Circulating heat exchangers for oscillating wave engines and refrigerators

In an oscillating-wave engine or refrigerator having a regenerator or a stack in which oscillating flow of a working gas occurs in a direction defined by an axis of a trunk of the engine or refrigerator, an improved heat exchanger comprising:

• first and second connections branching from the trunk at locations along the axis in selected proximity to one end of the regenerator or stack, where the trunk extends in two directions from the locations of the connections;
• a circulating heat exchanger loop connected to the first and second connections, wherein the length of the circulating heat exchanger loop is an integral number of wavelengths of the working gas at a temperature of the circulating heat exchanger loop;
• and
• at least one fluidic diode within the circulating heat exchanger loop to produce a superimposed steady flow component and oscillating flow component of the working gas in the circulating heat exchanger loop;
• wherein a local process fluid is in thermal contact with an outside portion of the circulating heat exchanger loop.