A parabolic dish solar collector system is one of the main types of concentrated solar power systems that are based on point focusing and is more beneficial than the other kinds of concentrated solar power systems. Most of the literature concerning concentrated solar power systems focused on thermal losses and their relationship to the receivers with different geometries. A few former researches have investigated the impacts of the real solar flux distribution on the receivers' absorber surface in parabolic dish solar collector systems. The inaccuracy level appertaining to the isothermal assumption is more than that of a receiver’, s walls with constant heat flux, simply due to heat transfer fluid running through the receiver. On the other hand, the constant heat flux approach cannot be so accurate due to the non-uniform distribution of solar heat flux at receiver's internal walls. The current paper investigates the usage of a two-phase nanofluid in a baffled parabolic dish solar collector under a non-uniform distribution of solar heat flux. The geometrical parameters of the collector are analyzed in this work,for this purpose, the SIMPLEC algorithm and Finite Volume Method are employed. The heat transfer fluid is based on water/Al2O3 two-phase nanofluid. The most expected average Nusselt number is achieved at Re = 15, 000 in June. In the next section, the effects of different Reynolds numbers and months on the predicted average Nusselt numbers will be investigated in detail. Finally, the PDSC with Z = 70 mm and F = 600 mm filled with nanofluid at 􀀁,= 4% and dnp = 20 nm is introduced as the most efficient model in the present investigation.

Ejector is important equipment in the chemical industry. It is mainly used for vacuuming and mixing of flows. In the present work a computer modeling of the flow inside an ejector is used to give a better understanding of the principle of the operation of an ejector. Since the fluid inside an ejector passes through sub sonic, sonic and super sonic regimens, the pressure field is used as the controlling variable and the density is found through the constitutive equations. The control volume method with a co-location grid, attached to the boundary is used to discretize the domain. The overall solution is obtained by the SIMPLE method and to dissociate the pressure and the velocity grid Rhie-Chow interpolation method is employed A central difference approximation method is used to approximate the density on the element borders and the upwind approximation is used to correct the density correction factors. Both upwind, quick and minimum gradient methods were used to approximate the momentum variables on the control volumes. The resultant matrices are solved with the tri-diagonal method the accuracy of the model is checked by simulating a flow regimen in a converging-diverging nozzle, and comparing the results with the available experimental data. The results show that for an inviscid fluid the first order approximation produce as accurate results as the higher order approximations while it has a better stability. However, for the viscous fluid the second order approximation produces a better understanding of the physics of the problem. The solution also shows that the flow field inside an ejector is a complex one and the shock wave has a great influence on the pressure field especially close to the walls. The upper convective quick method did not converg well in the shock calculations while the slowest descent method had a very stable behavior in the analysis of the shock behavior.

In the present study, the conjugate heat transfer in a rectangular cooling channel is numerically simulated in supercritical pressure conditions. The compressible methane flow is considered as a working fluid. A finite volume scheme is utilized for the discretization of the governing equations on a collocated grid. Moreover, the central differencing scheme is employed for the discretization of the diffusion fluxes and density approximation on the control volume boundaries. Upwind and hybrid schemes are used for the density correlation approximation and the convective fluxes discretization on the control volume surfaces, respectively. An iterative solution method based on the SIMPLEC (Semi-Implicit Method for Pressure Linked Equations-Consistent) algorithm is adopted to solve the equations. The solver is developed based on the thermodynamic and transport property relations corresponding to the coolant flow conditions in the transcritical regime. The solver is validated with the experimental data of the MTP test, and the thermal behavior of methane inside the rectangular cooling channel is investigated. Moreover, a relation is derived to calculate the pseudo-critical temperature of methane according to pressure. The relative error of this relation with NIST data is less than 0. 5 percent, and it operates in a range of pressure from 4. 6 MPa to 30 MPa. Furthermore, the Nusselt relations presented for coolant flow with supercritical pressures are studied and corrected for the methane coolant in supercritical pressure conditions in 3D rectangular cooling channels. The relative error of modified Nusselt relations with numerical data is less than 1. 0 percent.

In this paper, Turbulent mixed convective heat transfer of water and Al2O3 nanofluid has been numerically studied in a horizontal tube under non-uniform heat flux on the upper wall and insulation in the lower wall using mixture model. For the discretization of governing equations, the second-order upstream difference scheme and finite volume method were used. The coupling of pressure and velocity was established by using SIMPLEC algorithm. The calculated results demonstrated that the convective heat transfer coefficient of nanofluid is higher than of the base fluid and by increasing the nanoparticles volume fraction, the convective heat transfer coefficient and shear stress on the wall increase. On the other hand, with increasing the Grashof number, the shear stress and convective heat transfer coefficient decrease.

The main purpose of this paper is to study numerically the flow-field of an incompressible viscous flow in a curved pipe (1800) with two straight pipes attached to both ends. In order to extend the capabilities of the finite volume method, a boundary (body) fitted coordinate (BFC) method is used. Transformation of the partial differential equations to algebraic relations is based on the finite-volume method with collocated variables arrangement. For solving the obtained algebraic relations the TDMA in periodic state is used. To approximate the convective. fluxes, the differencing scheme of Van Leer is used and SIMPLEC handles the linkage between velocities and pressures. For verification of the code, a test case of flow in a (1800) curved pipe at Reynolds number of 242 is performed and the good agreement between the present results with the numerical and experimental data is obtained. This study showed that by adding two straight pipes at the ends of a curved (1800) pipe, the strength of the secondary flow in the curved zone is reduced.  

In the present study, novel channel geometries in a wavy channel heat sink (HS) are investigated using ANSYS-FLUENT software. The Ag/water-ethylene glycol (50%) nanofluid is selected for cooling the CPU in this HS. The second-order upwind method is employed to discretize the momentum Equation and the SIMPLEC algorithm is employed for coupling velocity and pressure fields. Comparison of the two HSs with and without microtube shows that the presence of the microtube increases the uniformity of the CPU surface temperature distribution and decreases the mean surface temperature of the CPU (TCPU-Mean). However, the pumping power consumption of the system increases about 10 times. The results also demonstrate that the addition of nanoparticles results in intensification in the Performance Evaluation Criterion (PEC) of the system and up to 30%, especially at high Reynolds numbers.

In this paper, thermal effect of plasma arc welding is investigated, and temperature field of ferrite stainless steel is acquired. Thermal effect of plasma arc and subsequently the generated temperature field in the work piece is the key for analysis and optimization of this welding process, which is the main goal of this paper. Finite element simulation of welding process by SIMPLEC method and ANSYS software is achieved, using FSI solver for getting stainless steel temperature field, effect of parameters variation on temperature field, and process optimization for different situations of plasma and shielding gases (Argon, Helium, and mixture of both). Lastly, the results of other papers are used to verify the correctness of this paper’s results. The temperate field results have determined the effects of welding parameters, and are used to optimize plasma welding process for improving weld quality. Optimization results for different gases indicates that due to special heat of Helium gas, there is extra potential with respect to Argon gas to narrow the plasma arc and concentrate inlet heat over stainless steel.

A two dimensional numerical model of shallow water equations was developed to calculate sub and super-critical open channel flows. Utilizing an implicit scheme the steady state equations were discretized based on control volume method. Collocated grid arrangement was applied with a SIMPLEC like algorithm for depth-velocity coupling. Power law scheme was used for discretization of convection and diffusion terms. Under relaxation factors were introduced in the model to prevent divergence. Momentum interpolation was used in calculating velocities on cell faces to avoid checker board water surface fluctuation in the collocated grid. The model was verified in different cases including complex water surface profiles and hydraulic jump. The results are compared with experimental and analytical data and the necessary values of under relaxation factors for a converged solution are discussed. No artificial viscosity was required, which is the advantage of the present model.