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Research Papers: Forced Convection

Fast Heating Induced Thermoacoustic Waves in Supercritical Fluids: Experimental and Numerical Studies

[+] Author and Article Information
Bakhtier Farouk

e-mail: bfarouk@coe.drexel.edu
Mechanical Engineering and Mechanics,
Drexel University,
Philadelphia, PA 19104

1Corresponding author.

Contributed by the Heat Transfer Division of ASME for publication in the Journal of Heat Transfer. Manuscript received May 17, 2012; final manuscript received March 17, 2013; published online July 11, 2013. Assoc. Editor: Robert D. Tzou.

J. Heat Transfer 135(8), 081701 (Jul 11, 2013) (12 pages) Paper No: HT-12-1229; doi: 10.1115/1.4024066 History: Received May 17, 2012; Revised March 17, 2013

Thermoacoustic waves in near-critical supercritical carbon dioxide are investigated experimentally on acoustic time scales using a fast electrical heating system along with high speed pressure measurements. Supercritical carbon dioxide (near the critical or the pseudocritical states) in an enclosure is subjected to fast boundary heating with a thin nickel foil and an R-C circuit. The combination of very high thermal compressibilities and vanishingly small thermal diffusivities of the near-critical fluid affect the thermal energy propagation, leading to the formation of acoustic waves as carriers of thermal energy (the so called piston effect). The experimental results show that under the same temperature perturbation at the boundary, the strength of the acoustic field is enhanced as the initial state of the supercritical fluid approaches criticality. The heating rate, at which the boundary temperature is raised, is a key factor in the generation of these acoustic waves. The effect of different rates of boundary heating on the acoustic wave formation mechanism near the critical point is studied. The thermoacoustic wave generation and propagation in near-critical supercritical fluid is also investigated numerically and compared with the experimental measurements. The numerical predictions show a good agreement with the experimental data.

Copyright © 2013 by ASME
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Figures

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Fig. 1

The p-v diagram for carbon dioxide

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Fig. 2

Variation of density, ρ and thermal diffusivity, α (inset) as functions of pressure and temperature for near-critical carbon dioxide [28]

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Fig. 3

(a) Schematic diagram of the experimental setup. Inset: Detailed schematic of the B&K microphone. (b) PTFE tubing with end piece and (c) Detailed view of the PTFE end piece with Ni thin-foil.

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Fig. 4

Electronic schematic of the foil heating circuit

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Fig. 5

Schematic diagram of the computational domain

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Fig. 6

Temporal variation of (a) voltage drop across the foil and (b) corresponding foil temperature (measured) with pi = 7.653 MPa (1110 psi), Ti = 315 K and V0 = 30 V

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Fig. 7

Temporal variation of pressure measured at the center of the cell by B&K microphone with pi = 7.653 MPa (1110 psi), Ti = 315 K and V0 = 30 V at (a) early time and (b) long time

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Fig. 8

Temporal variation of pressure measured at the center of the cell by B&K microphone (filtered) with Ti = 315 K, V0 = 30 K and at various initial pressures at (a) early time and (b) long time

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Fig. 9

Temporal variation of pressure measured at the center of the cell by B&K microphone (filtered) with pi = 7.515 MPa (1090 psi), V0 = 30 K and at various initial temperatures at (a) early time and (b) long time

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Fig. 10

Temporal variation of (a) voltage drops across the foil and (b) foil temperatures for different charging voltages

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Fig. 11

Temporal variation of pressure measured at the center of the cell by B&K microphone (filtered) with π = 7.515 MPa (1090 psi), Ti = 306 K and at various charging voltages at (a) early time and (b) long time

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Fig. 12

Measured foil voltage and calculated foil temperature at early times with V0 = 30 V

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Fig. 13

Measured, calculated and extrapolation of measured foil temperature with V0 = 30 V

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Fig. 14

Temporal variation of measured and calculated pressure at the center of the cell with pi = 7.515 MPa (1090 psi) and Ti = 306 K at early time

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Fig. 15

Temporal variation of measured and calculated pressure at the center of the cell with pi = 7.515 MPa (1090 psi) and Ti = 306 K at long time

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