Heat Transfer Characteristics of Passive, Active, and Hybrid Impinging Jets: A Review

In engineering applications, there is a need to reform the excitation methods used for jet impingement to achieve simpler and more effective thermal exchange. Jet impingement is a highly effective method for enhancing heat transfer, characterized by its ability to create high heat transfer coefficients. These characteristics make it a preferred method in applications requiring efficient thermal management, such as cooling of electronic components, turbine blade cooling in jet engines, and material processing. However, traditional excitation methods for jet impingement can be complex and challenging to implement. Therefore, there is a growing interest in developing new excitation methods that are simpler and more effective. The methods used can be categorized into three groups, including passive self-excited jets, active excited jets, and hybrid methods. Passive methods, such as annular, swirling, and sweeping jets, utilize the inherent characteristics of jet flow without requiring additional energy consumption. Active systems, on the other hand, involve supplementary devices such as fans or pumps to intensify heat transfer. Examples of active excited jets include synthetic and pulsed jets. Hybrid methods combine two or more methods to further thermal improvement that can reach more than 20%. This paper reviews experimental and numerical hybrid methods to enhance heat transfer to impinged surfaces. Experimental tools, including high-speed imaging, methods, such as Computational Fluid Dynamics (CFD), are reviewed. The efficacy of these methods is evaluated by comparing their performance, highlighting the potential for optimization and innovation in jet impingement heat transfer.