阅读说明：本技术 相变材料涂布的热交换管 (Heat exchange tube coated with phase change material ) 是由 S·T·阿塔瓦拉 I·格罗弗 T·格雷弗 J·戴维斯 J·B·舒尔茨 于 2019-09-11 设计创作，主要内容包括：本文公开了一种中空管,该中空管包括两端,一端适于接收流体,另一端适于排出流体,其中中空管具有内表面和外表面,并且可固化组合物围绕中空管的外表面的至少一部分布置,其中在固化之前所述可固化组合物包含：可固化组分、导热组分、相变材料和固化体系。(Disclosed herein is a hollow tube comprising two ends, one end adapted to receive a fluid and the other end adapted to expel the fluid, wherein the hollow tube has an inner surface and an outer surface, and a curable composition is disposed around at least a portion of the outer surface of the hollow tube, wherein the curable composition prior to curing comprises: a curable component, a thermally conductive component, a phase change material, and a curing system.)

1. A hollow tube comprising two ends, one end adapted to receive a fluid and the other end adapted to expel the fluid, wherein the hollow tube has an inner surface and an outer surface, wherein a composition is disposed about at least a portion of the outer surface of the hollow tube, wherein the composition comprises:

A.

i) a curable component;

ii) a thermally conductive component;

iii) a phase change material; and

iv) a curing system, wherein the curing system,

or

B.

i) A binder component;

ii) a thermally conductive component;

iii) a phase change material; and

iv) water.

2. The hollow tube of claim 1, wherein the hollow tube is made of metal.

3. The hollow tube of claim 2, wherein the metal is selected from aluminum, steel, copper, or combinations or alloys thereof.

4. The hollow tube of claim 1, wherein the composition further comprises an antioxidant, a corrosion inhibitor, a UV stabilizer, a heat stabilizer, a flame retardant, or a combination thereof.

5. The hollow tube of claim 1, wherein the fluid is aqueous.

6. The hollow tube of claim 1, wherein the fluid comprises one or more alkanes.

7. The hollow tube of claim 1, wherein the fluid comprises one or more alkanes, optionally branched and/or substituted with one or more halogen atoms.

8. The hollow tube of claim 1, wherein the fluid comprises isobutane, tetrafluoroethane, and combinations thereof.

9. The hollow tube of claim 1, wherein the curable component comprises an epoxy, a polyurethane matrix, a hot melt, a silicone component, (meth) acrylate, or combinations thereof.

10. The hollow tube of claim 1, wherein the curable component comprises an epoxy component selected from one or more saturated, unsaturated, cyclic or acyclic, aliphatic, alicyclic, aromatic or heterocyclic polyepoxide compounds.

11. The hollow tube of claim 1, wherein the curable component comprises a (meth) acrylate component selected from the group consisting of: one or more monofunctional, multifunctional, linear aliphatic, branched aliphatic, cycloaliphatic, aromatic, alkoxylated alkyl and aryl groups.

12. The hollow tube of claim 1, wherein the curable component is present in an amount of about 20 to about 80 weight percent, based on the total weight of the curable composition.

13. The hollow tube of claim 1, wherein the thermally conductive component is selected from boron nitride, silver, copper, or carbon.

14. The hollow tube of claim 1, wherein the thermally conductive component is present in an amount of from about 1 to about 40 weight percent, based on the total weight of the curable composition.

15. The hollow tube of claim 1, wherein the phase change material is encapsulated.

16. The hollow tube of claim 1, wherein the phase change material comprises a phase change material that transitions from a solid phase to a liquid phase at a temperature in the range of about 25 ℃ to about 60 ℃.

17. The hollow tube of claim 1, wherein the phase change material comprises a phase change material that transitions from a solid phase to a liquid phase at a temperature in a range of about 30 ℃ to about 40 ℃.

18. The hollow tube of claim 1, wherein the phase change material has a particle size in a range from about 15 μ ι η to about 30 μ ι η.

19. The hollow tube of claim 1, wherein the phase change material comprises paraffin, fatty acids, esters, alcohols, glycols, organic eutectics, petrolatum, beeswax, carnauba wax, mineral wax, glycerin, and/or certain vegetable oils.

20. The hollow tube of claim 1, wherein the phase change material comprises a salt hydrate and/or a low melting metal eutectic.

21. The hollow tube of claim 1, wherein the phase change material comprises about 75 to about 95 weight percent paraffin wax within a polymer shell.

22. The hollow tube of claim 1, wherein the phase change material comprises about 85 to about 90 weight percent paraffin wax within a polymer shell.

23. The hollow tube of claim 1, wherein the phase change material is stable against leakage at temperatures up to about 250 ℃.

24. The hollow tube of claim 1, wherein the phase change material is present in an amount of about 20 to about 80 weight percent, based on the total weight of the composition.

25. The hollow tube of claim 1, wherein the curing system comprises a curing agent and/or a free radical initiator.

26. The hollow tube of claim 1, wherein the curing system comprises a nitrogen-containing compound.

27. The hollow tube of claim 1, wherein the curing system comprises an amine compound, an amide compound, an imidazole compound, a guanidine compound, a urea compound, and combinations thereof.

28. The hollow tube of claim 1, wherein the curing system comprises a peroxide.

29. The hollow tube of claim 1, wherein the curing system is present in an amount of about 30 to about 50 weight percent based on the total weight of the curable composition.

30. The hollow tube of claim 1, wherein the curable composition has a thermal conductivity of about 0.2 to about 1.2W/m/K.

31. The hollow tube of claim 1, wherein the curable composition has a latent heat of fusion of from about 60 to about 200J/g.

32. The hollow tube of claim 1, wherein the curable composition has a latent heat of fusion of from about 60 to about 120J/g.

33. The hollow tube of claim 1, wherein the curable composition has a ratio of thermal conductivity to latent heat of fusion of 0.06.

34. A refrigeration unit comprising the hollow tube of claim 1.

35. A refrigeration unit including a compressor, a condenser coil, and at least one evaporator coil.

36. The refrigeration unit of claim 35, wherein the hollow tube of claim 1 is the condenser coil.

37. The refrigeration unit of claim 35, wherein the hollow tube of claim 1 is the evaporator coil.

38. The refrigeration unit of claim 35, wherein the fluid received by the hollow tube has a temperature of about 40 ℃.

39. The refrigeration unit of claim 35, wherein the fluid discharged by the hollow tube has a temperature of about 35 ℃.

40. The refrigeration unit of claim 35, wherein the phase change material is selected based on a comparison of a transition temperature of the phase change material and a temperature of a fluid received by a hollow tube.

41. The refrigeration unit of claim 35, wherein the phase change material has a melting temperature of about 39 ℃.

42. The refrigeration unit of claim 35, wherein the phase change material has a freezing temperature of about 34 ℃.

43. A domestic refrigeration appliance comprising a refrigeration unit as claimed in claim 36.

44. A domestic refrigeration appliance comprising a refrigeration unit as claimed in claim 37.

45. A curable composition comprising a curable component, a thermally conductive component, a phase change material, and a curing system.

46. A composition, comprising: a binder component; a thermally conductive component; a phase change material; and water.

Technical Field

The present invention relates generally to a coating including a phase change material for coating onto a heat exchange tube to improve heat exchange efficiency.

Background

The refrigeration unit typically includes a compressor, a condenser, an evaporator, and a refrigeration compartment. Refrigeration units typically function by passing a refrigerant through a compressor, a condenser, and an evaporator to cool the air inside a refrigeration compartment. The compressor and condenser are typically located outside the refrigeration compartment, while the evaporator is located inside the refrigeration compartment. In a typical refrigeration unit, a condenser converts refrigerant to its liquid state and dissipates the heat of condensation. A fan may be used to move air through the condenser and compressor and increase the efficiency of removing heat from the external surfaces of the compressor and condenser. The evaporator is within the refrigeration compartment such that heat from the refrigeration compartment is absorbed into the refrigerant within the evaporator and the refrigeration compartment is cooled.

Therefore, heat is absorbed in the refrigerating compartment by the evaporator and is drawn out to the outside of the refrigerating compartment by the condenser.

It is desirable to absorb and release heat as efficiently as possible in the evaporator and condenser throughout the refrigeration cycle. To this end, many different refrigeration designs have been developed. Some refrigeration designs include different condenser designs for increasing heat removal efficiency, such as wire-tube, fin, and spiral condensers.

Increased condenser tube length is also employed to increase heat transfer efficiency. However, increasing the length of the condenser tubes reduces the compactness of the condenser, which increases the required size of the refrigeration unit itself. Moreover, increasing the length of the condenser may introduce additional labor and material costs, present additional surface area for potential leaks, and negatively impact the pressure drop of the refrigerant. Further, this may lead to undesired rattling and reduced condenser reliability. Still further, many conventional condenser systems require periodic maintenance, such as cleaning the coils of dust, dirt, and other debris that deposits on the coil surfaces, reducing heat transfer efficiency and increasing the operating temperature of the condenser system.

In response, the present technology proposes the use of a liquid-filled bag to improve the heat transfer efficiency of the condenser. The liquid-filled bag can increase the efficiency of the condenser by absorbing the dissipated heat more efficiently than the surrounding air. One problem encountered with the use of liquid-filled bags is that there is no thermal contact with the condenser coil, and therefore heat transfer is not significantly more efficient than when ambient air is used.

Thus, while others have attempted to overcome these problems, they have met with little success.

Accordingly, it is desirable to provide a system that increases heat transfer efficiency without increasing the size of components in a heat exchange system (such as a refrigeration system).

Disclosure of Invention

In one aspect, a hollow tube coated with a curable composition is provided. The hollow tube includes two ends, one end adapted to receive a fluid and the other end adapted to expel the fluid, and an inner surface and an outer surface, wherein the composition is disposed about at least a portion of the outer surface. The composition comprises

A.

i) A curable component;

ii) a thermally conductive component;

iii) a phase change material; and

iv) a curing system, wherein the curing system,

or

B.

i) A binder component;

ii) a thermally conductive component;

iii) a phase change material; and

iv) water.

In another aspect, a refrigeration unit is disclosed that includes a compressor, a condenser coil, and at least one evaporator coil. The hollow tube is a condenser coil of a refrigeration unit.

In another aspect, a domestic refrigeration appliance is disclosed herein, comprising the above-described refrigeration unit.

Drawings

Figure 1 shows a refrigeration unit.

Figure 2 shows a plot of dissipated energy versus flow for three different coating compositions.

Figure 3 shows the condenser coil (bare).

Detailed Description

Disclosed herein are hollow tubes coated with a curable composition to increase the efficiency of heat transfer through the hollow tube. The hollow tube includes one end adapted to receive a fluid and another end adapted to discharge the fluid, and has an inner surface and an outer surface. The composition is disposed about at least a portion of the outer surface of the hollow tube. The composition comprises

A.

i) A curable component;

ii) a thermally conductive component;

iii) a phase change material; and

iv) a curing system, wherein the curing system,

or

B.

i) A binder component;

ii) a thermally conductive component;

iii) a phase change material; and

iv) water.

The hollow tube may be constructed in various sizes and diameters and made of various materials. For example, the hollow tube may be a metal, and the metal may be selected from aluminum, steel, copper, or combinations or alloys thereof. The hollow tube may be curved, straight, or have some portions that are curved and other portions that are straight. The dimensions of the hollow tube may also vary depending on the end use of the hollow tube. For example, if the hollow tube is used as a condenser coil in a household refrigerator, the hollow tube may have an outer diameter of 0.02 to 0.4 inches and an overall length of 1 to 100 feet, such as 25 to 75 feet, and particularly 54 feet. The dimensions and geometry of the hollow tube may be adjusted depending on the application without limitation.

The curable composition is disposed about at least a portion of the outer surface of the hollow tube. The curable composition may be applied to the pipe by spraying, painting, or any method suitable for applying a coating. The curable composition is used to enhance heat transfer throughout the hollow tube. As such, it is beneficial to coat the entire hollow tube with the curable composition to enhance heat exchange over the entire length of the hollow tube. In a particularly useful embodiment, 95% or more of the surface area of the hollow tube is coated with the curable composition.

The curable composition is thermally conductive, is securely disposed about the hollow tube, is capable of withstanding temperature changes, and is capable of absorbing and storing latent heat. The curable composition, prior to curing, comprises a curable component, a thermally conductive component, a phase change material, and a curing system. The curable composition may further optionally comprise an antioxidant, corrosion inhibitor, UV stabilizer, thermal stabilizer, or flame retardant. The curable composition may also contain wetting agents, dispersing agents, rheology modifiers, emulsifiers, pH adjusters to enhance emulsion stability, coalescing solvents, or deflocculating additives.

The curable component of the curable composition may be photocurable such that the curable composition may be photocured onto the hollow tube. The curable component may also be moisture or thermally cured. The curable component may be cured by one curing mechanism (such as being triggered by exposure to light) or multiple curing mechanisms (such as being triggered initially by exposure to light and then to heat and/or moisture). The curable component should be selected such that after curing it has high strength, moisture and temperature resistance under the operating conditions of the hollow tube.

As such, the curable component may comprise an epoxy component, a (meth) acrylate component, a polyurethane matrix, a hot melt, or a silicone component.

The epoxy resin component may be selected from one or more saturated, unsaturated, cyclic or acyclic, aliphatic, cycloaliphatic, aromatic or heterocyclic polyepoxide compounds.

Generally, a large number of polyepoxides having at least about two 1, 2-epoxy groups per molecule are suitable for use herein. The polyepoxide may be a saturated, unsaturated, cyclic or acyclic, aliphatic, cycloaliphatic, aromatic or heterocyclic polyepoxide compound. Examples of suitable polyepoxides include polyglycidyl ethers, which are prepared by the reaction of epichlorohydrin or epibromohydrin with a polyphenol in the presence of a base. Suitable polyphenols are therefore, for example, resorcinol, catechol, hydroquinone, bisphenol A (bis (4-hydroxyphenyl) -2, 2-propane), bisphenol F (bis (4-hydroxyphenyl) methane), bisphenol S, bisphenol, bis (4-hydroxyphenyl) -1, 1-isobutane, 4' -dihydroxybenzophenone, bis (4-hydroxyphenyl) -1, 1-ethane and 1, 5-hydroxynaphthalene. Other suitable polyphenols as the basis for the polyglycidyl ethers are the known condensation products of phenol and formaldehyde or acetaldehyde of the novolak resin type.

Other polyepoxides suitable for use herein are the polyglycidyl ethers of polyols or diamines. Such polyglycidyl ethers are derived from polyhydric alcohols such as ethylene glycol, diethylene glycol, triethylene glycol, 1, 2-propanediol, 1, 4-butanediol, triethylene glycol, 1, 5-pentanediol, 1, 6-hexanediol, or trimethylolpropane.

Still other polyepoxides are polyglycidyl esters of polycarboxylic acids, such as the reaction products of glycidol or epichlorohydrin with aliphatic or aromatic polycarboxylic acids (e.g., oxalic acid, succinic acid, glutaric acid, terephthalic acid, or dimeric fatty acids).

And still other epoxides are epoxidation products derived from ethylenically unsaturated cycloaliphatic compounds or from natural oils and fats.

Particularly desirable are liquid epoxy resins obtained by reacting bisphenol a or bisphenol F with epichlorohydrin. Epoxy resins that are liquid at room temperature typically have an epoxy equivalent weight of 150 to about 480.

The (meth) acrylate component may be selected from one or more monofunctional, multifunctional, linear aliphatic, branched aliphatic, cycloaliphatic, aromatic, alkoxylated alkyl and aryl groups. (meth) acrylates that may be used in the curable composition according to the invention include the compounds represented by H₂C═CGCO₂R, wherein G can be hydrogen, halogen, or an alkyl group having from 1 to about 4 carbon atoms, and R can be selected from an alkyl, cycloalkyl, alkenyl, cycloalkenyl, alkaryl, aralkyl, or aryl group having from 1 to about 16 carbon atoms.

More specific (meth) acrylates particularly suitable for use in the present invention include polyethylene glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, bisphenol a di (meth) acrylates such as ethoxylated bisphenol a (meth) acrylate ("EBIPMA"), and tetrahydrofuran (meth) acrylate and di (meth) acrylate, isobornyl acrylate, hydroxypropyl (meth) acrylate, and hexanediol di (meth) acrylate. Of course, combinations of these (meth) acrylates may also be used.

The polyurethane component may be selected from one or more di-and triisocyanates, such as toluene diisocyanate and methylene diphenyl diisocyanate, aliphatic and cycloaliphatic isocyanates, together with polyols, chain extenders, crosslinkers, catalysts and surfactants.

The amount of curable component may vary based on a number of factors, including whether the curing agent acts as a catalyst or directly participates in the crosslinking of the curable composition, the concentration of other reactive groups in the curable composition, the desired cure rate, the temperature of use, and the like.

For example, lower amounts of curable components may be used at lower operating temperatures, while higher amounts of curable components may generally be used at higher operating temperatures. The amount of curable component suitable for use in the curable composition can range from about 20 to about 80 weight percent, more specifically from about 40 to about 60 weight percent, desirably from about 45 to about 55 weight percent, based on the total weight of the curable composition.

Thermally conductive components are present in the curable composition and may also be selected based on the desired properties of the curable composition. In one useful embodiment, the thermally conductive component may be selected from graphite, aluminum oxide, aluminum, gold, copper, zinc oxide, titanium oxide, silicon carbide, silicon nitride, boron nitride, beryllium oxide, diamond, boron nitride, silver, copper, carbon, or various combinations thereof.

The amount of thermally conductive component may also be selected based on the desired properties of the curable composition. In one useful embodiment, the thermally conductive component can be present in an amount of from about 1 to about 40 weight percent based on the total weight of the curable composition, more specifically, from about 5 to about 25 weight percent based on the total weight of the curable composition, or desirably, from about 10 weight percent based on the total weight of the curable composition. The thermally conductive component may be present in the curable composition in the form of nanoparticles.

Phase change materials ("PCM") should be selected such that a phase change from solid or non-flowable to liquid or flowable occurs within a desired temperature range. Thus, the PCM may be selected based on the fluid in the hollow tube, the operating temperature of the hollow tube, and the ambient temperature. To select a PCM for a particular application, the operating temperature of the device should be considered and the PCM should be selected to match.

A variety of PCMs may be used in the curable compositions of the present invention.

The PCMs used herein may be encapsulated or dispersed within a matrix. For a general review of encapsulated PCMs, see, e.g., P.B. Salunkhe et al, "A review on effect of phase change material encapsulation on the thermal performance of a system",Renewable and Sustainable Energy Reviews,16,5603-16(2012)。

PCMs suitable for use herein may be organic or inorganic. For example, desirable PCMs include paraffins, fatty acids, esters, alcohols, glycols, organic eutectics (organic eutectics), petrolatum, beeswax, carnauba wax, mineral wax, glycerin, and/or certain vegetable oils. The phase change material may also include salt hydrates (salt hydrates) and/or low melting metal eutectics.

It is particularly desirable that the PCM used in the curable compositions herein may comprise from about 75 to about 95 weight percent paraffin wax within the polymeric shell, or more particularly from about 85 to about 90 weight percent paraffin wax within the polymeric shell.

The paraffin wax may be of standard commercial grade and should include paraffin waxes having melting points below about 40 c. The use of such a paraffin wax allows the matrix to be transformed from its solid state to its liquid state at a temperature below about 37 ℃. As mentioned above, in addition to paraffin, petrolatum, beeswax, carnauba wax, mineral wax, glycerin, and/or certain vegetable oils may also be used to form PCMs. For example, the paraffin and petrolatum components may be mixed together such that the weight ratio of these components (i.e., paraffin to petrolatum) is between about 1.0: 0 and 3.0: 1. In this regard, the PCM should increase softness as the petrolatum component increases relative to the paraffin component.

Representative commercially available PCMs include MPCM-32, MPCM-37, MPCM-52 and silver plated MPCM-37, where the number represents the temperature at which the PCM changes from a solid phase to a liquid phase. Suppliers include the Entrophy Solutions Inc. of Primeos, Minnesota, which PCM is sold under the trade name Puretemp; microtek Laboratories, inc, of morton, ohio; and Croda, the PCM of which is sold under the trade name crodature. Microtek describes encapsulated PCMs as being composed of an encapsulating substance with a high heat of fusion. Phase change materials absorb and release thermal energy to maintain a regulated temperature within products such as textiles, building materials, packaging, and electronics. If the PCM is encapsulated, the capsule wall or shell will provide a microscopic container for the PCM. Even if the core is in a liquid state, the capsule is still solid, preventing the PCM from "melting off". Croda International plc in the uk describes encapsulated PCMs as Croda therm microencapsulated phase change materials, which are durable core-shell particles that can be used in applications requiring PCM in particle form. As reported by the manufacturer, croda therm PCM is encapsulated in an acrylic shell so that when the bio-based core changes phase, the particles remain solid.

When the PCM undergoes its phase change from a solid to a liquid state, the matrix absorbs heat until the matrix transforms into a liquid state. When the PCM changes from a liquid state to a solid state; the liquid state releases the absorbed heat until the PCM transitions to a solid state.

Depending on the application of the curable composition, the PCM may transition from the solid phase to the liquid phase at a temperature in the range of about 25 ℃ to about 70 ℃, such as at a temperature in the range of about 30 ℃ to about 40 ℃. In a particularly useful embodiment, the PCM has a melting temperature of about 39 ℃. In another useful embodiment, the PCM has a freezing temperature (solidification temperature) of about 34 ℃. And in yet another embodiment that may be useful, the PCM has a freezing temperature of about 29 ℃. Further, the PCM should be stable against leakage at temperatures up to about 200 ℃.

The PCM may have a particle size in the range of about 15 μm to about 30 μm. Desirably, the PCM is present in the curable composition in an amount of about 20 to about 80 weight percent, based on the total weight of the curable composition.

The curing system may comprise a curing agent and/or a free radical initiator. The curing system may comprise a nitrogen-containing compound, such as those selected from the group consisting of amine compounds, amide compounds, imidazole compounds, guanidine compounds, urea compounds, and combinations thereof. The curing system may also comprise a peroxide.

The amine compound may be selected from aliphatic polyamines, aromatic polyamines, cycloaliphatic polyamines, and combinations thereof. The amine compound may be selected from the group consisting of diethylenetriamine, triethylenetetramine, diethylaminopropylamine, xylylenediamine, diaminodiphenylamine, isophoronediamine, menthenediamine, and combinations thereof.

Modified amine compounds may also be used herein. Useful modified amine compounds include epoxy amine additives formed by the addition of an amine compound to an epoxy compound, such as novolac-type resins modified by reaction with an aliphatic amine.

The imidazole compound may be selected from the group consisting of imidazole, isoimidazole, alkyl substituted imidazole, and combinations thereof. More specifically, the imidazole compound is selected from the group consisting of 2-methylimidazole, 2-ethyl-4-methylimidazole, 2, 4-dimethylimidazole, butylimidazole, 2-heptadecenyl-4-methylimidazole, 2-undecenylimidazole, 1-vinyl-2-methylimidazole, 2-n-heptadecylimidazole, 2-undecylimidazole, 1-benzyl-2-methylimidazole, 1-propyl-2-methylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole, 1-cyanoethyl-2-undecylimidazole, 1-cyanoethyl-2-phenylimidazole, 1-guanidinoethyl-2-methylimidazole and an addition product of imidazole and trimellitic acid, 2-n-heptadecyl-4-methylimidazole, aryl-substituted imidazoles, phenylimidazole, benzylimidazole, 2-methyl-4, 5-diphenylimidazole, 2,3, 5-triphenylimidazole, 2-styrylimidazole, 1- (dodecylbenzyl) -2-methylimidazole, 2- (2-hydroxy-4-tert-butylphenyl) -4, 5-diphenylimidazole, 2- (2-methoxyphenyl) -4, 5-diphenylimidazole, 2- (3-hydroxyphenyl) -4, 5-diphenylimidazole, 2- (p-dimethylaminophenyl) -4, 5-diphenylimidazole, 2- (2-hydroxyphenyl) -4, 5-diphenylimidazole, bis (4, 5-diphenyl-2-imidazole) -benzene-1, 4, 2-naphthyl-4, 5-diphenylimidazole, 1-benzyl-2-methylimidazole, 2-p-methoxystyrylimidazole, and combinations thereof.

Modified imidazole compounds may also be used, including imidazole adducts formed by adding imidazole compounds to epoxy compounds.

Guanidine, substituted urea, melamine resins, guanamine derivatives, cyclic tertiary amines, aromatic amines, and/or mixtures thereof. The hardener may participate in the hardening reaction in a stoichiometric amount; however, they may also be catalytically active. Examples of substituted guanidines are methylguanidine, dimethylguanidine, trimethylguanidine, tetramethylguanidine, methylisobiguanide, dimethylisobiguanide, tetramethylisobiguanide, hexamethylisobiguanide, heptamethylisobiguanide and cyanoguanidine (dicyandiamide). Representative guanamine derivatives include alkylated benzoguanamine resins, and methoxymethylethoxymethylbenzguanamine.

The curing system is present in the curable composition in an amount of about 30 to about 50 weight percent, based on the total weight of the curable composition.

Additionally, the curing system may be present in a separate part from the curable component. In this way, a two-part composition can be constructed in which the two parts are brought together shortly before application to the coil.

Other components may also be included depending on the desired end use of the composition of the present invention. For example, flame retardant materials and/or antioxidants may be included.

The curable composition can have a thermal conductivity of about 0.2 to about 1.2W/m/K and a latent heat of fusion (fusion) of about 60 to about 200J/g, more specifically about 60 to about 120J/g.

The ratio of the thermal conductivity to the latent heat of fusion of the curable composition is optimized to promote optimal heat transfer, storage and dissipation. In particular, the curable composition may have a ratio of thermal conductivity to latent heat of fusion of about 0.06.

The curable composition described above can be coated on the outer surface of the hollow tube by conventional coating methods. Such curable compositions can adjust the "skin" temperature of the hollow tube to minimize the temperature experienced by the end user in contact with the hollow tube when the hollow tube is in use, such as when the hollow tube is a condenser coil in a refrigeration unit.

The hollow tube described above may be included in the refrigeration unit shown in fig. 1. The refrigeration unit may be a domestic refrigeration appliance or a commercial refrigeration appliance. The refrigeration unit includes a condenser coil 2, an evaporator coil 8 and a compressor 3. The refrigeration unit may further comprise a refrigeration compartment 1 and a flow meter 4.

In particular, the hollow tube of the present invention may be a condenser coil 2 in a refrigeration unit 1. The condenser coil 2 may be straight, curved, or have a straight portion and a curved portion. Alternatively, the hollow tube of the present invention may be the evaporator coil 8 of a refrigeration unit.

In a closed system, liquid moves through the refrigeration unit. The liquid may be aqueous, or it may comprise one or more alkanes, such as branched alkanes and/or alkanes substituted with one or more halogen atoms. Examples of branched alkanes include isobutane, tetrafluoroethane, and combinations thereof. The liquid may comprise one or more alkanes that are branched and/or may be substituted with one or more halogen atoms. In particularly useful embodiments, the liquid may be a refrigerant. In particular, the refrigerant may be in liquid form as it enters the refrigeration unit.

The evaporator coil 8 may be disposed within the refrigeration compartment 1. The evaporator coil 8 may be a hollow tube through which the liquid flows. The evaporator coil 8 absorbs heat from the air within the refrigeration compartment 1 to cool the compartment. The liquid in the evaporator coil 8 is converted to gaseous form due to the heat absorbed from the refrigeration compartment 1.

The liquid in gaseous form then enters the compressor 3 from the evaporator coil 8, which compressor 3 increases the pressure of the gas. A flow meter 4 may be downstream of the compressor 3 to monitor and control the flow rate of the liquid. The compressor 3 delivers compressed gas to the condenser coil 2. The condenser coil 2 then removes heat from the gas, converting it to liquid form before recycling it to the refrigeration unit. The inlet temperature 5 and outlet temperature 6 of the condenser coil 2 can be measured. In a useful embodiment, the inlet temperature 5 is about 40 ℃ and the outlet temperature 6 is about 35 ℃.

The curable composition disclosed herein can be applied to both the condenser coil 2 and the evaporator coil 8. The curable composition absorbs sufficient heat to change the refrigerant to a liquid in the condenser coil 2 and absorbs heat from the refrigerated compartment 1 to more efficiently cool the refrigerated compartment 1. Thus, the PCM contained in the curable composition applied to the condenser coil 2 and the evaporator coil 8 may vary based on the operating temperature of each. Further, when the curable composition is applied to the condenser coil 2 or the evaporator coil 8, the need for a fan (not shown) can be reduced or eliminated, thereby increasing the overall energy efficiency of the refrigeration unit. Referring to fig. 3, a condenser coil is shown prior to application of the curable composition. The condenser coil shown is made of galvanized steel.

Additionally, in a refrigeration unit, such as that shown in fig. 1, if the curable composition is applied to the condenser coil 2, the ambient air surrounding the condenser 7 is sufficient to re-solidify the PCM in the curable composition. Desirably, the curable composition can be varied to match the liquid used in the refrigeration unit, the operating temperature of the refrigeration unit, and which components of the refrigeration unit the curable composition is applied to.

Examples

Compositions comprising a curable component, a thermally conductive component, a phase change material, and a curing system are prepared according to the present invention. These compositions are listed in table a. LOCTITE brand E-30CL is a two-part epoxy adhesive available from Henkel Corporation of Rocky Hill, Connecticut. Part B was used as received. To part a, one or more of EPODIL 749, MPCM 37D, and graphite 5095 are added. EPODIL 749 is available from Evonik Corporation of Parsippany, N.J., and is neopentyl glycol diglycidyl ether used to reduce the viscosity of epoxy resin systems.

TABLE A

| A Epichlorohydrin-4, 4 '-isopropylidenediphenol resin (90-100% by weight) and 4,4' -methylenediphenol polymer with 1-chloro-2, 3-epoxypropane (0.1-1% by weight) as reported by the manufacturer.

@ 3,3' -oxybis (ethyleneoxy) bis (propylamine) as reported by the manufacturer (50-60 wt%).

# behenyl as reported by the manufacturer.

Samples nos. 1-3 were coated on coils (each coil having the same dimensions and made of the same material) to achieve the addition levels shown in table 1. Sample nos. 1 and 2 were applied to the coil twice at different addition levels, respectively; sample No. 3 was applied to the coil three times at different addition levels.

Latent heat measurements were made using a Perkin Elmer DSC 8000. Thermal conductivity measurements were made on a TA Instruments DTC-300 thermal conductivity tester according to the known standard ASTM F-433, which is based on standard practice for evaluating the thermal conductivity of gasket materials.

TABLE 1

Fig. 1 shows the experimental equipment arrangement used in these examples. The condenser coil 2 is exposed to a constant ambient temperature 7 of 25 c +/-0.1 c and is connected to a pump 3 and a flow meter 4. The water in the system is heated to a constant temperature of 40 c in the cooling chamber 1. Water is then pumped through the condenser coil 2 at a controlled flow rate while maintaining the coil inlet temperature 5 constant at 40 ℃ and measuring the condenser coil outlet temperature 6. Measurements were made at five different flow rates from 0.25 liters per minute and 0.75 liters per minute. For each flow rate, five cycles of flow on for 10 minutes followed by 18 minutes off were completed. The instantaneous power consumption is calculated from the flow rate, water density, water heat capacity and temperature change across the condenser coil. The dissipated energy is then calculated by integrating the dissipated power over time for each on/off flow cycle, and then summing the dissipated energy for each of the 5 flow cycles. Measurements and calculations were made for each of the five flow rates.

Figure 2 shows the results of the relative energy dissipated from each of the coils evaluated. The output value of the relative energy dissipated is calculated from the energy dissipated by the condenser coil coated with the phase change material-containing composition compared to a control (i.e., a condenser coil without such phase change material-containing composition applied). In case of a phase change material with low latent heat and high thermal conductivity, an increase of dissipated energy of 4.4% compared to the control was observed. In the case of phase change materials with moderate latent heat and moderate thermal conductivity, an increase of 7.3% over the control was observed. In case of a phase change material with high latent heat and low thermal conductivity, an increase of 10.2% relative to the control is obtained.

A water-based composition comprising a binder, a thermally conductive component, and a phase change material is prepared according to the present invention. These compositions are listed in table B. EPS 2111 is an all acrylic adhesive that can be used in laminating adhesives, particularly for blending with latex polychloroprene. The polymer has broad adhesion to various substrates and has good 180 DEG peel and heat resistance. It is commercially available from Engineering Polymer Solutions of Marengo, Illinois. To EPS 2111 was added water, MPCM 37D, and graphite 2939 in the amounts specified. Sample No. 4 contained 7% water; sample No. 5 contained 8% water; and sample No. 6 contained 13% water.

TABLE B

Sample numbering	Graphite 2939	EPS 2111	MPCM 43D
				4	21.2	47.7	24.1
5	33.3	42.5	16.2
				6	3.1	33.1	50.8

Although acrylic adhesives were used for samples 4-6, other types of polymer emulsions or water-based polymer solutions could be used. For example, PUR dispersions, acrylic emulsions or solutions, and alkyd emulsions or solutions may also be used.