Water cooling HE

[_evg]

Dear all,

I need your help.

I want to estimate what would be the surface reduction if replace air-fin coolers for water-cooled HE in gas cooling operation.

What are the key parameneter I shall to take into account? Is there any rules of thumb for such estimate?

Thanks!

Evgeny

 

[srfish]

The key parameter is the required outlet temperature of the gas. As that design temperature approaches the inlet air temperature of the air cooler, the cost increases considerably.

 

[LittleInch]

Is there ROT - not that I know of.

Too many variables - incoming gas temp, outgoing gas temp, ambient air temp, incoming water temp, outgoing water temp.

Not sure what you're after. Surface area of water HE will be lower, but size of HX is different as the water needs to be contained.

Very vague question so vague answer.

Be more specific and we might get somewhere...

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[EdStainless]

Do some research, often people us air for initial cooling and then to get lower temps follow with water HEX.
You need to look at flows and temps, both the gas temps as well as the air and water temps.

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P.E. Metallurgy, Plymouth Tube

 

[Tothesky]

Normally, Water Cooling need smaller heat transfer area than Air Cooling.
The Heat Transfer Coefficient of Air is smaller than that of Water.

Best Regards,
Moon

 

[_evg]

Thanks all

we sized air-cooled heat exchanger for gas cooling in arctic climate where temperatures are in range -25 - + 25 C. It gave quite efficient cooling with T approach around 10-12 C.
However I believe that applying cold sea water via closed water loop can improve the area and reduce size of HE.

What I would like to know for the moment is after assuming all Tin and Tout are same for gas and cooling media, how much you can improve the area for water cooling HE compared with air-cooled? T approach for water HE will be lower as well right?

 

[georgeverghese]

Also check for the operating risk of gas hydrates / freezing of high mol wt fraction at -25degC at low gas flow conditions on air cooler tubeside.
If you must use air, then warm air recirculation - winterizing may be required to avoid gas hydrates or other solids.

 

[LittleInch]

Well go and crunch some numbers then. There are reasons why you do specific design and this in one of them.

your HX might reduce in size, but then you need a host of other pumps, pipes, special material (warmish oxygenated seawater eats most materials other than expensive ones), scaling, fouling etc are all process dependant.

How much it can be reduced by is affected by flow rate of air and water - very difficult to compare the two.

Not sure what you meant by T approach - do you mean delta T?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[srfish]

LittleInch mentions the requirement of special material required for the HX. Carbon steel is not good for sea water service. The best alloy is 90/10 copper-nickel. Stainless steels are seldom used.

 

[gruntguru]

Don't forget, the surface area required on the gas side of you HX will not reduce.

je suis charlie

 

[EdStainless]

srfish (Chemical)
6 Oct 16 15:03
LittleInch mentions the requirement of special material required for the HX. Carbon steel is not good for sea water service. The best alloy is 90/10 copper-nickel. Stainless steels are seldom used.

High alloy stainless grades (super-ferritic, super-austenitic, asnd super-duplex) are commonly used in seawater HX, along with Ti gr2. People only use 90/10 when they have no concern about erosion (requires low flow velocities) and they don't mind Cu in the discharge water.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube