JPH031599B2 - - Google Patents

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention is used, for example, in low temperature difference power generation plants or heat pumps that generate electricity by utilizing the temperature difference between the surface layer and the deep layer of seawater. Concerning improvements to falling film evaporators.

(Prior Art) A system diagram is shown in FIG. 4, and an overview of a low temperature difference power generation plant will be explained. A relatively high-temperature fluid from a high heat source is introduced into evaporator a to heat and evaporate a working medium (for example, a low-boiling point medium such as fluorocarbon), and this steam is introduced into turbine b to perform expansion work. drive. By driving this turbine b, the generator c is rotated to generate electricity. This turbine b
The exhaust steam expanded in
is stored in This stored condensate is returned to the evaporator a again by a circulation pump f. The amount of evaporation from the evaporator a is always kept constant, and the driving force of the turbine b is adjusted by opening and closing the turbine bypass g in response to changes in the load of the generator c.

FIG. 5 shows a system diagram of a heat pump, and an overview will be explained. Fluid is introduced into the evaporator h from a relatively low-temperature heat source (heated waste water, etc.) such as factory exhaust heat, the working medium is heated and evaporated, and the vapor is supplied to the compressor i to increase the pressure and temperature. By condensing in the condenser j, the relatively high temperature heat source fluid is further heated.
The condensed working medium is expanded in an expansion valve k, the temperature of which is lowered, and returned to the evaporator h.

Conventionally, evaporators of this type of low temperature difference power generation plants and heat pumps have poor heat transfer performance on the working medium side (evaporation side) and tend to be larger. Therefore, efforts have been made to make the system more compact by promoting heat transfer on the working medium side, but this is all done by promoting heat transfer by nucleate boiling, and is limited to flooded evaporators, that is, horizontal evaporators. However, when considering the space for the entire plant and the space for installing the heat pump, it is preferable to use a vertical evaporator.

As the vertical evaporator, a vertical falling film evaporator can be considered. However, in a vertical falling film evaporator, the heat transfer mechanism on the working medium side (evaporation side) is similar to that of film condensation, and promotion of transfer by nucleate boiling is impossible. Therefore, the actual situation is to use a membrane-like condensation transmission promotion tube to promote transmission, and to obtain an acceleration rate of about 4 times.

(Problems to be Solved by the Invention) There are various types of heat transfer promoting tubes that perform the above-mentioned film condensation, but the one used in the vertical falling film type evaporator is as shown in Fig. 6. It is a fluted tube l with many grooves formed in the longitudinal direction of the outer periphery. When this fluted tube l is used, transverse waves perpendicular to the flow direction are generated while the liquid film m flows down the outer periphery as shown in FIG. (crest) straddles the liquid film of the adjacent groove. As a result of the liquid film being intermittently formed on the top n of the groove and flowing down, evaporation is likely to occur and the heat transfer performance is improved.

However, in such a fluted tube, evaporation progresses as the liquid film flows down in the longitudinal direction, and the liquid film becomes thinner as it goes downward. Therefore, in order to prevent the surface of the lower part of the heat exchanger tube from drying out, a considerable flow rate is required, but conversely, if the flow rate increases, the liquid film will become too thick at the upper part of the heat exchanger tube. A sufficient effect of promoting heat transfer cannot be expected. In other words, even if a fluted tube is used, heat transfer is not uniformly promoted in the longitudinal direction.

An object of the present invention is to obtain a falling film type evaporator that can perform evaporative heat transfer uniformly in the longitudinal direction of a heat transfer tube.

[Structure of the invention]

(Means for Solving the Problems) The present invention includes a ring-shaped insulating spacer inserted through the outer periphery of a vertically arranged heat exchanger tube, and a fluid distribution hole provided in the insulating spacer in the longitudinal direction of the heat exchanger tube. and a linear electrode that faces the outer periphery of the heat transfer tube and is inserted through the insulating spacer.

(Function) In the above configuration, when a high voltage is applied to the linear electrodes facing around the heat transfer tube and the liquid film is made to flow along the outer peripheral surface of the heat transfer tube, the liquid film is attracted to the linear electrode side. As a result, the liquid film on the surface of the heat transfer tube becomes thinner and evaporative heat transfer is promoted.
However, when reaching the lower part of the heat exchanger tube in the longitudinal direction, evaporation progresses and the surface becomes dry.However, insulating spacers provided at appropriate positions allow the fluidized liquid attracted to the linear electrodes to pass through the fluid distribution holes. The heat exchanger is guided again to the surface of the heat exchanger tube to continue evaporation.

As described above, according to the present invention, the flowing liquid is evaporated while being attracted to the linear electrode side, and the sucked liquid is returned to the surface of the heat exchanger tube by the insulating spacer provided at an appropriate position, and then the liquid is continuously evaporated. By providing one to several insulating spacers in the longitudinal direction of the heat transfer tube depending on the length and amount of liquid, the liquid film on the surface of the heat transfer tube can be made thinner and more uniform in the longitudinal direction. This means that evaporation can be carried out.

(Embodiment) Fig. 1 shows an embodiment of the present invention, in which a ring-shaped insulating spacer 2 is inserted and fixed to the outer periphery of a smooth heat exchanger tube 1 installed vertically. A large number of linear electrodes 3 are inserted through the heat exchanger tube 1, which are arranged facing each other at positions equidistant from the surface of the heat exchanger tube 1. Further, the insulating spacer 2 is provided with liquid distribution holes 4 facing the heat exchanger tube 1 in the longitudinal direction of the heat exchanger tube 1 so as to alternate with the linear electrodes 3 .

Thus, while supplying a heating medium to the inside of the heat exchanger tube 1 and applying a high voltage to each linear electrode 3, the heat exchanger tube 1 is
When the fluid to be evaporated is made to flow down from the upper part of the tube along its surface, the liquid film 5 that evaporates the surface of the heat transfer tube 1 is drawn toward the linear electrode 3, as shown in FIG. The part of the liquid film 5 that does not face the electrode 3 becomes a thin layer, and this part becomes extremely easy to evaporate.

In this state, the liquid film 5 flows downward in the longitudinal direction of the heat transfer tube 1, but as it flows down, the part of the liquid film that does not face the linear electrode 3 rapidly evaporates, and eventually this part dries and flows down. The liquid is heat exchanger tube 1 and linear electrode 3
It will only flow down the area between. As shown in FIG. 3, an insulating spacer 2 is inserted in the area where dry areas begin to appear.
The flowing liquid flowing down in the area sandwiched between the heat transfer tube 1 and the linear electrode 3 or along the linear electrode 3 itself is blocked by the upper surface of the insulating spacer 2, and the flowing liquid is blocked by the upper surface of the insulating spacer 2. The liquid is guided to the separation hole 4 and continues to flow downward as a liquid film along the surface of the heat transfer tube 1 again. At this time, it is more effective to promote evaporation if the fluid distribution hole 4 is opened at a portion that does not face the linear electrode 3.

As in the case described above, a portion of the flowing liquid flowing out from the fluid distribution hole 4 of the insulating spacer 2 is attracted to the linear electrode 3, and as a result, the liquid film is thin in the portion that does not face the remaining linear electrode 3. This will form a layer and promote evaporation.

Note that, depending on the length and diameter of the heat transfer tube 1, the amount of fluid, etc., if a plurality of insulating spacers 2 are provided spaced apart in the longitudinal direction of the tube, the evaporation efficiency can be maximized. Furthermore, the performance can be improved by appropriately setting the number and position of the fluid distribution holes 4 depending on the flow rate.

〔Effect of the invention〕

As described above, the present invention has linear electrodes facing the heat exchanger tube and an insulating spacer having fluid distribution holes inserted therein, so according to the present invention,
It is possible to uniformly generate thin portions of the flowing liquid in the longitudinal direction of the tube, thereby improving the evaporation heat conductivity and increasing the evaporation efficiency.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing the main parts of a falling film evaporator according to an embodiment of the present invention, FIG. 2 is a diagram showing how a liquid film is attracted to a linear electrode 3, and FIG. Diagram showing how the flowing liquid is distributed by insulating spacers,
Figure 4 is a system diagram of a low temperature difference power generation plant, Figure 5 is a system diagram of a heat pump, Figure 6 is a schematic diagram of a fluted pipe, Figure 6a is a cross-sectional view, and Figure 6 is a diagram of a fluted pipe.
Figure b is a front view, and Figure 7 is a diagram illustrating the operation of the fluted tube. DESCRIPTION OF SYMBOLS 1... Heat exchanger tube, 2... Insulating spacer, 3... Linear electrode, 4... Fluid distribution hole, 5... Liquid film.

Claims (1)

[Claims] 1. A ring-shaped insulating spacer inserted through the outer periphery of a vertically arranged heat exchanger tube, a fluid distribution hole in the longitudinal direction of the heat exchanger tube provided in the insulating spacer, and the insulating spacer facing the outer periphery of the heat exchanger tube. A falling film evaporator with a linear electrode inserted through the evaporator.