Heat Rejection

[jeebusmn]

Hi,

I am trying to do heat rejection calculations for a few buildings on an ethanol plant that is being started up. I am supposed to just take the light and motor starters into account to calculate the heat rejection. Is there a standard for this and where can I find it? I was told to look through IEEE 141 and could not find anything on this.

Doug

 

[dpc]

You might search this forum - seems like there was a thread on this not too long ago.

As far as indoor lighting - every watt will end up as heat.

For motor starters, I know I posted this information here within the last couple of years. Or see MCC technical data from major vendors.

For motors, start with basic motor efficiency to determine heat rejected directly by the motor. Then add in pump/fan losses, then piping heat/friction losses.

What is the purpose of the calculation, exactly?

 

[jeebusmn]

The purpose is to be able to determine how much air condition will be required.

I have been digging through these forums and from what I have found it seems like people just assume that 10% of the power the motor consumes turns into heat. Is this how it is usually calculated?

 

[dpc]

thread238-29865

Link above is to an old thread with some typical data.

10% loss in a motor is a reasonable,conservative approximation for what you are doing, but my point was that there are many other sources of heat loss in addition to motors.

 

[nbucska]

Isn't fermentation an exothermal process, too?

If the liquid stays in the building 100 % of the pumps
energy input stays there, too.



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