JPH0231312B2 - BUNRIGATAHIITOPAIPUSHIKIKUKYONETSUKI - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to an air preheater that preheats air using a high-temperature fluid such as waste gas as a heat source, and particularly relates to an evaporator tube and a condensation tube of a heat pipe structure arranged separately from each other. This invention relates to a heat pipe type air preheater in which the air preheater is connected through a steam communication pipe and a liquid communication pipe.

Prior Art This type of air preheater is, for example,
This is as described in Publication No. 130967, and as shown in FIG. 4, a plurality of evaporation tubes 1 having a heat pipe structure are connected by an upper header 2 and a lower header 3. An evaporation tube group 4 is disposed in a high-temperature waste gas flow path 5, and a condensation tube group 9 is formed by connecting a plurality of condensation tubes 6 having a heat pipe structure with an upper header 7 and a lower header 8. A flow path 1 for air to be heated and heated at a position higher than the evaporation tube group 4
0, and these evaporator tube group 4 and condensation tube group 9
The upper headers 2 and 7 are connected to each other through a steam communication pipe 11, while the lower headers 3 and 7 are connected to each other through a steam communication pipe 11.
8 are communicated with each other through a vapor-liquid communication pipe 12. A working fluid 13 such as water is sealed in the loop constructed in this way, and this is evaporated in the evaporation tube 1 by the heat of the waste gas, and the steam flows through the upper header 2 and the steam communication tube 11. through condensing pipe 9
The working fluid 13 flows into the air and condenses and liquefies by giving heat to the air, whereby the working fluid 13 transports heat as latent heat accompanying the state change, and the condensed and liquefied working fluid 13 flows into the lower header 8 in the condensing tube group 9 The liquid is then refluxed to the evaporation tube group 4 via the liquid communication tube 12. Therefore, as the working fluid 13 evaporates and condenses as described above and circulates continuously, the air is heated and heated by the heat of the waste gas.

However, in the air preheater configured as described above, since the evaporation tube group 4 on the heat input side and the condensation tube group 9 on the heat output side are separated, the positions of each can be set arbitrarily, and the As a result, duct routing can be simplified and costs can be reduced accordingly, making it effective for large air preheaters and waste heat recovery equipment.

Problems to be Solved by the Invention However, in order to perform continuous heat exchange, it is necessary to constantly supply the liquid-phase working fluid 13 into the evaporator tube 1. The working fluid 13 in the liquid phase is distributed and supplied to each evaporation tube 1 according to the water head difference, and is distributed over 20 to 30 minutes of the total length of the evaporation tube 1.
% is always filled with liquid phase working fluid 13. The working fluid 13 evaporates as the pool boils. The above-mentioned device has many advantages as a large-sized and large-capacity heat exchanger, and therefore the evaporation tube 1
is often long, and in such cases it is difficult to form a uniform liquid film in the longitudinal direction of the evaporation tube. Furthermore, a phenomenon in which the liquid-phase working fluid blows up due to boiling (flooding phenomenon) occurs, and internal heat transfer becomes periodically unstable. Furthermore, in the conventional device described above, in the portion of the evaporator tube 1 filled with the liquid-phase working fluid 13, smooth evaporation of the working fluid does not occur, and the portion may not necessarily function effectively as an evaporator.

As described above, in conventional devices, the evaporation rate is reduced due to non-uniform internal heat transfer and a decrease in the heat transfer coefficient due to a decrease in the liquid film evaporation area due to the liquid phase working fluid filling the lower part of the evaporation tube 1. Working fluid 1 in pipe 1
3 had poor evaporation efficiency, and as a result, the number of evaporation tubes 1 had to be increased, resulting in economic problems.

In view of the above circumstances, it is an object of the present invention to provide a separate heat pipe type air preheater that can improve the heat transfer coefficient in the evaporator tube and achieve higher performance and smaller size. be.

Means for Solving the Problems In order to achieve the above object, the present invention provides a reservoir for temporarily storing liquid-phase working fluid in communication with the lower header of the condensing pipe, and stores the liquid-phase working fluid in the reservoir. It is characterized in that a distribution pipe for individually supplying each evaporation tube from the reservoir is inserted into each evaporation tube from its upper end.

Function: Therefore, in the air preheater of the present invention, when heat is input to the evaporator tube, the working fluid evaporates there, and the vapor flows into the condensing tube via the upper header and the steam communication tube, where it absorbs latent heat. Release and condense into liquid.
The resulting liquid phase working fluid flows from the lower header into a reservoir, from which it is distributed and supplied in equal amounts into each evaporator tube by the head pressure applied equally to each distribution tube. In that case, the liquid-phase working fluid is supplied to each evaporator tube from the upper end side, and as it flows down along the inner surface of the evaporator tube, it receives heat from the outside and evaporates, so that it spreads over the entire inner peripheral surface of the evaporator tube. The liquid-phase working fluid spreads and forms a liquid film, and the entire inner peripheral surface of the evaporation tube becomes an evaporation section. In addition, the supply of working fluid is sufficiently effected by gravity or head pressure and, if present, capillary pressure. Therefore, in this invention, in addition to being able to use the entire inner surface of the evaporation tube as an effective evaporation surface, there is no risk of so-called dryout occurring when the liquid-phase working fluid is no longer supplied, so that the operation within the evaporation tube is prevented. Good heat transfer to the fluid.

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic diagram showing the principle of an embodiment of the present invention. First, the configuration of the evaporator tube group 24 will be explained. A plurality of evaporator tubes 21 consisting of finch tubes have wicks (not shown in the figure) on their inner surfaces. It has a heat pipe structure in which the non-condensable gas is exhausted and one end of the evaporator pipe is connected to the upper header 22, and the other end of the evaporator pipe 21 is connected to the lower header 23. Therefore, they are connected to each other, and the upper header 22 is connected to the lower header 23.
It is located at a higher position and is installed so that the evaporation pipe 21 is located in the high temperature waste gas flow path 25.

Furthermore, the configuration of the condensing tube group 29 will be explained as follows.
The condensing tube group 29 has almost the same configuration as the former evaporation tube group 24, and the plurality of condensing tubes 26 made of finch tubes have a heat pipe structure that exhausts non-condensable gas, and one end thereof is connected to the upper header. 27, and the other ends of the condensing tubes 26 are connected to each other by a lower header 28, and the upper header 27 connects to the lower header 2.
8 and is installed so that the condensing pipe 26 is located in the air flow path 30.

The upper headers 22 and 27 are connected to each other by a steam communication pipe 31, and the condensing pipe group 2
A reservoir 34 installed at a lower position is connected to the lower header 28 of No. 9 through a liquid communication pipe 32, and furthermore, under the reservoir 34, there are the same number of distribution pipes 35 as the evaporation pipes 21. Each of the distribution pipes 35 passes through the upper header 22 and is inserted into each of the evaporation pipes 21 from the upper end thereof to a predetermined depth. Note that the distribution pipe 35 is constructed of a pipe having a sufficiently smaller diameter than the evaporation pipe 21.
A condensable fluid such as water is sealed as the working fluid 33 in the sealed flow path configured as described above, with non-condensable gas such as air being exhausted.
Furthermore, a vent valve 36 and a safety valve 37 are attached to the upper part of the reservoir.

The distribution pipe 35 is for distributing and supplying the liquid-phase working fluid 33 from the reservoir 34 to the evaporation pipe 21, but it is necessary to supply the liquid-phase working fluid to the inner peripheral surface of the evaporation pipe 21. Therefore, when the evaporation tube 21 is installed substantially vertically, it is preferable that the distal end of the distribution tube 35 be opened in contact with any part of the inner surface of the evaporation tube 21. When the distribution pipe 35 is opened in this way, the liquid phase working fluid 33 can be supplied to the inner surface of the evaporation pipe 21, but if the evaporation pipe 21 is in a vertical position,
The flow rate of the liquid-phase working fluid 33 increases, and even if a wick is provided on the inner circumferential surface of the evaporation tube 21, the ability to supply the liquid-phase working fluid to the entire inner circumferential surface decreases.
Therefore, in order to automatically and smoothly supply the liquid-phase working fluid to the entire inner circumferential surface of the evaporation tube 21, the evaporation tube 21 must be placed at a 50-degree angle with respect to the horizontal plane H as shown in FIG.
It is preferable to install it at an angle of ~60°. In this way, the flowing force of the liquid-phase working fluid is reduced, and the entire inner circumferential surface is sufficiently supplied.In addition, the liquid flow and the vapor flow are separated as shown by the arrows in Fig. 2. , heat transport by the gas phase working fluid is facilitated.

To heat and raise the temperature of air using the air preheater, waste gas is passed through the high-temperature waste gas flow path 25, and air to be heated and heated is flowed through the air flow path 30. At the beginning of the heat input from the high-temperature waste gas, the liquid-phase working fluid 33 descends to the lowest part of the evaporator tube group 24, but the liquid-phase working fluid gradually evaporates due to the heat input. The steam passes through the upper header 22 and the steam communication pipe 31 and reaches the condensing pipe group 29.
Here, heat is taken away by the air in the air flow path 30 and the air is condensed and liquefied. The liquid phase working fluid thus generated flows into the reservoir 34 via the lower header 28 of the condensing tube group 29 and the liquid communication tube 32. The amount of liquid-phase working fluid 33 flowing into the reservoir 34, that is, the amount of working fluid condensed in the condensing tube group 29, increases in accordance with the heat input flow in the evaporating tube group 24, and accordingly, the liquid level in the reservoir 34 gradually increases. Rising to evaporator tube group 2
4 becomes higher, and as a result, the liquid-phase working fluid 33 flows down equally from the reservoir 34 to each evaporation tube 1. The liquid-phase working fluid thus supplied flows along the inner circumferential surface of the evaporation tube 21, during which time it evaporates again due to heat input from the outside. In this case, since there is no particular force that acts to prevent the liquid-phase working fluid from flowing down, the liquid-phase working fluid is sufficiently distributed and supplied over the entire inner surface of the evaporation tube 21 . That is, the entire inner surface of the evaporation tube 21 becomes an evaporation section, and so-called dryout does not occur.

Furthermore, in the above air preheater, a space is always maintained inside the reservoir 34, so even if non-condensable gas is generated during operation, this gas will be absorbed into the reservoir 34.
It will be sent into the space No.4. In this case, by opening the vent valve 36 periodically, the non-condensable gas can be easily and completely exhausted, and as a result, the heat transport properties can be maintained in a good state.

In the above embodiment, the reservoir 34 is shown in the shape of a so-called tank, but in the present invention, a reservoir having an appropriate shape can be used as necessary, and an example thereof is shown in FIG. That's right. That is, the reservoir 34a shown in FIG.
is constructed as a cylindrical body with both ends closed, that is, a so-called header, and is arranged horizontally and parallel to the upper header 22 of the evaporator tube group 24, with a distribution pipe 35 connected to the lower part thereof. With such a configuration, it becomes easier to equalize the head pressure of the liquid phase working fluid to each evaporation tube 21 and to equalize the amount of liquid phase working fluid supplied to each evaporation tube 21.

Effects of the Invention As is clear from the above description, according to the air preheater of the present invention, the reservoir is disposed between the lower header of the condensing pipe and the upper end side of the evaporating pipe, and the condensed and liquefied working fluid is transferred to the reservoir. After being temporarily stored, the liquid phase working fluid is configured to be distributed and supplied to each evaporation tube individually, so that the liquid phase working fluid flows down from the upper end side on the inner peripheral surface of the evaporation tube, so that a sufficient amount of liquid phase working fluid can be supplied to the inside of the evaporation tube. In addition, since a so-called pool in which the liquid-phase working fluid accumulates inside the evaporation tube does not occur, the entire inner circumferential surface of the evaporation tube becomes the evaporation part, and a wide effective evaporation area can be obtained. Therefore, in this invention, heat transfer within the evaporator tube can be carried out efficiently, so heat transfer from the evaporator tube to the condensing tube, that is, heat transfer from high temperature waste gas to the air, can be made more efficient.In other words, air preheating It is possible to improve the performance of the device and to reduce its size accordingly. Further, in the present invention, since no pool of liquid-phase working fluid is generated inside the evaporation tube, a flooding phenomenon due to boiling of the working fluid does not occur, and therefore the maximum heat transport capacity can be increased. Further, in this invention, since non-condensable gas can be stored in the reservoir, there is an advantage that it can be easily evacuated.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing the principle of an embodiment of the present invention, FIG. 2 is a schematic diagram showing how the distribution pipe is inserted into the evaporation pipe, and FIG. 3 is a schematic exploded perspective view showing another example of the reservoir. FIG. 4 is a schematic diagram showing the principle of an example of a conventional separated heat pipe type heat exchanger. 21... Evaporation pipe, 22, 27... Upper header,
23, 28...lower header, 24...evaporation tube group,
25... High temperature waste gas flow path, 26... Condensing pipe, 29
... Condensing pipe group, 30 ... Air flow path, 31 ... Steam communication pipe, 32 ... Liquid communication pipe, 33 ... Working fluid,
34...Reservoir, 35...Distribution pipe.

Claims (1)

[Scope of Claims] 1. A plurality of evaporation tubes are arranged in a high-temperature fluid flow path with one end elevated, and each end of the evaporation tubes is connected by an upper header and a lower header, respectively. In addition, a plurality of condensing tubes are arranged in the flow path of the air to be preheated with their ends raised high, and each end of the condensing tubes is connected by an upper header and a lower header, and Each of the upper headers is communicated by a steam communication pipe, and the evaporation pipe and the condensation pipe are communicated by a liquid communication pipe, and the evaporation pipe and the condensation pipe are formed by the communication pipe. In an air preheater having a configuration in which a working fluid made of a condensable fluid that transfers heat as latent heat is sealed in a flow path, a reservoir for temporarily storing a liquid phase working fluid is provided in communication with a lower header of the condensing pipe. A separate heat pipe type air preheater characterized in that a distribution pipe for individually supplying the liquid-phase working fluid in the reservoir to each evaporation tube is inserted into each evaporation tube from its upper end.