摘要:

Arrays of heat pipes placed in soil may be used to good advantage for cooling or heating equipment. This paper gives results of a study that included the coupling of heat pipe thermal characteristics with soil thermal characteristics for such applications. A transient mathematical model was developed for the combination that accounted for thermal capacitance and resistance of the individual heat pipes, the number and arrangement of heat pipes in the soil, and soil properties. The model was verified by comparing it with published experimental and analytical results. Parametric studies were then performed, and the results were used to develop some correlation equations that may be used to predict the thermal performance of arrays of heat pipes in soil. The dependence of spacing, type of array, heat pipe properties, and soil properties is included in the simple correlation equations.

ISSN:1040-7782    

DOI:10.1080/10407789408956013

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Numerical analysis is performed for fluid flows in a supersonic nozzle with cooled walls. The numerical methodology is based on a modified form of the SIMPLER algorithm for compressible fluid, coupled with the scheme developed by Karki et al. for a generalized nonorthogonal coordinate system. The geometry of the supersonic nozzle used for calculations is a two-dimensional convergent-divergent configuration formed by linear walls with a diverging angle of 5° downstream of the throat. Calculations are performed for the conditions where the inlet temperature is 1200 K and walls are cooled and kept at 300 K. The back pressure is set at various values. The adiabatic flows are calculated for comparison. The calculated results for the flow with cooled walls are compared with the experimental data and agree with each other qualitatively.

ISSN:1040-7782    

DOI:10.1080/10407789408956014

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

A numerical model is presented, based on the local volume averaging formulation of transport phenomena in porous media, for simulating meltwater infiltration into unsaturated, frozen soil. With the defined flow and freezing boundary conditions at the snow-soil interface, using the concept of a surface local averaging volume, the time variation in profiles of temperature, liquid / ice content, infiltration / percolation rates, and rate of phase change in upper soil layers are predicted. In addition to a parametric analysis, model estimates of infiltration are compared with quantities calculated from field measurements of soil moisture changes and temperature during snow cover ablation, showing a reasonable agreement.

ISSN:1040-7782    

DOI:10.1080/10407789408956015

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

A numerical model of a direct-contact evaporator is developed, which is used to calculate performance information about direct-contact heat transfer between a rising dispersed refrigerant and a counterflow continuous fluid. Results are compared with the existing experimental data. The numerical scheme involves slicing the column of the evaporator into a finite number of horizontal slices and applying continuity, population, and energy balances to each slice. Temperature and holdup ratio distributions through the evaporator are obtained for the operation of a 0.1-m-diameter column, using n-butane as the dispersed refrigerant and distilled water as the continuous fluid. Results are given for a range of values of the initial drop diameter, mass flow rate of the dispersed fluid, and mass flow rate of the continuous fluid.

ISSN:1040-7782    

DOI:10.1080/10407789408956016

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The three-dimensional flow field and heat transfer in a radially rotating coolant passage are studied numerically. The passage chosen has a square cross section with smooth isothermal walls of finite length. The axis of rotation is normal to the flow direction with the flow radially outward. The effects of Coriolis forces, centrifugal buoyancy, and fluid Reynolds number on the flow and heat transfer have all been considered. The analysis has been performed by using a fully elliptic, three-dimensional, body-fitted computational fluid dynamics code based on pressure correction techniques. The numerical technique employs a multigrid iterative solution procedure and the standard κ − ϵ turbulence model for both the hydrodynamics and heat transfer. The effect of rotation is included by considering the governing equations of motion in a relative frame of reference that moves with the passage. The consequence of rotation is to bring higher velocity fluid from the core to the trailing surface, thereby increasing both the friction and heat transfer at this face. At the same time, the heat transfer is predicted to decrease along the leading surface. The effect of buoyancy is to increase the radial velocity of the fluid, thus generally increasing the heat transfer along both the leading and trailing surfaces. These effects and trends that have been predicted are in agreement with experimental heat transfer data available in the literature [1,2]. The quantitative agreement with the data was also found to be quite satisfactory.

ISSN:1040-7782    

DOI:10.1080/10407789408956017

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

A numerical study of laminar two-dimensional natural convection heat transfer from a uniformly heated horizontal cylinder rotating about its center, and placed in an isothermal rectangular enclosure, is performed using a spectral element method. The physical aspects of the flow and its thermal behavior are studied for a wide range of pure natural convection to mixed convection at low and high rotational speeds of the cylinder. The computer program has been validated against experimental correlations available on pure natural convection of heated bodies in enclosures. The rotation of the cylinder has been found to enhance the heat transfer. At low ratios of Rayleigh number to the square of the rotational Reynolds number, Ra / Reω2, the maximum temperature on the cylinder surface is decreased by as much as 25–35% from similar cases with fixed cylinders. At moderate values of Ra/ Reω2, the thermal plume rising above the cylinder is shifted in the rotation direction and the angular shift decreases as Ra / Reωincreases. The rotation produces more uniform temperature and shear stress distributions around the cylinder surface. At high Rayleigh numbers the increase in rotation reduces the cylinder mean Nusselt number by 2–10% as compared with the fixed cylinder.

ISSN:1040-7782    

DOI:10.1080/10407789408956018

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The problem of conjugate heat transfer involving mixed convection laminar ascending flow of water in inclined circular tubes uniformly heated on their outer surface has been studied numerically using a unified formulation for the solid and fluid domains. The highly coupled governing equations were discretized using the control volume approach, and solved according to the SIMPLER algorithm. Results have clearly demonstrated that the conduction within the tube wall has an important influence on both the hydrodynamic and thermal fields. High wall thermal conductivity or large thickness reduces the temperature stratification within the fluid and intensifies the secondary motion, consisting of two symmetrical vortices. The effects of wall conduction are particularly significant for horizontal tubes for which the average Nusselt number is bounded by two limits corresponding to the cases of infinite wall thermal conductivity and zero wall thermal conductivity. For Gr = 2 × 105these limits are 10.42 and 9.03, respectively. These effects are negligible for tubes inclined at 30° and for Grashof number below 3 × 104.

ISSN:1040-7782    

DOI:10.1080/10407789408956019

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Numerical investigation of two-dimensional (2D) laminar flow and solute transport in a channel with some sudden symmetric expansions and contractions has been performed using the fictitious regions method. This method allows us, instead of solving Navier-Stokes equations in a complex domain, to solve equations with suitably continued coefficients in a rectangle. Stream function-vorticity variables are used in the present paper. Dependence of the flow and solute transport from the dimensions of the channel expansions and contractions is numerically investigated for different values of Reynolds and Péclet numbers using a finite differences method on a relatively fine grid.

ISSN:1040-7782    

DOI:10.1080/10407789408956020

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor