A room is kept at −5°C by a vapor-compression refrigeration cycle with R-134a as the refrigerant. Heat is rejected to cooling wa
ter that enters the condenser at 20°C at a rate of 0.13 kg/s and leaves at 28°C. The refrigerant enters the condenser at 1.2 MPa and 50°C and leaves as a saturated liquid. If the compressor consumes 1.9 kW of power, determine (a) the refrigeration load, in Btu/h and the COP, (b) the second-law efficiency of the refrigerator and the total exergy destruction in the cycle, and (c) the exergy destruction in the condenser. Take T0 = 20°C and cp,water = 4.18 kJ/kg·°C
2 answers:
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Answer:
Explanation:
Diffusion flux of a gas, J is given by
where
is permeability coefficient,
P is pressure difference and x is thickness of membrane.
The pressure difference will be 10,000 Pa- 3000 Pa= 7000 Pa
At 298 K, the permeability coefficient of water vapour through polypropylene sheet is
Since the thickness of sheet is given as 1mm= 0.1 cm then
Therefore, the diffusion flux is
Answer with Explanation:
Assuming that the degree of consolidation is less than 60% the relation between time factor and the degree of consolidation is
Solving for 'U' we get
Since our assumption is correct thus we conclude that degree of consolidation is 50.46%
The consolidation at different level's is obtained from the attached graph corresponding to Tv = 0.2
i) = 71% consolidation
ii) = 45% consolidation
iii) = 30% consolidation
Part b)
The degree of consolidation is given by
Thus a settlement of 50.46 centimeters has occurred
For time factor 0.7, U is given by
thus consolidation of 85.59 % has occured if time factor is 0.7
The degree of consolidation is given by