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This paper discusses the oil retention characteristics in the evaporator and suction line in a vapor compression system. Oil retention in the components can lead to reduced compressor efficiency and potential breakdowns. Lubricant in the evaporator reduces heat transfer efficiency and increases pressure drop, particularly under high-quality conditions. However, lubricant can also have a beneficial effect by making refrigerant distribution in the evaporator better. Experimental studies on the critical mass flux for oil recovery and the measurement of oil retention in the suction line are presented, highlighting key findings. Additionally, prediction models for oil retention in both the evaporator and suction line are suggested and organized. Most of the refrigerants discussed in this paper have a high global warming potential (GWP), except for R1234yf and R32. Given the global focus on transitioning to low-GWP refrigerants, future research should target the oil retention characteristics in next-generation refrigerants. [ABSTRACT FROM AUTHOR]

Abstract This paper discusses the oil retention characteristics in the evaporator and suction line in a vapor compression system. Oil retention in the components can lead to reduced compressor efficiency and potential breakdowns. Lubricant in the evaporator reduces heat transfer efficiency and increases pressure drop, particularly under high-quality conditions. However, lubricant can also have a beneficial effect by making refrigerant distribution in the evaporator better. Experimental studies on the critical mass flux for oil recovery and the measurement of oil retention in the suction line are presented, highlighting key findings. Additionally, prediction models for oil retention in both the evaporator and suction line are suggested and organized. Most of the refrigerants discussed in this paper have a high global warming potential (GWP), except for R1234yf and R32. Given the global focus on transitioning to low-GWP refrigerants, future research should target the oil retention characteristics in next-generation refrigerants.

This article discusses the problem of combating pressure fluctuations in the suction line of piston compressors. As you know, incorrect calculation of communications can lead to accidents of compressor equipment. Therefore, special attention must be paid to the layout of pipelines and equipment, while avoiding resonance phenomena. One way to combat pressure pulsations in the suction line is to install diaphragms. This method is the cheapest and easiest to implement, especially for compressors already in operation. The experimental studies carried out confirmed the known data that the area of the diaphragm opening should be four times smaller than the diameter of the pipeline. At the same time, a threefold reduction in the amplitude of pressure fluctuations is achieved. Installation of a diaphragm design with parameters close to the recommended ones is possible anywhere in the suction line, since the change in amplitude at different pressure from the suction valves does not exceed 5...7 %. When installing a diaphragm with dimensions different from those recommended, it is necessary to install it closer to the suction valve.

Domestic refrigerators have caused various energy-related issues for years. Replacing old refrigerants, using more flexible components, and reducing power consumption have been the main concerns of manufacturers. It is an improper use of energy and resources to implement each new change in the construction of the refrigeration cycle by trial and error. Therefore, virtual labs can assist designers in investigating potential changes before implementing that in practice. This work describes the procedure by which a flexible software is developed to simulate each component of the refrigeration cycle and predict the desired variables in an efficient time. In this software, the amount of refrigerant charge and the degree of superheat are provided as input variables; geometrical parameters for each component are considered in detail. The tube-by-tube and map-based methods are implemented to model the heat exchangers and compressor, respectively. Heat transfer between the suction line and capillary tube is simulated as well. Eventually, the performance parameters with all thermodynamic properties of the cycle at any arbitrary location can be reported as outputs. The case studies showed that the coefficient of performance will increase from 1.58 to 2.1, and from 2 to 2.2 by tuning the suction-line-heat-exchanger and evaporator fan speed, respectively.

The presence of gas pressure pulsations in the suction and discharge pipes of reciprocating compressors is associated with their periodic connection and disconnection from the working chamber during the operation of self-acting valves. The present work is devoted to the development of a methodology for experimental investigation of pressure pulsations in gas communications of reciprocating compressors under various operating modes in relation to an existing laboratory installation and comparison of the results obtained with the results of calculations obtained on the basis of the use of well-known repeatedly tested techniques. This proven technique can be used to study pressure pulsations in gas communications of a wide class of low-flow reciprocating compressors.

The effect of suction line on the evaporator performance with the using of R-134a has been investigated experimentally. Three types of suction lines (lateral, concentric, coil) have been used with various refrigerant flow rates and air velocities. The results of the concentric suction line gave the highest values of the coefficient of heat transfer compared to the other types. Moreover, the maximum increase of the internal heat transfer coefficient (hi) and overall heat transfer coefficient (Uo) was achieved for the reference capillary tube as 16% and 50% respectively, when the mass flow rate of refrigerant is 14.87 kg/h and air velocity 3.8 m/s. In addition, the results displayed that the largest values of evaporator effectiveness (ε) have been obtained, when utilized the concentric suction line compared the other types. Thereby, the internal heat transfer coefficient was increased by 9.24% for the concentric suction line with the increasing of air speed from 1.8 m/s to 3.8 m/s at flow rate of the refrigerant is 14.87 kg/h. Finally, the best suction line according to all results such as hi, Uo and ε is the concentric line compared the other types.

Pressure drop in the suction line of the turbo compressor will affect the pressure in the inlet section of the compressor. Lower inlet pressure will require higher drive power. As a result, energy consumption for compressed air production will be higher because turbo compressors are machines with continuous operation. [ABSTRACT FROM AUTHOR]

• Oil retention amount and pressure drop of R32 with PVE oil in suction line were measured experimentally. • The influences of refrigerant mass flux, oil mass fraction, transport property and flow direction on oil retention and pressure drop were discussed. • Two consolidated databases of oil retention and pressure drop were amassed to conduct comparison and analysis. • Oil retention impact factor was proposed to reflect the oil transport difficulty and it integrated the influences of geometric dimension, working pairs and operation parameters. R32/PVE oil mixture has become a popular working pair of commercial refrigeration/heat pump systems in recent years. This paper presented experimental study of oil retention and pressure drop characteristics of R32/PVE VG68 mixture in the compressor suction lines. The test samples were two smooth copper pipes of horizontal and vertical flow orientations with 10.7mm inner diameter. The oil retention in suction lines were measured based on remove-and-weight technique (RWT). Three conditions of saturation temperature and superheat degree (7.5/12, 7.5/6 and 10/12°C) were tested, in order to obtain different thermophysical and transport properties. Refrigerant mass flux and nominal oil mass fraction (OMF no) were varied with the ranges of 90−230 kg•m−2·s−1 and 1−5%, respectively. The influences of refrigerant mass flux, oil mass fraction, mixture viscosity and flow configuration on oil retention and pressure drop were investigated. The results showed that the oil retention amount tends to increase with the increases of actual oil mass fraction (OMF act) and mixture kinematic viscosity ratio and the decrease of refrigerant mass flux. Two consolidated databases for oil retention and pressure drop of suction lines, which involved five working pairs, were collected from the existing literatures to perform a comparison. Finally, based on analysis of oil transport mechanism, a new dimensionless parameter called oil retention impact factor was proposed to characterize the difficulty of oil transport, which integrated the influences of geometric dimension, working pairs and operation parameters. It showed relatively satisfactory relationship with the oil retention data from the amassed database and the present study. [ABSTRACT FROM AUTHOR]