Method for delaying frost sticking of heat exchanger containing hydrogel coating layer

Abstract

A method for delaying frost sticking of a heat exchanger containing a hydrogel coating layer according to the present invention includes: absorbing moisture by means of the hydrogel coating layer; forming slurry ice inside the hydrogel coating layer that has absorbed the moisture; and regenerating the hydrogel coating layer when the formed slurry ice occupies 50% or more of the total area of the hydrogel coating layer.

Description

Method for delaying frost formation in a heat exchanger comprising a hydrogel coating layer

[0001] The present disclosure relates to a method for delaying frost formation in a heat exchanger including a hydrogel coating layer.

[0002] Frost forms when moisture in the air meets a surface at a temperature below freezing, causing numerous problems, including crop damage, frozen roads, and power outages in winter. In particular, frost primarily occurs in heat exchangers in industrial applications such as air conditioning systems, home air conditioners, refrigerators, and automobile radiators, reducing energy efficiency.

[0003] Frost growth on the cold surfaces of heat exchangers reduces air flow and increases surface temperature, degrading heat exchange performance. Furthermore, frost formation on heat exchangers inevitably requires a defrosting process to remove the frost, which consumes significant energy.

[0004] Superhydrophobic coating, a representative method for delaying and preventing frost growth, is an effective and practical way to delay frost growth without external power. However, the superhydrophobic coating method has a short frost formation delay time, and once frost has formed, the mechanism remains the same as standard frost growth, so it has not been significantly effective in delaying frost growth.

[0005] Meanwhile, hydrogel is attracting attention as an anti-frost material, as it has a low freezing temperature and can effectively delay frost growth by storing moisture in the air as antifreeze inside the hydrogel.

[0006] In this regard, a technique has been proposed to inhibit ice nucleation using a hydrogel cross-linked with a hydrophilic polymer electrolyte material containing counterions and hydrophobic PDMS (Polydimethylsiloxane). However, this technique only suppresses ice formation at temperatures below -30°C and cannot fundamentally control the frost formation process occurring in the hydrogel, thereby delaying frost growth.

[0007] One aspect of the present disclosure provides a method for delaying frost formation in a heat exchanger including a hydrogel coating layer, which can maximize hydrogel performance and frost formation delay effect by inducing desorption of moisture inside the hydrogel by repeatedly performing a hydrogel regeneration process to delay frost formation and increase the efficiency of the heat exchanger.

[0008] One aspect of the present disclosure provides a method for delaying frost formation in a heat exchanger including a hydrogel coating layer capable of delaying frost formation through hydrogel regeneration and further enabling operation of the heat exchanger without frost formation.

[0009] The technical problems to be achieved in this document are not limited to the technical problems mentioned above, and other technical problems not mentioned can be clearly understood by a person having ordinary skill in the technical field to which the present invention belongs from the description below.

[0010] A method for manufacturing a carbon dioxide adsorbent according to one embodiment of the present disclosure comprises: obtaining an oxide-carbon nanomaterial composite by mixing a carbon nanomaterial solution and an oxide nanoparticle solution, and obtaining an oxide-carbon nanomaterial composite having an amine group introduced therein by supporting an amine group on the oxide-carbon nanomaterial composite, and a method for delaying frost formation of a heat exchanger including a hydrogel coating layer according to one embodiment of the present disclosure on a surface of a substrate, the method comprising: regenerating the hydrogel coating layer when the hydrogel coating layer absorbs moisture, slurry ice is formed inside the hydrogel coating layer that has absorbed the moisture, and the formed slurry ice covers 50% or more of the total area of ​​the hydrogel coating layer.

[0011] Additionally, regeneration of the hydrogel coating layer may include heating the hydrogel coating layer.

[0012] Additionally, the regeneration of the hydrogel coating layer may include maintaining the surface temperature of the hydrogel coating layer at 30° C. to 80° C. for 1 to 20 minutes.

[0013] Additionally, the absorbed moisture may exist in the form of non-freezing water, intermediate water, or free water inside the hydrogel coating layer.

[0014] Additionally, the regeneration of the hydrogel coating layer may include shrinking the hydrogel coating layer by more than 80% compared to before regeneration.

[0015] Additionally, the progress of the frost implantation may include performing the process when the swollen hydrogel coating layer shrinks by 80% or more.

[0016] Additionally, the regeneration of the hydrogel coating layer may include performing the process more than once.

[0017] In addition, the hydrogel coating layer may include an ionic monomer selected from among a zwitterionic monomer, a cationic monomer, and an anionic monomer; a crosslinking agent including two or more acrylic groups; a polymerization initiator; and a solvent.

[0018] In addition, the hydrogel coating layer may include the ionic monomer in a molar concentration of 0.5 mol / L to 3 mol / L, and may include 0.5 mol% to 5 mol% of a crosslinking agent and 0.5 mol% to 2.5 mol% of a polymerization initiator based on the ionic monomer.

[0019] In addition, the zwitterionic monomer comprises any one selected from among 2-methacryloyloxyethyl phosphorylcholine, 3-[[2-(methacryloyloxy)ethyl]dimethylammonio]propionate and [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)ammonium hydroxide, and the cationic monomer comprises any one selected from among [2-(methacryloyloxy)ethyl]trimethylammonium chloride and trimethyl-3-[(1-oxoallyl)amino]propylammonium A compound comprising any one selected from trimethyl-3-[(1-oxoallyl)amino]propylammonium chloride, wherein the anionic monomer may include any one selected from 3-prop-2-enoyloxypropane-1-sulfonic acid (3-sulfopropyl acrylate), 3-(2-methylprop-2-enoyloxy)propane-1-sulfonic acid (3-sulfopropyl methacrylate), and acrylic acid.

[0020] In addition, the crosslinking agent including two or more acrylic groups may include any one selected from polyethylene glycol diacrylate, polyethylene glycol dimethacrylate, N,N'-methylenebisacrylamide, and trimethylolpropane triacrylate.

[0021] In addition, the heat exchanger further includes heat exchanger fins that are provided to transfer heat from a tube through which a refrigerant flows, and the hydrogel coating layer may be provided on the heat exchanger fins.

[0022] Additionally, the hydrogel coating layer may be formed on the heat exchanger fins to a thickness of 0.01 mm to 1 mm.

[0023] Additionally, the heat exchanger may further include an intermediate adhesive layer between the heat exchanger fins and the hydrogel coating layer.

[0024] In addition, the intermediate adhesive layer may include a silane compound including an acrylic group selected from among methacryloxypropyltrimethoxysilane, (3-acryloxypropyl)trimethoxysilane, and methacryloxypropylmethyldimethoxysilane.

[0025] According to the idea of ​​the present disclosure, by repeatedly performing a hydrogel regeneration process to induce desorption of moisture inside the hydrogel in order to delay frost formation and thereby increase the efficiency of the heat exchanger, the hydrogel performance and frost formation delay effect can be maximized, and further, a method for delaying frost formation of a heat exchanger including a hydrogel coating layer capable of operating the heat exchanger without frost formation can be provided.

[0026] The effects that can be obtained from the present disclosure are not limited to the effects mentioned above, and other effects that are not mentioned can be clearly understood by a person having ordinary skill in the art to which the present disclosure belongs from the description below.

[0027] FIG. 1 is a drawing illustrating the structure of a hydrogel coating layer included in a heat exchanger of the present disclosure.

[0028] FIGS. 2A to 2E are drawings illustrating a frost growth process in a hydrogel coating layer included in a heat exchanger of the present disclosure.

[0029] FIG. 3 is a drawing illustrating a process in which a hydrogel coating layer included in a heat exchanger of the present disclosure absorbs moisture in the air.

[0030] FIG. 4a is a drawing illustrating slurry ice formation inside a hydrogel coating layer included in a heat exchanger of the present disclosure.

[0031] Figure 4b is a drawing illustrating the frost growth process on the surface of the hydrogel coating layer on which the aforementioned slurry ice is formed.

[0032] Figure 5 is a diagram illustrating a regeneration process of a hydrogel coating layer included in a heat exchanger of the present disclosure.

[0033] FIG. 6 is a cross-sectional view of a heat exchanger including a hydrogel coating layer of the present disclosure.

[0034] FIG. 7 is a drawing illustrating a refrigerator to which a heat exchanger including a hydrogel coating layer of the present disclosure is applied.

[0035] Figure 8 is a drawing showing a cross-section of the refrigerator described above.

[0036] FIG. 9 is a drawing illustrating a heat exchanger including a hydrogel coating layer provided in the aforementioned refrigerator.

[0037] Fig. 10 is a drawing showing the fins of the heat exchanger described above.

[0038] Figure 11 shows a heat exchanger including a hydrogel coating layer of the present disclosure at a dry bulb temperature of 5°C and a relative humidity of 80% (absolute humidity of 0.00431 kg / kg). da ) is a drawing showing the surface photograph of the hydrogel after being left in an environment of 480 minutes.

[0039] Figure 12 is a drawing showing the frost formation delay performance before and after moisture saturation after sufficient moisture is absorbed into the hydrogel coating layer provided in the heat exchanger of the present disclosure.

[0040] FIG. 13 is a diagram illustrating changes in the surface temperature of a hydrogel coating layer during three cycles of regeneration and frost deposition of the hydrogel coating layer provided in the heat exchanger of the present disclosure.

[0041] FIG. 14 is a drawing showing the surface state of a hydrogel coating layer during three cycles of regeneration and frost deposition of the hydrogel coating layer provided in the heat exchanger of the present disclosure.

[0042] Preferred embodiments of the present invention are described below. However, the embodiments of the present invention may be modified in various ways, and the technical concept of the present invention is not limited to the embodiments described below. Furthermore, the embodiments of the present invention are provided to more fully explain the present invention to those of ordinary skill in the art.

[0043] The terminology used in this application is solely for the purpose of describing specific examples. Therefore, for example, singular expressions include plural expressions unless the context clearly dictates otherwise. Additionally, it should be noted that terms such as "comprise" or "have" used in this application are used to clearly indicate the presence of features, steps, functions, components, or combinations thereof described in the specification, and are not used to preliminarily exclude the presence of other features, steps, functions, components, or combinations thereof.

[0044] Meanwhile, unless otherwise defined, all terms used herein should be considered to have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention pertains. Therefore, unless explicitly defined herein, specific terms should not be interpreted in an overly idealistic or formal sense. For example, singular expressions herein include plural expressions unless the context clearly indicates otherwise.

[0045] In addition, the terms "about", "substantially", etc. in this specification are used in the sense of or close to the numerical value when manufacturing and material tolerances inherent to the meanings mentioned are presented, and are used to prevent unscrupulous infringers from unfairly using the disclosure contents in which exact or absolute numerical values ​​are mentioned to aid in the understanding of the present invention.

[0046] Hereinafter, a method for delaying frost formation of a heat exchanger including a hydrogel coating layer of the present disclosure will be described in detail.

[0047] A method for delaying frost formation in a heat exchanger including a hydrogel coating layer according to one embodiment of the present disclosure includes regenerating the hydrogel coating layer when the hydrogel coating layer absorbs moisture, slurry ice is formed inside the hydrogel coating layer that has absorbed the moisture, and the formed slurry ice covers 50% or more of the total area of ​​the hydrogel coating layer.

[0048] FIG. 1 is a drawing showing the structure of a hydrogel coating layer included in a heat exchanger of the present disclosure, and FIGS. 2a to 2e are drawings showing a frost growth process in a hydrogel coating layer included in a heat exchanger of the present disclosure.

[0049] The hydrogel coating layer included in the above heat exchanger is composed of water and a support that supports it, as illustrated in Fig. 1. The water that constitutes the hydrogel can be classified into three types based on the strength with which it is bonded to the polymer (Fig. 1 (d)). Free water (Fig. 1 (a)) is water with the weakest bonding strength and freezes at 0°C, like general bulk water. Intermediate water (Fig. 1 (b)) is water that is bonded to polymer chains but not tightly bound, and freezes below 0°C. Lastly, non-freezing water (Fig. 1 (c)) is water that is most tightly bound to the polymer and freezes at a very low temperature.

[0050] The frost growth process in the hydrogel coating layer having the above structure progresses through a process in which moisture in the air is absorbed into the hydrogel coating layer, and when sufficient moisture is absorbed into the hydrogel coating layer, slurry ice is formed inside the hydrogel coating layer, and frost grows on the surface of the formed slurry ice, as illustrated in FIG. 2.

[0051] Specifically, the frost growth process in a heat exchanger using a hydrogel coating layer according to one embodiment of the present disclosure proceeds as follows: moisture in the air is absorbed into the hydrogel coating layer (FIG. 2a); when sufficient moisture is absorbed into the hydrogel coating layer, that is, when the hydrogel coating layer is sequentially filled with floating water, intermediate water, and free water and the moisture is saturated, slurry ice is formed inside the hydrogel coating layer (FIG. 2b); and as the formed slurry ice propagates inside the hydrogel coating layer, frost is formed on the surface of the hydrogel coating layer on which the slurry ice is formed (FIG. 2c); and when the slurry ice propagates throughout the hydrogel coating layer (FIG. 2d), the frost thickness grows on the surface of the hydrogel coating layer on which the slurry ice is formed, following a general frost growth process (FIG. 2e).

[0052] As described above, when the moisture inside the hydrogel coating layer becomes saturated, slurry ice is formed, and when the slurry ice spreads throughout the inside of the hydrogel and frost is formed, the subsequent process proceeds in the same manner as the general frost growth process in which the thickness of the frost increases.

[0053] Therefore, in the present disclosure, during the frost growth process in a heat exchanger including the hydrogel coating layer as described above, the frost delay performance can be improved by lengthening the process in which moisture is absorbed into the hydrogel coating layer or lengthening the process in which slurry ice grows inside the hydrogel coating layer after moisture absorption.

[0054] To this end, in the present disclosure, the temperature of a hydrogel coating layer included in a heat exchanger is periodically increased to induce desorption of moisture within the hydrogel coating layer, thereby delaying frost growth and maximizing the frost formation delay performance of the hydrogel coating layer.

[0055] A method for delaying frost formation in a heat exchanger including a hydrogel coating layer of the present disclosure is described in detail with reference to the drawings as follows.

[0056] FIG. 3 is a diagram illustrating a process in which a hydrogel coating layer included in a heat exchanger of the present disclosure absorbs moisture from the air. FIG. 4a is a diagram illustrating the formation of slurry ice within the aforementioned hydrogel coating layer, and FIG. 4b is a diagram illustrating the frost formation process on the surface where the slurry ice has been formed. FIG. 5 is a diagram illustrating the regeneration process of the aforementioned hydrogel coating layer.

[0057] First, as shown in Fig. 3, the hydrogel coating layer included in the heat exchanger absorbs moisture in the air.

[0058] When moisture in the air is absorbed into the hydrogel coating layer due to the partial pressure difference of water vapor, the support material, i.e., the polymer, inside the hydrogel coating layer swells, and the absorbed moisture combines with the support material inside the hydrogel coating layer, sequentially storing floating water, intermediate water, and natural water. At this time, the hydrogel coating layer is transparent.

[0059] As shown in FIGS. 4a and 4b, when sufficient moisture is absorbed into the hydrogel coating layer and it becomes completely saturated, slurry ice begins to form and grow inside the hydrogel coating layer, and at this time, the transparent hydrogel becomes opaque due to the formation of slurry ice (FIG. 4a).

[0060] The slurry ice formed above propagates within the hydrogel coating layer, and at the same time, a frost formation process progresses in which irregular frost grows on the surface of the hydrogel coating layer where the slurry ice is formed (Fig. 4b).

[0061] That is, the growth of frost on the surface of the hydrogel coating layer on which slurry ice was formed means that moisture was completely saturated inside the hydrogel coating layer, and slurry ice was formed and grown.

[0062] Therefore, in the present disclosure, in order to delay frost growth by prolonging the process of the hydrogel coating layer absorbing moisture and the process of slurry ice growing after moisture saturation, a process of regenerating the hydrogel coating layer is performed when the slurry ice grown inside the hydrogel coating layer becomes 50% or more of the total area of ​​the hydrogel coating layer.

[0063] Regeneration of the hydrogel coating layer can be performed by heating the surface temperature of the hydrogel coating layer to a certain temperature or higher, as shown in Fig. 5.

[0064] When the surface temperature of the hydrogel coating layer increases, moisture evaporates from the hydrogel coating layer, and the water present inside the hydrogel coating layer is stored in the order of static water > intermediate water > free water.

[0065] The regeneration of the hydrogel coating layer is preferably performed at a surface temperature of 30°C to 80°C for 1 to 20 minutes, and more preferably at a temperature of 35°C to 70°C for 10 to 20 minutes.

[0066] If the regeneration temperature is too low, the regeneration process may be prolonged, such as requiring an increase in the regeneration time or number of times, and if it is too high, the reliability of the material may deteriorate, preventing smooth regeneration of the hydrogel coating layer. In addition, the regeneration time can be appropriately controlled depending on the regeneration temperature, but if the regeneration time is too short, the slurry ice generation time becomes faster, requiring more repetitions of the regeneration process, and if it is too long, the hydrogel coating layer may be overdried, resulting in destruction of the hydrogel coating layer. Therefore, the regeneration of the hydrogel coating layer is preferably performed at a surface temperature of 30°C to 80°C for 1 to 20 minutes.

[0067] When the hydrogel coating layer is regenerated as described above, the moisture stored in the hydrogel coating layer evaporates into the air, and accordingly, the polymer (shrinking) that serves as the support inside the hydrogel coating layer shrinks, and the water molecules inside the hydrogel coating layer diffuse and are stored in the order of immobile water > intermediate water > free water. Then, the hydrogel coating layer absorbs moisture in the air again, and when the moisture inside the hydrogel coating layer becomes saturated, slurry ice grows and propagates, and the process of frost growing on the surface of the hydrogel coating layer where the slurry ice has grown proceeds.

[0068] That is, in the present disclosure, in the process of moisture absorption, slurry ice formation, and frost growth in a hydrogel coating layer included in a heat exchanger, when slurry ice grows to a certain extent inside the hydrogel coating layer, a regeneration process of the hydrogel coating layer is performed to increase the surface temperature of the hydrogel coating layer to evaporate moisture from inside the hydrogel coating layer, thereby lengthening the time for the hydrogel coating layer to absorb moisture and simultaneously controlling the time for slurry ice growth inside the hydrogel coating layer to be long.

[0069] As described above, the hydrogel coating layer absorbs moisture in the air and swells, and then shrinks.

[0070] Specifically, the regeneration of the hydrogel coating layer can cause the hydrogel coating layer to shrink by more than 80% compared to before the regeneration.

[0071] The regeneration of the hydrogel coating layer described above can be repeated several times, and by repeating the regeneration process of the hydrogel coating layer, frost growth can be delayed, and further, the heat exchanger can be continuously used without frost formation.

[0072] In addition, when the regeneration or repetition of the regeneration process of the hydrogel coating layer described above is completed, slurry ice is formed in the hydrogel coating layer, frost deposition and growth occur on the surface of the hydrogel coating layer where the slurry ice is formed, and then a general frost deposition process proceeds in which the thickness of the frost formed on the surface of the hydrogel coating layer increases.

[0073] As described above, in the present disclosure, when using a heat exchanger including a hydrogel coating layer, the hydrogel coating layer absorbs moisture, slurry ice is formed and propagated, and during the process of frost growth on the surface of the hydrogel coating layer where the slurry ice is formed, the regeneration process of the hydrogel coating layer is repeated several times, thereby efficiently delaying frost growth without frost formation.

[0074] Below, the hydrogel coating layer included in the heat exchanger of the present disclosure is described.

[0075] The hydrogel coating layer may include an ionic monomer selected from among a zwitterionic monomer, a cationic monomer, and an anionic monomer; a crosslinking agent including two or more acrylic groups; a polymerization initiator; and a solvent.

[0076] The zwitterionic monomer may be a neutral chemical compound having both a positive charge and a negative charge, and may include, for example, any one selected from 2-methacryloyloxyethyl phosphorylcholine, 3-[[2-(methacryloyloxy)ethyl]dimethylammonio]propionate, and [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)ammonium hydroxide.

[0077] The cationic monomer is a monomer that has a positive charge or can have a positive charge, and may include, for example, any one selected from [2-(methacryloyloxy)ethyl]trimethylammonium chloride and trimethyl-3-[(1-oxoallyl)amino]propylammonium chloride.

[0078] The above anionic monomer is a monomer that has a negative charge or can have a negative charge, and may include, for example, any one selected from 3-prop-2-enoyloxypropane-1-sulfonic acid (3-sulfopropyl acrylate), 3-(2-methylprop-2-enoyloxy)propane-1-sulfonic acid (3-sulfopropyl methacrylate), and acrylic acid.

[0079] The above ionic monomer may include both a cationic monomer and an anionic monomer, in which case a hydrogel coating layer including a similar zwitterionic polymer and / or a copolymer thereof in which the cationic monomer and the anionic monomer are polymerized may be formed. At this time, in order to balance the negative and positive charges, the cationic monomer and the anionic monomer are preferably included in an equivalent ratio of about 1:1.

[0080] The above ionic monomer may be included in the hydrogel coating layer at a molar concentration of 0.5 mol / L to 3 mol / L. If the molar concentration of the ionic monomer is too low, the hydrogel may not be formed due to insufficient monomer content, and if it is too high, the hydrogel may have brittle mechanical properties, making it unsuitable for application to a heat exchanger.

[0081] The above crosslinking agent may be used without particular limitation as long as it is a crosslinking agent containing two or more acrylic groups, and may include, for example, any one selected from among polyethylene glycol diacrylate, polyethylene glycol dimethacrylate, N,N'-methylenebisacrylamide, and trimethylolpropane triacrylate.

[0082] The cross-linking agent may be included in an amount of 0.5 mol% to 5 mol% based on the ionic monomer. If the molar ratio of the cross-linking agent is too low, cross-linking between polymers may not be sufficiently formed, making it impossible to form a solid hydrogel coating layer. If the molar ratio is too high, the hydrogel coating layer may become brittle, resulting in defects or destruction.

[0083] The above polymerization initiator can be appropriately selected and used depending on the polymerization method, and a conventional thermal polymerization initiator or photopolymerization initiator can be used.

[0084] The above thermal polymerization initiator includes a persulfate initiator such as ammonium persulfate, sodium persulfate, potassium persulfate, 4,4-azobis-(4-cyanovaleric acid), 2,2-azobis(2-amidinopropane)dihydrochloride, 2,2-azobis-(N,N-dimethylene)isobutyramidine dihydrochloride, 2-carbamoyl azoisobutylonitrile, An azo initiator such as 2,2-azobis[2-(2-imidazolin-2-yl)propane] dihydrochloride can be used. In addition, as the photopolymerization initiator, 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, IRGACURE 500, IRGACURE 754, IRGACURE OXE02, etc. can be used.

[0085] The polymerization initiator may be included in an amount of 0.5 mol% to 2.5 mol% based on the ionic monomer. If the molar ratio of the polymerization initiator is too low, the rate of radical generation may be slower than the rate of radical extinction, preventing polymerization from being initiated by radicals. If the molar ratio is too high, there is a risk of weakening the mechanical properties of the hydrogel.

[0086] The solvent can dissolve the above-mentioned components, and examples of solvents that can be used include water, ethanol, ethylene glycol, diethylene glycol, triethylene glycol, 1,4-butanediol, propylene glycol, ethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monomethyl ether acetate, diethylene glycol monomethyl ether, diethylene glycol ethyl ether, and carbitol.

[0087] A hydrogel coating layer containing the above components can be coated on the heat exchanger fins and included in the heat exchanger.

[0088] As illustrated in FIG. 6, a heat exchanger (100) including a hydrogel coating layer of the present disclosure may further include a heat exchanger fin (120) provided to receive heat from a tube through which a refrigerant flows, and the hydrogel coating layer (121) may be provided by being coated on the heat exchanger fin (120).

[0089] The hydrogel coating layer (121) may be formed on the heat exchanger fin (120) to a thickness of 0.01 mm to 1 mm. If the thickness of the hydrogel coating layer is too thin, it may be difficult to obtain the desired frost growth delay effect, and if the thickness is too large, cracks or destruction of the hydrogel coating layer may occur.

[0090] Additionally, the heat exchanger (100) may further include an intermediate adhesive layer (not shown) between the heat exchanger fin (120) and the hydrogel coating layer (121).

[0091] The above intermediate adhesive layer may be formed to prevent the heat exchanger fin (120) and the hydrogel coating layer (121) from being separated due to swelling of the hydrogel coating layer (121), and may be formed of a silane compound including an acrylic group selected from, for example, methacryloxypropyltrimethoxysilane, (3-acryloxypropyl)trimethoxysilane, and methacryloxypropylmethyldimethoxysilane.

[0092] Hereinafter, as an example of the present disclosure, a refrigerator having a heat exchanger including a hydrogel coating layer is described.

[0093] FIG. 7 is a drawing showing a refrigerator to which a heat exchanger including a hydrogel coating layer of the present disclosure is applied, FIG. 8 is a drawing showing a cross-section of the refrigerator shown in FIG. 7, FIG. 9 is a drawing showing a heat exchanger including a hydrogel coating layer provided in the refrigerator of FIG. 7, and FIG. 10 is a drawing showing fins of the heat exchanger of FIG. 9.

[0094] Referring to FIGS. 7 to 10, the refrigerator includes a main body (10) forming an exterior, a storage compartment (20) provided so that the front is open inside the main body (10), a door (30) rotatably coupled to the main body (10) to open and close the open front of the storage compartment (20), and a hinge (40) that allows the door (30) to be rotatably coupled to the main body (10).

[0095] The main body (10) includes an inner case (11) forming a storage chamber (20) and an outer case (13) forming an outer case, and an insulating material (15) is foamed between the inner case (11) and the outer case (13) to prevent cold air from leaking out of the storage chamber (20). The main body (10) includes a partition wall (17) dividing the storage chamber (20) into a refrigerating chamber (21) and a freezing chamber (23) on the left and right sides, and a machine room (29) is provided at the lower rear side of the main body (10) in which a compressor (51) for compressing a refrigerant and a condenser (not shown) for condensing the compressed refrigerant are installed.

[0096] The storage room (20) is partitioned left and right by a partition wall (17), and a refrigerator room (21) is provided on the right side of the main body (10), and a freezer room (23) is provided on the left side of the main body (10). Inside the storage room (20), a plurality of shelves (25) and storage containers (27) can be provided to store food, etc.

[0097] The storage compartment (20) is opened and closed by a door (30) that is rotatably connected to the main body (10), and the refrigerator compartment (21) and the freezer compartment (23), which are partitioned left and right by a partition wall (17), are opened and closed by a refrigerator compartment door (31) and a freezer compartment door (33), respectively. A plurality of door shelves (35) are provided on the back surfaces of the refrigerator compartment door (31) and the freezer compartment door (33) to store food, etc.

[0098] A refrigerator may include a cold air supply device (50) that supplies cold air to a storage compartment (20). The cold air supply device (50) may include a refrigeration cycle consisting of an evaporator (100), a compressor (51), a condenser, and an expansion valve, a fan (53) for flowing cold air generated in the evaporator (100) to the storage compartment (20), and a duct (60, 70) that forms an air flow passage.

[0099] The cold air supply device (50) can be defined as including an evaporator (100), a fan (53), ducts (60, 70), etc. that are directly related to the cold air supply, excluding the compressor (51), condenser, etc. installed in the machine room (29). Therefore, the heat exchanger (100) included in the cold air supply device (50) described below means the evaporator (100).

[0100] In Fig. 8, the cold air supply device (50) is shown as being placed at the rear or back of the storage room (20), but is not limited thereto.

[0101] The cold air supply device (50) may include a heat exchanger (100) that generates cold air, a duct (60, 70) that forms an air flow passage inside the cold air supply device (50), and a fan (53) that forms an air flow inside the duct (60, 70).

[0102] The duct (60, 70) may include an intake duct (60) that forms an air inlet passage (61) through which air from the storage room (20) is introduced and passes through the heat exchanger (100), and an exhaust duct (70) that forms an air discharge passage (71) for supplying cold air that has passed through the heat exchanger (100) to the storage room (20). The intake duct (60) is arranged upstream of the fan (53), and the exhaust duct (70) is arranged downstream of the fan (53).

[0103] An inlet port (55) through which air from the storage room (20) flows in may be provided at the end of the intake duct (60), and a plurality of outlet ports (57) may be provided in the exhaust duct (70) so that cold air can be distributed to the storage room (20).

[0104] A cold air supply device (50) may include a heat exchanger (100) that generates cold air, a heater (150) that heats the heat exchanger (100) to regenerate the hydrogel coating layer (121) included in the heat exchanger and at the same time removes frost generated in the heat exchanger, a bracket (140, 141) that supports the heat exchanger (100) and the heater (150), a tray (130) that surrounds a part of the heat exchanger (100), etc. The tray (130) may be configured to collect and discharge frost formed on the heat exchanger (100) when it melts and turns into water droplets and falls to the bottom of the heat exchanger (100).

[0105] A heat exchanger (100) may include a tube (110) through which a refrigerant flows and fins (120) coupled to the outer surface of the tube (110). The heat exchanger (100) may include a plurality of heat exchanger fins (120). The heat exchanger fins (120) contact the outer surface of the tube (110) to facilitate heat exchange between the refrigerant flowing in the tube (110) and the air passing through the heat exchanger (100). The heat exchanger (100) may also be defined as including fins (120), tubes (110), etc., which are directly related to the generation of cold air.

[0106] The heat exchanger fin (120) can be made of various metal materials, including aluminum with high thermal conductivity. The heat exchanger fin (120) can be formed in a plate shape. A hydrogel coating layer (121) of the present disclosure, as described above, can be formed on the surface of the heat exchanger fin (120). A detailed description of the hydrogel coating layer is omitted as it is the same as described above.

[0107] A plurality of heat exchanger fins (120) may be arranged so as to be spaced apart in the left and right directions of the heat exchanger (100), which is a direction perpendicular to the direction in which air flows. The closer the spacing between the plurality of heat exchanger fins (120), the more heat exchanger fins (120) can be arranged. However, if the spacing is too narrow, there is a risk of pressure loss due to resistance to the air passing through the heat exchanger (100), so it is necessary to appropriately adjust the spacing.

[0108] A plurality of heat exchanger fins (120) may be arranged so as to be spaced apart in the vertical direction in which air flows. When air moves upward from the lower side to the upper side, the left-right spacing of the plurality of heat exchanger fins (120) arranged on the lower side may be wider than the left-right spacing of the plurality of heat exchanger fins (120) arranged on the upper side, taking air resistance into consideration.

[0109] The tube (110) may be arranged to pass through a plurality of heat exchanger fins (120) horizontally in the left and right directions of the heat exchanger (100), which is a vertical direction in which air flows. When a plurality of heat exchanger fins (120) are arranged in an up-and-down direction along the direction of air flow, the tube (110) may also be arranged to be bent so as to be able to cross multiple times along the direction of air flow.

[0110] Meanwhile, the field for implementing frost growth delay of a heat exchanger including a hydrogel coating layer of the present disclosure can be applied to home appliances such as refrigerators and air conditioners, automobile radiators, air conditioning systems, etc.

[0111] Hereinafter, the present invention will be described in more detail with reference to the following examples. However, the following examples are intended only to illustrate the present invention and the scope of the present invention is not limited to these examples.

[0112] Manufacturing example: Manufacturing of a heat exchanger including a hydrogel coating layer

[0113] A heat exchanger was manufactured by coating a hydrogel coating layer of a plate-type heat exchanger fin made of aluminum alloy material to a thickness of 0.5 mm using a hydrogel containing 2-methacryloyloxyethyl phosphorylcholine, polyethylene glycol diacrylate, and ammonium persulfate (molar ratio of 1:0.01:0.01) and water.

[0114] Using the heat exchanger manufactured above, the conditions in which frost growth easily occurs are dry bulb temperature 5 ℃, relative humidity 80% (absolute humidity 0.00431 kg / kg) da ) after being left for 480 minutes in an environment, the surface image of the hydrogel is shown in Fig. 11.

[0115] As shown in Fig. 11, in the case of the hydrogel coating layer provided in the heat exchanger, it was confirmed that frost grew on the surface of the hydrogel coating layer as time passed for 240 minutes and 480 minutes.

[0116] Experimental Example 1. Confirmation of frost-retardation performance before and after moisture saturation.

[0117] In order to determine a method for maximizing the frost retardation performance of the hydrogel, the hydrogel coating layer provided in the above-mentioned manufactured heat exchanger was sufficiently saturated with moisture, and then the frost retardation performance before and after moisture saturation was determined, and the results are shown in Fig. 12.

[0118] As illustrated in Fig. 12, before saturating the hydrogel coating layer with moisture (Fig. 12(a)), no frost growth occurred on the surface of the hydrogel coating layer. However, after saturating the hydrogel coating layer with moisture (Fig. 12(b)), it was confirmed that frost growth occurred on the surface of the hydrogel coating layer. From these results, it was predicted that frost growth would be possible if the degree of moisture saturation was controlled through regeneration of the hydrogel coating layer included in the heat exchanger of the present disclosure.

[0119] Experimental Example 2. Measurement of regeneration performance according to the hydrogel coating layer regeneration and frost implantation cycle.

[0120] Using the heat exchanger manufactured above, after sufficient moisture was absorbed into the hydrogel coating layer to saturate it, when the slurry ice inside the hydrogel coating layer grew to about 70% of the total area of ​​the coating layer, the surface temperature of the hydrogel coating layer was maintained at 35°C for 20 minutes to regenerate the hydrogel coating layer, and when the slurry ice inside the hydrogel coating layer became 0% or the hydrogel coating layer swollen by moisture absorption shrank by more than 80%, frost formation was performed for 90 minutes while maintaining the surface temperature of the hydrogel coating layer at -20°C under an external temperature of 5°C and a relative humidity of 80%. Next, when the slurry ice inside the hydrogel coating layer grew again to about 70% of the total area of ​​the coating layer, the surface temperature of the hydrogel coating layer was maintained at 35°C for 10 minutes to regenerate the hydrogel coating layer, and when the slurry ice inside the hydrogel coating layer became 0% or the hydrogel coating layer swollen by moisture absorption shrank by more than 80%, frost formation was performed for 90 minutes while maintaining the surface temperature of the hydrogel coating layer at -20°C under an external temperature of 5°C and a relative humidity of 80%. Next, when the slurry ice inside the hydrogel coating layer grew to about 70% of the total area of ​​the coating layer, the surface temperature of the hydrogel coating layer was maintained at 70°C for 10 minutes to regenerate the hydrogel coating layer, and when the slurry ice inside the hydrogel coating layer became 0% or the hydrogel coating layer swollen by moisture absorption shrank by more than 80%, frost formation was performed for 90 minutes while maintaining the surface temperature of the hydrogel coating layer at -20°C under an external temperature of 5°C and a relative humidity of 80%.

[0121] As described above, the surface temperature change of the hydrogel coating layer was measured while performing three cycles of regeneration and frost implantation of the hydrogel coating layer, and the regeneration performance was determined by checking the point in time when the frost implantation section entered after the end of the regeneration section.

[0122] Figure 13 illustrates changes in the surface temperature of a hydrogel coating layer. As illustrated in Figure 13, it was confirmed that the surface temperature changed as the regeneration and frost deposition of the hydrogel coating layer proceeded in three cycles.

[0123] Also, the state of the surface of the hydrogel coating layer during three cycles of regeneration and frost deposition of the hydrogel coating layer is shown in Fig. 14. As shown in Fig. 14, when the hydrogel coating layer was regenerated for the first time at 35°C for 20 minutes in the initial state, it took 5 minutes for frost deposition. After the second frost deposition, when the hydrogel coating layer was regenerated for the second time at 35°C for 10 minutes, it took 3 minutes for frost deposition. After the final 90 minutes of frost deposition, when the hydrogel coating layer was regenerated at 70°C for 10 minutes, it took 50 minutes for frost deposition. Therefore, as the regeneration time and the regeneration temperature increased, the amount of regenerated hydrogel increased, which resulted in an increase in the frost deposition delay time.

[0124] Through these results, it was confirmed that as the regeneration time and regeneration temperature of the hydrogel coating layer increased, the amount of hydrogel regeneration increased, which could increase the frost attachment delay time.

[0125]

Claims

1. A method for delaying frost formation in a heat exchanger including a hydrogel coating layer, The above hydrogel coating layer absorbs moisture, Slurry ice is formed inside the hydrogel coating layer that has absorbed the moisture, A method for delaying frost formation in a heat exchanger, comprising regenerating the hydrogel coating layer when the formed slurry ice occupies 50% or more of the total area of ​​the hydrogel coating layer.

2. In paragraph 1, A method for delaying frost formation in a heat exchanger, wherein the regeneration of the hydrogel coating layer comprises heating the hydrogel coating layer.

3. In paragraph 1, A method for delaying frost formation in a heat exchanger, wherein the regeneration of the hydrogel coating layer comprises maintaining the surface temperature of the hydrogel coating layer at 30°C to 80°C for 1 to 20 minutes.

4. In paragraph 1, A method for delaying frost formation in a heat exchanger, wherein the absorbed moisture exists in the form of non-freezing water, intermediate water or free water inside the hydrogel coating layer.

5. In paragraph 1, A method for delaying frost formation in a heat exchanger, wherein the regeneration of the hydrogel coating layer comprises shrinking the hydrogel coating layer by more than 80% compared to before the regeneration.

6. In paragraph 1, A method for delaying frost formation in a heat exchanger, comprising regenerating the hydrogel coating layer at least once.

7. In paragraph 1, A method for delaying frost formation in a heat exchanger, wherein the hydrogel coating layer comprises a hydrogel coating layer comprising: an ionic monomer selected from among a zwitterionic monomer, a cationic monomer, and an anionic monomer; a crosslinking agent including two or more acrylic groups; a polymerization initiator; and a solvent.

8. In paragraph 7, The above hydrogel coating layer Contains the above ionic monomer in a molar concentration of 0.5 mol / L to 3 mol / L, A method for delaying frost formation in a heat exchanger, comprising 0.5 mol% to 5 mol% of a crosslinking agent and 0.5 mol% to 2.5 mol% of a polymerization initiator based on the above ionic monomer.

9. In paragraph 7, The zwitterionic monomer comprises any one selected from among 2-methacryloyloxyethyl phosphorylcholine, 3-[[2-(methacryloyloxy)ethyl]dimethylammonio]propionate, and [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)ammonium hydroxide. The cationic monomer comprises any one selected from [2-(methacryloyloxy)ethyl]trimethylammonium chloride and trimethyl-3-[(1-oxoallyl)amino]propylammonium chloride, A method for delaying frost formation in a heat exchanger, wherein the anionic monomer comprises any one selected from among 3-prop-2-enoyloxypropane-1-sulfonic acid (3-sulfopropyl acrylate), 3-(2-methylprop-2-enoyloxy)propane-1-sulfonic acid (3-sulfopropyl methacrylate), and acrylic acid.

10. In paragraph 7, A method for delaying frost formation in a heat exchanger, wherein the crosslinking agent containing two or more acrylic groups comprises any one selected from among polyethylene glycol diacrylate, polyethylene glycol dimethacrylate, N,N'-methylenebisacrylamide, and trimethylolpropane triacrylate.

11. In paragraph 1, The above heat exchanger further includes heat exchanger fins that are arranged to transfer heat from a tube through which a refrigerant flows, A method for delaying frost formation in a heat exchanger, wherein the hydrogel coating layer is provided on the heat exchanger fins.

12. In paragraph 11, A method for delaying frost formation in a heat exchanger, wherein the hydrogel coating layer is formed on the heat exchanger fins to a thickness of 0.01 mm to 1 mm.

13. In paragraph 11, A method for delaying frost formation in a heat exchanger, wherein the heat exchanger further comprises an intermediate adhesive layer between the heat exchanger fins and the hydrogel coating layer.

14. In paragraph 13, A method for delaying frost formation in a heat exchanger, wherein the intermediate adhesive layer comprises a silane compound containing an acrylic group selected from among methacryloxypropyltrimethoxysilane, (3-acryloxypropyl)trimethoxysilane, and methacryloxypropylmethyldimethoxysilane.

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