Abstract Thermal chimney driven/enhanced air-cooled condensers have increasingly found extensive applications in buildings, thermal and geothermal power plants. A small scale model of thermal chimney with rectangular cross-section of constant area was designed and one-row electrical heaters were installed to mimic the shell-and-tube heat exchanger, and simulations of conjugate heat transfer in the chimney were carried out by using computational fluid dynamics (CFD) software-ANSYS CFX at various heater nominal temperatures and 22.5 ℃ ambient temperature. The heat transfer models adopted include steady three-dimensional Reynolds-averaged Navier-Stokes equations and k - ω turbulence model as well as Boussinesq buoyancy assumption. The radiation effect from the heaters to the air was considered. The heater temperature profile was mapped by using forward-looking infrared camera and the air velocity in the chimney was measured by employing particle image velocimetry to validate CFD velocity fields. The measured temperature profile was modelled and involved into CFX as temperature boundary conditions. It was shown that the heaters can induce an air flow in the chimney to generate a cooling effect. As the heater nominal temperature increases from 80 ℃ to 170 ℃ , the chimney energy gain coefficient rises from 0.40 to 0.60, but saturated beyond 130 ℃ , the Reynolds number of the chimney is ranged in 2000–4000, while the Reynolds number of the heaters varies in 140–270, and the Nusselt number of the heaters is as low as 7.0-8.2. Flow separation can occur at lower than 130 ℃ . The radiation from the heaters makes a slightly more 1/3 contribution in the heat transfer. It is suggested that the primary heat exchanger/heater should operate at a temperature above 130 ℃ .

中文翻译：

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风冷式冷凝器热烟囱的 CFD 建模

摘要 热力烟囱驱动/增强型风冷冷凝器在建筑、热力和地热发电厂中的应用越来越广泛。设计了等面积矩形截面热力烟囱的小比例模型，并安装一排电加热器模拟管壳式换热器，并利用该模型对烟囱内的共轭传热进行了模拟。计算流体动力学 (CFD) 软件-ANSYS CFX 在各种加热器标称温度和 22.5 ℃ 环境温度下。采用的传热模型包括稳态三维雷诺平均 Navier-Stokes 方程和 k - ω 湍流模型以及 Boussinesq 浮力假设。考虑了加热器对空气的辐射效应。通过使用前视红外相机绘制加热器温度分布图，并通过使用粒子图像测速法测量烟囱中的空气速度以验证 CFD 速度场。测量的温度分布被建模并作为温度边界条件加入到 CFX 中。结果表明，加热器可以在烟囱中产生气流以产生冷却效果。随着加热器标称温度从80℃升高到170℃，烟囱能量增益系数从0.40升高到0.60，但超过130℃饱和，烟囱雷诺数在2000-4000之间，而加热器雷诺数变化范围为 140-270，加热器的努塞尔数低至 7.0-8.2。低于130℃可发生流动分离。来自加热器的辐射在传热中贡献了略多于 1/3 的贡献。建议初级换热器/加热器应在130℃以上的温度下运行。