Numerical Investigations On Performance Of Personal Comfort System With Localized Heating Garment

Recently,the global climate is warming,and extreme weather and climate events are becoming of increasing frequency and intensity.Meanwhile,this has led to significant growth in building energy consumption and health risks due to cold exposure.Personal comfort system with localized heating garment focuses on the individual and combines heating functions with clothing to regulate thermally the human body.It can effectively enhance human thermal comfort,reduce energy consumption for building operations and meet thermal requirement.Therefore,it is of great significance to study personal comfort system with localized heating garment.To improve the system performance and provide a fundamental basis for optimisation,this paper used numerical simulation method to study the thermal physiological response of Chinese people in cold environments.Then personal electrically comfort system with localized heating garment was selected to analyze and discuss the system performance,influencing factors,and suitability in outdoor low-temperature environments.Firstly,there are noticeable differences in mass,body surface area distribution and thermos-physiological parameters between Chinese and Western standard humans.Based on the thermal characteristics of the Chinese people,parameters such as body surface area,mass,basal metabolism as well as heat capacity and thermal conductivity were modified to establish a new multi-node human thermal regulation model reflecting physiological differences.This model was also respectively validated for steady-state and transient operating conditions using the literature results.And the validation results show that the accuracy of the optimized model for Chinese people’s skin temperature in cold environments is significantly improved and the model can be used to analyze thermal demand.Secondly,the personal electrical comfort system with localized heating garment significantly increases the average and minimum human skin temperature.17°C and 7°C were chosen to simulate the indoor low-temperature environment and-3°C to simulate an outdoor low-temperature environment.The system increased the average skin temperature by 0.5°C,0.9°C and 1.31°C for the above three conditions respectively.At an ambient temperature of-3°C,the average skin temperature increased with increasing heating power q.When q ≥18W,the back skin temperature decreased with increasing heating duration;when q was 38 W,the stable value of back skin temperature was higher than the threshold value of skin scald.A heating power of 28 W should be adopted at-3°Cto maintain average skin temperature and avoids low-temperature burns.Additionally,the intermittent heating modes could contribute to saving energy without compromising average skin temperature.The four intermittent heating modes(every 5,10,20 and 30 min)achieved average skin temperature around 0.17°C to 0.35°C higher than the unheated condition.And when the average skin temperature is guaranteed and the battery capacity is the same,the intermittent heating mode of 5 minutes heating/5 minutes intermittent was the most energy efficient.Thirdly,the personal comfort system with localized heating garment could be effective in extremely low-temperature environments.To improve human ergonomics and ensure hand skin temperature,the highly efficient insulation materials,like aerogel,and the combined heating form for the torso and hand should be preferred.At an ambient temperature of-10°C,-15°C and-25°C,the system was effective in increasing the average skin temperature stability value by 1.45°C,1.22°C and 1.24°C respectively.Moreover,the comparative analysis of hand skin temperature showed that the combination of torso and forearm heating was not as beneficial in increasing hand skin temperature.