Effective removal of excess heat from electronics equipment is the key to its intended functionality. A DARPA hard problem is proposed in MACE (Microtechnologies for Air-Cooled Heat Exchangers) program that posed challenges to reduce the heat sink size four-fold while using only 50% of the current power budget. While numerous heat removal techniques have been proposed over the last several decades, Synthetic Jet Actuator (SJA) is one of the leading candidates to create a game-changing cooling performance. This is due to its inherent advantages such as size, low power consumption, ease of use, and affordability. This review paper looks at different actuation methods (electromagnetic, piston cylinder, piezoelectric, etc.) to generate synthetic jet cooling. The performances of these approaches vary and need a procedure to unify the predictive capability. The performances are evaluated based on actuation (stroke-length, operating frequency, and jet-to-heater spacing) and geometric parameters (shape and size of the cavity and the orifice). The flow characteristics and jet formation criterion are also discussed methods and a critical commentary is added to normalize previous findings. Available correlations for predicting Nu numbers are evaluated and summarized through data sets for a possible unification. Finally, an empirical correlation is proposed based on available data using non-linear regression via computational tools. To conclude, the challenges and research gaps are enumerated covering the fundamental and applied aspects of those jets for the implementation in electronics thermal management.

Drilling is an important machining process in various manufacturing industries. High-quality holes are possible with the proper selection of tools and cutting parameters. This study investigates the effect of spindle speed, feed rate, and drill diameter on the generated thrust force, the formation of chips, post-machining tool condition, and hole quality. The hole surface defects and the top and bottom edge conditions were also investigated using scan electron microscopy. The drilling tests were carried out on AA2024-T3 alloy under a dry drilling environment using 6 and 10 mm uncoated carbide tools. Analysis of Variance was employed to further evaluate the influence of the input parameters on the analysed outputs. The results show that the thrust force was highly influenced by feed rate and drill size. The high spindle speed resulted in higher surface roughness, while the increase in the feed rate produced more burrs around the edges of the holes. Additionally, the burrs formed at the exit side of holes were larger than those formed at the entry side. The high drill size resulted in greater chip thickness and an increased built-up edge on the cutting tools.

As electronic devices are becoming more compact each day, the more effective and efficient active cooling technologies are needed. Microfluidic devices, such as synthetic jets, serve as a potential candidate to fulfill the thermal management needs of the next generation electronics. An experimental and computational study has been performed for circular central-orifice synthetic jets. First, a series of experiments was performed to quantify the actuator deflection, air velocity, heat transfer augmentation, and power consumption for central-orifice synthetic jets. Later, a computational study was performed utilizing the same boundary conditions in order to predict the deflection of the diaphragm. The experiments were conducted on three different types of synthetic jets, namely, low-, medium-, and high-frequency synthetic jets. Although a number of correlations were proposed for the prediction of Nu number for slot synthetic jets, no correlation was found to predict the average Nu number for a synthetic jet with a round orifice. Therefore, two correlations were developed, one for low- and medium-frequency synthetic jets and the other for high-frequency synthetic jets to predict the heat transfer coefficient as a function of the geometry, position, and operating condition for impinging flows. The proposed correlations are able to predict the impingement heat transfer of a synthetic jet with an accuracy of ±25% for a wide range of operating conditions and geometrical variables. Normalized frequency had the minimum impact on the average Nu number of a high-frequency synthetic jet compared with dimensionless distance, both have moderate impact on low- and medium-frequency jets.