Question

02: 720 Ib, /min of Freon HFC 134a undergoing a change in state from (400 Psia and 60 F) to 10 Psia and 60 F. estimate the change in S,H and V?

Answer 1

Q2|

Given: m = 720 lb/min = 5.4431 kg/s

State 1 : P1 = 400 Psia; T1 = 60 F

At these values of P and T, from Table A–12E of Cengel

At P = 400 Psia, Tsat = 179.86 F > 60 F and thus the state is compressed refrigerant state.

As table for compressed refrigerant state is not available, thus we will use certain approximations.

In the absence of compressed liquid data, a general approximation is to treat compressed liquid as saturated liquid at the given temperature. This is because the compressed liquid properties depend on temperature much more strongly than they do on pressure.

Thus, From Table Table A–11E of Cengel

However, the error in h at low to moderate pressures and temperatures can be reduced significantly by evaluating it from

State 2 : P2 = 10 Psia; T2 = 60 F

At these values of P and T, from Table A–12E of Cengel

At P = 10 Psia, Tsat = -29.52 F < 60 F and thus the state is superheated refrigerant state.

From Table A-13E

At P = 10 Psia and T = 60 F

Now we will calculate change: