Visualization Study of Oscillating Flow Inside a Pulse Tube Refrigerator

Abstract

The flow inside typical pulse tube refrigerators which are a basic, an orifice and a double inlet type, has been observed by the visualization technique to investigate the effects of opening of the orifice and the bypass valves. A smoke-wire and a tuft flow visualization techniques are adopted. The displacement and the velocity of the working gas at cold end, middle of the pulse tube and in the bypass tube are measured by changing the valve openings and the flow is classified into 8 typical flow patterns. It is found that the flow pattern in the pulse tube is changed by the opening of the orifice and bypass valves. In the orifice type, phase difference between the pressure and the displacement increases as the increase of the orifice valve opening. It has maximum value at the optimum opening of the orifice valve. In the double inlet type, phase difference does not so change, but the flow behavior in the pulse tube is different from that of the orifice type.