Flow over Banks of Tubes

In shell-and-tube heat exchangers, the flow on the shell side takes place over a bank of tubes several rows deep. The flow is aligned at various angles to the axis of the tubes. However, for preliminary design work, the flow may be assumed to be transverse to the axis (i.e., a cross flow). This configuration has been extensively re-searched and experimentally determined data are available [91] for different values of aligned and staggered arrangement of tubes. The important geometric parameters are (see Figure 6.14) longitudinal pitch S _L, transverse pitch S _T, and tube diameter D. Here, we consider cases of S _L /D=S _T /D=2 for the inline array and S _L /D=S _T /D=1.5 for the staggered array.

Figure 6.14: Flow across banks of tubes.

For the purposes of computations, however, the smallest symmetric domain must be considered. Such domains are mapped by curvilinear grids as shown in Figure 6.15. In these domains, the north and south boundaries are partly symmetric and partly occupied by tube wall but the west and east boundaries are periodic. Note, however, that in the inline array, the periodicity is even whereas a cross-periodicity occurs in the staggered array with respect to the u ₂ velocity. Computations have been performed using 45 15 grids for the inline array and 41 15 grids for the staggered array. For turbulent flow, the standard HRE model with two-layer wall functions...