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Research Papers

Oscillating Heat Transfer Correlations for Spiral-Coil Thermoacoustic Heat Exchangers

[+] Author and Article Information
Kriengkrai Assawamartbunlue

Assistant Professor
Energy Technology Research Laboratory,
Mechanical Engineering Department,
Kasetsart University,
50 Ngamwongwan Road, Ladyao,
Jatujak, Bangkok 10900, Thailand
e-mail: fengkka@ku.ac.th

Channarong Wantha

Agricultural Engineering Department,
Rajamangala University of Technology Thanyaburi,
39 Moo 1, Rangsit-Nakhonnayok Road,
Thanyaburi,
Pathum Thaini 12110, Thailand
e-mail: cwantha@rmutt.ac.th

Contributed by the Heat Transfer Division of ASME for publication in the JOURNAL OF THERMAL SCIENCE AND ENGINEERING APPLICATIONS. Manuscript received December 29, 2014; final manuscript received March 11, 2015; published online April 15, 2015. Assoc. Editor: Zahid Ayub.

J. Thermal Sci. Eng. Appl 7(3), 031008 (Sep 01, 2015) (7 pages) Paper No: TSEA-14-1287; doi: 10.1115/1.4030171 History: Received December 29, 2014; Revised March 11, 2015; Online April 15, 2015

Heat exchangers are the important parts in thermoacoustic refrigerators. Types and configurations of the heat exchangers affect flow behaviors through stacks, and heat transfer behaviors between working fluids and the heat exchangers. Steady-flow heat transfer correlations to design a heat exchanger are not suitable for the thermoacoustic refrigerators due to their oscillatory flow conditions in resonator tubes. In this paper, a heat transfer correlation for a spiral-coil heat exchanger is presented. The results from the experimental study were used to develop an empirical equation between the Colburn-j factor, the Prandtl number, and the Reynolds number to correlate the oscillating heat transfer coefficient at the spiral-coil heat exchangers. The results showed that using steady-flow heat transfer correlations for analyses and design of the heat exchanger could result in distinguished errors. The heat transfer correlations developed for oscillatory flows on fin heat exchangers are also not suitable to predict heat transfer coefficients for spiral-coil heat exchanger due to difference in flow behaviors on the heat transfer surface. For oscillatory flows, the heat transfer coefficients can be improved by using curved-liked surface such as spiral coil instead of straightlike surface such as fin coil. The relationships between the oscillating heat transfer coefficients at the heat exchangers, drive ratios, and operating frequencies are also presented. Higher drive ratios and operating frequency result in greater heat transfer coefficients.

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References

Figures

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Fig. 1

Schematic of the standing-wave thermoacoustic refrigeration system

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Fig. 2

Schematic of the spiral-coil heat exchanger and thermocouple locations (dimensions in millimeters)

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Fig. 3

Experimental setup

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Fig. 4

The proposed Colburn-j factor (jH) correlation

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Fig. 5

Predictions of the proposed correlation compared with the experimental data

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Fig. 6

Comparisons of the proposed oscillating flow heat transfer correlation with the other correlations

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Fig. 7

Nu predictions on the hot and cold heat exchangers versus ReD

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Fig. 8

Heat transfer coefficients versus operating frequencies at the cold heat exchanger

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Fig. 9

Heat transfer coefficient versus drive ratios at the cold heat exchanger

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