间接膨胀式太阳能高温热泵系统运行性能实验研究

为研究间接膨胀式太阳能高温热泵系统实际应用的可行性和有效性,搭建实验平台,在天津地区气象条件下对高温热泵全天动态运行特性开展实验研究,分析太阳辐射强度、水箱储热性能、冷凝温度及膨胀阀开度对系统运行性能影响。结果表明:平均太阳辐射强度由396 W/m2增加到563 W/m2,高温热泵性能系数COP由3.62增至3.93;因水箱储热功能,间接膨胀式系统在太阳辐射强度剧烈波动时能够保持高温热泵相对稳定的蒸发温度;当蒸发温度固定时高温热泵COP随冷凝温度升高而降低,冷凝温度由70 ℃增至80 ℃,COP由4.32降至2.76;膨胀阀开度由150步增至250步,高温热泵全天平均COP由3.14升至5.12,排气压力降低46%。     

空气源热泵热水器的性能分析

为了预测空气源热泵热水器性能,在焓差实验室内采用控制水流量的方法,通过改变环境温度和出水温度研究空气源热泵热水器的性能参数的变化,结果表明吸排气压力随着环境温度的升高而升高,制热量和COP随着环境温度的升高而升高;机组在环境温度较低的情况下运行时压缩机的压比大,导致排气压力、排气温度过高,制冷量较低,效率低,不能达到所需的水温;环境温度与排气温度相差过大,热损失较为严重;空气侧换热器容易结霜造成换热热阻增大,风量减小,使机组的换热效率越来越低。     

空气源热泵热水器系统优化计算及实验研究

对现有的空气源热泵热水器系统部件提出了优化目标与方向,并进行相应计算和实验验证。通过分别对热泵工质充注量、冷凝盘管长度以及系统匹配问题的研究,结合实验结果证明了经过优化后,热泵热水器系统的性能COP显著提高,并且稳定性得到改善。     

热回收式CO2制冷系统性能研究

对热回收式CO2制冷系统性能COP进行了计算和分析,结果表明:蒸发温度、气体冷却器出口CO2温度、热水加热器入口水温是影响其COP的主要因素;回热器出口过热度对COP的影响较小,对压缩机的排气温度影响较大;随着排气压力的升高,COP是否出现峰值,取决于气体冷却器入口制冷剂的特征温度;在相同工况下,蒸发温度、气体冷却器出口CO2温度、回热器出口过热度对最佳排气压力的影响较小,热水加热器入口水温是影响最佳排气压力的主要因素。     

直流变频空气源热泵热水器的实验研究

针对普通定频空气源热泵热水器不能在宽负荷和宽温度条件下运行等缺陷,提出一种直流变频空气源热泵热水器。通过对样机进行实验,得出了制热量、功率、COP值、吸气温度、排气温度等性能参数随压缩机运行频率的变化规律。结果表明直流变频热泵热水器能在宽负荷、宽温度条件下稳定运行。     

太阳能辅助二氧化碳热泵热水系统实验研究

利用实验的方法,研究了太阳辐照度、外界气温和风速、初始水温、蒸发器出口温度和压力等对太阳能辅助二氧化碳热泵热水系统运行状况和COP的影响。实验结果表明,系统COP随初始水温的升高而增大;太阳辐照度、外界温度和风速对热泵系统性能的影响主要体现在对系统循环水温的影响;在一定范围内,蒸发压力和蒸发温度越高,热泵系统的COP越大。     

空气源热泵热水器的优化策略及性能分析

空气源热泵热水器具有运行工况广、冷凝温度时变的特点,机组在运行至较高水温时系统效率会有明显下降。针对这一问题通过实验比较不同外部工况下系统性能的变化规律,分析热泵热水器的实际运行特性和制热性能劣化的原因,并依此提出以控制电子膨胀阀开度和压缩机启停时机的优化策略来提升系统性能。实验结果表明,系统性能分别提升了24.8%和14.3%。同时分析了两种策略的优势与差异性,以期使空气源热泵热水器在实际应用中的制热效率得到最大程度地优化。     

空气源热泵

空气源热泵在运行中．蒸发器从空气中的环境热能中吸取热量以蒸发传热工质．工质蒸气经压缩机压缩后压力和温度上升．高温蒸气通过永久黏结在贮水箱外表面的特制环形管冷凝器冷凝成液体时．释放出的热量传递给了空气源热泵贮水箱中的水。冷凝后的传热工质通过膨胀阀返回到蒸发器,然后再被蒸发,如此循环往复。     

间接膨胀式太阳能多功能热泵系统换热性能的实验研究

间接膨胀式太阳能多功能热泵系统(indirect expansion solar assisted multifunction domestic heat pump,IESA-MDHP)的运行性能受到多种因素影响,利用带有太阳模拟发射器的焓差实验室可定量检测热泵系统的运行性能,并对不同条件下的运行性能进行比较。该文在稳定的外界条件下,对IESA-MDHP系统在太阳能制热水模式和太阳能制热模式下运行的换热性能进行实验研究。结果表明,在太阳能制热水模式中,随着水箱初温升高,蒸发侧和冷凝侧换热功率均会提高,在制热水的同时,向系统输入太阳辐照,与无辐照时相比,辐照强度从0 W/m~2上升到500 W/m~2时,系统在蒸发侧和冷凝侧的平均换热功率可分别提高30.11%和37.46%,平均COP可提高32.27%;在太阳能制热模式中,水箱作为系统的蒸发热源,水箱初始温度越高,蒸发侧换热功率越大,对应的冷凝侧换热功率随之增大。     

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.     

Performance analysis of an air-source heat pump using an immersed water condenser

A distributed model of an air-source heat pump (ASHP) system and its experimental setup using an immersed water condenser were presented. Dynamic performance of the ASHP was then evaluated by both simulation and experiment. The results indicated that the system coefficient of performance (COP) decreased as the condenser temperature increased, ranging from 4.41 to 2.32 with the average COP equaling 3.29 during the experiment. Comparisons between simulation results and experimental measurements demonstrated that the model was able to yield satisfactory predictions. Furthermore, temperature profiles of the refrigerant in the evaporator and condenser were also given. This paper provides the theoretical and experimental background for ASHP system optimization and a valuable reference for a solar air-source heat pump water heater when the solar irradiation energy is insufficient on cloudy or rainy days.     

Performance analysis of an air-source heat pump using an immersed water condenser

A distributed model of an air-source heat pump (ASHP) system and its experimental setup using an immersed water condenser were presented. Dynamic performance of the ASHP was then evaluated by both simulation and experiment. The results indicated that the system coefficient of performance (COP) decreased as the condenser temperature increased, ranging from 4.41 to 2.32 with the average COP equaling 3.29 during the experiment. Comparisons between simulation results and experimental measurements demonstrated that the model was able to yield satisfactory predictions. Furthermore, temperature profiles of the refrigerant in the evaporator and condenser were also given. This paper provides the theoretical and experimental background for ASHP system optimization and a valuable reference for a solar air-source heat pump water heater when the solar irradiation energy is insufficient on cloudy or rainy days.     

非共沸工质双压冷凝热泵热水器性能研究

提出一种双压冷凝梯级加热热泵热水器（DPS）系统新构型,采用碳氢非共沸工质作为制冷剂,可实现热水的连续梯级低损加热,采用黄金分割法对系统热力性能进行优化。结果表明,非共沸工质的DPS系统的热力学性能优于纯质的DPS系统和单级热泵系统,双压冷凝系统在最优中间水温时取得最大COP。名义工况下,采用R600/R601a(40/60)的DPS系统COP高达5.17,相对采用纯质的DPS系统和单级系统分别提高9.45%和14.25%。采用温度滑移合理的非共沸工质可显著减少损,改善冷凝器的热匹配特性,系统效率最高提升11.70%,名义工况下推荐R600/R601a(40/60)作为工质对。     

Experimental investigation of a vapor compression heat pump used for cooling and heating applications

The present work aims at evaluating the performance characteristics of a vapor compression heat pump (VCHP) for simultaneous space cooling (summer air conditioning) and hot water supply. In order to achieve this objective, a test facility was developed and experiments were performed over a wide range of evaporator water inlet temperature (14:26 °C) and condenser water inlet temperature (22:34 °C). R134a was used as a primary working fluid whereas water was adopted as a secondary heat transfer fluid at both heat source (evaporator) and heat sink (condenser) of the heat pump. Performance characteristics of the considered heat pump were characterized by outlet water temperatures, water side capacities and coefficient of performance (COP) for various operating modes namely: cooling, heating and simultaneous cooling and heating. Results showed that COP increases with the evaporator water inlet temperature while decreases as the condenser water inlet temperature increases. However, the evaporator water inlet temperature has more effect on the performance characteristics of the heat pump than that of condenser water inlet temperature. Actual COP of cooling mode between 1.9 to 3.1 and that of heating mode from 2.9 to 3.3 were obtained. Actual simultaneous COP between 3.7 and 4.9 was achieved.     

Effect of load pattern on solar-boosted heat pump water heater performance

The performance of a solar-boosted heat pump water heater (HPWH) operating under full load and part load conditions was determined in an outdoor experimental study. The system utilised flat unglazed aluminium solar evaporator panels to absorb solar and ambient energy. Absorbed energy was transferred to the water tank by means of the heat pump and a wrap around condenser coil on the outside of the tank. The system COP was found to be in the range of 5–7 under clear daytime conditions and 3–5 under clear night-time conditions. Using part load testing of the HPWH system it was found that concentrating the coils in the lower portion of the tank could increase the efficiency of the condenser coil. It was also shown that there exists a generalised linear relationship that can be used to describe the system COP in terms of the temperature difference between the water in the storage tank and the ambient air.     

System optimization and experimental research on air source heat pump water heater

This paper deals with the system optimization of air source heat pump water heater (ASHPWH), including calculating and testing. The ASHPWH system consists of a heat pump, a water tank and connecting pipes. Air energy is absorbed at the evaporator and pumped to storage tank via a Rankine cycle. The coil pipe/condenser releases condensing heat of the refrigerant to the water side. An ASHPWH using a rotary compressor heated the water from initial temperature to the set temperature (55 °C). The capillary tube length, the filling quantity of refrigerant, the condenser coil tube length and system matching are discussed accordingly. From the testing results, it could be seen that the system performance COP could be improved obviously.     

空气源热泵热水器与电热水器耦合选型研究

阐述了空气源热泵热水器选型的影响因素,对冷热水温度、干球温度、相对湿度和设备COP、结霜等影响因素进行了说明,给出了空气源热泵热水器和电热水器耦合使用时的选型方法,并利用贴现指标法对二者按不同配置时的经济效益进行比较分析,从而获取最优配比。     

提高热电厂效率的几项措施

从热经济性角度提出提高热电厂效率的几项技术和措施:通过凝汽器补充软化水,将外供蒸汽过热度降低;使用喷射式混合加热器回收热力除氧器排汽,作为生水加热器;利用压力匹配器代替减压减温器;用两相流加热器代替面式高压加热器等。