Optimierung der gebäudeinternen Abwasserwärmerückgewinnung auf der Grundlage experimenteller Untersuchungen am Versuchsstand und simulativen Systemvergleichen

Vogt, Alexander; van Treeck, Christoph Alban (Thesis advisor); Brunk, Marten F. (Thesis advisor); Stergiaropoulos, Konstantinos (Thesis advisor)

Aachen (2019, 2020)
Dissertation / PhD Thesis

Dissertation, Rheinisch-Westfälische Technische Hochschule Aachen, 2019

Abstract

In order to reduce the primary energy requirement of buildings, the present work is devoted to the investigation of possibilities for heating drinking water utilizing heat pumps in conjunction with waste water as a source of energy. For this, various system configurations are proposed and investigated simulatively. Based on this, an energetic and economic comparison to conventional systems is carried out. For the simulation of systems with waste water recovery, the behavior of waste water heat exchangers in relation to the heat transfer-diminishing biofilm formed has not been adequately investigated. A test stand was built in order to quantitatively measure the behavior of thermal resistances resulting from biofouling on waste water heat exchangers over the course of time. It could be shown, that employing a fluidic cleaning process can reduce the thermal resistance of the biofilm. Completely cleaning the biofilm is only possible using manual procedures. Based on the measurement results, an optimization of the heat exchanger with regard to the heat exchanger surface and the cleaning cycle was carried out simulatively. It can be seen that cleaning the heat exchanger does not result in significant energy savings. Instead, the heat exchanger should be designed efficiently larger. Based on further simulations, a capital value-optimized dimensioning of the wastewater heat exchanger was developed. Based on this, there is a simulative comparison of the system configurations. The simulation results show that by recovering the energy from domestic wastewater by using heat pumps, domestic hot water can be provided in an energy-efficient manner. A further optimization of the domestic hot water supply can be achieved by the arrangement of decentralized micro heat pumps. However, these high potential primary energy savings could not be represented economically over a period of 20 years. In systems that bivalently heat the drinking water, the total cost exceeds the cost of conventional systems slightly. With higher energy price increases, these systems will show significant cost-saving potential in the medium term.

Institutions

• Institute of Energy Efficiency and Sustainable Building [312410]