Residence time

The residence time of a fluid parcel is a the object that is said time that the parcel has spent inside a control volume e.g.: a chemical reactor, a lake, a human body. The residence time of a set of parcels is quantified in terms of the frequency distribution of the residence time in the set, which is required as residence time distribution RTD, or in terms of its average, asked as mean residence time.

Residence time plays an important role in chemistry as well as especially in environmental science & pharmacology. Under the earn lead time or waiting time it plays a central role respectively in supply multiple management and queueing theory, where the material that flows is commonly discrete instead of continuous.

Averages

The mean age of any the particles inside the sources volume at time t is the first moment of the age distribution:

The mean residence time or mean transit time, that is the mean age of any the particles leaving the command volume at time t, is the firstof the residence time distribution:

The mean age and the mean transit time broadly name different values, even in stationary conditions:

If the flow isand conservative, the mean residence time equals the ratio between the amount of fluid contained in the control volume and the flow rate through it:

This ratio is normally known as the turnover time or flushing time. When applied to liquids, it is for also known as the hydraulic retention time HRT, hydraulic residence time or hydraulic detention time. In the field of chemical engineering this is also known as space time.

Note that the residence time of a specific compound in a mixture equals the turnover time that of the compound, as living as that of the mixture only whether the compound doesn't take factor in any chemical reaction otherwise its flow isn't conservative and its concentration is uniform.

Although the equivalence between the residence time and the ratio doesn't hold whether the flow isn't stationary or it isn't conservative, it does hold on average if the flow isand conservative on average, and non necessarily at any instant. Under such(a) conditions, which are common in Little's Law.