JP2012083080A - Method for controlling heat pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for controlling a heat pump, which controls the opening of an expansion valve in view of the excessive heating of a refrigerant sucked into a compressor.SOLUTION: The method for controlling a heat pump evaporates a refrigerant reduced in pressure by an expansion valve 14 to absorb heat of external air, and compresses the heat by a compressor 16 to used as a heat source for heating water by a water-heat exchanger 13. A, B, and C are calculated when T=A×X+B×Y+C×Z is applied when COP being the maximum, where X is a temperature of water entered into a water-heat exchanger 13, Y is a temperature of hot water output from the water-heat exchanger 13, Z is excessive heating of the refrigerant sucked into the compressor 16, and T is a temperature of the refrigerant discharged from the compressor 16. A temperature X' of water entered into the water-heat exchanger 13, a temperature Y' of hot water output from the water-heat exchanger 13, and excessive heating Z' of a refrigerant sucked into the compressor 16 are measured, and the opening of the expansion valve 14 is adjusted to approach a target discharge temperature T1 calculated from A×X'+B×Y'+C×Z'.

Description

The present invention relates to a method for controlling a heat pump that heats water using atmospheric energy.

Heating water with a heat pump has attracted attention because it reduces power consumption and reduces carbon dioxide emissions. The heat efficiency (COP) of the heat pump is obtained from the value of heat energy given to the water with respect to the unit power consumption of the compressor, and methods for controlling the heat pump for increasing the heat efficiency are described in Patent Documents 1, 2, and 3. .
In Patent Documents 1, 2, and 3, the temperature of the refrigerant discharged from the compressor for maintaining the heat efficiency of the heat pump at a high level is determined as the target discharge temperature, and the temperature of the refrigerant discharged from the compressor is set as the target discharge temperature. Control is done to approach the temperature.

Japanese Patent No. 3518475 Japanese Patent No. 3856025 JP 2009-92331 A

However, although it is generally known that the degree of superheat of the refrigerant sucked into the compressor affects the heat efficiency of the heat pump, in Patent Documents 1, 2, and 3, the target discharge temperature is determined. There is a problem that the degree of superheat of the refrigerant sucked into the compressor is not directly considered.
The superheat degree of the refrigerant sucked into the compressor is closely related to the density of the refrigerant. When the superheat degree of the refrigerant becomes high, the refrigerant density becomes low, and when the superheat degree (heating degree) of the refrigerant becomes low, the refrigerant density becomes Get higher. And if the refrigerant density becomes too low, the amount of refrigerant that the compressor compresses at one time decreases and the heat efficiency of the heat pump decreases, and if the refrigerant density becomes too high, the resistance that acts on the compressor increases and the heat pump Therefore, the influence of the degree of superheat of the refrigerant on the heat efficiency of the heat pump is not small.
This invention is made | formed in view of this situation, and it aims at providing the control method of the heat pump which adjusts the opening degree of an expansion valve in consideration of the superheat degree of the refrigerant | coolant suck | inhaled by a compressor.

A heat pump control method according to the present invention that meets the above-described object includes: a heat source for evaporating a refrigerant decompressed by an expansion valve, absorbing heat of outside air, compressing the refrigerant by a compressor, and heating water with a water heat exchanger; In the heat pump control method, the temperature of the water entering the water heat exchanger when the heat energy given to the water by the water heat exchanger is maximum with respect to the unit power consumption of the compressor. X, temperature T of hot water discharged from the water heat exchanger, superheat degree Z of the refrigerant sucked into the compressor, and temperature T of the refrigerant discharged from the compressor are different from each other. 3 sets of X, Y, Z, and T are obtained by measurement under the condition of the value, and 3 sets of X, Y, Z, and T are substituted into T = A × X + B × Y + C × Z, respectively. Preparation step for calculating A, B, C from two equations, and the hydrothermal The temperature of the water entering the exchanger is X ′, the temperature of the hot water discharged from the water heat exchanger is Y ′, the superheat degree of the refrigerant sucked into the compressor is Z ′, and is discharged from the compressor T ′ is the temperature of the refrigerant to be measured, and X ′, Y ′, Z ′ and T ′ are measured at predetermined time intervals and A based on the measured X ′, Y ′ and Z ′. The target discharge temperature T1, which is a calculated value of XX '+ B * Y' + C * Z ', is obtained, and the opening of the expansion valve is adjusted so that the measured temperature T' approaches the target discharge temperature T1. A heating control step of adjusting and heating the water.

In the heat pump control method according to the present invention, in the preparation step, the temperature of the outside air is divided into a plurality of temperature regions, and A, B, and C are calculated for each temperature region, and in the heating control step, Along with measurement of X ′, Y ′, Z ′ and T ′, the temperature of the outside air is measured, and A, B, and C calculated in the preparation step with respect to the temperature region to which the measured temperature of the outside air belongs. It is preferable to calculate the target discharge temperature T1 from A × X ′ + B × Y ′ + C × Z ′.

In the heat pump control method according to the present invention, when A, B, or C calculated in the preparation step is a value outside a predetermined range W1 that can be actually stored, T = A × X + B × Y + C In place of × Z, T = A × X + B × Y + C × Z + D is used to determine A, B, C, and D in which A, B, and C are within the predetermined range W1, and in the heating control step, In calculating the target discharge temperature T1, it is preferable to use A × X ′ + B × Y ′ + C × Z ′ + D instead of A × X ′ + B × Y ′ + C × Z ′.

In the heat pump control method according to the present invention, in the preparation step, the temperature of the outside air is divided into a plurality of temperature regions, and the A, B, C, and D are calculated for each temperature region, and in the heating control step, A, B, calculated in the preparation step with respect to the temperature region to which the measured temperature of the outside air belongs, together with the measurement of the X ′, Y ′, Z ′ and T ′, It is preferable to calculate the target discharge temperature T1 from A × X ′ + B × Y ′ + C × Z ′ + D using C and D.

In the heat pump control method according to the present invention, when the target discharge temperature T1 is lower than the target hot water temperature Y1 of hot water discharged from the hydrothermal exchanger in the heating control step, the measured temperature T It is preferable to adjust the opening of the expansion valve so that 'approaches the target hot water temperature Y1.

In the heat pump control method according to the present invention, when the target discharge temperature T1 is higher than a preset limit temperature H in the heating control step, the temperature T ′ approaches the limit temperature H. Thus, it is preferable to adjust the opening of the expansion valve.

In the heat pump control method according to the present invention, in the heating control step, after the target discharge temperature T1 is maintained within a predetermined stable temperature region W2 for a preset time or more, the temperature X ′ is When the temperature becomes higher than a preset temperature and the target discharge temperature T1 reaches a temperature outside the stable temperature region W2, the expansion valve is adjusted so that the temperature T ′ approaches the temperature in the stable temperature region W2. It is preferable to adjust the opening degree.

The control method of the heat pump according to the present invention is the temperature X of water entering the water heat exchanger when the heat energy given to the water in the water heat exchanger is the maximum for the unit power consumption of the compressor, Measure the temperature Y of hot water discharged from the water heat exchanger, the degree of superheat Z of the refrigerant sucked into the compressor, and the temperature T of the refrigerant discharged from the compressor under conditions where the temperature T is different. 3 sets of X, Y, Z, and T are obtained, and A, B, and C are obtained from three equations obtained by substituting 3 sets of X, Y, Z, and T into T = A × X + B × Y + C × Z, respectively. Preparatory process to calculate, temperature of water entering the water heat exchanger is X ′, temperature of hot water discharged from the water heat exchanger is Y ′, superheat degree of refrigerant sucked into the compressor is Z ′, compression With the temperature of the refrigerant discharged from the machine as T ′, measurement of X ′, Y ′, Z ′ and T ′ at a preset time interval; Based on the measured X ′, Y ′, and Z ′, the target discharge temperature T1 that is a calculated value of A × X ′ + B × Y ′ + C × Z ′ is obtained, and the temperature T ′ is the target discharge temperature T1. Therefore, the heat pump can be controlled by adjusting the opening degree of the expansion valve in consideration of the degree of superheat of the refrigerant sucked into the compressor.

In the heat pump control method according to the present invention, the temperature of the outside air is divided into a plurality of temperature regions in the preparation step, and A, B, and C are calculated for each temperature region, and X ′, Y ′, Along with the measurement of Z ′ and T ′, the temperature of the outside air is measured, and A × X ′ + B × Y ′ using A, B, and C calculated in the preparation step for the temperature region to which the measured temperature of the outside air belongs. When calculating the target discharge temperature T1 from + C × Z ′, the target discharge temperature T1 can be calculated using A, B, and C calculated under conditions close to the actual outside air temperature, and an expansion valve that matches the outside air temperature The degree of opening can be adjusted.

In the heat pump control method according to the present invention, when A, B, or C calculated in the preparation step is a value outside the predetermined range W1 that can be actually stored, T = A × X + B × Y + C × Z Instead, T = A × X + B × Y + C × Z + D is used to determine A, B, C, and D within which A, B, and C are within a predetermined range W1, and in the heating control process, the target discharge temperature T1 When using A × X ′ + B × Y ′ + C × Z ′ + D instead of A × X ′ + B × Y ′ + C × Z ′ for the calculation, the numbers that can be set to A, B, and C are displayed on the mounting surface. Even if there is a limit, it is possible to use a value that falls within the number within the limit.

In the heat pump control method according to the present invention, the temperature of the outside air is divided into a plurality of temperature regions in the preparation step, and A, B, C, and D are calculated for each temperature region, and X ′ and Y are calculated in the heating control step. Together with the measurement of ', Z' and T ', the temperature of the outside air is measured, and A × X' using A, B, C, D calculated in the preparation step for the temperature region to which the measured temperature of the outside air belongs When calculating the target discharge temperature T1 from + B × Y ′ + C × Z ′ + D, the target discharge temperature T1 can be calculated using A, B, C, and D calculated under conditions close to the actual outside air temperature, The opening degree of the expansion valve can be adjusted according to the outside air temperature.

In the heat pump control method according to the present invention, when the target discharge temperature T1 is lower than the target hot water temperature Y1 of hot water discharged from the water heat exchanger in the heating control step, the measured temperature T ′ is the target temperature. When the opening degree of the expansion valve is adjusted so as to approach the tapping temperature Y1, the temperature Y 'of the hot water discharged from the water heat exchanger immediately after the start of boiling is low, and the target discharge temperature T1 is lower than the target tapping temperature Y1. When calculated, the temperature increase rate of the water temperature can be increased earlier than in the control in which the measured temperature T ′ is brought close to the target discharge temperature T1.

In the heat pump control method according to the present invention, when the target discharge temperature T1 is higher than a preset limit temperature H in the heating control step, the temperature of the expansion valve is adjusted so that the temperature T ′ approaches the limit temperature H. When adjusting the opening, the value of the temperature used when calculating the target discharge temperature T1 (for example, the temperature Y ′ of hot water discharged from the water heat exchanger) is a value that is far from the actual temperature for some reason. When the target discharge temperature T1 exceeds the assumed temperature, switching to control ignoring the target discharge temperature T1 can suppress the decrease in COP and equipment failure.

In the heat pump control method according to the present invention, in the heating control step, the temperature X ′ is set in advance after the target discharge temperature T1 is maintained in the predetermined stable temperature region W2 for a preset time or more. When the opening degree of the expansion valve is adjusted so that the temperature T ′ approaches the temperature in the stable temperature region W2 when the target discharge temperature T1 becomes a temperature outside the stable temperature region W2 Further, it is possible to avoid the decrease in COP caused by the temperature T ′ being decreased or increased more than necessary.

1 is a circuit diagram of a heat pump unit to which a heat pump control method according to an embodiment of the present invention is applied. It is a graph which shows various temperature changes at the time of boiling up hot water with the same heat pump unit.

Next, embodiments of the present invention will be described with reference to the accompanying drawings for understanding of the present invention.
As shown in FIG. 1, a heat pump unit 10 to which a heat pump control method according to an embodiment of the present invention is applied is a heating device that heats water in a hot water storage tank 11, and a refrigerant circulation circuit 12 in which refrigerant circulates. It has.

The refrigerant circulation circuit 12 includes a water heat exchanger 13 that heats water from the hot water storage tank 11 using the refrigerant as a heat source, an expansion valve 14 that decompresses the gas-liquid mixed refrigerant sent from the water heat exchanger 13, and An evaporator 15 that evaporates the decompressed refrigerant and absorbs heat of the outside air, and a compressor 16 that compresses the refrigerant that has become gaseous in the evaporator 15 are provided.
Further, in the refrigerant circulation circuit 12, when the pressure of the refrigerant sent from the compressor 16 becomes a predetermined value (for example, 13 MPa) or more, the pipes and devices constituting the refrigerant circulation circuit 12 are damaged. A pressure switch 17 for stopping the operation of the compressor 16 is attached so as not to be present.

The water heat exchanger 13 forms a hot water circulation circuit 18 together with the hot water storage tank 11 and the like. A circulating pump 19 is attached to the hot water circulation circuit 18. When the circulating pump 19 is activated, water is sent from the bottom of the hot water storage tank 11 to the water heat exchanger 13, heated by the water heat exchanger 13 to become hot water, It is returned to the upper part of the hot water storage tank 11.
The hot water circulation circuit 18 is provided with an incoming water thermistor 20 that measures the temperature of water entering the water heat exchanger 13 and an outgoing hot water thermistor 21 that measures the temperature of hot water discharged from the water heat exchanger 13.
Further, in the hot water circulation circuit 18, the bypass pipe 23 that connects the hot water outlet side of the water heat exchanger 13 and the bottom of the hot water storage tank 11, and the hot water destination from the water heat exchanger 13 are located at the upper part of the hot water storage tank 11. Alternatively, a three-way valve 24 is provided for switching between the hot water storage tank 11 and the bottom through the bypass pipe 23. The circulation pump 19 and the three-way valve 24 are signal-connected to a control device 26 including a chip on which a program is mounted and a storage device.

The heat pump unit 10 is provided with an HP control device 27 that controls the compressor 16 and the like.
The control device 26 is capable of signal communication with the HP control device 27, and outputs an operation command signal for the compressor 16 and the like to the HP control device 27 and transmits an operation signal to the circulation pump 19 to thereby store the hot water storage tank. Boil water in 11 is operated. Further, the control device 26 can measure the temperature of hot water discharged from the hydrothermal exchanger 13 measured by the hot water thermistor 21 via the HP control device 27, and the hot water temperature measured via the hot water thermistor 21 can be measured. When the temperature is lower than a preset temperature (for example, 40 ° C.), the three-way valve 24 is switched so that hot water from the water heat exchanger 13 is sent to the bottom of the hot water storage tank 11 through the bypass pipe 23, Control is performed so as not to lower the temperature of the hot water in the upper part of the hot water storage tank 11. When the control device 26 detects that the hot water temperature measured via the hot water thermistor 21 is higher than a preset temperature, the control device 26 switches the three-way valve 24 to supply hot water from the water heat exchanger 13. Is supplied to the upper part of the hot water storage tank 11.

The hot water storage tank 11 is provided with a plurality (five in the present embodiment) of remaining hot water thermistors 28a to 28e at different height positions. The control device 26 measures the temperature at different height positions of the hot water storage tank 11 at regular time intervals via the remaining hot water thermistors 28a to 28e, and detects the state of the hot water in the hot water storage tank 11.
A hot water storage tank 29 for supplying tap water to the hot water storage tank 11 and a hot water discharge pipe 29a for supplying hot water in the hot water storage tank 11 to a kitchen or a bathtub are connected to the bottom and top of the hot water storage tank 11, respectively. . The water supply pipe 29 is provided with a pressure reducing valve (not shown).

The opening of the expansion valve 14 provided in the refrigerant circulation circuit 12 is adjusted by a signal output from the HP control device 27, expands the liquid refrigerant, and reduces its pressure to a predetermined value.
The evaporator 15 can evaporate the refrigerant decompressed by the expansion valve 14 and cause the refrigerant to absorb the heat of the outside air. In the evaporator 15, a fan 30 that supplies outside air to the surface of the evaporator 15 and increases the work efficiency of the evaporator 15 is disposed close to the evaporator 15. The fan 30 rotates at a predetermined rotation speed in response to a signal from the HP control device 27.

The conduit connecting the evaporator 15 and the compressor 16 is provided with an internal heat exchanger 31 that heats the refrigerant from the evaporator 15 to the compressor 16 by using the refrigerant sent from the water heat exchanger 13 to the expansion valve 14 as a heat source. It has been. In the internal heat exchanger 31, the refrigerant sent out from the water heat exchanger 13 is usually at a higher temperature (for example, 10 ° C. higher) than the refrigerant gasified in the evaporator 15, so the water heat exchanger The refrigerant sent from 13 to the expansion valve 14 is used to heat the refrigerant sent from the evaporator 15 to the compressor 16 using the refrigerant as a heat source.
In addition, an evaporation thermistor 32 that measures the evaporation temperature of the refrigerant is attached to the evaporator 15, and the HP control device 27 can detect the evaporation temperature of the refrigerant via the evaporation thermistor 32.
The HP control device 27 includes a chip on which a program is mounted, a storage device, and the like.

The refrigerant heated by the internal heat exchanger 31 flows into the compressor 16 via the accumulator 33. The accumulator 33 is sent from the evaporator 15 through the internal heat exchanger 31 in a mixed state (that is, a gas-liquid mixed state) in which the refrigerant is not in a gaseous state in the evaporator 15 and the gaseous refrigerant and the liquid refrigerant are mixed. When it is, only the gaseous refrigerant is supplied into the compressor 16.
The compressor 16 is equipped with an inverter (not shown), and adjusts the amount of refrigerant compression by changing the frequency of the inverter in response to a signal from the HP control device 27. An outside air thermistor 34 for measuring the outside air temperature is attached to the heat pump unit 10, and the HP control device 27 can operate the inverter at a predetermined frequency according to the outside air temperature detected via the outside air thermistor 34.

The refrigerant circulation circuit 12 is equipped with a suction thermistor 35 that measures the temperature of the refrigerant sucked into the compressor 16 and a discharge pipe thermistor 36 that measures the temperature of the compressed refrigerant discharged from the compressor 16. The HP control device 27 is connected in signal to the suction thermistor 35 and the discharge pipe thermistor 36, and can detect each measured value of the suction thermistor 35 and the discharge pipe thermistor 36.

Further, the HP control device 27 detects the temperature of the water before being heated by the hydrothermal exchanger 13 and the temperature of the hot water heated by the hydrothermal exchanger 13 via the incoming water thermistor 20 and the outgoing hot water thermistor 21, respectively. Can do.
Then, the HP control device 27 calculates the unit power consumption of the compressor 16 based on the temperature values obtained via the incoming water thermistor 20, the hot water thermistor 21, the evaporation thermistor 32, the suction thermistor 35, and the discharge pipe thermistor 36. Thus, the opening degree of the expansion valve 14 is adjusted so that the heat energy (hereinafter also referred to as “COP”) given from the refrigerant to the water in the water heat exchanger 13 becomes a high level. Hereinafter, a method for adjusting the opening degree of the expansion valve 14 for maintaining the COP at a high level, that is, a method for controlling the heat pump will be described.

The heat pump control method according to the present embodiment is a preparatory step for obtaining a condition for maintaining the COP at a high level by obtaining the relationship between the measured values of the suction thermistor 35 and the discharge pipe thermistor 36 when the COP becomes maximum. And a heating control step of adjusting the opening degree of the expansion valve 14 based on the conditions obtained in the preparation step and heating water sent from the bottom of the hot water storage tank 11.
In general, a heat pump unit has a guaranteed operating temperature for the outside air temperature. The heat pump unit 10 is no exception, and there is an operation guarantee temperature. In this embodiment, the operation guarantee temperature is -10 ° C or more and 43 ° C or less.

In the preparation step, the temperature of the outside air is divided into a plurality of temperature regions within the guaranteed operating temperature, and a condition that maximizes the COP is obtained for each temperature region. In the heating control step, the HP control device 27 detects the temperature range to which the current outside temperature belongs from the outside temperature measured by the outside air thermistor 34, and expands based on the condition obtained in the preparation step for the temperature range. The opening degree of the valve 14 is adjusted.
In this embodiment, the opening temperature of the expansion valve 14 is adjusted by dividing the temperature of the outside air into three temperature ranges of −10 ° C. or higher and lower than 7 ° C., 7 ° C. or higher and lower than 16 ° C. Is going.

In the preparation step, for each predetermined outside air temperature range, first, COP is calculated while changing the opening of the expansion valve 14 to detect a state where the COP is maximized.
The COP is the amount of power consumed per unit time of the compressor 16 by the heat energy per unit time given by the water circulating in the hot water circulation circuit 18 from the refrigerant circulating in the refrigerant circulation circuit 12 in the water heat exchanger 13. Can be obtained by dividing.
When a state in which the COP is maximized is detected, the HP controller 27 detects the temperature X of water entering the water heat exchanger 13, the temperature Y of hot water discharged from the water heat exchanger 13, and the compressor. Each value of the superheat degree Z of the refrigerant | coolant suck | inhaled by 16 and the temperature T of the refrigerant | coolant discharged from the compressor 16 is memorize | stored.
Here, the HP control device 27 can acquire the temperature X, the temperature Y, and the temperature T via the incoming water thermistor 20, the outgoing hot water thermistor 21, and the discharge pipe thermistor 36, and the superheat degree Z is detected via the suction thermistor 35. By subtracting the temperature detected through the evaporation thermistor 32 from the measured temperature.

The process in which the HP controller 27 stores the values of the temperature X, the temperature Y, the superheat degree Z, and the temperature T is performed under three conditions in which the temperature T is different for each temperature range of the outside air. If at least one of the outside air temperature, the incoming water temperature to the water heat exchanger 13 and the tapping temperature from the water heat exchanger 13 is changed, the temperature T will be different.
The HP control device 27 obtains three sets of X, Y, Z, and T for each temperature range of the outside air, and sets these three sets of X, Y, Z, and T to T = A × X + B × Y + C × Z. The values of A, B, and C are calculated from three equations that are respectively substituted.

For example, the measurement results in a temperature range of −10 ° C. or more and less than 7 ° C. are as follows: 1) X = 9 ° C., Y = 90 ° C., Z = 6.3 ° C., T = 117.8 ° C., 2) X = 5 ° C. Y = 90 ° C., Z = 4.9 ° C., T = 119.9 ° C., 3) X = 9 ° C., Y = 85 ° C., Z = −1.2 ° C., T = 121 ° C.
117.8 = A × 9 + B × 90 + C × 6.3,
119.9 = A × 5 + B × 90 + C × 4.9,
121 = A × 9 + B × 85 + C × (−1.2)
Therefore, A, B, and C can be calculated from these simultaneous equations.
Note that Z is a negative value in the measurement result of 3) while Z is normally a positive value, which occurs when gaseous refrigerant is sent from the evaporator 15 to the compressor 16. This is due to pressure loss.

In addition, the range of numerical values that can actually be stored as the values of A, B, and C may be limited to a predetermined range due to mounting reasons due to the limitation of the memory capacity of the HP control device 27 and the like.
In this embodiment, the memory capacity storing numerical values that can be set for A, B, and C is 256 bits, and the values that can be set for A, B, and C are −128/32 or more and 127/32 or less. It is limited to a value within the range W1. Furthermore, the values that can be set for each of A, B, and C are limited to N / 32 values, where N is an integer. Therefore, normally, values that can be set to A, B, and C, and the values obtained by calculating the right side of each equation cannot be the same as the left side of each equation.
For this reason, A, B, and C are set to values in which the calculated value on the right side is within ± α% of the value on the left side in each equation (α is a number greater than 0 and less than or equal to 1, for example, 0 .5), A, B, and C are specifically set to A = −2 / 32, B = 45/32, and C = −44 / 32.
Then, when A = −2 / 32, B = 45/32, and C = −44 / 32, the opening degree of the expansion valve 14 in a later heating control step in a temperature range where the outside air is −10 ° C. or more and less than 7 ° C. This is a coefficient employed in the arithmetic expression that is the basis for performing the adjustment.
Note that the range W1 is not limited to the range of −128/32 or more and 127/32 or less, and may be other ranges.

On the other hand, the equation obtained from the measurement result in the temperature region where the outside air is 7 ° C. or more and less than 16 ° C. is
90 = A × 17 + B × 65 + C × 10.4,
94.2 = A × 9 + B × 65 + C × 7.7,
117.8 = A × 9 + B × 90 + C × 6.3
Then, when A, B, and C are obtained based on these equations, A, B, and C do not become values within the range W1.

Therefore, when A, B, or C is outside the predetermined range W1, the HP control device 27 uses the equation T = A × X + B × Y + C × Z + D instead of T = A × X + B × Y + C × Z. Using A, B, C and D, A, B, and C are within a predetermined range W1.
In particular,
90 = A × 17 + B × 65 + C × 10.4 + D,
94.2 = A × 9 + B × 65 + C × 7.7 + D,
117.8 = A × 9 + B × 90 + C × 6.3 + D
With respect to these three equations, values of A, B, C, and D in which the calculated value on the right side is within ± α% of the value on the left side are obtained, and A = −40 / 32 and B = 34/32, respectively. , C = 68/32, and D = 20.
And when A = −40 / 32, B = 34/32, C = 68/32, and D = 20, the opening degree of the expansion valve 14 in the heating control step in the temperature range where the outside air is 7 ° C. or more and less than 16 ° C. This is a coefficient used in the arithmetic expression that is the basis for adjustment.
For D, the settable value is limited to a range of 0 to 255 depending on the memory capacity of the HP control device 27.

As described above, the HP controller 27 determines the temperature of the refrigerant discharged from the compressor 16 for each of the outside air temperature ranges of −10 ° C. or higher and lower than 7 ° C., 7 ° C. or higher and lower than 16 ° C., and 16 ° C. or higher and 43 ° C. or lower. If A, B, and C are calculated under conditions where T has different values, and the calculated values A, B, and C are within the range W1, then the A, B, and C are used as the opening of the expansion valve 14. Stored as a coefficient of an arithmetic expression for adjustment.
On the other hand, for the temperature range where the calculated A, B, or C is not within the range W1, the HP control device 27 sets A, B, C, and D so that A, B, and C are within the predetermined range W1. And the values A, B, C, and D are stored as coefficients of an arithmetic expression for adjusting the opening degree of the expansion valve 14.
The preparation process is completed by the HP controller 27 storing the coefficients A, B, C, and D of the arithmetic expression for adjusting the opening degree of the expansion valve 14 for each temperature region of the outside air. The HP control device 27 is in a state where the heating control of the water in the hot water storage tank 11 is possible.

The heating control process is started when the HP control device 27 receives a boiling command signal for the hot water storage tank 11 from the control device 26.
The temperature of water entering the water heat exchanger 13 is X ′, the temperature of hot water discharged from the water heat exchanger 13 is Y ′, the superheat degree of the refrigerant sucked into the compressor 16 is Z ′, and the compressor 16 Assuming that the temperature of the discharged refrigerant is T ′, the HP control device 27 performs X at a preset time interval in the heating control step (in this embodiment, 10 seconds to 240 seconds, specifically 30 seconds). Together with the measurement of ', Y', Z 'and T', the temperature of the outside air is measured.
The HP control device 27 can measure the X ′, Y ′, T ′, and the outside air temperature via the incoming water thermistor 20, the outgoing hot water thermistor 21, the discharge pipe thermistor 36, and the outdoor air thermistor 34, respectively. Calculation is performed by subtracting the temperature detected via the evaporation thermistor 32 from the temperature detected via the thermistor 35.

Then, the HP control device 27 sets the target discharge temperature T1 based on the values of A, B, and C or the values of A, B, C, and D stored for the temperature region to which the measured outside air temperature belongs. Perform arithmetic processing.
Specifically, when the values of A, B, and C are stored for the temperature range (for example, the temperature range of −10 ° C. or higher and lower than 7 ° C.) to which the measured value of the outside air temperature belongs, the HP control device 27 Based on the measured X ′, Y ′ and Z ′, a calculated value of A × X ′ + B × Y ′ + C × Z ′ is acquired as the target discharge temperature T1.
On the other hand, A, B, C, and D are coefficients of an arithmetic expression for adjusting the opening degree of the expansion valve 14 for a temperature range (for example, a temperature range of 7 ° C. or more and less than 16 ° C.) to which the measured value of the outside air temperature belongs. If stored, the HP control device 27 acquires a calculated value of A × X ′ + B × Y ′ + C × Z ′ + D based on the measured X ′, Y ′, and Z ′ as the target discharge temperature T1. To do.

The HP control device 27 calculates the target discharge temperature T1 every time X ′, Y ′, Z ′, T ′ and the outside air temperature are measured, and expands so that the temperature T ′ approaches the calculated target discharge temperature T1. The opening degree of the valve 14 is adjusted.
The opening degree of the expansion valve 14 is adjusted by PID control which is general feedback control.
In the present embodiment, in order to avoid a so-called overshoot in which the temperature T ′ exceeds the target discharge temperature T1 due to a sudden change in the opening of the expansion valve 14, the latest measured value of the temperature T ′ (finally) The measured value) and a value obtained by adding the measured value of the temperature T ′ measured before a predetermined time (for example, 120 seconds before) and dividing by 2 and the latest target discharge temperature T1 are compared, and the expansion valve 14 Is determined.

Assuming that the time when the HP controller 27 starts boiling the hot water storage tank 11 is 0 minute, the transition of the target discharge temperature T1 and the temperature T ′ in the heating control process is as shown in FIG.
The target hot water temperature Y1 is determined by a signal transmitted to the HP control device 27 from the control device 26 together with a command signal for starting boiling of the hot water storage tank 11. Further, the temperature of the incoming water temperature X ′ is normally kept within a certain range until the hot water stored from the upper part of the hot water storage tank 11 reaches the lower part because of the temperature of the water discharged from the lower part of the hot water storage tank 11. .
FIG. 2 is a graph of experimental data obtained when the hot water storage tank 11 is boiled under conditions of an outside air temperature of 7 ° C., a target hot water temperature Y 1 of 65 ° C., and an incoming water temperature of 9 ° C.

The hot water temperature Y ′ is usually lower than the target hot water temperature Y1 at the time when boiling of the hot water storage tank 11 is started (at 0 minutes in FIG. 2), and rises as the temperature of the refrigerant circulating in the refrigerant circuit 12 increases. Thus, it becomes substantially the same temperature as the target hot water temperature Y1. In FIG. 2, the tapping temperature Y ′ is substantially the same as the target tapping temperature Y1 in the vicinity of 12 to 13 minutes.
After the hot water temperature Y ′ becomes substantially the same as the target hot water temperature Y1, the opening degree of the expansion valve 14 can be greatly changed as long as the target hot water temperature Y1 does not change and there is no significant change in outside air or the like. In other words, the discharge temperature T ′ and the target discharge temperature T1 are maintained at substantially the same temperature.

The HP controller 27 determines that the target discharge temperature T1 is equal to or longer than a predetermined stable temperature range W2 (from −3 ° C. over a preset time (in the range of 2 to 5 minutes, 3 minutes in the present embodiment). In this embodiment, in the range of + 3 ° C., in the present embodiment, it is detected that the temperature fluctuates within a temperature range of −2 ° C. to + 2 ° C., and the boiling of the hot water is detected to be stable. .
After the boiling of the hot water becomes stable, the HP controller 27 has a temperature X ′ higher than a preset temperature (in the range of 5 ° C. to 15 ° C., 10 ° C. in the present embodiment), and When the target discharge temperature T1 reaches a temperature outside the stable temperature region W2 (eg, 11 ° C.), the opening degree of the expansion valve 14 is adjusted so that the temperature T ′ approaches the temperature within the stable temperature region W2.

The reason why the temperature X ′ becomes higher than the preset temperature is that the hot water flowing in from the upper part of the hot water storage tank 11 and stored in the upper part of the hot water storage tank 11 reaches the lower part of the hot water storage tank 11, It means that it is getting boiled.
Then, even when the temperature X ′ becomes equal to or higher than a certain temperature, the target discharge temperature T1 is calculated, and the opening degree of the expansion valve 14 is adjusted so that the temperature T ′ approaches the calculated latest target discharge temperature T1. If this is done, a phenomenon may occur in which the temperature T ′ decreases more than necessary, leading to a decrease in COP. Therefore, the temperature adjustment target of the temperature T ′ is not set to the latest calculated target discharge temperature T1, The temperature is within the stable temperature region W2.
Here, the temperature in the stable temperature region W2 that is the target of the temperature T ′ can be any one of the average temperature, the lower limit temperature, and the upper limit temperature of the stable temperature region W2.

Further, the HP control device 27 is configured so that the temperature T ′ approaches the target hot water temperature Y1 when the target discharge temperature T1 is lower than the target hot water temperature Y1 of hot water discharged from the hydrothermal exchanger 13. The opening degree of the expansion valve 14 is adjusted.
This is because immediately after the start of boiling, the target discharge temperature T1 is usually low because the tapping temperature Y ′ is low, and if the temperature T ′ is controlled to approach this low target discharge temperature T1, the refrigerant sufficiently heats the water. This is because it takes a long time to be ready (for example, heated to 40 ° C.).
In the experimental data shown in FIG. 2, control is performed so that the target discharge temperature T1 is lower than the target hot water temperature Y1 and the temperature T ′ approaches the target hot water temperature Y1 until 2 to 3 minutes have elapsed since the start of boiling. ing.

When the target discharge temperature T1 is higher than a preset limit temperature H (in the range of 115 ° C. to 135 ° C., H = 125 ° C. in the present embodiment), the HP control device 27 detects the temperature T 'Adjusts the opening degree of the expansion valve 14 so as to approach the limit temperature H.
This takes into consideration that the target discharge temperature T1 may be higher than the assumed temperature due to a thermistor failure or the like, and when the target discharge temperature T1 becomes higher than the assumed temperature, the discharge temperature T ′. The target temperature is switched from the target discharge temperature T1 to the limit temperature H.
Further, the boiling operation of the hot water storage tank 11 by the heat pump unit 10 is continued until an operation stop instruction signal is transmitted from the control device 26 to the HP control device 27, and the HP control device 27 stops the operation from the control device 26. The compressor 16 and the fan 30 are stopped by the signal.

Here, the HP control device 27 performs A, B, C, A, B, C, D based on X, Y, Z, T measured in three conditions for each temperature range of the outside air in the preparation process. However, if the conditions for measuring X, Y, Z, and T are changed, the calculated values of A, B, and C, or A, B, C, and D will also change.
For example, in calculating A, B, and C in a temperature range of −10 ° C. or higher and lower than 7 ° C., X = 9 ° C., Y = 90 ° C., Z = 6.3 ° C., T = Instead of adopting the measurement result of 117.8 ° C, other measurement results X = 4 ° C, Y = 90 ° C, Z = 6.3 ° C, T = 113.2 ° C (the values of X and T are different) If A, B, and C are calculated using the above, the values of A, B, and C are different.

However, since the incoming water temperature X and the outgoing hot water temperature Y are closely related to the refrigerant discharge temperature T and the heating degree Z, actually, even if the conditions for measuring X, Y, Z, and T are changed, the calculation is performed. A, B, C, or A, B, C, D to be used does not change greatly.
Further, in the experiment, the opening degree of the expansion valve 14 was adjusted so that the COP was maximized in an environment where the outside air temperature = 20.5 ° C., the incoming water temperature X ′ = 20 ° C., and the tapping temperature Y ′ = 65 ° C. The COP at that time was 4.92 (Z ′ and T ′ at this time were Z ′ = 10.3 ° C. and T ′ = 85.9 ° C.), but in the same environment, the present embodiment When the heat pump was controlled and the boiling became stable, the COP was 4.91 (T ′ = 85.5 ° C., Z ′ = 10.4 ° C.), and the difference was 0.01. . This means that the heat pump control method according to the present embodiment can ensure a high level of COP.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and all changes in conditions and the like that do not depart from the gist are within the scope of the present invention.
For example, the temperature range of the outside air is not limited to three, and four, five, or other number of temperature regions can be provided.

10: heat pump unit, 11: hot water storage tank, 12: refrigerant circulation circuit, 13: water heat exchanger, 14: expansion valve, 15: evaporator, 16: compressor, 17: pressure switch, 18: hot water circulation circuit, 19 : Circulation pump, 20: Inlet thermistor, 21: Hot water thermistor, 23: Bypass pipe, 24: Three-way valve, 26: Control device, 27: HP control device, 28a-28e: Remaining hot water thermistor, 29: Water supply pipe, 29a Hot water pipe, 30: fan, 31: internal heat exchanger, 32: evaporation thermistor, 33: accumulator, 34: outside thermistor, 35: suction thermistor, 36: discharge pipe thermistor

Claims (7)

In the control method of the heat pump that evaporates the refrigerant decompressed by the expansion valve, absorbs the heat of the outside air, compresses it by the compressor, and uses it as a heat source for heating water with the water heat exchanger,
The temperature X of the water entering the water heat exchanger when the heat energy given to the water by the water heat exchanger is maximum with respect to the unit power consumption of the compressor, the water heat exchanger The temperature Y of hot water discharged from the compressor, the superheat degree Z of the refrigerant sucked into the compressor, and the temperature T of the refrigerant discharged from the compressor are measured under conditions where the temperature T has different values. Thus, three sets of X, Y, Z, and T are obtained, and three sets of X, Y, Z, and T are substituted into T = A × X + B × Y + C × Z, respectively, and A, B, A preparation step of calculating C;
The temperature of the water entering the water heat exchanger is X ′, the temperature of the hot water discharged from the water heat exchanger is Y ′, the superheat degree of the refrigerant sucked into the compressor is Z ′, and the compression The temperature of the refrigerant discharged from the machine is T ′, and X ′, Y ′, Z ′ and T ′ are measured at predetermined time intervals, and the measured X ′, Y ′ and Z ′ are used as the basis. The target discharge temperature T1 that is a calculated value of A × X ′ + B × Y ′ + C × Z ′ is acquired, and the expansion valve of the expansion valve is adjusted so that the measured temperature T ′ approaches the target discharge temperature T1. And a heating control step of heating the water by adjusting an opening degree. In the heat pump control method according to claim 1, in the preparation step, the temperature of the outside air is divided into a plurality of temperature regions, and the A, B, and C are calculated for each temperature region,
In the heating control step, the temperature of the outside air is measured together with the measurement of the X ′, Y ′, Z ′, and T ′, and is calculated in the preparation step for the temperature region to which the measured temperature of the outside air belongs. A method of controlling a heat pump, wherein the target discharge temperature T1 is calculated from A × X ′ + B × Y ′ + C × Z ′ using A, B, and C. 2. The heat pump control method according to claim 1, wherein when A, B, or C calculated in the preparation step is a value outside a predetermined range W <b> 1 that can be actually stored, T = A × X + B ×. Instead of Y + C × Z, use T = A × X + B × Y + C × Z + D,
Find A, B, C and D where A, B and C are within the predetermined range W1,
In the heating control step, A × X ′ + B × Y ′ + C × Z ′ + D is used instead of A × X ′ + B × Y ′ + C × Z ′ for calculating the target discharge temperature T1. To control the heat pump. In the heat pump control method according to claim 3, in the preparation step, the temperature of the outside air is divided into a plurality of temperature regions, and the A, B, C, and D are calculated for each temperature region,
In the heating control step, the temperature of the outside air is measured together with the measurement of the X ′, Y ′, Z ′, and T ′, and is calculated in the preparation step for the temperature region to which the measured temperature of the outside air belongs. A control method for a heat pump, wherein the target discharge temperature T1 is calculated from A × X ′ + B × Y ′ + C × Z ′ + D using A, B, C, and D. 5. The heat pump control method according to claim 1, wherein, in the heating control step, the target discharge temperature T <b> 1 is lower than a target hot water temperature Y <b> 1 of hot water discharged from the hydrothermal exchanger. In this case, the heat pump control method is characterized in that the opening degree of the expansion valve is adjusted so that the measured temperature T ′ approaches the target tapping temperature Y1. 5. The heat pump control method according to claim 1, wherein in the heating control step, when the target discharge temperature T <b> 1 is higher than a preset limit temperature H, the temperature T Adjusting a degree of opening of the expansion valve so as to approach the limit temperature H. 7. The heat pump control method according to claim 1, wherein, in the heating control step, the target discharge temperature T <b> 1 is maintained in a predetermined stable temperature region W <b> 2 for a preset time or more. When the temperature X ′ becomes higher than a preset temperature and the target discharge temperature T1 is outside the stable temperature region W2, the temperature T ′ is within the stable temperature region W2. A control method for the heat pump, wherein the opening degree of the expansion valve is adjusted so as to approach the temperature of the heat pump.

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