ashkan ghafouri - Academia.edu (original) (raw)

Papers by ashkan ghafouri

Heat and Mass Transfer, 2021

In this study two appropriate semi-experimental models based on none-linear regression over 800 e... more In this study two appropriate semi-experimental models based on none-linear regression over 800 extracted experimental data to predict the thermal conductivity coefficient of nanofluids were presented. Here, the used nanofluids were spherical nanoparticles of Al2O3, TiO2, CuO, ZnO, ZrO2, CeO2, MgO, SiO2, Fe2O3, Fe3O4, Al, Cu, Fe, Ag, SiC and diamond dispersed in water, ethylene glycol, radiator coolant and various oils as base fluids. The thermal conductivity coefficient of particles and base fluid, temperature in the range of 10–80 °C, volume fraction from 0.04% to 14% were considered as effective parameters to develop first model (model 4-P), whereas, the second model were presented by taking the effect of particle diameter from 4 to150 nm into account (model 5-P). The mean square error and correlation coefficient were found to be 0.00059 and 0.9939 for 4-P model, and 0.000548 and 0.9944 for 5-P model, respectively, for all data. The highest error of the predicted value using mode...

Laminar incompressible mixed-convective heat transfer in two-dimensional lid-driven cavity, fille... more Laminar incompressible mixed-convective heat transfer in two-dimensional lid-driven cavity, filled with nanofluid CuO-water, is studied numerically. Eight different viscosity models are compared to investigate the enhancement in the heat transfer and the increase in the average Nusselt number. The point of view of each model essentially differs in terms of whether it takes various parameters such as temperature effects, Brownian motion of the nanoparticles, the radii of aggregated particles, and the volume-fraction of nanoparticles into account or not. The governing stream-vorticity equations are solved using a second order central finite difference scheme, coupled to the conservation of mass and energy. The main sensitive parameters of interest to investigate the viscosity models are chosen as volume fraction of the nanoparticles φ, and Richardson number Ri. The performance study of the viscosity models and the interpretation of the corresponding results of velocity components are ...

Laminar incompressible mixed-convective heat transfer in 2-D lid-driven cavity, filled with nanof... more Laminar incompressible mixed-convective heat transfer in 2-D lid-driven cavity, filled with nanofluid CuO-water, is studied numerically. Eight different viscosity models are compared to investigate the enhancement in the heat transfer and the in-crease in the average Nusselt number. The point of view of each model essentially differs in terms of whether it takes various parameters such as temperature effects, Brownian motion of the nanoparticles, the radii of aggregated particles, and the volume-fraction of nanoparticles into account or not. The governing stream-vorticity equations are solved using a second order central finite difference scheme, coupled to the conservation of mass and energy. The main sensitive param-eters of interest to investigate the viscosity models are chosen as volume fraction of nanoparticles, and Richardson number. The performance study of the viscosity models and the interpretation of the corresponding results of velocity components are done in a different...

Thermal Science, 2021

The present study modifies the structural design of a shell-and-tube heat exchanger (STHE) by con... more The present study modifies the structural design of a shell-and-tube heat exchanger (STHE) by considering two key parameters such as the maximization of the overall heat transfer coefficient and minimization of the total pressure drop. Five geometric design variables which include the tube inside diameter, tube outside diameter, pitch size, baffle spacing, and the tube length are investigated for optimization. The governing equations for design and optimization of the STHE are evaluated; and the optimum design parameters are obtained by Bees Algorithm (BA). The selection of the important design parameters to achieve the proper design is evaluated by fixing each of these parameters, while the other the design parameters are selected as variable to optimize the effectiveness. Compared with the original STHE, the overall heat transfer coefficient is increased by 22.78 % with the minimum increase in the total pressure drop by 1.8%.

Feasibility of energy integration in soot production cycle in the Pars Industrial Soot Company ha... more Feasibility of energy integration in soot production cycle in the Pars Industrial Soot Company has been studied using pinch technology with retrofit view point. All necessary cold and hot streams and also corresponding mass flow rates, heat loads and properties are evaluated in the plant as the first step. Modeling of the streams, plotting the composite and finally ground composite curve, it is shown that this case is a threshold problem which needs hot utility only. The Amagaut’s ideal gas mixture model is implemented to determine the values of the mixture constants such as specific heat ratio, considering a working average temperature and pressure of the reactor products. It has been indicated that the furnace is the best source of providing the needed energy to make up the hot utility. The combustion calculations in the furnace have been done using an equilibrium thermodynamics model and considering the adiabatic flame temperature for products to analyze the corresponding thermod...

The main objective of the present numerical study is to investigate the transient heat transfer i... more The main objective of the present numerical study is to investigate the transient heat transfer in one kind of all-purpose longitudinal fin with the triangular profile. The lateral surface of the concerned fin and the tip of it are subjected to general situations included heat flux at the base and insulation on the tip. For this study developed a one dimensional in house code written by Fortran 90 programming language by using finite difference method with an implicit scheme in unsteady state condition. Generally, the result of this study in time variation state after 700 seconds is steady. The results also show the fin efficiency by increasing the time of study decreases due to a reduction in the total heat transfer which is happened in the fin. The grid independence study shows that for the number of nodes greater than 20 the result will not be changed and same as before. Finally, the result of Fortran code verified by commercial CFD code which relies on finite difference method a...

Journal of the Brazilian Society of Mechanical Sciences and Engineering, 2021

In this study, the thermal conductivity and dynamic viscosity of MgO-Ethylene Glycol nanofluid ar... more In this study, the thermal conductivity and dynamic viscosity of MgO-Ethylene Glycol nanofluid are investigated. MgO nanoparticles with three diameters of 20, 50, and 100 nm are used to prepare nanofluids. Ethylene Glycol and nanofluid with particle volume fraction of 0.25%, 0.5%, 0.75% and 1% are used as working fluid. The experiments are conducted in the temperature range of 25 to 50 °C with volume fraction up to 1%. The results have shown that thermal conductivity and dynamic viscosity increase by an increase in volume fraction and a decrease in particles’ diameter, while the temperature effect on thermal conductivity and dynamic viscosity are incremental and decremental, respectively. Moreover, the sensitivity of the thermal conductivity and dynamic viscosity to variations in key parameters such as temperature volume fraction and particles’ diameter is measured. Based on the experimental data and using multivariate linear regression method, new correlations were proposed to pred...

In this research the geometric parameters and nanofluid properties effects on heat transfer and p... more In this research the geometric parameters and nanofluid properties effects on heat transfer and pressure drop in helical tube, by using alumina-water nanofluid as cooling fluid, are numerically investigated. Friction factor and heat transfer coefficient are calculated by considering the effects of nanofluid properties, including nanoparticle diameter, nanofluid temperature, Reynolds number, and volume fraction, on the one hand, and the impact of geometric parameters, including tube diameter, coils diameter and coils pitch, on the other hand. Numerical analysis is performed in the Ansys Fluent 19.2 software using the SST k-ω turbulence model. By increasing the nanofluid volume fraction the heat transfer coefficient and pressure drop in helical coils increase, the same as the nanoparticle diameter reduction. The reduction of nanoparticle diameter causes an enhancement of heat transfer and friction factor, the best results happen in dp = 5 nm and φ = 4%, where the it was ~ 40.64% more ...

Journal of the Brazilian Society of Mechanical Sciences and Engineering

Journal of Theoretical and Applied Mechanics

The present study investigates eight design parameters such as seal coverage, core porosity, core... more The present study investigates eight design parameters such as seal coverage, core porosity, core volume ratio, core thickness, dimensionless core rotation rate, inner diameter of the core, air mass flow rate and exhaust mass flow rate to design and optimize a regenerator of a 20-MW power generation gas turbine with fixed pressure drop. The application of GA and Firefly algorithms to optimize the effectiveness of the regenerator is presented to demonstrate the efficiency and accuracy of the proposed algorithms. The effect of change in the seal coverage, core porosity, core volume ratio and dimensionless core rotation rate are evaluated as important design parameters having influence on the size and mass of the core of the regenerator. This could be done through fixing each of these parameters, while the other seven design parameters are selected as variables to optimize the effectiveness. The results show that the selection of all eight-design parameters proposed as operating variables is necessary to optimize the parameters to achieve the proper design of this regenerator.

SN Applied Sciences

This research presents a numerical study on heat transfer and flow characteristics for two pipe f... more This research presents a numerical study on heat transfer and flow characteristics for two pipe fitted by two different dimpled spiral center plate by utilizing Al 2 O 3 , CuO and TiO 2 nanofluids as cooling fluids. Considering the effect of dimples arrangement, nanoparticle diameter d p , nanofluids volume fraction φ and also the heat transfer coefficient, thermal property. Average amount of entropy generation S a and maximum local temperature of wall T max were discussed. Results demonstrate that the in-line arrangement geometry behaves better in compare to the geometry with the staggered arrangement. 47.3% is the maximum enhancement of convection heat transfer for the in-line arrangement in compare with the smooth spiral central plate with base flow. Using nanofluids improved the wall temperature distribution, and using nanofluid caused great improvement in thermal conductivity with a little raise in dynamic viscosity. Using nanofluids caused a considerable decrease in S a , which also as the result of rising φ, and S a maximum reduction is about 24.7%. T max considerably declines by using nanofluids and enhanced by a rising φ. Also, CuO-water nanofluid has a better effect on heat transfer and flow characteristics than the other nanofluids.

Iranian Journal of Science and Technology, Transactions of Mechanical Engineering

Journal of Thermal Analysis and Calorimetry