| Summary: | 碩士 === 國立海洋大學 === 水產食品科學研究所 === 83 === This study investigated the residence time distribution of particles in vertical tube flow. Convective mass transfer coefficient at particle-fluid interface was also determined to simulate heat transfer coefficient i the holding tube of aseptic processing systems by analogy theory.
Mass transfer experiment was conducted by injecting sucrose coated particle in suspensio flow. Results showed that particles with shorter residence time have higher mass transfer coefficient. Correlations in dimensionless form for two Reynolds numbers are
Sh=532-323t (1.51<t<1.60)
for Reynolds number 9750, and
Sh=551-333t (1.47<t<1.58)
for Reynolds number 15200.
In a vertical tube arrangement, the residence time of particles was normally distribution. Radial starting position of particle had little effect on particle residence time distribution. For particle concentration ranging from 0 to 0.21, the dimensionless mean of particle residence time increased, while dimensionless standard deviation decreased, with Reynolds number ranging from 6320 to 26100. Both dimensionless mean and standard deviation increased with the particle concentration at constant Reynolds number.
Linear equations correlating Reynolds number (Re), particle concentration(Φ), dimensionless mean (t) and standard deviation (O) of the particle residence time were obtained as following:
t=(3.58-6.98Φ)10-6Re+(0.965+0.873Φ)
for Reynolds number between 6320 and 26100,
O=-(1.11+1.54Φ)10-6Re+(0.0211+0.0394Φ)
for Reynolds number between 6320 and 9750,
O=-(0.0871+7.21Φ)10-7Re+(0.0105+0.0316Φ)
for Reynolds number between 9750 and 26100.
|
|---|
