JP5870915B2 - Refrigeration equipment - Google Patents

Description

  The present invention relates to a refrigeration apparatus, and more particularly to a refrigeration apparatus including a refrigeration circuit that performs a vapor compression refrigeration cycle.

  In a refrigeration apparatus having a compressor, a condenser, an expansion mechanism, and an evaporator, and having a refrigeration circuit that performs a vapor compression refrigeration cycle, the refrigeration circuit is arranged so that the state of the refrigerant at a predetermined location of the refrigeration circuit becomes a desired state. There is a way to control. For example, the refrigeration apparatus described in Patent Document 1 (Japanese Patent Publication No. 59-12942) uses a compressor so that the wetness of the refrigerant sucked into the compressor is maintained at a preset value. Control based on the temperature of the discharged refrigerant is performed.

  However, since the refrigeration apparatus described in Patent Document 1 is based on the assumption that the operating frequency of the compressor is fixed, the technology described in Patent Document 1 is used as a refrigeration apparatus capable of changing the operating frequency of the compressor. If this is simply applied, liquid compression may occur in the compressor, and in some cases, the compressor may be damaged.

  An object of the present invention is to prevent the occurrence of liquid compression in a compressor capable of changing the operating frequency by accurately controlling the wetness of the refrigerant sucked into the compressor in a refrigeration apparatus that performs a vapor compression refrigeration cycle. It is to be.

  A refrigeration apparatus according to a first aspect of the present invention includes a compressor, a condenser, an expansion mechanism, and an evaporator, and detects a refrigeration circuit that performs a vapor compression refrigeration cycle and a discharge temperature of refrigerant discharged from the compressor. Discharge temperature detector, evaporation temperature detector for detecting the refrigerant evaporation temperature in the evaporator, condensation temperature detector for detecting the refrigerant condensation temperature in the condenser, and a preset target Calculating the target discharge temperature of the compressor, which maintains the suction wetness of the compressor in terms of the wetness, using at least one of the rotation speed of the compressor and the refrigerant circulation amount of the refrigeration circuit, the evaporation temperature, and the condensation temperature as parameters. And a control device that controls the expansion mechanism so that the discharge temperature becomes the target discharge temperature.

  In the refrigeration apparatus according to the first aspect, the control device performs a calculation using at least one of the rotation speed of the compressor and the refrigerant circulation amount, the evaporation temperature, and the condensation temperature as parameters to obtain a target discharge temperature. The control device can control the suction wetness of the compressor to the target wetness by controlling the expansion mechanism using the acquired target discharge temperature.

  In the refrigeration apparatus according to the second aspect of the present invention, in the refrigeration apparatus according to the first aspect, the control device is a functional equation having the evaporation temperature and the condensation temperature as parameters for each rotation speed of the compressor or refrigerant circulation amount of the refrigeration circuit. To calculate the target discharge temperature.

  In the refrigeration system of the second aspect, since the control device controls the compressor and the expansion mechanism, the control device calculates the target discharge temperature by grasping the rotation speed of the compressor or the circulating refrigerant amount of the refrigeration circuit. The target discharge temperature can be easily obtained by substituting the evaporation temperature and the condensation temperature detected by the evaporation temperature detector and the condensation temperature detector into the function equation.

  In the refrigeration apparatus according to the third aspect of the present invention, in the refrigeration apparatus according to the first aspect or the second aspect, the refrigerant is an R32 single component refrigerant, and the control device holds physical property information regarding the pressure and enthalpy of R32. The target discharge temperature is calculated according to the physical property information.

  In the refrigeration apparatus of the third aspect, the control device sets the target discharge temperature according to the physical property information on the pressure and enthalpy of R32 for R32, which is a refrigerant whose target discharge temperature changes greatly due to changes in the rotational speed of the compressor and the refrigerant circulation rate. Since the calculation is performed, the target discharge temperature can be determined accurately according to the physical properties of the refrigerant.

  A refrigeration apparatus according to a fourth aspect of the present invention is the refrigeration apparatus according to any one of the first to third aspects, wherein the control device determines the rotation speed and the refrigerant circulation amount based on the physical properties of the refrigerant circulating in the refrigeration circuit. The input energy of the compressor can be calculated using at least one of them, the evaporation temperature and the condensation temperature as parameters, and using at least one of the rotational speed and the refrigerant circulation amount, the input energy, and the enthalpy at the target wetness The discharge enthalpy of the target discharge temperature is calculated, and the target discharge temperature is determined using the discharge enthalpy.

  In the refrigeration apparatus according to the fourth aspect, the control device uses the discharge enthalpy to determine the target discharge temperature, and the discharge enthalpy is determined based on at least one of the rotational speed and the refrigerant circulation amount, the input energy, and the target wetness. Therefore, the target discharge temperature can be easily determined.

  A refrigeration apparatus according to a fifth aspect of the present invention is the refrigeration apparatus according to the fourth aspect, wherein the control device is based on the physical properties of the refrigerant circulating in the refrigeration circuit and uses the rotation speed, the evaporation temperature, and the condensation temperature as parameters. The air-conditioning capacity is calculated and the refrigerant circulation amount is calculated using the air-conditioning capacity.

  In the refrigeration apparatus according to the fifth aspect, the control device uses the air conditioning capability to calculate the refrigerant circulation amount, and uses the rotation speed of the compressor, the evaporation temperature, and the condensation temperature as parameters for the calculation of the air conditioning capability. The refrigerant circulation amount can be obtained while operating the refrigeration apparatus using information obtained from the compressor, the evaporation temperature detector, and the condensation temperature detector.

  A refrigeration apparatus according to a sixth aspect of the present invention is the refrigeration apparatus according to the first aspect, wherein the control device is configured so that the rotation speed of the compressor and the refrigeration so that the refrigerant sucked by the compressor changes from a wet state to an overheated state. Temporarily change at least one of the refrigerant circulation rates in the circuit, and use the measured values obtained when the compressor is in the suction wet state and the suction overheat state, and the compressor rotation speed and the refrigerant circulation amount in the refrigeration circuit The target discharge temperature is calculated by executing a calculation using at least one of the parameters, the evaporation temperature, and the condensation temperature as parameters.

  In the refrigeration apparatus of the sixth aspect, the control device calculates the target discharge temperature using the actual measurement values obtained when the compressor is in the suction wet state and the suction overheat state. It becomes easy to reflect in control.

  In the refrigeration apparatus according to the first aspect of the present invention, although the refrigeration apparatus performs a vapor compression refrigeration cycle, the wetness of the refrigerant sucked into the compressor is accurately determined in consideration of the rotation speed of the compressor. It is possible to control, and it is possible to prevent the occurrence of liquid compression in a compressor in which the suction side is adjusted to a wet state and the operation frequency is changed.

  In the refrigeration apparatus according to the second aspect of the present invention, the calculation in the control apparatus can be simplified using the function formula, and the configuration and operation of the control apparatus can be simplified.

  In the refrigeration apparatus according to the third aspect of the present invention, the effect of preventing the occurrence of liquid compression is particularly prominent because R32 whose target discharge temperature varies greatly depending on changes in the rotational speed of the compressor and the amount of refrigerant circulation. appear.

  In the refrigeration apparatus according to the fourth aspect of the present invention, the target discharge temperature can be easily determined, and the control in the control apparatus can be easily performed.

  In the refrigeration apparatus according to the fifth aspect of the present invention, the refrigerant circulation amount can be easily obtained during operation, and control for maintaining the suction side of the compressor in the control apparatus in a wet state is facilitated.

  In the refrigeration apparatus according to the sixth aspect of the present invention, the actual state of the refrigeration apparatus can be reflected in the control by the actually measured value, and the suction side of the compressor can be controlled in a wet state in accordance with the actual state of the refrigeration apparatus.

The circuit diagram for demonstrating the structure of the freezing apparatus which concerns on embodiment of this invention. The ph diagram for demonstrating an example of control of the freezing apparatus of FIG. The flowchart for demonstrating an example of control of the refrigerating circuit of 1st Embodiment. The flowchart for demonstrating an example of control of the refrigerating circuit of 2nd Embodiment.

<First Embodiment>
Hereinafter, the refrigeration apparatus according to the first embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows an outline of the overall configuration of the refrigeration apparatus according to the first embodiment. FIG. 2 shows a Mollier diagram for explaining calculation of the target discharge temperature in the refrigeration apparatus. The flow shown in FIG. 3 is a procedure for calculating the target discharge temperature.

(1) Overall Configuration The refrigeration apparatus 10 shown in FIG. 1 is an air conditioning apparatus that includes a refrigeration circuit 20 that performs a vapor compression refrigeration cycle and a control device 50 that controls the refrigeration circuit. The refrigeration circuit 20 is formed by connecting an outdoor unit 30 and an indoor unit 40 by a liquid side connecting pipe 21 and a gas side connecting pipe 22. The refrigeration circuit 20 includes a compressor 31, a four-way switching valve 32, an outdoor heat exchanger 33, and an expansion mechanism 34 in the outdoor unit 30, and an indoor heat exchanger 41 in the indoor unit 40. The refrigerant circulating through the refrigeration circuit 20 is R32.

(2) Detailed Configuration (2-1) Outdoor Unit The compressor 31 housed in the outdoor unit 30 has the suction side connected to one end of the suction pipe 35 and the discharge side connected to one end of the discharge pipe 36. . The discharge pipe 36, that is, the discharge side of the compressor 31 is connected to the first port Po 1 of the four-way switching valve 32, and the suction pipe 35, that is, the suction side of the compressor 31 is connected to the third port Po 3 of the four-way switching valve 32. The compressor 31 is configured such that the built-in motor 31a can change the operating frequency, that is, the rotational speed in accordance with an instruction from the control device 50. The compressor 31 is configured so that the operating capacity can be changed by changing the rotational speed of the motor 31a. The change in the rotation speed of the compressor 31 causes a change in the refrigerant circulation amount of the refrigeration circuit 20.

  The outdoor heat exchanger 33 housed in the outdoor unit 30 has one inlet / outlet connected to the fourth port Po4 of the four-way switching valve 32 and the other inlet / outlet connected to the expansion mechanism 34. The outdoor unit 30 stores an outdoor fan 37 for blowing outdoor air to the outdoor heat exchanger 33. The outdoor heat exchanger 33 performs heat exchange between the outdoor air blown by the outdoor fan 37 and the refrigerant circulating in the refrigeration circuit 20. The rotation speed of the outdoor fan 37 is controlled by the control device 50, and the amount of blown air can be changed by changing the rotation speed.

  One end of the expansion mechanism 34 housed in the outdoor unit 30 is connected to the other inlet / outlet of the outdoor heat exchanger 33, and the other end is connected to the liquid side communication pipe 21. The expansion mechanism 34 depressurizes the refrigerant circulating in the refrigeration circuit 20 by throttle expansion. The expansion mechanism 34 is configured to be able to adjust the opening degree according to an instruction from the control device 50. Therefore, the control device 50 can adjust the refrigerant circulation amount by adjusting the opening degree of the expansion mechanism 34.

  The four-way switching valve 32 housed in the outdoor unit 30 has one end of the discharge pipe 36 connected to the first port Po1, and one end of the indoor heat exchanger 41 connected to the second port Po2 via the gas side connection pipe 22. The other end of the suction pipe 35 is connected to the third port Po3, and one outlet / inlet of the outdoor heat exchanger 33 is connected to the fourth port Po4. The four-way switching valve 32 is configured to be switched by the control device 50 between cooling and heating. During heating, the first port Po1 and the second port Po2 are opened as shown by the solid line in FIG. 1, and the third port Po3 and the fourth port Po4 are opened. On the other hand, during cooling, the first port Po1 and the fourth port Po4 are opened, and the second port Po2 and the third port Po3 are opened, as indicated by broken lines in FIG.

  A suction pressure sensor 61 for measuring the pressure of the refrigerant in the pipe is attached to the suction pipe 35. The value of the suction pressure of the compressor 31 measured by the suction pressure sensor 61 is transmitted to the control device 50. A suction temperature sensor 63 for measuring the temperature of the refrigerant in the pipe is attached to the suction pipe 35, and a discharge temperature sensor 64 for measuring the temperature of the refrigerant in the pipe is attached to the discharge pipe 36. The values of the suction temperature and the discharge temperature of the compressor 31 measured by the suction temperature sensor 63 and the discharge temperature sensor 64 are transmitted to the control device 50.

  The outdoor heat exchanger 33 is attached with an outdoor heat exchanger temperature sensor 65 that measures the temperature of the refrigerant that is undergoing phase change in the heat transfer tube of the outdoor heat exchanger 33 and is blown to the outdoor heat exchanger 33. An outdoor temperature sensor 66 for measuring the temperature of the outdoor air is attached. The temperature values measured by the outdoor heat exchanger temperature sensor 65 and the outdoor temperature sensor 66 are transmitted to the control device 50. The refrigerant temperature measured by the outdoor heat exchanger temperature sensor 65 is the condensation temperature during the cooling operation and the evaporation temperature during the heating operation. Further, an outdoor liquid side temperature sensor 67 for measuring the temperature of the liquid refrigerant passing through the other inlet / outlet of the outdoor heat exchanger 33 is attached to the other inlet / outlet of the outdoor heat exchanger 33. The temperature value measured by the outdoor liquid side temperature sensor 67 is transmitted to the control device 50.

(2-2) Indoor unit The indoor heat exchanger 41 housed in the indoor unit 40 has one inlet / outlet connected to the second port Po2 of the four-way switching valve 32 and the other inlet / outlet connected to the liquid side communication pipe 21. It is connected. The indoor unit 40 houses an indoor fan 42 for blowing indoor air to the indoor heat exchanger 41. The indoor heat exchanger 41 performs heat exchange between the indoor air blown by the indoor fan 42 and the refrigerant circulating in the refrigeration circuit 20. The rotation speed of the indoor fan 42 is controlled by the control device 50, and the amount of blown air can be changed by changing the rotation speed.

  An indoor liquid side temperature sensor 74 for measuring the temperature of the liquid refrigerant passing through the other inlet / outlet of the indoor heat exchanger 41 is attached to the other inlet / outlet of the indoor heat exchanger 41. The temperature value measured by the indoor liquid side temperature sensor 74 is transmitted to the control device 50.

  The indoor heat exchanger 41 is attached with an indoor heat exchanger temperature sensor 75 that measures the temperature of the refrigerant that is undergoing phase change in the heat transfer tube of the indoor heat exchanger 41 and is blown to the indoor heat exchanger 41. An indoor temperature sensor 76 for measuring the temperature of the indoor air is attached. The temperature values measured by the indoor heat exchanger temperature sensor 75 and the indoor temperature sensor 76 are transmitted to the control device 50. The temperature of the refrigerant measured by the indoor heat exchanger temperature sensor 75 is the condensation temperature during the heating operation and the evaporation temperature during the cooling operation.

(3) Overall Operation In the refrigeration apparatus 10, the refrigerant circulates through the refrigeration circuit 20 including the compressor 31, the outdoor heat exchanger 33, the expansion mechanism 34, and the indoor heat exchanger 41. In the refrigeration circuit 20, a vapor compression refrigeration cycle is performed. That is, during the cooling operation, the gas refrigerant compressed and discharged by the compressor 31 is sent to the outdoor heat exchanger 33 via the four-way switching valve 32. In the outdoor heat exchanger 33 of the outdoor unit 30, the high-temperature and high-pressure refrigerant exchanges heat with the outdoor air, the condensation heat is released from the high-pressure gas refrigerant, and the refrigerant liquefies. The refrigerant cooled by releasing heat to the outside is reduced in pressure by the expansion mechanism 34 until it is in a state where it can be easily evaporated even at a low temperature. The low-pressure refrigerant flows into the indoor heat exchanger 41 of the indoor unit 40. The indoor heat exchanger 41 exchanges heat with the indoor air, and the low-pressure liquid refrigerant takes heat from the indoor air by taking in the evaporation heat. Take away. The refrigerant that has taken away heat and vaporized (or phase-changed) in the indoor heat exchanger 41 is sucked into the compressor 31 via the four-way switching valve 32.

  In the heating operation, contrary to the cooling operation, the refrigerant is gas refrigerant compressed and discharged by the compressor 31 and sent to the indoor heat exchanger 41 via the four-way switching valve 32. In the indoor heat exchanger 41, the high-temperature and high-pressure gas refrigerant exchanges heat with room air, the condensation heat is released from the high-pressure gas refrigerant, and the refrigerant liquefies. The pressure of the refrigerant cooled by releasing heat into the room is reduced by the expansion mechanism 34 until it is easily evaporated even at a low temperature. And the refrigerant | coolant which became low pressure is heat-exchanged with outdoor air by the outdoor heat exchanger 33, and takes in heat of evaporation from a low-pressure liquid refrigerant. The refrigerant that takes heat and vaporizes (or changes in phase) in the outdoor heat exchanger 33 is sucked into the compressor 31 via the four-way switching valve 32.

  This vapor compression refrigeration cycle is shown in FIG. Curve L1 in FIG. 2 is a saturated liquid line, and curve L2 is a dry saturated vapor line. In FIG. 2, the states of points C <b> 1 and C <b> 11 correspond to the discharge side of the compressor 31, that is, the state of the discharge pipe 36. In other words, the state of the points C1 and C11 corresponds to the state of the condenser, that is, the inlet of the indoor heat exchanger 41 during the heating operation or the outdoor heat exchanger 33 during the cooling operation. The state of the next point C2 corresponds to the state of the outlet of the condenser, and corresponds to the state of the inlet of the expansion mechanism 34. The state of the next point C3 corresponds to the state of the outlet of the expansion mechanism 34. In other words, the state at the point C3 corresponds to the state of the inlet of the evaporator, that is, the indoor heat exchanger 41 during the cooling operation or the outdoor heat exchanger 33 during the heating operation. The states of the points C4 and C41 correspond to the state of the suction side of the compressor 31, that is, the state of the suction pipe 35.

(4) Calculation of target discharge temperature in control device Calculation of target discharge temperature TTd in control device 50 will be described. The target discharge temperature TTd is a discharge temperature when the humidity on the suction side of the compressor 31 reaches a preset target wetness (1-x _s ). In other words, the discharge temperature is such that the refrigerant at the suction side of the compressor 31, that is, the suction pipe 35, is maintained at the point C41 in FIG. Furthermore, at this time, since the refrigeration circuit 20 maintains the state of the point C41 in FIG. 2 and repeats the vapor compression refrigeration cycle, the target discharge temperature TTd is the value of the compressor 31 in the state of the point C11. This is the discharge temperature. In addition, the x _s is the target inhalation dryness.

  In order to calculate the target discharge temperature TTd, the control device 50 preliminarily stores the superheat setting value SH0 and the supercooling setting value SC0 used in the refrigeration apparatus 10 shown in FIG. Have been entered.

  Next, in the control device 50, the air conditioning capacity Q (kW) is obtained from the information 51 relating to the compressor curve in a state where the superheat degree SH and the supercool degree SC are set to the set values SH0 and SC0, respectively. The air conditioning capacity Q is obtained from the refrigerant state at the inlet and outlet of the compressor 31 and the number of revolutions using the information 51 relating to the compressor curve, and is calculated using the function fcq (TE, TC, Ft). That is, the air conditioning capacity Q is calculated by the control device 50 by substituting the evaporator evaporation temperature TE, the condenser condensation temperature TC, and the rotation speed Ft of the compressor 31 into the formula <1> described later.

  For this reason, the control device 50 stores information 51 relating to the compressor curve. Further, the controller 50 acquires the evaporation temperature TE and the condensation temperature TC as measurement results of the outdoor heat exchanger temperature sensor 65 and the indoor heat exchanger temperature sensor 75.

  Similarly, the input energy P (kW) of the compressor 31 is obtained using the information 51 relating to the compressor curve. Here, it is calculated using the function fcp (TE, TC, Ft). That is, the input energy P is calculated by the control device 50 by substituting the evaporator evaporation temperature TE, the condenser condensation temperature TC, and the rotation speed Ft of the compressor 31 into the formula <2> described later.

  Next, the control device 50 obtains the suction enthalpy h1 (2) of the compressor 31 using the set value SH0 using the physical property information 52 of the R32 refrigerant. Specifically, for example, the suction enthalpy h1 (2) is obtained from a simple physical property formula of the R32 refrigerant. This suction enthalpy h1 (2) is a specific enthalpy value when the suction side of the compressor 31 is in a dry state.

  Next, the control device 50 calculates the specific enthalpy h3 at the inlet of the evaporator, that is, the point C3 in FIG. 2, using the set value SC0 from the physical property information 52 of the R32 refrigerant.

  Next, the refrigerant circulation amount G is obtained by substituting the air conditioning capacity Q and the specific enthalpies h1 (2), h3 that have already been obtained into the following formula <3>.

  Next, using the physical property information 52 of the R32 refrigerant stored in the control device 50, the control device 50 uses the saturated gas enthalpy h5 at the evaporation temperature TE, the saturated liquid enthalpy h4 at the evaporation temperature TE, and the saturation at the condensation temperature TC. Gas enthalpy h6 is calculated.

Then, the controller 50 obtains the target wetness of _{(1-x s)} ratio satisfies the enthalpy h1 (1) from <4> expression. That is, the control device 50 acquires the specific enthalpy h1 (1) of the state of the point C41 by calculation.

  Furthermore, the control device 50 obtains the specific enthalpy h2 (1) in the state of the point C11 from the later-described <5> equation using the specific enthalpy h1 (1), the refrigerant circulation amount G, and the input energy P that have already been obtained.

  Finally, the control device 50 calculates the target discharge temperature TTd using the physical property information 52 of the R32 refrigerant from the difference Δh between the specific enthalpy h2 (1) in the state of the point C11 and the saturated gas enthalpy h6 at the condensation temperature TC. calculate.

(5) Control of discharge temperature of compressor The control of the discharge temperature of the compressor 31 is demonstrated along the flowchart of FIG. First, the control device 50 acquires the temperature of the refrigerant on the discharge side of the compressor 31 measured by the discharge temperature sensor 64 from the discharge temperature sensor 64, and the outdoor heat exchanger 33 measured by the outdoor heat exchanger temperature sensor 65. Is obtained from the outdoor heat exchanger temperature sensor 65, and the refrigerant temperature inside the indoor heat exchanger 41 measured by the indoor heat exchanger temperature sensor 75 is obtained from the indoor heat exchanger temperature sensor 75. (Step ST1). During the cooling operation, the temperature measured by the outdoor heat exchanger temperature sensor 65 is used as the condensation temperature TC, and the temperature measured by the indoor heat exchanger temperature sensor 75 is used as the evaporation temperature TE. During the heating operation, the temperature measured by the outdoor heat exchanger temperature sensor 65 is used as the evaporation temperature TE, and the temperature measured by the indoor heat exchanger temperature sensor 75 is used as the condensation temperature TC.

  Next, the control apparatus 50 acquires the rotation speed Ft of the compressor 31 from the control information of the compressor 31 (step ST2).

  Next, the control device 50 sets the target discharge temperature TTd by the calculation described in the above (4) using the evaporation temperature TE, the condensation temperature TC, and the rotation speed Ft of the compressor 31 obtained in steps ST1 and ST2 as parameters. Calculate (step ST3).

  And the control apparatus 50 adjusts the opening degree of the expansion mechanism 34 so that the temperature of the refrigerant | coolant by the side of the discharge of the compressor 31 measured with the discharge temperature sensor 64 may become the above-mentioned target discharge temperature TTd. Therefore, the discharge temperature of the compressor 31 is compared with the target discharge temperature TTd (step ST4). When the measured value of the discharge temperature sensor 64 is smaller than the target discharge temperature TTd, the opening degree of the expansion mechanism 34 is decreased (step ST6). Conversely, when the measured value of the discharge temperature sensor 64 is higher than the target discharge temperature TTd, the opening of the expansion mechanism 34 is increased and the temperature of the refrigerant on the discharge side of the compressor 31 is controlled to decrease (step ST5). .

(6) Features (6-1)
As described above, the control device 50 obtains the target discharge temperature TTd by executing the calculation using the rotation speed Ft of the compressor 31, the evaporation temperature TE, and the condensation temperature TC as parameters. Then, the controller 50 may control the suction wetness of the compressor 31 to the target wetness (1-x _s) by controlling the expansion mechanism 34 by using the target discharge temperature TTd acquired.

As a result, despite the refrigeration apparatus 10 performing the vapor compression refrigeration cycle, the wetness of the refrigerant sucked into the compressor 31 can be accurately controlled in consideration of the rotational speed Ft of the compressor 31. Further, it is possible to prevent the occurrence of liquid compression in the compressor 31 in which the suction side is adjusted to a wet state (target wetness (1-x _s )) and the operating frequency, that is, the rotation speed Ft can be changed.

  Since the control device 50 controls the compressor 31 and the expansion mechanism 34, the control device 50 grasps the number of rotations of the compressor 31 and calculates the target discharge temperature TTd into the function expressions fcq and fcp. By simply substituting the evaporating temperature TE and the condensing temperature TC detected by the heat exchanger temperature sensor 65 and the indoor heat exchanger temperature sensor 75 (an example of an evaporating temperature detector and a condensing temperature detector), the target discharge temperature TTd can be easily set. Can be acquired.

(6-2)
The above-described refrigeration circuit 20 is filled with R32, which is a refrigerant whose target discharge temperature TTd changes greatly according to changes in the rotational speed Ft of the compressor 31 and the refrigerant circulation amount G. Since the control device 50 calculates the target discharge temperature TTd in accordance with the physical property information 52 regarding the pressure and enthalpy of R32, the control device 50 can determine the target discharge temperature TTd appropriately according to the physical properties of the refrigerant. In the refrigeration apparatus 10 using the R32 refrigerant in which the target discharge temperature TTd greatly changes due to the change in the rotation speed Ft of the compressor 31 and the refrigerant circulation amount G, the effect of preventing the occurrence of liquid compression is particularly remarkable. appear.

(6-3)
The control device 50 uses the specific enthalpy h2 (1) (an example of the discharge enthalpy) in the state of the point C11 in order to determine the target discharge temperature TTd, and the specific enthalpy h2 (1) is set to the rotational speed Ft, the input energy P, and Since calculation is performed using the specific enthalpy h1 (1) at the target wetness (1-x _s ), the target discharge temperature TTd can be easily determined. In the first embodiment, the refrigerant circulation amount G is calculated and obtained using the rotational speed Ft, the evaporation temperature TE, the condensation temperature TC, and the specific enthalpy h1 (2), h3. Thereby, measurement of the refrigerant circulation amount G and the like can be omitted, the determination of the target discharge temperature TTd can be easily realized, and the control in the control device 50 can be easily performed.

(6-4)
The control device 50 uses the air conditioning capability Q to calculate the refrigerant circulation amount G, and uses the rotation speed Ft, the evaporation temperature TE, and the condensation temperature TC of the compressor 31 as parameters for calculating the air conditioning capability Q. Can determine the refrigerant circulation amount G while operating the refrigeration apparatus 10 using information obtained from the compressor 31, the outdoor heat exchanger temperature sensor 65 and the indoor heat exchanger temperature sensor 75, Control to maintain the wet state becomes easy.

(7) Modification (7-1) Modification 1A
In the refrigeration apparatus 10 described above, in order to obtain the target discharge temperature TTd, the rotation speed Ft of the compressor 31 that can be detected by the control apparatus 50 is used as a parameter. For example, the refrigerant circulation amount G is directly or indirectly used. If the refrigeration apparatus 10 is capable of measurement, the refrigerant circulation amount G may be used as a parameter. In this case, for example, if the function with the rotation speed Ft as a parameter is rewritten to a function with the refrigerant circulation amount G as a parameter, the target discharge temperature TTd is calculated in the control device 50 as in the above embodiment. .

(7-2) Modification 1B
In the refrigeration apparatus 10 described above, the case where the refrigerant discharge temperature, evaporation temperature, and condensation temperature are directly measured has been described. However, these may be measured indirectly, and devices that detect these indirectly also discharge temperature. It can be a detector, an evaporation temperature detector and a condensation temperature detector.

(7-3) Modification 1C
Since the above-described control device 50 controls the compressor 31 and the expansion mechanism 34, the control device 50 grasps the number of rotations of the compressor 31 and calculates the target discharge temperature TTd to the function expressions fcq and fcp. The target discharge temperature TTd is easily obtained by substituting the evaporation temperature TE and the condensation temperature TC detected by the outdoor heat exchanger temperature sensor 65 and the indoor heat exchanger temperature sensor 75.

  In order to reduce the information 51 relating to the compressor curve stored by the control device 50 and simplify the calculation, a function equation may be prepared for each function of the rotation speed or the refrigerant circulation amount. For example, functional expressions fcq1 (TE, TC) and fcp1 (TE, TC) are prepared for the rotational speed Ft1, and functional expressions fcq2 (TE, TC) and fcp2 (TE, TC) are prepared for the rotational speed Ft2. And so on. Then, with respect to the rotational speed Ftm between the rotational speed Ft1 and the rotational speed Ft2, a calculation by interpolation is performed. For example, assuming that Q1 = fcq1 (TE, TC), Q2 = fcp1 (TE, TC), P1 = fcq2 (TE, TC), and P2 = fcp2 (TE, TC), Qm = fcq (TE, TC) TC, Ftm) and Pm = fcp (TE, TC, Ftm) are calculated by the formulas <6> and <7>.

このように、回転数ごとに関数式ｆｃｑ１、ｆｃｑ２，ｆｃｐ１，ｆｃｐ２…を準備することで、制御装置５０における演算を簡素化でき、制御装置５０の構成や操作を簡素化できる。また、回転数の代わりに冷媒循環量を用いる場合についても同様の効果を奏する。

Thus, by preparing the functional expressions fcq1, fcq2, fcp1, fcp2,... For each rotation speed, the calculation in the control device 50 can be simplified, and the configuration and operation of the control device 50 can be simplified. The same effect can be obtained when the refrigerant circulation amount is used instead of the rotational speed.

Second Embodiment
(1) Overall Configuration In the refrigeration apparatus 10 of the first embodiment, the target discharge temperature TTd is obtained using the information 51 relating to the compressor curve stored in the control apparatus 50 and the physical property information 52 of R32. However, some of the parameters used when calculating the target discharge temperature TTd in the first embodiment can be replaced with values obtained from actual measurement values. The refrigeration apparatus according to the second embodiment is different from the refrigeration apparatus 10 of the first embodiment in that the state of the refrigeration circuit 20 is temporarily changed so that the refrigerant sucked by the compressor 31 changes from a wet state to an overheated state. Thus, it is only a point to obtain an actual measurement value. Therefore, the refrigeration apparatus according to the second embodiment has a configuration similar to that of the refrigeration apparatus 10 described with reference to FIG.

(2) Calculation of Target Discharge Temperature in Control Device In the refrigeration apparatus 10 according to the second embodiment, the control device 50 opens the opening of the expansion mechanism 34 based on the measured values of the suction pressure sensor 61 and the suction temperature sensor 63. And the refrigerant sucked into the compressor 31 is temporarily overheated. The control device 50 has a specific enthalpy h1 (2) of the suction refrigerant and a specific enthalpy h7 of the refrigerant flowing out of the outdoor heat exchanger 33 during the cooling operation or the refrigerant flowing out of the indoor heat exchanger 41 during the heating operation in the overheat state. Is detected.

  Specifically, the control device 50 calculates the specific enthalpy h1 (2) on the suction side of the compressor 31 based on the measured values of the suction pressure sensor 61 and the suction temperature sensor 63. During heating, the specific enthalpy h7 of the refrigerant flowing to the other inlet / outlet of the indoor heat exchanger 41 is calculated based on the measured values of the indoor heat exchanger temperature sensor 75 and the indoor liquid side temperature sensor 74. During cooling, the specific enthalpy h7 of the refrigerant flowing through the other inlet / outlet of the outdoor heat exchanger 33 is calculated based on the measured values of the outdoor heat exchanger temperature sensor 65 and the outdoor liquid side temperature sensor 67.

  The suction enthalpy h1 (2) of the compressor 31 thus measured is used. Further, the specific enthalpy h7 is used as the specific enthalpy h3 of the point C3 described above. Further, the set value of the above-described supercooling degree SC is also saturated in the saturated liquid enthalpy at the condensation temperature TC obtained from the physical property information 52 of the R32 refrigerant and the evaporation temperature TE in addition to the specific enthalpies h1 (2) and h3 obtained here. Calculated using gas enthalpy h5.

(3) Control of discharge temperature of compressor The control of the discharge temperature of the compressor 31 is demonstrated along the flowchart of FIG. First, similarly to the first embodiment, the control device 50 acquires the temperature of the refrigerant on the discharge side of the compressor 31 from the discharge temperature sensor 64, and sets the temperature of the refrigerant inside the outdoor heat exchanger 33 to the outdoor heat exchanger. It acquires from the temperature sensor 65, and acquires the temperature of the refrigerant | coolant inside the indoor heat exchanger 41 from the indoor heat exchanger temperature sensor 75 (step ST1). Next, the control apparatus 50 acquires the rotation speed Ft of the compressor 31 from the control information of the compressor 31 (step ST2).

  Then, the control device 50 reduces the opening degree of the expansion mechanism 34 and adjusts the degree of superheat on the suction side of the compressor 31 to the set value SH0 based on the measured values of the suction pressure sensor 61 and the suction temperature sensor 63. When the refrigeration circuit 20 is stabilized in such a state, the above-described actual measurement is performed to obtain an actual measurement value (step ST10).

  Next, by the calculation described in the above (2) using the evaporation temperature TE, the condensation temperature TC, the rotation speed Ft of the compressor 31 and the actual measurement value obtained in Steps ST1, ST2, ST10 as parameters, The discharge temperature TTd is calculated (step ST11).

  The operation of the control device 50 in steps ST4 to ST6 is performed in the same manner as in the first embodiment, and the temperature of the refrigerant on the discharge side of the compressor 31 is adjusted to the above-described target discharge temperature TTd.

(4) Features The control device 50 controls the expansion mechanism 34 so as to temporarily change the refrigerant circulation amount of the refrigeration circuit 20 so that the refrigerant sucked by the compressor 31 changes from a wet state to an overheat state. Actual measured values are obtained when the compressor 31 is in a suction wet state and a suction overheat state. Here, the above-described evaporation temperature TE and condensing temperature TC are values actually measured when in the suction wet state. In addition, when the suction pressure sensor 61, the suction temperature sensor 63, the outdoor heat exchanger temperature sensor 65, the outdoor liquid side temperature sensor 67, the indoor heat exchanger temperature sensor 75, and the indoor liquid side temperature sensor 74 are in the intake superheat state, they are actually measured. Value. Using such actually measured values, calculation using the rotation speed Ft, the evaporation temperature TE, and the condensation temperature TC of the compressor 31 as parameters is executed to calculate the target discharge temperature TTd.

  As described above, the control device 50 calculates the target discharge temperature TTd using not only the actual measurement value obtained in the suction wet state of the compressor 31 but also the actual measurement value obtained in the intake superheat state. The actual condition of the refrigeration apparatus 10 can be easily reflected in the control, and the suction side of the compressor 31 can be controlled in a wet state in accordance with the actual condition of the refrigeration apparatus 10.

(5) Modification (5-1) Modification 2A
In steps ST10 and ST11 described above, values actually measured by the suction pressure sensor 61, the suction temperature sensor 63, the indoor heat exchanger temperature sensor 75, and the indoor liquid side temperature sensor 74 are used as the actually measured values in the overheated state. The actual measurement values that are actually measured in the overheated state for calculating the target discharge temperature TTd are not limited to these, and other actual measurements are performed in the overheated state as long as they are actual values for calculating the target discharge temperature TTd. Also good.

DESCRIPTION OF SYMBOLS 10 Refrigeration apparatus 20 Refrigeration circuit 31 Compressor 33 Outdoor heat exchanger 34 Expansion mechanism 41 Indoor heat exchanger 61 Suction pressure sensor 63 Suction temperature sensor 64 Discharge temperature sensor 65 Outdoor heat exchanger temperature sensor 67 Outdoor liquid side temperature sensor 74 Indoor liquid Side temperature sensor 75 Indoor heat exchanger temperature sensor

Japanese Patent Publication No.59-12942

Claims (6)

A refrigeration circuit (20) having a compressor (31), a condenser (33, 41), an expansion mechanism (34) and an evaporator (41, 33), and performing a vapor compression refrigeration cycle;
A discharge temperature detector (64) for detecting the discharge temperature of the refrigerant discharged from the compressor;
An evaporation temperature detector (65, 75) for detecting the evaporation temperature of the refrigerant in the evaporator;
A condensation temperature detector (75, 65) for detecting the condensation temperature of the refrigerant in the condenser;
The target discharge temperature of the compressor that maintains the suction wetness of the compressor at a preset target wetness is set to at least one of the rotation speed of the compressor and the refrigerant circulation amount of the refrigeration circuit, and the A control device (50) that acquires the evaporation temperature and the condensation temperature as parameters, and controls the expansion mechanism so that the discharge temperature becomes the target discharge temperature;
A refrigeration apparatus comprising: The control device calculates the target discharge temperature by a function formula having the evaporation temperature and the condensation temperature as parameters for each rotation speed of the compressor or refrigerant circulation amount of the refrigeration circuit.
The refrigeration apparatus according to claim 1. The refrigerant is a R32 single component refrigerant,
The control device holds physical property information on the pressure and enthalpy of R32, and calculates the target discharge temperature according to the physical property information.
The refrigeration apparatus according to claim 1 or 2. The control device calculates input energy of the compressor based on the physical properties of the refrigerant circulating in the refrigeration circuit, using at least one of the rotation speed and the refrigerant circulation amount, the evaporation temperature, and the condensation temperature as parameters. A discharge enthalpy of the target discharge temperature is calculated using at least one of the rotational speed and the refrigerant circulation amount, the input energy and the enthalpy at the target wetness, and the discharge enthalpy is used. Determining the target discharge temperature;
The refrigeration apparatus according to any one of claims 1 to 3. The control device is configured to be capable of calculating the air conditioning capability of the refrigeration circuit using the rotation speed, the evaporation temperature, and the condensation temperature as parameters based on the physical properties of the refrigerant circulating in the refrigeration circuit, and using the air conditioning capability To calculate the refrigerant circulation amount,
The refrigeration apparatus according to claim 4. The control device temporarily changes at least one of the rotational speed of the compressor and the refrigerant circulation amount of the refrigeration circuit so that the state of the refrigerant sucked by the compressor is changed from a wet state to an overheated state, Using measured values obtained when the compressor is in a suction wet state and a suction overheat state, at least one of the rotation speed of the compressor and the refrigerant circulation amount of the refrigeration circuit, the evaporation temperature, and the condensation temperature, Is used as a parameter to calculate the target discharge temperature,
The refrigeration apparatus according to claim 1.

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