Energy
S. Bagheri; S. A. A. Oloomi; S. A. A. Mirjalily; A. Zare-Shahabadi
Abstract
The phenomenon of nuclear boiling has always been recognized suitable for heat transfer between different boiling regimes. Study on boiling is considered as a new field which meets different research and industrial needs such as heat transfer in nuclear reactors, cooling units, rocket motors, electronic ...
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The phenomenon of nuclear boiling has always been recognized suitable for heat transfer between different boiling regimes. Study on boiling is considered as a new field which meets different research and industrial needs such as heat transfer in nuclear reactors, cooling units, rocket motors, electronic equipment cooling, batteries, etc. In this study, a chamber with immiscible fluid, water, steam, and air, having a side wall with uniform heat flux has been studied in 3D. To do so, we first considered the prediction of the heat flux interval for which the boiling occurs in the form of nuclear boiling. In this study, two-phase fluid volume (VOF) approach was used for modelling boiling on the vertical wall and two-phase flow. In this research, Ansys software package was used for numerical modelling and numerical simulation. Distribution of the velocity field follows more uniform pattern in dimensionless heights less than 0.9. In this study, bubbles are only present near a wall with heat flux that has a lower Rayleigh number. Also, existence of these bubbles on the wall, which prevents fluid infiltration, affects vortices caused by natural convection. However, the general and uniform patterns of vortices remain unchanged in most part of the fluid, which is because of the limited amount of bubbles near the wall with heat flux. Natural convection increases the height of fluid inside the chamber, which leads to the formation of stronger vortices at a dimensionless height of 0.9 that has a high Raleigh number due to high heat flux. In this case, the continuous use of heat flux gives rise to the production of bubbles over time.
H. Abazari Bahnemiri; S. A. A. Oloomi; S. A. A. Mirjalily; A. Zare-Shahabadi
Abstract
In the present research, effects of nanoparticles and changing of tube diameter have been scrutinized on heat transfer parameters in the shell and helically coiled tube heat exchanger. A CFD analysis and also a modeling of the mentioned heat exchager have carried out by writing a code in MATLAB software ...
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In the present research, effects of nanoparticles and changing of tube diameter have been scrutinized on heat transfer parameters in the shell and helically coiled tube heat exchanger. A CFD analysis and also a modeling of the mentioned heat exchager have carried out by writing a code in MATLAB software for two regimes involving forced convection heat trasnfer in single phase fluid flow and sub-cooled boiling. In the case under analysis, considered nanoparticles in this research was Nickel nanoparticles with 0.1 and 1% volumetric concentration. Based on the results, both going up of volume concentration of nanoparticles and increasing of tube diameter are cause to make better heat transfer parameters. In truth, heat transfer coefficient and Nusselt number have been enhanced by 0.1 and 1 % volumetric concentration of Nickel nanoparticles.
