Waste heat recovery sytem

"The one area I think might be worth looking at is coupling exhaust heat recovery to RO watermakers. A fifty degree C feedwater increase could about double production from a given membrane."

Was there not an old way to distill sea water with heat and a vacuum pump. no membrane involved?

Might be time to upgrade century old tech?

 

displacement engine

from PAR "......how about using the exhaust heat to warm the hot side of a displacement engine, which can be employed to drive a generator (or whatever).........."

Not familiar with a "displacement engine", what is this?

 

Lookup "stirling engines". It's the old heat displacement theory and quite effective if you happen to have a wide temperature differential available.

https://en.wikipedia.org/wiki/Stirling_engine

 

Stirling Engines

OK, I am familiar with this type of engine, which shows some promise for the application you mentioned.

The referenced article does not quantify the facts that actual hi-temperature engines that have been produced (with the intent of commercialization) weigh more than 250 pounds per horsepower, and are quite large for their output, over 3 cubic feet volume per horsepower. Stirling engines running on the waste heat temperatures associated with spark ignition or Diesel internal combustion engine exhaust would be far larger.

With heavy subsidies or the checkbook of NASA, much higher performance is possible in smaller packages, but not yet a practical reality for IC engine waste heat use.

Interesting to note that my steamboat has weight and volume numbers which are close to 250 pounds per horsepower, and 3 cubic feet volume (including boiler) per horsepower, but that is a matter of personal choice. Steam plants have been made up to about 300 horsepower per cubic foot of volume (including boiler), but with military intent, and a military style checkbook.