# Vacuum Delivery Pipe System for a Double-storey Office

1. Jun 4, 2010

### CharlesL

Hello, I am trying to design a vacuum delivery piping system for a double-storey office for my project paper, which is a similar concept to the pneumatic tubes used in hospitals.

The idea is to use deliver a carrier/container with everyday office documents to various departments in the office with the help of a vacuum pump at one end of the piping system. The vacuum pump is used to vent out the air in the pipe system and create a low pressure region at the pump region. The system will consist of a single pipe design which will have an input point of the carrier from the sender (only one sender in the office) to the particular recipients in the first floor as shown in the figure attached.

My initial findings so far suggests that the carrier placed into the pipe should have a diameter which is almost the same as the diameter of the pipe system with minimal clearance between the carrier and the pipe wall so that the vacuum pump could generate the pressure difference between the pump and the inlet of the pipe. Circular rubber linings will be placed around the body of the cylindrical carrier to further to reduce air leakage. The pressure at the vacuum pump would be near to zero and the pressure difference would be the difference between atmospheric pressure and the pressure at the vacuum pump. This difference in pressure could be applied to the formula P=F/A, where P is the pressure, F is force while A is the cross sectional area of the carrier. With this I could determine the force acting on the carrier due to the pressure difference which would move the carrier in the pipe system. With the force determined, I could apply F=ma, where m is the mass of the carrier with the documents and a is acceleration to determine the acceleration of the carrier.
I wonder if I am on the right track or should I look into compressible flow to apply the Bernoulli's equation with the frictional losses and also the losses due to the bends and the vertical pipes?

The container is also proposed to be a cylindrical shape with possibly hemispheric ends. The hemispheric ends is to allow smoother movements during the bends. Since the carrier will be used to transport documents, the carrier will be a cylinder which has a length of about 300mm just enough to fit a rolled A4 sized paper. However, I am unsure of how I could determine the bend radius which would not cause the 300mm long cylinder carrier/container to be stucked at the bends. Please advice on what formulas should I apply to calculate the ideal radius bends. Should I still maintain the minimal clearance between the carrier and the pipe wall and use bigger diameter of piping at the bends?

Any suggestions or comments would be highly appreciated.

Thank you.

Regards

Charles

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