JP2007139415A - Heat pump water heater - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent freezing in a water circuit inside a heat pump unit 1a without circulating hot water inside a hot water tank 2a. <P>SOLUTION: When a three-way valve 14 is switched to a refrigerant bypass circuit 11a side, a freezing preventing operation for operating a heat pump cycle with low ability is set, and a controller 5 stops ordinary cycle operation, a freezing preventing operation is carried out if a water temperature detected by water temperature sensors 16 and 17 is below a predetermined value. In this way, when the heat pump cycle is operated with low ability and water supply for hot water is passed at a low flow rate through the water heat exchanger 7 and a bypass passage 19, hot water heated by the water heat exchanger circulates through a water circuit in the water heater via the bypass passage 19, so that freezing in the water circuit inside the heat pump unit 1a can be prevented. The hot water inside the hot water tank 2 is not affected. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a heat pump type water heater using a heat pump cycle as a means for heating hot water.

  Conventionally, as a method to prevent the water circuit in the water heater from being frozen and damaged in cold districts, water circulation in the water heater is stopped when the outside air temperature is low, and only the heating device is operated. Some water heat exchangers and surrounding water pipes are prevented from freezing.

  In JP-A-11-63661, water in the tank is circulated by a water pump to prevent the water circuit from freezing.

  However, in the method of operating only the conventional heating device, there is a problem that water pipes and water pumps in a part away from the water heat exchanger cannot be prevented from being frozen, and the method of circulating water in the tank of the above publication Then, when cold water flows into the tank, there is a problem that the hot water temperature in the tank decreases or the temperature distribution becomes uneven, making it difficult to control hot water at a desired temperature.

  The present invention has been made in view of the above-described conventional problems, and an object thereof is to provide a heat pump type water heater that can prevent freezing of a water circuit in a water heater without circulating hot water in a tank. There is to do.

  In order to achieve the above object, the present invention employs the following technical means.

  A hot water supply apparatus according to the present invention includes a hot water storage tank (2) for storing hot water supply water, a compressor (6) for pressurizing and discharging sucked refrigerant, and a refrigerant and hot water storage tank pressurized by the compressor (6). A water heat exchanger (7) configured to perform heat exchange with the hot water supplied from (2) via the flowing water pipe (3) so that the flow direction of the refrigerant and the flow direction of the hot water are opposed to each other. And an expansion valve (8) for depressurizing the refrigerant flowing out of the water heat exchanger (7), and an air heat exchanger (9) for exchanging heat between the refrigerant depressurized by the expansion valve (8) and the outside air A water supply pipe (3) for circulating hot water supply water between the cycle, the hot water storage tank (2) and the water heat exchanger (7), and a water pump (4) provided in the water supply pipe (3) for circulating hot water supply water (4) ), A bypass passage (19) for bypassing the hot water storage tank (2), A water flow path switching means (20) for switching the hot water flow path between the hot water storage tank (2) side and the bypass passage (19) side, water temperature detection means (16, 17) for detecting the water temperature of the flowing water pipe (3), The water flow switching means (20) is switched to the hot water storage tank (2) side, the heat pump cycle is operated, the normal cycle operation for circulating the hot water supply water, and the normal cycle operation are stopped. When the water temperature detected by the detection means (16, 17) is lower than a predetermined value, the heat pump cycle is operated with a lower capacity than during normal cycle operation, and the water heat exchanger has a flow rate with less hot water flow. The compressor (6), the water flow path switching means (20), and the water flow switching device (7) and the antifreezing operation for circulating the hot water supply water so as to pass through the bypass passage (19). Those having a control device for controlling the Taponpu (4) and (5).

  Thereby, in a state where the normal cycle operation is stopped, when the water temperature detected by the water temperature detection means (16, 17) becomes lower than a predetermined value, the heat pump cycle has a lower capacity than the normal cycle operation. The hot water heated by the water heat exchanger (7) is passed through the bypass passage (19) at a low flow rate and through the bypass passage (19), so that the hot water heated by the water heat exchanger passes through the bypass passage. Since the water circuit in the water heater is circulated, the freezing can be prevented. Moreover, since the hot water supply water is circulated through the bypass passage, the hot water in the hot water storage tank is not affected.

  In addition, during the freeze prevention operation, it is desirable to operate the compressor (6) at a lower speed than during normal cycle operation.

  Incidentally, the reference numerals in parentheses of each means described above are an example showing the correspondence with the specific means described in the embodiments described later.

  Next, the heat pump type water heater of the present invention will be described based on the drawings.

(First embodiment)
FIG. 1 is a schematic diagram showing a configuration of a heat pump type water heater in the first embodiment of the present invention. A heat pump type hot water heater 1 in this embodiment includes a hot water storage tank 2 for storing hot water supply water, a flowing water pipe 3 connected to the hot water storage tank 2, a water pump 4 for circulating hot water supply water through the flowing water pipe 3, and hot water supply water. A heat pump unit 1a of a supercritical heat pump cycle, which will be described later, which is a heating means, a control device 5 that controls the operation of the heat pump type hot water heater 1, and the like.

  The hot water storage tank 2 is made of metal (for example, made of stainless steel) having excellent corrosion resistance and has a heat insulating structure, and can keep hot hot water for a long time. Hot water for hot water stored in the hot water storage tank 2 is mixed with cold water at the time of use and adjusted in temperature, and then used mainly in kitchens, baths, etc. In addition to hot water supply, for example, for floor heating, indoor air conditioning, etc. It can also be used as a heat source.

  The flowing water pipe 3 includes a cold water pipe 3 a and a hot water pipe 3 b that connect the hot water storage tank 2 and a water heat exchanger 7 described later. One end of the cold water pipe 3 a is connected to a cold water outlet 2 a provided in the lower part of the hot water storage tank 2, and the other end is connected to an inlet of a water passage (not shown) provided in the water heat exchanger 7. One end of the hot water pipe 3 b is connected to the outlet of the water passage, and the other end is connected to a hot water inlet 2 b provided in the upper part of the hot water storage tank 2.

  As shown by an arrow in FIG. 1, the water pump 4 is configured so that hot water in the hot water storage tank 2 flows from the cold water outlet 2a through the cold water pipe 3a → water passage → hot water pipe 3b and returns to the hot water tank 2 from the hot water inlet 2b. To generate water flow. The water pump 4 can adjust the amount of flowing water according to the rotation speed of a built-in motor (not shown).

As shown in FIG. 1, the supercritical heat pump cycle includes a compressor 6, a water heat exchanger 7, an expansion valve 8, an air heat exchanger 9, an accumulator 10, and a refrigerant pipe (high pressure pipe 11 and low pressure pipe) connecting these devices. 12) and the like, and carbon dioxide (CO ₂ ) having a low critical temperature is enclosed as a refrigerant.

  The compressor 6 is driven by a built-in motor (not shown), and compresses and discharges the sucked gas refrigerant to a critical pressure or higher. The refrigerant discharge amount of the compressor 6 varies according to the rotation speed of the motor.

  The water heat exchanger 7 exchanges heat between the high-temperature and high-pressure gas refrigerant pressurized by the compressor 6 and hot water supply water, and is provided with a refrigerant passage (not shown) adjacent to the water passage described above. The flow direction of the refrigerant flowing through the refrigerant passage is configured to face the flow direction of the hot water supply water flowing through the water passage.

  The expansion valve 8 is provided between the water heat exchanger 7 and the air heat exchanger 9, decompresses the refrigerant cooled by the water heat exchanger 7, and supplies the decompressed refrigerant to the air heat exchanger 9. The expansion valve 8 has a configuration capable of electrically adjusting the valve opening degree, and is energized and controlled by the control device 5.

  The air heat exchanger 9 receives the air blown by the outside air fan 15 and evaporates the refrigerant decompressed by the expansion valve 8 by heat exchange with the outside air.

The accumulator 10 gas-liquid separates the refrigerant evaporated in the air heat exchanger 9 to store excess refrigerant in the cycle, and causes the compressor 6 to suck only the gas refrigerant.
Next, the main part of the present invention will be described.

  A water circuit heating section 13 is provided with a refrigerant bypass circuit 11a in the high-pressure pipe 11 between the water heat exchanger 7 and the expansion valve 8, and warms the chilled water pipe 3a upstream of the water pump 4 beyond the refrigerant bypass circuit 11a. Was provided.

  As shown in the perspective view in the circle of FIG. 1, the water circuit heating unit 13 wraps the refrigerant pipe 13a made of a copper capillary tube or the like around the outer periphery of the cold water pipe 3a formed of a brass pipe or the like so that the contact surface is It is joined by brazing or the like to facilitate heat exchange, and is covered with a heat insulating material 13b to insulate the outside air.

  Switching to the refrigerant bypass circuit 11a is performed by a three-way valve 14 which is a refrigerant flow switching means provided in the high-pressure pipe 11, and the bypassed refrigerant heats the hot water supply water in the cold water pipe 3a by the water circuit heating unit 13. The high pressure pipe 11 between the three-way valve 14 and the expansion valve 8 is returned. The three-way valve 14 is energized and controlled by the control device 5.

  The heat pump type water heater 1 described above includes a water temperature sensor 16 such as a thermistor as hot water supply temperature detecting means for detecting the temperature (water supply temperature) of hot water flowing into the water heat exchanger 7 and hot water flowing out of the water heat exchanger 7. A water temperature sensor 17 such as a thermistor is provided as hot water temperature detecting means for detecting the temperature of the water (hot water temperature), and detection signals from both sensors 16 and 17 are input to the control device 5.

  Next, normal cycle operation will be described.

  The refrigerant is pressurized by the compressor 6 to become high temperature and high pressure, is radiated and cooled to the hot water supply water by the water heat exchanger 7, is supplied to the expansion valve 8 without passing through the refrigerant bypass circuit 11 a, and The pressure is reduced according to the opening. The low-temperature and low-pressure refrigerant that has been decompressed absorbs heat from the outside air by the air heat exchanger 9 (outside air fan: ON), evaporates, is separated into gas and liquid by the accumulator 10, and then is a cycle in which only the gas refrigerant is sucked into the compressor 6. repeat.

  The hot water supply water is pressurized by the water pump 4, absorbs heat from the refrigerant by the water heat exchanger 7, becomes hot water, and is sent to the hot water storage tank 2 for storage. Then, when the water temperature sensor 16 detects that the hot water storage tank 2 is entirely warm water and the temperature of the water supply from the cold water pipe 3a side is increased, the circulation of the refrigerant and hot water supply water is stopped.

  Next, the antifreezing operation of the water circuit in the heat pump type hot water heater 1 during the cycle operation stop according to the present invention will be described. FIG. 2 is a flowchart showing a processing procedure in the control device 5.

  In step S1, the detection signals of the water temperature sensors 16 and 17 are fetched at a constant cycle, and it is determined whether or not the water temperature of the water circuit is a temperature that requires anti-freezing operation. In the present embodiment, 3 ° C. or less is set as the temperature required for the freeze prevention operation. If the temperature is higher than 3 ° C., the process returns to continue the determination of the water temperature. To start.

  In step S2, the three-way valve 14 is switched to the refrigerant bypass path 11a side, and the compressor 6 is driven at a low speed of about 1000 rotations with respect to the normal 4 to 5,000 rotations. Thereby, the said water circuit is warmed by the water heat exchanger 7 and the water circuit heating part 13, and freezing is prevented.

  In step S3, it is detected that the water temperature of the water circuit has sufficiently increased during the freeze prevention operation. In this embodiment, when it becomes higher than 10 degreeC, it progresses to step S4 and freeze prevention operation is stopped.

  In step S4, the compressor 6 is stopped and the three-way valve 14 is switched to the side not passing through the normal refrigerant bypass circuit 11a.

  In this way, by operating the heat pump cycle with a low capacity, the water heat exchanger 7 and the water circuit heater 13 provided at the tip of the refrigerant bypass circuit 11a, the portion of the chilled water pipe 3a away from the water heat exchanger 7 Since the water pump 4 is also warmed, the water circuit in the heat pump unit 1a can be prevented from freezing. Further, since the hot water supply water is not circulated, the hot water in the hot water storage tank 2 is not affected.

(Second Embodiment)
Drawing 3 is a mimetic diagram showing the composition of the heat pump type water heater in a 2nd embodiment of the present invention. The difference from the first embodiment of FIG. 1 is that a bypass passage 19 for bypassing the hot water storage tank 2 is provided in the flowing water pipe 3 in the water circuit instead of the refrigerant bypass circuit 11a in the high pressure pipe 11 part in the heat pump cycle. The switching to the bypass passage 19 is performed by a three-way valve 20 which is a water flow path switching means provided in the hot water pipe 3 b, and the three-way valve 20 is energized and controlled by the control device 5.

  Normal cycle operation is the same as in the first embodiment.

  Next, the antifreezing operation of the water circuit in the heat pump type hot water heater 1 during the cycle operation stop according to the present invention will be described. FIG. 4 is a flowchart showing a processing procedure in the control device 5.

  In step S5, the detection signals of the water temperature sensors 16 and 17 are fetched at a constant cycle, and it is determined whether or not the water temperature of the water circuit is a temperature that requires anti-freezing operation. In this embodiment, 3 ° C. or less is set as the temperature required for the freeze prevention operation. If the temperature is higher than 3 ° C., the process returns and only the water temperature determination is continued. To start.

  In step S6, the three-way valve 20 is switched to the bypass passage 19 side, and the water pump 4 is driven at a low speed, and the compressor 6 is driven at a low speed of about 1000 revolutions for the normal 4 to 5,000 revolutions.

  In step S7, it is detected that the water temperature of the water circuit has sufficiently increased during the freeze prevention operation. In this embodiment, when it becomes higher than 10 degreeC, it progresses to step S8 and stops freezing prevention driving | operation.

  In step S8, the compressor 6 and the water pump 4 are stopped, and the three-way valve 20 is switched to the side not passing through the normal bypass passage 19.

  As described above, the heat pump cycle is operated at a low capacity, and the hot water heated by the hydrothermal exchanger 7 is passed through the bypass passage 19 to circulate the water circuit in the heat pump unit 1a by circulating the hot water supply water at a low flow rate. Since it circulates, it can be prevented from freezing. Further, since the hot water supply water is circulated through the bypass passage 19, the hot water in the hot water storage tank 2 is not affected.

(Other embodiments)
In the first embodiment, the refrigerant bypass circuit 11a is provided on the heat pump cycle side, and in the second embodiment, the bypass passage 19 is provided on the water circuit side. Of course, both may be provided.

  Further, in the above-described embodiment, the rotation speed of the compressor 6 during the freeze prevention operation is set to a predetermined low speed rotation. However, depending on the temperature rise of the water circuit due to the heating, the degree of heating is determined by the rotation speed of the compressor 6 or the like. It is good also as control which adjusts.

  The present invention may be applied not only to the heat pump cycle but also to other refrigerant compression refrigeration cycles.

It is a schematic diagram which shows the structure of the heat pump type water heater in 1st Embodiment of this invention. It is a flowchart figure which shows the process sequence of a control apparatus. It is a schematic diagram which shows the structure of the heat pump type water heater in 2nd Embodiment of this invention. It is a flowchart figure which shows the process sequence of a control apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1a Heat pump unit 2 Hot water storage tank 3 Flowing water piping 4 Water pump 5 Control apparatus (control means)
6 Compressor 7 Water heat exchanger 8 Expansion valve 9 Air heat exchanger 10 Accumulator 11 High pressure pipe 11a Refrigerant bypass circuit 13 Water circuit heater 14 Three-way valve (refrigerant flow switching means)
16, 17 Water temperature sensor (water temperature detection means)
19 Bypass passage 20 Three-way valve (Water flow path switching means)

Claims (2)

A hot water storage tank (2) for storing hot water supply water;
A compressor (6) that pressurizes and discharges the sucked refrigerant, a refrigerant pressurized by the compressor (6), and hot water supply water supplied from the hot water storage tank (2) via a flowing water pipe (3) The water heat exchanger (7) configured so that the flow direction of the refrigerant and the flow direction of the hot water supply are opposed to each other, and expansion for reducing the pressure of the refrigerant flowing out of the water heat exchanger (7) A heat pump cycle having a valve (8) and an air heat exchanger (9) for exchanging heat of the refrigerant decompressed by the expansion valve (8) with outside air;
A flowing water pipe (3) for circulating the hot water supply water between the hot water storage tank (2) and the water heat exchanger (7);
A water pump (4) provided in the flowing water pipe (3) for circulating the hot water supply water;
A bypass passage (19) for bypassing the hot water storage tank (2);
Water flow path switching means (20) for switching the flow path of the hot water supply water between the hot water storage tank (2) side and the bypass passage (19) side;
Water temperature detecting means (16, 17) for detecting the water temperature of the flowing water pipe (3);
Switching the water flow path switching means (20) to the hot water storage tank (2) side, operating the heat pump cycle and circulating the hot water supply water;
In a state where the normal cycle operation is stopped, when the water temperature detected by the water temperature detecting means (16, 17) becomes lower than a predetermined value, the heat pump cycle is set lower than that during the normal cycle operation. In addition to operating at the capacity, the anti-freezing operation of circulating the hot water running water so that the hot water running water heated by the water heat exchanger (7) passes through the bypass passage (19) with a small flow rate is performed. As described above, a heat pump type hot water heater having the compressor (6), the water flow path switching means (20), and a control device (5) for controlling the water pump (4). The heat pump type water heater according to claim 1, wherein during the freeze prevention operation, the compressor (6) is operated at a lower speed than during the normal cycle operation.

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