Simulation In A Large-scale Greenhouse With A Fogging System Based On CFD

To solve the problem that the inner available space of the traditional Chinese solar greenhouse is usually small,a new-type large-scale greenhouse which was tunnel type and had a wide span with steel frame and south-north orientation was designed.The airflow and temperature patterns were analyzed and simulated in a naturally ventilated large-scale greenhouse without crops and in a spray cooling large-scale greenhouse by means of three-dimensional computational fluid dynamics?CFD?.Then as the boundary conditions the outdoor and indoor environment sensors were measured in the article.It's can be helpful for the research on ventilation and the spray cooling in the large-scale greenhouse.1.Under the typical sunny day the simulation model of the airflow and temperature patterns in a naturally ventilated large-scale greenhouse was established by means of three-dimensional computational fluid dynamics?CFD?.Then the model was validated via the comparison with the field experimental results at the same locations.Comparison between simulations and measurements showed that the average relative error was around 4.1%.So a good agreement existed between simulating results and experimental ones.Temperature distribution was uniform in the large-scale greenhouse when the vent opening degree was 100%.The outdoor wind speed had a significant positive correlation with the ventilation rate when vent opening degree was kept constant.For the purpose of cooling,the optimum vent opening degree was 75%¹00%.If the temperature of the greenhouse was suitable for crop growth and the outdoor wind speed was faster than about 3m·s^-1,the optimum vent opening degree should be less than 75%.2.The air temperature is high in summer in north China,it's hard to grow crops in greenhouses in summer so that the use efficiency of greenhouse is low.The spay cooling experiment was engaged in the large-scale greenhouse,the result was showed that the average air temperature in the spay cooling large-scale greenhouse was about 3.5?lower than that the average air temperature in the naturally ventilated large-scale greenhouse.The evaporative cooling efficiency of treatment 1,2,3 were 26.3%39.4%and 47.2%.The treatment 1 was that cooling system ran 60s and then closed 300s;the treatment2 was that cooling system ran 90s and then closed 300s;the treatment 3 was that cooling system ran 120s and then closed 300s.Finally the result showed that the cooling effect of treatment 3 was the best.3.Under the typical sunny day the simulation model of the airflow and temperature patterns in a naturally ventilated and spay cooling large-scale greenhouse was established by means of three-dimensional computational fluid dynamics?CFD?.Then the model was validated via the comparison with the field experimental results at the same locations.Comparison between simulations and measurements showed that the average relative error of air temperature and relative humility were10.55%and 9.9%.So a good agreement existed between simulating results and experimental ones.The model which was validated under different outdoor wind speeds and layout plannings of fog-spray nozzles showed that the average temperature in third layout plannings of fog-spray was the lowest when the outdoor wind speed was 1m·s^-1 And at the moment the average temperature was 31.2?,the most homogeneous distribution of the airflow and temperature patterns in all cases was achieved.