Drying characteristics and prediction of best fitted drying model for coriander leaves

Drying experiments were conducted on coriander leaves as affected by drying methods (solar greenhouse drying and open sun drying), pretreatments (dipping in a solution of magnesium chloride + sodium bicarbonate + potassium metabisulphite, boiled water blanching containing sodium metabisulphite, and untreated), and loading densities (2.0, 2.5 and 3.0 kg/m2). Validity of three commonly used drying models were examined to predict the most suitable drying model for coriander leaves. The increased drying temperature under solar greenhouse dryer (42°C) increases the amount of moisture removal from the coriander leaves and reduces the drying time by increasing the drying rate as compared to open sun drying (29°C), at all the selected levels of pretreatments and loading densities. Chemically treated coriander leaves dehydrated under a solar greenhouse dryer required less drying time than other treated leaves and dried leaves. Nevertheless, drying methods and loading densities had significant effects, while treatment effects were marginal. It was found that reduction of moisture and moisture removal rate per unit time occurred mostly in the falling rate period except some accelerated removal of moisture at the beginning up to 150 minutes. Page's model was found most appropriate for drying coriander leaves among the selected models.

KINETICS OF EVAPORATION OF A MODEL SOLUTION OF DISTILLERY DREGS CONTAINING PROTEIN, OIL AND SUGAR

Рассмотрена кинетика сушки послеспиртовой барды при 60°С. Объектом исследований была модельная смесь, состоящая из воды, белков, жиров и растворимых углеводов. Представлены результаты исследований кинетики испарения воды и смесей вода–масло, вода–белок, вода–сахар, вода–масло–белок–сахар, помещенных в чашку Петри. Процесс испарения в изотермических условиях протекал в сушильном шкафу Memmert. Установлено, что добавление вещества в воду снижает скорость испарения воды в периоде постоянной скорости сушки, в периоде падающей скорости сушки продолжительность испарения возрастает. По результатам кинетики сушки модельных смесей можно определять коэффициенты активности компонентов и проводить исследование процесса сушки реальных смесей при проектировании сушилок. The kinetics of drying of the distillery dregs at 60°C is considered. The model mixture containing water, proteins, oils and soluble carbohydrates was the object of research. The results of experimental studies of the kinetics of evaporation of water and mixtures of water-oil, water-protein, water-sugar, water-oil-protein-sugar, placed in a Petri dish, are presented. Evaporation under isothermal conditions was carried out in a Memmert drying cabinet. It is established that the addition of the substance into the water reduces the evaporation rate of water in the period of constant drying speed, the duration of evaporation in the period of falling drying speed increases. According to the results of the kinetics of drying model mixtures, it is possible to determine the activity coefficients of the components and conduct a study of the drying process of real mixtures in the design of dryers.

Drying Kinetics of Wheat (Triticum aestivum L., cv. ‘Pionier’) during Thin-Layer Drying at Low Temperatures

The management of moisture is one of the main challenges in anticipating and averting food decay and food losses during postharvest processing and storage. Hence, it is imperative to reduce the moisture of freshly harvested products to safe-storage limits in order to inhibit the occurrence of diverse biochemical, microbiological and other moisture-related deteriorative reactions which can contribute to quality degradation. A viable alternative to conventional hot-air drying is the application of low temperatures for drying, which has scarcely been investigated. In this regard, experimental-based modeling is a requisite to gain insights into drying processes. Thus, this study focused on investigating the drying kinetics of wheat (Triticum aestivum L.) cv. ‘Pionier’ under a coherent set of drying air temperatures (T = 10–50 °C), relative humidity (RH = 20–60%), and airflow velocity (v = 0.15–1.00 ms−1). A robust and automated measurement system using a high precision balance was utilized as a basis for the real-time and continuous acquisition of drying data. The analysis of the experimental results facilitated the establishment of generalized drying model for low temperatures able to describe at a high accuracy the behavior of moisture ratio X* (R2 = 0.997, RMSE = 1.285 × 10−2, MAPE = 6.5%). An analytical model for predicting the effective diffusion coefficients D (R2 = 0.988, RMSE = 4.239 × 10−2, MAPE = 7.7%) was also developed. In conclusion, the anticipated drying model has demonstrated the capability of modeling the drying behavior of wheat at low temperatures with a high temporal resolution and should be employed in the design, analysis and modeling of cooling, aeration and low-temperature drying processes of wheat bulks.

Theoretical Drying Model of Water Vapor Pressure for Imbibed Porous Material with Sea Water subjected to Weather Conditions

The drying model of porous material has been studied and solved. The drying model solves the drying of porous material if the porous material is saturated or unsaturated with salt solution. Local thermodynamic equilibrium was not assumed in the mathematical model for describing the multi-phase flow in the unsaturated porous media using the energy and mass conservation equations to describe the heat and mass transfer during the drying. The vapor pressure inside porous material voids is built from the vapor mass transport through material thickness and from the void’s water content evaporation. The new equation in the model is water vapor pressure’s equation. The drying model included advection and capillary transport of the water in porous material pores, the gases transport by advection and diffusion and soluble salt transports by diffusion only. The environment of the boundary condition of the model is atmospheric condition in the day’s hours. The model consists of 5 equations for mass and heat transfer phenomenon. The model was solved by Matlab software. The case study of the model is concrete block.

Solvent diffusion mechanism of PMMA/ acetone coated glass fiber fabric during curing process

Fabric it is not an impermeable substrate because of fiber porosity. To study the solvent diffusion mechanism of coated fabric in the curing process, the drying model of PMMA/acetone coated glass fiber fabric was established. This drying model was verified by confocal Raman spectroscopy. Finally, the impact of fabric structure, thickness and porosity on the solvent diffusion process in coated fabrics was studied by the model. It was shown that the predicted solvent concentrations by the model were consistent with the experimental values. This model can be used to quantitatively calculate the solvent concentration at any position and at any time inside the coating film during the drying process. Moreover, it can also predict the curing time and residual solvent concentration of the coating fabric required to reach drying equilibrium. Compared with coated 3/1 twill, 5/3 satin and 2/1 twill, the solvent diffusion of coated plain fabric was faster during curing. Under the same environmental conditions, the thinner the fabric was and the greater the porosity was, the shorter the curing time was. The fitting equations for fabric thickness, fabric porosity and drying time were obtained, which can provide a theoretical guidance for the preparation, performance research and drying conditions optimization of PMMA coated textile materials.