Conformal Two-Phase Switch for Sensor Thermal Control

A stable operating temperature is critical to many sensing systems. This can be challenging in the field when the sensors are exposed to extreme variations in the external thermal environment. Thermoelectric devices and heaters can be used to maintain sensor temperature but at the expense of additional power consumption. A more economical approach is the use of passive variable conductance devices that modulate their thermal resistance in response to changes in temperature. Advanced Cooling Technologies, Inc. (ACT) is developing a passive variable conductance device that can conform to a sensor of arbitrary shape. Heat is transferred passively via a two-phase working fluid and the effective thermal conductance of the device is a function only of the operating temperature. The device passively provides temperature stabilization, is compact, capable of operating in any orientation and can be designed for any sensor size and shape. The thermal control device is also capable of operating as a thermal diode to prevent heat leaks from a hot environment into a cooler sensor. During the Phase I program ACT experimentally demonstrated all key features of the Conformal Two-Phase Thermal Switch. A prototype device demonstrated a thermal turndown ratio of 11.5:1. The Phase II program will focus on improving the performance of the device, reducing the volume, and improving the fabrication process. It is anticipated that the maximum conductance can be improved by at least 3-5x while the minimum conductance can be reduced by nearly 10x.