooling requirements. The heat transfer method was also used to develop a combustor cooling correlation for a combustor whose local properties are computed one dimensionally by assuming a linear area variation and a given heat release schedule.
Heat Transfer Characteristics of Slush Nitrogen in Turbulent Pipe Flows
NASA Astrophysics Data System (ADS)
Ohira, K.; Ishimoto, J.; Nozawa, M.; Kura, T.; Takahashi, N.
2008-03-01
Slush fluids, such as slush hydrogen and slush nitrogen, are two-phase (solid-liquid) single-component cryogenic fluids containing solid particles in a liquid, and consequently their density and refrigerant capacity are greater than for liquid state fluid alone. This paper reports on the experimental results of the forced convection heat transfer characteristics of slush nitrogen flowing in a pipe. Heat was supplied to slush nitrogen by a heater wound around the copper pipe wall. The local heat transfer coefficient was measured in conjunction with changes in the velocity and the solid fraction. The differences in heat transfer characteristics between two-phase slush and single phase liquid nitrogen were obtained, and the decrease in heat transfer to slush nitrogen caused by the previously observed pressure drop reduction was confirmed by this study. Furthermore, for the purpose of establishing the thermal design criteria for slush nitrogen in the case of pressure drop reduction, the heat transfer correlation between the experimental results and the Sieder-Tate Equation was obtained.
Ultrasonic Heat Transfer Enhancement Using a Horn-Type Transducer
NASA Astrophysics Data System (ADS)
Nomura, Shinfuku; Yamamoto, Akira; Murakami, Koichi
2002-05-01
The purpose of this study is to clarify experimentally the influence of streaming induced by ultrasonic vibration on heat transfer using a horn-type ultrasonic vibrator. A horn tip of 6 mm diameter and 60.7 kHz resonant frequency was used as the ultrasonic transducer. Heat transfer experiments for a downward-facing horizontal heating surface with ultrasonic vibration from below were carried out in a natural convection region. The acoustic jet in the water from the horn tip of the transducer regarded as a nozzle exit was induced by this transducer, and as a result, up to a ten-fold increase in heat transfer coefficient was obtained by application of 20 W in both tap water and degassed water. It was found that the mechanism of heat transfer enhancement by ultrasonic vibration in tap water can be classified into four categories. In degassed water, heat transfer enhancement is influenced not by the acoustic jet, but by small-scale perturbations by cavitation microjets.
NASA Astrophysics Data System (ADS)
Koca, Aliihsan; Acikgoz, Ozgen; Çebi, Alican; Çetin, Gürsel; Dalkilic, Ahmet Selim; Wongwises, Somchai
2017-08-01
Investigations on heated ceiling method can be considered as a new research area in comparison to the common wall heating-cooling and cooled ceiling methods. In this work, heat transfer characteristics of a heated radiant ceiling system was investigated experimentally. There were different configurations for a single room design in order to determine the convective and radiative heat transfer rates. Almost all details on the arrangement of the test chamber, hydraulic circuit and radiant panels, the measurement equipment and experimental method including uncertainty analysis were revealed in detail indicating specific international standards. Total heat transfer amount from the panels were calculated as the sum of radiation to the unheated surfaces, convection to the air, and conduction heat loss from the backside of the panels. Integral expression of the view factors was calculated by means of the numerical evaluations using Matlab code. By means of this experimental chamber, the radiative, convective and total heat-transfer coefficient values along with the heat flux values provided from the ceiling to the unheated surrounding surfaces have been calculated. Moreover, the details of 28 different experimental case study measurements from the experimental chamber including the convective, radiative and total heat flux, and heat output results are given in a Table for other researchers to validate their theoretical models and empirical correlations.
Numerical simulation of transitional flows with heat transfer
NASA Astrophysics Data System (ADS)
Kožíšek, Martin; Příhoda, Jaromír; Fürst, Jiří; Straka, Petr
2016-06-01
The contribution deals with simulation of internal flows with the laminar/turbulent transition and heat transfer. The numerical modeling of incompressible flow on a heated flat plate was carried out partly by the k-kL-ω model of Walters and Cokljat [1] and partly by the algebraic transition model of Straka and Příhoda [2] connected with the EARSM turbulence model of Hellsten [3]. Transition models were tested by means of the skin friction and the Stanton number distribution. Used models of turbulent heat transfer were compared with the simplest model based on the constant turbulent Prandtl number. The k-kL-ω model is applied for the simulation of compressible flow through the VKI turbine blade cascade with heat transfer.
Comparative study of convective heat transfer characteristics of nanofluids
NASA Astrophysics Data System (ADS)
Muryam, Hina; Ramzan, Naveed; Umer, Asim; Awan, Gul Hameed; Hassan, Ali
2017-02-01
The present research is about to draw a comparison between heat transfer characteristics of gold/deionized water (DIW) and silver/DIW based nanofluid under same heat flux for laminar flow. Experiments are performed on both nanofluid by using different concentrations (0.015, 0.045, 0.0667%) of nano-particles (NPs) in DIW as a base fluid. The experimental study concludes that an appreciable intensification in heat transfer coefficient (HTC) of both nanofluid has been attained as compare to base fluid. However, gold/DIW based nanofluid exhibit better convective heat transfer intensification compared with silver/DIW based nanofluid but Shah correlation cannot predict as much augmentation as in experimental work for both nanofluid. It is also noticed that the anomalous enhancement in Nusselt number and HTC is not only due to the accession in thermal properties but also by the formation of thinner thermal boundary layer at the entrance of the tube due to NPs.
Heat Transfer Simulation for Reciprocating Compressor with Experimental Validation
NASA Astrophysics Data System (ADS)
Zhou, Ruixin; Guo, Bei; Chen, Xiaole; Tuo, Jinliang; Wu, Rui; Fagotti, Fabian; Zhao, Yali; Yang, Song; Xu, Bo
2017-08-01
The efficiency of reciprocating compressor can be influenced by heat transfer and the reliability can be also affected by the temperature distribution in compressor. In consideration of the complex relationship of heat transfer, the compressor is divided into six control volumes including the suction muffler, the cylinder, the discharge chamber, the discharge muffler, the discharge line and the compressor shell. The steady state energy balance equations of the open system for each control volume are built up after the crankshaft rotates one cycle. The heat flux of the cylinder is calculated by the existing correlation. The heat transfer coefficient correlations in energy equations are chosen in references and revised by experimental results. Three same type reciprocating compressors used in R290 system installed with themocouples are tested under some planed conditions in order to ensure accuracy. The simulation results are compared with the experimental results. It shows that the simplified method presented in this paper is effective.
Comparative study of convective heat transfer characteristics of nanofluids
NASA Astrophysics Data System (ADS)
Muryam, Hina; Ramzan, Naveed; Umer, Asim; Awan, Gul Hameed; Hassan, Ali
2017-07-01
The present research is about to draw a comparison between heat transfer characteristics of gold/deionized water (DIW) and silver/DIW based nanofluid under same heat flux for laminar flow. Experiments are performed on both nanofluid by using different concentrations (0.015, 0.045, 0.0667%) of nano-particles (NPs) in DIW as a base fluid. The experimental study concludes that an appreciable intensification in heat transfer coefficient (HTC) of both nanofluid has been attained as compare to base fluid. However, gold/DIW based nanofluid exhibit better convective heat transfer intensification compared with silver/DIW based nanofluid but Shah correlation cannot predict as much augmentation as in experimental work for both nanofluid. It is also noticed that the anomalous enhancement in Nusselt number and HTC is not only due to the accession in thermal properties but also by the formation of thinner thermal boundary layer at the entrance of the tube due to NPs.
Effect of boiling surface vibration on heat transfer
NASA Astrophysics Data System (ADS)
Alangar, Sathyabhama
2017-01-01
Experimental investigation of effect of forced vertical surface vibration on nucleate pool boiling heat transfer of saturated water at atmospheric pressure is presented in this paper. Vertical vibration was induced externally to the circular copper test surface on which boiling took place, using a vibration exciter. Frequency was varied in the range 0-25 Hz and amplitude of vibration was varied in the range 0-5 mm. Boiling takes place at much lower superheats for the same heat flux, slope of boiling curve decreases remarkably, when the surface is given external excitation. High frequency and high amplitude oscillations lead to more intensive heat transfer. There are some combinations of frequency and vibration amplitude, which cause up to two times increase in heat transfer coefficients.
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.
Boiling heat transfer enhancement in subsurface horizontal and vertical tunnels
Pastuszko, Robert
2008-09-15
Complex experimental investigations of boiling heat transfer on structured surfaces covered with perforated foil were taken up. Experimental data were discussed for two kinds of enhanced surfaces formed by joined horizontal and vertical tunnels: tunnel structures (TS) and narrow tunnel structures (NTS). The experiments were carried out with water, ethanol and R-123 at atmospheric pressure. The TS and NTS surfaces were manufactured out of perforated copper foil of 0.05 mm thickness (hole diameters: 0.3, 0.4, 0.5 mm) sintered with the mini-fins, formed on the vertical side of the 5 mm high rectangular fins and horizontal inter-fin surface. The effects of hole (pore) diameters, tunnel pitch for TS and tunnel width for NTS on nucleate pool boiling were examined. Substantial enhancement of heat transfer coefficient was observed. The investigated surfaces showed boiling heat transfer coefficients similar to those of existing structures with subsurface tunnels, but at higher heat fluxes range. (author)
Modeling of Radiative Heat Transfer in an Electric Arc Furnace
NASA Astrophysics Data System (ADS)
Opitz, Florian; Treffinger, Peter; Wöllenstein, Jürgen
2017-08-01
Radiation is an important means of heat transfer inside an electric arc furnace (EAF). To gain insight into the complex processes of heat transfer inside the EAF vessel, not only radiation from the surfaces but also emission and absorption of the gas phase and the dust cloud need to be considered. Furthermore, the radiative heat exchange depends on the geometrical configuration which is continuously changing throughout the process. The present paper introduces a system model of the EAF which takes into account the radiative heat transfer between the surfaces and the participating medium. This is attained by the development of a simplified geometrical model, the use of a weighted-sum-of-gray-gases model, and a simplified consideration of dust radiation. The simulation results were compared with the data of real EAF plants available in literature.
Heat transfer during intermittent/slug flow in horizontal tubes
Shoham, O.; Dukler, A.E.; Taitel, Y.
1982-08-01
Heat transfer characteristics for two-phase gas-liquid slug flow in a horizontal pipe have been measured. The time variation of temperature, heat transfer coefficients, and heat flux is reported for the different zones of slug flow: the mixing region at the nose, the body of the slug, the liquid film, and the gas bubble behind the slug. Substantial differences in heat transfer coefficient exist between the bottom and top of the slug. This results from the fact that each slug is effectively a thermally developing entry region caused by the presence of a hot upper wall just upstream of each slug. A qualitative theory is presented which explains this behavior. 18 refs.
Heat and Mass Transfer Model in Freeze-Dried Medium
NASA Astrophysics Data System (ADS)
Alfat, Sayahdin; Purqon, Acep
2017-07-01
There are big problems in agriculture sector every year. One of the major problems is abundance of agricultural product during the peak of harvest season that is not matched by an increase in demand of agricultural product by consumers, this causes a wasted agricultural products. Alternative way was food preservation by freeze dried method. This method was already using heat transfer through conduction and convection to reduce water quality in the food. The main objective of this research was to design a model heat and mass transfer in freeze-dried medium. We had two steps in this research, the first step was design of medium as the heat injection site and the second was simulate heat and mass transfer of the product. During simulation process, we use physical property of some agriculture product. The result will show how temperature and moisture distribution every second. The method of research use finite element method (FEM) and will be illustrated in three dimensional.
Modelling of heat and mass transfer processes in neonatology.
Ginalski, Maciej K; Nowak, Andrzej J; Wrobel, Luiz C
2008-09-01
This paper reviews some of our recent applications of computational fluid dynamics (CFD) to model heat and mass transfer problems in neonatology and investigates the major heat and mass transfer mechanisms taking place in medical devices such as incubators and oxygen hoods. This includes novel mathematical developments giving rise to a supplementary model, entitled infant heat balance module, which has been fully integrated with the CFD solver and its graphical interface. The numerical simulations are validated through comparison tests with experimental results from the medical literature. It is shown that CFD simulations are very flexible tools that can take into account all modes of heat transfer in assisting neonatal care and the improved design of medical devices.
NASA Astrophysics Data System (ADS)
Morris, J. F.
1985-03-01
This invention is directed to transferring heat from an extremely high temperature source to an electrically isolated lower temperature receiver. The invention is particularly concerned with supplying thermal power to a thermionic converter from a nuclear reactor with electric isolation. Heat from a high temperature heat pipe is transferred through a vacuum or a gap filled with electrically nonconducting gas to a cooler heat pipe. If the receiver requires gratr thermal power density, geometries are used with larger heat pipe areas for transmitting and receiving energy than the area for conducting the heat to the thermionic converter. In this way the heat pipe capability for increasing thermal power densities compensates for the comparative low thermal power densities through the electrically nonconducting gap between the two heat pipes.
NASA Technical Reports Server (NTRS)
Morris, J. F. (Inventor)
1985-01-01
This invention is directed to transferring heat from an extremely high temperature source to an electrically isolated lower temperature receiver. The invention is particularly concerned with supplying thermal power to a thermionic converter from a nuclear reactor with electric isolation. Heat from a high temperature heat pipe is transferred through a vacuum or a gap filled with electrically nonconducting gas to a cooler heat pipe. If the receiver requires gratr thermal power density, geometries are used with larger heat pipe areas for transmitting and receiving energy than the area for conducting the heat to the thermionic converter. In this way the heat pipe capability for increasing thermal power densities compensates for the comparative low thermal power densities through the electrically nonconducting gap between the two heat pipes.
Bae, Y. Y.; Hong, S. D.; Kim, Y. W.
2012-07-01
A number of computational works have been performed so far for the simulation of heat transfer in a supercritical fluid. The simulations, however, faced a lot of difficulties when heat transfer deteriorates due either to buoyancy or by acceleration. When the bulk temperature approaches the pseudo-critical temperature the fluid experiences a severe axial density gradient on top of a severe radial one. Earlier numerical calculations showed, without exception, unrealistic over-predictions, as soon as the bulk temperature exceeded the pseudo-critical temperature. The over-predictions might have been resulted from an inapplicability of widely-used turbulence models. One of the major causes for the difficulties may probably be an assumption of a constant turbulent Prandtl number. Recent research, both numerical and experimental, indicates that the turbulent Prandtl number is never a constant when the gradient of physical properties is significant. This paper describes the applicability of a variable turbulent Prandtl number to the numerical simulation of heat transfer in supercritical fluids flowing in narrow vertical tubes. (authors)
Curvature dependence of the interfacial heat and mass transfer coefficients
NASA Astrophysics Data System (ADS)
Glavatskiy, K. S.; Bedeaux, D.
2014-03-01
Nucleation is often accompanied by heat transfer between the surroundings and a nucleus of a new phase. The interface between two phases gives an additional resistance to this transfer. For small nuclei the interfacial curvature is high, which affects not only equilibrium quantities such as surface tension, but also the transport properties. In particular, high curvature affects the interfacial resistance to heat and mass transfer. We develop a framework for determining the curvature dependence of the interfacial heat and mass transfer resistances. We determine the interfacial resistances as a function of a curvature. The analysis is performed for a bubble of a one-component fluid and may be extended to various nuclei of multicomponent systems. The curvature dependence of the interfacial resistances is important in modeling transport processes in multiphase systems.
Quantification of convective heat transfer inside tree structures
NASA Astrophysics Data System (ADS)
Collin, Anthony; Lamorlette, Aymeric
2012-11-01
Convective heat transfer between a vegetal structure and its surrounding medium remains poorly described. However, for some applications, such as forest fire propagation studies, convective heat transfer is one of the main factors responsible for vertical fire transitions, from ground level to the tree crowns. These fires are the most dangerous because their rates of spread can reach high speeds, around one meter per second. An accurate characterization of this transfer is therefore important for fire propagation modelling. This study presents an attempt to formulate a theoretical modelling of the convective heat transfer coefficient for vegetal structures generated using an Iterated Function Systems (IFS). This model depends on the IFS parameters. The results obtained using this approach were compared with previously computed numerical results in order to evaluate their accuracy. The maximal discrepancies were found to be around 12% which proves the efficiency of the present model.
Dynamic heat and moisture transfer in bulky PAN nanofiber mats
NASA Astrophysics Data System (ADS)
Borhani, Sedigheh; Etemad, Seyed Gholamreza; Ravandi, Seyed Abdolkarim Hosseini
2011-07-01
In this study a non-conventional electrospinning technique was designed for the production of high bulky polyacrylonitrile (PAN) nanofiber mats. Optimum nanofiber mats are achieved with 15 wt.% solution of PAN in dimethylformamide. Such mats result in a bulk porosity which is as high as 99.9 and a density as low as 0.84 × 10-3 g/cm3. The effect of the porosity of nanofiber mats on the air permeability and coupled heat and moisture transfer of fibers was investigated. Based on the results, high bulky nanofiber mats possess high heat and moisture transfer. Experimental data reveal that upon a slight decrease in the bulk porosity, air permeability and heat transfer decrease noticeably, while moisture transfer variation is low.
Heat transfer enhancement accompanying Leidenfrost state suppression at ultrahigh temperatures.
Shahriari, Arjang; Wurz, Jillian; Bahadur, Vaibhav
2014-10-14
The well-known Leidenfrost effect is the formation of a vapor layer between a liquid and an underlying hot surface. This insulating vapor layer severely degrades heat transfer and results in surface dryout. We measure the heat transfer enhancement and dryout prevention benefits accompanying electrostatic suppression of the Leidenfrost state. Interfacial electric fields in the vapor layer can attract liquid toward the surface and promote wetting. This principle can suppress dryout even at ultrahigh temperatures exceeding 500 °C, which is more than 8 times the Leidenfrost superheat for organic solvents. Robust Leidenfrost state suppression is observed for a variety of liquids, ranging from low electrical conductivity organic solvents to electrically conducting salt solutions. Elimination of the vapor layer increases heat dissipation capacity by more than 1 order of magnitude. Heat removal capacities exceeding 500 W/cm(2) are measured, which is 5 times the critical heat flux (CHF) of water on common engineering surfaces. Furthermore, the heat transfer rate can be electrically controlled by the applied voltage. The underlying science is explained via a multiphysics analytical model which captures the coupled electrostatic-fluid-thermal transport phenomena underlying electrostatic Leidenfrost state suppression. Overall, this work uncovers the physics underlying dryout prevention and demonstrates electrically tunable boiling heat transfer with ultralow power consumption.
Finite Element Heat & Mass Transfer Code
Trease, Lynn
1996-10-10
FEHM is a numerical simulation code for subsurface transport processes. It models 3-D, time-dependent, multiphase, multicomponent, non-isothermal, reactive flow through porous and fractured media. It can accurately represent complex 3-D geologic media and structures and their effects on subsurface flow and transport. Its capabilities include flow of gas, water, and heat; flow of air, water, and heat; multiple chemically reactive and sorbing tracers; finite element/finite volume formulation; coupled stress module; saturated and unsaturated media; and double porosity and double porosity/double permeability capabilities.
FEHM. Finite Element Heat & Mass Transfer Code
Zyvoloski, G.A.
1996-10-10
FEHM is a numerical simulation code for subsurface transport processes. It models 3-D, time-dependent, multiphase, multicomponent, non-isothermal, reactive flow through porous and fractured media. It can accurately represent complex 3-D geologic media and structures and their effects on subsurface flow and transport. Its capabilities include flow of gas, water, and heat; flow of air, water, and heat; multiple chemically reactive and sorbing tracers; finite element/finite volume formulation; coupled stress module; saturated and unsaturated media; and double porosity and double porosity/double permeability capabilities.
NASA Astrophysics Data System (ADS)
Cieśliński, Janusz T.; Fiuk, Artur; Typiński, Krzysztof; Siemieńczuk, Bartłomiej
2016-09-01
This study is focused on experimental investigation of selected type of brazed plate heat exchanger (PHEx). The Wilson plot approach was applied in order to estimate heat transfer coefficients for the PHEx passages. The main aim of the paper was to experimentally check ability of several correlations published in the literature to predict heat transfer coefficients by comparison experimentally obtained data with appropriate predictions. The results obtained revealed that Hausen and Dittus-Boelter correlations underestimated heat transfer coefficient for the tested PHEx by an order of magnitude. The Aspen Plate code overestimated heat transfer coefficient by about 50%, while Muley-Manglik correlation overestimated it from 1% to 25%, dependent on the value of Reynolds number and hot or cold liquid side.
Generator-absorber-heat exchange heat transfer apparatus and method and use thereof in a heat pump
Phillips, Benjamin A.; Zawacki, Thomas S.
1998-07-21
Numerous embodiments and related methods for generator-absorber heat exchange (GAX) are disclosed, particularly for absorption heat pump systems. Such embodiments and related methods use, as the heat transfer medium, the working fluid of the absorption system taken from the generator at a location where the working fluid has a rich liquor concentration.
Generator-absorber-heat exchange heat transfer apparatus and method and use thereof in a heat pump
Phillips, B.A.; Zawacki, T.S.
1998-07-21
Numerous embodiments and related methods for generator-absorber heat exchange (GAX) are disclosed, particularly for absorption heat pump systems. Such embodiments and related methods use, as the heat transfer medium, the working fluid of the absorption system taken from the generator at a location where the working fluid has a rich liquor concentration. 5 figs.
Visualization of heat transfer for impinging swirl flow
Bakirci, K.; Bilen, K.
2007-10-15
The objective of the experimental study was to visualize the temperature distribution and evaluate heat transfer rate on the impingement surface kept at a constant wall temperature boundary condition for the swirling (SIJ), multi-channel (MCIJ) and conventional impinging jet (CIJ) using liquid crystal technique. The swirling jet assembly consisted of a housing tube and a solid swirl generator insert which had four narrow slots machined on its surface. The swirl angle, {theta}, was set as 0 , 22.5 , 41 , 50 to change the direction and strength of the swirl in the air flow exiting the housing tube. The local Nusselt numbers of the MCIJ ({theta} = 0 ) were generally much higher than those of CIJ and SIJs. As the swirl angle increased, the radial uniformity of the heat transfer was seen compared to MCIJ and SIJ; the best results were for {theta} = 50 and the jet-to-surface distance of H/D = 14. The location of the distance of the maximum heat transfer for the swirl angles of {theta} = 41 and 50 was shifted away from the stagnation point in a radial distance of nearly r/D = 2.5. Increasing Reynolds number for same swirler angle increased the heat transfer rate on the entire surface, and increased saddle shape heat transfer distribution on the surface, but had no significant effect on the position of the individual impingement regions, but increased saddle shape heat transfer distribution on the surface. The lower Reynolds number (Re = 10 000) and the highest H/D = 14 gave much more uniform local and average heat transfer distribution on the surface, but decreased their values on the entire surface. (author)
Combined heat and mass transfer in absorption processes
Grossman, G.
1982-01-01
The approach to theoretical analysis of the combined heat and mass transfer process taking place in absorption systems is described. The two tranfer phenomena are strongly coupled here. The purpose of the analysis is to relate, quantitatively, the heat and mass transfer coefficients to the physical properties of the working fluids and to the geometry of the system. The preferred configuration is that of a falling film of liquid on a metallic surface which serves to transfer heat from the absorbent in contact with the vapor of the absorbate. The model developed may be solved for laminar, turbulent, or transition flow regimes. The results of the solution describe the development of the thermal and concentration boundary layers and the variation of the temperatures, concentrations, and heat and mass fluxes. These quantities in their normalized, dimensionless form depend on two characteristic parameters of the system: the Lewis number Le and the dimensionless heat of absorption lambda. The length in the direction of flow is normalized with respect to the Peclet number and the film thickness. Heat and mass transfer coefficients for the system were calculated. The Sherwood number for mass transfer from the vapor-liquid interface to the bulk of the film reaches a constant value of 3.63 with fully developed boundary layers for both the adiabatic and constant temperature wall. The Nusselt number for heat transfer from the interface to the bulk reaches under the same conditions values of 3.63 and 2.67 for the adiabatic and constant temperature wall, respectively. The Nusselt number for heat tranfer from the bulk to the wall reaches 1.60.
Non-conductive heat transfer associated with frozen soils
NASA Astrophysics Data System (ADS)
Kane, Douglas L.; Hinkel, Kenneth M.; Goering, Douglas J.; Hinzman, Larry D.; Outcalt, Samuel I.
2001-06-01
The assertion that pure conductive heat transfer always dominates in cold climates is at odds with decades of research in soil physics which clearly demonstrate that non-conductive heat transfer by water and water vapor are significant, and frequently are for specific periods the dominant modes of heat transfer near the ground surface. The thermal regime at the surface represents the effective boundary condition for deeper thermal regimes. Also, surface soils are going to respond more quickly to any climatic fluctuations; this is important to us because most facets of our lives are tied to earth's surface. To accurately determine the surface thermal regime (for example, the detection of climate change), it is important to consider all potential forms of heat transfer. Gradients that have the potential to alter the thermal regime besides temperature include pore water pressure, gravitational, density, vapor pressure and chemical. The importance of several non-conductive heat transport mechanisms near the ground surface is examined. Infiltration into seasonally frozen soils and freezing (release of latent heat) of water is one mechanism for the acceleration of warming in surficial soils in the spring. Free convection due to buoyancy-induced motion of fluids does not appear to be an important heat-transfer mechanism; estimates of the Rayleigh number (the ratio of buoyancy to viscous forces) are generally around 2, which is too low for effective heat transfer. The Peclet number (ratio of convective to conductive heat transfer) is on the order of 0.25 for snowmelt infiltration and up to 2.5 for rainfall infiltration for porous organic soils. In mineral soils, both vertical and horizontal advection of heat can be neglected (Peclet number is approximately 0.001) except for snowmelt infiltration into open thermal contraction cracks. The migration of water in response to temperature or chemical gradients from unfrozen soil depths to the freezing front, and the
Heat transfer performance of Al2O3/water nanofluids in a mini channel heat sink.
Dominic, A; Sarangan, J; Suresh, S; Sai, Monica
2014-03-01
The high density heat removal in electronic packaging is a challenging task of modern days. Finding compact, energy efficient and cost effective methods of heat removal is being the interest of researchers. In the present work, mini channel with forced convective heat transfer in simultaneously developing regime is investigated as the heat transfer coefficient is inversely proportional to hydraulic diameter. Mini channel heat sink is made from the aluminium plate of 30 mm square with 8 mm thickness. It has 15 mini channel of 0.9 mm width, 1.3 mm height and 0.9 mm of pitch. DI water and water based 0.1% and 0.2% volume fractions of Al2O3/water nanofluids are used as coolant. The flow rates of the coolants are maintained in such a way that it is simultaneously developing. Reynolds number is varied from 400 to 1600 and heat input is varied from 40 W to 70 W. The results showed that heat transfer coefficient is more than the heat transfer coefficient of fully developed flow. Also the heat transfer is more for nanofluids compared to DI water.
Kendall, C.M.; Holman, J.P.
1996-06-06
Experiments were done using subcooled Freon-113 sprayed vertically downward. Local and average heat transfers were investigated fro Freon-113 sprays with 40 C subcooling, droplet sizes 200-1250{mu}m, and droplet breakup velocities 5-29 m/s. Full-cone type nozzles were used to generate the spray. Test assemblies consisted of 1 to 6 7.62 cm vertical constant heat flux surfaces parallel with each other and aligned horizontally. Distance between heated surfaces was varied from 6.35 to 76.2 mm. Steady state heat fluxes as high as 13 W/cm{sup 2} were achieved. Dependence on the surface distance from axial centerline of the spray was found. For surfaces sufficiently removed from centerline, local and average heat transfers were identical and correlated by a power relation of the form seen for normal-impact sprays which involves the Weber number, a nondimensionalized temperature difference, and a mass flux parameter. For surfaces closer to centerline, the local heat transfer depended on vertical location on the surface while the average heat transfer was described by a semi-log correlation involving the same parameters. The heat transfer was independent of the distance (gap) between the heated surfaces for the gaps investigated.
Advanced two-phase heat transfer systems
NASA Technical Reports Server (NTRS)
Swanson, Theodore D.
1992-01-01
Future large spacecraft, such as the Earth Observing System (EOS) platforms, will require a significantly more capable thermal control system than is possible with current 'passive' technology. Temperatures must be controlled much more tightly over a larger surface area. Numerous heat load sources will often be located inside the body of the spacecraft without a good view to space. Power levels and flux densities may be higher than can be accommodated with traditional technology. Integration and ground testing will almost certainly be much more difficult with such larger, more complex spacecraft. For these and similar reasons, the Goddard Space Flight Center (GSFC) has been developing a new, more capable thermal control technology called capillary pumped loops (CPL's). CPL's represent an evolutionary improvement over heat pipes; they can transport much greater quantities of heat over much longer distances and can serve numerous heat load sources. In addition, CPL's can be fabricated into large cold plates that can be held to tight thermal gradients. Development of this technology began in the early 1980's and is now reaching maturity. CPL's have recently been baselined for the EOS-AM platform (1997 launch) and the COMET spacecraft (1992 launch). This presentation describes this new technology and its applications. Most of the viewgraphs are self descriptive. For those that are less clear additional comments are provided.
Base fluid in improving heat transfer for EV car battery
NASA Astrophysics Data System (ADS)
Bin-Abdun, Nazih A.; Razlan, Zuradzman M.; Shahriman, A. B.; Wan, Khairunizam; Hazry, D.; Ahmed, S. Faiz; Adnan, Nazrul H.; Heng, R.; Kamarudin, H.; Zunaidi, I.
2015-05-01
This study examined the effects of base fluid (as coolants) channeling inside the heat exchanger in the process of the increase in thermal conductivity between EV car battery and the heat exchanger. The analysis showed that secondary cooling system by means of water has advantages in improving the heat transfer process and reducing the electric power loss on the form of thermal energy from batteries. This leads to the increase in the efficiency of the EV car battery, hence also positively reflecting the performance of the EV car. The present work, analysis is performed to assess the design and use of heat exchanger in increasing the performance efficiency of the EV car battery. This provides a preface to the use this design for nano-fluids which increase and improve from heat transfer.
Heat transfer measurements and CFD simulations of an impinging jet
NASA Astrophysics Data System (ADS)
Petera, Karel; Dostál, Martin
2016-03-01
Heat transport in impinging jets makes a part of many experimental and numerical studies because some similarities can be identified between a pure impingement jet and industrial processes like, for example, the heat transfer at the bottom of an agitated vessel. In this paper, experimental results based on measuring the response to heat flux oscillations applied to the heat transfer surface are compared with CFD simulations. The computational cost of a LES-based approach is usually too high therefore a comparison with less computationally expensive RANS-based turbulence models is made in this paper and a possible improvement of implementing an anisotropic explicit algebraic model for the turbulent heat flux model is evaluated.
An investigation of heat pipe meniscus heat transfer
NASA Technical Reports Server (NTRS)
Saaski, E. W.; Franklin, J. L.; Mccreight, C. R.
1978-01-01
The use of grooved evaporator surfaces in heat pipes has increased in popularity in the past few years primarily due to the reproducibility achievable with grooved walls and the relatively low costs of the threading or extrusion processes involved in their production. The present study combines both analyses and experiments on square groove geometries, with special emphasis on overcoming the limitations of earlier analyses with finite-difference methods and groove-fillet hydrodynamic simplifications. The groove fillet, which has in previous analyses been assumed constant in radius of curvature, is permitted to change in thickness and curvature consistent with hydrodynamics and heat loss from the groove. A model is developed for accurate determination of the effect of constriction resistance on groove performance. The grooved-surface tests to be conducted are briefly described which will provide data under closely controlled operation to allow comparison and verification of the analyses.
An investigation of heat pipe meniscus heat transfer
NASA Technical Reports Server (NTRS)
Saaski, E. W.; Franklin, J. L.; Mccreight, C. R.
1978-01-01
The use of grooved evaporator surfaces in heat pipes has increased in popularity in the past few years primarily due to the reproducibility achievable with grooved walls and the relatively low costs of the threading or extrusion processes involved in their production. The present study combines both analyses and experiments on square groove geometries, with special emphasis on overcoming the limitations of earlier analyses with finite-difference methods and groove-fillet hydrodynamic simplifications. The groove fillet, which has in previous analyses been assumed constant in radius of curvature, is permitted to change in thickness and curvature consistent with hydrodynamics and heat loss from the groove. A model is developed for accurate determination of the effect of constriction resistance on groove performance. The grooved-surface tests to be conducted are briefly described which will provide data under closely controlled operation to allow comparison and verification of the analyses.
Cohen, Aviv; Bar-Nun, Shoshana
2014-01-01
Stationary-phase cultures have been used as an important model of aging, a complex process involving multiple pathways and signaling networks. However, the molecular processes underlying stress response of non-dividing cells are poorly understood, although deteriorated stress response is one of the hallmarks of aging. The budding yeast Saccharomyces cerevisiae is a valuable model organism to study the genetics of aging, because yeast ages within days and are amenable to genetic manipulations. As a unicellular organism, yeast has evolved robust systems to respond to environmental challenges. This response is orchestrated largely by the conserved transcription factor Hsf1, which in S. cerevisiae regulates expression of multiple genes in response to diverse stresses. Here we demonstrate that Hsf1 response to heat shock and oxidative stress deteriorates during yeast transition from exponential growth to stationary-phase, whereas Hsf1 activation by glucose starvation is maintained. Overexpressing Hsf1 does not significantly improve heat shock response, indicating that Hsf1 dwindling is not the major cause for Hsf1 attenuated response in stationary-phase yeast. Rather, factors that participate in Hsf1 activation appear to be compromised. We uncover two factors, Yap1 and Sir2, which discretely function in Hsf1 activation by oxidative stress and heat shock. In Δyap1 mutant, Hsf1 does not respond to oxidative stress, while in Δsir2 mutant, Hsf1 does not respond to heat shock. Moreover, excess Sir2 mimics the heat shock response. This role of the NAD+-dependent Sir2 is supported by our finding that supplementing NAD+ precursors improves Hsf1 heat shock response in stationary-phase yeast, especially when combined with expression of excess Sir2. Finally, the combination of excess Hsf1, excess Sir2 and NAD+ precursors rejuvenates the heat shock response. PMID:25356557
Heat transfer and core neutronics considerations of the heat pipe cooled thermionic reactor
NASA Astrophysics Data System (ADS)
Determan, W. R.; Lewis, Brian
The authors summarize the results of detailed neutronic and thermal-hydraulic evaluations of the heat pipe cooled thermionic (HPTI) reactor design, identify its key design attributes, and quantify its performance characteristics. The HPTI core uses modular, liquid-metal core heat transfer assemblies to replace the liquid-metal heat transport loop employed by in-core thermionic reactor designs of the past. The nuclear fuel, power conversion, heat transport, and heat rejection functions are all combined into a single modular unit. The reactor/converter assembly uses UN fuel pins to obtain a critical core configuration with in-core safety rods and reflector controls added to complete the subassembly. By thermally bonding the core heat transfer assemblies during the reactor core is coupled neutronically, thermally, and electrically into a modular assembly of individual power sources with cross-tied architecture. A forward-facing heat pipe radiator assembly extends from the reactor head in the shape of a frustum of a cone on the opposite side of the power system from the payload. Important virtues of the concept are the absence of any single-point failures and the ability of the core to effectively transfer the TFE waste heat load laterally to other in-core heat transfer assemblies in the event of multiple failures in either in-core and radiator heat pipes.
Experiments of Transient Condensation Heat Transfer on the Heat Flux Senor
NASA Astrophysics Data System (ADS)
Wang, Xuwen; Liu, Qiusheng; Zhu, Zhiqiang; Chen, Xue
2015-09-01
The influence of transient heat transfer in different condensation condition was investigated experimentally in the present paper. Getting condensation heat and mass transfer regularity and characteristics in space can provide theoretical basis for thermodynamic device such as heat pipes, loop heat pipes and capillary pumped loops as well as other fluid management engineering designing. In order to study the condensation process in space, an experimental study has been carried out on the ground for space experiment. The results show that transit heat transfer coefficient of film condensation is related to the condensation film width, the flow condition near the two phase interface and the pressure of the vapor and non-condensable gas in chamber. On the ground, the condensation heat flux on vertical surface is higher than it on horizontal surface. The transit heat flux of film condensation is affected by the temperature of superheated vapor, the temperature of condensation surface and non-condensable gas pressure. Condensation heat flux with vapor forced convection is many times more than it with natural convection. All of heat flux for both vapor forced convection and natural convection condensation in limited chamber declines dramatically over time. The present experiment is preliminary work for our future space experiments of the condensation and heat transfer process onboard the Chinese Spacecraft "TZ-1" to be launched in 2016.
Heat transfer and core neutronics considerations of the heat pipe cooled thermionic reactor
NASA Technical Reports Server (NTRS)
Determan, W. R.; Lewis, Brian
1991-01-01
The authors summarize the results of detailed neutronic and thermal-hydraulic evaluations of the heat pipe cooled thermionic (HPTI) reactor design, identify its key design attributes, and quantify its performance characteristics. The HPTI core uses modular, liquid-metal core heat transfer assemblies to replace the liquid-metal heat transport loop employed by in-core thermionic reactor designs of the past. The nuclear fuel, power conversion, heat transport, and heat rejection functions are all combined into a single modular unit. The reactor/converter assembly uses UN fuel pins to obtain a critical core configuration with in-core safety rods and reflector controls added to complete the subassembly. By thermally bonding the core heat transfer assemblies during the reactor core is coupled neutronically, thermally, and electrically into a modular assembly of individual power sources with cross-tied architecture. A forward-facing heat pipe radiator assembly extends from the reactor head in the shape of a frustum of a cone on the opposite side of the power system from the payload. Important virtues of the concept are the absence of any single-point failures and the ability of the core to effectively transfer the TFE waste heat load laterally to other in-core heat transfer assemblies in the event of multiple failures in either in-core and radiator heat pipes.
Laboratory Investigations of Lava Flow Heat Transfer
NASA Astrophysics Data System (ADS)
Fagents, S. A.; Rumpf, M. E.; Hamilton, C. W.
2011-12-01
To investigate the effectiveness with which lava can heat substrates of different types, we conducted a suite of experiments in which molten basalt was poured onto solid or particulate materials, and the downward propagation of the heat pulse was measured. The motivation for this work lies in seeking to understand how lava flows on the Moon would have heated the underlying regolith, and thus to determine the depths at which solar wind particles implanted in the regolith would have been protected from the heat of the overlying flow. Extraction and analysis of ancient solar wind samples would provide a wealth of information on the evolution and fate of the Sun. Our experimental device consists of a box constructed from 1"-thick calcium silicate sheeting with interior dimensions of 20 x 20 x 25 cm. The substrate material (a particulate lunar regolith simulant or solid basalt) occupies the lower 15 cm of the box, which is embedded with an array of 8 thermocouples. Up to 6 kg of crushed basalt collected from the 2010 Kilauea lava flows is heated to supraliquidus temperatures and poured directly onto the substrate. The evolution of the temperature profile within the lava flow and substrate is recorded as the basalt cools, and the surface temperature distribution is recorded using a Forward Looking Infrared Radiometer (FLIR) video camera. We have been using the experimental data sets to validate a numerical model of substrate heating. If the physics is appropriately formulated, the model will accurately predict both surface and internal temperature distribution as a function of time. A key issue has been incorporation of valid temperature-dependent thermophysical properties, because particulate materials are not well characterized at elevated temperatures. Regolith thermal conductivity in particular exerts a strong control over the depth of penetration of the thermal wave, so its accurate description is essential for a robust model. Comparison of experimental vs. modeled
Stagnation Region Heat Transfer Augmentation at Very High Turbulence Levels
Ames, Forrest; Kingery, Joseph E.
2015-06-17
A database for stagnation region heat transfer has been extended to include heat transfer measurements acquired downstream from a new high intensity turbulence generator. This work was motivated by gas turbine industry heat transfer designers who deal with heat transfer environments with increasing Reynolds numbers and very high turbulence levels. The new mock aero-combustor turbulence generator produces turbulence levels which average 17.4%, which is 37% higher than the older turbulence generator. The increased level of turbulence is caused by the reduced contraction ratio from the liner to the exit. Heat transfer measurements were acquired on two large cylindrical leading edge test surfaces having a four to one range in leading edge diameter (40.64 cm and 10.16 cm). Gandvarapu and Ames [1] previously acquired heat transfer measurements for six turbulence conditions including three grid conditions, two lower turbulence aero-combustor conditions, and a low turbulence condition. The data are documented and tabulated for an eight to one range in Reynolds numbers for each test surface with Reynolds numbers ranging from 62,500 to 500,000 for the large leading edge and 15,625 to 125,000 for the smaller leading edge. The data show augmentation levels of up to 136% in the stagnation region for the large leading edge. This heat transfer rate is an increase over the previous aero-combustor turbulence generator which had augmentation levels up to 110%. Note, the rate of increase in heat transfer augmentation decreases for the large cylindrical leading edge inferring only a limited level of turbulence intensification in the stagnation region. The smaller cylindrical leading edge shows more consistency with earlier stagnation region heat transfer results correlated on the TRL (Turbulence, Reynolds number, Length scale) parameter. The downstream regions of both test surfaces continue to accelerate the flow but at a much lower rate than the leading edge. Bypass transition occurs
Characterizations and Convective Heat Transfer Performance of Nanofluids
NASA Astrophysics Data System (ADS)
Yang, Yijun
In recent years, many experimental studies have reported anomalous thermal conductivity enhancement and heat transfer increase in liquid suspensions of nanoparticles. In order to understand the mechanism of this phenomenon and examine the possible applications of nanofluids in heat transfer, the present study experimentally investigated thermal, rheological and heat transfer properties of nanofluids. In the first part of the work, several types of suspensions of near spherical nanoparticles and base fluids were examined. The results show that particles in suspensions without stabilizers agglomerate over time. The thermal conductivity and viscosity of a range of nanofluids were measured. These measurements indicate that the thermal conductivities of nanofluids are in the range predicted using effective medium theory. For example, Bruggeman predicted a 13% thermal conductivity increase for a 3.86% concentration of particles by volume; our experimental measurement indicated a 15% increase for this concentration. Viscosity measurements indicate that dispersions with larger agglomeration experience a larger increase in shear thinning. The results also suggest that finer particles and a narrow particle size distribution should result in a large viscosity increase. The second part of this study examined heat transfer performance of nanofluids in both laminar and transitional flows. Within experimental uncertainty, the non-dimensional heat transfer behavior of nanofluids in laminar flow region was the same as for base fluids without particles. The laminar flow data indicates that nanoparticles migrate from regions of high shear rate to regions of low shear rate, causing them to migrate away from the boundaries of pipe flow. For transitional flow (2,600 migrate away from the boundaries of pipe flow. For transitional flow (2,600
NASA Astrophysics Data System (ADS)
Lu, Bin; Chen, Ke; Meng, W. J.; Mei, Fanghua
2010-11-01
Low-profile, Cu-based microchannel heat exchangers (MHEs) with different geometric dimensions were fabricated, bonded and assembled. A transient liquid phase (TLP) process was used for bonding of Cu-based MHEs with total thicknesses ranging from 600 µm to 1700 µm. The structural integrity of TLP-bonded Cu MHEs was examined. Device-level heat transfer testing was performed on a series of Cu-based MHEs to study the influence of microchannel dimensions on overall heat transfer performance, corroborated by computational results from a simple 2D finite element analysis. The present results demonstrate the promise of low-profile metallic MHEs for high heat flux cooling applications.
Gravity and Heater Size Effects on Pool Boiling Heat Transfer
NASA Technical Reports Server (NTRS)
Kim, Jungho; Raj, Rishi
2014-01-01
The current work is based on observations of boiling heat transfer over a continuous range of gravity levels between 0g to 1.8g and varying heater sizes with a fluorinert as the test liquid (FC-72/n-perfluorohexane). Variable gravity pool boiling heat transfer measurements over a wide range of gravity levels were made during parabolic flight campaigns as well as onboard the International Space Station. For large heaters and-or higher gravity conditions, buoyancy dominated boiling and heat transfer results were heater size independent. The power law coefficient for gravity in the heat transfer equation was found to be a function of wall temperature under these conditions. Under low gravity conditions and-or for smaller heaters, surface tension forces dominated and heat transfer results were heater size dependent. A pool boiling regime map differentiating buoyancy and surface tension dominated regimes was developed along with a unified framework that allowed for scaling of pool boiling over a wide range of gravity levels and heater sizes. The scaling laws developed in this study are expected to allow performance quantification of phase change based technologies under variable gravity environments eventually leading to their implementation in space based applications.
Effects of Freestream Turbulence on Turbine Blade Heat Transfer
NASA Technical Reports Server (NTRS)
Boyle, Robert J.; Giel, Paul W.; Ames, Forrest E.
2004-01-01
Experiments have shown that moderate turbulence levels can nearly double turbine blade stagnation region heat transfer. Data have also shown that heat transfer is strongly affected by the scale of turbulence as well as its level. In addition to the stagnation region, turbulence is often seen to increase pressure surface heat transfer. This is especially evident at low to moderate Reynolds numbers. Vane and rotor stagnation region, and vane pressure surface heat transfer augmentation is often seen in a pre-transition environment. Accurate predictions of transition and relaminarization are critical to accurately predicting blade surface heat transfer. An approach is described which incorporates the effects of both turbulence level and scale into a CFD analysis. The model is derived from experimental data for cylindrical and elliptical leadng edges. Results using this model are compared to experimental data for both vane and rotor geometries. The comparisons are made to illustrate that using a model which includes the effects of turbulence length scale improves agreement with data, and to illustrate where improvements in the modeling are needed.
Heat transfer in rotating serpentine passages with smooth walls
NASA Technical Reports Server (NTRS)
Wagner, J. H.; Johnson, B. V.; Kopper, F. C.
1990-01-01
Experiments were conducted to determine the effects of buoyancy and Coriolis forces on heat transfer in turbine blade internal coolant passages. The experiments were conducted with a large scale, multi-pass, smooth-wall heat transfer model with both radially inward and outward flow. An analysis of the governing flow equations showed that four parameters influence the heat transfer in rotating passages (coolant-to-wall temperature ratio, Rossby number, Reynolds number and radius-to-passage hydraulic diameter ratio). These four parameters were varied over ranges which are typical of advanced gas turbine engine operating conditions. It was found that both Coriolis and buoyancy effects must be considered in turbine blade cooling designs and that the effect of rotation on the heat transfer coefficients was markedly different depending on the flow direction. Local heat transfer coefficients were found to decrease by as much as 60 percent and increase by 250 percent from no rotation levels. Comparisons with a pioneering stationary vertical tube buoyancy experiment showed reasonably good agreement. Correlation of the data is achieved employing dimensionless parameters derived from the governing flow equations.
Radiative heat transfer estimation in pipes with various wall emissivities
NASA Astrophysics Data System (ADS)
Robin, Langebach; Christoph, Haberstroh
2017-02-01
Radiative heat transfer is usually of substantial importance in cryogenics when systems are designed and thermal budgeting is carried out. However, the contribution of pipes is commonly assumed to be comparably low since the warm and cold ends as well as their cross section are fairly small. Nevertheless, for a first assessment of each pipe rough estimates are always appreciated. In order to estimate the radiative heat transfer with traditional “paper and pencil“ methods there is only one analytical case available in literature - the case of plane-parallel plates. This case can only be used to calculate the theoretical lower and the upper asymptotic values of the radiative heat transfer, since pipe wall radiation properties are not taken into account. For this paper we investigated the radiative heat transfer estimation in pipes with various wall emissivities with the help of numerical simulations. Out of a number of calculation series we could gain an empirical extension for the used approach of plane-parallel plates. The model equation can be used to carry out enhanced paper and pencil estimations for the radiative heat transfer through pipes without demanding numerical simulations.
Heat transfer from cylinders having closely spaced fins
NASA Technical Reports Server (NTRS)
Biermann, Arnold E
1937-01-01
The heat-transfer coefficients have been determined for five steel cylinders having fins 1.22 inches wide and the spacing between the fins ranging from 0.022 to 0.131 inch. The cylinders were tested with and without baffles in a wind tunnel; they were also tested enclosed in jackets with the cooling air supplied by a blower. A maximum heat transfer was reached at a fin space of about 0.45 inch for the cylinders tested with each of the three methods of cooling investigated. The rise in temperature of the air passing between the fins and the change in flow pattern were found to be important factors limiting the heat transfer that may be obtained by decreasing the fin space. The use of baffles for directing the air around the cylinders with closely spaced fins proved very effective in increasing the over-all heat-transfer coefficient, provided that the spacing was not appreciably less than that for maximum heat transfer.