The heat-pipe resembling action of boiling bubbles in endovenous laser ablation

Endovenous laser ablation (EVLA) produces boiling bubbles emerging from pores within the hot fiber tip and traveling over a distal length of about 20 mm before condensing. This evaporation-condensation mechanism makes the vein act like a heat pipe, where very efficient heat transport maintains a constant temperature, the saturation temperature of 100°C, over the volume where these non-condensing bubbles exist. During EVLA the above-mentioned observations indicate that a venous cylindrical volume with a length of about 20 mm is kept at 100°C. Pullback velocities of a few mm/s then cause at least the upper part of the treated vein wall to remain close to 100°C for a time sufficient to cause irreversible injury. In conclusion, we propose that the mechanism of action of boiling bubbles during EVLA is an efficient heat-pipe resembling way of heating of the vein wall

Bubble detachment criteria: some criticism of \'Das Abreissen von Dampfblasen an festen Heizflachen\'

This note discusses criteria for bubble detachment in general and presents some criticism on the article 'Das Abreissen von Dampfblasen an festen Heizflächen' of J. Mitrovic [Int. J. Heat Mass Transfer 26(7), 955-963 (1983)]. Force balances on a bubble as a whole should only be used in conjunction with some special bubble shape that only occurs at detachment if detachment criteria are to be derived. The criterion of Mitrovic is not useful

Measurement and prediction of solid sphere trajectories in accelerated gas flow

Trajectories are measured and compared with computed trajectories of solid particles with a diameter of 1–2 mm in downward gas flow near a solid cylinder with a diameter, dc, of 25 mm. The Reynolds number based on dc has been varied from 3000–13,000. The particle Reynolds numbers, based on the relative velocity |UG - Up|, ranged from 0 to 2000. Of all forces other than gravity, drag is dominant, although the pressure gradient and added mass forces for Rec > 10,000 have the same order of magnitude. The Basset force can be neglected. The correlation [3], originally derived by Sridhar and Katz (1995) for the lift force coefficient of bubbles, has been found to be appropriate for freely moving solid particles with shear number less than 0.04

Bubble deformation in nucleate boiling

Various aspects of boiling bubble deformation and oscillation have been examined or re-examined with an EulerLagrange approach. Anisotropic bubble deformation is easily converted into the acoustically powerful isotropic breathing mode. The structure of the added mass matrix involved explains this conversion. With a perturbation analysis, resonance cases in which this conversion is amplified or in which several different bubble sizes at a time are excited have been identified. The effects of finite disturbance amplitude and the proximity of the wall on oscillation frequency have been quantified. Experimental validation is reported of frequency reduction by the presence of the wall or by fixation of the bubble foot to a wall

Foreword

This is a time when hardback books are disappearing from university libraries and the gathering of knowledge becomes quick and flashy through Internet tools. But although hardback encyclopedias might be obsolete, there is still a need for thorough summaries that are well organized and well balanced and contain concentrated information in an accessible format. Such is the book you are reading now.\u3cbr/\u3e\u3cbr/\u3eThe books written by Landau and Lifshitz have always been some of my favorite learning books. Although they are overconcise, these books cover many topics in a thorough way. However, it is difficult to imagine that two authors would write a series of books like that in modern times. Two authors simply would not have the time anymore. That is also why the present book is written by several authors, each of them contributing in a particular field of expertise. The book is focused on flow with heat transfer in small-diameter tubes, but this topic is dealt with in an extensive way, summarizing most of the work of the past decades in this area. This makes the book a good read for both beginners and more experienced researchers in this area.\u3cbr/\u3e\u3cbr/\u3eThe topic has been very popular and was elaborated on all over the world, in famous laboratories in Israel, Switzerland, Germany, Brazil, China, and many other countries. It therefore stands to reason that the authors of this book also originate from various countries. We must admire them for their ability to conceive and realize a book with nine chapters without doubling certain aspects. The editor, Sujoy Kamar Saha, must have had a great hand in organizing in the endeavor.\u3cbr/\u3e\u3cbr/\u3eThis is a book that is bound to last for a long time in our libraries and on our laptops.\u3cbr/\u3

Prediction of dynamic contact angle histories of a bubble growing at a wall

A fast growing boiling bubble at the verge of detaching from a plane wall is usually shaped as a truncated sphere, and experiences various hydrodynamic forces due to its expansion and the motion of its center of mass. In a homogeneous flow field, one of the forces is the so-called bubble growth force that is essentially due to inertia. This force is usually evaluated with the aid of approximate expressions [Int. J. Heat Mass Transfer 36 (1993) 651, Int. J. Heat Mass Transfer 38 (1995) 2075]. In the present study an exact expression for the expansion force is derived for the case of a truncated sphere attached to a plane, infinite wall. The Lagrange–Thomson formalism is applied. Two Euler–Lagrange equations are derived, one governing the motion of the center of mass, the other governing expansion a kind of extended Rayleigh–Plesset equation. If a constitutive equation for the gas–vapor content of the bubble is given, initial conditions and these two differential equations determine the dynamics of the growing truncated sphere that has its foot on a plane, infinite wall. Simulations are carried out for a given expansion rate to predict the history of the dynamic contact angle. The simulations increase the understanding of mechanisms controlling detachment, and yield realistic times of detachment

On the importance of various forces on spherical particles accelerated in airflow near a cylinder

No abstract