Heat-Transfer Studies of Naval Boilers

Abstract

Abstract During World War II the double-furnace superheat-control type boiler was the prevailing type used on combatant ships. It operated at a pressure of 575 psig and temperature of 850 F. These boilers presented two serious operational difficulties: Adaptation of relatively simple automatic control systems for double-furnace operation; and maintenance of sufficient steam flow through the superheater to coincide with firing rates in the superheater furnace. Because of these and other difficulties associated with size and weight requirements, postwar naval boilers were predominantly the single-furnace integral superheater type. In single-furnace boilers all steam generated flows through and gases of combustion flow over the superheater. There are no positive means of superheat control such as dampers and attemperators, but steam temperature at superheater outlet may be varied by changing combination of lighted-off burners, amount of excess air, or temperature of feed. These or other changes of a similar type generally have a small effect upon final steam temperature and additionally affect cycle and operating efficiencies. Therefore it is imperative that these integral superheater boilers be designed to provide a required superheat temperature. These temperatures should be constant over as wide a range of rate as possible. Boilers that range in pressure from 600 to 2000 psig and temperature from 800 to 1050 F have been tested.