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ISSN Online: 2377-424X

ISBN Print: 0-85295-345-3

International Heat Transfer Conference 10
August, 14-18, 1994, Brighton, UK

CONVECTIVE HEAT TRANSFER IN A GAS-FIRED HEAT TREATMENT FURNACE

Get access (open in a dialog) DOI: 10.1615/IHTC10.5090
pages 141-146

Resumo

Thermal radiation is usually the dominant mode of heat transfer in industrial fossil-fuel fired furnaces so that a crude estimate of convection often suffices for design purposes. This estimate is generally based on a heat transfer coefficient derived from data for simple flows such as fully-developed pipe flow. However, gas-fired heat treatment furnaces can operate with very high excess combustion air levels over the soaking part of the processing cycle. Under these conditions both the emissivity and temperature of the flame and combustion products are low so that the convective contribution can be substantial. This paper thus reports measurements of convective heat transfer in ambient-temperature models of an industrial heat treatment system. A naphthalene sublimation technique was employed to provide mass transfer data which were subsequently converted to the corresponding heat transfer coefficients by means of the Chilton-Colburn analogy. Measurements were undertaken for a range of firing rates, burner sizes and arrangements, as well as for differing load geometries. The measured heat transfer coefficients were often significantly higher than those derived from semi-empirical relationships for pipe flow so that the use of these relatively crude values can lead to substantial under-estimation of convection.