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Physical property and resistance to airflow through bulk and thin-layer lemon fruit


  • Nomenclature

    A, B = constants; A1, A2, A3, B1, B2, B3 = product-dependent coefficients; L = length, mm; W = width, mm; H = height, mm; GMD = geometric mean diameter, mm; ε = porosity; R2 = coefficient of determination; RMSE = root mean square error; P % = mean relative percentage deviation modulus; Q = airflow rate, m3 s−1 m−2; ΔP = pressure drop, Pa m−1; ρ = air density, kg m−3; ρt = kernel density, kg m−3; ρb = bulk density, kg m−3; μ = air viscosity, m2 s−1; ϕ = sphericity(%).


Hamed Daraby, Department of Agricultural Engineering, Faculty of Agriculture, Shiraz University, Darabi1365 Shiraz, Iran. Tel: +989354234926; Fax: +988318331662; E-mail:



Physical properties of lemon fruit are important for drying system and Kept in stock.


The prediction of airflow resistance is fundamental to the design of efficient drying and aeration systems for lemon fruit.


Using a laboratory unit, two sets of experiments were carried out, namely thick and thin layers. In the thick-layer experiments, four bed depths, 11 flow rates and four temperatures 25, 35, 45 and 55 C. In the thin layer (two kernels depth, 3 cm), the kernels were put together in three arrangements: A, B and random; five moisture contents and 11 flow rates were studied.


Results indicated that resistance to airflow through a column of lemon fruit increased with increasing bed depth and airflow rate. In the latter experiment, pressure drop decreased with a decrease in moisture content. Airflow rate was the most significant factor affecting the pressure drop of lemon fruit in both experiments.


Three applicable models (Shedd, Hukill and Ives, and Ergun) were used to evaluate the pressure drop data. The Ergun model, with higher values for coefficient of determination and lower values for sum of square error and mean relative deviation modulus, is the best model for predicting pressure drop across lemon fruit bed for the conditions studied.