Comparison of contact cooling while touching cold surfaces with an artificial and human fingers

Abstract

Abstract An artificial finger (AF) was developed to determine the contact cooling rate induced by different cold surfaces. The purpose of this study was to compare the contact cooling rates of the artificial and human finger when touching cold surfaces. Aluminum, steel, nylon and wood blocks (95×95×95 mm) were used as contact materials. The temperatures of the materials were −40, −30, −20, −15, −10 and −4°C. The sensor of the artificial finger, simulating a finger pad, was designed and developed to measure the heat exchange of the contact interface when touching a cold surface. In the human experiments, 30 volunteers, 15 male and 15 female subjects, participated in the study. The contact temperature of the index finger was measured with a thermocouple (T-type, diameter 0.2 mm). Individual physical hand and finger characteristics were measured. For human measurements, the metal surfaces were tested only at temperatures of −15°C or higher. Cooling curves measured by the artificial finger followed a similar pattern to those measured by the human fingers when touching metal surfaces. When touching wood or nylon, the cooling curve of the artificial finger was significantly slower than that of the human fingers. Sex and hand/finger size partly explained the great variation in skin cooling rates between individuals. In conclusion, the present type of artificial finger could be used to assess contact cooling rates of cold materials with a very high thermal penetration coefficients (over 7200 J m −2 s −1/2 K −1 ) and at a surface temperature of below −4°C.