Surface Differential Scanning Calorimeter for Evaluation of Evaporative Cooling Efficiency

We developed a Surface Differential Scanning Calorimeter for the quantitative analyses of thermodynamic and heat transfer properties of thin fibrous and porous samples. It has been demonstrated that the calorimeter is capable of measuring cooling power as well as temperature decrease in a reliable and reproducible way. Considering its low cost the equipment can be a valuable option for studying cooling/heating systems in laboratory settings. INTRODUCTION Materials for protective clothing have a high fiber density that significantly decreases their permeability. A reduction of the material’s permeability results in a dramatic decrease of the natural efficiency of evaporative cooling of the human body and, in many cases, it leads to thermal stresses [1, 2]. Design of materials with an efficient heat transport characteristics requires a reliable instrument that would be able to evaluate the materials performance at different environmental conditions. Quantitative analysis of thermodynamic and heat transfer properties of thin fibrous and porous materials is a challenging task. In this paper, we demonstrate an instrument that allows one to evaluate the heat transfer properties of different fabrics. There are three major approaches to measure the fabric performance. The first method is based on the analysis of physiological data (skin temperature, heart rate, etc.) during various types of physical activities performed by humans. The majority of all available published papers on the subject of cooling utilize this method [3-9]. The second approach is evaluation of the system using a guarded sweating hot plate [10]. It is designed to determine the thermal and evaporative resistance of materials producing numerical values for both temperature and power gains in cooling systems. While this approach delivers reliable results, the high cost of the plate does not allow its widespread utilization in laboratory conditions. The third approach uses a thermal manikin and can be described as an advantageous combination of the former two approaches, with both temperature and heat values accessible [11-14]. However the apparent attractiveness of the last approach is diminished by the high expenses associated with the purchasing of the manikin. The goal of the presented studies has been to develop an inexpensive, reliable method for testing evaporative cooling systems in laboratory conditions. FIGURE 1. Schematic representation of the major components of the SDSC.