Cooling principles

Depending on the cooling principle a difference is made between... 

There is also a separate class of towers based on a dry cooling principle. Each of these major designs is described below. 

NOTE Free cooling from exhaust steam means, in reality, a low cost power source, and is not the same as the free cooling principle employed during winter months, when chilled or condenser water is circulated over the cooling tower without the necessity of switching on the tower fans. 

W.H. Brock, The Norton History of Chemistry, W.W. Norton Co., New York, 1993, p. 6. Brock notes that in Taoism, Yang is the male, hot principle, Yin is the female, cool principle. In Western alchemical beliefs, sulfur is the male principle (Sol) and mercury the female principle (Luna). 

Smaller zone spacing can be achieved due to the active cooling principle. Usual applications have 75 mm zonal spacing, 38 mm spacing is possible if the demands on caHper profile are very high. 

A very significant number of different ammonia synthesis converter designs have been used in industrial practice. In the following survey the different designs have been characterized, first by the cooling principle applied, and thereafter mainly by flow direction through the catalyst bed(s). 

Converters with indirect cooling are used in almost all large, new ammonia plants constructed today. The cooling principle is also introduced in many existing plants by converter revamps, whereby quench cooled converters are modified into converters with indirect cooling by reconstruction of the converter internals (see Sect. 6.4.3.4). 

A refrigeration system is a heat pump in which heat is absorbed below ambient temperature. Thus the appropriate placement principle for heat pumps applies in exactly the same way as for refrigeration cycles. The appropriate placement for refrigeration cycles is that they also should be across the pinch. As with heat pumps, refrigeration cycles also can be appropriately placed across utility pinches. It is common for refrigeration cycles to be placed across a utility pinch caused by maximizing cooling water duty. 

Measurement by Thermal Effects. When a fine wire heated electrically is exposed to a flowing gas, it is cooled and its resistance is changed. The hot-wire anemometer makes use of this principle to measure both the average velocity and the turbulent fluctuations in the flowing stream. The fluid velocity, L, is related to the current, /, and the resistances, R, of the wire at wire, and gas, g, temperatures via... 

Drum Drying. The dmm or roHer dryers used for milk operate on the same principles as for other products. A thin layer or film of product is dried over an internally steam-heated dmm with steam pressures up to 620 kPa (90 psi) and 149°C. Approximately 1.2—1.3 kg of steam ate requited per kilogram of water evaporated. The dry film produced on the roHer is scraped from the surface, moved from the dryer by conveyor, and pulverized, sized, cooled, and put iato a container. 

Although the continuous casting of steel appears deceptively simple in principle, many difficulties are inherent to the process. When molten steel comes into contact with a water-cooled mold, a thin soHd skin forms on the wall (Eig. 10). However, because of the physical characteristics of steel, and because thermal contraction causes the skin to separate from the mold wall shortly after solidification, the rate of heat abstraction from the casting is low enough that molten steel persists within the interior of the section for some distance below the bottom of the mold. The thickness of the skin increases because the action of the water sprays as the casting moves downward and, eventually, the whole section solidifies. 

Heating and Cooling. Heat must be appHed to form the molten zones, and this heat much be removed from the adjacent sohd material (4,70). In principle, any heat source can be used, including direct flames. However, the most common method is to place electrical resistance heaters around the container. In air, nichrome wine is useflil to ca 1000°C, Kanthal to ca 1300°C, and platinum-rhodium alloys to ca 1700°C. In an inert atmosphere or vacuum, molybdenum, tungsten, and graphite can be used to well over 2000°C. 

Distillers vary masking procedures, but generally conform to basic principles, especially in the maintenance of sanitary conditions. The cooking and conversion equipment is provided with direct or indirect steam, propeller agitation, and cooling coils. 

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