Temperature Oscillations of Working Gas Inside a Basic, an Orifice and a Double Inlet Pulse Tube Refrigerators

Abstract

The effect of the driving frequency on the oscillating behavior of working gas in pulse tube refrigerators is experimentally studied by directly measuring the pressure and temperature of the gas for three types of pulse tube refrigerators, which are a basic, an orifice, and a double inlet types. The condition for the optimum frequency, at which the minimum wall temperature is reached, is discussed from the point of view of the dependence of the temperature oscillation on the driving frequency. It is found that the characteristic feature of the temperature oscillation at lower frequencies than the optimum frequency can be clearly distinguished from that at higher frequencies for every type. In the case of the basic type, the time for the compression process specified by the compressor-valve system is nearly equal to the relaxation time for gas temperature, defined as a period for the temperature rise by gas compression process at the optimum frequency. In the case of the orifice and the double inlet types, the phase difference between the pressure and temperature oscillations is nearly zero around the optimum frequency, and it shifts from negative to positive with the increase of the driving frequency.