低压补气型空气源热泵（冷水）机组制热性能试验研究

为了研究低压补气型空气源热泵(冷水)机组的制热性能,搭建以R410A为制冷剂的空气源热泵(冷水)机组试验台。试验结果表明:相对于不补气模式,在低压补气模式下,当室外温度在7～-15℃范围时,机组制热量提升12.6%～33.0%,COP提升3.4%～15.1%,并且能够有效降低排气温度。     

Effects of vapor injection techniques on the heating performance of a CO2 heat pump at low ambient temperatures

The objective of this study is to investigate the effects of vapor injection techniques on the heating performance of a CO₂ heat pump. The performances of the flash tank vapor injection (FTVI), sub-cooler vapor injection (SCVI) and FTVI with a suction line heat exchanger (FTSX) cycles were measured and analyzed with variations of the outdoor temperature, compressor frequency, and injection mass flow rate. At the outdoor temperature of −15 °C and compressor frequency of 55 Hz, the heating capacity and COP of the optimized SCVI cycle were 12.1% and 12.7% higher than those of the optimized FTVI cycle, respectively, because the total mass flow rate in the SCVI cycle was higher than that in the FTVI cycle by the large temperature and pressure differences in the sub-cooler of the SCVI cycle. In addition, the optimum injection flow rate ratios in the vapor injection CO₂ cycles yielding the maximum COP were determined at various compressor frequencies.     

Experimental study on the performance of an inverter heat pump with a bypass orifice

An economical, fixed geometry, bypass orifice was invented to control more precisely the refrigerant flow in an inverter heat pump system. Flow characteristics of the bypass orifice were investigated as a function of orifice geometry and operating conditions. Experimental results of bypass orifices were compared with those of capillary tubes. The bypass orifice showed the best flow trend as a function of frequency: the flow slope of the bypass orifice with respect to frequency was the highest among the orifice, capillary, and bypass orifice. The performance of an inverter heat pump with a bypass orifice and then a capillary tube was measured with a variation of frequency in the psychrometric calorimeter. It was observed that the performance of the inverter heat pump was enhanced with the application of the bypass orifice in the system instead of a capillary tube. The improvement of COP in an inverter heat pump with a bypass orifice versus the capillary tube was prevalent at the low frequency region.     

On-field measurement method of vapor injection heat pump system

This paper examines air-to-air injection heat pumps (HPs) and proposes a method to determine both heating capacity and coefficient of performance (COP) in situ, allowing analyses of already-installed setups and long-term observation. Due to the uncertain nature of air enthalpy measurements, this method instead uses refrigerant enthalpies calculated from pipe contact temperatures and steady-state energy balances to determine the COP. However, these energy balances are highly dependent on the hypothesis that the working fluid remains strictly monophasic in certain locations, which is not always true in practice. A parametric variable analysis is conducted on the refrigerant vapor quality to calculate the deviation in the COP due to diphasic conditions at the compressor inlet, injection port, and condenser and flash tank outlets. A final in situ COP uncertainty is presented, due to both the measurement and vapor quality uncertainties.     

低温热泵用涡旋压缩机性能的试验研究

制定低温热泵用涡旋压缩机试验方案,对研制的原型机进行性能测试。试验结果表明：在冷凝温度不变的情况下,随着蒸发温度的降低,原型机的制热量有所减少,但减少的速度低于普通热泵系统用涡旋压缩机;压缩机的电功率有所增加,但增加的幅度不大,且压缩机的排气温度也有所降低,故在低温工况下采用准二级压缩热泵用涡旋压缩机比采用普通热泵用涡旋压缩机可以更有效地提高空气源热泵的低温制热性能,是寒冷地区用小型空气源热泵比较适宜采用的压缩机。     

空气源热泵型冷热水机组防冻性能试验研究

针对空气源热泵型冷热水机组（以下称机组）运行中经常出现的蒸发器（板换）冻裂问题，分析导致蒸发器冻裂的主要因素，提出采用单风机运行模式来防止机组运行中可能出现的蒸发器冻裂。通过不同机型的试验分析了低环境温度下的低回水温度和低流量状态下单风机运行时，蒸发器（套管换热器）人口处温度以及压缩机吸气压力的变化。试验结果表明，采用单风机模式防止套管换热器的冻裂是可靠的。     

Performance evaluation of a vapor injection heat pump system for electric vehicles

Battery-powered electric vehicles (EV) need an efficient electric heating system for extending the driving mileage. An air-source heat pump system offers an economical alternative for EV because it consumes less energy than a heating system using Joule heat and it can use the same components as an air conditioning system for cooling. However, its performance degradation is inevitable at very low ambient temperatures. Although vapor refrigerant injection is known as a good technology to overcome this problem in residential heat pump systems, the number of vapor injection heat pump studies for EV applications is quite limited. In this paper, considering the characteristics of EV application, the configuration of a vapor injection heat pump system for EV is introduced, and it was modeled, using a scroll compressor geometry-based thermodynamic analysis. The performance was estimated for cold ambient regions under the EV operational conditions.     

喷液旁通对空气源热泵性能影响的试验研究

分析一种喷液旁通对空气源热泵性能的影响,并进行额定制冷和制热验证试验。结果表明：当旁通率较小时,制冷能力和能效比对旁通率的变化不敏感;旁通率微调到一定区间时,制冷能力和能效比出现一定程度的提升,压缩机排气温度明显下降;当旁通率较大时,制冷能力和能效比显著下降。在额定制热条件下,旁通率微调到一定区间时,制热能力和性能系数出现一定程度的提升。     

Experimental investigation on vapor injection heat pump with a newly designed twin rotary variable speed compressor for cold regions

A newly designed twin rotary variable speed compressor was adopted to improve the heating performance of a vapor injection heat pump air conditioner (HPAC) at cold regions in this study. The performances of a R410A HPAC were measured and investigated. The results showed that an optimum intermediate pressure existed to achieve the maximum heating capacity and system $\text{COP}$ for the injection cycle, and the heating capacity was enhanced effectively by increasing compressor frequency, however, at the cost of $\text{COP}$ decrease. Comparative research on system performances between injection and non-injection cycles indicated that the newly designed compressor could improve the heating performance of the HPAC at low ambient temperatures. Specifically, the system's heating capacity was enhanced by 5.6%-14.4%, and $\text{COP}$ improvement reached up to 3.5%. Vapor injection cycle was not suggested at high ambient temperatures due to its lower $\text{COP}$ compared with non-injection cycles.     

Modelling the performance of a transcritical CO2 heat pump for high temperature heating

A prototype transcritical CO₂ heat pump was constructed for heating water to temperatures greater than 65°C while providing refrigeration at less than 2°C. The heating capacity was 115 kW at an evaporation temperature of +0.3°C and a hot water temperature of 77.5°C, with a heating coefficient of performance (COP) of 3.4. Performance data is presented for each of the compressor, the gas cooler, and the recuperator as well as for the overall heat pump system. Equipment performance data was incorporated into a computer model to enable parametric investigations of heat pump performance. Model predictions showed that the hot water temperature could be increased from 65 to 120°C with a relatively small reduction in heating capacity and heating COP of 33 and 21%, respectively. Model predictions also highlight the potential for significant capacity improvements by eliminating the recuperator in favour of a larger gas cooler.     

Experimental investigation of the surface temperature and water retention effects on the frosting performance of a compact microchannel heat exchanger for heat pump systems

Frost formation on a louvered fin microchannel heat exchanger was experimentally investigated in this paper with the aim of determining the dominant factors affecting the time of frosting and frost growth rate. A novel methodology was developed to measure frost thickness and frost weight at intervals during the frosting period. Frost mass and thickness growth rates, corresponding coil heat transfer, capacity degradations and air pressure drop are measured and discussed. The experimental data showed that at a given air dry bulb temperature, the fin surface temperature and air humidity are the primary parameters that influence the frost growth rates. Water retention and air velocity had a secondary impact on the frosting performance. From digital images of the frost growth it was observed that frost does not nucleate from the water droplets retained in between fins but it developed from the leading edges of the fins.     

多联机空气源热泵相变蓄能除霜特性试验研究

为了解决多联机空气源热泵常规除霜时间长、室内环境恶化等问题,提出多联机热泵相变蓄能除霜方法。针对提出的新方法,设计系统流程和试验方案,并在模拟室内外环境条件下完成试验研究。相对于常规除霜,新的除霜方法可以有效缩短33.7%的除霜时间,显著改善机组的除霜性能和室内供热环境。     

空气源热泵热水机高温工况运行研究与实验

介绍空气源热泵热水机高温工况运行时的两种常规控制方法，分析各自的优缺点，对两种控制方法提出使用建议。最后简要介绍一种适用于单风机机组和小型机组高温控制的根据压力调节蒸发面积的方法。     

Experimental transient performance of a heat pump equipped with a distillation column

A series of experiments were conducted on a heat pump equipped with a distillation column. The system was operated with R32 and with a 30/70% by mass mixture of R32/134a to examine the difference between the transient performance trends with a pure fluid (R32), and those with a zeotropic mixture (R32/134a). Additionally, the effects of varying heat transfer fluid mass flow, compressor speed, and accumulator sump heat input were examined. Each test was 1 h in duration. The heat pump capacities did not generally achieve steady state during the R32/134a tests. Steady state was generally achieved during the R32 tests. As a percentage of the final (end-of-test) capacity, the rate of capacity increase was greater during the R32/134a tests than during those conducted with the pure fluid. The R32/134a tests exhibited capacity oscillations early in each transient that were not present during the R32 tests. The results show that circulating refrigerant mass and composition are the primary controlling factors with regard to transient capacity.     

Research on air-source heat pump coupled with economized vapor injection scroll compressor and ejector

The performance of the heat pump can be improved further when running under low temperature conditions when an ejector is used in a heat pump system coupled with economized vapor injection (EVI) scroll compressor. In this paper, the design method of the heat pump system with ejector (EVIe) is presented, and the process for designing the heat pump with ejector has been summarized. The optimal location of the vapor injection inlets is at the place where the vapor can inject into the working chambers when they just be closed. The reasonable value for the entrainment ratio u of the ejector is between 0.1 and 0.2. One prototype heat pump was designed under the condition of the evaporation temperature of −20 °C, and an experimental setup was established to test the prototype. The measured results demonstrated that the heating EER of the heat pump system with ejector could reach about 4% higher than that of the system without ejector when the heating capacity remained nearly constant.     

采用喷水螺杆式水蒸气压缩机的高温热泵设计及性能分析

针对高温热泵的工业需求,设计并分析以水为介质的闭式高温热泵系统,系统引入喷水螺杆式水蒸气压缩机,利用喷水实现压缩机排气为饱和状态,满足工业应用高温升(高压比)的技术要求的同时,克服高排气温度会导致的机械及安全问题。计算结果表明:系统在蒸发温度为90℃,冷凝温度为100℃时,COP高达31.48,压缩机喷水注入比为0.019;蒸发温度为75℃,冷凝温度为100℃工况下,系统COP为5.99,对应的压缩机压比为7,注入比为0.103;压缩机比功率随压缩机压比升高而增加,增加幅度随蒸发温度的升高而增大;系统COP随注入水温度的升高而降低,但变化趋势并不大。     

Theoretical study of a thermoelectric-assisted vapor compression cycle for air-source heat pump applications

This paper proposes a thermoelectric-assisted vapor compression cycle (TVCC) for applications in air-source heat pump systems which could enhance the heating capacity of the system. Performances of TVCC are calculated and then compared with that of basic vapor compression cycle (BVCC). The simulation results show that when coefficients of performance (COPs) of the two cycles are almost equal, the TVCC under maximum COP condition of the thermoelectric modules still performs better than BVCC by 13.0% in heating capacity through selecting the appropriate intermediate temperature. In addition, the TVCC can also achieve an improvement of 16.4%–21.7% in both the heating COP and capacity when compared with the BVCC with an assistant electric heater that is provided with the equivalent power input of thermoelectric heat exchanger. Thus, the TVCC could be beneficial to the applications in small heat pumps if there is always need for auxiliary electric heat.     

Dynamic modeling and characteristic analysis of a two-stage vapor injection heat pump system under frosting conditions

This paper presents a distributed-parameter dynamic heat exchanger model integrated with a detailed frost growth model to account for non-uniform frost formation on a fan-supplied finned-tube coil. A novel, iteration-free approach is proposed to solve the air flow redistribution by linearizing a system of non-linear air pressure drop equalization equations, resulting in a significant improvement in the computational efficiency. As a continuation and extension of our previous work, the developed models along with the component models described in Qiao et al. (2015a) are applied for the first time to explore the frosting dynamics of a two-stage flash tank vapor injection heat pump system. It is found that frost formation degrades the heating performance of the system substantially. Meanwhile, the simulation indicates that air and refrigerant flow maldistribution, resulting from non-uniform frost growth on the outdoor heat exchanger, can lead to unstable system hunting behavior. Comparisons between the simulation results and experimental data indicate that the proposed models can reasonably predict the time-dependent heat transfer and fluid flow phenomena of the system.     

热泵型空调器运行特性的实验研究

用空气焓差实验法,在制冷工况下对一台热泵型空调器进行最佳充注量的实验研究,同时,分别在制冷工况和制热工况下测量冷凝器和蒸发器管壁的温度分布。实验结果表明,空调系统中存在一个最佳制冷剂充注量,使得空调系统的制冷量和能效比达到最大值。根据实验结果,分别给出在制冷工况和制热工况下进行冷凝器和蒸发器换热计算时,制冷剂与管壁之间的平均温差。     

一种热泵循环工质的试验研究

对新型混合工质ZCI-10与HcFc22和R417A在不同蒸发温度下的制热性能进行试验研究,并对其物理和化学性能进行分析。结果表明,ZCI-10能够用于原使用HCFC-22的系统,并且环境性能、制热量和能效比均优于R417A,是较理想的HCFC-22替代工质。