What are differences between Surface to Surface and Discrete Ordinates models in Ansys Fluent?

 The Surface-to-Surface (S2S) and Discrete Ordinates (DO) models in Ansys Fluent are both used for simulating radiative heat transfer, but they have different approaches and applications:

Surface-to-Surface (S2S) Model

• Assumptions: Assumes that the medium between surfaces does not participate in radiation (i.e., no absorption, emission, or scattering by the medium).
• Application: Best suited for enclosures with gray-diffuse surfaces where radiation exchange is significant.
• Method: Uses view factors to calculate the radiative exchange between surfaces. The view factor depends on the size, separation distance, and orientation of the surfaces¹.
• Computational Cost: Can be computationally expensive due to the need to calculate view factors for all surface pairs, but clustering techniques can reduce this cost¹.

Discrete Ordinates (DO) Model

• Assumptions: Solves the radiative transfer equation (RTE) for a finite number of discrete solid angles, allowing for absorption, emission, and scattering by the medium.
• Application: Suitable for complex geometries and participating media where the medium itself interacts with radiation.
• Method: Transforms the RTE into a set of transport equations for radiation intensity in different directions. This model can handle non-gray radiation by dividing the spectrum into wavelength bands².
• Computational Cost: Generally more flexible and can be more computationally intensive due to solving multiple transport equations, but it provides a more detailed analysis of radiative heat transfer².

In summary, the S2S model is ideal for scenarios where the medium does not interact with radiation, focusing on surface interactions, while the DO model is more versatile, handling interactions within the medium and complex geometries.

Case Stduies for each model

Surface-to-Surface (S2S) Model Case Studies

1. Radiative Heat Transfer in a Furnace:

   • Scenario: A furnace with multiple heating elements and reflective walls.
   • Objective: To analyze the radiative heat exchange between the heating elements and the walls.
   • Outcome: The S2S model was used to calculate view factors and predict temperature distribution, helping optimize the placement of heating elements for uniform temperature¹.

2. Thermal Management in Electronics:

   • Scenario: An electronic device with multiple heat-generating components.
   • Objective: To study the radiative heat transfer between components to prevent overheating.
   • Outcome: The S2S model provided insights into the radiative interactions, leading to better thermal management and improved device reliability¹.

Discrete Ordinates (DO) Model Case Studies

1. Solar Radiation Analysis in Buildings:

   • Scenario: A building exposed to varying solar radiation throughout the day.
   • Objective: To simulate the impact of solar radiation on indoor temperature and energy consumption.
   • Outcome: The DO model accurately predicted the solar heat gain, aiding in the design of energy-efficient buildings².

2. Radiation Dose Modeling:

   • Scenario: Simulation of UV dose distributions in a hydraulic system.
   • Objective: To evaluate the effectiveness of UV radiation for disinfection purposes.
   • Outcome: The DO model was used to generate UV incident radiation fields and track particle doses, ensuring effective disinfection³.

These case studies illustrate the practical applications and benefits of each model in different scenarios.