JP2010002090A - Refrigerating cycle device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a refrigerating cycle device capable of estimating a discharge pressure with high accuracy and using it for the prevention of an abnormal rise of discharge pressure and for the highly efficient operation of a refrigerating cycle by computing the enthalpy difference of a refrigerant and using adiabatic efficiency based on experimental data to estimate the discharge pressure. <P>SOLUTION: The refrigerating cycle device comprises a refrigerant circuit 5 formed by connecting at least a compressor 1, a radiator 2, a pressure reducing mechanism 3 and an evaporator 4 annularly and circulating the refrigerant, and a discharge pressure estimating means 28 estimating the discharge pressure. The discharge pressure estimating means 28 estimates the pressure of the refrigerant discharged from the compressor 1 using an arithmetic expression. The discharge pressure is appropriately estimated without providing a pressure detecting means or a pressure switch, and the estimated discharge pressure is used to prevent the abnormal rise of discharge pressure and to operate the refrigerating cycle device with high efficiency. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a refrigeration cycle apparatus mounted on a heat pump water heater or an air conditioner using a refrigerant that can be in a supercritical state on the high pressure side.

  Conventionally, this type of refrigeration cycle apparatus has a structure as shown in FIG. In the following description, a refrigeration cycle apparatus mounted on a heat pump water heater that generates hot water using the cooling heat of the refrigerant will be described as a representative example.

  In FIG. 9, reference numeral 1 is a compressor, 2 is a radiator, 3 is an expansion valve, and 4 is an evaporator, which are configured in an annular shape in this order to form a refrigerant cycle 5. A pressure switch 6 is provided between the compressor 1 and the radiator 2.

  Further, 11 is a hot water storage tank, 12 is a stacking pump, 13 is a three-way valve, and 14 is a hot water mixing valve. From the bottom of the hot water storage tank 11 to the top of the hot water storage tank 11 via the stacking pump 12, the radiator 2 and the three-way valve 13. The recirculating boiling circuit 16 is configured, and the hot water supply mixing valve 14 is provided in a mixing portion of the supply water pipe and the hot water supply pipe from the hot water storage tank 11.

  About the refrigerating-cycle apparatus comprised as mentioned above, the operation | movement is demonstrated below.

  The supercritical high-pressure refrigerant discharged from the compressor 1 is supplied to the radiator 2, performs heat exchange with water in the radiator 2, and the refrigerant whose temperature has decreased is supplied to the expansion valve 3. After being depressurized by the expansion valve 3, it is supplied to the evaporator 4, absorbs heat, and then sucked into the compressor 1. The pressure switch 6 is activated when the discharge pressure reaches a certain value and disconnects the electrical connection of the power supply circuit.

  On the other hand, the water heated in the radiator 2 is supplied from the bottom of the hot water storage tank 11, heated in the radiator 2, and then heated to return to the top of the hot water storage tank 11.

  The pressure switch 6 is provided to ensure safety when the discharge pressure rises abnormally beyond the design pressure.

  Therefore, generally, the pressure at which the pressure switch 6 operates is set to about the design pressure of the refrigeration cycle apparatus. In particular, in a refrigeration cycle apparatus mounted on a heat pump water heater using carbon dioxide as a refrigerant to be operated at a very high discharge pressure (about 10 MPa), its role plays a large role.

  However, although the pressure switch 6 plays a large role as a safety device against an abnormal increase in the discharge pressure, the refrigeration cycle apparatus cannot be operated with high efficiency by controlling the discharge pressure. Further, in the refrigeration cycle apparatus that operates with the refrigerant in a supercritical state, the discharge pressure becomes very high, and there is also a risk of refrigerant leakage from the refrigerant circuit including the pressure switch.

As a refrigeration cycle apparatus that solves such a problem, there is a refrigeration cycle apparatus described below (for example, see Patent Document 1). The refrigeration cycle apparatus described herein includes discharge pressure estimation means for estimating the discharge pressure from the operating state such as the temperature of each part of the refrigeration cycle apparatus and the compressor rotation speed, and can operate the refrigeration cycle apparatus with high efficiency. However, if this discharge estimation means is used, even if no pressure switch is provided, when the estimated discharge pressure rises abnormally beyond the design pressure, the compressor is stopped to prevent abnormal discharge pressure rise. Can do.
JP 20043692 A

  However, in the above-described conventional configuration, the discharge pressure is unambiguous with respect to the four physical quantities and the variables indicating the operating state of the refrigerant evaporation temperature in the evaporator, the refrigerant temperature at the radiator outlet, the compressor rotation speed, and the compressor driving power. It is necessary to have a large amount of data in four dimensions.

  Therefore, if the discharge pressure is estimated with high accuracy, the control microcomputer or ROM for storing the data requires a large capacity, and if the data amount is reduced, the accuracy of the estimated discharge pressure is impaired. was there.

  The present invention solves the above-described problem, and calculates the discharge pressure with high accuracy by calculating the enthalpy difference of the refrigerant and estimating the discharge pressure using the adiabatic efficiency based on the experimental data. An object of the present invention is to provide a refrigeration cycle apparatus that can be used for preventing abnormal rise of the refrigeration and for high efficiency operation of the refrigeration cycle.

  In order to achieve the above object, the present invention comprises at least a compressor, a radiator, a decompression mechanism, a refrigerant circuit in which an evaporator is connected in an annular shape and a refrigerant circulates, and a discharge pressure estimating means for estimating a discharge pressure. The discharge pressure estimation means estimates the refrigerant pressure discharged from the compressor using an arithmetic expression, and the estimated discharge pressure is used for operation control of the refrigeration cycle apparatus. It is what is used.

  According to the present invention, by calculating the enthalpy difference of the refrigerant and estimating the discharge pressure using the adiabatic efficiency based on the experimental data, the discharge pressure is estimated with high accuracy while reducing the amount of data required. Thus, it is possible to provide a refrigeration cycle apparatus that can be used for preventing an abnormal increase in discharge pressure and for highly efficient operation of the refrigeration cycle.

  The first invention includes at least a compressor, a radiator, a decompression mechanism, a refrigerant circuit in which an evaporator is annularly connected to circulate the refrigerant, and a discharge pressure estimating means for estimating a discharge pressure, the discharge pressure estimating means The refrigerant pressure discharged from the compressor is estimated using an arithmetic expression, and the discharge pressure is appropriately estimated and estimated without a pressure detecting means or a pressure switch. Using the discharged pressure, it is possible to prevent the discharge pressure from rising abnormally and to operate the refrigeration cycle apparatus with high efficiency.

  The second invention includes at least a compressor, a radiator, a decompression mechanism, a refrigerant circuit in which an evaporator is connected in an annular shape and a refrigerant circulates, and a temperature detection means for detecting the temperature of the refrigerant two-layer region of the evaporator, Detection means for detecting the suction temperature of the compressor, and the detection value of the temperature detection means for detecting the temperature of the refrigerant two-layer region of the evaporator, and the detection value of the detection means for detecting the suction temperature of the compressor And calculating a specific enthalpy difference of the refrigerant in the compressor from the amount of energy transmitted from the supply power source to the refrigerant and the refrigerant circulation amount based on the suction entropy of the compressor. Without the pressure detection means for detecting the intake pressure, the suction pressure can be estimated with the evaporator inlet refrigerant temperature as the saturation temperature.

According to a third aspect of the present invention, there is provided a compressor rotational speed detecting means for detecting the rotational speed of the compressor, and a current detecting means for detecting a power supply current, and based on the compressor rotational speed detected by the compressor rotational speed detecting means. And calculating the amount of energy transferred from the supply power source to the refrigerant based on the power source current detected by the current detecting means. Even if the power supply current changes, the discharge pressure can be estimated appropriately.

  According to a fourth aspect of the invention, there is provided voltage detection means for detecting a power supply voltage, and the amount of energy transmitted from the supply power source to the refrigerant is calculated based on the voltage value detected by the voltage detection means. Even if the power supply voltage fluctuates, the power consumed by the refrigeration cycle apparatus can be accurately detected, and the discharge pressure can be estimated appropriately.

  The fifth invention uses carbon dioxide as the refrigerant, and in the refrigeration cycle apparatus using the refrigerant that can be in a supercritical state on the high pressure side, the discharge pressure is appropriately estimated without the pressure detection means and the pressure switch, Using the estimated discharge pressure, it is possible to prevent the discharge pressure from rising abnormally and to operate the refrigeration cycle apparatus with high efficiency.

  Hereinafter, a refrigeration cycle apparatus equipped with a heat pump water heater in an embodiment of the present invention will be described with reference to the drawings. Although the embodiment describes a refrigeration cycle apparatus mounted on a heat pump water heater, the embodiment of the present invention is not limited to a heat pump water heater, and is a refrigeration cycle apparatus mounted on an air conditioner or the like. Also good.

(Embodiment 1)
First, the configuration of the refrigeration cycle apparatus in Embodiment 1 of the present invention will be described. A block diagram is shown in FIG. In FIG. 1, 21 is an evaporator inlet temperature detecting means, 22 is a compressor intake temperature detecting means, 23 is an outside air temperature detecting means, 24 is an intake pressure calculating means, 25 is a compressor rotational speed detecting means, and 26 is a voltage detecting means. , 27 is current detection means, and 28 is discharge pressure estimation means.

  Next, the operation and action of the refrigeration cycle apparatus configured as described above will be described. Since the operation of the refrigerant circulating in the refrigerant cycle 5 and the water circulating in the boiling circuit 16 is the same as that of the conventional refrigeration cycle apparatus, the description thereof is omitted here. The discharge pressure estimating means 28 estimates the discharge pressure at regular time intervals (for example, 10 seconds), and maintains the current operating state if the estimated discharge pressure is equal to or lower than a predetermined pressure, When the estimated discharge pressure exceeds a predetermined pressure, safety measures are taken such as reducing the rotational speed of the compressor 1, stopping the operation, or increasing the opening of the expansion valve 3.

Hereinafter, a method for estimating the discharge pressure in the discharge pressure estimating means 28 will be described. The discharge pressure estimation means 28 in the present embodiment calculates the refrigerant specific enthalpy difference Δh _COMP in the compressor 1 from the energy amount W transmitted from the supply power source to the refrigerant and the refrigerant circulation amount Gr, and calculates the calculated specific enthalpy. The discharge pressure is estimated using the difference Δh _COMP and various efficiencies (mechanical efficiency, adiabatic efficiency, volumetric efficiency) of the compressor 1.

The concept is shown in FIG. First, various state quantities (pressure, density, specific enthalpy, and entropy) of the compressor suction refrigerant are determined. Using an evaporator inlet temperature T _EI detected in the evaporator inlet temperature detecting means 21 for detecting the temperature of the refrigerant bilayer region of the evaporator, and estimates a suction pressure P _S in the suction pressure calculating means 24. Suction pressure calculating means 24, for example, it may be estimated suction pressure P _S has a physical property corresponding diagram as shown in FIG. 3, may be estimated using the estimating equation.

Then, using a compressor suction temperature _{T S} detected and the estimated suction pressure _{P S} in the compressor suction temperature detecting means 22, the suction density ^{_{d S (kg / m 3)}} , the suction specific enthalpy _h S (kJ / Kg) and inhalation entropy S _S (kJ / (kg · K)). At this time, for example, correspondence diagrams as shown in FIGS. 4 to 6 may be used.

Subsequently, the amount of energy W transmitted from the supply power source to the refrigerant in the compressor 1 is obtained, and the specific enthalpy difference Δh _COMP in the compressor 1 is determined by calculation using the refrigerant circulation amount Gr. The amount of energy W transmitted to the refrigerant in the compressor 1 is determined by the power supply voltage V detected by the voltage detection means 26, the power supply current I detected by the current detection means 27, and the mechanical efficiency ηm of the compressor 1.

Here, it is assumed that the mechanical efficiency ηm of the compressor 1 depends on the outside air temperature T _at as shown in FIG. On the other hand, the refrigerant circulation amount Gr is determined by the compressor rotational speed f detected by the compressor rotational speed detection means 25, the compression chamber volume V _C of the compressor 1, the suction density d _S and the volume efficiency ηv. Using these, the specific enthalpy difference Δh _COMP in the compressor 1 is calculated by the following equation 1.

If the compression process in the compressor 1 is complete adiabatic compression, the discharge pressure Pd can be determined using the suction ratio enthalpy h _S and the suction entropy S _S determined in advance, but the compression process in the compressor 1 is complete. Since the compression is usually performed with an adiabatic efficiency η _C of less than 1, rather than adiabatic compression, even if the discharge enthalpy h _d is determined using the calculated compressor specific enthalpy difference Δh _COMP , the discharge entropy S _d Since it is unknown, the discharge pressure Pd cannot be determined. Therefore, the compressor specific enthalpy difference Δh _COMP is corrected by the adiabatic efficiency η _C as shown in Equation 2.

The compressor ratio enthalpy difference Delta] h _COMP and theories compressor specific enthalpy difference when a complete adiabatic compression Delta] h _COMP the (theo) was computed to determine the theoretical discharge enthalpy _h d (theo) as in Equation 3, determined determining a discharge pressure Pd (MPa) using the theoretical discharge enthalpy _h d (theo) and the suction enthalpy _{S S.} At this time, for example, a correspondence diagram as shown in FIG. 8 may be used.

By providing the discharge pressure estimating means 28 for estimating the discharge pressure by the estimation method as described above, state quantities such as the suction pressure P _S , the suction density d _S , the suction ratio enthalpy h _S , and the suction entropy S _S and the mechanical efficiency are obtained. it is necessary to newly determine the [eta] m, both can be determined uniquely by the two following physical quantity, two physical quantity for the discharge pressure Pd is also a theoretical discharge enthalpy h _{d (theo)} intake enthalpy S _S Can be determined uniquely.

Therefore, the required data amount can be greatly reduced as compared with the discharge pressure estimating means that uniquely determines the discharge pressure from the variables indicating the four physical quantities and the operating state as described in the prior art. In this way, the discharge pressure can be estimated without sacrificing accuracy, so the amount of data required can be reduced, and the capacity of the control microcomputer and ROM for storing these data can be reduced. can do.

According to the present embodiment, in the refrigeration cycle apparatus using the refrigerant that can be in a supercritical state on the high pressure side by the above configuration, the operation state of the refrigeration cycle such as the compressor rotation speed, the power supply current, and the outside air temperature is used. By calculating the enthalpy difference Δh _COMP to estimate the discharge pressure, the control microcomputer that estimates the discharge pressure with high accuracy while saving the amount of data used for the estimation and stores the data used for the estimation of the discharge pressure or the like There is an effect that the capacity of the ROM can be reduced.

  When various detection means such as a voltage detection means and a compressor intake temperature detection means are not provided, the discharge pressure is estimated with each as a constant value. For example, when the voltage detection means is not provided, the voltage value is estimated to be set to 200 V or the like assuming an environment where the refrigeration cycle apparatus is used.

  The present invention also has an effect of avoiding the risk of refrigerant leakage from a refrigerant circuit including a pressure switch, a discharge pressure detecting means, and the like, and for energy saving and safe operation of a heat pump water heater and a vehicle air conditioner. Useful.

Configuration diagram of a refrigeration cycle apparatus according to Embodiment 1 of the present invention. Conceptual diagram of the discharge pressure calculation method Properties corresponding view of the evaporator temperature _{T EI} and the suction pressure _{P S} Properties corresponding view of the suction pressure _{P S} and the suction temperature _{T S} and the suction density _{d S} Properties corresponding view of the suction pressure P _S and the suction temperature T _S and the suction specific enthalpy h _S Properties corresponding view of the suction pressure _{P S} and the suction temperature _{T S} and the suction entropy _{S S} Outside temperature characteristic diagram of the compressor mechanical efficiency h _C Properties corresponding view of the theoretical discharge enthalpy _h d (theo) and the suction entropy _{S S} between the discharge pressure Pd Configuration diagram of a conventional refrigeration cycle system equipped with a heat pump water heater

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Compressor 2 Radiator 3 Expansion valve 4 Evaporator 5 Refrigerant circuit 21 Evaporator inlet temperature detection means 22 Compressor intake temperature detection means 23 Outside air temperature detection means 24 Suction pressure calculation means 25 Compressor rotation speed detection means 26 Voltage detection means 27 Current detection means 28 Discharge pressure estimation means

Claims (5)

A refrigerant circuit in which at least a compressor, a radiator, a decompression mechanism, and an evaporator are connected in an annular shape so that the refrigerant circulates, and a discharge pressure estimating unit that estimates a discharge pressure. In the discharge pressure estimating unit, from the compressor A refrigeration cycle apparatus characterized by estimating the pressure of refrigerant discharged using an arithmetic expression. A refrigerant circuit in which at least a compressor, a radiator, a decompression mechanism, and an evaporator are connected in an annular shape so that the refrigerant circulates; temperature detection means for detecting the temperature of a refrigerant two-layer region of the evaporator; and an intake temperature of the compressor And detecting means for detecting the temperature of the refrigerant two-layer region of the evaporator, and the detection value of the detecting means for detecting the suction temperature of the compressor based on the detected value of the compressor. A refrigeration cycle apparatus that calculates a specific enthalpy difference of refrigerant in a compressor from an amount of energy transmitted to a refrigerant from a supply power source and a refrigerant circulation amount. A compressor rotation speed detecting means for detecting the rotation speed of the compressor; and a current detection means for detecting a power supply current. The refrigerant circulation amount is determined based on the compressor rotation speed detected by the compressor rotation speed detection means. The refrigeration cycle apparatus according to claim 1 or 2, wherein the amount of energy transmitted from the supply power source to the refrigerant is calculated based on the power source current calculated and detected by the current detection means. 4. The refrigeration cycle according to claim 3, further comprising voltage detection means for detecting a power supply voltage, wherein the amount of energy transmitted from the supply power source to the refrigerant is calculated based on a voltage value detected by the voltage detection means. apparatus. The refrigeration cycle apparatus according to any one of claims 1 to 4, wherein carbon dioxide is used as the refrigerant.

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