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Dewsbury, Jonathan; Whiteley, R A

doi:10.1023/a:1015479114491

Cited by 7 publications

(6 citation statements)

References 1 publication

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“…An existing theoretical model for the hold time of a CEA starts from the sharp model proposed by DiNenno and Forssell [14]. The sharp model was extended to the wide model proposed by Dewsbury and Whiteley and modified to the thick model proposed by Todd [7,11,12]. The theoretical model is derived from the mass conservation equation for the agent inside the enclosure through several assumptions.…”

Section: Deviation Of the Theoretical Equations For The Hold Timementioning

confidence: 99%

Section: Deviation Of the Theoretical Equations For The Hold Timementioning

confidence: 99%

“…The theoretical model is derived from the mass conservation equation for the agent inside the enclosure through several assumptions. The assumptions for the hold time of a CEA are as stated below [7,[11][12][13][14][18][19][20][21][22]:  The protected has a constant cross-section according to its height.  The leakage areas through the protected enclosure boundaries occur only at the upper and the lower extremes.…”

Section: Deviation Of the Theoretical Equations For The Hold Timementioning

confidence: 99%

“…This time is called the hold time or retention time. Because the hold time secures the time required to extinguish a fire 2 of 15 manually, the longer this time is, the more the fire damage can be minimized [7]. Therefore, it is only possible to obtain approval from relevant authorities when evidence of a hold time exceeding the standard is secured.…”

Section: Introductionmentioning

confidence: 99%

“…The descending interface models are divided into three types based on differences in the interpretation of diffusion, but the interpretation of advection is the same [7][8][9][10]13]. In other words, the analysis of the advection for the wide model and the thick model is the same as in the sharp model.…”

Section: Introductionmentioning

confidence: 99%

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A Study on a Modified Model for the Hold Time of a Clean Extinguishing Agent

et al. 2021

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When estimating the theoretical hold time of a Clean Extinguishing Agent (CEA), the hold time is predicted using a leakage exponent and leakage characteristics that are measured through an Enclosure Integrity Test (EIT). In particular, the leakage exponent n is conventionally applied as 0.5, but recently, a variable exponent has been applied through measurement (approximately 0.48 to 0.85). When variable n is applied, the hold time varies greatly depending on the size of n. Therefore, in this study, a modified theoretical model for the hold time of a CEA is proposed to improve the accuracy of the hold time depending on the leakage exponent n. The modified theoretical model applies a different analysis of the inflow and outflow volumetric flow, and the results enable a more accurate hold time prediction. The modified theoretical equation shows an improvement of up to 8.6% for outflow volumetric flow V˙o and a maximum improvement of approximately 10.7% for hold time th.

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Section: Deviation Of the Theoretical Equations For The Hold Timementioning

confidence: 99%

Section: Deviation Of the Theoretical Equations For The Hold Timementioning

confidence: 99%

Section: Deviation Of the Theoretical Equations For The Hold Timementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

A Study on a Modified Model for the Hold Time of a Clean Extinguishing Agent

et al. 2021

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Clean Agent Total Flooding Fire Extinguishing Systems

DiNenno

Forssell

2016

SFPE Handbook of Fire Protection Engineering

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Analysis of Hold Time Models for Total Flooding Clean Extinguishing Agents

Hetrick

2008

Fire Technol

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This study documents the experimental results of a research program designed to evaluate the validity of the widely published hold time prediction models found in NFPA 2001, Annex C and ISO 14520-1, Annex E. The models discussed in these standards obtain a measure of the equivalent leakage area, which, when coupled with Ôworst caseÕ assumptions, can be used to determine the minimum hold time. Three hold time prediction theories are adopted from these standards for validation; a wide descending interface model as implemented in ISO 14520-1 and two sharp descending interface models from the 2004 and 2008 publications of NFPA 2001. The experimental program is comprised of 15 tests conducted in a 103 m 3 test enclosure. Three commercially available clean agents are selected to span a wide range of agent vapor densities including FK-5-1-12, HFC-125, and IG-541. A series of holes were drilled through enclosure boundaries at upper and lower elevations which were opened or closed as a means of regulating the amount of leakage area for any given test. Vertical profiles of agent concentration and ambient pressure are used to evaluate the agent concentration distribution, rates of agent draining, and the effective lower leakage fraction. A non-dimensional hold time is used to compare experimental results involving differing agent types and leakage areas. Results show that empirical values of the hold time are up to 50% longer than the theoretical hold time predictions when evaluated as the time to reduce the agent concentration to half its initial value. When evaluated as a 15% drop in concentration the model validity is significantly reduced. Under this condition, empirical hold time values are up to 50% shorter than the predictions of the sharp descending interface models and up to 100% longer than the wide descending interface model. A Theoretical orifice area (m 2 ) A F Enclosure floor area (m 2 ) A i Orifice area for gas flowing into enclosure (m 2 ) A LL Summed orifice area of all lower leakages (m 2 ) A o Orifice area for gas flowing out of enclosure (m 2 ) A T Total theoretical orifice area in the orifice flow equation (m 2 ) A UL Summed orifice area of all upper leakages (m 2 ) C Combined coefficient in the orifice flow equation (s 2n)1 /m 2n)3 )

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Untitled

Cited by 7 publications

References 1 publication

A Study on a Modified Model for the Hold Time of a Clean Extinguishing Agent

A Study on a Modified Model for the Hold Time of a Clean Extinguishing Agent

Clean Agent Total Flooding Fire Extinguishing Systems

Analysis of Hold Time Models for Total Flooding Clean Extinguishing Agents

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