Showing papers by "G. D. Raithby published in 1989"

The Measurement of Surface Heat Flux Using the Peltier Effect

Abstract: Calorimetric methods for measuring surface heat flux use Joulean heating to keep the surface isothermal. This limits them to measuring the heat flux of surfaces that are hotter than their surroundings. Presented in this paper is a method whereby reversible Peltier effect heat transfer is used to maintain this isothermality, making it suitable for surfaces that are either hotter or colder than the surroundings. The paper outlines the theory for the method and describes physical models that have been constructed, calibrated, and tested. The tested physical models were found capable of measuring heat fluxes with an absolute accuracy of 1 percent over a wide range of temperature (5-50C) and heat flux (15-500 W/m{sup 2}), while maintaining isothermality to within 0.03 K. A drawback of the method is that it appears to be suited only for measuring the heat flux from thick metallic plates.

Numerical simulation of the charging of liquid storage tanks; Comparison with experiment

Abstract: The degree of thermal stratification maintained in hot water storage tanks has a significant impact on the performance of a solar energy system. This paper presents an axisymmetric finite volume model analysis of the charging of a tank with hot water, and compares the predictions with experimental results from the literature. The results show the capabilities and deficiencies of such a modeling technique for this type of problem. The importance of inlet fluid turbulence to tank destratification is demonstrated and inclusion of a simple turbulence model is found sufficient to yield good agreement with measurement. The model predictions also provide insight into when a simple one-dimensional plug flow model will be adequate. In addition, the model is used to evaluate the effect during charging of heat conduction in the tank wall on the temperature field in the fluid. Recommendations are made regarding future work on the development of detailed numerical codes of simulating the charging of liquid storage tanks.

A total pressure correction for upstream weighted schemes

Abstract: SUMMARY Upwind differencing is known to lead to a substantial loss in total pressure. The present paper illustrates the importance of this error on two problems: flow in a converging-diverging duct and flow around a cylinder. A correction is proposed that reduces the total pressure error and yields dramatically improved results for the test problems.