EDS^® Thermal Simulation

Steady State (2D) Calculations

Routine Early Calculations Based On Broad Assumptions

During the early design stages of a project engineers may use ‘steady-state’ calculations to determine building heating and cooling loads. Steady-state calculations are based upon known criterion, such as outside temperatures and internal requirements, and examine only one scenario at a given time.
 
For example, the engineer looking to establish heating demands may assume an outside temperature of 0^oC and inside requirement of 22^oC.  Applying routine internal heat gain and material heat loss assumptions, they may then calculate the additional heat required to achieve comfort conditions for that particular scenario.

In a separate calculation to determine cooling requirements the engineer may assume an outside temperature of 25^oC and wish to maintain the inside at 22^oC.  Again, applying routine internal and solar heat gain assumptions they may then calculate additional cooling requirements.

«  Overview  Dynamic Thermal »

Dynamic Thermal Simulation & EDS^® Energy Modelling

Introducing Time, Operations, Airflow, Structural Thermal Capacity, Shading, and Weather

More accurate than Steady-State calculations, 'Dynamic Thermal' & 'Bulk Airflow' analyses consider time as a calculation parameter.  A three dimensional computer model, including surrounding obstructions, is used to represent the working environment.  The model is correctly orientated and a local weather file is attached (actual recorded weather data); the model is effectively located on-site. Occupancy schedules are also considered, as are materials and specific task-related heat gains. 

• Surface Temperatures
• Internal Space Temperatures (Dry Resultant, Mean Radiant, Dry Bulb, Wet Bulb)
• Dew-Point Temperatures (Condensation Analysis)
• Heat Loss (Fabric, Infiltration)
• Heat Gain (Casual, Solar)
• Heating Plant Loads
• Cooling Plant Load
• Free-Cooling offsets
• Relative Humidity
• De/Humidification Plant Load
• Occupancy Comfort Prediction
• Natural Ventilation Viability
• Air Quality (CO₂ Concentrations)

Occupancy figures appear as heat gains and CO₂ emitters in the overall calculations. Thermal capacities and free-cooling effects are considered in the calculation process.  As such, this yields more accurate results over steady-state calculations.

Further, the study examines the bulk flow, and velocity, of air within and around each zone in the building.
A bulk airflow study can be used to examine the overall airflow distribution and effectiveness of Heating and Natural Ventilation systems.  The study also considers control strategies for valve & window openings and offers input into the Building Management System (BMS) control strategy. Proportional control of opening windows and louvres can be examined; temperature AND/OR CO₂ setpoints are simulated.

«  Steady State  CFD »

Computational Fluid Dynamics (CFD)

Advanced Temperature & Airflow Calculations Producing A Graphical Output

CFD is used to model physical fluid flows and heat transfer.  An internal CFD analysis provides information on the distribution of fluid velocity, pressure and temperature (and several other calculated parameters) throughout the inside of building spaces.

Proposed changes to the working environment can be reflected in a 3D model to yield “cause & effect” scenarios before procurement & committing to works on-site.  Cost/benefit and value engineering analyses can then be graphically represented.

CFD examines a situation at an exact moment in time.  Typically, the results yielded in the Dynamic Thermal model indicate a time/case of interest.  In the as-built scenario the ‘Boundary Conditions’ for the CFD study can come from measured readings of air velocities, air temperatures and surface temperatures. 

A combination of a Digital Anemometer & IR Thermometer or Thermal Imaging equipment are the most accurate instruments to determine boundary conditions.  These are then applied to the model.  Airflow, pressure, and heat distribution can then be displayed on the same image.

EDS^® has used Dynamic Thermal Modelling and CFD to determine:

• The throw of air into an atrium or annexed space.
• Optimisation of mechanical services & control systems.
• The existence of draughts.

• The implications of fitting curtains to reduce/eliminate down-draughts near windows.
• The implications of introducing partitions.
• The implications of fitting auxiliary heaters.
• Smoke dispersion in fire scenarios.
• The optimal location of sensors.
• The implications of changing heating / ventilation schedules.
• Determine optimal time for systems to be ramped down.
• Determine optimal (real) demand from LPHW heating system.
• The optimal pulse duration and opening areas for windows in the ventilation schedule.
• Heat loss and insulation parameters.
• Determine the effectiveness of existing or proposed insulation and locations where it may be required.
• Predicted Mean Vote (PMV) & Predicted Percent Dissatisfied (PPD).
• Operative (comfort) & Draft Temperature.
• Air Diffusion Performance/Quality Index.
• Contaminant Removal Effectiveness (CRE).

«  Dynamic Thermal  Mechanical (HVAC) »

Heating Ventilation & Air Conditioning

Analyse & Optimise System Performance

Full air & water side HVAC systems modelling.  Each emitter/diffuser on the schematic is assigned to a zone in the model.  The results will reflect and compare any changes proposed to the original design.  This is particularly useful in sizing additional HVAC elements and optimising system schedules & performance.

«  CFD  Overview »