Air Conditioning Design Validation with CFD
As an HVAC engineer, you routinely go through the process of analyzing the designs being forwarded to you from the design department. Imagine having a Eureka moment! You think of a novel air conditioning design which would significantly enhance the overall performance with just a minor design change. Here comes the real challenge — how would you convince your manager of the validity of this design? Why would it be better than the current one?
This is where the power of Computational Fluid Dynamics can be exploited.
On 22nd of August, we’ll take a look at how web-based CFD simulation helps engineers design more efficient air conditioning systems in a 30-minute demo!
We’ll propose a new air conditioning design for server rack cooling and help you understand why the new design is better than conventional air conditioning systems, thereby displaying the validity of the new design. Join us!
Why You Should Care About Flow Simulation
The cost and performance of any physical product, including HVAC systems, are determined quite early in the design process when you begin to define your product concept. This is when the most impactful design decisions are made, and changes can be implemented at relatively low costs. It is, after all, much cheaper to have a design engineer sit in front of the computer than to perform field testing and building physical prototypes. And this impacts not only the design process but also the performance of the final product, meaning lower production costs, more efficient energy consumption, lower failure risk, and more.
Despite their benefits, until recently CFD simulation tools have been inaccessible for many air conditioning system designers due to the high software and hardware costs, as well as the complexity of the multiphysics involved. This status quo has been challenged with the emergence of cloud-based CFD tools, which are rapidly turning CFD into an industry standard for Heating, Ventilation and Air Conditioning (HVAC) by making it:
- Accessible: Traditional software needs to be installed locally and requires a significant amount of computing power and expensive hardware. With SimScale all simulations are run in the cloud, in a standard web browser.
- Cost-Efficient: Commercial simulation tools are known for their high licensing costs — SimScale starts with a free Comunity plan for evaluation and public use, with an option to upgrade to an individually packaged Professional subscription.
- Easy-to-Use: Current CFD tools are designed for experts in numerical analysis. This expertise gap can be minimized with intuitive UI, large public template project library, live support chat, and free training material. Any of the public projects in the SimScale Library can be imported into your workspace, so you can simply exchange the CAD model, reassign the boundary conditions and run it, even without having extensive prior knowledge about simulation.
To illustrate the benefits of integrating simulation into your product design process, let’s consider a real-life engineering problem of validating a novel air conditioning design for a server room.
The Engineering Problem: Air Conditioning Design Validation
Always required, but often overlooked, air conditioning design is an integral component of every data center or server room. With the recent technological developments, low-heat emitting servers are becoming available, they are still fairly new to the market and rare. Most organizations cannot afford to set up their data centers in sub-Arctic zones, making it the responsibility of a building’s AC system to maintain their performance by keeping them cool. And it’s the job of the HVAC engineer to design this system in the best possible way.
To illustrate how cloud-based flow simulation helps engineers design more efficient air conditioning systems, we will use one of the projects publicly available in the SimScale simulation project library — Novel Air Conditioning Design for Server Room Cooling. It can be freely copied and used as a template by any SimScale user. In this project, we’ll propose a new air conditioning design for server rack cooling to visualize why the new design is better than conventional air conditioning systems, thereby validating it.
Conventional air conditioning design (left) and novel design (right)
CFD Simulation Results
The underlying simulation project considered two equal capacity air conditioning systems. The design change here is a variation in the vent placement. In the new design, air conditioning vents were placed on the floor of the server room. The cooling capacity was maintained at a constant value in the two simulations by maintaining an equal mass flow rate.
As demonstrated by the chart, the new design shows a better cooling effect, reducing the server rack temperature by an additional 10%. This enhances the energy efficiency and although it may incur a higher installation cost, it would significantly reduce the recursive cost of the air conditioning system in the long run.
The highly efficient cooling effect of the new air conditioning system can be attributed to a more localized distribution of cooling air around the server rack in the server room.
Distribution of cooling air in the server room
The dark blue regions in the above pictures show how the cooling air is distributed in the room. As can be seen, there is a stronger concentration of the cooling air around the server racks leading to a better overall cooling efficiency.
To gain further insight into the distribution of the cooling air, we must ensure that the results have reached a steady state, i.e. the temperature in the two rooms is not changing over time. This is demonstrated by the temperature convergence plots, as below:
Temperature convergence plots
Now that it has been established that we are looking at results over a steady state, the three-dimensional distribution of the cooling air in the server room can be analyzed.
3D visualization of the cooling air distribution in the server room
The above animation of the cooling air distribution for the two designs brings us to the conclusion that it is distributed in a more uniform fashion for the new server rack design, leading to more effective convection of heat away from the rack.
With this project, we aimed to demonstrate how a minor change to a conventional air conditioning design can lead to a significant improvement in performance efficiency. Such novel designs often never get validated, when their impact is underestimated and the manufacturing costs are too high. With simulation, design engineers can validate their innovative design ideas in a matter of hours, with a minimal investment of manual effort on their part. As a result of our simulation, we were able to test a novel design achieving a reduction in the server rack temperature by an additional 10% — as well as overall a more efficient and reliable system, which, over time, can save a considerable amount of energy.
This is just one example of how an HVAC engineer can leverage CFD to improve his or her air conditioning design and validate innovative ideas. The SimScale Public Projects library has a wide selection of simulation templates covering various aspects of HVAC simulation, including thermal comfort, cleanroom design, wind engineering and more.
To learn more about practical applications of CFD in HVAC system optimization, read this case study, showing how the Austrian company IBEEE improved the flow rate of their ventilation system design by 40%.