JPS60194290A - Heat exchanger equipped with fins - Google Patents

Abstract

PURPOSE:To improve heat transfer performance by a method wherein a plurality of fins are arranged on a heat transfer tube orthogonally thereto with constant intervals, the fins are waved so as to be opposed to airflow, neighboring fins are laminated under deviating the wave form of the fins by half pitches of the wave form, the sections of airflow path are formed into continuous gourd shape and inflated parts are provided with rise-up cuts. CONSTITUTION:The heat transfer tube is provided with a plurality of fin groups 3, orthogonally attached thereto with constant intervals, the fins 3 are waved so as to be opposed to the airflow, neighboring fins 3 are deviated by the half pitches of the wave form of the fins 3 and the section of the path for the airflow is constituted so as to have the shape of continuous gourds. The inflated sections of the gourd-shaped airflow path is provided with the rise-up cut 4. Air, which flows around the rise-up cut 4, forms whirling stream around the rise-up cut 4 while the whirling stream becomes free vortex and is released into the air path, then, generates secondary stream in the air path. The secondary stream promotes the turbulence of the fluid and quickens the transition from the condition of laminor flow into the condition of turbulent flow.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a finned heat exchanger used for refrigeration and air conditioning, which takes in heat from the air or releases heat to the air.

Conventional Structure and Problems Conventionally, this type of finned heat exchanger, as shown in FIG. It has a structure in which airflow flows through the fins 1 in the direction of the arrow and exchanges heat with a heat medium such as fluorocarbon flowing inside the heat exchanger tubes 2.

In recent years, various improvements have been made to the shape of the fins 1 constituting this type of heat exchanger, and their heat transfer performance has also been significantly improved compared to when a simple flat plate is used. However, in this type of heat exchanger, the flow rate of air flowing between the fins is low, and it is often used at a relatively low Reynolds number.
The fluid behavior between them is laminar. For this reason, the fluid is difficult to disturb, and there is a certain limit to its performance improvement. Furthermore, it has been found that a method of involving the mainstream of the fluid onto the fin surface is a good way to improve the heat transfer performance between the fluid and the fins, but this has been difficult with conventional fin configurations.

Purpose of the Invention The present invention aims to improve the performance of a heat exchanger with fins, and by adding a swirl element to the fluid flowing between the fins, the laminar flow state that suppressed the performance improvement of conventional fins can be changed from a laminar flow state to a turbulent flow state. This aims to improve heat transfer performance by guiding the main flow flowing in the center between the fins, or the fluid portion that is less affected by heat from the fins, closer to the fin wall surfaces.

Structure of the Invention The present invention arranges a plurality of fins perpendicularly to the heat transfer tube at regular intervals, waves the fins in opposition to the airflow, and stacks the fins by shifting the wave shapes of adjacent fins by half a pitch. The cross section of the airflow passage is formed into a continuous gourd shape, and at the same time, the bulge portion of this gourd-shaped passage is cut and raised.

DESCRIPTION OF THE EMBODIMENTS One embodiment of the present invention has a fin heat exchanger as shown in FIGS. 2a, b,
Shown in c. FIG. 2a shows a part of an embodiment of the present invention as a perspective view. Airflow flows from the direction of the arrow. The fins 3 are installed in a undulating manner in a direction opposite to the airflow flowing from the direction of the arrow, and adjacent fins 3 are installed with a shift of half a pinch of the wave. Therefore, the cross section of the air passage of the fin 3 is shaped like a gourd, and most of the air passes through the bulge of the gourd-shaped passage. A cut and riser 4 is installed in this passage to add a swirling component to the airflow passing through it. The air flowing around the brim and the raised cut 4 forms a swirling flow around the raised cut 4, and the swirling flow becomes a free vortex and is released into the air passage, causing a secondary flow in the air passage.

This secondary flow promotes fluid turbulence and accelerates the transition from laminar to turbulent conditions. In this embodiment, the shape of the cut-and-raise 4 is shown as a cantilever cut-and-raise, but it may be cut and raised on both ends.

However, the purpose of this cutting and raising is to add a swirling component to the passing airflow, and this embodiment is merely shown as an example thereof.

Next, the vortex induced by the cut-and-raised part 4 flows backward while rotating along a path composed of smooth curves, and is transmitted by heat conduction from the fin collar 6 that is crimped to the heat exchanger tube 6. Give off or absorb heat. Although an embodiment in which the wave pinch of the fin is relatively large is shown here, the same effect can be expected even if the wave pinch is made smaller.

Figure 2 is a front view of Figure 2a, and Figure 2-0 is a front view of Figure 2a.
The figure shows a cross section along line 8-1.

The present invention constructs an air passage with a smooth curve, and gives a swirling component to the air flow guided into the passage by cutting and raising it, thereby creating an air flow that flows while swirling inside the passage. This has the effect of significantly improving the heat transfer coefficient between the air and the fin surface. One reason for this excellent effect is that the air near the fins is always replaced by the air near the center of the fins due to the secondary flow in the passage created by cutting and raising, resulting in a temperature gradient of the air in contact with the fins. This is because the temperature increases and heat transfer is promoted. Another reason is that this secondary flow accelerates the transition of the laminar state of air to a turbulent state, disturbs the boundary layer, and improves the heat transfer coefficient. Furthermore, according to the implementation of the present invention, the air hits the heat exchanger tube in a swirling state, so the air is also drawn into the rear of the heat exchanger tube, which significantly reduces the shape resistance of the heat exchanger tube, and at the same time, it This reduces the dead area that occurs at the rear, and allows the effective heat transfer surface of the fins attached to the heat transfer tube to be used without reducing the dead area.

Effects of the Invention As described above, the present invention induces a secondary flow due to swirling, promotes the transition from laminar flow to turbulent flow, and reduces the dead area behind the heat exchanger tubes, thereby improving the efficiency of the finned heat exchanger. It has the excellent effect of significantly improving heat transfer characteristics and reducing pressure loss at the same time.

[Brief explanation of drawings]

FIG. 1 is a perspective view of a conventional finned heat exchanger, FIG. 2a is a perspective view of a main part of a finned heat exchanger according to an embodiment of the present invention, FIG. Figure 2 C is Figure 2 A-
A' section 1! f) a. 3... Fin, 6... Heat exchanger tube, 4...
...Cut and raise, 5... Heat exchanger tube, 6...
...Fin color. Name of agent: Patent attorney Toshio Nakao and one other person No. 24 (b) 4 (C)

Claims (1)

[Claims] It has a plurality of fin groups installed perpendicularly to the heat exchanger tube at regular intervals, the fins are undulated in opposition to the airflow, and the adjacent fins are shifted by a half pitch of the undulations to improve the flow of the airflow. 1. A heat exchanger with fins, characterized in that a cross section of the passage is formed into a continuous gourd shape, and a bulge of the gourd-shaped air flow passage is provided with a cut and raised part.