Correlation analysis between microbial fouling resistance, flow rate and water quality parameters

Fouling reduces the heat transfer and increases the heat loss of the process units such as heat exchangers. Due to fouling, the costs of operation and maintenance are increasing significantly. In addition, heat transfer equipment is often overworked because of the expected fouling. Therefore, fouling is a major element in design and operation of heat exchangers. Through the grey correlation analysis, the relationship among microbial fouling thermal resistance, flow rate and water quality parameters are investigated. The fouling experiments are finished in a laboratory scale set-up of a tubular type heat exchangers. The fouling thermal resistance under different flow rates and different water quality parameters are obtained. And the changes of water quality parameters under different flow rates are also obtained. The results are analyzed. The analysis shows that the fouling resistance decreases with the increase of flow velocity under the same conditions of temperature and concentration, and it has different influences on thermal resistance when water quality parameters change in different periods. With the change of water quality parameters, the fouling resistance of slime forming bacteria gradually stabilized after 62 h. The correlation analysis of the three shows that the change of flow rate will affect the water quality parameters, and then affect the fouling resistance. The OD, pH and the conductivity are found to be related to changes of velocity. The strongest correlation is 0.6273 between conductivity and flow rate. The strongest correlation is 0.8755 between OD and fouling resistance. When the velocity increases, pH change rate increase 20%, but the changes rate in fouling resistance is slower than other two factors. It is necessary to analyze and study fouling from the perspective of heat and mass transfer.