Outlet Air Temperatures in Air Cooled Heat Exchanger 1

[Peregrino7]

Hello...!

Is there a limitation in Outlet Air temperature in Air cooled Heat Exchanger?
Is it possible to have the air at temperatures greater than 100°C when leaving the exchanger?
Thanks for the answers...!


G

 

[speco]

Dear Peregrino7,

The answer is clearly yes and no.

The yes part: The outlet air temperature can never be higher than the process inlet temperature. If you are designing a cooler, there are some practical limitations as well. Induced draft fans don't work as well in an extremely hot air stream. (Forced draft is definitely better in such a case). Also, the closer the air outlet temperature is to the process inlet temperature, the lower the LMTD. This is usually sorted out when desiging based on the economics of the cooler. Typically, the air outlet temperature is somewhere about the middle of the temperature range of the process fluid.

The no part: As long as the process temperatures are hot enough, and the heat transfer coefficient is high enough, the outlet air temperature can be as high as it needs to be, within the limitations mentioned above. For example, if you have a cooler for a hot heat transfer oil at, say, 250 deg C with a short cooling range, the air outlet temperature could easily be well above 100 deg C. In such cases it would be a good idea to keep the cooler well clear of personnel, however.

Regards,

Speco (

http://www.stoneprocess.com)

 

[rmw]

Normally the outlet air temperature is only limited by the metallurgical limitations of the cooler's materials of construction, usually dictated by the hot side.

I've seen 600°F easily reached on Combustion Air Preheaters, but I have also seen processes (in this forum) where the same type APH was unsuitable because the flue gas was too hot for any reasonably priced metal to handle.

rmw