Experimental study on an open-cycle conical Hampson-type miniature Joule-Thomson cryocooler

Hampson-type miniature Joule-Thomson (J-T) cryocooler is widely used for the fast cooling of infrared detectors. In this work, a conical Hampson J-T cryocooler is designed and fabricated, and an experimental setup is built to test its performance. Accordingly, the cooling capacity, heat transfer coefficient, and efficiency of the cryocooler are analyzed based on the experimental cooling curves, the axial temperature distribution, the mass flow rate, and the pressure of the expansion chamber. The results showed that a minimum cooling temperature of 168 K with cooling capacity of 393.5mW can be attained by employing nitrogen gas as the working fluid at inlet pressure of 10 MPa. In addition, it was found that the axial temperature of the cold finger shell is distributed exponentially in the vertical direction. Also, the comprehensive heat transfer coefficient between the incoming flow and the backflow decreases gradually with the increase in the height. Due to the heat leakage, the heat transfer coefficient is less than 150 W/(m(2).K) and the efficiency of the cryocooler is around 80%. With the increase in the inlet pressure, the minimum stable operating temperature, cooling capacity, mass flow rate, and expansion chamber pressure of the cryocooler are found to increase. On the other hand, this will negatively affect the efficiency of the cryocooler.