Experimental Investigation On The Microbial Fouling Characteristics And Heat Transfer Enhancement Of The Seawater Plate Heat Exchanger

Biofouling is a common phenomenon in heat transfer equipment. Adhesion ofmarine organisms, low flow rates and other factors directly affects the seawater plateheat exchanger effectiveness. It makes the thermal resistance of the device to increaseand the efficiency to reduce. This paper uses sulfate reducing bacteria which has apredominant role in the heat transfer equipment dirt as experimental strains to studythe microbial fouling characteristics of the seawater plate heat exchanger.Experimental investigation is done to explore the mechanical descaling coupled withboundary reconstruction.This is a new method of the heat transfer enhancement.Themain achievements of the dissertation are as follows:Firstly,experimental facility of the seawater plate heat exchanger was designedand used to investigate the microbial fouling characteristics. Sulfate reducing bacteria(SRB) are isolated by enrichment culture and attached to the seawater plate heatexchanger. Scanning electron microscopy and thermal resistance test bench are usedto do the experimental study on the formation, growth and heat transfer characteristicsof adherent fouling layer under different velocity. The results shows that the formationof microbial fouling is the result of combined action of many factors and the featuresand characteristics of the formation of fouling are different in different periods.Induction period exists when SRB is attached to plate heat exchanger.Spectralanalysis shows the main elements were C, H, O and Ca. The microbial fouling iscomposed of various organic matter and suspended particles.Secondly, according to the principle of plate heat exchanger,experimental facilityof the seawater plate heat exchanger is designed and used to add cleaning device forprepare.The comparative experiments of fouling resistance in the low flow rates underocean current environment are done. Experimental device is uses to measure the thermal conductivity of the microbial fouling.The results shows the foulingresistance conforms to the gradual fouling growth model. The fouling thermalresistance increases with the increase of flow velocity under low flow rates in lessthan1m/s.Finally, based on the original experimental system,mechanical descaling methodis used to achieve cleaning the fouling and remodeling boundary layers to enhanceheat transfer. Experimental studies are done on the effect of cleaning the fouling withusing brush and spicule means.Experimental results show spicule means arebetter.Cleaning the fouling and heat transfer enhancement can be achieved.The bestreconstruction period is2s.