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Air-water flow in a $90^{\circ}$ sharp elbow (mitre bend) is studied in a new purpose-built experimental facility at the University of Sheffield. For the first time, the two-phase flow is investigated in a mitre bend for water-based Reynolds numbers $R e_w=5600-12800$ and water-to-air mass flow rate ratios $\dot{m}_w / \dot{m}_a=10-3800$. Four different flow patterns are observed in the upstream pipe (plug, slug, slug-annular and annular) by using a high-speed high-resolution camera. The results show that the perturbation length upstream and downstream of the elbow and the pressure drop are significantly affected by the flow patterns. Two new values of the Lockhart-Martinelli parameter $C$ are found for the pressure drop across the elbow.
90° sharp elbow, flow patterns, pressure drop, two-phase flow
[1] Brennen, C., Fundamentals of Multiphase Flow. Cambridge University Press, 2005.
[2] Thome, J., Engineering data book III, 2004.
[3] Baker, O., Simultaneous flow of oil and gas. Oil and Gas Journal, 53, pp. 185–195, 1954.
[4] Mandhane, J., Gregory, G. & Aziz, K., A flow pattern map for gas-liquid flow in hori- zontal pipes. International Journal of Multiphase Flow, 1(4), pp. 537–553, 1974. https://doi.org/10.1016/0301-9322(74)90006-8
[5] Cheng, L., Ribatski, G. & Thome, J., Two-phase flow patterns and flow-pattern maps: fundamentals and applications. Applied Mechanics Reviews, 61(5), p. 050802, 2008. https://doi.org/10.1115/1.2955990
[6] Lockhart, R. & Martinelli, R., Proposed correlation of data for isothermal two- phase, two-component flow in pipes. Chemical Engineering Progress, 45(1), pp. 39–48, 1949.
[7] Chisholm, D., A theoretical basis for the Lockhart-Martinelli correlation for two-phase flow. International Journal of Heat and Mass Transfer, 10(12), pp. 1767–1778, 1967. https://doi.org/10.1016/0017-9310(67)90047-6
[8] Qiao, S., Mena, D. & Kim, S., Inlet effects on vertical-downward air–water two- phase flow. Nuclear Engineering and Design, 312, pp. 375–388, 2017. https://doi.org/10.1016/j.nucengdes.2016.04.033
[9] Kim, S., Park, J., Kojasoy, G. & Kelly, J., Local interfacial structures in horizontal bub- bly flow with 90-degree bend. International Conference on Nuclear Engineering, 2, pp. 219–226, 2006.
[10] Kong, R. & Kim, S., Characterization of horizontal air–water two-phase flow. Nuclear Engineering and Design, 312, pp. 266–276, 2017. https://doi.org/10.1016/j.nucengdes.2016.06.016
[11] Mishima, K. & Hibiki, T., Some characteristics of air-water two-phase flow in small diameter vertical tubes. International Journal of Multiphase Flow, 22(4), pp. 703–712, 1996. https://doi.org/10.1016/0301-9322(96)00010-9
[12] Zhao, T. & Bi, Q., Pressure drop characteristics of gas–liquid two-phase flow in verti- cal miniature triangular channels. International Journal of Heat and Mass Transfer, 44(13), pp. 2523–2534, 2001. https://doi.org/10.1016/s0017-9310(00)00282-9
[13] Lee, H. & Lee, S., Pressure drop correlations for two-phase flow within horizontal rect- angular channels with small heights. International Journal of Multiphase Flow, 27(5), pp. 783–796, 2001.
https://doi.org/10.1016/s0301-9322(00)00050-1
[14] Kim, S., Kojasoy, G. & Guo, T., Two-phase minor loss in horizontal bubbly flow with elbows: 45-degree and 90-degree elbows. Nuclear Engineering and Design, 240(2), pp. 284–289, 2008. https://doi.org/10.1016/j.nucengdes.2008.08.019
[15] Lemmon, E., Huber, M. & McLinden, M., NIST Standard ReferenceDatabase 23: Reference Fluid Thermodynamic and Transport Properties - REFPROP. 9.0., 2010.
[16] Taylor, J., An introduction to error analysis 2nd edn. University Science Books, Sausalito, CA, 1997.