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Mar 2002

Volume 73, Issue 3, pp. 1103-1683

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back to top GENERAL INSTRUMENTS

Photothermal device for water dynamics measurement and thermophysical characterization: Application on textile samples

T. Duvaut, A. Limare, and J. M. Bachmann

Rev. Sci. Instrum. 73, 1299 (2002); http://dx.doi.org/10.1063/1.1448902 (5 pages) | Cited 2 times

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The photopyroelectric method in a noncontact configuration (excitation source: diode laser at 1.94 μm) is capable of yielding information on the water content of a textile sample and on its influence on the thermal properties. A one-dimensional theoretical model was developed assuming the sample thermally homogeneous and taking into account the optical absorption and scattering. The experimental setup designed for this purpose included an excitation source resonant with water absorption, signal and data processing units and cells for conditioning the samples. We optimized the experimental conditions in order to identify the parameters related to the water content in the sample, and to monitor the dynamics of the process. The effective thermal conductivity and the volume specific heat were determined at different moments of time while the sample was taking up water. Two thermal parameters related to the comfort of a fabric were also calculated: the thermal effusivity and the thermal resistance. © 2002 American Institute of Physics.
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07.07.Vx Hygrometers; hygrometry
85.50.-n Dielectric, ferroelectric, and piezoelectric devices

Differential microcalorimeter for isothermal measurements of heat effects in two-phase systems and examples of its application

Victor E. Ostrovskii

Rev. Sci. Instrum. 73, 1304 (2002); http://dx.doi.org/10.1063/1.1448911 (9 pages) | Cited 8 times

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A differential heat-conducting double microcalorimeter intended for heat measurements at 300–700 K is described. Platinum resistance thermometers are applied as the heat-flux sensors. The calorimeter is a low-noise instrument with the baseline fluctuations ranging up to 0.02×10−6 V (5×10−6 W); it allows measurements of the heat effects with an error of 1%–1.5% at a recorded scale of about 1×10−2 J/cm2. The design features and the method of the heat-flux transformation to the electric signals, the calorimetric ampoules for measurements and for calibration and the calibrating device, the heat-balance equation and the equation for the temperature dependence of the calorimetric sensitivity, the results of the calibration and the verification of the calorimeter, and a number of illustrative examples of calorimetric measurements are presented. The calorimeters are applicable for studying solid–gas, solid–liquid, and liquid–gas interactions and thermophysical characteristics of solids and liquids. © 2002 American Institute of Physics.
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07.20.Fw Calorimeters
07.20.Dt Thermometers

Automated constant voltage anemometer for measurements with fluid temperature drifts

Garimella R. Sarma and Geneviève Comte-Bellot

Rev. Sci. Instrum. 73, 1313 (2002); http://dx.doi.org/10.1063/1.1447303 (5 pages) | Cited 8 times

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An automated procedure has been developed for a constant voltage anemometer to obtain in situ heated and cold resistances of a hot wire in each measurement cycle. From these parameters mean velocity can be deduced in the presence of ambient flow temperature variations, using a calibration curve based on, e.g., King’s law with the assumption of constant coefficients over a given temperature range. The method requires only one hot wire. This is a definite advantage over previous methods established for constant current or constant temperature anemometers where an additional temperature sensor is needed, with a separate temperature calibration of the hot wire. Results from a typical test are presented to demonstrate the procedure. The prototype tested was a 400 kHz bandwidth unit and the measurement cycle can be changed through software commands to suit each test requirements. © 2002 American Institute of Physics.
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06.30.Gv Velocity, acceleration, and rotation
47.80.-v Instrumentation and measurement methods in fluid dynamics
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