System for evaluating at least one operating condition of a heat exchanger comprising: - at least one temperature first double sensor comprising a stack of two temperature single probes (11, 12), thermally and electrically isolated from one another, and - a thermal exchanger wall through which a thermal transfer is intended to be performed between two fluids f and f' circulating on either side of the wall, and on which a clogging (50, 50') is likely to be deposited, each single probe (11, 12) of the first double probe being intended to be operationally connected to: - an electrical supply device of each single probe (11, 12), - an electrical current measuring device in each single probe (11, 12), and - a supervision device of the supply device and the measuring device, the first double probe being disposed on one from among a first side and a second side of the wall of the heat exchanger and having a known thermal resistance Rs 1, the first double probe being disposed at a first circulation height h 1 of the fluids f and f', the wall having a known thermal resistance Rp, and the measuring device being able to measuring the development of the electrical current in at least one of the single probes (11, 12) of the first double probe, the evaluation system being characterised in that it further comprises a temperature second double probe comprising a stack of two temperature single probes (21, 22), thermally and electrically isolated from one another, each single probe (21, 22) of the second double probe being intended to be operationally connected to the supply device, to the measuring device and to the supervision device, the second double probe being disposed on one from among a first side and a second side of the wall of the heat exchanger and having a known thermal resistance Rs 2, the second double probe being located at a second circulation height h 2 of the fluids f and f', the first height h 1 being different from the second height h 2, and the thermal exchanger having known geometric parameters. - at least one temperature first double sensor comprising a stack of two temperature single probes (11, 12), thermally and electrically isolated from one another, and - a thermal exchanger wall through which a thermal transfer is intended to be performed between two fluids f and f' circulating on either side of the wall, and on which a clogging (50, 50') is likely to be deposited, - an electrical supply device of each single probe (11, 12), - an electrical current measuring device in each single probe (11, 12), and - a supervision device of the supply device and the measuring device, the first double probe being disposed on one from among a first side and a second side of the wall of the heat exchanger and having a known thermal resistance Rs 1, the first double probe being disposed at a first circulation height h 1 of the fluids f and f', the wall having a known thermal resistance Rp, and the measuring device being able to measuring the development of the electrical current in at least one of the single probes (11, 12) of the first double probe, the evaluation system being characterised in that it further comprises a temperature second double probe comprising a stack of two temperature single probes (21, 22), thermally and electrically isolated from one another, each single probe (21, 22) of the second double probe being intended to be operationally connected to the supply device, to the measuring device and to the supervision device, the second double probe being disposed on one from among a first side and a second side of the wall of the heat exchanger and having a known thermal resistance Rs 2, the second double probe being located at a second circulation height h 2 of the fluids f and f', the first height h 1 being different from the second height h 2, and the thermal exchanger having known geometric parameters. the first double probe being disposed on one from among a first side and a second side of the wall of the heat exchanger and having a known thermal resistance Rs 1, the first double probe being disposed at a first circulation height h 1 of the fluids f and f', the wall having a known thermal resistance Rp, and the measuring device being able to measuring the development of the electrical current in at least one of the single probes (11, 12) of the first double probe, the evaluation system being characterised in that it further comprises a temperature second double probe comprising a stack of two temperature single probes (21, 22), thermally and electrically isolated from one another, each single probe (21, 22) of the second double probe being intended to be operationally connected to the supply device, to the measuring device and to the supervision device, the second double probe being disposed on one from among a first side and a second side of the wall of the heat exchanger and having a known thermal resistance Rs 2, the second double probe being located at a second circulation height h 2 of the fluids f and f', the first height h 1 being different from the second height h 2, and the thermal exchanger having known geometric parameters.