DK152414B - PROCEDURE FOR PREPARING A FLAT HEAT EXCHANGER OF METAL PLATE - Google Patents

Abstract

1. Process for the manufacture of a flat heat exchanger made from sheet metal and having at least one channel through which a medium which is to heated or cooled passes, in particular a roof skin for absorption of energy from the environment, in which process a metal block, preferably consisting of copper, and having at least one passage produced by drilling is first manufactured, a welding preventative is introduced into each passage, the metal block is stretched in the direction of the path of the passage(s), by rolling, to the final dimension, and thereafter each passage which has been rolled flat is inflated, characterised by the combination of the following features : a) the passages are produced in the metal block by drilling a deep hole from both end faces, and b) the metal sheet is soft-annealed in a tunnel-type annealing furnace, prior to the last reduction stage, which is effected by col-drolling in a manner known per se, and the last reduction stage is effected in the same pass as the annealing.

Description

in

DK 152414B

The. The present invention relates to a method for producing a flat plate heat exchanger of metal plate and of the kind specified in the preamble of claim 1.

With the growing lack of and costing of primary energy, such as oil, coal, natural gas, etc., the utilization of low-temperature natural heat, such as waste heat, heat from the ambient air and from the coming radiant energy, is becoming increasingly important. Various proposals have already been made to utilize the roofs of buildings to absorb this energy.

10 From the description to German usage pattern 7,540,889 a metallic cover plate for roofs and facades is known which has a reinforcing seam or corrugation for accommodating a heat carrier conducting pipe and which are interconnected via laterally arranged ribs. In this construction, the heat passes through the wall of the cover plate 15 into the area of the reinforcing seam and through the wall of the pipe and then reaches the heat carrier. Due to the method of manufacture, there is usually a small air gap between the pipe and the reinforcing nail, which counteracts the heat transfer with a resistance. For improved conductivity, in this construction, the cover plate as well as the pipe are preferably made of copper.

Flat collectors or flat absorbers, respectively, are already manufactured by applying a welding stopper to a metal band according to the pattern of the duct system, placing a second metal band on the metal band and rolling down both metal bands together. Thereby, the two metal bands are welded to each other at the places where there is no welding stop, while the areas where the welding stop prevents a metallic connection are inflated after the roller flattening. The disadvantage of this method is that it is expensive and expensive and cannot be used for all metals. Thus, in particular, cold welding of two copper bands is very problematic (see US Patent 3,667,266)

DK 152414 B

2

Pra GB PS 857.291 is known to produce a metal block with openings, to insert a tube filled with welding stopper into the openings, to roll the block and subsequently to inflate the ducts. According to one suggestion, the openings in the block can be made by drilling. This known method fails when introducing bores into a long block. However, for the sake of the economy of rolling, long blocks are inevitable. For long blocks, the drill wanders out of its path, ie. that the channels do not extend exactly parallel to the longitudinal edges. This changes the distance between the channels and their distance from the longitudinal edges, respectively. Furthermore, their internal dimensions are enlarged when the channels do not extend parallel to the longitudinal edges.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method in which it is possible to produce, in a particularly economical and simple way, flat heat exchangers in thin metal plate and which have properly extending channels for conveying a medium to be cooled or heated. In particular, it should also be possible to produce flat heat exchangers of copper ► · 20 or copper alloys.

This object is solved by the fact that the method mentioned in the introduction is peculiar to that of the characterizing part of claim 1. At the specified deep hole bore from both end walls, it has been possible to drill blocks with a length of 25 e.g. 5,000 mm. The bores have such a smooth surface that the welding stopper can be evenly distributed without clumping. By smoothing the metal plate before the last rolling pass, which last rolling pass is applied in the same working step as the annealing, a plate which can be easily formed, but which has a sufficient strength to produce the plate when, for example, is produced.

used as a heat exchanger mounted on a roof can withstand snow and wind pressure and also withstand when e.g. a chimney sweeper goes on the roof. The bleeding anneal, which eliminates the hardening produced by the previous cold operations, and the last cold 3

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the rolling passages which give an adjustable strength ^ are completed in a workflow so that no additional labor costs are incurred.

The semi-finished product for the heat exchanger can be manufactured in almost 5 arbitrary lengths. Accordingly, in accordance with the characterizing part of claim 2, it is possible in the same operation as the cold rolling to cut the copper strip to lengths of use and subsequently inflate each opening. On the other hand, however, it may also be advantageous to roll the copper plate onto a drum after 10 blow-ups of each opening of the copper plate. The reeling on a drum is possible without the opening or openings being deformed inadvertently. At the mounting location, the required length can then be pulled from the drum and cut off.

The heat exchangers produced by the process according to the invention exhibit a smaller wall thickness compared to the other strip material for manufacturing reasons in the area of the openings. This may in some cases be a disadvantage and it has therefore proved expedient to re-double the wall thickness across the openings direction preferably by rollers, for those adjacent to the opening areas or between these plate areas, respectively, after the last rolling in a separate cold rolling passes. The wall thickness reduction should be at least 25%, preferably 50%.

As welding stoppers intended to prevent a metallic connection of the inner wall of the bores by the subsequent rolling, especially oil, talc, quartz, lime, graphite, molybdenum sulfide, glycerine and other substances are suitable, as mixtures may also be used. The final blow-up of the 30 flat-rolled bores presents no major difficulties, because at different high pressure the blow-up different channel cross-sections become possible. Thus, the attitude is higher

DK 152414 B

4 press a circular cross section for the duct, while oval cross sections can be obtained at lower pressures.

On the basis of the drawing and the embodiment shown, the invention is further explained. In the drawing, FIG. 1 to 5 3 schematically illustrated embodiments.

In FIG. 1 shows a metal block 1, preferably of copper or a copper alloy, e.g. has been made by string casting. The metal block 1 has longitudinal openings or channels 2 that are either already made by the casting 10 or are later inserted into the metal block, e.g. by laser beams. With particularly great advantage, the channels 2 are produced by chip-removing machining, preferably by deep drilling. The metal block 1 has e.g. a width of 710 mm, a height of 210 mm and a length of 5,000 mm. By means of deep drilling, the ducts 2 are inserted from the front sides, if necessary from both sides, into the metal block 1.

Then a welding stop means, e.g. talc, quartz, lime, molybdenum sulfide, graphite powder, glycerine and mixtures thereof, respectively, in such an amount that the inner wall of the channels 2 is completely coated. The welding stop means must prevent the inner wall of the ducts 2 from welding together during the subsequent hot rolling process. In the hot rolling process, the height of the metal block 1 is rolled from 210 mm to approx. 12 mm, there being an extension of the metal block 1. The ducts 2, whose diameter e.g. is 25 mm, is then transformed into slots 3 (see Fig. 2). In connection with the hot rolling, which is preferably carried out at 700 ° C when rolling a copper block, the hot-rolled metal block 1 is milled on all sides, thereby removing the casting and rolling skin, respectively. The metal block thus prepared is then rolled in several cold rolling passes to the final target. The wall thickness of the finished flat heat exchanger shall in this connection not exceed 1 mm.

Claims (3)

5 The slots 3 are then opened at one end by means of the mandrels and closed at the other end, and at the region opened by the mandrels a pressure means, e.g. compressed air which at sufficiently high pressure causes the slits 3 to be channeled to ducts 4. Depending on the size of the pressure, the cross-section of the ducts 4 can be circular or even oval. By clamping before the blow-up, a semi-circular cross-section can also be created for the channel 4. The slit 3's blow-up can be made for both longitudinally cut metal sheets as well as for the total metal web in full condition. 15 Patent claims. A method of producing a flat sheet metal heat exchanger having at least one channel for conveying a medium to be heated or cooled, in particular a roof covering for simultaneously absorbing energy from the environment, wherein a metal block is first prepared with at least one through-opening through-hole, in which a welding stop is introduced into each through-opening and the metal block is extended by rolling in the direction of the through-opening (s) until the final target and each flat-rolled through-opening in connection for this purpose, the method is combined, comprising: a) that the through openings in the metal block are produced by deep hole drilling from both end walls; and (b) the metal plate is softened before the last rolling pass, which occurs in a manner known per se by cold rolling, and the last rolling pass is applied in the same working step as the annealing. Method according to claim 1, characterized in that the cold-rolled strip is cut to lengths of use in the same operation as the cold-rolling and that each through-opening opening thereafter is blown up. Method according to claim 1, characterized in that the tape is wound on a drum after opening of each of the tape's through openings.