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BTU Formula for Hot Air

Jim Davis_3
Jim Davis_3 Member Posts: 578
in THE MAIN WALL
The formula for heating is CFM X Delta T X .98 = BTU

The 1.08 multiplier was for cooling and cooler air 45 -55 degrees.

Heating BTU's are for warmer air 120 -140 degrees. The correction or BTU factor for hot air is .98 - .99. Or to keep it simple CFM X Delta T is close enough and you don't need a calculator.

Comments

  • Gene_2
    Gene_2 Member Posts: 59
    BTU Formula for Hot Air

    I am looking for a Formula to figure out the BTU's from the cold air in, hot air out and the heat difference multiplied or divided(???) by the CFM's. Thanks for your help.
  • ken wickre_8
    ken wickre_8 Member Posts: 8


    Btu/Hr = (CFM)(.018)(60 min/hr)(Temperature difference). Plug in the known factors and solve for the unknown. .018 are the Btu's one cubic foot of air will absorb/give up at a one degree temperature difference. Hope this helps.
  • kal_2
    kal_2 Member Posts: 60
    you are both right...

    Remember with water we use “times 500” in the deltaT calcs – cause btu are in pounds per hour and we deliver it at gallons per minute so 60 minutes, times 8.33 pounds per gallon = 499

    Same here:

    we deliver it at feet per minute, so .018 per foot pet hour , times 60 minutes = 1.08
  • Gene_2
    Gene_2 Member Posts: 59
    OK, but...

    What is Delta T?
  • Dave_4
    Dave_4 Member Posts: 1,404
    shorthand for change in temp...

    of the heat transfer medium across the load - eg if air is supplied at 110 and returns at 90, then the delta-T is 20
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