Please I need detailed answers Second question Consider power generation by an a
ID: 2998422 • Letter: P
Question
Please I need detailed answers
Second question
Consider power generation by an adiabatic steam turbine. The steam enters the turbine with a pressure of 3 MPa and temperature of 400 degree C, and leaves at 50 kPa and 150 degree C. For steady-state operation, the turbine power output is 5 MW. Neglect changes in kinetic and potential energy. Find the mass flow rate of the steam. Refrigerant 134a is to be cooled by water in a condenser The refrigerant enters the condenser with a mass flow rate of 6 kg/min at 1 MPa and 70 degree C, and leaves as a compressed liquid at 34 degree C. The cooling water enters at 300 Kpa and 15 degree C and leaves 25 degree C. Neglect any pressure drops, determine (a) The mass flow rate of the cooling water required (b) The heat transfer rate from the refrigerant to waterExplanation / Answer
(1) Given that
mass flow rate of refrigerant mr = 6 kg/min
temp at inlet of condensor of refrigerant = 70 oC
Pressure at the inlet of condensor = 1MPa
h1= 303.85 KJ/Kg
At 34 0C , h2 = 99.40 KJ/Kg
we know that heat lost by refrigerant = heat gained by water
(a) mr * (h1 - h2) = mw * Cpw * (Tw1 - Tw2)
mw = (6 * (303.85 - 99.40))/(4.187 * 10)
= 29.29 Kg/min
(b) Heat transfer from refrigerant = mr(h1 - h2)
= 6 (303.85 - 99.40)
= 1226.7 KJ/min
(2) Given that P3= 3MPa; T3 = 4000C, h3 = 3231.7 KJ/Kg
P4 = 50 KPa and h4 = 2645.2 KJ/Kg
From the steady flow energy equation,since K.E & P.E = 0
m *h3 + Q = m *h4 + W
m(h3 - h4 ) = W (since Q = 0)
Therefore m = W/(h3 - h4)
= 5000/(3231.7 - 2645.2)
= 8.52 Kg/s