【作者】 周燕；

【导师】 龚光彩；

【作者基本信息】 湖南大学 ， 供热、供燃气、通风及空调工程， 2013， 博士

【摘要】 能源是发展生产力和提高人类生活水平的基础，能源的短缺促使人们意识到节能的重要性，但是要回答何谓节能其实并不简单，只考虑能量平衡的热力学第一定律回答不了这一问题，从能量利用价值角度看，节能实质上是对常规能源中的可用能“火用”的节约与利用。本文基于热力学第二定律的火用分析方法，提出了从建筑能源的转换、输送到用户终端能量使用全过程，即从一次能源到围护结构建筑能量系统的火用分析理论模型，详细探讨了火用分析对环境状态选择的敏感性，主要研究内容和成果包括以下几方面：首先，以全国27个典型城市的气象数据为依据，研究静态和逐时变化的环境基准状态对空气处理过程火用分析结果的影响。结果表明，夏季气候高温湿热的地区，对空气冷却处理过程进行火用分析时，湿空气的化学火用不能忽略，静态和逐时变化的两种环境基准状态下火用分析结果误差不大，因此可用室外平均温度和湿度代替逐时变化的温度和湿度。对于有空调期的大部分城市来说，静态和逐时变化的两种环境基准状态下的化学火用误差较小，在计算湿空气火用值时，可用空调期室外平均湿度替代逐时变化的室外湿度。采暖期，对空气加热处理过程进行火用分析时，静态和逐时变化的两种环境基准状态下的火用分析结果误差较小，因此采暖期空气加热处理时可用室外平均温度代替逐时变化的温度作为环境基准温度。其次，以分体式热泵空调系统为例，以典型气象年逐时变化的室外温度和湿度作为环境基准状态，基于制冷状态下空调房间室内空气的化学火用，建立了从一次能源到围护结构分体式热泵系统能量流动的火用分析理论模型，并将其应用到工程实例中，结果表明，对于夏热冬冷地区，围护结构适度保温是必须的,但不应一味的增加保温层的厚度；在适度保温的前提下，应重点考虑提高热泵系统效率，这样建筑能量系统的能源利用效率才能达到最佳。一次能源阶段和热泵阶段的火用损耗约占系统总火用损耗的80%以上，因此改善这两个阶段是提高系统火用效率的关键。在此基础上，根据建筑供暖与制冷系统能量流动过程，包括围护结构、室内空气、末端设备、管网系统、冷热源和一次能源转换环节。建立系统各环节的火用分析理论模型及评价指标。应用火用分析理论模型，对某办公大楼不同方案的能量系统从围护结构到一次能源转换进行火用分析，计算各环节的火用流、火用损、火用损率和系统火用效率，根据火用分析计算结果，评价不同建筑能量系统的优劣。结果表明，系统中火用损最大的环节是一次能源转换，冷源方案一次能源阶段火用损率为64.8%~92.2%，热源方案一次能源阶段火用损率为64.6%~84.3%。另外，分析建筑能量系统时应考虑能量梯级利用的原则，在能量利用过程中,能级差越大,火用损失越大。本文提出了采用一次能源火用效率和能级平衡系数评价建筑冷热源和末端设备。以1KJ冷量和热量为例分析末端系统不同供回水温度火用效率和能级平衡系数，结果表明，采暖期末端设备尽量采用低温热水，且尽量减少供回水温差；空调期末端设备尽量提高供回水温度，且尽量增大供回水温差，这样系统火用效率和能级平衡系数才能达到最优。因此，在末端设备系统中，应尽量采用接近室温的冷热介质。最后，提出了火用分析结合建筑生命周期方法评价既有建筑改造后的节能效果，运用该方法对某建筑节能改造实例进行了分析，结果表明，对于建造年代久远的建筑，在进行围护结构节能改造时，应当把改造后的节火用效果、节能效果和环境影响作为一个整体进行综合分析。更多还原

【Abstract】 Productivity development and human life level improving are based on energy sources, theshortage of energy sources prompt people to be aware of the importance of energy efficiency.But answering what is energy efficiency is not so simple. The first law of thermodynamicscan not answer this question. The energy efficiency is essentially "exergy" efficiency from thevalue of energy usage perspective. The method based on exergy analysis is proposed from thebuilding envelope to the energy conversion system of the building energy system. Thesensitivity of the exergy analysis results with environment reference state is discussed indetail. The main content is outlined as follows.First, based on the meteorological data of27cities in China, the exergy analysis resultswith the dynamic and static environment reference state is researched. The results show thatthe chemical exergy of moist air can not be ignored in hot and humid climate of the airconditioning period through exergy analysis of air cooling process. The exergy result errorsbetween the static and dynamic state is small. So the average outdoor temperature andhumidity can be used to calculate. For most of the cities in cooling season, the chemicalexergy errors between dynamic and static state is small. So the chemical exergy of moist aircan be calculated with average outdoor humidity. In heating period, the exergy analysis resulterror between the two environment states is small. So the outdoor average temperature can beused to calculate instead of dynamic hourly temperature as environment reference state.Second, the exergy flow rate is calculated from the power plant to the building envelopewith hourly outdoor temperature and humidity as reference state. The chemical exergy ofroom air is considered in cooling mode. Exergy method is applied to analyze the heating andcooling system of an example building. Results show that building envelop insulation isnecessary in the hot summer and cold winter area of China in reducing the building exergyconsumption. On the premise of envelop necessary insulation, the more effective energyefficiency solution of the building is to increase the air conditioner efficiency rather thanincrease the envelop insulation layer. The total year larger exergy loss rates take place in theprimary energy transformation and heating/cooling production, which is about80%of thesystem total exergy loss.Next, according to the energy flowing process of building heating and cooling system,including the building envelope, indoor air, terminal equipment, pipe network system, coldand heat sources and primary energy conversion, the exergy analysis theoretical model and various evaluation index in every stage are established. A case of an office building isanalyzed with the exergy theoretical model from the building envelope to energy conversion.The exergy flow rate, exergy loss, exergy loss rate and exergy efficiency in evergy stage arecalculated to evaluate the pros and cons of the different cases. The results show that the mostexergy loss stage is the primary energy conversion. The exergy loss rate of the cold sourcecases are from64.8%to92.2%, and the heat source cases are from64.6%to84.3%.In addition, the principle of cascade utilization energy sources should be considered. Thegreater the energy level difference, the greater the exergy loss. An example of1KJ cold andheat energy are analyzed. The results show that it should use the lower temperature hot waterin heating season, and minimize the temperature difference between supply and return water.It should be use the higher cold water in cooling season, and maximize the supply and returnwater temperature. So the efficiency and energy level equilibrium coefficient are optimal.Therefore, it should be use the cooling and heating medium close to the room temperature inthe terminal equipment system.Finally, a kind of exergy analysis combined with life cycle assessment method is presentedto evaluate the effect of the building envelope energy efficiency retrofit. A typical case of theexisting building envelope energy efficiency retrofit is analyzed. The results show that thecumulative saved energy consumption in the use stage is roughly1.75times larger than thetotal embodied energy of the newly added insulation materials in the product stage. Thecumulative saved exergy consumption in the use stage is only about1/7of the embodiedexergy of the newly added insulation materials in the product stage. For the existing buildingwith age, it should be prudent to take any retrofit measures; and it should take the energy andexergy efficiency and environment impact of the retrofit measures as a whole to analyze.更多还原