Self-Regulating, Freezable Heat Exchanger for Spacecraft

Aspacecraft thermal control system must keep the vehicle, avionics, and atmosphere (if crewed) within a defined temperature range. Water coolant loops are typically used to transport heat to or from the cabin of a crewed spacecraft via heat exchangers to the heat sink systems that reject the heat to space. Water is non-toxic and good for heat transport, but it has a high freeze point. Thus, there is concern that the water loop can freeze and damage the thermal control system unless a low-freeze-point intermediate fluid loop is included. Incorporating a freeze-tolerant water/ice heat exchanger can eliminate this risk, and offers a novel approach to spacecraft thermal control, since parts of the heat exchanger can be selectively frozen to passively increase the turndown of the heat rejection rate. In addition, it has the potential to simplify the thermal control system and thereby reduce its size and mass.