Mathematical modelling for the condenser method of trans-epidermal water loss measurements

The condenser method with a closed chamber is a novel technology for measuring water vapour flux density, especially for trans-epidermal water loss (TEWL). Although it is originally designed for skin measurements, it can be used for many other materials, such as thin-film polymers, textile, fruit and food, building material, etc. By measuring the water vapour flux density that comes out of the material, we can understand the drying process, permeability and integrity of the material. In this paper, we model the temperature and humidity distribution within the measurement chamber, in order to have a better understanding on issues such as: the optimum position of relative humidity (RH) sensor and temperature sensor within the measurement chamber, the effect of condenser on sample surface temperature, the effect of air diffusivity, and the dynamic distributions of humidity and temperature within the measurement chamber during measurements.