Evident difference exists in choosing the value of fouling resistance of cooling water according to different references. The paper presents the study of fouling resistances of cooling water in condenser of chilling water unit. The experiment was carried on three different qualities of cooling water: microorganism -, fine silt and microorganism blending with fine silt in the cooling water respectively . Visualize the fouling on the inner surface of the tube, utilizing the industrial borescope and the CCD camera to transfer the image to the computer. The experimental results showed that the fouling resistance of cooling water which contain the microorganism is about 1 * 10~(-4)～2 * 10~(-4) m~2·°C/W> however, the convective heat transfer was enhanced if there are fine silt in cooling water. The coefficient of heat transfer will increase when increasing the water velocity and the concentration of fine silt in water. In summer, the load of chiller unit reached it's peak load and the temperature of cooling water is the highest, and microorganism in water breed easily and grow quickly, which inevitably result in fouling resistances of cooling water becoming maximum. So research, monitor and controlling of fouling resistances should focus on the cooling water containing microorganism.
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