Development of a new curve equation representing thin layer drying process

ABSTRACT

In this study, a new model for thin-layer drying process was developed, tested, and verified by using data from the literature and compared. In this regard, the required data were collected from the experiments of green tea leaves in fixed bed and swirling flow fluidized bed infrared drying system, fixed bed, and swirling flow fluidized bed microwave drying system, apricot and kiwi in microwave drying system, and mammoth pumpkin (Cucurbita Maxima) in a laboratory scale dryer. As a result, the proposed model called “Improved Midilli-Kucuk Model” was determined to be the best model among the thin-layer drying-curve equations in the literature. Correlation coefficient (r), the coefficient of determination (R²), reduced chi-square (${\chi }^2$), reduced sum square error (RSSE), and mean bias error (MBE) were calculated between 0.99583 and 1, 0.99543 and 1, 0.00273 and 0, 0.00103 and 0, and 0.00046 and 0, respectively. The highest values of r, R^2, and ${\bar{\mathrm{R}}}^2$and the lowest values of ${\chi }^2$, RMSE, RSSE, and MBE were obtained for green tea leaves drying in swirling flow fluidized bed infrared drying system at infrared power of 1000 W.

KEYWORDS:

• Drying
• thin-layer drying; drying-curve equation
• mathematical modeling

Nomenclature

a, b, c, g	=	Empirical constants in models
c, g, h, k, k0,k1,k2	=	Drying constants (min−1)
MBE	=	Mean bias error
MR	=	Dimensionless moisture ratio
Mt	=	Product moisture on dry basis at “t” (g water/g dry solid
M0	=	Initial product moisture on dry basis (g water/g dry solid)
Me	=	Equilibrium or final product moisture on dry basis (g water/g dry solid)
N	=	Number of observations
n	=	Number of constants
r	=	Correlation coefficient
R2	=	Coefficient of determination
${\bar{R}}^2$	=	Adjusted R2
RMSE	=	Root mean square error
RSSE	=	Reduced sum square error
Greek symbols	=
χ2	=	Reduced chi-square
Subscripts	=
avg	=	Average
exp	=	Experimental
pre	=	Predicted

Acknowledgements

The authors would like to thank Recep Tayyip Erdoğan University for technical supports.

Disclosure statement

No potential conflict of interest was reported by the authors

Additional information

Notes on contributors

Adnan Midilli

Adnan Midilli is currently a Full Professor at the Department of Mechanical Engineering, Faculty of Mechanical Engineering, İstanbul Technical University, İstanbul, Turkiye. He is an active member of various international scientific organizations and societies and serves as an editorial board member of various prestigious international journals. He is a recipient of several national research awards. He has been working as a researcher in national and international research projects. His research interest includes hydrogen technologies, sustainable development, thermodynamic design, and modelling.

Haydar Kucuk

Haydar Kucuk is currently a Full Professor in the Mechanical Engineering Department of the Faculty of Engineering and Architecture at Recep Tayyip Erdogan University, Rize, Türkiye. His research interests involve numerical heat transfer and fluid flow, drying and drying models, energy and exergy analyses, and thermodynamics. He serves as a referee for prestigious international journals. He has participated in national and international research projects as a researcher.