HK1015021B - A method for expansion control in a closed fluid circulation system and a closed fluid circulation system for carrying out such a method - Google Patents

Description

Closed liquid circulation system and expansion control method thereof

Technical Field

The present invention relates to a method for controlling the expansion of a closed liquid circulation system with variable temperature, and to a closed liquid circulation system in which the method can be implemented.

Background

Such a method is well known in central heating projects and measures to compensate for liquid expansion and contraction upon temperature changes usually comprise an expansion tank divided by a diaphragm into two separate spaces, one space being in communication with a network of pipes and the other space containing a gas, whereby the change in volume of liquid due to a change in temperature of the liquid can be compensated for by moving the diaphragm to cause the gas to compress and expand. Automatic venting may be achieved using a float controlled valve, one such example being U.S. patent 4,027,691.

In such a liquid circulation system, liquid leakage is practically always present, although usually only to a slight extent, the liquid used in the central heating system is water due to the small amount of liquid leakage, which evaporates almost directly after leakage, and it is often difficult to determine the location of the leakage. Therefore, the compensation function of the expansion tank cannot be exerted, and the pressure of the closed system may be reduced below the minimum pressure, which may cause the heating system to malfunction, and various unpleasant accidents may occur, such as too low temperature in the room and even pipeline freezing. The leakage of liquid also causes air to enter, which can be automatically vented if a float controlled vent valve corresponding to us 4,027,691 is installed, which also serves to depressurize the closed system. If the system is to be maintained in proper operation, the pressure should be checked regularly and the liquid replenished if necessary, which is a laborious and wet operation.

Disclosure of Invention

It is an object of the present invention to provide a method of expansion control for a closed fluid circulation system which can be operated automatically and continuously without periodic monitoring.

Another object of the invention is to achieve expansion control in a manner that is as simple and cost-effective as possible.

The present invention provides a method for expansion control in a closed, variable temperature liquid circulation system, in which system, the air or other gases present are separated from the circulating liquid by means of an air or gas head, in which the separated air or gas is collected, which can be discharged to the surroundings or a storage space by means of the control of a valve, meanwhile, measures for compensating the corresponding expansion and contraction of the liquid in the closed system when the temperature changes and measures for extracting the liquid from an external liquid source with pressure and adding the liquid into the system are also adopted, wherein the volume of the air or gas head is monitored by detecting the boundary between the air or gas head and the liquid, when the volume exceeds the set value, the liquid valve is opened, and liquid is introduced into the air or gas head through the liquid valve until the liquid valve is closed when the volume of the air head is again equal to the set value. By these measures, the liquid can be replenished automatically as long as the liquid volume in the closed system is below a predetermined minimum value, so that system malfunctions due to too low a pressure can be prevented.

Since the air or gas head is in direct communication with the liquid circulating in the circulation system, it always occurs that the liquid is below a set minimum value when the temperature of the circulating liquid and its corresponding pressure are the lowest. The pressure difference between the air or gas head and the replenishing liquid is then at its greatest and advantageously greater, as a result of which the majority of the gas in the liquid replenished into the air or gas head has been removed directly. For example, if the temperature of water is 100 ℃, the possible air absorption rate is reduced from 115 per cubic meter to 25 liters per cubic meter, i.e. 70%, when the pressure is reduced from 5 bar absolute to 1.5 bar absolute. The gases separated from the make-up liquid are collected directly in the air or gas head, where they are still in the circulation system. If the system pressure exceeds the set value due to the re-rising temperature of the circulating liquid, the dedicated valve will open and the gas separated from the make-up liquid will be discharged to the surroundings.

Since the air or gas head is directly connected to the liquid circulation system, when the liquid level in the air or gas head drops, for example due to leakage, the liquid can be replenished by a convenient, simple and reliable method according to another embodiment of the present invention, the volume of the air or gas head is monitored by a float connected to the liquid supply valve, the liquid supply valve is opened when the float is lower than a set height, the liquid supply valve is closed when the liquid level of the replenishing liquid rises to the set height, and the float and the valve are arranged such that the float does not affect the closed state of the liquid supply valve when the liquid level is higher than the set height. In this way, an effective and very reliable replenishment is achieved in a particularly simple manner. The float has the additional advantage that it reduces the area of the free surface of the water and thus reduces the chance of air being absorbed in the air or gas head, which, although it can be seen is in direct communication with the circulation system, is already completely outside the circulation circuit and thus is already small.

It is clear that the level of liquid in the air or gas head varies with the temperature of the circulating liquid, with virtually no gas absorption at its level. These conditions can be utilized and according to another preferred embodiment of the invention the air or gas head is dimensioned to be sufficiently large that during normal operation of the liquid circulation system its volume is larger than the maximum expansion volume calculated on the basis of the total amount of liquid in the liquid circulation system and the maximum temperature that can occur in the liquid during normal operation. By taking these measures, the usual built-in expansion tank with membrane can be dispensed with, since this function is already included in the air or gas head. Thus, the integrated control of continuous automatic exhaust, liquid replenishment, and expansion control can be achieved by a relatively extremely simple method.

According to another embodiment of the invention, the air or gas separated from the liquid is discharged from the air or gas head to the surroundings via an overpressure valve attached to the air or gas head, with which valve the maximum working pressure in the liquid circulation system can be defined. Thus, an overvoltage protection function is added.

According to a further embodiment of the invention, an air or gas head is provided on the bypass path, which can be easily temporarily disconnected from the circulation system for maintenance, e.g. cleaning. If the liquid circulation is performed by a pump and the inlet and outlet of the bypass channel are connected to the respective ends of the pump, the optimum static liquid level can be obtained in the air or gas head on the one hand, and the microbubbles can be trapped as quickly as possible at the place where the most microbubbles are generated, i.e., the circulation pump, on the other hand, thus forming an optimum exhaust system. For the same reason, the air or gas head is preferably located immediately adjacent to the location where the temperature of the circulating liquid is highest during normal operation.

The invention also relates to a closed liquid circulation system, which comprises a heating device, a pipeline network connected with the heating device and provided with an expansion device capable of compensating the expansion and contraction of the liquid in the closed system, and an automatic valve control exhaust device provided with a short pipe with one end communicated with the pipeline of the network and the other end closed with the outside, wherein the closed end of the short pipe is provided with an exhaust valve, and a floater capable of moving longitudinally is arranged in the short pipe. Such a liquid circulation system with an expansion tank is common in central heating applications and can be seen in us patent 4,027,691, which describes in detail an automatic valve-controlled air release arrangement. According to the invention, in order to achieve a combined degassing and replenishing function in such a system, the replenishing valve should be in communication with the closing end, the replenishing valve comprising a lever connected to the float, the lever opening the valve when the distance between the float and the lever exceeds a set value, and the lever remaining closed when the distance between the float and the lever is equal to or less than the set value. Thus, automatic liquid level control or volume control can be conveniently realized by using the exhaust device to supplement liquid.

The distance between the float and the control rod is set so that the volume of the short pipe corresponding to the set value between the float and the control rod is greater than the maximum expansion volume calculated according to the total liquid amount in the liquid circulation system and the possible maximum temperature difference of the liquid, so that the system combining exhaust and liquid supplement has the expansion control function, a diaphragm expansion tank can be omitted, the cost can be reduced due to the fact that the expansion tank is prone to failure, and the service life of the system is relatively short compared with the service life of the whole system. The short life is due, inter alia, to the rupture of the membrane, in which case the entire expansion vessel is usually replaced and the system, at least a part of it, is also emptied, which entails corresponding costs and operations. In the construction of the invention, such a diaphragm is not present, nor is it replaced by an element which is likewise susceptible to failure, so that the life of the expansion control and regulation device is greatly increased.

For a large volume liquid circulation system, i.e. the circulation system contains more liquid, the expansion volume is relatively large. In this case, according to another embodiment of the invention, it is preferable to add at least one further short pipe close to the short pipe, which short pipe communicates with the first short pipe at a position below the float and close to the closed end by means of a connecting member, the distance between the float and the control rod being set at a value such that the total volume of the short pipes between the float and the control rod corresponding to the value is greater than the maximum expansion calculated from the total volume of liquid in the liquid circulation system and the maximum temperature difference possible for the liquid in normal operation. By these measures a larger expansion volume can be obtained without leading to the use of a large volume tank or container. And with these measures it is in fact possible to use standard devices, to which a suitable number of short pipes are connected to adapt the expansion volume required by a specific system, to perform the combined functions of degassing, fluid infusion and expansion control.

In the automatic vent apparatus of us patent 4,027,691, the air release valve is controlled by a float. In the closed liquid circulation system according to the present invention, the float is used to control the replenishment valve. Although the float may be used to open the vent valve according to another embodiment of the invention, it is preferable to provide a vent valve at or near the closed end of the spool that opens when a set value is exceeded. This allows for replenishment of the liquid when necessary by means of a float-controlled valve, where the temperature of the circulating liquid is generally low, and the air or gas head is compressed by the expanding liquid during venting, where the temperature is relatively high. And the exhaust valve can also be provided with an overpressure protection device.

Drawings

Some possible implementations of the method and system of the present invention will be further discussed in conjunction with the embodiments shown in the figures, in which:

FIG. 1 is a cross-sectional view of a first system configuration in accordance with the present invention;

FIG. 2 is a schematic view of a first embodiment of a heating structure with a built-in system corresponding to FIG. 1;

FIG. 3 is a schematic view of a second embodiment of a heating structure with a built-in system corresponding to FIG. 1;

fig. 4 is a cross-sectional view of a second system configuration according to the invention.

Detailed Description

The system shown in fig. 1 comprises a cylindrical housing 1 with a top cover 2 and a bottom cover 3, the volume of the housing 1 being larger than the total amount of possible liquid expansion of the closed circulation system.

A cylindrical head 4 with a short tube 5 is mounted on the top cover 2, the short tube 5 has a valve 6, one end of which is connected to a water pipe 7, and the other end is connected to a control lever 8 which is turned downward to open the valve 6. The end of the control rod 8 remote from the valve 6 is suspended with a float rod 9, the float rod 9 is connected with a float positioned below the perforated plate 11, and the float rod 9 can freely slide in the hole of the perforated plate. The head 4 is also provided with an exhaust valve 12 which is overpressure retaining.

The T-piece 13 is connected to the bottom cover 3, and its short pipe 14 is connected in a straight line to a closed liquid circulation system (not shown). In the transverse part of the T-piece the tube 15 extends centrally to a position between the short tubes 14, and the wire 16 is wound in a double spiral over the tube 15. The steel wire 16 catches micro-bubbles in the flowing liquid and guides them upwards into the housing 1.

In fig. 2, a heating boiler 17 is hung on a wall, and hot water is supplied to a heating body 19 through a pipe 18. The heat is dissipated and the water flows back to the boiler 17 through the line 20. The T-piece 13 is connected into a pipe 18. As mentioned before, the volume of the housing 1 should be controlled to the maximum possible difference in volume of the cycle, i.e. the volume of water at the highest temperature minus the volume of water at the lowest temperature, the highest and lowest temperatures being the set values in operation. The head 4 of the housing 1 is connected to a tap 21 via a valve 6 and a conduit 7. Connected to the exhaust valve 12 of the head 4 is a conduit 22 which carries a moisture detector 23 which leads to a drainage system such as a sewer well (not shown).

In the heating device corresponding to fig. 2, the system of fig. 1 is able to compensate for the expansion of the circulating liquid, to automatically vent, and to automatically replenish the liquid in the event of a leak.

Under normal operating conditions, the liquid level at the lowest operating temperature is approximately at the position of the float 10 in fig. 1. If the temperature rises, the liquid expands and the level of the liquid in the housing 1 rises, while the plate 11 remains floating on the surface of the liquid, so that the free liquid surface area is relatively small. Accordingly, the gas above the liquid level is compressed. If the amount of gas trapped by the tube 15 with the wire 16 and fed into the shell 1 reaches a certain level, the discharge valve 12 is opened to discharge the gas when the pressure reaches a certain value during the compression process, and the discharged gas is discharged through the line 22.

If the temperature of the circulating liquid drops and, due to leakage liquid, escapes from the heating device, the liquid level will drop below the plate 11. If the liquid level drops further, the float 10 falls and opens the valve 6 to allow new liquid to be replenished through the line 7. The temperature and the corresponding pressure of the liquid in the housing 1 are then low. The replenished liquid thus undergoes a pressure drop, i.e. a direct, extensive degassing process. Residual gas in the top of the housing 1 and in the head 4 is vented through a valve 12 at the appropriate time.

In fig. 3, the system of fig. 1 is adapted for use with a large volume heating device. For this purpose more housings 24 are used, the top of which communicates with the head 4 via a duct 25 and the bottom of which communicates with the T-piece 13 via a duct 26. If the volume of each individual housing 24 is equal to the volume of the housing 1, the amount of expansion is increased by a factor of three. In this embodiment the T-piece 13 is connected to a line 29 from a boiler 28 via a bypass channel 27, which bypass channel 27 connects across a circulation pump 30 and can be disconnected from the circulation system by means of a valve 31, for example in connection with maintenance.

Fig. 4 is another version of the system of fig. 1. The housing 1 is actually omitted and the head 4 ' is connected directly to the T-shaped pipe 13 ', the pipe 13 ' also having a pipe 15 with steel wires 16. The float 10 'can, if necessary, be replenished with water in the line 7 by opening the valve 6 via the float rod 9' and the control lever. Due to the relatively small size of the head 4', the expansion volume of the head is not large enough. To obtain a sufficiently large expansion volume, a cylindrical housing 32 is provided, the centre line of which is in horizontal direction and the bottom surface of which is approximately at the level of the lowest position of the float 10'. The volume of the housing 32 can be set to the desired expansion volume. The bottom surface of the housing 32 communicates with the bottom surface of the T-shaped pipe 13 'via a pipe line 33, so that the pipe 13' is provided with a joint 34 at the location of the pipe 15. And the top of the housing 32 communicates with the top of the head 4' through a conduit 35. A vent valve 12' is also provided at the top of the housing 32 to vent excess gas from the heating device.

This modified embodiment operates in the same manner as described above in connection with the system of fig. 1, and further discussion may be omitted.

Naturally, many modifications and variations are possible within the scope of the invention as defined in the appended claims.

Claims (13)

1. A method for controlling the expansion of a closed liquid circulation system with variable temperature, in which system, the air or other gases present are separated from the circulating liquid by means of an air or gas head, in which the separated air or gas is collected, which can be discharged to the surroundings or a storage space by means of the control of a valve, meanwhile, measures for compensating the corresponding expansion and contraction of the liquid in the closed system when the temperature changes are adopted, and means (6-10) for withdrawing liquid from an external source (7) of liquid under pressure and for adding liquid to the system, it is characterized in that the volume of the air or gas head is monitored by detecting the boundary between the air or gas head and the liquid, when the volume exceeds the set value, the liquid valve is opened and liquid is introduced into the air or gas head through the liquid valve (6) until the liquid valve is closed when the volume of the air head again equals the set value.

2. A method according to claim 1, characterized in that the volume of the air or gas head is monitored by means of a float (10; 10 ') connected to the liquid supply valve (6) so that the latter is open when the float is lowered below a set position and is closed when the liquid level rises to a set position by the replenishing liquid, the condition of the connection (8, 9; 8, 9') between the float and the valve being such that the float does not affect the closed condition of the liquid supply valve at any liquid level above the set position.

3. Method according to claim 1 or 2, characterized in that the air or gas head is of a sufficiently large size that, in normal operation of the liquid circulation system (17-20), its volume is larger than the maximum expansion volume calculated on the basis of the total amount of liquid in the liquid circulation system and the maximum temperature of the liquid in normal operation.

4. Method according to claim 1, characterized in that the air or gas separated from the liquid is discharged through an overpressure valve (12; 12') mounted on the air or gas head, by means of which valve the maximum operating pressure in the liquid circulation system (17-20) can be set.

5. A method according to claim 1, characterized in that the air or gas head takes the form of a bypass channel (27).

6. A method according to claim 5, characterized in that the circulation of the liquid is effected by means of a pump (30), the inlet and outlet of the bypass channel (27) being provided at each end of the pump.

7. A method according to claim 1, characterized in that the air or gas head is arranged at least directly adjacent to the location (17; 28) where the temperature of the circulating liquid is highest during normal operation.

8. A closed fluid circulation system comprising heating means (17; 28), a network of pipes (18; 20; 29) communicating with the heating means and provided with expansion means compensating for the expansion and contraction of the fluid in the closed system, and an automatic valve-controlled venting means provided with a pipe stub (1, 4, 13; 4 ', 13 ', 32) communicating at one end with the network pipe (18; 29) and at the other end closed off from the outside, and provided with a venting valve (12; 12 ') at the closed end of the pipe stub, and provided with a longitudinally movable float (10; 10 ') in the pipe stub, characterized in that a fluid supply valve (6) is communicating with the closed end, the fluid supply valve comprising a control rod (8) connected to the float (10; 10 '), which rod opens the valve when the distance between the float and the rod exceeds a set value and which rod is equal to or less than the set value, the control lever maintains the valve in a closed state.

9. A closed fluid circulation system according to claim 8, characterized in that the distance between the float (10; 10 ') and the control rod (8) is set such that the volume of the pipe stub (1; 4') between the float and the control rod corresponding to the set value is larger than the maximum expansion volume calculated from the total amount of fluid in the fluid circulation system and the maximum temperature difference of the fluid in normal operation.

10. The closed fluid circulation system according to claim 8, characterized in that near the short pipe (1; 4 ') there is provided at least one further connection (25; 35), the short pipe (24; 32) communicating with the first short pipe below the float and near the closed end, the distance between the float (10; 10 ') and the control rod being set such that the sum of the volumes between the float and the control rod (8) of all short pipes (1, 24; 4 ', 32) corresponding to the set value is greater than the maximum expansion volume calculated from the total amount of fluid in the fluid circulation system and the maximum temperature difference of the fluid during normal operation.

11. The closed fluid circulation system according to claim 8, wherein a vent valve (12) openable above a set value is provided at or near the closed end of the short pipe (1; 4').

12. The closed fluid circulation system according to claim 8, wherein the open end of the stub pipe (13) communicates with a bypass passage (27) of a piping network (29).

13. The closed liquid circulation system according to claim 12, wherein the circulation pump (30) communicates with the piping network (29) at a location close to the heating means, and the bypass passage (27) is bridged with the pump.