Study on flow resistance characteristics of SiC foam ceramics

Porous media combustion has significant advantages of high thermal efficiency and low pollution emissions. However, the flow state in the porous media will affect the reaction rate. In order to increase the rate of chemical reactions, the fluid flow resistance in the porous media must be reduced. The pressure drop test of SiC foam ceramics was carried out. By changing the pore density of the experimental materials, the pressure drop characteristics of SiC foam ceramic are tested and analyzed. Based on the classical Ergun equation, a semi-empirical formula for calculating the pressure drop gradient of SiC foam ceramics with the airflow velocity is proposed. The two constants in the formula are calculated by measurement, and the applicability of the formula is verified. This formula can quickly analyze the pressure drop characteristics of SiC foam ceramic materials. The accurate measurement of pressure drop is helpful to determine the rated pressure of the head of foam ceramic burner and reduce the investment of front-end fans in industrial burners.

Front-end Solar Temperature And Humidity Control System

Solid dehumidification is one of the important components of the dehumidification air-conditioning system. As an important method of solid dehumidification, the dehumidification performance and regeneration performance of fixed-bed dehumidification have an important impact on the operation and energy saving of the dehumidification air-conditioning system. In view of the high air temperature and high humidity in South China, our design organically combines dehumidification fixed beds, semiconductor refrigeration devices, foam ceramic insulation panels and double-glazed windows. We have designed a photovoltaic-driven modular solar temperature regulating and dehumidifying purification wall suitable for building dehumidification. The dehumidification window can use daytime solar radiation to regenerate the dehumidification fixed bed after absorbing moisture, reducing the energy consumption of regeneration. At the same time, the design can also use semiconductor refrigeration devices to adjust the temperature and humidity of the window inlet air to improve the window's dehumidification and regeneration performance. We tested and studied the dehumidification and regeneration performance of the device under different working conditions through experimental tests, which provided a basis for the engineering application and theoretical analysis of the device.

Physical modeling of filtration processes of heat-resistant nickel alloys during casting in a vacuum induction installation

The article considers issues related to the efficiency of metal melts’ filtration depending on the size of non-metallic inclusions, parameters of ceramic foam filters and their location options. Studies of influence of the main structural elements on the filtration processes of nickel melts during casting in a vacuum induction installation were carried out on low-temperature physical models. Modeling of melt filtration processes is based on the hydrodynamic similarity of the processes of motion of melt flows and nonmetallic inclusions in casting tanks. A modeling technique has been developed, the scale has been determined and a model installation has been made. Influence of the arrangement of filtration and dividing walls on the dynamics of metal flows, non-metallic inclusions and filtration efficiency is considered. The efficiency of nickel melts filtration is described depending on the technical parameters both on the filter itself (effective filtration surface, filter thickness, channel dimensions, number of channels per unit area), as well as on the type and size of non-metallic inclusions, design features of the casting device and filter layouts. It was found that the overall filtration efficiency is influenced by the rate and uniformity of the melt flows’ distribution in front of the filter. To ensure uniform distribution of the melt flow rates, a dividing wall with bypass holes is installed in front of the filter, the location of which and their number was also the subject of research. As a result of the studies, the relationships were established between the filtration efficiency, the size and type of non-metallic inclusions when using vertical and horizontal foam ceramic filters during the casting of nickel melts in an intermediate casting tank of a vacuum induction installation. It was found that with a vertical arrangement of the filter, its efficiency is higher than with a horizontal one. An additional means of increasing efficiency of the filtration system is the use of a dividing wall. The optimal number of holes and the location of the baffle in the casting tank were determined, ensuring a uniform distribution of melt flows along the height in front of the filter and an increase in its operation time.