Heat Emission from Centrifugal Compressor and Dryer

[mistershark]

Hi men, i'm italian and i'm new on this forum.

I must make a technical report for a cooling system for conditioning a room where work 3 centrifugal compressor (oil free with removable slide-in-and-out intercooler and aftercooler) and 2 dryers with this technical specifications:

Compressor (data only for a machine):
Shaft power at coupling (guaranteed point): 447kW
Driver Rating: 550kW
inlet pressure: 1 bar(A)
outlet pressure: 6 bar(A)
capacity: 80.5 Sm3/min

Dryer (data only for a machine):
Compressed air flow rate: 4830 Nm³/h
Working pressure: 6,15 bar g
Dryer air inlet temperature / outlet temperature: 45/38,4 °C
Moisture flow rate: 47,97 kg/h
Absorbed power by the refrigerating compressor:
19,36 kW

i need to calculate the heat emission of this package of machines. i think the most emission is from the surface of electric compressor motor, and that it is a moltiplication of the active electric power per the efficiency (0,8-0,9 for electric motors). And if the electric motor in the room is covered (like the joined image) what is its heat emission?
And for the entier dryer?

thanks in advance

 

[marcoh]

Maybe take a different approach and calculate the theoretical power required to compress the air assuming 100% efficiency. The difference between this and the actual input power needs to go somewhere and most would be emitted as heat in the plant room somewhere?

 

[mistershark]

>ZNew Postmarcoh (Mechanical)
28 May 09 7:29
Maybe take a different approach and calculate the theoretical power required to compress the air assuming 100% efficiency. The difference between this and the actual input power needs to go somewhere and most would be emitted as heat in the plant room somewhere?

i don't understand very well what you ask me, but my scope is to calculate the heat load, in terms of quantity of heat generate from the compressor and dryer when they work.
After I want provide an air conditioning system to wipe out this quantity in the control volume of a compressor room.

 

[Zesti]

You mentioned an "intercooler and aftercooler": where does that heat go?

Why not consult the manufacturer, they should be able to help you.

They should also be able to tell you what the maximum operating temperature (environment) for the equipment is.
This temperature will also influence your cooling design.

For instance, if your highest possible outside air temperature is 35°C and the compressor will run in 45°C then you still have 10 degrees for cooling without using mechanical cooling equipment. Just ventilating the room with enough outside air will do the job.

 

[mistershark]

@ZESTI
thanks for the answer. I speak with the compressor supplier and he say that the 95% of energy supplied to the electrical motor of the machine is lost by heat load.
About "intercooler and aftercooler", they work in for the compression process and they are covered plate heat exchanger.

Can you provide me any kind of suggestions about my original question?

thanks in advance

 

[Zesti]

"I speak with the compressor supplier and he say that the 95% of energy supplied to the electrical motor of the machine is lost by heat load."

Well, in the end, 100% will be turned into heat.
The question is, how much is generated at the compressor and will therefore add to the heatload of the room.
If the supplier says it is 95% then you have your answer.
(This would mean only 5% of the energy leaves the room in the form of compressed air. Compressed air is expensive...)

"About "intercooler and aftercooler", they work in for the compression process and they are covered plate heat exchanger."

Are these watercooled and is the hot water cooled somewhere else, outside the room?

"Can you provide me any kind of suggestions about my original question?"

Your total cooling load would be close to 500kW, right?

That's around 150000 m3/h (!) of outside air at a 10K temperature difference (The 35°C to 45°C I mentioned before, check your local highest posible temperature and the maximum allowed temperature in the room)

Can't you just put the compressor outside, maybe under just a roof to shield it from rain?

I think mechanical cooling would be such a waste of energy and should only be a last resort.
(Maybe a coolingtower could be a solution.)

 

[mistershark]

"Are these watercooled and is the hot water cooled somewhere else, outside the room?"

the water pipes both inlet and outlet (hot water) incoming the compressor from outside the room. But I don't know any kind of traitment expected to it

"Can't you just put the compressor outside, maybe under just a roof to shield it from rain?"

No they are expected a closed room

So mr. Zesti

we have arranged with the client a volumetric air flow rate oh 84 FAD

so, I must arrange a value of heat emitted from the surface motor compressor of 500 kW
and for the dryer? what is the heat changed with the air in compressor room of the dryer condenser?

 

[Zesti]

"the water pipes both inlet and outlet (hot water) incoming the compressor from outside the room. But I don't know any kind of traitment expected to it"

Sounds to me like this is some form of cooling for compressor and/or the compressed air.
This water is taking heat outside the room. This is part of your 500kW heat load. The heat load inside the room is therefore less than 500kW

Again, ask with the supplier of the compressor.

"we have arranged with the client a volumetric air flow rate oh 84 FAD"

'84 FAD' , I do not understand...

"and for the dryer? what is the heat changed with the air in compressor room of the dryer condenser?"

Ask the supplier/manufacturer.

 

[mistershark]

For your information

FAD means Free Air Delivery that is the amount of atmospheric Air (free air) that can be sucked by the compressor at inlet conditions (suction side)
at these reference conditions:

1 atm (atmospheric pressure)
20°C/15°C (atmospheric temperature)
0% (R.U.)
the motor RPM at 100% of its rated value

as you can see at this link below

http://www.forbesmarshall-inc.com/Controller/Subproducts/Binaries/km_Compressed Air Meter1.pdf