Showing papers in "Advances in heat transfer in 1979"

Heat Transfer in Geothermal Systems

Abstract: Publisher Summary This chapter discusses the mathematical formulation of the problems of convective heat transfer in geothermal systems. Geothermal reservoirs may have numerous near-vertical faults and relatively impermeable intrusive interspersed in the aquifers. Both theoretical and experimental investigations of heat transfer in geothermal systems are reviewed. A qualitative understanding of the large-scale convection processes in a geothermal reservoir and the prediction of reservoir behavior under production can be obtained by idealizing it as a saturated porous medium. The identification of a viable geothermal reservoir and the estimation of its capacity remain major problems in the utilization of geothermal resources. Thermal anomalies in geothermal areas can be detected by surface manifestations, aerial infrared surveys, geochemical analyses, or exploratory drillings. Many of the analyses are applicable to a wide range of engineering problems whenever they can be idealized as convection in a porous medium. These include the problems of the secondary recovery of oil by thermal methods, the use of fibrous materials for thermal insulations, the design of aquifers as an energy storage system, and the deposition of mineral ore in the subsurface formation. Results from short-duration well testing are used to determine reservoir characteristics.

Electrohydrodynamically Enhanced Heat Transfer in Liquids—A Review

Abstract: Publisher Summary This chapter serves as a useful synopsis of the field of electrohydrodynamically (EHD) coupled heat transfer in liquids, so the equations of motion are those of a viscous incompressible fluid. An exhaustive published bibliography of work on EHD coupled heat transfer is provided and reviews the principal contributions made by Kronig and Ahsmann. The conventional formulation of the equations of EHD is provided to facilitate discussion of various theoretical contributions. The classification of important parameters used in EHD heat-transfer research is summarized. Some important aspects of EHD coupled heat-transfer enhancement including a succinct set of conditions that define the various regimes are reviewed. Specific application of the complex electrohydrodynamic mechanisms involved in EHD coupled heat transfer in liquids is considered. Potential applications of EHD heat transfer include general enhancement of pool boiling for heat exchanger equipment. Certain advantages and disadvantages of EHD coupled heat transfer in low temperature and cryogenic high-voltage cables should be assessed. The boiling and condensation heat transfer and basic configuration of an EHD heat pipe using electromechanical flow structure to promote condensate return flow are diagrammatically represented. The list of experimental observations and theoretical conclusions are summarized and the principal results of the papers are reviewed.

Heat Transfer Between a Gas Fluidized Bed and Immersed Tubes

Abstract: Publisher Summary Bed–to–surface heat transfer can be calculated with good reliability, if particle-residence times and their population near the surface are known The mechanism of heat transfer between boiler tubes and the fluidized bed is very complicated because of the many fluidized-bed variables and the variations in heat-transfer tube design Correlations are empirically developed on the basis of the observed data with limited attention to the mechanisms of the heat-transfer process This chapter reviews the design application of local as well as total heat-transfer coefficients for horizontal and slanted tubes, and for vertical tubes Single tubes and tube banks in different orientations to the bed are also considered The fundamental mechanisms of wall–to–bed heat transfer are reviewed and the criteria for evaluation of correlations for full-scale application are examined Particle movement is a complex function of the particle and gas properties, fluidization velocity, gas distributor, and geometry of the bed This approach generally gives the designer a good degree of assurance, requires a judicious choice of a representative system as well as the expense of pilot scale development The consideration must be given to the unsteady-state conduction component, the radiation component, and the gas convective component in boiler design

Influence of Radiative Transfer on Certain Types of Motions in Planetary Atmospheres

Abstract: Publisher Summary Both solar and thermal radiation transfer are essential elements in producing atmospheric motions. This chapter discusses the influence of radiation on turbulence to the case of stable stratification, which is the most representative for planetary atmospheres. The rate of radiative decay of temperature perturbations for local thermodynamic equilibrium (LTE) and non–LTE are described. Propagation of the acoustic-gravity waves (AGW) is accompanied by spatial and temporal oscillations of turbulent temperature fluctuations (T') and smoothing of T' because of radiative heat exchange leads to the damping of AGW. The problem of the influence of radiative heat exchange on motions is divided into two parts. First, the function (T') is considered and then the character and intensity of the influence of radiation on hydrodynamic motions. The influence of radiative heat exchange on turbulence and AGW is revealed in smoothing the inhomogeneity of the temperature field arising in these motions. The methods of taking into account the radiative decay of turbulent fluctuations T' in the motions of fluid are described. The approach to the problem of the influence of radiation on turbulence, based upon spectral representation of turbulence, shows a considerably weaker effect of radiative heat exchange on turbulence.