Heating Ventilation And Air Conditioning

The Unitary air conditioning system is a self-contained system used to cool individual rooms or small spaces.
It combines all major components like the compressor, condenser, expansion device, and evaporator in a single casing.
There are two main types:
1. Window AC: All parts are housed in a compact box mounted on a window or wall.
2. Split AC: Has two separate units — the outdoor unit (compressor and condenser) and indoor unit (evaporator and blower).
Unitary systems are easy to install and operate.
They are ideal for residential rooms, small offices, shops, and cabins where centralized AC is not practical.
Advantages include low cost, simple maintenance, and independent operation for each unit.

The Radial Perimeter duct system is a type of air distribution system used in air conditioning for efficient supply of conditioned air.
In this system, the main supply duct is connected to multiple branch ducts that extend radially from a central point towards the perimeter of the building or room.
This arrangement ensures uniform air distribution to all areas.
It is suitable for large open spaces where air needs to be delivered evenly around the perimeter.
Advantages include balanced airflow, simple design, and easy installation.
This system is commonly used in offices, halls, and large commercial buildings.
A typical diagram shows a central air handling unit with ducts radiating outwards like spokes of a wheel.

A well-designed air distribution system ensures effective and efficient cooling or heating.
Important points to consider include:
1. Proper duct sizing: Ducts must be correctly sized to carry the required airflow without excessive resistance.
2. Air velocity: The velocity of air should be within recommended limits to avoid noise and ensure comfort.
3. Balanced air flow: Air should be distributed evenly to all zones to maintain uniform conditions.
4. Location of outlets and inlets: Supply outlets and return inlets should be positioned to provide good air mixing and avoid drafts.
5. Insulation: Ducts should be properly insulated to prevent loss of cooling or heating.
6. Accessibility: The system should be easy to inspect, clean, and maintain.
Considering these points helps achieve good indoor air quality and energy efficiency.

Insulating materials are chosen based on the temperature range they can safely handle.
Glass wool is a fibrous insulating material made from glass fibers.
It has excellent thermal resistance and can operate safely from around to .
It is widely used in building insulation, refrigeration piping, and air conditioning ducts.
PUF (Polyurethane Foam) is good for low temperatures but usually has an upper limit around .
Cellulose insulation is mainly used in buildings but cannot handle very low temperatures like .
Thermocol (expanded polystyrene) is used for thermal insulation but is not recommended for such a wide temperature range.
Therefore, Glass wool is the best choice for this range.

Air conditioning systems are classified based on how air is cooled and distributed.
Unitary systems are small self-contained units like window ACs or split ACs used for single rooms.
Self-contained systems are similar — they have all components in one unit for individual zones.
Central station systems are large systems used to condition air for entire buildings using ducts.
An automatic expansion system is not an air conditioning system type — it refers to an automatic expansion valve used within a refrigeration cycle to regulate refrigerant flow.
So, it is a component, not a complete system for air conditioning.
Therefore, option (D) is correct.

In air conditioning and ventilation systems, conditioned air is delivered to different spaces using a network of passages.
These passages are called ducts.
A duct system distributes heated or cooled air from the air handler to rooms and returns it back for reconditioning.
Ducts can be made of sheet metal or flexible materials and are designed to minimize air leakage.
A shaft is a vertical passage used for lifts or services, not for air flow.
A channel is a general term and not the standard name in HVAC.
A pipe carries liquids or gases under pressure but is not used for distributing large volumes of air in buildings.
So, ‘duct’ is the correct answer.

Viscous filters are air filters that use a sticky coating to trap dust and particles from the air.
They are typically cleaned and reused rather than replaced entirely.
They can be dry type (without oil coating) or automatic type (self-cleaning).
They can also be manually cleaned by washing or replacing the sticky media.
However, they are not normally fully replaceable type like disposable filters that are thrown away after use.
Therefore, 'replaceable type' does not match the design of a true viscous filter.

A central air conditioning system is designed to maintain desired indoor conditions throughout the year.
It provides cooling in summer, heating in winter, ventilation, air filtration, and sometimes humidity control.
Such systems are large, serving multiple rooms or entire buildings through ductwork.
They can switch between cooling and heating modes automatically.
Options like only summer or winter air conditioning do not describe its full capability.
Dehumidification is just one function, not the entire system’s purpose.
Therefore, central AC systems are mainly for year round air conditioning.

In air conditioning systems, ducts are used to carry conditioned air to different zones of a building.
The most common shape for air ducts in buildings is rectangular.
Rectangular ducts are preferred because they can fit into narrow ceiling spaces and are easier to install along walls and partitions.
Round ducts are also used but mainly where space allows and for smaller applications.
Square and elliptical shapes are uncommon for practical duct design.
Therefore, rectangular is the correct standard shape for air conditioning ducts.