Air compressor room exhaust

[checonbill]

I have a compressor room with a 150 hp air compressor that I need to ventilate the compressor is air cooled The room is 15 x 18 x 12 what cfm fan do I need and what is the best way to bring air in with an intake fan or just intake louvers

Thanks

 

[imok2]

Rule of thumb is 2CFM/brake HP

 

[imok2]

Rule of thumb is 2CFM/brake HP and I would use mechanical ventilation

 

[BronYrAur]

2 cfm/bhp sounds way too low. that would only be 300 cfm. I have some info on this in the office and will respond to your other thread tomorrow.

 

[imok2]

Like I said that was a rule of thumb for a mechanical room maybe this is a better estimate:
If a motor is 90% efficient then that means that 10% is heat so if 1 hp = 42 btu/min and there are 150 HP and it runs 50% of the time wouldn’t that come out to 150 HP x 42 btu/HP x 0.10 (heat) x 0.50 (time) = 315 btu/min/hp, so CFM = 315 btu/min/1.08 x 45*F(DT) = ~6.5 cfm/hp x 150hp = 985cfm
or say it another way 15’x15’x12’=2.700 cuft x 20 air changes/hr = 54000cuft/hr/60min = 900 cfm
or if 1 hp = 2545 btu/hp x 0.10( heat) x 0.50 (time) x 150 hp = 19817 btu/60 min = 318 btu/min, so it Q = cfm x 1.08 x DT then 318 btu/min/ 1.08 x 45*F again = 6.6 cfm/hp x 150 = 994 cfm
Lets call it 1000 CFM

 

[walkes]

I received a pie chart in 1998 from Atlas Copco Compressors indicating a heat balance for an air-cooled compressor based on %of shaft input power.
Heat from oil cooler: 80%
heat from air cooler: 13%
radiation from compressor element: 1%
radiation from air/oil vessel: 3%
electric motor losses: 10%

Total 107% of shaft input rejected as heat.

 

[BronYrAur]

In lieu of specific manufacturer data, here is what I have used.

1 HP = 746 Watts
Assume 80% efficiency, so each compressor HP = 933 Watts

Add 1/10 HP per compressor HP for dryers or 93 Watts

This totals 1,026 Watts per compressor HP or roughly 3,500 BTUH per compressor HP.

(CFM/HP) = (BTUH/HP)/1.08/Delta-T

Your Delta-T is your allowable or desirable room temperature minus the outside air temp. In other words, if you want to keep the room at 105, and your outside air is 95, then your Delta-T is 10.

Using 10 deg Delta-T, your required CFM/HP is 3,500/1.08/10, or 324 cfm/HP

With a 150HP compressor, you will need 48,600 CFM. This is obviously a truckload for such a small room.

 

[imok2]

BronYrAur
Heat Rejection for Common Industrial Machinery


Air Compressors ………………………1,500 Btu/hr per HP
Air Compressor Aftercooler…………..1,500 Btu/hr per HP
Vacuum Pump Cooling………………..1,500 Btu/hr per HP
Hydraulic Cooling………………………2,544 Btu/hr per HP x .6
Hot Runner……………………………..3,420 Btu/hr pr kW

If component heat loads cannot be learned from customer supplied data, multiply the total input Hp or kW times the appropriate conversion factor. This represents the maximum possible heat load. Thought you might find this interesting!

 

[imok2]

BronYrAur

Lets assume you have the air compressor and intecooler in this room that = 3000 btu/hr per hp x 150 hp = 450,000 btu/hr x 0.2(I2R Heat) x 0.5 (run time) = 45,000 btu/hr. So, If Q = cfm x 1.08 x DT(10*F) then 45,000 btu/hr/10*F = ~ 4,500 cfm
Actually the efficiency on a 150 HP motor should be about 92% or 8% heat and the run time is just a guesstimate at best.

 

[VEEKRISH]

150 HP, with both the motor and driven machine in the space would mean you are looking at about 420,000 BTUs oer hour. So even if we are looking at all outside air and want to mainatain a differential with outside of 20 deg F, then we will be looking at about 19,500 CFM. For a room of this size that translates to over 360 air change sper hour. I would suggest - use about 50 air changes - about 2700 CFM. Use a well designed hood to extract the heated air over and in the immediate vicinity of the Machine. Bring in outside air with a separate fan and pump into the surrounding area. This will ensure adequate heat pick up, while maintaining the surrounding areas at tolerable temperatures.