Industrial Air Conditioning System

7/30/2019 Industrial Air Conditioning System

1/18

ASSIGNMENT

OF

PLFD


2/18

AIR CONDITIONING IN GARMENT/OTHER INDUSTRIES

Machines give off heat. For example, workers who use garment presses or die

casting equipment are always near hot machines and materials. If the factory does

not have good ventilation or a cooling system, the air around these machines can

become dangerously hot.

The best way to protect workers from too much heat is to keep the air inside the

factory cool. If the outside air is very hot and humid, air conditioning may be the only

way to keep the factory cool enough inside to be safe for all workers. The whole

factory does not have to be air conditioned. Cooled air can be blown through ducts to

the spot where each worker sits or stands. Most factory buildings can be kept cool

with a good ventilation system, plenty of air space, insulation, and shade.

AIR CONDITIONING

Air conditioning includes both the cooling and heating of air. It also cleans the air and

controls the moisture level.

An air conditioner is able to cool a building because it removes heat from theindoor air and transfers it outdoors. A chemical refrigerant in the system absorbs the

unwanted heat and pumps it through a system of piping to the outside coil. The fan,

located in the outside unit, blows outside air over the hot coil, transferring heat from

the refrigerant to the outdoor air.


3/18

Basic Operations

Most air conditioning systems have five mechanical components:

1. Compressor

2. Condenser

3. Expansion Device

4. Evaporator

1. Compressor:

The compressor (which is controlled by the thermostat) is the "heart" of the

system. The compressor acts as the pump, causing the refrigerant to flow

through the system. Its job is to draw in a low-pressure, low-temperature,

refrigerant in a gaseous state and by compressing this gas, raise the pressure

and temperature of the refrigerant. This high-pressure, high-temperature gas

then flows to the condenser coil.

2. Condenser:

The condenser coil is a series of piping with a fan that draws outside air

across the coil. As the refrigerant passes through the condenser coil and the

cooler outside air passes across the coil, the air absorbs heat from the

refrigerant which causes the refrigerant to condense from a gas to a liquid

state. The high-pressure, high-temperature liquid then reaches the expansionvalve.

3. Expansion Device:

The expansion valve is the "brain" of the system. By sensing the temperature

of the evaporator, or cooling coil, it allows liquid to pass through a very small

orifice, which causes the refrigerant to expand to a low-pressure, low-

temperature gas. This "cold" refrigerant flows to the evaporator coil.


4/18

4. Evaporator:

The evaporator coil is a series of piping connected to a furnace or air handler

that blows indoor air across it, causing the coil to absorb heat from the air.

The cooled air is then delivered to the house through ducting. The refrigerant

then flows back to the compressor where the cycle starts over again.

APPLICATION OF REFRIGERATION AND AIR CONDITIONING

The largest application of refrigeration is for air conditioning. In addition, refrigeration

embraces industrial refrigeration including the processing and preservation of food,

removing heat from substances in chemical, petroleum and petrochemical plants,

and numerous special applications such as those in the manufacturing and

construction industries.

In a similar manner, air conditioning embraces more than cooling. The comfort air

conditioning is the process of treating air to control simultaneously its temperature

humidity, cleanliness, and distribution to meet the comfort requirements of the

occupants of the conditioned space. Air conditioning, therefore, includes entire

heating operation as well as regulation of velocity, thermal radiation, and quality of

air, including removal of foreign particles and vapours.

Some applications of refrigeration and air conditioning are as follows :

1. Air Conditioning of Residential and Official Buildings

Most of the air conditioning units are devoted for comfort air conditioning that is

meant to provide comfortable conditions for people. Air conditioning of building is

required in all climates. In the summer, living/working spaces have to be cooled and

in the winter the same have to be heated. Even in places where temperature

remains normal, cooling of the building is required to remove the heat generated

internally by people, lights, mechanical and electrical equipment. Further in these


5/18

buildings, for the comfort, humidity and cleanliness of air has to be maintained. In

hospitals and other medical buildings, conditions on cleanliness and humidity are

more stringent. There ventilation requirements often specify the use of 100 percent

outdoor air, and humidity limits.

2. Industrial Air Conditioning

The term industrial air conditioning refers to providing at least a partial measure of

comfort for workers in hostile environments and controlling air conditions so that they

are favorable to processing some objects or materials.

Some examples of industrial air conditioning are the following:

Spot Heating

In a cold weather it may be more practical to warm a confined zone where a worker

is located. One such approach is through the use of an infrared heater. When its

surfaces are heated to a high temperature by means of a burner or by electricity,

they radiate heat to the affected area.

Spot Cooling

If a specific area has to be cooled, it will be unwise to cool entire room or factory. In

this case, conditions may be kept tolerable for workers by directing a stream of cool

air onto occupied areas.

3. Environmental Laboratories

The role of air conditioning may vary from one laboratory to the other. In one

laboratory, a very low temperature, say 40oC must be maintained to test certain

equipment at low temperatures, and in another, a high temperature and humidity

may be required to study behaviour of animals in tropical climates.


6/18

4. Printing

In printing industries, control of humidity is a must. In some printing processes the

paper is run through several different passes, and air conditioning must be

maintained to provide proper registration. If the humidity is not properly maintained

the problems of static electricity, curling or buckling of paper or the failure of the ink

to dry arise.

5. Textiles

Like paper, textiles are sensitive to changes in humidity and to a lesser extent

changes in temperature. In modern textile plants, yarn moves at very high speeds

and any changes in flexibility and strength of the yarn because of the change in

humidity and temperature will thus affect the production.

6. Precision Parts and Clean Rooms

In manufacturing of precision metal parts air conditioning helps to (a) keep the

temperature uniform so that the metal will not expand and contract, (b) maintain

humidity so that rust is prevented and (c) filter the air to minimize dust.

7. Photographic Products

Raw photographic materials deteriorate fast in high humidity and temperatures.

Other materials used in coating film also require a careful control of temperature.

Therefore, photographic-products industry is a large user of refrigeration and air

conditioning.


7/18

8. Computer Rooms

In computer rooms, air conditioning controls temperature, humidity and cleanliness

of the air. Some electronic components operate in a faulty manner if they become

too hot. One means of preventing such localized high temperature is to maintain the

air temperature in the computer room in the range of 20 to 23 0C. The electronic

components in the computer functions favourably at even lower temperatures, but

this temperature is a compromise with the lowest comfortable temperature for

occupants. A relative humidity of about 65% is maintained for comfort condition.

9. Air Conditioning of Vehicles

For comfortable journey, planes, trains, ships, buses are air conditioned. In many of

these vehicles the major contributor to the cooling load is the heat from solar

radiation and in case of public transportation, heat from people.

10. Food Storage and Distribution

Many meats, fish, fruits and vegetables are perishable and their storage life can be

extended by refrigeration. Fruits, many vegetables and processed meat, such as

sausages, are stored at temperatures just slightly above freezing to prolong their life.

Other meats, fish, vegetables and fruits are frozen for many months at low

temperatures until they are defrosted and cooked by consumer.

TYPES OF AIR CONDITIONING SYSTEMS USED IN INDUSTRIES

1. HVAC SYSTEM

Heating, Ventilating, and Air Conditioning (HVAC) equipment perform heating

and/or cooling for residential, commercial or industrial buildings. The HVAC

system may also be responsible for providing fresh outdoor air to dilute

interior airborne contaminants such as odours from occupants, volatile

organic compounds (VOCs) emitted from interior furnishings, chemicals used


8/18

for cleaning, etc. A properly designed system will provide a comfortable indoor

environment year round when properly maintained.

An air conditioner cools and dehumidifies the air as is passes over a cold coil

surface. The indoor coil is an air-to-liquid heat exchanger with rows of tubes

that pass the liquid through the coil. Finned surfaces connected to these tubesincrease the overall surface area of the cold surface thereby increasing the

heat transfer characteristics between the air passing over the coil and liquid

passing through the coil. The type of liquid used depends on the system

selected. Direct-expansion (DX) equipment uses refrigerant as the liquid

medium. Chilled-water (CW) can also be used as a liquid medium. When the

required temperature of a chilled water system is near the freezing point of

water, freeze protection is added in the form of glycols or salts. Regardless of


9/18

the liquid medium used, the liquid is delivered to the cooling coil at a cold

temperature.

In the case of direct expansion equipment, the air passing over the indoor

cooling coil heats the cold liquid refrigerant. Heating the refrigerant causes

boiling and transforms the refrigerant from a cold liquid to a warm gas. This

warm gas (or vapour) is pumped from the cooling coil to the compressor

through a copper tube (suction line to the compressor) where the warm gas is

compressed. In some cases, an accumulator is placed between the cooling

coil and the compressor to capture unused liquid refrigerant and ensures that

only vapour enters the compressor. The compression process increases the

pressure of the refrigerant vapour and significantly increases the temperature

of the vapour. The compressor pumps the vapour through another heat

exchanger (outdoor condenser) where heat is rejected and the hot gas is

condensed to a warm high pressure liquid. This warm high pressure liquid is

pumped through a smaller copper tube (liquid line) to a filter (or filter/dryer)

and then on to an expansion device where the high pressure liquid is reduced

to a cold, low pressure liquid. The cold liquid enters the indoor cooling coil and

the process repeats.

As this liquid passes through the indoor cooling coil on the inside of the heat

exchanger, two things happen to the air that passes over the coils surface on

the outside of the heat exchanger. The airs temperature is lowered (sensible

cooling) and moisture in the air is removed (latent cooling) if the indoor air

dew point is higher than the temperature of the coils surface. The total

cooling (capacity) of an AC system is the sum of the sensible and latent

cooling. Many factors influence the cooling capacity of a DX air conditioner.

Total cooling is inversely proportional to outdoor temperature. As the outdoor

temperature increases the total capacity is reduced. Air flow over the indoor

cooling coil also affects the coils capacity and is directly proportional to the

total capacity of an AC system. As air flow increases, the total capacity also

increases. At higher air flow rates the latent capacity of the cooling coil is

reduced. Indoor temperature and humidity also affect the total capacity of the

AC system. As indoor temperatures increase, the sensible capacity also

increases. Similarly, as indoor relative humidity increases the latent capacity


10/18

of the AC system increases. Manufacturers of AC equipment typically provide

a performance map of specific equipment to show how total, sensible, and

latent capacity change with changing indoor and outdoor temperatures and

humidity. Power consumption and energy efficiency are also provided in these

charts.

Types of AC systems available in HVAC are:

1) Cooling Only Split-System:

A split system is a combination of an indoor air handling unit and an

outdoor condensing unit. The indoor air handling unit contains a supply

air fan and an air-to-refrigerant heat exchanger (or cooling coil), and

the expansion device. The outdoor condensing unit consists of a

compressor and a condenser coil. Split-systems are typically found in

residential or small commercial buildings. These systems have the

highest energy efficiency rating (EER) of all the available AC systems.

Manufacturers are required to take the EER rating a step further and

provide a seasonal energy efficiency rating (SEER) for use by

consumers. SEER ratings vary widely and range from 10 to 20. The

higher the SEER rating, the more efficient the AC system operates. If

heating is required, an alternate method of heating the interior of the

building must be used, usually in the form of electric or gas heating.

2) Cooling Only Packaged-System

A packaged system is a single unit combining all the components

described in the split system. Since the unit is a package, it must be

placed outside the building and indoor air is ducted from the building

to the packaged system and back through an air distribution system.

These units typically have SEER rating from 10 to 18. If heating is

required, an alternate method of heating the interior of the building

must be used, usually in the form of electric or gas heating.


11/18

3) Heat Pump

Heat pumps are similar to cooling only systems with one exception. A

special valve in the refrigeration piping allows the refrigeration cycle to

be operated in reverse. A cooling only system cools the indoor air and

rejects heat to the outdoors. A heat pump can also cool the indoor air,

but when the valve is reversed, the indoor air is heated. A

supplementary electric resistance heater may also be used to assist

the heat pump at lower outdoor temperatures. In colder climates, heat

pumps require a defrost period. During defrost times the electric heater

is the only means of heating the interior of the building. These units are

manufactured as either split or packaged systems.

4) Chilled Water System

In a chilled water system, liquid water is pumped throughout the

building to chilled water coils. Since the liquid water needs to be at a

cold temperature, a cooling plant is required. The plant is typically

referred to as a chillier plant. Vapour compression equipment in the

plant, similar to that described in How does my AC work, cool water

to a cold temperature and pump the cold water to air-to-water heat

exchangers where needed.

5) Window Air Conditioners

As the name implies, a window air conditioner is typically installed in a

window or custom opening in a wall. The Window AC can only cool

small areas and are not intended to provide cooling to multiple rooms

or zones. These air conditioners are manufactured as cool only or can

provide both cooling and heating. An optional damper in the unit can

provide fresh outdoor air if necessary.

6) Packaged Terminal Heat Pump

Packaged terminal heat pumps (PTHP) are are similar to a window-

mounted air conditioner. These units are typically installed in a sleeve


12/18

passing through the outdoor wall of an apartment, hotel, school

classroom, etc. PTHPs are completely self contained and require only

an electrical connection in addition to the opening in the building shell.

They use the outdoor air as the heat source in winter and as a heat

sink in summer. They also can provide ventilation air. Flexibility and

lower installed cost are the primary advantages of the PTHP.

Disadvantages include in-room maintenance, higher operating cost,

relatively short life, imprecise "on-off" temperature control, and they

can be rather noisy.

How is humidity controlled with an AC system?

Humidity is becoming more of a concern to building operators and owners. High

indoor humidity leads to mold and mildew growth inside the building. There are

several methods of controlling indoor humidity. The simplest (and most expensive)

method is to connect a humidistat to an electric heater. When the humidity inside the

building rises above the humidistat set point, the heater is turned on. The additional

heat causes the air conditioning system to run longer and remove more moisture.

A more efficient method of controlling humidity is to use the waste heat from the

refrigeration cycle itself. Instead of rejecting the waste heat outdoors, the heat is

directed inside when humidity control is required. One form of heat reclaim is called

hot-gas reheat or refrigerant desuperheating where refrigerant is passed through a

heat exchanger located downstream of the cooling coil. The hot high pressure

vapour leaving the compressor passes through this heat exchanger prior to entering

the condenser coil. This in turn heats the indoor air and again causes the AC system

to run longer to meet the thermostat set point. Although more energy is used, this is

much more efficient than turning on an electric heater. Another form of heat reclaim

is called sub-cool reheat. This strategy takes the warm liquid refrigerant from the

condenser and passes it through a heat exchanger located downstream of the

cooling coil. Less heat is available using this method because the majority of the

heat has already been rejected at the condenser. Since more energy is used to

pump liquid (as opposed to a gas) through the heat exchanger it would appear that

this method is less efficient than the hot-gas method, however, the liquid in the heat

exchanger is sub-cooled in the cold supply air stream which increases the capacity


13/18

of the air conditioner. Since more capacity is available, the AC unit is able to meet

the thermostat more quickly.

Heat pipe heat exchangers or run-around coils perform a similar function when

humidity control is required. Two heat exchangers are placed in the air stream, one

upstream of the cooling coil and the other downstream of the cooling coil. These

heat exchangers are connected together with piping. A heat transfer fluid, whether it

be water or refrigerant, is either pumped or gravity fed from one heat exchanger to

the other. The heat exchanger downstream of the cooling coil (re-heat coil) cools the

liquid medium inside the heat exchanger and heats the air passing over the heat

exchanger. The cold liquid inside the heat exchanger is moved to the heat

exchanger upstream of the cooling coil (pre-cool coil) where it pre-cools the air

passing over the heat exchanger and warms the liquid passing through the heat

exchanger. The affect of a heat pipe or run-around coil is to reduce the sensible heat

capacity of the AC system. The latent capacity of the AC system increases if direct-

expansion equipment is used or remains relatively constant if chilled water

equipment is used. Since the sensible capacity of the AC system has been reduced,

the system must run longer to meet the thermostat set point thereby removing more

moisture.

How do refrigerants deplete the Ozone layer?

Refrigerant 22 (R-22 or MonoChloroDiFlouroMethane, CHClF2) is one of the most

common refrigerants and is used in a wide variety of applications such as

refrigeration, aerosol propellants, cleaning solvents, and foaming agents for plastics.

This refrigerant is believed to be partially responsible for damaging the earths ozone

layer and its use is being phased out over the next two decades. The ozone layer is

a result of sunlight reacting with oxygen to produce a layer in the stratosphere more

than 10 km above the earths surface. As R-22 refrigerant escapes from an AC

system through leaks or is released into the atmosphere by other means, the R-22

molecule containing the chlorine atom (monochloro) rises in the atmosphere.

Sunlight breaks down the R-22 molecule to yield a free chlorine radical (Cl-). The

free chlorine radical combines with ozone (O3), decomposing it into normal oxygen

(O2).


14/18

AC refrigerants come in many varieties. R-22 is the most common, however, due to

interactions with the ozone layer R-22 is being phased out. Refrigerants

manufactured as replacements for R-22 are HFC-134a, R-410a, R-410b to name a

few. The new refrigerants do not contain the chlorine atom and are not harmful to the

earths ozone layer.

2. INDUSTRIAL AIR CONDITIONING SYSTEM

In a commercial facility, personal comfort was often an adjunct to equipment

maintenance; those who worked with or near equipment that needed to be

kept cool were the incidental benefactors of industrial air conditioning. Much is

made today, however, of what is known as sick building syndrome.

They can relieve the discomfort of allergies by removing pollen from the air,

make long commutes less taxing on drivers and passengers alike, and even

help to preserve the health of patients in hospitals. In business and

industry, air conditioning systems can improve the efficiency of workers,

ensure uniformity in metal work, prevent too much or too little moisture from

damaging fragile paper products during manufacture, and keep food fresh

during longs periods of shipment and storage.


15/18

A deadly enemy of most electronic equipment and personal productivity is

heat. Air conditioning is the mechanical replacement of heat with cooled air. In

years past, most large commercial buildings and manufacturing facilities are

equipped with industrial air conditioning units in part to alleviate the problems

associated with overheating of electronic equipment such as computers,

electronic testing instruments, and precision electronic manufacturing

equipment. Machinery used to produce critical equipment, usually including

precise measurements and tolerances, requires constant cooling to function

properly. In a commercial facility, personal comfort was often an adjunct to

equipment maintenance; those who worked with or near equipment that

needed to be kept cool were the incidental benefactors of industrial air

conditioning.

Much is made today, however, of what is known as sick building syndrome.

This term refers to office buildings, schools, manufacturing, production, and

testing facilities where air quality is such that workers, students, customers,

clients, and visitors to these facilities were becoming ill simply from remaining

in such buildings for any length of time. These various illnesses were the

result of breathing and absorbing unhealthful vapors and contaminants

emitted by materials used in the construction of the building, as well as

inadequate heating, ventilation or air conditioning (HVAC) equipment. Thus,

industrial air conditioning is now critical to individual comfort and personal

health, not to mention optimum productivity of workers as well as equipment.

Nearly all modern industrial air conditioning units are now either ductless

orsplit air conditioning systems, or a combination of both. The cooling

machinery, fans, compressors, condensers, cooling towers, air handling,condensate recovery and discharge components are located at a remote

location outside the building or facilities, either on the roof or grounds of the

facility. The actual discharge of cooled air is accomplished by small, compact

units located in various rooms, offices and spaces throughout the interior of

the building. Often these room units are separately controlled via individual

thermostats. Such is the beauty ofductless air conditioning. Ducted

equipment, on the other hand, usually involves an inefficient dampening oflouvers to maintain individual room temperature.
http://www.wisegeek.com/what-are-air-conditioning-units.htmhttp://www.wisegeek.com/what-are-the-different-types-of-manufacturing-equipment.htmhttp://www.wisegeek.com/what-are-the-different-types-of-manufacturing-equipment.htmhttp://www.wisegeek.com/what-is-split-air-conditioning.htmhttp://www.wisegeek.com/what-is-ductless-air-conditioning.htmhttp://www.wisegeek.com/what-is-ductless-air-conditioning.htmhttp://www.wisegeek.com/what-is-split-air-conditioning.htmhttp://www.wisegeek.com/what-are-the-different-types-of-manufacturing-equipment.htmhttp://www.wisegeek.com/what-are-the-different-types-of-manufacturing-equipment.htmhttp://www.wisegeek.com/what-are-air-conditioning-units.htm


16/18

The size and capacity of industrial air conditioning equipment is, obviously

dependant on the size and design of the facility to be cooled. Industrial air

conditioning units commonly range from some two tons, or 24,000 British

Thermal Units (BTU) to 150 tons to 150 tons (1,800,000 BTU). A BTU is the

amount of heat necessary to raise the temperature of a pound of water one

degree, Fahrenheit.

3. Direct Expansion Air Conditioning

A direct expansion air conditioning (DX) system uses a refrigerant vapour

expansion/compression (RVEC) cycle to directly cool the supply air to an

occupied space.DX systems (both packaged and split) directly cools the air supplied to the

building because the evaporator is in direct contact with the supply air,

Expansion refers to the treatment of the refrigerant (a valve reduces its

pressure and temperature) prior to it entering the evaporator. DX systems

can come equipped with all the components in the unit (packaged system)

intended for installation on the rooftop or by the side of a building; or it may

have some components installed inside the building and some outside (split

system). DX systems require a ventilation fan to distribute the cool air and

resupply/re-circulate it.


17/18

A RVEC cycle has four basic components; an evaporator, compressor, condenser,

and thermal expansion control device. The evaporator (located inside the supply air

ductwork) absorbs heat through the process of expanding the refrigerant flowing

within it. The refrigerant then flows to a compressor which compresses it causing it to

condense in the condenser and release the heat it removed from the supply air. The

condensed liquid refrigerant then flows through the thermal expansion control device

which controls the flow and pressure of the refrigerant back into the evaporator.

Packaged Systems Packaged DX units contain all 4 parts of the RVEC

system, as well as fans and internal ducting. These units are designed to be

installed easily to serve local zones cooling needs; multiple units can be

installed to service multiple zones in a building.

Split Systems These systems generally have the evaporator and fans inside

the building, while the rest of the refrigerant vapour expansion/compression

(RVEC) system components are a separate unit placed outside the building.

This allows system designs that are more flexible, allowing performance that

can satisfy greater variations on system demands. Split units are made to an

incremental performance scale, meaning only certain working load sizes are

available.

Benefits:

DX systems are less expensive to install, and uses less space in mechanical

and electrical rooms than centralized cooling systems

DX systems can be expanded in an incremental fashion to match changing

building requirements

Packaged Systems have standardized operating performances per unit,

allowing more precise system sizing

Packaged Systems generally require less ventilation, and do not require

dedicated condensate lines

Packaged Systems occupy less space than comparable split systems

Split Systems tend to be larger allowing for fewer units, and therefore less

maintenance costs than a comparable Packaged system


18/18

Split Systems have lower noise levels because the compressor unit is located

further away from the cooling load area

Split Systems may allow vertical duct shafts to be smaller in size.

REFERENCES

1. http://www.hesperian.org/wp-

content/uploads/pdf/factory/Work_Dangers_5_other_dangers.pdf

2. http://www.estesair.com/Products/Air_Conditioning_Products/Air_Conditioning

_Basics/

3. http://www.ignou.ac.in/upload/Unit%201-32.pdf

4. http://www.fsec.ucf.edu/en/consumer/buildings/commercial/hvac.htm

5. http://www.wisegeek.com/what-is-industrial-air-conditioning.htm

6. http://www.nrgmanagement.ca/direct-expansion-air-conditioning-
http://www.hesperian.org/wp-content/uploads/pdf/factory/Work_Dangers_5_other_dangers.pdfhttp://www.hesperian.org/wp-content/uploads/pdf/factory/Work_Dangers_5_other_dangers.pdfhttp://www.hesperian.org/wp-content/uploads/pdf/factory/Work_Dangers_5_other_dangers.pdfhttp://www.hesperian.org/wp-content/uploads/pdf/factory/Work_Dangers_5_other_dangers.pdfhttp://www.estesair.com/Products/Air_Conditioning_Products/Air_Conditioning_Basics/http://www.estesair.com/Products/Air_Conditioning_Products/Air_Conditioning_Basics/http://www.estesair.com/Products/Air_Conditioning_Products/Air_Conditioning_Basics/http://www.estesair.com/Products/Air_Conditioning_Products/Air_Conditioning_Basics/http://www.ignou.ac.in/upload/Unit%201-32.pdfhttp://www.ignou.ac.in/upload/Unit%201-32.pdfhttp://www.fsec.ucf.edu/en/consumer/buildings/commercial/hvac.htmhttp://www.fsec.ucf.edu/en/consumer/buildings/commercial/hvac.htmhttp://www.wisegeek.com/what-is-industrial-air-conditioning.htmhttp://www.wisegeek.com/what-is-industrial-air-conditioning.htmhttp://www.nrgmanagement.ca/direct-expansion-air-conditioning-http://www.nrgmanagement.ca/direct-expansion-air-conditioning-http://www.nrgmanagement.ca/direct-expansion-air-conditioning-http://www.wisegeek.com/what-is-industrial-air-conditioning.htmhttp://www.fsec.ucf.edu/en/consumer/buildings/commercial/hvac.htmhttp://www.ignou.ac.in/upload/Unit%201-32.pdfhttp://www.estesair.com/Products/Air_Conditioning_Products/Air_Conditioning_Basics/http://www.estesair.com/Products/Air_Conditioning_Products/Air_Conditioning_Basics/http://www.hesperian.org/wp-content/uploads/pdf/factory/Work_Dangers_5_other_dangers.pdfhttp://www.hesperian.org/wp-content/uploads/pdf/factory/Work_Dangers_5_other_dangers.pdf

Industrial Air Conditioning System

Documents