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Research Papers

Feasibility Study on Thermoacoustic Cooling for Low-Power Handheld Electronic Devices

[+] Author and Article Information
Jangwoo Kim

Samsung Electronics,
Kiheung, South Korea
e-mail: jangwooo@gmail.com

Paul I. Ro

Mechanical and Aerospace Engineering
Department,
North Carolina State University,
Raleigh, NC 27695-7910
e-mail: ro@ncsu.edu

Contributed by the Heat Transfer Division of ASME for publication in the JOURNAL OF THERMAL SCIENCE AND ENGINEERING APPLICATIONS. Manuscript received May 31, 2013; final manuscript received December 1, 2014; published online January 13, 2015. Assoc. Editor: Mehmet Arik.

J. Thermal Sci. Eng. Appl 7(2), 021001 (Jun 01, 2015) (9 pages) Paper No: TSEA-13-1094; doi: 10.1115/1.4029351 History: Received May 31, 2013; Revised December 01, 2014; Online January 13, 2015

A feasibility study on developing a small-scale thermoacoustic cooler based on form and size factors for a typical cell phone is presented. First, an approximate analytical model for the temperature difference was derived using the linear theory of thermoacoustics. Cooling performance could be reasonably predicted with the analytical model proposed in this study. Air and helium as the working gases and the operating frequencies of 3 kHz for air and 9.2 kHz for helium are considered within the scope of typical cell phone configurations. A stack as a core of thermoacoustic cooler is designed to accomplish the most effective performance based on normalized parameters. For the 57 mm thermoacoustic cooler operating at 3 kHz with air, the maximum temperature difference of 23.13 °C across the stack in the resonance cavity is achieved with a drive ratio of 2% with air as the medium and Mylar as a stack material. This temperature difference varies depending on the stack placement along the length of the resonance cavity, but the maximum difference was achieved when the center of stack is placed at around 7 mm away from the driver end. The drive ratio, which is proportional to the power required to produce the thermoacoustic effect, is shown to be directly related to the cooling performance achieved by thermoacoustic drivers. For example, while a drive ratio of 2% results in a temperature difference of over 20 °C at its maximum, a drive ratio of 0.2% causes a temperature difference less than 1 °C. This will be one of hardware issues to be considered in making commercially viable products. The possibility of omitting heat exchangers in the thermoacoustic cooler is investigated considering their manufacturing cost and the relatively minute improvement they bring to overall cooling for small-scale systems. The numerical result of the thermoacoustic cooling system based on design environment for low-amplitude thermoacoustic energy conversion (DeltaEC) is compared to the theoretical result. Discrepancies between the two results exist in the range of 10–15% mainly due to the limitation imposed by short stack considerations and the linear theory of thermoacoustics.

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References

Figures

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Fig. 1

A typical thermoacoustic cooler and basic thermoacoustic cooling procedures

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Fig. 2

A schematic view of the stack

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Fig. 3

Temperature differences between the hot and cold sides of the resonance cavity with Mylar for air at the frequency of 3 kHz plotted versus the stack center position along the length of the resonance cavity for different analytical formulations. The initial temperature of air was 323.15 K.

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Fig. 4

A schematic of small-scale thermoacoustic cooler for a cell phone with air as a working gas. A speaker operating at 3 kHz results in a resonance cavity length of 57 mm.

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Fig. 5

A simple DeltaEC model with heat exchangers for thermoacoustic cooling

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Fig. 6

Temperature differences between the hot and cold sides of the resonance cavity with Mylar and Celcor for air and helium plotted versus the stack center position along the length of the resonance cavity

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Fig. 7

Temperature differences between the hot and cold sides of the resonance cavity with Mylar for air under various drive ratios plotted versus the stack center position along the length of the resonance cavity

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Fig. 8

Temperature differences between the hot and cold sides of the resonance cavity with Mylar for air in cases of without heat exchangers and with heat exchangers plotted versus the stack center position along the length of the resonance cavity

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Fig. 9

Temperature differences between the hot and cold sides of the resonance cavity with Mylar for air plotted versus the stack center position along the length of the resonance cavity for comparison between analytical and numerical results

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