KAJIAN NUMERIS KARAKTERISTIK ALIRAN UDARA KONVEKSI BEBAS PADA KONDENSOR TYPE CIRCULAR TUBE SUSUNAN DI TENGAH SALURAN TEGAK MENGGUNAKAN CFD

Abstract

Further numerical study of the experiment conducted to examine the confected air flow characteristics free of gap ratio(S/D 1.05-4.20) on condenser with the capillary pipe length standard of the condenser refrigeration unit isothermalcircular-type consisting of 20 in-line array in the middle of vertical channel was examined using CFD fluent. Numericalresult shows S/D 1.05-4.20. It was obtained that the condensor heat transfer increased 4.4% to 226 W, which is equal tothe experimental result. Started from S/D1.05, there was a strong blockage effect that the air flow characteristicsbetween the tubes was dominated by recirculation, impacting the small temperature gradient and slow tangentialvelocity (vt). On the other hands, S/D2.10 blockage effect reduced drastically and the buoyancy force produced a rapidair flow across the tubes. The Tangential velocity (Vt) increased rapidly, causing the local Nusselt number (Nuθ) to popup four times at θ = 0o on the upstream tube 20. The average Nusselt number ( Nu ) on the tubes surface increases 135%.The result qkond increased significantly. Effect of S/D 3.15-4.20 temperature gradient relatively unchanged. LocalNusselt number (Nuθ) did not undergo significant changes. The Air flow running across the channel only reduced theimpact on the confected wall that in the gap ratio area the qkond increases were no longer significant.