The tubeside (Chemical #2) enters as a liquid or gas and does not change phase throughout the exchanger. Zone 1 ends just a Chemical #1 begins to condense. In Zone 1, it releases heat to the tubeside chemical (Chemical #2). Chemical #1 enters the shell at 200 Â☌ as a superheated vapor.
These diagrams should accompany your basic (input-output) diagram of the heat exchanger. The diagram on the left illustrates the use of T-Q diagrams. The system is defined as co-current or countercurrent and the diagram is constructed. Using T-Q (Temperature-Heat) diagrams are the best way to pinpoint zones. 'Zones' can best be defined as regimes of phase changes where the overall heat transfer coefficient (Uo) will vary.
