JPS5925149B2 - mist cooling heat exchanger - Google Patents

Description

Detailed Description of the Invention The present invention relates to a mist cooling heat exchanger that exchanges heat between a mist airflow flowing outside the tube and a heat medium flowing inside the tube, particularly various condensers in which the heat medium inside the tube is condensed, and a condenser for geothermal power generation plants. This invention relates to a mist cooling heat exchanger suitable for use as a mist cooling heat exchanger.

Conventional mist cooling heat exchangers of this type have heat transfer tubes such as smooth tubes or finned tubes arranged in a grid or staggered pattern in the mist air flow passage, and spray nozzles that generate mist are placed in the upstream or downstream portion. It has a structure in which a blower is installed.

The mist cooling method aims to improve cooling performance by causing sprayed mist water to collide with the surface of the heat transfer tube to promote evaporation of the water film.

Therefore, in order to improve the wettability of smooth tubes and finned tubes, by creating fine grooves on the tube surface and fin sides,
Utilizing the capillary force of water in the grooves, the water film collected in the heat transfer tube is spread over the heat transfer surface to improve wettability and improve cooling performance.

In such a conventional heat exchanger, the mist generated by the nozzle collides with the most upstream heat exchanger tube (first stage) and the second stage heat exchanger tube. Therefore, the amount of mist reaching the heat exchanger tubes in the rear row on the downstream side decreases from the third day onwards.

Therefore, as the heat transfer tubes in the rear row move downstream, a water film exists on the heat transfer surface, and the dry surface spreads, reducing the cooling performance.

SUMMARY OF THE INVENTION An object of the present invention is to provide a mist cooling heat exchanger with high heat transfer performance in view of the problems of the prior art described above.

The present invention improves the wettability of the heat transfer surface if a large amount of mist water exists on the upstream side of the mist in the heat transfer tube group, and arranges heat transfer tubes with a large wetted area, and the presence of a small amount of mist water on the downstream side. Alternatively, a high-performance heat exchanger can be obtained by arranging heat transfer tubes whose heat transfer surfaces have good wettability even if little mist reaches them.

In the present invention, the grooved tube, which is a circular tube with grooves, can have relatively deep grooves, so the entire heat transfer surface can be wetted with a small amount of mist.

And since there are no fins, the tube pitch can be narrowed and many heat transfer tubes can be arranged.

Unfortunately, a grooved fin tube with grooves on the side of the fin has grooves on the fin, so deep grooves cannot be formed, but when a large amount of mist collides, the side of the fin gets wet well and the heat transfer area becomes circular. Since it is enormously larger than a tube, it maintains high cooling performance.

As a tube group structure that combines such high-performance heat transfer tubes,
Examples of the present invention are shown in FIGS. 1 to 6.

FIGS. 1 and 2 show a first embodiment.

In a duct 4 having an inlet 1, an outlet 2, and a water receiver 3, an upstream heat exchanger tube group 5 and a downstream heat exchanger tube group 6 are arranged.

The heat exchanger tube group 5 is a grooved fin tube 7 that is well wetted by a relatively large amount of mist.

The heat exchanger tube group 6 is a grooved tube 8 that can be wetted well even with a small amount of mist.

The nozzle 9 is arranged at the inlet 1 of the duct 4 and injects water toward the heat exchanger tube group 5.

A pipe 10 and a pump 11 are connected to the nozzle 9, and the water receiver pumps water from the section 3.

The water receiver is separately replenished when the amount of water in section 3 becomes low.

The blower 12 is installed at the outlet 2 of the duct 4 (or upstream of the heat exchanger tube group 5), and generates a flow of air from the inlet 1 to the outlet 2.

Next, the operation of this embodiment will be explained.

A heat medium such as refrigerant vapor flows inside the heat transfer tube group 5.6, and an air current flows outside the tubes from the inlet 1 to the outlet 2 as shown by the arrow.

The airflow is generated by a blower 12. Water is injected from the nozzle 9, becomes mist in the airflow, mixes, and flows into the heat exchanger tube group 5.

The mist wets the tubes and fin surfaces of the grooved fin tubes 7 of the heat transfer tube group 5 located on the upstream side of the airflow, thereby improving cooling performance.

A small amount of mist reaches the grooved tubes 8 of the heat exchanger tube group 6 located on the downstream side of the airflow, wets the surfaces of the heat exchanger tubes, and improves cooling performance by evaporating a water film.

The heat medium of the mist mixed in the air flow is the heat transfer tube groups 5 and 6.
By the time it comes out, most of it has condensed.

FIG. 3 shows a second embodiment of the invention.

When the mist airflow reaches a high speed, the mist captured in the upstream heat exchanger tube group 5 does not fall onto the lower heat exchanger tubes on the upstream side, but falls onto the lower heat exchanger tubes in the downstream heat exchanger tube group 6. do.

Therefore, the amount of mist also increases in this portion of the heat exchanger tube.

At this time, grooved fin tubes 7 similar to those in the upstream heat exchanger tube group 5 are also arranged in the lower heat exchanger tubes of the downstream heat exchanger tube group 6.

FIG. 4 shows a third embodiment of the invention.

In this embodiment, a heat exchanger tube group 13 made up of heat exchanger tubes effective for forced air cooling is arranged behind the heat exchanger tube groups 5 and 6.

Since there is almost no mist in this area, we placed a smooth bifin tube 14 etc. to improve the cooling performance and make effective use of the space.We also stopped spraying the mist and used this heat exchanger only for air cooling. When used for
This heat exchanger tube group 13 is advantageous for improving cooling performance.

FIG. 5 shows a fourth embodiment of the present invention.

This example is based on the second embodiment shown in FIG. 3 and the third embodiment shown in FIG.
In this case, the cooling performance can be further improved in the example shown in FIG. 4.

FIG. 6 shows a fifth embodiment of the present invention.

This example is based on the third embodiment shown in FIG. 4, in which a group 13 of forced air cooling heat transfer tubes 13 made up of smooth tubes 14 placed at the rearmost side is installed in front of the nozzle 9 with a population of 1 in the duct 4. It is something.

The airflow guided to the inlet 1 by the blower exchanges heat with the heat transfer tubes in each row, and its temperature increases sequentially.

At that time, when cooling is performed only by a simple air flow, the larger the temperature difference between the surface temperature of the heat exchanger tube and the temperature of the air flow, the better, so the cooling performance is improved by doing as shown in FIG. 6.

In the embodiments shown in FIGS. 1 to 6 above, the number of rows of heat exchanger tubes each having independent characteristics is not limited to what is shown in the figures, and may vary depending on the amount of mist sprayed from the nozzle, the temperature of the heat exchanger tubes, It is determined appropriately depending on the amount of heat exchange, the arrangement pitch of the heat exchanger tubes, etc.

As explained above, according to the present invention, a heat exchanger having high heat transfer performance can be obtained, and the motive power of the mist water circulation pump can be reduced by promoting the evaporation heat transfer of the mist water. I can do it.

[Brief explanation of the drawing]

Fig. 1 is a front sectional view showing a first embodiment of the mist cooling heat exchanger of the present invention, Fig. 2 is an enlarged sectional view of the main part of Fig. 1, and Figs. FIG. 7 is an enlarged sectional view of a main part showing another example of a cooling heat exchanger. 1...Inlet, 2...Outlet, 3...Water tray, 4...
...Duct, 5, 6, 13... Heat exchanger tube group, 7... Grooved fin tube, 8... Grooved tube, 14... Smooth bifin tube, 9... Nozzle.

Claims (1)

[Claims] 1 In a mist cooling heat exchanger that flows a mist airflow containing fine water droplets in a cooling airflow outside the tube and exchanges heat with a heat medium flowing inside the tube, at least one surface of the fins has fine water droplets on the upstream side of the mist airflow. A mist cooling heat exchanger characterized in that a group of heat transfer tubes made of grooved fin tubes with fine grooves is arranged, and a group of heat transfer tubes made of grooved tubes with fine grooves on the tube surface is arranged on the downstream side. vessel.