Study On Heat Loss And Influence Factors Of Cold Protective Clothing Containing PCMs

In low temperature environment,it can cause human body pain,frostbite and even frozen rigor without proper protection.In order to study heat loss and the influence factors of human torso in low temperature environment,guide the design of cold protective clothing containing phase change materials(PCMs),this paper improved and manufactured a PCMs cold protective clothing,and a thermal manikin dressing experiment was carried out.A multi-channel heat flow meter was used for measuring heat flux among different areas of torso and layers of clothing.By further analysing the relationship between environment temperature,dosage of PCMs,PCMs temperature and Surface heat loss of clothing,this paper established empirical formulas between all influence factors and evaluation indexes.First of all,the PCMs cold protective clothing system made up by four layers of clothing,known as the inner layer,heat retention layer,phase transition layer and the outer layer from inside to outside.According to Chinese national standard,the size 170/92 A was choosen for pattern design.The clothing was designed to be stand collar,shoulder segmentation and add yoke,sleeveless,add 2 cm side seam dart,placket with zipper.According to the requirements of the human body,the paraffin was choosen to be made of PCMs cold protective clothing by macroencapsulation,including 3kinds of dosage namely475 g,635g,950 g and 2kinds of phase transition temperature namely 28?,34?.Secondly,thermal manikin dressing experiment was carried out in artificial climate chamber.The environment temperature was 0,2,5 ?,relative humidity was 60%,wind speed was 0.1 m/s.The average skin temperature of thermal manikin was set up by 34?according to ISO 15831-2004.The multi-channel heat flow meter was used measuring the heat flux of chest,abdomen,shoulder and lower back,as well as skin layer,inner layer,outer layer when respectively wearing PCMs cold protective clothing and conventional warm clothing.The variation trend of heat flux can be divided into four stages when wearing PCMs cold protective clothing,heat flux of the skin layer and the inner layer rapidly decreased and then increased rapidly,finally increased slowly until reaching heat balance,while outer layer has completely opposite regulation.The variation trend of heat flux in conventional warm clothing can be divided into two stages.When the environment temperature is 5?,dosage of PCMs is 950 g and phase transition temperature is 34?,the total heat release(57.88 KJ)of skin layer is far less than that in conventional warm clothing(84.08 KJ),it indicates less human heat release when wearing PCMs clothing.But the total heat release(94.25KJ)of outer layer is far more than in conventional warm clothing(64.65KJ).It is because PCMs release a large amount of latent heat and increase the heat loss from clothing system to external environment.Thus the PCMs cold protective clothing has better heat preservation performance.Thirdly,two-way anova and multiple comparisons were conducted to analysis balancing heat flux and unit area heat dissipation among different layers and different areas of torso.The results have shown that balancing heat flux among neither different layer nor different areas of torso have no significant difference in PCMs cold protective clothing.It indicate that the heat flux among both different areas and different layer have reached a balancing state.However,balancing heat flux among different areas of torso has significant difference in conventional warm clothing,and the ranking of balancing heat flux is chest,abdomen,shoulder and lower back.The unit area heat dissipation among different areas of torso has no significant difference,but the unit area heat dissipation among different layers has extremely significant difference.Unit area heat dissipation in outer layer is much larger than in inner layer and skin layer and it is approximately 1.63 times of heat release in skin layer.The variable coefficient of unit area heat dissipation among different layers is 25.9%.Then,the partial correlation analysis was used analyzing the influence of environment temperature,dosage of PCMs and phase change temperature on external surface heat loss of clothing system.There is a significant linear negative correlation between environment temperature and balancing heat flux as well as environment temperature and thermoregulatory capacity,and a significant linear positive correlation relationshipbetween environment temperature and total heat release.Dosage of PCMs has a extremely significant linear negative correlation with balancing heat flux and has a extremely significant linear positive correlation with total heat release and thermoregulatory capacity.What's more,phase change temperature has extremely significant linear positive correlations with both balancing heat flux,thermoregulatory capacity and total heat release.Finally,SPSS statistical analysis software was used conducting multiple linear correlation analysis and establishing empirical formulas among environment temperature,dosage of PCMs,phase change temperature and balancing heat flux,effective protective time,total heat release,thermoregulatory capacity.The multiple correlation coefficients of the four empirical formulas are both larger than 0.98,and the results of F test are extremely significant.It indicate that the four empirical formulas have high Degree of regression and can be used for guiding the design of PCMs cold protective clothing.