Exergetic performance evaluation of heat pump systems having various heat sources

In this study heat pump systems having different heat sources were investigated experimentally. Solar‐assisted heat pump (SAHP), ground source heat pump (GSHP) and air source heat pump (ASHP) systems for domestic heating were tested. Additionally, their combination systems, such as solar‐assisted‐ground source heat pump (SAGSHP), solar‐assisted‐air source heat pump (SAASHP) and ground–air source heat pump (GSASHP) were tested. All the heat pump systems were designed and constructed in a test room with 60 m² floor area in Firat University, Elazig (38.41°N, 39.14°E), Turkey. In evaluating the efficiency of heat pump systems, the most commonly used measure is the energy or the first law efficiency, which is modified to a coefficient of performance for heat pump systems. However, for indicating the possibilities for thermodynamic improvement, inadequate energy analysis and exergy analysis are needed. This study presents an exergetic evaluation of SAHP, GSHP and ASHP and their combination systems. The exergy losses in each of the components of the heat pump systems are determined for average values of experimentally measured parameters. Exergy efficiency in each of the components of the heat pump systems is also determined to assess their performances. The coefficient of performance (COP) of the SAHP, GSHP and ASHP were obtained as 2.95, 2.44 and 2.33, whereas the exergy losses of the refrigerant subsystems were found to be 1.342, 1.705 and 1.942 kW, respectively. The COP of SAGSHP, SAASHP and GSASHP as multiple source heat pump systems were also determined to be 3.36, 2.90 and 2.14, whereas the exergy losses of the refrigerant subsystems were approximately 2.13, 2.996 and 3.113 kW, respectively. In addition, multiple source heat pump systems were compared with single source heat pump systems on the basis of the COP. Exergetic performance coefficient (EPC) is introduced and is applied to the heat pump systems having various heat sources. The results imply that the functional forms of the EPC and first law efficiency are different. Results show that Ex_loss,total becomes a minimum value when EPC has a maximum value. Copyright © 2008 John Wiley & Sons, Ltd.     

Performance of ejector heat pumps

An ejector-compression heat pump can use low-grade thermal energy in the neighbourhood of 93.3°C (200°F) to provide space cooling and heating. This paper applies the existing ejector theory to estimate the performance of an ejector heat pump system at various operating conditions. The study includes parametric, sensitivity and off-design analyses of the heat pump performance. The performance enhancement options and desired ejector geometry are also examined. Refrigerants 11, 113 and 114 are three of the halocarbons most suitable for the ejector heat pump system. The estimated coefficients of performance for a simple ejector heat pump are 0.3 for the cooling mode and 1.3 for the heating mode at a sample operating condition in which the refrigerant (R-11) boiling temperature is 93.3°C (200°F), condensing temperature 43.3°C (110°F) and evaporating temperature 10°C (50°F). A 24 per cent performance improvement is predicted for a heat pump with two-stage ejectors and regenerative heat exchangers. The off-design performance is relatively insensitive to the evaporator temperature variations.     

寒冷地区太阳能-土壤源热泵系统运行方式的探讨

在太阳能—土壤源热泵系统中，合理确定其运行工况，对系统运行的经济性、可靠性具有重要意义。该文对寒冷地区太阳能热泵系统在各种运行工况的运行特性及太阳能—土壤源热泵系统在各种运行方式下的运行时间分配比例进行理论研究，为太阳能—土壤源热泵系统的设计、运行管理提供参考。     

Performance assessment of contact heat pump drying

A comparative analysis is presented of a novel plate‐type isothermal heat pump dryer and a conventional adiabatic heat pump dryer. The energy performance and drying capacity of each dryer type is investigated subject to operational constraints on the maximum acceptable relative humidity and temperature of air passing over the product. The analysis demonstrates that for applicable products, a significant opportunity exists for improving the energy efficiency of heat pump drying, by a factor of 2–3 times compared with current adiabatic heat pump dryers. The moisture extraction rate is also increased in the contact heat pump dryer, by a similar factor. However, these improvements are shown to be sensitive both to the impact of product thickness on heat transfer and to the relative humidity constraint. Copyright © 2010 John Wiley & Sons, Ltd.     

厨房余热回收热电热泵储水式热水器的研究

在热电热泵热力学分析的基础上,设计研制了一台用于回收公共厨房排气余热、容积为36L的热电热泵储水式热水器,该装置采用热管散热器对热电热泵冷、热端散热,在回收厨房余热的同时制取生活热水.针对该热电热泵储水式热水器,对其制热性能进行实验研究,结果表明:热电热泵冷、热端温差是影响热电热泵制热性能的重要因素:排气温度越高,热水温度越低,则冷、热端温差越小,制热系数越大.在此基础上,对热电热泵储水式热水器进行优化,并对样机的性能进行测试,结果表明:工作电压对热水加热时间影响较大,工作电压越大,加热时间越短;在电压20V时将热水从28℃加热到46℃,样机相比普通电热水器节省电耗30%以上.     

Heat pump assisted distillation. V: A feasibility study on absorption heat pump assisted distillation systems

The problems in matching a heat driven absorption heat pump to a distillation process in heat pump assisted distillation are discussed. The performance of an absorption system is a function of the temperatures in the evaporator, the condenser, the absorber and the generator and the ratio of the mass flow rate in the secondary circuit to the mass flow rate in the primary circuit. In absorption systems design choices are limited by the Gibbs phase rule. Plots are given of the coefficient of performance against the temperatures of the top and bottom products and also against the energy saved.     

基于R125工质热泵循环的理论分析

通过对热泵循环流程的分析,构建了带有回热器热泵的数理模型.理论分析了以R125为工质的热泵系统,并对R125及几种热泵工质在标准工况和变工况下的循环性能进行了系统的理论计算及分析.结果表明,在标准工况下,R125制热系数优于R22,是极有潜力的热泵替代工质.     

太阳能热泵系统的试验研究与分析

为研究以太阳能为低温热源的供热运行特点,建立了太阳能热泵系统试验台及试验台测量系统,使用数据分析软件处理不同工况下的试验数据,分析了蒸发和冷凝温度对吸热量、制热量、压缩机状态、系统COP的影响。结果表明,太阳能热泵系统在运行期间节能效果明显,蒸发温度的增大有利于提高太阳能热泵系统的工作性能。     

地源热泵的分类及其若干问题的看法

针对地源热泵的分类和名称不很统一的现状，提出了按低温热源的来源统一分类的看法，并据此对目前常用的各种土壤源、水源热泵进一步分类；并提出目前把水环热泵当作水源热泵是不合适的，应该作为空气源热泵的一种。     

复合热源热泵循环的节能研究

本文介绍了热泵空调的原理及主要特点，分析了单一空气热源热泵存在的缺陷，介绍了空气－水复合热源热泵循环的工作原理，提出了相应的数学物理模型，并对其制热性能进行分析。结论是空气－水复合热源热泵的制热性能明显优于单一空气热源热泵，具有较好的调节性和显著的节能性。     

考虑热漏影响的热泵装置有限时间热力学性能

本文研究热漏对热泵装置最优性能的影响，导出存在热阻和热漏损失的定常态流不可逆卡诺热泵最佳供热系数与供热率关系，所得结果与仅存在热阻损失时的内可逆卡诺热泵供热系数供热率特性关系有量和质的区别。     

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。     

Optimum thermoeconomic and thermodynamic performance characteristics of an irreversible three-heat-source heat pump

The coefficient of performance and specific heating load of an irreversible three-heat-source heat pump are given by using a general cycle model affected by the finite-rate heat transfer, heat leak and internal irreversibility of the cyclic working fluid. The heat pumping load divided by the total cost per unit time is taken as a new objective function and used to investigate the performance of the heat pump. The thermoeconomic and thermodynamic performance characteristics of the heat pump are discussed in detail. Some important performance parameters such as the thermoeconomic objective function and coefficient of performance are optimized. The optimally operating regions of the heat pump and the bounds of several performance parameters are determined. Finally, it is pointed out that the Carnot heat pump may be taken as a special case of a three-heat-source heat pump and consequently its optimal performance can be directly derived from the results obtained here.     

相变储热预热式热泵热水器系统性能研究

对集储热、预热与放热于一体的相变储热预热式热泵热水器系统的工作性能进行了研究,并对储、放热过程中相变材料、制冷介质的温度变化及压缩机的功耗情况进行了分析,该储热式热泵热水器系统采用分段加热,利用储能材料对水的预热作用,减小水与系统工作介质之间的换热温差,降低压缩机的功率消耗,使系统COP提高,若储热阶段结合谷电的应用,系统节能效果将更加显著,该试验研究为此类热泵热水器的理论模拟及性能优化奠定了基础.     

An investigation of the heat pump performance and ground temperature of a piled foundation heat exchanger system for a residential building

Novel methods are sought to provide greater efficiency of the installation of ground heat exchangers for GSHPs (ground source heat pumps) in domestic buildings. An economically viable option is to utilise concrete foundation piles as ground heat exchangers. The objective of this study is to investigate the operation of utilising a piled foundation structure as a ground heat exchanger. A test plot of 72 m² (ground floor area) was produced with 21 × 10 m deep concrete piles, with a single U tube pipe in each. Ground heat was extracted by a heat pump with the heat loading being varied in line with the date and the average air temperature. Over the 2007/2008 heating season this study had investigated the temperature changes in the foundation piles and the surrounding ground in addition to the heat pump operational performance. The temperature changes observed in the region of the test plot were compared with variations naturally experienced in the ground due to the seasonal climatic influence. The SPF (seasonal performance factor) of the heat pump was 3.62 and the ground temperature at a distance of 5 m from the test plot was seen to be undisturbed by the heat extraction and followed the predicted seasonal variation.     

采集凝固热热泵技术凝固及换热性能的理论分析

介绍了一种新型的采集凝固热热泵技术,建立了凝固热采集装置中层流流动水在常壁温条件下的管内凝固问题的数学模型。采用准稳态近似方法进行了凝固特性的分析,使用当量平均表面换热系数和潜热显热比两个参数讨论了冰层对换热性能的影响。计算结果与所得结论对凝固热采集装置的设计和热泵系统性能的改善有一定指导作用。     

空气回热闭式热泵干燥系统实验研究

空气闭式热泵干燥装置和加装空气回热器的空气闭式热泵干燥装置的对比试验表明，后者比前者除湿能耗比ＳＰＣ在某些工况下降低达２０％。对两者的循环作了理论分析。     

Performance study of a heat pump dryer system for specialty crops—Part 1: Development of a simulation model

This research is concerned with the technology of heat pump assisted drying of specialty crops. A simplified procedure for modelling the performance of a low temperature heat pump dryer was developed. The system modelled consists of a vapour compression heat pump coupled to a continuous cross flow bed dryer. The model takes into account the detailed heat and mass transfer phenomena taking place in the heat pump and dryer circuits. Copyright © 2002 John Wiley & Sons, Ltd.     

水循环式热泵干燥装置的分析

热泵干燥装置具有节约能源、环境友好、可低温干燥等特点。水循环式热泵干燥装置是指热泵和干燥部分通过水循环耦合而成的热泵干燥装置,与热泵和干燥部分直接耦合相比,具有不向环境排放热量、机组调控性好、对干燥过程的匹配性好、成本低等优势,是一种较适宜于中小型热泵干燥装置的结构型式。     

空气源热泵制冷热回收机组的技术可行性

通过对一台普通的空气源热泵进行热回收改造，利用回收的热量加热生活热水。改造后的机组在实验台上进行了全年运行工况测试，通过对机组改造前后运行工况的分析对比，提出了带热回收装置的热泵是一种节能的空调热水机组，并对机组在冬季的运行过程中可能出现的问题作了说明。