A. Sagiv et al., EFFECT OF SHERWOOD NUMBER ON CRITICAL CONSTANTS OF DIFFUSION, International journal of heat and mass transfer, 41(12), 1998, pp. 1729-1738
Critical constants of mass diffusion through a membrane were related t
o a critical time, t(c)', which designates the conversion between tran
sient and steady-state conditions of the diffusion process. The critic
al time t(c)', is precisely defined and analytically derived. In their
dimensionless form, these critical constants depend solely on the She
rwood number (Sh). Values of dimensionless critical constants were det
ermined for the whole range of Sherwood numbers. The results are usefu
l in cases where small amounts of diffused mass must be detectable. E.
g.: in production from hazardous materials, in the design and evaluati
on of diffusion experimental processes and devices. The effect of meas
urement errors on the determination of the critical constants is also
analyzed. The main results show that the evaluation of the critical co
nstants is obtained a with minimum errors? when experiments are being
performed under convective boundary conditions (Sh > 100). The results
of this study are applicable to heat transfer problems as well. (C) 1
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