Convective Hot Air Research Articles

Multi-coupled mass transfer mechanisms during solvent removal of nitrocellulose-based propellant

This work has designed and developed an industrial-scale experiment system for studying the multi-coupled mass transfer mechanisms included in the solvent removal of the propellant grains. In this respect, the propellant grains were subjected to hot air convection for two hours at a temperature of 40.0°C and relative humidity of 85.0%, of which the mass flow rate was 595.0 kg·h−1 (or 720.0 kg·h−1). The measured data of the transient solvent content were analyzed based on the nonlinear least-squares regression. A slop method was used to predict the effective diffusivity of the solvents held in the propellant grains. In addition, the adsorption kinetics behavior and the mechanism of the propellant grains to the water vapor were studied in detail. As a result, both the vaporization of the solvents as well as the adsorption of the water vapor appeared on the surface of the propellant grains at the same time. The ethanol inside the propellant grains has a greater effective diffusivity compared to ether. The mass transfer in the solvent removal of the propellant grains was controlled by both the internal and external resistances. Moreover, the adsorption of the propellant grains to the water vapor was dominated by physical adsorption.

Osmotik ve Konvektif Kurutma Sonrası Dondurma İşleminin Enerji Verimliliğine ve Kırmızıbiberin Bazı Fizikokimyasal Özellikleri Üzerine Etkisi

The effect of osmotic and convective drying treatments on main physicochemical properties of frozen sliced red peppers was investigated. Sliced red peppers were dried partially using either osmotic dehydration or convective hot air drying before freezing in an air blast freezer at constant air velocity (2 m/s) and temperature (-25°C). The center temperature of osmo- and convective dehydrofrozen peppers reached -25°C in about 105 min, while it took 270 min for control samples. Frozen samples were stored at -18±2°C for 60 days, and the color, texture, ascorbic acid, enzyme activities, antioxidant activity (DPPH and ORAC) and total carotenoid content of samples were monitored during storage. Results showed that skin puncture values of samples decreased by storage time. The ascorbic acid content of sliced red pepper decreased by both treatments and storage time. The antioxidant activity values of control samples were higher than those of convective dehydrofrozen and osmo-dehydrofrozen samples. Both partial drying treatments reduced carotenoid loss significantly. The losses in total carotenoid contents were 58.0, 47.5 and 46.9% at the end of the storage period in control, osmo-dehydrofrozen and convective dehydrofrozen peppers, respectively. Significantly lower energy was used in osmotic dehydration compared to convective drying since no heating required for osmotic dehydration. Moreover, pre-drying of sliced red pepper required one-third of lower energy for freezing compared to direct freezing. This study showed that osmo-dehydrofreezing can be an economical method for sliced red peppers production.

Thin layer modeling of drying kinetics, rehydration kinetics and color changes of osmotic pre-treated pineapple (Ananas comosus) slices during drying: Development of a mechanistic model for mass transfer

This study aimed to develop an effective and safe drying protocol for pineapple fruits. The combination of different osmotic pre-treatments and drying temperatures were used to evolve a novel method that can reduce drying associated changes in pineapple fruits. The pre-treatment was accomplished by soaking fresh pineapple slices in four osmotic solutions (1% trehalose, 2% NaCl, 10% sucrose, and 10% fructose) for 30 min. A hot air convection dryer carried out the drying at 50, 55, and 60 °C temperatures maintaining a constant 30% relative humidity (RH). During the drying experiment, moisture content data were taken and transformed into moisture ratio (MR) and then fitted to the four thin layer models viz. Page, Logarithmic, Newton (Exponential model), and Henderson and Pabi's Model. The impact of pre-treatments and drying temperature on drying kinetics, mass transfer rate, moisture diffusion, rehydration capacity, and color changes of pineapple slices were observed. The drying process was affected by both osmotic pre-treatments and temperature. A satisfactory curve with good fitting as anticipated by the Page and Logarithmic models, with the Logarithmic model fitting best during the drying of pineapple slices. The ideal drying temperature integrated with pre-treatments was 55 °C at 30% RH based on maintaining the color and rehydration. The Page equation provided an excellent statistical fit to experimental rehydration data, with low mean percentage error values of 2.188–7.479%. The pre-treatment of dried pineapples, particularly with trehalose, improved structural retention as seen by increased rehydration capacity and lower color changes after reconstitution. The mechanistic model, which describes activation energy for the increase of moisture diffusion coefficient and mass transfer coefficient, and their correlation to drying conditions (temperature and time), showed a better fit for mass transfer and diffusion. Weibull's distribution model gave a better fit for the water loss model during drying at various temperatures. As a result, the combination of dipping in 1% trehalose solution and hot air drying at 55 °C appears to be a promising procedure for producing high-quality, nutritious dried pineapple products for consumers. This work will assist future researchers in understanding the influence of osmotic pre-treatments on plant foods and improve the existing literature.

Pilot-Scale Radio Frequency-Assisted Pasteurization of Chili Powders Prepacked by Different Packaging Films

Radio frequency (RF) can penetrate most packaging films and has the advantages of pasteurizing prepackaged low-moisture foods and avoiding secondary contamination. The suitable films for prepacking chili powders and the corresponding pasteurization process are unclear. This study aimed to select a suitable film for prepackaging chili powders, optimize the parameters of RF heating prepackaged chili powders, and evaluate the effects of RF-assisted pasteurization on the quality of chili powders. The results showed that the non-woven fabric (NWF) is suitable for prepackaging chili powders by evaluating the influence of RF heating on packaging films (appearance, sealing performance, mechanical properties.). Using NWF, chili powders inoculated with Salmonella enterica Enteritidis PT 30 still achieved 6.81 ± 0.64 log CFU/g reduction, treated by RF heating at an average temperature of 67.06 °C for 7.5 min with an electrode gap of 110 mm, held for 12.5 min at a hot-air convection oven. The pasteurization process had no significant (p > 0.05) effect on the quality (appearance, volatile, and capsaicin) of chili powders. The results indicated that chili powders packed with NWF could still be effectively pasteurized by RF-assisted hot air. This study proposed a viable approach to avoid secondary contamination by adding packaging before pasteurization.

Effect of different drying conditions on physicochemical, morphological, and rehydration properties, and adsorption characteristics of dried crab stick by‐product

The underspecification product obtained from crab stick production is considered as a crab stick by-product. To extend its shelf life, frozen storage is required but this process is costly due to electricity consumption. Then, the process for producing a shelf-stable crab stick by-product was focused in this study to reduce the cost of storage. For this experiment, the by-product (73% wet basis) was dried using different drying conditions such as freeze drying and convective hot air drying at 50, 60 and 70oC. The qualities of dried products including physicochemical, morphological and rehydration properties and adsorption characteristics were assessed. The results found that freeze drying was the best drying method to preserve dried sample qualities. Moreover, convective hot air drying at 70 and 60oC gave better qualities (higher porosity, % reconstruction and rehydration properties and less hardness) compared to 50oC. Adsorption isotherm types II and III were observed in this study.

Drying quality and energy consumption efficient improvements in hot air drying of papaya slices by step-down relative humidity based on heat and mass transfer characteristics and 3D simulation

Convective hot air drying technology is widely used for fruits and vegetables drying process due to its simplicity in usage, small investment, and convenience in operation. However, it is generally considered energy-intensive process with lower drying efficiency and quality because of unprecise control of drying process. In order to solve these problems, step-down relative humidity (RH) hot air drying technology was applied for papaya drying to improve drying efficiency and quality and reduce energy consumption. The effect of constant RH (20%, 30%, 40%, and 50%) and step-down RH of 50% with different holding times (10, 30, 60, and 90 min) and then decrease to 20% on heat and mass transfer process, drying quality, and energy consumption was examined. Results showed that decreasing RH contributed to improvement in the drying rate (DR). Compared to constant RH of 20%, the drying time under initial RH of 50% for 30 min followed by 20% RH shortened by 21.4%. Additionally, under this RH control strategy, the rehydration ratio (RR) and energy consumption achieved their maximum (7.71 ± 0.06) and minimum value (0.015 ± 0.001 kJ/g), respectively. During initial drying stage, high RH improved convective heat transfer coefficient (ht ) values and material temperature increased quickly. Furthermore, high RH contributed to maintaining pore structure formation, which benefited moisture diffusion. When RH was reduced, low RH enhanced convective mass transfer coefficient (hm ) significantly, resulting in rapid diffusion of internal moisture at high temperature, as well as rapid moisture evaporation from the surface. Therefore, step-down RH hot air drying was verified to improve drying of papaya slices, making it energy efficient process. The findings in current work indicate step-down relative humidity strategy is a promising technique to enhance hot air drying process, quality, and energy efficiency of papaya slices.

Specific energy consumption and quality of Citrus hystrix leaves treated using convective and microwave vacuum methods

This study compared the effects of three drying techniques on Citrus hystrix leaves: convective hot air drying (CAD), microwave vacuum drying (MVD), and convective hot air pre-drying followed by microwave vacuum finishing drying (CPD-MVFD). As a control, freeze-drying (FD) was employed. As a result, the modified Page model best described the drying kinetics of C. hystrix leaves. Furthermore, CPD-MVFD significantly lowered the specific energy consumption by 51.6%. Meanwhile, MVD, at density of 12 W/g, retained the greatest antioxidant capacity, TPC content and volatile compounds. In physical terms, CPD-MVFD and MVD performed best in retaining the color characteristics of C. hystrix leaves under all circumstances. Finally, all samples were microbiologically stable. In conclusion, it is suggested that MVD with a power density of 12 W/g be used for drying C. Hystrix leaves, due to its low specific energy consumption, strong antioxidant and TPC capacity, and good recovery of volatile organic compounds.

Using convective hot air drying to stabilize mango peel (Cv-Chausa): evaluating effect on bioactive compounds, physicochemical attributes, mineral profile, recovery of fermentable sugar, and microbial safety

Using convective hot air drying to stabilize mango peel (Cv-Chausa): evaluating effect on bioactive compounds, physicochemical attributes, mineral profile, recovery of fermentable sugar, and microbial safety

Different Types of Meatballs Enriched with Wild Thyme/Lemon Balm Aqueous Extract-Complex Characterization.

In the context of the increasing lactation problems among breastfeeding women, the development of a healthy lifestyle is needed. Different variants of pork, turkey, and beef meatballs, with added lemon balm (Melissa officinalis L.) and wild thyme (Thymus serpyllum L.) aqueous extract (6%), were obtained. These herbs were selected and used due to their antioxidant, antimicrobial, and lactogenic potential. Two thermal treatments, hot air convection (180 °C) and steam convection (94 °C), were applied for meatballs processing. The obtained meatballs were further subjected to a complex characterization. The functionality of the plant extracts was proved by the values of total content of polyphenols (2.69 ± 0.02 mg AG/g dw) and flavonoids (3.03 ± 0.24 mg EQ/g dw). FT-IR analysis confirmed the presence of trans-anethole and estragole at 1507–1508 cm−1 and 1635–1638 cm−1, respectively. Costumers’ overall acceptance had a score above 5.5 for all samples, on a scale of 1 to 9. Further analysis and human trials should be considered regarding the use of lactogenic herbs, given their health benefits and availability.

Numerical modeling of conjugate heat and mass transfer with water vaporization in solid materials inside a convective hot air tunnel

A two-dimensional conjugate model describes heat and mass transfer with liquid to vapor phase change of water in solid materials inside a hot air tunnel. Computational modeling allows to assess the evolution of convective fluid mechanics and heat convection in laminar airflow and coupled heat-mass transfer diffusion inside a rectangular solid. A transient finite volume method conjugate model characterizes the fluid mechanics and heat transfer in airflow, and the local convective heat (h(L)) and mass(hm(L)) transfer coefficients. The results indicate that h(L) was found to vary spatially on each surface of the solid between 5.71 and 101.62 W/m2K, while hm(L) varied from 5.05×10−6 to 1.38×10−6 m/s. Heat and mass transfer by unsteady diffusion inside the solid were accounted for by a second transient diffusion model. Experimental findings of apple slice dehydration kinetic reported in the literature allowed to validate the coupled heat and mass transfer model, with deviation lower than 2% for the water mass losses. Finally, the proposed model applied on a thin-layer of murta berry puree inside a hot air tunnel predicted transient non-uniform heat and mass transfer processes, with a difference of 13.5 K between the coldest and front areas.

Application on oxidation behavior of metallic copper in fire investigation

Abstract In fire investigations, the most important aspect is determining the presence of a liquid accelerant at the fire scene. The presence or absence of accelerants is critical evidence during trials for fire cases. Upon exposure to high temperatures, metallic substances undergo oxidation, which can be imparted by accelerants in the fire. Oxides and substrates found on metal surfaces offer valuable information on the characteristics of fire, including exposure temperature, duration, and involvement of a liquid accelerant. In this study, we investigated the oxidation behavior of copper at high temperatures in a simulated flame environment using ethanol combustion. After oxidation, the morphological, oxide phase composition, and microstructural features of specimens were characterized by observation, X-ray diffraction, X-ray photoelectron energy spectroscopy, transmission electron microscopy, and scanning electron microscopy with energy-dispersive spectroscopic analysis. The elemental carbon with a hexagonal structure deposited on the sample’s surface was found, which may be incomplete combustion and the chemical composition of ethanol. Copper has a preferred orientation of oxide on the (111) crystal plane, which differs from oxidation in ordinary hot air that is related to the large Coulomb force of the (111) crystal plane. Hot air convection due to combustion may cause large areas of oxide layer on the copper surface to crack and peel. Oxide properties and surface state of metals strongly depended on oxidation duration, temperature, and atmosphere. These data shall offer reference information for determining the presence of combustion accelerants at fire scenes.

Experimental investigation and statistical validation of mathematical models for hot air drying traits of carrot.

The purpose of this investigation is to analyze the influence of sample shapes or geometry and dryer temperature on drying kinetics of carrot. Three different geometrical shapes including rectangular slab, circular discs and cubical samples, at temperatures of 70 °C, 80 °C and 90 °C, respectively, are dehydrated through hot air convection drying and regression analysis is executed to adjust the outcomes to 4 thin layer drying models. The models were validated by parameters- R2 (0.957-0.999), RMSE (0.0066-0.093), AIC (-209 to -54.6 for Henderson and Pabis model, -74.8 to -11.8 for Wang and Singh model, -91.47 to -22.7 for Newton model and -140 to -46.6 for Page model), BIC (-206 to -54 for Henderson and Pabis model, -72.4 to -10.76 for Wang and Singh model, -90.3 to -20.28 for Newton model and -138 to -43.92 for Page model) and residual errors (-0.03 to 0.03). The statistical analysis indicated that Henderson and Pabis model is best suited for the drying purpose. Fick's second law of diffusion is applied to compute values of effective moisture diffusivity, which was maximum for circular disc samples in all the cases and rose with an increase in dryer temperature. It varied in the range of 3.02 × 10-8 m2/s to 1.86 × 10-6 m2/s whereas the values of activation energies varied from 68.512 kj/mol to 74.256 kj/mol. The results obtained from this study reveals the experimentally determined drying properties of carrot in order to infer that circular disc shapes possess the ability to optimize the drying process in industries.

Improving the thermal efficiency and energy consumption of convective dryer using various energy sources for tomato drying

High energy consumption and low thermal efficiency are the main problems associated with convection hot air dryers. The effect of various energy sources on tomato drying in a convective dryer was performed. In particular, drying experiments were performed on a convection dryer at two types of heat energy sources, electric and butane-gas, air velocity 1.0, 1.5, and 2 m/s, and air temperature 40, 50, and 60 °C. The rising temperature from 40 to 60 °C caused a reduction of the drying period by 24.8, 22.1, and 21.5% at 1.0, 1.5, and 2.0 m/s, respectively. Minimum energy consumption of 3.83 kW.h was recorded using the electrically heated system while minimizing energy consumption of 0.82 kW.h was detected for the convection gas dryer at 60 °C and 1.0 m/s. The lowest SEC was recorded at 17.44 kWh/kg using gas dryers, while a maximum SEC (112.05 kWh/kg) was observed at the electric dryer under 60 °C and 2.0 m/s. The gas dryer had a thermal efficiency ranging from 50.32 to 78.77%, while the electrically heated dryer had a thermal efficiency ranging from 34.86 to 50.34%. Moreover, applying the butane gas as a heat source for drying had various advantages over the conventional electric system, such as less overall energy consumption with more effectiveness under all conditions.

Prediction of total carotenoids, color, and moisture content of carrot slices during hot air drying using non‐invasive hyperspectral imaging technique

The objective of this paper was to evaluate the performance of Partial Least Square Regression (PLSR) model and to assess the statistical agreement between two different measurement techniques, that is, Vis–NIR hyperspectral imaging (HSI) and standard laboratory methods for quality evaluation of dried carrots throughout the hot-air drying process. Carrots at commercial maturity of 3.5 months after planting were harvested in two seasons (2017 and 2018) and dried in a convective hot air dryer at 50°C, 60°C, and 70°C. Quality measurements were examined at intervals of 30 minutes. PLSR was performed as a regression model to predict quality attributes in carrots, while Passing–Bablok and Deming regressions alongside Blant–Altman analysis were applied as method comparisons. Excellent prediction performance for moisture content was observed with high R2T and R2v at 0.92 and 0.90 with values of RMSET and RMSEv at 8.15% and 8.16%. Satisfactory prediction accuracies were observed for total carotenoids (R2v = 0.64 and RMSEv = 32.62) μg/g, L* (R2v = 0.68 and RMSEv = 32.62), a* (R2v = 0.69 and RMSEv = 1.18), and b* (R2v = 0.60 and RMSEv = 1.45). Selected wavelengths for total carotenoids, moisture content, L*, a*, and b* based on the highest score of VIP loadings were 531, 973, 531, 531, and 680 nm, respectively. An adequate agreement of Blant–Altman analysis between the two methods within the upper and lower limits of 95% confidence interval (CI) were obtained for total carotenoids from 95.68 μg/g to 82.34 μg/g, moisture content (25.18% to 22.93%), L* (2.88 to −3.30), a* (4.15 to 3.43), and b* (4.53 to −3.11) with mean differences at 6.67, 1.12, −0.21, 0.36, and 0.71, respectively. Good correlation coefficients (r) were also observed at 0.89, 0.91, 0.78, and 0.83 for moisture content, L*, a*, and b* with a moderate correlation of total carotenoids at 0.69. The results indicate the potential feasibility of using non-invasive measurement of quality attributes using hyperspectral imaging during the drying of carrots. Novelty impact statement non-invasive measurement using hyperspectral imaging for quality determination in carrots during convective drying demonstrated promising results. Multivariate analysis of Partial Least Square Regression showed a good modeling performance for quality prediction in dried carrots. A good statistical agreements between non-invasive quality measurements using hyperspectral imaging and standard laboratory analysis were achieved by comparative analysis using Blant–Altman plot, Deming, and Passing–Bablok regression.

Change in some physical characteristics of ultrasound pre-treated corn during hot-air convection and vacuum drying

The objective of this study was to investigate the effect of ultrasound pre-treatment (50% US and 100% US-soaking), temperature (80, 90 and 100 ᵒC) and dryer type (hot-air convection and vacuum) on some physical characteristics such as hectoliter weight, thousand kernel weight, dimensions (thickness, length, width, equivalent diameter and sphericity) of corn during drying. Before drying, corn samples were pre-treated without ultrasound (conventional-soaking) and with ultrasound (40 kHz 200 W, 50 and 100% amplitude) during 1 hour soaking. Pre-treated samples were dried at 80, 90 and 100 ᵒC in the laboratory type vacuum dryer and hot-air convection dryer. Moisture content, dimensions (length, width, thickness, equivalent diameter and sphericity), thousand kernel weight and hectoliter weight of pre-treated corn samples at each temperature were analyzed for every 60 min during 240 minutes of drying processes. When the research results were analyzed, the length, width and equivalent diameter values of the corn samples dried in vacuum and hot air convection dryer were found significantly different between 0-60 minutes (P≤0.05), but insignificant (P>0.05) in the following periods. While the decrease in thickness of corn samples dried in vacuum dryer was significant (P≤0.05), the decrease in thickness of corn samples dried in hot air convection dryer was found insignificant (P>0.05). The increase in sphericity of the corn samples dried in vacuum dryer during drying was significant (P≤0.05), but the increase in the hot air convection dryer was insignificant (P>0.05). The effect of ultrasonic pre-treatment and dryer temperature on the size of the corn samples was found to be insignificant (P>0.05), while the effect of vacuum drying on the size of the corn samples was significant (P≤0.05). The effect of ultrasound pre-treatment, drying temperature and drying time on moisture content, thousand kernel weight and hectoliter weight of corn grains were found to be significant (P≤0.05). As a result, the vacuum dryer, allowed the corn to dry in a short time without much change in the structure of the corn.

Numerical simulation and parameterization of the heating and evaporation of a titanium (IV) isopropoxide/p-xylene precursor/solvent droplet in hot convective air

Flame spray pyrolysis (FSP) is an excellent method to produce metal-oxide powders in the nano-size range. In this framework, the heating and evaporation of precursor solutions in hot oxidizing environments is investigated. A single spherically symmetric precursor/solvent droplets of titanium (IV) isopropoxide (TTIP) – Ti[OCH(CH3)2]4 in p-xylene – C6H4(CH3)2 at room temperature in convective hot air at atmospheric pressure is considered. Both variable liquid and gas thermophysical properties are incorporated and the non-random two-liquid (NRTL) model is used to describe the real behavior of the mixture. The bi-component droplet interior is not physically resolved and time-dependence is considered through the distillation-limit model for droplet heating and the rapid-mixing model accounts for droplet vaporization. A parameter study of the heating and evaporation characteristics of the single precursor/solvent droplet on the initial droplet size, the initial TTIP mass fraction in the droplet, the ambient air temperature, and the relative gas and droplet velocity is performed and discussed. The results are parameterized and tabulated in terms of polynomial fits of the individual mass evaporation rates of the components, the droplet surface temperature, and the normalized droplet surface area. A computer code in the programming language C is provided that can be incorporated into more complex simulations of FSP.

Effect of temperature on the microwave drying process and the viability of amaranth seeds

In this work, the microwave drying of amaranth seeds at different temperatures has been studied. The main objective of this study is to evaluate the effect of temperature on three key variables of the drying process and viability of amaranth seeds (drying time, energy consumption, and germination rate) after drying with microwave energy. The tests were performed in a domestic microwave oven, modified for research use, at six drying temperatures (between 35 and 60 °C). For comparative purposes, the amaranth seeds were dried by forced convection of hot air in an electric oven. It was observed that an increase in the drying temperature causes a simultaneous decrease in drying time (from 378 to 126 min) and in the energy consumption (from 9.07 to 2.61 Wh g −1 , and from 412.6 to 111.7 MJ kg −1 [H 2 O]) and cost (from $0.065 to 0.019 USD) required to dry the seeds. However, there is also an unacceptable decrease (from ∼85% up to 23%) in the germination rate of the seeds with the drying temperature. In order to ensure the amaranth seeds’ viability after the drying process, it is necessary to employ lower drying temperatures-i.e., between 35 and 40 °C. Moreover, drying of amaranth seeds with microwave energy at 40 °C proved to be a faster and more effective method than convective drying by reducing drying time by 22% (from 336 min to 261 min) and energy consumption by 74% (from 928.4 to 274.0 MJ kg −1 [H 2 O]) without significantly affecting their viability. • Microwave drying of amaranth seeds at different temperatures has been studied. • Temperature exerts a significant influence on the process and seeds' viability. • Higher temperatures favor the drying process but significantly impair the viability. • Microwave drying is a faster and more efficient method than convective drying. • Microwave drying, at controlled temperature, could be a viable alternative.

Study of the drying behaviour and color kinetics of convective drying of yam (Dioscorea hispida) slices

Drying is a crucial step in processing for enhancing the storability of yam (Dioscorea hispida) slices. In this present work, the drying of yam slices was carried out in a lab-scale auto weighing forced convective hot air drier at a temperature span of 50–70 0C after 30 min of boiling. The study focused on drying behavior, fitting mathematical models to drying and color kinetics, examining the texture and rehydration ratio of dries yam slices. To exhibit the mass and color change characteristics, experimental data were fitted to seven drying kinetics and two color kinetics models. Model fitness was compared and selected based on chi-square (X2), goodness of fit (R2), residual sum of squares (RSS), and root mean square error (RMSE). Moisture diffusivity ranged from 4.5133 × 10−10- 7.522 × 10−10 m2/s and increased with temperature. The activation energy of 23.53 kJ/mol was obtained. Midilli-kucuk model confirmed the superior fitting to experimental data followed by two-term model. Color kinetics was determined using L, a, b values, total color change (∆E), chroma, hue and browning index. L value reduced with drying time, while b and a value increased. Zero order kinetics fitted a and ∆E values adequately while first order kinetics described the changes in L and b values. It can be concluded that the Midilli-kucuk model can be used for predicting drying process behavor, system design of convective hot air drying of Dioscorea hispida for industrial scale up.

Study of Drying Behavior of Pumpkin by Convective Hot Air Drying– Cast Tape Drying

Study of Drying Behavior of Pumpkin by Convective Hot Air Drying– Cast Tape Drying

EVALUATION OF A SUITABLE THIN LAYER MODEL FOR DRYING OF PRETREATED COCOYAM SLICES USING A CONVECTIVE HOT AIR DRYER

This work evaluated the thin layer drying kinetics of pretreated cocoyam slices (Xanthosoma sagittifolium) in a convective hot air dryer. Seven thin layer theoretical and empirical models widely used in describing the drying behaviour of agricultural products were fitted to the experimental data in order to select the appropriate model for predicting the drying kinetics of cocoyam (Xanthosoma sagittifolium). The Page model showed the best fit under certain drying conditions based on the coefficient of determination (R 2 ) and sum of squares error (SSE). Comparison was made between the experimental and model predicted moisture ratio by non-linear regression analysis. Furthermore, the effect of drying temperature and pretreatment on the best model constants was evaluated. Consequently, the page model showed an excellent fit with the experimental data (R 2 > 0.99 and SSE < 0.0010) for the drying temperatures of 50, 60 and 70 °C at different sample pretreatments; untreated (raw), water soaked and brine soaked respectively. Thus, page model can adequately predict the drying kinetics of cocoyam under pretreatment conditions.