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Overall heat tr. coef. from measurements, "quick" procedure with mistereous factor

Overall heat tr. coef. from measurements, "quick" procedure with mistereous factor

Overall heat tr. coef. from measurements, "quick" procedure with mistereous factor

(OP)
Hi,

I found this russian norm extract where a "quick" procedure for overall heat transfer coeficient (K in the document) stimation in heated cabins is given.

Basically it says:
- set up some kW of heaters, and internal and external T sensors.
- let wait about 1.5-2h to reach what it calls "regular heating mode of the 2th kind", this time is called th
- then take mean Tª jump (internal-external) for these times:
time = th,
dTh
time = th + t1,
dT1, t1 about 30 minutes
time = th + t2 (where t2 = 2t1),
dT2
Total test time about 3,5 hours.

-then with the power, and effective cabin area F it says:
K = (Q/F) (2dT1 - dT2 - dTH) / (dT1^2 - dT2 - dTH)

Anybody have an idea about from where it comes that strange Temp factor?.
Probably I miss something because I would just use the last time.
K = (Q/F) (1/dT2)

Regards

RE: Overall heat tr. coef. from measurements, "quick" procedure with mistereous factor

Factor (dT1^2 - dT2 - dTH) is not dimensionally consistent, so it is difficult to judge, seems quite wrong to me.

prex
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