Patent Description:
Air conditioning apparatuses are apparatuses that maintain air in a predetermined space to the most proper state according to use and purpose thereof. In general, such an air conditioning apparatus includes a compressor, a condenser, an expansion device, and evaporator. Thus, the air conditioning apparatus has a refrigerant cycle in which compression, condensation, expansion, and evaporation processes of a refrigerant are performed to cool or heat a predetermined space.

The predetermined space may be variously provided according to a place at which the air conditioning apparatus is used. For example, the predetermined space may be a home or office space.

When the air conditioning apparatus performs a cooling operation, an outdoor heat exchanger provided in an outdoor unit may serve as a condenser, and an indoor heat exchanger provided in an indoor unit may serve as an evaporator. On the other hand, when the air conditioning apparatus performs a heating operation, the indoor heat exchanger may serve as the condenser, and the outdoor heat exchanger may serve as the evaporator.

In recent years, according to environmental regulations, there is a tendency to limit the type of refrigerant used in the air conditioning apparatus and to reduce an amount of refrigerant to be used.

To reduce an amount of used refrigerant, a technique for performing cooling or heating by performing heat-exchange between a refrigerant and a predetermined fluid has been proposed. For example, the predetermined fluid may include water.

An air conditioning apparatus in which cooling or heating is performed through heat-exchange between a refrigerant and water is disclosed in <CIT>) that is a prior art document.

The air conditioning apparatus disclosed in the prior art document includes a plurality of heat exchangers in which a refrigerant and water are heat-exchanged with each other and two valve devices connected to a refrigerant passage so that each of the heat exchangers operates as an evaporator or a condenser. That is, in the air conditioning apparatus according to the related art, an operation mode of the heat exchanger is determined through control of the valve device.

Also, the air conditioning apparatus according to the related art further includes three tubes connecting an outdoor unit to the heat exchange device. The three tubes include a high-pressure gas tube through which a high-pressure gas refrigerant flows, a low-pressure gas tube through which a low-pressure gas refrigerant flows, and a liquid tube through which a liquid refrigerant flows.

When a cooling operation is performed in the above-described three tube structure, the refrigerant condensed in the outdoor unit may flow into the liquid tube and be evaporated in the heat exchanger, and the evaporated refrigerant flows through the low-pressure gas tube so as to be introduced into the outdoor unit.

However, if a temperature of the refrigerant evaporated in the heat exchanger during this process is very low (e.g., when a temperature of the refrigerant is lowered to about <NUM> degree or less), water flowing through the heat exchanger is frozen, which may cause a problem that the heat exchanger is frozen to burst. When the heat exchanger is frozen to burst, the water and the refrigerant may be mixed due to internal leakage, and as a result, a major limitation in a system may occur.

<CIT> relates to an air conditioning system including a bypass pipe and a bypass valve controlled to be opened when a pressure in the system exceeds a working condition.

Embodiments provide an air conditioning apparatus that is capable of preventing a heat exchanger, in which a refrigerant and water are heat-exchanged with each other, from being frozen to burst during a cooling operation of the indoor unit.

Embodiments also provide an air conditioning apparatus that is capable of preventing a heat exchanger from being frozen to burst even when an indoor unit performs a simultaneous operation in which a cooling operation and a heating operation are performed at the same time.

Embodiments also provide an air conditioning apparatus that is capable of determining a heat exchanger, which may be frozen to burst, of a plurality of heat exchangers to supply a high-temperature refrigerant toward only the corresponding heat exchanger.

Embodiments also provide an air conditioning apparatus, in which an opening degree of a bypass valve is adjusted according to an operation mode of an indoor unit to prevent a heat exchanger from being frozen to burst while maintaining performance of the heat exchanger.

It is an object of the present invention and to achieve at least one of the above effects.

This object is solved by the present invention as defined in the independent claim.

The following aspects and examples are provided for a better understanding of the present invention. According to the invention the air conditioning apparatus includes: an outdoor unit which includes a compressor and an outdoor heat exchanger and through which a refrigerant is circulated; an indoor unit through which water is circulated; a heat exchanger in which the refrigerant and the water are heat-exchanged with each other; a high-pressure guide tube extending from a high-pressure gas tube of the outdoor unit so as to be connected to one side of the heat exchanger; a low-pressure guide tube extending from a low-pressure gas tube of the outdoor unit so as to be combined with the high-pressure guide tube; and a liquid guide tube extending from a liquid tube of the outdoor unit so as to be connected to the other side of the heat exchanger.

The air conditioning apparatus further includes: a bypass tube configured to connect a bypass branch point of the high-pressure gas tube to a bypass combination point of the liquid guide tube to bypass a high-pressure refrigerant existing in the high-pressure tube to the liquid guide tube; and a bypass valve installed in the bypass tube. Therefore, a high-temperature high-pressure refrigerant flowing to the high-pressure gas tube by the bypass tube may be bypassed to the heat exchanger to prevent the heat exchanger from being frozen to burst.

When the indoor unit performs a cooling operation, the bypass valve may be opened to bypass the high-pressure refrigerant of the high-pressure gas tube to the liquid guide tube. When the indoor unit performs a heating operation, the bypass valve may be closed to bypass the high-pressure refrigerant of the high-pressure gas tube to the liquid guide tube.

The heat exchanger can be provided in plurality, and when some of the plurality of heat exchangers function as condensers configured to condense the refrigerant, and remaining heat exchangers function as evaporators configured to evaporate the refrigerant, the bypass valve may be opened to bypass the high-pressure refrigerant of the high-pressure gas tube to the heat exchangers that function as the evaporators.

That is, when the indoor unit performs the simultaneous operation, the bypass valve may be opened so that the high-pressure refrigerant of the high-pressure gas tube is introduced into the heat exchanger, which serves as an evaporator, to prevent the heat exchanger from being frozen to burst.

The air conditioning apparatus further includes a high-pressure valve installed in the high-pressure guide tube, the high-pressure valve being configured to be opened and closed, a low-pressure valve installed in the low-pressure guide tube, the low-pressure valve being configured to be opened and closed, and a flow valve installed in the liquid guide tube to control a flow rate of the refrigerant.

The bypass combination point may be defined at a point between the heat exchanger and the flow valve.

The air conditioning apparatus further includes a refrigerant tube having one end defining a refrigerant branch point, at which the high-pressure guide tube and the low-pressure guide tube are combined with each other, and the other end connected to a refrigerant passage of the heat exchanger.

The air conditioning apparatus may further include: a gas refrigerant sensor installed in the refrigerant tube to detect a temperature of the refrigerant; a liquid refrigerant sensor installed in the liquid guide tube to detect a temperature of the refrigerant; and a controller configured to adjust an opening degree of the bypass valve based on the temperatures detected by the gas refrigerant sensor and the liquid refrigerant sensor.

The controller may be configured to determine whether the temperature detected by the gas refrigerant sensor or the liquid refrigerant sensor is equal to or less than a first reference temperature, and when the temperature detected by the gas refrigerant sensor or the liquid refrigerant sensor is equal to or less than the first reference temperature, the bypass valve may be opened.

The temperatures of the refrigerant, which are detected by the gas refrigerant sensor and liquid refrigerant sensor, may be detected again, and the controller may be configured to determine whether each of the temperatures detected by the gas refrigerant sensor and liquid refrigerant sensor is equal to or greater than a second reference temperature.

When each of the temperatures of the refrigerant, which are detected by the gas refrigerant sensor and the liquid refrigerant sensor is less than the second reference temperature, the controller may be configured to control the bypass valve so that the bypass valve increases in opening degree.

When each of the temperatures detected by the gas refrigerant sensor and the liquid refrigerant sensor is equal to or greater than the second reference temperature, the controller may be configured to control the bypass valve so that the bypass valve decreases in opening degree.

When each of the temperatures detected by the gas refrigerant sensor and the liquid refrigerant sensor is equal to or greater than the second reference temperature, the controller may be configured to determine whether the opening degree of the bypass valve is equal to or greater than a reference opening degree, and when the opening degree of the bypass valve is equal to or greater than the reference opening degree, the bypass valve may decrease in opening degree.

The air conditioning apparatus can further include: a first low-pressure guide tube extending from a low-pressure gas tube of the outdoor unit so as to be combined with the first high-pressure guide tube; a second low-pressure guide tube extending from the low-pressure gas tube of the outdoor unit so as to be combined with the second high-pressure guide tube; a first liquid guide tube extending from a liquid tube of the outdoor unit so as to be connected to the other side of the first heat exchanger; and a second liquid guide tube extending from the liquid tube of the outdoor unit so as to be connected to the other side of the second heat exchanger.

The air conditioning apparatus can include: a bypass tube configured to bypass a high-pressure refrigerant of the high-pressure gas tube to the first liquid guide tube or the second liquid guide tube; and a bypass valve installed in the bypass tube, wherein the bypass tube includes: a common tube branched from a first bypass branch portion of the high-pressure gas tube; a first bypass tube branched from a second bypass branch portion of the common tube, the first bypass tube being connected to a first bypass combination point of the first liquid guide tube; and a second bypass tube branched from the second bypass branch portion of the common tube, the second bypass tube being connected to a second bypass combination point of the second liquid guide tube.

Therefore, a high-temperature high-pressure refrigerant flowing to the high-pressure gas tube by the bypass tube may be bypassed to the first heat exchanger or the second heat exchanger to prevent the heat exchanger from being frozen to burst.

The bypass valve may include: a first bypass valve installed in the first bypass tube; and a second bypass valve installed in the second bypass tube.

When the indoor unit performs a cooling operation, at least one or more of the first bypass valve and the second bypass valve may be opened to bypass the high-pressure refrigerant of the high-pressure gas tube to at least one or more of the first liquid guide tube and the second liquid guide tube. Thus, the high-pressure refrigerant of the high-pressure gas tube may be selectively introduced into one or more of the first heat exchanger and the second heat exchanger.

The air conditioning apparatus may further include: a first high-pressure valve and a second high-pressure valve, which are installed in the first high-pressure guide tube and the second high-pressure guide tube, respectively; a first low-pressure valve and a second low-pressure valve, which are installed in the first low-pressure guide tube and the second low-pressure guide tube, respectively; and a first flow valve and a second flow valve, which are installed in the first liquid guide tube and the second liquid guide tube, respectively.

The first bypass combination point may be defined at a point between the first heat exchanger and a first flow valve, and the second bypass combination point may be defined at a point between the second heat exchanger and a second flow valve.

The air conditioning apparatus may further include: a first refrigerant tube having one end defining a first refrigerant branch point, at which the first high-pressure guide tube and the first low-pressure guide tube are combined with each other, and the other end connected to a refrigerant passage of the first heat exchanger; and a second refrigerant tube having one end defining a second refrigerant branch point, at which the second high-pressure guide tube and the second low-pressure guide tube are combined with each other, and the other end connected to a refrigerant passage of the second heat exchanger.

The air conditioning apparatus may further include: a gas refrigerant sensor installed in each of the first refrigerant tube and the second refrigerant tube to detect a temperature of the refrigerant; a liquid refrigerant sensor installed in each of the first liquid guide tube and the second liquid guide tube to detect a temperature of the refrigerant; and a controller configured to adjust an opening degree of the bypass valve based on the temperatures detected by the gas refrigerant sensor and the liquid refrigerant sensor.

Hereinafter, some embodiments of the present invention will be described in detail with reference to the accompanying drawings. It is noted that the same or similar components in the drawings are designated by the same reference numerals as far as possible even if they are shown in different drawings. In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted to avoid making the subject matter of the present invention unclear.

In the description of the elements of the present invention, the terms first, second, A, B, (a), and (b) may be used.

<FIG> is a schematic view of an air conditioning apparatus according to an example, and <FIG> is a cycle diagram illustrating constituents of an outdoor unit according to an embodiment of the present invention.

Referring to <FIG> and <FIG>, an air conditioning apparatus <NUM> according to an embodiment is connected to an outdoor unit <NUM>, an indoor unit <NUM>, and a heat exchange device <NUM> connected to the outdoor unit <NUM> and the indoor unit <NUM>.

The outdoor unit <NUM> and the heat exchange device <NUM> are fluidly connected by a first fluid. For example, the first fluid includes a refrigerant.

The refrigerant flows through a refrigerant-side flow path of a heat exchanger, which is provided in the heat exchange device <NUM>, and the outdoor unit <NUM>.

The outdoor unit <NUM> includes a compressor <NUM> and an outdoor heat exchanger <NUM>.

An outdoor fan <NUM> may be provided at one side of the outdoor heat exchanger <NUM> to blow external air toward the outdoor heat exchanger <NUM> so that heat exchange between the external air and the refrigerant of the outdoor heat exchanger <NUM> is performed.

The outdoor unit <NUM> may further include a main expansion valve <NUM> (EEV).

The air conditioning apparatus <NUM> may further include three tubes <NUM>, <NUM>, and <NUM> connecting the outdoor unit <NUM> to the heat exchange device <NUM>.

The three tubes <NUM>, <NUM>, and <NUM> include a high-pressure gas tube <NUM> through which a high-pressure gas refrigerant flows, a low-pressure gas tube <NUM> through which a low-pressure gas refrigerant flows, and a liquid tube <NUM> through which a liquid refrigerant flows.

That is, the outdoor unit <NUM> and the heat exchange device <NUM> may have a "three tube connection structure", and the refrigerant may circulate through the outdoor unit <NUM> and the heat exchange device <NUM> by the three tubes <NUM>, <NUM>, and <NUM>.

The heat exchange device <NUM> and the indoor unit <NUM> are fluidly connected by a second fluid. For example, the second fluid includes water.

The water flows through a water passage of the heat exchanger, which is provided in the heat exchange device <NUM>, and the indoor unit <NUM>.

The heat exchange device <NUM> may include a plurality of heat exchangers <NUM> and <NUM>. Each of the heat exchangers <NUM> and <NUM> may include, for example, a plate heat exchanger.

The indoor unit <NUM> may include a plurality of indoor units <NUM>, <NUM>, <NUM>, and <NUM>.

In this embodiment, the number of plurality of indoor units <NUM>, <NUM>, <NUM>, and <NUM> is not limited. In <FIG>, for example, four indoor units <NUM>, <NUM>, <NUM>, and <NUM> are connected to the heat exchange device <NUM>.

The plurality of indoor units <NUM>, <NUM>, <NUM>, and <NUM> may include a first indoor unit <NUM>, a second indoor unit <NUM>, a third indoor unit <NUM>, and a second indoor unit <NUM>.

The air conditioning apparatus <NUM> may further include tubes <NUM>, <NUM>, <NUM>, and <NUM> connecting the heat exchange device <NUM> to the indoor unit <NUM>.

The tubes <NUM>, <NUM>, <NUM>, and <NUM> may include first to fourth indoor unit connection tubes <NUM>, <NUM>, <NUM>, and <NUM>, which respectively connect the heat exchange device <NUM> to the Heat Exchanger units <NUM>, <NUM>, <NUM> and <NUM>.

The water circulates through the heat exchange device <NUM> and the indoor unit <NUM> via the indoor unit connection tubes <NUM>, <NUM>, <NUM>, and <NUM>. Here, the number of indoor units increases, the number of tubes connecting the heat exchange device 100a to the indoor units may also increase.

According to the above-described configuration, the refrigerant circulating through the outdoor unit <NUM> and the heat exchange device <NUM> and the water circulating through the heat exchange device <NUM> and the indoor unit <NUM> are heat-exchanged with each other through the heat exchangers <NUM> and <NUM> provided in the heat exchange device <NUM>.

The water cooled or heated through the heat-exchange may be heat-exchanged with indoor heat exchangers 61a, 62a, 63a, and 64a provided in the indoor unit <NUM> to perform cooling or heating in the indoor space.

In this embodiment, two or more indoor units may be connected to one heat exchanger. Alternatively, one indoor unit may be connected to one heat exchanger. In this case, the plurality of heat exchangers may be provided in the same number as the number of the plurality of indoor units.

Hereinafter, the heat exchange device <NUM> will be described in detail with reference to the drawings.

The heat exchange device <NUM> may include first and second heat exchangers <NUM> and <NUM> which are fluidly connected to the indoor units <NUM>, <NUM>, <NUM>, and <NUM>, respectively.

The first heat exchanger <NUM> and the second heat exchanger <NUM> may have the same structure.

Each of the heat exchangers <NUM> and <NUM> may include, for example, a plate heat exchanger and may be configured so that the water passage and the refrigerant passage are alternately stacked.

Each of the heat exchangers <NUM> and <NUM> include the refrigerant passage and the water passage.

Each of the refrigerant passages may be fluidly connected to the outdoor unit <NUM>, and the refrigerant discharged from the outdoor unit <NUM> may be introduced into the refrigerant passage, or the refrigerant passing through the refrigerant passage may be introduced into the outdoor unit <NUM>.

Each of the water passages may be connected to each of the indoor units <NUM>, <NUM>, <NUM>, and <NUM>, the water discharged from each of the indoor units <NUM>, <NUM>, <NUM>, and <NUM> may be introduced into the water passage, and the water passing through the water passage may be introduced into each of the indoor units <NUM>, <NUM>, <NUM>, and <NUM>.

The heat exchange device <NUM> may include a switching unit R for adjusting a flow direction and flow rate of the refrigerant introduced into and discharged from the first heat exchanger <NUM> and the second heat exchanger <NUM>.

In detail, the switching unit R includes refrigerant tubes <NUM> and <NUM> coupled to one sides of the heat exchangers <NUM> and <NUM> and liquid guide tubes <NUM> and <NUM> coupled to the other sides of the heat exchanger <NUM> and <NUM>.

The refrigerant tubes <NUM> and <NUM> and the liquid guide tubes <NUM> and <NUM> may be connected to a refrigerant passage provided in each of the heat exchangers <NUM> and <NUM> so as to be heat-exchanged with the water.

The refrigerant tubes <NUM> and <NUM> and the liquid guide tubes <NUM> and <NUM> guide the refrigerant to pass through the heat exchangers <NUM> and <NUM>.

In detail, the refrigerant tubes <NUM> and <NUM> may include a first refrigerant tube <NUM> coupled to one side of the first heat exchanger <NUM> and a second refrigerant tube <NUM> coupled to one side of the second heat exchanger <NUM>.

The liquid guide tubes <NUM> and <NUM> may include a first liquid guide tube <NUM> coupled to the other side of the first heat exchanger <NUM> and a second liquid guide tube <NUM> coupled to the other side of the second heat exchanger <NUM>.

For example, the refrigerant may be circulated through the first heat exchanger <NUM> by the first refrigerant tube <NUM> and the first liquid guide tube <NUM>. Also, the refrigerant may be circulated through the second heat exchanger <NUM> by the second refrigerant tube <NUM> and the second liquid guide tube <NUM>.

The liquid guide tubes <NUM> and <NUM> are connected to the liquid tube <NUM>.

In detail, the liquid tube <NUM> may define a liquid tube branch point 27a branching into the first liquid guide tube <NUM> and the second liquid guide tube <NUM>.

That is, the first liquid guide tube <NUM> may extend from the liquid tube branch point 27a to the first heat exchanger <NUM>, and the second liquid guide tube <NUM> may extend from the liquid tube branch point 27a to the second heat exchanger <NUM>.

The air conditioning apparatus <NUM> may further include gas refrigerant sensors <NUM> and <NUM> installed in the refrigerant tubes <NUM> and <NUM> and liquid refrigerant sensors <NUM> and <NUM> installed in the liquid guide tubes <NUM> and <NUM>.

The gas refrigerant sensors <NUM> and <NUM> and the liquid refrigerant sensors <NUM> and <NUM> may be referred to as "refrigerant sensors".

Also, the refrigerant sensors may detect a state of the refrigerant flowing through the refrigerant tubes <NUM> and <NUM> and the liquid guide tubes <NUM> and <NUM>. For example, the refrigerant sensors may detect a temperature and pressure of the refrigerant.

The gas refrigerant sensors <NUM> and <NUM> may include a first gas refrigerant sensor <NUM> installed in the first refrigerant tube <NUM> and a second gas refrigerant sensor <NUM> installed in the second refrigerant tube <NUM>.

The liquid refrigerant sensors <NUM> and <NUM> may include a first liquid refrigerant sensor <NUM> installed in the first liquid guide tube <NUM> and a second liquid refrigerant sensor <NUM> installed in the second liquid guide tube <NUM>.

The air conditioning apparatus <NUM> further includes flow valves <NUM> and <NUM> installed in the liquid guide tubes <NUM> and <NUM>.

Each of the flow valves <NUM> and <NUM> adjusts a flow rate of the refrigerant by adjusting an opening degree thereof. Each of the flow valves <NUM> and <NUM> may include an electronic expansion valve (EEV). Also, each of the flow valves <NUM> and <NUM> may be adjusted in opening degree to adjust a pressure of the refrigerant passing therethrough.

The electronic expansion valve may reduce a pressure of the refrigerant passing through the expansion valves <NUM> and <NUM> by adjusting the opening degree. For example, when the electronic expansion valves <NUM> and <NUM> are fully opened (full-open state), the refrigerant may pass without decompression, and when the opening degree of each of the expansion valves <NUM> and <NUM> is reduced, the refrigerant may be depressurized. A degree of decompression of the refrigerant may increase as the degree of opening decreases.

The flow valves <NUM> and <NUM> may include a first flow valve <NUM> installed in the first liquid guide tube <NUM> and a second flow valve <NUM> installed in the second liquid guide tube <NUM>.

The air conditioning apparatus <NUM> may further include strainers 148a, 148b, 149a, and 149b installed on both sides of the flow valves <NUM> and <NUM>.

The strainers 148a, 148b, 149a, and 149b are devices for filtering wastes of the refrigerant flowing through the liquid guide tubes <NUM> and <NUM>. For example, the strainers 148a, 148b, 149a, and 149b may be provided as a metal mesh.

The strainers 148a, 148b, 149a, and 149b may include a first strainer 148a and 148b installed on the first liquid guide tube <NUM> and second strainer 149a and 149b installed on the second liquid guide tube <NUM>.

The first strainers 148a and 148b may include a strainer 148a installed at one side of the first flow valve <NUM> and a strainer 148b installed at the other side of the first flow valve <NUM>. As a result, even if the flow direction of the refrigerant is switched, the wastes may be filtered.

Likewise, the second strainers 149a and 149b may include a strainer 149a installed at one side of the second flow valve <NUM> and a strainer 149b installed at the other side of the second flow valve <NUM>.

The refrigerant tubes <NUM> and <NUM> are connected to the high-pressure gas tube <NUM> and the low-pressure gas tube <NUM>. Also, the liquid guide tubes <NUM> and <NUM> are connected to the liquid tube <NUM>.

In detail, the refrigerant tubes <NUM> and <NUM> define refrigerant branch points <NUM> and <NUM> at one ends thereof, respectively. Also, the refrigerant branch points <NUM> and <NUM> are connected so that the high-pressure gas tube <NUM> and the low-pressure gas tube <NUM> are combined with each other.

That is, one ends of the refrigerant tubes <NUM> and <NUM> have refrigerant branch points <NUM> and <NUM>, and the other ends of the refrigerant tubes <NUM> and <NUM> may be coupled to the refrigerant passages of the heat exchangers <NUM> and <NUM>.

The switching unit R may further include high-pressure guide tubes <NUM> and <NUM> extending from the high-pressure gas tube <NUM> to the refrigerant tubes <NUM> and <NUM>.

That is, the high-pressure guide tubes <NUM> and <NUM> may connect the high-pressure gas tube <NUM> to the refrigerant tubes <NUM> and <NUM>.

The high-pressure guide tubes <NUM> and <NUM> are branched from the high-pressure branch point 20a of the high-pressure gas tube <NUM> to extend to the refrigerant tubes <NUM> and <NUM>.

In detail, the high-pressure guide tubes <NUM> and <NUM> may include a first high-pressure guide tube <NUM> extending from the high-pressure branch point 20a to the first refrigerant tube <NUM> and a second refrigerant guide tube <NUM> extending from the second high-pressure branch point 20a to the second refrigerant tube <NUM>.

The first high-pressure guide tube <NUM> may be connected to the first refrigerant branch point <NUM>, and the second high-pressure guide tube <NUM> may be connected to the second refrigerant branch point <NUM>.

That is, the first high-pressure guide tube <NUM> may extend from the high-pressure branch point 20a to the first refrigerant branch point <NUM>, and the second high-pressure guide tube <NUM> may extend from the high-pressure branch point 20a to the second refrigerant branch point <NUM>.

The air conditioning apparatus <NUM> further includes high-pressure valves <NUM> and <NUM> installed in the high-pressure guide tubes <NUM> and <NUM>.

Each of the high-pressure valves <NUM> and <NUM> restricts a flow of the refrigerant to each of the high-pressure guide tubes <NUM> and <NUM> through an opening and closing operation thereof.

The high-pressure valves <NUM> and <NUM> may include a first high-pressure valve <NUM> installed in the first high-pressure guide tube <NUM> and a second high-pressure valve <NUM> installed in the second high-pressure guide tube <NUM>.

The first high-pressure valve <NUM> may be installed between the high-pressure branch point 20a and the first refrigerant branch point <NUM>.

The second high-pressure valve <NUM> may be installed between the high-pressure branch point 20a and the second refrigerant branch point <NUM>.

The first high-pressure valve <NUM> may control a flow of the refrigerant between the high-pressure gas tube <NUM> and the first refrigerant tube <NUM>. Also, the second high-pressure valve <NUM> may control a flow of the refrigerant between the high-pressure gas tube <NUM> and the second refrigerant tube <NUM>.

The switching unit R may further include low-pressure guide tubes <NUM> and <NUM> extending from the low-pressure tube <NUM> to the refrigerant tubes <NUM> and <NUM>.

That is, the low-pressure guide tubes <NUM> and <NUM> may connect the low-pressure tube <NUM> to the refrigerant tubes <NUM> and <NUM>.

The low-pressure guide tubes <NUM> and <NUM> are branched from the low-pressure branch point 25a of the low-pressure gas tube <NUM> to extend to the refrigerant tubes <NUM> and <NUM>.

In detail, the low-pressure guide tube <NUM> and <NUM> may include a first low-pressure guide tube <NUM> extending from the low-pressure branch point 25a to the first refrigerant tube <NUM> and a second low-pressure guide tube <NUM> extending from the low-pressure branch point 25a to the second low-pressure refrigerant tube <NUM>.

The first low-pressure guide tube <NUM> may be connected to the first refrigerant branch point <NUM>, and the second low-pressure guide tube <NUM> may be connected to the second refrigerant branch point <NUM>.

That is, the first low-pressure guide tube <NUM> may extend from the low-pressure branch point 25a to the first refrigerant branch point <NUM>, and the second low-pressure guide tube <NUM> may extend from the low-pressure branch point 25a to the second refrigerant branch point <NUM>. Thus, the high-pressure guide tubes <NUM> and <NUM> and the low-pressure guide tubes <NUM> and <NUM> may be combined with each other at the refrigerant branch points <NUM> and <NUM>.

The air conditioning apparatus <NUM> further includes low-pressure valves <NUM> and <NUM> installed in the low-pressure guide tubes <NUM> and <NUM>.

Each of the low-pressure valves <NUM> and <NUM> restrict a flow of the refrigerant to each of the low-pressure guide tubes <NUM> and <NUM> through an opening and closing operation thereof.

The low-pressure valves <NUM> and <NUM> may include a first low-pressure valve <NUM> installed in the first low-pressure guide tube <NUM> and a second low-pressure valve <NUM> installed in the second low-pressure guide tube <NUM>.

The first low-pressure valve <NUM> may be installed between a point at which the first refrigerant branch point <NUM> and a first pressure equalization tube <NUM> to be described later are connected to each other.

The second low-pressure valve <NUM> may be installed between a point at which the second refrigerant branch point <NUM> and a second pressure equalization tube <NUM> to be described later are connected to each other.

The switching unit R may further include pressure equalization tubes <NUM> and <NUM> branching from the first refrigerant tube <NUM> to extend to the low-pressure guide tubes <NUM> and <NUM>.

The pressure equalization tubes <NUM> and <NUM> may include a first pressure equalization tube <NUM> branched from one point of the first refrigerant tube <NUM> to extend to the first low-pressure guide tube <NUM> and a second pressure equalization tube <NUM> branching from one point of the second refrigerant tube <NUM> to extend to the second low-pressure guide tube <NUM>.

Points at which the pressure equalization tubes <NUM> and <NUM> and the low-pressure guide tubes <NUM> and <NUM> are connected to each other may be disposed between the low-pressure branch point 25a and the low-pressure valves <NUM> and <NUM>, respectively.

That is, the first pressure equalization tube <NUM> may be branched from the first refrigerant tube <NUM> to extend to the first low-pressure guide tube <NUM> disposed between the low-pressure branch point 25a and the first low-pressure valve <NUM>.

Similarly, the second pressure equalization tube <NUM> may be branched from the second refrigerant tube <NUM> to extend to the second low-pressure guide tube <NUM> disposed between the low-pressure branch point 25a and the second low-pressure valve <NUM>.

The air conditioning apparatus <NUM> may further include pressure equalization valves <NUM> and <NUM> and pressure equalization strainers <NUM> and <NUM>, which are installed in the pressure equalization tubes <NUM> and <NUM>.

The pressure equalization valves <NUM> and <NUM> may be adjusted in opening degree to bypass the refrigerant in the refrigerant tubes <NUM> and <NUM> to the low-pressure guide tubes <NUM> and <NUM>.

Each of the pressure equalization valves <NUM> and <NUM> may include an electronic expansion valve (EEV).

The pressure equalization valves <NUM> and <NUM> may include a first pressure equalization valve <NUM> installed in the first pressure equalization tube <NUM> and a second pressure equalization valve <NUM> installed in the second pressure equalization tube <NUM>.

The pressure equalization strainers <NUM> and <NUM> may include a first pressure equalization strainer <NUM> installed in the first pressure equalization tube <NUM> and a second pressure equalization strainer <NUM> installed in the second pressure equalization tube <NUM>.

The pressure equalization strainers <NUM> and <NUM> may be disposed between the pressure equalization valves <NUM> and <NUM> and the refrigerant tubes <NUM> and <NUM>. Thus, the wastes of the refrigerant flowing from the refrigerant tubes <NUM> and <NUM> to the pressure equalization valves <NUM> and <NUM> may be filtered, or foreign substances may be prevented from passing therethrough.

The pressure equalization tubes <NUM> and <NUM> and the pressure equalization valves <NUM> and <NUM> may be referred to as a "pressure equalization circuit".

The pressure equalization circuit may operate to reduce a pressure difference between the high-pressure refrigerant and the low-pressure refrigerant in the refrigerant tubes <NUM> and <NUM> when an operation mode of the heat exchangers <NUM> and <NUM> is switched.

Here, the operation mode of the heat exchangers <NUM> and <NUM> may include a condenser mode operating as the condenser and an evaporator mode operating as the evaporator.

For example, when the heat exchangers <NUM> and <NUM> switch the operation mode from the condenser to the evaporator, the high-pressure valves <NUM> and <NUM> may be closed, and the low-pressure valves <NUM> and <NUM> may be opened.

The adjustment of the opening degree of each of the pressure equalization valves <NUM> and <NUM> may be performed gradually as the time elapses. Thus, the opening degree of the high-pressure valves <NUM> and <NUM> and the low-pressure valve <NUM> may also be controlled.

The pressures of the refrigerant tubes <NUM> and <NUM> may be lowered by the refrigerant introduced into the pressure equalization tubes <NUM> and <NUM>.

Thus, the pressure equalization valves <NUM> and <NUM> may be opened to reduce the pressure difference between the low-pressure guide tubes <NUM> and <NUM> and the refrigerant tubes <NUM> and <NUM> within a predetermined range, thereby realizing pressure equalization.

Also, the pressure equalization valves <NUM> and <NUM> may be closed again. Thus, the low-pressure refrigerant passing through the heat exchangers <NUM> and <NUM> may flow to the low-pressure guide tubes <NUM> and <NUM> without a large pressure difference.

As a result, since the heat exchangers <NUM> and <NUM> are stably switched to serve as the evaporator, noise generation and durability limitations caused by the above-described pressure difference may be solved.

The air conditioning apparatus <NUM> further includes bypass tubes <NUM>, <NUM>, and <NUM> connecting the high-pressure gas tube <NUM> to the low-pressure gas tube <NUM>.

The bypass tube <NUM>, <NUM>, and <NUM> bypass the high-pressure refrigerant flowing through the high-pressure gas tube <NUM> to the heat exchangers <NUM> and <NUM> to prevent the heat exchangers <NUM> and <NUM> from being frozen to burst.

For example, when the temperature of the refrigerant is very low in the process of the heat exchange between the water and the refrigerant (for example, when the temperature of the refrigerant is about <NUM> degree or less), the temperature of the water may be lowered below about <NUM> degree to cause freezing and bursting. When the heat exchangers <NUM> and <NUM> are frozen to burst, the water and the refrigerant may be mixed due to internal leakage, and as a result, a major limitation in the system may occur.

Thus, in this embodiment, to prevent the heat exchanger from being frozen to burst, when there is a risk of the freezing and bursting of the heat exchangers <NUM> and <NUM>, the high-temperature high-pressure refrigerant may be injected into the heat exchangers <NUM> and <NUM> through the bypass tubes <NUM>, <NUM> and <NUM>.

In detail, the bypass tubes <NUM>, <NUM>, and <NUM> may include a common tube <NUM> branching from one point of the high-pressure gas tube <NUM>, a second bypass tube <NUM> branched from the common tube <NUM> and connected to the first liquid guide tube <NUM>, and a third bypass tube <NUM> branched from the common tube <NUM> and connected to the second liquid guide tube <NUM>.

The common tube <NUM> may be branched from a first bypass branch point 20b of the high-pressure gas tube <NUM> to extend. The high-pressure refrigerant of the high-pressure gas tube <NUM> may flow through the common tube <NUM>.

The second bypass tube <NUM> may be branched from a second bypass branch point 141b of the common tube <NUM> to extend to a first bypass combination point 141a of the first liquid guide tube <NUM>.

The first bypass combination point 141a may be defined at a point between the first flow valve <NUM> and the first heat exchanger <NUM> in the first liquid guide tube <NUM>.

Specifically, the first bypass combination point 141a may be defined at a point between the first flow valve <NUM> and the first strainer 148b.

Alternatively, the first bypass combination point 141a may be defined at a point between the first flow valve <NUM> and the first liquid refrigerant sensor <NUM>.

The third bypass tube <NUM> may be branched from the second bypass branch point 141b of the common tube <NUM> and connected to the second bypass combination point 142a of the second liquid guide tube <NUM>.

The second bypass combination point 142a may be defined at a point between the second flow valve <NUM> and the second heat exchanger <NUM> in the second liquid guide tube <NUM>.

Specifically, the second bypass combination point 142a may be defined at a point corresponding to a point between the second flow valve <NUM> and the second strainer 149b.

Alternatively, the second bypass combination point 142a may be defined at a point corresponding to a point between the second flow valve <NUM> and the second liquid refrigerant sensor <NUM>.

The air conditioning apparatus <NUM> further include bypass valves <NUM> and <NUM> installed in each of the bypass tubes <NUM> and <NUM>.

Each of the flow valves <NUM> and <NUM> adjusts a flow rate of the refrigerant by adjusting an opening degree thereof.

Each of the bypass valves <NUM> and <NUM> may include an electronic expansion valve (EEV). Also, each of the bypass valves <NUM> and <NUM> may be adjusted in opening degree to adjust a pressure of the refrigerant passing therethrough.

The bypass valve <NUM> includes a first bypass valve <NUM> installed in the second bypass tube <NUM> and a second bypass valve <NUM> installed in the third bypass tube <NUM>.

Therefore, the first bypass valve <NUM> and the second bypass valve <NUM> may be opened or closed to selectively supply the high-pressure refrigerant flowing through the high-pressure gas tube <NUM> to the first heat exchanger <NUM> or the second heat exchanger <NUM>. Thus, the first heat exchanger <NUM> and the second heat exchanger <NUM> may be prevented from being frozen to burst.

The air conditioning apparatus <NUM> further includes a controller (not shown).

The controller (not shown) controls operations of the high-pressure valves <NUM> and <NUM>, the low-pressure valves <NUM> and <NUM>, the pressure equalization valves <NUM> and <NUM>, and the flow valves <NUM> and <NUM>, which are described so that the operation mode of the heat exchangers <NUM> and <NUM> are switched according to the heating or cooling mode required in the plurality of indoor units <NUM>, <NUM>, <NUM>, and <NUM>.

Also, the controller may adjust an opening degree of each of the bypass valves <NUM> and <NUM> based on the refrigerant temperature detected by the refrigerant sensor.

The heat exchange device <NUM> may further include heat exchanger inlet tubes <NUM> and <NUM> connected to the water passages of the heat exchanger <NUM> and <NUM> and heat exchanger discharge outlet tubes <NUM> and <NUM>.

The heat exchanger inlet tubes <NUM> and <NUM> include a first heat exchanger inlet tube <NUM> connected to an inlet of the water passage of the first heat exchanger <NUM> and a second heat exchanger inlet tube <NUM> to be connected to an inlet of the water passage of the second heat exchanger <NUM>.

The heat exchanger outlet tubes <NUM> and <NUM> include a first heat exchanger outlet tube <NUM> connected to an outlet of the water passage of the first heat exchanger <NUM> and a second heat exchanger outlet tube <NUM> to be connected to an outlet of the water passage of the second heat exchanger <NUM>.

A first pump <NUM> may be provided in the first heat exchanger inlet tube <NUM>, and a second pump <NUM> may be provided in the second heat exchanger inlet tube <NUM>.

A first combination tube <NUM> may be connected to the first heat exchanger inlet tube <NUM>. A second combination tube <NUM> may be connected to the second heat exchanger inlet tube <NUM>.

A third combination tube <NUM> may be connected to the first heat exchanger outlet tube <NUM>. A fourth combination tube <NUM> may be connected to the second heat exchanger outlet tube <NUM>.

A first water outlet tube <NUM> through which water discharged from each of the indoor heat exchangers 61a, 62a, 63a, and 64a flows may be connected to the first combination tube <NUM>.

A second water outlet tube <NUM> through which water discharged from the indoor heat exchangers 61a, 62a, 63a, and 64a flows may be connected to the second combination tube <NUM>.

The first water outlet tube <NUM> and the second water outlet tube <NUM> may be disposed in parallel to each other and be connected to the common water outlet tubes <NUM>, <NUM>, <NUM>, and <NUM> communicating with the indoor heat exchangers 61a, 62a, 63a, and 64a.

The first water outlet tube <NUM>, the second water outlet tube <NUM>, and each of the common water outlet tubes <NUM>, <NUM>, <NUM>, and <NUM> may be connected to each other by, for example, a three-way valve <NUM>.

Accordingly, the water of the common water outlet tube <NUM>, <NUM>, <NUM>, and <NUM> may flow through one of the first water outlet tube <NUM> and the second water outlet tube <NUM> by the three-way valve <NUM>.

The common water outlet tubes <NUM>, <NUM>, <NUM>, and <NUM> may be connected to the outlet tubes of the indoor heat exchangers 61a, 62a, 63a, and 64a, respectively.

First water inlet tubes 165a, 165b, 165c, and 165d through which water to be introduced into each indoor heat exchanger 61a, 62a, 63a, and 64a flows may be connected to the third combination tube <NUM>.

A second water inlet tube 167d through which water to be introduced into each of the indoor heat exchangers 61a, 62a, 63a, and 64a flows may be connected to the fourth combination tube <NUM>.

The first water inlet tubes 165a, 165b, 165c, and 165d and the second water inlet tube 167d may be arranged in parallel to each other and be connected to the common inlet tubes <NUM>, <NUM>, <NUM>, and <NUM> communicating with the indoor heat exchangers 61a, 62a, 63a, and 64a.

Each of the first water inlet tubes 165a, 165b, 165c, and 165d may be provided with a first valve <NUM>, and the second water inlet tubes 167d may be provided with a second valve <NUM>.

An operation in which all the operation modes of the plurality of indoor units <NUM>, <NUM>, <NUM> and <NUM> are the same is referred to as an "exclusive operation". The dedicated operation may be understood as a case in which the indoor heat exchangers 61a, 62a, 63a, and 64a of the plurality of indoor units <NUM>, <NUM>, <NUM>, and <NUM> operate only as the evaporators or as the condensers. Here, the plurality of indoor heat exchangers 61a, 62a, 63a, and 64a may be based on an operating (ON) heat exchanger rather than a stopped (OFF) heat exchanger.

Also, the operations of the plurality of indoor units <NUM>, <NUM>, <NUM>, <NUM> in different operation modes are referred to as a "simultaneous operation". The simultaneous operation may be understood as a case in which some of the plurality of indoor heat exchangers 61a, 62a, 63a, and 64a operate as the condenser, and the remaining indoor heat exchangers operate as the evaporator.

<FIG> is a cycle diagram illustrating a flow of the refrigerant in the heat exchange device during the cooling operation of the air conditioning apparatus according to an embodiment.

Referring to <FIG>, when the air conditioning apparatus <NUM> performs the cooling operation (when a number of indoor units perform the cooling operation), a high-pressure liquid refrigerant condensed in the outdoor heat exchanger <NUM> of the outdoor unit <NUM> is introduced into the switching unit R through the liquid tube.

A portion of the refrigerant introduced into the liquid tube <NUM> is branched at the liquid tube branch point 27a to flow into the first liquid guide tube <NUM>, and the other portion of the refrigerant is branched at the liquid tube branch point 27a to flow into the second liquid guide tube <NUM>.

The condensed refrigerant introduced into the first liquid guide tube <NUM> may be expanded while passing through the first flow valve <NUM>. In addition, the expanded refrigerant may be evaporated by absorbing heat of water while passing through the first heat exchanger <NUM>.

A temperature of the refrigerant flowing into the first heat exchanger <NUM> may be detected by the first liquid refrigerant sensor <NUM>.

The evaporated refrigerant discharged from the first heat exchanger <NUM> may be introduced into the first low-pressure guide tube <NUM> through the first refrigerant tube <NUM> to flow to the low-pressure gas tube <NUM>. Here, the first low-pressure valve <NUM> is opened, and the first high-pressure valve <NUM> is closed.

A temperature of the refrigerant discharged from the first heat exchanger <NUM> may be detected by the first gas refrigerant sensor <NUM>.

Likewise, the condensed refrigerant introduced into the second liquid guide tube <NUM> may be expanded while passing through the second flow valve <NUM>. Also, the expanded refrigerant may be evaporated by absorbing heat of water while passing through the second heat exchanger <NUM>.

A temperature of the refrigerant flowing into the first heat exchanger <NUM> may be detected by the second liquid refrigerant sensor <NUM>.

Likewise, the evaporated refrigerant discharged from the second heat exchanger <NUM> may be introduced into the second low-pressure guide tube <NUM> through the second refrigerant tube <NUM> to flow to the low-pressure gas tube <NUM>. Here, the second low-pressure valve <NUM> is opened, and the second high-pressure valve <NUM> is closed.

A temperature of the refrigerant discharged from the second heat exchanger <NUM> may be detected by the second gas refrigerant sensor <NUM>.

The refrigerant introduced into the low-pressure gas tube <NUM> may be suctioned into the compressor <NUM> of the outdoor unit <NUM> and then condensed in the outdoor heat exchanger <NUM> of the outdoor unit <NUM>. This refrigerant cycle may be circulated.

<FIG> is a flowchart illustrating a method for controlling the air conditioning apparatus to prevent the heat exchanger from being frozen to burst during the cooling operation according to an embodiment.

In <FIG>, a method for preventing the first heat exchanger <NUM> from being frozen to burst during the cooling operation will be described as an example. However, the embodiment is not limited thereto, and a method for preventing the second heat exchanger <NUM> from being frozen to burst may be applied in the same manner.

Referring to <FIG> and <FIG> together, in operation S10, an air conditioning apparatus <NUM> performs a cooling operation.

As described above, an outdoor heat exchanger <NUM> of an outdoor unit <NUM> may function as a condenser, and a plurality of indoor units <NUM>, <NUM>, <NUM>, and <NUM> may operate for cooling. In this case, each of a first heat exchanger <NUM> and a second heat exchanger <NUM> may function as an evaporator for evaporating a refrigerant.

That is, a refrigerant condensed in the outdoor heat exchanger <NUM> may be evaporated while passing through the first heat exchanger <NUM> and the second heat exchanger <NUM>.

In operation S20, the air conditioning apparatus <NUM> detects a temperature of the refrigerant through a first gas refrigerant sensor <NUM> and a first liquid refrigerant sensor <NUM>.

A temperature of the refrigerant introduced into the first heat exchanger <NUM> may be detected by the first liquid refrigerant sensor <NUM>, and a temperature of the refrigerant discharged from the first heat exchanger <NUM> may be detected by the first gas refrigerant sensor <NUM>.

In operation S30, the air conditioning apparatus <NUM> may determine whether the temperature detected by the first gas refrigerant sensor <NUM> or the first liquid refrigerant sensor <NUM> is less than or equal to a first reference temperature.

In detail, to detect a risk of freezing and bursting of the first heat exchanger <NUM>, the air conditioning apparatus <NUM> determines whether each of the temperature of the refrigerant introduced into the first heat exchanger <NUM> and the temperature of the refrigerant discharged from the first heat exchanger <NUM> is less than or equal to the first reference temperature.

When each of the temperature of the refrigerant introduced into the first heat exchanger <NUM> or the temperature of the refrigerant discharged from the first heat exchanger <NUM> is very low, the water flowing through the first heat exchanger <NUM> may be frozen to burst. In this case, the first reference temperature may be, for example, about <NUM> degree, which is a temperature at which water is frozen.

When the temperature detected by the first gas refrigerant sensor <NUM> or the first liquid refrigerant sensor <NUM> is less than or equal to the first reference temperature, in operation S40, the air conditioning apparatus <NUM> determines whether a time at which the temperature of the refrigerant is detected to be less than or equal to the first reference temperature is equal to or greater than a reference time.

That is, if the time at which the temperature of the refrigerant is detected below a first reference temperature is maintained for the reference time or more, since possibility of freezing and bursting of the first heat exchanger <NUM> is high, a time for which the temperature state maintained below the first reference temperature is detected may be confirmed. Here, the reference time may be, for example, about <NUM> minute.

When the time for which the refrigerant temperature is detected below the first reference temperature is equal to or greater than the reference time, the air conditioning apparatus <NUM> opens the first bypass valve <NUM> in operation S50.

In detail, when there is a risk of freezing and bursting of the first heat exchanger <NUM>, the air conditioning apparatus <NUM> opens the first bypass valve <NUM> to supply the high-temperature high-pressure refrigerant to the first heat exchanger <NUM>.

The air conditioning apparatus <NUM> may set an opening degree of the first bypass valve <NUM> as an initial opening value. Here, the initial opening value may be a maximum opening angle of the first bypass valve <NUM>. For example, the initial opening value may be about <NUM> pls (pulses).

When the first bypass valve <NUM> is opened, the high-temperature high-pressure refrigerant flowing through the high-pressure gas tube <NUM> may be introduced into the first heat exchanger <NUM> through the common tube <NUM> and the second bypass tube <NUM>. Accordingly, an internal temperature of the first heat exchanger <NUM> may gradually increase to prevent the heat exchanger from being frozen to burst.

In operation S60, the air conditioning apparatus <NUM> detects a temperature of the refrigerant through a first gas refrigerant sensor <NUM> and a first liquid refrigerant sensor <NUM> after a predetermined time elapses.

In operation S70, the air conditioning apparatus <NUM> may determine whether the temperature detected by each of the first gas refrigerant sensor <NUM> and the first liquid refrigerant sensor <NUM> is less than or equal to a second reference temperature.

Here, the second reference temperature may be, for example, about <NUM> degrees.

That is, when the temperature detected by each of the first gas refrigerant sensor <NUM> and the first liquid refrigerant sensor <NUM> is about <NUM> degrees or more, the air conditioning apparatus <NUM> determines that there is little risk of freezing or bursting of the heat exchanger.

If the temperature detected by each of the first gas refrigerant sensor <NUM> and the first liquid refrigerant sensor <NUM> is less than the second reference temperature, in operation S80, the air conditioning apparatus <NUM> allows the first bypass valve <NUM> to increase in opening degree.

For example, if the temperature detected by each of the first gas refrigerant sensor <NUM> and the first liquid refrigerant sensor <NUM> is less than the second reference temperature (e.g., about <NUM> degrees), the air conditioning apparatus <NUM> may determine that there is still a risk that the heat exchanger is frozen to burst and thus allow the first bypass valve <NUM> to increase in opening degree by about <NUM> pulses.

On the other hand, when the temperature detected by each of the first gas refrigerant sensor <NUM> and the first liquid refrigerant sensor <NUM> is equal to or greater than the second reference temperature, in operation S90, the air conditioning apparatus <NUM> determine whether the opening degree of the first bypass valve <NUM> is equal to or greater than the reference opening value, and when the opening degree of the first bypass valve <NUM> is equal to or greater than the reference opening value, the opening degree of the first bypass valve <NUM> decreases in operation S100,.

In detail, when the temperatures detected by each of the first gas refrigerant sensor <NUM> and the first liquid refrigerant sensor <NUM> is equal to or greater than the second reference temperature (e.g., about <NUM> degrees), it is determined that there is no risk of freezing and bursting of the heat exchanger.

However, when the opening value of the first bypass valve <NUM> is too large, an amount of high-pressure refrigerant introduced into the first heat exchanger <NUM> increases, and as a result, performance of the heat exchanger may be deteriorated. Thus, the amount of high-pressure refrigerant introduced into the first heat exchanger <NUM> may be adjusted to prevent the heat exchanger from being frozen to burst and also maintain the performance of the heat exchanger.

For example, when the opening degree of the first bypass valve <NUM> is above about <NUM> pulses to about <NUM> pulses, the air conditioning apparatus <NUM> may reduce the opening degree of the first bypass valve <NUM> by about <NUM> pulses. Also, the air conditioning apparatus <NUM> may enter operation S60 again.

According to this algorithm, the opening value of the first bypass valve <NUM> may be appropriately adjusted.

If the opening degree of the first bypass valve <NUM> is less than the reference opening value (e.g., about <NUM> pulses), the air conditioning apparatus <NUM> may terminate this algorithm.

On the other hand, in operation S70, if the temperature detected by each of the first gas refrigerant sensor <NUM> and the first liquid refrigerant sensor <NUM> is equal to or greater than the second reference temperature, the operation S90 may be omitted, and the process may proceed to operation S100 that is a next process to reduce the opening degree of the first bypass valve <NUM>.

<FIG> is a cycle diagram illustrating a flow of the refrigerant in the heat exchange device during the simultaneous operation of the air conditioning apparatus according to an embodiment.

Referring to <FIG>, when the air conditioning apparatus <NUM> performs a simultaneous operation (some of the plurality of indoor units perform the cooling operation, and remaining indoor units perform the heating operation), the high-temperature gas refrigerant compressed in the compressors <NUM> and <NUM> is introduced into the switching unit R through the high-pressure gas tube <NUM>.

The refrigerant introduced into the high-pressure gas tube <NUM> is introduced into the first refrigerant tube <NUM> through the first high-pressure guide tube <NUM>. Here, the first high-pressure valve <NUM> is opened, and the first low-pressure valve <NUM> is closed.

The compressed refrigerant introduced into the first refrigerant tube <NUM> may be introduced into the first heat exchanger <NUM> and may be condensed by being heat-exchanged with water.

Here, the water absorbing heat of the refrigerant may be circulated through the indoor units <NUM> and <NUM>, which require the heating operation.

A temperature of the refrigerant flowing into the first heat exchanger <NUM> may be detected by the first gas refrigerant sensor <NUM>.

A temperature of the refrigerant discharged from the first heat exchanger <NUM> may be detected by the first liquid refrigerant sensor <NUM>.

The condensed refrigerant passing through the first heat exchanger <NUM> may flow to the liquid tube branch point 27a through the first liquid guide tube <NUM>. Also, the condensed refrigerant may be branched from the liquid tube branch point 27a to pass through the second flow valve <NUM> through the second liquid guide tube <NUM>.

Here, the second flow valve <NUM> may operate as an expansion valve that expands the refrigerant by adjusting the opening degree thereof.

The expanded refrigerant passing through the second flow valve <NUM> may be evaporated by being heat-exchanged with the water while passing through the second heat exchanger <NUM>.

Here, the water cooled by heat exchange with the refrigerant may be circulated through the indoor units <NUM> and <NUM> requiring the cooling operation.

The evaporated refrigerant passing through the second heat exchanger <NUM> may flow to the second low-pressure guide tube <NUM> through the second refrigerant tube <NUM>.

Here, the second low-pressure valve <NUM> is opened, and the second high-pressure valve <NUM> is closed.

Also, the evaporated refrigerant may be introduced into the low-pressure gas tube <NUM> and collected into the compressors <NUM> and <NUM> of the outdoor unit <NUM>.

<FIG> is a flowchart illustrating a method for controlling the air conditioning apparatus to prevent the heat exchanger from being frozen to burst during the simultaneous operation according to an embodiment.

In <FIG>, a method for preventing the first heat exchanger <NUM> from being frozen to burst during the simultaneous operation will be described as an example.

Referring to <FIG> and <FIG> together, in operation S110, the air conditioning apparatus <NUM> performs the simultaneous operation.

As described above, some of the indoor units <NUM> and <NUM> of the plurality of indoor units <NUM>, <NUM>, <NUM>, and <NUM> may operate for the heating, and the remaining indoor units <NUM> and <NUM> may operate for the cooling. In this case, the first heat exchanger <NUM> may function as the condenser for condensing the refrigerant, and the second heat exchanger <NUM> may function as the evaporator for evaporating the refrigerant.

That is, the high-temperature refrigerant compressed by the compressor <NUM> of the outdoor unit <NUM> may be condensed in the first heat exchanger <NUM> and then evaporated in the second heat exchanger <NUM>.

In operation S120, the air conditioning apparatus <NUM> detects a temperature of the refrigerant through the second gas refrigerant sensor <NUM> and the second liquid refrigerant sensor <NUM>.

A temperature of the refrigerant introduced into the second heat exchanger <NUM> may be detected by the second liquid refrigerant sensor <NUM>, and a temperature of the refrigerant discharged from the second heat exchanger <NUM> may be detected by the second gas refrigerant sensor <NUM>.

Here, the reason for detecting the temperature of the refrigerant flowing through the second heat exchanger <NUM> is that there is a risk of freezing and bursting of only the second heat exchanger <NUM> because the second heat exchanger <NUM> functions as the evaporator during the simultaneous operation. That is, in this case, since the first heat exchanger <NUM> functions as the condenser, there is no risk of freezing or bursting.

In operation S130, the air conditioning apparatus <NUM> may determine whether the temperature detected by the second gas refrigerant sensor <NUM> or the second liquid refrigerant sensor <NUM> is less than or equal to a first reference temperature.

In detail, to detect a risk of freezing and bursting of the second heat exchanger <NUM>, the air conditioning apparatus <NUM> determines whether each of the temperature of the refrigerant introduced into the second heat exchanger <NUM> and the temperature of the refrigerant discharged from the second heat exchanger <NUM> is less than or equal to the first reference temperature.

When each of the temperature of the refrigerant introduced into the second heat exchanger <NUM> or the temperature of the refrigerant discharged from the second heat exchanger <NUM> is very low, the water flowing through the second heat exchanger <NUM> may be frozen to burst. In this case, the first reference temperature may be, for example, about <NUM> degree, which is a temperature at which water is frozen.

When the temperature detected by the second gas refrigerant sensor <NUM> or the second liquid refrigerant sensor <NUM> is less than or equal to the first reference temperature, in operation S140, the air conditioning apparatus <NUM> determines whether a time at which the temperature of the refrigerant is detected to be less than or equal to the first reference temperature is equal to or greater than a reference time.

That is, if the time at which the temperature of the refrigerant is detected below a first reference temperature is maintained for the reference time or more, since possibility of freezing and bursting of the second heat exchanger <NUM> is high, a time for which the temperature state maintained below the first reference temperature is detected may be confirmed. Here, the reference time may be, for example, about <NUM> minute.

When the time for which the refrigerant temperature is detected below the first reference temperature is equal to or greater than the reference time, the air conditioning apparatus <NUM> opens the second bypass valve <NUM> in operation S150.

In detail, when there is a risk of freezing and bursting of the second heat exchanger <NUM>, the air conditioning apparatus <NUM> opens the second bypass valve <NUM> to supply the high-temperature refrigerant to the second heat exchanger <NUM>.

The air conditioning apparatus <NUM> may set an opening degree of the second bypass valve <NUM> as an initial opening value. Here, the initial opening value may be a maximum opening angle of the second bypass valve <NUM>. For example, the initial opening value may be about <NUM> pls (pulses).

When the second bypass valve <NUM> is opened, the high-temperature high-pressure refrigerant flowing through the high-pressure gas tube <NUM> may be introduced into the second heat exchanger <NUM> through the common tube <NUM> and the third bypass tube <NUM>. Accordingly, an internal temperature of the second heat exchanger <NUM> may gradually increase to prevent the heat exchanger from being frozen to burst.

In operation S160, the air conditioning apparatus <NUM> detects a temperature of the refrigerant through a second gas refrigerant sensor <NUM> and a third liquid refrigerant sensor <NUM> after a predetermined time elapses.

In operation S170, the air conditioning apparatus <NUM> may determine whether the temperature detected by each of the second gas refrigerant sensor <NUM> and the second liquid refrigerant sensor <NUM> is less than or equal to a second reference temperature.

That is, when the temperature detected by each of the second gas refrigerant sensor <NUM> and the second liquid refrigerant sensor <NUM> is about <NUM> degrees or more, the air conditioning apparatus <NUM> determines that there is little risk of freezing or bursting of the heat exchanger.

If the temperature detected by each of the second gas refrigerant sensor <NUM> and the second liquid refrigerant sensor <NUM> is less than the second reference temperature, in operation S180, the air conditioning apparatus <NUM> allows the second bypass valve <NUM> to increase in opening degree.

For example, if the temperature detected by each of the second gas refrigerant sensor <NUM> and the second liquid refrigerant sensor <NUM> is less than the second reference temperature (e.g., about <NUM> degrees), the air conditioning apparatus <NUM> may determine that there is a risk that the heat exchanger is frozen to burst and thus allow the second bypass valve <NUM> to increase in opening degree by about <NUM> pulses.

On the other hand, when the temperature detected by each of the second gas refrigerant sensor <NUM> and the second liquid refrigerant sensor <NUM> is equal to or greater than the second reference temperature, in operation S190, the air conditioning apparatus <NUM> determine whether the opening degree of the second bypass valve <NUM> is equal to or greater than the reference opening value, and when the opening degree of the second bypass valve <NUM> is equal to or greater than the reference opening value, the opening degree of the second bypass valve <NUM> decreases in operation S200,.

In detail, when the temperatures detected by each of the second gas refrigerant sensor <NUM> and the second liquid refrigerant sensor <NUM> is equal to or greater than the second reference temperature (e.g., about <NUM> degrees), it is determined that there is no risk of freezing and bursting of the heat exchanger.

However, when the opening value of the second bypass valve <NUM> is too large, an amount of high-temperature refrigerant introduced into the second heat exchanger <NUM> increases, and as a result, performance of the heat exchanger may be deteriorated. Thus, the amount of high-temperature refrigerant introduced into the second heat exchanger <NUM> may be adjusted to prevent the heat exchanger from being frozen to burst and also maintain the performance of the heat exchanger.

For example, when the opening degree of the second bypass valve <NUM> is above about <NUM> pulses to about <NUM> pulses, the air conditioning apparatus <NUM> may reduce the opening degree of the second bypass valve <NUM> by about <NUM> pulses. Also, the air conditioning apparatus <NUM> may enter operation S160 again.

According to this algorithm, the opening value of the second bypass valve <NUM> may be adjusted.

If the opening degree of the second bypass valve <NUM> is less than the reference opening value (e.g., about <NUM> pulses), the air conditioning apparatus <NUM> may terminate this algorithm.

On the other hand, in operation S170, if the temperature detected by each of the second gas refrigerant sensor <NUM> and the second liquid refrigerant sensor <NUM> is equal to or greater than the second reference temperature, the operation S90 may be omitted, and the process may proceed to operation S200 that is a next process to reduce the opening degree of the second bypass valve <NUM>.

<FIG> is a cycle diagram illustrating a flow of the refrigerant in the heat exchange device during an oil collection operation of the air conditioning apparatus according to an embodiment.

Referring to <FIG>, the air conditioning apparatus <NUM> may perform an oil collection operation during the heating operation.

Here, the oil collection operation may be understood as an operation mode for collecting oil accumulated in the gas tube in addition to the tube and the heat exchanger when an oil shortage phenomenon occurs in the compressor during a long heating operation.

That is, when the air conditioning apparatus <NUM> performs the oil collection operation, it may be switched to the cooling mode through a cooling/heating switching valve (not shown). Here, an operation frequency of the compressor may increase to reduce the time for collecting the oil.

When the air conditioning apparatus <NUM> performs the oil collection operation, the high-pressure liquid refrigerant condensed in the outdoor heat exchanger <NUM> of the outdoor unit <NUM> is introduced into the switching unit R through the liquid tube.

<FIG> is a flowchart illustrating a method for controlling the air conditioning apparatus to prevent the heat exchanger from being frozen to burst during the oil collection operation according to an embodiment.

In <FIG>, a method for preventing the first heat exchanger <NUM> from being frozen to burst during the oil collection operation will be described as an example. However, the embodiment is not limited thereto, and a method for preventing the second heat exchanger <NUM> from being frozen to burst may be applied in the same manner.

Referring to <FIG> and <FIG> together, the air conditioning apparatus <NUM> performs the oil collection operation in operation S210.

As described above, when the oil shortage phenomenon of the compressor occurs during the heating operation, the air conditioning apparatus <NUM> may perform the oil collection operation to collect the oil accumulated in the gas tube.

The air conditioning apparatus <NUM> is switched from the heating operation to the cooling operation, the outdoor heat exchanger <NUM> of the outdoor unit <NUM> may function as the condenser, and the plurality of indoor units <NUM>, <NUM>, <NUM>, and <NUM> may operate for the cooling. In this case, each of a first heat exchanger <NUM> and a second heat exchanger <NUM> may function as an evaporator for evaporating a refrigerant.

In operation S220, the air conditioning apparatus <NUM> detects a temperature of the refrigerant through a first gas refrigerant sensor <NUM> and a first liquid refrigerant sensor <NUM>.

In operation S230, the air conditioning apparatus <NUM> may determine whether the temperature detected by the first gas refrigerant sensor <NUM> or the first liquid refrigerant sensor <NUM> is less than or equal to a first reference temperature.

When the temperature detected by the first gas refrigerant sensor <NUM> or the first liquid refrigerant sensor <NUM> is less than or equal to the first reference temperature, in operation S240, the air conditioning apparatus <NUM> determines whether a time at which the temperature of the refrigerant is detected to be less than or equal to the first reference temperature is equal to or greater than a reference time.

When the time for which the refrigerant temperature is detected below the first reference temperature is equal to or greater than the reference time, the air conditioning apparatus <NUM> opens the first bypass valve <NUM> in operation S250.

When the first bypass valve <NUM> is opened, the high-pressure refrigerant flowing through the high-pressure gas tube <NUM> may be introduced into the first heat exchanger <NUM> through the common tube <NUM> and the second bypass tube <NUM>. Accordingly, an internal temperature of the first heat exchanger <NUM> may gradually increase to prevent the heat exchanger from being frozen to burst.

In operation S260, the air conditioning apparatus <NUM> detects a temperature of the refrigerant again through a first gas refrigerant sensor <NUM> and a first liquid refrigerant sensor <NUM> after a predetermined time elapses.

In operation S270, the air conditioning apparatus <NUM> may determine whether the temperature detected by each of the first gas refrigerant sensor <NUM> and the first liquid refrigerant sensor <NUM> is less than or equal to a second reference temperature.

If the temperature detected by each of the first gas refrigerant sensor <NUM> and the first liquid refrigerant sensor <NUM> is less than the second reference temperature, in operation S280, the air conditioning apparatus <NUM> allows the first bypass valve <NUM> to increase in opening degree.

For example, if the temperature detected by each of the first gas refrigerant sensor <NUM> and the first liquid refrigerant sensor <NUM> is less than the second reference temperature (e.g., about <NUM> degrees), the air conditioning apparatus <NUM> may determine that there is a risk that the heat exchanger is frozen to burst and thus allow the first bypass valve <NUM> to increase in opening degree by about <NUM> pulses.

On the other hand, when the temperature detected by each of the first gas refrigerant sensor <NUM> and the first liquid refrigerant sensor <NUM> is equal to or greater than the second reference temperature, in operation S290, the air conditioning apparatus <NUM> determine whether the opening degree of the first bypass valve <NUM> is equal to or greater than the reference opening value, and when the opening degree of the first bypass valve <NUM> is equal to or greater than the reference opening value, the opening degree of the first bypass valve <NUM> decreases in operation S300,.

However, when the opening value of the first bypass valve <NUM> is too large, an amount of high-temperature refrigerant introduced into the first heat exchanger <NUM> increases, and as a result, performance of the heat exchanger may be deteriorated. Thus, the amount of high-temperature refrigerant introduced into the first heat exchanger <NUM> may be adjusted to prevent the heat exchanger from being frozen to burst and also maintain the performance of the heat exchanger.

For example, when the opening degree of the first bypass valve <NUM> is above about <NUM> pulses to about <NUM> pulses, the air conditioning apparatus <NUM> may reduce the opening degree of the first bypass valve <NUM> by about <NUM> pulses. Also, the air conditioning apparatus <NUM> may enter operation S260 again.

According to this algorithm, the opening value of the first bypass valve <NUM> may be adjusted.

On the other hand, in operation S270, if the temperature detected by each of the first gas refrigerant sensor <NUM> and the first liquid refrigerant sensor <NUM> is equal to or greater than the second reference temperature, the operation S290 may be omitted, and the process may proceed to operation S300 that is a next process to reduce the opening degree of the first bypass valve <NUM>.

Particularly, during the oil collection operation, the operation frequency of the compressor may increase to quickly collect the oil. When the operation frequency of the compressor increase, the low pressure is lowered, and as a result, the pressure difference between the high and low pressures increases, and the temperature of the refrigerant passing through the heat exchanger may be lowered rapidly.

Therefore, since the possibility that the heat exchanger is frozen to burst during the oil collection operation increases, when compared to the cooling operation or the simultaneous operation described above in the foregoing embodiment, the opening degree of the first bypass valve may be significantly adjusted to effectively prevent the heat exchanger from being frozen to burst.

According to the air conditioning apparatus according to the embodiment having the above configuration has the following effects.

First, when the indoor unit performs the defrosting operation, the heat exchanger in which the refrigerant and the water are heat-exchanged with each other may be prevented from being frozen to burst.

Particularly, since the high-temperature refrigerant of the high-pressure gas tube is introduced into the heat exchanger through the liquid guide tube via the bypass tube connecting the high-pressure gas tube to the liquid guide tube, the internal temperature of the heat exchanger may increase due to the high-temperature refrigerant.

Second, even when the indoor unit performs the simultaneous operation in which the cooling operation and the heating operation are performed at the same time, the heat exchanger may be prevented from being frozen to burst.

Particularly, the temperature sensors may be installed at the inlet and outlet sides of the refrigerant passages of the plurality of heat exchangers to detect the temperature of the refrigerant flowing into each of the heat exchangers and the temperature of the refrigerant discharged from each of the heat exchangers. Therefore, when the indoor unit operates, the heat exchanger that may occur to be frozen to burst may be determined, and thus, the high-temperature refrigerant may be selectively supplied to only the corresponding heat exchanger.

Third, the temperature of the refrigerant of the heat exchanger may be continuously detected through the temperature sensor to adjust the opening degree of the bypass valve, thereby prevent the heat exchanger from being frozen to burst while maintaining the performance of the heat exchanger.

Fourth, when the oil shortage occurs in the compressor during the heating operation, during the oil collection operation for collecting the oil accumulated in the gas tube, the opening degree of the bypass valve may be adjusted to effectively prevent the heat exchanger from being frozen to burst.

Claim 1:
An air conditioning apparatus comprising:
an outdoor unit (<NUM>) which comprises a compressor (<NUM>) and an outdoor heat exchanger (<NUM>) and through which a refrigerant is circulated;
an indoor unit (<NUM>) through which water is circulated;
a heat exchanger (<NUM>, <NUM>) in which the refrigerant and the water are heat-exchanged with each other;
a high-pressure guide tube (<NUM>, <NUM>) extending from a high-pressure gas tube (<NUM>) of the outdoor unit (<NUM>) so as to be connected to one side of the heat exchanger;
a high-pressure valve (<NUM>, <NUM>) installed in the high-pressure guide tube (<NUM>, <NUM>), the high-pressure valve (<NUM>, <NUM>) being configured to be opened and closed;
a low-pressure guide tube (<NUM>, <NUM>) extending from a low-pressure gas tube (<NUM>) of the outdoor unit (<NUM>) so as to be combined with the high-pressure guide tube (<NUM>, <NUM>);
a low-pressure valve (<NUM>, <NUM>) installed in the low-pressure guide tube (<NUM>, <NUM>), the low-pressure valve (<NUM>, <NUM>) being configured to be opened and closed;
a refrigerant tube (<NUM>, <NUM>) having one end defining a refrigerant branch point (<NUM>, <NUM>), at which the high-pressure guide tube (<NUM>, <NUM>) and the low-pressure guide tube (<NUM>, <NUM>) are combined with each other, and the other end connected to a refrigerant passage of the heat exchanger;
a liquid guide tube (<NUM>, <NUM>) extending from a liquid tube (<NUM>) of the outdoor unit (<NUM>) so as to be connected to the other side of the heat exchanger;
a flow valve (<NUM>, <NUM>) installed in the liquid guide tube (<NUM>, <NUM>) to control a flow rate of the refrigerant;
a bypass tube (<NUM>, <NUM>, <NUM>) configured to connect a bypass branch point (<NUM>, <NUM>) of the high-pressure gas tube (<NUM>) to a bypass combination point of the liquid guide tube (<NUM>, <NUM>) to bypass a high-pressure refrigerant existing in the high-pressure guide tube (<NUM>, <NUM>) to the liquid guide tube (<NUM>, <NUM>);
a bypass valve (<NUM>, <NUM>) installed in the bypass tube (<NUM>, <NUM>, <NUM>); and
a controller controls operations of the high-pressure valve (<NUM>, <NUM>), the low-pressure valve (<NUM>, <NUM>), the flow valve (<NUM>, <NUM>), and the bypass valve (<NUM>, <NUM>).