How should the water collection device for the water exiting a cooling tower be designed?

There are two types of water collection devices for the water discharged from cooling towers: collection trays and dedicated collection tanks (or cooling water tanks). The effective water depth of the collection basin in a typical cooling tower is 300–400 mm, while increasing it results in an effective water depth of 500–600 mm. When the system is operating continuously and normally, if the flow velocity V in the water pump’s suction pipe is greater than 1.0 m/s, a strong vortex forms at the suction inlet, making it very easy for air to be drawn in. When the flow velocity V in the water pump’s suction pipe is less than 0.6 m/s, the vortex at the suction inlet will not cause the water to be drawn out completely, nor will it lead to air entrainment in the system. During operation, water is continuously lost, and new water is automatically added by the float valve, keeping the collection tray at the highest water level. However, when the system starts up, the water adhering to the cooling tower’s supply pipes and packing does not have time to flow back into the collection tray, resulting in the tray’s water level dropping to zero. When the system shuts down, the water adhering to the supply pipes and packing continues to flow into the collection tray, causing the water level there to overflow.

There are two types of water collection devices for the water discharged from cooling towers: collection trays and dedicated collection tanks (or cooling water tanks). The effective water depth of the collection basin in a typical cooling tower is 300–400 mm, while increasing it results in an effective water depth of 500–600 mm. When the system is operating continuously and normally, if the flow velocity V in the water pump’s suction pipe is greater than 1.0 m/s, a strong vortex forms at the suction inlet, making it very easy for air to be drawn in. When the flow velocity V in the water pump’s suction pipe is less than 0.6 m/s, the vortex at the suction inlet will not cause the water to be drawn out completely, nor will it lead to air entrainment in the system. During operation, water is continuously lost, and new water is automatically added by the float valve, keeping the collection tray at the highest water level. However, when the system starts up, the water adhering to the cooling tower’s supply pipes and packing does not have time to flow back into the collection tray, resulting in the tray’s water level dropping to zero. When the system shuts down, the water adhering to the supply pipes and packing continues to flow into the collection tray, causing the water level there to overflow. Cooling towers are usually installed on the roof of the podium or the main building. Municipal tap water fails to meet the requirements in terms of both volume and pressure. If pressurized make-up water is used, the system becomes more complex, difficult to operate, and extremely uneconomical. Therefore, based on the above analysis and the feedback from users, during design, apart from some small towers that use deeper water trays, separate collection tanks should be provided for all others.