Central air conditioning and its types

Central air conditioning includes three main types:

1. Shiller
2. Al , Barakj Complex
3. Central Split

Chiller Central Air Conditioning

A chiller is a water-only cooling unit, and it works through cooling by cold water (Chilled Water System). Water is used as a cooling medium inside the places to be cooled, where the water is first cooled as it passes through the evaporator, and then cold water is pumped to heat exchangers inside the places to be cooled by special pumps. Heat exchange between cold water and the air of the place to be cooled is carried out by fans attached to those exchangers.

Condenser cooling can be done either by atmospheric air (air-cooled chiller) or by water that is transported by special pumps that transfer water from cooling towers to a heat exchanger where the coolant liquid is cooled with water (Water-cooled chiller).

core circuits of central air conditioning chiller

1. Cycle Refrigeration

This circuit consists of the basic elements of a normal cooling circuit, namely:

• Compressor: Several types of compressors are used in central air conditioning operations with ice water, such as: reciprocating compressor, screw compressor, rotary compressor, and centrifugal compressor. Central extruders use cooling capacities ranging from 35 to 10,000 Refrigerated Tons (TR) and have high rotation speeds ranging from 3,000 to 18,000 rpm. It is capable of handling high flow rates with small and medium pressure ratios. Centrifugal compressors work with different refrigerants such as R11, R12, R22, R113, R123, R500, R134a.

• Condenser: It is a heat exchanger during which heat is transferred from the refrigerant to the condensing medium (air or water). There are three types of capacitors:

  1. Air Cooling Condensers: These condensers are cooled by either natural air or forced air through a fan.
  2. Water cooling condensate: In this type of condensate, cooling is done by using water cooled by the cooling tower in cooling the coolant.
  3. Water-air cooling condensers: In this type of condensate, it is cooled with aerosolized water and air drawn from the bottom up by a fan installed on top of the condenser.

• Expansion Valve: There are several means of expansion through the central cooling system with ice water, including the Orifice Plate, which works on a sudden throttling of the refrigerant compound.

• Cooler: It is a heat exchanger in which the liquid refrigerant is converted into steam by drawing a quantity of heat from thermal loads. The coolant cools the water by heat exchange between the water and the refrigerant fluid. This cold water is passed through air distribution units such as Fan Coil or Air Handling Unit to cool the air passing through it.

2. Water Cycle

3. Oil Cycle

This circuit uses a submersible pump that draws oil from a tank under the compressor body and then expels it through a pipe to the oil cooling circuit, and then passes through a filter to purify it, and from there to the tank above the compressor (Emergency Oil) to lubricate the moving parts of the compressor. The oil then returns to the tank under the compressor. The oil tank contains an electric heater that heats the oil for easy expulsion through the pipes, and in the event of an increase in pressure, the Relief Valve works to return the oil Back to the tank.

Sheller components

The shiller consists of three main elements:

1. Pumps for pumping water from the building and drawing back water.
2. A water chiller consists of one or more compressors to cool water and a water cooling device.
3. Air Handling Unit: Its function is to receive cold water coming from the cooling device and treat it to obtain cold air.

Types of Shillers

1. Air cooling sheller: It is cooled by outside air, and this type is installed in an open place (Open Air).
2. Water cooling chiller: The water cooling system consists of two circuits:
   • The first circuit: in which the water is cooled by the schiller and forms chemically treated water to prevent corrosion of pipes and pumps. This water, after being cooled with chiller, is used to cool the rooms of the building by passing through a file of pipes, and through a fan the air is pushed to enter the place to be aired cold. The temperature is controlled by a solenoid valve.
   • The second circuit: is intended for cooling the schiller itself, and is connected to the cooling towers at the top of the building where water is sprayed and cooled with a huge fan, and then returned by pumps to the schiller itself to cool it.

Protection System in Chiller

The

protection system in the Chiller is an important system. The Flow Switch is used to ensure that water passes in the right direction and prevents it from returning in the opposite path, protecting the chiller from freezing and cracking the coolant.

Combined air conditioning units with condensing units (air – water)

1. Air-cooled combined air conditioning units:

   • Indoor single units: consists of a single internal condenser containing an air-cooled condensing unit, filter, blower (air intake and propeller fan), in addition to pipelines and control devices.
   • Multiple outdoor units: Each area of the air-conditioned space uses one air conditioning unit. Its capacity is determined based on the type of works, the suitability of the place, and the cooling loads required.

2. Shared units with separate air conditioning units: One common air conditioning unit is used for external air conditioning and distribution to other indoor air conditioning units.

3. Central units (central) with air ducts: They cool the interior of the air-conditioned space and distribute the rest of the cooling load to the air conditioning units placed in the walls.

Water-cooled combined air conditioning units

They are characterized by the fact that the condenser is cooled by water that is reused after cooling it in a cooling tower. These modules are used in large-capacity applications.

Characteristics and specifications of water-cooled combined air conditioning units:

• It is an alternative to central units especially those up to 70 tons of refrigeration.
• They are installed either single or separate from each other.
• The unit contains both cooling and condensing units, and the condenser is cooled with water directly from the water source either from the city water or from a cooling tower.

Components of water-cooled bundled units:

1. A
2. cooling coil unit consisting of an evaporator, a fan, an air conditioner intake, and a fan motor.
3. Air Filter
4. A condenser unit consisting of a compressor, a cooling medium and a water-cooled condenser.
5. Air ducts and air outlets.
6. Water pipes for cooling the condenser and a water pump between the unit and the cooling outlet and tower extensions.
7. Pipes of controller organizations to stop and turn on the unit.

Difference between combined units and central air conditioning:

1. Package Unit: Uses a DX direct cooling system, where freon passes inside the coil. While in central air conditioning, ice water comes from the central unit passes through the coil.
2. The combined unit includes compressor, condenser and evaporator: so it is called a combo unit. In central air conditioning, the air handling unit includes a

Mail, fan and some control devices.

1. The assembled unit is located on the roof of the building only: As for the central air conditioning, it can be distributed according to the desire and according to the air conditioning system to be implemented.
2. Central air conditioning with ice water needs larger units of at least 50 tons of refrigeration, while the combined unit depends on the size of the place to be aired.

central split air conditioning

The application of the central split air conditioning system depends on dividing the house into several zones that are controlled as needed, in order to save energy consumption by closing unused areas such as bedrooms or boards.

Some people prefer to use the central split system over the central air conditioning system with ice water due to its low cost in the event of a split