Design

=__**Optimization**__=

==== The design parameters of a heat exchanger is mainly consist of the tube size, bundle layout, and baffle type, and these concepts can be considered as initial decisions. For the tube size selection, it is recommended to start with a small tube and then increase the tube size to meet the pressure drop constraints.Also for the bundle layouts, a 45 degree tube layout is used with mechanical cleaning, while a 30 degree arrangement is used with chemical cleaning. Finally in types of baffles, it is suggested to select a single-segmental baffle; however, double- or triple-segmental baffles can be used to meet the shell-side pressure drop constraint. The following figures (figure 17- 20) show where the optimum design point locate with respect to the velocity, tube count and the tube length. ====









==== Also design space and baffle geometry are other considerations in shell-and-tube heat exchanger design. The design space requires the tubeside velocity and the pressure drop between a minimum and a maximum value, and it is considered to be two dimensional with tube count and tube length. The following figures (figure 21 &22) show some examples for the acceptable designs with respect to the design space. ====





==== Baffle geometry also has a marked effect on heat exchanger performance. The optimum cut occur to satisfy the full use of available shellside pressure drop and the baffle arrangement with equal window and crossflow flow areas. There is an example shown in the following figure 23: ====



==== Since the changes in the operating conditions also requires to reduce the propensity of fouling, it is necessary to increase the consumption of utilities to meet target values. On the other hand, the changes in the operating conditions also need to correspond to cost effectiveness. Therefore there is a trade-off among the operation conditions, the propensity of fouling and the cost effectiveness of the heat exchanger networks. ====