JP2018004128A - Hot water supply system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hot water supply system capable of improving heat exchange performance in a heat pump used as a heat source for hot water supply.SOLUTION: A boiling-up control unit 123 is configured to execute first expansion valve control of adjusting opening of an expansion valve 56 so that during execution of boiling-up operation of heating water in a hot water supply tank 11, a discharge overheating degree ΔTe between a detection temperature T2 of a heat medium temperature sensor 65 and a detection temperature T3 of a condensation temperature sensor 57 is within a range of a target discharge overheating degree to the target discharge overheating degree+α, and an overcooling degree ΔTc between the detection temperature T3 and a detection temperature T4 of a heat medium temperature sensor 62 is within a range of a target overcooling degree to the target overcooling degree+β.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a hot water supply system that heats water in a hot water storage tank by a heat pump.

  Conventionally, a heat pump that cools air or water supplied to a heat exchanger by a cooler (evaporator) connected in the middle of the heat medium circulation path is known (for example, see Patent Document 1).

  In the heat pump described in Patent Document 1, the temperature difference (pinch degree) obtained by subtracting the saturated suction temperature (SST), which is the temperature of the heat medium in the evaporator, from the temperature (CFT) of the heat medium in the cooler. Heat exchange performance is ensured by keeping it to a minimum.

JP 2001-280713 A

  The heat pump is also used as a heat source of the hot water supply system, and the improvement of heat exchange performance is also demanded in the hot water supply system.

  This invention is made | formed in view of the background which concerns, and it aims at providing the hot water supply system which improved the heat exchange performance in the heat pump used as a heat source of hot water supply.

The hot water supply system of the present invention is
A heat pump having a heat medium circulation path in which a heat medium is enclosed, and a compressor, a condenser, an expansion valve, and an evaporator connected in order by the heat medium circuit;
A hot water storage tank for storing hot water,
A tank circulation path that connects the upper and lower portions of the hot water storage tank, and the condenser is connected in the middle;
A tank circulation pump for circulating the water stored in the hot water storage tank through the tank circulation path;
By operating the heat pump and the tank circulation pump, in the condenser, heat exchange is performed between the heat medium flowing through the heat medium circulation path and the water flowing through the tank circulation path, and the hot water storage The present invention relates to a hot water supply system including a boiling control unit that performs a boiling operation for heating water in a tank.

And the hot water supply system of this invention is
A compressor discharge temperature detector for detecting the temperature of the heat medium discharged from the compressor to the heat medium circuit;
A condensation temperature detector for detecting the condensation temperature of the heat medium in the condenser;
An expansion valve inflow temperature detection unit for detecting the temperature of the heat medium flowing into the expansion valve from the heat medium circulation path,
During the boiling operation, the boiling control unit has a discharge superheat degree that is a difference between a detected temperature of the compressor discharge temperature detecting unit and a detected temperature of the condensing temperature detecting unit within a first predetermined range. And the degree of opening of the expansion valve is set so that the degree of supercooling, which is the difference between the temperature detected by the condensing temperature detector and the temperature detected by the expansion valve inflow temperature detector, falls within the second predetermined range. The first expansion valve control to be adjusted is executed.

  According to the present invention, as conditions for the heating operation that can heat the water in the hot water storage tank with high capacity and high efficiency, “the discharge heating degree is within the first predetermined range” and “the supercooling degree is the first. 2 ”is set within the predetermined range, and the boiling control unit executes the first expansion valve control for adjusting the opening degree of the expansion valve so that these conditions are satisfied during the boiling operation. . As a result, a high-efficiency hot water storage tank that satisfies the required output by maintaining the enthalpy difference in the Ph (pressure-enthalpy) diagram and Th (temperature-enthalpy) diagram in the heat pump cycle within the target range. The water in the inside can be heated.

  In addition, the boiling control unit prohibits the first expansion valve control when the detected temperature of the compressor discharge temperature detection unit exceeds a predetermined upper limit discharge temperature during execution of the boiling operation. The second expansion valve control for increasing the opening degree of the expansion valve is performed, and the discharge allowable temperature at which the detected temperature of the compressor discharge temperature detecting unit is set to be equal to or lower than the upper limit discharge temperature by the second expansion valve control. The second expansion valve control is terminated and the first expansion valve control is executed when the following occurs.

  According to this configuration, when the discharge temperature of the compressor becomes equal to or higher than the discharge upper limit, the opening degree of the expansion valve is increased by the second expansion valve control, so that the hot water supply is lower than the case where the rotation speed of the compressor is decreased. It is possible to protect the compressor by suppressing changes in the operating conditions of the system. The boiling control unit can end the second expansion valve control and promptly start the first expansion valve control when the temperature detected by the compressor discharge temperature detection unit becomes equal to or lower than the discharge allowable temperature.

A compressor suction temperature detector for detecting a temperature of the heat medium sucked into the compressor from the heat medium circulation path;
An evaporator inflow temperature detection unit for detecting the temperature of the heat medium flowing into the evaporator from the heat medium circulation path;
The boiling control unit, during execution of the boiling operation, a suction superheat degree that is a difference between a detected temperature of the compressor intake temperature detecting unit and a detected temperature of the evaporator inflow temperature detecting unit is a predetermined superheat. When the value is lower than the lower limit value, the first expansion valve control is prohibited and the third expansion valve control is executed to reduce the opening of the expansion valve, and the suction superheat degree is controlled by the third expansion valve control. Is equal to or greater than the overheat allowable value set above the overheat lower limit value, the third expansion valve control is terminated and the first expansion valve control is executed.

  According to this configuration, when the suction superheat degree is lower than the superheat lower limit value, there is a possibility that a liquid back from the evaporator to the compressor (a situation where a liquid heat medium is sucked into the compressor) may occur. By reducing the opening degree of the expansion valve by the third expansion valve control, it is possible to protect the compressor by suppressing changes in the operating conditions of the hot water supply system, compared to when the compressor is stopped. The boiling control unit can end the third expansion valve control and promptly start the first expansion valve control when the suction superheat degree becomes equal to or higher than the overheat tolerance.

The block diagram of a hot-water supply system. 2A is a Ph (pressure-enthalpy) diagram in the heat pump cycle, and FIG. 2B is a Th (temperature-enthalpy) diagram in the heat pump cycle. The 1st flowchart of total expansion valve control. The 2nd flowchart of total expansion valve control. The flowchart of the 1st expansion valve control. The flowchart of the 2nd expansion valve control. The flowchart of the 3rd expansion valve control.

  An example of an embodiment of the present invention will be described with reference to FIGS.

[1. Configuration of hot water supply system]
With reference to FIG. 1, the hot water supply system 1 of the present embodiment includes a hot water storage unit 10, a heat pump unit 50, an auxiliary heat source unit 80, and a controller 120 that controls the overall operation of the hot water supply system 1. This is a hybrid hot water supply system.

  In FIG. 1, one controller 120 is shown as the controller of the hot water supply system 1. However, the controller of the hot water storage unit 10, the controller of the heat pump unit 50, and the controller of the auxiliary heat source unit 80 are provided separately, It is good also as a structure which controls the whole action | operation of the hot water supply system 1 by communication.

  The hot water storage unit 10 includes a hot water storage tank 11, a water supply pipe 12, a hot water discharge pipe 13, and the like. The hot water storage tank 11 keeps hot water inside and stores the hot water inside the tank. The hot water storage tank 11 is disposed at substantially equal intervals in the height direction, and detects the temperature th2 to th5 of the hot water in the hot water storage tank 11 at each height. 17 and an in-tank temperature sensor 26 that is disposed above the hot water storage tank 11 and detects the temperature th1 of hot water supplied from the hot water storage tank 11 to the hot water discharge pipe 13 is provided.

  Further, in the vicinity of the connection point between the lower part of the hot water storage tank 11 and the lower part of the hot water storage tank 11 in the tank circulation path 41 connecting the upper part and the lower part of the hot water storage tank 11, the tank lower temperature for detecting the temperature th6 of hot water stored in the lower part of the hot water storage tank 11 A sensor 42 is provided. Furthermore, a drain valve 18 is provided at the bottom of the hot water storage tank 11 and is opened by an operator's manual operation.

  One end of the water supply pipe 12 is connected to a water supply (not shown) via a water supply port 30, and the other end is connected to the lower part of the hot water storage tank 11 to supply water to the lower part of the hot water storage tank 11. The water supply pipe 12 allows water to flow only in the direction from the water supply pipe 12 to the hot water storage tank 11 by preventing the internal pressure of the hot water storage tank 11 from becoming excessive, and to supply water from the hot water storage tank 11. A first hot water side check valve 20 is provided to prevent outflow of hot water to the pipe 12 side.

  A water supply branch pipe 34 branched from the water supply pipe 12 communicates with the hot water discharge pipe 13 at the connection point X through the hot water mixing valve 21, and hot water supplied from the hot water storage tank 11 to the hot water discharge pipe 13 by the hot water mixing valve 21. The mixing ratio with the water supplied from the feed water branch pipe 34 to the tapping pipe 13 is changed.

  The feed water branch pipe 34 detects the temperature Tw of water supplied to the feed water branch pipe 34 (hereinafter referred to as feed water temperature Tw) and the flow rate Fw of water flowing through the feed water branch pipe 34. The water-side flow rate sensor 23 and a water-side check valve 24 that enables water flow only in the direction from the water supply branch pipe 34 to the hot water supply pipe 13 and prevents outflow of hot water from the hot water supply pipe 13 to the water supply branch pipe 34 side. And are provided.

  The hot water discharge pipe 13 has one end connected to the hot water supply port 31 and the other end connected to the upper part of the hot water storage tank 11. Hot water stored in the upper part of the hot water storage tank 11 is supplied from a hot water outlet pipe 13 to a hot water tap (not shown) (kitchen, washroom, bathroom currant, shower, etc.) via a hot water outlet 31. A second hot water side check valve 25 that allows the hot water pipe 13 to pass water only in the direction from the hot water storage tank 11 to the hot water discharge pipe 13 and prevents the hot water from flowing into the hot water storage tank 11 side from the hot water storage pipe 11. A hot water flow rate sensor 27 for detecting the flow rate Fh of hot water supplied from the hot water storage tank 11 to the hot water discharge pipe 13 is provided.

  The auxiliary heat source device 80 is provided in the middle of the downstream side of the connection point X with the feed water branch pipe 34 of the tap water pipe 13, and the hot water storage unit 10 bypasses the auxiliary heat source device 80 and is downstream of the auxiliary heat source device 80. A hot water bypass pipe 33 that connects the hot water outlet pipe 13 to the upstream side and a hot water bypass valve 29 that opens and closes the hot water bypass pipe 33 are provided.

  A mixing temperature sensor 28 for detecting a temperature Tm of hot water supplied to the hot water pipe 13 through the hot water mixing valve 21 is provided between the branching point Y of the hot water pipe 13 and the hot water mixing valve 21. A hot water supply temperature sensor 32 that detects the temperature of the hot water discharged from the hot water supply port 31 is provided between the joining point Z of the hot water supply pipe 13 and the hot water supply bypass pipe 33 and the hot water supply port 31.

  Detection signals from the sensors provided in the hot water storage unit 10 are input to the controller 120. Further, the operation of the hot water mixing valve 21 and the hot water bypass valve 29 is controlled by a control signal output from the controller 120.

  Next, the heat pump unit 50 circulates the hot water in the hot water storage tank 11 through the tank circulation path 41 and heats it, and is installed outdoors. The heat pump unit 50 is an external air heat exchanger connected by a heat pump circuit 52 (corresponding to the heat medium circuit of the present invention) in which a heat medium (an alternative chlorofluorocarbon (HFC) or other chlorofluorocarbon, carbon dioxide, etc.) is enclosed. (Evaporator) 53, compressor 54, water heat exchanger (condenser) 55, and expansion pump 56 are included in heat pump 51.

  The outside air heat exchanger 53 performs heat exchange with a heat medium that absorbs heat from the air (outside air, air) supplied by the rotation of the fan 60 and circulates in the heat pump circulation path 52. The compressor 54 compresses the heat medium flowing out from the outside air heat exchanger 53 to high pressure and high temperature, and discharges it to the water heat exchanger 55. The expansion valve 56 depressurizes the heat medium pressurized by the compressor 54.

  The defrost valve 61 is provided by bypassing the expansion valve 56, and defrosts the outside heat exchanger 53 with a heat medium sent from the compressor 54. Heat medium temperature sensors 62, 63 for detecting the temperature of the heat medium flowing through the heat pump circuit 52 are provided upstream and downstream of the expansion valve 56 of the heat pump circuit 52 and upstream and downstream of the compressor 54. 64 and 65 are provided, respectively. The outside air heat exchanger 53 is provided with an outside air temperature sensor 67 that detects the temperature T6 of the air (outside air) sucked into the outside air heat exchanger 53.

  Hereinafter, the temperature of the heat medium (the temperature of the heat medium sucked into the compressor 54) detected by the heat medium temperature sensor 64 (corresponding to the compressor suction temperature detector of the present invention) is expressed as the compressor suction temperature T1, The temperature of the heat medium (the temperature of the heat medium discharged from the compressor 54) detected by the heat medium temperature sensor 65 (corresponding to the compressor discharge temperature detector of the present invention) is expressed as the compressor discharge temperature T2, the heat medium temperature. The temperature of the heat medium (the temperature of the heat medium flowing into the expansion valve 56) detected by the sensor 62 (corresponding to the expansion valve inflow temperature detection unit of the present invention) is defined as the expansion valve inflow temperature T4 and the heat medium temperature sensor 63 (this The temperature of the heat medium (corresponding to the evaporator inflow temperature detector of the invention) detected (the temperature of the heat medium flowing into the outside air heat exchanger 53) is referred to as the outside air AC input temperature T5.

  The water heat exchanger 55 is connected to the tank circulation path 41, and heat exchange between the heat medium that has been made high-pressure and high-temperature by the compressor 54 and the water circulating in the tank circulation path 41 causes the inside of the tank circulation path 41. Heat the water flowing through. The tank circulation path 41 is provided with a tank circulation pump 66 for circulating hot water in the hot water storage tank 11 through the tank circulation path 41.

  Hot water stored in the lower part of the hot water storage tank 11 is guided to the tank circulation path 41 by the tank circulation pump 66, heated to a predetermined temperature (boiling temperature) by the water heat exchanger 55, and returned to the upper part of the hot water storage tank 11. . Thereby, hot water of a predetermined temperature is sequentially stacked from the upper part of the hot water storage tank 11 and stored.

  On the upstream side of the water heat exchanger 55 in the tank circulation path 41, an incoming water temperature sensor 68 for detecting the temperature (incoming water temperature) T7 of water flowing into the water heat exchanger 55 from the tank circulation path 41 is provided. Further, on the downstream side of the water heat exchanger 55 in the tank circulation path 41, a water discharge temperature sensor 69 for detecting the temperature (water discharge temperature) T8 of water flowing out from the water heat exchanger 55 to the tank circulation path 41 is provided. Yes. Further, the water heat exchanger 55 is provided with a condensing temperature sensor 57 (corresponding to the condensing temperature detecting portion of the present invention) for detecting the condensing temperature T3 of the heat medium in the water heat exchanger 55.

  Detection signals from the sensors provided in the heat pump unit 50 are input to the controller 120. Further, the operations of the compressor 54, the expansion valve 56, the defrost valve 61, the tank circulation pump 66, the fan 60, and the like are controlled by a control signal output from the controller 120.

  Next, the auxiliary heat source unit 80 is for heating hot water flowing through the hot water discharge pipe 13, and includes a hot water supply burner 81 housed in the can body 87, a hot water supply heat exchanger 82 heated by the hot water supply burner 81, and the like. ing.

  A hot water filled pipe 100 communicating with the bathtub 105 is connected to a location downstream of the hot water supply heat exchanger 82 in the hot water discharge pipe 13. The hot water filling pipe 100 is provided with a hot water filling valve 103 for opening and closing the hot water filling pipe 100, and the controller 120 opens the hot water filling valve 103 to open the hot water filling pipe 103 through the hot water filling pipe 100. Hot water is supplied to the bathtub 105.

  Fuel gas is supplied to the hot water supply burner 81 from a gas supply pipe (not shown), and combustion air is supplied from a combustion fan (not shown). The controller 120 controls the amount of combustion of the hot water supply burner 81 by adjusting the flow rates of the fuel gas and the combustion air supplied to the hot water supply burner 81.

  The hot water supply heat exchanger 82 is connected in the middle of the hot water discharge pipe 13, and heats the hot water flowing inside by the combustion heat of the hot water supply burner 81. The hot water discharge pipe 13 is provided with a water stop valve 93 and a water amount sensor 88 in order from the upstream side. The upstream side and the downstream side of the hot water supply heat exchanger 82 are connected by a heat source bypass pipe 89, and the heat source bypass pipe 89 is provided with a heat source bypass valve 90 for adjusting the opening degree of the heat source bypass pipe 89. Yes. A heat exchanger hot water temperature sensor 91 is provided in the vicinity of the outlet of the hot water supply heat exchanger 82 of the hot water discharge pipe 13, and a heat source hot water temperature sensor 92 is provided downstream of the location where the hot water supply pipe 13 is connected to the heat source bypass pipe 89. ing.

  With this configuration, when there is no hot water in the hot water storage tank 11 (when the hot water is in a hot state), the water supplied from the water supply pipe 12 to the hot water discharge pipe 13 through the hot water storage tank 11 and the water supply branch pipe 34 is hot water supply heat. Hot water is heated by the exchanger 82 to be mixed with water from the heat source bypass pipe 89, and hot water having a target hot water supply temperature is supplied from the hot water supply port 31.

  The detection signal of each sensor provided in the auxiliary heat source device 80 is input to the controller 120. Further, the operation of the hot water supply burner 81, the heat source bypass valve 90, and the hot water filling valve 103 is controlled by a control signal output from the controller 120.

  The controller 120 is an electronic circuit unit configured by a CPU, a memory, and the like (not shown), and the hot water supply control unit 121 and the hot water filling control unit 122 are executed by executing a control program for the hot water supply system 1 held in the memory by the CPU. , And functions as a boiling control unit 123. Further, the memory stores various condition data 125 used for the operation of the hot water supply system 1.

  The controller 120 is connected to the remote controller 140 via a communication cable 130. The remote controller 140 includes a display 141 for displaying the operation status of the hot water supply system 1, setting of operation conditions, and the like, and a switch unit 142 provided with various switches. The user of the hot water supply system 1 operates the switch unit 142 of the remote controller 140 to set the temperature of the hot water supplied from the hot water supply port 31 (target hot water supply temperature) or the hot water supply temperature to the bathtub 105 in the hot water filling operation ( The target hot water filling temperature) and the hot water filling amount (target hot water filling amount) can be set.

  When the hot water storage tank 11 has not run out of hot water and the water-side flow rate sensor 23 detects water flow exceeding the lower limit flow rate, the hot water supply control unit 121 determines whether the mixed temperature sensor 28 or the hot water supply temperature sensor 32 Mixing temperature adjustment control is performed to adjust the distribution ratio of the hot and cold water mixing valve 21 so that the detected temperature becomes the target hot water supply temperature. At this time, the hot water supply control unit 121 closes the hot water bypass valve 29 when the hot water filling valve 103 is opened and hot water is supplied to the bathtub 105, and when the hot water filling valve 103 is closed. The hot water bypass valve 29 is opened.

  Further, the hot water supply control unit 121 closes the hot water bypass valve 29 when the hot water storage tank 11 has run out of water and the water flow rate sensor 23 detects water flow exceeding the lower limit flow rate. . Then, when the water amount sensor 88 detects water flow exceeding the lower limit flow rate, the combustion amount (heating amount) of the hot water supply burner 81 is adjusted so that the temperature detected by the heat source hot water temperature sensor 92 becomes the target hot water temperature. Execute heating temperature control.

  The hot water filling control unit 122 ends the hot water filling to the bathtub 105 when an operation for instructing hot water filling (hot water filling start operation) is performed by the switch unit 142 of the remote controller 140 or at a preset reserved time. Thus, the hot water filling operation is performed in which the hot water filling valve 103 is opened and the hot water filling pipe 13 supplies hot water for the target hot water amount to the bathtub 105 via the hot water filling pipe 100. The hot water filling control unit 122 sets the target hot water filling temperature to the target hot water supply temperature, and executes the hot water filling operation.

  The boiling control unit 123 recognizes the amount of hot water stored in the hot water storage tank 11 (hot water storage amount) by monitoring the detected temperatures of the tank temperature sensor 26 and the tank surface temperature sensors 14 to 17. Then, when the remaining amount of hot water in the hot water storage tank 11 falls below the lower limit amount, the tank circulation pump 66 and the heat pump 51 are actuated to bring the hot water in the hot water storage tank 11 to the target boiling according to the set hot water supply temperature. A boiling operation for heating to a raised temperature (for example, 45 ° C.) is performed.

[2. Operation of heat pump]
Next, referring to the Ph (pressure-enthalpy) diagram shown in FIG. 2A and the Th (temperature-enthalpy) diagram shown in FIG. 2B, the heat pump cycle (refrigeration cycle) of the heat pump 51 is described. explain.

  In the Ph diagram shown in FIG. 2A, the horizontal axis is set to the enthalpy h (kJ / kg) of the heat medium, and the vertical axis is set to the pressure P (kPa) of the heat medium. The heat pump cycle of the heat pump 51 (compressor 54 → water heat exchanger 55 → expansion valve 56 → outside air heat exchanger 53 → compressor 54 →...) Is drawn on the liquid line / saturated vapor line.

  In the compressor 54, the heat medium (P, h) changes from (P1, h1) to (P2, h2), and the temperature of the heat medium rises from T1 to T2. In the water heat exchanger 55, the (P, h) of the heat medium changes from (P2, h2) to (P2, h3 (= h4)), and the temperature of the heat medium decreases from T2 to T3 and further to T4. Yes.

  In the expansion valve 56, (P, h) of the heat medium is changed from (P2, h3) to (P1, h4 (= h3)), and the temperature of the heat medium is decreased from T4 to T5. In the outside air heat exchanger 53, the heat medium (P, h) changes from (P1, h4) to (P1, h1), and the temperature of the heat medium rises from T5 to T1.

  In the Th diagram shown in FIG. 2B, the horizontal axis is set to the enthalpy h (kJ / kg) of the heat medium, and the vertical axis is set to the temperature T (° C.) of the heat medium. The heat pump cycle of the heat pump 51 is drawn in the saturated liquid line / saturated vapor line. Tfw in FIG. 2B indicates a rise in temperature in the water heat exchanger 55 of the water flowing through the tank circulation path 41, and the temperature of the water rises from the incoming water temperature T7 to the outgoing water temperature T8.

  In the compressor 54, (T, h) of the heat medium is changed from (T1, h1) to (T2, h2) ((1) → (2)). In the water heat exchanger 55, the heat medium (T, h) is changed from (T2, h2) to (T4, h4) ((2) → (3) → (4), T Is the condensation temperature T3).

  In the expansion valve 56, (T, h) of the heat medium is changed from (T4, h4) to (T5, h4) ((4) → (5)). In the outdoor air heat exchanger 53, (T, h) of the heat medium is changed from (T5, h4) to (T1, h1) ((5) → (1)).

  Here, the heating capacity (boiling capacity) in the water heat exchanger 55 becomes higher as the discharge temperature T2 of the heat medium from the compressor 54 is higher and the inflow temperature T4 of the heat medium to the expansion valve 56 is lower. That is, in the Ph diagram of FIG. 2A and the Th diagram of FIG. 2B, the difference becomes higher as the difference in enthalpy h from (2): T2 to (4): T4 increases.

  Then, the boiling control unit 123 operates the compressor 54 at an optimum rotation speed that satisfies the required boiling capacity and achieves high efficiency operation at a certain boiling target temperature, incoming water temperature T7, and outside air temperature T6. Under the situation where the hot water boiling operation in the hot water storage tank 11 is being executed, there may be a situation where the outlet water temperature T8 does not reach the boiling target temperature due to the stable state of the heat pump cycle and other conditions.

  The optimum rotation speed of the compressor 54 is set according to the boiling target temperature, the incoming water temperature T7, and the outside air temperature T6 based on experiments or computer simulations.

  In this case, it is assumed that the discharge temperature T2 of the compressor 54 and the inflow temperature T4 of the expansion valve 56 are different from the optimum heat pump cycle state that can be confirmed in advance through experiments or the like. Therefore, the boiling control unit 123 can ensure the required boiling capacity (the water discharge temperature T8 becomes the target boiling temperature) “the optimum heat pump cycle state is reached (2): T2 to (4): T4 In order to perform a highly efficient boiling operation that secures the required boiling capacity by controlling the "state", and to protect the compressor 54, the following first to third expansion valve controls are performed. .

(1) First expansion valve control Expansion valve control in a state where the rotation speed instruction of the compressor 54 is constant (the rotation speed instruction of the compressor 54 is not changed). In order to optimize the heat pump cycle, the boiling control unit 123 has a discharge superheat degree ΔTe (= compressor discharge temperature T2−condensing temperature T3) within the range of the target discharge superheat degree to the target discharge superheat degree + α, and The degree of opening of the expansion valve 56 (electronic expansion valve) is adjusted so that the degree of supercooling ΔTc (= condensation temperature T3−expansion valve inflow temperature T4) falls within the range of the target supercooling degree to the target supercooling degree + β. .

(2) Second expansion valve control Control for protecting the compressor 54 when the compressor discharge temperature T2 becomes higher than the upper limit discharge temperature. The boiling control unit 123 monitors the compressor discharge temperature T2 during the boiling operation, and performs a process of increasing the opening degree of the expansion valve 56 when the compressor discharge temperature T2 becomes higher than the upper limit discharge temperature. Do.

(3) Third expansion valve control Control for preventing breakage of the compressor 54 due to liquid back (a phenomenon in which the heat medium in a liquid state that has not been vaporized in the outside air heat exchanger 53 is sucked into the compressor 54). The boiling control unit 123 monitors the intake superheat degree ΔTb (compressor intake temperature T1−external air heat AC input temperature T5) in the outdoor air heat exchanger 53 during the boiling operation, and the intake superheat degree ΔTb is the intake superheat. When it becomes lower than the lower limit value, a process for reducing the opening degree of the expansion valve 56 is performed.

[3. Total expansion valve control]
Next, overall control of the expansion valve (total expansion valve control) executed by the boiling control unit 123 will be described with reference to the flowcharts shown in FIGS. The boiling control unit 123 performs total expansion valve control when the boiling operation is performed.

  In the total expansion valve control, the control state of the expansion valve 56 is switched by the expansion valve control mode. When the second expansion valve control is executed, the first expansion valve control is prohibited and the expansion valve control mode is set to “discharge temperature protection”. When the third expansion valve control is executed, the first expansion valve control is prohibited and the expansion valve control mode is set to “liquid back protection”. Further, when the second expansion valve control and the third expansion valve control are not executed, the expansion valve control mode is set to “normal”.

  In STEP 1 of FIG. 3, the boiling control unit 123 determines whether or not the initial startup operation of the expansion valve 56 (such as the origin of the motor that sets the opening degree of the expansion valve 56) has been completed. Then, when the startup initial operation is completed, the process proceeds to STEP2. When the startup initial operation is not completed, the process branches to STEP 30, and the boiling control unit 123 executes the startup initial operation and proceeds to STEP 31.

  In STEP 31, the boiling control unit 123 determines whether or not an activation standby release condition for the expansion valve 56 is satisfied. Then, when the activation standby release condition is satisfied, the process branches to STEP3, and when the activation standby cancellation condition is not satisfied, the process proceeds to STEP10 of FIG.

  In STEP 2, the boiling control unit 123 determines whether or not the activation waiting time of the expansion valve 56 has elapsed. Then, when the activation standby time has elapsed, the process proceeds to STEP 3 and the control of the expansion valve 56 is started. At this time, the boiling control unit 123 sets the expansion valve control mode to “normal” as an initial setting. On the other hand, when the activation standby time has not elapsed, the process branches to STEP 31.

  In STEP 3, the boiling control unit 123 determines whether or not the heat pump 51 is in the defrosting operation (during operation for eliminating the frosting state of the outside air heat exchanger 53 that absorbs heat from the air). When the defrosting operation is in progress, the process branches to STEP 32, and the boiling control unit 123 executes the expansion valve control for the defrosting operation and proceeds to STEP10 of FIG. On the other hand, when not in the defrosting operation, the process proceeds to STEP4.

  In STEP 4, the boiling control unit 123 determines whether or not the compressor discharge temperature T2 is higher than the upper limit discharge temperature. When the discharge temperature T2 is higher than the upper limit discharge temperature, the process branches to STEP33, and the boiling control unit 123 sets the expansion valve control mode “discharge temperature protection” and proceeds to STEP34. In STEP 34, the boiling control unit 123 executes second expansion valve control (details will be described later), and proceeds to STEP 10 in FIG. On the other hand, when the compressor discharge temperature T2 is equal to or lower than the upper limit discharge temperature, the process proceeds to STEP5.

  In STEP 5, the boiling control unit 123 determines whether or not the expansion valve control mode is set to “discharge temperature protection”. When the expansion valve control mode is set to “discharge temperature protection”, the process branches to STEP34. On the other hand, when the expansion valve control mode is not set to “discharge temperature protection”, the process proceeds to STEP 6.

  In STEP 6, the boiling control unit 123 determines whether or not the suction superheat degree ΔTb is smaller than the suction superheat lower limit value. When the suction superheat degree ΔTb is lower than the suction superheat lower limit value, it is assumed that the liquid back state is in progress. When the suction superheat degree ΔTb is lower than the suction superheat lower limit value, the process branches to STEP35, and the boiling control unit 123 sets the expansion valve control mode to “liquid back protection” and proceeds to STEP36. On the other hand, when the suction superheat degree ΔTb is equal to or higher than the suction superheat lower limit value, the process proceeds to STEP7.

  In STEP 7, the boiling control unit 123 determines whether or not the expansion valve control mode is set to “liquid back protection”. When the expansion valve control mode is set to “liquid back protection”, the process branches to STEP 36. On the other hand, when the expansion valve control mode is not set to “liquid back protection”, the routine proceeds to STEP 8 in FIG.

  In STEP 8, the boiling control unit 123 determines whether or not the rotation speed instruction of the compressor 54 is in a constant state. The boiling control unit 123 branches to STEP 40 when there is a change in the rotation speed instruction of the compressor 54, and the boiling control unit 123 executes the expansion valve control when there is a change in the rotation speed instruction and proceeds to STEP 10. . On the other hand, when the rotation speed instruction of the compressor 54 is constant, the process proceeds to STEP9.

  In STEP 9, the boiling control unit 123 determines whether or not the expansion valve control update timer (timer for measuring the control period for adjusting the opening degree of the expansion valve 56) has expired. Then, when the control update timer is up, the process branches to STEP 41, where the boiling control unit 123 performs first expansion valve control (expansion valve control when the rotation speed instruction of the compressor 54 is in a constant state, Details will be described later), and the process proceeds to STEP42. In STEP 42, the boiling control unit 123 sets the control update timer to X seconds, starts timing, and proceeds to STEP 10.

  On the other hand, when the control update timer has not expired in STEP 9, the process proceeds to STEP10. In STEP 10, the boiling control unit 123 determines whether or not a boiling end condition is satisfied. As the boiling end condition, it is set that the boiling of water in the hot water storage tank 11 has been completed, and that the user has stopped the boiling of water in the hot water storage tank 11.

  When the boiling end condition is satisfied, the process proceeds to STEP 11 and the boiling control unit 123 executes expansion valve control at the end of boiling. On the other hand, when the boiling end condition is not satisfied, the process proceeds to STEP 1 in FIG.

[4. First expansion valve control]
Next, the processing of the first expansion valve control (expansion valve control when the rotation speed instruction of the compressor 54 is in a constant state) executed in STEP 41 of FIG. 4 will be described according to the flowchart shown in FIG.

  The boiling control unit 123 determines whether or not the boiling set temperature has been changed in STEP 50 of FIG. Then, when the boiling set temperature is changed, the process branches to STEP 60, and the boiling control unit 123 sets the target discharge superheat degree and the target supercooling degree according to the boiling set temperature and the incoming water temperature T7, and STEP51. Proceed to On the other hand, when the boiling set temperature is not changed, the process proceeds to STEP 51.

  In STEP 51, the boiling control unit 123 determines whether or not the discharge superheat degree Te is lower than the target discharge superheat degree. When the discharge superheat degree ΔTe is lower than the target discharge superheat degree, the process branches to STEP 61, and the boiling control unit 123 sets the control amount of the expansion valve 56 (change amount from the current opening of the expansion valve 56) to “ -A "(setting to decrease the opening degree of the expansion valve 56 by A) and proceed to STEP56. On the other hand, when the discharge superheat degree ΔTe is equal to or higher than the target discharge superheat degree, the process proceeds to STEP52.

  In STEP52, the boiling control unit 123 determines whether or not the discharge superheat degree ΔTe is equal to or higher than the target discharge superheat degree + α. When the discharge superheat degree ΔTe is equal to or greater than the target discharge superheat degree + α, the process branches to STEP 62, and the boiling control unit 123 sets the control amount of the expansion valve 56 to “+ A” (the opening degree of the expansion valve 56 is set to A). And proceed to STEP 56. On the other hand, when the discharge superheat degree ΔTe is lower than the target discharge superheat degree + α, the process proceeds to STEP53.

  In STEP 53, the boiling control unit 123 determines whether or not the degree of supercooling ΔTc is lower than the target degree of supercooling. When the supercooling degree ΔTc is lower than the target supercooling degree, the process branches to STEP 63, and the boiling control unit 123 sets the control amount of the expansion valve 56 to “−B” (the opening degree of the expansion valve 56 is set to B). And proceed to STEP 56. On the other hand, when the degree of supercooling ΔTc is equal to or greater than the target degree of supercooling, the routine proceeds to STEP54.

  In STEP54, the boiling control unit 123 determines whether or not the degree of supercooling ΔTc is equal to or greater than the target degree of supercooling + β. When the degree of supercooling ΔTc is equal to or greater than the target degree of supercooling + β, the process branches to STEP 64, and the boiling control unit 123 sets the control amount of the expansion valve 56 to “+ B” (the opening degree of the expansion valve 56 is set to B). And proceed to STEP 56. On the other hand, when the degree of supercooling ΔTc is lower than the target degree of supercooling + β, the routine proceeds to STEP55.

  In STEP 55, the boiling control unit 123 sets the control amount of the expansion valve 56 to “± 0” (setting not to change the opening degree of the expansion valve 56), and proceeds to STEP 56. In STEP 56, the boiling control unit 123 controls (changes or maintains) the opening degree of the expansion valve 56 according to the control amount of the expansion valve 56, and proceeds to STEP 50.

  Through the processing of STEP51 to STEP52, STEP61, and STEP62, the discharge superheat degree ΔTe is maintained within the range of the target discharge superheat degree to the target discharge superheat degree + α (corresponding to the first predetermined range of the present invention). Further, by the processing of STEP53 to STEP54, STEP63, and STEP64, the supercooling degree ΔTc is maintained within the range of the target supercooling degree to the target supercooling degree + β (corresponding to the second predetermined range of the present invention).

  Here, the target discharge superheat degree and the target supercool degree are set such that the operation of the heat pump becomes highly efficient according to the boiling set temperature and the incoming water temperature. For example, when the boiling set temperature is 45 ° C. and the incoming water temperature T 7 is 9 ° C., the target discharge superheat degree is set to 35 ° C., the target supercool degree is set to 30 ° C.

  In this way, by maintaining the discharge superheat degree ΔTe and the supercooling degree ΔTc within a certain range, the heat pump 51 can be operated with high efficiency while satisfying the required capacity.

[5. Second expansion valve control]
Next, according to the flowchart shown in FIG. 6, the second expansion valve control (control to prevent the compressor discharge temperature T2 from becoming high by adjusting the opening degree of the expansion valve 56) executed in STEP 34 of FIG. Processing will be described.

  The boiling control unit 123 determines whether or not the opening degree of the expansion valve 56 is less than the maximum opening degree in STEP 70 of FIG. 6. When the opening degree of the expansion valve 56 is less than the maximum opening degree, the process proceeds to STEP 71, and when the opening degree of the expansion valve 56 is the maximum opening degree, the process branches to STEP 80.

  In STEP 80, the boiling control unit 123 sets the control mode of the expansion valve to “normal” and proceeds to STEP 81. In STEP 81, the boiling control unit 123 sets the control amount of the expansion valve 56 to “± 0” (sets without changing the opening of the expansion valve 56), and proceeds to STEP 75.

  In STEP 71, the boiling control unit 123 determines whether or not the compressor discharge temperature T2 is higher than the upper limit discharge temperature. When the compressor discharge temperature T2 is higher than the upper limit discharge temperature, the process proceeds to STEP 72, and when the compressor discharge temperature T2 is equal to or lower than the upper limit discharge temperature, the process proceeds to STEP80.

  In STEP 72, the boiling control unit 123 determines whether or not the first protection update timer of the expansion valve 56 (timer for measuring the period for adjusting the opening degree of the expansion valve 56 according to the compressor discharge temperature T2) has expired. Determine whether. Then, when the first protection update timer is up, the process proceeds to STEP 73, and when the first protection update timer is not up, the process branches to STEP81.

  In STEP 73, the boiling control unit 123 sets the control amount of the expansion valve 56 to “+ C” (setting to increase the opening degree of the expansion valve 56 by C). In subsequent STEP 74, the boiling control unit 123 sets the first protection update timer to Y seconds and starts measuring time.

  In the next STEP 75, the boiling control unit 123 controls (changes or maintains) the opening degree of the expansion valve 56 in accordance with the control amount set in STEP 73 or STEP 81.

  When the compressor discharge temperature T2 exceeds the upper limit discharge temperature by the second expansion valve control (YES in STEP 71), a process of increasing the opening degree of the expansion valve 56 by C is performed (STEP 73). The flow rate of the heat medium sucked in increases. As the flow rate of the sucked heat medium increases, the temperature of the heat medium discharged from the compressor 54 decreases, and the compressor 54 is protected.

  When the compressor discharge temperature T2 becomes equal to or lower than the upper limit discharge temperature, the control mode of the expansion valve 56 can be set to “normal” (STEP 80), and the first expansion valve control can be resumed promptly. In this embodiment, when the compressor discharge temperature T2 becomes equal to or lower than the upper limit discharge temperature in STEP 71, the process branches to STEP 80 to return the expansion valve control mode to “normal”. A discharge temperature may be set, and the expansion valve control mode may be returned to “normal” when the compressor discharge temperature T2 becomes equal to or lower than the allowable discharge temperature.

[6. Third expansion valve control]
Next, according to the flowchart shown in FIG. 7, the third expansion valve control (control to prevent liquid back from the outside air heat exchanger 53 by adjusting the opening degree of the expansion valve 56) executed in STEP 36 of FIG. 3. Will be described.

  The boiling control unit 123 determines whether or not the opening degree of the expansion valve 56 is larger than the minimum opening degree in STEP90 of FIG. When the opening degree of the expansion valve 56 is larger than the minimum opening degree, the process proceeds to STEP91, and when the opening degree of the expansion valve 56 is the minimum opening degree, the process branches to STEP100.

  In STEP 100, the boiling control unit 123 sets the control mode of the expansion valve 56 to “normal”. In subsequent STEP 101, the boiling control unit 123 sets the control amount of the expansion valve 56 to “± 0” and proceeds to STEP 95.

  In STEP 91, the boiling control unit 123 determines whether or not the suction superheat degree ΔTb is equal to or higher than the suction superheat lower limit value (whether or not the liquid back state has been eliminated). When the suction superheat degree ΔTb is equal to or higher than the suction superheat lower limit value, the process branches to STEP 100, and when the suction superheat degree ΔTb is lower than the suction superheat lower limit value, the process branches to STEP92.

  In STEP 92, the boiling control unit 123 determines whether or not the second protection update timer (timer for measuring the period for adjusting the opening degree of the expansion valve 56 in accordance with the suction superheat degree ΔTb) is up. Then, when the second protection update timer has timed out, the process proceeds to STEP 93, and when the second protection update timer has not expired, the process branches to STEP101.

  In STEP 93, the boiling control unit 123 sets the control amount of the expansion valve 56 to “−D” (setting to decrease the opening degree of the expansion valve 56 by D). In subsequent STEP94, the boiling control unit 123 sets the second protection timer to Z seconds and starts measuring time.

  In the next STEP 95, the boiling control unit 123 controls (changes or maintains) the opening degree of the expansion valve 56 according to the control amount set in STEP 93 or STEP 101.

  When there is a possibility that the third expansion valve control unit is in a liquid back state (YES in STEP 6 in FIG. 3), a process of reducing the opening of the expansion valve 56 by D is performed (STEP 93 in FIG. 7). , STEP 95), the flow rate of the heat medium flowing into the outside air heat exchanger 53 decreases. Thereby, the vaporization of the heat medium in the outside air heat exchanger 53 is promoted to avoid the liquid back state, and the failure of the compressor 54 due to the suction of the liquid state heat medium can be prevented.

  Further, when the liquid back state is eliminated, the control mode of the expansion valve 56 is set to “normal” (STEP 100), the third expansion valve control is terminated, and the first expansion valve control can be restarted promptly. .

[7. Other Embodiments]
In the above-described embodiment, the example in which the first expansion valve control, the second expansion valve control, and the third expansion valve control are executed has been described. However, the effect of the present invention can be obtained by executing at least the first expansion valve control. The second expansion valve control and the third expansion valve control or both of them may not be executed. Or it is good also as a structure which performs combining the expansion valve control other than 2nd expansion valve control and 3rd expansion valve control, and 1st expansion valve control.

  In the above-described embodiment, the hot water supply system 1 that supplies hot water stored in the hot water storage tank 11 to the hot water discharge pipe 13 is shown, but the hot water stored in the hot water storage tank 11 is circulated and supplied to the heating terminal to radiate heat from the heating terminal. The present invention can also be applied to a hot water supply system.

  In the above embodiment, the condensation temperature of the heat medium in the water heat exchanger 55 is directly detected by the condensation temperature sensor 57 (configured by a thermistor or the like). However, the saturation pressure may be detected by detecting the condensation pressure. . Further, with respect to the evaporation temperature of the heat medium in the outdoor air heat exchanger 53, the saturation evaporation temperature may be detected by detecting the evaporation pressure.

  The adjustment values A, B, C, and D of the opening degree of the expansion valve 56 in the above embodiment may be fixed values or may be changed according to the boiling temperature or the rotation speed of the compressor 54.

  DESCRIPTION OF SYMBOLS 1 ... Hot water supply system, 10 ... Hot water storage unit, 11 ... Hot water storage tank, 12 ... Water supply pipe, 13 ... Hot water discharge pipe, 22 ... Water supply temperature sensor, 34 ... Water supply branch pipe, 41 ... Tank circulation path, 50 ... Heat pump unit, 51 ... Heat pump 52 ... heat pump circuit (heat medium circuit), 53 ... outside air heat exchanger (evaporator), 54 ... compressor, 55 ... water heat exchanger (condenser), 56 ... expansion valve, 57 ... condensation temperature Sensor (condensation temperature detection part), 62 ... Heat medium temperature sensor (expansion valve inflow temperature detection part), 65 ... Heat medium temperature sensor (compressor discharge temperature detection part), 66 ... Tank circulation pump, 67 ... Outside air temperature sensor, DESCRIPTION OF SYMBOLS 120 ... Controller, 121 ... Hot water supply control part, 122 ... Hot water filling control part, 123 ... Boiling control part.

Claims (3)

A heat pump having a heat medium circulation path in which a heat medium is enclosed, and a compressor, a condenser, an expansion valve, and an evaporator connected in order by the heat medium circuit;
A hot water storage tank for storing hot water,
A tank circulation path that connects the upper and lower portions of the hot water storage tank, and the condenser is connected in the middle;
A tank circulation pump for circulating the water stored in the hot water storage tank through the tank circulation path;
By operating the heat pump and the tank circulation pump, in the condenser, heat exchange is performed between the heat medium flowing through the heat medium circulation path and the water flowing through the tank circulation path, and the hot water storage In a hot water supply system including a boiling control unit that performs a boiling operation for heating water in a tank,
A compressor discharge temperature detector for detecting the temperature of the heat medium discharged from the compressor to the heat medium circuit;
A condensation temperature detector for detecting the condensation temperature of the heat medium in the condenser;
An expansion valve inflow temperature detection unit for detecting the temperature of the heat medium flowing into the expansion valve from the heat medium circulation path,
During the boiling operation, the boiling control unit has a discharge superheat degree that is a difference between a detected temperature of the compressor discharge temperature detecting unit and a detected temperature of the condensing temperature detecting unit within a first predetermined range. And the degree of opening of the expansion valve is set so that the degree of supercooling, which is the difference between the temperature detected by the condensing temperature detector and the temperature detected by the expansion valve inflow temperature detector, falls within the second predetermined range. A hot water supply system that performs first expansion valve control to be adjusted. The hot water supply system according to claim 1,
The boiling control unit prohibits the first expansion valve control when the detected temperature of the compressor discharge temperature detection unit exceeds a predetermined upper limit discharge temperature during execution of the boiling operation, The second expansion valve control for increasing the opening degree of the expansion valve is executed, and the detected temperature of the compressor discharge temperature detecting unit is set to be equal to or lower than a discharge allowable temperature set to be equal to or lower than the upper limit discharge temperature by the second expansion valve control. When this happens, the second expansion valve control is terminated and the first expansion valve control is executed. In the hot water supply system according to claim 1 or claim 2,
A compressor suction temperature detector for detecting the temperature of the heat medium sucked into the compressor from the heat medium circulation path;
An evaporator inflow temperature detection unit for detecting the temperature of the heat medium flowing into the evaporator from the heat medium circulation path;
The boiling control unit, during execution of the boiling operation, a suction superheat degree that is a difference between a detected temperature of the compressor intake temperature detecting unit and a detected temperature of the evaporator inflow temperature detecting unit is a predetermined superheat. When the value is lower than the lower limit value, the first expansion valve control is prohibited and the third expansion valve control is executed to reduce the opening of the expansion valve, and the suction superheat degree is controlled by the third expansion valve control. When the temperature becomes equal to or greater than the overheat allowable value set to be equal to or greater than the overheat lower limit value, the third expansion valve control is terminated and the first expansion valve control is executed.