Abstract
Heat exchangers are widely used in many mechanical, electronic, and bioengineering applications at macro and microscale. Among these, the use of heat exchangers consisting of a single fluid passing through a set of geometries at different temperatures and two flows in T-shape channels have been extensively studied. However, the application of heat exchangers for thermal mixing over a geometry leading to vortex shedding has not been investigated. This numerical work aims to analyse and characterise a heat exchanger for microscale application, which consists of two laminar fluids at different temperature that impinge orthogonally onto a rectangular structure and generate vortex shedding mechanics that enhance thermal mixing. This work is novel in various aspects. This is the first work of its kind on heat transfer between two fluids (same fluid, different temperature) enhanced by vortex shedding mechanics. Additionally, this research fully characterise the underlying vortex mechanics by accounting all geometry and flow regime parameters (longitudinal aspect ratio, blockage ratio and Reynolds number), opposite to the existing works in the literature, which usually vary and analyse blockage ratio or longitudinal aspect ratio only. A relevant advantage of this heat exchanger is that represents a low-Reynolds passive device, not requiring additional energy nor moving elements to enhance thermal mixing. This allows its use especially at microscale, for instance in biomedical/biomechanical and microelectronic applications.
Highlights
Heat exchangers are present in many mechanical, biomechanical, and electronic engineering applications such as automobile refrigeration [1], air conditioning systems [2], powerplants [3], cooling of microelectronics [4], blood warming [5], or pressure ventilators [6,7]
The numerical investigation consists of a 2D computational mesh, whose governing equations are solved with the computational fluid dynamics (CFD) software ANSYS-FLUENT 18.2
This paper investigated the performance of a microscale heat exchanger, which consists of a rectangular pillar structure in a microchannel, where two fluids at different temperature are mixing
Summary
Heat exchangers are present in many mechanical, biomechanical, and electronic engineering applications such as automobile refrigeration [1], air conditioning systems [2], powerplants [3], cooling of microelectronics [4], blood warming [5], or pressure ventilators [6,7]. Apart from the absence of works on heat transfer between two microfluids at different temperature in the vortex shedding problem, it has been noticed an important gap in the characterisation of single-object vortex shedding in channels: there are no correlation models for relevant parameters such as the pressure related parameters (pressure drop, drag forces or the pumping power) nor the critical Reynolds (above which the flow is unsteady and von Karman streets do appear) Those works which intended to characterise and analyse the underlying mechanics of the problem did only focus efforts in indicating the limit values of one geometric factor at a time (and only a couple of works investigated variations in AR), with poor generalisation.
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