Refrigerant distribution in horizontal headers with downward minichannel-branching conduits: Experiment, empirical correlation and two-phase flow pattern map

Agung Tri Wijayanta, Takahiko Miyazaki, Shigeru Koyama

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    9 Citations (Scopus)

    Abstract

    The system energy efficiency will decline with the decrease of evaporator capacity because the use of more branches in evaporators increases maldistribution. This paper presents experimental study of several design options for downward flow to reduce the maldistribution. Two-phase flow distribution in a header type evaporator applied for CO 2 have been experimentally investigated because the refrigeration system based on carbon dioxide (CO 2 ) as a refrigerant is near ideal. Since the CO 2 system works around critical pressure, an alternative method to predict the flow distribution of CO 2 header type evaporator is inevitable. R134a is used as the alternative working fluid in the present study. Similarity hypothesis between CO 2 and R134a is applied (refer to Wijayanta et al., 2016). R134a headers are tested and the experimental work is applicable to CO 2 . The R134a experiments were conducted at saturation temperature of about 21 °C, refrigerant mass flow range between 10 and 30 kg/h which corresponds to about 44 and 130 kg/m 2 s in the 9 mm i.d. header, and average vapor quality in the test section inlet of about 0.1–0.4. The test section consists of a horizontal header with 3 and 6 vertically downward replaceable branching conduits. The vapor-liquid phase mass flows enter into the branches are measured to propose the configuration of the header that has the minimum maldistribution. Empirical correlation of the vapor-liquid distribution is developed. Estimated CO 2 distribution for the proper header is determined based on R134a experimental data using the similarity hypothesis. The developed flow pattern map for R134a and CO 2 is also proposed.

    Original languageEnglish
    Pages (from-to)430-444
    Number of pages15
    JournalExperimental Thermal and Fluid Science
    Volume81
    DOIs
    Publication statusPublished - Feb 1 2017

    Fingerprint

    Refrigerants
    Evaporators
    Carbon Monoxide
    Two phase flow
    Flow patterns
    Vapors
    Experiments
    Liquids
    Refrigeration
    Energy efficiency
    Carbon dioxide
    Fluids
    Carbon Dioxide
    Temperature

    All Science Journal Classification (ASJC) codes

    • Chemical Engineering(all)
    • Nuclear Energy and Engineering
    • Aerospace Engineering
    • Mechanical Engineering
    • Fluid Flow and Transfer Processes

    Cite this

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    abstract = "The system energy efficiency will decline with the decrease of evaporator capacity because the use of more branches in evaporators increases maldistribution. This paper presents experimental study of several design options for downward flow to reduce the maldistribution. Two-phase flow distribution in a header type evaporator applied for CO 2 have been experimentally investigated because the refrigeration system based on carbon dioxide (CO 2 ) as a refrigerant is near ideal. Since the CO 2 system works around critical pressure, an alternative method to predict the flow distribution of CO 2 header type evaporator is inevitable. R134a is used as the alternative working fluid in the present study. Similarity hypothesis between CO 2 and R134a is applied (refer to Wijayanta et al., 2016). R134a headers are tested and the experimental work is applicable to CO 2 . The R134a experiments were conducted at saturation temperature of about 21 °C, refrigerant mass flow range between 10 and 30 kg/h which corresponds to about 44 and 130 kg/m 2 s in the 9 mm i.d. header, and average vapor quality in the test section inlet of about 0.1–0.4. The test section consists of a horizontal header with 3 and 6 vertically downward replaceable branching conduits. The vapor-liquid phase mass flows enter into the branches are measured to propose the configuration of the header that has the minimum maldistribution. Empirical correlation of the vapor-liquid distribution is developed. Estimated CO 2 distribution for the proper header is determined based on R134a experimental data using the similarity hypothesis. The developed flow pattern map for R134a and CO 2 is also proposed.",
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