exam 2 - ME 300 -D Thermodynamics Midterm Examination —ll...

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Unformatted text preview: ME 300 -D Thermodynamics Midterm Examination —ll Fall 2008 YOUR NAME: SoLU Tl 0N5 Answer all questions. Please do not consult any text book, class notes, home works or neighbor students. Strict penalties for violations will be imposed according to University rules. ' ' 1. Liquid propane enters an initially-empty cylindrical storage tank at a mass flow rate of 15 kg/s. The tank is ZO-m long and has a 3-m diameter. The density of the liquid propane is 450 kg/ma. Determine the time in HOURS to fill the tank. Volume (jgxal)(1°> M ; l1; “5 (10“ +50) 2' \~\'l8\n if, (\S)(3£OD> A well-insulated turbine operated at steady state with a steam flow rate of 40 kg/s. The steam enters the turbine at 360°C and 6 MPa (h = 3071.1 kJ/kg). At exit, a throttling valve is attached, which exhausts the steam into atmosphere as saturated vapor (h = 2671.1 kJ/kg). Neglecting effects of KE and PE, find the power developed. \m : 3cm» in: = Ila-H. \ {A3 in Q‘m waq) ' =(4o\ Q40) : moo kw C\l Steam enters a well-insulated horizontal nozzle operating at steady state. The inlet velocity is 25 m/s and the specific enthalpy decreases by 30 kJ/ kg. What is the velocity at the nozzle exit? M +13: k2 av;- Q '3? '2. 1 \JQ : v\ + 10m —- he.) : U15 + 21 kaoXmDO) A compressor operates at steady state taking in outside air at 300K. The compressor increases the pressure to 7 bars, and temperature of 500K. The work input to the compressor for a mass flow rate of 0.75 kg/s is 175 kW. Using a constant specific heat of 1 kJ/kg.K, find the heat lost to surroundings. Three kilograms of R134a initially at 1.4 bars, 60°C are isothermally compressed to saturated vapor at 60°C. What is the minimum heat transfer from refrigerant during compression? Use following data: Specific entropy, 1.4 bars, 60°C = 1.1690 kJ/kg.K Specific entropy, sat vapor 60°C = 0.8973 kJ/kg.K A5 1 .43 —r 0' , . T I . MCNCWAM AG“ NW 0— : 0 Ag :_ 1 AS : T "‘(91‘5‘ _ (333)(3)(osq73-imo) A heat pump heats a house and'supplies 2500 kJ/min. The house is kept at a constant temperature of 22°C. The temperature of the outside air is 0°C. What is the minimum power required to operate the heat pump? a“ :. 2500 ‘9 2 xxx-u. \«N 6:0 5 LCD?) : Ty. _ 23> : 53.140“) mot ' " W -‘ c w 2. c~5c\\m\-“ " 3 ‘07 k H ,c I 0’" r ‘7. Using one Of the two Tds relations, show that for an ideal gas with constant specific heats sz — 51 = c, In (T2/T1) + R In (vzlvl), where T is temperature, 5 is specific entropy, v is specific volume, and R is specific gas constant. 1' As - Au. A— ‘pATV' h; \9‘V‘ 7- 9T, A5 : qu é: "“ 3.6"“. , . 1' _-\- V-_ i ‘7';- ‘ 'v .V 1.1 R Ann v7- 5 ’5 : v CV ‘3“ _____ ____.- 2 ‘ Ti 8. Following T-s figure shows a Carnot power cycle With appropriate values shown. What is the work prOduced per cycle for a mass of 5 kg, and what" is the efficiency of the cycle? 6?“ . warm = 50:00 ~4—°°3 (“‘5 “'o) H ll I i} a. 9. Steam enters a turbine operating at steady state at 6 MPa, 600°C, with a mass flow rate of 120 kg/min. The inlet values of enthalpy and entropy arez' 3658.4 kJ/kg and 7.1677 kJ/kg.K. At exit, the vapor is saturated at 20kPa with entropy of 7.9085 kJ/kg.K. What is the rate of entropy produced per second if the turbine is well-insulated. s -5‘ —_ 1~fi0$5 ‘15: —-> 7'\‘°—’-7 “5 9. 51:0 0" 2 m (5.5 ) H h 6‘6 0‘0 v r‘ O 4 .C 0 00 v I J 5' c9 / d... \f a] ’10.Consider mixing 1 kg of hot water (60°C) with 1 kg of cold water (20°C). Assume a specific heat of 4.0kJ/(kg.K). Assume no heat loss to surroundings. Compute the entropy produced and show that the process is irreversible. ‘ “<9 2K9 3% 'Evifiibflum 5mm. .. {who} 5— (tho\ - : ‘32 T .. o A Q 3290 ‘2‘“? A'oc 3 45:17-Yo' 3 AQ=O .. 7+- .. m cv 9m -\- macwkkfi>z \ (QL‘V'QKL 33-3- + 9F» 3‘2) = momma: Xi. ...
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This note was uploaded on 08/12/2010 for the course ME 300 taught by Professor Staff during the Spring '08 term at University of Illinois, Urbana Champaign.

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exam 2 - ME 300 -D Thermodynamics Midterm Examination —ll...

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