A NOVEL F-T PLOT FOR SHELL-AND-TUBE HEAT-EXCHANGERS

Shell and tube heat exchangers are one Of the most widely used heat ex change equipment in the chemical process industry. The calculation of actual mean temperature difference in a shell and tube exchanger is do ne by using analytical expressions developed by Bowman et al. In this design practice, a correction factor F-T is introduced into basic heat exchanger design equation. Graphical correlations are presented by TE MA for calculation of F-T as a function of dimensionless ratios R and S. Since F-T is used to screen alternative designs, designs with unacc eptably low F-T values are discarded. A commonly used rule of thumb re quires F-T > 0.75 for the design to be considered practical. However, this criterian is arbitrary and is used mainly because of steep slopes of F-T curves in that region, which prohibits the designer from estim ating F-T correctly. However, this is not desirable. The need is to re move the deficiencies of the F-T charts. This can be done by using som e kind of transformation to ''expand'' the curves in the region of ste ep F-T fall. The present paper describes one such transformation and d iscusses its advantages. New plot have been constructed using these tr ansformations.