Thermoacoustic Refrigerator

A thermoacoustic refrigerator pumps heat with sound; a standing wave in a sealed tube drives a pressure gradient across a stack, moving heat with no moving parts and no refrigerant. TLDR, it's a classic heat engine/refrigerator cycle that uses standing waves instead of a compressor. I led a three-person IEEE-HKN team building one from scratch.

It only works if the driver runs at a frequency that puts the heat exchanger's stack at the right point in the wave. I modeled a pressure impulse in ANSYS Fluent and measured the time between pressure peaks at the endcap to find the resonator's natural frequency, around 370 Hz. Our stack was staged at the third harmonic, putting the operating frequency near 1100 Hz.

I developed the structural assembly in Onshape and manufactured the prototype. It reached a steady-state drop of 4°C at 1100 Hz — enough to validate the node placement, with the remaining gap down to thermal conduction and sealing losses.