Abstract
The paper presents results of flow visualization and mass transfer studies for fully developed turbulent flow of air in a square section wind tunnel with repeated chamfered rib roughness on the bottom of the tunnel (rib head chamfer angles ϕ of -15°, 0°, and 15°; relative roughness pitchp/e = 3, 5, 7.5, and 10). Direct video recordings of flow patterns were made using a simple technique of particles visualization. For the positively chamfered closely spaced ribs (p/e <- 5) vigorous vortex shedding has been seen compared to the square or negatively chamfered ribs, which is found to be a function of the Reynolds number. For the widely spaced ribs, the study shows flow separation at the ribs and reattachment in the inter-rib region. Local mass transfer studies, based on the variation in colour of cobaltous chloride solution impregnated paper due to evaporation of water, showed a significant improvement in mass transfer rate in the recirculating region in the wake of ribs with the change in the chamfer angle from -15° to 15°. The positively chamfered 15° ribs are found to be better than square section ribs atp/e <- 7.5. The performance of negatively chamfered ribs is found to be poor compared to other ribs irrespective of the relative roughness pitch.
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Rajendra Karwa: He received his B.E. degree in Mechanical Engineering from University of Jodhpur, Jodhpur (India) and M.E. (Honors) in Mechanical Engineering (Thermal Engineering) from the same university. He obtained his Ph.D. in 1998 from IIT Roorkee, India. Currently he is working as associate professor in Faculty of Engineering, Jai Narain Vyas University, Jodhpur, India since 1994. His areas of interest are heat transfer enhancement, solar energy and exergy analysis.
B.K. Maheshwari: He received his B.E. degree in Mechanical Engineering from University of Jodhpur, Jodhpur (India) and M.E. from the same university. Currently he is working as assistant professor in Faculty of Engineering, Jai Narain Vyas University, Jodhpur, India and also pursuing his Ph.D. course. His area of interest is heat transfer enhancement.
Nitin Karwa: He received his B.E. (Honours) degree in Mechanical Engineering from Jai Narain Vyas University, Jodhpur (India) and M.Tech. degree in 2005 from IIT Delhi, India. He worked on a project on spray technology for 2-1/2 years with GE, Bangalore (India) and is presently pursuing his Ph.D. course at Technical University Darmstadt, Germany. His areas of interest are heat transfer enhancement and spray cooling.
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Karwa, R., Maheshwari, B.K. & Karwa, N. Flow visualization and local mass transfer studies for turbulent flow in a wind tunnel with chamfered ribs. J Vis 11, 205–212 (2008). https://doi.org/10.1007/BF03181708
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DOI: https://doi.org/10.1007/BF03181708