Dilution refrigeration heat exchanger

In this section, we will describe the various types of mechanical coolers with reference to their working cycles. We shall start with a brief description of counterflow heat exchangers. This subject will be further dealt in Chapter 6 when treating dilution refrigerators. 

In this section, we will describe the so-called continuous heat exchangers which are used down to about 1K. For lower temperatures, due to the increasing importance of the Kapitza resistance (see Section 4.3) step exchangers are used. They will be described in Chapter 6 in connection with the dilution refrigerator. 

Fig. 6.6. Scheme of a counterflow heat exchanger for dilution refrigerator. 

In one continuous method (17), the waxy oil charge—for example, in the case of a topped crude—is diluted with an equal volume of propane and the mixture is chilled to about —25° F. by means of heat exchange with cold filtrate in double-pipe scraped-surface equipment. This chilled mixture is then mixed with propane which has been chilled by autorefrigeration to —45° F. to bring the ratio of propane to oil to about 5 to 1. Ninety per cent of the refrigeration required is accomplished in this manner the remaining 10% is obtained by evaporating propane from the diluted mixture. 

Solution heat exchanger. This H/Ex, transfers heat from hot, concentrated refrigerant (as it passes from the first stage vapor generation process to the absorber), to the dilute refrigerant solution (which is returned from the absorber to the generators). This H/Ex, is a process-to-process vessel, and is not normally inspected by the water treatment service company. 

Figure 8.26. Apparatus for melt DCC crystallization, using air as a coolant. A = Reservoir B = Data acquisition system C = Thermostatic baths and circulators D = Particle analysis sensor E = Dilution tank F= Temperature recorder G = Crystallizer H= Flowmeter I = Refrigerator J = Temperature programming controller K Heat exchanger. After Kim and Mersmann, 1997)...

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