JP2007155192A - Refrigerating cycle device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a refrigerating cycle device improving a heat exchange amount, and preventing easy frost formation even when a mixed coolant of dimethyl ether and carbon dioxide is used. <P>SOLUTION: The refrigerating cycle device is provided with a compressor, a condenser, an expansion device, and an evaporator. The mixed coolant of dimethyl ether and carbon dioxide is used as a coolant, and a pressure loss increasing means is provided for increasing a pressure loss in a coolant passage of the evaporator. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a refrigeration cycle apparatus, and more particularly to a refrigeration cycle apparatus suitable for using a mixed refrigerant composed of dimethyl ether and carbon dioxide.

Conventionally, an R22 refrigerant, which is an HCFC refrigerant, has been generally used as a refrigerant in a refrigeration cycle apparatus such as a heat pump type hot water heater, but in recent years, a CO ₂ (carbon dioxide) refrigerant, which is a natural refrigerant, has been used.

Since this CO ₂ is at a high pressure, it is necessary to take measures such as strengthening the pressure resistance to ensure safety against the high pressure. A mixed refrigerant of dimethyl ether (referred to as DME) and CO ₂ , which is expected to realize a highly efficient refrigeration cycle apparatus by lowering the working pressure, is a non-azeotropic mixed refrigerant, and as the dryness increases under the same pressure, It has the characteristic that the evaporation temperature increases.

Using such a mixed refrigerant of DME and CO ₂ , as shown in FIG. 12, in the refrigeration cycle apparatus 61 including the compressor 62, the condenser 63, the expansion device 64, and one evaporator 65 shown in FIG. The Mollier diagram (pressure-enthalpy diagram) shown in FIG. 14 is obtained.

  Each point (71) to (74) shown in this Mollier diagram corresponds to each point (71) to (74) of the refrigeration cycle apparatus shown in FIG. 12, and represents the pressure-enthalpy state at each position. .

  As shown in FIG. 12 (indicated by an arrow in the figure) and FIG. 14, after being discharged from the compressor 62 (point (71) in the figure) and condensed in the condenser 63 (point (72) in the figure), expansion is performed. The pressure is reduced by the device 64 (the point (73) in the figure, and it flows into the evaporator 65 and evaporates (the point (74) in the figure).

  As shown in FIG. 14, if the pressure is close to the same pressure in the evaporator 65, many isotherms will be crossed during the evaporation process. For this reason, when the pressure loss in the pipe (refrigerant side) of the evaporator 65 is small, the temperature distribution in the evaporator 65 becomes large, and the temperature difference with air becomes small or reverses on the refrigerant outlet side of the evaporator 65. This causes a problem that heat exchange is difficult to be performed. Further, under a low temperature such as in winter, if there is a temperature distribution (temperature difference) in the evaporator 65, a problem of frost formation near the refrigerant inlet of the evaporator 65 occurs.

As heat pump water heater using CO ₂ refrigerant JP 2001-201177 JP (e.g., see Patent Document 1) heat pump water heater has been proposed.
JP 2001-201177 A

  The present invention has been made in consideration of the above-described circumstances, and an object of the present invention is to provide a refrigeration cycle apparatus in which heat exchange is improved and frost formation is difficult even when a mixed refrigerant of dimethyl ether and carbon dioxide is used. To do.

  In order to achieve the above-described object, the refrigeration cycle apparatus according to the present invention uses a mixed refrigerant of dimethyl ether and carbon dioxide as a refrigerant in a refrigeration cycle apparatus including a compressor, a radiator, an expansion device, and an evaporator, Pressure loss increasing means for increasing pressure loss is provided in the refrigerant flow path of the evaporator.

  According to the refrigeration cycle apparatus according to the present invention, even if a mixed refrigerant of dimethyl ether and carbon dioxide is used, it is possible to provide a refrigeration cycle apparatus that improves the amount of heat exchange and hardly forms frost.

  Hereinafter, a refrigeration cycle apparatus according to a first embodiment of the present invention will be described with reference to the accompanying drawings.

  FIG. 1 is a configuration diagram of a refrigeration cycle apparatus according to the first embodiment of the present invention.

As shown in FIG. 1, the refrigeration cycle apparatus 1 of the first embodiment is provided in a compressor 2, a condenser 3 as a radiator, an expansion device 4, an evaporator 5, and a refrigerant flow path of the evaporator 5. A pressure loss increasing means for increasing the pressure loss, for example, a capillary tube 6 is provided, and a mixed refrigerant of DME and CO ₂ is used as a refrigerant.

  As shown in FIG. 2, the evaporator 5 allows a plurality of plate-like fins 5 a arranged side by side with a predetermined fin pitch to pass through a U-shaped heat transfer tube 5 b that forms a refrigerant flow path. It is a finned tube heat exchanger in which the open ends of the letter-shaped heat transfer tube 5b are connected by a return bend 16, and a capillary tube 6 (6a, 6b) that increases pressure loss is provided in the middle of the piping of the evaporator 5 to evaporate The vessel 5 is divided into, for example, three regions, and pressure differences are given to the respective evaporator portions 5A, 5B, 5C.

  FIG. 3 is a Mollier diagram for explaining the operation of the refrigeration cycle apparatus according to the first embodiment, and the points (11) to (16) shown in FIG. 3 indicate the refrigeration cycle apparatus shown in FIG. Corresponding to the points (11) to (16), and the pressure-enthalpy state at each position.

  As shown in FIGS. 1 and 3, according to the refrigeration cycle apparatus of the first embodiment having the above-described configuration, the high-temperature and high-pressure refrigerant discharged from the compressor 2 is Vapor has the highest pressure and enthalpy (point (11) in the figure), and after being condensed by the condenser 3 (point (12) in the figure), it is depressurized by the expansion device 4 (point (13) in the figure). It flows into the evaporator part 5A and evaporates and is depressurized by the capillary tube 6a (point (14) in the figure), flows into the evaporator part 5B and evaporates, and is further depressurized by the capillary tube 6b (point (15) in the figure). It flows into the evaporator part 6C and evaporates.

Generally, the mixed refrigerant of CO ₂ and DME, which is a non-azeotropic refrigerant, has a problem that the temperature distribution in the evaporator becomes large. However, as in this embodiment, the pressure loss increasing means is provided in the refrigerant flow path of the evaporator 5. As shown in FIG. 3, the state of the refrigerant in the evaporator 5 becomes a state diagram as shown in FIG. Compared to evaporating the refrigerant with an evaporator having no conventional pressure loss increasing means shown in FIGS. 12 and 14, the state of the refrigerant in the evaporating process is changed so as to follow the isotherm. You can get closer.

  Therefore, even if the non-azeotropic refrigerant mixture is used, it can be evaporated substantially along the isotherm, the rise in the evaporation temperature can be suppressed, the temperature difference with the air that is the heat exchange partner can be increased, and the heat exchange amount In addition, it is possible to prevent local chilling and prevent frost formation.

  In addition, as shown in FIG. 2, the flow of the refrigerant in each of the evaporator portions 5A, 5B, and 5C may be counterflow with the leeward heat transfer tube 5b1 as an inlet and the leeward heat transfer tube 5b2 as an outlet. preferable. That is, the temperature of the air in the evaporator 5 decreases from the windward to the leeward due to heat exchange. On the other hand, as shown in FIG. 3, the temperature of the refrigerant rises in each of the evaporator portions 5A, 5B, and 5C as the dryness on the refrigerant side increases. Therefore, by using the leeward heat transfer tube 5b1 as the inlet and the leeward heat transfer tube 5b1 as the outlet and performing heat exchange according to the characteristics of the refrigerant, a large temperature difference with the air that is the heat exchange partner can be obtained, and the heat exchange amount Can be improved.

  As the pressure loss increasing means, in addition to the capillary tube, a small diameter tube, an expansion valve, and the like are suitable. If an expansion valve is used, the pressure can be appropriately controlled according to the use conditions. In addition, the evaporator is not physically divided as in the first embodiment, but an example in which pressure loss increasing means is provided in the middle of the pipe and substantially divided is described. However, the evaporator is physically divided. May be.

  As described above, according to the refrigeration cycle apparatus of the first embodiment, even if a mixed refrigerant of dimethyl ether and carbon dioxide is used, a heat exchange amount is improved and a refrigeration cycle apparatus that hardly forms frost is realized.

  If the number of pressure loss means (the number of divisions of the evaporator) is increased, the temperature distribution in the evaporator can be made more uniform along the isotherm as shown in FIG.

  Next, the refrigeration cycle apparatus according to the second embodiment will be described.

  In the second embodiment, the diameter of the return bend connecting the open ends of the U-shaped heat transfer tubes is different from that of the first embodiment in which two capillary tubes are provided in the refrigerant flow path of the evaporator. Is smaller than the tube diameter of the U-shaped heat transfer tube.

  For example, as shown in FIG. 5, the evaporator 25 used in the refrigeration cycle apparatus of the second embodiment forms all return bends 26 connecting the open ends of the U-shaped heat transfer tubes 5b with capillary tubes. Thereby, since a pressure can be lowered | hung for every U-shaped heat exchanger tube, the temperature distribution in an evaporator can be made smaller. The return bend 26 is not limited to a capillary tube, and may be any one having a diameter smaller than the tube diameter of the U-shaped heat transfer tube 5b.

  Since the other configuration is not different from the evaporator shown in FIG.

  The refrigeration cycle apparatus according to the third embodiment will be described.

  In the third embodiment, all the return bends are connected by a short capillary tube in the second embodiment, but a long capillary tube is provided in part.

  For example, as shown in FIG. 7, the evaporator 35 used in the refrigeration cycle apparatus of the third embodiment includes an evaporator portion 5A and an evaporator portion 5B that are long capillary tubes 6a, and an evaporator portion 5B and an evaporator portion 5C. Are connected by a long capillary tube 6b, and all the U-shaped heat transfer tubes 5b of the evaporator 5 are connected by a capillary tube 36 forming a return bend. As a result, the state diagram as shown in FIG. 6 can be obtained, and the ideal state diagram as shown in FIG. 4 can be obtained.

  Moreover, it demonstrates about the refrigerating-cycle apparatus which concerns on 4th Embodiment.

  The fourth embodiment uses an inner spacer insertion tube, whereas the first embodiment uses a capillary tube as the pressure loss increasing means.

  For example, as shown in FIG. 8, the inner spacer insertion tube 46 as the pressure loss increasing means in the refrigeration cycle apparatus of the fourth embodiment is formed by inserting an inner spacer (rod-like member) 46b into the inner surface grooved heat transfer tube 46a. Is done. Thus, by narrowing the flow path of the heat transfer tube 46a by inserting the inner spacer 46b, the refrigerant speed can be increased and the pressure loss can be increased without reducing the surface area outside the tube in contact with the air side. Is also improved by increasing the flow velocity. FIG. 9 is a state diagram of the fourth embodiment. By increasing the pressure loss in the heat transfer tube, the ideal pressure change in FIG. 4 can be made closer.

  As shown in FIGS. 10A to 10C, a plurality of inner spacers 46b having different cross-sectional areas (diameters) are prepared (D1 <D2 <D3), and the inner spacers 46b are cut according to the position of the heat transfer tube in the evaporator. By using the inner spacers 46b having different areas, the pressure loss can be optimized.

  Moreover, it demonstrates about the refrigerating-cycle apparatus which concerns on 5th Embodiment.

  In the fifth embodiment, as the pressure loss increasing means, the number of refrigerant flow paths of the evaporator is decreased from the refrigerant inlet side to the outlet side.

  For example, as shown in FIG. 11, the evaporator 50 allows a plurality of plate-like fins 50a arranged side by side with a predetermined fin pitch to pass through U-shaped heat transfer tubes 50b that form a refrigerant flow path. A fin-tube heat exchanger in which the open ends of the U-shaped heat transfer tube 50b are connected by a return bend 51, and a refrigerant flow path on the refrigerant inlet side of the evaporator 50 (the refrigerant flow path on the leeward side in FIG. 11). The number is 2, and the number of refrigerant flow paths is reduced to 1 on the refrigerant outlet side (the upwind refrigerant flow path in FIG. 11).

  Thus, by reducing the refrigerant flow path number from the refrigerant inlet side to the outlet side, that is, by reducing the refrigerant flow path number along the refrigerant flow direction, the flow channel cross-sectional area with respect to the refrigerant flow rate is reduced, The pressure loss can be increased, and the same effect as in the first to fourth embodiments can be obtained. Further, the number of refrigerant flow paths can be easily adjusted by simply changing the connection between the open ends of the U-shaped heat transfer tubes 50b forming the refrigerant flow paths.

  In each of the above embodiments, the high-pressure side refrigerant discharged from the compressor has been described as being condensed by a condenser as a radiator, but the present invention is such that the high-pressure side refrigerant is in a condensed state. Not limited to this, the supercritical state at a higher pressure, that is, the state of the refrigerant discharged from the compressor may be equal to or higher than the pressure and temperature at the intersection of the saturated liquid line and the saturated vapor line on the Mollier diagram. .

The block diagram of the refrigerating-cycle apparatus which concerns on 1st Embodiment of this invention. The side view of the evaporator used for the refrigerating cycle device concerning a 1st embodiment of the present invention. The pressure-enthalpy diagram of the refrigerating cycle device concerning a 1st embodiment of the present invention. The ideal pressure-enthalpy diagram of the refrigerating cycle device concerning a 1st embodiment of the present invention. The side view of the evaporator used for the refrigerating cycle device concerning a 2nd embodiment of the present invention. The pressure-enthalpy diagram of the refrigerating cycle device concerning a 2nd embodiment of the present invention. The side view of the evaporator used for the refrigerating cycle device concerning a 3rd embodiment of the present invention. The longitudinal cross-sectional view of the inner spacer insertion pipe | tube of the evaporator used for the refrigerating-cycle apparatus which concerns on 4th Embodiment of this invention. The pressure-enthalpy diagram of the refrigerating cycle device concerning a 4th embodiment of the present invention. (A)-(c) is a longitudinal cross-sectional view of other embodiment of the inner-spacer insertion pipe used for the refrigerating-cycle apparatus of this invention. Explanatory drawing of the refrigerant | coolant flow path path | pass number of the evaporator of the refrigerating-cycle apparatus which concerns on 5th Embodiment of this invention. The block diagram of the conventional refrigeration cycle apparatus. The perspective view of the evaporator used for the conventional refrigeration cycle apparatus. The pressure-enthalpy diagram of the conventional refrigeration cycle apparatus.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Refrigeration cycle apparatus, 2 ... Compressor, 3 ... Condenser, 4 ... Expansion apparatus, 5 (5A, 5B, 5C) ... Evaporator, 6 (6a, 6b) ... Capillary tube.

Claims (7)

In a refrigeration cycle apparatus equipped with a compressor, a radiator, an expansion device, and an evaporator,
While using a mixed refrigerant of dimethyl ether and carbon dioxide as the refrigerant,
A refrigeration cycle apparatus comprising pressure loss increasing means for increasing pressure loss in a refrigerant flow path of the evaporator. The refrigeration cycle apparatus according to claim 1, wherein the pressure loss increasing means is a throttle means. The evaporator is a fin tube heat exchanger in which a plurality of plate-like fins arranged side by side with a predetermined fin pitch are penetrated by a heat transfer tube that forms a refrigerant flow path,
The heat transfer tubes are provided in a plurality of rows in the air main flow direction, and the refrigerant inlets of the respective evaporator parts divided by the throttle means are provided on the leeward side,
The refrigeration cycle apparatus according to claim 2, wherein a refrigerant outlet is provided on the windward side. The evaporator has a plurality of plate-like fins arranged side by side with a predetermined fin pitch, and
A U-shaped heat transfer tube provided through the plate fin;
A return bend connecting the open ends of the U-shaped heat transfer tubes;
The refrigeration cycle apparatus according to claim 2, wherein the throttle means is formed by making the tube diameter of the return bend smaller than the tube diameter of the U-shaped heat transfer tube. 2. The refrigeration cycle apparatus according to claim 1, wherein the pressure loss increasing means is an inner spacer that is provided in a refrigerant flow path of the evaporator and reduces a cross-sectional area of the refrigerant flow path. The refrigeration cycle apparatus according to claim 5, wherein a plurality of types of inner spacers having different cross-sectional areas are used. 2. The refrigeration cycle apparatus according to claim 1, wherein the pressure loss increasing unit decreases the number of refrigerant flow paths of the evaporator from the refrigerant inlet side to the outlet side.

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