JP2007232365A - Air conditioner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve heat efficiency of a heat radiator without increasing the pressure loss of air. <P>SOLUTION: This air conditioner is provided with: a flow rate control means 3 for controlling the flow rate of a carbon dioxide refrigerant; an evaporator 4 for evaporating the carbon dioxide refrigerant; a compressor 1 for compressing the evaporated carbon dioxide refrigerant; a first heat exchanger 2A composed by arranging heat transfer tubes for passing the carbon dioxide refrigerant therethrough in a predetermined number of fin plates; a second heat exchanger 2B composed by similarly arranging heat transfer tubes for passing the carbon dioxide refrigerant therethrough in a predetermined number of fin plates; and a blower 5 for supplying air to the first heat exchanger 2A and the second heat exchanger 2B. The air supplied from the flower 5 passes through the second heat exchanger 2B and thereafter flows into the first heat exchanger 2A, and the carbon dioxide refrigerant compressed by the compressor 1 is rapidly lowered in temperature while passing through the first heat exchanger 2A and flows into the second heat exchanger 2B after the lowering amount of the temperature is lowered. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an air conditioner, and more particularly to an air conditioner that adjusts a room temperature using a refrigerant.

  Since CFC refrigerants have a large global warming potential, carbon dioxide is attracting attention as an alternative refrigerant. Patent Document 1 is an example of disclosure of an air conditioner that uses carbon dioxide. This air conditioner includes a compressor, a radiator, a flow rate control unit, and an evaporator as main components, and these components are sequentially connected by heat transfer tubes (refrigerant piping).

  Carbon dioxide, which is a refrigerant, is discharged from the compressor as a supercritical fluid in a high-temperature and high-pressure state, and the temperature is lowered while heating the air with a radiator. (Liquid phase) Changes to a mixed fluid. Next, the refrigerant evaporates while cooling the air with the evaporator, changes to a low-temperature and low-pressure gas, and returns to the compressor.

  Here, the radiator having the fins is configured to exchange heat by making the air flow direction and the refrigerant flow direction face each other. By doing so, the temperature difference between the air and the supercritical carbon dioxide is kept almost constant during heat exchange.

Japanese Patent Laid-Open No. 2001-267372

  When carbon dioxide in the supercritical state exchanges heat with air in the radiator, the temperature of the carbon dioxide decreases rapidly, but the fins of the radiator have a large temperature distribution, and the carbon dioxide in the high temperature and high pressure state passes through these fins. Reheat the low temperature carbon dioxide rather than heat the air (see FIG. 7).

  To prevent this reheating, the length of the heat exchange member is increased in the direction of air flow, and the distance between the heat transfer tube through which high-temperature and high-pressure carbon dioxide flows and the heat transfer tube through which low-temperature carbon dioxide flows are determined. It needs to be bigger. However, this increases the size of the radiator and causes a reduction in the efficiency of the air conditioner due to an increase in air pressure loss. An object of the present invention is to improve the thermal efficiency of a radiator without causing an increase in pressure loss.

  An air conditioner according to the present invention includes a flow rate control unit that controls the flow rate of carbon dioxide refrigerant, an evaporator that vaporizes the carbon dioxide refrigerant, a compressor that compresses the vaporized carbon dioxide refrigerant, and a predetermined number of fin plates. A first heat exchanger configured by arranging heat transfer tubes through which carbon dioxide refrigerant passes, and a second heat exchange configured by arranging heat transfer tubes through which carbon dioxide refrigerant passes through a predetermined number of fin plates. And a blower for supplying air to the first heat exchanger and the second heat exchanger, and the air supplied from the blower passes through the second heat exchanger before the first heat exchange. The carbon dioxide refrigerant compressed by the compressor and the refrigerant flows into the second heat exchanger after the temperature is suddenly lowered while passing through the first heat exchanger and the amount of decrease in temperature is reduced. It is composed of.

  An air conditioner according to the present invention includes a flow rate control unit that controls the flow rate of carbon dioxide refrigerant, an evaporator that vaporizes the carbon dioxide refrigerant, a compressor that compresses the vaporized carbon dioxide refrigerant, and a predetermined number of fin plates. A first heat exchanger configured by arranging heat transfer tubes through which carbon dioxide refrigerant passes, and a second heat exchange configured by arranging heat transfer tubes through which carbon dioxide refrigerant passes through a predetermined number of fin plates. And a blower for supplying air to the first heat exchanger and the second heat exchanger, and the air supplied from the blower passes through the second heat exchanger before the first heat exchange. The carbon dioxide refrigerant compressed by the compressor and the refrigerant flows into the second heat exchanger after the temperature is suddenly lowered while passing through the first heat exchanger and the amount of decrease in temperature is reduced. By configuring the It is high.

Embodiment 1 FIG.
As shown in FIG. 1, the air conditioner according to the present invention includes a compressor 1, a radiator 2, a flow rate control valve 3, an evaporator 4, and a blower 5. These components 1 to 4 are sequentially connected by a refrigerant pipe (heat transfer pipe), and carbon dioxide as a refrigerant circulates. In an air conditioner using a chlorofluorocarbon refrigerant, the radiator 2 is often called a condenser.

  The radiator 2 according to the first embodiment includes a heat exchanger 2A and a heat exchanger 2B, and both are connected by a heat transfer tube so that the refrigerant passes through the heat exchanger 2A and then passes through the heat exchanger 2B. ing. The cooling air generated by the blower 5 reaches the heat exchanger 2A after passing through the heat exchanger 2B.

  FIG. 2 shows a state in which the heat exchangers 2A and 2B shown in FIG. 1 are viewed from a direction parallel to the paper surface. The heat transfer tube 6 is integrated with a fin plate 7 arranged in parallel at a predetermined interval. After passing through a through hole (not shown) provided in the fin plate 7, the heat transfer tube 6 is folded at both the left and right ends. Then, they are arranged so as to return to the fin plate again. The fin plate 7 is a single plate-like member having excellent thermal conductivity that communicates from the uppermost stage to the lowermost stage in each heat exchanger, and minimizes the temperature difference between the refrigerant inflow portion and the refrigerant outflow portion. To do. In this figure, eight fin plates are drawn, but it goes without saying that the present invention is not limited to the number, thickness, material, or the like.

  In FIG. 1, in order to shorten the length of the heat transfer tube connecting the heat exchanger 2A and the heat exchanger 2B, the refrigerant flows downward in the heat exchanger 2B. However, as shown in FIG. It is also possible to connect with a heat pipe so that the refrigerant flows upward in the heat exchanger 2B. In either case, since the heat exchanger 2A and the heat exchanger 2B are only connected by a heat transfer tube, there is a large thermal resistance between them, and the heat exchanger 2A conducts from the heat exchanger 2A to the heat exchanger 2B. The amount of heat generated is minimized. Note that the number of heat exchangers is not limited to two, and the number of stages can be freely increased within a range in which the air flow does not deteriorate.

  FIG. 4 shows a phase diagram (entropy-temperature curve) of carbon dioxide. Carbon dioxide exhibits a liquid phase, a two-phase (liquid phase and gas phase) mixture, a gas phase, and a supercritical phase depending on conditions. Under the standard cooling condition, the air suction temperature in the radiator 2 is 35 ° C., which is slightly higher than the critical temperature.

  Next, operation | movement of an air conditioning apparatus is demonstrated based on FIG. The supercritical carbon dioxide in the high temperature and high pressure state discharged from the compressor 1 flows in the heat exchanger 2 in the order of the heat exchanger 2A and the heat exchanger 2B, and exchanges heat with air to lower the temperature. At this time, the carbon dioxide in the supercritical state has a low specific heat at a high temperature (temperature range of about 40 to 100 ° C.), so the temperature rapidly decreases due to heat exchange (from (1) to (2) in FIG. 5). The specific heat is large at a low temperature (temperature range of about 30 to 40 ° C.), and the temperature changes only slightly ((2) to (3) in FIG. 5). The air flowing into the radiator 2 is first heated by the carbon dioxide having a relatively low temperature in the heat exchanger 2B, and then further heated by the high-temperature carbon dioxide in the heat exchanger 2A.

  The carbon dioxide whose temperature has been reduced is reduced in pressure by the flow control valve 3 and changed into a low-temperature gas-liquid two-phase state (from (3) to (4) in the figure) and then flows into the evaporator 4. In the evaporator 4, the refrigerant liquid evaporates while cooling the air, and the refrigerant changed to gas returns to the compressor 1 (from (5) to (1) in the figure).

  For comparison, a phase diagram (entropy-temperature curve) of a chlorofluorocarbon refrigerant is shown in FIG. Even in an air conditioner using a fluorocarbon refrigerant, the refrigerant is discharged from the compressor as a high-temperature and high-pressure gas ((1) in FIG. 6), and the condenser (heat radiator) heats the air while condensing the gas. It changes to a high-pressure liquid ((2) in FIG. 6). This liquid changes to a low-temperature and low-pressure two-phase state (4 in FIG. 6) by the flow rate control means. In the evaporator, only the liquid evaporates, changes to a low-temperature and low-pressure gas ((5) in FIG. 6) while cooling the air, and returns to the compressor.

  The chlorofluorocarbon refrigerant discharged from the compressor has a high temperature, and the temperature is lowered by heat exchange with air. However, since the high-temperature and high-pressure fluorocarbon refrigerant is a gas, its specific heat is extremely small, the temperature change is large, and the high-temperature region (shaded area shown in FIG. 6) is narrow. In the condenser, the temperature of the refrigerant is substantially constant ((2) to (3) in FIG. 6) in order to heat the air while the refrigerant is condensed, and the temperature of the fins constituting the condenser is also kept almost constant. In order to increase the heat exchange rate, it is important to keep the temperature difference between the air temperature and the refrigerant constant.

  On the other hand, carbon dioxide in a supercritical state has a large temperature change and a wide high temperature region (shaded area shown in FIG. 5). For this reason, a large temperature distribution occurs in the fins constituting the radiator, and the high temperature carbon dioxide does not heat the air through the fins, but reheats the low temperature carbon dioxide, and the temperature of the carbon dioxide at the outlet of the radiator As a result, the heat exchange rate was lowered (see FIG. 7).

  In the air conditioner according to the first embodiment, the heat exchanger 2A and the heat exchanger 2B are provided with independent fin plates 7, so that the high-temperature carbon dioxide heats the low-temperature carbon dioxide (reheating phenomenon). ) Can be prevented (see FIG. 7). Thereby, the heat transfer from a high temperature area | region to a low temperature area | region can be suppressed, and since the temperature of the carbon dioxide of the exit of a radiator can be made low, thermal efficiency improves. Furthermore, the configuration of the heat transfer tube of the radiator is simple and can be realized at low cost.

  Actually, heat exchangers 2A and 2B prepared using a heat transfer tube with a diameter of 7 mm and a fin plate interval of 1.5 mm are used as an air intake temperature of 35 ° C., an inlet temperature of carbon dioxide heat exchanger 2 A of 68 ° C., Operating at an inlet pressure of 9.3 MPa, the thermal efficiency was measured. The heat exchanger according to the first embodiment has a heat exchange heat amount improved by 6% or more compared to a heat radiator in which the fin plate is not independent (separated).

Embodiment 2. FIG.
FIGS. 8 and 9 show a heat radiator according to the second embodiment. The other components are the same as those shown in FIG. Although the heat radiator 2 consists of a 1st heat exchange part and a 2nd heat exchange part, both are integrated by the common fin plate 7, and there is no space | gap between both. The refrigerant flows into the second heat exchange section after passing through the first heat exchange section. The air that has flowed into the radiator 2 is divided into one that flows into the first heat exchange section and one that flows into the second heat exchange section.

  The first heat exchange unit is configured such that the refrigerant flows in a direction opposite to the air flow direction. That is, the refrigerant flows in from the heat transfer tubes arranged in the rear row located on the leeward side, and flows out from the heat transfer tubes arranged in the front row located on the upwind side. On the other hand, the second heat exchange unit is configured such that the refrigerant flows in a direction orthogonal to the air flow direction and in a direction away from the first heat exchange unit. That is, after passing through the first heat exchanging part, the refrigerant goes in a direction (upper end of the radiator) finally moving away from the first heat exchanging part while moving back and forth in a zigzag shape when viewed in cross section.

  Next, the operation will be described with reference to FIG. The supercritical carbon dioxide discharged from the compressor 1 flows into the radiator 2 and rapidly decreases its temperature while maintaining a substantially constant temperature difference with air in the first heat exchange section (in FIG. 10). (1) to (2)). Next, the carbon dioxide whose temperature has decreased flows into the second heat exchange section, and the temperature of the carbon dioxide further decreases due to heat exchange with the air, but the decrease in temperature is slight ((2 in FIG. 10). ▼ to ▲ 3 ▼).

  As a result, the temperature of the air that exchanges heat in the first heat exchanging section is kept constant from the high-temperature refrigerant, and efficient operation is possible. In addition, the air that exchanges heat in the second heat exchanging section can also maintain a substantially constant temperature difference although it is in a low temperature region where the temperature change is small. Furthermore, since the temperature difference is small in the second heat exchange section, the reheating phenomenon does not occur.

  Thereafter, the carbon dioxide is depressurized by the flow control valve 3, changes to a low-temperature gas-liquid two-phase state, and flows into the evaporator 4. In the evaporator 4, only the liquid evaporates while cooling the air, and the refrigerant changed to gas returns to the compressor 1.

  The air conditioner according to Embodiment 2 does not need to provide the first heat exchange unit and the second heat exchange unit independently, but the same effect as in Embodiment 1 can be obtained. Moreover, since air and the refrigerant can exchange heat with each other in the first heat exchanging section where the temperature change of the refrigerant is large, the thermal efficiency is further increased without increasing the size of the radiator and increasing the pressure loss of the air. .

Embodiment 3 FIG.
The form of the heat radiator concerning Embodiment 3 is shown in FIGS. The other components are the same as those shown in FIG. The radiator includes a heat exchanger 2C and a heat exchanger 2D, and each includes an independent fin plate 7. Both are connected by a heat transfer tube, and the refrigerant flows to the heat exchanger 2D after passing through the heat exchanger 2C.

  The heat exchanger 2C is configured so that the refrigerant flows in a direction opposite to the air flow direction. That is, the refrigerant flows in from the heat transfer tubes arranged in the rear row located on the leeward side, and flows out from the heat transfer tubes arranged in the front row located on the upwind side. The heat exchanger 2C can also separate between the heat transfer tubes arranged in the front row and the heat transfer tubes arranged in the rear row, as shown as 2C 'in FIG.

  On the other hand, the heat exchanger 2D is configured such that the refrigerant flows in a direction orthogonal to the direction in which air flows. In other words, in the heat exchanger 2D, the refrigerant may pass through the heat transfer tubes arranged in the rear row and then pass through the heat transfer tubes arranged in the front row (see FIGS. 11 and 12). The refrigerant may be passed in a staggered manner away from the heat exchanger 2C while moving back and forth (see FIG. 13). In the former, the outflow part of the refrigerant is provided in the middle of the radiator, whereas in the latter, the outflow part is provided at the end of the radiator 2.

  Next, the operation will be described. The supercritical carbon dioxide discharged from the compressor 1 flows into the radiator 2, and the temperature rapidly decreases while maintaining a substantially constant temperature difference from the air in the heat exchanger 2C ((1) in FIG. 10). To (2)). Next, it flows into the heat exchanger 2D and exchanges heat with air, so that the temperature slightly decreases (from (2) to (3) in FIG. 10). The carbon dioxide whose temperature has decreased is depressurized by the flow control valve 3, changes to a low-temperature gas-liquid two-phase state (from (3) to (4) in FIG. 10), and flows into the evaporator 4. The evaporator 4 changes to steam while cooling the air (from 4 to 5 in FIG. 10) and returns to the compressor 1 (from 5 to 1 in FIG. 10).

  The air flowing into the heat exchanger 2D is heated by carbon dioxide having a relatively low temperature while keeping the temperature difference with the refrigerant substantially constant. The heat exchanger 2C is also heated by high-temperature carbon dioxide while keeping the temperature difference between the air and the refrigerant substantially constant. Moreover, since the heat exchanger 2C and the heat exchanger 2D are only connected by a heat transfer tube, the amount of heat that is transmitted from the heat exchanger 2C to the heat exchanger 2D and contributes to reheating is minimized. ing.

  As described above, the air-conditioning apparatus according to the third embodiment can obtain the same effects as those of the second embodiment. Furthermore, since the configuration of the heat exchanger 2D can be determined regardless of the configuration of the heat exchanger 2C, the degree of freedom in arranging the heat transfer tubes of the heat exchanger 2D is high.

1 is a diagram illustrating a configuration of an air conditioner according to Embodiment 1. FIG. It is a figure for demonstrating the relationship between a heat exchanger tube and a fin plate. It is a figure which shows another structure of the air conditioning apparatus concerning Embodiment 1. FIG. It is a state figure showing the relation between the entropy of carbon dioxide and temperature. It is a figure for demonstrating the principle of operation of the air conditioning apparatus which uses a carbon dioxide. It is a figure for demonstrating the principle of operation of the air conditioning apparatus which uses a fluorocarbon refrigerant. It is a figure for demonstrating a reheating phenomenon. FIG. 4 is a diagram showing a configuration of an air conditioning apparatus according to Embodiment 2. It is a figure which shows another structure of the air conditioning apparatus concerning Embodiment 2. FIG. FIG. 6 is a diagram for explaining an operation principle of an air conditioner according to Embodiment 2. FIG. 6 is a diagram showing a configuration of an air conditioning apparatus according to Embodiment 3. It is a figure which shows another structure of the air conditioning apparatus concerning Embodiment 3. FIG. It is a figure which shows another structure of the air conditioning apparatus concerning Embodiment 3. FIG.

Explanation of symbols

1 compressor, 2 radiator, 3 flow control valve, 4 evaporator, 5 blower, 6 heat transfer tube, 7 fin plate.

Claims (6)

Flow rate control means for controlling the flow rate of the carbon dioxide refrigerant, an evaporator for vaporizing the carbon dioxide refrigerant, a compressor for compressing the vaporized carbon dioxide refrigerant, and the carbon dioxide refrigerant passes through a predetermined number of fin plates. A first heat exchanger configured by arranging heat transfer tubes, a second heat exchanger configured similarly by arranging heat transfer tubes through which the carbon dioxide refrigerant passes through a predetermined number of fin plates, and the first A heat exchanger for supplying air to one heat exchanger and the second heat exchanger;
The air supplied from the blower passes through the second heat exchanger and then flows into the first heat exchanger, and the carbon dioxide refrigerant compressed by the compressor passes through the first heat exchanger. An air conditioner configured to flow into the second heat exchanger after the temperature is rapidly reduced during passage and the amount of decrease in temperature is reduced. Flow rate control means for controlling the flow rate of the carbon dioxide refrigerant, an evaporator for vaporizing the carbon dioxide refrigerant, a compressor for compressing the vaporized carbon dioxide refrigerant, and the carbon dioxide refrigerant compressed on a predetermined number of fin plates Comprising a heat radiator configured by arranging heat transfer tubes passing through, and a blower for supplying air to the heat radiator,
The heat radiator includes a first heat exchange part in which a heat transfer pipe is piped so that a carbon dioxide refrigerant flows from the leeward side of the air supplied from the blower toward the windward side, and the first heat exchange part. The heat transfer tubes are arranged so that the carbon dioxide refrigerant whose temperature decrease is suddenly lowered while passing through the gas flows in a direction orthogonal to the direction of air flow and further away from the first heat exchange section. An air conditioner having a second heat exchange unit. The carbon dioxide refrigerant passes through a flow rate control means that controls the flow rate of the carbon dioxide refrigerant, an evaporator that vaporizes the carbon dioxide refrigerant, a compressor that compresses the vaporized carbon dioxide refrigerant, and a predetermined number of fin plates. A first heat exchanger configured by arranging heat transfer tubes, a second heat exchanger configured similarly by arranging heat transfer tubes through which the carbon dioxide refrigerant passes through a predetermined number of fin plates, and the first A heat exchanger for supplying air to one heat exchanger and the second heat exchanger;
In the first heat exchanger, heat transfer tubes are arranged so that the carbon dioxide refrigerant compressed by the compressor flows in order from the leeward side of the air supplied from the blower toward the windward side. In the heat exchanger 2, the heat transfer tube is arranged so that the carbon dioxide refrigerant whose temperature decrease is suddenly decreased while passing through the first heat exchanger flows in a direction perpendicular to the air flow direction. Arranged air conditioner. The carbon dioxide refrigerant passes through a flow rate control means that controls the flow rate of the carbon dioxide refrigerant, an evaporator that vaporizes the carbon dioxide refrigerant, a compressor that compresses the vaporized carbon dioxide refrigerant, and a predetermined number of fin plates. A first heat exchanger configured by arranging heat transfer tubes, a second heat exchanger configured similarly by arranging heat transfer tubes through which the carbon dioxide refrigerant passes through a predetermined number of fin plates, and the first A heat exchanger for supplying air to one heat exchanger and the second heat exchanger;
The carbon dioxide refrigerant compressed by the compressor passes through the first heat exchanger and then flows into the second heat exchanger at about 40 ° C., and the air supplied from the blower is the second heat exchanger. An air conditioner configured to flow to the first heat exchanger after passing through the heat exchanger. Flow rate control means for controlling the flow rate of the carbon dioxide refrigerant, an evaporator for vaporizing the carbon dioxide refrigerant, a compressor for compressing the vaporized carbon dioxide refrigerant, and the carbon dioxide refrigerant compressed on a predetermined number of fin plates Comprising a heat radiator configured by arranging heat transfer tubes passing through, and a blower for supplying air to the heat radiator,
The heat radiator includes a first heat exchange part in which a heat transfer pipe is piped so that a carbon dioxide refrigerant flows from the leeward side of the air supplied from the blower toward the windward side, and the first heat exchange part. The second heat exchange section in which the heat transfer tubes are arranged so that the carbon dioxide refrigerant flowing in at about 40 ° C. through the pipe flows in a direction perpendicular to the air flow direction and away from the first heat exchange section. An air conditioner comprising: The carbon dioxide refrigerant passes through a flow rate control means that controls the flow rate of the carbon dioxide refrigerant, an evaporator that vaporizes the carbon dioxide refrigerant, a compressor that compresses the vaporized carbon dioxide refrigerant, and a predetermined number of fin plates. A first heat exchanger configured by arranging heat transfer tubes, a second heat exchanger configured similarly by arranging heat transfer tubes through which the carbon dioxide refrigerant passes through a predetermined number of fin plates, and the first A heat exchanger for supplying air to one heat exchanger and the second heat exchanger;
In the first heat exchanger, heat transfer tubes are arranged so that the carbon dioxide refrigerant compressed by the compressor flows in order from the leeward side of the air supplied from the blower toward the windward side. In the heat exchanger 2, an air conditioner in which heat transfer tubes are arranged so that the carbon dioxide refrigerant that has passed through the first heat exchanger and flows in at about 40 ° C. flows in a direction perpendicular to the direction of air flow. .

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