In the summer season, natural ventilation is commonly used to reduce the inside air temperature of greenhouse when it rises above the optimal level. The greenhouse shape, vent design, and position play a critical role in the effectiveness of natural ventilation. In this study, computational fluid dynamics (CFD) was employed to investigate the effect of different roof vent designs along with side vents on the buoyancy-driven natural ventilation. The boussinesq hypothesis was used to simulate the buoyancy effect to the whole computational domain. RNG K-epsilon turbulence model was utilized, and a discrete originates (DO) radiation model was used with solar ray tracing to simulate the effect of solar radiation. The CFD model was validated using the experimentally obtained greenhouse internal temperature, and the experimental and computed results agreed well. Furthermore, this model was adopted to compare the internal greenhouse air temperature and ventilation rate for seven different roof vent designs. The results revealed that the inside-to-outside air temperature differences of the greenhouse varied from 3.2 to 9.6oC depending on the different studied roof vent types. Moreover, the ventilation rate was within the range from 0.33 to 0.49 min-1. Our findings show that the conical type roof ventilation has minimum inside-to-outside air temperature difference of 3.2oC and a maximum ventilation rate of 0.49 min-1.

Abstract
 Introduction
 Materials and Methods
  1. Experimental greenhouse
  2. CFD modeling
  3. Computational domain and boundary conditions
 Results and Discussion
 Conclusion
 Literature Cited

• Adnan Rasheed(Department of Agricultural Engineering, Kyungpook National University)
• Jong Won Lee(Department of Horticulture Environment System, Korea National College of Agriculture and Fisheries)
• Hyeon Tae Kim(Department of Bio-Industrial Machinery Enineering., GyeongsangNational University)
• Hyun Woo Lee(Department of Agricultural Engineering, Kyungpook National University/Institute of Agricultural Science & Technology, Kyungpook National University/Smart Agriculture Innovation Center, Kyungpook National University) Corresponding author