Question

In the boiler of a power plant are tubes through which water flows as it is brought from 0.8 MPa, 150°C to 240°C at essentially constant pressure. The total mass flow rate of the water is 100 kg/s. Combustion gases passing over the tubes cool from 1067 to 277 °C at essentially constant pressure. The combustion gases can be modeled as air as an ideal gas. There is no significant heat transfer from the boiler to its surroundings. Assuming steady state and neglecting kinetic and potential energy effects, determine (a) the mass flow rate of the combustion gases, in kg/s (b) the rate of exergy destruction, in kJ/s. (c) the exergetic efficiency given by Eq. 7.45. Let T0 = 25°C, p0 = 1 atm. Round your answers to 3 significant digits.

Answer 1