Fired Heaters 1

[unoerudite]

Hi all, I am new to this forums world, I have a Question on the fired heaters

Can anyone help me with the main importance of Convection in a fired heater?
question is silly but i want the answer

Thanks a lot in advance

 

[unoerudite]

I also have another question, how do we increase the convection section duty in a fired heater.

Thanks for your reply

 

[berkshire]

Is this a student question?
B.E.

 

[unoerudite]

@ Berkshire

no I am a mechanical engineer, but i want to know the process side of fired heaters.

 

[berkshire]

unoerudite (Mechanical)
You will have to give a little more detail On the type of heater, Is this a space heater, a convection heater, or a furnace.
B.E.

 

[lappygamer]

I'm assuming the OP is talking about furnaces which are called fired heaters in my line of work. My company supplies fired heaters primarily for oil refineries. While fired heaters come in many configurations, almost all have a radiant and a convection sections.

I'm not sure exactly what you were asking about the "importance" of a convection section. Flue gas temperatures are high in the radiant section (~1500F) which makes radiant heat transfer an efficient means of transferring heat. If you had only a radiant section the flue gas would be leaving at 1500F which is an awful waste of heat. The convection section allows for further heat extraction from the flue gas at lower temperatures. At these lower temperatures, convection is a more effective mechanism of heat transfer.

As far as increasing convection duty. It depends on what options might be available you. If you could lower the inlet temperature of the process stream you would pick up more duty. If you cannot change the process, the convection section could be modified. Additional convection tubes could be added. Convection tubes (at least some of them) usually have fins or studs to increase their heat transfer efficiency. It may be possible to install tubes with more fins.

If you provide a little more information we may be able to give you a better answer.

 

[unoerudite]

@Berkshire
thanks a lot for trying to answer my Q. Like Tbova said it is an industrial furnace callled fired heater, used in oil refineries for heating any medium.

 

[unoerudite]

@ tbova, thanks for your reply. your answer is really helpful.

 

[25362]

From what I remember, 10 to 20% of the heat transferred in the convection section (shock tubes) of those heaters is by radiation.

It is also frequent that the radiant section and part or all of the convection section are used for entirely different processes.