Investigating the Impact of Plumbing Configuration on Energy Savings for Falling-Film Drain Water Heat Recovery Systems

Ramin Manouchehri,Michael R Collins

doi:10.3390/en15031141

Abstract

Falling-film drain water heat recovery (DWHR) systems are heat exchangers utilized in residential buildings for recovering energy from greywater. A recent publication by the authors contained a validated model that can be used to predict the performance of DWHR heat exchangers under variable flowrates and temperatures, and this work shows the implementation of the model into Transient System Simulation Tool (TRNSYS) software to perform energy simulations. This work aims to show the different plumbing configurations in which DWHR heat exchangers could be installed, and to simulate their performance under various conditions. The results show that plumbing configuration has a significant impact on energy savings expected from DWHR heat exchangers, and maximum savings are achieved in equal-flow configuration. However, other plumbing configurations provide significant savings, and the mains temperature could dictate which configuration provides higher energy savings.

Highlights

Since 2000, water heating has consistently been the second largest contributor to the total energy consumption in residential buildings in Canada
Domestic water heating accounted for 14.8% of the total energy consumption in the residential sector in Europe [2]
A significant amount of energy that is consumed towards domestic water heating is not fully utilized during showers, which presents an opportunity to use heat exchangers to recover thermal energy from greywater in residential buildings

Summary

Introduction

Since 2000, water heating has consistently been the second largest contributor to the total energy consumption in residential buildings in Canada. In the year 2018, 281.3PJ of energy consumed in the Canadian residential sector was attributed to water heating; this represents 17.4% of the total energy consumption and 19.2% of greenhouse gas emissions [1]. Domestic water heating accounted for 14.8% of the total energy consumption in the residential sector in Europe [2]. According to a recent study by Chen et al, an estimated 34.8% of total hot water used in residential buildings within the United States is attributed to showers [3]. A significant amount of energy that is consumed towards domestic water heating is not fully utilized during showers, which presents an opportunity to use heat exchangers to recover thermal energy from greywater in residential buildings

Objectives

Methods

Results