ABSTRACT
The regenerator is one of three types of heat exchangers that occur in Stirling devices. The various Stirling engine structural conŽgurations of Figure 4.3 (in Chapter 4) include the typical series conŽgurations of a heater or acceptor (H), regenerator (R), and cooler or rejector (C). Regenerators are crucial in achieving good performance. In an engine, the regenerator solid surfaces store heat from the gas as relatively hot gas passes through the regenerator from the hot heater/expansion space to the cold cooler/compression space; the regenerator solid surfaces then restore heat to the gas as relatively cold gas returns from the cold cooler/compression space to the hot heater/expansion space. The amount of heat that the regenerator saves from the gas, and then restores to the gas, during one cycle is typically on the order of four times the amount of heat that enters through the heater/acceptor during one cycle. Thus, if a regenerator were removed from such an engine, the heater/ acceptor would need to absorb Žve times as much heat during a cycle to maintain the same power output as it did with a regenerator; because engine efŽciency is power out divided by heat in, removal of the regenerator with consequent increase of heat into the heater/acceptor by a factor of 5 would result in a Žve times decrease in engine efŽciency. Of course, the original heater could not be expected to achieve such an increase in heat transfer at the same operating conditions, so in a practical engine design-removal of such a regenerator would be very destructive to the performance of an engine-so destructive that it would very likely not operate. The regenerator types discussed in this chapter have been tested, and the data have been modeled via friction-factor and heat-transfer correlations. Correlations for the more conventional random-Žber and wire-screen matrices are given in Chapter 3. Correlations for the new segmented-involute-foil regenerators are given in Chapters 8 and 9.
