for first problem answer is c for second problem answer is a please tell me the

Question

for first problem answer is c

for second problem answer is a

please tell me the solution...

Which statement is always correct for adiabatic throttling process with an ideal gas? Delta s = 0 Delta P = 0 Delta T = 0 Sgcn = 0 A refrigeration cycle has a coefficient of performance that is 80% of a Carnot refrigerator operating between temperature reservoirs at 300K and 268K. The rate of heat transfer from the low temperature reservoir is 10 kw. What is the required power input to the real refrigerator'? 1.5 kw 1.2 kw 1 kw 0.8 kw

Explanation / Answer

4. For adiabatic throttling process, enthalpy remains constant

Applying steady state energy equation, we get

h1 =h2

Now for ideal gas h= Cp X T

So, Cp X T1 = Cp X T2

Cp gets cancelled and we get

T1 = T2

So we get that there is no change in temperature

Answer is (c)

5 temperature of hot reservoir , Tk = 300 K

Temperature of cold reservoir, To = 268 K

(COP)max =To/ (Tk - To) = 268/ ( 300-268)=8.375

(COP) actual = 0.8 X 8.375 = 6.7

Qo= 10 Kw

(COP) actual = Qo/W

Therefore power input, W= 10/6.7 = 1.492 = 1.5 Kw

so answer is (a)

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