Auto refrigeration of Ethylene 3

[Pluto110]

Dear All,

I've got Ethylene gas at 15 deg C and 12 Kg/cm2(g) pressure and I'm letting it down to 1.5 Kg/cm2 (g). I'm trying to calculate the auto refrigeration of Ethylene at 1.5 kg/cm2 which I got from Hysys as -76 deg C. I think this temperatue is quite low. I've checked the P-H diagram and it indicates a much higher temperature.

Can you please give me a idea whether this number seems completely wrong or somewhere close. Also I need to calculate the temperature which I need to heat ethylene to stay in the superheated vapour zone.

Thx in advance for your help..

Timewrap

 

[PaoloPemi]

Hi Pluto,
possibly you are doing something wrong with your simulator, I have not access to this tool so I can't comment, however my little Properties (see

http://www.prode.com

) with SRK returns for Joule Thomson about 1.17 C/Kg/cm2 at input conditions (12 Kg/cmq , 15 C), for a dp of 10.5 Kg/cm2 I would expect about 13 C temperature drop, accordingly the H-P flash returns about 2.6 C , similar data from REFPROP (outlet temperature about 2.3 C), I hope this helps to identify the problem.

 

[25362]

An isenthalpic expansion from 15^o and 13 bar abs. to 2.5 bar abs results in about 2.5^oC.

I suggest to use:

http://webbook.nist.gov/cgi/cbook.cgi?Name=ethylene&Units=SI

 

[Pluto110]

Dear PaoloPemi and 25362,

Thanks a lot for you time and for your responces..

Paolopemi - Can you please spare a moment to show that how you have used your table from

http://www.probe.com

to arrive at 2.3 deg C. Appreciate your help.

Pluto..

 

[PaoloPemi]

at 12 Kg/cmq , 15 C ethylene is in vapor phase, you can start with Joule Thomson (dt/dp) to get an idea of final temperature, with SRK model Properties returns a value of 1.17 C/Kg/cmq so we expect about 2.0 C at 1.5 Kg/cmq and the HP flash operation returns a value of 2.6 C , a similar result should be calculated by your simulator.
Properties (as REFPROP and other tools) can expose the methods directly in Excel so it's really a matter of few seconds to get these results, there is a free version which you can download from their site, however note that company is

http://www.prode.com

not probe,
hoping this helps.