Howdy all, I am developing a high altitude weather balloon project and I am thinking of using HDPE as a lens material for THz optics. I need to know the total heat transfer on the sheet of HDPE to see if it will reach critical temperatures. Since I am only looking for critical temperatures I can take an upper maximum on the heat transfer. To do this I am using the solar constant=1360W/m^2. However my results are crazy. The question is, how do I determine the heat transfer due to solar radiation on my material?