A Joule-Thomson cooling system with a Si/glass heat exchanger for 0.1–1 w heat loads

This paper reports a Joule-Thomson cooling system that provides 0.1-1 W cooling power using a micromachined Si/glass perforated plate heat exchanger. The gas expansion is performed through a micromachined valve that is piezoelectrically actuated, or alternatively through a commercial jewel orifice. The modulated J-T system using the microvalve can achieve 254.5 K at a pressure difference of 430 kPa and 5-8 K temperature modulation at a given pressure. With a jewel orifice, the temperature at the expansion orifice drops 76.1 K from the inlet temperature for an inlet pressure of 1 MPa (145 psia) when the ethane mass flow rate is 0.269 g/s. The system can reach a lower temperature at 200.3 K in a transient state. The cooling power of the system is 200 mW at 228K and 1 W at 239 K, in addition to a parasitic heat load of 300-500 mW.