How to Calculate the Length of a Capillary Tube for a Drip-Irrigation Emitter

AI Thread Summary
To calculate the length of a capillary tube for a drip-irrigation emitter under a constant pressure of 5 psi, one must convert all units to SI and apply relevant fluid mechanics principles. The Hagen-Poiseuille equation is suggested as a necessary tool for solving the problem, particularly for understanding viscous flow in the tube. The emitter needs to achieve a dripping rate of 2 liters per hour, which translates to a specific flow rate in cubic meters per second. The diameter of the tube is given as 1 mm, which is essential for calculating the cross-sectional area. Understanding these concepts will aid in determining the required length of the capillary tube.
maxnormal
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Homework Statement



A drip-irrigation emitter constructed of a coiled capillary tube is inserted into the wall of a drip irrigation line with a constant water pressure of 5 psi. Compute the required length of the emitter’s capillary tube to produce an emitter dripping rate of 2 litres per hour if the capillary tube diameter is 1mm.


Homework Equations



Pressure = Force * Area
Volume of Cylinder = ∏ * Length *Radius^2


The Attempt at a Solution



I converted all the units into SI. I know I need to solve for length of the cylinder, but when I try to equal the cylinder dimensions to 5psi nothing works out. Just don't know how to approach the problem yet. Any help would be appreciated. Thanks.

5 pounds/inch^2 = 34,473.7865 kg/ms^2
2Litres/hour = 5.55x10^-7 m^3/s
diameter = 1mm = 0.001m
radius = 0.001m/2 = 0.0005m
 
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Hi Maxnormal. Welcome to Physics Forums!

Are you learning fluid mechanics? Have you learned about the Hagen -Poiseuille viscous flow equation?

Chet
 
Chestermiller said:
Hi Maxnormal. Welcome to Physics Forums!

Are you learning fluid mechanics? Have you learned about the Hagen -Poiseuille viscous flow equation?

Chet

Hey! Right now I am learning Soil Physics. And I have not learned of that equation yet. Will I need that equation to solve the problem?
 
maxnormal said:
Hey! Right now I am learning Soil Physics. And I have not learned of that equation yet. Will I need that equation to solve the problem?

Google it and see if it satisfies your needs.

Chet
 

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