Models of human thermoregulation and the prediction of local and overall thermal sensations

This study aims at comparing the predictions of skin temperature from different models of human thermoregulation and investigating the currently available methods for the prediction of the local and overall thermal sensations. In this paper, the Fiala model, the University of California, Berkeley (UCB) thermoregulation model and a multi-segmental (MS) Pierce model were tested against recently measured data from the literature. The local and overall thermal sensations were predicted for different room conditions, obtained from a recent experimental study, using the UCB comfort model coupled with the MS-Pierce model. The overall thermal sensation was further predicted using three other models. The predictions were then compared with the subjective votes obtained from that study. The equivalent temperature approach was also investigated based on the same experimental study. The results show comparisons of the predicted skin temperature by the thermoregulation models, under steady state and dynamic conditions, with the measured data as well as the predictions of the thermal sensations from the different models.     

我国湿热地区人群基础热舒适反应研究(2):研究结果的对比分析

基于我国湿热地区人群的气候室实验结果,从心理热反应、生理热反应和生理-心理关系等多方面对国内外研究结果进行了系统对比与分析,发现现行国际标准不适用于我国湿热地区,生理热习服和心理热适应是其重要原因。考虑热习服和热适应的影响作用,建立我国湿热地区人群的生理热调节模型与心理-生理模型,是掌握其基础热舒适反应规律、合理制定热环境标准的重要途径。     

A comparison of the thermal adaptability of people accustomed to air-conditioned environments and naturally ventilated environments

It has been reported previously that people who are acclimated to naturally ventilated (NV) environments respond to hot and warm environments differently than people who are acclimated to air-conditioned (AC) environments. However, it is not clear whether physiological acclimatization contributes to this discrepancy. To study whether living and working in NV or AC environments for long periods of time can lead to different types of physiological acclimatization, and whether physiological acclimatization has an important influence on people's responses of thermal comfort, measurements of physiological reactions (including skin temperature, sweat rate, heart rate variability, and heat stress protein 70) and thermal comfort responses were conducted in a 'heat shock' environment (climate chamber) with 20 people (10 in the NV group and 10 in the AC group). The results showed that the NV group had a significantly stronger capacity for physiological regulation to the heat shock than the AC group. In other words, the NV group did not feel as hot and uncomfortable as the AC group did. These results strongly indicate that living and working in indoor thermal environments for long periods of time affects people's physiological acclimatization. Also, it appears that long-term exposure to stable AC environments may weaken people's thermal adaptability. PRACTICAL IMPLICATIONS: This study examined the psychological and physiological differences of thermal adaptability of people used to air-conditioned environments and naturally ventilated environments. The results suggested that long-term exposure to stable air-conditioned environments may weaken people's thermal adaptability. Therefore, it might be advantageous for people to spend less time in static air-conditioned environments; this is not only because of its possible deleterious impact on people's physiological adaptability, but also because the air-conditioners' high-energy consumption will contribute to the effects of global warming.     

A combined low temperature water heating system consisting of radiators and floor heating

Space heating load is decreasing in modern Finnish apartments due to lower U-values of the construction, tight envelopes and heat recovery from exhaust ventilation air. This makes it possible to develop a new combined low temperature water heating system with nominal supply/return water temperatures of 45 °C/35 °C. Such a system includes radiators in rooms and floor heating in bathrooms.In this study, the performance of an apartment building is determined by using dynamic simulation. The simulation results for the combined low temperature water heating system are compared with those for three conventional radiator and floor heating systems. The results show that the combined low temperature water heating system performs well and is able to maintain the zones within the required temperature levels. The thermal comfort analysis indicates that the drifts and ramps in operative temperature using the four studied heating systems are within the limits of Ashrae Standard 55-2004.Temperature measurements in a test room are carried out to find the vertical difference of air temperature using two methods: radiator heating and floor heating. These measurements indicate that there is only a small vertical temperature difference that would not produce any significant thermal discomfort.     

Flow generated by a thermal plume in a cooled-ceiling system

The transient and steady states of the flow generated by a heat source inside a closed room provided with a cooled-ceiling system at constant temperature are experimentally studied. During the transient regime the plume generated by the source interacts with the ambient fluid and, after it reaches the top contour, spreads under the latter giving place to the formation of a horizontal thermal front that eventually descends affecting the whole room. It is found that the formation and velocity of the descending front are determined by the filling-box model in an insulated space but with a smaller temperature difference between both sides of the front. The steady state is established when the heat supplied by the source is completely absorbed by the ceiling allowing a convective process to take place characterized by a turbulent flow in the major part of the room and by a thermal boundary layer developed below the ceiling, where vortexes and little plumes form, the detection of which is allowed by the application of synthetic schlieren technique. Analogies with the results obtained in the classical Rayleigh-Benard experiments allow an insight of the mechanisms of heat transfer in order to improve the indoor comfort in buildings under similar conditions to those discussed here.     

基于实际建筑环境的人体热适应研究（2）

对北京的5户集中供暖住户和5户使用壁挂炉的住宅进行了持续一个供暖季的现场调查,测量了室内热环境参数,并调查了居民的热舒适状况。结果显示,使用壁挂炉的住宅室内温度比较稳定,平均温度较低,中性温度为18．6℃;集中供暖住户中性温度为22．0℃;在相同的室内温度下,壁挂炉用户的热感觉投票值较高,对室内环境的接受度也较高。对独立调控对热适应的影响机理和夏热冬冷地区住宅供暖问题进行了讨论。     

地板辐射供暖的节能效应分析

利用热舒适理论讨论了地板辐射供暖方式与其他方式在房间,内人体热舒适方面的差异,并通过对其综合节能效果的定量估计,建议在采用地板辐射供暖的节能建筑中相应应降低室内供暖温度。     

Improved indoor thermal comfort during defrost with a novel reverse-cycle defrosting method for air source heat pumps

When an air-source heat pump (ASHP) unit is used for space heating at a low ambient temperature in winter, frost may be formed on its outdoor coil surface. Frosting affects its operational performance and energy efficiency, and therefore periodic defrosting is necessary. Currently, the most widely used standard defrosting method for ASHP units is reverse-cycle defrost. During a standard reverse-cycle defrosting process, the indoor coil in an ASHP unit actually acts as an evaporator, therefore, no heating is provided and hence indoor air temperature in a heated space can drop. Furthermore, a longer period of time is needed before space heating can become available immediately after the completion of defrosting. Consequently, occupants’ thermal comfort may be adversely affected. To improve the indoor thermal comfort for occupants during reverse-cycle defrosting, a novel thermal energy storage (TES) based reverse-cycle defrosting method has been developed and the improvement to occupants’ thermal comfort experimentally evaluated and is reported in this paper. Comparative experiments using both the novel TES based reverse-cycle defrosting method and the standard reverse-cycle defrosting method were carried out. Experimental results and the evaluated indoor thermal comfort indexes clearly suggested that when compared to the use of standard reverse-cycle defrost, the use of the novel reverse-cycle defrosting method can help achieve improved indoor thermal comfort, with a shorter defrosting period and a higher indoor supply air temperature during defrosting.     

An evaluation model for indoor environmental quality (IEQ) acceptance in residential buildings

The indoor environmental quality (IEQ) in residential buildings is examined from the prospect of an occupant's acceptance in four aspects: thermal comfort, indoor air quality, noise level and illumination level. Based on the evaluations by 125 occupants living in 32 typical residential apartments in Hong Kong, this study proposes empirical expressions to approximate the overall IEQ acceptance with respect to four contributors, namely operative temperature, carbon dioxide concentration, equivalent noise level and illumination level, via a multivariate logistic regression model. A range of IEQ acceptances for regular residential conditions is determined and the dependence of the predicted overall IEQ acceptance on the variations of the contributors is discussed. The proposed overall IEQ acceptance can be used as a quantitative assessment criterion for similar residential environments where an occupant's evaluation is expected.     

Experimental investigation of thermal and ventilation performances of stratum ventilation

Stratum ventilation has been proposed to cope for elevated indoor temperatures. Air speed, temperature and CO₂ concentration of a stratum ventilated office are investigated experimentally. The data obtained under well defined conditions and therefore can be used for validating numerical models. Thermal comfort conditions and ventilation efficiency are studied based on the experimental results of four experimental cases. Thermal comfort indices, i.e. PMV, PPD and PD are calculated from measured data. The values of these indices are found to satisfy the requirements of ISO 7730, CR 1752-1998 and ASHRAE 55-2010. In terms of thermal comfort, the two cases with supply air temperature of 21 °C are found to perform better compared with the two cases with supply air temperature of 19 °C. For all the cases, the ventilation effectiveness is close to 1.5. This ventilation method could therefore be expected to provide indoor air quality in an efficient way.     

Cross-city comparison of indoor air temperatures in air-conditioned spaces

Field measurements were collected through physical measurements and observations in the cities of Seoul, Korea; Eugene and Portland, Oregon; and Yokohama, Japan, during the fall, winter, and summer seasons from 2005 to 2006. A total of 1733 data sets were collected (Seoul - 713; Oregon - 807; Yokohama - 213) in variety of multi-use buildings with the goal of examining operative temperatures and conditions encountered during everyday life. Of the four cities measured, winter and autumn indoor operative temperatures were highest in Seoul and lowest in Yokohama when normalized to outdoor conditions. In contrast, summer indoor operative temperatures were highest in Yokohama and lowest in Oregon. Clothing levels changed seasonally, and differences were observed between 'long-term occupants', 'residents', and 'transients.'     

Thermal responses to different residential environments in Harbin

In China, adding space heating in residential buildings is normally scheduled at the end of October each year, with heat supplied by district heating systems. This paper describes a field study of thermal comfort conducted in Harbin during the winter from 2009 to 2010 before and after the space heating is added. The aim is to study human responses to thermal conditions in the two periods in cold climates. 23 buildings in six communities were investigated. 199 occupants from 135 families and 174 occupants from 104 families participated in the two surveys during the two periods, respectively. The neutral air temperature before adding the space heating is 25.1 °C, while during the space heating, it is 20.4 °C. The clothing insulation is 0.77 clo and 0.88 clo, respectively. If they were 0.88 clo instead of 0.77 clo before adding the space heating, the neutral air temperature should be 21.1 °C. Before and during space heating, more than 80% felt acceptable at the air temperature range between 17.5–24.0 °C and 19.0–26.5 °C for the two periods. The residents’ physiological acclimation may contribute to the differences. The preferred temperature is within the range of 23.0–24.0 °C and 21.5–24.0 °C, respectively. The preferred humidity is 47.7% and 40.5% during the two surveys. People felt cold generally before heating, while they felt comfortable at the same temperature range during space heating period. People often felt dry during heating when the relative humidity is lower than 30%, while they felt comfortable at the same relative humidity before heating.     

Design of an individually controlled system for an optimal thermal microenvironment

Individually controlled microenvironment has potential to satisfy more occupants in a space compared to a total volume uniform environment typically used at present. The performance of an individually controlled system comprising a convection-heated chair, an under-desk radiant heating panel, a floor radiant heating panel, an under-desk air terminal device supplying cool air, and a desk-mounted personalized ventilation as used and identified by 48 human subjects was studied using a thermal manikin at room temperatures of 20 °C, 22 °C and 26 °C. At a room air temperature of 20 °C, the maximum whole-body heating effect of the heating chair, the under-desk heating panel, and the floor heating panel corresponded to the effect of a room temperature increase of 5.2 °C, 2.8 °C, and 2.1 °C, respectively. The effect was 5.9 °C for the combination of the three heating options. The higher the room air temperature, the lower the heating effect of each heating option or heating combination. The maximum whole-body cooling effect of the tested system was only −0.8 °C at a room air temperature of 26 °C. The heating and cooling capacity of the individually controlled system were identified. These results, analyzed together with results obtained from human subject experiments, reveal that both the heating and the cooling capacity of the individually controlled system need to be increased in order to satisfy most occupants in practice.     

Thermal environment characterisation of a glass-covered semi-outdoor space subjected to natural climate mitigation

The human thermal sensation inside a semi-outdoor space enclosed by a semi-transparent pitched roof, located in Parma, north of Italy, is compared with the outdoor sensation under the same climate conditions. The assessment of the semi-outdoor setting was performed using the Physiological Effective Temperature (PET) thermal sensation index. With the aim of mitigating the semi-outdoor climate, some natural means were considered at the design stage, namely, the solar radiation absorptivity of the glass sheet roof, natural airflow, space thermal capacity and roof evaporative cooling. The dynamic thermal simulation of the semi-outdoor space was performed for three representative weeks of the months of January, March and July by accounting for the actual climate of the location. The results show that the semi-transparent roof can improve the human thermal sensation inside the semi-outdoor space with respect to that of the outdoor space. The results also demonstrate the effect of each design parameter on the PET index.     

大连住宅冬季热环境及热适应现场调研

2011～2012年冬季对大连住宅室内热环境、居民热感觉和热适应措施进行了现场测试,并收集了36户共102份热感觉主观问卷.结果表明大连居民对热环境的接受度是93.2％,热中性温度是20.44℃,热期望温度是20.81℃,80％可接受温度区间是17.38～24.28℃.57％的受试者认为室内湿度干燥,需要采取加湿的措施.     

西安某小区供热系统间歇运行供暖房间热环境分析

对西安市某小区集中供热系统间歇调节运行的室内热环境进行了动态实测分析,得出供水温度的变化规律及供暖房间热舒适的现况.指出只要适当调整供热时间就能明显地改善热舒适条件.     

A comparative analysis of urban and rural residential thermal comfort under natural ventilation environment

The paper presents a field study of occupants’ thermal comfort and residential thermal environment conducted in an urban and a rural area in Hunan province, which is located in central southern China. The study was performed during the cold winter 2006. Twenty-eight naturally ventilated urban residences and 30 also naturally ventilated rural residences were investigated. A comparative analysis was performed on results from urban and rural residences. The mean thermal sensation vote of rural residences is approximately 0.4 higher than that of urban residences at the same operative temperature. Thermal sensation votes calculated by Fanger’s PMV model did not agree with these obtained directly from the questionnaire data. The neutral operative temperature of urban and rural residences is 14.0 and 11.5 °C, respectively. Percentage of acceptable votes of rural occupants is higher than that of urban occupants at the same operative temperature. It suggests that rural occupants may have higher cold tolerance than urban occupants for their physiological acclimatization, or have relative lower thermal expectation than urban occupants because of few air-conditioners used in the rural area. The research will be instrumental to researchers to formulate thermal standards for naturally ventilated buildings in rural areas.