TOPOLOGICAL SHAPE AND PERFORMANCE OPTIMISATION OF MICROCHANNEL DIFFUSION-BONDED HEAT EXCHANGERS USED IN SCO2 BRAYTON CYCLE

Vishwakarma, SK and Srivastava, A and Kumar, P and Dutta, P and Somnath, N (2024) TOPOLOGICAL SHAPE AND PERFORMANCE OPTIMISATION OF MICROCHANNEL DIFFUSION-BONDED HEAT EXCHANGERS USED IN SCO2 BRAYTON CYCLE. In: 69th ASME Turbo Expo 2024: Turbomachinery Technical Conference and Exposition, 24 June 2024through 28 June 2024, London.

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Abstract

In recent years, Micro-Channel Heat Exchangers (MCHEs) have received significant interest in the context of energy systems and devices for supercritical carbon dioxide (sCO2) compact power blocks. The unprecedented ability of MCHEs to sustain extremities of both temperature and pressure makes them an ideal choice as recuperators/gas-cooler in a sCO2 Brayton cycle. The proposed approach uses a cylindrical-shaped heat exchanger with circular/non-circular channel holes that are topologically optimised. The channels are laser drilled into thin discs instead of electrochemically etched. The length is achieved by stacking and joining prepared discs with diffusion bonding. The MCHEs propose channels with different cross-sectional shapes and configurations defined in a cylindrical geometry as a novel alternative for conventional heat exchangers. The analysis focuses on enhancing heat transfer by arriving at suitable optimised forms and numbers of hot and cold channels based on the specified operating, manufacturing, and design constraints. The numerical analysis uses a three-dimensional computational fluid dynamics (CFD) model, which accommodates the non-axisymmetric behavior that arises in a global meshing system. The Navier Stokes (N-S) and energy equations are solved in cylindrical coordinates. The steady-state energy and momentum transport equations are discretised in a Finite Volume (FV) framework utilising a collocated grid. The approach provides flexibility to vary radial distribution of channels and the number of holes based on specified operating, manufacturing, and design constraints. The full-scale CFD model, which is an accurate method for performing property evolution studies, is computationally expensive. Hence, a parallel computing approach is adopted for a real, efficient, and versatile numerical model for evaluating the analyses and then performing optimization. Enhancement in heat exchanger performance is achieved using an Elite Genetic Algorithm (EGA), resulting in an optimised heat exchanger geometry. The geometric parameters used to guide the EGA in generating multiple improved heat exchanger geometries, allow for design trade-offs along the Pareto front between heat exchanger efficiency and geometric location of channels. The current approach offers a promising method for optimising heat exchanger performance, resulting in non-intuitive designs that were previously unattainable. The process is demonstrated with an optimized design. The results predicted are validated using a commercial CFD solver. Test cases have shown a close agreement in temperature and velocity distributions. Copyright © 2024 by ASME.

Item Type:	Conference Paper
Publication:	Proceedings of the ASME Turbo Expo
Publisher:	American Society of Mechanical Engineers (ASME)
Additional Information:	The copyright for this article belongs to Publishers.
Keywords:	Air conditioning; Bayesian networks; Binary trees; Convergence of numerical methods; Cryogenic equipment; Cylinder configurations; Cylinders (shapes); Directed graphs; Fuel storage; Gas turbines; Gradient methods; Graph Databases; Heat transfer performance; High level synthesis; Industrial heating; Marine education; Mesh generation; Navier Stokes equations; Network theory (graphs); Quadratic programming; Refrigerators; Shape optimization; Spheres; Steam turbines; Structural analysis; Structural dynamics; Structural optimization; Thermal conductivity of gases; Thermoelectric refrigeration; Ventilation, Brayton; Computational fluid dynamics modeling; Cylindrical coordinate systems; Design constraints; Manufacturing constraint; Microchannel heat exchanger; Numerical heat transfer; Operating constraints; Optimization problems; Topological shape optimization, Brayton cycle
Department/Centre:	Division of Mechanical Sciences > Mechanical Engineering
Date Deposited:	15 Oct 2024 05:55
Last Modified:	15 Oct 2024 05:55
URI:	http://eprints.iisc.ac.in/id/eprint/86512

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