9 replies to this topic

[jibinjosemathew]

Dear All,

 

In the design of a Reactor feed/effluent exchanger, the client have mentioned that the given  shell side and tube side fluid mass flowarate is including "free water".

 

What is meant by 'free water' ?

 

And also in the property chart of shell side fluid (condensing - inlet vp. frct. -0.101& outlet -0.051) the cleint has  also given the weight fraction and properties of water.

 

 

But normally in HTRI we give fluid properties at different temperature points at the operating pressure.I dont know where to give the properties of water.

 

How to give the properties of shell side fluid in htri ?

 

Please find the attached property chart given.

 

 

Thanks & Regards,

 

Jibin Jose

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Edited by jibinjosemathew, 26 November 2015 - 12:13 AM.

[shantanuk100]

Hello Jibin

 

Free water is the uncombined water in the fluid being taken. It is simply the amount of free water you have.

In a 3 phase fluid you can have a fluid, a vapour phase and also the possibilty of a third phase like water or oil etc.

 

For inputting any properties of the fluid you can go to the respective section shown.

Click cold fluid/hot fluid properties on the left and go to grid properties.

Please see the attached image.

 

Regards,

Shantanu.

 

 

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[jibinjosemathew]

Dear Shantanu.

 

Thank you for looking to my problem.

 

I have given the properties of the shell side fluid in the property grid. The property given included the vapour properties, liquid properties and then seperatly the 3rd phase, water properties. I dont know where I have to give the water properties in the property grid ?

 

Or Is the vapor and liquid properties given considering the all 3phases ?

 

plz chck the attached property table given and the input HTRI grid points.

 

Regards

 

Jibin

 

 

 

 

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[shantanuk100]

Jibin,

 

1. You can enter the individual mole fractions or weight fractions for the Shell side fluid if you know the balance of both the liquid components, by adding both components - ie. the fluid and water as well in the components tab just below grid properties tab. If you enter the values, you can see the respective specific properties of the overall shell side fluid. The overall fluid properties will then be inclusive of the water fraction as well, but you will be able to see only the combined fluid properties.

 

2. Otherwise you can separately use the standard mixing rules for mixing of the individual properties in proportion of their respective mole fractions / wt fractions depending on whether the specific property is based on moles or weight (Eg. enthalpy per mole or enthalpy per kg). and then enter the calculated combined fluid properties by yourself in htri.

But then you will have to separately account for evaporation of the fluid and evaporation of water and their individual vapour properties which will be a tedious task.

 

3. I would suggest another option is to consider using a process simulator like hysys where you can enter respective fluids, conditions and then calculate the properties from that for the mixed fluid. Then you can enter the mixed fluid properties in place of the shell side fluid.

 

4. Your water quantity is relatively very low in percentage terms.

If your flow is relatively low you can neglect it.

 

Regards,

Shantanu

Edited by shantanuk100, 03 December 2015 - 08:18 PM.

[jibinjosemathew]

Thank you Shantanu,

 

I will go for the 3rd suggestion. I think property calculating by process simulator will be easy for for my condition.

 

I have onemore doubt Mr.Shantanu. While doing the condenser design I always gets amessage that "A Negative value for latent heat is calculated for hot fluid". Why this message is coming and how to eliminate it.

 

Regards,

 

Jibin

[shantanuk100]

Yes. That's the better option if you want exact values.
What's your overdesign %, and B flow fraction ?

As for the error, I'm not sure but it could be due to various parameters.

So could you upload your htri file so that I can take a look at it ?

 

Regards,

Shantanu

Edited by shantanuk100, 27 November 2015 - 01:25 AM.

[jibinjosemathew]

I got it.It was due to the wrong heat duty.

 

Thank you Shantanu

 

Regards

Jibin

[Padmakar Katre]

Hi,

In HTRI user specified grid only vapor and liquid properties can be given.Although the stream is 3 phase you have generate mix liquid properties for HC liquid and water. The component option you can't use unless you have component mass balance.

[shantanuk100]

Hi Padmakar,

What you say is right but Jibin has already mentioned that he knows the component balance.
As for your comment about generating mixed fluid properties, what you say is correct and I had already mentioned it as well.
Pls refer point 3 of my earlier answer for it.

 

Regards,

Shantanu

[Padmakar Katre]

Hi Padmakar,

What you say is right but Jibin has already mentioned that he knows the component balance.
As for your comment about generating mixed fluid properties, what you say is correct and I had already mentioned it as well.
Pls refer point 3 of my earlier answer for it.

 

Regards,

Shantanu

 

Good so all have same points/suggestions...