When flow passes over the tube bundles, energy of flow transfers to the tubes. The Fluid Induced Vibrations (FIV) imposed on the tubes is one of the important problems in analyzing the tube bundles and causes several problems. In this work, first, laminar flow around circular cylinder asymmetrically in a channel is simulated. The Reynolds number is 20 and 100. The lift forces to tube are not zero. Also flow over tube bundle with twenty-four rods is simulated and flow characteristics are obtained. In this problem, the Reynolds Number is 50 to 40000 and the pressure contours, streamlines and velocity vectors are obtained. At last, turbulent flow over a tube bundle with special boundary condition is calculated. For turbulent modeling, the Large Eddy Simulation Method with Smagorinsky and Mix model and the Parallel programming method is used. Flow pattern and characteristics are obtained. Numerical results show a very good agreement with experimental results and reveal interesting flow behavior which is applicable to steam generators of nuclear power plants. پرونده مقاله

The Multi-Application Small Light Water Reactor (MASLWR) test loophas been built as a proof of concept for SMRs that is scaled down in size and has electric heater rods instead of a nuclear core. In this paper with using Drift-Flux Model (DFM), the thermal-hydraulic analysis of helical steam generator in MASLWR under steady-state conditions is simulated. This simulation is performed using the finite volume method. To ensure the accuracy and stability of solutions, User Defined Function (UDF) is written in C programming language. Distributions of velocities, local void fractions, temperature and pressure in the steam generator are calculated in different heights. To validate this simulation,the calculated primary side and secondary bulk fluid temperature are compared with experimental data. The experimental data have been provided by series of measurements of parameters of heat-transfer agent at Oregon State University. The calculated data are in good agreement with measured data and consequently the accuracy of this simulation is satisfied. Accuracy of the prediction shows that it is possible to use the DFM for thermal-hydraulic analysis in advanced models in nuclear power plant and other industries. پرونده مقاله

This article investigates the effect of magnetic field on the performance of a special shell-and-tube heat exchanger using ferro-nanofluid. The heat exchanger comprises seven twisted oval tubes with triangular array mounted on a hexagonal cross section. Water/iron oxide nanofluid with a volume ratio of 4% is used as hot fluid in tubes and water is employed as cooling fluid in the shell. The flow regime is laminar and calculations are performed at different Reynolds numbers and various magnetic fields. The governing equations include continuum, momentum, energy, and magnetic field equations that are solved using a finite volume method. It is demonstrated that the wall temperature of the tubes at the output is lower when the magnetic field is present compared to the case in which the magnetic field is not applied. Applying the magnetic field to the ferro-nanofluid leads to an increase in the Nusselt Number by about two times, leading to an increase in thermal efficiency of the heat exchanger. Also, the effect of the magnetic field was quite different with respect to the geometry and position of the tubes relative to the flow field. The effect of increasing the Nu in the first half of the twisting of the tube is approximately equal to the rate of reduction in the second half of the tube, resulting in a reduction in the impact of the magnetic field intensity. پرونده مقاله