DK1740888T3 - heat exchanger - Google Patents

Description

Heat exchanger

The invention relates to a heat exchanger having a primary-side flow path which is arranged between an inlet connection and an outlet connection, a secondary-side flow path which is arranged between an inflow connection and a return flow connection, a heat transfer surface arrangement formed between the primary-side flow path and the secondary-side flow path and a temperature sensor. A heat exchanger of this kind is used in a district heating system, for example, in order to heat service water which flows through the secondary-side flow path. The amount of heat required for heating is transported via the heat transfer fluid of the district heat network. This heat transfer fluid flows through the primary-side flow' path. The primary-side flow path and the secondary-side flow path he in a housing of the heal transfer fluid in heat-conducting connection to one another, so that a heat transfer can take place via the heat transfer surface arrangement. Similarly, service water used to heat a building can be heated using a heat exchanger of this kind, wherein here, too, the heat originates from a district heating network.

In order to obtain the most accurate temperature setting possible at the outlet, the flow of heat transfer fluid on the primary side is controlled depending on the heat removed on the secondary side. This will be explained below based on the example of sendee water which is heated in the heat exchanger. As soon as service water is extracted at the return flow' connection of the secondary' side, cold service water flows behind into the inflow connection. Accordingly', heat transfer fluid must be able to flow through the primary-side flow path practically simultaneously, so that sufficient heat can be transferred to the secondary side.

In order to control or even regulate a valve which controls the fluid flow on the primary side, a temperature sensor is in many cases necessary, with the help of which this kind of regulation can be performed.

Hence, WO 02/070976 A1 shows a heat exchanger of the kind referred to above, in which die temperature sensor exhibits an encapsulated space in which an expandable fluid or an expandable gas is located. This encapsulated space has a temperature-conductive connection to the heat exchanger. It may be arranged either on the outside or also in the middle of the heat exchanger, where it is then acted upon by the temperature on the primary side and the temperature on the secondary side. The fluid or gas which is then displaced from the encapsulated space acts directly on a valve, in order to open or close it. The temperature sensor has an extent in spatial terms which is adapted to the largest area of the heat exchanger. It therefore requires a relatively large installation space and is not readily capable of supplying the information necessary in order to control the flow of heat exchanger fluid through the primary-side flow path. Document WO 01/42729 A1 discloses the preamble of Claim 1.

The problem addressed by the invention is that of specifying a space-saving option for temperature measurement which nevertheless provides satisfactory results.

This problem is solved in a heat exchanger of the kind referred to above, in that the temperature sensor at the return flow connection is arranged within the secondary-side flow path in contact with or at a small distance from the heat transfer surface arrangement.

With this embodiment, the temperature is firstly measured directly in the return flow connection of the secondary-side flow path. The sensor is therefore capable of determining the temperature of the service water which flows through the flow path at the point where the heat transition from the primary side to the secondary side is completed. It is therefore possible with a temperature sensor of this kind for the heat supply to be regulated quickly and accurately based on the fluid flowing through the secondary flow path. The temperature sensor also adopts changes relatively quickly, which do not arise directly in the fluid flowing through the secondary-side flow path, but also in the environment, in particular on the primary side. These influences act via the heat transfer surface arrangement either directly on the temperature sensor, if it is in contact with this heat transfer surface arrangement, or with a small delay, if it is at a small distance therefrom. In any case, a very quick response to a temperature change can be achieved. Direct influencing of the temperature sensor by large metal masses which lie in the region of the fittings on the return flow connection is avoided. These large metal masses react substantially more slowly to temperature changes. Accordingly, no primary fluid is required either in order to heat these fittings. If, for example, the extraction of sendee tvater from the secondary-side flow path is terminated, then the temperature sensor can be heated up more quickly, because it is more effectively influenced from the primary side.

The inlet connection, the outlet connection, the Inflow' connection and the return flow connection preferably form comers of a quadrilateral and the temperature sensor is arranged within the quadrilateral. It is therefore easy to ensure that the temperature influences from the primary side can act on the temperature sensor. The temperature sensor is not therefore “shadowed” by the return flow connection. I f the temperature connections can also act oil the temperature sensor from the primary side, a quicker control and, above all, rapid closure of the valve on the primary side is possible.

The primary-side flow path and the secondary-side flow path preferably have opposing directions of through-flow. Since the temperature sensor is adjacent to the return flow connection of the secondary-side flow path, it is also exposed to the temperature at the inlet connection of the primary-side flow path on account of the opposite flow connections. Hence, when regulating the flow through the primary side, temperature influences from the primary side must also be taken into account, without the temperature sensor having to be completely installed in the primary' side.

The quadrilateral preferably has a relatively longer side and a relatively shorter side from the return flow connection, wherein the inlet connection bounds the relatively shorter side and the temperature sensor is arranged closer to the relatively shorter side than to the relatively longer side. It is thereby guaranteed that the primary-side temperature influence is caused by part of the heat transfer medium flowing through the primary side which flows into the heat exchanger. Through the arrangement of the temperature sensor in relation to the inlet connection, the influencing of the temperature sensor by the temperature on the primary side can be weighted.

The temperature sensor is preferably connected to the wall of the return flow connection in a non-thermally-conductive manner. The wall of the return flow connection is normally formed from a metal, for example brass. If the temperature sensor is not connected in a thermally conductive manner in this case, for example in that it is at a small distance from this wall, then a direct and relatively quick influence on the temperature sensor can be achieved by the fluid at the outlet of the secondary-side flow path. The influence of the larger metal masses with the correspondingly great thermal inertia can, on the other hand, be reduced.

The temperature sensor is preferably configured as an electronic sensor. The electronic sensor therefore produces electrical signals which depend on its temperature. Signals of this kind can easily be further processed electrically, so that the through-flow can be regulated by electrical means. Oth er kinds of temperature sen sors are possible.

The temperature sensor is arranged in a drilled hole in the housing of the heat exchanger. This is a relatively simple option for positioning and mounting the temperature sensor.

The invention is explained in greater d etail below with the help of preferred exemplary embodiments in conjunction with the drawing. In this case

Fig. 1 shows a schematic representation of a heat exchanger,

Fig. 2 shows a second embodiment of a heat exchanger as a schematic representation, Fig. 3 shows a schematic representation explaining the thermal reaction and Fig. 4 shows a schematic representation explaining the position of the temperature sensor in the heat exchanger. A heat exchanger 1 only depicted schematically in Fig. 1 comprises a housing 2 which has an inlet connection 3 and an outlet connection 4 of a primary-side flow path 5 depicted with solid lines and also an inflow" connection 6 and a return flow connection 7 of a secondary-side flow path 8 depicted in dotted lines. The flow" paths 5, 6 lie adjacent to one another across a heat transfer surface arrangement 9.

The depiction in Fig. 1 is only schematic. In real heat exchangers, the primary-side flow" path 5 and the secondary-side flow path 8 are implemented by virtue of the fact that corrugated or bent pieces of sheet metal are placed one against the other with the result that a honeycomb structure is produced in cross section. Some of these “honeycombs” then belong to the primary-side flow path 5, while the remaining “honeycombs” belong to the secondary-side flow path 8. The heat transfer surface arrangement is then formed by the walls of the honeycomb.

The return flow connection 7 is connected to a sendee water extraction point 10 which is depicted by a valve 11 in this case. When the valve 11 is opened, water flows through the secondary-side flow path 8. This water has a low temperature at the inflow connection 6 of 10 to 15°C, for example, and should exhibit a temperature of 50°C, for example, at the extraction point. Accordingly, synchronously with the removal of sendee water from the extraction point 10, it must be ensured that sufficient heat is supplied through the primary-side flow' path 5. A valve 12 is provided to control the flow through the primary-side flow' path 5, said valve being controlled by a control device 13. The control device 13 in turn receives temperature information from a temperature sensor 14 which is arranged at the return flow connection 7. The temperature sensor 14 in this case is inserted in a drill hole 15 in the housing 2 and configured in such a .manner that the temperature sensor 14 is located in the secondary-side flow' path 8. This fiowr path is denoted by the letter “K” in Fig. 4, while the primary-side flow path 5 in Fig. 4 is denoted by the letter “W”. The heat transfer surface arrangement 9 also emerges from Fig. 4. Two options for arranging the temperature sensor 14 are depicted in Fig. 4. On the left side, the temperature sensor 14 is at a certain small distance from the heat transfer surface arrangement 9; on the right side it is in contact with it. Both embodiments allow' the temperature sensor to be influenced by the temperature on the primary side too.

As can be seen from Fig. 1, the inlet connection 3, the return flow' connection 7, the outlet connection 4 and the inflow connection 6 form four comers of a quadrilateral. The temperature sensor 14 is arranged within this quadrilateral. It can also be seen that this quadrilateral has a short side and a long side. The short side in this ease is delimited by the return flow' connection 7 and by the inlet connection 3, for example. The temperature sensor 14 is arranged closer to this short side between the return flow connection 7 and the inlet connection 3 than the long side between the return flow connection 7 and the outlet connection 4. Accordingly, the temperature sensor 14 is mainly acted upon by the temperature in the return flow connection 7. However, it is also acted upon by the temperature of the heat transfer fluid which flows in through the inlet connection 3. A part 5a of the primary-side flow path 5 is depicted in such a manner that it runs past close to the temperature sensor 14. Accordingly, the temperature sensor 14 is acted upon, to a certain extent by heat conduction, also by the temperature of the fluid on the primary side. The heat radiation is only of secondary importance in this case.

The temperature sensor 14 is configured as an electronic sensor. In the simplest case, it is a PTC resistor, the resistance value whereof changes in a temperature-dependent manner. Semiconductor sensors are of course also possible, the current/voltage behaviour whereof changes as a function of the temperature.

The temperature determined by the temperature sensor 14 is evaluated via the control device 13 which controls the valve 12 at the outlet connection 4 as a function of this temperature.

The temperature sensor 14 does not require a large amount of space, which means that the size of the heat exchanger 1 does not have to be increased substantially, even when using a temperature sensor 14 of this kind. The temperature sensor 14 is shadowed by the return flow connection 7. It will preferably be arranged at an angle of 45° to 90° to a connecting line between the return flow connection 7 and the outlet connection 4 or at an angle in the region of 0 to 45° to a line between the inlet connection 3 and the return flow connection 7. The choice of angle co-determines how great the influence of the temperature of the primary side is on the control of the valve 12.

Fig. 2 shows a modified embodiment of a heat exchanger 1. Identical elements and those corresponding to one another are provided with the same reference numbers as in Fig. 1.

Unlike in the embodiment according to Fig. 1, the temperature sensor 14 is no longer configured as an electronic sensor, but as a temperature displacement sensor. It therefore contains a filling, the volume of which differs depending on the temperature. The temperature sensor 14 is connected to the valve 12 via a capillary line 16.

Otherwise, however, the arrangement of the temperature sensor 14 is precisely as depicted in connection with Fig. 1. A further difference is that the inlet connection 3 and the outlet connection 4 are arranged on the same side of the housing 2. On the opposite side, the inflow connection 6 and the return flow connection 7 of the secondary-side flow path 8 are arranged.

It can be seen from the comparison in Figs. 3a and 3b that the standard dead time Td in Fig. 3a, which stretches up to the start of a reaction to temperature changes, is reduced to almost zero (Fig. 3b). The reason for this is that the temperature sensor 14 sits directly in the fluid flow on the secondary side, without it being in contact with larger masses. With an arrangement of the temperature sensor 14 (a plurality of temperature sensors can of course also be used), the response to a temperature change is very much quicker and, depending on the distance from the primary side, said primary side can be included in the regulation.

In the connection region, there will be a larger mass of metal and fluid. In this case the temperature will only balance out slowly. If, however, the temperature sensor 14 is at a distance from the fitting region, then no temperature is required from the primary side, in order to heat this buffer.

Claims (4)

PATENTKRAY 1. Heat exchanger with a primary side flow path (5) located between an input connection (3) and an output connection (4), a secondary side flow path (8) arranged between an inflow connection (6) and a return flow connection ( 7), whereby primary side flow path (5) and secondary side flow path (8) are implemented by corrugated or bent pieces of metal plate facing each other resulting in the formation of a honeycomb structure in cross section. , a heat transfer surface device formed by the walls of honeycombs between the primary side flow path (5) and the secondary side flow path (8), and a temperature sensor (14) whereby the temperature sensor (14) is located in a drilled hole (15) in the housing of the heat exchanger (1), and the temperature sensor (14) is arranged on the return flow connection (7) in the secondary side flow path (8), characterized in that the temperature sensor (14) is placed in contact with heat transfer surface arrays. or at a short distance therefrom. Heat exchanger according to claim 1, characterized in that the input connection (3), the output connection (4), the inflow connection (6) and the return flow connection (7) form corners in a square and the temperature sensor (14) is located inside the square. Heat exchanger according to claim 2, characterized in that the primary side flow path (5) and the secondary side flow path (8) have opposite directed flow. Heat exchanger according to claim 3, characterized in that the square has a relatively long side and a relatively short side, starting from the return flow connection (7), whereby the input connection (3) limits the shorter side and the temperature sensor (14) is placed closer to it. shorter side than the longer side.