Feasibility of atmospheric freeze drying of wet canola bulk

The paper deals with the characteristic study of drying peppercorn using fluidized-bed dryer fitted with baffle vortex generators. The experiments were operated at three different superficial air velocities of 1.2Umf, 1.4Umf and 1.6Umf. Experiments were operated from the initial to final moisture contents of around 12% (dry basis). During the experiments, peppercorns were sampling every 5 minutes, for moisture analysis. A typical fluidized-bed dryer was also tested under similar operating conditions for the assessment. The results indicate that the influence of superficial air velocity on drying peppercorn characteristic in the fluidized-bed dryer fitted with baffle vortex generators is more significant than that in the typical fluidized-bed dryer. It is observed that fluidized-bed dryer fitted with baffle vortex generators shows better performance in reducing moisture content with faster drying rate than the typical fluidized bed dryer especially at high superficial air velocity due to the strong longitudinal vortex which helps in improving the fluid mixing, heat and mass transfer rates.

Water management studies in PEM fuel cells, Part II: Ex situ investigation of flow maldistribution, pressure drop and two-phase flow pattern in gas channels

Effect of superficial air and water velocities on the erosion of horizontal elbow in slug flow

Airflow versus pressure drop for a mixture of bulk wood chips and bark at different moisture contents

Hydrodynamics investigation of pepper drying in a swirling fluidized bed dryer with multiple-group twisted tape swirl generators

Proton exchange membrane (PEM) fuel cell liquid water management remains a topic of research as these technologies continue to penetrate commercial markets. Two-phase flow pressure drop may be considered an in-situ diagnostic tool that can reveal the amount of liquid water accumulating in a reactant flow channel. While the topic of two-phase flow has been studied extensively, having a reliable two-phase flow pressure drop model that can accurately predict the pressure drop in PEM fuel cell flow channels is still an issue. In this study, in-situ and ex-situ two-phase flow pressure drops in PEM fuel cell flow channels are measured and compared with existing models. The objectives of the current study are to compare experimentally measured two-phase flow pressure drops with existing models as well as to improve the two-phase flow pressure drop model for an accurate pressure drop prediction for the application of PEM fuel cell. In-situ and ex-situ experiments were conducted and analyzed for this purpose. The models focused on in this work are all based on experimentally determined two-phase flow pressure drop for channel hydraulic diameters ranging from 0.15 mm to 12 mm. These models were developed for various applications and fluid/gas combinations. For this study’s ex-situ experiments, liquid-gas two-phase flow pressure drops were measured over 20 cm of a 2 mm x 1 mm flow channel machined from an aluminum plate. Water was injected through a Toray (TGP-060) gas diffusion layer (GDL) and emerged on its surface within the flow channel supplied with air flow. Fig. 1 compares 108 experimentally measured ex-situ two-phase flow pressure drops with nine two-phase flow pressure drop models. Figures a-g are based on the separated flow model and figures h-i are based on the homogeneous equilibrium model. The general trend observed in Fig. 1 suggests that although separated flow models outperform homogeneous equilibrium models, they mostly under-predict the two-phase flow pressure drop, especially at lower pressure drops. The seven separated flow model shown in Fig. 1a-g are further compared with each other by defining the mean absolute error (MAE), shown by λ in Fig. 1, (insert Equation 1 from JPG file) In addition, ω, θ, and ε are defined as the percentage of data points predicted within ±10%, ±30%, and ±50%, respectively. It can be observed from Fig. 1 that the model proposed by Mishima and Hibiki [2], shown in Fig. 1c, reflects the best prediction capability with the lowest MAE value. The MAE was further studied at different mass flow qualities and superficial air velocities as shown in Fig. 2. The numbers shown in parentheses indicate the number of experiment runs considered to calculate the MAE at each mass flow quality or superficial air velocity. Fig 2a shows the MAE at different mass flow qualities for each of the separated flow models. Other than mass flow qualities x = 0.87 and x = 0.97, the model proposed by Mishima and Hibiki [2] resulted in the lowest MAE compared to the other six models. However, the model proposed by Saisorn and Wongwises [1] showed a smaller MAE in these two mass flow qualities. Fig. 2b shows the MAE calculated at different superficial air velocities and air flow rates in the flow channel. For superficial air velocities of less than 2 m/s, the model proposed by Saisorn showed a superior performance. However, for superficial air velocities greater than 2 m/s, Mishima and Hibiki's model [2] outperformed. In addition to ex-situ results, experimental in-situ liquid-gas two-phase flow pressure drops are also being measured in an operating PEM fuel cell as shown in Fig. 3. The PEM fuel cell used in this study has seven parallel flow channels, each with 1 mm x 1 mm cross section, machined through stainless steel bipolar plates backed with clear polycarbonate sheets to visualize water. Two high-precision pressure transducers measure pressure drop along 80 mm of two flow channels. In addition to pressure drop measurement, liquid water accumulation and transport with the flow channels is also recorded with a CCD camera mounted directly above the cathode. A combination of ex-situ and in-situ results will cover a large range of liquid/gas flow rates which will be useful for model validation.

A drying experiment with 36 mm thick softwood boards having an average initial moisture content of approximately 1.2 (dry basis) was performed. Drying temperatures of 40, 60 and 80°C were used. Relative humidity and superficial air velocity were maintained at 40% and 3.0 m s−1, respectively. Internal moisture content was monitored along the process in the single direction of the internal flux of water. Loss in mass of the entire timber board was also determined. An effective coefficient of mass transfer was tuned to internal experimental profiles of moisture content by involving the Fick’s second law. An explicit finite difference method for the numerical solution of the mass balance represented by the Fick’s equation was combined with the simplex method of optimization to obtain a mass transport parameter in the magnitude of 1.5–3.5 × 10−9 m2 s−1. A positive and significant effect of temperature on the effective diffusion coefficient, which was well described by an Arrhenius type expression, was deduced from this investigation. Although a negative effect of the average moisture content on the internal resistance to mass transfer was also observed, it was much less evident; mainly above the wood fiber saturation point. A negligible influence of the local moisture content on the investigated transport parameter was noticed when either a linear or a nonlinear model correlating these variables was adopted.

Stingless bees or “kelulut” also produce pot-pollen apart from honey. The pot-pollen is mixed with honey and bee secretion before stored in cerumen pots. It has high nutritive value and medicinal benefits. Pot-pollens are often neglected by the beekeepers due to difficulty in storing and preserving them due to high moisture content. Hence, fluidized bed dryer is proposed as a suitable method to dry and enable convenient storage and preservation of the pot-pollen. Pot-pollen sample of initial moisture content 30.5% is dried at three superficial air velocities, 1.0 m/s, 1.5 m/s, and 2.0 m/s for 30 minutes. Fluidized bed drying has managed to decrease the moisture content down to 23%, 20.5%, and 18.5%, respectively. Higher superficial air velocity lead to higher drying rate in of pot-pollen. Hence, using a fluidized bed dryer to dry stingless bee pot-pollen is a promising method for preserving them. Subsequently, the dried pot-pollen can be easily commercialized in the future.

In recent years, peltier-based cooling systems have been extensively developed in the automotive sector. However, these systems have primarily focused on single-phase fluid flow, utilizing either liquid or gas, while two-phase flow applications have predominantly been explored in industrial heat exchangers. This study aims to investigate the impact of two-phase air-water flow on the performance of peltier-based cooling systems. The research employed an experimental approach, maintaining a constant superficial water velocity of 0.19 m/s, while varying the superficial air velocity at 0 m/s, 3.7 m/s, 7.5 m/s, 11.7 m/s, 15.6 m/s, and 19.5 m/s. Additionally, three different waterblock designs were tested to evaluate their effectiveness in lowering the temperature of the peltier-based cooling system. Visual observations were conducted to identify the flow patterns formed under different combinations of superficial air and water velocities. The experimental results provided data on flow patterns (e.g., no flow patterns, roll waves, pseudo slugs, and entrained droplets), liquid film thickness, temperature reduction for each velocity variation, and the minimum temperature achieved across the three waterblock models. Statistical analysis using multiple linear regression revealed that superficial water velocity had no significant influence, whereas superficial air velocity demonstrated a significant effect. Furthermore, a one-way ANOVA test confirmed a statistically significant difference in the minimum temperatures achieved by the three waterblock designs.

Simulation of Intermittent Drying of Maitake Mushroom by a Simplified Model

A laboratory-scale foam separation system was employed to examine the enrichment and recovery of six proteins: sodium caseinate, β-casein, bovine serum albumin (BSA), β-lactoglobulin, plusmn;-Iactalbumin, and chymotrypsinogen A. In this report we present experimental data which demonstrate the effectiveness of the separation process in extracting proteins from single component solutions. In particular, we have examined the effects of: 1) the solution pH at a fixed air flow rate and initial protein concentration, 2) superficial air velocity at fixed values of pH and protein concentration, and 3) protein concentration at the optimum pH and at a given superficial air velocity. The maximum enrichment of BSA was obtained at its isoelectric point (pH 48), and for other proteins better enrichment was achieved at a pH higher than their isoelectric point. The lower the superficial velocity in the 079–02 cm/s range the higherthe enrichment for all the proteins except for plusmn;-lactalbumin and chymotrypsinogen A (for these proteins enrichment was insensitive to the superficial velocity). The higher enrichment was also obtained by foaming at a smaller initial protein concentration (in the 30–120 mg/L range).

In this paper, experimental results on air‐water two‐phase flow in a miniature T‐junction with hydraulic diameter of 1 mm are presented. Both superficial water velocities and superficial air velocities are taken as 0.01∼0.03 m/s in the experiments, respectively. When superficial air velocities are taken as 0.01∼0.03 m/s and superficial water velocity is 0.02 m/s. It is found that superficial air velocities have little effect on phase distribution. When superficial water velocities are taken as 0.01∼0.03 m/s and superficial air velocity is 0.02 m/s, X3/X1 of the branch increases with increasing superficial water velocity. Slug flow is the only pattern observed in our working condition.

Mixing and scale affect moving bed biofilm reactor (MBBR) performance

Influence of the nature of the Roots blower on pressure fluctuations in a fluidized bed

Air with carbon dioxide is bubbled through Photobioreactors (PBRs) to add carbon dioxide to the reactor medium, remove oxygen, and mix the medium. Most PBR systems use various types of spargers/diffusers that consist of straight or curved tubes with perforation in them to inject air into the PBR reactor volume. A possible novel approach to introducing air into the PBR reactor volume is to use a plenum under the PBR reactor volume in conjunction with a porous membrane that separates the air in the plenum from the liquid medium in the reactor volume. The resistance offered by the porous membrane and the liquid in the reactor volume to air flow needs to be established so that power requirements to provide the desired air flow through the PBR can be determined. Four types of porous membranes were tested: 1)Sintered High Density Polyethylene HDPE 1.59 mm thick with 15–45 μm pore size, 2) Sintered HDPE 0.79 mm thick with 20μm pore size, 3) Genpore black plastic sheet with 45 μm pore size, and 4) Porex 7896 HDPE with pore size of 35 μm). Specimens were tested in a 76.2 mm inside diameter reactor with a depth of 304.8mm and a 76.2 mm plenum depth. Water was used as the reactor medium and the depth was varied between 0 and 228.6 mm. Results showed that the Porex 7896 membrane had little resistance to air flow when the water depth was 0.0mm (1–22 Pa), 1–200 Pa for the Genpore plastic sheet, 1200–1400Pa for the Porex with 20μm pores, and 1100–2500 Pa for the Porex with the 15–45 μm pore sizes for superficial air velocities between 0.00345 m/s to 0.0242 m/s. Water depth was then increased to 228.6 mm in 25.4 mm increments and tested with the same air flow rates. The addition of water significantly increased the resistance to air flow for all membranes (highest being 4200 Pa). Least square correlations for the membranes using water depth and superficial air velocity indicate that resistance to air flow of the membranes was linear with superficial velocity but parabolic with water depth.