• Structural design of a novel bionic-inspired coaxial combination heat exchanger. • Coaxial heat exchanger units arranged in bionic lotus-seed layout configuration. • Two heat exchange fluids flow through cross-channels in coaxial heat exchanger unit. A novel bionic-inspired coaxial combination heat exchanger (CCHE) is proposed to enhance both the heat transfer performance and pressure resistance. This design possesses a compact structure, which reduces spatial requirements and enhances its suitability for large-scale industrial applications. The CCHE incorporates a coaxial heat exchanger unit (CHEU) consisting of smooth-walled tubes. Each CHEU is comprised of three coaxially assembled tubes, which form three flow channels and increase the overall heat transfer area. The heat transfer rate ( Q ), heat transfer coefficient ( h ) and pressure drop ( Δ p ) of the CCHE have been investigated through numerical simulation, with emphasis on the effects of a bionic lotus-seed layout configuration (BLS) and a spiral fin configuration. The overall performance has been assessed using the efficiency evaluation coefficient ( EEC ). The results indicate that, under shell-side Reynolds number ( Re sh ) ranging from 45,829 to 72017, compared to a single-wall plain tube heat exchanger (SPTHE), the CCHE demonstrates maximum increases of 106.9% in h , 55.35% in Δ p c , and 256% in effectiveness ( ε ). Although the CCHE exhibits a higher pressure drop, this is offset by a significantly greater heat transfer enhancement. Furthermore, the BLS improves both flow and thermal performance. Compared to the square-layout CCHE (CCHE-SQ), the bionic-layout version (CCHE-BLS) shows maximum increases of 0.79%, 0.89%, 2.10%, and 0.71% in Q c , h , EEC , and ε Re sh = 45829 ∼ 72017 , respectively. Additionally, the thermal performance is influenced by the winding direction of the spiral fins. The opposite-direction-wrapped configuration (CCHE-OD) has been found to exhibit superior performance parameters. Moreover, the Q c , h , Δ p c , and ε increase with decreasing pitch of spiral fins ( P fin ). The smallest fin pitch ( P fin = 40 mm ) achieves the highest heat transfer efficiency but has the lowest EEC (<1), indicating that maximum heat transfer performance does not equate to optimal energy efficiency. This study provides a reference for the development of high-efficiency heat transfer equipment.
Ye et al. (Fri,) studied this question.