Effect of flame heat flux on thermal response and fire properties of char-forming composite materials

Abstract The most common non-granular fillers are sheet and fiber. When they are distributed along the heat flux direction, the thermal conductivity of composite increases greatly. Meanwhile, the filler contact also has large effect on the thermal conductivity. However, the effect of filler contact on the thermal conductivity of composite with directional fillers has not been investigated. In this paper, the combined effects of filler contact, content and orientation are investigated. The results show that the effect of filler orientation on the thermal conductivity is greater than filler contact in low filler content, and exact opposite in high filler content. The effect of filler contact on fibrous and sheet fillers is far greater than cube and sphere fillers. This rule is affected by the filler contact. The filler content of 8% is the ideal percolation threshold of composite with fibrous and sheet filler. It is lower than cube filler and previous reports. The space for thermal conductivity growth of composite with directional filler is still very large. The effect of interfacial thermal resistance should be considered in predicting the thermal conductivity of composite under high Rc (>10-4).

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Thermal response of an unsteady laminar boundary layer on a flat plate due to step changes in wall temperature and in wall heat flux

Computer Methods in Applied Mechanics and Engineering ◽

10.1016/0045-7825(73)90005-4 ◽

1973 ◽

Vol 2 (3) ◽

pp. 323-338 ◽

Cited By ~ 4

Author(s):

Tuncer Cebeci ◽

J. Bard

Keyword(s):

Boundary Layer ◽

Heat Flux ◽

Flat Plate ◽

Laminar Boundary Layer ◽

Wall Temperature ◽

Thermal Response ◽

Wall Heat Flux

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Experimental Validation of Non-Fourier Thermal Response in Porous Media

10.1115/imece2001/htd-24279 ◽

2001 ◽

Author(s):

A. G. Agwu Nnanna ◽

K. T. Harris ◽

A. Haji-Sheikh

Keyword(s):

Heat Flux ◽

Porous Media ◽

Experimental Validation ◽

Thermal Response ◽

Lag Time ◽

Equation Model ◽

Thermal Parameters ◽

Solid Matrix ◽

Microscale Model ◽

Short Time

Abstract An experimental validation of non-Fourier behavior in porous media due to short time thermal perturbation is presented. The governing energy equation is formulated based on the two-equation model and the non-Fourier model. This formulation leads to the emergence of four thermal parameters: lag-time in heat flux τq, lag-time τt in temperature due to interstitial heat transfer coefficient h, and lag-time in the transient response of the temperature gradient τx in the heat flux equation. These parameters account for the microstructural thermal interaction between the fluid and neighboring solid matrix as well as the delay time needed for both phases to approach thermal equilibrium. An experimental verification of the microscale model was performed under standard laboratory conditions. The values of the aforementioned thermal parameters were determined to compute the fluid and solid temperatures. Results predicted from three models (classical Fourier, non-Fourier, and experimental) were compared. It indicates an excellent agreement between the non-Fourier and the experimental model, and a significant deviation of Fourier prediction from the experimental results.

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Embedded flame heat flux method for simulation of quasi-steady state vertical flame spread

Fire Safety Journal ◽

10.1016/j.firesaf.2019.01.011 ◽

2019 ◽

Vol 104 ◽

pp. 117-129 ◽

Cited By ~ 2

Author(s):

Kaiyuan Li ◽

Simo Hostikka

Keyword(s):

Heat Flux ◽

Steady State ◽

Flame Spread ◽

Quasi Steady State ◽

Flux Method ◽

Flame Heat Flux

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Two-dimensional hybrid analytical approach for the investigation of thermal aspects in human tissue undergoing regional hyperthermia therapy

Proceedings of the Institution of Mechanical Engineers Part C Journal of Mechanical Engineering Science ◽

10.1177/0954406220919460 ◽

2020 ◽

Vol 234 (20) ◽

pp. 3951-3966

Author(s):

Jaideep Dutta ◽

Balaram Kundu

Keyword(s):

Heat Flux ◽

Heat Conduction ◽

Cancer Treatment ◽

Thermal Response ◽

Skin Tissue ◽

Hyperbolic Heat Conduction ◽

Two Dimensional ◽

Regional Hyperthermia ◽

Hyperthermia Therapy ◽

The Impact

The formation of the present work is based on the development of the exact analytical solution of two-dimensional temperature response by employing the hyperbolic heat conduction bioheat model in a single-layered human skin tissue subjected to the regional hyperthermia therapy (RHT) for cancer treatment. The mathematical approach has been utilized as a hybrid form of ‘separation of variables’ and ‘finite integral transform’ method. Three kinds of surface heat fluxes (constant, sinusoidal and cosine) have been employed as an external heat source on the therapeutic surface of the square-shaped skin tissue of 100 mm × 100 mm. An innovative form of initial condition (spatially dependent) has been implemented in the present mathematical formulation as skin tissues are highly non-homogeneous and non-uniform in structure. The present research outcome indicates that cosine heat flux would be a suitable alternative for the sinusoidal heat flux. The impact of the relaxation time lag has been clearly noted in the thermal response with the waveform-like behaviour and it justifies the postulate of hyperbolic heat conduction. The two-dimensional temperature of the skin tissue has been observed in the range of 48.1 ℃–40 ℃ (in decreasing order). Estimated peak temperatures are in the proposed spectrum of hyperthermia therapy for an exposure time of 100 s, and this fact is true in an agreement with the medical protocol of the cancer treatment. The accuracy of the mathematical modelling and in-house computer codes are justified with the published numerical models and the maximum deviation of the thermal response has been noticed in order of 1.5–3%. The two-dimensional surface thermal contours have provided a glimpse of heat flow in the physical domain of skin tissue under different heating conditions and this research output may be beneficial to establish the theoretical standard of the regional hyperthermia treatment for cancer eradication.

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The Roseville Bomb Disaster Simulated Train Braking System Tests and Boxcar Wood Floor Ignition Experiments

Journal of Mechanical Design ◽

10.1115/1.2912756 ◽

1991 ◽

Vol 113 (1) ◽

pp. 91-99

Author(s):

B. Ross ◽

P. G. Parikh

Keyword(s):

Heat Flux ◽

Cast Iron ◽

Ignition Time ◽

Thermal Response ◽

Radiant Heat ◽

Full Scale ◽

Test Facility ◽

Shield Effectiveness ◽

Wood Floor ◽

Wood Surfaces

A massive chain of property damaging explosions involving an ammunition train occurred at the railroad yard, Roseville, California. The train had pulled into the yard after a night trip of some 100 miles across Donner Summit and down the extended Norden-Roseville grade. Physical evidence confirmed that first explosions were centered at a DODX type boxcar loaded with 250 lb. bombs. Further, bomb cook-off detonation tests established that the triggering bomb blast was not a result of shock loads but rather derived from an engulfing fire initiated in the boxcar wood plank floor under influence of extended heavy braking action on the mountain grade. It was also suspected that high friction composition brake shoes were fitted on the car as replacements for cast iron shoes but the brake mechanical linkage lever ratios had not been modified as required. Results of a comprehensive research program are presented within context of the explosion event, and include analytical computer simulation of train descent profiles on mountain grades through full scale dynamometer tests with actual rail wheels and ultimately more scientific scaled wood floor ignition experiments in the laboratory. The thermal response of a simulated DODX boxcar wood floor was studied through experiments, full scale at a rail wheel dynamometer test facility, and in the laboratory. Certain input data for the wood floor ignition test program were measured on an actual boxcar joined with a freight train consist in transit down the Norden-Roseville grade. Two series of scaled wood ignition experiments were conducted on simulated DODX boxcar floors. Objectives of these tests were to determine: Influence of a cooling air stream on the ignition behavior of radiantly heated wood surfaces, and effectiveness of DODX (stand-off) and AAR (flush) type spark shields in preventing ignition of wood surfaces under radiant heating. It was found that for radiant heat flux levels representative of high friction composition shoes under severe train braking conditions, low speed airflow (wind) exerts a dramatic influence on the wood ignition time. For example, average ignition time for a simulated boxcar floor at a heat flux level of 0.4 cal/cm2sec was determined to be 15.6 min. with a 5 mph wind as compared to 3.6 min. with no wind. In the spark shield effectiveness tests, conducted at heat flux levels representative of cast iron shoes under severe braking conditions, the DODX (stand-off) type spark shield failed to prevent spontaneous flaming ignition of a wood surface directly above it. Under identical conditions, no flaming ignition was encountered with the AAR (flush) type spark shield.

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