Design a stationary steam power plant operating on an ideal closed loop Rankine cycle that can deliver 85 MW of net power. The power plant is to be located at a site near a lake where the annual average temperature is 23 °C.
(1) Draw a diagram of the system, and state necessary assumptions. Specify inlet and outlet states for the pump, boiler, turbine and condenser.
(2) Select the maximum allowable temperature in the system and appropriate pressure range based on realistic constraints such as economic, environmental, social, political, ethical, health and safety, manufacturability, and sustainability, etc. You must justify your selection based on the constraints.
b) Find the mass flow rate that can generate 85 MW of power and determine the thermal efficiency of your system
(c) The condenser is cooled by running the cooling water from a nearby lake through the tubes of the condenser. If the temperature increase of the cooling water cannot be over 12 °C, what is the minimum mass flow rate of cooling water?
(d) The efficiency of the power plant can be improved by decreasing the condenser pressure. Select an appropriate condenser pressure lower than used in item for your Rankine cycle, and show the percent increase in efficiency.
(3) The efficiency of the power plant can also be improved by using a reheat cycle. For the reheat cycle select the same condenser pressure as in item 2, and the same exit temperature of reheater as the maximum temperature that you used in item (2), then, select an appropriate reheat pressure. Show the effects of reheat on the efficiency by comparing it with the efficiency of the basic Rankine cycle that you obtained in 2b and determine
(a) Percent increase in efficiency due to reheating, (b) Mass flow rate of the steam, (c) Mass flow rate of cooling water,
(d) For the same reheat cycle, select a higher reheat pressure than used in item (3) keeping all the other parameters same. Recalculate the quality at the turbine outlet to show that increasing the reheat pressure decreases the quality at the turbine exit.
(4) Discuss how you can further improve the efficiency of the power plant with realistic constraints stated in item (2).