Design And Evaluation Of Personal Cooling System With Spray Ventilation

Clothing is the “second skin” for human body,and as the supplement to relieve the body's short of temperature adjustment,personal cooling systems can help the body to resist heat stress.This paper designed a spray-ventilation for the personal cooling system,and studied its cooling performance and thermal and moist comfort properties.Firstly,this paper selected five types of fabrics which are commonly used for personal cooling systems: twilled cotton,plain cotton,and twilled polyester/cotton blended fabrics(thicker),twilled polyester/cotton blended fabrics(lighter),and plain Supplex nylon fabrics to be used as personal cooling systems' fabric.And those five types of fabrics were tested for physical properties,such as gas permeability,capillary effect,and MMT.The test results showed that cotton fabrics and Supplex fabrics have good air permeability and liquid water management capabilities.And the twilled cotton fabrics have strong hygroscopicity,while the Supplex fabrics have good moisture conductivity for which capillary effect's height can reach 14.3cm after 30 minutes with no obvious decay tendency in ascending rate.These two types of fabrics can dry quickly and keep the skin dry and comfortable.Therefore,these two fabrics are selected for further research.Secondly,this paper uses the SGHP sweating hot plate apparatus to simulate human sweating and simulates the back of a human body wearing a spray fan-cooled garment in an environment with a temperature of 30°C and a humidity of 65%,.The wind speed of the spray ventilation unit was designed to be like this: low-grade is3.1m/s,high-grade is 5.6m/s,spray atomization volume is 0.3ml/min,and air layer thickness was set as 5cm,7cm,and 9cm.Through the experiments,the two fabricsystems' moisture resistance,thermal resistance,total heat loss,and total cooling power of the system were studied.The analysis of the experimental results showed that: wind speed is the main factor influencing the heat dissipation of the fabric system.The higher the wind speed will result to the faster the heat dissipation,and has a significant effect on the total thermal resistance,total moisture resistance,total heat loss and total cooling efficiency.This is mainly due to the fan being turned on.After the simulation of the air layer under the clothing formed a strong air convection,which greatly accelerated the simulation of the skin surface heat.The spray has little effect on heat dissipation in Supplex fabrics system,but its addition makes the heat dissipation of the twill weave fabric system slightly increase,also the heat dissipation to the fabric system is reduced.The reason of this phenomenon is that Supplex fabrics are characterized by their moisture-conducting ability and fast dryness,but they have poor one-way transport ability and moisture absorption properties compared to cotton fabrics.Therefore,in the simulated air layer under the clothing,the moisture can be absorbed and transported to the outside by the cotton fabric,which caused a cooling effect.But with Supplex fabrics,the moisture cannot be transported to the outside in time and accumulates,and its heat capacity is larger than air,so it formed a certain insulation effect.Finally,two sets of cooling clothes made by cotton fabrics and Supplex fabrics were worn by people,which are equipped with a spray-ventilation.Based on the experiment,this paper gathers the skin temperature and humidity of their chest,back,and waist and makes subjective scoring of thermal-wet comfort.According to the experimental data,spray-type fan device has the greatest effect on the temperature and humidity of the human back,followed by the lower back,and has less impact on the chest.The wind speed is the main factor that causes the cooling effect.The effect is obvious when the wind speed is high.The addition of the spray can help cool the temperature.However,in the Supplex cooling garments,the temperature at the high-grade wind speed and spray is higher than the high-end wind speed alone.This is due to the poor unidirectional conductivity of the liquid water of the Supplex fabric,which is consistent with the experimental results of the fabrics.What's more,the addition of spray will not reduce the wet comfort,but to a certain extent,improve the body's hot and humid comfort,and the role of cooling clothing in the cotton fabric is more obvious,in which high-grade wind speed can be sprayed with the best coolingresult.Based on the research of Personal Cooling System with Spray Ventilation,the paper provides theoretical basis and scientific guidance for the further research of personal cooling system.In addition,it provides a reference for the manufacturers to design,research and produce cooling garment products,and it also brings good news for ordinary workers who always expose in high temperature.