相变材料和隔热材料降低顶层房间空调能耗效果之比较分析

针对合肥地区顶层房间,建立了在屋顶内外侧分别加装相变材料或隔热材料的房间的非稳态传热模型,比较分析了两种材料降低空调能耗的效果.研究发现:无论空调运行于恒温模式还是蓄冷模式,相变材料均未能完成一次凝固、熔解循环过程,相变材料利用率低,降低房间空调能耗的效果较隔热材料差;结合峰谷电价政策,房间空调蓄冷模式下日运行费用较小;综合考虑相变材料和隔热材料的节能性和经济性,选择隔热材料更为合理;在屋顶外侧加装隔热材料可使空调耗电量最大降幅为27.2%,空调日运行费用减少28.9%.     

Economical comparison between a solar-powered vapour absorption air-conditioning system and a vapour compression system in the Middle East

This paper presents an analysis of the general cost associated with single- and double-effect vapour absorption and vapour compression air-conditioning systems. The cost analysis covers the initial costs and the operating costs of each of the three systems. The vapour absorption system considered in this paper is based on water as the refrigerant and lithium bromide solution as the absorbent. The analysis is undertaken to help select an air-conditioning system that fulfils a 250 TOR cooling load of a five-floor student hospital in Alexandria, Egypt. The typical meteorological year database for Alexandria was used to estimate the cooling load for the building. The analysis is based on two different methods, the present worth value (PWC) and the equivalent annual cost (EAC), for initial and operating costs of each system. The selection depends on which system requires the minimum life-cycle cost (LCC) and can perform the intended function for its life span. The analysis also considers the interrelationship between economic and thermodynamic aspects, such as the dependence of operating cost on the surrounding climatic conditions. The method used and the results from this study offer useful guidelines for researchers and decision-makers when selecting an air-conditioning system. The results show that the double-effect vapour absorption system is the preferred option for its minimum present worth value as well as the equivalent annual cost.     

Life-cycle cost analysis for constant-air-volume and variable-air-volume air-conditioning systems

This study presents a life-cycle cost analysis using detailed load profiles and initial and operating costs to evaluate the economic feasibilities of constant-air-volume (CAV) and variable-air-volume (VAV) air-conditioning systems. The present-worth cost method for life-cycle cost analysis is applied to a sample building located in Adana, Turkey which can be conditioned with CAV or VAV systems. In the analysis, two different uses of the building (as a school or as an office center), two different operating scenarios for air-conditioning system (scenario 1 and scenario 2) and two different economic measures (developed and developing economy) are considered. It is found, for all the cases considered, that although initial cost of the VAV system is higher than that of the CAV system, the present-worth cost of the VAV system is lower than that of the CAV system at the end of the lifetime due to lower fan-operating costs.     

A study on residential heating energy requirement and optimum insulation thickness

Heat loss from buildings has a considerable share in waste of energy especially in Turkey since no or little insulation is used in existing and new buildings. Therefore, energy savings can be obtained by determining of heat loss characteristics with using proper thickness of insulation. For this purpose, in this study, calculations of optimum insulation thickness are carried out on a prototype building in Bursa as a sample city. Considering long term and current outdoor air temperature records (from 1992 to 2005), degree-hour (DH) values are calculated, and the variation of annual energy requirement of the building is investigated for various architectural design properties (such as air infiltration rate, glazing type, and area). Then, the effects of the insulation thickness on the energy requirement and total cost are presented. Based on life cycle cost (LCC) analysis, the optimum insulation thicknesses are determined for different fuel types. As a conclusion, the length of the heating period is average 221 days, and the mean heating DH value is found as 45 113.2 besides changing between 38 000 and 55 000. The optimum insulation thicknesses for Bursa vary between 5.3 and 12.4 cm depending on fuel types. In addition to this, the variation in Turkey is more dramatically.     

基于毛细管型辐射供暖与供冷系统影响因素的研究

随着建筑节能的推广和人们对室内生活舒适性要求的提高,采用一种更先进、更节能的室内空气调节系统就显得日趋重要。毛细管型辐射供暖与供冷系统因具有舒适度高、节能效果显著、节省建筑空间等的优点逐渐被广泛采用。对以毛细管为末端的毛细管型辐射供暖与供冷系统布置形式作了介绍,分析了该系统的组成及优点。以辐射供冷为例,探讨了辐射冷系统的末端一毛细管席供冷量的影响因素。     

Performance of antisolar insulated roof system

Rooms with concrete slab roofs directly exposed to the sun become unbearably hot during summer and very cold during winter. Huge amounts of energy are required to keep them comfortable. Application of thermal insulation on roofs significantly reduces energy required for heating and cooling. The effectiveness of roof insulations may be further enhanced if a layer of antisolar coating is applied on top of the insulation. The antisolar coating reflects most of the incident sunlight and prevents the roof from heating up. This reduces the daily cycles of thermal expansion and contraction which cause cracks in the roof slabs for the rainwater to leak through. The antisolar coating prolongs the useful life of the building structure as well as the life of the insulation that evaporates with heat. The method of application of the antisolar coating has been specially developed to eliminate thermal bridges formed between the edges of the tiles. This report presents the results of an experiment conducted at the Attock Refinery Limited (ARL) Rawalpindi to assess the performance of the antisolar insulated roof system. Record of the room temperature before and after the installation of the system shows a significant reduction in the indoor temperature. The room occupants, who used to experience a very high thermal stress after 10:30 am in spite of the 1.5-ton air conditioner operating in the room, felt much relieved after the installation. They had to turn back the thermostat of the air conditioner and even had to switch it off occasionally. A detailed thermal analysis of the room shows that cost of an antisolar system is paid back in less than a year in the form of savings of energy required for air-conditioning in summer and for gas heating in winter. In addition, the system prevents the addition of 150 kg per year of green house gases to the atmosphere for each square meter of the area covered by the system. It also provides a quieter environment by reducing the operational duration of the air-conditioning and gas heating appliances.     

Year round experimental study on a constant temperature and humidity air-conditioning system driven by ground source heat pump

Numerous studies about the ground source heat pump building heating and cooling systems have been constructed in office building, hotel, residential building and school et al. However, few researches about the constant temperature and humidity air-conditioning system driven by ground-coupled heat pumps were carried out. In this paper, a constant temperature and humidity air-conditioning system driven by ground source heat pump was designed and constructed in an archives building in Shanghai, China. During the operation in the cooling mode, the heat extraction from the condenser of the heat pump was divided: part was rejected to the soil while another was used to reheat the air in AHUs. According to the experimental results, the indoor temperature and relative humidity fulfilled the “Archives Design Code”. In summer, the heat rejected to the soil was reduced by 32%, which was helpful for the earth energy conservation. The soil temperature increased only 0.5 °C after the GSHP system operating for a year. The energy cost of the air-conditioning system was 56.1 kWh/m². Compared with air source heat pump system and water cooled unit with boiler system, the operating cost of ground source heat pump was reduced by 55.8% and 48.4%, respectively.     

Aquifer thermal storage (ATES) for air-conditioning of a supermarket in Turkey

A heating, ventilation and air-conditioning (HVAC) system with integrated aquifer thermal energy storage (ATES) was designed for a supermarket building in Mersin, a city near the Mediterranean coast in Turkey (36° 49′ N and 34° 36′ E). This is the first ATES application carried out in Turkey. The peak cooling and heating loads of the building are 195 and 74 kW, respectively. The general objective of the system is to use the groundwater from the aquifer to cool down the condenser of the HVAC system and at the same time storing this waste heat in the aquifer. Cooling with groundwater at around 18 °C instead of utilizing outside summer air at 30–35 °C decreases consumption of electrical energy significantly. In addition, stored heat can be recovered when it is needed in winter. The HVAC system with ATES started operation in August 2001 in cooling mode with an average coefficient of performance (COP) of 4.18, which is almost 60% higher than a conventional system.     

Energy efficient building strategies for school buildings in Oman

In this paper hour-by-hour computer simulations of cooling load for a public building were carried out under local weather conditions using TRNSYS building computer simulation software. Different passive measures to reduce the cooling load were investigated. These include the envelope insulation, space ventilation, shading, glazing, artificial lighting variation, and evaporative cooling of the structure. The results show as high as 43% reductions in peak cooling load can be achieved using a combination of well-established passive cooling techniques and technologies. The significance of these results stems from the fact that they were obtained under local weather conditions, a matter of importance to building architects, designers, contractors, and builders as well as air-conditioning equipment manufacturers. Although this work was undertaken to improve the thermal performance of school buildings the results were extended to cover the summer school vacation months so that they will benefit public buildings as well. Copyright © 2002 John Wiley & Sons, Ltd.     

基于建筑保温层厚度的冷热电联供系统优化配置

通过分析保温层厚度对建筑负荷的影响,设计了一种基于保温层厚度的冷热电联供系统设备容量优化匹配方法。针对北京地区某办公类建筑的冷热电联供系统进行经济性优化分析,确定最佳保温层厚度和各设备容量配置。结果表明,该建筑最佳保温层厚度为49 mm,燃气内燃机、余热补燃锅炉、吸收式制冷机和电压缩式制冷机容量分别为250、1 085、207、451 kW。总费用年值随保温层厚度增加呈抛物线变化趋势,当保温层厚度为49 mm时,总费用年值达到最低。所得结论对未来建筑节能改造具有一定指导意义。     

Solar hybrid air-conditioning system for high temperature cooling in subtropical city

Although solar energy is able to power the heat-driven refrigeration, its contribution is quite limited due to the conventional cooling requirement. In building air-conditioning, it is common to supply low temperature chilled water, usually in 5–7 °C. If this temperature can be elevated, it would enhance the effectiveness to harness solar energy and minimize auxiliary heating. Solar refrigeration would then be more effective through high temperature cooling, by providing 15–18 °C chilled water instead. In such provision, radiant ceiling cooling can be coupled to handle the space cooling load, particularly space sensible load. And the space latent load and ventilation load are handled by a separate dehumidification provision, like the heat-driven desiccant dehumidification. Therefore, a solar hybrid air-conditioning system is formulated, using adsorption refrigeration, chilled ceilings and desiccant dehumidification. In this study, the year-round performances of the proposed solar hybrid air-conditioning systems were evaluated for two typical office types. The performance metrics include the solar fraction, coefficient of performance, solar thermal gain, primary energy consumption and indoor conditions. Comparative study was conducted for the hybrid air-conditioning system worked with the three common types of chilled ceilings, namely the chilled panels, passive chilled beams and active chilled beams. The solar hybrid air-conditioning system was also benchmarked with the conventional vapour compression refrigeration for office use. It is found that the proposed solar hybrid air-conditioning system is technically feasible through high temperature cooling. Among the three types of chilled ceilings, the passive chilled beams is the most energy-efficient option to work with the solar adsorption refrigeration for space conditioning in the subtropical city.     

变频控制热泵式VRV空调机组运行特性与节能性能实验研究

本文对变频控制热泵式VRV空调系统冬夏季运行特性和节能性能作了一系列实验研究，分析了影响室内机制冷(热)量、机组功率的因素，得到了VRV空调系统的部分负荷运转特性，并在节能性能方面与普通风冷热泵冷热水机组作了比较，证明该空调机组比普通风冷热泵冷热水机组节能。     

建筑形式对太阳能热利用的影响研究

以上海地区的住宅建筑为研究对象,通过模拟分析的方法,采用DeST软件计算确定建筑逐时的采暖、空调能耗,研究分析窗墙比对建筑全年采暖能耗、全年空调能耗以及全年采暖、空调总能耗的影响规律,研究分析太阳辐射热增加所导致采暖能耗的降低幅度与外围护结构保温性能两者之间的定量关系。计算结果表示在夏季外窗遮阳和夜间通风的条件下,加大南向窗墙比可增强太阳能的热利用效率,降低建筑全年的采暖、空调总能耗;而外围护结构保温性能的增强则可降低室内向室外散热的程度,相应提高对冬季太阳辐射的热利用程度,从而达到降低采暖能耗的目的。     

Analytical periodic solution for the study of thermal performance and optimum insulation thickness of building walls in Tunisia

In Tunisia, the energy consumption in the building sector is rapidly increasing. Recently, very high electric energy consumption, used for air-conditioning loads, is reached during summer days. Insulation of building walls is recently applied with an insulation layer thickness typically ranging between 4 cm and 5 cm, regardless of the climatic conditions, type and cost of insulation material and other economic parameters. In the present study, an optimum insulation thickness is determined under steady periodic conditions. An analytical method, based on Complex Finite Fourier Transform (CFFT), is extended to rigorously estimate the yearly cooling transmission loads for two types of insulation materials and two typical wall structures. Estimated loads are used as inputs to a life-cycle cost analysis in order to determine the optimum thickness of the insulation layer. Results show that, the most profitable case is the stone/brick sandwich wall and expanded polystyrene for insulation, with an optimum thickness of 5.7 cm. In this case, energy savings up to 58% are achieved with a payback period of 3.11 years. The thermal performance of the walls under optimal conditions is also investigated. Then, comparison of the present study with the degree-days method is performed for different values of indoor design temperature.     

大型超市室内环境及空调系统能耗测试分析

深入了解掌握建筑空调系统实际运行状况,有助于准确地分析建筑能耗及空调系统能耗。为此作者选择了上海某一大型超市,通过测试其夏季室内热环境、空调机组、冷水机组水流量等参数,得出超市室内温湿度的分布状况、空调水系统的平衡程度以及冷水机组的能效比,发现实际运行中存在的问题,提出改进超市空调系统运行的方案。     

Thermal management of hydrogen refuelling station housing on an annual level

A housing insulation of hydrogen refuelling station is vital from the aspect of safe operation of equipment in an environment that is installed. To secure hydrogen supply during the whole year, this work brings the solution for both cooling and heating insulation equipment inside of hydrogen refuelling station installed in Croatia, Europe. This hydrogen refuelling station was designed as an autonomous photovoltaic-hydrogen system. In the interest of improving its energy efficiency, an optimal thermal management strategy was proposed. To select the best technological solution for thermal management design which will maintain optimal temperature range inside the housing in cold and warm months, a detailed analysis of the system components thermodynamic parameters was performed. Optimal operating temperatures were established to be 25 °C in summer and 16 °C in winter, considering components working specifications. Insulation, type of cooling units, and heaters have been selected according to the HRN EN 12831 and VDI 2078 standards, while the regime of the heating and cooling system has been selected based on the station's indoor air temperature. The annual required heating and cooling energy were calculated according to HRN EN ISO 13790 standard, amounting to 1135.55 kW h and 1219.55 kW h, respectively. Annual energy share obtained from solar power plant used for the heating and cooling system resulted in 5%. The calculated thermal management system load turned out to be 1.437 kW.     

深部地层储能技术与水源热泵联合应用工程实例

在详细阐述深部地层储能与水源热泵联合应用技术要点和设计方法的基础上，以天津市地矿珠宝公司改燃工程为实例，介绍了该工程运行系统的设计，并对系统冬季采暖运行实测数据进行了分析。结果表明：深部地层储能与水源热泵联合应用技术是一项与地质构造、水文地质条件、热(冷)负荷需求、室外温度变化、末端散热(冷)设备等多种因素相关的复杂系统。在地质条件和末端散热设备一定的前提下，室外温度是影响供暖系统运行状态参数变化的主要因素，随着室外温度的变化，系统运行参数也随之发生变化，系统运行时各参数之间相互变化规律可为今后相关的工程设计与应用提供有益的参考。     

Effect of wall orientation on the optimum insulation thickness by using a dynamic method

A comprehensive economic analysis has been performed to inter-relate the optimum thickness of insulation materials for various wall orientations. The yearly cooling and heating transmission loads of building walls were determined by use of implicit finite-difference method with regarding steady periodic conditions under the climatic conditions of Elaz??, Turkey. The economic model including the cost of insulation material and the present value of energy consumption cost over lifetime of 10 years of the building was used to find out the optimum insulation thickness, energy savings and payback periods for all wall orientations. Considered insulation materials in the analysis were extruded polystyrene and polyurethane. As a result, the optimum insulation thickness of extruded polystyrene was found to be 5.5 cm for south oriented wall and 6 cm for north, east and west oriented walls. Additionally, the lowest value of the optimum insulation thickness and energy savings were obtained for the south oriented wall while payback period was almost same for all orientations.     

Optimal roof structure with multilayer cooling function materials for building energy saving

Both cool roof and phase change thermal storage are promising technologies in decreasing building energy consumption. Combining these two technologies is likely to further enhance the thermal comfort of the building as well as reduce air condition loads. In this paper, the cooling performance and energy-saving effects of four types of roof (normal roof, phase change material [PCM] roof, cool roof, and cool PCM roof [cool roof coupled with PCM]) were investigated under a simulated sunlight. Experimental results indicate that compared with normal roof, the other three roofs are able to narrow the indoor temperature fluctuation and decrease the heat flow entering into the room. Among them, cool PCM roof gave the best energy-saving effect that can lower the indoor temperature and heat entering into rooms by 6.6°C and 52.9%, respectively. Besides, the PCM location, PCM thickness, and insulation thickness exerted great impacts on the cooling performance of the roof. Placing the PCM on the internal layer beneath the extruded polystyrene (XPS) insulation board can make the indoor temperature 1.2°C lower than that on the middle layer. Although thicker PCM panels or insulation boards can provide a better thermal insulation, 5 mm in PCM thickness and 20 mm in insulation thickness are enough to guarantee the indoor temperature of cool PCM roof system at a comfortable range (22°C-28°C) for a whole day. These findings will give guidance in designing buildings with a light and compact roof structure to decrease energy consumption and improve comfort level.     

Study on hybrid ground-coupled heat pump system for air-conditioning in hot-weather areas like Hong Kong

The ground-coupled heat pump (GCHP) system is becoming attractive for air-conditioning in some moderate-weather regions due to its high energy efficiency and reliable operation capability. However, when the technology is used in buildings where there is only cooling load in hot-weather areas like Hong Kong, the heat rejected into the ground by the GCHP systems will accumulate around the ground heat exchangers (GHE). This heat accumulation will result in degradation of system performance and increment of system operating costs. This problem can be resolved by using the hybrid ground-coupled heat pump (HGCHP) system, which uses supplemental heat rejecters to reject the accumulated heat. This paper presents a practical hourly simulation model of the HGCHP system by modeling the heat transfer process of the system’s main components. The computer program based on this hourly simulation model can be used to calculate the hour-by-hour operation data of the HGCHP system. As a case study, both a HGCHP system and a traditional GCHP system are designed for a hypothetic private residential building located in Hong Kong, and the economic comparisons are conducted between these two types of systems. The simulation results show that the HGCHP system can effectively solve the heat accumulation problem and reduce both the initial costs and operating costs of the air-conditioning system in the building.