The Experts below are selected from a list of 108 Experts worldwide ranked by ideXlab platform
Somchai Wongwises - One of the best experts on this subject based on the ideXlab platform.
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helical capillary tube sizing charts for all mixture ratios of r125 r134a and r32
International Journal of Air-conditioning and Refrigeration, 2016Co-Authors: Worachest Pirompugd, Somchai WongwisesAbstract:This research presents two helical capillary tube sizing charts for R407C and R410A, two correction charts for another tube size, and a correction chart for all mixture ratios of R125, R134a and R32. These charts are obtained from the Homogeneous Flow Model including the effect of gravitational force. It is verified by comparison with experimental data obtained from the published literature. From the Model, the sizing charts for a diameter of 1.63mm, length of 2.03m, and helix diameter of 500mm are developed. Two charts for size correction are also developed. The first one is for tube diameter of 0.5–5mm and length of 0.25–10m. The second one is for helix diameter of 20–1000mm. Finally, one more chart for mixture ratio correction is proposed. This chart can be applied to all mixture ratios of R125, R134a and R32.
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Flow pattern void fraction and pressure drop of two phase air water Flow in a horizontal circular micro channel
Experimental Thermal and Fluid Science, 2008Co-Authors: Sira Saisorn, Somchai WongwisesAbstract:Abstract Adiabatic two-phase air–water Flow characteristics, including the two-phase Flow pattern as well as the void fraction and two-phase frictional pressure drop, in a circular micro-channel are experimentally studied. A fused silica channel, 320 mm long, with an inside diameter of 0.53 mm is used as the test section. The test runs are done at superficial velocity of gas and liquid ranging between 0.37–16 and 0.005–3.04 m/s, respectively. The Flow pattern map is developed from the observed Flow patterns i.e. slug Flow, throat-annular Flow, churn Flow and annular-rivulet Flow. The Flow pattern map is compared with those of other researchers obtained from different working fluids. The present single-phase experiments also show that there are no significant differences in the data from the use of air or nitrogen gas, and water or de-ionized water. The void fraction data obtained by image analysis tends to correspond with the Homogeneous Flow Model. The two-phase pressure drops are also used to calculate the frictional multiplier. The multiplier data show a dependence on Flow pattern as well as mass flux. A new correlation of two-phase frictional multiplier is also proposed for practical application.
B N Mccord - One of the best experts on this subject based on the ideXlab platform.
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gas liquid two phase Flow in microchannels part ii void fraction and pressure drop
International Journal of Multiphase Flow, 1999Co-Authors: K A Triplett, S M Ghiaasiaan, S I Abdelkhalik, A Lemouel, B N MccordAbstract:Abstract Void fraction and two-phase frictional pressure drop in microchannels were experimentally investigated. Using air and water, experiments were conducted in transparent circular microchannels with 1.1 and 1.45 mm inner diameters and in microchannels with semi-triangular (triangular with one corner smoothed) cross-sections with hydraulic diameters 1.09 and 1.49 mm. Gas and liquid superficial velocities were varied in the 0.02–80 m/s and 0.02–8 m/s ranges, respectively, and void fractions were calculated by analyzing photographs taken from the test sections with circular cross-section. Measured void fractions were compared with several correlations. The Homogeneous Flow Model provided the best prediction of the experimental void fractions in bubbly and slug Flow patterns. The Homogeneous Flow Model and all other tested empirical correlations significantly over predicted the void fractions in annular Flow pattern, however. A one-dimensional Model, based on the numerical solution of mass and momentum conservation equations was applied for the calculation of test section pressure drops, using various two-phase friction Models. For bubbly and slug Flow patterns, the two-phase friction factor based on Homogeneous mixture assumption provided the best agreement with experimental data. For annular Flow the Homogeneous mixture Model and other widely used correlations significantly over predicted the frictional pressure drop.
Lei Chai - One of the best experts on this subject based on the ideXlab platform.
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two phase Flow pattern and pressure drop in silicon multi microchannel with expansion constriction cross section
Experimental Thermal and Fluid Science, 2015Co-Authors: Lei Chai, Liang Wang, Mingzheng Zhou, Guodong XiaAbstract:Abstract Gas–liquid two-phase intermittent Flow pattern and frictional pressure drop in new silicon multi-microchannel were investigated experimentally by means of the IDT high-speed camera mounted together with a Nikon microscope. Each test section consisted of 10 parallel microchannels with 0.1 mm wide and 0.2 mm deep in constant cross-section segment and each microchannel consisted of an array of periodic reentrant cavities. The major two-phase Flow pattern observed was intermittent in the test sections, and the intermittent sub regimes in the new microchannels were different from those displayed in the rectangular straight microchannel. Using nitrogen and deionized water as working fluids, the intermittent sub regime maps for the new multi-microchannel were obtained. Meanwhile, the pressure drops were compared with several existing correlations based on the Homogeneous or separated mixture assumption. Results show that the Homogeneous Flow Model cannot predict the two-phase pressure drop data well, while the separated Flow Model is proposed to provide a better prediction of the two-phase frictional pressure drop. Among the separated Flow Models investigated, the best two correlations of C value can provide mean deviations within less than 16% for all the three microchannels and all the predictions lie in the bound of ±30%.
Souvik Bhattacharyya - One of the best experts on this subject based on the ideXlab platform.
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Homogeneous versus separated two phase Flow Models adiabatic capillary tube Flow in a transcritical co2 heat pump
International Journal of Thermal Sciences, 2008Co-Authors: Neeraj Agrawal, Souvik BhattacharyyaAbstract:Abstract A comparative study of Flow characteristics of an adiabatic capillary tube in a transcritical CO2 heat pump system have been investigated employing separated and Homogeneous two phase Flow Models. Separated Flow Model is employed considering the annular Flow pattern. The Models are based on fundamental equations of mass, momentum and energy which are solved simultaneously. Two friction factor empirical correlations (Churchill, Lin et al.) and McAdams viscosity Model are used. Chisholm correlation is used to calculate slip ratio while void fraction is calculated based on Premoli correlation. Sub-critical and super-critical thermodynamic and transport properties of CO2 are calculated employing a precision in-house property code. The results indicate that both two phase Flow Models predict reasonably well. Discrepancy between the separated Flow Model and Homogeneous Flow Model has a maximum about 8 to 11%. Void fraction is influenced by vapour quality and follows the same trend as vapour quality. Liquid velocity and vapour velocity difference is relatively lower compared to R22.
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non adiabatic capillary tube Flow of carbon dioxide in a transcritical heat pump cycle
Energy Conversion and Management, 2007Co-Authors: Neeraj Agrawal, Souvik BhattacharyyaAbstract:Abstract Flow characteristics of a non-adiabatic capillary tube in a transcritical CO 2 heat pump cycle have been investigated employing Homogeneous Flow Model. The Model is based on fundamental equations of mass, energy and momentum which are solved simultaneously through an iterative process. Chosen empirical correlations are used for calculating viscosity and friction factor. Single and two phase heat transfer coefficients are estimated through appropriate empirical correlations. Sub-critical and super-critical thermodynamic and transport properties of CO 2 are calculated employing precision property subroutines. Three different cases are considered to optimise location of the heat exchange process: only single phase Flow region, only two phase Flow region, and both single and two phase Flow regions. Heat transfer is more prominent in single phase region due to larger temperature difference between suction line fluid and capillary tube fluid. Relatively superior performance is obtained when the heat exchanger is placed in the single phase region. Chances of condensation are lower as refrigerant quality is relatively higher at the time of inception of vaporisation. Design and simulation are employed to investigate the refrigerant Flow behaviour inside the non-adiabatic capillary tube.
K A Triplett - One of the best experts on this subject based on the ideXlab platform.
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gas liquid two phase Flow in microchannels part ii void fraction and pressure drop
International Journal of Multiphase Flow, 1999Co-Authors: K A Triplett, S M Ghiaasiaan, S I Abdelkhalik, A Lemouel, B N MccordAbstract:Abstract Void fraction and two-phase frictional pressure drop in microchannels were experimentally investigated. Using air and water, experiments were conducted in transparent circular microchannels with 1.1 and 1.45 mm inner diameters and in microchannels with semi-triangular (triangular with one corner smoothed) cross-sections with hydraulic diameters 1.09 and 1.49 mm. Gas and liquid superficial velocities were varied in the 0.02–80 m/s and 0.02–8 m/s ranges, respectively, and void fractions were calculated by analyzing photographs taken from the test sections with circular cross-section. Measured void fractions were compared with several correlations. The Homogeneous Flow Model provided the best prediction of the experimental void fractions in bubbly and slug Flow patterns. The Homogeneous Flow Model and all other tested empirical correlations significantly over predicted the void fractions in annular Flow pattern, however. A one-dimensional Model, based on the numerical solution of mass and momentum conservation equations was applied for the calculation of test section pressure drops, using various two-phase friction Models. For bubbly and slug Flow patterns, the two-phase friction factor based on Homogeneous mixture assumption provided the best agreement with experimental data. For annular Flow the Homogeneous mixture Model and other widely used correlations significantly over predicted the frictional pressure drop.