The dissertation is dedicated to solving a scientific and applied problem related to increasing the efficiency of the working process in the mixing chamber of a liquid–vapor jet apparatus (LVJA), which operates on the principle of jet thermocompression. The study focuses on profiling the flow path of the mixing chamber and investigating the influence of thermodynamic parameters and characteristics of the active and passive flows on the mixing process.
A comprehensive analysis of modern calculation methodologies for equipment based on two-phase jet devices was conducted to ensure improved efficiency of current heat-mechanical systems incorporating LVJAs. For experimental research, a mathematical model was developed and a calculation methodology for the LVJA with a mixing chamber was improved to enhance the efficiency of systems using such devices and to obtain flow and energy characteristics. The input parameters were based on the range of initial conditions for the working fluid exiting the nozzle of the active flow in the profiled diffuser section, at which the maximum efficiency of flow through the channels is achieved, as well as the initial parameters of the passive flow medium at the mixing chamber inlet.
Chapter 1 presents an analysis of modern methods for calculating two-phase jet devices, revealing that the mixing processes of two-phase flows depend on the physical parameters of the media and the geometric characteristics of the mixing chamber. Among key influencing factors are temperature (370–450 K), relative humidity (30–50%), the composition of the passive flow, pressure, and phase velocity. It was found that during water–steam mixing, condensation phenomena occur, which alter the energy balance of the flow mixture at the apparatus outlet. Effective mass transfer and minimized energy losses are achieved when the chamber length-to-diameter ratio is optimal. Profiling the chamber walls improves flow dynamics, reduces turbulent losses, and stabilizes mixing, while the optimal opening angle significantly enhances ejection efficiency.
The necessity of constructing a new mathematical model that considers the specific nature of active and passive flow mixing in a profiled geometry chamber was substantiated. The numerical modeling was based on a range of real operating parameters that ensure the highest efficiency of the active jet outflow and passive medium entrainment. Critical geometric characteristics were determined, including the chamber configuration, convergence angle, length, and profiling shape.
The results were verified using 3D modeling software, which enabled visualization of flow behavior and parameter variation during chamber operation, as well as identification of optimal conditions for physical experiments.
Chapter 2 presents a numerical study of the effect of mixing chamber geometry using CFD methods based on the developed mathematical model for a profiled mixing chamber. The study analyzed technical and energy characteristics of the LVJA. The influence of chamber geometric parameters revealed several practical patterns valuable for design optimization. Turbulence models (k–ε) and the Euler–Lagrange method were employed to analyze discrete particle motion and condensation processes. Spatial distributions of pressure, velocity, and vapor content were obtained, revealing zones of effective jet formation and intense mass transfer.
Simulation results confirmed the feasibility of using profiled mixing chambers of elliptical, parabolic, hyperbolic, and Vitoshynskyi-form geometries. The parabolic shape proved most effective, providing the highest velocity coefficient values (φ₃ = 0.892–0.943), surpassing those of conical chambers. The steam overproduction ratio (ψ₃ = 1.2–1.8) was broad enough to allow flexible operational tuning. The injection coefficient (u = 0.028–0.036) was higher than for conical chambers but slightly lower than for elliptical ones. Overall, the parabolic chamber exhibited the best performance.
In conclusion, the results of numerical and experimental modeling, along with the techno-economic justification, demonstrate that enhancing the mixing chamber by profiling its geometry is an effective method for improving the performance of liquid–vapor jet apparatuses. Integrating LVJAs into modern thermal energy systems enables significant energy savings, increased exergetic efficiency, and improved economic viability of technological processes, highlighting a strong potential for further development in this field
