Optimal performance characteristics of a solar-driven heat pump at maximum COP

The effect of the irreversibility of finite-rate heat transfer on the performance of a solar-driven heat pump is investigated by using the theory of finite time thermodynamics. Maximizing the COP of the system leads to some novel rules for the optimum choices of primary performance parameters, such as the operating temperatures of the solar collector and the working fluid in the heat exchangers and the heat transfer areas of the heat exchangers. These rules can guide the evaluation of existing real solar-driven heat pumps or influence the design of future solar-driven heat pumps.     

Heat and mass transfer in super active carbon/ethanol adsorption heat pump with a packed bed type adsorber

The possibility of producing cold heat energy by a super active carbon/ethanol adsorption heat pump (AHP) with a packed bed type adsorber is discussed on the basis of both experimental and calculated results of the transient behavior accompanied by this operation. The trend in experimental results for heat and mass transfer agrees well with computer simulation for closed-system, one-component, non-isothermal conditions in both the adsorption and desorption processes. The super active carbon/ethanol AHP proposed generates a high level of cold heat energy by raising the desorption temperature. Therefore, this AHP is applicable to a refrigerator. However, it is suggested that enhancement of heat transfer in the adsorber is indispensable to obtain a high power from this type of AHP. © 1997 Scripta Technica, Inc. Heat Trans Jpn Res, 25(7): 466–475, 1996     

Recent progress in the adsorption heat pump technology

吸附热泵是一种以低品位热能驱动的节能环保型热泵技术,利用吸附剂与吸附质间的吸附热实现制冷或制热效果,从文献检索结果来看该技术越来越受到广泛关注,国内外相关学者开展了大量的研究工作.本文首先介绍了开展吸附热泵相关研究的课题组和其主要研究方向,进而简要介绍了吸附式热泵技术;其次,着重描述了吸附热泵技术的国内外研究现状,对吸附工质的研究,床层的传热传质强化,热泵新技术及商业化热泵产品等进行了详细的叙述;最后,叙述了吸附式热泵当前存在的主要问题,指出了吸附热泵发展存在的挑战性问题和未来的发展方向.     

传热规律、热漏和内不可逆性对吸收式热泵循环性能的影响

建立了考虑泵热空间到环境热源的热漏、工质循环的内部不可逆性以及工质与热源之间传热Q∝△(T^a)服从传热规律时的不可逆四热源吸收式热泵循环模型,导出了循环泵热率和泵热系数的一般关系;并导出了线性唯象传热定律时循环泵热率和泵热系数的基本优化关系、性能极值、循环中工质的最佳工作温度和换热器传热面积的最佳分配关系;通过数值耸例分析了传热规律、热漏和内不可逆性对循环性能的影响规律,比较了传热面积最优分配前后循环的最优性能。     

Experiments on heat-regenerative adsorption refrigerator and heat pump

A heat-regenerative adsorption refrigerator using spiral plate heat exchangers as adsorbers and an adsorption heat pump for air conditioning using plate fin heat exchangers as adsorbers have been developed and researched, experimental research results are shown. The activated carbon–methanol adsorption pair is used for the two adsorption systems, which yield a refrigeration power density of more than 2·6 kg ice per day per kg activated carbon and 150 W kg⁻¹ activated carbon for air conditioning, respectively. © 1998 John Wiley & Sons, Ltd.     

Exergoeconomic performance of an endoreversible Carnot heat pump with complex heat transfer law

The finite-time exergoeconomic performance of an endoreversible Carnot heat pump with a complex heat transfer law, including generalized convective heat transfer law and generalized radiative heat transfer law q∝ (Δ T ⁿ ) ^m , is investigated in this paper. The focus of this paper is to obtain the compromised optimization between economics (profit) and the energy utilization factor (coefficient of performance, COP) for the endoreversible Carnot heat pump, by searching the optimum COP at maximum profit, which is termed as the finite-time exergoeconomic performance bound. The obtained results include those obtained in much of the literature and can provide some theoretical guidance for the design of practical heat pumps.     

The heat and mass transfer performance of facile synthesized silica gel/carbon-fiber based consolidated composite adsorbents developed by freeze-drying method

A series of experimental investigations had been performed to analyze the heat and mass transfer performance for two novel types of silica-based consolidated composite adsorbents developed by the freeze-drying method. The first type of adsorbent is silica gel consolidated with carboxymethyl cellulose (CMC) (SC), while the other is silica gel consolidated with CMC and carbon fiber powder (SCC). Results indicate that the thermal conductivity of consolidated composite adsorbents increases with the mass proportion of carbon fiber powder, while it decreases with the increasing moisture content in the preparation process of the adsorbents. When the mass ratio of silica gel, CMC, and carbon fiber powder is 4:1:4, the highest thermal conductivity of consolidated composite adsorbent obtained from experiments reaches 1.66 W m^?1 K^?1, which is 13.4 times greater than that of pure silica gel. Furthermore, the results of macroporous properties analysis of typical samples including SC20 and SCC20 (where the 20 means that the undried samples have a water content of 20% by mass during the preparation process) show that heat transfer additives effectively improve the macroporous porosity and permeability of the consolidated composite adsorbents. The study on adsorption dynamic performance indicates that the freeze-drying method helps to improve the adsorption performance including adsorption rate and equilibrium water uptake. The experimental results also show that the mass transfer coefficient K of the two typical samples are approximately stable at 5 × 10^?3 s^?1 when the adsorption temperature is ranged between 30 and 40°C, which are almost twice the corresponding values of the samples developed by heating–drying method. Therefore, the proposed approach which is the consolidation with heat transfer additives combined with freeze-drying method is effective for simultaneously enhancing the heat and mass transfer performance of the silica gel adsorbents.     

地源热泵垂直埋管的传热模型及计算

建立了垂直埋管地源热泵地热换热器的传热模型,采用有限差分法建立了垂直U型埋管换热器瞬态传热模型的解析解;并且在不同的工况下进行实验测试,与模拟结果进行了对比,结果表明模拟与实验能较好地吻合,从而使模型的正确性得到了验证。可为地源热泵的设计和运行提供理论指导。     

椭圆管散热器传热及阻力性能试验研究

对空气横掠片距不相等的叉排椭圆翅片管散热器的传热及阻力性能进行了试验研究,得到试件在一系列工况下的传热与管外流动阻力数据,并对试验数据进行分析计算,从总传热系数K中分离出管外空气侧的对流换热系数h,给出有工程应用价值的管外换热准则关系式及管外阻力准则关系式。认为椭圆管管外的平均换热效果优于圆管。在相同的流通截面积下椭圆管传热周边较长,换热面积相应增加,因此结构上允许布置得更紧凑。     

Experimental research on dynamic operating characteristics of a novel silica gel-water adsorption chiller

A novel silica gel-water adsorption chiller consisting of two adsorption/desorption chambers and an evaporator with one heat-pipe working chamber is experimentally studied. The dynamic operating characteristics of the chiller and the thermodynamic characteristics of the adsorber are obtained. The experimental results show that the dynamic operating characteristics of the chiller and the thermodynamic characteristics of the adsorber are satisfactory and that the cycle is a novel and effective adsorption cycle. A mass recovery process increases the cyclic adsorption capacity of the system and improves adaptability of the chiller to a low-grade heat source. In addition, the experiment indicates that this novel chiller is highly suitable for an air conditioning system with a low dehumidification requirement or a system with a large cycle flowrate and an industrial cooling water system. Translated from Journal of Shanghai Jiaotong University, 2006, 40(2): 306–310 [译自: 上海交通大学学报]     

Maximum profit performance of a three‐heat‐reservoir heat pump

The operation of a three‐heat‐reservoir heat pump is viewed as a production process with exergy as its output. The relations between the optimal profit and COP (coefficient of performance), and the COP bound at the maximum profit of the heat pump are derived based on a general heat transfer law. The results provide a theoretical basis for developing and utilizing a variety of heat pumps. The focus of this paper is to search the compromised optimization between economics (profit) and the utilization factor (COP) for finite‐time endoreversible thermodynamic cycles. Copyright © 1999 John Wiley & Sons, Ltd.     

Experimental study of heat transfer characteristics for a refrigerator by using reverse heat loss method

The present study has been carried out to predict the heat transfer characteristics of a residential refrigerator through insulation wall by using reverse heat loss method. The temperature time history characteristics were measured to achieve the steady state condition. In this experiment the steady state condition was reached at about 20 h of heating. The temperature and heat inputs were then averaged with one hour data and considered as the steady state temperature and heat input. From the measured values of temperature and heat input, one can conclude that, the temperature differences between the inside and outside of a refrigerator has a nearly linear relationship with heat input. The overall heat transfer coefficients have been derived by introducing the optimal heat loss function to analyze the heat loss characteristics. The accuracy of heat loss prediction has been checked with various experimental data and the normalized errors of the obtained result are found to be within 2.5%.     

Analysis of the performance of a multi-bed adsorption heat pump using a solid-side resistance model

An analysis of the coefficient of performance and specific cooling power for a four-bed adsorption heat pump, using a solid-side resistance model, is presented. Methanol and an activated carbon are the adsorption pair. An Arrhenius form of solid-side mass diffusivity was adopted. A plate-fin type insert was considered as the heating/cooling element in adsorbers. The result shows that, for large grain-size activated carbon, the intra-particle mass diffusion resistance significantly affects the adsorption and regeneration rates. Both the coefficient of performance and the specific cooling power increase with the overall heat transfer coefficient, regeneration and evaporation temperatures, but decrease with an increase of the condensing temperature and time constant of the insert. The coefficient of performance considerably increases with a decrease of the insert heat capacitance. An optimum cycle time, corresponding to a maximum specific cooling power, was found. To achieve a high specific cooling power for short cycle time operations, small grain-size activated carbon should be selected as the adsorbent. In addition, a small time constant of the insert and a large overall heat transfer coefficient are also highly recommended.     

Potential of a direct contact adsorption heat pump system for generating steam from waste water

An adsorption heat pump with a direct contact system for steam generation has been developed and the feasibility of the proposed system was confirmed both theoretically and experimentally. The basic cycle for the system has been proposed to use zeolite–water working pairs in the p‐T‐x equilibrium curve. To generate steam above 150°C from low‐energy level water at 80°C, a direct contact adsorption heat pump prototype was constructed. The experimental results show that steam could be generated by the direct contact system and the relationship between the amount of water adsorbed and the change in temperature with time is discussed. This study is expected to serve as a foundation for developing continuous adsorption heat pump systems for steam generation. Copyright © 2011 John Wiley & Sons, Ltd.     

Mathematics model for heat and mass transfer on an adsorption bed

In a solid adsorption refrigeration system, the real cycle with non‐equilibrium adsorption is different from the ideal cycle with equilibrium adsorption. To investigate the heat and mass transfer process inside the adsorption bed, a model was established. Mathematical models were then solved by numerical method. The best cycle time of 24 minutes was ascertained through the strategy of SCP priority and paying attention to COP. The influence of the length of adsorption cell tube to the performance of refrigeration system is discussed. © 2009 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.20271 Copyright © 2009 Wiley Periodicals, Inc.     

直接空冷机组冷端传热特性研究

以直接空冷机组冷端系统传热特性为研究对象,充分考虑排汽管道压损、水蒸气压差对排汽压力的影响,建立直接空冷机组冷端换热数学模型,并对影响空冷凝汽器传热的因素进行研究分析。研究结果对直接空冷机组冷端系统保持最佳运行状态,保障凝汽器的安全和经济运行具有重要的指导作用。     

两相闭式热虹吸管混沌特性及其传热性能研究

探究两相闭式热虹吸管的传热混沌,以及操作参数对其混沌性和传热性能的影响,建立混沌特征参数与传热性能间的联系。通过搭建实验台测量两相闭式热虹吸管稳定运行过程中不同工况下的管壁温度信号,基于非线性分析的混沌理论研究处理测量的温度脉动信号,绘制吸引子轨迹图,建立最大Lyapunov指数与传热特征参数的联系,揭示传热性能与混沌特性的关系。结果表明：两相闭式热虹吸管具有确定性混沌行为,操作参数对混沌性和传热性能具有显著影响,混沌性与传热性能呈正相关关系。     

Cooling characteristics of ground source heat pump with heat exchange methods

The objective of this study is to investigate the influence of the cooling performance for a water-to-water ground source heat pump (GSHP) by using the counter flow and parallel flow methods. The GSHP uses R-410A as a refrigerant, and its main components are a scroll compressor, plate heat exchangers as a condenser, an evaporator, a thermostatic expansion valve, a receiver, and an inverter. Based on our modeling results, the heat transfer rate of the counter flow evaporator is higher than that of the parallel flow evaporator for a heat exchanger length greater than 0.42 m. The evaporator length of the GSHP used in this study was set to over 0.5 m. The performance of the water-to-water GSHP was measured by varying the compressor speed and source-side entering water temperature (EWT). The cooling capacity of the GSHP increased with increased compressor RPMs and source side EWT. Also, using the counter flow method, compared to the parallel flow method, improves the COP by approximately 5.9% for an ISO 13256-2 rated condition.     

浅析地表水源热泵空调系统的节能特性

结合实际工程,阐明了地表水源热泵系统的节能原理,分析了系统在实际运行过程中的节能特性、经济效益和环境效益,表明该系统具有明显的节能效果、经济效益和环境效益,有一定的推广和应用价值。     

Seasonal cooling performance of a ground-coupled heat pump system in a hot and arid climate

The goal of the present study is to validate the cooling performance of a ground-coupled heat pump system established in Fırat University, Elazığ (38.41°N, 39.14°E), Turkey. The cooling load of the test room was 3.1 kW at design conditions. The experimental results were obtained from June to September in cooling season of 2003. The ground heat exchanger was used, and it was buried with in 2 m depth trench. The average cooling performance coefficient of the system (COP_overall) was obtained to be 2.01. The results obtained from experimental measurement showed that these systems could be used safely, reliably and efficiently at the lowest possible cost for Elazığ, Turkey climatic conditions. Especially, the seasonal energy efficiency ratio (SEER) of this system is moderate at longer-term testing.