室内温、湿度对人体热舒适和空调能耗影响的研究

以采用一次回风集中空调系统的办公建筑为例,就室内温、湿度设计参数对空调房间热舒适环境和空调系统能耗的影响进行了分析。研究结果表明,在同样的室内人体热舒适环境(等效温度)的条件下,随着室内温度的增加,一次回风系统的需冷量和总的耗能量是增加的。因此,夏季提高空调室内温度是不节能的。在相同热舒适(等效温度)条件下,要减少空调系统的冷负荷,室内设计温、湿度参数在推荐的热舒适区范围内,宜采用较大的室内相对湿度和较低的室内干球温度的组合,或采用较高的等效温度。     

对热舒适、空气感觉质量及能耗的模拟研究

室内空调设计温度和新风量对热舒适，室内空气质量及能耗量有重要影响，然而对它们之间相互关系进行研究的文献却较少。通过计算机模拟空调系统在7种室内设计温度和7种新风量条件下的运行情况，得到不同的设计条件组合对热舒适、人体感觉空气质量及建筑能耗量的影响。基于这项分析，提出了此办公建筑合理的室内设计温度和新风量取值。     

Evaluating the low exergy of chilled water in a radiant cooling system

In this paper, in order to make guidelines for designing a low-energy radiant cooling system with an air-handling unit (AHU) for dehumidification, we investigated the impact of various air-conditioning parameters on the exergies of chilled water supplied to radiant panels and a cooling coil. The cooling load, thermal comfort index PMV, relative humidity, area of radiant panels, sensible heat factor (SHF), temperature and air-flow rate of supply air of the AHU, and presence/absence of total heat exchanger were considered. We used computational fluid dynamics (CFD) code in order to analyze the indoor air-flow and thermal environments, and added models for the calculation of thermal transfer to radiant panels and a cooling coil. Furthermore, a feedback control algorithm was introduced to calculate the surface radiant panel temperature, targeting the average PMV of the task area in an office room. As a result, the impact of various air-conditioning parameters on the exergies of chilled water were demonstrated quantitatively. As an example, by reducing the cooling load rate from 100% to 57% and 27%, the exergy of chilled water decreased by 47% and 67%, respectively.     

A new method of determination of indoor temperature and relative humidity with consideration of human thermal comfort

A new method is described in this article for selecting indoor temperature and indoor relative humidity to achieve minimum energy consumption for a required indoor thermal comfort level which is evaluated with indoor effective temperature. This method is derived from a central air-conditioning system and is based on our investigation that under a same indoor effective temperature, the system cooling load and the system energy consumption increase with an increase of indoor temperature. As such, energy consumption cannot be reduced with increasing indoor temperature for a given human thermal comfort level. In order to reduce energy consumption while keeping a same indoor thermal comfort level, indoor temperature and relative humidity may be determined with the proposed method described in this article. With the proposed method, a parameter variation study has also been conducted, which suggests that for a given indoor effective temperature, a combination of high indoor relative humidity and low indoor temperature be generally taken. The proposed method is based on the central air-conditioning system; yet it can be easily extended to other systems.     

Performance of temperature and humidity independent control air-conditioning system in an office building

The temperature and humidity independent control (THIC) system, which controls indoor temperature and moisture separately, may be an attractive alternative to existing conventional HVAC systems for its prominent improvement on the overall system performance and utilization of low grade energy resources. In order to verify the effectiveness of THIC system, a pilot project has been implemented in an office building in Shenzhen, China. In the system, liquid desiccant fresh air handling units driven by heat pumps are utilized to remove the entire latent load of outdoor air supplied for the whole building, and chilled water at the temperature of 17.5 °C from chiller is pumped and distributed into dry fan coil units and radiant panels to control indoor temperature. This paper presents the results of field test of the system, which shows that the system can provide a comfortable indoor environment even in very hot and humid weather. The COP of the entire THIC system can reach 4.0. According to the energy usage data recorded from the year 2009, the energy consumption of the THIC system in the tested office building was 32.2 kWh/(m² yr), which demonstrates magnificent energy-saving potential compared with the conventional air-conditioning system (around 49 kWh/(m² yr)).     

A comparative study of different control strategies for indoor air humidity

There has been a rising concern in controlling the high indoor humidity of hot and humid countries. When an air-conditioned space experiences only part of its design heat load, its humidity tends to rise as a result of the air-conditioning system trying to control the indoor temperature by reducing its cooling capacity. In this study, the part-load dehumidification performances of three temperature control strategies are compared, namely, chilled water flow control, bypass air control and the variable air volume control. Coil simulations are employed to study the part-load performance of these control strategies. The coil model has been validated with experimental data to within ±6.5%. The relative humidity of a space depends of factors such as design sensible heat factor of the space, temperature control strategy employed and load condition experienced by the space. Simulation results have indicated that chilled water control strategy results in the highest indoor humidity throughout the range of conditions studied while variable air volume system provides highly effective dehumidification performance of the cooling coil. Bypass air control appears to be a good option for adoption as it is able to provide an acceptable humidity over a wide range of load conditions without having to affect the air movement within the space.     

室内空气设计参数与空调系统节能条件浅析

本文针对暖通空调系统设计过程中室内空气参数标准的合理取值对空调能耗的影响,探讨了空调负荷、空调能耗和空调系统节能的基本概念,对室内空气温度和相对湿度标准对空调系统能耗的影响进行了计算分析,结果表明科学认识室内空气参数标准的合理取值对空调系统能耗的影响对当前建筑节能意义重大;空调系统节能条件需要具体分析,针对不同类型的建筑和不同的空调方式,其室内空气设计标准的影响不同,空调过程设计对空调系统节能具有重要影响。另外,将典型空调案例的计算结果推广到一般工程,容易导致工程设计概念上的混淆。     

高层办公楼空调系统运行能耗分析

通过建立哈尔滨高层办公建筑空调全年运行能耗的分析模型,利用DOE-2软件,采用正交试验法分别对办公建筑中安装全空气系统和风机盘管加新风系统的全年运行能耗进行了模拟计算,得出了在该特定的气候条件和建筑物类型中,全空气系统的单位面积全年能耗要略高于风机盘管加新风系统。     

Simulation of a VAV air conditioning system in an existing building for the cooling mode

In this study, simulation of a variable air volume (VAV) air conditioning system in an existing office building is presented for the cooling mode. A building simulation package was used for the simulation [DOE, EnergyPlus Engineering Document, Version 1.3., U.S. Department of Energy, Washington, DC, 2005]. The design information of the existing office building, the actual number of the internal load sources such as occupants, lighting, office equipments and the manufacturer's data for the existing rooftop unit (RTU) and the VAV boxes were used in the building simulation package. The simulation results; RTU power consumption, indoor zone temperature and relative humidity, were validated with the data obtained from the on-site measurements performed in the existing office building under the same outdoor conditions. It was found that 71.1% of all simulated power consumption data falls within ±15% range from the experimental data. The reason for the existence of some data out of band is due to the possible errors associated with the difference in the solar data used for the location 40 km away from the experimental location. It was found that 90.6-94.7% of the indoor temperature experimental data fall within ±1.5 °C range from the simulated data, and 88.3-91.3% of the indoor relative humidity data fall within ±18% range from the simulated data.     

某办公楼空调系统故障分析及调试

针对某办公楼出现的室内相对湿度过高、新风量不足、空气有异味等问题,分析了设计资料进行现场调研,采取降低冷水机组供回水温度、调节风机盘管风速、适当关闭风机盘管台数、清洗在等措施,基本解决了室内空气品质问题。探讨了该工程空调系统设计中不足之处和运行管理中应注意的问题。     

Energy savings in a building using regenerative evaporative cooling

This paper explores the potential of reducing the annual energy consumption of a central air-conditioned building through advanced evaporative cooling systems. The building considered is a typical three floor library building of a University. The regenerative evaporative cooling technology is coupled with the liquid cooled water chiller system to accomplish the energy conservation objective. Comparisons of the regenerative evaporative cooling are made with simple evaporative cooling to bring out the importance such a system. The well-known building simulation software, TRNSYS is used to carry out the heat load calculations and the dynamic simulations of the building. Annual energy consumptions of different components of the air-conditioning system are estimated for the existing water chiller system as well as for both coupled evaporative cooling systems (simple and regenerative). The annual energy consumptions, the indoor temperature, the relative humidity and the thermal comfort index ‘PMV’ are compared for all the three different air-conditioning systems. The coupling of direct and regenerative evaporative cooling technologies with water chiller system has shown, respectively, 12.09% and 15.69% savings in annual energy consumption of the building, while maintaining PMV between ?1 and +1 for most of the hours in the year.     

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.     

毛细管平面空调系统简介

传统的空调系统普遍采用温湿度耦合的控制方法,存在能源利用品位上的浪费、难以适应温湿度比的变化以及室内空气品质差等问题,针对我国日益高涨的提高室内环境舒适性和降低建筑能耗的大好形势,介绍一种高效节能的室内环境调节系统:毛细管平面空调系统,分析了其具有的优点及面临的问题和机遇.     

基于EnergyPlus对南京地区应用夜间通风预测

为了对南京地区进行夜问通风的可行性进行预测,选取南京地区某典型办公楼,利用建筑全能耗模拟软件EnergyPlus进行了模拟研究。在典型气象条件下,分别考虑了通风时间,换气次数等因素对室内温湿度及空气比焓的影响。将室内空气焓值的变化等效为空气源热泵空调耗电量,通过对比空调的耗电量与通风风机的耗电量,得出最佳的换气次数,并进行了节能效果分析。结果表明：通风时间选择在室外温度较低的时间段内较为合适。换气次数在不同的通风时间下对应不同的临界点,当换气次数小于临界点的换气次数时,等效空调耗电量大于风机耗电量,此时具有节能效果。当通风时间为6：00～6：30时,换气次数为1-2ac／h时,等效空调的耗电量与风机的耗电量差值的绝对值最大,半小时通风的最大节能达到3．6kWh。     

上海世博园部分建筑室内空调环境状况测试分析

为了了解上海世博园建筑室内空调环境状况和行为节能情况,采用实测方法对上海世博园13栋建筑的夏季室内空调环境进行了测试分析。结果表明:一些被测建筑的夏季室内空气温度偏低,最低室温为21.7℃;对于南方湿热地区的剧场建筑,采用开敞式建筑方案不利于室内热舒适环境的营造和节能,且仅利用自然通风和蒸发冷却降温手段难以营造出满足人体基本热舒适性要求的室内环境;展厅观众人数快速增加时室温变化较大,但相对湿度变化较小;一些展馆外门常开,冷风渗漏现象比较严重,加强行为节能是展馆建筑节能设计和运行管理需要考虑的一个重要问题。     

A study on the energy penalty of various air-side system faults in buildings

Automatic fault detection and diagnosis (FDD) can help enhance building energy efficiency by facilitating early detection of occurrence of system faults, especially those of air-conditioning systems, thus enabling rectification of the faults before much energy is wasted due to such faults. However, building owners may not invest in FDD unless they are convinced of the energy cost savings that can be achieved. This paper presents the results of a study on the energy cost impacts of a range of common system faults in variable air volume (VAV) air-conditioning systems, which are widely adopted for their good part-load energy efficiency. The faults studied include room air temperature sensor offset, stuck VAV box damper, supply air temperature sensor offset, stuck outdoor air damper and stuck/leaking cooling coil valve. The simulation results indicate that some faults may significantly increase energy use in buildings, for example, negative room air temperature sensor offset, stuck open VAV box damper, negative supply air temperature sensor offset, stuck open outdoor air damper and stuck open and leaking cooling coil valve. Since building occupants may adapt to the symptoms of these faults, such as reduced room air temperature, and thus may not complain about them, the occurrence of such faults are not immediately apparent unless a FDD system is available. Some other faults, e.g. positive supply air temperature sensor offset, positive room air temperature sensor offset, stuck closed cooling coil valve and stuck closed VAV box damper, may allow less energy to be used but will lead to unbearable indoor environmental conditions, such as high indoor temperature. Such faults, therefore, can easily be detected even without a FDD system, as there will be feedback from the building occupants.     

Space temperature difference,cooling coil and fan—energy and indoor air quality issues revisited

In designing an energy-efficient air-conditioning system that also simultaneously addresses the needs of adequate ventilation and acceptable indoor air quality, several factors begin to play an important role. Among several others, the cooling coil, the fan and the temperature difference between the space and the supply air (commonly known as the Space ΔT) can be considered to be crucial. For a given space cooling load, the choice of a particular Space ΔT has an implication on the amount of supply air required, which further has an impact on the performance of the cooling and dehumidifying coil as well as the fan. Inherent in these implications are issues related to energy, ventilation and indoor air quality. This paper investigates these implications and quantifies them by considering a hypothetical building in a tropical climate and subjecting the design to several parametric variations involving different Space ΔTs for a given space temperature and humidity condition. The total power requirements, comprising additional cooling, reheating and higher fan power, for a design involving a Space ΔT of 5 °C can be as high as a factor of 2.2 of the total power for a design with a Space ΔT of 8 °C. The implication of higher supply air flow rates on duct design is qualitatively discussed. For a given space cooling load and a given Space ΔT, the implication of increased design ventilation rates to address part-load ventilation requirements can lead to an additional installed cooling capacity of 17.5%. Finally, emerging technologies that are aimed at addressing both energy efficiency and IAQ are discussed.     

Advancement of solar desiccant cooling system for building use in subtropical Hong Kong

The solar desiccant cooling system (SDCS) had a saving potential of the year-round primary energy consumption as compared to the conventional air-conditioning system for full fresh air application in the subtropical Hong Kong. In order to further enhance its energy efficiency, advancement of the basic SDCS was carried out through a strategy of hybrid design. Six hybrid system alternatives of SDCS were therefore proposed, three for full fresh air design while another three for return air design for the building zone. Year-round performance evaluation of each solar hybrid desiccant cooling system was conducted for typical office application under different climatic and loading conditions. All the six hybrid system alternatives were found technically feasible, with up to 35.2% saving of year-round primary energy consumption against the conventional air-conditioning systems. Among the hybrid alternatives, recommendations were made on the SDCS hybridized with vapour compression refrigeration for full fresh air design; and the SDCS hybridized with vapour absorption refrigeration for return air design, since they had the saving potentials of both primary energy and initial cost. These two hybrid system alternatives used evacuated tubes, a more economical type of solar collectors compared to the PV or PVT panels.     

温湿度独立控制空调系统和常规空调系统的性能比较

选择北京和广州相同的办公楼作为比较对象,常规空调系统采用典型的风机盘管+独立新风的形式。应用DeST软件计算了建筑全年逐时冷负荷,计算了两个系统的能效比EER(energy efficiency ratio)和能耗。结果表明,对于北京的办公建筑,温湿度独立控制空调系统全年能耗为14.75k Wh/m2,EER为4.5;常规空调系统全年能耗为18.63k Wh/m2,EER为3.6。对于广州的办公建筑,温湿度独立控制空调系统全年能耗为32.66k Wh/m2,EER为4.5;常规空调系统全年能耗为43.39k Wh/m2,EER为3.4。相比常规空调系统,温湿度独立控制空调系统的节能率在20%～30%。     

Optimal control of an HVAC system using cold storage and building thermal capacitance

This paper presents a comprehensive analysis on the optimal control protocol to minimize the daily operating cost of an air-conditioning system in a 33 600 m² office building. The system consists of two chillers, one designated for cold storage charging, the other for direct cooling, an air-handling unit, a cooling tower, and water pumps. This analysis determines the optimal protocol for indoor temperature and humidity control as well as operating point settings for the chiller control considering two thermal storage sources: (i) the thermal capacitance of the building, and (ii) a cold storage facility. The analysis is based on the thermodynamic modeling of the air-conditioning system including the thermal response of the building structure. A discussion of operating cost savings is presented for several outdoor conditions and electricity rates. Furthermore, the load shift potentials are discussed for each storage source. The results of this analysis indicate significant savings can be achieved by precooling the building during hours of low electricity rates. The resulting load shifting can be augmented by utilizing cold storage equipment. The results are discussed in detail for Seattle climatic conditions and electric rates. A regional comparison of the results for the four US locations, Seattle, WA; Phoenix, AZ; San Diego, CA; and the island of Hawaii, is given.