Fluid Mechanism Of Hybrid Ventilation And Thermal Storage Inside The Large Building Spaces And Their Reduced-Scale-Model Experiments

Under the dual pressures of energy shortage and ecological environment protection,Hybrid ventilation combined with the advantages of traditional natural ventilation and mechanical ventilation has gradually been favored by people.Its enormous potential for energy conservation and the comfort it brings,greatly suits people's expectations for this ventilation method.However,the basic fluid dynamics model of hybrid ventilation and its heat storage and heat transfer mechanisms are very complex;especially when applied to large space buildings,indoor heat storage,temperature stratification,or other internal couplings coupling,the hybrid ventilation process becomes more complicated and changeable.Based on this,present paper used the combination of computational fluid dynamics and scale model experiments to explore the performance of hybrid ventilation in a large space under a variety of operating conditions.Firstly,this paper constructs a large space physical model with centralized heat source,and uses computational fluid dynamics commercial software to simulate the indoor air flow behavior and ventilation characteristics under different heat source strengths and mechanical air supply conditions.The simulation results shows that under the thermal driven natural ventilation,obvious temperature stratification occurs inside the room;the temperature efficiency(ie,heat removal efficiency)decreases with the increase of the heat source strength.Under various heat strength,with the volume of mechanical air supply increase,the trend of temperature efficiency changes slightly,but it basically shows the trend of increasing first and then decreasing,then increasing,and then decreasing and finally keeping steady.Local mechanical air supply can significantly improve the indoor air quality,but the mechanical air supply is too strong to easily form a short-circuit type air circulation between the mechanical and natural inlets.Secondly,in order to investigate the ventilation characteristics of different modes of multi-nature ventilation combined with mechanical fans in various modes,the air flow characteristics and air temperature distribution status in the building with single ventilation and cross ventilation both coupled roof exhaust fans,were studied.Studies have shown that roof mechanical exhaust fans can effectively improve the air quality of the upper space in the building;however,it is not the higher the mechanical exhaust intensity is,the better the exhaust effect is,and sometimes it may have a deterrent effect on the ventilation effect;The wind-driven natural ventilation can provide good ventilation to the lower space of the building.In short,the building ventilation should be based on the internal and external environmental conditions of the building reasonable ventilation strategy.Finally,the indoor air temperature distribution and flow characteristics were studied experimentally using a reduced scale model.A non-contact temperature measurement system(infrared thermal imager)and a comprehensive numerical simulation method were used to perform model tests on the aforementioned typical physical model,and the accuracy of the aforementioned numerical simulation data was validated.The model test study showed that when the air supply volume was 0.58,the temperature of each point on the A-pillar increased with the increase of the heat source intensity and increased with the increase of the outdoor temperature.At an “outdoor” temperature of 35° C.and a heat source of 150 W,the temperature at each point on the A-pillar and B-pillar was 0.58L/s at a lower air temperature than that at 1.84L/s.This shows that increasing the air volume sometimes does not effectively improve the indoor environment.Comparing the temperature changes of other columns under different air supply rates,it is concluded that the “indoor” locations are affected differently by the “outdoor” air environment and the “indoor” heat source intensity,but all are significantly affected..In this paper,a variety of research methods are combined to study the performance of hybrid ventilation in buildings from different dimensions.The indoor air temperature distribution and flow characteristics under various combinations of indoor and outdoor influence factors were studied.This study has a theoretical significance for the study of hybrid ventilation;it has practical significance for improving indoor ventilation and saving energy also;at the same time,experimental data can provide data reference for research on building ventilation.