Abstract:

Due to the fact that the heat exchange wall surface is not absolutely smooth during the actual heat exchange process of the heat exchanger, and the rough heat exchange wall surface is easy to foul at some local locations. Therefore, based on the constructed local crystallization fouling model, the local deposition characteristics of CaCO₃ fouling under different roughness element structures are numerically simulated in this study. The roughness elements of three different shapes (rectangular, trapezoidal and triangular) are compared, and the influence of the relative height and relative width of the triangular roughness element is analyzed in detail. The results show that the average value of local fouling resistance in the three roughness element channels is smaller than that in the smooth channel, and the average value of local fouling resistance in the triangular roughness element is the smallest. The local fouling resistance of the three roughness element channels changes periodically along the channel length, and there are peaks in each cycle, and the maximum peak is located on the leeward side of the roughness element. In addition, the local fouling resistance decreases with the increase of the relative height of the triangular roughness element, and increases slightly with the increase of the relative width, indicating that the relative height has a greater influence on the local fouling deposition.

Key words: roughness elements, CaCO₃ fouling, model, local fouling resistance, fouling, numerical simulation

摘要：

由于换热器实际的热交换过程中换热壁面并非绝对光滑，而粗糙换热壁面很容易在部分局部位置处结垢，因此基于已构建的局部析晶污垢模型，对不同粗糙元结构下CaCO₃污垢局部沉积特性进行数值模拟研究。对比了三种不同形状（矩形、梯形和三角形）的粗糙元，并详细分析了三角形粗糙元的相对高度和相对宽度的影响。结果表明，三种粗糙元通道内的局部污垢热阻平均值均小于光滑通道，其中三角形粗糙元的局部污垢热阻平均值最小。三种粗糙元通道局部污垢热阻沿通道长度增加均呈周期性变化，且在每个周期内均存在峰值，其中最大峰值位于粗糙元背风侧。此外，局部污垢热阻随着三角形粗糙元相对高度的增加而减小，随着相对宽度的增加而略有增加，说明相对高度对局部污垢沉积影响更大。

关键词: 粗糙元, CaCO₃污垢, 模型, 局部污垢热阻, 结垢, 数值模拟