Process temp control via bypass or vfd?

[ch44all]

The process I am working on is preheat of natural gas prior to pressure reduction. Peak Process load is 385,000 btu. Target gas temp is 175 F. I am looking for some guidance to understand the differences in controlling gas temp with a 3 way valve for bypassing the hex and keeping constant hot water temp or controlling with vfds. Any general articles or advice in this would be appreciated.

 

[MortenA]

It depends on your set-up. If you expect fairly constant heat deamand (short term minutes not relevant for plant life time) then the valve solution would be the best design option. In a closed loop VFD may often be economical. If you have many consumers you must have valves at each consumer, but this _could_ be in combination with VFD and fixed temperature (as is used in many mordern district heating systems).