Inserting Heat Sink into Test Facility

Author: Grant Resler | Major: Mechanical Engineering | Semester: Fall 2023

Hello, my name is Grant Resler. I am an honors mechanical engineering student with minors in innovation and engineering management. I have been working with Dr. Han Hu from the mechanical engineering department in the Nano Energy and Data-Driven Discovery Laboratory since the fall of 2022. My research has been on optimizing air-cooled heat sinks for aerospace applications. Optimization of heat sinks happens when more heat transfers from a heat sink with the same amount of air flowing over it. In previous research I tested heat sinks in an environment that was not consistent with the amount of air flow over the heat sink which led to its own challenges. Also, in previous research I began experimenting with new designs as well as conducting literature review to come up with the current design of the test facility. My research this semester has been on revising my design and manufacturing of the wind tunnel test facility.

The wind tunnel test facility is composed of a few parts. There is a settling chamber, contraction cone, test section, diffuser, and fan. The settling chamber begins with a flow straightener which is like a bunch of straws in a honeycomb pattern that the air flows through. After the flow straightener, the air flows through the rest of the settling chamber which is a series of screens. The purpose of the settling chamber is to eliminate swirls in the air and create uniform air pressure entering the contraction cone. The contraction cone follows the flow straightener and further eliminates turbulence in the air flow, and it speeds up the air flow as it goes into the test section. The test section is a straight section of ducting that holds the heat sink. The test section is just large enough to fit the heat sink in which forces the air to flow through the heat sink and not over the heat sink. When air flows over the heat sink and not through it, that is called flow bypass. This test facility eliminates flow bypass in the test section. This allows for a pressure drop to be observed in the test section. Pressure drop is very important to optimizing the heat sink. When there is a low pressure drop, the fan doesn’t have to work as hard to move the air over the heat sink which will decrease the cost of cooling. The pressure drop was something that I tried to observe in the old test facility, but because the test facility allowed for flow bypass, I could not observe the pressure drop. This problem was a major restriction to optimizing heat sinks because it was impossible to quantify how the change of geometry positively or negatively impacted the pressure drop of the heat sink. After the air flows through the test section, the air flows into the diffuser which is used to slowly slow the air down and return the air to atmospheric pressure as it gets pulled though the fan on the backside of the diffuser.

The manufacturing of the wind tunnel was primarily with additive manufacturing via 3D printing. My original design for the flow straightener was to use straws in a honeycomb pattern and some window screening to hold the straws in place. This process failed because the straws continued to fall out and were very hard to make consistent. This led to a redesign of the flow straightener and the use of 3D printing to print a grid structure for the flow straightener. The screens that I used were window screens cut to size and they were secured in place with screws in the corners. The contraction cone was also manufactured which was a difficult pinch point this semester. It took many tries to get the contraction cone to print correctly, but when it was done, I was very pleased with the results. When the contraction cone was completed, it was the first time I began to feel the satisfaction of something that I envisioned was coming to life. This semester was very rewarding and very challenging. It was rewarding to see something that I had been working on for five months coming to life, but also very challenging because there were many things like the contraction cone that did not go as planned and required me to pivot and redesign. My fellow classmates were very helpful during the redesign process as I could tell them my ideas and show them what I was thinking, and they were able to show me strengths and weaknesses in what I was doing. Dr. Hu was also very helpful pointing me in the correct direction when I was heading in the wrong direction.

I am going to continue this project when I return to school next August. In the meantime, I will be doing the pilot co-op with Walmart’s Automation and Innovation engineering team. I start this co-op in January and will be working with the team until mid-August. I am excited to gain experience and learn from engineers in industry as well as building relationships with others. see what I am passionate about and get further motivation and direction for what I want to do in the future.