Identification of moisture transport mechanism in gypsum during convective drying

[EN] Gypsum is a popular building material. Drying and rewetting of gypsum is a process of practical importance. This work presents the experimental results of kinetic of drying, heating and internal pressure development in rewetted gypsum cylinders. Analysis of the observed changes is presented. Additionally sorption isotherms, permeability and dependence of Young’s modulus on moisture content were measured. These data will be used in the model of the process under development.Adamski, R.; Adamska, A.; Pakowski, Z. (2018). Identification of moisture transport mechanism in gypsum during convective drying. En IDS 2018. 21st International Drying Symposium Proceedings. Editorial Universitat Politècnica de València. 379-386. https://doi.org/10.4995/IDS2018.2018.7527OCS37938

Effective diffusivity of moisture in low rank coal during superheated steam drying at atmospheric pressure

The effective diffusivity of water in brown coal of Bełchatów mine was experimentally determined. The experiments were performed in superheated steam at 200 [degrees]C and atmospheric pressure using slightly compressed pellets of cylindrical shape. The drying and temperature curves of the sample were used to identify diffusivity. An inverse problem was formulated and solved by the finite element method for 3D axially symmetric cylindrical geometry of the sample. A satisfactory fit of the simulated curves to experimental results was obtained. The obtained dependence of effective diffusivity on moisture content and temperature may be used in designing lignite dryers

Measurement of drag coefficient and sphericity of floc particles

W literaturze brak informacji nt. współczynnika oporu cząstek typu flok. W tej pracy zmierzono współczynnik oporu metodą stanu nieustalonego i metodą stanu ustalonego oraz porównano wyniki obu metod. Na podstawie współczynnika oporu zidentyfikowano sferyczność w oparciu o równanie Haidera, Levenspiela. Stwierdzono, że zastosowanie teorii przepuszczalności Brinkmana daje lepszy opis współczynnika oporu dla cząstek typu flok.Drag coefficient of floe type particles is poorly described in literature. In this work drag coefficient was measured by two methods - unsteady state and steady state and the results were compared. On basis of drag coefficient the particle sphericity was identified using the Haider and Levenspiel formula. It was found that a better description of drag coefficient for floe particles was obtained using Brinkman's theory of permeability

Model of dynamic structure with coaxiality errors changing in time

W pracy przedstawiono wyniki modelowych badań wpływu charakterystyk sprzęgieł podatnych na odpowiedź dynamiczną układu w warunkach zmiennych w czasie błędów osiowania.In article results of a model research of influence of flexible coupling characteristics on the system dynamic response under conditions of coaxiality errors changing in time were shown

Selection of Sound Insulating Elements in Hydraulic Excavators Based Onidentification of Vibroacoustic Energy Propagation Paths

In spite of the fact that standardizing operations and increased awareness of hazards led to a significant improvement of vibroacoustic climate of operator’s stands of new machines, their long-term operation - often under difficult conditions - leads to a fast degradation of acoustic qualities of machines. Temporary operations performed during surveys and periodical overhauls are rarely effective, due to the lack of any guidelines. In this situation the authors propose the algorithm for selection of eventual screens or sound absorbing and sound insulating partitions, utilizing the measuring procedure aimed at identification, at the operator’s stand, of main noise components originated from various sources. On the basis of this procedure, the vibroacoustic energy propagation paths in the machine was estimated

Identyfikacja dynamicznego współczynnika przepuszczalności wody dla hydrożelu krzemionkowego

A novel method for the determination of liquid Darcy permeability in saturated porous solids shrinking during drying is presented in the paper. The experimental data were obtained during convective drying of silica hydrogel at 30°C and 40°C. The collected data allowed for the calculation of apparent sample density and thus the space occupied by liquid phase. The Darcy permeability was identified using a simple model. The values obtained were in a range of 2.5·10-16·14 ÷ 4.5·10-14 m2, depending on the current voidage. The pore size diminishes due to the shrinkage and the permeability decreases with drying progress.Przedstawiono nową metodę wyznaczania przepuszczalności cieczy z wykorzystaniem prawa Darcy'ego w nasyconych ciałach stałych, kurczących się podczas suszenia. Dane doświadczalne uzyskano poprzez konwekcyjne suszenie hydrożelu krzemionkowego w temperaturze 30°C oraz 40°C. Na podstawie zebranych danych obliczono gęstość pozorną próbek i przestrzeń zajętą przez ciecz. Współczynnik przepuszczalności Darcy’ego zidentyfikowano korzystając z prostego modelu. Otrzymane wartości mieściły się w zakresie od 2.5·10-16·14 ÷ 4.5·10-14 m2 w zależności od wielkości porów. Wraz z postępem suszenia zmniejsza się wielkość porów w wyniku skurczu, a przepuszczalność maleje