1Heat Transfer Analysis for Phase Change Materials (PCMs)

The heat transfer enhancement for phase change materials (PCMs) has received much attention nowadays, since most of PCMs have low thermal conductivities which prolong the charging and discharging processes. Metal foams, as a sort of novel material with relatively high thermal conductivity, are believed to be a promising solution to enhance heat transfer performance and shorten charging and discharging processes of PCMs for waste heat recovery and thermal energy storage systems. In this paper analytical analyses have been carried out for heat transfer enhancement in PCMs by using metal foams. The prediction results agree fairly well with the experimental data. The solid/liquid phase change heat transfer performance can be improved significantly by 3 to 10 times depending on the metal foam microstructures. Nomenclature qw = heat flux Tm = fusion temperature T0 = initial temperature HL = latent heat of fusion Cp = specific heat at constant pressure k = thermal conductivity L = length of PCM x = coordinate of location t = time tref = reference time T(x,t) = temperature function (continuous) Ti, j = temperature function (discrete) f(x,t) = heat source function (continuous) fi, j = heat source function (discrete) h = increment of x r = characteristic number Subscripts i = index number of location j = index number of time ref = reference value Superscripts * = dimensionless parameters + = right limit of certain function- = left limit of certain function Greek = density = thermal diffusivity = increment of t 1