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Heat exchangers are critical components in a wide range of industries, and optimizing their thermal performance remains an important research area. To augment the thermal efficiency in a heat exchanger, several investigations have been done to increase the wetted surface area using a rib profile. Still, there exists a lack of research attempts to change the geometrical shape, such as multiple-head ribbed geometry with coil revolution in a straight heat exchanger. Therefore, the present study takes a numerical approach to examine the effect of multiple ribbed geometries, considering the variable coil revolution of the rib profile in a straight-type heat exchanger. The study was initially validated from two experimental correlations and previous numerical work. Three rib surfaces (2 ribs, 3 ribs and 4 ribs) and three different coil revolutions (10 revolutions, 20 revolutions and 30 revolutions) were taken into consideration to make nine configurations. Air was used as fluid under heating conditions. The results have been represented in terms of velocity, temperature profiles, local Nusselt number (Nu), pressure drop, friction factors and entropy generations for all the configurations. A significant enhancement in heat transfer was found when the rib head number is lesser, whereas the coil revolution number is higher. Consequently, the highest Nusselt number (Nu) was observed in the configuration of 2 ribbed 30 revolutions, and the lowest was found in 4 ribbed 10 revolutions. Furthermore, the friction factor rises because of higher coil revolution for a specific rib head number. It is found that in four rib head geometry, the friction factor rises 2 times when the revolution number is 30 than the case of revolution number 10. It is also observed that the 4 rib head 10 revolution configurations provides the lowest entropy generations among the configurations. Thus, the study suggests choosing the right configuration to design a straight heat exchanger with ribbed head profile to get the highest thermal performance. Following this study, these design modifications can be applied to other types of heat exchangers as well.
Hasan et al. (Wed,) studied this question.