HVAC equipment: processes of cooling

The process of cooling is actually removal of heat. Comfort cooling is almost always accomplished by cooling air and then distributing the air into the space, where it mixes with the room air and cools down the entire volume.

There are four principal processes of cooling: a) mechanical compression refrigeration, b) absorption refrigeration, c) evaporative cooling, and d) natural ventilation. Cooling processes almost always involve circulating air through a machine that cools air down and blows it with a fan back into the space to be conditioned. The fluid that imparts the cooling effect to air is either a refrigerant which changes from a liquid to a gas or water. The central cooling generation equipment is referred to as DX(direct expansion) when the fluid used is a refrigerant. If the fluid is water, then the equipment called water chiller.

The mechanical vapor-compression cycle (Figure 3.13) is a method of transferring heat from one location to another. The cycle consists of four basic components: a) evaporator, b) compressor, c) condenser, and d) expansion valve.

Figure 3.13 Mechanical compression refrigeration system.

Ответьте на вопросы к тексту:

1. What isthe process of cooling?

2. How does the process of cooling work?

3. How many principal processes of cooling are there?

4. What do cooling processes involve?

5. What is the central cooling generation equipment referred to?

6. How is the equipment called if the fluid is water?

7. What is the mechanical vapor-compression cycle?

8. What does the cycle consist of?

 

 

Упражнение 1. Переведите слова и словосочетания на русский язык.

Removal (n.); comfort cooling; accomplish (v.); distribute (v.); entire volume; mechanical compression refrigeration; absorption refrigeration; evaporative cooling; natural ventilation; involve (v.); fan (n.); impart (v.); cooling effect; refrigerant (n.); central cooling generation equipment; refer to (v.); DX(direct expansion); water chiller; mechanical vapor-compression cycle; location (n.); consist of (v.); evaporator (n.); compressor (n.); condenser (n.); expansion valve.

Actually; almost; always; and; then; into; where; with; through; down; back; that; either; which; from; or; as; when; if.

 

Упражнение3. Переведите слова и словосочетания на английский язык.

Сжатие в компрессоре;испарение охлаждением;естественная вентиляция, аэрация; придавать, наделять;охлаждающее действие; холодильный агент;установка для охлаждения водой; цикл с механической компрессией пара;расширительный клапан, регулирующий вентиль.

Всегда; и; затем; где; с; через; назад; который; когда; что; либо; от; как, в качестве; если.

 

Упражнение 4. Найдите перевод слов списка А в списке В.

А

Evaporator; compressor; liquid; refrigeration; chiller; direct expansion; ventilation; valve; condenser; space; equipment; fan; fluid; absorption; location; volume; accomplish; distribute; impart; another; consist of; involve;

refer to; almost; always; through.

В

Жидкость; клапан; охлаждение; компрессор; текучая среда; испаритель; непосредственное охлаждение; пространство; через; оборудование; вентиляция; состоять из; всегда; относится к; придавать; другой; расположение; объем; завершать; тягодутьевое устройство; конденсатор; распределять; почти; абсорбция; включать; охладитель (охлаждающий теплообменник).

Упражнение 5. Найдите в тексте прилагательное с суффиксом -al и наречия с суффиксом –ly.

Упражнение 6. Сопоставьте элементы оборудования по охлаждению и подогреву (А) с их функциями (В).

(A) The essential elements of delivery side cooling and heating equipment are:

1) air handling equipment;

2) supply network;

3) return path;

4) exhaust outlet;

5) fresh air inlet;

(B) Functions:

a. required to replace exhaust air and maintain an acceptable level of air quality.

b. carries air back to the delivery unit (air handling unit). Ducting is optional.

c. distributes conditioned air to different part of the building. Ducts required.

d. controls temperature, humidity, and quality of air.

e. required to get rid of odors and air contaminants.

Урок 3.7

Упражнение 1. Прочитайте слова.

[i] e' xpansion; е' vaporators; e x ' changer; e' ffect; e' lectrical; e lect ' ricity; e 'xcept; e x'tract (v.); r e c 'i procating; d e gr ee; r e f 'r i gerant.

 

Упражнение 2. Сопоставьте слово с переводом и соответствующей ему транскрипцией.

1) evaporator; 2) medium; 3) vaporization; 4) reciprocating; 5) cylinder; 6) coil;

 

1) ['ÅJdIqÅ]; 2) ["ÈÂip(¶)Ïai'zÂi¿(Â)Í]; 3) [i'È∙p¶ÏÂitq]; 4) ['ÉIÎIndq]; 5) [ÏI'sIÃÏqÐÂIËIN]; 6) ['иIl ];

1) поршневой; 2) испаритель; 3) испарение; 4) среда (вещество); 5) змеевик; 6) цилиндр.

 

Текст А

Evaporators and Compressors

 

An evaporatoris a heat exchanger in which the liquid refrigerant is vaporized and extracts heat from the surrounding air, chilled water, brine, or other substance to produce a refrigeration effect. Evaporators used in air-conditioning can be classified according to the combination of the medium to be cooled and the type of refrigerant feed; broadly 2 types are used in comfort applications:

Direct expansion coils are air coolers, and the refrigerant is fed according to its degree of superheat after vaporization.

Flooded shell-and-tube liquid coolers is similar in construction to a shell-and-tube water-cooled condenser, except that it’s liquid refrigeration inlet is at the bottom and the vapor outlet is at the top. Water velocity inside the copper tubes is usually between 4 and 12 ft/sec and the water-side pressure drop is normally below 10 psig. Flooded liquid coolers can provide larger evaporating surface area and need minimal space. They are widely used in large central air-conditioning systems.

The compressorcompresses the refrigerant gas, causing it to become much warmer than the outside air. The refrigerant enters the compressor on the "suction side" and after it leaves the compressor, the refrigerant is referred to as "hot gas”. Four types of electrical chillers ( Figure 3.14) dominate the market: reciprocating compressors, scroll compressors, screw compressors, centrifugal compressors. Reciprocating compressors are driven by a motor and use pistons, cylinders and valves to compress the refrigerant. Scroll compressors feature two involute scrolls, one stationary and one orbiting around the first. Power input to the scroll compressor is about 5 to 10% less than to the reciprocating compressor. A scroll compressor also operates more smoothly and is quieter. Screw compressors are based on a mechanism made up of two threaded rotors (screws) that are coupled together. Twin-screw compressors are more efficient than reciprocating compressors.Centrifugal compressors are made up of a rotor located inside a special chamber. The characteristics of a centrifugal compressor make it ideal for air conditioning applications because it is suitable for variable loads, has few moving parts, and is economical to operate. They are the most widely used refrigeration compressors in large air-conditioning systems but are used only in water cooled configurations due to lower compression ratios.

Notes:

psig (pounds per square inch gauged) фунт на квадратный дюйм индикаторный.

 

Figure 3.14 Ciller system.

 

Ответьте на вопросы к тексту:

1. What is an evaporator?

2. How can evaporators used in air-conditioning be classified?

3. What is the difference between flooded shell-and-tube liquid coolers and shell-and-tube water-cooled condenser?

4. How does the compressor work?

5. What types of electrical chillers do dominate the market?

6. What are reciprocating compressors driven by?

7. How does a scroll compressor operate?

8. What are screw compressors based on?

9. What are the centrifugal compressors made up of?

10. Why is the centrifugal compressor ideal for air conditioning applications?

11. Why are the centrifugal compressors used only in water cooled configurations?

 

Упражнение 3. Переведите слова и словосочетания на русский язык.

Vaporize (v.); extract (v.); surrounding air; brine (n.); substance; classify (v.); according to; combination (n.); medium (n.); refrigerant feed; broadly (adv.); application; coil (n.); superheat (n.); vaporization (n.); flooded shell-and-tube liquid cooler; construction (n.); shell-and-tube water-cooled condenser; except (v.); liquid refrigeration inlet; bottom (n.); vapor outlet; top (n.); water velocity; inside; below; flooded liquid cooler; provide (v.); evaporating surface area; central air-conditioning systems; refrigerant gas, cause (v.); outside air; suction side; electrical chiller; dominate (v.); reciprocating compressor; scroll compressor; screw compressor; centrifugal compressor; drive by (v.); motor (n.); piston (n.); cylinder (n.); valve (n.); feature (n.); involute scroll; stationary; orbiting; power input; operate (v.); smoothly; base on (v.); threaded rotor; couple together; chamber (n.); compression ratio.

 

Упражнение 4. Переведите слова и словосочетания на английский язык.

Газообразный хладагент; сторона пониженного давления, сторона всасывания;поршневой компрессор; спиральный компрессор; винтовой компрессор; центробежный (ротационный) компрессор; скрученный, закрученный; спираль; потребляемая мощность; нарезной ротор(винт); соединять, связывать;коэффициент сжатия (уплотнения); охлаждающий раствор солей; перегрев, избыточное тепло; змеевик непосредственного охлаждения; окружающий воздух; затопленный кожухотрубный жидкостный охладитель;область парообразующей поверхности; центральная система кондиционирования воздуха.

 

Упражнение 5. Сопоставьте слово (A) с его определением (B).

(А)

1) refrigerant;

2) evaporator;

3) cooler;

4) compressor;

5) condenser;

6) scroll;

7) screw;

(В)

a) an apparatus or container for condensing vapour;

b) a machine used to supply air or other gas at increased pressure;

c) a device used to turn the liquid form of a chemical into its gaseous form;

d) a thin pointed piece of metal that you push and turn in order to fasten pieces of metal or wood together;

e) a substance used for refrigeration;

f) a machine for cooling something;

g) a design shaped like a piece of rolled up paper.

Упражнение 6. Переведите предложения и определите функцию причастия I и II (Participle I & II), обратите внимание на независимый причастный оборот.

1. Local systems may be totally shut off in the unused spaces providing potential energy savings.

2. Serving only a single zone, local heating systems have only one point of control.

3. Employees found under the influence of alcohol will be immediately removed from the job site.

4. Heat transfer oils used in liquid systems offer freeze protection.

5. Evaporators used in air-conditioning can be classified according to the combination of the medium to be cooled and the type of refrigerant feed.

6. Screw compressors are based on a mechanism made up of two threaded rotors.

7. An evaporatoris a heat exchanger extracting heat from the air.

8. The electrical chillers dominating the market are scroll compressors, screw compressors, centrifugal compressors and others.

9. Having few moving parts, centrifugal compressor is economical to operate.

10. Providing larger evaporating surface area, flooded liquid coolers need minimal space.

11. The system objectives having been determined, the architect choose the type of system.

12. The centrifugal compressor being ideal for air conditioning applications, the engineers used them a lot.

13. Time permitting, they will come next week.

14. Your attempt falling, no one will help us.

 

Упражнение 7. Заполните пропуски, используя данные слова.

Are used; is used; is; reenters; to absorb.

Expansion process

The final step in the refrigeration cycle …….. the expansion of the refrigerant in an expansion valve. This relieves the pressure built up by the compressor. Temperature is thus reduced even further allowing the refrigerant …….. more heat from the interior space when it …….. the evaporator. For large chillers, electronic thermostatic expansion valves ……. as expansion device, whereas in smaller systems such as window air conditioners capillary tube ……..

Упражнение 8. Образуйте существительные от следующих глаголов, используя суффикс –ment и переведите их.

Accomplish; assign; assess; govern; enforce; environ; equipment; move; manage; replace; require; supple; treat.

 

Упражнение 9. Задайте 5 вопросов различных типов к тексту А.

Текст В

Condenser

A condenseris a heat exchanger in which hot gaseous refrigerant is condensed into liquid and the latent heat of condensation is rejected to the atmospheric air, surface water, or well water. In a condenser, hot gas is first desuperheated, then condensed into liquid, and finally sub-cooled. Condensers can be either air-cooled (Figure 3.15)or water-cooled(Figure 3.16).

Air cooled condensersuse ambient air to remove heat from the refrigerant. Hot gas from the compressor enters the condensing coil from the top. A fan forces air across small tubes containing the hot refrigerant and discharges that heat into the ambient air. The volume flow of cooling air per unit of total heat rejection is typically 600 to 1,200 cfm/ton of refrigeration capacity and the optimum value is about 900 cfm/ton. The corresponding cooling air temperature difference — cooling air leaving temperature minus outdoor temperature is around 13°F. Air-cooled condensers are rated at a specific condenser temperature difference, depending on the evaporating temperature of the refrigeration system. The condenser temperature difference for an air-cooled condenser is defined as the difference between the saturated condensing temperature corresponding to the pressure at the inlet and the air intake temperature. For a refrigeration system having a lower evaporating temperature, it is more economical to equip a larger condenser with a smaller condenser temperature difference. For a comfort air-conditioning system having an evaporative temperature of 45°F; condenser temperature difference is 20 to 30°F.

Water-cooled condensers;water condensed units are more efficient than air condensed, often operating in the range of 15 EER (energy efficiency ratio) or better. Water-cooled chillers require a source of cooling water, such as cooling tower water, to extract heat from the refrigerant at the condenser and reject it to the ambient environment. Two types of water-cooled condensers are widely used for air-conditioning and refrigeration: double-tube condensers and horizontal shell-and-tube condensers.

 

 

 

Figure 3.15 Air-cooled condenser(HR-hot reheat; HRSG- heat recovery steam generation-паровой котел-утилизатор).

 

 

Figure 3.16 Water-cooled condenser.

Ответьте на вопросы к тексту:

1. What is a condenser?

2. What types of condensers are there?

3. How do air cooled condenserswork?

4. How is the condenser temperature difference for an air-cooled condenser defined?

5. What is more economical for a refrigeration system having a lower evaporating temperature?

6. How do water cooled condenserswork?

7. What types of water-cooled condensers are widely used for air-conditioning and refrigeration?

Упражнение 2. Переведите слова и словосочетания на русский язык.

Gaseous refrigerant; latent heat; reject (v.); atmospheric air; surface water; well water; desuperheat (v.); sub-cooled; air-cooled condenser; water-cooled condenser; ambient air; coil (n.); force (v.); discharge (v.); flow (n.); heat rejection; refrigeration capacity; optimum value; temperature difference; leaving temperature; outdoor temperature; rate; define (v.); saturated condensing temperature; air intake temperature; EER (energy efficiency ratio); cooling tower water; extract (v.).

In; which; into; and; then; either; from; that; cfm/ton; about; around; between; with; often; per unit; such as; °F.

 

Упражнение 3. Переведите слова и словосочетания на английский язык.

Вода из скважины;конденсатор с водяным охлаждением; до вскипания; окружающий воздух;отвод тепла;вода, охлажденная в градирне (башня); температура воздухозабора; поверхностные воды;температура на выходе; температура насыщенного пара; газообразный хладагент; коэффициент энергоэффективности; футы в минуту; в диапазоне; тонна.

Между; который; с; на единицу (длины, площади, объема); такой как; около (2); часто; от; что; затем; в; внутрь.

 

Упражнение 4. Найдите в тексте эквиваленты следующих словосочетаний.

Температура конденсации; давление конденсации; потребляемая мощность компрессора; конденсатор с воздушным охлаждением недостаточной величины; высокая температура поступающего охлаждающего воздуха; загрязненный охладительный змеевик; циркуляция нагретого воздуха; недостаточный зазор; степень сжатия компрессора; понижать температуру перегретого пара;энергопотребление.

 

Упражнение 5. Прочитайте текст и переведите его, не используя словарь.

Condensers

A higher condensing temperature, a higher condensing pressure, and a higher compressor power input may be due to an undersized air-cooled condenser, lack of cooling air or a high entering cooling air temperature, a dirty condensing coil, warm air circulation because of insufficient clearance

between the condenser and the wall, or a combination of these. The clearance should not be less than the width of the condensing coil. Compared to water, air is a poor conductor of heat and therefore air-cooled chillers are larger and less efficient. Air-cooled machines operate at higher compressor ratios – which mean less cooling per watt energy consumption.

 

Упражнение 6. Найдите в тексте причастия II (Participle II). Определите их функцию и переведите на русский язык.

 

Урок 3.8

Упражнение 1. Прочитайте слова.

[µ] o ne; t o n, f u nction; p u mp, b u lb; o ther; res u lt; c o mfort; j u st.

 

Упражнение 2. Сопоставьте слово с переводом и соответствующей ему транскрипцией.

1) quantity; 2) equal; 3) equivalent; 4) duty; 5) magnitude; 6) to cause;

 

1) ['Å∙ÑÍIË(j)u:Ì]; 2) ['Ìju:ti]; 3) ['i:ÐÆqÎ]; 4) [I'ÐÆiÈ(q)ÎqnË]; 5) ['ÐƸÍËqËI]; 6) ['и:Ê ];

1) эквивалент (равный по величине); 2) величина; 3) вызывать; 4) количество; 5) равный; 6) производительность (зд.).

 

Текст А

Cooling towers

A cooling tower (Figure 3.17)is a heat rejection device, installed outside of the building envelope, through which condenser water is circulated. Refrigerant in the refrigeration cycle is condensed in a refrigerant to water heat exchanger. Heat rejected from the refrigerant increases the temperature of the condenser water, which must be cooled to permit the cycle to continue. The condenser water is circulated to the cooling tower where evaporative cooling causes heat to be removed from the water and added to the outside air. The cooled condenser water is then piped back to the condenser of the chiller. A cooling tower is a latent heat exchanger, where the magnitude of heat flow is a function of the quantity of water that is evaporated which is primarily a function of the relative humidity of the outside air. Cooling Towers for HVAC duty are usually described by their tons of cooling capacity. The cooling capacity indicates the rate at which the cooling tower can transfer heat. One ton of cooling is equal to 12,000 BTUs (British thermal units) per hour, or 200 BTUs per minute. The heat rejected from an air conditioning system equals about 1.25 times the net refrigeration effect. Therefore the equivalent tonon the cooling tower side actually rejects about 15,000 Btu/hour (12,000 Btu cooling load plus 3,000 Btu’s per ton for work of compression). Cooling tower capacities at commercial, industrial, or institutional facilities typically range from as little as 50 tons to as much as 1,000 tons or more. Large facilities may be equipped with several large cooling towers.

 

Figure 3.17 Cooling tower.

 

Ответьте на вопросы к тексту:

1. What is cooling tower?

2. How does it work?

3. What is the magnitude of heat flow?

4. How are HVAC duty usually described?

5. What does the cooling capacity indicate?

6. How do the cooling tower capacities at commercial, industrial, or institutional facilities typically range?

Упражнение 3. Переведите слова и словосочетания на русский язык.

Heat rejection device; install (v.); outside (adv.); building envelope; refrigeration cycle; reject (v.); permit (v.); evaporative cooling; cooling tower; latent heat exchanger; relative humidity; cooling capacity; equal (adj.); equivalent (n.); net refrigeration effect; ton (n.);facility (n.); typically (adv.); range (v.); equipped with.

Through; which; therefore.

 

Упражнение 4. Переведите слова и словосочетания на английский язык.

Охлаждающая башня; отвергать, отводить; относительная влажность; охлаждающая вода в конденсаторе; варьироваться, изменяться в пределах; указывать, показывать; охлаждающая способность, производительность холодильной установки; расход холода (тепловая нагрузка); производительность системы ОВиК (Отопление, Вентиляция и Кондиционирование).

 

Упражнение 5. Сопоставьте слово (A) с его определением (B).

(А)

1) to permit;

2) cooling capacity;

3) to indicate;

4) cooling tower;

5) to reject;

6) to pipe;

7) to range;

(В)

a) to send a liquid or gas through a pipe to another place;

b) is the measure of a cooling system's ability to remove heat;

c) to point out, show;

d) a tall, open-topped, cylindrical concrete tower, used for cooling water or condensing steam from an industrial process;

e) to dismiss as inadequate, unacceptable, or faulty;

f) to allow (someone) to do something;

g) to vary or extend between specified limits.

Упражнение 6. Переведите письменно термины и дефиниции, используемые в производстве охлаждающих башен (градирни), используйте словарь при необходимости.

1. BTU (British thermal unit) -BTU is the heat energy required to raise the temperature of one pound of water one degree Fahrenheit in the range from 32°F to 212°F.

2. Cooling Range - The difference in temperature between the hot water entering the tower and the cold water leaving the tower is the cooling range.

3. Approach - The difference between the temperature of the cold water leaving the tower and the wet-bulb temperature of the air is known as the approach.

Establishment of the approach fixes the operating temperature of the tower and is the most important parameter in determining both tower size and cost.

4. Drift - Water droplets that are carried out of the cooling tower with the exhaust air. Drift loss does not include water lost by evaporation. Proper tower design can minimize drift loss. The drift rate is typically reduced by employing baffle-like devices, called drift eliminators, through which the air must travel after leaving the fill and spray zones of the tower.

5. Heat Load - The amount of heat to be removed from the circulating water within the tower. Heat load is equal to water circulation rate (gpm) times the cooling range times 500 and is expressed in BTU/hr. Heat load is also an important parameter in determining tower size and cost.

6. Ton - An evaporative cooling ton is 15,000 BTU's per hour. The refrigeration ton is 12,000 BTU’s per hour.

7. Wet Bulb Temperature (WBT) - The lowest temperature that water theoretically can reach by evaporation. Wet-Bulb temperature is an extremely important parameter in tower selection and design, and should be measured by a psychrometer.

8. Dry-Bulb Temperature - The temperature of the entering or ambient air adjacent to the cooling tower as measured with a dry-bulb thermometer.

9. Pumping Head - The pressure required to pump the water from the tower basin through the entire system and return to the top of the tower.

10. Makeup - The amount of water required to replace normal losses caused by bleed off, drift and evaporation.

11. Bleed off - The portion of the circulating water flow that is removed in order to maintain the amount of dissolved solids and other impurities at an acceptable level. As a result of evaporation, dissolved solids concentration will continually increase unless reduced by bleed off.

Упражнение 7. Переведите предложения, обращая внимание на условные придаточные предложения. Определите тип предложений.

1. If the temperature in the boiler rose to dangerous values, in that case the pipes of the boiler could melt down.

2. It will be very harmful for the boiler if it contains too little water.

3. If peek temperatures occur during combustion, NOx will be formed.

4. The air is cooler and drier if there is an air conditioning system in the room.

5. If unrealistically low allowable pressure drops were imposed, the designer would be forced to use lower fluid velocities to maintain the pressure drops limitations.

6. If the air is cooled directly by passing it over an evaporator, the process is known as direct expansion.

7. If customers did not understand HVAC design aspects, the engineer would guide and advise the customer on the best option.

8. If comfort is to be provided for occupants, a zone requires separate control.

9. If the longest duct run had been less than 200 feet from the heat source, furnaces would have provided effective heating in smaller buildings.

10. In general local heating system is a plus if majority of areas remain unoccupied and if the people preferences require different temperatures or they disagree about the most comfortable temperature.

 

Упражнение 8. Переведите предложения, обращая внимание на функцию герундия.

1. Evaporative cooling causes heat.

2. The field of heating and ventilation is a science and practice to provide health and comfortable interior conditions for occupants.

3. Sometimes the air is cooled directly by passing it over an evaporator.

4. The control of cooling, heating, and moisture provide the foundation for key HVAC system design and components.

5. Humidifier is a device for keeping the atmosphere in a room moist.

6. This unit works by moving heat from one area to another.

7. Employers and supervisors are responsible for reporting all injuries to the government authority.

8. An air solar system does not suffer from corrosion or freezing.

9. Deformation is the action or process of changing in shape or distorting, especially through the application of pressure.

10. Absorptance of solar radiation by the collector can be increased by using glass that has low iron content.

11. The drift rate is typically reduced by employing baffle-like devices.

12. Comfort cooling is almost always accomplished by cooling air and then distributing the air into the space.

13. This unit works by moving existing heat from one area to another.

Упражнение 9. Переведите предложения, обращая внимание на формы с суффиксом –ing.

1. Glass is a transparent solid substance used for making windows, bottles etc.

2. All kinds of online cleaning methods were developed.

3. Electroplated black nickel, black chrome, copper oxide or anodized aluminum are common types of selective coatings.

4. The contractor is responsible for obtaining appropriate medical and emergency assistance.

5. Local systems may be totally shut off in the unused spaces providing potential energy savings.

6. The burning of fuel takes place inside an enclosed metal container.

7. Furnaces provide effective heating in smaller buildings.

8. The ventilating of a kitchen uses ductwork and fans with a hood.

9. The exhaust gases including carbon-mono-oxide are vented to the exterior of the building.

10. All these surroundings have a uniform compjsition.

Упражнение 10. Задайте 5 различных типов вопросов к тексту А.

Текст В

Cooling Tower Materials (1)

Cooling tower structures are constructed using a variety of materials. While package cooling towers are generally constructed with fiberglass, galvanized steel (or stainless steel in special situations), many possibilities exist for field-erected structures. Field-erected towers can be constructed of douglas fir, redwood, fiberglass, steel or concrete (Figure 3.18). Each material has advantages and disadvantages.

Wood -In early days, towers were constructed primarily of redwood because of its natural tendency to inhibit decay. As the redwood resources diminished, douglas fir come into existence. Douglas fir however supports the growth and proliferation of micro-organisms causing rapid diglinification (eating of wood). Various methods of pressure treatment and incising are used to prevent micro-organisms attack to wood, which includes chrome copper arsenate and acid copper chromate treatment. Chromate copper arsenate was initially used as a preservative but because of its arsenic content, acid copper chromate has replaced it. Irrespective of any treatment, the leaching of chemicals is still a concern to the environment and sometimes extensive additional water treatment of blowdown and tower sediment is needed. Some drawbacks of wooden towers are stated below:

• The wooden structure is less durable and its life expectancy is low. Delignification (eating of wood) is controlled by adjusting the pH strictly between 7 and 7.5.

• The drift losses are over 1%.

• The tower has a larger footprint and needs more space when compared to other alternatives.

• Algae formation is a continuous problem in this type of Cooling Tower.

• The wooden structure is less durable.

• The wooden tower usually requires a large concrete tank that involves more cost, time and labor. Since this type of cooling tower is extremely heavy, it has to be installed on ground only.

• The nozzles on the wooden tower consume a significant amount of pressure head, which results in pressure drop.

 

 

Figure 3.18 Cooling towers.

Ответьте на вопросы к тексту:

1. What are package cooling towers generally constructed with?

2. What can field-erected towers be constructed of?

3. What advantages does wood have?

4. What are the drawbacks of wooden towers?

5. What does the wooden tower usually require?

6. Where does it have to be installed?

Упражнение 2. Переведите слова и словосочетания на русский язык.

Cooling tower structure; fiberglass (n.); galvanized steel; stainless steel; field-erected structure; douglas fir; redwood (n.); wood (n.); inhibit (v.); decay (v.); diminish (v.); support (v.); proliferation (n.); pressure treatment; prevent (v.); chrome copper arsenate; acid copper chromate; irrespective; chemical (n.); concern (n.); environment (n.); blowdown (n.); sediment (n.); drawback (n.); durable; life expectancy; strictly (adv.); algae formation; extremely (adv.); heavy (adj.); nozzle (n.); significant (adj.); amount (n.); result in (v.).

Below; between; which; still; while; for; however; into.

Упражнение 7. Найдите перевод списка А в списке В.

 

А

Pressure treatment; fiberglass; various; replace; results in; significant; involve; durable; initially; support; concern; diminish; irrespective; prevent; wooden; source; promote; distribute; footprint; inhibit; decay; erect; consume; adjust; require; primarily; field-erected; advantage; media; provide; properly; throughout; term; dumped into; mean; proliferation; life expectancy; drawback; content; come into existence; collectively; delivery device; approach; interface.

В

Подход; обработка под давлением; преимущество; возводить; оцинкованная сталь; различный; потреблять; перемещать; приводить к; существенный; включать, предполагать; недостаток; вещество; долговечный; первоначально; поддерживать; опасение, беспокойство; называть; снижать; регулировать; средство; быстрое разрастание; безотносительный; содержание; обеспечивать; предотвращать; деревянный; требовать; срок службы; надлежащим образом; главным образом; источник; повышать; распределять; повсюду, по всему; зона обслуживания; выводить в (атмосферу); возникнуть, начать существование; в собирательном значении, обобщенно; подающее устройство; контактная поверхность; препятствовать, подавлять; гниение, разложение; монтируемый на месте.

Упражнение 8. Переведите текст письменно.

HVAC delivery equipment

1. The heating or cooling effect produced at a source and distributed by a central system to spaces throughout a building needs to be properly delivered to each space to promote comfort. 2. In air-based systems, heated or cooled air could theoretically just be dumped into each space. 3. Such an approach, however, does not provide the control over air distribution. 4. In water-based systems, the heated or cooled media (water or steam) cannot just be dumped into a space. 5. Some means of transferring the conditioning effect from the media to the space is required. 6. Devices designed to provide the interface between occupied building spaces and distribution components are collectively termed delivery devices.

Найдите в тексте:

1.Participles I,functions; Participles II, functions; Infinitives, functions.

2. Participles II, functions; modal verb; passive voice.

3. Subject; predicate.

4. Participles II, functions; passive voice.

5. Subject; predicate; Gerund, function.

6. Subject; predicate; Participles II, functions; Infinitive, function.

Урок 3.9

Упражнение 1. Прочитайте слова.

[k]c oncrete, c onstruct, c urrently, c ost, thi ck ness, ar ch ite c tural, plasti c, e q ual, ch emistry, ch emically.

 

Упражнение 2. Сопоставьте слово с переводом и соответствующей ему транскрипцией.

1) submerge; 2) disguise; 3) measure; 4) height; 5) environment; 6) cylinder; 7) pultruded;

 

1) [ÃuÎ'ËϳdId,pAÎ-]; 2) ['ÉIÎIÍ̶]; 3) [dIÉ'ÑAIÊ];

4) [IÍ'ÈAI϶ÍÅ(¶)ÍË,ÔÍ-]; 5) ['ÅÔº¶]; 6) [ÒAIË ]; 7) [ɶÄ'Å´G];

1) цилиндр; 2) изменять внешний вид; 3) измерять; 4) высота; 5) погружать в воду; 6) окружающая среда; 7) одноосноориентированный.

 

Текст A

Cooling Tower Materials (2)

Galvanized Steel ( Figure 3.19) – The most cost-effective material of construction for packaged towers is G-235 hot-dipped galvanized steel, from both structural and corrosion resistance standpoint. G-235 is the heaviest galvanizing mill commercially available, and offers a substantial amount of protection as compared to the lighter zinc thicknesses used several decades ago, providing reliable corrosion protection for most HVAC and industrial system water chemistries. The most common upgrade from G-235 galvanized steel is type 304 stainless steel. Parts that are submerged during operation and/or at shutdown can benefit the most by upgrading to stainless steel.

Stainless Steel -Type 304 stainless steel construction is recommended for cooling towers that are to be used in a highly corrosive environment.

Concrete Towers -Larger field erected towers for power plant and refinery applications are constructed of concrete. Concrete towers will last more than 40 years, but they are the most expensive to build. Because of their cost, they represent only 2 to 3% of all field-erected towers. Sometimes concrete construction is also used for architectural reasons (where the tower is disguised to look like or blend in with a building), or the cooling tower is designed as a structure with a life expectancy equal to the facility it serves.

Fiber-Reinforced Plastic (FRP) Towers ( Figure 3.20) - Currently, the fastest growing segment of the cooling tower market is structures built with pultruded FRP sections. This inert inorganic material is strong, lightweight, chemically resistant and able to handle a range of pH values. Fire-retardant FRP can eliminate the cost of a fire protection system, which can equal 5 to 12% of the cost of a cooling tower.

Note that for the cooling towers erected over a concrete basin, height is measured from the elevation of the basin curb. "Nominal" heights are usually measured to the fan deck elevation, not including the height of the fan cylinder. Heights for towers, on which a wood, steel, or plastic basin is included within the manufacturer's scope of supply, are generally measured from the lowermost point of the basin.