9 replies to this topic

[Miccon]

Hi, i would like to ask if i set a value into the inlet in standard liquid volumetric flow, why after the compressor the flow still same, even the pressure ratio between inlet and discharge is high?? my inlet vapour ratio is 1. How to make the value more relevent to reality??

[wojtar]

Hi, i would like to ask if i set a value into the inlet in standard liquid volumetric flow, why after the compressor the flow still same, even the pressure ratio between inlet and discharge is high?? my inlet vapour ratio is 1. How to make the value more relevent to reality??

I'm not sure if I fully understand your question. If your stream is vapour why do you use liquid volumetric flow? On the other hand if you set the flow as standard vapour volumetric flow it should be the same because it refers to standard conditions.

[Miccon]

hi...for example, my inlet compositions are o2, n2 and argon with pressure 0.05 barg compressed to 5.5 barg with the 21000 Nm3/hr (normal m3/hr as inlet flow). the inlet vapor fraction is 1. however, why the discharge flow still in 21000 Nm3/hr. How to do it by using Hysys??

[shan]

hi...for example, my inlet compositions are o2, n2 and argon with pressure 0.05 barg compressed to 5.5 barg with the 21000 Nm3/hr (normal m3/hr as inlet flow). the inlet vapor fraction is 1. however, why the discharge flow still in 21000 Nm3/hr. How to do it by using Hysys??

You misunderstood the concepts of standard volume flow and actual volume flow. The stream actual volume flow will change with your process conditions (temperature and pressure), while standard volume flow is the stream volume flow at 0 barg and 20 C. No matter how high pressure you compressed it, the example gas volume flow is 21,000 Nm3/hr when you bring it under the standard conditions.

[wojtar]

Exactly...standard volume flow won't change whatever you do in that HYSYS. I guess you want to know actual volume flowrate. It should be somewhere in stream properties. There must be something like "stream properties" section where you can see all properties like density, viscosity etc. etc. together with actual volume flow. Unfortunatelly I'm working with CHEMCAD so I can't answer you directly.

[Miccon]

hi,,,one more question..if i know my inlet flow rate is normal flow rate in vapor fraction 1. do i need to convert to kgmole/hr?? if no need, where should i key in my inlet value?? thanks for help..

[David Southall]

Hi, i would like to ask if i set a value into the inlet in standard liquid volumetric flow, why after the compressor the flow still same, even the pressure ratio between inlet and discharge is high?? my inlet vapour ratio is 1. How to make the value more relevent to reality??

Dear Miccon,

Standard volumetric flows are usually evaluated against a set of reference conditions, and so are not the actual volumetric flow that I think you are looking for.

If all else fails you could consider adding a spreadsheet object from the object palette. You could then use "add import" to import the stream density, enter the desired volumetric flowrate in your spreadsheet, calculate the mass flowrate from the density and volumetric flow, then use "add export" to export the mass flowrate back to the compressor. You have to do it in this order; the calculation has to be established before exporting the variable.

This should allow you to work with volumetric flows within the spreadsheet object. There might be a more elegant way of doing it, but I find this approach works. If you want to work in terms of some different reference conditions, you could again handle this with a spreadsheet object and with a "dummy" stream somewhere in your model with the appropriate reference conditions entered manually and the composition defined from the process stream of interest.

Hope this helps,

David.

[demank]

hi,,,one more question..if i know my inlet flow rate is normal flow rate in vapor fraction 1. do i need to convert to kgmole/hr?? if no need, where should i key in my inlet value?? thanks for help..

For your question above, of course no need to convert, you just input the value of kgmole/hr in the same place where you input normal flow rate.

How long you have use HYSYS? I think you are newbie for this HYSYS.
Then my suggestion is you shall practicized yourself using it with a lot of example project.

[Claudia K.]

Dear Miccon,
Liquids are not compressible.
Claudia K.

Hi, i would like to ask if i set a value into the inlet in standard liquid volumetric flow, why after the compressor the flow still same, even the pressure ratio between inlet and discharge is high?? my inlet vapour ratio is 1. How to make the value more relevent to reality??

I'm not sure if I fully understand your question. If your stream is vapour why do you use liquid volumetric flow? On the other hand if you set the flow as standard vapour volumetric flow it should be the same because it refers to standard conditions.

[Padmakar Katre]

Hello All,
Why everyone is discussing about the volumetric flow when it is clear that the Nm3 is at NTP and its a function of gas molecular weight and it doesn't have any effect of pressure and temperature. To see the actual volumetric flow rate see the properties tab and see the Act Volumetric flowrate as well you can have the Sm3/hr i.e. at STP.