6 replies to this topic

[nivedita12]

To Team

 

I have to size a Temperature control valve installed in a 50% propylene+glycol and water line, used to heat Boil off gas coming from a compressor at -190 ^oF. 

 

1,300 lb/hr of Boil off gas (99% Methane) is heated from -190 ^oF to -10 ^oF.  The 50% propylene glycol is coming in at 90 ^oF and going out at 80 ^oF.  The flow rate of GW is 16,000  lb/hr.

 

A temperature control valve is installed in the Glycol water line coming into the shell and tube exchanger (attached sketch). which senses the Outlet temperature of the glycol water from the exchanger and sends the required amount. 

 

Please let me know how to size the temperature control valve. 

 

Thank you 

NB

 BOG-GW Datasheet.pdf   115.69KB   31 downloads

Edited by Art Montemayor, 07 March 2019 - 11:39 AM.
Typos, grammar, composition, vocabulary, structure, etc., etc.

[Art Montemayor]

Nivedita:

 

I edited your query because it was a literal mess.  You put two copies of the attachment into the body of the query and made it difficult to read.  Your composition is terrible and looks like it was copied+pasted from some directive.  I don't know what you mean by "team".  Did you do any original work on this query?

 

You want to know how to size the control valve.  Why don't you ask your instructor, who is supposed to have showed you how?  Anyway, the valve is already sized according to your information.  It should handle the 16,000 lb/hr indicated by you.  All you need to do is fill in a Data Sheet - which you can find and download from our Forum Library.  If you can't find it, ask and I'll upload it for you.

 

 

 

 

[nivedita12]

Sorry about the mess Art

 

I was looking at different flows in case the glycol water freezes. The freezing point for Glycol water is -29.8 F. So minimum flow must be maintained in the exchanger  so that GW does not freeze up . Hence the question is what should be a minimum flow of glycol water ?

 

Based on that the range for the flow has to be given in the TCV datasheet. 

 

Do you have any idea on this 

 

Thank you

NB

[SyedAhmed]

You query is not clear. Please give some background and about the required result. Clarification very important.

[Art Montemayor]

Nivedita:

 

The best thing our Forums can do for Students is to not work out their homework for them.  I respect you acknowledging your messed up query and returning for help with a much cleaned-up explanation.  For that reason I will try to give you a hint on how to approach your problem.  Bear in mind that it is up to you to use the theory and exercises given to you by your instructors and apply these with rational, common sense and an algorithm towards your solution.

 

The problem you face is one involving the sensible heat you can apply to the Boil-Off gas.  You must remove this with the heat sink available: the glycol+water flow.  You must identify the amount of heat to be applied to the gas.  For this you have the sensible heat equation and the attached spreadsheet.

 

Through the years I have expounded the availability of free thermodynamic data and its use in student problems.  This is another reminder that this is a quick, accurate, and free way of resolving this Thermo problem.  Use it with the Thermodynamic knowledge you should already have been taught.

 

 Boil-Off Methane Thermo Properties.xlsx   36.05KB   47 downloads

[nivedita12]

Thank you sir I will upload once i have the calculation 

[nivedita12]

The above said heater is sized for 116,085 Btu/hr with Glycol water flow rate of 15,790 lb/hr.

 

Now the question is propylene glycol freezes at -29.8 F and if the ambient conditions is less than -29.8 Deg F , then it will freeze in the exchanger, What should be the approach as to run a minimum flow of Glycol water through the exchanger .

 

For eg- say at ambient conditions at -40 F. The flow rate will be

 

116085 btu/hr /((0.799 Btu/lb F *(-29 F- (-40 F)) = 13208 lb/hr. 

 

at 65.60 lb/ft 3 of density the flow rate will be 25 gpm 

 

Please throw some light on the freezing of the glycol water in the tube side of the  exchanger as to how much flow should be circulating through it to prevent freezing.

 

Thank you 

Edited by nivedita12, 26 April 2019 - 04:19 PM.