Experimental study of forced convection from helical coiled tubes with different parameters

Abstract The forced convection from outside surfaces of helical coiled tubes is studied experimentally with a constant wall heat flux. Ten helical coiled-tubes of different parameters with a range of diameter ratio ( D / d o ) ranged from 7.086 to 16.142 and pitch ratio ( P / d o ) ranged from 1.81 to 3.205 are employed in the present study. The experiments are performed in an open-circuit airflow wind tunnel system operated in suction mode. The experiments covered a range of Reynolds number (Re) of 6.6 × 10 2 to 2.3 × 10 3 . The experimental results indicated that these parameters ( D / d o and P / d o ) have important effects on the average heat transfer coefficient. The average Nusselt number (Nu m ) increases with the increase of D / d o at constant Re and P / d o . Also, Nu m increases with the increase of P / d o at constant Re and D / d o . A considerable agreement between the present experimental data and previous work is achieved. The average Nusselt numbers is correlated with Re, D / d o and P / d o .

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