Analysis of the possibility of using R718 for a heat pump of a heating system based on a liquid-vapor ejector

We consider the influence of vapor content in the mixed flow leaving a liquid-vapor ejector on the energy efficiency of a vacuum unit. As shown by numerical studies of liquid-vapor ejectors, this issue is important as vapor overproduction, which accompanies the process of secondary flow ejection, directly impacts the efficiency of the working process of both the liquid-vapor ejector and the vacuum unit as a whole. The greater the degree of vapor overproduction, the greater the load on the vapor phase of the separator, which is part of the vacuum unit. In addition, the liquid phase must be returned to the cycle to ensure the constancy of the mass flow rate of the working fluid of the primary flow. Our numerical study results revealed the rational value of the degree of vapor overproduction at which the efficiency of the liquid–vapor ejector was maximized, and the amount of additional working fluid that needed to enter the cycle of the vacuum unit was minimal. Experimental condition monitoring studies on the liquid–vapor ejector were carried out on plane-parallel transparent models with different flow path geometries. Through experimental studies, we confirmed and adjusted the values of the achievable efficiency of the working process of a liquid–vapor ejector, depending on the degree of vapor overproduction. Using a comparative analysis of liquid–vapor ejectors with different flow path geometries, differences were revealed in their working processes, which consisted of the degree of completion of the mixing of the working media of primary and secondary flows. To determine the feasibility of using liquid–vapor ejectors with different flow path geometries, exergy analysis was performed, resulting in achievable efficiency indicators.

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 article describes the principle of jet thermal compression with reference to vacuum systems. We consider liquid-vapor ejectors, the working process of which is based on this principle, as an alternative to existing steam jet ejectors. The results of a theoretical and experimental investigations of the liquid-vapor ejector of a vacuum unit are presented. With the help of thermodynamic analysis of exergetic efficiency, the range of operation of the liquid-vapor ejector and the vacuum unit on its base is determined, at which its performance is at the maximum level. The efficiency of vacuum creation by such units is estimated by the example of various pumped media, such as saturated, superheated steam and steam-air mixture.