CN205002645U - A new type heat exchanger for fused salt medium - Google Patents

Abstract

The utility model relates to a new type of heat exchanger for molten salt medium, which comprises an inner tube through which molten salt medium flows and a spiral tube through which unsaturated water medium flows. The gap between the inner tube and the spiral tube is provided with intermediate heat conduction The material layer, the middle heat-conducting material layer is completely wrapped on the outer wall of the spiral tube, the outer side of the middle heat-conducting material layer is provided with an inner protection tube, the inner protection tube is used to accommodate and support the middle heat-conducting material layer, and the outer wall of the inner protection tube is provided with a heat-insulating material layer for heat preservation. The outer side of the material layer is provided with an integral outer sheath. The utility model has the advantages of simple structure and reasonable design, which can effectively reduce the risk of freezing blockage caused by the rise of molten salt viscosity as the temperature drops, and reduce the heat and pressure loss caused by long-distance transportation. The upper heat exchange area can make water and steam in various states flow in the cross section to generate secondary circulation, mix more fully, and enhance the heat transfer effect.

Description

A New Heat Exchanger for Molten Salt Medium

technical field

The utility model relates to a novel heat exchanger for molten salt medium, which belongs to the technical field of photothermal power generation.

Background technique

At present, solar power plants with heat storage function in the field of photothermal power generation use molten salt as the heat storage medium. By converging sunlight on the molten salt heat absorber, the temperature of the molten salt rises, and then the molten salt is introduced into the heat storage tank to store heat. The heat in the molten salt is converted into the heat of the working medium of the Rankine cycle through the heat exchanger. Generally, water is used as the working medium of the Rankine cycle. The liquid water absorbs heat in the heat exchanger and becomes superheated steam to drive the steam turbine to generate electricity. The molten salt flows in the traditional heat exchanger and its intermediate heat exchange tubes. The most important point of the molten salt heat exchanger is to prevent the temperature from being too low and freezing blockage. However, there is no corresponding design improvement for various types of heat exchangers. The heat exchangers currently used in photothermal power generation technology are traditional shell-and-tube heat exchangers, including heat transfer oil-water, molten salt-water, water-water heat exchange, etc. It has a good heat exchange effect for liquid-liquid or liquid-gas, but it cannot fully meet the requirements for the heat exchange form of molten salt-water. Since the melting point of molten salt (here, the binary salt sodium nitrate potassium nitrate is taken as an example) is 207°C, and the complete melting temperature is 238°C, solid crystals will appear when the molten salt is lower than 238°C, and the viscosity will increase sharply as the temperature decreases below 300°C , due to the structural layout of the shell-and-tube type, the distance between the tube bundle and the shell, and the heat exchange tubes, no matter whether the molten salt flows through the tube side or the shell side, it will cause the molten salt to hang on the wall or even freeze; the form of the wall heat exchanger It is not conducive to the flow of molten salt, and it is more likely to freeze and block; the hybrid type adopts the method of directly mixing two heat exchange media, which does not meet the requirements of molten salt-water heat exchange. For shell-and-tube heat exchangers, due to the size difference between the connecting pipe and the shell, the reaction time for the start and stop of the thermal system is increased, and the pressure loss is increased when the molten salt flows through the tube side. At present, the shell-and-tube heat exchanger has been applied in modularization, but for the commonly used combination, it is only two heat exchangers superimposed, and three superimposed ones are even rarer, mainly because of the limited strength of the heat exchanger. Or multiple heat exchangers are arranged on the same plane, but at this time, the molten salt needs to be connected by external pipelines no matter on the shell side or the tube side, so the lowest point of the external pipeline must appear, which will have a great impact on the emptying of the molten salt when the system is closed . Therefore, the flexibility and modularity of the traditional shell-and-tube heat exchanger meet the requirements in the traditional field, but there are still many defects in the field of photothermal power generation with molten salt as the medium. In the traditional shell-and-tube heat exchanger, the replacement cycle of the heat exchange tube is short, and the equipment maintenance cost is high. For the field of photothermal power generation, due to the frequent start and stop of the thermal system, the life of the heat exchange tube will be shorter. Therefore, the traditional tube Shell heat exchangers are also unsatisfactory in terms of service life.

Utility model content

The purpose of this utility model is to provide a new type of heat exchanger for molten salt medium, which can effectively reduce the risk of freezing blockage caused by the increase of the viscosity of molten salt as the temperature decreases, and reduce the current technology that cannot meet the existing needs. The heat and pressure loss caused by long-distance transportation is reduced. At the same time, the unique tube design increases the heat exchange area per unit length, enabling water and steam in various states to generate secondary circulation on the cross-section when flowing, and the mixing is more complete. Enhance heat transfer effect.

The technical solution adopted by the utility model is: a new heat exchanger for molten salt medium, including an inner tube through which the molten salt medium flows and a spiral tube through which the unsaturated water medium flows, between the inner tube and the spiral tube There is an intermediate heat-conducting material layer in the gap, and the intermediate heat-conducting material layer is completely wrapped on the outer wall of the spiral tube. An inner protection tube is provided outside the middle heat-conducting material layer. The inner protection tube is used to accommodate and support the intermediate heat-conducting material layer. The outer wall of the inner protection tube is provided with There is an insulating material layer, and the outer side of the insulating material layer is provided with an integral outer protective layer.

In the present utility model: the intermediate heat-conducting material layer is composed of concrete or heat-conducting sand, the heat-preserving material layer is composed of silicon dioxide or aluminum silicate cotton, and the overall outer protective layer is composed of environmentally friendly magnesium steel or colored Composed of steel plates.

In the utility model: the diameter of the inner pipe is greater than the diameter of the spiral pipe, and the diameters of the two need to be determined according to the specific heat load. The spiral pipe is wound along the inner pipe and the outer wall of the spiral pipe and the inner pipe is separated by 1mm- 2mm, where the inner wall of the spiral tube is sandblasted or turned to form a spiral pipeline.

In the utility model: the inner tube, the spiral tube and the outer tube wall of the inner protection tube are all provided with independent brackets, which are used to ensure the distance between them and avoid collapse and extrusion.

In the utility model: the independent brackets are all fixed on the supporting formwork, and a formwork base is provided under the supporting formwork.

The beneficial effects of the utility model:

1. The inner pipe adopts a straight pipe with a large diameter to ensure good circulation when the molten salt flows during the cold start of the system, and the entire heat exchange process does not need to change the diameter of the pipe, and there is no molten salt in the tube of the shell-and-tube heat exchanger. The weak point that is easy to freeze and block during the side-time heat exchange process, due to the large diameter of the molten salt, can meet the requirements of long-distance transportation, without worrying whether the inlet pressure of the heat exchanger meets the requirements after long-distance transportation;

2. The helical tube adopts a helical structure similar to that of a spring, thereby increasing the heat exchange area per unit length. The helical structure can make water and steam in various states flow on the cross-section to generate secondary circulation, more fully mixed, and enhanced transmission. thermal effect;

3. Spiral pipes are sandblasted or turned out of the spiral pipe, so that water and steam in various states can effectively avoid the reduction of the heat transfer coefficient of the pipe wall caused by film boiling;

4. The spiral tube is wound along the inner tube, and the outer wall of the spiral tube and the inner tube is not in contact, so as to prevent the friction between the spiral tube and the inner tube when it is heated and axially expands and wear the tube wall, and the intermediate heat-conducting material layer filled between the two tubes has fluidity , to ensure that the two tubes can freely stretch and deform when subjected to primary and secondary stresses;

5. In terms of service life, both the spiral tube and the inner tube can meet the pressure pipe standard, that is, the service life is 15 years, which is greatly improved compared with the service life of the traditional shell-and-tube heat exchange tube bundle;

6. The thermal insulation adopts the composite thermal insulation form in the pipeline, which reduces the thickness of the thermal insulation and improves the economy. At the same time, the heat exchanger is commonly used in power stations such as tower type, trough type, butterfly type, and linear Fresnel type that use molten salt or similar media. can be widely applied.

Description of drawings

Fig. 1 is a partial layered sectional view of the utility model;

Fig. 2 is a partial view of the heat exchange tube of the present invention;

Fig. 3 is a schematic diagram of the structure of the independent support in the utility model.

Among them: 1. Inner tube; 2. Spiral tube; 3. Intermediate heat-conducting material layer; 4. Inner protective tube; 5. Thermal insulation material layer; 6. Overall outer protective layer; 7. Independent support; . Formwork base.

detailed description

Below in conjunction with accompanying drawing and specific embodiment the utility model is described in further detail.

As shown in Figures 1 and 2, a new type of heat exchanger for molten salt medium, including the inner tube 1 through which the molten salt medium flows and the spiral tube 2 through which the unsaturated water medium flows, the inner tube 1 and the spiral tube 2 The gap between them is provided with an intermediate heat-conducting material layer 3, the intermediate heat-conducting material layer 3 is completely wrapped on the outer wall of the spiral tube 2, the outer side of the intermediate heat-conducting material layer 3 is provided with an inner protection tube 4, and the inner protection tube 4 is used to accommodate and support the intermediate heat-conducting material Layer 3, an insulating material layer 5 is provided on the outer wall of the inner protective tube 4, and an overall outer sheathing layer 6 is provided on the outer side of the insulating material layer 5. The intermediate heat-conducting material layer 3 is composed of concrete or heat-conducting sand, the heat-insulating material layer 5 is composed of silicon dioxide or aluminum silicate wool, and the overall outer sheath 6 is composed of environmentally friendly magnesium steel or color steel plate; The diameter of the inner tube 1 is greater than the diameter of the spiral tube 2, and the diameters of the two need to be determined according to the specific heat load. The spiral tube 2 is wound along the inner tube 1 and the outer wall of the spiral tube 2 and the inner tube 1 is separated by 1mm- 2mm, wherein the inner wall of the spiral tube 2 is sandblasted or turned to form a spiral pipeline; the inner tube 1, the spiral tube 2 and the inner protection tube 4 are all equipped with independent brackets 7 to ensure the distance between them so as not to collapse and squeeze Pressure; the independent support 7 is fixed on the support formwork 8, and the formwork base 9 is provided below the support formwork 8.

Since this type of heat exchanger is generally similar to pipelines, it can be installed mainly in the form of pipeline laying, such as laying installation on high, middle and low brackets, or direct buried installation. No matter which installation form is adopted, the two heat exchange tubes (inner tube and spiral tube) and the inner protection tube have relatively independent support measures to ensure the strength and rigidity requirements between different components after stress, and the material can freely expand and contract after being heated.

Due to the fact that the higher the ground utilization rate of photothermal power generation and the more sunlight collected, the thermal system layout space is often limited. This type of heat exchanger has small dimensions, flexible layout, and inherent advantages. It is used in some very special applications. Under the circumstances, intermittent installation can be realized without affecting the total heat exchange efficiency of the system.

The molten salt heat exchanger in the field of photothermal power generation can not only achieve the heat exchange effect of traditional heat exchangers, but also meet the requirements of salt discharge in thermal systems. It can automatically discharge salt by gravity; for sites without height difference, it can also realize automatic salt discharge by changing the height of the heat exchanger support and adopting a gentle slope design throughout the process; Gentle slope design, segmented salt discharge.

After the molten salt heat exchanger is put into operation, it is still allowed to modify the heat exchanger by changing the route, increasing or decreasing the heat exchange area; by setting bypasses, adding pipe fittings, etc., to change the control process and facilitate later project docking, etc. , which can meet the requirements of flexible change schemes.

The specific embodiments of the present utility model have been described above, but the present utility model is not limited to the above description. For those skilled in the art, any equivalent modifications and substitutions to the technical solutions are within the scope of the present utility model. Therefore, all equivalent transformations and modifications made without departing from the spirit and scope of the present invention shall fall within the scope of the present invention.

Claims (5)

1. the new type heat exchanger for fused-salt medium; it is characterized in that: comprise interior pipe that fused-salt medium flows through and the helix tube that unsaturated aqueous medium flows through; space between interior pipe and helix tube is provided with intermediate thermal conductivity material layer; intermediate thermal conductivity material layer is wrapped in helix tube outer wall completely; the outside of intermediate thermal conductivity material layer is provided with interior protection tube; interior protection tube supports intermediate thermal conductivity material layer for holding, and be provided with adiabator layer at the outer wall of interior protection tube, the outside of adiabator layer is provided with overall outer jacket.

2. a kind of new type heat exchanger for fused-salt medium according to claim 1, it is characterized in that: described intermediate thermal conductivity material layer is made up of concrete or thermal conductive sand, described adiabator layer is made up of silica or aluminium silicate wool, and described overall outer jacket is made up of environmental protection magnesium steel or color steel.

3. a kind of new type heat exchanger for fused-salt medium according to claim 1, it is characterized in that: described interior pipe caliber be greater than the caliber of helix tube, helix tube is wound around and the outer wall interval 1mm-2mm of helix tube and interior pipe along interior pipe, and the sandblasting of helix tube inwall or turning go out helical form pipeline.

4. a kind of new type heat exchanger for fused-salt medium according to claim 1, is characterized in that: the outer tube wall of described interior pipe, helix tube and interior protection tube is equipped with independent rack, independent rack for ensureing its mutual distance, unlikely extruding of subsiding.

5. a kind of new type heat exchanger for fused-salt medium according to claim 4, is characterized in that: described independent rack is all fixed on and supports on mould bases, and the below supporting mould bases is provided with mould bases base.