Efficiency of liquid cooling garments: prediction and manikin measurement.

INTRODUCTION

We studied the efficiency of liquid cooling garments (LCG) and their relationship to the insulation of outer clothing, perfusate inlet temperatures, and environmental conditions by both theoretical analysis and thermal manikin (TM) testing.

METHODS

An equation to estimate LCG cooling efficiency was developed on the basis of energy balance. Cooling efficiency is a function of the thermal resistance between the TM skin and perfusate in the LCG, the thermal resistance between the environment and the perfusate, and TM skin, ambient, and perfusate temperatures. Three ensembles, a cooling vest (CV) only, CV plus a battle dress uniform (CVB), and CVB plus a battle dress overgarment (CVO), were tested on a sweating TM in dry and wet conditions. The TM surface temperature was maintained at 33 degrees C and the environment was 30 degrees C and 50% RH. The LCG heat removal from the TM was calculated using the power inputs to the TM with and without perfusate flow.

RESULTS

The cooling efficiency was increased from approximately 0.45 for CV to approximately 0.70 for CVO in dry experiments and from approximately 0.53 for CV to 0.78 for CVO in wet experiments.

CONCLUSION

With additional outer clothing layers, higher thermal resistances increased the rate of heat removal from the TM surface, and decreased heat gain from the ambient environment, thus increasing efficiency. The perfusate inlet temperature had minimal influence on the efficiency. The equations developed can predict cooling efficiency and heat removal rates under a wider range of environmental conditions.