Effect of a narrow channel on heat transfer enhancement of a slot-jet impingement system

摘要

Slot-jet impingement systems are recognized in their ability to control fluid flow for high energy transfer on the target surface. For an energy saving point of view, enhancement of the energy transfer with a passive technique would be precious considering high air velocity being exerted in such system. The objective of this investigation was to demonstrate that a modified slot-jet impingement system with additional horizontal and vertical plates could enhance the overall heat transfer {Nu = Nusselt number) over the target impinging surface. The demonstration involved published experimental data and computational fluid dynamics simulations in evaluation of various positions of the horizontal (s = horizontal plate height) and vertical (L « distance from nozzle edge to vertical plate) plates. It was found that the s value has a stronger effect on the heat (Nu) distribution profiles on the target surface than that of the L value. The presence of the plates introduced more than one peak of Nu values. Only s = L - 0.5W (W= slot width) offered an excellent enhancement of heat transfer over that of the control (no plates) in the stagnation and wall-jet regions. Moreover, jet streamlines/recirculation and velocity vector on the y-axis at y = -5.95W were well related to the surface Nu distribution profiles. It was demonstrated that a proper design of the plate position significantly enhanced the overall energy transfer on the target surface and improved the cooling rate of food model.