Heat Transfer Analysis During the Process of Injera Baking by Finite Element Method

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Addis Ababa University


The main objective of this study was the modeling and simulation of the heat transfer during the process of injera baking. In doing these, mathematical models and finite element formulations for baking pan and injera during baking was developed. In this study, thermo physical properties of injera were studied analytically and were used for the temperature profile prediction using the numerical model. The main properties of interest were specific heat capacity, thermal conductivity, and density. The mathematical model of injera during baking employs the coupled partial differential equations proposed by Luikov. Resulting system of non linear partial differential equations in time and two space dimensions were reduced to algebraic system by applying the finite element numerical method. The fundamental two-dimensional axisymmetric transient finite element model with triangular elements to predict the heat transfer for the baking pan and heat and mass transfer that occur during baking of injera was solved using the Finite Element Method by MATLAB. The backward difference time stepping technique was used for the transient analysis. The simulation was done in terms of temperature profile during heat up, and cyclic injera baking. Simulation was carried out for four different input heated oil temperatures (250, 275, 300, and 325° ) and for four different electric power sources (1.867, 2.2, 2.5, and 3 ). Two types of baking pans (clay and ceramic) with different thicknesses were investigated. Experiments on conventional clay baking pan were conducted to measure heat up time, and mass balance of batter and injera. The heat up time obtained from simulation was compared with experimental test; from the comparison a relatively good agreement was obtained. The energy utilization and efficiency of electric baking pans were determined based on the amount of energy baking pans use in a baking session for a given power input. A relatively better efficiency was obtained for 10 thick clay and 8 thick ceramic baking pans with a power source of 2.5 . While the 10 pan was not practically realized, the 8 ceramic pan manufactured by Tabor ceramic factory is currently under study. Key Words: Finite element method, Injera, Heat and Mass Transfer, Simulation, Efficiency.



Finite element method; Injera; Heat and Mass Transfer, Simulation; Efficiency