Heat transfer investigation of a 90° zigzag channel diffusion-bonded heat exchanger

Abstract

Abstract Supercritical CO2 (S-CO2) Brayton cycle components are subject to high pressure and temperature conditions, which are intrinsic to the operation cycle. Among the equipment used for these applications, diffusion-bonded heat exchangers are receiving more attention to be used as pre-coolers on the cycle, due to their robustness and capability of operating at the demanded conditions. Currently, limited research focused on the influence of the pre-cooler’s cold-side fluid, water, on the thermal performance of the diffusion-bonded heat exchangers. In the present study, a novel zigzag channel for the diffusion-bonded heat exchangers with square cross-section was manufactured and experimentally investigated in a water-water configuration. During the experiments, the Reynolds number of the hot and the cold sides varied from 1529 to 8313 and from 1299 to 6618, respectively, covering laminar to turbulent flow regimes. A new heat transfer correlation is proposed based on dimensionless Reynolds and Prandtl numbers, covering a large Reynolds number range not yet experimentally investigated for the water. In the laminar regime, the current geometry increases the Nusselt number up to 4.1 times when compared to a straight channel. For the complete Reynolds number range evaluated, from 1299 to 8313, the average enhancement of a diffusion bonded heat exchanger with the proposed geometry compared to a straight channel one is of 2.2 times. Therefore, the current zigzag design proposed in this study provided a significant advantage in terms of heat transfer performance.