JP6347558B2 - Condensation or frost control carrier - Google Patents

Description

  The present invention relates to a carrier for suppressing condensation or frost formation, and more specifically, it can provide a maintenance-free heat exchange surface by preventing mass transfer on a heat exchange surface having a large temperature difference from the surroundings. Condensation or frosting that enables highly efficient and stable cooling on the heat exchange surface when the humid air is cooled through the heat exchange surface or when absorbing heat from below the freezing point in the temperature boundary layer The present invention relates to a suppressive carrier.

When heat exchange is performed between the fluid and the humid air via the heat exchange surface, the heat exchange surface temperature is lower than the air temperature between the fluid and the humid air on the heat exchange surface on the side in contact with the air. In some cases (hereinafter referred to as the cooling surface), condensation, frost formation or freezing occurs frequently.

Hereinafter, the conditions for the occurrence of the frosting phenomenon or the condensation phenomenon will be described with reference to FIG.
When the air temperature is 0 ° C or higher and the water vapor state of the atmosphere is a water saturated atmosphere (including the above), water droplets are generated by condensing water vapor to the condensation nuclei in the atmosphere, and then drop and accumulate on the cooling surface Then, water vapor condenses on the water droplets, and the water droplets grow and merge repeatedly to form large water droplets, and when the adhesive force cannot resist gravity, it flows down (falls) on the cooling surface.
In addition, when the air temperature is 0 ° C or lower and -40 ° C or higher, and the water vapor state of the atmosphere is a water saturated atmosphere (including the above), supercooled water droplets are generated by condensing water vapor to the condensation nuclei in the atmosphere. Then, it drops and accumulates on the cooling surface, and after the supercooled water droplets grow and merge, it freezes, and the frozen ice particles sublimate water vapor to cause frost growth.
In addition, in the same air temperature of 0 ° C or lower and -40 ° C or higher, and in the phenomenon where the water vapor state of the atmosphere is above ice saturation and below water saturation, ice crystals are generated by sublimation of water vapor to the sublimation nuclei in the atmosphere. After that, it falls and accumulates on the cooling surface, and water vapor sublimates to the ice crystals, resulting in a phenomenon of frost growth.

Here, the phenomenon of condensation and sublimation will be explained a little more. When the humid air is cooled, the water vapor in the air becomes saturated (called water saturation), and no more water vapor can be contained in the gas, and condensation begins. The air temperature at this time is called dew point temperature. When the temperature is below 0 ° C, there are two saturation phenomena of water vapor saturation: ice saturation and water saturation. This is because the amount of saturated water vapor in the ice state is smaller than the amount of saturated water vapor in the water state, so when cooling in humid air below 0 ° C, the ice saturated state starts first, and the amount of saturated water vapor exceeds Water vapor appears as ice crystals (called ice crystals) in ice crystal nuclei in the air by sublimation. Here, the air temperature is defined as the freezing point temperature. Note that when further cooling is performed at low temperatures, water saturation occurs, and condensation begins in the same way as above 0 ° C. However, when the air temperature is up to -40 ° C, the condensed droplets do not freeze immediately and the supercooled liquid It becomes a drop. The air temperature at this time is called dew point temperature, which is the same as 0 ° C. or higher. The supercooled liquid droplets are stochastically frozen over time. The frozen particles become ice, and the water vapor pressure of the ice is lower than the surrounding water vapor pressure, so the water vapor sublimes more actively on this ice surface, and the frost crystal P4 starts to grow rapidly. It will be.

When the air temperature is -40 ° C or lower, the water vapor state in the atmosphere is a water-saturated atmosphere (including the above), and water vapor condenses on the condensation nuclei in the atmosphere, but immediately becomes frozen particles, and then on the cooling surface. The phenomenon is that the frozen particles that fall and accumulate on the surface accumulate and form powdery frost. At this time, when the cooling surface is -40 ° C or lower, but the ambient air temperature is warmer than -40 ° C, the accumulated powdery frost becomes thick, and the surface temperature of the frost layer exposed to the atmosphere is -40 ° C. If it becomes above, water vapor | steam sublimates to the frost and it may become a phenomenon which grows frost.
Also, in the phenomenon where the atmospheric temperature is -40 ° C or lower and the atmospheric water vapor state is above ice saturation and below water saturation, ice crystals are generated by sublimation of water vapor to the sublimation nuclei of the atmosphere, and then cooled. It becomes a frosting phenomenon in which water vapor sublimates and grows on ice crystals that fall and accumulate on the surface.

In addition, although said description described that the condensation nucleus and the sublimation nucleus existed in the atmosphere in the temperature boundary layer of the cooling surface vicinity, since the condensation nucleus and the sublimation nucleus exist also on the cooling surface, the Even on the cooling surface, condensation, sublimation, and sublimation phenomena directly occur on the cooling surface. Thus, even if the supersaturation phenomenon does not occur in the air, if the cooling surface is equivalent to the atmosphere, condensation and sublimation phenomenon occurs on the cooling surface.

Condensation may cause deterioration of hygiene such as generation of fungi, or corrosion or leakage, contamination of the heat exchange surface, etc.On the other hand, frost formation or icing will cause problems similar to dew condensation when frosted. The ice layer is a heat resistance layer in heat exchange, and there is also an obstruction of ventilation due to physical thickness, which causes a large decrease in the amount of heat exchange together with the heat resistance layer due to liquid film formation on the heat exchange surface during condensation. Therefore, conventionally, various techniques for defrosting or dehumidifying the heat exchange surface have been performed.

In this regard, Patent Document 1 discloses a humidity control agent or a dew condensation preventing agent using a porous material.
More specifically, in this humidity control agent or anti-condensation agent, fine particles of nanometer order are packed and accumulated without impairing voids between the particles without using a material having porous particles. A porous material having nanometer-sized pores between fine particles, having a porous structure having a broad pore distribution in a pore radius range of 1 nm to 10 nm, Based on Kelvin's capillary condensation theory, it shows an increase in water vapor adsorption in the region of relative humidity of 75% to 93%. More specifically, the rise of the adsorption isotherm is about 80%, the moisture absorption in the range of 75% to 93% relative humidity is about 12 mass%, and the relative humidity is about 70 from the desorption isotherm. %, The water vapor adsorbed in the range of 75% to 93% relative humidity is released and the dew condensation preventing ability is restored.

According to such a humidity control agent or anti-condensation agent, it can be used repeatedly by adsorbing water vapor in the humid air that is the cause of dew condensation and recovering the anti-condensation ability by desorption. Since the pore radius is 1 nm to 10 nm, it is possible to capture water vapor in the humid air, but in the case where supercooled condensed droplets are generated in the humid air when the humid air is at a temperature below freezing point. Since the diameter of the supercooled condensed droplet is at least 1 μm, it is impossible to control humidity or prevent condensation by capturing the supercooled condensed droplet.
In this regard, maintenance-free heat exchange is prevented by preventing mass transfer on the heat exchange surface where the temperature difference from the surroundings is large, such as in humidifier coolers of refrigeration systems that handle humid air below freezing. Realization of a heat exchange surface maintenance method capable of providing a surface is desired.

On the other hand, especially when humid air such as a humid air cooler is cooled below the freezing point, or when absorbing heat from humid air such as an LNG vaporizer, when the humid air is below freezing point, the cooling surface that is the heat exchange surface has condensation. However, frost formation or icing occurs, but the frost layer becomes a heat resistance layer because of its low thermal conductivity, and the grown frost may impede the ventilation of the humid air that is to be cooled. This will cause a reduction in exchange efficiency.
In this regard, Patent Document 2 discloses a heat exchanger that can be continuously operated for a long time while utilizing heat of solidification by making it easy to mechanically remove frost. More specifically, this heat exchanger is a heat exchanger that can absorb heat from humid air, and has fine convex portions and concave portions on the surface, and a minimum width of 100 μm or more and 500 μm on the upper surface of the convex portion. It has the following plane portions, and the minimum width of the recess is 100 μm or more and 1000 μm or less. By providing convex portions and concave portions on the surface of the heat exchanger, it is possible to grow frost crystals P4 in the vertical direction on the flat portion on the upper surface of the convex portions, and frost crystals P4 grow on the convex portions, Since there is a gap above the recess, comb-like frost crystals P4 are formed as a whole. Since such a shape is structurally weak, it can be easily removed by mechanical removal means such as a brush or a scraper, thereby enabling heat exchange that enables continuous operation for a long time while using solidification heat. Can be provided.

Furthermore, Patent Literature 3 discloses a frost prevention member that suppresses frost growth. More specifically, the anti-frosting member has a water repellent part having a high water repellency and a hydrophilic part having a higher hydrophilicity than the water repellent part in a predetermined pattern on the surface of the member. Since the part has relatively high water repellency, it is difficult for frost to adhere to it, while the hydrophilic part tends to adhere to frost. Therefore, frost does not grow greatly in the water repellent part, but frost grows greatly in the hydrophilic part, so that the frost in the hydrophilic part grows large and then collapses when it cannot resist the flow of humid air and grows again. -Repeat the collapse. Thus, by forming the water repellent portion and the hydrophilic portion on the surface of the member in a predetermined pattern, the frost growth and collapse are promoted to suppress the frost growth.
However, when frost prevention is achieved by surface processing or surface treatment of the heat exchange surface as disclosed in Patent Document 2 and Patent Document 3, frost formation occurs over time, and it takes a long time. While it is difficult to maintain anti-frosting over time, the frosting condition changes depending on the temperature conditions, humidity conditions, or changes in the flow state of the humid air. It is difficult to deal with fluctuations in
Furthermore, since frosting of moist air itself is prevented, sensible heat exchange can be promoted by preventing frosting on the cooling surface, but latent heat exchange (solidification heat) associated with the phase change of water vapor is eliminated. The total heat exchange method is not necessarily an improvement.

In this regard, Patent Document 4 discloses a frost reduction device for a cooler. More specifically, this apparatus is disposed in the vicinity of a cooling heat exchanger in which a plurality of plate-like fins are joined to a heat transfer tube, and has an injection means having a plurality of nozzles perpendicular to or parallel to the plane direction of the fins, Drive means for reciprocating the injection means, and the injection means moves parallel or perpendicular to the plane direction of the fins to inject the humid air. By arranging a plurality of nozzles in a row and moving them parallel or perpendicular to the plane direction of the fins, and discharging the humid air along the fin surfaces of the cooler, the entire fin area of the cooling heat exchanger Wet air is injected onto the fin surface, and the pressure resistance of the fluid acts on the frost attached to the fin surface, so that the water droplets in the supercooled state and the frozen frost before becoming frost can be removed. As a result of reducing frost formation with a small discharge amount of moist air without stopping operation, cooling operation efficiency can be maintained high, and defrost prevention and defrost operation costs can be reduced.

However, this frost reduction device of the cooler forcibly removes frost by injecting moist air against the frost frosted on the fin surface, and does not prevent frost formation in the first place. Since the frost formed on the fin surface cannot be frosted, it is necessary to perform maintenance so that the nozzle opening is not blocked due to the separate arrangement of the frost reduction device in the vicinity of the cooling heat exchanger.

In this regard, Patent Documents 5 and 6 disclose an ice frost or ice / snow removal net that removes ice / snow from the windshield when ice or frost adheres to the windshield of an automobile or when snow has accumulated. .
More specifically, this ice / frost or ice / snow removal net is made of wire rods arranged in a planar grid pattern having a predetermined wire width and a predetermined mesh width, and is directly laid on the windshield of an automobile. It is.
According to such an ice frost or ice / snow removal net, the ice or frost formed in the mesh opening is integrated with the net and the snow falling on the mesh opening is integrated with the net, and the net is pulled or peeled through the mesh opening. It removes the ice, frost, or accumulated snow formed on the windshield together with the net.
Therefore, in order to integrate the ice, frost or snow to be removed with the net, the width of the wire is determined according to the thickness of the formed ice, frost or snow, and the adhesion of the wire to ice, frost or snow is determined. The mesh width is determined accordingly.

More specifically, if the thickness of ice, frost, or snow is about 3 mm, the wire width is set to 2 mm to 6 mm and the mesh width is set to 10 mm to 50 mm (Patent Document 5). If the thickness of ice, frost or snow is 2 mm or less, the wire width is set to 0.5 mm or more and less than 2 mm, and the mesh width is set to 1 mm or more and 10 mm or less (Patent Document 6).
In any case, the ice frost or ice / snow removal net simplifies the formation of ice frost or snow on the car windshield, as in the case of a car windshield with no parking roof. The ice frost or ice snow integrated on the net by the net formed in (1) above is merely removed by pulling or peeling the net together with the net.

As described above, the conventional heat exchanging surface cannot maintain the heat exchanging surface for a long time and cannot maintain the heat exchanging of the cooling surface with time.
As described above, the idea of causing these phenomena such as condensation and frost formation to act separately from the cooling surface is not disclosed or even suggested.

Japanese Patent No. 4599592 JP 2012-82989 A JP 2003-240487 A JP 2008-64326 A Utility Model Registration No. 3160488 Japanese Patent No. 4224121

  In view of the above technical problems, the object of the present invention is to provide a maintenance-free heat exchange surface by preventing mass transfer on the heat exchange surface with a large temperature difference from the surroundings, and heat exchange Enables efficient and stable cooling on the heat exchange surface when the humid air is cooled via the heat exchange surface or when absorbing heat from below the freezing point in the temperature boundary layer. The object is to provide a carrier for suppressing condensation or frost formation.

The present invention pays attention to the phenomenon of condensation, frost formation, and icing on the heat exchange surface, and causes these sublimation / condensation / freezing phenomena to act separately from the cooling surface instead of acting on the cooling surface. It is an idea.

Further, the carrier is planar, has a regular or irregular cross section, has a configuration in which predetermined widths and openings are alternately arranged, and has a predetermined depth from the cooling heat exchange surface. It may be.

Further, the planar carrier is mesh-shaped and may have a predetermined mesh opening width, a predetermined wire width and thickness.

Furthermore, the size of the planar carrier is such that the width of the carrier is 100 μm or more and 2000 μm or less, the width of the opening is 100 μm or more and 1000 μm or less, and the depth from the surface on the temperature boundary layer side of the carrier to the heat exchange surface for cooling is 100 μm. It may be the above.

In addition, the carrier may be a three-dimensional carrier having a three-dimensional structure having voids by superposing fibers of a predetermined length having a regular or irregular cross section in a nonwoven fabric shape.

In addition, the three-dimensional carrier is thickened so that a part of the three-dimensional carrier can be disposed in the main airflow outside the temperature boundary layer, and the airflow is guided into the carrier inside the boundary layer, so that the heat transfer on the heat exchange surface for cooling is performed. It may be promoted.

Further, the planar carrier is divided into a plurality of layers in the heat flow direction of the cooling heat exchange surface,
The upstream side of the plurality of layers in the heat flow direction is disposed in the main airflow outside the temperature boundary layer, and in the planar carrier adjacent to the heat flow direction, the openings are mutually open so as to guide the airflow into the carrier in the boundary layer. It is also possible to promote heat transfer on the heat exchange surface for cooling by arranging them so as to overlap each other.

Furthermore, by subjecting the surface of the carrier to a water repellency treatment, the surface property of the carrier is changed to improve the dehumidifying performance related to sublimation and condensation of water vapor on the carrier surface, and to close the opening in a liquid state. It may be avoided.

In addition, by adopting a structure having adsorption performance on the surface of the carrier, the surface property of the carrier may be changed to improve the dehumidification performance for water vapor sublimation and condensation on the carrier surface.

In addition, the use of high water-absorbent resin fibers as the carrier and improved water absorption, water retention, capillary water absorption, etc. as the properties of the carrier improve the dehumidification performance for water vapor sublimation and condensation on the carrier surface. It may be allowed.

A first embodiment of the present invention will be described below in detail with reference to the drawings.
Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The dimensions, materials, and other specific numerical values shown in the embodiments are merely examples for facilitating understanding of the invention, and do not limit the present invention unless otherwise specified. In the present specification and drawings, elements having substantially the same function and configuration are denoted by the same reference numerals, and redundant description is omitted, and elements not directly related to the present invention are not illustrated. To do.

Embodiments of the present invention will be described below with reference to the drawings, taking as an example a case where air is cooled below the freezing point using a refrigerant by a heat exchanger HX.

As shown in FIG. 1, a planar carrier having an opening is disposed in an atmosphere of humid air outside the heat exchanger HX.
The heat exchanger HX has a plate thickness t, allows a refrigerant having a temperature Tc to flow therein, and forms the heat exchange surface S on the outer surface of the heat exchanger HX.
The temperature Tm of the humid air that flows along the cooling surface passes through the temperature boundary layer B formed on the surface of the heat exchange surface S, forms a gentle temperature distribution, and forms a temperature distribution that reaches the low temperature Tout of the cooling surface. In the following description, the air temperature is 0 ° C. or lower and −40 ° C. or higher.

At this time, when C, which is a flat carrier having an opening in the temperature boundary layer BL, is formed with a gap from the heat exchange surface S, in the boundary layer of the anti-heat exchange surface S of the carrier C, wetting occurs. The water vapor in the air becomes saturated due to a temperature drop (air becomes the dew point temperature), and condensation occurs in the condensation nuclei in the air. The floating condensed droplets P1 fall and accumulate on the surface of the carrier C, and form droplets on the surface of the carrier C. The droplet group merges further falling and deposited droplets or condenses water vapor in the atmosphere into large droplets. In many cases, the droplets are supercooled, but when the thickness is about 100 μm, the supercooling is canceled and the ice surface becomes frozen. As a result, water vapor sublimates on the ice surface, and frost crystals P4 are rapidly formed. By forming frost, the opening O is closed, and the air-permeable frost is densely formed. When this happens, the water vapor in the humid air grows into the frost crystals P4 and is eaten by the surface of the frost crystals P4, reducing the amount of water vapor passing through the opening O and reaching the heat exchange surface S, thereby exchanging heat. Frost will no longer grow on surface S.

In this state, heat exchange as the sensible heat exchange from the beginning is stably performed on the heat exchange surface S by frost growth on the surface of the carrier C installed in the boundary layer. In the phenomenon in which the frost crystal P4 grows on the heat exchange surface S, the amount of heat transfer gradually decreases due to the increase in thermal resistance due to the frost layer, but this disappears and stable heat exchange can be performed. In addition, on the carrier C surface, latent heat exchange by frost formation can be performed in the same way as in the state of the conventional heat exchange surface S. Therefore, overall heat exchange is more than heat exchange in the frost growth state of only the heat exchange surface S. The result is an increased amount.

Thus, in the temperature boundary layer BL of the heat exchange surface S, by forming a carrier C having an opening O with a completely new concept, latent heat exchange on the carrier C surface and the original heat exchange surface S A new heat exchange mode was achieved by separating heat exchange from sensible heat exchange.

  In addition, although it is temperature boundary layer BL demonstrated here, the thickness of temperature boundary layer BL changes with installation environments. Usually, it is explained by its environmental temperature and fluid flow, which is omitted here. As shown in FIG. 2 (A), when there is a temperature boundary layer BL in the state where there is nothing in the temperature boundary layer BL, the carrier C in the boundary layer as shown in FIG. A frost layer growing on the surface will be described. As shown in FIG. 2 (B), the thin boundary layer in FIG. 2 (A) shows a state in which the boundary layer becomes thicker when the carrier C is inserted. Further, FIG. 2 (C) shows that the boundary layer further changes in thickness as frost grows. In this way, there may be cases where the carrier C can be installed and frost grows in the original boundary layer, but even if the boundary layer is very thin, the thermal conductivity of the carrier C is in comparison with air. When it was large, it was shown that the boundary layer might change thicker accordingly. Thus, if this carrier C can be installed even in a part of the conventional boundary layer, it is possible to grow in this way, and the utilization of this phenomenon is considered to increase.

(1) Conditions for expression of frost phenomenon and condensation phenomenon Conditions for expression of frost phenomenon and condensation phenomenon will be described with reference to FIG.
When the air temperature is 0 ° C or higher and the atmospheric water vapor state is a water-saturated atmosphere (including the above) (region A), water droplets are generated by condensing water vapor to the condensation nuclei in the atmosphere, and then heat exchange When water drops condense on the surface S, water vapor condenses on the water droplets, and the water droplets grow and merge repeatedly to form large water droplets that flow down the heat exchange surface S (drop) when the adhesion force cannot resist gravity. To do.
In addition, when the air temperature is 0 ° C or lower and -40 ° C or higher and the atmosphere is in a water-saturated atmosphere (including the above) (region C), supercooling occurs when water vapor condenses on the condensation nuclei in the atmosphere. Water droplets P3 are generated, and then fall and accumulate on the heat exchange surface S, and the supercooled water droplets P3 grow and merge, then freeze, and water vapor sublimates on the frozen ice particles to grow frost.
Also, in the generation phenomenon (area B) in the atmosphere with the same air temperature of 0 ° C or lower and -40 ° C or higher and the atmospheric water vapor state is above ice saturation and below water saturation, the water vapor sublimates to the sublimation nuclei in the atmosphere. Ice crystals are generated, and then fallen and deposited on the heat exchange surface S, and water vapor sublimates on the ice crystals to grow frost.

Here, the phenomenon of condensation and sublimation will be explained a little more. When the humid air is cooled, the water vapor in the air becomes saturated (called water saturation), and no more water vapor can be contained in the gas, and condensation begins. The air temperature at this time is called dew point temperature. When the temperature is below 0 ° C, there are two saturation phenomena of water vapor saturation: ice saturation and water saturation. This is because the amount of saturated water vapor in the ice state is smaller than the amount of saturated water vapor in the water state, so when cooling in humid air below 0 ° C, the ice saturated state starts first and the amount of saturated water vapor exceeds the amount of saturated water vapor. Water vapor appears as ice crystals (called ice crystals) in ice crystal nuclei in the air by sublimation. Here, the air temperature is defined as the freezing point temperature.

Note that when further cooling is performed at low temperatures, water saturation occurs, and condensation begins in the same manner as above 0 ° C. However, when the air temperature is in the range of -40 ° C, the condensed droplet P1 does not freeze immediately but is supercooled. It becomes a water droplet P3. The air temperature at this time is called dew point temperature, which is the same as 0 ° C. or higher. Then, the supercooled water droplet P3 is stochastically frozen over time. The frozen particles become ice, and the water vapor pressure of the ice is lower than the surrounding water vapor pressure, so the water vapor sublimes more actively on this ice surface, and the frost crystal P4 starts to grow rapidly. It will be.

In addition, when the air temperature is -40 ° C or lower, the water vapor state in the atmosphere is a water-saturated atmosphere (including the above). Thereafter, the frozen particles that have fallen and deposited on the heat exchange surface S accumulate and form a powdery frost.
At this time, when the heat exchange surface S is -40 ° C or lower, but the ambient air temperature is warmer than -40 ° C, the accumulated powdery frost becomes thick, and the surface temperature of the frost layer exposed to the atmosphere is- When the temperature exceeds 40 ° C., water vapor may sublimate to the frost, and frost growth may occur.
Also, in the phenomenon (area E) in the atmosphere with the same air temperature of -40 ° C or lower and the atmospheric water vapor state is above ice saturation or below water saturation, ice crystals are generated by sublimation of water vapor to the sublimation nucleus of the atmosphere. Then, a frosting phenomenon occurs in which water vapor sublimates and grows on ice crystals that have fallen and deposited on the heat exchange surface S.

In addition, although said description described that the condensation nucleus and the sublimation nucleus existed in the atmosphere in the temperature boundary layer BL near the heat exchange surface S, the condensation nucleus and the sublimation nucleus are also on the heat exchange surface S. Therefore, even on the heat exchange surface S, phenomena such as condensation and sublimation to the condensed nuclei and sublimation nuclei directly occur. Even if the supersaturation phenomenon does not occur in the air, the condensation and sublimation phenomenon occurs on the heat exchange surface S if the heat exchange surface S is equivalent to the atmosphere. That is, even if the atmosphere of the temperature boundary layer BL is not supersaturated, condensation and sublimation occur only on the surface of the carrier C if the surface temperature of the carrier C is in a supersaturated state corresponding to the atmosphere.

(2) This phenomenon has not been clarified yet regarding the phenomenon of frost formation on the carrier C in the temperature boundary layer BL and frost growth on the heat exchange surface S, but it is presumed as follows.
If it is explained above 40 ° C where supercooling occurs, as shown in Fig. 4, in the first state diagram 4 (A), there are many condensation nuclei and sublimation nuclei in the atmosphere including carrier C. Then, it becomes supersaturated and the condensed droplet P1 etc. in the atmosphere float. Thereafter, as shown in FIG. 4B, the condensed droplets P1 and the like are deposited on the carrier C surface and the heat exchange surface S, and the droplets grow on the heat exchange surface S due to condensation and sublimation by supplying water vapor. Next, as shown in FIG. 4 (C), the particles become frozen after becoming large supercooled water droplets P3 which are repeatedly joined. Then, since it is an ice particle, water vapor in the air sublimates to the ice particle, and frost growth starts as shown in FIG. 4 (D). At that stage, since the rapid growth on the surface of the support C starts, the water vapor in the atmosphere is eaten by that surface, and the amount of water vapor flowing into the heat exchange surface S atmosphere is reduced, thereby mitigating the supersaturation phenomenon.
As frost grows, frost grows on the upper part between the carriers C as shown in FIG. 4 (E), so that a large amount of water vapor cannot flow between the carrier C and the heat exchange surface S. It becomes the frost growth of water vapor on the carrier C surface, and the frost growth of water vapor on the heat exchange surface S does not occur. However, since convection exists, sensible heat exchange without frost formation is maintained on the heat exchange surface S, so that the sensible heat exchange amount can maintain the initial state. This enables the best heat exchange mode together with latent heat exchange on the carrier C surface.

In addition, although the phenomenon by forming the support | carrier C surface in parallel with the heat exchange surface S was demonstrated, since water vapor | steam does not form supersaturation in the heat exchange surface S by frost growth, frost growth on the heat exchange surface S is carried out. Because the mechanism that was lost, even if a heat transfer facilitator that constitutes a flow that breaks the boundary layer in order to more actively promote heat transfer on the heat exchange surface S is used, it will ultimately depend on the carrier C. When the water vapor is removed, the heat exchange surface S can promote heat transfer as sensible heat exchange as the convection becomes larger.
For example, as shown in FIG. 5A, when a plate-like heat transfer promoting body is installed outside the carrier C, a part of the fluid flow is guided to the carrier C side, and the fluid flow passing through the opening O of the carrier C is changed. Therefore, frost formation on the heat exchange surface S can be prevented and heat transfer can be promoted. FIG. 5B shows an example in which the carrier C and the heat transfer promoting body of FIG. A normal planar carrier C is divided in the flow direction, and a part of the upstream side thereof is arranged outside the boundary layer.

(3) Relationship between the shape and size of the carrier C and the opening O and the heat exchange surface S in the frost growth phenomenon The relationship between the shape and size of the carrier C and the opening O and the heat exchange surface S is shown in FIGS. I will explain it. The carrier C in frost growth in an atmosphere of 0 ° C. or lower and −40 ° C. or higher may have such a size that condensed water droplets are deposited to form a supercooled water droplet P3 group, and the cross-sectional shape is arbitrary. It is preferable that the opening O closes the opening O when the frost layer grown on the carrier C is in the growth stage.
An image in which the opening O between the carriers C is blocked by the frost growth on the carriers C at both ends may be used. The depth of the carrier C is arbitrary, and it is important that the space between the carrier C and the heat exchange surface S is open. If the carrier C is installed on the heat exchange surface S, the heat exchange is performed. Since the area of the surface S where sensible heat is exchanged is reduced, it is important to separate the latent heat exchange and the sensible heat exchange when separated by the carrier C.
Although the space between the heat exchange surface S and the carrier C has been described as a problem of water vapor passing through the opening O, it is assumed that water vapor does not enter from the left and right sides of the illustrated space. Since the form of the heat exchange surface S varies depending on the heat exchanger HX, it is not specifically described here, but it is specifically formed to prevent intrusion by the heat exchanger HX form. Is natural.

Specific examples of the cross-section of the carrier C shape are shown in FIGS. The cross section of the carrier C is arbitrary, and may have any shape as shown in FIGS. Since the opening O is formed in the planar carrier C, the opening O may be formed by a method such as mechanical cutting, electric discharge machining, sandblasting, etching, or press working. It does not specify a method. Moreover, you may utilize wire mesh-shaped things, such as a wire mesh, a punching metal, a metal lath (expanded metal), etc.

Regarding specific sizes, the width W of the carrier C is 100 μm or more and 2000 μm or less, and the width L of the opening O is 100 μm or more and 1000 μm or less. The depth from the surface of the carrier C to the heat exchange surface S is 100 μm or more. Further, it is not necessary to have a planar arrangement, and a non-woven carrier C may be used as shown in FIG. 7A. This non-woven fabric is advantageous in that even if it is installed on the heat exchange surface S without leaving a gap, it will function without problems in terms of functionality. Further, in the configuration in which the outside of the boundary layer is installed as shown in FIG. 7B, the carrier C portion outside the boundary layer may function as a heat transfer promoting body.

(4) About treatment of frost grown on the carrier C surface It is fundamental to suppress condensation and sublimation of the heat exchange surface S by dehumidification of the carrier C by condensation and sublimation, but another important thing is This is a treatment of frost grown on the surface of the carrier C due to a phenomenon of 0 ° C. or lower. Over time, frost grows thick and becomes a heat resistance layer, and its growth decreases, and it inhibits the passage of air and causes poor heat exchange. Need frost treatment. The frost treatment is different in each of “maintenance of heat exchange surface S”, “frosting”, and “separation of latent heat / sensible heat exchange”.
In “Maintenance of heat exchange surface S” and “Separation of latent heat and sensible heat exchange”, the purpose is heat exchange surface S, heat exchange on heat exchange surface S and carrier C surface, respectively, and frost treatment is not the purpose It is.
Therefore, there is no problem in any processing, and the method is diverse.
That is, a conventional defrosting method (hot gas, watering, off-cycle, electric heater, brine spraying, etc.) may be used. It is possible to use a new idea such as an air nozzle using a jet jet or a mechanical treatment with a brush. Further, the carrier C may be vibrated.

  In the case of the purpose of “frosting”, since frost is regarded as a heat storage body, it is necessary to make secondary use. Therefore, the frost that has increased on the surface of the carrier C over time is replaced with a carrier C that does not have new frost over time, and the carrier C to which the frost has adhered is moved to a predetermined use or processing place, Peeling with a jet jet or vibration, which is a physical peeling method, or a brush, which is mechanical peeling, is used for use. When considering use as a heat storage body, the carrier C may be used as it is depending on the method of use.

If you want to maintain high-efficiency latent heat exchange with `` separation of latent heat and sensible heat exchange '', it is necessary to perform frost treatment with high efficiency by frost growth on the carrier C surface. The carrier C may be exchanged.

Below, 2nd Embodiment is described, referring FIG. The feature of this embodiment is that the relationship between the carrier C and the heat exchange surface S in the dew condensation phenomenon is specified.
Regarding the dew condensation phenomenon at 0 ° C. or higher, regarding the relationship between the carrier C and the heat exchange surface S, the heat exchange surface S is basically a vertical surface. This condition is necessary for the condensed droplet P1 to act so as to drop by gravity. As shown in FIG. 8, regarding the relationship between the phenomenon of gravity drop and the carrier C, the problem of the condensation phenomenon of the heat exchange surface S is generally caused by the surface tension of the condensed droplet P1 on the heat exchange surface S. This is a decrease in heat transfer on the heat exchange surface S due to the formation of a water film. In the present invention, by installing the carrier C in the boundary layer of the heat exchange surface S, the condensed liquid droplet P1 is processed on the surface of the carrier C, and the carrier C surface is dropped by gravity, whereby the heat exchange surface. With S, good heat exchange can be sustained without any liquid film. Since the latent heat exchange due to the condensation phenomenon on the surface of the carrier C is also taken into account, the heat exchange phenomenon is more efficient than the heat exchange only on the heat exchange surface S. In addition, when water repellent treatment or the like is performed as the surface treatment of the carrier C, a droplet condensation phenomenon occurs, heat transfer of condensation can be further improved, and droplets also drop by gravity with a small droplet diameter. Therefore, a good condensation phenomenon can be expressed. Further, the liquid droplet does not block the opening O.

Unlike the frosting phenomenon of the first embodiment, since the secondary growth in which the opening O portion is blocked cannot be expected, the relationship between the width W of the carrier C, the width L of the opening O, and the depth cannot be expected. Since it is easy to reach the heat exchange surface S through O, it is presumed that the size of the opening O needs to be smaller than frost formation. In addition, since the water vapor in the atmosphere is reduced by condensation on the surface of the carrier C, the water vapor in the atmosphere in the space with the heat exchange surface S after passing through the opening O is reduced, and positive condensation is generated on the heat exchange surface S. This is expected to disappear.

For the purpose of realizing the phenomenon that the frost crystals P4 do not adhere on the heat exchange surface S, the present inventors have installed a micro object in the boundary layer, utilizing the condensation and solidification generated in the boundary layer. In addition, an experiment relating to a technology for suppressing the frost crystal P4 that controls the growth of the frost crystal P4 in the boundary layer was conducted, and the effectiveness of the present invention was confirmed.
(1) Experimental apparatus and method
In this study, a wire mesh was installed in the temperature boundary layer BL, and frost crystals P4 were grown on the wire mesh to investigate the suppression of frost formation on the heat exchange surface S surface.
It was formed by a constant temperature and humidity system device, a measurement system device, an observation system device, and a heat transfer unit for keeping the temperature and humidity of the air in the experimental cabin and the experimental room constant. The temperature and humidity of the experimental room were controlled by an air conditioner, humidifier, dehumidifier, and heater, and the temperature and humidity were measured by an Asman ventilated wet and dry bulb hygrometer installed in the experimental room.

(1-1) Observation of frost crystal P4
The photographs and 3D images of the wire mesh used in this study are shown in FIGS. The wire mesh is a 100 mesh plain weave with a wire diameter of 100 μm, an opening of 150 μm, and the material is SUS304. The heat exchange surface S is a heat exchange surface S made of oxygen-free copper polished on a mirror surface (contact angle θ of stationary droplet = 62 °), and the metal mesh shown in FIG. Furthermore, a space was provided between the heat exchange surface S and the wire mesh, and the condition was set such that a minute object was installed in the boundary layer. The observation of frost crystal P4 generation / growth was performed by using a digital microscope to capture images on the wire mesh side and the heat exchange surface S side, and to perform image processing using analysis software. The experimental conditions are the heat exchange surface S temperature tw = −25 ° C. and the heat exchange surface S orientation Θ = 0 ° (horizontal upward).
(1-2) Heat flux
The frosting phenomenon is unsteady because the frost layer adhering to the heat exchange surface S changes with time. In this study, the experiment was performed under the condition that the S temperature of the heat exchange surface changes with time. The heat exchange surface S is made of oxygen-free copper. The temperature history when the temperature of the heat exchange surface S rises was measured, and the heat flux qf [W / m2] was obtained by the concentrated heat constant system approximation.
FIG. 11 shows an outline of the heat transfer section. The heat transfer section was composed of five anoxic copper plates polished 40 mm wide x 18 mm long and 10 mm thick polished on a mirror surface. The side surface and the back surface of the heat transfer plate were insulated using a bakelite with cloth. Isowool (thermal conductivity k = 0.07 W / (m · K), 400 ° C.) was used as the heat insulating material on the back side of the heat exchange surface. In order to minimize the heat transfer from the bakelite to the heat transfer section, oxygen-free copper plates were embedded on the top and bottom and side surfaces of the measurement section. When cooling the heat transfer portion to a predetermined initial temperature, the heat transfer portion was covered with a polyethylene sheet so that frost formation did not occur until the start of the experiment. In the experiment, ethanol for cooling contained in a Dewar bottle was adjusted to an arbitrary temperature with liquid nitrogen, and was immersed in the ethanol to be cooled to a predetermined temperature. After maintaining the surface temperature of the heat exchange surface S constant for 10 minutes, the experiment was started by attaching it vertically to the experimental chamber. When evaluating the heat flux in this study, it is necessary to consider heat loss, but the heat loss was measured with the heat transfer part covered with a cover made of heat insulating material and measured for each experimental condition. .
Experimental conditions are humid air temperature ta = -25 ° C, heat exchange surface S initial temperature two = -40 ° C, heat exchange surface S surface wettability θ = 62 °, distance from leading edge y = 41, 61, 81 101mm.

(2) Experimental results and discussion
(2-1) Formation and growth mechanism of frost crystal P4
The inventors pay attention to the size of the supercooled water droplet P3 and change the surface property of the heat exchange surface S by artificially imparting a minute uneven surface of several hundred microns to the surface of the heat exchange surface S (heat We succeeded in preventing frost crystals P4 from growing on the heat exchange surface S surface (although part of the exchange surface S surface). At present, the region where the frost crystals P4 do not adhere reaches 75% of the entire surface of the heat exchange surface S. A representative example of the result of observing the generation / growth process of the frost crystal P4 when the lattice-shaped fine grooves are formed on the cooling rejection surface is shown in FIG.
When the grid-like groove processing is performed, the convex portion is square, but after the start of the experiment, supercooled water droplets P3 are generated on the surface of the convex portion, and the supercooled water droplets P3 coalesce and become larger. The supercooled water droplet P3 which repeated the coalescence became one on the surface of the square convex part, and became hill-shaped ice after the supercooling was eliminated. Up to 15 minutes after the start of the experiment, it is in a supercooled state, and a white ring of illumination can be confirmed in the center. Next, a plurality of frost crystals P4 were generated from the hill-shaped ice. Even when the frost crystal P4 grew, the frost crystal P4 could not be confirmed in the groove portion.
Based on the above observation results, we studied the growth of frost crystals P4 in the boundary layer. First, as a minute object to be installed in the boundary layer, a wire mesh having the same size as the convex portion in FIG. 12 was selected, and this was installed on the heat exchange surface S. FIG. 13 shows the observation result when the frost crystal P4 is generated when the wire mesh shown in FIG. 10 is placed on the smooth heat exchange surface S. Note that the observation was performed from above the surface of the heat exchange surface S. As a result of observation, first, it was confirmed that supercooled water droplets P3 were generated on the surface of the heat exchange surface S and the surface of the wire mesh, and after the supercooling was eliminated, a plurality of frost crystals P4 were generated from the hill-shaped ice on the wire mesh side. On the other hand, frost crystals P4 could not be confirmed on the heat exchange surface S surface side. Further, when the wire mesh was removed from the heat exchange surface S, the frost adhering to the wire mesh immediately melted. Further, the growth of frost crystals P4 on the heat exchange surface S that had been in contact with the wire mesh could not be confirmed. FIG. 14 shows a sketch diagram of the frost crystal P4 generation / growth mechanism. In the frost crystal P4, the convex part of the wire mesh has the fastest crystal growth rate, and after the supercooling is eliminated, spherical ice adheres to the surface of the heat exchange surface S, but this dimension is as small as 150 μm or less, and the frost crystal P4 never grew.

Next, an experiment was conducted by providing a space between the wire mesh used in the observation of FIG. 13 and the heat exchange surface S surface. FIG. 15 shows the observation results from the side, and FIG. 16 shows the sketches created based on the observation results. As shown in these figures, it was confirmed that the frost crystals P4 were generated and grown from the wire mesh surface, and the frost crystals P4 were not generated and grown on the heat exchange surface S.
From the above results, we believe that the effectiveness of the proposed method for controlling the formation and growth mechanism of frost crystals P4 was confirmed. Furthermore, since the frost layer did not grow on the surface of the heat exchange surface S when the wire mesh was removed, it is considered that frost formation on the surface of the heat exchange surface S could be prevented.

(2-2) Heat transfer with frost formation
Experiments were conducted with and without a wire mesh in the boundary layer (smooth surface), and the results were compared. The relationship between the heat flux and the heat exchange surface S temperature is shown in FIG. Note that the heat exchange surface S temperature when the wire mesh was attached was not the surface temperature of the wire mesh but the surface temperature of the oxygen-free copper heat transfer section. As is clear from the figure, since there was no significant change in the heat flux in any case, it was confirmed that the influence of the wire mesh on the heat flux was small.
FIG. 18 shows the temperature distribution in the temperature boundary layer BL with the frost layer surface position as a reference. In addition, the frost layer surface was made into the measurement position of frost layer thickness. The heat exchange surface S to which the frost crystals P4 adhere is horizontally upward. The heat exchange surface S is the end face of an oxygen-free copper prism with a width of 50 mm and a height of 50 mm, and a 1 mm thick copper plate was added to the surface with an Epoxy adhesive to make the surface of the heat exchange surface S. The surface temperature of the heat exchange surface S was measured by bonding a CA thermocouple (elementary linear 100 μm) to the back side of the copper plate. The frost layer surface temperature was measured by a thermocouple. The thermocouple was attached to a traverse apparatus that was movable in a horizontal and vertical direction with respect to the heat exchanging surface S via a metal support bar, attached to a support portion made of bakelite having a heat insulation effect. The measurement was performed by measuring the temperature in the boundary layer using a digital microscope while defining the temperature of the humid air portion at the measurement position of the frost layer thickness as the frost layer surface temperature. The side of the heat transfer unit is insulated with urethane foam and silicon adhesive, and the heat transfer unit main body was installed in an experimental chamber made by Dumpler. Even when a metal mesh was attached, the surface temperature of the frost layer was lower than 0 ° C., and it was confirmed that frost crystals P4 could grow.

The embodiments of the present invention have been described in detail above, but various modifications or changes can be made by those skilled in the art without departing from the scope of the present invention.
For example, in the present embodiment, a case has been described in which dehumidification is performed in the temperature boundary layer BL by disposing the planar carrier C and the mesh carrier C in the temperature boundary layer BL determined according to the temperature of the heat exchange surface. Without being limited thereto, the planar carrier C and the mesh-like carrier C may not be disposed as long as dehumidification is performed in the temperature boundary layer BL.
For example, in the present embodiment, by arranging the mesh carrier C in the temperature boundary layer BL determined according to the temperature of the heat exchange surface, the mesh carrier C is frosted on the surface of the mesh carrier C, and the frost formed is grown. In addition, the case where the carrier C is replaced has been described. However, the present invention is not limited to this, and by placing another material that can grow frost on the surface, frost formation or condensation on the heat exchange surface can be achieved. It only needs to be preventable.

1 is a schematic side view according to a first embodiment of the present invention. It is a schematic diagram which shows temperature distribution according to the frosting condition on the support | carrier C about 1st Embodiment of this invention. It is a conceptual graph which shows the expression of a frost phenomenon and a condensation phenomenon using a water saturation line and an ice saturation line. It is a schematic diagram which shows the frost formation condition on the support | carrier C about 1st Embodiment of this invention. It is a schematic diagram which shows the modification of the support | carrier C with respect to 1st Embodiment of this invention. It is a schematic diagram which shows the modification of the support | carrier C with respect to 1st Embodiment of this invention. It is a schematic diagram which shows the further modification of the support | carrier C with respect to 1st Embodiment of this invention. It is a schematic diagram which shows the further modification of the support | carrier C with respect to 1st Embodiment of this invention. It is a schematic diagram which shows the further modification of the support | carrier C with respect to 1st Embodiment of this invention. FIG. 6 is a schematic diagram showing still another modification example of the carrier C with respect to the first embodiment of the present invention. FIG. 6 is a schematic diagram showing still another modification example of the carrier C with respect to the first embodiment of the present invention. It is a conceptual diagram which shows the condensation phenomenon and the heat exchange surface S on the surface of the support | carrier C which concern on 2nd Embodiment of this invention. It is a plane photograph of the wire mesh in the Example of this invention. It is a computer 3D image of the wire mesh in the Example of this invention. It is the top view and side view which show the wire mesh in the Example of this invention. In the Example of this invention, it is a figure which shows the production | generation growth process of the frost crystal | crystallization P4 at the time of carrying out a groove process on the heat exchange surface S surface. In the Example of this invention, it is a figure which shows the observation result at the time of the production | generation of the frost crystal | crystallization P4 at the time of mounting the wire mesh of FIG. 9 on the heat exchange surface S. It is a sketch figure of the production | generation and growth mechanism of the frost crystal | crystallization P4 in FIG. In the Example of this invention, it is a figure which shows the observation result at the time of the production | generation of the frost crystal | crystallization P4 at the time of providing a space | interval between the metal-mesh of FIG. 9, and the heat exchange surface S from a side surface. It is a sketch figure of the production | generation and growth mechanism of the frost crystal | crystallization P4 in FIG. In the Example of this invention, it is a graph which shows the relationship between a heat flux and the heat exchange surface S temperature when the metal mesh is installed in the boundary layer and when it is not installed. In the Example of this invention, it is a graph which shows the temperature distribution in the temperature boundary layer BL on the basis of the frost layer surface position.

HX heat exchanger
C carrier
S Heat exchange surface
O opening
N Heat transfer accelerator
BL temperature boundary layer
Tc Refrigerant temperature
Tin inner surface temperature of heat exchanger
Tout Heat exchanger outer surface temperature
Tair humid air temperature
Tm Main air temperature
W mesh width
L opening width
t Heat exchanger wall thickness
Y interval
P1 condensed droplet
P3 Supercooled water droplets
P4 frost

Claims (11)

A carrier having a size enough to be blocked by frost formation on the surface, having an opening penetrating in the thickness direction, and having a thermal conductivity higher than that of humid air, on a cooling heat exchange surface in contact with the humid air On the other hand, by arranging the surfaces facing each other , at least a part of the carrier can be positioned in a temperature boundary layer determined according to the temperature of the heat exchange surface for cooling and the air flow by the humid air . An interval between the heat exchange surface and the surface of the carrier facing the cooling heat exchange surface is set, whereby the surface of the carrier opposite to the surface opposed to the cooling heat exchange surface has changed and grown. In the state of being arranged in the temperature boundary layer, the wet air is dehumidified by condensing or sublimating water vapor in the humid air on the surface of the carrier, thereby dew condensation or frost formation on the heat exchange surface for cooling. It is characterized by suppressing Carrier that. The carrier is placed on the cooling heat exchange surface such that a space is formed between the cooling heat exchange surface and a surface of the carrier facing the cooling heat exchange surface; The carrier according to claim 1. The carrier is a planar and a fixed form or irregular cross-section, has the configuration of arranging alternately before Symbol opening and a predetermined width, a planar carrier having a predetermined depth from the cooling heat exchanger surface The carrier according to claim 1 or 2. The carrier according to claim 3, wherein the planar carrier has a mesh shape and has a predetermined mesh opening width, a predetermined wire width and a thickness. The size of the planar carrier is such that the width of the carrier is 100 μm or more and 2000 μm or less, the width of the opening is 100 μm or more and 1000 μm or less, and the depth from the surface on the temperature boundary layer side of the carrier to the heat exchange surface for cooling is 100 μm or more. The carrier according to claim 4, wherein: 4. The carrier according to claim 3, wherein the carrier is a three-dimensional carrier having a three-dimensional structure having voids by superposing fibers of a predetermined length having a regular or irregular cross section in a nonwoven fabric shape. . The three-dimensional carrier is thickened so that a part of the three-dimensional carrier can be arranged in the main airflow outside the temperature boundary layer, and heat transfer is promoted on the heat exchange surface for cooling by guiding the airflow into the carrier inside the boundary layer. The carrier according to claim 6, wherein The planar carrier is divided into a plurality of layers arranged in the heat flow direction of the cooling heat exchange surface, and the upstream side of the heat flow direction of the plurality of layers is arranged in the main airflow outside the temperature boundary layer, and is adjacent to the heat flow direction. In the planar carrier, heat transfer is promoted on the heat exchange surface for cooling by arranging the openings so as to overlap each other so as to guide the air flow into the carrier in the boundary layer. Item 8. The carrier according to any one of Items 3 to 7. By applying a water repellency treatment to the surface of the carrier, the surface property of the carrier is changed, so that the dehumidification performance for water vapor sublimation and condensation on the carrier surface is improved and the opening is not blocked in a liquid state. The carrier according to claim 3, wherein The structure according to claim 3, wherein the surface property of the carrier is changed to improve the dehumidifying performance related to sublimation and condensation of water vapor on the surface of the carrier by adopting a structure having adsorption performance on the surface of the carrier. The carrier described. Utilizing high water-absorbent resin fibers for the carrier, and enhancing the water absorption, water retention, capillary water absorption, etc. as the properties of the carrier, the dehumidification performance for water vapor sublimation and condensation on the carrier surface has been improved. The carrier according to claim 3, wherein