Where the lower isotherm has become an isobar. Assume CPIG. a) For the original

Question

Where the lower isotherm has become an isobar. Assume CPIG. a) For the original Carnot cycle, find the efficiency, the heat transfer in, and the world done. b) For the broken cycle, find the heat transfer out, the net work, and the new efficiency: Q.3 As shown, a steam turbine at steady state is controlled by throttling the steam to a lower pressure be- fore it enters the turbine. Before throttling, the pressure and temperature are, respectively. 1.4 MPa and . After throttling, the pressure is 1 MPa. At the turbine exit, the steam is at 10 kPa and a quality of 90%. Heat transfer with the surroundings and all kinetic and potential energy effects can be ignored. a) Determine the enthalpy at and. b) Determine the enthalpy leaving the throttle at. c) Determine the power per mass flow rate developed by the turbine (in kj/kg). Q. 4 A de-superheated works by injecting liquid water at with a temperature T2 = and mixing with a superheated water vapor stream entering at of 10 kg/s with properties 300 kPa and the exiting water at is saturated vapor. This type of device is isobaric: p1 = p2 = p3. And neglect kinetic and potential energy changes; htot = h.

Explanation / Answer

a)

At P1 = 1.4 MPa and T1 = 350 deg C, we get h1 = 3150 kJ/kg

During throttling, h2 = h1 = 3150 kJ/kg

At P3 = 10 kPa and quality x3 = 0.9, we get h3 = 2340 kJ/kg

b)

h2 = h1 = 3150 kJ/kg

c)

Power = h2 - h3

= 3150 - 2340

= 810 kJ/kg

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