自然对流换热试验

自然对流换热试验目录(1.1)代码clc;clear;d=3.73e-3;l=99.6e-3;tw=[40.5742.4144.2746.4849.72];tf=[21.1221.5921.7721.7721.99];deltaP=[213.5180.3144.0108.574.4];U=[0.39460.39790.39850.39920.4004];I=[14.60114.68914.68814.68714.685];fprintf('1.定性温度（℃）：');tm=(tw+tf)/2fprintf('1.1以定性温度查的密度（kg/m^3）：');rou=(1.165-1.128)/(30-40)*(tm-30)+1.165fprintf('1.2以定性温度查的导热系数（W/(m·K)）：');lamda=(2.76e-2-2.67e-2)/(40-30)*(tm-30)+2.67e-2fprintf('1.3以定性温度查的运动粘度（m^2/s）：');miu=((16.96-16.00)/(40-30)*(tm-30)+16.00).*1e-6fprintf('1.4以定性温度查的普朗特数：');Pr=(0.699-0.701)/(40-30)*(tm-30)+0.701fprintf('2.流体速度（m/s）：');u=sqrt(2*deltaP./rou)fprintf('3.雷诺数：');Re=u.*d./miufprintf('4.实验测得努塞尔数：');h=(U.*I)./(pi*d*l)./(tw-tf);Nu=h.*d./lamdaNu_cal=zeros(1,5);fori=1:5if(Re(i)>=40)&&(Re(i)<=4000)Nu_cal(i)=0.683*(Re(i)^0.466)*(Pr(i)^(1/3));elseif(Re(i)>4000)&&(Re(i)<=40000)Nu_cal(i)=0.193*(Re(i)^0.618)*(Pr(i)^(1/3));endendfprintf('5.努塞尔数理论计算值：');Nu_calfprintf('6.相对偏差（%%）：');e=100*abs(Nu-Nu_cal)./Nu_calfprintf('7.对流换热量计算（单位J）：');qConvection=U.*Ifprintf('8.辐射换热量估算（取表面发射率为0.5，单位J）：');qRadiation=0.5*5.67e-8*(tw.^4-tf.^4)*(pi*d*l)。(1.2)运行结果1.定性温度（℃）：tm=30.845032.000033.020034.125035.85501.1以定性温度查的密度（kg/m^3）：rou=1.16191.15761.15381.14971.14331.2以定性温度查的导热系数（W/(m·K)）：lamda=0.02680.02690.02700.02710.02721.3以定性温度查的运动粘度（m^2/s）：miu=1.0e-04*0.16080.16190.16290.16400.16561.4以定性温度查的普朗特数：Pr=0.70080.70060.70040.70020.69982.流体速度（m/s）：u=19.170517.649515.798913.738211.40813.雷诺数：Re=1.0e+03*4.44664.06583.61763.12542.56934.实验测得努塞尔数：Nu=35.356133.377030.824028.011324.88915.努塞尔数理论计算值：Nu_cal=30.801829.140527.611525.789723.53546.相对偏差（%）：e=14.785914.538111.63468.61415.75187.对流换热量计算（单位J）：qConvection=5.76165.84485.85325.86315.87998.辐射换热量估算（取表面发射率为0.5，单位J）：qRadiation=1.0e-03*0.08310.09990.11970.14700.1945。(2.1)代码%用最小二乘拟合计算出实验关联式clc;clear;symsLnGrPr;GrPr=[458934.6128178.681973.5347893.6119037641523845241316.5586097.9811834.91291265];Nu=[12.779.539.428.0217.5117.0111.3915.1613.101315.54];ln_GrPr=log(GrPr);ln_Nu=log(Nu);p=polyfit(ln_GrPr,ln_Nu,1);%1次多项式拟合（即线性拟合）LnNu=vpa(poly2sym(p,LnGrPr),5)n=vpa(p(1),5)C=vpa(exp(p(2)),5)%求n和C。%双对数坐标图绘制曲线clc;clear;GrPr=[458934.6128178.681973.5347893.6119037641523845241316.5586097.9811834.91291265];Nu=[12.779.539.428.0217.5117.0111.3915.1613.101315.54];figure;loglog(GrPr,Nu,'*');holdon;gridon;p=polyfit(log(GrPr),log(Nu),1);x=min(GrPr):0.1:max(GrPr);y=exp(polyval(p,log(x)));loglog(x,y,'-');%legend('原始数据点','拟合曲线','location','northwest');xlabel('GrPr');ylabel('Nu');title('水平管外自然自然对流换热试验曲线');scatter(GrPr(9),Nu(9),'o');legend('原始数据点','拟合曲线','3#组数据点','location','northwest');gtext(['3#','(',num2s