Heat measurements accuracy

Several effects can play a role in the temperature measurement accuracy. Due to the small channel length, the temperature difference between the channel outlet and inlet can be as small as the sensor sensitivity. Thermocouples can have a size comparable to the channel dimensions and where is measured the temperature is questionable. Moreover, the heat flow rate through the thermocouple itself can be not negligible. The importance of these effects must be appreciated. 

The test procedure shall represent the real world operation of slow heat release appliances burning wood and take into account the transient parameters of a batch wise burning combustion process. It shall fulfill typical test laboratory requirements such as reproducibility of the results, laboratory independence, measuring accuracy and simple test procedures. The test procedure shall support the wood appliance industry for their high quality products and should have a good relation of price and performance. The test procedure shall refer as much as possible to existing international (ISO) and European (CEN, Austrian standards) test standards. 

Instrumental. The Mettler TA2000B thermal analysis system is equipped with an interface system, and Hewlett-Packard 9815 desk top calculator and 7225 plotter. Samples, weighing 5-10 mg, sealed in aluminum pans and under a nitrogen blanket, were heated in the calorimeter at a rate of 10 deg/min from -35 or 10 deg C to 180 deg C respectively, for specific heat and kinetic scans. Specific heat measurements were calibrated with alumina to an accuracy of 3%. Temperatures and enthalpies were calibrated with an Indium sample. The accuracies were .02 deg C and 2% (Indium 28.5 J/g), respectively. 

Formation heat is a basic parameter in the thermochemical calculation, which can be calculated from combustion heat of a compound according to Hess s law. The measurement accuracy of combustion heat has reached a very high level. In the design of a new explosive, in order to know its explosion properties and thermochemical properties, its formation heat can be calculated first, which is necessary to design and decide the formulation of explosive. 

Figure 2.2). (Such data are commonly collected in IMS smdies to determine K more precisely and verify that the measured K equals Klf)) needed to derive H using Equation 1.10.) A lower measurement accuracy obviously increases the apparent (E/AOc- In Ihs result, the high-field behavior is seen in differential IMS at much lower E/N than in conventional IMS (3.2.4). The distortion of Maxwell-Boltzmann distribution also causes ion heating by Equation 1.27. Hence a negligible deviation of K from K(relative measurement accuracy) is achieved when ATh < yT, where y is a coefficient dependent on x. Using Equation 1.27, that can be expressed as... 

The principle of heat-flux calorimetry is illustrated with a schematic of a classical DTA in Appendix 9. Accuracies of heat measurements by DSC range from 10% to 0.1%. Temperature can be measured to 0.1 K. Typical heating rates vary between 0.1 and 200 K min. Sample masses can be between 0.05 and 100 mg. The smaller masses are suitable for large heat effects, such as chemical reacdons (explosions), phase transidons, or when fast kinetics is studied. The larger masses are necessary for assessment of smaller heat effects as in studies of heat capacity or glass transitions. Sensitivities are hard to estimate, but effects as small as 1.0 pi s are observable. 

Recently, Emerson et al. (1999) have confirmed with careful specific-heat measurements previous findings of Nakazawa and Ishikawa (1989) and Moler et al. (1997) that in the overdoped regime a sharp increase of the Debye temperature takes place. This is shown in fig. 78. In their estimated oxygen content scale the abrupt increase of the Debye temperature takes place at x 6.98. In view of the fact that the oxygen determination was indirect, it seems reasonable to assume that this effect is related to the displacive martensitic transformation (x=6.95, determined directly, with high accuracy, sect. 3.1.3) and the series of structural phenomena which accompany it in the overdoped region the abrupt decrease of the unit-cell volume (fig. 25e), the decrease of the h-axis, the decrease of the orthorhombicity (figs. 25b,c) and the minimum of the c-axis (Rusiecki et al. 1990) (fig. 28a). 

Water adsorption onto a set of samples was studied using an adsorption apparatus with a McBain-Bark quartz scale. After evacuation to 10 Torr for 1-2h, samples were heated at 613 K for 3-4h to a constant weight, then cooled to 293 0.2 K, and adsorption of water vapor was studied at pressure (p) varied in the 0.06-0.999 p/po range. The measurement accuracy was 1 x 10 mg with relative mean error < 5%. 

In the following sections, the main deviations from classical theory for the calculation of heat transfer in microchaimels are discussed. This discussion includes axial heat conduction in the fluid, conjugate heat transfer, surface roughness, viscous dissipation, thermophysical property variations, electric double layers, entrance region and measurement accuracy. Whenever possible, the reader is referred to design criteria and Nu correlations when the different aspects have to be taken into account. 

The bq34z653 device from Texas Instruments includes all of the required functions plus an LCD display and external heater mechanism to ensure reliable operation in extreme conditions. (The heater can be used to heat the LCD display for low-temperature operation). The device also contains two thermistor temperature inputs for additional temperature-measuring accuracy. 

The method of differential scanning calorimetry (DSC) was used to delme temperature transitions and evaluate the phase state of blocks in PC PTMO. Investigations of PC and PC PTMO block copolymer resins were carried out with the help of seaiming ealorimeter DSK-2 ( by the firm Perkin-Almer ) in the temperature interval from 173 to 523 K at the heating speed 40° a minute. The measurement accuracy was 1-2 degrees. After the first scanning the specimen was quenched up to the primary temperature and the hardened specimen was scanned again. 

Modem DTA will convert the temperature and AT signals into a digital output. This output can then be fed into a computer for experiment control and data storage, treatment, and display. Typical accuracies of DTA in heat measurements range from perhaps 10% to a few tenths of one percent. In the measurement of temperature, an accuracy of 0.1 K can be reached. Typical heating rates are between 0.1 and 100 K/min. Naturally, not all favorable limits can be reached simultaneously. As a result, DTA may produce measurements that vary widely in quality. 

The accuracy and reproducibility of hard tissue analysis results can be significantly affected by a number of experimental parameters such as sample shape, size and mass, analysis atmosphere or sample thermal and mechanical history. Sample representativeness, adequacy of sample mass to the desired test accuracy, and avoidance of inducing changes or contamination are key factors that should be monitored in order to obtain reproducible results on kindred specimens. Achieving this goal can be difficult when the experimental and instrumental parameters are not identical, since the thermal analysis methods are sensitive to heat transfer and temperature measurement accuracy [7,21]. 

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