I have body in 55C air which, when I load it with a solar load, the global convective heat transfer rate is ~20W, which is expected based on the side of the object. When I turn off the solar load and add an 80W heat generator to the body, the global convective heat transfer rate is the expected 80W. When I combine both the 80W heat generator and the solar load the global convective heat transfer rate is 60W instead of the expected 100W. The body is also somewhat cooler than when loaded with only a 80W load and no solar load.
Any ideas what might be happening? The model body has a surface emissivity of 0.92 and an absorbtivity of 0.2. The solar load is set to Denver at noon. The ambient air is 55C and the body temperatures are in the 80C range when loaded.