Research Papers: Experimental Techniques

A Monochrome Light-Emitting Diode Moiré Deflectometry Technique for Two-Dimensional Temperature Measurement

[+] Author and Article Information
Jing-Nang Lee

Department of Refrigeration,
Air Conditioning and Energy Engineering,
National Chin-Yi University of Technology,
Taichung 41170, Taiwan
e-mail: jnl@ncut.edu.tw

Chien-Chih Chen

Graduate Institute of Mechanical
and Electrical Engineering,
National Taipei University of Technology,
Taipei 10608, Taiwan
e-mail: t8669030@ntut.edu.tw

Contributed by the Heat Transfer Division of ASME for publication in the JOURNAL OF HEAT TRANSFER. Manuscript received August 5, 2013; final manuscript received July 1, 2014; published online July 29, 2014. Assoc. Editor: Cila Herman.

J. Heat Transfer 136(10), 101601 (Jul 29, 2014) (7 pages) Paper No: HT-13-1394; doi: 10.1115/1.4027978 History: Received August 05, 2013; Revised July 01, 2014

This article develops low cost moiré deflectometry for two-dimensional temperature measurement in free boundary environment. Experimental setup uses a red monochrome light-emitting diode (LED) lamp with wavelength range of 625–635 nm as light source. In process, the light first runs through the convex lens and then propagates to the parabolic mirror with diameter of 406 mm and f/4.5 for generating the parallel light. The parallel light further propagates to test object and through two gratings both with pitch of 254 lpi which are printed by laser printer. Behind the two gratings, a CCD camera is applied to capture the image, the distorted fringes. Based on the moiré deflectometry theory, the two-dimensional temperature distribution in free boundary environment can be determined in terms of the captured fringe shift analysis. This work has successfully measured the two-dimensional temperature distribution in free boundary environment with heat source models of 40–95 °C vertical wall, 60 W light bulb, and burning candle flame. The measured temperature deviations between moiré deflectometry and thermocouple thermometer are all less than 5%.

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Fig. 1

Schematic illustration for the conventional arrangement of moiré deflectometry

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Fig. 3

Moiré deflectometry setup. (a) Schematics of the moiré deflectometry setup and (b) photo of the moiré deflectometry setup.

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Fig. 4

Moiré gratings and holders. (a) Schematics of the gratings and holders and (b) photo of the gratings and holders.

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Fig. 5

Monochrome LED lamp selection. (a) Photo of the LEDs color and (b) spectrum of the LEDs.

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Fig. 6

Original moiré fringes photos with different background color. (a) White, (b) red, (c) green, (d) blue, and (e) yellow (see color online).

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Fig. 7

Color decomposed photos of moiré fringes. (a) Red, (b) green, (c) blue, and (d) yellow (see color online).

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Fig. 8

Intensity of moiré fringes

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Fig. 9

Image processing. (a) Raw, (b) gray level, (c) white-black, and (d) skeleton centerline.

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Fig. 10

Photos of the test objects. (a) Vertical wall, (b) bulb, and (c) burning candle.

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Fig. 11

Moiré fringes pattern without heating

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Fig. 12

Moiré fringes pattern with heating. (a) Heated in 40 °C, (b) heated in 70 °C, and (c) heated in 95 °C.

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Fig. 13

The measured temperature distribution in comparison with theory

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Fig. 14

Temperature comparison between moiré deflectometry and thermocouple thermometer

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Fig. 15

Color schlieren photo and two-dimensional temperature distribution of the switched on incandescent bulb. (a) Color schlieren photo and (b) two-dimensional temperature distribution.

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Fig. 16

Half horizontal line temperature distribution starting at the top of the bulb

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Fig. 17

Color schlieren photo and two-dimensional temperature distribution. (a) Color schlieren photo and (b) two- dimensional temperature distribution.




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