A new virtual sphere method for estimating the role of thermal mass in natural ventilated buildings

The role of thermal mass is very important in natural ventilated buildings. Thermal mass can be classified as external thermal mass and internal thermal mass. In this paper, a heat balance model for naturally ventilated building is developed. The effect of external thermal mass is introduced by harmonic response method, and the effect of internal thermal mass is calculated by virtual sphere method which can lump different shapes and types into one virtual sphere. The effective convection heat transfer coefficient is presented to represents the effect of uneven distribution of internal thermal mass temperature. Through comparison with Li's model [1] and numerical calculation, it was found that the model is more suitable than the others, especially in estimating decrement factor of indoor air temperature. The errors of time lag become smaller when the fluctuation of indoor air temperature is smaller. Based on the model, a simple tool is developed to evaluate the indoor air temperature and required internal thermal mass for certain naturally ventilated buildings.     

广州市自然通风类建筑围护结构内表面温度的计算与分析

在完全靠自然通风调节而没有空调的建筑中,围护结构内表面温度对人体的热舒适性影响很大.分析了自然通风类建筑各种围护结构的内表面温度,并针对广州地区的气候特征,提出了围护结构的合理隔热保温措施.研究表明在该地区完全靠自然通风的建筑中使用重质材料加外保温层的围护结构对于改善室内热环境是非常有利的.     

A new integrated design tool for naturally ventilated buildings part 2: integration and application

A major problem in the design of naturally ventilated buildings is the complicated interaction between the flow rates and the indoor air temperatures. The natural ventilation flow rates are influenced by the indoor air temperatures while the indoor air temperatures are in turn influenced by the flow rates. A good design tool should therefore consist of a flow model to determine the flow rates and a thermal to determine the indoor air temperatures. These two should be solved simultaneously in an integrated manner. Existing design tools lack the ability to address this.

This paper describes the implementation and verification of the new flow model derived in Part 1 of this paper into such an integrated natural ventilation design tool. The thermal model is based on existing theory that has been verified extensively. An iterative solution algorithm is employed to ensure simultaneous solution of these two models.

Continuous tracer gas and temperature measurements show that the integrated tool can be used with confidence in the design of naturally ventilated buildings. A case study is also presented that illustrates how the new tool can be used successfully to optimize the design of a naturally ventilated factory building.     

厦门某海滨住宅夏季自然通风与室内热环境实测与分析

本文采用自动记录仪,对厦门某海滨住宅夏季自然通风与室内热环境进行实测。根据测得的自然通风时段,分析了自然通风对房间风速及室内热环境的影响。主要结论有:(1)在自然通风条件下,房间白天室内风速均值及波动值较夜间大。(2)房间在自然通风时段,室内气温均值略低于室外,室内气温波动明显低于室外且各房间气温波动差别不大;房间在非自然通风时段,室内气温均值与室外气温相当,室温变化相当平缓。(3)无论是自然通风还是非自然通风,房间的黑球温度与室内空气温度差别很小。(4)当房间处于非自然通风状态时,室内热环境总是处于"不可接受"水平,当房间处于自然通风状态时,其室内热环境几乎全时段达到"可接受"水平,且有的房间在某些时段可达到"热舒适"水平。     

空心砌块通风墙体二维简化传热模型研究

空心砌块通风墙体是一种新型的建筑围护结构,该结构可以利用空调系统排风、地道风或夏季夜间凉风对空心砌块墙体的空腔进行通风,实现墙体内部冷、热量的转移。该技术将热回收或可再生能源利用与降低墙体内部冷/热量结合起来,可削弱室外气候对室内环境的影响,减小墙体内表面温度的波动,从而改善人体的热舒适性。为了研究该新型通风墙体的传热特性,建立了空心砌块通风墙体的二维简化传热模型。并且在稳态情形下,计算分析了该通风墙体内表面的平均温度。还进一步研究了空心砌块通风墙体的当量热阻及其影响因素。结果表明空心砌块通风墙体能获得较低的墙体内表面温度和较高的当量热阻,同时,也降低了室内负荷。     

上海市自然通风建筑围护结构的节能分析

通过对上海市几种围护结构内壁温度的计算分析，提出了合理的隔热保温措施，认为在该地区自然通风建筑中采用重质材料加外保温层的围护结构对提高室内热环境很有利，建议在设计中推广应用。     

Thermal comfort: use of controls in naturally ventilated buildings

A field study of the thermal comfort of workers in natural ventilated office buildings in Oxford and Aberdeen, UK, was carried out which included information about use of building controls. The data were analysed to explore that what effect the outdoor temperature has on the indoor temperature and how this is affected by occupants’ use of environmental controls during the peak summer (June–August). The proportion of subjects using a control was related to indoor and outdoor temperatures to demonstrate the size of the effect. The results suggest that the use of controls is also related to thermal sensation and their appropriate use is a significant part of adaptive behaviour to modify the indoor thermal conditions. The results make it possible to predict the effect of temperature on the ventilation rate in naturally ventilated buildings.     

重庆农村住宅热环境调查与能耗模拟分析

通过对重庆地区农村住宅的实地调研和对农村典型住宅室内外温度的连续监测,获得农村住宅的主要围护结构类型及典型农村住宅供暖季与空调季的室内、外热环境状况,利用重庆地区自然通风适应性热舒适性评价模型进行分析。在现有农村住宅围护结构热工性能条件下,供暖季室内温度达到舒适范围的有0 d,空调季有73 d;室内热环境状况差,冬季保温要求比夏季隔热要求更高。在供暖空调设备典型运行模式下,以调研数据为基础,借助DeST-h软件对农村典型住宅供暖空调能耗进行模拟,获得了农村住宅单位建筑面积供暖空调设备耗电量。     

长沙地区几种屋面隔热性能的测试研究

屋面的隔热性能对顶层住户夏季室内热环境影响很大,因此对几种常用屋面的实际隔热效果进行测试研究,具有实用价值。选择长沙市区某住宅小区两栋相邻的住宅,在2013年夏季按住宅屋面常用构造做法设置了几种实验模块,在外界条件、层高、墙体等都相同的情况下,连续测试各模块屋面的内表面温度、室内空气温度、室外空气温度并进行对比分析。结果表明:种植屋面的隔热效果最好;无隔热措施传统屋面的隔热效果较差,增设保温层后,其隔热效果有一定提高,如果外表面再刷白,隔热性能明显改善;通风屋面有一定的隔热效果,加设保温层后效果更好。     

基于风速补偿的自然通风房间热舒适性模拟研究

为获得自然通风条件下室内的热舒适评价方法,利用Fluent软件,根据杭州市典型室外气象参数确定边界条件,模拟居住建筑室外绕流场、室内通风场和温度场的分布规律;运用基于风速补偿的热适应性评价模型分析室内热舒适状况,并将此法与PMV模型结果对比,表明前者定义舒适的阈值较小,且正向偏离较大,后者则能较好反映自然通风房间的热环境。     

民用建筑夏季热环境计算与实验研究

建筑热环境是评估建筑能耗的重要基础,而围护结构内表面温度和室内空气温度则对建筑能耗有着最直接的影响。本文建立了自然通风条件下围护结构与室内外环境进行热交换的理论模型,测量并计算了初夏某一天围护结构内表面温度和室内空气温度随时间的变化,其计算值与测量值变化规律基本一致。而后计算了夏至日该建筑围护结构内表面温度和室内空气温度,结果表明:夏季室内空气温度随着室外空气温度的变化而变化,且上午室内外空气的温差逐渐拉大,直到14:00左右才开始缩小;夏至日上午围护结构内表面温度变化比较平缓,下午则呈现较明显的上升趋势,直到16:00温度才趋于平缓;除了屋顶外,同一时刻各围护结构内表面之间的温差较小,围护结构内表面温度低于室内空气温度,建筑围护结构对室内空气起到一定的冷却作用。     

The night purging of a two-storey atrium building

We examine the fluid mechanics of night purging in a two-storey naturally ventilated atrium building. We develop a mathematical model of a simplified atrium building and focus on the rate at which warm air purges from each storey and the atrium by displacement ventilation into a still cool night environment of a constant temperature. To develop a first insight into how the geometry of the building influences the rate at which warm air purges from each storey via the atrium we neglect heat exchange with the fabric (so there is no thermal buffering) and furthermore assume that the warm air layers in each storey and the atrium are of uniform temperature.     

Effects of outdoor air conditions on hybrid air conditioning based on task/ambient strategy with natural and mechanical ventilation in office buildings

This research aims to clarify the effects and indoor environmental characteristics of natural and mechanical hybrid air-conditioning systems in office buildings during intermediate seasons and to obtain design data. Natural and mechanical hybrid air conditioning is an air-conditioning system that utilizes natural ventilation and mechanical air-conditioning systems to improve the quality of the indoor thermal and air environment, and to reduce energy consumption. This report first categorizes the available natural ventilation conditions and estimates the amount of natural ventilation available in a model building. Furthermore, based on the concept of task-ambient air conditioning, after controlling the average temperature in the task zone to a target air conditioning temperature (26°C), changes in the outdoor temperature/humidity and the inflow rate, and the indoor environment and amount of cool heat input were studied with changes in the size of the natural vent using three-dimensional Computational Fluid Dynamics (CFD) analysis. The results of these studies indicated that natural ventilation at temperatures lower than the indoor temperature effectively covered the lower indoor task zone through negative buoyancy, which enabled energy-saving air conditioning in the task zone.     

内部热源高度对热压自然通风流场的影响

对具有内部热源的居住建筑,采用CFD技术对不同内部热源高度下室内热压自然通风流场特性进行数值模拟.得出了排风量、排风温度随内部热源高度的变化,分析了不同内部热源高度下的速度场和温度场,得出了中和面高度、有效热量系数随内部热源高度的变化.     

Empirical validation and modelling of a naturally ventilated rainscreen façade building

In this paper the thermal behaviour of a rainscreen ventilated façade has been investigated both experimentally and numerically. Field measurements were performed during the 2009/10 winter season in a test building located in San Mauro Pascoli (Italy) having a squared base of internal dimension of 2.89 m and a total internal height of 7.75 m. The external walls of this tower are rainscreen ventilated façades with a 24 cm air cavity and an external side composed of stoneware with open joints. Ventilation grills are located at the top and at the bottom of the tower. In this work the modelling of the test building using a dynamic thermal simulation program (ESP-r) is presented and the main results discussed. In order to study the rainscreen ventilated façade three different multi-zone models were defined and the comparison with the experimental results has been used in order to select the best ESP-r air flow network for the modelling of this kind of envelope component. The thermal analysis of this envelope component evidenced that the ventilated façade is able to reverse the direction of the heat flux through the envelope in regions characterized by large solar irradiation during the winter and moderate wind velocity, when the indoor-outdoor air temperature difference is small, thereby reducing the energy consumption required for indoor heating.     

北京韩美林艺术博物馆空调冷热源及系统设计

介绍了空调冷热源及系统的设计特点和控制方法,详细阐述了土壤换热器的结构及设计形式。采用地板辐射供冷供热结合新风置换通风的方案,重点考虑了围护结构的热工性能、楼板蓄热效应以及防结露措施。采用带室温反馈的室外温度控制方式(前馈-反馈控制)解决了地板辐射供冷系统调节反应速度延迟问题。     

Indoor thermal environment evaluations and parametric analyses in naturally ventilated buildings in dry season using a field survey and PMVe-PPDe model

The PMV model predicts thermal sensation well in HVAC buildings while it predicts a warmer thermal sensation than the occupants actually feel in naturally ventilated buildings. For using PMV model to predict thermal sensation well in a naturally ventilated building, the extended PMV model (PMVe) including an expectancy factor (e) and PMV was proposed by Fanger. Besides, calculations of PMV are too complex to be applied in practice. To obtain simple and applicable correlations, taking Qujing of Yunnan province, China, as example, a dry season (6-month) field measurement was conducted in a naturally ventilated residential room. Based on the collected data, PMVe values were calculated by using Newton’s iterative method. It is shown that the PMVe values approximately vary from −1.3 to 0.20 and the indoor thermal environment is somewhat discomfortable on some cloudy or rainy days. Parameters relationships and indoor air temperature gradients (vertical and horizontal) were also studied by using linear regression technique and quadratic polynomial fit technique. Numerous correlations with high relativities have been developed. It is convenient to use these results to evaluate the indoor thermal environment in naturally ventilated buildings under similar climatic conditions.     

A naturally ventilated cavity roof as potential benefits for improving thermal environment and cooling load of a factory building

The impact of natural ventilation of a roof cavity on improvement of the thermal environment and reduction of cooling load of a factory building is discussed. A computer program was developed with the logic in a companion paper [1] to observe the effect of cavity ventilation on the operative temperature of the occupied zone in the factory. Comparisons were made between factories with a cavity roof and a single roof in the Japanese climate. Results showed that the cavity roof was superior to the single roof in lowering the operative temperature by about 4.4 °C. When the factory was air conditioned, the cooling load reduction reached approximately 50% during the summer to maintain an operative temperature of 26 °C. Results showed that a naturally ventilated cavity roof has excellent potential for improving the indoor thermal environment and energy savings of factory buildings without complicated cooling installations and life time power consumption.     

Natural ventilation potential model considering solution multiplicity, window opening percentage, air velocity and humidity in China

The paper brings about a two-opening naturally ventilated building potential model considering solution multiplicity, window opening percentage, air velocity and humidity in China. Based on previous research by Yang et al. and Luo et al., this paper developed a revised model to estimate the natural ventilation potential. There are four main improvements: Firstly, counteract of wind and thermal pressure was included and method for multiple solutions was introduced accordingly. Secondly, the model considered the natural ventilation hours for windows opening percentage. Thirdly, wind velocity and humidity were considered lastly. Fourthly, cooling and heating hours were also estimated.In case study, the paper analyzes natural ventilation potential in cities in four typical climate regions in China. Results show that there are more natural ventilation hours than previous models estimated, especially in cold climate regions.Any parameter in this model can be changed according to practical situation, such as climate data, building orientation, window size, opening position, etc. All estimated information can provide reference for architects in early stages of building design. Meanwhile, this model can be used for energy efficiency estimation and indoor environment research.