Influence of the drying conditions on the drying constants and moisture diffusivity during the thin-layer drying of figs

Abstract In order to establish the influence of the drying air characteristics on the drying performance of figs ( ficus carica ) several drying tests have been carried out in a laboratory scale tunnel-dryer. The dryer using ambient heated air and working in closed loop was equipped with a continuous monitoring system. The investigation of the drying characteristics has been conducted in the temperature range of 55–85 °C and the airflow in the range of 0.5–3 m/s. An Arrhenius-type equation was used to interpret the influence of the drying air parameters on the effective diffusivity, calculated with the method of slopes in terms of energy of activation, and this was found to be insensitive to air velocity values higher than 2 m/s. The effect of the air temperature and velocity on the drying constants was determined by fitting the experimental data using regression analysis techniques. The influence of the air temperature on the drying kinetics of figs has been shown to follow the Arrhenius relationship. The strong influence of air temperature and velocity at the early stages of drying was evident, as well as the relative insensitivity of the drying process at the later stages. A value beyond which the increase of the airflow velocity has no significant effect on the drying rate was encountered and was determined to be 2 m/s, indicating the predominance of the internal mass transfer resistance over the external one. The investigation revealed that the drying kinetics is most significantly affected by temperature, with the airflow velocity having a limited influence on the drying process. Correlations expressing the drying constants and effective moisture diffusivity dependence on the drying-air parameters are reported.

[1]  Da-Wen Sun,et al.  Applications of computational fluid dynamics (cfd) in the food industry: a review , 2002 .

[2]  R. Vance Morey,et al.  Ambient Air Wheat Drying , 1981 .

[3]  Z. Maroulis,et al.  Moisture Diffusivity Data Compilation in Foodstuffs , 1996 .

[4]  Mehmet Pala,et al.  Hot-air drying characteristics of red pepper , 2002 .

[5]  W. Jomaa,et al.  Moisture diffusivity and drying kinetic equation of convective drying of grapes , 2002 .

[6]  H. Pahlavanzadeh,et al.  DETERMINATION OF PARAMETERS AND PRETREATMENT SOLUTION FOR GRAPE DRYING , 2001 .

[7]  P. Panchariya,et al.  Thin-layer modelling of black tea drying process , 2002 .

[8]  Arun S. Mujumdar,et al.  Advances in drying , 1980 .

[9]  R. S. Rapusas,et al.  The Thin-Layer Drying Characterstics of White Onion Slices , 1995 .

[10]  T. Labuza,et al.  Moisture Transfer Properties of Dry and Semimoist Foods , 2006 .

[11]  Vassilis Belessiotis,et al.  Simulation of air movement in a dryer by computational fluid dynamics : Application for the drying of fruits , 1998 .

[12]  Ray A. Bucklin,et al.  Effects of Drying Air Parameters on Rice Drying Models , 1985 .

[13]  A. Berna,et al.  EFFECT OF AIR FLOW RATE ON CARROT DRYING , 1987 .

[14]  Robert H. Driscoll,et al.  The thin-layer drying characteristics of garlic slices , 1996 .

[15]  J. Chirife,et al.  ON THE APPLICATION OF FICK'S LAW FOR THE KINETIC ANALYSIS OF AIR DRYING OF FOODS , 1978 .

[16]  R. C. Hansen,et al.  Thin-layer Drying of Cultivated Taxus Clippings , 1993 .

[17]  A. Mujumdar.  Handbook of Industrial Drying , 2020 .

[18]  Vaios T. Karathanos,et al.  Comparison of Two Methods of Estimation of the Effective Moisture Diffusivity from Drying Data , 1990 .

[19]  Ş. Karataş.  Determination of Moisture Diffusivity of Lentil Seed During Drying , 1997 .

[20]  Digvir S. Jayas,et al.  REVIEW OF THIN-LAYER DRYING AND WETTING EQUATIONS , 1991 .

[21]  P. K. Pathak,et al.  THIN-LAYER DRYING MODEL FOR RAPESEED , 1991 .

[22]  M. Özilgen,et al.  Effects of velocity and temperature of air on the drying rate constants of apple cubes , 1996 .

[23]  D. R. Pangavhane,et al.  DETERMINATION OF DRYING CONSTANTS AND THEIR DEPENDENCE ON DRYING AIR PARAMETERS FOR THIN LAYER ONION DRYING , 1999 .

[24]  V. Karathanos,et al.  Application of a Thin-Layer Equation to Drying Data of Fresh and Semi-dried Fruits , 1999 .

[25]  Juming Tang,et al.  A MODEL FOR THIN-LAYER DRYING OF LENTILS , 1994 .

[26]  J. H. de Boer,et al.  The dynamical character of adsorption , 1968 .

[27]  V. Belessiotis,et al.  Sun and artificial air drying kinetics of some agricultural products , 1997 .

[28]  M. Maskan,et al.  Hot air and sun drying of grape leather (pestil) , 2002 .

[29]  C. Peri,et al.  Kinetics of sun and air drying of different varieties of seedless grapes , 1986 .

[30]  K. A. Jackson.  Mathematics of Diffusion , 2005 .