Papers by Keyword: Packed Bed

Abstract: The effective thermal conductivity (ETC) of the spherical packed-bed porous media in stagnant fluid case is estimated by modifying the color surface of the porous media as black surface. The Alumina-Cordierite (Al-Co) ceramic balls having average diameter (d) of 5.0 cm is constructed as the porous media and, then, a porosity (f) has 0.398. For development of the porous media as black surface, the Al-Co ceramic balls are painted by black color and then it is composed of 600 °C × 8 hr. The experimental procedure to evaluate the ECT is based on ASTM E1225. A higher temperature (T_H) is investigated in the range of 400 to 800 K at the constant power of 350 W. The ETC of three surfaces of the Al-Co ceramics ball, i.e., original surface (_λorg), combined black-painted and original surface (λ_com) and black surface (λ_blk), are examined. From experiment, it is found that all ETC of three surfaces decrease with increasing T_H. The value of three ETCs are in the range of 6.2 to 27.1 W/(m K). The l_blk gives highest for the present research and, exactly, the worst case is obtained by λ_org. Thus, the ETC of spherical packed-bed porous media with stagnant fluid can be improved by developing the color surface as black color.

Abstract: A novel vacuum cleaner was designed and tested. The testing results showed that the PM2.5 of new cleaner was130μg/m³, compared to the traditional one was 440μg/m³ when they were working in a same condition. After being used 4 months, the resistance of the new cleaner remained about 50Pa, while the traditional one was more than 200Pa. The filters replacement cycle of the novel cleaner was changed from 3 times a year to 1 time a year. The relative humidity and temperature were improved from 21% and 18^oC to 25^oC and 45% in the winter respectively. The amount of average bacterial content was changed from 3560 cfu/m³ to 1790 cfu/m³ in a closed ward of a hospital.

Abstract: The correlation of an effective thermal conductivity (k_eff) on spherical packed bed porous media with stagnant fluid was proposed. Alumina-Cordierite ceramic ball (Al-Co) having average diameter (d) of 2.1 cm and porosity (Φ) of 0.468 was examined. The experimental procedure was operated based on ASTM E1225. The tested porous sample was sandwiched by references materials (Solid Brass, 70%Cu, 30%Zn). A higher temperature (T_H) on the top of test set was obtained from wire heater with a constant electrical power of 350 W. The water cooling set was installed at the bottom of to generate a lower temperature (T_L). Four previous models established from geometrical structure were compared to validate the present correlation. From experiment, it was found that k_eff decreased with increasing T_H. Thus, the relation between k_eff and T_H was appropriately proposed by a correlating linear-equation (k_eff/k_f = 329.2(1-0.1028(T_H/100)). Agreement between the present correlation and literature models was satisfied particular.

Abstract: In this report, the modeling and simulation of a double pass solar air absorber was carried out using combination of Simscape and Simulink modeling tools. The solar system air mass flow rate and the porous media were critically investigated by using local weather data of Seri Iskandar, Perak, Malaysia. Optimal inlet air flow rate of 0.034kgm^-2s^-1 was obtained and one of the packed beds, sandstone extended the thermal transfer period of solar collector system by 1150s which displayed good agreement with the reported model and experimental outcomes. The results obtained have shown that it is a promising alternative tool for solar thermal experimentation modeling.

Abstract: Several applications in chemical industry use randomly packed bed of particles, such as particulate separation systems, chemical reactors or fixed bed drying. Fluid dynamic behavior, heat and mass transfer, in addition to structural properties of the bed are fundamental issues to design of these processes. Several studies about heat transfer in packed beds aiming drying application have been performed in order to contribute with the process. Seeds drying temperature is especially important for the seeds quality indices and must be carefully controlled in drying process. In this paper temperature profiles experimentally obtained in a packed bed composed by soybean seeds are presented and discussed. Axial profiles of temperature were applied for obtaining effective thermal conductivity following previous studies from literature. The results indicate that thermal homogeneity can be achieved inside the bed for controlled air flow conditions. Axial effective thermal conductivity presented results in agreement with previous studies from literature.

Abstract: This paper is centred on a compact finite differences method for the calculation of two-dimensional viscous flows through complex geometries. The immersed boundaries are set through body forces that allow for the imposition of boundary conditions that coincide with the computational grid. Two different flow configurations are simulated. First, the flow past a cylinder with square cross-section inside a plane channel is calculated. The computed average drag coefficient and Strouhal number are compared to data available in the literature. The agreement between the results is good. The second flow configuration analyzed is the flow through a porous matrix composed of equal size staggered square cylinders. Flow visualization results are shown. The work presented in this paper illustrates the potential of the immersed boundary method in general and of this implementation in particular to simulate the flow through porous matrices.

Abstract: Packed beds composed of spherical balls are used for the study of transfer processes in porous media at turbulent filtration. The paper summarizes the development of a physical modelling of transfer processes in packed beds. It is shown that the available quantitative measurements of structural characteristics of infiltrated flow in packed beds such as the near-wall zone velocity and temperature profiles and velocity pulsation spectra follow the similarity laws of turbulent separated flows that have been developed by the author and are represented in the first part of the paper. These facts supported by visual observations of flow patterns in packed beds from various authors allow implementing the analogy between transfer processes mechanism in turbulent separated flows and convective transfer processes in near-wall zone of surfaces embedded in grainy layers, or ducts filled with packed bed, at high Reynolds numbers. This approach has resulted in the asymptotic heat and mass transfer law. The universal character of the heat and mass transfer law for the surfaces embedded in grainy layer is confirmed by the authors data and data from many other studies.

Abstract: According to the assumption of local thermal non-equilibrium and the heat transfer controlled regime, a mathematical model describing the coupling between the heat and mass transfer processes in a porous packed bed with endothermic chemical reactions was established and solved by the alternate dimension implicit method. The calculated results showed that, the profiles of the temperature distributions of the two phases and the solid conversion ratio all decay near the radial boundary wall corresponding to the momentum boundary layer. However, the concentration of the product gas increases near the wall owing to the slower speed layer. The temperatures difference between the gas flow and solid pellets can not be ignored during the study of ore decomposition in the porous packed bed. The reaction features of the packed bed with endothermic reactions under different conditions can be analyzed by the established model.

Abstract: Through the experiment on a special designed packed bed, the performances of dehumidification on this packed bed are present in this paper. By testing 3 positions inside the bed, the results are following. During the regeneration process, the average desorption rate of the tail position in this bed is 10.6 g/kg per second, which is respectively 1.93 times that of the fore position and 2.23 times that of the middle position. And for the inlet air of 23 oC, 90% and 1500m3/h, in the stable adsorption process, the adsorbent dehumidification rate of the tail position is 9.51 g/kg per second, which is respectively 2.87 times that of the fore position and 3.51 times that of the middle position. The tail position of the bed holds the best performance both in the regeneration and the adsorption.