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Air Conditioning Explained

Air Conditioning

The air conditioning system for human comfort was considered as luxury a few decades back, by now a days it has become a necessity. The air conditioning industry is vastly developing through out the world, owing to the rapid rise in the standard of living of the people.

The human life is becoming more uncomfortable in rapidly developing cities, due to the increase in population and industrial growth. Therefore the application of air conditioning for the industrial purposes has opened a new era in air conditioning industry. The critical time of air conditioning becomes clear when the temperature and humidity conditions become intolerable and industrial population and various activities are often affected.

The application of air conditioning may be considered necessary to meet a variety of circumstances especially where the work has to be carried out in a confined space. Properly conditioned air results in greater comfort to occupants when applied to public places, offices and factories.

Industrially, it has many benefits including better control of product quality, texture and uniformity. So the air conditioning system is no longer luxury but has an essential part of modern living.

To design an air conditioning system, the design engineer has to consider several parameters like temperature, humidity, purity, velocity and noise level including customers desire and his ability to spend. The design engineer after considering all the above factors selects proper air conditioning system which will satisfy the customer.

There are many factors to be considered while designing an air conditioning system.

1. The space to be air conditioned must be selected whether it is an office, school, restaurant or home.

2. Geographical location of the space and its size, orientation and many moire.

3. The owners capacity to afford the air conditioning system.

4. The external environmental conditions like temperature, humidity, exposure to sun and many more.

5. The internal load due to the heat released by the sun, occupants, light and other equipment.

6. The location of equipment to be installed.

Psychometric charts are prepared graphically to represent all the properties of moist air that is employed for air conditioning calculations.Psychometric or Hygrometry measures the properties of humid air and deals with the behavior of water vapor present in the atmospheric air. These charts represents the most convenient coordinates. Dry bulb temperature is plotted on the abscissa whereas the moisture content or vapor pressure is plotted on the ordinate axes. Depending on the weather conditions the chart can be classified into Mollier chart and Carrier chart. The carrier chart gives the wide range of application when compared to Mollier chat.

All the related terms are described below-

1. Dry Bulb Temperature-

Dry bulb temperature are indicated by vertical lines that are equally spaced. The temperature ranges from -5 degrees centigrade to 45 degrees centigrade.

2. Dew Point Temperature-

The Dew point temperature are horizontal lines parallel to abscissa and is non uniformly spaced. But any point on the saturation curve, the Dry Bulb Temperature and the Dew Bulb Temperature must be equal.

3. Enthalpy lines-

The Enthalpy lines are inclined straight lines and is uniformly spaced. These lines are drawn up to the saturation curve and is parallel to wet bulb temperature.The values of the total enthalpy lines are above saturation curve.

4.Relative Humidity-

Relative Humidity are curved lines depicting the quantity of moisture present in the air in percentage of total possible DBT and specific humidity locations.These lines are drwan up to 100% relative humidity with a difference every 10%.

5. Specific Humidity-

Specific Humidity are horizontal lines, parallel to abscissa and is spaced uniformly. Usually the moisture content varies from 0 to 0.03 kg/kg of dry air with a difference of every 1 gram.

6. Specific Volume-

It is the volume of air vapor mixture per kg of dry air. The lines are drawn at an angle of 60 degrees with the horizontal and is spaced uniformly. The values of specific volume can be observed at the base of the chart.

7. Vapor Pressure-

Vapor Pressure lines are horizontal lines and are spaced uniformly. It gives the absolute pressure of the steam.

8. Wet Bulb Temperature-

The Wet Bulb Temperature are inclined straight lines which is non uniformly spaced. The wet bulb temperature at any point on the saturation curve sis equal to the dry bulb temperature. These lines are towards the downward right at an angle of 30 degrees to the horizontal.

This is all you need to know about Air Conditioning.

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