浅谈供热系统中主动式和被动式水力平衡概念及其应用

本文提出了供热系统中主动式与被动式水力平衡的概念,并结合应用实例进行了分析。这些概念的提出对于供热系统改善控制,实现节能具有参考价值。     

Developing a new library of materials and structural elements for the simulative evaluation of buildings’ energy performance

Contemporary building energy simulation programs are not only used by researchers but also are common tools in the hands of engineers and architects. Most of them are using databases of materials and structural elements, with characteristics originating from the country or the broader region where the specific program was developed. Thus, often the particularities met in other countries are not considered. Such a database of materials and constructions systematically used in the Greek building sector was developed for use with the simulation program EnergyPlus, which has become quite popular over the last years. In order to determine the applicability of the database, the energy behaviour of a typical multistory, multifamily building was simulated, having the exact materials and structural elements and patterns used in Greece. Furthermore, different thicknesses of insulation were simulated, corresponding to local climatic conditions and, even more important, to different dates of the building's construction. The results are presented and discussed in this paper.     

Exergetic life-cycle assessment (ELCA) for resource consumption evaluation in the built environment

Resource management becomes a key issue in the development of sustainable technology. This paper envisages a quantification of all energy and material needs for a family dwelling, both for the construction aspects (‘embodied energy and materials’) and usage aspects. To do so, an exergetic life-cycle assessment has been carried out that enables the quantification of all necessary natural energy and material resources simultaneously. The case study covered 65 optimized Belgian family dwelling types with low energy input (56 MJ/(m³ year)). The study shows that cumulative annual exergy demand is of the order of 65 GJ_exergy/year, with a limited dependency on the construction type: cavity wall, external insulation or wooden frame. For the cavity wall and external insulation building type, non-renewable inputs are dominant for the construction with 85–86% of the total exergy to be extracted out of the environment. For the wooden frame, non-renewable resource intake for construction remains 62%. Despite the low-energy building type, heating requirements during the use phase are dominant in the overall resource intake with a 60% of the total annual exergy consumption. In order to make family dwellings less fossil resource dependant, the study learns that particularly reduction of heating requirements should be envisaged.     

Exergy analysis of renewable energy-based climatisation systems for buildings: A critical view

Exergy is naturally related to the concept of quality of energy. Therefore, exergy analysis has been widely applied in parallel with energy analysis in order to find the most rational use of energy. Within the built environment a wide margin for exergy saving may be found. Actually, buildings require mostly low quality energy for thermal uses at low temperatures and nowadays their energy demand is mainly satisfied with high quality sources. Exergy analysis of renewable energy-based climatisation systems may be considered an emerging field, where different and often contrasting approaches are followed. Then, in this paper a comprehensive and critical view on the most recent studies on this topic is presented. Special attention is paid to the methodological aspects specifically related to climatisation systems and renewables, and to the comparison of the results. Main renewable energy-based heating and cooling systems are considered in detail. Finally, conclusions regarding the state of the art and possible trends on this field are derived, with the aim to highlight future research issues and promote further developments of this method. Furthermore, conclusions regarding the usability of the exergy method as a tool to promote a more efficient use of available energy sources are also derived.     

Optimum insulation thicknesses for building walls with respect to cooling and heating degree-hours in the warmest zone of Turkey

Thermal insulation is one of the most effective energy conservation measures for cooling and heating in buildings. Therefore, determining and selecting the optimum thickness of insulation is the main subject of many engineering investigations. In this study, the determination of optimum insulation thickness on external walls of buildings is comparatively analyzed based on annual heating and cooling loads. The transmission loads, calculated by using measured long-term meteorological data for selected cities, are fed into an economic model (P₁−P₂ method) in order to determine the optimum insulation thickness. The degree-hours method that is the simplest and most intuitive way of estimating the annual energy consumption of a building is used in this study. The results show that the use of insulation in building walls with respect to cooling degree-hours is more significant for energy savings compared to heating degree-hours in Turkey's warmest zone. The optimum insulation thickness varies between 3.2 and 3.8 cm; the energy savings varies between 8.47 and 12.19 $/m²; and the payback period varies between 3.39 and 3.81 years depending on the cooling degree-hours. On the other hand, for heating load, insulation thickness varies between 1.6 and 2.7 cm, energy savings varies between 2.2 and 6.6 $/m², and payback periods vary between 4.15 and 5.47 years.     

中国过渡地区居住建筑的制冷、采暖、通风现状

介绍了中国过渡地区的地理位置及其气候特点,介绍了常用的制冷、采暖、通风的技术措施设备及其使用性能。并对常用设备的能耗指标进行了比较。     

Exergoeconomic evaluation on the optimum heating circuit system of Simav geothermal district heating system

Simav is one of the most important 15 geothermal areas in Turkey. It has several geothermal resources with the mass flow rate ranging from 35 to 72 kg/s and temperature from 88 to 148 °C. Hence, these geothermal resources are available to use for several purposes, such as electricity generation, district heating, greenhouse heating, and balneological purposes. In Simav, the 5000 residences are heated by a district heating system in which these geothermal resources are used. Beside this, a greenhouse area of 225,000 m² is also heated by geothermal. In this study, the working conditions of the Simav geothermal district heating system have been optimized. In this paper, the main characteristics of the system have been presented and the impact of the parameters of heating circuit on the system are investigated by the means of energy, exergy, and life cycle cost (LCC) concepts. As a result, the optimum heating circuit has been determined as 60/49 °C.     

Exergy performance and thermodynamic properties of the ideal liquid desiccant dehumidification system

In this paper, an ideal liquid desiccant dehumidification system is presented as the idealization of practical liquid desiccant dehumidification systems, along with an exergy analysis that considers the effects of various parameters like dehumidification temperature, water vapor pressure and temperature of surrounding environment on the system performance. Exergy formulations are developed and validated for the ideal system. These results show that the ideal system is strongly influenced by these impact factors, with respect to operating condition and exergy efficiency, and should be used with caution when comparing with condensation-based dehumidification systems.     

Potential for energy saving in building transition spaces

This paper reports on an analytical investigation into the energy saving potential associated with modified comfort limits in transitional spaces in buildings. Such spaces may not require the same high level and close environmental control of more fully occupied spaces and thus a wider variation in conditions and interpretation of thermal comfort may be permitted. Estimations are made of energy saving potential based upon typical floor area proportions utilised for transition spaces of various types in office/commercial buildings. The data are combined with suggested norms for comfort expectation that have wider temperature limits than for normally occupied office zones. The method has been applied to a series of building types situated in the climate of the East Pennines area of the UK using a thermal analysis tool. The results show that useful energy savings (particularly for heating) are possible by allowing for a modest (and realistic) relaxation of prescribed comfort standards in transition spaces. Further work is now required to confirm the limits and assess energy saving in practice.     

冷凝式燃气热风炉在我国采暖中的应用及其节能分析

本文介绍了冷凝式燃气热风炉用于房间采暖的系统及其特点,分析了其节能性以及用于住宅采暖的特点,冷凝式燃气热风炉将以其特有的优势逐步进入我国采暖行业。     

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.     

塔式太阳能热电站集热子系统火用分析

集热子系统是塔式太阳能热发电不同于火力发电的主要部分.定日镜和吸热器是集热子系统的关键部件.以八达岭1 MW塔式太阳能热发电系统为研究对象,以热力学第一、第二定律为理论基础,结合塔式太阳能热发电系统模型,采用能量系统的白箱模型分析方法对塔式太阳能热发电集热子系統进行火用分析.对系统用能状况作出合理评价,找出系统用能的"薄弱环节",为系统节能提供依据.     

Experimental behaviour of composite slabs during the heating and cooling fire stages

Most theoretical and experimental research investigating the effect of fire on structures has previously concentrated only on the structural behaviour during the heating stages of the fire, partly due to the fact that internationally accepted standard fire tests only consider this stage of the fire. Evidence from real fires in real buildings has highlighted that the cooling phase of a fire is equally important and it is possible for structures to fail during this stage of the fire even though they have survived the heating stage up to a maximum fire temperature. This paper provides an insight into the behaviour of composite slabs under different fire scenarios considering both the heating and cooling phase of the fire. Extensive test data is presented which shows the redistribution of moments and strains in the deck and steel mesh, together with displacements during the full duration of the fire. The results show that the behaviour of composite slabs is dependent on the heating rate, the maximum temperature reached and the cooling rate. In terms of overall performance, displacements and the temperature on the non-fire side of the slab are important. For the tests presented in this paper it was shown that one fire scenario resulted in the maximum displacement but another fire scenario resulted in the maximum temperature on the unexposed face. In addition the maximum temperature of the unexposed side of the slab and the mesh reinforcement within the slab occurring during the cooling stages of the fire. This highlights the fact that the performance of structures must be checked in design under a range of possible fire scenarios, which must include both the heating and cooling stages of a fire.     

Resilience engineering and the built environment

The possible relations between resilience engineering and built environments are explored. Resilience engineering has been concerned with the safe and efficient functioning of large and small industrial systems. These may be described as built systems or artefacts. The resilience engineering approach argues that if the performance of systems is to be resilient, then they must be able to respond, monitor, learn and anticipate. The last ability in particular means that they must be able to consider themselves vis-à-vis their environment, i.e. be sentient and reflective systems. In practice, this means people individually or collectively can adjust what they do to match conditions, identify and overcome flaws and function glitches, recognize actual demands and make appropriate adjustments, detect when something goes wrong and intervene before the situation becomes serious. It is particularly important to understand the range of conditions about why and how the system functions in the ‘desired’ mode as well as ‘unwanted’ modes. Resilience is the capacity to sustain operations under both expected and unexpected conditions. The unexpected conditions are not only threats but also opportunities.     

Energetic and exergetic analysis and assessment of a thermal energy storage (TES) unit for building applications

The main objective of this study is to investigate the energetic and exergetic performances of a latent energy storage system in both charging (solidification) and discharging (melting) processes. A shell-and-tube TES unit was designed, constructed and tested in Dokuz Eylul University, Izmir, Turkey. This experimental unit basically consisted of a heat exchanger section, a measurement system and flow control systems. For the charging mode, the inlet temperatures varied to be −5 °C, −10 °C and −15 °C, while the volumetric flow rates changed to be 2 l/min, 4 l/min and 8 l/min. The experiments were performed for three different tube materials, copper, steel and PE32 and two various shell diameters of 114 mm and 190 mm to investigate the tube material and shell diameter effects on energetic and exergetic efficiencies. It may be concluded that for the charging period, the exergetic efficiency increased with the increase in the inlet temperature and flow rate. For discharging period, irreversibility increased as the temperature difference between the melting temperature of the PCM and the inlet temperature of the heat transfer fluid (HTF) increased and hence the exergy efficiency increased.     

Determining the optimal design of a closed loop earth to air heat exchanger for greenhouse heating by using exergoeconomics

This investigation deals with an exergoeconomic evaluation of the earth to air heat exchanger (EAHE) application for determining the optimal design greenhouse heating in Izmir, Turkey. The exergy destructions in the system are quantified and illustrated using tables for a reference temperature of 6 °C. The results indicate that the exergy destructions in the system occur primarily as a result of blower losses and heat exchanger losses. These average losses account for 85% and 4.5%, respectively. Both COP and exergy efficiency of the overall system was investigated to analyze and improve the systems performance. The average COP and exergetic efficiency were determined to be 10.51 and 89.25%, respectively. The results may provide useful insights into the relations between thermodynamics and economics for the EAHE heating systems.     

Three-years operation experience of a ground source heat pump system in Northern Greece

The paper presents the basic parameters and the energy flows of a ground source heat pump system (GSHP) used for air conditioning the New City Hall of Pylaia (Thessaloniki area—Northern Greece). The building is a typical public one, with an air-conditioned area of 1350 m². The ground source heat pump installation is the largest in Greece, and its operation is monitored with the aid of a DAQ system. The energy flows presented in the paper are based on DAQ recordings of the first 3 years of system's operation. It is proved that the energy demand of the system is significantly lower, compared to that of conventional heating and cooling systems. The seasonal COP of the system has not yet been stabilized, gradually increasing, as it is expected due to the operation of the ground heat exchanger.