1. Development of a Thermoelectric Cooling Prototype
Thomas Coull and Dr. Steven Girard University of Wisconsin – Whitewater, Department of Chemistry
Results
Effect of using a Al spacer between the TE unit and the cold side of the heat sink.
Future Work
In future work we intend to continue our research into optimizing the design of the cooling unit and testing the feasibility of using TE units for cooling purposes. Changes we intend to make include:
Using more powerful TE units (230 W) and potentially using two in sync.
The composition of the metal spacer (Cu vs. Al)
Use of specialized shrouds to optimize heat distribution/dispersion
Introduction
Maintaining a precise temperature a precise temperature is important in many areas of science such as during temperature dependent reactions/synthesises. Here, we investigate a modular thermoelectric cooling prototype that could potentially be used for a variety of cooling applications where a typical refrigerator would be undesirable, such as home fermentation (i.e. beer brewing, yogurt, kimchi, etc.), medical storage, or food preservation (i.e. meat curing).
Blower position
Shroud
Flow of air
Thermoelectric Cooling background information
Thermoelectric units are capable of generating a temperature change through a phenomenon known as the Peltier effect, where an electrical current is passed through semiconductors and the result of this electrical current causes one side of the unit to become hot and one side to become cold.
A typical thermoelectric cooler will consist of an array of p- and n- type semiconductor elements. The array of elements is soldered between two ceramic plates, electrically in series and thermally in parallel.
Effect of Spacer orientation Al TE
Cold
Insulation
Blower
Fan
Hot
When we believe we have optimized the design of the cooling unit we plan to interface it with the insulating box and see if we are able to induce a temperature on:
Air within the box
Varying volumes of water
Actively fermenting wort
We need to see that the cooling unit is capable of inducing and maintaining a desirable temperature range in each of the above mediums. Successful result in each medium would allow us to progress to the next.
The lowest blue line shows the temperature on the surface of the cold heat sink with the Al spacer in direct contact with the cold side of the TE unit. As shown on the graph it achieved a lower final temperature than when the cold side was in direct contact with the heat sink, which is depicted by the red points.
Conclusion
As of the work conducted thus far we cannot make any conclusions about the maximum cooling potential of TE units and their feasible applications for temperature control.
We have made significant improvements in optimizing the cooling efficiency of the TE units used and obtaining greater temperature changes on the surface of the heat sinks compared to where the project began. We now also have a much deeper understanding of how factors such as: thermal contact, thermal shorts and relative resistance within the TE unit affect the ultimate cooling capacity of the cooling unit. We can consistently achieve temperatures of 50-60°F on the surface of the heat sink.
We believe the aforementioned modifications will increase the temperature change seen on the cold heat sink, thus improving the cooling efficiency. We hope to achieve temperatures of 40°F within the confines of the cooler.
Effect of thermal grease on cooling efficiency.
Methods
Our recent work has been focused on optimizing the design of the cooling unit. To do this we have been systematically investigating how altering individual components of the cooling unit impact the cooling efficiency of the TE unit and ultimate temperature change observed.
Aspects of the cooling unit design (shown below) that we have modified thus far include:
Use of a metal spacer
Orientation of the spacer
Mass of thermal grease used.
Power of TE unit used (96 W & 154 W)
From this data 0.4g is the optimal mass of thermal grease to ensure good thermal contact, but not induce thermal shorts between the TE plates.
Cold
Hot
Insulation
Al Spacer TE
Blower
Fan
Metal spacer
TE unit
Effect of Thermoelectric Unit Power on Cooling Ability
References
J.G. Jeffrey and E.S. Toberer, Nature Materials 7, (2008)
American Homebrewers Association
Acknowledgements
We would like to acknowledge the university of Wisconsin-Whitewater Undergraduate Research Program which supported this project.
Increasing the power of the TE unit from 96 W to 154 W had a dramatic effect on the temperature change seen on the surface of the cold heat sink