Numerical Simulation of the Heat Transfer from a Heated Solid Wall to an Impinging Swirling Jet

Abstract

Swirling jets are frequently used in many industrial applications such as those related with propulsion, cleaning, combustion, excavation and, of course, with heat transfer (e.g. cooling/heating), among others. The azimuthal motion is usually given to the jet by different mechanisms, being the most used bymeans of nozzles with guided-blades (e.g. Harvey, 1962); by entering the fluid radially to the device (e.g. Gallaire et al., 2004); by the rotation of some solid parts of the device (e.g. Escudier et al., 1980); or by inserting helical pieces inside a cylindrical tube (e.g. Lee et al., 2002), among other configurations. The way the swirl is given to the flow will finally depend on the particular application it will be used for. Impinging swirling (or not swirling) jets against heated solid walls have been extensively used as a tool to transfer heat from the wall to the jet. In the literature, one can find many works that study this kind of heat transfer related problem from a theoretical, experimental or numerical point of view, being the last two techniques presented in many papers during the last decade. In that sense, Sagot et al. (2008) study the non-swirling jet impingement heat transfer problem from a flat plate, when its temperature is constant, both numerically and experimentally to obtain an average Nusselt number correlation as a function of 4 non-dimensional parameters. And, what is most important from a numerical point of view, their numerical results, obtained with the commercial code Fluent© and the Shear Stress Transport (SST) k − ω turbulence model for values of Reynolds number (Re) ranging from 10E3 to 30E3, agree very well with previous experimental results obtained by Fenot et al. (2005), Lee et al. (2002) and Baughn et al. (1991). More experimental results are given by O’Donovan & Murray (2007), who studied the impinging of non-swirling jets, and by Bakirci et al. (2007), about the impinging of a swirling jet, against a solid wall. The last ones visualize the temperature distribution on the wall and evaluate the heat transfer rate. In Bakirci et al. (2007), the swirl is given to the jet by means of a helical solid insert with four narrow slots machined on its surface and located inside a tube. The swirl angle of the slots can be varied in order to have jets with different swirl intensity levels. This is a commonly extended way of giving swirl to impinging jets in heat transfer applications, as can be seen in Huang & El-Genk (1998), Lee et al. (2002), Wen & Jang (2003) or Ianiro et al. (2010). On the other hand, Angioletti et al. (2005), and for Reynolds numbers ranging between 1E3 and 4E3, present turbulent numerical simulations of the impingement of a non-swirling jet against a solid wall. Their results are later validated by Particle Image 8