High pressure fan

[snow_man]

Hi All I need some advice I have a chilled water coil with a high pressure fan after the coil the air off the coil is 5 degrees C and after the fan is 15 degrees C is there any way I can lower the air temp without lowering my water temp .Thanks

[NoNickName]

Basically you are telling us the fan is warming the air by 10K? If I understand correctly, then the fan is running too hot!
This is a common problem for fans with low slip (high torque)... you probably need a fan with a different number of poles and high slip.

[lana]

Hi snow-man,

For 1kPa total fan pressure , there will be 1.2°C temp. rise for the air which passes through.
What you have seems that the motor is too hot. Is the motor inside the AHU?
10°C is too :eek: much.
Cheers:)

[snow_man]

The motor is on the outside ,so no motor heat is gained by the air ,Thanks

[NoNickName]

So, how the air is warmed up? The off coil condition is 5°C, then the temperature after the fan is 15°C.
Where is the heat gained from? :confused:

[lana]

Hi snow-man,
Please tell us what is between the cooling coil and the fan?
Is there any crackage in the AHU body?
Cheers

[Brian_UK]

Is there any airflow through the system?

It almost sounds as though the fan is just generating heat within its' own scroll without moving much air.

[autt]

The fan is the high pressure type, that's the problem.

If back pressure must be higher, there is no way to lower down fan outlet temp, except if you can change a more efficient fan.

So try to see if the back pressure can be lowered down or to decrease unit pressure drop.

[NoNickName]

Sorry, I give up. I don't see the problem here. I don't even see how a high pressure fan can increase temperature by 10°c

[Ravi]

Brian hit the nail on the head. The fan may be running near the dead head condition and that is why air gets heated up to 10C. Try to open the outlet damper a bit and check.

[autt]

For some application, as our ground a/c cart for airplane, the supply air pressure usually more than 3kPa, some fighter planes even need 45kPa, so the a/c has to use high pressure centrifugal fan, temperature through the fan rises very much depends on it back pressure, even more than 30 degC @40~50kPa.