Longitudinal Temperature Distribution Research Articles

Full-field temperature prediction in tunnel fires using limited monitored ceiling flow temperature data with transformer-based deep learning models

In practical tunnel scenarios, full-field coverage of sensors is impractical and costly. During a tunnel fire, the available information is constrained and localized, making the prediction of full-field smoke temperature distribution becoming a noteworthy challenge. This study proposes a transformer-based deep learning model to predict full-field smoke temperature distributions during fire incidents in real-time using limited temporal data from the sensors installed in localized regions below the ceiling, considering heat release rate of the fire source is unknown. The results indicate that proposed approach can predict the longitudinal temperature distribution throughout the tunnel with a length of 750 m by leveraging temperature data from limited sensors within a monitoring length of 210 m. It can further predict the vertical temperature profiles, and eventually estimate the full-field temperature distribution within the tunnel. The transformer model achieved R2 of 0.95 and 0.87 for longitudinal and vertical temperature distribution predictions, respectively. Under the influence of the self-attention mechanism, the transformer model has an advantage over the long short-term memory model in capturing global information, enhancing the accuracy of longitudinal temperature distribution predictions by 18.8%. This study significantly contributes to effective emergency response and rescue strategies during tunnel fire incidents.

Study on the influence of slope on smoke overflow and temperature characteristics of carriages with lateral openings in subway fires

This research explores the impact of slope on fire hazards in train carriages with multiple lateral openings in underground tunnel fires. Utilizing FDS software, a comprehensive full-scale fire scenario is simulated to study smoke overflow and temperature distribution in inclined tunnels with slopes ranging from 0 % to 4 % and Heat Release Rates (1 MW–10 MW) under natural ventilation. The study reveals that smoke mainly originates from the upstream end door and the door near the fire source, with smoke overflow from the upstream end door increasing significantly with the slope. Fire power has minimal impact on smoke overflow. When fire power is large, the longitudinal temperature distribution inside the carriage exhibits an overall increasing trend with increasing slope. The maximum carriage temperature decreases steadily with the slope for Q˙ ≤ 5 MW, while the slope has less influence on temperature variation for Q˙ > 5 MW. A modified prediction model is proposed to forecast maximum ceiling temperature during fire scenarios, providing valuable insights for structural fire protection, fire detection, and smoke control in metro areas. This study enhances understanding of smoke movement and temperature distribution in train carriage fires in inclined tunnels, contributing to engineering practices.

Experimental study on fire behaviours of double fires with asymmetric heat release rates in the tunnel with natural ventilation

This study experimentally investigates fire behaviors of double fires with asymmetric heat release rates in a naturally ventilated tunnel including flame merging and longitudinal ceiling gas temperature distribution. The comparison between double fires with symmetric and asymmetric heat release rates was also made. The results show that the flame merging possibility increases as the heat release rate on one side increases. The ratio of heat release rates between double fire sources still influences the flame merging possibility under a given total heat release rate. The ceiling gas temperature distribution is related to the flame merging state. As the fire separation distance increases from zero, the position of peak temperature is closer to the fire source with a larger heat release rate due to a smaller flame tilt angle. For scenarios with mean flame merged, the ceiling gas temperature distribution on both sides is equal. For scenarios with mean flame not merged, the ceiling gas temperature on the side with a larger heat release rate is much higher. Finally, different empirical models are established to predict the excess ceiling gas temperature attenuation, considering different flame merging states and smoke spread regions.

Effect of width and slope of large cross-section tunnel on ceiling smoke temperature under natural ventilation

ABSTRACT When a fire occurs in a large cross-section tunnel with slope, the distribution characteristic of ceiling smoke temperature illustrates special laws under the effect of chimney effect, the thermal radiation feedback, and the air entrance limit from walls. A series of numerical simulations are conducted through FDS simulation software based on the actual size of highway tunnel. The influence of large cross-section tunnel width and slope on ceiling smoke temperature when fire occurs are discussed. The research results show that (1) as the tunnel slope increases from 5° to 20°, the distance between the maximum ceiling smoke temperature point and the fire source is 0.5 m, 1 m, 1.7 m, 2.4 m, respectively, and the distance between the ceiling impact point and the fire source is 1 m, 1.8 m, 2.3 m, 3 m, respectively. As the tunnel width increases from 10 m to 20 m, the distance between maximum ceiling smoke temperature point and fire source increases 0.9 m, 1.1 m, 1.3 m, 1.8 m, 2.5 m, and 2.6 m. (2) The prediction formula of maximum ceiling smoke temperature is modified, and a dimensionless relationship among the maximum ceiling smoke temperature and tunnel slope and tunnel width is established. (3) The formula of longitudinal ceiling smoke temperature distribution is modified, and the relationship among tunnel slope, tunnel width, tunnel height, and longitudinal ceiling smoke temperature distribution is established. The research conclusions can provide a theoretical basis for fire prevention design, smoke control and evacuation of this kind of large cross-section tunnel fire.

Study on the smoke evolution mechanism of a subway tunnel with a multi‐door carriage fire under longitudinal ventilation

AbstractThis paper has analyzed the longitudinal ventilation on the effect of the efficiency of the smoke evolution mechanism in a metro tunnel of multi‐window carriage fires. These were simulated by Large Eddy Simulation (LES) with Fire Dynamics Simulator (FDS). In the past, analyses of smoke temperature under the tunnel ceiling and smoke overflow characteristics have been conducted. However, longitudinal ventilation has a different impact on temperature than natural ventilation, especially in a subway tunnel with a multi‐door carriage fire. Consequently, several simulations were run in a subway tunnel (360‐m long, 6.0‐m wide, and 4.8‐m high). The longitudinal ventilation velocity is set by 0–10 m/s with the heat release rate of 1–10 MW. The results show that there is a linear relationship between the maximum temperature and the longitudinal ventilation velocity. An empirical model considering various longitudinal ventilation velocities was developed to predict the maximum smoke temperature underneath the subway tunnel ceiling. The effects of the longitudinal ventilation velocity, the heat release rate, and the distance of the fire source on the characteristics of longitudinal temperature distribution were analyzed. What's more, smoke overflow characteristics under different longitudinal ventilation velocities have been described. The findings and results can also provide a reference for the fire risk assessment of a metro tunnel of multi‐window carriage fires.

Numerical study for the combustion analysis of wood volatiles in porous radiant burner for the application of biomass cooking stove

This article presents a computational study of wood volatiles combustion in a two-layer porous radiant burner (PRB) at different power inputs (1–3 kW) and porosity ranges from 0.7 to 0.9 respectively. A 2-D computational model is designed to numerically solve the combustion of wood-volatiles and air. A finite volume technique is utilized to solve governing equations including; continuity equation, momentum equation, species transport equation, radiative transport equation, and gas and solid phases energy equations. The utilized model is validated with previous literature for a two-layer porous radiant burner and the deviation of comparison is found within the acceptable range. The results reveal that the higher temperature was found in the central part of the burner and the minimum at the circumference. The longitudinal temperature distribution along the central line ruled out the occurrence of flashbacks. Moreover, the transport species contours reveal that the maximum combustion reactions occur in the upper layer of the porous zone. Further, the radiation efficiency decreases with input power and increases with porosity. The maximum value of radiation efficiency is found 36% at 1 kW and porosity of 0.9. while the minimum is 26% found at 3 kW and porosity of 0.7. The overall assessment showed that the PRB-based cooking stove is capable for providing a desired temperature range and efficient radiation efficiency in the range of 1–3 kW of power input.

Natural convection in vertical solar heat collector nanotextured with reduced graphene oxide and silver nanowires

In this study, a vertical shaft is coated using silver nanowires (AgNWs) together with reduced graphene oxide (rGO) via the supersonic spray-coating technique to enhance the absorption of solar radiative heat for use in solar air heaters. The rGO/AgNW-coated surface induces multiple light reflections, similar to that in a perfect black body inside a Helmholtz jar, thus enhancing the collection of solar radiation. Air fed into the vertical heated shaft ascends owing to buoyancy. The air temperature difference, ΔT, between the outlet and inlet is measured for various mass flow rates to quantify the heat transferred to the air from the solar-heated vertical shaft. The longitudinal air velocity and temperature distributions inside the shaft are numerically simulated using the fire dynamics simulator. Both two- and three-dimensional simulations are performed, and the results are compared with experimental data for various mass flow rates. The results confirm that the trends observed in both the experiments and simulations agree well for all cases. Multiple metal meshes are installed inside the vertical shaft to induce turbulence, which enhances the heat transfer intensity. This turbulence enhancement is confirmed via smoke visualization and infrared images.

Thermal uniformity enhancement of the motorcycle exhaust thermoelectric generator—Theory model for predicting heat exchanger fin profile

This paper develops the theoretical model to predict the fin profile of the Hot-side heat exchanger (HHE) to enhance the uniformity of its longitudinal temperature distribution. The developed model can be applied to general cases where heat exchangers have different numbers, heights, pitches, and materials of fins, as well as the thermodynamic and heat transfer parameters of the working fluid. Numerical investigations of two fin profiles' thermal performance are conducted to validate the theoretical model. According to the results, the optimal profile improves the temperature uniformity by 91.3% compared to the original profile. The improvement in the temperature uniformity between thermoelectric modules (TEMs) can be achieved at the cost of reducing the thermoelectric generator unit power. The reductions in heat absorption of the HHE in the current study are not significant, varying from 1.3% to 2.9% at different engine speeds. However, the temperature uniformity can restrict the output power loss due to the significant differences in voltages and amperages produced by TEMs and also can eliminate the deterioration of TEMs’ lifespan.

Statistical Analyses of the Non-Uniform Longitudinal Temperature Distribution in Steel Box Girder Bridge

The frequently conventional assumption that bridge temperature is uniformly distributed on long-span bridges could lead to uncertainty when analyzing temperature effects. This study investigated the surface temperature of steel box girders on a long-span suspension bridge, emphasizing the distribution characteristics in the longitudinal (spanwise) direction. The girder surface temperature distribution was monitored using the long-term structural health monitoring system (SHMS). First, the probability density functions (PDF) of the girder surface temperature were analyzed. The results showed that the PDFs had bimodal characteristics and could be well-fitted using the weighted superposition of two normal distributions. Meanwhile, there was an obvious difference between the PDFs of the measuring points at different longitudinal sections of the bridge, which is inconsistent with the assumption that the temperature was uniformly distributed in the longitudinal direction. Subsequently, the longitudinal distributions of the girder surface temperature were statistically analyzed, and polynomial functions were introduced to fit the distribution curves along the left and right sides of the mid-span. A correlation analysis was then performed, highlighting the variability in temperature in the longitudinal direction. Additionally, the longitudinal temperature distribution pattern could be summarized as (i) the highest in the mid-span, the lowest in the tower, and increasing along the side span; (ii) there were also significant differences between the left and right sides of the mid-span. Finally, the time- and space- distributions of the temperature were studied, and a contour map was displayed. The results showed that the girder surface temperature had significant three-dimensional spatial characteristics and was not only non-uniformly distributed in space but also in time. This work is useful for a more accurate analysis of temperature effects on long-span bridges.

Study on the maximum excess temperature and temperature distribution under the influence of lateral smoke exhaust in tunnel fires

This paper numerically investigates the temperature characteristics of tunnel fire under the ceiling with the effect of lateral smoke exhaust. In the past, analyses of maximum excess temperature under the ceiling and temperature distribution with extraction flows have been conducted. However, the lateral exhaust has a different impact on temperature than the ceiling exhaust. Consequently, several simulations were run in a tunnel (60m long, 9m wide, and 6m high). The lateral exhaust velocity is set by 0 – 10 m/s with a fire heat release rate of 5 – 20 MW. The temperature beneath the tunnel ceiling is measured by 9 rows of thermocouples. The results show that there is a linear relationship between the maximum excess temperature and the lateral exhaust velocity. The longitudinal temperature distributions at different transverse positions are distinct because of the lateral smoke exhaust especially when the hot smoke passes by the vent. The transverse temperature difference expands with the lateral exhaust velocity increases and the heat release rate decreases. Several modified models are proposed to provide references for predicting the temperature characteristics of tunnel fires with lateral smoke exhaust.

The Impact of Geometric Parameters on Three-Layer Flow Patterns in a Horizontal Channel: A Comprehensive Study

This paper focuses on studying stationary flows in horizontal layers, taking into consideration the effects of heat and mass transfer. A mathematical model is presented for a three-layer flow in an infinite channel with solid, impermeable walls. The gas-vapor mixture flows over one-component immiscible liquids in the lower and middle layers. The paper considers the processes of heat and mass transfer at the "liquid-gas" and "liquid-liquid" thermocapillary boundaries, respectively. The Dufour and Soret effects are also considered in the upper layer of the system. Mathematical modeling is based on exact solutions of a special form of the Navier-Stokes equations in the Boussinesq approximation. The procedure for determining unknown parameters is explained. The paper derives dependencies of the longitudinal temperature gradients at the system boundaries from each other. The influence of the flow region's geometry on the nature of the process is studied using the "silicone oil-water-air" system as an example. The paper presents longitudinal velocity profiles and temperature distribution for different values of the liquid layer heights while other parameters of the system remain fixed. The paper concludes that, in this case, the thickness of the lower layer is more influential than the thickness of the middle layer.

Pore-scale numerical simulation and LTNE analysis for fully-developed forced convective heat transfer in packed beds of mono-sized rough spheres covering near-wall and core regions

This work presents a novel method to acquire the effective convection heat transfer coefficients on the interfaces of wall-fluid contacts and sphere-fluid in both the near-wall region and core region of sphere-packed beds. Pore-scale numerical simulations are first conducted for different porosities pertaining to two regular body-centered cubic and face-centered cubic packings, packing lattice angles, inflow velocities, and ratios of the thermal conductivities of the solid and fluid. A finite-thickness metal reactor wall is included in the pore-scale simulation to make the heating boundary conditions more realistic. The outer surface of the metal wall is subjected to a uniform heat flux. The heat then passes through the metal wall and dispenses into the solid and liquid phases of the packed bed through the wall-sphere and the wall-fluid interfaces at the inner wall according to the physical mechanisms. Within the reactor, the heat transfer mechanism is separately considered in the near-wall region and the core region due to the intrinsic differences in the flow pattern. For each packing, different inflow angles are examined and exhibit different flow patterns and heat transfer performances. After the whole domain is hydrodynamically and thermally fully-developed, the local effective convection heat transfer coefficients can then be calculated. These coefficients reflect the realistic local convection either on the reactor wall or on the sphere-fluid interface. These convection heat transfer coefficients, along with the effective solid thermal conductivity through the contacting spheres obtained in our previous work, are implanted into a modified two-equation LTNE model. This modified LTNE model yields linear longitudinal fully-developed temperature distributions within the reactor having discrepancies in the temperature slopes less than ±10% from those by the pore-scale numerical simulations. In contrast, the conventional model even fails to reach linear distributions of the solid- and liquid-phase temperatures, which are expected for fully-developed packed-bed flows.

Optimizing Device Performance of Multi-Pass Flat-Plate Solar Air Heaters on Various Recycling Configurations

Various external-recycle configurations of multi-pass flat-plate solar air collectors were studied theoretically to examine the optimal thermal performance under the same working dimension and operation conditions. An absorber plate and insulation sheet were implemented horizontally and vertically, respectively, into an open rectangular conduit to conduct a recycling four-pass operation, which the device lengthens the air flow channel and increases the air mass flow rate within the collector, and thus, a more heat transfer efficiency is obtained. Four recycling types with different external-recycle patterns were introduced and expected to augment the heat transfer rate due to the turbulent convective intensity through four subchannels in the present study. Coupling energy balances into one-dimensional modeling equations were derived by making the energy-flow diagram within a finite element, which the longitudinal temperature distributions for each subchannel were obtained. The theoretical predictions show that the improved four-pass device is accomplished due to the multiple heating pathways over and under the absorber plate, from which the turbulence intensity augmentation results in the heat transfer rate as compared to that in the device without inserting the absorber plate and insulation sheet (say a downward-type single-pass solar air collector). The theoretical results also show that the external-recycle configuration (say Type C in the present study) acts as an optimal collector thermal efficiency and leading to a beneficial design in multi-pass solar air collectors for improving heat-transfer rate and increasing resident time under the same operation conditions. Theoretical predictions show a higher heat-transfer efficiency for the present recycling configurations up to a maximum 115% device enhancement in comparison to that of a single-pass device. Examination of implementing the absorber plate and insulation sheet on the heat-transfer efficiency enhancement as well as the hydraulic dissipated power increment were also delineated, and deliberated the suitable external-recycle configuration with respect to an economic consideration.

Experimental Study on Freezing Front Model of Alpine Tunnel under Wind Field

In order to study the freezing front characteristics of alpine tunnels under the condition of wind flow field and relying on the Osaka Mountain tunnel in Qinghai Province, the physical model test of an alpine tunnel was built. By using the Surfer software combined with the laboratory test data, the radial and longitudinal temperature variation trends of the tunnel were obtained, and the overall temperature vector graph of the tunnel was simulated; the radial and longitudinal evolutionary laws of a freezing front in an alpine tunnel under airflow conditions were systematically analyzed, and the radial and longitudinal governing equations of a freezing front in the tunnel model under airflow conditions were proposed. The results show that: With the decrease of the test air temperature, the thermonuclear area in the surrounding rock gradually shrinks, the frozen area of surrounding rock at the bottom of the arch gradually increases, and the frozen area of surrounding rock at the top of the arch gradually expands to the interior of the mountain. The influence degree of ventilation on the longitudinal and radial temperature distribution of the tunnel is obvious, and the greater the wind speed, the greater the influence degree. In particular, the fluctuation range of the longitudinal temperature distribution of the tunnel is more extensive under the influence of ventilation. The freezing front distance in the inverted arch area is the largest, and the expansion distance of the freezing front in the wall foot area is obviously higher than that in the vault; the variation of the longitudinal freezing front at different positions of the tunnel shows parabolic attenuation and with an increase in tunnel depth, the trend of freezing front gradually eases and becomes stable and disappears; the three radial regions of the freezing front and the longitudinal quadratic parabola governing equations can predict the specific distribution characteristics of the freezing front at different depths of the tunnel.

EXPERIMENTAL STUDY ON HEAT STORAGE AND RELEASE OF EG/Li2CO3-Na2CO3 HIGH-TEMPERATURE PHASE-CHANGE HEAT STORAGE UNIT

In this paper, a shell-and-tube high-temperature phase-change heat storage unit used in solar high-temperature phase-change heat storage systems was designed and manufactured by using 5:95 expanded graphite EG/Li<sub>2</sub>CO<sub>3</sub>-Na<sub>2</sub>CO<sub>3</sub> as heat storage medium. The temperature distribution, heat exchange efficiency, and energy efficiency of the heat storage unit were studied by testing the heat storage and heat release processes. It was found that a thermostatic platform appeared in the lateral temperature distribution, and a distinct layered distribution appeared in the longitudinal temperature distribution. When the heating power of the heat storage unit is 640 W, the exothermic air flow rate is 400 L/min, and the phase change material was completely melted, the total heat storage and latent heat of the phase change material are 12,321 kJ and 4466 kJ, respectively. The proportion of the latent heat was 0.36, heat storage efficiency and heat release efficiency are 0.57 and 0.47, respectively. In addition, it was also found from the experiment that the greater the heating power, the higher the heat storage efficiency of the heat storage unit, and the greater the heat release air flow, the higher the heat release efficiency.

Superheated steam similarity simulation on longitudinal distribution of maximum smoke temperature rise in tunnel fires

• The superheated steam is used to simulate the migration and heat transfer process of fire smoke. • The similarity between fire smoke and superheated steam motions is demonstrated. • The maximum steam temperature rise is related to buoyant flux and tunnel height. • A calculation model for predicting the longitudinal distribution of maximum smoke temperature is developed. Physical simulation of smoke migration and temperature evolution is an important measure for studying tunnel fires. In this work, based on the similarity theory of fluid dynamics, the motion of superheated steam in the air is used to simulate the migration and heat transfer process of high-temperature smoke generated by tunnel fires. The similarity criteria and similarity scales between the motion of superheated steam and fire smoke are derived by the similarity transformation method. The migration pattern and temperature evolution of superheated steam under natural ventilation are investigated by using a self-built superheated steam experimental system. Then, fire tests are conducted on a combustion wind tunnel to verify the feasibility of this method. The results show that the similarity between fire smoke and superheated steam motions is demonstrated by considering geometric conditions, kinematic conditions and dynamic conditions. The maximum steam temperature rise increases as a power function of the buoyant flux and depends on the 5/3 power of the tunnel height. Moreover, the maximum ceiling steam temperature rise attenuates exponentially with the increasing distance from the steam source. Finally, the calculation model for predicting the longitudinal distribution pattern of the maximum smoke temperature rise beneath the tunnel ceiling is developed, which agrees well with the experimental results.

Study on smoke propagation in tunnel construction of a hydropower station: A full-scale fire experiment

In this study, full-scale fire experiments were conducted in a hydropower station to investigate smoke propagation during tunnel construction. The flame height, smoke temperature and stratification, smoke descent and spread velocity were analyzed via measurements and on-site observations. The initial combustion stage was largely affected by ignition source during tunnel construction for diesel pool fire, and the average flame height in the fully developed stage could reach 1.4–2.1 m in experimental fire scenarios. The gradient of the smoke temperature evolution near the fire was the opposite for the upstream and downstream regions. The longitudinal temperature distribution was concentrated in a small range at the heights of the smoke layer, and gradually decreased by air entrainment as the height decreased, while further increasing in the lower half of the tunnel height in the near-fire region under heat radiation from the fire source. Moreover, distinct and stable smoke stratification formed during the fully developed combustion stage, and the smoke layer interface was at approximately half the tunnel height. Smoke descent was aggravated in the decay stage of combustion, and the fire risk remained high after the fully developed period. The smoke front spread velocity was empirically determined for the full-scale tunnel fire scenarios. Conclusions from full-scale experiments can support smoke control design and on-site fire emergency response plans for hydropower stations.

Study on smoke temperature induced by two fires in a naturally ventilated tunnel

The temperature of smoke flow beneath the tunnel ceiling induced by two fires in a naturally ventilated tunnel is studied. The two fires are located in the lateral direction of the tunnel, and the distance between two fires is varied. Both the maximum temperature rise and the temperature distribution beneath the tunnel ceiling are investigated. For temperature distribution in the tunnel longitudinal direction, there is decrease in temperature with the increasing burner separation distance at the near fire region, while at the region far away from the fire location, the smoke temperature gets very close. Results show that the longitudinal temperature distribution exhibits an exponential decay law along the tunnel ceiling. A formula is established to predict the longitudinal temperature distribution and results show that there is good agreement between the numerical data and formula calculations. Comparison of temperature distribution in the tunnel longitudinal direction and transverse direction shows that at separation distance ofL=0m, there is obvious decrease in temperature with the increasing distance from the zero point both in the tunnel longitudinal direction and transverse direction, while at separation distance ofL=6m, there is obvious increase in temperature at the near fire location in the transverse direction, and at other regions, the temperature is very close in both directions. The maximum temperature rise in the tunnel longitudinal direction decreases with the increasing burner separation distance. A model by considering the fire heat release rateQ̇, the effective tunnel height Hef and the burner separation distance L is proposed to express the maximum temperature rise, and results show that the model can well predict the numerical data. The findings obtained in this work could provide reference for the design of tunnel fire safety with two fire sources.

Full-scale experimental study on fire characteristics induced by double fire sources in a two-lane road tunnel

The vehicle collisions, intense heat radiation and convection from flame and high-temperature smoke can easily cause double-source fire disasters in tunnels. In this paper, four full-scale fire experiments were performed in Jiangpu road tunnel to investigate the characteristics of double fire sources. The whole process of the ventilation velocity, heat release rate, longitudinal ceiling temperature, vertical temperature, carbon monoxide and flame deflection angle are analyzed. The results indicate that the interaction between the double fire sources affects the heat release rate and flame deflection angle and other parameters of each fire source. The ventilation and the fire source spacing can change the coupling state of thermal feedback mechanism and the shielding and entrainment effect of double fire sources. The fire source spacing affects the interaction mechanism and the smoke flow state between the ceiling jets of the double fire sources, which leads to the difference in the longitudinal ceiling temperature distribution between the double fire sources. According to the characteristics of smoke movement between double fire sources, the schematic diagrams of ceiling jets between double fire sources are established. The longitudinal ceiling temperature rise of double fire sources is analyzed from the perspective of steady state and unsteady state. The longitudinal ceiling temperature data of full-scale fire tests is compared with the prediction models proposed by other researchers. The “barrier effect” phenomenon was also observed in the double-source fire tests, especially in the vertical smoke temperature. The findings contribute to deepening the understanding of the fire characteristics of the double-source fire disasters.

Experimental study and physical modeling of ceiling temperature and heat flux profiles by wall-attached fires in inclined tunnels

In this work, the longitudinal heat flux, temperature distribution and flame spread length, beneath a sloping tunnel ceiling caused by fire sources attached to the sidewall were experimentally investigated. The effect of heat release rate (HRR) and tunnel slope on the flame spread length, temperature and heat flux profile were comprehensively considered. The present results show that, in the longitudinal direction, the temperature and heat fluxes under ceiling decrease with increasing distance in the downstream and upstream directions from the flame stagnation point. Thermal and flame buoyancy will change the forces on the ceiling jet caused by a wall-attached fire, resulting in differences in the mass flow rate of fire plumes in upstream and downstream directions. A correlation is developed for the flame extent in the longitudinal upward and downward directions. The temperature and heat flux under ceiling increase in the upstream direction for a given distance in the longitudinal direction compared with the downstream direction and with increasing slopes of the tunnel inclination. This is due to the fact that the upstream thermal flow increases, and the flame extension length becomes larger, while the downstream thermal flow decreases exacerbating the difference of heat flux between upstream and downstream. In addition, the correlation between the dimensionless heat flux and the temperature profile under inclined ceiling in the upstream and downstream directions was further analyzed as a function of the flame length variation. These correlations are well described by physically based models for all the experimental results, including the heat flux under the tunnel ceiling at stagnation point and along the longitudinal flame extension.