带有横向微沟槽的矩形紧凑式通道换热器内超临界液化天然气工质换热强化特性模拟研究

Simulated research of enhanced heat transfer characteristics of LNG in rectangular small channels with horizontal micro-grooves

中文关键词: 强化换热、3D打印、微通道、超临界流体

英文关键词: Heat  transfer enhancement, 3Dprinting, Microchannel, Supercrtical fluid

中文摘要:

      提出了一种用于超临界液化天然气换热的微小通道换热器整体性能提高的被动式强化技术并进行了数值模拟验证和设计优化。在普通的矩形微小通道内利用3D激光打印技术在壁面加工横向圆弧形微沟槽以强化换热能力。首先对圆弧形微沟槽的槽深、槽宽和相邻两槽道中心距等几何尺寸进行了优化计算，然后讨论了在使用强化技术后工质温度在跨越临界温度的120K-250K范围内的换热强化和流动特性，进一步考察了工质温度、质量流量（雷诺数）和进口压力对换热系数（努塞尔数）、摩擦因子和综合效益系数的影响。此外，通过微沟槽附近的局部流动特性分析强化换热机理，数值模拟结果表明带有横向微沟槽的紧凑式换热器的综合换热效益得到30%左右增加，显示了优异的换热强化综合效果

英文摘要:

      Numerical simulations of heat transfer enhancement and flow resistance characteristics of LNG in a rectangular small channel with horizontal micro-grooves on both bottom and top wall are performed. The geometrical dimensions such as the groove depth, the groove width and the center distance between two adjacent micro-grooves were optimized, and then the heat transfer enhancement and flow of LNG within the range of 120 K-250 K which across the critical temperature after the use of the strengthening technology were discussed. Then, further effects of working fluid temperature, mass flow (Reynolds number), and inlet pressure on heat transfer coefficient (Nusselt number), friction factor, and comprehensive coefficient were investigated. In addition, by the analysis of local flow characteristics near the micro-grooves, the heat transfer mechanism is discussed. Numerical simulation results show that the heat transfer characteristics of the microchannel heat exchanger with lateral micro-grooves are strengthened by about 60%, and increase with the increase of Reynolds number. While, thee friction factor is minimal.