56) For maximum discharge through a chimney, the temperature of flue gases inside the chimney should the slightly more than the atmospheric temperature.

57) The internal flue tubes of a Lancashire boiler are reduced in diameter at the back to provide access to the lower part of the boiler.

58) A device in which some portion of waste heat of flue gases is recovered to heat the air before it passes to the furnace for combustion purpose, is knwon as

59) In a fire tube boiler, the water is contained inside the tubes which are surrounded by flames and hot gases from outside.

60) Steam engines are called external combustion engines.