Patent Description:
Refrigeration systems are commonly used for many types of units, such as full heat recovery units, air conditioning/hot water multifunctional units and four-tube refrigeration/hot water units. Existing full heat recovery units, air conditioning/hot water multifunctional units and four-tube refrigeration/hot water units generally have three or more heat exchangers. During unit operation, some of the heat exchangers in the refrigeration system are not operational, and liquid refrigerant will accumulate inside the non-operational heat exchangers, resulting in a shortage of refrigerant during unit operation, and affecting the normal running of the unit. Document <CIT> discloses a refrigeration system having provisions for evacuating inactive heat exchangers.

The present application provides a refrigeration system as defined by appended independent claim <NUM>. Embodiments of the inventive refrigeration system inter alia comprise: refrigeration system components, connecting pipelines and a switch structure. The refrigeration system components comprise a compressor, a first heat exchanger, a second heat exchanger, a third heat exchanger, a first throttle valve and a second throttle valve; the connecting pipelines are capable of connecting all of the abovementioned refrigeration system components, and capable of combining the refrigeration system components in different ways to form multiple different operating systems; the switch structure is configured to be capable of connecting the connecting pipelines to form one operating system, and capable of selecting, from the first heat exchanger, the second heat exchanger and the third heat exchanger, two heat exchangers for connection into said one operating system, and isolating a non-selected heat exchanger from said one operating system.

The refrigeration system as described above further comprises a discharge path, the discharge path being selectively arranged between the non-selected heat exchanger and a low-pressure side of said one operating system, and capable of controllably connecting the non-selected heat exchanger to the low-pressure side of said one operating system.

In the refrigeration system as described above, the discharge path is arranged between the non-selected heat exchanger and the low-pressure side of said one operating system when the temperature of a medium, which undergoes heat transfer with a refrigerant, in the non-selected heat exchanger or the temperature of an environment in which the non-selected heat exchanger is located is lower than a saturation temperature of refrigerant in the non-selected heat exchanger.

In the refrigeration system as described above, when the discharge path is arranged between the non-selected heat exchanger and the low-pressure side of said one operating system, the refrigeration system is configured such that: (i) when a pressure of the low-pressure side of said one operating system is lower than a pressure in the non-selected heat exchanger, the discharge path is connected so that refrigerant in the non-selected heat exchanger flows into the low-pressure side of said one operating system; (ii) when the pressure of the low-pressure side of said one operating system is not lower than the pressure in the non-selected heat exchanger, the first throttle valve or second throttle valve is first adjusted to lower the pressure of the low-pressure side of said one operating system, so that refrigerant in the non-selected heat exchanger is able to flow into the low-pressure side of said one operating system, the discharge path is then connected so that refrigerant in the non-selected heat exchanger flows into the low-pressure side of said one operating system, and the discharge path is disconnected when discharge has taken place for a period of time.

In the refrigeration system as described above, the discharge path comprises a discharge switch device for controlling the connection and disconnection of the discharge path.

In the refrigeration system as described above, the discharge switch device comprises a first disconnection device and a second disconnection device; the first disconnection device is configured to connect the second heat exchanger to or disconnect the second heat exchanger from a low-pressure side of an operating system formed by the compressor, the first heat exchanger, the third heat exchanger and either one or both of the first throttle valve and the second throttle valve; the second disconnection device is configured to connect the third heat exchanger to or disconnect the third heat exchanger from a low-pressure side of an operating system formed by the compressor, the first heat exchanger, the second heat exchanger and either one or both of the first throttle valve and the second throttle valve.

In the refrigeration system as described above, the refrigeration system further comprises a pressure detection device and a temperature detection device; the pressure detection device is configured to be capable of detecting the pressure of the low-pressure side of the operating system, and providing a pressure detection signal; the temperature detection device is configured to be capable of detecting a temperature in the non-selected heat exchanger, and providing a temperature detection signal.

In the refrigeration system as described above, the refrigeration system further comprises a control device, the control device being in communicative connection with the discharge switch device, and being configured to control the connection and disconnection of the discharge path according to the pressure detection signal detected by the pressure detection device and the temperature detection signal detected by the temperature detection device.

In the refrigeration system as described above, the operating system comprises a first operating system and a second operating system; the first operating system is formed by connection of a first series-connected path, the first series-connected path series-connecting in sequence the compressor, the first heat exchanger, the second heat exchanger, the first throttle valve and the third heat exchanger, wherein the first heat exchanger and the second heat exchanger act as condensers, and the third heat exchanger acts as an evaporator; the second operating system is formed by connection of a second series-connected path, the second series-connected path series-connecting in sequence the compressor, the first heat exchanger, the third heat exchanger, the first throttle valve and the second heat exchanger, wherein the first heat exchanger and the third heat exchanger act as condensers, and the second heat exchanger acts as an evaporator; the switch structure comprises a path switching device, and the first operating system and the second operating system can be selectively switched by means of the path switching device.

In the refrigeration system as described above, the switch structure further comprises a third disconnection device, a fourth disconnection device and a fifth disconnection device; the third disconnection device is connected between the first heat exchanger and the path switching device; the fourth disconnection device is connected between the second heat exchanger and the first throttle valve; the fifth disconnection device is connected between the third heat exchanger and the first throttle valve; the second throttle valve has one end connected between the first heat exchanger and the third disconnection device, and another end connected between the fourth disconnection device and the first throttle valve; the operating system further comprises a third operating system and a fourth operating system; the third operating system is formed by a third series-connected path, and when the third operating system is formed, the third series-connected path is configured such that: the third disconnection device and the fourth disconnection device are disconnected, the second heat exchanger in the first series-connected path is separated from the first series-connected path, and the sequential series connection of the compressor, the first heat exchanger, the second throttle valve, the first throttle valve and the third heat exchanger is maintained, wherein the first heat exchanger acts as a condenser, and the third heat exchanger acts as an evaporator; the fourth operating system is formed by a fourth series-connected path, and when the fourth operating system is formed, the fourth series-connected path is configured such that: the third disconnection device and the fifth disconnection device are disconnected, the third heat exchanger in the second series-connected path is separated from the second series-connected path, and the sequential series connection of the compressor, the first heat exchanger, the second throttle valve and the second heat exchanger is maintained, wherein the first heat exchanger acts as a condenser, and the second heat exchanger acts as an evaporator.

In the refrigeration system as described above, the path switching device is a four-way valve, provided with a first pair of controllable paths and a second pair of controllable paths; the first pair of controllable paths comprises a first controllable path and a second controllable path, the first controllable path being connected between the third disconnection device and the second heat exchanger, and the second controllable path being connected between the third heat exchanger and the compressor; the second pair of controllable paths comprises a third controllable path and a fourth controllable path, the third controllable path being connected between the third disconnection device and the third heat exchanger, and the fourth controllable path being connected between the second heat exchanger and the compressor; wherein the first pair of controllable paths can connect the first series-connected path and the third series-connected path; and the second pair of controllable paths can connect the second series-connected path and the fourth series-connected path.

In the refrigeration system as described above, the operating system comprises a first combined operating system and a second combined operating system; the switch structure comprises a first switching assembly, the first switching assembly being configured to switch the first combined operating system and second combined operating system; the first combined operating system comprises a fifth operating system and a sixth operating system; the fifth operating system is formed by a fifth series-connected path, the fifth series-connected path comprising the compressor, the third heat exchanger, the second throttle valve and the second heat exchanger connected in sequence, wherein the third heat exchanger acts as a condenser, and the second heat exchanger acts as an evaporator; the sixth operating system is formed by a sixth series-connected path, the sixth series-connected path comprising the compressor, the second heat exchanger, the second throttle valve and the third heat exchanger connected in sequence, wherein the second heat exchanger acts as a condenser, and the third heat exchanger acts as an evaporator; the switch structure comprises a second switching assembly, and the fifth operating system and the sixth operating system can be switched by means of the second switching assembly.

In the refrigeration system as described above, the second combined operating system comprises a seventh operating system and an eighth operating system; the seventh operating system is formed by a seventh series-connected path, the seventh series-connected path comprising the compressor, the first heat exchanger, the first throttle valve and the second heat exchanger connected in sequence, wherein the first heat exchanger acts as a condenser, and the second heat exchanger acts as an evaporator; and the eighth operating system is formed by an eighth series-connected path, the eighth series-connected path comprising the compressor, the first heat exchanger, the first throttle valve and the third heat exchanger connected in sequence, wherein the first heat exchanger acts as a condenser, and the third heat exchanger acts as an evaporator; the switch structure further comprises a third switching assembly, and the seventh operating system and the eighth operating system can be switched by means of the combination of the second switching assembly and the third switching assembly.

In the refrigeration system as described above, the first switching assembly is a three-way valve, provided with a first three-way controllable path and a second three-way controllable path, the first three-way controllable path being connected between the first heat exchanger and the compressor, and the second three-way controllable path being connected between the second switching assembly and the compressor; wherein the first three-way controllable path can connect the seventh series-connected path and the eighth series-connected path; the second three-way controllable path can connect the fifth series-connected path and the sixth series-connected path; the second switching assembly is a four-way valve, provided with a first set of control paths and a second set of control paths; the first set of control paths comprises a first control path and a second control path, the first control path being connected between the first switching assembly and the second heat exchanger, and the second control path being connected between the third heat exchanger and the compressor; the second set of control paths comprises a third control path and a fourth control path, the third control path being connected between the first switching assembly and the third heat exchanger, and the fourth control path being connected between the second heat exchanger and the compressor; wherein the first set of control paths can connect the sixth series-connected path and the eighth series-connected path; the second set of control paths can connect the fifth series-connected path and the seventh series-connected path; the third switching assembly comprises a sixth disconnection device and a seventh disconnection device; the sixth disconnection device is connected between the second heat exchanger and the first throttle valve, and the seventh disconnection device is connected between the third heat exchanger and the first throttle valve; wherein the sixth disconnection device can connect the seventh series-connected path; and the seventh disconnection device can connect the eighth series-connected path.

In the refrigeration system as described above, the first heat exchanger and the second heat exchanger are both water-side heat exchangers, and the third heat exchanger is a wind-side heat exchanger.

In the refrigeration system as described above, a gas/liquid separator is provided at a gas suction side of the compressor.

In embodiments of the refrigeration system, the switch structure is added at two ends of the heat exchanger which might not be operational, and a liquid extraction return path is added between the non-operational heat exchanger and the low-pressure side of the operating system, so that when refrigerant accumulates inside the heat exchanger because it is not operational, the refrigeration system of the present embodiment can disconnect the two ends of the non-operational heat exchanger from the currently running refrigeration cycle by means of the switch structure, and extract the accumulated refrigerant into the currently running refrigeration cycle by means of the liquid extraction return path. This arrangement avoids shortage of refrigerant in the system circulation when a unit in the refrigeration system is running, thereby facilitating the normal running of the refrigeration system.

An object of the present invention is to provide a refrigeration system, such that when the refrigeration system is operating and a saturation temperature of refrigerant corresponding to pressure inside a non-operational heat exchanger in the refrigeration system is higher than the temperature of an environment or a medium in the heat exchanger, refrigerant that has accumulated in the non-operational heat exchanger can be extracted into the operating system, so that the operating system can run normally.

Various particular embodiments of the present invention are described below with reference to the drawings, which form part of this specification.

<FIG> shows a refrigeration system <NUM> in a first embodiment of the present invention. As shown in <FIG>, the refrigeration system <NUM> comprises a compressor <NUM>, a first heat exchanger <NUM>, a second heat exchanger <NUM>, a third heat exchanger <NUM>, a first throttle valve <NUM>, a second throttle valve <NUM>, a first liquid reservoir <NUM>, a second liquid reservoir <NUM> and a gas/liquid separator <NUM>. The compressor <NUM> is configured to compress refrigerant to a high-temperature, high-pressure fluid. The first heat exchanger <NUM> and second heat exchanger <NUM> are both water-side heat exchangers. When refrigerant flows through the first heat exchanger <NUM> and second heat exchanger <NUM>, it can exchange heat with a water medium in the first heat exchanger <NUM> and second heat exchanger <NUM> that is supplied to a user, so that the temperature of the refrigerant rises or falls. The third heat exchanger <NUM> in the present embodiment is a wind-side heat exchanger. When refrigerant flows through the third heat exchanger <NUM>, it can exchange heat with external air via the third heat exchanger <NUM>, so that the temperature of the refrigerant rises or falls. The first liquid reservoir <NUM> and second liquid reservoir <NUM> are configured to store refrigerant in the refrigeration system <NUM>. The gas/liquid separator <NUM> is configured to separate gaseous refrigerant and liquid refrigerant entering the gas/liquid separator <NUM>, so that the refrigerant which flows out of the gas/liquid separator <NUM> is gaseous refrigerant.

The refrigeration system <NUM> further comprises a switch structure, configured to enable the refrigeration system <NUM> to switch among different operating systems. The switch structure comprises a path switching device <NUM>, a third disconnection device <NUM>, a fourth disconnection device <NUM> and a fifth disconnection device <NUM>. Specifically, the third disconnection device <NUM>, fourth disconnection device <NUM> and fifth disconnection device <NUM> are solenoid valves. The path switching device <NUM> is a four-way valve, having a total of four ports, specifically a first port m, a second port n, a third port p and a fourth port q. The four-way valve is provided with a first pair of controllable paths and a second pair of controllable paths. The first pair of controllable paths comprises a first controllable path mn and a second controllable path pq. The first controllable path mn can connect the first port m and the second port n. The second controllable path pq can connect the third port p and the fourth port q. The second pair of controllable paths comprises a third controllable path mq and a fourth controllable path np. The third controllable path mq can connect the first port m and the fourth port q; the fourth controllable path np can connect the second port n and the third port p.

As shown in <FIG>, the various components mentioned above are connected by connecting pipelines to form the refrigeration system <NUM>. Specifically, the third port p of the path switching device <NUM> is connected to a gas suction end t of the compressor <NUM>; the gas/liquid separator <NUM> is disposed between connecting pipelines of the third port p and the gas suction end t of the compressor <NUM>. A gas discharge end a of the compressor <NUM> is connected to an end b of the first heat exchanger <NUM>; another end c of the first heat exchanger <NUM> is connected to an end s of the third disconnection device <NUM>; another end r of the third disconnection device <NUM> is connected to the first port m. The first liquid reservoir <NUM> is disposed on the connecting pipeline between the end c of the first heat exchanger <NUM> and the end s of the third disconnection device <NUM>.

The second port n of the path switching device <NUM> is connected to an end i of the second heat exchanger <NUM>; another end h of the second heat exchanger <NUM> is connected to an end u of the fourth disconnection device <NUM>. Another end v of the fourth disconnection device <NUM> is connected to an end e of the second throttle valve <NUM>. Another end d of the second throttle valve <NUM> is connected at a connection point A between the first liquid reservoir <NUM> and the third disconnection device <NUM>. The second liquid reservoir <NUM> is disposed on the connecting pipeline between the other end h of the second heat exchanger <NUM> and the end u of the fourth disconnection device <NUM>.

The fourth port q of the path switching device <NUM> is connected to an end k of the third heat exchanger <NUM>; another end j of the third heat exchanger <NUM> is connected to an end w of the fifth disconnection device <NUM>; another end x of the fifth disconnection device <NUM> is connected to an end g of the first throttle valve <NUM>; another end f of the first throttle valve <NUM> is connected at a connection point B between the fourth disconnection device <NUM> and the second throttle valve <NUM>.

The refrigeration system <NUM> further comprises a discharge path. Specifically, the discharge path comprises a first discharge path <NUM> and a second discharge path <NUM>. The first discharge path <NUM> and second discharge path <NUM> can be controllably connected or disconnected by a discharge switch device. As an example, the discharge switch device comprises a first disconnection device <NUM> and a second disconnection device <NUM>. The first disconnection device <NUM> and second disconnection device <NUM> are solenoid valves.

One end of the first discharge path <NUM> is connected at a connection point C between the gas/liquid separator <NUM> and the third port p; another end of the first discharge path <NUM> is connected at a connection point D between the second liquid reservoir <NUM> and the second heat exchanger <NUM>. The first disconnection device <NUM> is disposed on the first discharge path <NUM>. One end of the second discharge path <NUM> is connected at a connection point E between the third heat exchanger <NUM> and the fifth disconnection device <NUM>; another end of the second discharge path <NUM> is connected at a connection point F between the connection point C and the first disconnection device <NUM>. The second disconnection device <NUM> is disposed on the second discharge path <NUM>.

The refrigeration system <NUM> shown in <FIG> can realize four operating systems, comprising a first operating system, a second operating system, a third operating system and a fourth operating system, through the cooperation of the switch structure, the first throttle valve <NUM> and the second throttle valve <NUM>. When the refrigeration system <NUM> is set to the first operating system and third operating system, the first pair of controllable paths in the path switching device <NUM> are connected and the second pair of controllable paths are disconnected. When the refrigeration system <NUM> is set to the second operating system and fourth operating system, the second pair of controllable paths in the path switching device <NUM> are connected and the first pair of controllable paths are disconnected.

<FIG> is a schematic diagram of control components in the refrigeration system <NUM> shown in <FIG>. As shown in <FIG>, the refrigeration system <NUM> further comprises a first temperature detection device <NUM>, a second temperature detection device <NUM> and a pressure detection device <NUM>. The first temperature detection device <NUM> is disposed in the second heat exchanger <NUM>, and configured to detect the temperature in the second heat exchanger <NUM>. The second temperature detection device <NUM> is disposed in the third heat exchanger <NUM>, and configured to detect the temperature in the third heat exchanger <NUM>. The pressure detection device <NUM> is disposed at connection point C, and configured to detect a pressure of an operating system low-pressure side of the refrigeration system <NUM>.

The refrigeration system <NUM> further comprises a control device <NUM>. The control device <NUM> is in communicative connection with the first throttle valve <NUM>, the second throttle valve <NUM>, the path switching device <NUM>, the third disconnection device <NUM>, the fourth disconnection device <NUM>, the fifth disconnection device <NUM>, the first disconnection device <NUM>, the second disconnection device <NUM>, the pressure detection device <NUM>, the first temperature detection device <NUM> and the second temperature detection device <NUM>. The control device <NUM> is configured to be able to control the degree of opening of the first throttle valve <NUM> and second throttle valve <NUM> according to the different operating systems of the refrigeration system <NUM>, and thereby control a pressure drop of refrigerant flowing through the first throttle valve <NUM> and second throttle valve <NUM>. The control device <NUM> is configured to be able to control the switching of different paths in the path switching device <NUM> according to the different operating systems of the refrigeration system <NUM>, and control the opening or closing of the third disconnection device <NUM>, the fourth disconnection device <NUM> and the fifth disconnection device <NUM>. The control device <NUM> is further configured to be able to control the opening or closing of the first disconnection device <NUM> and second disconnection device <NUM> according to a pressure value provided by the pressure detection device <NUM> and temperature values provided by the first temperature detection device <NUM> and second temperature detection device <NUM>, and thereby control the connection and disconnection of the first discharge path <NUM> and second discharge path <NUM>.

<FIG> shows a circulation path when the refrigeration system <NUM> shown in <FIG> is set to the first operating system. When the refrigeration system <NUM> is set to the first operating system, hot water can be supplied to a user end via the first heat exchanger <NUM>, and cooling water for air conditioning/refrigeration can be supplied to the user end via the second heat exchanger <NUM>. Specifically, when the refrigeration system <NUM> is set to the first operating system, a first series-connected path <NUM> can be formed. The third disconnection device <NUM>, fourth disconnection device <NUM>, fifth disconnection device <NUM> and first throttle valve <NUM> are in an open state; the second throttle valve <NUM>, first disconnection device <NUM> and second disconnection device <NUM> are in a closed state; and in the path switching device <NUM>, the first pair of controllable paths are connected and the second pair of controllable paths are disconnected. The arrows in <FIG> show the flow direction of refrigerant in the first series-connected path <NUM>.

As shown in <FIG>, the first series-connected path <NUM> sequentially connects the compressor <NUM>, first heat exchanger <NUM>, first liquid reservoir <NUM>, third disconnection device <NUM>, first controllable path mn, second heat exchanger <NUM>, second liquid reservoir <NUM>, fourth disconnection device <NUM>, first throttle valve <NUM>, fifth disconnection device <NUM>, third heat exchanger <NUM>, second controllable path pq and gas/liquid separator <NUM>. At this time, the first heat exchanger <NUM>, second heat exchanger <NUM> and third heat exchanger <NUM> are all in an operational state. The first heat exchanger <NUM> and second heat exchanger <NUM> act as condensers, and the third heat exchanger <NUM> acts as an evaporator.

<FIG> shows a circulation path when the refrigeration system <NUM> shown in <FIG> is set to the second operating system. When the refrigeration system <NUM> is set to the second operating system, hot water can be supplied to the user end via the first heat exchanger <NUM>, and hot water for air conditioning/heating can be supplied to the user end via the second heat exchanger <NUM>. Specifically, when the refrigeration system <NUM> is set to the second operating system, a second series-connected path <NUM> can be formed. The third disconnection device <NUM>, fourth disconnection device <NUM>, fifth disconnection device <NUM> and first throttle valve <NUM> are in an open state; the second throttle valve <NUM>, first disconnection device <NUM> and second disconnection device <NUM> are in a closed state; and in the path switching device <NUM>, the second pair of controllable paths are connected and the first pair of controllable paths are disconnected. The arrows in <FIG> show the flow direction of refrigerant in the second series-connected path <NUM>.

As shown in <FIG>, the second series-connected path <NUM> can sequentially connect the compressor <NUM>, first heat exchanger <NUM>, first liquid reservoir <NUM>, third disconnection device <NUM>, third controllable path mq, third heat exchanger <NUM>, fifth disconnection device <NUM>, first throttle valve <NUM>, fourth disconnection device <NUM>, second liquid reservoir <NUM>, second heat exchanger <NUM>, fourth controllable path np and gas/liquid separator <NUM>. At this time, the first heat exchanger <NUM>, second heat exchanger <NUM> and third heat exchanger <NUM> are all in an operational state. The first heat exchanger <NUM> and third heat exchanger <NUM> act as condensers, and the second heat exchanger <NUM> acts as an evaporator.

When the refrigeration system <NUM> is set to the first operating system or second operating system, since the first heat exchanger <NUM>, second heat exchanger <NUM> and third heat exchanger <NUM> are all in an operational state, there is no accumulation of refrigerant in non-operational heat exchangers in the first operating system and second operating system.

<FIG> shows a circulation path when the refrigeration system <NUM> shown in <FIG> is set to the third operating system. When the refrigeration system <NUM> is set to the third operating system, hot water can be supplied to the user end via the first heat exchanger <NUM>. Specifically, when the refrigeration system <NUM> is set to the third operating system, a third series-connected path <NUM> can be formed. The fifth disconnection device <NUM>, first throttle valve <NUM> and second throttle valve <NUM> are in an open state; the first disconnection device <NUM>, second disconnection device <NUM>, third disconnection device <NUM> and fourth disconnection device <NUM> are in a closed state; and in the path switching device <NUM>, the first pair of controllable paths are connected and the second pair of controllable paths are disconnected. The arrows in <FIG> show the flow direction of refrigerant in the third series-connected path <NUM>.

As shown in <FIG>, the third series-connected path <NUM> sequentially connects the compressor <NUM>, first heat exchanger <NUM>, first liquid reservoir <NUM>, second throttle valve <NUM>, first throttle valve <NUM>, fifth disconnection device <NUM>, third heat exchanger <NUM>, second controllable path pq and gas/liquid separator <NUM>. The first heat exchanger <NUM> acts as a condenser, the third heat exchanger <NUM> acts as an evaporator, and the second heat exchanger <NUM> is in a non-operational state. Here, the statement "the second heat exchanger <NUM> is in a non-operational state" means: refrigerant can flow through the second heat exchanger <NUM>, but refrigerant in the second heat exchanger <NUM> is not used for the heating or cooling of water supplied to the user end.

When the third operating system is running, since the second heat exchanger <NUM> is not operational, the temperature of a medium in the second heat exchanger <NUM> (i.e. water that participates in heat exchange in the second heat exchanger <NUM> and is supplied to the user end) will gradually approach the temperature of the environment in which the second heat exchanger <NUM> is located. When a saturation temperature corresponding to pressure in the second heat exchanger <NUM> is higher than the temperature of the medium in the second heat exchanger <NUM> or the environment in which it is located, the refrigerant in the second heat exchanger <NUM> will liquefy to liquid refrigerant, thereby causing the pressure in the second heat exchanger <NUM> to drop, with the result that gaseous refrigerant in the third series-connected path <NUM> continuously migrates to the non-operational second heat exchanger <NUM>, and is continuously converted to liquid refrigerant that accumulates therein. This will result in a reduction in the amount of refrigerant moving in the third series-connected path <NUM>, thereby affecting the normal operation of the refrigeration system <NUM>.

Thus, when the third operating system is running, the pressure of the operating system low-pressure side (i.e. at point C) is detected by means of the pressure detection device <NUM>, and the temperature in the second heat exchanger <NUM> is detected by means of the first temperature detection device <NUM>. Saturation temperatures corresponding to different pressures of refrigerant are stored in the control device <NUM>; thus, based on the pressure value detected by the pressure detection device <NUM>, the saturation temperature of the refrigerant at this pressure can be obtained. When the saturation temperature of refrigerant corresponding to the pressure of the operating system low-pressure side (i.e. at point C) is lower than the temperature in the second heat exchanger <NUM> as detected by the first temperature detection device <NUM>, the pressure of the operating system low-pressure side (i.e. at point C) is also lower than the pressure in the second heat exchanger <NUM>, and the control device <NUM> will open the first disconnection device <NUM>, thus connecting the first discharge path <NUM>, and thereby enabling the refrigerant that has accumulated inside the second heat exchanger <NUM> to migrate towards the operating system low-pressure side of the refrigeration system <NUM> due to the pressure difference. When the saturation temperature of refrigerant corresponding to the pressure of the operating system low-pressure side (i.e. at point C) is not lower than the temperature in the second heat exchanger <NUM> as detected by the first temperature detection device <NUM>, the control device <NUM> will reduce the degree of opening of the second throttle valve <NUM> and/or first throttle valve <NUM>, such that the pressure of the operating system low-pressure side (i.e. point C) drops, so that the pressure of the operating system low-pressure side (i.e. at point C) is lower than the pressure in the second heat exchanger <NUM>, at which time the saturation temperature corresponding to the pressure of the operating system low-pressure side (i.e. point C) is also lower than the temperature in the second heat exchanger <NUM>. The control device <NUM> then opens the first disconnection device <NUM>, thus connecting the first discharge path <NUM>, and thereby enabling the refrigerant that has accumulated inside the second heat exchanger <NUM> to migrate towards the operating system low-pressure side due to the pressure difference. After discharge has taken place through the first discharge path <NUM> for a period of time, the pressure of the operating system low-pressure side (i.e. at point C) is the same as the pressure in the second heat exchanger <NUM>, i.e. the saturation temperature corresponding to the pressure of the operating system low-pressure side (i.e. point C) is the same as the temperature in the second heat exchanger <NUM>; at this time, the control device <NUM> disconnects the first discharge path <NUM> by closing the first disconnection device <NUM>. In some embodiments, the control device <NUM> closes the first disconnection device <NUM> when the first discharge path <NUM> has been connected (i.e. refrigerant inside the second heat exchanger <NUM> has been discharged) for <NUM> - <NUM> minutes.

The arrangement described above enables refrigerant that has accumulated inside the second heat exchanger <NUM> to migrate into the third series-connected path <NUM> of the third operating system, thereby avoiding shortage of refrigerant in the operating system when the refrigeration system <NUM> is running in the third operating system.

It can be seen from <FIG> and <FIG> that the first operating system and third operating system can be implemented by opening and closing the third disconnection device <NUM>, fourth disconnection device <NUM> and second throttle valve <NUM>. Specifically, taking the first series-connected path <NUM> as a starting configuration, the third disconnection device <NUM> and fourth disconnection device <NUM> are closed and the second throttle valve <NUM> is opened, such that the sequential connection of the compressor <NUM>, first heat exchanger <NUM>, first liquid reservoir <NUM>, second throttle valve <NUM>, first throttle valve <NUM>, fifth disconnection device <NUM>, third heat exchanger <NUM>, second controllable path pq and gas/liquid separator <NUM> is maintained while the second heat exchanger <NUM> is separated from the first series-connected path <NUM>, thereby switching the first series-connected path <NUM> to the third series-connected path <NUM>.

<FIG> shows a circulation path when the refrigeration system <NUM> shown in <FIG> is set to the fourth operating system. When the refrigeration system <NUM> is set to the fourth operating system, hot water can be supplied to the user end via the first heat exchanger <NUM>, and cooling water for air conditioning/cooling can be supplied to the user end via the second heat exchanger <NUM>. Specifically, when the refrigeration system <NUM> is set to the fourth operating system, a fourth series-connected path <NUM> can be formed. The fourth disconnection device <NUM> and second throttle valve <NUM> are in an open state; the third disconnection device <NUM>, fifth disconnection device <NUM>, first disconnection device <NUM>, second disconnection device <NUM> and first throttle valve <NUM> are in a closed state; and in the path switching device <NUM>, the second pair of controllable paths are connected and the first pair of controllable paths are disconnected. The arrows in <FIG> show the flow direction of refrigerant in the fourth series-connected path <NUM>.

As shown in <FIG>, the fourth series-connected path <NUM> can sequentially connect the compressor <NUM>, first heat exchanger <NUM>, first liquid reservoir <NUM>, second throttle valve <NUM>, fourth disconnection device <NUM>, second liquid reservoir <NUM>, second heat exchanger <NUM>, fourth controllable path np and gas/liquid separator <NUM>. The first heat exchanger <NUM> acts as a condenser, the second heat exchanger <NUM> acts as an evaporator, and the third heat exchanger <NUM> is in a non-operational state. Here, the statement "the third heat exchanger <NUM> is in a non-operational state" means: refrigerant can flow through the third heat exchanger <NUM>, but refrigerant in the third heat exchanger <NUM> is not used for the heating or cooling of external air.

When the fourth operating system is running, since the third heat exchanger <NUM> is not operational, the temperature of a medium in the third heat exchanger <NUM> (i.e. air that participates in heat exchange in the third heat exchanger <NUM>) will gradually approach the temperature of the environment in which the third heat exchanger <NUM> is located. When a saturation temperature corresponding to pressure in the third heat exchanger <NUM> is higher than the temperature of the air medium in the third heat exchanger <NUM> or the environment in which it is located, the refrigerant in the third heat exchanger <NUM> will liquefy to liquid refrigerant, thereby causing the pressure in the third heat exchanger <NUM> to drop, with the result that gaseous refrigerant in the fourth series-connected path <NUM> continuously migrates to the non-operational third heat exchanger <NUM>, and is continuously converted to liquid refrigerant that accumulates therein. This will result in a reduction in the amount of refrigerant moving in the fourth series-connected path <NUM>, thereby affecting the normal operation of the refrigeration system <NUM>.

Thus, when the fourth operating system is running, the pressure of the operating system low-pressure side (i.e. at point C) is detected by means of the pressure detection device <NUM>, and the temperature in the third heat exchanger <NUM> is detected by means of the second temperature detection device <NUM>. Saturation temperatures corresponding to different pressures of refrigerant are stored in the control device <NUM>; thus, based on the pressure value detected by the pressure detection device <NUM>, the saturation temperature of the refrigerant at this pressure can be obtained. When the saturation temperature of refrigerant corresponding to the pressure of the operating system low-pressure side (i.e. at point C) is lower than the temperature in the third heat exchanger <NUM> as detected by the second temperature detection device <NUM>, the pressure of the operating system low-pressure side (i.e. at point C) is also lower than the pressure in the third heat exchanger <NUM>, and the control device <NUM> will open the second disconnection device <NUM>, thus connecting the second discharge path <NUM>, and thereby enabling the refrigerant that has accumulated inside the third heat exchanger <NUM> to migrate towards the operating system low-pressure side due to the pressure difference. When the saturation temperature of refrigerant corresponding to the pressure of the operating system low-pressure side (i.e. at point C) is not lower than the temperature in the third heat exchanger <NUM> as detected by the second temperature detection device <NUM>, the control device <NUM> will reduce the degree of opening of the second throttle valve <NUM>, such that the pressure of the operating system low-pressure side (i.e. point C) drops, so that the pressure of the operating system low-pressure side (i.e. at point C) is lower than the pressure in the third heat exchanger <NUM>, at which time the saturation temperature corresponding to the pressure of the operating system low-pressure side (i.e. point C) is also lower than the temperature in the third heat exchanger <NUM>. The control device <NUM> then opens the second disconnection device <NUM>, thus connecting the second discharge path <NUM>, and thereby enabling the refrigerant that has accumulated inside the third heat exchanger <NUM> to migrate towards the operating system low-pressure side due to the pressure difference. After discharge has taken place through the second discharge path <NUM> for a period of time, the pressure of the operating system low-pressure side (i.e. point C) is the same as the pressure in the third heat exchanger <NUM>, i.e. the saturation temperature corresponding to the pressure of the operating system low-pressure side (i.e. point C) is the same as the temperature in the third heat exchanger <NUM>; at this time, the control device <NUM> disconnects the second discharge path <NUM> by closing the second disconnection device <NUM>. In some embodiments, the control device <NUM> closes the second disconnection device <NUM> when the second discharge path <NUM> has been connected (i.e. refrigerant inside the third heat exchanger <NUM> has been discharged) for <NUM> - <NUM> minutes.

The arrangement described above enables refrigerant that has accumulated inside the third heat exchanger <NUM> to migrate into the fourth series-connected path <NUM> of the fourth operating system, thereby avoiding shortage of refrigerant in the operating system when the refrigeration system <NUM> is running in the fourth operating system.

It can be seen from <FIG> and <FIG> that the second operating system and fourth operating system can be implemented by opening and closing the third disconnection device <NUM>, fifth disconnection device <NUM> and second throttle valve <NUM>. Specifically, taking the second series-connected path <NUM> as a starting configuration, the third disconnection device <NUM> and fifth disconnection device <NUM> are closed and the second throttle valve <NUM> is opened, such that the sequential connection of the compressor <NUM>, first heat exchanger <NUM>, first liquid reservoir <NUM>, second throttle valve <NUM>, fourth disconnection device <NUM>, second liquid reservoir <NUM>, second heat exchanger <NUM>, fourth controllable path np and gas/liquid separator <NUM> is maintained while the third heat exchanger <NUM> is separated from the second series-connected path <NUM>, thereby switching the second series-connected path <NUM> to the fourth series-connected path <NUM>.

It must be explained that although the fifth disconnection device <NUM> and first throttle valve <NUM> are provided in the refrigeration system <NUM>, due to the fact that the fifth disconnection device <NUM> and first throttle valve <NUM> are connected in series and the first throttle valve <NUM> is configured such that the degree of opening thereof (i.e. the flow rate through the first throttle valve <NUM>) can be controlled, it is also possible to omit the fifth disconnection device <NUM>, and realize the opening and closing functions of the fifth disconnection device <NUM> through the opening and closing of the first throttle valve <NUM>.

<FIG> shows a refrigeration system <NUM> in a second embodiment of the present invention. As shown in <FIG>, the refrigeration system <NUM> comprises a compressor <NUM>, a first heat exchanger <NUM>, a second heat exchanger <NUM>, a third heat exchanger <NUM>, a first throttle valve <NUM>, a second throttle valve <NUM>, a first liquid reservoir <NUM>, a second liquid reservoir <NUM> and a gas/liquid separator <NUM>. The compressor <NUM> is configured to compress refrigerant to a high-temperature, high-pressure fluid. The first heat exchanger <NUM> and second heat exchanger <NUM> are both water-side heat exchangers. When refrigerant flows through the first heat exchanger <NUM> and second heat exchanger <NUM>, it can exchange heat with a water medium in the first heat exchanger <NUM> and second heat exchanger <NUM> that is supplied to a user, such that the temperature of the refrigerant rises or falls. The third heat exchanger <NUM> in the present embodiment is a wind-side heat exchanger. When refrigerant flows through the third heat exchanger <NUM>, it can exchange heat with external air via the third heat exchanger <NUM>, so that the temperature of the refrigerant rises or falls. The first liquid reservoir <NUM> and second liquid reservoir <NUM> are configured to store refrigerant in the refrigeration system <NUM>. The gas/liquid separator <NUM> is configured to separate gaseous refrigerant and liquid refrigerant entering the gas/liquid separator <NUM>, so that the refrigerant which flows out of the gas/liquid separator <NUM> is gaseous refrigerant.

The refrigeration system <NUM> further comprises a switch structure, configured to enable the refrigeration system <NUM> to switch among different operating systems. The switch structure comprises a first switching assembly <NUM>, a second switching assembly <NUM>, a sixth disconnection device <NUM> and a seventh disconnection device <NUM>. Specifically, the sixth disconnection device <NUM> and seventh disconnection device <NUM> are solenoid valves. The first switching assembly <NUM> is a three-way valve having three ports b', c' and d', and the three-way valve has a first three-way controllable path b'c' and a second three-way controllable path b'd'. Specifically, the first three-way controllable path b'c' can connect ports b' and c', and the second three-way controllable path b'd' can connect ports b' and d'.

The second switching assembly <NUM> is a four-way valve having a total of four ports, specifically a first port m', a second port n', a third port p' and a fourth port q'. Moreover, the four-way valve is provided with a first set of control paths and a second set of control paths. The first set of control paths comprises a first control path m'n' and a second control path p'q'. The first control path m'n' can connect the first port m' with the second port n', and the second control path p'q' can connect the third port p' with the fourth port q'. The second set of control paths comprises a third control path m'q' and a fourth control path n'p'. The third control path m'q' can connect the first port m' with the fourth port q', and the fourth control path n'p' can connect the second port n' with the third port p'.

The refrigeration system <NUM> further comprises a first one-way valve <NUM> and a second one-way valve <NUM>, for ensuring that refrigerant flows in a single direction in circulation pipelines in which the first one-way valve <NUM> and second one-way valve <NUM> are located.

As shown in <FIG>, the various components mentioned above are connected by connecting pipelines to form the refrigeration system <NUM>. Specifically, the port c' of the first switching assembly <NUM> is connected to an end e' of the first heat exchanger <NUM>, another end f' of the first heat exchanger <NUM> is connected to an end g' of the first throttle valve <NUM>, another end h' of the first throttle valve <NUM> is connected to an inlet end of the first one-way valve <NUM>, an outlet end of the first one-way valve <NUM> is connected to an end l' of the sixth disconnection device <NUM>, another end k' of the sixth disconnection device <NUM> is connected to an end j' of the second heat exchanger <NUM>, and another end i' of the second heat exchanger <NUM> is connected to the first port m' of the second switching assembly <NUM>. The first liquid reservoir <NUM> is disposed on the connecting pipeline between the other end f' of the first heat exchanger <NUM> and the end g' of the first throttle valve <NUM>. The second liquid reservoir <NUM> is disposed on the connecting pipeline between the other end k' of the sixth disconnection device <NUM> and the end j' of the second heat exchanger <NUM>. The port b' of the first switching assembly <NUM> is connected to a gas discharge end a' of the compressor <NUM>, a gas suction end a" of the compressor <NUM> is in communication with the second port n' of the second switching assembly <NUM>, and the gas/liquid separator <NUM> is disposed between connecting pipelines of the gas suction end a" of the compressor <NUM> and the second port n' of the second switching assembly <NUM>.

The third port p' of the second switching assembly <NUM> is connected to an end r' of the third heat exchanger <NUM>, another end s' of the third heat exchanger <NUM> is connected to an end u' of the seventh disconnection device <NUM>, another end v' of the seventh disconnection device <NUM> is connected to an outlet end of the second one-way valve <NUM>, and an inlet end of the second one-way valve <NUM> is connected at a connection point M between the other end h' of the first throttle valve <NUM> and the inlet end of the first one-way valve <NUM>. An end x' of the second throttle valve <NUM> is connected at a connection point N between the outlet end of the first one-way valve <NUM> and the end l' of the sixth disconnection device <NUM>; another end y' of the second throttle valve <NUM> is connected at a connection point O between the other end v' of the seventh disconnection device <NUM> and the outlet end of the second one-way valve <NUM>.

The fourth port q' of the second switching assembly <NUM> is connected to the port d' of the first switching assembly <NUM>.

One end of the first discharge path <NUM> is connected at a connection point P between the second liquid reservoir <NUM> and the sixth disconnection device <NUM>; another end of the first discharge path <NUM> is connected at a connection point Q between the gas/liquid separator <NUM> and the second port n' of the second switching assembly <NUM>. The first disconnection device <NUM> is disposed on the first discharge path <NUM>. One end of the second discharge path <NUM> is connected at a connection point R between the third heat exchanger <NUM> and the seventh disconnection device <NUM>; another end of the second discharge path <NUM> is connected at a connection point S between the connection point Q and the first disconnection device <NUM>. The second disconnection device <NUM> is disposed on the second discharge path <NUM>.

The refrigeration system <NUM> shown in <FIG> can realize four operating systems, comprising a fifth operating system, a sixth operating system, a seventh operating system and an eighth operating system, through the cooperation of the switch structure, the first throttle valve <NUM> and the second throttle valve <NUM>.

When the refrigeration system <NUM> is set to the fifth operating system and the sixth operating system, the second three-way controllable path b'd' in the first switching assembly <NUM> is connected and the first three-way controllable path b'c' is disconnected. When the refrigeration system <NUM> is set to the seventh operating system and the eighth operating system, the first three-way controllable path b'c' in the first switching assembly <NUM> is connected and the second three-way controllable path b'd' is disconnected.

When the refrigeration system <NUM> is set to the fifth operating system and the seventh operating system, the first set of control paths in the second switching assembly <NUM> are connected and the second set of control paths are disconnected. When the refrigeration system <NUM> is set to the sixth operating system and the eighth operating system, the second set of control paths in the second switching assembly <NUM> are connected and the first set of control paths are disconnected.

<FIG> is a schematic diagram of control components in the refrigeration system <NUM> shown in <FIG>. As shown in <FIG>, the refrigeration system <NUM> further comprises a first temperature detection device <NUM>, a second temperature detection device <NUM> and a pressure detection device <NUM>. The first temperature detection device <NUM> is disposed in the second heat exchanger <NUM>, and configured to detect the temperature in the second heat exchanger <NUM>. The second temperature detection device <NUM> is disposed in the third heat exchanger <NUM>, and configured to detect the temperature in the third heat exchanger <NUM>. The pressure detection device <NUM> is disposed at connection point Q, and configured to detect a pressure of an operating system low-pressure side of the refrigeration system <NUM>.

The refrigeration system <NUM> further comprises a control device <NUM>. The control device <NUM> is in communicative connection with the first throttle valve <NUM>, second throttle valve <NUM>, first switching assembly <NUM>, second switching assembly <NUM>, sixth disconnection device <NUM>, seventh disconnection device <NUM>, first disconnection device <NUM>, second disconnection device <NUM>, pressure detection device <NUM>, first temperature detection device <NUM> and second temperature detection device <NUM>. The control device <NUM> is configured to be able to control the degree of opening of the first throttle valve <NUM> and second throttle valve <NUM> according to the different operating systems of the refrigeration system <NUM>, and thereby control a pressure drop of refrigerant flowing through the first throttle valve <NUM> and second throttle valve <NUM>. The control device <NUM> is configured to be able to control the switching of different paths in the first switching assembly <NUM> and second switching assembly <NUM> according to the different operating systems of the refrigeration system <NUM>, and control the opening or closing of the sixth disconnection device <NUM> and the seventh disconnection device <NUM>. The control device <NUM> is further configured to be able to control the opening or closing of the first disconnection device <NUM> and second disconnection device <NUM> according to a pressure value provided by the pressure detection device <NUM> and temperature values provided by the first temperature detection device <NUM> and second temperature detection device <NUM>, and thereby control the connection and disconnection of the first discharge path <NUM> and second discharge path <NUM>.

<FIG> shows a circulation path when the refrigeration system <NUM> shown in <FIG> is set to the fifth operating system. When the refrigeration system <NUM> is set to the fifth operating system, cooling water for air conditioning/refrigeration can be supplied to the user end via the second heat exchanger <NUM>. Specifically, when the refrigeration system <NUM> is set to the fifth operating system, a fifth series-connected path <NUM> can be formed. The sixth disconnection device <NUM>, seventh disconnection device <NUM> and second throttle valve <NUM> are in an open state; the first disconnection device <NUM> and second disconnection device <NUM> are in a closed state; the second three-way controllable path b'd' in the first switching assembly <NUM> is connected and the first three-way controllable path b'c' is disconnected; and the first set of control paths in the second switching assembly <NUM> are connected and the second set of control paths are disconnected. The first one-way valve <NUM> and second one-way valve <NUM> can prevent the flow of fluid from the outlet end of the one-way valve towards the inlet end. The arrows in <FIG> show the flow direction of refrigerant in the fifth series-connected path <NUM>.

As shown in <FIG>, the fifth series-connected path <NUM> sequentially connects the compressor <NUM>, second three-way controllable path b'd', second controllable path p'q', third heat exchanger <NUM>, seventh disconnection device <NUM>, second throttle valve <NUM>, sixth disconnection device <NUM>, second liquid reservoir <NUM>, second heat exchanger <NUM>, first controllable path m'n' and gas/liquid separator <NUM>. At this time, the third heat exchanger <NUM> acts as a condenser, the second heat exchanger <NUM> acts as an evaporator, and the first heat exchanger <NUM> is in a non-operational state.

<FIG> shows a circulation path when the refrigeration system <NUM> shown in <FIG> is set to the sixth operating system. When the refrigeration system <NUM> is set to the sixth operating system, hot water for air conditioning/heating can be supplied to the user end via the second heat exchanger <NUM>. Specifically, when the refrigeration system <NUM> is set to the sixth operating system, a sixth series-connected path <NUM> can be formed. The sixth disconnection device <NUM>, seventh disconnection device <NUM> and second throttle valve <NUM> are in an open state; the first disconnection device <NUM> and second disconnection device <NUM> are in a closed state; the second three-way controllable path b'd' in the first switching assembly <NUM> is connected and the first three-way controllable path b'c' is disconnected; and the second set of control paths in the second switching assembly <NUM> are connected and the first set of control paths are disconnected. The first one-way valve <NUM> and second one-way valve <NUM> can prevent the flow of fluid from the outlet end of the one-way valve towards the inlet end. The arrows in <FIG> show the flow direction of refrigerant in the sixth series-connected path <NUM>.

As shown in <FIG>, the sixth series-connected path <NUM> sequentially connects the compressor <NUM>, the second three-way controllable path b'd', the third controllable path m'q', the second heat exchanger <NUM>, the second liquid reservoir <NUM>, the sixth disconnection device <NUM>, the second throttle valve <NUM>, the seventh disconnection device <NUM>, the third heat exchanger <NUM>, the fourth control path n'p' and the gas/liquid separator <NUM>. At this time, the second heat exchanger <NUM> acts as a condenser, the third heat exchanger <NUM> acts as an evaporator, and the first heat exchanger <NUM> is in a non-operational state.

When the refrigeration system <NUM> is set to the fifth operating system or sixth operating system, the first heat exchanger <NUM> is in a non-operational state. The statement "the first heat exchanger <NUM> is in a non-operational state" means: refrigerant can flow through the first heat exchanger <NUM>, but refrigerant in the first heat exchanger <NUM> is not used for the heating or cooling of water supplied to the user end. However, since the first heat exchanger <NUM> is used to supply hot water to the user side, the temperature of the medium of the first heat exchanger <NUM> is high. As an example the temperature of the medium in the first heat exchanger <NUM> is higher than a saturation temperature corresponding to the pressure inside the first heat exchanger <NUM>; thus, there is no condensation and consequent accumulation of refrigerant in the first heat exchanger <NUM>. Therefore, in an embodiment of the present invention, no discharge path is provided between the first heat exchanger <NUM> in the refrigeration system <NUM> and the operating system low-pressure side of the refrigeration system <NUM>.

It can be seen from <FIG> and <FIG> that the fifth operating system and sixth operating system can be implemented by path switching in the second switching assembly <NUM>. Specifically, the fifth series-connected path <NUM> can be switched to the sixth series-connected path <NUM> by switching the second switching assembly <NUM> from a configuration in which the first pair of controllable paths are connected, to a configuration in which the second pair of controllable paths are connected.

It must be explained that although the first one-way valve <NUM> and second one-way valve <NUM> are provided in the refrigeration system <NUM> to control the flow of refrigerant so as to form the fifth series-connected path <NUM> and sixth series-connected path <NUM>, those skilled in the art will understand that another device such as a solenoid valve or pump could also be used to realize the connection and disconnection functions of the first one-way valve <NUM> and second one-way valve <NUM>.

<FIG> shows a circulation path when the refrigeration system <NUM> shown in <FIG> is set to the seventh operating system. When the refrigeration system <NUM> is set to the seventh operating system, hot water can be supplied to the user end via the first heat exchanger <NUM>, and cooling water for air conditioning/refrigeration can be supplied to the user end via the second heat exchanger <NUM>. Specifically, when the refrigeration system <NUM> is set to the seventh operating system, a seventh series-connected path <NUM> can be formed. The sixth disconnection device <NUM> and first throttle valve <NUM> are in an open state; the second throttle valve <NUM>, seventh disconnection device <NUM>, first disconnection device <NUM> and second disconnection device <NUM> are in a closed state. In the first switching assembly <NUM>, the first three-way controllable path b'c' is connected and the second three-way controllable path b'd' is disconnected; and in the second switching assembly <NUM>, the first set of control paths are connected and the second set of control paths are disconnected. The arrows in <FIG> show the flow direction of refrigerant in the seventh series-connected path <NUM>.

As shown in <FIG>, the seventh series-connected path <NUM> sequentially connects the compressor <NUM>, first three-way controllable path b'c', first heat exchanger <NUM>, first liquid reservoir <NUM>, first throttle valve <NUM>, first one-way valve <NUM>, sixth disconnection device <NUM>, second liquid reservoir <NUM>, second heat exchanger <NUM>, first control path m'n' and gas/liquid separator <NUM>. The first heat exchanger <NUM> acts as a condenser, the second heat exchanger <NUM> acts as an evaporator, and the third heat exchanger <NUM> is in a non-operational state. The statement "the third heat exchanger <NUM> is in a non-operational state" means: refrigerant can flow through the third heat exchanger <NUM>, but refrigerant in the third heat exchanger <NUM> is not used for the heating or cooling of external air.

When the seventh operating system is running, since the third heat exchanger <NUM> is not operational, the temperature of a medium in the third heat exchanger <NUM> (i.e. air that participates in heat exchange in the third heat exchanger <NUM>) will gradually approach the temperature of the environment in which the third heat exchanger <NUM> is located. When a saturation temperature corresponding to pressure in the third heat exchanger <NUM> is higher than the temperature of the air medium in the third heat exchanger <NUM> or the environment in which it is located, the refrigerant in the third heat exchanger <NUM> will liquefy to liquid refrigerant, thereby causing the pressure in the third heat exchanger <NUM> to drop, with the result that gaseous refrigerant in the seventh series-connected path <NUM> continuously migrates to the non-operational third heat exchanger <NUM>, and is continuously converted to liquid refrigerant that accumulates therein. This will result in a reduction in the amount of refrigerant moving in the seventh series-connected path <NUM>, thereby affecting the normal operation of the refrigeration system <NUM>.

Thus, when the seventh operating system is running, the pressure of the operating system low-pressure side (i.e. at point Q) is detected by means of the pressure detection device <NUM>, and the temperature in the third heat exchanger <NUM> is detected by means of the second temperature detection device <NUM>. Saturation temperatures corresponding to different pressures of refrigerant are stored in the control device <NUM>; thus, based on the pressure value detected by the pressure detection device <NUM>, the saturation temperature of the refrigerant at this pressure can be obtained. When the saturation temperature of refrigerant corresponding to the pressure of the operating system low-pressure side (i.e. at point Q) is lower than the temperature in the third heat exchanger <NUM> as detected by the second temperature detection device <NUM>, the pressure of the operating system low-pressure side (i.e. at point Q) is also lower than the pressure in the third heat exchanger <NUM>, and the control device <NUM> will open the second disconnection device <NUM>, thus connecting the second discharge path <NUM>, and thereby enabling the refrigerant that has accumulated inside the third heat exchanger <NUM> to migrate towards the operating system low-pressure side of the refrigeration system <NUM> due to the pressure difference. When the saturation temperature of refrigerant corresponding to the pressure of the operating system low-pressure side (i.e. at point Q) is not lower than the temperature in the third heat exchanger <NUM> as detected by the second temperature detection device <NUM>, the control device <NUM> will reduce the degree of opening of the first throttle valve <NUM>, such that the pressure of the operating system low-pressure side (i.e. at point Q) drops, so that the pressure of the operating system low-pressure side (i.e. at point Q) is also lower than the pressure in the third heat exchanger <NUM>, at which time the saturation temperature of refrigerant corresponding to the pressure of the operating system low-pressure side (i.e. at point Q) is lower than the temperature in the third heat exchanger <NUM>. The control device <NUM> then opens the second disconnection device <NUM>, thus connecting the second discharge path <NUM>, and thereby enabling the refrigerant that has accumulated inside the third heat exchanger <NUM> to migrate towards the operating system low-pressure side. After discharge has taken place through the second discharge path <NUM> for a period of time, the pressure of the operating system low-pressure side (i.e. at point Q) is the same as the pressure in the third heat exchanger <NUM>, i.e. the saturation temperature corresponding to the pressure of the operating system low-pressure side (i.e. at point Q) is the same as the temperature in the third heat exchanger <NUM>; at this time, the control device <NUM> disconnects the second discharge path <NUM> by closing the second disconnection device <NUM>. In some embodiments, the control device <NUM> closes the second disconnection device <NUM> when the second discharge path <NUM> has been connected (i.e. refrigerant inside the third heat exchanger <NUM> has been discharged) for <NUM> - <NUM> minutes.

The arrangement described above enables refrigerant that has accumulated inside the third heat exchanger <NUM> to migrate into the seventh series-connected path <NUM> of the seventh operating system, thereby avoiding shortage of refrigerant in the operating system when the refrigeration system <NUM> is running in the seventh operating system.

<FIG> shows a circulation path when the refrigeration system <NUM> shown in <FIG> is set to the eighth operating system. When the refrigeration system <NUM> is set to the eighth operating system, hot water can be supplied to the user end via the first heat exchanger <NUM>. Specifically, when the refrigeration system <NUM> is set to the eighth operating system, an eighth series-connected path <NUM> can be formed. The seventh disconnection device <NUM> and first throttle valve <NUM> are in an open state; the second throttle valve <NUM>, sixth disconnection device <NUM>, first disconnection device <NUM> and second disconnection device <NUM> are in a closed state. In the first switching assembly <NUM>, the first three-way controllable path b'c' is connected and the second three-way controllable path b'd' is disconnected; and in the second switching assembly <NUM>, the second set of control paths are connected and the first set of control paths are disconnected. The arrows in <FIG> show the flow direction of refrigerant in the eighth series-connected path <NUM>.

As shown in <FIG>, the eighth series-connected path <NUM> sequentially connects the compressor <NUM>, first three-way controllable path b'c', first heat exchanger <NUM>, first liquid reservoir <NUM>, first throttle valve <NUM>, second one-way valve <NUM>, seventh disconnection device <NUM>, third heat exchanger <NUM>, fourth control path n'p' and gas/liquid separator <NUM>. The first heat exchanger <NUM> acts as a condenser, the third heat exchanger <NUM> acts as an evaporator, and the second heat exchanger <NUM> is in a non-operational state. The statement "the second heat exchanger <NUM> is in a non-operational state" means: refrigerant can flow through the second heat exchanger <NUM>, but refrigerant in the second heat exchanger <NUM> is not used for the heating or cooling of water supplied to the user end.

When the eighth operating system is running, since the second heat exchanger <NUM> is not operational, the temperature of a medium in the second heat exchanger <NUM> (i.e. water that participates in heat exchange in the second heat exchanger <NUM>) will gradually approach the temperature of the environment in which the second heat exchanger <NUM> is located. When a saturation temperature corresponding to pressure in the second heat exchanger <NUM> is higher than the temperature of the water medium in the second heat exchanger <NUM> or the environment in which it is located, the refrigerant in the second heat exchanger <NUM> will liquefy to liquid refrigerant, thereby causing the pressure in the second heat exchanger <NUM> to drop, with the result that gaseous refrigerant in the eighth series-connected path <NUM> continuously migrates to the non-operational second heat exchanger <NUM>, and is continuously converted to liquid refrigerant that accumulates therein. This will result in a reduction in the amount of refrigerant moving in the eighth series-connected path <NUM>, thereby affecting the normal operation of the refrigeration system <NUM>.

Thus, when the eighth operating system is running, the pressure of the operating system low-pressure side (i.e. at point Q) is detected by means of the pressure detection device <NUM>, and the temperature in the second heat exchanger <NUM> is detected by means of the first temperature detection device <NUM>. Saturation temperatures corresponding to different pressures of refrigerant are stored in the control device <NUM>; thus, based on the pressure value detected by the pressure detection device <NUM>, the saturation temperature of the refrigerant at this pressure can be obtained. When the saturation temperature of refrigerant corresponding to the pressure of the operating system low-pressure side (i.e. at point Q) is lower than the temperature in the second heat exchanger <NUM> as detected by the first temperature detection device <NUM>, the pressure of the operating system low-pressure side (i.e. at point Q) is also lower than the pressure in the second heat exchanger <NUM>, and the control device <NUM> will open the first disconnection device <NUM>, thus connecting the first discharge path <NUM>, and thereby enabling the refrigerant that has accumulated inside the second heat exchanger <NUM> to migrate towards the operating system low-pressure side due to the pressure difference. When the saturation temperature of refrigerant corresponding to the pressure of the operating system low-pressure side (i.e. at point Q) is not lower than the temperature in the second heat exchanger <NUM> as detected by the first temperature detection device <NUM>, the control device <NUM> will reduce the degree of opening of the first throttle valve <NUM>, such that the pressure of the operating system low-pressure side drops, so that the pressure of the operating system low-pressure side (i.e. at point Q) is also lower than the pressure in the second heat exchanger <NUM>, at which time the saturation temperature corresponding to the pressure of the operating system low-pressure side (i.e. at point Q) is lower than the temperature in the second heat exchanger <NUM>. The control device <NUM> then opens the first disconnection device <NUM>, thus connecting the first discharge path <NUM>, and thereby enabling the refrigerant that has accumulated inside the second heat exchanger <NUM> to migrate towards the operating system low-pressure side. After discharge has taken place through the first discharge path <NUM> for a period of time, the pressure of the operating system low-pressure side (i.e. at point Q) is the same as the pressure in the second heat exchanger <NUM>, i.e. the saturation temperature corresponding to the pressure of the operating system low-pressure side (i.e. at point Q) is the same as the temperature in the second heat exchanger <NUM>; at this time, the control device <NUM> disconnects the first discharge path <NUM> by closing the first disconnection device <NUM>. In some embodiments, the control device <NUM> closes the first disconnection device <NUM> when the first discharge path <NUM> has been connected (i.e. refrigerant inside the second heat exchanger <NUM> has been discharged) for <NUM> - <NUM> minutes.

The arrangement described above enables refrigerant that has accumulated inside the second heat exchanger <NUM> to migrate into the eighth series-connected path <NUM> of the eighth operating system, thereby avoiding shortage of refrigerant in the operating system when the refrigeration system <NUM> is running in the eighth operating system.

It can be seen from <FIG> and <FIG> that the seventh operating system and eighth operating system can be implemented by path switching in the second switching assembly <NUM> and connection or disconnection of the sixth disconnection device <NUM> and seventh disconnection device <NUM>. Specifically, the seventh series-connected path <NUM> can be switched to the eighth series-connected path <NUM> by switching the second switching assembly <NUM> from a configuration in which the first set of control paths are connected, to a configuration in which the second set of control paths are connected, closing the sixth disconnection device <NUM> and opening the seventh disconnection device <NUM>.

It must be explained that although the first heat exchangers <NUM>, <NUM> and second heat exchangers <NUM>, <NUM> in the refrigeration system <NUM> and refrigeration system <NUM> in some embodiments are water-side heat exchangers, and the third heat exchangers <NUM>, <NUM> are wind-side heat exchangers, those skilled in the art could configure them as different types of heat exchangers according to actual needs. In addition, the first switching assembly <NUM> is not limited to using a three-way valve, the path switching device <NUM> and second switching assembly <NUM> are not limited to using four-way valves, and the first disconnection device <NUM>, second disconnection device <NUM>, third disconnection device <NUM>, fourth disconnection device <NUM>, fifth disconnection device <NUM>, sixth disconnection device <NUM> and seventh disconnection device <NUM> are not limited to using solenoid valves, but could be configured as various types of device capable of achieving connection and disconnection, e.g. a pump, etc., according to actual needs.

It must also be explained that although the gas/liquid separator and liquid reservoir are provided in some embodiments, it is also possible for the gas/liquid separator and/or the liquid reservoir not to be provided.

Furthermore, although the present detailed description shows embodiments of two refrigeration systems having three heat exchangers, those skilled in the art will understand that in the case of a refrigeration system having four or more heat exchangers, when the temperature of the medium in a non-operational heat exchanger or the temperature of the environment in which it is located might be lower than the saturation temperature corresponding to the pressure in the heat exchanger, such that refrigerant will be likely to accumulate in the heat exchanger, it is also possible to provide a discharge path for the refrigerant in the heat exchanger to migrate into the currently operating system circulation, so that there is enough refrigerant in the currently operating system.

It must also be explained that although the non-operational heat exchanger is connected to the operating system low-pressure side point C via the discharge path in the first embodiment, and the non-operational heat exchanger is connected to the operating system low-pressure side point Q via the discharge path in the second embodiment, in other embodiments the discharge path could also connect the non-operational heat exchanger to another position at the operating system low-pressure side, for example, connect the non-operational heat exchanger directly to the gas suction end of the compressor.

Claim 1:
A refrigeration system, wherein the refrigeration system comprises:
- refrigeration system components, comprising a compressor (<NUM>; <NUM>), a first heat exchanger (<NUM>; <NUM>), a second heat exchanger (<NUM>; <NUM>), a third heat exchanger (<NUM>; <NUM>), a first throttle valve (<NUM>; <NUM>) and a second throttle valve (<NUM>; <NUM>);
- connecting pipelines, capable of connecting all of the abovementioned refrigeration system components, and capable of combining the refrigeration system components in different ways to form multiple different operating systems;
- a switch structure, configured to be capable of connecting the connecting pipelines to form one operating system, and capable of selecting, from the first heat exchanger (<NUM>; <NUM>), the second heat exchanger (<NUM>; <NUM>) and the third heat exchanger (<NUM>; <NUM>), two heat exchangers for connection into said one operating system, and isolating a non-selected heat exchanger from said one operating system;
- a discharge path (<NUM>, <NUM>; <NUM>, <NUM>), the discharge path (<NUM>, <NUM>; <NUM>, <NUM>) being arranged between the non-selected heat exchanger and a low-pressure side of said one operating system, and capable of controllably connecting the non-selected heat exchanger to the low-pressure side of said one operating system, the discharge path (<NUM>, <NUM>; <NUM>, <NUM>) comprising a discharge switch device for controlling the connection and disconnection of the discharge path (<NUM>, <NUM>; <NUM>, <NUM>);
- a control device (<NUM>; <NUM>), the control device (<NUM>; <NUM>) being in communicative connection with the discharge switch device, wherein the control device is configured to connect the discharge path between the non-selected heat exchanger and the low-pressure side (C; Q) of said one operating system when the temperature of a medium, which undergoes heat transfer with a refrigerant, in the non-selected heat exchanger or the temperature of an environment in which the non-selected heat exchanger is located is lower than a saturation temperature of refrigerant in the non-selected heat exchanger.