(8.1.1)--4.7-1Adiabaticprocessoftheidealg.pdf

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1、Adiabatic process of the ideal gasAdiabatic process of the ideal gas General adiabatic process1 Quasi-static adiabatic process equation of the ideal gas2 Work and change of temperature in adiabatic process of the ideal gas3 Adiabatic compression and adiabatic expansion of the ideal gas4 1.General ad

2、iabatic process Adiabatic process:if the system has no heat exchange with the outside world all the time.Absolute adiabatic processes can not exist,but some processes can be regarded as adiabatic processes approximately.For example,the process carried out in a system surrounded by good thermal insul

3、ation materials;For example,the process is fast,and it is too late to exchange heat with the outside world.On the contrary,the ocean current in the deep sea often takes decades to circulate once.Although it changes for a long time,the heat exchange between ocean current and the outside world is insi

4、gnificant compared with its own internal energy due to the great quality and heat capacity of seawater,which can also be regarded as an adiabatic process.绝热WUU12SIn the quasi-static adiabatic process of the ideal gas,there areTvCVpmVdd,TvRpVVpdddvRpVVpTdddpVCVpRCmVmVdd)(,p mV mCCRmvmpCC,2.Quasi-stat

5、ic adiabatic process equation of the ideal gas Differentiate the two sides of the ideal gas state equationThat isSubstituting the above formula,it can be obtained thatBecause ,if the specific heat capacity ratio is expressed as it can be simplified asdd0pVpV12211CVpVpCpVmddV pp V Poisson formula21CT

6、VThree forms of process equation for quasi-static adiabatic process31CTp1CpV C1,C2 and C3 are all constants,but they are not equal to each other.p Comparison between adiabatic line and isothermal lineTppVV CpV0dd1VpVpVsppVV p Compare This shows that the adiabatic line A is steeper than the isotherma

7、l line B as shown on the right.,1p mV mCCTppVV sppVV OpVisothermal lineadiabatic lineVapaacb V(p)Q(p)TExplain by gas dynamic theoryk23pnThinking,35,23V mCR57,25,RCmV1112111VVVpMonoatomic ideal gas(such as helium and argon,etc.)Common diatomic ideal gases at normal temperature(such as hydrogen,oxygen

8、,nitrogen,etc.)Common polyatomic ideal gases at normal temperature(such as CO2,methane,etc.)3.Work and change of temperature in adiabatic process of the ideal gas,43,3V mCR1)(1)(11221212,12VpVpTTvRTTvCUUWmV绝热S221111ddVVVVVWp VpVV 绝热S4.Adiabatic compression and adiabatic expansion of the ideal gasExa

9、mple:The gas moves fast in the cylinder,but the heat transfer is slow,which is considered as an adiabatic process approximately.How high are the final temperatures when the air at 300K and 1atm is compressed to 10atm and 100atm respectively?11CTp11212ppTT1.4Solve:For air 02579K306 CT 021118K845 CT The higher the compression ratio,the higher the final temperature.10If12pp010If12pp Quasi-static adiabatic process equation of the ideal gas Quasi-static adiabatic process work of the ideal gas21CTV31CTp1CpVThanks1)(1)(11221212,12VpVpTTvRTTvCUUWmV绝热S