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翅片管束管外放热和阻力实验
测试数据
表1 测试数据表
测试次数动压头(Pa)静压(Pa)空气温度(℃)热电偶测热管蒸汽温度—
—读数(mV)箱温(mV)电压(V)电流(A)ΔPHtitot1t2t3t4t5100359.713.93.9983.6413.054.7840.3452485.89200509.812.73.7143.2122.6384.4430.3482485.9300909.912.33.5652.9372.3944.2440.3582485.914001109.811.93.4742.7862.264.1320.3582485.915001401011.73.4082.6822.1684.0530.3812485.916001609.811.43.3572.5912.0823.9850.3852485.91
物性参数的确定
管内蒸汽温度的确定
表2 试验管内蒸汽平均温度
热电偶测管内蒸汽温度——读数(mV)t1t2t3t4tm蒸汽温度(℃)3.9983.6413.054.7843.86890.93.7143.2122.6384.4433.50282.93.5652.9372.3944.2443.28578.13.4742.7862.264.1323.16375.43.4082.6822.1684.0533.07873.53.3572.5912.0823.9853.00471.9
空气平均温度及空气参数的确定
测试次数空气温度(℃)空气物性参数入口出口平均温度tf密度(kg/m3)出口处密度(kg/m3)比热(J/kg.K)导热系数(W/m.K)运动粘度(m2/s)19.713.911.81.2391.231 1005.00 0.0252 1.43E-059.812.711.251.2421.236 1005.00 0.0252 1.43E-059.912.311.11.2421.237 1005.00 0.0252 1.43E-059.811.910.851.2431.239 1005.00 0.0252 1.42E-051011.710.851.2431.240 1005.00 0.0252 1.42E-059.811.410.61.2441.241 1005.00 0.0251 1.42E-05
实验数据的整理计算
计算风速和风量
表3 风速和风量计算表
测试次数动压头(Pa)测速处风速(m/s)风量 Ma(kg/s)测速外流道截面积(m2)空气侧吸热量 (W)110012.700.380.0241583.63220017.950.531551.27330021.980.651574.08440025.360.751591.88550028.360.841441.74660031.050.921487.33其中,空气侧吸热量:
电加热器功率
加热器箱体散热
因箱体温度很低,散热量小,可由自然对流计算,其中,自然对流散热系数近似取5W/m2.℃。
表4 加热器箱体散热量
测试次数箱 温环境温度(℃)箱体散热面积箱体散热量(W)读数(mV)温度(℃)0.3458.58.44*0.58*0.32=
0.74240.370.3488.98.41.860.3589.28.42.970.3589.28.42.970.3819.78.44.830.3859.88.45.2
计算热平衡误差
表5 热平衡误差表
空气侧吸热量Q1箱体散热量Q3功率(W) Q2热平衡误差%1583.630.371460.77.78451551.271.861463.25.79691574.082.971465.77.0751591.882.971465.78.1141441.744.831465.7-1.3251487.335.21465.71