Application of the thermal wave resonator to the measurement of the thermal diffusivity of gas mixtures

Lima, J. A. P.; Marı́n, E.; Silva, M. G. da; Sthel, Marcelo Silva; Cardoso, Simone C.; Vargas, H.; Miranda, L. C. M.

doi:10.1063/1.1334622

Cited by 22 publications

(19 citation statements)

References 4 publications

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“…The signal components due to CO 2 deactivation and CO 2 -N 2 energy transfer are separately shown together with their superposition. 18)]. In particular, CO 2 (001) molecules are responsible for promoting N 2 molecules to the first vibrational level just after the application of the pump.…”

Section: Discussionmentioning

confidence: 99%

Observations of laser cooling by resonant energy transfer in CO2-N2 mixtures

Liakhou

Paoloni

Bertolotti

2004

Journal of Applied Physics

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The effects produced by absorption of an intensity modulated CO2 laser in CO2-N2 mixture are investigated here by means of the photothermal deflection technique. The deflection signal arises from CO2 molecule deactivation and energy transfer from CO2 to N2 molecules, which are responsible for heating and cooling the mixture, respectively. The dominant mechanism is determined by the pressure of the gas mixture, which, in turn, affects the CO2 molecule lifetime. A theoretical model based on rate equations for the CO2-N2 system is presented, in which the deflection signal is given as a function of the excited molecule populations. The theoretical predictions are shown to be in reasonable agreement with the experimental results.

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Section: Discussionmentioning

confidence: 99%

Observations of laser cooling by resonant energy transfer in CO2-N2 mixtures

Liakhou

Paoloni

Bertolotti

2004

Journal of Applied Physics

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“…The pyroelectric sensor ͑usually polyvinilidene fluoride film, PVDF͒ converts the thermal waves into a voltage signal, which can be measured and recorded by a lock-in amplifier. This configuration has been widely used to measure thermal diffusivity of gases [1][2][3][4][5] and liquids. [6][7][8][9][10] Several other versions of the original configuration were then introduced in litera-ture.…”

Section: Introductionmentioning

confidence: 99%

Optimally accurate thermal-wave cavity photopyroelectric measurements of pressure-dependent thermophysical properties of air: Theory and experiments

Kwan

Matvienko

Mandelis

2007

Review of Scientific Instruments

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An experimental technique for the measurement of thermal properties of air at low pressures using a photopyroelectric (PPE) thermal-wave cavity (TWC) was developed. In addition, two theoretical approaches, a conventional one-dimensional thermal-wave model and a three-dimensional theory based on the Hankel integral, were applied to interpret the thermal-wave field in the thermal-wave cavity. The importance of radiation heat transfer mechanisms in a TWC was also investigated. Radiation components were added to the purely conductive model by linearizing the radiation heat transfer component at the cavity boundary. The experimental results indicate that the three-dimensional model is necessary to describe the PPE signal, especially at low frequencies where thermal diffusion length is large and sideways propagation of the thermal-wave field becomes significant. Radiation is found to be the dominant contributor of the PPE signal at high frequencies and large cavity lengths, where heat conduction across the TWC length is relatively weak. The three-dimensional theory and the Downhill Simplex algorithm were used to fit the experimental data and extract the thermal diffusivity of air and the heat transfer coefficient in a wide range of pressures from 760 to 2.6 Torr. It was shown that judicious adjustments of cavity length and computational best fits to frequency-scanned data using three-dimensional photopyroelectric theory lead to optimally accurate value measurements of thermal diffusivity and heat transfer coefficient at various pressures.

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“…As discussed in previous papers, [16][17][18] the method consists of measuring the temperature fluctuation of sensor 2 as a function of the TWI gas layer thickness. To this end, sensor 2 is assembled on a micrometer stage coupled to a computercontrolled stepping motor so that the cavity length can be varied.…”

Section: Experimental Procedures and Methodsmentioning

confidence: 99%

“…The TWI experimental setup has been discussed in detail elsewhere, − and it is schematically shown in Figure . It consists of a temperature-controlled closed glass cell in which the TWI cavity is enclosed.…”

Section: Experimental Procedures and Methodsmentioning

confidence: 99%

“…The temperature rise at the sensor 2 surface, which results from the superposition of all arriving waves, is probed by connecting its output signal to the current input of a lock-in amplifier (EG&G model 5210) interfaced to a personal computer. As discussed in previous papers, − the method consists of measuring the temperature fluctuation of sensor 2 as a function of the TWI gas layer thickness. To this end, sensor 2 is assembled on a micrometer stage coupled to a computer-controlled stepping motor so that the cavity length can be varied.…”

Section: Experimental Procedures and Methodsmentioning

confidence: 99%

See 1 more Smart Citation

Thermal Diffusivity as an Automotive Fuel Characterization Parameter: Correlation with Motor Octane Number

Lima

Cardoso

Silva

et al. 2001

Ind. Eng. Chem. Res.

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The standard method for evaluating the quality of automotive fuels is based on the determination of its motor octane number (MON) using the ASTM motor testing. The resulting figures of merit of this standard testing are known to be strongly linearly correlated to the fuels' vapor thermodynamic properties such as, for instance, their vapor pressure. In this paper we explore this strong correlation between the MON parameter and the fuels' vapor thermal properties to seek the development of an alternative low-cost method. The proposed method is based upon the photothermal measurement of the thermal diffusivity of the fuels' vapor in a closed air cell. It is found that the thermal diffusivity is well correlated with the corresponding MON values of the fuels investigated. The eventual improvements of the proposed method aimed at gaining accuracy and developing a portable device for field applications are also discussed.

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Application of the thermal wave resonator to the measurement of the thermal diffusivity of gas mixtures

Cited by 22 publications

References 4 publications

Observations of laser cooling by resonant energy transfer in CO2-N2 mixtures

Observations of laser cooling by resonant energy transfer in CO2-N2 mixtures

Optimally accurate thermal-wave cavity photopyroelectric measurements of pressure-dependent thermophysical properties of air: Theory and experiments

Thermal Diffusivity as an Automotive Fuel Characterization Parameter: Correlation with Motor Octane Number

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