Research Of A Novel Urban Vortex System For Urban Heat Island Remediation

Urbanization collectively with industrialization and deforestation are the leading causes of the increase in greenhouse gas emissions,which have caused severe environmental degradation.The main problems for most medium and large cities are the increase in the electric power demand,the increase in emissions of CO₂,and the reduction of urban vegetation.As a result,a higher urban ambient temperature compared to the surrounding urban environment is produced,known as"Urban Heat Island."In order to alleviate the UHI effect,this paper presents a new concept called the urban vortex system?UVS?to reduce the adverse effects of urban climate.The UVS couples a vortex generator?VG?that produces updraft by artificial vortex and a vortex stability zone?VSZ?consisting of an assembly of four buildings pretending a chimney.Through this system,a stable upward vortex flow?similar to tornado?can be generated,so as to break the urban heat island effect.The following conclusions were obtained:?1?The UVS experiments?linear scale ratio 1:40 test bench?indicate that the use of a gas burner and a water sprayer could generate the warm fluid necessary for the operation of the vortex generator,where the buoyancy of the flow was the main power of the vortex engine.The UVS test bench was able to spontaneously absorb in the surrounding air at the inlet of the vortex generator zone and the air inlet of the vortex stability zone,thus achieving the design purpose.?2?Reynolds Averaged Navier-Stokes?RANS?simulation was carried out to investigate the flow field in the UVS model.The Renormalized Group?RNG?k–?turbulent model was selected in order to solve the complex turbulent flow modeling.The results report that a steady-state vortex could be formed when a steam-air mixture at 2[m/s]and 450[K]enters the vortex generator.This vortex presented a maximum negative central pressure of-6.81[Pa]and a maximum velocity of 5.47[m/s].?3?The optimization process of the UVS model was carried out by using the method Goal-driven optimization?GDO?.A candidate point was found by this method,which obtained the best adjustment in the optimization,with maximum value for the outlet velocity of 1.84[m/s]and a maximum value of 6.30[N]in the output force.These values are obtained when inserting the steam-air mixture at 2.2[m/s]and 384.5[K].?4?The principle of similarity between the model and a full-scale prototype indicates that the geometric similarity was achieved by preserving all the angles and dimensions.The kinematic and dynamic similarity was achieved by applying the method of repeating variables.The results obtained from this method were four non-dimensional parameters,which related the resulting buoyancy force to all the variables that were present in the UVS study,such as the Reynolds,Prandtl,and Grashof numbers.?5?The calculation of the thermal efficiency and the power for a real full-scale application indicates that approximately 20%of the heat received is converted into work during the convection process.It is concluded that a full-scale prototype would have a maximum power of 2[MW],a specific work of 3[kJ/kg],velocity at 200[m]of 6.1[m/s],and raised air at an upward airflow of 7x10²[kg/s].It is considered feasible to establish an urban vortex system in the city center.In this paper,there are 63 figures,15 tables,and 78 references articles.