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(searched for: doi:10.1115/1.2803640)
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IOP Conference Series: Materials Science and Engineering, Volume 413; https://doi.org/10.1088/1757-899x/413/1/012071

Abstract:
Rotary kilns are very important to the construction industry and many others. These machines are very inefficient, and this is a big concern since they rely on fossil fuels to operate. The aim of this research is to use the power of computational fluid dynamics to save costs and time to optimize the indirectly heated rotary kiln. The research will mainly focus on the thermal analysis of the rotary kiln. The significance of this research mainly lies in the ever-growing need to preserve natural resources and in this case, it is by optimizing highly inefficient machinery such rotary kilns. The numerical model study was conducted using steady state conditions and was also validated. It was found that the numerical model results deviated from experimental results by 10.63%. The optimization process was conducted where the mass flow rate of the air was varied and while the fuel flow rate was kept constant. The reverse was done where the mass flow rate of fuel was varied while the flow rate of air was kept constant. It was concluded that there exists an inverse relationship between the increase of the flow rate of air and the temperature distribution and there exists a directly proportional relationship between the increase of fuel flow rate and the temperature distribution.
, Shabina Khanam
Case Studies in Thermal Engineering, Volume 9, pp 14-27; https://doi.org/10.1016/j.csite.2016.11.001

Abstract:
2D CFD model of rotary kiln of sponge iron process is developed to study the effects of angle of inclination, number of rotation and mass flow rate of iron ore on output parameters. Based on grid independent test for temperature profile optimum mesh size is selected. The result shows that optimum angle of inclination, number of rotation and flow rate of iron ore are found as 2.7 degree, 4.8 rpm and 10 kg/s, respectively. At these optimum conditions the % metallization is predicted as 89.5%, which is 3.24% less in comparison to the existing system. The temperature profiles of gas and bed are also found within acceptable temperature limits. The results are compared well with the published work as well as industrial data.
, Shabina Khanam
Journal of the Taiwan Institute of Chemical Engineers, Volume 63, pp 473-481; https://doi.org/10.1016/j.jtice.2016.02.035

The publisher has not yet granted permission to display this abstract.
Koustubh Sinhal, , Bhaskar Dasgupta
Journal of Thermal Science and Engineering Applications, Volume 4; https://doi.org/10.1115/1.4005256

Abstract:
The present work reports a computer simulation study of heat transfer in a rotary kiln used for drying and preheating food products such as fruits and vegetables with superheated steam at 1 bar. The heat transfer model includes radiation exchange among the superheated steam, refractory wall and the solid surface, conduction in the refractory wall, and the mass and energy balances of the steam and solids. The gas convection is also considered. Finite-difference techniques are used, and the steady state thermal conditions are assumed. The false transient approach is used to solve the wall conduction equation. The solution is initiated at the inlet of the kiln and proceeds to the exit. The output data consist of distributions of the refractory wall temperature, solid temperature, steam temperature, and the total kiln length. The inlet of the kiln is the outlet of the gas (superheated steam), since the gas flow is countercurrent to the solid. Thus, for a fixed solid and gas temperature at the kiln inlet, the program predicts the inlet temperature of the gas (i.e., at the kiln exit) in order to achieve the specified exit temperature of the gas. In the absence of experimental results for food drying in a rotary kiln, the present model has been satisfactorily validated against numerical results of Sass (1967, “Simulation of the Heat-Transfer Phenomena in a Rotary Kiln,” Ind. Eng. Chem. Process Des. Dev., 6(4), pp. 532–535) and limited measured gas temperature as reported by Sass (1967, “Simulation of the Heat-Transfer Phenomena in a Rotary Kiln,” Ind. Eng. Chem. Process Des. Dev., 6(4), pp. 532–535) for drying of wet iron ore in a rotary kiln. The results are presented for drying of apple and carrot pieces. A detailed parametric study indicates that the influence of controlling parameters such as percent water content (with respect to dry solids), solids flow rate, gas flow rate, kiln inclination angle, and the rotational speed of the kiln on the axial solids and gas temperature profiles and the total predicted kiln length is appreciable. The effects of inlet solid temperature and exit gas temperature on the predicted kiln length for carrot drying are also shown in this paper.
, Ankit Agarwal
Journal of Thermal Science and Engineering Applications, Volume 1; https://doi.org/10.1115/1.3224964

Abstract:
The present work reports a computer simulation and optimization study of heat transfer in a rotary kiln used for drying and preheating wood chips with superheated steam at 1 bar. A rotary kiln employed for drying and preheating wet solids consists of a refractory lined cylindrical shell mounted at a slight incline from the horizontal plane. The kiln is slowly rotated about its longitudinal axis. Wet solids are fed into the upper end of the cylinder, and during the process, they are dried and heated by the counter-current flow of the hot gas. Finally, it is transferred to the lower end, where it reaches the desired temperature and is discharged. The heat transfer model includes radiation exchange among hot gas, refractory wall and the solid surface, transient conduction in the refractory wall, and mass and energy balances of the hot gas and solids. A finite-difference based computational heat transfer approach is used. A univariate search method has been used to obtain the minimum kiln length with respect to various kiln operating parameters subject to a constraint on the inlet gas temperature. The parametric study lent a good insight into the physics of the drying process in a rotary kiln. The optimization study reveals that for the same predicted kiln length, lower inlet steam temperature can be used, which will result in saving of energy cost.
, P. Nowak, M. Salcudean, I. S. Gartshore
The Canadian Journal of Chemical Engineering, Volume 83, pp 212-223; https://doi.org/10.1002/cjce.5450830208

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Bijan Farhanieh, M. M. Heydari
Published: 1 March 2008
Heat Transfer Engineering, Volume 29, pp 272-283; https://doi.org/10.1080/01457630701758039

Abstract:
The objective of this article is to study the estimation of an overall heat transfer coefficient in a partially filled rotating cylinder. Herein is an inverse analysis for estimating the overall heat transfer coefficient in an arbitrary cross-section of the aforementioned system from the temperatures measured on the shell. The material employs the finite-volume method to solve the direct problem. The hybrid effective algorithm applied here contains the local optimization algorithm to estimate the unknown parameter by minimizing the objective function. The data measured here are simulated by adding random errors to the exact solution. An investigation is made of the impact of the measurement errors on the accuracy of the inverse analysis. Two-optimization algorithms in determining the overall heat transfer coefficient are used. It is determined that the Conjugate Gradient Method is better than the Levenberg-Marquardt Method because the former produces greater accuracy for the same measurement errors. The resulting observation indicates that good agreement exists between the exact value and estimated result for both algorithms.
† Shijie Wang, Jidong Lu, † Weijie Li, † And Jie Li, Zhijuan Hu‡
Published: 6 September 2006
Energy & Fuels, Volume 20, pp 2350-2356; https://doi.org/10.1021/ef060027p

The publisher has not yet granted permission to display this abstract.
, G. Bhargava, R. P. Chhabra
Published: 1 November 2002
Drying Technology, Volume 20, pp 19-35; https://doi.org/10.1081/drt-120001364

Abstract:
In the present study, an improved numerical heat transfer model has been developed for a rotary kiln used for drying and preheating of wet iron ore. The present model includes radiation exchange among hot gas, refractory wall and the solid surface, transient conduction in the refractory wall, and mass and energy balances of the hot gas and the solids. The contribution of gas convection has also been taken into account in terms of a fraction of the radiative heat transfer to the inner refractory wall and the solid surface. The computer results show that the present model can predict the length of the kiln as well as axial solid and gas temperature distributions with reasonably good accuracy. A detailed parametric study reveals that a good design of a rotary kiln requires medium gas flow rate, small angle of inclination and low rotational speed of the kiln.
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