Reduced fouling of sewage water heat pumps

To promote the use of sewage water as a heat source for heat pump systems, the EBARA Corporation in Hapan have developed solutions to the problems caused by filtration and fouling. An auto-strainer was developed to remove suspended solids in sewage water, along with an automatic cleaning device to prevent fouling inside heat transfer tubes. In addition, a number of materials wer studied in order to establish their suitalbility as heat transfer tubes for heat exchangers. By using the new devices and the results of studies, EBARA have been able to commercialise sewage source heat pump systems. The system described here is installed in a sewage treatment plant in Tokyo. It achieves COPs of 4.65 and 3.59 in the cooling and heating cycles respectively, providing a saving of approximately 30% in the plant's airconditioning running costs.