WO1996001375A1

WO1996001375A1 - Device for accumulating or guiding liquid

Info

Publication number: WO1996001375A1
Application number: PCT/NL1995/000233
Authority: WO
Inventors: Jan Henk Cnossen
Original assignee: Jan Henk Cnossen
Priority date: 1994-07-01
Filing date: 1995-07-03
Publication date: 1996-01-18
Also published as: CA2170779A1; EP0716725A1

Abstract

The invention relates to a device (1) for accumulating or guiding a liquid under varying pressure, which comprises a container (2) connected to an inlet (4) and an outlet (5). The device (1) comprises at least one elastically compressible body (6) in the container (2). The device comprises enclosing means for enclosing the or each body in the container (2).

Description

DEVICE FOR ACCUMULATING OR GUIDING LIQUID

The invention relates to a device for accumulating or guiding a liquid under varying pressure, which comprises a container connected to an inlet and an outlet.

In a first embodiment such a device forms an accumulator, or expansion tank, which is generally applied in systems in which flows of liquid under pressure are used. Examples hereof are hydraulic installations and cooling and heating installations. Such an accumulator is used in these cases as storage container for the liquid under pressure or to damp pressure peaks.

In a normal central heating device the accumulator is used to absorb the volume changes in the heating water as resulting from variations in temperature of that water. In cooling installations the expansion tank likewise functions to absorb the volume changes in the cooling medium resulting from variations in the temperature of that medium.

Pressure accumulators are usually embodied with a flexible membrane which closes off on one side a space in which the liquid can be absorbed and on the other side is loaded with spring or gas pressure. It is known that the life-span of usual accumulators, particularly of the membrane thereof, is limited. During the total life-span of a central heating installation therefore, the expansion tank has to be replaced a number of times because the membrane has developed a leak. In another embodiment such a device forms a tube in a piping system in which flows of liquid under pressure are again used. In such a system the tubes can for instance be connected to other tubes or flow control elements, such as valves, taps and vents.

A known phenomenon in piping systems comprising valves, taps or vents is the so-called water shock. This phenomenon involves a shock wave moving through the liquid, and therefore through the system, when a valve, tap or vent is abruptly closed or opened.

A drawback hereof is that it results in a loud noise.

Another drawback is that disturbances can be caused in any measuring or control equipment present in the system as a result of the water shock. The structural reliability of the system can also be adversely affected if the water shock occurs regularly over a period of time.

In order to obviate the above stated drawbacks, a device is provided according to the invention which is distinguished by at least one elastic compressible body in the container.

With increasing pressure of the liquid for accumulating or guiding, the volume of the body decreases so that the free volume available for the liquid increases. As the pressure decreases the body again expands.

In a preferred embodiment of the invention the container forms a heat exchanger, for example a convector in a heating installation or a condenser in a cooling installation. When a heat exchanger with the properties of a device according to the invention is incorporated in such a system, it fulfills the function of the accumulator or expansion tank, thus doing away with the need for a separate accumulator or expansion tank. This provides a particular advantage with regard to the cost and complexity of the system.

The body is preferably manufactured from a foam - material with a closed cell structure. Materials suitable for application in the invention are polyethylene foam, ethylene-vinyl-acetate foam and foamed silicone rubber and the like. The choice of the material depends inter alia on the operating temperature, the compatibility with the liquid for accumulating and the maximum pressure occurring.

The invention will be further elucidated in the following description with reference to the annexed figures.

Figure l shows in partly broken away perspective view a device according to the invention embodied as expansion tank in a heating installation. Figure 2 shows a diagram of a central heating system in which is incorporated the expansion tank shown in figure 1.

Figure 3 shows the graph of the expansion of CH water plotted against the temperature. Figure 4 shows a partly broken away perspective view of a device according to the invention, which is embodied as heating convector.

Figure 5 shows schematically an example of a hydraulic device in which a device according to the invention is applied.

The accumulator 1 shown in figure 1 is intended to function as expansion tank in a CH installation. The device 1 consists of tank 2 which encloses a space 3. By means of a connection 4 CH water can flow via the inlet/outlet 5 into this space 3 and then out again therefrom.

In the preferred embodiment of the invention shown here the body is formed by a block of foam material 6 with a closed cell structure, which block of foam material 6 is received in space 3 and fixed to the inlet/outlet 5, wherein the block of foam material 6 hangs in the space 3 so that in the embodiment shown here the inlet/outlet 5 forms the fixing means for the block of foam material 6. This foam material 6 is for example polyethylene foam with a closed cell structure. Because the foam material 6 has a closed cell structure, it does not absorb any significant amount of water, so that it remains operational as expansion body for a long period. The foam material 6 has a structure, in particular a cell size, such that it can be compressed well with the occurring pressures.

Figure 2 shows schematically a CH installation 10 with a heating boiler 11, to which a piping system 13 is connected. The CH water is pumped round the piping system 13 by means of a pump 12. A plurality of heating convectors 14 is incorporated in the piping system in the usual manner. If the accumulator 1 is arranged at or close to the highest point of the installation 10, the pressure of the CH water at this location will vary between a minimum of 0.5 bar and a maximum of 3 bar. With placing at a lower level these pressures are higher, corresponding with the height of the water column above the expansion tank.

As shown in figure 3, the water expands by about 3% with an increase in temperature from 10 to 80"C. The accumulator must therefore have a capacity which is at least equal to 3% of the volume of the CH system. If it is further given that, as described above, the minimum pressure amounts to about 0.5 bar and the maximum pressure amounts to 3 bar, the desired elasticity and the desired volume of the foam material are simple to calculate.

As figure 4 shows, the accumulator according to the invention can be embodied in favourable manner as heating convector. A separate expansion tank can then be dispensed with. The convector 20 of figure 4 comprises in the usual manner a feed connection 21 which is connected to a feed pipe via a tap 22, and a drain connection 23. Defined in the convector 20 is a space 24 through which the heating water flows. A body formed from a quantity of foam material 25 with a closed cell structure is received in this space.

By embodying the accumulator according to the invention in this manner, it becomes possible to arrange a very large volume of foam material in the system in simple manner. The requirement of the smallest possible volume, which must be met by a separate expansion tank, is hereby no longer of any importance. The foam material can in that case be optimized in respect of other requirements, such as cost price.

Depending on the choice of the foam material, the device according to the invention can operate at a diversity of pressures. The device according to the invention can thus also be applied as accumulator 36 in a hydraulic system 30 as shown schematically in figure 5. In this hydraulic system 30 a pump 32 carries hydraulic oil under pressure out of a reservoir 31. The oil under pressure is stored in the accumulator 36 according to the invention. The maximum pressure is limited using a pressure-relief valve 35. By operating a valve 34 a hydraulic motor 33 can be fed uniformly with oil under pressure.

This hydraulic system is only given as an indication. In any installation operating with liquid under pressure, wherein it is desired to store this liquid under pressure, an accumulator can be used which forms an accumulator according to the invention with the said advantages.

It is self-evident that the invention is not limited to the above described embodiments.

In the above described embodiments of the invention the container comprises one body placed in the interior thereof which is manufactured from foam material with a closed cell structure and occupies a large part of the available volume in the container. It is however also possible for a large number of smaller elements to be placed in the container. In this latter case the device comprises enclosing means for the elements in order to prevent these elements falling into the liquid system. These enclosing means can be formed by a partition between the space in the tank and the outlet through which the liquid can flow unobstructed. In an embodiment (not shown) of a device according to the invention the container comprises one or more than one body, wherein the or each body is placed in an elastically expandable shell closed off from the liquid as embodiment of the enclosing means, which shell is fixed to the inner wall of the container. In this case it is not required that the or each elastically compressible body be manufactured from foam material with a closed cell structure, whereby a larger number of materials are suitable for use.

When such a shell forms a tensioned partition in the container, this fulfills the function of membrane, such as in known expansion tanks, wherein the or each body provides the necessary counter-pressure as a result of the elastic compressibility thereof. Also in this case the or each body does not have to be made from a foam material with a closed cell structure, provided the membrane is water-tight. The body can be arranged in the container in pre- compressed state. In this case the compression of the body begins above a determined minimum pressure corresponding to the degree of pre-compression.

When a device according to the invention is applied in the embodiment of a tube through which liquid flows and which is incorporated in a system with flow control elements, the body is preferably placed close to a connection to such a flow control element or to another element in the tube to damp water shock. The body herein preferably forms a layer which is fixed to the inner wall of the tube, which covers the inner surface wholly or partially in radial direction at that location and which extends from the connection in axial direction over a distance which is at most equal to the length of the tube. When such a layer extends in axial and radial direction over the entire inner surface of the tube, it is suitable to serve as thermal insulation, in addition to the use as insulation against shock waves manifesting themselves for instance as water shock. Alternatively or additionally, a body can have an elongate form and be arranged in floating suspension in the flow to the inside wall of the tube.

Claims

1. Device for accumulating or guiding a liquid under varying pressure, which comprises a container connected to an inlet and an outlet, characterized by at least one elastically compressible body in the container.

2. Device as claimed in claim 1, characterized by enclosing means for enclosing the or each body in the container.

3. Device as claimed in claim 1 or 2, characterized by fixing means for fixing at least one body at a fixed position in the container.

4. Device as claimed in any of the foregoing claims, characterized in that the body is in a pre-compressed state in order to be compressible only above a threshold value of the pressure.

5. Device as claimed in any of the foregoing claims, characterized in that the body takes the form of a layer at least partially covering the inner wall of the container.

6. Device as claimed in any of the foregoing claims, characterized in that the container forms an expansion tank in a temperature control system.

7. Device as claimed in claim 6, characterized in that the expansion tank forms a heat exchanging element.

8. Device as claimed in any of the foregoing claims, characterized in that the container forms a tube in a tube assembly, wherein at least one body extending in axial direction is fixed at least close to an end of the tube.

9. Device as claimed in claim 8, characterized in that the body takes the form of a layer at least partially covering the inner surface of the tube in radial direction.

10. Device as claimed in any of the foregoing claims, characterized in that the body comprises foam material with a closed cell structure.

11. Device as claimed in claim 10, characterized in that the body contains ethylene-vinyl-acetate foam.

12. Device as claimed in claim 10 or 11, characterized in that the body contains silicone rubber.

13. Device as claimed in claim 10, 11 or 12, characterized in that the body contains polyethylene foam.

14. Tube assembly for transporting a liquid which comprises at least one tube, characterized in that the tube comprises a device as claimed in any of the claims 1 to 13.