Papers by Keyword: Drying

Abstract: The main purpose of this work is to evaluate the influence of the thickness and thermophysical properties of insulating materials on the maximum external surface temperature and energy gain provided for an intermittent ceramic kiln operating with natural gas as fuel. To evaluate the influence of independent variables on response variables, a factorial experimental design was developed. From the analysis of variance (ANOVA), it was possible to determine significant and well-adjusted mathematical models for both response variables. It was verified that the thickness and thermal conductivity of thermal insulation are the independent variables that have the greatest influence on the process efficiency.

Abstract: Drying is a complex process of coupledheat and mass transfer of wet porous material. Wet clay products when exposed to drying without control can suffer cracks and deformations, reducing its quality post-drying. Thus, this work aims to study the hollow ceramic materials drying with arbitrary shape using lumped models. Here, the exact solution of the governing equations were obtained using the method of separation of variables. Results of the average moisture constant and temperature of the material along the process are presented and analyzed. It was observed that the moisture loss process occurs at a lower speed than the heating of the ceramic material because its thermal diffusivity is greater than the mass diffusivity and that the area/volume relationship strongly affects the heat and mass transfer of the material.

Abstract: This work presents a theoretical drying study of sisal fiber. Fibers with moisture content of around 11.2% were dried in an oven in the temperature 90°C. A transient and three-dimensional mathematical modeling to predict heat and mass transfer in a bed of fiber was proposed and numerically solved by using the finite-volume method. Results of the average moisture content and surface temperature were compared with experimental data to verify the consistence of the proposed model, and good agreement was verified.

Abstract: Drying is an essential pre-treatment step that plays a critical role in the energy balance of biomass power plants. This has motivated the search by cost-effective drying technologies. Within this context, the present work aims to investigate the application of a spouted bed dryer with inert solids for drying sugarcane bagasse, the most important biomass used for generating energy in Brazil. Effects of the biomass volume fraction, inlet air temperature and spouting gas flow rate on the drying time and thermal efficiency of the equipment were examined. Results show that drying time decreases by decreasing the biomass fraction and by increasing air temperature. Highest values of biomass percentage and air temperature allied to the lowest velocity of the spouting air greatly improve the efficiency of the biomass drying. Based on a balance between the energy that the product is capable of suppling and the total energy consumed by the dryer the optimum operating conditions recommended for making feasible the use of the bagasse dehydrated in spouted bed for energy purposes are: air temperature of 67°C, biomass volume fraction of 0.6 and air flow rate equal to the minimum stable spouting condition.

Abstract: This work presents a drying study of banana fruit (cylindrical slices) using heat, mass and shrinkage lumped models, and experiments in different drying conditions. Whole bananas were peeled, sliced manually (cylindrical pieces) and dried in an oven at constant drying condition (40 and 70°C). Drying, heating and shrinkage lumped models were proposed and fitted to experimental data. Results revealed which air temperature affects significantly the moisture removal, heating and shrinkage of bananaslices. Furthermore, results revealed which air temperature affects significantly the moisture migration, heating and shrinkage rates of banana slices. The fitted results presented good agreement with experimental data.

Abstract: The present work has the objective to study the water diffusion in the process of intermittent solar drying of mangabas. Osmotic dehydration (OD) pretreatment was performed in sucrose solution and the drying took place in a direct solar dryer with the fruits arranged in stainless steel screens, temperatures varying between 30 and 45°C along the day with peaks of 70°C. The period of intermittence was approximately 16 h reaching equilibrium after 6 days. The diffusional model based on the second Fick’s law was proposed for each of the daily drying periods of 360 minutes, considered that the process is controlled by internal diffusion, negligible external resistance, spherical geometry, shrinkage based on the average radius. The coefficients of effective diffusion (D_ef) obtained by using 4 terms of the infinite series, present values of D_ef ranging from 0.2 to 3.30x10^-10 m2/s with R2≥ 0.868 and average relative deviations MRD≤10^-2.

Abstract: Several studies about drying of ceramic materials have been developed in many engineering and fabrication sectors. This process requires high investments and high energy consumption, resulting in high costs to the companies of this sector. In many situations, it is common the use of theoretical solutions that allow, with relative ease and low cost, to change the operational and geometrical conditions of the dryer or object of drying, to obtain the optimized operational conditions. In this sense, this work aims to predict the drying process of a ceramic brick in an oven using the computational fluid dynamics analysis. For a drying temperature of 80°C, the results of the drying and heating kinetics, and the moisture content and temperature distributions of the product and the air and the air velocity and pressure in the oven are shown and analyzed. A comparison between the predicted and experimental data of the average moisture content and temperature of the brick along the process was done and a good agreement was obtained.

Abstract: Food drying is one of the most used methods of preservation. To accurately describe moisture migration within biological products (grains, fruits, vegetables, etc.) during drying and explain the effects of this process on the quality of the material, have been proposed several mathematical models, but few incorporate the phenomena of simultaneous heat and mass transport applied to complex geometry. In this sense, this paper aims to present a mathematical model, based on the thermodynamics of irreversible processes to describe the heat and mass transfer (liquid and vapor) during the drying of bodies with oblate spheroidal geometry. This model was applied to describe drying of lentil, considering the variables transport coefficients and equilibrium conditions at the surface of the solid. Results of the average moisture content, average temperature, liquid flux, vapor flux, and moisture content and temperature distributions inside a lentil kernel during drying process, at different temperatures (40 and 60 oC) were presented and analyzed.

Abstract: Tamarind is a fruit of foreign origin, more precisely African, but it has an excellent adaptation to the different types of climatic conditions in other continents. In Brazil, for example, it is possible to find it in several states. Although tamarind has a considerable yield on both its constituent parts, shell, pulp and seeds, and have a low purchasing power, the fruit is largely wasted and there are few in-depth studies on the same. As a way of reuse, the aim was to transform the fruit into new products, such as flours used in human food. The objective of this study was to make the drying of the tamarind fruits to obtain the ideal characteristics for the development of a food flour and to evaluate the physical-chemical quality and to determine the bioactive compounds of the tamarind flour. Drying was done at 60 °C in a greenhouse, during different drying periods, which varied according to each part of the fruit, after which the flours were elaborated and characterized for the physicochemical and bioactive parameters. In the physico-chemical characterization, a good presence of proteins in the seed flour (7.09%), low sugar content in the pulp flour (0.74%), good values ​​for lipids in the seed flour (3, 41%) and good ash values in the bark flour (2.69%). In general, the flour besides proteins had a good source of energy and minerals. Among the bioactive compounds present in the tamarind flour were the high contents of phenolic compounds (1564.9 mg/100g), vitamin C (80.95%), lycopene (89.62 mg/g), flavonoids (20.44 mg/100g) and anthocyanins (12.84mg / 10g) in the seed flour, carotenoids (20.80 mg/g) in the pulp flour. In general, flours produced from tamarind had excellent characteristics for the preparation of bakery products.

Abstract: This paper studied the influence of porous burner effect on drying kinetics of Nile tilapia drying using stainless steel mesh porous burner as heat source. Drying kinetics was analyzed by determination of drying rate (DR), drying specific energy consumption (SEC) and dryer thermal efficiency (). In this study, the stainless steel mesh was used as porous media with porosity of 10, 20 and 50 pore per inch (PPI), drying air velocity of 0.5, 1.0 and 1.5 m/s, and drying temperature of 50, 60 and 70 °C, respectively. The results were found that the application of porous burner as heat source can improve the drying kinetics. It was found, at the porosity of 50 PPI, the drying temperature of 70 °C and the air velocity of 1.5 m/s, the moisture ratio of the drying was decreased rapidly, the highest drying rate was found to be 150 g (water evap.)/hr., the lowest drying energy consumption was found to be146.75 MJ/kg, and the thermal efficiency of the dryer was found to increase by 17.79% and the CO and NOx concentration in case of applying porous burner as heat source is lower than without porous burner.