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Not only colorful pictures – CFD saves time and money

Author Sanna Sierilä
Posted on

Did you know that by using computational fluid dynamics (CFD) you can save as much as 80 % in design time and 60 % in design costs? During the past 20 years, I’ve been lucky enough to participate in many interesting simulation projects both in Finland and abroad and have seen how clients have received instant help. But what is CFD really? Where can it be applied and why should it be utilized?

Let’s start with an example from real life where we assume that the salaries of a lab engineer and a simulation engineer are the same. It is also assumed that the initial costs for lab equipment and simulation software are equivalent.

In this specific project, altogether 48 different simulations were performed for a device, which was still under development. In calendar time, these simulations took about one year, along with some other projects. If the same concepts had been studied in a laboratory, it would have taken 240 weeks, which is almost five years! This is the result, if we are fairly optimistic and assume that the manufacturing of a new prototype takes four weeks and measurements only one week.

In real life, this was not possible since 11 of the simulated cases couldn’t be measured at all due to the complex set-up requirements. The rest of the concepts would have required 38 different prototypes. If one costs 1000 euros, the total cost would have been 38 000 euros for prototypes only.

If the cost of the annual technical support and license fee for all simulations during that year is considered, the cost of simulations would only be 40 % of that of prototypes. Isn’t having simulations done like laughing all the way to the bank?

To summarize: based on the simulations, a single prototype was needed to verify the measurements. This took only 20 % of the time that testing would have taken and cost only 40 % of what testing would have.

What is CFD?

Computational fluid dynamics (CFD) is a branch of fluid mechanics: a science that uses numerical methods to predict fluid flows and heat and mass transfers. A complex set of equations describing the conservation of momentum, mass and energy are solved iteratively using supercomputers.

Because of the abbreviation “CFD”, it is often referred to as “colorful fluid dynamics”, due to the common way to present quantitative results as colorful pictures. It may not require much to produce colorful pictures, but to really get something out of a simulation a skilled simulation engineer, state-of-the-art software, and powerful computational resources are needed. I won’t dig into the theory but discuss instead why and when CFD should be used.

Why should CFD be used?

In a traditional product development project, each idea is first designed and then tested by ordering a prototype. It is measured in the lab using a specific test set-up, after which the results are analyzed and fed back to design for the required modifications. This cycle is then repeated until the desired design is reached. The procedure is very time consuming and expensive as multiple prototypes are required.

When computational fluid dynamics is integrated as a part of product development, many benefits are achieved.

In traditional product development, each idea is first designed and then tested by building a prototype. When design engineer and simulation engineer work together, analysis can be performed to a product that doesn’t exist yet. This brings significant savings in costs and reduces time-to-market.

 

When a design engineer and simulation engineer work together right from the beginning, analysis can be performed for a product or process that doesn’t exist yet.
The analysis helps one to understand phenomena, which might be impossible to measure. Like in the real-life example, usually at least one prototype is manufactured for verification of the simulation results, but even this is not always possible. The final product might be a 40-meter-high industrial boiler or deposition facility for nuclear waste, which is currently under construction. Then simulations play even a bigger role. If simulations were not used, most likely only a few of prototypes would be built in order to save money. With the help of CFD, even wild ideas can be tested by thinking outside the box. One of these crazy ideas might be just the one that ends up in the final design.

As a result, the final product is finished faster i.e. time-to-market is shorter. We also achieve significant savings, since there is no need to build an extensive number of prototypes and test them. Everyone’s knowledge on the product increases simulation by simulation, and this knowledge can then be used further in similar projects or, for example, in customer care when the product is already on the market. But what is most important: by using simulations we can ensure that the final product is functional, safe and ecological.

When should CFD be used?

CFD analysis can be applied almost everywhere! We can study internal flows, for example, the flow in a duct. We can study external flows, for example, the flow over a car to create as aerodynamic a design as possible. We can study environmental flows, for example, air flows in a city center to determine how wind affects pedestrian comfort.

In CFD, size doesn’t matter. Many applications, which in real life are very different in size, might in fact be very similar on the computer screen. The physics of ventilation is very similar compared to the physics of desktop cooling, just to mention one.

Simulations should be applied as early as possible. Usually, decisions made early in the design process define the biggest part of the total cost of the project. The biggest advantage is reached when, based on the simulation results, changes really can be made. If the majority of the design parameters are already locked, the most optimal solution might be out of the question. It’s important to remember that for simulation purposes, the device does not need to be final.

Numerous applications

There are numerous applications where computational fluid dynamics brings benefits:

  • Concept design: when the basic idea for a new project is selected
  • Evaluation of a business idea: are there any risks or risks worth taking?
  • Product development: e.g. design of a new battery-driven drill
  • Optimization: improving an existing application or e.g. pursuing maximum heat transfer ability for a heatsink with minimum weight
  • Ergonomics: e.g. ensuring sufficiently low temperature on the handle of a battery-driven drill
  • Comfort: e.g. ensuring there is no windchill effect next to an air conditioning unit
  • Emission control: source can be e.g. a car or a factory, target can be e.g. as low Nitrogen Oxide (NOx) emissions as possible
  • Risk analysis: how hazardous substances, fires or pressure waves from explosions advance in an urban environment
  • Energy efficiency: e.g. reducing hydrodynamic resistance of a ship in order to reduce fuel consumption
  • Troubleshooting: when product or process does not work as expected
  • Digital twin: model for searching the limits of a running device and maintaining it
  • Customer care: when the product or process is thoroughly known, the customer can be served and helped better

Finally

You might already have a question you want to have answered, or goal you want to accomplish. Most likely, you have most of what is required to perform a simulation, such as a 3D CAD model, a description of the product or process, and the circumstances where it is used. With the help of computational fluid dynamics, it is then easy to ensure that your end product or process is functional, safe and environmentally friendly.

Sanna Sierilä

Sanna Sierilä, Simulation Specialist (Fluid Dynamics), M.Sc.
Sanna Sierilä has 20 years’ experience in computational fluid dynamics and has worked as a consultant both at the office and on site in Finland and abroad. She holds a degree in energy and process engineering, and her main interests are electronics, cooling, and HVAC simulations.
Ms. Sierilä enjoys teamwork with different specialists and wants to follow how simulation results really benefit the client. Besides performing actual simulations, she enjoys spreading the joy of simulations by participating in marketing and sales.

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Cleaner marine fossil fuels – Do they exist?

Author Tobias Eriksson
Posted on

The ongoing pandemic has taken a significant toll on people across the world beyond anyone’s imagination. However, if there is something positive to take from this terrible crisis, it could be the welcome change of cleaner air and a clear blue sky in some of the most polluted megacities around the world. It is a first taste of what it could be like in a low-carbon future. As the world slowly begins to return back to normal business, however, the risk is that the largest ever global air pollution “experiment” we are conducting may become nothing but a memory. How can we, the maritime industry, contribute to ensuring that the skies will remain blue even after the pandemic has passed?

Today’s bunker fuels predominantly consist of various residual fuels and to some extent distillates. Fossil fuels that are literally the bottom layer of the oil distillate barrel, which when combusted releases large amounts of harmful emissions. Obviously, with various – and, nowadays, mandatory – exhaust gas treatment systems, the majority of the harmful emissions can be mitigated. However, exhaust gas treatment systems add a significant amount of weight to the ship, and more auxiliaries onboard also increases complexity, which consequently increases fuel consumption. It is time for the shipping industry to begin cleaning up its dirty fuels.

When speaking about emissions, it is worthwhile to separate them into two categories. To keep it simple, let’s call them local emissions and climate/global emissions.

Local emissions are pollutants that contribute to the deterioration of human health and loss of well-being. Locally, they also have a direct impact on the natural flora and fauna. Local emissions emerging from the ship smokestacks are mainly nitrogen oxides (NOx), sulfur oxides (SOx) and fine particulate matter (PM). Today, only SOX and NOx emissions are regulated.

Climate emissions or global emissions directly contribute to global warming, but they have no – or only very low – direct impact on human health and the natural environment in the short term. Where these emissions are emitted is not relevant either since climate change is a global problem. The emissions from shipping which primarily contribute to global warming are CO2 and CH4.

In the fossil fuel portfolio, there usually is a conflicting interest between the two categories. Generally, the lower amount of local emissions emitted during combustion, the more GHG-intense the fuel is, and vice versa. Renewable fuels could solve the global emissions problem, but they are not yet available on the commercial fuel market. As a short-term strategy, shipping may, therefore, need to introduce other alternatives such as “cleaner” fossil fuels, which could later offer an easier transition to renewables, once the production of such fuels takes off. While alternative fossil fuels do not solve the issue with global emissions, they can significantly reduce the harmful local emissions. Consequently, to meet the emission requirements, the exhaust gas treatment systems may be reduced or in the best case not needed at all, which in turn will lead to a more efficient ship, making it a win-fail-win situation, so to speak.

 

 

The maritime industry consumes approximately 320 million tons of fuel annually, of which around 70% are residuals (HFO), 28% distillates (diesel or MGO) and the remaining 2% are other fuels (mainly LNG). Due to the new IMO 2020 regulations, a reshaping of the bunker fuel market is to be expected, particularly with an increased demand of distillates and very low sulphur fuel oil (VLSFO) – at least initially. Although alternative fuels are being introduced to the marine bunkering market, they will continue to only comprise a small share of the total fuel demand due to limited infrastructure support. While their total share of the fuel market will remain small, they can still be worthy alternatives to consider for meeting the ever-increasing emission regulations. Some of the most prominent fossil fuels to replace the dirty bunker fuels are LNG, LPG and methanol.

LNG is leading the race when it comes to alternative marine fuels. Currently, there are 165 LNG-powered ships in operation, and an additional 154 confirmed orders for vessels that will be built in the next five years. The annual LNG consumption in shipping is approximately 6.5 million tons, or about 2% of the total marine fuel consumption. While the uptake of LNG in newbuilds is growing, the economics of LNG retrofits have remained challenging. However, due to the extensive experience in LNG newbuilding projects and technology improvements, it is no longer a question of if but rather when LNG will also become a feasible retrofit solution.

LPG, short for liquified petroleum gas, is any mixture of propane and butane in liquid form. Due to the relatively high boiling points of gas, LPG can be kept as liquid at elevated pressure and ambient temperatures and, therefore, it is easier to store than other gaseous fuels such as LNG. LPG is primarily derived from two sources: as a co-product recovered during the extraction of natural gas or as a by-product from oil refining. Global LPG production is around 310 million tons, but is expected to increase, especially in North America, which is attributed to the substantial increase in shale gas production. Currently, around 60% of the world’s LPG originates from the extraction process of natural gas, and the remaining 40% from oil refining. As a marine fuel, however, LPG is still in its infancy, but with the ever-tightening emission regulations being implemented across the shipping sector, LPG is becoming an ever more prominent solution. To date, there are no ships operating on LPG, but there are five LPG-fuelled ships on order with the first set for delivery in 2020. For retrofits, the interest of LPG as fuel is also emerging, with four conversions expected in 2020. All the planned newbuilds and conversions are mainly gas carriers.

Methanol is often considered as the dark horse in the alternative fuel race. Methanol is a worldwide produced chemical with annual production around 100 million tonnes The main feedstock, which is also methanol’s major downside today, is that it is predominantly produced from fossil fuels, mostly from natural gas, but coal and residual fractions from refineries are also common production sources. Since methanol is a fuel that is manufactured, its well-to-wake CO2 emissions are naturally higher than that of the extracted fuels LNG and LPG. However, as methanol is a liquid at ambient conditions, it is easier to store than the other alternative fossil fuels LNG and LPG. Consequently, the investment costs into infrastructure and storage tanks should be lower. Methanol is, therefore, considered as one of the most promising fuels for retrofits. Methanol as fuel in the maritime industry is also to some degree known, and both operational experience and test results have shown that methanol could comply with even the most stringent emission reduction legislation. Still, the uptake of methanol as fuel in shipping has been low. Currently, there are only 12 methanol-fuelled ships in operation or on order.

It is tough to make predictions, especially about the future. There are no obvious show-stoppers for any of the alternative fossil fuels, but the ultimate decision will be based on economics and availability. The dilemma shipowners are facing with alternative fuel choices can be summarised with the following aphorism: available, cheap and clean – pick two.

 

There is no magic bullet to reduce harmful emissions from shipping; all the solutions will be needed. While alternative fossil fuels’ share in the bunker fuel mix will remain small in the coming years, they will be one of the many important tools to reduce harmful emissions from shipping. With its renowned competence in the marine sector, Elomatic can offer comprehensive and tailor-made services on how to introduce alternative fuels:

  • Retrofit feasibility – from concept to reality
  • Technology readiness for alternative fuels
  • Transparent fuel lifecycle emissions, conversion and operational cost estimations

Let’s explore the possibilities together for a cleaner marine industry!

Tobias Eriksson

Project Engineer

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