Study On Influence Of Environment On The Warmth Retention Of Down Jacket

As common cold-proof and warm clothing in winter,the warmth retention of down jackets has become a major concern of people.The warmth retention of down jackets is affected by clothing material and structure,wearing environment,and wearing styles.Existing researches pay more attention to the influence of factors such as filling amount,motion state and temperature on thermal resistance.However,there are few studies on the influence of environmental temperature,wind speed and clothing collocation on the thermal comfort of down jackets by simulating the real wearing environment of winter down jackets.Therefore,it is of great significance to clarify the influence of different environments on the warmth retention of down jackets in the field of scientific research and actual production and purchase.This paper simulated the real wearing environment of down jackets in an artificial climate warehouse,and used the LD-1 clothing thermal insulation tester to explore the influence of environmental temperature,wind speed and clothing matching methods on the warmth retention of four different fillings of down jackets.The experimental results show that as the temperature decreases,the heat exchange between the human body and the environment increases.When the ambient temperature decreases from 10?to-2?,the heat flux density,convective heat transfer and radiation heat transfer increase on average by 44.95W/m2,37.10W/m2and 9.84W/m2,respectively.The temperature of quilting on the surface of down jacket is high and does not change with gram weight,and the surface temperature decreases gradually with the increase of thickness in other positions.With the increase of unit filling,the effective thermal resistance of down jacket increases,and the increase amplitude gradually increases.The effective thermal resistance of down jacket with a weight of 80 g/m2?110g/m2and 140 g/m2per unit filling increased by 18.00%,49.00%and 92.93%respectively compared with the down jacket which are distributed in 50g/m~2.The heat flux lost by the body is positively correlated with wind speed.When the ambient temperature is 10?,as the wind speed increases from 0.5m/s to 13.0m/s,the heat flux density of the sample increases by an average of 53.29%;when the ambient wind speed increases,the thermal resistance and inherent thermal resistance of the air layer on the garment surface are both decrease,the convective heat transfer on the surface of the garment increases,and the heat flux density increases.When the wind speed rises from 0.5m/s to 7.0m/s,the surface air insulation drops by 73.26%,which is a large drop;when the wind speed continues to increase to 13.0m/s,compared with 0.5m/s,the surface air insulation decreased by 81.63%,and the decrease rate was slow and close to zero.As the wind speed increases,the convective heat transfer on the surface of the clothing increases,and the high-speed fluid takes away part of the heat on the surface of the clothing,so that the surface temperature of the clothing decreases,and the temperature difference between the surface of the clothing and the environment decreases,so that the radiant heat transfer decreases.The collocation of down jacket and submachine jacket can reduce the heat flux loss of human body,increase the overall heat resistance of clothing,reduce the temperature difference between the outer surface and environment of submachine jacket,and make the convection and radiation heat exchange of down jacket and winter jacket lower.The heat flux density,convection heat transfer and radiation heat transfer of down jackets when worn with submachine jacket are on average 60.48W/m2,51.02W/m2and 8.57W/m2lower than the down jacket samples.Under windy conditions,human body heat dissipation is mainly through convection hot way.The results show that the jacket has a certain improvement effect on the quilting and zipper on the surface of the down jacket.As the ambient temperature rises,the unit filling volume of down jackets suitable for wearing to maintain the thermal comfort of the human body decreases.Under the conditions of an ambient temperature of-2?and a wind speed of 0.5m/s,at a 2MET exercise intensity,a 140g/m2down jacket is not enough to keep warm.When the ambient temperature rises to 10?,90g/m2down jacket can guarantee better thermal comfort.As the environmental wind speed increases,the unit filling volume of down jackets that maintains the thermal comfort of the human body increases.Under the conditions of an ambient temperature of 10?and a wind speed of 1.47?5.89m/s and a2MET exercise intensity,a 140g/m2down jacket can provide sufficient heat preservation,but when the wind speed is greater than 5.89m/s,it cannot provide sufficient heat preservation.Under the same ambient temperature and wind speed condition,the clothing unit filling quantity required to ensure better thermal comfort is different when the down jacket is worn with submachine jacket.Under the condition that the ambient temperature is-2?and the wind speed is more than 7.53m/s,the down jacket with 50 g/m2and 80 g/m2can't meet the requirement of keeping warm when people are in 4 sports intensity,but they can provide enough warmth when worn with submachine jackets.