1) The pressure drop coefficient increases with the Reynolds
number but decreases with gas temperatures. When the
gas temperature rises, the optimum inlet velocity grows larger.
A cyclone can be operated at a much higher inlet velocity
under high temperatures.
2) The overall collection efficiencies of a cyclone decrease
with increases in temperature, especially in the relatively
high temperature range where the decrease of the overall
collection efficiency becomes much steeper than in the low
temperature range.
3) The fractional efficiency curve at high temperatures is
hook-shaped. There exists a critical particle size below that
where fractional efficiency increases as the particle size
decreases due to a reduction of the drag coefficient and
enhancement by particle agglomeration. For particles larger
than the critical size the fractional efficiency also decreases
Fig. 12 Comparison between predicted fractional efficiencies by
Shi et al.’s approach and experimental measurements
Fig. 13 Comparison between predicted overall efficiencies by
Shi et al.’s approach and experimental measurements
the extrapolation of this approach to high temperatures without
accounting for both particle agglomeration and the role of
reduction of tangential velocity in particle separation. A further
study is still desired on upgrading this approach to better
predict the effect of temperature on collection efficiencies.
with increases in temperature mainly owing to the increase of
gas viscosity and the decrease of gas tangential velocity.
4) The overall collection efficiency of the cyclone at high
temperatures is fairly well predicted by Shi’s approach,
although the prediction is still not sufficiently precise owing
to the neglect of the effect of temperatures on tangential
velocity and the influence of particle agglomeration. The work is still in progress.