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.

The airborne wind turbine (AWT) employs a flying energy conversion to harvest the stronger winds blowing at higher altitudes. This study presents an aeroelastic evaluation of AWT which carries a flying rotor installed inside a buoyant shell. A considerable aerodynamic impact on the structural integrity of the full-scale system is modeled using fluid–structure interaction (FSI) approach. Both the fluid model and structure model are formulated separately and validated by a series of benchmark numerical data. To analyze the structural aeroelasticity, the aerodynamic loads from the fully-resolved computational model are coupled using one-way FSI to the structural model of the blade and shell to perform the non-linear static analysis. For detailed investigation, various wind loads from the bare and shell rotor configurations are imposed on the flexible structure. The generated torque, aerodynamic loads, tip deflection, stress estimation and operational stability of the proposed energy system are computed. The nonlinear aeroelastic characteristics in each case are found to be within the chosen design criteria according to material, operational speed and structural limits. Most importantly, the significant power gain justifies the structural response of the blade to withstand the shell induced loads at rated conditions in the shell configuration.