Recirculation closed

Figure 1.2 Schematic of closed recirculating cooling system.

The arrangement for closed recirculation is shown in Fig. 4.40. It overcomes many of the problems encountered with the open system. Typical applications include engine cooling and heat rejection from refrigeration plant. 

FIGURE 4.40 Cooling water system (closed recirculation). 

Figure 8-3 Three basic types of cooling water systems. Top the once-through system where the cooling water is used once and then discharged. Middle the open recirculation system where the water is cooled and recycled through a system in which it comes in direct contact with air. Bottom a closed recirculation system where the water is cooled and recycled without coming in direct contact with the atmosphere.

The closed recirculation system (see Fig. 8-3) is used when it is necessary or economical to produce cooling water at a temperature below that feasible with an open system, or it is important to prevent foreign matter from getting into the water.14 Here secondary heat exchangers are used to remove the energy. The only water loss is due to leaks, and since it is an isolated system, any water pretreating that is required is minimal. 

Because of the independence of stages it is easy to evaluate what happens to the C curve when tanks are added or subtracted. Thus this model becomes useful in treating recycle flow and closed recirculation systems. Let us briefly look at these applications. 

Closed Recirculation System. If we introduce a 8 signal into an N stage system, as shown in Fig. 14.5, the recorder will measure tracer as it flows by the first time, the second time, and so on. In other words it measures tracer which has passed through tanks, tanks, and so on. In fact it measures the superposition of all these signals. 

This form of curve is encountered in closed recirculation systems in which tracer is broken down and removed by a first-order process, or in systems using... 

Measurement with the Infrared Analyzer. The infrared analyzer was operated in the absorbance mode at 8.02 ym with a slit width of 1 mm, path length of 5.25 m, and response time of 1s. A closed recirculating loop containing a metal-bellows pump, a glass tee, and the infrared analyzer was assembled using low-volume tubing the total volume of the system was 5.64 L. 

As the motor-driven syringe slowly injected 1 yL of pure vinyl acetate into the closed recirculating loop at 3.89 nL/s, the change in absorbance was recorded. This procedure was repeated five times and the results were averaged. The calculated concentration plotted against the absorbance gave a straight line calibration curve. 

In order to compare the catalytic action of SOuj LrOi with that of H-mordenite (H-Mor), the reaction of pentane was performed in a closed recirculation system. The changes of product yields against reaction time are shown in Figure 17.4 [135]. The reaction rate with S04/Zr02 at 0°C is almost constant during the reaction, and the main product is isopentane, with small amounts of isobutane and hexanes being detected. 

The configuration depicted in Fig.4.3-5 comprises of two interacting reactors forming a closed recirculation system. The pulse introduced into reactor 1 is distributed at steady state between reactors 1 and 2. 

Catalytic disproportionation of alkylsilanes such as diethylsilane (E2), triethylsilane (E3) and diethyidimethylsilane (E2M2) were examined at 373-623 K in a closed recirculation apparatus. Strongly acidic catalysts, SA, HY, MgY, CaY, S03/Zr02and alumina, exhibited high activities. 

Catalytic alkylation of alkylsilanes with olefinic and acetylenic compounds using solid catalysts was examined in a closed recirculation reactor at 373 - 473 K. Alkylation of diethylsilane(E2) with these compounds took place smoothly on silica-alumina (SA) and S03/Zr02 catalysts but not on alumina, which means protonic solid acid catalyzed the reaction. n-Alkylated products were the main products and the /so-alkylated ones were the minor products regardless the type of olefins. The product distribution indicates the reaction takes place via a nucleophilic attack of olefins on a Si cation. 

The disproportionation (or alkyl exchange) and the alkylation reactions of alkylsilanes have been carried out in a closed recirculation reactor at 373 - 623 K and 373 - 473 K, respectively, by using 100 - 200 mg of catalysts. For the disproportionation reaction, 30 Torr of diethylsilane (E2), diethyidimethylsilane (E2M2), and triethylsilane (E3) were used. For the alkylation reaction, 30 Torr of E2 and 30 Torr of alkylating reagents (propene, 1- and c/s-2-butene, 2-methyl-1-butene, 1,3-butadiene, methylacetylene, ethylacetylene) were used. Cyclic olefins, nitriles, benzene and carbonyl compounds were also tested. 

DEWT L. [Drew Ind. Div.] Chromate/ (xgaiic blend corrosion inhibitor for closed recirculating water systems. 

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