Study On Optimization Of CFD Simulation Of Energy-Saving Cooling By South China-Styled Multi-Span Greenhouse

Disastrous weather is frequent in hot summer of southern China area.Southern China-styled thin film multi-span greenhouse employing sunshade and wet curtain-draught fan system may dramatically reduce heat aggregation in greenhouses,providing a suitable environment for crops growing,and resultant improved high yields allow higher income to peasants.However,a series of shortcomings have bottlenecked the popularization and application of this type of greenhouse,including high energy consumption and low evenness in cooling process,high workload in regular design and management computation and low accuracy that are responsible to difficulties in revelation of distribution of micro-climate parameters(eg.temperature)within the greenhouse,in energy-saving management,and in production practice(high-cost).In recent years,application of computational fluid dynamics(CFD)has been reported,but the previous studies included no effectiveness estimation of energy-saving and their optimization for greenhouses of different area-styles.According to referenced methodology,in this study,we constructed a greenhouse structure ideal model,three-dimension model and physical model with boundary conditions,and chose k-? turbulence model and DO irradiance model for numerical simulation and analogue simulation of outdoor environmental diameters.We investigated the out-door cooling environmental factors for southern China-styled thin film multi-span greenhouse with wet curtain-draught fan system.Five “wet curtain style-draught fan number” combinations,108 NE,208E,306 E,404E and 502 E,were tested for the outdoor environmental conditions(irradiance,temperature and humidity)when cooling,as well as temperature distribution and energy-saving effectiveness after cooling.Based on the obtained results,we carried out numerical simulation of the above-mentioned five combinations using ANSYS FLUENT14.0.Then the numerical simulation result was compared with the experimental one,and the relation between cooling effectiveness and energy consumption was analyzed.The conclusions are drawn as follows:1.The experimental outdoor solar radiation intensity and temperature changed over time,the closer the noon radiation intensity and temperature is higher,the outdoor environment average solar radiation intensity of 937.83 w/m2,including process 306 E the outdoor environment of solar radiation up to 1035.67 w/m2.The average outdoor temperature was 32.19?,with the technology of 108 NE at 33.70?.2.In open the curtain and fan cooling after 15 min,five kinds of processes by respectively after cooling,the temperature within greenhouse were close to a stable state,the average temperature of 3.77?,fan open quantity increased with a large range of cooling.Meantime,it has a high energy consumption.In the five kinds of cooling process,after 306 E cooling process,the Z=1.2 m height of each point in the plane of the temperature is below 26?,and the results of the 208 E cooling close,are lower than other processes after cooling temperature.During the cooling of 15 min,the electric power of 306 E decreased by 20.66% compared with the process 208 E.3.Comparison of the simulation process(306S)temperature and experimental process(306E)temperature change curve with the same change trend,greenhouse inner plane from the top to the ground,high temperature layer and lower,at the top of the highest temperature,lowest temperature below the Z=1.2 m.After cooling the greenhouse,it is similar to the temperature at the height of Z=1.2m plane and Z=2.4 m plane,along the wet curtain-fan direction,distance from the wet curtain and high temperature in the greenhouse.By comparing 306 S simulation temperature for 15 min and 306 E cooling at the end of each measuring point temperature in greenhouse,it was indicated that the maximum relative error is 1.79?,the maximum relative error rate was 5.6%,and the rest to collect relative error control within 1.5?,the average error rate control in 2.44%.4.The energy saving effect of the simulation and optimization of different installation modes of the wet curtain-fan system was optimized.In the case of not changing the direction of the wet curtain-fan system,the 404 S energy saving was 23.74%,which was 49.67% compared with 208 S.In the same process with six fans opened,under the process of 306S? will wet curtain-draught fan system along the long axis X direction to decorate,could effectively improve the efficiency of cooling,under the equivalent energy consumption,cooling rate is about 0.5? higher than that of the 306 S,saving 3% energy.