Water-cooled cooler

The steam and gas mixture enters water-cooled cooler 9 and through phase separator 10 enters salt-cooled cooler 77. The condensed alcohol is sent into collector 7, and hydrogen chloride vapours are sent through phase separator 12 to be purified in bubble tanks (not shown in the diagram). After the excess alcohol and hydrogen chloride are distilled, the mixture is sampled at 140°C to determine hydrogen chloride content. If HC1 content is below 0.5%, the reactive mass is cooled with water sent into the tank jacket. If hydrogen chloride content exceeds 0.5%, the distillation is continued. 

For fan failure on air coolers, credit may be taken for normal convection according to API 521. The credit shall be 25% of the normal design duty. In case precise calculation is required, a check shall be performed for natural convection using a heat exchanger rating program. In case of a water-cooled cooler, credit is not allowed if the cooling water flow stops. 

Cooler, water-cooled, rates are about 5 percent lower. 

Trim Coolers Conventional air-cooled heat exchangers can cool the process fluid to within 8.3°C (15°F) of the design dry-biilb temperature. When a lower process outlet temperature is required, a trim cooler is installed in series with the air-cooled heat exchanger. The water-cooled trim cooler can be designed for a 5.6 to 11.1°C (10 to 20°F) approach to the wet-biilb temperature (which in the United States is about 8.3°C (15°F) less than the diy-bulb temperature). In arid areas the difference between diy- and wet-bulb temperatures is much greater. 

Maintenance cost. Maintenance for air-cooled equipment as compared with sheU-and-tube coolers (complete with coohng-tower costs) indicates that air-cooling maintenance costs are approximately 0.3 to 0.5 those for water-cooled equipment. 

In cooling by means of forced ventilation, or where the machine has water-cooled air or gas coolers, the temperature of the air or gas, where it enters the motor must be considered as the cooling air or gas temperature. For motors fitted with heat exchangers the temperature reading of incoming air or gas or water should also be tiikcn. 

Anodic protection today allows safe and efficient protection of air coolers and banks of tubes in sulfuric acid plants. In 1966 the air cooler in a sulfuric acid plant in Germany was anodically protected. Since then more than 10,000 m of cooling surfaces in air- and water-cooled sulfuric acid plants worldwide have been protected. The dc output supply of the potentiostats amounts to >25 kW, corresponding to an energy requirement of 2.5 W per m of protected surface. As an example. Fig. 21-9 shows two parallel-connected sulfuric acid smooth tube exchangers in a production plant in Spain. 

Where hot ambient temperatures are expected, overall turbine efficiency and horsepower output can be increased by installing an evaporative cooler in the inlet. Inlet air flows through a spray of cold water. The temperature of the water and the cooling effect caused by the inlet air evaporating some of the water cools the inlet air. In desert areas where the inlet air is dry and thus able to evaporate more water before becoming saturated with water vapor, this process is particularly effective at increasing turbine efficiency. 

In direct contact heal exchange, there is no wall to separate hot and cold streams, and high rales of heal transfer are achieved. Applications include reactor off-gas quenching, vacuum condensers, desuperheating, and humidification. Water-cooling lowers are a particular example of a direct contact heal e.xchanger. In direct contact cooler-condensers, the condensed liquid is frequently used as the coolant. 

A mixture of 3,000 scfin, dry basis, (14.7 psia and 60°F), 60% methane and 40% nitrogen is to be compressed from 16 psig to 3500 psig. Suction temperature is 90°E Intercoolers will use 85°F water cooling gas to 90°F, and the installation is essentially at sea level. The gas is saturated with water vapor. Five lb pressure drop is to be allowed for the interstage coolers. 

In chilled-water systems, pump shaft power adds to the heat of the circulating water. Similarly, if the chiller has a water-cooled condenser pump heat is added to that handled by the final cooler. Power is proportional to the flow and pressure ... 

In conventional compressed air systems, vapor and liquid removal is limited. Most two-stage compressors will include an intercooler between stages. On air-cooled units for 100 to 200psig service, the air between stages is not cooled sufficiently to cause substantial liquid drop out and provision is not usually made for its removal. Water-cooled intercoolers used on larger compressors will usually cool sufficiently to condense considerable moisture at cooler pressure. Drainage facilities must always... 

Cold suction gas provides cooling for the compressor and is sufficient to keep small machines at an acceptable working temperature. Refrigerantshaving high discharge temperatures (mainly ammonia) require the use of water-cooled cylinder heads. Oil coolers are needed under some working conditions which will be specified by the manufacturer. These maybe water cooled or take refrigerant from the system. 

In a water cooling tower, the temperature profiles depend on whether the air is cooler or hotter than the surface of the water. Near the top, hot water makes contact with the exit air which is at a tower temperature, and sensible heat is therefore transferred both from the water to the interface and from the interface to the air. The air in contact with the water is saturated at the interface temperature and humidity therefore falls from the interface to the air. Evaporation followed by mass transfer of water vapour therefore takes place and latent heat is carried away from the interface in the vapour. The sensible heal removed from the water is then equal to the sum of the latent and sensible heats transferred to the air. Temperature and humidity gradients are then as shown in Figure 13.18 . 

Near room temperature most gases become less soluble in water as the temperature is raised. The lower solubility of gases in warm water is responsible for the tiny bubbles that appear when cool water from the faucet is left to stand in a warm room. The bubbles consist of air that dissolved when the water was cooler it comes out of solution as the temperature rises. In contrast, most ionic and molecular solids are more soluble in warm water than in cold (Fig. 8.22). We make use of this characteristic in the laboratory to dissolve a substance and to grow crystals by letting a saturated solution cool slowly. However, a few solids containing ions that are extensively hydrated in water, such as lithium carbonate, are less soluble at high temperatures than at low. A small number of compounds show a mixed behavior. For example, the solubility of sodium sulfate decahydrate increases up to 32°C but then decreases as the temperature is raised further. 

Metallic Ca is prepared in the laboratory by reducing CaO with A1 powder. The reaction mixture is charged in an evacuable steel bomb, designed such that one end can be heated while the other end is water cooled. After the bomb has been evacuated, the charge is heated to 1200-1300 C in vacuum and the Ca condenses at the cooler end of the bomb. After cooling, the bomb is filled with Ar and the metal recovered. Metallic Ca can also be prepared by reducing CaCl2 with metallic Na. 

Convection As water cools, convection currents within the sample occur as cooler, more dense water sinks, causing the water to circulate. However, water is most dense at 4°C, so at some point, colder liquid water will sink and a film of less dense ice will form at the top and insulate the sample from the cold. Some people speculate that the warmer sample will have more convection currents and will cool quicker. 

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