Problem 28P

At a steam power plant, steam engines work in pairs, the output of heat from one being the approximate heat input of the second. The operating temperatures of the first are 670°C and 440°C, and of the second 430°C and 290°C. If the heat of combustion of coal is 2.8 × 107 J/kg, at what rate must coal be burned if the plant is to put out 1100 MW of power? Assume the efficiency of the engines is 60% of the ideal (Carnot) efficiency.

SolutionStep 1 of 5In order to calculate the energy transferred to each eardrum per second at 30 m fromthe loudspeaker , first we need to find the intensity of sound on the eardrum.Intensity of a sound is the energy transmitted per unit area perpendicular to thedirection of propagation per unit time.Since energy per unit time is given by power.The intensity can be defined as the power radiated per unit area perpendicular to thedirection of propagation.That is I = P AWhere I is the intensity, P is the power and A is the area.