Numerical analysis of pumped two-phase loop: Characterization of steady-state performance

With growing heat dissipation from advanced electronics, two-phase cooling promises effective and unmatched cooling. A pumped two-phase loop (P2PL) can acquire high power and heat flux from the electronics (heat source) and transport and dissipate it to a heat sink with small total thermal resistance at negligible pumping power consumption because of highly effective phase change (boiling and condensation) heat transfer. Owing to many advantages, in recent years, extensive research efforts have been dedicated to understanding fundamental mechanisms of heat and mass transfer in phase change heat exchangers (evaporators or condensers) at a component level. However, there is little work done for an entire two-phase cooling system as a closed loop which is essential to study the system performance characteristics and the contributions/interactions of each component to the system performance. A comprehensive thermal-hydraulic flow network model was developed to study the system performance characteristics. The pressure variation of the P2PL was calculated by consid-ering the compressibility of the vapor volume in the P2PL to account for the effect of the amount of vapor in the system. The numerical results on the thermal and hydraulic performance characteristics of the P2PL for various operating and design parameters - evaporator heat load, mass flow rate, heat sink temperature, and micro -channel dimensions - are discussed. It was found that the numerical results match well with the measured steady-state temperature and pressure profiles of the P2PL. The study also highlights the trade-off between the total system thermal resistance reduction and the increased pressure drop (pumping power) with an increase in mass flow rate. It was also found that the microchannels with smaller hydraulic diameters had significant heat transfer enhancement in the evaporator but poor system performance.