Refrigeration is the process in which heat of a certain product is being removed or transfer from one location to another. It also includes the process of reducing and maintaining the temperature of a body below the general temperature of its surrounding. This is done, traditionally, by a mechanical system. But nowadays, it can be driven out by heat, magnetism, electricity laser or by other means.
There are many methods of refrigeration that can be classified, namely: non-cyclic, cyclic, thermoelectric and magnetic.
In this method, the cooling is accomplished by melting the ice or subliming the dry ice. This method is commonly used for small-scale refrigeration such as in laboratories, workshops and portable coolers.
This method removes the heat from a low-temperature space or source and rejected to a high-temperature sink with the help of external work, and its inverse, the thermodynamic power cycle.
Thermoelectric cooling uses the Peltier effect to create a heat flux between the junctions of two different types of materials. This effect is commonly used in camping and portable coolers and for cooling electronic components and small instruments.
This cooling method is based on the magneto caloric effect, an intrinsic property of magnetic solids. The refrigerant is often a paramagnetic salt, such as cerium magnesium dipoles in this case are those of the electron shells of the paramagnetic atoms.
Most of us are mistakenly thinks that refrigeration stops the spoilage of a goods or products. But the truth is that refrigeration does not stop the food spoilage, it just delays it. Most spoilage microorganisms are not active when it is cold, so spoilage takes longer. Some spoilage like in over ripe fruits, may be caused by enzymes and enzymatic activity is also reduced be the colder temperature.
The Main Purpose of Refrigeration
The fundamental reason for having a refrigerator is to keep food cold. Cold temperatures help food stay fresh longer. The basic idea behind refrigeration is to slow down the activity of bacteria (which all food contains) so that it takes longer for the bacteria to spoil the food.
For example, bacteria will spoil milk in two or three hours if the milk is left out on the kitchen counter at room temperature. However, by reducing the temperature of the milk, it will stay fresh for a week or two -- the cold temperature inside the refrigerator decreases the activity of the bacteria that much. By freezing the milk you can stop the bacteria altogether and the milk can last for months (until effects like freezer burn begin to spoil the milk in non-bacterial ways).
Refrigeration is main reason why we can preserve and extend the shelf life of perishable goods. It is the reason why we can taste and experience a food as fresh as it was just harvested.