CFD Advantages and Practical Applications

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by Heejin Park, Director of CFD Modeling

Introduction To Computational Fluid Dynamics (CFD)

CFD is an acronym that refers to "Computational Fluid Dynamics". CFD uses numerical methods to solve the fundamental nonlinear differential equations that describe fluid flow (the Navier-Stokes and allied equations) for predefined geometries and boundary conditions. The result is a wealth of predictions for flow velocity, temperature, density, and chemical concentrations for any region where flow occurs.

A key advantage of CFD is that it is a very compelling, non-intrusive, virtual modeling technique with powerful visualization capabilities, and engineers can evaluate the performance of a wide range of HVAC/IAQ system configurations on the computer without the time, expense, and disruption required to make actual changes onsite.

CFD has seen dramatic growth over the last several decades. This technology has widely been applied to various engineering applications such as automobile and aircraft design, weather science, civil engineering, and oceanography. Today, the HVAC/IAQ industry is one of the fields that has initiated utilizing CFD techniques widely and rigorously in its design.

Practical Advantages of Employing CFD

The many reasons CFD is being widely used today are as follows:

CFD predicts performance before modifying or installing systems:

Without modifying and/or installing actual systems or a prototype, CFD can predict which design changes are most crucial to enhance performance.

CFD provides exact and detailed information about HVAC design parameters:

The advances in HVAC/IAQ technology require broader and more detailed information about the flow within an occupied zone, and CFD meets this goal better than any other method, (i.e., theoretical or experimental methods).

CFD Saves Cost and Time:

CFD costs much less than experiments because physical modifications are not necessary. (Note that the cost and time for physical changes/modifications increase almost exponentially as the size of the system increases).

CFD is Reliable:

The numerical schemes and methods upon which CFD is based are improving rapidly, so CFD results are increasingly reliable. CFD is a dependable tool for design and analyses.

Where Can CFD be Utilized?

In validation/optimization of HVAC design parameters:

CFD data can be utilized to validate various design parameters such as the location and number of diffusers and exhausts, and temperature and flow rate (CFM) of supplied air to meet design criteria. For example, CFD simulation helps design verification of the following systems: natural ventilation systems, displacement ventilation systems, raised floor system, atrium smoke system, etc.

In modification/improvement of malfunctioning HVAC systems:

The system with suggested modifications can be simulated computationally without actual physical modifications to the existing systems. The information from CFD reveals what modification satisfies the design criteria.

In comparisons between alternative systems:

Under some circumstances, there may be several different options for designing HVAC systems for a space (for example, mixing ventilation or displacement ventilation). Computer simulation data can provide crucial information to find the best possible system.

In an engineering investigation:

CFD analysis of temperature, velocity and chemical concentration distributions can help engineers understand the problem correctly and provide ideas for the best resolution.

Examples of CFD Applications for HVAC Systems

General office/room simulations

Contaminant/species simulations

Fume hood design

Copy machine rooms (VOC)

Contamination control chemical lab design

Industrial ventilation design

Smoking lounges

External building flows

Problem solving simulations

AHU mixing enhancement investigation

Fire and smoke management