Layout of Typical Domestic Refrigerator

LAYOUT OF TYPICAL DOMESTIC REFRIGERATOR

Domestic Refrigerator (Fridge) works on Vapour Compression Refrigeration System. In the domestic refrigerator, the most commonly used refrigerant is Freon 12. Fridges are available in capacities ranging from 4 liters to 600 liters.

Description

Fig. 2 shows the Layout of a Typical Domestic Refrigerator.

1. Evaporator or Cooling Coil

2. Compressor

 3. Condenser

4. Capillary Tube (Expansion Valve or Throttling Valve)

 5. Thermally Insulated Cabinet

1. Evaporator or Cooling Coil

As the name implies, the liquid refrigerant is evaporated in the Evaporator by absorbing heat from the contents (perishable vegetables, fruits, etc.) of the domestic refrigerator.

 The evaporator consists of copper metal tubing. The purpose of metal tubing is to produce cooling effect required for lowering the temperature of perishables or for freezing ice. Since the evaporator coil produces the cooling effect, it is also known as Cooling Coil. The Evaporator is the coldest part of the refrigerator located in the Freezer Compartment.

2. Compressor

Compressor compresses the refrigerant vapour to a high pressure. Reciprocating Compressor is used for low capacity domestic refrigerator. It is in a hermetically sealed casing. [Centrifugal Compressor is used for high capacity refrigerators.]

The compressor suction is connected to the evaporator. Its delivery is connected to the condenser. An Electric Motor runs the compressor.

3. Condenser

In the condenser, the heat from the refrigerant at a high temperature is rejected to the atmospheric air. In domestic refrigerators, Air Cooling of refrigerant is arranged. Thus, the heat is rejected from the refrigerated space to the atmosphere, by the air passing over the condenser coil.

4. Capillary Tube (Expansion Valve or Throttling Valve)

Capillary Tube is an Expansion Valve or Throttling Valve. The low capacity systems such as domestic refrigerator and window air conditioner use small diameter tube called Capillary Tube. [Solenoid Valve is used as an expansion device in large capacity refrigerators.]

Capillary Tube is used to reduce the temperature and pressure of the liquid refrigerant, before it passes to the evaporator. The high pressure refrigerant liquid is to be depressurized in the expansion device for reuse in the evaporator.

5. Thermally Insulated Cabinet

The refrigerator. Cabinet is thermally insulated to minimize heat flow from the atmosphere into the refrigerator. Without thermal insulation, the refrigerator would be heavily loaded, resulting in large consumption of power. The Cabinet is therefore double-walled. The space in-between the walls is filled with insulation material such as poly-urethane foam.

Working Principle

The refrigeration effect is produced in the Evaporator. The wet refrigerant at Low Pressure Low Temperature (LPLT) enters the Evaporator coil. It absorbs its latent heat of vapourization from the Contents (perishable vegetables, fruits, etc.) in the Freezer Compartment and evaporates. This, in turn, lowers the temperature in the freezing compartment and cools the contents.

The evaporated dry refrigerant enters the Compressor. The compressor compresses it to High Pressure and High Temperature (HPHT). This is necessary to condense the vapour to a liquid form.

The HPHT vapour from the compressor flows into the Condenser. In the condenser, the vapour gives off its latent heat to the surrounding atmospheric air and condenses into liquid.

The high pressure condensed liquid refrigerant at room temperature flows into the Capillary Tube (Expansion Valve). The expansion of the refrigerant in the Capillary Tube lowers its pressure and temperature. At the same time, the refrigerant partly evaporates. Therefore, the refrigerant coming out of the Capillary Tube will be a wet vapour at low temperature.

This wet vapour passes to the evaporator coil, where it absorbs its latent heat. It is then re-circulated and the cycle is repeated.

Thermostat Switch

 The required low temperature is maintained in the refrigerator by a Thermostat Switch. It switches ON and OFF the compressor motor by a relay as and when the temperature either falls below or rises above the required temperature.

Freezer Compartment

 Freezer Compartment is used to make ice and store ice-cream and other frozen desserts at about -15°C. It is also used to store meats, poultry, fish, fruit pulp and other frozen foods for extended periods of 8-12 weeks.

Chiller Tray

 In this chamber, food is stored at close to 0° C, which keeps items like milk packets, paneer, etc., soft. It eliminates the need for thawing the food before cooking.

Bottom-most Compartment

 The bottom-most compartment is for vegetables where a very low temperature is not necessary.

 

1. TIPS ABOUT FOOD STORAGE

1. All food items should be fresh before freezing, as food can be only preserved, but cannot be rejuvenated

2. All frozen food should be either packed in containers or wrapped in polythene or aluminum foil.

 3. Loosely wrap all vegetables, especially the leafy ones in polythene bags.

4. Fruits and vegetables that have a strong odour should be wrapped tightly.

5. Certain vegetables like beans and lady finger should not be washed before storing.

 6. Mushrooms, melons and peaches can only be chilled in the refrigerator and not preserved.

 7. If fruits and vegetables are washed before storing, they should be thoroughly drained off all the water.

Reason: Too much moisture can increase the possibility of decay or spoilage.

8. Cooked food should not be stored for more than two days.

 9. Hot food should not be stored in the refrigerator. It should be cooled to room

temperature.

Reason: Hot food increases the temperature inside the refrigerator and causes

unnecessary condensation which can spoil other food.

10. Ice cream should always be stored in the freezer with thermostat in coolest setting.

 11. Wipe-off all moisture and dirt in the bottles and cans before storing. Bottles containing water and other liquids should be closed with caps before storing.

 12. Tight stacking of items, large plates and utensils hinder the circulation of air in the refrigerator and affect cooling efficiency. It is, therefore, best to avoid this.

 13. Defrosting

Defrosting reduces running time and therefore power consumption. It cools the refrigerator faster. Also, it reduces condensation of moisture on the internal walls and components. It allows efficient evaporation of defrost water. Further, it avoids lingering odour, absorbed from the foods.

Regular defrosting is essential. It should be carried out at least once a week. To ensure efficient operation, do not allow the frost formation to exceed 6 mm. If defrosting is delayed, the water evaporation pan will evaporate less defrost water. This may cause water to overflow and require use of a drain pan to collect the overflow.

 

2. TROUBLESHOOTING TIPS

• What must you do, if the refrigerator cabinet is not cold enough?

- May be the temperature control is not properly set.

 - The door may be kept open for long periods. Or opened too frequently.

- There are frequent and/or long interruptions in power supply.

• What should we do if there are water droplets under the vegetable tray cover?

- This is normal during humid days and monsoons. This should be wiped dry with a

cloth.

• What would be the cause of foul odour from the refrigerator?

- Check for spoiled food / cleanliness of interiors.

 - Food stored inside is not covered properly. Defrost water evaporation pan / drainage needs cleaning.

• What are the reasons for moisture collection on the inside?

- Too frequent or too long door openings.

- Storage of hot food or under utilization of refrigeration compartment.

- In humid weather, when doors are opened, air carries moisture inside the refrigerator. This moisture condenses on the inside surfaces of the refrigerator.