Analysis of performance of heat exchangers used in practical micro miniature refrigerators

Micro miniature refrigerators are employed to cool small infra-red sensors and other electronic devices in a number of applications. In a micro miniature refrigerator the heat exchanger, expansion valve and evaporator are all machined on a thin glass or stainless steel sheet (typically about 1 mm thick). Unlike normal heat exchangers, the volume of the flow channels of the heat exchanger is much smaller than that of the walls of the heat exchanger. Also, a large temperature gradient (up to 200 K) is sustained between the two ends of the exchanger which are typically 50–100 mm long. The performance of the heat exchanger is therefore largely controlled by the heat conduction that takes place through the walls of the heat exchanger. In this paper the governing equations of practical micro miniature refrigerator heat exchanger are solved numerically to understand the complex convection–conduction interactions. Some guidelines are presented for the design of these heat exchangers.