Papers by Hakan Fehmi Öztop
Analysis of mixed convection of nanofluid in a 3D lid-driven trapezoidal cavity with flexible side surfaces and inner cylinder
International Communications in Heat and Mass Transfer
A B S T R A C T Numerical study of mixed convection in a lid-driven 3D flexible walled trapezoida... more A B S T R A C T Numerical study of mixed convection in a lid-driven 3D flexible walled trapezoidal cavity with nanofluids was performed by using Galerkin weighted residual finite element method. Effects of various pertinent parameters such as Richardson number (between 0.05 and 50), elastic modulus of the side surfaces (between 1000 and 10 5), side wall inclination angle (between 0° and 20°) and solid particle volume fraction (between 0 and 0.04) on the fluid flow and heat transfer characteristics in a 3D lid-driven-trapezoidal cavity were numerically examined. It was observed that these characteristics are influenced when the pertinent parameters change. Flexible side surface can be used as control element for heat transfer rate. Increment and reduction in the space which are provided by the flexible side walls result in heat transfer enhancement and deterioration for side wall inclination angle of 0° and 10°. Average Nusselt number enhances by about 9.80% when the value of the elastic modulus is increased from 1000 to 10 5 for side wall inclination angles of θ = 0°. Adding nanoparticles to the base fluid results in linear increment of heat transfer and at the highest volume fraction, 25.30% of heat transfer enhancement is obtained. A polynomial type correlation for the average Nusselt number along the hot wall was proposed and it has a fourth order polynomial dependence upon the Richardson number and first order dependence upon the solid particle volume fraction.
Effects of magnetic field on 3D double diffusive convection in a cubic cavity filled with a binary mixture
International Communications in Heat and Mass Transfer, 2013
ABSTRACT This paper presents a numerical study of a double diffusive convection in a cubic cavity... more ABSTRACT This paper presents a numerical study of a double diffusive convection in a cubic cavity filled with a binary mixture. The vertical walls are given different temperatures and concentrations. The potential-vorticity formulation in three-dimensional configuration using the finite volume method is utilized in this study. The results are given for Rayleigh number Ra = 105, Prandtl number Pr = 10 and Lewis number Le = 10, characterizing the case of aqueous solutions. The influence of the magnetic field on the structure of the three-dimensional flow, the distribution of temperature and concentration and the different characteristics of heat and mass transfer of the thermal and solutal dominated region are presented.
In this paper, the effects of volumetric heat sources on natural convection heat transfer and flo... more In this paper, the effects of volumetric heat sources on natural convection heat transfer and flow structures in a wavy-walled enclosure are studied numerically. The governing differential equations are solved by an accurate finite-volume method. The vertical walls of enclosure are assumed to be heated differentially whereas the two wavy walls (top and bottom) are kept adiabatic. The effective governing parameters for this problem are the internal and external Rayleigh numbers and the amplitude of wavy walls. It is found that both the function of wavy wall and the ratio of internal Rayleigh number (Ra I) to external Rayleigh number (Ra E) affect the heat transfer and fluid flow significantly. The heat transfer is predicted to be a decreasing function of waviness of the top and bottom walls in case of ðRa I =Ra E Þ > 1 and ðRa I =Ra E Þ < 1.
International Journal of Thermal Sciences, 2011
In this paper, the effects of volumetric heat sources on natural convection heat transfer and flo... more In this paper, the effects of volumetric heat sources on natural convection heat transfer and flow structures in a wavy-walled enclosure are studied numerically. The governing differential equations are solved by an accurate finite-volume method. The vertical walls of enclosure are assumed to be heated differentially whereas the two wavy walls (top and bottom) are kept adiabatic. The effective governing parameters for this problem are the internal and external Rayleigh numbers and the amplitude of wavy walls. It is found that both the function of wavy wall and the ratio of internal Rayleigh number (Ra I ) to external Rayleigh number (Ra E ) affect the heat transfer and fluid flow significantly. The heat transfer is predicted to be a decreasing function of waviness of the top and bottom walls in case of ðRa I =Ra E Þ > 1 and ðRa I =Ra E Þ < 1.
The effect of radiation on laminar and turbulent mixed convection heat transfer of a semitranspar... more The effect of radiation on laminar and turbulent mixed convection heat transfer of a semitransparent medium in a square enclosure was studied numerically using the Finite Volume Method. A structured mesh and the SIMPLE algorithm were utilized to model the governing equations. Turbulence and radiation were modeled with the RNG -model and Discrete Ordinates (DO) model, respectively. For Richardson numbers ranging from 0.1 to 10, simulations were performed for Rayleigh numbers in laminar flow (10 4 ) and turbulent flow (10 8 ). The model predictions were validated against previous numerical studies and good agreement was observed. The simulated results indicate that for laminar and turbulent motion states, computing the radiation heat transfer significantly enhanced the Nusselt number (Nu) as well as the heat transfer coefficient. Higher Richardson numbers did not noticeably affect the average Nusselt number and corresponding heat transfer rate. Besides, as expected, the heat transfer rate for the turbulent flow regime surpassed that in the laminar regime. The simulations additionally demonstrated that for a constant Richardson number, computing the radiation heat transfer majorly affected the heat transfer structure in the enclosure; however, its impact on the fluid flow structure was negligible.
Uploads
Papers by Hakan Fehmi Öztop