Theoretical and CFD investigations on a 200 Hz thermoacoustic heat engine using pin array stack for operations in a pulse tube cryocooler

Thermoacoustic heat engines (TAHEs) convert heat energy into acoustic energy without using any moving part. The acoustic energy can lead to a high frequency linear oscillating motion in a gas which in turn can be used to drive a pulse tube cryocooler (PTC). Thus, the PTC becomes contamination free and offers an extended maintenance-free life with high reliability. In any TAHE, the stack is the heart of the TAHE. Out of various stack designs, e.g. parallel plates, circular pores, rectangular pores and pin array stack etc., reported studies indicate pin array stacks offer superior performance over others. In this paper, investigations are carried out on the pin array stack for a 200 Hz TAHE. The 100 mm long stack is designed using many numbers of 0.3 mm diameter SS wires inside a 24.5 mm diameter resonance tube. Theoretical analyses are carried out for finding the optimum stack centre position. The theoretical results show that maximum acoustic efficiency of 24.5% occurs when the stack centre position is at a distance of λ/32 from the closed end. Pressure and velocity oscillations near the stack are also studied using Ansys® Fluent 17.1 software.