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%.     

Thermal sensation and comfort with different task conditioning systems

Subjective experiments with task conditioning systems, 3DU⁺, PEM, TU, and RCU were conducted to investigate the effect of three different types of Task air-conditioning systems on thermal comfort in a climate chamber. The chamber was conditioned at 28 °C/50%RH with task systems and 26 °C/50%RH without them. Under the condition with the task conditioning systems, the average rating of comfort sensation was between comfortable (0) and slightly uncomfortable (−1). For males it was between −0.5 and −0.7 and for females between −0.3 and −0.4. This was equal to or even better than that in condition without task system. It was found that these systems were effective in providing thermal comfort. The parts to which subjects wanted to diffuse air were different for each system. However, the individual control of task conditioning system contributed to create the preferred environment.     

A study on the thermal comfort in sleeping environments in the subtropics—Developing a thermal comfort model for sleeping environments

In the subtropics, air conditioning serves to maintain an appropriate indoor thermal environment not only in workplaces during daytime, but also at night for sleeping in bedrooms in residences or guestrooms in hotels. However, current practices in air conditioning, as well as the thermal comfort theories on which these practices are based, are primarily concerned with situations in which people are awake in workplaces at daytime. Therefore, these may not be directly applicable to air conditioning for sleeping environments. This paper, reports on a theoretical study on a thermal comfort model in sleeping environments. A comfort equation applicable to sleeping thermal environments was derived by introducing appropriate modifications to Fanger's comfort model. Comfort charts which were established by solving the comfort equation, and can be used for determining thermally neutral environmental conditions under a given bedding system have been developed. A related paper reports on an experimental study on measuring the total thermal insulation values of a wide range of bedding systems commonly used in the subtropics, which are an essential input to the comfort equation developed and reported in this paper.     

Neurobehavioral approach for evaluation of office workers' productivity: The effects of room temperature

Indoor environment quality has great influence on worker's productivity, and how to assess the effect of indoor environment on productivity remains to be the major challenge. A neurobehavioral approach was proposed for evaluation of office workers' productivity in this paper. The distinguishing characteristic of neurobehavioral approach is its emphasis on the identification and measurement of behavioral changes, for the influence of environment on brain functions manifests behaviorally. Therefore worker's productivity can be comprehensively evaluated by testing the neurobehavioral functions. Four neurobehavioral functions, including perception, learning and memory, thinking, and executive functions were measured with nine representative psychometric tests. The effect of room temperature on performance of neurobehavioral tests was investigated in the laboratory. Four temperatures (19 °C, 24 °C, 27 °C, and 32 °C) were investigated based on the thermal sensation from cold to hot. Signal detection theory was utilized to analyze response bias. It was found that motivated people could maintain high performance for a short time under adverse (hot or cold) environmental conditions. Room temperature affected task performance differentially, depending on the type of tasks. The proposed neurobehavioral approach could be worked to quantitatively and systematically evaluate office workers' productivity.     

Additive model for thermal comfort generated by matrix experiment using orthogonal array

In addition to ensuring the thermal comfort of occupants, monitoring and controlling indoor thermal environments can reduce the energy consumed by air conditioning systems. This study develops an additive model for predicting thermal comfort with rapid and simple arithmetic calculations. The advantage of the additive model is its comprehensibility to administrators of air conditioning systems, who are unfamiliar with the PMV–PPD model but want to adjust an indoor environment to save energy without generating complaints of discomfort from occupants. In order to generate the additive model, a laboratory chamber experiment based on matrix experiment using orthogonal array, was performed. By applying the analysis of variance on observed thermal sensation votes and percentage of dissatisfaction, the factor effects of environmental variables that account for the additive model were determined. Additionally, the applicability of the PMV–PPD model in hot and humid climates is discussed in this study, based on experimental results.     

Predictions of thermal comfort in stratified room environment

Studies of thermal comfort of occupants started in the early part of the 20th century to describe the comfort level in terms of environmental variables. Field studies have indicated that many of the complaints about unsatisfactory indoor environment can be attributed to the thermal environment. Hence, heating, ventilation, and air conditioning (HVAC) systems are used in buildings to create thermal environments that are capable of providing comfort to the occupants. Among different ventilation systems, displacement ventilation (DV) systems have become popular as more energy efficient room air distribution systems compared with the other more common forms of air distribution systems, such as mixing ventilation. However, local cold discomfort at the lower extremities due to vertical temperature gradient is often reported with DV systems. Although many studies are reported in the literature that compare the performance of the DV systems with the other more conventional types of ventilation systems, the performance of different displacement ventilation types in providing thermal comfort need further investigation. The aim of the current work is to compare the ventilation performance, as predicted by an advanced thermal comfort model, of three commonly used DV air terminal devices (ATDs) for room ventilation: a flat wall diffuser (ATD1), semi-cylindrical wall diffuser (ATD2) and floor swirl diffusers (ATD3). The CBE (Center for the Built Environment at Berkeley) comfort model has been implemented in this study to compare the thermal comfort provided by the three ATDs due to its good performance in non-uniform thermal environments. Based on the test conditions and the results obtained from the comfort model, the predicted occupant’s local sensations for the case of ATD2 were better than those for ATD1 and ATD3 and it showed better overall thermal sensation. Since the local comfort of the CBE model is a function of both local and overall thermal sensations, the predicted occupant’s local comfort values for ATD2 were better than those for ATD1 and ATD3 and consequently it provided better overall thermal comfort.     

A field investigation of the thermal environment and adaptive thermal behavior in bedrooms in different climate regions in China

Sleep thermal environments substantially impact sleep quality. To study the sleep thermal environment and thermal comfort in China, this study carried out on-site monitoring of thermal environmental parameters in peoples’ homes, including 166 households in five climate zones, for one year. A questionnaire survey on sleep thermal comfort and adaptive behavior was also conducted. The results showed that the indoor temperature for sleep in northern China was more than 4°C higher than that in southern China in winter, while the indoor temperatures for sleep were similar in summer. Furthermore, 70% of people were satisfied with their sleep thermal environment. Due to the use of air conditioning and window opening in various areas in summer, people were satisfied with their sleep thermal environments. Due to the lack of central heating in the southern region in winter, people feel cold and their sleep thermal environment needs further improvement. The bedding insulation in summer and winter in northern China was 1.83clo and 2.67clo, respectively, and in southern China was 2.21clo and 3.17clo, respectively. Both northern China and southern China used air conditioning only in summer. People in southern China opened their windows all year, while those in northern China opened their windows during the summer and transitional periods.     

国外工位空调系统研究进展

本文对当前国际上工位空调领域内的研究工作进行了回顾和总结,介绍了不同工位空调系统的构成形式,及其在提高工作区热舒适性及空气品质等方面的效果,提出了空调领域中一个新的发展模式,分析并指出了我国在该领域内研究和发展的方向。     

Research on seasonal indoor thermal environment and residents' control behavior of cooling and heating systems in Korea

Indoor thermal environments and residents' control behavior of cooling and heating systems were investigated in Seoul, Korea and compared with the results of previous studies. Twenty-four houses in summer, six houses in autumn and 36 houses in winter were used in this study. The measurement of temperature, humidity and air conditioner usage behavior was carried out. The clo-value, thermal comfort, sensation and basic data of the houses were also investigated. The indoor thermal environment in the summer had a high temperature and a high humidity ratio compare to standard comfort zone. Most of the indoor thermal environments at the time of starting the air conditioner in the summer were out of the comfort zone. Some of the data recorded while the air conditioner was stopped were in the comfort zone, but in many cases the temperature was relatively higher than comfort zone. Most indoor climate distributions in the winter were in the comfort zone and the indoor climate in autumn coincided well with the criteria of the comfort zone. Compared with results of previous studies in these 25 years, indoor ambient average temperature in winter has increased and the comfort temperature has increased in the heating period and decreased in the cooling period. This result indicates that the development of an HVAC system has created an expectation of comfort for residents and has shifted their thermal comfort zone warmer in winter and cooler in summer.     

空调系统送风方式对热舒适性的影响

本文介绍了地板送风、工位送风和置换通风的基本原理,分析了影响3种送风方式热舒适性的主要因素,如温度梯度、气流速度及送风口形式等。对3种送风方式的使用条件、热舒适性及系统运行能耗进行了比较。     

夏季空调热舒适响应空间及节能潜力研究

在满足人体热舒适要求的前提下,通过对空调热舒适方程的仿真分析,建立了空调系统环境参数的舒适空间,确立各参数对舒适性指标的影响程度;通过对空调建筑房间冷负荷计算分析,验证了空调系统在热舒适环境参数空间内存在一定节能潜力。     

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.     

A global approach of indoor environment in an air-conditioned office room

This study presents a multi-criteria method used for analysing the quality of an air-conditioned indoor environment. Indoor air flow induced by an actual Heating Ventilation and Air Conditioning system was experimentally studied under various conditions. The attention was focused on thermal comfort, acoustical comfort and indoor air distribution by considering spatial statistic studies of comfort indices. The compounded electric power of fan, compressor and pumps was measured in order to get information about energy consumption. A first analysis of these parameters showed that indoor comfort cannot be described by a general law. Thus, to reach the objective of a global approach of comfort by a spatial statistical study of the various discomforts, a multi-criteria analysis based on ELECTRE II method adapted to the comfort of air-conditioned indoor environment was applied. In this way the operating rules for coherent air conditioning systems can be defined, with a requirement for quality of indoor environment.     

Predictive controllers for thermal comfort optimization and energy savings

The present work is focused on the study of indoor thermal comfort control problem in buildings equipped with HVAC (heating, ventilation and air conditioning) systems. The occupants’ thermal comfort sensation is addressed here by the well-known comfort index known as PMV (predicted mean vote) and by a comfort zone defined in a psychrometric chart. In this context, different strategies for the control algorithms are proposed by using an only-one-actuator system that can be associated to a cooling and/or heating system. The first set of strategies is related to the thermal comfort optimization and the second one includes energy consumption minimization, while maintaining the indoor thermal comfort criterion at an adequate level. The methods are based on the model predictive control scheme and simulation results are presented for two case studies. The results validate the proposed methodology in terms of both thermal comfort and energy savings.     

空调房间气流组织与人体热舒适

介绍了人体热舒适的定义和环境影响因素:空气温度、空气速度、相对湿度和平均辐射温度。分析了气流组织与人体热舒适的关系。以下送风空调为例,阐述了此种空调方式的气流组织形式及其对人体热舒适的影响。     

关于个性化送风若干问题的讨论

每个人对热舒适的要求不尽相同,同时也有越来越多的人对室内空气品质产生抱怨,因此工位送风和个性化送风的概念被业内人士提出且逐渐得到重视,随着相关研究的不断深入,这种送风方式有了很大的发展。然而,围绕着"人体微环境"空调系统的讨论,一些在混和送风和置换送风中不显著的问题也逐渐被人们所认识,如非均匀环境下的热舒适问题、可吸入空气品质和感受到的空气品质问题、个性化系统能耗问题等,本文将针对这些问题进行讨论。     

Testing of Localized Ventilation Systems in a New Controlled Environment Chamber

This paper describes tests of thermal comfort and air distribution performance of two relatively new occupant-controlled localized ventilation (also called task ventilation) systems. The first is a raisd-floor distribution system providing air through grilles in the floor panels, and the second is a desk-mounted unit supplying conditioned air at desktop level. The tests were performed in a new controlled environment chamber (CEC) having unique capabilities for detailed studies of space conditioning and thermal comfort in office environments. Measurements were made in a mockup of a typical partitioned open-plan office, and the resulting temperature and air velocity distributions are reported for a variety of system- and locally controlled conditions. Comfort model predictions are presented to describe the degree of environmental control and range of occupant comfort levels produced in the workstations. The results are also compared to those produced by a conventional ceiling supply system. The tests investigated the effects of supply volume, supply location, supply vent orientation, supply/return temperature difference, heat load density, and workstation size and layout. Temperature differences in the range of 1–2.5°C were observed between adjacent workstations, and local air velocities in the vicinity of outlets could exceed 3 m/s. Such wide-ranging values could violate existing comfort standards (ASHRAE, 1981; ISO, 1984), if strictly interpreted. However since these systems put the local thermal conditions within the workstations under the direct control of their occupants, it is recommended that the standards grant exceptions to such systems.     

A new predictive thermal sensation index of human response

The purpose of this paper is to investigate the problem of determining a human thermal sensation index that can be used in feedback control of HVAC systems. We present a new approach based on fuzzy logic to estimate the thermal comfort level depending on the state of the following six variables: the air temperature, the mean radiant temperature, the relative humidity, the air velocity, the activity level of occupants and their clothing insulation. The new fuzzy thermal sensation index is calculated implicitly as the consequence of linguistic rules that describe human's comfort level as the result of the interaction of the environmental variables with the occupant's personal parameters. The fuzzy comfort model is deduced on the basis of learning Fanger's `Predicted Mean Vote' (PMV) equation. Unlike Fanger's PMV, the new fuzzy PMV calculation does not require an iterative solution and can be easily adjusted depending on the specific thermal sensation of users. These characteristics make it an attractive index for feedback control of HVAC systems. The simulation results show that the new fuzzy PMV is as accurate as Fanger's PMV.     

Effect of personal and microclimatic variables on observed thermal sensation from a field study in southern Brazil

Urban climate, which is influenced by land use patterns, heat-generating activities, and the physical texture of urban fabric, has a great impact on outdoor comfort as well as on a building’s energy consumption. A climate-responsive urban planning can provide optimal, comfortable thermal conditions not only for the permanence of humans in outdoor spaces but also reducing the need of air conditioning systems in buildings. The purpose of this article is to present results of an outdoor comfort research with passers-by in downtown Curitiba, Brazil (25°31′S, 917m elevation). Urban locations have been monitored regarding standard comfort variables: air temperature and humidity, wind speed and globe temperature. Alongside the quantitative assessment of comfort conditions, a survey of pedestrian’s thermal comfort perception according to ISO 10551 was carried out on each monitoring campaign by means of questionnaires with the local population. As a whole, from fourteen monitoring campaigns using a couple of weather stations, beginning on January 9 through August 12, 1654 valid comfort votes were obtained. In this paper, we perform a data consistency check, evaluating the relationship between personal (gender and age of respondents) and objective, microclimatic (comfort variables) factors on observed thermal sensation.     

冷吊顶系统的研究进展

冷吊顶技术是一种节能的空调新技术。其优越性主要表现在它极佳的热舒适性、较低的能耗和运行费用上。本文综述了国内外对冷吊顶技术的研究进展情况。分别从空调系统的工况参数和热环境指标方面，评价了冷吊顶系统优于传统空调系统的热舒适性；从风机能耗、辐射传热特性和供冷工质的替代等方面，分析了冷吊顶空调系统独特的节能优势。就冷吊顶系统的模拟研究方法，评述了几种模拟模型、应用软件和实验方法等。并建议国内相关行业的研发人员在完善冷吊顶的模型模拟和实验方法后，应着重冷吊顶产品的设计方法、材料替代和制造工艺的研究。