JPS61114091A - Finned heat exchanger - Google Patents

Abstract

PURPOSE:To improve the heat transfer performance by a method wherein the dead water regions of heat transfer pipes and the thicknesses of boundary layers on fins are reduced in the finned heat exchanger such as the outdoor heat exchanger of a heat pump type air conditioner or the like. CONSTITUTION:The titled finned heat exchanger is provided with fins 8 and 9, which are arranged in and parallel to the incoming air flow 11 and at the upstream side ends of each of which concavities 12 and convexities 13 are alternately arranged, and a plurality of heat transfer pipes 7, which are inserted in the fins 8 and 9 and arranged normal to the air flow 11. A group of a plurality of upstream side upright walls 15a-15c and that of downstream side upright walls 16a and 16b, both groups of which are respectively located on the upstream side and downstream side of the air flow 11 under the state that the line connecting the centers of the heat transfer pipes 7 forms the boundary line between the upstream side and the downstream side of the fin and respectively inclined to the direction of the incoming air flow, are provided onto the fins 8 and 9. In addition, a plurality of the fins 8 and 9 are arranged so that the concavities 12 and convexities 13 at the upstream side end of the fins 8 and 9 are alternately positioned in the direction of the axis of the heat transfer pipe.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a finned heat exchanger used as an outdoor heat exchanger in a heat pump type air conditioner or the like that uses air as a heat source.

Conventional configuration and its problems During heating or hot water supply operation of a heat pump air conditioner that uses air as a heat source, the outdoor heat exchanger functions as an evaporator, and when the ambient air temperature drops, the evaporation temperature drops below 0°C. However, water vapor in the air adheres as frost and forms a frost layer. In this case, a frost layer is likely to be formed at the upstream end of the airflow where the absolute humidity difference between the ambient air and the saturated humid air corresponding to the heat exchanger heat transfer surface temperature is greatest. Defrosting is necessary because the amount of heat exchange is significantly reduced due to the reduction in the passing wind and the insulation effect caused by this frost layer.

FIG. 1 shows a front view of the fins of a conventional heat exchanger. As shown in FIG. 1, fins 2.3 are vertically inserted alternately at predetermined intervals into a plurality of heat transfer tubes 1 through which a fluid for heat exchange with air flows.

Air flows between them in the four directions of arrows to perform heat exchange. The fins 2 and 3 are cut out so that the upstream ends of the fins have concave portions 6 and convex portions 6 alternately in the direction perpendicular to the air flow, that is, in the step direction. Because of this configuration, as is clear from the cross-sectional views of the n and n+1 stages of the heat exchanger tube 1 shown in FIGS. Since the interval between the airflow upstream ends of the fins 2.3 arranged in the axial direction is widened, the operation time can be extended until the space between the fins is blocked by the frost layer 7 during frost formation and defrosting is required. . However, since the fins 2 and 3 are notched, the heat transfer area is reduced and the amount of heat exchange is reduced. In addition, in order to prevent a decrease in the amount of heat exchange, it is possible to promote heat transfer by providing slits with raised slits on the fins, but the promotion of heat transfer by slits with raised slits is due to the boundary layer leading edge effect. Because of this, material transfer at the raised part of the slit is promoted and a frost layer is formed.
Not only does it not have the effect of promoting heat transfer, but it also has the disadvantage that this portion becomes clogged in a short period of time, reducing the amount of air passing through it and significantly reducing the amount of heat exchanged in a short period of time.

OBJECTS OF THE INVENTION An object of the present invention is to eliminate the above-mentioned conventional drawbacks and provide a finned heat exchanger with good heat transfer performance.

Structure of the Invention In order to achieve the above object, the finned heat exchanger of the present invention has the following features:
1. A plurality of fins arranged in parallel, through which gas flows, and a plurality of heat transfer tubes inserted into the plurality of fins and arranged in a direction perpendicular to the air flow.1. The fins are provided with concave portions and convex portions alternately at the end on the upstream side of the airflow, and with a line connecting the centers of the plurality of heat transfer tubes as the boundary, a plurality of fins are provided on the upstream side of the airflow and the downstream side of the airflow, respectively, and are inclined with respect to the airflow direction. A downstream vertical wall and a downstream vertical wall are provided, and a plurality of fins are arranged such that concave portions and convex portions at the upstream end of the fins are alternately located in the axial direction of the heat exchanger tube.
-Description of one embodiment Hereinafter, a finned heat exchanger according to one embodiment of the present invention will be explained with reference to the drawings. FIGS. 3a and 3b are front views of a finned heat exchanger according to an embodiment of the present invention.

Reference numeral 7 indicates a plurality of heat transfer tubes through which a fluid for exchanging heat with the air flows, fins 8 and 9 are alternately arranged in parallel at predetermined intervals, and a plurality of holes 1o provided in the fins 8 and 9 are provided.
Heat exchanger tubes 7 are inserted into the air, and the plurality of heat exchanger tubes 7 are arranged in a direction perpendicular to the airflow. Multiple fins8. An air current generated by a blower (not shown) flows between -9 in the direction of arrow 11. The ends of the fins 8 and 9 on the upstream side of the airflow are cut out so as to have recesses 12 and protrusions 13 alternately in a direction perpendicular to the airflow. Further, the downstream end of the airflow is cut out so that the convex part 13 corresponds to the concave part 12 at the upstream end of the airflow, and the concave part 12 corresponds to the convex part 13, respectively.

Further, on the upstream side of the airflow, with a line connecting the centers of the plurality of holes 1o, that is, a line 14 connecting the centers of the plurality of heat exchanger tubes 7 as a boundary, there are a plurality of upstream vertical walls 151L to 150 inclined with respect to the airflow flow direction 11. Further, on the downstream side of the airflow, there are provided downstream vertical walls 161L and 18b which are inclined in a direction opposite to the upstream vertical walls 151L to 150 with respect to the airflow flow direction 11. Also, the upstream standing wall 16 & ~ 150 and the downstream standing wall 1'6
a and 16b are provided asymmetrically with respect to the line 14.

Next, Fig. 4 a and b show n and n+1 of the heat exchanger tube 7, respectively.
This is a diagram of the cross section at the step viewed from above, and the fins 8,
9 into a plurality of heat transfer tubes 7, the upstream end of the airflow is arranged such that long fins and short fins are lined up in the tube axis direction at each stage.

The fluid flowing through the plurality of heat transfer tubes 7 exchanges heat with the air flow via the heat transfer tubes 7 and the fins 8.9. 17 is a frost layer.

This configuration has the following functions and effects. When the finned heat exchanger of this embodiment acts as a condenser, the airflow colliding with the upstream vertical walls 16 & ~ 15 OK is transferred to the heat exchanger tubes 7 due to the inclination of the upstream vertical walls 15 & ~ 150.
This results in an airflow 18 that is deflected in the direction.

Therefore, the dead area generated at the trailing edge of the heat transfer tube due to the airflow 18 is greatly reduced compared to the dead area of conventional fins. Therefore, heat transfer performance is improved. Next, the airflow condition at the fins 8.9 is shown in FIG. The airflow 19 that has passed over the upstream standing wall 15b is deflected in the direction of adhering to the fins 8 and 9 again, and then the upstream standing wall 15b.

By interfering with the airflow 2o passing between the airflows 21 and 150, airflows 21 and 22 having swirling components are generated. And the upstream side standing wall 15&~150 and the downstream side standing wall 16&.

16b is provided so as to be asymmetrical with respect to the line 14, so the airflow 21.22 collides with the downstream vertical wall 162L and is deflected, and also the upstream vertical wall 151L.

The airflow 2 with a very strong swirling component interferes with the airflow 23 that has passed between the space 15b and the downstream vertical wall 16&.
Generate 4.25. The airflow having such a strong swirling component disturbs the boundary layer on the fins 8 and 9 and reduces the thickness of the boundary layer, so that the heat transfer coefficient is significantly improved.

Next, when the finned heat exchanger of this embodiment acts as an evaporator, the airflow inlet end of the finned heat exchanger has a wider fin spacing in the tube axis direction for each stage, so that when frost forms, The space between the fins is blocked by the frost layer 17, and the operating time until defrosting becomes necessary becomes significantly longer. Also upstream side standing wall 16&~15
The heat transfer promotion by the 0 and downstream vertical walls 16a and 16b is not due to the boundary layer leading edge effect as described above;
This is due to the effect of reducing the dead area due to the deflection airflow and reducing the boundary layer thickness of the fin due to the airflow with a swirling component, so the effect of promoting heat transfer without forming a frost layer on the vertical wall itself and blocking it. Heat transfer performance is significantly improved without sacrificing performance.

Furthermore, if the number of stages of the heat exchanger tubes is an odd number, the fins 9 of this embodiment are the fins 8 upside down, so the fins 8. When manufacturing Q, material collection can be done efficiently and the amount of leftover material can be minimized. Or if the number of stages is even,
A similar effect can be obtained by notching the airflow upstream end so that a concave portion corresponds to a concave portion and a convex portion corresponds to a convex portion.

In addition, as an embodiment of the present invention, the fins are cut and raised.
11 and a standing wall was provided, but it goes without saying that the same effect can be obtained by providing a standing wall using other processing methods.

Effects of the Invention As described above, the finned heat exchanger of the present invention has a fin that is placed in a flowing airflow, and has fins that are alternately provided with concave portions and convex portions at the upstream end of the airflow, and a fin that is inserted into the fin and is placed in a flowing airflow. Equipped with a plurality of heat exchanger tubes arranged in the vertical direction, the fins have a line connecting the centers of the plurality of heat exchanger tubes as a boundary, and an airflow upstream side and an airflow downstream side.

A plurality of upstream and downstream vertical walls are provided, each inclined with respect to the air flow direction, and a plurality of fins are arranged so that concave portions and convex portions are alternately located in the axial direction of the heat exchanger tube. This has the effect of reducing the dead zone in the flow section and further reducing the thickness of the boundary layer on the fins, significantly improving heat transfer performance. Since it is wider, the operating time until defrosting becomes necessary due to the frost layer blocking the space between the fins during frost formation can be significantly lengthened. Furthermore, the promotion of heat transfer by standing walls is not due to the leading edge effect of the boundary layer, but is due to the reduction of the dead area and the thickness of the boundary layer, so that the standing walls themselves are not blocked by the formation of a frost layer. Heat transfer performance is significantly improved without impairing the effect of promoting heat transfer.

[Brief explanation of the drawing]

Figures 1a and b are front views of the fins of a conventional finned heat exchanger, Figures 2a and b are horizontal sectional views of the same finned heat exchanger, and Figures 3a and b are one embodiment of the present invention. FIGS. 4A and 4B are horizontal sectional views of the finned heat exchanger, and FIG. 6 is a perspective view of the main parts thereof. 7... Heat exchanger tube, 8, 9... Fin, 1
2...Concave portion, 13...Convex portion, 16&~
15C...Upstream standing wall, 152L, 15b...
...Downstream standing wall. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure (α) 66 No. 2 (Q) (b) No. 3 ((1) 'b No. 5c

Claims (2)

[Claims] (1) A plurality of fins arranged in parallel, through which gas flows, and a plurality of heat transfer tubes inserted into these fins and arranged perpendicularly to the airflow; a plurality of upstream vertical walls that are provided with concave portions and convex portions alternately on the side end portions, and that are inclined with respect to the air flow direction on the air flow upstream side and the air flow downstream side, respectively, with a line connecting the centers of the plurality of heat exchanger tubes as the boundary; A finned heat exchanger in which a downstream vertical wall is provided and a plurality of fins are arranged such that concave portions and convex portions at the airflow upstream end of the fins are alternately located in the axial direction of the heat transfer tube. (2) The finned heat exchanger according to claim 1, wherein the upstream vertical wall and the downstream vertical wall are respectively inclined in opposite directions with respect to the air flow direction.