THERMODYNAMICS II
MIDTERM, OCTOBER 20, 2008
MECH 351/2
CONCORDIA UNIVERSITY
FACULTY OF ENGINEERING AND COMPUTER SCIENCE
DEPARTMENT OF MECHANICAL ENGINEERING
Student's Name:
I.D.:
_______________________
_______________________
Notes:
State clearly any assumptions you make. If applicable, draw a sketch of the problem.
Return the questions paper with the answers book.
The maximum grade is 100.
Question no. 1 (60 Points)
Consider a steam power plant that operates on the ideal regenerative Rankine
cycle with a closed feed water heater as shown in figure. The plant maintains the
turbine inlet at 3000 kPa and 350 oC; and operates the condenser at 20 kPa. Steam
is extracted at 1000 kPa to serve the closed feed water heater, which discharges
into the condenser after being throttled to condenser pressure. Properties of
selected states are given in table 1.
a.
b.
c.
d.
Sketch the cycle on a T-s diagram.
Calculate the work produced by the turbine.
Calculate the heat rejected by the condenser.
Calculate the thermal efficiency of the cycle.
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THERMODYNAMICS II
MIDTERM, OCTOBER 20, 2008
MECH 351/2
Table 1
Property
h1
h2
h3
h4
s4
h5
h6
h7
Value
251.40 kJ/kg
254.45 kJ/kg
763.53 kJ/kg
3116.10 kJ/kg
6.745 kJ/kg.K
Determine it
2311.10 kJ/kg
Determine it
Question no. 2 (40 Points)
An air-standard Diesel cycle operates with a compression ratio of 16 and a cutoff ratio of
2. At the beginning of compression process the conditions are 37°C, 0.10 MPa,
respectively. Assuming constant specific heats for air at room temperature (Cp = 1.005
kJ/kg.K; Cv = 0.718 kJ/kg.K and R=0.287 kJ/kg.K), determine:
(a)
(b)
(c)
(d)
(e)
The maximum temperature in the cycle.
The pressure after the isentropic expansion.
The net work per cycle and thermal efficiency.
The mean effective pressure.
The volume flow rate of air in m3/min, measured at conditions at the beginning of
compression, needed to produce 200 KW.
Isentropic relations
 T2 
v 
 1 
 
 T1  s cte  v2 
k 1
 T2 
P 
 2 
 
 T1  s cte  P1 
 P2 
v 
 1 
 
 P1  s cte  v2 
C
k p
Cv
k 1
k
k
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