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Thesis (Ph. D.)--Oregon State University, 1990. / Typescript (photocopy). Includes bibliography (leaves 230-239). Also available via the World Wide Web.

Chemical reaction fouling is one of several categories of fouling of heat exchangers. It is encountered mostly in petroleum, petrochemical, and food processing industries, where it results in severe economic penalties. Olefins have been associated with fouling during heating of organic mixtures, and gum formation during storage and use of hydrocarbon fuels. In this work, thermal fouling studies are reported for a number of olefins, present at 10 % wt. in kerosene, undergoing sensible heating in the liquid phase at relatively high heat fluxes. Experimental work was done on an available fouling rig consisting of an annular probe and a coiled wire probe mounted in parallel. The annular probe with its heated central core operated in turbulent flow whilst the coiled wire, with flow normal to it, was in the laminar flow regime. Runs were conducted both under oxygenated (air-saturated) and deoxygenated conditions. The range of bulk temperatures was from 70 - 85 ℃, the initial wall temperatures were 180 - 205 °C, with a system pressure of 410 kPa (abs.). The range of heat fluxes was 150 - 350 kW/m². Only minor differences were noted between the extent or rate of fouling on the two different probes. Runs at heat fluxes below 180 kW/m² and bulk temperatures below 80 °C generally showed no measurable fouling with any of the olefins tested. Linear and falling rate fouling curves were observed at more severe conditions over 45 hours of typical runs. Under air saturated conditions, straight chain terminal olefins of C₈ - C₉ showed little or no measurable fouling. The longer chain length hexadecane-1, showed a significant increase in fouling. Moderate fouling was observed for 4-vinylcyclohexene. The cyclic olefins, dicyclopentadiene and indene, yielded the greatest R[formula omitted] values, being about 30 - 50 times those of the straight chain terminal olefins. Under deoxygenated conditions, typical R[formula omitted] values were a factor of about 30 below the corresponding values for air saturated conditions. R[formula omitted] generally increased with increasing heat flux. Where the antioxidant initially present in the olefin was not removed before use, very little fouling occurred. The effects of deoxygenation, heat flux and species effects are discussed and a probable fouling mechanism involving formation of polymeric peroxides by autoxidation of the olefins suggested. The fouling rates over the linear portions of the fouling curves have been calculated and the deposit thermal conductivity based on the maximum fouling resistance and deposit thickness have been estimated. Analyses of selected deposits have been presented and compared with both theoretical calculations for the expected polymeric peroxides and values in the literature. / Applied Science, Faculty of / Chemical and Biological Engineering, Department of / Graduate

The fouling characteristics of a desalted crude oil were investigated in a systematic investigation. There are two main parts in this study, the dry bulk tests (dehydrated crude oil) and the wet bulk tests (to which desalter brine was added). Three barrels of desalted crude oil provided by Amoco Oil Company were studied. For the dry bulk tests, no brine was added to the crude oil. The effects of fluid velocity and surface temperature on fouling were investigated. The higher the surface temperature the greater the fouling was observed. Fouling decreased with an increase of fluid velocity. Fluid velocity had a stronger effect on fouling at low surface temperatures than at high surface temperatures. It was also observed that the fouling behavior of crude oil depended on small difference in composition. The threshold surface temperatures for the initiation of fouling were 400-450 °F (3.0 ft/sec), 525-550 °F (5.5 ft/sec), 550-600 °F (8.0 ft/sec) and about 600 °F (10.0 ft/sec) for Barrel No. 2 and Barrel No. 3. For Barrel No. 1 however, the threshold surface temperatures were about 550 °F (3.0 ft/sec) and 600 °F (5.5 ft/sec). For the wet bulk tests, a certain amount desalter brine (weight percentage = 0.8%) was added to the crude oil for each run. The effects of fluid velocity, surface temperature and the presence of brine on fouling were investigated. Higher surface temperature enhanced fouling considerably. Fouling was reduced as fluid velocity was increased. It was shown that brine had a strong effect on fouling. No fouling occurred for velocities of 5.5 and 8.0 ft/sec at a surface temperature of 350 °F which was a condition for which an aqueous phase was present and the salt remained in solution. Significant fouling occurred for velocities of 5.5 and 8.0 ft/sec at a surface temperature operated at a low 400 °F (Tb = 300 °F) which was a condition for which the aqueous phase at the heat transfer surface was dissolved or boiled to extinction and the salt was deposited on the heat transfer surface. / Graduation date: 1991

Thesis (M.S.)--Mississippi State University. Department of Mechanical Engineering. / Title from title screen. Includes bibliographical references.

yes / Fouling in heat exchangers (HE) is a major problem in industry and accurate prediction of the onset or degree of fouling would be of a huge benefit to the operators. Modelling of the fouling phenomenon however, remains a challenging field of study. Cleaning of heat exchangers, coulpled with the down time, is a financial burden and for industrialized nations and costs can reach to almost 0.25 % of the country’s Gross National Product (Pritchard, 1988).This work presents the development of a dynamic fouling model based on experimental data collected using a laboratory concentric tube heat exchanger handling a saline system. Heat transfer coefficients were obtained from first principles as well as from either the Sieder-Tate or Petukhov-Kirillov correlations modified by Gnielinski depending on the flow regime. The outlet temperatures were calculated using the Effectiveness-NTU method. The dynamic fouling factor was based on the Kern and Seaton fouling model and validation was completed by comparing the experimental outlet temperatures with those predicted by the model. The model predicts the outlet temperatures with an average discrepancy of 1.6 °C and 0.4 °C for the cold and hot streams respectively.

published_or_final_version / Mechanical Engineering / Master / Master of Philosophy