Thermal capacities

The two major difficulties facing the analyst/mass spectrometrist concern firstly how to get the whole of the sample into the plasma flame efficiently and secondly how to do so without destabilizing or extinguishing the flame. Although plasma flames operate at temperatures of 6000 to 8000 K, the mass of gas in the flame is very small, and its thermal capacity is correspondingly small (Figure 15.1). 

In the second bounding case (Fig. 3b) the thermal capacity rate of the cold stream is much greater than that of the hot stream. Then, the minimum outlet temperature attainable by the hot stream would be the inlet temperature of the cold stream, and therefore ... 

Optimum heat-transfer results when the thermal capacity rates of the two fluid streams are balanced, ie, where or = 1.0. 

In order to vaUdate this concept, an experiment was performed using an ice-water slurry and it was found that a 25% ice slurry had a two-to-four-times higher thermal capacity than chilled water (44). As the concentration of ice particles in the ice-slurry mixture increased up to 30%, no significant change of pressure drop was reported compared to pure water. 

Many polymer films, eg, polyethylene and polyacrylonitrile, are permeable to carbon tetrachloride vapor (1). Carbon tetrachloride vapor affects the explosion limits of several gaseous mixtures, eg, air-hydrogen and air-methane. The extinctive effect that carbon tetrachloride has on a flame, mainly because of its cooling action, is derived from its high thermal capacity (2). 

Time constants. Where there is a capacity and a throughput, the measurement device will exhibit a time constant. For example, any temperature measurement device has a thermal capacity (mass times heat capacity) and a heat flow term (heat transfer coefficient and area). Both the temperature measurement device and its associated thermowell will exhibit behavior typical of time constants. 

Fluid-filled bulbs dehver enough power to drive controller mechanisms and even directly actuate control valves. These devices are characterized by large thermal capacity, which sometimes leads to slow response, particularly when they are enclosed in a thermal well for process measurements. Filled-system thermometers are used extensively in industrial processes for a number of reasons. The simplicity... 

Adequate single-phase protection is provided on low-voltage ac motor starters by three overload relays, which are now standard. Rotor heating is not particularly a problem on smaller motors which have more thermal capacity, but it is important to protect the stator windings of these machines against burnout. 

Manual rheostats can be used in series with the motor armature for the current-limiting func tion. If the rheostat has ample thermal capacity, it can also Be usedto vaiy speed. If this system is used, interlocks should be included to prevent closing of the contactor unless maximum resistance is in the circuit. 

The over-current relay selection or its setting may not have been appropriate, otherwise the starter would have tripped under such a faulty condition. Selection and over-current setting of the relay should have been consistent with the motor s thermal capacity. 

Thermal capacity to perform the required switching duties and sustain the fault conditions, at least up to the cut-off time of the short-circuit protective device, say, the HRC fuses. 

This may be substituted with the estimated maximum ground grid current, /q (Section 22.9.6), that may occur during the life of the grounding station thermal capacity factor from Table 22.5, in J/cmV°C. This is derived from formula (4,184) p), Ps in Ws/cm V °C (for details refer to lEEE-80)... 

AM ler we have assessed the optirriLini power level it becomes easy to decide the type and amount oF reactive power control required to achieve this level, assuming that the lines can be loaded up to their thermal capacity tind the optimum power derived above can be attained. 

Processes in which solids play a rate-determining role have as their principal kinetic factors the existence of chemical potential gradients, and diffusive mass and heat transfer in materials with rigid structures. The atomic structures of the phases involved in any process and their thermodynamic stabilities have important effects on drese properties, since they result from tire distribution of electrons and ions during tire process. In metallic phases it is the diffusive and thermal capacities of the ion cores which are prevalent, the electrons determining the thermal conduction, whereas it is the ionic charge and the valencies of tire species involved in iron-metallic systems which are important in the diffusive and the electronic behaviour of these solids, especially in the case of variable valency ions, while the ions determine the rate of heat conduction. 

The fundamental reason for runaway at transient changes is the large difference in the thermal capacity of the catalyst charge and the flowing fluid, especially if it is a gas-phase reaction. In these cases, if the reaction is running close to the runaway limit but still somewhat below it, sudden changes can start a thermal runaway. 

N Reactor accidents are expected at lower fuel temperatures than LWR accidents. The large thermal capacity of the graphite moderator stack, the low melting point of the fuel (1,407"K) and the GSCS contribute to lower accident temperatures which retains heavy metals in the fuel. 

The temperature of air supplied by the air curtain should not exceed 70 °C in case the technological process does not require any other temperature. The thermal capacity of the air curtain is determined according to the equation... 

To determine the supply temperature of the curtain, 0g, and the thermal capacity P, we use... 

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