Ajmal Shah

Numerical Simulation of Direct-contact Condensation from a Supersonic Steam Jet in Subcooled Water

Abstract The phenomenon of direct-contact condensation, used in steam driven jet injectors, nuclear reactor emergency core cooling systems and direct-contact heat exchangers, was investigated computationally by introducing a thermal equilibrium model for direct-contact condensation of steam in subcooled water. The condensation model presented was a two resistance model which takes care of the heat transfer process on both sides of the interface and uses a variable steam bubble diameter. The injection of supersonic steam jet in subcooled water tank was simulated using the Euler-Euler multiphase flow model of Fluent 6.3 code with the condensation model incorporated. The findings of the computational fluid dynamics (CFD) simulations were compared with the published experimental data and fairly good agreement was observed between the two, thus validating the condensation model. The results of CFD simulations for dimensionless penetration length of steam plume varies from 2.73-7.33, while the condensation heat transfer coefficient varies from 0.75-0.917 MW·(m 2 ·K) −1 for water temperature in the range of 293-343 K.

CFD analysis of heat transfer within a bottom heated vertical concentric cylindrical enclosure

The CFD analysis of heat transfer within a bottom heated vertical concentric cylindrical enclosure is important with respect to the process in the chemical and process industries. The research work focuses on the CFD analysis of the enclosure with respect to the machines used for the segregation of chemicals in the chemical industries. The CFD simulations are performed to study the effects of inner cylinder material and outer cylinder geometric configurations on the heat transfer mechanism in the enclosure. The CFD simulations are conducted at a bottom disc temperature of 393 K and compared with the published results at a temperature of 433 K. This research study depicts the behavior of bottom heated vertical concentric cylindrical enclosure at different bottom disc temperatures. This study also investigates the heat transfer mechanism of the enclosure using different inner cylinder materials and different configurations of the outer cylinder. In such enclosures a uniform temperature is required for the segregation of chemicals. A more uniform temperature is observed in the enclosure by using aluminum inner cylinder of the bottom disc and using two different diameter outer cylinders as compared to the mild steel and stainless steel.

Numerical study of conjugate heat transfer within a bottom heated cylindrical enclosure

The conjugate heat transfer within a bottom-heated non-conventional cylindrical enclosure is important with respect to the processes in chemical and nuclear industries. In this research work numerical analysis of the enclosure with respect to the centrifuge machines used in the process industry is presented. Various CFD simulations of the experimental work of [1] are performed to study the effects of materials of the disc and inner cylinder and geometries of outer cylinder on the enclosure. Generally, a uniform temperature is required in such enclosures. A more uniform temperature is observed in the enclosure by using aluminum inner cylinder at a temperature of 433K of the bottom disc and using two different diameter outer cylinders as compared to the mild steel and stainless steel.

Numerical simulation of naturally air cooled electronic equipments casing

With the passage of time size of electronic equipments decreases but power consumption remains constant due to which rise in temperature is the major issue to address in order to increase the life of electronic equipments. Failures of electronic systems due to high temperature have urged engineers to design efficient cooling systems. In natural convection heat transfer the position of vents and heater should be considered as an important variable. They must be placed in order to facilitate the flow rather than obstruct it. Effect of variation of outlet height, outlet area and heater height on mean rise in temperature inside the naturally cooled electronic equipments casing has been studied using Computational Fluid Dynamics (CFD) in this research work. CFD study shows that when heater position is close to outlet, outlet height and area is minimum then maximum mean rise in temperature inside the casing occurs. At the end, computational results have been validated with experimental data available in literature. Computational results have been found to be highly in accordance with experimental values. Percentage difference between computational and experimental values are less than 5%.

Dust particle collection efficiency of venturi scrubber with varying number of orifices using CFX

In the present study, computational fluid dynamics (CFD) investigation of dust particle collection efficiency in a force feed venturi scrubber has been performed using ANSYS CFX. A Venturi scrubber provides an effective way to remove dust particles flowing in a contaminated gas which are captured in fine droplets formed due to disintegration of a liquid as a result of high kinetic energy of air. Eulerian-Lagrangian approach is used to analyze the dust particle collection in a venturi scrubber for gas (air) flow rate at 1 g/s and liquid flow rate of 6 g/s with 2, 4, 6 and 8 orifices placed at the start of throat, end of throat and on the converging section. Cascade atomization and breakup model (CAB) is used for the prediction of liquid breakup in the venturi scrubber. Dust particles (TiO2) having diameter of 1 μm are used in this research. Velocity of gas at the throat, droplet size, volume fractions and collection efficiency are studied to analyze the working of venturi scrubber.