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TECHNICAL PAPERS: Microscale Heat Transfer

Thermal-Fluid Phenomena Induced by Nanosecond-Pulse Heating of Materials in Water

[+] Author and Article Information
I. Ueno, M. Shoji

Department of Mechanical Engineering, The University of Tokyo, 7-3-1-Hongo, Bunkyo-Ku, Tokyo 113-8658, Japan

J. Heat Transfer 123(6), 1123-1132 (Apr 27, 2001) (10 pages) doi:10.1115/1.1409264 History: Received May 07, 1999; Revised April 27, 2001
Copyright © 2001 by ASME
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Figures

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Schematic layout of experimental apparatus for nanosecond-pulse heating of materials. Pressure transducer is omitted in the figure for the sake of brevity (see Fig. 2).
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(a) Schematic layout of PVDF pressure transducer; and (b) typical result of the pressure decay in propagation.
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Bubble formation and shock wave generation/propagation in heating with (i) F=1.4×103 mJ/cm2 (on the left hand side) and (ii) F=2.0×102 mJ/cm2 (on the right) taken with frame speeds of (a) 40,000 fps [exposure time: 150 ns], (b) 1,000,000 fps [150 ns], and (c) 4,000,000 fps [100 ns] in the system of ΔHg=10 mm and ΔH2O=50 mm. All photographs were taken with a little depression angle as shown schematically in (iii). (iv) The image captured in each frame.
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Experimental results of pressure values Pmax and the prediction of the generated pressure Pth obtained by applying the physical model 17 to this experimental system. Experimental results of (tpeak−trise) and the numerical result of assumed nucleation time tHN*, as shown in Fig. 10 are also shown. In addition, calculated superheated layer thickness of water δt* when the surface temperature reaches THN of water is indicated.
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Generated pressure variations upon pump laser fluence F in Hg-water system in different Hg layer thicknesses. Plotted values are equivalent to the extrapolated pressure values measured at the surface. Solid line in the figure indicates the prediction of the pressure generation in heating of Hg in water 17.
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Mercury surface heating (i) in the water (on the left hand side) and (ii) in the air (on the right) taken with frame speeds of (a) 10,000 fps [exposure time: 150 ns], and (b) 2,000,000 fps [150 ns]. Pump laser fluence F=1.4×103 mJ/cm2 for both cases.
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Shock wave generation/propagation in heating of Si of 0.6 mm in thickness with F=2.0×102 mJ/cm2 (i) in the water (on the left hand side) and (ii) in the air (on the right), taken with frame speeds of (a) 10,000,000 fps [exposure time: 20 ns] (top), and (b) 20,000,000 fps [10 ns] (middle). All photographs were taken with an angle parallel to the Si surface as shown schematically in (iii). (iv) The schematic image captured in each frame.
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Shock wave generation/propagation and Si vaporization in heating of Si (i) in the water (on the left hand side) and (ii) in the air (on the right) with the pump laser fluence F=(a)3.8×102 mJ/cm2 (top), and (b) 7.1×102 mJ/cm2 (middle) taken with a frame speed of 20,000,000 fps [exposure time: 10 ns]. Arrows in (i)–(a) and (i)–(b) indicate the generated shock waves and those in (ii)–(a) and (ii)–(b) indicate the Si vapor, respectively. In (ii)–(b2) the later stage of induced phenomenon in the same case of (ii)–(b) Si-air system is shown. Arrow indicates the shock wave. All photographs were taken with an angle parallel to the heated Si surface.
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(a) Time-resolved reflectance (TRR) signals (top and middle) of probe laser in the case of heating with F=5.1×102 mJ/cm2. Top curve and the middle indicate the cases of Si-air system and of Si-water system, respectively. The bottom shows the pump-laser light profile. (b) Detail of reflectance signals as shown in (a). Noted that TRR signal detected in the Si-air system is offset to coincide with the initial intensity in the Si-water system for the sake of convenience for comparison.
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(a) Schematic of time lags due to the light travels along the paths of pump laser and probe laser and time lags due to photo detectors. d1 and d2 indicate the distances between pump detector and test material surface, and between probe detector and test material surface, respectively. ΔA and ΔB indicate time lags involved in pump detector and probe detector, respectively. (b) Estimation of time lags involved in the measuring system. tA(=d1/c) and tB(=d2/c) are equivalent to flight time along d1 and d2, respectively.
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Variations of trise (time when TRR signal rises), tpeak (time when TRR signal reaches maximum), tpeak−trise and time lag (ΔB−ΔA)+(tA+tB) lied in the measuring system as shown in Fig. 9 in the Si-water system.
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Nucleation threshold temperatures THN,12 and THN,22 obtained from the conventional thermodynamics, the theoretical nucleation temperature TNu,Asai derived from heterogeneous nucleation theory in the field with temperature distribution by Asai 23, the corresponding nucleation times tHN* and tNu,Asai variations in the case of Si-water system, and the measured value of (tpeak−trise) versus pump laser fluence F. Nucleation time tHN* indicates the time when Si surface temperature reaches THN,12 in the one-dimensional heat conduction problem.

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