utilising exhaust energy for cooling of machinery spaces

Normally waste heat from the exhaust of generators are taken to a waste heat recovery boiler to generate steam to inject into steam system or to generate hot water to operate hot water chillers. Nothing new. What is new is this waste heat now directly used to operate Chillers without any boiler in-between.

Build your own Thermoacoustic cooling system. Here's a paper: http://www.mecheng.adelaide.edu.au/avc/publications/public_papers/2005/preprint_zoontjens_tar_speaker_aas2005.pdf

Dear Shikhar Bisht, I have always thought that the wasted heat released to the atmosphere should be used to 'boil' a liquid to form gas and that gas then cools down using a condensing radiator. This process I am talking about is the old 'Kerosene' Refrigerator, only it could be used instead as an 'Air-Conditioner' to supply cooling to the hot areas of a ship. Not all ships use steam these days as many are bunker oil diesel or jet turbine driven. Both these power systems deliver huge amounts of wasted heat energy that should be harnesed by as simple a process as heating an air-conditioner as you suggest.

You will battle to find either a steam or gas turbine driven commercial ship in this day and age.

Every ship I ever sailed in had a waste heat recovery system, normally in the form of an exhaust gas boiler. Whether you use the energy to cool air or to heat the HFO tanks or something else is irrelevant.

Most engine-rooms these day have an air-conditioned control room - the AC is more for the electronics benefit than the engineer's though. To cool the entire engine-room of a large commercial vessel is just insane. The huge flow of air created by the swallowing capacity of the main engine makes the high temperatures livable.

I agree with your comments on refrigeration, but I question what actual effect this cooling would really have in a modern diesel drive ship's engineroom.

Remember the engine gets its air from the engineroom. The volume of air drawn into the engine is enormous and to make any significant difference to the engine room temperature, a huge heat exchanger would be required.

To put it into perspective, a modern Sulzer RTA96 requires about 1,299,480 litres of air per minute. (This is of course the biggest engine afloat at the moment.)

Ship owners utilise the waste heat in the form of boilers and I can assure you that they are not particularly concerned with the comfort of the engineers.

Yes Dear,

Your reply/comment contains good amount of required informatiom on the topic under discussion.

How-ever the following lines:

The normal "gas Fridge" cycle is too bulky and inefficient for large scale use. It only works on a fridge because you have a well insulated enclosure and hence a fairly small heat load to deal with.

conveys the meaning that Ammonia water system is OK for small applications like fridges etc, and may not be suitable for large size or industrial applications.

I would like to add here that these systems are in use and have been in use for quite some time (say 20 yrs or so) in various application, where a large amount heat is to handled specially cold storages and ware houses. So there is no (Technical) upper limit to which the system can be scaled up ward. Systems of 100 or 200 TR rating are in use in industry.

Regards-

Dr N P Singh

Did you mean a "Chippie"? Hull repairs and woodworking etc? (It used to be wooden hulls!!)

I have personally never heard of a "Shippie"......

Utilizing waste exhaust heat to power an air conditioning system is certainly feasible, but may not be practical. Before undertaking any design work, I strongly suggest you check with the licensing authority where the ship is registered. They may not permit use of ammonia aboard ship. It is highly toxic and heavier than air so it presents special hazards that must be considered.

Hey Keith,

Just an FYI, Ammonia: NH3 has a molecular weight of 17 g/gmole

Air has a molecular weight of 28.97 g/gmole

potentially hazardous: Yes.

Heavier than air: No

Cheers,

Don

Lithium Bromide is also used in absorption chillers. It does not have the problems of ammonia.

Dear Shikhs,

As much what you suggest is considered very nice from a humanitarian point of view, but I don't think Diesel engine makers will be happy about it. Increasing the temperature of engine rooms is a must, because most of big ships run on heavy oil, which requires to keep it hot, and air conditioning the engine room, will increase the heat losses in the oil. Also, it will cool down the engines, which in my opinion will decrease the thermal efficiency of the whole plant ... or so I think.

Then they should learn how to both insulate pipes and to use the exhaust heat to warm the oil.......

Heavy fuel oil is heated using steam usually from the waste heat boiler. Lines are lagged etc so no problem there.

We spend a lot of energy trying to keep the engine cool, so this would not be a problem, in fact because the engine aspirates the engineroom air, the cooler the better. (That's why we have intercoolers on the turbochargers).

It looks like a good idea but during the 60's my father, in Brazil, applied for a patent of something very similar.

He wanted to use the heat on the exhaust pipe of a car to run the airconditioning system.

The problem then was the cost from one side and handling certain chemical materials in a car that may have a collision someday and exhale these chemicals in the atmosphere on the other side.

After some tests he gave up. I don't know how would it be now.

Dear Shikhar Bisht,

Like you I too have sailed for 6 yrs. on ONGC ship for offshore oil exploration.

I completely agree with U that the waste heat should be recovered to run a/c so that the living/dining areas of ship can be cooled at proper temp.

Reply to your question is YES it is possible to run a cooling machine called Vapour absorption system from waste heat recovery.

Vapour absorptiojn cycle (Typically Ammonia-water and a small amount of hydrogen dashed in it) is a established technique for generating cooling effectt using heat.

There are practical applications (vehicles) which uses vapor absorption system (VARS) for air conditioning the automobile. Many vehicles (running long distances )specially the large size container carriers which transport material/items (to be stored/transported under refrigerated condition) , do use vapor absorption system (VARS) for air conditioning the automobile driver cabins and the containers volumes.

Few of old luxary cars ( of Gandhi jee's era) were using vapor absorption system running on heat recovered from exhaust pipe (Silencer pipe) for air conditioning the car.

In my house I have recently acquired a Refrigerator having Vapour absorption cycle, which runs on either a small Kerocene lamp or a 400 watt heater element at its bottom for supply of heat.

To run a Vapor absorption system, temperature range of 130 - 150 degree cels. is sufficient, which can be easily achieved from silencer pipe heat recovery.

Dr N P Singh

(I've never hurd of a shippie either) Dear all, I'm curious, how are you gonna get rid of the heat taken from the air you want to chill? It's gotta be driven somewhere.

Yahlasit

There may be a simpler method, use the heat to warm air in a vertical tube, that is open at the top (with suitable arrangements to prevent water ingress in heavy weather), causing the air to be expelled by convection.....the longer the chimney, the more effective it becomes.....

No chemicals, no pumps and dead simple, just a few long vertical tubes.......

Some testing will be required to elicit the tube length and diameter that works best.....