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This study prepares an experimental examination of thermal and hydraulic analysis of an absorber plate integrated with different arrangements of twisted turbulators, including longitudinal, transversal, and oblique orientations. These arrangements are considered for both the integral and the interrupted turbulators over Reynolds number range from 9174 to 55048. Nu ratio and f ratio range from 1.15–2.21 and 1.73–7.79, respectively. The interrupted turbulators with oblique arrangements with the attach angles of 30° and 60° come in the second and third places, respectively, and the maximum criterion value in the latter cases is 1.29 and 1.21. [ABSTRACT FROM AUTHOR]

In this study, a novel method for numerical simulation of drying is proposed and the process is optimized by Taguchi method. A 2D numerical solution is performed to analyze coupled heat and mass transfer occurring during drying of a rectangular moist object. The dryer section and the moist object are conjugately simulated where the coupled heat and mass transfer equations are solved together. The lattice Boltzmann method is employed to solve hydrodynamic, heat, and mass transfer equations. This study applied the Taguchi method to determine optimum conditions for drying so as to minimize the drying time and energy consumption. The control factors included temperature, air velocity, and thickness ratio (the moist object thickness to channel width). The following optimal conditions were obtained: temperature (T = 60 °C), velocity (V = 0.1 m/s), and thickness ratio (TR =0.1). The results of numerical solution are then compared to the measured data available in the literature, presenting a reasonable agreement. [ABSTRACT FROM AUTHOR]

Numerical simulations are used to analyze the thermal performance of turbulent flow inside heat exchanger tube fitted with cross-cut twisted tape with alternate axis (CCTA). The design parameters include the Reynolds number (5000

The present work investigates the natural convection of nanofluids in Rayleigh-Benard problem. New models, particularly some enhancement factors, are presented in this research to calculate the heat transfer characteristics of nanofluids around critical Rayleigh numbers, including the criteria in which the creation of Rayleigh-Benard and transition to turbulent flow occurs. The present models are compared with available models in the literature to reveal discrepancies of theoretical models in prediction of nanofluids heat transfer characteristics. This research is conducted for SiO2, Cu,CuO and Al2O3 as nanoparticle and water as the base fluid and discussed the SiO2-water nanofluid in more detail. Results indicate that the Nusselt number and convective heat transfer ratio are reduced for SiO2-water nanofluid for almost all volume fractions and as a result using SiO2 as nanoparticle into water (the base fluid) is not desired for a natural convection in Rayleigh-Benard problem. Moreover, the onset of natural convection is delayed due to the reduction in enhancement factor. [ABSTRACT FROM AUTHOR]

In this paper, an optimization procedure is presented by response surface method to optimize the temperature and velocity of drying air and thickness of the moist object inside the dryer. The optimization procedure is performed to determine the minimum drying time and energy consumption as responses. A two-dimensional (2D) numerical solution is accomplished to analyze coupled heat and mass transfer occurring during drying of an apple slice. The air flow and the moist object are solved conjugate, while the heat and mass transfer equations are solved coupled together using lattice Boltzmann method (LBM). Beside this, a sensitivity analysis is executed to calculate the sensitivity of the responses (drying time and energy consumption) to the control factors. Results reveal that the real optimized parameters for the minimum drying time and energy consumption are temperature (T = 80 °C), velocity (V = 0.10404 m/s), and thickness ratio (TR = 0.1). The results of numerical solution are compared to the experimental results, presenting a reasonable agreement. This analysis could be useful in food drying. [ABSTRACT FROM AUTHOR]

The present work investigates an analytical study on the problem of laminar film condensation on a nanosphere. Due to the microscale interaction, the problem is analyzed by taking into account the effects of slip in velocity and Jump in temperature. A relation is derived for the liquid film thickness in the form of a nonlinear differential equation which is solved numerically using the fourth order Runge-Kutta method. Finally, the effect of velocity slip and temperature jump on different condensation parameters including the liquid film thickness, velocity and temperature profiles, Nusselt number, and liquid mass flow rate is discussed. It is found that the increase in the velocity slip and temperature jump results in a thinner liquid film and therefore increases the heat transfer coefficient. [ABSTRACT FROM AUTHOR]

The present work studies heat transfer of the gas fluid in open microchannels at constant wall heat flux boundary conditions. The proposed model assumes the fluid is a continuum, but employs a slip boundary condition on the channel wall. Using appropriate similarity variables, the fundamental equations of the boundary layer are transformed to ordinary differential equations containing a Prandtl number. These ordinary differential equations are solved numerically using a fifth order Runge-Kutta and shooting method. Consequently, the velocity profiles, the temperature profiles, the wall shear stress and the local Nusselt number exhibit a dependence on the slip coefficient. The results illustrate that the thermal creep term has a very small effect on the solution. It is shown that laminar boundary layer of gas fluid with slip flow tends to increase near wall fluid axial velocity and temperature jump on the wall as the flow becomes more rarefied. It will be seen that heat transfer in open microchannels is affected with temperature jump more than slip velocity under constant wall heat flux boundary condition. [ABSTRACT FROM AUTHOR]

Convective heat transfer of Al 2 O 3 –water nanofluid over an equilateral triangular obstacle with an optimization analysis is carried out to determine the optimum conditions for the maximum heat transfer rate and the minimum drag coefficient. Orientations of the obstacle, values of the solid volume fraction, and Reynolds number are selected as the input parameters. The analysis is performed according to the Response Surface Methodology. The response surface equation is obtained using the design of the experiments features. Two-dimensional unsteady equations with the relevant boundary conditions have been solved using finite volume method. Three different orientations of the triangular obstacle are defined for the optimization procedure. The computational simulations are done for different Reynolds numbers ( 1 ≤ Re ≤ 180 ), solid volume fractions ( 0 ≤ φ ≤ 0.05 ) and orientations of the triangular obstacle ( 0 ° ≤ θ ≤ 60 ° ). Also, a comparison is performed between the results of CFD analysis and Response Surface Methodology. It is found that the minimum drag coefficient is occurred at θ = 35.13°, Re = 97.6 and φ = 0.01 and the maximum Nusselt number is found at θ = 8.49°, Re = 180 and φ = 0.05. [ABSTRACT FROM AUTHOR]