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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 initiallyempty cylindrical storage tank at a mass
flow rate of 15 kg/s. The tank is ZOm long and has a 3m 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 wellinsulated 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: = IlaH. \
{A3 in Q‘m waq) ' =(4o\ Q40) : moo kw C\l Steam enters a wellinsulated 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)(osq73imo) 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 xxxu. \«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 Ts 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 wellinsulated. 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 45:17Yo' 3 AQ=O .. 7+
.. m cv 9m \ macwkkﬁ>z \
(QL‘V'QKL 333 + 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.
 Spring '08
 Staff

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