Florian,
i have a problem with my temperatures of the collector output side.I changed my efficency values to (0,55 / 0,007128 / 0,0000324), and the result is ,that the output temperature is rising at some timesteps to endless values. The values ,i used before (0,34 / 1,39 / 0,128) ,were worser and the simulation works good.The values will sound undersized, but they are right.
If you are referring to the intercept efficiency an the first and second order loss coefficients of a solar collector, yes, your values look strange to me. I am assuming you use W (although TRNSYS needs those parameters in kJ/h) so your first order loss coefficient would be 0.007128 W/m²-K. This means that your collector efficiency is virtually constant. Usual values of the first-order loss coefficient are between 1 and 2 for evacuated tube collectors, between 3 and 5 for flat-plate collectors and "around 15" (wind-dependent) for unglazed collectors.
With your values, the stagnation temperature of your collector is something like 4000°C. The other values you mention are also unusual to me but they give a more realistic stagnation temperature, which probably explains why TRNSYS likes them better.
I hope this helps, Michaël Kummert -- _________________________________________________________ Michaël Kummert Solar Energy Laboratory - University of Wisconsin-Madison 1303 Engr Res Bldg, 1500 Engineering Drive Madison, WI 53706 Tel: +1 (608) 263-1589 Fax: +1 (608) 262-8464 E-mail: kummert@engr.wisc.edu SEL Web Site: http://sel.me.wisc.edu TRNSYS Web Site: http://sel.me.wisc.edu/trnsys