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Comparison of the H2OMAP SWMM5 Hazen Williams Force Main Solution to a HW Solution

Note:  Comparison of the H2OMAP SWMM Hazen Williams Force Main Solution to a HW Solution

 

In this example, we compare the force main head loss in four links in H20Map SWMM to the head loss in a steady state HazenWilliams solution for the same length pipe, diameter and flow (Figure 1).  The H2OMap SWMM model has a large constant dry weather inflow at the wet wells which floods the wet well and causes a constant pump flow to the force main (Figure 2).  TheHW calculator is located here http://www.engineeringtoolbox.com/william-hazens-equation-d_645.html and a comparison forHW head loss in PSI for 5000 feet long, 3 inch diameter pipes with HW Coefficients of 130, 120, 110 and 100, respectively, is shown in Table 1.   The SWMM 5 equation loss (PSI Diff) and the PSI loss from the HW calculator are very close for all four links. 

 

 

Table 1.  Steady State comparison between HW Calculator and H2OMAP SWMM/SWMM 5 Force Main calculations.

 

HW

SWMM5

SWMM5

SWMM5 Loss

Loss 

Coefficient

Psi UP

PSI Dn

PSI Diff

PSI HW Calculator

130

84.563

44.88

39.683

39.82

120

88.772

43.765

45.007

45.16

110

91.798

41.426

50.372

50.54

100

95.354

38.727

56.627

56.82

 

 

Figure 1.   H2OMAP SWMM Wet Well, Pump, Force Main and Gravity Main Network.

 

Figure 2.  Constant Pump Flows

 

 

via Blogger http://www.swmm5.net/2013/08/comparison-of-h2omap-swmm5-hazen.html

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