Answer:
Actual COP = 5.368
Maximum theoretical COP = 6.368
Explanation:
Given - An ideal vapor compression refrigeration cycle operates with a condenser pressure of 900 kPa. The temperature at the inlet to the compressor is -5oC.
To find - If this device operates using R134a as the working fluid. Calculate the actual COP of this device as well as the maximum theoretical COP.
Proof -
Given that,
An ideal vapor compression refrigeration cycle operates with a condenser pressure of 900 kPa.
From Refrigerant 134-a Table
At T1 = -5°C
h1 = 247.505 KJ/kg
S1 = 0.93434 KJ/kg
At P2 = 900 KPa
S1 = S2
h2 = 274.679 Kj/Kg
h3 = h4 = 101.61 KJ/g
So,
Compressor work (Wc) = h2 - h1
= 274.679 - 247.505
= 27.174
⇒Compressor work (Wc) = 27.174 KJ/kg
Now,
Heat out (Qout) = h2 - h3
= 274.679 - 101.61
= 173.069
⇒Heat out (Qout) = 173.069 KJ/kg
Now,
Heat input (Qin) = h1 - h4
= 274.505 - 101.61
= 145.895
⇒Heat input (Qin) = 145.895 KJ/kg
So,
Actual COP at the refrigerator is -
(COP)R = (Qin)/(Wc)
= (145.895)/ (27.174)
= 5.368
⇒Actual COP = 5.368
Now,
Maximum theoretical COP is -
(COP) = (Qout)/(Wc)
= (173.069)/ (27.174)
= 6.368
⇒Maximum theoretical COP = 6.368
The power factor of the circuit is 0.7071
<h3>What is Power factor?</h3>
Power factor (PF) is the ratio of working power, measured in kilowatts (kW), to apparent power, measured in kilovolt amperes (kVA). Apparent power, also known as demand, is the measure of the amount of power used to run machinery and equipment during a certain period. It is found by multiplying (kVA = V x A). The result is expressed as kVA units.
Power factor is expressed as the cosine of the phase angle.
The phase angle is given as 45°
Therefore the power factor in the circuit is cos45° = 0.7071
learn more about power factor from
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Answer:
The correct option is;
A) Steel becomes too hot in the Sun and can burn the children
Explanation:
The properties of steel includes;
Low specific heat capacity, high thermal and electrical toughness, high hardness, high tensile strength, high yield strength, appreciable elongation, high fatigue strength, can easily corrode, high malleability and ability to creep
Therefore, due to the low specific heat capacity, which is 0.511 J/(g·°C) and high conductivity of steel which is about 32 W/(m·k), the temperature of the steel can rapidly rise and the hot steel surface can readily conduct the heat, (due to the temperature difference) to other bodies that come in contact
Answer:
Explanation:
Lets take the numerator of the fraction to be = x
So the denominator of the fraction is 4 more than the numerator = x+4
The fraction is ;
Now add 4 to the numerator and add 7 to the denominator as;
This new fraction is equal to 1 half =1/2
write the equation as;
perform cross-product
2(x+4 )=1( x+11 )
2x+8 = x + 11
2x-x = 11-8
x=3
The original fraction is;