Heat generation, physical processing

Heat generation, physical processing, screening methods, 41-42... 

Third, design constraints are imposed by the requirement for controlled cooling rates for NO reduction. The 1.5—2 s residence time required increases furnace volume and surface area. The physical processes involved in NO control, including the kinetics of NO chemistry, radiative heat transfer and gas cooling rates, fluid dynamics and boundary layer effects in the boiler, and final combustion of fuel-rich MHD generator exhaust gases, must be considered. 

Equipment Constraints These are the physical constraints for individual pieces of eqiiipment within a unit. Examples of these are flooding and weeping limits in distillation towers, specific pump curves, neat exchanger areas and configurations, and reactor volume limits. Equipment constraints may be imposed when the operation of two pieces of equipment within the unit work together to maintain safety, efficiency, or quahty. An example of this is the temperature constraint imposed on reactors beyond which heat removal is less than heat generation, leading to the potential of a runaway. While this temperature could be interpreted as a process constraint, it is due to the equipment limitations that the temperature is set. 

Is any heat generated during the mixing or physical processing of substances ... 

Note that heat effects do not necessarily indicate that a chemical reaction is taking place. Some physical processes such as mixing or dilution can generate or absorb heat. However, heat effects are very often the result of a chemical process. 

An important question to consider is whether the mixing or physical processing of substances generates heat (e.g., a mixture gets warm or hot upon combining the ingredients, or would get warm or hot if cooling was lost). 

Possible causes of uncontrolled reactions associated with heat-generating mixing or physical processing operations include abnormal events such as the following ... 

Is any heat generated during the mixing or physical processing of substances NO No indication of heat generation from previous batch or from nature of blend... 

In general, the cell energy balance states that the enthalpy flow of the reactants entering the cell will equal the enthalpy flow of the products leaving the cell plus the sum of three terms (1) the net heat generated by physical and chemical processes within the cell, (2) the dc power output from the cell, and the rate of heat loss from the cell to its surroundings. 

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