Research on determination method of greenhouse wet pad-fan operating parameters based on numerical simulation
In order to improve the cooling effect of the wet pad-fan system in the greenhouse and reduce the operating cost of the greenhouse,this paper uses the Computational Fluid Dynamics(CFD)to build a three-dimensional model of the greenhouse,simulate the operation of the wet-pad fan system and explore the impact of the operation related parameters on the temperature field inside the greenhouse.Through the combination of wet pad area,fan wind speed and wet pad circulating water temperature,the appropriate parameters of wet pad-fan cooling system are selected by the cost analysis,temperature proportion and the temperature distribution uniformity.The results show that the maximum error between simulated values and measured values is 3.983％,which verifies the effectiveness of the CFD model.The numerical simulation shows gradient variability presents in the horizontal and vertical directions of the greenhouse,and the temperature in the greenhouse drops to 27.9 ℃ after the wet pad-fan cooling system is on for 210 s.In summer,when the temperature of the greenhouse is as high as 35 ℃,CFD was used to optimize the configuration parameters of the wet curtain-fan cooling system as the wet curtain area of 0.5 m2,and the fan wind speed of 4 m/s,the initial wet pad circulating water temperature is 23.85 ℃,the temperature decreases from 35 ℃ to 30 ℃ after the wet pad-fan cooling system is on for 300 s.The temperature deviation coefficient in the greenhouse is 0.077,which meets the crop growth needs.Therefore,the parameter selection method of the greenhouse wet pad-fan cooling system based on CFD proposed in this paper can be applied to the double-arch greenhouse in Shaanxi.
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