凹陷阵列印刷电路板式换热器里超临界甲烷换热和流动特性模拟研究

为了强化液化甲烷在印刷电路板式微通道换热器中的换热能力,提出了一种凹陷阵列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。研究了流体温度范围125—265 K范围内的超临界甲烷在凹陷阵列结构微通道内的换热和流动特性,考察了凹陷阵列微通道和光滑微通道下,流体温度、质量流量、雷诺数和进口压力对传热系数、努塞尔数、摩擦因子和综合效益系数(PEC)的影响。此外,通过凹陷结构的局部流动特性分析强化换热机理,数值模拟结果表明相较于光滑微通道,凹陷阵列微通道的换热特性得到大大强化,且随雷诺数(由质量流量或者流体温度改变)的增大而增强,而摩擦因子只是有较弱的劣化。

Numerical study on enhanced heat transfer and flow characteristics of supercritical methane in square micro-channels with dimple-shaped array

The heat transfer and flow characteristics of supercritical methane in square micro channels with dimple-shaped array were studied numerically to enhance the thermal performance of liquid natural gas in the micro-channels heat exchanger.The bulk temperature of fluid is varied from 125K to 265K,which covers the critical temperature of supercritical methane.The study focused on the effects of Reynolds number or the mass flow rate,the bulk temperature or inlet temperature and the pressure on the Nusselt number,flow friction and PEC after substituting dimple-shaped enhancing channel for the smooth channel.Moreover,the local flow pattern and thermal performance were analyzed to reveal the mechanism of enhanced heat transfer.The results show that the heat transfer of supercritical methane in the dimple-shaped enhancing channels has been intensified compared to the smooth channel.While,the flow friction in the dimple-shaped enhancing channel appeared to deteriorate slightly.It is found that the thermal enhancement is attributed to the dimple-shaped structure which results in a small vortex in a dimple and the increase of turbulent kinetic energy.