A Comparative Study of Different Drying Processes for a Deformable Saturated Porous Medium

Drying of a deformable saturated porous medium based on convective tempering is a novel method that can enhance energy efficiency and the quality of the dried product itself.In this experimental investigation,the performances of this specific technique are compared with those of a standard stationary drying process in terms of deformation,drying kinetics,moisture redistribution,and energy consumption.In particular,the response of a deformable saturated porous medium(Kaolin)is considered.The results are critically discussed pointing out advantages and drawbacks.

Effect of Pectin Lyase Enzyme on Fermentation and Drying of Cocoa (Theobroma cacao L.): An Alternative to Improve Raw Material in the Industry of Chocolate

Cocoa (Theobroma cacao), in all its presentations, is consumed all over the world and is one of the main drivers of the economic in several countries. The world’s Cocoa tendency is focused on developing special beans. This category is subject to postharvest processes of utmost importance such as the fermentation and dry, which are currently carried out with traditional and poorly effective devices, which need to be improved to obtain a high quality product. The aim of this study was to evaluate the influence of the pectin lyase enzyme (E.C.4.2.2.10) on the postharvest cocoa process. We evaluated the enzyme dosage (1.0% and 0.5%) in fermentation and its effect on the variables temperature, acidity and drying time by convection at 60°C. The Pectin lyase activity during fermentation does not cause a significant effect on the variables of temperature and acidity;however, the drying process time required to achieve 7.0% moisture was reduced. The enzyme dosage of 1.0% was the best result, the amount of exudate obtained (115 ml) during fermentation and the best degree of fermentation (77% ± 3.8) were increased and further shows a change in porosity facilitating the scale surface and internal moisture diffusion. The drying rate (Nw) expressed in kgwater/m2 * min was determined based on the empirical model of Newton, where the higher speed was obtained during the falling period. In conclusion, enzyme dosage 1% was the best concentration evaluated because weaken grain husk, which allowed an adequate fermentation,and subsequent time drying reduction until 10.8 h.

A Convective Thin Layer Drying Model with Shrinkage for Kent Mango Slices

In this work, a model of convective drying of mango slices was developed and validated by experiments. This model was established by considering slices shrinkage in the energy and the mass balances during the thin layer drying. The drying kinetics and the temperature curves of the product were simulated using the model at various drying temperatures. The simulated curves were then compared to the experimental curves obtained using a convective dryer controlled in temperature and moisture. The results showed that the drying curves were suitably fitted by the thin layer drying model with a correlation coefficient r2 = 0.997. Thus, taking shrinkage into account, it is possible to predict more effectively the thin layer drying kinetics of mango slices. This study therefore contributed to the mango drying modelling and to the mango dryer setting.

Development of a Single-Column Model in RegCM4 and Its Preliminary Application for Evaluating PBL Schemes in Simulating the Dry Convection Boundary Layer

A single-column model(SCM)is developed in the regional climate model RegCM4.The evolution of a dry convection boundary layer(DCBL)is used to evaluate this SCM.Moreover,four planetary boundary layer(PBL)schemes,namely the Holtslag-Boville scheme(HB),Yonsei University scheme(YSU),and two University of Washington schemes(UW01,Grenier-Bretherton-Mc Caa scheme and UW09,Bretherton-Park scheme),are compared by using the SCM approach.A large-eddy simulation(LES)of the DCBL is performed as a benchmark to examine how well a PBL parameterization scheme reproduces the LES results,and several diagnostic outputs are compared to evaluate the schemes.The results show that the SCM is properly constructed.In general,with the DCBL case,the YSU scheme performs best for reproducing the LES results,which include well-mixed features and vertical sensible heat fluxes;the simulated wind speed,turbulent kinetic energy,entrainment flux,and height of the entrainment zone are all underestimated in the UW09;the UW01 has all those biases of the UW09 but larger,and the simulated potential temperature is not well mixed;the HB is the least skillful scheme,by which the PBL height,entrainment flux,height of the entrainment zone,and the vertical gradients within the mixed layer are all overestimated,and a inversion layer near the top of the surface layer is wrongly simulated.Although more cases and further testing are required,these simulations show encouraging results towards the use of this SCM framework for evaluating the simulated physical processes by the RegCM4.

What Process Optimizes Convective Drying of Farm Products with Complex Constitution:Case of Okra(Abelmoschus esculentus)

In this paper, we propose an optimized process for farm product convective drying. Above and beyond the influence of the air parameters on foodstuff convective drying, this work shows that product internal parameters and drying proceedings must be taken into account during the evaluation of their convective drying. Results indicate that okra maturity influences its convective drying. It dries faster when it is too young or when it is advanced age. Drying time of okra of 1, 2, 3, 4 and 5 days old is respectively 580 min, 780 min, 990 min, 1200 min and 850 min. Also, one observes that considering okra on its three zones according it length, i.e. its base, middle and extremity parts have not the same resistance to transfers during convective drying. These three zones have respectively 400 min, 520 min and 600 min of drying time. Okra cut reveals a major importance on its convective drying evaluation. The longitudinal cut di-viding okra on four parts, sliced with 5 mm and 10 mm of thickness and the whole okra put respectively 150 min, 200 min, 280 min and 400 min for their drying. At last, three (03) different constituents of okra, namely, the skin, the seeds and central material behave differently during convective drying. The drying time of the central material, the seeds and the skin is about 70 min, 150 min and 190 min respectively, against 400 min for the whole okra.

3D Model Simulating the Hydro-mechanical State of Unsaturated and Deformable Material during Hot air Drying

A three dimensional model to predict the hydro-mechanical state of unsaturated and deformable material during hot air drying has been proposed.The material viscoelastic behaviour was formulated using Bishop’s effective stress theory for partially saturated material using the liquid saturation as the Bishop parameter.The hydro-thermal and mechanical equations were coupled by the fluid pressure and the solid matter velocity.The model was applied to a deformable material(innovative clay-cellulose fibers composite)subjected to convective drying.A generalized Maxwell model with five elements,whose parameters were measured experimentally and correlated to water content was used to describe the material’s viscoelastic behavior.The hydro-thermal part of the proposed model was validated on the basis of a comparison of experimental and simulated drying rate curves.The Von Mises stress was simulated and compared to the experimental tensile strength in order to predict the time and the region of material failure.For a drying process at 95°C,the region of failure risk was identified.The failure may occur on the lateral surface of the slab in contact with air at a drying time of 2.5h.

Characterization of Okra Convective Drying, Influence of Maturity

An experimental study for the drying kinetics of whole okra was carried out. In the study, different ages were considered by taking into account influence of okra maturity on its convective drying. The 2D moisture evolution inside the product and its maturity were evaluated by fitting experimental data versus drying time. The water effective diffusion coefficient of okra at different maturity states was gotten by the experimental model using Fick’s second law. A parametric study was carried out in the ranging of okra age from 2 to 7 days at 60℃, both fruits gathered on the same plant to avoid divergences due to okra varieties that can induce difference on physical structure and the chemical composition. It was found from the experimental results that okra maturity has important influence on its behaviour during convective drying. At 2, 3, 4, 5 and 7 days old, the drying effective time was respectively 780, 1000, 1155, 850 and 750 min. Effective diffusivity of the okra in this order of age was 1.38 × 10-10, 6.09 × 10-11, 1.23 × 10-11, 8.98 × 10-11, and 1.05 × 10-10 m2/s in the present study, while the average initial moisture content was respectively 12.27, 9.00, 7.53, 5.97 and 4.92 Kgw/Kgdm.

Taking into Account the Complex Nature and the Intrinsic Parameters of Agro-Food

In this paper, we perform experiments on the drying of widely consumed food products in Africa. Tomatoes and peppers are considered as products with a complex structure. Zucchini, cucumber, eggplant and cabbages are the other products used in these drying experiments, having different intrinsic parameters. Most food products have three components, namely skin, flesh containing seeds and the central spongy structure, that do not have the same behavior during their convective drying. Skin is the component that significantly reduces drying while the flesh is easy to dry. By drying the samples considering their intrinsic parameters, one quickly realizes the complex nature of mass and heat transfers during the drying of biological products.

ANFIS and ANNs model for prediction of moisture diffusivity and specific energy consumption potato,garlic and cantaloupe drying under convective hot air dryer

The main purpose of this study was to develop and apply an adaptive neuro-fuzzy inference system(ANFIS)and Artificial Neural Networks(ANNs)model for predicting the drying characteristics of potato,garlic and cantaloupe at convective hot air dryer.Drying experiments were conducted at the air temperatures of 40,50,60 and 70
C and the air speeds of 0.5,1 and l.5 m/s.Drying properties were including kinetic drying,effective moisture diffusivity(Deff)and specific energy consumption(SEC).The highest value of Deff obtained 9.76×10^-9,0.13×10^-9 and 9.97×10^-10 m^2/s for potato,garlic,and cantaloupe,respectively.The lowest value of SEC for potato,garlic,and cantaloupe were calculated 1.94
105,4.52
105 and 2.12
105 kJ/kg,respectively.Results revealed that the ANFIS model had the high ability to predict the Deff(R^2=0.9900),SEC(R^2=0.9917),moisture ratio(R^2=0.9974)and drying rate(R^2=0.9901)during drying.So ANFIS method had the high ability to evaluate all output as compared to ANNs method.

Investigation of the structural changes of cocoa bean (with and without seed coat) during convective drying

The influence of seed coat on the behaviour of heterogeneous structure of cocoa bean(frosteros sp.)during convective drying with tempering period was investigated in an isothermal condition.It was found that the removal rate of moisture and air diffusion between the cocoa kernel and seed coat is not the same especially at the temperature of 55℃and initial drying time for all temperatures used.When the drying temperature increased to 70℃and 81℃,the cocoa kernel and the seed coat shrinks simultaneously,indicating that the rate of moisture and air removal from the kernel through the seed coat are the same.Change in sphericity of the bean was more pronounced at the temperature of 55℃for the seeds with seed coat while for all other drying conditions it remains fairly constant after one-hour drying.