NUMERICAL SIMULATION AND PARAMETERS OPTIMIZATION OF HEATED GLASS GREENHOUSE

Although green house air heaters are often used throughout the southern Yangtze River basin in China, few data exist to indicate the proper placement of warm-air-delivery ducts, the arrangement of their air outlets, and the impact of thermal screens on the heated green houses environment. To better understand these issues, we develop herein a thermal-environment model of a Venlo-type glass green house on a winter night. The model is based on the standard k - epsilon turbulence model, the buoyancy model, and the porous-medium model, and simulations based on this model are done by using commercial computational fluid dynamics software. The results indicate that the thermal distribution at the crop-canopy height significantly impacts crop growth and quality, so we used temperature distribution to evaluate the effect of the various heating parameters. We find that a higher average temperature and a greater temperature difference occur for downward vents than for horizontal vents. In addition, higher average temperature and smaller temperature difference occur for a thermal screen 3.6 m above the floor than for no thermal screen. Finally, we optimize the placement of the warm-air-delivery duct and the location of the outlet openings to obtain a more uniform thermal distribution and, thereby, better crop growth.