Air conditioning

An air-conditioning cycle comprises several air-conditioning processes that are connected in a sequential order. The working substance to condition air may be chilled or hot water, refrigerant, desiccant, etc.

Air-conditioning cycles can be grouped into two categories: 1. Open cycle, in which the moist air at its end state does not resume its original state. An air conditioning cycle with all outdoor air is an open cycle. 2. Closed cycle, in which moist air resumes its original state at its end state. Air-conditioning cycle that conditions the mixture of recirculating and outdoor air, supplies it; recirculates part of the return air, and mixes it again with outdoor air is a closed cycle.

A basic air-conditioning system is a packaged system of supply air at a constant volume flow rate, serving a single zone, equipped with only a single supply/return duct.

Figure 5. A basic air-conditioning schematic for summer mode.

Here, return air from the conditioned space (2) mixes with required amount of outdoor air (1) at point (3) for acceptable indoor air quality and energy saving. The mixture is then cooled and dehumidified to (Apparatus Dew Point)ADP (4) at the cooling coil. The actual off-coil condition is represented (5) due to inefficiency (bypass) of cooling coil. The conditioned air is supplied to the room through the supply fan, supply duct, and ceiling diffuser (6). Supply air then absorbs the sensible and latent load from the space, becoming the space air (2). Room air is returned back to the cooling unit again and forms a closed cycle. Part of the return air is exhausted to balance the outdoor air intake and infiltration.

Figure 6. The psychrometric diagram below shows a typical winter cycle.

An air conditioning system has to handle a large variety of energy inputs and outputs in and out of the building where it is used. The efficiency of the system is essential to maintain proper energy balance. The system will operate properly if well maintained and operated.

Vocabulary:

cycle ['ÉÕIÐÎ] n.– цикл;

sequential order [ÉÁ"ÐÆÂÍ¿Î'²dq] – последовательный порядок;

working substance ['wWkIN "sAbstqns] – рабочая среда;

refrigerant [ÏI'ÇÏI»qÏqÍË] n.– холодильная установка;

desiccant ['ÌÂÉIÐqÍË] n.– поглотитель влаги/осушитель;

return air [rI'tWn 'eq] – отработанный/рециркулирующий воздух;

supply air [sq'plaI 'eq] – поступающий/подаваемый воздух;

constant volume flow rate ["kPnstqnt "vPlj³m "flqu 'reIt] – постоянная величина скорости потока;

exhaust [ÁÑ'ʸ:ÉË] v.– выпускать/разрежать.

Answer the following questions:

1. What working substance do you know?

2. What can air-conditioning cycles be grouped into?

3. What cycle is called a closed cycle?

4. What is a basic air-conditioning system?

5. What does an air-conditioning cycle comprise?

6. How does a basic air-conditioning system work?

7. How is the conditioned air supplied to the room?

8. What forms a closed cycle?

9. Why is part of the return air exhausted?

10. What does an air conditioning system have to handle?

11. Why is the efficiency of the system essential?

12. In what case will the system operate properly?

Оглавление

ABOUT MYSELF AND MY STUDY 3

BUILDING MATERIALS 6

SHEAR WALL AND FRAME SYSTEMS 7

BOULTON HOUSE, CAMBRIDGE, ENGLAND 9

SAINT PETERSBURG 12

URBAN DESIGN 15

ECO-ARCHITECTURE 17

COMPUTER SYSTEMS 19

THE WIDE WORLD WEB 21

COMPUTER SOFTWARE AND HARDWARE 23

INTERNAL COMBUSTION ENGINE 25

AUTOMOBILE SAFETY 26

HYBRID CARS 27

CRANES 29

EXCAVATORS 30

POWER INSTALLATIONS OF CONSTRUCTION

MACHINERY 32

PRICE ELASTICITY OF DEMAND AND SUPPLY 34

FISCAL POLICY 35

FOREIGN TRADE 36

HEAT EXCHANGERS 38

BOILERS 42

AIR CONDITIONING 45

Date: 2015-10-19; view: 427; Нарушение авторских прав