Thermodynamic Comparison of Two-Stage Pulse Tube Refrigerators for Two Different Configurations
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Using exergy analysis, control thermodynamic models of two-stage Pulse Tube Refrigerators (PTRs) are developed for two different configurations. The models assume that phase shift controllers exist that control the phase shift between the mass flow and pressure in the pulse tubes. In one configuration, using thermally-coupled stages, separate gas circuits are used, thus requiring two compressors. This configuration provides flexibility for thermodynamic optimization. In another configuration, a conventional gas-coupled two-stage PTR is used where a constraint exists for mass flow allocations and the implementation of the phase shift control. The models include controllers for flow conductance, heat transfer effectiveness, and conduction heat transfer parameters in the regenerators in both stages for each configuration. The effects of the allocation of the values of flow conductance and ineffectiveness parameters in the regenerators, the mid-stage temperature, and the phase shift in each stage on the performance of the refrigerators are investigated. Important dimensionless parameters controlling the thermodynamic performance of the two-stage PTRs for each configuration is developed and discussed.