Experimental study on long-term fouling of enhanced tubes: Effect of water quality

In order to investigate the impact of water quality on fouling process of enhanced tubes, two continuous fouling tests on eight enhanced tubes (with different internal and external tube geometries) and one plain tube (with a plain inside surface and an enhanced outside surface) were carried out in duration of 98 days, using cooling water with medium and low fouling potential respectively at a water velocity of ∼1.6 m/s. Compared with the medium fouling potential water, the introduction period of fouling on a plain tube in low fouling potential water test was much longer than enhanced tubes. Test results suggested that the influence of water quality on fouling development was much larger than geometry of heat transfer tubes when the water quality changed from low to medium fouling potential. For one heat transfer tube, the asymptotic fouling resistance was continuously increasing with the increase of fouling potential of water. In this study the length index ((Formula presented.)) determined by the geometry of enhanced tube was introduced to improve the accuracy of previous fouling model. Finally, an improved fouling prediction model considering the effect of water quality was developed, which had a maximum error of 22.94%.