MRF project

CHALLENGE:

To Model real fan behaviour using MRF modelling approach.

MODEL:

1. The model have been given as .tzr file and it was unpacked and visually inspected to define meshing approach.

2. The moving fluid zones necessary for the MRF modelling have been created over CAD models of blade geometry.

MESH:

1. The initial mesh have been generated for default settings with size 1/20th of cabinet dimensions.

2. Multi level mesh settings have been defined for CAD model of baldes.

3. The meshing priority have been changed for the fluid zones and CAD model to ensure all geometries are meshed.

4. Several N/C assemblies have been generated to contain mesh bleeding and mesh count.

5. Good quality mesh which satifies the required quality criteria have been created.

6. The above mesh shows mesh view from XYZ axis. some of the components are hollow as they are not thermally contributing.

7. The above mesh shows the refinement level ised to capture the CAD geometry of the fans. the mesh which satifies all aspects of solver requiement is generated.

CASE SETUP:

1. The fluid blocks use for modelling MRF have been edited and RPM value of 6000 is defined.

2. Power dissipation settings are defined as given.

3. The model is solved for forced convective hea transfer as fan primitive will give impoper temperature levels in cabinet.

4. The poblem is solved for 2000 iterations and solution residuals are converged properly with coupled solver settings.

5. The below image shows the convergence plot of the problem which shows very good and steady convergence.

POSTPROCESSING:

1. The flow lines generated due to fan rotation is visualized below and it is observed that real fan behaves differently than fan primitives.

2. The difference between fan primitive and real fan is in primitive normal flow is considered but in real fan swirl has important characteristics with axial and tangential components.

3.The below image shows the cut plane view of velocity cmoponent across fans, which shows real characteristics of the fan high velocity and low velocity region.

4. The below image shows the cut plane speed characteristics for single fan with its speed characteristics in its casing.

5. The below image shows the vaiation plot of velocity from grille to fan shows that velocity is peak exactly outside the fan case.

6. The temperature contours shows that the maximum temperature of 27deg and it is safe. since we are using MRF modelling approach this results will get matched with the real time temperature behaviour.

IMPRESSION:

1. The temperature levels are safe in domain and fluid flow are equally distributed in the cabinet hence no changes is required.