Fluids & Structural Mechanics > CM Projects > Thermal System Management (TSM)

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The CM Division has extensive capabilities to analyze thermal impacts on fluid flow and to design cooling ponds, buildings, and vehicles with full interaction between the thermal systems and the bounding fluids.

Underwater Vehicle Thermal Signature Study:
The objective of this CFD study was to assess potential thermal plume signature due to heating from battery packs. Two cases were considered, a warm ocean case and a cold ocean case. The study used ARL’s internally developed NPHASE CFD code. The fluid area surrounding the vehicle was filled with 935,000 cell unstructured tetrahedral elements with grid refinement in the region of thermal plume. The flow field was modeled using 2nd order accurate discretization, the k-e turbulence model with wall functions, Boussinesq heating (since Δ T << 10oC), and heating induced buoyancy convection. The surface signature of the thermal plume is evident.

Thermal management for building design:
Thermal effects impact the flow around and within structures. This study used full thermal coupling between the CM CFD model, NPHASE, and a heat transfer simulation tool, RadTherm, to analyze thermally induced flow for an environmentally friendly building, including thermal radiation, conduction, and convection effects for both the interior and exterior of the building. The calculation included environmental variables such as solar angle, time of day, sky cover, temperature, and humidity. Detailed information on building materials impact the local thermal heating of the building. These coupled features affect the relative heating and buoyancy, and thus, the resulting flow about and inside a building. Figure 2a shows the impact of diurnal variations in heating on the temperatures of the building for an example September day. Note the inclusion of shading effects. Unique features such as Trombe walls add to heat transfer mechanisms. Figure 2b demonstrates the detail available. At that time, solar radiation was entering the front windows of the building and causing very local heating on portions of the first story walls.

Unique features such as Trombe walls add to heat transfer mechanisms. Figure 3a indicates warm air emerging from the top of the Trombe walls and circulating throughout the interior of the building. The accompanying movies trace a particles as they emerge from the Trombe wall for two different views. Figure 3b plots the velocity vectors within the Trombe wall for both the upper and lower level of the building. See animations 1 and 2.

Figure 4 shows the thermal impact on the exterior flow field. Note the large buoyant plume in the vicinity of the Trombe wall windows. This study demonstrates CM division’s capabilities to include details of thermal analysis coupled with full scale CFD modeling for both the interior and the exterior of buildings. Such studies are useful for building design, analysis of the urban heat island, and studying building contaminant infiltration and exfiltration for Homeland Security studies.

Thermal Management for Armored Vehicles:
PSU/ARL Computational Mechanics analyzed thermal limits for the Crusader tank engine. This analysis required a full suite of relevant physical models, very large models with requisite numerical accuracy and computer resources for detailed 3D simulation, and the thermal signature and crew compartment applications (classified) see Figure 5. The physical model was based on the compressible Navier-Stokes equations and includes:

  • Bulk modeling of heat exchangers + cooling fans
  • Inter-component radiation
  • Radiation to/from atmosphere/exhaust
  • Free (buoyancy) and forced convection
  • Turbulence
  • Multiple flow streams
  • Various conduction treatments
  • Numerous materials/properties

The simulation required large unstructured meshes with parallel execution for rapid turnaround. The time dependent simulations were obtained with 2nd order accuracy.

The result was a first principles based assessment tool to interrogate and maximize armored vehicle thermal performance:

  • Material limits
  • Crew comfort
  • Thermal signature
  • Exhaust design
  • Subsystem thermal limits

Thermal Management Of Power Plant Cooling Ponds
The CM division accomplished an assessment and optimization of cooling pond performance based on a full suite of relevant physical models to Demonstrate effectiveness for alternate baffle and guide vane designs. The simulation included large unstructured meshes for resolution of a wide range of scales and complex geometries. The time dependent simulations considered the diurnal and seasonal cycles, leading to time dependent boundary conditions. It was calibrated with a 1D MITEMP code for the existing system validation, see Figure 6. Physical modeling elements include:

  • Evaporation
  • Radiation to/from atmosphere
  • Surface convection
  • Lake bottom convection
  • Lake bed sediment conduction
  • Thermal stratification/buoyancy
  • Turbulence
  • Time varying boundary conditions
  • Multiple feed water streams
  • Bulk modeling of plant

This analysis resulted in a first principles based assessment tool to interrogate and maximize cooling pond performance for baffle systems, Inflow vanes, and increased residence time and stratification. It resulted in Reduced plant inlet temperatures, allowing higher plant load operation; Improved efficiency leading to a more economical operation; and a system specific design tool calibration for real-time PC based performance predictions.

Images
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Figure 1:


Underwater Vehicle Thermal Signature Study
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Figure 2:


Figure 2a:
The impact of diurnal variations in heating on the temperatures on a building for an example September day.

Figure 2b:
Detail, solar radiation entering the front windows of the building and causing very local heating on potions of the first story walls.
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View Image (196kb)

Figure 3:

Figure 3a:
This figure indicates warm air emerging from the top of Trombe walls and circulating throughout the interior of the building.

Figure 3b:
This figure plots the velocity vectors within the Trombe wall for both the upper and lower level of the building.
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View Image (119kb)

Figure 4:
Image of the thermal impact on the exterior flow field. Note the large buoyant plume in the vicinity of the Trombe wall windows
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View Image (182kb)		 Figure 5:
Thermal management for armored vehicles
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View Image (227kb)		 Figure 6:
Thermal management of power plant cooling ponds

Animations
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(Flash Player 3.7mb)
 Animation 1:
View 1 showing particles as they emerge from the Trombe wall
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(Flash Player 359kb)		 Animation 2:
View 2 showing particles as they emerge from the Trombe wall