Residence Time (other)
Residence time is the time that a particle of matter spends in a system. Residence time may also refer to: * Residence time of lake water, the time that water spends in a particular lake * Residence time (statistics) In statistics, the residence time is the average amount of time it takes for a random process to reach a certain boundary value, usually a boundary far from the mean. Definition Suppose is a real, scalar stochastic process with initial value , ...

Residence Time
The residence time of a fluid parcel is the total 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 known as residence time distribution (RTD), or in terms of its average, known as mean residence time. Residence time plays an important role in chemistry and especially in environmental science and pharmacology. Under the name '' lead time'' or ''waiting time'' it plays a central role respectively in supply chain management and queueing theory, where the material that flows is usually discrete instead of continuous. History The concept of residence time originated in models of chemical reactors. The first such model was an ''axial dispersion model'' by Irving Langmuir in 1908. This received little attention for 45 years; other models were developed such as the plug flow reactor model an ...
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Residence Time Of Lake Water
Lake retention time (also called the residence time of lake water, or the water age or flushing time) is a calculated quantity expressing the mean time that water (or some dissolved substance) spends in a particular lake. At its simplest, this figure is the result of dividing the lake volume by the flow in or out of the lake. It roughly expresses the amount of time taken for a substance introduced into a lake to flow out of it again. The retention time is especially important where pollutants are concerned. Global retention time The global retention time for a lake (the overall mean time that water spends in the lake) is calculated by dividing the lake volume by either the mean rate of inflow of all tributaries, or by the mean rate of outflow (ideally including evaporation and seepage). This metric assumes that water in the lake is well-mixed (rather than stratified), so that any portion of the lake water is much like any other. In reality, larger and deeper lakes are general ...
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