WO2017150353A1

WO2017150353A1 - Heat exchanger

Info

Publication number: WO2017150353A1
Application number: PCT/JP2017/006964
Authority: WO
Inventors: 卓哉布施; 稲垣　孝治; 裕太才賀; 侑樹小中出; 上仁柴田
Original assignee: 株式会社デンソー
Priority date: 2016-03-03
Filing date: 2017-02-24
Publication date: 2017-09-08

Abstract

Provided is a heat exchanger configured such that heat is exchanged between air having a specified humidity and a fluid having a temperature lower than the air, and comprises a heat-transferring part (20) disposed so as to contact at least the air. The heat-transferring part has at least a first layer (21) and a second layer (22) positioned between the first layer and the air. The second layer is formed from multiple molecules that are hydrophilic or lypophilic and comprises phosphonic acid at a first terminal of the multiple molecules facing the first layer. The oxygen in the phosphonic acid has a chemical bond that is covalent with the first layer. Frost growth can be sufficiently controlled with this heat exchanger.

Description

Heat exchanger

Cross-reference of related applications

The present application includes Japanese Patent Application 2016-040789 filed on March 3, 2016 and Japanese Patent Application 2017- filed on January 27, 2017, the disclosures of which are incorporated herein by reference. Based on 0128804.

This disclosure relates to a heat exchanger that exchanges heat between air having a predetermined humidity and a low-temperature fluid.

The heat exchanger is indispensable when transferring heat 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.

If frost grows, there is a risk of blocking the air flow path of the heat exchanger. 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, according to the study by the present inventors, there is a probability that the contamination is frozen before sliding off due to contamination components entering the water. For this reason, there exists a possibility that frost growth cannot fully be suppressed.

This indication aims at providing the heat exchanger which can fully suppress frost growth in view of the above-mentioned point.

According to one aspect of the present disclosure, the heat exchanger is configured to exchange heat between air having a predetermined humidity and a fluid having a temperature lower than that of air, and is disposed so as to be in contact with at least air. With a heat transfer section. The heat transfer unit includes at least a first layer and a second layer located between the first layer and air. The second layer is composed of a plurality of molecules having hydrophilicity or hydrophobicity, and includes phosphonic acid at the first end of the plurality of molecules facing the first layer, and oxygen in the phosphonic acid is combined with the first layer. Shares chemical bonds.

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

Also, phosphonic acid is provided at the end of the plurality of molecules facing the first layer, and oxygen in the phosphonic 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.

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

Hereinafter, a plurality of modes for carrying out the present disclosure will be described with reference to the drawings. In each embodiment, parts corresponding to the matters described in the preceding embodiment may be denoted by the same reference numerals, and redundant description may be omitted. When only a part of the configuration is described in each mode, the other modes described above can be applied to the other parts of the configuration. Not only combinations of parts that clearly show that combinations are possible in each embodiment, but also combinations of the embodiments even if they are not explicitly stated unless there is a problem with the combination. Is also possible.

(First embodiment)
Hereinafter, a first embodiment of the present disclosure 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 tube 13 is a tube member 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, respectively. 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 section 20 has two layers of 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 may be located between the first layer 21 and the air.

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 the present 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 phosphonic acid-based hydrophilic molecule and has phosphonic acid on one end side located on the first layer 21 side. Phosphorus in the phosphonic acid shares a chemical bond with one end 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). One end of the second layer 22 may be the first end, and the other end may be the second end.

Aluminum constituting the first layer 21 as a base material shares a chemical bond with oxygen in the phosphonic 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, a method for manufacturing the heat transfer section 20 of the present embodiment will be described with reference to FIGS.

[First step: Pretreatment]
As shown in FIG. 3, a boehmite treatment is performed as a pretreatment to boehmite the surface of a substrate made of an aluminum plate. 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 phosphonic acid-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 phosphonic acid-based hydrophilic molecule for 24 hours at room temperature. As a result, the phosphonic acid-based hydrophilic molecule is hydrogen-bonded to the hydroxyl group formed on the surface of the aluminum substrate, and the phosphonic acid-based hydrophilic molecule is introduced to the surface of the aluminum substrate.

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

Thereafter, the aluminum substrate to which the phosphonic acid-based hydrophilic molecule is bonded is immersed in alcohol, ultrasonic waves are applied for 10 minutes, ethanol washing is performed, and drying is further performed.

[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 phosphonic acid hydrophilic molecule. Specifically, an aluminum base material to which phosphonic acid-based hydrophilic molecules are bonded is immersed in a saturated aqueous NaHCO3 solution at room temperature for 20 minutes. Thereby, the hydrogen of the carboxylate group is replaced with sodium, and sodium chloride can be performed.

After that, 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 unit 11 will be described with reference to 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 this embodiment, and FIG. 5B condenses on the surface of the heat exchange unit 11 that includes the heat transfer unit 20. The case where water is generated 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 in FIG. 5A, in the configuration in which the heat exchanger 10 does not include the heat transfer unit 20, the condensed water adheres as water droplets W1 on the cooling surface 30. 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, there exists a possibility that the growth of the frost pillar based on the water droplet W1 may be accelerated | stimulated.

On the other hand, as shown in FIG. 5B, in the configuration in which the heat exchanger 10 includes the heat transfer section 20, the air side in the heat transfer section 20 is hydrophilized, so that condensed water adheres as a thin film W2. 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 section 20 of the present embodiment described above, the surface of the heat transfer section 20 is covered by covering the surface of the first layer 21 as the base material with the second layer 22 made of phosphonic acid-based hydrophilic molecules. 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, phosphonic acid is provided at the end of the second layer 22 on the first layer 21 side, and oxygen in the phosphonic acid is chemically bonded to aluminum in 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 disclosure 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 first layer 21 on the side facing the second layer 22. The rust preventive layer 21 a shares a chemical bond with oxygen in the phosphonic 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 base material, 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 disclosure, 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, a method for manufacturing the heat transfer section 20 of the second embodiment will be described. 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), the fourth step (sodium chloride) similar to 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.

The present disclosure is not limited to the above-described embodiment, and various modifications can be made as follows without departing from the spirit of the present disclosure. Further, the means disclosed in each of the above embodiments may be appropriately combined within a practicable range.

In the above embodiment, the first layer 21 is made of aluminum, but is not limited thereto, and may be made of 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, SiO2.

In the above embodiment, the second layer 22 is configured as a phosphonic acid-based hydrophilic molecule. However, the present invention is not limited thereto, and the second layer 22 may be configured as a phosphonic acid-based hydrophobic molecule. When the second layer 22 is a phosphonic acid-based hydrophobic molecule, 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, phosphonic acid is provided on one end side of the phosphonic acid-based hydrophobic molecule located on the first layer 21 side, and oxygen in the phosphonic acid and aluminum in the first layer 21 share a chemical bond. Good.

Although the present disclosure has been described based on the embodiments, it is understood that the present disclosure is not limited to the embodiments and structures. The present disclosure includes various modifications and modifications within the equivalent range. In addition, various combinations and forms, as well as other combinations and forms including only one element, more or less, are within the scope and spirit of the present disclosure.

Claims

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 part has at least a first layer (21) and a second layer (22) positioned between the first layer and the air,
The second layer is composed of a plurality of molecules having hydrophilicity or hydrophobicity, and has a phosphonic acid at a first end of the plurality of molecules facing the first layer, and oxygen in the phosphonic acid A heat exchanger sharing a chemical bond with the first layer.
The heat exchanger according to claim 1, wherein the second layer is made of hydrophilic molecules.
The heat exchanger according to claim 1 or 2, wherein the first layer is made of any material of 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 the phosphonic 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 the phosphonic acid contained in the second layer is one end of the polymer. The heat exchanger according to claim 1, which shares a chemical bond with the heat exchanger.
The heat exchange according to any one of claims 1 to 5, wherein each of the plurality of molecules includes a carboxylate group and an alkali metal ion as a counter cation at a second end opposite to the first end. vessel.
The surface of the first layer facing the second layer has a rust prevention layer (21a) containing a transition element,
The heat exchanger according to any one of claims 1 to 6, wherein oxygen in the phosphonic acid in the second layer shares a chemical bond with the antirust layer.
The heat exchanger according to claim 7, wherein the first layer is made of aluminum, and the antirust layer includes one or more of Zr, Ti, V, Cr, Ni, Zn, and Mo as the transition element. .