Development and Application of Fiber Optic-Based Thermal Wave Resonant Cavity Technique for Measurement of Thermal Diffusivity of Liquids
In the study a thermal wave resonant cavity technique (TWRC) was set up and was used to measure thermal diffusivity of various types of liquids. In this technique the thermal diffusivity was determined by scanning the cavity length, instead of frequency, that has a high signal-to-noise ratio in t...
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| Format: | Thesis |
| Language: | English English |
| Published: |
2007
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| Subjects: | |
| Online Access: | http://psasir.upm.edu.my/id/eprint/5023/1/FS_2007_31.pdf |
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| Summary: | In the study a thermal wave resonant cavity technique (TWRC) was set up and was
used to measure thermal diffusivity of various types of liquids. In this technique the
thermal diffusivity was determined by scanning the cavity length, instead of
frequency, that has a high signal-to-noise ratio in thermally thick case.
By using metal foil that attached to a tube as the thermal wave (TW) generator the
calibration of the conventional TWRC set up was done on distilled water and the
thermal diffusivity value, i.e. 1.44×10-3 cm2/s, agrees with literature value. Further, a
few liquids thermal diffusivity, including crude palm (0.988×10-3 cm2/s), soy bean
(1.06×10-3 cm2/s), corn oil (0.934×10-3 cm2/s), were determine by using this set up.
In this set up the TW is enough to be regarded as rays reflecting and transmitting in
cavity. Later the metalized optical fiber tip was used to generate TW instead of metal foil
attached to a tube as in the case of conventional TWRC technique. A polymer optical
fiber tip or free end coated with silver conductive paint was used to generate TW, by
moving this tip with respect to detector and the liquid thermal diffusivity was
obtained in a thermally thick region. The thermal diffusivity of distilled water,
glycerol, and five different types of cooking oil used which are sunflower, soy bean,
olive, corn and palm oils were determined with four-significant-figure at room
temperature. These values are in good agreement to the values reported in literatures.
The TW field was calculated in a three-dimensional approach. The calculations show
that the dimensionality of the TW field in the cavity depends on the lateral (radial)
heat transfer boundary conditions and the relation between the laser beam spot size
and TW generator diameter. The three-dimensional treatment of the metalised fiber
tip was reduced to one-dimensional treatment by using a relatively bigger TW
generator diameter compared to laser beam spot size.
The set up using optical fiber end also was used to determine thermal diffusivity of a
two-layer which is normally difficult to achieve in the conventional large area metal
foil due to contact problem. In order to check the validity of the proposed model, the
method was experimentally tested for distilled water and glycerol; the values
obtained were close to the literature values. A good linear relation of the amplitude
with respect to cavity length in thermally thick region of both media was observed.
In other TWRC methods the thermal diffusivity values can be obtained by measuring
the relative distance of two adjacent extrema. The thermal diffusivity values were
obtained by this method compare with “fitting data” method. |
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