Abstract
The main objective of this article is to increase the flow mixing within a tube; in this regard, the helical tape with external inserts was developed and studied. CuO based nanofluids was used as a working fluid, and a novel testing fluid model was based on the previous empirical formulation by a three-dimensional (3D) computational fluid dynamic model established for velocity, temperature profiles, exergy, and irreversibility for Reynolds number 5000 and 20,000. The impact of external inserts and Reynolds number were discussed on Nu, f, temperature, and Sgen. The insertion of external inserts increases the Nu and f. When Re increases from 5000 to 20000, Nu increments about 204.21% without external inserts in the twisted tape. For the twisted tapes with external inserts, Nu increases about 202.87%. With external inserts, the entropy generation is reduced to 45% at Re = 5000 and 7% when Re is increased from 5000 to 20,000. An increment in Nusselt number and frictional entropy generation and a reduction in friction factor and thermal irreversibility are observed with an increase in Reynolds number. Consequently, it can be determined that employing nanofluids and twisted tapes in heat exchanger decreases exergy losses and enhance heat transfer performance due to a decrement in thickness of thermal boundary layer.