Simulation of the flow of an explosive atmosphere exposed to a hot surface

TL;DR

This study investigates how the orientation of hot surfaces influences the ignition of combustible atmospheres, combining experimental measurements with detailed 3D numerical simulations to analyze flow structures and temperature evolution.

Contribution

The paper introduces a comprehensive approach combining experiments and validated 3D simulations to understand ignition processes on hot surfaces with varying orientations.

Findings

Orientation affects the location of hot spots and ignition points.

Flow structures and temperature gradients are significantly influenced by surface tilt.

Simulation results align well with experimental data.

Abstract

The accidental ignition of combustible atmospheres by hot surfaces is of great concern for chemical and process plant safety. In this paper, we present our research regarding the evolution of thermal plumes originating from hot hemispheres and discs. In particular, we focus on the effect of the orientation of the surface on the ignition process. The auto-ignition temperatures and ignition locations were studied experimentally. To get further insight, we conducted detailed numerical simulations and validated them with measurements. Three-dimensional simulations were performed on hot hemispheres and hot discs for different orientations ranging from 0{\deg} to 180{\deg}. The solver employs a transient, implicit scheme which is based on the coupled heat transfer and flow equations. The mesh in the vicinity of the hot surfaces is refined to resolve the steep temperature gradients and to capture the boundary layer separation. The influence of the orientation on critical hot spots in the gas mixture is analysed by examining the flow structures and the temperature evolution of the buoyancy-driven flow. Using the obtained results, we discuss the change of the onset and location of the ignition.