Heat release determination

Scheme 12.17 The principle of the heat release determination used in a cone calorimeter...

A small amount of core melt and lower decay heat release determine the relatively low heat fluxes from the melt to the vessel bottom in this, the problem of keeping the melt inside the reactor vessel could be solved by external vessel cooling, i.e., by filling the reactor caisson with water in emergencies. Keeping the melted core inside the vessel reduces the consequences of accidents and eliminates some uncertainties associated with maximum loads on the protective shell. 

The following eonsiders a situation that involves all vapor relief. The size of a vapor phase rupture disk required is determined hy assuming that all of the heat energy is absorbed by the vaporization of the liquid. At the set temperature, the heat release rate q is... 

The stopwatch technique for determining emission volume flow rate is based on measuring with a stopwatch the elapsed time for fume to rise between two known levels (e.g., Zj, Z,). For this test procedure to be valid, the test must be carried out in a region where the rising fume clearly exhibits buoyancy-dominated plume behavior. The calculation procedure depends on a good estimate of the location of the virtual origin of the plume and the heat release for the process. 

In order to investigate the kinetics, heat of reaction and other aspects of the system, the RCl reaction calorimeter was employed. This system allows to perform the reaction in a 2 liters glass reactor, while controlling the reactor and jacket temperatures. Following the reaction, the heat released at any time period can be determined. The operation and application of this system has been discussed in numerous publications (refs. 5,6). 

Flame dynamics is intimately related to combustion instability and noise radiation. In this chapter, relationships between these different processes are described by making use of systematic experiments in which laminar flames respond to incident perturbations. The response to incoming disturbances is examined and expressions of the radiated pressure are compared with the measurements of heat release rate in the flame. The data indicate that flame dynamics determines the radiation of sound from flames. Links between combustion noise and combustion instabilities are drawn on this basis. These two aspects, usually treated separately, appear as manifestations of the same dynamical process. 

In this description the temperature field has been taken to be linear in the coordinate y and to be independent of the shape of the melt/crystal interface. This is a good assumption for systems with equal thermal conductivities in melt and crystal and negligible convective heat transport and latent heat release. Extensions of the model that include determination of the temperature field are discussed in the original analysis of Mullins and Sekerka (17) and in other papers (18,19). 

Determine the amount of heat released and the molar energy of combustion of caffeine. 

Professor Bothwell determined from the wrapper the number of calories in a candy bar. He then burned the entire candy bar and measured the amount of heat released. His experiment was most likely designed to demonstrate —... 

Instrumental methods for the determination of water in polymeric materials often rely on heat release of water from the polymer matrix. However, in some cases (e.g. PET) the polymer is hydrolysed and a simple Karl Fischer method is then preferred. Small quantities of water (10 pg-15mg) of water in polymers (e.g. PBT, PA6, PA4.6, PC) can be determined rapidly and accurately by means of a coulometric titration after heating at 50 to 240 °C with a detection limit in the order of 20 ppm. 

In Figure 16.27, the flue gas is cooled to pinch temperature before being released to atmosphere. The heat released from the flue gas between pinch temperature and ambient is the stack loss. Thus in Figure 16.27, for a given grand composite curve and theoretical flame temperature, the heat from fuel and stack loss can be determined. 

Callisto orbits Jupiter at a distance of 1.9 million kilometres its surface probably consists of silicate materials and water ice. There are only a few small craters (diameter less than a kilometre), but large so-called multi-ring basins are also present. In contrast to previous models, new determinations of the moon s magnetic field suggest the presence of an ocean under the moon s surface. It is unclear where the necessary energy comes from neither the sun s radiation nor tidal friction could explain this phenomenon. Ruiz (2001) suggests that the ice layers are much more closely packed and resistant to heat release than has previously been assumed. He considers it possible that the ice viscosities present can minimize heat radiation to outer space. This example shows the complex physical properties of water up to now, twelve different crystallographic structures and two non-crystalline amorphous forms are known Under the extreme conditions present in outer space, frozen water may well exist in modifications with as yet completely unknown properties. 

It is, of course, not necessary to use a heat-flow microcalorimeter in order to determine the heat released by rapid adsorption phenomena. Dell and Stone (74), for instance, using an isoperibol calorimeter of the Garner-Veal type, found an initial heat of 54 4 kcal mole-1 for the adsorption of oxygen on nickel oxide at 20°C. The agreement with the value (60 2 kcal mole-1) in Fig. 19 is remarkably good, particularly if it is considered that very different methods were used for the preparation of the nickel-oxide samples (19, 74)-... 

Two general procedures have been used to obtain AH values. The first involves the measurement of log K values over a range of temperatures the observed variation may be used to derive the required AH value. However, because of the usual errors inherent in log K determinations coupled with the limited temperature range normally possible, AH values obtained in this manner tend to be somewhat unreliable. In contrast, the direct determination of AH using calorimetry commonly results in values which are considerably more accurate. Nevertheless, such calorimetric determinations may still not be easy for particular macrocyclic systems. Difficulties can arise in measuring the total heat evolved for metal complexation when long equilibration times are necessary. To lessen such problems, sensitive calorimeters have been used which are able to integrate the heat released over an extended time. 

Heat Release Rate From Walls. The heat release rate from the wall assemblies should be the difference between (jfurnace and Qfuel However, a direct subtraction is not correct because of the assumption that 13.1 MJ/kg oxygen consumed is released for all fuels. In fact, the heat release per unit oxygen consumed is 12.54 MJ/kg for methane as given by Huggett (14) and 12.51 MJ/kg for the fuel mixture as determined by Brenden and Chamberlain (6). Thus, the heat release from the wall is determined using a correction factor of 13.1/12.51 = 1.048 ... 

Amounts of heat released in pyrolysis trials were small. Even heats measured at around 130 C, far above the 80"C margin, could adiabatically raise the temperature by less than one centigrade in an hour (6). With so little heat, inaccuracies of measurements could cause qualitative mistakes. Additionally, temperatures were usually determined with thermocouples, whose metallic wires conducted heat up to one thousand times faster than the pyrolzed material, and could again involve substantial errors, especially with small samples and steep temperature gradients. 

True fire hazard can be determined only in a specific scenario. Therefore, it is necessary to determine which fire properties are most relevant to the scenario in question. These fire properties will then have to be measured and combined in order to obtain an overall index of fire hazard. As a general rule, it is clear that the most important individual property that governs levels of fire hazard is the rate of heat release the peak rate of heat release is proportional to the maximum intensity a fire will reach. 

Smoke has usually been measured in the NBS smoke chamber. Such results cannot be correlated with full scale fire results and do not predict fire hazard. Rate of heat release (RHR) calorimeters (e.g. NBS Cone (Cone) and Ohio State University (OSU)) can be used to determine the best properties associated with fire hazard, as well as smoke. Results from the Cone RHR correlate with full-scale fire results. The best way to determine the fire hazard associated with smoke, for materials which do not burn up completely in a fire, is by using RHR to measure combined smoke and heat release variables, such as smoke parameter or smoke factor. 

Fire hazard is associated with a variety of properties of a product in a particular scenario [1]. It is determined by a combination of factors, including product ignitability, flammability, amount of heat release on burning, rate at which this heat is released, flame spread, smoke production and smoke toxicity. 

This parameter, the smoke parameter, is based on continuous mass loss measurements, since the specific extinction area is a function of the mass loss rate. A normal OSU calorimeter cannot, thus, be used to measure smoke parameter. An alternative approach is to determine similar properties, based on the same concept, but using variables which can be measured in isolation from the sample mass. The product of the specific extinction area by the mass loss rate per unit area is the rate of smoke release. A smoke factor (SmkFct) can thus be defined as the product of the total smoke released (time integral of the rate of smoke release) by the maximum rate of heat release [19], In order to test the validity of this magnitude, it is important to verify its correlation with the smoke parameter measured in the Cone calorimeter. 

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