Experimental investigation on forced convective heat transfer and pressure drop of ethylene glycol in tubes with three-dimensional internally extended surface

A new type of tube is introduced that has a three-dimensional internally extended surface used to enhance convective heat transfer inside the tube. Results are presented from experimental investigations into heat transfer performance in seven copper tubes of about 13.5 mm I.D. with three-dimensional internally extended surfaces (3-DIESTs) varying in axial pitch, circumferential pitch, height, width, and fin arrangement. The heat transfer and pressure drop characteristics of ethylene glycol flowing in the 3-DIESTs were tested in the Re range 250–7000 and Pr range 60–90. The average Stanton number in the most superior 3-DIEST can be increased by about 2.8-fold in laminar flow and 4.5-fold in transitional and turbulent flow compared with that in the smooth tube. The corresponding friction factor is 1.7-fold as high in laminar flow and fourfold in transitional and turbulent flow inside the 3-DIEST compared to that inside a smooth tube. The correlations of heat transfer and friction factor are obtained separately in the different flow regions that can be used in practical design.