paraffin wax deposition and fouling

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the large fouling studies aparatus. Some indication wan, however,
found of more wax depositing in the first hour than at subsequent
times, particularly at low Reynolds numbers as in run A1O—4
shown
in figure 4.6.2.2.
7.7 Other Considerations
At turbulent flow conditions the shearing stresses are probably
greater than those existing at the standard pour point condition.
As was shown in section 2.2.4, increased shear stresses can oreak
down the structure of solidified hydrocarbon solutions such that
they show Newtonian behaviour.
For the experimental conditions
existing in the present work a particle suspension
there fore
probably exist at temperatures below the standard pour point.
As deposition progresses the resulting increase in shear
forces will mean that wax particles are more effectively moved
across the shear fields away from the tube surface.
hen paraffir. wax derosits it will give u its heat of fusion
(see Appendix 2) and thereby raise the temperature of the depcsi—
tion site.
The effect of roughness on paraffin deposition would be to
increase the shear stresses at the wall and hence decrease the
deposition.
Fewer particles would have the cohesive properties
for deposition.
increased shear fields in boundary layers, heat of fusicn and
roughness will therefore all contribute to lower deposition rates.
7.8 :echanism of Deosition
A
derosition and fling mechar.ism must explain the buZdup
of deposits and the final asymrtotice values reached before break
down. : the foulinç stuc.es (Section it was found that a;
syr:rtotic conditions the aeos1D1Dn ‘as less at high
and ten era;ures, bu; greater a; high concn;ra;ions.
Eowrn;es
:n the