California Institute for Energy and Environment (CIEE)

A thermal analysis was conducted on a typical 5-ton rooftop air-conditioner to determine the effects on the supply air temperature and cooling performance by adding a highly reflective coating material to its external surfaces. The analysis considered several emissivity values. Under typical conditions, low emissivity (highly reflective) surfaces produced a reduction in the supply air temperature of 0.21°F when compared to high emissivity (low reflectivity) surfaces. In addition, the mixed air temperature was reduced by 0.07°F when a low emissivity (ε = 0.2) surface was considered. The result of this reduced mixed air temperature is a lower coil-entering air temperature, which, in turn, produced an increase of 0.29 percent in the cooling capacity of the unit. B