Firetube Questions

[COLOR=#282828][FONT=helvetica]I’m projecting a heat treater as shown below.[/FONT][/COLOR]
[COLOR=#282828][FONT=helvetica]In my study I’m using a 30°API oil with an inlet flow rate of 3800bbl/d, 1170bbl/d water flow rate and 0.8MMscfd gas flow rate, the operating temperature is 120°F and field temperature 68°F[COLOR=#4F81BD]. [/COLOR]The fuel used in the firetube is natural gas and the Inferior calorific value is 47MJ/kg. The capacity for the firetube in our project needs to be 1,75MMBTU/hr and we would like a firetube with 24’’ diameter.[/FONT][/COLOR]
[COLOR=#282828][FONT=helvetica] [/FONT][/COLOR]
[COLOR=#282828][FONT=helvetica]Data:[/FONT][/COLOR]
[COLOR=#282828][FONT=helvetica]Vessel Size 8’x25’: Diameter 8 ft x Length 25 ft[/FONT][/COLOR]
[COLOR=#282828][FONT=helvetica]Inferior calorific value: 1,75MMBTU/hr[/FONT][/COLOR]
[COLOR=#282828][FONT=helvetica]Firetube diamater: 24 inches[/FONT][/COLOR]
[COLOR=#282828][FONT=helvetica]Oil: 30°API[/FONT][/COLOR]
[COLOR=#282828][FONT=helvetica]Field ( ambient) temperature(inlet): 68°F[/FONT][/COLOR]
[COLOR=#282828][FONT=helvetica]Vessel Operating temperature: 120°F[/FONT][/COLOR]
[COLOR=#282828][FONT=helvetica]Oil flow rate: 3,800bbl/d (barrels per day)[/FONT][/COLOR]
[COLOR=#282828][FONT=helvetica]Water flow rate: 1170bbl/d [/FONT][/COLOR]
[COLOR=#282828][FONT=helvetica]Gas flow rate: 0.8MMscfd[/FONT][/COLOR]
[COLOR=#282828][FONT=helvetica]Inferioc caloric value: 47MJ/kg[/FONT][/COLOR]
[COLOR=#282828][FONT=helvetica] [/FONT][/COLOR]
[COLOR=#282828][FONT=helvetica] [/FONT][/COLOR]
[COLOR=#282828][FONT=helvetica]i)Which would be the firetube length ? How do I calculate this?[/FONT][/COLOR]
[COLOR=#282828][FONT=helvetica]ii)About the convection section of the firetube, do you include a firetube turbulator? If yes, how do you evaluate the influence of this in the firetube length?[/FONT][/COLOR]
[COLOR=#282828][FONT=helvetica]iii)Which would be the firetube flux (Q/A)?[/FONT][/COLOR]
[COLOR=#282828][FONT=helvetica]iv)If I use a forced draft blower the firetube flux(Q/A) would increase ? If yes, what is the ideal air flow rate forced by the blower?[/FONT][/COLOR]
[COLOR=#282828][FONT=helvetica]v)What would be the operation pressure inside the firetube?[/FONT][/COLOR]