The Air Distribution Design And Method In Summer Of A Large Space In Lanzhou' Playground

With the development of social economy and the improvement of living standards,building energy consumption which is increasing year by year accounts for a considerable share of the total energy consumption of the entire society,public buildings with large spaces of various shapes are constantly appearing,and how to reasonably design HVAC systems and air distribution is a huge challenge for designers.While,Computer Fluid Dynamics(CFD)is a time-saving and efficient method to optimize the pre-design and develop air-conditioning operation plan effectively,which provides reference for rational design and operation.At present,scholars' research on large spaces is becoming more and more abundant in terms of theoretical analysis,numerical simulation,and experimental demonstration.Especially,the methods of dealing with turbulence models and internal heat sources have gradually matured.But in general,there are relatively few cases using CFD simulation technology to assist the design of large spaces with complex structures,and most of the studies on boundary conditions are based on the steady-state method,which have neglected the dynamic changes of outdoor solar radiation,so it is impossible to predict varying airflow organization and thermal comfort of the building during working time.Based on above analysis,the paper validates the numerical model and method of CFD airflow simulation based on the measured airflow data of an activity center in Lanzhou firstly.Several feasible schemes is designed based on the meteorological parameters and normative standards of Lanzhou area secondly,and a better air conditioning design scheme in summer is determined by CFD simulation and technical comparison.PMV-PPD index of the children 's playground in working time under the design scheme is simulated by CFD unsteady-state simulation.After the study,the following conclusions can be drawn:1)The method that dividing the solar radiation of the transparent skylight into the roof heat flow and the internal heat source by numerical simulation is reasonable in this paper.2)The establishment of a fluid-solid coupled three-dimensional heat transfer model in the CFD non-steady state simulation.In which,a solid domain model is established based on the actual thickness of the envelope structure,which can more realistically describing the heat transfer process of outdoor temperature through the solid domain of envelope structure to the indoor fluid domain.3)The determination of the initial calculation state in the CFD unsteady simulation and the simulation method of UDF boundary conditions could more reasonably reveal the impact of time-varying outdoor meteorological conditions on indoor airflow organization such as temperature field and velocity field.4)The method of UDM to output PMV-PPD cloud map that achieve the secondary compilation of Fluent simulation results,which effectively reduces the post-processing workload and reflects the thermal comfort of the flow field clearly.5)According to the unsteady simulation results,PMV-PPD in 90% of the working area meets the requirements except for the 8:00am and 18:00pm working conditions,which indicates that the second airflow design of the children's playground is reasonable and feasible.6)We propose the following for the working time of the air-conditioning system in the children's playground: at 8:00am,PMV in nearly 90% area is 0.5 ~ 1 and PPD in 60% area is more than 10%,people will feel overheated,so it is recommended to turn on the air conditioner before the opening time for 0.5~1h to eliminate the residual heat;while at18:00pm,PMV in 11% area is-1 ~-0.5,and PPD in 10% area rises to 15%,people could feel a little bit cold,so it is recommended to operate the air conditioner at low load such as appropriately increasing the supply air temperature.