LNG liquid to gas phase change simulation Simscape

Good day everyone,

I want to simulate LNG to gas system (liquid phase to gas phase). Currently, I am using Thermal Liquid library (I am considering Two-phase library as well) to show liquid phase of LNG but I am not able to vaporise liquid into gas phase.

(LNG liquid phase part in simulation)

(In next step, I need to simulate LNG tank where high pressure LNG and partial natural gas stored in the same tank. I am thinking to use Tank (G-TL) block)

In liquid-to-gas part, I need to heat liquid LNG with a heat source (heating water) to increase temperature of LNG forcing to evaporate. After this step, LNG will be transformed into gas form. And I would like to clearly show in which phase LNG is (gas phase to be shown with gas library).

(Brief configuration of Liquid to Gas LNG transformation. TL(or 2P) library to Gas library)

Can you please guide me in liquid to gas phase LNG simulation?

Thanks in advance.

Answer 1

[Yifeng Tang]

Hi @Anil

I suggest that you try something like this:

Model the LNG and its evaporization in the 2P domain. The Receiver Accumulator block can be your LNG tank. You can heat it or use a 2P-TL heat exchanger to vaporize the LNG. The water should be in the TL domain.

Once the natural gas is in the gas phase, if you have an extensive gas network to model, you may choose to use an interface block to conserve the flow rate and temperature of the 2P flow in the gas flow. Make sure you attach an appropriate property block for both 2P and Gas domains.

This example on liquid hydrogen storage may provide some modeling ideas:

https://www.mathworks.com/help/hydro/ug/LiquidHydrogenStorageAndTransportationExample.html

[Anil]

Hi @Yifeng Tang,

Thanks for your answer. I will use your suggested domains for LNG-natural gas-water. I tried to utilize Interface (2P-G in this example), but I wasn't able to run the simulation. Since there is not built-in LNG parameters in a property block, I have to write all inputs. Which parts of 2P property and G property block should be aligning?

Thanks for sharing liquid hydrogen example. I am familiar with this example and it helped me a lot.

Thanks for your answer!

[Yifeng Tang]

Do you have access to REFPROP (needs a license) or Coolprop (free)? The twoPhaseFluidTables command can extract two-phase properties from these databases and populate the two-phase property fluid property table.

[Anil]

I can investigate about twoPhaseFluidTables to populate 2P property block. Can I use these results to populate Gas property block (same as vapor 2P property part)?

[Yifeng Tang]

After looking at the information needed for the Gas Property block, I would say it's possible to use the information from the 2P table in the vapor region to populate the gas properties, but it'll take some effort.

I would suggest you stay in 2P for now, and don't do the interface just yet. When you have to build a Gas network, the first step would be to use the "Perfect" option later, which requires much less information. You should be able to get pretty far without worrying about updating with detailed properties :D

[Anil]

I will only follow 2P library for now. I couldn't find LNG properties in CoolProp and create mixture of differents elements.

Thanks for your advices and time!

[Yifeng Tang]

will methane be sufficient? NG is 95% methane, right?

[Anil]

Apparently, I can create any mixture in CoolProp (super nice).For now I use 95% methane and 5% ethane. CoolProp works fine with this mixture!

I will work with different temperature and pressures for LNG.

[Anil]

@Yifeng Tang, I am trying to use twoPhaseFluidTables command. However, after determining Umin, Umax, Tmin, Tmax, Pmin, and Pmax, code is not giving error regarding critical pressure. After, Ilimited Tmax to 250K (and corresponding Pmax) in order to get table values but I had same error again.

I read different answers ( #2026939 Add fluids to Simscape model using twoPhaseFluidTables() ) and increased Pmin with coef. of 1.001.

For fluid I tried 3 options:

Methane or 95%Methane-5%Ethane or more complex LNG composition.

Can you please guide me finding twoPhaseFluidTables values?

[Yifeng Tang]

Hi @Anil, I'm less familiar with Coolprop. In REFPROP, what I would try is to plot a p-u diagram in REFPROP, and see what range I can get for p & u. I'll then use that range for the twoPhaseFluidTables command. The error is usually with the validity range of the functional form used in REFPROP or Coolprop to fit the properties. Not much I could do from the MATLAB side other than try to find a more limited range of p & u.