Air conditioning

Air conditioning means: Operating on the air in order to make the desired conditions of living, working or industrial operations comfort and hygiene and reach the desired limit. Air conditioning causes the air condition to automatically stay or change according to a specific method.
Air conditioning or pleasant air conditioning is a branch of mechanical engineering. Its task is to provide the conditions that cause human’s welfare and to be needed to maintain a particular product or process. For this purpose, a machine with proper capacity must be installed and monitored throughout the year. The capacity of the device is determined by the maximum actual instantaneous load, and the type of control is determined according to the conditions that must be provided during peak load and partial load.

Heating, Ventilation and Air Conditioning are one of the most important topics in industry and mechanical science. These systems can be abbreviated as HVAC. An important point to note is that air conditioning is part of the science of HVAC, but in many states and industries, the two words are considered the same and are studied in the name of air conditioning and HVAC.
Heating, ventilation and air conditioning systems consists an important part of an urban, commercial and industrial building. Note that a good air conditioning system is constructed to control the temperature, humidity and air quality of the building, and the purpose of controlling these parameters is to create a comfortable space to be able to consider the personal and business affairs. Air conditioning science is widely used in the design of clean room as well as the control of pollutants in the clean room.

The way of performance of HVAC and air conditioning systems


The following figure shows basically and accurately how a particular air conditioning and HVAC system works. Note that in HVAC and air conditioning systems, there is usually an automatic adjustment device that determines whether the room should be warm or cool. It also has the task of determining the temperature that the room temperature should reach it.

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Figure 9: The way of performance of HVAC and air conditioning systems

The important point in the figure above is that the system is designed so that the coils in the set can be heated or cooled. Note that according to the figure, the coils are cooled by the chiller, and hot by the boiler.

According to figure above, the air first enters the system from the outside and then passes through the coils and eventually transfers into the room after heating or cooling.
Note that as the air enters the room from the air conditioning and the HVAC, part of the room air returns to the air conditioner via one of the outlets. In fact, by using this process, room air is replaced with fresh air.

There are other types of air conditioners, these are mini air conditioners. The way of performance of the system in general is that first, heat is collected inside a room and then transferred out of the room, as a result of this process, the room air temperature reduces. This system can be found in places like cars. The mechanism of operation of this system is illustrated in detail below.

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Figure 10: View of a mini air conditioning system

The above mechanism shows how a system receives heat from a room and then stores the received heat inside a set and ultimately transfers this heat to the air outside the room.
The system shown above is made of five important parts, and all five parts must function correctly for correct performance of this set.

Types of air conditioning and HVAC systems

Six main types of HVAC systems will be discussed in this section. The overall performance of these six systems is slightly different from those discussed in the previous sections.

Heat pump

As we know, heat usually tends to move from a hot object to a cold object or from a high temperature environment to a low temperature environment. But the heat pump is a set that generates the path of heat movement against the usual motion. In fact, the heat pump transmits heat from an object or environment with low temperature to an object or higher temperature environment.

The figure below depicts a view of a heat pump.

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Figure 11: The way of performance of a heat pump

The heat pump is a high-efficiency system that controls room temperature using the procedure described at the beginning of the section. Consider a state that the goal of using a heat pump is to heat the environment. In this case, the heat pump uses the cycle and refrigeration cycle used in air conditioning and cold storage , but transfers the generated warm air to the opposite, ie into the room.

Note that by inverting the air flow in the heat pump, this device can be used to cool a room. Another important point to note is that when the heat pump is used for cooling, the location of the coils changes in the system, but its operating cycle does not change.
In a heat pump, the liquid in the evaporator is converted to steam and receives heat from the environment during this process. In the next step, the pressure of the steam is increased by the compressor, then; the high pressure gas enters the condenser, where it is converted into a liquid during the condensation process. Note that the condenser is an exothermic process, the gas in the heat system transfers to the environment during this process.

Rooftop Unit

The Rooftop Unit is widely used in the field of air conditioning and related industries. Note that this is also known as the “Air Handler”.

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Balanced ground temperatures improve efficiency of the air conditioner and HVAC. Note that the above applies to different types of heat pumps, such as working in the water or on the ground. This is also true for both heating and cooling modes. The following figure shows an overview of a heat pump system using hot liquids.

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Figure 13: The overall view of the heat pump system using hot liquids

The next step in this system is to create a hole near the air conditioning system or HVAC. Therefore, underground cold water can be transported upstream by the system to supply drinking water and water needed for the heat pump cycle. So, the water upstream from the ground is first filtered and then placed in a heat exchanger. So heat is taken from water and used to raise the temperature of the home’s water system.

As stated above, by the heat pump system using hot liquids, it can provide heating and cooling as well as hot water consumed in residential, office and commercial buildings. The following figure shows another view of a geothermal system that could be either horizontally or vertically in the ground, or it could be considered a river and water reservoir near the area.

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Figure 14: Performance of Geothermal Source

The following figure briefly illustrates the use of geothermal source in winter and summer. According to this figure, as well as the descriptions and figures described above, the precise application and method of the heat pump system using hot liquids can be easily evaluated.

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Figure 15: Geothermal source in winter and summer

Air conditioning and HVAC package systems

Air conditioning package systems are a bit like a rooftop unit system, but the air conditioning package systems are designed for home use.

Air conditioners such as window coolers and mini splits are used to cool small rooms and have a mass of about five thousand tonnes. In contrast to the mini air conditioners, there are also central air conditioners, designed for large spaces weighing about 20 tonnes.
Air conditioning package systems are also between the two systems. In fact, these systems are suitable for people that the amount of consumption and volume of home are between the two systems. Note that two different models of air conditioning package systems are designed which will be discussed below.

The first type of these systems (air conditioning package systems) is “Water Cooled Condenser”. As the name implies, these models of air conditioners are cooling systems and their condenser is operated by water.

Note that for operation of this type of air conditioner, water must be supplied in a constant and sufficient amount. These models of systems are usually installed indoors. The following figure depicts the performance of these types of systems.

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Air conditioning and HVAC package systems

A view of the system is shown below

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Figure 17: A view of ventilation package systems

Air conditioning and HVAC

The overall performance of this set is also illustrated below.

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Figure 18: The way of performance of the air conditioning and HVAC package systems

There are also other types of air conditioning package systems, known as “Air Cooled Condenser”. These types of systems are cooled by the air in the atmosphere, so they are external units and are placed outside the home.

These types of air conditioners consist of a fan that intakes air into the chamber before passing through the condenser coils. This issue is similar to the state observed in rooftop units.
These types of air conditioners are much more popular than the previous one (water cooled). In fact, these types of air conditioners do not require careful design and regular maintenance for presence of uniform water flow. The following figure shows an overview of these types of systems.

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Figure 19: Different components of the central air conditioning system with the package

The way of various components of the complex in a building is illustrated below. As it can be seen, the complex is placed outside the building and is considered outdoor units. There are also special channels in the house to use this system. Therefore, this system is considered as one of the systems with channel.

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Figure 20: The way of performance of the central air conditioning system with the package

Split-type air conditioning and HVAC system

The Split system is simply referred to a state that its components are separated from each other and located in different locations. In fact, the name Split in English means separated. In fact, part of the system consists of a condenser and a compressor outside the room and another part such as a blower and evaporator are inside the room.

These types of systems are divided into two general categories. The first group is called the Mini Split, also known as the Ductless System. The second group is called the central system.

These types of systems fall into two general categories. The first group is called the Mini Split, also known as the Ductless System. The second category is called the central system.
Air conditioning using the central system has two different models. In the figure above (previous section), an example of a centralized package system is showed. In the central package systems, the compressor, condenser and evaporator are placed inside a package, which is installed near a home or on the roof of the house.

There are other types of central systems that are known as split central systems. In this type of air conditioning systems, the condenser and compressor are placed outside the complex and the evaporator placed indoor and the air flow is distributed through the channel in the house. The following figure shows an example of split-type central systems.

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Figure 21: The way of performance of central air conditioning system with split

  The central system is actually considered systems with a duct and they are capable of controlling temperature in different environments. In fact, by installing ventilators of controlling airflow, it is possible to adjust the temperature of some rooms to a higher degree and others less.

Therefore, when a room or space is rarely used, it does not need to be cooled and its cooling can be stopped using this central system and thus a great deal of energy and cost is saved.
In a split-type air conditioner, the heat exchanger is placed in a central compartment and, using a blower, the air passes through the evaporator and cools, eventually the cooled air is transferred into the room.

The following figures illustrate an example of a ductless or mini-split system. Carefully, the various components of a split system are well observed. In these figures, the part that is inside the room and the part of the split system that is outside the room are depicted separately.

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Figure 22: Different Components of the Inside Room of a Split

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Figure 23: Different Components of the Outside Room of a Split

The way of placing these types of systems is shown below. As it can be seen, the various components of this system are placed separately. Part of this system is outside, and another part that includes an evaporator and an air blower are inside the room. In fact, the cool part of the system is inside the room and the hot part is outside the room.

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Figure 24: The way of placing different components of a split

Ductless systems

The smallest and best-selling types of air conditioning and HVAC systems are ductless systems. That’s why we allocated a separate section to these systems. Ductless or small split systems are designed for relatively small sized spaces, such as a large room or a few small rooms.

This type of air conditioning system requires the least amount of space in the room. The compressor and its heat exchanger can also be located further away from the main building.

So there is a lot of flexibility in how to use these types of ventilation systems.

Ductless systems allocate the largest and most market share. In fact, according to the flexible design of these systems and the ability to use them in residential homes, the use of these types of air conditioners has a great use. These systems are easily installed and they have a special beauty, and in some cases, they are considered part of home decoration.

The disadvantage of ductless systems than central systems is that they have higher operating cost. But these systems also have some positive features. One of their positive features is that they do not need a duct to be installed throughout the building. Therefore, in a building that has been completed, the ductless system is the best option and requires no major changes to install the duct and channel.

Note that creating a duct after completing a building is a very difficult task, and the easiest work is to use a ductless system. These types of air conditioners are illustrated in the following figure.

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Figure 25: Ductless systems

Therefore, it can be stated that a heating, ventilation and air conditioning system is one of the most important parts of a building that provides health and comfort in the building and it has a significant impact on energy consumption. So choosing a right air conditioning system will greatly help to save energy, reduce cost and increase comfort and health. Another point to be carefully considered is that there are different types of air conditioners and HVACs depending on the location and size of the building, six cases were thoroughly examined.

One of the key points in air conditioning of buildings is that a proper air conditioning system is created to control the temperature, humidity and air quality of building. Another point is that the topics discussed in the field of air conditioning are widely used in the design of a clean room as well as the control of pollutants in the clean room. Note that the correct design of an air conditioner requires careful simulation and different computations in the computational fluid dynamics science.

This study first examined in detail the general concepts used in air conditioning and HVAC and then the different types in an air conditioning and HVAC system such as heating and cooling were investigated. Afterwards, the performance of air conditioning and HVAC systems was stated and finally different types of air conditioning systems along with their advantages and applications were studied. Subsequent blogs for a detailed understanding of air conditioning issues, the concept of dew point and how to use a psychometric chart was studied in detail.

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