Experimental investigation on heat transfer performance of drain water heat recovery heat exchangers

Easwaran N. Krishnan; M. Muneeshwaran; Joseph Rendall; Jamieson Brechtl; Kashif Nawaz

doi:10.1016/j.enbuild.2025.116213

Experimental investigation on heat transfer performance of drain water heat recovery heat exchangers

Easwaran N. Krishnan, M. Muneeshwaran, Joseph Rendall, Jamieson Brechtl, Kashif Nawaz

Research output: Contribution to journal › Article › peer-review

1 Scopus citations

Abstract

Water heating accounts for 18 % of residential energy consumption, and a substantial portion of this energy can be recovered through drain water heat recovery systems. This paper investigates the heat transfer performance of drain water heat recovery heat exchangers. Two heat exchanger configurations were studied: vertical (gravity film exchanger) and horizontal. The heat recovery performance of the exchangers was quantified using sensible effectiveness and characteristic curves following the ε-NTU approach. Depending on the flow conditions, heat exchangers with a vertical configuration offered higher heat transfer effectiveness compared with the horizontal configuration under similar operating conditions. Furthermore, the results showed that properly designed and sized heat exchangers can effectively recover considerable amounts of waste heat from drains, depending on flow rates. Additionally, in the vertical heat exchanger configuration, low flow rates result in partially wet conditions, resulting in lower heat transfer effectiveness. Therefore, two distributor configurations are proposed to improve the heat transfer performance of vertically configured heat exchangers at low flow rates. The proposed distributor configurations and data presented in this paper will be useful in the design and development of drain water heat recovery systems in building applications.

Original language	English
Article number	116213
Journal	Energy and Buildings
Volume	346
DOIs	https://doi.org/10.1016/j.enbuild.2025.116213
State	Published - Nov 1 2025

Funding

Notice: This manuscript has been authored by UT-Battelle, LLC, under contract DE-AC05-00OR22725 with the US Department of Energy (DOE). The US government retains and the publisher, by accepting the article for publication, acknowledges that the US government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this manuscript, or allow others to do so, for US government purposes. DOE will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan (https://www.energy.gov/doe-public-access-plan). This work was sponsored by the US Department of Energy ’s Building Technologies Office under Contract No. DE-AC05-00OR22725 with UT Battelle , LLC. The authors would like to acknowledge Dr. Payam Delgoshaei, Technology Manager of HVAC&R, Water Heating, and Appliance, US Department of Energy Building Technologies Office . The authors also would like to thank Brian Kolar, James Manley, and Michael Day for technical support. This work was sponsored by the US Department of Energy's Building Technologies Office under Contract No. DE-AC05-00OR22725 with UT Battelle, LLC. The authors would like to acknowledge Dr. Payam Delgoshaei, Technology Manager of HVAC&R, Water Heating, and Appliance, US Department of Energy Building Technologies Office. The authors also would like to thank Brian Kolar, James Manley, and Michael Day for technical support.

Keywords

Drain water heat recovery
Effectiveness
Energy recovery
Gravity film exchangers
Heat exchangers

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10.1016/j.enbuild.2025.116213

Cite this

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title = "Experimental investigation on heat transfer performance of drain water heat recovery heat exchangers",

abstract = "Water heating accounts for 18 \% of residential energy consumption, and a substantial portion of this energy can be recovered through drain water heat recovery systems. This paper investigates the heat transfer performance of drain water heat recovery heat exchangers. Two heat exchanger configurations were studied: vertical (gravity film exchanger) and horizontal. The heat recovery performance of the exchangers was quantified using sensible effectiveness and characteristic curves following the ε-NTU approach. Depending on the flow conditions, heat exchangers with a vertical configuration offered higher heat transfer effectiveness compared with the horizontal configuration under similar operating conditions. Furthermore, the results showed that properly designed and sized heat exchangers can effectively recover considerable amounts of waste heat from drains, depending on flow rates. Additionally, in the vertical heat exchanger configuration, low flow rates result in partially wet conditions, resulting in lower heat transfer effectiveness. Therefore, two distributor configurations are proposed to improve the heat transfer performance of vertically configured heat exchangers at low flow rates. The proposed distributor configurations and data presented in this paper will be useful in the design and development of drain water heat recovery systems in building applications.",

keywords = "Drain water heat recovery, Effectiveness, Energy recovery, Gravity film exchangers, Heat exchangers",

author = "Krishnan, \{Easwaran N.\} and M. Muneeshwaran and Joseph Rendall and Jamieson Brechtl and Kashif Nawaz",

note = "Publisher Copyright: {\textcopyright} 2025 Elsevier B.V.",

year = "2025",

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doi = "10.1016/j.enbuild.2025.116213",

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AU - Krishnan, Easwaran N.

AU - Muneeshwaran, M.

AU - Rendall, Joseph

AU - Brechtl, Jamieson

AU - Nawaz, Kashif

PY - 2025/11/1

Y1 - 2025/11/1

N2 - Water heating accounts for 18 % of residential energy consumption, and a substantial portion of this energy can be recovered through drain water heat recovery systems. This paper investigates the heat transfer performance of drain water heat recovery heat exchangers. Two heat exchanger configurations were studied: vertical (gravity film exchanger) and horizontal. The heat recovery performance of the exchangers was quantified using sensible effectiveness and characteristic curves following the ε-NTU approach. Depending on the flow conditions, heat exchangers with a vertical configuration offered higher heat transfer effectiveness compared with the horizontal configuration under similar operating conditions. Furthermore, the results showed that properly designed and sized heat exchangers can effectively recover considerable amounts of waste heat from drains, depending on flow rates. Additionally, in the vertical heat exchanger configuration, low flow rates result in partially wet conditions, resulting in lower heat transfer effectiveness. Therefore, two distributor configurations are proposed to improve the heat transfer performance of vertically configured heat exchangers at low flow rates. The proposed distributor configurations and data presented in this paper will be useful in the design and development of drain water heat recovery systems in building applications.

AB - Water heating accounts for 18 % of residential energy consumption, and a substantial portion of this energy can be recovered through drain water heat recovery systems. This paper investigates the heat transfer performance of drain water heat recovery heat exchangers. Two heat exchanger configurations were studied: vertical (gravity film exchanger) and horizontal. The heat recovery performance of the exchangers was quantified using sensible effectiveness and characteristic curves following the ε-NTU approach. Depending on the flow conditions, heat exchangers with a vertical configuration offered higher heat transfer effectiveness compared with the horizontal configuration under similar operating conditions. Furthermore, the results showed that properly designed and sized heat exchangers can effectively recover considerable amounts of waste heat from drains, depending on flow rates. Additionally, in the vertical heat exchanger configuration, low flow rates result in partially wet conditions, resulting in lower heat transfer effectiveness. Therefore, two distributor configurations are proposed to improve the heat transfer performance of vertically configured heat exchangers at low flow rates. The proposed distributor configurations and data presented in this paper will be useful in the design and development of drain water heat recovery systems in building applications.

KW - Drain water heat recovery

KW - Effectiveness

KW - Energy recovery

KW - Gravity film exchangers

KW - Heat exchangers

UR - https://www.scopus.com/pages/publications/105012399679

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VL - 346

JO - Energy and Buildings

JF - Energy and Buildings

M1 - 116213

ER -

Experimental investigation on heat transfer performance of drain water heat recovery heat exchangers

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