Research On The Flow And Heat Transfer In Air Cooling Garment Based On Thermoelectric Cooling

In the new age,the people’s yearning for a better life has become the goal of the whole society.Under such background,the bad working environment in military,police,fire,mining and other special industries is getting increasing attention.Practitioners in special industries must bear high temperature that maybe above 37℃.In such environment,they are faced with the threat to their health and safety.The ambient temperature is so high that the body heat can not be dissipated in time but can be stored in the body only.The body temperature rises,leading to heat stress,the operator’s attention down and physical strength gradually exhausted.It not only reduces the work efficiency,but also be easy to cause physiological abnormalities or even life-threatening.Therefore,it is necessary to develop a set of around body temperature regulating device system to improve the human microenvironment.It is required to guarantee the thermal comfort of human body,and fundamentally prevent the occurrence of safety accidents even in bad conditions.This dissertation focuses on the research of the air cooling garment system which is based on thermoelectric cooling.The device is applied to the professionals of the special industry.The main work of this dissertation includes the following parts:(1)This dissertation explained the theoretical model of human thermal balance system,introduced the essential mechanism of human heat production and heat dissipation,grasped the key links of thermoregulation,and researched and discussed the air cooling garment system based on the thermal balance model.(2)In Chapter3,the air cooling service system components were introduced.This Chapter focused on the design of piping system which includes three pipeline models,spiral type,horizontal type and vertical type respectively.By the method of numerical simulation analysis,the results showed that: In the condition of low flow velocity,the air mass flow of each outlet on vertical pipeline was well-distributed mostly.In the condition of high flow velocity,the air mass flow of each outlet on spiral pipeline was well-distributed mostly,and vertical pipeline got second.Meanwhile,there were mutation values of outlet mass flow in horizontal and vertical pipeline.(3)Thermoelectric cooler was taken as cooling system in air cooling garment.Because of the shortcomings that the traditional symmetric type thermoelectric cooler is too thick,the heat pipe was introduced to guide heat transversely.By this way,the microscopic structure of thermoelectric cooler was changed.The heat guided type thermoelectric cooler was created.Then,after the optimum design,the thermoelectric cooler not only decreased the thickness of 29.33%,and the cooling capacity and the coefficient of performance were increased by 3.67% and 4.14% respectively.From the microcosmic perspective,the geometric factor γ was defined as the radio of the cross sectional area to the height of thermoelectric leg.The influence of γ on the cooling performance of thermoelectric element was studied.The results showed that: to achieve the best cooling performance,the thermoelectric elements with high value of γ were suitable for high power condition,while the thermoelectric elements with low value of γ were suitable for small power operation.The results have important guiding significance to improve the cooling capacity of air cooling garment system.(4)Standard body size parameters were referred,and a coupling physical model with garment,pipeline and body was established.The regulation of air flow and heat transfer in air cooling garment was researched by the method of numerical simulation.The results showed that: In spiral model,the body surface temperature on upper part of body is higher than that on lower part of body.In horizontal model,the body surface temperature on upper part of body is lower than that on lower part of body.In vertical model,the body surface temperature on back part of body is higher than that on front part of body.Meanwhile,the relationships between average body surface temperature,temperature difference which is between body inside and outside and inlet velocity,inlet temperature were achieved.The mathematical formulas were derived.In spiral model,the relationships between average body surface temperature,temperature difference and inlet velocity are linear functions.In horizontal model,they are quadric functions.In vertical model,they are cubic functions.For the relationships between average body surface temperature,temperature difference and inlet temperature,the three models show linear functions similarly.