Acopper sheet of thickness 2 mm has an initial temperature of 140°c. it is suddenly quenched in liquid water, resulting in boiling at its two surfaces. for boiling, newton’s law of cooling is expressed as , where is the solid surface temperature and is the saturation temperature of the fluid (in this case 100°c). the convection heat transfer coefficient may be expressed as . determine the time needed for the sheet to reach a temperature of 104°c.

Steam is generated in a boiler of a cogeneration plant at 10 mpa and 450°c at a steady rate of 5 kg/s. in normal operation, steam expands in a turbine to a pressure of 0.5 mpa and is then routed to the process heater, where it supplies the process heat. steam leaves the process heater as a saturated liquid and is pumped to the boiler pressure. in this mode, no steam passes through a condenser, which operates at 20 kpa. (a) determine the power produced in the turbine and the rate at which process heat is supplied in this mode. (b) determine the power produced in the turbine and the rate of process heat supplied if only 60 percent of the steam is routed to the process heater and the remainder is expanded to the condenser pressure. (3.32 mw; 9.69 mw; 4.25 mw; 5.82 mw)

Which transition by an electron will release the greatest amount of energy? oa ob oc od

Oxygen undergoes an isentropic expansion from 120 degree c and 280 kpa absolute to 140 kpa absolute. determine the final temperature of the oxygen and the amount of work per kg of o_2 produced in the process if it is adiabatic.