An idea for using waste heat

[barts]

While working on the design of our proposed 37' steamer for use in the US Pacific Northwest, one idea that has been rattling around my head is to use a inboard plate-style condenser like Rainer's boat, but instead of cooling it using raw salt water we'd run a RV antifreeze loop and a keel condenser. We'd use the hot glycol mix to warm the boat (warm the cabin sole?), heat domestic hot water, and make sure the wet weather gear locker stays warm and dry before dumping the rest of the heat into the sea. A 6 roller Hypro pump would circulate the cooling water, using less than 1/8 hp to provide 7 gpm.

The pump would draw from a vented day tank; the pumping losses would likely amount to less than 10 psi. In order to regulate the amount of cooling, a portion of the flow from the pump could be bypassed back to the day tank. This would allow regulating the exit temperature of the condensate, and also keep the temperature of the circulating antifreeze up to insure proper heating inside the boat when steaming more slowly. The heating circuits inside the boat would each have their own bypass ball valves.

- Bart

[Lopez Mike]

I see no serious problems.

You know, of course, that you will still be sending most of your heat back into the sea. I think you can go nuts in freezing weather and not use of fraction of your waste heat.

[fredrosse]

Great idea. One of the reasons I avoid plate heat exchangers with raw water cooling (on my day job) is because the very small passages in a plate heat exchanger tend to get clogged up with debris, and they are very difficult to clean compared to a shell/tube heat exchanger. The glycol mix with a closed system will avoid that problem. A small brazed plate heat exchanger as a condenser on a steamer, with clean RV antifreeze on the cooling side, should not have fouling problems. The heat exchanger may get fouled on the steamside with cylinder oil, and it can be blown out with live steam for cleaning if needed.

As you probably know, Ethylene Glycol (automotive anti-freeze) is not allowed if used in a heat exchanger for potable water. Propelene Glycol is allowed, and not much difference in thermal performance nor cost.