you might look at my lecture. you can calculate the temperature by using the equations in the slides

Please try to check the following papers:

http://www.sci.sdsu.edu/SOCOL/FortranJournalArt.doc

http://www.powerfromthesun.net/Book/chapter05/chapter05.html

http://elth.ucv.ro/fisiere/anale/2006/4_22.pdf

http://www.iitj.ac.in/CSP/material/scan0001.pdf

* You didn't mention which type of solar collector in your question?

you might look at my lecture. you can calculate the temperature by using the equations in the slides

Thanks a lot! I will take a look inside the papers and slides. I will give you feedback.

*I want to use the equation for flat plate collectors and evacuated tube collectors...

you can use utilizability equations to estimate the temperature of solar collector.

kindly do through " solar engineering of thermal processes": Duffie and Beckman - utilizabity of flat plate solar collector. 

you may get some idea regrading  what are the controlling variable in a solar collector and ways to maximize the performance of solar collector.