Simulation of thermal processes in greenhouse

Abstract

Maintaining a greenhouse efficiency throughout the year is an important task for greenhouse economy. One of the main problems in this area is the maintenance of optimal growing and fruiting conditions of crops, in particular, the maintenance of optimal temperatures, regardless of external conditions. The distribution of temperatures inside a greenhouse depends on many factors, including: a design of a greenhouse, its geographical location, a type and capacity of equipment used for heating, its placement inside greenhouses. The presence of a wide range of factors complicates the accurate thermal calculation of a greenhouse and opens up opportunities for computer modelling of thermal processes using modern physical modelling devices. The purpose of modelling thermal processes occurring in a greenhouse is to identify advantages and disadvantages of selected methods of heating a greenhouse in winter, as well as to obtain a model, changing input parameters of which will show the distribution of temperature fields inside a greenhouse. To maintain the temperature in the greenhouse in winter, cable heating systems, air heaters, heat generators, and infrared panels are used. The cable heating system and air heaters were selected for comparative analysis in the framework of this study. The design of the greenhouse and its shape were chosen in accordance with the models of greenhouses used today. Using the Comsol package blocks "Heat Transfer", "Laminar Flow", "Surface-to-Surface Radiation", a wide set of thermal processes was described, the necessary parameters of which were interconnected using "Multiphysics" interface. With the help of "Events" block, a mechanism of maintaining the set temperature was implemented. The main physical and geometric parameters of the objects under study were also introduced. The analysis was carried out for a dynamic mode of the system. As a result of the simulation, thermal fields and air flow directions were obtained for each time interval of the model under study. Based on the data obtained, the analysis was carried out, and graphs of temperature changes for selected objects were constructed. Conclusions are drawn about the influence of a number of factors on energy efficiency of a greenhouse and considered methods of heating. Ways to optimize the operation of greenhouse heating are proposed. The resulting model can be used for further research of unaffected methods of heating and increasing energy efficiency of a greenhouse.