Simulation of turbulence boiling, generation of vapour and predication of its behaviour are still subject to debate in the two-phase flow area and they receive a high level of worldwide attention. In this study, a new arrangement of the three dimensional governing equations for turbulence two-phase flow with heat and mass transfer are derived by using ensemble averaging two-fluid model and utilizing the latest approved constitutive equations. Then, the governing equations are simplified for bulk boiling in a Vertical Channel. A computer program with SIMPLE algorithm is written for the simplified equations, and the results are compared with available experimental data and a boiling water reactor in operating condition.

Forced convective condensation in Vertical Channel is investigated numerically. The condensation boundary layers that occur due to temperature difference between the walls and saturation temperature of steam is simulated by the volume of fluid (VOF) method. The effect of variations in the hydraulic diameter, steam velocity, Re number and temperature difference between the wall and saturation temperature of inlet steam on heat transfer coefficients are investigated. Simulation results showed that the condensation length and heat transfer coefficient increase by the increase in the amount of inlet velocity and Reynolds number of inlet steam. Also, it was seen a reduction in temperature difference between the wall and saturated steam.

Semi-circular cylinders provide better space economy than circular and other non-circular cylinders. The cylinders are frequently used in a tandem arrangement in heat transfer equipment. The present study aims to obtain the flow and heat transfer characteristics for the tandem arrangement of semi-circular cylinders. The cylinders are placed in a Vertical Channel with a blockage (β) of 0.2. The upward flow under the reverse gravity is considered here. The influence of various parameters such as Reynolds number (Re), Prandtl number (Pr), Richardson number (Ri), and spacing between cylinders (YC) is observed. The governing parameters are varied in a range of 1 ≤ YC ≤ 6, 1 ≤ Re ≤ 50, 0.7 ≤ Pr ≤ 50, and 0 ≤ Ri ≤ 2. The numerical results are obtained by solving governing equations using FVM (Finite volume method). The velocity field, thermal field, drag coefficient (CD), pressure coefficient (Cp), and average Nusselt number (Nuavg) are presented. The increase in Re and Pr has enhanced the Nuavg and CD, whereas Ri and YC have shown complex dependency. The obtained results show that the mutual interaction of upstream and downstream cylinders has vanished for YC > 4. The upstream and downstream cylinders have shown different behavior at identical operating conditions. The drag coefficient for the upstream cylinder varies with YC for 1 ≤ Re ≤ 10, whereas for 10 ≤ Re ≤ 50, it shows negligible change except for the case of Pr = 0.7 and Ri = 2. The drag on the downstream cylinder increases monotonically with an increase in YC. The average Nusselt number for both cylinders increased with an increase in YC except for the downstream cylinder at Re = 1 and Pr = 0.7. Overall, the complex interplay of governing parameters has been observed in the flow and thermal characteristics.

Water supply from rivers is accomplished with flow diversion through an intake structure. A lateral intake like bifurcation is the simplest method to withdraw water. However, flow at a Channel bifurcation is turbulent, highly three-dimensional (3D) and so has many complex features. This paper reports a 3D numerical investigation of these features in an open Channel flow. Simulations have been done on rectangular Channel geometry, with smooth bed and sidewalls. The standard k-e, k-w model of the Wilcox, and RSM turbulence models are compared using the commercial code FLUENT. The simulation results have been compared with available experimental data. It was found that all of the turbulence models tested here accurately predicted velocity profiles in the main Channel but in the branch Channel, the RSM model with the k-w model performing better than the k-e model. Predicted flow physics are in close agreement with previously reported experimental results.

Critical heat flux has been recognized as the upper limit for the safe operation of many cooling systems which may lead to the occurrence of dryout causing a large temperature gradient in the heated wall. One way to increase the amount of the critical heat flux is to put in nanoparticles such as Al2O3 to the base fluid. The current research investigates the nanoparticles effect on dryout phenomenon using computational fluid dynamics. Boiling phenomena are simulated using the mechanistic model organized in Rensselaer Polytechnic Institute which is extended to analyze the critical heat flux by partitioning wall heat flux to liquid and vapor phases. It was shown that the dryout phenomenon can be delayed by increasing the nanoparticles concentration, and in certain concentration of nanoparticles (5 percent), dryout would not take place.

An analysis is carried out to study the effects of temperature-dependent transport properties on the fully developed free and forced MHD convection flow in a Vertical Channel. In this model, viscous and Ohmic dissipation terms are also included. The governing nonlinear equations (in non-dimensional form) are solved numerically by a second order finite difference scheme. A parametric study is performed in order to illustrate the interactive influences of the model parameters; namely, the magnetic parameter, the variable viscosity parameter, the mixed convection parameter, the variable thermal conductivity parameter, the Brinkmann number and the Eckert number. The velocity field, the temperature field, the skin friction and the Nusselt number are evaluated for several sets of values of these parameters. For some special cases, the obtained numerical results are compared with the available results in the literature: Good agreement is found. Of all the parameters, the variable thermo-physical transport property has the strongest effect on the drag, heat transfer characteristics, the stream-wise velocity, and the temperature field.