This heat problem is impossible! Please help!?

Question

A heat engine consists of an oil-fired steam turbine driving an electric power generator with a power output of 120megawatts. The thermal efficiency of the heat engine is 40 percent.

(a.) Determine the time rate at which heat is discarded by the engine.

(b.) If the heat of combustion of oil is 4.4 x 10^7 joules per kilogram, determine the rate in kilograms per second at which the oil is burned.

(c.) Determine the time rate at which heat is discarded by the engine.

(d.) If the discarded heat is continually and completely absorbed by the water in a full tank measuring 200 meters by 50 meters by 10 meters, determine the change in the temperature of the water in 1 hour. (Density of water is 1.0 x 10^3 (kg/m^3); specific heat of water is 4.2 x 10^3 (J/kg x degrees C))

Answer 1

a.) A thermal efficiency of 40% means that the power output is 40% of the total power consumption. So total power consumption is 120 MW/0.4, and the discarded heat is 60% of that total power consumption.

b.) One watt is one joule per second. The heat of combustion is the amount of energy provided per unit mass of the fuel. You know the total power consumption now, so divide the power consumption in j/s by j/kg to get fuel consumption in kg/s.

c.) This is question b.) repeated?

d.) You know the rate of waste heat, in j/s, from a.). Multiply that by the number of seconds to get the amount of heat discarded. Temperature rise is waste heat divided by thermal mass (mass of water times specific heat).