Synytsyna Y. Hydropneumatic system of a medium-sized greenhouse facility

Our country has long been famous for its high-quality agricultural products around the world. Unfortunately, today not every country can boast of such opportunities. The climate conditions are different and not all products can grow there. Greenhouses use mechanical microclimate control, which takes a lot of time to maintain and is economically unprofitable. For large areas, automatic systems are used, which, in turn, do not always cover the entire amount of information. Such systems usually do not operate efficiently and cannot predict the system's performance when various external and internal parameters change. Sudden changes in temperature and humidity have a negative impact on plant cultivation. Modern methods of regulating the microclimate of greenhouse facilities are reduced to the simplest - controlling the flow rate, humidity and temperature of air masses. Therefore, the question arises of creating a universal system for growing agricultural products, namely, effective automation of engineering systems. In this thesis, we have developed an automated mechatronic greenhouse microclimate system. The thesis consists of five chapters, the main content and results of each of which are presented below. The introduction substantiates the relevance of the thesis topic, defines the purpose and objectives of the study, presents the research methods, formulates the scientific novelty and practical value of the results, and presents data on the work's testing. The first section provides an overview of the engineering systems of the greenhouse facility and their design features. A comparative analysis of greenhouses in terms of their overall dimensions, complexity of installation, availability of engineering systems and control systems is carried out. The direction of research is determined, the purpose and objectives of the dissertation are formulated. In the second chapter, the basis for the development of the structure of the mechatronic system of a medium-sized greenhouse object is formed. The general functions of the microclimate system are considered and the requirements for the control system are defined. The structure of the mechatronic system with a greenhouse model is proposed. The schematic diagram of the ventilation and recirculation system is developed, and the air duct system is designed and calculated. The fan is selected, the torque is calculated, and the force to be provided by the pneumatic actuator when closing and opening the damper is determined. The greenhouse heating system was calculated and a heater was selected. A general scheme of actuators for the ventilation, curtaining, heating, and ventilation windows was developed. The system of irrigation and humidification of the greenhouse is calculated. The general structure and computer model of the greenhouse object are proposed. In the third section, the physics of heat and mass transfer processes inside the greenhouse is studied in order to determine the requirements for the model of the control object. The heat and mass transfer processes in a greenhouse based on the balance of air heat flows are theoretically substantiated. The heat losses through the polycarbonate greenhouse envelope are theoretically substantiated and the overall heat transfer coefficient is determined. The equations of heat balance and aerodynamic processes are theoretically determined through the Navier-Stokes equation. The tasks for the computer model are defined. The fourth chapter presents the stages of studying heat and mass transfer processes in a medium-volume greenhouse. A 3-D computer model of the greenhouse was created and the following variables were set for modeling the processes: pressure, temperature, air flow rate, air parameters, and time. The model describes a greenhouse object as a given volume of air bounded by walls, roof, and floor. The temperature inside the closed greenhouse volume should be uniform and stable, independent of the influence of external factors. The greenhouse object was modeled in Ansys and SOLIDWORKS. At the first stage of the study, a series of test experiments were conducted: the process of heat exchange in the greenhouse, the rate of heat exchange and pressure changes, as well as the time of temperature and air velocity stabilization. The second stage was the study of heat exchange between the greenhouse and the environment. The next step was to study the stabilization of the temperature inside the greenhouse under a given weather forecast. The fourth stage was the study of heat transfer through the greenhouse envelope to the environment. The fifth stage of the study was the distribution of water vapor inside the closed volume of the greenhouse. The fifth section presents the general algorithm of the heater control program. The operating mode and the nozzle control program were developed.A comparative calculation of the efficiency of the mechatronic system with proactive control was performed.