Abstract
We discuss the heat flow and work flow of an orifice pulse-tube refrigerator and a heat-driven thermoacoustic cooler consisting of a single looped tube. It is shown that, while the orifice of the orifice pulse-tube refrigerator is essential for increasing the cooling power, it decreases the efficiency because of the dissipation introduced by itself. It is also shown from the energy flow diagram that dissipation of the work flow inherently occurs in the heat-driven thermoacoustic cooler, resulting in a reduction in efficiency. We present that these unwanted dissipations would be avoided by the addition of a feedback path for the work flow. The modified refrigerator and the cooler would achieve efficiencies much higher than those of the original ones, especially at noncryogenic temperatures.
