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Circulating Heaters

Principle of Operation of Circulating Heaters

Circulating Heaters are classified as “open tank heaters” that entrain suction liquids using two high-velocity steam flows issuing through a double nozzle. This composite nozzle has a short annular suction jet designed to draw liquids into the heater. It also has a longer center jet used to force liquids from the heater. The heated liquid exits the heater at high velocities imparting vigorous circulation and good agitation to the tank liquid.

Figure 315 Circulating Heaters are recommended for use where heating and strong directional circulating action in open tanks are required. This heater must be submerged in the liquid it heats. Only one pipe, for steam, is needed.

Figure 315 Circulating Heater sectional drawing with alternate steam connection
Figure 315 Circulating Heater's strong directional flow enables efficient heating of irregular tanks with dead spots

Figure 315 Circulating Heaters, because of their good agitating and circulating characteristics, can augment or replace mechanical agitators while enhancing heat transfer. Strong directional flow enables efficient heating of irregular tanks with dead spots that a resistance or bayonet heater cannot reach.

  • Figure 315 Circulating Heaters used in heating and agitating the solutions used in pickling tanks in steel plants and foundries.
  • Sterilizing molasses in the fermentation tanks used in alcohol plants.
  • Dissolving chemical salts in the various liquids employed in process work in chemical plants and for any other installations where heating, circulating and agitation of water or other liquids are required.
Circulating Heater heating and agitating solutions
Fig. 315 Circulating Heater Used in Heating and Agitating Solutions.
Because the jet discharges in only one direction, there is a back thrust that is likely to cause vibration of the steam pipe. To eliminate this, the heater should be anchored in some way. The usual method of doing this is to locate the heater against a block along the side of the tank. The heater is started by opening the stop valve in the steam line, and is shut off by closing this valve. Circulating and agitating action can be regulated by throttling the steam pressure.