Heating rate description

De Haven [127] gives an overview of the results of accelerating rate calorimeter (ARC) experiments. The ARC was described in Section 2.3.2.3. As mentioned in the previous description, care must be taken in scale-up of results from experiments with relatively high phi-factors. For direct simulation of plant operating conditions, a phi-factor of 1.0 to 1.05 is required. As stated in [127], a decrease in the phi-factor from 2.0 to 1.0 increases the adiabatic temperature rise by a factor of 2, but the maximum self-heat rate increases by a factor of 20. Later in Chapter 3 (Section 3.3.4.6), an example of scale-up of ARC results is given. 

A short descriptive model showed how the combustion heat rate was calculated. No discussion is presented about limitations and assumptions of the method. 

Aho [8] presented a short descriptive model of the relationship between combustion heat rate and mass loss rate of bed. He applies the same method as Koistinen et al [7]. It is clear that the method used presents time average values of combustion heat rate. No verification method is applied and no uncertainty analysis is carried out. The... 

R.A. Beyer, Molecular Beam Sampling Mass Spectrometry of High Heating Rate Pyrolysis. Description of Data Acquisition System and Pyrolysis of HMX in a Polyurethane Binder ,... 

A sample of 80 g was introduced into the batch retort. All the pyrolysis tests were performed at a temperature of 500°C, a total pressure of about 8 kPa and a heating rate of 12°C/min. The holding time of the solid residue after con Ietion of the test was one hour. Vapours formed in the reactor were removed and condensed in three traps connected in scries and maintained at -30°C, -78 C and -78 C, respectively. The non condensable gas was removed by the vacuum pump and stored in a vessel previously depressurized. A detailed description of the apparatus is available elsewhere [11]... 

The true temperature of a sample heated using a filament pyrolyzer can be quite different from the above profile temperature, significantly lower temperatures being recorded inside the samples [4]. In order to obtain a correct Teq, modern equipment uses a feedback controlled temperature system (see e g. [5] for a more detailed description of this type of pyrolyzer). Several other procedures for a precise temperature control of the filament are available, such as the use of optical pyrometry or thermocouples [6, 7], Special pyrolysis systems that allow programmed heated rates at different time intervals also are available [8]. 

Thermal analysis measurements were made using a duFont 990 Thermal Analyzer using aluminum pans and a heating rate of 10 C/ min. Melting endotherms were determined In the presence of helium. Oxidative Induction times were measured Isothermally at 200 C In the presence of oxygen. A detailed description of this technique Is given in reference 4. 

Fig. 6. Differential scanning calorimetry melting points of extrudates (at a heating rate of 10 K/min). Extrusion temperature 100 °C, die diameter 2.5 mm. (O) H020-54, (A) R006-60, (V) R40 (for sample description see Table 2)35)...

It follows from the description of the different set-ups, that in the case of the DTA a transformation of the temperature difference signal into a power signal is necessary, which can only be accomplished with the help of a calibration function. This is not necessary with the DSC set-up, as the target value (the heating rate) may directly be obtained by multiplying the power amount necessary to compensate for the difference between sample and reference container with (-1). This is actually one of the reasons why the results obtained from a DSC measurement have a higher accuracy compared to those from DTA-tests [14]. 

The fundamental flaw of single heating rate methods is that they produce significantly differing kinetic triplets, most of which provide quite satisfactory description of the same dataset [85]. This occurs because of the mutually compensating correlation of E and A. Known as a compensation effect, this correlation takes the following form... 

Most of the heat in the active center is transferred to the exchange gas the amount transported laterally through the membrane is about 50 times smaller when using helium gas. The temperature-dependent heat capacity Cq can be determined from the respective measurements with the empty calorimeter system it proved to be about 100 nj at 100 K, increasing monotonously to 200 nJ at 600 K. With these parameters and a given heating rate, the unknown heat capacity C(T) of the sample can be calculated. For a detailed description of the thermal behavior and the temperature distribution in such a nanocalorimeter system and the theoretical background of the evaluation procedure, see Minakov et al. (2006, 2007). 

The problem focused on in our laboratory has been the behavior of energetic materials (propellants and explosives) at fast heating rates. This subject requires the description of complex physicochemical processes in the condensed phase and the near surface regime. New sample cells and experimental methods needed to be developed that simulate the dynamic... 

---