Exhaust temperature reduction

[meche001]

I am working on an industrial scrubber, which is operated by a three speed 0.97L diesel engine. The scrubber is made of rotomolded parts which are very sensitive to heat. Since the exhaust temperature of the engine is around 1200 deg F it is melting the rotomolded components (chassis) around it. Currently heat wraps are used to insulate the exhaust pipe but they are very expensive( over $600). We cannot use EGR as it is against the regulations. Is there a solution to bring down or safely dissipate the exhaust heat without damaging the plastic around it. Thanks!

 

[Lou Scannon]

I don't think you'll find any cheaper solution than add-on heat wrap. The better types should be quite durable.

"Schiefgehen wird, was schiefgehen kann" - das Murphygesetz

 

[gruntguru]

Stainless steel heat shields are effective but very dependent on the layout of the installation. If the offending section of hot pipe is straight and not far from the outlet you could add a larger diameter concentric pipe, open at both ends and extended slightly past the outlet to act as an ejector and draw cool air through the annular space.

je suis charlie

 

[Panther140]

Jet skis had this problem 30 years ago and fixed it by putting a cooling jacket around the first part of the exhaust pipe

http://i144.photobucket.com/albums/r198/laserman222/WATERROUTING.jpg

"Formal education is a weapon, whose effect depends on who holds it in his hands and at whom it is aimed." ~ Joseph Stalin

 

[btrueblood]

Jet skis having an advantage of operating amidst an abundant supply of water...

 

[BrianPetersen]

Lots of newer trucks with diesel engines having DPF use a special tailpipe design which is meant to draw in outside air to dilute the high temperature exhaust before it gets near the perimeter of the vehicle.

 

[Tmoose]

Is the exhaust mounted to the rotomolded components (chassis), or vice versa, so conducted heat is a problem in addition to radiated heat? I'm guessing convection of air heated by the exhaust is not a big part of the problem, although I guess if the chassis is above the pipes it could be.

if there is room for a single or better yet double wall heat shield with an air space it can be pretty effective for radiated heat.

It is pretty common to use a double shield around the potentially VERY hot catalytic converter.

http://www.heeltoeauto.com/files/pitboard/tsxproject/007_003.jpg

 

[Overrun]

Painting both the rotomolded and exhaust surfaces silver or gold is worth a try for the cost.

 

[ivymike]

It is not uncommon in the case of naturally aspirated diesels in hazardous (potentially explosive) environments to use an exhaust-to-water heat exchanger inside the exhaust manifold, such that exhaust temperatures leaving the exhaust manifold are below relevant limits (commonly 200C). These are often used in conjunction with water-jacketed surfaces on the outside of the manifold. That may all be a bit expensive for your application, though...

 

[Panther140]

If you cant cool the exhaust itself, then figure out a way to cool the parts around it that you dont want to melt. Put cooling jackets, of some sort, on the stuff that keeps melting. Is there a blower fan inside of the compartment already? Put a blower in there. If that doesn't work, liquid cool some things.

"Formal education is a weapon, whose effect depends on who holds it in his hands and at whom it is aimed." ~ Joseph Stalin

 

[Panther140]

ivymike I didnt see your post before I made my follow up post. Glad to see my idea isn't crazy though!

You could get a small radiator with a fan and a transfer pump to flow the coolant through it. Weld a box around the exhaust pipe that is water tight and put an inlet and outlet for coolant on opposite sides of it. It might be a fun project since it probably doesn't need to be perfect

"Formal education is a weapon, whose effect depends on who holds it in his hands and at whom it is aimed." ~ Joseph Stalin