Cooling of Microchannel Heat Sinks with Gaseous Coolants

In this paper, the optimization of the cooling performance of a rectangular microchannel heat sink is investigated with four different gaseous coolants; air, ammonia gas, dichlorodifluoromethane (R-12) and chlorofluoromethane (R-22). A systematic robust thermal resistance model together with a methodical pumping power calculation is used to formulate the objective functions, the thermal resistance and pumping power. The non-dominated sorting genetic algorithm (NSGA-II), a multi-objective algorithm, is applied in the optimization procedure. The optimized thermal resistances obtained are 0.178, 0.14, 0.08 and 0.133°K/W for the pumping powers of 6.4, 4, 22.4 and 16.5 W for air, ammonia gas, R-12 and R-22, respectively. These results show that among all the gaseous coolants investigated in the current study, ammonia gas exhibited balanced thermal and hydrodynamic performances. Due to the Montreal Protocol, the coolant R-12 is no longer produced while R-22 will eventually be phased out. The results from ammonia provide a strong motivation to conduct more investigations on the potential usage of this gaseous coolant in the electronic cooling industry.