The Experts below are selected from a list of 5175 Experts worldwide ranked by ideXlab platform

Matthew S Hoehler - One of the best experts on this subject based on the ideXlab platform.

Matthew F Bundy - One of the best experts on this subject based on the ideXlab platform.

Fei Tang - One of the best experts on this subject based on the ideXlab platform.

  • merging behavior of facade flames ejected from two windows of an under ventilated Compartment Fire
    Proceedings of the Combustion Institute, 2015
    Co-Authors: Fei Tang, Z Qiu, Michael A Delichatsios
    Abstract:

    Abstract This paper investigates the merging behavior of flames ejected from two parallel windows of an under-ventilated Compartment Fire using a LPG gas burner. A reduced-scale model (about 1:4) of a Compartment Fire with a facade wall has been constructed where the window dimensions and the separation distance between them varied during the experiments. The flames ejected from the windows were recorded by a CCD camera. The excess heat release of the fuel burning outside the windows was high enough to produce flames controlled by three-dimensional entrainment. Temperatures inside the Compartment, the flame merging probability, the distance from neutral plane to flame lowest merging point, and the height of the facade flames before and during merging were measured. The temperature measurements inside the under-ventilated Compartment Fires do not change with total heat release rate or the window separation distance, thus indicating that the same heat is produced inside the Compartments. The flame merging probability and the flame merging point distance are normalized and well correlated using the facade flame height for completely non-merging flames and the separation distance between the windows. Finally, the facade flame height normalized by the facade flame height for completely non-merging flames is well correlated with the ratio of surface of the air entrained between the windows as the separation distance changes divided by the total surface area from all sides available for entrainment. For the present case this ratio is a function of the ratio of the flame merging point distance over the facade flame height for completely non-merging flames which is finally used for the correlation of merging flame heights.

  • experimental investigation on window ejected facade flame heights with different constraint side wall lengths and global correlation
    International Journal of Heat and Mass Transfer, 2014
    Co-Authors: K H Lu, Longhua Hu, Fei Tang, Linghui He, Xiaochun Zhang
    Abstract:

    Abstract This paper presents an experimental investigation on the effect of side wall length (normal to the facade direction) on the ejected facade flame height from a window of an under-ventilated Compartment Fire. The ejected facade flames are recorded by a CCD camera with various side wall lengths L at different side wall separation distances D. Results show that, as the length of the side wall increases, the change in behavior of the flame height can be categorized into two regimes: (1) the flame-entrainment-controlled regime in which flame height increases with side wall length for “(half) axisymmetric Fire” but independent of side wall length for “wall Fire”; and (2) the combustion-efficiency-controlled regime where the flame heights for both these two Fire types decrease with side wall length due to decrease of the combustion efficiency inside the Fire room, for L = 3D or greater. A global parameter K is then proposed based on scaling analysis for the air entrainment of the flame with side wall length, in relation to characteristic length scales l 1 and l 2 of the window, which well collapse the experimental data for different window dimensions, side wall lengths and separation distances.

  • heat flux profile upon building facade with side walls due to window ejected Fire plume an experimental investigation and global correlation
    Fire Safety Journal, 2014
    Co-Authors: Fei Tang, Xiaochun Zhang, Zengwei Qiu
    Abstract:

    Abstract This paper investigates the heat flux profile upon building facade with side wall constraints due to ejected Fire plumes from a window of an under-ventilated Compartment Fire. A reduced-scale model (1:8), consisting of a cubic Fire Compartment with a facade wall attached and two side walls located symmetrically at both sides of the window is developed. The window dimensions and the side wall distances are changed in experiments, representing different ventilations and constraints on Fire plume entrainment. Five heat flux gauges are employed in measurement of vertical heat flux profile upon the facade wall. Results show that with the decrease in separation distance of side walls, the heat flux increases for small windows where dimensionless excess heat release rate Q e x ⁎ ≥ 1.3 (“(half) axisymmetric Fire” regime), meanwhile shows weak dependency on side wall separation distance for large windows where Q e x ⁎ 1.3 (“wall Fire” regime). A new global formula is proposed to characterize the vertical profile of heat flux based on Lee’s model without side walls as further modified by a parameter K in relation to the separation distance of side walls and characteristic length scales of the window. Experimental data for different windows and side wall separation distances are well collapsed by the proposed formula.

  • a global non dimensional factor characterizing side wall constraint effect on facade flame entrainment and flame height from opening of Compartment Fires
    International Journal of Heat and Mass Transfer, 2014
    Co-Authors: Longhua Hu, Fei Tang, Michael A Delichatsios, K H Lu, Liqun He
    Abstract:

    Abstract This paper investigates experimentally the side wall constraint effect on facade flame behavior ejected from the opening of an under-ventilated Compartment Fire. Experiments are carried out in a reduced-scale experimental model of 1:8, consisting of a cubic Fire Compartment (including one opening) with a vertical facade wall and two side walls. The facade flame heights for different opening geometries (width, height) are recorded by a CCD camera under various side wall separation distances. It is found that as the distance of the two side walls decreases, the change of the flame height can be categorized into two regimes, due to correspondingly the two different facade flame entrainment behaviors distinguished by the dimensionless excess heat release rate Q ex ∗ , outside the opening: (a) for the “wall Fire” ( Q ex ∗  ⩽ 1.3), the flame height is shown to change little with decrease of side wall distance as the dominant entrainment is from the front direction (normal to the facade wall) irrelevant to the side wall distances; (b) for the “axis-symmetrical Fire” ( Q ex ∗  > 1.3), flame height increases prominently with decrease in side wall distance as both the entrainment from two side directions (parallel to the facade wall) and that from the front direction (normal to the facade wall) together dominate. A global non-dimensional factor K is then brought forward based on physically the side wall constraint effect on the facade flame entrainment, to characterize the side wall effect on the flame height, by including the dimensionless excess heat release rate, the characteristic length scales of the opening as well as the side wall separation distance. The experimental data are shown to be well correlated by the proposed global factor.

  • a mathematical model on lateral temperature profile of buoyant window spill plume from a Compartment Fire
    International Journal of Heat and Mass Transfer, 2013
    Co-Authors: Fei Tang, Michael A Delichatsios
    Abstract:

    A Gaussian-based mathematical model is theoretically brought forward to describe the lateral temperature profile (in the direction normal to the facade wall) of a spill buoyant plume from window of a Compartment Fire. The model is built up physically based on that this buoyant plume is conceptually produced by a rectangular Fire source with characteristic side dimensions of l1 (beside wall, physical length scale related to the effective area of the outflow) and l2 (normal to wall, physical length scale representing the length after which the outflow turns from horizontal to vertical due to buoyancy) sitting beside an adiabatic facade wall at the neutral plane height of the window. A deduced length scale, by accounting for the entrainment of air mass flow rate into the plume from the non-constrained sides, is brought forward to characterize the effective plume thickness in the direction normal to the facade wall, which will be used in the Gaussian profile function. Experiments are carried out in an experimental device to validate the model developed for six different windows. Results show that the length scale proposed for describing the effective plume thickness can successfully collapse the experimental data of different total heat release rates for various window geometries, and the proposed Gaussian-based model can predict the lateral temperature profile measurements. Furthermore, an exponential function is proposed for the parameter β in the Gaussian profile of such a spill plume in relation to the window aspect ratio (H/W).

Michael A Delichatsios - One of the best experts on this subject based on the ideXlab platform.

  • merging behavior of facade flames ejected from two windows of an under ventilated Compartment Fire
    Proceedings of the Combustion Institute, 2015
    Co-Authors: Fei Tang, Z Qiu, Michael A Delichatsios
    Abstract:

    Abstract This paper investigates the merging behavior of flames ejected from two parallel windows of an under-ventilated Compartment Fire using a LPG gas burner. A reduced-scale model (about 1:4) of a Compartment Fire with a facade wall has been constructed where the window dimensions and the separation distance between them varied during the experiments. The flames ejected from the windows were recorded by a CCD camera. The excess heat release of the fuel burning outside the windows was high enough to produce flames controlled by three-dimensional entrainment. Temperatures inside the Compartment, the flame merging probability, the distance from neutral plane to flame lowest merging point, and the height of the facade flames before and during merging were measured. The temperature measurements inside the under-ventilated Compartment Fires do not change with total heat release rate or the window separation distance, thus indicating that the same heat is produced inside the Compartments. The flame merging probability and the flame merging point distance are normalized and well correlated using the facade flame height for completely non-merging flames and the separation distance between the windows. Finally, the facade flame height normalized by the facade flame height for completely non-merging flames is well correlated with the ratio of surface of the air entrained between the windows as the separation distance changes divided by the total surface area from all sides available for entrainment. For the present case this ratio is a function of the ratio of the flame merging point distance over the facade flame height for completely non-merging flames which is finally used for the correlation of merging flame heights.

  • a global non dimensional factor characterizing side wall constraint effect on facade flame entrainment and flame height from opening of Compartment Fires
    International Journal of Heat and Mass Transfer, 2014
    Co-Authors: Longhua Hu, Fei Tang, Michael A Delichatsios, K H Lu, Liqun He
    Abstract:

    Abstract This paper investigates experimentally the side wall constraint effect on facade flame behavior ejected from the opening of an under-ventilated Compartment Fire. Experiments are carried out in a reduced-scale experimental model of 1:8, consisting of a cubic Fire Compartment (including one opening) with a vertical facade wall and two side walls. The facade flame heights for different opening geometries (width, height) are recorded by a CCD camera under various side wall separation distances. It is found that as the distance of the two side walls decreases, the change of the flame height can be categorized into two regimes, due to correspondingly the two different facade flame entrainment behaviors distinguished by the dimensionless excess heat release rate Q ex ∗ , outside the opening: (a) for the “wall Fire” ( Q ex ∗  ⩽ 1.3), the flame height is shown to change little with decrease of side wall distance as the dominant entrainment is from the front direction (normal to the facade wall) irrelevant to the side wall distances; (b) for the “axis-symmetrical Fire” ( Q ex ∗  > 1.3), flame height increases prominently with decrease in side wall distance as both the entrainment from two side directions (parallel to the facade wall) and that from the front direction (normal to the facade wall) together dominate. A global non-dimensional factor K is then brought forward based on physically the side wall constraint effect on the facade flame entrainment, to characterize the side wall effect on the flame height, by including the dimensionless excess heat release rate, the characteristic length scales of the opening as well as the side wall separation distance. The experimental data are shown to be well correlated by the proposed global factor.

  • a mathematical model on lateral temperature profile of buoyant window spill plume from a Compartment Fire
    International Journal of Heat and Mass Transfer, 2013
    Co-Authors: Fei Tang, Michael A Delichatsios
    Abstract:

    A Gaussian-based mathematical model is theoretically brought forward to describe the lateral temperature profile (in the direction normal to the facade wall) of a spill buoyant plume from window of a Compartment Fire. The model is built up physically based on that this buoyant plume is conceptually produced by a rectangular Fire source with characteristic side dimensions of l1 (beside wall, physical length scale related to the effective area of the outflow) and l2 (normal to wall, physical length scale representing the length after which the outflow turns from horizontal to vertical due to buoyancy) sitting beside an adiabatic facade wall at the neutral plane height of the window. A deduced length scale, by accounting for the entrainment of air mass flow rate into the plume from the non-constrained sides, is brought forward to characterize the effective plume thickness in the direction normal to the facade wall, which will be used in the Gaussian profile function. Experiments are carried out in an experimental device to validate the model developed for six different windows. Results show that the length scale proposed for describing the effective plume thickness can successfully collapse the experimental data of different total heat release rates for various window geometries, and the proposed Gaussian-based model can predict the lateral temperature profile measurements. Furthermore, an exponential function is proposed for the parameter β in the Gaussian profile of such a spill plume in relation to the window aspect ratio (H/W).

  • experimental study on flame height and temperature profile of buoyant window spill plume from an under ventilated Compartment Fire
    International Journal of Heat and Mass Transfer, 2012
    Co-Authors: Fei Tang, Michael A Delichatsios, W Zhu
    Abstract:

    Abstract Fire experiments were carried out in a scale model, consisting of an 0.8 m cubic Fire Compartment with six window like geometries and an attached 3 m (wide) × 5 m (high) facade wall. A propane porous gas burner with controlled fuel supply rate was the Fire source. Gas temperature profiles were measured inside the Compartment and near the facade wall. The outside spill flame heights were recorded by a CCD Digital camera. Temperature and flame heights are correlated with heat release rate and the window geometry using physically non-dimensional analysis. The steady gas temperatures inside the Compartment are determined by an overall energy balance between the heat release rate inside the Compartment and the wall conduction and opening radiation heat losses using an effective overall heat loss coefficient. Flame heights on the facade are non-dimensionally correlated by the excess fuel heat release rate outside the enclosure and a characteristic length scale for the window. These results agree with previous results in the literature. Vertical gas temperatures near the facade wall outside the enclosure are non-dimensionally correlated with the total convective heat flow rate above the flames and the same characteristic window length scale as the flame height, with the additional necessary determination of a virtual origin of the convective flow above the flame. These results and correlations are new and a significant improvement over previous results in the literature.

Longhua Hu - One of the best experts on this subject based on the ideXlab platform.

  • Flame height and temperature profile of window ejected thermal plume from Compartment Fire without facade wall
    International Journal of Thermal Sciences, 2018
    Co-Authors: Longhua Hu, Kaizhi Hu
    Abstract:

    Abstract This paper investigates experimentally the flame height and temperature profile of window ejected thermal plume from Compartment Fire without facade wall. The previous works and correlations on these characteristics of such thermal plume mainly concern the condition with a facade wall, where the air entrainment of the thermal plume from the side of the facade wall is restricted. However, such entrainment constraint effect does not exist when the Fire occurs at the top floor of the building noting that there is no facade above the top floor, for which scenario the flame height and temperature profile of the thermal plume characteristics have not been quantified in the literature. In this work, comprehensive experiments were carried out by employing a reduced-scale model (1:8), consisting of a 0.4 m cubic Fire Compartment with six different window openings corresponding to various ventilation factors ( A H ). A propane square porous burner was set as Fire source with various fuel mass flow meters and hence heat release rate. All the tests were designed as un-ventilated condition that stable flame was observed outside the window. The flame height outside the window was recorded through a CCD camera from the side view. The temperature profiles of the ejected Fire plume outside the window were measured by the thermocouple arrays (7 rows, 7 columns) located above the top of the Compartment. These measured quantities without the facade wall were compared from those with a facade wall. Results showed that the flame height can be still well correlated non-dimensionally by the excess fuel heat release rate and the characteristic length scale ( l 1 = ( A H ) 2 / 5 ) of the window. However, the flame height with a facade wall was higher, being 1.31 times of those without a facade wall. This difference was physically quantified by the air entrainment change due to constraint effect from the facade wall. The radial temperature profile in the ejected thermal Fire plume at various height can be globally represented by the Gaussian function ( T z , x − T ∞ T z , m a x − T ∞ = e [ − β ( x − x m FWHM ) 2 ] ) with and without facade wall, where the value of β was found to be 2 ln 2 . These quantifications and correlations on window-ejected thermal plume characteristics without a facade wall, providing a significant supplementary over previous works focusing on condition with the facade wall, will be an important addition for the estimation of such thermal plume characteristics and its thermal impacts. This work, providing experimental data and correlations on window ejected thermal plume characteristics from Compartment Fire at the top level of the building without the effect of facade wall, will be an important supplementary over previous knowledge focusing on the scenario with the effect of facade wall.

  • experimental investigation on window ejected facade flame heights with different constraint side wall lengths and global correlation
    International Journal of Heat and Mass Transfer, 2014
    Co-Authors: K H Lu, Longhua Hu, Fei Tang, Linghui He, Xiaochun Zhang
    Abstract:

    Abstract This paper presents an experimental investigation on the effect of side wall length (normal to the facade direction) on the ejected facade flame height from a window of an under-ventilated Compartment Fire. The ejected facade flames are recorded by a CCD camera with various side wall lengths L at different side wall separation distances D. Results show that, as the length of the side wall increases, the change in behavior of the flame height can be categorized into two regimes: (1) the flame-entrainment-controlled regime in which flame height increases with side wall length for “(half) axisymmetric Fire” but independent of side wall length for “wall Fire”; and (2) the combustion-efficiency-controlled regime where the flame heights for both these two Fire types decrease with side wall length due to decrease of the combustion efficiency inside the Fire room, for L = 3D or greater. A global parameter K is then proposed based on scaling analysis for the air entrainment of the flame with side wall length, in relation to characteristic length scales l 1 and l 2 of the window, which well collapse the experimental data for different window dimensions, side wall lengths and separation distances.

  • a global non dimensional factor characterizing side wall constraint effect on facade flame entrainment and flame height from opening of Compartment Fires
    International Journal of Heat and Mass Transfer, 2014
    Co-Authors: Longhua Hu, Fei Tang, Michael A Delichatsios, K H Lu, Liqun He
    Abstract:

    Abstract This paper investigates experimentally the side wall constraint effect on facade flame behavior ejected from the opening of an under-ventilated Compartment Fire. Experiments are carried out in a reduced-scale experimental model of 1:8, consisting of a cubic Fire Compartment (including one opening) with a vertical facade wall and two side walls. The facade flame heights for different opening geometries (width, height) are recorded by a CCD camera under various side wall separation distances. It is found that as the distance of the two side walls decreases, the change of the flame height can be categorized into two regimes, due to correspondingly the two different facade flame entrainment behaviors distinguished by the dimensionless excess heat release rate Q ex ∗ , outside the opening: (a) for the “wall Fire” ( Q ex ∗  ⩽ 1.3), the flame height is shown to change little with decrease of side wall distance as the dominant entrainment is from the front direction (normal to the facade wall) irrelevant to the side wall distances; (b) for the “axis-symmetrical Fire” ( Q ex ∗  > 1.3), flame height increases prominently with decrease in side wall distance as both the entrainment from two side directions (parallel to the facade wall) and that from the front direction (normal to the facade wall) together dominate. A global non-dimensional factor K is then brought forward based on physically the side wall constraint effect on the facade flame entrainment, to characterize the side wall effect on the flame height, by including the dimensionless excess heat release rate, the characteristic length scales of the opening as well as the side wall separation distance. The experimental data are shown to be well correlated by the proposed global factor.