Abstract:
A comparison of the pin stack geometry with the conventional rolled geometry has been made in a prime mover which uses low-pressure neon gas held between room and liquid nitrogen temperatures. The pin stack was constructed by hand sewing a 75-(mu)m Constantan wire back and forth about 2300 times between hot and cold heat exchangers. The wire forms a hexagonal lattice with wires along the acoustic axis spaced 750 (mu)m apart with a 3.2% error rate. Preliminary results are that the onset of sound occurs at a mean pressure which is 40% lower for the pin stack compared to the rolled stack, the sound produced is generally 18% louder for the pin stack, and the efficiency of the pin stack is about 25% better than the rolled stack, although this last result has the most uncertainty due to the difficulties of reliably measuring the heat flow. [Work supported by ONR.]