Flow rate

Flow rate is defined at the volume of fluid that passes through a given surface over a period of time. It is measured in m3 per sec.

 

flow rate = amount of volume added
                          time taken

If a tank is 30m long, 7m wide with a depth of 4 m and it takes 60 minutes to fill, what is the flow rate?

First note that the question uses minutes not seconds so at the end we need to convert from minutes to seconds.

flow rate = volume
                   time

flow rate = (30 x 7 x 4)
                      60
flow rate = 14m³ per minute (but the answer needs to be in seconds)

To convert into m³ per sec

flow rate = 14
                 60

flow rate = 0.23 m³ per sec

To calculate the volume of liquid added over a period of time the equation can be rearranged.

volume = flow rate × time

(2nd)
Sometimes, different time units are used.

To convert minutes into seconds

1 minute = 1 x 60 seconds

 

What volume is added if the liquid is flowing into a tank at a flow rate of 3m³ per second and flows for three minutes.

convert minutes into seconds
time = 3 × 60 seconds
time = 180 seconds

volume = flow rate × time
volume = 3 x 180
volume = 540 m³

After three minutes, 540m³ liquid will have been added to the tank.

Flow rate is inversely proportional to the length of time to fill the tank.

increase flow rate = decrease in time
decrease in flow rate = increase in time

increase in time = decrease in flow rate
decrease in time = increase in flow rate

If you need more practice, use the worksheet provided to practice calculating flow rates and volume based on flow rate.
Worksheet - calculating flow rates and volume based on flow rate (Word doc 96 kb)

 

Top