Thermal-hydraulic performance enhancement of solar receiver channel by flapped V-baffles

Abstract

Thermal-hydraulic performance investigation in a solar receiver channel equipped with a vortex flow generator, namely, flapped V-shaped baffle (FVB) on the absorber has been experimentally carried out. The purpose of using the square flaps on the V-baffle was to decline the pressure drag by directing the impact air to the absorber surface. The working fluid was air flowing into the uniform heat-fluxed channel at Reynolds number (Re) between 5300 and 23,600. The FVBs with 45°attack angle (α) were placed periodically on the absorber with the upstream V-apex arrangement. The FVB characteristics included three relative baffle-pitches (RP) and four flap angles (β)at one relative baffle height (RB=0.5) and flap length (b1/b = 0.4) were examined to obtain the optimum RP and β values. The present investigation has revealed that the FVB gives a considerable decrease in friction loss when compared with the solid V-baffle (β = 0) while the heat transfer rate reduces a little. The FVB with β = 45°, RP = 1.5 yields the greatest thermal performance around 2.5 as a result of the injecting air flows from the flap opening aside from the reduced friction loss. For the current experimental data, the Nusselt number and friction factor correlations were determined in the form of a function of the geometric FVB parameters and Re.