What is a Refrigeration Cycle?

Ch 4, Lesson F, Page 7 - What is a Refrigeration Cycle?

• A refrigeration cycle uses work to transfer heat from a cold reservoir into a hot reservoir.
• A refrigeration cycle is just like a power cycle except it runs backwards !
• We put work in.  We take heat FROM the cold reservoir and transfer heat TO the hot reservoir !
• All of the energy flows go in the opposite direction relative to a power cycle.
• Now, let’s consider the common household refrigerator that sits in the kitchen.
• A home refrigerator transfers heat from the cold space inside the refrigerator to the high temperature reservoir, which is the warm air in your kitchen.
• Work input is required to accomplish this.
• This should come as no surprise.  Your refrigerator won’t keep your food cold for long unless you plug it in, right ?  When you plug in the refrigerator, you are supplying electrical work to operate its compressor.
• The working fluid in a refrigerator is called a refrigerant.  There are many common refrigerants including ammonia and R-134a.  Thermodynamic data tables for these refrigerants and about 6 others are available from the NIST WebBook.
• Now that we have an understanding of the purpose and function of a refrigerator, let’s apply the 1st Law to our refrigeration cycle and try to develop a way to compare the performance of different refrigerators.