All-year copnditioning, ventillaion, gas supply (part 1)

(1) Air conditioning implies the control of temperature, humidity, purity and motion of the air in an enclosure. In our modern world of science and highly developed technology air conditioning is of great importance for industrial processes and for human comfort. Air conditioning for human comfort is employed in large and small installations, such as theatres, office buildings, department stores, residences, airplanes, railways, cars and submarines. According to their purpose air conditioning systems may be described as winter, summer and all-year systems.

(2) All year-conditioning systems must provide means for performing all the processes required for winter and summer air conditioning. The basic pieces of equipment are the filters, preheat coils, humidifiers, dehumidifiers, reheat coils, additional cooling coils, fans and controls. The control of air purity can be achieved in various degrees. As a minimum control some sort of filtering must be done near the entrance of the air-conditioning system. Possibly the most efficient filtering device is the electrostatic precipitator.

(3) In order to establish the size and operation requirements of an air-conditioning system, the maximum probable heating and co-demands have to be calculated. The maximum probable heating demand is usually for winter air conditioning and it involves heating and humidifying. The maximum probable cooling demand is generally for summer applications and requires cooling and dehumidifying. The inside design conditions depend upon the purpose for which air conditioning is used. Certain industrial process requirements and human comfort are the two major factors to be considered. With ever increasing tendency to use air-conditioning a building engineer must have good knowledge of the subject.

 

Вариант 16.

ALL-YEAR COPNDITIONING, VENTILLAION, GAS SUPPLY (part 2)

(4) As far as ventilation is concerned the purpose of ventilation is to carry away excess heat and odours. In buildings such as homes, the leakage of air through cracks on doors and windows is usually sufficient to meet this requirement. Although ventilation was formerly concerned with the supply of fresh air and the removal of hot and contaminated air from the space it is also associated with cleaning of air.

(5) Industrial buildings often present special problems in ventilation. There are certain industrial processes that are accompanied by the production of air-born dust, fumes, toxic vapours and gases which are hazardours to the health of workers. Three types of ventilation are in use so that to control dangerous gases and dusts: exhaust systems, dilution systems and combination of both.

(6) Another indispensable part of modern amenities is gas supple. At the present time natural gas is put to large-scale economic use. The principal utilization of natural gas is as clean, convenient, economical source of heat. In homes it is used for cooking, water heating, and refrigeration for food as well (а также) for space heating. Nowadays most of the homes are heated by natural gas and the number of gas-supplied homes was increasing at a rate limited chiefly by the ability of steel industry to produce the pipe through which the gas is transported. Natural gas supply is used also as a heat source in commercial establishments such as restaurants and bakeries for cooking and in stores, offices and other commercial buildings for heating and comfort cooling.

Вариант 17.

WATER SUPPLY

(1)Water is an important part of nature which surrounds us and of those natural conditions we are changing constantly and intensively: the flora, the soil, the mountains, mineral resources, the deserts, the marches, the steppes and the taiga.

(2) Vast depressions in the earth are filled with water through the medium of natural water sources such as rivers, lakes, etc. over the earth’s surface. These bodies of water are classified as inland lakes and are excellent sources of water. Often a water body deep in the soil consists of a sand or gravel stratum which connects or empties into the basin of an inland lake and provides a splendid source of water supply through the medium of a drilled well.

(3) Man uses water for domestic and sanitary purposes and returns it to the source through sewage disposal system. It is of prime importance that the supply must be protected against pollution, because no one can predict how disastrous may be the results.

(4) An adequate supply of pure, wholesome and palatable water is essential to the maintenance of high standards of health and to provide the convenience and comfort to the community. In some localities water is available in unlimited quantities and converting it to use is not a difficult problem. This is especially true of towns situated on large inland lakes or rivers. But there are cities where geographical location requires elaborate systems of water supply, and to provide a satisfactory supply of water in these localities becomes a large engineering task.

(5) The importance of a sufficient supply of water for domestic and industrial purpose has long been a deciding factor in the location of cities. The earliest settlers realized this need and took advantage of natural water resources by establishing colonies in close proximity to them.

(6) Water may be taken from any source of water for human consumption after it has undergone a preliminary treatment to assure its purity. As man’s communities grew in population, the demand for water increased and the need for protection of the source of water supply against the possibility of contamination became evident. Progress and civilization have called for elaborate and various systems and methods of water treatment.

 

 

Вариант 18.

SEWERAGE

 

(1)The problem of protecting natural water resources has grown very urgent for many countries since the beginning of the second half of the 20^th century. The rivers, lakes and ground water contain today a considerable amount of the products of mechanical, chemical and biological pollution due to the development of human society, social and technical progress.

(2) The waste products that result from the daily activities in a community are of two general types: the liquid waste as sewage and the solid wastes, known as refuse. Sewage may be also divided according to its source into the following three classes. The sewage from residences, institutions and business buildings is called domestic sewage, sanitary sewage or house sewage; the resulting from industrial processes is known as industrial waste, and that of from run-off during storms is called storm sewage. A combination of domestic sewage, industrial waste and storm water is called combined sewage.

(3) Sewage and refuse must be removed promptly in order to avoid endangering the health of the community. The removal of all kinds of sewage is usually accomplished by means of sewers. The sewers are placed in the streets at several feet below the ground surface. The entire system of sewers including a sewage treatment plant is known as a sewerage system.

(4) The method of sewage treatment to be adopted in a particular case will depend entirely on local conditions. The usual methods of sewage treatment consist of preliminary treatment alone or primary treatment followed by secondary treatment. During primary treatment the larger and heavier solid particles settle out from the liquid. Secondary treatment is required to remove decomposable materials from the sewage. An auxiliary treatment, which may be used with primary or secondary treatment is disinfection or the killing of the most of the bacteria in the sewage by means of chemicals.

 

Вариант 19.