Transcribed Text
the property tables moind the stated properties for the following
1
Glyouthink any quantity is undefined enter the value 1)
phase
saturated liquid
liquid

saturated
Prapour mature
compressed
A six cylinder four stroke internal combustion engine can be ideal Diesel cycle. The inlet air temperature
and pressure are 19.3°C and 95kPa, respectively. The compression is 17.4, and the peak temperature is 1870K
(Work to four significant figures throughout.)
2
a)
Calculate the pressure and temperature at the end of the compression stroke
pressure
kPa
temperature =
K
b)
What is the cutoff ratio?
c)
Calculate the pressure and temperature at the end of the power stroke
pressure
kPa
temperature
K
d)
Complete the following table for specific heat and work for all four processes
(take state to be the beginning of the compression stroke)
Process
q(kJ/kg)
w (kJ/kg)
1>2
2>3
3>4
e)
Calculate the following
specific net work out 
kJ/kg
specific heat supplied
kJ/kg
thermal efficiency
f)
lithe bore diameter is 95mm, the stroke is 119mm, and the engine running at 4000rpm, calculate the following
volume of the cylinder
mass
net power output
kW
An ideal vapour compression refrigeration cycle uses R134a as the working fluid. During the throttle process, the temperature
3
drops from 35°C to 20°C.
a)
Determine the lower and upper pressures in the cycle (give your answer to as many significant figures as in the property
tables)
lower pressure
bar
upper pressure
bar
b)
Determine the specific enthalpy and specific entropy of the fluid entering the compressor
specific enthalpy =
kJ/kg (to S isignificant figures)
specific entropy
KJ/kg. K (to significant figures)
c)
Calculate the specific entropy and specific enthalpy of the fluid leaving the compressor
specific entropy =
kJ/kg.K (to 5 significant figures)
specific enthalpy =
kJ/kg (to decimal place)
d)
Determine the specific enthalpy in the throttle
specific enthalpy
kJ/kg (to 5 significant figures)
e)
Complete the table for specific heat and work for all four processes (give your answers to 1 decimal place)
(take state 1 to be the start of the compressor)
specific heat
specific work
Process
(kJ/kg)
(kJ/kg)
1+2
2>3
3>4
4>1
f)
Evaluate the coefficients of performance of the cycle if the device is acting as refrigerator and as heat pump (give
answers to 3significant figures)
COP
COP
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