JP2006071175A - Heat pump water heater - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To secure the capability of heating water for hot water supply while stably operating a refrigerating cycle by controlling the operation to avoid pressure at a gas-liquid separator 50 from being refrigerant critical pressure or higher. <P>SOLUTION: A control device 70 determines whether pressure at the gas-liquid separator 50 is refrigerant critical pressure or higher or not and varies a maximum target boiling temperature TpMAX to be lower when determining that it is the critical pressure or higher. Thus, the required capability of heating the water for hot water supply is secured while varying (restricting) the maximum target boiling temperature TpMAX to be lower to prevent the breakdown of the cycle. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an ejector type having an ejector that raises the suction pressure of a compressor by converting expansion energy into pressure energy while decompressing and expanding a refrigerant in a vapor compression refrigeration cycle that moves heat on a low temperature side to a high temperature side. The present invention relates to a water heater that absorbs heat from the atmosphere using a heat pump cycle, and is particularly applied to a refrigeration cycle in which the high-pressure side is operated at or above the critical pressure of the refrigerant.

As a conventional technique, there is a technique shown in Patent Document 1 previously filed by the present applicant. In the ejector cycle, a carbon dioxide (hereinafter abbreviated as CO ₂ ) refrigerant is separated into a gas phase refrigerant and a liquid phase refrigerant by a gas-liquid separator.
JP 2003-222419 A

  However, in a water heater using an ejector heat pump cycle configured as described above, the operation of the heat pump cycle when the boiling temperature is high at a high outside air temperature increases the evaporation pressure due to the outside air temperature (endothermic temperature), and the discharge temperature Therefore, it is necessary to increase the high pressure to ensure the boiling temperature. Since the high pressure side of the water heater is limited by the design pressure resistance of the device, if the high pressure reaches the limit, the flow rate of the water pump is lowered to ensure the boiling temperature, and the heating capacity is reduced.

  On the other hand, on the refrigerant side, the temperature at the outlet of the refrigerant water heat exchanger rises and the expansion loss energy increases, so the pressure increase by the ejector increases and the low pressure system becomes higher than the supercritical pressure. In such a state, a cycle state as indicated by a thick broken line in FIG. 1 is obtained, and the cycle fails against the design intention. That is, there is a problem in that the output (heating ability) with respect to the input of the compressor is extremely reduced because the endotherm is drastically reduced.

For example, when the outside air temperature is 31 ° C. or higher, which is the critical temperature of the CO ₂ refrigerant, and the inlet refrigerant temperature of the refrigerant air heat exchanger is also 31 ° C. or higher, the pressure at the gas-liquid separator position becomes higher than the critical pressure. It will run, and sufficient heating capacity cannot be obtained.

  The present invention has been made in view of the above-mentioned problems of the prior art, and its purpose is to stabilize the refrigeration cycle by controlling the operation so that the gas-liquid separator portion does not exceed the critical pressure of the refrigerant. An object of the present invention is to provide a heat pump type hot water heater that can be operated to ensure the heating capacity of hot water.

In order to achieve the above object, the present invention employs technical means described in claims 1 to 2. That is, according to the first aspect of the present invention, the water heater uses a vapor compression heat pump cycle that moves the heat on the low temperature side to the high temperature side, and the compressor (10) compresses the refrigerant to a critical pressure or higher. A refrigerant water heat exchanger (20) that heat-exchanges the hot-water supply water by exchanging heat between the generated high-temperature and high-pressure refrigerant and hot-water supply water, a refrigerant-air heat exchanger (30) that evaporates the low-temperature and low-pressure refrigerant, It has a nozzle (41) that expands under reduced pressure, sucks the vapor-phase refrigerant evaporated in the refrigerant air heat exchanger (30) by the high-speed refrigerant flow injected from the nozzle (41), and converts the expansion energy into pressure energy. An ejector (40) that converts and raises the suction pressure of the compressor (10), and a refrigerant that flows out of the ejector (40) is separated into a gas-phase refrigerant and a liquid-phase refrigerant, and the gas-phase refrigerant is compressed into the compressor (10). Supplied to the suction side , The liquid phase refrigerant of the refrigerant-air heat exchanger (30) liquid air supplied to the side separator (50), the heat pump type water heater and a control means for controlling the state of the heat pump cycle (70),
The control means (70) determines whether or not the pressure at the gas-liquid separator (50) position is equal to or higher than the critical pressure of the refrigerant, and if it is determined to be equal to or higher than the critical pressure, the maximum target boiling temperature ( TpMAX) is variable to a low level.

  According to the first aspect of the present invention, by making the maximum target boiling temperature (TpMAX) variable (restricted) to be low, it is possible to prevent cycle failure and to secure the necessary heating capacity for hot water supply. it can.

  In the second aspect of the invention, whether or not the refrigerant is equal to or higher than the critical pressure is determined by determining the suction pressure of the compressor (10), the suction temperature of the compressor (10), the refrigerant air heat exchanger (30). ) Inlet / outlet pressure, refrigerant / air heat exchanger (30) inlet refrigerant temperature, outside air temperature, ejector (40) outlet pressure, ejector (40) outlet refrigerant temperature, or a combination of two or more It is characterized by doing.

  According to the second aspect of the present invention, whether or not the pressure at the position of the gas-liquid separator (50) is equal to or higher than the critical pressure of the refrigerant by examining the temperature and pressure of these low pressure systems alone or in combination. Can be determined. Incidentally, the reference numerals in parentheses of the above means are examples showing the correspondence with the specific means described in the embodiments described later.

(First embodiment)
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic diagram of the overall configuration of a heat pump water heater according to an embodiment of the present invention. The heat pump type hot water heater of this embodiment heats hot water supply water to a high temperature (the maximum target boiling temperature in this embodiment is 90 ° C.) using a supercritical heat pump cycle, and performs hot water supply while storing hot water.

  The supercritical heat pump cycle refers to a heat pump cycle in which the refrigerant pressure on the high pressure side is equal to or higher than the critical pressure of the refrigerant. For example, the heat pump cycle uses carbon dioxide, ethylene, ethane, nitrogen oxide or the like as the refrigerant. The heat pump type hot water heater is roughly divided into a heat pump unit that mainly stores a refrigeration cycle apparatus, which will be described later, and a tank unit that mainly stores a hot water storage tank 1.

The heat pump unit is roughly divided into a refrigerant circuit for a heat pump cycle and a hot water supply heating circuit for hot water supply. First, the refrigerant circuit includes a compressor 10 that compresses refrigerant, a refrigerant water heat exchanger 20 that is a heating means for hot water supply, an ejector 40 that is a refrigerant decompression means, and a refrigerant air heat exchanger 30 that absorbs heat from the atmosphere. Are connected by a refrigerant piping path as shown in FIG. 1, and CO ₂ having a low critical temperature is enclosed as a refrigerant.

  In addition, 60 connected to the refrigerant circuit flows out of the high-pressure refrigerant (refrigerant before being depressurized by the ejector 40) flowing out from the refrigerant water heat exchanger 20, and flows out from the gas-liquid separator 50 and sucked into the compressor 10. It is an internal heat exchanger which heat-exchanges with the low-pressure refrigerant | coolant made.

  The compressor 10 includes a built-in drive motor and a high-pressure compressor that discharges the sucked gas refrigerant to a high pressure equal to or higher than the critical pressure, and these are housed in a sealed container. Then, energization control is performed by a control device 70 which is a control means of the entire device. When the heating capacity of the refrigerant water heat exchanger 20 is increased, the compressor 10 increases the rotational speed of the compressor 10 to increase the flow rate of the refrigerant discharged from the compressor 10, while reducing the heating capacity. Sometimes, the rotational speed of the compressor 10 is decreased, and the flow rate of the refrigerant discharged from the compressor 10 is decreased.

  The refrigerant water heat exchanger 20 heats hot water by exchanging heat between the high-temperature and high-pressure gas refrigerant boosted by the high-pressure compressor and the hot-water supply water, and a hot-water supply water passage is provided adjacent to the high-pressure refrigerant passage. The flow direction of the refrigerant flowing through the high-pressure refrigerant passage and the flow direction of the hot water supply water flowing through the hot water supply passage are opposed to each other.

Incidentally, in this embodiment, since CO ₂ is used as the refrigerant, the refrigerant pressure in the refrigerant water heat exchanger 20 is equal to or higher than the critical pressure of the refrigerant, and the refrigerant is condensed in the refrigerant water heat exchanger 20. The temperature distribution is such that the refrigerant temperature decreases from the refrigerant inlet side toward the refrigerant outlet side.

  The refrigerant air heat exchanger 30 is a heat exchanger that absorbs heat from outdoor air by exchanging heat between outdoor air and liquid phase refrigerant and evaporating the liquid phase refrigerant. The outside air fan 30 a is a blowing unit that supplies outside air to the refrigerant air heat exchanger 30, and is energized and controlled by the control device 70. The ejector 40 expands the refrigerant under reduced pressure and sucks the gas-phase refrigerant evaporated in the refrigerant air heat exchanger 30 and converts the expansion energy into pressure energy to increase the suction pressure of the compressor 10. Details of the ejector 40 will be described later.

  The gas-liquid separator 50 is a gas-liquid separator in which the refrigerant flowing out from the ejector 40 flows in, separates the flowing-in refrigerant into a gas phase refrigerant and a liquid phase refrigerant, and stores the liquid refrigerant. The gas-phase refrigerant outlet 50 is connected to the suction side of the compressor 10, and the liquid-phase refrigerant outlet is connected to the inlet side of the refrigerant air heat exchanger 30.

  Here, the structure of the ejector 40 will be described with reference to FIG. The ejector 40 converts the pressure energy of the inflowing high-pressure refrigerant into velocity energy, a nozzle 41 that decompresses and expands the refrigerant, and a gas-phase refrigerant evaporated in the refrigerant air heat exchanger 30 by a high-speed refrigerant flow injected from the nozzle 41 The mixing unit 42 that mixes with the refrigerant flow injected from the nozzle 41 while sucking the refrigerant, and the velocity energy is converted into pressure energy while mixing the refrigerant injected from the nozzle 41 and the refrigerant sucked from the refrigerant air heat exchanger 30. It consists of a diffuser 43 and the like for increasing the pressure of the refrigerant.

  In the mixing unit 42, mixing is performed so that the sum of the momentum of the refrigerant flow injected from the nozzle 41 and the momentum of the refrigerant flow sucked into the ejector 40 from the refrigerant air heat exchanger 30 is preserved. The static pressure of the refrigerant also increases at the portion 42. On the other hand, in the diffuser 43, the dynamic pressure of the refrigerant is converted into a static pressure by gradually increasing the passage cross-sectional area. Therefore, in the ejector 40, the refrigerant pressure is increased by both the mixing unit 42 and the diffuser 43. . Therefore, the mixing unit 42 and the diffuser 43 are collectively referred to as a boosting unit.

  That is, in the ideal ejector 40, the refrigerant pressure increases so that the sum of the momentum of the two types of refrigerant flows is stored in the mixing unit 42, and the refrigerant pressure increases so that energy is stored in the diffuser 43. It is desirable to do. Incidentally, a suction chamber 45 formed by the body 44 is formed around the nozzle 41, and the gas-phase refrigerant sucked from the refrigerant air heat exchanger 30 passes through the suction chamber 45 to the mixing unit 42. Flowing. In addition, the ejector 40 of the present embodiment is integrally provided with a variable throttle mechanism 40 a that changes the throttle diameter (nozzle outlet portion diameter), and is energized and controlled by the control device 70.

  A hot water supply heating circuit related to hot water supply has an annular structure including a hot water supply passage of the refrigerant water heat exchanger 20 that is a heating means for hot water supply, a water pump 2 that circulates hot water supply water, and a hot water storage tank 1 that stores hot water supply water. Connected to and configured. As shown in FIG. 1, the water pump 2 has a high temperature provided in the upper part of the hot water storage tank 1 through the hot water passage of the refrigerant water heat exchanger 20 from the low temperature water outflow part provided in the lower part of the hot water storage tank 1. A water flow is generated so as to return from the water inflow portion. Further, the water pump 2 can adjust the amount of flowing water in accordance with the number of rotations of a built-in motor, and is energized and controlled by the control device 70.

  The hot water storage tank 1 is made of metal (for example, made of stainless steel) excellent in corrosion resistance and has a heat insulating structure, and can keep hot hot water supply water for a long time. Hot water stored in the hot water storage tank 1 is mixed with hot water from a hot water outlet at the upper part of the hot water tank 1 and cold water from the water supply by a hot water mixing valve (not shown) which is a low temperature water mixing means at the time of hot water. After adjustment, hot water is supplied mainly to kitchens and baths. The hot water mixing valve is also energized and controlled by the control device 70.

  And the control apparatus 70 is a control means which controls each refrigeration apparatus of the heat pump cycle mentioned above, and is comprised including functions, such as CPU, ROM, RAM, and I / O port, and has a well-known structure in itself. Built-in microcomputer.

  As the sensor group of this heat pump cycle, the suction pressure sensor 11 and the suction temperature sensor 12 for detecting the suction pressure and the suction temperature of the compressor 10 and the inlet pressure, the outlet pressure and the inlet refrigerant temperature of the refrigerant air heat exchanger 30 are detected. The refrigerant air heat exchanger inlet pressure sensor 31, the refrigerant air heat exchanger outlet pressure sensor 32, the refrigerant air heat exchanger inlet temperature sensor 33, the outside air temperature sensor 34 for detecting the outside air temperature, and the outlet pressure / outlet temperature of the ejector 40. There are an ejector outlet pressure sensor 46 and an ejector outlet temperature sensor 47 to be detected.

  The sensor signals from these sensor groups are configured to be input to the control device 70 after being A / D converted by an input circuit (A / D conversion circuit) (not shown). The control output is output to the pump 2, the compressor 10, the outside air fan 30a, the variable throttle mechanism 40a, and the like.

  Next, an outline of control in the control device 70 which is a main part of the present invention will be described. FIG. 3 is a flowchart of the heat pump type water heater control in one embodiment of the present invention, and FIG. 4 is a map of the maximum boiling temperature change in one embodiment of the present invention.

When this control starts, first, in step S1, it is determined whether or not the pressure at the position of the gas-liquid separator 50 (that is, the low pressure side) is equal to or higher than the critical pressure of the refrigerant. In the present embodiment, an example of determination based on the outside air temperature will be described. Therefore, more specifically, it is determined whether or not the outside temperature detected by the outside temperature sensor 34 is larger than a predetermined value α (for example, 30 ° C. with respect to the critical temperature 31 ° C. of the CO ₂ refrigerant).

  When the determination result in step S1 is NO and it is determined that the pressure at the gas-liquid separator 50 position is less than the critical pressure, the process proceeds to step S2, and the maximum target boiling temperature TpMAX is set to 90 ° C. as normal control. The water heater is operated by setting to.

  However, when the determination result in step S1 is YES and it is determined that the pressure at the position of the gas-liquid separator 50 is equal to or higher than the critical pressure, the process proceeds to step S3, and the maximum target boiling temperature is determined according to the map of FIG. TpMAX is set low and variable. Incidentally, in the example of FIG. 3, the maximum target boiling temperature TpβMAX when the outside air temperature rises to a predetermined value β (for example, 50 ° C. as the upper limit of the outside air temperature) is set to 70 ° C. Like to do.

  Next, features and effects of this embodiment will be described. The control device 70 determines whether or not the pressure at the position of the gas-liquid separator 50 is equal to or higher than the critical pressure of the refrigerant, and when it is determined to be equal to or higher than the critical pressure, the maximum target boiling temperature TpMAX is varied to be low. I am doing so. According to this, by making the maximum target boiling temperature (TpMAX) variable (restricted) to be low, it is possible to prevent a cycle failure and to secure a necessary heating capacity for hot water supply.

(Second Embodiment)
The determination as to whether or not the refrigerant is equal to or higher than the critical pressure is not limited to the outside air temperature, the suction pressure of the compressor 10 detected by the suction pressure sensor 11, the suction temperature of the compressor 10 detected by the suction temperature sensor 12, and the refrigerant Refrigerant air heat detected by a refrigerant air heat exchanger inlet temperature sensor 33 and an inlet / outlet pressure of the refrigerant air heat exchanger 30 detected by an air heat exchanger inlet pressure sensor 31 and a refrigerant air heat exchanger outlet pressure sensor 32 Whether one of the inlet refrigerant temperature of the exchanger 30, the outlet pressure of the ejector 40 detected by the ejector outlet pressure sensor 46, and the outlet refrigerant temperature of the ejector 40 detected by the ejector outlet temperature sensor 47 is greater than a predetermined value. Or a combination of two or more judgments.

  According to this, it is possible to determine whether the pressure at the position of the gas-liquid separator 50 is equal to or higher than the critical pressure of the refrigerant by trying these temperature and pressure of the low-pressure system alone or in combination.

It is a whole schematic diagram of a heat pump type hot water heater concerning an embodiment of the present invention. It is a cross-sectional schematic diagram of the ejector 40 which concerns on embodiment of this invention. It is a flowchart of the heat pump type water heater control in one Embodiment of this invention. It is a map of the maximum boiling temperature change in one Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Compressor 20 ... Refrigerant water heat exchanger 30 ... Refrigerant air heat exchanger 40 ... Ejector 41 ... Nozzle 50 ... Gas-liquid separator 70 ... Control apparatus (control means)
TpMAX: Maximum target boiling temperature

Claims (2)

A water heater using a vapor compression heat pump cycle that moves the heat on the low temperature side to the high temperature side,
A refrigerant water heat exchanger (20) for heating the hot water supply water by exchanging heat between the high temperature and high pressure refrigerant compressed to the critical pressure or higher of the refrigerant in the compressor (10) and the hot water supply water;
A refrigerant air heat exchanger (30) for evaporating the low-temperature and low-pressure refrigerant;
It has a nozzle (41) that decompresses and expands the high-pressure refrigerant, and sucks the vapor-phase refrigerant evaporated in the refrigerant air heat exchanger (30) by the high-speed refrigerant flow injected from the nozzle (41) and expands it. An ejector (40) for converting energy into pressure energy to increase the suction pressure of the compressor (10);
The refrigerant flowing out from the ejector (40) is separated into a gas phase refrigerant and a liquid phase refrigerant, and the gas phase refrigerant is supplied to the suction side of the compressor (10), and the liquid phase refrigerant is supplied to the refrigerant air heat exchanger ( 30) a gas-liquid separator (50) to be supplied to the side,
In a heat pump water heater provided with a control means (70) for controlling the state of the heat pump cycle,
The control means (70) determines whether or not the pressure at the position of the gas-liquid separator (50) is equal to or higher than the critical pressure of the refrigerant. A heat pump type water heater characterized in that the temperature (TpMAX) can be varied low.   Whether or not the refrigerant is equal to or higher than the critical pressure is determined by the suction pressure of the compressor (10), the suction temperature of the compressor (10), the inlet / outlet pressure of the refrigerant air heat exchanger (30), The refrigerant air heat exchanger (30) has an inlet refrigerant temperature, an outside air temperature, an outlet pressure of the ejector (40), an outlet refrigerant temperature of the ejector (40), or a combination of two or more. The heat pump type water heater according to claim 1.

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