Two-Phase Flow Distribution in Multipass Tube.

Watanabe, Manabu; Katsuta, Masafumi; A, Katsuya Nag At; Sakuma, Xiyoshi

doi:10.1299/kikaib.60.4145

Cited by 16 publications

(18 citation statements)

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“…In addition, the liquid takeoff ratio is also related to the inlet quality. At any given inlet quality, the liquid take-off ratio reduces as Reynolds number increases at the same inlet quality, similar as the findings in Watanabe et al (1995) and Byun and Kim (2011). The vapor phase Froude number is also introduced into the distribution function to consider the effects of fluid properties.…”

Section: Figure 8: Coefficient Of Variation Decreases As Liquid Mass supporting

confidence: 60%

“…The distribution functions of Watanabe et al (1995) and Byun and Kim (2011) relating liquid take-off ratio (ratio of liquid mass flow rate in the tube to liquid mass flow rate in the header immediately upstream) with vapor phase Reynolds number were proved to be good choice. The distribution function in this study is developed adopting the same parameters in the two-phase flow region in the header, i.e.…”

Section: Figure 8: Coefficient Of Variation Decreases As Liquid Mass mentioning

confidence: 99%

“…Fei and Hrnjak (2002), Vist and Pettersen (2004), Webb and Chung (2005), Bowers et al (2006), and Hwang et al (2007) studied the two-phase flow in the horizontal headers and refrigerant distribution into the vertical parallel tubes, which usually appeared in the indoor MCHX. Watanabe et al (1995), Cho and Cho (2004), Lee (2009), Byun and Kim (2011), and Zou and Hrnjak (2013a, 2013b investigated the refrigerant distribution in the inlet and/or intermediate vertical headers, which were commonly used in the outdoor MCHX. Maldistribution in the outdoor MCHX was also very important when it was used as an evaporator in the heat pump mode.…”

Section: Introductionmentioning

confidence: 99%

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Comparison and generalization of R410A and R134a distribution in the microchannel heat exchanger with the vertical header

Hrnjak

2015

Science and Technology for the Built Environment

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This paper explores the effects of fluid properties on two-phase flow in the vertical header and refrigerant distribution into horizontal branch tubes. R410A and R134a are used as the working fluid. Refrigerant enters into the header by five microchannel tubes in the bottom pass and exits through the five microchannel tubes in the top pass representing the flow in the outdoor microchannel heat exchanger of reversible systems under heat pump mode. The difference of fluid properties causes the flow pattern and refrigerant distribution results of R410A and R134a different between each other. Non-dimensional analysis shows that the inertia of R410A is higher than that of R134a. At low qualities, when the flow regime is churn, the higher inertia enables top tubes to receive more liquid so that the distribution of R410A is a little better than that of R134a. At high qualities, when it is likely semiannular, the higher inertia causes more bottom tubes are bypassed by the liquid film of semi-annular flow. It results in worse R410A distribution than R134a, though more liquid reaches the top tubes for R410A. The coefficient of variation of refrigerant distribution is applied in this study to generalize the results of both R410A and R134a at various header geometries and inlet flow conditions. A distribution function is derived for predicting R410A and R134a distribution in future.

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Section: Figure 8: Coefficient Of Variation Decreases As Liquid Mass supporting

confidence: 60%

Section: Figure 8: Coefficient Of Variation Decreases As Liquid Mass mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Comparison and generalization of R410A and R134a distribution in the microchannel heat exchanger with the vertical header

Hrnjak

2015

Science and Technology for the Built Environment

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“…(c) In the final evaluation method, the liquid and the vapor flow rates of the refrigerant at every individual branch tube after distributions are measured, respectively. In this case, the number of flow meters and liquid-vapor separators corresponding to the number of branch tubes are required (3,4) . This method is the most precise and gives enough information to understand the distribution phenomena.…”

Section: Previous Test Methodsmentioning

confidence: 99%

Performance Evaluation and Optimization of A Refrigerant Distributor for Air Conditioner

Yoshioka

Kim

Kasai

2008

JTST

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Refrigerant mal-distribution in a distributor located at the inlet of a heat exchanger used for an air conditioning system plays an important role in the heat exchanger performance. Distribution performance in the distributor is greatly affected by the flow conditions as well as the geometrical parameters of the distributor. To clarify the distribution characteristics, it is essential to know flow rates of both liquid and vapor states at every branch tube after distribution. This paper proposes a relatively simple test method, which enables to measure the inlet quality and the flow rate of refrigerant at every branch of the distributor. By using the proposed evaluation method, optimization on the geometrical parameters of the distributor was conducted to reduce the refrigerant mal-distribution. It was confirmed that the optimized distributor was able to reduce the mal-distribution of the refrigerant over branches despite the flow condition changes. By the flow visualization of the refrigerant in the distributor, it was observed that certain amount of liquid refrigerant remained and swayed unstably at the bottom of the distributor. It is supposed that the liquid refrigerant behavior in the distributor great affects the distribution performance.

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“…The thermal performance of the evaporator is greatly affected by the flow distribution characteristics of the multi-pass channel, and a uniform distribution of liquid to all the branches is desirable to the evaporator. Therefore, the two-phase flow distribution in multi-pass channels has been a major problem in development of compact heat exchangers, and many studies have been conducted on this subject in real refrigerant flow system [2][3][4][5][6][7][8][9] or in isothermal air-water flow system [10][11][12][13][14][15][16][17]. Recently, an extensive review of researches on the gas-liquid flow distributions in T-junctions and multi-pass channels was published by Lee et al [18].…”

Section: Introductionmentioning

confidence: 99%

Gas-Liquid Flow Distributions in Multipass Channels with Vertical Upward Branches

Razlan¹,

Goshima²,

Hirota³

et al. 2011

TOTPJ

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The gas-liquid flow distributions in multi-pass channels that simulate a compact evaporator used for an automobile air-conditioning system was examined experimentally. The test channel had a horizontal header with a square cross section of 20mm × 20mm and a length of 255mm, and ten upward branches with a length of 200mm were connected to it. Experiments were conducted in an isothermal air-water flow system. Special attention was directed to influences of (i) flow-inlet condition at the header entrance (stratified-flow inlet and mist-flow inlet), (ii) pressure condition at the branch outlets (uniform backpressure and non-uniform backpressure) and (iii) pressure-loss characteristics of branches (flat tubes and multi-port tubes) on the gas-liquid distribution characteristics. In addition to the gas-liquid distributions to branches, the pressure distributions in the headers were measured to make clear the pressure condition in a real evaporator. It was found that the outlet pressure condition of branches exerts great influence on the gas-liquid distributions to branches in the channel with flat tube branches, but it has only minor influence in the channel with multiport tube branches. The flow-inlet condition at the header entrance has significant influence on the gas-liquid distribution, and the uniformity of the liquid distribution to branches is improved under the mist-flow inlet condition. The pressure in the headers showed uniform distributions in the longitudinal direction, suggesting that the uniform backpressure condition at the branch outlets is appropriate for reproducing the flow in a real compact evaporator with multi-pass channels.

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Two-Phase Flow Distribution in Multipass Tube.

Cited by 16 publications

References 0 publications

Comparison and generalization of R410A and R134a distribution in the microchannel heat exchanger with the vertical header

Comparison and generalization of R410A and R134a distribution in the microchannel heat exchanger with the vertical header

Performance Evaluation and Optimization of A Refrigerant Distributor for Air Conditioner

Gas-Liquid Flow Distributions in Multipass Channels with Vertical Upward Branches

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