Enhanced printed-circuit heat exchanger for supercritical CO2 Brayton cycle pre-coolers with innovative convergent-divergent mini-channel design

IF 4.9 2区工程技术 Q1 ENGINEERING, MECHANICAL

International Journal of Thermal Sciences Pub Date : 2025-03-10 DOI:10.1016/j.ijthermalsci.2025.109857

Joffin Jose Ponnore , Fayez Aldawi

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引用次数: 0

Abstract

Supercritical CO₂ (sCO₂) operates under extreme pressure and temperature conditions, with its thermophysical properties changing rapidly near the critical point. These conditions exceed the capabilities of common welded heat exchangers to handle the substance in sCO₂ Brayton Cycle power plants. Among the most suitable heat exchangers for this application is the Printed Circuit Heat Exchanger (PCHE), which has been extensively adopted in sCO₂ power systems. This unique heat exchanger offers the thermal effectiveness of a plate-type heat exchanger combined with the temperature/pressure capability of a shell-and-tube heat exchanger. Additionally, PCHEs are 75 %–85 % smaller and lighter than the shell-and-tube heat exchangers required in the mentioned cycle. The only drawback of PCHEs is the complexity and cost of the manufacturing process. That is why any proposed thermal improvement techniques for PCHEs are expected not to increase the cost or complexity of the manufacturing or tooling process. As shown in the graphical abstract, precise parallel mini channels are created on thin metal sheets using the photochemical etching process and then joined together with the diffusion bonding technique, making it a single solid-state bond (free from joints, gaskets, brazing, and welding). This research proposes an innovative modification for the mentioned mini-channels in which the diameter of the semi-cylindrical channels is gradually increased or decreased along the sheets, creating convergent-divergent fluid flow behavior to boost its thermal performance without affecting the production cost or complexity of the process. Various convergent/divergent arrangement scenarios are possible, all of which are examined under various area ratios (A_r), inlet temperatures, mass flux (G), and operating pressures from thermal, frictional, and exergetic viewpoints. According to the validated 3D numerical simulation results, this modification is found to be so promising that, in some cases, the improved heat transfer coefficient is over two times higher than that in the base model due to enhanced turbulence and fluid mixing from the convergent-divergent scenario. All other detailed results are presented and discussed in this paper.

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增强型印刷电路热交换器，用于超临界CO2布雷顿循环预冷却器，具有创新的收敛发散迷你通道设计

超临界CO2 （sCO2）在极端压力和温度条件下工作，其热物理性质在临界点附近迅速变化。这些条件超过了普通焊接热交换器在sCO2布雷顿循环电厂中处理这种物质的能力。最适合这种应用的热交换器是印刷电路热交换器（PCHE），它已广泛应用于sCO2电力系统。这种独特的热交换器提供了板式热交换器的热效率，结合了壳管式热交换器的温度/压力能力。此外，PCHEs比上述循环中所需的壳管式热交换器体积小75% - 85%，重量轻。pch的唯一缺点是制造过程的复杂性和成本。这就是为什么任何提出的pch热改进技术都不会增加制造或加工过程的成本或复杂性。如图所示，使用光化学蚀刻工艺在薄金属片上创建精确的平行微型通道，然后用扩散键技术连接在一起，使其成为单一的固态键（没有接头，垫圈，钎焊和焊接）。本研究提出了对上述迷你通道的创新修改，其中半圆柱形通道的直径沿着薄片逐渐增加或减少，产生会聚-发散流体流动行为，以提高其热性能，而不影响生产成本或工艺复杂性。在不同的面积比（Ar）、进口温度、质量通量(G)以及从热、摩擦和火用角度出发的操作压力下，可以对所有的收敛/发散布置方案进行检查。经过验证的三维数值模拟结果表明，这种改进是非常有希望的，在某些情况下，由于收敛-发散情景的湍流增强和流体混合，改进的换热系数比基本模型高两倍以上。所有其他的详细结果都在本文中提出和讨论。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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来源期刊

International Journal of Thermal Sciences 工程技术-工程：机械

CiteScore

8.10

自引率

11.10%

发文量

531

审稿时长

55 days

期刊介绍： The International Journal of Thermal Sciences is a journal devoted to the publication of fundamental studies on the physics of transfer processes in general, with an emphasis on thermal aspects and also applied research on various processes, energy systems and the environment. Articles are published in English and French, and are subject to peer review. The fundamental subjects considered within the scope of the journal are: * Heat and relevant mass transfer at all scales (nano, micro and macro) and in all types of material (heterogeneous, composites, biological,...) and fluid flow * Forced, natural or mixed convection in reactive or non-reactive media * Single or multi–phase fluid flow with or without phase change * Near–and far–field radiative heat transfer * Combined modes of heat transfer in complex systems (for example, plasmas, biological, geological,...) * Multiscale modelling The applied research topics include: * Heat exchangers, heat pipes, cooling processes * Transport phenomena taking place in industrial processes (chemical, food and agricultural, metallurgical, space and aeronautical, automobile industries) * Nano–and micro–technology for energy, space, biosystems and devices * Heat transport analysis in advanced systems * Impact of energy–related processes on environment, and emerging energy systems The study of thermophysical properties of materials and fluids, thermal measurement techniques, inverse methods, and the developments of experimental methods are within the scope of the International Journal of Thermal Sciences which also covers the modelling, and numerical methods applied to thermal transfer.