自然對流換熱試驗(yàn)

自然對流換熱試驗(yàn)?zāi)夸?1.1)代碼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.定性溫度（℃）：');tm=(tw+tf)/2fprintf('1.1以定性溫度查的密度（kg/m^3）：');rou=(1.165-1.128)/(30-40)*(tm-30)+1.165fprintf('1.2以定性溫度查的導(dǎo)熱系數(shù)（W/(m·K)）：');lamda=(2.76e-2-2.67e-2)/(40-30)*(tm-30)+2.67e-2fprintf('1.3以定性溫度查的運(yùn)動(dòng)粘度（m^2/s）：');miu=((16.96-16.00)/(40-30)*(tm-30)+16.00).*1e-6fprintf('1.4以定性溫度查的普朗特?cái)?shù)：');Pr=(0.699-0.701)/(40-30)*(tm-30)+0.701fprintf('2.流體速度（m/s）：');u=sqrt(2*deltaP./rou)fprintf('3.雷諾數(shù)：');Re=u.*d./miufprintf('4.實(shí)驗(yàn)測得努塞爾數(shù)：');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.努塞爾數(shù)理論計(jì)算值：');Nu_calfprintf('6.相對偏差（%%）：');e=100*abs(Nu-Nu_cal)./Nu_calfprintf('7.對流換熱量計(jì)算（單位J）：');qConvection=U.*Ifprintf('8.輻射換熱量估算（取表面發(fā)射率為0.5，單位J）：');qRadiation=0.5*5.67e-8*(tw.^4-tf.^4)*(pi*d*l)。(1.2)運(yùn)行結(jié)果1.定性溫度（℃）：tm=30.845032.000033.020034.125035.85501.1以定性溫度查的密度（kg/m^3）：rou=1.16191.15761.15381.14971.14331.2以定性溫度查的導(dǎo)熱系數(shù)（W/(m·K)）：lamda=0.02680.02690.02700.02710.02721.3以定性溫度查的運(yùn)動(dòng)粘度（m^2/s）：miu=1.0e-04*0.16080.16190.16290.16400.16561.4以定性溫度查的普朗特?cái)?shù)：Pr=0.70080.70060.70040.70020.69982.流體速度（m/s）：u=19.170517.649515.798913.738211.40813.雷諾數(shù)：Re=1.0e+03*4.44664.06583.61763.12542.56934.實(shí)驗(yàn)測得努塞爾數(shù)：Nu=35.356133.377030.824028.011324.88915.努塞爾數(shù)理論計(jì)算值：Nu_cal=30.801829.140527.611525.789723.53546.相對偏差（%）：e=14.785914.538111.63468.61415.75187.對流換熱量計(jì)算（單位J）：qConvection=5.76165.84485.85325.86315.87998.輻射換熱量估算（取表面發(fā)射率為0.5，單位J）：qRadiation=1.0e-03*0.08310.09990.11970.14700.1945。(2.1)代碼%用最小二乘擬合計(jì)算出實(shí)驗(yàn)關(guān)聯(lián)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次多項(xiàng)式擬合（即線性擬合）LnNu=vpa(poly2sym(p,LnGrPr),5)n=vpa(p(1),5)C=vpa(exp(p(2)),5)%求n和C。%雙對數(shù)坐標(biāo)圖繪制曲線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('原始數(shù)據(jù)點(diǎn)','擬合曲線','location','northwest');xlabel('GrPr');ylabel('Nu');title('水平管外自然自然對流換熱試驗(yàn)曲線');scatter(GrPr(9),Nu(9),'o');legend('原始數(shù)據(jù)點(diǎn)','擬合曲線','3#組數(shù)據(jù)點(diǎn)','location','northwest');gtext(['3#','(',num2s