Distributions of the local convective heat transfer from a tandem arrangement of wall-mounted cubes in a turbulent channel flow

摘要

Distributions of the local convective heat transfer characteristics of a tandem arrangement of two cubes in a fully developed turbulent channel flow are discussed in this paper.An infrared system was used to measure the surface temperatures distributions of the cubes,needed to obtain the local convective heat fluxes.the mean flow and turbulence fields were documented with Laser Doppler Velocimetry measurements and flow visuali-sation.Complementary measurements of shedding frequencies in the wake of the leading obstacle showed a minimum in the shedding frequency at a critical distance.Further,the results showed large variations in distributions of local convective heat transfer for the various distances between the two cubes studied.For the smallest streamwise distance considered, S_x/H=2, the shear layer reattached at the leading side and top edges of the down-stream cube,causing a monotonic decay in the convective heat transfer.In contrast,for a large distance,for example S_x/H=8,the shear layer reattached in the inter-obstacle spacing leading to flow separation at the leading edges of the downstream cube.The resulting vortex structure subsequently caused a minimum and a maximum in the convective heat transfer at these faces.Despite substantial variations in the distributions of the local heat transfer coefficient, the face-averaged and cube-averaged heat transfer coefficient varied only slightly with the streamwise distance.