1 1

Swg is plotted in Fig. 11-8. Swt can be calculated from

11. Equivalent diameter of window Dw [required only if laminar flow, defined as (NRe)s < 100, exists] 4S

(rc/2)Nr(1 - Fc) Do + DsQh where 0h is the baffle-cut angle given by 0h = 2 cos-1 - —

12. Number of baffles Nb

where le is the entrance/exit baffle spacing, often different from the central baffle spacing. The effective tube length L must be known to calculate Nh, which is needed to calculate shell-side pressure drop. In designing an exchanger, the shell-side coefficient may be calculated and the required exchanger length for heat transfer obtained before Nh is calculated.

Shell-Side Heat-Transfer Coefficient Calculation 1. Calculate the shell-side Reynolds number (NRe)s.

where W = mass flow rate and |lb = viscosity at bulk temperature. The arithmetic mean bulk shell-side fluid temperature is usually adequate

w wg wt

0 0

Post a comment