Quote:
Originally Posted by basslover911
Thats EXACTLY what I have had in mind. The only thing is weather the fluid will work by natural convection or not (it WILL if the fluid can become steam, but I dont know if it stays in a fluid state).
Another thing, doesn't R-134a have to be pressurized? That (1) raises the boiling point and (2) makes the system a tiny bit more complicated than a non pressured system.
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Re convection: Hmm... you might need a solenoid valve and a high pressure bypass in order to charge your system. As the fluid is heated by your exchanger, the pressure goes up. Orient the exchanger so that the hot side tap is on top, ensuring that only vapor leaves the unit for your engine (sterling, turbine, or whatever). Put the solenoid valve in the hot line, along with a pressure relief bypass (for when you turn the car off!). From your engine, you run through the condenser to extract the remaining heat and increase the pressure differential across your turbine. From the condenser, run through the check valve and back to the exhaust exchanger. If you can use the check valve to force the fluid to flow in a particular direction, then convection will do fine.
Yes, it does have to be pressurized, so I can fully acknowledge issue 2. That's why I'd just rob the parts off of a junkyard AC. Yes, the boiling point is raised, by the high pressure, but that's not actually a problem. R-134a buys you two phase operation in a lower temperature regime than water. Google "R-134a table" for info. At atmospheric pressure, R-134a boils at -15degF. Hike the pressure up to 160psia and the boiling point only becomes 110degF. If I were designing a system, I'd want my cold side to condense around the 110-120degF mark, allowing me to dump the heat off in almost any weather condition (depending on where you mount the condenser).