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数 序 号 项目 据 K[W/m2?K] 164.380 151.965 136.722 125.776 102.684 Nu 87.971 80.918 72.413 66.127 53.482 表3

Re 43692.707 39094.017 33888.966 29917.224 23206.682 log10Nu log10Re 1 2 3 4 5 1.944 1.908 1.860 1.820 1.728 4.640 4.592 4.530 4.476 4.366 lgNu—lgRe关系曲线图2.001.951.901.851.801.751.704.354.404.454.504.554.604.654.70

图1

Nu?0.0228Re0.79Pr0.4

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八、计算举例：

取第4组数据举例计算

1.传热系数K的计算：

Vs?Vh/3600?22.83m/s?0.00633m3/s 3600??0.4645???pa?RP????0.4645?273?t1???761?58.2?33??273?30.6??kg/m?1.253kg/m??tm??t1?t2?/2?30.6?90.6?C?60.60?C

2Cp?1009?0.04tm?1009?0.04?60.60?1011.42J/kg?K

q?Vs?Cp?t2?t1??0.00633?1.253?1011.42??90.6?30.6??481.716WAm??dmL?3.14159?18.8?16.8?10?3?1224?10?3m2?0.069565m22?t1??T?t1???121.0?30.6??C?90.4?C ?t2??T?t2???121.0?90.6??C?30.4?C

?tm??t1??t290.4?30.4?K?55.06K ?t190.4lnln30.4?t2K?qAm??tm?481.716W/m2?k?125.776W/m2?k

0.069565?55.06同理，其他组数据计算结果如表2和表3. 2.传热膜系数（给热系数）及其关联式的计算：

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??　?Ai?tW?tm?q?Am?T?tm?q481.716W/m20.069565??121.0?60.60?　?114.647W/m2??0.0244?7.8?10?5tm　?0.0244?7.8?10?5?60.60W/m?K 　?0.02913W/m?KNu?d114.647?16.8?10?3???66.127 ?0.02913u?Vs?d???????2?2?0.00633?16.8?103.14159???2??3????2m/s?28.571m/s

??1.72?10?5?4.8?10?8tm　?1.72?10?5?4.8?10?8?60.60Pa/s 　?0.0000201Pa/sRedu?16.8?10?3?28.571?1.253???29917.224

?0.0000201log10Nu?log1066.127?1.820 log10Re?log1029917.224?4.476

同理，其他组数据计算结果如表2和表3. 作log10Nu?log10Re关系曲线图如图1. 由图像可得：

m?1.944?1.728?0.79

4.640?4.366log10A'?log10Nu?mlog10Re?1.820?0.79?4.476??1.7

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A'?10?1.7?0.0197 A?A'0.865?0.0197?0.0228

0.865所以传热膜系数的通用关联式为：

Nu?0.0228Re0.79Pr0.4页脚