Study On Airflow Characteristics In Trombe Wall Solar Chimney

As a passive solar energy absorption structure,the Trombe wall solar chimney structure can enhance indoor building ventilation and play an important role in reducing building energy consumption and energy saving.The bottom-up flow characteristics of airflow in the Trombe wall solar chimney passage have a direct impact on the enhancement of indoor ventilation of the building,which will directly affect the building’s air-conditioning energy consumption.Therefore,it is necessary to conduct an in-depth analysis on the flow characteristics of airflow in the Trombe wall solar chimney passage.In this paper,the flow characteristics in the chimney of two-story building with Trombe wall were analyzed by means of experiment and numerical simulation.The results show that Trombe wall solar chimney through the absorption of solar energy,can enhance indoor ventilation,the ventilation of the upper and lower rooms increased with the increase of solar radiation intensity,The ventilation of the lower room increased by 41%~56% compared with that of the upper room in a day.There is a temperature boundary layer from the Trombe wall to the transparent glass where the temperature gradually decreases.The higher the heat flux,the higher the temperature in the chimney passage.Under different heat flux,Trombe wall and transparent glass surface are the lowest temperature change at the bottom,and the highest temperature change is found on the top of the chimney.For the two-story building model,the Gr number in the chimney increases with the curve of constant heat flux as a quadratic function,but the growth rate gradually decreases.Meanwhile,The number of Gr and Ra in the lower floor of the channel is greater than the number of Gr and Ra in the upper floor.As a result,the ventilation volume of the lower room is higher than that of the upper room.Therefore,the number of Gr and Ra in the chimney should be increased to the maximum extent in order to achieve the best ventilation.The Trombe wall chimneys of 1-10 floors was simulated and analyzed bynumerical simulation method,and the back-flow problem at the entrance of the10-layer channel and the flux at the entrance of each layer was optimized.The results show that at different heights,the relation between Gr number and heat flow density is a quadratic function,which is consistent with the fitting results in the second floor building.Gr number increases with heat flow density,but due to the limitation of the width of the Trombe wall channel,the growth rate gradually decreases.The chimney outlet size has the best value at different heights.In different outlet sizes,the higher the height,the better the ventilation effect.When two parameters are changed at the same time,the flow state is better than that when a single variable is changed.The chimney effect in the chimney is significant.There is no back-flow phenomenon at the 10 th floor entrance,and the ventilation is significantly increased.Taking a 24-story high-rise building as an example,the numerical simulation method was used to study airflow characteristics in chimney of high-rise buildings,results display: the Trombe wall chimney passage is provided with an unobstructed opening at the top,which can effectively alleviate the upstream phenomenon in the top floor room,and at the same time does not affect the ventilation of other floors.Triangular flow guiding ribs are provided at the outlets of the chimney passages for optimization.And when guide ribs size is 0.3 m,the negative pressure at the entrance of each floor and above the entrance of each floor is the highest,it make the inlet have the best air flow,ventilated effect is best.In the chimney of 0.4m,a triangular guide ribs with a size of 0.3m is set.The smaller the inclined angle of the guide rib,the greater the negative pressure at the entrance of each floor and above the entrance of each floor,the better the air flow at the entrance,and the greater the ventilation.Through the optimization of the chimney passage in the Trombe wall of the 24-storey building,the top of the chimney passage is provided with an unobstructed opening and a triangular flow guide rib in the chimney,which can increase the ventilation frequency of the inlet of channel by 112%-383%,enhance the ventilation effect obviously,and eliminate the back-flow phenomenon.Meanwhile,the optimized ventilation frequency can meet the standard requirement of ventilation frequency in the office.