The cooling performance of passive helically finned heat sink (HFHS) under constant heat flux boundary condition (10-100 W/cm²) is evaluated vis-α-vis conventional circular finned heat sink (CFHS) using the commercial software COMSOL Multiphysics^® 5.3. One-to-one comparison is conducted by keeping the same fin heat transfer area, pitch (P) in HFHS equal to fin spacing in CFHS, equal fin stack length and number of revolutions in HFHS equal to the number of turns in CFHS. The flow and heat transfer characteristics are investigated for Ra = 5.63×10³, with emphasis on swirl induced flow and cooling in the vicinity of the fin under laminar flow and steady state condition. The performance is assessed primarily based on the estimate of operating wall temperature and fin efficiency. Results establish higher efficiency of HFHS over CFHS on account of the swirl flow caused by its shape.