Energy transfer processes of working gas-in pulse tube

Abstract

The pulse tube cooler is a device for cooling to low temperatures. It runs on a modified Stirling cycle but has no cold moving parts and the gas flow in the pulse tube can carry heat energy away from a low temperature point under certain conditions. An orifice or other device controlling the flow at the end of the cooler provides the condition for cooling to occur. Pulse tube coolers have great commercial potential; offering low cost, low vibration and high reliability and they can be designed in variety of configurations including linear, U-tube (folded 180 in the middle) and concentric. They can be designed to cool to 200 K, to as low as 2 K, or to any temperature in between. The cooling power ranges from milliwatts to kilowatts depending on cooler size and operating temperature. In the development of pulse tube coolers, it is important to study the energy transfer process of the working fluid in the pulse tube. The enthalpy flow in the pulse tube is the gross cooling power of the cooler. Since the pulse tube section is nearly adiabatic, there are large temperature oscillations yielded by pressure oscillation. To evaluate the temperature oscillation, a mathematical model was developed. With this model, the analytical result is that the temperature ratio of the working fluid is the function of pressure ratio between hot and cold heat exchanges.