Experimental investigation of thermo-physical properties, convective heat transfer and pressure drop of functionalized graphene nanoplatelets aqueous nanofluid in a square heated pipe

In the present study, a facile method is used for preparation of functionalized graphene nanoplatelets (f-GNP) nanofluids. The effective thermal conductivity, density, viscosity, specific heat capacity, overall heat transfer coefficient and friction factor for fully developed turbulent flow of f-GNP/water nanofluids flowing through a square pipe at a constant heat flux were studied. f-GNP uniform nanocomposite was produced from a simple acid treatment reaction procedure. The surface characterization was performed by various techniques such as XRD, FESEM, FTIR and Raman. The f-GNP nanofluids were prepared by dispersing the functionalized nanoparticles in base fluid (water) without the assistance of a surfactant. As made nanofluids were stable for a long time and no sedimentation was observed. The experimental data for f-GNP nanofluids have shown significant enhancement in thermal conductivity and overall heat transfer coefficient in comparison to the corresponding water data. The percentage of enhancement is a function of weight concentration of nanoparticles and temperature. Highest improvement of overall heat transfer coefficient is 19.68% with 9.22% raise in friction factor for the weight concentration of 0.1% at a Reynolds number of 17,500 compared to those data from the base fluid

Convective heat transfer enhancement with graphene nanoplatelet/platinum hybrid nanofluid

The work here looked into heat transfer performance in addition to friction loss of graphene nanoplatelet (GNP) - Platinum (Pt) hybrid nanofluids. The experiments were performed with non-changing limit parameters of heat-flux. Nanofluid movement was turbulent at a weight percentage ranging between 0.02 and 0.1%, with the Reynold number from 5000 to 17,500. The experimental findings revealed that compared with the base liquid, all nanofluid samples had higher heat transfer abilities. Nusselt number elevation and the increment of the heat transfer coefficient were found to be dependent on Reynold number, and the weight concentration of the nanocomposite. The greatest value recorded for Nusselt number was 28.48%, accompanied by a 1.109-fold penalty. There was a rise in friction factor with regards to the highest load of nanocomposite (0.1 wt%), with the Reynolds number of 17,500

Parametric study of radial functionally graded femoral prostheses with different geometries

Due to complex loading and chemical conditions of the human body, the artificial replacements of the body organs demand materials with superior characteristics. Therefore, recently using composite materials have gained a lot of popularity for this purpose. As a special case of the composite materials, functionally graded materials (FGMs) exhibit very interesting behavior that makes them a very suitable candidate where this study is aimed to examine the performance of femoral prostheses made of a FGM. The internal and external layers of the prostheses were composed of stainless steel and hydroxyapatite, respectively. The finite element method was used to compute the strain energy density in the proximal metaphysis of the bone, von Mises stress over the femoral prostheses, and maximum and minimum principal stress developed in the bone. The results revealed dependency of the strain energy density, interface stresses, and implanted femur component stresses on the gradient index and geometrical properties of the prostheses. Moreover, among the geometrical factors, profile and proximal cross-section were the key factors to alter strain energy density, whereas the distal cross-section effect was minor. Besides, changes in interface stresses were related to all geometrical properties of prostheses. However, stress changes in prosthesis and bone were less evident under the influence of prosthesis geometrical properties, while strains in bone showed a significant dependency to the gradient index and geometrical properties of the prosthesis

Nanofluid based on activated hybrid of biomass carbon/graphene oxide: Synthesis, thermo-physical and electrical properties

In the present study a mixture of empty fruit bunch (EFB) fiber as a matrix material and graphene oxide (GO) as a guest was activated by processing with KOH. The structural characterization was performed by various techniques such as field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and Raman. The as-synthesized hybrid containing activate carbon/graphene (ACG) was dispersed in ethylene glycol (EG) at various mass fractions in order to evaluate the thermo-physical and electrical properties such as thermal conductivity, electrical conductivity, viscosity, density and specific heat capacity of the suspensions at different temperatures. Thermal conductivity of ACG dispersed in EG based nanofluid shows an enhancement of 6.47% at 40 °C and weight fraction of 0.06%

Study of synthesis, stability and thermo-physical properties of graphene nanoplatelet/platinum hybrid nanofluid

In the present study a new synthesis method has been introduced for the decoration of platinum (Pt) on the functionalized graphene nanoplatelet (GNP) and also highlighted the preparation method of nanofluids. GNP–Pt uniform nanocomposite was produced from a simple chemical reaction procedure, which included acid treatment for functionalization of GNP. The surface characterization was performed by various techniques such as XRD, FESEM and TEM. The effective thermal conductivity, density, viscosity, specific heat capacity and stability of functionalized GNP–Pt water based nanofluids were investigated in different instruments. The GNP–Pt hybrid nanofluids were prepared by dispersing the nanocomposite in base fluid without adding any surfactant. The examined nanofluids were stable and no significant sedimentation was observed for a long time (22 days). Thermal conductivity of GNP–Pt nanocomposite dispersed in distilled water nanofluids shows an enhancement of 17.77% at 40 °C and 0.1% weight concentration

Graphene nanoplatelets–silver hybrid nanofluids for enhanced heat transfer

In the present experimental work, a new synthesis method is introduced for decoration of silver on the functionalized graphene nanoplatelets (GNP-Ag) and preparation of nanofluids is reported. The thermo-physical properties, heat transfer performance and friction factor for fully developed turbulent flow of GNP-Ag/water nanofluids flowing through a circular tube at a constant heat flux were investigated. GNP-Ag uniform nanocomposite was produced from a simple chemical reaction procedure, which includes acid treatment for functionalization of GNP. The surface characterization was performed by various techniques such as XRD, FESEM, TEM and Raman. The GNP-Ag nanofluids were prepared by dispersing the nanocomposite in distilled water without the assistance of a surfactant and/or ultrasonication. The prepared nanofluids were found to be stable and no sedimentation was observed for a long time. The experimental data for GNP-Ag nanofluids were shown improvements of effective thermal conductivity and heat transfer efficiency in comparison with the corresponding to the base-fluid. The amount of enhancement was a function of temperature and weight concentration of nanoparticles. Maximum enhancement of Nusselt number was 32.7% with a penalty of 1.08 times increase in the friction factor for the weight concentration of 0.1% at a Reynolds number of 17,500 compared to distilled water. Improved empirical correlations were proposed based on the experimental data for evaluation of Nusselt number and friction factor