HumCooler: Fluid Parcel in the Resonator

HumCooler: Fluid Parcel in the Resonator
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Consider a tiny "parcel" of air in the middle of the tube. As the tube resonates, the parcel moves back and forth a little bit, and it gets squeezed and stretched a little bit -- it has both pressure and velocity components. The key is that when the parcel gets squeezed, it gets a little bit hotter -- and then when it stretches out, it gets a little bit cooler. Furthermore, because the parcel is moving, the place where it's hottest is a little towards the closed end, and the place where it's coolest is a little towards the open end.

Figure 2.

So far, the heat doesn't go anywhere or do anything: first, because the parcel is surrounded by other parcels that are doing pretty much the same thing, and second, because the air is a poor conductor of heat. Physicists say the parcel is adiabatic, meaning no heat energy flows in or out of it. Ordinarily, that's all there is to it.

This page maintained by Wil Howitt
Last updated 4 June 2003