Plate heat exchangers (PHEs) are extensively used in various thermal systems due to their compact designs, high heat transfer coefficients, and superior scalability compared to other heat exchanger types. However, their performance often deteriorates due to uneven fluid distribution among channels, leading to non-uniform heat transfer and increased pressure drops. Performance enhancements can be achieved through the redesign of in-plane flow structures (fins) and modifications to header configurations. This study introduces novel three-dimensional twisted S-shaped fins to enhance thermal performance and presents comprehensive reduced-order thermo-hydraulic models to investigate flow maldistribution and rapidly optimize PHE designs for various header shapes.The first part of this dissertation presents a PHE design incorporating three-dimensional twisted S-shaped fins, fabricated using additive manufacturing technology. These fins promote controlled fluid swirl and enhance heat transfer. Turbulent conjugate heat transfer simulations are conducted to assess the thermal and hydraulic performance of the proposed configurations. By systematically varying mass flow rates and fin geometries, an optimized design suitable for high-temperature, high-pressure applications is identified.The second part of the study addresses flow maldistribution in PHEs caused by suboptimal header design. Computational Fluid Dynamics (CFD) analyses are conducted on PHEs with both straight and tapered header configurations to identify the optimal header design for achieving uniform flow distribution. While the introduction of a tapered header can reduce the recirculation zone observed in straight headers, contrary to existing research, the study reveals that tapered headers can increase flow maldistribution compared to straight headers. However, these CFD analyses are computationally intensive, making it challenging to identify conditions where tapered headers are advantageous.To significantly reduce computational expenses, a reduced-order model is developed to rapidly assess the potential impact of tapered headers. This model, validated against existing research, is capable of estimating both flow distribution and pressure drop within PHEs with minimal computational resources. Key structural parameters such as header diameter, number of channels, channel area, and taper ratio are identified as critical factors influencing flow distribution. These parameters play a crucial role in determining the choice between tapered and uniform headers. One of the most significant findings is the identification of the range of ζ values, representing flow resistance inside the channels, where tapered headers provide more uniform flow compared to straight headers.The predictive modeling framework is further extended to more complex header geometries, including parabolic and hyperbolic shapes, thereby advancing the understanding of fluid distribution in complex geometries and contributing to the design of more efficient, reliable, and cost-effective PHEs.Finally, a comprehensive heat transfer model developed for PHEs is integrated with the predictive model. The resulting thermo-hydraulic model incorporates the role of header configuration in flow maldistribution and constitutes a tool for selecting appropriate structural parameters. This integrated model enables rapid evaluation of the impact of flow maldistribution on the effectiveness of PHEs without extensive computational resources. Overall, this dissertation contributes a novel design framework for PHEs, supporting applications in sustainable energy systems and industrial processes.
Read
