[TRNSYS-users] SDHW template Tin and Useful energy gain- strange behaviour

[Philip Horn]

Hi All,

I played around a little bit with different efficiency equations for the collector, and wanted to compare the results.
Therefore I used the SDHW template (with TYPE1 as collector), which uses the outlet of the Tank as inlet temp to the collector.
I erased this connection and set the inlet temp to a fixed 10 deg but in fact is it still varying when I plot it (from 10-13deg).
How come? 

Another thing that I experienced: when I used the system in the normal mode (Tout tank connected to Tin collector), the useful energy gain of the collector is higher than with a fixed (and in average 10 deg K lower) input temperature.

Shouldn't it be the opposite?
As Q=m*cp*(Tout-Tin) , the smaller Tin, the higher Quse (assuming that Tout is not that heavily affected)?

Clarification highly appreciated!!

Best,
Philip