Browsing by Author "Coban S.O."
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Item An efficient method for optimizing the unsteady heat and mass transport features for convective drying of two porous moist objects in a channel(Elsevier Ltd, 2021) Selimefendigil F.; Coban S.O.; Öztop H.F.In the present study, an efficient methodology is proposed for optimizing the convective drying performance of multiple porous moist objects in a channel. As the first step of the method, a PDE constraint optimization routine is utilized to obtain the optimum values of distance between the objects for maximizing the transfer rates while in the second part, unsteady coupled field equations for the channel and porous moist object domains are invoked for convective drying of multiple objects for the optimum spacing values. Finite element method is used for the numerical simulations. It was observed that the recirculation zones established behind the rectangular objects are profoundly affected with the distance between the objects. There is 12.5% variation in the average Nu for the first block with varying the horizontal distance between the objects. The effects of vertical spacing on the average Nu is profound for the second object. while up to 80% enhancement in the average Nu is obtained when the value is changed from sy = 0 to sy = 1.5hp. However, the optimum values of the distance that maximize the heat transfer are obtained as sx = 1.1hp and sy = 1.931hp for the horizontal distance and vertical distance. At this optimum values of parameters, reduction in the moisture content becomes 33.4% and 98.015% for drying times at 1000 s and 5000 s. These values are also checked with the parametric unsteady coupled field equations for the porous moist objects which shows the improved time dependent drying features for the two blocks at the optimum points. © 2021 Elsevier LtdItem Numerical analysis of heat and mass transfer of a moving porous moist object in a two dimensional channel(Elsevier Ltd, 2021) Selimefendigil F.; Coban S.O.; Öztop H.F.The aim of this study is to investigate heat and mass transfer during convective drying of a moving porous medium in a 2D rectangular channel with laminar flow conditions. Finite element method is used with ALE to model the movement of the porous moist object. Hot dry air with different temperatures flowed in the channel with varying velocities and the porous object also has a movement with parallel direction to the flow. The code is validated by using experimental results. Results indicated that the heat transfer coefficient of the moving porous moist object is time dependent and varying locally. Significant impacts of increasing values of air temperature and velocity on the heat and mass transfer features are observed. © 2020 Elsevier LtdItem Convective drying performance of porous moist objects under turbulent flow conditions: effects of object shape and material(Emerald Publishing, 2022) Coban S.O.; Selimefendigil F.; Oztop H.Purpose: The purpose of this paper is to examine the coupled heat and mass transport of different shaped porous moist objects in a rectangular channel under the effects of convective drying. Numerical simulations were performed under turbulent conditions for cylindrical, triangular and rectangular shaped different food products in a two-dimensional channel. Design/methodology/approach: Finite element method was used for the unsteady problem and, effects of drying air velocity (AV) and temperature on transport mechanism were evaluated. Three different food materials were used for the circular shaped object and drying performance of the products under different conditions was compared. Findings: Results showed that, changing the air temperature has an important effect on drying for all shaped objects and all materials. The same effect was seen for the AV as, increasing the velocity had positive effects on drying. Two identical objects were placed in the channel one behind the other, and this configuration showed that location of the object in the channel is also important for drying. The moisture content in the object at the front is lower than in the object behind at the end of drying. Originality/value: This paper can provide technical support to optimize drying performance in the industry with comprehensive data for the process. © 2021, Emerald Publishing Limited.Item Comparative study and hybrid modeling approach with POD for convective drying performance of porous moist object with multi-impinging jet and channel flow configurations(Elsevier Ltd, 2022) Selimefendigil F.; Coban S.O.; Öztop H.F.Comparative studies for convective drying performance of a porous moist object in channel flow and with multi-impinging jet flow configuration are performed with finite element method. The analysis is conducted for different Re numbers (between 100 and 300), hot inlet temperature (between 50 and 80 °C), porous moist object size (between w and 3.5w) and jet flow arrangement parameters in unsteady configuration for times up to 1000 min. Flow re-circulations and isotherms within the channel and jet flow arrangement vary with Re number, size of the object and jet flow parameters. The moisture reduction (MR) becomes higher for the jet flow arrangement and higher Re number while at Re = 300, its value is 59.66%. Increasing the hot air inlet temperate resulted in increment of MR by about 17.5% for multi-impinging jet flow configuration while it is only 10% for channel flow arrangement. There is nearly 20% deviation in the MR value when cases with porous moist object with the lowest and highest size are compared. The vertical distance between the inlet jets to the porous object becomes more effective on the convective drying performance when compared to horizontal distance in between the jets while the MR values reduces from 61% to 48.5% when configurations with lowest and highest vertical distances are considered. An efficient hybrid model with proper orthogonal decomposition (POD) is proposed for efficient computations of convective drying. The computational cost for one case is reduced from 1.3 h for fully coupled high fidelity computational fluid dynamics simulations to 0.1 h with the proposed hybrid approach. The method is also flexible to handle complex external flow configurations and will be more efficient in 3D simulation case. © 2022 Elsevier LtdItem Optimization of convective drying performance of multiple porous moist objects in a 3D channel(Elsevier Masson s.r.l., 2022) Selimefendigil F.; Coban S.O.; Öztop H.F.In this study, a procedure for optimizing the convective drying performance of multi porous moist objects in a three dimensional channel is proposed. The numerical simulation is performed by using the finite element method and COBYLA optimization algorithm is used to find the optimum spacing between the objects without mass transfer in the first stage. Then, heat and mass transfer equations for the porous moist objects are coupled with the channel flow equations at the optimum spacing which delivers the best convective drying performance. It is observed that the flow recirculation and flow reversal in the inter-spacing with various distances between the objects resulted in thermal gradient variations along the multi object surfaces. The average Nusselt number rises for second block while it shows non-monotonic behavior for the first block when the distance between the first and second group objects are varied. Distance between the second and third objects also affected the average Nu variation for all of the objects. The lateral distance between first and second group objects resulted in up to 50% variation in the average Nu for the second block. The optimum spacing between the objects for the maximum Nusselt number of the objects are obtained as d1=5.93hc, d2=7hc and d3=0.584hc. The moisture reduction amounts for each of the object at the optimums spacing are found higher as compared to parametric variation of unsteady simulation results. The computational cost for the parametric unsteady coupled heat and mass transport equations in the channel and in the porous moist objects is 75 h 12 min while the optimization assisted simulation results reduced the computational cost to 2 h 33 minutes. Also, artificial neural networks are utilized to obtain the dynamic feature of convective drying at the optimum spacing considering various values of hot dry air temperature which delivers fast and accurate prediction results when compared to high fidelity computational fluid dynamics simulation results. © 2021 Elsevier Masson SASItem CONVECTIVE DRYING OF DIFFERENT SHAPED POROUS MOIST OBJECTS IN VENTILATED SQUARE AND L-SHAPED CAVITIES(Begell House Inc., 2022) Selimefendigil F.; Coban S.O.; Öztop H.F.This study deals with the convective drying characteristics of porous moist objects in different shaped enclosures which are important in the design of drying chambers and the development of energy efficient systems. In numerical analysis of these systems, the coupled heat and mass transport equations in the moist object domain and enclosure domain should be solved simultaneously to obtain accurate results while different soft computing techniques can be used to assist high-fidelity parametric computational analysis of convective drying. In this work, two-dimensional heat and mass transfer of different shaped porous moist objects inside square and L-shaped cavities are investigated by using Galerkin weighted residual finite element method. The porous objects have three different geometries: square, triangle, and circle with equal edge and diameter sizes. Effects of cavity geometries for varying Reynolds numbers (Re), inlet/exit port sizes, and distances between objects are investigated on a coupled transport mechanism. The results show that the increasing value of Re has a positive effect on moisture transfer, although the effects are different for objects with different geometries. The maximum difference in moisture content values is seen between triangle and circle objects with a value of 36.6%, although highest heat transfer values are achieved in the square geometry. The shape of cavity and distance between the objects are also effective. The L-shaped cavity leads to higher impact on evaporation, and heat and moisture transfer is higher when the spacing between the objects is narrower. The maximum difference in moisture content values is observed between triangle and circle objects, with the triangle object having 36.6% lower moisture content. There is 61.22% variation in the moisture content between the highest and lowest values of the distance between the objects. An artificial neural network is used in convective drying performance estimation for Lshaped cavity using a four input, two output system. Dynamic features and moisture reduction amount are efficiently obtained by using 25 neurons in the hidden layer. © 2022 by Begell House, Inc.Item A REVIEW ON COMPUTATIONAL FLUID DYNAMICS SIMULATION METHODS FOR DIFFERENT CONVECTIVE DRYING APPLICATIONS(Serbian Society of Heat Transfer Engineers, 2023) Coban S.O.; Selimefendigil F.; Oztop H.F.; Hepbasli A.This paper focuses on the CFD studies on one of the commonly used drying processes for different applications. First, a brief information about drying is given with determining important properties that effect drying characteristics. Next, basic principles of CFD modelling are explained while capabilities of computational processing are presented. A detailed literature survey about CFD studies in convective drying process is then conducted. Finally, some sound concluding remarks are listed. It may be concluded that the CFD is a powerful and flexible tool that can be adopted to many different physical situations including complex scenarios, results of CFD simulations represent good predictions for fluid-flow, heat and mass transfer of various drying methods and those numerical studies can be used for validation and controlling of applicability of new drying systems. © 2023 Society of Thermal Engineers of Serbia