Refrigerant 134a expands in an adiabatic turbine from 12 MPa

Refrigerant 134a expands in an adiabatic turbine from 1.2 MPa and 100degreeC to 0.18 MPa and 50degreeC at a rate of 1.25 kg/s. Draw the T-s diagram and determine (a) the power output from the turbine and (b) the rate of entropy generated in the turbine.

Solution

The Inlet and outlet entalphy calculated by using Refrugants R-134a,

h_g for R-134a is 271.13 at the temperature of 100 degree (Taken value from standard table)

h_in = 263 kj/kg

h_out = h (0.18 at 50degree)

hout = 273 kj/kg

W = m (h_in - hout )

W = 1.25 * (-10)

W = -12.5 kw

Rate of change of Entrophy = m * C_V* (T₂ - T₁)

C_{V = R / (Y-1)}

_Consider

R = 0.287 kj/kg

Y = 1.4

C_V = 0.755 KJ/KG K

Rate of change of Entrophy = m * C_V* (T₂ - T₁)

= 1.25 * 0.755 * (-50)

= -47.18