U.S. patent application number 10/551183 was filed with the patent office on 2006-09-07 for heat exchanger and method for treating the surface of said heat exchanger.
Invention is credited to Snjezana Boger, Peter Englert, Klaus Fischle, Oliver Mamber, R Sabine Sedlmeir.
Application Number | 20060196644 10/551183 |
Document ID | / |
Family ID | 32980909 |
Filed Date | 2006-09-07 |
United States Patent
Application |
20060196644 |
Kind Code |
A1 |
Boger; Snjezana ; et
al. |
September 7, 2006 |
Heat exchanger and method for treating the surface of said heat
exchanger
Abstract
The invention relates to a heat exchanger provided with a
hydrophilic surface coating (12) comprising a gel produced by a
sol-gel method.
Inventors: |
Boger; Snjezana; (Esslingen,
DE) ; Englert; Peter; (Bad Friedrichshall, DE)
; Fischle; Klaus; (Tamm, DE) ; Mamber; Oliver;
(Stuttgart, DE) ; Sedlmeir; R Sabine; (Mosbach,
DE) |
Correspondence
Address: |
FOLEY AND LARDNER LLP;SUITE 500
3000 K STREET NW
WASHINGTON
DC
20007
US
|
Family ID: |
32980909 |
Appl. No.: |
10/551183 |
Filed: |
March 8, 2004 |
PCT Filed: |
March 8, 2004 |
PCT NO: |
PCT/EP04/02336 |
371 Date: |
September 29, 2005 |
Current U.S.
Class: |
165/133 |
Current CPC
Class: |
F28F 13/04 20130101;
F28F 2245/02 20130101; F28F 19/02 20130101; F28F 13/18
20130101 |
Class at
Publication: |
165/133 |
International
Class: |
F28F 13/18 20060101
F28F013/18 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 31, 2003 |
DE |
10314775.6 |
Claims
1. A heat exchanger having an in particular hydrophilic surface
coating, characterized in that the surface coating includes a gel
which is produced in particular in a sol-gel process.
2. The heat exchanger as claimed in claim 1, characterized in that
the sol, which functions as a coating substance in a sol-gel
process, contains alkoxy compounds of elements from main group III
and/or of elements from main group IV and/or of transition
metals.
3. The heat exchanger as claimed in claim 2, characterized in that
the transition metals belong to transition group IV and/or V.
4. The heat exchanger as claimed in claim 2, characterized in that
in the alkoxy compounds some of the hydrolysable alkoxy radicals
are substituted by alkyl and/or aryl radicals, or in that a mixture
of pure alkoxy compounds and alkoxy compounds which partly contain
alkyl and/or aryl radicals is provided.
5. The heat exchanger as claimed in claim 1, characterized in that
the surface coating contains nanoparticles, coated nanoparticles
and/or grafted nanoparticles comprising or consisting of
oxides.
6. The heat exchanger as claimed in claim 5, characterized in that
oxides of the elements from main group II and/or main group III
and/or oxides of germanium, tin, lead and/or oxides of the
transition metals and/or oxides of zinc and/or oxides of cerium are
provided.
7. The heat exchanger as claimed in claim 6, characterized in that
the transition metals belong to transition IV and/or V.
8. The heat exchanger as claimed in claim 1, characterized in that
the surface coating contains nanoparticles, coated nanoparticles
and/or grafted nanoparticles comprising or consisting of hydrated
oxides and/or nitrides and/or carbides.
9. The heat exchanger as claimed in claim 8, characterized in that
the hydrated oxides, nitrides and carbides comprise elements from
main group III and/or main group IV and/or transition metals and/or
cerium.
10. The heat exchanger as claimed in claim 9, characterized in that
a transition metal belongs to transition group IV and/or V or is
zinc.
11. The heat exchanger as claimed in claim 1, characterized in that
the nanoparticles, coated nanoparticles and/or grafted
nanoparticles have a mean diameter of from 1 to 1000 nm.
12. The heat exchanger as claimed in claim 1, characterized in that
the surface coating includes constituents with an antimicrobial
action.
13. A process for coating a heat exchanger with an in particular
hydrophilic surface coating the surface coating being produced by
means of a sol-gel process.
14. The process for coating a heat exchanger as claimed in claim
13, characterized in that the surface coating is applied by means
of dipping, flooding and/or spraying.
15. The process for coating a heat exchanger as claimed in claim
13, characterized in that a pre-treatment by means of an acidic or
alkaline pickle is carried out, with subsequent scale removal
and/or a conversion treatment.
16. The process for coating a heat exchanger as claimed in claim
15, characterized in that mixed oxides and/or mixed fluorides are
formed during the conversion treatment.
17. The process for coating a heat exchanger as claimed in claim
13, characterized in that a drying process is carried out after a
pre-treatment by means of an acidic or alkaline pickle with
subsequent scale removal and/or a conversion treatment.
18. The process for coating a heat exchanger as claimed in claim
13, characterized in that the operation of applying the surface
coating is followed by a drying operation.
19. The process for coating a heat exchanger as claimed in claim
13, characterized in that a surface coating which contains
nanoparticles, coated nanoparticles and/or grafted nanoparticles is
applied.
Description
[0001] The invention relates to a heat exchanger, in particular for
a motor vehicle, as described in the preamble of claim 1 and to a
process for the surface treatment of a heat exchanger.
[0002] In conventional heat exchangers, there are often problems
with corrosion, microbiological growth and dirt. These problems are
caused, inter alia, by the precipitation of condensate from the air
which is flowing through the sets of corrugated fins which are
arranged between the plates or tubes through which refrigerant
flows. Furthermore, there is also an accumulation of dust and dirt,
which means that microorganisms can colonize the wet, dirty
surface, which can lead to the formation of undesirable odors.
[0003] The flow of condensate off the surface can be boosted by
making the surface of the heat exchanger hydrophilic, the
hydrophilicity forming a thin film of liquid which can continuously
flow off the corrugated fin surface. This leads to a so-called
self-cleaning effect or rinsing effect, making it possible to
reduce permanent accumulation of dust and dirt and to avoid
colonization of microorganisms on the surface of the heat
exchanger. Furthermore, the corrugated fin surface dries more
quickly. This maintains or improves the overall performance of the
heat exchanger.
[0004] EP 115 40 42 A1 has disclosed an agent for the chemical
surface treatment of heat exchangers, in which silicate particles
with a mean diameter of from 5 to 1000 nm and polyvinyl alcohol are
applied in aqueous solution to the surface of heat exchangers. To
pretreat the surface, the surface is first of all subjected to an
acidic cleaning step and then a chromium-containing or
zirconium-containing conversion layer is built up. The heat
exchanger which has been prepared in this way is coated with the
abovementioned hydrophilic chemicals, so that the correspondingly
treated surface has hydrophilic properties.
[0005] It is an object of the invention to provide an improved heat
exchanger.
[0006] This object is achieved by a heat exchanger having the
features of claim 1. Advantageous configurations form the subject
matter of the subclaims.
[0007] According to the invention, the preferably hydrophilic
surface coating, in particular in the case of a heat exchanger for
a motor vehicle, includes a gel, the gel advantageously being
applied by a sol-gel coating operation. The gel may contain
nanoparticles, coated nanoparticles and/or grafted nanoparticles. A
hydrophilic surface coating ensures that a thin, continuous film of
liquid is formed on the surface and can continuously flow off the
corrugated fin surface or off the plates/tubes of the heat
exchanger. This leads to a self-cleaning effect or rinsing effect,
allowing a permanent accumulation of dust and dirt to be reduced
and a colonization of microorganisms on the surface of the heat
exchanger to be avoided. Furthermore, the corrugated fin surface
dries more quickly.
[0008] In modified embodiments of the invention, the surface
coating, in addition or instead of the hydrophilic action, has one
or more other advantageous actions, such as for example a
corrosion-inhibiting or corrosion-preventing action.
[0009] Starting materials preferably used in the sol-gel process
are alkoxy compounds of elements from main group III, i.e. for
example aluminum, boron, indium, and/or of elements from main group
IV, i.e. for example silicon, tin, and/or of transition metals,
preferably from transition group IV, such as titanium, zirconium,
hafnium, and/or from transition group V, such as vanadium, niobium,
tantalum.
[0010] In the alkoxy compounds, it is preferable for some of the
hydrolysable alkoxy radicals to be substituted by alkyl and/or aryl
radicals or else it is preferable to provide a mixture of pure
alkoxy compounds and alkoxy compounds which partly contain alkyl
and/or aryl radicals. These compounds are preferably halogenated,
particularly preferably fluorinated.
[0011] It is preferable for the hydrophilic surface coating to
include nanoparticles. It is preferable for the nanoparticles to
comprise approximately 100% or entirely oxides.
[0012] In the case of the coated nanoparticles, it is also possible
for other compounds to be present in the coating instead of or in
addition to oxides, which are provided at least in the core of the
coated nanoparticles. The coating of the nanoparticles may include
organic and/or inorganic components, as well as organic and/or
inorganic components with an antimicrobial action.
[0013] The grafted nanoparticles are nanoparticles with a core
comprising or consisting of oxides which carry side groups. These
side groups are chemically bonded to the surface of the
nanoparticle core, e.g. by oxygen or nitrogen bridges. By way of
example, bifunctional compounds, e.g. diamines and/or dialcohols,
are used to produce nanoparticles of this type. As a result, the
surface properties of a nanoparticle can be varied (e.g. made
hydrophobic, hydrophilic, stabilized in the dispersion or
solution). Moreover, it is possible for a polymer chain with a
reactive side chain which, for example, contains an OH or COOH or
OR group, or a reactive group which has not fully reacted in the
polymer network, e.g. OH or COOH or OR, to be grafted onto the
nanoparticle.
[0014] Unless expressly stated to the contrary, it is preferable
for the nanoparticles (in the text which follows, this term is also
to be understood as encompassing coated and/or grafted
nanoparticles, for the sake of simplicity) to contain oxides and/or
hydrated oxides and/or nitrides, and/or carbides. In this context,
it is preferable to provide oxides of the element from main group
II and/or main group III and/or oxides of germanium, tin, lead
and/or oxides of the transition metals, preferably from transition
group IV and V, and/or oxides of zinc and/or of cerium.
[0015] The hydrated oxides, nitrides and carbides preferably
comprise elements from main group III and/or main group IV and/or
transition metals, preferably from transition group IV and V,
and/or zinc and/or cerium.
[0016] It is preferable for the nanoparticles, coated nanoparticles
and the grafted nanoparticles to have a mean diameter of from 1 to
1000 nm, in particular between 50 and 500 nm.
[0017] It is preferable for the surface coating to include
constituents with an antimicrobial action. These may form part of
the nanoparticles, for example in the case of grafted or coated
nanoparticles, or may be contained in the remaining part of the
surface coating. Additives of this type improve the antimicrobial
action of the surface coating and prevent colonization of
microorganisms on the surface of the heat exchanger or at least
impede such colonization.
[0018] It is preferable for the surface coating to be applied by
means of dipping, flooding or spraying.
[0019] It is preferable to carry out a pre-treatment by means of an
acidic or alkaline pickle with subsequent scale removal and/or a
conversion treatment. This pre-treatment is also preferably carried
out by means of dipping, flooding or spraying. The conversion
treatment is used to build up passivation layers which form a very
firm bond to the surface, for example by forming mixed oxides. A
passivation layer of this type inter alia prevents corrosive
attack.
[0020] A drying operation may be carried out after the
pre-treatment, and a drying operation is necessary after the actual
surface coating.
[0021] The invention is explained in detail below on the basis of
three exemplary embodiments, in part with reference to the drawing.
In the drawing:
[0022] FIG. 1 shows a section through the region of a heat
exchanger close to the surface with a coating in accordance with a
first exemplary embodiment of the invention, and
[0023] FIG. 2 shows a section through the region of a heat
exchanger close to the surface with a coating in accordance with a
second exemplary embodiment of the invention.
[0024] FIG. 1 shows the region of a corrugated finned metal sheet 1
of a heat exchanger made from aluminum close to the surface in
accordance with a first exemplary embodiment, which is provided
with a hydrophilic surface coating 2. In this case, this surface
coating 2 is formed from a sol which contains nanoparticles 3
comprising substantially pure aluminum oxide. The nanoparticles 3
have a mean diameter of between 10 and 100 nm and are distributed
relatively uniformly through the entire surface coating 2.
[0025] The sol includes alkoxy compounds of aluminum, a mixture of
pure alkoxy compounds and alkoxy compounds in which some of the
hydrolysable alkoxy radicals are substituted by alkyl radicals
being used.
[0026] The surface coating 2 is applied following a surface
cleaning using an acidic pickle, by dipping in a colloidal sol
solution in which nanoparticles of aluminum oxide are dispersed.
This is followed by a drying process.
[0027] FIG. 2 shows a region of a corrugated finned metal sheet 11
of a heat exchanger close to the surface in accordance with a
second exemplary embodiment. In this case, a conversion layer 14 is
provided between a hydrophilic surface coating 12 which contains
nanoparticles 13. The conversion layer 14 includes, inter alia,
mixed oxides of aluminum and zirconium.
[0028] The nanoparticles 13 are what are known as grafted
nanoparticles which carry side groups. In this case, the
nanoparticles 13 contain an oxide-containing core which is
surrounded by bifunctional organic compounds which are chemically
bonded to the surface of the nanoparticle core. The bifunctional
organic compounds include, inter alia, side groups with an
antimicrobial action. As in the first exemplary embodiment, the
actual surface coating 12 comprises a gel. The oxide-containing
core of the grafted nanoparticles 13 substantially comprises
zirconium dioxide and titanium dioxide.
[0029] To prepare the surface for the application of the actual
surface coating 13, the surface is provided with the conversion
layer 14, which contains mixed oxides of aluminum and zirconium.
For this purpose, a zirconium-containing chemical is applied by
means of dipping, and mixed oxides of aluminum and zirconium are
formed, so as to produce a very secure bond to the surface.
[0030] The surface coating 12 is applied following a drying
operation, by dipping in a sol-nanoparticle dispersion containing
the nanoparticles 13. This is followed by a further drying
process.
[0031] According to a further exemplary embodiment (not shown in
the drawing), a surface coating is carried out using a sol which
does not contain any nanoparticles. The sol includes alkoxy
compounds of silicon, with a mixture of pure alkoxy compounds and
alkoxy compounds in which some of the hydrolysable alkoxy radicals
are substituted by alkyl radicals being used.
* * * * *