A. fuel B. moderate C. transferred D. distribute
E. hydronics F. supplemental G. appliances
H. fiberglass I. oxygen J. coil K. dust L. sources
1. Heaters are …… whose purpose is to generate heat (warmth) for the building.
2. The heat can be …… by convection, conduction, or radiation.
3. Heaters exist for various types of ……, including solid fuels, liquids, and gases.
4. Electrical heaters are often used as backup or …… heat for heat pump systems.
5. Initially, heat pump HVAC systems were used in …… climates.
6. Heat pumps can extract heat from various …….
7. The use of water as the heat transfer medium is known as …….
8. Warm air systems …… heated air through ductwork systems of supply and return air through metal or fiberglass ducts.
9. The air supply is typically filtered through air cleaners to remove …… and pollen particles.
10. Incomplete combustion occurs when there is insufficient …….
UNIT 28 Ventilation
Read, translate the following text and be ready to fulfil the tests:
"Mechanical" or "forced" ventilation is provided by an air handler and used to control indoor air quality. Excess humidity, odors, and contaminants can often be controlled via dilution or replacement with outside air. However, in humid climates much energy is required to remove excess moisture from ventilation air. Kitchens and bathrooms typically have mechanical exhausts to control odors and sometimes humidity. Factors in the design of such systems include the flow rate (which is a function of the fan speed and exhaust vent size) and noise level. Direct drive fans are available for many applications, and can reduce maintenance needs.
Natural ventilation is the ventilation of a building with outside air without using fans or other mechanical systems. It can be via operable windows, louvers, or trickle vents when spaces are small and the architecture permits. In more complex schemes, warm air is allowed to rise and flow out high building openings to the outside (stack effect), causing cool outside air to be drawn into low building openings. Natural ventilation schemes can use very little energy, but care must be taken to ensure comfort. In warm or humid climates, maintaining thermal comfort solely via natural ventilation may not be possible. Air conditioning systems are used, either as backups or supplements. Air-sideeconomizers also use outside air to condition spaces, but do so using fans, ducts, dampers, and control systems to introduce and distribute cool outdoor air when appropriate.
An air conditioning system, or a standalone air conditioner, provides cooling and humidity control for all or part of a building. Air conditioned buildings often have sealed windows, because open windows would work against the system intended to maintain constant indoor air conditions. Outside, fresh air is generally drawn into the system by a vent into the indoor heat exchanger section, creating positive air pressure. The percentage of return air made up of fresh air introduce and distribute cool outdoor air when appropriate. Typical fresh air intake is about 10%. Air conditioning and refrigeration are provided through the removal of heat. Heat can be removed through radiation, convection, or conduction. Refrigeration conduction media such as water, air, ice, and chemicals are referred to as refrigerants. A refrigerant is employed either in a heat pump system in which a compressor is used to drive thermodynamic refrigeration cycle, or in a free cooling system which uses pumps to circulate a cool refrigerant (typically water or a glycol mix).
The refrigeration cycle uses four essential elements to cool. The system refrigerant starts its cycle in a gaseous state. The compressor pumps the refrigerant gas up to a high pressure and temperature. From there it enters a heat exchanger (sometimes called a condensing coil or condenser) where it loses energy (heat) to the outside, cools and condenses into its liquid phase. An expansion valve (also called metering device) regulates the refrigerant liquid to flow at the proper rate. The liquid refrigerant is returned to another heat exchanger where it is allowed to evaporate; hence the heat exchanger is often called an evaporating coil or evaporator. As the liquid refrigerant evaporates, it absorbs energy (heat) from the inside air, returns to the compressor, and repeats the cycle. In the process, heat is absorbed from indoors and transferred outdoors, resulting in cooling of the building. In variable climates, the system may include a reversing valve that switches from heating in winter to cooling in summer.
Read and memorize the active vocabulary to the text:
Active Vocabulary
1. forced ventilation искусственная (принудительная, механическая) вентиляция
2. air handler камера обработки воздуха (в установке кондиционирования воздуха)
3. dilution разбавление, разжижение; разведение
4. exhaust выхлопная труба, вытяжка
5. flow rate скорость потока, пропускная способность
6. direct drive непосредственный привод, прямая передача
7. louver жалюзи, вентиляционная решётка
8. trickle vent вентиляционное отверстие
9. stack effect эффект тяги; естественная тяга
10. air-side полость аппарата со стороны воздуха
11. economizer экономайзер, воздухонагреватель, воздухо-воздушный теплоутилизатор
12. standalone отдельный, автономный
13. sealed герметичный; уплотненный
14. percentage процентное содержание; процентное отношение
15. adjusting регулировка; настройка; юстировка
16. refrigerant хладагент
17. essential непременный, обязательный, необходимый
18. expansion valve терморегулирующий вентиль (ТРВ)
19. to absorb всасывать, впитывать, абсорбировать
20. to repeat повторять
21. variable изменчивый
22. reversing valve реверсивный клапан
CONTROL TESTS
TEST I
Decide whether these statements are true or false:
1. a). "Mechanical" or "forced" ventilation can have antibacterial/ultraviolet treatment against the growth of bacteria/organisms in the condensed water storage tray.
b). "Mechanical" or "forced" ventilation is provided by an air handler and used to control indoor air quality.
c). "Mechanical" or "forced" ventilation is run back to the discharge plenum, through the return filter, then back into the air handling unit, completing the system circuit.
2. a). In humid climates much energy is required to remove any dust, smoke or other undesirable particles or fumes.
b). In humid climates much energy is required to circulate air through the coils.
c). In humid climates much energy is required to remove excess moisture from ventilation air.
3. a). Natural ventilation is the ventilation of a building with outside air without using fans or other mechanical systems.
b). Natural ventilation ensures, that air is distributed evenly and in the required direction into the rooms and offices of the buildings.
c). Natural ventilation supplies air to the building by the fans that draw the air through coils in the air handling unit.
4. a). In warm or humid climates diffusers are normally located in the room’s ceilings.
b). In warm or humid climates maintaining thermal comfort solely via natural ventilation may not be possible.
c). In warm or humid climates volume control dampers should be incorporated into the ducting to control the quantity and velocity of the air flow.
5. a). An expansion valve regulates the quantity and velocity of the air flow.
b). An expansion valve regulates the refrigerant liquid to flow at the proper rate.
c). An expansion valve regulates uniform room temperatures.
TEST II
Match words in columns A and B (synonym match):
A B
1. excess a). contrast b). surplus
c). perfection d). ingredient
2. contaminant a). mortar b). assembly
c). plaster d). pollution
3. to include a). to cover b). to convert
c). to contain d). to drive
4. to permit a). to obtain b). to enclose
c). to allow d). to fill
5. to manipulate a). to affect b). to involve
c). to reinforce d). to twist
6. to regulate a). to prepare b). to add
c). to spray d). to control
7. removal a). purpose b). condition
c). application d). elimination
8. device a). method b). moisture
c). instrument d). sheet
9. vent a). rock b). valve
c). paint d). piece
10. condition a). state b). integration
c). feature d). need
TEST III
Select the best possible answer out of the choices from the list to the statements (multiple choice):
1. The refrigeration cycle …
2.
a. provides cooling and humidity control for all or part of a building.
b. uses four essential elements to cool.
c. causes cool outside air to be drawn into building openings.
2. The percentage of return air made up of fresh air …
a. depends on the requirement of hot air or air conditioning.
b. is controlled by the quantity and velocity of the air flow.
c. can usually be manipulated by adjusting the opening of this vent.
3. Air conditioned buildings …
a. often have sealed windows.
b. often have installed fire and smoke dampers.
c. are a worthwhile investment.
4. Air-side economizers …
a. use outside air to condition spaces.
b. draw the air through heating/cooling coils.
c. shut automatically in the event of a fire.
5. Air conditioning and refrigeration …
a. use an evaporator / condenser, supplying the hot or cold medium.
b. are provided through the removal of heat.
c. can be made more efficient by using modern diffusers and grilles.
TEST IV
