JP6847023B2 - Control method of heat pump device and heat pump device - Google Patents

Description

The present invention includes a compressor that compresses the refrigerant, a condenser that condenses the refrigerant compressed by the compressor, and a first expansion valve and a second expansion valve as expansion valves that expand the refrigerant condensed by the condenser. , The refrigerant circulation that circulates the refrigerant in the order described in the evaporator for evaporating the refrigerant expanded by the expansion valve, the compressor, the condenser, the first expansion valve, the second expansion valve, and the evaporator. The present invention relates to a control method of a heat pump device provided with a passage and the refrigerant circulation path provided between the first expansion valve and the second expansion valve without a receiver for storing a refrigerant, and a heat pump device.

Recently, as a heat pump device, a condenser that condenses the refrigerant compressed by the compressor, a first expansion valve and a second expansion valve as expansion valves that expand the refrigerant condensed by the condenser, and expansion with an expansion valve. A heat pump device including an evaporator for evaporating the generated refrigerant and a refrigerant circulation path for circulating the refrigerant in the order described in the compressor, the condenser, the first expansion valve, the second expansion valve, and the evaporator is known ( See Patent Document 1).
In the technique disclosed in Patent Document 1, in order to reduce the influence on the environment when the refrigerant leaks from the refrigerant circulation path, the amount of the refrigerant filled in the refrigerant circulation path is reduced during operation of the heat pump device. It is disclosed that the refrigerant circulation path from the first expansion valve to the second expansion valve is controlled in a gas-liquid mixed phase state by reducing the pressure at the first expansion valve.

WO2015-029160

Although the technique disclosed in Patent Document 1 discloses that the pressure is reduced by the first expansion valve, the purpose is to reduce the amount of refrigerant to be filled in the refrigerant circulation path.
Further, Patent Document 1 does not disclose or suggest the relationship between the control of the pressure difference before and after the first expansion valve and the COP, and the study thereof is not made at all.
That is, although the technique disclosed in Patent Document 1 discloses that the opening degree is controlled by the first expansion valve to reduce the pressure, the COP of the heat pump device is determined by how the control is executed. It was not examined how it contributes to the above, and there was room for improvement.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to reduce the amount of refrigerant charged in the refrigerant circulation path, in order to reduce the amount of refrigerant in the refrigerant circulation path from the first expansion valve to the second expansion valve. In the case of a gas-liquid mixed phase state, the pressure difference generated between the condenser and the second expansion valve, which changes due to the opening degree of the first expansion valve or the opening degree of the first expansion valve, is specifically controlled. , A method of controlling a heat pump device capable of minimizing the compression power and maximizing the COP, and providing a heat pump device.

The control method of the heat pump device for achieving the above object is
A compressor for compressing refrigerant, a condenser for condensing refrigerant compressed by said compressor, a first expansion valve and the second expansion valve as an expansion valve for expanding the refrigerant condensed by the condenser, the An evaporator that evaporates the refrigerant expanded by the expansion valve, and a refrigerant circulation path that circulates the refrigerant in the order described in the compressor, the condenser, the first expansion valve, the second expansion valve, and the evaporator. Equipped with
A control method for a heat pump device in which the refrigerant circulation path is provided between the first expansion valve and the second expansion valve without a receiver for storing refrigerant, and the characteristic configuration thereof is.
The pressure difference generated between the compressor and the second expansion valve, which changes due to the opening degree of the first expansion valve or the opening degree of the first expansion valve, is the refrigerant at the outlet of the first expansion valve. Is in a gas-liquid mixed state, and the compression power in the compressor is controlled to be minimized to maximize the COP.
A stability determination step for determining that the rate of change of each parameter as an operating condition of the heat pump device is within a predetermined stability determination ratio over the stability determination time, and a stability determination step.
When it is determined in the stability determination step that the heat pump device is in the stable state, the current operating conditions are supported from the map data which is the relationship between the operating conditions and the opening degree or the pressure difference for each operating condition of the heat pump device. The pressure difference reading step of reading the opening degree or the pressure difference to be performed, and
A compression power calculation step of calculating the compression power of the compressor while maintaining the opening degree or the pressure difference at the value read in the pressure difference reading step.
It has a pressure difference control step of controlling the opening degree or the pressure difference so that the compression power calculated in the compression power calculation step becomes the minimum value and the COP becomes the maximum value .

The heat pump device for achieving the above purpose is
A compressor for compressing refrigerant, a condenser for condensing refrigerant compressed by said compressor, a first expansion valve and the second expansion valve as an expansion valve for expanding the refrigerant condensed by the condenser, the An evaporator that evaporates the refrigerant expanded by the expansion valve, and a refrigerant circulation path that circulates the refrigerant in the order described in the compressor, the condenser, the first expansion valve, the second expansion valve, and the evaporator. Equipped with
A heat pump device including the refrigerant circulation path between the first expansion valve and the second expansion valve without a receiver for storing the refrigerant, wherein the heat pump device has a characteristic configuration.
The pressure difference generated between the condenser and the second expansion valve, which changes due to the opening degree of the first expansion valve or the opening degree of the first expansion valve, is the refrigerant at the outlet of the first expansion valve. A pressure difference control unit that controls the compression power of the compressor to be minimized and the COP to be maximized in a gas-liquid mixed phase state .
A stability determination unit that determines that the rate of change of each parameter as an operating condition of the heat pump device is in a stable state within a predetermined stability determination ratio over the stability determination time.
When the stability determination unit determines that the heat pump device is in the stable state, it corresponds to the current operating condition from the map data which is the relationship between the operating condition and the opening degree or the pressure difference for each operating condition of the heat pump device. A pressure difference reading unit that reads out the opening degree or the pressure difference
It has a compression power calculation unit that calculates the compression power of the compressor while maintaining the opening degree or the pressure difference at the value read by the pressure difference reading unit.
The pressure difference control unit controls the opening degree or the pressure difference so that the compression power calculated by the compression power calculation unit becomes the minimum value and the COP becomes the maximum value .

In a heat pump device having a first expansion valve and a second expansion valve as expansion valves and no receiver, the inventors of the present invention first expand the first expansion in order to reduce the amount of refrigerant charged in the refrigerant circulation path. In a state where the refrigerant in the refrigerant circulation path from the valve to the second expansion valve is in a gas-liquid mixed state, "the opening degree of the first expansion valve or the condenser and the second caused by the opening degree" at the outlet of the condenser. By controlling the pressure difference (hereinafter, sometimes referred to as "pressure difference before and after the first expansion valve") that occurs between the two expansion valves, the compression power of the heat pump device takes the minimum value and the COP takes the maximum value. We have newly discovered the finding that it changes in the form of gain, and have completed the invention.
Hereinafter, a description will be added based on FIG. Note that FIG. 2 describes a situation in which the “pressure difference before and after the first expansion valve” changes from a small case (chain line in the pH diagram of FIG. 2) to a large case (solid line in the pH diagram of FIG. 2). Incidentally, in the following, the reason why the COP of the cooling capacity in the evaporator (for example, the cooling capacity in the cooling operation) can be maximized will be described.
In the heat pump device having the first expansion valve and the second expansion valve as the expansion valve shown in FIG. 1 and not having a receiver, as shown in FIG. 2, the refrigerant circulation from the first expansion valve to the second expansion valve. When the "pressure difference before and after the first expansion valve" is increased while the refrigerant in the path is in a gas-liquid mixed state, the dryness of the refrigerant in the refrigerant circulation path between the first expansion valve and the second expansion valve becomes dry. Since the increase, that is, the density of the refrigerant decreases, the amount of the refrigerant stays in the condenser. This phenomenon occurs remarkably when the refrigerant circulation path between the first expansion valve and the second expansion valve is relatively long, as in the Birmal type. In order to increase the amount of refrigerant retained in the condenser, it is necessary to increase the degree of supercooling at the outlet of the condenser, but the phenomenon that the temperature at the outlet of the condenser decreases and its specific enthalpy decreases, and the phenomenon of the outlet of the condenser It is considered that two phenomena that the refrigerant pressure increases may occur.

In the former case, the specific enthalpy introduced into the evaporator is also low (Δh in FIG. 2), so that the cooling capacity (specific enthalpy difference) in the evaporator is before the “pressure difference before and after the first expansion valve” is increased. Assuming that the cooling capacity is dh ₁ and the cooling capacity after increasing the "pressure difference before and after the first expansion valve" is dh ₂ , it is expressed by the following (Equation 1).
dh ₂ = dh ₁ + Δh ... (Equation 1)

On the other hand, in the latter case, the condensing pressure increases (ΔP _{c in} FIG. 2), and the compression work (specific enthalpy difference) in the compressor increases accordingly (Δw in FIG. 2). The specific enthalpy difference) is as follows, assuming that the "pressure difference before and after the first expansion valve" is dw ₁ before the increase and the "pressure difference before and after the first expansion valve" is dw _{2 after the increase.} It is expressed by (Equation 2) of.
dw ₂ = dw ₁ + Δw ... (Equation 2)

_{Here, the COP c} corresponding to the cooling capacity is expressed by the following equation.
COP _c = dh ₂ / dw ₂ ... (Equation 3)

As for the COP _c , when the "pressure difference before and after the first expansion valve" becomes large, Δh as _{dh 2} leading to an increase in _{COP c} increases, while Δw as _{dw 2} leading to a decrease in _{COP c increases.} Since there is a trade-off between the two, it can be estimated that there is a maximum value _{in COP c.} Since the theoretical lower limit of the refrigerant temperature at the outlet of the condenser is up to the outside air temperature, there is an upper limit for Δh. On the other hand, if there is no limit on the withstand voltage of the heat pump device, there is no upper limit on _{ΔP c.} Therefore, if Δw, which increases in correlation with _{ΔP c , increases to Δh × dw 1} / dh ₁ or more, it is considered that the effect of improving _{COP c disappears.
The COP h} corresponding to the heating capacity (for example, the heating capacity in the heating operation) will not be described, but for _{the same reason as the COP c} during the cooling operation, "pressure difference before and after the first expansion valve". A maximum value occurs when is changed.

As a supplement to the above, if the "pressure difference before and after the first expansion valve" is increased, the specific enthalpy difference in the evaporator will increase if the air conditioning (cooling) capacity is the same, so the amount of refrigerant circulation will increase. Decrease. Therefore, under the condition that the maximum value is generated in COP, the compression power itself, which is the product of the compression work (specific enthalpy difference) and the amount of refrigerant circulation, becomes the minimum value.
Further, when the amount of refrigerant circulation decreases, the heat exchange area of the evaporator and the condenser increases relatively, so that the evaporation pressure increases and the condensation pressure decreases. However, in evaporation, it is necessary to evaporate from a state where it is closer to the liquid and has a small specific enthalpy (less dryness), and in condensation, it is necessary to condense to a state where the specific enthalpy with a higher degree of supercooling is small. It has the opposite effect on the pressure of. Actually, it will be operated at the evaporation pressure and the condensation pressure in consideration of the heat transfer phenomenon in the evaporator and the condenser.
Incidentally, when the amount of refrigerant circulation is reduced, the pressure loss generated in the pipes connecting the indoor unit and the outdoor unit (particularly the gas pipe) is reduced, so that the effect of further improving the COP can be expected in practice.
From the above, it is possible to realize a control method of the heat pump device capable of minimizing the compression power and maximizing the COP by concretely controlling the pressure difference before and after the first expansion valve, and the heat pump device.
In the configuration having a receiver, the refrigerant is accumulated in the receiver and the amount of the refrigerant held by the condenser does not increase. Therefore, the refrigerant at the outlet of the first expansion valve is controlled by "controlling the pressure difference before and after the first expansion valve". It is considered that the maximization of COP cannot be expected as described above even if the gas-liquid mixed phase state is set.

Further features of the control method of the heat pump device
For each operating condition of the heat pump device, the opening or the pressure difference corresponding to the current operating condition is read out from the map data which is the relationship between the operating condition and the opening or the pressure difference, and the current operating condition is read. The point is to calculate the compression power in the compressor corresponding to the above, and control the opening degree or the pressure difference so that the compression power is minimized and the COP is maximized.

By the way, the opening degree of the first expansion valve or the pressure difference generated between the condenser and the second expansion valve caused by the opening degree (“pressure difference before and after the first expansion valve”) is the number of revolutions of the compressor. , Outside air temperature, indoor temperature (indoor unit suction air temperature), indoor unit operating load factor (ratio of total capacity of operating indoor unit to outdoor unit rated capacity), condensation pressure, evaporation pressure, supercooling degree (condenser) It is determined based on operating conditions such as outlet), degree of superheat (compressor inlet), outdoor unit fan rotation speed, and refrigerant filling amount.
Therefore, in the present invention, these operating conditions and the pressure difference before and after the first expansion valve (the opening degree in the first expansion valve and between the condenser and the second expansion valve caused by the opening degree). The pressure difference before and after the first expansion valve corresponding to the current operating conditions is read out from the map data which is the relationship with the map data (concept meaning the pressure difference generated in), and the compression power corresponding to the acquired operating conditions is calculated. The pressure difference before and after the first expansion valve is controlled so that the calculated compression power is minimized and the COP is maximized.
The operating conditions of the stored map data can be stored discretely, and when the current operating conditions are conditions between the discretely stored conditions, the value between the two is interpolated. Then, the pressure difference before and after the first expansion valve corresponding to the current operating conditions is calculated and read out.

Further features of the control method of the heat pump device
In the pressure difference control step, the compression power corresponding to the opening degree or the pressure difference is compared with the compression power after changing the current opening degree or the pressure difference by a predetermined change amount, and the smaller one is compared. The opening that minimizes the compression power and maximizes the COP by a local search method that continuously executes a process of continuously converting the opening or the pressure difference corresponding to the compression power into the current opening or the pressure difference. The point is to derive the degree or the pressure difference.

As described above, the inventors of the present invention use a heat pump device having a first expansion valve and a second expansion valve as expansion valves and no receiver to optimize the pressure difference before and after the first expansion valve. It was newly found that the compression power has a minimum value and the COP has a maximum value.
Therefore, by executing the above-mentioned local search method in the pressure difference control step, it is possible to satisfactorily derive the pressure difference that minimizes the compression power and maximizes the COP.
In this case, it is also possible to apply the learning control together.

Further features of the control method of the heat pump device
The point of controlling the opening degree or the pressure difference in a form in which the stability determination step, the pressure difference reading step, the compression power calculation step, and the pressure difference control step are executed in real time during the operation of the heat pump device. is there.

When controlling the pressure difference before and after the first expansion valve, if the above operating conditions change over time, there is a possibility that the compression power will not reach the minimum value (COP properly) at the controlled pressure difference. There is.
Therefore, in the above-mentioned feature configuration, the compression power is appropriately minimized by executing the stability determination step, the pressure difference reading step, the compression power calculation step, and the pressure difference control step in real time during the operation of the heat pump device. The pressure difference before and after the first expansion valve can be controlled so as to maintain the value (COP appropriately maintains the maximum value).

Schematic configuration diagram of the heat pump device according to the embodiment In the heat pump device according to the embodiment, a graph showing a pH diagram before and after adjusting the pressure difference before and after the first expansion valve. Control flow of the heat pump device according to the embodiment Graph diagram showing the dependence of COP on the refrigerant charge when the outside air temperature is 35 ° C in rated load operation Graph diagram showing the pressure difference dependence of COP when the outside air temperature is 35 ° C in rated load operation Graph graph showing the COP pressure difference dependence for each refrigerant filling amount when the outside air temperature is 35 ° C in rated load operation. Graph graph showing the COP pressure difference dependence for each refrigerant filling amount when the outside air temperature is 35 ° C in partial load operation. Schematic configuration diagram of the heat pump device according to another embodiment

The control method of the heat pump device 100 and the heat pump device 100 according to the embodiment of the present invention relate to those capable of minimizing the compression power and maximizing the COP by specifically controlling the pressure difference before and after the first expansion valve.
In the control method of the heat pump device 100 and the heat pump device 100 according to the embodiment, the air conditioning capacity is not changed when the pressure difference before and after the first expansion valve is changed.

As shown in FIG. 1, the heat pump device 100 according to the embodiment includes a compressor 11 that is rotationally driven by the engine 14 to compress the refrigerant, a condenser that condenses the refrigerant compressed by the compressor 11, and a condenser. A first expansion valve and a second expansion valve as expansion valves for expanding the condensed refrigerant, an evaporator for evaporating the refrigerant expanded by the expansion valve, a compressor 11, a condenser, a first expansion valve, and a second expansion valve. The expansion valve and the compressor are provided with a refrigerant circulation path C1 that circulates the refrigerant in the order described. That is, in the embodiment, the refrigerant circulation path C1 is provided between the first expansion valve and the second expansion valve without a receiver for storing the refrigerant.
The refrigerant circulation path C1 has a four-way valve 20 that switches the refrigerant circulation state between a cooling operation (an operation that exerts a cooling capacity in an evaporator) and a heating operation (an operation that exerts a heating capacity in a condenser). Is provided.
Further, an accumulator 15 for storing the refrigerant is provided at the inlet of the compressor 11 to prevent the refrigerant in the liquid phase state from being guided to the compressor 11.
Further, an oil separator 16 that separates the oil mixed into the refrigerant pipe from the compressor 11 from the refrigerant is provided at the outlet of the compressor 11, and an oil flow that connects the oil separator 16 and the inlet of the compressor 11 in communication with each other. An oil valve V3 that opens and closes the passage Lo and the oil flow path Lo is provided, and the oil stored in the oil separator 16 periodically shifts the oil valve V3 from the closed state to the open state, and is a compressor. You will be guided to the entrance of 11.

During the cooling operation, as shown in FIG. 1, the refrigerant flowing through the refrigerant circulation path C1 exchanges heat between the outdoor air blown by the compressor 11, the oil separator 16, and the fan (not shown) and the refrigerant. A room blown by a heat exchanger 12 (corresponding to a condenser), a heating expansion valve Vh (corresponding to a first expansion valve), a cooling expansion valve Vc (corresponding to a second expansion valve), and a fan (not shown). The four-way valve 20 is switched so as to circulate in the order described in the indoor heat exchanger 13 (corresponding to an evaporator) that exchanges heat between air and the refrigerant.
On the other hand, during the heating operation, although not shown, the refrigerant flowing through the refrigerant circulation path C1 exchanges heat between the refrigerant and the indoor air blown by the compressor 11, the oil separator 16, and the fan (not shown). Air is blown by the indoor heat exchanger 13 (corresponding to the condenser), the cooling expansion valve Vc (corresponding to the first expansion valve), the heating expansion valve Vh (corresponding to the second expansion valve), and the fan (not shown). The four-way valve 20 is switched so as to circulate in the order described in the outdoor heat exchanger 12 (corresponding to an evaporator) that exchanges heat between the outdoor air and the refrigerant. In many cases, a heat exchanger that evaporates a part of the refrigerant by using the exhaust heat of the engine 14 is also installed, but the illustration is omitted.

In the heat pump device 100 according to the embodiment, the control device 50 that controls the operation in order to minimize the compression power (to maximize the COP) is the rotation speed of the compressor 11, the outside air temperature, and the like. Indoor temperature (indoor unit suction air temperature), indoor unit operating load factor (ratio of total capacity of operating indoor unit to outdoor unit rated capacity), condensation pressure, evaporation pressure, degree of overcooling (compressor outlet), overheating Pressure difference before and after the first expansion valve (opening in the first expansion valve) determined from the operating conditions and the operating conditions for each operating condition such as degree (compressor inlet), outdoor unit fan rotation speed, refrigerant filling amount, etc. , Or a control unit 51 that stores map data that is the relationship between the condenser and the second expansion valve caused by the opening degree) and executes the following various controls. 52 is provided in a form in which software and hardware cooperate with each other.
Adding an explanation, the control unit 52 is in a stable state in which the rate of change of each of the parameters as the above-mentioned operating conditions is within a predetermined stability determination ratio over the stability determination time (for example, 5 minutes). The pressure difference reading unit and the first expansion valve that read the pressure difference before and after the first expansion valve corresponding to the current operating conditions from the map data when the stability determination unit and the stability determination unit determine that the vehicle is in a stable state. With the front and rear pressure difference maintained at the value read by the pressure difference reading unit, the compression power calculation unit that calculates the compression power in the compressor 11 and the compression power calculated by the compression power calculation unit A pressure difference control unit that controls the pressure difference before and after the first expansion valve while the refrigerant at the outlet of the first expansion valve is in a gas-liquid mixed state so that the pressure difference is the minimum value and the maximum value of COP. And have.

Here, the stable state within the stability determination ratio in the stability determination unit is, for example, the ratio of the maximum value to the average value in the stability determination time and the ratio of the minimum value to the average value in the stability determination time. It shall mean that both are less than or equal to the prescribed ratio.
Specifically, the above ratios are, for example, the number of revolutions of the compressor, outdoor fan, etc. within 2% (based on the value in rated operation), outside air temperature, indoor temperature (indoor unit suction air temperature), superheat degree, etc. A stable state is defined as a state in which the degree of supercooling is within 1 K, the condensation pressure and evaporation pressure are within 2% (based on the values in rated operation), and the indoor unit operating load factor does not change.

As the map data stored in the storage unit 51, for example, as shown in a part of FIG. 1, the relationship that the pressure difference before and after the first expansion valve increases as the rotation speed of the compressor 11 increases is determined by the outside air. It is stored for each other operating condition such as temperature.
In the map data, the pressure difference before and after the first expansion valve is a value that also depends on the pipe length of the refrigerant circulation path C1. Therefore, it is desirable that the map data is stored for each pipe of the refrigerant circulation path C1 for each facility such as a building in which the heat pump device is installed, specifically, for each length of the connecting pipe between the outdoor unit and the indoor unit.

Although not shown, the heat pump device 100 according to the embodiment is appropriately provided with sensors for measuring the refrigerant pressure and the refrigerant temperature. The compression power calculation unit calculates the enthalpy at the inlet and outlet of the compressor 11 based on the output of the sensor, and compresses the enthalpy at the outlet of the compressor 11 minus the enthalpy at the inlet of the compressor 11. The compression power W is calculated in the form of integrating the refrigerant circulation amount calculated as the product of the rotation speed of the machine 11, the volume efficiency, the exclusion volume, and the refrigerant density at the compressor inlet.
All the calculations by the compression power calculation unit are executed in a state where the pressure difference before and after the first expansion valve is maintained at the value read by the pressure difference reading unit.

Next, the control for minimizing the compression power (maximizing the COP) in the heat pump device 100 according to the embodiment will be described based on the control flow of FIG.
In the heat pump device 100 according to the embodiment, the control flow shown in FIG. 3 is executed in real time during the operation of the heat pump device 100, whereby the first expansion follows a change in operating conditions. The pressure difference between the front and rear of the valve will be controlled.

The control by minimizing the compression power due to the pressure difference before and after the first expansion valve is executed in real time at the timing when a predetermined time (for example, 5 minutes) elapses from the previous control or at the timing when the operating conditions change significantly. To.
The control unit 52 acquires the operating conditions (# 01).
As a stability determination step, the control unit 52 is in a stable state in which the rate of change of each parameter as each operating condition acquired in step # 01 is within a predetermined stability determination ratio over the stability determination time. The stability determination step for determining whether or not it is determined is executed (# 02), and if it is not in a stable state, it waits for a predetermined time (for example, 2 minutes) (# 03), and then the stability determination step is executed again (#). 02).
When it is determined to be stable in the stability determination step, the control unit 52 reads out the pressure difference before and after the current first expansion valve based on the map data stored in the storage unit 51. Is executed (# 04).
The control unit 52 performs stability determination (# 06) of each operating condition and standby (# 07) for a predetermined time while maintaining the pressure difference before and after the first expansion valve at the value read in the pressure difference reading step. After that, the compression power calculation step of calculating the compression power in the compressor 11 is executed (# 08).

By executing the following steps # 09 to # 16, the control unit 52 controls the pressure difference before and after the first expansion valve so that the compression power calculated in the compression power calculation step becomes the minimum value. Perform the pressure loss control step.
In other words, in the pressure difference control step, the control unit 52 changes the compression power corresponding to the current pressure difference before and after the first expansion valve and the current pressure difference before and after the first expansion valve by a predetermined amount of change. Comparing with the compression power corresponding to the later pressure difference, the process of making the pressure difference before and after the first expansion valve corresponding to the smaller compression power the current pressure difference before and after the first expansion valve is continuously executed. The pressure difference before and after the first expansion valve that minimizes the compression power is derived by the local search method.
Although detailed description is omitted, the control unit 52 also applies learning control to execute control for deriving the pressure difference before and after the first expansion valve that minimizes the compression power and maximizes the COP. It doesn't matter.
If the refrigerant filling amount changes over time and the filling amount decreases due to refrigerant leakage, the compression power will deviate from the optimum value (minimum value of compression power) only with the information from the map data prepared in advance. .. Even in such a case, it can be dealt with to some extent by controlling by the above-mentioned local search method.

Specifically, the control unit 52 sets n = 1 (# 09), and at n = 1, the compression power W _{n corresponding to the current pressure difference dP n} before and after the first expansion valve and the pressure difference are predeterminedly changed. _{Calculate W n + 1} corresponding to _{the pressure difference dP n + 1} before and after the first expansion valve after changing by the amount (# 10), and the absolute value of the difference between _{W n + 1} and W _{n (| W n + 1} −W _n | ) Is smaller than the specified value α (# 11).
When the absolute value of the difference between _{W n + 1} and W _{n (| W n + 1} −W _n |) is smaller than the specified value α (Yes in # 11), the control unit 52 has a pressure difference dP before and after the current first expansion valve. _{It is determined that n} is in the vicinity of the value that minimizes W, and the _{control is continued with the current pressure difference dP n} (# 16).
On the other hand, the control unit _52, the absolute value of the difference between _{W n + 1} and _{W n (| W n + 1} -W n |) If it is the prescribed value α or more (No in # 11), _{W n + 1} after the pressure difference change is _{It is judged whether or not it is smaller than W n} before the pressure difference change (# 12), and if it is smaller (# 12 is Yes), the change direction of the pressure difference before and after the first expansion valve is maintained (# 13). ), When W _{n + 1} after the pressure difference change is W _n or more before the pressure difference change (No in # 12), the change direction of the pressure difference before and after the first expansion valve is reversed (# 14, 15).
The control unit 52 continues the control of # 12 to # 15 until the absolute value of the difference between _{W n + 1} and W _{n (| W n + 1} −W _n |) becomes smaller than the specified value α.

The inventors of the present invention have set the COP of the optimum refrigerant filling amount when the refrigerant in the refrigerant pipe (liquid pipe) from the first expansion valve to the second expansion valve (cooling expansion valve Vc) is in the liquid phase. It was newly found by calculation that the COP can be increased by "controlling the pressure difference before and after the first expansion valve" even when the refrigerant filling amount is lowered.

When the refrigerant in the refrigerant pipe (liquid pipe) from the first expansion valve to the second expansion valve (cooling expansion valve Vc) is in the liquid phase and the pressure difference before and after the first expansion valve is fixed. As shown in FIG. 4 (b), there is an effect by lowering the outlet temperature of the condenser 12 (improving the COP with the improvement of the cooling capacity) as the refrigerant filling amount increases, and FIG. 4 (d). As shown in the above, as the amount of refrigerant charged increases, the outlet pressure of the condenser 12, that is, the outlet pressure of the compressor 11 increases (the COP decreases as the compression power increases), and both trade. It can be seen that there is a refrigerant filling amount (about 18.0 kg) capable of maximizing the COP as shown in FIG. 4 (a) due to the off relationship. The COP at this time is about 4.0.
Incidentally, the calculation conditions in FIG. 4 are: cooling capacity: 50 kW, compression efficiency in the compressor: 80%, volume efficiency: 90%, superheat degree SH at the inlet of the compressor: 5 K, outside air temperature: 35 ° C., outdoor fan. The air air volume was 1.6 m / s, the outdoor temperature was 27 ° C. (WB19 ° C.), the indoor fan air air volume was 0.8 m / s, the refrigerant was R410A, the cooling was none, and the pressure difference was about 50 kPa. As shown in FIG. 4C, the refrigerant in the refrigerant pipe (liquid pipe) from the first expansion valve to the second expansion valve (cooling expansion valve Vc) can secure the degree of supercooling and becomes a liquid phase. As described above, the pressure difference before and after the first expansion valve is fixed at a relatively low value.

Next, in the control of the heat pump device 100 according to the embodiment, a graph showing the result of calculating the change in COP corresponding to the change in the compression power W when the pressure difference before and after the first expansion valve is controlled is shown. Shown.
FIG. 5 shows a case where the cooling operation is performed at the rated load, the cooling capacity: 50 kW, the compression efficiency: 80%, the volume efficiency 90%, the degree of superheat at the inlet of the compressor 11 SH: 5K, and the outside air temperature. : 35 ° C., outdoor fan air flow rate: 1.6 m / s, indoor temperature: 27 ° C. (WB19 ° C.), indoor fan air flow rate: 0.8 m / s, refrigerant: R410A. Further, the lengths of the refrigerant circulation path C1 (liquid pipe) from the outlet of the outdoor unit to the indoor unit and the refrigerant circulation path C1 (gas pipe) from the indoor unit to the outdoor unit were set to 20 m, respectively. The amount of refrigerant charged is 14.7 kg, which is less than the appropriate value of 18.0 kg in FIG.
In addition, in the graph, as shown in FIG. 8 (described later), the calculation result in the configuration corresponding to the configuration in which the cooling flow path is provided is also shown. It was assumed that the degree of superheat of the refrigerant was SH: 10K.

As shown in FIG. 5 (b), as the pressure difference before and after the first expansion valve increases, the temperature at the outlet of the condenser 12 decreases (COP increases as the cooling capacity improves), and FIG. 5 (c) shows. As shown in the above, as the pressure difference before and after the first expansion valve increases, the outlet pressure of the condenser 12, that is, the pressure at the outlet of the compressor 11 increases (COP decreases as the compression power increases). Since the two are in a trade-off relationship, as shown in FIG. 5A, it can be confirmed that the COP has a maximum value at a predetermined value as the pressure difference before and after the first expansion valve increases. It was. Without cooling, the pressure difference before and after the first expansion valve is about 1100 kPa and the COP is about 4.0. With cooling, the pressure difference before and after the first expansion valve is about 1200 kPa and the COP is about 4.0.

FIG. 6 shows the calculation results including the case of 13.0 kg in which the amount of refrigerant charged is further reduced. The calculation conditions in FIG. 6 are the same as the calculation conditions in FIG. 4 except for the amount of refrigerant charged, and there is no cooling. Even when the refrigerant charge is 13.0 kg, the qualitative tendency is the same as the refrigerant charge of 14.7 kg. The pressure difference before and after the first expansion valve is about 1300 to 1400 kPa, and the COP is about 4.0, which is the maximum value.

Further, as shown in FIG. 7, it has been confirmed that the same effect can be obtained even when the air conditioning load is different. The calculation result when the air conditioning load is changed is shown in FIG. The calculation conditions in FIG. 7 are the same as the calculation conditions in FIG. 6 except that the air conditioning load is changed (cooling capacity: 25 kW), and no cooling is performed. The qualitative tendency is the same even when the air conditioning load is halved. When the refrigerant filling amount is reduced, there is a pressure difference before and after the first expansion valve at which the COP is maximized, and the value becomes the same level as the COP with an appropriate refrigerant filling amount.

[Another Embodiment]
(1) The calculation result of the above embodiment has been described by taking the case of cooling operation as an example, but even in heating operation, the pressure difference dP before and after the first expansion valve that minimizes the compression power and maximizes COP is Exists.
In this case, the first expansion valve used to control the pressure difference can be implemented by the cooling expansion valve Vc, but in the case of the Birmal type, there are a plurality of indoor units, each of which has a cooling expansion valve. Therefore, the control of the pressure difference may be complicated. Therefore, for example, in the refrigerant circulation path C1 between the heating expansion valve Vh and the cooling expansion valve Vc, an expansion valve as a separate first expansion valve is provided in the circulation path on the side where the compressor 11 is not provided. It is desirable to provide it.

(2) In the above embodiment, the engine-driven heat pump device has been described as an example, but the object of the present invention can be satisfactorily achieved even with the electric-driven heat pump device.

(3) In the above embodiment, a configuration example including one compressor 11 is shown, but a configuration including a plurality of compressors may be adopted.
In this configuration, as the "compressor rotation speed" according to the above embodiment, an operation pattern including the rotation speeds of each of the plurality of compressors is adopted.

(4) When the piping length of the refrigerant circulation path C1 becomes long as in air-conditioning equipment such as buildings, it is considered that the piping length of the refrigerant circulation path C1 becomes a parameter that affects the value of the pressure difference before and after the first expansion valve. Be done.
Therefore, as in the above characteristic configuration, the pipe length of the refrigerant circulation path (liquid pipe or gas pipe) may be stored as map data as a value that affects the pressure difference before and after the first expansion valve. Absent.

(5) As shown in FIG. 8, the heat pump device 100 and the control method thereof according to the present invention may be configured to include a cooler 17 for temporarily storing the refrigerant circulation path C1 and a cooling flow path C2. Demonstrate its function.
FIG. 8 shows an example of the circuit configuration of the cooling flow path C2 during the cooling operation.
In the following, only the configuration related to the cooling flow path C2, which is a configuration different from the above embodiment, will be described, and the configuration without explanation will be the same as the above embodiment.
As shown in FIG. 8, the cooler 17 is provided in the refrigerant circulation path C1 in which the heating expansion valve Vh (an example of the first expansion valve) and the cooling expansion valve Vc (an example of the second expansion valve) are directly communicated with each other. It is provided.
The upstream end of the cooling flow path C2 is connected to the refrigerant circulation path C1 between the cooler 17 and the cooling expansion valve Vc (an example of the second expansion valve), and the downstream end is the accumulator 15 and the compressor 11. It is connected to the refrigerant circulation path C1 (more specifically, the refrigerant circulation path C1 between the downstream end of the oil flow path Lo and the accumulator 15).
The cooling flow path C2 is provided with a flow path portion through which the refrigerant expanded by the expansion valve V4 passes through the inside of the cooler 17, thereby cooling the refrigerant in the cooler 17. It is something to do.
A case where the pressure difference dP before and after the first expansion valve is changed when the configuration is adopted will be described. When the pressure difference dP before and after the first expansion valve is increased, the temperature of the refrigerant at the inlet of the cooler 17 decreases, so that the temperature difference during cooling tends to decrease and the degree of decrease in the specific enthalpy tends to decrease. For the same reason as in the embodiment, there is a pressure difference dP that minimizes the compression power and maximizes the COP.
Note that FIG. 8 shows an example in which there is a cooling circuit, and there is also a specification in which the portion branched for cooling is not after cooling but before cooling.

(6) The compression power means the compression power itself by the compressor 11 or the amount of fuel supplied to the engine when the compressor 11 is driven by the engine.

The configuration disclosed in the above embodiment (including another embodiment, the same shall apply hereinafter) can be applied in combination with the configuration disclosed in other embodiments as long as there is no contradiction. The embodiments disclosed in the present specification are examples, and the embodiments of the present invention are not limited thereto, and can be appropriately modified without departing from the object of the present invention.

The heat pump device control method of the present invention and the heat pump device are as a heat pump device control method capable of minimizing compression power and maximizing COP by concretely controlling the pressure difference before and after the first expansion valve, and as a heat pump device. , Can be used effectively.

11: Compressor 12: Outdoor heat exchanger 13: Indoor heat exchanger 14: Engine 50: Control device 51: Storage unit 100: Heat pump device C1: Refrigerant circulation path Vc: Cooling expansion valve Vh: Heating expansion valve W: Compressive power dP: Pressure difference dh: Air conditioning capacity such as cooling (specific enthalpy difference)
α: Specified value

Claims (5)

A compressor for compressing refrigerant, a condenser for condensing refrigerant compressed by said compressor, a first expansion valve and the second expansion valve as an expansion valve for expanding the refrigerant condensed by the condenser, the An evaporator that evaporates the refrigerant expanded by the expansion valve, and a refrigerant circulation path that circulates the refrigerant in the order described in the compressor, the condenser, the first expansion valve, the second expansion valve, and the evaporator. Equipped with
A control method for a heat pump device in which the refrigerant circulation path is provided between the first expansion valve and the second expansion valve without a receiver for storing refrigerant.
The pressure difference generated between the compressor and the second expansion valve, which changes due to the opening degree of the first expansion valve or the opening degree of the first expansion valve, is the refrigerant at the outlet of the first expansion valve. Is in a gas-liquid mixed state, and the compression power in the compressor is controlled to be minimized to maximize the COP.
A stability determination step for determining that the rate of change of each parameter as an operating condition of the heat pump device is within a predetermined stability determination ratio over the stability determination time, and a stability determination step.
When it is determined in the stability determination step that the heat pump device is in the stable state, the current operating conditions are supported from the map data which is the relationship between the operating conditions and the opening degree or the pressure difference for each operating condition of the heat pump device. The pressure difference reading step of reading the opening degree or the pressure difference to be performed, and
A compression power calculation step of calculating the compression power of the compressor while maintaining the opening degree or the pressure difference at the value read in the pressure difference reading step.
A control method for a heat pump device including a pressure difference control step of controlling the opening degree or the pressure difference so that the compression power calculated in the compression power calculation step becomes a minimum value and COP becomes a maximum value. For each operating condition of the heat pump device, the opening or the pressure difference corresponding to the current operating condition is read out from the map data which is the relationship between the operating condition and the opening or the pressure difference, and the current operating condition is read. The control method of the heat pump device according to claim 1, wherein the opening degree or the pressure difference is controlled so as to calculate the compression power of the compressor corresponding to the above and minimize the compression power to maximize the COP. .. In the pressure difference control step, the compression power corresponding to the opening degree or the pressure difference is compared with the compression power after changing the current opening degree or the pressure difference by a predetermined change amount, and the smaller one is compared. The opening that minimizes the compression power and maximizes the COP by a local search method that continuously executes a process of continuously converting the opening or the pressure difference corresponding to the compression power into the current opening or the pressure difference. The method for controlling a heat pump device according to claim 1 or 2, wherein the degree or the pressure difference is derived. A claim for controlling the opening degree or the pressure difference in a form in which the stability determination step, the pressure difference reading step, the compression power calculation step, and the pressure difference control step are executed in real time during the operation of the heat pump device. The method for controlling a heat pump device according to any one of 1 to 3. A compressor that compresses the refrigerant, a condenser that condenses the refrigerant compressed by the compressor, a first expansion valve and a second expansion valve as expansion valves that expand the refrigerant condensed by the condenser, and the above. An evaporator that evaporates the refrigerant expanded by the expansion valve, and a refrigerant circulation path that circulates the refrigerant in the order described in the compressor, the condenser, the first expansion valve, the second expansion valve, and the evaporator. Equipped with
A heat pump device including the refrigerant circulation path between the first expansion valve and the second expansion valve without a receiver for storing the refrigerant.
The pressure difference generated between the condenser and the second expansion valve, which changes due to the opening degree of the first expansion valve or the opening degree of the first expansion valve, is the refrigerant at the outlet of the first expansion valve. A pressure difference control unit that controls the compression power of the compressor to be minimized and the COP to be maximized in a gas-liquid mixed phase state.
A stability determination unit that determines that the rate of change of each parameter as an operating condition of the heat pump device is in a stable state within a predetermined stability determination ratio over the stability determination time.
When the stability determination unit determines that the heat pump device is in the stable state, it corresponds to the current operating condition from the map data which is the relationship between the operating condition and the opening degree or the pressure difference for each operating condition of the heat pump device. A pressure difference reading unit that reads out the opening degree or the pressure difference
It has a compression power calculation unit that calculates the compression power of the compressor while maintaining the opening degree or the pressure difference at the value read by the pressure difference reading unit.
The pressure difference control unit is a heat pump device that controls the opening degree or the pressure difference so that the compression power calculated by the compression power calculation unit becomes the minimum value and the COP becomes the maximum value.

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