Pumps Total Dynamic Head (TDH) and Pressure using EMT

Topic: Visual Plot of Pump's Pressure Head and Volumetric Flow;

Subject: Fluid Mechanics;

Tool: Euler Math Toolbox;

by: Gani Comia, Nov. 2024;

In one scenario, a 100 GPM volumetric flow of water is being required in a building's fire protection system. Your facility manager is asking if it can be achieved from existing < 70 GPM and if the pressure setting can be adjusted from the current 100 psi to something like 160 psi. As a technical resource person in mechanical, you need to provide an explanation with the supporting calculation and visual simulation in layman's terms.

EMT Script

Pumps Total Dynamic Head & Pressure

The pump's horsepower (HP) is calculated from a given volumetric flow rate (Q) of fluid and the total dynamic head (H):

HP=QH1714e

To determine the total dynamic head (TDH), H:

Solution:

>HP = 10+2.5;         // hp, e.g. fire pump + jockey pump
>Q  = 50:120;         // gpm, volumentric flow from 50 to 100
>e  = 0.80;           // %, efficiency (assumed)
>H  = (1714*HP*e/Q);  // ft, total dynamic head

Pressure head calculation:

P=γh

where:

>gamma = 62.4;        // lb/ft^3, weight density of H2O
>h = H;               // ft, pressure head
>P = (gamma*h)/144;   // psi (from lb/ft^2), pump pressure

Data Visualization:

>aspect(1);
>plot2d(P,Q,title="Fire & Booster Pump Characteristic", ...
 xl="Pump Pressure [psi]",yl="Pump Vol. Flow [gpm]");

Shown in fig. 1. is plot generated by EMT script.

Fig. 1. Visual representation of the pump's characteristics.

Feel free to comment for inquiry, clarification, or suggestion for improvement. Drop your email to request the softcopy of the file.