RU2772386C2 - Device for chamber of latent heat exchanger - Google Patents

Abstract

FIELD: heat engineering.

SUBSTANCE: invention relates to the field of heat engineering; it can be used in a chamber of latent heat exchangers, used in distillation devices. In a device for a chamber of a latent heat exchanger, the chamber contains an evaporator in a capillary evaporation mode on its inner surface and a condenser in a capillary condensation mode on its outer surface, with a system of dosed liquid supply to micro-grooves or micro-waviness of the inner surface of the evaporator.

EFFECT: in the device, the formation of thin water films on the evaporator surface is prevented, wherein the device provides high coefficients of latent heat transfer.

9 cl, 5 dwg

Description

FIELD OF TECHNOLOGY

The present invention relates to an apparatus for a latent heat exchanger chamber comprising an evaporator on its inner surface and a condenser on its outer surface, applicable to distillation devices.

BACKGROUND OF THE INVENTION

Technical problems to be solved:

- Horizontal tube and shell or chamber latent heat exchangers are known with smooth or corrugated pipes or chambers, the outer surface of which is evaporative and on which the liquid evaporates in the thin downward film mode, having its own latent heat transfer coefficient, limited by the thermal resistance of the thin downward liquid film on the evaporation surface and the resistance of condensed water layers on the condensation surface. The use of tubes or chambers with corrugated surfaces increases the heat exchange surface and creates effective fluid flow turbulence effects that improve thermal performance, but the added heat transfer coefficient is still limited by the thermal resistance of the fluid layers. The thermal resistance of a thin descending liquid layer, especially when it is water or aqueous solutions, reduces the added latent heat transfer coefficient of pipes or chambers, which determines the currently used thermal gradient between the temperature of the evaporating vapor at the outer evaporative surface and the temperature of the condensed vapor at the inner condensing surface.

- Known vertical tubular and shell heat exchangers with smooth or corrugated pipes, which operate on their outer surface as condensers and on their inner surface as lowering or raising film evaporators, having their own thermal latent heat transfer coefficient, limited by the thermal resistance of the liquid layers on both side of the heat exchanger tube. The use of corrugated tubes with double corrugation on both sides improves the added latent heat transfer coefficient due to the turbulence that occurs in the fluid flows and the increased heat transfer surface, but this coefficient is still limited by the thermal resistance of the liquid layers. The known temperature difference between both sides of the pipes or chambers of these devices is also due to the thermal resistance of the liquid films which cover at least partially both sides of the vertical wall of the pipe, especially when it is water or aqueous solutions.

- Known evaporative tube heat exchangers in capillary condensation on the inner surface and capillary evaporation on the outer surface present the following practical problems of supplying a liquid evaporative fluid to the evaporating outer surface.

It is very difficult to achieve a liquid supply that does not overflow through the microgrooves or micro undulations when attempting to provide liquid fluid inside the micro grooves or micro undulations found on the evaporative outer surface of the tubes located in the tube bundle, as these are usually located in latent heat exchangers. The difficulty in supplying liquid is that it is introduced in an orderly manner into the capillary structures of the evaporative outer surface and causes thin descending layers due to excess supply of liquid fluid to the evaporating capillaries or causes dry areas when the supply is insufficient. Both phenomena limit the actual total latent heat transfer coefficient of the walls of these latent heat exchangers.

It is practically impossible to supply liquid for evaporation to the outer surface of horizontal pipes located in the center of the tube bundle without liquid overflow above the microgrooves, since the flow rate required to supply all the tubes in the bundle is greater than the flow rate that can be directed inside the microgrooves of each tube. Thus, the liquid intended for evaporation eventually forms thin films that cover the microgrooves on the outer surface, preventing them from capillary evaporation and creating heat insulating layers that reduce the added heat transfer coefficient of the latent heat of the heat exchanger tube.

DISCLOSURE OF THE INVENTION

The present invention is directed to increasing the overall latent heat transfer coefficient and reducing the temperature difference or gradient between the condensing surface and the evaporating surface of the latent heat exchanger by providing a latent heat exchange chamber as defined in the claims.

The latent heat exchange chamber has the following characteristics:

- this is a chamber with a level of tightness sufficient to maintain a difference or gradient between the pressure inside it and the pressure in the housing containing the specified chamber;

- it can be manufactured for use in a horizontal or vertical latent heat exchanger;

- its outer surface is a condenser, in which the condensing gas phase releases the heat of condensation, its inner surface is an evaporator, in which the evaporating liquid phase absorbs the latent heat of evaporation;

- its inner evaporative surface is covered with microgrooves or micro undulations, inside which the evaporating liquid flows, forming menisci with a concave liquid-vapor interface;

- its outer condensing surface is covered with microgrooves or other capillary structure, on which the condensed vapor condenses in the capillary condensation mode, forming menisci with a concave liquid-vapor interface;

- the chamber wall may have a zigzag, serrated or corrugated section, so that the condensing meniscus and the evaporating meniscus are adjacent on both sides of the chamber wall or separated by a short thermal path between both menisci;

- layers of heat-insulating liquid are reduced or eliminated in the thermal path due to the latent heat of condensation released on the condensing outer surface and the latent heat absorbed on the evaporative inner surface, due to a combination of the following elements:

- microgrooves or other capillary structure of the condensing surface have the necessary shape, slope and section for the removal of condensed liquid, so that between the condensing meniscus and the end of the capillary structure in which it is located, there is a region free from liquid layers;

- the microgrooves or micro undulations on the evaporative surface have the necessary shape, slope and section to guide the evaporated liquid and drain the rest of the non-evaporated liquid with the required salt concentration and to ensure that between the evaporative meniscus and the end of the microgroove or micro undulations in which it is located, there was at least one liquid-free zone along the microgroove or microwaviness;

- orderly supply of the evaporating liquid into microgrooves or micro undulations on the evaporating surface; The location of the evaporator surface within the chamber allows for easy access to the inside of each chamber and an orderly and uniform supply of liquid into the microgrooves or micro-undulations of the evaporator surface of each chamber, minimizing liquid overflow over the microgrooves and minimizing dry areas, so that the well-known problem of heat exchange tubes configured in a horizontal tube bundle is overcome. , the evaporating surface of which is located on the outer surface of a known pipe, in which it is practically impossible to supply liquid to the pipes located in the central part of the tube bundle of the heat exchanger without the formation of liquid films, since the supply of water to the pipe-pipe cascade implies a higher flow rate than the microgrooves can accommodate outer evaporation surface. In the known horizontal tube bundle configuration, thin water films are necessarily formed on the outer evaporative surface, which reduces the added latent heat transfer coefficient. On the other hand, if the surface of the evaporator is located inside the pipe, it is possible to provide access directly to the inside of each pipe and make a controlled, metered, uniform and accurate supply into the microgrooves, without the formation of overflowing layers of water.

The combination of good liquid dosing by means of a supply system to the evaporating inner surface, combined with evaporation within the capillary structure that covers it, makes it possible to reduce or eliminate liquid layers on the evaporating surface.

The absence of liquid layers with thermal resistance on the path between the point of release of the latent heat of condensation and the point of absorption of the latent heat of evaporation allows higher latent heat transfer coefficients achieved in the heat exchanger, which allows to reduce differences or temperature gradients between the steam on the condensing side and the steam on the evaporation side.

BRIEF DESCRIPTION OF THE DRAWINGS

A more detailed explanation of the invention is given in the following description, which is based on the accompanying drawings:

in fig. 1 is a cross-sectional view of a latent heat exchange chamber and its internal evaporative liquid supply system, as well as a view of the condensing outer wall of the latent heat exchange chamber covered at least in part by microgrooves or other capillary structure;

in fig. 2 shows a longitudinal section of a latent heat exchange chamber in an embodiment with microgrooves perpendicular to the chamber axis and an enlarged detail of its zigzag section;

in fig. 3 shows a cross-section of a horizontal body and a chamber device, in an embodiment with chambers arranged in overlapping rows;

in fig. 4 shows a cross-section of the chamber in an embodiment with a corrugated irregular section and with a view of its outer surface with microgrooves or micro-undulations; and

in fig. 5 shows a cross section of a device with vertically arranged chambers and a detail of a chamber with an internal brine supply system.

IMPLEMENTATION OF THE INVENTION

In FIG. 1 and 2 show the location of the heat exchange chamber 1 of latent heat condensing on its outer surface and evaporating on its inner surface.

The outer surface of the heat exchange chamber 4 is covered, at least in part, with microgrooves or other capillary structure in which the vapor is condensed in a capillary condensation mode. The condensed liquid on the outer surface forms menisci 8 with a concave liquid-vapor interface. Capillary condensation occurs on this meniscus, and energy is released in the form of latent heat.

The inner surface of the latent heat exchange chamber is covered, at least in part, with micro-grooves or micro-undulations, in which the evaporation liquid flows in an orderly manner, forming menisci 7 with a concave liquid-vapor interface. From the upper end of these menisci 7 the most efficient evaporation takes place and the latent heat is absorbed.

The latent heat exchanger, which condenses on its outer surface and evaporates on its inner surface, can be implemented in a horizontal configuration as shown in FIG. 1 or in a vertical configuration. One embodiment is one with microgrooves or micro undulations parallel to the chamber axis for installation in a vertical configuration. Another embodiment is one with microgrooves or micro undulations perpendicular to the chamber axis for mounting in a horizontal configuration.

The latent heat exchange chamber has an oval section 1 as shown in FIG. 1, or it may also have a square, rectangular, circular, or irregular section, as shown in FIG. 4. The cross section is a parameter that will depend on the characteristics of the device in which the heat exchanger is built and on what kind of distillation will be carried out.

For chambers operating in a horizontal configuration, at least one mechanism 2 is built into the chamber for supplying an evaporating liquid, the excess of which 3 is removed from the lower region of the heat exchange chamber. This evaporating liquid supply mechanism 2 may be of the shower, sprinkler, atomizer or mist type, which wets the microgrooves or micro undulations, forming menisci and without creating overflows over the microgrooves. Excess liquid 3 and steam released during the evaporation process are removed from at least one of the ends of the chamber or from special openings created in the chamber for this purpose.

As shown in FIG. 5, for chambers operating vertically, evaporative liquid may be supplied to the evaporative inner surface of the chamber by a pressurized liquid supply system 19 at least at the top of each chamber, and gravity feed mechanisms or structures may be used within the evaporative liquid chamber.

In FIG. 2 shows a longitudinal section 5 of the wall of the latent heat exchange chamber in an embodiment with microgrooves perpendicular to the axis of the chamber, and an increase in its zigzag section 6 in order to match or bring the evaporating meniscus 8 closer to the evaporating meniscus 7 and achieve a thermal path 9 free from liquid layers. This proximity of the meniscus and the thermal path free of water layers can also be achieved with a serrated or corrugated section.

The inner surface of the latent heat exchange chamber is covered with microgrooves or micro undulations, in which the evaporating liquid forms a meniscus 7 with a concave liquid-vapor interface. The most efficient evaporation of the liquid occurs from the upper end of this meniscus 7. The cross section of the microgroove or micro-waviness and its slope are sufficient to ensure that between the end of this meniscus 7 and the end of the micro-groove or micro-waviness in which it is located, there is an area free from liquid layers or films.

The outer surface of the latent heat exchange chamber is covered with microgrooves or other capillary structures, in which the vapor condenses in the capillary condensation mode and forms menisci 8 with a concave liquid-vapor interface. The cross section of the microgroove or other capillary structure and its slope are sufficient to ensure that there is a region free of liquid layers or films between the end of the condensed liquid meniscus 8 and the end of the capillary structure in which it is located.

The latent heat exchange chamber 1, 5, 20 with capillary evaporation inside and capillary condensation outside minimizes the formation of heat-insulating liquid films due to a combination of the following factors:

1 - Between the end of the condensing meniscus 8 and the end of the capillary structure on the outer surface of the chamber wall there is a region free from layers of condensed liquid, through which the released energy is effectively transferred in the form of latent heat of condensation. On the evaporating inner surface there is also a zone free from liquid layers between the end 7 of the meniscus and the end of the capillary structure in which it is located. Thus, there is an effective thermal path 9, free from layers of liquid, between the top of the condensing meniscus 8, where the latent heat of condensation is released on the outer surface, and the upper end of the meniscus 7 of the evaporating liquid on the inner surface, where the latent heat is absorbed.

2 - The liquid supply to the inner evaporating surface is not performed in the descending film mode. The evaporated liquid is fed into microgrooves or micro undulations through which it flows, forming menisci. In the horizontal configuration of the latent heat exchange chamber, at least one channel 2 is built inside the chamber with devices arranged along the pipe for distributing the evaporated liquid. Some forms of such liquid distribution may be in the form of showering, splashing, spraying, or fogging, creating microdroplets or mist within the chamber that wets any microgrooves or micro undulations.

In the vertical configuration of the heat exchange chamber, the evaporative liquid is supplied through at least one channel 19 with at least one liquid distribution mechanism at the top of the chamber. Some forms of distribution of the liquid to be evaporated may be by showering, splashing, spraying or fogging. It is also possible to use at least one overflow or gravity evaporative liquid supply system located in the upper part of the chamber for orderly supply of evaporable liquid into microgrooves or micro-undulations on the inner surface of the chamber.

3 - The location of the evaporation surface inside the chamber allows you to supply the amount of liquid for evaporation in a uniform and dosed way into the microgrooves or micro-undulations on the evaporation surface of each chamber, without the formation of liquid overflows above the microgrooves, which would lead to the formation of heat-insulating liquid layers. Thus, the well-known problem of tube bundles in a horizontal configuration with an outer evaporative surface is overcome, in which it is impossible to supply liquid to the outer surface of the tubes located in the center of the bundle without creating liquid films having a thickness greater than the evaporative microgrooves, since the flow rate required for delivery to all pipes requires thicknesses that exceed the volume of liquid that can flow inside the microgrooves. In vertical configurations, placing a dispenser, dispenser, or nebulizer within each chamber ensures uniform and accurate delivery to all micro-grooves or micro-ripples of the evaporative surface within the chamber.

In vertical configurations, it is also possible to have at least one uniform and accurate metered gravity overflow system to allow evaporation of liquid within the micro-grooves or micro-undulations of each chamber.

Thus, between the point where the latent heat of condensation is released on the meniscus 8 on the outer condensing surface and the point of absorption of the latent heat of evaporation at the end of the meniscus 7 on the inner evaporating surface, energy is transferred along a thermal path 9 free from liquid layers, reducing or eliminating thermal resistance created by liquid layers.

This path 9, free from liquid layers or films, can also theoretically be implemented in evaporator-condenser tubes with capillary structures on their inner condensate surface and on their outer evaporator surface. But in practice, when these tubes are arranged to form a tube bundle in a latent heat exchanger, it is difficult to access the outer surface of the tubes inside the bundle, especially in horizontal configurations, and the supply of liquid to the evaporative outer surface of these tubes ends up overflowing with microgrooves and forming descending films that cover the microgrooves and form dry areas. Both phenomena reduce the total latent heat transfer coefficient. To avoid these problems with the supply of liquid to the microgrooves on the evaporative surface, it is necessary to reposition the evaporative surface and place it in a latent heat exchange chamber, where the exact amount of liquid to be evaporated can be fed into the microgrooves or micro undulations.

The location of the evaporation zone on the inner surface of the chamber also facilitates periodic chemical cleaning processes by ensuring that the entire evaporation surface is immersed in the cleaning liquid for a programmed period of time. The supply system 2 also allows periodic pressure cleaning inside the chamber.

Latent heat exchange chambers may have a height equal to the diameter of the housing in which they are placed, or they may have a lower height. Figure 3 shows a cross-section of an embodiment with a housing device with horizontal chambers grouped in rows at different levels. The height of the chamber can be adapted to the distillation conditions. Among other factors, its height can be a function of a combination of the flow rate that can pass through the microgrooves or micro undulations, the evaporation rate, and the desired unevaporated brine concentration.

Figure 4 shows a cross-sectional view and a view of the outer surface of an embodiment with a chamber covered with microgrooves with an irregular corrugated section 10. This section 10 allows the chamber to occupy a volume similar to that occupied by a tube bundle in a known configuration of a known shell and tube latent heat exchanger.

The location of the latent heat exchange chambers with capillary condensation on their outer surface and evaporation from the end of the meniscus in capillaries on their inner surface and the effective distribution of liquid inside microgrooves or micro undulations, achieved with an accurate supply of the liquid to be evaporated inside the chamber, allow:

1 - to achieve in practice higher latent heat transfer coefficients than those obtained in known latent heat exchangers;

2 - work with temperature differences between the temperature of the condensed vapor on the outer surface and the temperature of the vaporized vapor on the inner surface, reaching gradients of only 0.2 ° C or less, plus obtain the necessary temperature jump by raising the boiling point of the evaporated brine;

3 - Achieve these heat transfer coefficients and temperature gradients when operating at low temperatures. In particular, in the case of desalination devices operating at temperatures that may be equal to or close to the medium temperature of the desalination liquid.

Claims (9)

1. A device for a latent heat exchange chamber condensing on its outer surface and evaporating on its inner surface, characterized in that the outer surface of this chamber is covered, at least in part, with microgrooves or other capillary structure in which condensation is carried out in a capillary mode, and the menisci of the condensing liquid are formed with a concave liquid-vapor interface; the inner surface of the chamber is covered, at least in part, with microgrooves or micro-undulations, in which the evaporated liquid flows and forms menisci with a concave liquid-vapor interface, and evaporation occurs from the upper end of the meniscus, where evaporation is most effective; the evaporating liquid is applied without obstruction in a direct and controlled manner to the evaporating inner surface of each chamber without unwanted overflows of liquid in micro-grooves or micro-undulations and reducing or eliminating dry areas; and the chamber has thermal paths free of liquid layers between the surface of the condensing meniscus, where the gas phase condenses and releases the latent heat of condensation, and the end of the evaporating meniscus, where the liquid phase evaporates and absorbs the latent heat of evaporation. 2. The device according to claim. 1, characterized in that one section of the chamber wall in the direction of microgrooves or micro-undulations has a zigzag, serrated or corrugated shape. 3. Device according to claim 1, characterized in that the latent heat exchange chamber has an oval cross section (1). 4. Device according to claim 1, characterized in that the latent heat exchange chamber has a circular cross section (1). 5. Device according to claim 1, characterized in that the latent heat exchange chamber has a rectangular or square section (1). 6. Device according to claim. 1, characterized in that the microgrooves or micro-undulations are located perpendicular to the central axis of the chamber, for the use of latent heat exchangers in horizontal configurations. 7. Device according to claim. 1, characterized in that the micro-grooves or micro-undulations are located parallel to the central axis of the chamber for the use of latent heat exchangers in vertical configurations. 8. The device according to claim 1, characterized in that the latent heat exchange chamber contains inside at least one channel for supplying the evaporated liquid, equipped with at least one dosing device for watering, spraying, spraying or fogging the liquid. 9. The device according to claim 1, characterized in that the latent heat exchange chamber has a vertical configuration and has at the upper end of each chamber at least one mechanism or structure for gravitational dosing of the evaporated liquid on the inner surface of the chamber.

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