Drying is a common process in a number of industries. Products such as furs, wools, textiles, clay, timber, grains, fruits, and vegetables, at some stage, require drying. Review of the literature reveals that commercial dryers are highly inefficient due to various factors. One such factor is that commercial dryers are generally not equipped with heat recovery facilities. Heat pumps can provide a very efficient means of recovering both sensible and latent heat, hence energy loss can be substantially reduced. Furthermore, a heat pump always delivers more heat than the work input to the compressor. These two salient features render heat pump drying a premium alternative for efficient use and conservation of energy in drying industries.

The aim of this work has been to minimize the thermal energy required to dry malt in deep beds while maintaining malt quality, and without increasing the drying time more than one hour. Malt drying usually takes place in deep bed (. 7-1 m) driers by forcing hot air through the bed. Measurements of inlet and outlet relative humidity, temperature, and airflow at a drier at Great Western Malting Company's Vancouver, Washington facility were made to find average moisture content versus time. The measurements were used to develop a wetted surface model of a malt bed. However, the model was not detailed enough to accurately fit the drying data taken from the kiln. Thus it was necessary to consider a more complex model. A diffusion based mathematical model of malt drying was coded using malt properties and drying equations found in the research of Bala (Ph.D. thesis, 1983). This program calculates moisture content and malt temperature in horizontal layers of a malt bed. Energy saving drying tests by airflow reduction methods were simulated with the program. The methods were designed to take advantage of the malt's internal drying mechanism, and they were effective at reducing energy consumption. However, model verification was necessary, and maintaining malt quality was essential. A deep bed experimental malt drier was built at Portland State University to allow malt temperature and average moisture content data collection. Drying experiments were performed at constant airflow, for several different drying temperature cases, and the highest experimental temperature with acceptable malt quality was found to be 7 5 C. Drying at 70 C (158 F) rather than at 63 C (145 F) was found to cause a 20% reduction in the thermal energy consumption, but higher temperatures did not significantly improve efficiency. The experimental moisture contents and grain temperatures generally compared well with diffusion model simulations of the experiments. Airflow reduction experiments decreased thermal consumption by 20% compared to typical drying schedules. These experiments were based on the airflow reduction methods learned from the diffusion model. However, diffusion model simulations using the experimental conditions showed thermal energy reductions of 11 %.

The fundamental and quantitative study of heat and mass transfer processes in wood plays an important role for understanding many important production processes, such as wood drying and hot-pressing. It will help us improve the existing products and production techniques and develop new manufacturing technology. The most difficult aspect of the study is the complicated interactions of heat and mass transfer mechanisms. Extensive characterization of these physical processes using a strictly experimental approach is extremely difficult because of the excessively large number of variables that must be considered. However, mathematical modeling and numerical techniques serve as a powerful tool to help us understand the complicated physical processes. The goal of this research is to model the simultaneous heat and mass transfer in wood. The specific objectives of this research are: 1) develop a computer simulation program, implementing an existing one-dimensional mathematical drying model, using a finite difference approach, to numerically evaluate the mathematical model. 2) study sensitivity of the heat and mass transfer model to determine the effects of wood physical properties and environmental conditions on the drying processes. / Master of Science

Submitted by Josirene Barbosa (josirene.henrique@ufcg.edu.br) on 2018-01-25T12:14:24Z No. of bitstreams: 1 MARCONDES BARRETO DE SOUSA - TESE PPGEP 2013.pdf: 2754211 bytes, checksum: cfa419eec5485d15508d11ab77a2eeed (MD5) / Made available in DSpace on 2018-01-25T12:14:24Z (GMT). No. of bitstreams: 1 MARCONDES BARRETO DE SOUSA - TESE PPGEP 2013.pdf: 2754211 bytes, checksum: cfa419eec5485d15508d11ab77a2eeed (MD5) Previous issue date: 2013-02 / Capes / A torta de mamona é o principal subproduto da cadeia produtiva da mamona, produzida a partir da extração do óleo das suas sementes. Em todo o mundo, seu uso predominante tem sido como adubo orgânico, apesar do seu elevado teor de proteínas. A torta é produzida na proporção aproximada de 1,2 tonelada para cada tonelada de óleo extraída. A elevada produção de biocombustíveis a partir das sementes de mamona ocasionará um aumento na produção da torta, a qual, apesar do alto valor nutritivo, não pode ser empregada para o consumo animal por possuir proteínas tóxicas (ricina) e alergênicas (albumina 2S). O objetivo deste trabalho foi estudar métodos de desintoxicação e secagem da torta de mamona para que seja possível seu aproveitamento como ração para animais. A caracterização e a composição química, físico-química e física da torta “in natura” foram constituídas pelas análises dos teores de água, óleo, proteína bruta, carboidratos, ricina, pH, acidez titulável, cinzas, fibras, valor calórico e calor específico. A umidade de equilíbrio da torta de mamona foi determinada pelo método estático, em soluções de sais e água destilada, para uma faixa de umidade relativa de 10, 30, 50,70 e 90%, nas temperaturas de 15, 25, 35 e 45°C. As amostras da torta de mamona foram colocadas dentro de recipientes herméticos contendo soluções de sais, em câmara com temperatura controlada, até atingir o equilíbrio. Para o ajuste das isotermas de sorção da torta de mamona foram utilizados os modelos de Halsey, Henderson modificado por Thompson, Oswin e Cavalcanti Mata, e os dados experimentais submetidos a uma análise de regressão não linear, utilizando-se programa computacional Statistica7.0. Exceto o modelo de Oswin, os demais descreveram suficientemente o comportamento das isotermas de umidade de equilíbrio para as umidades relativas e temperaturas estudadas, com valores dos coeficientes de determinação (R2) superiores a 99% e desvios percentuais médios (P) inferiores a 10%. Constatou-se que a umidade de equilíbrio higroscópico é diretamente proporcional à atividade de água e decresce com o aumento de temperatura, para um mesmo valor de atividade de água. O processo de desintoxicação da torta de mamona foi feito à base de hidróxido de cálcio Ca(OH)2, em solução aquosa, nas concentrações de 1, 2, 3, 4 e 5%. A secagem da torta de mamona foi feita nas temperaturas de 50, 60, 70, 80 e 90°C, em um secador de leito fixo, em camadas fina, com ajustes satisfatórios dos modelos matemáticos de Henderson, Page, Midilli e Cavalcanti Mata. A secagem em camada espessa ocorreu nas temperaturas de 50, 70 e 90°C, nas concentrações de 1, 3 e 5% e as xix isotermas ajustadas pelo modelo de Thompson, apresentando coeficiente de determinação superior a 99%. Após tratamento e secagem, foi realizada a quantificação da torta de mamona referente aos parâmetros químicos e físico-químicos, constando-se alterações dos teores de pH e acidez, causadas pelo aumento da concentração; quanto ao teor de ricina, verificou-se que quanto maior a concentração de hidróxido de cálcio presente no tratamento e a temperatura de secagem, maior foi sua remoção, atingindo 0% de ricina na concentração de 5% e temperatura de secagem de 90°C, podendo, portanto, ser utilizada na alimentação de animais. / The castor bean is the main by-product of castor oil production chain, produced from the extraction of oil from its seeds. Around the world, its use has been rife as organic fertilizer, despite its high protein content. The bean is produced in the ratio of approximately 1.2 tons for every ton of oil extracted. The high production of bio-fuel from the seeds of castor lead to an increase in the production of the bean, which, despite its high nutritional value, cannot be used for animal consumption, for possessing toxic protein (ricin) to allergen (2S albumin). The aim of this work was to study methods of detoxification and drying of castor bean to be able to take advantage of it as animal feed. The characterization and chemical, physical-chemical and physical composition of the bean "in nature" were established by analysis of the levels of water, oil, protein, carbs, ricin, pH, nameable acidity, ash, fiber, calories and specific heat. The humidity equilibrium contained in castor bean was determined by the static method, in salt solutions and distilled water to a relative humidity range of 10, 30, 50, 70 and 90% at temperatures of 15, 25, 35 and 45° C. Samples from the castor bean were placed in sealed containers containing salt solutions in a chamber with controlled temperature, until they achieve equilibrium. For adjustment of the sorption isotherms of the castor bean Halsey, Henderson, modified by Thompson, Oswin and Cavalcanti Mata models were used, and experimental data subjected to nonlinear regression analysis using a computer program Statistica7.0. With the exception of the Oswin model, the others sufficiently described the behavior of the humidity equilibrium isotherms for the relative humidity and studied temperatures, with the values of the coefficients of determination (R2) superior to 99% and average percent deviations (P) inferior to 10%. We found that the humidity of hygroscopic equilibrium is directly proportional to the water activity and decreases with the increase of temperature, to the same value for water activity. The detoxification process of the castor bean was made by basic hydrated calcium hydroxide Ca(OH)2 in aqueous solution at concentrations of 1, 2, 3, 4 and 5%. The drying of castor beans was made at temperatures of 50, 60, 70, 80 and 90° C, in a fixed bed dryer, in thin layers, with satisfactory adjustments of the mathematical models of com Henderson, Page, Midilli and Cavalcanti Mata. The thick layered drying xxi occurred in temperatures of 50, 70 and 90°C, in the concentrations of 1, 3 and 5% and the isotherms adjusted by the Thompson model, showing a coefficient of determination superior to 99%. After treatment and drying, the quantification of the castor bean was done, referring to the chemical and physical-chemical parameters, finding alterations in the pH content and acidity, caused by the increase in concentration; as to the ricin content, it was verified that the higher the concentration of calcium hydroxide present in the treatment and the drying temperature, the more it was removed, reaching 0% of ricin in the concentration of 5% and the drying temperature of 90°C, making it edible for animals.