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Research Papers: Two-Phase Flow and Heat Transfer

Microchannel Two-Phase Flow Oscillation Control With an Adjustable Inlet Orifice

[+] Author and Article Information
Brent A. Odom

e-mail: brentodom@hotmail.com

Patrick E. Phelan

School for Engineering of Matter,
Transport, and Energy,
Arizona State University,
Engineering G-Wing,
501 E. Tyler Mall,
Tempe, AZ 85281

Contributed by the Heat Transfer Division of ASME for publication in the JOURNAL OF HEAT TRANSFER. Manuscript received September 7, 2011; final manuscript received July 3, 2012; published online October 5, 2012. Assoc. Editor: W. Q. Tao.

J. Heat Transfer 134(12), 122901 (Oct 05, 2012) (8 pages) doi:10.1115/1.4007202 History: Received September 07, 2011; Revised July 03, 2012

This work describes the experimental setup, method, and results of utilizing a micrometer to move an adjustable orifice immediately in front of an array of microchannels. Research by others indicates potential for significant improvement in delaying critical heat flux and increasing heat transfer coefficients when placing an orifice in front of each individual channel of a microchannel array. The experimental setup in this work allows incremental orifice size changes. This ability allows the experimentalist to find which orifice size provides enough pressure drop immediately in front of the channels to reduce oscillations. The design also allows for rapid change of orifice size without having to remove and replace any components of the test setup. Signal analysis methods were used to identify frequency and amplitude of pressure and temperature oscillations. Low mass flux experiments (300 kg m−2 s−1 and 600 kg m−2 s−1 of R134a in a pumped loop) showed reduced channel wall temperatures with smaller orifice sizes. The orifice concept was found to be effective at reducing oscillations for the higher 600 kg m−2 s−1 flow rate, but the data indicate that wall temperature reduction with inlet orifice use is not solely due to elimination of oscillations. Signal analysis was an effective method of identifying oscillations without the availability of pictorial representation of flow patterns in the channels.

Copyright © 2012 by ASME
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References

Figures

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Fig. 1

Cooling loop schematic

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Fig. 2

Adjustable orifice concept sketch (not to scale)

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Fig. 3

Micrometer and steel plate (a), cover and dam (b), top block (c), microchannels (d), dam (e), assembly (f), copper heating block (g)

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Fig. 4

Average of 2 min of data for different orifice sizes under steady-state conditions, 300 kg m-2 s-1 mass flux, and heat flux = 178 W cm-2

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Fig. 5

Average of 2 min of data for different orifice sizes under steady-state conditions, 600 kg m-2 s-1 mass flux, and heat flux = 337 W cm-2

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Fig.  6

Representative time domain comparison for 300 kg m-2 s-1 mass flux

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Fig.  7

Representative time domain comparison for 600 kg m-2 s-1 mass flux

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Fig. 8

Inlet pressure FFT results, 300 kg m-2 s-1 mass flux, heat flux = 178 W cm-2

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Fig. 9

Outlet wall temperature FFT results, 300 kg m-2 s-1 mass flux, heat flux = 178 W cm-2

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Fig. 10

Inlet wall temperature FFT results, 300 kg m-2 s-1 mass flux, heat flux = 178 W cm-2

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Fig. 11

Inlet pressure FFT results, 600 kg m-2 s-1 mass flux, heat flux = 337 W cm-2

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Fig. 12

Outlet wall temperature FFT results, 600 kg m-2 s-1 mass flux, heat flux = 337 W cm-2

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Fig. 13

Inlet wall temperature FFT results, 600 kg m-2 s-1 mass flux, heat flux = 337 W cm-2

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Fig. 14

Average of 2 min of data for different orifice sizes, steady-state conditions, 300 kg m-2 s-1 mass flux, and heat flux = 178 W cm-2. Both inlet and outlet conditions were a saturated liquid–vapor mixture.

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Fig. 15

Average of 2 min of data for different orifice sizes, steady-state conditions, 600 kg m-2 s-1 mass flux, and heat flux = 337 W cm-2. Inlet conditions were slightly subcooled while outlet conditions were a saturated liquid–vapor mixture.

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