paraffin wax deposition and fouling

experienced in other runs by Walker. The standard deviation from
temperature. See section 7.4 for details. The magnitude of the
waiier(1) was at a high flowrate and concentration but a low
tration but decreased with flowrate and temperature. Run F38 by
7.6 Random Fluctuations
—o —
The magnitude of the random fluctuations in the overall heat
random fluctuations was therefore substantial, about double those
:ndeed, the tube surfaces were observed to be covered with patches.
merefore give rise to random fluctuations.
establish some average cverage of the tube surface by deposits.
per cent from the fouling resistance. The maximum fluctuation in
using the Dittus Boelter equation to evaluate the film resistances.
fouling resistance for run F38 was R = 1.7483 (kW/m
2 °c)’ when
the average overall heat transfer resistance R = 2.398? (kW/m
was calculated as 0.1585 (kW/m
The standard deviation therefore, represents a deviation of 9.1
run F38 from the average overall resistance was found to be
0.3100 (kW/m
The calculations show that the amount of wax required to break
down or build up, giving rise to the fluctuations, is typically
10—20 per cent of the average wax deposited. It is therefore
The rap rtia_ 3uaup 01 OCO51t5 was not aetectae or.
ny additional buildup or breakdown of paraffin wax deposits oula
surface. These deposits probably broke down in a short time to
studies, a deposit was rapidly laid down over most of the cola tube
typically only by 2 standard deviations.
standard deviations going from minimum to maximum, but more
resistance. The fouling resistance therefore changes by about 4
2 oc)_l, representing 17.7 per cent of the fouling
2 oc)l As shown in section 7. the
2 °C)
anticipated that, at the start of an experiment in the fouling
transfer resistance in the fouling studies, increased with concen