CHAPTER 1
INTRODUCTION
1.1
1.1AIR CONDITIONING 1.1
1.2COMFORT AND PROCESSING AIR
CONDITIONING SYSTEMS 1.2Air Conditioning Systems 1.2Comfort Air Conditioning Systems 1.2Process Air Conditioning Systems 1.3
1.3CLASSIFICATION OF AIR
CONDITIONING SYSTEMS ACCORDING
TO CONSTRUCTION AND OPERATING
CHARACTERISTICS 1.3Individual Room Air Conditioning Systems 1.4Evaporative-Cooling Air Conditioning Systems 1.4Desiccant-Bad Air Conditioning Systems 1.4Thermal Storage Air Condi
tioning Systems 1.5Clean-Room Air Conditioning Systems 1.5Space Conditioning Air Conditioning Systems 1.5Unitary Packaged Air Conditioning Systems 1.6
1.4CENTRAL HYDRONIC AIR
CONDITIONING SYSTEMS 1.6Air System 1.6Water System 1.8Central Plant 1.8Control System 1.9Air, Water, Refrigeration, and Heating Systems 1.10
1.5DISTRIBUTION OF SYSTEMS
USAGE 1.10
1.6HISTORICAL DEVELOPMENT 1.11Central Air Conditioning Systems 1.11Unitary Packaged Systems 1.12Refrigeration Systems 1.12
1.7POTENTIALS AND CHALLENGES 1.13Providing a Healthy and Comfortable Indoor Environment 1.13The Cleanest, Quietest, and Most Preci and Humid Processing Environment 1.13Energy U and Energy Efficiency 1.13Environmental Problems—CFCs and Global Warming 1.15Air Conditioning or HVAC&R Industry 1.151.8AIR CONDITIONING PROJECT DEVELOPMENT 1.16Basic Steps in Development 1.16Design-Bid and Design-Build 1.17The
Goal—An Environmentally Friendlier,Energy-Efficient, and Cost-Effective HVAC&R System 1.17Major HVAC&R Problems 1.171.9DESIGN FOR AIR CONDITIONING SYSTEM 1.18Engineering Responsibilities 1.18Coordination between Air Conditioning and Other Trades, Teamwork 1.19Retrofit, Remodeling, and Replacement 1.19Engineer’s Quality Control 1.20Design of the Control System 1.20Field Experience 1.21New Design Technologies 1.211.10DESIGN DOCUMENTS 1.21Drawings 1.22Specifications 1.221.11CODES AND STANDARDS 1.231.12COMPUTER-AIDED DESIGN AND DRAFTING (CADD) 1.25Features of CADD 1.25Computer-Aided Design 1.25Computer-Aided Drafting (CAD) 1.26Software Requirements 1.26REFERENCES 1.26
1.1AIR CONDITIONING
Air conditioning is a combined process that performs many functions simultaneously. It conditions the air,transports it,and introduces it to the conditioned space. It provides heating and cooling from its central plant or rooftop units. It also controls and maintains the temperature,humidity,air movement,air cleanliness,sound level,and pressure differential in a space within predetermined
1.2CHAPTER ONE
limits for the comfort and health of the occupants of the conditioned space or for the purpo of
product processing.
The term HVAC&R is an abbreviation of heating,ventilating,air conditioning,and refrigerating.
The combination of process in this commonly adopted term is equivalent to the current definition
of air conditioning. Becau all the individual component process were developed prior to the
more complete concept of air conditioning,the term HVAC&R is often ud by the industry.
1.2COMFORT AND PROCESSING AIR CONDITIONING
SYSTEMS
Air Conditioning Systems
An air conditioning,or HV AC&R,system is compod of components and equipment arranged in
quence to condition the air,to transport it to the conditioned space,and to control the indoor envi-
ronmental parameters of a specific space within required limits.
Most air conditioning systems perform the following functions:
1.Provide the cooling and heating energy required
2.Condition the supply air,that is,heat or cool,humidify or dehumidify,clean and purify,and
attenuate any objectionable noi produced by the HV AC&R equipment
3.Distribute the conditioned air,containing sufficient outdoor air,to the conditioned space
4.Control and maintain the indoor environmental parameters–such as temperature,humidity,
cleanliness,air movement,sound level,and pressure differential between the conditioned space
and surroundings—within predetermined limits
Parameters such as the size and the occupancy of the conditioned space,the indoor environmental parameters to be controlled,the quality and the effectiveness of control,and the cost involved deter-
mine the various types and arrangements of components ud to provide appropriate characteristics.
Air conditioning systems can be classified according to their applications as (1) comfort air conditioning systems and (2) process air conditioning systems.
Comfort Air Conditioning Systems
Comfort air conditioning systems provide occupants with a comfortable and healthy indoor envi-
ronment in which to carry out their activities. The various ctors of the economy using comfort air
conditioning systems are as follows:
1.The commercial ctor includes office buildings,supermarkets,department stores,shopping
centers,restaurants,and others. Many high-ri office buildings,including such structures as the
World Trade Center in New York City and the Sears Tower in Chicago,u complicated air condi-
tioning systems to satisfy multiple-tenant requirements. In light commercial buildings,the air con-
ditioning system rves the conditioned space of only a single-zone or comparatively smaller area.
For shopping malls and restaurants,air conditioning is necessary to attract customers.
2.The institutional ctor includes such applications as schools,colleges,universities,libraries,
muums,indoor stadiums,cinemas,theaters,concert halls,and recreation centers. For example,
one of the large indoor stadiums,the Superdome in New Orleans,Louisiana,can at 78,000 people.
3.The residential and lodging ctor consists of hotels,motels,apartment hous,and private
homes. Many systems rving the lodging industry and apartment hous are operated continu-
ously,on a 24-hour,7-day-a-week schedule,since they can be occupied at any time.
4.The health care ctor encompass hospitals,nursing homes,and convalescent care facilities.
Special air filters are generally ud in hospitals to remove bacteria and particulates of submicrometer
INTRODUCTION 1.3 size from areas such as operating rooms,nurries,and intensive care units. The relative humidity in a
general clinical area is often maintained at a minimum of 30 percent in winter.
5.The transportation ctor includes aircraft,automobiles,railroad cars,bus,and cruising
ships. Pasngers increasingly demand ea and environmental comfort,especially for long-
distance travel. Modern airplanes flying at high altitudes may require a pressure differential of
about 5psi between the cabin and the outside atmosphere. According to the Commercial Buildings
Characteristics(1994),in 1992 in the United States,among 4,806,000 commercial buildings hav-
ing 67.876 billion ft2(6.31 billion m2) of floor area,84.0 percent were cooled,and 91.3 percent
were heated.
Process Air Conditioning Systems
Process air conditioning systems provide needed indoor environmental control for manufacturing,
product storage,or other rearch and development process. The following areas are examples of
process air conditioning systems:
1.In textile mills,natural fibers and manufactured fibers are hygroscopic. Proper control of hu-
midity increas the strength of the yarn and fabric during processing. For many textile manufactur-
ing process,too high a value for the space relative humidity can cau problems in the spinning
process. On the other hand,a lower relative humidity may induce static electricity that is harmful
for the production process.
2.Many electronic products require clean rooms for manufacturing such things as integrated cir-
cuits,since their quality is adverly affected by airborne particles. Relative-humidity control is
also needed to prevent corrosion and condensation and to eliminate static electricity. Temperature
control maintains materials and instruments at stable condition and is also required for workers who
wear dust-free garments. For example,a class 100 clean room in an electronic factory requires a
temperature of 72Ϯ2°F (22.2Ϯ1.1°C),a relative humidity at 45Ϯ5 percent,and a count of dust
particles of 0.5-m (1.97ϫ10Ϫ5in.) diameter or larger not to exceed 100 particles/ft3(3531 parti-
cles/m3).
3.Precision manufacturers always need preci temperature control during production of preci-
sion instruments,tools,and equipment. Bausch and Lomb successfully constructed a constant-
temperature control room of 68Ϯ0.1°F (20Ϯ0.56°C) to produce light grating products in the
木笼1950s.
4.Pharmaceutical products require temperature,humidity,and air cleanliness control. For in-
stance,liver extracts require a temperature of 75°F (23.9°C) and a relative humidity of 35 percent.
If the temperature exceeds 80°F (26.7°C),the extracts tend to deteriorate. High-efficiency air filters
must be installed for most of the areas in pharmaceutical factories to prevent contamination.
5.Modern refrigerated warehous not only store commodities in coolers at temperatures of
27to 32°F (Ϫ2.8 to 0°C) and frozen foods atϪ10 toϪ20°F (Ϫ23 toϪ29°C),but also provide
relative-humidity control for perishable foods between 90 and 100 percent. Refrigerated storage
is ud to prevent deterioration. Temperature control can be performed by refrigeration systems
only,but the simultaneous control of both temperature and relative humidity in the space can only
be performed by process air conditioning systems.
1.3CLASSIFICATION OF AIR CONDITIONING SYSTEMS
ACCORDING TO CONSTRUCTION AND OPERATING
CHARACTERISTICS
Air conditioning systems can also be classified according to their construction and operating
如何设置行高
characteristics as follows.
1.4CHAPTER ONE
Individual Room Air Conditioning Systems
Individual room,or simply individual air conditioning systems employ a single,lf-contained
room air conditioner,a packaged terminal,a parated indoor-outdoor split unit,or a heat pump. A
heat pump extracts heat from a heat source and rejects heat to air or water at a higher temperature
for heating. Unlike other systems,the systems normally u a totally independent unit or units in
each room. Individual air conditioning systems can be classified into two categories:
q Room air conditioner (window-mounted)
q Packaged terminal air conditioner (PTAC),installed in a sleeve through the outside wall
The major components in a factory-asmbled and ready-for-u room air conditioner include the following:An evaporator fan pressurizes and supplies the conditioned air to the space. In tube-
and-fin coil,the refrigerant evaporates,expands directly inside the tubes,and absorbs the heat en-
ergy from the ambient air during the cooling ason; it is called a direct expansion (DX) coil. When叉烧包馅料的做法
the hot refrigerant releas heat energy to the conditioned space during the heating ason,it acts as
a heat pump. An air filter removes airborne particulates. A compressor compress the refrigerant
from a lower evaporating pressure to a higher condensing pressure. A condenr liquefies refriger-
杨梅坑自驾游攻略ant from hot gas to liquid and rejects heat through a coil and a condenr fan. A temperature control
system ns the space air temperature (nsor) and starts or stops the compressor to control its
cooling and heating capacity through a thermostat (refer to Chap. 26).
The difference between a room air conditioner and a room heat pump,and a packaged terminal air conditioner and a packaged terminal heat pump,is that a four-way reversing valve is added to all
room heat pumps. Sometimes room air conditioners are parated into two split units:an outdoor
condensing unit with compressor and condenr,and an indoor air handler in order to have the air
handler in a more advantageous location and to reduce the compressor noi indoors.
Individual air conditioning systems are characterized by the u of a DX coil for a single room.
This is the simplest and most direct way of cooling the air. Most of the individual systems do not
employ connecting ductwork. Outdoor air is introduced through an opening or through a small air
damper. Individual systems are usually ud only for the perimeter zone of the building.
Evaporative-Cooling Air Conditioning Systems
Evaporative-cooling air conditioning systems u the cooling effect of the evaporation of liquid
water to cool an airstream directly or indirectly. It could be a factory-asmbled packaged unit or a
强制报废年限field-built system. When an evaporative cooler provides only a portion of the cooling effect,then it
becomes a component of a central hydronic or a packaged unit system.
An evaporative-cooling system consists of an intake chamber,filter(s),supply fan,direct-contact or indirect-contact heat exchanger,exhaust fan,water sprays,recirculating water pump,and water
sump. Evaporative-cooling systems are characterized by low energy u compared with refrigera-
tion cooling. They produce cool and humid air and are widely ud in southwest arid areas in the
United States (refer to Chap. 27).
Desiccant-Bad Air Conditioning Systems
A desiccant-bad air conditioning system is a system in which latent cooling is performed by
desiccant dehumidification and nsible cooling by evaporative cooling or refrigeration. Thus,a
considerable part of expensive vapor compression refrigeration is replaced by inexpensive evapora-
tive cooling. A desiccant-bad air conditioning system is usually a hybrid system of dehumidifica-
tion,evaporative cooling,refrigeration,and regeneration of desiccant (refer to Chap. 29).
There are two airstreams in a desiccant-bad air conditioning system:a process airstream and a regenerative airstream. Process air can be all outdoor air or a mixture of outdoor and recirculating
INTRODUCTION 1.5 air. Process air is also conditioned air supplied directly to the conditioned space or enclod manu-
facturing process,or to the air-handling unit (AHU),packaged unit (PU),or terminal for further
treatment. Regenerative airstream is a high-temperature airstream ud to reactivate the desiccant.
鸟与花香A desiccant-bad air conditioned system consists of the following components:rotary desiccant
dehumidifiers,heat pipe heat exchangers,direct or indirect evaporative coolers,DX coils and vapor
compression unit or water cooling coils and chillers,fans,pumps,filters,controls,ducts,and piping.
Thermal Storage Air Conditioning Systems
In a thermal storage air conditioning system or simply thermal storage system,the electricity-driven
refrigeration compressors are operated during off-peak hours. Stored chilled water or stored ice in
tanks is ud to provide cooling in buildings during peak hours when high electric demand charges
and electric energy rates are in effect. A thermal storage system reduces high electric demand for
HV AC&R and partially or fully shifts the high electric energy rates from peak hours to off-peak hours.
A thermal storage air conditioning system is always a central air conditioning system using
chilled water as the cooling medium. In addition to the air,water,and refrigeration control systems,
there are chilled-water tanks or ice storage tanks,storage circulating pumps,and controls (refer to
Chap. 31).
Clean-Room Air Conditioning Systems
Clean-room or clean-space air conditioning systems rve spaces where there is a need for critical
control of particulates,temperature,relative humidity,ventilation,noi,vibration,and space pres-
surization. In a clean-space air conditioning system,the quality of indoor environmental control
directly affects the quality of the products produced in the clean space.
A clean-space air conditioning system consists of a recirculating air unit and a makeup air
unit—both include dampers,prefilters,coils,fans,high-efficiency particulate air (HEPA) filters,
ductwork,piping work,pumps,refrigeration systems,and related controls except for a humidifier in
the makeup unit (refer to Chap. 30).
Space Conditioning Air Conditioning Systems
日文输入法Space conditioning air conditioning systems are also called space air conditioning systems. They
have cooling,dehumidification,heating,and filtration performed predominately by fan coils,water-
source heat pumps,or other devices within or above the conditioned space,or very near it. A fan
教育见习计划coil consists of a small fan and a coil. A water-source heat pump usually consists of a fan,a finned
coil to condition the air,and a water coil to reject heat to a water loop during cooling,or to extract
heat from the same water loop during heating. Single or multiple fan coils are always ud to rve
a single conditioned room. Usually,a small console water-source heat pump is ud for each con-
trol zone in the perimeter zone of a building,and a large water-source heat pump may rve veral
rooms with ducts in the core of the building (interior zone,refer to Chap. 28).
Space air conditioning systems normally have only short supply ducts within the conditioned space,and there are no return ducts except the large core water-source heat pumps. The pressure
drop required for the recirculation of conditioned space air is often equal to or less than 0.6 in. wa-
ter column (WC) (150 Pa). Most of the energy needed to transport return and recirculating
air is saved in a space air conditioning system,compared to a unitary packaged or a central
hydronic air conditioning system. Space air conditioning systems are usually employed with a
dedicated (parate) outdoor ventilation air system to provide outdoor air for the occupants in the
conditioned space.
Space air conditioning systems often have comparatively higher noi level and need more periodic maintenance inside the conditioned space.
