# Simulation Analysis and Experimental Study of the Cooker Hoods of High-Rise Residential Buildings
## 4 Results and Discussion  
Taking the case of the 20-storey residential building, with the cooker hood installed on the bottom floor and the operating rate of 50%, the numerical simulation of the exterior flow field of the cooker hood was done using the commercial software Fluent. The oil fumes concentration, pressure distribution, and temperature distribution were analyzed when the window was opened and closed in the kitchen. To facilitate observation, the transverse section and longitudinal section of the oil fumes maximum escape position were selected to extract the results of analysis. The position is shown in Figure 8.  
According to the calculation results extracted from the sections, the pressure distributions are shown in Figures 9 and 10. It should be noted that because the reference pressure in the calculation is set to 101,325 Pa (standard atmospheric pressure), the actual pressure in the calculation result is the pressure value in the figure plus the standard atmospheric pressure. Figure 8: Extraction position of the exterior flow field analysis result of cooker hood. Figure 7: Finite element model of exterior flow field of cooker hood. (**a**) An analysis grid model of the flow field of cooker hood; (**b**) The local grid effect of cooker hood. It can be seen from the calculation results that the oil fumes flow channel is narrowed due to the existence of the oil baffle plate at the fumes outlet. There was a low-pressure region that formed between the oil baffle plate and the fumes outlet, which was conducive to oil fumes emissions. For both sides of the oil baffle plate, the pressure difference is 6 Pa when the state of window is open, and the pressure difference is 9 Pa when the state of window is closed, in the transverse section and longitudinal section. In addition, the pressure drops on both sides of the oil baffle plate are larger when the window is opened at the same section compared with when the window is closed. When the window is opened, the air flow is good; the kitchen ventilation is smooth, and oil fumes' exhaust is smooth. However, this is not conducive to oil fumes' exhaust due to poor air flow when the window is closed. At this time, the air compensation mainly depends on the intake from kitchen door, as the distance is far away, the air intake is not smooth, and a large negative pressure is formed at the rear of the oil baffle plate close to the outlet, so that the flow velocity is increased to meet the requirements of the oil fumes' exhaust. This phenomenon is better reflected in the calculation results of flow rate in streamline distributions of oil fumes. The temperature distributions of the exterior flow field for the cooker hood are shown in Figures 11 and 12; the initial temperature of the kitchen is 300 K, and the outlet temperature of the oil pan is 340 K. The results show that, when the window is closed, the temperature on the same section of the kitchen is obviously higher than when the window is opened. In fact, the level of the temperature is closely related to whether the oil fumes are discharged smoothly. When the oil fumes escape, it causes the temperature in the kitchen to rise, and the higher the temperature rises, the more the oil fumes escape. Therefore, when the oil fumes are not discharged smoothly, the temperature in the kitchen rises to a maximum of 315 K. The influence of heat conduction on the increase of ambient temperature is also related to the air flow in the kitchen. The more air flow, the better the heat dissipation and  
Figure 10: Exterior flow field pressure analysis results of cooker hood (longitudinal section) under the window conditions of: (**a**) open and (**b**) close. Figure 9: Exterior flow field pressure analysis results of cooker hood (transverse section) under the window conditions of: (**a**) open and (**b**) close. the lower the temperature rise in the kitchen. When the window is opened, the temperature rise is reduced by 5 K compared to when the window is closed.