2 replies to this topic

[processengbd]

One of our fellow process engineer did some calculation regarding water bath hater, His source is API 12K.

 

Where he has used a heat flux of 10,000 Btu/hr.ft sq deg F

Flux density of 12,000 Btu/hr.in sq

 

My consideration is that Api 12K is for fired heater does it apply to water bath heater design?

 

He has used same heat flux for fire tube design and process gas surface area calculation.

In my view the flux generated in the fire tube (Temperature Gradient) should be much higher then the flux generated in the process has tube.

 

My another query is that he has used a header to divide the gas flow into three separate tube. Which will also have four pass  DSC_0111.jpg   116.45KB   12 downloads(attached hand drawing) . In my view the flow through all the tubes will not be same.

 

Please advice 

Regadrs

Edited by processengbd, 23 December 2013 - 03:32 AM.

[Bobby Strain]

Best to give your specification to a vendor who supplies this equipment. Don't try to design your own.

 

Bobby

[Jiten_process]

Indirect water bath heater is typically used in oil field services. This is very much typical and identical you see in early production facility or testing skids. API 12K is basically for such type of indirect type fired heaters. If you go to the figure-1, you will see that the assembly arrangement is similar to what sketch you have shown. 

 

This water bath heaters are always a vendor item, however one can do a preliminary design. we shiver only when it comes to a gurantee.  the heat flux and heat density value you have mentioned in typical given in API-12K. 

 

There is no tube sheet in water bath heaters. process coils is sized based on pressure drop and heat transfer requirement. heat transfer from coil to a water bath can be calculated the same way with basic heat transfer calculation method. Outside the coil, its natural circulation depending on temperature of water bath. 

 

Normally for fired tubes, extensive rigorous calculation is done however, it is experimental and experienced base method. preliminary sizing is done based on heat flux value given in API-12K and assuming overall thermal efficiency of water bath heater. 

 

May be other experts have more to say on this.