The Refrigerated Storage

Most people assume that a refrigerator or freezer is designed to make food cold and keep it cold. However, this is a common misconception. In fact, the basic principle of refrigeration is the transfer of heat out of an enclosed space. Therefore, cold is the absence of heat. The goal of any refrigerator is to remove heat. Removing heat extends the useful life of the refrigerated food, by protecting it against decay and deterioration.

Now, let's take it one more step. Heat and heat energy are part of any food product, whether it is raw or cooked. Heat enters the refrigerator in three simple ways:
1. Through opening the refrigerator door (This is the major cause of heat transfer.)
2. Through products stored inside the refrigerator
3. Through the door edges and rubber grommets (tiny leaks, indeed, but significant because they are continuous).

The more heat that can be removed from a product (without the side effects that can be caused by too much cold), the longer the product can be held in usable condition.

To achieve this ideal, three things are going on simultaneously in the enclosed, conditioned environment you probably thought, until now, was "just a fridge": 1. Temperature reduction 2. Air circulation 3. Humidity Wide fluctuations in any of these conditions cause faster deterioration of the stored food; once deterioration begins, the process cannot be reversed. Cold can inhibit, but not completely prevent, the growth of most microorganisms associated with food poisoning. The temperature needed to accomplish this varies with the type of food: they require refrigeration temperatures of at least 40 degrees Fahrenheit (or for the food itself to have an "internal temperature" of 41 degrees Fahrenheit).

Overall, the best refrigerator is one that has the ability to hold constant temperature and humidity levels and to circulate air at a steady rate. The other thing to note is that no "conditioned" environment will be absolutely perfect. No matter what it's made of or how well it works, no freezer or refrigerator can fully halt deterioration, and it certainly can't improve the quality of the food over time. There are two terms you'll hear a lot in refrigeration: the refrigeration cycle and the refrigeration circuit. The cycle is the process of removing heat from the refrigerated space. The circuit is the physical machinery that makes the cycle possible.

It's important to keep them straight as we delve into the inner workings of your refrigerator. Heat transfer, from inside the refrigerator to the outside environment, cannot take place without a temperature difference between the two. Different materials transfer heat at different rates, which also has an impact. There are four basic components of a refrigeration system. Their names and functions are: Evaporator, Refrigerant, Compressor, Condenser. These make up the major physical parts of the refrigeration circuit. The circuit is a closed system. space. The warm air rises and is drawn into an evaporator, a series of copper coils surrounded by metal plates called fins.

The fins conduct heat to and from the coils. The evaporator coils hold liquid refrigerant, which becomes vapor (gas) as it winds through them. The vaporized gas is pumped by the compressor into the condenser (another series of coils surrounded by fins), where it turns back into liquid. As the gas is compressed, its temperature and pressure increase. The expansion valve is the small opening between the "low-pressure" (evaporator) side and the "high-pressure" (condenser) side of the system. This valve allows a little refrigerant or a lot to flow, depending on how much cooling is needed.

An alternative to the expansion valve is the capillary tube, or "cap tube" for short. Here's the difference: Expansion valves respond more quickly to temperature changes, and are best suited to environments where doors are constantly being opened and closed. They are more expensive than cap-tube systems. The capillary tubes work well for storage-type refrigeration, when doors are not opened often.

In either system, the last step is the job of the refrigerator's thermostat. When it indicates colder air is needed, the compressor turns on. Air circulates past the two sets of fins, removing heat from the circuit as the refrigerant flows. There are top-mounted and bottom-mounted refrigeration systems-that is, the condenser coils can be located near the floor or at the top of the cabinet, above where the food is stored. In food service, top-mounted units are worth considering, because the coils don't accumulate grease and dust as quickly as they do closer to the floor.

The goal in refrigeration, as with HVAC units, is a balanced system. The compressor, evaporator and condenser functions must be sized to work well together.

Franco Zinzi has been involved with online marketing for nearly 3 years and likes to write on various subjects. Come visit his latest website which discusses of restaurant fridges and refrigerators supplies for the owner of his own business.