Enhancing scalar transport in confined laminar flows

Laburpena

Experimental research is carried out to shed light over the kind of some flow topologies and mechanisms that may enhance mixing in confined flows. The purpose is to understand said mechanisms to find suitable ways of optimization and application for the industry. A summary of results has been published in journals that appear in the Journal Citation Reports. In the first place, enhancement caused by flow induced vibration in a channel with high blockage ratio is studied. Research was carried out both with tethered (moving) prisms and with a fixed one. It is to be noted that passive scalar transport, such as temperature, is a goal of the industry as a whole, especially when dealing with high density fluids or small scales, which leads to low Reynolds' numbers and thus laminar flows. The ability to evacuate heat from warm walls and mix thermal boundary layer is studied at Reynolds' numbers between 80 and 800, based on the prism cross section. In a second place, a previously tested geometry for a finned heat sink is studied so as to comprehend the causes of its good performance. A lid is placed against square section channels connecting two stagnation chambers. A pump induces enough pressure drop so as to the fluid to circulate along those channels and theoretically evacuate heat from them. Tip clearance effects are studied, which can be summarised in reducing the pressure losses a factor of five times more than the heat extraction losses. All the experimental results are compared to CFD simulations which are also used to provide further knowledge of the problem. Needless to say that the application of more efficient cooling systems is a very broad field.