A Comparative Study Of Discomfort Caused By Indoor Air Pollution,Thermal Load And Noisec

The relative importance of sensory air pollution, thermal load and noise was studied under controlled conditions in two identical environmental chambers. In one chamber subjects were exposed to various levels of either thermal load or poor indoor air quality. For each condition tested in this chamber, the subjects were exposed to a number of noise levels in an adjacent chamber with neutral thermal conditions and good indoor air quality in order to determine a noise level causing the same degree of discomfort. A total of 68 comparisons of the conditions in the two chambers were made by the same group of 16 subjects after one-minute exposure in each chamber. In the operative temperature range of 23–29°C, a 1°C change in operative temperature was found to have the same effect on human comfort as a change in perceived air quality of 2.4 decipol or a change in noise level of 3.9 dB. For levels of perceived air quality up to 10 decipol, a 1 -decipol change in perceived air quality had the same effect on human comfort as a change in noise level of 1.2 dB. A relationship between traffic noise level and percentage dissatisfied was established     

水幕空调的应用分析

某五星级酒店利用人造瀑布形成的水池来改善室内热环境,分析比较了在热压通风、夜间风机运行、空调运行三种工况下水池中采用10～16℃不同温度的冷水改善室内热环境的效果。结果显示,利用风机和水池的低温冷水可以使酒店部分区域在不开启空调的情况下满足人体热舒适要求。建议设置水池温度为10℃,白天运行空调,夜间部分区域运行风机,部分区域运行空调,可以达到一定的节能效果。     

A study of occupant cooling by personally controlled air movement

This study addresses the effectiveness of air movement cooling, an alternative to compressor-based cooling of the air itself. Subjects in an environmental chamber were exposed to a range of warm temperatures and allowed to adjust air movement to suit their individual preferences, while answering a series of questions about their comfort. Air movement was from the subject's side, in two modes of turbulent flow. The air speeds chosen by the subjects, and their subjective responses, are evaluated in the context of existing comfort standards and prediction techniques. Choosing air speeds up to 1.4 m/s, over 80% of subjects at 1.2 met were comfortable up to 29 °C, and at 1.0 met up to 31 °C. The cooling effectiveness was significantly affected by the nature of the turbulence. A zone is proposed within which personally controlled air movement provides a likely alternative to mechanical air conditioning.     

The effect of structures on indoor humidity--possibility to improve comfort and perceived air quality

The research presented in this paper shows that moisture transfer between indoor air and hygroscopic building structures can generally improve indoor humidity conditions. This is important because the literature shows that indoor humidity has a significant effect on occupant comfort, perceived air quality (PAQ), occupant health, building durability, material emissions, and energy consumption. Therefore, it appears possible to improve the quality of life of occupants when appropriately applying hygroscopic wood-based materials. The paper concentrates on the numerical investigation of a bedroom in a wooden building located in four European countries (Finland, Belgium, Germany, and Italy). The results show that moisture transfer between indoor air and the hygroscopic structure significantly reduces the peak indoor humidity. Based on correlations from the literature, which quantify the effect of temperature and humidity on comfort and PAQ for sedentary adults, hygroscopic structures can improve indoor comfort and air quality. In all the investigated climates, it is possible to improve the indoor conditions such that, as many as 10 more people of 100 are satisfied with the thermal comfort conditions (warm respiratory comfort) at the end of occupation. Similarly, the percent dissatisfied with PAQ can be 25% lower in the morning when permeable and hygroscopic structures are applied.     

Reflections on the history of indoor air science,focusing on the last 50 years

The scientific articles and Indoor Air conference publications of the indoor air sciences (IAS) during the last 50 years are summarized. In total 7524 presentations, from 79 countries, have been made at Indoor Air conferences held between 1978 (49 presentations) and 2014 (1049 presentations). In the Web of Science, 26 992 articles on indoor air research (with the word “indoor” as a search term) have been found (as of 1 Jan 2016) of which 70% were published during the last 10 years. The modern scientific history started in the 1970s with a question: “did indoor air pose a threat to health as did outdoor air?” Soon it was recognized that indoor air is more important, from a health point of view, than outdoor air. Topics of concern were first radon, environmental tobacco smoke, and lung cancer, followed by volatile organic compounds, formaldehyde and sick building syndrome, house dust‐mites, asthma and allergies, Legionnaires disease, and other airborne infections. Later emerged dampness/mold‐associated allergies and today's concern with “modern exposures‐modern diseases.” Ventilation, thermal comfort, indoor air chemistry, semi‐volatile organic compounds, building simulation by computational fluid dynamics, and fine particulate matter are common topics today. From their beginning in Denmark and Sweden, then in the USA, the indoor air sciences now show increasing activity in East and Southeast Asia.     

Optimization of indoor air temperature set-point for centralized air-conditioned spaces in subtropical climates

Current Building Management System (BMS) does not integrate well with real-time occupant response. In order to fine-tune the system to meet individual demands and to maximize the occupant acceptance of indoor thermal environment, a new notion of Bayesian control algorithm was developed in this study. Control parameters of a weighting function for air temperature control (namely, the control temperature constant k_T and the probable acceptance of the air temperature set-point λ) and two prior distribution functions of air temperature set-point, namely the uniform prior and the expert's prior, were examined. Optimum air temperature set-points of air-conditioning systems obtained from certain Hong Kong offices were then used to demonstrate the applicability of the new algorithm for controlling an example air temperature set-point ranged between 0.2 °C and 1 °C. This algorithm would be useful for adaptive thermal comfort control in a large, post-occupied air-conditioned space.     

Perceived air quality and cognitive performance decrease at moderately raised indoor temperatures even when clothed for comfort

This study investigated whether adjusting clothing to remain in neutral thermal comfort at moderately elevated temperature is capable of avoiding negative effects on perceived acute subclinical health symptoms, comfort, and cognitive performance. Two temperatures were examined: 23°C and 27°C. Twelve subjects were able to remain thermally comfortable at both temperatures by adjusting their clothing. They rated the physical environment, their comfort, the intensity of acute subclinical health symptoms, and their mental load, and they performed a number of cognitive tasks. Their physiological reactions were monitored. Their performance of several tasks was significantly worse at 27°C, and they reported increased mental load at this temperature. Skin temperature and humidity and respiration rate were higher, while blood oxygen saturation (SpO2) and pNN50 were lower at this temperature, the latter indicating increased stress. It is inferred that the observed physiological responses were mainly responsible for the negative effects on performance, as the subjects did not indicate any increased intensity of acute subclinical health symptoms although perceived air quality was worse at the higher temperature. The present results suggest that moderately elevated temperatures should be avoided even if thermal comfort can be achieved, as it may lead to reduced performance.     

Decreased humidity improves cognitive performance at extreme high indoor temperature

In this study, we examined the cognitive performance of subtropically acclimatized subjects at an extreme high indoor temperature and the effect of decreased humidity on the cognitive performance at the high temperature. Forty-eight healthy subjects experienced the three exposure conditions: 26°C/relative humidity (RH) 70%, 39°C/RH50%, and 39°C/RH70% in a climate chamber. During 140-minute-long exposures to each thermal condition, they were required to perform cognitive tests that assess the perception, spatial orientation, concentration, memory, and thinking abilities. Meanwhile, their heart rate, core temperature, skin temperature, blood pressure, and body weight were measured and subjective responses, that is, thermal comfort, perceived air quality, and acute health symptoms were investigated. At the relative humidity of 70%, increasing indoor temperature from 26°C to 39°C caused a significant decrease in the accuracy of these cognitive tests. However, when the relative humidity decreased from 70% to 50% at 39°C, the accuracy of the cognitive tests increased significantly. Accordingly, the physiological and subjective responses of the subjects changed significantly with the changes in indoor temperature and humidity, which provided a basis to the variation in the cognitive performance. These results indicated that decreasing indoor humidity at extreme high temperature could improve the impaired cognitive performance.     

The effect of slightly warm temperature on work performance and comfort in open‐plan offices – a laboratory study

The aim of the study was to determine the effect of a temperature of 29°C on performance in tasks involving different cognitive demands and to assess the effect on perceived performance, subjective workload, thermal comfort, perceived working conditions, cognitive fatigue, and somatic symptoms in a laboratory with realistic office environment. A comparison was made with a temperature of 23°C. Performance was measured on the basis of six different tasks that reflect different stages of cognitive performance. Thirty‐three students participated in the experiment. The exposure time was 3.5 h in both thermal conditions. Performance was negatively affected by slightly warm temperature in the N‐back working memory task. Temperature had no effect on performance in other tasks focusing on psychomotor, working memory, attention, or long‐term memory capabilities. Temperature had no effect on perceived performance. However, slightly warm temperature caused concentration difficulties. Throat symptoms were found to increase over time at 29°C, but no temporal change was seen at 23°C. No effect of temperature on other symptoms was found. As expected, the differences in thermal comfort were significant. Women perceived a temperature of 23°C colder than men.     

Energy conservative building air conditioning system controlled and optimized using fuzzy-genetic algorithm

In this work, the combined effect of the energy conservative variable refrigerant volume (VRV) system and the variable air volume (VAV) system was experimentally investigated using genetic fuzzy optimization method that yielded better thermal comfort, indoor air quality (IAQ) requirements without compromising on the energy savings potential. The proposed system was tested using the demand controlled ventilation (DCV) combined with the economizer cycle ventilation (ECV) techniques and examined for a year-round building air conditioning (A/C) application. The supply air temperature (SAT) set points were varied under three distinct strategies and the optimal solutions obtained for the fuzzy systems designed resulted in an enhanced energy conservative potential. The test results of the proposed system were compared with the conventional fan coil A/C system. Based on the three strategies of the supply air temperature, the proposed system yielded an improved per day energy savings potential of 54% in summer and 61% in winter design conditions. Furthermore, for the strategies considered the proposed system achieved an annual energy conservative potential of 36% and exhibited more possible ways to achieve thermal comfort, IAQ and energy conservation.     

Effects of increased humidity on physiological responses,thermal comfort,perceived air quality,and Sick Building Syndrome symptoms at elevated indoor temperatures for subjects in a hot-humid climate

Recently, studies suggest that the average indoor temperature is typically >30°C and that the maximum temperature can reach 37.5°C in hot-humid areas. However, the effects caused by increasing the humidity at high indoor temperatures are not clear. In this study, twelve female and twelve male subjects were exposed to different operative temperature (26.6, 30.6, and 37.4°C) and relative humidity (50% and 70%) in a climate chamber. Data concerning thermal sensation, perceived air quality, and Sick Building Syndrome (SBS) were collected during 190-min-long exposure to each thermal condition. Heart rate, respiration rate, respiratory ventilation rate, mean skin temperature, and eardrum temperature were measured. It was found that increasing the relative humidity from 50% to 70% at 26 and 30°C had no significant effects on the physiological responses, thermal comfort, perceived air quality, or SBS symptoms of the subjects. However, when the temperature was elevated to 37°C, the heart rate, respiration rate, respiratory ventilation rate, mean skin temperature, and eardrum temperature increased significantly as a result of the increase in the relative humidity from 50% to 70%. The subjects felt hotter and more uncomfortable, and they found indoor air quality was more difficult to accept. The subjects are acclimatized to hot environments and more tolerant to heat. Therefore, the results are applicable to the acclimated people living in hot-humid climate.     

空调大温差研究(2):空调大温差送风系统设计方法

提出用定露点法计算常规空调大温差系统,逐项介绍了设计步骤;认为定露点法不但可以较准确地控制室内设计参数,掌握室内实际空气状态,而且可以利用计算机,使大温差送风的设计计算更加简捷、直观。强调采用定露点法计算时,单个系统不宜过大,热湿比不同的房间宜采用不同的空调系统,空调机组风量或风压较大时,宜采用风机压出式布置。     

Multivariable control of indoor air temperature and humidity in a direct expansion (DX) air conditioning (A/C) system

Controlling indoor humidity at an appropriate level is very important since this affects occupants' thermal comfort and indoor air quality (IAQ). The paper presents an investigation on developing a multi-input multi-output (MIMO) control strategy for simultaneously controlling the indoor air temperature and humidity by varying the speeds of both compressor and supply fan in an experimental DX A/C system. The MIMO-based controller was designed based on the linearized dynamic model of the experimental DX A/C system. The Linear Quadratic Gaussian (LQG) technique was used in designing the MIMO-based controller. The controllability tests with respect to both the disturbance rejection capability and the command following capability were carried out to assess the control performance of MIMO controller. The results of disturbance rejection capability test showed that the MIMO control strategy can effectively maintain the indoor air temperature and humidity to their respective settings after an unmeasured heat load disturbance was imposed by simultaneously varying speeds of both the compressor and the supply fan of the DX A/C system. Furthermore, in the command following capability test for indoor air temperature, the test results showed that the indoor air temperature can be controlled to its new setting while indoor humidity remained unchanged. Similar test results were also observed in the command following capability test for indoor humidity. Therefore, the MIMO controller developed can effectively control indoor air temperature and humidity simultaneously by varying compressor speed and supply fan speed of the DX A/C system. Compared to the previous related studies using conventional on–off control method or single-input single-output (SISO) control strategy, which can only effectively control either air temperature or relative humidity, the MIMO controller can simultaneously control the indoor air temperature and humidity with adequate control sensitivity and accuracy. The application of MIMO control strategy developed can be extended to other HVAC systems in the future to improve their operating performance and energy efficiency.     

The impact of temperature on mean local air age and thermal comfort in a stratum ventilated office

The influence of the supply air temperature on the mean local air age and thermal comfort of a typical individual office under stratum ventilation is investigated by a numerical method, which is validated by an experiment carried out by the authors. The results show that for an office, when the supply air temperature is increased from 19 °C to 21 °C, the corresponding mean occupied zone temperature rises from 24.5 °C to 26.5 °C. The inhaled air quality for the occupant is improved when supply air temperature rises from 19 °C to 21 °C. Also, the thermal comfort indices (predicted mean vote or PMV, predicted percentage of dissatisfied or PPD and predicted dissatisfied or PD) fulfill the requirements of ISO 7730 and CR 175 1998. For summer cooling operation, stratum ventilation may offer a feasible solution to elevated indoor temperatures, which are recommended by several governments in East Asia.     

办公楼地板送风系统应用与研究现状

就地板送风的系统特点、室内气流分布、热舒适与室内空气品质、送风静压层的性能、室内冷负荷和风机能耗等方面介绍了国内外的研究现状。指出有待于进一步研究的一些方面。     

一次回风送风再热与新风预冷互补的节能研究

对于一次回风空调系统,夏季工况,当空调区湿负荷较大时,采用露点送风只能保证设定温度,而湿度将会偏大,影响人体热舒适;若增加再热,又会出现冷热抵消现象。提出了利用室外新风热量再热来改善室内热舒适状况的方案。通过工程案例计算分析,结果表明:利用新风再热可减少再热送风系统6%~15%的能耗,认为送风再热与新风预冷互补措施能在一定程度上降低空调能耗,提高室内热舒适。     

Physiological and psychological reactions of sub‐tropically acclimatized subjects exposed to different indoor temperatures at a relative humidity of 70%

Thermal comfort, self‐reported acute health symptoms, cognitive performance, and physiological reactions were examined at four temperatures (26, 30, 33, and 37°C) at a relative humidity of 70%. Thirty‐two sub‐tropically acclimatized subjects experienced each condition for 175 minute, in balanced order, in a climatic chamber. The perception of heat gradually increased with increasing temperature, but the subjects felt hot only at 37°C. The temperature of 33°C was on average rated as acceptable and only just uncomfortable. The acceptability of air quality decreased linearly with increasing temperature. The intensity of acute health symptoms reported by the subjects increased with increasing temperature, but it was no more than moderate even at the highest temperature; dryness of skin and eye were alleviated. The eardrum temperature, skin temperature and moisture, heart rate, end‐tidal carbon dioxide, and weight loss increased significantly with increasing temperature, whereas the percentage of adjacent heart inter‐beat intervals differing by >50 ms decreased significantly. These results suggest that the perceived heat, self‐reported symptoms, and physiological reactions occurred concurrently. They show additionally that acclimatization to heat may shift the boundary of thermal discomfort to a higher temperature. The role of psychological adaptation and of the contextual aspects of this process still requires clarification in future experiments.     

Associations of indoor carbon dioxide concentrations,air temperature,and humidity with perceived air quality and sick building syndrome symptoms in Chinese homes

The indoor environment influences occupants’ health. From March 1, 2018, to February 28, 2019, we continuously monitored indoor temperature (T), relative humidity (RH), and CO₂ concentration in bedrooms via an online system in 165 residences that covered all five climate zones of China. Meanwhile, we asked one specific occupant in each home to complete questionnaires about perceived air quality and sick building syndrome (SBS) symptoms at the end of each month. Higher CO₂ concentration was significantly associated with a higher percentage of perceived stuffy odor and skin SBS symptoms. Higher relative humidity was associated with higher percentage of perceived moldy odor and humid air, while lower RH was associated with a higher percentage of perceived dry air. Occupants who lived in residences with high RH were less likely to have mucosal and skin SBS symptoms (adjusted odds ratio (AOR): 0.73–0.78). However, the benefit of high humidity for perceived dry air and skin dryness symptoms is weaker if there is a high CO₂ concentration level.     

冬季集中供暖房间和空调房间热环境调查分析

定量比较了集中供暖房间和使用家用热泵空调房间的热环境测试数据，并通过分析其对人体舒适性的影响，指出采用空调时应充分考虑送热风时的气流组织，避免吹风感；集中供暖房间的温度设置应比空调的低，可同时满足舒适感、节能和空气品质的要求。     

舒适性空调系统的临界净化效率与最小换气次数

指出舒适性空调应同时满足健康和舒适要求，从室内空气中有害物质量平衡方程导出舒适性空调系统临界净化效率和最小换气次数，认为依靠增加新风量来改善室内空气品质的作用是有限的，在满足室内要求的基本新风量后，提高各级空气净化器效率才有助于改善空气品质，据作者的观点设计空调系统其方法将有别于传统设计。