Experimental Evaluation of Microclimate Cooling Garments Under Controlled Ambient Conditions

A testing chamber was designed to evaluate the performance of microclimate cooling systems, which are used to extend human performance duration in heat stress environments by flowing fluids through flexible tubing in a conforming garment, carrying excess heat away from the wearer. The flexible experimental system accommodates changes in materials and garment design. In this study, one side of a chamber was able to output heat at a rate equivalent with that of human; a second, opposed chamber controls ambient conditions experienced by the garment. Temperature changes in both the interior and exterior sides of the chamber were measured. The cooling garment was tested at different conditions, transient and non-transient styles, with and without flowing fluid, and at various wattage densities (367.3 W/m2 and 576.8 W/m2). The designed testing chamber was validated for proper functionality. It was observed that, having a flowing fluid through the garment was more effective at higher body temperatures (∼45 °C) carrying away the excess amount of heat from the body.

Viability of Spray Cooling an Air-Cooled Condenser in a Personnel Microclimate Cooling System

Attaining a reasonable size and weight for a personnel microclimate cooling system for an individual person who operates away from logistical support remains a problem. This work analyzes whether spray cooling the ambient air before it cools the condenser in a small vapor compression cycle is worthwhile in terms of battery weight savings. The analysis specifies essential characteristics of each of the main components of an ideal vapor compression cycle in order to determine equations describing their expected performance. Then, a mathematical technique is used to find balance points for the model system at different ambient air temperatures. The balance points show the decrease in condensing temperature and compressor work that result from a decrease in ambient air temperature. The saved compressor work is converted to battery weight savings and compared to the weight of water required to reduce the air temperature. It is found that the potential battery weight savings do not offset the amount of cooling water required, i.e., spray cooling the air-cooled condenser should not be pursued to decrease system weight.