Better thermoregulation of brain temperature using phase change material-mediated head cooling system

Abstract

Regulation of the brain temperature is critical for managing heat stress related adverse events. It can be achieved by external cooling of the head. Head cooling systems that are lightweight, portable, and suitable for active work scenarios such as firefighting, mining, and construction work are currently unavailable in the market. This study proposes a novel active head cooling system that a) uses phase change material for thermal storage and b) can be designed for portability. The closed-loop bench-top system consists of two heat exchangers: a water cooled heat exchanger with an attached heater, mimicking heat generated from the head, and a helical tube heat exchanger surrounded with ice as heat sink. These heat exchanges are interconnected by tubing for water circulation. The system performance is assessed by cooling duration that depends on mass of ice used and heat transfer rate. The system was evaluated for different a) heat loads varying from rest to exercise conditions (20 W – 40 W) and b) flowrates (0.25 l/min – 0.65 l/min). The results show that the system can handle heat generation rate of 40 W from the head for 100 min (for the flowrate of 0.25 l/min), which is about 3 times the safe duration of firefighting drills. The cooling time increases linearly with decreasing heat load: 138 min for 30 W and 190 min for 20 W, an increase of 38% and 90%, respectively. It also increases with decreasing flowrate. The range of Nusselt number for helical coil flow is about 4.4 – 6.8 times higher when compared to that of a straight pipe flow. The helical design of heat exchanger led to enhanced heat transfer owing to the formation of Dean's vortical flow. The results suggest that the head cooling system, having possible features of being portable, cost-effective, light weight, and easy to use, can assist in the thermoregulation of brain temperature for workers during elevated thermal stress conditions.