Numerical prediction of thermal environment and energy consumption in tunnel-type greenhouse with supplementary air-mixing and heating device

Owing to the fact that the growing of agricultural crops can be directly affected by climate conditions, large-scale greenhouses are usually used to control the indoor climate conditions for cultivation in agriculture. The envelope of greenhouses generally consists of a polyvinyl chloride (PVC) sheet, which produces a so-called greenhouse effect and protection for crops from harmful insects. The research concerning indoor environmental conditions formed in greenhouses and precise numerical predictions of airflow and temperature distribution in large-scale greenhouses are important to develop effective designs from the viewpoint of energy-saving and the development of suitable indoor environments for agricultural products. To this end, this paper presents a numerical analysis of flow and temperature distributions in greenhouse and the effect of an air circulation fan for mixing air in the greenhouse. The uses of a PVC curtain inside the greenhouse and feedback control of supply air temperature were evaluated by coupled numerical analysis of Computational Fluid Dynamics. From the viewpoint of heat load of the supplementary heating device, the energy-saving effects of about 10-30% were confirmed upon introduction of a PVC curtain and air-mixing fan in a large-scale PVC greenhouse. The sensor position in the greenhouse was confirmed to have a great impact on energy consumption.