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

[xj25]

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

 

[prex]

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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