Numerical Simulation Of Natural Convection From Seperated Elements And Wire-On-Tube Condenser

Natural convection heat transfer is absent from the consumption of mechanical power. It has an important practical significance to study the enhancement of natural convection heat transfer. The mechanism of natural convection from separated elements is more complicated than that from a single element. The former is also of large importance in engineering. An array of tubes or screens which are typical examples of separated elements, are used widely in industry. Tube arrays can be found in the area of heat exchanger, solar collector, electronic cooling and electrodes used in the plating bath. Wire-on-tube condensers are a typical example of the screens. It was widely used in refrigeration.The detail of the implementation of the specified pressure boundary condition for the natural convection in an infinite space was given out first. This method was applied for the simulation of natural convection from a cylinder in an infinite space in Ra range of 10-2 to 107 with the high resolution scheme and primitive variable method. Numerical results were compared with other experimental results, numerical results and theoretical results. The correlation between the average heat transfer coefficient and the Ra was given out based on present numerical results.It is the first time to perform a systematical numerical simulation of natural convection from tube arrays in an infinite space with multiple tubes. The effect of the Ra, distance between tubes to the average heat transfer coefficient ,local heat transfer coefficient and the total heat transfer coefficient of the tube arrays were studied wildly.The comparison between other experimental results were good.It is the first time to perform a numerical simulation of tube arrays in an finite space with multiple tubes. The effect of the Ra, distance between tubes to the average heat transfer coefficient and the total heat transfer coefficient of the tube arrays were studied wildly. It was found that the placement of shrouding wall can enhance the natural convection heat transfer.Three dimensional numerical simulation was also performed for the tube-on-wire condenser in an infinite space. The effects of Ra and the distance between the vertical wire were studied. It was found that both of them have an important effect to the heat transfer coefficient.