JPH0213233B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a countercurrent type heat exchanger, and particularly to a heat exchanger capable of promoting mist evaporation.

[Technical background of the invention and its problems]

In recent years, power plants that use the thermal energy of hot water as a high-temperature heat source for turbine cycles such as the Rankine cycle have started using so-called mixed media, which is a mixture of two or more types of low-boiling hydrocarbons, fluorocarbons, etc., as the working fluid. It is considered to constitute This mixed medium has the characteristic that the evaporation temperature increases as it evaporates, so more heat energy can be recovered from the hot water with less working fluid circulation than in the case of a single component working fluid. This has the advantage that it is possible to reduce in-house power such as pump power, and it is possible to obtain a large output at the power transmission end.

However, in order to bring out the characteristics of this mixed medium, it is necessary that the temperature change of the mixed medium is accompanied by a change in the liquid and vapor composition caused by the difference in the evaporation rate or condensation rate of the components during the evaporation or condensation process. Because it appears as
The evaporator or condenser must be a completely countercurrent, once-through heat exchanger.

However, in both heat exchangers that flow the working fluid inside the heat transfer tubes or outside the heat transfer tubes, the mass ratio (quality) of steam during the evaporation process reaches approximately 0.8 to 0.9. If the temperature rises, the heat transfer surface will not be wetted by the liquid and boiling will not occur on the heat transfer surface, resulting in an extremely poor heat transfer coefficient, making it impossible to completely vaporize the working fluid, and causing the unevaporated liquid to turn into a liquid. There is a problem that it remains in the form of drops (mist). Therefore, for example, when operating a turbine with the steam obtained from the heat exchanger, it is necessary to separate the mist with a mist separator and send only the steam to the turbine. Therefore, all of the working fluid fed to the heat exchanger cannot be used to drive the turbine;
There are disadvantages such as lower efficiency of the entire plant.

[Purpose of the invention]

In view of these points, it is an object of the present invention to provide a heat exchanger that can obtain high heat transfer coefficients in each quality range and can completely evaporate even the mist.

[Summary of the invention]

The present invention relates to a counterflow type heat exchanger in which fluids flowing inside and outside of a heat exchanger tube flow in opposite directions to each other. It is characterized by having a mist collection layer.

[Embodiments of the invention]

In FIG. 1, reference numeral 1 denotes the main body of the heat exchanger, and the lower end of the main body 1 is provided with a water chamber 2 on the hot water inlet side, and the upper end is provided with a water chamber 3 on the hot water outlet side. It is being Inside the main body 1, a large number of parallel heat exchanger tubes 5 are disposed with both ends attached to tube plates 4, 4, respectively, and a plurality of butt-full plates 6 perpendicular to the heat exchanger tubes 5 are arranged in a zigzag shape. Furthermore, an inlet 7 and an outlet 8 for a working fluid are formed in the upper and lower parts of the main body shell 1, respectively.

In addition, in the space inside the main body shell 1, that is, on the outside of the heat exchanger tubes 5, as shown in FIG. Both sides of the wire mesh layer are brought into contact with the heat exchanger tubes 5, and at least a portion of the mist collection layer 9 is brought into contact with a portion of the surface of the heat exchanger tubes 5.

Thus, the hot water supplied to the hot water inlet side water chamber 2 flows through a large number of heat transfer tubes 5, passes through the hot water outlet side water chamber 3, and is discharged to the outside of the heat exchanger. On the other hand, the working fluid vapor containing mist enters the main body shell 1 from the working fluid inlet 7 and flows down inside the main body shell 1, while the hot water flowing in the heat transfer tube 5 in the opposite direction to the flow of the working fluid vapor flows. The working fluid is heated by heat exchange and flows out from the working fluid outlet 8. Incidentally, the mist portion of the working fluid that has entered the main body shell 1 from the working fluid inlet 7 is gradually collected by the mist collecting layer 9 made of the plate-shaped wire mesh layer. Therefore, the collected mist reaches the surface of the heat exchanger tube 5 due to the above-mentioned shear force and surface tension, where it is heated by the hot water in the heat exchanger tube 5, evaporates, and becomes vaporized. .

In this way, the mist in the working fluid evaporates and becomes steam, but from the beginning it is
The incoming heat also touches the heat transfer tube and is gradually heated in the flow direction, reaching a temperature above the saturation temperature. Therefore, even if there is some mist that is collected in the mist collection layer 9 but cannot reach the surface of the heat exchanger tube, it is heated by the high temperature steam that flows one after another and turns into steam.
That is, the mist trapping layer 9 traps the mist and widely distributes the liquid on the surface of the wire mesh, etc., thereby increasing the contact area of steam and increasing the heat transfer area. It acts to increase the heat transfer coefficient by increasing the relative speed with the heat transfer coefficient.
In this case, since the length of the flow path through which the working fluid flows is sufficiently long, the mesh of the wire mesh does not need to be extremely narrow, and the pressure loss of the working fluid can also be small.

Further, in the above embodiment, a plate-shaped wire mesh layer was provided parallel to the heat exchanger tubes, but as shown in FIG. A mist trapping layer 9 may be provided, and as shown in FIG.
It may be shaped so that the heat exchanger tube 5 passes through it.

〔Effect of the invention〕

As explained above, the present invention provides a mist collection layer on the outside of the heat transfer tube, at least a portion of which is in contact with the heat transfer tube, so that the mist contained in the working fluid is captured by the mist collection layer. It reaches the surface of the heat exchanger tube and is heated by the heat exchanger tube, or is heated by the steam flowing inside the main body shell and becomes steam,
As a result, the mist in the working fluid can be completely vaporized, and the steam flowing out of the heat exchanger can be completely free of mist. That is, the heat transfer coefficient can be significantly improved even in a high quality mist flow region. Therefore, the heat transfer area required for the entire evaporation process can be smaller than that of a mere conventional heat exchanger.

[Brief explanation of drawings]

FIG. 1 is a longitudinal cross-sectional view of a heat exchanger according to the present invention, FIG. 2 is a partial cross-sectional view taken along the line X-X in FIG. 1, and FIGS. 2 is a diagram corresponding to FIG. 1...Main body shell, 2...Hot water inlet side water chamber, 3...
Hot water outlet side water chamber, 5... heat transfer tube, 9... mist collection layer.

Claims (1)

[Scope of Claims] 1. In a counterflow type heat exchanger that causes fluid flowing inside and outside of a heat transfer tube to flow in opposite directions, a mist trap is provided on the outside of the heat transfer tube, at least a part of which contacts the heat transfer tube. A heat exchanger characterized by having a laminated layer. 2. The heat exchanger according to claim 1, wherein the mist collection layer is a wire mesh layer. 3. The heat exchanger according to claim 1, wherein the mist collection layer is a large number of plate-shaped wire meshes arranged in parallel with the heat exchanger tubes. 4. The heat exchanger according to claim 1, wherein the mist collection layer is a wire mesh layer arranged concentrically with the heat transfer tube. 5. The heat exchanger according to claim 1, wherein the mist collection layer is a wire mesh layer disposed in a plane perpendicular to the heat transfer tubes.