Modeling and numerical analysis of single droplet drying

Dalmaz, Nesip
A new single droplet drying model is developed that can be used as a part of computational modeling of a typical spray drier. It is aimed to describe the drying behavior of a single droplet both in constant and falling rate periods using receding evaporation front approach coupled with the utilization of heat and mass transfer equations. A special attention is addressed to develop two different numerical solution methods, namely the Variable Grid Network (VGN) algorithm for constant rate period and the Variable Time Step (VTS) algorithm for falling rate period, with the requirement of moving boundary analysis. For the assessment of the validity of the model, experimental weight and temperature histories of colloidal silica (SiO2), skimmed milk and sodium sulfate decahydrate (Na2SO4·10H2O) droplets are compared with the model predictions. Further, proper choices of the numerical parameters are sought in order to have successful iteration loops. The model successfully estimated the weight and temperature histories of colloidal silica, dried at air temperatures of 101oC and 178oC, and skimmed milk, dried at air temperatures of 50oC and 90oC, droplets. However, the model failed to predict both the weight and the temperature histories of Na2SO4·10H2O droplets dried at air temperatures of 90oC and 110oC. Using the vapor pressure expression of pure water, which neglects the non-idealities introduced by solid-liquid interactions, in model calculations is addressed to be the main reason of the model resulting poor estimations. However, the developed model gives the flexibility to use a proper vapor pressure expression without much effort for estimation of the drying history of droplets having highly soluble solids with strong solid-liquid interactions. Initial droplet diameters, which were calculated based on the estimations of the critical droplet weights, were predicted in


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Anew micro heat spreader (MHS) concept for efficient transport of large, concentrated heat loads is introduced. The MHS is a single-phase, closed microfluidic system, which utilizes reciprocating flow forced convection. This microfluidic device has the potential to control transient heat loads by active control strategies. Hence, it can be utilized in various thermal management applications, mainly in electronic cooling. The MHS concept is validated by numerical solutions of two-dimensional Navier-Stokes an...
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Özdemir, Segah; Tekinalp, Ozan; Department of Aerospace Engineering (2005)
Multiple Cooling Multi Objective Simulated Annealing algorithm has been combined with a conceptual design code written by the author to carry out a multi objective design optimization of an Agricultural Aerial Robot. Both the single and the multi objective optimization problems are solved. The performance figures of merits for different aircraft configurations are compared. In this thesis the potential of optimization as a powerful design tool to the aerospace problems is demonstrated.
Turgay, M. B.; Güvenç Yazıcıoğlu, Almıla (Informa UK Limited, 2009-01-01)
In this study, the effect of surface roughness on convective heat transfer in two-dimensional parallel plate microchannels is analyzed numerically for steady-state, single-phase, developing, and laminar air flow in the slip flow regime. Slip velocity and temperature jump at wall boundaries are imposed to observe the rarefaction effect. The effect of triangular roughness elements on Nusselt number are compared to cases with smooth surfaces. The results indicate that increasing surface roughness reduces heat ...
Yield curve estimation by spline-based models
Baki, İsa; Ergenç, Tanıl; Department of Scientific Computing (2006)
This thesis uses Spline-based model, which was developed by McCulloch, and parsimonious model, which was developed by Nelson-Siegel, to estimate the yield curves of zero-coupon bonds in Turkey. In this thesis, we construct the data by using Turkish secondary government zero-coupon bond data, which contain the data from January 2005 to June 2005. After that, relative performances of models are compared using in-sample goodness of fit. As a result, we see that performance of McCulloch model in fitting yield i...
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Eraslan, Elvan; Aksel, Mehmet Haluk; Department of Mechanical Engineering (2006)
This study investigates the accuracy and efficiency of several flux splitting methods for the compressible, two-dimensional Euler equations. Steger-Warming flux vector splitting method, Van Leer flux vector splitting method, The Advection Upstream Splitting Method (AUSM), Artificially Upstream Flux Vector Splitting Scheme (AUFS) and Roe’s flux difference splitting schemes were implemented using the first- and second-order reconstruction methods. Limiter functions were embedded to the second-order reconstruc...
Citation Formats
N. Dalmaz, “Modeling and numerical analysis of single droplet drying,” M.S. - Master of Science, Middle East Technical University, 2005.