大學物理課件 熱力學2

1、dQ = 0dEdA pdVdA RdTipdV 2 dTCpdVV RdTidE 2 RTpV R)i(Cp21 VdpCpdVCVp VdpCpdVCRVV )(VCR dTCpdVV RTpV RdTVdppdVRVdppdVCpdVVpdpVdVCCVp 1cpV 21cTV 31cTp vpCC VdpCpdVCVp lnlnCpVlnCpVPVA0等等溫溫絕絕熱熱.絕熱線的斜率大于絕熱線的斜率大于等溫線的斜率等溫線的斜率1cpV 2211VPVP11A1cpV 2121VVVVpdVdAA2111VVdVVVp211111()1VVp VV V pS1S2O. . .0, 0dAd

2、Q21TT 0 dE111RTVp 222RTVp 1221VVpp AQ Q1高溫熱源高溫熱源Q Q2低溫熱源低溫熱源熱機工作示意圖熱機工作示意圖氣氣輪輪機機發(fā)電機發(fā)電機A發(fā)電廠蒸汽動力循環(huán)示意圖發(fā)電廠蒸汽動力循環(huán)示意圖冷凝器冷凝器冷冷卻卻水水Q Q220C0給水泵給水泵Q Q1鍋鍋爐爐550C0高溫高壓蒸汽高溫高壓蒸汽A2低溫熱源低溫熱源Q( (冷凍室冷凍室) )1高溫熱源高溫熱源Q( (周圍環(huán)境周圍環(huán)境) )節(jié)節(jié)流流閥閥散熱器散熱器200C10atm200CQ1儲儲液液器器氟氟利利昂昂壓壓縮縮機機2冷凍室冷凍室蒸發(fā)器蒸發(fā)器3atm100CQEAQ 1QA12QQ1 1QA 121QQQ

3、121QQQ 2122QQQAQw21QQQA121QQ 1211VVlnRTQ 3422VVlnRTQ 123412VVlnVVlnTT1 abT1d2TbadcQQ 1112213TVTV 111214TVTV 11121413VVVV 1243VVVV 124312lnln1VVVVTT 121TT abT1d2T12TT1 2122QQQAQw 212TTTwc 2Q1Q p (atm) T (K) 300 400 O 5 a b c d P V (l )(atm)2211abcd000AE0ababQAEcb 00cbAEE0bcbcQAE0cdQ0 daQ A)(abbaVVpp

4、adVp ba daabbccdPV2211abcdQQQQ0(l )(atm)()2adiR TT)(2)()21(daaabappViVVpi aaVpi)431( 1QdaabQQ ()pbaC TT()VadCTT)()21(abTTRi =10.5%daabbccdPV2211abcdQQQQ0(l )(atm)adVpA aaVpiQ)431(1 aaadVpiVp)431( 1QA 2)431(1i 1925 iP PV VP PV V0 00 00 0等等溫溫a ab bc c0 02 2V VQabQcaQbc)(abpabTTCQQ吸)(1bcVbcTTCQQ放caccaV

5、VRTQQln2放吸吸放放QQ 1 )()21 (21ln)(21abcbcTTRiRTTTRi=18.7%3iK1TJ209A10解：解：TRiE2 J7 .124131. 81023 J3 .842097 .124AEQ例題例題2 一定量的理想氣體經歷一定量的理想氣體經歷acb過程時過程時吸熱吸熱200J,則經歷則經歷acbda過程時，吸熱為：過程時，吸熱為： J1000BJ1200A J1000DJ700C過過程程：氣氣體體經經歷歷解解：acbda0E 由熱一定律得：由熱一定律得：dabdacbAAAAQ等等容容過過程程0Abd apPo3mV13104231235104acbd等等壓壓

6、過過程程ad daadaVVPA apPo3mV13104231235104acbd335104101104J1200?AacbJ200QacbabvacbTTCEaabbVPVP2i0J200QAacbacb因因此此，有有：12000200AQJ1000選（選（B）1212111TTQQQA90012004003001122QTTQ300411200)1 (121TTQA2122122TTTQQQAQ160030030040011200122121TTTQQ40030010012002212TTTQApVaVbcbaababAQ)(bcpbcTTCQ) 1/(27baaaVVVp)(caVcaTTCQ)/1 (25baaaVVVpabaVVRT ln03lnaaVp) 1/(bcapTTTC037aaVp)/1 (bca