电子膨胀阀开度对R32水源热泵系统性能的影响

以R32为制冷剂的变制冷剂流量(VRF,Variable Refrigerant Flow)转子式水源热泵系统为研究对象,通过改变电子膨胀阀开度(从6%到60%),对在不同压缩机频率(从40Hz到60Hz)下热泵系统性能的变化进行了实验分析。结果表明:在压缩机吸气口由过热状态向带液状态转变的过程中,电子膨胀阀开度的调节范围呈先减小后增大的变化趋势;随着电子膨胀阀开度的增加,系统的压比持续下降;在压缩机少量吸气带液(0. 98相似文献   

电子膨胀阀调节对空气源热泵热水器性能的影响

节流装置的调节对空气源热泵热水系统的性能有着重要影响,电子膨胀阀因其调节范围广而逐渐得到应用,因此需要对其深入研究。以空气源热泵热水器实验系统为研究对象,通过改变电子膨胀阀开度,研究不同调节方式对系统性能的影响。结果表明:1)相同膨胀阀开度下,系统制热量和系统COP随加热的进行均呈先上升后下降的趋势;不同膨胀阀开度下,在加热前期(20~30℃),膨胀阀开度越大,系统COP越大;在加热后期(45~55℃)结果相反;2)在加热过程中,各膨胀阀开度下系统COP趋势线相互交叉,由于压缩机少量吸气带液可以改善系统性能,因此交叉点与各阀开度下过热度达到0 K的点相近但并不重合;3)以水箱平均温度为控制对象调节电子膨胀阀的方法(优化1#)对系统COP的最大优化率为24.8%;以压缩机吸气过热度为控制对象调节电子膨胀阀的方法(优化2#)与优化1#系统COP相比,最大相差4.2%,且经过实验验证具有适用性。     

电子膨胀阀开度对SAHP系统稳定性的影响

压缩机频率不变,不同的电子膨胀阀开度下,对太阳能热泵系统的动态性能进行了实验和分析。根据实验结果分析发现,在电子膨胀阀开度一定时,随着太阳辐照度的升高,压缩机功率出现振动,当电子膨胀阀开度最大时,系统振动更加明显。由此提出了太阳能热泵系统稳定性原理。同时指出优化太阳能热泵系统的关键问题是找到系统集热／蒸发器的MSS线（Q—Tsh关系曲线）。     

基于变频压缩机的跨临界CO_2热泵热水器名义工况的试验研究

搭建基于变频压缩机的跨临界CO_2热泵热水器试验台。在系统制冷剂充注量为950 g,测试工况为名义工况的前提下,分析电子膨胀阀开度和压缩机运行频率对系统参数,包括压缩机吸气温度和压力,排气温度和压力,系统制热量和制热性能系数COP_h的影响。试验结果表明:随着电子膨胀阀开度的增大,压缩机吸气温度降低,吸气压力升高,而排气温度和排气压力趋势性走低,中间偶有起伏;制热量随着电子膨胀阀开度的增大逐渐降低,制热性能系数COP_h在电子膨胀阀一定开度范围内存在一个最优值;压缩机吸气温度受频率的影响较小,吸气压力则随着频率的增加而降低,排气温度和排气压力均随频率的增加而升高;制热量随着频率的升高而增大,制热系数COP_h最大值出现在低频率范围。     

补气对热泵低温工况性能影响的试验研究

经济器热泵主回路与补气回路均采用开度可调的电子膨胀阀,分别在环境温度-15℃、-10℃、7/6℃下,试验研究不同主回路电子膨胀阀EEV_1和补气回路电子膨胀阀EEV_2开度组合时的系统性能,得到了经济器热泵低温工况下运行时的控制策略:在吸气压力不至过低,排气温度不超过保护温度的前提下尽可能的降低主回路电子膨胀阀开度,同时控制补气回路电子膨胀阀开度使得补气过热度尽可能较小。相比不补气而言,在试验工况下,补气时的制热量和COP最高可分别提升28.7%和11.1%。     

不同类型膨胀阀对热泵热水器性能影响的研究

目前热泵热水器大多采用热力膨胀阀作为系统的节流元件,但是其仅能控制过热度,而无法根据其他热力参数对系统进行更加优化的控制.首先建立了热泵热水器稳态数学模型,搭建了实验装置,并将模拟结果与实验进行了对比,验证了模型的精确性.然后,对系统中采用热力膨胀阀和电子膨胀阀等两种情况进行了模拟分析,结果显示,采用电子膨胀阀后可有效...     

充注量对空气源热泵热水器性能的影响

本文通过实验比较了热泵热水器在不同制冷剂充注量下的制热性能和电子膨胀阀的调节特性,定量研究了电子膨胀阀调节方式对制热性能的影响。结果表明:阀开度16%和定过热度10℃工况下的最佳充注量均为1.1 kg,相应的最佳整体制热性能COP_a分别为3.05和3.68;过大的充注量降低了制热性能和电子膨胀阀的调节范围;与阀开度调节相比,过热度调节可避免吸气带液的发生;在最佳充注量下,对比阀开度和过热度两种电子膨胀阀调节方式得出,后者制热性能更优。     

R32空气源热泵热水器的实验研究

为了解 R32 和 R410A 制冷剂应用于空气源热泵热水器时的性能优劣,采用同轴套管换热器与空调室外机组相匹配,使用电子膨胀阀作为节流装置,在国标GB/T 23137-2008 规定下实验测试 R32 和R410A 在同一套空气源一次加热式热泵热水器样机上的性能.实验结果表明,R32 的充注量仅为 R410A 充注量的74%左右;在各种实验条件下,R32 空气源热泵热水器的能效比不低于 R410A 系统;在3℃低温环境下,R32 样机的性能系数提高31.1%,但排气温度达到101.9℃.不利于 R32 制冷剂在低温条件下的应用;因容积制热量较大,在相同设计能力下 R32 压缩机的排气量可以比 R410A 系统降低4.5%.     

小型风冷热泵节流装置的替代实验研究

本文以R22为工质，通过对风冷热泵冷热水机组节流装置替代后在不同的试验工况下进行实验测试，比较了系统使用热力膨胀阀和电子膨胀阀下制冷量和能效比，得出了使用电子膨胀阀可以提高系统性能的结论。     

3种跨临界二氧化碳热泵热水器系统的实验研究

研制了跨临界二氧化碳热泵热水器实验台,在一定蒸发温度下,分别对常规系统、带回热器系统及带喷射器和回热器系统这3种跨临界二氧化碳热泵热水器系统在制取不同温度热水时的性能进行了实验研究,分析了制热系数、制热量、压缩机耗功量、压缩机压比等参数随热水出水温度的变化趋势,并分析了回热器、喷射器的工作性能,实验结果表明:和常规系统相比,引入回热器后系统制热系数可以提高约10％,引入喷射器和回热器后系统制热系数可以提高约20％.     

Investigation of the heat pump water heater using economizer vapor injection system and mixture of R22/R600a

This paper presents the experimental study of a heat pump water heater (HPWH) using economizer vapor injection system and mixture of R22/R600a. Performances of HPWH using economizer vapor injection system are compared with that at different mixed mass ratios of R22/R600a. Study demonstrates that the heating capacity and energy efficiency ratio (EER) of the unit increased, and the discharge temperature of compressor decreased when using vapor injection and mixing refrigerant of R22/R600a. It is also found that the HPWH unit with economizer vapor injection system has a better performance for the high outlet water temperature under lower temperature conditions at 15% mass ratio of R600a for the mixing refrigerant. In addition, fundamental and practical influence of vapor injection pressure on the HPWH performance has been investigated experimentally. The simplified model is proposed for predicting the optimal vapor injection pressure of compressor using the mixing refrigerant R22/R600a.     

Preliminary theoretical analyses of thermal performance and available energy consumption of two-stage cascade cycle heat pump water heater

In this paper, the analysis model of thermal performance and available energy of two-stage cascade cycle heat pump water heater (HPWH) was established. For the first time, the equivalent transformation thermodynamic analysis method and available energy consumption equation were employed to carry out the theoretical analyses of thermal performance and available energy consumption for two-stage cascade cycle HPWH. And the correctness of the analysis approach proposed in this paper was verified by an example. The calculation results showed a significant agreement with the results derived by the first law of thermodynamics and energy conservation law. The available energy analysis of two-stage cascade cycle HPWH clearly revealed the available energy consumption rates for different working processes, including heat transfers of heat exchangers, flow of heat-carrying fluid, working medium cycle, output of hot water, etc. This approach could be conveniently used in the analyses of thermal performance and available energy consumption for actual complex thermal system with irreversible process. This paper provided the theoretical basis for the actual optimization design and operation analysis of cascade type heat pump systems, and furthermore, the results of the calculation instance would also have a certain reference value.     

Performance characteristics of a simultaneous cooling and heating multi-heat pump at partial load conditions

A simultaneous cooling and heating multi-heat pump can improve thermal comfort and energy efficiency through heat recovery at partial load conditions. The performance of a simultaneous heating and cooling multi-heat pump with four indoor units was measured by varying the compressor speed, EEV opening, and fan speed at full and partial load conditions in five operating modes. In the cooling-only and heating-only modes, the heating and cooling capacities were properly controlled by varying the compressor speed. However, in the cooling-main and heating-main modes under partial load conditions, a large imbalance between the cooling and heating capacities was observed even though the compressor speed was optimized. This capacity imbalance under partial load conditions was optimized by adjusting the EEV openings in the mode change unit and the outdoor unit. In addition, in the entire-heat recovery mode, rating compressor speed ratios were proposed under the full and partial load conditions.     

Refrigerant charge optimisation for propane heat pump water heaters

Hydrocarbons can be interesting refrigerants in domestic facilities such as heat pumps for domestic hot water production called heat pump water heaters (HPWH). However, due to flammability and submission to severe regulations, the use of hydrocarbons requires improvements in design and optimisation of components to reduce the refrigerant charge. This paper first reviews the regulations applied to hydrocarbon technologies then discusses possibilities of charge reduction for a R290 HPWH. Mainly by selecting condensers with high thermal efficiency and low internal volume, the charge may be reduced to extremely low levels. Using the same base of refrigerating system, three types of condensers were tested: tank-wrapped D-tube, roll-bond and microchannel heat exchangers. The D-tube has a low compactness. Microchannels are penalised by the diameter of their distributors. The best performance is obtained by the roll-bond HPWH with a charge of 224 g: COP of 3.17 and heating time under 7 h.     

Effects of flash gas generation at the expansion device inlet on the dynamic characteristics of a refrigeration system

The flash gas generation at the expansion device inlet in multi-air-conditioners causes rapid reduction of refrigerant mass flow rate and irregular distribution of refrigerant into multi-indoor units. The objective of this study is to evaluate the influence of the flash gas generation on the dynamic characteristics of a refrigeration system. The dynamic characteristics of a refrigeration system with an electronic expansion valve (EEV) were measured with time at various levels of flash gas generation, which were expressed as flash gas ratio. In addition, the averaged operating parameters and system COP were investigated with the variation of flash gas ratio. As the EEV inlet condition changed from the subcooled to the two-phase state, the refrigerant flow rate decreased rapidly due to the flash gas generation at the EEV inlet. At two-phase inlet conditions, the system operating parameters, such as mass flow rate, suction and discharge pressures, fluctuated periodically with time. As the flash gas ratio increased, the average COP decreased and the discharge temperature increased, degrading the system performance and reliability more severely.     

A novel defrosting control method based on the degree of refrigerant superheat for air source heat pumps

When an air source heat pump (ASHP) unit operates for space heating at a frosting environment, periodic defrosting is necessary to maintain a high system performance. To defrost efficiently, it is necessary to find an effective defrosting control method. In this paper, an experiment was carried out on an ASHP unit with a capillary tube as a throttle device, under simulated frosting and defrosting conditions using time control defrosting method, and the experimental results are firstly presented. Secondly, a novel defrosting control method based on the degree of refrigerant superheat (DS) is reported. To validate the novel defrosting control method, a further experiment was conducted on another ASHP unit with an electronic expansion valve (EEV) as a throttle device, under simulated frosting and defrosting conditions. The experimental results demonstrated that when applying the novel defrosting control method, defrosting was initiated before the operating performances of ASHP unit rapidly deteriorated, which was more reasonable.     

空气源热泵热水器全年综合性能系数评估

介绍空气源热泵热水器全年综合性能系数APF的基本评价准则,通过对环境温度进行分区,建立计算全年综合性能系数APF的基本公式。以热泵实测数据为基础,研究BIN分区数量、特征温度、待机功率、水箱容积、热泵加热功率、热泵工作温度下限等因素对APF的影响,建议进行APF计算时BIN分区数为5。     

Experimental study on the performance of a vapor injection high temperature heat pump

In this study, a vapor injection technique was applied in a high temperature heat pump (HTHP) for providing hot water at temperatures up to 88 °C. A prototype HTHP system with economizer vapor injection was developed and its performance was experimentally investigated under various operating conditions. Results showed that the vapor injection pressure had a large effect on heating capacity and on refrigerant temperature at the inlet of the electronic expansion valve (EEV). As the injection pressure increased from 0.82 to 0.98 MPa, the vapor injection flow ratio increased from 7.3% to 22.61% and the heating capacity increased by 7%. The system COP did not show significant change although the COP trend showed an optimal value for the injection pressure. The refrigerant temperature at the EEV inlet showed a subcooling of more than 16 °C under all studied conditions, which improved the EEV operating reliability.     

CO_2热泵热电池储能性能实验研究

CO_2热泵热电池系统由跨临界二氧化碳水源热泵与蓄冷蓄热装置组成,其在储能过程中系统的效率会逐渐降低。本文实验研究了CO_2热泵热电池的储能性能,分析了储冷罐、储热罐循环水体积流量、压缩机频率和电子膨胀阀开度对储能效率的影响。结果表明:低循环水流量既可使储能罐获得良好的温度分层,又能获得较大的换热量;压缩机频率越高,系统效率越大;同时电子膨胀阀开度也影响系统的储能效率。当压缩机频率为50 Hz,电子膨胀阀开度为330脉冲,储冷罐、储热罐循环水体积流量分别为0.2 m~3/h、0.1 m~3/h时,总体COP最大,为5.49。同时数学拟合了系统COP与储冷罐、储热罐出水温度、控制参数的关联式,提出了一种基于遗传算法的优化控制策略,系统总COP可达6.29。     

Experimental study on the performance of a simultaneous heating and cooling multi-heat pump with the variation of operation mode

The cooling load in the winter season becomes significant in commercial buildings and hotels because of the wide usage of office equipment and improved wall insulation. In this study, a simultaneous heating and cooling multi-heat pump having four indoor units and an outdoor unit was designed and tested in five operation modes: cooling-only, heating-only, cooling-main, heating-main, and entire heat recovery. The performance of the system with R410a was optimized by adjusting the system's control parameters. In the cooling-main mode, the rate of the bypass flow to the heating-operated indoor unit was optimized by controlling the EEV opening of the outdoor unit. In the heating-main mode, the mass flow rate to the cooling-operated indoor unit was optimized by adjusting the EEV opening in the outdoor unit. In the entire heat recovery mode, the compressor speed was controlled to improve the system COP with appropriate heating and cooling capacities.