Numerical investigation for heat transfer enhancement of nanofluid in the solar flat plate collector with insertion of multi-channel twisted tape

Numerical analysis of heat transfers and nanofluid flow structure inside a tube with multi-channel twisted tapes in a solar flat plate collector has been investigated. Al2O3/water nanofluid with a volume fraction of 3% was used as working fluid. Nanofluid with Reynolds number (Re) ranged from 4000 to 20000 was investigated. Effect of the number of channel (n=2, 3, 4, 5 and 6), twisting ratio (N=4, 5, 6 and 7) and diameter ratio (D*=0.1, 0.12 and 0.14) on heat transfer rate and friction loss have been presented separately. The results demonstrated that the insertion of multi-channel twisted tapes induce multi-swirling flows. Consequently, fluid mixing improves and heat transfer rate enhances. Augmenting number of channel, twisting ratio and diameter ratio leads to higher values of heat transfer and pressure loss. The maximum thermal performance factor is obtained by using twisted tapes with n=2, D*=0.14 and N=7 when Reynolds number has lowest value