Waste Heat Recovery 1

[wr180561]

I’m looking for a good manufacturer & supplier of waste heat recovery equipments, i.e. exhaust gas boilers, absorption chillers, fresh water generators etc..
I’ll appreciate it if anyone can post the names & web site addresses of such manufacturers. May thanks, WR.

 

[bever]

This is a very interesting topic. We have been dabbeling (not using company money)with wasted heat as a generator for use in absorption/desorption refrigeration. Using the waste heat surrounding the exhaust manifold. I'm interested in the replies to this group..........good luck.

 

[jimkden]

The reason you don't find this equipment is because the internal combustion engine efficiency is too great and the invested cost plus annual maintenance of the recovery equipment and systems does not have a great enough rate of return. So, equipment manufacturers concentrate on the lower efficiency types of engines like gas turbine engines.
On a personal basis it is probably worth the effort but if you bought the installation, paid to operate and maintain it, the economics won't be there.

 

[jrnsr]

I just submitted a few proposals to DOE relating to waste heat recovery... this is one... absorption refrigeration air conditioning. Probably won't find out till summer on getting grant to do it.

 

[carnage1]

internal combustion efficiency is quite low, more energy is lost than used. as far as waste heat recovery thermovoltaic materials are great, they transfer a percentage of the waste heat directly into electricity.

how about this nifty little product?

http://www.hi-z.com/websit07.htm

 

[wr180561]

Happy new year to everyone.

The efficiency of a diesel engine is approximately 33% with 30% heat rejected to the cooling water, 30% heat rejected to the exhaust gas and the remaining 7% is radiated to atmosphere. Theoretically, we are able to recover all the heat rejected to the cooling water and only 50% of the heat rejected to the exhaust gas and that is to say, the recoverable waste heat of a diesel engine represents almost 45% of input energy which is a great amount of energy and should give a reasonable return of investment provided that it is efficiently utilized.

My question now to Jimkden and others, your statement “if you bought the installation, paid to operate and maintain it, the economics won't be there” is it based on practical experience with existing installations or just based on mathematical work ? WR.

 

[gbent]

How valuable the waste heat is depends on what you are trying to do with it. The coolant heat is of little value, it is only at about 180 F. If you have a great need for space heating, it may have a value, but only probably for part of a year.

What is your application, or how are you planning to capture and use the heat? Is this a year around need, or is it seasonal?

 

[wr180561]

The application would be HVAC. Engine cooling water shall be used to preheat the feed water before an exhaust gas boiler, the generated steam will then be used to fire an absorption or adsorption chiller(s), this certainly would be used all year around. Has anyone tried a similar application ? WR

 

[wr180561]

Note:

We are talking here on large diesel engines of over 3000 Kw output. WR

 

[j2bprometheus]

The peak brake thermal efficiency of a large modern diesel is more like 43-50 %, depending on the size of the diesel, engine speed, percent load, etc. The 33 % that wr18061 gave is quite low. The diesel used in a semi has a peak efficiency of about 43 %, and making the engine larger only helps the efficiency of a diesel.

The exhaust waste heat of an IC engine is difficult to recover. This is because it is hard, but not impossible, to transfer heat into or out of a gas due to the low thermal conductivity of the gas. Heat exhangers used to cool gases often have liquid on one side of the heat exhanger and gas on the other. Gas to gas heat exchange requires large surface areas to get reasonable heat transfer rates. Regenerators are occasionally used to recover heat from a gas and send it to another gas.

Also, if you successfully get the heat out of the engine exhaust, condensation of the water vapor in the exhaust can be a problem. The condensate is usually acidic and corrodes most metals used in heat exchangers.


There are some SAE papers from the 1970's on bottoming cycles for IC engines. These papers would probably have some info on recovering the engine exhaust heat.

When I was in the Navy, we had a lithium bromide absorption type chiller. It worked well but that particular model required a skilled operator.

 

[wr180561]

j2bprometheus is quiet write. The efficiency of a modern diesel engine can possibly be as much as 43 % but this is when the effect of turbocharging is considered. The 33 % which I previously mentioned, does not however take the effect of turbocharging into consideration.

The heat available in the exhaust gases of a diesel engine isn’t in fact difficult to recover, an exhaust gas boiler would utilize the heat available in the exhaust gases and generate hot water or steam. In order to avoid formation of sulphuric acid, the temperature of the exhaust gases is always maintained above the temperature at which the water vapor in the exhaust gases will begin to condensate and therefore a chemical reaction between sulphur & water would be avoided. WR

 

[GregLocock]

Non-turbo diesels can be much more efficient than 33%.

After all, there is a production naturally aspirated spark ignition engine that manages 37%.

Cheers

Greg Locock