Abstract
Accurate evaluation of microclimate conditions in a greenhouse can assist producers to manage crop production and designers to optimize climate control systems. An assessment of the variable thermo-environmental behavior of a heated Venlo-type greenhouse under the influence of naturally changing climate conditions in the Yangtze River Delta region was undertaken. A three-dimensional transient computational fluid dynamics (CFD) model was developed to analyze the airflow pattern and dynamic distribution of temperature and humidity inside the greenhouse. Validation of the numerical model showed a satisfactory agreement between measured and simulated values of air velocity, temperature, and absolute humidity, with mean hourly air temperature mean absolute error (MAE) and root mean square error (RMSE) values of 7.7% and 7.9%, respectively, and mean hourly air humidity MAE and RMSE values of 16.18% and 16.42%, respectively. Simulation results demonstrated that the airflow pattern shaped the distribution of temperature and absolute humidity, and homogeneity of both variables was prevalent inside the greenhouse. These results could be adopted by growers and designers in the Yangtze River Delta region and other sub-tropical climatic regions to improve crop production and optimize climate control systems.
Highlights
In the Yangtze River Delta region of China, greenhouses are rarely equipped with environmental control systems due to the high installation, operational, and maintenance costs of these systems, which are exacerbated by an ever-increasing energy cost [1]
The results obtained in this study could be adopted by producers and designers in this region and other sub-tropical climatic regions in the world to improve crop production and optimize climate control systems. This leads to the research hypotheses in this study: to refute or confirm that (1) the developed computational fluid dynamics (CFD) model has the capability to predict the air velocity, temperature, and humidity behavior in a heated Venlo-type greenhouse; that (2) the 3-D transient model allows for a detailed assessment of the spatio-temporal distribution of the microclimate variables; that (3) the airflow pattern inside the greenhouse has an influence on the spatial distribution of temperature and humidity; and that (4) utilization of multiple air heaters would result in a homogeneous microclimate within the greenhouse
The results of the statistical analysis undertaken to evaluate the capability of the CFD model to predict air velocity, temperature, and humidity in the greenhouse showed that there was no significant difference in the measured and simulated datasets, indicating that the developed transient 3-D numerical model could be applied as a tool to evaluate the dynamic thermo-environmental behavior inside the heated Venlo-type greenhouse
Summary
In the Yangtze River Delta region of China, greenhouses are rarely equipped with environmental control systems due to the high installation, operational, and maintenance costs of these systems, which are exacerbated by an ever-increasing energy cost [1]. The results obtained in this study could be adopted by producers and designers in this region and other sub-tropical climatic regions in the world to improve crop production and optimize climate control systems This leads to the research hypotheses in this study: to refute or confirm that (1) the developed CFD model has the capability to predict the air velocity, temperature, and humidity behavior in a heated Venlo-type greenhouse; that (2) the 3-D transient model allows for a detailed assessment of the spatio-temporal distribution of the microclimate variables; that (3) the airflow pattern inside the greenhouse has an influence on the spatial distribution of temperature and humidity; and that (4) utilization of multiple air heaters would result in a homogeneous microclimate within the greenhouse
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