16.40 A gas engine working on the constant-volume cycle gave the following results during a one-hour test run. Cylinder diameter 24 cm; stroke 48 cm; torque 770 Nm; average speed 220 rpm; average explosion per minute 77; mep 7.5 bar; volume of gas used 12 m³ at 17 °C and 770 mm of mercury pressure; lower calorific value of gas 21 MJ/m3 at NTP; inlet and outlet temperature of cooling water are 25 °C and 60 °C respectively; cooling water used 600 kg. Determine (i) the mechanical efficiency (ii) the indicated specific gas consumption in m3/kW h and (iii) the indicated thermal efficiency. Draw up a heat balance for the engine on minute basis, explaining why friction power has been included in or omitted from your heat balance. NTP conditions are 760 mm of Hg and 0 °C.