Two-dimensional numerical simulation and performance analysis of tapered pulse tube refrigerator

Numerical simulation of two-dimensional viscous compressible oscillating flow was carried out for the uniform cross-section and tapered pulse tubes. Based on the numerical results, it was found that for the taper pulse tube refrigerator, there was an optimum taper angle, with which the performance of a cryogenic refrigerator can be greatly improved. However, on the other hand, the results also demonstrated that when the taper angle becomes much larger than this optimum value, the cooling performance becomes weaker than that of the circular tube. We discussed the effect of the tapered pulse tube on the performance of pulse tube refrigerator based on an evaluation of the secondary flow in the pulse tube. It was found that in comparison with the uniform cross-section pulse tube, the magnitude of the secondary flow in the tapered pulse tube decreases while its distribution becomes less uniform, which explains why the performance of the tapered pulse tube can be improved compared with the uniform cross-section pulse tube.