JPH08145490A - Heat exchanger for heat pump air conditioner - Google Patents

Abstract

PURPOSE: To improve the performance of a heat exchanger for a heat pump air conditioner corresponding to a non-azeotrope refrigerant used as the candidate of a substitute refrigerant recently to prevent the ozonosphere depletion in the heat exchanger for communicating heat between the refrigerant and a fluid such as the air used for the conditioner used also for cooling or heating. CONSTITUTION: This heat exchanger for a heat pump air conditioner comprises a heat exchanging core in which a plurality of refrigerant tubes 5 are passed, branch tubes 6a, 6b for forming a refrigerant circuit together with the tubes 5 and a four-way valve 7 as a refrigerant circuit switching means, wherein the number of passes of the refrigerant circuit at the time of evaporating is set to smaller than that of the refrigerant circuit at the time of condensing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat exchanger used in a heat pump air conditioner for both cooling and heating, and for exchanging heat between a refrigerant and a fluid such as air. The present invention relates to a heat exchanger for a heat pump air conditioner, which corresponds to a non-azeotropic mixed refrigerant recently proposed as a candidate for.

[0002]

2. Description of the Related Art In recent years, heat pump air conditioners are of a type in which a refrigerant circuit is switched between a cooling operation and a heating operation by a four-way valve, as disclosed in JP-A-5-256527 and JP-A-5-272828. In general, heat exchangers used in heat pump air conditioners have both outdoor heat exchangers and indoor heat exchangers with the refrigerant flowing in opposite directions in the same heat exchanger during cooling operation and heating operation. The configuration that flows through is common.

An outline of a conventional heat exchanger for a heat pump air conditioner will be described below with reference to the drawings.

FIG. 4 is a refrigerant circuit diagram of a conventional heat exchanger for heat pump air conditioner. In FIG. 4, 1 is a general heat exchange core composed of fins and a refrigerant pipe. Reference numeral 2 denotes a refrigerant pipe penetrating the inside of the heat exchange core 1, and the refrigerant pipes 2 are connected in a meandering manner to form a refrigerant circuit. 3a and 3b are branch pipes that branch or join the refrigerant circuit.
Thus, the refrigerant circuit in the heat exchange core 1 is branched into two paths of the refrigerant pipe 2c and the refrigerant pipe 2d.

The operation of the heat exchanger for heat pump air conditioner configured as described above will be described.

First, in the condensation process (the indoor heat exchanger during heating operation, the outdoor heat exchanger during cooling operation), the refrigerant is the refrigerant pipe 2
After flowing in from a and being divided into two paths in the branch pipe 3a, the refrigerant pipes 2c in the heat exchange core 1 and the refrigerant pipes 2d in the heat exchange core 1 indirectly exchange heat with the air flows flowing outside the refrigerant pipes 2 to be condensed. . The heat-exchanged refrigerants merge in the branch pipe 3b and flow out from the refrigerant pipe 2b.

Evaporation process (indoor heat exchanger during cooling operation,
In the outdoor heat exchanger during the heating operation), the refrigerant flows in from the refrigerant pipe 2b and is divided into two paths in the branch pipe 3b, and then the refrigerant pipe 2c in the heat exchange core 1 and the refrigerant pipe 2d in the refrigerant pipe 2d. It indirectly evaporates by exchanging heat with the air flow flowing outside. The heat-exchanged refrigerant merges in the branch pipe 3a and flows out to the refrigerant pipe 2a.

At this time, although the flow of the refrigerant is reversed in the condensation process and the evaporation process, the same refrigerant circuit is used,
The evaporation process and the condensation process naturally have the same number of passes. Regarding the number of passes, the smaller the number of passes of the refrigerant circuit, the higher the flow velocity of the refrigerant, so the heat transfer coefficient on the refrigerant side is improved,
At the same time, the pressure loss also increases. In a conventional heat pump air conditioner, a single component refrigerant such as HCFC22 has been used. With a single-component refrigerant, if the pressure is constant, the temperature is also constant. When the suction and discharge conditions of the compressor are constant,
When the pressure loss is increased, the average temperature of the refrigerant rises during the evaporation process, and the average temperature of the refrigerant decreases during the condensation process.
In both cases, the temperature difference with the airflow for heat exchange is reduced. Therefore, in the conventional heat pump heat exchanger, the pressure loss cannot be increased in both the evaporation process and the condensation process in order to obtain a large heat exchange amount.

[0009]

However, when a non-azeotropic mixed refrigerant, which has been recently proposed as a candidate for an alternative refrigerant for preventing ozone depletion, is used as a refrigerant for a heat exchanger for a conventional heat pump air conditioner, it is When the pressure loss is small, the temperature of the refrigerant rises as the refrigerant evaporates.
Therefore, if the temperature of the refrigerant at the outlet of the heat exchanger is about the same as that of the single-component refrigerant, the temperature of the refrigerant at the inlet of the heat exchanger will be extremely low, and the amount of frost will increase extremely in the indoor heat exchanger during heating operation. If the temperature at the inlet of the heat exchanger is set to the same level as that of the single-component refrigerant, on the contrary, the temperature at the outlet of the heat exchanger rises significantly, and the temperature difference with the airflow to be heat-exchanged becomes small. There was a problem that the amount decreased. If the pressure loss is increased, the temperature rise of the refrigerant due to evaporation can be suppressed and the above-mentioned problem can be solved. However, in the condensation process, the temperature of the refrigerant decreases as the refrigerant condenses. When the pressure loss is increased, the temperature of the refrigerant is significantly decreased, and the average temperature of the refrigerant is decreased, so that the temperature difference between the refrigerant and the airflow to be heat-exchanged is reduced and the heat exchange amount is decreased.

The present invention solves the above-mentioned conventional problems, and prevents a decrease in the average temperature difference between the refrigerant and the air flow, which occurs when a non-azeotropic mixed refrigerant is used as the refrigerant, in both the evaporation process and the condensation process, It is an object of the present invention to provide a heat exchanger for a heat pump air conditioner that obtains the same amount of heat exchange as when a single component refrigerant is used.

[0011]

In order to achieve this object, a heat exchanger for a heat pump air conditioner according to the present invention comprises a heat exchange core having a plurality of refrigerant tubes penetrating therethrough and a branch forming a refrigerant circuit together with the refrigerant tubes. It is composed of a pipe and a four-way valve as a refrigerant circuit switching means, and the number of passes of the refrigerant circuit in the evaporation process is smaller than the number of passes of the refrigerant circuit in the condensation process by switching the four-way valve.

[0012]

With this configuration, in the heat exchanger for a heat pump of the present invention, when a non-azeotropic mixed refrigerant is used as the refrigerant, the pressure loss of the refrigerant is increased in the evaporation process to increase the temperature of the refrigerant accompanying the evaporation. The temperature change of the refrigerant from the inlet to the outlet of the heat exchanger can be reduced, and the amount of frost on the heat exchanger inlet side in the indoor heat exchanger during heating operation can be extremely increased, In addition to preventing problems such as a decrease in the amount of heat exchange due to a rise in the refrigerant temperature on the outlet side of the exchanger, in the condensation process, pressure loss of the refrigerant is reduced to prevent an extreme temperature drop on the outlet side of the heat exchanger and It is possible to prevent the heat exchange amount from decreasing due to the decrease in the temperature difference.

[0013]

Embodiments of the heat exchanger for a heat pump according to the present invention will be described below with reference to the drawings.

FIG. 1 is a refrigerant circuit diagram of a heat exchanger for a heat pump according to an embodiment of the present invention. In FIG. 1, 4 is a general heat exchange core composed of fins and a refrigerant pipe.
Reference numeral 5 denotes a refrigerant pipe penetrating the inside of the heat exchange core 4, and the refrigerant pipes 5 are connected to each other to form a meandering refrigerant circuit. Reference numerals 6a and 6b are branch pipes that divide or join the refrigerant circuit. The branch pipe 6a connects the refrigerant pipe 5a to the refrigerant pipes 5c and 5f, and the branch pipe 6b connects the refrigerant pipe 5e to the refrigerant pipes 5c and 5d. It is branched. 7 is a four-way valve as a means for switching the refrigerant circuit. The four-way valve 7 has a refrigerant pipe 5b.
The refrigerant pipe 5d, the refrigerant pipe 5e, and the refrigerant pipe 5f are connected to each other.

With respect to the heat pump heat exchanger configured as described above, the operation when a non-azeotropic mixed refrigerant is used as the refrigerant will be described with reference to FIGS. 2 and 3.

FIG. 2 shows the refrigerant circuit during the condensation process.
In the condensation process, the four-way valve 7 connects the refrigerant pipe 5b and the refrigerant pipe 5e, and the refrigerant pipe 5d and the refrigerant pipe 5f, respectively. The refrigerant flowing from the refrigerant pipe 5a is first divided into the branch pipe 6
At a, it is branched into a refrigerant pipe 5c and a refrigerant pipe 5f. Refrigerant pipe 5
The refrigerant flowing through c is condensed while exchanging heat with the air flow in the heat exchange core 4. The refrigerant flowing through the refrigerant pipe 5f also obtains the four-way valve 7 and flows into the refrigerant pipe 5d, and is condensed while exchanging heat with the air flow in the heat exchange core 4. The refrigerants that have exchanged heat with the refrigerant pipes 5c and 5d merge in the branch pipes 6b, and then flow out from the refrigerant pipes 5b through the refrigerant pipes 5e and the four-way valve 7. Therefore, in the condensation process,
The refrigerant flows through the heat exchange core 4 in the same two passes as in the conventional case. Since the pressure loss of the refrigerant is small, the temperature drop of the refrigerant due to the condensation is small, and the average temperature difference between the heat exchange air flow and the refrigerant is large. Does not lower the heat exchange amount.

FIG. 3 shows the refrigerant circuit during the evaporation process.
In the evaporation process, the refrigerant pipe 5b and the refrigerant pipe 5d communicate with each other by the four-way valve 7, and the refrigerant pipe 5f and the refrigerant pipe e are sealed. In contrast to the condensation process, the refrigerant flowing from the refrigerant pipe 5b is
It flows into the refrigerant pipe 5d through the four-way valve 7 and evaporates while exchanging heat with the air flow in the heat exchange core 4. The refrigerant heat-exchanged in the refrigerant pipe 5d flows into the refrigerant pipe 5c through the branch pipe 6b, and is further evaporated while exchanging heat with the air flow in the heat exchange core 4. Refrigerant pipe 5
The refrigerant heat-exchanged in c flows out of the refrigerant pipe 5a through the branch pipe 6a. Therefore, in the evaporation process, the refrigerant flows through the heat exchange core 4 in one pass, which is less than in the condensation process,
Since the pressure loss of the refrigerant is large, the temperature rise of the refrigerant due to evaporation can be suppressed, and the amount of frost on the heat exchanger inlet side of the indoor heat exchanger during heating operation will extremely increase and the heat exchanger will also increase. It is possible to prevent a decrease in the amount of heat exchange due to a rise in the refrigerant temperature on the outlet side.

As described above, in the heat pump heat exchanger of this embodiment, the heat exchange core 1 having the plurality of refrigerant tubes 5 penetrating the inside thereof, and the branch tube 6 forming the refrigerant circuit together with the refrigerant tubes 5.
a and 6b and a four-way valve 7 as a refrigerant circuit switching means, and by switching the four-way valve 7, the number of passes of the refrigerant circuit in the evaporation process is made smaller than the number of passes of the refrigerant circuit in the condensation process. Since the pressure loss of the refrigerant is large, the temperature rise of the refrigerant due to evaporation can be suppressed, and the amount of frost on the heat exchanger inlet side in the indoor heat exchanger during heating operation can be extremely increased, It is possible to prevent a decrease in the heat exchange amount due to a rise in the refrigerant temperature on the outlet side of the exchanger. At the same time, in the condensation process, since the pressure loss of the refrigerant is small, the temperature drop of the refrigerant due to the condensation is small, and the average temperature difference with the airflow to be heat-exchanged is large, and the heat exchange amount is not reduced even in the condensation process. .

[0019]

As described above, the present invention comprises a heat exchange core having a plurality of refrigerant pipes penetrating therethrough, a branch pipe forming a refrigerant circuit together with the refrigerant pipes, and a four-way valve as a refrigerant circuit switching means. By switching the four-way valve as the refrigerant switching means, by making the number of passes of the refrigerant circuit in the evaporation process smaller than the number of passes of the refrigerant circuit in the condensation process, in the evaporation process, because the pressure loss of the refrigerant is large, It is possible to suppress the temperature rise of the refrigerant due to evaporation, and with the extreme increase in the amount of frost on the heat exchanger inlet side in the indoor heat exchanger during heating operation, and the rise in the refrigerant temperature on the heat exchanger outlet side. It is possible to prevent a decrease in heat exchange amount. At the same time, in the condensation process, since the pressure loss of the refrigerant is small, the temperature drop of the refrigerant due to the condensation is small, and the average temperature difference with the airflow to be heat-exchanged is large, and the heat exchange amount is not reduced even in the condensation process. .

[Brief description of drawings]

FIG. 1 is a refrigerant circuit diagram of an embodiment of a heat exchanger for heat pump according to the present invention.

FIG. 2 is a refrigerant circuit diagram showing a refrigerant flow in a condensation process in the embodiment.

FIG. 3 is a refrigerant circuit diagram showing a refrigerant flow in a condensation process in the embodiment.

FIG. 4 is a refrigerant circuit diagram of a conventional heat exchanger for heat pump.

[Explanation of symbols] 4 heat exchange core 5 refrigerant pipes 6a, 6b branch pipe 7 four-way valve

Claims (1)

[Claims] 1. A heat exchange core having a plurality of refrigerant pipes penetrating the inside thereof, a branch pipe forming a refrigerant circuit together with the refrigerant pipes, and a four-way valve as a refrigerant circuit switching means. A heat exchanger for a heat pump air conditioner in which the number of passes of the refrigerant circuit in the process is smaller than the number of passes of the refrigerant circuit in the condensation process.