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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]

Entropy generation analysis for the Cu–water nanofluid flow through a heat exchanger tube equipped with perforated conical rings is numerically investigated. Frictional and thermal entropy generation rates are defined as functions of velocity and temperature gradients. Governing equations are solved by using finite volume method, and Reynolds number is in the range of 5000–15,000. The effects of geometrical and physical parameters such as Reynolds number, number of holes and nanoparticles volume fraction on the thermal and viscous entropy generation rates and Bejan number are investigated. The results indicate that the thermal irreversibility is dominant in most part of the tube. But it decreases with increasing the nanoparticle volume fraction. Frictional entropy generation reduces with increasing the number of holes from 4 to 10. This is because of stronger velocity gradient near the perforated holes. Bejan number decreases with augment of Reynolds number. [ABSTRACT FROM AUTHOR]

• The effect of an external magnetic field on hemodynamics of blood flow in a bend vessel was studied. • Blood was studied as a biomagnetic fluid through the ferrohydrodynamic approach. • Effect of curvature coefficient and the susceptibility of blood were investigated. • The maximum magnetic field strength with no effect on hemodynamics was presented. Targeted delivery of therapeutic agents such as stem cells and drugs using magnetic nanoparticles with the aid of an external magnetic field is an emerging treatment modality for many diseases. To this end, understanding the effect of magnetic field on hemodynamics in human body is of great importance. In this article, the effect of external magnetic field, induced by a straight current wire, on hemodynamics of blood flow in a 90° horizontal bend vessel with circular cross section was investigated numerically using ANSYS Fluent®. The blood was considered as laminar, Newtonian, steady and incompressible. To investigate the effect of non-uniform magnetic field effects on the blood flow, the ferrohydrodynamics principles (FHD) were employed. A user-defined function (UDF) was developed to apply the magnetic field effects as source terms. The magnetic susceptibility of blood in oxygenated (in arteries) and deoxygenated (in veins) blood vessels were considered negative and positive values, respectively. The effect of magnetic number, Reynolds number, curvature coefficient and the position of the current wire on flow velocity, static pressure, and shear stress were investigated. The results showed that the Wall Shear Stress (WSS) and static pressure were enhanced with the increase of magnitude of magnetic number. In addition, it was observed that magnetic field has superior impact on the hemodynamic of venous vessel (deoxygenated blood) in comparison with the hemodynamic of artery vessel (oxygenated blood). By studying the effect of curvature coefficient and Reynolds number on WSS, it is concluded that in high curvature coefficient and low Reynolds number, the effect of magnetic field is greater than low curvature coefficient and high Reynolds number, respectively. [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

In this paper the effect of accelerated flow over a moving airfoil is considered and based on the flow field around the airfoil the dynamic stall is evaluated. In contrast to ordinary pitching motion, the dynamic stall evaluation in this study is performed with a different motion pattern, in which the airfoil has a heaving motion in one direction. This motion pattern is also similar to rotation of an element of blade in horizontal axis wind turbines (HAWTs). In present investigation, the Reynolds number is changed during simulation time and variations of this parameter from initial to final values are shown by acceleration parameter. The operating Reynolds number is more than 106, and a S809 airfoil is selected to move with accelerations of 1, 4 and 6 m/s2 in normal direction to free stream. To resolve accelerated flow filed in the two-dimensional computational domain and to achieve results within a reasonable computation time, the unsteady Reynolds-Averaged Navier-Stokes (URANS) equations are employed. The governing equations are discretized based on the finite volume approach and semi-implicit method for pressure linked equations algorithm is used for pressure-velocity coupling. Furthermore, turbulence effect on flow field is accounted using shear stress transport (SST) κ-ω model. It is shown that the accelerated flow can significantly influence on the aerodynamic loads and dynamic stall trend. This study may introduce a new concept regarding dynamic stall and aerodynamic loads when the rotational acceleration is involved in HAWTs. [ABSTRACT FROM AUTHOR]

In this paper, a new application is presented for a helical screw tape insert in a 3D tube. In this application, an eccentricity is created between the centrelines of helical screw tape and tube. Accordingly, the effects of this eccentricity on thermal-hydraulic performance and entropy generation are investigated numerically. A three-dimensional SSTk − ω turbulence model is applied to simulate this problem. All simulations are made for eight values of the eccentricity in the range of 0 to 3.5 and Reynolds numbers in the range of 5000 to 12,000. The calculated results showed that incorporating the helical screw tape near the tube wall (by increasing the eccentricity value) diverts the swirling flow from the core region towards the tube surface where high velocity flow impinges over the tube wall, hence extracting higher amount of thermal energy. Moreover, 42% and 237% increments are observed in the frictional and thermal entropy generations, respectively for an eccentricity in the range of 0 to 3.5. [ABSTRACT FROM AUTHOR]