In this section of Hometips for home improvement, we will learn about refrigerators and how a refrigerator works.

Refrigerators are a must have kitchen appliance to make your kitchen smart. With advancement of electronics and technology, there has been significant improvement in design, model and features of refrigerators. Today we have all kinds of refrigerators that are safer and convenient.

Today's refrigerators are frost free and offer all kinds of useful features such as - chilled water and ice in the door, adjustable shelves and trays, and cooling zones. Now there are refrigerators that are small sized to huge models with freezer combinations.

Let us now understand the basic principles of a refrigerator and how a refrigerator works.

Refrigerators and other cooling home appliances such as the air conditioner use almost the same basic refrigeration principles (called hermetic system) to extract heat from the air and for cooling.

To remove heat from the air, a compressor, housed in the refrigerator, pushes a refrigerant through copper tubing between two sets of coils called condenser and evaporator.

As the refrigerant moves from condenser to evaporator, it changes from a high-pressure, high-temperature liquid to a low-pressure, low-temperature vapor and liquid. This low pressure cold liquid "boils" in the evaporator coils, absorbing heat from inside the refrigerator and area to be cooled and turns into a cool low-pressure vapor.

This cool vapor is removed from the evaporator by the compressor and is then compressed into a high-temperature, high-pressure vapor and pumped into the condenser. In the condenser, the high-temperature, high-pressure gas gives up its heat as cooling air moves through the condenser coils and then returns to a high-pressure liquid. This cools even more as it moves to the metering device in which it then again becomes a low-pressure, low-temperature gas and liquid to begin the cooling process over again.

We all know that when a liquid boils it absorbs heat. When a vapor cools it releases heat and returns to a liquid state. This physical process is repeated over and over in a refrigerator and keeps it cool.

The basic refrigeration principle of a refrigerator is already discussed above. As explained above, the refrigerant circulates between an evaporator and a condenser in a closed system and maintains the cooling process in a refrigerator.

The refrigerator cabinet or housing is well insulated so that very little heat is absorbed from the outside air and least cold air escapes from inside. Many refrigerators push chilled air into the freezer section from where cold air can passes into the refrigerator. How much air would pass is controlled by a regulator.

Most of the modern refrigerators are frost-free. They have automatic defrosting systems so that you don't have to take everything out of your refrigerator to melt built-up the ice in the freezer. An automatic defrost system includes a timer, a limit switch, and a heater, which melts away all the frost.

• Refrigerator Buying Guide

• Refrigerator Repair and Care (Troubleshooting and fixing problems)