A commercial refrigerator with refrigerant -134a as the working fluid is used to keep the refrigerated space at -30C by rejectin
g its waste heat to cooling water that enters the condenser at 18C at a rate of 0.25 kg/s and leaves at 26C. The refrigerant enters the condenser at 1.2 MPa and 65C and leaves at 42C. The inlet state of the compressor is 60 kPa and -34C and the compressor is estimated to gain a net heat of 450 W from the surroundings. Determine
a. the quality of the refrigerant at the evaporator inlet,
b.the refrigeration load,
c. the COP of the refrigerator, and
d. the theoretical maximum refrigeration load for the same power input to the compressor.
a. the quality of the refrigerant at the evaporator inlet,
b.the refrigeration load,
c. the COP of the refrigerator, and
d. the theoretical maximum refrigeration load for the same power input to the compressor.
3 answers:
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Answer:
the net work per cycle Btu per cycle
the power developed by the engine, W = 88.0144746 hp
Explanation:
the information given includes;
diameter of the four-cylinder bore = 3.7 in
length of the stroke = 3.4 in
The clearance volume = 16% = 0.16
The cylindrical volume
the crankshaft N rotates at a speed of 2400 RPM.
At the beginning of the compression , temperature = 60 F = 519.67 R
and;
Otto cycle with a pressure = 14.5 lbf/in² = (14.5 × 144 ) lb/ft²
= 2088 lb/ft²
The maximum temperature in the cycle is 5200 R
From the given information; the change in volume is:
the mass in air ( lb) can be determined by using the formula:
where;
R = 53.3533 ft.lbf/lb.R°
m = 0.0018962 lb
From the tables of ideal gas properties at Temperature 519.67 R
At state of volume 2; the relative volume can be determined as:
The specific energy at
is 184.7 Btu/lb
From the tables of ideal gas properties at maximum Temperature T = 5200 R
To determine the relative volume at state 4; we have:
The specific energy at
is 591.84 Btu/lb
Now; the net work per cycle can now be calculated as by using the following formula:
Btu per cycle
the power developed by the engine, in horsepower. can be calculated as follows;
In the four-cylinder, four-stroke internal combustion engine; the power developed by the engine can be calculated by using the expression:
where ;
N' = 1200 cycles/min
N' = 1200 cycles/60 seconds
N' = 20 cycles/sec
W = 4 × 20 cycles/sec × 0.777593696
W = 62.20749568 Btu/s
W = 88.0144746 hp
Answer:
Final length of the rod = 13.90 in
Explanation:
Cross Sectional Area of the polythene rod, A = 0.04 in²
Original length of the polythene rod, l = 10 inches
Tensile modulus for the polymer, E = 25,000 psi
Viscosity,
Weight = 358 lbs - f
time, t = 1 hr = 3600 sec
Stress is given by:
Based on Maxwell's equation, the strain is given by:
Strain = Extension/(original Length)
0.39022 = Extension/10
Extension = 0.39022 * 10
Extension = 3.9022 in
Extension = Final length - Original length
3.9022 = Final length - 10
Final length = 10 + 3.9022
Final length = 13.9022 in
Final length = 13.90 in
Answer:
Test code:
>>u=10;
>>g=9.8;
>>q=100;
>>m0=100;
>>vstar=10;
>>tstar=fzero_rocket_example(u, g, q, m0, vstar)
Explanation:
See attached image
