An experimental comparison of a pin stack to a conventional stack in a thermoacoustic prime mover

Abstract

This thesis is an experimental comparison of a pin stack to a conventional stack in a thermoacoustic prime mover. A thermoacoustic prime mover is a type of natural heat engine which converts a temperature gradient across a stack into acoustic energy. A pin stack uses wires which are arranged in a hexagonal array instead of the parallel or rolled plates of a conventional stack. The pin stack was constructed by by threading 75 micron constantan wire between the hot and cold heat exchangers 2312 times. Computer modeling with the program DeltaE predicts that a pin stack will significantly improve the efficiency of the prime mover. In the experiment the temperature gradient across the stack was supplied by submerging the cold end in liquid nitrogen while holding the hot end at ambient temperature. The experiment was conducted for both the pin stack and a conventional rolled stack. The pin stack produced 20% higher acoustic pressures than the rolled stack and the efficiency was up to 31% better. The pin stack went into onset at a 41% lower mean pressure than the rolled stack.