Effects of a non-equilibrium two-phase refrigerant flow at subcooled temperatures on the performance of an R-600a refrigeration system

Ko, Jaedeok; Jeong, Ji Hwan

doi:10.1016/j.ijrefrig.2017.10.029

Cited by 9 publications

(7 citation statements)

References 19 publications

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“…The authors subsequently proposed a method to calculate the enthalpy for non-equilibrium refrigerant conditions and could estimate the vapor quality for different condensing pressures ranging from 2.44% to 4.29% at the condenser outlet. Ko and Jeong (2017) complemented previous work by studying the effect of a nonequilibrium subcooled two-phase flow on the performance of a vapor compression refrigeration system. The authors estimated that the COP may be overestimated by 19.4% if the thermodynamic properties table is used for a refrigerant non-equilibrium state.…”

Section: Introductionmentioning

confidence: 76%

“…First, the refrigerant mass flow rate measurement could be less accurate than expected because of variations in oil concentration or influence of the oil on the measurement, which is unknown. Second, an assumption of thermodynamic equilibrium at the refrigerant outlet for the evaluation of the condensing capacity (Q̇cond) as found out by Ko and Jeong (2017).…”

Section: ̇=̇(mentioning

confidence: 99%

“…However, all measurements clearly indicated subcooled conditions for both liquid and vapor, and visualization of the inlet of the capillary tube revealed the entrance of vapor and liquid. Lee et al (2016) and Ko and Jeong (2017) have observed this paradoxical state and attributed it to non-equilibrium conditions of the flow where both subcooled gas and subcooled liquid coexist.…”

Section: ̇=̇(mentioning

confidence: 99%

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How to achieve full liquid conditions at the capillary tube inlet of a household refrigerator

Bardoulet¹,

Corberán²,

Martínez-Ballester³

2019

International Journal of Refrigeration

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Capillary tube with liquid-to-suction heat exchanger is a component widely used in household refrigerators. Recent works have indicated that even when measuring subcooled conditions at the condenser outlet, the actual capillary tube inlet is two phase-flow.The original refrigerant-to-air condenser of a household refrigerator was replaced by a refrigerant-to-water condenser to assess, from the heat balance between refrigerant and water capacities, the refrigerant conditions at the condenser outlet at the capillary tube inlet.Measurements indicate a non-equilibrium two-phase flow composed of subcooled vapor and liquid at the capillary tube inlet.The test bench design was modified by using a smaller capillary tube diameter and increasing compressor speed. Full liquid conditions at the capillary tube inlet were reached with this new configuration.A performance analysis comparison between both the original and the new design reveals that COP were higher in cases of fully liquid conditions at the capillary tube inlet.

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Section: Introductionmentioning

confidence: 76%

Section: ̇=̇(mentioning

confidence: 99%

Section: ̇=̇(mentioning

confidence: 99%

See 1 more Smart Citation

How to achieve full liquid conditions at the capillary tube inlet of a household refrigerator

Bardoulet¹,

Corberán²,

Martínez-Ballester³

2019

International Journal of Refrigeration

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“…The subcooled conditions at the capillary tube inlet, estimated from measuring the temperature on the wall surface, are always reported in the literature. However, the cited problems of noise and conclusions of others works [14], [16], [17] point out that these conditions may not be real, which, if true, would mean that there is a room for efficiency improvement and, more generally, energy consumption.…”

Section: Motivationsmentioning

confidence: 99%

“…Different reasons may offer explanation, namely: non-equilibrium between subcooled phase and saturated vapour at the capillary inlet [14], non-equilibrium between subcooled liquid and subcooled vapour [16], [17] and/or insufficient compressor capacity compared with the expansion device capacity of the capillary tube used, which would mean a capillary tube too large for that compressor.…”

Section: Motivationsmentioning

confidence: 99%

Non-adiabatic capillary tubes in high efficiency household refrigerator: an experimental study

Bardoulet¹

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Capillary tube with liquid-to-suction heat exchanger (CT-LSHX) is a component widely used in household refrigerators. Recent works have indicated that even when measuring subcooled conditions at the condenser outlet, the actual capillary tube inlet is two phase-flow. The aim of this PhD thesis is to examine the actual conditions at the capillary tube inlet of a household refrigerator by using an innovative test bench. Transparent tubes were set up at the condenser outlet and capillary tube inlet. The experimental visualisation campaign reveals that the capillary tube inlet was twophase flow despite the measurement of a certain subcooling, regardless of the filter position (horizontal or vertical), flow direction (upward or downward) and refrigerant charge. This study also demonstrates that the filter was not acting as an accumulator since the liquid level of the capillary always followed the capillary tube entrance, regardless of the capillary tube length inside the filter. Two hypotheses were then posed to explain the phenomenon: a non-equilibrium condition of the refrigerant and/or an unbalanced matching between compressor and capillary tube, that is, the system would be equipped with a capillary tube with a notably large expansion capacity compared to the needs of the compressor. The original refrigerant-to-air condenser was replaced by a refrigerant-towater condenser to assess, from the heat balance at the water condenser, the refrigerant conditions at the condenser outlet and therefore, at the capillary tube inlet. Measurements indicate a non-equilibrium two-phase flow composed of subcooled vapour and liquid at the capillary tube inlet. To verify if the presence of two-phase flow was due to unbalanced matching between the capillary tube and compressor, the test bench design was modified by using a smaller capillary tube diameter and increasing compressor speed. Fully liquid conditions at the capillary tube inlet were reached with this new configuration. A performance analysis comparison between a capillary tube inlet composed of vapour and liquid and a capillary tube inlet composed of only liquid was also performed. Results reveal that COP were higher in cases of fully liquid conditions at the capillary tube inlet. viii xiii Content Acknowledgements .

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Effects of 3-way valve faults and capillary tube clogging on the dynamic behavior of compressor power consumption during start-up operation of a household refrigerator-freezer

Ko,

Hwan Jeong

2024

Applied Thermal Engineering

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Effects of a non-equilibrium two-phase refrigerant flow at subcooled temperatures on the performance of an R-600a refrigeration system

Cited by 9 publications

References 19 publications

How to achieve full liquid conditions at the capillary tube inlet of a household refrigerator

How to achieve full liquid conditions at the capillary tube inlet of a household refrigerator

Non-adiabatic capillary tubes in high efficiency household refrigerator: an experimental study

Effects of 3-way valve faults and capillary tube clogging on the dynamic behavior of compressor power consumption during start-up operation of a household refrigerator-freezer

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