Chapter 66 - Three dimensional numerical computation of the flow field in a pulse tube

Abstract

This chapter describes a physical and numerical model of the pulse tube in the pulse tube refrigerator. Three-dimensional computation of a compressible and oscillating flow field in pulse tube is numerically investigated using a self-developed code. The distributions of the velocity and pressure waves and the velocity vector in the pulse tube are provided in the chapter. The velocity wave near the hot end of the pulse tube lags behind that near cold end. At the some cross section of the middle part of the pulse tube the direction of the axial velocity reverses, the changing of the axial velocity direction starts from the center part of the pulse tube. Secondary flows are resulted from the combined effect of forced convection of the pulsating streaming and the natural convection caused by the large temperature difference between the hot and cold ends. The secondary flow and the mass streaming in a pulse tube can be a major heat loss mechanism. It carries heat from the hot heat exchanger (i.e, hot end) to the cold heat exchanger (cold end), thereby reducing the cooling power of a PTR.