Minto Wheel a solar Refrigerator
Nerdyee, introduced me to the minto wheel. After a little research it turned out not to be a very efficient solar heat engine, but it had another very amazing quality. At temperatures of a little over 100f it produced 250 psi using Freon 12 as the working fluid. Quote from refrigeration manual:(Example of a more theoretical air conditioner or heat pump pressure and temperature at the compressor and at the cap tube or thermostatic expansion valve during normal operation: at an outdoor temperature of 72 degF, liquid refrigerant (R12 for example) leaving the outdoor condensing coil and entering the cap tube or TEV might be at 100 psi and 95 degF.)
This beats using poisonous toxic ammonia like most other solar refrigerators use. It is relatively simple to construct.
Quote from Mother Earth: (Result: At least based on our experiments, Steve Baer was right. The wheel will turn and it will do useful work (if you call lifting Dennis Burkholder off the ground as shown in the Image Gallery "useful work"). It'll even break two-by-fours in two (as we found out) when you stick them through its spokes in an effort to stop the turning of the monster. And it'll run a cement mixer (which we just happened to have handy in the shop and which we hooked up with a rope "belt" to our wheel. But the dang thing turns over so slowly. (We were shooting for a one-revolution-per-minute speed with our 22-foot wheel loaded with Freon 12 . . . but the close-to-250-pounds-per-square-inch pressure we were getting in the tanks was too scary. So we switched to Freon 11 . . . which cut our operating pressures down to 48 pounds per square inch . . . and the wheel's rpm to one every five minutes!)
Why does it have to be a wheel? Why not vertical steel pipes? You are not trying to get mechanical movement. The fluid could flow up, release pressure as a coolant, condense and flow down to the heat source. A parabolic trough could move hot water around a copper coil at the bottom and circulate it back to the parabolic trough, like a steam engine but at lower temperatures. It is not just a cylinder filled with an expanding gas, it also uses water that is pushed up by the expanding gas and used to increase pressure. As the gas contracts and gravity pulls the water down or at least that’s on the model.
Discussion on Stirling or "hot air" engines (all types)
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