Compressed air

[MrReds]

Hallo to everybody.

I am facing to following problem:
I have to calculate an heat exchanger to reduce temperature of compressed air.

Please, I’d like to know if, according to your knowledge, there is something that differs from traditional heat exchanger dimensioning.

Are there further factors to consider when dealing with compressed air with respect of dealing with standard air (at 1 atm pressure) ?

Is it basically as to consider an heat exchanger that it's working at different altitudes ?
Nevertheless,the difference in pressure is extremely high

Many thanks

 

[MintJulep]

You have fluids of known properties and flow rate on both sides.

 

[gr2vessels]

MrReds,
Most of the higher powered compressors have a finned after-cooler inseted on the compressor exhaust, in order to remove the heat accumulated by the compressed air during the compressioncprocess. Unless you have some extraordinary cooling process requirements, your design is probably limited to an air to air cooler, similar to a car radiator. A closed circuit shell and tube exchanger used to cool compressed air would probably be an expensive overkill, but much more efficient than the air cooler I mentioned.
As MintJulep mentioned, the compressed air properties are readily available, on the internet or in your engineering books, then you need the cooling fluid properties to calculate the energy balance for the heat transfer required. The rest is simply a selection of heat exchanger type you need and mechanical design for sizing the various components. Just note that in comparison to the high pressure of the compressed air you have hinted, the altitude of your exchanger counts only if you employ an aircooler (the cooling air density varies with altitude).
cheers,
gr2vessels

 

[I3iG]

Why don't you consider to cool down the inlet air? What temperature decreases you want to acheive?

Don't forget to pay particular attention once you decrease the compressed air temperature about the water condensation you will get in anycase.

 

[dcasto]

Biggest errors I've seen in compressor aftercoolers is forgetting to include heat of condensation of liquids, whether its water or in the process fluids.

 

[crjones]

What type of aftercooler are you considering? Do you have a receiver in the system? What are you trying to achieve in temperature and pressure drop?

 

[TBP]

Why not just talk to some heat exchanger manufacturers. They'll have software to run your conditions, and size a HX in a lot less time than it will take you to grind through this.

 

[MrReds]

I would like to thank you all for your answers.
Sorry for the delay of answers but all possible crashes occured in my PC !

Mr Crjones: I haven't got a receiver in the system.

Mr. TBP: unfortunately the heat exchanger manufatures contacted consider this kind of application unusual for their usual calculation. Please, could you suggest me some manufacturers I can contact ?

thanks in advance

 

[srfish]

There must be something you are not telling us if the heat xchanger manufacturers think this application is too unusual for them?

 

[crjones]

A receiver will act like a big aftercooler sometimes more effective than is found on most plant compressor systems.

Since you say the pressures are high, a traditional plant air compressor aftercooler manufacturer will not want to look at it. You need to talk to gas compressor heat exchanger folks.

 

[MrReds]

many thanks

Mr. SrFish
The heat exchanger producers I've contacted are not able to calculate the heat exchanger.
I suppose that the reason is that they are used - or they have got correlations - for traditional refrigerants.



Mr. Crjones
could you kindly suggest me any useful link ?

 

[crjones]

I have had good luck in the past with Super Radiator Coils out of Chaska, Minnesota, USA on 5000psig natural gas compressors.

Here's a address listing some others:

http://www.processregister.com/Heat_Exchangers_for_High_Pressure_Service/Suppliers/pid3480.htm