- #1
Tom Hardy
- 46
- 1
Here is an illustration of something that came into my head:
http://imgur.com/a/V9V8S
(also attached to question)
If we do a energy balance (in terms of head) between point 1 and point 2 (ignoring friction for now, it's not really important):
$$\frac{P_1}{\rho g} + \frac{v^2_1}{2g} + z_1 + h_p = \frac{P_2}{\rho g} + \frac{v^2_2}{2g} + z_2 $$
Assume the pressure is the same so..:
$$ h_p = \bigg( \frac{v^2_2}{2g} - \frac{v^2_1}{2g} \bigg) + (z_2 - z_1)$$
Fine, but this is what I have an issue with, the end result doesn't really take into account the huge distance the liquid has to go up by. When I'm trying to choose a pump, I have to pick an operating head and flow rate. The issue is, the above equation could give me a required pump head that's very small say 5m or something. If the big distance the liquid has to go up is 100m, this 5m head pump won't provide, so how do I pick a pump in this case?
http://imgur.com/a/V9V8S
(also attached to question)
If we do a energy balance (in terms of head) between point 1 and point 2 (ignoring friction for now, it's not really important):
$$\frac{P_1}{\rho g} + \frac{v^2_1}{2g} + z_1 + h_p = \frac{P_2}{\rho g} + \frac{v^2_2}{2g} + z_2 $$
Assume the pressure is the same so..:
$$ h_p = \bigg( \frac{v^2_2}{2g} - \frac{v^2_1}{2g} \bigg) + (z_2 - z_1)$$
Fine, but this is what I have an issue with, the end result doesn't really take into account the huge distance the liquid has to go up by. When I'm trying to choose a pump, I have to pick an operating head and flow rate. The issue is, the above equation could give me a required pump head that's very small say 5m or something. If the big distance the liquid has to go up is 100m, this 5m head pump won't provide, so how do I pick a pump in this case?