Convective Heat Transfer in a Thermal Chimney for Freshwater Production in Geothermal Total Flow Systems
Convective Heat Transfer in a Thermal Chimney for Freshwater Production in Geothermal Total Flow Systems
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DOI：
10.1016/j.applthermaleng.2023.120848
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发表时间：
2023-05
影响因子：
6.4
通讯作者：
Wenguang Li;Guopeng Yu;Z. Yu
中科院分区：
文献类型：
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作者：
Wenguang Li;Guopeng Yu;Z. Yu
为验证地热全流程制水系统的设计思想，在实验室规模的等截面矩形热烟囱中，采用两排电加热器模拟两个换热器，在顶排加热器的标称温度为60-200℃，低位加热器的标称温度为100℃，环境温度为20℃的条件下，对空气在热烟囱中的对流换热进行了实验和数值研究。基于三维稳态雷诺平均Navier-Stokes方程、Boussinesq浮力模型、k-ω湍流模型和能量方程，在ANSYS 2019 R CFX中对空气对流换热进行了计算流体力学模拟。考虑了加热器表面与烟囱壁面之间的热辐射。得到了烟囱的整体传热特性、温度场和流场。讨论了加热器表面边界条件和排间热辐射对传热的影响。双排加热器烟囱的热工性能优于单排加热器烟囱。计算结果与实验数据吻合较好，低排加热器的对流努塞尔数比单排加热器提高了（11.6-29.8）%。顶排加热器的最佳运行标称温度应高于140℃，最佳中心排距比为5。观察到加热器之间的间隙中的多个射流和穿过每排的温度跳变。最大速度和温度跃变随着加热器标称温度的增加而增加。
The convective heat transfer of air in a laboratory-scale thermal chimney with rectangular cross-section of constant area and two row electrical heaters simulating two heat exchangers was studied experimentally and numerically at 60–200℃ nominal temperatures of the top row heaters, 100℃ of the low row heaters and 20℃ ambient temperature to verify our design concept on freshwater production in geothermal total flow systems. Computational fluid dynamics simulations of air convective heat transfer were performed in ANSYS 2019R CFX based on the three-dimensional, steady Reynolds-averaged Navier-Stokes equations, Boussinesq buoyancy model, k-ω turbulence model, and energy equation. The thermal radiation between heater surfaces and chimney walls was considered. The overall thermal and heat transfer characteristics, temperature and flow fields in the chimney were obtained. Effects of boundary condition of heater surface and thermal radiation between two row heaters on heat transfer were discussed. The thermal characteristics of the chimney with two row heaters are better than that with single row heaters. The predicted thermal power and convective Nusselt number agree with the experimental data, and the convective Nusselt number of the low row heaters is enhanced by (11.6–29.8)% compared with the single row heaters. The optimal operating nominal temperature of top row heaters should be higher than 140℃, and the optimal centre-to-centre row gap ratio is 5. Multiple jets in the gaps among the heaters and temperature jump crossing each row were observed. The maximum velocity and temperature jump rise with increasing heater nominal temperature.