Experimental and numerical investigation on composite phase change material (PCM) based heat exchanger for breathing air cooling

In the field of human survivability in elevated temperature situations such as firefighting, inhalation injuries cause a much higher mortality rate than skin burns. Conventional rescue respirators merely deal with the filtering of the toxics and smokes, while cooling left out of their consideration. This work aims to fill the gap. In this work, we propose a new scheme by utilizing the paraffin/expanded graphite composite materials to construct a heat exchanger. The material itself plays the mechanical support, the heat spreader and the heat absorber at the same time, which circumvents the use of multi-level designs. In the enclosure or semi-enclosure fire, the 500 K hot air flows through the heat exchanger and is cooled down to breathable temperature ( < 313 K). By normal human breath flux, this process can sustain for more than 20 min for personnel emergency escape. We also discussed the optimized conditions of material parameters and structural configurations. We suggested that these optimum conditions may subject to change in varying scenarios. This work is promising as a comprehensive solution to the breathing air cooling problem, while demonstrating the methodology for solving similar problems.