Numerical Analysis And Experimental Research Of Heated Glass Greenhouse Thermal Environment In Winter

Crop yeild and growth cycle can be adjusted by the greenhouse control system. In recent years, some glass greenhouses, especially multi-span glass greenhouses, have been introduced to China from the foreign, but their high energy consumption, especially in winter, leading to make a loss for many greenhouses or even be demolished, which has become an obstacle to the development of facility agricultural. To solve the problem, the thermal distribution in the greenhouse must be predicted and mastered. But the traditional research methods, such as greenhouse model experiment and physical model simulation, can not fundamentally solve the above problems because of their limitations. In recent years, with the improvement of computer technology and performance, Computational Fluid Dynamics(CFD) is a new powerful tool for studying greenhouse environment, this paper selected an intelligent Venlo-type glass greenhouse in the campus of Zhejiang University of Technology for the research object, three-dimensional turbulent flow CFD model of thermal environment of the greenhouse with crop model based on the aerodynamics and thermodynamics principle was built, and meanwhile the corresponding boundary conditions with the practical situation were tested and defined, then the results verify that the built CFD model is effective and the simulation method about temperature and airflow filed in the greenhouse by CFD technology is feasible by comparing with Fluent simulation and experimental values; the thermal environment of different greenhouse structures were simulated by different three-dimensional CFD models based on the above effective model and boundary conditions to optimize its structure parameters, then the greenhouse prediction model for energy consumption was built to predict the different greenhouse energy consumption, which can have an important and practical significance in improving the crop environment in greenhouses, supplying the theoretical base for greenhouse low-cost and optimum design and environmental energy-saving control of Venlo-type greenhouses in subtropical climate in China. The main work and innovations of this paper are as follows:1. A greenhouse environmental physical model was built, and the mapping relation of physical model and CFD model was analyzed, then the optimal method of greenhouse parameters based on the three-dimensional CFD digital and complex field model was present with three-dimensional CFD transient model technology.2. According to internal flow filed and boundary characteristics of Venlo-type glass greenhouse, three-dimensional transient and digital field model with the crop under the condition of hot-blast heating using the model mapping, porous medium and the improvement technology of momentum and energy equations was built and experimental study was conducted.3. A CFD optimization model was built on the hot-blast heating system with multiphase flow analysis, and simulating and analyzing the corresponding thermal environmental distribution.4. For the Venlo-type intelligent glass greenhouse, an energy consumption prediction model was built based on energy balance.5. Finally, to sum up the paper and further study in the future is offered.