EP2281151B1

EP2281151B1 - Heating system with expansion device

Info

Publication number: EP2281151B1
Application number: EP09734468.3A
Authority: EP
Inventors: Dimitri Wasil Kemper; Jan Henk Cnossen
Original assignee: Flamco BV
Current assignee: Flamco BV
Priority date: 2008-04-24
Filing date: 2009-04-22
Publication date: 2018-06-06
Anticipated expiration: 2029-04-22
Also published as: NL1036252C2; WO2009131450A2; EP2281151A2; WO2009131450A3

Description

The invention relates to a heat transport system with an assembly of a cold or heat source having connected thereto a conduit system with heat exchangers, and an expansion device connected to the assembly. The heat transport system is here of a type which functions with a closed liquid circuit along the heat exchangers and the cold or heat source and under pressure during operation.
Incorporated on the one hand as source in the liquid circuit is a heating boiler or cold pump or the like in which heat or cold is fed to the liquid circulating in the circuit. Incorporated on the other hand in the liquid circuit are radiators and/or convectors or other heat exchangers by means of which cold or heat is relinquished from the liquid to spaces for cooling or heating.
An air transport system can be applied instead of or in addition to convectors and radiators.
The invention likewise relates to a cooling installation although, for the sake of the readability of the application, the invention is described herein below only with reference to a heating device.
Devices of this type comprise an expansion device, usually comprising a liquid reservoir or expansion tank, which takes up the extra volume of liquid created by expansion resulting from heating of the liquid. When the liquid in the liquid circuit in the assembly cools, liquid is carried back again from the reservoir into the circuit in the assembly so as to compensate for the decrease in volume due to this cooling.
A safety valve is mounted in order to prevent an overpressure in the liquid circuit or the assembly. A heating device of this type is described in the European patent (application)s EP 0947777 and EP 0740759 or NL 9400106 .
A feature of this expansion device known from said documents is that a lower pressure prevails in the reservoir or expansion tank relative to the pressure in the liquid circuit (assembly). For this reason a pump is used to return liquid into the assembly with the liquid circuit during cooling. This pump is situated in a connecting conduit between the assembly with the liquid circuit and the expansion device, and is intended to overcome the pressure difference between the liquid in the reservoir of the expansion device and the liquid in the assembly with the liquid circuit. In order to take up liquid from the assembly with the liquid circuit, during heating of the liquid and the resulting volume increase, use is made of the higher pressure in the assembly with the liquid circuit. By opening of a valve present for this purpose in the connecting conduit between the assembly with the liquid circuit and the expansion device, the liquid can flow into the expansion device from the assembly with the liquid circuit where the higher pressure prevails, to the expansion tank or reservoir of the expansion device until the pressure in the assembly with the liquid circuit has reached a desired lower value.
The pump and the valve can be activated by a switch mechanism or control, wherein a small decrease or increase in pressure in the assembly with the liquid circuit activates respectively the pump or the valve. The valve must be equipped for this purpose with an auxiliary drive. The pressure regulation of the assembly with the liquid circuit has hereby become automatic. The pressure of the liquid in the assembly will continue to be held constant within a desired, usually small bandwidth.
A great problem in dimensioning of the pump and the valve in the known configurations is that undesirable hydraulic effects can occur. If a pump capacity is too great, a pressure can rise uncontrollably high in the assembly with the liquid circuit. Too small a choice of pump capacity has the consequence that, as a result of the decrease in the liquid volume, the cooling process in the assembly with the liquid circuit cannot be followed, resulting in too low a pressure in the assembly with the liquid circuit.
A similar problem applies for the valve in the connecting conduit between the assembly with the liquid circuit and the expansion device. A valve dimensioned too large allows the pressure in the assembly with the liquid circuit to fall uncontrolledly quickly. With a valve dimensioned too small, pressure in the assembly with the liquid circuit can possibly rise too high when, due to rapid heating, the expansion of the liquid in the assembly with the liquid circuit proceeds more rapidly than the quantity of liquid which can be discharged via the valve from the assembly with the liquid circuit to the reservoir or expansion tank of the expansion device. In both cases control of the pressure in the assembly with the liquid circuit will not be achieved without problem, and undesirable defects can occur as a result of extreme pressure peaks.
Both the pump and the valve in the connecting conduit between the assembly with the liquid circuit and the expansion device are in practice usually dimensioned too large, and are subsequently modified to the specific conditions by additional measures. For a pump such a measure can consist of a soft-start control with which the pump motor is brought slowly to speed, or a load-dependent rotation speed control by means of for instance a frequency converter. A hand-operated second valve with choke function can be arranged connected in series to the valve in order to realize a desired liquid speed.
Another problem of known heating systems or an entirely different order relates to the setting into operation of an expansion device of this type with pump and valve. When the pump still contains air, it functions poorly or not at all. The hydraulic properties of a pump are only shown to advantage when the pump is fully filled with liquid and contains no air or gas.
Moreover, it is acknowledged that from US-5007583 , EP-0945686 and/or EP-1855060 , DE 4407936 , EP 1102012 and FR 2505459 systems are known according to the preamble of claim 1 or 4. In these known systems a configuration is provided with which in a simple manner an optimized effective liquid flow can be found in the assembly, both during the pump action or the intake action via the valve, and whereby the pump in determined preferred embodiments can moreover be automatically vented, by placing a valve with variable opening between the assembly with the liquid circuit and the valve. it has become possible to regulate the liquid flow in both directions with a standard pump.
According to the invention the additional features from the characterizing portion of the appended independent claim are provided, that the expansion device comprises an expansion tank with a pump connected thereto for the purpose of carrying heat transfer fluid selectively to the assembly during operation of the pump, and that the valve with variable opening is connected via a check valve to a suction side of the pump, between supply and return conduits connecting the tank with the system. This allows for the thus new and inventive configuration to function without rotation speed control and a standard valve without an additional valve with choke function. With the invention it has become possible using a standard pump unit (pump with valve) to adapt automatically to any hydraulic situation (pressure and volume). Moreover, the pump can always start substantially without pressure difference. Thus, it has become very simple to expel possible air inclusions in the pump. This is because the system pressure is available here at both the suction side and the pressure side of the pump, whereby the pump action, after switch-on, generates sufficient thrust to discharge via (float) vent any air possibly still present in the pump housing.
The air present in pump is however discharged even without (float) vent, but then disappears into the system and is subsequently removed via system vent(s), or will eventually be degassed as a result of the improved degassing measures according to the invention.
Preferred embodiments of the invention are defined in the dependent claims.
In order to elucidate the invention several embodiments of the invention are further described herein below by way of example, and not for the purpose of limiting the invention, with reference to the accompanying drawing, in which the same or similar parts, components and aspects are designated with the same reference numerals, and in which:

Figure 1 shows a heating installation 24 with an expansion provision 1 in an embodiment according to the invention;
Figure 2 shows a heating installation 24 with conventional expansion provision 2;
Figure 3 shows an example relating to a circuit of valve 24 with variable passage in an embodiment according to the invention;
Figure 4 shows a detail of an alternative embodiment relative to that of figure 1, not covered by the invention;
Figure 5 shows an additional embodiment relative to that of figure 4, not covered by the invention;
Figure 6 shows an alternative embodiment relative to figure 1;
Figures 7 and 8 show operating modes in separate operating situations of the expansion device in the heating system according to the invention;
Figure 9 shows an additional alternative embodiment with some similarity to that of figure 6;
Figure 10 and Figure 11 show further embodiments not covered by the invention.

Figure 1 shows how automatic pressure regulation takes place in hydraulic-mechanical manner in expansion device 1 according to the invention. A pressure sensor 11 transmits the system pressure in the assembly with liquid circuit 25 to a usually electronically controlled (not shown) control unit with which expansion device 1 is actuated. Because of temperature variations in the assembly with liquid circuit 25, the volume of the liquid present therein is subject to changes. An increase in the liquid volume will cause a pressure increase in the assembly with liquid circuit 25, and the reverse takes place when the liquid volume decreases. By means of an interplay of pump 4 and a valve 24 with variable passage, in particular controllable valve 5 in combination with valve 24, the liquid volume in liquid circuit 25, and consequently the system pressure therein, can be held almost constant, or at least constant within a predetermined bandwidth.
Figure 3 shows the overall control of the pressure regulation. On the x-axis of figure 3 is shown the cycle time T and on the y-axis the system pressure P. The ideal system pressure is shown on the horizontal line indicated with S. The immediately adjacent lines parallel to this line are those at which valve 24 with variable passage is activated. The parallel outer lines relate to the extreme (upper and lower) limit values for the installation pressure in the assembly with liquid circuit 25 which is still allowable relative to the ideal pressure according to line S in the graph of figure 3. If we follow the curved broken line, which symbolizes an imaginary system pressure reading from pressure sensor 11, upward from the left, we then see how, when the first parallel line is passed, valve 24 with variable passage is activated to the 'closed' position. As soon as the system pressure has reached the extreme (upper) limit value for the installation pressure in liquid circuit 25, valve 5 is opened and simultaneously herewith valve 24 with variable passage is activated to the 'open' position (from the closed position). The variable passage of valve 24 will always reciprocate in slowed manner from the closed position to the opened position, and vice versa. Particular use is made according to the present invention of this slowing effect (slow reciprocation between closed and open), in addition to the possibility of fixedly holding any intermediate position. A time duration between the open and closed position of the variable passage of valve 24 can amount to as much as about 10 seconds or more, although a shorter time duration need not be a problem. In the case of a faster action valve the movement of the drive can after all be repeatedly interrupted.
In the embodiment according to figure 1 use is made of electrically actuated valves 5, 24, although it is also possible to opt for pneumatic or hydraulic drives.
It is then easy to establish in figure 1 how the liquid flow from the assembly with liquid circuit 25 will slowly begin to move in the direction of reservoir 3 of expansion device 1 forming an expansion tank, as a valve 24 with variable opening is opened slowly or is at least gradually opened increasingly further. As soon as a desired pressure drop has been reached in the system pressure in the assembly with liquid circuit 25 (or rather the desired system pressure), the variable opening of valve 24 remains in the position reached. Valve 5 closes at the moment the ideal system pressure is reached in liquid circuit 25. The variable opening of valve 24 is activated (further) to the 'open' position as soon as the first parallel line below the ideal pressure line is reached. Pump 4 is activated when the extreme (lower) limit value for the system pressure in the assembly with liquid circuit 24 has been reached. Valve 24 is also activated, with variable opening from fully open to the closed position.
Figure 1 subsequently shows how the liquid can be circulated via connecting conduits 6 and 7 and the assembly with liquid circuit 25 without the installation pressure changing. This is possible because the variable opening of valve 24 is still situated in opened position. By making the variable passage of valve 24 smaller, the desired pressure increase in the system pressure in liquid circuit 25 is eventually reached or, if this takes place sooner, the desired system pressure. The variable opening of valve 24 remains in the position reached.
As soon as the desired system pressure in the assembly with liquid circuit 25 has been reached, pump 4 stops and the variable passage of valve 24 closes completely.
During a process wherein the temperature in the assembly with liquid circuit 25 varies, and consequently the liquid volume continuously changes, the system pressure will move dynamically between the extreme limit values as illustrated in figure 3, and continuously repeat a switching pattern as described above.
The importance of the invention according to figure 1 becomes most clearly manifest when it is compared with figure 2, which shows a liquid circuit 25 with a conventional expansion device 2 without the new valve with variable passage 24.
A particular feature of expansion device 1 in figure 1 is that reservoir 3 is embodied without membrane 27 as utilized in the known configuration according to figure 2. The particular embodiment of expansion device 1 makes it possible to generate a below-atmospheric pressure at liquid levels in the lower part of reservoir 3, whereby degassing of the liquid can be effected very well.
At liquid levels in the upper part of reservoir 3 an above-atmospheric pressure is formed, whereby gases released during the below atmospheric can be discharged easily via a vent 22. A result of this method is that the pressure can vary from below-atmospheric pressure to above-atmospheric pressure. This makes a static startup of pump 4 exceptionally difficult in a known configuration of figure 2, even if this were embodied as in figure 2 with soft-start or variable rotation speed control 20.
It becomes almost impossible to provide an expansion device 2 with a reservoir 3 and to start it in conditions of varying pressure by means of only valve 5 in combination with a manually operated valve 8 with choke. Such a static startup is not suitable for regulation in a dynamic hydraulic process, something which can however be achieved with a configuration as shown in figure 1, with continuously variable pressure difference between reservoir 3 and the assembly with liquid circuit 25.
In the embodiment according to the invention as shown in figure 1 optimum adjustment of the liquid flows between the assembly with liquid circuit 25 and reservoir 3 of expansion provision 1 is always particularly simple in response to the pressure prevailing in reservoir 3 and liquid circuit 25. This adjustment can be controlled fully automatically in simple manner by means of valve 24 with variable passage in the embodiment according to figure 1 and the switch pattern as shown in figure 3.
As possible embodiment of valve 24 with variable opening, valve 24 can be embodied with a position recognition, whereby it is possible to pre-activate the desired passage to a desired position (from the control unit). It is however also possible to apply a simple drive without position indication for valve 24 with variable passage. In this case the control unit (not shown) measures the speed or liquid flow and adjusts the variable passage of valve 24 thereto.
When a valve 5 with a greater capacity than required is applied in pump 4, it is readily possible using the variable passage of valve 24 to operate a large operating range of smaller heating or cooling systems, such as liquid circuit 25, using a standard version of expansion device 1.
A further important advantage of the invention relates to setting of expansion device 1 of figure 1 into operation. When an expansion device 1 is taken into use for a first time, the assembly with liquid circuit 25 and expansion device 1 will - even after being fully filled with liquid - possibly contain enclosed quantities of gas at vital parts such as a pump 4, and therefore be unable to function.
Only in an embodiment according to the invention as shown in figure 1 can a pump 4 be vented and fully filled with water without manual intervention being necessary. By holding valve 24 with variable passage in fully opened position it is necessary to wait a short time to vent enclosed gases via vent 19, for instance a float vent associated with pump 4, and to then start pump 4. This pump 4 can now circulate water substantially without pressure difference via connecting conduits 6 and 7 and liquid circuit 25 until all enclosed gases have been removed. Once filled with liquid, pump 4 is fully operational.
Such an action can be preprogrammed in the control unit, whereby in the case of suspected air problems in pump 4 this procedure can be repeated.
It is noted that the operation of the other components in figures 1 and 2 will be apparent to the skilled person, i.e. sensor 10, filter 13, valves 12, 14, 15, 17 and non-return valve 18 and mains water connection 16 for replenishing the assembly via expansion device 1, water volume meter 9 and so on, particularly in the shown and described relation.
In figure 1 a check valve 28 is further arranged between valve 24 with variable passage, in particular (as shown more clearly in figure 4) a motor valve 24, and pump 4. Although the intended effect of the motor valve remains the same, check valve 28 serves, during intake of water from assembly 25 to expansion tank 3, to prevent water flowing in opposite direction through pump 4, this being undesirable.
The embodiment of expansion device 30 according to figure 4 further differs from that of figure 1 in that check valve 28 with the whole connection between motor valve 24 and the suction side of pump 4 is removed. Many of the advantages intended with the device can then still be realized.
In the embodiment shown in figure 5 the expansion device 31 differs again from that of figures 1 and 4 in that a pressure-regulated valve 29 is arranged, in particular parallel to valve 24 with variable and preferably also adjustable passage and to the usual valve 5 or shutter for intake of liquid from assembly 25. An additional overpressure safety can hereby be realized, wherein the pressure-regulated safety valve 29 is opened at a fixed preset pressure value in assembly 25 with liquid circuit 25 in order to admit liquid from the assembly to expansion device 31, and in particular expansion tank 3 (not shown in figure 5) .
If desired, in the embodiment of figures 4 and 5 a connection can also be arranged from motor valve 24 to the suction side of pump 4, as in the configuration according to figure 1.
The embodiment of figure 6 differs from the foregoing embodiments in that pump 4 is incorporated in a pump unit 32 having therein motor valve 4, non-return valves 12, 28 and the driven valve 5. A temperature sensor 33 is moreover arranged in the same pump unit. A compact configuration of the whole expansion device 34 can be realized by providing these elements in a combined unit 32.
In addition, some modifications have been introduced in the actual expansion tank 3, 26. A measuring sensor 10 measures the weight of the whole expansion tank 3. By determining the weight of the expansion tank beforehand, i.e. without it being filled with heat transfer liquid, the amount of water (liquid) in expansion tank 3 can be derived in simple manner on the basis of the change in weight of expansion tank 3 with water therein. The filling level can thus also be derived, this in relation to the volume of expansion tank 3.
A further pressure sensor 35 is herein arranged which measures the pressure in the gas part of expansion tank 3. Two valves are arranged here in combination with pressure sensor 35. These two valves 36,37 serve to draw in air or to allow escape of air subject to a pressure recorded by pressure sensor 35. The operation is as follows.
In the gas-side part of the expansion tank air can be drawn in via valve 36 in the case of a fall in the pressure in the expansion tank of for instance 0.3 bar. Conversely, an excess of gas in expansion tank 3 can result in second valve 37 being opened to allow this excess to escape. Such a higher pressure in the gas in the expansion tank is for instance the result of an increase in the expansion liquid in expansion tank 3. Air or gas at atmospheric pressure can thus be blown off. An operating pressure in expansion tank 3 lies here between -0.3 and 0 bar relative to the atmospheric pressure. A considerable improvement can thus be provided for the purpose of degassing of heat transfer liquid. This is because an additional method can thus be provided for degassing the heat transfer fluid in expansion tank 3 relative to the already provided option with float valve 22.
The embodiment of 40 of figure 9 shows a strong resemblance to the embodiment of figure 6, but differs therefrom in respect of the following aspects and features.
Some modifications have been introduced in respect of expansion tank 3, 26. A pressure sensor 41 measures the pressure in the water section in expansion tank 3, 26 from a lowest point.
A second pressure sensor 38 measures the pressure in a liquid column 39, the end of which extends into the centre of expansion tank 3, 26. Because water from liquid circuit 25 flows into expansion tank 3, 26 via liquid column 39 at each intake, column 39 continuously remains almost wholly filled with water. The liquid level or volume of the water in the water section in expansion tank 3, 26 will always vary in response to the temperature in liquid circuit 25.
Because of the pressure variations described below in the gas pressure in expansion tank 3, 26 it is almost impossible to determine the liquid level or the volume using a simple pressure sensor. It is now however possible to determine a level difference which occurs by applying the two pressure sensors 41, 38.
By calculating the pressure difference between pressure sensors 41, 38 the liquid level in the lower half can be determined, wherein the variable gas pressure is eliminated.
When the two pressure sensors 41, 38 record the same pressure, the liquid level is the same at the outflow end of liquid column 39, halfway along expansion tank 3, 26. The liquid level or the volume in the upper half of expansion tank 3, 26 can then be derived from historical measurement values relating to the lower half, and relates to liquid column 39 increased by the gas pressure.
It is noted that in an embodiment (not shown) the liquid column can further be provided with measures to further enhance degasification, such as turbulence generating means for the purpose of further enhancing release of gases from the liquid. Such turbulence generating means can thus be formed by ratchet rings in liquid column 39.
Typical of the measured pressure values in the upper part of expansion tank 3, 26 is that the pressures of both pressure sensors 41, 38 will always equal each other because the same liquid column with gas pressure is applicable.
Now further also arranged in the embodiment of figure 9 are the two valves 36, 37, with which the gas pressure in expansion tank 3, 26 can be manipulated in this embodiment.
Valve 36, with which air can be drawn in, is in this embodiment a spring-loaded valve which opens in one direction at a pressure difference of preferably 0.3 bar, and remains closed in the opposite direction. Valve 37, along which air can escape, opens in one direction almost without pressure difference, and remains closed in an opposite direction.
When the liquid volume in expansion tank 3, 26 now decreases, the gas volume will increase. However, because air can only enter via valve 36, the gas pressure in expansion tank 3, 26 falls to a pressure of for instance 0.3 bar below atmospheric pressure.
Conversely, an excess of gas in expansion tank 3, 26 can result in opening of second valve 37 in order to allow this excess to escape. The just above-atmospheric pressure in the gas in the expansion tank is for instance the result of an increase in the expansion liquid in expansion tank 3, 26. Air or gas which has separated from the water as a result of the low pressure, and is situated in the water section of expansion tank 3, 26, can thus be blown off at atmospheric pressure via vent or float valve 22.
In this embodiment an operating pressure in expansion tank 3 also lies here between -0.3 and 0 bar relative to atmospheric pressure as maintained in expansion tank 26 of figure 2. A considerable improvement can thus be provided for the purpose of degassing heat transfer liquid. This is because an additional method can thus be provided for degassing the heat transfer fluid in expansion tank 3 relative to the already provided option with float valve 22. This is because valves 36, 37, as well as being controlled in mechanical manner as a spring-loaded embodiment, can also be controlled by a switching mechanism or control in interaction with the recorded pressure in expansion tank 3, 26. The same applies for the embodiment in figure 6. In the embodiment of figure 9 however, it has been made possible, in combination with the control, to realize a fully self-learning configuration.
Figures 7 and 8 each show three situations demonstrating how unique the positioning of motor valve 24 is in combination with the other components of expansion device 1.

Because

In the top view of figure 7 high pressure is circulated in the system through pump 4 and motor valve 24, which is in fully open position.
In the middle view of figure 7 the motor valve 24 is gradually closing, this being indicated with arrow A. Motor valve 24 can be held fixedly in any position depending on a desired circulation. The bottom view in figure 7 clearly shows that motor valve 24 has closed completely. It will hereby be apparent that the whole flow generated with pump 4 is carried to the assembly with liquid circulation 25. It is thus made apparent how the pressure in the assembly with liquid circulation 25 can be increased by controlling the motor valve in appropriate manner. Liquid required to increase the pressure in assembly 25 then comes entirely from the expansion tank, at least in the bottom view of figure 7.
The opposite situation is likewise possible, wherein the pressure in the assembly must be decreased because the pressure in assembly 25 has become too high, for instance as a result of a temperature increase when a burner or other heat source is set into operation. From the situation in the top view of figure 8 the valve 24 is opened gradually from a fully closed position with pump 4 not in operation. The arrow B in the middle view of figure 8 shows that motor valve 24 is opening, and it is once again noted that any intermediate position can be held fixedly for any desired flow. The sequence from top to bottom in figure 8 then reaches a situation in which motor valve 24 is fully open, indicated with the continuous arrow B. In such a situation maximum liquid is extracted from assembly 25 and carried to the expansion tank.
A particular embodiment not covered by the the invention is shown in figure 10. The incoming flow of liquid into the expansion device from the installation is regulated here by a water dynamo 42. Such a water dynamo 42 comprises a water motor which drives a generator with which electric current can be generated.
As in the case of the motor valve, an ideal liquid flow can now also always be realized. In order to obtain a very low liquid flow the generator is manipulated, for instance by forcing a high volume throughput, such that the water motor rotates with great difficulty. Conversely, the generator, and consequently the water motor, rotates substantially without resistance when a highest liquid flow must be realized.
The same advantages are in this way obtained in respect of the automatic venting of the pump and always being able to generate an ideal liquid flow in continuously variable manner.
An additional great advantage is that the electricity supply can be used for feedback to the mains or to charge a battery with which the control system with a number of basic functions such as valve control can be powered.
When the control system can have available a self-generated operating voltage, this provides, in addition to an energy-saving, a greater operational reliability, for instance in the case of (mains) power outage.
It is self-evident that such a water dynamo 42 can also be used for other situations. Energy can in fact be produced in this way anywhere where there is a pressure difference, wherein a liquid flow is an essential component of a process.
According to the embodiment not covered by the invention additional energy will be supplied in order to fill a system with liquid from a pressureless expansion tank, although a large part of the energy required for the general control, such as keeping this system to pressure, replenishing and degassing activities, can be covered with the energy generated by water dynamo 42.
As in the embodiment not covered by the invention of figure 10, a water dynamo 42 is also incorporated in figure 11. The functions and advantages of water dynamo 42 in figure 11 are the same as that of figure 10, with the difference that water dynamo 42 is not connected to the inlet of the pump. The pump cannot therefore be vented in the above described manner. In figure 11 a tube 43 is further arranged under vent 22 (embodied here with protection against return flow) on the expansion tank, relating to an embodiment with a membrane.
The highest point at which gases can be discharged from the liquid-holding part of the expansion tank is in this way lowered to the bottom side of tube 43. Owing to this measure a small quantity of gas will always remain in the liquid-holding part of the expansion tank, this being desirable in determining a water level when operation takes place with two pressure sensors 38, 41 in an expansion tank with membrane, as described above with reference to the embodiment of figure 9.
Instead of the coupling of a water motor to a generator, a water motor can be manipulated to form a variable liquid passage using a braking device. There is no energy-saving advantage here, although a lower cost price can however be realized with this simplified method.
It will be apparent that various alternative and additional embodiments will occur to the skilled person upon examination of the foregoing. All these alternative and additional embodiments lie however within the scope of protection of the present invention to the extent they do not depart from the letter of the definitions of this scope of protection in the appended claims. It is thus possible for a valve other than a check valve 28 to be applied between motor valve 24 and pump 4, and even an open connection can suffice, although a situation which is per se undesirable can then occur in that liquid from the suction side of pump 4 could flow to motor valve 24. Any random operative mode can be set, regulated or programmed in a control (not shown). A control unit is therefore not shown in further detail, although the individual components will be under the control of such a control unit. It is possible to have a position, particularly of motor valve 24, recorded with one or other sensor and transmitted to the relevant control unit. Such a recorded position of motor valve 24 can be useful in respect of recording operating modes, subsequent monitoring, for instance after a breakdown, and normal operating modes. Such a recorded position can moreover be preset and utilized in a determined operating mode, at least if such an operating mode is detected by approximation. Fine adjustment relative to such a recorded value can then take place easily without an interactive process requiring different iterations in order to arrive at a desired setting of the motor valve. This contributes toward the simplicity and therefore elegance of the activation and the control and the monitoring of motor valve 24.

Claims

Heat transport system, comprising:
- a heating system comprising an assembly of a cold or heat source and a conduit system (25) with heat exchangers connected to the source, and

- an expansion device (1) connected to the assembly, wherein a valve (8; 24; 42) with variable opening is arranged between the heating system and the expansion device in a first conduit (7) along which heat transfer medium is carried from the heating system to the expansion device, wherein
the expansion device (1) comprises an expansion tank with a pump (4) connected thereto in a second conduit (6) along which heat transfer medium is carried from the expansion device to the heating system for the purpose of carrying heat transfer fluid selectively to the assembly (25) during operation of the pump (4),
CHARACTERIZED IN THAT
the valve (8; 24; 42) with variable opening is connected via a check valve (28) to a suction side of the pump (4) between the first conduit (7) and the second conduit (6).
Heat transport system as claimed in at least claim 1, wherein a pressure-regulated valve is arranged parallel to the valve with variable opening (8; 24; 42) as safeguard against overpressure in the assembly.
Heat transport system as claimed in at least one of the foregoing claims, wherein the valve with variable passage (8; 24; 42) comprises a motor valve.
Expansion device, suitable for a heat transport system comprising a heating system comprising an assembly of a cold or heat source and a conduit system (25) with heat exchangers connected to the source, said expansion device (1) being connected to the assembly, wherein a valve (8;24;42) with variable opening is arranged between the heating system and the expansion device in a first conduit (7) along which heat transfer medium is carried from the heating system to the expansion device, wherein the expansion device (1) comprises an expansion tank with a pump (4) connected thereto in a second conduit (6) along which heat transfer medium is carried from the expansion device to the heating system for the purpose of carrying heat transfer fluid selectively to the assembly (25) during operation of the pump (4), CHARACTERIZED IN THAT the valve (8;24;42) with variable opening is connected via 20 a check valve (28) to a suction side of the pump (4) between the first conduit (7) and the second conduit (6).