Volumetric Flow Triangle

Volumetric Flow Triangle

All mathematical triangles work by covering over the component you want to find to reveal the equation required.

Q = A x V

A = Q / V

= Quantity

V = Q / A

All mathematical triangles require you to know two pieces of information to calculate the third.

= Area

= Velocity

Volumetric Flow Triangle

m3/s

m2

m/s

Q=

A=

V=

Mass Flow Rate Triangle Units

Q = Volumetric flow rate in cubic metres per second

A = Cross-sectional Area in square metres

V = Flow Rate in metres per second

Target velocity range for domestic heating systems is between 0.5m/s to 1.5m/s. 0.9m/s & 1m/s are widely regarded as optimal as these achieve the best balance between efficiency and energy output.

Calculating Quantity

Worked Example: Q = A x V

m3/s

m2

m/s

Q=

A=

V=

Using the example covered in calculating cross-sectional area for 22mm copper pipe: A = 0.000314m2. We will use a target velocity of 0.9m/s.

0.000314 x 0.9 = 0.0002826m3/s

For the purpose of keeping the numbers more managable, we will round answers to a maximum of 6 decimal places: 0.0002826m3/s becomes 0.000283m3/s.

Calculating Area

m3/s

m2

m/s

Q=

A=

V=

Worked Example: A = Q / V

Using the Quantity calculated in the previous example: Q = 0.000283m3/s V = 0.9m/s.

0.000283 / 0.9 = 0.00031444m2

For the purpose of keeping the numbers more managable, we will round answers to a maximum of 6 decimal places: 0.00031444m2 becomes 0.000314m2.

Calculating Velocity

m3/s

m2

m/s

Q=

A=

V=

Worked Example: V = Q / A

Using the figures calculated in previous examples: Q = 0.000283m3/s A = 0.000314m2

0.000283 / 0.000314 = 0.90127389m/s

When dealing with flow rates it's unlikely to ever need to go above 1 decimal place: 0.90127389m/s becomes 0.9m/s.