# Homework Help: Orifice problem

1. Mar 7, 2012

### matthew_hanco

Orifice problem ive been given a list of quantities

Pipe before orifice head = 255mm
Diameter = 31.75mm

Pipe after orifice head = 230mm
Diameter= 20mm

Time for 10litres to fill in collection tank 67.09seconds
Assuming g= 9.81 and density = 1000

from the experiment difference in pressure head = 25mm
They wanted to know the theorectical.

Calling everything before head 1 and after head 2

u1= Q/ A where Q= 0.149 x 10^-3 m^3/s and A = 0.791x10^-3 m^2

u1 = 0.188

u2= Q/ A where Q= 0.149 x 10^-3 m^3/s and A =0.314x 10^-3 m^2

u2= 0.475

putting into equaton

P1-P2/p x g = u2^2/2g - u1^2/2g where p=density

gives the difference in theoretical head = 9.7mm

Im not sure if that is right as its a third of the experiment, if it is right how can it be because surely the theory should be higher as you dont take into account the local or frictional losses.

Hope someone can help.

2. Mar 7, 2012

### rude man

Diagram or complete staement of the problem?

3. Mar 8, 2012

### matthew_hanco

The problem was find the theoretical difference in head pressure before and after orifice. Then compare with experimental difference in head pressure. No diagram wasnt given one to begin with. sorry