Heat exchange – Flow passages for two confined fluids – Interdigitated plural first and plural second fluid passages
Reexamination Certificate
2000-02-08
2001-07-31
Lazarus, Ira S. (Department: 3743)
Heat exchange
Flow passages for two confined fluids
Interdigitated plural first and plural second fluid passages
C165SDIG003
Reexamination Certificate
active
06267175
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to heat exchangers. More specifically, the invention relates to a method of bonding together members of a composite heat exchanger.
An aircraft environmental control system typically includes an air cycle machine and a heat exchanger upstream the air cycle machine. The heat exchanger is used to transfer heat from bleed air to a coolant (e.g., ambient air).
Heat exchangers for aircraft environmental control systems should be lightweight and strong. During operation, the heat exchanger is subjected to large thermal stress and high pressure. The heat exchanger should have sufficient strength to withstand the stress and pressure. Moreover, the walls of the heat exchanger should be made as thin as possible in order to reduce weight. Reducing the weight of the heat exchanger reduces fuel consumption of the aircraft. Reducing fuel consumption, in turn, reduces aircraft operating costs.
The assignee of the present invention has been making aircraft heat exchangers out of carbon/carbon composites. Carbon/carbon composites offer high strength and light weight.
A method of manufacturing a carbon/carbon composite plate-fin heat exchanger core is disclosed in Anderson et al. U.S. Ser. No. 08/601,754 filed Apr. 12, 1996, entitled “CARBON/CARBON HEAT EXCHANGER MANUFACTURING METHOD” and assigned to the assignee of the present invention. A first plurality of woven sheets of low modulus Pitch carbon fibers are impregnated with resin and shaped into fins. A second plurality of sheets of carbon fibers are impregnated with resin and shaped into plates. The resin-impregnated fins are stacked between the resin-impregnated plates to form a stacked assembly, the stacked assembly is then cured, pyrolized, densified and annealed to form a fully graphitized plate-fin heat exchanger core.
Joints between plate and fin tends to be the weakest part of the composite heat exchanger core. It is most likely to separate, especially if subjected to large thermal stress and high pressure. The plate-fin joints also tend to have the lowest thermal conductivity and, therefore, do not maximize the transfer of heat from the bleed air to the coolant.
It would be desirable to increase joint strength. It would also be desirable to increase joint thermal conductivity.
SUMMARY OF THE INVENTION
According to one aspect of the present invention, a heat exchanger comprises a first composite member having a first contacting surface; and a second composite member having a second contacting surface. The second contacting surface is in contact with the first contacting surface. The heat exchanger further comprises a plurality of stiff fibers extending into both contacting surfaces and being embedded in both members.
The fibers can strengthen joints between plates and extended heat transfer surfaces, closure bars and plates, and manifolds and closure bars. The fibers can also increase thermal conductivity in their direction of orientation.
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Honeywell International , Inc.
Lazarus Ira S.
McKinnon Terrell
Zak, Jr. Esq. William J.
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