Feedwater Preheat using Engine Exhaust

[JonRiley56]

Howdy All,

I am not enthused about tryng to set up an economizer in my boiler, given its fit and finish and my options for feedwater entry points, so I am going to pre-heat using the temp from my exhaust. I have been playing with a marine pwer steering fluid cooler and it seems to be working quite nicely. The though bore is about 1" so it does not restrict my exhaust unduly. I have also been able to get adequate volume of water through it.

Are people aware of any other "off the shelf" type of exchangers that would work ? I recall Rainer having a video of what looked like a plate heat exchanger on his exhaust side with cool water being fed through it to condense the steam. It seems to me that I would get a lot of back pressure from that type of set up. If they are suitable, how would I know what to look for ?

Comments ?

I have included a pic of the unit I am using now.

jon

[artemis]

Howdy All,

I am not enthused about tryng to set up an economizer in my boiler, given its fit and finish and my options for feedwater entry points, so I am going to pre-heat using the temp from my exhaust. I have been playing with a marine pwer steering fluid cooler and it seems to be working quite nicely. The though bore is about 1" so it does not restrict my exhaust unduly. I have also been able to get adequate volume of water through it.

Are people aware of any other "off the shelf" type of exchangers that would work ? I recall Rainer having a video of what looked like a plate heat exchanger on his exhaust side with cool water being fed through it to condense the steam. It seems to me that I would get a lot of back pressure from that type of set up. If they are suitable, how would I know what to look for ?

Comments ?

I have included a pic of the unit I am using now.

jon

If the unit you've got now does the job, don't change it. The unit appears to be durable and, relative to many heat transfer devices, a lot less expensive than a plate heat exchanger - KISS principle in action.

Because of the "cooling" going on, there should be a drop in pressure from the exhaust inlet to the outlet (put a pressure gauge across the input and another on the exhaust side). Any pressure decrease - below atmospheric - means you're picking up free "work" on the engine side and, if you measure the feed temperature going in and out you'll see how much heat you're picking up.

[Lopez Mike]

That looks great. I have one that looks like that but was intended as a transmission oil cooler on a power boat. I scrounged this one but they normally cost an arm and half of a leg. I'd go with it.

I'm planning on both an exhaust feed water heater and an economizer. Trying to be as efficient as I can with my single cylinder engine.

Mike

[SL Ethel]

Your current heat exchanger looks great, and like Ron said - don't fix it if it ain't broke. However, if you do want something with more surface area, just type in "heat exchanger" on ebay, and start doing a bit of patient searching. I got my hands on a 5" diameter, 2' long tubular heat exchanger - all brass - for about $50 a couple years ago. The thing weighs over 50 pounds!

The only downside I have found is that it doesn't have the same high volume pass through capacity as the unit you describe. I use mine as a condenser. When I had to run without cooling water, essentially using it as a muffler, it produced a few pounds of back pressure - not ideal. In your application, you won't be condensing all the steam, so this might be an issue. Also the baffles in most tubular heat exchangers mean you have to be mindful of mounting orientation so that you don't get water pockets on the steam side.

You can also find flat plate heat exchangers on ebay, and they might be easier to work with. I'm just partial to the old style ones.

Cheers,
Scott