Temperature measurement local

Individual Coefficient of Heat Transfer Because of the comphcated structure of a turbulent flowing stream and the impracti-cabifity of measuring thicknesses of the several layers and their temperatures, the local rate of beat transfer between fluid and solid is defined by the equations... 

The laser-Doppler anemometer measures local fluid velocity from the change in frequency of radiation, between a stationary source and a receiver, due to scattering by particles along the wave path. A laser is commonly used as the source of incident illumination. The measurements are essentially independent of local temperature and pressure. This technique can be used in many different flow systems with transparent fluids containing particles whose velocity is actually measured. For a brief review or the laser-Doppler technique see Goldstein, Appl. Mech. Rev., 27, 753-760 (1974). For additional details see Durst, MeUing, and Whitelaw, Principles and Practice of Laser-Doppler Anemometry, Academic, New York, 1976. 

The temperature for methane and butane calculated with the isothermal model is a factor 1.4 times greater than the average temperature measured by Lihou and Maund (1982) in their small-scale tests, although higher local maximum temperatures were measured. In this model, combustion is stoichiometric, thus leading to very high fireball temperatures which, in turn, lead to high radiation emissions. Effective surface emissions measured experimentally were one-half the value calculated from this model, because combustion is not stoichiometric and emissivity is less than unity. 

Temperature measurement is a case in point. A large transducer in close contact with the body whose temperature is being measured will act as a heat sink and consequently produce a localized reduction at the point where the temperature is being measured. On the other hand, if an air gap exists between the transducer and the hot surface then the air (rather than the surface) temperature will be measured. 

One of the most challenging aspects of modeling turbulent combustion is the accurate prediction of finite-rate chemistry effects. In highly turbulent flames, the local transport rates for the removal of combustion radicals and heat may be comparable to or larger than the production rates of radicals and heat from combustion reactions. As a result, the chemistry cannot keep up with the transport and the flame is quenched. To illustrate these finite-rate chemistry effects, we compare temperature measurements in two piloted, partially premixed CH4/air (1/3 by vol.) jet flames with different turbulence levels. Figure 7.2.4 shows scatter plots of temperature as a function of mixture fraction for a fully burning flame (Flame C) and a flame with significant local extinction (Flame F) at a downstream location of xld = 15 [16]. These scatter plots provide a qualitative indication of the probability of local extinction, which is characterized... 

Microwave-mediated reactions can also be easily carried out without solvents (see Section 4.1). The requirements for these dry media reactions are different to those for reactions in solution. As no solvent is involved, the pressure built-up is rather low, and in most instances such reactions are performed under open-vessel conditions. On the other hand, these mixtures can easily be locally overheated, even though the overall bulk temperature may be comparatively low (macroscopic hotspot formation). Stirring and accurate temperature measurement can prove rather difficult within such a matrix, impeding the investigation of certain reaction conditions. Thus, degradation or decomposition of reagents can be a severe problem for these kind of reactions. 

NMR spectra and Tj measurements at different temperatures. The local polymer chain motion varies over a frequency range of 104-106 Hz in the nematic phase. The activation energy of this motion is found to increase with decreasing number ( ) of methylene units in the spacer, and exhibits odd-even fluctuations. In a study of a homologous series of main-chain LC polyesters, 13C CP/MAS and variable-temperature experiments reveal a conformation-ally more homogeneous and a less dynamic nature for the even-chained than for the odd-chained polymer structures.300... 

Figure 11. Schematic representation of a laser heating experiment in the DAC. The IR laser beam is directed onto the absorbing sample immersed in a compression medium acting also as thermal insulator. The thermal emission of the sample is employed for the temperature measurement, while the local pressure is obtained by the ruby fluorescence technique (see next section).

A couple points are emphasized 1) the authors have found no published effort to determine the forces on the barrel as a function of material type and solids conveying discharge pressure, and 2) unlike conventional barrels that are thick to induce a maximum thermal capacitance and strength, the barrel in this device was machined to a minimum thickness in order to enhance heat transfer and thus allow a good estimate of the inner wall temperature from the outside temperature measurements and the local heat flux. 

From deviations in the kinetic laws observed, it could be deduced that even the very thin catalyst layers under consideration can become considerably hotter than the rest of the apparatus. This was confirmed by measuring local temperature rises by means of a thermocouple in the center of the catalyst tube. With half-value times of the reaction shorter than 5 min. temperature rises became too high. In this way, an upper limit was set to the temperature of the experiments. On the other hand, the turbine could not be run for too long in succession. This made the range of temperatures applicable of the order of 20° C. 

The most commonly utilized embedded sensor for temperature distribution mapping is the thermocouple. Wilkinson et al.130 developed a simple, in-situ, and noninvasive method of measuring the temperature distribution of a fuel cell with micro-thermocouples. In this study, thermocouples were located in the landing area of the flow field plates (in contact with the GDL of the MEA) of a fuel cell. The temperature data taken at different locations along the flow channel was then used to find each temperature slope, which in turn were related through mathematical equations to the local current density of each location. Thus, the current density distribution in the fuel cell was determined by simple temperature measurements. The results of this approach are discussed in more detail in Section... 

As mentioned previously in Section 2.6, Wilkinson et al.130 demonstrated that local temperature measurements at specific experimental conditions correlate well with local current densities determined through other published current density approaches. Then-results suggest that current mapping can be indirectly conducted through local temperature measurements using an array of microthermocouples in the active area. 

The range of techniques discussed in this volume measure local elevation, local relief, erosion and several environmental variables including precipitation, temperature, seasonality, and enthalpy. Relief, erosion and environmental records are related to paleoaltimetry through (1) empirically and theoretically determined climate-elevation relationships, and (2) assumptions about how erosion and relief relate to elevation change. While reading this volume, the reader should consider the specific measurement provided by a particular technique and its sensitivities to other factors. A broad range of approaches provides the opportunity to be both circumspect and comprehensive with tectonic and geomorphic interpretations based on paleoaltimetry data. 

Whenever a new well is completed, the abstracted aquifer should be studied in detail, including water table and temperature measurements and complete laboratory analysis of dissolved ions and gases, stable isotopes, and age indicators such as tritium, 14C, and 36Cl. Analysis for suspected pollutants, for example, fertilizers, pesticides, pollutants from local industries, and domestic sewage, should be carried out as well. This wealth of data is needed to provide answers to the questions raised in section 1.4. 

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