Study On Thermal Comfort Of Phase Change Cooling Vest

With the continuous development of global warming,high temperature weather is becoming more and more frequent.Long-term exposure to the hot environment not only endangers human health,but also reduces work efficiency,which in turn affects economic development.Wearing phase change cooling vest is an effective way to deal with heat stress.Compared with using air conditioner,this method is more environmentally friendly and can meet the needs of more occasions.The main purposes of this paper are to improve the comfort of phase change cooling vest and optimize the weight of material packets.Firstly,the mechanism of human body temperature regulation is analyzed,and the heat balance equation of body in hot environment is obtained to determine the amount of paraffin wax.Then,we design and make a phase change cooling vest with inner liner,and the appropriate melting temperature and layout are selected through the human trial.Finally,the FLUENT simulation is used to obtain the heat absorption law of the paraffin packet,and the packaging method at different temperatures is determined.The main conclusions are listed as follows:1.According to the human body heat balance equation,combined with the simplified calculation of the actual situation,the power required for the cooling vest is at least 41 W when performing light physical labor in a hot environment of 35?,and the cooling time is2 h,which requires 295.2k J of cooling capacity.2.In the range of 26? to 16?,any type of phase change cooling vest can significantly improve the human comfort,and the lower the phase change temperature,the higher the human comfort.For different parts of the trunk,the chest,back and waist are suitable for placing a relatively low temperature,in which the chest is better,while the abdomen is suitable for placing a relatively high temperature.Considering comfort and perspiration,placing 16? on the chest and upper back,while 26? on the waist and abdomen is the best choice.3.In the design time of 2h,for paraffin at 16?,as the thickness increases,the total amount of melting also increases,so it is not efficient to extend the cooling time by this method.For paraffin packages at 26?,as the thickness increases,the melting weight is almost unchanged.Paraffin wax at 16? has three stages in its endothermic process,while paraffin wax at 26? has two stages.Before the height of solid paraffin decrease,the power of paraffin with different thickness is consistent.When the height is reduced,the heat absorption power of paraffin with different thickness is significantly different.4.By changing the thickness of the paraffin pack,the average power of the combined cooling vest can be increased by 7.2% and 9.6%,respectively,or the total weight can be reduced by 15%.It is finally determined that the optimized packaging form is 13 mm thick for paraffin wax at 16°C and 7mm thick for paraffin wax at 26°C.In this paper,the phase change cooling vest is optimized in terms of comfort and material package,which can be summarized as the combination arrangement of 16? and 26? in a cooling vest,and the mass of paraffin package with lower temperature is heavier.The conclusions and methods provide some guidance for the development of phase change cooling vest.