HU199980B - Heat-transfer system for dynamic latent storage heaters - Google Patents

Abstract

The solution according to the invention relates to the field of heat storage technology, in particular using the properties of phase change materials. The object of the invention to improve the heat input in a latent heat storage is achieved by the fact that the necessary on the heat input side of the memory heat transfer medium consists of two modules. One part of the heat exchanger is a system of conventional design. The second part of the heat transfer conveyor according to the invention consists of a frusto-conical pipe pipe, on whose (imaginary) lateral surface a multiplicity of stranded pipes, pipe loops or coiled tubing are arranged, wherein the pipe casing is almost completely in the phase change material of the storage tank. This can be created in the phase change material Aufschmelzkanaele that allow a performance increase in heat input up to 30%.

Description

FIELD OF THE INVENTION The present invention relates to a heat transfer system for dynamic latent heat accumulators operating with a phase change medium which is heated and cooled by direct contact with an evaporating and condensing heat transfer medium in a closed vessel or recirculation line.

Various variants and modes of operation of latent heat accumulators are known, such as known

(a) use of phase change media in which the phase transition heat is very high in order to maintain a low storage volume;

(b) the use of different materials and auxiliaries to compensate for material properties that adversely affect the heat transfer or snow removal from the phase change medium or from the medium.

Such a solution is described, for example, in DE-2 937 959, DD-209 902. and DD-154 126; economic patent description.

A common feature of the above solutions is the use of heat transfer media which are in direct contact with the phase change medium to increase the heat transfer capacity and are in motion to increase the convective component of the heat transfer.

They recommend the use of poorly volatile liquids (such as oils) as a heat transfer medium that remain in a liquid state during the introduction of heat or the removal of heat. However, it is also known to use volatile liquids, such as refrigerants, which pass from evaporation to condensation during heat and snow removal.

A prerequisite for the application is that the heat transfer medium and the phase change medium do not dissolve and separate from each other.

For solutions based on the use of difficult to evaporate liquids, it is essential that the heat transfer medium is driven by a circulating pump. In other embodiments, the heat transfer medium may move during the evaporation process without a separate drive, so mechanical movement is not necessarily required.

Solutions using circulating pumps are described, for example, in DE-2 826 404. DE 3 023 494; and DE-2 916 514; rock release document.

Solutions based on the use of an evaporative and condensing heat transfer medium without a recirculating pump are described, for example, in DD-225 857. and U.S. Patent No. 0,079,452. European patent.

Both solutions have the following problem:

The phase change medium is not at all, or only poorly permeable to all heat transfer fluids in the solid state. Due to poor permeability, the heat input to the phase change medium is severely limited.

For this reason, difficult to evaporate liquids can be circulated with little or no high pump pressure. The volatile liquids can only be circulated through capillaries and cracks in the phase change medium, or through phase change media which appear in crystalline bulk form under the influence of various additives, through the gaps between the crystals.

During evaporation, the vapor generated in the phase change medium and the reflux precipitate in the passageways mutually obstruct each other and thus prevent good snow transfer performance.

DE-3 010 625 discloses a solution to this problem. U.S. Patent No. 4,268,128 to heavy vaporizing liquids is a so-called "volatile liquid". It proposes a melting wire which is vertically passed through the phase change medium and which allows the phase change medium to be melted channel-wise.

The heat transfer medium can circulate freely within the heat reservoir through the channel thus formed.

This solution is only applicable to difficult to evaporate liquids.

In the case of highly volatile liquids, the above suggestion is not applicable since, on the one hand, the vapor bubbles required for snow transfer rise up through the channel without releasing heat on contact with the phase change medium; subsequent precipitation or repeated evaporation could occur.

For highly volatile liquids, expanding the heat transfer surfaces, for example by means of ribs and plates in a phase change medium, may be a useful solution. However, increasing the contact areas in this way results in increased material costs and has a limited effect on the evaporation and condensation process, so this way of increasing the cooling performance is only used in static latent heat storage units which do not operate without such surfaces.

It is an object of the present invention to improve the heat transfer performance of dynamic latent heat accumulators with evaporative and condensing heat transfer fluids, while reducing material consumption and increasing operational safety. The problem to be solved is to increase the thermal vapor content of the dynamic latent heat exchangers to the phase change medium by means of structural elements.

The object of the present invention has been solved by providing in a snow storage system having a conventional heat transfer part directly in contact with a heat transfer medium and directly in a phase change medium

HU 199980 Β has a contacting portion with melting conductors, in accordance with the present invention, the melting conductors are arranged along the circumferential surface of a frustoconical cone formed at an angle of 50-85 ° to the horizontal, and the melting conductors are adjacent to the lower circumferential boundary of

Preferably, the melting conduits according to the present invention are formed as forming pendulum tubes, which connect the lower circular conduit arranged in the heat transfer region with an upper circular conduit in the phase change medium. Thus, in such a solution, the pendulum pendulum tubes, with their associated lower and upper circuits, form a kiss cage.

The conventional snow transfer portion of the snow transfer system directly in contact with the heat transfer medium may be connected in series or in parallel to the trench.

In a parallel connection, a portion of the heating fluid from the heat source may be routed to a conventional portion of the heat transfer system via a bottom loop distributor.

From the lower conduit, the heating medium flows upwards through the hanging pipes and enters the upper conduit. In the upper circular conduit, the fuel is collected and passed through a return pipe into a container with the fuel leaving the conventional part of the snow transfer system.

In the case of a serial connection between the conventional part of the heat transfer system and the tubing cage, the heating medium is first completely passed through the tubing cage and only then flows into the conventional part of the heat transfer system.

In the heat transfer system of the present invention, the pendulum tubes may also be formed as loop-folded tubes at the top.

Optionally, a helical arrangement of the melting line or melting lines may also be advantageous. In this case, the melting line is formed as a helically rising melting sheet on the circumferential surface of the truncated cone.

Further, the melting conduits can be formed as hanging pipes with a closed end at the bottom, which connect to the lower circular conduit.

It is important that the melting lines or hanging tubes defining the truncated cone surface run along the truncated conical circumference of the desired angle range and that the kiss cage does not protrude above the phase change medium.

The oblique arrangement of the hanging pipes and the limited height of the kiss cage ensure that steam bubbles rising from the traditional part of the heat transfer system can only move in oblique and over closed channels. In this way, the rising vapor bubbles can be prevented from leaving vertically without touching the phase change medium, such as without 4 snow releases. In the proposed arrangement, the vapor bubbles are in continuous contact with the phase change medium and provide proper snow release.

The rising vapor bubbles contact the upper side of the oblique channel, while the post-heat condensing fuel particles travel down the lower side of the channel while they are also in continuous contact with the phase change medium and release additional snow. The snow transmitted by the condensed particles preheats the phase change medium. As a result, the heat input to the phase change medium is significantly increased.

As will be seen from the foregoing, according to the invention, the heat transfer of the phase change medium to the medium is due to the kinetic improvement of heat transfer through the kissing cage rather than to the increase of heat transfer surfaces. As a result, the advantage is that relatively few tubes are sufficient to achieve the desired result, resulting in a reduction in material input.

The cage defining the truncated cone surface according to the invention is configured so that the snow power delivered through the tubular cage is about 5-20% of the snow power applied to the phase change medium, while the component of the truncated cone forms an angle of 50-85 ° with the horizontal.

In the special case of using refrigerant as the heating medium, which condenses in the cage through the heat release, the overhead line may be missed and the hanger pipes closed at the top. The hanging pipes then act as heating pipes filled with refrigerant.

In a preferred embodiment of the invention, the hanging pipes arranged on the side of the boating cage defining the truncated cone surface are replaced by pipe cones. According to the invention, this can be accomplished by placing the upper circumference within the imaginary truncated cone just above the lower circumference. Preferably, the diameter of the lower and upper circuits is slightly different.

In a further embodiment of the invention the kissing cage defining the truncated cone surface is formed by a helical melting tube bent along the side surface of the truncated cone. In this case, no separate guides are needed.

According to the present invention, it is also possible to provide a tubular cage defining the truncated cone surface by connecting to the single lower guiding tube the superposed pendulum tubes arranged on the truncated cone surface.

The invention will be described in more detail with reference to the drawing. In the drawing, Figure 1 is a schematic diagram of an exemplary embodiment of a snow transfer system according to the invention.

-3HU 199930 Β

As can be seen from the drawing, the heat transfer system of the present invention has a known heat transfer region 4 (conventional part) in the heat conducting region 1 of the container bordered by a jacket 3 and a parallel trap arranged above it. The cage consists of a lower perimeter 9, an upper perimeter 10 and hanging pipes 7 connecting them. The bottom edge of the truncated cone base plate 9 is formed by the upper circumference 10 the edge of the top plate of the truncated cone and the pendulum tubes 7 form the parts of the truncated cone. A fuel distributor 14 is connected to the inlet of the heat exchanger 4 and the lower circuit 9. The outlet of the heat exchanger 4 and via the return pipe 6 is connected to the upper conductor 10 by a heating medium collector 15.

The bottom of the tank 1 is filled with a heat transfer medium. Above the heat transfer medium, 2 phase change media are provided. There are 5 snow transducers in the upper area of the tank 13 in the snow discharge region above the phase change medium 2. The snow discharge region 13 is not filled with a separate medium and is filled with the vapor from the heat transfer medium.

The baffle cage is arranged so that it is predominantly located in the phase change medium 2 and does not extend beyond it. The horizontal angle of the hanging tubes to oC is in the range of 50-85 °.

In the figure, 11 arrows indicate the flow direction of the heating medium and 12 arrows indicate the flow direction of the heat transfer medium.

The heat transfer system of the present invention operates as follows:

For the purpose of thermal communication, the heating medium is supplied through the heating medium distributor 14 in the direction of the arrow 11 through both the heat transfer unit 4 and the tube cage at a temperature higher than the melting point of the phase change medium.

As a result of the flow of fuel, the following processes occur simultaneously:

On the one hand, the phase change medium 2 melts along the hanging pipes 7, thereby creating melt channels, on the other hand, part of the heat transfer medium in the heat transfer region 1 evaporates on the heat transfer surface 4 and the fume bubbles 8 Due to the oblique position of the melt passages 8, the vapor bubbles are in continuous contact with the outwardly facing boundary surface of the melt passages 8, i.e. the phase change medium 2, as they move upwards. Since in the selected heat transfer system the evaporation of the heat transfer medium occurs at a temperature higher than the melting point of the phase change medium, the temperature of the vapor bubbles of the heat transfer medium is higher than the temperature of the phase change medium 2 not yet dissolved . Condensation heat contributes both to the warming of the phase change medium 2 and, upon reaching the phase change temperature, to phase change (melting).

The particles precipitated from the vapor bubbles of the heat transfer medium drop by drop on the inward facing side of the melt passages 8, where, due to the upward position of the melt passages 8, they are again in direct contact with the unmelted phase change medium. The reflux on the heat transfer surface 4 evaporates again and the whole process is repeated continuously.

Since the cage does not extend from the phase 2 medium, the above process takes place inside the phase 2 medium with very good heat transfer efficiency.

Based on our experiments using Na2SO410 H2O as a phase change medium and a refrigerant, it was found that the pendulum tubes were horizontally closed at an angle of 78 °, when 8% of the amount of fuel fed into the latent heat reservoir was flushed. performance gains can be achieved. A similar increase in performance can be achieved by conventional means, i.e., by increasing the heat transfer surfaces, by about 8 times the material turnover.

Claims (5)

A snow transfer system for dynamic latent heat storage tanks, comprising a conventional heat transfer portion arranged within the heat storage tank and directly in contact with a heat transfer medium and a melting line portion directly in contact with a phase change medium, characterized in that the melting lines are angled They are arranged along their circumferential surface and communicate with the lower circumference (9) which defines the major base of the stump cone below. Snow transfer system according to Claim 1, characterized in that the melting wires are formed as forming hanging wings (7) which form a lower perimeter line (9) arranged in the heat transfer region (1) with the upper perimeter line (2) in the phase change medium (2). 10) knit together. Heat transfer system according to Claim 2, characterized in that the hanging pipes (7) are formed as loops folded at the top. Heat transfer system according to claim 1, characterized in that the melting conductors are formed as a helically melting melting pipe along the circumferential surface of the truncated cone. Heat transfer system according to Claim 1, characterized in that the melting pipes are formed as hanging pipes with a closed end at the bottom, which are connected to the lower circular pipe (9).