If you have one of those Chinese diesel heater so call parking car truck rv air heater, and thinking of the hot exhaust hose can be use to heat water or create more heat etc. think again. I did the experiment and didn’t work. I have watched many youtube videos with many youtube videos showing how to do it, but I never seen them really do a stress test, all they did was a 15 mins test or 1 hour test.
I did my test with various heat exchanger or so call car egr heat exchanger or even a pool heat exchanger, none of them work. Why doesn’t it work? all I can tell you is it is dangerous because the moment you put something to cool down the exhaust hose or pipe of the diesel heater, carbon or oil start to build up because it’s not hot anymore and it doesn’t seem to burn those oil instead it get clog up about 5 hours later and the next thing you know is the diesel heater struggling to push out the exhaust but it couldn’t and it back flush into where ever for it to go, either that or it will be smoking with white black smoke. Basically if you have cold water running through the heat exchanger or even a copper coil around the exhaust hose will cause it to cool or too cold and the exhaust hose will have carbon build up like charcoal oil and clog up, so don’t do it, let the exhaust hose be the exhaust hose it burn the oil and push the burned stuff out, don’t let it clog.