Calculate

1. Heat produced by combustion of the gas

2. Heat taken away in the flue gas (assume properties similar to air)

3. Heat taken up by the water

4. Calculate the thermal efficiency of the boiler

\begin{tabular}{|l|l|l|l|} \hline condition 1 & Water, liter/min & Gas, liter / min & Air flow rate liter/min \\ \hline & 10 & 50 & 550 \\ \hline \end{tabular} \begin{tabular}{|l|l|l|l|l|l|l|l|l|} \hline No. & Condition & Time & Fluelgas, ('C) & Hot water output, ('C) & Heat exchanger water side, ('C) & Cold water Out & Reference, ('C) \\ \hline 1 & 1 & 13:53:59 & 22.1 & 21.7 & 21.7 & 21.5 \\ \hline \end{tabular}