Without refrigeration, the modern world wouldn’t be able to keep food cold. Refrigerated trucks would not be able to deliver perishable food items to neighborhood grocery stores. There would be no refrigerated shipping containers to deliver fruits, vegetables and meat from one country to another. There would be no refrigerators or freezers at home to keep food from spoiling and no HVAC. So, how does refrigeration technology work?
The Second Law of Thermodynamics
The Second Law of Thermodynamics holds that heat naturally moves from a high temperature area (hot or warm area) to a low temperature (cold) area. In order for heat to move from a cold to a hot area, external force must be applied. Refrigerators and air conditioning units use a condenser to force heat to move from a cold area to a hot one. The condenser is the external force that causes heat to move contrary to its natural cycle.
From Liquid to Gas and Vice Versa
Refrigerators and air conditioning units use refrigerant that can be repeatedly pumped through the unit. Refrigerant leaves the compressor as a hot gas, turns into liquid and is then converted into a cool gas. The cool gas is sent back to the compressor and the cycle starts all over again. 1
Refrigerators and air conditioners have pipes that are partly inside the unit and partly outside the unit. Inside the unit, the pipe is wide, allowing pent-up gas to move with ease. As the gas expands, it cools down and absorbs heat from the unit. The liquid refrigerant then moves to the part of the pipe on the unit’s exterior. At this point, the pipe narrows, compressing the refrigerant into a small space. As the liquid refrigerant is compressed, it heats up and turns back into a gas. The heat from the gas is at this point transferred to the outside of the unit, which is why the back and sides of a refrigerator feel warm to the touch. 2
Conservation of Energy
Another scientific law that applies to refrigeration is Conservation of Energy 3. The law states if energy were put in a “box” energy cannot be created or destroyed but can transfer (i.e. from a liquid to a gas and then back to a liquid).
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While not all of them can be discussed, a number of scientific principles and rules govern the proper function of refrigerants. As long as these rules apply, heat can be moved from a cold area to a hot one in order to help a particular area remain cool for as long as necessary. If you’d like to learn more about refrigeration technologies, consider taking some courses at HVAC and refrigeration school, where you can begin to make a career out of these principles.
1 – http://www.wisdompage.com/SEUhtmDOCS/3SE5.htm
2 – http://www.explainthatstuff.com/refrigerator.html
3 – http://www.explainthatstuff.com/refrigerator.html