Window Air Conditioning (Window Type Room Air Conditioner)
Construction
● Window room air conditioner consist of a casing which is divided into two parts by a vertical partition, ie, outdoor part and indoor part.
● The partition has a small opening at the top. The outdoor part which is fitted outside the room and consists of hermetically sealed compressor, condenser, motor driven fan and a tray.
● The outdoor portion also divide into two parts by partition having small opening to the left side.
● Indoor part fitted into the room, consist of evaporator, motor driven fan, expansion device (capillary) and control panel an air filter, power connection and a tray. This indoor portion is divided into two parts by a partition which has small opening to the right side. Two trays are connected by a pipe line.
● Condenser is connected to evaporator by capillary tube through filter. Evaporator is connected to compressor by suction Mpe line and compressor is connected to condenser by discharge pipe line.
Working
● In this simple vapour compression refrigeration system is used.
● The low pressure, low temperature refrigerant vapour is sucked by hermetically sealed compressor and compressed to high pressure, high temperature and discharge to condenser and vapour condenses rejecting the latent heat.
● This liquid refrigerant passes through the filter into the capillary tube where it is throttled and then flow to the evaporator coil at low pressure.
● The liquid refrigerant at low pressure in the evaporator coil rapidly boils and pickup evaporation enthalpy from the evaporator surface.
● The fan or blower drive the air from room through air filter from the lower part of the unit and forces it to flow over the evaporator coil, temperature of the cooling coil is much lesser than the room air, the refrigerant inside the cooling coil absorbs the heat from the air and circulated back into the conditioned room.
● Due to this the temperature of the room air reduces hence air becomes chilled and circulated back into the conditioned room.
● Due to reduction in the temperature of the air, dew is formed on the surface of the cooling coil. For this purpose the temperature of the cooling coil is lower than the dew point temperature of the air.
● Moisture present in circulating air is removed and flow from coil surface to downward direction and drips in the tray at bottom. Which flow to the pan in outdoor part through pipe line. This moisture in the tray (pan) evaporates to some extent which helps in cooling the compressor and condenser.
● The compressor and condenser are fitted such that, the fan draws outside air from lower portion of outside unit and flow over condensing coil and discharge outside while passing air over the coil, condenser reject the heat to air, refrigerant vapour condenses into liquid form. When required temperature is achieved the compressor is automatically stop by control panel.
● This type of air conditioning is used for office, bed room, drawing office, etc. It cools the air and dehumidified, as it operates automatically one it put in operation.
Limitation of Window A.C. :
1. It has no control over humidity through it carries out dehumidification
2. In most A/C do not provide heating for winter.
3. No provision for humidification is possible.
Split Air Conditioning System :
● A split air conditioner is a window air conditioner which split in two unit, of the room air conditioner are separated out into two casing.
● A split air conditioner is modification of a window air conditioner which is divided into two unit, by using two separate casing.
● The indoor room unit consists of the evaporator coil, evaporator blower (fan) driven with its own motor, capillary tube control panel, air filter, supply and return air grills.
● It is situated inside the room to be conditioned. It can be ceiling suspended, wall mounted. The two units are connected with a harness electrical wires and tubing used to pass the air between the two units.
● The indoor and outdoor unit are located at small distance as possible. As the distance increases, the pressure drop in the suction and liquid line also increase resulting in decrease in capacity. The precautions must be taken in selecting and laying the suction and liquid lines to avoid the problem of oil return.
● To avoid refrigerant siphon action to compressor from evaporator during the off condition of the unit, the outdoor unit is installed or located higher level than indoor unit.
● Since the compressor (inside the outdoor unit is controlled by a thermostat that detects warm air, it activates the compressor outdoors.
● The compressor circulates a refrigerant gas, increasing the pressure and temperature of the refrigerant and easily discharges to condenser.
● Condenser removes heat from the refrigerant and the gas changes forces through tubing indoors until it reaches the evaporator system.
● Evaporator fan collects warm air and passes it over a coil containing the chilled liquid refrigerant. The fan system blow this cooled air back into the room by lowering the overall temperature of the space or room.
● The compressor is remotely installed from the room to be air-conditioned, the noise level will be appreciably decrease than window air conditioner and also providing the capillary tube in the outdoor unit to keep away the hissing or gurgling noise of the refrigerant at the outlet end of the capillary tube.
Advantages of a Split A.C.:
1. Easy for maintenance : These systems are easy to maintain as they have washable filters and require only routine cleaning periodically. Outdoor units are designed for easy to access and maintenance and repair.
2 Quieter in operation.
3. There is no need to block windows
4. Free from noise
5. Suitable for large capacity building or offices.
Disadvantages of a Split AC in Comparison to a Window A.C. :
1. Initial Cost of a split AC might be cost more than twice as much as a window AC.
2. The overall installation Cost is greater than a window AC due to labor charges and requires a mounting stand for the compressor unit, tubing needed to carry the cooled air.
3. Lack of Mobility
4. More heat transfer loss as cooling unit inside and compressor unit outside.
Difference between split air conditioning system and window air conditioning system:
Split air conditioning system → Window air conditioning system
1. High capital cost per ton of refrigeration. → Low capital cost per ton of refrigeration.
2. More noise and vibration → Less noise and vibration
3. Heat loss to surrounding → No heat loss to surrounding
4. Duct work is necessary → Duct work is eliminated.
5. Installation cost is more → Installation cost less
6. It comes in two units, cooling unit inside and compressor unit outside → It is one unit conditioner
7. This has to connect the exterior and interior units through rubber tubes, which might cause troubles. → This is easy to install
8. Some heat loss → No heat loss
9. Mostly used for large offices and big rooms → Suitable for small rooms only
Package Air Conditioning :
● These can be considered as the bigger versions of the room air conditioner and are used for air conditioning o beyond the capacity range of the room air conditioners. They are available in nominal capacities of 3, 5. 7. 10. and ton.
● The package unit also houses the air filtering, cooling-dehumidifying and air handling components and is factory assembled.
● The components for heating and humidifying purpose can also be included within the unit. The condenser can be of water cooled or air cooled type.
● The water cooled can be completely factory assembled, charged and tested. Therefore the laying of refrigerant piping pressure, leakage testing, charging, etc. need not have to be carried out in the field. This reduce field labour.
● The air cooled cannot be factory assembled and charged.
● Laying of the refrigerant piping between the indoor and outdoor unit, pressure testing, charging, etc. carried out in the field because of the scarcity of water air cooled unit are favoured, and capacity will be less than the water cooled condenser.
● In the packaged units with the water cooled condenser, the compressor is located at the bottom along with the condenser. Above these components the evaporator or the cooling coil is located.
● The air handling unit comprising of the centrifugal blower and the air filter is located above the cooling coil.
● The centrifugal blower has the capacity to handle large volume of air required for cooling a number of rooms. From the top of the package air conditioners the duct comes out that extends to the various rooms that are to be cooled.
● This type of air conditioning unit may be console type and remote unit type.
Type of air conditioning unit
(a) Console Type
(b) Remote
(a) Console Type : All the component of unit are in one single cabinet and placed in the room below the window sill and having suitable fresh air inlet opening provided in the wall.
(b) Remote Type : In this type, unit air handling and condensing unit are separated like split air conditioning system.
