Finite element analysis of heat transfer through salt bath furnace insulation

Heat flow patterns in two salt bath furnaces are studied in this work using finite element (FE) analysis. One design had a purely refractory brick back-up after the embedded heating element with ceramic fiber blanket insulation and IS2042 Type II hot face and IS2042 Type III cold face insulation just before the outer steel shell. The other had an additional air-gap insulation formed by cylindrical steel belts with spacers placed after the hot face insulation. It is observed that the design with additional air-gap insulation had tremendous insulation effect, decreasing heat loss through skin of the furnace. It also increases the inside wall temperature, necessitating a drastic thinning down of the silica brick thickness with substitute to ceramic blanket. The performance of oil fired reheating furnace is analyzed theoretically to calculate the efficiency of the furnace. The conjugate heat transfer in multi layer furnace wall including an air layer is analyzed, using Gambit and Fluent. An air layer with 115 mm of thickness and 4 parallel partitions presents the best insulating capacity.