Non-Uniformities in Heat Exchangers: A Two-Decade Review of Causes, Effects, and Mitigation Strategies

Shehryar Ishaque, Naveed Ullah, Qazi Shahzad Ali, Naveed Ullah, Sanghun Choi and Man-Hoe Kim ()
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Shehryar Ishaque: Institute of Engineering Design & Technology (IEDT), Kyungpook National University, Daegu 41566, Republic of Korea
Naveed Ullah: School of Mechanical Engineering, College of Engineering, Kyungpook National University, Daegu 41566, Republic of Korea
Qazi Shahzad Ali: Institute of Engineering Design & Technology (IEDT), Kyungpook National University, Daegu 41566, Republic of Korea
Naveed Ullah: Institute of Engineering Design & Technology (IEDT), Kyungpook National University, Daegu 41566, Republic of Korea
Sanghun Choi: Institute of Engineering Design & Technology (IEDT), Kyungpook National University, Daegu 41566, Republic of Korea
Man-Hoe Kim: Institute of Engineering Design & Technology (IEDT), Kyungpook National University, Daegu 41566, Republic of Korea

Energies, 2025, vol. 18, issue 11, 1-26

Abstract: While extensive research has focused on improving the efficiency and performance of heat exchangers (HXs), identifying the underlying causes of performance degradation remains equally important. Flow and temperature non-uniformities are among the most critical factors affecting performance, often reducing thermo-hydraulic efficiency by approximately 5–10%. These non-uniformities commonly manifest as thermal inconsistencies, airflow maldistribution, and uneven refrigerant distribution. Researchers have observed a notable performance degradation—up to 27%—due to flow maldistribution. Therefore, a clear understanding of their causes and effects is essential for developing effective mitigation strategies to enhance system performance. Despite the notable progress in this area, few studies have systematically classified the dominant non-uniformities associated with specific HX types. This article presents a two-decade review of the causes, impacts, and mitigation approaches related to non-uniformities across different HX configurations. The primary objective is to identify the most critical form of non-uniformity affecting performance in each category. This review specifically examines plate heat exchangers (PHXs), finned and tube heat exchangers (FTHXs), microchannel heat exchangers (MCHXs), and printed circuit heat exchangers (PCHXs). It also discusses mathematical models designed to account for non-uniformities in HXs. This article concludes by identifying key research gaps and outlining future directions to support the development of more reliable and energy-efficient HXs.

Keywords: temperature non-uniformity; flow maldistribution; refrigerant non-uniformity; performance deterioration (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2025
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