Working Performance Investigation On A High-Power Integral-Type Stirling Cryocooler

Urgent requirements of high temperature superconducting (HTS) technology have spurred the rapid development of high-power cryocoolers. Integral-type Stirling cryocoolers are promising candidates for HTS technologies, due to the features of high efficiency, wide temperature range, fast cool-down and compact structure.A high-power integral-type Stirling cryocooler was studied numerically using Sage software. According to the simulation, the cold head is able to reach a cooling power of1082W at77K with a PV power of7935W. The experimental result shows that a cooling power of602W at77K with an electric input power of11.6kW has been achieved up to now. The simulated pressure wave in the compression space, the load curve, the effect of charging pressure and chill water on cooling performance shows good agreements with experiment results in the change laws respectively. The value difference between experimental and simulation results arises from unavoidable calculation errors, oil pollution and some frictional dissipation.Simulated energy flows agree well with ideal ones. The ideal cooling power minus simulated one equals available losses simulated by Sage. Among them, loss caused by incomplete heat exchange takes the largest proportion of53.6%, followed by flow friction loss (34.1%) and conduction loss (11.6%). In the cryocooler, losses mainly occur in the regenerator (35.1%)and after cooler (34.8%). Simulation results show that the diameters of regenerator have been close to the optimal value, while there is a large room for improvement in the length. Using stainless steel mesh as the packing in the regenerator instead of copper velvet, the simulated cooling power can increase in the optimal mesh size. According to the calculation, Shorter, thinner and more tubes in the after cooler can provide higher cooling power.The phasor diagram shows that the phase difference between flow and pressure at both ends of the regenerator is departure from the desired value. The desired value can not be reached by optimizing the piston phase because of the existence of displacer back pressure cavity. It has been proved by calculations of ideal cooling power and mass flow in the regenerator using the isothermal model that the performance of a β-type Stirling cryocooler is worse than a α-type one with the same feature size. The phasor of flow and pressure of the compression space shows that the cryocooler system appears as a capacitive reactance. An inductive reactance should be added into the system in order to increase the use efficiency of motors.