Safe touch temperatures for hot plates

A finite difference heat transfer model has been developed to predict the S afe Touch Temperatures (STT) for plates made of different materials. SST ca rt be defined as the highest temperature at which no pain is felt when the surface is touched for a long enough period to allow safe handling of the e quipment. The criterion used to quantify damage is the ''damage function'' that was originally proposed by Henriques and Moritz. There are several unc ertainties present in the physiological and thermal properties of the skin that give rise to a solution range rather than a single solution. Certain s implifying assumptions are made that tend to yield solutions for STT that a re toward the lower or ''safe" end of the solution range. The model develop ed is a two-dimensional axisymmetric model in cylindrical coordinates. A fi nite difference scheme that uses the Alternating Direction Implicit method is used to solve the problem. It is a second-order scheme in both space and time domains. A parametric analysis of the model is performed to isolate t hose factors that affect the STT to the greatest extent. Data are presented for a variety of cases, which cover commonly observed ranges in material a nd geometric properties. It is found that the material properties, namely t hermal conductivity and volumetric heat capacity, and the plate thickness r atio are the three most important parameters. These three parameters accoun t for a range of STT from 56 degrees C-100 degrees C with thick metals at t he low end and thin metals and plastics in the high range. This method repr esents a significant improvement over existing standard practices.