FI78981C - Heat exchanger. - Google Patents

Abstract

Heat exchanger intended to be flown through by two media and for heat exchange via heat exchanging surfaces in such a way, that the media do not directly contact each other, where the heating surfaces are located rotation symmetrical in relation to, for example, an axis, and the main flow direction of the media is in parallel with said axis. The object is to reduce the overall height and material consumption while maintaining the size of the heat exchanging surfaces. When the heat exchanger is used as an evaporator, the overall height additionally is reduced in that the expansion chamber, which normally is located above the heat exchanger unit, can be positioned centrally within the evaporator (heat exchanger). The said improvement is achieved in that the heating surfaces D are located in an annular area about said axis, so that a central hollow space without heat exchanging surfaces is formed about the central axis.

Description

78981 Heat exchanger Värmeväxlare 5 The present invention relates to a heat exchanger for the flow of media and the exchange of heat through heat exchange surfaces so that the media do not directly contact each other, the heating surfaces being rotationally symmetrical with respect to the axis and the main flow direction .

The object of the present invention is to reduce the structural height and to reduce the material consumption while keeping the size of the heat exchange surfaces constant. In addition, when the kek-15 is used as an evaporator, a reduction in the structural height is achieved due to the fact that the expansion chamber, which is usually located above the heat exchanger unit, can be placed centrally inside the evaporator (heat exchanger).

The features of the invention 20 set out in the following claim 1 fulfill said purpose and provide the advantages alone with a very reasonable increase in diameter (e.g. 10-20%).

With a special embodiment of the invention according to the following claim 2, the possibility is achieved that the structure 25 can withstand high internal pressure without increasing the material thickness as a result. In addition, the maintenance of the liquid film along the heat exchange surfaces is improved by continuously causing the flowing liquid to change direction as it flows downward, so that jets 30 and droplets are formed which moisten the underlying surfaces upon contact with them.

A special embodiment of the invention according to the following claim 2 provides a structure which, without special means, such as bellows or the like, 55 can withstand the high tensile and compressive stresses which may arise due to large temperature differences.

The previously known problem of enriching horizontal seams in a corrosive liquid is eliminated by a further embodiment of the invention according to claim 3.

Some embodiments of the invention will now be described with reference to the accompanying drawing figures.

Figure 1 then shows a schematic view of a heat exchanger according to the invention.

Figure 2 shows a schematic cross-section.

Figure 3 shows a longitudinal section of a lamella assembled from two plates.

Figure 4 shows the upper end of the lamella viewed towards the plate surface.

Figure 5 shows a view in Figure 4 in the direction of arrow C-C of Fig.

Figure 6 shows a view in Figure 4 in the direction of arrow D-D in 15 directions.

Figure 7 shows a top view of Figure 4 the direction of the arrow A-A direction.

Fig. 8 shows a section along the line B-B in Fig. 4.

Figure 9 shows a longitudinal section through the invention when it is arranged as an evaporator.

Figure 1 shows a heat exchanger 1 in which both media are liquids, the device being fully welded, but of course it can be formed by suitable flange joints if simple disassembly is required for inspection and cleaning.

The heating surface is annular, see Fig. 2, and consists of a plurality of radially mounted lamellar units 2, each consisting of two heeled plates 3,4 »welded together along the longitudinal sides.

The heat exchanger 30 is rotationally symmetrical and consists of an outer jacket 5, an inner jacket 6 with a roof, lamellar elements 2 placed between the inner and outer jacket, an inlet duct 7 leading to the inner jacket 6, an outlet duct 8 leading therefrom, from the outlet 10 leading therefrom. Reference numeral 13 denotes a distribution box for the medium inside the lamella and reference numeral 14 denotes a collection box for the medium outside the lamellae. Reference numeral 15 denotes an assembly box for the medium inside the lamellae. Dashed arrows show the route of the second medium (e.g., heat transferable medium inside the lamellae 5) through the heat exchanger, and dashed arrows indicate the route of the medium outside the lamellae. The lamella element 2 is shown in more detail in one embodiment in Figures 7 and 8, and each lamella consists of two parallel corrugated plates 3 and 4 welded together with the corrugations along parallel edges 11,12. The flow channel parallel to the edges is thus formed by means of a lamella. As can be seen from Figures 7 and 8, the height of the corrugations hi, h2, h3 increases from the inside of the heat exchanger outwards so that the opposite lamellae are against each other at the vertices of the corrugations, through which the lamellae 2 support each other.

Figure 3 shows a longitudinal section through the lamella transverse to the plane of the plates 3,4, the plates being bent at points 16 and 17 so that they can lengthen and shorten in the longitudinal direction of the heat exchanger.

This reduces, or completely eliminates, the stresses in the structure that can arise in devices where the temperature difference between the media is large or where strong, momentary fluctuations in temperatures and flows occur. The elements become "prestressed". Prestressed heat exchanger tubes have appeared on the market a few years ago.

The lamellae can be embossed in the press to the desired widths and thicknesses. Figures 7 and 8 show a type of lamella heel stamping and the shape of the end connection rings. Figure 1 shows that the lamellae are cut obliquely from the ends at 18 and 19. Thus, it is achieved that the so-called blind corners disappear due to the better flow pattern. In addition, the risk of crack corrosion is reduced due to better drainage and exchange of flowing fluid.

A major advantage of the thermosetting and embossing of Figures 7 and 8 is that the material thickness of the sheets can be reduced compared to spot welded structures without any loss of mechanical strength. This is very important in structures that are titanium or similar very expensive material.

5 The outer collecting box 15 is connected to the heating surface so that the medium flows inside the element 2. The material present in the collection boxes, both in the outer and inner collection boxes, as well as in the heating surfaces provided with the inner and outer connection rings, can thus be selected according to the expected corrosion effect. Standard calculation standards apply to mechanical strength.

The inner jacket 6 shown in Fig. 1 forces the medium flowing from the outside into the center inside the heating surface outside the elements 2, after which the medium continues to flow upstream of the downstream medium inside the elements 2, the medium at the upper end of the heating surface is led inwards towards the center The length of the inner jacket 6 is adjusted so as to provide the necessary openings 20 for inflow and outflow.

The inner jacket 6 can be made of a very thin material, as it is only exposed to an internal overpressure corresponding to the maximum pressure drop of the medium flow through the heat exchanger.

The outer sheath 5 in Figure 1 is sealed tightly against the outer connecting rings 20. In terms of strength, the outer jacket is dimensioned for the internal overpressure, which corresponds to the pressure and temperature prevailing in the medium flowing outside the element. The outer sheath is usually also dimensioned for the full vacuum inside. In most cases, the sheath is reinforced with so-called vacuum reinforcement rings placed at a suitable distribution along the length of the sheath.

An interesting advantage of the annular radially positioned lamellar heating surface 35 is that it serves in part as a vacuum reinforcement. How much of the reinforcement the lamellae 2 form depends on the width and length of the plates 3,4 on the sheath to be vacuum reinforced. The vacuum reinforcement rings can be a relatively expensive part of the device in relative terms, so that the possibility of being able to lower it all or part into the lamellae is of considerable value.

The mechanically weakest point in the lamellar heat exchanger 5 is the connection to the collection boxes, where the strength of the welding connection between the plates and the connection part completely determines the pressure and temperature at which the device can operate. The connection method shown in Figures 4-6 has proven to be very efficient and can withstand an explosion pressure of more than 300 kp / cm 2.

Furthermore, it is known that the thermal load prevailing in welding, depending on the stresses then formed in the structure, is of great importance for the service life of the device. As for the heat exchanger, the longitudinal welds of the lamella unit and the joint welds against the outer and inner connection rings (20 and 21 in Fig. 1) are made by fusion welding without additive, which means welding with moderate heat load and a significant risk of internal crack formation of the welds. In addition, if the softest possible method is chosen, e.g. by biasing the lamel-20 large elements, a very stress-free structure can be obtained.

By embossing / pressing the lamella plates with a certain angle and support points according to Figures 7 and 8, an annular, circular heating surface in cross-section can be constructed which is completely self-supporting or self-supporting, regardless of the pressure conditions inside / outside the lamella element. or seam welding to hold the elements together at the internal overpressure prevailing in the ducts, is completely unnecessary. This means that the clamping forces required to form channels with transverse grooves and support points will be substantially lower (probably 70-90% lower) than if complete contact surfaces for spot or 55 seam welding were to be provided. The low required compressive forces also cause the stresses in the plates to become relatively insignificant and the risks of crack formation at the depression points are eliminated. Because no 6,789,881 welding contacts are required, except for the longitudinal sides, the tool is simple to manufacture and has a long service life due to low compressive stresses. Spot welding to hold lamellar elements together requires quite 5 flat depressed surfaces for each point (approximately φ 10 mm), which poses increased risks for both stress and crack corrosion. Furthermore, when constructing lamellar devices, plate thicknesses must be selected which provide sufficient strength in spot welding to withstand the load measurements during use. The lamellar surface according to Figures 7 and 8 can be made of a very thin sheet by means of a suitable embossing pattern with support points. Because the support points are small and even rounded in surface area, it is. the risk of crack corrosion is eliminated, compared to 15 spot welding surfaces as described above. The risk of solid particles forming at the support points is also greatly reduced. The prestressing of the lamellae provides a nearly stress-free structure, which is of great benefit.

The evaporator according to Fig. 9 operates with operating steam inside the lamellar element 2. The curve is taken to the dispensing chamber 22 at the top of the device and goes from there into the top of the element. The dispensing chamber is slightly enlarged so that it can be entered for inspection. The operating steam, together with the concentration formed, flows downwards through the element. Due to the fact that the heating surface is provided with grooves, ridges and support points, the condensate film on the walls is constantly broken and thinned, which results in an improved heat transfer to the wall (5-10%). The condensate drains down to the condensate space 23 below the heating surface and is discharged therefrom. Uncondensed gases are taken out of the same space through a separate nozzle 24 provided with a "splash guard" 25, which may also be annular.

7- 78981

The outer and inner sheaths 5,6 are practically tightly connected to the annular western surface over almost the entire length. A dispensing chamber 26 is arranged upwards, inside which the outer jacket 5 is cut downwards the distance of the kappa-5 to provide an annular gap 27 around the upper part of the heating surface for even distribution of the solution circulating outside the lamella elements. For discharge, an opening / slit 28 is provided in the lower part so that the inner jacket has a smaller diameter. in the middle of the device, the inner jacket 10 forms at its apex 29 a large separation chamber 30 corresponding to the expansion tank or steam hood with which the conventional evaporator devices are usually equipped. The lower part has an inner cylinder 31 which is tightly welded against the lower inner connecting ring 32 of the heating surface and 15 also tightly welded against the bottom of the device at a point 33, which may be a crown, as in the draft, or a domed end. If necessary, a droplet separator can be built into the central separation chamber.

The solution to be evaporated is circulated by the pump 20 from the buffer space at the bottom of the device to the distribution chamber 26 around the top of the heating surface. The annular gap 27 for the incoming circulating solution is dimensioned for a certain reasonable pressure drop to ensure even distribution. In the first step, the entire free cross-section outside the lamella elements 2 is filled with a completely inflowing circulating solution, which then flows downwards in the form of a film on the heating surfaces. The circulating solution is very close to the boiling point, so that boiling / steam generation starts practically immediately. The free space is thus filled with strongly supersaturated / moist steam, which contains droplets of liquid, the size of which varies from the mist upwards. Equipping the heating surface with grooves, ridges, and support points quickly creates a vortex formation in the steam, causing moisture and droplets to strike the walls. Of course, the vortex formation becomes more intense as the amount of steam increases as it goes down.

The design of the heating surface thus ensures complete wetting of all parts of the heating surface 8 78981, which is a prerequisite for perfect operation and 100% utilization of the installed heating surface. The conditions on the drop membrane side, as described above, make it possible to operate the device with a minimal excess of liquid, which means lower power consumption of the recirculation pump.

a gap 28 is provided in the lower part of the heating surface between the heating surface and the inner jacket, so that the generated steam 10 and the excess recycled liquid can leave the heat package. The mixture of steam and liquid first passes a series of cover plates 35 where the first rough separation takes place. Most of the liquid collides with the cylinder, which forms an extension of the lower, inner connecting ring of the heat exchanger, and then flows into the buffer space 34 for the circulating solution. The steam makes a U-turn, further separating the liquid droplets, and then passes up through the main separation column. .

Claims (3)

9,78981 A heat exchanger for flowing two media and exchanging heat through 5 heat exchange surfaces so that the media do not directly contact each other, the heating surfaces being rotationally symmetrical about an axis and the main flow direction of the media being parallel to said axis and the heating surfaces being positioned around said axis , so that a central cavity without heat exchange surfaces is formed around the central axis, characterized in that the heat exchange surfaces are formed in pairs of lamellae (2) by plates (3,4) corrugated parallel to said axis, the height of said corrugations (hi, h2,. ..) increases with the distance outwards from the shaft, so that the corrugations in the opposite lamellae (2) are against each other and form support points between the lamellae. Heat exchanger according to claim 1, characterized in that the plates (3, 4) are bent or turned somewhat flush around a plane arranged in the plane, which line is perpendicular to said axis. Heat exchanger according to claim 1, wherein the lamellae are connected side by side at their two end edges (18, 19) by welding, characterized in that the connecting edge (18, 19) is inclined obliquely downwards to facilitate drainage.