2007Final key

2007Final key - ENGR 225 FilnalExtrr W 11,2007 December...

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/-11\. 1. T(.]U The following are conserved during all processes: energy, mass, and entropy. 2. A system a) is a region in space or a quantity of space b) can interact with the surroundings exchanging both mass and energy c) must be chosen by the person doing the analysis @ all of the above e) none of the above ,l.od 3. The A law of thermodynamics stipulates that processes occur in a certain direction. 4. @f When a pure substance changes phase the properties change. 5. An intensive property a) might have units of kJ/m' b) might have units of Pa c) does not depend on the size of the system 6D Et n. T 0 Both turbines and fans add energy to a moving fluid through work, 14. The magnitude of the enthalpy per unit mass of a refrigerant l34a at a given state depends on the reference state usedto defure zero b) path by which the system got to the current state c) whether the NIST program or the tables at the back of the book are used to determine the value d) all of the above none ofthe above 15. The quantities Plp,Y2/2, and gz all have units of ENGR 225 December 11,2007 Name FilnalExtrr, W please takc this in account) Recitation: _8:30 _10:15 _l:15 Short answer (2 pts. Eacb, for T/F and multiple choice circle the best answer ofthe choices eiven, fill in the blank must be completed with a meaningful word or phrase) 6. Ifa pur€ substance can exist in two or more conditions ofdifferent intemal atomic order, it is said to be in one ofthe multiple ? tvtscS that ar€ possible. 7. g) F The fire piston is well approximated by adiabatic compression of an ideal gas. In this a case, mechanical equilibrium is established without thermal equilibrium. 8. Applying the state principle, the state of a simple compressible system could be determined knowing values for a) pressure and mass b)_ specific volume and density 4fl temperature and entropy per unit mass d) 9. The intemal enerry of I kg of sleam at 1000C is Al{.Alcr than the intemal energy of I kg liquid waler at l00oc. -1J-- 10. T Energy cannot cross the boundary of a closed system. I l. Work a) is defined in your book as negative when work is done by the system on the surroundings b) can move energy into an isolated system f} is the name gir,,en to all processes that move energy into or out of a system except for heat transfer ts 12. If energy is entering the system, but the temperature of the system is not changing it is said to be at St*dS ("I ,.'satfu",,"-f \ *fi'f ^iru a! r"?k,-a
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- [email protected] One meaning of the word "quality" in thermodynamics is the mass fraction of vapor in a 2-phase mixture of vapor and liquid. 17. Thermal enerry that has a low potential for being converted into work a) describes low ternperature €nergy b) is called energr of lower quality 9l cannot be efficiently converted even in a fully reversible machine. @) all ofrhe above e) none ofthe a.bove 18. The properties ofa compressed liquid are well-approximated by the properties of sahpated liqu i6 v1111s sanrc fe^(zro.k re- re. r€J Thermodynamic cycles can only move in one direction. The second law of thermodynamics prevents the cycle from being executed in the opposite direction.
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2007Final key - ENGR 225 FilnalExtrr W 11,2007 December...

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