TS Diagram for the Regenerative Cycle

Ch 10, Lesson E, Page 5 - TS Diagram for the Regenerative Cycle

• In the ideal, regenerative gas refrigeration cycle, the compressor takes in stream 1 and raises its pressure isentropically.
• Stream 2 then rejects heat to the hot reservoir isobarically.
• Stream 3 is still fairly warm when it enters the regenerator.
• In the regenerator, stream 3 rejects heat into stream 6.
• In an ideal regenerator, stream 4 would leave the regenerator at the same temperature that stream 6 enters.
• That would require an infinitely large HEX though.
• In a real regenerator, stream 4 must leave slightly hotter than stream 6, as shown in the TS Diagram.
• In either case, the nice cold air in stream 4 then enters the turbine, where it expands isentropically.
• Its temperature drops sharply and stream 5 is the coldest stream in the cycle.
• Stream 5 absorbs heat from the refrigerated space in HEX #1.  This is an isobaric process in the ideal cycle.
• Stream 6 is still quite cold.  In order to make the best use of this low temperature stream, it is fed into the regenerator to cool the turbine feed.
• Notice the large temperature difference between the two streams that enter the regenerator.
• This drives a great deal of heat transfer in the regenerator from streams 3 & 4 to streams 6 and 1.
• In fact, in the cycle shown here, most of the change in temperature from the maximum to the minimum temperature in the cycle is attributed to the regenerator and NOT to heat exchange with the thermal reservoirs ! 
• That concludes this lesson on gas refrigeration as well as the chapter on refrigeration cycles.
• We have a good example problem for you to look over next.
• Then, review the lesson summary and try the quiz !