Simulation comparison of VAV and VRF air conditioning systems in an existing building for the cooling season

Performance of two widely used air conditioning (AC) systems, variable air volume (VAV) and variable refrigerant flow (VRF), in an existing office building environment under the same indoor and outdoor conditions for an entire cooling season is simulated by using two validated respective models and compared. It was observed that the indoor temperatures could not be maintained properly at the set temperature by the VAV no-reheat boxes. However, it could be maintained by the VAV boxes with reheat with a significant energy consumption penalty. It was found that the secondary components (indoor and ventilation units) of the VRF AC system promised 38.0-83.4% energy-saving potential depending on the system configuration, indoor and outdoor conditions, when compared to the secondary components (heaters and the supply fan) of the VAV AC system. Overall, it was found that the VRF AC system promised 27.1-57.9% energy-saving potentials depending on the system configuration, indoor and outdoor conditions, when compared to the VAV AC system.     

上海某酒店式公寓空调设计

从节能与舒适的角度出发,对上海张江某酒店式公寓空调末端采用温湿度独立控制系统,即吊顸辐射供冷供热系统加独立新风系统.采用高效热泵式溶液调湿机组处理新风,地源热泵机组供冷、供热、供生活热水.详细介绍了整个空调系统及自控系统,并分析了吊顶防结露、厨房风量平衡等设计难点及其解决措施.     

某机关住宅楼基坑支护工程实践

结合实例介绍预应力管桩-钢结构内支撑的支护方案、及施工中的部分技术要点控制     

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.     

The loss factors of building openings for wind-driven ventilation

This study used wind tunnel experiments to determine the loss factors of building openings for wind-driven ventilation. It is found that the loss factor is a function of internal porosity, but independent of Reynolds number. The loss factor of a partially open door increased as the door angle decreased. In addition, the influence of thickness ratio on the loss factor is much smaller than the internal porosity. The present study also derived the relationship between the loss factor and the discharge coefficient used in the orifice equation. The experimental results demonstrate that the ventilation rate of wind-driven cross ventilation can be predicted by a resistance model, once the loss factors of the openings and external pressure coefficients are known. Besides, it was found that the flow resistance of the internal opening dominated the ventilation rate when the external openings are large. But the resistance of external opening is the governing parameter when the external openings are small.     

Causes of structural deformations of an apartment building on weak foundations in Verkhnekamsk

The results of monitoring are analyzed to ascertain the causes of structural deformation and settlement nonuniformity of an apartment building on pile foundations. Translated from Osnovaniya, Fundamenty i Mekhanika Gruntov, No. 5, pp. 19–20, September–October, 1999.     

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。     

Reducing peak requirements for cooling by using thermally activated building systems

This paper presents general guidelines for the required cooling capacity of an entire office building using thermally activated building systems (TABS). By activating the thermal mass of the building using pipes embedded in the floor, peak loads can be reduced. On-site measurements were performed to obtain the required cooling power of an entire building as well as individual zones. Beside this, the internal climate conditions of rooms and surface temperatures of the TABS were measured. The measured data were used to analyze the predictive performance of a simulation model. In order to acquire general guidelines for the required cooling capacity of a standard office building, simulations of an entire building were used to determine the impact of variable internal heat gains and different sized windows. The required cooling capacity was compared to the cooling capacity of a system without energy buffering (e.g. chilled ceiling panels). It was found that reductions up to 50% of the cooling capacity for a chiller can be achieved using TABS. The presented results within this paper can be used as design guidelines in the first stage of a design process. The results focus on temperate climates and were derived using Dutch climate conditions.     

A review of wind-driven rain research in building science

Wind-driven rain (WDR) or driving rain is rain that is given a horizontal velocity component by the wind. WDR research is of importance in a number of research areas including earth sciences, meteorology and building science. Research methods and results are exchangeable between these domains but no exchanges could yet be noted. This paper presents the state-of-the-art of WDR research in building science. WDR is the most important moisture source affecting the performance of building facades. Hygrothermal and durability analysis of facades requires the quantification of the WDR loads. Research efforts can be classified according to the quantification methods used. Three categories are distinguished: (1) experimental methods, (2) semi-empirical methods and (3) numerical methods. The principles of each method are described and the state-of-the-art is outlined. It has been the intent of the present paper to bring together the reports, papers and books—published and unpublished—dealing with WDR research in building science to provide a database of information for researchers interested in and/or working in WDR research, independent of their field of expertise.     

南昌联发广场公寓楼结构设计与计算分析

介绍了南昌联发广场工程的公寓楼(高位转换)在方案设计、扩大初步设计和抗震设计中所要求进行的弹性分析、弹塑性分析、性能设计等过程。分析结果表明,在地震和风荷载作用下,工程的主体结构具备较好的承载和变形能力,刚度等指标满足计算要求,无明显的薄弱层,能够达到小震弹性、中震弹性和大震不倒的性能目标,满足了设计规范和使用的要求。     

万国金融大厦空调冷热源方案选择

大厦空调冷热源可以有不同形式。文中通过对五种空调方案在初投资、占地面积、维护管理、能耗费用及对环境影响等方面作综合比较后，认为离心式或螺杆式冷水机组＋燃油（气）锅炉是最适合于该大厦的空调方案。     

Life cycle primary energy use and carbon emission of an eight-storey wood-framed apartment building

In this study the life cycle primary energy use and carbon dioxide (CO₂) emission of an eight-storey wood-framed apartment building are analyzed. All life cycle phases are included, including acquisition and processing of materials, on-site construction, building operation, demolition and materials disposal. The calculated primary energy use includes the entire energy system chains, and carbon flows are tracked including fossil fuel emissions, process emissions, carbon stocks in building materials, and avoided fossil emissions due to biofuel substitution. The results show that building operation uses the largest share of life cycle energy use, becoming increasingly dominant as the life span of the building increases. The type of heating system strongly influences the primary energy use and CO₂ emission; a biomass-based system with cogeneration of district heat and electricity achieves low primary energy use and very low CO₂ emissions. Using biomass residues from the wood products chain to substitute for fossil fuels significantly reduces net CO₂ emission. Excluding household tap water and electricity, a negative life cycle net CO₂ emission can be achieved due to the wood-based construction materials and biomass-based energy supply system. This study shows the importance of using a life cycle perspective when evaluating primary energy and climatic impacts of buildings.     

Exergetic and sustainability performance comparison of novel and conventional air cooling systems for building applications

This study presents energy and exergy analyses and sustainability assessment of one novel and three conventional types of air cooling systems for building applications. First, effectivenesses of the systems are determined using energy analysis method. Second, exergy aspects of the systems are investigated for twelve different dead state temperatures varying from −5 °C to 50 °C with a temperature interval of 5 °C. The specific exergy flows of humid air, dry air and water, exergy efficiency, and specific exergy destruction are then calculated. Sustainability index is also used to define and discuss the systems’ sustainability aspects. Finally, the results obtained here show that at the dead state temperatures of higher than 23 °C (comfort temperature), exergy efficiency and sustainability of the novel system, which is based on the novel Maisotsenko cycle (M-Cycle), is higher than those of the conventional systems. At a dead state temperature of 50 °C, novel cooling system's exergy efficiency can reach 60.329% as the maximum, while the minimum exergy efficiency of other conventional cooling systems becomes as low as 35.866%, respectively.     

Using spatial indicators to predict ventilation and energy performance-correlation analysis for an apartment building in five Chinese cities

In the early design stages, architects are in constant search of a design direction that can determine the success or failure of the final design. However, in real design practice, most of the prediction methods for building performances, in this paper energy and thermal comfort, are utilised in the later design stages. Spatial configuration is one of the most important issues for architectural design in the early design stage. This study investigates the correlations between the spatial indicators connected with architectural design and the building physics indicators ventilation performance and energy performance. The main objective is to explore the potential of applying spatial indicators using space syntax to predict ventilation performance and energy performance in order to support architects for the evaluation of their concepts and schemes in early design stages. The layout of a high-rise apartment in China in five different cities is chosen as a case study. The results show that the selected three indicators: connectivity value, air change rate and annual cooling saving ratio are linearly correlated, not just at building level but also at room level. R², the correlation coefficient of determination, is between 0.53 and 0.90 (except for the case of Chongqing at building level).     

Energy consumption and conservation in the Russian apartment building stock

Energy consumption of buildings in Russia and other states of the former Soviet Union has typically been reported in very coarse terms, as annual energy use normalized by weather and floor area. Reported figures, based on estimates derived from available energy-delivery data, have shown that Russian residential buildings consume on the order of twice as much primary energy for space-heating as those in some developed Western countries. Reports have been accompanied with qualitative assertions that higher levels of insulation, reduced air infiltration, and better control of heating systems could reduce energy use. However, there has been a dearth of data that first distinguish Russian buildings by construction type and insulation level, and second attempt to quantitatively pinpoint causes for the relatively high energy use. Such data are needed to focus contemporary energy-conservation efforts in Russia on the most promising areas. This paper presents a preliminary set of information that illuminates these areas, concentrating on the city of Moscow. The analysis breaks down Moscow's district-heated apartment building stock by type and year of construction and by the required thermal standards in force at the time of construction. It aggregates these buildings into three classes according to the type of external wall construction — brick or large block, single-layer panel, and three-layer panel — and estimates overall annual energy use for space-heating via a steady-state model. It then compares predicted and measured energy use, for the aggregation and, more accurately, for a single building for which detailed energy-use data are available. In both cases there is a large discrepancy, with actual space-heating energy use exceeding design predictions by at least 60%. Analytical efforts to reconcile the excess energy consumption for the metered building strongly suggest that the most important cause of relatively high space-heating energy use in the building is poor control of heat delivery from the district heating system.     

单元式中高层住宅的垂直交通构造

对单元式中高层住宅设置一台电梯的可行性进行了论证,并提出了电梯、楼梯及露台走道组合的垂直交通方案,指出该方案降低了住宅的建造成本,且构造简单,经济实用,以推广该方案在实际工程中的应用.     

冷却水制冷在某商业建筑中的应用

作为三大能耗产业之一,建筑能耗受到人们广泛关注。在大型公共建筑中空调用电在建筑能耗中占据很大比例,而在暖通空调能耗中,冷热源设备用能为空调用电中主要能耗。为达到建筑节能的目的,可以在一定范围内尽量减少空调主机运行时间,因此当空调负荷降低到一定程度时,可通过冷却水接入空调末端设备,可以在一定程度上降低空调主机运行时间,以达到节能目的。     

南方地区塔式高层住宅设计有关消防问题探讨

本文回顾和分析了塔式高层住宅公共部位的常见设计类型。针对目前在消防设计方面存在的有关前室和走道布局等方面的矛盾和问题,结合自己对规范的理解,进行了思考和探讨。对在我国南方地区充分利用自然排烟的有利条件,以达到消防的安全性、可靠性与使用的合理性、经济性的统一,表达了自己的见解;并就目前存在问题可能的解决途径,提出初步设想。     

Thermal performance of a non-air-conditioned building for passive solar air-conditioning: Evaluation of roof cooling systems

A periodic heat transfer analysis has been presented to predict the dynamic thermal behaviour of a non-air-conditioned building with evaporative cooling systems over the roof. Three different cases of evaporative cooling systems, namely, open roof pond, moving water layer over the roof, and water spray over the roof, have been studied in detail to assess their effectiveness for passive space air-conditioning. The effects of air ventilation, furnishings and ground heat conduction have been incorporated in the present analysis. Numerical computations using typical data of a harsh summer day in the Delhi climate, have been made to assess the analytical results quantitatively.It was found that the maximum cooling is achieved by water spray over the roof. However, the roof pond system with stationary water is more effective in stabilizing the fluctuations of indoor temperature as well as heat flux entering through the roof. Furthermore, with the increase in the number of air changes per hour, the time variation of indoor air approaches to that of outdoor air in phase as well as in magnitude.