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# How to find density, enthalpy, thermal conductivity, specific heat and viscosity of separated phase

## How to find density, enthalpy, thermal conductivity, specific heat and viscosity of separated phase

(OP)
Hi,

I'm not familiar with chemical process engineering, I need advise and help on how do I determine the density, enthalpy, thermal conductivity, specific heat and viscosity of separated vapor and liquid phase.

I'm designing heat two-phase stream heat exchanger and I need to use mixture properties, instead I only got the separated phase properties. I know there must be some equation I could use to determine mixture properties from the separated phase properties.

Really looking forward and hope to learn more on chemical process engineering.

### RE: How to find density, enthalpy, thermal conductivity, specific heat and viscosity of separated phase

today is your lucky day . . .

see: https://webbook.nist.gov/chemistry/fluid/

### RE: How to find density, enthalpy, thermal conductivity, specific heat and viscosity of separated phase

What does the heat transfer correlation you are using say to use for the mixture properties? That is where I would look.

Good luck,
Latexman

To a ChE, the glass is always full - 1/2 air and 1/2 water.

### RE: How to find density, enthalpy, thermal conductivity, specific heat and viscosity of separated phase

(OP)
Hi Latexman,

Basically I have two separate properties for liquid and vapor. Each separate phase have it's own physical properties along with molecular weight. I wanted to know how do I determine a mixture properties from these separate properties.

For example, what I had in mind previously is use average between, say densities, where I find average of let say 146 kg/cu-m and 30 kg/cu-m to determine the mixture properties but I'm sure that is not the correct way, it had to something to do with molecular weight I might think.

The component is not general component so I cannot use nitrogen, carbon etc. to determine the properties.

### RE: How to find density, enthalpy, thermal conductivity, specific heat and viscosity of separated phase

Again, what does your heat transfer correlation say to do? The heat transfer correlation used some method of determining the mixture properties for it's development. Well, you must use the same method to determine mixture properties to utilize the heat transfer correlation correctly.

Good luck,
Latexman

To a ChE, the glass is always full - 1/2 air and 1/2 water.

### RE: How to find density, enthalpy, thermal conductivity, specific heat and viscosity of separated phase

If you are using design information from a client for this, I would go back to this client and ask them to supply the necessary information. Not including this info is a clear sign the client is sloppy and / or is ignorant of what info is required for thermal design. They should not penalise you for asking for this data - incomplete design info is not a valid reason for discrediting your company's capabilities. I would even go so far as asking for a schedule extension due to the delay incurred by this incomplete design package.

### RE: How to find density, enthalpy, thermal conductivity, specific heat and viscosity of separated phase

(OP)
georgeverghese,

That is what we usually did. We would go and ask client for complete vapor-liquid enthalpy so that we could determine the true LMTD for the heat exchanger.
Common response we get "don't you know how to determine the LMTD?". Following this, we would usually ignore these kind of client as we know they aren't an engineering company nor have a decent process engineering background.

I often told these client(s) that we need the vapor-liquid enthalpy and not separate the liquid and vapor enthalpy and expect us to combine those to find the vapor-liquid enthalpy as we may not know whether the vapor-liquid enthalpy we calculated is correct or not.

### RE: How to find density, enthalpy, thermal conductivity, specific heat and viscosity of separated phase

this discussion appears strange to me.
in more than 30 years of work as process engineer in the refining sector, for the major engineering and operating companies, I've been always forced to provide the so-called vaporization curves with separated liquid and vapor properties.
i know that the thermal engineers don't know a lot of mixing rules but the calculation routines they use (eg HTRI etc) work with the single phase input data.
no one told me to be sloppy, ignorant or, worst, refused the data...so i've the doubt that i didn't catch the exact meaning of this discussion.
moreover, in these days, the NIST site is unavailable, because of the us federal government shutdown

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