Numerical Modeling of Transient Operation of a Plate Fin and Tube Heat Exchanger at Transition Fluid Flow in Tubes

In the article will be presented mathematical modeling of plate fin and tube heat exchanger at small Reynolds numbers on the water-side. The Reynolds number of the water flowing inside the tubes varied in the range from 4000 to 12000. A detailed analysis of transient response was modeled for a decrease in the water volume flow in time.Based on the experimental data correlations for the air and water-side were determined using the least squares method. The form of the relationship for the water-side Nusselt number is identical to the theoretically derived formula for the transition range.Also, the same correlation for the Nusselt number on the air-side was found. This correlation was used for the simulation of transient heat exchanger operation, but using correlation theoretically determined for pipes to calculate the heat transfer coefficient on the inner surface of the tube.The results of the numerical simulation of a heat exchanger using experimentally determined water-side heat transfer correlation and theoretical correlation derived for the transition tube flow agree very well.