WE CLAIM:
1) A pair of heat exchanger plates comprising a first (A) and a second heat exchanger plate (B), arranged face to face and spaced apart so as to define an inner volume (V) capable of forming a channel for flow of a first fluid (F), each plate (A, B)

5 comprising a central panel, said central panels of said first and second plates being preferably substantially quadrilateral, optionally with truncated, cut or rounded edges, and said central panels of said first and second plates (A, B) being plane and parallel to one another, characterized in that said central panel of each plate (A, B) comprises at least one groove (101, 102), preferably a substantially rectilinear groove, protruding into 10 said inner volume (V), and each groove (101) of said first plate (A) is parallel to each groove (102) of said second plate (B).

2) A pair of plates as claimed in claim 1, wherein each groove (101, 102) is inclined at a non-zero and non-right angle a to one side of said central panel, angle a being greater than or equal to 10°, preferably ranging between 10° and 80°, inclusive, more

15 preferably ranging between 30° and 70°, inclusive, and most preferably ranging between 40° and 50°, inclusive.

3) A pair of plates as claimed in any one of the previous claims, wherein each groove (102) of said second plate (B) is offset with respect to each groove (101) of said first plate (A) in a direction (DD) perpendicular to said grooves (101, 102) of said first and second

20 plates (A, B).

4) A pair of plates as claimed in any one of the previous claims, wherein each central panel of each plate (A, B) comprises a plurality of grooves (101, 102) parallel to one another, and preferably evenly spaced apart.

5) A pair of plates as claimed in claim 4, wherein the pitch (p) between said grooves

25 (101) of said first plate (A) is identical to pitch (p) between said grooves (102) of said

second plate (B).
6) A pair of plates as claimed in claims 3 and 5, wherein the offset (s) in direction (DD) perpendicular to said grooves (101,102) has a distance between one third and two thirds of said pitch (p), and it is preferably half of said pitch (p).

7) A pair of plates as claimed in any one of claims 4 to 6, wherein pitch (p) between 5 two successive grooves ranges between 10 mm and 80 mm, inclusive, preferably

between 20 mm and 60 mm, inclusive.

8) A pair of plates as claimed in any one of the previous claims, wherein each groove (101, 102) has a cross section whose shape is selected from among an arc of a circle, a semicircle, a U, a V, an ellipse, an airplane wing, a spearhead, and the shape is

10 preferably selected from among an arc of a circle and an airplane wing.

9) A pair of plates as claimed in any one of the previous claims, wherein the width (w) of each groove (101, 102) ranges between 4 mm and 30 mm, inclusive, preferably between 6 mm and 25 mm, inclusive.

10) A pair of plates as claimed in any one of the previous claims, wherein the 15 protrusion height (e) of each groove ranges between 1.5 mm and 6 mm, inclusive,

preferably between 2 mm and 5 mm, inclusive.