CFD Modelling to Study Mechanical Ventilation and Thermal Comfort in an Indoor Bus Interchange

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Problem Statement

In the hot tropical weather, passengers are exposed to high temperature and humidity conditions while waiting for buses at the interchange. The proposed solution was to construct a sheltered bus interchange with air-conditioned passenger boarding and alighting areas.

Challenge

The engine of a commuter bus will generate large amounts of pollution and heat. The sizing and placement of the mechanical ventilation devices within the interchange must be adequately optimized in order to ensure that the heat and pollution levels at the parking, driveway, alighting and boarding areas are kept within acceptable levels.

Solution

A detailed 3-dimensional computational domain is created to scale. Computational Fluid Dynamics (CFD) is used to simulate the heat and pollution produced by the busses in the parking, driveway, alighting and boarding areas of the interchange. The sizing and placement of mechanical ventilation (MV) devices were iteratively optimized using CFD until the pollutant and temperature levels are brought within acceptable limits.

Results

After optimizing the MV system, the CFD contour plots show that the carbon monoxide (CO) pollution levels within the interchange are kept below 12ppm (CO TLV = 25ppm). The temperature plots also shows that the temperatures at the driveway and alighting bay are not more than 2oC above ambient. The CFD results show that the optimised MV system is able to keep pollution and heat produced by the busses to a safe and comfortable level.

Fig 1: Computational Domain of the Indoor Bus Interchange

 

Fig. 2: COPPM Contour at 1.7m Height

Fig. 3: COPPM Contour at Vertical Plane

Fig. 4: Temperature Contour at 1.7m Height

Fig. 5: Temperature Contour at Vertical Plane along Axis of Domain