Patent Description:
In general, heat pump hot-water supply devices are devices that supply hot-water using heat pumps to supply discharge water having a high temperature or to heat indoor floors. In the heat pump, a refrigeration cycle in which a refrigerant is compressed, condensed, expanded, and evaporated may be driven.

The heat pump hot-water supply device may be used a lot when outdoor air has a relatively low temperature. Also, according to a range of temperature of the outdoor air, a desired temperature of the discharge water may vary.

For example, in winter when the temperature of the outdoor air is relatively low, a user may desire to use discharge water having a relatively high temperature. On the other hand, in spring or autumn when the temperature of the outdoor air is relatively high, the user may desire to use discharge water having a relatively low temperature. That is, a load required for the heat pump hot-water supply device may vary depending on the temperature of the outdoor air.

However, in the heat pump hot-water supply device according to a related art, as a same refrigeration cycle always operates regardless of the temperature of the outdoor air, an operation efficiency of the heat pump hot-water supply device is reduced. A prior art related to the heat pump hot-water supply device is Korean Application No. <CIT>.

<CIT>) relates to a heat pump that includes a primary output condenser and a secondary input evaporator that are exchangers between a respective refrigerating fluid and a coolant of an intermediate circuit and discloses a method according to the preamble of claim <NUM>. In order to solve the problems from which the prior art systems suffer the present invention provides a method for controlling a heat pump hot-water supply device according to claim <NUM>. Preferred embodiments of the invention are the subject of the dependent claims.

The invention is best understood by referring to the accompanying drawings. Where possible, like reference numerals have been used to indicate like elements, and repetitive disclosure has been omitted.

<FIG> is a schematic diagram of a heat pump hot-water supply device. <FIG> is a perspective view of a water-refrigerant heat exchanger. <FIG> is a schematic diagram illustrating an inner flow path of the water-refrigerant heat exchanger.

Referring to <FIG>, a hot water supply device <NUM> may include a first refrigerant cycle, in which a first refrigerant may circulate, and a second refrigerant cycle, in which a second refrigerant may circulate. The first refrigerant cycle may include a first compressor <NUM> that compresses the first refrigerant, an outdoor heat exchanger <NUM>, and a flow switch <NUM> that guides the refrigerant compressed in the compressor <NUM> to the outdoor heat exchanger <NUM> or a water-refrigerant heat exchanger <NUM>. The first compressor <NUM> may include an inverter compressor in which a frequency is adjustable.

The refrigerant compressed in the first compressor <NUM> may flow to the outdoor heat exchanger <NUM> or the water-refrigerant heat exchanger <NUM> according to a control state of the flow switch <NUM>. The water-refrigerant heat exchanger <NUM> may be understood as one component of the first refrigerant cycle.

The first refrigerant cycle may further include a first expansion device <NUM> that expands the refrigerant condensed in the outdoor heat exchanger <NUM> or the water-refrigerant heat exchanger <NUM>, and a first gas-liquid separator <NUM> provided at a suction-side of the first compressor <NUM> to separate a gaseous refrigerant from the refrigerant. The gaseous refrigerant separated by the first gas-liquid separator <NUM> may be suctioned into the first compressor <NUM>. The first expansion device <NUM> may include an electronic expansion valve (EEV) which is adjustable in opening degree, for example.

As a heat pump cycle is driven to supply hot-water, the first refrigerant cycle has a structure in which the refrigerant compressed in the first compressor <NUM> is condensed in the water-refrigerant heat exchanger <NUM> and expanded in the first expansion device <NUM> and then evaporated in the outdoor heat exchanger <NUM>. The refrigerant evaporated in the outdoor heat exchanger <NUM> may be suctioned again into the first compressor <NUM> via the first gas-liquid separator <NUM>. A fan <NUM> may be provided adjacent to the outdoor heat exchanger <NUM>.

The second refrigerant cycle may include a second compressor <NUM> that compresses a second refrigerant, the water-refrigerant heat exchanger <NUM> that condenses and evaporates the refrigerant compressed in the second compressor <NUM>, a second expansion device <NUM> that expands the refrigerant condensed in the water-refrigerant heat exchanger <NUM>, and a second gas-liquid separator <NUM>. The second expansion device <NUM> may include an EEV which is adjustable in opening degree, for example.

The refrigerant expanded in the second expansion device <NUM> may be introduced again into the water-refrigerant heat exchanger <NUM> to heat-exchange with the first and second refrigerants and water supplied thereto. That is, the second refrigerant cycle may further include a guide tube <NUM> that re-introduces the condensed refrigerant discharged from the water-refrigerant heat exchanger <NUM> to the water-refrigerant heat exchanger <NUM>. The guide tube <NUM> may extend from a second outflow <NUM> of the water-refrigerant heat exchanger <NUM> and be connected to a third inflow <NUM>. The second expansion device <NUM> may be disposed in the guide tube <NUM>.

The heat pump hot-water supply device <NUM> may further include a water introduction path <NUM> connected to the water-refrigerant heat exchanger <NUM> to supply water, and a water discharge path <NUM> through which the water heat-exchanged in the water-refrigerant heat exchanger <NUM> may be discharged. For example, the water introduced to the water-refrigerant heat exchanger <NUM> through the water introduction path <NUM> may be heated by the first refrigerant or the second refrigerant, and then, may be discharged through the water discharge path <NUM>.

The heat pump hot-water supply device <NUM> may further include a bypass tube <NUM> that guides the condensed second refrigerant so that the second refrigerant may be supplied to the outdoor heat exchanger <NUM> of the first refrigerant cycle. The bypass tube <NUM> may extend from an outlet-side tube from which the refrigerant condensed in the water-refrigerant heat exchanger <NUM> is discharged to the outdoor heat exchanger <NUM>.

The outdoor heat exchanger <NUM> may include a refrigerant tube through which the first refrigerant may flow and a heat exchange fin coupled to the refrigerant tube to increase a heat exchange area. The bypass tube <NUM> may be provided in at least one refrigerant tube of the outdoor heat exchanger <NUM>, for example, the bypass tube <NUM> may be provided to contact a lowermost refrigerant tube. Thus, the second refrigerant having a high temperature flowing through the bypass tube <NUM> may provide heat to the outdoor heat exchanger <NUM> to delay or prevent frost formation on the outdoor heat exchanger <NUM>.

A bypass valve <NUM> that selectively opens and closes the bypass tube <NUM> may be provided in the bypass tube <NUM>. For example, the bypass valve <NUM> may include a solenoid valve controlled in an on/off operation.

When the heat pump hot-water supply device <NUM> performs a high temperature operation, that is, when the first and second refrigerant cycles simultaneously operate, an operating pressure range of the first refrigerant cycle may be less than an operating pressure range of the second refrigerant cycle. For example, a low pressure of the first refrigerant cycle may be less than a low pressure of the second refrigerant cycle, and a high pressure of the first refrigerant cycle may be less than a high pressure of the second refrigerant cycle (see <FIG>). Thus, the first refrigerant cycle may be referred to as a "low-stage cycle", and the second refrigerant cycle may be referred to as a "high-stage cycle".

A difference in operating pressure between the first and second refrigerant cycles may occur when the first and second refrigerants are different kinds of refrigerants. For example, the first refrigerant may include R410a, and the second refrigerant may include R134a.

Referring to <FIG> and <FIG>, the water-refrigerant heat exchanger <NUM> may include a plate heat exchanger. The water-refrigerant heat exchanger <NUM> may include a heat exchanger body <NUM>, and a plurality of inflows <NUM>, <NUM>, <NUM>, and <NUM> and a plurality of outflows <NUM>, <NUM>, <NUM>, and <NUM> which may be coupled to the heat exchanger body <NUM>.

The heat exchanger body <NUM> may include a plurality of plates <NUM> spaced apart from each other and stacked on each other. Each of the plurality of plates <NUM> may include a thin plate. A space between the plurality of plates <NUM> may define a flow path through which the first refrigerant, the second refrigerant, or the water may flow.

The plurality of inflows <NUM>, <NUM>, <NUM>, and <NUM> may include a first inflow <NUM>, to which the first refrigerant of the first refrigerant cycle may be introduced (see reference symbol Ain), and second and third refrigerant inflows <NUM> and <NUM>, to which the second refrigerant of the second refrigerant cycle may be introduced. The second and third refrigerant inflows <NUM> and <NUM> may include a second inflow <NUM>, to which the refrigerant compressed in the second compressor <NUM> may be introduced (see reference symbol Bin) and a third inflow <NUM>, to which the refrigerant decompressed in the second expansion device <NUM> may be introduced (see reference symbol Cin). The plurality of inflows <NUM>, <NUM>, <NUM>, and <NUM> may further include a fourth inflow <NUM> connected to the water introduction path <NUM> to guide introduction Din of the supplied water.

The plurality of outflows <NUM>, <NUM>, <NUM>, and <NUM> may include a first outflow <NUM>, from which the first refrigerant introduced through the first inflow <NUM> and heat-exchanged may be discharged (see reference symbol Aout), and second and third refrigerant outflows <NUM> and <NUM>, from which the second refrigerant may be discharged. The second and third refrigerant outflows <NUM> and <NUM> may include a second outflow <NUM>, from which the second refrigerant introduced through the second inflow <NUM> and heat-exchanged may be discharged (see reference symbol Bout), and a third outflow <NUM>, from which the second refrigerant introduced through the third inflow <NUM> and heat-exchanged may be discharged (see reference symbol Cout). The plurality of outflows <NUM>, <NUM>, <NUM>, and <NUM> may further include a fourth outflow <NUM> connected to the water discharge path <NUM> to guide the water heat-exchanged in the water-refrigerant heat exchanger <NUM> so that the water may be discharged to the water discharge path <NUM> (see reference symbol Dout).

The water-refrigerant heat exchanger <NUM> may include four flow paths heat-exchanged with each other. The four flow paths may be defined between the plurality of plates <NUM>, which may be spaced apart from each other. The four flow paths may include a first flow path <NUM> that extends from the first inflow <NUM> to the first outflow <NUM> and through which the refrigerant may flow; a second flow path <NUM> that extends from the second inflow <NUM> to the second outflow <NUM> and through which the second refrigerant compressed in the second compressor <NUM> may flow; and a third flow path <NUM> that extends from the third inflow <NUM> to the third outflow <NUM> and through which the second refrigerant decompressed in the second expansion device <NUM> may flow; a fourth flow path <NUM> that extends from the fourth inflow <NUM> to the fourth outflow <NUM> and through which the water may flow.

As the first refrigerant flowing through the first flow path <NUM> may be condensed by the second refrigerant and the water, the first flow path may be referred to as a "first condensation flow path". As the second refrigerant flowing through the second flow path <NUM> may be condensed by the first and second refrigerant and the water, the second flow path may be referred to as a "second condensation flow path". As the second refrigerant flowing through the third flow path <NUM> may be evaporated by the first and second refrigerants and the water, the third flow path <NUM> may be referred to as an "evaporation flow path", and the fourth flow path <NUM> may be referred to as a "water flow path". Each of the first to fourth flow paths <NUM>, <NUM>, <NUM>, and <NUM> may be divided into a plurality of flow paths or combined with each other.

Operations of the heat pump hot-water supply device <NUM> will be described hereinafter.

First, in the first refrigerant cycle, the first refrigerant compressed in the first compressor <NUM> may be introduced to the first flow path <NUM> in the water-refrigerant heat exchanger <NUM> through the first inflow <NUM>, and then may be heat-exchanged with the second refrigerant and water flowing through the water-refrigerant heat exchanger <NUM>, that is, heat-exchanged with the second to fourth flow paths <NUM>, <NUM>, and <NUM>, and thus, be condensed. The condensed first refrigerant may be discharged from the water-refrigerant heat exchanger <NUM> through the first outflow <NUM> and decompressed in the first expansion device <NUM> and then evaporated in the outdoor heat exchanger <NUM>. The evaporated first refrigerant may be suctioned again into the first compressor <NUM>. This cycle may be repeated.

In the second refrigerant cycle, the second refrigerant compressed in the second compressor <NUM> may be introduced into the second flow path <NUM> in the water-refrigerant heat exchanger <NUM> through the second inflow <NUM>, and then, may be heat-exchanged with the first and second refrigerants and water flowing through the water-refrigerant heat exchanger <NUM>, that is, heat-exchanged with the first, third, and fourth flow paths <NUM>, <NUM>, and <NUM>, and thus, be condensed. The condensed second refrigerant may be discharged from the water-refrigerant heat exchanger <NUM> through the second outflow <NUM> and decompressed in the second expansion device <NUM>, and then, may be introduced again into the water-refrigerant heat exchanger <NUM> through the third inflow <NUM>. The introduced second refrigerant may flow through the third flow path <NUM> and be heat-exchanged with the first and second refrigerants and water flowing through the first, second, and fourth flow paths <NUM>, <NUM>, and <NUM>, and thus, be evaporated. The evaporated second refrigerant may be suctioned into the second compressor <NUM>. This cycle may be repeated.

When the outdoor temperature is less than a preset or predetermined temperature, frost may form on the outdoor heat exchanger <NUM> of the first refrigerant cycle. Thus, in this case, the bypass valve <NUM> may be opened. For example, an opening/closing operation of the bypass valve <NUM> may be controlled according to a preset or predetermined cycle. According to the opening of the bypass valve <NUM>, at least a portion of the second refrigerant discharged from the second outflow <NUM> may flow to the bypass tube <NUM>.

The bypass tube <NUM> may be divided from the guide tube <NUM> to extend to the outdoor heat exchanger <NUM>. As the bypass tube <NUM> contacts the refrigerant tube forming the outdoor heat exchanger <NUM>, heat of the bypass tube <NUM> may be transferred to the outdoor heat exchanger <NUM>. Thus, the frost formation of the outdoor heat exchanger <NUM> may be delayed or prevented.

The supplied water to supply hot-water may be introduced into the water-refrigerant heat exchanger <NUM> through the water introduction path <NUM> and the fourth inflow <NUM>. The introduced water may be heat-exchanged with the first and second refrigerants flowing through the first to third flow paths <NUM>, <NUM>, and <NUM>, and thus, may be heated. The heated water may be discharged through the fourth outflow <NUM> and the water discharge path <NUM>. The discharged water may be stored in a hot-water storage tank, for example.

<FIG> is a block diagram of the heat pump hot-water supply device. Referring to <FIG>, the heat pump hot-water supply device <NUM> may include an outdoor air temperature detector <NUM> that detects a temperature of outdoor air and a controller <NUM> that determines whether the first refrigerant cycle only operates (a medium temperature operation) or whether the first and second refrigerant cycles simultaneously operate (a high temperature operation) on the basis of the outdoor air temperature recognized or detected by in the outdoor air temperature detector <NUM>.

The heat pump hot-water supply device <NUM> may further include a discharge water temperature input <NUM> that allows a desired temperature of discharge water to be set, and a discharge water temperature detector <NUM> that detects a temperature of the water actually discharged. The discharge water temperature detector <NUM> may be provided on the fourth outflow <NUM> or the water discharge path <NUM>.

The controller <NUM> may control a frequency of the first compressor <NUM> or the second compressor <NUM> on the basis of a preset or predetermined discharge water temperature input through the discharge water temperature input <NUM> and actual discharge water temperature information recognized in or detected by the discharge water temperature detector <NUM>.

For example, when the actual discharge water temperature is less than the predetermined discharge water temperature, the controller <NUM> may increase the frequency of the first compressor <NUM> or the second compressor <NUM>. On the other hand, when the actual discharge water temperature reaches or is greater than the predetermined discharge water temperature, the controller <NUM> may maintain or decrease a frequency of the first compressor <NUM> or the second compressor <NUM>.

The heat pump hot-water supply device <NUM> may further include a condensation temperature detector <NUM> that detects a condensation temperature of the first refrigerant cycle. The condensation temperature detector <NUM> may include a temperature sensor or a pressure sensor.

For example, the temperature sensor may be provided on or at the first flow path <NUM>, on or at a first outflow part-side to detect a temperature of the first refrigerant passing through the water-refrigerant heat exchanger <NUM>. A pressure sensor may be provided on or at an outlet-side tube of the water-refrigerant heat exchanger <NUM> to detect a high pressure of the first refrigerant cycle. When the refrigerant is in a liquid state or in a two-phase state, a temperature value of the refrigerant may be determined depending on a pressure value. Thus, the pressure value detected in the pressure sensor may be converted to a condensation temperature value.

The controller <NUM> may determine an ability of the first refrigerant cycle on the basis of a first temperature value detected in or by the condensation temperature detector <NUM> and a second temperature value of the actually discharged water detected in or by the discharge water temperature detector <NUM>. For example, while the first refrigerant cycle operates on the basis of information of the predetermined discharge water temperature and the actual discharge water temperature, when it is detected that the first temperature value is greater than the second temperature value by a preset or predetermined value, it may be recognized that the discharge water temperature is sufficiently increased by only operation of the first refrigerant cycle. Thus, the controller <NUM> may not command the simultaneous operations of the first and second refrigerant cycles.

On the other hand, when it is detected that the first temperature value is not greater than that the second temperature value by a preset or predetermined value, it may be recognized that the discharge water temperature is not sufficiently increased by only the operation of the first refrigerant cycle. Thus, the controller <NUM> may command the simultaneous operations of the first and second refrigerant cycles.

<FIG> is a flowchart of a method for controlling a heat pump hot-water supply device according to the invention. Referring to <FIG>, in operation S11, a heat pump hot-water supply device <NUM> may be turned on, and a preset or predetermined discharge water temperature may be input through a discharge water temperature input, such as discharge water temperature input <NUM> of <FIG>. In operation S12, an outdoor air temperature may be detected.

In operation S12, it may be determined whether the outdoor air temperature is greater than a preset or predetermined temperature. When the outdoor air temperature is greater than the predetermined temperature, that is, when the outdoor air temperature is relatively high, it is less necessary to generate discharge water having a high temperature, and thus, a controller, such as controller <NUM> of <FIG>, may control the hot-water supply device to perform a medium temperature operation.

When the hot-water supply device performs the medium temperature operation, only the first refrigerant cycle may operate. That is, a first compressor, such as first compressor <NUM> of <FIG>, may be driven, and the first refrigerant compressed in the first compressor may be introduced into a first inflow, such as first inflow <NUM> of <FIG>, of a water-refrigerant heat exchanger, such as, water-refrigerant heat exchanger <NUM> of <FIG>.

The first refrigerant introduced into the first inflow may flow through a first flow path, such as first inflow path <NUM> of <FIG>, and may be heat-exchanged with the water flowing through a fourth flow path, such as fourth flow path <NUM> of <FIG>. The water may be a medium supplied through a water introduction path, such as water introduction path <NUM> of <FIG>, and a fourth inflow, such as fourth inflow <NUM> of <FIG>, to flow through the water-refrigerant heat exchanger.

While the first refrigerant is heat-exchanged with the water, the first refrigerant may be condensed, and the water may be heated. Also, the heated water may be discharged to the outside through a fourth outflow, such as fourth outflow <NUM> of <FIG>, and a water discharge path, such as water discharge path <NUM> of <FIG>.

The condensed first refrigerant may be discharged from the water-refrigerant heat exchanger through a first outflow, such as first outflow <NUM> of <FIG>, and decompressed in a first expansion device, such as first expansion device <NUM> of <FIG>, and then, may be evaporated in an outdoor heat exchanger, such as outdoor heat exchanger <NUM> of <FIG>. The evaporated first refrigerant may be suctioned into the first compressor via a first gas-liquid separator, such as first gas-liquid separator <NUM> of <FIG>. In operation S14, this first refrigerant cycle may be repeated.

In operation S15, while the first refrigerant cycle operates, a condensation temperature may be detected through or by a condensation temperature detector, such as condensation temperature detector <NUM> of <FIG>, and a discharge water temperature may be detected through or by a discharge water temperature detector, such as discharge water temperature detector <NUM> of <FIG>. A difference value between the condensation temperature and the discharge water temperature may be determined. The condensation temperature may be greater than the discharge water temperature. When the difference value is greater than a preset or predetermined value, as it may be recognized that the supplied water is heated only by the operation of the first refrigerant cycle, and the first refrigerant cycle may continuously operate.

The operation of the first refrigerant cycle may be performed until the discharge water temperature detected in or by the discharge water temperature detector reaches the predetermined discharge water temperature. The controller may control an operation frequency of the first compressor on the basis of the difference value between the detected discharge water temperature and the predetermined discharge water temperature.

For example, in operations S16 and S17, when the difference value is greater than a preset or predetermined difference value, an operation frequency of the first compressor may be increased to above a reference frequency. On the other hand, when the difference value is less than a preset or predetermined difference value, the operation frequency of the first compressor may be maintained at a reference frequency or may be decreased to less than the reference frequency. The reference frequency may be a frequency less than a maximum frequency of the first compressor, which is a predetermined frequency.

In operation S13, when the outdoor air temperature is less than a preset or predetermined temperature, that is, when the outdoor air temperature is relatively low, it is more necessary to generate discharge water having a high temperature, and thus, the controller may control the hot-water supply device to perform a high temperature operation.

When the hot-water supply device performs the high temperature operation, the first and second refrigerant cycles may simultaneously operate. That is, first and second compressors, such as first and second compressors <NUM> and <NUM> of <FIG>, may be driven. Also, the first refrigerant compressed in the first compressor may be introduced into the first inflow of the water-refrigerant heat exchanger, and the second refrigerant compressed in the second compressor may be introduced into a second inflow, such as second inflow <NUM> of <FIG>, of the water-refrigerant heat exchanger.

The first refrigerant introduced into the first inflow may flow through the first flow path and may be heat-exchanged with the second refrigerant and water flowing through second to fourth flow paths, such as second to fourth flow paths <NUM>, <NUM>, and <NUM> of <FIG>. The second refrigerant introduced into the second inflow may flow through the second flow path and may be heat-exchanged with the first and second refrigerant and water flowing through the first, third, and fourth flow paths.

The second refrigerant flowing through the second flow path may be discharged from the water-refrigerant heat exchanger through a second outflow, such as second outflow <NUM> of <FIG>, and expanded in a second expansion device, such as second expansion device <NUM> of <FIG>, while flowing through a guide tube, such as guide tube <NUM> of <FIG>. The expanded second refrigerant may be introduced into the water-refrigerant heat exchanger through a third inflow, such as third inflow <NUM> of <FIG>.

The second refrigerant introduced through the third inflow part may flow through the third flow path and may be heat-exchanged with the first and second refrigerants and water flowing through the first, second, and fourth flow paths.

In the water-refrigerant heat exchanger, while the first to fourth flow paths are heat-exchanged with each other, the first refrigerant and the second refrigerant of the second flow path may be condensed, and the second refrigerant of the third flow path may be evaporated. The water may be heated and discharged to the outside through the fourth outflow and the water discharge path.

The condensed first refrigerant may be discharged from the water-refrigerant heat exchanger through the first outflow and decompressed in the first expansion device, and then, may be evaporated in the outdoor heat exchanger. The evaporated first refrigerant may be suctioned into the first compressor via the first gas-liquid separator. This first refrigerant cycle may be repeated.

Also, in operations S18 and S19, the evaporated second refrigerant may be suctioned into the second compressor via a second gas-liquid separator, such as second gas-liquid separator <NUM> of <FIG>. This second refrigerant cycle may be repeated.

The operation of each of the first and second refrigerant cycles may be performed until the discharge water temperature detected in the discharge water temperature detector reaches the predetermined discharge water temperature. The controller may control an operation frequency of each of the first and second compressors on the basis of a difference value between the detected discharge water temperature and the predetermined discharge water temperature.

For example, when the difference value is greater than a preset or predetermined difference value, an operation frequency of at least one of the first and second compressors may be increased to above a reference frequency. On the other hand, when the difference value is less than a preset or predetermined difference value, the operation frequency of at least one of the first and second compressor may be maintained at a reference frequency or decreased to less than the reference frequency. The reference frequency may be a frequency less than a maximum frequency of the first compressor or the second compressor, which is a predetermined frequency.

Also, depending on a preset or predetermined cycle, the bypass valve may be opened. In operation S20, according to the opening of the bypass valve, at least a portion of the second refrigerant discharged from the second outflow to flow through the guide tube may flow to the bypass tube, and the refrigerant in the bypass tube may supply heat to the outdoor heat exchanger to delay or prevent frost formation of the outdoor heat exchanger.

In operation S16, when the difference between the condensation temperature and the discharge water temperature is less than a preset or predetermined value, it may be recognized that heating of the supplied water is restricted by only the operation of the first refrigerant cycle. Thus, an additional operation of the second refrigerant cycle, that is, high temperature operation of the hot-water supply device before the operation S18 may be performed.

As the medium temperature operation or the high temperature operation of the hot-water supply device is determined on the basis of the outdoor air temperature, and even though while the hot-water supply device operates the medium operation, the medium operation is switched to the high temperature operation on the basis of the difference value between the condensation temperature and the discharge water temperature, the hot-water supply device may be improved in operation efficiency.

<FIG> are graphs of a P-H diagram of a refrigerant when the heat pump hot-water supply device operates at a medium temperature and a high temperature, respectively. <FIG> shows a P-H diagram of the first refrigerant cycle when the heat pump hot-water supply device performs a medium temperature operation. For example, the first refrigerant circulating in the first refrigerant cycle may be R410a. A pressure difference between a low pressure and a high pressure of the first refrigerant cycle may be Pds1. The low pressure of the first refrigerant cycle may represent a suction pressure Ps1 of the first compressor <NUM>, and the high pressure of the first refrigerant cycle may represent a discharge pressure Pd1 of the first compressor <NUM>.

In consideration of a material property of R410a, it is difficult for the discharge pressure Pd1 to have a sufficiently high pressure. Also, in consideration of a compression ratio of the first compressor <NUM>, it is difficult for the pressure difference Pds1 to have a sufficiently high value. Thus, when the first refrigerant cycle only operates, the heat pump hot-water supply device <NUM> performs the medium temperature operation.

When the hot-water supply device <NUM> performs the medium temperature operation, it may be understood that the first refrigerant forming a low pressure of the first refrigerant cycle absorbs heat Q1in from the outdoor air passing through the outdoor heat exchanger <NUM>, and the first refrigerant forming a high pressure of the first refrigerant cycle discharges heat Q1out to the water.

On the other hand, <FIG> shows a P-H diagram of the first and second refrigerant cycles when the heat pump hot-water supply device performs a high temperature operation. For example, the first refrigerant circulating in the first refrigerant cycle may be R410a, and the second refrigerant circulating in the second refrigerant cycle may be R134a.

According to the combination of the two refrigerant cycles, the heat pump hot-water supply device <NUM> may form a cascade system. A pressure difference between a low pressure and a high pressure of the first and second refrigerant cycles is Pds2.

The low pressure of the first and second refrigerant cycles may represent a suction pressure Ps2 of the first compressor <NUM>, and the high pressure of the first and second refrigerant cycles may represent a discharge pressure Pd2 of the second compressor <NUM>.

In consideration of a material property of R134a, the discharge pressure Pd2 is greater than the discharge pressure Pd1. Also, in consideration of the combined compression ratio of the first and second compressors <NUM> and <NUM>, the pressure difference Pds2 may be greater than the pressure difference Pds1. Thus, when the first and second refrigerant cycles simultaneously operate, the heat pump hot-water supply device <NUM> may perform the high temperature operation.

When the hot-water supply device <NUM> performs the high temperature operation, it may be understood that the first refrigerant forming the low pressure of the first and second refrigerant cycles absorbs heat Q2in from the outdoor air passing through the outdoor heat exchanger <NUM>, and the second refrigerant forming the high pressure discharges heat Q2out to the water.

According to components and operations of the above-described heat pump hot-water supply device <NUM>, system efficiency may be improved.

According to embodiments disclosed herein, as the medium temperature operation and the high temperature operation of the heat pump hot-water supply device is selectively performed according to the outdoor air temperature, the heat pump hot-water supply device may be improved in operation efficiency. When the outdoor air temperature is greater than the predetermined temperature, as the desired temperature of the discharge water is low, and the device has a relatively low operation load, the first compressor may be only driven to allow the first refrigerant to be heat-exchanged with the supplied water (the medium temperature operation). On the other hand, when the outdoor air temperature is less than the predetermined temperature, as the desired temperature of the discharge water is high, and the device has a relatively high operation load, the first and second compressors may be simultaneously driven to allow the first and second refrigerants to be heat-exchanged with the supplied water (the high temperature operation).

Further, when the medium temperature operation is performed, as the first compressor is only driven to operate the cycle, the cycle may be more quickly stabilized when compared to a case in which the first and second compressors are simultaneously driven. Furthermore, when the high temperature operation is performed, as the refrigerant condensed in the second refrigerant cycle is supplied to the outdoor heat exchanger of the first refrigerant cycle, frost formation of the outdoor heat exchanger may be delayed. Also, as the water-refrigerant heat exchanger may include a plate heat exchanger, heat exchange efficiency between the first and second refrigerants and the supplied water may be improved.

Examples disclosed herein provide a heat pump hot-water supply device having improved operation efficiency and a method for controlling a heat pump hot-water supply device.

Examples disclosed herein provide a heat pump hot-water supply device that may include a first refrigerant cycle, in which a first refrigerant may circulate, the first refrigerant cycle including a first compressor, an outdoor heat exchanger, and a first expansion device; a second refrigerant cycle, in which a second refrigerant may circulate. The second refrigerant cycle may includes a second compressor and a second expansion device. The heat pump hot-water supply device may include a water-refrigerant heat exchanger to which the first refrigerant compressed in the first compressor and the second refrigerant compressed in the second compressor may be introduced. A water introduction path may be coupled to one or a first side of the water-refrigerant heat exchanger and into which supplied water may be introduced. A water discharge path may be coupled to the other or a second side of the water-refrigerant heat exchanger and from which the water heat-exchanged in the refrigerant heat exchanger may be discharged.

The water-refrigerant heat exchanger may include a first inflow part or inflow that guides introduction of the first refrigerant, and a first outflow part or outflow from which the first refrigerant heat-exchanged in the water-refrigerant heat exchanger may be discharged.

The water-refrigerant heat exchanger may further include a second inflow part or inflow that guides introduction of the second refrigerant compressed in the second compressor, and a second outflow part or outflow from which the second refrigerant introduced through the second inflow part and heat-exchanged may be discharged.

The heat pump hot-water supply device may further include a guide tube that allows the refrigerant discharged from the second outflow part to be suctioned again into the water-refrigerant heat exchanger. The second expansion device may be disposed on the guide tube.

The water-refrigerant heat exchanger may further include a third inflow part or inflow connected to the guide tube and to which the second refrigerant may be introduced, and a third outflow part or outflow from which the second refrigerant introduced through the third inflow part and heat-exchanged may be discharged.

The water-refrigerant heat exchanger may further include a fourth inflow part or inflow connected to the water introduction path to guide introduction of the supplied water, and a fourth outflow part or outflow connected to the water discharge path to allow the water introduced through the fourth inflow part and heat-exchanged to be discharged therefrom.

The heat pump hot-water supply device may further include a bypass tube divided from the guide tube to extend to the outdoor heat exchanger. The heat pump hot-water supply device may also include a bypass valve disposed in or on the bypass tube to allow the second refrigerant flowing through the guide tube to selectively flow to the outdoor heat exchanger.

The heat pump hot-water supply device may further include an outdoor air temperature detecting part or detector that detects a temperature of outdoor air. The heat pump hot-water supply device may further include a controller that controls operation of the first refrigerant cycle and the second refrigerant cycle. A single operation of the first refrigerant cycle or simultaneous operations of the first and second refrigerant cycles may be determined on the basis of whether the outdoor air temperature detected in the outdoor air temperature detecting part is greater than a preset or predetermined temperature.

The heat pump hot-water supply device may further include a discharge water temperature input that receives input of a desired water temperature from a user; and a discharge water temperature water detector that detects an actual temperature of water discharged from the water-refrigerant heat exchanger. The controller may further control a frequency of the first compressor or the second compressor on the basis of an input temperature and the actual temperature.

The heat pump hot-water supply device may further include a condensation temperature detector that detects a condensation temperature of the first refrigerant cycle. The controller may further determine an ability of the first refrigerant cycle by comparing the condensation temperature detected by the condensation temperature detector to the actual temperature of water discharged from the water-refrigerant heat exchanger.

The first refrigerant cycle may have an operating pressure range that is less than that of the second refrigerant cycle. The first refrigerant may include R410a, and the second refrigerant may include R134a.

Examples disclosed herein further provide a heat pump hot-water supply device that may include a first compressor in which a first refrigerant may be compressed; a second compressor in which a second refrigerant may be compressed; a water-refrigerant heat exchanger to which the refrigerant compressed in the first compressor and the refrigerant compressed in the second compressor may be introduced and in which the supplied water may be heat-exchanged with the first and second refrigerants; and a second expansion device disposed at an outlet side of the water-refrigerant heat exchanger to decompress the second refrigerant condensed in the water-refrigerant heat exchanger. The water-refrigerant heat exchanger further may include an introduction part to which the second refrigerant decompressed in the expansion device may be introduced.

The water-refrigerant heat exchanger may include a first condensation flow path through which the first refrigerant may flow; a second condensation flow path through which the second refrigerant compressed in the second compressor may flow; an evaporation flow path through which the second refrigerant decompressed in the expansion device may flow; and a water flow path through which the supplied water may flow. The water-refrigerant heat exchanger may further include an outflow part or outflow from which the second refrigerant may be discharge, and a guide tube that extends from the outflow part to the inflow part and on which the expansion device may be disposed.

The heat pump hot-water supply device may further include a first expansion device that decompresses the first refrigerant condensed in the water-refrigerant heat exchanger, and an outdoor heat exchanger that evaporates the refrigerant decompressed in the first expansion device. The heat pump hot-water supply device may further include a bypass tube divided from the guide tube to extend to the outdoor heat exchanger and disposed to contact the outdoor heat exchanger.

Claim 1:
A method for controlling a heat pump hot-water supply device (<NUM>) including
a first refrigerant cycle in which a first refrigerant circulates, and including a first compressor (<NUM>), an outdoor heat exchanger (<NUM>), and a first expansion device (<NUM>);
a second refrigerant cycle, in which a second refrigerant circulates, and including a second compressor (<NUM>) and a second expansion device (<NUM>);
a water-refrigerant heat exchanger (<NUM>), to which the first refrigerant compressed in the first compressor (<NUM>) and the second refrigerant compressed in the second compressor (<NUM>) is introduced;
a water introduction path (<NUM>) coupled to a first side of the water-refrigerant heat exchanger (<NUM>) and into which supplied water is introduced; and
a water discharge path (<NUM>) coupled to a second side of the water-refrigerant heat exchanger (<NUM>) and from which the water heat-exchanged in the water-refrigerant heat exchanger (<NUM>) is discharged;
the method comprising:
turning on the heat pump hot-water supply device (<NUM>) and inputting a predetermined discharge water temperature;
determining whether an outdoor air temperature is greater than a predetermined temperature; when the outdoor air temperature is greater than the predetermined temperature, driving only the first compressor (<NUM>), and when the outdoor air temperature is less than the predetermined temperature, driving the first (<NUM>) and second (<NUM>) compressors; and
determining additional driving of the second compressor (<NUM>) on the basis of a temperature of water discharged from the water-refrigerant heat exchanger (<NUM>) and a condensation temperature of the first refrigerant cycle, while only the first compressor (<NUM>) is driven,
characterized in that
when a first difference value between the condensation temperature of the first refrigerant cycle and a discharge water temperature of the water-refrigerant heat exchanger (<NUM>) is greater than a first value, the first refrigerant cycle operates by driving of the first compressor only,
wherein the condensation temperature is detected via a condensation temperature detector (<NUM>) and the discharge water temperature is detected via a discharge water temperature detector (<NUM>).