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The efficiency, availability, and reliability of thermal management for various engineering applications present a crucial challenge facing the designers and engineers. The rapid development and sophisticated technological advancement require innovative devices possessing high operating capacities that are launched into the prodigious growing markets in all engineering sectors. As a result of pronounced advancements, the jet impingement required to transfer high heat fluxes with a target surface becomes one of the essential priorities for researchers. The intensification of jet impingement can be achieved with different techniques such as passive self-exciting jets, active exciting jets, and hybrid exciting jets. The active methods of self-exciting jets include annular, swirling, and sweeping jets, while the active ones contain pulsed and synthetic jets. In the current study, the heat transfer characteristics and the fluid flow behavior of jet impingement with recent modifications of jets are reviewed comprehensively. As well, the critical methods of passive and active exciting jets considering the jet geometrical and operating parameters are introduced. Moreover, the physical phenomena for each technique in comparison to the conventional circular straight jet as well as the published empirical correlations as available, are studied. The present work reviews the published numerical and experimental investigations considering the different modified jets and its application with various installation geometries that provide a higher efficiency with the augmentation of heat transfer rate. The jet excitation causes topological metamorphosis of flow and hence has a remarkable effect on the intensification of heat transfer. • The intensification of jet impingement can be achieved with different techniques. • Active, passive, and hybrid methods of jet excitation were reviewed. • Heat transfer and fluid flow characteristics of each exciting jet were studied. • The geometrical and operating parameters of each exciting jet were introduced. • Jet excitation increased turbulence intensity and hence intensified heat transfer. [ABSTRACT FROM AUTHOR]

The three-fluid heat exchanger is a multi-stream heat exchanger that provides three streams at different temperatures for certain usage objectives. Recently, optimizing heat exchangers generally and three-fluid heat exchangers especially have received great attention in the energy field. The current study objective is to get the optimal mass flow rate of the three streams to minimize the entropy generation number and maximize effectiveness. Optimization is performed on the inserted coiled tube type for 24 cases with different usage objectives and different mass flow rate constraints. The optimization is done using an analytical approach for the temperature profiles and a regressed model for the overall heat transfer coefficients. Single-objective and multi-objective genetic algorithms are the optimization algorithms. The result shows that cooling the hot fluid is the most efficient usage objective; however, heating the intermediate-temperature fluid is the less efficient usage objective. Also, the study shows that the entropy generation number is dependent on the mass flow rate constraint. The maximum effectiveness of 0.693 occurs when the usage objective is cooling the hot fluid. In this case, the mass flow rate of the cold and the intermediate-temperature fluids are maxima while the mass flow rate of the hot fluid is minimum. The minimum entropy generation number 0.0486 occurs when the mass flow rate of the cold fluid is maximum while the mass flow rate of the hot fluid and intermediate-temperature fluid are minimal. [Display omitted] • Heat transfer of a three-fluid heat exchanger is investigated. • A model for optimizing the inserted coiled tube three-fluid heat exchanger is developed. • The maximum errors for the regression models of heat transfer coefficients are 1.72% and 2.81%. • The maximum effectiveness reached about 0.69323. [ABSTRACT FROM AUTHOR]