Thermo-fluid-dynamic analysis of the flow in a rotating channel with a sharp “U” turn

Abstract

Infrared thermography has been employed to carry out a detailed convective heat transfer measurements at Re = 20,000 in a two-pass square channel both for the static case (absence of channel rotation) and for the rotating case (Ro = 0.3). At the same time, the main and secondary flow fields have been measured by means of particle image velocimetry with the aim to investigate how the flow behavior affects the local distributions of the convective heat transfer coefficient for the two cases. The normal-towall velocity component (w) and the turbulent kinetic energy, both measured close to the heat exchanging wall, have been used to formulate an empirical heat transfer correlation within an attempt to identify the role performed by these two quantities on the convective heat transfer coefficient distributions. The latter ones have been reported in terms of normalized Nusselt number (Nu/Nu*) maps, where Nu* is the Nusselt number evaluated with the classical Dittus-Bölter correlation.

Some Experimental Investigations on Gas Turbine Cooling Performed with Infrared Thermography at Federico II

“…In the outlet duct, the Nusselt number distribution relative to the trailing wall exhibits two high heat transfer coefficient zones located on the centre and downstream near the partition wall, respectively. Again, the reason for such behaviour can be found in the paper by Gallo et al [19].…”

“…This inversion makes the flow separate on the trailing side and abruptly reattach towards the leading one, with a strong increase of the normalised Nusselt number at the reattachment point. Other low and high heat transfer zones are clearly visible in the normalised Nusselt number map and their cause is explained in detail by flow field measurements made with particle image velocimetry in the work of Gallo et al [19].…”

“…Researchers are working on the enhancement of spatial resolution and measurement accuracy [29] which could undoubtedly also produce further comprehensive benchmarks for computational methods. Some thermographic measurements, concurrently performed with standard PIV, have already appeared in [19].…”

“…Normalised Nusselt number Nu/Nu * distributions for a smooth rotating channel: (a) leading wall and (b) trailing wall; adapted from Gallo et al[19]. 3D temperature reconstruction for = 4 mm, = 30 ∘ , = 1.0, and / = 15: (a) adiabatic wall temperature (foil not heated) and (b) wall temperature (heated foil); adapted from Imbriale et al[20].…”

Influence of turn geometry on turbulent fluid flow and heat transfer in a stationary two-pass square duct

“…Gallo et al [18] were investigated the turbulent fluid flow and convective heat transfer in a sharp U-turn square duct at a Reynolds number of 20,000. IRT technique has been employed for measurement of local convective heat transfer and the mean and secondary flow fields have been measured using PIV.…”