![\"The](\"https:\/\/frontend-assets.simscale.com\/media\/2022\/07\/3d-model-of-the-LED-heatsink.png\")
<\/a>Using the Conjugate Heat Transfer (CHT) simulation type in SimScale a full thermal analysis was performed with a focus on radiative heat loss contribution.<\/p>\n\n\n\n
In order to better understand the influence of radiation on the proposed LED heat sink, multiple design considerations were investigated:<\/p>\n\n\n\n
- Radiation: Disabled vs Enabled – <\/strong>To understand if we should consider radiation in further design iterations<\/li>
- Surface finish: Anodized aluminum vs radiative paint – <\/strong>To understand the influence of increasing the emissivity of the heat sink surfaces<\/li>
- Heat sink design: \u2018Dense\u2019 vs \u2018Sparse\u2019 heat sink – <\/strong>To understand the influence of increasing the total surface area of the heat sink on the overall heat transfer.<\/li>
- Cooling strategy: Natural vs forced convection – <\/strong>To understand the overall contribution of radiation in both cooling scenarios.<\/li><\/ul>\n\n\n\n
The comparisons were done by varying one parameter at a time as illustrated in the figure below.<\/p>\n\n\n\n
![\"An](\"https:\/\/frontend-assets.simscale.com\/media\/2022\/07\/Design-variations.png\")
<\/a>Design variations simulated as a comparison against the base design.<\/figcaption><\/figure><\/div>\n\n\n\n Simulation Setup<\/strong><\/h3>\n\n\n\n
- \u00a0A steady-state Conjugate Heat Transfer (CHTv2) simulation is used to model convection, conduction, and radiation<\/li>
- \u00a0\u00a0The flow volume that encloses the LED CAD module can be created using our CAD mode<\/em><\/a> feature, which is used to create two flow regions as follows:
- Box: To emulate the setting of a natural convection scenario where the device sits open to the environment. The flow is allowed to enter and exit freely through the boundaries of the box.<\/li>
- Cylinder: To emulate the effect of a forced convection flow. Where a flow rate of 0.04887 m3<\/sup>\/s was applied to the inlet face.<\/li><\/ul><\/li>
- The materials used:
- \u00a0\u00a0PCB: Aluminum (emissivity = 0.3)<\/li>
- \u00a0\u00a0LED chip: Silicon (emissivity = 0.9)<\/li>
- \u00a0\u00a0Heat sink:\u00a0 Anodized Aluminum (emissivity = 0.7)<\/li>
- \u00a0Aluminum with radiative paint (emissivity = 0.95)<\/li><\/ul><\/li>
- The ambient temperature is 19.85 \u00b0C<\/li>
- The total power dissipated by the LED chip equals 10 W.<\/li>
- The standard mesher with automatic settings was used.<\/li>
- The average time to complete one of the particular design iterations mentioned above is between two to three hours. However, because SimScale allows all simulations to be run in parallel with cloud computing, this now becomes the total time needed to run all design scenarios.<\/li><\/ul>\n\n\n\n
![\"flow](\"https:\/\/frontend-assets.simscale.com\/media\/2022\/07\/LED-heat-sink-natural-convection.png\")
<\/a><\/figure><\/div>\n\n\n\n![\"flow](\"https:\/\/frontend-assets.simscale.com\/media\/2022\/07\/LED-heat-sink-forced-convection.png\")
<\/a>The enclosed LED heat sink CAD model inside two different flow domains to simulate the effect of natural convection (top) and forced convection (bottom).<\/figcaption><\/figure><\/div>\n\n\n\n Simulation Results<\/strong><\/h3>\n\n\n\n
The chart below compares the results obtained from the base setup with its design variations.<\/p>\n\n\n\n
- The left axis provides the maximum LED temperature in \u00b0C.<\/li>
- The right axis provides the contribution of radiation to the overall heat loss in the system.<\/li>
- The bottom axis shows the design variations simulated.<\/li><\/ul>\n\n\n\n
Radiation Enabled vs Disabled<\/strong><\/p>\n\n\n\n
The first design variant stems from asking, \u201cDo I need to include thermal radiation effects in my further design iterations?\u201d<\/p>\n\n\n\n
The answer is yes. If we compare the results obtained from the base setup with the results from the simulation without radiation, we can clearly see that the maximum LED temperature obtained with radiation activated was around 46 \u00b0C while in the case without radiation was 53 \u00b0C. That\u2019s about 27% increase in temperature when radiation effects were not included in the base design, and a sufficient indication that thermal radiation effects should be considered. Moreover, it can be seen that in the base setup radiation contributed close to 30% of the total heat loss in the system.<\/p>\n\n\n\n
Surface Finish: Anodized vs Radiative Paint<\/strong><\/p>\n\n\n\n
Using Anodized Aluminum as a material for the heat sink contributed to lower radiative heat loss when compared to its radiative paint finish counterpart. Subsequently, this resulted in a higher LED temperature with a value of around 47 \u00b0C.<\/p>\n\n\n\n
Heatsink Design: \u2018Dense\u2019 vs \u2018Sparse\u2019 Heatsink Fins<\/strong><\/p>\n\n\n\n
Interestingly, the maximum LED temperature obtained for the design with a dense heat sink proved to be higher than the design with a sparse heat sink; 53 \u00b0C in comparison to the 46 \u00b0C of the base setup. This is simply due to the low velocities that are usually encountered in natural convection which results in insufficient flow penetrating the gaps between the fins and hence not providing adequate cooling.<\/p>\n\n\n\n
On the other hand, the radiative heat loss contribution was almost 5% higher than in the base design.<\/p>\n\n\n\n
Cooling Strategy: Natural vs Forced Convection<\/strong><\/p>\n\n\n\n
In the forced convection case the maximum LED temperature recorded was significantly lower than the other design variants with a natural convection cooling strategy. In this case, 25 \u00b0C in comparison to 46 \u00b0C with natural convection. Moreover, the contribution of radiation to the overall heat loss is about 2% which is minimal.<\/p>\n\n\n\n
- The materials used:
- Surface finish: Anodized aluminum vs radiative paint – <\/strong>To understand the influence of increasing the emissivity of the heat sink surfaces<\/li>