Determination of the optimal heat exchanger configuration for wastewater heat recovery

Abstract

The work aims to increase the efficiency of the hot water supply system based on local recovery of the heat of wastewater generated in the shower room for preheating cold water. The work uses mathematical modeling of the thermal operation of the heat exchanger under study. Physical modeling of the heat exchange process between media flows in a heat exchanger was carried out (experimental test). Temperatures of media flows were measured. The temperature distribution inside media flows was compared experimentally with data obtained analytically. In conclusion, an analysis and generalization of the results obtained is made. The result of the research was a designed recovery heat exchanger. Data were obtained on the thermal inertia of the device, i.e., about the required time for the device to achieve a stationary thermal regime from the moment it is turned on. Data were obtained on the potential energy effect from introducing a recovery heat exchanger, taking into account its thermal inertia. The number of showers required to pay off the heat exchanger was calculated. Data were obtained on the influence of changes in the geometric and operating parameters of the heat exchanger on the efficiency of wastewater thermal energy utilization. A methodology for designing a heat exchanger for specific operating conditions was developed. The developed method for designing a recovery heat exchanger allows one to determine the optimal configuration of the device under particular operating conditions and mode of use of the heat exchanger, taking into account its thermal inertia. It is planned to continue the work by assessing the energy and economic effect of using local wastewater heat recovery within the heat supply system of a separate settlement/region.