中高温热泵工质应用的现状与选择

为了消除现有热泵技术利用温度比较低,对于高温的工业余热和地热尾水利用率低的问题,指出中高温热泵工质技术替代常温热泵技术的必要性。介绍热泵系统的组成部分、中高温热泵工质的循环特性、热泵工质对环境的影响以及中高温热泵工质的研究现状。中高温热泵提高了热泵的工作温度,扩大了低位热能资源的回收和供热范围。     

高温热泵及热泵蒸汽机的研究进展

本文从新型工质的研发和系统效率的提高两方面综述了高温蒸汽压缩式热泵的研究现状,对于高温吸收式热泵,则从新型循环设计、系统控制与仿真、参数优化、提高换热效率等方面做了综述。文章最后介绍了国内外最新研制的两种热泵蒸汽机的运行原理和结构特点,并根据热泵蒸汽机组的运行要求,提出了今后的研究方向和要解决的主要技术问题。     

水—水热泵替代工质循环性能及其动态可燃特性研究

水－水热泵在建筑能量系统的环境保护,开发和利用余热资源中起着重要作用,为了研究这种热泵的工质替代问题,就目前具有成功实验结果的水－水热泵的替代工质之一：R32／134a进行热力学及循环性能模拟分析,结果发现R32／134a当浓度为（30／70）时作为常规水－水热泵工质具有较大的优势,针对此替代物在生产使用中的重要环节一贮存和运输中的安全性问题,研究其在贮运过程中由于泄漏引起的动态燃爆特性,得出了具有实际应用价值的规律。     

CO2跨临界热泵高温化途径分析

CO2作为一种环境友好的自然工质,以其为循环工质的跨临界热泵制热能力突出.建立CO2跨临界增压和CO2跨临界热泵理论分析模型,研究不同增压过程对热泵系统COP、气冷器中水的出口温度及质量流量的影响规律.结果表明,2种热泵高温化方案均会提升压缩机等熵效率、功耗和压缩机出口工质温度,且提升了气冷器出口水温,但COP和热水的...     

高温热泵在木材加工行业中的应用

分析了国内外木材加工行业中高温热泵的研究与应用现状,提出了采用高温热泵回收单板干燥尾气的方案,认为当前要重视高温热泵工质及相应热泵系统的研制,发展高温热泵与太阳能和常规蒸汽干燥的联合干燥技术,使高温热泵干燥装置标准化和规范化,保证机械的产品质量与稳定性,扩大高温热泵干燥机在我国的使用范围。     

中高温空气源热泵热水器的工质优选

热泵热水器的工质对机组的性能和热水器的出水温度都有较大的影响,是研发高性能热泵热水器的重要课题之一。对目前热泵热水器常用的工质、部分中高温热泵工质以及新开发的中高温热泵热水器工质TJR01从基本物性、安全性、环保性、溶油性进行了分析,又通过CSD方程对循环特性进行了计算和分析。结果表明,新工质TJR01直接充灌到R22压缩机里,既能保证热水器的出水温度要求,又能保证机组高效稳定运行。     

高温热泵系统稳态仿真

针对水-水高温热泵实验台建立了系统稳态仿真模型.模型输入参数为系统结构参数和载热流体参数,输出参数则为系统性能参数和换热器温度场.采用P-T状态方程计算工质相平衡性质,故模型适用于新型纯质和混合工质.在压缩机建模中,根据实验数据辨识拟合了压缩机容积效率、定熵效率和热效率,在两器模型中考虑了压降和输运性质对换热过程的影响...     

用于高温热泵蒸汽系统的几种工质的循环性能

建立了高温热泵蒸汽系统的热力学模型。在蒸发温度为60℃,冷凝温度为120~140℃的工况下,进行经过初步筛选的4种高温热泵纯工质(R123,R141b,R245ca,R245fa)和传统高温热泵工质(R114)的循环性能对比研究。结果表明:R245fa的综合循环性能良好,单位容积制热量最高,其性能系数(COP)比R114平均高13.65%,压缩比与R114最接近;在符合干压缩要求的前提下,排气温度较低,而且环境友好,可作为高温热泵蒸汽系统的工质。     

采用不同工质的高温复合热泵开水器特性研究

热泵开水器具有较高的能源利用效率,是公共场所电加热开水装置的理想替代品。从提高能源效率和一机两用的角度,构建了一种高温复合热泵开水器系统。建立了系统热力学模型,选R236fa、R245fa、R365mfc、R245ca、RC318和R236ea等6种较高临界温度的制冷工质,通过能量分析和[火用]分析的方法,探讨了不同制冷工质对高温复合热泵开水器系统性能的影响。研究结果表明:R245fa作为工质的高温复合热泵开水器系统具有最佳的性能,而以RC318作为工质的系统性能最差。在给定工况下,R245fa作为工质系统制热性能系数(COP_h)为2.47,而其制冷性能系数(COP_c)为3.37,[火用]损失和[火用]效率分别为9.47 kW和49.07%;与R245fa相比,RC318作为工质系统的总能耗增加了39.53%。     

中高温热泵技术在工业余热回收中的应用

我国许多行业对热源的需求温度多集中在75～200℃之间，且存在着低温余热大量浪费的情况，可以把热能由低温位热源转移到高温位热源的中高温热泵技术有着巨大的应用空间。对高温热泵的研究多集中在适宜工质的选择和制热效率提高这两个方面。国外的研究起步较早，混合工质方面的研究成果目前仍处于技术保密阶段。国内研究起步较晚，主要研究成果集中在高校，但尚未找到一种公认的环境友好、性能优越的高温热泵工质。近几年，国内在油田含油污水的余热回收．坑口电厂冷却水和矿井涌水的余热回收，涂装、电镀车间余热回收等领域进行了高温热泵技术的实际性工程应用，经济效益和环保显著．不仅节省了大量的化石能源，而且减少了二氧化碳的排放。但高温热泵技术在实际应用中还存在设备腐蚀等问题．需要结合余热源的具体情况采取相应的措施加以解决。     

Development of a beta-type Stirling heat pump with rhombic drive mechanism by a modified non-ideal adiabatic model

In this paper, a thermodynamic model is developed for predicting the performance of a beta-type Stirling heat pump with rhombic drive mechanism for water heater and the model is validated by a 1-kW class prototype Stirling heat pump. In the present model, the working space is divided into expansion space, heat absorber, regenerator, heat rejecter and compression space. The pressure, mass and temperature variations of working fluid in each working space are predicted. The temperature variation of wall boundary is also taken into consideration. The temperature of working fluid in each working space and the temperature of wall boundary are obtained by solving energy equations simultaneously. Eventually, the pressure of working fluid in each working space can be corrected by using empirical formula of pressure drop. All the thermal properties of working fluid and wall boundary in each working space at each time step can be obtained by repeating the above process. Then, the performance of heat pump such as absorbing heat, rejecting heat, indicated power and COP can be calculated. A series of experimental measurements and comparisons are also conducted for validating present model. The results show that the prototype heat pump can produce 904 W heating power and 38°C hot water under 1 LPM water flow rate with 5 bar helium at 1000 rpm.     

Theoretical thermodynamic analysis of Rankine power cycle with thermal driven pump

A new approach to improve the performance of supercritical carbon dioxide Rankine cycle which uses low temperature heat source is presented. The mechanical pump in conventional supercritical carbon dioxide Rankine cycle is replaced by thermal driven pump. The concept of thermal driven pump is to increase the pressure of a fluid in a closed container by supplying heat. A low grade heat source is used to increase the pressure of the fluid instead of a mechanical pump, this increase the net power output and avoid the need for mechanical pump which requires regular maintenance and operational cost. The thermal driven pump considered is a shell and tube heat exchanger where the working fluid is contained in the tube, a tube diameter of 5 mm is chosen to reduce the heating time. The net power output of the Rankine cycle with thermal driven pump is compared to that of Rankine cycle with mechanical pump and it is observed that the net power output is higher when low grade thermal energy is used to pressurize the working fluid. The thermal driven pump consumes additional heat at low temperature (60 °C) to pressurize the working fluid.     

Evaluation of a microcomputer-based control system for a domestic sized engine-driven water-to-water heat pump

Steady-state performance data have been obtained on a domestic sized engine-driven water-to-water heat pump. The optimum working fluid suction superheat for the system was found to be 12°C. Over a range of heat sink conditions, increasing the engine speed linearly increased the total heat prouduced by the unit. Similarly, over a range of heat source conditions, increasing the engine speed linearly increased the working fluid evaporation rate. To produce water at 80°C, the heat pump was designed to operate with a heat sink temperature of 70°C, but its efficiency was improved by operating with the heat sink at 55°C. With a heat sink temperature of 55°C the primary energy ratio of the unit was observed to vary from 0–85 to 1–16, over a range of heat source temperatures. Algorithms developed from the steady-state experiments were incorporated as control function subroutines in a microcomputer program. Using this program, the microcomputer was employed to control the heat pump outlet water temperature and the working fluid suction superheat. The control system was tested in a series of dynamic experiments and was found to operate effectively and achieved its control requirements. In certain tests, the transient time period was extended because the electrically-controlled expansion valve was too large for the system and created instability in the suction superheat.     

Experimental study of the operating characteristics of a heat pump assisted distillation system using R11 as the external working fluid

Heat pump assisted distillation with an external working fluid is one of the most obvious methods to reduce the energy consumption in a distillation process. The heat pump working fluid extracts heat from the top of the column, increases the temperature of the recovered heat and recycles it to provide the heat input to the reboiler.The interaction between the external parameters and the internal parameters for a specially designed heat pump assisted distillation system has been studied experimentally. The external parameters were mass flow rate, temperature and concentration of the feed, the concentration of the top and bottom products and the mass flow rate of the working fluid. The effects of the variations of these external parameters on the internal parameters such as the energy (steam) consumption, the actual coefficient of performance and the temperatures at the top and bottom of the column, together with the condensation and evaporation temperatures, are presented.     

海上油气平台余热朗肯循环发电系统热力学分析

海上油气平台存在大量的燃气轮机余热。通过建立海上平台余热朗肯循环发电系统仿真模型,开展平台余热发电热力学及热经济性分析。选取工质泵功率、发电机输出功率、系统热效率、换热面积和单位面积发电量等参数作为优化目标,研究不同冷凝温度下优化目标函数随蒸发器烟气进出口温差的变化规律。结果表明:随着蒸发器烟气进出口温差的增加,工质泵功率、发电机输出功率和系统APR先增大后减小。冷凝温度越高,工质泵功率越大,发电机输出功率和系统热效率越小。当冷凝温度为65℃时,系统APR最大。受透平出口蒸汽干度的限制,所研究工况下,系统发电机最大输出功率为7 496 kW,系统最大热效率和APR分别为14.16%和5 kW·m~(-2)。研究结果可为撬装化、集成化海上油气平台余热发电系统研制提供理论参考。     

基于海底黑烟囱的海洋温差发电热力循环系统研究

与传统的海洋温差发电系统不同,海底黑烟囱海洋温差发电系统是以海洋地热为热源,以深海冷水为冷源的发电系统。文章分别分析和计算了以水蒸气为工质的开式系统和以纯氨为工质的闭式系统的循环热效率、换热器负荷、泵耗以及循环净功等相关参数。结果表明,与以纯氨为工质的闭式系统相比,开式系统的热水泵功耗过大,降低高温海水的温度和提高闪蒸压力对开式系统是不利的;以水蒸气为动力循环工质有利于降低换热器的负荷,这对换热器的设计是十分有利的。     

Performance trends and heat transfer considerations in an ammonia–water resorption cycle

An experimental test facility was constructed to examine the potential of ammonia–water mixtures as the working fluid in high‐temperature heat pumps. The nature of the working fluid necessitates an alternative design to the conventional vapour compression cycle. The addition of a solution circuit in parallel with the compressor leads to the resorption cycle. The composition of the working fluid can be altered by varying the flow ratio between the compression and solution pump circuits. Changes in the composition of the circulating fluid are accompanied by changes in the dryness fraction at the end of the heat transfer process in the desorber. Higher rates of heat transfer from the source to the working fluid were measured at higher concentrations of ammonia in the circulating fluid, though this was accompanied by lower overall flow rates of the circulating fluid. A 70/30 ammonia/water mass concentration is thought to be the optimum composition of the working fluid due to a combination of temperature glide and circulation ratio. Significant differences were observed in the overall heat transfer coefficient achieved in the two heat exchangers, which may restrict the range of likely applications. Copyright © 2001 John Wiley & Sons, Ltd.     

Heat pump assisted distillation. III: Experimental studies using an external heat pump

An experimental study has been carried out on a continuously operated pilot fractional distillation column equipped with an external heat pump. The distillation column was a 15 cm diameter glass unit containing eleven single bubble cap plates. A methanol-water mixture was fed to the column and the heat pump working fluid was R114. The actual coefficient of performance (COP)_A of the heat pump increased with an increase in the mass flow rate of the working fluid. A maximum (COP)_A value of 4–3 was obtained with a gross temperature lift of 41–3°C. The performance of two reciprocating compressors was compared. The experiments have shown that continuous heat pump assisted distillation using an external working fluid can greatly reduce the energy used in a distillation process. No control problems were encountered in the experiments.     

城市污水源热泵工质流变特性研究

城市污水是一种优良的可再生性低温余热源，污水源热泵能够充分利用城市污水的废热，是一项具有节能和环保意义的应用技术。而污水源热泵工质的流变特性是表征其热分析及流动性的重要依据。本文以实验为基础，分析得出了城市污水源热泵工质剪切速率和剪应力的关系。应用系统辨识的方法，确定了该工质的本构方程。研究结果表明，污水源热泵工质呈现非牛顿流体特性，属于屈服-假塑性流体。