EF 152 Exam #3, Spring 2016 Page 1 of 6

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1 EF 5 Exam #3, Spring 06 Page of 6 Name: Setion: Instrutions Do not open te exam until instruted to do so. Do not leave if tere is less tan 5 minutes to go in te exam. Wen time is alled, immediately stop writing, remain seated, and pass your exam to te enter aisle. Do not stand up or leave until all exams ave been olleted. Working after time is alled results in an automati 0 point dedution. Guidelines Assume 3 signifiant figures for all given numbers unless oterwise stated Sow all of your work no work, no redit Write your final answer in te box provided ermal Expansion Linear l l 0 Linear, Stresses E Volumetri V V 0 Ideal Gas Law pv nr R = 8.34 J/(mol-K) Avogadro s Number: 6.0x0 3 Standard Pressure and emp 73K.00 atm (0.3kPa) st Law of ermodynamis U internal energy W work done by termal system eat flow into termal system U W A B AB Marosopi Definitions m mass M molar mass n number of moles N total number of moleules N A Avogadro s Number k Boltzmann onstant = J/ K m n M N n k N A R N A Conversions al = 4.86 J L = 000 m 3 m 3 = 000 L Work of ermal Systems W V V Effiieny General W Otto Cyle r ompression ratio r Carnot Cyle pdv Isobari (onstant pressure) W pv B V A np Isoori (onstant volume) W 0 nv Isotermal (onstant temp) V W nr ln V W Adiabati ( = 0) W p AV A pbvb pv V p onstant onstant onstant Heat eat speifi eat κ termal ondutivity R termal resistane Heat Capaity m ermal Condutivity t Refrigerators General K oeffiient of performane H eat urrent P power input W K W Water Properties L f = 79.6 al/g = al/(g- C) = 4.86J/(g- C) L v = 540 al/g ρ = g/m 3 = kg/l L f = Latent eat of fusion = 000 kg/m 3 = 6.4 lb/ft 3 L v = Latent eat of vaporization H P EER = 3.43 K Carnot K Carnot A L A R ermal Resistane L R ermal Resistane, Series R eff R R ermal Resistane, Parallel R eff A A A R A R

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3 EF 5 Exam #3, Spring 06 Page 3 of 6. ( pts) Wi of te following is FALSE? A. e van der Walls equation an be used to alulate te relationsip between state variables wen a gas is non-ideal based on gas-speifi empirial onstants. B. e transfer of eat by radiation is proportional to (emperature) 4 C. e maximum possible COP of a refrigerator is te Carnot effiieny. D. An irreversible proess as more eat effiieny tan a reversible proess. E. e oeffiient of performane of a refrigerator an be greater tan.. ( pts) Under onditions of a fixed temperature and amount of gas, Boyle s law requires I. P V = P V II. PV = onstant III. (P V ) = (P V ) A. I only B. I and II C. III D. none of te above 3. ( pts) Wi as iger termal resistane (m C/W) A. Air B. Glass C. Copper 4. ( pts) Wi of te following yles best desribes an internal ombustion engine. A. Adibiati ompression, Heating at onstant volume, Adiabati expansion, ooling at onstant volume B. Adibiati ompression, Heating at onstant pressure, Adiabati expansion, ooling at onstant volume C. Adiabati ompression, Heating at onstant temperature, Adiabati expansion, ooling at onstant temperature D. Adibiati ompression, Heating at onstant pressure, Adiabati expansion, ooling at onstant pressure 5. (4 pts) A refrigerator absorbs 5 kj of energy from a old reservoir and rejets 8 kj to a ot reservoir. Find te oeffiient of performane of te refrigerator.

4 EF 5 Exam #3, Spring 06 Page 4 of 6 6. ( pts) An oxygen olding tank as a volume of 30,000 L, an absolute pressure of 50kPa and a temperature of 300 K. A ylinder ontains kg of ompressed Oxygen (moleular mass of O =3g/mol). If te gas in te ylinder is added to te olding tank, wat is te new pressure in te olding tank at 300 K? Assume an ideal gas. 7. (6 pts) A piee of eated metal alloy as a mass of 35 g, density of 6.8 g/m 3, a speifi eat of 0. al/(g K) and a oeffiient of volume expansion 3.3x0-5 / C. Wat amount of ie at 0 C is required to make te metal ontrat by 0.06 m 3 wile just melting all of te ie?

5 EF 5 Exam #3, Spring 06 Page 5 of 6 8. (4 points).5 moles of an ideal gas is at 7 C. e gas is isoorially (at onstant volume) ooled to a pressure times smaller tan te initial pressure. e gas is ten expanded at onstant pressure so tat in te final state te temperature oinides wit te initial temperature, 7 C. Calulate te work done by te gas. Pressure P P 3 Volume State Vol P V i P V i P 3 V f P 9. (6 pts) Determine te effiieny of te Ramanator Cyle, sown below. Assume air and an ideal gas ( =.4, p =7R/, v =5R/). e work input from 4 to is 5940 Joules and te work output from to 3 is 568 Joules. e eat added, H, is 9890 Joules. p (kpa) V (m 3 ) x0 8x0 State Vol (m^3) P (kpa) (K)

6 EF 5 Exam #3, Spring 06 Page 6 of 6 0. (6 pts) Dr. Bennett s Donut Sop is 3 m ig, 6 m long, and 6 m wide. e storefront is 3 m ig by 6 m wide wit a termal resistane of 0.50 m - C/W. e oter tree walls ave a termal resistane of.50 m - C/W. e roof as a termal resistane of.75 m - C/W. Ignoring te effet of te floor and doors and any leakage, determine te eletrial power required to run an air onditioner wit an EER rating of 0 wen it is 35 C outside and 0 C inside. 3 m 6 m. (4 pts) A eat engine is used to blow up a balloon at a onstant absolute pressure of atm. e engine extrats 4 kj from a ot reservoir at 0 C. e volume of te balloon inreases by 5 L, and eat is exausted to a old reservoir at a temperature. If te effiieny of te eat engine is 60% of te effiieny of a Carnot engine working between te same reservoirs, find te temperature.