JP5935742B2 - Heat pump water heater - Google Patents

Description

  The present invention relates to a heat pump water heater that heats hot water in a plurality of heat pump cycles.

  Conventionally, a heat pump system that heats hot water by exchanging heat between the high-temperature and high-pressure refrigerant discharged from the compressor in the water-refrigerant heat exchanger of the heat pump cycle and the hot water, and stores the heated hot water in a hot water storage tank. A water heater is known.

  For example, Patent Document 1 discloses a water pump that pumps hot water to a water passage of a water-refrigerant heat exchanger and a boiling temperature that detects the boiling temperature of hot water flowing out of the water passage of the water-refrigerant heat exchanger. There is disclosed a heat pump type hot water heater that includes a temperature detection means and controls the rotation speed (water pumping capacity) of a water pump so that the boiling temperature detected by the boiling temperature detection means approaches the target boiling temperature. Yes.

  More specifically, in the heat pump type water heater disclosed in Patent Document 1, for example, when the boiling temperature detected by the boiling temperature detection means is lower than the target boiling temperature, the water pumping capacity of the water pump is reduced. Thus, the boiling temperature is raised, and low temperature hot water is prevented from flowing into the hot water storage tank.

  Further, Patent Document 2 includes a plurality of heat pump cycles, the water passages of the water-refrigerant heat exchangers of the respective heat pump cycles are connected in parallel to the hot water storage tank, and each water-refrigerant heat exchange is further connected. There is disclosed a heat pump type hot water heater provided with a plurality of water pumps for pumping hot water to a water passage of a vessel.

  In the heat pump type hot water heater of this patent document 2, by heating hot water in a plurality of heat pump cycles, the heating capacity of the hot water is higher than that of a heat pump type hot water heater configured to heat the hot water in one heat pump cycle. It is improved so that a large amount of hot water can be heated at a time.

JP 2007-147108 A JP 2006-29658 A

  By the way, in the heat pump type water heater of patent document 2, since the water passage of the water-refrigerant heat exchanger of several heat pump cycles is only connected in parallel with respect to the hot water storage tank, heating of some heat pump cycles is carried out. If the capacity decreases, there is a risk that low-temperature hot water that has not been sufficiently heated in some heat pump cycles where the heating capacity has decreased will flow into the hot water storage tank.

  On the other hand, in the heat pump type hot water heater of Patent Document 2, by controlling the water pumping capacity of each water pump in the same manner as in Patent Document 1, it is possible that low temperature hot water flows into the hot water storage tank. Means to suppress are conceivable. However, in the heat pump type water heater of Patent Document 2, if the water pumping capacity of each water pump is controlled in the same manner as Patent Document 1, the water pumping capacity of each water pump may be different.

  For example, when frost formation occurs in the evaporators of some heat pump cycles, if defrosting operation is performed to defrost them using the heat of the refrigerant circulating in the cycles, the hot water supply in some of the heat pump cycles Water heating capacity is reduced. Accordingly, the water pumping capacity of the water pump applied to this part of the heat pump cycle must be lowered than the water pumping capacity of the water pump applied to the other heat pump cycle.

  However, if the water pumping capacity of some water pumps is lowered, the discharge head of this water pump becomes lower than the necessary discharge head (operating point) necessary for pumping hot water (that is, In some cases, the discharge head becomes insufficient, and the water pump cannot pump hot water.

  Furthermore, if the water pump becomes insufficient in the discharge head and can no longer pump hot water, the water-refrigerant heat exchanger of the heat pump cycle to which the water pump is applied cannot radiate high-temperature and high-pressure refrigerant to the hot water. As a result, the high-pressure side refrigerant pressure of the heat pump cycle abnormally increases. Such an abnormal increase in the high-pressure side refrigerant pressure causes a negative effect on the durability life of the cycle component equipment such as a compressor.

  In view of the above points, in the present invention, in a heat pump hot water heater that heats hot water in a plurality of heat pump cycles, low temperature hot water in the hot water storage tank while suppressing a shortage of a discharge pump of a water pump that pumps hot water. The purpose is to suppress the inflow.

The present invention has been devised to achieve the above object. In the invention according to claim 1, a plurality of heat pump cycles (10a to 10d) for heating hot water and a plurality of heat pump cycles (10a to 10a). A hot water storage tank (20) for storing hot water heated in 10d), and the plurality of heat pump cycles (10a to 10d) are water for heating hot water by exchanging heat between the high-temperature refrigerant and the hot water. -Water passages (122a-122d) which have refrigerant heat exchangers (12a-12d) and distribute hot water in each of the water-refrigerant heat exchangers (12a-12d) are hot water storage tanks (20) Heat pump water heaters connected in parallel to each other,
Furthermore, a plurality of water pumps (28a-28d) for pumping hot water to the respective water passages (122a-122d), and a water pressure feeding capability control means for controlling the water pumping capability of the plurality of water pumps (28a-28d), A minimum water pumping capacity determining means (S43) for determining the minimum water pumping capacity (Npmin) of the plurality of water pumps (28a to 28d),
The water pressure feeding capacity control means controls the operation of the water pumps (28a to 28d) so that the water pressure feeding capacity of the water pumps (28a to 28d) is equal to or higher than the minimum water pressure feeding capacity (Npmin). The minimum water pumping capacity determining means (S43) determines to decrease the minimum water pumping capacity (Npmin) as the average value (Npave) of the water pumping capacities of the water pumps (28a to 28d) decreases. It is a thing to do.

  According to this, since the operation of the plurality of water pumps (28a-28d) is controlled so that the water pumping capacity of the plurality of water pumps (28a-28d) is equal to or higher than the minimum water pumping capacity (Npmin), the minimum water pressure By appropriately determining the minimum water pumping capacity (Npmin) by the feeding capacity determining means (S43), it is easily suppressed that the water pump (28a to 28d) becomes insufficient in the discharge head and cannot pump hot water. it can. As a result, it is possible to easily suppress an abnormal increase in the high-pressure side refrigerant pressure of the heat pump cycle (10a to 10d).

  Further, the minimum water pumping capacity determining means (S43) decreases the minimum water pumping capacity (Npmin) as the average value (Npave) of the water pumping capacities of the water pumps (28a to 28d) decreases. Since it determines, it can suppress that the minimum water pumping capacity (Npmin) is determined unnecessarily high.

  In other words, although the water pumping capacity of some water pumps is low as in the defrosting operation of some heat pump cycles, the water pumping capacity of other water pumps is high, and multiple water pumps ( When the average value (Npave) of the water pumping capacity of 28a to 28d) is relatively high, the total flow rate of hot water flowing through each of the water passages (122a to 122d) is increased, so that the hot water is supplied to each water passage. The pressure loss generated when circulating (122a-122d) etc. increases and the required discharge head also rises.

  For this reason, when the average value (Npave) of the water pumping ability of the plurality of water pumps (28a to 28d) is relatively high, a part of the water pumps having the lowered water pumping ability is prevented from having an insufficient discharge head. It is necessary to determine the minimum water pumping capacity (Npmin) to a relatively high value.

  On the other hand, when the average value (Npave) of the water pumping capacity of the plurality of water pumps (28a to 28d) is low, such as when starting the plurality of heat pump cycles (10a to 10d), Therefore, the pressure loss generated when hot water flows through each of the water passages (122a to 122d) is reduced, and the required discharge head is also lowered.

  For this reason, when the average value (Npave) of the water pumping capabilities of the plurality of water pumps (28a to 28d) is relatively low, even if the minimum water pumping capability (Npmin) is determined to be a relatively low value, The water pump (28a to 28d) does not become insufficient in the discharge head.

  Therefore, the minimum water pumping capacity determining means (S43) decreases the minimum water pumping capacity (Npmin) as the average value (Npave) of the water pumping capacity of the plurality of water pumps (28a to 28d) decreases. By determining, when the average value (Npave) of the water pumping capacity of the plurality of water pumps (28a to 28d) is low, the minimum water pumping capacity (Npmin) is determined to be an unnecessarily high value, and in the hot water storage tank It is possible to prevent low temperature hot water from flowing in.

  That is, according to the invention described in this claim, in a heat pump hot water heater that heats hot water in a plurality of heat pump cycles (10a to 10d), a shortage of discharge heads of the plurality of water pumps (28a to 28d) is suppressed. However, it is possible to prevent the low temperature hot water from flowing into the hot water storage tank (20).

  Here, “connected in parallel” in the claims means that the water passages (122a to 122d) are completely connected to the hot water storage tank (20) in parallel by independent water pipes. It does not mean only. For example, the inlet side of each of the water passages (122a to 122d) is connected to the hot water storage tank (20) via a diversion part (24) that divides the flow of hot water, or each water passage (122a to 122d). ) Is connected to the hot water storage tank (20) via a merging section (25) for merging the flow of hot water.

  In addition, the code | symbol in the bracket | parenthesis of each means described in this column and the claim shows the correspondence with the specific means as described in embodiment mentioned later.

1 is an overall configuration diagram of a heat pump type water heater according to an embodiment. It is a flowchart which shows the control processing of the heat pump type water heater of one Embodiment. It is a flowchart which shows the principal part of the control processing of the heat pump type water heater of one Embodiment. It is a control characteristic figure used for control processing which determines the minimum number of rotations of a water pump in control processing of a heat pump type hot water heater of one embodiment. It is a graph which shows the relationship between the discharge head P and the discharge flow rate Q in the 1st-4th water pump at the time of the defrost operation of the heat pump type water heater of one Embodiment. It is a graph which shows the relationship between the discharge head P and the discharge flow volume Q in the 1st-4th water pump at the time of starting of the heat pump type water heater of one Embodiment.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. As shown in the overall configuration diagram of FIG. 1, the heat pump type water heater 1 of the present embodiment includes a plurality of (four in the present embodiment) heat pump cycles, and the plurality of heat pump cycles 10 a to 10 d includes The hot-water supply heated in this way is stored in a common hot-water storage tank 20.

  First, the first to fourth heat pump cycles 10a to 10d will be described. Since the basic configurations of the first to fourth heat pump cycles 10a to 10d are equivalent to each other, the first heat pump cycle 10a will be described first. The first heat pump cycle 10a is a vapor compression refrigeration cycle configured by sequentially connecting a compressor 11a, a water-refrigerant heat exchanger 12a, an electric expansion valve 13a, and an evaporator 14a by piping.

  In the first heat pump cycle 10a, carbon dioxide is used as the refrigerant, and the high-pressure side refrigerant pressure in the cycle from the discharge port side of the compressor 11a to the inlet side of the electric expansion valve 13a is equal to or higher than the critical pressure of the refrigerant. It constitutes a supercritical refrigeration cycle. The refrigerant is mixed with refrigerating machine oil for lubricating the compressor 11a, and the refrigerating machine oil circulates in the cycle together with the refrigerant.

  The compressor 11a sucks the refrigerant in the first heat pump cycle 10a, and compresses and discharges the refrigerant until it becomes a critical pressure or higher. In the present embodiment, as the compressor 11a, an electric compressor that drives a fixed displacement type compression mechanism with a fixed discharge capacity by an electric motor is employed. The operation (number of rotations) of the electric motor of the compressor 11a is controlled by a control signal output from a control device described later.

  The refrigerant discharge port of the compressor 11a is connected to the inlet side of the refrigerant passage 121a of the water-refrigerant heat exchanger 12a. The water-refrigerant heat exchanger 12a has a refrigerant passage 121a for circulating the high-temperature and high-pressure refrigerant discharged from the compressor 11a and a water passage 122a for circulating hot water, and exchanges heat between the high-temperature and high-pressure refrigerant and the hot water. It is a heat exchanger for heating which heats hot water.

  Further, in the present embodiment, a counter flow type heat exchanger in which the flow direction of the refrigerant flowing through the refrigerant passage 121a and the flow direction of the hot water flowing through the water passage 122a are opposed to each other is adopted as the water-refrigerant heat exchanger 12a. Yes.

  In such a counter-flow heat exchanger, the hot water supplied on the inlet side of the water passage 122a and the refrigerant on the outlet side of the refrigerant passage 121a are heat-exchanged, and the hot water on the outlet side of the water passage 122a and the refrigerant passage 121a are exchanged. Since heat can be exchanged with the refrigerant on the inlet side, a temperature difference between the hot water and the refrigerant can be secured over the entire heat exchange region, and heat exchange efficiency can be improved.

  In addition, since the first heat pump cycle 10a of the present embodiment constitutes a supercritical refrigeration cycle as described above, the refrigerant is not condensed in the refrigerant passage 121a of the water-refrigerant heat exchanger 12a. Dissipate heat.

  The inlet side of the electric expansion valve 13a is connected to the outlet side of the refrigerant passage 121a of the water-refrigerant heat exchanger 12a. The electric expansion valve 13a is a decompression unit that decompresses the refrigerant flowing out of the refrigerant passage 121a.

  More specifically, the electric expansion valve 13a includes a valve body that can change the throttle opening degree and an electric actuator that includes a stepping motor that changes the throttle opening degree of the valve body. Variable aperture mechanism. Further, the operation of the electric actuator of the electric expansion valve 13a is controlled by a control signal output from the control device.

  The refrigerant inlet side of the evaporator 14a is connected to the outlet side of the electric expansion valve 13a. The evaporator 14a performs heat exchange between the low-pressure refrigerant decompressed by the electric expansion valve 13a and the outside air (outdoor air) blown by the blower fan 15a, thereby evaporating the low-pressure refrigerant and exerting an endothermic effect. It is a heat exchanger for use.

  The blower fan 15a is an electric blower whose rotation speed (amount of blown air) is controlled by a control voltage output from the control device. Further, the refrigerant inlet of the compressor 14 is connected to the refrigerant outlet side of the evaporator 14a. Furthermore, each component apparatus 11a-14a of the 1st heat pump cycle 10a mentioned above is accommodated in one housing | casing or a frame structure as shown with the broken line of FIG. 1, and is comprised integrally as a heat pump unit.

  As described above, the basic configuration of the second to fourth heat pump cycles 10b to 10d is the same as that of the first heat pump cycle 10a. Therefore, in the following description, as shown in FIG. 1, in the second to fourth heat pump cycles 10 b to 10 d, for the same configuration as the first heat pump cycle 10 a, the subscripts are changed from a to b to d, respectively. Changed to represent.

  In addition, with regard to control parameters and the like to be described later, the subscript is a for the first heat pump cycle 10a, and the subscript is changed from a to bd for the second to fourth heat pump cycles 10b to 10d. Changed to represent.

  Next, the hot water storage tank 20 will be described. The hot water storage tank 20 is formed of a metal having excellent corrosion resistance (for example, stainless steel) and has a heat insulating structure in which the outer periphery thereof is covered with a heat insulating material or a vacuum heat insulating structure with a double tank, etc. It is a hot water tank that can keep warm.

  Hot water stored in the hot water storage tank 20 is discharged from a hot water outlet provided in the upper part of the hot water storage tank 20, mixed with cold water from a water tap at a temperature control valve (not shown), and then adjusted indoors. Hot water is supplied to places. Further, tap water is supplied from a water supply port provided at the lower part of the hot water storage tank 20.

  Next, a water circulation circuit 21 for circulating hot water between the hot water storage tank 20 and the water-refrigerant heat exchangers 12a to 12d of the first to fourth heat pump cycles 10a to 10d will be described.

  The water circulation circuit 21 supplies hot water flowing out from a hot water outlet 22 provided on the lower side of the hot water storage tank 20 through each of the first to fourth heat pump cycles 10a to 10d via the outflow pipe 23 and the diverter 24. While diverting to the water passages 122a to 122d of the water-refrigerant heat exchangers 12a to 12d, hot water flowing out from the respective water passages 122a to 122d is supplied to the hot water storage tank 20 via the junction 25 and the inflow pipe 26. This is a water circulation circuit that flows into a hot water supply inlet 27 provided on the upper side.

  The outflow pipe 23 is a water pipe that guides hot water flowing out from the hot water outlet 22 to the hot water inlet of the diverter 24. The diversion unit 24 divides the flow of hot water that has flowed out from the outflow pipe 23 and causes the hot water to flow out to the respective water passages 122a to 122d, and has a joint structure having a plurality of hot water inflow / outflow ports. . Such a diversion part 24 may be configured by providing a plurality of hot water supply passages in a metal block or the like, or may be configured by combining a plurality of three-way joints or the like.

  The junction 25 joins the flows of hot water flowing out from the respective water passages 122 a to 122 d, and the basic configuration is the same as that of the branch 24. The inflow pipe 26 is a water pipe that guides hot water flowing out from the hot water outlet of the junction 25 to the hot water inlet 27.

  Thereby, in this embodiment, the water passages 122a to 122d of the water-refrigerant heat exchangers 12a to 12d are connected in parallel to the hot water outlet 22 and the hot water inlet 27 of the hot water storage tank 20, respectively. .

  Further, in the water circulation circuit 21, hot water is supplied to the water passages 122 a to 122 d in the water pipes extending from the diversion unit 24 to the inlet side of the water passages 122 a to 122 d of the water-refrigerant heat exchangers 12 a to 12 d. First to fourth water pumps (water circulation pumps) 28a to 28d for pumping are arranged. Therefore, these first to fourth water pumps 28a to 28d are also connected in parallel with the suction ports and the discharge ports communicating with each other.

  The first to fourth water pumps 28a to 28d are electric water pressure feeding means having the same basic configuration, and the rotation speed (water pressure feeding capacity) is controlled by a control voltage output from the control device. Further, the control device can independently control the water pressure feeding capacities of these first to fourth water pumps 28a to 28d. That is, the control device can operate the first to fourth water pumps 28a to 28d with different water pressure feeding capabilities.

  In addition, these 1st-4th water pumps 28a-28d are the 1st-4th heat pumps provided with the water-refrigerant heat exchangers 12a-12d to which each water pump is connected, as shown with the broken line of FIG. Together with the cycles 10a to 10d, the heat pump unit is integrally configured.

  Next, an outline of the electric control unit of the present embodiment will be described. Each control device (not shown) includes a known microcomputer including a CPU, a ROM, a RAM, and the like and peripheral circuits thereof. On the output side of the control device, there are control target devices such as the component devices 11a to 11d, 13a to 13d, 15a to 15d and the first to fourth water pumps 28a to 28d of the first to fourth heat pump cycles 10a to 10d. The control device controls the operation of these control target devices.

  Further, on the input side of the control device, a tank temperature sensor (tank temperature detecting means) for detecting the temperature of hot water stored in the hot water storage tank 20, and a water passage 122a of each water-refrigerant heat exchanger 12a. First to fourth boiling temperature sensors (first to fourth boiling temperature detecting means) for detecting first to fourth boiling temperatures Twoa to Twood, which are hot water supply water temperatures on the outlet side, and respective evaporators 14a to 14a The first to fourth evaporator temperature sensors (first to fourth evaporator temperature detecting means) for detecting the refrigerant evaporation temperature (temperatures of the evaporators 14a to 14d) Tea to Ted at 14d, and the evaporators 14a to 14d. An outside air temperature sensor (outside air temperature detecting means) that detects an outside air temperature Tam that exchanges heat with the low-pressure refrigerant is connected, and detection signals of these control sensor groups are input to the control device.

  The in-tank temperature sensor of the present embodiment is composed of a plurality of temperature sensors arranged in the hot water storage tank 20 in the vertical direction. Thereby, in a control apparatus, the temperature and temperature distribution of the hot water supply according to the water level in the hot water storage tank 20 can be detected with the output signal of a some tank temperature sensor.

  Moreover, the 1st-4th evaporator temperature sensor of this embodiment has specifically detected the heat exchange fin temperature of each evaporator 14a-14d. Of course, as the first to fourth evaporator temperature sensors, temperature detecting means for detecting the temperature of other portions of the evaporators 14a to 14d may be employed, or the refrigerant itself flowing through the evaporators 14a to 14d. You may employ | adopt the temperature detection means which detects the temperature of this directly.

  Further, an operation panel (not shown) is connected to the input side of the control device. This operation panel has an operation switch for outputting an operation request signal for requesting the operation of the heat pump type hot water heater 1 and a stop request signal for requesting a stop, and a target for setting a boiling temperature (target boiling temperature) Twot of hot water. A boiling temperature setting switch or the like as a boiling temperature determining means is provided, and operation signals of these switches are input to the control device.

  Note that the control device of the present embodiment is configured integrally with control means for controlling various control target devices connected to the output side thereof, but the operation of each control target device in the control device is performed. The structure to control (hardware and software) comprises the control means which controls the action | operation of each control object apparatus.

  For example, among the control devices, the configuration that controls the operation of the compressors 11a to 11d (the refrigerant discharge capability of the compressors 11a to 11d) constitutes the discharge capability control means, and the first to fourth water pumps 28a to 28d. The structure which controls the operation | movement (water pressure feeding capability of the 1st-4th water pumps 28a-28d) comprises the water pressure feeding capability control means.

  Further, the discharge capacity control means and the water pressure feeding capacity control means may be configured as separate devices with respect to the control device, or the control means for controlling the operation of each component device of each heat pump cycle 10a to 10d in the control device. May be configured as separate devices as the first to fourth heat pump side control devices.

  Next, operation | movement of the heat pump type water heater 1 of this embodiment in the said structure is demonstrated using FIGS. The flowchart of FIG. 2 shows the control process of the main routine executed by the control device during the boiling operation for heating hot water. This control process is executed when an operation request signal for the heat pump water heater 1 is output from the operation panel to the control device in a state where power is supplied to the heat pump water heater 1 from the outside.

  First, in step S1, flags, timers, and the like are initialized. In subsequent step S2, an operation signal of the operation panel and a detection signal detected by the control sensor group described above are read. Next, it progresses to step S3 and the control state of the various components which comprise the 1st-4th heat pump cycle 10a-10d is determined based on the operation signal and detection signal which were read at step S2.

  For example, for the control signals output to the compressors 11a to 11d (specifically, the electric motors of the compressors 11a to 11d), the target boiling temperature Twot and the outside air temperature sensor set on the operation panel are used. Is determined with reference to a control map stored in advance in the control device based on the outside air temperature Tam detected by the above.

  More specifically, the target rotational speed (target refrigerant discharge capacity) of each of the compressors 11a to 11d is determined to increase as the target boiling temperature Twot increases and the outside air temperature Tam decreases.

  Moreover, about the control signal output to each electric expansion valve 13a-13d (specifically, electric actuator of each electric expansion valve 13a-13d), each 1st-4th heat pump cycle 10a-10d. The high-pressure side refrigerant pressure is determined to be the target high pressure for each of the heat pump cycles 10a to 10d.

  This target high pressure is based on the control temperature stored in advance in the controller based on the outside air temperature Tam and the discharge refrigerant temperature of each of the compressors 11a to 11d estimated from the refrigerant discharge capacity of each of the compressors 11a to 11d. This is a value determined so that the coefficient of performance (COP) of the first to fourth heat pump cycles 10a to 10d is substantially maximized.

  Moreover, about the control voltage output to each ventilation fan which ventilates external air toward each evaporator 14a-14d, it determines with reference to the control map previously memorize | stored in the control apparatus based on outside temperature Tam. .

  Next, it progresses to step S4 and the rotation speed Npa-Npd of the 1st-4th water pumps 28a-28d is determined. Details of step S4 will be described with reference to the flowchart of FIG.

  First, in step S41, the rotation speeds Npa to Npd of the first to fourth water pumps 28a to 28d are detected from the applied voltages applied to the first to fourth water pumps 28a to 28d. In subsequent step S42, the average value Npave of the rotational speeds of the first to fourth water pumps 28a to 28d detected in step S41 is calculated, and the process proceeds to step S43.

  In step S43, based on the average value Npave calculated in step S42, the minimum rotation speed Npmin of the first to fourth water pumps 28a to 28d is determined with reference to the control map stored in advance in the control device. Note that the control map for determining the minimum rotational speed Npmin in this embodiment is determined so as to decrease the minimum rotational speed Npmin as the average value Npave decreases, as shown in the control characteristic diagram of FIG.

  Here, the rotation speeds Npa to Npd of the first to fourth water pumps 28a to 28d are indexes representing the water pressure feeding capabilities of the first to fourth water pumps 28a to 28d, respectively. Accordingly, the control step S43 of the present embodiment constitutes the minimum water pumping capacity determining means described in the claims, and the minimum rotation speed Npmin is set to the minimum water pumping capacity described in the claims. It corresponds.

  Further, in the minimum water pumping capacity determining means configured in the control step S43, even if one water pump among the first to fourth water pumps 28a to 28d has the minimum rotation speed Npmin, the discharge head of this water pump. However, the minimum rotational speed Npmin is determined so as to be higher than the necessary discharge head (operating point) necessary for pumping hot water, that is, so that the water pump operating at the minimum rotational speed Npmin can pump hot water. To do.

  The necessary discharge head (operating point) necessary for pumping hot water is the pressure generated when hot water flows through the water circulation circuit 21 and the water passages 122a to 122d of the water-refrigerant heat exchangers 12a to 12d. It is a value determined from loss etc.

  In the following step S44, it is determined whether or not the first to fourth boiling temperatures Twoa to Twood detected by the first to fourth boiling temperature sensors are equal to or higher than the target boiling temperature Twot. If it is determined in step S44 that the first to fourth boiling temperatures Twoa to Twood are equal to or higher than the target boiling temperature Twot, the rotation of the first to fourth water pumps 28a to 28d is performed in step S45. The number Npa to Npd is increased by a predetermined amount, and the process proceeds to step S47.

  On the other hand, if it is determined in step S44 that the first to fourth boiling temperatures Twoa to Twood are lower than the target boiling temperature Twot, the first to fourth water pumps 28a to 28d are determined in step S46. The rotation speeds Npa to Npd are reduced by a predetermined amount, and the process proceeds to step S47. That is, in control steps S44 to S46, the rotation speeds of the first to fourth water pumps 28a to 28d are increased or decreased so that the first to fourth boiling temperatures Twoa to Twood approach the target boiling temperature Twot.

  In FIG. 3, the control steps S44 to S46 include the first to fourth boiling temperatures Twoa to Twood, the rotation speeds Npa to Npd of the first to fourth water pumps 28a to 28d, etc. However, in actual control, the boiling temperatures Twoa to Twood and the target boiling temperature Two are sequentially compared, and the rotational speeds Npa to Npd of the water pumps 28a to 28d are successively increased or decreased. I am letting.

  That is, the first boiling temperature Twoa and the target boiling temperature Twot are compared to increase or decrease the rotational speed Npa of the first water pump 28a. Thereafter, the second boiling temperature Twob and the target boiling temperature Twot are compared to increase or decrease the rotation speed Npb of the second water pump 28b. Thereafter, the third boiling temperature Twoc and the target boiling temperature Twot are compared to increase or decrease the rotational speed Npc of the third water pump 28c, and then the fourth boiling temperature Twood and the target boiling temperature Twot are compared. The rotation speed Npd of the fourth water pump 28d is increased or decreased.

  In subsequent step S47, it is determined whether or not the rotation speeds Npa to Npd of the first to fourth water pumps 28a to 28d are equal to or higher than the minimum rotation speed Npmin determined in step S43. If it is determined in step S47 that the rotation speeds Npa to Npd of the first to fourth water pumps 28a to 28d are equal to or higher than the minimum rotation speed Npmin, the process proceeds to step S5.

  On the other hand, when it is determined in step S47 that the rotation speeds Npa to Npd of the first to fourth water pumps 28a to 28d are not equal to or higher than the minimum rotation speed Npmin, the rotation speeds Npa to Npd are set in step S48. The minimum speed Npmin is changed and the process proceeds to step S5. That is, in the control steps S47 and S48, the rotation speeds Npa to Npd of the first to fourth water pumps 28a to 28d are set to be equal to or higher than the minimum rotation speed Npmin.

  In FIG. 3, the control steps S47 and S48 also show the rotational speeds Npa to Npd of the first to fourth water pumps 28a to 28d for clarity of illustration, but in actual control, Similarly to the control steps S44 to S46, the rotation speeds Npa to Npd of the first to fourth water pumps 28a to 28d are compared with the minimum rotation speed Npmin and the rotation speeds Npa to Npd are sequentially changed.

  Next, in step S5 of FIG. 2, each of the constituent devices 11a to 11d and 13a to 13a of the first to fourth heat pump cycles 10a to 10d is obtained from the control device so that the control state determined in steps S3 and S4 is obtained. A control signal is output to 13d, 15a to 15d, the first to fourth water pumps 28a to 28d, etc., and the process proceeds to step S6.

  In step S6, when the operation stop signal of the heat pump type hot water heater 1 is input from the operation panel to the control device, the operation of various control target devices is stopped to stop the system. On the other hand, when the operation stop signal is not input, after waiting for a predetermined control period, the process returns to step S2.

  Here, as in the first to fourth heat pump cycles 10a to 10d of the present embodiment, in the configuration in which the refrigerant is evaporated by exchanging heat between the refrigerant and the outside air in the evaporators 14a to 14d, in the evaporators 14a to 14d. If the refrigerant evaporation temperature is equal to or lower than the frosting temperature (specifically, 0 ° C.), frosting may occur in the evaporators 14a to 14d. Such frosting closes the outside air passages of the evaporators 14a to 14d, and causes a decrease in the heat exchange performance of the evaporators 14a to 14d.

  Then, the control apparatus of this embodiment performs defrost control for defrosting this, when frost formation arises in the evaporators 14a-14d. Specifically, in the defrosting control, the temperatures Tea to Ted of the evaporators 14a to 14d detected by the first to fourth evaporator temperature sensors are set to a predetermined reference frosting temperature KTeA (specifically, −10 ° C.) or less, it is determined that frost formation has occurred in the evaporator.

  When it is determined that frost formation has occurred in any of the evaporators, a defrosting operation is performed on the evaporator that has been determined to have frost formation. Specifically, in the defrosting operation, the evaporator is operated until the temperature of the evaporator that has been determined to be frosting reaches a predetermined defrosting completion temperature KTeB (specifically, 5 ° C.). The throttle opening of the electric expansion valve of the heat pump cycle provided is increased to a predetermined opening.

  Thereby, the temperature of the refrigerant flowing into the evaporator is raised, and the frost of the evaporator is removed using the heat of the refrigerant flowing into the evaporator. In addition, the control process of this defrost control is performed for every predetermined control period as a subroutine of the main routine mentioned above.

  Also in this defrost control, in the actual control, as in control steps S44 to S46, etc., the comparison between the temperatures Tea to Ted of the evaporators 14a to 14d and the reference frosting temperature KTeA and the evaporators 14a Comparison between the temperatures Tea to Ted of ˜14d and the defrosting completion temperature KTeB is sequentially performed.

  When the heat pump type hot water heater 1 of the present embodiment is operated by the above control process, during normal boiling operation for heating hot water, the compressors 11a to 11d of the first to fourth heat pump cycles 10a to 10d are used. The discharged high-temperature and high-pressure refrigerant flows into the refrigerant passages 121a to 121d of the water-refrigerant heat exchangers 12a to 12d.

  The high-temperature and high-pressure refrigerant that has flowed into the refrigerant passages 121a to 121d of each of the water-refrigerant heat exchangers 12a to 12d is discharged from the lower side of the hot water storage tank 20 by the first to fourth water pumps 28a to 28d and the branching section. 24, heat exchange is performed with hot water supplied to the water passages 122a to 122d of the water-refrigerant heat exchangers 12a to 12d.

  Thereby, the hot water supplied into each of the water passages 122a to 122d is heated. At this time, the control device sets the rotation speeds of the first to fourth water pumps 28a to 28d so that the boiling temperatures Twoa to Twood of the hot water flowing out from the water passages 122a to 122d approach the target boiling temperature Twot. Control.

  Hot water heated in each of the water passages 122a to 122d is pumped to the upper side of the hot water storage tank 20 via the junction 25 and the inflow pipe 26 and stored. Hot hot water stored on the upper side of the hot water storage tank 20 is supplied to a kitchen or the like via a hot water outlet and a temperature control valve provided on the upper side of the hot water storage tank 20.

  On the other hand, the high-pressure refrigerant flowing out of the refrigerant passages 121a to 121d of the water-refrigerant heat exchangers 12a to 12d is decompressed by the electric expansion valves 13a to 13d, respectively. The refrigerant decompressed by the electric expansion valves 13a to 13d flows into the evaporators 14a to 14d, respectively, absorbs heat from the outside air blown from the blower fan, and evaporates. And the refrigerant | coolant which flowed out from each evaporator 14a-14d is each suck | inhaled by compressor 11a-11d, and is compressed again.

  Furthermore, in the heat pump type water heater 1 of the present embodiment, when it is determined that frosting has occurred in any of the evaporators during normal boiling operation, a defrosting operation is performed to defrost this.

  Since the heat pump type hot water heater 1 of this embodiment operates as described above, the hot water heated in the first to fourth heat pump cycles 10a to 10d can be stored in the hot water storage tank 20. Therefore, in the heat pump type hot water heater 1 of the present embodiment, the heating capacity of the hot water supply can be improved compared to the configuration in which the hot water is heated in one heat pump cycle, and a large amount of hot water can be heated at a time.

  In addition, when frosting occurs in any of the evaporators 14a to 14d of the first to fourth heat pump cycles 10a to 10d, the frost is removed by performing a defrosting operation. be able to.

  By the way, in the heat pump cycle in which the defrosting operation is performed, since the opening degree of the electric expansion valve is increased, the heating capacity of the hot water supply is reduced. Therefore, as explained in the control steps S44 to S46, the control device decreases the rotation speed of the water pump applied to the heat pump cycle in which the defrosting operation is performed.

  On the other hand, in the heat pump type water heater 1 of the present embodiment, the discharge head of the water pump that operates at the minimum rotation speed Npmin becomes higher than the operating point in the control step S43 that constitutes the minimum water pumping capacity determination means. Thus, since minimum rotation speed Npmin is determined, it can suppress that the 1st-4th water pumps 28a-28d cannot pump hot-water supply by lack of a discharge head.

  Furthermore, since such minimum rotation speed Npmin can be easily determined by experimental or experimental means, in the heat pump type water heater of this embodiment, the first to fourth water pumps 28a to 28d are discharged. It can be easily suppressed that the hot water supply cannot be pumped due to insufficient head. As a result, it is possible to easily suppress an abnormal increase in the high-pressure side refrigerant pressure of the first to fourth heat pump cycles 10a to 10d.

  Moreover, in the heat pump type water heater 1 of this embodiment, as shown in FIG. 4, in the control step S43 which comprises the minimum water pumping capability determination means, the average of the rotation speed of the 1st-4th water pumps 28a-28d is shown. Since the minimum rotational speed Npmin is determined to decrease as the value Npave decreases, it is possible to suppress the minimum rotational speed Npmin from being unnecessarily high.

  This will be described with reference to FIGS. 5 and 6 are graphs showing the relationship between the discharge head P and the discharge flow rate Q in each of the first to fourth water pumps 28a to 28d. This relationship is called a so-called PQ characteristic. 5 and FIG. 6, the PQ characteristics of the first to fourth water pumps shown in the upper part are shown together in one graph. That is, the horizontal axis of the lower graph in FIG. 5 indicates the total discharge flow rate Qs obtained by adding the discharge flow rates Q of the first to fourth water pumps.

  More specifically, in the upper part of FIG. 5, for the first to third water pumps 28 a to 28 c, normal boiling operation is executed in the first heat pump cycles 10 a to 10 c, and the respective rotation speeds (water pressure The PQ characteristic at a relatively high rotational speed that is assumed during normal boiling operation is shown by a bold solid line. Moreover, about the 4th water pump 28d, the defrost operation is performed in the 4th heat pump cycle 10d, and the PQ characteristic at the time of the rotation speed becoming the minimum rotation speed Npmin is shown with a thick broken line ing.

  As shown in FIG. 5, when only the fourth heat pump cycle 10 d is performing the defrosting operation and the other first to third heat pump cycles 10 a to 10 c are performing the normal boiling operation, Although the rotational speed Npd of the 4-water pump 28d is low, the rotational speeds Npa to Npc of the first to third water pumps 28a to 28c are high. Therefore, the average value Npave of the rotation speeds of the first to fourth water pumps 28a to 28d is relatively high.

  As described above, when the average value Npave of the rotation speeds of the first to fourth water pumps 28a to 28d is relatively high, the total discharge flow rate Qs increases. As shown by the broken line in the lower part of FIG. The pressure loss generated when water flows through the water circulation circuit 21, the water passages 122a to 122d of the water-refrigerant heat exchangers 12a to 12d, etc. increases, and the operating point also becomes a high value.

  For this reason, as shown in the condition A of FIG. 4, when the average value Npave of the rotation speeds of the first to fourth water pumps 28a to 28d is relatively high, the fourth water pump 28d having a reduced rotation speed is It is necessary to determine the minimum rotational speed Npmin to a relatively high value so that the discharge head is not insufficient.

  On the other hand, in the upper part of FIG. 6, when the heat pump type hot water heater 1 is activated, that is, when the first to fourth heat pump cycles 10 a to 10 d are activated, the first to fourth heat pump cycles 10 a to 10 d are activated. PQ characteristics when the heating capacity is low and the rotation speeds of the first to fourth water pumps 28a to 28d are all low are shown by solid lines.

  As shown in FIG. 6, the rotation speeds of the first to fourth water pumps 28a to 28d are all low, and the average value Npave of the rotation speeds of the first to fourth water pumps 28a to 28d is relatively low. Since the total discharge flow rate Qs decreases, as shown in the lower part of FIG. 6, when hot water flows through the water circulation circuit 21 and the water passages 122a to 122d of the water-refrigerant heat exchangers 12a to 12d, etc. The pressure loss occurring at the time is reduced and the operating point is also lowered.

  For this reason, when the average value Npave of the rotation speeds of the first to fourth water pumps 28a to 28d is relatively low, the minimum rotation speed Npmin is lower than the condition A as shown in the condition B of FIG. Even if it determines to, the 1st-4th water pumps 28a-28d will not run short of a discharge head.

  Therefore, as in this embodiment, the minimum water pumping capacity determination means determines to decrease the minimum rotation speed Npmin as the average value Npave of the rotation speeds of the first to fourth water pumps 28a to 28d decreases. Thus, when the average value Npave of the rotation speeds of the first to fourth water pumps 28a to 28d is relatively low, the minimum rotation speed Npmin is determined to be an unnecessarily high value, and the hot water storage tank 20 has a low temperature. It is possible to suppress the inflow of hot water.

  That is, according to the heat pump type hot water heater 1 of the present embodiment, low temperature hot water flows into the hot water storage tank 20 while suppressing shortage of the discharge head of the first to fourth water pumps 28a to 28d. Can be suppressed.

  Further, in the water circulation circuit 21 of the present embodiment, the flow of hot water flowing out from one outflow pipe 23 is diverted by the diverter 24 to the water passages 122a to 122d of the water-refrigerant heat exchangers 12a to 12d. In addition to adopting a circuit configuration to be supplied, a circuit configuration is adopted in which the flow of hot water flowing out from each of the water passages 122a to 122d is merged at the merging portion 25 and guided to the hot water storage tank 20 through one inflow pipe 26. ing.

  In such a circuit configuration, when the hot water storage tank 20 and each of the water passages 122a to 122d are connected by a plurality of pipes, a change in flow rate of hot water flowing through the outflow pipe 23 or the inflow pipe 26 becomes large. Cheap. Accordingly, the amount of change in pressure loss that occurs in the outflow pipe 23 or the inflow pipe 26 accompanying the change in the flow rate of hot water is likely to increase, and the amount of change in the operating point tends to increase.

  Therefore, in the configuration including the outflow pipe 23 and the diversion part 24 or the confluence part 25 and the inflow pipe 26 as in the present embodiment, the minimum water pumping capacity determination means is the first to fourth water pumps 28a to 28d. As the average value Npave of the engine speed decreases, it is determined to decrease the minimum engine speed Npmin, thereby effectively suppressing the low temperature hot water flowing into the hot water storage tank 20. be able to.

(Other embodiments)
The present invention is not limited to the above-described embodiment, and can be variously modified as follows without departing from the spirit of the present invention.

  (1) In the above-described embodiment, both the outflow pipe 23 and the diversion section 24, the merging section 25 and the inflow pipe 26 are provided, and the water passages 122a to 122d of the water-refrigerant heat exchangers 12a to 12d are provided. Although the example connected in parallel with respect to the hot water storage tank 20 was demonstrated, the connection of each water passage 122a-122d and the hot water storage tank 20 is not limited to this.

  For example, any one of the outflow pipe 23 and the diversion part 24, and the confluence part 25 and the inflow pipe 26 may be provided, and the water passages 122a to 122d and the hot water storage tank 20 may be connected in parallel. The water passages 122a to 122d may be connected to the hot water storage tank 20 completely in parallel by independent water pipes.

  (2) In the above-described embodiment, the example in which the rotation speeds Npa to Npd of the first to fourth water pumps 28a to 28d are detected from the applied voltages applied to the water pumps 28a to 28d has been described. Rotational speed detection means for directly detecting the rotational speeds of the first to fourth water pumps 28a to 28d are provided, and the detection values detected by the respective rotational speed detection means are supplied to the water pressure of the first to fourth water pumps 28a to 28d. It may be used as a capability.

  Moreover, in the above-mentioned embodiment, although the example which employ | adopted the rotation speed of the 1st-4th water pumps 28a-28d was demonstrated as water pumping capability of the 1st-4th water pumps 28a-28d, it replaced with this. The applied voltage applied to the first to fourth water pumps 28a to 28d, the applied current applied to the first to fourth water pumps 28a to 28d, and the like may be adopted as the water pressure feeding capability. Of course, it is good also as water pumping capability combining these parameters | indexes.

  (3) In the first to fourth heat pump cycles 10a to 10d of the above-described embodiment, carbon dioxide is adopted as the refrigerant to constitute a supercritical refrigeration cycle. An HC refrigerant or the like may be employed to constitute a subcritical refrigeration cycle in which the refrigerant pressure on the high pressure side of the cycle does not exceed the critical pressure of the refrigerant.

10a-10d heat pump cycle 12a-12d water-refrigerant heat exchanger 122a-122d water passage 20 hot water storage tank 28a-28d water pump

Claims (5)

A plurality of heat pump cycles (10a to 10d) for heating hot water,
A hot water storage tank (20) for storing hot water heated in the plurality of heat pump cycles (10a to 10d),
Each of the plurality of heat pump cycles (10a to 10d) includes water-refrigerant heat exchangers (12a to 12d) that heat-exchange hot water by exchanging heat between the high-temperature refrigerant and hot water.
A heat pump system in which water passages (122a to 122d) through which the hot water is circulated in the water-refrigerant heat exchangers (12a to 12d) are connected in parallel to the hot water storage tank (20). A water heater,
Furthermore, a plurality of water pumps (28a to 28d) for pumping the hot water to each of the water passages (122a to 122d),
Water pumping capacity control means for controlling the water pumping capacity of the plurality of water pumps (28a to 28d);
A minimum water pumping capacity determining means (S43) for determining a minimum water pumping capacity (Npmin) of the plurality of water pumps (28a to 28d),
The water pressure feed capacity control means controls the operations of the water pumps (28a to 28d) so that the water pressure feed capacity of the water pumps (28a to 28d) is equal to or higher than the minimum water pressure feed capacity (Npmin). Is,
The minimum water pumping capacity determining means (S43) decreases the minimum water pumping capacity (Npmin) as the average value (Npave) of the water pumping capacities of the water pumps (28a to 28d) decreases. A heat pump type water heater characterized by being determined by Furthermore, an outflow pipe (23) for flowing hot water from the hot water storage tank (20),
A diversion section (24) for diverting a flow of hot water flowing out from the outflow pipe (23) to the respective water passages (122a to 122d) is provided. The described heat pump type hot water heater. Furthermore, a merging section (25) for merging the flows of hot water flowing out from the water passages (122a to 122d),
The heat pump type hot water heater according to claim 1 or 2, further comprising an inflow pipe (26) for guiding the refrigerant flowing out from the junction (25) to the hot water storage tank (20) side.   The water pressure-feeding capacity control means includes a plurality of water pumps (28a to 28d) such that the boiling temperature of the hot water flowing out from the water passages (122a to 122d) approaches the target boiling temperature (Twot). The heat pump type hot water supply device according to any one of claims 1 to 3, wherein the water pumping capability is controlled.   The minimum water pressure-feeding capacity determining means (S43) includes a rotation speed of the plurality of water pumps (28a to 28d), an applied voltage applied to the plurality of water pumps (28a to 28d), and the plurality of water pumps ( The heat pump type hot water heater according to any one of claims 1 to 4, wherein at least one of the applied currents applied to 28a to 28d) is used as the water pumping capacity.

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