JP2016075425A - Hot water supply system and operation control method of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress temperature drop in a secondary side outlet of a heat exchanger to a minimum even in the case where a winter defrosting operation is necessary, in a hot water supply system in which a heat pump water heater and the heat exchanger are disposed.SOLUTION: A hot water supply system 1 includes: a heat pump water heater 11; a heat exchanger 12; a hot water storage tank 15 for storing hot water supplied from an outlet of a secondary side flow passage 14 of the heat exchanger; temperature sensors 37, 38 for detecting water temperature T3 of a primary side inlet of the heat exchanger 12 and water temperature T4 of a secondary side outlet of the heat exchanger 12 respectively; a circulation pump 17 for supplying cold water to the secondary side flow passage 14 from a lower part water outlet 24 of the hot water storage tank 15; and a control unit 20. In a predetermined period after the completion of a defrosting operation of the heat pump water heater 11, the control unit 20 controls a circulation flow rate supplied to the secondary side flow passage 14 so that the temperature T4 of the secondary side flow passage 14 outlet maintains constant preset temperature without following the temperature T3 of the primary side flow passage 13 inlet.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a hot water supply system in which a heat pump hot water heater is connected to a hot water storage tank that stores hot water and supplies it to a hot water supply load, and a control method thereof.

  A heat pump water heater (hereinafter referred to as “HP” as appropriate) is often used to store hot water in a hot water storage tank at night and use it the next morning. There is also a system in which a heat pump water heater is not directly connected to a hot water storage tank, but a heat exchanger is interposed between the heat pump water heater and the hot water storage tank. Since the capacity of the hot water storage tank can be reduced by increasing the heat storage temperature, equipment and control capable of maintaining the hot water temperature as high as possible are required even in a system using a heat exchanger.

  For example, what is shown in the following patent document 1 is mentioned as a system which installed the heat pump water heater and the heat exchanger.

  FIG. 5 schematically shows a schematic configuration of a hot water supply system for a small-scale facility. The heat pump water heater 11, the heat exchanger 12, and the hot water storage tank 15 are installed at 1: 1: 1, and the HP outlet temperature (the inlet temperature of the primary side flow path 13 of the heat exchanger) T3 and the secondary side of the heat exchanger The circulation flow rate on the secondary side is controlled so that the difference (T3-T4) in the outlet temperature T4 of the flow path 14 maintains a constant temperature. Thereby, HP inlet temperature (outlet temperature of the primary side flow path 13 of the heat exchanger) can always be kept low, and high COP (Coefficient of Performance: coefficient of performance) can be maintained.

  In this hot water supply system, the heat pump water heater 11 is generally defrosted once every 60 minutes in winter (frosting period). During the defrost operation, the heating capacity becomes 0, and both the heating capacity and the outlet temperature T3 decrease for about 5 to 20 minutes after the completion of the defrost operation until the steady operation is performed. Of course, while the defrosting operation, the circulation pump 18 with a built-in HP does not stop and operates at a low speed, but if the circulation pump 17 on the secondary side is stopped, the heat storage temperature (T1, T2) in the hot water storage tank does not decrease. . However, for about 5 to 20 minutes after the completion of the defrost operation, the secondary outlet temperature T4 also decreases following the decrease in the HP outlet temperature T3, causing a decrease in the heat storage temperature of the hot water storage tank. For this reason, the capacity of the hot water storage tank is determined in consideration of a decrease in the heat storage temperature.

  In contrast, FIG. 6 schematically shows a schematic configuration of a hot water supply system for medium and large-scale facilities. 6 shows a plurality of sets (two sets here) of the heat pump water heater 11 (11a, 11b) and the heat exchanger 12 (12a, 12b) in FIG. 5, each connected to a common hot water storage tank 15. Thus, each is controlled such that the difference (T3−T4) between the HP outlet temperature T3 and the secondary outlet temperature T4 maintains a constant temperature. The defrost operation is performed individually according to the operation state of the HP, and the tank heat storage temperature (T1, T2) does not decrease if the secondary circulation pump of the target heat exchanger is stopped. However, as in FIG. 5, the secondary side outlet temperature T4 decreases during a predetermined period after completion of the defrost operation, causing a decrease in the heat storage temperature of the hot water storage tank. Here, since the number of defrost operations is the same for each heat pump water heater regardless of the number of installed heat pump water heaters, the influence of a decrease in the heat storage temperature increases in proportion to the number of installed heat pump water heaters. For this reason, as the number of installed heat pump water heaters increases, the amount of low-temperature hot water in the hot water storage tank increases.

JP 2010-65852 A

  As described above, since the HP outlet temperature T3 is lowered during the predetermined period after the completion of the defrost operation, the secondary outlet temperature T4 of the heat exchanger is lowered, and the amount of low-temperature hot water is increased in the hot water storage tank. In the method of controlling the circulation flow rate on the secondary side so that the difference between the HP outlet temperature T3 and the secondary outlet temperature T4 is maintained at a constant temperature, the secondary outlet temperature T4 decreases as the HP outlet temperature T3 decreases. Is inevitable.

  In view of the above problems, the present invention controls a decrease in the secondary side outlet temperature T4 to a minimum even when a defrost operation in winter is necessary in a hot water supply system including a heat pump water heater and a heat exchanger. It is an object of the present invention to provide a hot water supply system and an operation control method thereof.

In order to achieve the above object, a hot water supply system according to the present invention includes:
Heat pump water heater,
Heat exchanger,
Hot water storage tank,
A first pipe provided between an inlet of the heat pump water heater and a primary outlet of the heat exchanger;
A second pipe provided between the outlet of the heat pump water heater and the primary inlet of the heat exchanger;
A third conduit provided between the secondary side outlet of the heat exchanger and the upper water inlet of the hot water storage tank;
A fourth conduit provided between the secondary side inlet of the heat exchanger and the lower outlet of the hot water storage tank;
A temperature sensor that detects a first temperature as the water temperature at the primary side inlet of the heat exchanger and a second temperature as the water temperature at the secondary side outlet of the heat exchanger,
A circulation pump interposed on the third pipe line or the fourth pipe line; and
Based on the detected values of the first temperature and the second temperature, from the lower outlet of the hot water storage tank through the fourth pipe, the secondary flow path of the heat exchanger, and the third pipe. A control unit for adjusting the circulation flow rate of the circulation path to the upper water inlet of the hot water storage tank,
The controller is
A first control for controlling the circulation flow rate so that the second temperature does not follow the change in the first temperature and maintains a constant first adjusted temperature for a predetermined period after the defrosting operation of the heat pump water heater is completed. It is characterized by performing.

The hot water supply system according to the present invention having the above characteristics further includes:
After the elapse of the predetermined period, the control unit
It is preferable to execute a second control for controlling the circulation flow rate so that a difference between the first temperature and the second temperature is maintained at a constant first set temperature difference.

The hot water supply system according to the present invention having the above characteristics further includes:
In the predetermined period, the control unit
When the detected value of the first temperature is higher than the detected value of the second temperature by a second set temperature difference smaller than the first set temperature difference, the first control is executed,
When the difference between the detected value of the first temperature and the detected value of the second temperature is less than the second set temperature difference that is smaller than the first set temperature difference, the second temperature is more than the second temperature than the first temperature. It is preferable to execute the third control for controlling the circulation flow rate so as to maintain the low adjustment temperature equal to or lower than the set temperature difference.

The hot water supply system according to the present invention having the above characteristics further includes:
A temperature sensor that detects a third temperature as a water temperature at the outlet of the primary side of the heat exchanger;
In the predetermined period, the control unit
It is preferable to prioritize the fourth control for controlling the circulation flow rate over the first and third controls so that the rising speed of the third temperature does not exceed a predetermined speed based on the detected value of the third temperature.

The hot water supply system according to the present invention having the above characteristics further includes:
A plurality of sets including one heat pump water heater and one heat exchanger are provided,
It is preferable that the secondary outlets of the heat exchangers of the sets are connected to the upper water inlet of the common hot water storage tank.

In order to achieve the above object, an operation control method for a hot water supply system according to the present invention includes:
Heat pump water heater,
Heat exchanger,
Hot water storage tank,
A first pipe provided between an inlet of the heat pump water heater and a primary outlet of the heat exchanger;
A second pipe provided between the outlet of the heat pump water heater and the primary inlet of the heat exchanger;
A third conduit provided between the secondary side outlet of the heat exchanger and the upper water inlet of the hot water storage tank;
A fourth conduit provided between the secondary side inlet of the heat exchanger and the lower outlet of the hot water storage tank;
A temperature sensor that detects a first temperature as a water temperature at the primary side inlet of the heat exchanger and a second temperature as a water temperature at the secondary side outlet of the heat exchanger, and
An operation control method for a hot water supply system comprising a circulation pump interposed on the third pipeline or the fourth pipeline,
In a predetermined period after the defrost operation of the heat pump water heater is completed,
From the lower outlet of the hot water storage tank, the fourth pipe, the secondary of the heat exchanger, so that the second temperature does not follow the change in the first temperature and maintains a constant first adjusted temperature. The first control for adjusting the circulation flow rate of the circulation path reaching the upper water inlet of the hot water storage tank through the side flow path and the third pipe line is performed.

The operation control method of the hot water supply system according to the present invention having the above characteristics further includes:
After elapse of the predetermined period,
It is preferable to execute a second control for adjusting the circulation flow rate so that a difference between the first temperature and the second temperature is maintained at a predetermined first set temperature difference.

The operation control method of the hot water supply system according to the present invention having the above characteristics further includes:
Using a temperature sensor that detects a third temperature as the water temperature of the primary side outlet of the heat exchanger,
In the predetermined period, it is preferable that priority is given to the control for adjusting the circulation flow rate over the first control so that the rising speed of the third temperature does not exceed the predetermined speed.

  According to the hot water supply system having the above characteristics or the operation control method thereof, the water temperature (second temperature: T4) at the secondary side outlet of the heat exchanger during a predetermined period in which the heat pump hot water heater shifts to the steady operation after the completion of the defrost operation. ) Controls the circulation flow rate of the secondary flow path so as to maintain a constant temperature without following the change in the water temperature (first temperature: T3) at the primary side inlet of the heat exchanger. As a result, even when winter defrost operation is necessary, the decrease in the secondary side outlet temperature T4 accompanying the decrease in the primary side inlet temperature T3 after the defrost operation is controlled to the minimum, and the heat storage temperature of the hot water storage tank is reduced. Can be suppressed.

The system block diagram which shows typically the schematic structure in one Embodiment of the hot water supply system which concerns on this invention The flowchart which shows the operation control method in one Embodiment of the hot water supply system which concerns on this invention. The flowchart which shows the operation control method in one Embodiment of the hot water supply system which concerns on this invention. The system block diagram which shows typically the schematic structure in one Embodiment of the hot water supply system which concerns on this invention System configuration diagram schematically showing an example of a schematic configuration of a conventional hot water supply system System configuration diagram schematically showing an example of a schematic configuration of a conventional hot water supply system

  Hereinafter, embodiments of a hot water supply system according to the present invention and an operation control method thereof (hereinafter referred to as “the present invention method” as appropriate) will be described with reference to the drawings. In the present embodiment, the same components and the same parts as those of the hot water supply system having the conventional configuration shown in FIG. 5 will be described with the same reference numerals for easy understanding of the present invention.

  FIG. 1 is a system configuration diagram schematically showing a schematic configuration in an embodiment of a hot water supply system 1 according to the present invention. In the drawing, piping through which hot water flows is shown by a solid line for simplicity, and a control signal line for controlling the hot water supply system is shown by a dotted line. As shown in FIG. 1, the hot water supply system 1 includes a heat pump water heater 11, a heat exchanger 12, a hot water storage tank 15, and a control unit 20.

The heat pump water heater 11 is configured by a CO ₂ heat pump adopting, for example, CO ₂ as a refrigerant of the heat pump circuit, and the heat pump water heater 11 of the heat pump water heater 11 is connected from the primary side outlet of the heat exchanger 12 via the pipe line (first pipe line) 31. The low temperature water supplied to the water inlet is heated by exchanging heat with heat released from the condenser of the heat pump circuit, and hot water is supplied at the water outlet of the heat pump water heater 11. This hot water is provided to the primary side inlet of the heat exchanger 12 through a pipe line (second pipe line) 32.

  The heat exchanger 12 includes a primary flow path 13 and a secondary flow path 14, and as described above, the hot water heated by the heat pump water heater 11 passes through the pipe line 32 and enters the primary flow path 13 ( To the primary inlet). On the other hand, the outlet (secondary outlet) of the secondary side flow path 14 is connected to the upper water inlet 21 of the hot water storage tank through the conduit (third pipe) 33 via the motor-operated valve 16. The lower water outlet 24 passes through a pipe line (fourth pipe line) 34 and is connected to an inlet (secondary side inlet) of the secondary side flow path 14 via a circulation pump 17 interposed on the pipe line 34. The Thereby, the cold water supplied to the secondary side flow path 14 is heated by heat exchange with the hot water supplied to the primary side flow path 13, and the hot water heated by the heat exchange is the upper water inlet 21 of the hot water storage tank 15. To be supplied.

  The hot water storage tank 15 stores hot water supplied from the secondary side outlet of the heat exchanger 12 and provides hot water from a water outlet 22 provided on the upper part when a hot water supply load is generated. The wall of the hot water storage tank 15 is provided with a water inlet through which water flows into the hot water storage tank 15 and a water outlet through which water flows out of the hot water storage tank 15. Specifically, the water inlet 21 and the water outlet 22 are provided in the upper part, and the water inlet 23 and the water outlet 24 are provided in the lower part, respectively. When the heat pump water heater 11 is in operation, the cold water from the lower outlet 24 is supplied to the secondary inlet of the heat exchanger 12 by the circulation pump 17 and is heated by heat exchange with the primary flow path 13. It is supplied to the upper water inlet 21.

  Thereby, in the hot water supply system 1, in the heat pump water heater 11, the pipe line 32, the primary side flow path 13 of the heat exchanger 12, and the primary side circulation path consisting of the pipe line 31, the hot water storage tank 15, the pipe line 34, A secondary-side circulation path composed of the secondary-side flow path 14 and the pipe line 33 of the heat exchanger 12 is formed, and the water in these two circulation paths is not mixed.

  Further, the hot water storage tank 15 is provided with temperature sensors 35 and 36 for detecting the water temperature at a predetermined position in the vertical direction in the hot water storage tank 15.

  Water has a property of moving upward as the temperature increases, so-called convection. The hot water storage tank 15 is supplied with low-temperature water from a water inlet 23 provided in the lower part and is supplied with high-temperature water from a water inlet 21 provided in the upper part. The water temperature distribution which becomes high temperature will be shown.

  Further, a temperature sensor 37 that detects the temperature of water flowing into the primary side flow path 13 on the primary side inlet side of the heat exchanger 12 on the pipe line 32, and a secondary side outlet of the heat exchanger 12 on the pipe line 33. The temperature sensor 38 for detecting the temperature of the water flowing out from the secondary channel 14 on the side, the temperature of the water flowing out from the primary channel 13 on the primary outlet side of the heat exchanger 12 on the conduit 31 A temperature sensor 39 for detection is provided for each.

  Control unit 20 controls the operation of hot water supply system 1 based on the temperature detected by temperature sensors 35-39. In particular, the control unit 20 controls the motor-operated valve 16 or the circulation pump 17 based on the temperature detected by the temperature sensors 37 to 39, and the upper water inlet 21 of the hot water storage tank 11 during the defrost operation and a predetermined period after the defrost operation. Suppresses the supply of low temperature water. In addition, the control method of the motor operated valve 16 or the circulation pump 17 at this time will be described later.

  Further, the control unit 20 controls the operation and stop of the heat pump water heater 11. On the other hand, in the present embodiment, once the heat pump water heater 11 is operated, the heat pump water heater 11 is basically set to a discharge water temperature (here, 70 ° C.) independently of the control from the control unit 20. Thus, the water temperature is automatically controlled. Here, the water temperature control of the heat pump water heater 11 is performed by flow control by the built-in circulation pump 18 and output adjustment of the compressor.

  In addition, on the pipes 31 to 34, necessary ones such as an on-off valve (two-way valve), a check valve, a pressure reducing valve, a constant flow valve, a safety valve, and an automatic air vent valve are interposed. The illustration is omitted.

  Below, the operation control of the hot water supply system 1 is demonstrated in detail.

  First, the operation during normal operation will be described. In the present embodiment, the operation control of the hot water supply system 1 is performed based on the temperature detected by the temperature sensors 35-39. Here, the detected temperatures of the temperature sensors 35 to 39 are T1 to T5, respectively. The operation control is executed almost in real time based on the temperature detected by the temperature sensors 35-39.

<Operation during normal operation>
When a hot water supply load is generated, cold water is supplied to the hot water storage tank 15 through the lower water inlet 23. As a result, the temperature of the hot water in the hot water storage tank decreases, and the temperature detected by the temperature sensors 35 and 36 decreases. Among these, when the detection temperature T1 of the temperature sensor 35 provided on the upper side of the hot water storage tank 15 falls below a predetermined temperature (for example, 35 ° C.), the heat pump water heater 11 is operated, the circulation pump 17 is operated, Heated hot water (here, 60 ° C.) heat-exchanged through the exchanger 12 is replenished from the upper water inlet 21. As a result, the hot water temperature in the hot water storage tank rises, and the heat pump water heater 11 and the circulation until the temperature T2 detected by the temperature sensor 36 provided on the lower side of the hot water storage tank 15 reaches a predetermined temperature (for example, 50 ° C.) or higher. Run the pump. As a result, the hot water storage tank is filled with hot water at a substantially set temperature (here, 60 ° C.) from the top to the position of the temperature sensor 36. The water temperature at the secondary side outlet of the heat exchanger 12, which is the temperature of hot water supplied to the hot water storage tank at this time, will be referred to as a first adjusted temperature.

  At this time, the control unit 20 determines the difference between the detected temperature T3 at the primary side inlet of the heat exchanger 12 detected by the temperature sensor 37 and the detected temperature T4 at the secondary side outlet of the heat exchanger 12 detected by the temperature sensor 38. The opening of the motor-operated valve 16 is controlled so that T3-T4 maintains a predetermined first set temperature difference ΔT1 (for example, about 10 ° C.), and the flow rate flowing into the secondary side flow path of the heat exchanger is set. Control.

  Here, the flow rate per unit time of the hot water flowing through the primary side flow path 13 is f1, and the flow rate per unit time of the hot water flowing through the secondary side flow path 14 is f2. Although not shown in FIG. 1, the water temperature on the pipe 34 on the secondary inlet side of the heat exchanger 12 is T6. Since the amount of heat per unit time released in the primary flow path 13 of the heat exchanger 12 and the amount of heat Q per unit time absorbed in the secondary flow path 14 are equal, the following equation 1 is approximated: It holds true. Here, C is the specific heat of the fluid.

[Equation 1]
Q = C (T3-T5) f1 = C (T4-T6) f2

  If T3, T5, and f1 do not change from Equation 1, T4 increases by decreasing f2, and T4 decreases by increasing f2. Therefore, for example, when the detected temperature T4 is lower than T3-ΔT1, the motor-operated valve 16 is throttled, and the flow rate f2 is controlled stepwise until T3-T4 matches ΔT1, and the detected temperature T4 is lower than T3-ΔT1. If it is higher, the motor-operated valve 16 is opened, and control is performed to increase f2 step by step until T3-T4 matches ΔT1, whereby T3-T4 can be maintained and controlled at a constant temperature difference ΔT1.

On the other hand, the heat quantity Q exchanged in the heat exchanger can be generally expressed by the following formula 2 where K is the overall heat transfer coefficient and A is the heat transfer area. Here, ΔT _LMTD is called the logarithmic average temperature difference.

[Equation 2]
Q = K ・ A ・ ΔT _LMTD
ΔT _LMTD = (ΔT _A −ΔT _B ) / ln (ΔT _A / ΔT _B )
ΔT _A = T3-T4, ΔT _B = T5-T6

  The overall heat transfer coefficient K is a proportionality coefficient determined by the shape of the heat exchanger, the physical properties of the fluid, and the flow rate. In the present invention, the overall heat transfer coefficient K may be considered constant as long as the flow rate does not change significantly. Assuming that T3 and T6 are known, T4 and T5 can be calculated from the above equations 1 and 2.

<Operation during defrost operation>
In the winter season (frosting season), the defrost operation is performed once every about 60 minutes for about 5 minutes. The frequency and time of the defrost operation vary depending on the outside air temperature and humidity. During this period, the heating capacity of the heat pump water heater 11 becomes zero. At this time, the circulation pump 18 built in the heat pump water heater 11 is stopped or operated at a low flow rate. The control unit 20 stops the circulation pump 17. As a result, the flow rate at the secondary outlet of the heat exchanger becomes zero, and the heat storage temperature of the hot water storage tank does not decrease.

<Operation after defrost operation>
After completion of the defrost operation, the temperature T3 at the primary side inlet of the heat exchanger 12 is decreased (for example, from 70 ° C. to 55 ° C.). For this reason, the control unit 20 gives priority to the maintenance of the secondary side outlet temperature T4 regardless of the temperature difference T3-T4 from the secondary side outlet for a predetermined period (for example, 20 minutes) until the steady operation is performed. Take control.

From Equation 1, when the detected temperature T4 is lower than the target temperature TA (here, 60 ° C.), the motorized valve 16 is throttled to control the flow rate f2 step by step, and the detected temperature T4 is lower than the target temperature TA. When it is high, the motor-operated valve 16 is opened, and when it is high, T2 can be controlled toward a predetermined target temperature by performing control to increase f2 stepwise. Alternatively, by obtaining a flow rate f1 from a flow meter or heat pump water heater 11 separately provided on the pipe line 31 or 32 and separately providing a temperature sensor for detecting T6 on the pipe line 36, T4 can be directly obtained from the equation (1). Can be set to the optimum flow rate f2.
When the detected temperature T3 is lower than the target temperature TA, as will be described later, the target temperature TA can be set to a temperature lower than T3 by a predetermined temperature difference ΔT2, and the flow rate f2 can be controlled. .

However, the temperature difference T3−T4 (= ΔT _A ) decreases by maintaining the secondary outlet temperature T4 constant despite the primary inlet temperature T3 being lowered. If the exchange heat quantity Q does not change, the temperature difference T5-T6 (= ΔT _B ) increases so that the logarithmic average temperature difference ΔT _LMTD becomes the same. Therefore, T5 rises assuming that T6 does not change.

  As a result, in the operation control method of the present invention in which T4 is controlled to be constant without following the temperature difference T3-T4, the primary side outlet temperature T5 is increased more than the method in which the temperature difference T3-T4 is controlled to be constant. The temperature difference of T5 becomes small. As a result, the coefficient of performance (COP) of the heat pump water heater 11 is lower than that during normal operation.

  As described above, the heat pump water heater 11 tries to control the HP outlet temperature (substantially equal to the primary inlet temperature T3 of the heat exchanger 12) to be constant, and the HP inlet temperature (primary side of the heat exchanger 12). With the change in the outlet temperature T5, the flow rate f1 and the compressor output are automatically adjusted. However, if the rising speed of T5 is fast, the output of the compressor will change abruptly in accordance with it, and the burden on the compressor will greatly affect the life. Therefore, it is preferable to suppress the rising speed of the primary side outlet temperature T5 to a certain speed or less (for example, within 1 ° C./min) according to the capability of the heat pump water heater.

  Therefore, in order to protect the heat pump water heater 11, priority is given to suppressing the rising speed of T5 over maintaining T4, and when the rising speed of T5 exceeds the reference value, f2 is increased so that the rising speed is increased. It is preferable to control so as to keep it below a certain level.

  Further, the temperature difference T3-T4 in the case where T4 is maintained at a constant temperature is a temperature TA to be maintained at a constant temperature so that a second set temperature difference ΔT2 which is smaller than the temperature difference ΔT1 during normal operation is maintained. It is good to set. Preferably, ΔT2 is about 50% or more of ΔT1, and for example, if ΔT1 = 10 ° C., TA may be set so that T3-T4 maintains a temperature difference of 5 ° C. or more. Therefore, when T3 is higher by ΔT2 or more than the secondary side outlet temperature (first adjustment temperature) during normal operation, TA is set to the first adjustment temperature, but the temperature difference between T3 and the first adjustment temperature is When T3 decreases until it becomes less than ΔT2, TA is reset to T3-ΔT2 (second adjustment temperature) lower than the first adjustment temperature. In other words, the target temperature TA at which T4 should be maintained at a constant temperature may be set to the lower of the first adjustment temperature and the second adjustment temperature.

  As a result, when the outlet temperature T3 of the heat pump water heater 11 decreases by ΔT1-ΔT2 or more after the defrost operation or when the rising speed of T5 is faster, T4 decreases from the first adjustment temperature, and the hot water storage tank In some cases, hot water having a temperature lower than that during normal operation may flow in. However, by performing the control based on the secondary side outlet temperature T4 instead of the control based on T3-T4, the decrease in the hot water temperature is suppressed to the minimum. Thereby, it becomes possible to suppress the fall of secondary side exit temperature T4, making the heat pump water heater 11 operate stably.

  2 and 3 are flowcharts showing the operation control method of the hot water supply system 1.

  In step S101 in FIG. 2, the control unit 20 refers to the temperature detected by the temperature sensor 35 and determines whether or not T1 has decreased below a predetermined temperature (in this case, 35 ° C.). If T1 is lower than the predetermined temperature (YES branch in step S101), the process proceeds to step S102.

  In step S102, the heat pump water heater 11 is operated, and in step S103, the operation of the secondary circulation pump 17 is started.

  In step S104, the heat pump water heater 11 determines whether or not a predetermined period (here, 20 minutes) has elapsed since the completion of the defrost operation. When the elapsed time after completion of the defrost operation is within the predetermined period (YES branch in step S104), the process proceeds to step S109 in FIG. On the other hand, when the predetermined period has already elapsed since the completion of the defrost operation (NO branch in step S104), the process proceeds to step S105.

  In step S105, as a control operation during normal operation, the control unit 20 determines that the difference T3-T4 between the detected temperature T3 of the temperature sensor 37 and the detected temperature T4 of the temperature sensor 38 is a predetermined temperature difference ΔT1 (for example, 10 C) is controlled so as to adjust the flow rate f2 flowing into the secondary side flow path 14.

  After step S105, in step S106, the control unit 20 refers to the temperature detected by the temperature sensor 36 and determines whether T2 has exceeded a predetermined temperature (in this case, 50 ° C.). If T2 exceeds the predetermined temperature (YES branch in step S106), the process proceeds to step S107. On the other hand, if T2 is equal to or lower than the predetermined temperature (NO branch in step S106), the process returns to step S104.

  In step S107, the operation of the heat pump water heater 11 is stopped. In step S108, the secondary circulation pump 17 is stopped, and the process returns to step S101.

  On the other hand, when the elapsed time after the completion of the defrost operation is within the predetermined period (YES branch in step S104), in step S109 in FIG. 3, the control unit 20 determines that the detected temperature T4 of the temperature sensor 38 is constant. Control is performed to adjust the flow rate flowing into the secondary channel 14 so as to maintain TA. The set temperature TA here is basically the same as the secondary outlet temperature (first adjustment temperature, here 60 ° C.) during normal operation (step S105), but as described above, T3-T4 When the temperature difference between T3 and the first adjustment temperature is less than ΔT2, the second adjustment temperature lower than the first adjustment temperature may be set so that the temperature difference is maintained at the above-described second set temperature difference ΔT2. is there.

  After step S109, in step S110, the control unit 20 detects the changing speed of the inlet side temperature T5 of the heat pump water heater 11, and determines whether or not the rising speed of T5 exceeds the reference value. When the rising speed of T5 exceeds the reference value (YES branch in step S110), the process proceeds to step S111 to perform a control to increase the flow rate f2 flowing into the secondary side flow path 14, and thereafter, step S106 in FIG. Proceed to On the other hand, if T5 has not increased, or if the increasing speed of T5 is below the reference value (NO branch in step S110), the process proceeds to step S106 in FIG. 2 without executing step S111.

  FIG. 4 shows another configuration example of the hot water supply system of the present invention. The hot water supply system 2 shown in FIG. 4 includes a plurality of sets (here, two sets) of sets of heat pump water heaters 11a and heat exchangers 12a and heat pump water heaters 11b and heat exchangers 12b. The side flow paths 14a and 14b are connected to the common hot water storage tank 15 by pipe lines 40 and 41, respectively. The control unit 20 controls the opening degree of the electromagnetic valve 16a interposed on the pipe line 33a based on the detected temperatures of the temperature sensors 37a to 39a, adjusts the flow rate of the secondary side flow path 14a, and the temperature sensor 37b. Based on the detected temperature of .about.39b, the opening degree of the electromagnetic valve 16b interposed on the pipe line 33b is controlled to adjust the flow rate of the secondary side flow path 14b. When the operation is controlled according to the flow shown in FIG. 2 and FIG. 3, each heat pump water heater is configured so that the detected temperature T1 of the temperature sensor 31 is lower than a predetermined temperature (if the defrost operation is being performed, The operation is started (waiting for completion), and when the detected temperature T2 of the temperature sensor 32 rises from another higher set temperature, the operation of all the heat pump water heaters is stopped. However, in order that the periods during which the defrost operation is performed in the respective heat pump water heaters do not have to coincide with each other, the flow rate adjustment control may be one of control for maintaining T3-T4 and control for maintaining T4 constant. In accordance with the timing of completion of the defrost operation of each heat pump water heater, the heat pump water heater is performed independently in each group.

  In the case of a configuration including a plurality of heat pump water heaters as shown in FIG. 4, the timing of each defrost operation is shifted, and the period during which the secondary side outlet temperature T4 may decrease in at least one set increases. By controlling the operation of the hot water supply system, it is possible to suppress the supply of low-temperature hot water to the hot water storage tank, and to suppress the decrease in the heat storage temperature of the hot water storage tank.

  As described above, in the hot water supply systems 1 and 2 of the present invention, the secondary outlet temperature T4 of the heat exchanger 12 is changed to the primary inlet temperature T3 during a predetermined period in which the heat pump water heater 11 shifts to the steady operation after the completion of the defrost operation. By controlling the circulation flow rate of the secondary side flow path 14 so as to maintain a constant temperature without following the change of the secondary side temperature T4 of the secondary side outlet temperature T4 accompanying the decrease in the primary side inlet temperature T3 after the defrost operation. The decrease can be controlled to the minimum, and the decrease in the heat storage temperature of the hot water storage tank can be suppressed. Moreover, since it can return to setting temperature in a short time even if primary side inlet_port | entrance temperature T3 falls, heat storage temperature can be made high and it becomes possible to implement | achieve the system with a large heat storage amount with respect to a small hot water storage tank capacity.

  In addition, since the rate of increase in the primary side outlet temperature (HP inlet temperature) T5 can be controlled below the reference value, stable operation without sudden changes in the refrigerant pressure or hot water temperature of the heat pump water heater becomes possible.

<Another embodiment>
Another embodiment will be described below.

  <1> The operation control of the hot water supply system of the present invention can also be applied to the operation control of a hybrid hot water supply system in which a combustion water heater is provided on the secondary side of the hot water storage tank. In the case of the hybrid hot water supply system, control with priority given to the COP of the heat pump water heater may be required over the heat storage temperature of the hot water storage tank. However, this control method uses the reference value of the inlet temperature T5 of the heat pump water heater and its rising speed. Since it can be freely adjusted, it is possible to switch to control giving priority to COP.

  That is, in step S110 of FIG. 3, the reference value of the rising speed of the primary outlet temperature (HP inlet temperature) T5 is set low, thereby suppressing the increase in T5 and suppressing the decrease in T3-T5. The water heater can be operated with priority on efficiency. On the other hand, by setting the reference value of the rate of increase of the inlet temperature T5 low, T4 cannot be maintained at the set temperature, and there is a high possibility that the heat storage temperature of the hot water storage tank decreases. Is reheated to prevent low-temperature hot water from being supplied to the hot water supply load. By applying the operation control of the hot water supply system of the present invention, the hybrid hot water supply system can operate the heat pump water heater with high efficiency even in the winter season when the defrost operation of the heat pump water heater is necessary, and the hot water by the combustion water heater By optimizing the fuel consumption required for the reheating of the system, the system as a whole can save more energy.

  <2> In the above embodiment, when the flow rate control of the secondary flow path 14 (14a, 14b) of the heat exchanger 12 (12a, 12b) is performed by proportional control of the opening degree of the electric valve 16 (16a, 16b). However, the discharge amount may be adjusted by inverter control of AC power supplied to the circulation pump 17 (17a, 17b). Moreover, you may carry out by control of both the motor operated valve 16 and the circulation pump 17. FIG.

  <3> In the above embodiment, the circulation pump 17 is on the pipe line 34 upstream of the secondary side flow path 14 of the heat exchanger 12, and the motor operated valve 16 is on the pipe line 33 downstream of the secondary side flow path 14. However, the circulation pump 17 can be interposed on the pipe line 33 and the motor-operated valve 16 can be interposed on the pipe line 34, respectively.

  <4> Further, as the heat exchanger 12, a parallel flow type may be used in addition to the counter flow type shown in FIG.

  <5> In the above embodiment, for the operation and stop control of the heat pump water heater 11, the heat pump water heater is operated based on the detected temperature T1 of the temperature sensor 35, and the heat pump is based on the detected temperature T2 of the temperature sensor 36. The hot water heater is controlled to stop. However, the present invention is not limited to this, and other control conditions may be set for each of operation and stop.

  On the other hand, when the operation control method of the above embodiment is used, for the temperature sensors 35 and 36, whether or not the hot water temperature T1 in the hot water storage tank 15 is lower than a predetermined temperature (for example, 35 ° C.), or T2 is a predetermined temperature. (For example, it is used to determine whether or not the temperature exceeds 50 ° C.), it is not necessary to detect the actual temperature. For example, a switch such as a thermostat that switches on and off at a predetermined temperature. Can be substituted.

  <6> Furthermore, in the said embodiment, although the one tank type thing was assumed as the hot water storage tank 11, the multiple tank type which connected the some hot water storage tank in series may be sufficient. In this case, the water temperature distribution of the hot water storage tanks is formed not only in the vertical direction in each tank but also in the order in which the tanks are arranged. Therefore, the temperature sensor 35 is provided in the tank existing in the middle in the arrangement order. The temperature sensor 36 can be provided in a tank closest to the pipe line 34.

  <7> Moreover, in the said embodiment, the temperature setting demonstrated by the operation control of the hot water supply system is an example, and this invention is not limited to this.

  A hot water supply system and an operation control method thereof according to the present invention are hot water supply systems that supply hot water heated by a heat pump hot water supply to a hot water supply load, and a heat exchanger is disposed between the heat pump hot water supply and a hot water storage tank that stores hot water. It can be used for operation control of a hot water supply system.

1, 2: Hot water supply system 11 (11a, 11b) according to the present invention: Heat pump water heater 12 (12a, 12b): Heat exchanger 13 (13a, 13b): Primary channel 14 (14a, 14b): Secondary Side channel 15: Hot water storage tank 21: Upper water inlet 22: Upper water outlet 23: Lower water inlet 24: Lower water outlet 16 (16a, 16b): Electric valve 17 (17a, 17b): Circulation pump 18: Heat pump water heater Built-in circulation pump 20: Control units 31-34, 31a, 13b, 32a, 32b, 33a, 33b, 34a, 34b, 40, 41: Pipe lines 35-39, 37a, 37b, 38a, 38b, 39a, 39b: Temperature sensor

Claims (8)

Heat pump water heater,
Heat exchanger,
Hot water storage tank,
A first pipe provided between an inlet of the heat pump water heater and a primary outlet of the heat exchanger;
A second pipe provided between the outlet of the heat pump water heater and the primary inlet of the heat exchanger;
A third conduit provided between the secondary side outlet of the heat exchanger and the upper water inlet of the hot water storage tank;
A fourth conduit provided between the secondary side inlet of the heat exchanger and the lower outlet of the hot water storage tank;
A temperature sensor that detects a first temperature as the water temperature at the primary side inlet of the heat exchanger and a second temperature as the water temperature at the secondary side outlet of the heat exchanger,
A circulation pump interposed on the third pipe line or the fourth pipe line; and
Based on the detected values of the first temperature and the second temperature, from the lower outlet of the hot water storage tank through the fourth pipe, the secondary flow path of the heat exchanger, and the third pipe. A control unit for adjusting the circulation flow rate of the circulation path to the upper water inlet of the hot water storage tank,
The controller is
A first control for controlling the circulation flow rate so that the second temperature does not follow the change in the first temperature and maintains a constant first adjusted temperature for a predetermined period after the defrosting operation of the heat pump water heater is completed. A hot water supply system characterized by executing. After the elapse of the predetermined period, the control unit
2. The hot water supply system according to claim 1, wherein a second control is performed to control the circulating flow rate so that a difference between the first temperature and the second temperature maintains a constant first set temperature difference. In the predetermined period, the control unit
When the detected value of the first temperature is higher than the detected value of the second temperature by a second set temperature difference smaller than the first set temperature difference, the first control is executed,
When the difference between the detected value of the first temperature and the detected value of the second temperature is less than the second set temperature difference that is smaller than the first set temperature difference, the second temperature is more than the second temperature than the first temperature. 3. The hot water supply system according to claim 1, wherein a third control for controlling the circulating flow rate is performed so as to maintain the low second adjustment temperature or more by a set temperature difference. A temperature sensor that detects a third temperature as a water temperature at the outlet of the primary side of the heat exchanger;
In the predetermined period, the control unit
Based on the detected value of the third temperature, the fourth control for controlling the circulation flow rate is prioritized over the first and third controls so that the rising speed of the third temperature does not exceed a predetermined speed. The hot water supply system according to any one of claims 1 to 3. A plurality of sets including one heat pump water heater and one heat exchanger are provided,
The hot water supply according to any one of claims 1 to 4, wherein the secondary side outlet of each of the heat exchangers of the set is connected to the upper water inlet of the common hot water storage tank. system. Heat pump water heater,
Heat exchanger,
Hot water storage tank,
A first pipe provided between an inlet of the heat pump water heater and a primary outlet of the heat exchanger;
A second pipe provided between the outlet of the heat pump water heater and the primary inlet of the heat exchanger;
A third conduit provided between the secondary side outlet of the heat exchanger and the upper water inlet of the hot water storage tank;
A fourth conduit provided between the secondary side inlet of the heat exchanger and the lower outlet of the hot water storage tank;
A temperature sensor that detects a first temperature as a water temperature at the primary side inlet of the heat exchanger and a second temperature as a water temperature at the secondary side outlet of the heat exchanger, and
An operation control method for a hot water supply system comprising a circulation pump interposed on the third pipeline or the fourth pipeline,
In a predetermined period after the defrost operation of the heat pump water heater is completed,
From the lower outlet of the hot water storage tank, the fourth pipe, the secondary of the heat exchanger, so that the second temperature does not follow the change in the first temperature and maintains a constant first adjusted temperature. An operation control method for a hot water supply system, comprising: performing a first control for adjusting a circulation flow rate of a circulation path that reaches a top water inlet of the hot water storage tank through a side flow path and the third pipeline. After elapse of the predetermined period,
The second control for adjusting the circulating flow rate is executed so that a difference between the first temperature and the second temperature is maintained at a predetermined first set temperature difference. Operation control method for hot water supply system. Using a temperature sensor that detects a third temperature as the water temperature of the primary side outlet of the heat exchanger,
The hot water supply system according to claim 6 or 7, wherein priority is given to control for adjusting the circulating flow rate over the first control so that an increase rate of the third temperature does not exceed a predetermined rate during the predetermined period. Operation control method.

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