JP2006292302A - Control method of heat pump device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat pump device with high usability by attaining a stable refrigerating cycle without an increase in cost in a heat pump device using a refrigerant out of critical pressure. <P>SOLUTION: In a heat pump device comprising a refrigerant circuit constituted by successively connecting a compressor 1, a radiator 2, a decompression means 3, and an evaporator 4, a heat absorbing quantity change means 11 adjusting the capability of the evaporator 4, and a temperature detection means 14 detecting the temperature of air supplied to the evaporator 4, pressure in the evaporator 4 is reduced by the change means 11 when a detection value of the temperature detection means 13 reaches the vicinity of a temperature equal to the critical pressure of the used refrigerant or exceeds it. A stable refrigerating cycle is attained without an increase in cost in the heat pump device using the refrigerant out of the critical pressure, whereby a heat pump device with high usability can be obtained. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a control method for a heat pump device used in a range exceeding a critical pressure.

As a conventional technique, a heat pump device is configured by connecting a compressor 1, a heat dissipation (condenser) 2, a decompression means 3, and an evaporator 4 in a ring shape as shown in FIG. When a pressurized refrigerant (for example, carbon dioxide) is used, the Mollier diagram of the heat pump device is as shown in FIG. 6 (see, for example, Patent Document 1).
Japanese National Patent Publication No. 3-503206

  Here, when the evaporator absorbs heat from the intake air by an air-cooled fan under an overload condition (outside air temperature 43 ° C.) in Japan, a Mollier diagram as shown in FIG. 2 is obtained. That is, when the pressure in the evaporator approaches the critical pressure Pc, the latent heat of evaporation Δhe is rapidly reduced. If the compressor operating speed, the throttle opening of the decompression means, and the heat release amount are constant, the capacity of the evaporator will be significantly reduced due to the overload condition on the endothermic side, and the refrigeration such as discharge pressure and discharge temperature will be reduced. The cycle becomes unstable.

  Further, when the valve opening degree of the pressure reducing means can be adjusted electrically, the valve opening degree increases or decreases due to a sudden change in the discharge temperature or the like, and the pressure increases or decreases. The sudden increase in pressure leads to an increase in design pressure, which in turn increases costs for strengthening the pressure resistance of refrigeration cycle components, and when high-pressure protection control is performed using a pressure switch as a safety protection device, high-pressure protection control is frequently performed. This causes problems such as operation and inability to drive.

  The present invention solves the above-described conventional problems, and in a heat pump device that uses a refrigerant in a state where the critical pressure is exceeded, by realizing a stable refrigeration cycle without increasing the cost, the usability It is an object of the present invention to provide a control method for a heat pump device having a high height.

  In order to solve the above-described problems, a control method for a heat pump device according to the present invention adjusts the capacity of the evaporator, and a refrigerant circuit configured by sequentially connecting a compressor, a radiator, a decompression unit, and an evaporator. An endothermic amount changing means and a temperature detecting means for detecting the temperature of the air supplied to the evaporator are provided, and the detected value of the temperature detecting means reaches the vicinity of the temperature corresponding to the critical pressure of the refrigerant used. Or, if it exceeds that, the heat absorption amount changing means will reduce the pressure in the evaporator, and it will detect the pressure rise to near the critical pressure caused by the high load of the evaporator, etc. In addition, by reducing the amount of heat absorption, the latent heat of vaporization in the evaporator can be secured, and stable operation can be secured. As a result, even when the evaporator load is high, there is no sudden pressure increase or decrease, and the design pressure of pressure vessels and functional parts (electromagnetic expansion valves, open / close valves, etc.) can be reduced, ensuring reliability. Cost increase (such as increased meat pressure) can be prevented. The heat absorption amount changing means can use existing parts provided in the evaporator, and can prevent an increase in cost due to the addition of functions.

According to the present invention, in a heat pump device that uses a refrigerant in a state where the critical pressure is exceeded, a stable refrigeration cycle is realized without causing an increase in cost.
A pumping device can be provided.

  A first aspect of the invention is a refrigerant circuit configured by sequentially connecting a compressor, a radiator, a decompression unit, and an evaporator, an endothermic amount changing unit that adjusts the capability of the evaporator, and is supplied to the evaporator Temperature detection means for detecting the temperature of the air, and when the detected value of the temperature detection means reaches or exceeds the temperature corresponding to the critical pressure of the refrigerant being used, the endothermic change means By the heat pump device control method configured to reduce the pressure in the evaporator, the pressure increase to near the critical pressure generated due to the high load of the evaporator is detected in advance, and the heat absorption amount is reduced. As a result, the latent heat of vaporization in the evaporator can be secured and stable operation can be secured. As a result, even when the evaporator load is high, there is no sudden pressure increase or decrease, and the design pressure of pressure vessels and functional parts (electromagnetic expansion valves, on-off valves, etc.) can be reduced, ensuring reliability. Cost increase (such as increased meat pressure) can be prevented. The heat absorption amount changing means can use existing parts provided in the evaporator, and can prevent an increase in cost due to the addition of functions.

  The endothermic amount changing means has the same effect as the adding means for reducing the opening area of the evaporator depending on the installation state of the outdoor unit or adding a medium lower than the endothermic load (for example, cooling water spray).

  In addition, by detecting the temperature of the air supplied to the evaporator (outside air temperature), it is possible to estimate that the pressure of the evaporator is detected in a correlated manner, so that pressure detection means (pressure switch, pressure sensor, evaporator) The pressure on the low-pressure side can be estimated with an inexpensive outside temperature sensor that does not have a complicated structure and a sealing function, such as a heat exchanger temperature sensor provided in the above.

  In a second aspect of the invention, in particular, in the first aspect of the invention, a fan for supplying outside air to the evaporator is provided, and the rotation speed of the fan is reduced from that of normal operation, or the fan is stopped to It is configured to reduce the pressure, and since the evaporating pressure is estimated by constantly detecting by the outside air temperature sensor on the air suction side of the evaporator, there is an error in the evaporating pressure change due to transient refrigerant flow fluctuation Without increasing the evaporating pressure under overload conditions.

  The third invention is characterized in that, in particular, in the first or second invention, the refrigerant is carbon dioxide, and in this case, the pressure in the cycle is increased to a critical pressure or higher of the refrigerant. The low-pressure side parts can be operated below the critical pressure, and the design pressure of the high-pressure parts can be suppressed by preventing a sudden rise in high pressure, and further the design pressure of the low-pressure parts can be suppressed by operating the pressure-resistant parts below the critical pressure. It is possible to suppress the system cost of the pressure vessel (evaporator) and the functional component (expansion valve).

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the embodiment.

(Embodiment 1)
FIG. 1 shows a heat pump device according to the first embodiment. The heat pump device according to the present embodiment includes a refrigerant circuit configured by connecting a compressor 1, a heat radiating (condensing) device 2, a pressure reducing means 3, and an evaporator 4 in an annular shape by a refrigerant pipe 5, and uses carbon dioxide as a refrigerant. Carbon is used. FIG. 2 shows a Mollier diagram (Ph diagram) in the present apparatus.

The compressor 1 compresses and discharges the sucked refrigerant to a critical pressure Pc or higher, and the discharged high-temperature and high-pressure refrigerant exchanges heat with the liquid (water) supplied from the hot water tank 6 through the radiator 2. Is done. Since the refrigerant (carbon dioxide) flowing through the radiator 2 is pressurized to a critical pressure Pc or higher by the compressor 1, it condenses even if the temperature is lowered by radiating heat to the liquid passing through the radiator 2 (refrigerant two-phase region). Never do. The decompression means 3 is a device for decompressing the refrigerant (carbon dioxide) flowing out from the radiator 2, and is an electromagnetic expansion valve that electrically controls the valve opening degree by a capillary tube or a control device using a capillary tube. . The refrigerant (carbon dioxide) is decompressed by the decompression means 3 until it reaches the refrigerant two-phase region, and after the endothermic refrigerant evaporates by the evaporator 4, it is sucked into the compressor 1 again.

  However, as shown in FIG. 2, when the load on the evaporator side becomes an overload condition (in the case of air cooling, the intake air temperature is 43 ° C. or higher, and in the case of water cooling, the incoming water temperature is 45 ° C. or higher) As Pe (pressure at the outlet of the pressure reducing means to the inlet of the evaporator in FIG. 2) approaches the critical pressure Pc, the latent heat of vaporization Δhe decreases rapidly. If the compressor operating speed, the throttle opening of the decompression means, and the heat release amount are constant, the capacity of the evaporator will be significantly reduced due to the overload condition on the endothermic side, and the refrigeration such as discharge pressure and discharge temperature will be reduced. The cycle becomes unstable.

  Further, when the valve opening of the pressure reducing means 3 can be adjusted electrically, the valve opening is increased or decreased due to a sudden change in the discharge temperature or the like, and further the pressure is increased or decreased. A sudden increase in pressure leads to an increase in design pressure, resulting in a great cost for strengthening the pressure resistance of refrigeration cycle components, and when high-pressure protection control is performed using a pressure switch as a safety protection device, the high-pressure protection control is frequently activated. This causes problems such as inability to drive.

  In order to solve such a problem, the present invention includes a pressure detection means 12 on the low pressure side from the outlet of the pressure reduction means 3 to the compressor 1, and approaches or exceeds the critical pressure Pc of the refrigerant used by the pressure detection means 12. By reducing or stopping the heat absorption amount changing means (in the case of FIG. 1, the evaporator side fan 11) for reducing the refrigerating capacity on the evaporator side by the microcomputer 10, the inside of the evaporator 4 is reduced. The evaporation pressure Pe1 close to the rated condition can be obtained by reducing the pressure, and the pressure and temperature in the discharge / suction of the compressor can be stably operated.

  The endothermic amount changing means reduces or stops the speed of the evaporator 4 side pump in water cooling, reduces the opening area of the evaporator 4, or adds a medium lower than the endothermic load (for example, cooling water spray or the like). The additional means has the same effect.

  FIG. 3 shows the state of refrigerant flowing through the heat pump device in the present embodiment. As the pressure detection means 12 in FIG. 5, an outside air temperature detection means 14 is provided on the evaporator suction air side of the low-pressure side heat pump device. The heat pump device in the present embodiment is configured to supply outside air to the evaporator 4 and evaporate the refrigerant after passing through the decompression means 3.

  According to this, since the outside air temperature (the temperature of the intake air of the evaporator 4) can be detected and the evaporation pressure can be estimated in correlation, the pressure detecting means (pressure switch, pressure sensor, evaporator) The pressure on the low pressure side can be estimated with an inexpensive temperature sensor that does not have a complicated structure and a sealing function such as a heat exchanger temperature sensor.

  Here, the operation of the present embodiment will be described with reference to FIGS. FIG. 3 shows a state in which functional parts such as the compressor 1 in the heat pump device are operated and the pressure and temperature of each part of the refrigeration cycle are stabilized. FIG. 4 shows a state in which the compressor 1 is started. It shows a transitional state when the load or load suddenly changes. From FIG. 3, when the refrigerant used is stable with carbon dioxide, the high-temperature and high-pressure refrigerant discharged from the compressor 1 is in the critical pressure region from the inlet of the heat dissipation (condenser) 2 to the decompression means inlet 3-a. The refrigerant enters the refrigerant state 16-b of gas-liquid two-phase by the decompression means 3, and the refrigerant evaporates by the evaporator 4, and after exiting the radiator 4, the refrigerant becomes the gas phase region 16-c and enters the compressor 1. Since the air is sucked, it is possible to estimate the low-pressure side pressure in correlation with the outside air temperature by detecting the outside air temperature on the evaporator air suction side by the outside air temperature detecting means 14.

  However, in the overload condition in which the load on the evaporator side becomes high as shown in FIG. 4, as explained in FIG. 2, the pressure in the evaporator 4 approaches the critical pressure Pc, and the latent heat of evaporation ΔPe decreases. The refrigerant state 15-c in the gas phase region from the intermediate point of the evaporator to the evaporator outlet is obtained, and the evaporating pressure detecting means 12 cannot accurately detect the pressure in the refrigerant gas phase (overheating) region even in a stable operation state. It is impossible to estimate the correct pressure. Therefore, the temperature detection means 14 is provided on the air suction side of the evaporator 4 to estimate the refrigerant state according to the change in the outside air temperature, and to change the fan speed of the evaporator with respect to the outside air temperature. The refrigeration cycle instability during transient operation such as stable operation and compressor start-up is not recognized by the pressure sensor or heat exchanger temperature sensor as unstable, and the outside air temperature and gas-liquid It is possible to estimate the evaporation pressure from the correlation characteristics in the phase region refrigerant state.

  Therefore, even if the refrigerant to be used is a refrigerant such as carbon dioxide whose low pressure side pressure approaches the critical pressure when overloaded, such as carbon dioxide, the outside air temperature detecting means 13 estimates the pressure of the low pressure side heat pump device, and the amount of heat absorbed. By reducing or stopping the speed of the changing means, that is, the heat absorption side fan 11, it is possible to reduce the pressure of the low-pressure side heat pump device to a pressure at which stable operation is possible.

  As shown in the present embodiment, the liquid in the hot water storage tank 6 may be used not only for hot water supply but also for floor heating and indoor air conditioning. As an alternative, heat may be radiated by the fan 14 without using the liquid in the hot water tank 6. Furthermore, even if an accumulator for storing the refrigerant is installed on the refrigerant suction side of the compressor 1, the effect of the present embodiment can be obtained similarly. In addition, the pressure in the evaporator 4 can be reduced by an electromagnetic expansion valve that can electrically control the valve opening degree in the pressure reducing means 3, but at that time, the discharge pressure rapidly increases. Note that there is no.

Refrigeration cycle diagram of the heat pump device in the first embodiment of the present invention Explanatory drawing of the operation of the heat pump device (Mollier diagram) Refrigerant state explanatory diagram of the heat pump device (at standard load and rated operation) Refrigerant state explanatory diagram of the heat pump device (overload condition / rated operation) Refrigeration cycle diagram of a conventional heat pump device Explanatory drawing (Mollier diagram) of the driving | running operation | movement in conventional embodiment

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Compressor 2 Radiator 3 Pressure reducing means 3-a Pressure reducing means inlet 3-b Pressure reducing means outlet 4 Evaporator 4-a Evaporator midpoint 5 Refrigerant piping 6 Hot water tank 7 Pump (water pump)
8 Water piping 10 Microcomputer (control unit)
DESCRIPTION OF SYMBOLS 11 Evaporator side fan 12 Pressure detection means 13 Heat exchanger (evaporator) temperature detection sensor 14 Outside temperature detection means (sensor)
15 Radiator-side fan 16 In-pipe refrigerant condition (carbon dioxide)
16-a Refrigerant state in critical pressure region 16-b Refrigerant state in gas-liquid two-phase region 16-c Refrigerant state in gas phase (overheating) region

Claims (3)

A refrigerant circuit configured by sequentially connecting a compressor, a radiator, a decompression unit, and an evaporator, a heat absorption amount changing unit that adjusts the capability of the evaporator, and a temperature of air supplied to the evaporator Temperature detection means, and when the detected value of the temperature detection means reaches or exceeds the temperature corresponding to the critical pressure of the refrigerant being used, the endothermic amount changing means A control method of a heat pump device configured to reduce pressure. The fan according to claim 1, further comprising a fan for supplying outside air to the evaporator, wherein the rotation speed of the fan is reduced from that of normal operation or the pressure in the evaporator is reduced by stopping the fan. -Control method of the pumping device. The heat pump apparatus according to claim 1 or 2, wherein the refrigerant is carbon dioxide.

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