材料热力学习题答案VIP免费

Theproblemsofthefirstlaw1.aleadbulletisfiredatafrigidsurface.Atwhatspeedmustittraveltomeltonimpact,ifitsinitialtemperatureis25℃andheatingoftherigidsurfaceoftherigidsurfaceisneglected?Themeltingpointofleadis327℃.Themolarheatoffusionoftheleadis4.8kJ/mol.ThemolarheatcapacityCPofleadmaybetakenas29.3J/(molK)(1.1)Solution:)/(5.112.20721]108.4)25327(3.29[2121)(2322smVvnnWQnMvmvWHTCnQQQabsorbmeltingpmeltincreaseabsorb2.whatistheaveragepowerproductioninwattsofapersonwhoburns2500kcaloffoodinaday?Estimatetheaverageadditionalpowderproductionof75Kgmanwhoisclimbingamountainatehrateof20m/min(1.2)Solution)/(24560208.975)/(12160602410467000//)(104670001868.4102500sin3SJthmgPSJtQtWPJQgincreaBurningBurning3Onecubicdecimeter(1dm3)ofwaterisbrokenintodropletshavingadiameterofonemicrometer(1um)at20℃.(1.3)(a)whatisthetotalareaofthedroplets?(b)Calculatetheminimumworkrequiredtoproducethedroplets.Assumethatthedropletsarerest(havezerovelocity)Waterhaveasurfacetensionof72.75dyn/cmat20℃(NOTES:thetermsurfaceenergy(ene/cm2)isalsousedforsurfacetensiondyn/cm)Solution)(25.218)106103(1075.72)(103)101(4)101(34)101(232523263631JSWmnSSSingletotal4.Gaseousheliumistobeusedtoquenchahotpieceofmetal.Theheliumisinstorageinaninsulatedtankwithavolumeof50Landatemperatureof25℃,thepressureis10atm.Assumethatheliumisanidealgas.(a)whenthevalveisopenedandthegasescapesintothequenchchamber(pressure=1atm),whatwillbethetemperatureofthefirstgastohitthespecimen?(b)Astheheliumflows,thepressureinthetankdrops.Whatwillbethetemperatureoftheheliumenteringthequenchchamberwhenthepressureinthetankhasfallento1atm?(1.4)Solution:)(180118298)(1185.229810101325501010101325)5500(1)()(118)101(298)()(0334.0/00KTTTKRRnCWTbKTPPTTAdiabaticapCRP5Anevacuated(P=0),insultedtankissurroundedbyaverylargevolume(assumeinfinitevolume)ofanidealgasatatemperatureT0.Thevalveonthetankisopenedandthesurroundinggasisallowedtoflowquicklyintothetankuntilthepressureinsidethetankisequalsthepressureoutside.Assumethatnoheatflowtakesplace.Whatisthefinaltempetureofthegasinthetank?Theheatcapacityofthegas,CpandCveachmaybeassumedtobeconstantoverthetemperaturerangspannedbytheexperiment.YouanswermaybeleftintermsofCpandCvhint:onewaytoapproachtheproblemistodefinethesystemasthegasendsupinthetank.(1.5)solution0/000/00)0()(TPPTTPPTTAdiabaticPPCRCR6.Calculatetheheatofreactionofmethanewithoxygenat298K,assumingthattheproductsofreactionareCO2andCH4(gas)[Thisheatofreactionisalsocalledthelowcalorificpowerofmethane]converttheanswerintounitesofBtu/1000SCFofmethane.SCFmeansstandardcubicfeet,takenat298and1atmNOTE:thisvalueisagoodapproximationforthelowcalorificpowderofnaturalgas(1.6)DATA:)()()(224gOHgCOgCHFOR80.5705.9489.17]/[0298molgKcalHsolution)1000/(9.2610252103048.01101076.191)/(76.191)89.1780.57205.94()2(22333332982982224422SCFBtumolgKcalHHHHHOHCOOCHCHOHCO7.Methaneisdeliveredat298Ktoaglassfactory,whichoperatesameltingfurnaceat1600K.Thefuelismixedwithaquantityofair,alsoat298K,whichis10%inexcessoftheamounttheoreticallyneededforcompletecombustion(airisapproximately21%O2and79%N2)(1.7)(a)Assumingcompletecombustion,whatisthecompositionofthefluegas(thegasfollowingcombustion)?(b)Whatisthetemperatureofthegas,assumingnoheatloss?(c)Thefurnaceprocesses2000kgofglasshourly,anditsheatlossestothesurroundingsaverage400000kJ/h.calculatethefuelconsumptionatSTP(inm3/h)assumingthatforgasH1600-H298=1200KJ...