JPS593273Y2 - Heat exchanger - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a heat exchanger using heat pipes.

Conventionally, heat pipes are known as excellent heat transfer elements, and heat exchangers using heat pipes are also known.

As is well known, a heat pipe confines a working fluid within the pipe and evaporates and condenses it to the heating side and cooling side, and transfers heat in the form of latent heat. It is possible to increase the amount of heat transported per cross-sectional area of the pipe while keeping the difference small.

Furthermore, when it is incorporated into a heat exchanger, the heating side and heated side fluids can be handled outside the pipes, so the heat transfer area by the fins can be increased, making the device compact.

However, for example, when considering this as a heat exchanger for waste heat recovery, it is desired to recover as much waste heat as possible (reduce the temperature that escapes as much as possible), and therefore it is necessary to reduce the temperature of the waste heat source. Accordingly, heat transfer elements (heat pipes) with different boiling points are required, and heat exchangers configured in this way for waste heat recovery have been developed, but the devices are surprisingly large and complex, and require frequent maintenance. However, it had drawbacks such as poor reliability.

The present invention was developed in order to eliminate these drawbacks of the conventional technology, and its purpose is to effectively recover waste heat from factories and various heat engines, etc., and to utilize waste heat energy effectively. It is something that you do.

In order to achieve this objective, the heat exchanger of the present invention has a high-pressure cooling chamber installed in parallel with the high-pressure heating chamber, and a low-pressure cooling chamber installed in parallel with the low-pressure heating chamber, so that the high-pressure heating chamber and the low-pressure heating chamber are connected. to cause the heating medium to pass from the high pressure heating chamber to the low pressure heating chamber, and to communicate the high pressure cooling chamber and the low pressure cooling chamber to allow the fluid to be heated to pass from the low pressure cooling chamber to the high pressure cooling chamber, A heat pipe is installed spanning from a high-pressure heating chamber to a high-pressure cooling chamber, and the upper half of the heat pipe interposed in the high-pressure heating chamber forms a high-pressure heating section, and the lower half serves as a high-pressure cooling section, and the heat pipe serves as a high-pressure cooling section. A heat pipe is installed across the low-pressure cooling chamber, and the heat pipe has an upper half interposed in the low-pressure heating chamber that threatens the low-pressure heating section, and a lower half that impinges the low-pressure cooling section. The high-pressure heating section is communicated with a conduit, the high-pressure cooling section and the low-pressure heating section are communicated with a conduit including a reservoir and a flush valve, and a purge pipe is installed in the reservoir. .

The present invention will be further described below with reference to the accompanying drawings, but for ease of understanding, an example in which the invention is applied to waste heat recovery from a heat engine (boiler) will be described.

First, there is a heat exchanger that uses heat pipes, and a heat exchanger for waste heat recovery that uses an air preheater that uses a conventional regenerative rotary heat exchanger to increase thermal efficiency by raising the temperature of combustion air. will be compared and explained based on FIG.

In the figure, when the horizontal axis is the distance L along the heat exchanger and the vertical axis is the temperature T, the temperature drop of the gas that is the waste heat source is indicated by G.

Due to this temperature drop, the heated side (air) in the case of a heat exchanger for waste heat recovery using a conventional heat storage type rotary air preheater
The temperature gradient of is shown by a nearly straight line R.

On the other hand, the temperature gradient on the heated side according to the present invention and other methods using heat pipes is shown by curve H.

This difference is because the heat exchanger uses a heat pipe, and the temperature change of the working fluid is shown by the broken line W (accompanied by a phase change), and the heated side has a temperature gradient along it. It is.

To further explain this from the perspective of heat transfer, in normal gas/air heat exchange, the thermal resistance of each tube wall via the heat transfer wall is extremely large (the temperature difference between the heat transfer surfaces is large), so the curve H Instead of looking like this, it becomes almost like a straight line R.

When using a heat pipe, there is a medium that undergoes a phase change in between, so the heat transfer surface on the heating side (gas) and the heated side (air), that is, the tube wall of the heat pipe, has a significant influence on the working fluid side of the heat pipe. Since a boundary layer with low thermal resistance (on the inner wall surface side of the heat pipe) is formed, the temperature difference on the heat transfer surface becomes smaller, and the temperature increase gradient on the air side forms an upwardly convex curve.

This means that the heat transfer coefficient (overall heat transfer coefficient) of the entire heat transfer surface has increased.

Therefore, the heat transfer area of the entire heat pipe device can be significantly reduced.

Since heat pipes have remarkable advantages as mentioned above,
It has traditionally been commonly used in heat exchangers, and to give an example, Figure 2 shows a conventionally proposed heat exchanger for waste heat recovery using a well-known heat pipe. A heat pipe according to a method using a known heat pipe has a lower part as a heating side and an upper part as a cooling side.

Heat pipes contain a heating medium with organic medium or water as the working fluid, so the pressure inside the pipe is determined by the temperature on the heating side, so when recovering waste heat, there is a limit to the amount of heat recovered. has.

In order to avoid this, it is necessary to use working fluids with different boiling points and arrange them separately into high pressure sides 1 and 4 and low pressure sides 2 and 3 as shown in the figure.

In this way, the heat pipe, which is an excellent heat transfer element, can be effectively configured as a heat exchanger for waste heat recovery, and the design can be made more compact than conventional rotary air preheaters.

However, in this method, the purge pipe 22'. 22
This is provided to periodically purge gas other than the working fluid generated in the heat pipe.Although not shown, it has a mechanism to separate it from the working fluid. , it is necessary to provide purge equipment for each, which has the disadvantage of complicating the equipment.

In addition, conventional heat pipes have the disadvantage that it is not possible to select the optimal pressure for the enclosed working fluid in response to various load fluctuations, which is inconvenient in this respect. Ta.

The present invention is intended to eliminate the drawbacks of the prior art, and therefore has a configuration as illustrated in FIG. 3.

In this example, 1 is a high-pressure heating chamber of the heat exchanger, 2 is a low-pressure heating chamber, 3 is a low-pressure cooling chamber, 4 is a high-pressure cooling chamber, 5 and 6 are heating fluid inlets and outlets, respectively, and 7 and 8 are cooling chambers, respectively. Fluid inlet and outlet.

A heat pipe 30 is installed spanning from the high-pressure heating chamber 1 to the high-pressure cooling chamber 4, and the upper half of the heat pipe 30 interposed in the high-pressure heating chamber 1 forms the high-pressure heating section 9, and the lower half forms the high-pressure heating section 9. A cooling section 12 is formed.

Further, a heat pipe 40 is installed spanning from the low pressure heating chamber 2 to the low pressure cooling chamber 3, and the upper half of the heat pipe 40 interposed in the low pressure heating chamber 2 forms the low pressure heating section 10, and the lower half forms the low pressure heating section 10. A low pressure cooling section 11 is formed.

9 a , 10 a , lla , and 12 a are fins provided in the respective heating sections 9 and 10 and cooling sections 11 and 12 .

In this heat exchanger, for example, high-temperature waste gas discharged from a heat engine (boiler) is transferred to a high-pressure heating chamber as shown by arrow A.
The heated fluid flows in from the heated fluid port 5, is given heat by the high-pressure heating section 9, is sent to the low-pressure heating chamber 2, is further given heat again by the low-pressure heating section 10, and is discharged from the heated fluid outlet 6.

On the other hand, the fluid (air) on the heated side flows into the low-pressure cooling chamber 3 from the cooling flow lower part of the low-pressure cooling chamber 3 as shown by arrow B, and the working fluid in the heat pipe evaporates in the low-pressure heating section 10. is condensed in the low-pressure cooling section 11 and imparts latent heat of condensation to the air, so the temperature of the air increases.

After that, the air is further sent to the high-pressure cooling chamber 4, and the working fluid in the heat pipe that has evaporated in the high-pressure heating section 9 is condensed in the high-pressure cooling section 12, imparting latent heat of condensation to the air, thereby further increasing the temperature of the air. The air becomes high temperature air and is discharged from the cooling fluid outlet 8, completing all of the desired heat exchange.

In the process of heat exchange, the working fluid condensed in the low pressure region is pressurized by the pump 18 from the low pressure outlet header 15 and flows into the high pressure inlet header 13 through the conduit 20.

On the other hand, the condensed working fluid that flows into the high pressure region from the high pressure inlet header 13 flows into the reservoir 21 from the high pressure outlet header 16 due to gravity.

The working fluid stored in the reservoir 21 is reduced in pressure via the flush valve 17 that controls the liquid level in response to load fluctuations, flows into the low pressure inlet header 14 through the conduit 19, and flows into the low pressure heating section 10. After flash evaporation in the low pressure heating chamber 2, low pressure cooling chamber 3, high pressure cooling chamber 4, high pressure heating chamber 5
is forcibly recirculated to the low-pressure heating chamber 2 through the

Note that the purge pipe 22 in this embodiment is provided to perform the same function as the conventional one, but
The number may be one.

Further, post-processing equipment (not shown) such as purge gas is also provided, but only one post-processing equipment is required, making the apparatus extremely simple.

As mentioned above, the present invention has a high pressure heating chamber 1 and a high pressure cooling chamber 4.
are installed in parallel, and a low-pressure cooling chamber 3 is installed in parallel with the low-pressure heating chamber 2, and the high-pressure heating chamber 1 and the low-pressure heating chamber 2 are communicated with each other, so that the heating medium passes from the high-pressure heating chamber 1 toward the low-pressure heating chamber 2. Furthermore, the high pressure cooling chamber 4 and the low pressure cooling chamber 3 are communicated with each other to allow the fluid to be heated to pass from the low pressure cooling chamber 3 to the high pressure cooling chamber 4, and from the high pressure heating chamber 1 to the high pressure cooling chamber 4. A heat pipe 30 is installed, and the upper half of the heat pipe 30 located in the high-pressure heating chamber 1 acts on the high-pressure heating section 9, and the lower half acts on the high-pressure cooling section 12, and the heat pipe 30 is arranged in the high-pressure heating chamber 1. A heat pipe 40 is installed across the low-pressure cooling chamber 3, and the upper half of the heat pipe 40 located in the low-pressure heating chamber 2 threatens the low-pressure heating section 10, and the lower half threatens the low-pressure cooling section 11. , the low-pressure cooling section 11 and the high-pressure heating section 9 are connected through a conduit 20, and the high-pressure cooling section 1
2 and the low-pressure heating section 10 are communicated through a conduit 19 including a reservoir 21 and a flush valve 17, and a purge pipe 22 is installed in the reservoir 21, so that the working fluid of the heat pipe flows from the low-pressure cooling chamber 3 to the high-pressure heating chamber. Flows to 1,
Furthermore, since the heat flows from the high-pressure cooling chamber 4 to the low-pressure heating chamber 2, the apparatus itself can be simplified without reducing heat recovery efficiency.

That is, according to the present invention, since only one purge pipe 22 and one processing equipment for purge gas are required, the structure of the apparatus itself is simplified accordingly.

[Brief explanation of drawings]

Figure 1 is a graph showing the relationship between distance and temperature in various heat exchangers, Figure 2 is a schematic illustration of a conventional heat exchanger using a heat pipe, and Figure 3 is a heat exchanger according to the present invention. FIG. 2 is a schematic illustration of one embodiment of the vessel. 1...High pressure heating chamber, 2...Low pressure heating chamber, 3...Low pressure cooling chamber, 4...High pressure cooling chamber, 5...・Heating fluid inlet, 6... Heating fluid outlet, 7... Cooling fluid inlet, 8...
・Cooling fluid outlet, 9...High pressure heating part of heat pipe, 10...Low pressure heating part, 11...
Low pressure cooling section, 12... High pressure cooling section, 17...
...Flush valve, 18...Pump, 21...
...Reservoir, 22...Purge pipe.

Claims (1)

[Scope of utility model registration request] A high-pressure cooling chamber 4 is installed in parallel with the high-pressure heating chamber 1, and a low-pressure cooling chamber 3 is installed in parallel with the low-pressure heating chamber 2, and the high-pressure heating chamber 1 and the low-pressure heating chamber 2 are communicated with each other to allow low-pressure heating from the high-pressure heating chamber 1. A heating medium is passed towards the chamber 2 and the high pressure cooling chamber 4
The low pressure cooling chamber 3 is communicated with the low pressure cooling chamber 3 to allow the fluid to be heated to pass from the low pressure cooling chamber 3 to the high pressure cooling chamber 4, and a heat pipe 30 is installed spanning from the high pressure heating chamber 1 to the high pressure cooling chamber 4. The heat pipe 30 has an upper half interposed in the high-pressure heating chamber 1 that acts on the high-pressure heating section 9, and a lower half that acts on the high-pressure cooling section 12, and heats from the low-pressure heating chamber 2 to the low-pressure cooling chamber 3. A pipe 40 is installed, and the heat pipe 40
The upper half interposed in the low-pressure heating chamber 2 is the low-pressure heating section 1
At the same time, the lower half serves as a reservoir for the low-pressure cooling section 11, communicating the low-pressure cooling section 11 and the high-pressure heating section 9 through a conduit 20, and connecting the high-pressure cooling section 12 and the low-pressure heating section 10 as a reservoir. 21 and a conduit 19 including flush valve 17
and connect the purge pipe 2 to the reservoir 21.
A heat exchanger characterized in that 2 is installed.