EP2813793A1

EP2813793A1 - Heat exchanger and outdoor unit for air-conditioner having the same

Info

Publication number: EP2813793A1
Application number: EP20140169726
Authority: EP
Inventors: Hong Suk Kim; Seung Hoon Kal; Myong Jong Kwon; Seung Jin Oh; Choong Hyo Jang; Yong Hwa Choi; Hayase Gaku; Sung Hun Hong
Original assignee: Samsung Electronics Co Ltd
Current assignee: Samsung Electronics Co Ltd
Priority date: 2013-06-13
Filing date: 2014-05-23
Publication date: 2014-12-17
Also published as: KR20140145504A; US20140366568A1

Abstract

A heat exchanger includes a refrigerant pipe through which a refrigerant flows, and a plurality of fins coupled to an outer circumference surface of the refrigerant pipe, wherein each fin includes a first region disposed upstream with respect to an air flow direction, and a second region which forms a boundary with the first region and is disposed downstream with respect to the air flow direction, and wherein the first region and the second region have different surface energies in order to prevent formation of condensation water on the fin.

Description

BACKGROUND

1. Field

Embodiments of the present disclosure relate to a heat exchanger which has a structure improved to enhance efficiency thereof and an outdoor unit for air-conditioners having the same.

2. Description of the Related Art

A heat exchanger is mounted and used in an apparatus using refrigeration cycles such as air-conditioners or refrigerators, which includes a plurality of heat exchanger fins and a plurality of refrigerant pipes which are mounted such that they guide a refrigerant and pass through the heat exchanger fins. The heat exchanger fins increase a contact area with outside air flowing in the heat exchanger and thereby improve heat exchange efficiency between refrigerant flowing in the refrigerant pipes and outside air.
In general, heat exchange efficiency increases as a gap between heat exchanger fins decreases and a contact area between the heat exchanger fins and the outside air increases.
In a case in which an evaporator is used as the heat exchanger, a surface of the evaporator is maintained at a low temperature due to circulation of cold refrigerant, while inflowing air has a relatively high temperature. Accordingly, inflowing air containing moisture contacts the heat exchanger fins of the evaporator maintained at a low temperature and a dew point of air which contacts the heat exchanger fins is dropped, dew is formed on the surface of the heat exchanger fins and accumulated dew forms condensation water.
In addition, when the air flowing in the heat exchanger has a high temperature and a high humidity, air passing through the heat exchanger while contacting the fins is heat-exchanged with the refrigerant and is thus approximately saturated, while air passing through the fins while not contacting the fins maintains a relatively high temperature and high humidity. As such, air having different properties is mixed and fog is thus formed on the fins. In particular, fog is readily formed in an area of the heat exchanger where air having a low velocity and a high temperature difference is mixed.
In addition, the condensation water formed on the fins is cooled and ice is thus formed.
In addition, frosting may occur on the fins. Frosting is a phenomenon in which, when wet air contacts a cooling side maintained at a low temperature of 0° or below, a porous frost layer is formed on the cooling side. That is, the frosting phenomenon may occur on the fin surface when high-temperature high-humidity air flowing in the heat exchanger contacts the fins maintained at a low temperature due to the refrigerant.
As such, condensation water formed on the heat exchanger fins of the evaporator is formed between the heat exchanger fins of the heat exchanger, or creates a bridge between the heat exchanger fins. The condensation water, fog, ice and the like present between the heat exchanger fins interrupt air flow between the heat exchanger fins and thus hinder smooth heat exchange.
In addition, condensation water causes corrosion of a metal material constituting the heat exchanger fins, produces white powder oxides and causes microorganism propagation.
In addition, a frost layer is grown due to frosting phenomenon, disadvantageously causing an increase in thermal resistance of the heat exchanger and decreasing a flow rate of air passing through the heat exchanger due to flow channel closure.

SUMMARY

Therefore, it is an aspect of the present disclosure to provide a heat exchanger which has an improved structure so as to remove condensation water and a frost layer derived from a frosting phenomenon and thereby enhance heat exchange efficiency.
Additional aspects of the disclosure will be set forth in part in the description which follows and, in part, will be apparent from the description, or may be learned by practice of the disclosure.
According to the present invention there is provided an apparatus and method as set forth in the appended claims. Other features of the invention will be apparent from the dependent claims, and the description which follows.
In accordance with one aspect of the present disclosure, a heat exchanger includes a refrigerant pipe through which a refrigerant flows, and a plurality of fins coupled to an outer circumference surface of the refrigerant pipe, wherein each fin includes a first region disposed upstream with respect to an air flow direction, and a second region which forms a boundary with the first region and is disposed downstream with respect to the air flow direction, and wherein the first region and the second region have different surface energies in order to prevent formation of condensation water on the fin.
The boundary may be formed such that a width of the first region in a longitudinal direction of the fin is uniform.
The first region may have a width of about 5mm or less.
The boundary may be formed such that the width of the first region in the longitudinal direction of the fin is non-uniform.
The first region may be coated with a hydrophilic agent having a high surface energy so as to facilitate discharge of condensation water formed in the first region.
The hydrophilic agent may include at least one of a carboxyl group (-COOH), an alcohol group (-OH), an amine group (-NH2), a sulfonic acid group (-SO3H) and a urea group (-NHCONH2).
The first region may be coated with a hydrophobic agent having a low surface energy so as to prevent formation of condensation water in the first region.
The hydrophobic agent may include at least one of an inorganic nanopowder and a fluorine compound.
When the first region is coated with a hydrophilic agent having a high surface energy, the second region may be coated with a hydrophobic agent or be uncoated.
When the first region is coated with a hydrophobic agent having a low surface energy, the second region may be coated with a hydrophilic agent or be uncoated.
When the first region is uncoated, the second region may be coated with a hydrophilic agent or a hydrophobic agent.
One of the first region and the second region may be covered with a mask, the entire surface of the fin may be coated with a hydrophobic agent, the mask may be removed and the region covered with the mask may be coated with a hydrophilic agent.
In addition, one of the first region and the second region may be covered with a mask, the entire surface of the fin may be coated with a hydrophilic agent, the mask may be removed and the region covered with the mask may be coated with a hydrophobic agent.
The first region or the second region may be coated with a hydrophilic agent and the uncoated region is coated with a hydrophobic agent by dipcoating.
The first region and the second region may be coated by at least one of dip coating, spray coating and vacuum evaporation such that a difference in surface energy between the first region and the second region is present.
In accordance with another aspect of the present disclosure, a heat exchanger includes a refrigerant pipe having a flow channel through which a refrigerant flows, and a plurality of fins coupled to an outer circumference surface of the refrigerant pipe, wherein each fin includes a first region which is disposed upstream with respect to a high-temperature air flow direction and has a constant width, and a second region which contacts air passing through the first region and forms a boundary with the first region, wherein both surfaces of the first region are coated with a hydrophobic agent having a low surface energy to prevent formation of condensation water in the first region upon heat-exchange between the high-temperature air flowing in the first region and the refrigerant flowing in the refrigerant pipe, and both surfaces of the second region are coated with a hydrophilic agent having a high surface energy to facilitate discharge of condensation water formed in the second region upon heat-exchange between the high-temperature air passing through the first region and the refrigerant flowing in the refrigerant pipe.
The refrigerant pipe may be bent in a zigzag form, and the second region may have a plurality of through holes formed by which the refrigerant pipe passes through the fin in a zigzag form.
The hydrophilic agent may include at least one of a carboxyl group (-COOH), an alcohol group (-OH), an amine group (-NH2), a sulfonic acid group (-SO3H) and a urea group (-NHCONH2), and the hydrophobic agent may include at least one of an inorganic nanopowder and a fluorine compound.
Both surfaces of the first region may be covered with a mask, the entire surface of the fin may be coated with a hydrophilic agent, the mask may be removed and the region covered with the mask may be coated with a hydrophobic agent.
In accordance with another aspect of the present disclosure, an outdoor unit for air-conditioners includes a body, a compression unit disposed in the body, the compression unit compressing a refrigerant, and a heat exchanger to heat-exchange the refrigerant compressed by the compression unit with outdoor air, wherein the heat exchanger includes a refrigerant pipe through which a refrigerant flows, and a plurality of fins adhered to an outer circumference surface of the refrigerant pipe, wherein each fin includes a first region disposed upstream with respect to an air flow direction, and a second region forming a boundary with the first region and disposed downstream with respect to the air flow direction, wherein the first region and the second region are coated such that the first and second regions have different surface energies in order to prevent formation of condensation water on the fin.
The first region may have a constant width in a longitudinal direction of the fin and may be coated with a hydrophobic agent which prevents formation of condensation water due to low surface energy.

BRIEF DESCRIPTION OF THE DRAWINGS

These and/or other aspects of the disclosure will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:

FIG. 1 is a perspective view illustrating a configuration of a heat exchanger according to an embodiment of the present disclosure;
FIG. 2 is a view illustrating a fin provided in the heat exchanger according to the present embodiment;
FIG. 3 is a view illustrating a contact angle of condensation water formed on the fin provided in the heat exchanger according to the present embodiment.
FIGS. 4A to4D are views illustrating a boundary formed on the fin provided in the heat exchanger according to the present embodiment; and
FIG. 5 is a perspective view illustrating a schematic structure of an outdoor unit for an air-conditioner including the heat exchanger according to the present embodiment.

DETAILED DESCRIPTION

Hereinafter, preferred embodiments of the present disclosure will be described with reference to the accompanying drawings.
FIG. 1 is a perspective view illustrating a configuration of a heat exchanger according to an embodiment of the present disclosure.
As shown in FIG. 1, the heat exchanger 10 includes a refrigerant pipe 20 in which a refrigerant flows and a fin 30 coupled to an outer circumference surface of the refrigerant pipe 20.
The refrigerant pipe 20 has a hollow tubular shape, enabling the fluid refrigerant to flow. The refrigerant pipe 20 is preferably as long as possible to increase a heat exchange area between the refrigerant flowing in the refrigerant pipe 20 and outside air. However, if the refrigerant pipe 30 extends to a great length in a single direction, spatial utilization efficiency is poor. Accordingly, the refrigerant pipe 20 is bent in a direction opposite to a direction in which the refrigerant pipe 20 extends from both ends of the heat exchanger 10 and bending is repeated several times, thereby efficiently increasing a heat exchange area in a limited space.
As the refrigerant flowing in the refrigerant pipe 20, a plurality of refrigerants including R-134a and R410A which are mixtures of Freon having different properties are used.
The refrigerant is heat-exchanged with outside air while undergoing phase change (compression) from a gas state to a liquid state or is heat-exchanged with outside air while undergoing phase change (expansion) from a liquid state to a gas state. When the refrigerant is phase-changed from a gas state to a liquid state, the heat exchanger 10 is used as a condenser and when the refrigerant is phase-changed from a liquid state to a gas state, the heat exchanger 10 is used as an evaporator.
The refrigerant is compressed or expanded and, at the same time, emits heat to the outside or absorbs heat from the outside when while passing through the refrigerant pipe 20. Upon compression or expansion, the fin 30 is coupled to the refrigerant pipe 20 so that the refrigerant efficiently emits or absorbs heat.
A plurality of fins 30 including the fin 30 are laminated at a constant distance in a direction in which the refrigerant pipe 20 extends.
The fin 30 is made of one of various metal materials including aluminum having high thermal conductivity, and contacts and is coupled to the outer circumference surface of the refrigerant pipe 20 and thereby functions to increase a contact area between the fin 30 and the refrigerant pipe 20.
As the gap between the fins 30 laminated becomes narrow, the number of fins 30 disposed increases. However, as the gap is excessively narrowed, as shown in FIG. 1, the gap acts as a resistance to the air flowing in the heat exchanger 10 and may cause pressure loss. Accordingly, it may be necessary to suitably control the gap.
A louver (not shown) which is bent to form a predetermined angle may be formed on the surface of the fin 30. The louver increases a contact area in which the fin 30 contacts outside air and thereby facilitates heat-exchange.
The surface of the fin 30 includes a first region 50 and a second region 60.
The first region 50 may be formed upstream with respect to an air flow direction and the second region 60 may form a boundary 80 with the first region 50 and be formed downstream with respect to the air flow direction.
A material for the refrigerant pipe 20 and the fin 30 constituting the heat exchanger 10 may be aluminum, copper or the like.
FIG. 2 shows a fin provided in the heat exchanger according to the present embodiment, and FIG. 3 shows a contact angle of condensation water formed on the fin provided in the heat exchanger according to the present embodiment.
As shown in FIG. 2, the surface of the fin 30 may include the first region 50 and the second region 60.
In addition, the second region 60 may be provided with a plurality of through holes 40 which enable the refrigerant pipes 20 to pass through the fins 30 in a zigzag form.
In addition, the boundary 80 disposed between the first region 50 and the second region 60 is formed such that a width of the first region 50 in a longitudinal direction of the fin 30 is uniform.
The boundary 80 may be formed at a position which enables the first region 50 to have a width of 5mm or less.
In addition, the boundary 80 may be formed such that a width of the first region 50 in the longitudinal direction of the fin 30 is non-uniform.
The boundary 80 may have a linear shape.
The air flowing in the heat exchanger 10 sequentially passes through the first region 50 and the second region 60 and then flows outside of the heat exchanger 10.
The first region 50 and the second region 60 may be treated so as to prevent formation of a condensation water 70 on the surface of the fin 30 or facilitate discharge of the formed condensation water 70.
The first region 50 and the second region 60 may have different surface energies.
Each of the first region 50 and the second region 60 may be coated with a hydrophilic agent or a hydrophobic agent or may be uncoated.
Hydrophobicity is a property of an object in which hemispheric drops are formed when a surface of the object is wet with water. Hydrophilicity is a property of an object in which hemispheric drops are not formed but are aggregated together and widely spread when a surface of the object is wet with water.
Hydrophobic and hydrophilic substances have different surface energies.
When a heterogeneous substance is placed on a liquid or solid surface, the surface of the liquid or solid has a high energy as compared to an inside of the liquid or solid, and an excessive energy of the liquid or solid surface tends to contract a surface at all times and this is referred to as surface energy.
That is, the fin 30 in a solid state has a predetermined surface energy and has a property of drawing the condensation water 70 formed on the surface of the fin 30 toward the fin 30 as the surface contraction property.
In general, when the fin 30 is coated with a hydrophobic agent, the fin 30 has a low surface energy, and when the fin 30 is coated with a hydrophilic agent, the fin 30 has a high surface energy.
Accordingly, as shown in FIG. 3, when the fin 30 is coated with a hydrophobic agent, the condensation water 70 formed on the fin 30 has a large contact angle (regarding a liquid and a solid which contact each other, an angle formed by the surface of the liquid and the surface of the solid), and when the fin 30 is coated with a hydrophilic agent, the condensation water 70 formed on the fin 30 has a small contact angle.
When the contact angle between the fin 30 and the condensation water contacts is 40 degrees or less, the fin 30 is considered to be hydrophilic, and when the contact angle is 10 degrees or less, the fin 30 is considered to be super hydrophilic. In addition, when the contact angle is 70 degrees or above and is 100 degrees or below, the fin 30 is considered to be hydrophobic, and when the contact angle is 110 degrees or above and is 180 degrees or below, the fin 30 is considered to be super hydrophobic.
In a case of non-coating, the contact angle between the fin 30 and the condensation water ranges from a hydrophilic value to a hydrophobic value because a surface of the raw material of the fin 30 is used without any treatment.
Contact angle increases in order of hydrophilic coating, non-coating and hydrophobic coating.
When the first region 50 is coated with a hydrophobic agent, the second region 60 may be coated with a hydrophilic agent or be uncoated.
When the first region 50 is coated with a hydrophilic agent, the second region 60 may be coated with a hydrophobic agent or be uncoated.
When the first region 50 is uncoated, the second region 60 may be coated with a hydrophilic agent, or be uncoated.
The first region 50 may be coated with a hydrophobic agent and the second region 60 may be coated with a hydrophilic agent.
Formation of the condensation water 70 in the first region 50 upon heat exchange between high-temperature air flowing in the first region 50 and the refrigerant flowing in the refrigerant pipe 20 is prevented by coating the first region 50 with a hydrophobic agent. Discharge of the condensation water 70 formed in the second region 60 upon heat exchange between the high-temperature air passing through the first region 50 and the refrigerant flowing in the refrigerant pipe 20 is facilitated by coating the second region 60 with a hydrophilic agent.
In addition, although the condensation water 70 is formed in the first region 50 coated with a hydrophobic agent, the condensation water 70 formed in the first region 50 is transferred together with the air flowing in the first region 50 to the second region 60.Then, in the second region 60 coated with a hydrophilic agent, the condensation water 70 formed in the first region 50 joins with the condensation water 70 formed in the second region 60 and flows out in a downward direction of the fin 30.
The hydrophilic agent may include a substance having at least one of a carboxyl group (-COOH),an alcohol group (-OH),an amine group (-NH2),a sulfonic acid group (-SO3H) and a urea group (-NHCONH2).
The hydrophobic agent comprises a substance comprising at least one of an inorganic nanopowder and a fluorine compound.
In addition, the hydrophobic agent may comprise a nanopowder containing at least one of Al2O3, TiO2and SiO2.
In addition, the fluorine compound used as the hydrophobic agent may comprise polytetrafluoroethylene (PTFE).
The coating may be carried out by dipcoating, spraycoating, vacuum evaporation or the like.
Dipcoating is a method for forming a coating film by immersing an object to be coated in a coating solution or slurry to form a precursor layer on a surface of the object and baking the precursor layer at a suitable temperature.
Spraycoating is a coating method which includes spraying compressed air or a coating material squeeze-pumped into a fog state on a surface of an object using a spray.
Vacuum evaporation is a coating method in which a metal is heated at a high-temperature to produce a vapor and the metal is deposited as a thin film using the vapor.
A patterning method may be used to coat the first region 50 and the second region 60 with a hydrophilic agent and/or a hydrophobic agent, respectively, which have different surface energies.
Specifically, one of the first region 50 and the second region 60 is covered with a mask, the entire surface of the fin 30 is coated with a hydrophobic agent, the mask is removed and the region covered with the mask is coated with a hydrophilic agent.
Alternatively, one of the first region 50 and the second region 60 is covered with a mask, the entire surface of the fin 30 is coated with a hydrophilic agent, the mask is removed and the region covered with the mask is coated with a hydrophobic agent.
Meanwhile, one of the first region 50andthe second region 60 is coated with a hydrophilic agent and the region not-coated with the hydrophilic agent is coated with a hydrophobic agent by dipcoating.
Alternatively, one of the first region 50 and the second region 60 is coated with a hydrophobic agent and the region not-coated with the hydrophilic agent is coated with a hydrophilic agent by dipcoating.
At least one surface of the fin 30 may be coated.
The refrigerant pipe 20 may be also coated with a hydrophilic agent or a hydrophobic agent.
By thinly coating the refrigerant pipe 20 and the fin 30 with a hydrophilic agent or a hydrophobic agent, thermal conductivity of the heat exchanger 10 is improved, surface roughness is decreased and discharge of the condensation water 70 is thus advantageous.
FIGS. 4A to 4D are views illustrating a boundary formed on a fin provided in the heat exchanger according to the present embodiment.
Based on the boundary 80 formed on the surface of the fin 30, the first region 50 and the second region 60 are divided.
As shown in FIGS. 4A and 4B, the boundary 80 may have a bent straight line shape.
In addition, as shown in FIGS. 4C and 4D, the boundary 80 may have a curved shape.
The boundary 80 may have a curved shape including continuously repeated ridges and valleys.
The boundary 80 may have a shape in which a straight line is combined with a curve.
The shape of the boundary 80 may be varied and is not limited to the examples described above.
FIG. 5 is a perspective view illustrating a schematic structure of an outdoor unit for an air-conditioner, including the heat exchanger according to the present embodiment.
The air-conditioner may be classified into a separation-type and an integrated type. Of these, the separation-type air-conditioner includes an indoor unit which is mounted indoors and absorbs indoor air and thereby exchanges heat with a refrigerant and emits the heat-exchanged air indoors again, and an outdoor unit which heat-exchanges the refrigerant received from the indoor unit with outside air and makes the refrigerant into a state which may heat-exchange with indoor air again and supplies the same to the indoor unit.
As shown in FIG. 5, an outdoor unit for air conditioners 100 may include a body 1 to form an outer appearance and a partition 2 to divide an inner space of the body 1.
The inner space of the body 1 is divided into a heat-exchange area 3 and a compression area 4 by the partition 2. The heat-exchange area 3 is provided with a heat exchanger 10 which is bent along the insides of a back surface 5 and a left surface 6 of the body 1, and an air blower 7 which admits outside air so as to facilitate heat-exchange by the heat exchanger 10. An absorption unit 8 to absorb outside air is formed on the back surface 5 and the left surface 6 of the body 1and a discharge unit 11 to discharge the heat-exchanged air is formed on a front surface 9 of the body 1.
A compression unit 12 to compress the refrigerant supplied from the indoor unit (not shown) is mounted on the compression area 4 of the body 1. A plurality of openings 14 to connect the compression area 4 to the outside are formed on a right surface 13 of the body 1.
As shown in FIG. 1, the heat exchanger 10 may include a refrigerant pipe 20,through which the refrigerant flows, and a plurality of fins 30 connected to an outer circumference surface of the refrigerant pipe 20.
The fin 30 may include a first region 50 disposed upstream with respect to an air flow direction and a second region 60 which forms a boundary with the first region 50 and is disposed downstream with respect to the air flow direction.
The first region 50 and the second region 60 may be coated such that there is a difference in surface energy therebetween, so as to prevent occurrence of frosting on the fin 30.
Specifically, when the first region 50 is coated with a hydrophobic agent having a low surface energy, the second region 60may be coated with a hydrophilic agent or be uncoated.
When the first region 50 is coated with a hydrophilic agent having a high surface energy, the second region 60 may be coated with a hydrophobic agent or be uncoated.
When the first region 50 is uncoated, the second region 60 may be coated with a hydrophilic agent or be uncoated.
The first region 50 may have a constant width.
The first region 50 may have a width of 5 mm or less in a longitudinal direction of the fin 30.
The heat exchanger 10 may be applied to an outdoor unit for air-conditioners 100 as well as to an indoor unit for air conditioners.
The heat exchanger 10 may be applied to not only to air conditioners but also to refrigerators.
By coating fins with a thin film, formation of condensation water and occurrence of frosting are prevented and, although the condensation water is formed, discharge of the condensation water is facilitated.
By coating fins with a thin film, formation of fog or ice is prevented, heat exchange efficiency is improved, and microorganism propagation and foreign matter decay caused by condensation water are prevented.
Although a few embodiments of the present disclosure have been shown and described, it would be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the claims and their equivalents.
Attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.
All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive.
Each feature disclosed in this specification (including any accompanying claims, abstract and drawings) may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.
The invention is not restricted to the details of the foregoing embodiment(s). The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

Claims

A heat exchanger comprising:
a refrigerant pipe through which a refrigerant flows; and

a plurality of fins coupled to an outer circumference surface of the refrigerant pipe,

wherein each fin comprises:
a first region disposed upstream with respect to an air flow direction; and

a second region which forms a boundary with the first region and is disposed downstream with respect to the air flow direction, and

wherein the first region and the second region have different surface energies in order to prevent formation of condensation water on the fin.
The heat exchanger according to claim 1, wherein the boundary is formed such that a width of the first region in a longitudinal direction of the fin is uniform.
The heat exchanger according to claim 1, wherein the first region has a width of about 5 mm or less.
The heat exchanger according to claim 1, wherein the boundary is formed such that the width of the first region in the longitudinal direction of the fin is non-uniform.
The heat exchanger according to claim 1, wherein the first region is coated with a hydrophilic agent having a high surface energy so as to facilitate discharge of condensation water formed in the first region.
The heat exchanger according to claim 5, wherein the hydrophilic agent comprises at least one of a carboxyl group (-COOH), an alcohol group (-OH), an amine group (-NH₂), a sulfonic acid group (-SO3H) and a urea group (-NHCONH₂).
The heat exchanger according to claim 1, wherein the first region is coated with a hydrophobic agent having a low surface energy so as to prevent formation of condensation water in the first region.
The heat exchanger according to claim 7, wherein the hydrophobic agent comprises at least one of an inorganic nanopowder and a fluorine compound.
The heat exchanger according to claim 1, wherein, when the first region is coated with a hydrophilic agent having a high surface energy, the second region is coated with a hydrophobic agent or is uncoated.
The heat exchanger according to claim 1, wherein, when the first region is coated with a hydrophobic agent having a low surface energy, the second region is coated with a hydrophilic agent or is uncoated.
The heat exchanger according to claim 1, wherein, when the first region is uncoated, the second region is coated with a hydrophilic agent or a hydrophobic agent.
The heat exchanger according to claim 1, wherein one of the first region and the second region is covered with a mask, the entire surface of the fin is coated with a hydrophobic agent, the mask is removed and the region covered with the mask is coated with a hydrophilic agent.
The heat exchanger according to claim 1, wherein one of the first region and the second region is covered with a mask, the entire surface of the fin is coated with a hydrophilic agent, the mask is removed and the region covered with the mask is coated with a hydrophobic agent.
The heat exchanger according to claim 1, wherein the first region and the second region are coated by at least one of dip coating, spray coating and vacuum evaporation such that a difference in surface energy between the first region and the second region is present.
The heat exchanger according to claim 1, wherein the first region or the second region is coated with a hydrophilic agent and the uncoated region is coated with a hydrophobic agent by dip coating.