Mathematical modelling of lemon verbena leaves drying in a continuous flow dryer equipped with a solar pre-heating system

Main Article Content

S. Soodmand-Moghaddam
M. Sharifi
H. Zareiforoush
H. Mobli


air velocity, air temperatures, drying kinetic, Midilli and Kucuk’s model


The modelling of the drying process of lemon verbena leaves in a continuous flow dryer equipped with a solar pre-heating system was performed at three levels of drying temperature (50, 40, and 30 °C) and three levels of air velocity (2, 1.5 and 1 m/s). During the experiments, lemon verbena leaves were dried to the final moisture content of 10 from 76% wet basis in the continuous flow dryer. Drying kinetic showed to drying temperature and air velocity exerted significant influence on the drying time. Also, the dried lemon verbena leaves quality was obtained by determining the essential oil content of the product after drying in different conditions in the dryer. Finally, it was observed that the highest essential oil content was maintained at a temperature of 40 °C and air velocity of 1 m/s. Suitability of 10 different mathematical drying models was used to describe drying lemon verbena leaves in this dryer. The results have shown that Midilli and Kucuk’s model can successfully predict the experimental data in all air temperatures and air velocities. In Midilli and Kucuk’s model, the amounts of R2 were above 999 × 10–3 and the amounts of root-mean-square error (RMSE) and chi-square (χ2) were less than 174 × 10–4 and 19 × 10–4.

Abstract 741 | PDF Downloads 459 HTML Downloads 535 XML Downloads 3


Abd El-Gaber, A.S., El Gendy, A.N.G., Elkhateeb, A., Saleh, I.A. and El-Seedi, H.R., 2018. Microwave extraction of essential oil from Anastatica hierochuntica (L): comparison with conventional hydro-distillation and steam distillation. Journal of Essential Oil Bearing Plants 21: 1003–1010.
Akhondi, E., Kazemi, A. and Maghsoodi, V., 2011. Determination of a suitable thin layer drying curve model for saffron (Crocus sativus L) stigmas in an infrared dryer. Scientia Iranica 18: 1397–1401.
Akpinar, E.K., 2010. Drying of mint leaves in a solar dryer and under open sun: modelling, performance analyses. Energy Conversion and Management 51: 2407–2418.
Aral, S. and Beşe, A.V., 2016. Convective drying of hawthorn fruit (Crataegus spp.): effect of experimental parameters on drying kinetics, color, shrinkage, and rehydration capacity. Food Chemistry 210: 577–584.
Aregbesola, O.A., Ogunsina, B.S., Sofolahan, A.E. and Chime, N.N., 2015. Mathematical modeling of thin layer drying characteristics of dika (Irvingia gabonensis) nuts and kernels. Nigerian Food Journal 33: 83–89.
Arslan, D. and Özcan, M.M., 2012. Evaluation of drying methods with respect to drying kinetics, mineral content, and color characteristics of savory leaves. Food and Bioprocess Technology 5: 983–991.
Asekun, O.T., Grierson, D.S. and Afolayan, A.J., 2007. Effects of drying methods on the quality and quantity of the essential oil of Mentha longifolia L. subsp. Capensis. Food Chemistry 101: 995–998.
Asiru, W.B., Raji, A.O., Igbeka, J.C. and Elemo, G.N., 2013. Mathematical modelling of thin layer dried cashew kernels. Nigerian Food Journal 31: 106–112.
Badaoui, O., Hanini, S., Djebli, A., Haddad, B. and Benhamou, A., 2019. Experimental and modelling study of tomato pomace waste drying in a new solar greenhouse: evaluation of new drying models. Renewable Energy 133: 144–155.
Baini, R. and Langrish, T.A.G., 2008. An assessment of the mechanisms for diffusion in the drying of bananas. Journal of Food Engineering 85: 201–214.
Benseddik, A., Azzi, A., Zidoune, M.N. and Allaf, K., 2018. Mathematical empirical models of thin-layer airflow drying kinetics of pumpkin slice. Engineering in Agriculture, Environment and Food 11: 220–231.
Bhardwaj, A.K., Kumar, R. and Chauhan, R., 2019. Experimental investigation of the performance of a novel solar dryer for drying medicinal plants in Western Himalayan region. Solar Energy 177: 395–407.
Borah, A., Hazarika, K. and Khayer, S.M., 2015. Drying kinetics of whole and sliced turmeric rhizomes (Curcuma longa L.) in a solar conduction dryer. Inf. Process. Agric. 2: 85–92.
da Cunha, A.P., Nogueira, M.T., Roque, O.R. and Barroso, J.M.G., 2012. Plantas aromáticas e óleos essenciais: composiçã;o e apli¬cações, Fundaçã;o Calouste Gulbenkian publisher, Português, pp. 35–39.
Doymaz, I., 2011. Drying of thyme (Thymus Vulgaris L.) and selection of a suitable thin-layer drying model. Journal of Food Processing and Preservation 35: 458–465.
Doymaz, İ. and Karasu, S., 2018. Effect of air temperature on drying kinetics, colour changes and total phenolic content of sage leaves (Salvia officinalis). Quality Assurance and Safety of Crops & Foods 10: 269–276.
Doymaz, I., Tugrul, N. and Pala, M., 2006. Drying characteristics of dill and parsley leaves. Journal of Food Engineering 77: 559–565.
Duffie, J.A. and Beckman, W.A., 2013. Solar engineering of thermal processes, John Wiley & Sons, pp. 98–100
El-Sebaii, A.A. and Shalaby, S.M., 2013. Experimental investigation of an indirect-mode forced convection solar dryer for drying thymus and mint. Energy Conversion and Management 74: 109–116.
Erenturk, S., Gulaboglu, M.S. and Gultekin, S., 2004. The thin-layer drying characteristics of rosehip. Biosystems Engineering 89: 159–166.
Ertekin, C. and Yaldiz, O., 2004. Drying of eggplant and selection of a suitable thin layer drying model. Journal of Food Engineering 63: 349–359.
Essalhi, H., Benchrifa, M., Tadili, R. and Bargach, M.N., 2018. Experimental and theoretical analysis of drying grapes under an indirect solar dryer and in open sun. Innovative Food Science and Emerging Technologies 49: 58–64.
Ishkeh, S.R., Asghari, M., Shirzad, H., Alirezalu, A. and Ghasemi, G., 2019. Lemon verbena (Lippia citrodora) essential oil effects on antioxidant capacity and phytochemical content of raspberry (Rubus ulmifolius subsp. sanctus). Scientia Horticulturae 248: 297–304 (Amsterdam).
Javed, H.U., Wang, D., Wu, G.-F., Kaleem, Q.M., Duan, C.-Q. and Shi, Y., 2019. Post-storage changes of volatile compounds in air-and sun-dried raisins with different packaging materials using HS-SPME with GC/MS. Food Research International 119: 23–33.
Jayatunga, G.K. and Amarasinghe, B., 2018. Mathematical modeling of drying kinetics of black pepper in a spouted bed dryer with and without non porous draft tubes. 2nd International Conference on Trends in Multidisciplinary Business and Economic Research (TMBER), March 23–24, 2018, Sydney Australia, pp. 118–134.
Labed, A., Moummi, N., Aoues, K. and Benchabane, A., 2016. Solar drying of henna (Lawsonia inermis) using different models of solar flat plate collectors: an experimental investigation in the region of Biskra (Algeria). Journal of Cleaner Production 112: 2545–2552.
Meisami-Asl, E., Rafiee, S., Keyhani, A. and Tabatabaeefar, A., 2010. Determination of suitable thin layer drying curve model for apple slices (variety-Golab). Plant Omics 3: 103.
Mghazli, S., Ouhammou, M., Hidar, N., Lahnine, L., Idlimam, A. and Mahrouz, M., 2017. Drying characteristics and kinetics solar drying of Moroccan rosemary leaves. Renewable Energy 108: 303–310.
Motevali, A., Minaei, S., Banakar, A., Ghobadian, B. and Darvishi, H., 2016. Energy analyses and drying kinetics of chamomile leaves in microwave-convective dryer. Journal of the Saudi Society of Agricultural Sciences 15: 179–187.
Motevali, A., Minaei, S., Banakar, A., Ghobadian, B. and Khoshtaghaza, M.H., 2014. Comparison of energy parameters in various dryers. Energy Conversion and Management 87: 711–725.
Motevali, A., Minaei, S., Khoshtaghaza, M.H., Kazemi, M. and Nikbakht, A.M., 2010. Drying of pomegranate arils: comparison of predictions from mathematical models and neural networks. International Journal of Food Engineering 6(3): 1556–3758.
Movagharnejad, K. and Nikzad, M., 2007. Modeling of tomato drying using artificial neural network. Computers and Electronics in Agriculture 59: 78–85.
Mujaffar, S. and John, S., 2018. Thin-layer drying behavior of West Indian lemongrass (Cymbopogan citratus) leaves. Food Science & Nutrition 6: 1085–1099.
Omolola, A.O., Kapila, P.F. and Silungwe, H.M., 2018. Mathematical modeling of drying characteristics of Jew’s mallow (Corchorus olitorius) leaves. Information Processing in Agriculture 6(1): 109–115.
Panchariya, P.C., Popovic, D. and Sharma, A.L., 2002. Thin-layer modelling of black tea drying process. Journal of Food Engineering 52: 349–357.
Pirbalouti, A.G., Mahdad, E. and Craker, L., 2013. Effects of drying methods on qualitative and quantitative properties of essential oil of two basil landraces. Food Chemistry 141: 2440–2449.
Rabha, D.K., Muthukumar, P. and Somayaji, C., 2017. Experimental investigation of thin layer drying kinetics of ghost chilli pepper (Capsicum Chinense Jacq.) dried in a forced convection solar tunnel dryer. Renewable Energy 105: 583–589.
Saleh, I.A., El Gendy, A.N.G., Afifi, M.A. and El-Seedi, H.R., 2019. Microwave extraction of essential oils from senecio serpens GD Rowly and comparison with conventional hydro-distillation method. Journal of Essential Oil Bearing Plants 22(4): 955–961. https://
Sari, I., 2018. Evaluation of industrial cosmetic products and replacing them with natural products according to modern, traditional and islamic medicine. Health Biotechnology and Biopharma 1(4): 19–31. DOI: 10.22034/HBB.2018.02
Shamekhi-Amiri, S., Gorji, T.B., Gorji-Bandpy, M. and Jahanshahi, M., 2018. Drying behaviour of lemon balm leaves in an indirect double-pass packed bed forced convection solar dryer system. Case Studies in Thermal Engineering 12: 677–686.
Shi, Q., Zheng, Y. and Zhao, Y., 2013. Mathematical modeling on thin-layer heat pump drying of yacon (Smallanthus sonchifolius) slices. Energy Conversion and Management 71: 208–216.
Torki-Harchegani, M., Ghanbarian, D., Pirbalouti, A.G. and Sadeghi, M., 2016. Dehydration behaviour, mathematical modelling, energy efficiency and essential oil yield of peppermint leaves undergoing microwave and hot air treatments. Renewable and Sustainable Energy Reviews 58: 407–418.
Verma, L.R., Bucklin, R.A., Endan, J.B. and Wratten, F.T., 1985. Effects of drying air parameters on rice drying models. Trans. ASAE 28: 296–301.
Vijayan, S., Arjunan, T.V. and Kumar, A., 2016. Mathematical modeling and performance analysis of thin layer drying of bitter gourd in sensible storage based indirect solar dryer. Innovative Food Science and Emerging Technologies 36: 59–67.
Yogendrasasidhar, D. and Setty, Y.P., 2018. Experimental studies and thin layer modeling of pearl millet using continuous multistage fluidized bed dryer staged externally. Engineering Science and Technology, an International Journal 22(2): 428–438.
Zheng, X., Jiang, Y. and Pan, Z., 2005. Drying and quality characteristics of different components of alfalfa, In: 2005 ASAE Annual Meeting. American Society of Agricultural and Biological Engineers, p. 1. August 13–15, 2005, Hong Kong, pp, 1157–1164.