暖通空调中的评价指标评述

现代空调发展的趋势是节能、舒适、健康、环保,围绕这四个方面对现代空调的评价方法进行了介绍,并从能耗模拟、热舒适、室内空气品质及空调系统的环境性能等方面进行了分析论证.     

暖通空调系统与建筑节能浅析

在介绍节能与住宅建筑能耗的基础上,根据供暖建筑的热舒适性及经济性,从合理选择冷热源系统,减少冷(热)媒介输送过程的能耗,合理选择采暖、通风与空调系统,应用废热及可再生能源等方面阐述了暖通系统的节能措施.     

基于使用者行为聚类的杭州居住建筑低能耗策略研究

杭州位于夏热冬冷地区,冬季的室内热舒适条件较少,因此该地区的居民形成了特有的热适应行为来提高自身的舒适性.文章通过问卷调查和模拟分析的方法,对居住建筑的空调采暖时间、设定温度和开窗习惯进行分析,阐明不同行为模式下的节能潜力.该模拟结果有助于指导杭州市居民的热适应性行为,减少空调能耗并提高室内热环境质量.     

别墅建筑不同空调系统的热舒适与能耗分析

利用建筑能耗分析软件Energyplus建立辐射吊顶加冷冻除湿新风系统形式的温湿度独立控制空调系统和风机盘管加新风系统形式的常规空调系统形式的仿真模型,比较分析夏热冬冷地区典型别墅建筑的空调系统室内热舒适性以及全年运行的总能耗。结果表明:温湿度独立控制空调系统的热舒适性比风机盘管加新风系统更能满足人们需求,全年的单位面积运行能耗也有所降低。     

办公室空调房间热环境数值模拟研究

运用k-ε湍流模型对某办公室空调房间气流组织和热舒适性进行了数值模拟,利用有限容积法和SIMPLE算法对微分方程进行离散求解.研究了室内空气龄云图、温度云图、速度矢量图、PMV云图、PPD云图分布规律.模拟结果表明:室内热环境满足健康、舒适、节能等方面的要求.利用TEST0445型多功能测量仪对人员办公区的空气温度、气流速度进行了测量,测量数据与模拟结果基本一致.在空调系统设计阶段,采用CFD技术可预测室内气流组织、热舒适性及为空调系统优化设计方案提供理论依据和科学指导.     

辐射冷吊顶系统夏季室内设计参数探讨

基于经典的热舒适理论,利用PMV指标计算方法,研究了辐射冷吊顶系统夏季室内设计参数的选取问题,构建了该系统的室内设计参数的舒适性区域。通过与对流空调系统常用的夏季室内设计参数对比,给出了辐射冷吊顶系统等效热舒适条件下的夏季室内干球温度取值建议。     

冷辐射吊顶+独立新风空调系统的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顶(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。     

不同辐射供冷方式下室内热舒适和能耗模拟分析

辐射供冷空调系统是一种舒适、节能的系统形式。为了比较相同面积,不同辐射面位置组合下的室内人体热舒适和能耗情况,研究以长沙某办公房间为建筑对象,采用EnergyPlus能耗分析软件对不同辐射供冷形式进行了设计日的热舒适和能耗模拟,以PMV=0为控制条件,以分体式空调系统为对照模拟,综合比较了不同辐射供冷方式下的热舒适性和能耗情况。模拟结果表明,风机盘管+顶板辐射+双壁面辐射这一组合供冷方式,在达到相同舒适条件下,节能性最优,为最佳的组合形式。     

暖通空调低碳节能技术应用的案例分析

本文以某项目为例,探讨了在其空调系统中应用的低碳节能技术。从空调冷热源系统、变频调速、热回收、置换式通风、多元通风、可再生能源利用等方面,对其节能技术进行了具体的研究与分析。并对该项目的室内空气质量、能耗情况进行了分析,证明了其节能效果比较显著。     

夏热冬冷地区住宅建筑新风热回收系统夏季节能效果研究

随着夏热冬冷地区住宅建筑空调负荷的日益增长,运用新型节能技术减少住宅建筑能耗,已成为一个很重要很紧迫的问题。新风热回收系统可以通过对新风的预热或预冷,降低空调制热或制冷能耗。为了验证新风热回收系统在夏热冬冷地区住宅建筑内的节能效果,本研究实际测量了华东地区某实验建筑中的新风热回收系统的实际节能效率。实验表明在夏季工况下热回收系统可节约14.5%的空调能耗;在梅雨季工况下可节约4.96%的空调能耗;在过渡季节则无显著节能效果。本文利用Energyplus模拟了真实工况下的热回收节能效率,并与实验数据进行对比,同时模拟了夏季全周期新风热回收装置的节能效率。     

A combined system of chilled ceiling,displacement ventilation and desiccant dehumidification

Different types of heating, ventilation, and air-conditioning (HVAC) systems consume different amounts of energy yet they deliver similar levels of acceptable indoor air quality (IAQ) and thermal comfort. It is desirable to provide buildings with an optimal HVAC system to create the best IAQ and thermal comfort with minimum energy consumption. In this paper, a combined system of chilled ceiling, displacement ventilation and desiccant dehumidification is designed and applied for space conditioning in a hot and humid climate. IAQ, thermal comfort, and energy saving potential of the combined system are estimated using a mathematical model of the system described in this paper. To confirm the feasibility of the combined system in a hot and humid climate, like China, and to evaluate the system performance, the mathematical model simulates an office building in Beijing and estimates IAQ, thermal comfort and energy consumption. We conclude that in comparison with a conventional all-air system the combined system saves 8.2% of total primary energy consumption in addition to achieving better IAQ and thermal comfort. Chilled ceiling, displacement ventilation and desiccant dehumidification respond consistently to cooling source demand and complement each other on indoor comfort and air quality. It is feasible to combine the three technologies for space conditioning of office building in a hot and humid climate.     

香港地区应用干式风机盘管系统节能和室内空气品质分析

冷板辐射加置换通风空词系统在保证室内环境的前提下比常规全空气空调系统节能,但在天气湿热的香港地区应用会出现冷板凝露现象,且采用置换通风方式,风量有限从而影响热舒适性.本文将干式风机盘管系统与独立除湿通风系统组合应用于香港地区办公楼,干式风机盘管系统处理室内显热负荷,独立除湿通风系统承担室内湿负荷和室外全热负荷.采用EnergyPlus软件模拟分析了该空调系统在香港地区某办公楼中的使用性能,结果表明该系统能很好地控制室内温、湿度,特别是湿度,与常规全空气空调系统相比,全年节能达10.3%.     

Displacement ventilation environments with chilled ceilings: thermal comfort design within the context of the BS EN ISO7730 versus adaptive debate

The current design standard BS EN ISO7730 [Moderate thermal environments—determination of the PMV and PPD indices and specification of the conditions for thermal comfort, International Standards Organisation (1995)] is based upon the work of Fanger, and essentially comprises a steady-state human heat balance model that leads to a prediction of the sensation of human thermal comfort for a given set of thermal conditions. The model was derived from laboratory-based measurements conducted in the mid-1960s in relatively ‘conventional’ environments. However, a chilled ceiling operated in combination with displacement ventilation represents a more sophisticated environment as compared with the original conditions in which the Fanger model was derived. This raised a question about the applicability of the current standard when designing for thermal comfort in offices equipped with chilled ceiling/displacement ventilation systems. This paper presents findings from an EPSRC-funded study that sought to answer the above question. Human test subjects (184 in total) carried out sedentary office-type work in a well-controlled environmental test room that simulated an office fitted with the above system. Measurements of environmental variables were taken at a number of locations near the subjects, each of whom wore a typical office clothing ensemble. The reported thermal comfort sensations were compared with values predicted from BS EN ISO7730 over a range of system operating conditions. It was shown that the current standard BS EN ISO7730 may be used, without modification, when designing for the thermal comfort of sedentary workers in offices equipped with chilled ceiling/displacement ventilation systems. These findings are interpreted within the context of a proposed modification to thermal comfort design standards that includes adaptive effects, and the influence of BS EN ISO7730 on the development of other radiant surface/displacement ventilation configurations is discussed.     

Influence of the ventilation system on thermal comfort of the chilled panel system in heating mode

In heating mode, fresh air is still essential for a chilled panel system in order to ensure the indoor air quality. In this paper, a chilled ceiling panel system was designed and built in a typical office room. The thermal environment and thermal comfort in the room were fully measured and evaluated by using the Fanger's PMV-PPD model and the standard of ISO 7730 respectively, when room was heated in two modes, one of which is the chilled panel heating mode and the other of which is the combined heating mode of chilled panel and supply air. The research results indicate that in the combined mode, ceiling ventilation improves the general thermal comfort and reduces the risk of local discomfort. Under the condition of same general thermal comfort, the heating supply upper limit of chilled panel can be increased by 12.3% because of air mixing effect caused by introduction of air ventilation.     

Modelling of enhanced passive and conventional cooling systems

This study modelled a recently completed typical steel-framed speculative office development in the UK. It investigated the comparative performance of the building for various servicing regimes. These included natural and mechanical ventilation, two types of active fabric energy storage (FES) system (AirDeck and AirCore), air-conditioning (a conventional all-air system and chilled ceiling with mechanical ventilation), and mixed-mode solutions combining some of the above approaches. The assessment covered both summer and winter (heating) performance. The main objective was to evaluate overall performance of these systems in terms of thermal comfort and energy use and to compare the findings with more conventional servicing options for the same building. The study demonstrates that active FES can enhance thermal comfort while reducing energy use and emissions. In comparison with conventionally and naturally ventilated systems, the studied FES systems reduced temperature excess hours and peak temperatures, supplied cooler air as a result of overnight cooling, and reduced chiller consumption and boiler ratings as well as emissions. The annual operating costs of these active FES systems increase energy costs by only 13% over that of the naturally ventilated option. The mixed-mode solutions reduce them by over 35% when compared with all-mechanically cooled alternatives.     

Modelling of enhanced passive and conventional cooling systems

This study modelled a recently completed typical steel-framed speculative office development in the UK. It investigated the comparative performance of the building for various servicing regimes. These included natural and mechanical ventilation, two types of active fabric energy storage (FES) system (AirDeck and AirCore), air-conditioning (a conventional all-air system and chilled ceiling with mechanical ventilation), and mixed-mode solutions combining some of the above approaches. The assessment covered both summer and winter (heating) performance. The main objective was to evaluate overall performance of these systems in terms of thermal comfort and energy use and to compare the findings with more conventional servicing options for the same building. The study demonstrates that active FES can enhance thermal comfort while reducing energy use and emissions. In comparison with conventionally and naturally ventilated systems, the studied FES systems reduced temperature excess hours and peak temperatures, supplied cooler air as a result of overnight cooling, and reduced chiller consumption and boiler ratings as well as emissions. The annual operating costs of these active FES systems increase energy costs by only 13% over that of the naturally ventilated option. The mixed-mode solutions reduce them by over 35% when compared with all-mechanically cooled alternatives.     

Thermal comfort and energy consumption of the radiant ceiling panel system.: Comparison with the conventional all-air system

The purpose of this study is to investigate the various characteristics of a radiant ceiling panel system and their practical application to office buildings. The radiant ceiling panel system and conventional air-conditioning system were compared in terms of thermal comfort, energy consumption, and cost. Thermal environment, along with human response, was tested by using a small meeting room equipped with radiant ceiling panels. The responses were collected by questionnaires given to the male subjects in the room. The experiment for the female subjects was conducted separately. Results show that the radiant ceiling panel system is capable of creating smaller vertical variation of air temperature and a more comfortable environment than conventional systems. When using a cooled ceiling, a small volume of supplied air creates a less draught environment, which reduced the discomfort of feeling cold in the lower part of the body. Numerical simulation of yearly energy consumption and cost estimation were conducted. Typical office rooms located on the 3rd, 4th, and 5th floor of a six-floor building in the Tokyo area were simulated. Since part of the sensible heat load is handled by radiant ceiling panels, the volume of supplied air can be reduced, leading to lower energy consumption for air transport. By using the radiant ceiling panel system in one of the three floors of the simulated building, energy consumption can be reduced by 10%. Estimated pay back time was from 1 to 17 years depending on the market price of the radiant ceiling panel.     

Development of a radiant heating and cooling model for building energy simulation software

Efficient radiant heating and cooling systems are promising technologies in slashing energy bills and improving occupant thermal comfort in buildings with low-energy demands such as houses and residential buildings. However, the thermal performance of radiant systems in buildings has not been fully understood and accounted for in currently available building energy simulation software. The challenging tasks to improve the applicability of radiant systems are the development of an accurate prediction model and its integration in the energy simulation software. This paper addresses the development of a semi-analytical model for radiant heating and cooling systems for integration in energy simulation software that use the one-dimensional numerical modeling to calculate the heat transfer within the building construction assemblies. The model combines the one-dimensional numerical model of the energy simulation software with a two-dimensional analytical model. The advantage of this model over the one-dimensional one is that it accurately predict the contact surface temperature of the circuit-tubing and the adjacent medium, required to compute the boiler/chiller power, and the minimum and maximum ceiling/floor temperatures, required for moisture condensation (ceiling cooling systems), thermal comfort (heating floor systems) and controls. The model predictions for slab-on-grade heating systems compared very well with the results from a full two-dimensional numerical model.     

Chilled ceiling displacement ventilation design charts correlations to employ in optimized system operation for feasible load ranges

This paper expands Ghaddar et al. [N. Ghaddar, K. Ghali, R. Saadeh, A. Keblawi, Design charts for combined chilled ceiling displacement ventilation system (1438-RP), ASHRAE Transactions, 143 (2) (2008) 574-587] design charts of combined chilled ceiling (CC) displacement ventilation (DV) system to operating sensible load ranges from 40 W/m² to 100 W/m². It develops a global correlation of system load and operational parameters, with comfort measured by vertical temperature gradient and indoor air quality measured by the stratification height. The correlations are used for a known transient load profile in generating optimal settings of the CC/DV system operational parameters and associated energy consumption.An example is illustrated to show how the correlation could be used to size the system and to provide optimized control of the CC/DV system operation at low computational cost. Results of the current model are compared to the published case study of an optimized operation based on transient simulations of the space thermal model to achieve minimum operation cost [M. Mossolly, N. Ghaddar, K. Ghali, L. Jensen, Optimized operation of combined chilled ceiling displacement ventilation system using genetic algorithm, ASHRAE Transactions, 143 (2) (2008) 541-554]. The design correlations resulted in good agreement with published data (within 3% error in energy consumption and average 6% error in predictions of comfort and stratification height) at 1/4 of the computational time. The presented methodology provides an alternative for using the correlation for supervisory online controllers for the CC/DV system based on physically derived correlations.     

某高层写字楼冷梁空调系统的设计与分析

以天房中新天津生态城南部次中心项目为例,根据该项目自身特点,通过对办公部分各空调末端系统进行对比分析,选择冷梁系统作为最终末端形式。采用冷梁系统,初投资虽然高,但是它可以减少调试周期和工作量,降低吊顶净高高度,辐射还能带来更好的舒适感,结合本项目冷热源采用地源热泵系统,更加节能,并且特别符合生态城绿色建筑的要求。