In-field evaluation of the absorption coefficient of the external surface of the insulated box in a refrigerated vehicle

The ATP (Agreement Transport Perishables) is mainly focused on the insulated boxes of the refrigerated vehicles. Until now, in the design of these boxes, the heat flux due to the sun radiation has been neglected despite its importance. The heat flux is driven by the solar absorption coefficient of the outer surfaces of the boxes; recently a thermal approach for the quick evaluation of this parameter has been proposed. A small region of the external surface is varnished with a paint of known absorption coefficient, then the whole surface is subjected to a variation of illumination that leads to a temperature increase. If the thermal parameters are the same all over the panel, the comparison between the two temperature profiles gives the absorption coefficient value. In this paper a varnish is characterized and the thermal technique is applied on specimens and vehicles using different data acquisition systems.