Calculation of pressure drop caused by friction in fittings etc.
To calculate pressure drop in fittings we use resistance coefficients normally. The resistance coefficients are in the most cases found through practical tests. If the resistance coefficient is known we can calculate the pressure drop:
The element "Dyn. pressure change" calculates these pressure changes. Normally you input the dimension of begin and end of the whole pipe.
Pressure drop in gases and vapor
Compressible fluids expands caused by pressure drops (friction) and the velocity will increase. Therefore is the pressure drop along the pipe not constant.
SF Pressure drop calculates these pressure drops with an approximate equation (pressure drop at arbitrary heat transfer):
We set the pipe friction number as a constant and calculate it with the input-data. The temperature, which is used in the equation, is the average of entrance and exit of pipe.
You can calculate pressure drops of gases with the same formula as liquids if the relativ change of density is low (change of density/density = 0.02).