Foundations of Thermodynamics and its Industrial Applications

Investigate the effect of reheat pressure on the performance of an ideal Rankine cycle. The maximum and minimum pressure in the cycle are 15MPa and 10kPa, respectively, and steam enters both stages of the turbine at 500C. The reheat pressure is varies from 12.5 to 0.5MPa. Determine the optimum reheat pressure that maximizes the thermal efficiency of the cycle. 

A power plant wants to maximize the net thermal efficiency of a gas turbine engine (with regeneration, if possible). The maximum operating temperature is 1425C. The power plant decided to use two compressor (low and high compressor) with intercooling. The overall pressure ratio of the two compressor is 25. The power plant want to removes heat after the low pressure compressor using a refrigeration cycle. The Refrigeration cycle is powered by a Rankine cycle and the Rankine cycle is power by a heat exchanger from the exhaust of the gas turbine cycle (which can also be used for regeneration if possible). Both the Rankine cycle and Refrigeration cycle reject heat at atmospheric condition. Both compressor in the Brayton cycle have isentropic efficiency of 88% and the turbine isentropic efficiency is 92%. The Rankine cycle pump isentropic efficiency is 85% and the steam turbine efficiency isentropic is 87%. The refrigeration compressor isentropic efficiency is 93.8%. The mechanical energy transferred is 90% efficient. Design a schematic of the combine cycle. List and label all the states in each system (temperature, pressure, enthalpy, and entropy). Which working fluid would you recommend for the refrigeration and Rankine cycle? What is the mass flow rate ratio of the refrigeration cycle to Brayton cycle and the mass flow rate ratio of the Rankine to Brayton Cycle? Plot the net thermal efficiency vs low pressure ratio from 2.5 to 10.  Draw a T-s diagram of your combine cycle. Discuss the various cycle attempt to meet your design goal as well as the positive and negative aspect of your design. Please include a sample calculation in your report.

Steam enters the turbine steadily at 7 Mpa and 25kPa with a velocity of 60m/s and leaves with a quality of 95%. A heat loss 20kJ/kg occurs during the process. Investigate the effects of turbine exit area and turbine exit pressure on the exit velocity and power output of the turbine as the exit pressure varies from 10 kPa to 50 kPa (with the same quality), and the exit area to varies from 1000 cm2 to 3000 cm2. Plot the exit velocity and the power output against the exit pressure for the exit areas of 1000, 2000, and 3000 cm2.

Consider an ideal steam regenerative Rankine cycle with two feedwater heaters, one closed and one open. Steam enters the turbine at 10 MPa and 600°C and exhausts to the condenser at 10 kPa. Steam is extracted from the turbine at 1.2 MPa for the closed feedwater heater and at 0.6 MPa for the open one. The feedwater is heated to the condensation temperature of the extracted steam in the closed feedwater heater. The extracted steam leaves the closed feedwater heater as a saturated liquid, which is subsequently throttled to the open feedwater heater. Investigate the effects of turbine and pump efficiencies as they are varied from 70% to 100% on the mass flow rate for a net power output of 400 MW and thermal efficiency. Plot the mass flow rate and the thermal efficiency as a function of turbine efficiency for pump efficiencies of 70, 85, and 100%, and discuss the results. Also plot the T-s diagram for turbine and pump efficiencies of 85%.