RU2236660C2 - Liquid-to-liquid heat exchanger for hot water supply systems - Google Patents

Abstract

FIELD: heat-power engineering; hot water supply systems.

SUBSTANCE: proposed liquid-to-liquid heat exchanger includes stack of intermediate plates with passages for flow of liquid to be heated and heating medium and extreme load-bearing plates; passages are provided with rectilinear sections and bends and are communicated with collectors supplying and discharging liquid to be heated and heating medium. Intermediate plates are provided with half-passages on either side for liquid to be heated and heating medium; rectilinear sections of half-passages on different sides of plate are matched. Passages for flow of liquid to be heated and heating medium are formed by matched half-passages of adjacent intermediate plates and half-passages of extreme intermediate plates on side of load-bearing plates. Internal and external walls of passages are profiled at turn at smooth change of curvature of contours, thus providing for continuous flow after turn. Sealing plates with holes for collectors may be laid between adjacent intermediate sheets and extreme intermediate plates and load-bearing plates. Sealing sheets may be provided with cuts according to shaped of half-passages. Flat surfaces of intermediate and load-bearing plates may be provided with sealing coats. Adjacent intermediate and extreme intermediate and load-bearing plates may be hermetically interconnected by soldering.

EFFECT: minimizing of salt deposition in passages; enhanced thermal and service characteristics; facilitated procedure of manufacture.

7 cl, 11 dwg

Description

The invention relates to a power system and can be used for hot water supply of buildings and structures.

The liquid-liquid heat exchanger for hot water supply must satisfy two basic requirements: ensuring effective heat exchange between the heating and heated media, the minimum precipitation of hardness salts in the channels of the heated medium (water).

Effective heat transfer between liquids is provided by heat transfer through a thin wall separating the fluid channels and the side walls of the channels. The channels for the flow of two fluids must be consistent, i.e. located on opposite sides of a thin wall. The flow of liquids in the heat exchanger should be organized according to the “counterflow” scheme.

Precipitation of hardness salts is observed in the channels of flowing heated water for hot water supply. The heating water undergoes preliminary water treatment and circulates in a closed hot water supply circuit, which minimizes the deposition of hardness salts in the heating water channels. Factors that prevent the deposition of hardness salts are the increase in the flow rate of water in the channels of the heated medium (water) and the transition to a turbulent flow regime in the channels, in which the profile of the flow rate is more full and, as a result, the tangential force at the channel walls increases, causing drift particles.

An unfavorable factor that increases the deposition of hardness salts on the channel walls is the presence of recirculation (separation) zones behind the ledges, in the region behind the flow turn at small turning radii or at right angles. In recirculation zones, the flow rate decreases by about 3 times compared with the main flow rate, which contributes to the deposition of hardness salts.

Efficient heat transfer and minimal deposition of hardness salts could be achieved in rectilinear channels at high speed (over 1 m / s) and turbulent flow in them. However, as the calculation analysis shows, for example, with a hydraulic channel diameter of 5-6 mm, the required channel length can be 5-6 m, which is difficult to implement in compact heat exchangers. In this case, it is necessary to use channels with straight sections and turns, for example, 180 °.

A compact heat exchanger can also be implemented in the laminar flow regime at a significantly lower flow velocity, which will be accompanied by more intense deposition of hardness salts in the heat exchanger channels. So in the case of rectilinear channels in a heat exchanger, for example, 0.5 m long and a hydraulic diameter of the channel 2-3 mm, the flow velocity in the heat exchanger channels will be less than 0.1-0.2 m / s, and a laminar flow regime is realized.

Known heat exchanger (EP 0183008 In 1, class F 28 F 3/08) containing a package of plates. In the upper parts of the plates, straight channels are made parallel to the side walls of the plates, and the lower part of the plates is flat. The heating or heated fluid is led to the channel of the plates and from the channels through the respective collectors in the plates located in the end parts of the plates, while the liquids are not mixed. The flow rate in the channels of the heat exchanger is small, the flow is laminar. The bag is assembled from alternately arranged plates for one and the other liquids without sealing elements, i.e. the heat exchanger is non-separable. When using a heat exchanger in a hot water supply system, disassembling a heat exchanger to clean it from deposits of hardness salts is impossible.

Known plate heat exchangers "liquid-liquid" (EP 0327574 B 1, class F 28 F 3/08, F 28 F 17/00, B 21 D 53/14) and (EP 0463298 B 1, class F 28 F 3/08). Collapsible plate heat exchangers contain a package of plates with channels for the flow of heated and heating media, including dividing plates, extreme power plates and collectors for supplying / removing heated and heating media.

The corrugated surface of the separation plates provides rigidity to the design of the heat exchanger. Each dividing plate is provided with a gasket made of heat-resistant rubber, sealing the connection of the plates and directing various flows of liquids into the corresponding channels.

The disadvantage of these collapsible plate liquid-liquid heat exchangers is that the use of the corrugated surface of the separation plates leads to a separation of the flow behind the corrugations and the formation of recirculation zones behind them. The heat exchanger operates at a low fluid flow rate in the channels; the flow regime in the channels is laminar. Low flow rates, especially in recirculation zones, contribute to the deposition of hardness salts contained in the hot water flowing through the heat exchanger. In the manufacture of dividing plates of the heat exchanger and rubber gaskets of complex shape, it is necessary to use expensive equipment.

Known plate heat exchanger “liquid-liquid” (EP 1136782 A1, class F 28 F 3/08, F 28 D 9/02), taken as a prototype heat exchanger “liquid-liquid” for hot water supply. The plate heat exchanger comprises a stack of plates assembled between the two end plates. In each plate, a channel mask is performed for one of the two liquids. The channel masks contain straight sections and 180 ° turns that are in communication with the collector holes for supplying / discharging the corresponding fluid. Turns are carried out either twice at right angles or the turns are U-shaped. The assembly of the package is carried out in such a way that plates for different liquids are alternately used. Between the plates for different liquids there is a dividing wall with collector holes. On different sides of the dividing wall, the channels of different liquids are aligned and aligned. The location of the collector holes in the plates and the assembly of the bag prevent fluid from communicating with each other. The tightness of the channels and the heat exchanger as a whole is ensured either by vacuum welding, or by soldering the assembled bag and end plates. Thus assembled heat exchanger is non-separable.

As options for a heat exchanger, plates made of rubber material are proposed. In this case, a variant of a collapsible heat exchanger is possible.

The option is considered when in each plate two mask masks are made for each fluid communicated with the collector holes for each fluid, respectively, when assembling the dividing wall is not used. The assembled bag and end plates are connected by welding or soldering, and the heat exchanger itself is non-separable.

The proposed use of channels with straight sections and 180 ° rotations makes it possible to obtain a sufficiently large channel length in a compact plate.

The disadvantages of the proposed technical solution include the following:

- the heat exchanger according to the main embodiment (with metal plates) is not disassembled, which excludes its mechanical cleaning from deposits of hardness salts, the manufacture of the heat exchanger requires sophisticated high-precision equipment;

- the heat exchanger with plates of rubber material can be made collapsible, but the manufacturing technology and especially the assembly of such a heat exchanger seems extremely complicated due to the configuration of the channel mask.

The basis of the invention is the task to develop a liquid-liquid heat exchanger, which will minimize the deposition of hardness salts of the heated medium in the channels of the heat exchanger and ensure high thermal characteristics of the heat exchanger with a relatively simple manufacturing technology.

This goal is achieved by the fact that in the heat exchanger "liquid-liquid" for hot water supply, containing a package of intermediate plates with channels for the flow of heated / heating media and extreme power plates, while the channels are made with straight sections and rotations, for example, 180 °, and communicated with the inlet / outlet collectors of the heated / heating media, in the intermediate plates on both sides there are half-channels for the heated / heating media in such a way that the straight sections of the semi-channels on different sides of the plate with agreed, the channels for the flow of heated and heating media are formed by the coordinated half-channels of adjacent intermediate plates and half-channels of the extreme intermediate plates from the side of the power plates, the inner and outer walls of the channels during rotation are made profiled with a smooth change in the curvature of the contours, providing an uninterrupted flow behind the turn.

In the heat exchanger, the inner and outer walls of the channels during rotation can be made profiled at the exit of the rotation.

In the heat exchanger, the inner and outer walls of the channels during rotation can be profiled symmetrically at the entrance and exit of the rotation.

In the heat exchanger between adjacent intermediate plates and the extreme intermediate plates and power plates can be placed sealing sheets with holes for the collectors.

In the heat exchanger, the sealing sheets can be made with cuts in the shape of half channels.

In the heat exchanger, sealing coatings can be made on the flat surfaces of the intermediate and power plates.

In the heat exchanger adjacent intermediate and extreme intermediate and power plates can be hermetically connected along their planes, for example, by soldering.

The proposed technical solution for the implementation of the heat exchanger allows you to implement an uninterrupted flow of heated and heating media in the channels of the heat exchanger at high speeds, which, as the operating experience of boiler rooms shows, minimizes the deposition of hardness salts contained in hot water (heated medium) flowing through the heat exchanger as in straight sections channels, and on channel turns. Moreover, the turbulent flow regime of the heated and heating media will be realized in the channels and, as a result, the heat transfer conditions between the heated and heating media will improve. The execution of straight sections of the half-channels on different sides of the plate coordinated also improves heat transfer conditions (by 15-20%), since heat will be transferred not only through the partition separating the half-channels of different media in the plate, but also through the side walls of the half-channels. Thus, the overall performance of the heat exchanger as a whole will increase both in terms of improving heat transfer, and in terms of reducing the deposition of hardness salts. Performing continuous channel turns will eliminate the formation of recirculation zones around the turn and, as a result, reduce the deposition of hardness salts and the pressure drop during the turn, i.e. the hydraulic resistance of the heat exchanger as a whole will decrease.

The inner and outer walls of the channels during rotation must be profiled with a smooth change in the curvature of the contours. In this case, an uninterrupted flow behind the corner should be ensured. Such an internal contour is calculated for a given gap width between the straight sections of the half-channels and the curvature of the inner contour on the axis of the gap using the separation criterion of the turbulent boundary layer as a limiting case.

Permissible positive longitudinal (downstream) pressure gradients are determined from transverse (across the flow) pressure gradients when the flow is rotated for the given characteristics of the turbulent boundary layer (displacement thickness or impulse loss thickness), for example, for a tube velocity profile. The external contour is determined from the condition of constant cross-sectional area. Calculations show that a smooth change in the curvature of the inner contour of rotation can be performed with the width of the gap between the straight sections of the half-channels equal to the width of the half-channel. Moreover, the area of a single plate can be small with the required total length of the channel, and the heat exchanger is compact.

Figure 1 presents the results of the calculation of the change in relative curvature (H / R) of the inner contour of rotation depending on the relative longitudinal coordinate (X / H), counted from the center of the radius of the rotation and directed towards the rotation. Here R is the radius of curvature, X is the longitudinal coordinate, H is the width of the gap between the straight sections of the half-channels. Figure 1 also shows the change in the relative curvature of the inner contour in the case of a radial rotation. We note that in the latter case, the curvature at the entrance and exit of the rotation changes abruptly.

In the circuit of the heating medium (heat carrier), water is used that has passed the appropriate water treatment and excludes the deposition of hardness salts. In this case, performing continuous rotation will have the goal of reducing the hydraulic resistance of the heat exchanger.

In the heat exchanger, the inner and outer walls of the channels during rotation can be made profiled at the exit of the rotation or at the entrance and exit of the rotation. In the latter case, all the intermediate plates are identical, which facilitates the manufacture and assembly of the heat exchanger.

Sealing adjacent intermediate plates and extreme intermediate plates and power plates can be performed in various ways.

When placing sealing sheets with openings for collectors between adjacent intermediate plates (or extreme intermediate plates and power plates), sheets with cuts in the shape of half channels and without cuts can be made. In the case of sheets without cuts due to a decrease in the hydraulic diameter of the channel, the heat transfer coefficient increases by about 20%, but the hydraulic resistance increases by 1.5-2 times, which is undesirable.

When performing sealing coatings on flat surfaces of intermediate and power plates, plate manufacturing technology is complicated, but assembly and operating conditions are facilitated.

When tightly connecting adjacent intermediate and power plates along their planes, for example by soldering, the heat exchanger becomes non-separable.

Figure 2 presents a diagram of a liquid-liquid heat exchanger for hot water supply. Figure 3, 4 is a diagram of the implementation of the intermediate plate. Figure 3 shows a view of the plate from the front side, the arrows show the direction of movement of the medium in the channel, for example a heated medium. Figure 4 shows a view of the plate from the back side, the arrows show the direction of movement of the medium in the channel, for example a heating medium. Figure 5, 6 presents the sealing sheets without cuts and with cuts in the form of half channels, respectively. Figures 7-10 show various sealing methods for adjacent plates. 7, the intermediate plates are hermetically connected along their planes, for example by soldering. In Fig. 8, the extreme intermediate and power plates are hermetically connected along their planes, for example, by soldering. In figures 9, 10, the plates are hermetically connected along their planes of the sealing sheets without cutouts and with cutouts in the form of half-channels, respectively. Figure 11 shows the implementation of the sealing coating on the flat surfaces of the intermediate plates.

The liquid-liquid heat exchanger 1 for hot water supply contains a package of intermediate plates 2 with channels 3 for the flow of heated / heating media, extreme power plates 4, while the channels are made with straight sections 5 and turns 6 and communicated with collectors 7 of the inlet / outlet of the heated / heating medium.

In the intermediate plates from two sides there are made semi-channels 8 for heated / heating media. The straight sections of the half-channels 8 from different sides of the plate are matched (Figs. 3, 4). Channels 3 for the flow of heated and heating media are formed by matched half-channels 8 of adjacent intermediate plates 2 and half-channels of the extreme intermediate plates from the side of the power plates 4 (Figs. 7, 8). The inner and outer walls of the channels when turning 6 are made profiled with a smooth change in the curvature of the contours, providing an uninterrupted flow behind the turn.

In the heat exchanger, the inner and outer walls of the channels during rotation 6 can be made profiled at the exit of the rotation or symmetrically at the entrance and exit of the rotation (figure 3).

In the heat exchanger between adjacent intermediate plates 2 and extreme intermediate plates 2 and power plates 4, sealing sheets 9 with holes 10 for collectors 7 can be placed (FIGS. 5, 9).

In the heat exchanger, the sealing sheets 9 can be made with cutouts 11 in the form of half channels 8 (6, 10).

In the heat exchanger on the flat surfaces of the intermediate 2 and power 4 plates can be made of sealing coating 12 (Fig.11).

In the heat exchanger adjacent intermediate 2 and extreme intermediate 2 and power 4 plates can be hermetically connected along their planes, for example by soldering (Fig.7, 8).

Claims (7)

1. The liquid-liquid heat exchanger for hot water supply, comprising a package of intermediate plates with channels for the flow of the heated / heating media and extreme power plates, the channels being made with straight sections and turns and communicated with the collectors of the supply / removal of the heated / heating media, characterized in that in the intermediate plates half-channels are made on both sides for the heated / heating media in such a way that the straight sections of the half-channels on different sides of the plate are aligned, channels for the heating flow Vai and the heating medium are formed consistent hemichannels adjacent intermediate plates and intermediate plates hemichannels extreme by the security plate, the inner and outer walls of the channels when turning made profiled with a smooth change of curvature contours, providing unseparated during the bend. 2. The heat exchanger according to claim 1, characterized in that the inner and outer walls of the channels during rotation are profiled at the exit of the rotation. 3. The heat exchanger according to claim 1, characterized in that the inner and outer walls of the channels during rotation are symmetrically shaped at the input and output of the rotation. 4. The heat exchanger according to claim 1, characterized in that between the adjacent intermediate plates and the extreme intermediate plates and power plates are placed sealing sheets with holes for the collectors. 5. The heat exchanger according to claim 4, characterized in that the sealing sheets are made with cutouts in the form of half channels. 6. The heat exchanger according to claim 1, characterized in that the sealing surfaces are made on the flat surfaces of the intermediate and power plates. 7. The heat exchanger according to claim 1, characterized in that the adjacent intermediate and extreme intermediate and power plates are hermetically connected along their planes, for example, by soldering.

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