Continuous Liquid Bath Furnaces

CONTINUOUS LIQUID HEATING FURNACES 4.7.1. Continuous Liquid Bath Furnaces 

The capacity of metal, glass, or salt baths for continuous operation differs from that of batch-type (dipping) baths because the coefficient of heat transfer is increased by the movement through the bath of the strip or pieces being coated. That movement also enhances temperature uniformity as well as finished product quality. 

An empirical relation, developed by J. E. Keller, equation 4.2 is for the heat transfer coefficient between a moving molten liquid and a solid. 

The capacity of a bath also depends on the purpose for which the bath is to be used. The time required to heat wire for coating in a metal bath is considerably less 

Burner input should be enough to maintain the bath temperature at least 100°F (55°C) of superheat above the liquid metal s melting point when operating at the maximum production rate. 

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With the ultrasonic treatment of a melt in the ingot mold, the narrowing of the supercooling region near the solidification front with development of cavitation processes occurs due to an inner heat source without preliminary overheating of the melt in a holding furnace. Besides that, the melt in the liquid bath is continuously supplied by additional solidification nuclei as it passes through the zone of the cavitation treatment. 

Muffle Furnaces or Retorts of Graphite or Silicon Carbide. The metal is fed into the furnace either batchwise as a solid or continuously as a liquid. The heat of vaporization is supplied by heating the outside of the retort with a burner. In a muffle furnace the vaporizing section is separated by a silicon carbide arch from the heating chamber. The heat from burning gas or oil in the heating chamber is transferred to the zinc bath from the arch by radiation. 

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