H.B. Kim

The effect of operating parameters in the Stirling cryocooler

This paper presents design, manufacturing process and test results in the optimum operating condition for the free piston free displacer (FPFD) type Stirling cryocooler designed and manufactured by Korea Institute of Machinery and Materials. FPFD Stirling cryocooler is currently under development for cooling infrared detector. The compressor in the Stirling cryocooler uses opposed linear motors to drive opposed pistons. The performance of FPFD Stirling cryocooler is evaluated as a function of charging pressure and operating frequency. In general, as the charging pressure is increased, optimum-operating frequency of the compressor is increased but resonant frequency of the displacer is almost constant. The prototype has achieved no load temperature of 49 K and cooling power of 0.5 W at 72 K.

The Behavior of Mass Flow Rate of a Joule‐Thomson Refrigerator

Cooling capacity and cool‐down time of a Joule‐Thomson (J‐T) refrigerator depends on mass flow rates of refrigerants and their enthalpy changes. It is obvious that the mass flow rate through the J‐T refrigerator depends on supply pressure; it increases as the supply pressure increases. Furthermore the mass flow rate increases as the temperature of the cold end decreases when the supply pressure does not change during the cool‐down process. In this study, the cool‐down characteristics of a miniature J‐T refrigerator (fixed orifice / demand flow type) with different pressures of nitrogen and argon gas, were investigated by experiment. To analyze the cool‐down characteristics of the refrigerator, the supply and exhaust pressure, the temperatures on the surface of the cryostat, and the mass flow rate were measured simultaneously. The results show the effect of the supply pressure on the performance of the refrigerator. The influence of the supply pressure and the temperature on the mass flow rate during the c...

The effects of the clearance in the cold finger on the performance of the Stirling refrigerator

Publisher Summary This chapter investigates the influences of the radial clearance on the performance of Stirling refrigerator by numerical simulation. The Stirling refrigerator has the clearance in the compressor and cold finger. Its cooling capacity comes from the relation of the pressure in the expansion space and motion of displacer. In the radial clearance of the cold finger, the parasitic dynamic losses from the leakage flow and shuttle heat losses are inevitably occurred. Therefore, to get the maximum performance of the refrigerator, the radial clearance should be optimized. The SAGE is used to investigate the effects of the operating frequency, the stroke of the displacer and the radial clearance between the seal rings and the expander on the cooling performance. The calculation results show that the enthalpy flow through the refrigerator is a dominant heat loss. The leakage flow through the clearance has the effects on the cooling capacity through the gross refrigeration, the enthalpy flow, and the shuttle heat loss. The enthalpy flow through the clearance depends on the operating frequency and the radial clearance of the cold end, whereas the shuttle loss depends on the stroke of the displacer.