An industrial reference fluid for moderately high viscosity

In industrial practice, there is a demand for a reference standard for viscosity that is established for a readily available fluid to simplify the calibration of industrial viscometers for moderately high viscosities [(50 to 125) mPa · s]. Diisodecyl phthalate (DIDP) has been suggested as that reference fluid, and a number of studies of its properties have been carried out in several laboratories throughout the world, within the auspices of a project coordinated by the International Association for Transport Properties. That project has now progressed to the point where it is possible to collate the results of studies of the viscosity of the fluid by a number of different techniques, so as to lead to a proposed standard reference value which will be included in the paper. To support this recommended value, the various measurements conducted have been critically reviewed, and the sample purity and other factors affecting the viscosity have been studied. Density and surface tension measurements have also been performed. This paper does not describe the individual viscosity determinations carried out in independent laboratories because these are the subject of individual publications, but it does describe the ancillary studies conducted and their relevance to the viscosity standard. In addition, the paper contains recommended values for the viscosity of liquid DIDP. The samples of DIDP to which the recommended values refer are isomeric mixtures available commercially from certain suppliers, with a minimum purity by gas chromatography of 99.8 %. The recommended values result from a critical examination of all the measurements conducted to date and are supported by careful arguments dealing with the likely effects of the isomeric content of the sample as well as of other impurities. The proposed reference standard is intended particularly to serve an industrial need for a readily available calibration material with a viscosity close to that required in practical situations. To that end, the recommended value has an overall relative uncertainty of approximately 1 %. It is therefore not intended to supersede for the reference value for the viscosity of water at 20 °C, which is known much more accurately, but rather to complement it

Temperaturbestimmung in Gasen mittels linearer und nichtlinearer Raman-Prozesse

SIGLETIB: DP 5128 / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

ROTATIONAL COHERENT ANTI-STOKES RAMAN SCATTERING FOR COMBUSTION RESEARCH

Coherent Anti-Stokes Raman Scattering (CARS) has been used extensively as a diagnostic technique for temperature measurements in combustion system, in general by employing the relative intensities of the vibrational band of the investigated gas species (mostly N2). Pure rotational CARS is superior to vibrational CARS for thermometry near room temperature, since the spectra are easily resolvable compared with the congestion of the rotational lines in the vibrational bands of the Q-branch spectra. The rotational Raman cross section for rotational CARS is larger than tlie vibrational CARS cross section and the Raman linewidth is more narrow for rotational CARS than for vibrational CARS, both tending to give a higher rotational CARS intensity. On the other hand, rotational CARS intensities are substantially reduced at higher temperatures, and in technical flames an interference of CARS contributions in the rotational spectra of different gas molecules present may complicate a temperature and concentration evaluation. The difficulty in separating these different contributions may be overcome by using Fourier analysis, which also can be used simultaneously for data reduction. Applying this technique to calculated pure and noisy rotational CARS spectra and also to experimentally obtained ones, temperature and concentration, determination is demonstrated for simple flames

A SIGNAL ENHANCED PORTABLE RAMAN PROBE FOR ANESTHETIC GAS MONITORING

The spontaneous Raman scattering technique is an excellent tool for a quantitative analysis of multi-species gas mixtures. It is a noninvasive optical method for species identification and gas phase concentration measurement of all Raman active molecules, since the intensity of the species specific Raman signal is linearly dependent on the concentration. Applying a continuous wave (CW) laser it typically takes a few seconds to capture a gas phase Raman spectrum at room temperature. Nevertheless in contrast to these advantages the weak Raman signal intensity is a major drawback. Thus, it is still challenging to detect gas phase Raman spectra in alow-pressure regime with a temporal resolution of only a few 100 ms. In this work a fully functional gas phase Raman system for measurements in the low-pressure regime (p ≥ 980 hPa (absolute)) is presented. It overcomes the drawback of a weak Raman signal by using a multipass cavity. A description of the sensor setup and of the multipass arrangement will be presented. Moreover the complete functionality of the sensor system will be demonstrated by measurements at an anesthesia simulator under clinical relevant conditions and in comparison to a conventional gas monitor