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Access type: UnknownAuthor: search.filters.author.Wongpromma, Pakorn

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    An investigation of horizontal and vertical flow boiling in a single channel with a confinement number beyond the threshold of micro-scale flow
    (2021-11-01)
    Saisorn, Sira
    ;
    Suriyawong, Adirek
    ;
    Srithumkhant, Pochai
    ;
    Wongpromma, Pakorn
    ;
    Wongwises, Somchai
    The gravitational force effect is of concern when designing flow boiling systems deployed on Earth and in space. A study of the R-134a flow boiling inside the horizontal and vertical channels was experimentally performed to explore the flow orientations' effect on flow pattern and heat transfer characteristics. The test section was a 0.5 mm diameter tube from which the corner effect was excluded. The single channel was used to avoid disturbances that flow maldistribution could possibly cause in the multiple channels. The experimental two-phase flow corresponded to a 1.75 confinement number, which was above the threshold for micro-scale flow. The results indicated the flow regime map, which was less affected by the channel orientation except for that slug flow pattern that was unable to survive during the vertical downflow and vertical upflow. Also, based on the present micro-scale flow, the heat transfer results were mostly independent of the gravitational force effect, and the nucleate boiling and convective mechanisms tended to govern them.
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    The difference in flow pattern, heat transfer and pressure drop characteristics of mini-channel flow boiling in horizontal and vertical orientations
    (2018-04-01)
    Saisorn, Sira
    ;
    Wongpromma, Pakorn
    ;
    Wongwises, Somchai
    Flow pattern, heat transfer, and pressure drop data for different flow orientations was presented in this study. The data was obtained based on flow boiling experiments with R-134a flow through a 1 mm diameter channel which was aligned in different orientations, i.e. horizontal flow, vertical upward flow, and vertical downward flow. A constant surface heat flux condition was performed under a saturation pressure of 8 bar, a heat flux range of 1–60 kW/m<sup>2</sup>, and a mass flux range of 250–820 kg/m<sup>2</sup>s. The experimental results showed the importance of the change in the flow direction. The shape of the gas slug during horizontal flow did not look the same as in the vertical orientations. Heat transfer coefficient and pressure drop became increased when the refrigerant flowed in the vertical downward direction. The experimental data was also compared with the existing prediction methods.
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    Flow pattern, heat transfer and pressure drop behaviors of micro-channel flow boiling
    (2018-01-01)
    Saisorn, Sira
    ;
    Srithumkhant, Pochai
    ;
    Wongpromma, Pakorn
    ;
    Suchatawat, Maturose
    ;
    Wongwises, Somchai
    Two-phase flow of R-134a with high confinement number was experimentally carried out in this study. Flow boiling conditions for different orientations were controlled to take place in a stainless steel tube having a diameter of 0.5 mm. Based on a saturation pressure of 8 bar, a heat flux range of 2-26 kW/m<sup>2</sup>, and a mass flux range of 610-815 kg/m<sup>2</sup>s, a constant surface heat flux condition was controlled by applied DC power supply on the test section. The flow behaviors were described based on flow pattern and pressure drop data while heat transfer mechanisms were explained by using heat transfer coefficient data. In this work, nucleate boiling was observed, and the importance of the change in the flow direction was neglected, corresponding to the confinement number of around 1.7.
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    Two-phase heat transfer behaviors of r-134a refrigerant and air-water mixture in A 1 MM internal diameter tube
    (2016-01-01)
    Saisorn, Sira
    ;
    Wongwises, Somchai
    ;
    Wongpromma, Pakorn
    ;
    Benjawun, Phakkhanan
    ;
    Suriyawong, Adirek
    Flow boiling of R-134a refrigerant was experimentally conducted in a test section which is a stainless steel tube having internal diameter of 1 mm. The DC power supply was connected to the test section to provide constant surface heat flux conditions. Flow pattern and heat transfer data were obtained for a mass flux range of 252-820 kg/m2s, a heat flux range of 1-21 kW/m2 and a saturation pressure of 8 bar. The flow visualization results showed four different flow patterns including slug flow, throat-Annular flow, churn flow, and annular flow. The flow boiling heat transfer behaviors were also compared with those based on non-boiling two-phase air-water flow in the same test section under constant surface heat flux conditions. For non-boiling two-phase flow experiment, an airwater T-shaped mixer was served to introduce fluids smoothly along the test section. The results indicated that based on the same gas and liquid Reynolds numbers, flow boiling tends to have Nusselt number higher than that for non-boiling gas-liquid flow.