T. Hayat

Bio: T. Hayat is an academic researcher from Quaid-i-Azam University. The author has contributed to research in topics: Homotopy analysis method & Heat transfer. The author has an hindex of 33, co-authored 124 publications receiving 3301 citations. Previous affiliations of T. Hayat include COMSATS Institute of Information Technology & Pakistan Academy of Sciences.

Heat transfer enhancement with Ag–CuO/water hybrid nanofluid

Abstract: Nanofluids are of great importance to researchers as they have significant uses industrially due to their high heat transfer rates. Recently, a new class of nanofluid, “hybrid nanofluid” is being used to further enhance the heat transfer rate. This new model in 3D is employed to examine the impact of thermal radiation, heat generation and chemical reaction over stretching sheet in the presence of rotation. It is concluded from the current research that even in the presence of radiation, heat generation and chemical reaction the heat transfer rate of Hybrid nanofluid is higher than the simple nanofluid.

Rotating flow of Ag-CuO/H 2 O hybrid nanofluid with radiation and partial slip boundary effects.

Abstract: The main object of the present paper is to examine and compare the improvement of flow and heat transfer characteristics between a rotating nanofluid and a newly discovered hybrid nanofluid in the presence of velocity slip and thermal slip. The influence of thermal radiation is also included in the present study. The system after applying the similarity transformations is solved numerically by using the bvp-4c scheme. Additionally, numerical calculations for the coefficient of skin friction and local Nusselt number are introduced and perused for germane parameters. The comparison between water, nanofluid and hybrid nanofluid on velocity and temperature is also visualized. It is observed that the velocity and temperature distributions are decreasing functions of the slip parameter. Temperature is boosted by thermal radiation and rotation. It is found that the heat transfer rate of the hybrid nanofluid is higher as compared to the traditional nanofluid.

Darcy-Forchheimer flow with variable thermal conductivity and Cattaneo-Christov heat flux

Abstract: Purpose The objectives of present communication are threefolds. First is to model and analyze the two-dimensional Darcy-Forchheimer flow of Maxwell fluid induced by a stretching surface. Temperature-dependent thermal conductivity is taken into account. Second is to examine the heat transfer process through non-classical flux by Cattaneo-Christov theory. Third is to derive convergent homotopic solutions for velocity and temperature distributions. The paper aims to discuss these issues. Design/methodology/approach The resulting non-linear system is solved through the homotopy analysis method. Findings An increment in Deborah number β causes a reduction in velocity field f′(η) while opposite behavior is observed for temperature field θ(η). Velocity field f′(η) and thickness of momentum boundary layer are decreased when the authors enhance the values of porosity parameter λ while opposite behavior is noticed for temperature profile θ(η). Temperature field θ(η) is inversely proportional to the thermal relaxation parameter γ. The numerical values of temperature gradient at the sheet − θ′(0) are higher for larger values of thermal relaxation parameter γ. Originality/value To the best of author’s knowledge, no such consideration has been given in the literature yet.

Homogeneous-heterogeneous reactions in the stagnation point flow of carbon nanotubes with Newtonian heating

Abstract: This work addresses the stagnation point flow of carbon nanotubes over an impermeable stretching cylinder with homogeneous-heterogeneous reactions. Modern heat transfer technique (i.e., Newtonian heating) and Carbon nanotubes (CNTs) and water are used to explore the impacts of heat transfer characteristics. Two types of CNTs are used as nanoparticles (i) Single-wall carbon nanotubes (SWCNTs) and (ii) multi-wall carbon nanotubes (MWCNTs). A system of ordinary differential equations is obtained by using suitable transformations. Convergent series solutions are derived via homotopic procedure. Impacts of various pertinent parameters on the velocity, temperature and concentration distributions are discussed graphically. Numerical values of skin friction coefficient and Nusselt number are computed and analyzed.

A Benchmark Study on the Thermal Conductivity of Nanofluids

Abstract: This article reports on the International Nanofluid Property Benchmark Exercise, or INPBE, in which the thermal conductivity of identical samples of colloidally stable dispersions of nanoparticles or “nanofluids,” was measured by over 30 organizations worldwide, using a variety of experimental approaches, including the transient hot wire method, steady-state methods, and optical methods. The nanofluids tested in the exercise were comprised of aqueous and nonaqueous basefluids, metal and metal oxide particles, near-spherical and elongated particles, at low and high particle concentrations. The data analysis reveals that the data from most organizations lie within a relatively narrow band (±10% or less) about the sample average with only few outliers. The thermal conductivity of the nanofluids was found to increase with particle concentration and aspect ratio, as expected from classical theory. There are (small) systematic differences in the absolute values of the nanofluid thermal conductivity among the various experimental approaches; however, such differences tend to disappear when the data are normalized to the measured thermal conductivity of the basefluid. The effective medium theory developed for dispersed particles by Maxwell in 1881 and recently generalized by Nan et al. [J. Appl. Phys. 81, 6692 (1997)], was found to be in good agreement with the experimental data, suggesting that no anomalous enhancement of thermal conductivity was achieved in the nanofluids tested in this exercise.

Solving nonlinear fractional partial differential equations using the homotopy analysis method

Abstract: In this article, the homotopy analysis method is applied to solve nonlinear fractional partial differential equations. On the basis of the homotopy analysis method, a scheme is developed to obtain the approximate solution of the fractional KdV, K(2,2), Burgers, BBM-Burgers, cubic Boussinesq, coupled KdV, and Boussinesq-like B(m,n) equations with initial conditions, which are introduced by replacing some integer-order time derivatives by fractional derivatives. The homotopy analysis method for partial differential equations of integer-order is directly extended to derive explicit and numerical solutions of the fractional partial differential equations. The solutions of the studied models are calculated in the form of convergent series with easily computable components. The results of applying this procedure to the studied cases show the high accuracy and efficiency of the new technique. © 2009 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2010