EP2578966A1

EP2578966A1 - Refrigeration device and cooling and heating device

Info

Publication number: EP2578966A1
Application number: EP20110786271
Authority: EP
Inventors: Kazuhiko Marumoto; Akira Fujitaka; Yoshikazu Kawabe; Shoichi Yokoyama
Original assignee: Panasonic Corp
Current assignee: Panasonic Corp
Priority date: 2010-05-27
Filing date: 2011-04-22
Publication date: 2013-04-10
Anticipated expiration: 2031-04-22
Also published as: WO2011148567A1; BR112012029878A2; EP2578966B1; EP2578966A4; CN102918338A; JP2011247482A; KR20130088020A

Abstract

When an indoor heat exchanger serves as an evaporator, the indoor heat exchanger is made up of an inlet region, an intermediate region and an outlet region along a flow of refrigerant. A mass speed per unit capacity of the refrigerant flowing through heat-transfer tubes in the inlet region, the intermediate region and the outlet region is greater than or equal to 0.44 g/mm²hW and less than 0.50 g/mm²hW, greater than or equal to 0.14 g/mm²hW and less than 0.16 g/mm²hW, and greater than or equal to 0.13 g/mm²hW and less than 0.15 g/mm²hW, respectively.

Description

TECHNICAL FIELD

The present invention relates to a refrigerating appliance and an air conditioner both employing a refrigerant therein.

BACKGROUND ART

Chlorofluorocarbons have been used as a refrigerant in a refrigerating appliance, but have posed a problem of ozone layer depletion. Accordingly, HCFCs are recently used as a substitute refrigerant and, in particular, an HFC (R410A) is mostly used now, as shown in Fig. 11.

Patent Document(s)

Patent Document 1: JP 2000-81223 A

SUMMARY OF INVENTION

Problems to be solved by the Invention

However, the R410A refrigerant has a high global warming potential (GWP) of 2088 and is problematic in terms of prevention of global warming.
From a viewpoint of prevention of global warming, a refrigerant such as an HFO1234yf of GWP4 has been proposed as a refrigerant having a low GWP, but this refrigerant is smaller than the R410A refrigerant in refrigerating capacity per unit volume.
Accordingly, if this refrigerant is employed in a conventional apparatus to obtain the same capacity as the R410A refrigerant, it is necessary to increase a refrigerant circulation volume by increasing a speed of a compressor.
In order to increase the refrigerant circulation volume to obtain the same capacity as the R410A refrigerant, if a cylinder volume of the compressor is increased, a pressure loss in a heat exchanger increases, particularly, during cooling and, hence, a predetermined cooling capacity cannot be secured.
The present invention has been developed to overcome the above-described problem inherent in the conventional technology. It is accordingly an objective of the present invention to provide a highly efficient refrigerating appliance and air conditioner capable of securing a predetermined cooling capacity by reducing the pressure loss in the heat exchanger even using a refrigerant that is smaller than the R410A refrigerant in refrigerating capacity per unit volume.

Means to Solve the Problems

In accomplishing the above objective, the present invention is directed to a refrigerating appliance including at least a compressor, an outdoor heat exchanger, a throttling device and an indoor heat exchanger, all connected to one another via connecting pipes to form an annular refrigerant circuit. The refrigerant circuit is designed to be filled with a refrigerant that has a small refrigerating capacity per unit volume compared with an R410A refrigerant. The indoor heat exchanger includes a plurality of fins arrayed at regular intervals and a plurality of heat-transfer tubes extending through the fins in a direction generally perpendicular thereto with the refrigerant flowing through the heat-transfer tubes. The indoor heat exchanger also includes at least three regions, in which the refrigerant flows through the heat-transfer tubes at different mass speeds.
By this construction, even when using a refrigerant that has a small refrigerating capacity per unit volume compared with an R410A refrigerant, a pressure loss in the heat exchanger can be reduced.

Effects of the Invention

According to the present invention, because the pressure loss in the heat exchanger can be reduced even if a refrigerant that has a smaller refrigerating capacity per unit volume than the R410A refrigerant is used, not only can a cooling capacity of a refrigerating appliance be ensured, but an efficiency thereof can be also enhanced.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a piping diagram of an air conditioner according to a first embodiment of the present invention.
Fig. 2 is a table indicating refrigerating capacities per unit volume of an R410A refrigerant and an HFO1234yf refrigerant.
Fig. 3 is a piping diagram of an indoor heat exchanger for the R410A refrigerant.
Fig. 4 is a table indicating mass speeds, qualities of wet vapor, saturated temperature differences and refrigerating capacities when the indoor heat exchanger for the R410A refrigerant was used.
Fig. 5 is a PH diagram when the indoor heat exchanger for the R410A refrigerant was used.
Fig. 6 is a piping diagram of the indoor heat exchanger according to a first embodiment of the present invention.
Fig. 7 is a table indicating mass speeds, qualities of wet vapor, saturated temperature differences and refrigerating capacities when the indoor heat exchanger of Fig. 6 was used.
Fig. 8 is a PH diagram when the indoor heat exchanger of Fig. 6 was used.
Fig. 9A is a schematic layout of the indoor heat exchanger of Fig. 6.
Fig. 9B is another schematic layout of the indoor heat exchanger of Fig. 6.
Fig. 10 is a table indicating calculation results where the mass speed per unit capacity was changed.
Fig. 11 is a piping diagram of a conventional air conditioner.

DESCRIPTION OF EMBODIMENTS

A refrigerating appliance according to a first aspect of the present invention uses, as a refrigerant filled in a refrigerant circuit, a refrigerant having a small refrigerating capacity per unit volume compared with an R410A refrigerant and is provided with an indoor heat exchanger that includes a plurality of fins arrayed at regular intervals and a plurality of heat-transfer tubes extending through the fins in a direction generally perpendicular thereto with the refrigerant flowing through the heat-transfer tubes. The indoor heat exchanger also includes at least three regions, in which the refrigerant flows through the heat-transfer tubes at different mass speeds, thereby optimizing an area of passage. This aspect of the present invention optimizes the mass speed to reduce a pressure loss during cooling, thereby making it possible to obtain an appropriate temperature difference between air and the refrigerant.
A second aspect of the present invention is such that in the refrigerating appliance according to the first aspect, when the indoor heat exchanger serves as an evaporator, the at least three regions include an inlet region, an intermediate region and an outlet region along a flow of the refrigerant, wherein a mass speed per unit capacity of the refrigerant in the heat-transfer tubes in the inlet region is greater than or equal to 0.44 g/mm²hW and less than 0.50 g/mm²hW, that of the refrigerant in the heat-transfer tubes in the intermediate region is greater than or equal to 0.14 g/mm²hW and less than 0.16 g/mm²hW, and that of the refrigerant in the heat-transfer tubes in the outlet region is greater than or equal to 0.13 g/mm²hW and less than 0.15 g/mm²hW. This aspect of the present invention optimizes the mass speed to reduce a pressure loss during cooling, thereby making it possible to obtain an appropriate temperature difference between air and the refrigerant.
A third aspect of the present invention is such that in the refrigerating appliance according to the first or second aspect, a quality of wet vapor of the refrigerant in the inlet region, the intermediate region and the outlet region in a standard cooling capacity is greater than or equal to 0.215 and less than 0.437, greater than or equal to 0.437 and less than 0.8, and greater than or equal to 0.8 and less than or equal to 1.0, respectively. This aspect of the present invention optimizes the mass speed to reduce a pressure loss during cooling, thereby making it possible to obtain an appropriate temperature difference between air and the refrigerant.
A fourth aspect of the present invention is such that in the refrigerating appliance according to any one of the first to third aspects, a quality of wet vapor of the refrigerant in the inlet region, the intermediate region and the outlet region in an intermediate cooling capacity is greater than or equal to 0.23 and less than 0.408, greater than or equal to 0.408 and less than 0.645, and greater than or equal to 0.645 and less than or equal to 1.0, respectively. This aspect of the present invention optimizes the mass speed to reduce a pressure loss during cooling, thereby making it possible to obtain an appropriate temperature difference between air and the refrigerant.
A fifth aspect of the present invention is such that in the refrigerating appliance according to any one of the first to fourth aspects, when the indoor heat exchanger serves as a condenser, a mass speed per unit capacity of the refrigerant in the outlet region, the intermediate region and the inlet region is greater than or equal to 0.120 g/mm²hW and less than 0.121 g/mm²hW, greater than or equal to 0.127 g/mm²hW and less than 0.129 g/mm²hW, and greater than or equal to 0.446 g/mm²hW and less than 0.451 g/mm²hW, respectively. This aspect of the present invention can restrain a reduction in performance even in a heating operation and achieve a good balance between a heating performance and a cooling performance, thus making it possible to obtain an optimized annual efficiency.
A sixth aspect of the present invention is such that in the refrigerating appliance according to any one of the first to fifth aspects, a quality of wet vapor of the refrigerant in the outlet region, the intermediate region and the inlet region in a standard heating capacity is greater than or equal to 0.408 and less than 1.00, greater than or equal to zero and less than 0.408, and 0.00, respectively. This aspect of the present invention can restrain a reduction in performance even in a heating operation and achieve a good balance between a heating performance and a cooling performance, thus making it possible to obtain an optimized annual efficiency.
A seventh aspect of the present invention is such that in the refrigerating appliance according to any one of the first to sixth aspects, a quality of wet vapor of the refrigerant in the outlet region, the intermediate region and the inlet region in an intermediate heating capacity is greater than or equal to 0.681 and less than 1.00, greater than or equal to 0.163 and less than 0.681, and greater than or equal to 0.00 and less than or equal to 0.681, respectively.
In an eighth aspect of the present invention, an air conditioner includes the refrigerating appliance according to any one of the first to seventh aspects and a four-way valve provided in the refrigerating appliance, wherein a direction of flow of the refrigerant flowing through the outdoor heat exchanger and the indoor heat exchanger can be changed for cooling and heating. This aspect of the present invention can switch between a cooling operation and a heating operation.
A ninth aspect of the present invention is such that in the refrigerating appliance or the air conditioner according to any one of the first to eighth aspects, a fan is further provided to supply the indoor heat exchanger with air, wherein when the indoor heat exchanger serves as a condenser, a downstream side of a flow of the refrigerant in the indoor heat exchanger is an upstream side of a flow of air created by the fan. This aspect of the present invention can enhance an efficiency during heating.
A tenth aspect of the present invention is such that in the refrigerating appliance or the air conditioner according to any one of the first to ninth aspects, a refrigerant whose main component is hydrofluoroolefin having a carbon-carbon double bond or a mixture refrigerant including this refrigerant is filled in the refrigerant circuit. This aspect of the present invention makes use of a refrigerant having a small global warming potential and can accordingly minimize, even if part of the refrigerant that cannot be collected is vented to atmosphere, the influence of the refrigerant on global warming.
Embodiments of the present invention are described hereinafter taking the case of an air conditioner, but the present invention is not limited to the embodiments.

(Embodiment 1)

Fig. 1 is a piping diagram of an air conditioner according to this embodiment.
The air conditioner according to the first embodiment includes a compressor 1 for compressing a refrigerant, a four-way valve 2 for switching a refrigerant circuit between a heating operation and a cooling operation, an outdoor heat exchanger 3 for exchanging heat between the refrigerant and outdoor air, a throttling device 4 for reducing a pressure of the refrigerant, and an indoor heat exchanger for exchanging heat between the refrigerant and indoor air. The compressor 1, the four-way valve 2, the outdoor heat exchanger 3, the throttling device 4 and the indoor heat exchanger 5 are circularly connected to one another via connecting pipes. An outdoor unit 10 includes the compressor 1, the four-way valve 2, the outdoor heat exchanger 3 and the throttling device 4, while an indoor unit 11 includes the indoor heat exchanger 5. The outdoor unit 10 and the indoor unit 11 are connected to each other via a connecting pipe A12 and a connecting pipe B13.
In a cooling operation, a refrigerant compressed by the compressor 1 turns into a high-temperature and high-pressure refrigerant, which passes through the four-way valve 2 and is introduced into the outdoor heat exchanger 3. The refrigerant exchanges heat with outdoor air in the outdoor heat exchanger 3 for radiation of heat and turns into a high-pressure liquid refrigerant, which is sent to the throttling device 4. The refrigerant is then reduced in pressure by the throttling device 4 and turns into a low-temperature and low-pressure two-phase refrigerant, which enters the indoor heat exchanger 5 via the connecting pipe B13. The refrigerant exchanges heat with indoor air to absorb heat in the indoor heat exchanger 5. The refrigerant then evaporates and turns into a low-temperature gas refrigerant. In this event, indoor air is cooled to cool an interior of a room and the refrigerant returns to the compressor 1 via the connecting pipe A12 and the four-way valve 2.
In a heating operation, the refrigerant compressed by the compressor 1 turns into a high-temperature and high-pressure refrigerant, which passes through the four-way valve 2 and is introduced into the indoor heat exchanger 5 via the connecting pipe A12. In the indoor heat exchanger 3, the refrigerant exchanges heat with indoor air and is cooled upon radiation of heat. The cooled refrigerant turns into a high-pressure liquid refrigerant. In this event, indoor air is heated to heat the interior of the room. Thereafter, the refrigerant is sent to the throttling device 4 via the connecting pipe B13. The refrigerant is then reduced in pressure by the throttling device 4 and turns into a low-temperature and low-pressure two-phase refrigerant, which is introduced into the outdoor heat exchanger 3. The refrigerant exchanges heat with outdoor air and evaporates in the outdoor heat exchanger 3 before it returns to the compressor 1 via the four-way valve 2. The cooling operation and the heating operation are conducted in the above-described manner.
The refrigerant circuit constituting the air conditioner according to this embodiment is filled with a refrigerant that has a refrigerating capacity per unit volume smaller than that of the R410A refrigerant. This refrigerant is a refrigerant whose main component is tetrafluoropropene in hydrofluoroolefin having a carbon-carbon double bond. In this embodiment, an HFO1234yf is employed as such a refrigerant.
A case where the indoor heat exchanger 5 serves as an evaporator is explained hereinafter in detail.
Fig. 2 is a table in which the refrigerating capacity per unit volume of the R410A refrigerant and that of the HFO1234yf refrigerant are compared.
Fig. 2 indicates, when an evaporative temperature of the evaporator is 5°C and 10°C, a saturated gas density, evaporative latent heat and the refrigerating capacity per unit volume of the evaporator (saturated gas density x evaporative latent heat) of the R410A refrigerant and those of the HFO1234yf refrigerant.
As shown in Fig. 2, when the evaporative temperature is 5°C, the refrigerating capacity per unit volume of the R410A and that of the HFO1234yf in the cooling operation are 7715.1 kJ/m³ and 3310.5 kJ/m³, respectively, and when the evaporative temperature is 10°C, the refrigerating capacity per unit volume of the R410A and that of the HFO1234yf in the cooling operation are 8742.6 kJ/m³ and 3791.7 kJ/m³, respectively. That is, the HFO1234yf is about 1/2.3 times greater than the R410A in the refrigerating capacity per unit volume. Accordingly, in order for the HFO1234yf to have the same refrigerating capacity as the R410A, it is necessary to make a volumetric flow rate per unit time (hereinafter referred to as "refrigerant circulation volume") of the HFO1234yf about 2.3 times greater than that of the R410A.
Fig. 3 depicts an example of the indoor heat exchanger 5 for the R410A refrigerant.
This indoor heat exchanger 5 includes a plurality of fins 19 arrayed at regular intervals and a plurality of heat-transfer tubes extending through the fins 19 in a direction generally perpendicular thereto with the refrigerant flowing through the heat-transfer tubes. The indoor heat exchanger 5 also includes a fan 18 to convey air for heat exchange with the refrigerant. The indoor heat exchange 5 has an inlet region 80, an intermediate region 81 and an outlet region 82 along a flow of refrigerant, in which regions the refrigerant flows at different mass speeds.
A refrigerant sent from the throttling device 4 enters a heat-transfer tube 50, then passes through a heat-transfer tube 51 and a heat-transfer tube 52, and reaches a heat-transfer tube 53. The heat-transfer tube 53 is branched into four heat- transfer tubes 60, 61, 62, 63, through which respective refrigerants pass before they reach heat-transfer tubes 60', 61', 62', 63'. The refrigerants passing through the heat-transfer tubes 60', 61', 62', 63' reach, for example, a header (not shown), from which two heat- transfer tubes 70, 71 are branched so that almost the same amount of refrigerant may flow through each of the two heat- transfer tubes 70, 71. Having passed through the heat- transfer tubes 70, 71, the refrigerants reach heat-transfer tubes 70', 71', pass through the connecting pipe B13 and returns to the compressor 1 via the four-way valve 2.
Fig. 4 indicates a mass speed, a quality of wet vapor (dryness), a saturated temperature difference and a refrigerating capacity of a refrigerant in each region when the indoor heat exchanger 5 for the R410A refrigerant shown in Fig. 3 was used and the R410A and the HFO1234yf were used as refrigerants.
It is to be noted that the saturated temperature difference was used as an indicator of a pressure loss. The saturated temperature difference is a difference between a saturated temperature of a refrigerant obtained from a refrigerant pressure at an inlet of the indoor heat exchanger 5 and that of a refrigerant obtained from a refrigerant pressure at an outlet of the indoor heat exchanger 5. The reason for this is that a relationship between the pressure and the temperature differs depending on the kind of refrigerants and, hence, the pressure losses pertaining to the performance cannot be simply compared as pressure differences. For comparison of the pressure losses of different refrigerants, the saturated temperature differences corresponding thereto are generally utilized. It is considered that the pressure loss increases with an increase in saturated temperature difference.
Fig. 4 indicates data obtained under the condition that the cooling capacity was maximized by increasing the refrigerant circulation volume with the use of the HFO1234yf. As can be seen from Fig. 4, the performance of the HFO1234yf is about 74% (=2890÷3903x100) of that of the R410A. This results from the fact that the pressure loss of the HFO1234yf is large, as can be known from the saturated temperature difference. Explanation is further made with reference to Fig. 5.
Fig. 5 depicts a PH diagram under the condition of Fig. 4 when the indoor heat exchanger 5 for the R410A refrigerant as shown in Fig. 3 and the HFO1234yf refrigerant were used.
A point A indicates an inlet portion of a compressor, a point B indicates a discharge portion of the compressor, a point C indicates an inlet portion of a condenser, a point D indicates an outlet portion of the condenser, a point E indicates an inlet portion of an evaporator, and a point F indicates an outlet portion of the evaporator.
As can be seen from Fig. 5, a gradient of a line extending from the point E at the inlet portion of the evaporator to the point F at the outlet portion of the evaporator is large. This means that an increase in refrigerant circulation volume results in a large pressure loss. Also, because the refrigerant temperature increases from the point F toward the point E, a temperature difference between the refrigerant and air, i.e., a heat exchange fluid gradually becomes small and is minimal at the point E, i.e., at the inlet of the indoor heat exchanger 5. A reduction in temperature difference between the refrigerant and air is followed by a reduction in the amount of heat exchange and, hence, a predetermined cooling capacity cannot be ensured.
It can be accordingly said that an increase in refrigerant circulation volume results in an increase in pressure loss, which in turn results in a reduction in temperature difference, thus making it impossible to ensure the capacity.
Fig. 6 depicts an example of an indoor heat exchanger 5 according to the present invention.
The indoor heat exchanger 5 includes a plurality of fins 19 arrayed at regular intervals and a plurality of heat-transfer tubes extending through the fins 19 in a direction generally perpendicular thereto with the refrigerant flowing through the heat-transfer tubes. The indoor heat exchanger 5 also includes a fan 18 to convey air for heat exchange with the refrigerant. A direction of flow of the refrigerant is the same as that of air. The indoor heat exchange 5 has an inlet region 15, an intermediate region 16 and an outlet region 17 along a flow of refrigerant, all of which regions have different mass speeds per unit capacity.
A refrigerant sent from the throttling device 4 enters two heat- transfer tubes 20, 21, through which respective refrigerants pass before they reach heat-transfer tubes 20', 21'. The refrigerants passing through the heat-transfer tubes 20', 21' reach, for example, a header (not shown), from which heat- transfer tubes 30, 31, 32, 33, 34, 35, 36 are branched so that almost the same amount of refrigerant may flow through each of the heat- transfer tubes 30, 31, 32, 33, 34, 35, 36. Having passed through the heat- transfer tubes 30, 31, 32, 33, 34, 35, 36, the refrigerants reach heat-transfer tubes 30', 31', 32', 33', 34', 35', 36' and then reach heat-transfer tubes 40', 41', 42', 43', 44', 45' via, for example, a header (not shown) and via heat- transfer tubes 40, 41, 42, 43, 44, 45. The refrigerants then pass through the connecting pipe B13 via, for example, a header (not shown) and return to the compressor 1 via the four-way valve 2.
The heat-transfer tubes in the inlet region 15 and those in the intermediate region 16 have a diameter of, for example, 6.35 mm and those in the outlet region 17 have a diameter of, for example, 7 mm. In respect of the number of passes, the inlet region 15, the intermediate region 16 and the outlet region 17 may have two, seven and six passes, respectively.
Fig. 7 indicates a mass speed, a quality of wet vapor, a saturated temperature difference and a refrigerating capacity of a refrigerant in each region calculated from a simulation in a standard cooling capacity when the indoor heat exchanger 5 according to the present invention as shown in Fig. 3 was used and the HFO1234yf was used as a refrigerant.
As can be seen from Fig. 7, the mass speed per unit capacity of the refrigerant in the heat-transfer tubes in the inlet region 15 is greater than or equal to 0.44 g/mm²hW and less than 0.50 g/mm²hW, that of the refrigerant in the heat-transfer tubes in the intermediate region 16 is greater than or equal to 0.14 g/mm²hW and less than 0.16 g/mm²hW, and that of the refrigerant in the heat-transfer tubes in the outlet region 17 is greater than or equal to 0.13 g/mm²hW and less than 0.15 g/mm²hW. Also, the quality of wet vapor of the refrigerant in the inlet region 15, the intermediate region 16 and the outlet region 17 in the standard cooling capacity is greater than or equal to 0.215 and less than 0.437, greater than or equal to 0.437 and less than 0.8, and greater than or equal to 0.8 and less than or equal to 1.0, respectively.
Also, the quality of wet vapor of the refrigerant in the inlet region 15, the intermediate region 16 and the outlet region 17 in an intermediate cooling capacity is greater than or equal to 0.23 and less than 0.408, greater than or equal to 0.408 and less than 0.645, and greater than or equal to 0.645 and less than or equal to 1.0, respectively.
The saturated temperature difference is about 9.5K and the cooling capacity is 3912W, which is about the same as in the case where the R410A refrigerant was used, as shown in Fig. 4, thus making it possible to ensure the cooling capacity.
Fig. 8 depicts a PH diagram under the condition of Fig. 7 when the indoor heat exchanger 5 according to the present invention shown in Fig. 6 and the HFO1234yf refrigerant were used.
A point A indicates an inlet portion of a compressor, a point B indicates a discharge portion of the compressor, a point C indicates an inlet portion of a condenser, a point D indicates an outlet portion of the condenser, a point E' indicates an inlet portion of an evaporator, and a point F indicates an outlet portion of the evaporator. Also, a point E indicates an inlet portion of an indoor heat exchanger when the indoor heat exchanger 5 for the R410A was used.
As can be seen from Fig. 8, when the indoor heat exchanger 5 for the R410A was used, the pressure loss is large and a gradient of a line extending from the point F to the point E is accordingly large, while when the indoor heat exchanger 5 according to the present invention was used, a gradient of a line from the point F to the point E' is gentle. Accordingly, appropriate air temperatures are maintained with the use of an appropriate refrigerant, thus making it possible to ensure a predetermined amount of heat exchange and a predetermined cooling capacity.
A case where the indoor heat exchanger 5 serves as a condenser is explained hereinafter.
The indoor heat exchanger 5 according to the present invention as shown in Fig. 6 was used. The flow of refrigerant in the heating operation is the reverse of that in the cooling operation.
Having passed through the connecting pipe B13, a gas refrigerant reaches heat-transfer tubes 40', 41', 42', 43', 44', 45', through which respective refrigerants pass and reach, for example, a header (not shown) via heat- transfer tubes 40, 41, 42, 43, 44, 45. The header is branched into heat-transfer tubes 30', 31', 32', 33', 34', 35', 36' so that almost the same amount of refrigerant may flow through each of them. Having passed through the heat-transfer tubes 30', 31', 32', 33', 34', 35', 36', the refrigerants reach heat- transfer tubes 30, 31, 32, 33, 34, 35, 36, through which the refrigerants pass and reach, for example, a header (not shown). The refrigerant in the header is almost equally divided into two to enter heat-transfer tubes 20', 21'. Having passed through the heat-transfer tubes 20', 21', the refrigerants reach heat- transfer tubes 20, 21, respectively, and are sent to the connecting pipe A13. In the heating operation, the refrigerant flows through the outlet region 17, the intermediate region 16 and the inlet region 15 in this order, in which regions the refrigerant has different mass speeds per unit capacity. The mass speed per unit capacity calculated from a simulation is greater than or equal to 0.120 g/mm²hW and less than 0.121 g/mm²hW in the outlet region 17, greater than or equal to 0.127 g/mm²hW and less than 0.129 g/mm²hW in the intermediate region 16, and greater than or equal to 0.446 g/mm²hW and less than 0.451 g/mm²hW in the inlet region 15.
The simulation also reveals that the quality of wet vapor in a standard heating capacity is greater than or equal to 0.408 and less than 1.00, greater than or equal to zero and less than 0.408, and 0.00, respectively, and that the quality of wet vapor in an intermediate heating capacity is greater than or equal to 0.681 and less than 1.00, greater than or equal to 0.163 and less than 0.681, and greater than or equal to 0.00 and less than or equal to 0.681, respectively.
At this moment, the refrigerant or refrigerants exchange heat with air conveyed by the fan 18. A direction of flow of the refrigerant is the same direction of air conveyed by the fan 18. A downstream side of the flow of refrigerant in the indoor heat exchanger 5 is an upstream side of the flow of air created by the fan 18, i.e., the refrigerant flows in a direction counter to a direction in which air conveyed by the fan 18 flows. Accordingly, a larger average temperature difference can be obtained compared with a case where the refrigerant and air flow in the same direction, thus resulting in an increase in efficiency.
Fig. 9A or 9B depicts an arrangement of the inlet, intermediate and outlet regions. The indoor heat exchanger 5 includes the inlet region 15, the intermediate region 16 and the outlet region 17 arranged in a manner as shown in Fig. 9A or 9B. The three regions may be arranged separately, as shown in Fig. 9A or assembled in a row, as shown in Fig. 9B. The arrangement of the inlet, intermediate and outlet regions is not limited to these figures.
Fig. 10 indicates calculation results where the indoor heat exchanger 5 according to the present invention was used and where the mass speed per unit capacity was changed in each of the inlet region 15, the intermediate region 16 and the outlet region 17. The case where the indoor heat exchanger 5 according to the present invention was used is indicated by boldface in the center of each table, in which the capacity during standard cooling, intermediate cooling, standard heating or intermediate heating was set to 100% and the term-efficiency, i.e., the efficiency during each operation was similarly set to 100%.
As can be seen from Fig. 10, there are no cases that exceed the term-efficiency of 100% when using the indoor heat exchanger 5 according to the present invention.
However, particularly in the outlet region indicated by (3) in Fig. 10, the heating capacity is higher when the mass speed per unit capacity is 0.117 g/mm²hW, but Fig. 10 reveals that in terms of the characteristic features of the refrigerant in this invention, it is important to increase the cooling capacity even if the heating capacity is slightly reduced.
It is to be noted that because the tube diameter is standardized, it cannot be arbitrarily selected. Accordingly, the tube diameter or the number of passes is appropriately selected so that the mass speed and the quality of wet vapor as indicated in the above-described embodiment or those close to them can be obtained in any way possible.
Although in the above-described embodiment explanation has been made taking the case of HFO1234yf, a refrigerant whose main component is hydrofluoroolefin having a carbon-carbon double bond may be used. Hydrofluoroolefin may be, for example, HFO1234ze if it is tetrafluoropropene to which HFO1234yf belongs. Also, such a refrigerant may be used alone or in combination with another refrigerant such as, for example, hydrofluorocarbon having no double bond.
More specifically, a mixture refrigerant having tetrafluoropropene (HFO1234yf or HFO1234ze) as an alternative for hydrofluoroolefin and also having difluoromethane (HFC32) as an alternative for hydrofluorocarbon may be used as a refrigerant.
Also, a mixture refrigerant having tetrafluoropropene (HFO1234yf) as an alternative for hydrofluoroolefin and also having pentafluoroethane (HFC125) as an alternative for hydrofluorocarbon may be used as a refrigerant.
Further, a three-component mixture refrigerant having tetrafluoropropene (HFO1234yf) as an alternative for hydrofluoroolefin and also having pentafluoroethane (HFC125) and difluoromethane (HFC32) as an alternative for hydrofluorocarbon may be used as a refrigerant.
Although an air conditioner has been described in the above-described embodiment, the present invention is applicable to a refrigerating appliance having no four-way valve such as, for example, a water heater exclusively for heating or a cooler, a freezer and the like exclusively for cooling. In those cases, an indoor heat exchanger and an outdoor heat exchanger serve as a condenser and an evaporator, respectively.

Industrial Applicability

The present invention can make use of a refrigerant having a small GWP such as, for example, an HFO1234yf of GWP4.

Explanation of reference numerals

1 compressor
2 four-way valve
3 outdoor heat exchanger
4 throttling device
5 indoor heat exchanger
6 refrigerant having a small refrigerating capacity per unit volume
15 inlet region
16 intermediate region
17 outlet region
18 fan
19 fin
20, 21, 20', 21', 30, 31, 32, 33, 34, 35, 36, 30', 31', 32', 33', 34', 35', 36', 40, 41, 42, 43, 44, 45, 40', 41', 42', 43', 44', 45' heat-transfer tube

Claims

A refrigerating appliance comprising at least a compressor, an outdoor heat exchanger, a throttling device and an indoor heat exchanger, all connected to one another via connecting pipes to form an annular refrigerant circuit, the refrigerant circuit being designed to be filled with a refrigerant that has a small refrigerating capacity per unit volume compared with an R410A refrigerant;
the indoor heat exchanger comprising a plurality of fins arrayed at regular intervals and a plurality of heat-transfer tubes extending through the fins in a direction generally perpendicular thereto with the refrigerant flowing through the heat-transfer tubes; and
the indoor heat exchanger also comprising at least three regions, in which the refrigerant flows through the heat-transfer tubes at different mass speeds.
The refrigerating appliance according to claim 1, wherein when the indoor heat exchanger serves as an evaporator, the at least three regions comprise an inlet region, an intermediate region and an outlet region along a flow of the refrigerant and wherein a mass speed per unit capacity of the refrigerant in the heat-transfer tubes in the inlet region is greater than or equal to 0.44 g/mm²hW and less than 0.50 g/mm²hW, that of the refrigerant in the heat-transfer tubes in the intermediate region is greater than or equal to 0.14 g/mm²hW and less than 0.16 g/mm²hW, and that of the refrigerant in the heat-transfer tubes in the outlet region is greater than or equal to 0.13 g/mm²hW and less than 0.15 g/mm²hW.
The refrigerating appliance according to claim 1 or 2, wherein a quality of wet vapor of the refrigerant in the inlet region, the intermediate region and the outlet region in a standard cooling capacity is greater than or equal to 0.215 and less than 0.437, greater than or equal to 0.437 and less than 0.8, and greater than or equal to 0.8 and less than or equal to 1.0, respectively.
The refrigerating appliance according to any one of claims 1 to 3, wherein a quality of wet vapor of the refrigerant in the inlet region, the intermediate region and the outlet region in an intermediate cooling capacity is greater than or equal to 0.23 and less than 0.408, greater than or equal to 0.408 and less than 0.645, and greater than or equal to 0.645 and less than or equal to 1.0, respectively.
The refrigerating appliance according to any one of claims 1 to 4, wherein when the indoor heat exchanger serves as a condenser, a mass speed per unit capacity of the refrigerant in the outlet region, the intermediate region and the inlet region is greater than or equal to 0.120 g/mm²hW and less than 0.121 g/mm²hW, greater than or equal to 0.127 g/mm²hW and less than 0.129 g/mm²hW, and greater than or equal to 0.446 g/mm²hW and less than 0.451 g/mm²hW, respectively.
The refrigerating appliance according to any one of claims 1 to 5, wherein a quality of wet vapor of the refrigerant in the outlet region, the intermediate region and the inlet region in a standard heating capacity is greater than or equal to 0.408 and less than 1.00, greater than or equal to zero and less than 0.408, and 0.00, respectively.
The refrigerating appliance according to any one of claims 1 to 6, wherein a quality of wet vapor of the refrigerant in the outlet region, the intermediate region and the inlet region in an intermediate heating capacity is greater than or equal to 0.681 and less than 1.00, greater than or equal to 0.163 and less than 0.681, and greater than or equal to 0.00 and less than or equal to 0.681, respectively.
An air conditioner comprising a refrigerating appliance according to any one of claims 1 to 7 and a four-way valve provided in the refrigerating appliance, wherein a direction of flow of the refrigerant flowing through the outdoor heat exchanger and the indoor heat exchanger can be changed for cooling and heating.
The refrigerating appliance or the air conditioner according to any one of claims 1 to 8, further comprising a fan operable to supply the indoor heat exchanger with air, wherein when the indoor heat exchanger serves as a condenser, a downstream side of a flow of the refrigerant in the indoor heat exchanger is an upstream side of a flow of air created by the fan.
The refrigerating appliance or the air conditioner according to any one of claims 1 to 9, wherein a refrigerant whose main component is hydrofluoroolefin having a carbon-carbon double bond or a mixture refrigerant including this refrigerant is filled in the refrigerant circuit.