Ventilation & Air Conditioning of Buildings

VENTILATION

Heating, Ventilation and Air Conditioning (HVAC) systems play an important role in buildings and homes. They can effectively be used in industrial areas as well as residential complexes. A good HVAC system provides proper ventilation inside a building and maintains a comfortable temperature. Ventilation acts like the lungs of the building. Ventilation is a process that has to be done to maintain adequate indoor environment quality. Ventilation circulates air from the outside into the building while removing contaminants from the air already present inside. This keeps the air quality at a steady pace. The primary purpose of ventilation is to prepare healthy air for the breathing of people in that place. The different types of ventilation are as follows:

❖ Natural Ventilation is a process where the difference in pressure between air inside and outside a building creates an envelope of circulation. The air filters itself through the windows and doors of the structure. Natural or traditional ventilation systems depend on natural forces such as wind and thermal buoyancy to drive outdoor air throughout the building's openings. Well-designed natural ventilation could be used to access higher levels of daylight.

❖ Mechanical Ventilation is used in most buildings as it is easier to control the quality of the indoor air environment. However, it should be done carefully as to not compromise on the overall quality of the indoor environment. Mechanical fans conduct mechanical ventilation. Fans can be installed in windows or walis directly or in air ducts to supply air to or from the room.

❖ Hybrid Ventilation (mixed mode) depends on natural driving forces to prepare the desired flow rate. When natural ventilation has a very low flowrate, the role of mechanical ventilation is prominent. When natural ventilation is not acceptable alone, exhaust fans can be installed to increase the ventilation rate. These have enough pre-testing and planning in order to work properly.

❖ Spot Ventilation is another kind of ventilation. In order to improve the effectiveness of both natural and mechanical ventilation systems, spot ventilation came into existence. In other words, it is better to say that it is an auxiliary system. This involves deploying local exhaust fans, the same as those used in the bathrooms or kitchens. It removes the moisture and inside air pollution at its source, and as a result, it improves the usefulness of the ventilation system.

AIR CONDITIONING

Air conditioning is the process of giving comfort to the occupant in a particular space irrespective of any external climatic conditions. It can be defined as the treatment of indoor air in order to control certain conditions required for human comfort. The desirable conditions may be temperature, humidity, dust particle level, odor level, and air motion. It is known that the physical properties of air can be controlled by cooling, heating, humidification, and dehumidification. These processes may be employed to maintain specific conditions desirable for comfort. Thus, simultaneous control of temperature, humidity, air motion, and cleanliness is known as air conditioning. Air conditioning systems are broadly classified as follows:

❖ Comfort Air Conditioning- The objective of this is to provide thermal comfort to the occupants. Thermal comfort may be defined as the state of mind that expresses satisfaction with its surroundings.

❖ Industrial Air conditioning - It is the process of providing air at required temperature and humidity to perform a specific industrial process successfully.

Following are the important equipments used for air conditioning:

❖ Air circulation fan.

❖ Air-conditioned

❖ Supply duct

❖ Supply outlet (grill)

❖ Return outlet duct

❖ Filter

FACTORS AFFECTING AIR CONDITIONING

The four important factors for comfort conditioning are to be observed and maintained:

❖ Temperature: The control of temperature is necessary in air conditioning. Even though the outdoor temperature is varying, the indoor temperature is maintained to be constant which is the desired condition. The heat may be either removed or added to the conditioned space depending upon the surrounding conditions. The person may feel comfortable when the temperature is 20°C.

❖ Humidity: Humidity control means an increase or a decrease in moisture content inside the space to be air-conditioned. It is necessary not only for human comfort but also to increase the working capability. In summer, the relative humidity should be 60% and in winter it should it should be 40%. Purity/Cleanliness: It is one of the most important factors which affect the air conditioning. In addition to the control of temperature and humidity for human comfort, it is necessary to clean air, i.e., to make the indoor air free from dust, dirt, and odor. It is necessary that proper filtration and purification of air should be done and the supply of air free from dust and dirt should be made in air-conditioned space.

❖ Air Motion: Air motion or proper circulation of air is also a factor affecting the human comfort. In order to maintain constant temperature throughout the conditioned space, it is necessary that there should be equal distribution of conditioned air in the space. The air movement is maintained at the desirable velocity of about 8 m/min using appropriate distribution system, grills, etc.

TYPE OF AIR-CONDITIONING

Based on the working conditions and position air conditioning can be broadly classified as follows:

❖ Window air-conditioning system

❖ Split air-conditioning system

❖ Package air-conditioning system

❖ Centralized air-conditioning system

Window air conditioner is the most commonly used air conditioner for single rooms. In this air conditioner all the components, namely the compressor, condenser, expansion valve or coil, evaporator and cooling coil are enclosed in a single box. This unit is fitted in a slot made in the wall of the room, or more commonly a window sill.

Split type air conditioners are named because they split the components of a traditional air conditioning system into two individual units - one indoor and one outdoor. The outdoor unit houses the compressor and condenser components, while the indoor unit contains the distribution and filter components.

Packaged Air Conditioner: This type of air conditioner is preferred if more than two rooms or a larger space at your home or office needs to be cooled. There are two possible arrangements with the package unit. In the first one, all the components, namely the compressor, condenser (which can be air cooled or water cooled), expansion valve and evaporator are housed in a single box. The cooled air is thrown by the high capacity blower, and it flows through the ducts laid through various rooms. In the second arrangement, the compressor and condenser are housed in one casing. The compressed gas passes through individual units, comprised of the expansion valve and cooling coil, located in various rooms.

Central air conditioning is used for cooling big buildings, houses, offices, entire hotels, gyms, movie theaters, factories etc. If the whole building is to be air conditioned, then putting individual units in each of the rooms is very expensive making this a better option. A central air conditioning system is comprised of a huge compressor that has the capacity to produce hundreds of tons of air conditioning. Cooling big halls, malls, huge spaces, galleries etc is usually only feasible with central conditioning units.

ADVANTAGES AND DISADVANTAGES OF AIR-CONDITIONING

Advantages

❖ Filters the air, improving air quality.

❖ Dehumidifies the ambient air, providing greater comfort.

❖ Easily control the temperature using a simple wall control unit.

Disadvantages

❖ Spending too much time in an air-conditioned room may have a bad effect on your skin as air conditioning may have a drying effect on it and the mucous membranes.

❖ Almost every kind of air-conditioning creates some ambient noise.

❖ The central air-conditioning can transmit infectious respiratory diseases and airborne fungi and dust can cause allergic reactions.

❖ A more comfortable environment makes people lazy and they may start avoiding going out in the sun.

❖ Increase in electricity bills.