A Critical Review on Thermo-Hydraulic Performance of Wire Screen Matrix Packed Solar Air Heaters

Solar air heaters (SAHs) have an important role in applications such as space heating and industrial drying worldwide. The packing of SAH bed not only increases the heat transfer area but also increases the pumping power losses thereby limiting the thermo-hydraulic performance. In the present study, efforts have been made for a critical assessment of the literature dealing with the impact of collector bed and operating parameters over thermal and thermo-hydraulic performance for different configurations of wire screen matrix packed SAH. The porosity of bed and mass flow rate of the air have a major influence on the thermo-hydraulic performance of wire screen matrix packed SAH. It is found that the enhancement in the volumetric heat transfer coefficient due to a decrease in bed porosity is obtained at the expense of increase in pumping power which ultimately affects the thermo-hydraulic performance of wire screen matrix packed SAH. In general it is observed that porosity is an important parameter that affects the thermo-hydraulic performance. It is seen that matrix having porosity 0.937 yields thermo-hydraulic performance of 68% at mass flow rate 0.023 kg/s where as for the same mass flow rate porosity of 0.887 results thermo-hydraulic performance of only 42%.

Numerical Study of a Solar-Powered Stirling Engine With a Transparent Top Cover

The present work is focused on the numerical study of a solar-powered Stirling engine, with the particularity that the solar radiation is injected through a transparent top cover. Thus, the working fluid absorbs the heat across a porous layer of a steel woven wire screen placed alongside the inner side of the transparent wall. The engine output net power and efficiency are studied as a function of the porosity, engine speed, temperature of the expansion chamber, and wire diameter of the screen. It is found that the engine efficiency remains practically constant for porosity values over 0.7, but there is a relevant increase of the engine output net power compared to the same working conditions without the absorbing layer. For a given porosity value, the most significant increase of net power due to introducing the porous layer was reached when doubling the engine speed resulting in an increment close to 40%.

Design and computer simulation of automatically controlled hydromechanical system for looped wedge wire screen elements fabrication

The article presents a design of mechatronic system used for the production of wire elements used in looped wedge wire screen manufacturing. Details related to the design of the hydromechanical subsystem, the control subsystem, as well as the simulation of the operation process of the entire system are presented

OPTIMIZATION OF DESIGN PARAMETERS OF HOPPER DEVICE

Based on previous theoretical studies, the main design parameters of the device were established, such as angle of installation of wire screens, the number of wire screens in hopper, the location of wire screens in hopper, and the minimum size of the gap and bridge in wire screens. It is established that in order to determine the optimal width of the gap in the wire screen, it is necessary to know the height of bulk material layer passing through the gap of the hopper device element and speed of bulk material on the second bridge. To ensure optimal operation of the element (wire screen) of the device for controlling technological process of loading, storage and unloading, it is necessary that loaded material passes evenly through the wire screen that is throughput capacity of each slot of the device is the same. The obtained equations allow us to determine the minimum gap width depending on the radius of bulk material particle, falling speed of the material on the screen, coefficient of friction and width of crossbar of the screen. For experimental research, a laboratory model of a bunker-type device was created and tested. The model allows you to quickly change parameters such as the angle of inclination of wire screen, gap width in the wire screen, the length of the wire screen, the distance between the wire screens and the height of the loaded layer. At the same time, it was found that the loading process is influenced by the coefficients of uniformity of distribution of bulk material over the entire cross-section of container, as well as the coefficient of material segregation when filling the loading device. The method of conducting experiments included determining the parameters of developed hopper device: the angle of inclination of the wire screen, the length of the wire screen, gap width in the screen and the interval between the sieves. The initial levels were selected based on analysis of previous studies of the bulk material loading process. The results of these studies identified the optimal values of main parameters of the developed device depending on the downloadable material: the angle of inclination of wire screen - 36...38°; length of wire screen...0,19 0,28 m; the distance between screens - 2,3...2,8 m. The obtained numerical values of parameters can be used in the design of bunkers or silos for similar purposes.

Improving the Energy Balance of Hydrocarbon Production Using an Inclined Solid–Liquid Separator with a Wedge-Wire Screen and Easy Hydrocarbon Recovery from Botryococcus braunii

The green colonial microalga Botryococcus braunii produces large amounts of hydrocarbons and has attracted attention as a potential source of biofuel. When this freshwater microalga is cultured in a brackish medium, the hydrocarbon recovery rate increases; furthermore, the colony size becomes large. In this study, the effects of such changes on the energy balance of harvesting and hydrocarbon recovery were studied via filtrate experiments on an inclined separator and extraction from a concentrated slurry. The inclined separator was effective for harvesting large-colony-forming algae. The water content on the wire screen of slit sizes larger than 150 µm was <80% and a separation rate of >85% could be achieved. The input energy of the harvesting using the brackish medium with this separator was ≈44% of that using the freshwater medium with vacuum filtration, while the input energy of the hydrocarbon recovery using the brackish medium was ≈88% of that using the freshwater medium with pre-heating before n-hexane extraction. Furthermore, the energy profit ratio of the process in the brackish medium was 2.92, which was ≈1.2 times higher than that in the freshwater medium. This study demonstrated that filtration techniques and hydrocarbon recovery from B. braunii with a low energy input through culture in a brackish medium are viable.

Electrical Material Properties of Carbon Reinforced Concrete

Carbon fiber reinforced concrete is poised to be the building material of the future. We present a study to quantify the influence of this novel reinforcement material on RF propagation in the range from 0.4 to 67 GHz. The measured attenuation effects of the reinforcement material are explained and quantified using a metallic wire screen model. It can be used to as a simple model of the material’s influence in radio propagation scenarios. For reference and completeness, data on the complex dielectric permittivity of the investigated concrete brand is also included. The production process of the concrete samples used for the measurements is documented, facilitating comparability and reproducibility. Finally, implications for current and future radio communication applications are outlined.

Numerical Investigation of Two-Phase Flow Over Unglazed Plate Collector Covered With Porous Material of Wire Screen for Solar Water Heater Application

This paper presents three-dimensional numerical simulation results of the effect of surface tension on two-phase flow over unglazed collector covered with a wire screen. The homogenous model is used to simulate the flow with and without the effect of porous material of wire screen and surface tension. The Eulerian-Eulerian multiphase flow approach was used in this study. The phases are completely stratified, the interphase is well defined (free surface flow), and interphase transfer rate is very large. The liquid–solid interface, gas–liquid interface, and the volume fraction for both phases were considered as boundaries for this model. The results show that the use of porous material of wire screen will reduce the velocity of water flow and help the water flow to distribute evenly over unglazed plate collector. The possibility of forming any hot spot region on the surface was reduced. The water velocity with the effect of surface tension was found higher than the one without this effect, due to the extra momentum source added by surface tension in longitudinal direction. The use of porous material of wires assures an evenly distribution flow velocity over the inclined plate, therefore helps a net enhancement of heat transfer mechanism for unglazed solar water collector application.