Analysis of the Possibility of Using R718 for A Heat Pump of A Heating System Based on A Liquid-vapor Ejector

The study explores the possibility of using water (R718) as a refrigerant for a heat pump installation of a heating system. This unit is a vapor compression heat pump with a regenerative heat exchanger in which the vacuum unit based on a liquid-vapor ejector is used instead of a scroll refrigeration compressor. The working process of such an apparatus is based on implementing a fundamentally new cycle that does not require the supply of working steam from the outside. Instead, steam is generated inside the vacuum unit. The article describes the proposed installation and its differences from the traditional one, both in terms of circuit solutions and in terms of the operating cycle. A thermodynamic calculation was performed for the proposed installation with R718 as the working medium and the traditional heat pump systems operating on refrigerants R142b, R254fa, and R410a. As a result of the calculation, the parameters of all the devices included in these schemes were obtained, and the conversion factors of the cycles were determined. To assess the feasibility of using R718 as a working substance and replacing the scroll refrigeration compressor with a liquid-vapor ejector, an exergy analysis was performed. This made it possible to fairly accurately determine the effectiveness of each circuit, since it implemented the possibility of comparing systems using several types of energy (for example, electrical and thermal). As a result, the values of exergetic efficiency of traditional and proposed schemes were obtained. The final stage of the study was the performance of a thermoeconomic analysis. The estimated cost was determined for a unit of heat quantity per ton of the product and per unit of the heated area obtained in a unit with the working substance R718 and traditional installations with the working substances R142b, R254fa, and R410

Improvement of Cavitation Erosion Characteristics of the Centrifugal Inducer Stage with the Inducer Bush

The impact of the inducer bush, which is a stator bush with longitudinal straight grooves installed over the inducer in the model centrifugal stage on its performance, was studied. A physical experiment was performed with the use of the experimental design techniques to solve the problem of geometrical parameter optimization of the stator bush with longitudinal straight grooves in the multi-factorial problem regarding the improvement of cavitation erosion characteristics of the centrifugal inducer stage using the inducer bush. The frequency spectrum of excited oscillations of the studied centrifugal inducer stage caused by cavitation was determined in order to use the cavitation erosion resistance parameter as an optimization parameter. The optimal dimensions of the inducer bush of the studied centrifugal inducer stage were experimentally determined: Z=32, b=14, l1=20, and l2=20. This data allowed us to improve the cavitation erosion resistance of the centrifugal inducer stage without changing its overall dimensions and deteriorating head and power characteristics. An additional physical experiment was performed using an alternative method for determining the cavitation and erosion characteristics in order to confirm the results obtained in the study due to inducer bushes installed in the centrifugal inducer stage. The use of inducer bushes as a part of the centrifugal inducer stage was mainly intended to improve the centrifugal stage cavitation performance. This study proposes to use this part to overcome the negative effects of cavitation erosion. The possibility of such use was confirmed and research and methodological design recommendations for inducer bushes as part of the centrifugal inducer stage were developed. The installation of the improved first centrifugal stages with inducer bushes in the existing centrifugal pumps will increase the operating time to failure, which is relevant for all industries where centrifugal pumps are used

Удосконалення вакуумної системи охолодження установки виробництва біодизельного палива

У статті вирішено актуальну проблему підвищення ефективності вакуумних систем охолодження установок виробництва біодизельного палива шляхом застосування вакуумних агрегатів на базі рідинно-парового ежектора, що працює за принципом струминної термокомпресії. Метою даного дослідження є підтвердження доцільності застосування вакуумних агрегатів на базі рідинно-парового ежектора, що працює за принципом струминної термокомпресії, у вакуумних системах охолодження установок виробництва біодизельного палива. Подано опис базової схеми системи охолодження установки виробництва біодизельного палива, яка містить трьохступеневий пароструминний ежектор. Запропоновану схему на базі рідинно-парового ежектора. Виконано порівняльний аналіз вакуумних систем охолодження установок виробництва біодизельного палива, схеми яких порівнювались, у тому числі на базі існуючих триступеневих пароструминних ежекторів і нового одноступеневого вакуумного агрегату на базі рідиннопарового ежектора. Як порівняльний аналіз застосовано ексергетичний метод оцінювання ефективності застосування запропонованого устаткування, оскільки у робочому процесі відбувається перетворення двох видів енергії: електричної (для приводу насоса) і теплової (для підігріву робочої рідини активного потоку у теплообміннику-підігрівачі). У результаті досягнуті більші показники ефективності застосування нової технології за оптимізаційним параметром – проміжним тиском між рідинно-паровим ежектором та рідиннокільцевим вакуумним насосом.The article deals with the actual problem of improving the vacuum cooling efficiency systems during the biodiesel production by using vacuum devices account for the liquid-vapor ejector, which operates on the principle of jet thermal compression. The purpose of this study is the feasibility of using vacuum devices, that based on the liquid-vapor ejector, and takes as a basis the principle of jet thermal compression in vacuum cooling systems of biodiesel production units. This article describes the basic scheme of the cooling system devices during the biodiesel production, which includes a three-stage steam-jet ejector and the proposed scheme based on the liquid-vapor ejector. A comparative analysis of the vacuum cooling systems during biodiesel production units was realized, where the schemes were compared on the basis of existent three-stage steam-jet ejectors and a new single-stage vacuum unit based on a liquid-vapor ejector. An exergy method of assessing the effectiveness of the proposed equipment was used as a comparison, because in the working process there is a transformation of two energy types: electric for the pump drive and heat for heating the working fluid of the active flow in the exchanger-heater. The intermediate pressure between the liquid-vapor ejector and the liquid-ring vacuum pump can help to achieve the highest characteristics of the new technology on the optimization parameters