| OCR Text |
Show Background Presently, there exists a wide variety of batch type industrial thermal processes in the 1200°F to 2400°F temperature range which are performed to obtain specific material properties. In the temperature range under consideration, the primary mode of heat transfer is thermal radiation, however, the importance of convective heat transfer is significant. The geometry of the material being processed is most often highly irregular and, therefore, the thermal radiation view factor varies over the surface. This condition obviously results in non-uniform heat fluxes to the material surface and consequently temperature variations throughout the geometry. Since the material properties being established during the thermal process cycle are usually a function of time and temperature, production of homogeneous material properties imposes the necessity of effecting uniform heat transfer to the material surface. Thus, the exigency for convective heat transfer within the furnace enclosure has been recognized. Adequate convection in batch type thermal processes is usually difficult to obtain due to the nature of the process and the method of controlling temperature. In the initial stages of batch type heating process operations, a considerable quantity of energy may be introduced via the burner nozzles. As the material approaches the desired temperature, the amount of energy required by the process to maintain setpoint temperature is equal to furnace losses and may diminish by a factor of 10 to 50 relative to the initial rate of energy input. In addition, in the 7-3 |
