Optimized Design of a Furnace Cooling System

Abstract

This paper presents a case study of manufacturing furnace optimized re-design. The bottleneck in the production process is the cooling of heat treatment furnaces. These ovens are on an approximate 24-hour cycle, heating for 12 hours and cooling for 12 hours. Pressurized argon and process water are used to expedite cooling. The proposed modifications aim to minimize cycling by reducing cooling time; they are grouped into three fundamental mechanisms. The first is a recommendation to modify current operating procedures. This entails opening the furnace doors at higher than normal temperatures. A furnace temperature model based on current parameters is used to show the reduction in cooling time in response to opening the furnace doors at higher temperatures. The second mechanism considers the introduction of forced argon convection. Argon is used in the process to mitigate part oxidation. Cycling argon through the furnace during cooling increases convection over the parts and removes heat from the furnace envelope. Heat transfer models based on convective Nusselt correlations are used to determine the increase in heat transfer rate. The last mechanism considers a modification to the current heat exchanger. By decreasing the temperature of the water jacket and increasing heat exchanger efficiency, heat transfer from the furnace is increased and cooling time is shortened. This analysis is done using the Effectiveness-NTU method.