JP6847022B2 - 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 receiver that stores the refrigerant, the evaporator that evaporates the refrigerant expanded by the expansion valve, the compressor, the condenser, the first expansion valve, the receiver, the second expansion valve, and the evaporator. The present invention relates to a control method of a heat pump device including a refrigerant circulation path for circulating a refrigerant in the order described in the above, 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 a receiver that stores the refrigerant. 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 receiver, the second expansion valve, and the evaporator. A heat pump device including the heat pump device is known (see Patent Document 1).
In the technique disclosed in Patent Document 1, the amount of refrigerant circulating in the refrigerant circulation path is reduced when the partial load operation is performed in which the number of compressors in operation and the number of revolutions are smaller than those in the rated operation. At that time, if the opening degree of the first expansion valve is fully opened, the condensing pressure in the condenser cannot be maintained, and the problem of insufficient condensation is focused on.
Then, in order to solve the problem, by executing the control of adjusting the opening degree of the first expansion valve from the fully open side to the closed side, the condensing pressure in the condenser is maintained and the insufficient condensing is prevented. ..
Further, Patent Document 1 discloses that "the degree of supercooling of the condenser can be adjusted depending on the operating conditions, and the cooling efficiency of the heat pump device is improved".

Japanese Unexamined Patent Publication No. 2016-173200

Although the technique disclosed in Patent Document 1 discloses adjusting the opening degree of the first expansion valve, the purpose is to maintain the condensing pressure in the condenser and prevent insufficient condensing. Is.
Further, although Patent Document 1 discloses that "the degree of supercooling of the condenser can be adjusted according to the operating conditions and the cooling efficiency of the heat pump device is improved", what kind of index is adopted as the operating conditions? There is no disclosure or suggestion of what and how to improve the cooling efficiency of the heat pump device under what conditions the index is, and no study has been made.
That is, although the technique disclosed in Patent Document 1 discloses that the opening degree of the first expansion valve is controlled, how the control is executed affects the COP of the heat pump device. It was not examined whether it would contribute to the above, and there was room for improvement.

The present invention has been made in view of the above problems, and an object of the present invention is the pressure generated between the condenser and the receiver, which changes depending on the opening degree of the first expansion valve or the opening degree of the first expansion valve. It is an object of the present invention to provide a control method of a heat pump device capable of minimizing the compression power and maximizing the COP by concretely controlling the difference, and providing the 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 refrigerant Described in the receiver, the evaporator that evaporates the refrigerant expanded by the expansion valve, the compressor, the condenser, the first expansion valve, the receiver, the second expansion valve, and the evaporator. It is a control method of a heat pump device including a refrigerant circulation path that circulates a refrigerant in the order of, and the characteristic configuration thereof is.
The pressure difference generated between the condenser and the receiver, which changes due to the opening degree of the first expansion valve or the opening degree of the first expansion valve, is minimized by the compression power of the compressor to reduce the COP. Control to maximize
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 refrigerant Described in the receiver, the evaporator that evaporates the refrigerant expanded by the expansion valve, the compressor, the condenser, the first expansion valve, the receiver, the second expansion valve, and the evaporator. It is a heat pump device provided with a refrigerant circulation path that circulates a refrigerant in the order of, and its characteristic configuration is:
The pressure difference generated between the condenser and the receiver, which changes due to the opening degree of the first expansion valve or the opening degree of the first expansion valve, is minimized by the compression power of the compressor to reduce the COP. a pressure differential controller configured to maximize,
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 .

The inventors of the present invention have described in a heat pump device having a first expansion valve and a second expansion valve as expansion valves and a receiver, "a condenser generated due to the opening degree of the first expansion valve or the opening degree thereof. By controlling the pressure difference (hereinafter, sometimes referred to as "pressure difference before and after the first expansion valve") generated between the receiver and the receiver, the compression power of the heat pump device takes the minimum value and the COP takes the maximum value. He found the finding that it changes in the form of gain, and 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. For the sake of simplification of the explanation, the pressure loss generated in the piping and the heat exchanger will not be considered here.
In the heat pump device having the receiver shown in FIG. 1, the refrigerant is filled so that the receiver has a liquid level under various assumed operating conditions. When the liquid level is present in the receiver in this way, as shown in FIG. 2, since the refrigerant in the saturated liquid state enters and exits the receiver, the refrigerant in the receiver is always located on the saturated liquid line on the Ph diagram. .. Therefore, when the "pressure difference before and after the first expansion valve (dP in FIG. 2)" between the condenser and the receiver is increased, the refrigerant temperature at the outlet of the condenser, that is, the saturated liquid temperature (which is the refrigerant temperature at the receiver) ( It is considered that there are two possibilities: a phenomenon in which the pressure of the refrigerant saturated liquid at the receiver decreases and its specific enthalpy decreases, and a phenomenon in which the refrigerant pressure at the outlet of the condenser increases.

In the former case, the specific enthalpy introduced into the evaporator decreases (Δh in FIG. 2), so that the cooling capacity (specific enthalpy difference) in the evaporator is the cooling before increasing the “pressure difference before and after the first expansion valve”. Assuming that the 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. 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} of the cooling capacity (during cooling operation) 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.} , Both are in a trade-off relationship, and 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} of the heating capacity (for example, the heating capacity in the heating operation) will not be described, but the “pressure difference before and after the first expansion valve” is changed for the same reason as the _{COP c during the cooling operation.} A maximum value is generated when the value is increased.

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.

Details will be described later, but as shown in FIGS. 4 (a), 5 (a), and 6 (a), the calculation considering the heat transfer characteristics of the heat exchanger is not related to the load and the outside air temperature. However, it was confirmed that a maximum value was generated in _{COP c} when the "pressure difference before and after the first expansion valve" was changed.
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.

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 of the compressor corresponding to the above, and control the opening degree or the pressure difference so as to minimize the compression power and maximize the COP.

By the way, the opening degree of the first expansion valve or the pressure difference generated between the condenser and the receiver caused by the opening degree is the compressor rotation speed, the outside air temperature, the indoor temperature (indoor unit suction air temperature), and the indoor unit. Machine operating load factor (ratio of the total capacity of the indoor units in operation to the rated capacity of the outdoor unit), condensation pressure, evaporation pressure, overcooling degree (condenser outlet), overheating degree (compressor inlet), outdoor unit fan rotation It is determined based on the operating conditions such as the number.
Therefore, in the present invention, these operating conditions and the pressure difference before and after the first expansion valve (the opening degree of the first expansion valve and the pressure difference between the condenser and the receiver caused by the opening degree) occur. From the map data that stores the relationship with the pressure difference), the pressure difference before and after the first expansion valve corresponding to the current operating conditions is read out, 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 becomes the minimum and the COP becomes the maximum.
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 a receiver to optimize the pressure difference between the front and rear of 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 local search method as described above 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-mentioned operating conditions change with time, the COP may not reach an appropriate maximum value in the controlled pressure difference.
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 graph showing the pressure difference dependence before and after the first expansion valve of COP when the outside air temperature is 35 ° C in rated load operation. Graph graph showing the pressure difference dependence before and after the first expansion valve of COP when the outside air temperature is 35 ° C in partial load operation. Graph graph showing the pressure difference dependence before and after the first expansion valve of COP when the outside air temperature is 29 ° C in partial load operation. Schematic configuration diagram of the heat pump device according to another embodiment In the heat pump device according to another embodiment, a graph showing a pH diagram before and after adjusting the pressure difference between the first expansion valve and the first expansion valve.

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, a receiver 17 for storing the refrigerant, an evaporator for evaporating the refrigerant expanded by the expansion valve, a compressor 11 and a condenser. The first expansion valve, the receiver 17, the second expansion valve, and the refrigerant circulation path C1 for circulating the refrigerant in the order described in the first expansion valve, the receiver 17, and the evaporator are provided. The refrigerant circulation path C1 is provided with a four-way valve 20 that switches the refrigerant circulation state between a cooling operation (an example of operation when demonstrating cooling capacity) and a heating operation (an example of operation when demonstrating heating capacity). Has been done.
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. Blower by heat exchanger 12 (corresponding to a condenser), heating expansion valve Vh (corresponding to the first expansion valve), receiver 17, cooling expansion valve Vc (corresponding to the second expansion valve), and 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 the indoor 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). By indoor heat exchanger 13 (corresponding to a condenser), cooling expansion valve Vc (corresponding to the first expansion valve), receiver 17, heating expansion valve Vh (corresponding to the second expansion valve), 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 blown 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 For each operating condition such as degree (compressor inlet) and outdoor unit fan rotation speed, the pressure difference between the operating condition and the pressure difference before and after the first expansion valve determined from the operating condition (opening in the first expansion valve or its opening). A storage unit 51 that stores map data, which is the relationship between the pressure difference between the compressor and the receiver caused by the degree, is provided, and the control unit 52 that executes the following various controls is provided with software and hardware. Are prepared in a collaborative manner.
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 It has a pressure difference control unit that controls the pressure difference before and after the first expansion valve so that the value becomes the minimum value and the COP becomes the maximum value.

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 within 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 length of the refrigerant circulation path C1 for each facility such as a building where 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 will be omitted, the control unit 52 may also apply learning control to execute control for deriving the pressure difference before and after the first expansion valve that minimizes the compression power.

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.

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. ..
FIG. 4 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.
In addition, in the graph, the calculation result in the configuration corresponding to another embodiment of the present invention provided with the supercooling flow path shown in FIG. 7 (described later) is also shown, and when supercooling (SC) is present, it is also shown. It was assumed that the degree of superheat of the refrigerant after receiving heat by supercooling was SH: 10K.

As shown in FIG. 4 (b), as the pressure difference before and after the first expansion valve increases, the temperature of the liquid pipe between the receiver 17 and the second expansion valve decreases (COP increases), and FIG. 4 (B) As shown in c), 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). Since the two are in a trade-off relationship, as shown in FIG. 4A, 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.

Further, when the cooling operation is performed with a partial load (intermediate load of about half of the rated load) and the outside air temperature is 35 ° C. (shown in FIG. 5), and the cooling operation is performed with a partial load (intermediate load of about half of the rated load). As is clear from the case where the outside air temperature is 29 ° C. (shown in FIG. 6), even if the operating load changes or the outside air temperature changes, the pressure difference before and after the first expansion valve is changed. It was confirmed that the COP had a maximum value.

[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, it is desirable to provide a separate expansion valve as the first expansion valve immediately before the receiver.

(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. 7, the heat pump device 100 and its control method according to the present invention satisfactorily exhibit their functions even in a configuration including a supercooling flow path C2.
FIG. 7 shows an example of the circuit configuration of the supercooling flow path C2 during the cooling operation.
In the following, only the configuration related to the supercooling 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. 7, the upstream end of the supercooling flow path C2 is connected to the refrigerant circulation path C1 between the receiver 17 and the cooling expansion valve Vc (an example of the second expansion valve), and the downstream end is connected to the refrigerant circulation path C1. , It is connected to the refrigerant circulation path C1 between the accumulator 15 and the compressor 11 (more specifically, the refrigerant circulation path C1 between the downstream end of the oil flow path Lo and the accumulator 15).
In the supercooled flow path C2, a flow path portion through which the refrigerant expanded by the expansion valve V4 flows passes through the liquid refrigerant storage portion inside the receiver 17, whereby the inside of the receiver 17 is provided. The degree of supercooling is adjusted by cooling the refrigerant in the above.
When this configuration is adopted, the Ph diagram when the pressure difference dP before and after the first expansion valve is changed is as shown in FIG. When the pressure difference dP before and after the first expansion valve is increased, the temperature of the refrigerant at the inlet of the receiver 17 is lowered, so that the temperature difference at the time of supercooling tends to be small and the degree of supercooling tends to be slightly small. For the same reason as in the form, there is a pressure difference dP that minimizes the compression power and maximizes the COP.
Note that FIG. 7 shows an example of a supercooling circuit, in which the supercooling heat exchange is not built in the receiver, and the specifications that are externally attached and the parts that branch due to supercooling are after supercooling. There is also a specification that is before supercooling.

(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 17: Receiver 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 refrigerant Described in the receiver, the evaporator that evaporates the refrigerant expanded by the expansion valve, the compressor, the condenser, the first expansion valve, the receiver, the second expansion valve, and the evaporator. It is a control method of a heat pump device including a refrigerant circulation path that circulates a refrigerant in the order of.
The pressure difference generated between the condenser and the receiver, which changes due to the opening degree of the first expansion valve or the opening degree of the first expansion valve, is minimized by the compression power of the compressor to reduce the COP. Control to maximize
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 a refrigerant. Described in the receiver, the evaporator that evaporates the refrigerant expanded by the expansion valve, the compressor, the condenser, the first expansion valve, the receiver, the second expansion valve, and the evaporator. A heat pump device including a refrigerant circulation path that circulates refrigerant in the order of
The pressure difference generated between the condenser and the receiver, which changes due to the opening degree of the first expansion valve or the opening degree of the first expansion valve, is minimized by the compression power of the compressor to reduce the COP. A pressure difference control unit that controls to maximize
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.
A heat pump device in which 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.

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