Does back cooling improve human thermal comfort in warm environments?A device for heat conduction by the semiconductor Peltier effect

The hot environment and the metabolic heat of commuting in summer caused individual overheating and intense thermal discomfort.Local cooling presents huge potential for optimizing thermal comfort.This study investigates the performance of a back cooling device,based on the semiconductor Peltier effect,in improving thermal comfort after summer commuting.We studied one case without cooling,and three cases with surface temperatures of the cooling device of 29,27,and 25℃using a simulated summer commute at a moderate activity level.The results showed that thermal sensation,perceived sweating rate,and skin temperature decreased markedly in the cooling cases compared to the non-cooling case,with the changes being most notable in the lower back,in contact with the cooling device.The decrease in overall thermal sensation and mean skin temperature was approximately 0.52 score and 0.31℃on average,respectively,with a 1.71 score increase in overall thermal comfort.We contend that the surface temperature of local contact cooling devices should not be lower than 22℃to minimize local overcooling.Back cooling devices present a huge potential for building energy-savings at ambient air temperature exceeding 30℃.Moreover,the functional paradigms for individual comfort predict improved comfort performance in future applications.This study contributes to the understanding on the well-being and physiological recovery of individuals after a summer commuting.

Climate chamber investigation of the effect of indoor thermal histories on thermal adaptation in different seasons

The indoor thermal history of residents in the hot summer and cold winter climate zone in China have undergone a significant change in recent years,which also changes their seasonal thermal adaptations and this has formed feed-back effects to the increasing usage of air conditioning units in this area.To study the seasonal variations of thermal adaptation,the thermal comfort experiments were conducted on two groups of participants.Each groups included 20 participants who had indoor history mainly with natural ventilation(NV group)and air-conditioning(AC group),respectively.The results demonstrated that the thermal sensation vote(TSV)in warm environments did not differ between AC and NV subjects in summer.However,the TSV of AC subjects were much lower than that of NV subjects in the same standard effective temperature and skin temperature in a cold environment in winter.Overall,the participants who spent most of their time in AC space in winter showed a low level of thermal adaptation with a narrower acceptable skin temperature range of 32.6-33.5℃.Thus,this study presents the basic information regarding the seasonal effects on human thermal adaptation due to different long-term indoor thermal histories.

How green building rating systems affect designing green

Storing thermal energy in mass concrete floors would have a major impact on the stability of the temperature in buildings.The concept of a thermal battery refers to storing the supplied radiant heat and releasing this heat the next day through radiation and convection.In this study,an approach is introduced to examine the idea of thermal battery in thick concrete flooring(1.22 m)using the earth as a heat source.Controlled experiments were built and conducted on an instrumented 3000 m 2 industrial facility.The heating radiant floor combining with ground source system was operated during off-peak hours and the air conditioning system was disabled for 24 h during the test period.The heat pumps were operated in single stage using less power compared to when operated on demand.Indoor air temperature showed that 100(37.78℃)supply temperature at the ground source heat pump would be enough to maintain a stable warm temperature during cold days.Two weather conditions in the winter were selected to do the tests.The second test had a colder ambient temperature to verify the procedure.The indoor air temperature showed that the night heating system performs well for both cases because it maintained a constant temperature for the entire operational day even in the daytime when every heating unit was off.This approach of applying the heating at nighttime with lower electricity rates would lead to significant operational cost savings in the building.

空气湿度对人员可接受热环境的影响及评价

室内温湿度对人员舒适健康有着显著影响,尤其在偏热和偏冷环境下.如何评价较大空气湿度范围内温湿度耦合作用及其影响尚缺乏系统认识.我们在人工气候室分别开展了冬夏季涵盖偏冷到偏热(16~32℃)、低湿到高湿(15%~85%)共40个工况的人体热舒适实验,累计800余人次.结果显示,相对湿度对人员热舒适的影响随温度升高逐渐显著(夏季32℃/冬季28℃),湿感觉随相对湿度增加而显著增加;低温下空气绝对含湿量低,人体各部位刺激感比例随相对湿度降低而增加;低温下人员感知空气品质随暴露时间增加而降低,高温下人员适应性提高了人员对空气品质感知.研究计算了不同工况下人体呼吸总热损失,并建立其与人员热感觉(thermal sensation vote,TSV)和可感知空气品质(air quality vote,AQV)的关系:随着呼吸总损失增加,人员热感觉线性降低(回归系数:-0.66),感知空气品质升高(回归系数:0.2).基于TSV∈(-0.5,+0.5)和TSV∈(-0.75,+0.75),得到了冬夏季满足90%和80%人员满意率的标准有效温度(standard effective temperature,SET)上下限值,和等SET条件下温度-相对湿度(30%~70%)舒适区间,且大于国际标准ASHRAE 55推荐的温度区间.研究量化了空气湿度对人员热感觉的影响,揭示了低湿和高湿通过影响皮肤表面散热和呼吸蒸发热损失影响人员可接受温度区间,研究结果可为提出合理室内空气湿度设计参数、保障室内热环境舒适健康营造提供一定参考.

南方地板辐射供暖的舒适性地板温度范围

地板辐射供暖系统应用数量在我国南方地区日益增长,但人们对如何设定适宜的地板温度范围存在一定的疑惑.本文通过标准解读、文献调研和实地人体实验,对舒适性地板温度范围进行了研究.文献总结表明,东亚地区人群偏好的地板温度普遍高于现有标准推荐值(约25~29℃).在重庆某住宅中,招募了45名当地受试者,对25~35℃的6个不同地板温度进行了问卷投票人体实验研究.结果表明,夏热冬冷地区人们偏好较高的地板温度.长期停留时,中性地板温度约为28℃,但热舒适性地板温度约为29~32℃,期望的地板温度在32℃左右;而短暂停留时,期望的地板温度在33~35℃.因此,针对夏热冬冷地区的分散式地板辐射供暖系统,建议将经常停留和短暂停留区域的地板设计温度上限值分别提高到32和34℃.

Individual thermal comfort prediction using classification tree model based on physiological parameters and thermal history in winter

Individual thermal comfort models based on physiological parameters could improve the efficiency of the personal thermal comfort control system.However,the effect of thermal history has not been fully addressed in these models.In this study,climate chamber experiments were conducted in winter using 32 subjects who have different indoor and outdoor thermal histories.Two kinds of thermal conditions were investigated:the temperature dropping(24-16℃)and severe cold(12℃)conditions.A simplified method using historical air temperature to quantify the thermal history was proposed and used to predict thermal comfort and thermal demand from physical or physiological parameters.Results show the accuracies of individual thermal sensation prediction was low to about 30%by using the PMV index in cold environments of this study.Base on the sensitivity and reliability of physiological responses,five local skin temperatures(at hand,calf,head,arm and thigh)and the heart rate are optimal input parameters for the individual thermal comfort model.With the proposed historical air temperature as an additional input,the general accuracies using classification tree model C5.0 were increased up by 15.5%for thermal comfort prediction and up by 29.8%for thermal demand prediction.Thus,when predicting thermal demands in winter,the factor of thermal history should be considered.

Long-term dermal exposure to diisononyl phthalate exacerbates atopic dermatitis through oxidative stress in an FITC-induced mouse model

Diisononyl phthalate （DINP）, considered to be an environmentally friendly plasticizer, is now widely used. However, the toxic effects of DINP need to be examined, particularly the effects of long-term dermal DINP exposure. Research into the mechanisms underlying these effects is urgently needed. In this study we examined the exacerbation effect of long-term dermal exposure to DINP in flnorescein isothiocyanate （FITC）-induced contact hypersensitivity （CHS） in mice, and sought the potential molecular mechanisms. Forty-nine male Balb/c mice were subjected to a 40-day dermal exposure to saline or one of three concentrations of DINP and then three rounds of sensitization with vehicle or 0.5% FITC. The results of a histopathological examination and measurement of ear swelling as well as immunological and inflammatory biomarkers （total-immunoglobulin （Ig）E and Th cytokines） supported the notion that high doses of DINP may aggravate atopic dermatitis. We also showed that melatonin, an antioxidant, could decrease the levels of oxidative stress and alleviate FITC-induced CHS suggesting that oxidative stress may be one of the molecular mechanisms to explain the exacerbation effect induced by DINP.

Effect of natural resource on improving indoor thermal environment in Chongqing

This paper analyzes the potential of natural resources to improve the indoor thermal environment in Chongqing through the statistical analysis of natural resources including solar energy,wind,water,and earth,etc.The building form,systems,and principle of usage of natural resources are briefly analyzed through the building site decision,building form design,and computer simula-tion,which will be the real reference for the design of building energy efficiency.