The design of tube bundle arrangements strongly influences the thermal performance and pressure drop in compact heat exchangers, especially in low-Reynolds number applications where efficiency is critical. In this study, numerical analysis of the effect of unconventional tube bundle arrangements on heat transfer and flow characteristics was conducted, and their performance was compared with that of a conventional arrangement. Three different tube arrangements: diamond (9 tubes), staggered (13 tubes), and serpentine/sinusoidal (15 tubes) are considered for 1026 ≤ Re ≤ 10268. Two-dimensional, steady, incompressible, thermally coupled flow analysis is performed using the commercial CFD tool ANSYS Fluent. Turbulence is modelled using the SST k-ω turbulence model. The streamline pattern over tube bundle arrangement reveals that the flow structure in the vicinity of the tubes is altered by the tube arrangement and the flow velocity. The diamond-shaped configuration incorporates a tubular arrangement that diverts the incoming flow while maintaining a low pressure drop. Staggered and serpentine tube arrangements force air to flow through the passages created by arranging the tubes in the bundle. Higher turbulent kinetic energy (TKE) and a higher number of tubes in these arrangements enhance heat transfer, at the cost of increased pressure drop. Over the range of Reynolds numbers considered, the serpentine arrangement exhibits an approximately 3% higher average Nusselt number Nu_avg than the other two arrangements. The serpentine arrangement has three tubes in each row. In a serpentine arrangement, higher turbulent kinetic energy (TKE) and greater heat transfer area facilitate increased heat transfer (Q̇). At low Re = 1026, the serpentine arrangement provides a 39% higher heat transfer rate for the same pressure drop compared to the staggered arrangement, whereas the diamond arrangement yields 14% lower heat transfer rate. At higher Re, the performance of the serpentine arrangement is offset by a larger pressure drop, and the diamond arrangement is superior. The performance parameter, Pi, (ratio of Q̇ and the pumping power) for the serpentine tube arrangement is high at low Re and comparable at higher Re whereas for the diamond layout, Pi remains almost constant throughout the range of Re. The serpentine arrangement outperforms other configurations in achieving a higher heat transfer rate and an optimal pressure drop. The novelty of this work lies in investigating the biomimetic serpentine (sinusoidal) and diamond-shaped tube arrangements, which are relatively unexplored compared to conventional inline or staggered tube banks.