A Highly Stable Two-Phase Thermal Management System for Aircraft

Future electronics and photonics systems, weapons systems, and environmental control systems in aircraft will require advanced thermal management technology to control the temperature of critical components. Two-phase Thermal Management Systems (TMS) are attractive because they are compact, lightweight, and efficient. However, maintaining stable and reliable cooling in a two-phase flow system presents unique design challenges, particularly for systems with parallel evaporators during thermal transients. Furthermore, preventing ingress of liquid into a vapor compressor during variable-gravity operation is critical for long-term reliability and life. To enable stable and reliable cooling, a highly stable two-phase system is being developed that can effectively suppress flow instability in a system with parallel evaporators. Flow stability is achieved by ensuring that only single-phase liquid enters the evaporators. The two-phase flow leaving the evaporators flows through a membrane phase separator to produce a liquid stream and a vapor stream. The liquid stream recirculates at low pressure, drawn back to the evaporator inlets by the suction produced in an ejector pump with no moving parts. The vapor streams from the phase separators flow back to the compressor. Flow restrictors at the inlet to each evaporator enhance stability by ensuring that most of the pressure drop in each parallel leg is due to single-phase flow through the restrictor. This paper presents performance data for key components in the system, as well as analysis results for flow restrictors to prevent dryout in evaporators due to flow redistribution associated with heat load variation.