How Does A Refrigerator Work
Below is a MRR and PLR article in category Food Beverage -> subcategory Other.
How Does a Refrigerator Work?
Overview
Have you ever felt chilly after getting out of a pool, even when standing in the sun? That's because the water on your skin evaporates, taking away heat. This concept is similar to how refrigerators function, although they use chemicals instead of water.
Basic Principles of Refrigeration
To understand refrigeration, two key principles are essential:
1. Gas Cools on Expansion: When a gas expands, it cools down.
2. Heat Transfer: When two surfaces at different temperatures come into contact, heat flows from the warmer to the cooler surface, according to the Second Law of Thermodynamics.
How Older Refrigerators Work
In older refrigerators, a long, thin tube winds through the back or bottom, connected to a pump powered by an electric motor. This system uses Freon, a type of chlorofluorocarbon (CFC) that starts as a liquid.
Process:
1. The pump circulates CFC through coils in the freezer, where it vaporizes and absorbs heat, chilling the coils and the freezer compartment.
2. Fewer coils in the refrigerator section absorb less heat, maintaining a slightly higher temperature.
3. The pump compresses the CFC vapor into a liquid in thin pipes outside, releasing heat absorbed by the air. This process is why the space behind the refrigerator feels warm.
4. The cycle repeats as the liquid goes back through the system.
Modern Refrigerators
Today’s refrigerators use ammonia gas instead of CFCs, which is more environmentally friendly. Ammonia liquefies at -27°F (-6.5°C).
Process:
1. Compression: The motor and compressor pressurize ammonia gas, heating it up. It then travels through external coils, releasing heat to the room.
2. Expansion: The cooled, compressed ammonia passes through an expansion valve into a low-pressure area, vaporizing again.
3. Cooling: The cold ammonia gas moves through coils in the freezer and refrigerator, absorbing heat and cooling the compartments.
4. Cycle Continuation: The compressor recirculates the ammonia gas, maintaining the cycle.
Temperature Regulation
A thermocouple, acting as a thermometer, monitors the refrigerator's temperature. Once the desired temperature is reached, it cuts power to the compressor. However, minor leaks around doors and pipes can let cold air escape.
When the internal temperature rises, the thermocouple reactivates the compressor to restore cooling. This cycle is why you hear your refrigerator’s compressor turning on and off.
Energy Efficiency
Modern refrigerators are highly energy-efficient, consuming about one-tenth the electricity of models made 20 years ago. Replacing an old refrigerator with a new one can save money and energy over time.
Additional Resources
For further reading, visit:
- [Argonne National Laboratory - Ask A Scientist](http://newton.dep.anl.gov/newton/askasci/1993/eng/ENG30.HTM)
- [Mr. Hand's 8th Grade Science Site](www.mansfieldct.org/schools/mms/staff/hand/heatrefrig.htm)
- [How Stuff Works - Refrigerator](www.howstuffworks.com/refrigerator.htm)
- [Science Treasure Trove - Refrigerator Page](www.education.eth.net/acads/treasure_trove/refrigerator.htm)
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