JP2017161215A - Heat exchanger - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat exchanger in which frost growth can be sufficiently controlled.SOLUTION: The heat exchanger is configured in such a manner that heat is exchanged between air having a specified humidity and a fluid having a temperature lower than that of the air, and comprises a heat-transferring part 20 disposed so as to contact at least the air. The heat-transferring part 20 has at least a first layer 21, and a second layer 22 which is located at an air side rather than the first layer 21. The second layer 22 comprises a phosphoric acid at one end side located at the first layer 21 side, and oxygen in the phosphorous acid shares a chemical bond with the first layer 21. The second layer 22 is composed of phosphate hydrophilic molecules. The first layer 21 is constituted of aluminum, and the aluminum of the first layer 21 and oxygen in the phosphorous acid contained in the second layer 22 share a chemical bond.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a heat exchanger for exchanging heat between air having a predetermined humidity and a low-temperature fluid.

  A heat exchanger is indispensable when performing heat transfer between two fluids, and high performance has been studied. For example, a case where the air is cooled by exchanging heat between the outside air and the evaporative refrigerant as two fluids, such as an outdoor unit, can be considered. In this case, the air has a predetermined humidity, and water inevitably condenses and freezes on the heat transfer wall. As a result, “frost” grows on the heat transfer surface.

  When frost grows, the air flow path of the heat exchanger may be blocked. Therefore, generally, when a predetermined frost growth is detected, a so-called “defrosting operation” for removing frost is often performed. This defrosting operation not only takes extra energy for melting the frost, but also the air conditioning does not function during that period. For this reason, it is required to earn as much time as possible before shifting to the defrosting operation mode.

  On the other hand, techniques for suppressing the growth of frost on the heat transfer surface have been developed. For example, Patent Document 1 proposes a technique in which a super-water-repellent treatment is performed on a heat transfer surface of a heat exchanger, and moisture contained in the air is condensed on the water-repellent surface and then slides down before freezing. Thereby, suppression of frost growth is anticipated.

International Publication No. 2012/147288

  However, in the above-described conventional technology, there is a probability that the contamination component freezes before it slides due to entering the water. For this reason, there exists a problem that frost growth cannot fully be suppressed. Therefore, a technique for sufficiently suppressing frost growth is desired.

  An object of this invention is to provide the heat exchanger which can fully suppress frost growth in view of the said point.

  In order to achieve the above object, according to the first aspect of the present invention, heat exchange is performed between air having a predetermined humidity and a fluid having a temperature lower than that of the air, and is in contact with at least the air. The heat transfer section (20) is arranged, and the heat transfer section has at least a first layer (21) and a second layer (22) located on the air side of the first layer. The second layer is composed of a hydrophilic molecule or a hydrophobic molecule, and has phosphoric acid at one end located on the first layer side, and oxygen in the phosphoric acid has a chemical bond with the first layer. It is characterized by sharing.

  As a result, the surface of the second layer can be covered with the second layer made of phosphoric acid molecules, and even when condensed water is generated on the surface of the heat transfer section, frost growth is effectively suppressed. can do.

  Further, phosphoric acid is provided at the end of the second layer on the first layer side, and oxygen in the phosphoric acid shares a chemical bond with the first layer. Thereby, a 1st layer and a 2nd layer can be couple | bonded firmly and the coverage of the 1st layer by a 2nd layer can be made high.

  In addition, the code | symbol in the bracket | parenthesis of each said means shows the correspondence with the specific means as described in embodiment mentioned later.

It is a perspective view of the heat exchanger which concerns on 1st Embodiment of this invention. It is a schematic diagram which shows the structure of the heat-transfer part of 1st Embodiment. It is a figure which shows the manufacturing process of a heat-transfer part. It is a figure which shows the manufacturing process of a heat-transfer part. (A) is the figure which showed a mode that the stagnation of air generate | occur | produced because the water droplet adhered to the cooling surface, (b) is the figure which showed the mode that the thin film of water was formed in the air side of the heat-transfer part. . It is a schematic diagram which shows the structure of the heat-transfer part of 2nd Embodiment.

(First embodiment)
Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. The heat exchanger is a heat exchanger for absorbing heat, and is an evaporator that cools air for air conditioning in a refrigeration cycle of a vehicle air conditioner, for example.

  As shown in FIG. 1, the heat exchanger 10 includes a heat exchange unit 11 and a pair of header tanks 12 connected to the heat exchange unit 11. The heat exchanging portion 11 includes a plurality of tubes 13 having a flat cross section and corrugated fins 14 interposed between the tubes 13. The tube 13 and the fin 14 are made of aluminum.

  The tubes 13 are tube members through which a refrigerant as a heat medium flows, and both ends of each tube 13 are connected to communicate with the inside of the pair of header tanks 12. The refrigerant is a fluid having a temperature lower than that of air. The fin 14 is a heat transfer member that is formed in a wave shape from a thin strip material and forms a heat transfer surface. The fin 14 is joined to the tube 13.

  In such a configuration, the refrigerant that has been depressurized in the refrigeration cycle to low temperature and low pressure flows through the plurality of tubes 13. Further, air passes through the outside of the tube 13 and around the fins 14 (outside of the heat exchange unit 11), and the air is cooled by the low-temperature refrigerant.

  Next, a specific configuration of the heat transfer section 20 that separates the refrigerant from the air will be described with reference to FIG. The heat transfer unit 20 is a part of the heat exchanger 10 that is configured to exchange heat between air and the refrigerant, and is disposed so as to be in contact with at least air. In the case of the tube 13, the outer surface in contact with air corresponds to the heat transfer unit 20, and in the case of the fin 14, both sides of the plate surface in contact with air correspond to the heat transfer unit 20.

  As shown in FIG. 2, the heat transfer unit 20 includes two layers, a first layer 21 and a second layer 22. The first layer 21 is made of a material having a higher thermal conductivity among the two layers of the heat transfer section 20. The 1st layer 21 is a substrate which constitutes tube 13 and fin 14, and is constituted from aluminum in this embodiment.

  The second layer 22 is formed on the air side surface of the first layer 21. That is, the second layer 22 is located on the air side with respect to the first layer 21. The 2nd layer 22 is positioned as a film formed in the surface of the 1st layer 21 which is a substrate. The second layer 22 is configured to share chemical bonds with the first layer 21.

  The second layer 22 is made of a material having a higher affinity for water among the two layers of the heat transfer section 20. Specifically, the second layer 22 is configured as a rod-shaped molecule having a linear structure.

  The rod-like molecule of this embodiment is a hydrophilic molecule, and includes a polymer composed of repeating unit structures represented by the following chemical formula 1 or chemical formula 2.

  In Chemical Formula 1 and Chemical Formula 2, n is an integer of 1 or more, for example, n = 1 to 20000. The second layer 22 of the present embodiment contains polyethylene glycol (PEG) as a polymer.

  The second layer 22 is a phosphoric acid-based hydrophilic molecule and includes phosphoric acid on one end side located on the first layer 21 side. Phosphorus in phosphoric acid shares a chemical bond with one end side of the polymer contained in the second layer 22. The second layer 22 includes a carboxylate group and an alkali metal ion as a counter cation on the other end located on the air side. Specifically, the air side of the second layer 22 is sodium carboxylate (COONa).

  Aluminum constituting the first layer 21 as the base material shares a chemical bond with oxygen in the phosphoric acid of the second layer 22. Thereby, the 1st layer 21 and the 2nd layer 22 are combined firmly, and the coverage of the 1st layer 21 by the 2nd layer 22 can be increased.

  Next, the manufacturing method of the heat-transfer part 20 of this embodiment is demonstrated using FIG. 3, FIG.

[First step: Pretreatment]
As shown in FIG. 3, a boehmite treatment is performed as a pretreatment to boehmite the surface of a base material made of an aluminum plate material. The boehmite treatment can be performed, for example, by boiling an aluminum base material in ion exchange water for 10 minutes. By the boehmite treatment, hydroxyl groups are generated on the surface of the aluminum substrate.

[Second step: hydrophilic molecule introduction step]
Next, the above-described phosphate-based hydrophilic molecule is introduced into the surface of the boehmite-treated aluminum substrate. Specifically, the aluminum substrate is immersed in an ethanol solution containing a phosphate-based hydrophilic molecule for 24 hours at room temperature. Thereby, the phosphoric acid hydrophilic molecule is hydrogen-bonded to the hydroxyl group formed on the surface of the aluminum substrate, and the phosphoric acid hydrophilic molecule is introduced to the surface of the aluminum substrate.

[Third step: Baking step]
Next, as shown in FIG. 4, the baking process which heats the aluminum base material with which the phosphate hydrophilic molecule was introduce | transduced on the surface is performed. Specifically, the aluminum base material into which the phosphate-based hydrophilic molecules are introduced is heated at 140 ° C. for 6 hours. As a result, the dehydration reaction proceeds, oxygen contained in phosphoric acid of the phosphate-based hydrophilic molecule and aluminum contained in the aluminum substrate are covalently bonded, and the phosphate-based hydrophilic molecule is firmly attached to the surface of the aluminum substrate. Join.

  Thereafter, the aluminum base material to which the phosphate-based hydrophilic molecules are bonded is immersed in alcohol, and ultrasonic waves are applied for 10 minutes to perform ethanol cleaning, followed by drying.

[Fourth step: Sodium chloride step]
Next, a sodium chloride step is performed in which sodium is introduced into the carboxylate group located on the air side of the phosphate-based hydrophilic molecule. Specifically, an aluminum substrate to which phosphate-based hydrophilic molecules are bonded is immersed in a saturated aqueous NaHCO ₃ solution at room temperature for 20 minutes. Thereby, the hydrogen of the carboxylate group is replaced with sodium, and sodium chloride can be performed.

  Then, pure water washing and acetone washing are performed and further dried. Thereby, the heat-transfer part 20 provided with the 1st layer 21 and the 2nd layer 22 of this embodiment can be obtained.

  Next, the case where condensed water adheres to the surface of the heat exchange part 11 is demonstrated using FIG. When air having a predetermined humidity is cooled by the heat exchange unit 11 and the temperature of the air falls below the dew point temperature of the water vapor contained in the air, the water vapor becomes condensed water and adheres to the surface of the heat exchange unit 11.

  FIG. 5A shows a case where condensed water is generated on the surface of the heat exchange unit 11 that does not include the heat transfer unit 20 of the present embodiment, and FIG. 5B shows heat exchange that includes the heat transfer unit 20. The case where the condensed water generate | occur | produces on the surface of the part 11 is shown. The surface of the heat exchange unit 11 that does not include the heat transfer unit 20 (hereinafter referred to as the cooling surface 30) is formed of only the first layer 21 without the second layer 22 of the heat transfer unit 20 formed. .

  As shown to Fig.5 (a), in the structure where the heat exchanger 10 is not provided with the heat-transfer part 20, condensed water adheres in the cooling surface 30 as the water droplet W1. The water droplet W1 has a large contact angle, and air stagnation is formed on the cooling surface 30, so that water vapor easily collects in the water droplet W1. For this reason, the growth of the frost pillar from the water drop W1 is promoted.

  On the other hand, as shown in FIG.5 (b), in the structure with which the heat exchanger 10 was provided with the heat-transfer part 20, since the air side in the heat-transfer part 20 is hydrophilizing, condensed water turns into the thin film W2. Adhere to. The water thin film W2 has a small contact angle and inhibits air flow from being inhibited. Thereby, it becomes difficult to cause air stagnation by the thin film W2, and water vapor hardly collects in the thin film W2. For this reason, the growth of frost based on the thin film W2 of water is suppressed.

  According to the heat transfer unit 20 of the present embodiment described above, the surface of the heat transfer unit 20 is covered by covering the surface of the first layer 21 as the base material with the second layer 22 made of a phosphate-based hydrophilic molecule. Even when condensed water is generated, the growth of frost can be effectively suppressed.

  Further, according to the heat transfer section 20 of the present embodiment, phosphoric acid is provided at the end of the second layer 22 on the first layer 21 side, and oxygen in the phosphoric acid is chemically bonded to the aluminum of the first layer 21. Share. Thereby, the 1st layer 21 and the 2nd layer 22 can be combined firmly, and the coverage of the 1st layer 21 by the 2nd layer 22 can be made high.

(Second Embodiment)
Next, a second embodiment of the present invention will be described. Hereinafter, description of the same parts as those in the first embodiment will be omitted, and only different parts will be described.

  As shown in FIG. 6, in the heat transfer section 20 of the second embodiment, a rust prevention layer 21 a is formed on the side of the first layer 21 that faces the second layer 22. The rust prevention layer 21 a shares a chemical bond with oxygen in the phosphoric acid in the second layer 22.

  That is, the rust prevention layer 21a is formed on the surface of the first layer 21 constituting the substrate, and the second layer 22 constituting the coating layer is formed on the surface of the rust prevention layer 21a. The rust prevention layer 21 a has a function of suppressing corrosion that occurs in the first layer 21.

  The rust prevention layer 21a includes a transition element. In the present specification, the transition element is an element between the Group 3 element and the Group 12 element of the periodic table. The anticorrosive layer 21 a containing the transition element has a higher bonding strength with the second layer 22 than the first layer 21.

  The rust prevention layer 21a may be composed of only a transition element, or may contain a substance other than the transition element. The transition element contained in the rust prevention layer 21a may be one kind or plural kinds. The effect of suppressing corrosion of the first layer 21 is higher when there are a plurality of types of transition elements contained in the rust prevention layer 21a. The transition element contained in the rust prevention layer 21a exists in an oxide state.

  When the first layer 21 is aluminum, by using one or more kinds of Zr, Ti, V, Cr, Ni, Zn, and Mo as transition elements constituting the rust prevention layer 21a, the first layer 21 is used. Can effectively suppress corrosion. In particular, when V is contained in the rust prevention layer 21a, the effect of suppressing the corrosion of the first layer 21 made of aluminum is high.

  Here, the manufacturing method of the heat-transfer part 20 of this 2nd Embodiment is demonstrated. The manufacturing method of the second embodiment is mainly different from the first embodiment in the first step (pretreatment).

  In the second embodiment, in the first step (pretreatment), a transition element-containing layer containing a transition element is formed on the surface of the aluminum substrate. The aluminum base material constitutes the first layer 21 of the heat transfer section 20, and the transition element-containing layer constitutes the rust prevention layer 21 a of the heat transfer section 20.

  The transition element-containing layer can be formed, for example, by immersing the aluminum base material in a solution containing a transition element. Next, a hydroxyl group is introduced into the surface of the transition element-containing layer by performing plasma treatment or chemical treatment on the surface of the transition element-containing layer.

  Next, the second step (hydrophilic molecule introduction step), the third step (baking step), and the fourth step (sodium chloride) similar to those in the first embodiment are performed on the aluminum base material on which the transition element-containing layer is formed. Steps) are performed in order. By performing the first to fourth steps described above, the heat transfer section 20 including the first layer 21, the rust prevention layer 21a, and the second layer 22 of the second embodiment can be obtained.

  According to the second embodiment described above, the bonding strength between the rust preventive layer 21 a formed on the first layer 21 and the second layer 22 by forming the rust preventive layer 21 a on the surface of the first layer 21. Can be improved. Thereby, detachment | leave of the 2nd layer 22 in the heat-transfer part 20 can be suppressed, and the hydrophilic property by the 2nd layer 22 can be maintained over a long period of time.

  Even if the second layer 22 is detached from the heat transfer section 20 and the first layer 21 is exposed, the transition element contained in the rust prevention layer 21a moves to the surface of the first layer 21 and The surface is covered with a rust prevention layer 21a. Thereby, the 1st layer 21 corrodes by contact with water, it can control that this corrosion spreads, and the further secession of the 2nd layer 22 resulting from corrosion of the 1st layer 21 can be controlled. As a result, the film molecular structure of the second layer 22 aligned with the surface of the heat transfer section 20 is maintained, and the hydrophilicity of the second layer 22 can be maintained over a long period of time.

(Other embodiments)
The present invention is not limited to the above-described embodiment, and can be variously modified as follows without departing from the spirit of the present invention. Further, the means disclosed in each of the above embodiments may be appropriately combined within a practicable range.

(1) In the said embodiment, although the 1st layer 21 was comprised with aluminum, you may comprise not only this but other materials, such as copper and SUS. When the first layer 21 is made of copper or SUS, by providing a binder layer between the first layer 21 and the second layer 22, these layers can be firmly bonded to each other. The binder layer can be made of, for example, SiO ₂ .

  (2) In the above embodiment, the second layer 22 is configured as a phosphate-based hydrophilic molecule. However, the present invention is not limited thereto, and the second layer 22 may be configured as a phosphate-based hydrophobic molecule. When the second layer 22 is made of phosphoric acid-based hydrophobic molecules, even if condensed water is generated on the surface of the heat transfer section 20, the condensed water is quickly removed. As a result, it is possible to prevent the condensed water from freezing and growing frost on the surface of the heat transfer section 20. In this case, phosphoric acid is provided on one end side of the phosphoric acid-based hydrophobic molecule located on the first layer 21 side, and oxygen in phosphoric acid and aluminum in the first layer 21 share a chemical bond. Good.

DESCRIPTION OF SYMBOLS 10 Heat exchanger 20 Heat transfer part 21 1st layer 21a Rust prevention layer 22 2nd layer

Claims (8)

It is configured to perform heat exchange between air having a predetermined humidity and a fluid having a temperature lower than that of the air, and includes a heat transfer section (20) disposed so as to be in contact with at least the air. ,
The heat transfer section includes at least a first layer (21) and a second layer (22) located on the air side of the first layer,
The second layer is composed of a hydrophilic molecule or a hydrophobic molecule, and has phosphoric acid on one end located on the first layer side, and oxygen in the phosphoric acid is chemically bonded to the first layer. Sharing heat exchanger.   The heat exchanger according to claim 1, wherein the second layer is made of a hydrophilic molecule.   The heat exchanger according to claim 1 or 2, wherein the first layer is made of any material selected from aluminum, copper, and SUS.   The heat exchanger according to claim 3, wherein the first layer is made of aluminum, and the aluminum in the first layer and oxygen in phosphoric acid contained in the second layer share a chemical bond. The second layer includes a polymer composed of at least a repeating unit structure represented by the following chemical formula 1 or chemical formula 2, and phosphorus in phosphoric acid contained in the second layer is one end of the polymer. 5. A heat exchanger according to any one of claims 1 to 4, which shares a chemical bond with the side.

  The heat exchanger according to any one of claims 1 to 5, wherein the second layer includes a carboxylate group and an alkali metal ion as a counter cation on the other end located on the air side. On the side of the first layer facing the second layer, a rust prevention layer (21a) containing a transition element is formed,
The heat exchanger according to any one of claims 1 to 6, wherein oxygen in the phosphoric acid in the second layer shares a chemical bond with the antirust layer.   The said 1st layer is comprised from aluminum, and the said rust prevention layer is comprised including 1 type or multiple types among Zr, Ti, V, Cr, Ni, Zn, Mo as said transition element. The described heat exchanger.

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