Ceiling Temperature Research Articles

Experimental and machine learning studies of thermal impinging flow under ceiling induced by hydrogen-blended methane jet fire: Temperature distribution and flame extension characteristics

Hydrogen-blended natural gas has a winged used in such thermal and combustible systems, the ceiling thermal characteristics have important parameters of impinging jet configurations. In this paper, a series of experiments were carried out to study the ceiling flame extension characteristics and temperature profile in a thermal impinging flow of methane jet diffusion flame with hydrogen addition. It was found that: for the given volume flow rate of methane fuel, the ceiling temperature increases although ceiling flame extension area (length) decreases, with the volume flow of hydrogen mixing ratios increasing. Then, a physical and mathematical model, combined influence of flame shape hypothesis based on physically the unburnt fuel, hydrogen addition, heat release rate, the effects of source-ceiling height and nozzle diameter is estimated to predict the flame extension area of methane jet diffusion flames with different hydrogen mixing ratios. Moreover, the fire plume temperature between buoyant plume and intermittent flame increased with the increase in hydrogen addition due to the fire plume temperature increased. The temperature profile models of the ceiling jet are proposed for methane diffusion flames with different hydrogen mixing ratios. Furthermore, to perform the calculation quickly and facilitate rapid thermal engineering design, this paper used machine learning methods (GABP neural network) to derive the volume flow rate of gas leak from the temperature data of the ceiling detected by thermocouples. The results show that the AI prediction for the heat release rates has a good correlation with the verification experimental value. The results of this paper may demonstrate the potential for industrial combustion systems and fire safety engineering applications of methane jet diffusion flame with hydrogen addition.

Experimental field study on smoke characteristics and CO concentration of high-altitude tunnel fires induced using gasoline and diesel

High-altitude environments exhibit reduced atmospheric pressure, low oxygen density, and low air temperature conditions, which considerably affect tunnel fire characteristics. In this study, small-scale tunnel fire field experiments were performed at high altitudes to investigate the heat release rate (HRR), smoke temperature, and CO concentration of gasoline and diesel pool fires. The results revealed that with the increase in altitude, the HRR declined but the combustion duration increased. Furthermore, the maximum ceiling temperature decreased with the increase in altitude. The longitudinal ceiling temperature declined slowly in the high-altitude tunnel. By contrast, the smoke temperature spread rapidly among the cross-section in the high-altitude tunnel. The ceiling CO concentration behaviors for gasoline and diesel pool fires were categorized into four and three stages, respectively. Furthermore, the steady ceiling CO concentration and the maximum ceiling CO concentration decreased slightly with the increase in the altitude for gasoline pool fires, whereas the differences were greater for diesel pool fires. However, the steady ceiling CO concentration per unit mass burning rate increased linearly with the altitude for both fuels. The results revealed that the steady CO concentration at the height of 110 mm in the cross-section was nearly identical for various altitudes in the case of gasoline pool fires. However, for diesel pool fires, the CO concentration was higher at higher altitudes.

Prediction of maximum ceiling temperature of rectangular fire against wall in longitudinally ventilation tunnels: Experimental analysis and machine learning modeling

In this work, experimental analysis and machine learning modeling of maximum ceiling temperature for wall fire in longitudinally ventilation tunnels were conducted. The results indicate that the maximum ceiling temperature is restrained by the longitudinal ventilation, and the maximum ceiling temperature induced by a free fire is significantly lower than that of a wall fire. The aspect ratio of the burner has an impact on the maximum ceiling temperature. The larger the aspect ratio of the burner, the higher the maximum temperature. Based on the “mirror” assumption, the difference in maximum ceiling temperature caused by the changes in entrainment characteristics between wall fires and free fires can be explained. The influence of longitudinal wind inertia forces on the aspect ratio of the burner was analyzed. It was found that when the aspect ratio was large, it is affected by the smaller longitudinal wind inertia force to generate a higher flame height, and this will lead to higher maximum ceiling temperatures. The classical model cannot explain the difference in maximum ceiling temperature between wall fires and free fires, as well as the effect of aspect ratio on the maximum ceiling temperature. Further explanation and verification were conducted by combining the temperature field and the flow field. In addition, genetic algorithms were applied to compensate for the shortcomings of back propagation neural networks in randomly generating initial weights and initial biases. A new model-free calculation (GA-BPNN) model was proposed to predict the maximum ceiling temperature in a ventilation tunnel. Experimental results were compared with the predicted results, and error analysis was conducted on the data from the training and testing sets, with a relative error within ±20%. The GA-BPNN algorithm proved to be a promising method that can provide direct guidance for the experimental analysis and the determination of relevant parameters in the fire situation analysis.

Analysis of Fire and Smoke Spread in Ki Hajar Dewantara Auditorium, State University of Jakarta, Using Fire Dynamics Simulator

Fire behavior and smoke spread are influenced by various factors, including the amount and condition of combustible material, ventilation openings, and ceiling height. A high amount of combustible material in the auditorium poses a significant fire hazard, hence, efforts need to be made to minimize the risk. One approach is to use Computational Fluid Dynamic software, such as Fire Dynamics Simulator (FDS), to model fire combustion. In this research, it provides an overview of the heat release rate (HRR) of fires that occur as well as the effect of differences in ceiling height and the effect of ventilation on fire spread. This research employed Polyurethane foam, commonly used for auditorium seats, as the sample material. Furthermore, it modeled two fire points, one on the 9th floor and the other on the 10th floor, in the middle of seat rows. The development of fire in the modeling was described by the results of visualization, HRR, burning rate, and temperature rise. These results provided insight into the speed at which fire and smoke spread. The starting point on the 9th floor had the highest flame spread rate due to the ceiling jet phenomenon, where a high amount of combustible material caused the ceiling temperature to increase, producing a heat flux that could burn surrounding seats. In both scenarios, the smoke spread rapidly toward the ventilation openings. However, it was denser on the 9th floor as the starting point was farther from the ventilation openings, and the smoke on the 10th floor was less dense.

Insights into substitution strategy towards thermodynamic and property regulation of chemically recyclable polymers

The development of chemically recyclable polymers serves as an attractive approach to address the global plastic pollution crisis. Monomer design principle is the key to achieving chemical recycling to monomer. Herein, we provide a systematic investigation to evaluate a range of substitution effects and structure−property relationships in the ɛ-caprolactone (CL) system. Thermodynamic and recyclability studies reveal that the substituent size and position could regulate their ceiling temperatures (Tc). Impressively, M4 equipped with a tert-butyl group displays a Tc of 241 °C. A series of spirocyclic acetal-functionalized CLs prepared by a facile two-step reaction undergo efficient ring-opening polymerization and subsequent depolymerization. The resulting polymers demonstrate various thermal properties and a transformation of the mechanical performance from brittleness to ductility. Notably, the toughness and ductility of P(M13) is comparable to the commodity plastic isotactic polypropylene. This comprehensive study is aimed to provide a guideline to the future monomer design towards chemically recyclable polymers.

Effects of Fire Location and Forced Air Volume on Fire Development for Single-Ended Tunnel Fire with Forced Ventilation

Single-ended tunnels are a typical structure and an important part during tunnel construction. In the case of a fire in a single-ended tunnel, forced ventilation is commonly used to create a safe area near the excavation face. This work is aimed at examining the effects of fire location and air volume on fire development for single-ended tunnel fires with forced ventilation. A single-ended tunnel was built in Fire Dynamics Simulator (FDS), and twenty simulation tests were carried out. In the simulation, the distribution of flow field, temperature, and CO concentration in the tunnel were measured and analyzed. The results show that three regions can be identified based on airflow directions and velocity: (1) turbulent flow zone, (2) turbulent flow transition zone, and (3) steady flow zone. It was found that the maximum ceiling temperature rise decreases first with the distance between the fire source and the excavation face (XL), and then increases with a further increase in XL. The simulation results also showed that CO can easily accumulate on the ventilation duct side at the fire source position and the opposite side of the ventilation duct 5.0–15.0 m downstream of the fire source. Both the CO concentration and the maximum ceiling temperature rise decrease with increasing air volume, while the larger forced air volume will result in a higher risk for the downstream regions. The present results are of practical importance in firefighting and personnel evacuation in single-ended tunnels with a forced ventilation system.

Kinetic Investigation for Chemical Depolymerization of Post-Consumer PET Waste Using Sodium Ethoxide

Reaction kinetics provides significant insights into the reaction rate and mechanism to control a chemical reaction. In the present work, the detailed kinetics of glycolytic depolymerization of post-consumer polyethylene terephthalate (PET) waste in the presence of sodium ethoxide (EtONa) was investigated. The glycolysis experiments were conducted in a batch reactor over a temperature range of 160 to 197 °C. The confirmation of the product, the bis(2-hydroxyethyl)terephthalate monomer, was carried out using nuclear magnetic resonance spectroscopy, high-performance liquid chromatography, differential scanning calorimetry, and X-ray diffraction techniques. Investigations on the influence of particle size and temperature showed that conversion increased with a decrease in particle size and increasing temperature. Equilibrium conversions were found at different temperatures, and a van ’t Hoff plot was used to confirm that the depolymerization reaction is endothermic. Gibbs’ free energy was used to calculate the ceiling temperature (TC = 156 °C). Three kinetic models were tested for their applicability. It was found that the EtONa-catalyzed glycolysis of PET follows a first-order reversible reaction kinetic model at higher temperatures (170–197 °C). However, a heterogeneous shrinking core mechanism was applicable in a lower temperature range (160–170 °C). The kinetic evaluation revealed that the PET glycolysis reaction consists of heterogeneous and homogeneous mechanisms depending upon the depolymerization stages at various temperatures.

Can heavy rainfall affect the burning and smoke spreading characteristics of fire in tunnels?

Extreme rainfall events are increasingly common under the current trend of global warming. This work investigates how a heavy rainfall on one exit affects the fire burning and the smoke spread in tunnels. Several reduced-scale tests are designed with various rainfall intensities (up to 60 mm/h, equivalent to 232 mm/h in nature), raindrop sizes (1.0-1.5 mm, equivalent to 4-6 mm in nature), and tunnel fire heat release rates (2.1-6.7 kW, equivalent to 2-6 MW in real scale). Experiments show that heavy rainfall on one exit can induce a longitudinal airflow inside the tunnel, and the induced airflow is caused by the increased pressure at the rainfall exit. The airflow pushes the flame tilting towards the no-rainfall portal, and the correlation models of the flame length and flame inclination are characterized by considering the induced airflow and rainfall. The rainfall-induced airflow has a limited effect on the burning rate of pool fires, but it can change the ceiling temperature and limit the smoke back-layering toward the rainfall portal. In contrast, the ceiling temperature distribution towards the no-rainfall portal is found not sensitive to rainfall, which can be well described by an empirical model.

A multiple back propagation neural network fusion algorithm for ceiling temperature prediction in tunnel fires

This study presents a multiple back propagation neural network (BPNN) fusion algorithm to predict the ceiling temperature distribution and the maximum ceiling temperature in tunnel fires for better firefighting decision-making. The algorithm belongs to a kind of data-driven artificial intelligence methods, which is not limited to the special tunnel fire scenes. To improve the prediction precision, a strong multiple BPNN including some sub-BPNNs and an additional external iteration procedure are used in the algorithm. Large-scale pool fire experiments under different ventilation conditions were carried out to investigate the ceiling temperature character of tunnel fires and verify the algorithm. The results show that the algorithm can predict well the ceiling temperature distribution and the maximum ceiling temperature under different ventilation conditions, which has a higher prediction precision than the traditional single BPNN algorithm and some developed theoretical models.

Experimental study and machine learning on the maximum temperature beneath tunnel ceiling induced by adjacent tandem fires in longitudinally ventilated tunnel

This study experimentally investigated the effects of longitudinal ventilation on the maximum temperature rise under tunnel ceilings induced by adjacent tandem fires. Because the tunnel is a narrow building structure, the fire source may ignite the surrounding flammable materials (such as adjacent vehicles, etc.), causing the simultaneous burning of multiple fires. The experiments were conducted in a 1:8 reduced-size tunnel. The ceiling temperature were measured for 60 repeatable test conditions, including five separation distances between adjacent fire sources at various heat release rates with different longitudinal wind speeds. As regards the effect of fire separation distance, the maximum ceiling temperature rise was recorded and measured for five different fire separation distances; as the fire separation distance increased to 0.9 m for a given test condition, the maximum ceiling temperature rise gradually decreased. Meanwhile, the maximum ceiling temperature rise decreased as the crosswinds increased. A new correlation was proposed between the maximum ceiling temperature rise as a function of the change in fire plume due to the fire separation distance and the Froude number representing flame tilting caused by crosswinds. Meanwhile, machine learning algorithm is used to predict the fire heat release rate. The model was shown to be able to effectively explain the experimental results and can provide a reference for examining the evolution of tunnel fire situations.

Maximum ceiling temperature and longitudinal distribution in a corridor-like enclosure with opening

This paper reports a quantitative study on the effects of a side opening on the transition between the fuel-controlled and the ventilation-controlled condition and temperature distribution in a corridor-like enclosure fire. A side opening was introduced to simulate breakage of glass window in case of fire. Experiments were carried out in a 1/8 model tunnel with the dimensions of 3.14 m×0.42 m×0.368m(length×width×height), including 56 test conditions arising from variations of heat release rates (HRR) and opening sizes. The results showed that the transition was correlated with the fraction of the heat released to the heat convected through the opening and the ratio of the heat lost through enclosure boundary to the heat convected through the opening. The maximum temperature rise in the fuel-controlled condition was positively correlated with the fire heat release rate, but it was negatively correlated with the opening aspect ratio. There were two combustion stages in the ventilation-controlled condition, one with flame oscillation inside the corridor-like enclosure and the other with persistent flame ejection through the opening. The maximum temperature rise in the stage of flame oscillation inside the compartment was positively correlated with the air mass supply through the opening and negatively correlated with the heat loss through the corridor-like enclosure boundary. Non-dimensional correlations between the maximum temperature rise and the heat release rates (HRRs), opening sizes and the heat loss were proposed. Moreover, a piecewise equation was proposed to predict the longitudinal decay along the centerline of the corridor-like enclosure with an opening. All the proposed correlations were found to fit well with the experimental data, which established a basic relationship to quantify the (i) temperature variation, (ii) critical heat release rate and (iii) transition for various opening sizes and HRRs in a corridor-like enclosure fire. These new findings and the proposed non-dimensional model provide the basis for understanding fire growth and temperature distribution inside a corridor-like enclosure with opening.

Experimental study on the maximum temperature under the ceiling in a metro depot with one end closed

Metro systems have been widely developed in many countries all over the world, and its operation safety and environmental control are the key issues need to be investigated, especially for the cases of a fire scenario. In this work, a 1/10th scaled subway tunnel with one end closed was constructed to study the ceiling temperature profiles in the metro tunnel when a fire occurs, and the temperature prediction model was proposed. The heat release rates (13 kW-19 kW) and tunnel slopes (0 %-3 %) were changed, and the horizontal temperature in both the longitudinal and transverse direction under the metro tunnel ceiling were measured. The results showed that the temperature distribution in the longitudinal direction were divided into three stages. The dimensionless temperature rise decreases exponentially with the distance from the plume impingement point, and the attenuation rate increases with the tunnel slope. The maximum temperature of the lateral corresponds to the location at the longitudinal centerline of the tunnel, and the temperature decreases from the highest value and presents a symmetrical distribution. Through dimensional analysis, three prediction models were constructed to forecast the temperature under the ceiling at each stage for different HRRs (heat release rates) and tunnel slopes, and the predicted models were verified by the experimental data, and showed good agreements.

Modeling the influence of temperature, salt and osmotic stresses on seed germination and survival capacity of Stipa tenacissima L.

This work stands for a modelling approach to identify the cardinal temperature of germination of Stipa tenacissima L., its capacity to recover and its adaptation potential considering dormancy and viability after exposure to salinity and drought. Seed traits characterised before germination were tested. The seeds were incubated at temperatures of 10 to 30 °C and low osmotic potentials were induced using sodium chloride (NaCl) or polyethylene glycol (PEG 6000) solutions of 0 to −1.6 MPa. The capacity of seeds to recover and remain viable under stress conditions was quantified. Our results proved that the seed yields and sizes were uniform. The analysis of cardinal temperature by thermal time model exhibited an optimal germination temperature (T o) of about 19 °C, a base temperature (T b) of 0.6 °C and a ceiling temperature (T c) of 31 °C at 0 MPa. The base water potential Ψb (50) values ranged between −0.83 and −1.54 MPa and between −0.97 and −2.27 MPa for osmotic and salt stresses, at 30 °C and 20 °C, respectively. In conclusion, the species showed a lower seed recruitment related to a low drought tolerance (drought tolerance index = −0.5 MPa), To requirement and threshold sensitivity. Under salt stress, S. tenacissima used osmotic adjustment in order to germinate in a lower osmotic potential.

An experimental study of the influence of environmental wind on the smoke flow behaviour and temperature distribution in room-corridor fire

As buildings are always in a windy environment, in many cases the influence of the environmental wind cannot be neglected. Therefore, this work conducted an experimental study of the influence of environmental wind on the smoke flow behaviour and temperature distribution in the typical room-corridor fire. In the experiments, different wind velocity and HRR (heat release rate) were tested. Experimental results indicated that the environmental wind would exhibit an obvious influence on the spilled smoke flow in the corridor. When the wind velocity is relatively small, the environmental wind has a positive effect on the spilled smoke flow, and the smoke distribution would show a symmetrical and high temperature region, which would become larger with the wind velocity. With the continuous increase in the velocity, the smoke would be blown downstream of the corridor, causing an obvious decrease in the maximum ceiling temperature. To characterize the temperature distribution along the corridor ceiling, a one-phase exponential correlation is proposed to predict the ceiling temperature distribution in both the upstream and downstream directions of the corridor. The research findings may benefit the design and management of the smoke control system and provide guidance in improving the fire safety level of the commonly existing room-corridor structures.

Ceiling temperature distribution and decay in tunnel fires: Effect of longitudinal velocity, bifurcated shaft exhaust and fire location

This paper establishes a model tunnel to investigate the impact of longitudinal velocity (u), bifurcated shaft exhaust velocity (BSEV) and fire location on ceiling temperature and decay. The experimental results show that a longitudinal velocity of 0.6 m/s can control the upstream high temperature within 2.5 m when the distance between fire and shaft (D) is 1.0 m, and further increase in longitudinal velocity has little effect on upstream temperature distribution. Downstream temperature profile should be divided into two cases according to the magnitude of longitudinal velocity: the difference between the temperature decay model in low-speed region (u ≤ 0.5 m/s) and that in the high-speed region (u > 0.5 m/s) is particularly obvious with D at 1.0 m, and the downstream temperature decay rate in the low-speed region is the slowest compared to all the working conditions in this paper. For D more than 1.0 m, the range of high temperature distribution increases with D for certain longitudinal velocities (0.6-0.7 m/s); however, at particularly large longitudinal velocity (0.8 m/s), D has almost no effect on the upstream temperature distribution. The effect of longitudinal velocity on upstream temperature is stronger than that of BSEV. The downstream ceiling temperature decay model is little affected by longitudinal velocity and BSEV with D more than 1.0 m. The temperature decay rate first decreases, then increases, and finally decreases again as the D increases. Existing temperature attenuation models cannot predict the temperature profile in longitudinally ventilated tunnels with BSEV, but the temperature decay model considering fire location proposed in this paper can provide a reference value for tunnels with synergistic ventilation of longitudinal ventilation and BSEV.

Experimental study on temperature distribution beneath tunnel ceiling under the condition of transverse double fire sources

The maximum ceiling temperature and transverse temperature distribution under the condition of transverse double fire sources are experimentally and theoretically studied. A series of experiments were carried out in a scaling tunnel (1:20) to investigate the effects of heat release rates (HRR) and distance of the two fire sources (S) on the maximum temperature and the transverse temperature distribution beneath tunnel ceiling. Results shown that when the fire sources were set close to each side of the wall, the location of the maximum temperature was found at the middle ceiling of the tunnel. A inverted “N” shape ceiling temperature distribution, with the ceiling temperature firstly decreased and increased and then decreased, was found along the half-cross section of the tunnel. New maximum and transverse ceiling temperature models were developed with considering the distance and heat release rate of the two fire sources, and considering the air entrainment restrictions by the sidewall. New findings of this work can provide a significant reference for the risk assessment of tunnel fires with two transverse fire sources.

Numerical study of the flame geometry of pool fires in longitudinally ventilated tunnels

In a windy environment, the flame tilt angle and base drag length are two parameters used to describe the flame geometry of liquid fuel fires. This work describes a numerical investigation using the FDS code to model three typical fire sizes in a longitudinally ventilated tunnel and a windy open space. The CFD modelling methodology was validated against experimental data from the literature. According to the findings, when the ventilation is weak, a backlayering flow occurs in the tunnel and causes a two-layer flow pattern upstream, which reduces the flow space and accelerates the ventilation. Consequently, the flame base drag length tends to remain constant, and the flame tilt angle becomes very difficult to predict. Unlike open fires, when the upstream is free of backlayering, the tunnel area and the heat release rate have been proven to be two additional factors that influence the flame geometry. The confined space causes more concentrated momentum of wind and speeds up the fuel consumption upstream of the dragging flame base. The former results in a more significant flame tilt, and the latter shortens the stay of fuel vapor on the floor. By introducing a dimensionless heat release rate and dimensionless tunnel cross-sectional area, a series of new prediction models covering all the governing parameters were derived, which have successfully estimated the longitudinal distance from the fire center to the maximum ceiling temperature in the tunnel.

Study of slope effect on smoke back-layering length and ceiling temperature in tunnel fires under natural ventilation

In this paper, experiments focus on the fire smoke flow characteristics under different slopes in a vaulted tunnel and no-mechanical ventilation conditions. Explored the smoke back-layering length Lb and ceiling temperature, with the main research factors tunnel slope and heat release rate (HRR). Research showed that the influences of HRR on the length Lb decreases with increasing slope (especially after 10%) for all slopes where the lengths Lb are present (4%–35%). The slope will also intensify the flow of smoke in the downstream ceiling and the heat exchange between the smoke-wall, resulting in a decrease in the ceiling temperature, while the decay trend remains consistent at the three heat release rates. Combined with the dimensional analysis, the respective dimensionless expressions were established. The results indicated dimensionless smoke back-layering length (Lb*) and the 0.12 power of the normalized HRR decrease with the slope as a power function, while dimensionless ceiling temperature rise and the 3/5 power of the dimensionless HRR decrease exponentially with the slope. These conclusions can provide useful suggestions for engineering practice.

Investigation on the maximum ceiling temperature of the weak plume impingement flow in tunnel fires under longitudinal ventilation

This paper numerically investigated the characteristics of the fire plume behavior and the ceiling maximum temperature with increasing fire source height, in the longitudinal ventilated tunnel fires. Results show that with the continued increase of the longitudinal velocity, the fire plume gradually tilts to the downstream of the tunnel, causing significantly decrease of the ceiling temperature. With the elevation of the fire source, a circulation area forms at the leeward side of the fire source, the pulling effect of the circulation area and the accumulated smoke layer can protect the fire plume from the effect of ventilation airflow, which can weaken the fire plume inclination. To quantify the influence of the longitudinal flow, the dimensionless velocity v* is adopted and divided into three regions, i.e., v*= 0, 0 < v*≤ 0.19 and v*> 0.19. When 0 < v*≤ 0.19, a velocity influence factor f (v) is added to the original equation to represent the effect of ventilation velocity for increasing fire source locations and the ceiling maximum excess temperature varies as the 2/3 power of the dimensionless heat release rate and linear function of dimensionless ventilation velocity. When v* > 0.19, a concept of virtual fire source is proposed to quantify the effects of the inclined fire plume on the maximum temperature and the ceiling maximum excess temperature varies as the 2/3 power of the dimensionless heat release rate and exponential function of dimensionless ventilation velocity. Besides, the applicability and reliability of the predictive correlations are further verified by comparing to the experimental data of different scales.

Temperature Limits for Seed Germination in Industrial Hemp (Cannabis sativa L.)

Industrial hemp (Cannabis sativa L.) as a grain and fiber crop is experiencing a resurgence in North America. Due to governmental prohibition, there has been limited information on regional agronomic production systems including basic information on seed germination. This study was initiated to provide basic information on the relationship between temperature and germination in hemp seed. Germination was measured at constant temperatures ranging from 3 to 42 °C. Cardinal temperatures were determined for two industrial oil crop hemp cultivars (‘Georgina’ and ‘Victoria’). The optimal germination temperature indicated by a high mean germination percentage and rate was between 19 and 30 °C. Optimal (29.6 °C), base (3.4 °C) and ceiling (42.6 °C) temperatures were calculated from a linear regression of the germination rates to reach 50% germination for each temperature. The thermal time for ‘Georgina’ and ‘Victoria’ to reach 50% germination at suboptimal temperatures was 694 and 714 °C h, respectively. The osmotic and solid matrix-primed hemp seeds germinated faster than the untreated seeds, but the final germination percentages were not different. The primed seeds germinated faster at supraoptimal temperatures but did not impact final germination percentages in the thermally inhibited seeds.