A four stroke gas engine has a cylinder diameter of 25 cm and stroke 45 cm. The effective diameter of brake is 1.6 m. The observations made in a test of the engine were as follows. Duration of test = 40 min. Total no. of revolutions = 8080 Total no. of explosions = 3230 Net load on brake = 90 kg Mean effective pressure = 5.8 bar Volume of gas used = 7.5 m3 Pressure of gas = 136 mm of water Atm. temp. = 17°C Calorific value of gas = 19 MJ/m3 at NTP Rise in temp. of jacket cooling water = 45°C Cooling water supplied = 180 kg Draw heat balance sheet and estimate indicated thermal efficiency and brake thermal efficiency. Assume atmospheric pr. as 760 mm of Hg.