I have designed the parabolic surface using the parabola tool and place a copper tube at its focal point. Now in flowsimulation, I have set the solar radiation in general settings and inlet flow rate/outlet pressure as boundary conditions. I have also set the parabolic surface to be symmetrc in radiative surfaces. When I run it, the temperature of the liquid has barely changed, the problem is that, the sun rays are not being reflected by the parabolic surface or not being absorbed by the copper pipe. What am I missing?