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Test results are described for a coldplate heat exchanger designed to remove electronics heat loads of up to 100 W/cm2 while maintaining device junction temperatures of 90 °C. The heat exchanger was designed to operate within a notional fighter aircraft environment with the following constraints: 0 °C minimum coolant temperature, poly alpha olefin (PAO) coolant, and minimized flow rate and pressure drop. The heat exchanger was configured to Standard Electronics Module, Format “E” (SEM-E) specifications. High heat flux capability was achieved by combining the high heat transfer characteristics of multiple jet impingement with the compact extended surface area enhancement of laminated construction. Thermal tests verified 100 W/cm2 local capability, and 2000 W total module heat load capability, with wall-to-fluid thermal resistance of 0.281 °C/(W/cm2). Repeatable thermal and hydraulic performance was obtained over a one-month period of testing, including 22 hours of flowing coolant.

A two-phase thermosyphon cooler coupled with phase change material (PCM) energy storage was built to demonstrate a concept for cooling a 26 kW actuator motor. FC75®, a Fluorinert® compound, was used as the working fluid to transfer heat to the phase change material, acetamide. The PCM was contained in alternating layers of a plate-fin compact heat exchanger core. At the 90 percent power condition the peak motor temperature was within 90°C of the heat sink, showing good source to sink thermal coupling by the thermosyphon and conductive links. Conversely, when the motor was cooled by natural convection and conduction alone, the peak temperature was 190°C above sink temperature. Testing shows that the PCM material provides additional useful thermal inertia during the melting process. However, test data revealed that the melt temperature of the acetamide had been depressed from 80°C to 68°C by absorbed water, highlighting the need to process the PCM in a dry atmosphere.