JPH07318276A - Evaporator with fins - Google Patents

Abstract

PURPOSE:To prevent the decrease of the heat transfer coefficient of refrigerant side and to obtain suitable heat exchanging rate by increasing the pitch of fins in which a heat transfer tube in which the refrigerant component having low boiling point of refrigerant flows is passed larger than that of fins in which a heat transfer tube in which the refrigerant component having high boiling point of the refrigerant flows is passed. CONSTITUTION:Air current is indirectly heat exchanged with refrigerant via fins 6a, 6b and heat transfer tubes 7a, 7b. In this case, since single-component refrigerant flows through the channels 9a, 9b in the tubes 7a, 7b, the heat transfer coefficient of refrigerant side can be raised than that of refrigerant which flows to an evaporator with fins flows through the channels 9a, 9b, thereby preventing the decrease of the heat transfer coefficient of the refrigerant side. Further, the pitch of the fins 6b in which the tube 7b in which refrigerant having low boiling point flows is passed is increased larger than that of the fins 6a in which the tubes 7a in which refrigerant having high boiling point is passed. Thus, the decrease of the flow rate of the air current of the part in which the refrigerant having the low boiling point flows and water droplets, frost are easily adhered is suppressed to the same degree as that of the refrigerant having the high boiling point in which water droplets are hardly adhered to suppress the decrease of its heat exchanging rate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to an air conditioner, a refrigerating machine,
The present invention relates to a finned evaporator that transfers heat between a phase-changeable refrigerant such as automobile equipment and a fluid such as air. Especially, it is a non-azeotropic mixed refrigerant that has been recently proposed as a candidate for an alternative refrigerant that prevents ozone layer destruction. It relates to a corresponding finned evaporator.

[0002]

2. Description of the Related Art Recently, finned evaporators have been required to be compact in view of equipment design. For example, slits or louvers are provided on the fin surface, or grooves or cavities are provided on the inner surface of the heat transfer tube. In addition, the size and efficiency of the heat transfer tubes have been greatly reduced by devising measures such as making the heat transfer tubes thinner. As a conventional finned evaporator, the paper "Small and high efficiency heat exchanger (Na
tional Technical Report Vol.35 No.6 Dec. 1989 P7
The shape shown in 1) is common.

An outline of a conventional finned evaporator will be described below with reference to the drawings. FIG. 2 is a front view of a conventional finned evaporator. In FIG. 2, 1 is a fin that is arranged in parallel at regular intervals, and 2 is a heat transfer tube that penetrates the fin 1 and that is provided in a plurality of stages in the vertical direction. Reference numeral 3 denotes a flow divider, which is connected to an inlet side of a refrigerant flow passage 4 formed by connecting the heat transfer tubes 2. The flow divider 4 divides the flow passage 4 into a flow passage 4a and a flow passage 4b.
Has been branched into. Further, 5 is a confluencer that joins the branched flow paths 4a and 4b.

In the finned evaporator having the above-described structure, the airflow flows between the fins 1 and the fins 1 and the outer surfaces of the heat transfer tubes 2 exchange heat with the airflow. After the flow is divided by 3, the flow path 4a and the flow path 4b in the heat transfer tube 2 flow, and the refrigerant and the inner surface of the heat transfer tube 2 exchange heat.

As a result, the air flow and the refrigerant indirectly exchange heat via the fins 1 and the heat transfer tubes 2. At this time, the heat transfer coefficient on the air flow side is considerably smaller than the heat transfer coefficient on the refrigerant side. Therefore, on the air flow side, the fins 1 increase the heat transfer area to reduce the heat resistance.

[0006]

However, when a non-azeotropic mixed refrigerant, which has recently been proposed as a candidate for an alternative refrigerant for preventing ozone depletion, is used as the refrigerant for a conventional finned evaporator, the heat transfer coefficient on the refrigerant side is increased. Is significantly lower than the heat transfer coefficient of the single-component refrigerant, and as a result, the amount of heat exchange between the refrigerant and the air flow is reduced.

In the finned evaporator described above, the fin surface is mostly used at a temperature below the dew point of the air flow, and in some cases, the fin surface is used at a negative temperature.

Under these conditions, water drops and frost adhere to the fin surface, so that the pressure loss gradually increases and the flow rate of the air flow decreases, which also causes a problem that the heat exchange amount decreases. Was.

The present invention solves the above-mentioned conventional problems. Even when a non-azeotropic mixed refrigerant is used as the refrigerant, it prevents the reduction of the heat transfer coefficient on the refrigerant side and is equivalent to the case where a single component refrigerant is used. An object of the present invention is to provide a fin-equipped evaporator in which the amount of heat exchange is obtained and the degree of decrease in the amount of heat exchange due to water droplets or frost adhering to the fin surface is small.

[0010]

In order to achieve this object, the finned evaporator of the present invention is provided with a non-coordinator such as a packing tower at the inlet side of a refrigerant flow path formed by connecting heat transfer tubes to each other. A plurality of non-azeotropic mixed refrigerants having different composition ratios, preferably a single-component refrigerant separator, is provided with a refrigerant separator, and a heat transfer tube through which a low-boiling-point refrigerant flows. The pitch of the fins is made larger than the pitch of the fins through which the heat transfer tubes through which the high boiling point refrigerant flows.

Further, the heat transfer tube through which the high boiling point component refrigerant flows is located above the heat transfer tube through which the low boiling point component refrigerant flows.

[0012]

With this structure, the finned evaporator of the present invention is a non-azeotropic mixed refrigerant having a composition ratio closer to that of a single-component refrigerant than the non-azeotropic mixed refrigerant flowing into the finned evaporator, preferably a single-component refrigerant. Since the refrigerant can flow in the flow path in the heat transfer tube, the heat transfer coefficient on the refrigerant side can be made higher than that of the non-azeotropic mixed refrigerant flowing into the finned evaporator with the same composition as that in the flow path. It is possible to prevent the heat exchange amount of the finned evaporator from decreasing.

Further, by making the pitch of the fins through which the heat transfer tubes through which the low boiling point component refrigerant flows penetrate larger than the pitch of the fins through which the heat transfer tubes through which the high boiling point component refrigerant flows passes, water droplets and frost are likely to adhere. Since the flow rate of the air flow in the part where the low boiling point component refrigerant flows can be suppressed to the same level as in the part where the high boiling point component refrigerant where the water droplets or frost does not easily adhere can be suppressed, the amount of heat exchange due to the attachment of water drops or frost Can be suppressed.

Further, by arranging the heat transfer tube through which the high boiling point component refrigerant flows above the heat transfer tube through which the low boiling point component refrigerant flows, the heat transfer tube through which the low boiling point component refrigerant flows is formed on the surface of the fin. When a large amount of water droplets flow down due to the effect of gravity, they do not hinder the heat transfer on the surface of the high boiling point component refrigerant, without hindering the heat transfer on the surface of the fins through which the heat transfer tubes through which the high boiling point component refrigerant flows. Since this also does not occur, this also makes it possible to suppress the decrease in the heat exchange amount.

[0015]

Embodiments of the finned evaporator according to the present invention will be described below with reference to the drawings.

FIG. 1 is a front view of a finned evaporator according to an embodiment of the present invention. In FIG. 1, 6a and 6b are fins arranged in parallel at regular intervals, and the fin pitch of the upper fin 6a is smaller than the fin pitch of the lower fin 6b in the direction of gravity.

Reference numerals 7a and 7b denote heat transfer tubes penetrating the fins 6a and 6b. The heat transfer tube 7a penetrates the upper fin 6a and the heat transfer tube 7b penetrates the lower fin 6b to be thermally coupled. .

Reference numeral 8 is a refrigerant separator having a function of separating a non-azeotropic mixed refrigerant such as a packed tower into a plurality of non-azeotropic mixed refrigerants having different composition ratios, preferably a single component refrigerant.
a, 7b are connected to the inlet side of the refrigerant channel 9 formed by connecting them, and the refrigerant having a high boiling point component among the refrigerants separated by the refrigerant separator 8 is in the upper channel 9a and the low boiling point component. The refrigerant is branched into the lower channel 9b. Further, 10 is a confluencer that joins the branched flow passages 9a and 9b.

The operation of the finned evaporator constructed as described above when a non-azeotropic mixed refrigerant is used as the refrigerant will be described. The airflow flows between the fins 6a and 6b,
At the same time that the fins 6a, 6b and the outer surfaces of the heat transfer tubes 7a, 7b exchange heat with the airflow, the refrigerant is separated into a refrigerant having a composition ratio close to that of a single component, preferably a single component refrigerant, by a refrigerant distributor 8. After that, of the separated refrigerants, the high boiling point component refrigerant flows in the channel 9a inside the upper heat transfer tube 7a, and the low boiling point component refrigerant flows in the channel 9b inside the lower heat transfer tube 7b. Then, heat is exchanged with the inner surfaces of the heat transfer tubes 7a and 7b.

As a result, the fins 6a, 6b and the heat transfer tube 7
The airflow and the refrigerant indirectly exchange heat via a and 7b.

At this time, a refrigerant having a composition ratio close to that of a single-component refrigerant, preferably a single-component refrigerant, flows through the flow passages 9a and 9b in the heat transfer tubes 7a and 7b, so that the refrigerant flows into the finned evaporator. The heat transfer coefficient on the refrigerant side can be made higher than that flowing through the flow paths 9a and 9b, and the decrease in the heat transfer coefficient on the refrigerant side due to the use of the non-azeotropic mixed refrigerant as the refrigerant can be prevented.

Further, the heat transfer tube 7 through which the refrigerant having a low boiling point flows.
By making the pitch of the fins 6b through which the b penetrates larger than the pitch of the fins 6a through which the heat transfer tubes 7a through which the refrigerant of the high boiling point component flows, the air flow of the portion through which the refrigerant of the low boiling point component where water droplets or frost easily attach flows Since the decrease in the flow rate can be suppressed to the same extent as the portion in which the high boiling point component refrigerant in which water drops or frost hardly adheres can be suppressed, it is possible to suppress the decrease in the heat exchange amount due to the adhesion of water drops or frost.

Further, the heat transfer tube 7 through which the refrigerant having a high boiling point flows.
Since a is located above the heat transfer tube 7b through which the low boiling point refrigerant flows, a large amount of water droplets generated on the surface of the fin 6b through which the heat transfer tube 7b through which the low boiling point refrigerant flows penetrates due to gravity. When flowing down, the heat transfer on the surface of the fins 6a through which the heat transfer tubes 7a through which the high boiling point component refrigerant flows does not hinder the heat transfer on the high boiling point component refrigerant side. Also, the reduction of the heat exchange amount can be suppressed.

As described above, in the finned evaporator of this embodiment, a non-azeotropic mixed refrigerant such as a packing tower is provided at the inlet side of the refrigerant passage 9 formed by connecting the heat transfer tubes 7a and 7b. A fin 6b provided with a refrigerant separator 8 having a function of separating into a plurality of non-azeotropic mixed refrigerants having different composition ratios, preferably a single component refrigerant, and through which a heat transfer pipe 7b through which a refrigerant having a low boiling point component flows is penetrated. By making the pitch of the fins larger than the pitch of the fins 6a through which the heat transfer tubes 7a through which the high boiling point component refrigerant flows, the refrigerant having a composition ratio closer to that of the single component refrigerant than the refrigerant flowing into the finned evaporator, desirably, Since the single-component refrigerant can flow through the flow passages 9a and 9b in the heat transfer tubes 7a and 7b, the refrigerant flowing into the finned evaporator has the same composition as that of the flow passages 9a and 9b. High heat transfer rate It is possible to prevent the decrease of the heat exchange amount of the evaporator with fins, and to reduce the flow rate of the air flow in the portion where the refrigerant of the low boiling point component where water droplets and frost easily adhere is attached to water droplets and frost. Because it can be suppressed to the same level as the part where the refrigerant of the high boiling point component is difficult to flow,
It is possible to suppress a decrease in heat exchange amount due to adhesion of water drops or frost.

Further, the heat transfer tube 7 through which the high boiling point component refrigerant flows.
Since a is located above the heat transfer tube 7b through which the low boiling point component refrigerant flows, a large amount of water droplets generated on the surface of the fin 6b through which the heat transfer tube 7b through which the low boiling point component refrigerant flows penetrates due to gravity. When flowing down, the heat transfer on the surface of the fins 6a through which the heat transfer tubes 7a through which the high boiling point component refrigerant flows does not hinder the heat transfer on the high boiling point component refrigerant side. Also, the reduction of the heat exchange amount can be suppressed.

[0026]

As described above, according to the present invention, a plurality of non-azeotropic mixed refrigerants having different composition ratios, such as a packed tower, are provided at the inlet side of the refrigerant passage formed by connecting the heat transfer tubes. An azeotropic mixed refrigerant, preferably a refrigerant separator having a function of separating into a single-component refrigerant, in which a refrigerant having a high boiling point flows through a pitch of fins through which a heat transfer tube through which a refrigerant having a low boiling point flows By making the pitch of the fins through which the heat transfer tube penetrates, the refrigerant having a composition ratio closer to that of the single-component refrigerant than the refrigerant flowing into the finned evaporator, preferably the single-component refrigerant is used as a flow path in the heat transfer tube. Since it can flow, the refrigerant flowing into the finned evaporator can have a higher heat transfer coefficient on the refrigerant side than the refrigerant having the same composition as that in the flow path, and prevents a decrease in the heat exchange amount of the finned evaporator. While being able to Since it is possible to suppress the decrease in the flow rate of the air flow in the portion where the refrigerant of the low boiling point component where the droplets or frost easily adheres flows to the same level as the portion where the refrigerant of the high boiling point component where the water droplets or frost hardly adheres flows, It is possible to suppress a decrease in heat exchange amount due to adhesion of frost.

Further, since the heat transfer tube through which the high boiling point component refrigerant flows is located above the heat transfer tube through which the low boiling point component refrigerant flows, the heat transfer tube through which the low boiling point component refrigerant flows is formed on the surface of the fin. When a large amount of water droplets flow down due to the effect of gravity, they do not hinder the heat transfer on the surface of the high boiling point component refrigerant, without hindering the heat transfer on the surface of the fins through which the heat transfer tubes through which the high boiling point component refrigerant flows. Since this also does not occur, this also makes it possible to suppress the decrease in the heat exchange amount.

[Brief description of drawings]

FIG. 1 is a front view of an embodiment of a finned evaporator according to the present invention.

FIG. 2 is a front view of a conventional finned evaporator.

[Explanation of symbols]

 6a, 6b Fins 7a, 7b Heat transfer tube 8 Refrigerant separator 9, 9a, 9b Flow path

Claims (2)

[Claims] 1. Fins that are arranged in parallel at regular intervals and through which gas flows between them, heat transfer tubes that penetrate the fins and through which a refrigerant flows, and the heat transfer tubes are connected to each other. On the inlet side of the flow path of the refrigerant, a plurality of non-azeotropic mixed refrigerants having different composition ratios, such as a non-azeotropic mixed refrigerant such as a packing tower, preferably a refrigerant separator having a function of separating into a single component refrigerant, Further, a finned evaporator in which a pitch of fins through which a heat transfer tube through which a refrigerant having a low boiling point component flows is made larger than a pitch of fins through which a heat transfer tube through which a refrigerant having a high boiling point component flows passes. 2. The finned evaporator according to claim 1, wherein the heat transfer tube through which the high boiling point component refrigerant flows is located above the heat transfer tube through which the low boiling point component refrigerant flows.