Fouling of Polymeric Hollow Fiber Heat Exchanger by Wastewater

Warm wastewater can be used as a source of heat for heat pumps in buildings such as gyms, swimming pools, and laundries. Unfortunately, heat exchangers installed in a sewage channel are negatively affected by fouling because deposits on the heat exchange surface create additional resistance to heat transfer and decrease the efficiency of the system. Heat exchangers consisting of polypropylene hollow fibers were prepared and tested to transfer heat from two types of wastewater: from a shower and from laundry. It was found that these devices have high thermal performance (with an overall heat transfer coefficient of up to 2,020 W/m2 K) while working in clean conditions. Fouling tests showed that fouling strongly depends on the type of wastewater. During the experiment with shower wastewater the observed fouling was low because it was associated with the accumulation of a small amount of solid particles (particulate fouling). No significant decrease of overall heat transfer coefficient was observed during the two-week test in this case. The experiment with laundry wastewater showed that fouling was more extensive because it was associated with both types of fouling: particulate fouling and biofouling. The overall heat transfer coefficientwas decreased by two times (from 1747 W/m2 K to 863 W/m2 K) during the 35-day experiment.