Specific heat removal

The Accelerating Rate Calorimeter (ARC ) is another adiabatic test instrument that can be used to test small samples. The ARC with the clamshell containment design can handle explosive compounds. It is a sensitive instrument that can indicate the onset of exothermicity where the reaction mixture can be accurately simulated (HSE 2000). ARC testing results can be used in determining a time to maximum rate of decomposition, as well as in calculating a temperature of no return for a container or vessel with specific heat removal characteristics. Further information and references related to the ARC are given in CCPS (1995a) and Urben (1999). 

The S shape of the curve results from the Arrhenius dependent rate coefficients, while it follows from Eq. 10.4 -3 that leads to (essentially) straight lines. Any of the points 1, 2, 3,4, and 5 represent possible steady states that is, solutions of the combined mass and energy balances for a particular design. Since the slope of Qn is the specific heat removal rate, the steepest line Qgi is for high heat removal, and consequently steady-state point 1 means that the reactor will operate at a low temperature, low-heat generation rate, and, consequently, low conversion. 

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. 

Polymer Melt temperature i°C) Mould temperature (X) SG Specific heat (Jkg- K ) Heat required to melt Heat removed on cooling ... 

Extrusion blow moulding of bottles has been successfully accomplished in reeent years by attention to the points mentioned above. It is to be noted here that UP VC has a much lower average specific heat between the proeessing temperature and room temperature than polyethylene and, being essentially amorphous, no latent heat of fusion. This leads to much less heat needing to be removed on cooling of mouldings and very short cycle times are possible. 

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