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Heat Release Rates of Multiple Objects at Varying Distances
Mälardalen University, School of Sustainable Development of Society and Technology. (Safety Science Lab)ORCID iD: 0000-0002-8326-2860
Mälardalen University, School of Sustainable Development of Society and Technology. (Safety Science Lab)
2012 (English)In: Fire safety journal, ISSN 0379-7112, E-ISSN 1873-7226, Vol. 52, p. 1-10Article in journal (Refereed) Published
Abstract [en]

Simple theoretical calculations of the overall heat release rate (HRR) of multiple objects at both constant and varying distances have been carried out. The results were compared to both fire experiments in a longitudinal ventilated model tunnel (scale 1:15) using piles of wooden pallets placed at varying distance from each other and with model scale fire experiments (scale 1:4) conducted with a freight truck commodity without roof over the piles of wooden pallets. Two different methods are presented which are based on physical relations for fire spread between the piles of wooden pallets. The first method uses a critical heat flux as ignition criteria while the other method uses an ignition temperature. The method using the critical heat flux as ignition criteria shows very good agreement with the corresponding experimental results used. The method using the ignition temperature as ignition criteria did not agree well with the corresponding experimental results. The prerequisite that the burning objects should not necessarily have to be positioned at equal distance was fulfilled.

Place, publisher, year, edition, pages
2012. Vol. 52, p. 1-10
National Category
Other Engineering and Technologies
Research subject
Energy- and Environmental Engineering
Identifiers
URN: urn:nbn:se:mdh:diva-11305DOI: 10.1016/j.firesaf.2012.03.007ISI: 000307132800001Scopus ID: 2-s2.0-84860509088OAI: oai:DiVA.org:mdh-11305DiVA, id: diva2:383377
Projects
GRUVANAvailable from: 2011-01-04 Created: 2011-01-04 Last updated: 2017-09-27Bibliographically approved
In thesis
1. Design fires in underground hard rock mines
Open this publication in new window or tab >>Design fires in underground hard rock mines
2011 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

During several decades considerable research activities have been conducted with respect to fires in coal mines, but the research activities with respect to hard rock mines have been limited. As the hard rock mines are getting more complex the need for deeper understanding of fires in underground hard rock mines are getting more in demand. The more urgent demands are the need for more specific heat release rate curves as design fires, applicable fire experiments and any method that would allow for the calculation of the total heat release rate curve of an object. This thesis presents a number of examples on design fire curves applicable to underground hard rock mines; it also presents the results of model scale fire experiments and methods for calculating the total heat release rate of several objects at uniform as well as non-uniform conditions. Tests were carried out in a model scale tunnel using wooden pallets as fire load. The parameters tested were the distance between piles of pallets and longitudinal ventilation rate. It was found that an increasing ventilation rate also increases the peak heat release rate. When studying the curves of heat release rates it was found that when the distance between the ignited pile and the second pile increased to a certain level the delayed ignition of the second pile will result in that the peak heat release rate of the adjacent piles will not occur simultaneously. The ignition data indicated that the ignition time of adjacent piles decreased as the longitudinal ventilation increased.  A method using a critical heat flux as ignition criterion exhibited very good agreement with the corresponding experiments for both uniform as well as non-uniform conditions. The methods using the ignition temperature as ignition criterion did not agree very well with any of the corresponding experiments.

Place, publisher, year, edition, pages
Västerås: Mälardalen University, 2011. p. 86
Series
Mälardalen University Press Licentiate Theses, ISSN 1651-9256 ; 127
Keywords
Design fire, underground, hard rock mine, vehicle fire, smoke spread
Research subject
Energy- and Environmental Engineering
Identifiers
urn:nbn:se:mdh:diva-11297 (URN)978-91-7485-000-0 (ISBN)
Presentation
2011-01-28, Gamma, Mälardalens högskola, Västerås, 13:00 (English)
Opponent
Supervisors
Projects
GRUVAN
Available from: 2011-01-04 Created: 2011-01-03 Last updated: 2014-01-07Bibliographically approved
2. Study of heat release rates of mining vehicles in underground hard rock mines
Open this publication in new window or tab >>Study of heat release rates of mining vehicles in underground hard rock mines
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

A unique study on fire safety in hard rock underground mines with focus on heat release rates of mining vehicles is presented. A literature inventory was conducted with respect to fires in underground hard rock mines, which revealed that the most common fire cause in underground mines was flammable liquid sprayed onto hot surface and the most common fire object was a vehicle. A major concern was the lack of documented fire experiments in mining vehicles and heat release rate curves. It also revealed the limited research carried out on fire safety and fire development on vehicles found in hard rock underground mines.

In order to fill the gap of knowledge lack on heat release rates, fire experiments were carried out on wood cribs and wooden pallets in a model-scale tunnel with longitudinal ventilation where the distance between the fuel items were kept constant as well as varied. Different ignition criteria were applied in the ensuing calculations. It was found that the critical heat flux criterion generally showed very good agreement with the corresponding results of performed fire experiments but tended to have too short ignition times when the distance between the fuel items was increased. The ignition temperature criterion generally performed poorly compared with the measured results, but it was found that the accuracy improved considerably as the distance between the fuel items and the amount of energy accumulated on the fuel surface was increased.

As a final approach, two full-scale fire experiments were carried out in an operative underground mine using a wheel loader and a drilling rig respectively. The resulting heat release rates of the experiments were compared with calculated overall heat release rates applying the different ignition criteria. It was found that the critical heat flux criterion resulted in ignition times very close to the observed ignition times. The ignition temperature criterion resulted in surface temperatures that never achieved the corresponding ignition temperatures. Some difficulties were experienced when calculating the heat release rate curve of the wheel loader, as it was difficult to accurately predict the mechanical failure of a significant part initiating the highly significant fire in the hydraulic oil. Additional heat terms were added to the heat balance, where the added flame radiation term was found to have a large impact on the output results while the heat loss terms were found to have very little effect.

Place, publisher, year, edition, pages
Västerås: Mälardalen University, 2015
Series
Mälardalen University Press Dissertations, ISSN 1651-4238 ; 178
National Category
Other Engineering and Technologies not elsewhere specified
Research subject
Energy- and Environmental Engineering
Identifiers
urn:nbn:se:mdh:diva-27776 (URN)978-91-7485-201-1 (ISBN)
Public defence
2015-05-27, Delta, Västerås, 13:15 (English)
Opponent
Supervisors
Available from: 2015-04-02 Created: 2015-03-31 Last updated: 2015-06-29Bibliographically approved

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