首页|Study on the discharge coefficient of wind-driven naturally ventilated Chinese solar greenhouses
Study on the discharge coefficient of wind-driven naturally ventilated Chinese solar greenhouses
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NETL
NSTL
万方数据
The Chinese solar greenhouse(CSG)is a prevalent feature in agricultural practices within China.Nevertheless,the regulation of natural ventilation within this architectural structure remains suboptimal.Consequently,the development of a natural ventilation model becomes imperative for the effective management of the greenhouse environment.Of particular significance within these models is the consideration of the discharge coefficient as a pivotal parameter.Conducting a multi-case investigation into the variable-dependent discharge coefficient is crucial for both practical application and model advancement.This research delved into the impact of various factors,including the upper-lower vents area ratio(Aup/Alow),vent-greenhouse area ratio(Alow/Agreenhouse),lower vent position height(h/H),the incident angle of the external wind,and altitude,on the discharge coefficient(Cd)of CSG.A CFD model was developed for a scaled CSG with validation conducted through field experiments and wind tunnel tests.Results indicated a 61.6％reduction in Cd on average corresponding to an 80％decrease in Aup/Alow.Cd levels remained consistent following the attainment of an Aup/Alow ratio of 1.0.Besides,there was an average increase of 52.5％in Cd levels for every 0.09 decline in h/H,attributed to the blocking effect of the cover.Moreover,the ventilation rate and the pressure coefficient difference were utilized to construct a model of Cd pertaining to greenhouse design and ventilation operation,exhibiting a notable accuracy level of R2=0.95.Furthermore,the blocking effect of higher h/H was relieved as the incident angle e decreased under the windward conditions.The increase in Aup/Alow and the decrease in Alow/Agreenhouse were identified as crucial factors contributing to the growth of Cd under leeward conditions.Ultimately,the high-altitude environment led to a rise in Cd levels in contrast to the low-altitude region.The increasing rate of Cd correlated positively with Alow/Agreenhouse and h/H initially,but exhibited a decline once Aiow/Agreenhouse reached 0.036,remaining stable thereafter once h/H reached 0.18.In summary,a comprehensive examination of the discharge coefficient of CSG was undertaken,addressing a significant knowledge deficiency and laying the groundwork for advancements in the natural ventilation model and the intelligent control system for CSG.
Chinese solar greenhousedischarge coefficientarea ratioposition heightwind directionaltitude
NETL
NSTL
万方数据
