With building energy requirements ever more stringent HVAC CFD simulation is already complementing traditional design methods in HVAC. Fields of application go from the engineering of individual cooling and heating units to the design of whole air conditioning layouts. SimWorks and SimWorks Manager include specific CFD methods capable of simulating natural ventilation in buildings and monitor humidity and temperature parameters to evaluate the energy of a building even in the initial concept phase.
HVAC CFD simulations of air conditioning layouts require to model the natural flow convention including the physical modelling of flow buoyancy and the humidity distribution, in addition to the forced convection due to ventilation outlets. The overall office space is modelled with simplified geometries replicating the building spaces, office furniture, equipment and people. The air conditioning system outlets are then added to the model with the predicted mass flow rates and relative temperature. To increase the fidelity of the model, external wall temperatures can be calculated from external air temperature, solar radiation and wall insulation parameters.
SimWorks allows to define all the above in a direct way via its Graphical User Interface (GUI) and includes the necessary solvers to correctly assess internal flows and their impact on human comfort. SimWorks Manager also includes the functionality of simulating the dispersion of a passive scalar which allows to simulate and contain the dispersion of a pathogen inside an enclosed environment.
CFD is used to dimension cooling system layout for offices
It is also possible to quickly iterate through multiple cooling system layouts changing for example the number and position of ventilation outlets or the overall mass flow rate by re-using the setup of the initial simulation. The air conditioning system can therefore be optimised in order to comply with the project specifications and limiting the risk of oversizing it.
Data centres and server rooms are becoming common in industrial buildings and as the power densities of modern computers are increasing cooling and ventilation of server rooms is becoming a challenge. HVAC CFD simulations can be used to simulate the airflow within the room, the heat exchange of the servers and to size the room cooling system. The first step in the CFD analysis is to simulate the servers as blocks with an assigned heat flux on their surface replicating the machine cooling requirement. Those blocks are placed within the room and then cooling system inlets are added with their technical specifications of temperature and mass flow rate. SimWorks allows to effectively complete simulations of different layouts and configurations which helps assessing the margin of safety of all the individual servers to overheating and therefore correctly sizing the cooling system to meet its design requirements.
Data centre design is driven by cooling layout effectiveness
The same approach used to simulate the cooling of data centres can be applied on a smaller scale to evaluate the cooling of electronic units. In this case individual electronic boards can be modelled as an assembly of blocks simulating the internal electronic components of the board using the thermal specifications as derived by the supplied technical data sheets. Multiple boards can be placed within their prescribed case and fans, air inlets and heat sinks can be added to simulate the cooling and ventilation of entire unit. SimWorks allows to quickly evaluate the results of different configurations by reusing the previously defined electronic boards as building blocks for more complicated analysis with minimal user interaction.
CFD simulations results show a good agreement with experimental data and showing that CFD is an essential tool to develop the new generation of electronic boards.
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