玻璃传热系数k值.docx

［新版］玻璃传热系数k值玻璃传热系数K值幕墙中空玻璃传热系数计算方法如下：1.公式P r=uc /入式中U——动态黏度，取1.761X10-5kg/(m?s);c——比热容，空气取 1.008X103J/(kg?K)、氩气取 0.519X103J/(kg?K);入——导热系数，空气取2.496X10-2W/(m?K)、氩气取1.684X10- 2W/(m?K)G r=9.81s 3ATP2/Tmu2式中s—— 中空玻璃的气层厚度(m);AT——外片玻璃表面温差，取15K;P ——密度，空气取1.232kg/m3、氩气取1.669 kg/m3;T m——玻璃的平均温度，取283K;U——动态黏度，空气取1.761X10-5kg/(m?s)、氩气取2.164X10- 5kg/(m?s)N u= 0.035(G r Pr)0.38，如计算结果 Nu,1，取 Nu=1H g= N u 入/s W/(m2?K)H T =4Z(1/e1+1/e2-1)-1XTm 3 式中 Z——常数，取 5.67X10-8 W/(m2?K4);8 1 外片玻璃表面的校正辐射率；8 2 内片玻璃表面的校正辐射率； 8 1、82取值：普通透明玻璃nv,15% 0.837(GB/T2680 表 4)真空磁控溅射镀膜玻璃nv?15% 0.45 (GB/T2680表4)nv,15% 0.70 (GB/T2680表4) LOW-E镀膜玻璃nv,15%应由试验取得，如 无试验资料时可取 0.09~0.115。

h s = h g + h T1/h t=1/h s+5 / r1式中5——两片玻璃总厚度；r1——玻璃热阻，取1(m?K)/W1/U=1/h e +1/h i+1/h t式中h e——玻璃外表面换热系数，取23(19)W/(m2?K);h i——玻璃内表面换热系数，取8(8.7)W/(m2?K)括号中数字为GB50176有 关规定2.例题例1求12mm白玻+12mm(空气)+ 12mm白玻中空玻璃的传热系数解 P r=uc/入二1.761X10-5X1.008X103 /2.496X10-2=0.711Gr=9.81s3ATp2/Tmu 2=9.81X0.0123X 15X 1.2322/283X(1.761X 10-5)2= 4398N u 0.035(G r Pr)0.38= 0.035(0.711X4398)0.38=0.745取 Nu=1H g= N u 入/s =1X2.496X10-2/0.012=2.08 W/(m2?K)hT = 4Z(1/e1+1/e2-1)-1XTm 3=4X5.67X 10-8X(1/0.837+1/0.837-1)-h s = h g + h T =2.08+3.7=5.78 W/(m2?K)1/h t=1/h s+5 / r1=1/5.78+0.024/1=0.197(m2?K)/ W1/U=1/h e +1/h i+1/h t=1/8+1/23+0.197=0.365m2?K)/ WU=1/0.365=2.74 W/(m2?K)例 2 求 12mm 热反射(nv,15% e1 =0.70)+12mm(空气)+ 12mm白玻中空玻璃的传热系数。

解 P r = uc/入二1.761X10-5X1.008X103 /2.496X10-2 =0.711Gr=9.81s3ATp2/Tmu 2=9.81X0.0123X 15X 1.2322/283X(1.761X 10-5)2= 4398N u 0.035(G r Pr)0.38= 0.035(0.711X4398)0.38=0.745 取 Nu=1H g= N u 入/s =1X2.496X10-2/0.012=2.08 W/(m2?K)H T =4Z(1/e1+e2-1)-1XTm 3=4X5.67X10-8X(1/0.70+1/0.837-1)-1X2833=3.17 W/(m2?K)h s = hg + hT =2.08+3.17=5.25 W/(m2?K)1/h t=1/h s+6/r1=1/5.25+0.024/1=0.2.14(m2?K)/ W1/U=1/h e +1/h i+1/h t=1/8+1/23+0.214=0.382m2?K)/ WU=1/0.382=2.62 W/(m2?K)例3求12mm白玻+12mm(空气)+ 12mm LOW-E中空玻璃的传热系数解 P r= uc/入二1.761X10-5X1.008X103 /2.496X10-2 =0.711Gr=9.81s3ATp2/Tmu 2=9.81X0.0123X 15X 1.2322/283X(1.761X10-5)2= 4398N u 0.035(Gr Pr)0.38= 0.035(0.711X4398)0.38=0.745 取 Nu=1H g= Nu 入/s =1X2.496X10-2/0.012=2.08 W/(m2?K)HT=4Z(1/e1+1/e2-1)-1XTm 3=4X5.67X 10-8X(1/0.837+1/0.10-1)-1X2833=0.504 W/(m2?K)h s = hg + h T =2.08+0.504=2.584 W/(m2?K)1/h t=1/h s+5 / r1=1/2.584+0.024/1=0.411(m2?K)/ W1/U=1/h e +1/h i+1/h t=1/8+1/23+0.411=0.579m2?K)/ WU=1/0.579=1.73 W/(m2?K)例4求12mm白玻+12mm(氩气)+ 12mm白玻 中空玻璃的传热系数。

解 P r=uc/入二2.164X10-5X0.519X103 /1.684X10-2 =0.6669Gr=9.81s3ATp2/Tmu 2=9.81X0.0123X 15X 1.6992/283X(2.164X 10-5)2= 5538Nu 0.035(Gr Pr)0.38= 0.035(0.6669X5538)0.38=0.794取 Nu=1hg= Nu 入/s =1X1.684X10-2/0.012=1.4 W/(m2?K)h T =4Z(1/e1+1/e2-1)-1XTm 3=4X5.67X 10-8X(1/0.837+1/0.837-1)-1X2833=3.7 W/(m2?K)h s = hg + hT =1.4+3.7=5.10 W/(m2?K)1/h t=1/h s+5 / r1=1/5.10+0.024/1=0.22(m2?K)/ W1/U=1/h e +1/h i+1/h t=1/8+1/23+0.22=0.388 m2?K)/ W例5求12mm白玻+12mm(氩气)+ 12mm LOW-E中空玻璃的传热系数解 P r=uc/入二2.164X10-5X0.519X103 /1.684X1Q-2=0.6669Gr=9.81s3ATp2/Tmu 2=9.81X0.0123X 15X 1.699 2/283X(2.164X 10-5)2=5538Nu 0.035(Gr Pr)0.38= 0.035(0.6669X5538)0.38=0.794 取 Nu=1hg= Nu 入/s =1X1.684X10-2/0.012=1.4 W/(m2?K)hT =4Z(1/e1+1/e2-1)-1XTm 3=4X5.67X 10-8X(1/0.837+1/0.10-1)-1X2833=0.504 W/(m2?K)h s = hg + hT =1.4+0.504=1.904 W/(m2?K)1/h t=1/h s+6/r1=1/1.904+0.024/1=0.549(m2?K)/ W1/U=1/h e +1/h i+1/h t=1/8+1/23+0.549=0.717m2?K)/ WU=1/0.717=1.39 W/(m2?K)。