On Thermal Stability Analysis of a Convective and Radiative Slab of Variable Thermal Conductivity with Reactant Consumption

2018 ◽  
Vol 389 ◽  
pp. 195-204
Author(s):  
Ramoshweu Solomon Lebelo ◽  
K.C. Moloi ◽  
C.C. Chitumwa ◽  
M.W.R. Sadiki ◽  
P. Baloyi ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Kinetic Parameters ◽  
Nonlinear Differential Equations ◽  
Combustion Process ◽  
Variable Thermal Conductivity ◽  
Nonlinear Interactions ◽  
O2 Consumption ◽  
Shooting Technique ◽  
Surrounding Environment ◽  
Rectangular Slab

Thermal stability in a stockpile of reactive materials that are assumed to lose heat to the surrounding environment by convection and radiation is studied in this article. The reactant (O2) consumption is also considered and the investigation is modeled in a rectangular slab. The complicated combustion process results with nonlinear interactions and therefore, the nonlinear differential equations governing the problem are solved numerically with the Runge-Kutta Fehlberg Method (RKF45) that is coupled with the Shooting Technique. The behaviors of the temperature and the reactant, due to effects of some embedded kinetic parameters, are depicted graphically and discussed accordingly. The results show that kinetic parameters that increase the temperature of the system, correspondingly increase the reactant consumption.

Transient Heat Analysis in a Two-Step Radiative Combustible Slab

2021 ◽  
Vol 872 ◽  
pp. 15-19
Author(s):  
Ramoshweu Solomon Lebelo ◽  
Kholeka Constance Moloi
Keyword(s):  
Heat Transfer ◽  
Kinetic Parameters ◽  
Chemical Reaction ◽  
Transfer Rate ◽  
Heat Transfer Analysis ◽  
Shooting Technique ◽  
Surrounding Environment ◽  
Article Analysis ◽  
Exothermic Chemical Reaction ◽  
Rectangular Slab

In this article, analysis of heat transfer in a stockpile of reactive materials modelled in a rectangular slab is carried out. A two-step exothermic chemical reaction is assumed and the heat loss to the surrounding environment is by radiation. The ordinary differential equation (ODE) governing the problem is tackled numerically by Runge-Kutta Fehlberg (RKF45) method coupled with Shooting technique. The heat transfer analysis is simplified by investigation some kinetic parameters’ effects on the temperature of the combusting system. It was found out that some kinetic parameters raise the levels of the temperature by encouraging the exothermic chemical reaction, whereas some, reduce the levels of the temperature to slow down the heat transfer rate. The results are depicted graphically and discussed accordingly.

Investigating Thermal Stability in a Two-Step Convective Radiating Cylindrical Pipe

2021 ◽  
Vol 408 ◽  
pp. 99-107
Author(s):  
Ramoshweu Solomon Lebelo ◽  
Radley Kebarapetse Mahlobo ◽  
Samuel Olumide Adesanya
Keyword(s):  
Differential Equation ◽  
Thermal Stability ◽  
Kinetic Parameters ◽  
Numerical Solutions ◽  
Combustion Process ◽  
Numerical Approach ◽  
Cylindrical Pipe ◽  
Surrounding Environment ◽  
Exothermic Chemical Reaction ◽  
Governing Differential Equation

Thermal stability in a stockpile of reactive materials is analyzed in this article. The combustion process is modelled in a long cylindrical pipe that is assumed to lose heat to the surrounding environment by convection and radiation. The study of effects of different kinetic parameters embedded on the governing differential equation, makes it easier to investigate the complicated combustion process. The combustion process results with nonlinear molecular interactions and as a result it is not easy to solve the differential equation exactly, and therefore the numerical approach by using the Finite Difference Method (FDM) is applied. The numerical solutions are depicted graphically for each parameter’s effect on the temperature of the system. In general, the results indicate that kinetic parameters like the reaction rate promote the exothermic chemical reaction process by increasing the temperature profiles, whilst kinetic parameters such as the order of the reaction show the tendency to retard the combustion process by lowering the temperature of the system.

scholarly journals Heat loss analysis in a radiating slab of variable thermal conductivity

2018 ◽  
Vol 7 (2.23) ◽  
pp. 228 ◽  
Author(s):  
Ramoshweu S. Lebelo ◽  
Kholeka C. Moloi
Keyword(s):  
Differential Equation ◽  
Thermal Conductivity ◽  
Chemical Reaction ◽  
Combustion Process ◽  
Variable Thermal Conductivity ◽  
Temperature Profiles ◽  
Reactive Material ◽  
Loss Analysis ◽  
Exothermic Chemical Reaction ◽  
Rectangular Slab

This article investigates the transfer of heat in a stockpile of reactive materials, that is assumed to lose heat to the environment by radiation. The study is modeled in a rectangular slab whose materials are of variable thermal conductivity. The stockpile’s reactive material in this context is one that readily reacts with the oxygen trapped within the stockpile due to exothermic chemical reaction. The study of the combustion process in this case is conducted theoretically by using the Mathematical approach. The differential equation governing the problem is tackled numerically by applying the Runge-Kutta Fehlberg (RKF45) method coupled with the Shooting technique. To investigate the heat transfer phenomena, some kinetic parameters embedded in the governing differential equation, are varied to observe the behavior of the temperature profiles during the combustion process. The results obtained from the temperature profiles, are depicted graphically and discussed accordingly. It was discovered that kinetic phenomena such as the reaction rate parameter, accelerates the exothermic chemical reaction. However, the radiation parameter decelerates the exothermic chemical reaction by lowering the temperature profiles.  

Transient Heat and Reactant Consumption Investigation in a Cylindrical Pipe of Variable Thermal Conductivity

2019 ◽  
Vol 392 ◽  
pp. 178-188
Author(s):  
Ramoshweu Solomon Lebelo
Keyword(s):  
Thermal Conductivity ◽  
Combustion Process ◽  
Reaction System ◽  
Variable Thermal Conductivity ◽  
Heat Generation Rate ◽  
Cylindrical Pipe ◽  
Reactive Material ◽  
Surrounding Environment ◽  
Exothermic Chemical Reaction ◽  
Rate Of Heat Release

This article investigates the transfer of heat with reactant (oxygen) consumption in a stockpile of reactive material. A reactive material is any carbon or hydrocarbon containing component in a stockpile that readily reacts with the oxygen due to exothermic chemical reaction, where self-ignition may take place if heat generation rate during the combustion process within the stockpile, may exceed the rate of heat release to the surrounding environment. The study is modeled in a long cylindrical pipe whose material thermal conductivity varies with the temperature at a given time. The heat and mass transfer partial differential equations governing the problem were solved numerically using the finite difference method (FDM). Kinetic parameters embedded within the reaction system were analyzed to understand their effects on the temperature and the reactant consumption process. The results shew that the parameters that influence the increase in temperature, increase also the consumption rate of the reactant.

Reactant Consumption and Thermal Decomposition Analysis in a Two-Step Combustible Slab

2019 ◽  
Vol 393 ◽  
pp. 59-72 ◽  
Author(s):  
Ramoshweu Solomon Lebelo ◽  
Radley Kebarapetse Mahlobo ◽  
Samuel Olumide Adesanya
Keyword(s):  
Activation Energy ◽  
Thermal Decomposition ◽  
Combustion Process ◽  
Decomposition Analysis ◽  
O2 Consumption ◽  
O2 Concentration ◽  
Rate Of Reaction ◽  
Exothermic Chemical Reaction ◽  
Rectangular Slab ◽  
The One

The significance of this paper is to analyse thermal decomposition and reactant consumption in a stockpile of reactive materials, such as that of coal, hay or wood, for example. The study is modelled in a rectangular slab and a two-step combustion process like the one taking place in fuel combustion of an automobile is assumed. The coupling of Runge-Kutta-Fehlberg (RKF) method and Shooting technique is applied to solve the differential equations governing the problem. The combustion process that is so complicated is investigated by consideration of effects of some embedded kinetic parameters, such as the activation energy, on the temperature and the reactant (O2) consumption. It was discovered that parameters such as the activation energy, tend to lower the temperature of the system and correspondingly reduce the O2 consumption rate, whereas parameters like the rate of reaction, increase the temperature during the combustion process, to reduce the O2 concentration of the system. The results also indicate that parameters like the rate of reaction, which increase the temperature profiles, fast-track the exothermic chemical reaction to deplete the reactant faster. However, those that reduce the temperature of the system preserve the reactant concentration.

Effect of Variable Thermal Conductivity Calibration Functions on Fin Temperature Distribution

2019 ◽  
Vol 393 ◽  
pp. 47-58 ◽  
Author(s):  
Partner Luyanda Ndlovu ◽  
Raseelo Joel Moitsheki
Keyword(s):  
Thermal Conductivity ◽  
Temperature Distribution ◽  
Variational Iteration Method ◽  
Variable Thermal Conductivity ◽  
Solution Technique ◽  
Physical Parameters ◽  
Calibration Function ◽  
Shooting Technique ◽  
Extended Surfaces ◽  
Fourth Order Method

In this article, we introduce a new thermal conductivity calibration function in modeling heat transfer through extended surfaces. The variable thermal conductivity functions are studied on a stand alone basis and further compared to one another. The calculations are carried out using the Variational Iteration Method (VIM) which is an analytical solution technique. The series solutions are bench-marked against the numerical results obtained by applying the Runge-Kutta fourth order method coupled with shooting technique. The effects of some physical parameters such as the thermogeometric fin parameter and thermal conductivity gradient, on temperature distribution are illustrated and explained.

Study on Combustion Characteristics of Impurity Coal Based on TG-DTG-DTA

2012 ◽  
Vol 568 ◽  
pp. 360-363
Author(s):  
Zhan Wen He ◽  
Chuan Cheng Zhang
Keyword(s):  
Kinetic Equation ◽  
Kinetic Parameters ◽  
Heating Rate ◽  
Ignition Temperature ◽  
Combustion Process ◽  
Combustion Characteristics ◽  
Diffusion Kinetic

Abstract.Based on TG-DTG-DTA, combustion characteristics and kinetic parameters of impure coal in the 10 °C / min heating rate were studied. The results showed that with the increase in the proportion of impurities, ignition temperature, burned temperature significantly improved; combustion characteristics of index clearly decreased; combustion process can be described by a diffusion kinetic equation

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