Question

1. You are to do a preliminary design study for a small demonstration steam turbine power plant.
- Steam will be provided by a small steam generator fired by natural gas.   - Your system will take in steam at 30 bar and 400 oC.
- The steam passes through a two stage turbine. At a pressure of 10 bars, the steam leaves the first stage of the turbine and will pass through a reheat loop in the steam generator which will boost the temperature back up to 400 oC at this pressure. The steam will then enter the second stage of the turbine.
- When the steam leaves the turbine, the quality should be at least 95% at the turbine exit / condenser inlet.
- The design condenser pressure is 0.70 bar.   
- Heat is removed from the condenser and rejected to the environment through a cooling tower.
a) Assuming isentropic expansion, what are the temperature, enthalpy, and entropy of the steam when it leaves the first stage of the turbine? (5 pts)

b) What are the enthalpy and the entropy of the steam as it leaves the reheater and enters the second stage of the turbine? How much heat (kJ/kg) goes into the steam in the reheat process? (10 pts)

c) Based on an isentropic expansion, what will the quality be at the exit? Will it meet this design limit? (10 pts)
For the following parts use the design turbine power output of 2.5 kW.
d) What mass flow rate is required? (10 pts)

e) At what rate must heat be produced by natural gas burners in the steam generator to produce the steam at the turbine inlet, and how much heat must be produced to reheat the steam between the stages? For a heating rate range of 950-1150 BTU/scf and a cost of $8 per 100 cubic feet, what is the fuel cost per hour to run this unit? (10 pts)

f) What is the feed water pump power demand, and what is the BWR? (10 pts)


2. A refrigeration machine has been designed based on R134a. The design capacity is 15 tons.   The evaporator coil design temperature is 8 oC. The refrigerant enters the compressor as a slightly superheated vapor at 15 oC. The condenser coil design pressure is 14 bar. Refrigerant enters the expansion valve as a compressed (subcooled) liquid at 44 C. Note that the temperature of the air passing over the tubing in the evaporator coil will be higher than 8 oC and the temperature of the air passing over the condenser coil will be lower than the coil temperature. Use 80% for the compressor isentropic efficiency.
a. Calculate the power required to run the compressor under these design conditions and the required mass flow rate of R134a. (30 pts)

b. Find the rate of heat transfer for the condenser (high pressure side) of the system. (15 pts)

c. Find the quality of the refrigerant as it enters the evaporator. (10 pts)



3. A small gas turbine engine is used to produce power for auxiliary systems. This is a simple gas turbine open to the atmosphere. Air enters the compressor at 1 bar, 300 K. The compressor pressure ratio is 3.5:1. After passing through the combustion chamber, the air enters the turbine at a temperature of 1300 K. Determine the mass flow rate of air needed for the turbine to produce 60 kW of power. Also determine the heat that must be generated in the combustors. (30 pts) Solar collector …

Answer 1

****In question 1, in 'd' part the turbine output given as 2.5 kW.......it should be 2.5 MW intead of 2.5 kW, so i am solving peoblem for 2.5 MW power output. It makes no sense for 2.5 kW power output from power plant. Thank you, hope you understand.