化工原理空氣蒸汽給熱系數(shù)測定實驗報告

空氣－蒸汽給熱系數(shù)測定一、試驗?zāi)康牧私忾g壁式傳熱元件，把握給熱系數(shù)測定的試驗方法。把握熱電阻測溫的方法，觀看水蒸氣在水平管外壁的冷凝現(xiàn)象。理解強化傳熱對傳熱系數(shù)的影響。二、根本原理冷流體的對流傳熱所組成。到達傳熱穩(wěn)定時，有Q=m1cp1(T1-T2)=m2cp2(t2-t1)=α1A1(T-TW)M=αA(t-t)m

2 2 wQ－傳熱量，J/s；m1－熱流體的質(zhì)量流率，kg/s；cp1－熱流體的比熱，J/(kg?℃)；T1－熱流體的進口溫度，℃；T2－熱流體的出口溫度，℃；m2－冷流體的質(zhì)量流率，kg/s；J/(kg?℃)；t1－冷流體的進口溫度，℃；t2－冷流體的出口溫度，℃；1α－熱流體與固體壁面的對流傳熱系數(shù)，W/(m2?℃)；1A1－熱流體側(cè)的對流傳熱面積，m2；(T?T )－熱流體與固體壁面的對數(shù)平均溫差，℃；Wmα2－冷流體與固體壁面的對流傳熱系數(shù)，W/(m2?℃)；A2－冷流體側(cè)的對流傳熱面積，m2；(tW-t)m－固體壁面與冷流體的對數(shù)平均溫差，℃；KA為基準的總給熱系數(shù)，W/(m2?℃)；Δt－冷熱流體的對數(shù)平均溫差，℃；m數(shù)是人們廣泛承受的一種試驗爭論手段。測定m2、t1、t2、T1、T、并查t c

、換熱面積A，即2 平均 p2可由上式計算得總給熱系數(shù)K。α2對于流體在圓形直管內(nèi)作強制湍流對流傳熱時，傳熱準數(shù)閱歷式為Nu=0.023Re0.8PrnNu=αd/λ，無因次；Re－雷諾數(shù)，Re=duρ/μ，無因次；Pr－普蘭特數(shù)，Pr=cpμ/λ，無因次；n＝0.4n＝0.3；W/(m2·℃)；d－換熱管內(nèi)徑，m；λ－流體的導(dǎo)熱系數(shù)，W/(m·℃)；u－流體在管內(nèi)流淌的平均速度，m/s；ρ－流體的密度，kg/m3；μ－流體的粘度，Pa·s；cp－流體的比熱，J/(kg·℃)。對于水或空氣在管內(nèi)強制對流被加熱時，令d2肯定時，m也X、YX～Y圖上m。任一冷流體流量下的給α2可用下式求得，4．冷流體物性與溫度的關(guān)系式0～100℃之間，冷流體的物性與溫度的關(guān)系有如下擬合公式?！?〕空氣的密度與溫度的關(guān)系式：ρ=10-5t2-4.5E-10+1.2916空氣的比熱與溫度的關(guān)系式：60℃以下Cp＝1005J/(kg·℃)，70Cp＝1009J/(kg·℃)。λ=-2E-8t2+8E-5t+0.0244；μ=(-2E-6t2+5E-3t+1.7169)E-5；四、試驗步驟與留意事項〔一〕試驗步驟是否正常。處于保溫狀態(tài)。器里充有肯定量的空氣。45、在通水蒸汽前，將蒸汽發(fā)生器到試驗裝置之間管道中的冷凝水排解。610因突然受熱、受壓而爆裂。0.01MPa。的流量，在每個流量下，必需等熱交換過程穩(wěn)定前方可記錄試驗數(shù)值。轉(zhuǎn)變流量，記錄8組試驗數(shù)據(jù)。9、然后向另一根紫銅管通入空氣，重復(fù)操作步驟8，測量另一根管的傳熱系數(shù)。、試驗完畢，先關(guān)閉蒸汽發(fā)生器，關(guān)閉蒸汽進口閥，關(guān)閉儀表電源，待系統(tǒng)漸漸冷卻水冷卻后將發(fā)生器內(nèi)的剩余水排盡。五、數(shù)據(jù)處理一般管冷空氣熱蒸汽序號:冷空氣熱蒸汽序號體積流量進口溫度出口溫度進口溫度出口溫度1Qv2(m3/h)13.4t〔℃〕135.2t〔℃〕278.3T〔℃〕1102.2T〔℃〕2101.5210.934.978.5102.3101.9310.534.178.8102.31024933.178.9102.2101.957.532.579.6102.5102.165.931.679.9102.7102.374.330.779.7102.2101.882.830.378.7102.5102序號空氣流速序號空氣流速u〔m/s〕對數(shù)平均溫差tm冷流體平均溫t空氣密度ρ〔Kg/m3)空氣質(zhì)量流q空氣黏度μm2(Kg/h)Pa/s×10-5空氣的導(dǎo)熱系λW?m-1?K-1118.5222045341.5559391156.751.145590415.350911361.99421E-050.028875589215.0665693641.7388465856.71.146730112.499358091.99397E-050.028871702314.5136677341.8459092656.451.149778112.072670051.99278E-050.028852268412.4402866242.02261265561.153606110.38245491.99063E-050.02881728510.3669055242.0104697156.051.15591258.669343751.99087E-050.028821168683262643255.751.15938566.840375041.98943E-050.02879783975.94369249842.2398588155.21.16287495.000362071.98681E-050.02875505983.87031139443.434689554.51.16443093.260406521.98346E-050.028700595序給熱系數(shù)傳熱系數(shù)誤差2序給熱系數(shù)傳熱系數(shù)誤差2號XKYα試驗值理論值13.1612122.11730.0452167.4051382.402101-0.18199723.7220418.13790.0551355.27749869.907994-0.20928233.8249717.91480.0558254.59746367.981052-0.19687244.3157615.71940.0636247.90679360.236051-0.20468254.9714113.50210.0740641.14946752.145849-0.21087765.9936710.84350.0922233.04697643.132911-0.23383477.730148.058030.1241024.55781333.557396-0.268185810.83625.047010.1981415.3813723.823376-0.3543581.4號 Re Pr Nu ln(Re) ln(Nu/Pr0.)122344.502580.694074149.02091310.0143364.0383176218196.011990.694084540.2064089.80895773.840091317585.383590.694136339.738539.77482343.828356415139.694670.694229734.911099.62507543.6987855512640.119860.694219329.9827829.44463123.546610269980.6212930.694281624.0985629.20840063.328103277305.5543950.69439617.9347258.89639023.032623984771.5072470.69454211.2544278.47041752.5665627序以 ，依據(jù)表1.3計算數(shù)據(jù)作線性擬合，得到的結(jié)果如圖1：序1一般管冷流體對流傳熱系數(shù)擬合曲線m=0.001984，截距=-0.02085R2=0.99097。Nu/Pr0.4=Ar1.4中數(shù)據(jù),ln(Nu/P0.4ln(Re為橫坐標，2：2直管冷流體準數(shù)式擬合曲線截距=-5.345R2=0.9967，A=4.7729×10-3。加強管冷空氣熱蒸汽序號:冷空氣熱蒸汽序號體積流量進口溫度出口溫度進口溫度出口溫度1Qv2(m3/h)8.5t〔℃〕136t〔℃〕293.6T〔℃〕1102T〔℃〕2101.427.535.393.6102.2101.736.634.493.5102.2101.745.733.593.3102.4101.954.832.493.1102.4101.963.831.892.9102.6102.172.831.191.8102.8102.281.930.789.6102.9102.4序號空氣流速u序號空氣流速u〔m/s〕對數(shù)平均溫差tm冷流體平均溫t空氣密度ρ〔Kg/m3)空氣質(zhì)量流qm2(Kg/h)空氣黏度μPa/s×10-5空氣的導(dǎo)熱系數(shù)λW?m-1?K-1111.7491595927.7738451464.81.142569.711762.0325E-050.029500019210.3669055228.278787864.451.14521098.589081752.03084E-050.02947292439.12287685828.6435302363.951.14863367.580981762.02847E-050.02943420847.87884819529.3986647763.41.15207256.566813252.02586E-050.02939160956.63481953329.9307066562.751.15629765.550228482.02277E-050.02934124965.25256546430.5960795962.351.15861244.402727122.02087E-050.0293102573.87031139432.2046166461.451.16132213.251701882.0166E-050.02924047882.62628273234.6643758760.151.16287492.209462312.01041E-050.02913964序給熱系數(shù)給熱系數(shù)誤差序給熱系數(shù)給熱系數(shù)誤差2號XKYα試驗值理論值14.643027.97940.0357485.27054457.4301630.484769325.108824.59850.0406574.96682552.0429060.440481235.639821.72900.0460266.22180447.0809240.406552846.307318.55590.0538956.55133541.9560510.347870857.206315.63640.0639547.65376336.658740.299929167.649512.21380.0818737.22303830.4504740.2224124710.98128.51400.1174525.94752323.8809860.0865348814.90585.21520.1917515.89399717.515651-0.0925832.4序號RePrNuln(Re)ln(Nu/Pr0.)113869.926150.692428260.7010269.53747824.2529809212276.588170.692498953.4152419.41544934.1250756310848.354390.692647.2463169.29176874.002295849409.1895930.692711440.4053439.14944213.845818857964.7194520.692843334.1065598.9827773.676270366323.9656030.692924626.6692998.75210183.430246774680.5685050.69310818.6350578.4511