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Air Handling Unit Test - Air Heating Problem

  1. Aug 14, 2009 #1
    We are testing an Air Handling Unit, we need to raise the internal temperature by 30 degrees to pass the test, but cannot exceed an energy input of 500W.

    It is a completely sealed unit.

    We have four fans constantly running, consuming 384W. Firstly, how can I work out what temperature they will raise the unit to? The fan manufacturer says that all energy input becomes heat (due to it being a closed system, but please lets not debate this, just accept it for the purpose of this question and use the full 384W).

    Secondly (if part 1 doesn't raise the temperature by 30 degrees), what size heater would we need to achieve the increase?

    Box Dimensions: 1.2x1.2x3.0m
    Fan Input: 384W
    Must not exceed: 500W (but I would like some answers even if they do exceed it to show me what we would need to do to achieve the required temperature increase)

    Also, is there a way to work out how many Watts are required to raise the temperature of air by 1 degree celsius in one hour?
  2. jcsd
  3. Aug 14, 2009 #2


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    Staff: Mentor

    Nothing to debate - it's true!
    Air volume times specific heat times power = temperature rise.
  4. Aug 15, 2009 #3
    I know it's true, but I put that because with someone in work who didn't understand it I had to spend an hour explaining the concept to him and didn't fancy having to go through the same thing again.

    Thank you for this.
  5. Aug 15, 2009 #4
    Hi, that gives me 4.23cubic metres of air, specific heat of 1.005kg/kg K and a power of 384W. Which is over 1600 when multiplied together, which is one hell of a temperature rise.

    Is the formula correct or am I making a mistake somewhere?
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