ISSN Online: 2377-424X
ISBN Print: 978-1-56700-421-2
International Heat Transfer Conference 15
The Applied Condition of Lumped Parameter Method for Finite Mass Transfer Duration
Abstrakt
The lumped parameter method is one of the most convenient ways to address unsteady mass transfer problems.
Similar to heat transfer, the classical applied condition of the lumped method in mass transfer has been obtained
as that the Biot number (Bim/K = hmL/(DK)) is less than 0.1. It should be called out that if the criterion above is
satisfied, the time range within which the lumped parameter method applies is from zero to infinite. However, in
practice, the duration of mass transfer process of interest may be finite, instead of infinite. For example, in most
cases, the indoor residence time of airborne particles is in the order of one hour. The concerned time duration
regarding the mass transfer between particles and gas-phase semivolatile organic compounds is the same as the
residence time of particles. During this finite duration, the condition for the lumped parameter method is unclear.
In this study, the applied condition of the lumped parameter method for finite mass transfer duration is
examined, using mass transfer in a sphere as an example. It has been shown that the applied condition for finite
duration is less strict than Bim/K < 0.1. Empirical correlations to calculate critical Bim/K are obtained. Results indicate that for the unsteady mass transfer process of some SVOCs with small mass diffusivity in airborne
particles, the lumped parameter method applies during the finite residence time of particles. A similar
examination can be conducted for the scenario of mass transfer in plates and cylinders.