Closed Loop Flat Plate Oscillating Heat Pipes: An Overview on the Thermohydraulic Principles, Thermal Performances, and Developing Trends

Thermal management of latest micro- and high-power electronic systems has become a progressively challenging issue due to current trends in miniaturization and increased heat generation. Traditional cooling techniques, such as natural and forced convection, have proven inadequate in addressing the emerging demands within the electronics industry, transportation, and space applications. In these domains, the size, mass, autonomy, high density, and overall reliability of thermal management systems play pivotal roles. Unlike active technologies, heat pipes serve as passive heat transfer devices devoid of moving components, resulting in prominent reliability, albeit constrained by factors like capillarity, viscosity, and gravity. In contrast, the closed loop flat plate oscillating heat pipe (CL-FP-OHP) has recently become a source of increasing interest: first, due to fascination for the complexity of the internal two-phase heat transfer; and secondly, due to emerging applications, which are rapidly increasing the technology readiness level of this heat pipe, for both ground and space environments. Several experimental and theoretical investigations have been carried out on CL-FP-OHP over the past few decades since it was first proposed by Akachi in 1990. Nevertheless, due to the intricate coupling effects of hydrodynamics and thermodynamics, the operational mechanism of CL-FP-OHP remains exceptionally intricate and has yet to be fully elucidated. With high hopes for future applications of CL-FP-OHP, this paper aims to examine the development of CL-FP-OHP by systematically summarizing the most recent findings from both experimental and theoretical studies. Simultaneously, it also highlights some promising and groundbreaking applications of CL-FP-OHP. This paper is anticipated to serve as a fundamental point of reference for future research endeavors.