A heat exchanger of the finned tube (34) type in which the tubing (34) is formed in a single, continuous length which is bent into a zigzagged or serpentine shape (22) and then inserted through elongated slots (16) formed in a series of fin plates (15)

Finned tube heat exchanger and method of manufacture

A flux for brazing is prepared from 31.5% to 56.2% of KF and 68.5% to 43.8% of at least one of γ-AlF₃ and finely divided β-AlF₃. The KF is dissolved in water, and the AlF₃ is then placed into the resulting KF aqueous solution to react the KF with the AlF3. The reaction product is dried.

Process for producing flux for brazing

PROBLEM TO BE SOLVED: To improve internal pressure breaking performance of a snap tap with a resin saddle. SOLUTION: A groove 121 is arranged over the whole periphery on the reverse of a metallic adapter 12 threadedly joined with a metallic snap tap body 11, and the resin saddle 2 is molded by embedding the metallic adapter 12.

Snap tap with resin saddle

The heat exchanger tube set is designed particularly for the fuel heat exchanger. The set comprises two heat exchange zones positioned one after another with respect to the combustion chamber (8), where zone one (1) is formed exclusively of tubes (3), and zone two (2) is composed of tubes (4) and finned elements (5) positioned in between the tubes (4). Preferably, the tubes (3) of zone one (1) are smooth, of any shape in cross-section, and the tubes (4) of zone two (2) are either flat or oval. Preferably, the finned element (5) consists of a band with profiled plates (6).

Heat exchanger tube set

The invention relates to a manufacturing process of a U-shaped bent pipe of a copper pipe heat exchanger. The manufacturing process is characterized in that under the condition of no change of the external diameter of an original copper pipe, the thickness of the pipe wall is reduced, and the upsetting process is additionally performed. The manufacturing process of the U-shaped bent pipe comprises the following steps of preparing a pipe material; before forming, determining the upsetting position and upsetting length; before pipe bending, upsetting; during pipe bending, bending the thickened and upset copper pipe on a common pipe bending machine, wherein the thickness of the thinnest part of the outer half part of the bent pipe is equal to or greater than the thickness of the copper pipe after the U-shaped bent pipe is formed. The manufacturing process has the advantage that under the condition of guaranteeing no change of the internal diameter of the copper pipe, the thinner copper pipe is selected, so the thickness of the thinnest part of the outer half part of the bent pipe is equal to or greater than the thickness of a base pipe, the heat exchange area is the same, the strength equal to the strength of the thicker copper pipe is realized, and the material cost is greatly reduced.

Manufacturing process of U-shaped bent pipe of copper pipe heat exchanger

PURPOSE:To suppress the local reduction of outer wall thickness at a bent part and consequently uniformize the thickness by a structure wherein the bent part of the heat exchange pipe in zigzag is bent by connecting curves, which have at least two kinds of radii of curvature or variable curvatures. CONSTITUTION:The thickness reduction value epsilono of the outer wall to the locus of the center of the tube bent with a single bending radius of curvature r0 of a half of the pitch P between straight tube parts lS adjoining to each other becomes maximum near the middle of the bent part. On the other hand, the thickness reduction value epsilonn, which does not exceed the maximum value of the thickness reduction value epsilono produced in case of the bending with said single bending radius of curvature r0, can be obtained by bending the bending range in such a way that firstly said range is divided into five parts and the divided five parts are smoothly connected by curves with a radius of curvature r1, which is same as the single bending radius of curvature r0 with a radius of curvature r2, which is 0.8 times the single bending radius of curvature r0, and with a radius of curvature r3, which is twice the single bending radius of curvature r0. In such a way as mentioned above, the local thinning is prevented and consequently the pressure and erosion resistance are improved and furthermore spring-back force is suppressed due to the thinner parts epsilonp being separated into two positions and consequently the proper gaps requested for mounting fins are easily obtained and, in addition, because the height of the arcuate part is small than the single bending radius of curvature r0, the straight tube parts lS can be made longer and more fin equipments can be installed, resulting in enabling to improve the heat exchange performance.

Forming method of heat exchange tube

PURPOSE:To produce a fluoride flux having excellent solderability at a low cost by mixing AlF3.3H2O and KF which are the powder finer than AlF3 at a specific rate with water to form a paste then drying the paste to remove moisture. CONSTITUTION:AlF3.3H2O obtd. in the form of the powder finer than hardly meltable AlF3 is used and AlF3.3H2O and KF are mixed with water respectively at 64-68% and 36-32% ratios to form a paste. The paste is then dried at <=200 deg.C to remove moisture so that the brazing performance is improved and the cost of production is reduced.

Production of fluoride flux

PURPOSE:To obtain the corrugated type heat exchanger with excellent heat- exchange performance by a method wherein corrugation forming grooves with the same pitch as that of corrugated fins are provided on the surface of flat tubes so as to realize uniform pitch intervals of the corrugated fins after being assembled and at the same time to keep the straight line portions of the corrugated fins precisely at right angle to the flat tubes. CONSTITUTION:The respective pitches of the corrugated fins 4 and 5 are surely kept at constant and at the same time the straight line portions of the corrugated fins 4 and 5 are allowed to take the direction at right angle to the flat tubes 3B-3D by matingly joining the trough and crest parts of the corrugation formed on the flat tubes 3B-3D with the crest and trough parts of the corrugated fins 4 and 5. In addition, the genration of turbulent flow in the coolant flowing within the flat tubes due to the corrugation brings the effect to improve the heat- exchange efficiency of the heat exchanger. Furthermore, because of the pitches of the corrugated fins 4 and 5 being kept at constant, the resistance of the air flow passing through corrugated fin portions is reduced and consequently the effect to contrive to save energy as a whole is developed.

Uchida Takeshi

Papers

Forming method of heat exchange tube

Production of fluoride flux

Corrugated type heat exchanger