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Auto refrigeration of Ethylene
3

Auto refrigeration of Ethylene

Auto refrigeration of Ethylene

(OP)
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  

RE: Auto refrigeration of Ethylene

2
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 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.

RE: Auto refrigeration of Ethylene

(OP)
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 www.probe.com to arrive at 2.3 deg C. Appreciate your help.

Pluto..

 

RE: Auto refrigeration of Ethylene

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 www.prode.com not probe,
hoping this helps.

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