Vapor Density calcuation method in Vertical Thermosyphon Reboilr

[hswang2]

Dear Sir/Madam

I have a trivial question to bother you and it is about vapor density calculation question . I tried figure out using excep spreadsheet to calculatie the minmium vertical thermosypon reboiler height, but I don’t quite know how to get the vapor density ( please see the attached file with the red cloud).

And, the other question is how to choose he maximum allowable flux to get the heat exchanger surface area.

Could anyone kindly help me out?



Thank you so much.

 

[ione]

Molar mass of buthane = 58.123 g/mol approx 58 g/mol

Standard condition :
T1 = 32 °F = 491.7 R approx 492 R
P1 = 14.7 psia
Rho1 (density) = 0.16 lb/ft^3 (that is approx your factor 58/359)

In standard conditions one mole of a gas (58 g or 0.126878 lb) occupies a volume of 22.414 l or 0.792496 ft^3


Working contitions:
T2 = 228 °F = 687.7 R approx 688 R
P1 = 275 psig = 289.7 psia approx 290 psia

Then apply the ideal gas law

Rho1 =P1/(RT1)
Rho2 = P2/(RT2)

Rho2 = Rho1/[(P1/P2)*(T2/T1)]

 

[ione]

Further to your second question.

Upper limit for water base substances 30,000 Btu/(hr*ft^2) and for organic substances 12,000 Btu/(hr*ft^2). These values proposed by Mr. Donald Kern, derived from industrial experiences, and are widely adopted (Heat Transfer in Process Engineering By Eduardo Cao Publisher: McGraw-Hill Professional)

 

[hswang2]

Thank you very much.