JP4832355B2 - Refrigeration air conditioner - Google Patents

Description

  The present invention relates to a refrigeration air conditioner, and more particularly to a refrigeration air conditioner using propane or isobutane which is a hydrocarbon refrigerant as a refrigerant.

  In order to protect the ozone layer and prevent global warming, hydrocarbon refrigerants are attracting attention as refrigerants used in refrigeration air conditioners. Propane and isobutane, which are hydrocarbon refrigerants, have good characteristics such as lower global warming potential (GWP) and higher theoretical coefficient of performance (refrigerator efficiency: COP) than R410A and R407C, which are HFC refrigerants. On the other hand, since it is flammable, reduction of the amount of filling refrigerant | coolants is a big technical subject.

  Therefore, it has been proposed to reduce the amount of refrigerant charged by reducing the size of the heat exchanger by setting the upper limit of the pipe diameter of the indoor heat exchanger and the fin pitch (distance between fins). ing.

JP2003-148755A (FIG. 1, Table 4)

  However, the necessary heat transfer performance cannot be ensured even if the amount of refrigerant can be reduced only by proportionally reducing the volume of the heat exchanger as described above.

  In view of the above, the present invention uses a combustible hydrocarbon refrigerant, propane or isobutane, and combines a high-performance heat exchanger with a small refrigerant retention amount with a refrigeration cycle technology, and a charged refrigerant below a regulation value. The purpose is to obtain a high-performance air conditioning device in quantity.

The refrigerating and air-conditioning apparatus according to the present invention has the following configuration. That is, a refrigerant circuit in which a compressor, a four-way valve, a heat source side heat exchanger, a decompression means, a use side heat exchanger, a liquid refrigerant pipe and a gas refrigerant pipe connecting the outdoor unit and the indoor unit are coupled in a closed loop; An internal refrigerant flow path of a heat source side heat exchanger or a use side heat exchanger in a refrigeration air conditioner that uses a combustible hydrocarbon refrigerant as a refrigerant and supplies cold temperature from the use side heat exchanger. The pipe cross-sectional area of the pipe forming the pipe is further increased in circumferential length in the pipe cross-section of the pipe so that the cross-sectional area of the pipe in the longitudinal direction is larger than the cross-sectional area of the pipe in the middle of the longitudinal direction. The value divided by the area is set so that the middle portion in the longitudinal direction of the pipe is larger than both longitudinal ends of the pipe .

According to the refrigerating and air-conditioning apparatus of the present invention, the in-pipe cross-sectional area of the pipe forming the internal refrigerant flow path of the heat source side heat exchanger or the use side heat exchanger is set so that the cross-sectional areas in the pipes at both longitudinal ends are intermediate in the longitudinal direction. Further, the value obtained by dividing the circumferential length of the pipe in the pipe cross section by the area of the pipe cross section so as to be larger than the pipe cross sectional area of the pipe is the intermediate portion in the longitudinal direction of the pipe rather than both longitudinal ends of the pipe. Since the heat transfer coefficient in the pipe can be improved with a small refrigerant retention amount, the pipe heat transfer area of the pipe in the middle portion in the longitudinal direction is increased and the liquid film is thinned. be able to. For this reason, heat transfer performance improves.

Embodiment 1 FIG.
The present invention will be described below with reference to illustrated embodiments.
FIG. 1 is a perspective view showing a piping configuration of a heat exchanger (a heat source side heat exchanger or a use side heat exchanger) that is a main part of the refrigeration air-conditioning apparatus according to Embodiment 1 of the present invention, and FIG. 3 is an exploded perspective view of the heat exchanger, FIG. 3 is a perspective view showing the relationship between the pipe of the heat exchanger and the heat transfer fins, FIG. 4 is a schematic view showing an example of the pipe cross-sectional shape of the pipe of the heat exchanger, and FIG. FIG. 6 is a schematic diagram showing another modification of the pipe cross-sectional shape of the pipe of the heat exchanger, FIG. 6 is a schematic diagram showing another modification of the pipe cross-sectional shape of the pipe of the heat exchanger, and FIG. 7 uses the heat exchanger. It is the refrigerant circuit figure of the air conditioner which was.

  As shown in FIG. 7, the refrigerating and air-conditioning apparatus of the present embodiment includes a compressor 11, a four-way valve 12, a heat source side heat exchanger 13, decompression means 14a and 14b, a use side heat exchanger 15, and a gas extension that is a refrigerant pipe for gas. A pipe 16 and a liquid extension pipe 17 which is a liquid refrigerant pipe are provided, and these are coupled in a closed loop to constitute a refrigerant circuit. The outdoor unit X is provided with a compressor 11, a four-way valve 12, a heat source side heat exchanger 13, and a pressure reducing means 14 a, and the indoor unit Y is provided with a pressure reducing means 14 b and a use side heat exchanger 15. Although not shown in the figure, the heat source side heat exchanger 13 and the use side heat exchanger 15 are provided with a fan and a fan motor, and the compressor 11, the fan motor, and the pressure reducing means 14a and 14b are a control means and a communication line. Tied.

  The compressor 11 is a low-pressure container type compressor whose operating capacity can be variably adjusted. Here, a fully enclosed type in which a motor is housed in the container is used. The decompression devices 14a and 14b are both of variable opening type here, but the decompression device 14b is opened if the liquid extension pipe 17 is in a gas-liquid two-phase refrigerant state for both the cooling operation and the heating operation. It is also possible to adopt a fixed degree type.

  The heat source side heat exchanger 13 and the use side heat exchanger 15 have the same structure. That is, as shown in FIGS. 1 to 3, these heat exchangers are composed of a pipe part that forms the internal refrigerant flow path and a fin part 8 that serves as a heat transfer surface. The piping section includes a refrigerant introduction section pipe 1 (hereinafter referred to as “heat exchanger pipe A”), a longitudinal intermediate section pipe 2 (hereinafter referred to as “heat exchanger pipe B”), and the other end side. The refrigerant lead-out pipe 3 (hereinafter referred to as “heat exchanger pipe C”) and the branch header parts 4a and 4b that branch the heat exchanger pipe B into a plurality of lines to form parallel refrigerant flow paths. Yes.

  More specifically, the heat exchanger pipe A and the heat exchanger pipe C are configured as a staggered pipe, and the folded portion is formed of a U-shaped tube 5 as shown in FIG. The heat exchanger pipes A and C and pipes connected to both ends thereof (for example, extension pipes) are distinguished depending on whether or not the heat transfer fins 8 exist outside the pipes.

  Next, the refrigerant | coolant state in each heat exchanger piping AC when using the heat exchanger of FIG. 1 as a condenser is demonstrated. When the condenser is used, the high-pressure gas refrigerant flows in from one end of the heat exchanger pipe A, flows into the heat exchanger pipe B and the heat exchanger pipe C, and flows out as high-pressure liquid refrigerant from one end of the heat exchanger pipe C. To do. That is, in the heat exchanger pipe A, the high-pressure gas refrigerant flows in and condenses, the high-pressure gas refrigerant whose specific enthalpy is small, the high-pressure saturated gas refrigerant, or the high-pressure gas-liquid two-phase refrigerant with high quality (dryness). It becomes one of the spills. That is, the high-pressure gas refrigerant is dominant in the heat exchanger pipe A.

  In the heat exchanger pipe B, high-pressure gas refrigerant, high-pressure saturated gas refrigerant, or high-pressure gas-liquid two-phase refrigerant of high quality (dryness) that flows out of the heat exchanger pipe A flows in and condenses, and the specific enthalpy is It flows out as either a reduced high-pressure gas-liquid two-phase refrigerant, a high-pressure saturated liquid refrigerant, or a high-pressure liquid refrigerant. That is, in the heat exchanger pipe B, the high-pressure gas-liquid two-phase refrigerant is dominant.

  In the heat exchanger pipe C, either the high-pressure gas-liquid two-phase refrigerant, the high-pressure saturated liquid refrigerant, or the high-pressure liquid refrigerant that has flowed out of the heat exchanger pipe B flows in and is condensed, and the specific enthalpy is reduced. Liquid refrigerant flows out. That is, the high-pressure liquid refrigerant is dominant in the heat exchanger pipe C.

  1 to 3, the number of paths of the heat exchanger pipe A in the gas refrigerant flow area and the heat exchanger pipe C in the liquid refrigerant flow area is one, but it goes without saying that the paths may be branched into a plurality of paths.

  In addition, here, the pipe cross-sectional shape of the heat exchanger pipes A and C is circular, and the pipe cross-sectional shape of the heat exchanger pipe B is provided with a plurality of thin tubes 2a in the flat cross section as shown in FIG. As the tube cross-sectional shape of the heat exchanger tube B, an elliptic tube 2b as shown in FIG. 5 or a polygonal tube 2c with rounded corners as shown in FIG. 6 can be used. In any case, the pipe cross-sectional area of the heat exchanger pipe B is smaller than the pipe cross-sectional areas of the heat exchanger pipes A and C.

  The heat exchanger pipes A and C are formed in a zigzag shape with a cross-sectional shape as a circular pipe, and a U-shaped pipe 5 or a hairpin in which the circular pipe is formed in a U-shape is provided at the folded portion, that is, the end portions 6 and 7 shown in FIG. Used.

  Since the cross-sectional shape of the heat exchanger pipe B is a non-circular pipe, there is a possibility that the pipe shape may be crushed when the pipe is bent into a U shape like the circular pipe. In particular, when the pipe cross-sectional area is small, the possibility of crushing increases. Therefore, both ends of the heat exchanger pipe B can be easily connected to the header 4 of the cylindrical container as shown in FIG. However, in this structure, the pipe length per pass cannot be made longer than the heat exchanger stack width (length L in FIG. 1), and the refrigerant flow rate is reduced and the heat transfer performance is lowered as the number of passes is increased. There are disadvantages such as

  Next, the effect of making the cross-sectional shape of the heat exchanger pipes A and C connected to both ends of the heat exchanger pipe B circular will be described. The basic concept of heat transfer was organized with reference to “Compact Heat Exchanger” by Seshita, Fujii, and Nikkan Kogyo Shimbun P.83-P.104.

In the heat exchanger pipes A and C, as described above, the gas or liquid single-phase refrigerant is dominant. The Nusselt number Nu, which is a dimensionless number of heat transfer performance in a pipe when a single-phase refrigerant flows, can be expressed by the following Dittus-Boelter approximation.
Nu = 0.023 * Re0.8 * Pr0.4 (1)
Where Re is the Reynolds number
Pr is the Prandtl number. The Reynolds number Re in the equation can be expressed as follows.
Re = v * d / ν ……………………………………………………………………………………………………………………………… (2)
Where v is the flow velocity
d is the representative length
ν is a kinematic viscosity coefficient d is a value uniquely determined from the pipe diameter, and Pr and ν are physical property values of the refrigerant. From the above formulas (1) and (2), it can be seen that increasing the refrigerant flow rate is effective in increasing the pipe heat transfer coefficient of the gas or liquid single-phase refrigerant with the same pipe diameter and the same refrigerant.

  When a circular pipe is used for the heat exchanger piping shape, the end of the heat exchanger piping can be connected with a U-shaped tube or hairpin, so the length per pass can be increased, the number of passes can be reduced, and the refrigerant flow rate can be increased. it can. Therefore, it is preferable to adopt circular pipes for the heat exchanger pipes A and C in which the single-phase refrigerant is dominant.

  Table 1 below shows the results of comparison of the refrigerant physical properties (Prandtl number Pr, kinematic viscosity coefficient ν) at the same temperature of R407C and R410A, which are HFC refrigerants, and propane, which is an HC refrigerant. Table 1 shows physical property values of saturated gas at a temperature of 40 ° C.

  As is clear from Table 1, when compared with the same refrigerant flow rate and the same heat exchanger pipe diameter, propane is smaller in both Reynolds number and Prandtl number than R407C and R410A. As a result, Nusert obtained from the Dittus-Boelter equation The number is also small.

  In order to increase the Nusselt number, it is effective to increase the refrigerant flow rate. If the heat exchanger pipes A and C are configured with circular pipes that can connect the heat exchanger pipe ends with U-shaped tubes or hairpins, the length per pass can be increased and the number of passes can be reduced, so the refrigerant flow rate can be increased. .

  Increasing the pipe diameter at the same flow rate is also effective for increasing the Nusselt number. Generally, when the pipe diameter is increased, the refrigerant flow rate is reduced. However, since the density of the propane refrigerant is smaller than that of the R407C and R410A refrigerants, the flow speed per the same pipe diameter and the same refrigerant mass flow rate is increased. In other words, when the propane refrigerant is used, it can be said that the pipe diameter is easily increased as compared with the case where the R407C and R410A refrigerants are used. Furthermore, if the heat exchanger pipes A and C are configured with circular pipes that can connect the heat exchanger pipe ends with U-shaped tubes or hairpins, the length per pass can be increased and the number of passes can be reduced. Can be increased.

  When a combustible propane refrigerant is employed, a heat exchanger is often designed only for reducing the volume of the pipe in order to reduce the amount of refrigerant charged. However, although the heat exchanger pipe B in which the gas-liquid two-phase refrigerant is dominant for the reasons described above may be considered to reduce the volume in the pipe, the heat exchanger pipes A and C in which the single-phase refrigerant is dominant are It is necessary to design to increase the refrigerant flow rate by increasing the pipe diameter and increasing the length per pass.

  In order to ensure the same heat transfer performance at the time of propane refrigerant filling, the heat exchanger pipes A and C are used to secure the same heat transfer performance as when the HFC refrigerant is filled in the cooling air conditioner equipped with the heat exchanger for condensing composed only of the heat exchanger pipe B. It is necessary to make the pipe diameter larger than that of the HFC refrigerant and to make the refrigerant flow rate equal or higher. As described above, by adopting a circular pipe, the pipe diameter is increased, and the pipe length per path is increased to reduce the number of paths, thereby ensuring the number of Nusselts equivalent to HFC.

  Next, the effect of making the pipe cross-sectional shape of the heat exchanger pipe B non-circular and making the pipe cross-sectional area smaller than the pipe cross-sectional areas of the heat exchanger pipes A and C will be described. The basic concept of heat transfer was organized by referring to “Compact Heat Exchanger” by Seshita, Fujii, and Nikkan Kogyo Shimbun P.83-P.104.

  The heat transfer mode in the gas-liquid two-phase refrigerant flow area can be roughly divided into two. The first is a low quality region with a small proportion of the vapor phase, and heat transfer is governed by nucleate boiling on the heat transfer surface (evaporation accompanied by generation of bubbles from the heat transfer surface). The larger the heat transfer area, the more nucleate boiling can be generated.

  Second, there is a thin liquid film on the wall surface, and the high quality region is an annular flow in which steam flows through the center of the tube. Convective heat transfer of the liquid film flowing along the heat transfer surface and evaporation from the liquid film surface It is an area that becomes dominant. In this heat transfer mode, the thinner the liquid film, the better the heat transfer performance. And in the same pipe | tube internal volume, the same residence refrigerant | coolant amount, and the same refrigerant | coolant flow velocity, a liquid film becomes thin, so that the pipe | tube heat transfer area is large.

  As an example, comparison is made when the tube cross-sectional shape is a circle (FIG. 4), an ellipse (FIG. 5), or a quadrangle (FIG. 6). Ignore tube wall thickness. The perimeter of each shape when the tube cross-sectional area is 10 mm 2 was calculated, and the results are shown in Table 2 below.

  As is apparent from Table 2, when compared, the ellipse is 11.89 mm and the square is 12.65 mm with respect to the circle of 11.21 mm, and the circumference of the ellipse or square is longer than the circle.

  As the Reynolds number and Prandtl number described in the case of the single-phase refrigerant are larger, the heat transfer coefficient in the pipe is improved in the gas-liquid two-phase state.

  That is, in the gas-liquid two-phase refrigerant flow region, the pipe heat transfer coefficient is improved as the refrigerant flow rate and the pipe diameter are increased as in the case of the single-phase refrigerant, but the pipe heat transfer coefficient is improved as the pipe heat transfer area is further increased.

  Since propane has a larger kinematic viscosity coefficient than R407C and R410A, the flow velocity near the tube wall decreases and the liquid film thickness increases. In propane refrigerant, it is particularly effective to increase the heat transfer area in the pipe by using the non-circular heat exchanger pipe B. This is because even when R407C and R410A adopt a circular heat exchanger pipe B to ensure the desired performance, it is necessary to make the cross-sectional shape of the heat exchanger pipe B non-circular in order to apply the propane refrigerant. Means that.

  Next, when the gas or liquid single-phase refrigerant is circulated through the heat exchanger pipe B, the influence of the flow viscosity becomes larger than that of the pipe 1 because the pipe diameter is small. As a result, the pressure loss due to the refrigerant flow increases. In addition, since the number of passes is large, the refrigerant flow rate per pass is small and the refrigerant flow rate is reduced. As a result, the heat transfer performance of the condenser decreases. It is desirable to adopt a heat exchanger pipe having a circular cross section in the flow area of the liquid or gas single-phase refrigerant.

  This content applies to both the heat source side heat exchanger 13 and the use side heat exchanger 15. Moreover, the ratio of the basin of the gas single phase refrigerant is usually as small as less than 10%. Therefore, it is possible to employ a pipe configuration in which the gas single-phase refrigerant flow area and the gas-liquid two-phase refrigerant flow area use the pipe 2, and the liquid single-phase refrigerant flow area uses the pipe 1. In this case, the heat exchanger is downsized. Contributes to reducing the amount of refrigerant charged. Here, the length of the middle part in the longitudinal direction of the pipe forming the internal refrigerant flow path of the heat exchanger, that is, the gas-liquid two-phase refrigerant basin, is the total length of the basin pipe combined with the gas single-phase refrigerant basin and the liquid single-phase refrigerant basin on both sides The pipe length of the gas single-phase refrigerant basin through which the gas single-phase refrigerant flows when used as a condenser is 0% to 15% of the total length of the basin pipe, and is a liquid single-phase refrigerant. The pipe length of the liquid single-phase refrigerant basin through which the refrigerant flows is set to 5% or more and 40% or less of the entire length of the basin pipe. As a result, the heat exchanger can be miniaturized and the amount of charged refrigerant can be reduced.

  Propane and isobutane are heavier than air. Therefore, in both the heat source side heat exchanger 13 and the use side heat exchanger 15, the heat exchanger part of the liquid refrigerant flow region when the heat exchanger is used as a condenser is from the power line connection part of the electric component or the compressor. Also place it at a lower position (far position). Thereby, even if the spark of the electrical component occurs, the possibility of being in contact with the refrigerant and burning is reduced.

  Next, the operation of the refrigerant during the cooling operation of the refrigerating and air-conditioning apparatus of the present embodiment will be described based on FIG. 7 and with reference to FIGS. First, the high-pressure and high-temperature gas refrigerant discharged from the compressor 11 flows into the heat source side heat exchanger 13 via the four-way valve 12, where it is condensed by exchanging heat with ambient air and flows out as high-pressure liquid refrigerant. After that, after being decompressed by the decompression means 14a to become a low-pressure gas-liquid two-phase refrigerant, it flows into the use-side heat exchanger 15 via the liquid extension pipe 17 and the decompression means 14b, where heat is exchanged with ambient air. Evaporates and flows out as a low-pressure gas refrigerant. Thereafter, the gas reaches the suction port of the compressor 11 through the gas extension pipe 16 and the four-way valve 12.

  Since the pressure is reduced by the pressure reducing means 14a, the refrigerant in the liquid extension pipe 17 becomes a low-pressure gas-liquid two-phase refrigerant.

  Next, the operation of the refrigerant during the heating operation of the refrigerating and air-conditioning apparatus of the present embodiment will be described based on FIG. 7 and with reference to FIGS. First, the high-pressure and high-temperature gas refrigerant discharged from the compressor 11 flows into the utilization side heat exchanger 15 via the gas extension pipe 16 via the four-way valve 12, where it is condensed by exchanging heat with ambient air. It flows out as a liquid refrigerant. Thereafter, the pressure is reduced by the decompression means 14b to become a low-pressure gas-liquid two-phase refrigerant, and then flows into the heat source side heat exchanger 13 through the liquid extension pipe 17 and the decompression means 14a, where heat is exchanged with ambient air. Evaporates and flows out as a low-pressure gas refrigerant. Thereafter, the intake port of the compressor 11 is reached via the four-way valve 12.

  Since the pressure is reduced by the pressure reducing means 14b, the refrigerant in the liquid extension pipe 17 becomes a low-pressure gas-liquid two-phase refrigerant.

  In the cooling operation and the heating operation, the refrigerant state in the liquid extension pipe 17 has been described as low pressure. However, since the pressure reducing devices 14a and 14b are provided at both ends, the medium pressure is accurate.

  In this way, by providing two decompression means and changing the main decompression means for cooling and heating, the refrigerant in the liquid extension pipe 17 can be made into a gas-liquid two-phase refrigerant at all times, and the amount of retained refrigerant can be reduced.

  By the way, the discharge temperature of the HC refrigerant is lower than that of the HFC refrigerant or the HCFC refrigerant. As a result, when the capacity reduction during the heating operation or the compressor discharge superheat degree decreases, the amount of refrigerant dissolved in the refrigeration oil in the compressor increases and the oil concentration decreases. As a result, the oil viscosity required for the shaft sliding portion of the compressor cannot be ensured, and the compressor may break down. Next, means for solving these problems will be sequentially described.

  As described above, propane and isobutane, which are HC refrigerants, have characteristics that the theoretical COP is better and the discharge temperature is lower than R410A and R407C refrigerants that are HFC refrigerants. Table 3 below shows physical property values of R410A and R407C as HFC refrigerants, and propane and isobutane as HC refrigerants. The refrigerant physical properties in Table 3 are the values under the conditions assuming that the condensation temperature of the refrigeration cycle is 45 ° C., the evaporation temperature is 5 ° C., the compressor inlet superheat is 5 ° C., the condenser outlet supercool is 5 ° C., and the compression process is isentropic. The theoretical discharge temperature Td, power ΔIcomp, and evaporator enthalpy difference ΔIe are obtained using the refrigerant property calculation software Refprop Ver.

  As is clear from Table 3, propane and isobutane, which are HC refrigerants, have lower discharge temperatures than the R410A and R407C refrigerants.

Embodiment 2. FIG.
FIG. 8 is a refrigerant circuit diagram showing a refrigerating and air-conditioning apparatus according to Embodiment 2 of the present invention to which the heat exchanger of FIG. 1 described above is applied. In the figure, the same parts as those of Embodiment 1 are shown. The same reference numerals are given. In the description, reference is made to FIGS. 1 to 3 described above.

  The refrigerating and air-conditioning apparatus of the present embodiment is provided with a pressure reducing means 18 between the discharge port of the compressor 11 and the four-way valve 12 and between the compressor 11 suction port and the four-way valve 12 to increase the compressor discharge temperature. It is a thing. Other configurations are the same as those of the first embodiment.

  When a part of the refrigerant discharged from the compressor 11 during the cooling and heating operation is returned to the suction side of the compressor 11 through the decompression means 18 as in the refrigerating and air-conditioning apparatus of this embodiment, the suction temperature of the compressor 11 is restored. Will increase. As a result, the discharge temperature of the compressor 11 can be increased. Therefore, it becomes possible to increase the heating capacity at the time of heating or to ensure the degree of discharge superheat during low compression ratio operation.

Embodiment 3 FIG.
FIG. 9 is a refrigerant circuit diagram showing a refrigerating and air-conditioning apparatus according to Embodiment 3 of the present invention to which the heat exchanger shown in FIG. 1 is applied. In the figure, the same parts as those in Embodiment 1 are shown. The same reference numerals are given. In this case as well, the description will be made with reference to FIGS. 1 to 3 described above.

  The refrigerating and air-conditioning apparatus of the present embodiment generates heat between the refrigerant flowing between the heat source side heat exchanger 13 and the decompression means 14a and the refrigerant flowing between the suction port of the compressor 11 and the four-way valve 12. Means 19A for replacement is provided. Other configurations are the same as those of the first embodiment.

  In the refrigerating and air-conditioning apparatus of the present embodiment, the intake refrigerant of the compressor 11 is heated by exchanging heat with the high-pressure liquid refrigerant via the heat exchanging means 19A, so that the intake refrigerant temperature of the compressor 11 is increased. Can do. This circuit is effective in cooling operation.

Embodiment 4 FIG.
FIG. 10 is a refrigerant circuit diagram showing a refrigerating and air-conditioning apparatus according to Embodiment 4 of the present invention to which the heat exchanger shown in FIG. 1 is applied. In the figure, the same parts as those of Embodiment 1 are shown. The same reference numerals are given. In this case as well, the description will be made with reference to FIGS. 1 to 3 described above.

  The refrigerating and air-conditioning apparatus of the present embodiment generates heat between the refrigerant that circulates between the use-side heat exchanger 15 and the decompression means 14a and the refrigerant that circulates between the suction port of the compressor 11 and the four-way valve 12. An exchange means 19B is provided. Other configurations are the same as those of the first embodiment.

  In the refrigerating and air-conditioning apparatus of the present embodiment, the intake refrigerant of the compressor 11 is cooled by exchanging heat with the low-pressure gas-liquid two-phase refrigerant, and the intake refrigerant temperature of the compressor 11 can be lowered. This circuit is effective in heating operation.

Embodiment 5 FIG.
FIG. 11 is a refrigerant circuit diagram showing a refrigerating and air-conditioning apparatus according to Embodiment 5 of the present invention to which the heat exchanger shown in FIG. 1 is applied. In the figure, the refrigerant circuit shown in Embodiments 1 and 2 is used. The same parts as those in FIG. In this case as well, the description will be made with reference to FIGS. 1 to 3 described above.

  The refrigerating and air-conditioning apparatus of this embodiment partially separates the refrigerant flowing between the heat source side heat exchanger 13 and the pressure reducing means 14a and the refrigerant flowing between the heat source side heat exchanger 13 and the pressure reducing means 14a and further reduces the pressure. A means 20A for exchanging heat with the refrigerant obtained by reducing the pressure by means 21A is provided, and a pipe 22A for returning the separated refrigerant between the suction port of the compressor 11 and the four-way valve 12 is provided. Other configurations are the same as those of the first and second embodiments.

  In the refrigerating and air-conditioning apparatus of the present embodiment, during the cooling operation, the separated high-pressure liquid refrigerant is decompressed by the decompression means 21A to become a low-pressure gas-liquid two-phase refrigerant, and is evaporated by exchanging heat with the high-pressure liquid refrigerant by the heat exchange means 20A. Then, it flows out as a low-pressure superheated gas refrigerant and merges with the compressor suction refrigerant. In this way, the superheated gas is joined to the compressor suction refrigerant, thereby increasing the suction temperature and, as a result, increasing the compressor discharge temperature. This circuit is effective in cooling operation.

Embodiment 6 FIG.
FIG. 12 is a refrigerant circuit diagram showing a refrigerating and air-conditioning apparatus according to Embodiment 6 of the present invention to which the heat exchanger of FIG. 1 described above is applied. In the drawing, those of Embodiment 1 and Embodiment 2 described above are shown. The same parts as those in FIG. In this case as well, the description will be made with reference to FIGS. 1 to 3 described above.

  The refrigerating and air-conditioning apparatus of this embodiment partially separates the refrigerant flowing between the use-side heat exchanger 15 and the decompression means 14a and the refrigerant flowing between the use-side heat exchanger 15 and the decompression means 14a and further reduces the pressure. A means 20B for exchanging heat with the refrigerant obtained by reducing the pressure by means 21B is provided, and a pipe 22B for returning the separated refrigerant between the suction port of the compressor 11 and the four-way valve 12 is provided. Other configurations are the same as those of the first and second embodiments.

  In the refrigerating and air-conditioning apparatus of the present embodiment, during the heating operation, the separated low-pressure gas-liquid two-phase refrigerant is further depressurized by the decompression means 21B to become a low-pressure gas refrigerant, and the heat exchange means 20B and the low-pressure gas-liquid two-phase refrigerant and heat. It is exchanged and cooled, and it flows out and joins the compressor suction refrigerant. The suction temperature is lowered by joining the low-pressure gas to the compressor suction refrigerant, and as a result, the compressor discharge temperature is lowered. This circuit is effective in heating operation.

Embodiment 7 FIG.
FIG. 13 is a refrigerant circuit diagram showing a refrigerating and air-conditioning apparatus according to Embodiment 7 of the present invention to which the heat exchanger shown in FIG. 1 is applied. In the figure, the same parts as those in Embodiment 1 are shown. The same reference numerals are given. In this case as well, the description will be made with reference to FIGS. 1 to 3 described above.

  In the refrigerating and air-conditioning apparatus of this embodiment, when propane and isobutane of HC refrigerants circulate in the circular pipe, the pressure loss is larger than that of the HFC refrigerant as described above. The pressure loss of the gas refrigerant flowing through the circular pipe is proportional to the power of 1 to the second power. Table 4 below shows the speed ratio when the superheat degree of each refrigerant is 5 ° C and the temperature of each gas refrigerant is 10 ° C.

  One technique for reducing pressure loss is an injection circuit. As shown in FIG. 13, the compressor 24 according to this embodiment includes an injection port. Further, a gas-liquid separation means 25 for separating the refrigerant into a gas and liquid is provided between the heat source side heat exchanger 13 and the pressure reduction means 14a, and a pressure reduction means for reducing the pressure of the gas refrigerant separated by the gas-liquid separation means 25. 26 is provided, and the medium-pressure saturated gas refrigerant decompressed by the decompression means 26 is configured to circulate to the injection port of the compressor 24 via the injection bypass pipe 23. Other configurations are the same as those of the first and second embodiments.

  In the refrigerating and air-conditioning apparatus of the present embodiment, the flow rate of the refrigerant flowing through the use side heat exchanger 15 can be reduced during the cooling operation, so that the pressure loss can be reduced. On the other hand, the refrigerant specific enthalpy at the inlet of the use side heat exchanger 15 is reduced and the capacity is hardly changed.

  In addition, it is also effective to reduce the amount of refrigerant by adopting a low-pressure container compressor that lowers the internal pressure of the compressor.

It is a perspective view which shows the piping structure of the heat exchanger which is the principal part of the refrigerating air conditioning apparatus which concerns on Embodiment 1 of this invention. It is a disassembled perspective view of the heat exchanger which is the principal part of the refrigeration air conditioning apparatus which concerns on Embodiment 1 of this invention. It is a perspective view which shows the relationship between the piping of the heat exchanger which is the principal part of the refrigerating air conditioner which concerns on Embodiment 1 of this invention, and a heat-transfer fin. It is a schematic diagram which shows an example of the pipe cross-sectional shape of piping of the heat exchanger which is the principal part of the refrigerating air conditioning apparatus which concerns on Embodiment 1 of this invention. It is a schematic diagram which shows the modification of the pipe cross-sectional shape of piping of the heat exchanger which is the principal part of the refrigerating air conditioning apparatus which concerns on Embodiment 1 of this invention. It is a schematic diagram which shows the other modification of the pipe cross-sectional shape of piping of the heat exchanger which is the principal part of the refrigerating air conditioning apparatus which concerns on Embodiment 1 of this invention. It is a refrigerant circuit diagram of the air conditioner using the heat exchanger of the refrigeration air conditioner according to Embodiment 1 of the present invention. It is a refrigerant circuit diagram of the refrigerating and air-conditioning apparatus according to Embodiment 2 of the present invention. It is a refrigerant circuit diagram of the refrigerating and air-conditioning apparatus according to Embodiment 3 of the present invention. It is a refrigerant circuit diagram of the refrigerating and air-conditioning apparatus according to Embodiment 4 of the present invention. It is a refrigerant circuit diagram of the refrigerating and air-conditioning apparatus according to Embodiment 5 of the present invention. It is a refrigerant circuit diagram of the refrigerating and air-conditioning apparatus according to Embodiment 6 of the present invention. It is a refrigerant circuit diagram of the refrigerating and air-conditioning apparatus according to Embodiment 7 of the present invention.

Explanation of symbols

  1 Longitudinal end pipe (heat exchanger pipe A), 2 Longitudinal intermediate pipe (heat exchanger pipe B), 2a Narrow pipe, 2b Elliptic pipe, 2c Polygon pipe, 3 Longitudinal end pipe ( Heat exchanger piping C), 4, 4a, 4b header, 5 U-shaped tube, 11, 24 compressor, 12 four-way valve, 13 heat source side heat exchanger, 14a pressure reducing means, 15 use side heat exchanger, X outdoor unit , Y indoor unit, 16 gas extension pipe (gas refrigerant pipe), 17 liquid extension pipe (liquid refrigerant pipe), 18, 21A, 21B, 26 pressure reducing means, 19A, 19B, 20A, 20B means for heat exchange, 22A , 22B Piping, 25 Means for separating the gas-liquid refrigerant.

Claims (15)

Compressor, four-way valve, heat source side heat exchanger, pressure reducing means, usage side heat exchanger, refrigerant circuit for liquid and gas refrigerant pipe for connecting outdoor unit and indoor unit, and closed loop, and control means In a refrigerating and air-conditioning apparatus that uses a combustible hydrocarbon refrigerant as a refrigerant and supplies cold / hot heat from the use side heat exchanger,
The cross-sectional area in the pipe of the pipe forming the internal refrigerant flow path of the heat source side heat exchanger or the use side heat exchanger is such that the cross-sectional area in the pipe at the longitudinal end is larger than the cross-sectional area in the pipe at the middle in the longitudinal direction. In addition, the value obtained by dividing the circumferential length of the pipe in the pipe cross section by the area of the pipe cross section is set so that the middle portion in the longitudinal direction of the pipe is larger than both longitudinal ends of the pipe. Refrigeration air conditioner characterized by. The longitudinal end portion of the pipe forming the internal refrigerant flow path of the heat exchanger having a large cross-sectional area in the pipe is a side on which the liquid refrigerant flows when the heat exchanger is used as a condenser. 1 Symbol placement of the refrigerating and air-conditioning apparatus. The in-pipe cross-sectional shape of the intermediate portion in the longitudinal direction of the pipe forming the internal refrigerant flow path of the heat exchanger is an ellipse, a polygon, or a shape having a plurality of thin tubes in an oval cross section. The refrigeration air conditioner according to claim 1 or 2 . The refrigerating and air-conditioning apparatus according to any one of claims 1 to 3 , wherein an in-tube cross-sectional shape of a longitudinal end portion of a pipe forming an internal refrigerant flow path of the heat exchanger is circular. Longitudinal end of the pipe forming an internal refrigerant flow path of the heat exchanger consists of two straight pipe end from pipe connected by a circular tube of U-shape, the longitudinal direction intermediate portion of the pipe has a header at both ends The refrigerating and air-conditioning apparatus according to any one of claims 1 to 4 , wherein the refrigerating and air-conditioning apparatus is formed in parallel flow paths. The length of the intermediate portion in the longitudinal direction of the pipe forming the internal refrigerant flow path of the heat exchanger is not less than 60% and not more than 90% of the total length of the pipe, and when used as a condenser, on the side where the gas single-phase refrigerant circulates The length of the pipe is 0% to 15% of the total length of the pipe, and the length of the pipe on the side through which the liquid single-phase refrigerant flows is 5% to 40% of the total length of the pipe. The refrigerating and air-conditioning apparatus according to claim 4 . The piping having a pressure reducing means is connected between the discharge port of the compressor and the four-way valve of the refrigerant circuit and between the suction port of the compressor and the four-way valve. The refrigerating and air-conditioning apparatus according to any one of claims 1 to 6 . Means for exchanging heat between the refrigerant flowing between the heat source side heat exchanger of the refrigerant circuit and the pressure reducing means and the refrigerant flowing between the suction port of the compressor and the four-way valve; The refrigerating and air-conditioning apparatus according to any one of claims 1 to 6 , wherein the refrigerating and air-conditioning apparatus is provided. Means for exchanging heat between the refrigerant flowing between the use side heat exchanger of the refrigerant circuit and the pressure reducing means and the refrigerant flowing between the suction port of the compressor and the four-way valve; The refrigerating and air-conditioning apparatus according to any one of claims 1 to 6 , wherein the refrigerating and air-conditioning apparatus is provided. Refrigerant obtained by partially separating and depressurizing the refrigerant flowing between the heat source side heat exchanger and the pressure reducing means of the refrigerant circuit and the refrigerant flowing between the heat source side heat exchanger and the pressure reducing means. either provided with means for heat exchange, of claims 1 to 6, characterized in that it comprises a pipe for returning the refrigerant to the separation between the inlet and the four-way valve of the compressor with the The refrigeration air conditioner described in 1. Refrigerant obtained by partially separating and depressurizing the refrigerant flowing between the use side heat exchanger and the pressure reducing means of the refrigerant circuit and the refrigerant flowing between the use side heat exchanger and the pressure reducing means. either provided with means for heat exchange, of claims 1 to 6, characterized in that it comprises a pipe for returning the refrigerant to the separation between the inlet and the four-way valve of the compressor with the The refrigeration air conditioner described in 1. The compressor of the refrigerant circuit has an injection port, and has means for separating gas-liquid refrigerant between the heat source side heat exchanger and the pressure reducing means, and means for separating the gas-liquid refrigerant. The refrigerating and air-conditioning apparatus according to any one of claims 1 to 6 , further comprising means for reducing the pressure of the separated gas refrigerant and flowing it to the injection port of the compressor. The refrigerating and air-conditioning apparatus according to any one of claims 1 to 12 , wherein a portion of the heat exchanger through which the liquid single-phase refrigerant flows is disposed at a position far from electrical components and a power line connection portion. The refrigerating and air-conditioning apparatus according to claim 13 , wherein a portion of the heat source side heat exchanger through which the liquid single-phase refrigerant circulates is disposed at a position lower than a power line connecting portion of the compressor and a heat source side electric infrastructure. . The refrigerating and air-conditioning apparatus according to claim 13, wherein a portion of the use side heat exchanger in which the liquid single-phase refrigerant flows is disposed at a position lower than the use side electric infrastructure.

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