Patent Description:
In general, an air conditioner is a device for cooling or heating indoor air using a refrigeration cycle device that is composed of a compressor, an outdoor heat exchanger, an expansion device, and an indoor heat exchanger.

In the case of cooling indoor air, the outdoor heat exchanger functions as a condenser, the indoor heat exchanger functions as an evaporator, and a refrigerant is circulated in the order of the compressor, the outdoor heat exchanger, the expansion device, the indoor heat exchanger, and the compressor.

In the case of heating indoor air, the outdoor heat exchanger functions as an evaporator, the indoor heat exchanger functions as a condenser, and a refrigerant is circulated in the order of the compressor, the indoor heat exchanger, the expansion mechanism, the outdoor heat exchanger, and the compressor.

<CIT> relates to a technique for improving operation performance of an outdoor heat exchanger by allowing a refrigerant to flow smoothly at a low outside temperature. However, the aforementioned related patent document does not disclose a technique of separating a refrigerant by a flow pattern inside an evaporator and controlling a degree of superheat of the separated refrigerant.

<CIT>) relates to an outdoor heat exchanger and an air-conditioner having the same capable of separating liquid-phase refrigerant and gas-phase refrigerant from a refrigerant flowing therein.

<CIT>) discloses an outdoor device for an air conditioner.

The present invention generally concerns a technique relating to an air conditioner that superheats a refrigerant, separated by a flow pattern, inside an evaporator to prevent damage to a compressor and improve reliability.

The invention is specified by the independent claim.

Specific details of other embodiments are included in the detailed description and drawings.

The above and other aspects, features, and advantages of certain embodiments will be more apparent from the following detailed description taken in conjunction with the accompanying drawings, in which:.

Hereinafter, air conditioners which are helpful to understand the present invention or which form part of the present invention will be described in detail with reference to the accompanying drawings.

Hereinafter, the same or similar elements are assigned the same reference numbers regardless of the reference numerals, and overlapping descriptions thereof will be omitted. The suffixes "module" and "part" for components used in the following description are given or mixed only considering the ease of writing the specification, and do not have meanings or roles that are distinguished from each other. In addition, in the description of the embodiments disclosed herein, when it is determined that detailed descriptions of related known technologies may obscure the gist of the embodiments disclosed herein, detailed descriptions thereof will be omitted. In addition, the accompanying drawings are used to help easily understand various technical features and it should be understood that the embodiments presented herein are not limited by the accompanying drawings. The present invention is only limited by the features of the appended independent claim.

Terms including ordinal numbers such as first and second may be used to describe various components, but the components are not limited by the terms. The terms are used only for the purpose of distinguishing one component from other components.

When an element is said to be "connected" or "connected" to another component, it is understood that other components may be directly connected to or connected to the other component, but there may be other components in between. On the other hand, when a component is said to be "directly connected" or "directly connected" to another component, it should be understood that no other component exists in the middle.

Singular expressions include plural expressions unless the context clearly indicates otherwise.

In this application, terms such as "comprises" or "have" are intended to indicate that a feature, number, step, operation, component, part, or combination thereof described in the specification exists, and that one or more other features are present. It should be understood that the existence or addition possibilities of fields or numbers, steps, operations, components, parts or combinations thereof are not excluded in advance.

In describing the embodiments, descriptions of technical contents well known in the technical field to which the present disclosure pertains and which are not directly related to the present disclosure will be omitted. This is to more clearly and without obscuring the subject matter of the present disclosure by omitting unnecessary description.

For the same reason, some components in the accompanying drawings are exaggerated, omitted, or schematically illustrated. Also, the size of each component does not entirely reflect the actual size. The same reference numbers are assigned to the same or corresponding elements in each drawing.

Advantages and features of the present invention, which is defined by appended independent claim <NUM>, and a method of achieving them will be apparent with reference to embodiments described below in detail together with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, and may be implemented in various different forms, and only the embodiments allow the disclosure of the present disclosure to be complete, and common knowledge in the technical field to which the present disclosure pertains. The same reference numerals refer to the same components throughout the specification.

<FIG> is a diagram illustrating an air conditioner including an indoor unit and an outdoor unit.

Referring to <FIG>, the air conditioner may include an indoor unit <NUM> and an outdoor unit <NUM>. In the air conditioner, the indoor unit <NUM> is depicted as a standing type, but may be a wall-mounted type or a ceiling-mounted type. The indoor unit <NUM> is not limited to a standing type, a wall-mounted type, or a ceiling type, and may be installed indoors in any of various shapes.

The outdoor unit <NUM> may be connected to the indoor unit <NUM> and transfer refrigerant necessary for air conditioning in the indoor unit <NUM> to the indoor unit <NUM>. The indoor unit <NUM> may exchange heat between the transferred refrigerant and air, and discharge the heat-exchanged air into an indoor space.

The indoor unit <NUM> and the outdoor unit <NUM> may be connected through a refrigerant pipe so that refrigerant circulates through the indoor unit <NUM> and the outdoor unit <NUM> via the refrigerant pipe. Hot or cold air may be discharged into the indoor space from the indoor unit <NUM> that performs a heating operation or a cooling operation according to circulation of the refrigerant. At this point, at least one indoor unit <NUM> may be connected to the outdoor unit <NUM>, and <FIG> shows connection between one outdoor unit <NUM> and one indoor unit <NUM> as an example.

The indoor unit <NUM> and the outdoor unit <NUM> may be connected via a cable for communication, and hence, control commands may be transmitted or received according to a predetermined communication method.

The indoor unit <NUM> may include an inlet for suctioning indoor air, and an outlet for discharging heat-exchanged air from an inside. The indoor unit <NUM> may include an air direction control apparatus provided in the outlet. The air direction control apparatus may open and close the outlet or may control a direction of air discharged from the outlet. In addition, the indoor unit <NUM> may control a volume of air discharged from the outlet. The indoor unit <NUM> may include a vane installed at the inlet or the outlet. The vane may open and close at least one of the inlet and the outlet, and may guide an air flow direction.

The indoor unit <NUM> may further include a display for displaying an operating state and setting information of the indoor unit <NUM>, and an input part for inputting setting data. When the user inputs an operation command for the air conditioner through the input part, the outdoor unit <NUM> may be operated for a cooling operation or a heating operation in response to the input operation command. At this point, the user may input an operation command for the air conditioner manually or through communication.

When the air conditioner is in a cooling operation, the outdoor heat exchanger included in the outdoor unit may function as a condenser in which a refrigerant flowing to the outdoor heat exchanger is condensed by outdoor air. Also, when the air conditioner is in a heating operation, the outdoor heat exchanger may function as an evaporator in which liquid-phase refrigerant flowing into the outdoor heat exchanger can be evaporated by outdoor air.

The indoor unit may include an indoor heat exchanger <NUM> for performing heat exchange between indoor air and refrigerant, and an indoor blower <NUM> for blowing the indoor air to the indoor heat exchanger <NUM>. When the air conditioner is in a cooling operation, the indoor heat exchanger included in the indoor unit may function as an evaporator in which refrigerant flowing into the indoor heat exchanger is evaporated by indoor air. In addition, when the air conditioner is in a heating operation, the indoor heat exchanger included in the indoor unit may function as a condenser in which a refrigerant flowing to the indoor heat exchanger is condensed by indoor air.

<FIG> is a diagram showing a system of an air conditioner according to an embodiment which does not form part of the present invention but which is helpful to understand the present invention.

Referring to <FIG>, the air conditioner may include at least one of: a compressor <NUM>, a four way valve <NUM>, a condenser <NUM>, a first expansion device, an second expansion device, a flow rate control valve, a subcooler <NUM>, an evaporator <NUM>, and an accumulator <NUM>.

The compressor <NUM> may compress a refrigerant. The condenser <NUM> may condense the refrigerant passing through the compressor <NUM>. In addition, the evaporator may evaporate the refrigerant passing through the first expansion device and the second expansion device. In addition, the first expansion device and the second expansion device may expand the refrigerant passing through the condenser <NUM>. The first expansion device may be installed at a refrigerant pipe between the subcooler <NUM> and the evaporator <NUM>, and the second expansion device may be installed at a refrigerant pipe between the subcooler <NUM> and the condenser <NUM>. At this point, an opening degree of each of the first expansion device and the second expansion device may be adjusted to or not to expand the refrigerant flowing therein. For example, when the air conditioner is in a heating operation, the second expansion device may be fully opened so that the refrigerant passing through the condenser is not expanded, and an opening degree of the first expansion device may be adjusted to partially open the first expansion device, so that the refrigerant passing through the condenser is expanded.

When the air conditioner is in the cooling operation, the outdoor heat exchanger may function as a condenser, and the indoor heat exchanger may function as an evaporator. In the cooling operation of the air conditioner, a refrigerant may circulate in the order of the compressor, the condenser, the first expansion device, the second expansion device, the evaporator, the accumulator and the compressor.

When the air conditioner is in a heating operation, the outdoor heat exchanger may function as an evaporator, and the indoor heat exchanger can function as a condenser. In the heating operation of the air conditioner, a refrigerant may circulate in the order of the compressor, the condenser, the first expansion device, the second expansion device, the evaporator, the accumulator and the compressor.

As such, the air conditioner may be an air conditioner capable of both the cooling operation and the heating operation. Hereinafter, the case where the air conditioner is operated for the heating operation will be described. Yet, the scope of the present disclosure is not limited thereto and may also include the case where the air conditioner is operated for the cooling operation.

When the air conditioner is in the heating operation, the indoor unit may include a condenser <NUM> which corresponds to an indoor heat exchanger, and the outdoor unit may include an evaporator <NUM> which corresponds to an outdoor heat exchanger. In addition, the outdoor unit may include at least one of a compressor <NUM>, a four way valve <NUM>, a subcooler <NUM>, and an accumulator <NUM>.

The four way valve <NUM> may allow a refrigerant discharged from the compressor <NUM> to flow either to the outdoor heat exchanger or to the indoor heat exchanger. Further, the accumulator <NUM> may separate a gas refrigerant from a two-phase refrigerant that includes the gas refrigerant and a liquid refrigerant. The liquid refrigerant separated by the accumulator <NUM> may be received in a lower side of the accumulator <NUM>, and the gas refrigerant may be received above the separated liquid refrigerant. The gas refrigerant separated by the accumulator <NUM> may flow to the compressor <NUM>, and the liquid refrigerant separated by the accumulator <NUM> may remain in the accumulator <NUM>.

When the air conditioner is in the heating operation, a refrigerant may pass through the compressor <NUM> and the indoor heat exchanger <NUM>, expand in the first expansion device, and be then heat exchanged with outdoor air in the outdoor heat exchanger <NUM>. At this point, the second expansion device may be fully opened, and an opening degree of the first expansion device may be adjusted to expand the refrigerant.

Specifically, when the air conditioner is in the heating operation, a refrigerant discharged from the compressor may flow to the indoor heat exchanger <NUM> by the four way valve <NUM>. A refrigerant condensed in the indoor heat exchanger <NUM> may be subcooled by the subcooler <NUM> and then flow to the outdoor heat exchanger <NUM>.

The refrigerant condensed in the indoor heat exchanger <NUM> may flow through the refrigerant pipe <NUM>. The refrigerant may flow to the subcooler <NUM> through the refrigerant pipe <NUM>. In addition, the refrigerant passing through the subcooler <NUM> may flow to the evaporator through the refrigerant pipe <NUM>. Here, the refrigerant flowing through the refrigerant pipe <NUM> and the refrigerant pipe <NUM> will be referred to as a first refrigerant.

In order to inject refrigerant into the compressor <NUM>, a portion of the first refrigerant may be branched by the bypass pipe <NUM>. Hereinafter, the portion branched from the first refrigerant will be referred to as a second refrigerant. That is, the second refrigerant may be a refrigerant flowing through the bypass pipe <NUM>.

The flow rate control valve installed at the bypass pipe <NUM>, and the amount of the second refrigerant flowing through the bypass pipe <NUM> may be determined by adjusting the opening degree of the flow rate control valve. When the flow rate control valve is opened, the second refrigerant may flow to the subcooler <NUM> through the bypass pipe <NUM> and then may be discharged from the subcooler <NUM> to flow to the compressor. At this point, the second refrigerant discharged from the subcooler <NUM> may be injected into the compressor <NUM>.

The first refrigerant flowing through the refrigerant pipe <NUM> and the refrigerant pipe <NUM> may flow through a plurality of inner tubes inside the subcooler <NUM>, and the second refrigerant may flow through an outer tube. At this point, the plurality of inner tubes may be disposed in an inner space of the subcooler <NUM>, and the first refrigerant flowing through the plurality of inner tubes may be heat exchanged with the second refrigerant flowing through the outer tube. Specifically, the second refrigerant may be expanded by the flow rate control valve to have a lower temperature and a lower pressure compared to the first refrigerant, and the second refrigerant of the lower temperature and the lower pressure may, while flowing through the outer tube, exchange heat with the first refrigerant flowing through the inner tube. At this point, the first refrigerant may be subcooled, and the second refrigerant may be superheated. At this point, the subcooled first refrigerant may flow to the evaporator <NUM> through the refrigerant pipe <NUM>. The evaporator <NUM> may evaporate a liquid refrigerant into a gas refrigerant through heat exchange with outdoor air.

In some examples, the subcooler <NUM> can include a heat exchanger or a refrigerant passage or pipe configured to exchange heat with the refrigerant that has passed through the refrigerant pipe <NUM>. In some examples, the subcooler <NUM> can be a portion of a refrigerant pipe that carries a liquid-phase refrigerant, a gas-phase refrigerant, or both.

<FIG> is a diagram illustrating a system of an air conditioner according to an embodiment of the present invention.

Referring to <FIG>, the air conditioner includes a compressor <NUM>, optionally a four way valve <NUM>, further a condenser <NUM>, a first expansion device, a second expansion device, a flow rate control valve, a subcooler <NUM>, an evaporator <NUM>, and an accumulator <NUM>.

The compressor <NUM> may compress a refrigerant. The condenser <NUM> may condense the refrigerant passing through the compressor <NUM>. In addition, the evaporator may evaporate the refrigerant passing through the first expansion device and the second expansion device. When the air conditioner is an embodiment of the present invention, all these aspects, referred to as a possibility by using the modal verb "may", are actually present. The present invention is defined by the subject-matter of appended independent claim <NUM>. In addition, the first expansion device and the second expansion device may expand the refrigerant passing through the condenser <NUM>. Here, the first expansion device may be installed at a refrigerant pipe between the subcooler <NUM> and the evaporator <NUM>, and the second expansion device may be installed at a refrigerant pipe between the subcooler <NUM> and the condenser <NUM>. At this point, an opening degree of each of the first expansion device and the second expansion device may be adjusted to or not to expand the refrigerant flowing through the refrigerant pipes <NUM> and <NUM>. For example, when the air conditioner is in a heating operation, the second expansion device may be fully opened so that the refrigerant passing through the condenser is not expanded, and an opening degree of the first expansion device may be adjusted to partially open the first expansion device, so that the refrigerant passing through the condenser is expanded.

When the air conditioner is in the cooling operation, the outdoor heat exchanger functions as a condenser, and the indoor heat exchanger functions as an evaporator. In the cooling operation of the air conditioner, a refrigerant may circulate in the order of the compressor, the condenser, the first expansion device, the second expansion device, the evaporator, the accumulator and the compressor.

When the air conditioner is in a heating operation, the outdoor heat exchanger functions as an evaporator, and the indoor heat exchanger functions as a condenser. In the heating operation of the air conditioner, a refrigerant may circulate in the order of the compressor, the condenser, the first expansion device, the second expansion device, the evaporator, the accumulator and the compressor. Wherever, in this disclosure, such steps or structural aspects are described as being only a possibility, by usage of the modal verb "may", the skilled person understands that these steps are actually taking place and that these structures are actually present in an air conditioner forming an embodiment of the present invention.

When the air conditioner is in the heating operation, the indoor unit may include the condenser <NUM> which corresponds to an indoor heat exchanger, and the outdoor unit may include the evaporator <NUM> which corresponds to an outdoor heat exchanger. In addition, the outdoor unit may include at least one of the compressor <NUM>, the four way valve <NUM>, the subcooler <NUM>, and the accumulator <NUM>.

The four way valve <NUM> may guide a refrigerant discharged from the compressor <NUM> to flow either to an outdoor heat exchanger or to an indoor heat exchanger. Further, the accumulator <NUM> may separate a gas refrigerant from a two-phase refrigerant that includes a liquid refrigerant and the gas refrigerant. The liquid refrigerant separated from the accumulator <NUM> may be received in a lower side of the accumulator <NUM>, and the gas refrigerant may be received above the separated liquid refrigerant. The gas refrigerant separated in the accumulator <NUM> may flow to the compressor <NUM>, and the liquid refrigerant separated in the accumulator <NUM> may remain in the accumulator <NUM>.

When the air conditioner is in the heating operation, a refrigerant may expand in the first expansion device after passing through the compressor <NUM> and the indoor heat exchanger <NUM>, and then may be heat exchanged with outdoor air in the outdoor heat exchanger <NUM>. At this point, the second expansion device may be fully opened, and an opening degree of the first expansion device may be adjusted to expand the refrigerant.

Specifically, when the air conditioner is in the heating operation, a refrigerant discharged from the compressor may flow to the indoor heat exchanger <NUM> by the four way valve <NUM>. The refrigerant condensed in the indoor heat exchanger <NUM> may be subcooled in the subcooler <NUM> and then flow to the outdoor heat exchanger <NUM>.

The air conditioner may include a gas-liquid separator. Here, the gas-liquid separator may separate a gas refrigerant in the evaporator <NUM> and guide the gas refrigerant to the compressor <NUM>. Specifically, the gas-liquid separator may include at least one of: a connection pipe <NUM>, a header <NUM>, a flow rate control valve, and a bypass pipe <NUM>. At this point, a refrigerant separated by the gas-liquid separator to flow through the bypass pipe <NUM> will be referred to as a second refrigerant.

The connection pipe <NUM> connected to a refrigerant pipe inside the outdoor heat exchanger that operates as an evaporator during a heating operation. The connection pipe <NUM> separates a refrigerant from the two-phase refrigerant flowing through the refrigerant pipe inside the outdoor heat exchanger. A plurality of connection pipes <NUM> connected to the header <NUM>, and a refrigerant separated through the plurality of connection pipes <NUM> flows through the header <NUM>. The header <NUM> is connected to the bypass pipe <NUM> that guides a flow of the refrigerant to the compressor. For details of the connection pipe <NUM> and the header <NUM>, <FIG> can be referred to. The flow rate control valve is installed at the bypass pipe <NUM> to control a flow rate of the refrigerant flowing through the bypass pipe <NUM>. For example, the flow rate control valve may include an electromagnetic expansion valve or a solenoid valve.

The air conditioner includes a subcooler <NUM>, and heat exchange between the first refrigerant and the second refrigerant flowing through the bypass pipe <NUM> occurs in the subcooler <NUM>. The second refrigerant may flow to the subcooler <NUM> through the bypass pipe <NUM>, and the second refrigerant and the first refrigerant may be heat exchanged in the subcooler <NUM>. At this point, due to the heat exchange between the refrigerants in the subcooler <NUM>, the first refrigerant may be subcooled and the second refrigerant is superheated. The first refrigerant may flow through a plurality of inner tubes inside the subcooler <NUM>, and the second refrigerant may flow through an outer tube. At this point, the plurality of inner tubes may be arranged in an inner space of the subcooler <NUM>, and the first refrigerant flowing through the plurality of inner tubes may exchange heat with the second refrigerant flowing through the outer tube. Specifically, the second refrigerant may be expanded by the flow rate control valve to have a lower temperature and lower pressure compared to the first refrigerant, and the second refrigerant of the lower temperature and the lower pressure may, while flowing the outer tube, exchange heat with the first refrigerant flowing through the plurality of inner tubes. The first refrigerant may be subcooled and the second refrigerant may be superheated. At this point, the first refrigerant subcooled may flow to the evaporator <NUM> through the refrigerant pipe <NUM>, and the second refrigerant superheated may flow to the compressor <NUM>. As the second refrigerant is superheated, a gas refrigerant may account for a greater proportion in refrigerants flowing to the compressor <NUM> through the bypass pipe <NUM>, and accordingly, stability and reliability of operation of the compressor <NUM> may be further improved.

The air conditioner may include a first temperature sensor for measuring a temperature of the second refrigerant flowing into the subcooler <NUM>. In addition, the air conditioner may include a second temperature sensor for measuring a temperature of the second refrigerant discharged from the subcooler <NUM>. That is, the first temperature sensor may measure a temperature of the second refrigerant at an inlet of the subcooler <NUM>, through which the second refrigerant is introduced into the subcooler <NUM>, and the second temperature sensor may measure a temperature of the second refrigerant at an outlet of the subcooler <NUM>, through which the second refrigerant is discharged to flow to the compressor <NUM>.

The air conditioner includes a controller for controlling an opening degree of the flow rate control valve. When the flow rate control valve is closed, the refrigerant separated from the two-phase refrigerant flowing through the refrigerant pipe inside the outdoor heat exchanger during a heating operation may not flow to the bypass pipe <NUM>. In addition, when the flow rate control valve is opened, the refrigerant separated from the two-phase refrigerant flowing through the refrigerant pipe inside the outdoor heat exchanger during the heating operation may flow to the bypass pipe <NUM>. During the heating operation, the controller estimates a flow velocity of the two-phase refrigerant flowing through the refrigerant pipe inside the outdoor heat exchanger based on relevant information, according to the definitions provided by the appended independent claim, and controls the opening degree of the flow rate control valve by comparing the estimated flow velocity with a reference flow velocity.

When the two-phase refrigerant flowing through the refrigerant pipe inside the outdoor heat exchanger <NUM> during the heating operation flows in the form of an annular flow, the controller may control the flow rate control valve to be opened. When the flow rate control valve is opened before the annular flow occurs, a large amount of liquid refrigerant may flow through the bypass pipe <NUM> to the compressor <NUM>, thereby damaging the compressor and deteriorating the reliability of the air conditioner. Therefore, in order to improve the reliability of the air conditioner, it is necessary that the second refrigerant flowing to the compressor does not include a liquid refrigerant.

To this end, the controller may control the opening degree of the flow rate control valve based on a comparison between a refrigerant flow velocity and a reference flow velocity, and the controller may also control the opening degree of the flow rate control valve based on information obtained by the first temperature sensor and the second temperature sensor.

Specifically, the controller estimates a refrigerant flow velocity of a two-phase refrigerant flowing inside the evaporator in consideration of a type of the compressor, a frequency of the compressor, the number of paths of the outdoor unit, and an outside temperature. The controller may estimate a refrigerant flow velocity V1 of the two-phase refrigerant flowing inside the evaporator by Equation <NUM> below.

Here, N may be determined according to the type of the compressor, P may be determined as a current number of paths of the evaporator compared to <NUM> paths, and A and B may be statistical values determined according to a current frequency. For example, if a current number of paths of the evaporator is <NUM>, P may be <NUM>, and N may be a value predetermined according to the type of the compressor. Also, A and B may be determined by Equation <NUM> below. Here, A1, A2, B1, and B2 may be statistical values determined by experiments.

In addition, the reference flow velocity is a flow velocity at a time when two-phase refrigerant flowing through the refrigerant pipe inside the evaporator flows in the form of an annular flow, and a reference flow velocity V2 may be determined by Equation <NUM> below. Here, C and D may be statistical values determined by experiments.

The controller controls whether to open or close the flow rate control valve, based on a comparison between an estimated refrigerant flow velocity and the reference flow velocity. Specifically, when the estimated refrigerant flow velocity is greater than the reference flow velocity at a predetermined ratio or more with respect to the reference flow velocity, the controller may open the flow rate control valve so that the refrigerant flows from the evaporator to the bypass pipe. Alternatively, when the estimated refrigerant flow velocity is not greater than the reference flow velocity at the predetermined ratio or more, the controller may close the flow rate control valve so that the refrigerant is prevented from flowing into the bypass pipe. At this point, the predetermined ratio, which is a ratio that takes into consideration a margin between the estimated refrigerant flow velocity and the reference flow velocity, may be a value set for reliability. For example, in the case where it is determined that reliability is ensured when the refrigerant flow velocity is <NUM>% greater than the reference flow velocity, the flow rate control valve may be opened if the refrigerant flow velocity is <NUM> times or greater the reference flow velocity, or in the case where it is determined that reliability is ensured when the refrigerant flow velocity is <NUM>% greater than the reference flow velocity, the flow rate control valve may be opened if the refrigerant flow velocity is <NUM> times or greater the reference flow velocity.

When the flow rate control valve is opened by the controller, the second refrigerant separated from the two-phase refrigerant flowing through the refrigerant pipe inside the evaporator may flow through the bypass pipe <NUM>. At this point, the second refrigerant separated from the two-phase refrigerant flowing through the refrigerant pipe inside the evaporator may consist mostly of a gas refrigerant and may also include a small proportion of a liquid refrigerant. At this point, when a portion of the liquid refrigerant in the two-phase refrigerant is introduced into the compressor <NUM>, the compressor <NUM> may be damaged. For this reason, the second refrigerant may be superheated in order to ensure the reliability of the air conditioner. Specifically, since the second refrigerant and the first refrigerant are heat exchanged in the subcooler <NUM>, a temperature of the second refrigerant discharged from the subcooler <NUM> may be higher than a temperature of the second refrigerant introduced into the subcooler <NUM>. In addition, since the second refrigerant and the first refrigerant are heat exchanged in the subcooler <NUM>, a temperature of the first refrigerant discharged from the subcooler <NUM> may be lower than a temperature of the first refrigerant introduced into the subcooler <NUM>.

As the second refrigerant is superheated in the subcooler <NUM>, a portion of the liquid refrigerant included in the second refrigerant may be vaporized, thereby restricting the introduction of the liquid refrigerant into the compressor <NUM> through the bypass pipe <NUM> whereas allowing the gas refrigerant to flow into the compressor <NUM>. Therefore, damage to the compressor <NUM> may be prevented, thereby improving the reliability of the air conditioner.

More specifically, the controller may control the opening degree of the flow rate control valve based on information obtained by the first temperature sensor and the second temperature sensor. The first temperature sensor may measure a temperature of a portion of the subcooler <NUM>, through which the second refrigerant is introduced, and the second temperature sensor may measure a temperature of a portion of the subcooler <NUM>, from which the second refrigerant is discharged. A degree of superheat of the second refrigerant may be estimated based on a difference between the temperature measured by the first temperature sensor and the temperature measured by the second temperature sensor. At this point, when the degree of superheat of the second refrigerant is higher than a reference value, the compressor <NUM> may be prevented from being damaged, and thus, the controller may increase the opening degree of the flow rate control valve than before. In addition, when the degree of superheat of the second refrigerant is less than the reference value, the compressor <NUM> is likely to be damaged, and thus, the controller may decrease the opening degree of the flow rate control valve than before. When the opening degree of the flow rate control valve is increased, a flow rate of the second refrigerant may be increased, and when the opening degree of the flow rate control valve is decreased, a flow rate of the second refrigerant may be decreased. Here, the reference value may be a statistical value determined by experiments in order to ensure the reliability of the air conditioner. For example, when the degree of superheat is <NUM>% greater than the reference value, the controller may increase the opening degree of the flow rate control valve by <NUM>% than before, or when the degree of superheat is <NUM>% greater than the reference value, the controller may increase the opening degree of the flow rate control valve by <NUM>% than before. In another example, when the degree of superheat is <NUM>% less than the reference value, the controller may reduce the opening degree of the flow rate control valve by <NUM>% than before, or when the degree of superheat is <NUM>% less than the reference value, the controller may reduce the opening degree of the flow rate control valve by <NUM>% than before. That is, the controller may control the opening degree of the flow rate control valve based on a comparison between the degree of superheat and the reference value.

<FIG> may be a diagram illustrating a refrigerant pipe of an evaporator according to an embodiment.

Referring to <FIG>, an evaporator which functions as an outdoor heat exchanger during a heating operation may include a plurality of refrigerant flow channels <NUM>, <NUM>, and <NUM> through which a two-phase refrigerant flows, and a plurality of heat exchange pins <NUM>. A plurality of connection pipes <NUM> of the gas-liquid separator in <FIG> may be connected to a plurality of refrigerant pipe <NUM>, <NUM>, and <NUM> in <FIG>, and a refrigerant separated from the plurality of refrigerant pipes <NUM>, <NUM>, and <NUM> may flow into the bypass pipe <NUM> through the plurality of connection pipes <NUM>. Here, the plurality of refrigerant flow channels <NUM>, <NUM>, and <NUM>, the plurality of heat exchange pins <NUM>, and a plurality of refrigerant straight-type pipes <NUM> in <FIG> are merely examples, and the scope of the present disclosure is not limited thereto.

The plurality of refrigerant flow channels <NUM>, <NUM>, and <NUM> may pass through the plurality of heat exchange pins <NUM>. The plurality of heat exchange pins <NUM> may have through holes respectively formed therein, and the plurality of refrigerant flow channels <NUM>, <NUM>, and <NUM> may pass through the respective through holes. In a state in which the plurality of refrigerant flow channels <NUM>, <NUM>, and <NUM> passes through the respective through holes, outer circumferential surfaces of the plurality of refrigerant flow channels <NUM>, <NUM>, <NUM> may contact inner circumferential surfaces of the respective through holes.

The plurality of heat exchange pins <NUM> may contact air, thereby improving heat exchange performance between refrigerants flowing in the plurality of refrigerant flow channels <NUM>, <NUM>, and <NUM> and air outside the plurality of refrigerant flow channels <NUM>, <NUM>, and <NUM>. The plurality of heat exchange pins <NUM> each may be formed of a rectangular plate body, for example. The plurality of heat exchange pins <NUM> each may have one surface disposed parallel to each other.

The plurality of connection pipes <NUM> of the gas-liquid separator may be installed to correspond to the plurality of refrigerant flow channels, respectively. For example, if there are ten flow channels <NUM>, <NUM>, and <NUM>, the number of the connection pipes <NUM> may be <NUM>, as shown in <FIG>. In another example, if there are three refrigerant flow channels <NUM>, <NUM>, and <NUM>, the number of the connection pipes <NUM> may be <NUM>, as shown in <FIG>.

At this point, the plurality of connection pipes <NUM> each may be installed at a position where a dryness of the two-phase refrigerant flowing inside the evaporator corresponds to a predetermined range. Specifically, the plurality of refrigerant pipes <NUM>, <NUM>, and <NUM> may be installed at positions where a dryness of the two-phase refrigerant flowing inside the evaporator corresponds to the predetermined range, and the plurality of connection pipes may be connected to the plurality of installed refrigerant pipes <NUM>, <NUM>, and <NUM>, respectively. For example, the plurality of refrigerant pipes <NUM>, <NUM>, and <NUM> may be installed at positions where a dryness of the two-phase refrigerant flowing inside the evaporator corresponds to <NUM> to <NUM>, and the plurality of connection pipes may be connected to the plurality of installed refrigerant pipes <NUM>, <NUM>, and <NUM>. In another example, a dryness of the two-phase refrigerant near portions where the plurality of refrigerant pipe <NUM>, <NUM>, and <NUM> are connected to the plurality of connection pipes may be included in the range of <NUM> to <NUM>.

In some examples, the refrigerant pipe includes a coupling portion connected to the connection pipe, and a composition ratio of the two-phase refrigerant at the coupling portion can be maintained within a predetermined range. The composition ratio of the two-phase refrigerant can be a ratio between a gas-phase refrigerant and a liquid-phase refrigerant, and define a dryness of the two-phase refrigerant.

The refrigerant flow channel <NUM> may include a plurality of refrigerant straight-type pipes <NUM> and a plurality of refrigerant pipes <NUM> and <NUM>. The plurality of refrigerant straight-type pipes <NUM> each may be formed straight in a longitudinal direction. The plurality of refrigerant straight-type pipes <NUM> each may be arranged in parallel to one another. The plurality of refrigerant straight-type pipes <NUM> may pass through the plurality of heat exchange pins <NUM>. The plurality of heat exchange pins <NUM> may have through holes respectively formed therein, and the plurality of refrigerant straight-type pipes <NUM> may pass through the respective through holes. In a state in which the plurality of refrigerant straight-type pipes <NUM> passes through the respective through holes, outer circumferential surfaces of the plurality of refrigerant straight-type pipes <NUM> may contact inner circumferential surfaces of the respective through holes. The refrigerant pipe <NUM> included in the refrigerant flow channel <NUM> may be a U-shaped refrigerant pipe, and the refrigerant pipe <NUM> included in the refrigerant flow channel <NUM> may be an h-shaped refrigerant pipe. The U-shaped refrigerant pipe <NUM> may connect refrigerant straight-type pipes <NUM> adjacent to each other among the plurality of refrigerant pipes <NUM>. At least one h-shaped refrigerant pipe <NUM> may be disposed at the refrigerant flow channel <NUM>. A refrigerant may be separated from the two-phase refrigerant through the refrigerant pipe <NUM>. At this point, the separated refrigerant may consist mostly of a gas refrigerant and may include a small proportion of a liquid refrigerant. The refrigerant flow channels <NUM> and <NUM> may be applied in the same manner as the refrigerant flow channels <NUM>.

<FIG> is a diagram illustrating a flow pattern of a liquid refrigerant and a gas refrigerant according to an embodiment.

Referring to <FIG>, a flow pattern of a two-phase refrigerant including a liquid refrigerant and a gas refrigerant may differ according to a dryness and a flow velocity. When a constant dryness and a constant flow velocity are ensured, the liquid refrigerant may flow along a wall surface of a refrigerant pipe and the gas refrigerant may flow inside the liquid refrigerant. As a result, the liquid refrigerant and the gas refrigerant may be separated. A flow pattern occurring when the liquid refrigerant and the gas refrigerant are separated and flow inside the refrigerant pipe may be referred to as an annular flow.

When the annular flow occurs, the liquid refrigerant may flow along the wall surface of a refrigerant pipe <NUM> and the gas refrigerant may flow inside the liquid refrigerant. In doing so, the gas refrigerant may be separated from the two-phase refrigerant flowing inside the evaporator and may flow to the connection pipes and the header. At this point, a small amount of the liquid refrigerant as well as the gas refrigerant may flow to the connection pipes and the header.

A refrigerant separated from the two-phase refrigerant flowing inside the evaporator may flow to the header <NUM> through the connection pipes, and a refrigerant not separated may flow to a refrigerant pipe <NUM>.

<FIG> is a diagram illustrating a P-H line according to an embodiment.

Referring to <FIG>, a pressure-enthalpy change caused by a refrigerant flowing inside the air conditioner may be as shown in a graph <NUM>. However, a pressure-enthalpy change caused by the second refrigerant separated by the gas-liquid separator and flowing through the bypass pipe may be as shown in a graph <NUM>. That is, the second refrigerant separated by the gas-liquid separator and flowing through the bypass pipe is heated in a subcooler and thus does not contain liquid refrigerant. Therefore, pressure may increase from the graph <NUM> to the graph <NUM>.

According to an embodiment of the present specification, one or more of the following effects are provided.

First, it is possible to prevent damage to a compressor and improve reliability of an air conditioner by controlling a degree of superheat of a separated refrigerant based on a flow pattern in an evaporator.

Second, if a degree of superheat of the separated refrigerant is controlled based on the flow pattern inside the evaporator, a larger amount of refrigerant are bypassed, thereby improving the performance of the air conditioner.

Third, as a refrigerant is separated based on a refrigerant flow velocity in the evaporator and a degree of superheat of the separated refrigerant is controlled using a temperature sensor and a subcooler, it is possible to prevent introduction of liquid refrigerant into the compressor more effectively, thereby improving reliability of the air conditioner.

Effects of the present disclosure are not limited to the effects mentioned above, and other effects not mentioned may be apparent to those skilled in the art from the description of the claims.

Claim 1:
An air conditioner, comprising:
a compressor (<NUM>);
a first heat exchanger (<NUM>) connected to the compressor (<NUM>) and configured to operate as a condenser during a cooling operation and to operate as an evaporator during a heating operation;
a refrigerant pipe disposed inside the first heat exchanger (<NUM>) and configured to carry a two-phase refrigerant;
a connection pipe (<NUM>), out of a plurality of connection pipes (<NUM>), connected to the refrigerant pipe and configured to guide a refrigerant separated from the two-phase refrigerant in the refrigerant pipe to a header (<NUM>);
the header (<NUM>) being connected to the connection pipe (<NUM>);
the header (<NUM>) being further connected to the other connection pipes (<NUM>) out of the plurality of connection pipes (<NUM>);
the header (<NUM>) being configured to guide the refrigerant flowing from the connection pipes (<NUM>) to a bypass pipe (<NUM>);
a bypass pipe (<NUM>) connected to the header (<NUM>) and configured to guide the refrigerant to the compressor (<NUM>);
a flow rate control valve installed at the bypass pipe (<NUM>) and configured to control a flow rate of the refrigerant;
a subcooler (<NUM>) configured to superheat the refrigerant flowing through the bypass pipe (<NUM>); and
a controller configured to control an opening degree of the flow rate control valve;
characterized in that
the controller is configured to control the opening degree of the flow rate control valve based on a comparison between a refrigerant flow velocity of the two-phase refrigerant inside the first heat exchanger (<NUM>) and a reference flow velocity,
wherein the controller is configured to estimate the refrigerant flow velocity of the two-phase refrigerant flowing inside the first heat exchanger (<NUM>) in consideration of a type of the compressor (<NUM>), an operation frequency of the compressor (<NUM>), a number of paths of an outdoor unit (<NUM>) of the air conditioner, and an outside temperature.