高层建筑空调水系统中的热压作用

分析计算了多种工况条件下空调水系统之热压值及其对空调水系统运行状况的影响程度，指出在高层建筑空调水系统中热压的作用在夏季运行工况下完全可以忽略不计，而在冬季运行工况下，可能会引起比较严重的垂直失调现象。最事指出了减轻其不利影响程度的途径。     

空调房间两种典型送回风方式的数值模拟

基于商用CFD软件,在FLUENT中将材料定义为水汽混合物的湿空气,通过对同一典型空调房间,采取同一送风工况,不同的送回风方式,运用k—ε模型进行数值模拟,得到两种送回风方式的速度分布、温度分布、压力分布,从而为该典型空调房间选择了最优的送回风方式。     

空调系统柔性风管压力损失特性实验与分析

介绍了柔性风管压力损失的理论模型。通过实验研究了两种常用柔性风管在全伸展状态时的压力损失,得出了它们的绝对粗糙度值。给出了柔性风管完全展开时的阻力计算图,可供工程设计时使用。     

The impact of using chilled water storage systems on the performance of air cooled chillers in Kuwait

In the air conditioning (AC) industry chilled water storage (CWS) systems are one form of cool thermal storage technology that can be used to time shift the electrical load of the system from the peak day periods to off peak night time periods. In this paper the data for the actual exported and generated electrical energy obtained for the power stations in Kuwait has been used to estimate the electrical energy consumption and the peak electrical load of AC systems. Since the chiller in an air cooled AC system represent more than 75% of the total electrical power consumed by an AC system during the peak demand period, the impact of using CWS systems with alternative operating strategies including partial (load levelling), partial (demand limiting) and full load has been investigated. In our conclusions we estimate that approximately 45% of the total annual exported electrical energy is consumed solely by AC systems as a result of the very high ambient temperatures occurring between March and October. Furthermore, it is estimated AC systems represent about 62% of the peak electrical load. The results demonstrate that CWS can reduce the peak electrical load of a chiller in an air cooled AC system by up to 100% and reduce the nominal chiller size by up to 33% depending upon the operating strategy adopted. This is achieved with only a 4% increase in power consumption of the chiller for all CWS strategies except for full storage where the energy consumption actually decreases by approximately 4%.     

Heat transfer and pressure drop characteristics of the underfloor air distribution system

This paper reports experimental data for forced convection heat transfer in a heat exchanger, which is a key part of the underfloor distribution system. The experiments were performed to study heat transfer and pressure drop characteristics of tested units with different geometry of flow ducts. The heat exchanger was made of Plexiglas and PVC. The top side of plastic exchanger was covered by a layer of a concrete screed with thickness of 0.035 m. The bottom side was insulated with 0.1 m of polystyrene. The length of the tested units was 1 m and the width 0.5 m. The fluid in the heat exchanger was air. The results of experimental study were presented in a dimensionless form. The average Nusselt number and Fanning friction factor were expressed in terms of the Reynolds number. The experimental results presented in this paper provide useful information for designing of an underfloor air distribution system in the residential housing sector.     

温湿度独立控制空调系统及性能分析

空调系统承担着排除室内余热、余湿．CO2与异味的任务。由于排除室内余热与排除CO2、异味所需要的新风量与变化趋势一致．即可以通过新风同时满足排余湿、CO2与异味的要求．而排除室内余热的任务则通过其他的系统（独立的温度控制方式）实现。由于无需承担除湿的任务,因而较高温度的冷源即可实现排除余热的控制任务。温湿度独立控制空调系统中,采用温度与湿度两套独立的空调控制系统,分别控制．调节室内的温度与湿度．     

Influence of household air-conditioning use modes on the energy performance of residential district cooling systems

During technical evaluations of cooling systems in residential buildings, it is necessary to consider the influence of the household air-conditioning (AC) use modes. In other words, how the occupants control the AC, for instance, when it is turned on, what the temperature setting is, and how long it is used. Field measurements and spot interviews indicate that AC usage by residents should be environmental, event and random related. A reduced-order AC conditional probability (CP) model was developed in this study to describe AC usage. The AC CP model was integrated with a building energy modeling program (BEMP) to reflect the interaction of the AC operation and the indoor environment. With consideration of stochastic AC use modes, the uncertainty of user compositions was studied. Additionally, simulation results revealed that AC use modes and user compositions can cause up to a 4.5-fold difference in the system efficiency of district cooling systems. The Lorenz curve and Gini coefficient were applied in this study to describe the load distribution in a quantitative manner. Through a comparison with the constant schedule definition model, the study also identified inclusion of the stochastic feature of AC use modes and their compositions in simulations as being important to the technical evaluation of district cooling systems.     

Environmental impact assessment using a weighting method for alternative air-conditioning systems

Requirements for the design of HVAC systems with low environmental impact have become accepted in the past decade. However, the environmental performance is complicated to evaluate, because the process is affected by several parameters. This paper presents a case study, in which a previously established method for environmental evaluation is adapted. Two alternative air handling units were analysed using life cycle assessment including the weighting step. The results, according to the weighting method applied as well as the material assumptions, show that the user stage of the life cycle of both units is the critical part of the overall impact.     

Investigation of operation performance of air carrying energy radiant air-conditioning system based on CFD and thermodynamic model

This study aims to investigate the operation performance of a new terminal form of radiant air-conditioning system called the air carrying energy radiant air-conditioning system (ACERS). Three summer operation conditions, namely steady condition (without opening door and window), open-door condition and open-window condition, are researched in a residential apartment using experimental, computational fluid dynamics (CFD) simulation and thermodynamic methods. The concept of dynamic synergistic operation of mechanical ventilation driven by the air-conditioning system and natural ventilation driven by the open door or window is proposed. A thermodynamic model formulated by the dynamic enthalpy equation, dynamic temperature equation and dynamic moisture equation is developed to analyze the heat and mass transfer process of the test room under the synergistic operation of mixing ventilation. Moreover, the CFD simulation results are used to analyze the synergistic operation and thermodynamic energy transfer of the test room under the mixing ventilation of ACERS and open door/window. It is indicated that ACERS is an important technology with a low temperature gradient of less than 0.1 °C between the head (1.5 m) and ankle level (0.1 m) and low velocity of approximately 0.1 m/s in the occupied zone under the steady condition. The thickness of the boundary zone under the orifice plate of ACERS under the steady, open-door and open-window conditions is 12, 6, and 8 cm, respectively, which can effectively prevent condensation. This study proves that ACERS is a promising technology for air conditioning in residential buildings in regions with hot and humid summers.     

溶液除湿空调系统蓄能性能分析

介绍了溶液除湿蒸发冷却空调系统的蓄能原理,分析了蓄能密度的影响因素。与冰蓄冷、水蓄冷和气体水合物蓄冷等常规蓄冷方式的比较结果表明,溶液除湿空调系统在蓄能方面有明显的优势,其蓄能密度远大于常规蓄冷方式。该系统可以利用太阳能作为再生能源,白天蓄存浓溶液用于夜间制冷,节能效果显著。     

空气过滤器玻纤滤料纤维排布对初始过滤性能的影响

应用格子玻尔兹曼方法(LBM)研究了亚高效滤料(F6)中2种不同直径纤维排布方式对过滤效果的影响,寻找最易穿透粒径(MPPS),比较了这2种排布方式对应的压降与捕集效率,并用解析解对模拟结果进行了验证。结果表明,对于直径为0.10~0.90μm的颗粒物,模型1(小纤维在后、大纤维在前)的捕集效率比模型2(小纤维在前、大纤维在后)低,最大差值可达17%;当增大纤维的行间距时,捕集效率会增大50%以上;在扩散、惯性和拦截效应下,前方纤维的捕集数量明显高于后方纤维,前一半纤维捕集的颗粒物数量超过总捕集数的83%;F6滤料的MPPS值为0.20~0.40μm。     

医院集中空调管理

针对医院空调的特点，提出了医院集中空调系统运行管理和维护的具体措施，供运行管理人员参考。     

平直翅片管换热器的换热性能和压降特性研究

应用Fluent软件对换热器在不同的工况下换热性能进行模拟,结果表明:换热系数、Nu和压降随翅片进口风速增大而增大,摩擦因子随进风速度增大而减小;换热系数、Nu、压降和摩擦因子随翅片间距增大而减小;换热系数和Nu随进风温度增大而先增后减,压降和摩擦因子随进风温度增大而增大。     

Initial studies of oxidation processes on filter surfaces and their impact on perceived air quality

Used filters can be a strong sensory pollutant source. Oxidation processes, especially those initiated by ozone, may contribute to the pollutants emitted from such filters. In the present study, ozone was added to the airstream passing through used ventilation filters. Two flow rates were examined. While the upstream ozone concentration was approximately 75 ppb, the concentrations downstream of the filter were initially 35-50% lower. However, within an hour downstream concentrations were only 5-10% lower than those upstream. These filter samples were then placed for 48 h in nitrogen, ambient air containing less than 5 ppb ozone, or ambient air at an elevated temperature. This resulted in partial regeneration of the ozone removal capability of the filter. In analogous experiments, lower ozone removal occurred when the filter samples were first ventilated for 24 h with ozone-free air before making the measurements. Samples from a new filter removed <10% of the ozone in the airstream, and removal remained relatively constant over time. In companion studies, human subjects assessed the air passing through various used filter samples. In the initial evaluation each of the four filter samples, taken from the same filter and ventilated for 24 h, were assessed to be equivalent. The next evaluation was immediately after the samples had been kept for 24 h in either nitrogen, air, air at an elevated temperature or ozone. The nitrogen-treated filter was assessed to be best, while the ozone-treated filter was assessed to be the worst. The final evaluation occurred after ambient air had passed through the 'treated' filters for 2 h. All such ventilated filters were assessed to be more acceptable than immediately after the 24-h treatments; the ozonized and air-treated filters were the most polluting of the four. Practical Implications The present paper supports previous findings that loaded ventilation filters can be significant sources of sensory pollution. Replacing a loaded filter with a new filter temporarily removes this source of pollution. However, the present study does not provide an answer to how frequently changes are needed under different conditions. The results indicate that in cases of intermittent operation of ventilation systems, the airflow through the polluted filters should be restarted in sufficient time prior to occupancy to purge odorous pollutants that have accumulated on the filter surface. Removal of ozone upstream of the particle filters may further improve perceived air quality in the space downstream of the filter bank. Future efforts related to the development and application of low-polluting filtration systems are warranted.     

The influence of street canyons on the cooling loads of buildings and the performance of air conditioning systems

The impact of microclimatic conditions in urban areas on the thermal loads of buildings has been appreciated fairly recently. The modulation of street canyons has led, inter alia, to temperature conditions that depart from the climatic data monitored at meteorological stations, affecting the heating balance of buildings, while the building operation affects the present conditions. The installation of air conditioning units leads to heat emission, which, at a microscale level, strengthens this phenomenon. The present paper outlines a computational approach to the street canyon phenomenon, with the determination of flow and temperature fields which are developed, and discusses their influence on the dynamic thermal balance of the building.     

Control of air-conditioning systems in heating mode to enhance transient performance and steady-state efficiency

In this paper, a control framework for the air-conditioning system operated in heating mode is proposed. The control framework possesses a cascade structure for dealing with the fast and slow dynamics respectively contributed by the vapor compression cycle and the indoor dynamics. Under the control framework, the control performances associated with two strategies, the condenser superheat regulation (CSR) strategy and the evaporator superheat regulation (ESR) strategy are examined. It is shown experimentally that while ESR strategy demonstrates more superior transient response, CSR strategy is more advantageous in reducing the compressor power at steady state. In order to achieve both transient performance and steady-state power savings, the two strategies are combined in the way that ESR strategy is responsible for the control action during the startup/transient phase of operation, CSR strategy takes over the control when steady state is reached, and a bumpless compensator is used to smooth the control action during control switching. Experiments demonstrate that the combined strategy can simultaneously enhance transient performance and steady-state efficiency.     

A study on the energy performance of three schemes for widening application of water-cooled air-conditioning systems in Hong Kong

The Hong Kong Government intends to reduce greenhouse gases emissions from power stations through widening application of the more energy efficient water-cooled air-conditioning systems (WACS) in buildings. Consideration is being given to the development of centralized, district wide systems for supplying seawater for once-through condenser cooling (the CPSSCC scheme), or for make-up of water losses at cooling towers (the CPSSCT scheme) such that buildings that are restricted to using air-cooled air-conditioning systems (AACS) may adopt or convert to WACS. Development of district cooling systems (DCS) for supplying chilled water to buildings is another feasible option. This paper describes a study into the energy benefits of implementing these schemes in Hong Kong. Application of the analysis method to a territory-wide study for Hong Kong showed that these schemes were all technically feasible and economically viable. It was estimated that compared with all buildings using AACS, the economic saving that could be realized through implementing these schemes in large scale are around 6% for the CPSSCC scheme, 2–3% for the CPSSCT scheme and 20–23% for the DCS scheme.     

自动喷水灭火系统对环境的影响

1执行摘要当前,人们提高可持续发展能力及减少生活碳排放的努力,主要通过提高房屋的能源效率和减少潜在碳排放量来实现。最近,一种新的计算方式应运而生。它扩展了生活碳排放的评估范围,加入了诸如火灾之类的风险因素。这种方法表明,对于不同用途的建筑,无论是民居住宅、写字楼,还是高危险性厂房,如果没有适当风险管理和有效的消防设备,例如自动喷水灭火系统,统计碳排放量就会在建筑的生命周期期间增加。     

Effect of internal partitions on the performance of under floor air supply ventilation in a typical office environment

This paper presents a case to investigate the effect of partitions in an office on the performance of under floor air supply ventilation system via computational fluid dynamics. The assessment is in terms of thermal comfort and indoor air quality with the use of a validated computer model. The results indicate that the partitions may significantly affect airflow and performance of a under floor air supply ventilation system. In particular, the presence of a gap above the partition wall is able to improve air distribution owing to less air re-circulation in the upper zone. Its effect on thermal comfort and indoor air quality indicators are evaluated.     

Impact of shading air-cooled condensers on the efficiency of air-conditioning systems

Shading is a technique used to reduce the cooling demand in buildings and save energy. This paper investigates the possibility of reducing the electrical demand and saving energy by shading the condensers of air-conditioning (A/C) equipment. A limiting analysis compares the performance of several A/C systems with ideal shade to those with ideal solar heat gain. The comparison is based on a theoretical model and data from equipment catalogs. The results show that the theoretical increase in the coefficient of performance (COP) due to shading is within 2.5%. Furthermore, this small improvement in ideal efficiency decreases at higher ambient temperatures, when enhancements to efficiency are more needed. A sensitivity analysis shows that the small COP enhancement is not significantly affected by assumed variables. The actual efficiency improvement due to shading is not expected to exceed 1%, and the daily energy savings will be lower. The findings indicate that condenser shading alone, without evapo-transpiration, is not an effective measure to improve efficiency or save energy.