A re-examination of entrainment constant and an explicit model for flame heights of rectangular jet fires

Flame heights of buoyant turbulent jet fires produced by rectangular nozzles whose aspect ratio varied from 1:1 to 1:71 are investigated experimentally in this work. The change of the entrainment constant parameter C-1 with aspect ratio is discussed based on the comprehensive data obtained. It is found the value of C-1 does not need to be transformed from 0.179 to 0.444 with an increase in aspect ratio from axisymmetric one to linear one as proposed previously in the classic correlation due to limited data, a change which might be misleading. It is revealed to in fact change little with rectangular fire source aspect ratio and can be constantly taken as 0.185. A new explicit model to predict flame heights for given heat release rates of rectangular jet fires is then proposed, which is shown to be in good agreement with the measured values for different source aspect ratios. (c) 2014 The Combustion Institute. Published by Elsevier Inc. All rights reserved.