【作者】 郭俊杰；

【导师】 吴静怡；

【作者基本信息】 上海交通大学 ， 制冷及低温工程， 2013， 博士

【摘要】 空气源热泵热水技术是一种节能型热水技术。随着能源和环保压力的日益加大，通过优化现有空气源热泵热水装置（Air-source heat pump water heater，简称ASHPWH）的设计，拓展使用范围，是一条促进节能减排的有效途径。但是，囿于设计理论和实验条件的限制，多数研究者着眼于部件如何匹配、设计参数如何选取和经济性评价等问题，而对如何在实践上对运行策略进行优化使装置保持长期高性能运行、如何改善变工况下的热力学性能满足能量需求的多样化方面，鲜有考虑。此外，空气源热泵热水装置具有变工况运行的特点，特定工况下的有效能分析难以全面准确地反映系统的热力学特性，为了实现有效能理论在该类型系统中更好地应用，通过结合空气源热泵热水装置变工况运行的特点和有效能的基本理论建立相应的分析模型，将有助于更加准确发现系统设计和运行的薄弱环节。为此，本文从系统优化设计和运行的角度进行了实验和理论分析，主要体现在以下几个方面：(1)针对冷凝器采用板式换热器循环加热的小型家用空气源热泵热水装置，采用实验与数值仿真方法，研究了环境参数、装置结构参数对系统性能的影响，以指导优化。仿真数据和实验对比结果显示，仿真模型具有较好的精度。数值分析结果表明，对于采用该类型冷凝器的系统，冷凝器和蒸发器的面积比在一定范围内系统可以确保较高的热力学效率，计算条件下，最佳面积比在0.1到0.118之间。循环水进水高度(即水箱热水入口的位置)是影响系统性能的重要因素，循环水进水高度越高，系统COP越高。当其他条件固定，进水高度从水箱高度的0.167调整到水箱顶部，系统COP会从2.58增加到2.70，有4.65%的增幅。尽管水箱整体的等效平均温升随着进水高度的提升略有下降，约1℃，但其差别几乎可以忽略不计。从提高系统COP的角度来说，最佳进水口应位于水箱的顶部。(2)结合空气源热泵热水装置变工况运行的特点和有效能的基本理论建立了当量有效能分析模型，并通过样机实验验证了其分析结论，该模型综合考虑了热泵热水装置热水不断升温的影响。模型分析结果表明，环境温度7℃时，在其他部件不变的情况下，当压缩机绝热效率从0.6增加到0.85，压缩机有效能损失减少三分之二，系统有效能效率从35%增加到45.5%，系统不可逆程度改善10.5%。当压缩机的绝热效率低于0.78时，压缩机为有效能损失最大的环节。从本模型的分析中也可以发现，当其他条件不变，冷凝器换热温差从8℃降低到3℃，系统有效能效率从41.5%提高到46.2%，系统的不可逆程度改善了4.7%。当其他条件不变，蒸发器换热温差从15℃降低到10℃，系统有效能效率则从41.4%提高到46.3%，系统的不可逆程度改善了4.9%。基于实验数据的分析显示，压缩机的平均有效能损失系数最高，冷凝器平均有效能损失所占的比例仅次于压缩机损失所占的比例。考虑到提高压缩机的效率涉及到整个制造工艺的提升，非短期可实现，因此，从改进系统热力学循环的角度来讲，强化冷凝器的换热过程更加关键。(3)基于上述理论和实验研究，考虑到实际运行时存在昼夜温度的差异以及用户热水需求曲线的不同，为了实现运行策略的优化，分别对定时和定温两种典型的控制模式进行了研究。研究结果表明，对于定时控制而言，昼夜温差的差异和峰谷电价政策是设定启动加热时刻最大的影响因素。在定温控制模式中，设定水温直接影响到热泵系统的热力学特性和热水的供应能力，而这两个因素往往又是互相冲突的。为了解决这一矛盾，引入一个参数，即送水系数，定义为每天满足用户45℃水温要求的热水实时放出量与热水需求曲线之间的比值，反映的是居民对热水的满足程度。设定水温越高，送水系数也会越高，但系统COP会越低。当送水系数达到100%时，进一步提高设定水温，送水系数将维持100%不变，而系统COP仍会降低。因此，为了最大程度的满足用户基本热水需求，同时达到良好的节能效果，以满足送水系数为100%的最低设定水温为基准点，实现运行优化。优化分析结果表明，空气源热泵热水系统的最佳设定水温应该根据季节气温的变化进行调整，以上海气候为例，夏季、过渡季和冬季的最佳设定水温分别为46℃、48.2℃和55.4℃。(4)以前述工作为基础，利用灰色系统理论建立了空气源热泵热水装置的家庭热水消耗和能耗模型，并对典型上海家庭全年各月的热水消耗和能耗进行了预测，旨在利用灰色理论通过少量历史数据实现大时间跨度预测的特性，实现准确预测并节省实地测试成本。样本数据分析显示，尽管样本数据随着时间表现出一定的无序性，但样本数据的分布满足灰色理论的要求，且样本累加值呈现指数增加的趋势，符合灰色理论的适用条件。建模过程中发现，模型精度会随着采样周期的变长而逐渐提高，当采样周期达到四周时即可满足灰色理论的精度要求。基于此，建立了以四周为采样周期的灰色预测模型，并和后续场地测试数据进行了比较，预测和实测对比表明，模型预测精度良好。基于此模型，可以获得COP、全年各月的各个参数、碳减排量以及节省的费用。(5)通过实验测试与数值仿真，详细分析了空气源热泵热水装置分级供热的热力学过程。为了更好的利用冷凝热量，对热泵工质进行了筛选，并设计了相应的测试样机和测试平台。针对空气源热泵分级供热热水装置的工质选优结果表明，由于更佳的热力学循环特性和物性，R410A和R22为较优选择。样机实验结果显示，该实验样机能够在确保高效的前提下同时满足两种不同温度范围的供热需求，对于同时存在生活热水和地板采暖两种热水品质需求的场合，能够实现一机两用的功能。在此基础上，建立了空气源热泵分级供热热水装置的数学模型，并对影响系统性能的各参数进行了讨论。研究结果显示，在分级供热的模式下，两个冷凝器的进水温度直接影响冷凝器内部的换热模式，其中，初级进水温度是系统热力性能的最大影响因素。当初级进水温度上升到一定的临界值时，初级冷凝器内的换热全部为过热蒸气和水之间的单相换热，且环境温度越高，临界值越低。更多还原

【Abstract】 This paper concentrated on air-source heat pump water heater (ASHPWH) system fordomestic use. In experimental research, researchers pay more attention to the matching ofdifferent components in this kind of system; in theory analysis, most of the scholars havedone lots of work about matching, design parameters and estimation of thermodynamicperformance. However, there was little work reported about long-term operation optimizationof this kind of system.Additionally, ASHPWH are almost in off-design conditions during operation. Correctevaluation of thermodynamic performance of this system under variable working conditionsis the fundamental prerequisite for optimization of design and operation. While, there isinsufficiency when conventional exergy anlysis is applied on this kind of system. In order tobetter utilize the optimization tool—exergy theory in ASHPWH, it is expected that theweakness of design and operation can be correctly found based on the relative model whenthe basic exergy theory and thermodynamic performance of the system are combined. Thus,the emphasis should be taken on matching, components design and performance assessment,so as to find a more reasonable and comprehensive optimization method. As to meet differentdomestic energy consumption, some research work has been obtained by scholars. While forsome sites with different temperature domestic hot water consumption, the conventionalmethod is to meet hot water demand with several types of equipments, such as oil boiler, heatpump and solar concentrator. As a result, higher running cost and complex managementcannot be avoided. In order to solve this kind of problem and take ASHPWH’s advantages onenergy-saving, multi-function of hot water system should be integrated. Therefore, it is veryimportant to save energy and initial cost considering the thermodynamic performance of ASHPWH system. The main works are summarized as follows:(1) An experimental set-up of domestic ASHPWH system was constructed and someexperimental data were obtained. In this research, the thermodynamic performance of thesystem was investigated. Additionally, the mathematical model of this kind of system wasestablished, and the effect of environment and design variants was analysized. The simulatedresults showed that it is uncessary to enlarge the area of heat exchangers when COP increasesto some extant. Based on the case, the optimal thermodynamic performance can be achievedwhen the area ratio of condenser and evaporator is among given range0.1-0.118. It was alsofound that the effect of inlet site of hot water to water tank cannot be ignored, the higher theinlet site of hot water, the higher COP the system will obtain. When the inlet site of hot wateris lift from0.167height of water tank to the top, the COP will increase from2.58to2.70, with4.65%increment. Simultaneously, the average water temperature of water tank decreasedabout1℃, which can be ignored. From the viewpoint of improving thermodynamicperformance of system, the optimal site is on the top of the water tank.(2) In this study, an equivalent exergy analysis model was presented according to unstableworking condition characteristic of ASHPWH system and verified by experiments. In thismodel, the exergy loss of different components and stages could be analysized, and thepriority optimization goal of this system was pointed out. The analyzied result indicated that,based on the assumption, the exergy efficiency of system is very sensitive to the adiabaticcoefficient of compressor. The exergy loss of compressor would reduce2/3when adiabaticcoefficient of compressor increases from0.6to0.85under ambient temperature7℃, whilethe exergy efficiency will increase from35%to45.54%, with10.5%improvement. Thecompressor should be chief optimized when the adiabatic coefficient of compressor is lowerthan0.78. When the temperature difference of heat transfer on condenser decreases from8℃to3℃, and the exergy efficiency of system will increase from41.5%to46.2%, with4.7%improvement. Similarly, when the temperature difference of heat transfer on evaporatordecreases from15℃to10℃, and the exergy efficiency of system will increase from41.4%to46.3%, with4.9%improvement. It could be found that, based on the experiments, thehighest average exergy loss of component is from compressor, and the following is from condenser. From viewpoint of improving system thermodynamic performance and cost,improving the performance of compressor is a long-term process, thus, enhance the heattransfer process of condenser is more urgent, for example, optimize the design of condenserand water tank.(3) Based on the mathematical model of this ASHPWH system and validation, the effect ofdifferent parameters to the system performance was estimated. Additionally, the indicator ofoptimization operation strategy was presented and tested according to domestic hot waterdemand profiles. In this study, the influence of ambient temperature fluctuation, setting watertemperature, starting time and electricity price policy under two typical controlling patternswas also discussed. For the timing controlling pattern, the key factors are ambient temperaturedifference between day and night and electricity price policy. For the thermostatic controlpattern, the delivery coefficient was introduced and as an index which scales the degree ofsatisfaction for customers. The higher the setting temperature, the higher the deliverycoefficient is, while, it also leads to lower COP. In order to balance the meet of degree ofsatisfaction for customers and energy-saving concern,100%was selected as the critical pointof delivery coefficient to optimize the system performance. The optimized results showed thatthe optimal setting water temperature should be adjusted according to different seasons. Takethe climate of Shanghai for instance, it was investigated that the optimal setting watertemperature should be set above46℃,48.2℃and55.4℃, in summer, transitional season andwinter, respectively.(4) A new approach to energy consumption prediction of domestic air source heat pumpwater heater was presented based on grey system theory. Investigations with the modelindicated that grey system theory can be used to predict the domestic hot water heat andelectricity consumption, and satisfactory prediction accuracy can be obtained by the improvedgrey model. It can be found that, during the modeling, the samples could be applied in greysystem theory although they appeared unordered. Furthermore, the experimental resultindicated that correct accuracy can be assured only the data sample interval is no less thanfour weeks. Based on the improved model and weather data of Shanghai, the electricity costsaving, the monthly average heat and electricity consumption and the annual carbon emission reduction related to the use of the ASHPWH for the two typical families were evaluated andcompared with those of the conventional electric resistance water heater. It is noteworthy thatthe developed model requires few data in order to predict energy consumption and theprediction error is reasonable, hence some field test expenditure can be saved.(5) Combined with the experiments and simulation results, the air-sourced heat pumpdouble-stage water heating system was elaborated in this study. And then, the mathematicalrelationship between superheat and latent heat release in the condenser was analysized. Basedon the principle of thermodynamic law and theoretical model, the heat pump refrigerants wereselected and relative test-rig was established. In order to learn the thermodynamicperformance of this system, a new mathematical model of ASHPWH was developed andvalidated, in addition, the effect of different parameters to the system was investigated. Theexperimental results showed that the prototype could supply different temperature ranges hotwater and higher thermodynamic performance can be obtained. For instance, it can be appliedin the sites which consume domestic hot water and floor heating simultaneously. The resultsof modeling revealed that the most important factor which affected the system performancewas inlet water temperature of first condenser. Furthermore, the sensible heat could bereleased in the first condenser only when the inlet water temperature of first condenserincreased to certain critical value. With the increase of ambient temperature, the critical valuewould decrease simultaneously.更多还原