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Journal of Enhanced Heat Transfer

Theory and Application in High Performance Heat and Mass Transfer

ISSN for PRINT: 1065-5131

Institutional price:	$577.00
Issues per year:	4

Best Paper Award Selection - Editorial Board Site

2008, Volume15

103 pages

DOI: 10.1615/JEnhHeatTransf.v15.i1

Issue price - $173.00

Effect of Boundary on the Onset of Rayleigh-Bénard Convection in a Horizontal PCM Slurry Layer

Chuanshan Dai
College of Mechanical Engineering, Tianjin University, Tianjin, 300072, P. R. China

Lu-Biao Yang
College of Mechanical Engineering, Tianjin University, Tianjin, 300072, P. R. China

Wei Li
State Key Laboratory of Clean Energy Utilization, College of Mechanical and Energy Engineering, Zhejiang University, Hangzhou, 310027, P. R. China

ABSTRACT

The natural convection heat transfer in a horizontal phase-change-material (PCM) slurry layer between two plates, with the outer surface exposed to constant temperature boundary condition, has been studied. The critical Rayleigh number for the onset of Rayleigh−Bénard convection in the slurry, with various boundary conditions, was calculated by using the linear stability theory. The PCM slurry investigated undergoes a process of phase changing and during this process the apparent specific heat of the slurry has a maximum value. The optimum heat convection mode with the boundary effect was also predicted. A Gaussian function model was adopted for simulating the change of the apparent specific heat with temperature. The theoretical results show an agreement with previous experimental studies where the maximum or enhanced heat transfer status was achieved. In experiments, the correlation of the Nusselt number, Nu, to the Rayleigh number, Ra, indicates that the mathematical average temperature is no longer able to be recognized as the characteristic temperature for calculating the apparent specific heat. The proposed integral average and the supercriticality (Ra/Ra_cr) methods have less standard deviation in the correlation between the experimental data of Nu with Ra.