This paper deals with a "real-world" case study of a large capacity industrial ammonia flooded evaporator. Ethylene glycol brine was the process fluid that had to be cooled. Several options were analyzed, e.g., different versions of shell and tube and plate and frame heat exchangers. Because of mechanical integrity, control issues and maintenance requirements the option of choice was a flooded shell and tube. A conventional flooded shell and tube with prime surface carbon steel tubes would have been too big, resulting in a large space requirement and greater refrigerant charge. Almost every local code requires careful audit of ammonia inventory in an industrial plant. The goal of the designers, engineers, contractors, and the end-users is to reduce the refrigerant charge to a minimum. In view of design and operational constraints, an evaporator was designed, fabricated and installed that included a tube bundle with various kinds of tubes. Three different types of tubes were used along the height of the tube bundle. Highly efficient nucleate boiling characteristics doubly-enhanced tubes were used in the lower section and inside-only enhanced tubes were used in the top section to minimize the adverse effects of vapor blanketing. Tubes in the mid section were doubly-enhanced with different outside structure than the tubes in the lower section. This resulted in a very efficient evaporator at a minimum refrigerant charge.
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