Domestic Refrigerator | Layout of a Typical Domestic Refrigerator

LAYOUT OF TYPICAL DOMESTIC REFRIGERATOR

Refrigerators, once considered a luxury, are now a necessity of daily life. They have usage in homes, hotels, office, laboratories, hospitals, shops restaurants, etc. They are manufactured in several sizes and many brands are available. The different models are rated on the basis of gross volume such as 100 litres, 165 litres, 200 litres, 250 litres and so on.

Description

The construction of household refrigerator, with location of main components.

01 - DOMESTIC REFRIGERATOR - COMPONENTS OF A DOMESTIC REFRIGERATOR

1. Evaporator: The evaporator is located in a coil form on the freezer box. The liquid refrigerant is evaporated in the evaporator by absorbing heat from the contents of the domestic refrigerator in the cabinet. The evaporator consists of copper metal rubbing surrounding the freezing and cooling compartments.

2. Condenser: The condenser is located as zigzag tubes behind the refrigerator on a mesh. In the condenser, the heat from the refrigerant at a higher temperature is rejected to the atmospheric air.

3. Compressor: The compressor is located at the base at the rear end. It compresses the refrigerant vapour to a high pressure. Reciprocating compressor is used for low capacity domestic refrigerator.

4. Expansion Valve or Throttling Valve: An expansion valve is used to reduce the temperature and pressure of the liquid refrigerant, before it passes to the evaporator. The expansion capillary is located inside the refrigerator body hear the wall. The capillary tube is small diameter tube used as an expansion device.

5. Refrigerator cabinet: The refrigerator cabinet is thermally insulated to minimize heat flow from the atmosphere into the refrigerator. The insulation is glass fiber and the external body is of stainless steel.

Working Principle

01 - LAYOUT OF TYPICAL DOMESTIC REFRIGERATOR - REFRIGERATOR LAYOUT

The refrigerator works on the vapour compression refrigeration cycle. The refrigerant vapour is first compressed in the compressor. The compressor is a special one known as the hermetic compressor. In this unit, the compressor is sealed casing along with an electrical motor to run. This sealing prevents leakage of refrigerant and lubrication oil. The pressure and temperature of the refrigerant increases after compression and is subsequently condensed in a condenser. In the condenser, the refrigerant rejects heat to a coolant and cools down and finally gets condensed. The condensate is then allowed to pass through capillary to reduce temperature and pressure by expansion of refrigerant. The refrigerant is filtered before entering the capillary tube. The pressure of the refrigerant, when it leaves the capillary, is maintained above atmospheric and temperature corresponds to saturation temperature so that the refrigerant can absorb heat in the evaporator. The refrigerant enters the evaporator and is heated by the heat absorbed from the body or space thereby producing the refrigeration effect. The vapour refrigerant enters the compressor again and the cycle is completed.

When power to the compressor is switched on, a humming sound is heard and the refrigerator is functional. The refrigerant flows through its circuit and ice is produced in the freezer. Frost, i.e., moisture from ambient air, gets deposited on the evaporator coil. Defrosting removes this frost. The water from defrosting is collected in a tray to be removed manually. Articles to be refrigerated are placed on shelves. Fruits and vegetables, which contain moisture, are stored at the base. The temperature here is around 8°C. Thus there are temperature gradients in the refrigerator, negative temperature in the freezer and positive temperature at the base.

Vapour Compression Refrigeration System | Refrigeration System

Vapour compression refrigeration system

The most important of all the refrigeration system is the vapour compression refrigeration system with the view point of commercial and domestic utility. This system is the most practical form of refrigeration.

Principle

01 - VAPOUR COMPRESSION REFRIGERATION SYSTEM -  REFRIGERATION SYSTEMS

in this system Freon-12 or freon-22 is used as refrigerant. This refrigerant is capable of readily evaporation and condensation without leaving the plant during the evaporation state it absorbs heat from heated body. This absorbed heat is used as latent heat for converting it from liquid to vapour state. In the condensation or cooling process it rejects the heat to the external body. Thus it produces a cooling effect in the working fluid.

Description

Vapour compression refrigeration system consists of the following parts.

01 - VAPOUR COMPRESSION REFRIGERATION SYSTEM -  REFRIGERATION SYSTEM

Compressor: The purpose of the compressor is to raise the temperature and pressure of the input refrigerant which has low pressure and low temperature.

Discharge line: A discharge line is used for delivering the high pressure, high temperature vapour from the discharge of the compressor to the condenser.

Condenser: The temperature of the hot refrigerant is reduced using a coolant with the help of condenser.

Receiver tank: Receiver tank is used to provide storage for a condensed liquid so that a constant supply of liquid is available to the evaporator as required.

Liquid line: A liquid line transmits the liquid refrigerant from the receiver tank to the refrigerant flow control.

Expansion valve: The proper amount of refrigerant liquid to the evaporator is controlled by the expansion valve.

Evaporator: An evaporator provides a cooling effect to the refrigerated space. The liquid refrigerant absorbs heat from the refrigerated surface and gets converted into refrigerant vapour.

Suction line: The low pressure vapour from the evaporator is transferred to the suction inlet of the compressor with the help of suction line.

Working principle

A simple vapour compression system follows the following chain,

                 Compression – condensation – expansion – vaporization

The vapour at low temperature and low pressure enters the compressor where it is compressed which makes the temperature and pressure to increase considerably. From the compressor the vapour enters the condenser where it is condensed to a very high pressure liquid and it is collected in a receiver tank. From the receiver tank, the refrigerant slowly passes through the expansion valve, where it is throttled down to a lower pressure. Finally it reaches the evaporator where it extracts heat from the surrounding where it is being refrigerated and vaporizes to low pressure vapour. Thus the surrounding is cooled. From the evaporator the low pressure refrigerant vapour enters the compressor. This process is repeated as a cycle.

Advantages of vapour compression refrigeration system

· Running cost of this system is low

· For a fixed capacity of refrigeration, it is compact in size.

· This is employed for a large range of temperatures.

· The size of the evaporator is small.

· This system is available in variety of sizes.

Disadvantages of vapour compression refrigeration system

· Cost of the refrigerant is high.

· Refrigerant leakage is a problem.

· Initial cost is high.

· Energy consumption in the form of electricity is high.