PCM cooling vest for improving comfort under hot environment -

Abstract

This work investigates a passive method to extend cooling of the human body under hot environments for longer periods. A cooling vest containing phase change materials (PCM) made of salt mixtures that melts at a specific temperature helps in maintaining the skin temperature of the covered parts at a comfortable level. A transient mathematical model of heat and mass transfer through clothing layers containing PCM packets is developed. Two experiments were done on a clothed heated cylinder in a controlled environment to validate the proposed model. Good agreement was found between model-predicted and measured temperatures of the microclimate air between the cylinder and the PCM in both experiments. The PCM vest model is integrated with a segmental bio-heat model to provide realistic skin boundary conditions. The results from the integration were also validated with a published experiment on a human wearing a PCM vest subjected to hot environment. A simulation study on the different parameters affecting the performance of the vest is done. The parameters include the melting temperature, the covering area of the PCM and its mass .It was found that a lower melting temperature must be used when a fast cooling effect is desirable. Moreover, it is found that covering area is the factor that affects the cooling rate while the thickness or the mass of the PCM affect the cooling duration. These findings meet well with experimental conclusions of published data. The bio-heat model used divides the torso into eight different segments allowing studying the effect of the PCM on the upper and lower torso segments. It is found that the upper torso releases more sensible losses than the lower one when covered with the same number of PCMs.