Begell House Inc.
Heat Transfer Research
HTR
1064-2285
42
8
2011
Thermal Buoyancy-Aided Flow around a Heated/Cooled Spherical Particle
689-710
Partha P.
Gopmandal
Department of Mathematics, Indian Institute of Technology Kharagpu, Kharagpur-721302, West Bengal, India
Somnath
Bhattacharyya
Department of Mathematics, Indian Institute of Technology, Kharagpur, India
Mixed convective heat transfer around a heated or cooled sphere is analyzed for a wide range of Reynolds and Richardson numbers. The complexity of numerical algorithms coupling the momentum and heat transfer equations limits the number of such direct simulation. The coupled flow and thermal field are solved through an upwind based finite volume method. The numerical accuracy of our code was validated by comparing with several published results. The role of the temperature-induced baroclinic vorticity on the wake is analyzed. The increase or decrease of surface temperature delays or enhances, respectively, the critical Reynolds number for flow separation. The buoyancy-induced jet due to the heated sphere delays the flow separation and enhances the drag coefficient as well as the rate of heat transfer. For a cooled sphere, the opposing effect on the inertial forces lowers the critical Re for flow separation, the wake size increases and the thermal boundary layer becomes thicker compared to the Ri ≥ 0 case. The drag coefficient and rate of heat transfer are evaluated as functions of Ri (−0.5 ≤ Ri ≤ 1.5) and Re (Re ≤ 200), respectively. The correlation formula for the Nusselt number valid for forced convection is extended for the mixed convection regime by introducing the concept of effective temperature. Our computed results for heat transfer are found to be close to the estimated values obtained by the modified correlation formula for a moderate range of Reynolds numbers.
Mixed Convection of Water-Based Nanofluids in a Lid-Driven Square Enclosure with a Heat Source
711-735
Kamil
Kahveci
Department of Mechanical Engineering, Faculty of Engineering and Architecture, Trakya University, 22030, Edirne, Turkey
Elif Buyuk
Ogut
Vocational School of Gebze, Kocaeli University, 1410 Çayirova-Kocaeli, Turkey
This study is concerned with mixed convection of water-based nanofluids in a lid-driven square enclosure with a constant heat flux heater. The governing equations are solved numerically using the differential quadrature method. The computational results are obtained for the heater lengths of 0.25, 0.50, and 0.75. The Grashof number is kept at a constant value of 104, and the Reynolds number is varied so that the Richardson number will have values in the range of 0.1 to 10. The nanoparticles volume fraction φ is varied as 0%, 5%, and 10% and the value of the ratio of the nanolayer thickness to the original particle radius η is fixed to 0.1. The results show that the presence of nanoparticles in the base fluid causes a significant enhancement of heat transfer. The results also show that the heat transfer rate increases considerably with a decrease in the Richardson number and the length of the heater.
Heat Transfer Flow of Steady Couple Stress Fluids between Two Parallel Plates with Variable Viscosity
737-780
Muhammad
Farooq
Department of Mathematics,
National University of Computer and Emerging Sciences, Peshawar, Pakistan
Saeed
Islam
Department of Mathematics, Abdul Wali Khan University Mardan, 23200 Pakistan
M. T.
Rahim
Department of Mathematics, National University of Computer and Emerging Sciences, Peshawar, Pakistan
Tahira
Haroon
Department of Mathematics, COMSATS Institute of Information Technology, Islamabad, Pakistan
In this paper, we study the nonisothermal flow of couple stress fluids between two heated parallel plates for a Reynolds viscosity model. Depending on the relative motion of the plates, we consider four different problems, namely, the plane Couette flow, plug flow, plane Poiseuille flow, and generalized plane Couette flow. Approximate analytical expressions for velocity and temperature distribution are obtained by using the perturbation technique. The influence of different parameters on the flow pattern has been discussed and presented with the help of graphs.