KR101987700B1 - Method for forming lubricating layer of heat exchanger - Google Patents

Abstract

A method of forming a lubricating layer of a heat exchanger provided in the present invention includes the steps of: (a) forming a pore on a surface of aluminum constituting a refrigerant pipe or a cooling fin of a heat exchanger, or improving the surface roughness of the aluminum; (b) a step of forming a binder layer in which the aluminum is put into an aqueous solution of PTFE (Polytetrafluoroethylene), taken out, and then dried; And (c) a lubricating layer forming step of putting the aluminum into a fluorine-based oil, followed by taking out and drying the lubricating layer, wherein (c) drying the lubricating layer comprises: (c1) drying the aluminum taken out from the fluorine- Placing it on a surface and leaving it in an inclined state; (c2) primary drying the aluminum for a predetermined time at a predetermined temperature; And (c3) drying the aluminum at a temperature lower than the drying temperature of the primary drying step and for a time longer than the drying time of the primary drying step.

Description

METHOD FOR FORMING LUBRICATING LAYER OF HEAT EXCHANGER < RTI ID = 0.0 >

The present invention relates to a method of forming a lubricating layer of a heat exchanger having an excellent retarding effect on the impregnation and maintaining durability for a long time.

The heat exchanger is used in various technical fields such as an air conditioner and a refrigerator. However, when the heat exchanger is continuously operated, moisture is formed on the surface of the heat exchanger. For example, when the heat exchanger is used as the indoor unit (evaporator) of the air conditioner, the temperature of the indoor unit becomes lower than the normal temperature when the air conditioner is operated in the cooling mode. As a result, condensed water is formed on the surface of the indoor unit.

The condensed water formed on the surface of the heat exchanger may cause deterioration of performance of the heat exchanger, occurrence of frost, and propagation of bacteria. Therefore, the condensed water formed on the surface of the heat exchanger must be quickly removed to maintain the performance of the heat exchanger, and the occurrence of frost and the propagation of bacteria can be suppressed.

It may be considered to impart lubricity to the surface of the heat exchanger in order to remove the condensed water formed on the surface of the heat exchanger. Korean Patent Laid-Open Publication No. 10-2014-0047136 (Apr. 21, 2014) discloses a liquid impregnated surface containing a liquid therein. Since the liquid can be composed of a lubricant, the surface of the article including the liquid and the liquid impregnated surface is lubricated. Thus, the liquid which impinges on the liquid impregnated surface is easily repelled.

However, the patent document does not disclose a configuration capable of maintaining the revolution performance of the liquid impregnated surface for a long time. Particularly, since the liquid is filled in the exposed well, the possibility that the liquid is released from the well due to a physical impact applied to the article can not be excluded.

Korean Patent Publication No. 10-2014-0047136 (Apr. 21, 2014)

An object of the present invention is to propose a method of forming a lubricant layer that maintains durability for a long period of time.

Another object of the present invention is to provide a method of forming a lubricant layer capable of rapidly discharging condensed water in a gravitational direction due to low surface energy and small sliding angle.

The lubricant layer of the heat exchanger formed through the above method has excellent retardation performance and antibacterial performance.

In order to accomplish the object of the present invention, a method of forming a lubricating layer of a heat exchanger according to an embodiment of the present invention comprises the steps of: (a) forming a surface feature on a surface of aluminum constituting a refrigerant pipe or a cooling fin of a heat exchanger; A preprocessing step; (b) a binder layer forming step of forming a binder layer with PTFE; And (c) a lubricating layer forming step of forming a lubricating layer with a fluorine-based oil.

In the pretreatment step (a), pores are formed on the surface of aluminum or the surface of aluminum is modified to improve surface roughness.

In the step (b) of forming the binder layer, aluminum is put into an aqueous solution of PTFE (Polytetrafluoroethylene), taken out and dried.

In the lubricant layer forming step (c), aluminum is put into a fluorine-based oil, taken out, and then dried.

The step (c) of drying the lubricating layer comprises: (c1) placing the aluminum taken out from the fluorinated oil on an inclined surface and leaving it in a tilted state; (c2) primary drying the aluminum for a predetermined time at a predetermined temperature; And (c3) drying the aluminum at a temperature lower than the drying temperature of the primary drying step and for a time longer than the drying time of the primary drying step.

(A) washing the aluminum with a sodium hydroxide (NaOH) aqueous solution having a molar concentration of 1 to 1.5M at a temperature of 50 to 80 ° C for 30 seconds to 2 minutes; (a2) washing the aluminum with distilled water; And (a3) boiling the aluminum in water for 10 to 30 minutes to form pores on the surface of the aluminum.

(a1) washing said aluminum for 30 seconds to 2 minutes with an aqueous solution of sodium hydroxide (NaOH) at a temperature of from 50 to 80 DEG C with a molar concentration of from 1 to 1.5M; (a2) washing the aluminum with distilled water; And (a3 ') adding the aluminum for 30 seconds to 2 minutes to an aqueous solution of hydrochloric acid (HCl) at a temperature of 50 to 70 DEG C having a molar concentration of 1 to 2M to improve the roughness of the aluminum, .

The step (b) of forming the binder layer comprises the steps of: (b1) introducing the aluminum into a PTFE (Polytetrafluoroethylene) aqueous solution diluted with distilled water for 10 to 20 minutes; And (b2) drying at a temperature of 240 to 400 DEG C for 10 to 40 minutes.

In the step (b1), the aluminum is taken out from the PTFE aqueous solution at a rate of 2 to 4 cm / min.

The thickness of the binder layer formed by the (b) binder layer forming step is thinner than 1 탆.

In the lubricating layer forming step (c), the aluminum is introduced into the fluorine-based oil having a viscosity of 50 to 100 cSt for 10 to 60 minutes.

In the lubricating layer forming step (c), the aluminum is charged into the fluorine-containing oil for a first period of time. In the step (c1), the aluminum is allowed to stand at room temperature for a second time, 1.5 times to 2.5 times of one hour.

In the step (c1), the aluminum is dried at a temperature of 140 to 160 ° C for 10 to 30 minutes, and in the step (c2) of drying the aluminum, The aluminum is dried at a low temperature of 30 DEG C for 90 to 120 minutes.

A lubricating layer having a contact angle of 115 to 135 占 and a sliding angle of 10 to 20 占 is formed on the surface of the aluminum by the steps (a) to (c).

According to the present invention having such a constitution, surface features are formed on the surface of aluminum through a pretreatment step. The durability of the binder layer and the lubricating layer is improved in the surface features, and the retarding effect of the fusing of the heat exchanger can be obtained.

Further, according to the present invention, a lubricating layer having low surface energy and small sliding angle characteristics can be formed by the binder layer forming conditions. Accordingly, when the lubricant layer is formed in the heat exchanger according to the present invention, the lubricant layer can quickly discharge the condensed water in the gravity direction.

Further, in the present invention, the fluorine-based oil remaining on the surface of aluminum can be dried to the critical point through the viscosity of the fluorine-based oil and the primary drying and secondary drying temperature conditions determined therefrom. Accordingly, the lubricating layer can maintain durability without loss of the fluorine-based oil.

Furthermore, the antimicrobial properties provided by fluorine, which is a raw material of the fluorine-based oil, can be imparted to the heat exchanger.

1 is a conceptual view showing an example of a heat exchanger including a lubricating layer formed by the method of the present invention and the lubricating layer.
2 is a flowchart showing a method of forming a lubricant layer of a heat exchanger proposed in the present invention.
FIG. 3 is a flow chart showing details of a pre-treatment step of forming pores on the surface of aluminum.
4A to 4C are conceptual diagrams showing the preprocessing step of FIG.
5 is a flow chart showing a detail of a pretreatment step for improving the surface roughness by modifying the surface of aluminum.
6A to 6D are conceptual diagrams showing the preprocessing steps of FIG.
FIG. 7 is a flowchart showing the binder layer forming step of FIG. 2 in detail.
8A to 8B are conceptual diagrams showing the binder layer forming step of FIG.
FIG. 9 is a flowchart showing the lubricant layer forming step of FIG. 2 in detail.
10A to 10D are conceptual diagrams showing the lubricant layer forming step of FIG.
11 is a graph for explaining the retarding effect of the lubricating layer formed by the present invention.

Hereinafter, a method of forming a lubricating layer of a heat exchanger according to the present invention will be described in detail with reference to the drawings. In the present specification, the same reference numerals are given to the same components in different embodiments, and the description thereof is replaced with the first explanation. As used herein, the singular forms "a", "an" and "the" include plural referents unless the context clearly dictates otherwise.

1 is a conceptual view showing an example of a heat exchanger including a lubricating layer formed by the method of the present invention and the lubricating layer.

The refrigerant pipe (110) forms a flow path of the heat exchange fluid. The heat exchange fluid can be, for example, a refrigerant. The coolant pipe 110 may form a structure in which the coolant pipe 120 passes through the cooling fin 120 in a linear direction and turns around outside the coolant fin 120 and passes through the coolant pin 120 repeatedly .

The cooling fins 120 extend the heat exchange area to enhance the heat exchange efficiency of the heat exchanger. The cooling fin 120 is coupled to the refrigerant pipe 110. Referring to FIG. 1, the cooling fin 120 is formed in the form of a flat plate and is shown as being coupled to the periphery of the refrigerant tube 110. In the heat exchanger, the plurality of cooling fins 120 may be provided, and the respective fins may be spaced apart from each other.

It can be assumed that the heat exchanger operates as an indoor unit or an outdoor unit of the air conditioner. The air conditioner can be operated in various operating modes such as cooling operation, heating operation, dehumidification operation, and drying operation.

Cooling operation refers to the operation of cooling the heat exchange target area of the heat exchanger. The refrigerant flows through the refrigerant pipe at a lower temperature than the room. The indoor air is cooled through heat exchange between the refrigerant and the indoor air.

When the temperature of the heat exchanger used as the indoor unit becomes lower than the dew point of the room temperature, the unsaturated air reaches the saturated state and condensation of the water vapor starts. As a result, condensed water is formed on the surface of the heat exchanger.

Condensation does not necessarily occur only during the cooling operation of the air conditioner. When the air conditioner is heated, the outdoor unit cools the outdoor air. Condensate can form on the surface of the heat exchanger used as an outdoor unit.

The condensed water formed on the surface of the heat exchanger may cause deterioration of performance of the heat exchanger, occurrence of frost, and propagation of bacteria. Therefore, in order to suppress the performance degradation of the heat exchanger, the occurrence of frost, and the propagation of bacteria, the condensed water formed on the surface of the heat exchanger must be quickly removed.

A lubricant layer 130 is formed on the surface of the heat exchanger for rapid removal of condensate. The lubricating layer 130 can rapidly discharge the condensed water formed on the surface of the cooling fin in the gravity direction due to the low surface energy and the small sliding angle (contact hysteresis angle).

Surface energy refers to the energy that attracts an external substance by the attractive force of an atom present in the outermost layer. Therefore, the lower the surface energy, the smaller the attraction force by the atoms of the outermost layer, and the condensate flows easily in the direction of gravity. The surface energy promotes the wetting of the liquid, and the wettability of the liquid can be evaluated by the contact angle of the liquid. For example, the larger the contact angle of the liquid, the smaller the wettability and surface energy.

The angle of slide means a slope at which the liquid existing on the plane begins to flow when the plane is inclined with respect to the horizontal direction. For example, if the liquid on the plane begins to flow down when the plane is tilted by 10 ° with respect to the horizontal direction, the sliding angle of this plane may be 10 °. The smaller the sliding angle, the more easily the liquid flows down.

Therefore, if the lubricant layer 130 having a large contact angle and a small sliding angle is formed on the surface of the heat exchanger, the condensed water can be quickly discharged. The present invention provides a method for forming a lubricating layer 130 having a contact angle of 115 to 135 degrees and a sliding angle of 10 to 20 degrees on the surface of a heat exchanger. In particular, the present invention provides a method of forming a lubricant layer 130 on the surface of a coolant pipe 110 or a cooling fin 120 formed of aluminum.

2 is a flowchart showing a method of forming a lubricant layer of a heat exchanger proposed in the present invention.

The lubricating layer forming method of the heat exchanger mainly includes a pre-treating step (S100), a binder layer forming step (S200), and a lubricating layer forming step (S300).

In the pretreatment step (S100), a plurality of pores are formed on the surface of the aluminum constituting the refrigerant pipe or the cooling fin of the heat exchanger, or the surface roughness of aluminum is improved. When the binder layer or the lubricant layer is formed on the smooth surface, the durability of the binder layer or the lubricant layer is deteriorated. Whereby peeling of the binder layer or the lubricating layer can be observed.

Therefore, in order to improve the durability of the lubricating layer, a surface feature should be formed on the surface of the aluminum which will constitute the refrigerant pipe or the cooling fin. Surface features are structures that make the surface of smooth aluminum rough. For example, the pores formed on the aluminum surface correspond to the surface features.

It is possible to modify the surface of smooth aluminum instead of pore to improve the surface roughness. The rough surface of aluminum is also a surface feature. Particularly, when the surface of aluminum is roughened, the heat exchange area is enlarged.

The detailed configuration of the preprocessing step will be described later with reference to Figs. 3, 4A to 4C, 5, 6A to 6D.

Next, in a binder layer forming step (S200), a binder layer to serve as a primer of the lubricant layer is formed. Primer means that the surface of the object is first coated on the surface of the object to protect it from corrosion or physical impact and smooth subsequent coating. The binder layer serves to protect the surface of aluminum and adhere the lubricant layer to be coated on the binder layer to the surface of aluminum.

The binder layer is formed by dipping the pretreated aluminum in an aqueous solution of PTFE (Polytetrafluoroethylene), removing the aluminum, and drying the pretreated aluminum. The detailed process of forming the binder layer will be described later with reference to Figs. 7 and 8A to 8B.

Finally, in the lubricating layer forming step (S300), a lubricating layer having low surface energy, large contact angle and small sliding angle characteristic is formed on the surface of aluminum. When the lubricating layer is formed on the surface of the aluminum, the condensed water is quickly discharged in a gravitational direction and discharged immediately as soon as it is formed on the surface of the lubricating layer.

The lubricating layer is formed by feeding aluminum in which a binder layer is formed into a fluorine-based oil, removing it, and drying it. In particular, the present invention is characterized in that the fluorine-based oil is dried several times under different conditions to form a lubricating layer. The detailed process for forming the lubricant layer will be described later with reference to Figs. 9, 10A to 10D.

Hereinafter, the details of the preprocessing step will be described first. In the pretreatment step, pores may be formed on the surface of aluminum, or the surface of aluminum may be modified to improve the surface roughness.

FIG. 3 is a flow chart showing details of a pre-treatment step of forming pores on the surface of aluminum. 4A to 4C are conceptual diagrams showing the preprocessing step of FIG.

(S110, FIG. 4A) First, aluminum (Al) constituting the refrigerant pipe or the cooling fin is washed with an aqueous solution of sodium hydroxide (NaOH). When the aluminum is washed with an aqueous solution of sodium hydroxide, the surface of the aluminum is etched.

The molar concentration of the sodium hydroxide aqueous solution is preferably 1 to 1.5 M, and the washing time is preferably 30 seconds to 2 minutes. If the molar concentration of aqueous sodium hydroxide solution is less than 1 M or the cleaning time is shorter than 30 seconds, the etching effect is insufficient. Conversely, if the molar concentration of aqueous sodium hydroxide solution is thicker than 1.5M or the cleaning time is longer than 2 minutes, the aluminum surface may be excessively damaged.

The temperature of the sodium hydroxide aqueous solution is preferably 50 to 80 ° C. The temperature of the aqueous sodium hydroxide solution affects the reaction time. Therefore, if the temperature of the sodium hydroxide aqueous solution is lower than 50 ° C, the washing time is long. In order to keep the temperature of the sodium hydroxide aqueous solution at 50 to 80 캜, the aqueous sodium hydroxide solution can be heated by the heater (H).

(S120, Fig. 4B). Then, the aluminum washed with the aqueous solution of sodium hydroxide is washed again with distilled water (DW). The aqueous sodium hydroxide solution remaining on the surface of the aluminum will have a continuous effect on the surface of the aluminum. Therefore, an aqueous solution of sodium hydroxide must be removed from the surface of aluminum using distilled water.

The time for washing aluminum in distilled water is about 5 to 20 seconds, and aluminum can be washed more than twice in distilled water. If the aluminum is washed more than twice, do not wash the aluminum again with the distilled water from which the aluminum is removed, but wash the aluminum with fresh distilled water.

(S131, Fig. 4C) Finally, aluminum is placed in water (W) and boiled to form pores on the surface of aluminum. Aluminum washed with distilled water is immediately added to boiling water and boiled for 10 to 30 minutes to form pores on the surface of aluminum. The water can be heated by the heater H to keep the water in a boiling state.

5 is a flow chart showing a detail of a pretreatment step for improving the surface roughness by modifying the surface of aluminum. 6A to 6D are conceptual diagrams showing the preprocessing steps of FIG.

(S110, FIG. 6A) and (S120, FIG. 6B) are overlapped with the description of FIG. 3, FIG. 4A, and FIG. 4B. Therefore, these descriptions are replaced with those described above.

(S132, FIGS. 6C to 6D) Aluminum (Al) is put into an aqueous solution of hydrochloric acid (HCl) to remove roughness of aluminum sequentially washed with an aqueous solution of sodium hydroxide and distilled water, and then taken out and washed with distilled water (DW).

The molar concentration of the hydrochloric acid aqueous solution is preferably 1 to 2 M, and the time for introducing aluminum into the hydrochloric acid aqueous solution is preferably 30 seconds to 2 minutes. If the molar concentration of the hydrochloric acid aqueous solution is lighter than 1 M or the injection time is shorter than 30 seconds, the effect of increasing the surface roughness is insufficient. Conversely, if the molar concentration of the hydrochloric acid aqueous solution is thicker than 2M or the injection time is longer than 2 minutes, the aluminum surface may be excessively damaged.

The temperature of the aqueous hydrochloric acid solution is preferably 50 to 70 ° C. The temperature of the aqueous hydrochloric acid solution affects the reaction time. Therefore, if the temperature of the hydrochloric acid aqueous solution is lower than 50 캜, the reforming time becomes long. In order to keep the temperature of the aqueous hydrochloric acid solution at 50 to 70 캜, the aqueous hydrochloric acid solution may be heated by the heater (H).

After the aluminum is broken in the aqueous hydrochloric acid solution, the aluminum is washed with distilled water. The time for washing aluminum in distilled water is about 5 to 20 seconds, and aluminum can be washed more than twice in distilled water. If the aluminum is washed more than twice, do not wash the aluminum again with the distilled water from which the aluminum is removed, but wash the aluminum with fresh distilled water.

Through this process, the aluminum surface is modified to improve the surface roughness.

Next, the detailed process of the binder layer forming step (S200) will be described.

FIG. 7 is a flowchart showing the binder layer forming step of FIG. 2 in detail. 8A to 8B are conceptual diagrams showing the binder layer forming step of FIG.

(S210, FIG. 8A) First, the pretreated aluminum is poured into a PTFE (Polytetrafluoroethylene) aqueous solution (or a Teflon aqueous solution, Teflon) diluted with distilled water. It is experimentally best to mix distilled water and PTFE in a 1: 1 ratio.

The time for introducing aluminum into the PTFE aqueous solution is suitably about 10 to 20 minutes. This time is to penetrate the PTFE aqueous solution into the pores or rough surface of the aluminum. If the time for introducing aluminum into the PTFE aqueous solution is shorter than 10 minutes, the penetration effect is insufficient. If the time for introducing aluminum into the PTFE aqueous solution is longer than 20 minutes, the penetration effect is saturated.

The thickness of the binder layer formed by the PTFE aqueous solution can be controlled by the speed at which aluminum is taken out from the PTFE aqueous solution. If the thickness of the binder layer is too thick, it can not sustain its own weight and collapses. Therefore, the thickness of the binder layer is preferably thinner than 1 탆, and more preferably about 700 nm.

In order to adjust the thickness of the binder layer to about 700 nm, aluminum is preferably taken out from the PTFE aqueous solution at a rate of 2 to 4 cm / min. The aluminum can be left at room temperature for 5 to 10 minutes after it is taken out from the PTFE aqueous solution.

(S220, Fig. 8B). Next, the aluminum is repeatedly dried once or twice at a temperature of 240 to 400 DEG C for 10 to 40 minutes. The aluminum can be dried in the dryer (D).

The drying of the aluminum taken out from the PTFE aqueous solution is a process of hardening the aqueous PTFE solution adhering to the surface of the aluminum. 240 to 400 占 폚 is a curing temperature, and 10 to 40 minutes is a curing time. The contact angle and the sliding angle of the lubricant layer to be described later can be determined according to the curing time and the curing temperature of the PTFE aqueous solution.

In the present invention, it is aimed that the lubricating layer has a contact angle characteristic of 115 to 135 degrees and a sliding angle characteristic of 10 to 20 degrees. The curing temperature and cure time are conditions that allow the contact angle of the lubricant layer to be controlled at 115 to 135 degrees and the sliding angle to be controlled at 10 to 20 degrees.

Finally, the detailed configuration of the lubricant layer forming step (S300) will be described.

FIG. 9 is a flowchart showing the lubricant layer forming step of FIG. 2 in detail. 10A to 10D are conceptual diagrams showing the lubricant layer forming step of FIG.

(S310, FIG. 10A) First, aluminum is introduced into the fluoric oil (O) at normal temperature. The fluorine-based oil may be, for example, Krytox. The term " bolometer system " means a polymer oil containing fluorine (F). It is known that only a small amount of fluorine-based oil is harmless to the human body.

The viscosity of the fluorine-based oil is preferably 50 to 100 cSt (centistokes). In order to prevent peeling of the lubricating layer from the surface of aluminum, it is necessary to dry the fluorine-based oil to a critical point through a drying process to be described later. The effect of maintaining the durability of the lubricating layer by drying the fluorinated oil to the critical point is influenced by the viscosity of the fluorinated oil, and this effect appears only at the viscosity of 50 to 100 cSt of the fluorinated oil.

The viscosity of the fluorine-based oil is related to the drying temperature described later. As the viscosity of the fluorine-based oil increases, the drying temperature must also increase. Therefore, the temperature conditions of the primary drying and the secondary drying to be described later are determined from the viscosity of the fluorine-based oil from 50 to 100 cSt.

Fluorine itself is a material with strong antimicrobial properties. Therefore, if the lubricant layer of the heat exchanger is formed of fluorine, the surface of the heat exchanger may be given antimicrobial properties.

Aluminum may be added to the fluorinated oil for 10 to 60 minutes. The time during which aluminum is introduced into the fluorine-based oil is related to the time the fluorine-based oil penetrates the pores present on the surface of the aluminum or the modified surface. If the injection time of aluminum is shorter than 10 minutes, the penetration effect is insufficient. If the injection time of aluminum is longer than 60 minutes, the effect becomes saturated.

(S320, FIG. 10B). Next, aluminum taken out from the fluorinated oil is placed on a tilted surface (T) and left in a tilted state. Aluminum may be allowed to stand at an inclined state at room temperature.

The time for which the aluminum is allowed to remain in the inclined state should be longer than the time for which aluminum is introduced into the fluorinated oil. It is preferable that the time for introducing aluminum into the fluorine-based oil is the first time, and the time for leaving the aluminum in a tilted state is the second time, and the second time is preferably 1.5 to 2.5 times the first time. For example, if the first time is 10 minutes, then the second time may be 20 minutes.

Leaving the aluminum in an inclined state is intended to cause aluminum to flow down from the surface of the excess fluorine-based oil remaining on the surface of the aluminum. The longer the time the aluminum is charged into the fluorine-based oil, the more fluorine-based oil remains on the surface of the aluminum. Therefore, it is preferable that the longer the time for introducing aluminum into the fluorine-based oil is, the longer the time for leaving the aluminum in a tilted state is longer. For example, the second time is preferably about twice the first time.

If the step of leaving the aluminum in an inclined state is omitted, the fluorine-based oil is completely lost in the subsequent primary drying and secondary drying steps. Therefore, in order to form a durable lubricating layer, it is necessary to leave the aluminum in an inclined state.

(S330, Fig. 10C). Then aluminum is primarily dried in the dryer (D). The primary drying of aluminum is for rapid drying of the fluorinated oil. The aluminum may be dried at a temperature of 140 to 160 DEG C for 10 to 30 minutes. The reason why the aluminum is dried at a high temperature for a short time is to remove even the fluorine-based oil remaining on the surface.

(S340, Fig. 10d) Finally, aluminum is secondarily dried in the dryer (D). The secondary drying of the aluminum is intended to penetrate the pore or rough surface of the aluminum with the fluorinated oil. The secondary drying temperature is lower than the primary drying temperature, and the secondary drying time is longer than the primary drying time. For example, aluminum can be secondarily dried for 90 to 120 minutes at a temperature 10 to 30 占 폚 lower than the temperature of the primary drying step (e.g., 120 to 140 占 폚).

In the drying process described above, the fluorine-based oil is dried to the critical point on the surface of the aluminum, and only a certain amount of fluorine-based oil remains on the surface of the aluminum until the lower limit that can be saturated in the inside of the pore or on the rough surface of aluminum.

If the temperature and time conditions of the primary drying are changed with the secondary drying temperature and time conditions, all of the fluorinated oil is evaporated in the secondary drying process. Also, if only the second drying temperature is used without the first drying, it takes 13 hours or more for the drying time, which is uneconomical.

The lubricating layer formed by the present invention described above has a contact angle characteristic of 115 to 135 degrees and a sliding angle characteristic of 10 to 20 degrees. Whereby the lubricant layer is capable of quickly discharging the condensed water in the direction of gravity.

On the other hand, the durability of the lubricating layer can be tested through freezing and thawing processes.

The heat exchanger having the lubricating layer formed according to the present invention is frozen to -10 DEG C for 30 minutes and then thawed to normal temperature for 5 minutes. After that, it was confirmed that the heat exchanger quickly discharged the condensed water. Also, it was confirmed that the fluorine-based oil was detected in the condensed water discharged from the heat exchanger, but the fluorine-based oil was not detected in the condensed water. It can be seen from this that the lubricating layer of the heat exchanger maintains its durability.

11 is a graph for explaining the retarding effect of the lubricating layer formed by the present invention.

The abscissa of the graph indicates the conception time (min), and the ordinate axis of the graph indicates air pressure (mmAq). When an impregnation occurs in the heat exchanger, the flow path of the air passing through the heat exchanger is blocked. As a result, the air pressure difference increases. Therefore, it is possible to indirectly determine whether or not the heat exchanger is implanted from the air pressure difference.

(a) is a heat exchanger having a lubricating layer formed by the present invention, (b) is a heat exchanger having a lubricating layer formed without a pretreatment step, and (c) is a heat exchanger having a hydrophilic surface. (A) was about 86 minutes, (b) was about 47 minutes, and (c) was about 43 minutes when the air pressure difference reached 30 mmAq. (b) is about 108% and (a) is about 197% when the reference value (c) is 100% of the reference value.

Therefore, it was confirmed that the lubricating layer of the present invention formed through the pretreatment step had about two times as much delaying effect as compared with the lubricating layer or the hydrophilic surface formed without the pretreatment step.

The above-described method of forming the lubricant layer of the heat exchanger is not limited to the configuration and the method of the above-described embodiments, but the embodiments may be modified such that all or some of the embodiments are selectively combined .

110: Refrigerant pipe
120: cooling pin
130: lubricating layer
Al: Aluminum
NaOH: aqueous solution of sodium hydroxide
H: heater
DW: distilled water
W: Water
HCl: aqueous hydrochloric acid solution
PTFE: PTFE (Polytetrafluoroethylene) aqueous solution
D: Dryer
O: Fluorine oil
T: sloped surface

Claims (11)

(a) a pre-treatment step of forming pores on the surface of aluminum constituting the refrigerant pipe or the cooling fin of the heat exchanger or improving the surface roughness of the aluminum;
(b) a step of forming a binder layer in which the aluminum is put into an aqueous solution of PTFE (Polytetrafluoroethylene), taken out, and then dried; And
(c) a lubricating layer forming step of putting the aluminum into a fluorine-based oil,
The drying process of the lubricant layer forming step (c)
(c1) placing the aluminum taken out from the fluorinated oil on an inclined surface and leaving it in a tilted state;
(c2) drying the aluminum for a predetermined time at a predetermined temperature so as to remove the fluorine-based oil remaining on the surface of the aluminum; And
(c3) the fluorine-based oil penetrates into the pores and the rough surface formed on the surface of the aluminum through the pretreatment step (a), so that only the fluorine-based oil that can be saturated in the pores or on the rough surface, Drying the aluminum at a temperature lower than the drying temperature of the primary drying step and for a time longer than the drying time of the primary drying step so as to remain on the surface of the aluminum Of the lubricating layer. (a) a pre-treatment step of forming pores on the surface of aluminum constituting the refrigerant pipe or the cooling fin of the heat exchanger or improving the surface roughness of the aluminum;
(b) a step of forming a binder layer in which the aluminum is put into an aqueous solution of PTFE (Polytetrafluoroethylene), taken out, and then dried; And
(c) a lubricating layer forming step of putting the aluminum into a fluorine-based oil,
The drying process of the lubricant layer forming step (c)
(c1) placing the aluminum taken out from the fluorinated oil on an inclined surface and leaving it in a tilted state;
(c2) primary drying the aluminum for a predetermined time at a predetermined temperature; And
(c3) secondary drying the aluminum at a temperature lower than the drying temperature of the primary drying step and for a time longer than the drying time of the primary drying step,
The pre-processing step (a)
(a1) washing said aluminum with an aqueous solution of sodium hydroxide (NaOH) having a molar concentration of 1 to 1.5M at a temperature of 50 to 80 DEG C for 30 seconds to 2 minutes;
(a2) washing the aluminum with distilled water; And
(a3) boiling the aluminum in water for 10 to 30 minutes to form pores on the surface of the aluminum. (a) a pre-treatment step of forming pores on the surface of aluminum constituting the refrigerant pipe or the cooling fin of the heat exchanger or improving the surface roughness of the aluminum;
(b) a step of forming a binder layer in which the aluminum is put into an aqueous solution of PTFE (Polytetrafluoroethylene), taken out, and then dried; And
(c) a lubricating layer forming step of putting the aluminum into a fluorine-based oil,
The drying process of the lubricant layer forming step (c)
(c1) placing the aluminum taken out from the fluorinated oil on an inclined surface and leaving it in a tilted state;
(c2) primary drying the aluminum for a predetermined time at a predetermined temperature; And
(c3) secondary drying the aluminum at a temperature lower than the drying temperature of the primary drying step and for a time longer than the drying time of the primary drying step,
The pre-processing step (a)
(a1) washing said aluminum for 30 seconds to 2 minutes with an aqueous solution of sodium hydroxide (NaOH) at a temperature of from 50 to 80 DEG C with a molar concentration of from 1 to 1.5M;
(a2) washing the aluminum with distilled water; And
(a3 ') The aluminum is put into an aqueous solution of hydrochloric acid (HCl) at a temperature of 50 to 70 DEG C having a molar concentration of 1 to 2M for 30 seconds to 2 minutes to improve the roughness of the aluminum, and then taken out and washed with distilled water ≪ / RTI > further comprising the step of: (a) a pre-treatment step of forming pores on the surface of aluminum constituting the refrigerant pipe or the cooling fin of the heat exchanger or improving the surface roughness of the aluminum;
(b) a step of forming a binder layer in which the aluminum is put into an aqueous solution of PTFE (Polytetrafluoroethylene), taken out, and then dried; And
(c) a lubricating layer forming step of putting the aluminum into a fluorine-based oil,
The drying process of the lubricant layer forming step (c)
(c1) placing the aluminum taken out from the fluorinated oil on an inclined surface and leaving it in a tilted state;
(c2) primary drying the aluminum for a predetermined time at a predetermined temperature; And
(c3) secondary drying the aluminum at a temperature lower than the drying temperature of the primary drying step and for a time longer than the drying time of the primary drying step,
In the (b) binder layer forming step,
(b1) introducing the aluminum into an aqueous solution of PTFE (Polytetrafluoroethylene) diluted with distilled water for 10 to 20 minutes; And
(b2) drying at a temperature of 240 to 400 DEG C for 10 to 40 minutes. 5. The method of claim 4,
Wherein the aluminum is removed from the PTFE aqueous solution at a rate of 2 to 4 cm / min in the step (b1). 6. The method of claim 5,
Wherein the thickness of the binder layer formed by the binder layer forming step (b) is thinner than 1 占 퐉. delete (a) a pre-treatment step of forming pores on the surface of aluminum constituting the refrigerant pipe or the cooling fin of the heat exchanger or improving the surface roughness of the aluminum;
(b) a step of forming a binder layer in which the aluminum is put into an aqueous solution of PTFE (Polytetrafluoroethylene), taken out, and then dried; And
(c) a lubricating layer forming step of putting the aluminum into a fluorine-based oil,
The drying process of the lubricant layer forming step (c)
(c1) placing the aluminum taken out from the fluorinated oil on an inclined surface and leaving it in a tilted state;
(c2) primary drying the aluminum for a predetermined time at a predetermined temperature; And
(c3) secondary drying the aluminum at a temperature lower than the drying temperature of the primary drying step and for a time longer than the drying time of the primary drying step,
In the lubricant layer forming step (c), the aluminum is charged into the fluorinated oil for a first time,
In the step (c1), the aluminum is allowed to stand at room temperature for a second time,
Wherein the second time is 1.5 to 2.5 times the first time. (a) a pre-treatment step of forming pores on the surface of aluminum constituting the refrigerant pipe or the cooling fin of the heat exchanger or improving the surface roughness of the aluminum;
(b) a step of forming a binder layer in which the aluminum is put into an aqueous solution of PTFE (Polytetrafluoroethylene), taken out, and then dried; And
(c) a lubricating layer forming step of putting the aluminum into a fluorine-based oil,
The drying process of the lubricant layer forming step (c)
(c1) placing the aluminum taken out from the fluorinated oil on an inclined surface and leaving it in a tilted state;
(c2) primary drying the aluminum for a predetermined time at a predetermined temperature; And
(c3) secondary drying the aluminum at a temperature lower than the drying temperature of the primary drying step and for a time longer than the drying time of the primary drying step,
In the (c2) primary drying step, the aluminum is dried at a temperature of 140 to 160 DEG C for 10 to 30 minutes,
Wherein the aluminum is dried for 90 to 120 minutes at a temperature lower than the temperature of the primary drying step by 10 to 30 DEG C in the step (c3) of the secondary drying step. The method according to any one of claims 1 to 4, 8, and 9,
Wherein a lubricating layer having a contact angle of 115 to 135 DEG and a sliding angle of 10 to 20 DEG is formed on the surface of the aluminum by the steps (a) to (c). The method according to any one of claims 1 to 4, 8, and 9,
Wherein the aluminum is introduced into the fluorine-based oil having a viscosity of 50 to 100 cSt for 10 to 60 minutes in the step (c) of forming the lubricant layer.

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