Freezer

Freezers can range from very basic, bare bones versions to very expensive luxury items that may increase the value of your home. This site will explain how freezers work, explain the differences in the various models and styles and show you where to purchase.

Freezer - Basics
A freezer is generally used to describe an appliance that keeps foods frozen. Freezers are common as household units for storing food but are also used in commercial settings. Most Freezers operate around -18°C (0°F).

Domestic freezers can be included with a refrigerator or can be stand alone units. Domestic freezers are generally upright units, resembling a refrigerator, or a chest, which resemble an upright unit laid on its back.

Window to the Past
Early refrigerator models (1916 and on) featured a cold compartment for ice cube trays. Successful processing of fresh vegetables through freezing began in the late 1920s by the Postum Company (the forerunner of General Foods) which had acquired the technology when it bought the rights to Clarence Birdseye’s successful fresh freezing methods.

The first successful example of the benefits of frozen foods occurred when General Foods heiress Marjorie Merriweather Post (then wife of Joseph E. Davies, United States Ambassador to the Soviet Union ) deployed commercial grade freezers to Spasso House (US Embassy) in Moscow in advance of the Davies’ arrival. Post, fearful of the food processing safety observed in the USSR, then fully stocked the freezers with product processed from General Foods Birdseye unit. The frozen food stores allowed the Davies’ to lavishly entertain and serve fresh frozen foods that would otherwise be out of season. Upon returning from Moscow, Post (who resumed her maiden name after divorcing Davies) directed General Foods to market frozen product to upscale restaurants.

Introduction of home freezer units occurred in the United States in 1940, and frozen foods began to make the transition from luxury to necessity.

Evolution
Early freezer units accumulated ice crystals around the freezing units. This was a result of humidity introduced into the units when the doors to the freezer was opened. This build up of frost required the periodic thawing of the units, to maintain their efficiency. Advances in frost-free refrigeration eliminated the thawing task were introduced in the 1950s.

Later advances included automatic ice units and self compartmentalized freezing units.

Electric Coolers
You may have seen the new coolers that don't use ice, plugging into your car's cigarette lighter instead. These coolers rely on a process known as the Peltier effect, or thermoelectric effect, to produce cold temperatures electronically.

You can create the Peltier effect with a battery, two pieces of copper wire and a piece of bismuth or iron wire. Just connect the copper wires to the two poles of the battery, and then connect the bismuth or iron wire between the two pieces of copper wire. The bismuth/iron and copper must touch -- it is this junction that causes the Peltier effect.

The junction where current flows from copper to bismuth will get hot, and the junction where current flows from bismuth to copper the junction will get cold. The maximum temperature drop is about 40 F from the ambient temperature where the hot junction is located.

To create a Peltier cooler, the hot junction is placed outside the refrigerator, and the cold junction is placed inside. Normally, you create a module containing many junctions to amplify the effect. See the links at the end of this article for details on the Peltier effect.

Parts of a Refrigeration System
The basic idea behind a freezer is very simple: It uses the evaporation of a liquid to absorb heat. You probably know that when you put water on your skin it makes you feel cool. As the water evaporates, it absorbs heat, creating that cool feeling. Rubbing alcohol feels even cooler because it evaporates at a lower temperature. The liquid, or refrigerant, used in a freezer evaporates at an extremely low temperature, so it can create freezing temperatures inside the freezer. If you place your freezer's refrigerant on your skin (definitely NOT a good idea), it will freeze your skin as it evaporates.

There are five basic parts to any freezer (or air-conditioning system):

Compressor

Heat-exchanging pipes - serpentine or coiled set of pipes outside the unit

Expansion valve

Heat-exchanging pipes - serpentine or coiled set of pipes inside the unit

Refrigerant - liquid that evaporates inside the freezer to create the cold temperatures

Many industrial installations use pure ammonia as the refrigerant. Pure ammonia evaporates at -27 degrees Fahrenheit (-32 degrees Celsius).

Cycles of Refrigeration
The freezer in your kitchen uses a cycle that is similar to the one described in the previous section. But in your freezer, the cycle is continuous. In the following example, we will assume that the refrigerant being used is pure ammonia, which boils at -27 degrees F. This is what happens to keep the freezer cool:

The compressor compresses the ammonia gas. The compressed gas heats up as it is pressurized (orange).

The coils on the back of the freezer let the hot ammonia gas dissipate its heat. The ammonia gas condenses into ammonia liquid (dark blue) at high pressure.

The high-pressure ammonia liquid flows through the expansion valve.

You can think of the expansion valve as a small hole. On one side of the hole is high-pressure ammonia liquid. On the other side of the hole is a low-pressure area (because the compressor is sucking gas out of that side).

The liquid ammonia immediately boils and vaporizes (light blue), its temperature dropping to -27 F. This makes the inside of the freezer cold.

The cold ammonia gas is sucked up by the compressor, and the cycle repeats.

By the way, if you have ever turned your car off on a hot summer day when you have had the air conditioner running, you may have heard a hissing noise under the hood. That noise is the sound of high-pressure liquid refrigerant flowing through the expansion valve.

Pure ammonia gas is highly toxic to people and would pose a threat if the freezer were to leak, so all home freezers don't use pure ammonia. You may have heard of refrigerants know as CFCs (chlorofluorocarbons), originally developed by Du Pont in the 1930s as a non-toxic replacement for ammonia. CFC-12 (dichlorodifluoromethane) has about the same boiling point as ammonia. However, CFC-12 is not toxic to humans, so it is safe to use in your kitchen. Many large industrial freezers still use ammonia.

In the 1970s, it was discovered that the CFCs then in use are harmful to the ozone layer, so as of the 1990s, all new freezers and air conditioners use refrigerants that are less harmful to the ozone layer.

Sub-Zero Technology
Sub-Zero Refrigerator is a brand of luxury domestic refrigerator in the USA.

The company was founded in 1945, by Wesyte F. Bakke in Madison, Wisconsin. In the 1990's, the company acquired Wolf Appliance, a luxury cooking appliance manufacturer of ranges, cook tops and grills.

Sub-Zero claims to have invented the concept of dual refrigeration which is said to provide clean air flow, and to result in fresher and longer lasting food. Its refrigerators are designed with a 24" depth and can be installed flush with kitchen cabinets of the same standard depth to provide an integrated look. This kind of built-in refrigerator is usually wider than normal to compensate for the shallower depth in order to maintain acceptable storage volume. It is claimed that Sub-Zero was first in the built-in refrigerator market, and that consequently people still associate the look with Sub-Zero. Some people feel these appliances increase the value of their homes.

Before you Buy
Here are some things to consider before you buy:

Buy for adequate capacity

EnergyStar® rated will provide the best energy savings, and energy ratings vary per models.

Ice maker feature

An exterior that is textured is easier to maintain

A seamless interior is easier to clean

Fast freeze section or other freezing features

Defrost drain or hose

Check that hinges are heavy duty

Freezer coils that extend to all side walls, will help to keep the temperature constant

Tradeshow Information
Osborne/Jenks Productions, Inc. is proud to produce the largest and most popular consumer home shows on the East Coast. This home show series is a dynamic showcase of home products and home services that will help you with all your home building, design and improvement needs.

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