JPS63254396A - Finned heat exchanger - Google Patents

Abstract

PURPOSE:To completely divide growth of a temperature boundary layer and to enable maintenance of a heat transfer rate between an air flow and a fin at a high value, by a method wherein a cut-rise surface extending in parallel to the direction of an air flow is formed in a fin surface, and the height of the cut rise is changed in a stepped manner to form a meandering pattern. CONSTITUTION:Fins 5 are fixed in a corrugated manner to a heat transfer pipe 4 at intervals of a fin pitch. Cut rise surfaces 6 formed on both surfaces of the fin 5 are formed so as to extend in parallel to the direction of an air flow B. The height of the cut-rise surface 6 from the fin 5 is set to values in two stages of the one being 1/5 of a fin pitch and the other being 2/5 of the fin pitch. The cut-rise surface 6 in a five-stage is changed by 1/5 of a fin pitch at each stage to form a meandering pattern. Since, during heat exchange, an air flow B flows a flow passage where increase and decrease in a distance between the fins are repeated, a pressure difference is produced between both surfaces of the fin 5, and by dividing growth of the temperature boundary layer of the air flow B generated on the cut-rise surface 6, a heat transfer rate can be maintained at a high value.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a finned heat exchanger used in air conditioning equipment, refrigeration equipment, etc.

BACKGROUND OF THE INVENTION In recent years, the performance of finned heat exchangers has improved markedly, and finned heat exchangers equipped with corrugated fins characterized by a large heat transfer area on the air side have already been put into practical use.

Hereinafter, the conventional finned heat exchanger mentioned above will be explained with reference to the drawings.

FIG. 4 shows a schematic shape of a finned heat exchanger according to the present invention, and FIGS. 5 and 6 show fin shapes of a conventional finned heat exchanger. In Figures 4 to 6,
Reference numeral 1 denotes a flat heat exchanger tube bent in a meandering manner, with straight tube portions 1' substantially parallel to each other. Fins 2 are provided between the opposing straight pipe portions 1' of the heat exchanger tube 1, and are fixed to the heat exchanger tube 1 in a wave shape with a fin pitch Pa at a constant interval. 3
is a cut-and-raised surface provided on the surface of the fin 2 parallel to the air inflow direction, which is cut and raised continuously from both sides of the fin 2 in the air inflow direction alternately up and down with a width Wa, and is provided on the surface of the fin 2 with a width Wa. They are all formed in the same direction with the same cut-and-raise pattern.

The operation of the finned heat exchanger constructed as above will be described below with reference to FIGS. 4 to 7.

Heat exchange is performed between the airflow A flowing between the fins of the fins 2 and the heat medium flowing inside the heat exchanger tube 1 via the fins 2 and the heat exchanger tube 1. At that time, a cut and raised surface 3 is provided on the surface of the fin 2, and the temperature boundary Ja of the airflow A generated on the surface of the fin 2 because the fin 2 is divided in the air inflow direction.
This suppresses the development of fins 2 and improves the heat transfer coefficient between the airflow A and the fins 2.

Problems to be Solved by the Invention However, in the above configuration, as shown in FIG.
The temperature boundary layer a traces its tail to the cut-and-raised surface 3 on the downstream side and is not divided, and the temperature boundary layer a gradually develops as it goes downstream. The problem was that the heat transfer coefficient decreased.

The present invention addresses the above problems and maintains a high heat transfer coefficient with the airflow throughout the entire area from the upstream fins to the downstream fins,
The present invention provides a finned heat exchanger with excellent heat exchange performance.

Means for Solving the Problems In order to solve the above-mentioned problems, the finned heat exchanger of the present invention has a cut-and-raised surface parallel to the direction of the airflow passing between the fins, which is continuously cut from the fin surface in the direction of the airflow. The cut-and-raised height of the cut-and-raised surface from the fin surface is changed stepwise in multiple steps in the airflow direction to meander, and the distance between the fins is expanded/reduced in the airflow direction. : It is equipped with a configuration in which a reversible fin flow path is provided.

Effect The present invention has the above-described configuration, and since the inter-fin flow path repeatedly expands and contracts, a pressure difference is generated on both sides of the fins when the airflow passes between the fins. A part of the airflow is condensed and flows into the gap between the surfaces, and this condensed flow completely disrupts the development of the temperature boundary layer of the airflow that occurs on the surface of the cut-up surface, and the gap between the airflow and the fins. This means that the heat transfer coefficient can be maintained extremely high.

EXAMPLE Hereinafter, a finned heat exchanger according to an example of the present invention will be described with reference to the drawings.

FIG. 1 and FIG. 2 show the fin shape of a finned heat exchanger in an embodiment of the present invention.

In FIGS. 1 and 2, reference numeral 4 denotes a heat transfer tube, which has the same structure as the conventional example, and includes a straight tube portion 4'.

Fins 5 are provided between the straight pipe portions 4' of the heat exchanger tube 4, and are fixed to the heat exchanger tube 4 in a wave shape at constant fin pitch b intervals. 6 is a cut-and-raised surface provided on both sides of the fins 5, and f! : It is cut and raised from the surface of the fin 5 with a width wb so as to be parallel to the flowing air IB direction, and the cut and raised heights hl and h2 of the cut and raised surface 6 from the fin 5 are respectively 5 of the fin pitch pb on both sides. The cut-and-raised surface 6 is formed in two steps of 1/5 and 2/5, and the 5-step cut-and-raised surface 6 including the remaining fins 5' without being cut and raised is 1/5 of the fin pitch pb.
A serpentine pattern shown by a polygonal line m is formed while changing the dimensions of .

In addition, the arrangement pattern of the cut and raised surfaces 6 is arranged to be symmetrical across the inter-fin center line n between the adjacent fins 5, and the distance between the fins with the adjacent fins repeats expansion and contraction. This forms a flow path.

The operation of the finned heat exchanger configured as above will be explained below with reference to FIGS. 1 to 3.

Heat exchange is performed between the airflow B flowing between the fins of the fins 5 and the heat medium flowing within the heat exchanger tubes 4 via the fins 5 and the heat exchanger tubes 4. At this time, since the airflow B flows through the inter-fin flow path in which the distance between the fins has been repeatedly expanded and contracted, a pressure difference is generated on both sides of the fins 5, and this pressure difference causes the cut-and-raised surfaces 6 to be arranged in a step-like manner. A part of the airflow B flows into the gap S between them in a contracted flow, and this contracted flow completely interrupts the development of the temperature boundary layer of the airflow B generated on the surface of the cut and raised surface 6. , heat transfer between fin 5 and airflow B! f can be maintained extremely high.

In addition, since the gaps S between the cut and raised surfaces 6 are all formed to have the same size, and the flow paths between the fins are also symmetrical in the direction of the airflow B, the air condenses uniformly in every gap S. Which cut-and-raised surface 6
Almost uniform heat transfer coefficient can also be obtained.

Effects of the Invention As described above, the present invention provides a cut-and-raised surface that is parallel to the direction of airflow passing between the fins and is continuously cut and raised from the fin surface in the airflow direction, and that the cut-and-raised surface is cut and raised from the fin surface. By creating an inter-fin flow path in which the height is changed stepwise in multiple steps in the airflow direction and the distance between the fins is repeatedly expanded and contracted in the airflow direction, the fins and airflow are connected from upstream to downstream. It is possible to obtain a finned heat exchanger with excellent heat exchange performance by maintaining an extremely high heat transfer coefficient between the fins.

[Brief explanation of drawings]

Fig. 1 is a perspective view of a main part showing the fin shape of a finned heat exchanger according to an embodiment of the present invention, Fig. 2 is a sectional view of a main part of Fig. 1, and Fig. 8 is a temperature of the air flow in Fig. 1. FIG. 4 is a sectional view of the main part showing the state of the boundary layer, FIG. 4 is a perspective view showing the schematic shape of the finned heat exchanger according to the present invention, and FIG. 5 is the main part showing the fin shape of the conventional finned heat exchanger. 6 is a sectional view of the main part of FIG. 5, and FIG. 7 is a sectional view of the main part showing the state of the temperature boundary layer of the air flow in FIG. 5. 4... Heat exchanger tube, 5... Fin, 6... Cut and raised surface. 5--Fin Fig. 2 Δ-
--Cut and raised surface b Fig. 3 Fig. 4 Fig. 5 Fig. 6

Claims (3)

[Claims] (1) A heat exchanger tube and a fin fixed to the heat exchanger tube are provided, and a cut-and-raised surface parallel to the direction of airflow passing between the fins is continuously cut and raised from the surface of the fin in the direction of the airflow, and the The height of the cut and raised surface from the fin surface is changed in multiple steps in the airflow direction to create a meandering flow path between the fins, which repeatedly expands and contracts the distance between the fins in the airflow direction. Heat exchanger with fins. (2) The cut-and-raised pattern of the cut-and-raised surface is provided line-symmetrically between adjacent fins across the center line between the fins,
2. The finned heat exchanger according to claim 1, wherein the fin-to-fin flow passages are symmetrical in the air flow direction. (3) The cut-and-raised height of the cut-and-raised surface from both sides of the fin is formed in two steps on each side, and the fin surface that is not cut-and-raised is also included to form a cut-and-raised surface of 5 steps on both sides, and the fin pitch is 3. The finned heat exchanger according to claim 1, wherein the cut-and-raised height is changed in steps of one-fifth of the dimension.