Cooling capacity

In thermoelectric cooling appHcations, extensive use has been made of cascaded systems to attain very low temperatures, but because the final stage is so small compared to the others, the thermal flux is limited (Eig. 3). The relative sizes of the stages ate adjusted to obtain the maximum AT. Thus, for higher cooling capacity, the size of each stage is increased while the area ratios ate maintained. 

Continuous polymerization systems offer the possibiUty of several advantages including better heat transfer and cooling capacity, reduction in downtime, more uniform products, and less raw material handling (59,60). In some continuous emulsion homopolymerization processes, materials are added continuously to a first ketde and partially polymerized, then passed into a second reactor where, with additional initiator, the reaction is concluded. Continuous emulsion copolymerizations of vinyl acetate with ethylene have been described (61—64). Recirculating loop reactors which have high heat-transfer rates have found use for the manufacture of latexes for paint appHcations (59). 

Because chloroprene is a flammable, polymerisable Hquid with significant toxicity, it must be handled with care even in the laboratory. In commercial quantities, precaution must be taken against temperature rise from dimerisation and polymerisation and possible accumulation of explosive vapor concentrations. Storage vessels for inhibited monomer require adequate cooling capacity and vessel pressure rehef faciUties, with care that the latter are free of polymer deposits. When transportation of monomer is required, it is loaded cold (< — 10° C) into sealed, insulated vessels with careful monitoring of loading and arrival temperature and duration of transit. 

Example 15 Cooling Capacity of a Spray Pond Determine the cooling capacity of a spray pond operating at the following conditions ... 

Acceptance Testing Test procedures to determine the water cooling capacity of towers. Instrumentation used and measurement procedures should be those recommended by the Cooling Tower Institute (CTI) in its "Acceptant Text Procedures. "... 

Impurities or the delayed addition of a catalyst causes inhibition or delayed initiation resulting in accumulation in the reactors. The major hazard from accumulation of the reactants is due to a potentially rapid reaction and consequent high heat output that occurs when the reaction finally starts. If the heat output is greater than the cooling capacity of the plant, the reaction will run away. The reaction might commence if an agitator is restarted after it has stopped, a catalyst is added suddenly, or because the desired reaction is slow to start. 

Similarly, the collective cooling capacity of the cold process stremns within the zth interval is evaluated as follows ... 

Similarly, the cooling capacities of the cold utilities through the following expression ... 

In the summer, the COP of an air-to-air heat pump decreases as the outdoor temperature rises, reducing the cooling capacity. Normally the thermal needs of the building are met since it is common practice to size a heat pump so that it will deliver adequate cooling capacity in all but the most extreme summer conditions. The winter heating capacity of the system is then determined by this tradeoff, and if the heating capacity is inadequate, supplemental electric or fossil fuel heat is required. 

The theoretical maximum cooling capacity of a heat exchanger for a hydraulic system will never have to be greater than the input horsepower to the system. Usually its capacity can be considerably less, based on the calculated input horsepower. A mle of thumb is to provide a heat exchanger removal capacity of about 25 per cent of the input horsepower. Rarely, even on inefficient systems, would a capacity of more than 50 per cent be required. 

If the main fractionator bottoms temperature is limited to 690°F, adding a pool quench can provide additional LCO product recovery. Assuming there is no penalty for the bottoms product quality and there is available cooling capacity in the upper section of the fractionator, this incremental LCO yield is valuable. 

Increasing lean oil rate. This rate is often limited by the debutanizer hydraulic and reboiling/cooling capacity. A 50% increase in lean oil/off-gas ratio increases Cj s recovery about 2%. 

Table 2.2 Energy per 100 kW cooling capacity at 3°C evaporation, 42°C condensation...

For the convenience of users, the refrigerating effect of compressors is usually tabulated (Table 4.1) or given in graphical form (Figure 4.19), and is shown as the net cooling capacity based on the evaporating and condensing temperatures or pressures. Such published data will include absorbed power and indicate any limitations of the application. 

Example 6.1 The following figures from a compressor catalogue give the cooling capacity in British thermal units per hour X 10 and the shaft horsepower, for a range of condensing temperatures... 

Example 6.2 A condenser manufacturer gives a heat rejection capacity factor at 26°C wet hulh temperature of 1.22. What is the condenser duty if the cooling capacity is 350 kW ... 

As an example of these large air flows required, the condenser for an air-conditioning plant for a small office block, having a cooling capacity of 350 kW and rejecting 430 kW, would need 40.85 kg/s or about 36 m /s of air. This cooling air should be as cold as possible, so the condenser needs to be mounted where such a flow of fresh ambient air is available without recirculation. 

Example 6.6 The hardness of water in Coventry is given as a maximum of 560 ppm (parts per million) and the water treatment can permit a concentration of solids to 1200 ppm. The cooling capacity is 700 kW and the compressor power 170 kW. How much water should be bled to waste and what is the total make-up required ... 

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