Experimental Characterization of Two-Phase Cold Plates Intended for High-Density Data Center Servers Using a Dielectric Fluid

Abstract

High Performance Computing (HPC) data centers demand cutting edge cooling techniques like direct contact liquid cooling (DCLC) for safe and secure operation of their high-power density servers. Two-phase flow boiling heat transfer technique is widely believed to address the heating problem posed by HPC racks. In this study, a novel liquid cooled cold plate containing microchannel and jet impingement arrangement was characterized for its two-phase flow and thermal behavior. A sophisticated bench top setup involving a mock package was developed to carry out the experiments in a controlled fashion using a dielectric fluid Novec/HFE-7000. Two-phase flow boiling in cold plates which has a strong dependency on surface phenomena was carefully studied at various levels of inlet pressure, subcooling, flow rates and heat flux levels to the mock package. A resistance network was invoked to determine the average heat transfer coefficient at various exit qualities estimated by energy balance equation. While the results make it evident that, the high heat generating components can be kept at operable conditions using the two-phase cooling; a deeper insight at the outcomes could pave way for more energy efficient cold plate designs. The experiment was carried out with a large heated surface of 6.45 cm2 and maximum dissipated heat flux was around 63.6 W/cm2 corresponding to chip power of 410 W. Base temperature was kept below 75 oC and pressure drop did not exceed 21 kPa.

Effects of the Gap on Microchannel Heat Sink Cooling Performance

“…Sulaiman and Wang [7] introduced a contraction before straight-fin microchannels in a cold plate, which improved the performance of microchannels heat sinks significantly for various cooling applications. Ramakrishnan et al [8] implemented a jet impingement arrangement in microchannels using a dielectric fluid Novec/HFE-7000. Two-phase flow boiling in cold plates, which strongly depends on surface geometry, was carefully studied at various levels of inlet subcooling, heat flux, and flow rates.…”