• Energy Research

The problem of increasing the efficiency of individual heating systems is solved by using heat pumps based on a liquid-vapor ejector with the working fluid R718 (water). The research object was the working process of the liquid-vapor ejector, based on the principle of jet thermal compression. It involves the generation of vapor in the nozzle of the motive flow of the liquid-vapor ejector and does not require its supply from an external source. Schemes and descriptions of the traditional system and the proposed scheme were given. Their difference from the traditional ones was indicated according to the schematic solution and working cycle. The article compared the proposed schemes’ thermodynamic calculation with the working flow R718 and traditional heat pump systems with carried-out refrigerants R134a, R410a, and R32. As a result, the values of the thermodynamic parameters of all system components were obtained. The coefficients of performance (COP) for the traditional and proposed cycles were determined. Applying the new scheme made it possible to increase the COP by an average of 40 %. An exergy analysis assessed the expediency of implementing vacuum units based on liquid-vapor ejectors in individual heating systems. This made it possible to compare systems that use several types of energy (e.g., electrical, thermal) and to determine their efficiency with high accuracy. As a result of the exergy analysis, the value of the proposed scheme’s exergy efficiency was obtained.

The article deals with the theoretical description and experimental study of the hydrodynamic and heat transfer properties regarding the operation of multistage gravitational devices of the fluidized bed with inclined perforated shelves. The peculiarities of the work and the implementation field of the multistage shelf units are described. A theoretical model to define the solubilizer’s velocity above the perforation holes, in the above-shelf space of the device and in the outloading gap, as well as the residence time of the dispersed phase at the stage (perforated shelf contact) of the device is presented. The results of experimental studies regarding the influence, made by the structural parameters of the perforated shelf contacts, on the distribution pattern of single-phase and gas-dispersed flows in the workspace of the device, on the intensity of interphase heat transfer are presented. The conditions to create active hydrodynamic operating modes of multistage gravitational shelf devices, which provide higher efficiency of heat-mass transfer processes, and with lower gas consumption and hydraulic resistance compared to typical fluidized bed devices, are proved. Peculiarities regarding the implementation of heat-mass transfer processes in multistage devices are described using heat treatment and drying processes as examples.

The article solves the problem of heat utilization from combustion products in boiler plants. The proposed solution involves extracting heat to preheat the network water for the heating system and implementing additional heat utilization using a liquid-vapor jet apparatus. This will allow for additional working steam generation in the main steam generator and the unit based on the liquid-vapor jet apparatus. The article provides schemes and descriptions of traditional and proposed plants, indicating their design differences from the basic scheme. Comparative thermodynamic analysis of the proposed installation for additional recuperative heat utilization and the basic scheme is carried out, in which heat utilization occurs due to the extraction of heat from combustion products to preheat the network water of the heating system. As a result, the main thermodynamic parameters of the cycles of basic and proposed schemes are obtained, and the values of the capacities on the apparatuses included in these installations are determined. The energetic potential obtained from additional heat utilization is 8 %, which can be used for electricity generation. Exergy analysis assesses the efficiency of additional heat utilization in boiler plants using units based on liquid-vapor jet apparatus. As a result of the exergy analysis, the value of the exergetic efficiency of the scheme with additional heat utilization was obtained, which is 1.47 times higher than that of the basic scheme. A thermoeconomic analysis was performed to determine the cost values. Implementing the new scheme enables reducing the specific cost of the heating unit by 48 % and increasing the amount of steam generated in the installation by an additional 18 %.

The object of this study is a polydisperse mixture of granular superphosphate. It is emphasized that existing technologies of granulation and processing of granules lead to the formation of dusty fractions of small particles. The content of small fractions in the finished product should be minimal and, in connection with this problem, the task is to remove small particles from the mixture. The purpose of the current experimental study is to classify a polydisperse mixture of granular superphosphate in a pneumatic classifier. The device includes an inclined perforated shelf with an unloading space between its end and the wall of the apparatus. It has been experimentally revealed that the maximum efficiency of extraction into the entrainment of small particles is achieved with a width of the discharge space equal to 0.5 of the length of the cross-sectional side of the apparatus; the degree of perforation of the shelf is 5 %; the angle of inclination of the shelf is 25–30°; the speed of the gas flow in the free section of the apparatus is 3.7 m/s. It is shown that the degree of extraction into the entrainment of a small fraction less than 1 mm in size reaches 70–75 %, the content of the small fraction in the carry-over is 96–98 %, and the large fraction is less than 5 %. By processing experimental data, an empirical equation was built that makes it possible to determine the concentration of particles in the gas stream for individual fractions of the material. It is shown that due to the implementation of an active aerodynamic weighing mode, the shelf pneumatic classifier works at specific loads for air flow rate less than the typical designs of fluidized bed separators. It is noted that the effective operation of the shelf pneumatic classifier in the production of granular mineral fertilizers is ensured at a productivity of no more than 10–12 t/h. With greater productivity, there is a need to install several devices in the technological line