A Mathematical Model for Simulating Liquid and Vapor Two-Phase Compression Processes and Investigating Slugging Problems in Compressors

Liu, Zheji; Soedel, W.

doi:10.1080/10789669.1995.10391312

Cited by 12 publications

(4 citation statements)

References 1 publication

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“…A similar type of development can be made if the fluid is saturated. Liu and Soedel, 1995 have shown that the derivative of the temperature can be expressed as:…”

Section: Conservation Equations and Derivation Of Differential Equatimentioning

confidence: 99%

Detailed Experimental and Model-Based Analysis of a Swash-Plate Piston Expander for ORC Application

Oudkerk

Lemort

2020

Front. Energy Res.

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A 195 cm 3 swash-plate piston expander was tested in an ORC using R245fa as working fluid. Rotational speeds ranging from 1,000 to 4,000 RPM and pressure ratios from 7 to 12 were imposed. In total, 65 steady state points were measured. With these measurements, performance maps were generated to point out the influence of rotational speed and levels of pressure on mechanical power and isentropic efficiency. These maps have highlighted the existence of an optimal rotational speed of around 3,000 RPM maximizing the mechanical power, while the speed that maximizes the isentropic efficiency lies between 2,000 and 2,500 RPM. The maximal mechanical power and isentropic efficiency were 2.8 kW and 53%, respectively. Then the measurements were used to analyze the losses. This analysis has shown that, under the expansion and compression limit, the theoretical isentropic efficiency has values comprised between 90 and 70% for pressure ratios of 7-12. The filling factor affects the isentropic efficiency for low rotational speeds and low pressure ratios. Indeed, indicated isentropic efficiency is around 60% for 1,000 RPM and around 75% for 4000 RPM. These values stay quite constant with the pressure ratio. Finally, a mechanical efficiency comprised between 40 and 90% was observed, which lowers the isentropic efficiency to values comprised between 30 and 53%. Finally, a model based on energy and mass conservation inside a cylinder volume was successfully calibrated and was able to predict mass flow rate, mechanical power, and exhaust temperature with good agreement. This model has enabled disaggregation of the influence of pressure drops and leakages on the filling factor, then on the isentropic efficiency. This analysis has shown that pressure drops mainly affect the compactness of the expander, and not so much the isentropic efficiency (except for low rotational speeds where pressure drops can lower the isentropic efficiency by 14%). In contrary, leakages have a strong impact. The importance of the different sources of losses varies with the speed. For the optimal speed of 2,500 RPM, under-expansion and compression have the strongest impact, followed by mechanical losses, leakages and pressure drops, respectively.

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“…A similar type of development can be made if the fluid is saturated. Liu and Soedel, 1995 have shown that the derivative of the temperature can be expressed as:…”

Section: Conservation Equations and Derivation Of Differential Equatimentioning

confidence: 99%

Detailed Experimental and Model-Based Analysis of a Swash-Plate Piston Expander for ORC Application

Oudkerk

Lemort

2020

Front. Energy Res.

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“…The homogeneous model based on energy and mass conservation equations was proposed by many researchers. Liu 9 derived the thermodynamic equation to simulate the two-phase refrigerant compression process in a rotary compressor. This paper also discussed the influence of compressor type on liquid slugging.…”

Section: Introductionmentioning

confidence: 99%

Simulation on two-phase refrigerant compression in the cylinder of rotary compressors using CFD method

Guo,

Lin,

2024

Sci Rep

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The two-phase compression process in the rotary compressor often occurs, such as defrosting and startup processes, which has a significant impact on the performance and reliability of air conditioning systems. In this paper, the CFD simulations predicting the two-phase refrigerant compression process in the compressor cylinder are conducted using the commercial software ANSYS Fluent. The dynamic mesh for the fluid domain and phase change model for the refrigerant are considered in the simulation. Effects of initial liquid volume fraction, refrigerant type and compressor type on the two-phase compression characteristics using R290 as refrigerant are carried out. Variations of the pressure, temperature, gas fraction distribution and evaporation rate in the cylinder are discussed. The results show that most liquid accumulates near the leakage gap and the bottom of the compression chamber during the two-phase compression process. The peak pressure during the two-phase compression decreases with the increase of the liquid volume fraction. The evaporation rate of R32 in the cylinder is much higher than that of R290. The maximum pressure of the reciprocating compressor is 2.26 times higher than that of the rotary compressor.

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“…It was shown that the advantage of a wet compression cycle offers the highest possible efficiency for thermodynamic cycles operating between two temperatures with a heat sink and heat source [2,3]. While some earlier works [4,5] showed improvements in the isentropic and volumetric efficiency of the compressor, they did not recommend using wet compression due to the following possible dangers. Firstly, wet compression may cause an abrupt increase of pressure at the cylinder head, which may damage the valve or cylinder.…”

Section: Introductionmentioning

confidence: 99%

“…However, the vapor-liquid mixture compression could be useful for performance improvement and a reduction in the discharge temperature, if the liquid droplets are fully vaporized by an internal heat transfer process that requires a finite amount of time [22]. Among the three most widely used positive displacement compressors (reciprocating, rolling-piston rotary, and scroll), the scroll compressor could also be appropriate for the wet compression technique, since the scroll compressor is less likely to have liquid slugging problems [4]. Thus, more extensive research, such as a durability test, is needed in this regard in the future.…”

Section: Appl Sci 2017 7 248mentioning

confidence: 99%

The Effects of Wet Compression by the Electronic Expansion Valve Opening on the Performance of a Heat Pump System

Seong

Lee

2017

Applied Sciences

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Abstract:In this study, by controlling the Electronic Expansion Valve opening, the influence of wet compression on a heat pump system was experimentally investigated in different heating conditions. The results demonstrate that the discharge temperature decreased and the mass flow rate increased, due to quality of the rising liquid droplets. It was also found that the heating capacity and power input of wet compression increased more than that of dry compression, with a superheat of 10 • C. The maximum COP (Coefficient of Performance) exists at a specific quality of ca. 0.94 to 0.90, as the power input in the region of wet compression is proportionally larger than the increase in the heating capacity, according to the decreasing quality. When the Entering Water Temperature of the Outdoor Heat Exchanger was 10 • C, 5 • C, and 0 • C, the COP increased by a maximum of ca. 12.4%, 10.6%, and 10.2%, respectively, in comparison to the superheat of 10 • C. In addition, the superheat at the discharge line is proposed as a proper controlling parameter to adjust the quality at the suction line, by varying the opening of the expansion valve during wet compression.

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A Mathematical Model for Simulating Liquid and Vapor Two-Phase Compression Processes and Investigating Slugging Problems in Compressors

Cited by 12 publications

References 1 publication

Detailed Experimental and Model-Based Analysis of a Swash-Plate Piston Expander for ORC Application

Detailed Experimental and Model-Based Analysis of a Swash-Plate Piston Expander for ORC Application

Simulation on two-phase refrigerant compression in the cylinder of rotary compressors using CFD method

The Effects of Wet Compression by the Electronic Expansion Valve Opening on the Performance of a Heat Pump System

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