Effect of buoyancy on turbulent convection heat transfer in corrugated channels - A numerical study

The results show that, for buoyancy-aided flows, the heat transfer decreases with Grashoff number until a certain point where it starts to recover. For buoyancy-opposed flows, heat transfer monotonically increases with Grashoff number. It is the same trend as has already been reported in the literature for vertical pipes; however, for the same Reynolds number, the critical Grashoff number at which buoyancy can affect the heat transfer in a corrugated channel is higher. These Grashoff numbers increase with the width-to-pitch ratio of the channel. If the wall heat flux (thus Grashoff number) is kept constant, Reynolds number must be 3-7 times smaller in corrugated channels with aspect ratios of 0.2-0.5, respectively, compared to a vertical pipe so that buoyancy can affect heat transfer.