Toward compact helical heat exchanger with fins-based design

Toward a compact heat exchanger, an innovative design of a helical heat exchanger is proposed. The new design features fins arranged in different patterns and a thin-conductive tubular fin (TCTF) that is integrated into the annulus of the heat exchanger. The impact of TCTF on the heat transfer process, the friction factor, and the performance evaluation criteria is studied. The performance of the proposed helical heat exchanger configurations with fins (Hcfx) is compared to that of a helical heat exchanger without fins (Hcx). Proposed configurations of Hcfx showed significant improvement over conventional unfinned ones. The enhanced mixing due to secondary flow and the increased heat transfer area of the two-fin Hcfx arrangement increased the Nusselt number by 32 % when the fins were positioned vertically. However, this resulted in a 38 % increase in the friction factor compared to Hcx. The four-fin Hcfx configuration increased the Nusselt number by 47 % compared to an unfinned helical heat exchanger, primarily due to its greater heat transfer area. However, it also increased the friction factor by 99 %, making it about 61 % higher than the two-fin Hcfx arrangement. A two-fin Hcfx arrangement, with TCTF included, improved the Nusselt number by 20 % compared to the same configuration without TCTF. A Hcfx four-fin arrangement, with TCTF included, improved the Nusselt number by 7 % compared to the same configuration without TCTF. Therefore, the beneficial influence of TCTF on the heat transfer process is more pronounced in the two-fin Hcfx configuration than in the four-fin Hcfx configuration. Due to the higher friction factor of the four-fin configuration, the heat transfer-to-pressure drop ratio and performance evaluation criterion are 19 % and 24 % lower, respectively, than those of the two-fin Hcfx configurations. The effectiveness of the two-fin Hcfx configuration is 0.55, compared to 0.31 for the unfinned conventional helical heat exchanger, and when TCTF is included, the effectiveness increases to 0.87. This study therefore recommends the two-fin helical configuration with TCTF and fins positioned vertically due to its high compactness and higher overall performance compared to conventional and other finned helical configurations. The results of this study clearly indicate that incorporating the TCTF into a helical heat exchanger has a substantial impact on enhancing the heat transfer process. Additionally, it is straightforward to fabricate and incorporate TCTF into a heat exchanger through interference fit.