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JOULE-THOMSON EFFECT 6

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hianbotech

Petroleum
Aug 23, 2004
45
We are designing a pipeline to send Extra heavy Oil diluted with a water composition of 0.135 % mol. We are making the hydraulics calculations in Pipephase. However we are getting from the program that the stream increases their temperature when the pressure drop. It is possible this effect on hydrocarbons???

See the study cases:

First Case
Operation Temperature (source) = 98° F
Ambient Temperature = 98° F
The pipeline has 300 meters; the initial pressure is 500 psig and arrives to the Plant at 50 psig. However the temperature is increased at 103 °F in the plant.

Second Case
Operation Temperature (source) = 66° F
Ambient Temperature = 66° F
The pipeline has 300 meters; the source pressure is 1281 psig and arrives to the Plant at 50 psig. However the temperature is increased at 77 °F in the plant.

We consult this issue with the provider of the simulation program, and they mentioned that this effect it is possible in some fluids. They gave me an internet address in order to see an possible explanation of this behavior:

Joule Thompson effect

I would like to know if this thermal effect is possible in hydrocarbons.
 
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hianbo (Petroleum)The admin response of that website stating that there is no temp change for perfect gas is only correct if there is no change in kinetic energy between inlet and outlet. Of course this assumes no heat transfer or change in elevation(delta z can be neglected for a typical nozzle).

For liquid flow, the change in kinetic energy can usually be neglected and therefore with no heat transfer the J-T effect is applicable. However, your case is with a mixture.
The program vendor should justify their formulation, etc. for the J-T effect with mixtures?
 
As the oil flows down the pipe, it loses momentum to friction. This results in a loss of kinetic energy, which is manifested in the form of heat in the fluid or pipe wall. The attached paper gives a more detailed account of Pipeline Thermal Models.

 
Dear Hianbo,
Basic point is the pressure energy which the liquid has at the inlet has come down and it has to appear in some other form of energy. Assuming the dia of pipe is same at inlet and outlet, it has to appear as expanded specific volume and increased temperature. As the volume change is negligible for liquids, it mostly appears as increase in temperature. Look at it this way: The frictional energy has eaten up the pressure drop and what happens to the frictional energy produced? It has to appear as heat(especially for liquids). Simple as that!!
 
Sailoday28:

For liquid flow, the change in kinetic energy can usually be neglected and therefore with no heat transfer the J-T effect is applicable.

I am confused. Are you saying that the Joule-Thomson effect applies to liquids?

Milt Beychok

Milton Beychok
(Contact me at www.air-dispersion.com)
.

 

J-T expansions applies to real fluids.
There are three cases where negative J-T coefficients may be encountered:

1. A high-temperature gas
2. A low-temperature liquid
3. A very high-pressure fluid (gas or liquid)

Table 3-150 on Perry VI brings the "reduced" conditions P/Pc, T/Tc, to give the approximate configuration of the J-T inversion curve.

When dealing with a mixture of hydrocarbons, pseudo-reduced conditions are generally used.

The table shows that fluids with Tr values less than about 0.7, or greater than approximately 5, as well as for Pr > 12, there is a good chance that fluids heat up on expansion ([&mu;]J-T<0).

 
mbeychok (Chemical)
Consider the enthalpy of a fluid in terms of temperature and pressure
h=h(T,P), the J-T,coef,(mu), may be obtained with partial differentiation keeping h as a constant.
mu= dt/dp at h=constant
Regards
 
I am checking all information that you guys gave me. Thanks a lot for your valuable answers. It has been very useful for me.

Regards
 
Isthe effect of heat exchange with the surroundings in the calculations disregarded in the calculations?

In practise i have never heard about the JT effect giving a significant contribution to liquids - however as reena1957 points out the frictional energy leads to heating of the liquid. This is most visible in valves. In pipeline heat exchange with the surroundings will make this "invisible".

On a related note: A pressuredrop of 450 psi (31 bar) or 1200 psi 83 in just 300 metres indicates to me that you have a very high velocity (even with high density/viscosity). Is this an emulsion?

Best regards

Morten
 

There is an article worth reading titled Working with fluids that warm upon expansion by John J. Carroll, under the general heading of Engineering Practice in the ChE issue of September 1999.
 
MortenA, I would like clarify that the 300 meters that I mentioned is the differential height between initial point and the final point. The fluid losses height in the hydraulics. Also the fluid velocity is inside of the recomended range.

It was a mistake in the original message.

25362 I am trying to found this article, thanks againt to all for your valuable contibutions.

Regards,
 
Ah - so the length of the line is not 300 m but muc longer and the 300 m is just additional hydrostatic head?

Best regards

Morten
 
My vote goes for the simple explanation offered by RGasEng and reena1957 above, and by lilliput1 in thread378-133017.

Using the numbers given by hianbo above in a simple energy balance (i.e. ignoring any J-T effect) and assuming an SG of 0.8 and a specific heat of 0.5 I get an expected temperature rise of 5.8 degrees F. I believe it is as simple as that.

katmar

 
Katmar: Does your calc. ignor heat exchanged with the surroundings?

Best regards

Morten
 
Morten,

Sorry, yes I should have stated that. I have assumed no heat in or out of the system at all. I have also assumed that all the power goes to heat and nothing is left over as kinetic energy (I imagine that would be relatively small).

I was surprised that I have not seen this effect before, until I realised that this particular example has an unusually large pressure drop and still has a relatively small temperature rise. I'm sure any temperature rise that I might potentially have seen before would have been negligible, or lost to the atmosphere.

katmar
 
MortenA and katmar:

I agree with both of you in that I believe the simple explanation given by RGasEng and reena1957 is much more credible than is any possible liquid J-T effect.

Milton Beychok
(Contact me at www.air-dispersion.com)
.

 
For information only
If the J-T coef is zero, or its effect negligible, then the fluid will follow for a constant process
specific volume/absolute Temp =constant.
 

One wonders why, in a very long crude oil pipeline crossing truely cryogenic surroundings, the oil arrives at terminus with almost no loss of temperature.
 
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