Some ideas for making a special device with no moving parts except air, which can produce hot and cold air using regular ol' compressed air.
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The exact mechanism of the operation of this device is still open to some speculation, but the example is basically comprised of an air jet of about a 2mm diameter exhausting into the minor diameter of a cylindrical single turn spiral chamber which has on one end a washer or diaphram with a small hole of about 4.3 mm diameter leading to an approximately 4" long pipe which is open to the outside.
The other side of the cylindrical spiral chamber leads through a length of pipe roughly equal to 285mm (The inside diameter of the pipe is about 9.5mm) to a stopcock. The stopcock can be adjusted to optimise for hot or cold air delivery at the appropriate end of the device.
the relatuionships of the dimensions are fairly important, but the device can be scaled fairly easily. It seems that the larger the device and resulting airflow, the greater the achievable temperaturwe differential. With adjustment of the stopcock, a temperature differential of +/-70 deg.C was atainable at about 200psi. The greatest cooling was obtained with the stopcock set for a ratio of hot to cold air mass of about 3 to 1.
