1.  “Modeling of a Coal Fired Natural Circulation Boiler”, ASME Journal of Energy Resources and Technology, in press.

Abstract-

      Modeling of natural circulation boiler for a coal fired thermal power station is presented here. The boiler system is divided into seven sub-components and for each section, models based on conservation of mass, momentum and
energy are formulated. The pressure drop at various sections and the heat transfer coefficients are computed using empirical correlations. Solutions are obtained by using SIMULINK. The model is validated by comparing its steady
state and dynamic responses with the actual plant data. Open loop responses of the model to the step changes in the operating parameters like pressure, temperature, steam flow, feed water flow, are also analyzed. The present model can be used for the development and design of effective boiler control systems.
 

2. “CFD Modeling of Two Phase Bubbly Flow with Heat and Mass Transfer” Joint ISHMT- ASME, Heat and Mass Transfer Conference, 2006.

Abstract- 

     Sub-cooled flow boiling is a case of two phase bubbly flow, which is encountered in various engineering applications such as boilers, reactors, refrigeration systems, heat exchangers and various power generation systems. If there is very high heat flux, the film boiling burnout or flow instability may lead to failure of components. Prediction of void fraction profile, flow pattern, thermal field and velocity distribution, is essential for design and safety analysis of such systems.

In this paper, three dimensional two fluid model (continuous liquid phase and dispersed vapor phase) is solved to estimate void fraction, velocity and temperature profiles with inclusion of inter phase heat and mass transfer processes. Commercial CFD software CFX-5.7.1 is used to solve the problem. The above parameters are evaluated for upward bubbly flow in a vertical pipe with six heated rods for high pressure. The various drag and non-drag forces are tested. Model developed by Rensselaer Polytechnic Institute (RPI), is used to distribute the wall heat flux between vapor generation and heating sub-cooled liquid. The results of present study are compared with numerical results of Anglart-Nylund and experimental data of Nylund et.al. The present study shows a good agreement with experimental data and numerical results in the literature.