Passive Cooling LED Panel Heat Sink

Concept:

 

The purpose of this project was to eliminate the energy that is required to cool of LEDs, specifically LED panels used in the indoor agriculture industry. The goal was to achieve this through the utilization of multiple simultaneous passive cooling techniques, such as heat sinks and heat pipes, to dissipate the excess heat that is generated. The advantage with these passive cooling techniques is that they will effectively dissipate the heat generated but will not consume any additional energy. This, in turn, translates to the system requiring little to no maintenance because of the simplicity and lack of moving or electrical parts. 

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Requirements:

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1. Utilize only passive cooling methods

2. Design for manufacturing

3. ​Achieve results comparable to or better ​than active cooling methods

 

Process and Design:

 

The first step was to attain baseline measurements of the overall heat rise of the LED panel sans heat sink.

 

In terms of the design, the first component that was focused on was the heat sink fins. I personally drafted several different designs on  SolidWorks and simulated them in ANSYS applying conduction at the base, to represent the LED panel, and convection at the fin surfaces, to represent the ambient air. Ultimately, due to the consideration of manufacturing and time constraints, we chose a simple straight fin design with optimized fin spacing (determined through fin spacing calculations). However, we decided that the optimal case would have jagged edges on the fin profile (in order to increase surface area).

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The next element that was introduced was heat pipes. The heat pipes were to be fitted to the base of the heat sink fins via machined holes. They were inserted with thermal paste to fill the gaps and thereby increase efficiency of heat transfer. When the heat sink base was attached to the LED panel thermal paste was applied between the two as well.

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Results:

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Ultimately, the combination of passive cooling elements surpassed the active cooling methods that were set as the standard. In the baseline temperature distribution results it was seen that the active cooling methods dropped the panel temperature down to 90 degrees C. Furthermore, a potential, optimized heat sink design was created for future iterations of the project. Unfortunately, the heat pipes were not able to perform to their full extent. Due to excessive heat requirement, condensation did not occur within the heat pipes conforming to the simulation and experiment. For future iterations it is recommended to implement thermosiphons rather than heat pipes due to their lower temperature threshold.