Experimental investigation of heat transfer and friction factor characteristics using helical surface ring turbulators in an annulli of double pipe heat exchanger

Abstract

Augmentation in heat transfer is very useful for variousengineering and scientific applications due to the call forenergy and cost saving. The heat transfer and pressure dropcharacteristics in annuli of double pipe heat exchanger usinghelical and plain surface ring turbulators are studied throughexperimental investigation. The effect of helical surface ringturbulators and plain surface ring turbulators are studied forvaried range of pitch ratio (4.0-6.4), Reynolds Number (3,000-10,500) and two different diameter ratios (0.475 and 0.54).Water (hot fluid) flows in the inner tube and air (cold fluid)flows through the annulus. The tests are conducted for air withuniform wall temperature condition. The heat exchanger withleast pitch and least diameter ratio is found to exhibit thehighest Nusselt number and pressure drop. Results indicate thatmaximum enhancement is obtained for smallest diameter ratio0.475 and pitch ratio 4.0 at lowest Reynolds Number. Also,thermal performance factor is always greater than unity for theDPHE using helical surface turbulators. Correlations have beendeveloped for enhancement in Nusselt number and frictionfactor; show the good agreement with experimental test datawithin test range. © 2018 ASME.