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Thread: How do you correctly calculate the heath transfer load?

  1. #1
    Associate Engineer
    Join Date
    Feb 2020
    Posts
    1

    How do you correctly calculate the heath transfer load?

    I'm trying to determine the heat transfer load of a sealed cabinet I'm a bit confused about the formula that is apparently used for it. I would appreciate some help. The formula is:
    (q = (To - Ti ) ÷ [(1/ho ) + (1/hi ) + R] x 5.67
    Definition of Variables— q = Heat transfer load per unit of surface area To = Maximum ambient temperature outside the enclosure Ti = Maximum rated temperature of the electrical components ho = Convective heat transfer coefficient outside the cabinet Still air: h = 1.6 Relatively calm day: h = 2.5 Windy day (approx. 15 mph): h = 6.0 hi = Convective heat transfer coefficient inside the cabinet Still air: h = 1.6 Moderate air movement: h = 2.0 Blower (approx. 8 ft.3/sec.): h = 3.0 R = Value of insulation lining the interior of the enclosure walls No insulation: R = 0.0 1/2 in. or 12 mm: R = 2.0 1 in. or 25 mm: R = 4.0 1-1/2 in. or 38 mm: R = 6.0 2 in. or 51 mm: R = 8.0

  2. #2
    Lead Engineer
    Join Date
    Aug 2013
    Location
    Houston TX USA
    Posts
    421
    The formula seems very straightforward, so what about it confuses you?

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