2 research outputs found
Design construction and testing of a heat loop for study of fouling and its interrelationship to corrosion in heat exchanger tubes
A heat loop suitable for the study of thermal fouling and its
relationship to corrosion processes was designed, constructed and
tested. The design adopted was an improvement over those used by
such investigators as Hopkins and the Heat Transfer Research Institute
in that very low levels of fouling could be detected accurately, the
heat transfer surface could be readily removed for examination and
the chemistry of the environment could be carefully monitored and
controlled. In addition, an indirect method of electrical heating of
the heat transfer surface was employed to eliminate magnetic and
electric effects which result when direct resistance heating is
employed to a test section.
The testing of the loop was done using a 316 stainless steel
test section and a suspension of ferric oxide and water in an attempt
to duplicate the results obtained by Hopkins. Two types of thermal
·fouling resistance versus time curves were obtained .
(i) Asymptotic type fouling curve, similar to the fouling behaviour
described by Kern and Seaton and other investigators, was the
most frequent type of fouling curve obtained. Thermal fouling
occurred at a steadily decreasing rate before reaching a final
asymptotic value.
(ii) If an asymptotically fouled tube was cooled with rapid cir-
·culation for periods up to eight hours at zero heat flux, and heating
restarted, fouling recommenced at a high linear rate. The fouling results obtained were observed to be similar and
1n agreement with the fouling behaviour reported previously by Hopkins
and it was possible to duplicate quite closely the previous results .
This supports the contention of Hopkins that the fouling results
obtained were due to a crevice corrosion process and not an artifact
of that heat loop which might have caused electrical and magnetic
effects influencing the fouling.
The effects of Reynolds number and heat flux on the asymptotic
fouling resistance have been determined. A single experiment to study
the effect of oxygen concentration has been carried out.
The ferric oxide concentration for most of the fouling trials
was standardized at 2400 ppM and the range of Reynolds number and
heat flux for the study was 11000-29500 and 89-121 KW/M², respectively