Numerical Simulations of Organic Peroxide Pool Fires

Post Doctorate

Simulation of Organic Peroxide Pool Fires: It is estimated from the simulations that 80% of this heat flux is due to the continuous flame zone. A better explanation of longer flame heights of organic peroxide fires is provided. The worst case scenario regions are identified to get a conservative estimate for a stability test of any package or any object in organic peroxide pool fires.

Radiative Heat feedback: A methodology is developed to estimate the contribution of the thermal radiation from different zones of the flame to the pool surface. This method is verified for heptane and DTBP pool fires of different diameters and also with cross-wind. Most of the thermal radiation is from the flame of height one times the pool diameter.

Characterization of Open Pool Fires and Study of Heat Transfer in Bodies engulfed in Pool Fires

Doctoral Thesis

The aim of the present study is to develop a simplified methodology of predicting the heat transfer to a body engulfed in pool fire. The body represents a thermal cask simulated as a stainless steel cylinder filled with insulation. To begin with, pool fires are studied without any body immersed in them. The fuels used for this study are diesel, gasoline and hexane. The pool diameters considered are in the range of 0.3 m to 1.0 m.

Some of the important properties are flame emissivity, radiative fraction, gas velocity, temperature and emissive power distributions. Flame emissivity along the height of the pool fire is measured using the Infrared thermography. Radiation fraction is measured using single-location and multi-location measurements. Gas velocity of the pool fires is measured using a bidirectional probe.

Subsequently, pool fires are studied with casks engulfed in them. In this study, the ratio of the projected area of the cask to the pool surface area is less than 14.4%. There is no significant change in the mass burning rate of the pool fire in spite of the presence of the cask. Thermocouples are welded inside the cask to measure the subsurface temperature. Inverse heat conduction methodology is applied to the measured subsurface temperature to estimate the heat flux to the cask.

The heat flux to the cask engulfed in a pool fire is also predicted using numerical simulations. Adiabatic surface temperature (AST) is measured for pool fires using plate thermometers. This measured AST along with the convective heat transfer coefficient is given as mixed boundary condition in the numerical simulations of the cask. A good conservative estimate is obtained from numerical simulations. The radiative heat transfer to the cask predominates the convective heat transfer due to the low gas velocities.

Adiabatic surface temperature for a given diesel pool fire is also computed using Fire dynamics simulator (FDS). Numerical simulations of the cask are carried out using this computed AST to obtain the heat flux to the cask. The maximum deviation of the heat flux computed is less than 10% as compared to experimental results. Thus, using AST computed from FDS along with a conduction model circumvents the need for pool fire experiments.

Liquid Sloshing in a Baffled Tank

Master Thesis

Any motion of a free liquid surface is termed as sloshing. It can be caused by any disturbance to a partially filled liquid tank. The noise due to sloshing fuel within automotive fuel tanks remains as a source of irritation, especially in case of more expensive cars with increased claims of the customers. The main objective of this study is to minimize the internal sloshing motion, with suppression devices, in a fuel tank using Computational Fluid dynamics (CFD) package, FLUENT v6.2 and to determine an effective comparison tool in order to compare the effectiveness of different baffles in reducing the sloshing motion. The effects of vertical baffle, horizontal baffle and multiple baffles on sloshing are determined. The results show that the Vertical baffles are more effective in reducing internal sloshing motion than horizontal baffles. Experimental validation shows that the CFD tools used are so powerful to handle the non-linear type motions of fluids in an accurate way and are able to reproduce the sloshing event. Also it is found that sloshing effect is high at its natural frequency. In a slosh sensitive problem where the complexity of the geometry is not of much important, one can use multiple baffles. Using the parameter, Percentage Reduction (PR), one can easily compare the effectiveness of different baffles.