A boiler produces $6$ tonnes$/$hour of steam at a pressure of $1\mathrm{.}8$MPa and a temperature of $250C.$

Feedwater enters at a temperature of $39C.$ At the exit from the economiser, the feedwater

temperature is $72C.$ At the exit from the evaporator, the steam is $90\%$ dry. Energy is supplied by

$650kg$ of coal per hour, with a calorific value of $36M\frac{J}{k}g.$ The $\frac{A}{F}$ ratio is $25$:$1.$ The air temperature

increased by $83C$ before being channelled to the combustion chamber. The average specific heat at constant

pressure of air is $1005\frac{J}{k}g.$ K$.$

$5\mathrm{.}1$ Calculate the overall efficiency of the plant.

$[70\mathrm{.}5\%]$

$5\mathrm{.}2$ Draw up an energy balance on a $k\frac{J}{k}g$ of coal basis, with percentages of the total energy

supplied. $[$Eco$.=3\mathrm{.}5\%$; Evap. $=59\mathrm{.}1\%$;$SH=(7\mathrm{.}87\%)8\%$;$AP=6\%$; other $23\mathrm{.}53\%]$