Determination of the diameter of the gravity overflow pipe
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Container A contains vegetable oil, with a temperature of 10 degrees Celsius, a viscosity of 65 cP, and a density of 930 kg/M3； A pipe opening was made at the bottom of the oil tank, and there is a U-shaped overflow pipe that allows the fluid to flow by gravity into tank B. The outlet of this overflow pipe is 200 mm below the liquid level in tank A. According to Bernoulli’s equation, with a height difference of 200 mm, the flow velocity is 1.98 m/s ； But it seems that the flow rate is a bit too high. The flow rate of vegetable oil into tank A is 18 M3/h; at a velocity of 1.98 m/s, a DN65 overflow pipe is sufficient. However, the overflow pipe on-site must be at least DN150; otherwise, Tank A is prone to overflowing. Could everyone please help calculate what size the overflow pipe should be under the aforementioned flow rate (18 M3/h) and at the given viscosity and height difference (200 mm)? Thank you.
The data provided by the poster is insufficient; if we estimate based on a pipe length of 10 meters, 2 elbows, and 2 gate valves, it is necessary to take into account the sudden changes at one inlet and one outlet during the calculations. The pipeline size selected for the calculation results is DN125. In this type of hydraulic calculation based on gravity-driven flow, the number of fittings in the pipes has a significant impact on the calculations, and special attention must be paid to this.