In order to examine the laminar convective heat transfer of nanofluid, experiments carried out using silver-oil nanofluid in a concentric annulus with outer constant heat flux as boundary condition. Silver-oil nanofluid prepared by Electrical Explosion of Wire technique and observed no nanoparticles agglomeration during nanofluid preparation process and carried out experiments. The average size of particles established to 20 nm. Nanofluids with various particle weight fractions of 0.12%wt., 0.36%wt. and 0.72%wt. were employed. The nanofluid flowing between the tubes is heated by an electrical heating coil wrapped around it. The effects of different parameters such as flow Reynolds number, diameter ratio and nanofluid particle concentration on heat transfer coefficient are studied. Results show that, heat transfer coefficient and Nusselt number increased by using naanofluid instead of pure oil. Maximum enhancement of heat transfer coefficient occurs in 0.72% wt. also results indicate that heat transfer coefficient increase slightly by using low wt. concentration of nanofluids.

Background: Klebsiella pneumoniae (K. p) is one of the pathogens causing hospital-acquired infections, which has been prioritized by the WHO due to its increased resistance to a variety of antibiotics. Cytokines are pro-inflammatory markers and their secretion in macrophages changes in pulmonary pneumoniae. Carbon nanotubes (CNTs), as novel approaches in drug delivery, despite their pros, may induce acute inflammation in animal lungs. Objective(s): The present study aimed to evaluate the effects of functionalized multi walled carbon nanotubes and ciprofloxacin (f-MWCNTs+cip) combination on the immune responses, by cytokine assessment in the treated THP1-derived macrophages and the A549 cell line infected with resistant and ATCC 700, 603 K. p strains. Methods: Nanofluid containing f-MWCNTs were prepared using ultrasonic method. THP1 cells were differentiated to macrophages and were infected with resistant and ATCC 700, 603 K. p. The infected THP1–, derived macrophages and A549 cells were treated with f-MWCNT+cip. ELISA and real-time PCR assays were performed to assess the TNF-α,and IL-1β,cytokines in the THP1-derived macrophages and A549 cell line before and after the treatments. Results: The level of TNF-α,and IL-1β,cytokines after exposure to the f-MWCNT+ cip were upregulated significantly, in the resistant and ATCC K. p strains, from infected THP1–, derived macrophages and the A549 cell line in comparison with control. Conclusions: Our findings showed that f-MWCNTs noticeably upregulated the expression of IL-1β,and TNF-α,genes in comparison with controls. Combination of f-MWCNTs+ciprofloxacin induced inflammatory response in both infected THP1-derived macrophages and A549 cell lines compared to the ciprofloxacin treatment.

The effect of thermal and solutal buoyancy induced by a discrete source of heat and mass transfer in a square duct under the influence of magnetic field, especially at the turbulent regime for the first time is reported. Al2O3/water nanofluid is used with constant heat flux from three discrete heat sources. In the present study, the effects of Reynolds number (100 to 3000), particle volume fraction (0 to 2%) and magnetic field (Ha = 10 to 90) on the Nusselt number, pressure drop and wall temperature (at the axial and height directions) are represented graphically and discussed quantitatively. Two percent Al2O3-water nanofluid under Ha = 10 can produce 81% increase in Nusselt number with only 60% increase in pressure drop when compared to base fluid at Re = 100. Four percent enhancement in nanofluids cooling effect in the vicinity of a centre of the final heat source can be utilized in hot spots cooling.

In this paper, a theoretical investigation has been carried out to study the combined effect of AC electric field and temperature depended internal heat source on the onset of convection in a porous medium layer saturated by a dielectric nanofluid. The model used for nanofluid incorporates the combined effect of Brownian diffusion, thermophoresis and electrophoresis, while for porous medium Darcy model is employed. The flux of volume fraction of a nanoparticle with the effect of thermophoresis is taken to be zero on the boundaries and the eigenvalue problem is solved using the Galerkin method. Principle of exchange of stabilities is found to be valid and subcritical instability is ruled out. The results show that increase in the internal heat source parameter HS, AC electric Rayleigh-Darcy number Re, the Lewis number Le, the modified diffusivity ratio NA and the concentration Rayleigh-Darcy number Rn are to hasten the onset of convection. The size of convection cells decreases with increasing the internal heat source parameter HS and the AC electric Rayleigh-Darcy number Re.

In this study, forced convection heat transfer of non-Newtonian nanofluids in a horizontal tube with constant wall temperature under turbulent flow conditions was investigated using computational fluid dynamics tools. For this purpose, non-Newtonian nanofluids containing three types of nanoparticles (Al2O3, TiO2 and CuO) with carboxymethylcellulose aqueous solution as a liquid single phase with three average particle sizes of 10, 25 and 40 nm nanofluids were investigated. Effects of nanoparticle type and Peclet number on the convective heat transfer coefficient were investigated in fully turbulent region of a horizontal tube. A correlated equation was obtained for Nusselt number using the dimensionless numbers by applying the simulation results. Results showed that the correlated data were in very good agreement with the experimental ones obtained from the literature. The maximum error was 12%.

The present paper deals with the linear thermal instability analysis of viscoelastic nanofluid saturated porous layer. We consider a set of new boundary conditions for the nanoparticle fraction, which is physically more realistic. The new boundary condition is based on the assumption that the nanoparticle fraction adjusts itself so that the nanoparticleflux is zero on the boundaries. We use Oldroyd-B type viscoelastic fluid that incorporates the effects of Brownian motion and thermophoresis. Expressions for stationary and oscillatory modes of convection have been obtained in terms of the Rayleigh number, which are found to be functions of various parameters. The numerical results have been presented through graphs.

Transient natural convection is numerically investigated in an enclosure using variable thermalconductivity, viscosity, and the thermal expansion coefficient of Al2O3-water nanofluid. The study has beenconducted for a wide range of Rayleigh numbers (103≤ Ra ≤ 106), concentrations of nanoparticles (0% ≤ ϕ ≤ 7%), the enclosure aspect ratio (AR =1), and temperature differences between the cold and hot walls (Δ T= 30). Transientparameters such as development time and time-average Nusselt number along the cold wall are also presented as anon-dimensional form. Increasing the Rayleigh number shortens the non-dimensional time of the initializing stage. By increasing the volume fraction of nanoparticles, the flow development time shows different behaviors forvarious Rayleigh numbers. The non-dimensional development time decreases by enhancing the concentration ofnanoparticles.

Heat pipe is an effective device for heat transferring. Using nanofluid as working fluid can significantly increase heat pipe thermal performance. But rate of the performance improvement, is dependent on parameters of the suspended nanoparticles in nanofluid. In this article, by considering nanoparticle volume fractions and diameters as design variables and the difference between the wall temperature of evaporator and condenser and liquid pressure drop as objective functions, the heat pipe performance has optimized. The used heat pipe is a cylindrical heat pipe with aluminum oxide nanofluid as working fluid. Heat pipe thermal performance while using nanofluid has modeled by CFD method and then GEvoM software has used to relate between design variables and objective functions. Using the modified NSGAII approach, pareto front has plotted and the values of recommended optimum points has obtained by mapping method. Recommended design points unveil interesting and important optimal design principles that would not have been obtained without the use of a multi-objective optimization approach.

Nanofluids are gaining much importance over the past decade due to their enhanced thermal conductivity, specific heat, cooling capacity, electrical conductivities. Novel properties of nanofluids are yet to be explored to the highest potential applications. One of the prominent applications of nanofluids is in thermal conduction. The presence of nanoparticle in a fluid can enhance the thermal conductivities by several orders of magnitude (100-250). Experimental techniques involved in measuring thermal conductivity are transient hot wire method, steady state technique, and temperature oscillation technique, but suffer from drawbacks arising during measurement. Theoretical models are also proposed by Maxwell, Hamilton Crosser, Yu and Choi, Koo and Kleinstreuer, and Kumar. The present paper deals with identification of the best combination of nanoparticle and fluid by making use of existing models.