Investigation of “Thermal Touch” Response of Coated Steel Plates Employing Square-Wave-Excited Photothermal Infrared Radiometry

When a person is touching an object, which is at a different temperature than the person’s body, heat starts to flow from the body to the object (or in the other direction), and as a result, the temperature of the skin starts to decrease (increase), leading to a cold (warm) perception of the object’s temperature. It is well accepted that the degree of thermal impact of touching the free surface of a bulk material is determined by the thermal effusivity of that material. In this study, the more complicated situation of touching a coating covering a substrate with different thermal properties is studied. Insight in the involved heat transport effects and their effect on the thermal touch is gained by a photothermal model experiment in which the effect of touching on the measured surface temperature, and from there, the calculated heat flux is mimicked by the effect of illumination by laser light.