Assignment 03 – Compartment fires by Dr Juan Hidalgo
Introduction Assignment 03 consists of a project on compartment fires where fire modelling shall be applied (Weeks 09, 10, 11 and 12). Assignment 03 is due on October 27th, 2019 at 23:59. The assignments submission must be completed via Turnitin. The submission link can be found in Blackboard. The assignment must be 25 pages at maximum. Appendices may be used but will not be used for marking.
Project description You are asked to assess the fire dynamics within a compartment of dimensions of 5 m (width) x 5 m (length) x 5 m (height). The compartment has a vertical opening (a door) of dimensions 1 m (width) x 2.4 m (height) and a horizontal opening of 1 m x 1 m located at the centre of the ceiling. The design fire within the compartment is a parabolic (αt2) fire, with a medium growth rate. Three different scenarios are to be considered where the compartment boundaries are (a) adiabatic (no heat losses), (b) made of a 2 mm thick steel sheet and (c) made of a 30 mm thick plasterboard.
In this project, you are asked to use both a zone model (CFAST) and a computational fluid dynamics model (FDS) to assess the fire dynamics for the three scenarios noted above. The outcomes from these models must be used in conjunction, wherever possible, to elaborate a detailed description of the following aspects:
– Fire dynamics during the pre-flashover stage (fuel-controlled, well-ventilated). [25 points] – Conditions for flashover (transition from pre-flashover to post-flashover). [25 points] – Fire dynamics during the post-flashover stage (ventilation-controlled, underventilated). [25 points] – Mass transfer through openings for both pre-flashover and post-flashover conditions. [25 points]
You will have to make several assumptions regarding model input parameters that must be stated and justified. It is also very important to discuss the validity and limits of applicability
SCHOOL OF CIVIL ENGINEERING
FIRE7620 – Fire Dynamics of the models used for each part of the assignment. You are advised to use analytical/experimental correlations taught in class to strengthen your discussion.
As a guideline, a series of aspects that may be useful to develop each part of the assignment is provided below. Note that the assignment does not consist of presenting this data individually, but using this data to complement/reinforce your description of the fire dynamics based on the understanding built in class.
Study of pre-flashover conditions: – Descent of the smoke layer in the compartment. – Density and temperature evolution of the gas-phase (hot and cold layer). – Flow fields in the compartment. – Oxygen concentration in the compartment. – Effect of the different linings on the fire dynamics.
Study of flashover conditions: – Establishing conditions for describing flashover. – Time to reach critical conditions for flashover. – Energy balance within the compartment. – Effect of the different lining on the fire dynamics. – Comparison with simplified analytical/experimental correlations
Study of post-flashover conditions: – Density and temperature in the gas-phase. – Flow fields in the compartment. – Energy balance within the compartment. – Oxygen concentration in the compartment. – Comparison with simplified analytical/experimental correlations. – Effect of the different linings on the fire dynamics.
Study of mass and heat transfer through the openings: – Flow fields at the openings. – Neutral pressure plane location. – Comparison with simplified analytical/experimental correlations.
Marking criteria Essential marking criteria include:
– Adequate development and use of models. – Technically-sound description and discussion of the results. – Coherence, conciseness and clarity in writing the report.
