I'm looking at various ways to control the outlet temperature of a tube and shell water heater. There seem to be a few ways to do this and I'm wondering if there is a stardard process control system to do this.

System is as follows:
50# steam is feed to the shell of the heater and water is contained in the tubes within the heater.
As I see it primary temperature control would based on the hot water/condensate level within the heater and a level controller would modulate the condensate discharge valve, but other systems also employ a control valve located on the steam inlet, and this valve is modulated based on the outlet temp as well.

Any suggestions on the process control?

 

Better is to use the outlet temperature as primary of a cascade loop. With the steam-side pressure as secondary and controlling the steam inlet valve. The level loop should be stand-alone.