Kambiz Vafai

Bio: Kambiz Vafai is an academic researcher from University of California, Riverside. The author has contributed to research in topics: Heat transfer & Porous medium. The author has an hindex of 69, co-authored 387 publications receiving 23927 citations. Previous affiliations of Kambiz Vafai include University of California, Berkeley & Pacific Northwest National Laboratory.

Buoyancy-driven heat transfer enhancement in a two-dimensional enclosure utilizing nanofluids

Abstract: Heat transfer enhancement in a two-dimensional enclosure utilizing nanofluids is investigated for various pertinent parameters. A model is developed to analyze heat transfer performance of nanofluids inside an enclosure taking into account the solid particle dispersion. The transport equations are solved numerically using the finite-volume approach along with the alternating direct implicit procedure. Comparisons with previously published work on the basis of special cases are performed and found to be in excellent agreement. The effect of suspended ultrafine metallic nanoparticles on the fluid flow and heat transfer processes within the enclosure is analyzed and effective thermal conductivity enhancement maps are developed for various controlling parameters. In addition, an analysis of variants based on the thermophysical properties of nanofluid is developed and presented. It is shown that the variances within different models have substantial effects on the results. Finally, a heat transfer correlation of the average Nusselt number for various Grashof numbers and volume fractions is presented.

Handbook of porous media

Abstract: General Characteristics and Modeling of Porous Media Multiscale Modeling of Porous Medium Systems Amanda L. Dye, James E. McClure, William G. Gray, and Cass T. Miller Advanced Theories of Two-Phase Flow in Porous Media S. Majid Hassanizadeh Characterization of Fractures and Fracture Network of Porous Media Muhammad Sahimi Thin Porous Media Marc Prat and Tristan Agaesse Magnetically Stabilized and Fluidized Beds in Science and Technology: A Review Teresa Castelo-Grande, Paulo A. Augusto, Angel M. Estevez, Domingos Barbosa, Jesus Ma. Rodriguez, Audelino Alvaro, and Carmen Torrente Lift Generation in Highly Compressible Porous Media: From Red Cells to Skiing to Soft Lubrication Qianhong Wu Transport in Porous Media Theoretical Analysis of Transport in Porous Media: Multiequation and Hybrid Models for a Generic Transport Problem with Nonlinear Source Terms Yohan Davit and Michel Quintard Porous Media Theory for Membrane Transport Phenomena A. Nakayama, Y. Sano, T. Nishimura, and K. Nagase Effective Transport Properties of Porous Media by Modeling Moran Wang Effective Transport through Porous Media under Nonequilibrium Relaxation Conditions Faruk Civan Modeling Approach for Gradient-Based Motion of Microorganisms in Porous Media and Applications in Biosystems Zineddine Alloui and Tri Nguyen-Quang Turbulence in Porous Media Feedback Control for Promoting or Suppressing the Transition to Weak Turbulence in Porous Media Convection Peter Vadasz Advances in Modeling Turbulence Phenomena in Heterogeneous Media: Reactive Systems Marcelo J.S. de Lemos Heat Transfer of Nanofluids in Porous Media Effects of Nanofluids on Convection in Porous Media A. Nield and A.V. Kuznetsov Analyzing Nanofluids Suspension Using the Porous Media Interface Heat Transfer Model Peter Vadasz Thermal Transport in Porous Media Thermal Transport in Highly Porous Cellular Materials Raymond Viskanta Convection of a Bingham Fluid in a Porous Medium Andrew S. Rees High-Heat-Flux Distributed Capillary Artery Evaporators Gisuk Hwang, Chanwoo Park, and Massoud Kaviany Impinging Jets in Porous Media Bernardo Buonomo, Oronzio Manca, and Sergio Nardini Thermohydromechanical Behavior of Poroelastic Media A. Patrick S. Selvadurai Thermogravitational Diffusion in a Porous Medium Saturated by a Binary Fluid Abdelkader Mojtabi, Marie Catherine Charrier-Mojtabi, Bilal El Hajjar, and Yazdan Pedram Razi Geological Applications in Porous Media Digital Petrophysics: Imaging, Modeling, and Experimental Challenges Related to Porous Media in Oil Fields Peter Tilke Modeling of Subsurface CO2 Migration at Geological Carbon Sequestration Sites in Deep Saline Aquifers Sumit Mukhopadhyay Groundwater Flows and Velocity Measurements Shigeo Kimura Geostatistical Simulation and Reconstruction of Porous Media Pejman Tahmasebi and Muhammad Sahimi Microbially Induced Carbonate Precipitation in the Subsurface: Fundamental Reaction and Transport Processes James Connolly and Robin Gerlach

Boundary and inertia effects on flow and heat transfer in porous media

Abstract: The present work analyzes the effects of a solid boundary and the inertial forces on flow and heat transfer in porous media. Specific attention is given to flow through a porous medium in the vicinity of an impermeable boundary. The local volume-averaging technique has been utilized to establish the governing equations, along with an indication of physical limitations and assumptions made in the course of this development. A numerical scheme for the governing equations has been developed to investigate the velocity and temperature fields inside a porous medium near an impermeable boundary, and a new concept of the momentum boundary layer central to the numerical routine is presented. The boundary and inertial effects are characterized in terms of three dimensionless groups, and these effects are shown to be more pronounced in highly permeable media, high Prandtl-number fluids, large pressure gradients, and in the region close to the leading edge of the flow boundary layer.

A critical synthesis of thermophysical characteristics of nanofluids

Abstract: A critical synthesis of the variants within the thermophysical properties of nanofluids is presented in this work. The experimental results for the effective thermal conductivity and viscosity reported by several authors are in disagreement. Theoretical and experimental studies are essential to clarify the discrepancies in the results and in proper understanding of heat transfer enhancement characteristics of nanofluids. At room temperature, it is illustrated that the results of the effective thermal conductivity and viscosity of nanofluids can be estimated using the classical equations at low volume fractions. However, the classical models fail to estimate the effective thermal conductivity and viscosity of nanofluids at various temperatures. This study shows that it is not clear which analytical model should be used to describe the thermal conductivity of nanofluids. Additional theoretical and experimental research studies are required to clarify the mechanisms responsible for heat transfer enhancement in nanofluids. Correlations for effective thermal conductivity and viscosity are synthesized and developed in this study in terms of pertinent physical parameters based on the reported experimental data.

The role of porous media in modeling flow and heat transfer in biological tissues

Abstract: Flow and heat transfer in biological tissues are analyzed in this investigation. Pertinent works are reviewed in order to show how transport theories in porous media advance the progress in biology. The main concepts studied in this review are transport in porous media using mass diffusion and different convective flow models such as Darcy and the Brinkman models. Energy transport in tissues is also analyzed. Progress in development of the bioheat equation (heat transfer equation in biological tissues) and evaluation of the applications associated with the bioheat equation are analyzed. Prominent examples of diffusive applications and momentum transport by convection are discussed in this work. The theory of porous media for heat transfer in biological tissues is found to be most appropriate since it contains fewer assumptions as compared to different bioheat models. A concept that is related to flow instabilities caused by swimming of microorganisms is also discussed. This concept named bioconvection is different from blood convection inside vessels. The works that consider the possibility of reducing these flow instabilities using porous media are reviewed.

I and i

Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

Boundary Layer Theory

Abstract: The boundary layer equations for plane, incompressible, and steady flow are $$\matrix{ {u{{\partial u} \over {\partial x}} + v{{\partial u} \over {\partial y}} = - {1 \over \varrho }{{\partial p} \over {\partial x}} + v{{{\partial ^2}u} \over {\partial {y^2}}},} \cr {0 = {{\partial p} \over {\partial y}},} \cr {{{\partial u} \over {\partial x}} + {{\partial v} \over {\partial y}} = 0.} \cr }$$

Buoyancy-driven heat transfer enhancement in a two-dimensional enclosure utilizing nanofluids

Abstract: Heat transfer enhancement in a two-dimensional enclosure utilizing nanofluids is investigated for various pertinent parameters. A model is developed to analyze heat transfer performance of nanofluids inside an enclosure taking into account the solid particle dispersion. The transport equations are solved numerically using the finite-volume approach along with the alternating direct implicit procedure. Comparisons with previously published work on the basis of special cases are performed and found to be in excellent agreement. The effect of suspended ultrafine metallic nanoparticles on the fluid flow and heat transfer processes within the enclosure is analyzed and effective thermal conductivity enhancement maps are developed for various controlling parameters. In addition, an analysis of variants based on the thermophysical properties of nanofluid is developed and presented. It is shown that the variances within different models have substantial effects on the results. Finally, a heat transfer correlation of the average Nusselt number for various Grashof numbers and volume fractions is presented.

Heat transfer characteristics of nanofluids: a review

Abstract: Research in convective heat transfer using suspensions of nanometer-sized solid particles in base liquids started only over the past decade Recent investigations on nanofluids, as such suspensions are often called, indicate that the suspended nanoparticles markedly change the transport properties and heat transfer characteristics of the suspension This review summarizes recent research on fluid flow and heat transfer characteristics of nanofluids in forced and free convection flows and identifies opportunities for future research

Heat transfer augmentation in a two-sided lid-driven differentially heated square cavity utilizing nanofluids

Abstract: The behaviour of nanofluids is investigated numerically inside a two-sided lid-driven differentially heated square cavity to gain insight into convective recirculation and flow processes induced by a nanofluid. A model is developed to analyze the behaviour of nanofluids taking into account the solid volume fraction χ. The transport equations are solved numerically with finite volume approach using SIMPLE algorithm. Comparisons with previously published work on the basis of special cases are performed and found to be in excellent agreement. The left and the right moving walls are maintained at different constant temperatures while the upper and the bottom walls are thermally insulated. Three case were considered depending on the direction of the moving walls. Governing parameters were 0.01 < Ri < 100 but due to space constraints only the results for 0.1 < Ri < 10 are presented. It is found that both the Richardson number and the direction of the moving walls affect the fluid flow and heat transfer in the cavity. Copper–Water nanofluid is used with Pr = 6.2 and solid volume fraction χ is varied as 0.0%, 8%, 16% and 20%. Detailed results are presented for flow pattern and heat transfer curves.