Effect of corrugation depth on heat transfer enhancement and flow characteristics for corrugated tubes

Abstract EN

Three.corrugated.tubes.withvariouscorrugation.depthsare.experimentallyand numerically.investigated.Air.is usedas a working.fluid.in.tube.side.heated.bysaturated.steam.passing.through.the.shell.of heat.exchanger where.constant wall temperature.at the.tube side was achieved.

The dimensionless corrugation depth (e/Dh) are 0.0216, 0.0469 and 0.0798.However, the corrugation angle (θ)and pitch to diameter ratio (p/Dh) were keptnearly constant of9οand 0.5, respectively.

The experiments were carried out over the turbulent range of Reynolds number from 5000 to 50,000.The results reveal that the average Nusselt number is increased by 46%, 67% and 105% for corrugation depth ratios of 0.0216, 0.0469 and 0.0798, respectively compared with the smooth tube.

However, the average friction factor of the corrugated tube with e/Dh =0.0216, 0.0469 and 0.0798are 90%, 135% and 500% higher than of smooth tube, respectively.

At the same pumping power, the optimumNusselt number ratio was 1.4 obtained by corrugated tube with intermediate depth ratio (e/Dh =0.0469).

To.visualize the.Flow behaviorof flow.inside corrugated.tubes, the numerical.approach.wasused.tosolvethree-dimensional.governing equations.with.shear stress transport k-ω model by usingANSYS,Fluent 15.

Solid work was used to generate the physical domain of corrugated tube.

The numerical.resultshowed.that.there is .mainvortex.Generatedin.themain .flow .due to rotational flow induced .alongthe helical path.In addition, secondary vortex is originated behind the rib.

These.two vortices .can promote .flow .mixing between .theflow.layers.andbreak.the boundary layer.

Consequently, achieve high heat transfer improvement.