EXAMPLE 6.2.3. APPLICATION OF MOODY DIAGRAM

Determine the pressure drop (head lost due to pressure) in pounds per square inch per 1000 ft of pipe and the horsepower lost in pipe friction when 0.50 cfs of crude oil (sp gr = 0.86, v=0.0001 square feet per second) is pumped through level 4-in new cast-iron pipe.

The two requirements for this example are:

1. head lost,  
2. horsepower lost in pipe friction, 


The given parameters are as follows:

              L= 1000ft
              Q= 0.50 cfs
              Crude oil: sp gr = 0.86
                                                 
              D=4 inches                             
                          

In order to solve for f, check Reynold's number and relative roughness.

                   

So, Reynold's number can be computed as:

                    

The relative roughness is:

               k = new cast iron pipe = 0.00085

               

Since the flow is turbulent, use the Moody diagram to identify f:

Friction factor, f = 0.031

So, pressure drop (head lost due to pressure):
                       
                            
                       
                           

Convert the head into pressure:[Topic 6.3]

                         

                       
                         



The horsepower lost in friction is computed as follows:

                           

                           




RELATED TOPIC:

6.2. GENERAL METHOD OF DETERMINING DARCY WEISBACH'S FRICTION FACTOR- THE MOODY DIAGRAM