冬季室内热环境与被褥微气候的匹配

冬季睡眠状态下,室内热环境与被褥微气候分别对人体头部和被覆躯体的热感觉造成直接影响。为了分析两个热环境的匹配关系以满足睡眠人体的热舒适水平,实验在不同的室内温度下,调节被褥微气候温度,测试了受试者的皮肤温度,并记录了热感觉和热可接受水平。研究结果表明:睡眠状态下,相比于室内热环境,人体热感觉对被褥微气候更敏感;此外,通过分析室内热环境和被褥微气候分别与整体热感觉和整体不满意率的关系,得到了睡眠热环境舒适区间。     

Investigation of indoor thermal comfort under transient conditions

In industrialized countries about 90% of the time is spent indoors. In indoor, thermal comfort can be basically predicted by the environmental parameters such as temperature, humidity, air velocity and by the personal parameters as activity and clothing resistance. In this study, a mathematical model of thermal interaction between human body and environment was established and the effect of clothing and air velocity was examined under transient conditions. By the developed model, human body has been separated to 16 segments and possible local discomforts are taken into consideration. Using the model, changes in the sensible and latent heat losses, skin temperature and wettedness, thermal comfort indices were calculated. In a hot environment latent heat loss increases by means of sweating. Because of over wetted skin, comfort sense goes worse. Especially, at feet and pelvis skin wettedness reaches maximum level. Sensible and latent heat losses rise and the skin temperature and wettedness decrease with increasing air velocity.     

Local body cooling to improve sleep quality and thermal comfort in a hot environment

The effects of local body cooling on thermal comfort and sleep quality in a hot environment were investigated in an experiment with 16 male subjects. Sleep quality was evaluated subjectively, using questionnaires completed in the morning, and objectively, by analysis of electroencephalogram (EEG) signals that were continuously monitored during the sleeping period. Compared with no cooling, the largest improvement in thermal comfort and sleep quality was observed when the back and head (neck) were both cooled at a room temperature of 32°C. Back cooling alone also improved thermal comfort and sleep quality, although the effects were less than when cooling both back and head (neck). Mean sleep efficiency was improved from 84.6% in the no cooling condition to 95.3% and 92.8%, respectively, in these conditions, indicating good sleep quality. Head (neck) cooling alone slightly improved thermal comfort and subjective sleep quality and increased Stage N3 sleep, but did not otherwise improve sleep quality. The results show that local cooling applied to large body sections (back and head) could effectively maintain good sleep and improve thermal comfort in a hot environment.     

Thermal sensation and comfort models for non-uniform and transient environments: Part I: Local sensation of individual body parts

A three-part series presents the development of models for predicting the local thermal sensation (Part I) and local comfort (Part II) of different parts of the human body, and also the whole-body sensation and comfort responses (Part III). The models predict these subjective responses to the environment from thermophysiological measurements or predictions (skin and core temperatures). The models apply to a range of environments: uniform and non-uniform, transient and stable. They are based on diverse results from the literature and from body part-specific human subject tests in a climate chamber. They were validated against a test of passengers in automobiles. This series is intended to present the rationale, structure, and coefficients for these models so that others can test and develop them further as additional empirical data becomes available. The experimental methods and some measured results from the climate chamber tests have been published previously.Part I describes thermal sensation models representing 19 individual local body parts. The models' structure and coefficients were derived by regression of skin and core temperatures against thermal sensation votes obtained in the chamber experiments. The sensation for each local body part is predicted by a logistic function with four inputs: local skin temperature, mean-skin temperature presenting the whole-body thermal state, and the time derivatives of skin and core temperatures representing the response to transients. These inputs can be obtained from thermophysiological computer programs that treat the body as multiple segments.     

Effect of humidity and small air movement on thermal comfort under a radiant cooling ceiling by subjective experiments

Radiant air-conditioning systems are expected to be more comfortable and superior energy-saving systems than convective air conditioning ones generally used. There are some studies on radiant cooling systems. However, they were seldom put to practical use because of dew point problem in Japan. The objective of this study is to investigate the thermal comfort of local parts of the body and the whole body, in particular, including the effects of humidity (45% rh, 65% rh, 85% rh) and small air movements, by subjective experiments under a radiant cooling system. The experiments have been performed by using radiant cooling panels in a climate chamber. Subjects were seated on a chair under the radiant cooling panels, and voted their thermal sensation and comfortable sensation. The following results were obtained. Even in the radiant cooling system, the influence of humidity and small air movement on thermal sensation votes of the whole body could be correctly estimated by using a standard new effective temperature (SET*) within one scale error of thermal sensation. Small air movement with the radiant cooling system had a possibility of improving the comfortable sensation votes in the radiant cooling.     

Comfort,perceived air quality,and work performance in a low-power task–ambient conditioning system

Zhang's thermal comfort model [Zhang H. Human thermal sensation and comfort in transient and non-uniform thermal environments, Ph.D. thesis, UC Berkeley; 2003. 415 pp.] predicts that the local comfort of feet, hands, and face predominates in determining a person's overall comfort in warm and cool conditions. We took advantage of this in designing a task–ambient conditioning (TAC) system that heats only the feet and hands, and cools only the hands and face, to provide comfort in a wide range of ambient environments. Per workstation, the TAC system uses less than 41 W for cooling and 59 W for heating. We tested the TAC system on 18 subjects in our environmental chamber, at temperatures representing a wide range of practical winter and summer conditions (18–30 °C). A total of 90 tests were done. We measured subjects' skin and core temperatures, obtained their subjective responses about thermal comfort, perceived air quality, and air movement preference. The subjects performed three different types of tasks to evaluate their productivity during the testing. The TAC system maintains good comfort levels across the entire temperature range tested. TAC did not significantly affect the task performance of the occupants compared to a neutral ambient condition. Whenever air motion was provided, perceived air quality was significantly improved, even if the air movement was re-circulated room air. In our tests, subjects found thermal environments acceptable even if they were judged slightly uncomfortable (−0.5). By reducing the amount of control normally needed in the overall building, the TAC system saves energy. Simulated annual heating and cooling energy savings with the TAC system are as much as 40%.     

Indoor thermal environment and energy saving for urban residential buildings in China

The purpose of this survey is to investigate the actual conditions of the residential indoor thermal environment in urban areas in China for evaluating thermal comfort and predicting the energy conservation feasibility for space heating and cooling.The apartment homes under investigation were located in the urban areas of nine major cities. The questionnaire survey revealed building characteristics, the types of space heating and cooling system in use, aspects of life style, during winter and summer seasons, and so on. The measurement showed that winter indoor temperatures in Harbin, Urumqi, Beijing and Xi’an remain at a relatively stable level near 20 °C due to the central heating system installed. However in the other cities lacking central heating systems, indoor temperatures fluctuated as a function of the change of outdoor temperature. On the other hand, summer indoor evening temperatures in Shanghai, Changsha, Chongqing and Hong Kong were higher than the comfort zone of ASHRAE. Therefore it is expected that energy use for space heating and cooling in the southern China will increase in the near future because of occupants’ requirement for comfortable indoor environment. Based on the results yielded by this study, in Beijing the calculation of space heating and cooling loads indicated that the energy used to heat indoor spaces can be halved by installing thermal insulation and properly sealing the building.     

Thermal pleasure in built environments: spatial alliesthesia from contact heating

The comfort zone is bounded by thermal environmental conditions that may be described as acceptably cool or acceptably warm, and engineering out of existence these innocuous thermal conditions on the fringes of the adaptive comfort range may not be necessary. In contrast to the conventional understanding of local discomfort, spatial alliesthesia exploits corrective differences in the rate of change in skin temperature between individual body segments to elicit positive affective sensations. This paper examines reverse instances of local discomfort, or spatial alliesthesia, from warm contact stimuli applied to hand and feet when exposed to ambient conditions towards the lower margin of the comfort zone. It was found that subjects with moderate feelings of displeasure or even indifference were still capable of experiencing a pleasant response to localized thermal stimuli. Brief whole-body thermal pleasure was observed from in-situ skin temperature changes at a single distal body site. These effects were subtle and not universally experienced, so the success of their deliberate implementation in built environments depends heavily on some form of individual control. Spatial alliesthesia therefore complements the body of literature investigating personal environmental control and local thermal discomfort by providing a theoretical framework of thermal perception in non-neutral environments.     

湿热地区室外动态热环境中二节点模型的验证及修正

快速城镇化和全球变暖使城市室外环境的热不舒适加剧,热安全风险提高。为了解湿热地区室外动态热环境中人体生理量的变化规律,为快速评价室外热环境提供依据,开展了室外人体热反应观测实验。基于实测数据,对二节点模型进行了模拟精度分析和吻合度检验,研究得到了人体在室外受风速、MRT和自身调节的作用下,皮肤温度和体核温度呈现不同的变化规律及二节点模型修正方法。在室外动态热环境中应用二节点模型,需从皮肤、体核调定温度、人体标准模型、肌体启动体温调节的环境温度值及人体与室外环境的对流换热系数4个方面对人体二节点模型进行修正,相关参数和调节过程应写成可赋值的变量或数学表达式,修正后的二节点模型对室外人体热反应预测具有通用性和适用性。     

Development of Artificial Neural Network based heat convection algorithm for thermal simulation of large rectangular cross-sectional area Earth-to-Air Heat Exchangers

An Earth-to-Air Heat Exchanger (ETAHE) is a low energy cooling and heating building component. It uses the ground's thermal storage to dampen ambient air temperature oscillations by delivering the air through a horizontally buried duct. To reduce airflow resistance, some hybrid ventilated buildings have recently adopted large cross-sectional area ducts. This paper describes the development of an Artificial Neural Network based Heat Convection (ANN-HC) algorithm to predict local average Nusselt Numbers along the duct surfaces. Furthermore, the ANN-HC algorithm is integrated with a transient three-dimensional heat transfer model based on finite element analysis of heat conduction in the ground domain surrounding the ETAHE to establish a new thermal modeling method for ETAHEs. A case study is presented to demonstrate the working principle of the new method. It is shown that the method can very well simulate the interactions between an ETAHE and its environment.     

Room air temperature affects occupants’ physiology,perceptions and mental alertness

Thermal environment that causes thermal discomfort may affect office work performance. However, the mechanisms through which occupants are affected are not well understood. This study explores the plausible mechanism linking room air temperature and mental alertness through perceptual and physiological responses in the tropics. Ninety-six young adults participated as voluntary subjects in a series of experiment conducted in the simulated office settings. Three room air temperatures, i.e. 20.0, 23.0 and 26.0 °C were selected as the experimental conditions. Both thermal comfort and thermal sensation changed significantly with time under all exposures (P < 0.0001). Longer exposure at 20.0 °C led to cooling sensations due to lower skin temperatures (P < 0.0001) and was perceived as the least comfortable. Nevertheless, this moderate cold exposure induced nervous system activation as demonstrated by the increase of α-Amylase level (P < 0.0001) and the Tsai–partington test (P < 0.0001). A mechanism linking thermal environment, occupants' responses and performance is proposed.     

Evaluation and comparison of thermal comfort of convective and radiant heating terminals in office buildings

Radiant heating systems are increasingly widely utilized in buildings for its energy conservation potential and enhanced thermal comfort. This paper presented an experiment to compare the thermal comfort performance of radiant heating system with convective heating system through objective measurement and subjective survey. Six physical parameters which might influence occupants' thermal satisfaction, including the Mean Radiant Temperature(MRT), humidity, air movement, A-weighted sound level,temperature fluctuation and vertical temperature difference, were measured. In addition, 97 subjects participated in the subjective survey part of this experiment, experiencing all the three environments heated by air source heat pump, radiator and floor heating.And they were asked to vote in six thermal comfort related aspects, i.e. thermal sensation, humidity, draught, local discomfort,overall thermal satisfaction and overall preferences, plus the acoustic environment, since the operation noise of heating system might lead to complains of the occupants. It was found that in continuous heating, no significant difference between radiant and convective heating system was observed in the Mean Radiant Temperature(MRT), indoor humidity and noise issue. Though radiant heating systems resulted in lower draught risk and less local discomfort complains in the feet region due to the less significant temperature fluctuations and vertical temperature gradients, radiant heating did not have significantly higher overall thermal satisfaction votes and was not significantly more preferred by occupants.     

A simplified model of thermal comfort

The purpose of conditioning the air in a building is to provide a safe and comfortable environment for its occupants. Satisfaction with the environment is composed of many components, the most important of which is thermal comfort. The principal environmental factors that affect human comfort are air temperature, mean radiant temperature, humidity, and air speed; virtually all heating, ventilating and air-conditioning (HVAC) systems, however, are usually controlled only by an air-temperature set-point. Significant efficiency improvements could be achieved if HVAC systems responded to comfort levels rather than air-temperature levels. The purpose of this report is to present a simplified model of thermal comfort based on the original work of Fanger, who related thermal comfort to total thermal stress on the body. The simplified solutions allow the calculation of predicted mean vote (PMV) and effective temperature which (in the comfort zone) are linear in the air temperature and mean radiant temperature, and quadratic in the dew point, and which can be calculated without any iteration. In addition to the mathematical expressions, graphical solutions are presented.     

南方村镇住宅被动式致凉研究

致凉和采暖是一组相对概念。我国南方村镇数目众多,人口较密集,经济较发达,广大村镇住宅共同面临夏季炎热气候。良好的致凉措施是南方村镇住宅在炎热夏季获得舒适居住环境的必要条件。基于节能理念,在理论上阐释了"被动式致凉"概念,总结出了通风致凉、遮阳致凉、隔热致凉和环境致凉等四种致凉方法及其具体技术手段,分析了这些致凉方法的原理、特点,并确立了村镇住宅致凉设计的被动式为主、与建筑一体化以及因地制宜等三个原则。     

Double cooling coil model for non-linear HVAC system using RLF method

The purpose of heating, ventilating and air conditioning (HVAC) system is to provide and maintain a comfortable indoor temperature and humidity. The objective of this work is to model building structure, including equipments of HVAC system. The hybrid HVAC model is built with physical and empirical functions of thermal inertia quantity. Physical laws are used to build the sub-model for subsystems that have low thermal inertia while the empirical method is used to build the sub-model for subsystems with high thermal inertia. The residential load factor (RLF) is modeled by residential heat balance (RHB). RLF is required to calculate a cooling/heating load depending upon the indoor/outdoor temperature. The transparency, functionality of indoor/outdoor temperatures and simplicity of RLF makes it suitable for modeling. Furthermore, the parameters of the model can be calculated differently from room to room and are appropriate for variable air volume (VAV) factor. Nowadays, a VAV system is universally accepted as means of achieving both energy efficiency and comfortable building environment. In this research work, a pre-cooling coil is added to humidify the incoming air, which controls the humidity more efficiently inside conditioned space. The model presented here is verified with both theoretical and numerical methods.     

Indoor cooling/heating load analysis based on coupled simulation of convection,radiation and HVAC control

A computational fluid dynamics (CFD) simulation for analyzing indoor cooling/heating load is presented in this study. It is coupled with a radiative heat transfer simulation and heating, ventilating, and air-conditioning (HVAC) controlling system in a room. This new method feeds back the outputs of the HVAC system control to the input boundary conditions of the CFD, and this method includes a human model to evaluate the thermal environment. It would be used to analyze the heating/cooling loads of different HVAC systems under the condition of the same human thermal sensation (e.g. PMV, operative temperature, etc.) even though the temperature and air-velocity distribution in the room are different from each other.To examine the performance of the new method, a cooling load and a thermal environment within a semi-enclosed space, which opens into an atrium space, is analyzed under the steady-state conditions during the summer season. This method is able to analyze the indoor cooling load with changes of target thermal environments of a room and/or changing clothing conditions of occupants considering the temperature and air-velocity distribution in the room. In this paper, two types of HVAC system are compared; i.e. radiation-panel system and all-air cooling system. The radiation-panel cooling system is found to be more energy efficient for cooling the semi-enclosed space. Changes of the level of thermal environment reduce cooling load effectively in case of the all-air cooling system while the radiation-panel system does not reduce cooling load even though the targeted thermal condition is relaxed. Energy saving effect is expected by easing the clothing conditions of occupants. In this study, the reducing effect of cooling load is quantitatively evaluated with clothing conditions also.     

Predicting natural ventilation flows in whole buildings. Part 2: The Esherick House

In an effort to address residential energy needs and find ways to improve energy utilization of homes, heating and passive cooling was examined by using computational fluid dynamics. The Esherick House, whose spatial composition was intentionally designed for natural ventilation, was modeled and simulated for different environmental conditions. The simulations were used to examine spatial layout effects on the ability of natural ventilation to maintain a comfortable thermal environment. Results for the heating and passive cooling scenarios compared the effects of the temperature and velocity fields when the environmental conditions were changed. For a typical summer day, it was found that the entire house cooled quickly when a breeze was modeled to enter a few windows, both with and without solar heating. The heating scenario for a winter day modeled the two fireplaces, one located on the first floor in the great room and one on the second floor in the master bedroom. It was found that the temperatures on the second floor were too high and too low on the first floor for acceptable levels of thermal comfort.     

Revisiting thermal comfort models in Iranian classrooms during the warm season

The validity of existing thermal comfort models is examined for upper primary school children in classroom settings. This is of importance to enhance productivity in the learning environment and to improve the control of artificial heating and cooling, including the potential for energy savings. To examine the thermal perceptions of children aged 10–12 years in non-air-conditioned classrooms, three sets of field experiments were conducted in boys’ and girls’ primary schools in Shiraz, Iran. These were undertaken during regular class sessions covering cool and warm conditions of the school year, polling responses from 1605 students. This paper illustrates the overall methods and reports the results of the warm season field survey (N?=?811). This investigation suggests that predicted mean vote-predicted percentage of dissatisfied (PMV/PPD) underestimates children's actual thermal sensation and percentage dissatisfied in the investigated classrooms. The analysis shows that sampled children may be slightly less sensitive to indoor temperature change than adults. The upper acceptable temperature derived from children's responses corresponding to mean thermal sensations of +0.85 is 26.5°C, which is about 1°C lower than the ASHRAE upper 80% acceptability limit. This implies that sampled children feel comfortable at lower temperatures than predicted by the ASHRAE Adaptive model during the warm season.     

Thermal comfort of rural residents in a hot–humid area

ABSTRACT

The thermal comfort of rural residents in China is studied to improve their living conditions and safeguard agricultural development. The present study recruited 30 healthy young people (50% male and 50% female) from rural areas of the hot and humid region of China and exposed them to a wide range of temperatures (20–32°C) and humidities (50% and 70%) in a climate chamber. Both the psychological and physiological responses were observed. The thermal neutral standard effective temperature (SET) was determined to be 26.8°C and the 90% thermal acceptable SET range was 22.9–30.7°C. Mean skin temperature and skin wetness were found to be good predictors for thermal comfort in the neutral-cool and neutral-warm conditions, respectively. When compared with the previous results from similar studies of urban participants living in naturally ventilated buildings, a significant divergence is found. Rural participants reported the same thermal sensation but felt more comfortable and acceptable under identical cool or warm conditions. Rural participants had the same neutral temperature, but a much wider acceptable temperature range. The reason for these differences between rural and urban people may be attributed to differences in local culture, expectations and environmental cognition.     

Investigation of transient thermal environments

Human beings are commonly exposed to transient thermal environments in their daily life. But most of the studies on indoor thermal environment have been conducted under steady-state conditions. The aim of this paper is to summarize the investigation on human responses to transient thermal environment carried out by the indoor environment group at Tsinghua University, and to predict the possibility of using their research findings in practice. Human responses to transients have some special characteristics, which could be beneficial to environmental control. Air movement is especially effective at realizing a transient thermal environment, offsetting higher air temperature or operative temperature in warm climates. Based on the analysis of measured data, the characteristics of air movement outdoors are different from artificial air supply such as fans or air supply outlets, in the probability distribution of their velocities, turbulence intensity, and power spectrum. Based on subjective experiments, it is evident that artificial air movement, which is mainly simulated with outdoor airflow characteristics, has the highest occupant preference in warm conditions. Experimentally simulated air movement improves not only whole-body cooling, but also local cooling as from personal air supplies. Finally, it is important that introducing simulated natural air movement into the space in warm or hot conditions could significantly decrease the building's energy consumption.