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。     

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.     

间接膨胀式太阳能多功能热泵单独制热水性能实验研究

简要介绍了间接膨胀式太阳能多功能热泵(IESA-MDHP)系统的功能模式.在冷凝侧采用强制循环和自然循环两种运行模式,对系统在冬季工况下利用中低温水源单独制热水性能进行实验测试.实验结果表明,在两种运行模式下热泵COPhp、系统COPsys及(火用)性能系数COPEX都明显高于空气源热泵热水器系统.实验同时对不同初始水温下IESA-MDHP系统单独制热水性能进行对比,发现初始水温对热泵COPhp、系统COPsys影响不大,而对(火用)性能系数COPEX影响较明显.     

热泵循环的分析及太阳能热泵系统的效率

本文以热力学第二定律为基础,用“(火用)”参数对热泵系统的四种工质R-12、R-22、R-113和NH_(?)进行了计算分析,作出曲线和(火用)流图,对热泵系统从质的方面作出评价,指出了改进的方向。同时,与以太阳能热水为热源的太阳能热泵系统的(火用)效率进行比较。     

直膨式太阳能热泵运行特性的实验研究

对直接膨胀式太阳能热泵热水系统进行了实验研究,实验期间,太阳能辐照度变化范围为143.12~664.6 W/m2,分别采用三种不同结构的集热器和蒸发器,得出系统COP为2.49~3.47,表明该系统在各种天气情况下均能够可靠地生产45℃的生活热水,热性能稳定,可以全天候地提供生活热水且具有节能效果;同时选取双集热器的两组数据,分析了太阳辐照度对热泵系统运行的影响。     

冷暖联供太阳能喷射制冷系统的一次能耗

太阳能喷射式制冷(热泵)系统在满足供冷、供热需求时，通常需要补充一定量的一次常规能源。该文在系统能量平衡的基础上，引入太阳能倍率、冬夏负荷比等参数，推导了太阳能制冷系统与电压缩制冷系统的一次能耗比计算公式。进而对太阳能双元混合工质喷射式制冷(热泵)系统、单元工质喷射式制冷系统、太阳能直接供热系统与电压缩制冷系统的一次能源消耗进行了对比分析。结果表明，太阳能喷射式热泵比太阳能直接供暖系统节约一次常规能源；太阳能喷射式制冷(热泵)系统，在其太阳能倍率位于节能区时，比电压缩制冷(热泵)系统节约一次常规能源。     

新型太阳能热泵干燥系统的设计与理论研究

结合金属氢化物热泵的特点,提出了一种耦合氢能的太阳能热泵干燥系统。具体介绍了其系统工作原理及流程,建立了系统各设备的能量转换及炯分析模型;以干燥种子的算例分析了不同参数对系统性能的影响。结果表明,系统具有较高的除湿率(SMER)值,且其主要与太阳能辐射量大小有关;系统优化应以太阳能辐射量为基础,以提高金属氢化物热泵的(火用)效率为目标,而系统与太阳能蓄热技术的耦合运用是发展的另一个方向。     

空气式PCM太阳能热泵供暖系统实验研究与分析

为实现太阳能高效利用,将相变储能材料(PCM)、空气式太阳能集热器和热泵系统结合,设计了空气式PCM太阳能热泵供暖系统,并对该系统的运行模式进行研究和理论分析。结果表明,在四种不同运行工况下,室内平均温度均可维持在298 K,可满足采暖需求;平均太阳能辐射强度为556.7 W/m~2时,集热器可为室内持续供暖10 h,日平均集热效率可达36.4%;相变储能芯储存的热量可维持热泵高效运行4 h,热泵的平均能效比(COP)可达3.1;阴雨天热泵可提供室内总供热量的92.6%,平均COP为2.6。系统整体运行稳定,节能效果显著。     

直膨式太阳能热泵系统性能分析及优化

直膨式太阳能热泵利用少量电能将太阳能的低品位能量转移至高品位,具有清洁、高效的优点,目前正成为节能领域的研究热点,近年来取得了飞速发展.国内外众多学者作了相关研究并取得了一定的成果.概述了直膨式太阳能热泵在国内外的研究进展,总结了内部参数和外部参数等方面对直膨式太阳能热泵系统性能的影响.针对不同的影响因素,给出了多种提高直膨式太阳能热泵系统性能的策略,以期对直膨式太阳能热泵的发展有一定的促进作用.     

直膨式太阳能热泵系统的模型仿真

考虑了集热器中制冷剂压降的存在,利用平衡均相理论建立了太阳能集热/蒸发器的两相流模型,同时建立了压缩机、冷凝器的数学模型.从理论上分析了集热器中制冷剂的压降、集热器的类型、集热面积、太阳能辐照度、环境温度、压缩机容积以及冷凝温度等因素对直膨式太阳能热泵系统热工性能的影响,并在此基础上给出了改善系统性能的建议.     

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.     

Experimental performance analysis and optimization of a direct expansion solar-assisted heat pump water heater

In this study, a direct expansion solar-assisted heat pump water heater (DX-SAHPWH) with rated input power 750 W was tested and analyzed. Through experimental research in spring and thermodynamics analysis about the system performance, some suggestions for the system optimization are proposed. Then, a small-type DX-SAHPWH with rated input power 400 W was built, tested and analyzed. Through exergy analysis for each component of DX-SAHPWH (A) and (B), it can be seen that the highest exergy loss occurs in the compressor and collector/evaporator, followed by the condenser and expansion valve, respectively. Furthermore, some methods are suggested to improve the performance of each component, especially the collector/evaporator. A methodology for the design optimization of the collector/evaporator was introduced and applied. In order to maintain a proper matching between the heat pumping capacity of the compressor and the evaporative capacity of the collector/evaporator under widely varying ambient conditions, the electronic expansion valve and variable frequency compressor are suggested to be utilized for the DX-SAHPWH.     

Transient simulation of a capacity-modulated, direct-expansion, solar-assisted heat pump

The long-term thermal performance of a direct-expansion, solar-assisted heat pump is determined from the transient simulation of the system. The system employs a bare collector that also acts as the heat pump evaporator. Of particular interest in this study is the configuration in which the compressor and the collector area are properly matched from the long-term thermal performance point of view. This matching is achieved through multistep as well as two-step compressor capacity modulation. In addition to examining the effects of compressor capacity modulation, the effects of various system parameters such as collector area, storage volume, load temperature, wind speed, collector slope, and refrigerant properties are also studied in detail.Monthly averaged thermal performance parameters such as the heat pump system coefficient of performance are determined by executing a computer simulation program that uses the typical meterological year (TMY) solar data for Norfolk, Virginia. Results indicate that the system performance is governed strongly by collector area, compressor RPM, load temperature, and refrigerant properties. The remaining parameters have only weak influence on the long-term system performance of direct expansion solar-assisted heat pump (SAHP) system considered in this study.     

Experiments on a solar-assisted heat pump and an exergy analysis of the system

In this work a experimental study of a solar assisted heat pump with direct expansion of the refrigerant within the solar collector, is presented. The maximum exergy efficiency, defined as the ratio of the outlet to the inlet exergy flow in every component of the heat pump cycle, is determined taking into account the typical parameters and performance coefficients. The results of this exergy analysis point out that the main source of irreversibility can be found in the evaporator of the heat pump (that is, the solar collector) emphasizing that incoming solar radiation is not used to full advantage in this piece of equipment.     

1000MW机组回热系统损分布的矩阵方法

基于热力学第二定律的分析法为评价能量转换的"量"和"质"提供了一个统一的尺度,比基于第一定律的能分析法更科学、更合理。根据平衡原理,对于一般的回热系统,建立回热系统中各级加热器的平衡方程,经过严谨的数学推理,获得类似于热力系统汽水分布矩阵的通用的损矩阵方程。该损矩阵方程与回热系统中各级加热器的类型存在一定的对应关系,利用该方程可以方便地得出不同机组回热系统的损分布,为较准确的评价热力系统的热经济性提供有力的依据。     

Experimental study on heat and exergy balance of a dual-fuel combined injection engine with hydrogen and gasoline

In this paper, a dual-fuel engine test rig with gasoline injected in the intake port and gasoline (or hydrogen) injected directly into the cylinder is built up; therefore, two injection models are realized. One is port fuel injection + gasoline direct injection (PFI + GDI), the other is port fuel injection + hydrogen direct injection (PFI + HDI). And the effects of two injection models on heat and exergy balance are investigated experimentally. The results show that, from the perspective of the first law of thermodynamics (heat balance), no matter what the injection mode is, the heat proportion of cooling water is the largest, the exhaust heat ratio and brake power are the second, which two are roughly equivalent, and the uncounted loss is the least. In PFI + GDI mode, the local mixture is too dense due to the increase of mixing ratio, which leads to insufficient combustion and a slight decrease of brake power ratio. However, due to the special characteristics of hydrogen, the increase of direct injection ratio improves the brake power ratio in PFI + HDI mode. Moreover, because of the short quenching distance of hydrogen, the cooling loss rises up with the increase of hydrogen ratio. The engine speed and load also have great impacts on heat distribution, but on account of the different physical and chemical properties between gasoline and hydrogen, resulting in varying degrees of impact and trends. On the basis of the second law of thermodynamics (exergy balance), it is found that no matter what injection mode is, the ratio of exergy destruction is always the highest, accounting for half of the total fuel energy, and the exhaust exergy ratio is lower than the brake power ratio. However, the proportion of exergy contained in cooling water is the smallest, which is quite different from the result of the first law of thermodynamics. The influences of several factors on engine energy balance are analyzed, and the differences and similarities between heat balance and exergy balance are compared. The two analytical methods are interrelated and complementary, and the purpose is to find a reasonable and comprehensive energy balance analysis method for internal combustion engine.     

太阳能辅助R744热泵系统在中原地区的性能分析

针对中原地区典型气象年(辐射极大)的冬季气象条件,通过所建立的跨临界循环热泵系统性能模拟平台,计算并对比分析了太阳能辅助R744跨临界循环及单一R744热泵系统在中原地区的运行特性;讨论了热水出水温度、传热窄点温差改变时系统制热性能系数和最优放热侧压力的变化规律。研究结果表明,在设定工况下,联合应用太阳能集热系统,R744热泵系统性能在冬季可得到大幅度提高,平均提高34.4%;热水出水温度低于70℃时,系统性能提高幅度超过36.0%;但传热窄点温差增大,系统性能有一定程度下降。     

基于PVT集热/蒸发器的补气增焓热泵性能分析

传统直膨式太阳能辅助热泵系统在低温环境适应性欠佳,影响其在寒冷地区使用,通过采用补气增焓技术可以有效提高其低温条件下的供热能力。以所提出的采用PVT集热/蒸发器的补气增焓热泵系统为研究对象,计算分析环境条件、太阳辐射强度、注入蒸汽质量流量对该热泵系统性能的影响。研究结果表明： 当环境温度为-10℃,太阳照强度为500 W/m²时,性能系数（COP）可达4.3,比使用补气增焓（VI）循环的空气源热泵（ASHP）系统高63.6%。以当量热价（LCOH）作为指标与其他3种供热系统进行比较,所提出的系统经济性也具有一定的优势,可为补气增焓热泵系统在寒冷气候地区的应用提供新思路。     

纯低温余热发电系统的热力学分析

介绍了能量平衡分析法和(火用)分析法,并将余热发电系统分为AQC锅炉、SP锅炉和汽轮机发电系统3个单元,分别建立了热平衡分析和(火用)平衡分析模型,推导了一套余热发电系统热力学分析的计算方法.根据某水泥厂2 500 t/d的新型干法水泥生产线配套建设的5MW纯低温单压余热发电系统的现场运数据,计算了余热回收热效率和(火...