Determination of heat transfer coefficient in a short-tube economiser operating in the transition region

An attempt to experimentally and theoretically analyse the performance of an industrial short-tube ($\text{L/D < 25}$) economiser operating within transitional flows ($\text{2000 < Re < 10,000}$) led to the development of a successful algorithm which predicted the gas-side heat transfer coefficient in this regime within $\text{± 15\%}$. By using the successive summation technique the algorithm combined previous correlations for long-tube transition heat transfer with that for a developing velocity profile in laminar flow. The common procedure of extrapolating into the transition region by processing standard turbulent and laminar correlations with effectiveness was found to be grossly erroneous (+65–120-%).