Air Conditioning

Treating air with window type Air Conditioning  unit

Air conditioning is defined as the process of treating air for the purpose of providing human comfort. Basically, this is the main reason why the air must be conditioned. But since controlled air temperature has a lot of benefits and is highly in demand, the application of air conditioning has extended into many different fields.

The process of treating air involves several sub-processes to attain the desired air quality. This involves air purification or removing dust, odor and any foreign particles, maintaining proper ventilation or providing enough source of air to circulate in a given room, maintaining equal air circulation and distribution, controlling humidity and lastly controlling the amount of heat that is present in the air. To make it more understood, let me enumerate.

1.    Air Cleaning and Purification
2.    Proper Ventilation
3.    Air Circulation and Distribution
4.    De-humidification and Humidification
5.    Temperature Control

The above processes are the prime tasks of air conditioning unit that must be accomplished simultaneously to treat air that circulates in any confined area or room. 

One of the most important aspects that must be understood in air conditioning is the fact that, it is just one application of refrigeration technology with concern on treating air. With this concept, we can also define air conditioning as the process of treating air to provide human comfort by means of refrigeration and air purification.

Air Purification and Distribution

Ultraviolet rays for air purification

The process of air purification involves air filtering. This is done by providing a specially designed air filter in front of most air conditioning units. This air filter traps dust and other tiny particles that goes together with air.

The use of ultraviolet rays in some air conditioning units help to kill germs and bacteria that causes odor in the air.  It is done by allowing the cooled air to pass through an ultraviolet light  before being distributed to the conditioned area. This makes the air really pure, healthy and clean.

In residential rooms and hotels, to accomplished the equal distribution and circulation of clean air, a forced air flow is required. It is done by the used of radial fan with its louver and air swing to distribute air to all angles possible from the air conditioning unit. 

In large air conditioning installation, air distribution is accomplished by using air duct and diffusers to convey treated air in all rooms. In short, this is made possible by the used of mechanical parts designed for this purpose.

Proper Ventilation

This  should not create confusion against providing air circulation and distribution. To maintain proper ventilation in a conditioned room means to provide enough supply of air that must be treated and equally distributed.  This is however only required when the supply of air to ventilate the area is quite limited due to locations and some factors. If an air conditioning unit is installed in a bit distant from the room to be conditioned, the design of air duct, auxiliary fans, blowers, and diffusers must convey enough volume of air to ventilate the whole area.

De-humidification and Humidification

During the process of heat absorption to control air temperature, another air treatment process also occurred simultaneously. This is called air de-humidification or reducing the amount of  humidity in the air.  Humidity is the water content that evaporates into the atmosphere and holds a certain amount of heat.

Water dripping produced  by split ac unit

During the heat absorption process done by air conditioning  unit, water vapor condenses and turns into liquid reducing its amount in the air. This is done by allowing the raw air (containing heat and moisture) to pass through evaporator coil. At this point,  heat  transfers from air to the evaporator fins, to the evaporator tube and to the refrigerant inside.

As the latent heat that holds the water vapor moves to the refrigerant, moisture or humidity condenses and flow to the drain pan of any air conditioning unit. This is how AC unit produces water from the air.

When humidity is extremely low beyond human comfort, some units called humidifier aids the air conditioning unit. This is done by simply adding or spraying vaporized water in the air to make the air partially wet.

Effect of Dry Air

Humidity may vary according to locations. Jungles and mountains are less humid compared to places like coastal areas or any places where there is a body of water that may evaporate anytime. Humidity  could  be brought by an open air from highly humid areas as it travels  freely from one place to another.

When air is less humid or dry, it also has a negative effect on human body.  It can cause human skin to look dry and unhealthy. This is the reason why some products like skin moisturizers are sometimes needed to protect our skin from dry air. Sometimes extreme dry air can cause our lips to crack.

Human Comfort Zone

Human comfort zone

To maintain human comfort, humidity must not be totally removed from the air as well as the heat. There is just a certain level that must be attained by air conditioning units in terms of controlling heat and humidity.

Human body was said to be comfortable at air temperature of 20 ⁰C - 28 ⁰C with relative humidity of 30% to 70%. Relative humidity is the ratio of moisture content in the air, to the actual amount of moisture the air can hold. If the relative humidity is 100% air is totally saturated with water vapor.

Human Discomfort

As we all know, when heat hits the body of water, water evaporates and turns into vapor.  It means our atmosphere is composed of mixture of different gasses including water vapor (hydrogen and oxygen). When air is wet, the humidity is high or it is saturated with water vapor. In this condition, if the  air temperature is also high, human being feels uncomfortable.

By magnificent design,  human body maintains a certain level of temperature automatically. We simply called it as our normal body temperature. At this level of temperature, parts of our body can perform well in whatever functions they may have to make us alive.

When our body temperature increases  due to some external reasons (when we stay in a hot or humid area or when we use our energy just like when doing some work or exercise), our body will automatically release a liquid we called sweat. Sweat must quickly evaporate and leave no spot in our skin to make our body cool down. From the principle that when liquid evaporates, it absorbs heat and go away.

This is what happens when we came from a long walk and arrived home, tired and sweaty, and turn on the electric fan as we rest. As  air hits our body, sweat evaporates carrying the heat  that increases our body temperature.  This makes us feel cool and re energized as our body temperature normalizes.

When staying in a hot and humid place, perspiration persist and we become uncomfortable. As our body temperature increases due to heat transfer from the hot air, our body keeps on releasing more liquids to cool as down. But due to the moisture content in the air  or high relative humidity, air could no longer accommodate more water vapor.

This prevents our sweat to evaporate and heat cannot be released from our body. As our body temperature remains high above the required level, more perspiration will come out. This is the failure of our body to adjust against outside circumstances.

Human discomfort is basically due to the amount of heat and humidity that is present in the air. Heat triggers our body to release  liquid or sweat to cool us down and maintain our normal body temperature, but humidity blocks the evaporation of that liquid substance. Therefore, heat cannot be taken away from our body. In dealing with this chaos, air conditioning units played a very significant role.

Temperature Control

If other processes are required to make the air pure, clean and properly distributed, the process of controlling air temperature or heat content in the air can only be accomplished by means of heat absorption and extraction, which is called refrigeration. With this in mind, we can clearly conclude that without refrigeration, air conditioning may not also be possible or effective as what we have today.

From the above paragraph, it is understood that treating air in terms of controlling heat is accomplished by means of refrigeration. This is where the heat that is present in the air is being absorbed and extracted to the place  where it can do no harm.  The process of heat absorption leaves the air cooled as the amount of heat decreases.

In places where weather temperature reaches below human comfort during winter, air conditioning units are used to provide warm air. This is done by using some source of heat to increase air temperature and blow to the conditioned room.

Other Applications of Air Conditioning

Air conditioned room for electronics manufacturing

Aside from the standpoint of providing human comfort, air conditioning has been also widely used in some related areas. The basic idea of the term human comfort is to provide a good sleep at night and comfortable feeling when staying at home, when in a shopping mall or when on travel on board in a public transportation vehicle.

But beyond these aspects, air conditioning  extends into other areas where controlled air temperature is required. In most manufacturing companies where some processes need pure and clean air to maintain product quality, air conditioning unit does the work to take care about the air issue.

Some machinery and electronic related parts also needs to be kept in a controlled room temperature. In places like this, air conditioning has really played a vital role. Aside from the mentioned above, hospitals, laboratories, food processing companies and many others need air conditioning unit to maintain clean air as requirement for health and sanitary related purposes.