Regrigeration is the human-aided cooling of food and other objects to a lower temperature than ambient. It is a common practice in industrialized nations and affluent areas of the developing world to preserve food and other products at low temperatures, inhibiting the growth of bacteria, yeasts and molds that would spoil them and degrade their organoleptic properties. Refrigeration also allows perishable foods to be stored for months or even years, allowing people to have access to fresh and delicious food when they need it. It is an important component of modern life and is a crucial technology for the food industry.
Foods that are typically preserved at colder temperatures include mature cheeses, drinks (beer, wine and fruit juice), ice cream, fresh meat and fish and delicatessen items in general. The refrigeration process slows the growth of bacteria in these products, helps to preserve their organoleptic properties and extends their shelf life, making them suitable for longer storage.
The principle behind most refrigeration Adams Regrigeration systems is quite simple. It relies on the fact that a liquid in its saturated, or condensed, state has a lower enthalpy of vaporization than its gaseous state. If the liquid can be coaxed to evaporate into its gaseous state, the latent heat of vaporization that it releases will cool the surrounding region. This is why we use chemicals known as refrigerants, such as methyl chloride (CH3Cl), ammonia and sulfur dioxide, to cool our refrigerators.
When a refrigerator is operating, the refrigerant flows through the compressor, which compresses it and raises its pressure. As it does so, the refrigerant releases its latent heat of vaporization into the evaporator, which in turn cools the food or other product. When the evaporator is cool enough, it releases its heat into the environment via conduction and convection. The expansion valve is the next stage in the refrigeration cycle. It reduces the pressure on the liquid refrigerant by opening and closing in response to a signal from a thermostat, or through a mechanical device such as a float switch.
The refrigerant then leaves the evaporator and enters the compressor again, where it is compressed to a higher pressure and released its latent heat of vaporization again. The process repeats itself until the refrigerator reaches the desired temperature. Refrigeration is one of the most important advancements in modern human society, changing our lifestyles, our economies and our settlement patterns. From ice harvesting and the ice trade to refrigerated rail cars and refrigerated trucks, to the ubiquitous refrigerators and freezers in our homes and offices, refrigeration has transformed how we live, work, eat and travel around the world. The principles of refrigeration are at the heart of our modern air-conditioning systems as well, reducing our energy consumption in our pursuit of comfort. A basic understanding of how refrigeration works can help to reduce our ecological footprints. This article is a part of our “How it Works” series on science and technology. Read the other articles in the series here: