Era, you Do know that the alcohol in windshield washing fluid is NOT drinkable, where as the RV antifreeze is safe for drinking water systems; right? If you have tried stuff that is "oily" I would switch brands. The red stuff should only have water color water and alcohol in there...no oils. Who knows what nasty stuff is in windshield fluid...might grow hair on things you don't want hair growing on....
Polarisrider, the geothermal process is a modern marvel, pulling "heat" out of the water which never goes below 33 degrees. "Heat" is relative, in that if you "warm" the gaseous material being "pumped" around-- thru an exchanger you can extract heat from things even below freezing aka, 32 degrees F. There is always some heat to be "extracted" from a gas that is cooled well below that temperature.
Your can of beer warms because your hand is warmer than the can and fluid inside the can, and eventually it will "neutralize" to the same temp as the surrounding temperature (assuming you get busy scrubbing that boat, and forget about the can of beer you opened...course you drink it anyway, warm or not....) All things want to neutralize in temperature, and water surrounding a pipe, will tend to try and neutralize the contents of the pipe and warm it provided that the material inside the pipe is colder than the water it is being pumped thru.
Water draws the relative cold away from the chilled gas while in the piping very well, and once the gas is re-pressurized, it forms heat which is extracted via a fan. Like a radiator extracts heat from fluid aka coolant, a radiator can do the same with compressed gas which heats under compression, and the returned gas is warmed back up by temp of the water. The warmer the water the better it works. But even down to ice water there is always some relative "heat" to be extracted.
It might help to think of it as a refrigerator.
Gas is pressurized causing heat (fins in the back of the refrig) dissipate the heat from the compressed gas) then the gas is released in the fins inside the refrig and the released gas causes cooling, which is extracted by fan chilling the inside of the frig. Cooling results from the decompression of the gaseous material.
Nearly all gaseous materials which are released out of a spray can causes the can to chill down significantly...(you have had this happen when you emptied a spray can of nearly anything).
There are air to air exchangers which simply use the outside air to "warm" the pumped gas up, and there are geothermal equipment which uses the ground and surrounding water table to extract heat. Since the air temp can get well below freezing and the ground doesn't do that far below the frost line, it is a better source to extract heat from than air in cold temps. Lake water is warmer than the air in winter, most the time.
The bubble system on your boat (if you leave it in all the time) uses the relatively warmer water in the lower levels of the boat slip, to circulate up and prevent the above water from freezing.<font color="ff0000">•</font><font color="ff0000">•</font><font color="ff0000">•</font><font color="ff0000">•</font> is the mixing of this water that prevents freezing the boat into the slip.