Experimental investigation of startup characteristics of R290 rotary compressor under low ambient temperature heating condition

The cold and warm startup characteristics of an R290 heat pump system and its rotary compressor were experimentally investigated under a low ambient temperature heating condition. These startup characteristics included the temperatures in the compressor shell and system and the pressures in the cylinder and system. The results showed that the minimum suction gauge pressure (−48 kPa) during a cold startup was lower than that during a warm startup (155 kPa) under a low ambient temperature heating condition. In addition, the time required for the R290 heat pump system to reach a steady pressure was much longer than that of a system using R410A as the refrigerant. Compared with that of the cooling condition, smaller amounts of liquid were generated in the cylinder at the beginnings of both the cold and warm startup processes under the low ambient temperature heating condition.     

Pressure-viscosity coefficient of a refrigerant-oil mixture: Coefficient pression-viscositéd'un mélange frigorigène-huile

A coaxial cylinder viscosimeter has been used to determine the pressure-viscosity coefficient of a pure refrigeration oil and of a mixture of refrigerant and oil at gauge pressures up to 15 MPa. The test fluid, Gargoyle Arctic oil 300, is a naphthenic-base oil. The refrigerant was R22, chlorodifluoromethane, which is a commercially important refrigerant. In a gap apparatus the refrigerant-oil mixture has been visually inspected at different pressures. Two different mechanisms are involved in the refrigerant-oil mixture: the change in solubility with pressure and the change in viscosity with refrigerant concentration. If the mixture is pressurized with excess refrigerant available then the concentration of refrigerant will increase with increasing pressure and therefore the viscosity will decrease. If the concentration is kept at a constant level then the viscosity will increase with pressure. The results from the cylinder viscosimeter showed that the viscosity increase with pressure for the mixture was almost the same as for the pure oil.     

R1270在制冷系统中的应用研究

随着全球环境问题的加剧以及R22制冷剂淘汰进程的加快,世界各国对碳氢化合物制冷剂,尤其是R1270和R290非常关注。碳氢化合物已经在冰箱、空调系统和小型热泵空调中得到初步应用,在应用过程中需要注意的问题为安全性和性能水平。本文主要介绍R1270的在制冷系统中的应用研究现状,并将R1270和R290制冷剂进行对比,分析R1270今后的一些研究方向,建议下一步应对R1270进行更多更全面的试验性研究,并对R1270压缩机、换热器及节流机构进行研究,针对其可燃性问题,今后应对如何减少R1270制冷剂充注量,防止其泄漏以及R1270与阻燃剂的混合物的安全性能进行深入研究。     

Experiment and simulation on the performance of an autocascade refrigeration system using carbon dioxide as a refrigerant

The main purpose of this study is to investigate the performance of an autocascade refrigeration system using zeotropic refrigerant mixtures of R744/134a and R744/290. One of the advantages of this system is the possibility of keeping the highest pressure of the system within a limit by selecting the composition of a refrigerant mixture as compared to that in the vapor compression system using pure carbon dioxide. Performance test and simulation have been carried out for an autocascade refrigeration system by varying secondary fluid temperatures at evaporator and condenser inlets. Variations of mass flow rate of refrigerant, compressor power, refrigeration capacity, and coefficient of performance (COP) with respect to the mass fraction of R744 in R744/134a and R744/290 mixtures are presented at different operating conditions. Experimental results show similar trends with those from the simulation. As the composition of R744 in the refrigerant mixture increases, cooling capacity is enhanced, but COP tends to decrease while the system pressure rises.

Résumé

The main purpose of this study is to investigate the performance of an autocascade refrigeration system using zeotropic refrigerant mixtures of R744/134a and R744/290. One of the advantages of this system is the possibility in keeping the highest pressure of the system within a limit by selecting the composition of a refrigerant mixture as compared to that in the vapor compression system using pure carbon dioxide. Performance test and simulation have been carried out for an autocascade refrigeration system by varying secondary fluid temperatures at evaporator and condenser inlets. Variations of mass flow rate of refrigerant, compressor power, refrigeration capacity, and coefficient of performance (COP) with respect to the mass fraction of R744 in R744/134a and R744/290 mixtures are presented at different operating conditions. Experimental results show similar trends with those from the simulation. As the composition of R744 in the refrigerant mixture increases, cooling capacity is enhanced, but COP tends to decrease while the system pressure rises.     

多制冷剂、宽电压范围工业空调用转子式压缩机设计

针对客户希望同一款工业空调能够实现不同制冷量的要求,提出一种多制冷剂、宽电压范围转子式压缩机,并通过理论分析和试验研究多制冷剂、宽电压范围定速压缩机的设计要点,开发一款电源为三相380~415 V 50 Hz/380~460 V 60 Hz,制冷量在3.9~9.5 kW范围内可兼容R410A/R407C/R134a这3种制冷剂的转子式压缩机,并已实现批量生产。     

Topology optimization of a single-phase induction motor for rotary compressor

The oil circulation rate of the rotary compressor is a crucial factor affecting the performance and reliability of air-conditioning systems-too much oil in the refrigerant-oil mixture causes poor heat transfer and early failure of parts; too little oil means excessive friction and wear of the journal bearing. In this paper, we show how finite-element analysis and topology optimization of a single-phase induction motor of a rotary compressor can be used to reduce the oil circulation rate to the minimum safe level. We analyze the nonlinear transient characteristics of the single-phase induction motor for the rotary compressor by using the program FLUX2D. We optimize the topology of the electromagnetic systems by using finite-element analysis. For validation, we have manufactured and tested optimized induction motors.     

R290/CO2复叠式制冷系统的性能实验

通过对R290／C02复叠式制冷系统的性能实验，对低温循环用CO2作为制冷工质，高温循环分别用R22和R290为制冷工质的性能进行比较，结果表明，随着蒸发温度的升高，冷凝温度的降低，R290／CO2复叠式制冷系统的最佳质量流量比增大，COP增加。随着高温循环压缩机入口温度的升高，R290压缩机的功耗略高于R22压缩机的功耗，R290循环的COPh要高于R22循环的COPh。结果表明自然工质R290／CO2复叠式制冷系统具有很好的发展前景。     

Diesel combustion of oil and refrigerant mixture during pump-down of air conditioners

Compressor-destruction accidents during the pump-down operation of air conditioners were experimentally investigated. Assuming air penetration into refrigerant tubes, the gaseous mixture of the air, refrigerant, and lubricating oil for a compressor was compressed by the compressor with different refrigerant concentrations, and the diesel combustion of the mixture was examined. The compressor was simulated by a small-scale engine. R1234yf, R32, R410A, R134a, R22, and R125 were tested as refrigerants. The mixture burned via adiabatic compression when the refrigerant concentration was low, which means that accidents during the pump-down were caused by the diesel combustion of the mixture. The refrigerant burned and caused intense pressure increase. The mixture without the oil did not burn under any refrigerant concentration, which suggests that oil is necessary for the combustion. These phenomena were observed in the results for R1234yf, R32, R410A, R134a, and R22. Thus, combustion was observed under certain conditions even for refrigerants categorized as non-flammable.     

压缩机表面产生凝露的原因及其解决措施

变频多联机中距离室内机近的压缩机表面在运行中出现凝露现象,并伴随压缩机内油翻泡,油面下降。从理论方面分析该现象：在名义制冷、最大制冷工况下,制冷剂循环量没有控制好,导致过多的制冷剂进入压缩机后继续蒸发,温度降低到露点温度以下,从而出现压缩机表面凝露。为此,提出相应的控制措施,较好地解决了该问题,对保证多联机系统的稳定安全可靠运行具有一定的指导意义。     

Simulation and comparison of leakage characteristics of R290 in rolling piston type rotary compressor

This paper presents a comparative analysis on leakage losses of a rolling piston type rotary compressor with refrigerants of R290, R22 and R410a. In particular, the difference of leakage losses characteristics between R290 compressor and that of other refrigerant compressors has been studied. Leakage losses through radial clearance, clearances between rolling piston faces and the cylinder head walls, clearances between the sliding vane faces and the cylinder head walls, as well as the clearances between the sides of the sliding vane and the side walls of the chutes inside the cylinder have been studied in the present methodology. Radial leakage caused by the wall velocity has been taken into account in the present study. Simulation results indicate that smaller radial clearance is required for R290 compressor to obtain relatively high efficiency comparing to that of R22 and R410a compressors under the same condition.     

Experimental study of a mixed refrigerant Joule–Thomson cryocooler using a commercial air-conditioning scroll compressor

Mixed refrigerant Joule–Thomson (MR J–T) cryocoolers have been used to create cryogenic temperatures and are simple, efficient, cheap, and durable. However, compressors for MR J–T cryocoolers still require optimization. As the MR J–T cryocooler uses a commercial scroll compressor developed for air-conditioning systems, compressor overheating due to the use of less optimized refrigerants may not be negligible, and could cause compressor malfunction due to burn-out of scroll tip seals. Therefore, in the present study, the authors propose procedures to optimize compressor operation to avoid the overheating issue when the MR J–T cryocooler is used with a commercial oil lubricated scroll compressor, and the present experimental results obtained for a MR J–T cryocooler. A single stage 1.49 kW (2 HP) scroll compressor designed for R22 utilizing a mixture of nitrogen and hydrocarbons was used in the present study. As was expected, compressor overheating and irreversible high temperatures at a compressor discharge port were found at the beginning of compressor operation, which is critical, and hence, the authors used a water injection cooling system for the compressor to alleviate temperature overshooting. In addition, a portion of refrigerant in the high-pressure stream was by-passed into the compressor suction port. This allowed an adequate compression ratio, prevented excessive temperature increases at the compressor discharge, and eventually enabled the MR J–T cryocooler to operate stably at 121 K. The study shows that commercial oil lubricated scroll compressors can be used for MR J–T cryocooling systems if care is exercised to avoid compressor overheating.     

自然制冷剂R290与冷冻机油的相溶性研究

为了探讨制冷剂R290与冷冻机油的相溶性,建立了一套油与制冷剂相溶性测试实验台,考察了制冷剂R290与矿物油、POE油、PAG油、AB油五种类型冷冻机油的相溶性。结果表明,制冷剂R290在五种冷冻机油中的溶解质量百分含量顺序为：AB油＞环烷基矿物油＞烷基矿物油＞POE油＞PAG油;R290在烷基矿物油、POE油、PAG油中的溶解质量百分含量均随温度的增大而降低,随压力的增大而升高;在环烷基矿物油、POE油、PAG油中的溶解质量百分含量均随运动粘度增大而降低;与运动粘度相比,温度和压力对R290在冷冻机油中的溶解质量百分含量影响较大。     

机房空调负落差长连管系统膨胀阀前过冷度研究

机房空调在负落差长连管安装方式下会产生启动时低压报警和过冷度较小等问题,对机组运行的稳定性、可靠性和性能产生影响。本文理论计算R407C制冷剂名义工况下不同负落差时膨胀阀前过冷度和压缩机排气压力,发现膨胀阀前过冷度与负落差呈负相关关系,制冷剂在膨胀阀中可能会闪发。基于此,采用带储液罐的空调机组,试验分析储液罐分别位于冷凝器出口处和膨胀阀进口处时膨胀阀前的过冷度,结果表明,储液罐位于膨胀阀进口处可以有效保障膨胀阀前过冷度并降低压缩机排气压力。     

An experimental investigation and modelling of the viscosity refrigerant/oil solutions

This paper presents experimental data for the viscosity of solutions of refrigerant R600a (isobutane) with mineral compressor oils Azmol, Reniso WF 15A, and R245fa (1,1,1,3,3-pentafluoropropane) with polyolester compressor oil Planetelf ACD 100 FY on the saturation line. The experimental data were obtained for solution of R600a with mineral compressor oil Azmol in the temperature range from 294.7 to 338.1 K and the concentration range 0.04399 ≤ w_R ≤ 0.3651, the solution of R600a with mineral compressor oil Reniso WF 15A at the temperatures from 285.8 to 348.4 K and the concentration range 0.03364 ≤ w_R ≤ 0.2911, the solution of R245fa with polyolester compressor oil Planetelf ACD 100 FY at the temperatures from 309 to 348.2 and the concentration range 0.06390 ≤ w_R ≤ 0.3845. The viscosity was measured using a rolling ball method. The method for prediction of the dynamic viscosity for refrigerant/oil solutions is reported.     

An investigation of the performance of a scroll compressor under liquid refrigerant injection

In this study, fundamental and practical influence of liquid refrigerant injection on the performance of a refrigerant scroll compressor has been investigated experimentally and theoretically. In the theoretical analysis, a compression model of vapor/liquid mixture is developed by taking account of heat transfer from the cylinder wall to suction, compression and injection refrigerant. An experiment has been done under the condition of keeping the oil temperature constant in order to investigate the fundamental influence of the liquid refrigerant injection on the compressor performance, and the results were compared with the theoretical ones. It was found that the injection basically increases the compression power and decreases the compressor efficiency, though the situation depends on the condition of the heat transfer to the injection refrigerant. And furthermore, the performance of the liquid refrigerant injection compressor under practical operating condition without controlling the oil temperature has been investigated. Under this condition, the compressor showed recovery and slight improvement of performance due to the decrease of the oil and cylinder temperatures by the injection. In addition, influence of the refrigerant injection on the oil viscosity and refrigerant solubility in the oil, which relate mechanical loss and reliability of the compressor, have been discussed.     

Experimental investigation of oil retention in air conditioning systems

In air conditioning and refrigeration systems a small amount of oil is carried with the refrigerant and is retained in the system components. Oil retention characteristics in the condenser, evaporator, liquid and suction lines were measured and are presented and discussed here. Refrigerants R22, R410A, and R134a with miscible and non-miscible lubricants were considered to investigate oil retention physics in the widest possible range of transport properties. A parametric analysis in the suction line showed that oil retention depends on the oil mass fraction, vapor refrigerant mass flux, mixture viscosity ratio and orientation of the pipe. In the suction line, an increase in mixture viscosity of about 55% caused a rise in oil retention in the range of 50%, depending on the oil mass fraction. Oil retention in the upward vertical suction line is about 50% higher than in the horizontal line at similar conditions.     

An experimental study on oil discharge ratio at inverter-driven high shell pressure scroll compressor using R410A/PVE

In this study, the oil discharge characteristics of a high shell pressure scroll compressor, which uses R410A as the refrigerant and PVE as the oil, were measured according to the conditions for oil management. The measurement of oil discharge ratio (ODR) in the system is very important to secure the operational reliability. It was made in real time through the refractive index sensor. ODR was greatly influenced by the mass flow rate and the dynamic viscosity of the refrigerant. As the rotation frequency of the compressor became higher, ODR increased rapidly. ODR at 120 Hz was 4.22 times higher than that at 60 Hz. At the same rotation frequency of the compressor, the increase of the suction pressure also played a role in increasing the ODR. In addition, in the zone where the ODR increased rapidly, the compressing efficiency of the compressor decreased significantly.     

制冷系统湿压缩时吸气干度控制方法的实验研究

不完全湿压缩能大幅度降低压缩机排气温度,然而该应用的最大难点是如何控制实时压缩机吸气干度在合适的范围内。本文提出了假拟饱和等熵压缩排气温度控制压缩机吸气该干度的方法,理论分析了在AHRI(空调供暖制冷协会)空调和低温制冷两种典型工况下,R22、R32、R134a和R410A四种制冷剂作为冷媒时,应用该方法控制压缩机吸气带液时系统性能的变化,并通过R32实验验证该结论的正确性。结果表明:利用假拟饱和等熵压缩排气温度可以将压缩机吸气状态控制在少量湿蒸气的状态;在T-s图上具有钟型饱和线形状的R32制冷剂,利用假拟饱和等熵压缩所控制的制冷系统,当吸气干度在0.96~1时,制冷量和COP均能达到最大值。     

某地铁列车空调制冷系统的仿真与优化

我国的地铁建设正处于高速发展期,但目前典型地铁列车空调制冷系统的能效比只有2.2～2.3,远低于同类工况下住宅空调制冷系统的能效水平。针对此问题,先建立了某地铁空调制冷系统模型,仿真与系统测试结果吻合良好。然后通过详细的仿真分析,改进蒸发器和冷凝器的制冷剂流路设计、采用小排量高能效比压缩机等方法,使得系统在冷量和成本基本不变的情况下能效比提升了21.7%。最后,研究了制冷剂R410A替代R407C的系统性能变化,系统能效比可进一步提升11.3%,达到3以上。该研究方法及结果对于设计高效节能的地铁列车空调制冷系统具有参考价值。     

Lubricity evaluation of oil–refrigerant mixtures with R134a and R290

The article presents an assessment method of lubricity properties of oils for refrigeration compressors in a mixture with a refrigerant. The assessment has been based on sample wear volume in the block-on-ring node under the conditions similar to the operation of the compressor following an extensive standstill.The authors assessed the lubricity properties of the following mixtures POE/R134a and MO/R290 (three different oils for each group).In all the analyzed cases it was found that the sample wear after the tests in the oil–refrigerant mixture is significantly (2–32 times) higher than for the oil itself. The test results also showed significant differences in the lubricity properties of oils, which are substitutes in operating conditions. Therefore, the only valid method of assessing lubricity properties of oils for refrigerating compressors are studies on the mixtures of these oils with a refrigerant in the conditions similar to the real operation.