Absorption System

-
A few household units, called gas refrigerators, operate on the absorption principle. In such gas refrigerators a strong solution of ammonia in water is heated by a gas flame in a container called a generator, and the ammonia is driven off as a vapor, which passes into a condenser. Changed to a liquid state in the condenser, the ammonia flows to the evaporator as in the compression system. Instead of the gas being inducted into a compressor on exit from the evaporator, however, the ammonia gas is reabsorbed in the partially cooled, weak solution returning from the generator, to form the strong ammonia solution. This process of reabsorption occurs in a container called the absorber, from which the enriched liquid flows back to the generator to complete the cycle.

Increasing use of absorption refrigeration now occurs in refrigeration units for comfort space cooling, for which purpose refrigerant temperatures of 45° to 50° F (7.2° to 10° C) are suitable. In this temperature range, water can be used as a refrigerant with an aqueous salt solution, usually lithium bromide, as the absorbent material. The very cold boiling water from the evaporator is absorbed in concentrated salt solution. This solution is then pumped into the generator, where, at elevated temperature, the surplus water is boiled off to increase the salt concentration of the solution; this solution, after cooling, recirculates back to the absorber to complete the cycle. The system operates at high vacuum at an evaporator pressure of about 1.0 kPa (0.145 psi); the generator and condenser operate at about 10.0 kPa (1.45 psi). The units are usually direct-fired or use steam generated in a boiler.

Comments

Post a Comment

Popular posts from this blog

Hanaoka Seishu

-
Image
A stamp depicting the image of Hanaoka Seishu. Hanaoka Seishu (1760-1835), Japanese physician and pioneer of anesthetic surgery. Hanaoka studied traditional Sino-Japanese medicine, as well as what was then known about Western surgery in Japan. For over two decades he experimented with various drugs. Ultimately he created mafutsusan, an anesthetic compound made from six traditional plant-based drugs, including the alkaloids aconite (from the monkshood plant) and datura (from jimsonweed ). In 1805, using mafutsusan as an anesthetic, Hanaoka removed a tumor during breast cancer surgery. This was the world's first recorded successful surgical operation with anesthesia. Later, Hanaoka used the drug for other surgical operations, developing techniques for bladder stone removal and for amputation. Hanaoka attracted many students, and his surgical techniques became known as the Hanaoka method.
Read more

Brahe, Tycho

-
Image
Brahe, Tycho (1546-1601), Danish astronomer, who made precise, comprehensive astronomical measurements of the solar system and more than 700 stars . The data Brahe accumulated was superior to all other astronomical measurements made until the invention of the telescope in the early 17th century. Brahe was born in Knudstrup in southern Sweden (then part of Denmark). He studied law and philosophy at the universities of Copenhagen and Leipzig; at night, however, Brahe busied himself with observing the stars. With no instruments other than a globe and a pair of compasses, he succeeded in detecting grave errors in the standard astronomical tables, and set about correcting them. In 1572 he discovered a supernova in the constellation Cassiopeia . After Brahe had spent some time traveling and lecturing, Frederick II, king of Denmark and Norway, offered to provide Brahe with funds to construct and equip an astronomical observatory on the island of Hven (now Ven). Brahe accepted the proposal,
Read more

Modern Agriculture

-
In the N and W United States the era of mechanized agriculture began with the invention of such farm machines as the reaper, the cultivator, the thresher, and the combine. Other revolutionary innovations, e.g., the tractor, continued to appear over the years, leading to a new type of large-scale agriculture. Modern science has also revolutionized food processing; refrigeration, for example, has made possible the large meatpacking plants and shipment and packaging of perishable foods. Urbanization has fostered the specialties of market gardening and truck farming. Harvesting operations (see harvester) have been mechanized for almost every plant product grown. Breeding programs have developed highly specialized animal, plant, and poultry varieties, thus increasing production efficiency. The development of genetic engineering has given rise to genetically modified transgenic crops and, to a lesser degree, livestock that possess a gene from an unrelated species that confers a desired quali
Read more