JP7151262B2 - Heat pump device and refrigerant flow rate calculation method - Google Patents

Description

The present invention is a heat pump device in which a refrigerant is evaporated by an external heat source in an evaporator in a refrigerant circulation circuit, the refrigerant is condensed in a condenser, and a medium to be heated is heated, and the flow rate of the refrigerant flowing through the condenser in the heat pump device is calculated. The present invention relates to a refrigerant flow rate calculation method.

The heat pump device forms a refrigerant circulation circuit, evaporates the refrigerant with an external heat source in the evaporator in the circuit, condenses the refrigerant in the condenser, and heats the medium to be heated. Some heat pump devices have a two-stage compression and two-stage expansion cycle in which a compressor and an expansion valve are each configured in two stages. In the two-stage compression and two-stage expansion cycle, the compression ratio per single stage of the compressor can be reduced by using two stages of compression, and the low-stage compression can be reduced by minimizing the refrigerant flow rate on the low-stage side. Since power can be minimized, efficiency can be improved compared to a single-stage cycle (see Patent Document 1).

JP 2014-119157 A

By the way, when the medium to be heated is heated by the condenser in the heat pump device, it is necessary to detect the flow rate of the refrigerant flowing through the condenser in order to control the output. For this reason, conventionally, a flow meter was provided in the middle of the pipeline. Since the flow meter is expensive, it is desired to obtain the refrigerant flow rate by an inexpensive and simple means.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a heat pump device and a method for calculating a refrigerant flow rate that can determine the refrigerant flow rate without using a flow meter.

In order to solve the above-described problems and achieve the object, the heat pump device according to the present invention includes an evaporator that evaporates a low-pressure refrigerant with an external heat source, and a low-stage compressor that compresses the evaporated low-pressure refrigerant into an intermediate-pressure refrigerant. a high-stage compressor that compresses intermediate-pressure refrigerant into high-pressure refrigerant, a condenser that condenses the high-pressure refrigerant and heats the medium to be heated, and a high-stage compressor that decompresses and expands the condensed high-pressure refrigerant to intermediate pressure. an expansion mechanism, a gas-liquid separator for separating the intermediate pressure refrigerant introduced from the high-stage expansion mechanism into gas and liquid, and an intermediate-pressure refrigerant introduced from the gas phase side outlet of the gas-liquid separator to the low-stage compressor. An intermediate pipe introduced into the intermediate pressure gas phase flow path between the discharge port of and the suction port of the high-stage compressor, and the intermediate pressure refrigerant introduced from the liquid phase side outlet of the gas-liquid separator is decompressed and expanded. A low-stage expansion mechanism that reduces the pressure and introduces it into the evaporator, a high-pressure gas-phase pressure detection means that detects the high-pressure gas-phase pressure of the refrigerant at the discharge port of the high-stage compressor, and a High pressure gas phase temperature detecting means for detecting the high pressure gas phase temperature of the refrigerant, medium pressure gas phase pressure detecting means for detecting the medium pressure gas phase pressure of the refrigerant in the intermediate pipe or the medium pressure gas phase flow path, and the high stage compressor a rotational speed detection means for detecting the rotational speed of the high-stage compressor; a storage unit for storing characteristic data indicating the adiabatic efficiency, volumetric efficiency and displacement of the high-stage compressor; a medium-pressure gas-phase density calculator for calculating a medium-pressure gas-phase density of the medium-pressure gas-phase flow path based on the medium-pressure gas-phase pressure and the adiabatic efficiency; and a refrigerant flow rate calculator that calculates the refrigerant flow rate based on the efficiency.

The low stage compressor and the high stage compressor may be an integrated multi-stage compressor.

a high-pressure gas-phase enthalpy calculator for calculating a high-pressure gas-phase enthalpy at a discharge port of the high-stage compressor based on the high-pressure gas-phase pressure and the high-pressure gas-phase temperature; and a medium pressure gas phase temperature calculation unit for calculating the medium pressure gas phase temperature of the medium pressure gas phase flow path, wherein the medium pressure gas phase density calculation unit calculates the medium pressure gas phase temperature and the medium pressure gas phase pressure based on the medium pressure gas phase temperature and the medium pressure gas phase pressure. may be used to calculate the intermediate pressure gas phase density.

a high-pressure gas-phase enthalpy calculation unit for calculating a high-pressure gas-phase enthalpy at a discharge port of the high-stage compressor based on the high-pressure gas-phase pressure and the high-pressure gas-phase temperature; Assuming an assumed intermediate pressure gas phase density corresponding to the intermediate pressure gas phase density, calculating an assumed adiabatic efficiency corresponding to the adiabatic efficiency based on the high pressure gas phase enthalpy and the assumed intermediate pressure gas phase density, and calculating the adiabatic efficiency and A loop calculation is performed by re-assuming the assumed intermediate pressure gas phase density based on the difference from the assumed adiabatic efficiency, and when the difference becomes equal to or less than a threshold value, the assumed intermediate pressure gas phase density is set as the intermediate pressure gas phase density. good too.

Further, a refrigerant flow rate calculation method according to the present invention includes an evaporator that evaporates a low-pressure refrigerant with an external heat source, a low-stage compressor that compresses the evaporated low-pressure refrigerant to an intermediate-pressure refrigerant, and a low-stage compressor that compresses the intermediate-pressure refrigerant. a high-stage compressor that converts the high-pressure refrigerant into a high-pressure refrigerant, a condenser that condenses the high-pressure refrigerant and heats the medium to be heated, a high-stage expansion mechanism that decompresses and expands the condensed high-pressure refrigerant to an intermediate pressure, and the high-stage expansion mechanism. A gas-liquid separator that separates gas and liquid from the introduced intermediate-pressure refrigerant, and the intermediate-pressure refrigerant introduced from the gas-phase side outlet of the gas-liquid separator is separated from the discharge port of the low-stage compressor and the high-stage compressor. An intermediate pipe introduced into the intermediate pressure gas phase flow path between the suction port, and an intermediate pressure refrigerant introduced from the liquid phase side outlet of the gas-liquid separator is decompressed and expanded to a low pressure and introduced into the evaporator. A refrigerant flow rate calculation method for determining the flow rate of refrigerant flowing through the condenser in a heat pump device having a stage expansion mechanism, wherein the high-pressure vapor phase pressure of the refrigerant at the discharge port of the high-stage compressor, A medium-pressure gas phase density of the medium-pressure gas-phase channel is calculated based on the high-pressure gas-phase temperature of the refrigerant, the medium-pressure gas-phase pressure of the refrigerant in the medium-pressure gas-phase channel or the intermediate pipe, and the adiabatic efficiency of the high-stage compressor. and calculating the refrigerant flow rate based on the intermediate pressure gas phase density, the rotation speed of the high-stage compressor, the displacement amount of the high-stage compressor, and the volumetric efficiency of the high-stage compressor. and a refrigerant flow rate calculation step.

In the heat pump device and refrigerant flow rate calculation method according to the present invention, the intermediate pressure gas phase density in the intermediate pressure gas phase flow path is calculated based on the high pressure gas phase pressure, the high pressure gas phase temperature, the intermediate pressure gas phase pressure, and the adiabatic efficiency of the high-stage compressor. Then, the intermediate pressure gas phase density is used to calculate the refrigerant flow rate. This makes it possible to obtain the refrigerant flow rate without using a flow meter.

FIG. 1 is a block diagram of a heat pump device according to an embodiment. FIG. 2 is a ph diagram of the heat pump device. FIG. 3 is a block diagram of the controller. FIG. 4 is a flow chart showing the control procedure of the heat pump device. FIG. 5 is a flow chart showing a modification of the control procedure of the heat pump device.

EMBODIMENT OF THE INVENTION Below, embodiment of the heat pump apparatus concerning this invention and a refrigerant|coolant flow rate calculation method is described in detail based on drawing. In addition, this invention is not limited by this embodiment.

FIG. 1 is a block diagram showing a heat pump device 10 that is an embodiment of the invention. The heat pump device 10 has a circuit portion 12 that is a refrigerant circulation circuit, a control portion 14 that controls the circuit portion 12 , and an inverter 13 provided between the circuit portion 12 and the control portion 14 .

The circuit unit 12 includes an evaporator 16, a compressor 18, a condenser 20, a high-stage expansion valve (high-stage expansion mechanism) 22, a gas-liquid separator 24, and a low-stage expansion valve ( low-stage expansion mechanism) 26. Note that the circuit section 12 in FIG. 1 shows a basic configuration, and other elements may be provided in the circuit. The evaporator 16 and the compressor 18 are connected by a flow path 28a, the compressor 18 and the condenser 20 are connected by a flow path 28c, the condenser 20 and the high-stage expansion valve 22 are connected by a flow path 28d, The high-stage expansion valve 22 and the gas-liquid separator 24 are connected by a flow path 28e, and the liquid phase outlet of the gas-liquid separator 24 and the low-stage expansion valve 26 are connected by a flow path 28f. It is connected to the evaporator 16 via a flow path 28g.

In the following description, the states of the refrigerant are referred to as medium-pressure liquid phase, medium-pressure gas phase, high-pressure gas phase, and high-pressure liquid phase. Immediately after the start, each phase may be mixed to some extent.

The evaporator 16 evaporates the low-pressure refrigerant with an external heat source to produce a low-pressure vapor-phase refrigerant. An external heat source is, for example, waste water supplied from another system.

The compressor 18 is a two-stage compression type (that is, a multi-stage compressor) in which a low-stage compressor 18a and a high-stage compressor 18b are integrated. A medium-pressure gas-phase flow path 28 b between the outlet is provided inside the housing of the compressor 18 . The compressor 18 is, for example, a single shaft scroll compressor. The low-stage compressor 18a compresses the low-pressure vapor-phase refrigerant into medium-pressure vapor-phase refrigerant. The high-stage compressor 18b compresses the medium-pressure gaseous-phase refrigerant into a high-pressure gaseous-phase refrigerant. The condenser 20 condenses the high-pressure vapor-phase refrigerant into a high-pressure liquid-phase refrigerant and heats the medium to be heated. The medium to be heated is, for example, water supplied from a pump (not shown), which is converted into steam by the condenser 20 and utilized.

The high-stage expansion valve 22 decompresses and expands the high-pressure liquid-phase refrigerant to produce an intermediate-pressure refrigerant. The gas-liquid separator 24 separates the intermediate pressure refrigerant into gas and liquid. The low-stage expansion valve 26 decompresses and expands the refrigerant introduced from the liquid phase side outlet of the gas-liquid separator to obtain a low-pressure refrigerant, which is introduced into the evaporator 16 .

The circuit unit 12 further has an intermediate pipe 32 for introducing the refrigerant introduced from the gas-phase side outlet of the gas-liquid separator 24 into the medium-pressure gas-phase flow path 28b and joining the refrigerant. The circuit section 12 forms a two-stage compression and two-stage expansion cycle, with the gas-liquid separator 24 and the intermediate pipe 32 as boundaries in FIG.

The circuit section 12 also has a high pressure gas phase pressure gauge 34 , a high pressure gas phase thermometer 36 , a high pressure liquid phase pressure gauge 38 , a high pressure liquid phase thermometer 40 and an intermediate pressure gas phase pressure gauge 42 . In FIG. 1, a plurality of signal lines of some pressure gauges and thermometers are collectively illustrated as one. Also, electric signal lines are indicated by dashed lines.

A high-pressure gas-phase pressure gauge 34 detects a high-pressure gas-phase pressure Pa of the refrigerant at the discharge port of the high-stage compressor 18b. A high-pressure gas-phase thermometer 36 detects a high-pressure gas-phase temperature Ta of the refrigerant at the discharge port of the high-stage compressor 18b. The high-pressure gas-phase pressure gauge 34 and the high-pressure gas-phase thermometer 36 may be provided anywhere in the flow path 28c. It is good to provide between stage compressor 18b.

A high pressure liquid phase pressure gauge 38 detects the high pressure liquid phase pressure Pb of the refrigerant at the discharge port of the condenser 20 . If the pressure drop in the condenser 20 is small, either one of the high-pressure gas-phase pressure gauge 34 or the high-pressure liquid-phase pressure gauge 38 may be omitted, and Pb=Pa may be approximated. If the high-pressure gas-phase pressure gauge 34 is omitted, the high-pressure liquid-phase pressure gauge 38 also serves as the high-pressure gas-phase pressure detection means. A high pressure liquid phase thermometer 40 detects the high pressure liquid phase temperature Tb of the refrigerant at the discharge port of the condenser 20 . The medium pressure gas phase pressure gauge 42 detects the medium pressure gas phase pressure Ps. This medium-pressure gas phase pressure Ps is the pressure of the refrigerant in the medium-pressure gas-phase flow path 28b or the intermediate pipe 32. Of these, the medium-pressure gas-phase flow path 28b is inside the housing of the compressor 18, so the medium-pressure gas-phase pressure Ps is 42 is provided on the intermediate pipe 32 . It goes without saying that each pressure gauge can be substituted with other pressure detection means, and similarly, the thermometer can be substituted with other temperature detection means.

The inverter 13 controls the rotation speed of the compressor 18 so that the rotation speed N is the command value supplied from the control unit 14 .

A ph diagram showing the thermal cycle of the heat pump device 10 will be described with reference to FIG. In FIG. 2, portions corresponding to the flow paths 28a, 28b, 28c, 28d, 28e, 28f and 28g in FIG. These symbols La to Lg also indicate the flow paths 28a to 28g in FIG.

In the evaporator 16, the steam moves from the Lg point to the La point, exceeds the saturated steam line, and becomes superheated steam. In the low-stage compressor 18a, compression moves from point La to point Lb via point _Lb0 . The reason why the specific enthalpy h slightly drops from the Lb ₀ point to the Lb point is that the medium-pressure gas-phase refrigerant from the intermediate pipe 32 joins. In the high-stage compressor 18b, compression shifts from the Lb point to the Lc point, and the pressure P and the specific enthalpy h increase. In the ideal compression process, the point Lb is shifted to the point Lci, but the slope from the Lb point to the Lc point is smaller than the slope from the Lb point to the Lci point. The compression path from the Lb point to the Lc point is determined by the adiabatic efficiency _ηad of the high-stage compressor 18b. The adiabatic efficiency _ηad will be described later.

In the condenser 20, the condensation moves from the Lc point to the Ld point, exceeds the saturated vapor line, and further exceeds the saturated liquid line, resulting in a supercooled state. In the high-stage expansion valve 22, the gas moves from the Ld point to the Le point due to the expansion, and again exceeds the saturated steam line to enter a gas-liquid mixed state. The Le point is the intermediate gas phase pressure Ps. In the gas-liquid separator 24, the gas is separated into a gas phase and a liquid phase, and the gas phase moves onto the saturated vapor line, merges with the intermediate gas phase path 28b of the compressor 18, and moves to point Lb. The liquid phase moves above the saturated liquid line. The low-stage expansion valve 26 moves from the Lf point to the Lg point due to expansion.

As shown in FIG. 3 , the control unit 14 has a storage unit 44 , a calculation unit 46 and a rotation speed control unit 48 . The control unit 14 does not necessarily need to be installed near the circuit unit 12, and may be connected via a communication line, for example. The storage unit 44, the calculation unit 46, and the rotation speed control unit 48 do not necessarily have to be integrally provided, and the storage unit 44 may be of a cloud type, for example.

The storage unit 44 is a portion that stores programs and data, and is, for example, a hard disk, and stores characteristic data 50 . The characteristic data 50 is data indicating the characteristics of the compressor 18, and particularly stores data indicating the adiabatic efficiency _ηad , the volumetric efficiency ηv, and the displacement _V of the high-stage compressor 18b. These adiabatic efficiency η _ad , volumetric efficiency η _V , and displacement volume V may be stored as direct numerical values, or may be indirectly stored by some conversion from one or more parameters, Any data that substantially indicates the adiabatic efficiency η _ad , the volumetric efficiency η _V , and the displacement V may be used.

The adiabatic efficiency η _ad is the ratio of the work actually required when the high stage compressor 18b compresses the refrigerant to the ideal work. The volumetric efficiency _ηV is an efficiency that takes into account refrigerant leakage from the suction port to the discharge port of the high-stage compressor 18b. The displacement volume V is the refrigerant volume that is displaced per revolution of the input shaft. The characteristic data 50 may also store other characteristics of the circuit section 12 and its elements.

The calculation unit 46 has a high pressure gas phase enthalpy calculation unit 52 , an intermediate pressure gas phase temperature calculation unit 54 , an intermediate pressure gas phase density calculation unit 56 , a refrigerant flow rate calculation unit 58 and a thermal output calculation unit 60 . These calculation units do not need to be clearly distinguished in the calculation unit 46. For example, some calculation units may overlap, and one calculation unit may be included in another calculation unit. . The computing unit 46 may be implemented by software, for example, by causing a processing device such as a CPU (Central Processing Unit) to execute a program, or may be implemented by hardware such as an IC (Integrated Circuit). However, it may be implemented using both software and hardware.

The high-pressure gas-phase enthalpy calculator 52 calculates the high-pressure gas-phase enthalpy ha at the discharge port of the high-stage compressor 18b based on the high-pressure gas-phase pressure Pa and the high-pressure gas-phase temperature Ta.

The medium pressure gas phase temperature calculator 54 calculates the medium pressure gas phase temperature Ts based on the high pressure gas phase pressure Pa, the high pressure gas phase temperature Ta, the medium pressure gas phase pressure Ps and the adiabatic efficiency ηad. This intermediate-pressure gas phase temperature Ts is the temperature of the refrigerant in the intermediate-pressure gas-phase flow path 28b (that is, the temperature at point Lb in FIG. 2). , it is difficult to provide a thermometer, and the calculation by the medium-pressure vapor phase temperature calculator 54 is useful. Also, by omitting the thermometer for this portion, the cost can be reduced accordingly. Intermediate enthalpy hs in medium-pressure gas phase flow path 28b (that is, enthalpy at point Lb in FIG. 2) may be obtained as an intermediate calculation for obtaining medium-pressure gas phase temperature Ts.

The intermediate pressure gas phase density calculator 56 calculates the intermediate pressure gas phase density ρs of the intermediate pressure gas phase flow path 28b based on the intermediate pressure gas phase pressure Ps and the intermediate pressure gas phase temperature Ts. The intermediate pressure gas phase density ρs is a physical property value unique to the refrigerant, and is obtained based on the state equation ρs=f _s (Ps, Ts). By the way, when the high-pressure gas-phase enthalpy calculator 52, the medium-pressure gas-phase temperature calculator 54, and the medium-pressure gas-phase density calculator 56 are put together, the medium-pressure gas-phase density ρs is the high-pressure gas-phase pressure Pa, the high-pressure gas-phase temperature Ta, It is calculated using the four parameters of medium-pressure gas-phase pressure Ps and adiabatic efficiency η _ad , and the number of parameters is small and the computational load is small, but depending on the conditions, another parameter may additionally be used.

The refrigerant flow rate calculator 58 calculates the refrigerant flow rate G of the refrigerant flowing through the condenser 20 based on the medium-pressure gas phase density ρs, the number of rotations N, the displacement _V , and the volumetric efficiency ηV. The refrigerant flow rate G is a mass flow rate and is obtained by G=ρs·N· _V ·ηV. Displacement V and volumetric efficiency η _V are supplied from characteristic data 50 . Since the number of revolutions N is supplied from the number of revolutions control section 48, the number of revolutions control section 48 also serves as means for detecting the number of revolutions. may be provided separately.

The thermal output calculator 60 calculates the thermal output Q with which the condenser 20 heats the medium to be heated. The heat output calculator 60 first calculates the enthalpy hb at the discharge port of the condenser 20 based on the high-pressure liquid phase pressure Pb and the high-pressure liquid phase temperature Tb. Then, the heat output Q is obtained as Q=G.(ha-hb). The high-pressure gas-phase enthalpy ha obtained by the high-pressure gas-phase enthalpy calculator 52 can be used. It is more accurate to determine the enthalpy ha' from the pressure and temperature just before the mouth and the thermal power Q as Q=G.(ha'-hb).

The rotation speed control unit 48 controls the rotation speed of the inverter 13 so that the heat output Q of the condenser 20 becomes a target value, and the refrigerant flow rate G is adjusted. Furthermore, the supply amount of the medium to be heated that is heated by the condenser 20 may be adjusted.

FIG. 4 is a flowchart showing the control procedure of the heat pump device 10, including the flow rate calculation method according to the present embodiment. This procedure is repeatedly executed every minute time.

Step S1 is a high pressure gas phase enthalpy calculation step, and the high pressure gas phase enthalpy calculator 52 calculates the high pressure gas phase enthalpy ha. Step S<b>2 is a medium pressure gas phase temperature calculation step, and the medium pressure gas phase temperature calculation unit 54 calculates the medium pressure gas phase temperature Ts. Step S3 is a medium pressure gas phase density calculation step, in which the medium pressure gas phase density calculator 56 calculates the medium pressure gas phase density ρs. Step S<b>4 is a refrigerant flow rate calculation step, and the refrigerant flow rate G is calculated by the refrigerant flow rate calculator 58 . Step S5 is a thermal output calculation step, and the thermal output Q is calculated by the thermal output calculator 60. FIG. Step S<b>6 is a rotation speed control step, and the rotation speed N of the inverter 13 is controlled by the rotation speed control unit 48 .

As described above, in the heat pump device 10 and the refrigerant flow rate calculation method, it is difficult to provide a temperature sensor in the medium pressure gas phase flow path 28b inside the compressor 18, but the high pressure gas phase pressure Pa, the high pressure gas phase temperature Ta, A medium pressure gas phase temperature Ts is calculated based on the medium pressure gas phase pressure Ps and the adiabatic efficiency ηad, and a medium pressure gas phase density ρs is obtained. As a result, the heat output Q can be obtained, and appropriate output control can be performed.

Furthermore, expensive flowmeters (for example, refrigerant flowmeters, steam flowmeters, etc.) are not required, and the system can be configured simply and inexpensively.

In a series of calculation processes for obtaining the refrigerant flow rate G, the value of the adiabatic efficiency ηad can be adjusted and corrected based on the operating conditions (pressure difference, pressure ratio, rotation speed, etc.) of the high-stage compressor 18b to enable more accurate calculations. Become. The same applies to the example of the flowchart of FIG. 5, which will be described next.

Next, a modification of the procedure for obtaining the coolant flow rate G will be described with reference to FIG.

At step S11 in FIG. 5, first, the high-pressure vapor phase enthalpy ha is calculated. This is the same high-pressure vapor phase enthalpy calculation step as step S1 above.

In step S12, an assumed intermediate pressure gas phase density ρs' corresponding to the intermediate pressure gas phase density ρs is assumed to be an assumed appropriate value. The initial value of the assumed intermediate pressure gas phase density ρs' may be a fixed value. Here, the suffix "'" indicates a hypothetical value. The same applies hereinafter.

In step S13, an assumed intermediate enthalpy hs', hs'=f(ρs', Ps) is obtained based on the assumed intermediate pressure gas phase density ρs' and intermediate pressure gas phase pressure Ps. The hypothetical intermediate enthalpy hs' corresponds to the hypothetical value of the intermediate enthalpy hs described above.

In step S14, an assumed adiabatic efficiency ηad' is obtained. The assumed adiabatic efficiency ηad' corresponds to the assumed value of the adiabatic efficiency ηad described above, and is obtained as ηad'=(h _{d_ad} -hs')/(hd-hs'). Here, _{hd_ad} is the ideal discharge enthalpy, that is, the enthalpy when changed in an isentropic process. The isentropic process changes on the line connecting point Lb to point Lci in FIG. hd is the actual discharge enthalpy. In FIG. 2, _{hd_ad} conceptually corresponds to point Lci, and hd conceptually corresponds to point Lc.

In step S15, the stored adiabatic efficiency ηad and the calculated assumed adiabatic efficiency ηad' are compared. If the adiabatic efficiency ηad and the assumed adiabatic efficiency ηad' are equal or the difference is sufficiently small (Y), the process proceeds to step S17.

In step S16, the solver changes and re-assumes the assumed intermediate pressure gas phase density ρs', and the process returns to step S13. By returning to step S13, a loop calculation is performed between steps S13 to S16, and the difference between the adiabatic efficiency ηad and the assumed adiabatic efficiency ηad' gradually converges, and eventually the process moves to step S17.

In step S17, the adiabatic efficiency ηad and the assumed adiabatic efficiency ηad' are equal or the difference is sufficiently small. At this time, the intermediate pressure gas phase density ρs and the assumed intermediate pressure gas phase density ρs' are equal or the difference is sufficiently small. Therefore, by substituting .rho.s=.rho.s', the intermediate pressure gas phase density .rho.s is determined and obtained. Thereafter, the heat output Q is calculated in step S18, and the rotation speed of the inverter 13 is controlled in step S19. These are the same processes as steps S5 and S6 described above.

In such a method of calculating the intermediate pressure gas phase density ρs, it is not necessary to find the intermediate pressure gas phase temperature Ts in the middle. Convergence calculations by solvers and loops are also useful for computational applications.

There may be various methods for calculating the intermediate pressure gas phase density ρs based on the high pressure gas phase pressure Pa, the high pressure gas phase temperature Ta, the intermediate pressure gas phase pressure Ps, and the adiabatic efficiency ηad. The refrigerant flow rate G is calculated based on the intermediate pressure gas phase density ρs obtained by various methods.

It goes without saying that the present invention is not limited to the above-described embodiments, and can be freely modified without departing from the gist of the present invention.

10 heat pump device 12 circuit unit 13 inverter 14 control unit 16 evaporator 18 compressor 18a low-stage compressor 18b high-stage compressor 20 condenser 22 high-stage expansion valve (high-stage expansion mechanism)
24 gas-liquid separator 26 low-stage expansion valve (low-stage expansion mechanism)
28b Intermediate-pressure gas-phase flow path 32 Intermediate pipe 34 High-pressure gas-phase pressure gauge (high-pressure gas-phase pressure detection means)
36 high-pressure gas-phase thermometer (high-pressure gas-phase temperature detection means)
38 High pressure liquid phase pressure gauge 40 High pressure liquid phase thermometer 42 Medium pressure gas phase pressure gauge (means for detecting medium pressure gas phase pressure)
44 Storage unit 46 Calculation unit 48 Rotation speed control unit 50 Characteristic data 52 High pressure gas phase enthalpy calculation unit 54 Medium pressure gas phase temperature calculation unit 56 Medium pressure gas phase density calculation unit 58 Refrigerant flow rate calculation unit 60 Thermal output calculation unit

Claims (3)

an evaporator that evaporates the low-pressure refrigerant with an external heat source;
a low-stage compressor that compresses the evaporated low-pressure refrigerant into an intermediate-pressure refrigerant;
a high-stage compressor that compresses intermediate-pressure refrigerant into high-pressure refrigerant;
a condenser for condensing the high-pressure refrigerant and heating the medium to be heated;
a high-stage expansion mechanism that decompresses and expands the condensed high-pressure refrigerant to an intermediate pressure;
a gas-liquid separator for gas-liquid separation of the intermediate-pressure refrigerant introduced from the high-stage expansion mechanism;
an intermediate pipe for introducing the intermediate-pressure refrigerant introduced from the gas-phase side outlet of the gas-liquid separator into the intermediate-pressure gas-phase flow path between the discharge port of the low-stage compressor and the suction port of the high-stage compressor; ,
a low-stage expansion mechanism that decompresses and expands the intermediate-pressure refrigerant introduced from the liquid phase side outlet of the gas-liquid separator to a low pressure and introduces it into the evaporator;
high-pressure gas-phase pressure detection means for detecting the high-pressure gas-phase pressure of the refrigerant at the discharge port of the high-stage compressor;
high-pressure gas-phase temperature detection means for detecting the high-pressure gas-phase temperature of the refrigerant at the discharge port of the high-stage compressor;
intermediate pressure gas phase pressure detection means for detecting the intermediate pressure gas phase pressure of the refrigerant in the intermediate pipe or the intermediate pressure gas phase flow path;
rotation speed detection means for detecting the rotation speed of the high-stage compressor;
a storage unit for storing characteristic data indicating adiabatic efficiency, volumetric efficiency and displacement of the high-stage compressor;
a medium-pressure gas-phase density calculator that calculates the medium-pressure gas-phase density of the medium-pressure gas-phase channel based on the high-pressure gas-phase pressure, the high-pressure gas-phase temperature, the medium-pressure gas-phase pressure, and the adiabatic efficiency;
a refrigerant flow rate calculation unit that calculates a refrigerant flow rate flowing through the condenser based on the medium pressure gas phase density, the rotation speed, the displacement amount, and the volumetric efficiency;
a high-pressure gas-phase enthalpy calculation unit that calculates a high-pressure gas-phase enthalpy at a discharge port of the high-stage compressor based on the high-pressure gas-phase pressure and the high-pressure gas-phase temperature;
has
The medium pressure gas phase density calculation unit
Assuming an assumed intermediate pressure gas phase density corresponding to the intermediate pressure gas phase density, calculating an assumed adiabatic efficiency corresponding to the adiabatic efficiency based on the high pressure gas phase enthalpy and the assumed intermediate pressure gas phase density, and calculating the adiabatic efficiency and performing a loop calculation by re-assuming the assumed intermediate pressure gas phase density based on the difference from the assumed adiabatic efficiency;
A heat pump device , wherein the assumed medium-pressure gas phase density is set to the medium-pressure gas phase density when the difference becomes equal to or less than a threshold value . In the heat pump device according to claim 1,
A heat pump apparatus, wherein the low-stage compressor and the high-stage compressor are integrated multi-stage compressors. an evaporator that evaporates the low-pressure refrigerant with an external heat source;
a low-stage compressor that compresses the evaporated low-pressure refrigerant into an intermediate-pressure refrigerant;
a high-stage compressor that compresses intermediate-pressure refrigerant into high-pressure refrigerant;
a condenser for condensing the high-pressure refrigerant and heating the medium to be heated;
a high-stage expansion mechanism that decompresses and expands the condensed high-pressure refrigerant to an intermediate pressure;
a gas-liquid separator for gas-liquid separation of the intermediate-pressure refrigerant introduced from the high-stage expansion mechanism;
an intermediate pipe for introducing the intermediate-pressure refrigerant introduced from the gas-phase side outlet of the gas-liquid separator into the intermediate-pressure gas-phase flow path between the discharge port of the low-stage compressor and the suction port of the high-stage compressor; ,
a low-stage expansion mechanism that decompresses and expands the intermediate-pressure refrigerant introduced from the liquid phase side outlet of the gas-liquid separator to a low pressure and introduces it into the evaporator;
In a refrigerant flow rate calculation method for determining the refrigerant flow rate flowing through the condenser in a heat pump device having
high-pressure vapor phase pressure of the refrigerant at the discharge port of the high-stage compressor, high-pressure vapor-phase temperature of the refrigerant at the discharge port of the high-stage compressor, medium-pressure vapor phase pressure of the refrigerant in the medium-pressure gas-phase passage or the intermediate pipe, and a medium-pressure gas-phase density calculating step of calculating a medium-pressure gas-phase density of the medium-pressure gas-phase passage based on the adiabatic efficiency of the high-stage compressor;
a refrigerant flow rate calculating step of calculating the refrigerant flow rate based on the medium-pressure gas phase density, the rotation speed of the high-stage compressor, the displacement of the high-stage compressor, and the volumetric efficiency of the high-stage compressor;
a high-pressure gas-phase enthalpy calculation step of calculating a high-pressure gas-phase enthalpy at a discharge port of the high-stage compressor based on the high-pressure gas-phase pressure and the high-pressure gas-phase temperature;
has
The medium pressure gas phase density calculation step includes:
Assuming an assumed intermediate pressure gas phase density corresponding to the intermediate pressure gas phase density, calculating an assumed adiabatic efficiency corresponding to the adiabatic efficiency based on the high pressure gas phase enthalpy and the assumed intermediate pressure gas phase density, and calculating the adiabatic efficiency and performing a loop calculation by re-assuming the assumed intermediate pressure gas phase density based on the difference from the assumed adiabatic efficiency;
A refrigerant flow rate calculation method , wherein the assumed intermediate-pressure gas phase density is set to the intermediate-pressure gas phase density when the difference is equal to or less than a threshold value .

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