K-value estimation on refrigerated vehicles by thermographic analysis

IR thermography is joined to a simplified thermal model for evaluating thermal performance of insulated containers. The method is illustrated with experimental results obtained into a test tunnel working under controlled environmental conditions. Insulated vehicles are tested in parallel according to the accepted standard "Agreement on the international carriage of perishable foodstuff" (ATP) and the thermographic method. A thermographic apparatus is used to map the temperature of the external walls of the insulated box. Defective zones are identified and the local heat flux mapped basing on a heat flux meter measurement in a reference point and on the thermographic temperature maps. The proposed thermographic method allows also determining thermal bridges magnitude and air leakages location. These results are important in order to enhance manufacture. Some experimental data are presented in order to compare K-values measured along ATP rules and calculated by the thermographic inspection. The comparison allows verifying the accuracy. Such a quality test is particularly useful for periodic control of insulation ageing.