A questionnaire survey on sleeping thermal environment and bedroom air conditioning in high-rise residences in Hong Kong

This paper reports on the results of a questionnaire survey on sleeping thermal environment and bedroom air conditioning in high-rise residential buildings in Hong Kong. The survey aimed at investigating the current situation of sleeping thermal environment and bedroom air conditioning, in order to gather relevant background information to develop strategies for bedroom air conditioning in the subtropics. It focused on the use patterns and types of bedroom air conditioning systems used, human factors such as the use of bedding and sleepwear during sleep, preference for indoor air temperature settings in bedrooms, ventilation control at nighttime with room air conditioner (RAC) turned on, etc. The results of the survey showed that most of the respondents would prefer a relatively low indoor air temperature at below 24 °C. Most of the respondents might however not be satisfied with the indoor air quality (IAQ) in bedrooms in Hong Kong. On the other hand, 68% of the respondents did not use any ventilation control intentionally during their sleep with their RACs turned on. A lack of knowledge of the ventilation control devices provided on window type room air conditioners (WRACs) indicated an urgent need for user education.     

The characteristics of space cooling load and indoor humidity control for residences in the subtropics

For residential buildings located in the subtropics, it is more challenging and difficult to deal with space latent cooling load than space sensible load, using a room air conditioner (RAC), partly due to hot and humid climates. This paper reports a simulation study on the characteristics of space cooling load and indoor humidity control for residences in the subtropics, using a building energy simulation program. Both the weather conditions and the typical arrangements of high-rise residential blocks in subtropical Hong Kong were used in the simulation study. The simulation results on both the space cooling load characteristics and the hourly application sensible heat ratio (SHR) in the living/dining room and the master bedroom in a selected west-facing apartment under different operating modes of RACs in the summer design day are presented. The problem of indoor humidity control due to the mismatching between an application SHR and an equipment SHR in the two rooms both in the summer design day and during part load operations and the influences of indoor furnishings acting as moisture capacitors on indoor RH level are discussed.     

The outdoor air ventilation rate in high-rise residences employing room air conditioners

Ventilation is important because it affects indoor environmental conditions, including air pollutant concentrations that may modify the health of the occupants of a building, or their perceptions and comfort. This paper reports, first of all, on field studies monitoring indoor overnight CO₂ levels and outdoor ventilation rates in bedrooms employing room air conditioners (RACs), so the current situation of ventilation in actual high-rise residential buildings in Hong Kong can be appreciated. This is followed by a report of the results of laboratory experiments where two typical RACs were used in an examination of outdoor air ventilation characteristics in rooms employing RACs. The results of field studies showed that the outdoor ventilation rates in the measured bedrooms equipped with RACs in high-rise residential buildings in Hong Kong could not meet the ventilation requirement specified in the ASHRAE standard 62-2001 even if there was only one occupant in a bedroom. Although the use of a window-type air conditioner (WRAC) may provide a higher outdoor ventilation rate than the use of a split-type air conditioner (SARC), this may be ascribed to the fact there is more natural infiltration when a WRAC is used. The ventilation damper currently available in a WRAC does not significantly affect the outdoor ventilation rate. Therefore, such a damper cannot be expected to provide the ventilation rate as required by a ventilation code and its intended function of controlling ventilation is limited. In addition, the air exhausted from indoors to outdoors through the ventilation outlet in a WRAC is air that has just been cooled by the cooling coil (evaporator). This is unreasonable, because exhausting just-cooled and dehumidified air is a waste of energy. Therefore, an improved design for a WRAC has been suggested. Finally, the outdoor ventilation requirement for bedrooms at nighttime, when occupants are asleep, is discussed. A new ventilation rate of 3.0 l/s per person for the sleeping environment in high-rise residential buildings is proposed.     

住宅建筑夏季自然通风方式下热环境分析

文章采用模拟分析软件Dest，模拟乌鲁木齐地区某住宅建筑在采用三种不同的夜间通风模式的条件下，室温变化情况，分析了自然通风对室温的影响。同时指出白天关窗夜间开窗通风模式的室内热环境更适于人们居住，不但可以满足舒适度要求，还可以免去夏季开空调，节约能源。     

住宅户式中央空调及独立机械通风系统设计

介绍了绵阳市某住宅户式中央空调及独立机械通风系统的设计,住宅的空调方式选用风冷式（冷热水型）户式中央空调系统,同时设置独立机械通风系统,有利于改善室内空气品质,并对投资及运行费用进行分析,认为该空调及通风方式完全可以推广应用。     

住宅建筑采暖空调能耗模拟方法的研究

住宅建筑的采暖空调能耗受室内居住人员行为方式的影响,在调查研究基础上,确定了两种反映室内居住人员行为方式的计算模式。在两种不同计算模式下,利用建筑热环境模拟工具DeST对上海地区同一住宅建筑能耗进行模拟,并将模拟结果与调研结果进行比较,分析计算模式对上海地区住宅建筑采暖空调能耗大小的影响,从而获得能正确反映上海地区住宅建筑采暖空调能耗大小的模拟计算方法。此方法可用于上海地区住宅建筑采暖空调的能耗分析与评价,并正确指导住宅建筑的节能设计。     

夏热冬冷地区居住建筑空调方式的能耗评价

利用DeST软件模拟计算了夏热冬冷地区某一典型居住建筑的全年8760h逐时空调负荷值;考虑空调设备变工况和变负荷率情况下的二次能耗,计算了6种常见住宅空调方式的全年能耗值;利用空调能耗指标CEC,对住宅空调方式进行了能耗评价。     

厦门农村住宅用能状况与建筑能耗模拟分析

以厦门农村住宅为调查研究的对象,采取实地调研和计算机模拟相结合的方法,根据农宅住户实际用电特征将厦门农村住宅分为6种基本类型,从中归纳出3种不同的空间原型作为计算机模拟的模型,通过De ST-h模拟软件进行能耗模拟,得出典型农村住宅基本能耗,分析其建筑能耗的特点。结果表明,农宅的用能方式导致不同的建筑形态其能耗也不同,通过典型气象年的运算发现,空调冷负荷在建筑总能耗中占比最大,3种计算模式的空调开启时间和运行时间均不同,3种计算模型的空调能耗占比分别是81.5%、84.6%、96.8%。     

An experimental study on the inherent operational characteristics of a direct expansion (DX) air conditioning (A/C) unit

For residential buildings located in the subtropics, direct expansion (DX) air conditioning (A/C) units are commonly used for environmental control. However, the use of standard DX A/C units having constant-speed compressor and relying on on–off cycling often leads to either space overcooling or an uncontrolled indoor humidity level, due to high latent cooling load resulted from hot and humid climates. This paper reports on an experimental study to investigate the inherent operational characteristics of a DX A/C unit at a fixed inlet air state when the speeds of both its compressor and supply fan are varied. The experimental results of the inherent operational characteristics related to both equipment sensible heat ratio (SHR) and operating efficiency are reported. Issues related to the practical applications of the inherent characteristics and their possible constrains are discussed.     

住宅环境设备的现状与发展

探讨了住宅的环境需求和设计保证，叙述了我国住宅设备现状，详细列举并比较了各种户式中央空调方式的特点及其适用性，介绍了日本在家用空调方面采用的新技术；讨论了集中式住宅空调的可行性，住宅空调与热水供应的一体化，住宅的全面换气设备，介绍了日本的环境共生型住宅及其设备。     

Thermal comfort and IAQ characteristics of naturally/mechanically ventilated and air-conditioned bedrooms in a hot and humid climate

The characteristics of thermal comfort and indoor air quality (IAQ) in bedrooms, occupants’ perceptions and their impact on sleep quality are not often studied. It becomes even more interesting if climatic conditions allow Naturally/Mechanically Ventilated (NMV) concepts as opposed to Air-conditioning (AC) and this becomes very significant from an energy perspective. This paper reports our findings from such a study conducted in a hot and humid climate. Objective measurements of thermal comfort and IAQ were carried out during sleeping period in 12 NMV and 12 AC bedrooms over a period of 2 months. Questionnaire responses were sought from each subject at the end of the objective measurements to assess their perceptions on thermal comfort and indoor air quality of the bedrooms during sleep and their sleeping conditions. Although the “Historical” and “Immediate” responses for the NMV and AC bedrooms indicate that there was a good level of acceptability for both Thermal Comfort and Perceived Air Quality (PAQ), it was found that NMV bedroom was a better sleeping environment. The subjects’ immediate perception of PAQ and thermal comfort were reasonably correlated with their historical perceptions. The subjects’ perception of PAQ was fairly closely correlated to their perception of Thermal Comfort. There was a considerable increase in the carbon dioxide level in an AC bedroom relative to a NMV bedroom. However, there was no clear evidence to substantiate that sleeping duration decreased with increasing level of carbon dioxide, but the findings do suggest that high level of carbon dioxide may hinder the duration of sleep.     

中国国家博物馆暖通空调系统设计

介绍了国家博物馆兼顾文物保护、参观者舒适感和运行调节手段确定室内环境参数的原则。分析了采用部分负荷冰蓄冷、大温差低温冷水系统在负荷保证、提高除湿能力和节能方面的优势。结合CFD模拟,采用了分层空调加地板辐射供冷的空调系统以改善高大空间的室内环境。探讨了博物馆中文物库房和展厅恒温恒湿空调系统的设计方法。     

大空间建筑分区空调负荷的研究

在空调设计中,往往把大面积的空调房间的冷热负荷视作均匀分布,事实上,在大面积空调房间的不同位置,冷热负荷不同,各处的温度将有差异,造成室内空调系统效果欠佳。针对此问题,采用TRANSYS软件,结合实例对分区温度分布和空调负荷进行了模拟与分析。应重视室内建筑冷热负荷分布的不均匀性,以此为依据来设计室内空调系统。     

冷辐射吊项＋独立新风窒调系统的CFD模拟研究——新型空调系统在居室中的运用

利用CFD数值模拟的方式分析冷辐射吊项（CRCP）＋独立新风（DOAS）空调系统的热工性能,与传统的全空气系统（VAV）不同的是,这种新型空调系统采用直接辐射和间接对流的方式来消除室内的热负荷,冷辐射吊顶通过直接辐射和间接对流来承担室内的部分显热负荷,独立新风承接室内的全部潜热负荷与部分显热负荷。以上海某居室为例,分析了冷辐射员顶和独立新风空调系统的原理,并建立了居室的物理模型与数学模型,利用CFD软件模拟了居室内的气流组织,分析了速度场与温度场的分布特征,并对室内热舒适性进行了模拟,并采用PMV—PPD指标对室内热舒适性进行了评价。模拟结果显示,这种新型空调系统能提供较好的热舒适环境和较高的空气品质。     

地铁通风空调系统的设计特点

介绍了现行国家标准对地铁通风空调系统的要求.对地铁空调系统室内外空气计算参数的确定、冷负荷构成、冷负荷指标的选取、冷负荷计算方法及通风空调系统的构成进行了探讨.     

不同制冷量空调器在住宅中应用的实测对比研究

通过实验测试对比了不同制冷量的定速房间空调器用于住宅卧室中时的室内温湿环境状况和空调器的耗电量情况。实验结果表明,当空调器容量过大时,空调器的除湿能力下降,室内相对湿度偏高,空调器耗电量大,实验日条件下,使用1.5 HP空调器时的室内相对湿度比使用1 HP空调器的室内相对湿度高5%,而1 HP空调器耗电量比1.5 HP空调器减少12.7%。     

双层玻璃幕墙对办公建筑照明能耗及负荷影响的模拟与分析

双层玻璃幕墙在现代建筑中的应用越来越广泛,其天然采光与照明控制方式是影响照明能耗的主要因素,而照明能耗的改变会使室内冷热负荷发生改变,从而影响室内采暖空调能耗。以天津市某双层玻璃幕墙办公建筑为模型,应用DAYSIM软件模拟有无双层玻璃幕、墙幕墙朝向以及照明控制方式的不同对照明能耗的影响,并结合TRNSYS软件分析不同照明控制方式对室内冷热负荷的影响。     

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.     

Modeling ventilation rates in bedrooms based on building characteristics and occupant behavior

Air change rate (ACR) data obtained from the bedrooms of 500 Danish children and presented in an earlier paper were analyzed in more detail. Questionnaires distributed to the families, home inspections and interviews with the parents provided information about a broad range of residential characteristics and occupant behavior. These were tested in several linear regression models to identify the degree of effect each selected independent variable has on the total ACR. The measured ACRs are summarized by some of the most significant variables such as room volume (higher ACR in smaller rooms), number of people sleeping in the bedroom (higher ACR with more people), average window and door opening habits (higher ACR with more opening), sharing the bedroom with other family members (higher ACR in shared rooms), location of the measured room (higher ACR above ground floor), year of construction (lowest ACR in buildings from early 1970s), observed condensation on the bedroom window (higher ACR at less condensation), etc. The best-fitting model explained 46% of the variability in the air change rates. Variables related to occupant behavior were stronger predictors of ventilation rate (model R² = 0.30) than those related to building characteristics (model R² = 0.09). Although not perfectly accurate on a room-to-room basis, our best-fitting model may be useful when a rough estimate of the average air change rate for larger study populations is required in future indoor air quality models.     

Speculation in the feasibility of evaporative cooling

The use of evaporative air cooling, for residential air conditioning, cannot be taken for granted in all situations. It depends on the climatic conditions and the specific nature of application. This work establishes a general foundation for judging the feasibility of evaporative cooling with different evaporative-system configurations, under different climatic conditions and for different applications. Two feasibility criteria were stipulated; the rate of air supply to space and the indoor relative humidity. Systematic procedures are presented for evaluating the required air-flow rate and predicting the achievable indoor condition. Explicit mathematical expressions are derived to define the limitations on outdoor conditions for any allowable specific air flow. The impacts of various pertinent factors are investigated. These include the required indoor temperature, the quality of space load represented by its SHF and the performance index of the system. Computer programs were devised to automate, hence facilitate, the repetitive computations and to evade the graphical work on the psychrometric chart. Samples of program results are graphically displayed.