5 replies to this topic

[Propacket]

Dear All,

Can anyone help me calculate pressure drop through coil? Actually, i am designing an indirect fired line heater. There are number of coil passes. I have calculated the pressure drop through straight pipe but i want to calculate pressure drop through turns.

[shan]

Figure out the equivalent length for the turns in order to calculate the pressure drops through the turns.

[ankur2061]

P. Engr,

The pressure drop criteria for fired heaters is not so straightforward as that of a pipe carrying any liquid. Pressure drop criteria for the radiant section and convection section of a fired heater are different. For radiant section coils of a fired heater the basic criteria for fluid flow through the coils is to maintain sufficient mass velocity to prevent coking/fouling of the fluid in the tubes. Obviously a high mass velocity would mean a higher pressure drop. As a rule of thumb a mass velocity of 1200-1500 kg/s-m2 should be maintained in the radiant section to operate without possible coking/fouling on a reasonably long term basis. For turndown conditions mass velocity should be kept above 700 kg/s-m2.

The convection section coils of the fired heater are normally designed for much lower pressure drops since the restrictions of minimum mass velocity as mentioned above do not apply.

It must be obvious to you now that coil design of a fired heater is a complex design done by specialists & a handful of fired heater manufacturers worldwide.

Hope this helps.

Regards,
Ankur.

[Propacket]

This is what i am looking for. I need equivalent pipe length for 180 degree turn. I have tried with two 90 degree elbows joined together to form a 180 degree turn but i think this is not a good method for calculating pressure drop since actually radius of 180 turn will be much smaller than that formed by two 90 degeree elbows.

[ankur2061]

P. Engr,

Regular 180 degree return bends are used for coil fabrication of fired heaters. Here is the link for equivalent lengths for regular 180`degree return bends:

http://www.engineeri...ngth-d_192.html

Regards,
Ankur.

[Propacket]

Thanks Ankur