Ansys Fluent is professional computational fluid dynamics (CFD) software for detailed simulation of indoor airflow, heat transfer and thermal comfort. It calculates the key comfort indices - PMV and PPD - and is used for HVAC design, ventilation optimisation and energy performance analysis of buildings.
Objectives and value of thermal comfort simulation
The main objective of a CFD comfort simulation is an indoor environment that gives occupants maximum comfort at minimum energy use. The analysis shows the temperature and air velocity distribution precisely and identifies discomfort zones while the building is still at the design stage.
This makes it possible to adjust the architectural design or the HVAC systems before any construction costs are incurred.
Compliance with international standards
An analysis in Fluent verifies the design against ASHRAE 55 and ISO 7730. ASHRAE 55 requires PMV to stay within −0.5 to +0.5, which corresponds to fewer than 10% of occupants dissatisfied (PPD).
ISO 7730 defines comfort categories for different building types - for new buildings the PMV range is −0.5 to +0.5, while for older buildings more lenient criteria of −0.7 to +0.7 are accepted.
Benefits: lower costs, optimised HVAC, sustainable design
CFD simulations remove the need for costly physical models and allow many design options to be analysed in a short time. They help size heating and cooling plant accurately and optimise the layout of supply and extract terminals - avoiding stagnant zones, draughts and overheating near glazing.
The analysis also supports low-energy design: passive measures (natural ventilation, solar shading, thermal mass) can be assessed, and building orientation and insulation optimised.
Accuracy: turbulence models and the computational mesh
Simulation accuracy depends on the quality of the geometry, the mesh, the turbulence model and the boundary conditions. The k-epsilon model performs better for isothermal flows, while the SST model is more accurate in non-isothermal cases with buoyancy effects.
The precision of the results depends strongly on mesh density. Technologies such as Ansys Mosaic, with cell sizes from 0.1 mm to 10 cm in critical areas, give a detailed picture of thermal and flow phenomena and resolve temperature and velocity gradients more accurately.
Summary
Thermal comfort CFD in Ansys Fluent is an investment with measurable returns - from lower energy costs, through occupant comfort, to meeting demanding international standards. Every analysis comes with a detailed report visualising the temperature and air velocity distribution and the PMV and PPD indices.
Related service