Effect Of Thermal Inertia Research Articles

Investigation on the Influence of Thermal Inertia on the Dynamic Characteristics of a Gas Turbine

In mini-grids and marine-isolated grids, power generation gas turbines are subjected to rapid start-up, shutdown, and acceleration/deceleration. This sudden load change can pose a significant impact on the power grid, severely affecting the operational characteristics of gas turbines. To understand the dynamic characteristics of the gas turbine in the transitional processes, this testing takes twin-shaft medium-sized power generation gas turbines as the test object, and goes through the process of startup, acceleration, deceleration, acceleration, shutdown in one hour, and repeats this process 40 times continuously. With fuel flow as the control parameter and power turbine outlet temperature and high-pressure turbine speed as the controlled parameters, the parameter response rate of the gas turbine under various transition processes is analyzed and the effect of thermal inertia on the gas turbine mass temperature as well as speed is studied. Research findings: During the transition processes, the gas temperature exhibited an axial gradient distribution in the channel. In both the acceleration and deceleration processes, the working fluid temperature gradually decreased along the flow direction. And thermal inertia posed different extents of impact on the dynamic characteristics of the gas turbine under different transitional processes. In the same transition process, the impacts of thermal inertia on the response speeds of temperature and rotational speed varied. The results of this study help to more accurately predict the operating state of the gas turbine during the transition process and lay the foundation for the dynamic simulation model of the non-adiabatic gas turbine.

Investigation of temperature gradient effects and effective thermal inertia during adiabatic decomposition of substances with varying exothermic characteristics

To further study adiabatic parameters distortion, the adiabatic decomposition of 2,4-DNT, 20%DTBP, and 45%Glucose was systematically analyzed using thermal analysis calorimetry and numerical simulation methods. The study revealed the variation laws and influence mechanisms of the temperature gradient effects and thermal inertia in adiabatic systems. A numerical model for decomposition in a closed adiabatic system was developed by integrating the apparent kinetics into the CFD code. The results show that the temperature gradient effects during adiabatic decomposition initially increase and then decrease until reaching zero. The temperature gradient effects become more pronounced as the exothermic characteristics of substances increase. They are the most significant at the peak self-heating rate, with gradients of 182.4 °C·cm−1, 21.6 °C·cm−1, and 0.78 °C·cm−1, respectively. Specific data segments for adiabatic analysis should maintain α values below 0.138 for 2,4-DNT, 0.484 for 20%DTBP, and should utilize complete 100 % adiabatic data for 45%Glucose, aiming to mitigate potential distortion in adiabatic parameters. Furthermore, Фeff varies with the reaction, initially increasing and then decreasing in deviation from the theoretical value, with peak deviations of 60 %, 20 %, and 0.3 % for three substances, respectively. These findings lay the foundation for further optimizing the temperature gradient effects and establishing a dynamic Фeff correction model.

Effect of structural characteristics on charring shrinkage and cracking of densified wood under radiative heatings

Densified wood (DW) is a novel engineering material with excellent mechanical properties. It forms a thermally insulating and hardly-cracked char layer during pyrolysis and combustion. However, the scientific fundamentals regarding how wood structural characteristics (e.g. density) affect its charring behavior remain unknown, which is important for the fire safety of wood. In this work, the charring shrinkage and cracking of NW and DW with various densities (ρ) under heating exposures (Qr) are investigated and analyzed. Partial crack closure was observed due to the oxidation. As wood ρ increases or Qr decreases, the number of cracks (Nc) decreases and cracking time (tc) is delayed because both the surface temperature (Tsurf) and altered thermal stress concentrations on the wood surface are reduced. DW presents an earlier mass loss peak and lower peak value due to the delignification. DW presents high fluctuations in Tsurf due to the combing effect of thermal inertia and radial rebound. As wood ρ increases, char shrinkage depth at tc decreases and shrinkage gradient at tc increases first and then decreases. An empirical correlation is proposed and well-predicts the Nc based on ρ and Qr. It can be potentially implemented in the combustion model to improve prediction accuracy.

The Role of Particle Inertia and Thermal Inertia in Heat Transfer in a Non-Isothermal Particle-Laden Turbulent Flow

We present an analysis of the effect of particle inertia and thermal inertia on the heat transfer in a turbulent shearless flow, where an inhomogeneous passive temperature field is advected along with inertial point particles by a homogeneous isotropic velocity field. Eulerian–Lagrangian direct numerical simulations are carried out in both one- and two-way coupling regimes and analyzed through single-point statistics. The role of particle inertia and thermal inertia is discussed by introducing a new decomposition of particle second-order moments in terms of correlations involving Lagrangian acceleration and time derivative of particles. We present how particle relaxation times mediate the level of particle velocity–temperature correlation, which gives particle contribution to the overall heat transfer. For each thermal Stokes number, a critical Stokes number is individuated. The effect of particle feedback on the attenuation or enhancement of fluid temperature variance is presented. We show that particle feedback enhances fluid temperature variance for Stokes numbers less than one and damps is for larger than one Stokes number, regardless of the thermal Stokes number, even if this effect is amplified by an increasing thermal inertia.

Expanding Building Archetypes to Estimate the Indoor Environment Thermal Storage Capacity in the Danish Building Stock when Performing Demand Response

Short-term demand response leveraging the energy flexibility of the building stock is a key solution to decarbonise and ensure the reliability and sustainability of smart energy grids dominated by intermittent renewable energy sources. Most of the building demand response capacity depends on different forms of energy storage in the built environment. In addition to electric batteries, hot water storage tanks, ground source heat exchanger or dispatchable on-site renewable energy sources, buildings possess a tremendous thermal storage capacity within the thermal inertia of their structure and indoor environment. The latter can easily be harnessed with heating/cooling indoor temperature setpoint modulation strategies. However, there is a clear lack of large-scale estimates of this indoor environment thermal storage capacity in the different building stocks. To tackle this issue, detailed dynamic numerical models of the different building typologies in European countries are generated to assess the potential of demand response strategies at nationwide levels. The current paper presents the preliminary results on the thermal storage capacity in the Danish building stock when performing heating temperature setpoint modulation. These results are based on estimates of the effective thermal inertia of the different building archetypes in Denmark. They show that the Danish building stock contains immense thermal storage capacity, which is comparable to all combined batteries in a large fleet of electric vehicles or all industrial-size storage tanks in district heating plants.

Thermal performances of a bioclimatic building in hot and dry tropical climate

This paper is concerned with the thermal comfort of a double-walls seven stories bioclimatic building built with local construction materials. First of all, we use a numerical code to investigate the construction materials thermal inertia effects on the optimization of the building envelop. Second, the outer and inner surface temperatures are determined utilizing the TRNSYS code. A system of trap is then design to evacuate during nighttimes, the stored daily heat. The conditioned air thermal load differences between the double and simple walls are also investigated. Similarly, the linear thermal loss coefficients and the thermal bridge losses are computed utilizing respectively the ‘Heat’ software and the Degree Day method. The results show a difference of 6 to 7 oC between the outer and the inner maxima surface temperatures. The computation of the conditioned air thermal load indicates a net energy gain of the order of 5.8 % in the office spaces and 12.1% in the bedrooms, respectively for the double and simple walls. The double-walls thermal bridge losses amount to 16.46 % of the total building losses and 20.77 % for the 20 cm thick simple wall. The building envelop optimisation process continues with the study of the effects of the addition of a garden roof on the thermal comfort.

Linear and Nonlinear Stability Analysis of Molten Salt Natural Circulation Loop

Abstract A molten salt natural circulation loop (MSNCL) has been setup to study the steady-state, transient, and stability characteristics of molten nitrate salt, mixture of sodium nitrate, and potassium nitrate in 60:40 ratios by weight. Natural circulation experiments in a temperature range of 290 °C–600 °C have been performed. A semi-analytical linear model was derived for stability analysis of rectangular natural circulation loops with conventional localized surface heating and cooling. The developed model includes the effect of wall thermal inertia, variable internal heat transfer coefficient, finite secondary side heat transfer coefficient at cooler, and heat losses for predicting the stability map. These effects are incorporated considering their significant role in modeling high-temperature molten salt-based natural circulation systems. The developed model has been first validated with the experimental data of water loop available in literature. The developed model is then validated with the experimental data generated in MSNCL. Validation of in-house developed nonlinear model has also been performed against the same experimental data. The comparison of both linear and nonlinear stability analysis with the experimental data shows good agreement and articulates the importance of various parameters which have been included in the developed model.

Short-term cooling and heating loads forecasting of building district energy system based on data-driven models

Accurate forecasting of cooling and heating loads is critical for optimizing the energy usage of devices and planning for energy storage in building district energy systems (BDESs). Data-driven models offering high prediction accuracy and efficiency are receiving significant attention for addressing short-term load prediction problems. However, load forecasting for district building levels, as well as interpretable studies of deep learning models, are still the minority of existed research. To satisfy the cooling and heating loads forecasting of an actual BDES, a framework that includes raw data acquisition, data processing, model development, and evaluation is developed and analyzed. The performance of a multi-input-multi-output prediction strategy evaluated using five data-driven models, namely extreme gradient boost (XGB), long short-term memory (LSTM), gated recurrent units (GRU), and attention-added LSTM/GRU, is investigated. The results show that XGB performs the best, with CV-RMSE values of 14.51% and 11.95% for the one-hour-ahead forecasting of cooling and heating loads, respectively. In terms of 24-hour ahead prediction, the most accurate condition is “48–24” attention-added LSTM in both cooling and heating loads forecasting, where the CV-RMSE values recorded are 26.61% and 27.58%, respectively. The accuracy and interpretability of the models improved after an attention mechanism is introduced. The most significant enhancement in the prediction accuracy is reflected by a reduction in the CV-RMSE by 2.01%. The visualized heat maps of attention weights indicate the mechanism by which the models learn and extract the load patterns, where LSTM and GRU indicate different priorities. Further analysis of the attention weight distribution reveals the effects of building thermal inertia and load periodicity.

SIMULATION OF FLOW AND HEAT EXCHANGE IN A HEAT ACCUMULATOR TANK

The article deals with the research of thermal energy storage tanks. It is proposed to use a «thermal core» to minimize the effects of thermal stratification and high thermal inertia. The thermal core consists of a binary tube placed along the central axis of the tank, filled with a paraffin mixture with a melting point of 45 to 65oC and a density of 0,880 to 0,915g/cm3 at 15oC. In the study the Fluent software package was used to model the temperature distribution in the tank under free convection conditions, the data was then converted to the Transient Thermal module of the ANSYS software package for further calculations of the unsteady temperature distribution in the thermal core. The study showed that a 1400-liter thermal energy storage device, heated for 1 hour by a heat-transfer fluid at 115oC, cools down to 50oC in 4 hours. The research also revealed the need to improve the tank design based on the analysis of the hydrodynamic structure of the flow in the tank, as evidenced by the trajectory distribution of free convective flows. The authors concluded that the use of a heat core, regardless of the type of paraffin used to form it, helps to reduce temperature stratification by height in the tank and that the type of paraffin used has no significant effect on the overall cooling of the tank. However, using ceresin as a core filler results in a slightly higher average tank temperature. Based on the results of the study, the time of complete cooling of the tank was determined by the non-uniform temperature field of all elements of the tank.

A Critical Review of All Mathematical Models Developed for Solar Air Heater Analysis

In this paper, three mathematical models to predict the air collector temperature are reviewed and analyzed. These three models were drawn from 30 publications between 1980 and 2022. The models include lumped model (model 1), a one-dimensional (1D) steady model (model 2), and 1D unsteady model (model 3). The models are established based on the energy balance of the heat exchanger surfaces and the airflow. Solution techniques for models are presented using a system of linear equations, numerical integral, and finite difference method. The results of the sensitivity analysis of the models indicate that the temperatures of the air exiting the collector are similar. Model 3 considers the thickness of the glass cover, absorber plate, and bottom plate thus having the effect of thermal inertia in the morning and afternoon. The maximum difference of outlet air temperature between models 1 and 2 is 0.18 K. The highest outlet air temperature deviation of 0.77 K between models 1 and 3 occurred at 8 AM. When the thicknesses are negligible, the temperature distribution along the air collector of models 2 and 3 is the same. In other words, model 3 should be used when there is the presence of the thickness of the plates and the glass cover.

Thermal inertia effect of reactive sources on one-dimensional discrete combustion wave propagation

In the present work, the discrete flame model developed by Shoshin et al. (Doklady Akademii Nauk SSSR, 1986) and further scrutinized by Tang et al. (Combustion Theory and Modelling, 2009) is augmented by introducing the thermal inertia of particles in the preheating zone. The effect of particle thermal inertia on the speeds, propagation limits, and near-limits dynamics of one-dimensional discrete combustion waves is studied using the new model. It is found that, with the increase of particle thermal inertia, the propagation velocity of the discrete flame decreases due to the smaller heating rate of the particles. Besides, particle thermal inertia extends the propagation limits compared to the prediction of the old model. Furthermore, it is mathematically proven that the nonphysical branch of the solutions for the discrete flame speeds, found using the old discrete model, is a set of solutions for the propagation limits of steady-state discrete flames with particle thermal inertia included. The flame speed predicted using the new model is also compared with that determined analytically using a continuum model considering the thermal inertia of the condensed phase, attributed to Goroshin et al. (Combustion and Flame, 1996). We find that the discrete flame speeds predicted by the both models become closer to each other with increasing particle thermal inertia. Finally, the two models converge regardless of the discrete nature of the heat sources when particle thermal inertia is large enough so that can limit the flame propagation. The particle thermal inertia controlled flames could be regarded as a new kind of combustion regime.

Study on Dynamic Line Rating of Overhead Transmission Line Based on Large-Scale New Energy Power Grid Connection

With increasing new energy power grid connections and increasingly complex user loads, higher ampacity is required during peak power demand. Construction of new transmission lines can cost a lot and is limited by the environment and the shortage of land resources. Considering the intermittency of new energy power generation, dynamic line rating can increase the power transmission capacity of existing lines by exploiting their potential capacity. In this paper, the ampacity of transmission lines is calculated accurately, and influencing factors of ampacity are studied. Additionally, temperature change patterns and field distribution of the lines are studied. The results show that wind speed, ambient temperature, and sunshine intensity are the three main factors affecting the ampacity. Wind speed is proportional to ampacity, while ambient temperature and sunshine intensity are opposite. Then, it is found that the thermal inertia effect of transmission lines that temperature change lags behind current change can be utilized for ampacity enhancement. Furthermore, the radial temperature difference is found in the lines, and excessive temperature differences may accompany the risk of strand breakage. It is of great significance to study the temperature field of the lines for dynamic line rating based on large-scale new energy power grid connections.

Thermo-elasticity displacement formulation for constrained articulated mechanical systems

This paper proposes an approach for thermal analysis of articulated systems subject to boundary and motion constraints (BMC). The solution framework is designed to capture large temperature fluctuations, significant change in geometry due to reference configuration and deformations, and geometric nonlinearity due to articulated mechanical systems (AMS) large displacements and spinning motion. Thermal-expansion displacements, which do not contribute to rigid-body translations, are determined from thermal stretch of position-gradient vectors using a new sweeping matrix technique designed to eliminate dependence on translational rigid-body modes. A new quadratic thermal-energy kinetic form is defined and used to formulate a dynamic force vector that accounts for thermal transient and inertia effects. Nodal thermal displacements are used in formulating AMS differential/algebraic equations (DAEs), and consequently, thermal stresses due to BMC equations are automatically accounted for based on integration of thermal analysis and Lagrange-D’Alembert principle, which is the foundation of computational multibody system (MBS) algorithms. The approach used in this study for large-displacement constrained and unconstrained thermal expansions is based on multiplicative decomposition of position-gradient matrix, instead of strain additive decomposition, for solution of thermo-elasticity problems. Four configurations are used to define continuum geometry and displacements: straight configuration, reference configuration, thermal-expansion configuration, and current configuration. The proposed approach allows applying thermal loads during constrained large displacements, does not impose restrictions on the choice of thermal coefficients, captures reference-configuration geometry and change in inertia forces due to temperature fluctuations, accounts for thermal displacement in formulating AMS nonlinear constraint equations, and allows for integration with MBS algorithms for the study of a wide range of thermo-elasticity problems.

Temperature, storage, and natural gas futures prices

AbstractPrevious literature suggests that daily changes in US natural gas (NG) futures prices and their variance can be explained by changes in oil futures prices and volatilities, storage announcements, and temperature shocks. These studies measure temperature shocks using the National Oceanic and Atmospheric Administration definitions of heating degree day (HDD) and cooling degree day (CDD). We show how hourly temperatures can be used to better measure how long as well as how much temperatures depart above and/or below the “comfort level” within a day, the effects of temperature variability within a day, and the effects of thermal inertia. Hourly temperatures also allow us to construct measures of extreme temperatures that better match the timing of release of other market information. Another innovation is that we use more economically relevant weights to convert regional temperature shocks to national averages, and measure expected values of variables via econometric models instead of historical averages. Our results show that the proposed measures of HDD and CDD and temperature changes are important for explaining weekly changes in NG in storage and daily changes in NG futures prices and their variance.

Liquid film and heat transfer characteristics during superheated wall cooling via pulsed injection of a liquid jet

Pulse firing is one of the major operation modes of bipropellant thrusters for the attitude control of small-scale spacecrafts. In the pulse-firing mode, the operational range of the thruster depends on the deterioration of liquid film cooling performance. Because cooling performance is determined by the balance of heat removed by the liquid film and transferred to the manifold, the behavior and heat transfer characteristics of liquid films under the intermittent injection of liquid jets must be understood to enable a wider range of operational patterns. We conducted cooling tests on a superheated metal plate via the pulsed injection of a liquid jet for better understanding of the pulsed cooling process. Different injection patterns, including continuous injection, with the same injection quantity were examined on two types of metal plates (aluminum alloy and copper), because the thermal properties of metal plates affect both the heat transfer characteristics of the liquid film and temperature rise of the plate during the inter-pulse duration. The cooling process was evaluated based on the evolution of the liquid film on the metal plate and rear-side temperature of the metal plate. The evolution and temperature were simultaneously visualized using a high-speed camera and infrared camera, respectively. To link the liquid film state to the heat transfer process, the temperature and heat flux on the cooled surface were estimated by solving the inverse problem of three-dimensional transient heat conduction. The results indicate that the wetting front position corresponds to the position of the maximum temperature gradient. Additionally, the residual liquid film is consumed through the evaporation and the droplet dispersion related to the nucleate boiling. The effects of thermal inertia and diffusivity of the metal plate highlight the differences in the amount of heat removed by the liquid film. The heat removed by the liquid film during pulsed cooling exhibited a peak and was higher than that removed by continuous injection on the aluminum alloy plate. Less heat was removed under low-duty-cycle conditions, and the amount of heat removed by the liquid film was lower than that removed by continuous injection on the copper plate.

Research on multi‐time scale modeling and interaction of electro‐thermal coupling integrated energy system

AbstractWith the enhancement of the coupling degree and interaction of the electro‐thermal integrated energy system, the fault propagation characteristics under multi‐time scale characteristics become more complex, which may trigger cascading failures and affect the safe operation of the system. Therefore, this article proposes to construct a multi‐time scale comprehensive model based on the steady‐state model and quasi‐dynamic model of electro‐thermal coupling integrated energy system, and uses the strategy of global iteration combined with local simultaneous solution to calculate the energy flow distribution of electro‐thermal coupling system under multi‐time scale. Combined with the characteristics of multi‐time scale energy flow distribution, the interaction mechanism and the fault propagation process of electro‐thermal coupling are analyzed. The simple electro‐thermal coupling integrated energy system and Barry Island electro‐thermal coupling integrated energy system are used as examples to analyze the electro‐thermal coupling characteristics and interaction of the system. The calculation results show that the disturbance of both electrical and heat loads will have a certain impact on the power system and heating system. Due to the thermal inertia of the heating system, there is a large time delay of fault propagation in the heating system. In the process of operation and scheduling of the electro‐thermal coupling integrated energy system, the slow dynamic characteristics of the heating system and the positive effect of thermal inertia on resisting the uncertainty factors in the system should be fully considered.

Steady state performance of molten salt natural circulation loop with different orientations of heater and cooler

Molten salts are proposed as a coolant and sensible heat storage medium for Solar Thermal Power Plant (STPP) as well as fuel and coolant for Molten Salt Reactor (MSR). The objective of the present study is to investigate the steady state behavior of molten salt in natural circulation flow condition along with effect of different orientations of heater and cooler on the steady state mass flow rate. For which a Molten Salt Natural Circulation Loop (MSNCL) has been setup with molten nitrate salt (mixture of Sodium Nitrate and Potassium Nitrate in 60:40 ratio by wt.) as working fluid. Steady state experiments in four different orientations of heater and cooler [Horizontal Heater Horizontal Cooler (HHHC), Horizontal Heater Vertical Cooler (HHVC), Vertical Heater Horizontal Cooler (VHHC) and Vertical Heater Vertical Cooler (VHVC)] have been performed and data generated are compared with the steady state correlations available in open literature which are derived considering either standard friction factor correlations or friction factor correlations deduced from their experiments and theoretical studies. Based on the deviations observed in the experimental values and correlation predictions, an improved formulation has been derived. The steady state formulation has been improved by incorporating Wall Thermal Inertia (WTI) effect and Heat Loss (HL) effect considering the importance of WTI & HL in dealing with high temperature molten salt loop. The improved formulation has been compared with the experimental results for different orientations of heater and cooler. Further, a new friction factor correlation has also been deduced from the experiments for vertical heater orientation. Description of MSNCL along with validation studies performed for different steady state correlation against experimental data generated in MSNCL, are reported in this paper.

A hybrid transient CFD-thermoelectric numerical model for automobile thermoelectric generator systems

Dynamic performance prediction of the automobile thermoelectric generator system is one of the research hotspots in the field of thermoelectric technology. In this work, a hybrid transient CFD-thermoelectric numerical model is proposed for the first time to predict the dynamic response characteristics of an automobile thermoelectric generator system. Taking the exhaust gas of a heavy truck under a highway fuel economy test driving cycle as the transient heat source, the transient numerical study on the automobile thermoelectric generator system is carried out. It is found that the dynamic output power of the automobile thermoelectric generator system changes more smoothly than exhaust temperature due to the effect of thermal inertia, while the conversion efficiency fluctuates greatly. The transient output power at t = 467 s and transient conversion efficiency at t = 635 s reach the highest values of 45.16 W and 39.68 %, respectively. Within the period of 765 s, the total power generation and average conversion efficiency of the automobile thermoelectric generator system are 26460 J and 3.29 %, respectively. Through the transient experimental validation, the average error of transient output voltage between experimental and model results is 6.43 %. This work fills the gap in the dynamic performance prediction of thermoelectric devices used for fluid waste heat recovery. The findings are helpful in better understanding the dynamic response characteristics of the automobile thermoelectric generator system.

Effect of thermal inertia and natural ventilation on user comfort in courtyards under warm summer conditions

Thermal inertia and natural ventilation are strategies widely used and studied in indoor building performance. However, little analysis has been done on its effect on the outdoor microclimate. Furthermore, this analysis is needed for the specific case of inner courtyards, given that these outdoor spaces are highly affected by their surrounding building surfaces. This study takes a real-scale prototype constructed for the 2019 Solar Decathlon competition in Hungary as a case study to analyze the thermal inertia and ventilation effects on the thermal performance of courtyards. Monitoring data are used to calibrate a simulation model that combines BES and CFD to predict the thermal performance for three wall configurations with different inertia and two situations: the closed courtyard and the ventilated courtyard. Results show that the thermal inertia and ventilation effects inside the courtyard are similar to what is generally observed inside the buildings. Thermal inertia for the close courtyard was able to increase the courtyard tempering effect up to 1.6 °C and comfort up to 1.4 °C UTCI. The ventilation reduced the tempering potential of the courtyard during the day, but it also reduced overheating during the night. Depending on the wind speed it can also increase thermal comfort.

Numerical study on the impact of wall thermal inertia on maximum smoke temperature and longitudinal attenuation in long channel fires

In order to better understand the law of smoke propagation in long channel fires and enhance the fire protection of channel structure with different lining materials, a series of fire simulations were carried out by Fire Dynamics Simulator (FDS) to investigate the impact of wall thermal inertia on the maximum smoke temperature and longitudinal attenuation under the channel ceiling. Five wall materials corresponding from the foam concrete to the steel with thermal inertia ranging from 0.1 to 165 kW2•s/(m4·K2) and four heat release rates (5 MW, 7.5 MW, 10 MW and 12.5 MW) were employed. The maximum smoke temperature above the fire source and the temperature distribution under the ceiling along the channel longitudinal centerline were attained and analyzed. The results show that the maximum smoke temperature is significantly affected by the channel wall thermal property and increases with the decrease of wall thermal inertia. Based on the simulative data, a modified model taking the influence of wall thermal inertia into consideration is put forward to predict the maximum gas temperature below the ceiling. Further, the effect of channel wall thermal inertia on the longitudinal smoke temperature decay can be negligible when the thermal inertia is greater than or equal to 1.21 kW2•s/(m4·K2), however, the foam concrete wall with the thermal inertia of 0.1 kW2•s/(m4·K2) results in a smaller attenuation rate due to less heat conducted into the channel wall. Meanwhile, the smoke temperature distribution along the channel longitudinal centerline is also related to the heat release rate (HRR), and the larger the HRR, the slower the temperature decay. The investigation indicates that the temperature distribution along the longitudinal direction follows an exponential attenuation in the near fire field but presents a form of the sum of two exponential functions in the one-dimensional smoke propagation stage. Then taking the effect of wall thermal inertia and heat release rate into account, two novel models characterizing the law of longitudinal temperature attenuation were developed near fire source and in the one-dimensional smoke spread stage respectively.