Flownex Modeling for Combined Cycle Power Plant

[This was auto-generated. There may be mispellings.]

Flownex Modeling for Combined Cycle Power Plant-1 Hello everyone, this is Mohsen Seraj from the Ozen Engineering team. Today I want to talk about modeling a power plant, a full cycle of a power plant using the Flownex software.

Basically, Flownex is like a 1D program that helps us to determine the pressure drop of the flow and perform heat transfer analysis to find the temperature within and between the connected components such as pumps, compressors, turbines, tanks, pipes, valves, or heat exchangers that we are using in power generation systems, and we can do steady-state analysis and transient analysis.

This is a schematic of a power plant with a combined cycle. By combined cycle, I mean that we have a gas turbine for power generation and we have another turbine, which is a steam turbine. The system uses the heat from the exhaust hot gases from the gas turbine and uses it for producing steam.

Here, as you can see, we have the system for steam generation, which is a boiler, basically, and also water from the condenser that feeds the boiler system.

So, the generator in this power plant basically receives two powers, one output power from the gas turbine and another power from the steam turbine, so that's why we expect to see more efficiency and more output power, total power from this cycle for the power plant.

In Flownex, basically, we have two thermodynamic cycles, one is for the gas turbine that models with the Brayton cycle, and another one for the steam turbine that is basically based on the Rankine system, and boiler steam generation, and the cooling water circuit that we have.

Flownex has a separate tutorial on that.

The good thing is that for the design and analysis, we can run steady-state and transient analysis, and we can have a calculator to find the amounts for the efficiency cycle efficiency and total output power, and in this way, we can run the model for, for example, different inputs that we can have, say, for example, changing the fuel gas that we have, changing also the atmospheric condition that we have, it depends if it is a rainy day or a non-rainy day.

Thank you for watching this video. Here we have a pump, for example, here for the feed water pump, it could be variable speed, we can have other types of pumps in Flownex.

We have a heat transfer element, okay, that here we use it when we want to use the heat from the hot exhaust gas from the gas turbine.

And then a variety of pipes and also some elements that we have to model the resistance to the flow within the pipeline, and if there is any loss that we can model that. These are the main components that you're going to see in the Flownex model. Let's now look at the model inside the software.

This is the Flownex model for the combined cycle of the power plant. This part is for the gas turbine. You can see that basically we have air intake, we have a compressor, turbine, and here this is the heat transfer element, it is a flame.

And we have here for increasing the pressure and gas, here pressure and here is the temperature. So this is the air intake coming to the compressor and then after that going toward this flame section for the combustion going back to the turbine.

The turbine and the compressor are connected with the shaft, and after that, we have the hot exhaust gas that will be sent to or you can also call it a boiler or we call it here heat recovery for steam generation, okay, this is what you are going to see here, okay, hot gas, okay, this is the line for that, and it will exit and vent it out to the atmosphere.

Before that, we have the steam turbine. As you can see here, this is the steam turbine that it has this line for the steam that is generated within this system, that basically for the steam cycle. We have one two-phase tank, which is for the boiler, for producing the steam.

So, and the way is that it receives water from this pump, okay, that coming through these lines. Thank you for watching this video. If you check the material, you can see that here we have two-phase fluid, general, and it is water.

If I want to see what is that, for two-phase flow, we can have the diagram for entropy in terms of the pressure, temperature, and other things like enthalpy.

Okay, for example, if we go for pressure versus enthalpy, you can see that where we have the different regimes for the two-phase flow, where we have the sub-cooled regime, and where we have the superheat region, and here we have the, as you can see, we have the two-phase flow.

If we go for temperature versus enthalpy, again you can see that here we are in the region for the two-phase flow, this is for the sub-cooled region, and this is for the superheat. And so on for enthalpy or whatever.

So, we have two-phase flow for these pipes, okay, as you can see, and these are connected to this drum. This is the drum that basically it is like we call it a two-phase tank.

And the same material, it is a two-phase hot water, and if you look at the temperature of the hot exhaust gas from the gas turbine, okay, you can see that it is the gas turbine that we have it, and if you look at the pipeline, you can see that here this is the next one is mixed fluid, because it is a product of the combustion from air, mixing of the air and the fuel.

The fuel here is natural gas. Let's see what is the combination of that. So in Flownex, we have a variety of models for mixture. It could be gas mix, it could be liquid mix, and then a combination of the liquid and gas or particle and liquid. That we have it.

So here, as you can see, we have a mixture of argon, methane, carbon dioxide, water, nitrogen, and oxygen. So we have one pipeline that after the gas turbine is the product of the operating fluid after, from the outlet of the turbine.

You can see that the temperature is almost 860 degrees Celsius, for example. And as we give heat to the steam, to this pipe network from the boiler, gradually its temperature reduces from 860 to 734 to 600 degrees Celsius. And for the exit line, for the exhaust line to ambient, it is 400 degrees.

You can see that here. So, back to the gas turbine cycle, okay, this is what we have from the fuel. And for the rest of the cycle for the steam generation, this part is for the condensation that provides cold water for producing the steam in the boiler.

So here you can see that, okay, if we come here, okay, we have the steam after being used in the turbine for producing the power, it just goes to another tank that it is now, it is for the condenser tank.

And for the compressor and turbine, okay, and also pumps, okay, this is the component for the compressor, we have turbines, and also we have this component, variable speed component for the pumps.

We have a variety of piping, pipelines here, it is a simple pipe that we see it here, and we can model the resistance and loss in the pipeline, by here that we have it, the custom losses, okay, this is the flow resistance that is being used here.

Here in the pipeline for the hot exhaust gas, this is the flow resistance that we modeled that.

And another loss that we can have here, and another one, it is to calculate if you want to apply the restriction, okay, it is like changing the diameter or basically if we want to close or open suddenly a pipe.

Also, we have a generator that has a calculator for finding how much is the efficiency and the total power that it receives from the gas turbine and the steam turbine.

This is the script, a simple script, if you double click that, you can see that these are the formulas that are used for the calculation of the efficiency and total power, and here also, if you click here, you can find the list of the inputs, parameters, and outputs.

So I already initialized this model. This model is provided by the Flownex team. So I'm at first running this for a steady condition.

You can see that now we have a calculation for the overall efficiency and for the total power, and we have information also that what is the output power from the gas turbine and how much is from the steam turbine.

And also some calculation, okay, for example, for the air intake, as you can see that how much it is, and also this magnitude is constant that it is governed by this bond condition here for now.

And also the range of the temperature changing of the hot exhaust gas that's being used for steam production, and the temperature for the exhaust here. So this is what we have so far from the steady-state condition.

If I click on the boiler, boiler drum, and look at the results, if you check here, the heat source, you see that we have negative values. It means that although we are using the heat from the hot gas pipeline, but we need to optimize it.

I'm going to use the designer here with the goal to reduce this energy source to zero. In this way, we have much efficiency regarding the heat transfer in the boiler system.

The designer that it is here, if you go to the configuration and check the designer setup, basically, if you have here, this is for the boiler drum, and I want to make this one and set the value to zero. So this is the target for us.

We put this constraint here, and if you look at here, okay, this is the boundary condition, and the pressure for this boundary condition that, or you can use the same method to apply to the boiler drum. It can be changed in the range of 2500 up to 2800 kPa.

So if I run this designer and see what's happening, can we optimize the boiler system that we see zero energy sources? So it goes to the iterations to find the best solution for that by changing the boundary condition here. The pressure boundary condition here.

Okay, you can see that it is almost zero, and if you check the console, okay, you see here, you can see that we already found the converged solution, which is good, okay. So this is what we have so far. Now let's run the transient simulation.

For the transient simulation, we just consider these are the graphs that already created for the output power of the steam turbine and the output power of the gas turbine. You can see that, and you can see maybe changes here during the transient simulation that we have.

Check these values for the output power, and for the gas turbine, and for the steam turbine. You can see that it is changing, and the total output power, so 17.1, okay, and let's see the graphs now, we have six seconds, seven seconds, 17.2 megawatts.

As you see, the output power for the gas turbine is almost constant, but the steam turbine is increasing. You can see that here. If you remember that after running in a steady condition, it was 16. 8. Okay, it starts from a value here, almost 16.849 MW.

And now, so far, after about 10 minutes, it increases to 17.3, and it is still increasing. We can maybe see also changes here to the temperature of the exit gas.

I didn't see much because the output power is constant, but maybe changes to the steam cycle that we have it here, see now, okay, we are at about 18 seconds, the total time is about 20 seconds. So this is one of the loading scenarios for the plant. So, we are almost done, we are done.

Ok, 20 seconds. The power it is about 17.5.6, ok, you can see that here, for the output power, and for the steam, this is for steam. The total power received to the generator from these two is 63.4, and the efficiency is 28.8%.

So, in this video, I just showed you how to use this power plant model available from Flownex, the power plant, it is a combined cycle, it means that we have a gas turbine, and we have a steam turbine, and we have a heat recovery system using in the boiler to make steam from the water, and send out steam to the gas turbine.

So we have combined outputs from the steam turbine and gas turbine, and this is where we can see the total output power and efficiency. Many components are used here, as you can see, and the way that you use it, you need to first initialize it with the snap that it is available.

And then you will go for a steady-state solution. Be sure that after running the steady-state solution, that you have zero energy source, because we don't want to have this non-zero energy source for optimizing the boiler system. And in this way, I just use a designer that it is implemented.

I just come here, go to the designer setup. The aim is to get zero energy source for that by changing the design. And this is by changing the pressures here for the pressure of the boiler drum. And after that, we are ready to move on for transient analysis here.

Transient analysis that we done it here, and we see that in these two gears, the output power for the steam generation, and for the gas generation.

Here we have some numbers that show you what's going on, like here, for example, for the gas turbine, for the output power, and steam turbine, same, and also the temperatures during the gas exhaust, hot gas exhaust that went out to the ambient, and also at the same time heating the water cycle here, and converted that to the steam that needs to be set.

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