Heat exchange – Tubular structure
Reexamination Certificate
1999-12-29
2001-09-18
Leo, Leonard (Department: 3743)
Heat exchange
Tubular structure
C165S153000, C165S179000
Reexamination Certificate
active
06289982
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a heat exchanger, and more particularly to an evaporator for a heating and/or air conditioning apparatus, suitable for motor vehicles, to a heating and/or air conditioning apparatus including such an evaporator and to a motor vehicle including such an apparatus.
BACKGROUND OF THE INVENTION
It is usual to produce evaporators or heat exchangers, exchanging heat between a cooling fluid and air, as a stack of plates, virtually identical for preference, positioned symmetrically in pairs. A pair of plates arranged opposite each other forms a substantially U-shaped duct whose inlet is connected to the outlet of the U-shaped duct of the preceding pair of plates (if there are any, that is to say if it is not the first pair of plates), and whose outlet is connected to the inlet of the U-shaped duct formed by the next pair of plates (if there are any, that is if it is not the last pair of plates). Cooling air flows between the consecutive pairs of plates. It is known for stamped dimples to be formed on at least one of the pairs of plates forming a duct. These dimples are identical in shape, position and orientation. They project into the interior of the duct formed by the pairs of plates and thus allow better heat exchange by agitating the cooling fluid flow, and especially by promoting its movement in a turbulent flow. These dimples can be formed by an assembly method, particularly by brazing two bosses opposite each other. In this case, the plates forming a pair of plates are the same as one another, and each boss has an equivalent height of half the depth of the U-shaped duct, that is to say of the distance from the opposing plates.
Moreover, the dimples can be formed by brazing the bosses of a first plate against the flat surface of a second plate. In this case, the two plates of a pair of plates can be identical and each dimple has a height equal to the depth of the U-shaped ducts.
Unfortunately the flow of cooling fluid in this known type of evaporator produces a noise, particularly a whistling, which is extremely unpleasant for the vehicle occupants, and vibrations detrimental to the longevity of the evaporator. The amplitude of the radiated noise is accentuated by the geometry of the evaporator including an overlaying of the sets of plates.
OBJECTS OF THE INVENTION
As a consequence it is one aim of the invention to provide a heat exchanger particularly for a heating and/or air conditioning device for motor vehicles which allows a flow of cooling fluid minimizing the generation of the noise and/or vibration liable to annoy the occupants of a motor vehicle.
It is equally an aim of the invention to offer a heat exchanger of great solidity, and especially with a very good resistance to the internal pressure of the cooling fluid.
It is also an aim of the present invention to offer such a heat exchanger giving excellent thermodynamic effectiveness.
It is equally an aim of the invention to offer a heat exchanger with a long life.
The applicant has noted that the whistling caused by the known type of evaporator originates from the regular distribution of the dimples. A gas passing at a given speed through an aperture of specific cross-section emits a very shrill noise around a particular frequency (Strouhal effect). Thus, the fact that the dimples are of identical shape and orientation, and are equidistant, creates an overlay of sound of the same frequency, hence an acoustic discomfort. An effect of the present invention is to diversify the frequencies emitted while the fluid is flowing, so that the noise emitted (overlay of sounds at different frequencies) may be more neutral.
SUMMARY OF THE INVENTION
According to the a first aspect of the present invention there is provided a heat exchanger including a number of ducts for the flow of a cooling fluid, which are connected in series, each duct being produced as a pair of plates comprising a concave region delimited by an edge and provided with a number of bosses forming dimples wherein a random distribution of the dimples is used.
An embodiment of the present invention relates to a plate evaporator including dimples distributed randomly, that is to say dimples distributed in a random way over the surface of the duct formed between two consecutive plates of one pair of plates and/or by the shape of the dimples.
Advantageously, these obstacles are arranged symmetrically in relation to an axis passing halfway between the two branches of the U. Thus, a U-shaped duct can be formed by assembling two identical plates, turned over in relationship to each other, with their concave faces placed facing each other.
The invention relates to a heat exchanger including a number of ducts for the flow of a cooling fluid which are connected in series, each duct being produced as a pair of plates including a concave region delimited by one edge and provided with a number of bosses forming dimples, characterized by the use of a random distribution of the dimples.
The dimples can have a cylindrical or substantially cylindrical shape. Each dimple can have a shape chosen at random from a set of different shapes of dimple.
REFERENCES:
patent: 4330036 (1982-05-01), Satoh et al.
patent: 4470452 (1984-09-01), Rhodes
patent: 5111878 (1992-05-01), Kadle
patent: 5538077 (1996-07-01), So et al.
patent: 5918664 (1999-07-01), Torigoe
patent: 3313422 (1984-10-01), None
patent: 0 206 836 (1986-12-01), None
patent: 2 276 937 (1994-10-01), None
patent: 58 140597 (1983-08-01), None
patent: 6-221789 (1994-08-01), None
Leo Leonard
Morgan & Finnegan , LLP
Valeo Climatisation
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