JPH023918B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method of improving the flow characteristics of two-phase flow in a conduit using an electric field.

(Prior art) Conventionally, in a heat exchanger that transfers heat to a liquid such as water or fluorocarbon flowing in a pipe to boil it, the flow direction is a bubble flow, annular flow, spray flow, or vapor flow. Heat transfer is not very good in the bubble flow and annular flow areas, and the pressure loss for pumping the liquid is large at the annular flow position, making it difficult to match the liquid flow rate to the gas flow rate. There was a problem.

In order to clarify this problem, FIG. 2 shows the flow characteristics of the liquid flowing through the pipe line 1 in the heat exchanger. Heat Q outside the pipe 1 is applied to the liquid 2 flowing through the pipe 1.
is transmitted, gas 3 appears as bubbles in liquid 2, resulting in a two-phase flow.

This two-phase flow is a uniform bubble flow at the beginning of the flow (region A). According to the flow, the gas 3 flows near the center of the pipe 1, and the liquid 2 forms an annular flow that flows in a circular shape near the inner wall surface 4 of the pipe 1 (region B). Next, the liquid 2 becomes a spray stream in which droplets form (region C).
Finally, it becomes steam (region D).

(Problems to be Solved by the Invention) In the area A of the conduit 1 of the conventional heat exchanger, air bubbles are gathered near the inner wall 4 of the conduit 1 to disturb the boundary layer and increase heat transfer efficiency. It is desirable that the flow rate of the liquid 2 is large in the part corresponding to the annular flow in the region B, where the friction between the liquid 2 and the inner wall surface 4 of the pipe line 1 is large and the gas 3 in the center flows in large quantities. It was becoming less and less. That is, since heat transfer is undesirable and the pressure loss for pumping the liquid 2 is large, there is a problem in that it is not possible to achieve a desirable flow of vapor and liquid.

The present invention improves the flow characteristics in the above-mentioned regions A and B. That is, an object of the present invention is to allow the liquid to flow near the center of the pipe and collect bubbles near the inner wall of the pipe, thereby improving the heat transfer coefficient and reducing pressure loss. The purpose of this invention is to provide a method for increasing the flow rate.

(Means for Solving the Problems) In order to achieve the above object, the present invention improves the flow characteristics of two-phase flow as follows.

A wire electrode is provided along the axis of the pipe at a position of bubble flow and/or annular flow in a pipe in which a two-phase flow is flowing, a mesh electrode is provided surrounding the outside of the wire electrode, and a mesh electrode is provided surrounding the outside of the wire electrode. A high voltage is applied between the electrode and the mesh electrode to collect gas near the inner wall surface of the pipe, creating a liquid flow near the center of the pipe.

Note that the present invention is not limited to improving the flow characteristics of a heat exchanger, but also includes improving the flow characteristics of two-phase flows of liquid and gas in general.

(effect) The invention works as follows.

When a voltage is applied to a wire electrode and a mesh electrode, the electric field of the wire electrode is stronger than that of the mesh electrode. In gas bubbles that have a lower dielectric constant than liquid, the same electrode charge as a wire electrode with a strong electric field is generated at the gas-liquid interface. Therefore, the bubbles are expelled in the direction of the mesh electrode where the electric field is weak.

Further, since the electric field is zero between the mesh electrode and the inner wall of the tube, the bubbles are also repelled from the mesh electrode and exist between the inner wall of the tube and the mesh electrode.

(Example) An example of the present invention will be described below based on FIGS. 1 and 2. This embodiment relates to a heat exchanger in which the flow characteristics of liquid are improved so that a small amount of power is required.

FIG. 1 shows the A of the above-mentioned pipe line 1 in the heat exchanger.
This figure shows that a device 11 for improving flow characteristics is installed at a location corresponding to area and area B.

12 wire electrodes are provided in the pipe 1 along the axial direction of the pipe 1, and a mesh electrode 13 is provided surrounding the outside of the wire electrode 12. The wire electrode 12 and the mesh electrode 13 are in a non-contact state. A high voltage is applied between the wire electrode 12 and the mesh electrode 13. 14 is a power source.

The electric field of the wire electrode 12 is stronger than the electric field of the mesh electrode 13. At the gas-liquid interface, there is a wire electrode 1 with a strong electric field.
The same charge as 2 (positive charge in this example) is generated,
The gas 3 is expelled in the direction of the mesh electrode 13 where the electric field is weak. In this way, the gas 3 gathers near the inner wall surface 4 of the pipe 1, and the liquid 2 flows near the center of the pipe 1.

Since the liquid 2 flows near the center of the pipe line 1, pressure loss is small and the flow rate of the liquid 2 can be increased.

In addition, by using this embodiment at a stage when only a small amount of gas 3 is generated, the boundary layer 15 on the inner wall surface 4 of the pipe line 1 is disturbed to help generate more bubbles, thereby reducing the amount of heat transferred to the liquid 2. It is also possible to increase it. That is, when the method according to the present invention is applied to a heat exchanger, it is possible to increase the flow rate of liquid flowing through the pipe line 1 and also to improve the amount of heat transfer.

Other examples include the following. There is a technology that mixes air bubbles into fuel such as gasoline and sends it to a heat engine to prevent the generation of harmful gases. Even in this two-phase flow, the fuel flows along the inner wall surface of the pipe 1, and the fuel flows along the inner wall surface of the pipe 1.
There is a risk of an annular flow in which air flows through the center of the air. An annular flow is unfavorable for combustion because a large amount of air is sent and only a small amount of fuel is sent.

Therefore, the two-phase flow of fuel and bubbles is carried out by using the same device 11 shown in FIG. 1 to collect the bubbles near the inner wall surface 4 of the conduit 1 so that the fuel flows through the center of the conduit. This allows fuel and air to be delivered in a preferred ratio.

(Effect of the invention) According to the present invention, the following effects are achieved.

Heat transfer can be improved at the location of bubble flow and annular flow in boiling heat exchangers.

Since the liquid flows near the center of the pipe in a two-phase flow in the pipe, there is little pressure loss, and a large amount of liquid can be flowed with a small amount of power.

Furthermore, when transferring a two-phase flow, it is possible to avoid transferring only a large amount of gas.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view showing an embodiment of the present invention;
FIG. 2 is a cross-sectional view taken along the - line in FIG. 1, and FIG. 3 is a vertical cross-sectional view showing the flow characteristics of liquid flowing through the pipes of a conventional heat exchanger. 1: Pipe line, 2: Liquid, 3 : Gas, 4: Inner wall surface,
12: Line electrode, 13: Mesh electrode.

[Claims]

1. A wire electrode is installed at a distance from a condensing heat transfer surface that is cooled by a cooling medium, and this wire electrode is used as one electrode, and the heat transfer surface is used as the other electrode, and the heat transfer surface In a heat transfer promoting device that applies a high voltage between the wire electrode and the wire electrode to draw and remove condensate that has condensed and adhered to the heat transfer surface from the heat transfer surface to the wire electrode, the wire electrode is applied with a negative high voltage and the The high voltage applied to the wire electrode is applied to the heat transfer surface as a negative low voltage via a resistor, and the cooling medium is grounded to apply a negative low voltage between the heat transfer surface and the cooling medium, thereby causing the transfer. A corrosion prevention device for a heat transfer promotion device using an electric field, which is characterized by preventing corrosion on a hot surface and preventing sludge adhesion.