A domestic gas boiler is used to transfer heat to the water in a central heating system. The inlet pipe has a diameter of $15$ mm$.$ The feed water temperature is $15$oC and has a velocity of $1\mathrm{.}2$ m$/$s$.$

Heat energy is produced at a rate of $38\mathrm{.}2$ kW$,$ during combustion of the gas and the thermal efficiency of the boiler is $66\mathrm{.}2\%.$

Water has a density of $1000$ kg$/$m$3$ and a specific heat capacity, C$,$ of $4200$ J$/$kgK$.$

You are required to calculate the temperature of the water leaving the boiler.

What is the mass flowrate of the water leaving the boiler?

$($Input your answer below in Kiliograms per Second $($kg$/$s$),$ accurate to four decimal places$)$

Answer:

Feedback

The correct answer is:

Question $2$

Tries remaining: $2$

Marked out of $1\mathrm{.}0$

Flag question

Question text

What is the rate of heat energy transfer to the water?

$($Input your answer below in Kilo$-$Watts $($kW$),$ accurate to two decimal places$)$

Answer:

Question $3$

Tries remaining: $2$

Marked out of $1\mathrm{.}0$

Flag question

Question text

What is the temperature of the water leaving the boiler?

$($Input your answer below in Degrees Celsius $($ oC$),$ accurate to one decimal place$)$

Answer:

Question $4$

Tries remaining: $2$

Marked out of $1\mathrm{.}0$

Flag question

Question text

The boiler is serviced and the heat exchanger is replaced. As a result, the temperature of the water exiting the boiler increases to $50$oC$.$

What is the thermal efficiency of the boiler, after the service has been completed?

$($Input your answer below, as a Percentage $(\%),$ accurate to one decimal place$)$

Answer: