Heat losses

occur in all vessels containing melts at high temperatures. In the case of channel holding furnaces, the losses are determined by the melt contact surface, the bath surface and the inductor idle losses. For a 120 kW inductor the inductor losses amount to approx. 25 kW and for a 2,000 kW inductor approx. 100 kW. With opti- mum vessel design, the melt diameter also corresponds to the height of the melt- ing bath, thus achieving the lowest possible contact/bath surface with the largest possible capacity. Holding furnaces can act like a “thermos flask” depending on the heat insulation and the lining. With a 13-t crucible furnace, the following losses must be expected: 120 kW thermal wall loss, 20 kW bottom loss, 35 kW surface loss with closed cover, totalling 175 kW idling losses.