Modeling and optimization of energy consumption and performance characteristics of a solar assisted fluidized bed dryer


1 Department of Mechanical Engineering, Takestan Branch, Islamic Azad University, Takestan, Iran

2 Department of Mechanization Engineering, Faculty of Agricultural Sciences, University of Guilan, P.O.Box 41635-1314, Rasht, Iran



The major problem regarding conventional rice mills is the use of fixed-bed drying systems, which is accompanied by high energy consumption. In this study, a novel solar-assisted fluidized-bed system for drying paddy grains was used. The system included a solar water heater, an infrared lamp powered by photovoltaic panels, along with a gas water heater, which were used together to provide the required thermal energy. The working factors were drying air temperature (35, 45, and 55 °C), drying air velocity (7, 8, and 9 m/s), and the angle of the desiccant wheel regeneration gate (0, 45, and 90 degrees). The performance characteristics of the drying system were measured in terms of drying rate, total energy consumption, solar fraction and energy efficiency. Several mathematical models were also applied to fit the moisture ratio curves. In order to analyze the results and obtain the optimized working conditions of the drying system, Response Surface Methodology (RSM) based on the Box–Behnken technique was used. In all of the evaluated conditions, the model entitled “Approximation of diffusion” had the best results for fitting the moisture ratio curves with a correlation coefficient value of at least 0.9729. The selected optimum point included drying air velocity of 7 m/s, drying air temperature of 52.77 ºC and regeneration gate angle of 0. Under the mentioned working conditions, the drying time of 75.99 min, the total energy consumption of 0.297 kWh, solar energy fraction of 0.540 and energy efficiency of 47.67% could be obtained with a desirability value of 0.970.

[1] Noorpoor, A., et al., A thermodynamic model for exergetic performance and Optimization of a solar and biomass-fuelled multigeneration system. Energy Equipment and Systems, 2016. 4(2): p. 281-289.
[2] IME, Energy Balance Sheet. 2011, Iran Ministry of Energy: Tehran, Iran.
[3] Kumar, A., S. Chamoli, and M. Kumar, Experimental investigation on thermal performance and fluid flow characteristics in heat exchanger tube with solid, hollow circular disk inserts. Applied Thermal Engineering, 2016. 100: p. 227-236.
[4] Zareiforoush, H., et al., Design, development and performance evaluation of an automatic control system for rice whitening machine based on computer vision and fuzzy logic. Computers and Electronics in Agriculture, 2016. 124: p. 14-22.
[5] Gazor, H.R., M.R. Alizadeh, and M. Younesi Alamouti, Comparison of Operational Parameters and Energy Consumption in Rice Milling Systems (Case Study in Mazandaran Province). Journal of Engineering Research in Agricultural Mechanization and Systems, 2016. 17(66): p. 15-28.
[6] Li, H., et al., Characteristics of fluidisation behaviour in a pressurised bubbling fluidised bed. The Canadian Journal of Chemical Engineering, 2013. 91(4): p. 760-769.
[7] Senadeera, W., O. Alves-Filho, and T. Eikevik, Influence of drying conditions on the moisture diffusion and fluidization quality during multi-stage fluidized bed drying of bovine intestine for pet food. Food and Bioproducts Processing, 2013. 91(4): p. 549-557.
[8] Si, C., et al., Experimental and numerical simulation of drying of lignite in a microwave-assisted fluidized bed. Fuel, 2019. 242: p. 149-159.
[9] Yahya, M., Design and performance evaluation of a solar assisted heat pump dryer integrated with biomass furnace for red chili. International Journal of Photoenergy, 2016. 2016.
[10] Delele, M.A., F. Weigler, and J. Mellmann, Advances in the application of a rotary dryer for drying of agricultural products: A review. Drying technology, 2015. 33(5): p. 541-558.
[11] Eltawil, M.A., M.M. Azam, and A.O. Alghannam, Energy analysis of hybrid solar tunnel dryer with PV system and solar collector for drying mint (MenthaViridis). Journal of Cleaner Production, 2018. 181: p. 352-364.
[12] Hamdi, I., et al., Drying of red pepper slices in a solar greenhouse dryer and under open sun: Experimental and mathematical investigations. Innovative Food Science & Emerging Technologies, 2019.
[13] Karthikeyan, A. and S. Murugavelh, Thin layer drying kinetics and exergy analysis of turmeric (Curcuma longa) in a mixed mode forced convection solar tunnel dryer. Renewable Energy, 2018. 128: p. 305-312.
[14] Yahya, M., A. Fudholi, and K. Sopian, Energy and exergy analyses of solar-assisted fluidized bed drying integrated with biomass furnace. Renewable energy, 2017. 105: p. 22-29.
[15] Ziaforoughi, A. and J.A. Esfahani, A salient reduction of energy consumption and drying time in a novel PV-solar collector-assisted intermittent infrared dryer. Solar Energy, 2016. 136: p. 428-436.
[16] Shirinbakhsh, M. and M. Amidpour, Design and Optimization of solar-assisted conveyer-belt dryer for biomass. Energy Equipment and Systems, 2017. 5(2): p. 85-94.
[17] Nazghelichi, T., M.H. Kianmehr, and M. Aghbashlo, Thermodynamic analysis of fluidized bed drying of carrot cubes. Energy, 2010. 35(12): p. 4679-4684.
[18] Nassiri, S.M. and S.M. Etesami, Energy Use Efficiency of Different Drying Methods for Two Rough Rice Cultivars. Food Science and Technology, 2015. 3(2): p. 23-28.
[19] Jafari, H., D. Kalantari, and M. Azadbakht, Semi-industrial continuous band microwave dryer for energy and exergy analyses, mathematical modeling of paddy drying and it’s qualitative study. Energy, 2017. 138: p. 1016-1029.
[20] Nosrati, M., et al., Modeling and Optimization of Rough Rice Drying under Hot Air-Infrared Radiation in a Laboratory Scale Vibratory Bed Dryer. Int. J. Biomed. Sci. Eng, 2018. 49: p. 423-435.
[21] Gharnasi Gharavi, O., et al., Optimization of paddy rice drying using response surface methodology. Electronic Journal of Food Processing and Preservation, 2017. 10(1): p. 99-116.
[22] Pourbagher, R., et al., Modeling and Optimization of drying process of paddy in infrared and warm air fluidized bed dryer. Agricultural Engineering International: CIGR Journal, 2018. 20(3): p. 162-171.
[23] Elhami, B., et al., Application of ANFIS and linear regression models to analyze the energy and economics of lentil and chickpea production in Iran. Energy Equipment and Systems, 2016. 4(2): p. 255-270.
[24] Sarker, M., et al., application of simulation in determining suitable operating parameters for industrial scale fluidized bed dryer during drying of high impurity moist paddy. Journal of Stored Products Research, 2015. 61: p. 76-84.
[25] Zomorodian, A., D. Zare, and H. Ghasemkhani, Optimization and evaluation of a semi-continuous solar dryer for cereals (Rice, etc.). Desalination, 2007. 209(1-3): p. 129-135.
[26] Golmohammadi, M., et al., Energy efficiency investigation of intermittent paddy rice dryer: Modeling and experimental study. Food and bioproducts processing, 2015. 94: p. 275-283.
[27] Sarker, M.S.H., et al., Energy and exergy analysis of industrial fluidized bed drying of paddy. Energy, 2015. 84: p. 131-138.
[28] Atthajariyakul, S. and T. Leephakpreeda, Fluidized bed paddy drying in optimal conditions via adaptive fuzzy logic control. Journal of food engineering, 2006. 75(1): p. 104-114.
[29] Rao, P.S., S. Bal, and T. Goswami, Modelling and Optimization of drying variables in thin layer drying of parboiled paddy. Journal of Food Engineering, 2007. 78(2): p. 480-487.
[30] Behera, G. and P. Sutar, A comprehensive review of mathematical modeling of paddy parboiling and drying: Effects of modern techniques on process kinetics and rice quality. Trends in Food Science & Technology, 2018. 75: p. 206-230.
[31] ASABE, Moisture Measurement—Unground Grain and Seeds. 2019, American Society of Agricultural and Biological Engineers.
[32] Labed, A., et al., 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, 2016. 112: p. 2545-2552.
[33]Doymaz, Effect of citric acid and blanching pre-treatments on drying and rehydration of Amasya red apples. Food and Bioproducts Processing, 2010. 88(2-3): p. 124-132.
[34]Balbay, A. and Ö. Şahin, Microwave drying kinetics of a thin-layer liquorice root. Drying Technology, 2012. 30(8): p. 859-864.
[35]Tohidi, M., M. Sadeghi, and M. Torki-Harchegani, Energy and quality aspects for fixed deep bed drying of paddy. Renewable and Sustainable Energy Reviews, 2017. 70: p. 519-528.
[36]Firouzi, S., M.R. Alizadeh, and D. Haghtalab, Energy consumption and rice milling quality upon drying paddy with a newly-designed horizontal rotary dryer. Energy, 2017. 119: p. 629-636.
[37]Sharifi, H., Babapour, Sh., Sherkati, Sh., Evaluation of Problems Caused By Thermal Degradation of Consumed Gas in Iran’s Thermal Power Stations, in 18th International Conference of Electronics. 2004: Tehran, Iran.
[38]Duffie, J.A. and W.A. Beckman, Solar engineering of thermal processes. 2013: John Wiley & Sons.
[39]Doymaz, I., Convective air drying characteristics of thin layer carrots. Journal of food engineering, 2004. 61(3): p. 359-364.
[40]Minaei, S., et al., Mathematical models of drying pomegranate arils in vacuum and microwave dryers. 2012.
[41] Akpinar, E.K., Drying of mint leaves in a solar dryer and under open sun: modelling, performance analyses. Energy conversion and management, 2010. 51(12): p. 2407-2418.
[42]Erenturk, S., M. Gulaboglu, and S. Gultekin, The thin-layer drying characteristics of rosehip. Biosystems Engineering, 2004. 89(2): p. 159-166.
[43]Torki-Harchegani, M., et al., Dehydration behaviour, mathematical modeling, energy efficiency and essential oil yield of peppermint leaves undergoing microwave and hot air treatments. Renewable and Sustainable Energy Reviews, 2016. 58: p. 407-418.
[44]Özbek, B. and G. Dadali, Thin-layer drying characteristics and modeling of mint leaves undergoing microwave treatment. Journal of Food Engineering, 2007. 83(4): p. 541-549.
[45]Myers, R.H., D.C. Montgomery, and C.M. Anderson-Cook, Response surface methodology: process and product optimization using designed experiments. 2016: John Wiley & Sons.
[46]Mghazli, S., et al., Drying characteristics and kinetics solar drying of Moroccan rosemary leaves. Renewable Energy, 2017. 108: p. 303-310.
[47]Spence, J., et al., Investigation into thin layer drying rates and equilibrium moisture content of abattoir paunch waste. Renewable Energy, 2018. 124: p. 95-102.
[48]Kingsly, R.P., et al., Effects of pretreatments and drying air temperature on drying behaviour of peach slice. International journal of food science & technology, 2007. 42(1): p. 65-69.
[49]Akbulut, A. and A. Durmuş, Thin layer solar drying and mathematical modeling of mulberry. International journal of energy research, 2009. 33(7): p. 687-695.
[50]Singh, G.D., et al., Drying and rehydration characteristics of water chestnut (Trapa natans) as a function of drying air temperature. Journal of Food Engineering, 2008. 87(2): p. 213-221.
[51]Benseddik, A., et al., Mathematical empirical models of thin-layer airflow drying kinetics of pumpkin slice. Engineering in Agriculture, Environment and Food, 2018. 11(4): p. 220-231.
[52]Ndukwu, M.C., Effect of drying temperature and drying air velocity on the drying rate and drying constant of cocoa bean. Agricultural Engineering International: CIGR Journal, 2009.
[53]Taheri-Garavand, A., S. Rafiee, and A. Keyhani, Effect of temperature, relative humidity and air velocity on drying kinetics and drying rate of basil leaves. Electronic Journal of Environmental, Agricultural and Food Chemistry, 2011. 10(4): p. 2075-2080.
[54]Chamoli, S., P. Yu, and S. Yu, Multi-objective shape optimization of a heat exchanger tube fitted with compound inserts. Applied Thermal Engineering, 2017. 117: p. 708-724.