Comparison of R-1233zd and HFE-7000 Condenser Performance in Pumped Two-Phase Cooling Systems

The increasing heat flux from chips and high server- and rack-level heat densities in high-performance computing infrastructure have resulted in an increased interest in pumped two-phase cooling. It has been demonstrated that pumped two-phase cooling using dielectric fluorinated fluids in cold plates significantly reduces case temperature and improves case temperature uniformity over single-phase water cooling. Karwa and Yana Motta [1] compared the performance of low-pressure dielectric heat transfer fluids with system pressure less than 60 psi in microchannel cold plates and showed that R-1233zd(E) (normal boiling point: 18.26 °C) provided improved performance over HFE-7000 (normal boiling point: 34.2 °C). The present study extends their work and presents results of experimental and theoretical evaluation of condenser performance in pumped two-phase cooling systems. Tube-fin type air-cooled condensers were simulated using a detailed tube-by-tube model in Genesym™, and the performance of brazed plate water-cooled condensers was determined experimentally. The performance of air-cooled and water-cooled condensers for low-pressure heat transfer fluids R-1233zd(E) and HFE-7000 were compared. It is demonstrated that, for the same performance, R-1233zd(E) requires almost 35% smaller air-cooled condenser as compared to HFE-7000 and the fluid charge in the system can be reduced by 65%. It has been shown that dielectric fluid side heat transfer coefficient is the controlling heat transfer coefficient in brazed plate water-cooled condenser, and up to 20% higher dielectric fluid heat transfer coefficient was achieved for R-1233zd than HFE-7000 in brazed plate condensers. This study shows that R-1233zd(E) is a feasible low-pressure heat transfer fluid option for both air- and water-cooled pumped two-phase cooling systems.