Heating target

Sheehan, E. W., Ketkar, S. and Willoughby, R. C., Volatility enhancement of nonvolatile solutes by the combination of a heated target and a solvent depleted particle beam , in Proceedings of the 39th ASMS Conference on Mass Spectrometry and Allied Topics, Nashville, TN, May 19-24, 1991, pp. 1306-1307. 

Here 81 are the values of the uncertain variables and H1 the minimum heating target at corner point / and Lv is the index set for the corner points. 

In a particle-beam interface (PBI), the column effluent is nebulized, either pneumatically or by TSP nebulization, into a near atmospheric-pressure desolvation chamber, which is connected to a momentum separator, where the high molecular-mass analytes are preferentially transferred to the MS ion source, while the low molecular-mass solvent molecules are efficiently pumped away. The analyte molecules are transferred in small particles to a conventional EI/CI ion source, where they disintegrate in evaporative collisions by hitting a heated target, e.g., the ion source wall. The released molecules are ionized by El or conventional CL... 

Heat Exchanger Network and Utilities Energy Targets... 

The analysis of the heat exchanger network first identifies sources of heat (termed hot streams) and sinks (termed cold streams) from the material and energy balance. Consider first a very simple problem with just one hot stream (heat source) and one cold stream (heat sink). The initial temperature (termed supply temperature), final temperature (termed target temperature), and enthalpy change of both streams are given in Table 6.1. 

Stream Type Supply temp. Ts CO Target temp. Tr (°C) AH (MW) Heat capacity flow rate CP (MW°C )... 

Where the cold composite curve extends beyond the start of the hot composite curve in Fig. 6.5a, heat recovery is not possible, and the cold composite curve must be supplied with an external hot utility such as steam. This represents the target for hot utility (Q niin)- For this problem, with ATn,in = 10°C, Qnmin 7.5 MW. Where the hot composite curve extends beyond the start of the cold composite curve in Fig. 6.5a, heat recovery is again not possible, and the hot composite curve must be supplied with an external cold utility such as cooling water. This represents the target for cold utility (Qcmin)- For this problem, with AT in = 10°C, Qcmm = 10-0 MW. 

Specifying the hot utility or cold utility or AT m fixes the relative position of the two curves. As with the simple problem in Fig. 6.2, the relative position of the two curves is a degree of freedom at our disposal. Again, the relative position of the two curves can be changed by moving them horizontally relative to each other. Clearly, to consider heat recovery from hot streams into cold, the hot composite must be in a position such that everywhere it is above the cold composite for feasible heat transfer. Thereafter, the relative position of the curves can be chosen. Figure 6.56 shows the curves set to ATn,in = 20°C. The hot and cold utility targets are now increased to 11.5 and 14 MW, respectively. 

In other words, to achieve the energy target set by the composite curves, the designer must not transfer heat across the pinch by... 

These rules are both necessary and sufficient to ensure that the target is achieved, providing the initialization rule is adhered to that no individual heat exchanger should have a temperature difference smaller than... 

Details of how this design was developed in Fig. 6.9 are included in Chap. 16. For now, simply take note that the targets set by the composite curves are achievable in design, providing that the pinch is recognized, there is no transfer of heat ac ss it, and no inappropriate use of utilities occurs. However, insight into the pinch is needed to analyze some of the important decisions still to be made before network design is addressed. 

After maximizing heat recovery in the heat exchanger network, those heating duties and cooling duties not serviced by heat recovery must be provided by external utilities. The outer-most layer of the onion model is now being addressed, but still dealing with targets. 

Although the composite curves can be used to set energy targets, they are not a suitable tool for the selection of utilities. The grand composite curve is a more appropriate tool for understanding the interface between the process and the utility system. It is also, as is shown in later chapters, a useful tool for study of the interaction between heat-integrated reactors and separators and the rest of the process. 

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