DOI: 10.1615/ICHMT.1988.20thAHT
ISBN Print: 978-0-89116-877-5
ISSN: 0899-5311
FIRST ESTIMATES OF INDUSTRIAL FURNACE PERFORMANCE - THE ONE-GAS-ZONE MODEL REEXAMINED
ABSTRACT
The design of a furnace, more specifically the prediction of the performance of a chosen design, can be carried out at several levels of sophistication. Although a determination of the distribution of heat-flux density over the surface of the stock is desirable - sometimes, in high flux-density systems, necessary - the attainment of the simpler objective of determining the total heat transfer rate as a function of firing rate and excess air is a proper orienting first step; and often it suffices. Even if that is the sole objective, knowledge of the detailed interaction of radiation and convection with mass transfer and combustion is in principle necessary. But integral formulations are tolerant of casual treatment of detail, especially in the presence of the leveling effect of radiation, responsive to a high power of temperature; and a surprisingly accurate overall performance is predictable from a relatively simple model. Even though the knowledge of flux distribution over the stock may be the ultimate objective, it is still good engineering practice to start with an almost-quantitative understanding of the overall process. In fact, it may be asserted that prospects of success with the zone method are poor if the simpler and less ambitious approach, which is after all a one-gas-zone example of the zone method, is not thoroughly understood.
It is the object here to set up a simple overall furnace performance model, in form as general as is consistent with the assumption of a single-gas-radiating temperature, a single equilibrium refractory temperature and, a single equilibrium refractory temperature and a single term characterizing the exchange area between the combustion gases and the sink.