Window air conditioner or room air conditioner

 WINDOW AIR CONDITIONER or ROOM AIR CONDITIONER

As the name implies, all the components of an Air Conditioner are assembled inside a casing installed in the window of a room at the window sill level. Hence, it is called Window Air Conditioner. Fig. 1 shows the pictorial view of a window air conditioner.

Window Air Conditioner is designed to condition the air in a single room and is hence known as Room Air Conditioner.

Description

 See Fig. 2. The window air conditioner consists of a Vapour Compression Refrigeration System, Air Filter, Double Shaft Motor, Centrifugal Blower and Propeller Type Fan. The vapour compression refrigeration system consists of:

1. Evaporator

2. Compressor

3. Condenser

4. Expansion Valve in the form of a Capillary Tube

The Evaporator part is facing the room (INDOOR). The Condenser part projects outside the room (OUTDOOR). The evaporator part is insulated from the condenser part. That is, the evaporator and condenser coils are separated by an Insulated Partition to avoid the air movement between the room and atmosphere.

A common Double Shaft Motor drives a Fan at one end and a Blower at the other end. Adjustable Louvers continuously change the direction of air flow to ensure uniform distribution of conditioned air inside the room.

Working Principle

 Commonly used refrigerants are: Freon-12 and Freon-22.

 Evaporator

Evaporator is a cooling coil made of copper. The Centrifugal Blower is instalied behind the evaporator.

The Blower sucks warm air from the room and sends it to the evaporator through the Air Filter. [Air filter cleans the air by removing dust and dirt particles.] The Low Pressure Low Temperature (LPLT) refrigerant inside the evaporator coil absorbs the heat from the room air and evaporates. Therefore, the room air is cooled as well as dehumidified by continuous heat removal. The dehumidified-cooled air is blown back into the room.

The desired temperature of 20°C to 25°C in the room for human body comfort is maintained using the Control Panel.

Compressor

The LPLT evaporated refrigerant is drawn by the suction of the Compressor. compressor compresses it to High Pressure High Temperature (HPHT) vapour. vapour flows into the Condenser Coil.

Condenser

The Fan draws the atmospheric air, which is circulated over the condenser coil. The HPHT refrigerant vapour inside the condenser condenses by giving-off the heat to the air, which absorbs the heat. This hot air is discharged to the atmosphere. The HPHT vapour is condensed to High Pressure Low Temperature (HPLT) liquid refrigerant in the condenser.

Capillary Tube

Then the HPLT liquid expands to LPLT liquid in the Capillary Tube. This liquid refrigerant is re-circulated through the evaporator. The cycle is repeated.

 The evaporator outer surface is cold, as it contains low temperature liquid refrigerant. So, water vapour in the warm humid air condenses to form water droplets on the outer surface of the evaporator.

[Have you observed the formation of water droplets on the outside of an ice-filled glass tumbler, due to the condensation of moisture in the surrounding air?] These droplets are collected and drained.

 Window air conditioners operate on 230 V, singe phase AC supply.

Capacity of Air Conditioner

 Unit of Refrigeration is expressed in terms of Ton of Refrigeration (briefly written as TR). A Ton of Refrigeration is the amount of heat absorbed to produce 1 ton of ice at 0°C within 24 hours when the initial condition of water is also at 0°C. The value of 1 ton of refrigeration is 3.5 kJ / second or 3.5 kW in S.I. units. Air conditioners are also specified by the same unit TR.

The room air conditioners have capacities ranging from 0.75 to 4 TR in sizes of 0.75, 1, 1.5, 1.6, 2, 3 and 4 TR.

1. ADVANTAGES

1. Self-Contained Unit: Window air conditioner is a self-contained single-package unit.

2. For more than one room in a residential building, several window units can be used. A separate temperature control is provided in each room in which the unit is installed.

 3. No Ducks: Ducts are not required for air distribution. This advantage is especially noticeable in residences in mild climates where central heating systems are not required.

 4. Installation: Installation is simple and plumbing is not required.

2. DISADVANTAGES

1. Suitability: Not suitable for large halls and applications where heat and moisture loads are high.

2. Air Circulation: The unit has circulation of a fixed air quantity.

3. Installation Constrain: The installation must be made only on an external wall of the room.