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Unformatted text preview: 4-12Refrigerant-134a in a cylinder is heated at constant pressure until its temperature rises to a specified value. The boundary work done during this process is to be determined. AssumptionsThe process is quasi-equilibrium. PropertiesNoting that the pressure remains constant during this process, the specific volumes at the initial and the final states are (Table A-11 through A-13) [email protected]vTPPfAnalysisThe boundary work is determined from its definition to be kg233.1/kgm0.0008580m0.23311vVmand kJ557133121221out,mkPa1kJ1/kgm0.0008580)413kPa)(0.027kg)(900(233.1)()(vvVVVmPPdPWbDiscussion The positive sign indicates that work is done by the system (work output). 4-22CO2gas in a cylinder is compressed until the volume drops to a specified value. The pressure changes during the process with volume as 2VaP. The boundary work done during this process is to be determined. AssumptionsThe process is quasi-equilibrium. AnalysisThe boundary work done during this process is determined from kJ53.333361221221out,mkPa1kJ1m0.31m0.11)mkPa(811VVVVVadadPWbDiscussion The negative sign indicates that work is done on the system (work input). 4-34E R-134a contained in a rigid vessel is heated. The heat transfer is to be determined. Assumptions1 The system is stationary and thus the kinetic and potential energy changes are zero. 2 There are no work interactions involved 3 The thermal energy stored in the vessel itself is negligible. vP 900 12P V P = aV--20.1 0.3 12AnalysisWe take R-134a as the system. This is a closed system since no mass enters or leaves. The energy balance for this stationary closed system can be expressed as 0)=PE=KE(since)(12inenergiesetc.potential,kinetic,internal,in Changesystemmassandwork,heat,by nsferenergy traNet outinuumUQEEEThe properties at the initial and final states are (Tables A-11E, A-13E)...
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This note was uploaded on 09/05/2010 for the course MEEN 315 taught by Professor Ramussen during the Summer '07 term at Texas A&M.
- Summer '07