JP2007212098A - Heat pump water heater - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat pump water heater for preventing compressor operating pressure from being too high even when a supply water temperature rises. <P>SOLUTION: The heat pump water heater comprises a compressor 10, a water-refrigerant heat exchanger 20, a pressure reducer 30, and an evaporator 40 connected together in sequence via refrigerant pipes. Herein, part of refrigerant discharged from the compressor is sucked through an on-off valve 70 and the pressure reducer 80 into the compressor. The on-off valve is opened when the discharge pressure of the compressor is a predetermined value or greater. The on-off valve is also opened during defrosting operation. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a heat pump water heater that heats water with a refrigerant.

  From the viewpoint of energy saving in recent years, heat pump type water heaters that are more energy efficient than gas combustion type or electric heating type water heaters have attracted attention. In order to improve efficiency, the configuration of a heat pump type hot water heater is important, and an example as shown in Patent Document 1 is known.

JP 10-1111014 A (particularly paragraph “0014”)

  In the above prior art, there is a method for increasing the feed water temperature by increasing the discharge pressure of the compressor. However, if the discharge pressure of the compressor becomes too high, there is a problem that the reliability of the compressor is lowered.

  An object of the present invention is to obtain a heat pump type water heater having high reliability.

  In order to solve the above-described problem, according to one aspect of the present invention, a heat pump type water heater is provided with pressure detection means for detecting the pressure of refrigerant discharged from the compressor, and a part of the refrigerant discharged from the compressor is opened and closed. In addition, the compressor is sucked into the compressor through the decompressor, and the on-off valve is opened when the pressure detected by the pressure detecting means becomes a predetermined pressure value or more.

  In another aspect of the present invention, the heat pump water heater is configured such that a part of the refrigerant discharged from the compressor is sucked into the compressor through the open / close valve and the decompressor, and the open / close valve is opened during the defrosting operation. Yes.

  In another aspect of the present invention, a heat pump type hot water heater is provided with a first pressure reducer, a liquid receiver, and a second pressure reducer sequentially between a water / refrigerant heat exchanger and an evaporator.

  Furthermore, in the above configuration, it is desirable that the refrigerant be a refrigerant that operates below the critical point, R410A or R407C, carbon dioxide, or HC refrigerant.

  According to the present invention, a highly reliable heat pump type hot water heater can be obtained.

  In the above-described conventional technology, the refrigerant is put in a necessary amount or an accumulator is provided to store surplus refrigerant. FIG. 2 is a block diagram of a heat pump type hot water heater that stores excess refrigerant in the accumulator 60. The high-temperature and high-pressure refrigerant from the compressor 10 raises the temperature of the water in the water / refrigerant heat exchanger 20, and is itself cooled. The pressure is reduced by the decompressor 30, heat is drawn up by the evaporator 40 from the air sent by the blower 50, passes through the accumulator 60, and is again pressurized by the compressor 10. Water enters the water / refrigerant heat exchanger 20 through the water pump 110 from the water inlet 100a and reaches the water outlet 100b. A ph diagram of this cycle is shown in FIG. Assume that the cycle A is stable. When there is a request to increase the water temperature and the discharge temperature of the compressor 10 is increased, the discharge temperature is increased by reducing the decompressor 30 (cycle B). In this case, the suction pressure of the compressor is reduced by reducing the pressure, and if there is surplus refrigerant in the accumulator, the refrigerant in the accumulator 60 moves to the water / refrigerant heat exchanger 20 and the degree of supercooling increases. At the same time, the discharge pressure increases. The compressor is normally designed with the highest discharge pressure and the lowest suction pressure that can be operated from the viewpoint of reliability. When the outside air is low, the suction pressure decreases, the water supply temperature or the boiling temperature is high. The increase in the discharge pressure may exceed the operating range of the compressor, which may cause a problem in reliability. Conversely, if the decompressor 30 is opened to lower the discharge pressure, the refrigerant in the water / refrigerant heat exchanger 20 moves to the accumulator 60 and the discharge pressure decreases. At the same time, however, the discharge temperature also decreases, raising the boiling temperature. I can't. In addition, the accumulator has a problem that the cycle performance is degraded due to pressure loss. In a cycle without an accumulator, there is no means for reducing the pressure because excess refrigerant does not move from the water / refrigerant heat exchanger.

  In an air conditioner using an inverter-driven compressor, the discharge pressure is lowered or the suction pressure is raised because the condensation heat exchange amount and the evaporation heat exchange amount are reduced by lowering the refrigerant circulation amount by lowering the rotation speed of the compressor. Driving is possible. Similarly, in the case of a heat pump water heater equipped with a compressor that can be driven by an inverter, the amount of refrigerant circulation can be reduced by lowering the compressor frequency, and the suction pressure can be increased by lowering the evaporation heat exchange amount. However, even if the capacity as a heat pump is reduced, the boiling temperature cannot be lowered, so that the amount of water is lowered to ensure the boiling temperature, resulting in a reduction in heat transfer rate and the discharge pressure does not drop. That is, in order to lower the discharge pressure while ensuring the boiling temperature, it is necessary to move the refrigerant in the water / refrigerant heat exchanger somewhere.

  FIG. 1 is a block diagram of a heat pump type hot water heater according to the first embodiment. The high-temperature and high-pressure refrigerant from the compressor 10 raises the temperature of the water in the water / refrigerant heat exchanger 20 and is cooled by itself. The pressure is reduced by the compressor 30, the heat is drawn from the air sent by the blower 50 by the evaporator 40, and the pressure is increased again by the compressor 10. An on-off valve 70 and a fixed decompressor 80 are provided. Water enters the water / refrigerant heat exchanger 20 through the water pump 110 from the water inlet 100a and reaches the water outlet 100b. The refrigerant is a refrigerant that operates at a critical pressure or less, such as a CFC refrigerant such as R410A or R407C, or a HC refrigerant, or a CO2 refrigerant whose high pressure exceeds the critical pressure.

  FIG. 4 is a ph diagram of this cycle. The figure shows the case of R410A operating at a critical pressure or lower, but the concept is the same when the high pressure part is a carbon dioxide refrigerant exceeding the critical pressure. Cycle A is a cycle when the on-off valve 70 is closed. When this cycle is higher than the operating pressure range in the design of the compressor, the on-off valve 70 is opened. This cycle is designated as cycle C. In the figure, a to f correspond to FIG. By opening the on-off valve 70, a mixture of the refrigerant e from the evaporator 40 and the refrigerant f from the decompressor 80 is supplied to the suction of the compressor 10. The refrigerant from the decompressor 80 is at a high temperature because it only decompresses the refrigerant discharged from the compressor. Therefore, the refrigerant e from the evaporator 40 is supplied in a state of low airiness. For this reason, the amount of heat generated from the evaporator 40 is small, and the suction pressure increases. Further, since the degree of preserving throughout the evaporator 40 is reduced, the amount of refrigerant held in the evaporator is increased, and the refrigerant is taken away from the water / refrigerant heat exchanger 20. That is, a part of the refrigerant in the water / refrigerant heat exchanger 20 is transferred to the evaporator 40. Therefore, the discharge pressure decreases due to the decrease in the degree of supercooling. At this time, since the compressor discharge refrigerant temperature is kept high by the decompressor 30, the boiling temperature does not decrease. That is, when the outside air is low and the suction pressure is too low, or when the supply water temperature or the boiling temperature is high and the discharge pressure is too high, the discharge pressure can be reduced without lowering the boiling temperature by opening the on-off valve 70. Therefore, a reliable operation range of the compressor is realized by increasing the suction pressure. FIG. 5 is a ph diagram when the defrosting operation is performed in this cycle. First, the water pump 110 is stopped and the water flow is eliminated. Then, the refrigerant is not cooled and flows into the decompressor 30. Here, the refrigerant is depressurized to a pressure capable of defrosting, and while being heated, the evaporator 40 (which becomes a condenser in this case) heats and melts the frost while cooling itself and becomes a refrigerant e having a low degree of freshness. go. If this refrigerant is directly sucked into the compressor, liquid compression of the compressor and a decrease in the viscosity of oil in the compressor cause a decrease in reliability. Therefore, the reliability of the compressor is ensured by opening the on-off valve 70 and mixing it with a high-temperature refrigerant so that the refrigerant is superheated and sucked into the compressor. Moreover, in order to prevent the liquid refrigerant in the evaporator 40 from being suddenly supplied to the compressor 10 when shifting from the stopped state to the operating state, the open / close valve 70 is opened to increase reliability, leading to improved reliability. In the configuration of this embodiment, since defrosting is not performed in a reverse cycle using a four-way valve, there is no heat transfer in the high-temperature part and the low-temperature part inside the four-way valve that occurs during normal operation, thereby improving efficiency. The combination of the on-off valve and the fixed pressure reducer may be a variable pressure reducer.

  FIG. 7 shows a second embodiment, and symbols in the figure are the same as those in the first embodiment. There are an on-off valve 72 and a fixed pressure reducer 82 as additional parts. This is provided so as to bypass the discharge from the compressor 10 to the inlet of the evaporator 40. In the first embodiment, the high-temperature refrigerant from the compressor 10 is depressurized by the variable pressure reducer 30 at the time of defrosting. However, when the water pump 110 cannot be stopped, the refrigerant is cooled. Decreases. Some variable pressure reducers cannot withstand high temperatures. In the second embodiment, the variable pressure reducer 30 is closed during defrosting so that the refrigerant does not flow, and instead, by opening the on-off valve 72, the high-temperature refrigerant is guided to the evaporator 40 and defrosted. By doing so, even if water is circulating, the refrigerant is not cooled, and the variable decompressor 30 is not exposed to high temperatures.

  FIG. 6 shows a third embodiment, in which a receiver 65 and a decompressor 35 are added between the decompressor 30 and the evaporator 40, and a four-way valve 15 for switching the refrigerant flow is provided. In general heat pump water heaters, when the feed water temperature is low, the degree of supercooling is increased and the specific enthalpy difference is increased, leading to improved efficiency. In the present invention, the degree of supercooling can be ensured by transferring the refrigerant in the liquid receiver 65 to the water / refrigerant heat exchanger 20 using the pressure reducer 30 for securing the degree of supercooling. Moreover, since the decompression device 35 is used to secure the discharge temperature, it is possible to cope with high temperature boiling. When the discharge pressure rises and the reliability exceeds the pressure range where reliability is ensured when the feed water temperature or the boiling temperature is high, the decompressor 30 is opened and the refrigerant in the water / refrigerant heat exchanger 20 is received by the receiver 65. Move to. By doing so, the discharge pressure is reduced due to the decrease in the degree of supercooling, and the reliability is improved. Defrosting is based on a reverse cycle by switching the four-way valve 15.

It is a block diagram of the heat pump type hot water heater which shows the 1st Embodiment of this invention. It is a block diagram of the heat pump type water heater which is a conventional form. It is the ph diagram of the heat pump type hot water heater which is the conventional form. It is a ph figure of the heat pump type water heater which shows the 1st Embodiment of this invention. It is a ph figure at the time of defrosting of the heat pump type water heater which shows the 1st Embodiment of this invention. It is a block diagram of the heat pump type water heater which shows the 3rd Embodiment of this invention. It is a block diagram of the heat pump type water heater which shows the 2nd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Compressor, 20 ... Water / refrigerant heat exchanger, 30 ... Variable decompressor, 40 ... Evaporator, 50 ... Blower, 60 ... Accumulator, 70/72 ... Open / close valve, 80/82 ... Fixed decompressor, 100a ... Water inlet, 100b ... Water outlet, 110 ... Water pump, 65 ... Liquid receiver, 35 ... Variable decompressor.

Claims (7)

In a heat pump water heater in which a compressor, a water / refrigerant heat exchanger, a decompressor, and an evaporator are sequentially connected by refrigerant piping,
Pressure detecting means for detecting the pressure of refrigerant discharged from the compressor is provided, and a part of the refrigerant discharged from the compressor is sucked into the compressor through an on-off valve and a pressure reducer, and the pressure detecting means detects The heat pump type hot water heater is characterized in that the open / close valve is opened when the applied pressure exceeds a predetermined pressure value. In a heat pump water heater in which a compressor, a water / refrigerant heat exchanger, a decompressor, and an evaporator are sequentially connected by refrigerant piping,
A heat pump type water heater, wherein a part of the refrigerant discharged from the compressor is sucked into the compressor through an on-off valve and a decompressor, and the on-off valve is opened during a defrosting operation. In a heat pump type hot water heater in which a compressor, a four-way valve, a water / refrigerant heat exchanger and an evaporator are sequentially connected by a refrigerant pipe,
A heat pump type hot water heater, wherein a first pressure reducer, a liquid receiver, and a second pressure reducer are sequentially provided between the water / refrigerant heat exchanger and the evaporator.   The heat pump type hot water heater according to claim 1, wherein a refrigerant that operates below the critical point is used as the refrigerant.   5. The heat pump type hot water heater according to claim 4, wherein the refrigerant is R410A or R407C.   The heat pump type hot water heater according to claim 1, wherein the refrigerant is carbon dioxide. The heat pump type hot water heater according to claim 1, wherein the refrigerant is an HC refrigerant.

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