Heat exchange – Radiator core type – Deformed sheet forms passages between side-by-side tube means
Reexamination Certificate
1998-06-17
2001-06-05
Leo, Leonard R. (Department: 3743)
Heat exchange
Radiator core type
Deformed sheet forms passages between side-by-side tube means
C165S176000
Reexamination Certificate
active
06241011
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to layered heat exchangers useful as evaporators for motor vehicle air conditioners.
Already known as such layered beat exchangers are two types; those having headers at one of the upper and lower sides of an assembly of plates in layers, and those having headers at these sides, respectively. Those of the former type have a heat exchange portion which is greater than in the latter type and are therefore expected to exhibit improved performance.
Stated more specifically, layered heat exchangers having the headers at one side comprise pairs of generally rectangular adjacent plates, each of the plates being formed in one side thereof with a U-shaped channel recess and a pair of header recesses continuous respectively with one end and the other end of the channel recess and each having a fluid passing opening, the plates being joined together in layers with the corresponding recesses of the plates in each pair opposed to each other to thereby form juxtaposed flat tubes each having a U-shaped fluid channel, and front and rear headers communicating respectively with opposite ends of each flat tube for causing a fluid to flow through all the flat tubes and the headers.
However, the conventional layered heat exchanger having the headers at one side has the problem that when used as an evaporator for motor vehicle air conditioners, the refrigerant fails to flow smoothly along the turn portion of U-shaped channel recess of each plate and to achieve as high an efficiency as is expected. This is because if the plates are designed, for example, to produce a rectifying effect, the refrigerant flow pressure loss can be diminished, but a reduced heat transfer coefficient and therefore an impaired heat exchange efficiency will result, whereas if the plates are conversely adapted to give a mixing effect chiefly, the refrigerant flow pressure loss increases to an undesirable level despite an improved heat transfer coefficient. The refrigerant is then liable to stagnate or flow unevenly especially in the vicinity of U-shaped turn portion of the refrigerant channel of each flat tube, consequently permitting the evaporator to exhibit impaired performance.
Further with the conventional evaporator, the joint between the plates is made by point contact, which therefore entails the problem that it is difficult to ensure pressure resistant strength.
SUMMARY OF THE INVENTION
The present invention provides a layered heat exchanger which is free of the foregoing problems.
The invention provides a layered heat exchanger wherein the headers are disposed at one side and which is characterized in that the U-shaped recess of each plate has a turn portion provided with a fluid mixing portion having a multiplicity of small projections and a rectifying portion having parallel long projections, the plates in each pair being joined to each other with their recesses opposed to each other to provide a fluid mixing portion and a rectifying portion in a channel turn portion of U-shaped fluid channel of the resulting flat tube.
The turn portion of U-shaped channel forming recess of each plate is provided with a fluid mixing portion at its central part and a rectifying portion at each of front and rear sides of the mixing portion. Alternatively, the rectifying portion is provided at the central part of the turn portion, and the fluid mixing portion at each of front and rear sides of the rectifying portion.
In the former case wherein the rectifying portion is provided at each of front and rear parts of the channel forming recess of the plate, the parallel long projections are, for example, generally L-shaped, have inward horizontal portions and arc larger in size when positioned closer to the outside. Accordingly, the fluid rapidly flows through the turn portion and is thoroughly mixed in the central part where the multiplicity of small projections are formed to provide the mixing portion.
In the latter case wherein the rectifying portion is provided in the central part of the turn portion, the rectifying portion comprises, for example, rearwardly downwardly inclined parallel projections, horizontal parallel projections and forwardly downwardly inclined parallel projections, permitting the fluid to flow from the rear channel portion through the central part of the turn portion and to the front channel portion rapidly. In this case, many small projections are disposed in front of and in the rear of the rectifying portion to provide the fluid mixing portions, where the fluid is, fully mixed.
With the layered heat exchanger thus constructed, the mixing portion and the rectifying portion provided in the turn portion of U-shaped channel of each flat tube rectify the flow of fluid and mix the fluid at the same time, enabling the fluid to flow through the channel turn portion smoothly to achieve an improved heat transfer coefficient. With the U-shaped channel of the conventional flat tube, the flow of fluid stagnates in the return channel portion upon passing through the turn portion, whereas the flat tube of the invention causes no stagnation, enabling the fluid to smoothly flow in the vicinity of channel turn portion of the tube free of stagnation or flow irregularities. The present flat tube is therefore diminished in fluid pressure loss and can be expected to exhibit greatly improved performance.
The small projections for forming the fluid mixing portion and the long projections for constituting the rectifying portion have a height equal to the depth of the recess, or a height which is twice the depth.
In the former case, the opposed small projections of the recess turn portions of the adjacent plates as fitted together with their recesses opposed to each other, as well as the opposed long projections, are joined together end-to-end.
In the latter case, the small projections and long projections in the recess turn portion are joined at their top ends to the bottom wall of turn portion of the plate opposed thereto. This gives an increased joint area and increases the pressure resistant strength of the heat exchanger.
The small projections for the mixing portion in the turn portion of U-shaped fluid channel of each flat tube at the central part thereof, or the long projections for forming the rectifying portion in the central part have a height equal to the depth of the recess. When the adjacent plates are joined to each other, these small or long projections are opposed to each other in corresponding relation, and are joined together end-to-end.
The layered heat exchanger of the invention is further characterized in that the U-shaped channel recess of each plate has front and rear straight channel forming portions provided with vertically elongated rectifying ridges having a height twice the depth of the recess, each pair of adjacent plates as fitted together having the rectifying ridges arranged alternately in different positions, the rectifying ridges each having an end joined to a bottom wall of the straight channel forming portion of the plate opposed thereto.
With this heat exchanger, the elongated rectifying ridges provided on the front and rear channel forming portions of channel recess of each plate permit the fluid to flow straight through the front and rear portions of U-shaped channel of the flat tube, consequently eliminating tale likelihood of the fluid pressure loss increasing.
Further these elongated rectifying ridges have their top ends joined to the bottom wall of straight channel forming portion of the plate opposed thereto. This results in an increased joint area and imparts enhanced pressure resistant strength to the heat exchanger.
The vertically elongated rectifying ridges are arranged alternately in different positions in the assembly of adjacent plates as joined together. The turn portions of the opposed channel recesses have a multiplicity of small projections for forming the fluid mixing portion and long projections four forming the rectifying portion, and these projections are also alternately arranged in different positions in the assembly o
Go Nobuaki
Hanafusa Tatsuya
Nakamura Jumpei
Shibata Hiroki
Yamazaki Keiji
Armstrong, Westerman Hattori, McLeland & Naughton
Leo Leonard R.
Showa Aluminium Corporation
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