外掠管束间空气-水蒸发冷却传热传质及压降特性模拟

为进一步揭示外掠管束间蒸发冷却传热传质及压降特性，综合考虑了管束壁面水膜的形成及湿空气-喷淋水间传质过程，采用DPM(Discrete phase model)与水膜耦合的欧拉-拉格朗日方法，建立了外掠管束间空气-水蒸发冷却传热传质及压降特性分析模型。首先，采用文献实验数据验证了模型的可靠性，其误差在1%范围内；然后，采用模拟方法，研究了外掠管束间传热传质及压降沿竖直高度方向的变化特征。结果表明：由于湿空气焓差和饱和空气焓差的变化，导致传质系数沿盘管高度方向发生波动，但总体呈降低趋势；在同一工况下，湿空气焓差对传质系数的影响较大，传质系数的波动主要是湿空气焓变化造成的；外掠交错管束间喷淋水膜温度并非保持恒定不变，而是随盘管高度的降低而降低，即沿下落方向液膜温度逐渐降低；交错管束底部区域喷淋水蒸发量最大，沿盘管高度方向，喷淋水蒸发量降低；喷淋水发过程主要发生在管束表面及管束尾流区，通过在管束间增加挡板或者减小管间距，可以强化管束表面及尾流区流场扰流作用，增强喷淋水的蒸发冷却作用；交错管束间传热系数在换热盘管中间稳定区域变化较小，其受进气温度、喷淋水温度及相对湿度的影响较小；交错管束间压力...

Simulation of heat/mass transfer and pressure drop characteristics of air-water evaporative cooling between staggered tube bundles

To further reveal the heat/mass transfer and pressure drop characteristics of evaporative cooling between staggered tube bundles, considering the formation of water film on the tube bundle wall and the mass transfer process between wet air and spray water, an analytical model was established by using the Euler-Lagrange method based on the coupling of discrete phase model (DPM) and wall film. First, the reliability of the model was verified by the experimental data from literature, and the error was within 1%. Then, the characteristics of heat/mass transfer and pressure drop between staggered tube bundles along the vertical direction were studied by simulation method. Results show that the mass transfer coefficient fluctuated along the coil height due to the variation of the enthalpy differences of wet air and saturated air, but the overall trend was decreasing. Under the same working condition, the influence of the enthalpy difference of wet air was greater on the mass transfer coefficient, and the fluctuation of mass transfer coefficient was mainly caused by the enthalpy variationof wet air. The temperature of the spray water film between staggered tube bundles was not constant, but it decreased with the decrease in the coil height, that is, the temperature of the liquid film gradually decreased along the falling direction. The spray water evaporation in the bottom area of the staggered tube bundle was the largest, and it decreased along the height of the coil. The spraying process mainly occurred on the surface of the tube bundle and the wake area of the tube bundle. By adding baffles or reducing the distance between the tube bundles, the turbulence of the flow field on the surface and the wake area of the tube bundles was strengthened, and the evaporative cooling effect of the spray water was enhanced.The heat transfer coefficient between the staggered tube bundles had little changes in the middle stable region of the heat exchange coil, and it was less affected by the inlet air temperature, spray water temperature, and relative humidity. The pressure loss between the staggered tube bundles had little changes along the coil height, and it was the largest in the air inlet transition area of the heat exchange coil. The above research results provide theoretical basis for the design of heat/mass transfer and pressure drop performance of air-water evaporative cooling between staggered tube bundles.