=0.0004+0.00058+0.000062+0.000625+0.025 =0.0267m2·K/W K=37.5W/m2·K 2)a1增大一倍,即a1=5000m2K时的传热系数K 0.0002+0.00058+0.000062+0.000625+0.025 K 00265m2.K/W K′=377W/m2.K 2021/2/21 上页下及
2021/2/21 = 0.0004+0.00058+0.000062+0.000625+0.025 0.0267m K /W 2 = K = W m K 2 37.5 / (2)α1增大一倍，即α1 =5000W/m2·K时的传热系数K’ 0.0002 0.00058 0.000062 0.000625 0.025 1 = + + + + K 0.0265m K /W 2 = K = W m K 2 37.7 /
K值增加的百分率 K′-K 37.7-37.5 1009 1009 K 37.5 =0.53 (3)a2增大一倍,即a2=100Wm2k时的传热系数K 1 0.0004+0.00058+0.000062+0.000625+00125 K =00142m2.K/W K"=70.4W/m2.K K-K 70.4-37.5 K值增加的百分率= 100 K 375×100%=87.8% 2021/2/21 上页下页
2021/2/21 K值增加的百分率 100% − = K K K 100% 37.5 37.7 37.5 − = = 0.53% （3）α2增大一倍，即α2 =100W/m2·K时的传热系数 K 0.0004 0.00058 0.000062 0.000625 0.0125 1 = + + + + K 0.0142m K /W 2 = K = W m K 2 70.4 / K值增加的百分率 100% − = K K K 100% 37.5 70.4 37.5 − = = 87.8%