Computational Fluid Dynamics (CFD)
Sajad Rezazadeh; Mohammadreza Mataji Amirrud; Mohammad Raad; Davoud Abbasinezhhad Fallah
Abstract
A numerical simulation of laminar fluid flow and heat transfer over built-in cylinders in a channel is presented. Effects of cylinders that located in a rectangular channel with constant wall temperature on flow and heat transfer have been investigated by the drag coefficient on cylinders wall, skin-friction ...
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A numerical simulation of laminar fluid flow and heat transfer over built-in cylinders in a channel is presented. Effects of cylinders that located in a rectangular channel with constant wall temperature on flow and heat transfer have been investigated by the drag coefficient on cylinders wall, skin-friction factor on channel wall, Strouhal number, pumping factor, Nusselt number, and Performance Index (PI) factor, which denote the heat transfer in terms of the pressure drop. Results are validated by the most reliable published works in the literature. Effects of Reynolds number and blockage ratio (β) for the equilateral triangular cylinder for 120≤Re≤180 and 0.15≤β≤0.55 on flow and heat transfer are investigated with more details. Results indicated that by increasing Re for constant blockage ratio, the drag coefficient, Strouhal number, and Nusselt number increase; but the skin-friction coefficient, pumping factor, and PI factor decrease subsequently. Additionally, with an increase in blockage ratio at constant Re, the drag coefficient, skin-friction coefficient, pumping factor, and Strouhal number grow up; but Nusselt number diminishes and PI factor has an optimum range. Furthermore, results reveal that variation in blockage ratio has more significant effects on the flow and heat transfer than variation in Reynolds number.
Thermodynamics and Cumbustion
Satyananda Tripathy; Manmatha K Roul; Akshaya K Rout
Abstract
Theoretical investigation of turbulent flame impinging normally on plane surfaces isdone to determine the average Nusselt number and the plate heat flux distribution as functions of jet Reynolds number, equivalence ratio, and separation distance. The analysis is established on the mathematical formulation ...
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Theoretical investigation of turbulent flame impinging normally on plane surfaces isdone to determine the average Nusselt number and the plate heat flux distribution as functions of jet Reynolds number, equivalence ratio, and separation distance. The analysis is established on the mathematical formulation of the governing equations for conservation of mass, momentum, and energy. The turbulence phenomenon is analyzed with the help of the RNG k-ε turbulence model. The radiative heat transfer model has been designed by using the Discrete Ordinates radiation model. Results show that the heat flux graduallyincreases with the radial distance towards the plate center and attains a maximum value at a location slightly away from the stagnation point. The peak value in the local heat flux comes closer to the stagnation point when the height between the plates and the nozzle increases. Effects of variation of dimensionless separation distance on heat transfer characteristics are investigated. It is observed that heat flux gradually improves when the value of separation distance changes from 12 to 8 and decreases near the stagnation region with the further decrease in separation distance from 8 to 4.
Heat and Mass Transfer
Hasan Najafi Khaboshan; Hamid Reza Nazif
Abstract
In this research, the convective heat transfers of turbulent water fluid flow in alternating oval tubes is studied using computational fluid dynamics. The purpose of the study is to analyze the heat transfer enhancement and secondary internal flows under different alternate angles. Also, comparing the ...
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In this research, the convective heat transfers of turbulent water fluid flow in alternating oval tubes is studied using computational fluid dynamics. The purpose of the study is to analyze the heat transfer enhancement and secondary internal flows under different alternate angles. Also, comparing the effect of two schemesfor the domain discretization to be used in the solution variables’ gradients on simulation results is investigated. The secondary flow causes an increase in the numbers of multi-longitudinal vortices (MLV) by changing the angle of pitches. These phenomena permit the cold fluid flow to stream in more paths from center to tube wall and better condition for mixing of fluids. Consequently, the heat transfer enhances by using the alternating oval tubes. However, forming the multi-longitudinal vortices causes an increase in pressure drop. Also, by raising the angle of pitches, the friction factor and the average of Nusselt number are amplified. It is also observed that the average heat transfer coefficient in the transition range is more than other areas. The mean Nussult numbers of this kind of tubes in the angles of 40, 60, 80, and 90 improved 7.77%, 14.6%, 16.93%, and 24.42%, respectively in comparison with the round tube. The performance evaluation criteria (PEC) for all alternating oval tubes under the constant inlet velocity boundary condition indicated that the highest value (PEC=1.09) had been obtained at the lowest Reynolds number (Re=10,000) in the alternating oval tube 90°.
Heat and Mass Transfer
M. Nasiri; B. Ghasemi
Abstract
This paper modeled heating air of a room through examining free convection in a 3D chamber. The chamber had cold and hot sources with Tc and Th temperatures, respectively. Its other walls were adiabatic. This study aimed at predicting effect of temperature difference, displacement of hot and cold sources ...
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This paper modeled heating air of a room through examining free convection in a 3D chamber. The chamber had cold and hot sources with Tc and Th temperatures, respectively. Its other walls were adiabatic. This study aimed at predicting effect of temperature difference, displacement of hot and cold sources and their aspect ratio on flow field, temperature and heat transfer rate. To conduct the study, mass conservation, momentum and energy equations were applied in laminar and 3D states while assuming fluid constant properties, except density, in the power of buoyancy (Boussinesq approximation). Final difference method (FDM) was used for numerical solution of the governing equations based on the volume control and SIMPLE algorithm. According to the modeling results, the most favorable temperature distribution in the chamber (room) was obtained when the heat source (radiator) was located on the wall under the cold source (window). Reducing the distance between the two sources would result in increasing heat transfer from the heating sources.
