Airflow Drying Research Articles

Research on key technologies of finite element flow field in airflow drying process analysis

Research on key technologies of finite element flow field in airflow drying process analysis

DS 02 - Real-world Evaluation of Endoscope Drying Using a Turbulent Airflow Drying System

DS 02 - Real-world Evaluation of Endoscope Drying Using a Turbulent Airflow Drying System

Low-Temperature Airflow-Drying Cracking Coupling with Flexible Mechanical Deshelling for Camellia oleifera Fruit: Process and Mechanism

Addressing the problems of high seed-breaking ratio and difficult seed-shell separation in the current mechanical deshelling of Camellia Oleifera fruit (COF), this work innovatively proposed a strategy of low-temperature airflow-drying cracking coupling with flexible mechanical deshelling. The cracking ratio of COF reached 100% after airflow-drying at 20–50 °C for 4–10 h. Moreover, the tissue structure of the Camellia shell remained unchanged after airflow drying. The mechanical shelling ratio of cracked fruits (cracking gap 6 mm) reached 98.37%, and the shells present as integrated lamelliform for facilitating later sorting. The results of low-field nuclear magnetic resonance (LF-NMR) and shrinkage equation showed that the free water of outer layers in the Camellia shell evaporated first, then the free water of inner layers transferred to outer layers to further evaporate, creating a moisture gradient and moisture stress to cause the shrinkage of shell and cracking of COF.

Effects of time related operating conditions on the effective drying time and drying rate during interval IR drying of squash (Cucurbita moschata)

Infrared drying is increasingly used in the food industry. Infrared energy can improve drying operations and reduce energy consumption compared to convective drying. Often energy is lost during drying in the form of sensible energy, which increases the temperature of the sample and thus causes irreversible damage. Interval drying was applied to infrared by well-defined intervals. The new drying process IIRAD (Interval Infrared Airflow Drying) was implemented using infrared energy coupled with ambient temperature (18 ± 1 ◦C) airflow (1.41 m s − 1) drying and 0.7 W cm− 2 as IR power. In order to estimate the operating time intervals, the calculation of the energy necessary to evaporate a thin layer of water was estimated according to the initial moisture content. The intervals were then defined with 5s of action time (tON) and a tempering time (tOFF) of 2 min. A second set of time related operating conditions was achieved by modulating tON during the drying process: constant tOFF = 2 min while tON varied from (i) 5 s during the first 240 min (till water content reaches W = 4 g H2O/g db), (ii) tON = 4 s during the next 273 min (till W = 2.6 g H2O/ g db), and finally (iii) tON = 2 s till the end of the process. The three modes, continuous, IIRAD type I and II were compared through the drying kinetics, the effective drying time and the energy consumption. The moisture content rapidly decreased during IIRAD type I and II compared to continuous IR drying. The effective drying time was significantly reduced, which allowed a significant energy gain. The moisture migration from the deep layers to the surface of the samples mainly occurred during the tempering time, which accelerated the water evaporation during the following active times. Calculation and experimental tests showed that the energy required decreased throughout the drying process with water content decrease. Indeed, reducing tON from 5 to 2 s had a positive effect on drying since a higher evaporation rate was noted. Interval Infrared drying appears to be a promising method to intensify drying and save energy. The intervals must be defined according to the sample nature, the operating conditions and the water content of the sample which varies throughout the process.

Coupling Interval Hyper-Active Drying (IHAD) with Instant Controlled Pressure Drop (D.I.C.) to define new swell-drying processes

To respond to the various issues of conventional drying (textural defects of collapse-shrinkage and case hardening, microbiological contamination, poor rehydrability, degradation of active molecules caused by high wet-bulb temperature, weak drying kinetics, and marketing difficulty), swell-drying has proven high relevance in combining conventional drying processes with the Instant Controlled Pressure Drop (D.I.C.). The international team of "Research & Engineering Platform for intensifying Drying Processes (REPID)" has studied phenomenological models and experimental trials combining D.I.C. with new Interval Hyper-Active Drying (IHAD) processes. Currently, IHAD includes interval starting accessibility drying (ISAD), interval infrared airflow drying (IIRAD), and interval microwave airflow drying (IMAD). All these "interval operations" are sandwiched into cycles, each comprising double separate independent mechanisms; a short, hyper-focused active period (that generates and sweeps out vapor to the surrounding environment) alternated by a passive period of internal water diffusion/moisture homogenization. Since surface evaporation is highly intensive, the wet-bulb temperature stays low, although highly effective drying kinetics. Thus, the operation results in avoiding biochemical damage risks. Coupled with the D.I.C. texturing-decontamination, these drying operations are very effective in terms of drying kinetics, energy consumption, and product quality of heat-sensitive solids. It has led to the manufacturing of effective drying equipment.

Efficient inorganic perovskite solar cells made by drop-coating in ambient air

Inorganic perovskites are receiving growing attention due to good thermal stability and fast-improving photovoltaic performance. However, most of the high-efficiency inorganic perovskite solar cells (PSCs) were fabricated in inert atmosphere. Herein, we report an additive-assisted airflow drying (AAD) method to make mixed-halide inorganic perovskite films in ambient air. The nucleation and crystal growth during film formation are controlled by using airflow dying and lead acetate trihydrate additive, producing pinhole-free film with low defect density. Consequently, efficiency of CsPbI2.25Br0.75 PSCs is improved to 18.49%, which is the highest for wide-bandgap (>1.8 eV) inorganic PSCs. An efficiency of 17.08% is achieved for PSCs made under moderate relative humidity (40–50%). Moreover, PCEs of 17.39% and 11.54% are achieved for CsPbI2Br and CsPbIBr2 PSCs, respectively, which are among the best PCEs for CsPbI2Br and CsPbIBr2 PSCs. This work provides a convenient and efficient method to make efficient inorganic PSCs in ambient air.

Airflow Drying Licking Countercurrent of Mango (Mangifera Indica L): Experimental Determination of Drying Parameters

Abstract: This work focused on the experimental determination of drying parameters during airflow drying licking countercurrent of Mangifera Indica L. The samples were dried in a modular electric dryer operating in forced convection. The data collected made to draw the different drying kinetics of the mango at 40, 50 and 60°C. The solution of the Fick equation and the exploitation of the experimental data by the slope method have used.

Measurement of Water Absorption of Recycled Aggregate.

Owing to the high absorption capacity of recycled aggregate (RA), it is crucial to accurately measure its saturated-surface-dried water absorption (WSSD), which largely affects an effective water-to-binder ratio of recycled aggregate concrete. In this study, existing measurement methods for the WSSD of RA are extensively reviewed, including Wiping, Slumping, Centrifugation, Infrared, Evaporation, Airflow drying, Conductivity, Pycnometer, Hydrostatic balance, and Extrapolation. In particular, the physical principles and operability of these methods are emphasized. It was determined that the accuracy of all test results was not satisfactory. For example, the water in pores with an open-ended direction that was opposite to the centrifugal force could largely be retained. In Airflow drying, the temperature change was significantly delayed. In addition, in Hydrostatic balance, RA would pre-absorb water before determining the initial reading. Therefore, several suggestions for optimizing these methods are presented, such as the combination of Evaporation and Airflow drying, the liquid selection in Hydrostatic balance, and the addition of a tiny mixer in each centrifuge tube. In summary, this review facilitates the development of an accurate and convenient method for measuring the WSSD of RA.

Energy consumption computing of cold plasma‐assisted drying of apple slices (Yellow Delicious) by numerical simulation

AbstractEnergy consumption is a great challenge during fruit drying. New techniques such as cold plasma are used as pretreatment or the main treatment for food drying. In this work, apple drying with cold plasma was investigated with COMSOL simulation. Two treatments were designed: (a) traditional air drying at 60°C and 0.5 m/s airflow, and (b) cold plasma treatment at 100 W, and 60 Hz with laminar airflow at 60°C and 0.5 m/s. The samples were two apple slices with a 6 cm diameter and 0.3 cm thickness. Results show that plasma technology without airflow does not have an effective role in drying. But the combination of plasma and airflow drying reduced the drying time from the 9,600 s to 3,600 s. The plasma‐treated samples reached a constant moisture content faster than the air‐dried samples. The energy consumption of drying with plasma was 85‐fold lower than a traditional air‐drying method. The shrinkage of plasma‐treated samples was low and the total shrinkage was near the undried sample (0.008). Cold plasma probably can reduce the energy consumption, drying time, and final drying costs of fresh food drying.Practical applicationDrying with a combination of methods can reduce the processing time. In this work, the plasma technology was combined with air drying and the results show lower process time, lower shrinkage, and lower energy consumption. Plasma technology in combination with traditional air drying can reduce the drying time of food material from 9,600 s to 3,600s. The energy consumption of plasma drying was significantly lower than air drying. It can be concluded from these results that this drying method can be applied to study the drying of different types of food material.

Development and Evaluation of Mobile Two-way Reversible Air Flow Flat-bed Paddy Dryer

A mobile two-way air flow flat-bed paddy dryer of 3-tonne capacity was developed and evaluated. With the provision of a two-way air flow arrangement for reversal of air direction, drying was uniform along the grain bed depth of 500 mm without the need to mix the grain during drying. The moisture content differential among different layers at 200 mm spacing was 3.1% and 0.80% for one-way upward and two-way reversible air flow mode, respectively. Specific energy consumption was 4.86 MJ.kg-1 and 4.34 MJ.kg-1, whereas the drying efficiency was 49.4% and 55.3% for conventional onedirectional and bi-directional reversible air flow mode, respectively. Head rice yield was 4.4% more for paddy dried in two-way reversible air flow mode as compared to conventional one-direction upward air flow drying. The cost of drying was less in twoway (reversible) air flow mode (` 9.80 per kg water) as compared to one-direction air flow mode ( ₹ 11.06 per kg water).

Study of interval infrared Airflow Drying: A case study of butternut (Cucurbita moschata)

Interval process is defined as a means of operating short-time intervals configured to allow the material to attain characteristics to match higher drying rate. The innovative Interval Infra-Red Airflow Drying (IIRAD) involves successive heating intervals (tON) of several seconds followed by tempering periods (tOFF) of a few minutes. IIRAD provides heat only when the product surface is fully rewetted. Drying of winter squash slices was performed in three cases; continuous IR-drying, IIRAD-I: tON = 5 s and tOFF = 2 min, and IIRAD-II: tON varies throughout the process with tOFF = 2 min. A higher drying rate was observed during IIRAD-I. Measured evaporating-bulb temperatures were below 21 °C with energy consumption of 0.98 and 0.77 kWh/kg of evaporated water for I-IIRAD and II-IIRAD, respectively, wherein they exceeded 66 °C and 2.19 kWh/kg of evaporated water for continuous drying. IIRAD resulted in better preservation of flavonoids and better retention of color. However, continuous IR-dried samples displayed better rehydration and higher total polyphenol content. Overall, IIRAD is shown to be a promising drying technique for heat sensitive materials in terms of efficiency, energy consumption, and preservation of key quality attributes linked to lower operating temperature, but with increased drying time.

Effect of drying processes on the final quality of potimarron pumpkin (Cucurbita maxima) powders

This research work focuses on a comparative study of the impact of four drying processes (Air Flow Drying (AFD), Freeze-Drying (FD), Vacuum Multi Flash Drying (VMFD), and Swell-Drying (SD) coupling Instant Controlled Pressure-drop (DIC) to standard Air Flow) on the biochemical, physicochemical, thermochemical, and biological properties of the pumpkin potimarron (Cucurbita maxima) powders. The main results showed that the availability of bioactive substances was much more related to the drying process and attributed to the porosity. VMFD, SD, and FD drying processes had the best preservation of Total Polyphenols (TPP) and Total Flavonoids (TF) much better than AFD. It is worth noting that FD and SD improve the availability thanks to the presence of multi-particulate pores, while VMFD keeps better preservation of thermo-sensitive products.

Selective extraction of neutral lipids and pigments from Nannochloropsis salina and Nannochloropsis maritima using supercritical CO2 extraction: Effects of process parameters and pre-treatment

Supercritical CO2 extraction experiments were conducted to investigate the effects of pretreatment and process parameters on neutral lipids, chlorophylls and carotenoids recovery on two species of Nannochloropsis. For Nannochloropsis maritima, a factorial experimental design was performed (P: [100–300] bar, T: [313–333] K). The highest extraction yields were obtained at the highest pressures and temperatures. Two drying modes, ring drying and air flow drying, were compared. Although total extraction yield and extraction kinetics were observed to be greater using air flow dried microalgae, extracts from this drying method resulted in partial degradation of glycerides in free fatty acids. Ring dried extracts maintained the same neutral lipid composition as the initial biomass. Based on these results, ring dried Nannochloropsis salina was extracted using supercritical CO2 at 333 K and both 300–400 bar. Extraction curves were modelled using the Sovová’s mathematical model.

Antioxidant Content of Frozen, Convective Air-Dried, Freeze-Dried, and Swell-Dried Chokecherries (Prunus virginiana L.).

Chokecherry (Prunus virginiana L.) is rich in bioactive molecules as phenolics, which can act as antioxidants, anti-inflammatory, anticancer, among others; however, due to its high perishability, most of this fruit is wasted. Freezing and sun drying have been the most adopted techniques to avoid its postharvest deterioration. Nevertheless, both processes have presented some drawbacks as high storage costs and losses of bioactive molecules. Therefore, to preserve these molecules, this study compared the impact of convective airflow drying (CAD), freezing (FR), freeze drying (FD), and swell drying (SD). Total phenolics content (TPC), total flavonoids content (TFC), kuromanin concentration (KC), and antioxidant activity (antiradical activity (ARA) and Trolox equivalent antioxidant capacity assay (TEAC)) of chokecherries were measured. “Swell drying” is a drying process coupling convective airflow drying to the Instant Controlled Pressure Drop (DIC) expansion. A central composite rotatable design was applied to optimize the DIC variables and responses. Results showed that both freezing and swell drying effectively preserve the TPC, TFC, KC, and ARA. Moreover, SD samples also presented the highest TEAC. Contrary, in the case of CAD, it caused the highest losses of both antioxidant content and activity. Swell drying remedies the shrinkage and collapsing of dried food structure, which results in a better antioxidants extraction.

Instant controlled pressure drop (DIC) coupled to intermittent microwave/airflow drying to produce shrimp snacks: Process performance and quality attributes

Effects of operating parameters of the instant controlled pressure drop (DIC) texturing process followed by intermittent microwave (MW) and airflow drying were studied for the manufacture of novel swell-dried shrimp snacks. The DIC processing parameters were the absolute pressure of saturated steam (P = 0.4, 0.55, and 0.7 MPa) and the treatment time (t = 70, 100, and 130 s). Intermittent MW drying with active time tON of 30 s and tempering time tOFF of 60 s followed DIC-texturing of blanched shrimp samples (30 g cubes of 1 cm3). The MW density power levels tested were 6, 12, and 24 W/g wb (wet basis). The airflow condition was fixed at 3.2 m/s, 20 °C, and 276 Pa water vapor pressure. Drying performance along with the organoleptic, structural, and functional quality parameters was measured for the dried product. The results showed that the highest DIC processing parameters of P = 0.7 MPa for 170 s were the best texturing conditions, while the MW power level of 24 W/g wb yielded the most effective drying performance when 90% of moisture was removed in 10 min, with organoleptic quality attributes and structural properties better than those of conventionally dried shrimp. Furthermore, the aroma was better preserved, and the exceptionally high absolute expansion ratio (Ɛabs = 13.84) and porosity (φ = 92.83%) allowed enhancement of the desired crispness of the snacks as well. The highly porous microstructure also results in improved rehydration performance.

Study on rapid drying and spoilage prevention of potato pulp using solid-state fermentation with Aspergillus aculeatus

Effects of solid-state fermentation on rapid drying and spoilage prevention of potato pulp were evaluated. Pectin hydrolyzing and antibacterial ability of pectinase-secreting Aspergillus aculeatus and Bacillus subtilis were compared. A. aculeatus grew better in potato pulp, with highest pectinase yield of 342.71 ± 5.09 U/mL and rapid pH reduction to 3.76 ± 0.01. Next generation sequencing showed that the abundance of genera Candida and Enterobacter, which probably caused undesirable fermentation and spoilage, were significantly reduced after inoculation with A. aculeatus. In addition, fermentation with A. aculeatus significantly reduced water holding capacity from 16.63 ± 0.36 g/g to 7.78 ± 0.12 g/g, which resulted in lower viscosity and water binding capacity, and concomitantly significantly decreased moisture content from 76.05 ± 0.24% to 12.95 ± 0.19% after filtration and airflow drying. These results suggested that solid-state fermentation might be a promising technology for efficient processing and utilization of potato pulp.

Experimental Study of the Drying Kinetics of Mango (<i>mangifera indica L.</i>) during Airflow Drying Licking Countercurrent

This work was conducted to study the thin-film drying kinetics of mango (mangifera indica L.) using a modular electrical dryer licking countercurrent and forced convection. Drying experiments were carried out in the Laboratory of Energetics and Applied Thermal (LETA) of the National School of Agro-Industrial Sciences of the University of Ngaoundere under different conditions of drying air temperature (40, 50 and 60°C) for a speed 0.6 m/s. Four trays were used to spread the products in the dryer. To estimate and select the appropriate drying model, ten different models were applied to the experimental data and compared. The performances of these models were compared using the R², the χ² and the RMSE between the observed and predicted moisture ratios values, which ranged from 0.925 to 0.999; 4.10-6 - 0.00540 and 0.0021 - 0.0736 respectively. Among the models used, the Midilli et al., model was found to best explain the thin-film drying airflow drying licking countercurrent of mango.

Microwave airflow drying of pecans at variable microwave power

AbstractIn this study, the dielectric properties of two varieties of pecan nuts at different moistures (10–30% w.b.), temperatures (25–85°C) were determined and the effect of microwave (MW) power density (0.8–2.6 W/g) and exposure time (30–300 s) on moisture content of pecan were approximated by response surface analysis. According to a comprehensive assessment of these results, phased varying power design for MW‐assisted air drying (PPMAD) was appropriate designed to dry pecan nuts. The result indicated that the penetration depths of MW at 2,455 MHz to pecan nuts was distributed in the range of 4.05–10.45 cm in terms of different moisture content and temperature. The moderate output power density (1.7 W/g) is an optimized parameter during the primary stage of MW drying. In PPMAD scheme, 1.7 W/g was delivered in first 150 s, followed by cooling 30 s, and 2.6 W/g was applied in the final 120 s. The results showed that the hybrid drying of PPMAD was efficacious, leading to water losses of 19% in pecan and 16% in hickory without affecting their major compositions and sensory qualities. Further preservation showed that the oxidation degree of PPMAD‐dried nuts was lower than that of the control after 90 days of storage.Practical applicationsMicrowave hybrid drying has been reported to process food and provides a significantly increased shelf‐life for fruits and vegetables, such as apples, carrots, oranges, tomatoes, and spinach. There are no literatures focused on the parameter optimization of microwave drying on pecan and hickory during exposure. The present study provide an optimal method of microwave hybrid using a phased varying power design for MW‐assisted air drying which supply a foundation for large‐scale industrial applications of microwave drying.

Empirical and diffusion models of rehydration process of differently dried pumpkin slices

Abstract The present study investigated the rehydration kinetics of dried pumpkin slices issued from different drying operations, namely airflow drying (AFD), freeze-drying (FD), Vacuum Multi Flash Drying (VMFD) and Swell-drying (SD) which inserts Instant Controlled Pressure Drop (DIC) Texturing between two AFD stages (AFD + DIC + AFD). Rehydration process depends on dehydration methods. It has been noticed that the slowest rehydration process has been observed for AFD whilst VMFD, FD, and SD averred short rehydration time. Experimental rehydration curves were performed through empirical and diffusion models. Hence, it has been noticed that Weibull has provided the best rehydration fitting curve. In other hand, Fick's diffusion models were also used to describe kinetics of rehydration process. They were characterized by two effective diffusivity coefficients D eff 1 and D eff 2 for AFD and VMFD, and three effective diffusivity coefficients in the case of FD and SD (AFD + DIC + AFD). The temperature dependence of the diffusivity coefficients was also described by Arrhenius-type relationship, with adequate activation energy levels.

Response surface methodology (RSM) as relevant way to study and optimize texturing by instant controlled pressure drop DIC in innovative manufacturing of egg white and yolk powders

ABSTRACTThis study aimed to use the Instant Controlled Pressure Drop as a texturing pretreatment prior to air flow drying as a new way for the manufacturing of egg white and yolk powders evaluating the impact of DIC operating parameters; the saturated steam pressure and processing time, on the physical and functional properties of the end products. The obtained results showed that the DIC-textured egg white and yolk powders had high quality attributes compared to those obtained from classical air flow drying. Moreover, it was better than freeze dried powders in terms of water absorption capacity, emulsifying capacity, and foaming capacity and stability.