Search

This paper analyzes the mechanism of the symmetry-nozzle instead of needle valve or orifice to improve the performance of pulse tube refrigerator in experiments. Their identifications are to result in a similar reciprocal movement in the hot end of the pulse tube; their differences are that their flow coefficients have different characteristics. The flow coefficient of the symmetry-nozzle has a positive feedback to flow rate while the orifice has little relation to flow rate generally. Further analysis shows that this feature results in large refrigeration when the pressure ratio and mass flow amount are same, which explains the reason for even lower temperature and a larger refrigeration amount when using the symmetry-nozzle.

Through analyzing phase relation between pressures and flow characteristics of double-inlet and multi-bypass, mechanism of double-inlet to lower the temperature of pulse tube refrigerator is proposed. Then another proposal is put forward to replace the low temperature multi-bypass valve, which is another double-inlet valve at room temperature and a small tube prolonging to the low temperature part of pulse tube. Through experiment, this multi-double-inlet version proves effective to lower the refrigeration temperature. Test acquires a lowest temperature of 37 K with two double inlet valves and 50 K with one double inlet valve. The concept of low temperature double-inlet is proposed here for the first time.