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Numerical study on the two-phase flow pattern due to the presence of bubbles caused by nucleate boiling in a tall cavity containing two incompatible fluids
Abstract:   (71 Views)
Among the methods of heat transfer, the bubble boiling phenomenon as a method with high heat transfer coefficient is considered by many researchers. On the other hand, natural convection and nucleate boiling have interactions on each other which lead to strengthening and weakening each other in different situations. In the present numerical study, a three-dimensional tall cavity filled with incompatible fluids of water, vapor, and air with a uniform heat flux on the main wall has been investigated.  At first in this study, the range of the critical heat flux for nucleate boiling has been predicted and then, the interaction between the natural convection and nucleate boiling and the effective parameters on heat transfer have been studied.
 The results show that increase in the Raleigh number due to increase in the dimensionless height of fluid in the tall cavity  has improved the enhance of separation of gas bubbles due to boiling pheromone on the wall surface and as a result,  has delayed the film boiling regime.  However, in lower dimensionless heights of fluid in the cavity  (lower Rayleigh number), streams of fluid due to natural convection haven’t got enough strength to separate bubbles from the surface and bubbles slip on the surface instead of separating from it. In addition, vortexes of fluid caused by natural convection, first form in the down parts of the cavity and then they gradually develop and be active in other parts of the fluid. Also in this paper is well shown that the production and separation of the gas bubbles cause turbulence in the fluid flows. 
Keywords: Nucleate Boiling, vertical Surface, Natural Convection, Two Phase Flow, Tall Cavity
     
Type of Study: Research | Subject: Special
Received: 2021/08/3 | Accepted: 2021/10/2
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مجله علمی تخصصی مهندسی مکانیک تبدیل انرژی Journal of Energy Conversion
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