Systematic Analysis of Thermal Resistances in Data Center Two-Phase Cooling

This technical report presents a systematic analysis of thermal resistances in two-phase direct-to-chip (DTC) cooling systems for data centers. It addresses the challenges posed by increasing power densities in processors and server racks, which necessitate efficient thermal management solutions. The report outlines the methodology for breaking down the end-to-end temperature difference into three thermal resistances: cold plate thermal resistance, vapor line pressure drop-induced thermal resistance, and condenser thermal resistance. It emphasizes the importance of using refrigerant temperatures at the cold plate outlet and condenser inlet as key temperature nodes for analysis. The study develops models for two refrigerants, R1233zd(E) and R515B, and compares their performance against single-phase DTC cooling. The findings indicate that two-phase cooling can achieve comparable or superior performance, particularly for processors with higher thermal design power. This work aims to provide a framework for evaluating and comparing 2P DTC components, facilitating the adoption of this cooling technology in data centers.