[TRNSYS-users] Problem with the outlet collector temperature in static mode (type 540)

[ANTOINE FREIN <antoine.frein@gmail.com>]

Dear all,

I am using TRNSYS Version 16.01.0003 with TESS libs 2.0 with the simulation studio.

In my project I am using a solar collector area of 165m2 for my solar heat plant. The condition to start the pump of my primary circuit is depending on the outlet temperature of my collector. 

My problem is that I am using a large solar collector area and the calculation of outlet temperature in the static mode with the type 1a is not correct (because increases of 40 degrees in summer after one time step 1min20sec).

I changed the type of the collector and used the type 540 from the TESS library where the capacitance of the collector is a parameter. But now my problem is that I don't understand how this parameter is used. In fact in my case I have of solar collector array of 38 panels of 4.3m2 each one.

The capacitance of one collector is: 14 kJ/K (solar collector without fluid) + 17 kJ/K (4.5L of water/glycol) = 31 kJ/K for one solar collector. Thus I multiplied this value by the number of collectors, 38, and I get 1147kJ/K.

I implemented this value and the outlet temperature of the collector obtained is not correct (for instance :T_coll_outlet increases of only 2°C (from 33° to 35°C), with a radiation of approx 600W/m2, during 3 hours).

Did anybody come along the same problem and knows advice? Did you know if the detailed mathematical description of the type 540 is finished?

Thanks for any help



Antoine Frein
Politecnico di Milano