Air is to be heated by condensing steam. Two heat exchangers are available (i) a shell and tube heat exchanger and (ii) a finned tube heat exchanger. Tube side heat transfer area are equal in both the cases. The recommended arrangement is

• finned tube heat exchanger with air inside and steam outside.
• finned tube heat exchanger with air outside and steam inside.
• shell and tube heat exchanger with air inside tubes and steam on shell side.
• shell and tube heat exchanger with air on shell side and steam inside tubes.