head loss and also discharge of a tank througha vertical pipe

[docmartin]

I have two different questions.

First one goes like this. I have need to size a pump and am calculating the head loss. The major requirement is that there must be 70psi coming out of the discharge end into atmospheric pressure. There is also a 35 foot elevation change. Am I correct in saying that with these two combined, and neglecting pipe friction losses, I already have calculated 196 feet of head?

The second question is this. In a 4x8x4 chest, there is a verticle pipe. The verticle pipe only extends about 30 inchs vertically into the tank. When water rises above this level, it flows through the pipe. During operation, water will be about 7 inches above the end of the pipe. What i need to know is, what flow in GPM will go through that pipe. The flow into the tank varies. The pipe is 10 inches in diameter.

Can anyone help me with these questions?
thanks

 

[kyong]

If your first question has right requirement and pump inlet pressure is 0 psig, your calculation would be correct. But, it's impossible to have 70 psi at end of pipe discharging into atmosphere. If the location you check pressure is a little upstream from discharge nozzle and nozzle size is small enough, 70 psi may possible.

For the second question, I assume pipe end is open to atmosphere. Major factors determining flow rate are 1) pipe head loss that depend on length, number of elbows, valves,...
2) height difference between outlet of the pipe and water level.

 

[MortenA]

For liquids you loose 1 velocity heigh when going into the pipe (from the tank) and another 1/2 when discharging (liquids usually dont choke).

To get dP in head multiply 1.5 with V^2/(2g).
V is with respect to the liquid velocity in the pipe.

Best regards

Morten