JP2005265278A - Refrigeration equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a refrigeration device to perform a supercritical cycle, capable of enhancing the efficiency using an expanding machine having specifications to suit the operating conditions. <P>SOLUTION: The refrigeration device is configured so that the low pressure in its refrigerating cycle in the reference operating conditions and the refrigerant temperature at the outlet from a radiator are used as the reference low pressure and reference refrigerant temperature, respectively, and the high pressure in the refrigerating cycle where the performance factor of the refrigerating cycle in the reference operating conditions maximizes is used as a reference high pressure. In the expanding machine 60, the volume v<SB>2</SB>of the first fluid chamber 72 immediately after being shut off from the influx side is set as v<SB>2</SB>=ρ<SB>1</SB>×v<SB>1</SB>×r/ρ<SB>2</SB>, while the volume v<SB>3</SB>of the second fluid chamber 82 immediately before being put in communication with the outflow side is set as v<SB>3</SB>=ρ<SB>2</SB>×v<SB>2</SB>/ρ<SB>3</SB>, where ρ<SB>1</SB>is the density of the saturated gas refrigerant at the reference low pressure, ρ<SB>2</SB>is the density of the refrigerant at the reference high pressure and the reference refrigerant temperature, ρ<SB>3</SB>is the density of the refrigerant at the reference high pressure and the reference refrigerant temperature subjected to a adiabatic expansion to the reference low pressure, v<SB>1</SB>is the volume of the compression chamber in the compressor immediately after the compression chamber is shut off from the suction side, and r is the ratio of the rotating speed of the compressor to that of the expanding machine. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a refrigeration apparatus that performs a refrigeration cycle in which a high pressure is set to be equal to or higher than a critical pressure of a refrigerant.

2. Description of the Related Art Conventionally, refrigeration apparatuses that perform a refrigeration cycle by circulating refrigerant in a closed circuit refrigerant circuit are widely used as air conditioners and the like. As this type of refrigeration apparatus, for example, as disclosed in Patent Document 1, an apparatus in which the high pressure of the refrigeration cycle is set higher than the critical pressure of the refrigerant is known. This refrigeration apparatus includes an expander as a refrigerant expansion mechanism. The expander and the compressor are connected by a shaft, and the power obtained by the expander is used for driving the compressor to improve COP (coefficient of performance).
JP 2001-107881 A

  When designing the refrigeration apparatus having an expander, the specifications of the expander must be determined. In particular, in the case of using a type of positive displacement fluid machine in which the volume of the fluid chamber that has become a closed space changes as an expander, immediately after the fluid chamber is shut off from the inflow side (that is, the expansion of the fluid in the fluid chamber). And the volume of the fluid chamber immediately before the fluid chamber communicates with the outflow side (that is, when the fluid expansion ends in the fluid chamber). In order to determine these values, it is necessary to set the state of the refrigerant at the inlet and outlet of the expander. Further, when the expander and the compressor are connected by a shaft or the like and the rotational speed ratio between them is fixed, it is necessary to consider the capacity of the compressor.

  Here, when the capacity required for the refrigeration apparatus is determined, the design value of the capacity of the compressor can be set accordingly. In addition, when the use of the refrigeration apparatus is determined, it is possible to assume a target from which the refrigerant radiates heat (a heat dissipation target) and a target from which the refrigerant absorbs heat (a heat absorption target). For example, when an air conditioner is configured by a refrigeration apparatus, if the cooling operation is being performed, the heat release target is outdoor air and the heat absorption target is room air.

As shown in the Mollier diagram (pressure-enthalpy diagram) in FIG. 11, when the temperature condition of the heat release target is determined, the refrigerant evaporation temperature T ₁ is set accordingly, so that the low pressure P _{L of the} refrigeration cycle is set. Design value is determined. However, when the high pressure of the refrigeration cycle exceeds the critical pressure of the refrigerant, the high pressure refrigerant does not condense even if it releases heat. Therefore, even if the temperature condition for heat radiation is determined, only the refrigerant temperature T ₂ after heat radiation can be set accordingly. Since the state of the refrigerant after heat dissipation can not be determined only be a point isotherm of the temperature T _2, the design value of the high-side pressure of the refrigeration cycle is uniquely not determined.

  As described above, the design value of the high-pressure pressure of the refrigeration cycle cannot be set only by determining the use of the refrigeration apparatus provided with the expander and the high-pressure pressure of the refrigeration cycle is equal to or higher than the critical pressure of the refrigerant. If the high pressure of the refrigeration cycle is not determined, the state of the refrigerant at the inlet of the expander (state indicated by the point X in the figure) cannot be set, and further, the state of the refrigerant at the outlet of the expander (see the figure). The state represented by the point Y) cannot be set. For this reason, the conventional refrigeration apparatus has a problem that the specifications of the expander do not necessarily match the use conditions of the refrigeration apparatus, and the efficiency improvement by the expander becomes insufficient.

  This invention is made | formed in view of this point, The place made into the objective is providing the expander suitable for the driving | running condition, and providing the refrigeration apparatus with which high efficiency is obtained.

The first invention includes a refrigerant circuit (15) in which a compressor (50), a radiator (16), an expander (60), and an evaporator (17) are connected, and the refrigerant circuit (15) And a refrigeration apparatus that performs a refrigeration cycle in which the high pressure is equal to or higher than the critical pressure of the refrigerant.
The compressor (50) and the expander (60) are both constituted by a positive displacement fluid machine in which the volume of the fluid chamber changes, and the ratio of the rotation speed of one to the other is constant. Are connected to each other in the state, while the low pressure of the refrigeration cycle and the refrigerant temperature at the outlet of the radiator (16) at the standard operating conditions as design criteria are respectively set as the reference low pressure and the reference refrigerant temperature. The high pressure of the refrigeration cycle that gives the highest coefficient of performance is the reference high pressure, the density of the saturated gas refrigerant at the reference low pressure is ρ ₁ , the refrigerant density at the reference high pressure and the reference refrigerant temperature is ρ ₂ , and the reference high pressure and a reference refrigerant temperature of the refrigerant and ₃ the density ρ but was adiabatically expanded to the reference low pressure, fluid immediately after the fluid chamber in the compressor (50) is cut off from the suction side The volume and v _1, the ratio of rotational speed of the compressor (50) rotational speed of the expander (60) in the case of the r, the fluid chamber in the expander (60) is cut off from the inlet side The volume v ₂ of the fluid chamber immediately after is v ₂ = ρ ₁ · v ₁ · r / ρ ₂ , and the volume v ₃ of the fluid chamber immediately before the fluid chamber communicates with the outflow side in the expander (60). V ₃ = ρ ₂ · v ₂ / ρ ₃ .

  According to a second invention, in the first invention, the refrigerant circuit (15) is provided with a receiver (18) between the outlet side of the evaporator (17) and the suction side of the compressor (50). is there.

  According to a third aspect, in the first aspect, the refrigerant circuit (15) includes a refrigerant directed from the radiator (16) toward the expander (60) and a refrigerant directed from the evaporator (17) toward the compressor (50). And an internal heat exchanger (20) for exchanging heat with each other.

-Action-
In the said 1st invention, a refrigerant | coolant circulates in the refrigerant circuit (15) of a freezing apparatus (10), and a refrigerating cycle is performed. The refrigerant circulating in the refrigerant circuit (15) is compressed by the compressor (50) and becomes supercritical, then dissipates heat in the radiator (16), and then expands in the expander (60) before evaporating. The container (17) absorbs heat and evaporates, and then is sucked into the compressor (50) and compressed again. The expander (60) is connected to the compressor (50), and the power recovered from the refrigerant by the expander (60) is used to drive the compressor (50). In the refrigeration apparatus (10), the ratio of the rotational speed of the expander (60) to the rotational speed of the compressor (50) is fixed. For example, the ratio of the rotational speed is “1” when the compressor (50) and the expander (60) are directly connected by a single shaft, and the speed reduction of the speed reducer is achieved when they are connected via a speed reducer. Equal to the ratio.

In designing the refrigeration apparatus (10), the volume v ₁ of the fluid chamber immediately after the fluid chamber is shut off from the suction side in the compressor (50), that is, the suction volume of the compressor (50) It can be set according to the required value of ability. Also, if the use of the refrigeration apparatus (10) is determined, the reference low pressure that is the low pressure of the refrigeration cycle and the reference refrigerant temperature that is the refrigerant temperature at the outlet of the radiator (16) based on the operating conditions assumed for that use However, it is not possible to set the high pressure of the refrigeration cycle. On the other hand, if the low-pressure of the refrigeration cycle and the refrigerant temperature at the outlet of the radiator (16) are set, the coefficient of performance (COP) is the highest under the operating conditions by performing an operation test or simulation under the operating conditions. It is possible to determine the high pressure of the refrigeration cycle.

Therefore, in the present invention, in the reference operation state in which the low pressure of the refrigeration cycle is the reference low pressure and the refrigerant temperature at the outlet of the radiator (16) is the reference refrigerant temperature, the refrigeration cycle has the highest coefficient of performance for the refrigeration cycle. The high pressure is the reference high pressure. The specifications of the expander (60) in the refrigeration apparatus (10) are set based on the reference low pressure, the reference refrigerant temperature, the reference high pressure, and the physical properties of the refrigerant charged in the refrigerant circuit (15). Specifically, the volume v _{2 of the} fluid chamber immediately after the fluid chamber is shut off from the inflow side in the expander (60) (that is, immediately before the expansion of the refrigerant in the fluid chamber), and the expander (60) The volume v ₃ of the fluid chamber immediately before the fluid chamber communicates with the outflow side (that is, immediately after the expansion of the refrigerant in the fluid chamber) is set based on the above-described reference high pressure or the like.

  In the said 2nd invention, a receiver (18) is provided in a refrigerant circuit (15). A part of the refrigerant filled in the refrigerant circuit (15) is stored in a liquid refrigerant state in the receiver (18). When the amount of liquid refrigerant in the receiver (18) increases or decreases, the amount of refrigerant circulating in the refrigerant circuit (15) changes accordingly. The receiver (18) is installed between the outlet side of the evaporator (17) and the suction side of the compressor (50). In the refrigerant circuit (15), the refrigerant flowing out of the evaporator (17) is introduced into the receiver (18), and the refrigerant in the receiver (18) is sucked into the compressor (50). Since liquid refrigerant exists in the receiver (18), the refrigerant in the receiver (18) sucked into the compressor (50) is saturated.

  In the said 3rd invention, an internal heat exchanger (20) is provided in a refrigerant circuit (15). In the internal heat exchanger (20), the refrigerant from the radiator (16) to the expander (60) is cooled by exchanging heat with the refrigerant from the evaporator (17) to the compressor (50). The refrigerant flowing into the expander (60) is cooled by the internal heat exchanger (20), so that its enthalpy is lowered. Along with this, the enthalpy of the refrigerant sent from the expander (60) to the evaporator (17) also decreases.

  In the present invention, the high pressure of the refrigeration cycle at which the coefficient of performance (COP) is maximized under a constant condition of the low pressure of the refrigeration cycle (reference low pressure) and the refrigerant temperature (reference refrigerant temperature) at the outlet of the radiator (16). Paying attention to the characteristic of the refrigeration apparatus (10) that the (reference high pressure) is uniquely determined, the refrigeration apparatus (10) is provided with an expander (60) whose specification is determined using this characteristic. Therefore, according to the present invention, it is possible to use the expander (60) having specifications suitable for the use conditions of the refrigeration apparatus (10), and the refrigeration apparatus (60) can reliably recover power from the refrigerant by the expander (60). 10) The coefficient of performance can be increased.

  In the second aspect, the refrigerant flowing out from the evaporator (17) is introduced into the receiver (18), and the compressor (50) sucks the refrigerant from the receiver (18). For this reason, the compressor (50) sucks the saturated refrigerant in the receiver (18) even in the operation state in which the refrigerant flowing out of the evaporator (17) is overheated. Therefore, according to the present invention, the state of the refrigerant sucked by the compressor (50) can be matched with the state assumed when the refrigeration apparatus (10) is designed, and the refrigeration cycle in the refrigeration apparatus (10) is stabilized. Can be made.

  In the third aspect of the invention, the refrigerant circuit (15) is provided with the internal heat exchanger (20) to cool the refrigerant flowing into the expander (60) and sent from the expander (60) to the evaporator (17). Reduces the enthalpy of the refrigerant. For this reason, the enthalpy difference of the refrigerant | coolant in the entrance / exit of an evaporator (17) can be expanded, and the cooling capability in the case of cooling a target object with an evaporator (17) can be increased.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

Embodiment 1 of the Invention
A first embodiment of the present invention will be described. The air conditioner (10) of the present embodiment is configured by a refrigeration apparatus according to the present invention.

As shown in FIG. 1, the air conditioner (10) includes a refrigerant circuit (15). The refrigerant circuit (15) is filled with carbon dioxide (CO ₂ ) as a refrigerant. The refrigerant circuit (15) is provided with a radiator (16), an evaporator (17), and a compression / expansion unit (30). The radiator (16) has an inlet side connected to the discharge pipe (36) of the compression / expansion unit (30) and an outlet side connected to the inlet port (34) of the compression / expansion unit (30). The evaporator (17) has an inlet side connected to the outflow port (35) of the compression / expansion unit (30) and an outlet side connected to the suction port (32) of the compression / expansion unit (30). The radiator (16) and the evaporator (17) cause the refrigerant in the refrigerant circuit (15) to exchange heat with air.

  As shown in FIG. 2, the compression / expansion unit (30) includes a casing (31) which is a vertically long and cylindrical sealed container. Inside the casing (31), a compressor (50), an electric motor (45), and an expander (60) are arranged in order from the bottom to the top.

  A discharge pipe (36) is attached to the casing (31). The discharge pipe (36) is disposed between the electric motor (45) and the expander (60) and communicates with the internal space of the casing (31).

  The electric motor (45) is arranged at the center in the longitudinal direction of the casing (31). The electric motor (45) includes a stator (46) and a rotor (47). The stator (46) is fixed to the casing (31). The rotor (47) is disposed inside the stator (46). Further, the main shaft portion (44) of the shaft (40) passes through the rotor (47) coaxially with the rotor (47).

  The shaft (40) constitutes a rotating shaft. In the shaft (40), two lower eccentric portions (58, 59) are formed on the lower end side, and two large-diameter eccentric portions (41, 42) are formed on the upper end side.

  The two lower eccentric portions (58, 59) are formed to have a larger diameter than the main shaft portion (44), the lower one being the first lower eccentric portion (58) and the upper one being the second. A lower eccentric portion (59) is formed. In the first lower eccentric portion (58) and the second lower eccentric portion (59), the eccentric directions of the main shaft portion (44) with respect to the axial center are reversed.

  The two large-diameter eccentric parts (41, 42) are formed with a larger diameter than the main shaft part (44), the lower one constitutes the first large-diameter eccentric part (41), and the upper one is A second large-diameter eccentric portion (42) is configured. The first large-diameter eccentric part (41) and the second large-diameter eccentric part (42) are both eccentric in the same direction. The outer diameter of the second large-diameter eccentric part (42) is larger than the outer diameter of the first large-diameter eccentric part (41). Further, the amount of eccentricity of the main shaft portion (44) with respect to the shaft center is larger in the second large-diameter eccentric portion (42) than in the first large-diameter eccentric portion (41).

  The compressor (50) constitutes an oscillating piston type rotary compressor. The compressor (50) includes two cylinders (51, 52) and two pistons (57). In the compressor (50), in order from bottom to top, the rear head (55), the first cylinder (51), the intermediate plate (56), the second cylinder (52), and the front head (54) Are stacked.

  One cylindrical piston (57) is disposed inside each of the first and second cylinders (51, 52). Although not shown, a flat plate-like blade projects from the side surface of the piston (57), and this blade is supported by the cylinder (51, 52) via a swing bush. The piston (57) in the first cylinder (51) engages with the first lower eccentric portion (58) of the shaft (40). On the other hand, the piston (57) in the second cylinder (52) engages with the second lower eccentric portion (59) of the shaft (40). Each piston (57, 57) has its inner peripheral surface in sliding contact with the outer peripheral surface of the lower eccentric portion (58, 59), and its outer peripheral surface is in sliding contact with the inner peripheral surface of the cylinder (51, 52). A compression chamber (53) is formed between the outer peripheral surface of the piston (57, 57) and the inner peripheral surface of the cylinder (51, 52).

  One suction port (33) is formed in each of the first and second cylinders (51, 52). Each suction port (33) penetrates the cylinder (51, 52) in the radial direction, and its terminal end opens on the inner peripheral surface of the cylinder (51, 52). Each suction port (33) is extended to the outside of the casing (31) by piping.

  One discharge port is formed in each of the front head (54) and the rear head (55). The discharge port of the front head (54) allows the compression chamber (53) in the second cylinder (52) to communicate with the internal space of the casing (31). The discharge port of the rear head (55) allows the compression chamber (53) in the first cylinder (51) to communicate with the internal space of the casing (31). Each discharge port is provided with a discharge valve consisting of a reed valve at its end, and is opened and closed by this discharge valve. In FIG. 2, the discharge port and the discharge valve are not shown. The gas refrigerant discharged from the compressor (50) into the internal space of the casing (31) is sent out from the compression / expansion unit (30) through the discharge pipe (36).

  The expander (60) is a so-called oscillating piston type fluid machine. The expander (60) is provided with two pairs of cylinders (81, 82) and pistons (75, 85) which are paired. The expander (60) includes a front head (61), an intermediate plate (63), and a rear head (62).

  In the expander (60), a front head (61), a first cylinder (71), an intermediate plate (63), a second cylinder (81), and a rear head (62) are laminated in order from bottom to top. It is in a state. In this state, the first cylinder (71) has its lower end face closed by the front head (61) and its upper end face closed by the intermediate plate (63). On the other hand, the second cylinder (81) has its lower end face closed by the intermediate plate (63) and its upper end face closed by the rear head (62). The inner diameter of the second cylinder (81) is larger than the inner diameter of the first cylinder (71). The shaft (40) passes through the stacked front head (61), first cylinder (71), intermediate plate (63), second cylinder (81), and rear head (62).

  As shown in FIGS. 3 and 4, a first piston (75) is provided in the first cylinder (71), and a second piston (85) is provided in the second cylinder (81). The first and second pistons (75, 85) are both formed in an annular shape or a cylindrical shape. The outer diameter of the first piston (75) and the outer diameter of the second piston (85) are equal to each other. The first large-diameter eccentric portion (41) penetrates the first piston (75), and the second large-diameter eccentric portion (42) penetrates the second piston (85). A first fluid chamber (72) is formed in the first cylinder (71) between the inner peripheral surface thereof and the outer peripheral surface of the first piston (75). A second fluid chamber (82) is formed in the second cylinder (81) between the inner peripheral surface thereof and the outer peripheral surface of the second piston (85).

  One blade (76, 86) is provided integrally with each of the first and second pistons (75, 85). The blades (76, 86) are formed in a plate shape extending in the radial direction of the piston (75, 85), and protrude outward from the outer peripheral surface of the piston (75, 85).

  Each cylinder (71, 81) is provided with a pair of bushes (77, 87). Each bush (77, 87) is a small piece formed such that the inner surface is a flat surface and the outer surface is a circular arc surface. The pair of bushes (77, 87) are installed with the blade (76, 86) sandwiched therebetween. Each bush (77, 87) slides on its inner side with the blade (76, 86) and its outer side with the cylinder (81, 82). The blade (76, 86) integral with the piston (75, 85) is supported by the cylinder (71, 81) via the bush (77, 87) and is rotatable with respect to the cylinder (71, 81). And you can move forward and backward. The first cylinder (71) and the second cylinder (81) are arranged in such a posture that the positions of the bushes (77, 87) in the respective circumferential directions coincide.

  The first fluid chamber (72) in the first cylinder (71) is partitioned by a first blade (76) integral with the first piston (75), and the left side of the first blade (76) in FIG. The first high pressure chamber (73) on the high pressure side is formed, and the right side thereof is the first low pressure chamber (74) on the low pressure side. The second fluid chamber (82) in the second cylinder (81) is partitioned by a second blade (86) integral with the second piston (85), and the left side of the second blade (86) in FIG. A high pressure side second high pressure chamber (83) is formed, and a right side thereof is a low pressure side second low pressure chamber (84).

  The first cylinder (71) has an inflow port (34). The inflow port (34) opens at a position slightly on the left side of the bush (77) in FIGS. 3 and 4 in the inner peripheral surface of the first cylinder (71). The inflow port (34) can communicate with the first high pressure chamber (73). On the other hand, the outflow port (35) is formed in the second cylinder (81). The outflow port (35) opens at a position slightly on the right side of the bush (87) in FIGS. 3 and 4 in the inner peripheral surface of the second cylinder (81). The outflow port (35) can communicate with the second low pressure chamber (84).

  A communication passage (64) is formed in the intermediate plate (63). The communication path (64) penetrates the intermediate plate (63) in the thickness direction. On the surface of the intermediate plate (63) on the first cylinder (71) side, one end of the communication path (64) is opened at a location on the right side of the first blade (76). On the surface of the intermediate plate (63) on the second cylinder (81) side, the other end of the communication path (64) is opened at a location on the left side of the second blade (86). As shown in FIG. 3, the communication path (64) extends obliquely with respect to the thickness direction of the intermediate plate (63), and connects the first low pressure chamber (74) and the second high pressure chamber (83). Communicate with each other.

  In the expander (60) configured as described above, the first cylinder (71), the bush (77) provided therein, the first piston (75), and the first blade (76) are provided. A first rotary mechanism (70) is configured. The second cylinder (81), the bush (87) provided there, the second piston (85), and the second blade (86) constitute a second rotary mechanism (80). . Further, in this expander (60), the displacement volume of the second rotary mechanism section (80) (in comparison with the displacement volume of the first rotary mechanism section (70) (that is, the maximum volume of the first fluid chamber (72)) ( That is, the maximum volume of the second fluid chamber (82) is larger.

  As described above, in the expander (60), the timing at which the first blade (76) is most retracted to the outside of the first cylinder (71) and the second blade (86) is to the outside of the second cylinder (81). The timing of the most withdrawal is synchronized. That is, the process in which the volume of the first low pressure chamber (74) decreases in the first rotary mechanism (70) and the volume of the second high pressure chamber (83) increases in the second rotary mechanism (80). The going process is synchronized (see FIG. 4). In addition, as described above, the first low pressure chamber (74) of the first rotary mechanism (70) and the second high pressure chamber (83) of the second rotary mechanism (80) communicate with the communication path (64). Are in communication with each other. The first low pressure chamber (74), the communication passage (64), and the second high pressure chamber (83) form one closed space, and this closed space constitutes the expansion chamber (66).

-Driving action-
In the air conditioner (10), a refrigeration cycle is performed by circulating the refrigerant in the refrigerant circuit (15). During the cooling operation, the refrigerant radiates heat to the outdoor air sent to the radiator (16), and the refrigerant absorbs heat from the indoor air sent to the evaporator (17). This cools the room air. On the other hand, during the heating operation, the refrigerant radiates heat to the indoor air sent to the radiator (16), and the refrigerant absorbs heat from the outdoor air sent to the evaporator (17). As a result, the room air is heated.

<Refrigeration cycle in refrigerant circuit>
The refrigeration cycle in the refrigerant circuit (15) will be described with reference to the Mollier diagram (pressure-enthalpy diagram) in FIG.

The refrigerant in the state indicated by the point A in the drawing is sucked into the compressor (50). In the compressor (50), the refrigerant in the state of point A is compressed to be in the state of point B. In the state of point B, the refrigerant pressure is higher than its critical pressure P _C. The refrigerant discharged from the compressor (50) in the state of point B is sent to the radiator (16). In the radiator (16), the refrigerant in the state of point B dissipates heat to the air, and the enthalpy is reduced to a state of point C while the pressure is constant. During the period from point B to point C, the temperature of the refrigerant gradually decreases.

  The refrigerant flowing out of the radiator (16) in the state of point C is introduced into the expander (60). In the expander (60), the refrigerant in the state of point C is adiabatically expanded and power recovery from the refrigerant is performed. In the expander (60), the refrigerant changes from the state at the point C to the state at the point D substantially along the isentropic line. The refrigerant flowing out of the expander (60) in the state of point D is sent to the evaporator (17). In the evaporator (17), the refrigerant in the state of point D absorbs heat from the air, the enthalpy increases with the pressure kept constant, and the state of point A is reached. During the period from the point D state to the point A state, the refrigerant temperature is constant. The refrigerant flowing out of the evaporator (17) in the state of point A is sucked into the compressor (50) and compressed again.

<Operation of the expander>
The operation of the expander (60) will be described with reference to FIG.

  First, a process in which the supercritical high pressure refrigerant flows into the first high pressure chamber (73) of the first rotary mechanism (70) will be described. When the shaft (40) rotates slightly from the state where the rotation angle is 0 °, the contact position between the first piston (75) and the first cylinder (71) passes through the opening of the inflow port (34), and the inflow port ( 34) The high-pressure refrigerant begins to flow from the first high-pressure chamber (73). Thereafter, as the rotation angle of the shaft (40) gradually increases to 90 °, 180 °, and 270 °, the high-pressure refrigerant flows into the first high-pressure chamber (73). The inflow of the high-pressure refrigerant into the first high-pressure chamber (73) continues until the rotation angle of the shaft (40) reaches 360 °.

  Next, a process of expanding the refrigerant in the expander (60) will be described. When the shaft (40) is slightly rotated from the state where the rotation angle is 0 °, the first low pressure chamber (74) and the second high pressure chamber (83) communicate with each other via the communication passage (64), and the first low pressure chamber The refrigerant begins to flow from (74) into the second high pressure chamber (83). Thereafter, as the rotation angle of the shaft (40) gradually increases to 90 °, 180 °, and 270 °, the volume of the first low pressure chamber (74) gradually decreases and the volume of the second high pressure chamber (83) gradually increases. As a result, the volume of the expansion chamber (66) gradually increases. This increase in the volume of the expansion chamber (66) continues until just before the rotation angle of the shaft (40) reaches 360 °. The refrigerant in the expansion chamber (66) expands while the pressure drops in the process of increasing the volume of the expansion chamber (66). Torque is generated by the internal pressure difference between the first high pressure chamber (73) and the first low pressure chamber (74) and the internal pressure difference between the second high pressure chamber (83) and the second low pressure chamber (84). (40) is driven to rotate. Thus, the refrigerant in the first low pressure chamber (74) flows through the communication passage (64) while expanding into the second high pressure chamber (83).

  Finally, the process in which the refrigerant flows out from the second low pressure chamber (84) of the second rotary mechanism (80) will be described. The second low pressure chamber (84) starts to communicate with the outflow port (35) when the rotation angle of the shaft (40) is 0 °. That is, the refrigerant starts to flow from the second low pressure chamber (84) to the outflow port (35). After that, the shaft (40) has a rotation angle gradually increased to 90 °, 180 °, and 270 °, and after the expansion from the second low pressure chamber (84) until the rotation angle reaches 360 °. The low-pressure refrigerant flows out.

-Expander specifications-
As described above, in the expander (60), the displacement volume of the second rotary mechanism portion (80) is larger than the displacement volume of the first rotary mechanism portion (70). The displacement volume of the first rotary mechanism (70) is the maximum volume of the first fluid chamber (72), that is, the volume of the first fluid chamber (72) immediately after being shut off from the inflow port (34). The displacement volume of the second rotary mechanism (80) is the maximum volume of the second fluid chamber (82), that is, the volume of the second fluid chamber (82) immediately before communicating with the outflow port (35).

  Here, how the displacement volume of each rotary mechanism (70, 80) is set in the expander (60) will be described.

In the air conditioner (10), the refrigerant exchanges heat with indoor air or outdoor air in the radiator (16) and the evaporator (17). Therefore, taking into consideration the conditions of indoor air and outdoor air, the low-pressure pressure (reference low-pressure P _L ) of the refrigeration cycle and the refrigerant temperature at the outlet of the radiator (16) (reference refrigerant temperature T ₂ ) and are set. Also, assuming the air conditioning capacity required for the air conditioner (10), the refrigerant circulation amount (refrigerant flow rate) in the refrigerant circuit (15) required to obtain the air conditioning capacity is determined, and the compressor A suction volume v ₁ is set. Moreover, since the expander (60) is connected with the compressor (50) by one shaft (40), the rotation speeds of the expander (60) and the compressor (50) are the same. That is, the ratio r of the rotational speed of the compressor (50) to the rotational speed of the expander (60) is “1”.

  As described above, in a refrigeration cycle (so-called supercritical cycle) in which the high pressure is equal to or higher than the critical pressure of the refrigerant, the high pressure of the refrigeration cycle cannot be set only by considering the state of indoor air or outdoor air. On the other hand, as shown in FIG. 6, in the supercritical cycle, when the low pressure of the refrigeration cycle and the refrigerant temperature at the outlet of the radiator (16) are fixed, the COP (coefficient of performance) of the refrigeration cycle depends on the high pressure of the refrigeration cycle. Changes, and when this high pressure reaches a specific value, the COP of the refrigeration cycle is maximized.

The vertical axis of the graph shown in the figure, a COP in the case of heating the object in the radiator (16) is a value represented by _{Δh BC / (Δh BA -Δh CD} ). As shown in FIG. 5, Δh _BC is the amount of heat that the refrigerant radiates to the object in the radiator (16), Δh _BA is the power required to compress the refrigerant by the compressor, and Δh _CD is the refrigerant in the expander. The power recovered from each is expressed as a value per kg of refrigerant.

  In the expander (60) of the present embodiment, the supercritical cycle characteristic that “the high pressure at which the COP becomes maximum is uniquely determined when the low pressure of the refrigeration cycle and the refrigerant temperature at the outlet of the radiator (16) are fixed” is determined. Paying attention to this, the displacement volume of each rotary mechanism (70, 80) is set using this characteristic.

This point will be described in detail. Assuming that the compressor (50) sucks saturated gas refrigerant, the density of the refrigerant sucked into the compressor (50) becomes the density ρ ₁ of the saturated gas refrigerant at the reference low pressure. The amount of refrigerant discharged every rotation of the compressor (50) is a value (ρ ₁ · v ₁ ) obtained by multiplying the density ρ ₁ of the saturated gas refrigerant at the reference low pressure by the suction volume v ₁ of the compressor. . Let ρ ₂ be the density of the refrigerant at the reference high pressure and the reference refrigerant temperature, that is, the density of the refrigerant introduced into the expander (60). Ideally, the amount of refrigerant introduced into the expander (60) is equal to the amount of refrigerant discharged from the compressor (50). For this reason, the displacement volume of the first rotary mechanism (70), that is, the maximum volume v ₂ of the first fluid chamber (72) is set to v ₂ = ρ ₁ · v ₁ · r / ρ ₂ .

Assuming that the refrigerant adiabatically expands in the expander (60), the density ρ ₃ of the refrigerant at the outlet of the expander (60) is determined. The amount of refrigerant flowing out of the expander (60) is always equal to the amount of refrigerant introduced into the expander (60). For this reason, the displacement volume of the second rotary mechanism (80), that is, the maximum volume v ₃ of the second fluid chamber (82) is set to v ₃ = ρ ₂ · v ₂ / ρ ₃ .

A specific example is shown. A case will be described in which the refrigerant evaporating temperature is set to 0 ° C. and the refrigerant temperature at the outlet of the radiator (16) is set to 35 ° C. under the reference operating conditions as design criteria. In this case, the reference refrigerant temperature is set to 35 ° C. On the other hand, the reference low pressure is set to a pressure of 3.5 MPa at which the evaporation temperature of carbon dioxide (CO ₂ ) as a refrigerant becomes 0 ° C. The density ρ ₁ of the saturated gas refrigerant at the standard low pressure of 3.5 MPa is 97.32 kg / m ³ . Further, under the operating conditions where the reference low pressure is 3.5 MPa and the reference refrigerant temperature is 35 ° C., the high pressure at which the COP of the refrigeration cycle is maximum, that is, the reference high pressure is 9 MPa (see FIG. 6). The refrigerant density ρ ₂ at a reference high pressure of 9 MPa and a reference refrigerant temperature of 35 ° C. is 662.5 kg / m ³ . The density ρ _{3 of} the refrigerant adiabatically expanded from the state of the reference refrigerant temperature of 35 ° C. to the reference low pressure of 3.5 MPa at the reference high pressure of 9 MPa is 220 kg / m ³ . Therefore, the displacement of the first rotary mechanism (70) is set to v ₂ = (97.32 / 662.5) v ₁ = 0.15v _1, and the displacement of the second rotary mechanism (80) is v ₃ = (662.5 / 220) v ₂ = 0.44v ₁ is set.

-Effect of Embodiment 1-
In the present embodiment, the high pressure (reference high pressure) of the refrigeration cycle at which the COP is maximum under the condition that the low pressure (reference low pressure) of the refrigeration cycle and the refrigerant temperature (reference refrigerant temperature) at the outlet of the radiator (16) are constant. ) Is determined uniquely, and the expander (60) whose specifications are determined by using this characteristic is provided in the air conditioner (10) as the refrigeration system. Therefore, according to the present embodiment, the expander (60) having the optimum specification can be used in the operating condition of the air conditioner (10), and the power recovered from the refrigerant by the expander (60) is increased to perform air conditioning. The COP of the machine (10) can be increased.

<< Embodiment 2 of the Invention >>
A second embodiment of the present invention will be described. Here, about the air conditioner (10) of this embodiment, a different point from the said Embodiment 1 is demonstrated.

  As shown in FIG. 7, the refrigerant circuit (15) of the air conditioner (10) is provided with a receiver (18). The receiver (18) is formed in a cylindrical sealed container shape, and is installed between the outlet side of the evaporator (17) and the suction side of the compressor (50). A part of the refrigerant filled in the refrigerant circuit (15) is stored in a liquid refrigerant state in the receiver (18). When the amount of liquid refrigerant in the receiver (18) increases or decreases, the amount of refrigerant circulating in the refrigerant circuit (15) changes accordingly.

  In the refrigerant circuit (15) of the present embodiment, the refrigerant flowing out of the evaporator (17) is introduced into the receiver (18), and the refrigerant in the receiver (18) is sucked into the compressor (50). Since liquid refrigerant exists in the receiver (18), the refrigerant in the receiver (18) sucked into the compressor (50) is saturated. That is, the refrigerant sucked by the compressor (50) is kept in a saturated state even in an operation state in which the refrigerant is overheated at the outlet of the evaporator (17).

  As described in the description of the first embodiment, the displacement of each rotary mechanism (70, 80) in the expander (60) is based on the assumption that the suction refrigerant of the compressor (50) is a saturated gas refrigerant. Is set. For this reason, if the intake refrigerant of the compressor (50) is kept saturated regardless of the operating conditions by providing the receiver (18), the operation assuming the refrigeration cycle conditions in the refrigerant circuit (15) at the time of design. It is possible to approach the state, and it is possible to stabilize the refrigeration cycle in the refrigerant circuit (15).

<< Embodiment 3 of the Invention >>
Embodiment 3 of the present invention will be described. Here, about the air conditioner (10) of this embodiment, a different point from the said Embodiment 2 is demonstrated.

  As shown in FIG. 8, the refrigerant circuit (15) of the air conditioner (10) is provided with an internal heat exchanger (20). The internal heat exchanger (20) is provided with a first channel (21) and a second channel (22). The first flow path (21) has an inlet side connected to the radiator (16) and an outlet side connected to the inflow port (34) of the expander (60). The second channel (22) has an inlet side connected to the evaporator (17) and an outlet side connected to the suction port (32) of the compressor (50) via the receiver (18).

  In the internal heat exchanger (20), the refrigerant from the radiator (16) to the expander (60) is cooled by heat exchange with the refrigerant from the evaporator (17) to the receiver (18). The refrigerant flowing into the expander (60) is cooled by the internal heat exchanger (20), so that its enthalpy is lowered. Along with this, the enthalpy of the refrigerant sent from the expander (60) to the evaporator (17) also decreases. For this reason, the enthalpy difference of the refrigerant | coolant in the entrance / exit of an evaporator (17) can be expanded, and the calorie | heat amount which a refrigerant | coolant absorbs from air in an evaporator (17) can be increased. Therefore, according to the present embodiment, it is possible to increase the cooling capacity of the air conditioner (10) by providing the internal heat exchanger (20).

-Modification of Embodiment 3-
In the refrigerant circuit (15) of the present embodiment, as shown in FIG. 9, the second flow path (22) of the internal heat exchanger (20) is connected between the receiver (18) and the compressor (50). Also good. Specifically, in the second heat flow path (22) of the internal heat exchanger (20) in this modification, the inlet side is connected to the evaporator (17) via the receiver (18), and the outlet side is the suction port of the compressor. (32) is connected to each. Also in the internal heat exchanger (20) of this modification, the refrigerant from the radiator (16) to the expander (60) is cooled by heat exchange with the refrigerant from the evaporator (17) to the compressor (50). The enthalpy difference of the refrigerant at the inlet / outlet of the evaporator (17) increases.

<< Embodiment 4 of the Invention >>
Embodiment 4 of the present invention will be described. In this embodiment, the configuration of the expander (60) is changed in the first embodiment.

  As shown in FIG. 10, the expander (60) of the present embodiment is constituted by a scroll type fluid machine. The expander (60) includes a movable scroll (91) and a fixed scroll (93). The movable scroll (91) includes a movable side wrap (92). The movable wrap (92) is formed in the shape of a spiral wall whose upper end draws an involute curve. The movable scroll (91) is engaged with the shaft (40) and performs only the revolving motion in a state where the rotational motion is restricted. The fixed scroll (93) includes a fixed side wrap (94). The movable side wrap (92) is formed in a spiral wall shape corresponding to the movable side wrap (92), and both side surfaces thereof constitute an envelope surface of the fixed side wrap (94) that undergoes revolving motion. Further, the fixed scroll (93) has an inflow port (34) opened at the center thereof and an outflow port (35) opened at the peripheral portion thereof.

  In the expander (60), the movable side wrap (92) of the movable scroll (91) and the fixed side wrap (94) of the fixed scroll (93) are engaged with each other. A first chamber (95) and a second chamber (96), both of which are fluid chambers, are formed in pairs between the movable wrap (92) and the fixed wrap (94). As shown in the order (A) to (D) in the figure, when the movable scroll (91) moves, the volumes of the first chamber (95) and the second chamber (96) change.

FIG. 10A shows a state immediately after the first chamber (95) and the second chamber (96) are blocked from the inflow port (34). In this state, the volumes of the first chamber (95) and the second chamber (96) are minimum. In the expander (60) of the present embodiment, the sum of the volumes of the second chamber of the first chamber (95) in this state (96) is v _2. On the other hand, FIG. 10D shows a state immediately before the first chamber (95) and the second chamber (96) communicate with the outflow port (35). In this state, the volumes of the first chamber (95) and the second chamber (96) are maximum. In the expander (60) of the present embodiment, the sum of the volumes of the second chamber of the first chamber (95) in this state (96) is v _3.

  As described above, the present invention is useful for a refrigeration apparatus that includes an expander and performs a refrigeration cycle in which a high pressure is set to be equal to or higher than a critical pressure of a refrigerant.

It is a schematic block diagram which shows the refrigerant circuit of the air conditioner in Embodiment 1. 2 is a schematic cross-sectional view of a compression / expansion unit in Embodiment 1. FIG. FIG. 3 is an enlarged view of a main part of the expander according to the first embodiment. It is sectional drawing which shows the state of each rotary mechanism part for every 90 degrees of rotation angles of the shaft in the expander of Embodiment 1. FIG. It is a Mollier diagram (pressure-enthalpy diagram) showing a refrigeration cycle in a refrigerant circuit. FIG. 6 is a relationship diagram between high pressure and COP when the low pressure and the refrigerant temperature at the radiator outlet are fixed in the supercritical cycle. It is a schematic block diagram which shows the refrigerant circuit of the air conditioning machine in Embodiment 2. It is a schematic block diagram which shows the refrigerant circuit of the air conditioner in Embodiment 3. It is a schematic block diagram which shows the refrigerant circuit of the air conditioner in the modification of Embodiment 3. It is a schematic sectional drawing which shows the structure and operation | movement of an expander in Embodiment 4. It is a Mollier diagram (pressure-enthalpy diagram) showing the characteristics of the supercritical cycle.

Explanation of symbols

(15) Refrigerant circuit (16) Radiator (17) Evaporator (18) Receiver (20) Internal heat exchanger (50) Compressor (53) Compression chamber (60) Expander (72) First fluid chamber (73 ) First high pressure chamber (74) First low pressure chamber (82) Second fluid chamber (83) Second high pressure chamber (84) Second low pressure chamber (95) First chamber (96) Second chamber

Claims (3)

The refrigerant circuit (15) is connected to the compressor (50), the radiator (16), the expander (60), and the evaporator (17), and the refrigerant is circulated through the refrigerant circuit (15) to increase the pressure. Is a refrigeration apparatus that performs a refrigeration cycle in which the refrigerant has a critical pressure or higher,
The compressor (50) and the expander (60) are both constituted by a positive displacement fluid machine in which the volume of the fluid chamber changes, and the ratio of the rotation speed of one to the other is constant. While connected to each other
The low-pressure pressure of the refrigeration cycle and the refrigerant temperature at the outlet of the radiator (16) under the standard operating conditions that are the design standards are the standard low-pressure and the standard refrigerant temperature, respectively.
The high pressure of the refrigeration cycle at which the coefficient of performance of the refrigeration cycle is the highest in the above standard operating state is the reference high pressure,
The density of the saturated gas refrigerant at the reference low pressure is ρ ₁ ,
The density of the refrigerant at the reference high pressure and the reference refrigerant temperature is ρ ₂ ,
The density of the adiabatic expansion of the refrigerant at the reference high pressure and the reference refrigerant temperature to the reference low pressure is ρ ₃ ,
In the compressor (50), the volume of the fluid chamber immediately after the fluid chamber is shut off from the suction side is v ₁ ,
When the ratio of the rotational speed of the compressor (50) to the rotational speed of the expander (60) is r,
In the expander (60), the volume v ₂ of the fluid chamber immediately after the fluid chamber is shut off from the inflow side is v ₂ = ρ ₁ · v ₁ · r / ρ ₂ ,
The refrigeration apparatus in which the volume v ₃ of the fluid chamber immediately before the fluid chamber communicates with the outflow side in the expander (60) is v ₃ = ρ ₂ · v ₂ / ρ ₃ . The refrigeration apparatus according to claim 1,
In the refrigerant circuit (15), a refrigeration apparatus in which a receiver (18) is provided between the outlet side of the evaporator (17) and the suction side of the compressor (50). The refrigeration apparatus according to claim 1,
The refrigerant circuit (15) has an internal heat exchanger (20) for exchanging heat between the refrigerant from the radiator (16) to the expander (60) and the refrigerant from the evaporator (17) to the compressor (50). Refrigeration equipment provided.

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