Head Evaporative Cooling From Forced and Natural Convection for Two Helmet-Pad Configurations

Computational simulations of the flow generated about a standing warfighter without a helmet and with two helmet pad arrangements are presented to determine the potential for delivering better thermal performance through passive design considerations. Cases considered include buoyancy-driven natural convection and wind-driven forced convection. The transport generated by each combination of geometry and flow conditions is assessed to determine each design’s efficiency in facilitating evaporative cooling via perspiration from the head. As anticipated, forced convection generates higher evaporative cooling rates than natural convection, averaging approximately 50% more cooling for the cases studied here. Helmet configuration had a greater impact on vapor transport away from the head during forced convection in the cases studied. Comparative metrics for assessing the relative effectiveness of a helmet design to facilitate cooling can be quantified based on these simulations, but more extensive exploration for the parameter space including wind direction for the forced convection scenarios would produce more insight into the relative benefits of particular designs. The results suggest that operationally-significant passive cooling could be achieved under conditions seen in theater, and that design and configuration decisions impact the evaporative cooling delivered and are therefore viable targets for optimization.