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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
11

Estudo das isotermas de adsorção do bagaço de mandioca proveniente da indústria de fécula / Study of the adsorption isotherms of cassava bagasse from the starch industry

Betiol, Lilian Fachin Leonardo [UNESP] 21 November 2016 (has links)
Submitted by LILIAN FACHIN LEONARDO BETIOL null (lilianfacleo@hotmail.com) on 2016-12-04T18:12:23Z No. of bitstreams: 1 Tese - Formatada (1) Corrigida.pdf: 1975637 bytes, checksum: a2ca74a2f726452b217e860e0c11c866 (MD5) / Approved for entry into archive by Felipe Augusto Arakaki (arakaki@reitoria.unesp.br) on 2016-12-06T13:52:01Z (GMT) No. of bitstreams: 1 betiol_lfl_me_sjrp.pdf: 1975637 bytes, checksum: a2ca74a2f726452b217e860e0c11c866 (MD5) / Made available in DSpace on 2016-12-06T13:52:01Z (GMT). No. of bitstreams: 1 betiol_lfl_me_sjrp.pdf: 1975637 bytes, checksum: a2ca74a2f726452b217e860e0c11c866 (MD5) Previous issue date: 2016-11-21 / As isotermas de sorção tornaram-se importantes para prever o comportamento da cinética de secagem e as condições de armazenamento de resíduos da indústria alimentícia. O conhecimento de tal propriedade é útil para projetar equipamentos ou operações para fins de armazenamento ou processamento. O bagaço quando é apenas descartado, representa um desperdício de matéria prima, de compostos orgânicos com categoria bioquímica definida (proteínas, açúcares, ceras, graxas, resinas), que poderia ser aproveitada. Dentro deste contexto, a presente pesquisa teve como objetivo caracterizar quimicamente o bagaço de mandioca e fazer a determinação experimental das isotermas de sorção destes resíduos da indústria de fécula, além de calcular a entalpia e entropia, temperatura media harmônica e calor isostérico de adsorção. Para isso, o teor de umidade de equilíbrio nas isotermas de sorção, de bagaço de mandioca, foi determinado utilizando o método gravimétrico estático nas temperaturas de 20 a 80 °C. Modelos teóricos e empíricos foram usados para representar os valores experimentais das isotermas de sorção, sendo que o modelo de GAB foi o que apresentou os melhores ajustes. Utilizando o modelo de GAB foi possível determinar o calor isostérico de adsorção como função do teor de umidade. A teoria da compensação foi confirmada pela relação linear entre entalpia e entropia. Maiores valores de temperatura isocinética do que a temperatura harmônica reforçam a teoria da compensação e sugeriram que a adsorção de água pelo bagaço de mandioca é considerado um processo conduzido pela entalpia. / The sorption isotherms become important to predict the drying kinetics behavior and waste storage conditions of the food industry. The knowledge of such property is useful for designing equipment or operations for storage or processing. The bagasse is only when discarded, is a waste of raw materials, organic compounds with defined biochemical category (proteins, sugars, waxes, greases, resins), which could be harnessed. Within this context, this study aimed to chemically characterize the Cassava Bagasse and make the experimental determination of the sorption isotherms of these starch industry waste and calculates the enthalpy and entropy, harmonic average temperature and isosteric heat of adsorption. For this, the equilibrium moisture content in the sorption isotherms of cassava bagasse was determined using the gravimetric static method in temperatures 20-80 ° C. Theoretical and empirical models were used to represent the experimental values of sorption isotherms, and the GAB model was the one that presented the best fit. Using the GAB model was possible to determine the isosteric heat of adsorption and moisture content of the function. The theory of compensation was confirmed by the linear relationship between enthalpy and entropy. Isokinetic higher temperature values than the harmonic temperature reinforce the theory of compensation and suggested that the adsorption of water by mancioca bagasse and considered one of enthalpy driven process.
12

Tepelně-vlhkostní analýza konstrukcí masivních dřevostaveb / Hygrothermal analysis of massive wooden structures

Uherka, Pavel January 2016 (has links)
This thesis deals with massive wooden buildings especially with regard to the current approach to their design, assessment and approval. In this thesis are shown future possibilities of development of traditional wooden buildings with regard to current thermal technical requirements. Theoretical considerations are then compared with measurements which were performed on massive wooden wall samples.
13

Soil water movement through swelling soils

Ekanayake, Jagath C. January 1990 (has links)
The present work is a contribution to description and understanding of the distribution and movement of water in swelling soils. In order to investigate the moisture distribution in swelling soils a detailed knowledge of volume change properties, flow characteristics and total potential of water in the soil is essential. Therefore, a possible volume change mechanism is first described by dividing the swelling soils into four categories and volume change of a swelling soil is measured under different overburden pressures. The measured and calculated (from volume change data) overburden potential components are used to check the validity of the derivation of a load factor, ∝. Moisture diffusivity in swelling soil under different overburden pressures is measured using Gardner's (1956) outflow method. Behaviour of equilibrium moisture profiles in swelling soils is theoretically explained, solving the differential equation by considering the physical variation of individual soil properties with moisture content and overburden pressure. Using the measured volume change data and moisture potentials under various overburden pressures, the behaviour of possible moisture profiles are described at equilibrium and under steady vertical flows in swelling soils. It is shown that high overburden pressures lead to soil water behaviour quite different from any previously reported.
14

Capillary pore-size distribution and equilibrium moisture content of wood determined by means of pressure plate technique

Zauer, Mario, Meissner, Frank, Plagge, Rudolf, Wagenführ, André 23 June 2020 (has links)
This paper deals with the determination of the capillary pore-size distribution (CPSD) and equilibrium moisture content (EMC) of untreated and thermally modified (TM) Norway spruce [Picea abies (L.) Karst.] by means of the pressure plate technique (PPT). Desorption experiments were conducted at very high values of relative humidity (RH) in the range between 99.2% and 100%. The thermal modification of spruce results in an alteration of the CPSD, owing to the formation of intercellular cracks in the middle lamella, as a result of cell-wall compression. The desorption curves for both untreated and TM spruce show an extremely upward bend at 99.97% RH. This step reflects an EMC of 38.1% for untreated spruce and 33.8% for TM spruce. None of the samples shrunk during the PPT measurements. Following desorption experiments at 97.4% RH, all samples shrunk. This step reflects an EMC of 27.9% for untreated spruce and 21.7% for TM spruce.
15

Teplotně-vlhkostní posouzení prvků krovu s nadkrokevním systémem zateplení / Temperature-moisture Assessment of Members in Truss with Above-rafter Thermal Insulation

Soudek, Pavel January 2014 (has links)
This thesis deals with the temperature-moisture assessment of members in truss with above-rafter thermal insulation. Within this system it focuses on the details of creating a roof overhang because that is where the timber elements are under the greatest amount of moisture stress. Different variations of this detail are presented including the extent to which thermo-technical requirements and requirements surrounding the built-in timber elements are satisfied. Theoretical calculations are then compared with measurements which were performed on a real building. This task of measurement involved developing a new measuring device. The development of this device is also described in this paper.

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