Simple TWRC technique by using optical fiber

Abstract

The metalized optical fiber tip was used to generate thermal wave instead of metal foil attached to a tube as in the case of conventional thermal wave resonance cavity (TWRC) technique. The liquid thermal diffusivity was obtained through scanning the cavity length by moving this tip with respect to pyroelectric detector in liquid media, in a thermally thick region. Three-dimensional treatment of the metalized fiber tip was reduced to one-dimensional treatment using diameter of thermal wave generator relatively bigger than that of laser spot size. This applicability can be seen in two diameter size of optical fiber where the thermal diffusivity value of water obtained by this technique agrees with the values obtained by the conventional TWRC technique. This technique has a potential to be used in measuring thermal diffusivity of small liquid volume.

Optical-fiber thermal-wave-cavity technique to study thermal properties of silver/clay nanofluids

“…The principle and procedures of the PPE method, named the OF-TWC technique, have been described elsewhere [15,16]. Matvienko and Mandelis (2006) [17] reduced the three-dimensional model of the OF-TWC technique to a onedimensional model by using a thermal wave generator with a larger diameter than that of the laser spot size.…”

“…Our experimental method has been reported in detail elsewhere [15,16]. Briefly, as shown in Figure 1, a 200-mW CW diode-pumped solid-state laser [MGL 150 (10)] was modulated to 6.8 Hz by using an optical chopper (SR540); this frequency is considered optimal in our system for thermally thick samples, both for detection and SNR at a satisfactory signal amplitude.…”

“…The major advantage of cavity length scan is fixed the modulated frequency, which improves the signal-to-noise ratio (SNR). In a previous work [15], we developed the optical-fiber-based TWC (OF-TWC) technique, which has many advantages over the traditional TWC technique, including its high sensitivity in PE signal, simple operation, and low cost; it is especially advantageous because of the smaller sample volume it requires, while, the measurement time can be significantly shorter [16].…”

The reliability of optical fiber-TWRC technique in liquids thermal diffusivity measurement

“…In the OF-TWRC technique, the TW propagates in the cavity which consists of two parallel walls; the metalized optical fiber tip surface, which acts as TW generator and the second one, is a pyroelectric (PE) transducer. Smaller diameter optical fibers have found to produce smaller PE signal compared to that of bigger one [5]. This technique has several advantages, among others are; it can be used to measure thermal diffusivity in a small liquid volume, the arrangement TW generator-PE detector can be made not necessarily in vertical position as the laser beam always follows and illuminates the optical fiber metalized surface, and thirdly if one deals with two layers of non-mixing fluid, e.g.…”

“…The latest TWRC simplification the metal foil was entirely removed and the TW now is generated by a metalized optical fiber tip and the set-up is known as an optical fiber-TWRC technique or shortly as OF-TWRC technique [5]. In this set-up the optical fiber was used to guide the light beam as well as to produce TW in the fluid sample.…”