Countercurrent cooling

Countercurrent Cooling TowerPeformance, J. F. Prichard Co., Kansas City, Mo., 1957. 

In the multistage process described on Fig. 20-14 feed enters one of several crystallizers installed in series. Crystals formed in each crystallizer are transferred to a hotter stage and the liquid collected in the clarified zone of the crystallizer is transferred to a colder stage and eventually discharged as residue. At the hot end, crystals are transferred to a vertical purifier where countercurrent washing is performed by pure, hot-product reflux. TSK refers to this multistage process as the countercurrent cooling crystallization (CCCC) process. In... 

COOL - Three-Stage Reactor Cascade with Countercurrent Cooling... 

CONTROL AND STARTUP OF A 3-STAGE CSTR CASCADE MULTIPLE OPERATING STATES AND COUNTERCURRENT COOLING... 

Figure 5-21 Temperature profiles for cocuirent and countercurrent cooled PFTR with feed temperature To and coolant feed temperature Too.

Fig. 3.23. Heat transfer characteristics of countercurrent cooled tubular reactor...

To illustrate the problem of thermal sensitivity we will analyse the simple one-dimensional model of the countercurrent cooled packed tubular reactor described earlier and illustrated in Fig. 3.25. We have already seen that the mass and heat balance equations for the system may be written ... 

Figure 5.12 Important design parameters for the countercurrent cooling tower operation.

Figure 6.1 Countercurrent cooling diagram for constant conditions, variable L G ratios.

Figure 6.4 Countercurrent cooling tower rating chart for 15° range. McDowell [ 1 ] provides a family of charts for different ranges.

Investigation of the Behavior of a (Semi-Industrial) Trickle Film, Countercurrent Cooling Tower... 

Experimental Studies on the Contribution of the Splash Zones in Countercurrent Cooling Water Towers... 

Next we consider the heat balance for the cooling jacket in incremental form as depicted in Figure 7.2. Note first that ours is a case of cocurrent flow in the jacket and reactor. This simplifies the mathematical problem when compared with countercurrent cooling. Countercurrent cooling is physically more efficient, but it transforms the problem mathematically into a more demanding two point boundary value problem which we want to avoid here see problem 3 of the Exercises. 

Develop the model equations for a countercurrent cooling jacket and the same tubular reactor. This will lead to several coupled boundary value problems with boundary conditions at l = 0 and l = Lt. 

Industrial fixed-bed catalytic reactors have a wide range of different configurations. The configuration of the reactor itself may give rise to multiplicity of the steady states when other sources alone are not sufficient to produce the phenomenon. Most well known is the case of catalytic reactors where the gas phase is in plug flow and all diffusional resistances are negligible, while the reaction is exothermic and is countercurrently cooled. One typical example for this is the TVA type ammonia converter [38-40]. 

The conversion and selectivity of the reaction can be decisively influenced by the design and the operation of the heat transfer circuit. The most obvious, although technically most complex solution, is to arrange different heat transfer circuits so as to achieve a stepwise approximation of an optimum temperature profile. The purposeful utilization of the temperature change of the heat transfer medium flowing through the reactor is technically simpler, and will be discussed here in connection with cocurrent or countercurrent cooling of a fixed-bed reactor with an exothermic reaction. 

In the next section we shall explore the problem of choosing T z) optimally in an effort to see what the maximum performance of a tubular reactor may be. In Sec. 9.7 we shall look at the cocurrent and countercurrent cooled reactors, and other problems of the third sort. For the moment, however, we need... 

It will be convenient to divide this section more formally than the others, according to the following scheme. Under Sec. 9.7.1 we discuss the genera form of the equations when the wall temperature is constant and illustrate this by considering an endothermic cracking reaction. Under Sec. 9,7.2 we shall consider cocurrent and countercurrent cooled reactors and use the ammonia synthesis reactor as an illustration. These correspond to the two subcases of the third type of design problem mentioned in Sec. 9.5. 

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