Study of the thermohydraulics of CO2 discharge from a high pressure reservoir

Rapid depressurization of a CO2 pipeline – an experimental study

Progress in fire safety science strongly relies on the use of Computational Fluid Dynamics (CFD) to simulate a wide range of scenarios, involving complex geometries, multiple length/time scales and multi-physics (e.g., turbulence, combustion, heat transfer, soot generation, solid pyrolysis, flame spread and liquid evaporation), that could not be studied easily with analytical solutions and zone models. It has been recently well recognised in the fire community that there is need for better modelling of the physics in the near-wall region of boundary layer combustion. Within this context, heat transfer modelling is an important aspect since the fuel gasification rate for solid pyrolysis and liquid evaporation is determined by a heat feedback mechanism that depends on both convection and radiation. The paper focuses on convection and reviews the most commonly used approaches for modelling convective heat transfer with CFD using Large Eddy Simulations (LES) in the context of fire-driven flows. The considered test cases include pool fires and turbulent wall fires. The main assumptions, advantages and disadvantages of each modelling approach are outlined. Finally, a selection of numerical results from the application of the different approaches in pool fire and flame spread cases, is presented in order to demonstrate the impact that convective heat transfer modelling can have in such scenarios.

https://www.mdpi.com/2076-3417/11/11/5240/pdf

Review of Convective Heat Transfer Modelling in CFD Simulations of Fire-Driven Flows

Abstract A series of measurements designed to investigate the heat feedback in pool fires burning liquid fuels are reported. Such measurements are essential for the development and validation of detailed models which predict the burning rate of liquid hydrocarbons and solid polymers. The radial variation of the local radiative and local net heat flux incident on the surface of 0.30 m diameter pool fires were measured. A water-cooled, nitrogen purged, narrow view-angle gauge was developed to measure the radiative flux incident on the fuel surface. Measurements of the mass burning rate in a burner composed of annular rings was used to estimate the local heat feedback. A number of different fuels were studied, yielding flames with a wide range of heat release rates and luminosities. Consideration of the heat balance for a control volume enclosing the liquid PPOI indicated that radiation was an important component of the heat feedback for non-luminous fires and a dominant component in luminous fires.

/pdf/heat-feedback-to-the-fuel-surface-in-pool-fires-nist-sp-971-376vyw4pg0.pdf

Heat Feedback to the Fuel Surface in Pool Fires (NIST SP 971) | NIST

Numerical investigations have been carried out for a postulated enclosure fire scenario instigated due to methanol pool ignition in a chemical cleaning facility. The pool fire under consideration is radiation-dominated and poses a risk to the nearby objects if appropriate safety requirements are not met. The objective of the current study was to numerically evaluate the postulated fire scenario and provide safety recommendations to prevent/minimize the hazard. To do this, the fire scenario was first modeled using the finite volume method (FVM) based solver to predict the fire characteristics and the resulting changes inside the enclosure. The FDS predicted temperatures were then used as input boundary conditions to conduct a three-dimensional heat transfer analysis using the finite element method (FEM). The coupled FVM–FEM simulation approach enabled detailed three-dimensional conjugate heat transfer analysis. The proposed FVM–FEM coupled approach to analyze the fire dynamics and heat transfer will be helpful to safety engineers in carrying out a more robust and reliable fire risk assessment.

/pdf/numerical-simulations-of-a-postulated-methanol-pool-fire-1a9d3c4l.pdf

Numerical Simulations of a Postulated Methanol Pool Fire Scenario in a Ventilated Enclosure Using a Coupled FVM-FEM Approach

To improve numerical simulation of liquid pool fires and remove the need for experimentally measured or empirically calculated mass burning rates as boundary conditions, a fully coupled three-dimensional (3-D) numerical formulation, which directly solves convective motion in the fuel region by incorporating inhomogeneous heat feedback, is formulated. The fire dynamics is modelled using the large eddy simulation (LES) approach. Incompressible laminar flow formation is applied to the liquid fuel region, assuming constant thermo-physical properties except for the density which follows the Boussinesq approximation. The numerical formulation of the two phases is solved using a fully coupled conjugate heat transfer approach at the pool surface. The coupled model is validated against published measurements for a thin-layer heptane pool fire and a deep methanol pool fire. The convective motion within the liquid phase is found to have important effects on the pool fire mass burning rate and its neglection would result in a fast rise and over-prediction of the mass burning rate.

/pdf/the-effect-of-convective-motion-within-liquid-fuel-on-the-1f2fudhrrf.pdf

The effect of convective motion within liquid fuel on the mass burning rates of pool fires – A numerical study

A CFD based pipeline blowdown model has been developed and validated against experimentaldataforrichgas,gaseousanddensephasecarbondioxide.Themulti-componentfullycompressibletwo-phase solver is coupled with the homogeneous equilibrium model which assumes that the twophases share identical velocity, temperature and pressure. Real gas behavior is considered by twoequations of state. The liquid-vapour phase equilibrium of a multi-component rich gas is deter-mined by ﬂash calculations. A conjugate heat transfer problem is solved simultaneously for thepipe ﬂow and wall heat transfer. The conserved transport equations are solved using an ArbitraryLagrangian-Eulearian method. Predictions carried out for some previously tested blowdownscenarios are found to be in reasonably good agreement with the experimental data.KEYWORDS: Carbon dioxide, rich gas, blowdown, CFD, homogeneous equilibrium model

/pdf/numerical-study-of-compressed-co2-pipeline-decompression-4c0kxhlv22.pdf

Baopeng Xu

Papers

The effect of convective motion within liquid fuel on the mass burning rates of pool fires – A numerical study

Numerical study of compressed CO2 pipeline decompression characteristics using CFD-DECOM