Heat exchangers cooling curves

Figure 3.26 compares the Nyquist plots for four different cases. The jacket-cooled Nyquist plot is much closer to the critical (—1,0) point. As more area is used in the external heat exchanger, the curves move deeper into the third quadrant, indicating the potential for improved closedloop control. However, the point where they cross the negative real axis moves further to the left. The ultimate gains for the three areas with the external heat exchanger are = 39.8/24.9/15.1 (dimensionless) for areas of 45.2/58.1/ 100 m2. These results are counter-intuitive since we would expect the controllability to improve with increasing area. 

Figure 4.6 Heating and cooling curves for a heat exchanger.

When a process stream is both heated and vaporized, or both cooled and condensed, the minimum approach temperature can occur within the exchanger, away from either end. This can be determined from heating and cooling curves, as illustrated in the following example. 

Figure B.l shows a pair of composite curves divided into vertical enthalpy intervals. Also shown in Fig. B.l is a heat exchanger network for one of the enthalpy intervals which will satisfy all the heating and cooling requirements. The network shown in Fig. B.l for the enthalpy interval is in grid diagram form. The network arrangement in Fig. B.l has been placed such that each match experiences the ATlm of the interval. The network also uses the minimum number of matches (S - 1). Such a network can be developed for any interval, providing each match within the interval (1) satisfies completely the enthalpy change of a strearh in the interval and (2) achieves the same ratio of CP values as exists between the composite curves (by stream splitting if necessary).

Fig. 5. Simple heat-exchange network where stream C is heated, and streams A and B are cooled (a) schematic (b) temperature—cumulative duty curve...

The plenum chamber design may be a simple box shape, formed by flat sides and bottom, or curved transition sections may be used to obtain a tapered smooth transition from the rectangular bundle to the circular fan. Either design may be used for forced-draft or induced-draft air cooled heat exchangers. 

If the heat exchanger was of infinite size, the space-temperature curves would eventually meet and no further heat could be transferred. The fluid in Example 1.11 would cool the water down to 3°C. The effectiveness of a heat exchanger can be expressed as the ratio of heat actually transferred to the ideal maximum ... 

Figure 8.24. Left schematic diagram of an adiabatical three-bed, indirectly cooled reactor with two heat exchangers. Right a diagram showing the equilibrium curve to the upper right, the optimal operating line and the operation line for the reactor are to the left. [Adapted from C.J.H. Jacobsen, S. Dahl, A. Boisen, B.S. Clausen,...

A set of curved tube or coil in which refrigerant or glycol solution run is installed in a tank and cooled inside of the coil. Ice is formed on the surface of the coil and melted from boundary between ice and water. Stored heat is usually recovered by supplying water directly to secondary system. Some systems use heat exchanger to reduce water head loss. This type of ice storage... 

The operation of TET. First, the gas flow is cooled in heat exchanger under approximately constant pressure, then gas flow works in the turbine and is cooled further. (Note that this process is not isentropic, i.e. even in ideal case the losses are inevitable). Thus it founds itself under the condensation curve and the condensation process takes place. Further, gas again passes through heat exchanger and finally is additionally compressed by compressor. 

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