Unexpected Negative Conduction on Hot Day

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SOLVED:

The unexpected results were due to the significant impact of radiation on heat transfer within the space. In the Surface Heat Balance equation: Surface Conduction to Exterior = Surface Received Radiation – Convection to Zone Air, the result turned negative because the incoming radiation exceeded the convective heat transfer to the zone air.

Notes:

• This was confirmed by reducing the solar absorptance and thermal absorptance of the interior material to near zero, which minimized the effect of radiation.
• It was also observed that as the windows of the space begin to receive sunlight, surface conduction progressively decreases. This confirms that increased radiation reduces conduction—potentially enough to make it negative.
• To better understand the phenomenon, the following outputs were compared: Surface Inside Face Conduction, Surface Outside Face Conduction, and Surface Heat Storage.
• An image showing the comparison and supporting the explanation is attached.