The Research And Evaluation On Cooling Performance Of A Novel Portable Hybrid Personal Cooling Garment Incorporated With Phase Change Materials And Ventilation Fans

When human expose in hot environment with a long time,which will lead to body temperature increase,work efficiency decrease,and then,it will appear hyperthermia,heat cramps,heatstroke and other heat diseases.How to take effective measures to alleviate the individual heat stress,so as to protect the personal safety of workers in the thermal environment is particularly important.In our study,we analyzed the advantages and disadvantages of several cooling methods,developed a novel portable hybrid personal cooling garment incorporated with Phase Change Materials and Ventilation Fans,and then do some manikin tests and human trials to investigate the performance respectively.In the manikin tests,the cooling effect was evaluated in three different thermal environments:hot humidity,hot dry and warm.The evaluation parameters of cooling effect mainly include that:the thermal insulation（I_t）,the evaporative resistance(R_et),the heat loss（HL）and the cooling power.Four test scenarios were chosen:Fan-off（no PCMs,fans turned off）,Fan-on（no PCMs,fans turned on）,PCM+Fan-off（PCMs were added but fans were turned off）and PCMs+Fan-on（PCMs were added and fans were turned on）.Results showed that the thermal insulation and evaporative resistance of the hybrid personal cooling garment were significantly reduced when turning on the ventilation fans.In the initial stage,Phase change material could greatly increase the cooling rate,but the main cooling effect was provided by the ventilation fans in this hybrid personal cooling garment.At the end of the phase change,the fully melted phase change material increased the impermeability of the hybrid personal cooling garment,and suppressed the whole evaporation of the hybrid personal cooling garment.Using the ventilation fans and phase change material at the same time,could greatly prolong the cooling effect of hybrid personal cooling garment.The human trials were carried out by collecting the physiological parameters and subjective sensations in the hot humidity environment to evaluate the thermal comfort for the hybrid personal cooling garment.Two test scenarios were chosen:Fan-off（no PCMs,fans turned off）,and PCMs+Fan-on（PCMs were added and fans were turned on）.Results showed that using the hybrid personal cooling garment in hot environment could effectively inhibit the mean skin temperature increase and maintain the mean skin temperature in the thermoneutral range.Phase change materials must be tightly contacted with the human body in order to exert the best cooling effect.In addition,the body posture of physically activity will also affect the contact of phase change material.In hot environment,wearing hybrid personal cooling garment could effectively enhance subjective feelings,such as the body thermal sensation,comfort sensation and skin humidity sensation.