空气源热泵空调系统节能分析

节能的分析及优化已不仅仅是能的量的问题，而是能的质与量的综合评价的问题。采用yong分析方法得出空气源热泵空调系统的能耗分布，明确系统yong损失较大的环节。从yong分析得知：压缩机的yong损失占机组能耗的20．5％，冷凝器的yong损失接近总能耗的30％。由此提出了空气源热泵空调系统的节能措施，即应该选用高效率的压缩机，采用强化传热措施，提高传热系数，减小传热温差，同时还应注意改善热泵机组的周围环境，使系统yong损失最小，yong效率最大，实现空气源热泵空调系统的节能优化.     

Thermodynamic analysis of a hybrid geothermal heat pump system

A thermodynamic analysis of a hybrid geothermal heat pump system is carried out. Mass, energy, and exergy balances are applied to the system, which has a cooling tower as a heat rejection unit, and system performance is evaluated in terms of coefficient of performance and exergy efficiency. The heating coefficient of performance for the overall system is found to be 5.34, while the corresponding exergy efficiency is 63.4%. The effect of ambient temperature on the exergy destruction and exergy efficiency is investigated for the system components. The results indicate that the performance of hybrid geothermal heat pump systems is superior to air-source heat pumps.     

Comparison of energy and exergy analysis of fossil plant,ground and air source heat pump building heating system

The energy and exergy flow for a space heating systems of a typical residential building of natural ventilation system with different heat generation plants have been modeled and compared. The aim of this comparison is to demonstrate which system leads to an efficient conversion and supply of energy/exergy within a building system.The analysis of a fossil plant heating system has been done with a typical building simulation software IDA–ICE. A zone model of a building with natural ventilation is considered and heat is being supplied by condensing boiler. The same zone model is applied for other cases of building heating systems where power generation plants are considered as ground and air source heat pumps at different operating conditions. Since there is no inbuilt simulation model for heat pumps in IDA–ICE, different COP curves of the earlier studies of heat pumps are taken into account for the evaluation of the heat pump input and output energy.The outcome of the energy and exergy flow analysis revealed that the ground source heat pump heating system is better than air source heat pump or conventional heating system. The realistic and efficient system in this study “ground source heat pump with condenser inlet temperature 30 °C and varying evaporator inlet temperature” has roughly 25% less demand of absolute primary energy and exergy whereas about 50% high overall primary coefficient of performance and overall primary exergy efficiency than base case (conventional system). The consequence of low absolute energy and exergy demands and high efficiencies lead to a sustainable building heating system.     

二类热泵在利用余热供热中的热力分析

对单级二类吸收式热泵进行热力分析,建立了热泵系统各部分质量守恒、能量平衡和火用分析数学模型。根据火用平衡方程计算了各个部分的火用损失和热泵系统的火用效率。分析了溶液换热器稀溶液温差、热源温差、余热源温度和冷却水温度对火用损失、循环倍率和COP等的影响。对热泵系统进行了火用能质量评定,确定了火用能的薄弱环节。     

地热-高温水源热泵供热系统的分析

运用能量系统的为(火用)分析方法.建立地热-高温水源热泵供热系统的炯分析理论模型.以实际工程项目为例,分析和讨论了系统运行条件下的能量有效利用,并计算了地热-高温热泵供热系统的火甩效率和各部分(火用)损失、(火用)效率.从计算结果看出,板式换热器的火用损失所占比例较大.     

Exergy analysis and experimental study of heat pump systems

Exergy analysis of heat pump—air conditioner systems has been carried out. The irreversibilities due to heat transfer and friction have been considered. The coefficient of performance based on the first law of thermodynamics as a function of various parameters, their optimum values, and the efficiency and coefficient of performance based on exergy analysis have been derived. Based on the exergy analysis, a simulation program has been developed to simulate and evaluate experimental systems. The simulation of a domestic heat pump—air conditioner of 959 W nominal power (Matsushita room air conditioner model CS-XG28M) is then carried out using experimental data. It is found that COP based on the first law varies from 7.40 to 3.85 and the exergy efficiency from 0.37 to 0.25 both a decreasing function of heating or cooling load. The exergy destructions in various components are determined for further study and improvement of its performance.     

Energy and exergy analysis of fossil plant and heat pump building heating system at two different dead-state temperatures

In this paper, we deal with the energy and exergy analysis of a fossil plant and ground and air source heat pump building heating system at two different dead-state temperatures. A zone model of a building with natural ventilation is considered and heat is being supplied by condensing boiler. The same zone model is applied for heat pump building heating system. Since energy and exergy demand are key parameters to see which system is efficient at what reference temperature, we did a study on the influence of energy and exergy efficiencies. In this regard, a commercial software package IDA-ICE program is used for calculation of fossil plant heating system, however, there is no inbuilt simulation model for heat pumps in IDA-ICE, different COP (coefficient of performance) curves of the earlier studies of heat pumps are taken into account for the evaluation of the heat pump input and output energy. The outcome of the energy and exergy flow analysis at two different dead-state temperatures revealed that the ground source heat pumps with ambient reference have better performance against all ground reference systems as well as fossil plant (conventional system) and air source heat pumps with ambient reference.     

压缩式热泵系统火用效率定义方法初探

对压缩式热泵系统(火用)效率的定义式进行了分析,指出了该定义式在实际应用过程中存在的一些不足.即当低温热源为环境时,此定义式合理,否则即使热泵系统内部可逆,系统火用效率仍不为1,文中对产生这一问题的原因进行了分析.以热泵系统的火用平衡方程为依据,参照火用效率定义方法及火用效率的基本特征,对压缩式热泵的系统(火用)效率进行了重新定义.通过对两个不违背火用效率定义特征的表达式的对比分析,确定了热泵系统合理的(火用)效率表达式.最后说明,在压缩式制冷系统中当高温热源不为环境时,(火用)效率定义也存在同样缺陷,改进方法与本文类似.     

污水源冷热水机组的热力学分析

阐述了污水源冷热水机组在制冷和热泵工况下的各个设备的火用损失及整个机组的的火用效率计算公式,计算分析了机组在夏季制冷和冬季制热工况下各个设备在不同污水温度下的火用损失系数及整个机组的火用效率。     

变温热源地热热泵系统的可用能分析

地热能作为一种新能源已成为许多国家的研究重点，如何提高地热能的利用率是其重要的研究方向，而热泵又是其中一项关键技术。本文针对地热热泵系统的变温热源，从减小可用能损失的角度进行了详尽的理论分析。首先，对该地热热泵系统中的各个主要部件进行了可用能分析，发现和能损失情况均与循环工质的性能有关；其次，在实际工况下比较了纯工质和非共沸混合工质的可用能损失情况；最终提出了几种有可能应用于实际地热热泵工况下的循环工质。     

Exergy analysis on combustion and energy conversion processes

When we consider exergy analysis on combustion and thermodynamic processes, we introduce another concept against energy analysis, which is supported by an evaluation of its temperature level. When a higher temperature energy than that an ambient level is taken into consideration, it can be put for some domestic or industrial purpose. A medium temperature energy of 30–60 °C is used for domestic heating, and a high temperature of 200 °C and above is suitable for power generation or process heating. Therefore, we study exergy concept supported by temperature level. When we discuss power generation, a high temperature energy of 1500 °C and above in combined cycle has a higher conversion efficiency than that of 500–600 °C in steam cycle. If we try to apply high temperature air combustion, a preheated air temperature of 1000 °C and above can be produced by exhaust heat recovery from stack gas, which has been developed as a new technology of energy conservation. In this study, the authors present an exergy analysis on combustion and energy conversion processes, which is based on the above-mentioned concept of exergy and energy supported by temperature level. When we discuss high temperature air combustion in furnace, this process shows a higher performance than that of the ambient air combustion. Furthermore, when we discuss the power generation and heat pump processes, the minimum ambient temperature would already be known for each season, and the conversion performance can be estimated by the maximum operating temperature in their cycles. So, the authors attempt to calculate the exergy and energy values for combustion, power generation and heat pump processes.     

Comprehensive exergy analysis of a ground-source heat pump system for both building heating and cooling modes

This paper presents a comprehensive exergy analysis of three circuits and whole system of a ground-source heat pump (GSHP) for both building heating and cooling modes. The purpose is to search out the key potential energy saving components. The analytical formulae of exergy loss, exergy efficiency, exergy loss ratio, exergy loss coefficient and thermodynamic perfect degree are derived, respectively. The results show that these exergy indexes should be used integratively, and in the whole system the location of maximum exergy loss ratio is the compressor, while the location of minimum exergy efficiency and thermodynamic perfect degree is the ground heat exchanger, so that the compressor and the ground heat exchanger should be primarily improved. The results also indicate that the exergy loss of a GSHP system for building heating mode is bigger than that of cooling mode, and the exergy efficiency of a whole GSHP system is obviously lower than those of its components for both building heating and cooling modes. Therefore, a comprehensive exergy analysis of a GSHP should be paid more attention to. The results may provide guidelines for the design and optimization of GSHP systems.     

Efficiencies of exergy transductions

Exergy is conserved in thermodynamically reversible heat engines and heat pumps. Using a reversible heat engine to stimulate a reversible heat pump, available power and exergy may be exchanged, the total amount of exergy being conserved. For such a combined system, either more heat may be released at a lower temperature or energy may be consumed to achieve a local entropy reduction. From such an analysis, it becomes apparent that the introduction of efficient systems to conserve exergy in cascaded heating applications should be given high priority.     

不可逆三热源热泵的损率优化

基于不可逆三热源热泵模型,应用最大泵热率与性能系数间的关系,导出三热源热泵损率与性能系数以及损率与泵热率间的优化关系,并由此讨论三热源热泵的有关性能界限。研究结果可为太阳能热泵的开发利用和优化设计提供新理论依据。     

Study of integrated metal hydrides heat pump and cascade utilization of liquefied natural gas cold energy recovery system

The traditional cold energy utilization of the liquefied natural gas system needs a higher temperature heat source to improve exergy efficiency, which barricades the application of the common low quality thermal energy. The adoption of a metal hydride heat pump system powered by low quality energy could provide the necessary high temperature heat and reduce the overall energy consumption. Thus, an LNG cold energy recovery system integrating metal hydride heat pump was proposed, and the exergy analysis method was applied to study the case. The performance of the proposed integration system was evaluated. Moreover, some key factors were also theoretically investigated about their influences on the system performance. According to the results of the analysis, some optimization directions of the integrated system were also pointed out.     

Component exergy analysis of solar powered transcritical CO<Subscript>2</Subscript> rankine cycle system

In this paper,exergy analysis method is developed to assess a Rankine cycle system,by using supercritical CO2 as working fluid and powered by solar energy.The proposed system consists of evacuated solar collectors,throttling valve,high-temperature heat exchanger,low-temperature heat exchanger,and feed pump.The system is designed for utilize evacuated solar collectors to convert solar energy into mechanical energy and hence electricity.In order to investigate and estimate exergy performance of this system,the energy,entropy,exergy balances are developed for the components.The exergy destructions and exergy efficiency values of the system components are also determined.The results indicate that solar collector and high temperature heat exchanger which have low exergy efficiencies contribute the largest share to system irreversibility and should be the optimization design focus to improve system exergy effectiveness.Further,exergy analysis is a useful tool in this regard as it permits the performance of each process to be assessed and losses to be quantified.Exergy analysis results can be used in design,optimization,and improvement efforts.     

燃气机热泵的热力学分析

燃气机热泵是以燃气机作为动力来驱动的压缩式热泵。对燃气机热泵的热力学第一定律、Yong分析和能级平衡理论分析结果表明：其一次能源利用率可达1.76，Yong效率为0.291，能级平衡系数为0.394。与电动热泵等其他供热装置相比，燃气机热泵有着较高的热力学完善性，是一项高效节能技术。由于能级平衡理论分析考虑了Wu的作用，而热泵供暖时其性能系数的提高主要是利用了环境热量，所以建议采用能级平衡理论来分析评价热泵的性能。     

不同工质条件下污水源冷热水机组的性能分析

介绍污水源冷热水机组的工作原理及污水的特性,推导出了污水源冷热水机组在制冷和热泵工况下的各个设备的（火用）损失、整个机组的（火用）效率以及一次能源利用率的计算公式。分析比较不同工质条件下机组在夏季制冷和冬季制热工况时,整个机组的（火用）效率、机组COP值、一次能源利用率等,得出R407C是污水源热泵理想工质的结论。     

Exergy analysis and optimization of a solar-assisted heat pump

A theoretical and experimental exergy analysis of a solar-assisted heat pump for air heating is presented. An experimental prototype that operates as a solar-assisted or as a conventional heat pump was tested to determine exergetic efficiency, total system irreversibility and component irreversibilities. A methodology for determination of the optimum temperature of the working fluid in the evaporation and condensation steps is proposed. The methodology is based on maximization of efficiency in these two parts of the system.     

Preliminary investigation of a transcritical CO2 heat pump driven by a solar‐powered CO2 Rankine cycle

In this paper, a transcritical carbon dioxide heat pump system driven by solar‐owered CO₂ Rankine cycle is proposed for simultaneous heating and cooling applications. Based on the first and second laws of thermodynamics, a theoretical analysis on the performance characteristic is carried out for this solar‐powered heat pump cycle using CO₂ as working fluid. Further, the effects of the governing parameters on the performance such as coefficient of performance (COP) and the system exergy destruction rate are investigated numerically. With the simulation results, it is found that, the cooling COP for the transcritical CO₂ heat pump syatem is somewhat above 0.3 and the heating COP is above 0.9. It is also concluded that, the performance of the combined transcritical CO₂ heat pump system can be significantly improved based on the optimized governing parameters, such as solar radiation, solar collector efficient area, the heat transfer area and the inlet water temperature of heat exchange components, and the CO₂ flow rate of two sub‐cycles. Where, the cooling capacity, heating capacity, and exergy destruction rate are found to increase with solar radiation, but the COPs of combined system are decreased with it. Furthermore, in terms of improvement in COPs and reduction in system exergy destruction at the same time, it is more effective to employ a large heat transfer area of heat exchange components in the combined heat pump system. Copyright © 2012 John Wiley & Sons, Ltd.