Numerical Simulation of Pulse Tube Cryocoolers
要約
Orifice pulse-tube refrigerators show promise as potentially low cost, reliable and efficient small cryocoolers. This paper presents results from numerical simulation of the device, together with a discussion of some of the challenges involved. The physical model includes a one-dimensional representation of the cryocooler geometry, including compressor, heat exchangers, regenerator, tube, orifice and reservoir. Since the one-dimensional model does not allow for proper simulation of transverse diffusion, there is no alternative to empirical models for viscous losses and convective heat transfer with the heat exchanger walls and the regenerator matrix. The numerical solution is based upon a Godunov scheme, consisting of a Lagrangian step followed by reconstruction step on an Eulerian grid. Some global performance prediction results are presented, and, more importantly, the crucial issue of pressure drop and pressure phase shift across the regenerator is analyzed in detail. A consistent physical explanation of the phenomenon is presented, showing that the pressure drop and phase shift is due to strong viscous friction in the regenerator.