GEM$$ KAZAN TES$$SLER$2.$ V$$ZE

$1)$ On a ship with a $7500$ kW main engine with a thermal efficiency of $35\%,70\%$ of the waste heat is discharged through the chimney. It is desired to obtain hot water at $90\backslash$deg C from the exhaust gas. Distilled water is taken into the boiler at a temperature of $30\backslash$deg C$.$ Main engine exhaust gas outlet temperature is $650\backslash$deg C and chimney atmosphere outlet temperature is $210\backslash$deg C$.$ The boiler working order is considered as $2$ pass and single stage. Body diameter is $90$ cm$,$ inner pipe diameter is $10$ mm$,$ inner pipe wall thickness is $2$ mm and body length is $3$ meters,

a$)$ Find the total amount of heat transfer.

b$)$ Find the total heat transfer coefficient.

c$)$ Find the number of pipes to be used $(2$pas$=1$ pipe$)$