Targeted heat transfer augmentation in circular tubes using a corona jet

Natural convection heat transfer can be noticeably enhanced by corona wind in tubes and channels. A corona-induced secondary flow may be generated in tubes with no major changes in the geometry, or causing any noise or vibration. In this investigation, it is shown that the eccentric configuration of a wire electrode inside a tube forms a local jet along the eccentricity direction, which impinges on the tube wall and improves the local heat transfer. Since the direction of the corona jet is determined by the eccentricity direction of the electrode, the jet may be oriented properly to target the desired spots.     

Blow‐up phenomena for a system of semilinear parabolic equations with nonlinear boundary conditions

This paper deals with the blow‐up phenomena for a system of parabolic equations with nonlinear boundary conditions. We show that under some conditions on the nonlinearities, blow‐up occurs at some finite time. We also obtain upper and lower bounds for the blow‐up time when blow‐up occurs. Copyright © 2014 John Wiley & Sons, Ltd.     

“Bubble Bunch” phenomenon in operation of a bubble column

While studying the operation of a rectangular bubble column in laboratory scale, it was observed that under certain circumstances tiny bubbles attach to larger bubbles without causing them to coalesce. In other words, bubbles with large diameters (d > 5 mm) swept tiny bubbles (d < 1 mm) in their way to the top of the column resulting in grapelike clusters of bubbles. This phenomenon was named “bubble bunch” by us and its effect on total gas holdup and interfacial area was discussed. Although it was found to have almost no affect on gas holdup, bubble bunch can increase the interfacial area up to 10% more than what is anticipated in the literature. The process of film thinning was modeled for this phenomenon and coalescence efficiency was calculated as a function of interfacial tension.