[TRNSYS-users] QUA and Qheat in a cube

Joana Margarida Vieira Batista joana.batista at tecnico.ulisboa.pt
Tue Jun 24 07:40:11 PDT 2014

Dear Trnsys users,

I have a cubic building with 64 m^3. The cube doesn't have any incident 
radiation, and its walls are only made of concrete (without windows and 
doors). The temperature outside the cube was set to 10 ºC. The cube 
doesn't have occupation, ventilation or infiltration. The only thing 
inside the cube is a radiator with constant value 3000 kJ/hr with no 
radiative part.
I tried to use the internal calculation for the convective heat 
transfer coefficient, calculated with the constants given in 
"properties" of trnbuild. I defined as output Qheat (that gives me 2999 
kJ/hr), QUA=UAdT (static UA transmission loss of the zone, that gives me 
5600 kJ/hr) and also Qcsurf (total convection to air from all surfaces 
within zone, that gives me 2600 kJ/hr).
Shouldn't the values be similar?
Is there anything else I should take into consideration?
If I look to the parameters for internal calculation of heat transfer 
coefficients I have a constant in kJ/(m^2K) and an exponential. The heat 
transfer coefficient is given by "constant*(∆T)exp", so how does trnsys 
get units in (W/m^2K) with this expression?

Thanks in advance,

Joana Batista

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