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.     

Influence of building parameters and HVAC systems coupling on building energy performance

The performance of different HVAC systems varies when coupled with different buildings. This paper examines the relationship between building heating and cooling load and subsequent energy consumption with different HVAC systems. Two common HVAC systems in use throughout the UK office building stock, variable air volume (VAV) system and fan coil (FC) with dedicated outside air system, have been coupled with a typical narrow plan office building with and without daylight control and for both cellular and open plan.The results presented in this paper clearly indicate that it is not possible to form a reliable judgment about building energy performance based only on building heating and cooling loads. For the two investigated systems, variable air volume system and fan coil with dedicated outside air system, the difference between system demand and building demand varied from over −40% to almost +30% for cooling and between −20% and +15% for heating. If a heat recovery unit is used, the difference in heating performance is even greater, rising to −70%.     

深圳市某办公楼空调系统节能潜力分析

通过对深圳市某办公楼空调系统运行状况的调查测试和模拟，分析了该工程冷水机组及冷水系统的运行方案，提出了空调系统节能改造方案并讨论了其经济性。     

Model-based analysis and simulation of airflow control systems of ventilation units in building environments

Model-based analysis and simulation of the airflow control system of ventilation units is of primary importance for the design and maintenance of the entire HVAC system in building environments. In this paper, we develop a mathematical model to simulate such airflow control systems. The model is implemented and a systematic analysis of the system is carried out, including its dynamic simulations in SIMULINK. The simulation results are compared with data obtained from analytical predictions as well as with experimental results available for a lab-scale ventilation unit. Finally, based on the combination of temperature and airflow regulations with conventional PI controllers, we provide the results of simulations of the entire ventilation unit control system for two different types of loading conditions.     

Analysis of annual heating and cooling energy requirements for office buildings in different climates in Turkey

A great amount of world energy demand is connected to the built environment. Electricity use in the commercial buildings, accounts for about one-third of the total energy consumption in Turkey and fully air-conditioned office buildings are important commercial electricity end-users since the mid-1990s. In the presented paper, the interactions between different conditions, control strategies and heating/cooling loads in office buildings in the four major climatic zones in Turkey – hot summer and cold winter, mild, hot summer and warm winter, hot and humid summer and warm winter – through building energy simulation program has been evaluated. The simulation results are compared with the values obtained from site measurements done in an office building located in Istanbul. The site-recorded data and simulation results are compared and analyzed. This verified model was used as a means to examine some energy conservation opportunities on annual cooling, heating and total building load at four major cities which were selected as a representative of the four climatic regions in Turkey. The effect of the parameters like the climatic conditions (location), insulation and thermal mass, aspect ratio, color of external surfaces, shading, window systems including window area and glazing system, ventilation rates and different outdoor air control strategies on annual building energy requirements is examined and the results are presented for each city.     

哈尔滨阎家岗国际机场航空站楼暖通空调设计

概要介绍了建立在高寒地区的大型空港航站楼的暖通空调系统设计，阐述了设计原则和设计思路。强调要根据航站楼使用功能及建筑特点，对各区域空间采用不同的空调系统方案和灵活的设计手法，认为既应考虑满足室内环境的舒适度和运行管理的便利，又要考虑节能；要针对高寒地区冬季室内外温差大的特点，采取切实可行的防寒保温措施和合理的供暖方案。在负荷计算时，出港层人数按误机２ｈ计算。     

北京某既有办公楼的节能诊断

以北京某既有办公楼节能诊断为例,从建筑概况、围护结构、空调系统、供暖系统、通风系统等方面介绍了办公类建筑节能诊断的主要内容及方法,并通过技术经济比较给出了节能改造的建议。     

Changing microbial concentrations are associated with ventilation performance in Taiwan's air-conditioned office buildings

Our study conducted serial environmental measurements in 12 large office buildings with two different ventilation designs to obtain airborne microbial concentrations in typical office buildings, and to examine the effects of occupant density, ventilation type and air exchange efficiency on indoor microbial concentrations. Duplicate samples of airborne fungi and bacteria, a total of 2477 measurements, were collected based on a scheme of conducting sampling three times a day for at least seven consecutive days at every study building. Air change rates (ACHs) were also estimated by tracer gas concentration decay method, and measured by continuous Multi-Gas monitor for each building. Most sampling sites were with total fungal and bacteria concentrations higher than 1000 CFU/m(3), an often-quoted guideline in earlier research. Significantly higher concentrations of fungi and bacteria, as well as higher indoor/outdoor (I/O) ratios across most groups of airborne microbes, were identified in buildings with fan coil unit (FCU) system than those with air-handling unit (AHU) system (Student's t test, P < 0.0001). Older buildings and higher air exchange rates were statistically associated with greater indoor bacteria levels in FCU ventilated buildings (R(2) = 0.452); a pattern not found in AHU buildings. Increasing ACH seemed to be the determinant factor for rising indoor fungal and Cladosporium concentrations in those FCU buildings (R(2) = 0.346; 0.518). Our data indicated that FCU ventilated buildings might have provided more outdoor matters into indoor environments through direct penetration of outdoor air. Results also demonstrated a quantitative association between rising numbers of occupants and increasing indoor levels of yeast in both FCU and AHU ventilated buildings. The regression model identified in this study may be considered a reference value for proposing an optimal ACH, while with adequate filtration of fresh air, as an effective strategy in lowering indoor microbial concentrations in air-conditioned buildings. PRACTICAL IMPLICATIONS: As control of indoor microbial contamination has become an increasing concern around the world, feasibility and effectiveness of adopting ventilation approach has attracted a significant interest. This field investigation demonstrated, quantitatively, critical variables to be taken into consideration while applying such a measure, including the kinds of microbes to be removed and the types of ventilation system already in place.     

Eawag Forum Chriesbach—Simulation and measurement of energy performance and comfort in a sustainable office building

The Eawag's new headquarters “Forum Chriesbach” is an exemplary illustration of a ‘sustainable’ construction design for office buildings. With a unique combination of architectural and technical elements the building reaches a very low 88 kWh/m² overall primary energy consumption, which is significantly lower than the Swiss Passive House standard, Minergie-P. A monitoring and evaluation project shows that the building is heated mainly by using the sun and internal heat gains from lighting, electrical appliances and occupants, resulting in an extremely low space heating demand. Cooling is provided by natural night time ventilation and the earth-coupled air intake, which pre-cools supply air and provides free cooling for computer servers. However, values for embodied energy and electricity consumption remain significant, even with partial on-site electricity production using photovoltaics. TRNSYS computer simulations show the contributions of individual building services to the overall energy balance and indicate that the building is resilient towards changes in parameters such as climate or occupancy density. Measurements confirm comfortable room temperatures below 26 °C, even during an extremely hot summer period, and 20-23 °C in the winter season. An economic analysis reveals additional costs of only 5% compared to a conventionally constructed building and a payback-time of 13 years.     

写字楼估价中的区位因素分析

针对写字楼估价中对区位因素分析的不规范,首先探讨了写字楼的概念和特点,然后分析了房地产估价中的区位和区位因素,最后着重介绍了写字楼物业估价中区位因素分析应包含的内容,以保证写字楼估价的合理性,从而推动写字楼市场的发展.     

教化小区综合楼暖通空调设计

文中介绍了教化小区综合楼暖通空调系统的设计,阐述其在空调系统、通风系统、冷热源、水系统、防排烟、空调自控及消声减振等方面的设计及空调方式和新风量的选取。保持大厦内温度、湿度分布均匀,活动区风速在设计范围内,空调设备噪声较小。     

Energy use and thermal comfort in a rammed earth office building

A two-storey rammed earth building was built on the Thurgoona Campus of Charles Sturt University in Albury-Wodonga, Australia, in 1999. The building is novel both in the use of materials and equipment for heating and cooling. The climate at Wodonga can be characterised as hot and dry, so the challenge of providing comfortable working conditions with minimal energy consumption is considerable. This paper describes an evaluation of the building in terms of measured thermal comfort and energy use. Measurements, confirmed by a staff questionnaire, found the building was too hot in summer and too cold in winter. Comparison with another office building in the same location found that the rammed earth building used more energy for heating. The thermal performance of three offices in the rammed earth building was investigated further using simulation to predict office temperatures. Comparisons were made with measurements made over typical weeks in summer and winter. The validated model has been used to investigate key building parameters and strategies to improve the thermal comfort and reduce energy consumption in the building. Simulations showed that improvements could be made by design and control strategy changes.     

某既有办公建筑空调系统净化改造分析

以某既有办公建筑空调系统净化改造项目为例,通过分析项目的实际需求,提出了分别采用风机盘管和新风机组的改造方案。研究确定了室内和室外PM2.5的设计计算浓度及新风机组过滤器效率计算公式,并得出了渗透换气次数和人均新风量对选择新风机组过滤器效率的影响。通过综合对比分析不同新风机组过滤方案的优缺点,选择G4过滤器+静电过滤器+F8过滤器作为最终方案。介绍了建筑漏洞封堵、空调系统清洗、精细化运行等方面的改造措施和方法。     

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)).     

Comparison of underfloor and overhead air distribution systems in an office environment

This study compares thermal environment of two air distribution systems in an office setting. Airflow, heat and mass (water vapor and contaminant gas) transfer in steady-state condition are modeled for an underfloor air distribution system and an overhead air distribution system. The models include a typical cubicle in a large office floor with a chair, a desk with a personal computer on top, and heat sources such as seated person, desktop computer, and lights. For underfloor air distribution system, cool air enters the occupied zone through an inlet located at the floor level supplying a vertical upward inflow. Three different locations of the inlet diffuser are considered. For overhead air distribution, the inlet is located on the ceiling with slower and cooler inflow. Three inlet angles are considered. For both systems, the air return location is on the ceiling at the same place. Distributions of velocity, temperature, relative humidity, and contaminant concentration in various cases for both systems are computed. Thermal comfort factors are assessed for the two systems. The results are compared among cases of each system, as well as between two typical cases of the two systems and to experimental data for an actual office building given in literature. The results provide a detailed understanding of air transport and its consequence on thermal comfort and indoor air quality that are useful for office building air conditioner design. It is found that underfloor system gives better performance than overhead system in contaminant removal and significantly in energy saving while maintaining the same thermal comfort condition.     

某医院门诊综合大楼暖通设计

本文详细介绍了某医院门诊综合大楼的暖通设计全过程,主要包括了空调冷负荷计算、空调调节系统方案、风机盘管的选择及地下室送风量计算等,可供相关类似工程设计参考。     

A simulation environment for performance analysis of HVAC systems

Due to the lack of a building simulation program that can simulate in details the combined heat, vapor, and liquid transfer in porous elements and the HVAC (heating, ventilation and air-conditioning) systems, a flexible computational algorithm has been elaborated in order to integrate models for both HVAC systems and multizone hygrothermal building model. In the algorithm, models for the primary system-composed of chiller, cooling tower, primary pumps, and condensation pumps—have been described. For the secondary system, models for the cooling and dehumidifying coil, humidifier, fan, and mixing box have been considered. Those mathematical models have been integrated into the whole-building PowerDomus simulation environment. The simulation environment is presented, and results show the usability aspects of the proposed computer environment by comparing air- and water-cooled equipment.     

办公建筑空调系统运行管理节能的探讨

通过对福州市某办公建筑空调系统的运行状况和能耗进行现场调查和测试,可知在空调系统总能耗中,冷水机组主机的能耗占比最大,为60%左右;其次为整个水输送系统的能耗,约为30%。分别从机组的启动策略、冷冻水和冷却水系统的节能管理、制冷机组冷冻水出水温度的控制、空调末端的运行管理以及用户的用能习惯等五个方面,讨论分析了空调系统不合理的运行状态及其节能潜力,并探讨了相应的节能管理措施。     

Reducing particle exposures in a tropical office building using electrostatic precipitators

Epidemiological surveys have shown that indoor fine particle exposures are associated with various health outcomes. Concomitantly, empirical data on the impact of electrostatic precipitation filter use on indoor particles in an office building has not been published. This research reports an intervention study on the impact of various filters within the air-handling unit (AHU) of a tropical office building. The following filtration methods were tested: (1) media filters (MED); (2) electrostatic precipitation filters (EAC); and (3) electrostatic precipitation filters enhanced with a media pre-filter (EAC-PF). The efficiencies of EAC filters were significantly superior to media filters for the removal of fine particles. Enhancement of EAC with media pre-filters (PF) augments the fine particle removal resulting in overall efficiencies comparable to that of HEPA filters. However, there was no difference in the removal efficiencies of coarse particles between MED, EAC and EAC-PF filters. When indoor particle removal effectiveness was evaluated, EAC and EAC-PF filters were more effective than MED filters for submicron particles. Further, effectiveness of EAC-PF was significantly superior to EAC due to effects of PF filtration of large particles, backpressure and lesser re-entrainment of large particles into the supply air stream. Effectiveness of EAC and EAC-PF were lower in occupied compared to non-occupied periods due to the higher particle loadings on collection plates. Using mass balance models, the results showed that effectiveness of electrostatic precipitation filters will improve as recirculation rates increase. These findings suggest that employing electrostatic precipitator filters under high recirculation rates can be an energy efficient strategy to reduce harmful indoor fine particle exposures.