After an initial, provisional selection the rater has an idea of the size of the exchanger needed. The first selection is not necessarily the best choice. Several iterations are usually needed to reach this goal. The number of iterations often increases with exchanger size. The engineer should decide if the provisional selection is competitive and has a reasonable chance of being selected for the application. If not, will varying the design make this selection more feasible? A “no” answer to both questions should stop work on the selection. No exchanger is suitable for all applications. To make selections and prepare quotations takes time and money.
Several designs can be named that are rarely used in specific applications. Double-pipe and plate exchangers are seldom placed in service on over-the-road vehicles because of their length and piping needs. Wide exchangers may be competitive if shipped by barge. Code-constructed shell-and-tube units smaller than 15 inches in diameter in liquid service are seldom competitive with double-pipe exchangers. If you are aware that a product is competitive, work should proceed. Otherwise, it should cease. Conclusion: Knowing the limits of your chosen product and those of competing products will make this decision easier.