DE3225764A1 - Multi-layer lightweight unit, especially panel heat exchanger, and process and injection head for manufacturing it from plastics - Google Patents

Abstract

A multi-layer lightweight hollow unit is proposed, especially a panel heat exchanger made of plastic, for use as a solar energy absorber, underfloor heating or lightweight board, which consists of two or more thin sheets (1a, 1b) which are integrally and homogeneously connected together (3a, 3b) by a plurality of thin rods (2a ... 2d) which are disposed in an inclined manner in the edges of an imaginary system of pyramids and between which the heat exchange fluid can flow over the entire surface (Fig. 2). In the continuous single-stage manufacturing process the rod elements (2a ... 2d) extruded between the sheets (1a, 1b) are deflected at the die mouths in a three-dimensional zig-zag manner by pulses of compressed air striking them obliquely in an alternate manner and directly welded by the heat of formation to the sheets (1a, 1b) as triangular or trapezoidal bracing (3a, 3b, Fig. 3). For sub-division into closed individual units, the continuously extruded hollow unit web is simultaneously welded tight, cut laterally and shaped in a flow-promoting manner (21, 22, 23, Fig. 3). <IMAGE>

Description

Multi-shell, lightweight hollow body, in particular flat

heat exchanger as well as process and spray head for its manufacture made of plastic The invention relates to a multi-shell lightweight hollow body, in particular Surface heat exchanger, made of plastic, which is primarily used as a solar energy absorber predominantly indirect production of environmental energy from the ambient air for the Building heating should also be used as underfloor heating.

Such hollow absorber panels are constantly from a relative to Water tougher heat transfer fluid, the temperature of which is reduced by a heat pump the ambient level is maintained, flows through with overpressure. Flow and heat transfer resistance may only be small in order to avoid losses. In energetic terms it is it is best if the heat-emitting (inner) surface is the same as the heat-absorbing one (outer) surface and the wall has a small thickness. Hence the leadership the fluid and thus the formation of the core structure is of decisive importance.

You must also fully meet the opposing strength requirements correspond; because large plate-like hollow bodies tend even with a small amount Overpressure for bulging and bursting.

Because of the temporarily very low ambient energy density are relative large absorber areas required. This requires an economical manufacturing process. These efficiency-related conditions, plus additional, obvious requirements such as corrosion and weather resistance should be considered when designing such heat exchangers should be taken into account as far as possible.

There is an already known system of the type described above made of two plastic-coated fabric panels, which are connected by a textile inner fabric made of binding threads are kept at a distance under internal pressure. The edges are with that Coating process has been closed by a special manufacturing process. Two connection pieces are diagonally opposite each other (magazine Sonnenenergie & Heat Pump "Volume 6/1981, Issue 1, Pages 27 to 34). These thin spacer fabric threads are not designed to withstand pressure and kinking and deform even with a slight external impact Load. When walking on or bending the fabric webs are compressed, the inner cross-section narrows and the flow is disturbed. Since the absorber track is not is self-supporting, it must be bulky in order to utilize the surfaces of both sides Frame racks are clamped. It is therefore also available as an underfloor heating mat has been designed with favorable transport and installation properties. A sufficient one Light transmission, for example for use as a wall and roof construction element with absorber function, cannot be achieved. The brine liquid has when flowing through the tendency, predominantly diagonally, to take the shortest route, from entry to flow to the outlet connection and in the other diagonal corners dormant or swirled Form areas.

The well-known absorber systems also include the so-called double-walled sheet, in which two plastic plates are connected by parallel full webs, so that seen in cross-section, a number of juxtaposed roughly square ones Form pipe channels. Although this plate is self-supporting and stable, it differs However, it differs from the previously treated type of absorber by some disadvantages: The end faces must in an additional complex gluing, welding or vulcanizing process each with a manifold and connecting piece to be connected to all individual channels summarize.

Another significant disadvantage is that relative to the full area Corruption caused great friction loss of the brine in the many narrow channels. He diminishes the degree of wind considerably. In addition, the web surfaces extend the heat path. Weight and material costs are greater due to the fully continuous webs.

(Brochure from BBC: Solarwatt collector M).

Other common designs are the pipe register and the ~ Rollbond "plate heat exchangers. You also have many complex and fault-prone ones Connection points, large friction losses of the heat transfer fluid or longer Heat paths (brochures from Genkinger and VDM). None of the systems mentioned is transformed from a plastic raw material into a finished absorber plate in a single work step manufactured (excluding the assembly of the connecting pieces).

The object of the invention is to provide a self-supporting lightweight hollow body, especially surface heat exchangers, with favorable heat transfer properties and the possibility of light transmission, which the inner and external mechanical loads and the evenly distributed flow of the Heat transfer fluid offers low resistance and this by an economical Extrusion process as a homogeneous material unit fully automatically in one work step can be produced by a simply constructed spray head.

This object is achieved according to the invention according to claim 1 in that that the enclosing shells are connected to one another via a triangular rod framework core cohesive unit are connected and that the hollow body is overall homogeneous having internal structure. Such a spatial triangular bar framework is fulfilled as a static support system, the requirement for high compression, tension, bending, shear and Torsional strength in equal measure, with little space and weight in the cheapest way. Four kink-resistant and four tensile-resistant rods each, which are in the edges a pyramid system are arranged, meet alternately at one point inside, on or near a surrounding shell. You can either use the bowls or each penetrate a rib-like projection of the enclosing shells materially. This geometry of the lightweight body allows the shells to be dimensioned relatively thin, because of the large number of thin rods with narrow spacing of the connection points, and it can be used as a continuous unit directly and easily in the extrusion process produce.

From the peculiarity of the energy-saving manufacturing process according to Claim 3, in which all parts of the entire lightweight body cross-section simultaneously extruded and directly from the heat generated by pressure medium surges are welded, there is the possibility that according to claim 2 enclosing shells as well as core rods and weld areas approximately the same strength-appropriate molecular Have orientation states. Other connection methods with prefabricated Parts, such as welding or gluing, are cumbersome and require reheating and thus impairment of the orientation structure (general is the weldability plastic parts with frozen orientation more difficult than non-oriented ones, isotropic parts) or are unsafe - e.g. when gluing polyolefins - change the structure by dissolving and contain the absorption of foreign substances with corrosion and risk of notch effects.

The manufacturing process as it is according to the characteristic features of the Claim 3 is proposed is based on the DE-PS 17 79 330 and the DE-OS 23 36 313 known processes. However, there are completely different products with other areas of application and the disadvantage of coarser material requirements: The deflection of the flat string takes place on the shortest path, its system geometry is not zigzag-spatially, but remains in a cylinder jacket or ebe # en'F1äöhe. The alternating direction of movement is for two individual ~ core rods on the other hand, with the invention spatially skewed towards each other and at the same time towards each other directed one of the enclosing shells, after which the simultaneous point-shaped All three freshly extruded elements are welded together. With the known The strip-shaped honeycomb wall elements with their entire exterior are method Side surface in a subsequent work step continuously with only one outer jacket tied together. With these known methods and spray heads, the lightweight body do not produce according to the invention.

The advantages of the method according to the invention are in particular in the development of a further, lightweight dimension for the swinging one Movement of the entire constant cross-section of the core rod elements with considerable Material savings with contactless operation without the use of movable ones Share, see.

By the measure according to claim 4, the subsequent stretching in longitudinal and / or the transverse direction of the still thermoplastic hollow body, becomes the molecular orientation and thus increases the strength. In addition, there is the possibility of to reduce the thickness of the hollow body like this for a surface heat exchanger is desirable, that allows the pressure medium nozzles and the plastic mass nozzles to be larger to design and to gain structural space for the spray head.

The continuous production method requires cutting to length in accordance with the cycle and sealing welding to form the closed individual hollow body. According to claim 5 is for advantageous simultaneous closing of the end of the finished part and the beginning of the new part as well Cut a pinch seam at right angles to the extrusion direction two pressure sealing bars moving together, and a separating cut through one of them Executed knife blade arranged in the middle.

In addition, inclined transverse notches are created on both sides at the same time embossed in the upper and / or lower outer shell. You have the rheological Task to adjust the flow rates of the heat transfer fluid the free flow cross-sections to the pressure conditions evenly over the whole Distribute the width of the hollow body: The cross-section is close to the connecting piece narrowed; it expands with the distance from the nozzle. So become loss-making Avoid vertebrae and resting areas. The two holes for the Adhesive or welded assembly of the connecting pieces are punched.

To exercise the method according to claims 3, 4 or 5 eigqnt in a special way the spray head according to the characterizing features of the Claim 6. It solves the demanding task of constant, precisely controlled Movement sequences and welding processes in a small space with a simple structure. Wanted to alternatively, for example, to move the freshly extruded core rods mechanically Using controlled deflection and welding pressure fingers, difficulties would arise quite apart from the touch because of the adhesive effect of the hot plastic compound from the problems with the kinematically complicated and because of the cramped space very small gears, wear, sealing and drive problems are on the other hand completely avoided here. Movable control parts in contact with the plastic compound are dispensable. Compressed gases (compressed air), liquids, too, can be used as pressure medium Foaming agents, granulates and vapors that can be generated economically at the place of work (Water vapor) serve. Due to the changing transverse offset in the arrangement of the pressure medium nozzles within a zigzag line between those evenly lined up Plastic core rod nozzles are the sequence of movements of the core rods compared to the known Spray heads expanded by one degree of freedom. All of them can be processed in the spray head weldable and bondable molded materials, including (glass) fiber-reinforced types.

In general, plastics are very suitable as materials for large areas Solar absorbers, because of their corrosion and weather resistance, easy malleability and affordable prices. The lower thermal conductivity compared to metals falls hardly any weight, since they are only a small part of the overall process of heat exchange Has influence.

Design variants are proposed in claims 7, 8 and 9; first the spray head for the normal product shape, the level, large hollow slab; or for a hollow-wall tubular body with concentric wall shells, and then for a hollow body with a corrugated sheet-like cross-section and a more than double-shell structure. The application for greenhouse construction can, for example three shells are provided: One cavity serves as a solar absorber through which brine flows and the other hollow space filled with insulating material or air or evacuated as Thermal insulation.

Embodiments of the invention are shown in the drawings. They are described in more detail below.

1 shows a perspective overall view of the plate-shaped Lightweight hollow body (without mounting rim Ig) as a surface heat exchanger Fig. 2 a enlarged section of the front corner of the lightweight hollow body of FIG. 1, with exposed system of the core rods Fig. 3 shows a longitudinal section through the extrusion head and Lightweight hollow body, corresponding to the section along line C - D of Fig. 4 (scale approx. 2: 1 to 3: 1, enlarged) Fig. 4 shows a cross section through the lightweight hollow body (left) with the representation of two welding phases (middle and right), accordingly the section along line A - B of FIG. 3 and the section along line E - F of FIG. 1 (scale approx. Iff to 5 enlarged) FIG. 5 shows a detail from FIG. 3 with a Variant of the pressure medium nozzles (axially movable).

Fig. 1 is a schematic perspective illustration of the lightweight hollow body as a surface heat exchanger. In natural size it has the usual dimensions of for example about 4 to 10 mm thick, 0.6 to 1.2 m wide and 1.0 to 3.0 m long; however, they can be changed within wide limits. Below and above are the Mainly heat-absorbing plate-like enclosing shells la and Ib. the strip-shaped narrow walls lc and ld form the side walls on the right and left Longitudinal limitation. The front and rear walls close the le and lf with the - Pinch seams 22 (not shown) (see Fig. 3) the hollow body. Also the optional Mounting edges lg to be provided (see Fig. 4) are not shown in Fig. 1, The connecting pieces Ih, e.g.

for the brine inlet and left for the brine outlet are in two each other arranged diagonally opposite corners of the shells la and lb. To achieve the inclined notches 23 next to the itouts serve for an even flow, These connecting pieces (lh, li) can of course also be found elsewhere, for example in the middle of the panel width. The transverse notches 23 would also be here reach deepest into the cavity near the nozzle and after both longitudinal walls lc, ld taper off flat. The space between the bowls la and Ib fill the pyramidal shape assembled core rods 2a to 2d, with them below and above in the tip areas 3a and 3b converge and each with each other as well as with the shells la, Ib are firmly connected as shown schematically in FIG. All elements la to 2d form a homogeneous material unit.

Through material and dimensional changes, strength, Elasticity and heat transfer vary. The flat plate geometry can through subsequent deformations received variously modified shapes, for example to Production of a compact energy stack, meandering shape, the one Concentration of a large surface in a small space is allowed with only two connection pieces. Furthermore, a spiral shape can be expedient, with a transverse side as the inner side The beginning of the hollow body is clamped or freely rotatable and the other, outer transverse side can be moved freely by the wind. This results in an improved Heat transfer. Pulsating pressure surges in the brine circulation pump cause vibrations Movements of the spiral hollow body, even in the absence of wind. That Bourdon tube effect also arises when training as an open cylinder or screw. An ice crust which form at lower ambient air temperatures and their removal in a conventional manner Way can cost a lot of heating energy, can be reduced by increased pressure surges and the Easily remove the elastic deformations caused by this.

The structure of the spray head for the production of the lightweight hollow body is based on that of a common slot nozzle. The ones used in these Devices for setting uniform flow conditions such as damming bars, nozzle lip adjustment etc. are omitted in FIG. According to FIG. 3, it consists essentially of the Housing with inlet part 13, in which the flange and connection opening 12 for a Not shown extruder are located, the outer middle part 14a, the inner middle part 14b - which are connected by webs lOb between passage channels lOa on both sides Are connected -, the distributor insert 16 and the spray head outlet part 17. Lower and upper calibration walls 18a and 18b determine the finished thickness of the hollow body. The parts 13, 14a (14b), 17, 18a, 18b are firmly screwed together.

In the middle between the slot nozzles 6a, 6b lie evenly Distributed over the width of the hollow body, the core rod nozzles 7 with connection channels 7a and 7b, Fig. -5 shows a modification of the pressure medium nozzle tube 15a and 15b from FIG. 3. They are not fixed in the middle part 14b here, but axially movably mounted (15c and 15d). The compressed air blast 4a, (4b) moves the tubes 15d in groups, initially piston-like forward and then hits through the nozzles 5a (5b) as a free jet onto the core rod strands 7. The moving jet can as a result, they act at right angles and in a more concentrated manner over a longer period of time. Springs 19b (19a) or the like fetch the nozzle tubes after switching the pressure back to the unpressurized position.

The core rod cross-sections can also deviate from the round, full shape, e.g. have a ring shape (hollow bar).

In general, a free jet of compressed air has a self-centering effect a round transverse string element, even if it is only touched. The compressed air jet therefore does not need to be aimed directly at the core rod strand; he sucks it automatically into its midst and takes it with it, but also becomes something itself diverted from the strand (see Fig. 4> right part, at pos. 4b). This effect can with small thicknesses of the hollow body bring structural advantages. In addition, there is with a correspondingly large setting of the blowing angle between the two compressed air nozzle openings 5a the effect of a pneumatic toggle lever ": The core rod strands 2a to 2d meet before reaching the surrounding shell la, Ib together and only then after Redirection to the vertical, together on the shell.

Blank page 5 shows a modification of the pressure medium nozzle tube 15a and 15b from FIG. 3. They are not fixed in the middle part 14b here, but axially movably mounted (15c and 15d). The compressed air blast 4a, (4b) moves the tubes 15d in groups, initially piston-like forward and then hits through the nozzles 5a (5b) as a free jet onto the core rod strands 7. The moving jet can as a result, they act at right angles and in a more concentrated manner over a longer period of time. Springs 19b (19a) or the like fetch the nozzle tubes after switching the pressure back to the unpressurized position.

The core rod cross-sections can also deviate from the round, full shape, e.g. have a ring shape (hollow bar).

In general, a free jet of compressed air has a self-centering effect a round transverse string element, even if it is only touched. The compressed air jet therefore does not need to be aimed directly at the core rod strand; he sucks it automatically into its midst and takes it with it, but also becomes something itself deflected from the strand (see Fig. 4, right part, at pos. 4b). This effect can with small thicknesses of the hollow body bring structural advantages. In addition, there is with a correspondingly large setting of the blowing angle between the two compressed air nozzle openings 5a the effect of a "pneumatic toggle lever": the core rod strands 2a to 2d hit before reaching the surrounding shell la, lb together and only then after Redirection to the vertical, together on the shell.

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Claims (9)

Multi-shell lightweight hollow body, in particular surface heat exchanger, as well as method and spray head for its production from plastic. 1. Multi-shell lightweight hollow body, in particular surface heat exchanger made of plastic, characterized in that the surrounding shells (ia ... l.f) over a triangular bar framework core (2a ... 2d) with each other to form a cohesive one Unit are connected and that the hollow body has a homogeneous internal structure. 2. Hollow body according to claim 1, characterized in that enclosing shells (yes ... 19) as well as core rods (2a ... 2d) and connecting areas (3a, 3b) about the same have strength-appropriate molecular orientation states. 3. Process for the production of a multi-layered lightweight hollow body, in particular surface heat exchanger, according to claim 1 and / or 2, wherein pressure medium surges the welding of individual extruded strands together directly from the Cause generating heat, characterized in that that together with the continuous surrounding shells (#a ... 1d) extruded core rods (2a ... 2d) by pressure medium surges acting on them transversely and / or diagonally, preferably compressed air surges (4a, 4b), alternately at an angle to each other and to the surrounding shells (la ... ld) and planes (El, E2) lying parallel to the extrusion direction (R) in a zigzag shape are moved back and forth, so that each in a periodic sequence two one-sided Adjacent core rods (2a, 2b) and a (lower / inner) surrounding shell (la) with one another come into contact and weld (3a) and then, after changing the direction of the pressure medium surges (4a, 4b), two adjacent core rods (2c,) and the other <upper / outer) Enclosing shell (lb) come into contact with each other and weld (3b). #. Method according to claim 3, characterized in that the hollow body is subsequently stretched. 5. The method according to claim 3 or 4, characterized in that the Hollow body in the thermoplastic state continuously cut in individual lengths and, simultaneously with the cutting process (21), on both sides of the cut surfaces is tightly welded by a pinch seam (22) and near the pinch seam (22) a or several inclined transverse notches (23) in one or more of the. Enclosing shells (la, ib) must be pressed. 6. Spray head for performing the method according to claims 3, 4 or 5, characterized in that in the mouth plane (M) at right angles to the extrusion direction (R) the fixed or movable nozzle openings (5a, 5b) for the pressure medium (4a, 4b) in the area within the slot nozzle openings (6a, 6b) for the enclosing shells (la ... ld) in the vertices (3a, 3b) of a zigzag line (Z) and the nozzle openings (7) for the core bars (2a ... 2d) in between on each leg of the zigzag line (Z) lie, the pressure medium nozzles (5a, 5b) in two action groups (a, b) are divided, with the assignment of all one-sided, close to the upper / outer Surrounding shell (lb) arranged nozzles (5a) to a first distribution channel (8) and in each case all other sides, near the lower / inner surrounding shell (la) arranged nozzles (5b) to a second distribution channel (9), which, in the continuous Change controllable, can be connected to a pressure medium source. 7. Injection head according to claim 6, characterized in that for production of a flat hollow body, the slot nozzle openings (6a, 6b) as straight slot nozzles are trained. 8. Injection head according to claim 6, characterized in that for production a tubular or in some other way, preferably wave-shaped curved hollow body, the Slot nozzle openings (6a, 6b) as concentric ring nozzles or correspondingly curved are trained. 9. Injection head according to claim 6, 8 or 8, characterized in that the slot nozzle openings to produce a hollow body with more than two shells (6a, 6b) in the corresponding number and the zigzag lines (Z) with the pressure medium nozzle openings (5a, 5b) are provided in the same number less one.