JP2007327725A - Heat pump type water heater - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent a compressor from being protectively stopped by abnormal rise of the temperature or pressure of a gas coolant in boiling up water. <P>SOLUTION: This heat pump type water heater is provided with: a boiling-up circulation passage used for extracting water in a bottom part of a hot-water storage tank 11 by a circulation pump 13 to return it to an upper part of the hot-water storage tank by heating it by a water-coolant heat exchanger 2 arranged in a heat pump cycle; and a control device controlling the temperature of the hot water output from the water-coolant heat exchanger to a boiling-up preset temperature. The control device controls the circulation pump 13 by determining a target value Fw* of a circulation flow rate in the boiling-up circulation passage based on a target heating capability value Q* in the water-coolant heat exchanger, a boiling-up preset temperature Two* and a detection temperature Twi of influent water of the water-coolant heat exchanger (31), and controls a detection value Fw of the circulation flow rate to the target value Fw*, whereby the abnormal rise of the temperature or pressure of the gas coolant is prevented. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a heat pump type water heater, and more specifically, to a technique for storing hot water at a desired temperature in a hot water storage tank using midnight power or the like.

  2. Description of the Related Art A heat pump type hot water heater having a boiling function for driving a heat pump cycle using midnight power or the like and heating low temperature water to store hot water at a desired temperature in a hot water storage tank is known (for example, Patent Document 1). . Such a heat pump water heater is configured to circulate low-temperature water extracted from the bottom of the hot water storage tank to a water-refrigerant heat exchanger provided in the heat pump cycle, raise it to a set temperature, and return it to the upper part of the hot water storage tank. Has been. Thereby, the required amount of hot water of the desired temperature can be secured in the hot water storage tank.

  In such a heat pump type water heater, generally, the maximum heating capacity of the heat pump is planned so that it can be boiled up in a predetermined time. Moreover, it is planned on the assumption that the low temperature water is boiled to a desired temperature by passing it through the water-refrigerant heat exchanger once. Therefore, according to the boiling control described in Patent Document 1, it is necessary to detect the temperature of the low-temperature water flowing into the water-refrigerant heat exchanger and to heat the low-temperature water to a desired boiling set temperature. The amount of heat is calculated, and the circulation flow rate of low-temperature water that can be heated to the boiling upper temperature is calculated by the heating capacity of the heat pump. And the rotation speed of the circulation pump which draws out low temperature water from the bottom part of a hot water storage tank, and flows in into a water-refrigerant heat exchanger is controlled, and it is made to control to the target circulation flow volume. According to Patent Document 1, since the heating capacity of the heat pump varies depending on the outside air temperature, the circulation flow rate is corrected and controlled based on the outside air temperature.

JP 2003-222396 A

  By the way, the circulation pipes forming the boiling circulation path have different lengths depending on the distance between the hot water storage tank and the water-refrigerant heat exchanger. Further, the number of bends varies depending on the route of the piping. Therefore, the value of the pressure loss of the boiling circuit differs depending on the installation status of the heat pump type hot water heater.

  Therefore, as described in Patent Document 1, in the case of a system in which the circulation flow rate is controlled by the rotation speed of the circulation pump, the pump flow rate corresponding to the pump rotation speed changes according to the pressure loss of the boiling circulation path. There is a problem that the target circulating flow rate cannot be controlled. For example, if the actual circulation flow rate is less than the target circulation flow rate, the heat balance of the heat pump cycle is lost, the temperature and pressure of the gas refrigerant discharged from the compressor rises abnormally, and a stop function is provided to protect the compressor. There is a risk of working automatically. Even if the operation of the heat pump can be performed normally, the boiling operation time may be longer because it is less than the target circulation flow rate. Conversely, if the actual circulation flow rate is higher than the target circulation flow rate, the amount of heating in the water-refrigerant heat exchanger will be insufficient, and hot water that does not reach the boiling set temperature will be stored and will not meet customer requirements. There is a fear.

  Therefore, it is conceivable to change the control data of the pump flow rate corresponding to the rotation speed of the circulation pump in accordance with the pressure loss of the actual boiling circuit, but this will hinder the standardization of the control device. In particular, due to secular change, scales or the like may accumulate in the piping of the boiling circuit, and the pressure loss may change. In such a case, it is substantially difficult to change the control data.

  A first object of the present invention is to realize boiling control that can prevent the compressor from being stopped due to an abnormal increase in gas refrigerant temperature or pressure during boiling control.

  Further, in addition to the above problem, a second problem is to keep the boiling operation time at a predetermined time.

  The present invention relates to a compressor that compresses a refrigerant, a water-refrigerant heat exchanger that heats water using a gas refrigerant discharged from the compressor, and an expansion valve that flows from the water-refrigerant heat exchanger. An evaporator for evaporating liquid refrigerant and returning it to the compressor; a hot water storage tank connected to a water supply source; and water in the hot water storage tank is extracted by a circulation pump and distributed to the water-refrigerant heat exchanger to be supplied to the hot water storage tank And a heat pump type hot water heater provided with a control circuit for controlling the hot water temperature heated by the water-refrigerant heat exchanger to the boiling upper set temperature.

  The control device according to the first aspect of the present invention for solving the first problem includes a heating capacity in the water-refrigerant heat exchanger, a set boiling temperature, and a detected temperature of the inflowing water in the water-refrigerant heat exchanger. Based on the above, a target value for the circulation flow rate in the circulation path is determined, the circulation flow rate in the circulation path is detected by a flow sensor, and the circulation pump is controlled to match the detection value of the circulation flow rate with the target value It is characterized by doing.

  That is, since the circulation pump is feedback-controlled so that the detected value of the circulating flow detected by the flow sensor matches the target value, the target circulating flow rate can be set regardless of the pressure loss in the boiling circuit. It can flow. As a result, an abnormal increase in gas refrigerant temperature or pressure during boiling control can be avoided, and the compressor can be prevented from being protected from being stopped.

  In addition, since the heating capacity in the water-refrigerant heat exchanger can be maintained at the planned value, it is possible to prevent the boiling time from becoming longer than planned, and to secure a hot water storage amount at a necessary temperature within the time when midnight power can be used. be able to. Furthermore, since it is not necessary to change the pump flow rate control data corresponding to the rotational speed of the circulation pump in accordance with the actual pressure loss in the boiling circuit, the standardization of the control device can be maintained. In some cases, it may be difficult to adapt the compression capacity of the compressor to all changes in the external environment such as the outside air temperature. In this case, there arises a problem that the boiling water temperature is not stable at a certain limit.

  The control device according to the second aspect of the present invention for solving the first problem detects a hot water temperature heated by the water-refrigerant heat exchanger by a temperature sensor, and sets the detected temperature to the boiling set temperature. The compression capacity of the compressor is controlled to match.

  That is, the heating capacity is controlled by feedback control of the compression capacity of the compressor so that the detected temperature of the hot water heated by the water-refrigerant heat exchanger matches the set boiling temperature. Regardless of the pressure loss of the circulation path and the circulation flow rate, the hot water temperature can be controlled to the boiling upper set temperature. As a result, similarly to the first aspect, it is possible to avoid an abnormal increase in the gas refrigerant temperature or pressure during the boiling control, and it is possible to prevent the compressor from being protected and stopped.

  In the case of the second mode, it is only necessary to provide a temperature sensor that detects the temperature of hot water heated by the water-refrigerant heat exchanger. The number of sensors can be reduced as compared with the first mode that requires a sensor and a flow rate sensor for circulating water. However, since the compression capacity of the compressor is reduced when the hot water temperature exceeds the boiling set temperature, there may be a problem that the heating capacity falls below the planned value and the boiling time becomes longer than planned. . In such a case, if the circulation pump has a capacity, it can be dealt with by changing the set value of the rotation speed.

  In order to solve the second problem, the third aspect of the present invention is characterized by including both the control devices of the first and second aspects. This makes it possible to avoid the problems of the control devices of the first and second modes, to avoid an abnormal increase in gas refrigerant temperature or pressure during boiling control, and to stop the compressor from being protected. It is possible to provide a heat pump type hot water heater that can prevent boiling down and that the boiling temperature does not decrease and the boiling time does not become longer than planned.

  According to the present invention, it is possible to avoid the protection of the compressor being stopped due to an abnormal rise in the gas refrigerant temperature or pressure during the boiling control.

  Moreover, according to the other invention of this invention, in addition to said effect, boiling operation time can be kept at predetermined time.

  Hereinafter, an embodiment of a heat pump type water heater of the present invention will be described with reference to the drawings.

(Embodiment 1)
FIG. 1 shows a system configuration diagram of an embodiment of a heat pump type hot water heater of the present invention, and FIG. 2 shows a block configuration diagram of a control device that is a characteristic part of the present invention.

  As shown in FIG. 1, the heat pump type hot water heater of the present embodiment is connected to a heat pump cycle on the left side of the drawing and a hot water supply system on the right side through a water-refrigerant heat exchanger 2. The heat pump cycle includes a compressor 1 that compresses refrigerant, a water-refrigerant heat exchanger 2 having a heat transfer pipe 2a through which a gas refrigerant discharged from the compressor 1 is circulated through a refrigerant pipe 3, and a heat transfer pipe 2a. An evaporator 5 into which the liquid refrigerant that flows out flows through the refrigerant pipe 6 and the expansion valve 4, and a refrigerant pipe 7 that returns the gas refrigerant that flows out from the evaporator 5 to the compressor 1 are formed. . Outside air is passed through the evaporator 5 by a fan 8.

  The hot water supply system includes a hot water storage tank 11 for storing a required amount of hot water, a circulation pump 13 communicated with the bottom of the hot water storage tank 11 via a pipe 12, and water discharged from the circulation pump 13 as water-refrigerant heat exchanger 2. A circulation pipe 14 that leads to the heat transfer pipe 2 b and a circulation pipe 15 that returns hot water flowing out from the heat transfer pipe 2 b to the top of the hot water storage tank 11 are formed. In addition, a water supply source such as a water supply (not shown) is connected to the bottom of the hot water storage tank 11 via a water supply pipe 16, and a hot water supply pipe 17 for supplying hot water to a place of use is connected to the top.

  In the vicinity of the evaporator 5, an outside air temperature sensor 23 for measuring the outside air temperature is provided. The circulation pipe 14 is provided with an incoming water temperature sensor 25 that measures the temperature of the water flowing into the heat transfer pipe 2 b of the water-refrigerant heat exchanger 2. Further, the circulation pipe 14 on the discharge side of the circulation pump 13 is provided with a flow rate sensor 27 for measuring the boiling circulation flow rate.

  The basic operation of this embodiment configured as described above will be described. First, water is supplied from a water supply pipe 16 to a circulation path including a hot water storage tank 11 and a circulation pipe 12, a circulation pipe 14, a heat transfer pipe 2 b, and a circulation pipe 15. Next, the circulation pump 13 is driven to circulate the water in the hot water storage tank 11 through the circulation path, and the compressor 1 is driven to start up the heat pump cycle. When the compressor 1 is driven, the compressed high-temperature gas refrigerant flows in the direction indicated by the arrow 24 in the figure, and is introduced into the heat transfer tube 2 a of the water-refrigerant heat exchanger 2. The high-temperature gas refrigerant introduced into the heat transfer tube 2a condenses by heating the water flowing through the heat transfer tube 2b. The liquid refrigerant condensed in the heat transfer tube 2 a is guided to the expansion valve 4, is adiabatically expanded, and flows into the evaporator 5. The liquid refrigerant that has flowed into the evaporator 5 is heated by the heat of the outside air that is passed through the fan 8 and evaporated to return to the compressor 1, and the above-described heat pump cycle is continuously performed. Thereby, the water circulated through the circulation path is heated by the heat transfer pipe 2 b of the water-refrigerant heat exchanger 2, boiled up, and hot water is stored in the hot water storage tank 11.

  Next, an outline of the boiling control will be described. First, the amount of hot water used in a day varies depending on the time of day, and when it is divided into daytime, nighttime, and midnight, the amount of midnight usage is generally small. Therefore, in order to average the load of the heat pump cycle, the hot water is boiled and stored in the hot water storage tank 11 at a time when the amount of hot water supply is small, for example, at midnight, and hot water is supplied from the hot water storage tank 11 when the hot water supply load is large in the daytime or night I am doing so.

  Moreover, there are various usage modes of hot water to be supplied such as mixing water and adjusting the temperature. Therefore, design specifications such as the boiling water temperature, the capacity of the hot water storage tank (the amount of hot water storage), the boiling time, and the heating capacity of the heat pump are determined according to the usage mode and usage of hot water. Then, when boiling up, the compressor 1 is operated with the compression capacity held at a set value, and the circulation pump 13 is rotated so that the hot water temperature flowing out from the water-refrigerant heat exchanger 2 becomes the set boiling temperature. The boiling circulation flow rate is controlled by controlling the number. In addition, when using hot water, the hot water temperature and the amount of hot water stored in the hot water storage tank 11 are monitored, and the compressor 1 and the circulation pump 13 are operated as necessary to increase the boiling temperature as in the case of boiling. .

  Here, the control device of the present embodiment according to the features of the present invention will be described with reference to FIG. In FIG. 2, when the boiling control start command 32 is input, the calculator 31 calculates the target heating capacity value (for example, maximum heating capacity) Q * of the heat pump and the incoming water temperature measured by the incoming water temperature sensor 25. The detection value Twi and the boiling set temperature Two * that is variably set are taken in. The target heating capacity value Q * is calculated by a calculator (not shown) based on a preset setting value of the heating capacity of the heat pump per unit time and the outside air temperature Ta measured by the outside air temperature sensor 23. Is done. The computing unit 31 calculates the target value Fw * of the circulating flow rate of boiling by the following equation (1) based on the input information. In the equation, k is a constant.

Fw * = kQ * / (Two * -Twi) (1)
The target value Fw * of the circulating flow output from the calculator 31 is input to the subtractor 33, and a difference ΔFw from the detected value Fw of the circulating flow measured by the flow sensor 27 is obtained. This ΔFw is input to the motor controller 34 that controls the rotational speed of the circulation pump 13. The motor control device 34 controls the rotational speed of the circulation pump 13 so as to reduce the inputted ΔFw. Thereby, the discharge amount of the circulation pump 13 is controlled, and the flow rate of the low-temperature water circulated through the water-refrigerant heat exchanger 2 is controlled to the target value Fw * of the circulation flow rate. In the case where the motor that drives the circulation pump 13 is, for example, a DC motor, the motor control device 34 can be configured to control the rotational speed of the circulation pump 13 by controlling the DC voltage supplied to the motor.

  That is, the control device in FIG. 2 circulates in the boiling circuit based on the heating capacity in the water-refrigerant heat exchanger 2, the boiling upper temperature, and the detected temperature of the inflow water of the water-refrigerant heat exchanger. A target value of the flow rate is determined, and the circulating pump 13 is controlled to control the detected value of the circulating flow rate in the boiling circulation path to the target value.

  According to the present embodiment, the flow rate sensor 27 is provided in the boiling circulation path, and the flow rate of the circulation pump is feedback controlled according to the target value of the circulation flow rate, so regardless of the pressure loss in the boiling circulation path. The target circulation flow rate can be flowed. As a result, at the time of boiling, the heat balance of the heat pump cycle is lost due to pressure loss in the circulation path, and the temperature of the gas refrigerant sucked into the compressor 1 is abnormally increased, or the pressure of the gas refrigerant is abnormally increased. To avoid inconvenience. Generally, when the temperature or pressure of the gas refrigerant rises abnormally, the compressor 1 is stopped and protected, but according to the present embodiment, such a protection operation can be avoided.

  In addition, according to the present embodiment, since the compression capacity of the compressor is held at the set value, the heating capacity can be held at the planned value, the boiling time can be prevented from becoming longer than planned, and the midnight power can be reduced. The amount of hot water stored at the required temperature can be secured within the available time.

  Furthermore, since it is not necessary to change the pump flow rate control data corresponding to the rotation speed of the circulation pump in accordance with the actual pressure loss in the boiling circuit, the standardization of the control device can be maintained. In addition, according to this embodiment, it may be difficult to make the compression capacity of the compressor 1 correspond to all changes in the external environment such as the outside air temperature. In this case, there may be a problem that the boiling water temperature is not stable within a certain limit.

(Embodiment 2)
FIG. 3 shows a system configuration diagram of the heat pump type water heater of the present embodiment, and FIG. 3 shows a block configuration diagram of the main part of the control device of the present embodiment. The present embodiment is different from the first embodiment in that a hot water temperature sensor 26 flowing out from the heat transfer pipe 2b is provided in the circulation pipe 15, and a flow rate sensor 27 is not provided. Since others are the same as those of the first embodiment, the same reference numerals are given and description thereof is omitted. The control device of the present embodiment is characterized in that instead of controlling the circulation flow rate in the boiling circuit, the compression amount of the compressor 1 is controlled so that the temperature detected by the tapping temperature sensor 26 is maintained at the boiling temperature. It is in that.

  That is, as shown in FIG. 4, the control device takes in the boiling set temperature Two * that is variably set, takes in the temperature Two detected by the tapping temperature sensor 26, and in the subtractor 41, the temperature difference ΔTwo (= Two * −Two) is obtained, and the temperature difference ΔTwo is output to the motor controller 42. The motor control device 42 controls the heating capacity of the heat pump by controlling the rotation speed of the compressor 1 so as to reduce the temperature difference ΔTwo and controlling the compression capacity. Here, when the motor that drives the compressor 1 is, for example, an AC motor, the motor control device 42 has an inverter that controls the frequency of the AC voltage supplied to the motor to control the rotation speed of the compressor 1. Can be configured.

  Since it is configured in this way, according to the control device of the present embodiment, even if the planned circulation flow rate does not flow due to the difference in pressure loss of the circulation piping, etc., by reducing the heating capacity of the heat pump, The heat balance of the heat pump cycle can be taken. As a result, it is possible to avoid the disadvantage that the temperature of the gas refrigerant sucked into the compressor 1 abnormally rises or the pressure of the gas refrigerant rises abnormally, so that it is possible to avoid stopping the compressor due to the protective operation.

  Moreover, since the sensor of this embodiment is only the tapping temperature sensor 26, the number of sensors can be reduced compared with Embodiment 1 in which the outside temperature sensor 23, the incoming water temperature sensor 25, and the flow sensor 27 are required.

  According to the present embodiment, when the hot water temperature exceeds the boiling set temperature, the compression capacity of the compressor 1 is reduced, so that the heating capacity is lower than the planned value, and the boiling time is longer than planned. Will occur. In this case, if there is a margin in the pump capacity of the circulation pump 13, it can be dealt with by changing the set value of the rotational speed.

(Embodiment 3)
Here, an embodiment of the present invention that includes both the boiling control of the first embodiment and the second embodiment will be described. According to the first embodiment, it may be difficult to make the compression capacity of the compressor 1 compatible with all changes in the external environment such as the outside air temperature. In this case, there arises a problem that the boiling water temperature is not stable within a certain limit. On the other hand, according to the second embodiment, when the hot water temperature exceeds the boiling set temperature, the compression capacity of the compressor is reduced, so that the heating capacity is lower than the planned value, and the boiling time becomes longer than planned. appear.

  According to the present embodiment, it is not necessary to hold the set value of the compression capacity of the compressor described in the first embodiment, and a planned circulation flow rate can be obtained due to a difference in circulation piping.

(Embodiment 4)
FIG. 5 shows a block diagram of another embodiment of the control device of the present invention. This embodiment is provided independently in addition to the control devices of the first and second embodiments. As shown in the figure, the control device of the present embodiment includes a computing unit 51 and starts the operation of the fan 8 by the input fan operation command 52, and also detects the detected value Ta of the outside air temperature and the rotational speed of the compressor 1. The rotational speed command Nf of the fan 8 is determined according to Nc, and the rotational speed command Nf is output to the motor control device 53. The motor control device 53 controls the rotational speed of the fan 8 by changing the voltage supplied to the fan 8 driven by, for example, a DC motor in accordance with the rotational speed command Nf. Since it is comprised in this way, according to this embodiment, the change of boiling temperature can be suppressed.

It is a system lineblock diagram of the heat pump type hot water supply machine of one embodiment of the present invention. It is a block block diagram of one Embodiment of the control apparatus which concerns on the characteristic of this invention. It is a system | strain block diagram of the heat pump type water heater of other embodiment of this invention. It is a block block diagram of other embodiment of the control apparatus which concerns on the characteristic of this invention. It is a block block diagram of further another embodiment of the control apparatus which concerns on the characteristic of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Compressor 2 Water-refrigerant heat exchanger 4 Expansion valve 5 Evaporator 11 Hot water storage tank 13 Circulation pump 23 Outside temperature sensor 25 Incoming water temperature sensor 27 Flow rate sensor 31, 51 Calculator 33, 41 Subtractor 34, 42, 53 Motor control Device 42 Motor control device

Claims (4)

A compressor that compresses the refrigerant, a water-refrigerant heat exchanger that heats water using gas refrigerant discharged from the compressor, and a liquid refrigerant that flows from the water-refrigerant heat exchanger through an expansion valve evaporates An evaporator for returning to the compressor, a hot water storage tank connected to a water supply source, and a circulation path for extracting water from the hot water storage tank through a circulation pump and circulating it to the water-refrigerant heat exchanger and returning it to the hot water storage tank And a controller for controlling the hot water temperature heated by the water-refrigerant heat exchanger to a boiling set temperature,
The control device determines a target value of the circulation flow rate in the circulation path based on the heating capacity in the water-refrigerant heat exchanger, the set boiling temperature, and the detected temperature of the inflow water of the water-refrigerant heat exchanger. A heat pump type hot water heater that determines a circulating flow rate in the circulation path by a flow rate sensor and controls the circulating pump so that a detected value of the circulating flow rate matches the target value. A compressor that compresses the refrigerant, a water-refrigerant heat exchanger that heats water using gas refrigerant discharged from the compressor, and a liquid refrigerant that flows from the water-refrigerant heat exchanger through an expansion valve evaporates An evaporator for returning to the compressor, a hot water storage tank connected to a water supply source, and a circulation path for extracting water from the hot water storage tank through a circulation pump and circulating it to the water-refrigerant heat exchanger and returning it to the hot water storage tank And a controller for controlling the hot water temperature heated by the water-refrigerant heat exchanger to a boiling set temperature,
The control device detects a hot water temperature heated by the water-refrigerant heat exchanger with a temperature sensor, and controls a compression capacity of the compressor so as to match the detected temperature with the set boiling temperature. Machine. A compressor that compresses the refrigerant, a water-refrigerant heat exchanger that heats water using gas refrigerant discharged from the compressor, and a liquid refrigerant that flows from the water-refrigerant heat exchanger through an expansion valve evaporates An evaporator for returning to the compressor, a hot water storage tank connected to a water supply source, and a circulation path for extracting water from the hot water storage tank through a circulation pump and circulating it to the water-refrigerant heat exchanger and returning it to the hot water storage tank And a controller for controlling the hot water temperature heated by the water-refrigerant heat exchanger to a boiling set temperature,
The control device determines a target value of the circulation flow rate in the circulation path based on the heating capacity in the water-refrigerant heat exchanger, the set boiling temperature, and the detected temperature of the inflow water of the water-refrigerant heat exchanger. A first means for detecting a circulating flow rate in the circulation path by a flow sensor and controlling the circulating pump so as to match a detected value of the circulating flow rate with the target value;
A temperature sensor for detecting the temperature of the hot water heated by the water-refrigerant heat exchanger, and a second means for controlling the compression capacity of the compressor so as to match the detected temperature with the set boiling temperature. A heat pump type hot water heater. In the heat pump type water heater according to any one of claims 1 to 3,
The said control apparatus variably controls the rotation speed of the fan which distribute | circulates external air to the said evaporator according to external temperature and the rotation speed of the said compressor, The heat pump type hot water heater characterized by the above-mentioned.

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