12-06-2012, 01:38 PM
Centrifugal Pump Basics
[attachment=24182]
Open & Closed Systems
A “Closed” hydronic system is one that has only one interface with air or flexible membrane
An “Open” hydronic system is one that has more than one interface with air or a flexible membrane
Conversion Factors Between Head and Pressure
Head (feet of liquid) =Pressure in PSI x 2.31 / Sp. Gr.
Pressure in PSI = Head (in feet) x Sp. Gr. / 2.31
PSI is Pounds per Square Inch
Sp. Gr. is Specific Gravity which for water is equal to 1
For a fluid more dense than water, Sp. Gr. is greater than 1
For a fluid less dense than water, Sp. Gr. is less than 1
Head
Head and pressure are interchangeable terms provided that they are expressed in their correct units.
The conversion of all pressure terms into units of equivalent head simplifies most pump calculations.
System Performance Curves
System Performance Curve is a mapping of the head required to produce flow in a given system
A system includes all the pipe, fittings and devices the fluid must flow through, and represents the friction loss the fluid experiences .
Energy Loss in Valves
Function of valve type and valve position
The complex flow path through valves can result in high head loss (of course, one of the purposes of a valve is to create head loss when it is not fully open)
Ev are the loss in terms of velocity heads.
[attachment=24182]
Open & Closed Systems
A “Closed” hydronic system is one that has only one interface with air or flexible membrane
An “Open” hydronic system is one that has more than one interface with air or a flexible membrane
Conversion Factors Between Head and Pressure
Head (feet of liquid) =Pressure in PSI x 2.31 / Sp. Gr.
Pressure in PSI = Head (in feet) x Sp. Gr. / 2.31
PSI is Pounds per Square Inch
Sp. Gr. is Specific Gravity which for water is equal to 1
For a fluid more dense than water, Sp. Gr. is greater than 1
For a fluid less dense than water, Sp. Gr. is less than 1
Head
Head and pressure are interchangeable terms provided that they are expressed in their correct units.
The conversion of all pressure terms into units of equivalent head simplifies most pump calculations.
System Performance Curves
System Performance Curve is a mapping of the head required to produce flow in a given system
A system includes all the pipe, fittings and devices the fluid must flow through, and represents the friction loss the fluid experiences .
Energy Loss in Valves
Function of valve type and valve position
The complex flow path through valves can result in high head loss (of course, one of the purposes of a valve is to create head loss when it is not fully open)
Ev are the loss in terms of velocity heads.