Abstract: A thermal apparatus (1) which comprises at least one primary circuit (P1) in which a heat transfer primary fluid is moved, in a reciprocating movement, by a displacement device, and at least one heat exchange interface (I1,1, I1,2), of the primary fluid, in which a secondary fluid that unidirectionally in a secondary circuit (S1,1, S1,2). The apparatus is characterized in that the exchange interface (I1,1, I1,2) comprises at least one heat exchange zone (ZN, NN+1, Z?N, Z?N+1) in which the primary fluid and the secondary fluid flow unidirectionally and countercurrent with respect to one another.