N°7 – Mass flow rates training – level 2 to 3

Mass flow rate indicates the displacement of a given mass per time unit.

The international unit for mass flow rate is [kg/s].
In our professional sector very little happens in the space of 1 second. We often indicate flow rates per hour and sometimes per minute.
The common measuring units used in HVAC(Heating Ventilation and Air Conditioning) are: [kg/s], [kg/h], [t/h] (tonnes per hour), [kg/min].

The usual symbol representing flow rate is: q
The usual symbol representing mass flow rate is: q_m

We can therefore define a flow either by expressing the displaced volume (qv), or the displaced mass (qm).
Obviously when we are talking about the same flow there is a relation between the two ways of describing the same phenomenon. The mass volume or density enables us to pass from the one form of expression to the other.

It is not necessary to know a formula for converting a mass flow to volume flow and vice-versa. It just requires common sense.