Patent Description:
As conventional refrigeration cycle devices of this kind, there is one including a refrigerant circuit and an intermediate injection circuit. The refrigerant circuit uses refrigerant whose a high-pressure side becomes supercritical pressure, and the refrigerant circuit is formed by annularly connecting, to one another through a pipe, a two-stage compressing type compressor, a heating heat exchanger which heats hot water, a cooler, a first electric expansion valve and an evaporator. The intermediate injection circuit branches off from the refrigerant circuit between the heating heat exchanger and the cooler. The intermediate injection circuit includes a second electric expansion valve and the cooler in the middle of the refrigerant circuit. The intermediate injection circuit returns a portion of refrigerant discharged from the heating heat exchanger to an intermediate portion between a low-pressure side and a high-pressure side of the compressor.

This refrigeration cycle device includes a first temperature detection sensor which detects high-pressure side refrigerant discharge temperature of the compressor, a second temperature detection sensor which detects refrigerant temperature of an outlet of the heating heat exchanger, and a third temperature detection sensor which detects refrigerant temperature of an outlet of the cooler. When detected temperature which is detected by the first temperature detection sensor is within a first predetermined temperature range, control is performed such that an opening degree of the first electric expansion valve is maintained, and when a difference between detected temperature detected by the second temperature detection sensor and detected temperature detected by the third temperature detection sensor is within a second predetermined temperature range, control is performed such that an opening degree of the second electric expansion valve is maintained. According to this, a circulation amount of refrigerant which flows into the intermediate injection circuit is suppressed within a constant range, and an expected refrigerant circuit can be formed.

If a heating load of a heating appliance is reduced, returning temperature of water to a heating heat exchanger from a hot water circuit rises, and refrigerant discharge temperature of high-stage side rotation compressing element also rises. Therefore, control is performed such that the refrigerant discharge temperature of the high-stage side rotation compressing element is lowered by opening the first electric expansion valve (see patent document <NUM> for example).

A further conventional refrigeration cycle device is provided with a compression mechanism, a heat radiator, a first pressure reducer, an evaporator, a second pressure reducer, an internal heat exchanger, a temperature detection unit and a control device. The compression mechanism discharges a high-pressure refrigerant in a supercritical state, and introduces an intermediate-pressure refrigerant. The temperature detection unit detects the temperature of a heat exchange medium flowing into the heat radiator.

When the temperature detected by the temperature detection unit is higher than the critical temperature of the refrigerant, the control device adjusts the pressure of the high-pressure refrigerant so that the higher the detected temperature, the higher the pressure of the high-pressure refrigerant becomes, and also adjusts the flow rate of the intermediate-pressure refrigerant so that the higher the detected termperature, the greater the flow rate of the intermediate-pressure refrigerant becomes (see patent document <NUM>). Patent document <NUM> discloses a heat pump system comprising: a main refrigerant circuit formed by sequentially connecting, through a pipe, a compression mechanism composed of a compression rotation element, a usage-side heat exchanger for heating usage-side heat medium by refrigerant which is discharged from the compression rotation element and which exceeds critical pressure, an intermediate heat exchanger, a first expansion device, and a heat source-side heat exchanger; a bypass refrigerant circuit branched off from the pipe between the usage-side heat exchanger and the first expansion device, in which branched refrigerant is decompressed by a second expansion device and thereafter, heat of the refrigerant is exchanged with that of the refrigerant flowing through the main refrigerant circuit by the intermediate heat exchanger, and the refrigerant joins up with the refrigerant which is in middle of a compression operation of the compression rotation element; and a control device, wherein when temperature of the usage-side heat medium which flows into the usage-side heat exchanger rises, the control device controls a valve opening of at least the second expansion device, and increases a ratio of an amount of the refrigerant which flows through the bypass refrigerant circuit to an amount of the refrigerant which flows on a side of the main refrigerant circuit of the intermediate heat exchanger, a heat medium inlet temperature thermistor for detecting the temperature of the usage-side heat medium which flows into the usage-side heat exchanger, wherein when detected temperature which is detected by the heat medium inlet temperature thermistor rises, the control device operates to increase the valve opening of the second expansion device wherein the control device operates to reduce a valve opening of the first expansion device.

However, according to the conventional configuration, in the refrigeration cycle device whose high-pressure side is under supercritical pressure and having the heating heat exchanger which heats hot water and the intermediate injection circuit, there is a problem that COP of the refrigeration cycle device is lowered when the returning temperature of water to the heating heat exchanger rises, but technique for suppressing this phenomenon is not disclosed.

The present invention is achieved to solve the conventional problem, and it is an object of the invention to provide a heat pump system in which even if temperature of usage-side heat medium which flows into a usage-side heat exchanger rises, a high-pressure side which suppresses deterioration of COP is operated under supercritical pressure by performing appropriate control.

To solve the conventional problem, the present invention provides a heat pump system including: a main refrigerant circuit formed by sequentially connecting, through a pipe, a compression mechanism composed of a compression rotation element, a usage-side heat exchanger for heating usage-side heat medium by refrigerant which is discharged from the compression rotation element and which exceeds critical pressure, an intermediate heat exchanger, a first expansion device, and a heat source-side heat exchanger; a bypass refrigerant circuit branched off from the pipe between the usage-side heat exchanger and the first expansion device, in which branched refrigerant is decompressed by a second expansion device and thereafter, heat of the refrigerant is exchanged with that of the refrigerant flowing through the main refrigerant circuit by the intermediate heat exchanger, and the refrigerant joins up with the refrigerant which is in middle of a compression operation of the compression rotation element; and a control device, a heat medium inlet temperature thermistor for detecting the temperature of the usage-side heat medium which flows into the usage-side heat exchanger, a discharge temperature thermistor which detects temperature of the refrigerant discharged from the compressing rotation element, wherein when temperature of the usage-side heat medium which flows into the usage-side heat exchanger rises, the control device controls a valve opening of at least the second expansion device, and increases a ratio of an amount of the refrigerant which flows through the bypass refrigerant circuit to an amount of the refrigerant which flows on the side of a main refrigerant circuit of the intermediate heat exchanger, wherein when detected temperature which is detected by the heat medium inlet temperature thermistor rises, the control device operates to increase the valve opening of the second expansion device and operates to reduce a valve opening of the first expansion device, and wherein the control device brings the temperature detected by the discharge temperature thermistor close to a target value by adjusting the valve opening of the first expansion device and the valve opening of the second expansion device.

According to this, even if temperature of the usage-side heat medium which flows into the usage-side heat exchanger rises, since an amount of refrigerant which circulates through the bypass refrigerant circuit, the high-stage side compressing rotation element and the usage-side heat exchanger is increased, it is possible to suppress deterioration of heating ability in the usage-side heat exchanger.

Further, even if temperature of the usage-side heat medium which flows into the usage-side heat exchanger rises, since a heat exchanging amount between high pressure refrigerant which flows through the main refrigerant circuit and intermediate pressure refrigerant which flows through the bypass refrigerant circuit in the intermediate heat exchanger is increased, it is possible to suppress the reduction in an enthalpy difference between an outlet of refrigerant and an inlet of refrigerant in the usage-side heat exchanger.

Hence, even if temperature of usage-side heat medium which flows into a usage-side heat exchanger rises, it is possible to provide a heat pump system whose high-pressure side which suppresses deterioration of COP is operated under supercritical pressure.

According to the present invention, it is possible to provide a heat pump system whose high-pressure side which suppresses deterioration of COP is operated under supercritical pressure by performing appropriate control even if temperature of usage-side heat medium which flows into a usage-side heat exchanger rises.

Claim <NUM> of the present invention provides a heat pump system including: a main refrigerant circuit formed by sequentially connecting, through a pipe, a compression mechanism composed of a compression rotation element, a usage-side heat exchanger for heating usage-side heat medium by refrigerant which is discharged from the compression rotation element and which exceeds critical pressure, an intermediate heat exchanger, a first expansion device, and a heat source-side heat exchanger; a bypass refrigerant circuit branched off from the pipe between the usage-side heat exchanger and the first expansion device, in which branched refrigerant is decompressed by a second expansion device and thereafter, heat of the refrigerant is exchanged with that of the refrigerant flowing through the main refrigerant circuit by the intermediate heat exchanger, and the refrigerant joins up with the refrigerant which is in middle of a compression operation of the compression rotation element; and a control device, a heat medium inlet temperature thermistor for detecting the temperature of the usage-side heat medium which flows into the usage-side heat exchanger, a discharge temperature thermistor which detects temperature of the refrigerant discharged from the compressing rotation element, wherein when temperature of the usage-side heat medium which flows into the usage-side heat exchanger rises, the control device controls a valve opening of at least the second expansion device, and increases a ratio of an amount of the refrigerant which flows through the bypass refrigerant circuit to an amount of the refrigerant which flows on the side of a main refrigerant circuit of the intermediate heat exchanger, wherein when detected temperature which is detected by the heat medium inlet temperature thermistor rises, the control device operates to increase the valve opening of the second expansion device and operates to reduce a valve opening of the first expansion device, and wherein the control device brings the temperature detected by the discharge temperature thermistor close to a target value by adjusting the valve opening of the first expansion device and the valve opening of the second expansion device.

According to this, even if temperature of usage-side heat medium which flows into the usage-side heat exchanger rises, since a heat exchanging amount between high pressure refrigerant which flows through the main refrigerant circuit and intermediate pressure refrigerant which flows through the bypass refrigerant circuit in the intermediate heat exchanger increases, it is possible to suppress the reduction of an enthalpy difference between an outlet and an inlet of refrigerant in the usage-side heat exchanger.

Further, since an amount of refrigerant which circulates through the bypass refrigerant circuit, the high-stage side compressing rotation element and the usage-side heat exchanger increases, it is possible to suppress deterioration of heating ability in the usage-side heat exchanger.

Hence, even if temperature of the usage-side heat medium which flows into the usage-side heat exchanger rises, it is possible to provide a heat pump system whose high-pressure side which suppress the deterioration of COP is operated under supercritical pressure.

Furthermore, even if temperature of the usage-side heat medium which flows into the usage-side heat exchanger rises, since the amount of refrigerant which circulates through the bypass refrigerant circuit, the high-stage side compressing rotation element and the usage-side heat exchanger increases, it is possible to suppress the deterioration of the heating ability in the usage-side heat exchanger.

Moreover, the pressure of the high-pressure side of refrigerant of the main refrigerant circuit rises. Therefore, even if temperature of the usage-side heat medium which flows into the usage-side heat exchanger rises, it is possible to suppress the reduction of the enthalpy difference between the outlet of refrigerant and inlet of refrigerant in the usage-side heat exchanger.

Further, it is possible to increase the heat exchanging amount between the high pressure refrigerant which flows through the main refrigerant circuit and the intermediate pressure refrigerant which flows through the bypass refrigerant circuit in the intermediate heat exchanger, and to increase the amount of refrigerant which circulates through the bypass refrigerant circuit, the high-stage side compressing rotation element and the usage-side heat exchanger while preventing excessive rise or reduction of discharge temperature of refrigerant which is discharged from the compressing rotation element.

Hence, it is possible to realize the discharge temperature of stable refrigerant, and even if temperature of the usage-side heat medium which flows into the usage-side heat exchanger rises, it is possible to suppress the reduction of the enthalpy difference between the outlet of refrigerant and inlet of refrigerant in the usage-side heat exchanger, and suppress deterioration of the heating ability in the usage-side heat exchanger.

According to claim <NUM>, there is provided a heat pump system including: a main refrigerant circuit formed by sequentially connecting, through a pipe, a compression mechanism composed of a compression rotation element, a usage-side heat exchanger for heating usage-side heat medium by refrigerant which is discharged from the compression rotation element and which exceeds critical pressure, an intermediate heat exchanger, a first expansion device, and a heat source-side heat exchanger; a bypass refrigerant circuit branched off from the pipe between the usage-side heat exchanger and the first expansion device, in which branched refrigerant is decompressed by a second expansion device and thereafter, heat of the refrigerant is exchanged with that of the refrigerant flowing through the main refrigerant circuit by the intermediate heat exchanger, and the refrigerant joins up with the refrigerant which is in middle of a compression operation of the compression rotation element; and a control device, a heat medium inlet temperature thermistor for detecting the temperature of the usage-side heat medium which flows into the usage-side heat exchanger, a high pressure-side pressure detector which detects pressure of the refrigerant discharged from the compressing rotation element, wherein when temperature of the usage-side heat medium which flows into the usage-side heat exchanger rises, the control device controls a valve opening of at least the second expansion device, and increases a ratio of an amount of the refrigerant which flows through the bypass refrigerant circuit to an amount of the refrigerant which flows on the side of a main refrigerant circuit of the intermediate heat exchanger, wherein when detected temperature which is detected by the heat medium inlet temperature thermistor rises, the control device operates to increase the valve opening of the second expansion device and operates to reduce a valve opening of the first expansion device, and wherein the control device brings a pressure value detected by the high pressure-side pressure detector close to a target value by adjusting the valve opening of the first expansion device and the valve opening of the second expansion device.

According to this, it is possible to prevent excessive rise or reduction of pressure of refrigerant which is discharged from the compressing rotation element, and even if temperature of the usage-side heat medium which flows into the usage-side heat exchanger rises, it is possible to suppress the reduction of the enthalpy difference between the outlet of refrigerant and the inlet of refrigerant in the usage-side heat exchanger.

According to claim <NUM>, the heat pump system of any one of claims <NUM> or <NUM> further includes a usage-side heat medium circuit which includes a conveying device and which circulates the usage-side heat medium by the conveying device.

According to this, even if temperature of the usage-side heat medium which flows into the usage-side heat exchanger rises, it is possible to suppress the deterioration of COP, and to provide a heat pump system capable of utilizing high temperature usage-side heat medium and whose high-pressure side is operated under supercritical pressure.

According to claim <NUM>, in the heat pump system of any one of claims <NUM> to <NUM>, the usage-side heat medium is water or antifreeze liquid.

According to this, it is possible to store high temperature water in the hot water tank, and to provide a heat pump system whose high-pressure side which heats a room using the high temperature water is operated under supercritical pressure.

The invention is not limited to the embodiment.

<FIG> is a block diagram of a heat pump system according to the embodiment of the invention. The heat pump system is composed of a refrigeration cycle device <NUM> which is a supercritical vapor compressing type refrigeration cycle, and a usage-side heat medium circuit <NUM>. The refrigeration cycle device <NUM> is composed of a main refrigerant circuit <NUM> and a bypass refrigerant circuit <NUM>.

The main refrigerant circuit <NUM> is formed by sequentially connecting, through a pipe <NUM>, a compression mechanism <NUM> which compresses refrigerant, a usage-side heat exchanger <NUM> which is a radiator, an intermediate heat exchanger <NUM>, a first expansion device <NUM> and a heat source-side heat exchanger <NUM> which is an evaporator. Carbon dioxide (CO2) is used as refrigerant.

The compression mechanism <NUM> is composed of a low stage-side compression rotation element 11a and a high stage-side compression rotation element 11b. The usage-side heat exchanger <NUM> heats usage-side heat medium by refrigerant discharged from the high stage-side compression rotation element 11b.

A volume ratio of the low stage-side compression rotation element 11a and the high stage-side compression rotation element 11b which configure the compression mechanism <NUM> is constant, these rotation elements use a common driving shaft (not shown), and the rotation elements are composed of a single compressor placed in one container.

This embodiment is described using a two-stage compression mechanism <NUM> in which the compression rotation element is composed of the low stage-side compression rotation element 11a and the high stage-side compression rotation element 11b, but the present invention can be applied also to a single compression mechanism in which the compressing rotation element is not divided into the low-stage side compressing rotation element 11a and the high-stage side compressing rotation element 11b.

Here, when a single compression mechanism is employed, a position where refrigerant from the bypass refrigerant circuit <NUM> joins up is defined as a middle position of being compressed by the compression rotation element, a portion of the compression rotation element up to a position where refrigerant from the bypass refrigerant circuit <NUM> joins up is defined as the low stage-side compression rotation element 11a, and a portion of the compression rotation element after the position where the refrigerant from the bypass refrigerant circuit <NUM> joins up is defined as the high stage-side compression rotation element 11b.

The low-stage side compressing rotation element 11a and the high-stage side compressing rotation element 11b may be a two-stage compression mechanism <NUM> which is composed of independent two compressors.

The bypass refrigerant circuit <NUM> branches off from the pipe <NUM> between the usage-side heat exchanger <NUM> and the first expansion device <NUM>, and is connected to the pipe <NUM> between the low stage-side compression rotation element 11a and the high stage-side compression rotation element 11b.

The bypass refrigerant circuit <NUM> is provided with a second expansion device <NUM>. A portion of high pressure refrigerant after it passes through the usage-side heat exchanger <NUM>, or a portion of high pressure refrigerant after it passes through the intermediate heat exchanger <NUM> is decompressed by the second expansion device <NUM>, and becomes intermediate pressure refrigerant and after that, this refrigerant is heat-exchanged with high pressure refrigerant which flows through the main refrigerant circuit <NUM> by the intermediate heat exchanger <NUM>, and the refrigerant joins up with refrigerant between the low stage-side compression rotation element 11a and the high stage-side compression rotation element 11b.

The usage-side heat medium circuit <NUM> is formed by sequentially connecting the usage-side heat exchanger <NUM>, a conveying device <NUM> which is a conveying pump, and the heating terminal 32a through a heat medium pipe <NUM>. Water of antifreeze liquid is used as the usage-side heat medium.

The usage-side heat medium circuit <NUM> in this embodiment includes a hot water storage tank 32b in parallel to the heating terminal 32a. The usage-side heat medium circuit <NUM> circulates the usage-side heat medium through the heating terminal 32a or a hot water storage tank 32b by switching between a first switching valve <NUM> and a second switching valve <NUM>. The usage-side heat medium circuit <NUM> may include any one of the heating terminal 32a and the hot water storage tank 32b.

High temperature water produced by the usage-side heat exchanger <NUM> radiates heat in the heating terminal 32a and is utilized for heating a room, and low temperature water whose heat is radiated in the heating terminal 32a is again heated by the usage-side heat exchanger <NUM>.

High temperature water produced by the usage-side heat exchanger <NUM> is introduced into the hot water storage tank 32b from an upper portion of the hot water storage tank 32b, low temperature water is sent out from a lower portion of the hot water storage tank 32b and heated by the usage-side heat exchanger <NUM>.

A hot water supplying heat exchanger <NUM> is placed in the hot water storage tank 32b, and the hot water supplying heat exchanger <NUM> exchanges heat between supplied water from a water supplying pipe <NUM> and high temperature water in the hot water storage tank 32b. That is, if a hot water supplying plug <NUM> is opened, water is supplied from the water supplying pipe <NUM> into the hot water supplying heat exchanger <NUM>, the water is heated by the hot water supplying heat exchanger <NUM>, temperature of the water is adjusted to predetermined temperature by the hot water supplying plug <NUM>, and hot water is supplied from the hot water supplying plug <NUM>.

Water is supplied from the water supplying pipe <NUM> and heated by the hot water supplying heat exchanger <NUM>, and hot water supplied from the hot water supplying plug <NUM> and high temperature water in the hot water storage tank 32b are not mixed with each other, and they are indirectly heated.

The hot water supplying heat exchanger <NUM> is a water heat exchanger using a copper pipe or stainless steel pipe as a heat transfer pipe, and the water supplying pipe <NUM> extending from a water supplying source (running water) and the hot water supplying plug <NUM> are connected to the hot water supplying heat exchanger <NUM> as shown in <FIG>. The water supplying pipe <NUM> sends normal temperature water into a lower end of the hot water supplying heat exchanger <NUM>, i.e., into a lower portion in the hot water storage tank 32b.

The normal temperature water sent into the hot water supplying heat exchanger <NUM> from the water supplying pipe <NUM> draws heat from the high temperature water in the hot water storage tank 32b while moving upward in the hot water storage tank 32b from downward, and the normal temperature water becomes high temperature heated water and is supplied from the hot water supplying plug <NUM>.

To measure temperature of hot water at a plurality of different height positions, the hot water storage tank 32b is provided with a plurality of hot water storage tank temperature thermistors, e.g., a first hot water storage tank temperature thermistor 55a, a second hot water storage tank temperature thermistor 55b and a third hot water storage tank temperature thermistor 55c.

The normal temperature water which enters the hot water supplying heat exchanger <NUM> from the water supplying pipe <NUM> draws heat from high temperature water in the hot water storage tank 32b while moving upward in the hot water storage tank 32b from downward. Therefore, temperature of hot water in the hot water storage tank 32b naturally becomes high at an upper portion and lower at a low portion in the hot water storage tank 32b.

The main refrigerant circuit <NUM> is provided with a high pressure-side pressure detector <NUM> and a discharge temperature thermistor <NUM> in the pipe <NUM> on the discharge side of the high stage-side compression rotation element 11b.

The high pressure-side pressure detector <NUM> is provided in the main refrigerant circuit <NUM> from a discharge side of the high stage-side compression rotation element 11b to an upstream side of the first expansion device <NUM>. It is only necessary that the high pressure-side pressure detector <NUM> can detect pressure of high pressure refrigerant in the main refrigerant circuit <NUM>.

Further, the discharge temperature thermistor <NUM> is also provided in the main refrigerant circuit <NUM> from the discharge side of the high-stage side compressing rotation element 11b to the upstream side of the first expansion device <NUM>. It is also only necessary that the discharge temperature thermistor <NUM> can detect temperature of the high pressure refrigerant of the main refrigerant circuit <NUM>.

The usage-side heat medium circuit <NUM> includes a heat medium inlet temperature thermistor <NUM> for detecting temperature of usage-side heat medium which flows into the usage-side heat exchanger <NUM>.

The control device <NUM> controls operation frequencies of the low-stage side compressing rotation element 11a and the high-stage side compressing rotation element 11b, a valve opening of the first expansion device <NUM>, a valve opening of the second expansion device <NUM> and a conveying amount of the usage-side heat medium conveyed by the conveying device <NUM> based on detected pressure detected by the high pressure-side pressure detector <NUM>, detected temperature detected by the discharge temperature thermistor <NUM> and detected temperature detected by the heat medium inlet temperature thermistor <NUM>.

<FIG> is a pressure-enthalpy diagram (P-h diagram) under the ideal condition concerning the refrigeration cycle device in the embodiment.

Points a to e and points A and B in <FIG> correspond to points in the refrigeration cycle device shown in <FIG>.

First, high pressure refrigerant (point a) discharged from the high stage-side compression rotation element 11b radiates heat in the usage-side heat exchanger <NUM> and after that, the high pressure refrigerant branches off from the main refrigerant circuit <NUM> at a refrigerant branch point.

(point A), the high pressure refrigerant is decompressed to intermediate pressure by the second expansion device <NUM> and becomes intermediate pressure refrigerant (point e), and the intermediate pressure refrigerant is heat-exchanged by the intermediate heat exchanger <NUM>.

The high pressure refrigerant which flows through the main refrigerant circuit <NUM> after it radiates heat by the usage-side heat exchanger <NUM> is cooled by intermediate pressure refrigerant (point e) which flows through the bypass refrigerant circuit <NUM>, and the high pressure refrigerant is decompressed by the first expansion device <NUM> in a state (point b) where enthalpy thereof is reduced.

According to this, refrigerant enthalpy of refrigerant (point c) which flows into the heat source-side heat exchanger <NUM> after it is decompressed by the first expansion device <NUM> is also reduced. Dryness (weight ratio occupied by gas phase component to the entire refrigerant) of refrigerant when it flows into the heat source-side heat exchanger <NUM> is reduced and liquid component of refrigerant is increased. Therefore, this contributes to evaporation in the heat source-side heat exchanger <NUM>, a refrigerant ratio is increased and an endothermic energy amount from outside air is increased, and it returns to the suction side (point d) of the low stage-side compression rotation element 11a.

On the other hand, refrigerant of an amount corresponding to gas phase component which does not contribute to evaporation in the heat source-side heat exchanger <NUM> is made to bypass by the bypass refrigerant circuit <NUM>, and becomes low temperature intermediate pressure refrigerant (point e), the refrigerant is heated by high pressure refrigerant which flows through the main refrigerant circuit <NUM> in the intermediate heat exchanger <NUM>, and the refrigerant reaches a refrigerant joining point B located between the low stage-side compression rotation element 11a and the high stage-side compression rotation element 11b in a state where refrigerant enthalpy is increased.

Therefore, on the suction side of the high stage-side compression rotation element 11b (point B), since refrigerant pressure is higher than that on the suction side of the low stage-side compression rotation element 11a (point d), refrigerant density is also high, and refrigerant which joins up with refrigerant discharged from the low stage-side compression rotation element 11a is sucked, further compressed by the high stage-side compression rotation element 11b and is discharged. Therefore, a flow rate of the refrigerant which flows into the usage-side heat exchanger <NUM> is largely increased, and ability of heating water which is usage-side heat medium is largely enhanced.

A case where the hot water storage tank 32b is used in the usage-side heat medium circuit <NUM> will be described below.

Among the plurality of hot water storage tank temperature thermistors, if detected temperature detected by the first hot water storage tank temperature thermistor 55a which is placed at the highest position in the hot water storage tank 32b is lower than a predetermined value, the control device <NUM> determines that high temperature water is insufficient in the hot water storage tank 32b.

The control device <NUM> operates the low stage-side compression rotation element 11a and the high stage-side compression rotation element 11b and heats low temperature water by the usage-side heat exchanger <NUM>. The control device <NUM> operates the conveying device <NUM> such that detected temperature detected by the heat medium outlet temperature thermistor <NUM> which is heating producing temperature becomes equal to the target temperature.

With this, low temperature water which is sent out from the lower portion of the hot water storage tank 32b is heated by the usage-side heat exchanger <NUM>. According to this, high temperature water is produced, and the high temperature water is introduced into the hot water storage tank 32b from the upper portion of the hot water storage tank 32b.

Since high temperature water is gradually stored in the hot water storage tank 32b from the upper portion, detected temperature detected by the heat medium inlet temperature thermistor <NUM> gradually increases.

A case where the heating terminal 32a is used in the usage-side heat medium circuit <NUM> will be described.

The control device <NUM> operates the low stage-side compression rotation element 11a and the high stage-side compression rotation element 11b and heats circulated water by the usage-side heat exchanger <NUM>, and the control device <NUM> operates the conveying device <NUM> such that a temperature difference, which is the temperature difference of the circulated water, between detected temperature detected by the heat medium outlet temperature thermistor <NUM> and detected temperature detected by the heat medium inlet temperature thermistor <NUM> becomes equal to a target temperature difference.

According to this, high temperature water produced by the usage-side heat exchanger <NUM> radiates heat in the heating terminal 32a and is utilized for heating a room, and low temperature water whose heat is released by the heating terminal 32a is again heated by the usage-side heat exchanger <NUM>. At that time, since control is performed such that a temperature difference between detected temperature detected by the heat medium outlet temperature thermistor <NUM> and detected temperature detected by the heat medium inlet temperature thermistor <NUM> becomes equal to the target temperature difference.

Since the heating load is gradually reduced, control is performed such that a temperature difference between detected temperature detected by the heat medium outlet temperature thermistor <NUM> and detected temperature detected by the heat medium inlet temperature thermistor <NUM> becomes equal to the target temperature difference. Therefore, the detected temperature detected by the heat medium outlet temperature thermistor <NUM> and the detected temperature detected by the heat medium inlet temperature thermistor <NUM> increase gradually.

A case where temperature of the usage-side heat medium which flows into the usage-side heat exchanger <NUM> in the usage-side heat medium circuit <NUM>, i.e., a case where detected temperature detected by the heat medium inlet temperature thermistor <NUM> rises will be described below using <FIG>.

In <FIG>, a solid line is a pressure-enthalpy diagram when temperature of the usage-side heat medium which flows into the usage-side heat exchanger <NUM> rises with respect to broken lines.

In <FIG>, if temperature of the usage-side heat medium which flows into the usage-side heat exchanger <NUM> rises, inlet temperature (point a) of refrigerant toward the usage-side heat exchanger <NUM> moves to an increasing direction (point a') of enthalpy. Further, outlet temperature (point A) of refrigerant from the usage-side heat exchanger <NUM> moves to the increasing direction (point A') of enthalpy.

Similarly, outlet temperature (point B) of refrigerant from the bypass refrigerant circuit <NUM> of the intermediate heat exchanger <NUM> also moves to the increasing direction (point B') of enthalpy. Further, inlet temperature (point e) of refrigerant toward the bypass refrigerant circuit <NUM> of the intermediate heat exchanger <NUM> also moves to the increasing direction (point e') of enthalpy.

In a state where pressure exceeds critical pressure, if temperature moves to the increasing direction of enthalpy, inclination of isothermal line with respect to pressure also becomes steep.

Hence, even if temperature of the usage-side heat medium which flows into the usage-side heat exchanger <NUM> rises, to suppress the deterioration of COP of the refrigeration cycle device <NUM>, the control device <NUM> must control the valve opening of the second expansion device <NUM> such that a temperature difference between the outlet temperature (point B') of refrigerant from the bypass refrigerant circuit <NUM> of the intermediate heat exchanger <NUM> and the inlet temperature (point e') of refrigerant toward the bypass refrigerant circuit <NUM> to the intermediate heat exchanger <NUM> does not become as small as possible in the intermediate heat exchanger <NUM>.

Further, even if temperature of the usage-side heat medium which flows into the usage-side heat exchanger <NUM> rises, it is necessary that heating ability of the usage-side heat medium is not deteriorated as small as possible by refrigerant which is discharged from the high-stage side compressing rotation element 11b in the usage-side heat exchanger <NUM>.

More specifically, a ratio of an amount of refrigerant which flows through the bypass refrigerant circuit <NUM> to an amount of refrigerant which flows on the side of the main refrigerant circuit <NUM> of the intermediate heat exchanger <NUM> is increased.

That is, the valve opening of the second expansion device <NUM> is increased and a ratio of an amount of refrigerant which circulates through the bypass refrigerant circuit <NUM>, the high-stage side compressing rotation element 11b and the usage-side heat exchanger <NUM> to an amount of refrigerant which circulates through the main refrigerant circuit <NUM> is increased.

According to this, even if temperature of the usage-side heat medium which flows into the usage-side heat exchanger <NUM> rises, the heat exchanging amount between the high pressure refrigerant which flows through the main refrigerant circuit <NUM> and the intermediate pressure refrigerant which flows through the bypass refrigerant circuit <NUM> in the intermediate heat exchanger <NUM> is increased.

Hence, it is possible to suppress the reduction of an enthalpy difference (point a' to point A') between the outlet of refrigerant and the inlet of refrigerant in the usage-side heat exchanger <NUM>.

The enthalpy difference between the high pressure refrigerant (point a') discharged from the high-stage side compressing rotation element 11b and the refrigerant (point A') of a branch point of refrigerant after heat is released at the usage-side heat exchanger <NUM> is equal to a total of an enthalpy difference between refrigerant (point B') on the suction side of the high-stage side compressing rotation element 11b and the intermediate pressure refrigerant (point e') which flows through the bypass refrigerant circuit <NUM> and an enthalpy difference of the high-stage side compressing rotation element 11b.

Hence, in order to increase the enthalpy difference (point a' to point A') between the outlet of refrigerant and the inlet of refrigerant in the usage-side heat exchanger <NUM>, it is necessary to increase the enthalpy difference (point B' to point e') of the bypass refrigerant circuit <NUM> of the intermediate heat exchanger <NUM>.

Since the amount of refrigerant which circulates through the bypass refrigerant circuit <NUM>, the high-stage side compressing rotation element 11b and the usage-side heat exchanger <NUM> is increased, it is possible to suppress the deterioration of the heating ability in the usage-side heat exchanger <NUM>.

The control device <NUM> operates to reduce the valve opening of the first expansion device <NUM>. According to this, since pressure on the high-pressure side of refrigerant of the main refrigerant circuit <NUM> rises, even if temperature of the usage-side heat medium which flows into the usage-side heat exchanger <NUM> rises, it is possible to suppress the reduction of the enthalpy difference (point a' to point A') between the outlet of refrigerant and the inlet of refrigerant in the usage-side heat exchanger <NUM>.

The control device <NUM> adjusts the valve opening of the first expansion device <NUM> and the valve opening of the second expansion device <NUM>. According to this, temperature detected by the discharge temperature thermistor <NUM> is brought close to a target value. The target value of discharge temperature is preset in the control device <NUM>.

According to this, it is possible to prevent the discharge temperature of refrigerant discharged from the high-stage side compressing rotation element 11b from being excessively increased or reduced, it is possible to increase the heat exchanging amount between the high pressure refrigerant which flows through the main refrigerant circuit <NUM> and the intermediate pressure refrigerant which flows through the bypass refrigerant circuit <NUM> in the intermediate heat exchanger <NUM>, and it is possible to increase the amount of refrigerant which circulates through the bypass refrigerant circuit <NUM>, the high-stage side compressing rotation element 11b and the usage-side heat exchanger <NUM>.

The control device <NUM> adjusts the valve opening of the first expansion device <NUM> and the valve opening of the second expansion device <NUM>. According to this, a pressure value detected by the high pressure-side pressure detector <NUM> is brought close to a target value.

According to this, it is possible to prevent pressure of refrigerant discharged from the high-stage side compressing rotation element 11b from being excessively increased or reduced. Even if temperature of the usage-side heat medium which flows into the usage-side heat exchanger <NUM> rises, it is possible to suppress the reduction of the enthalpy difference (point a' to point A') between the outlet of refrigerant and the inlet of refrigerant in the usage-side heat exchanger <NUM>.

The compressing rotation element may be a single compressing rotation element which is not divided into the low-stage side compressing rotation element 11a and the high-stage side compressing rotation element 11b. If the single compressing rotation element is employed, a position where refrigerant from the bypass refrigerant circuit <NUM> joins up is defined as a middle position of being compressed by the compression rotation element.

By using water or antifreeze liquid as usage-side heat medium, it is possible to use the usage-side heat medium in the heating terminal 32a or high temperature water can be stored in the hot water tank 32b.

Claim 1:
A heat pump system comprising:
a main refrigerant circuit (<NUM>) formed by sequentially connecting, through a pipe (<NUM>), a compression mechanism (<NUM>) composed of a compression rotation element (11a, 11b), a usage-side heat exchanger (<NUM>) for heating usage-side heat medium by refrigerant which is discharged from the compression rotation element (11a, 11b) and which exceeds critical pressure, an intermediate heat exchanger (<NUM>), a first expansion device (<NUM>), and a heat source-side heat exchanger (<NUM>);
a bypass refrigerant circuit (<NUM>) branched off from the pipe (<NUM>) between the usage-side heat exchanger (<NUM>) and the first expansion device (<NUM>), in which branched refrigerant is decompressed by a second expansion device (<NUM>) and thereafter, heat of the refrigerant is exchanged with that of the refrigerant flowing through the main refrigerant circuit (<NUM>) by the intermediate heat exchanger (<NUM>), and the refrigerant joins up with the refrigerant which is in middle of a compression operation of the compression rotation element (11a, 11b); and
a control device (<NUM>),
a heat medium inlet temperature thermistor (<NUM>) for detecting the temperature of the usage-side heat medium which flows into the usage-side heat exchanger (<NUM>),
a discharge temperature thermistor (<NUM>) which detects temperature of the refrigerant discharged from the compressing rotation element (11a, 11b),
wherein when temperature of the usage-side heat medium which flows into the usage-side heat exchanger (<NUM>) rises, the control device (<NUM>) controls a valve opening of at least the second expansion device (<NUM>), and increases a ratio of an amount of the refrigerant which flows through the bypass refrigerant circuit (<NUM>) to an amount of the refrigerant which flows on a side of the main refrigerant circuit (<NUM>) of the intermediate heat exchanger (<NUM>),
wherein when detected temperature which is detected by the heat medium inlet temperature thermistor (<NUM>) rises, the control device (<NUM>) operates to increase the valve opening of the second expansion device (<NUM>) and operates to reduce a valve opening of the first expansion device (<NUM>), and
wherein the control device (<NUM>) brings the temperature detected by the discharge temperature thermistor (<NUM>) close to a target value by adjusting the valve opening of the first expansion device (<NUM>) and the valve opening of the second expansion device (<NUM>).