申論題

5.A small nuclear reactor is cooled by passing liquid sodium (Na) through it. The liquid sodium leaves the reactor at 0.2 MPa and 400°C. It is cooled to 320°C by passing through a heat exchanger before returning to the reactor. In the heat exchanger, heat is transferred from the liquid sodium to water, which enters the exchanger at 10 MPa and 49°C(enthalpy is 176.38 kJ/kg) and leaves at the same pressure as a saturated vapor (enthalpy is 2724.7 kJ/kg). The mass flow rate of sodium is 10,000 kg/h, and its specific heat is constant at L25J/(g)(°C). Determine the mass flow rate of water evaporated in the heat exchanger, in kg/h, and the heat-transfer rate between the two fluids, in kJ/h. (15%)