Note: Descriptions are shown in the official language in which they were submitted.
CA 022120~1 1997-07-31
WO g~l24021 PC~ /O~GO
Heat exchanger
The invention relates to a heat exchanger,
especially for regulating the temperature of air by
means of a liquid supplied into the heat exchanger, or
vice versa, whereupon the heat exchanger comprises a
pipe section for liquid circulation and fins that are
attached to the outer surfaces of the pipe section in
order to enlarge the heat-exchange surface.
This kind of heat exchangers are presently well
known in different fields of technology. An example of
technical fields utilizing such heat exchangers is
ventilation technology. Ventilation installations are
often provided with heat exchangers of the
aforementioned type, situated in connection with either
air treatment apparatuses or ducts. In the most ~m~n
situation, licluid flows inside the pipes and air outside
the pipes. In, order to provide better heat transfer,
fins that extend the heat-exchange surface are att~chPA
to the outer surface of the pipes. The fins are often
wavy and mutually very closely positioned in order to
provide a goo~ heat-transfer ratio.
The air is warmed in a supply air device in the
winter and possibly cooled in the summer in order to
obtain the desired state for the supply air. The heating
sta!~e often consists of two or three steps. The first
step is the process of heat recovery wherein, in case
of a liquid heat exchanger, the liquid is a liquid
protected from freezing. The next step is the actual
hea-ting radialor which is used to increase the heat, or
if there is no step of heat recovery, to supply heat so
that the desired air temperature is obtained either as
a final or intermediate s~ate. The third step, which is
the after-heating step, occurs in an after-heating
rad:iator that is usually required after a humidifying
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WO96t24021 PCT~96100060
part, after a dehumidification process performed by
cooling, or for the purpose of zone-specific heating.
The cooling process takes place not only in the
supply air heat exchanger in the summer, but also in the
heat recovery radiator of the exhaust air device in the
winter, in which case the liquid is a liquid prevented
from freezing. In other respects, the process
corresponds to the above-described process.
If liquid radiators are added to the process
circuit, the purpose is to provide the liquid circuit
with the desired temperature either partly or entirely,
at the same time as the air system usually also benefits
from this. There are also such liquid radiators that are
used for both heating and cooling in series or at
different times.
The structure of fin-type heat exchangers is
conventionally un~h~nging. The structure consists of the
following components: a radiator supply water connection
that is attached to a distributor pipe from which pipe
sections, or so-called tube pipes, diverge and circulate
in depth through the radiator fins according to a
specific geometry that is recurrent and that is
determined by apertures provided in the fins. The tube
pipes form water routes through the radiator and end in
a collecting pipe from which the water exits via a
connecting pipe for water leaving the radiator. Such
radiators comprise one distributor pipe, or bypass
manifold, and one collecting pipe, or collecting
manifold, for the discharge of water.
In all the above-described cases, the radiators
conventionally operate in such a way that a change in
the temperature occurs in a radiator that is homogenous
in the direction of motion of air. A case wherein the
fin is extended by means of manufacturing technique may
constitute an exception, but in such a case the
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W<~ 96124021 PCT~FDS~ C0
operation of the radiators remains the same, however.
The capacity of the radiator is usually controlled by
adjusting the liquid flow or its temperature, or by
regulating the temperature of the air, depending on the
direction of :Elow of energy.
Efficient energy exploitation often leads to
very small temperature differences. In the fin area of
the radiator, there occur in the air side temperature
stratifications that can be considerable and that
deteriorate the total heat-transfer coefficient,
depending on the pipe routes. The temperature of the
liquid varies between the different water routes
depending on how evenly the liquid flow divides. Small
temperature differences result in deep radiators. In
practice, the number of pipe rows in the flow direction
of air can be as high as twelve. Together with the small
fin pitch, wavy fins and a possible production-technical
fin extension, this makes the efficient cleaning of the
radiator impossible. Since the radiator cannot be
cle,~ned, a contamination layer forming on its surface
deteriorates the heat transfer, wherefore the radiator
cap;~city decreases. In order to obtain the desired
capacity, the radiator has to be overdesigned utilizing
a so-called contamination coefficient which can be about
1.3 for example in industrial applications. In addition
to a consequent increase in the investment costs, the
dra!~ of the radiator and the resultant consumption of
the electrica:L power of the blower increase. Since the
contamination layer also makes the flow ducts between
the fins narrower, the flow resistance and the
consumption oE electrical power increase as a result.
The total effect can increase the flow resistance of the
radiator and the electrical power consumption that is
directly prop~rtionate with the flow resistance more
than 50~ for the radiator. This leads to a need to
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overdesign also the driving motor, belt drives,
contactors, cables etc. This results in a considerable
increase in both running and investment costs.
According to studies, in some cases the
increasing flow resistance decreases the air flow as
much as 30~ when the radiator becomes dirty. Especially
in industrial processes, but also in normal ventilation
installations, the whole system must be readjusted in
such a case by increasing the rotational velocity of the
blower with special dampers or the like. This naturally
produces considerable costs.
Due to the greater flow resistance, the noise
level of the blower increases. The noise suppression
system must also be overdesigned, or an additional
suppression ?chAnism must be constructed afterwards.
The contamination of radiators used for heat
recovery is particularly harmful. In addition to the
aforementioned drawbacks, the efficiency of heat
recovery decreases. This means that in addition to the
consumption of electrical power, the consumption of
thermal energy also increases, in some cases it is even
doubled.
A very serious drawback is the health hazard
associated with contamination. The contamination layer
forms a substrate for bacterial and fungal populations
which comprise spores that may get into the air flow and
cause allergic reactions, at worst a fever known as a
"printer's disease" in printing houses and in textile
industry. Another known problem is an unpleasant odour,
which spreads from some plants at the beginning of the
heating season and which is caused by the fact that
populations which were generated on the cool radiator
surfaces during the summer start secreting evaporable
substances when the temperature of the radiators
increases.
CA 022l20~l l997-07-3l
WO 96/24021 PCT)Fl~)CJOC l~
The purpose of the invention is to provide a
heat exchange~r by means of which the prior art drawbacks
can be eliminated. This is achieved with the heat
exchanger according to the invention, the first
embodiment thereof being characterized in that the fin
parts are div:ided into at least two zones, and that the
pipe sections of the fin zones are connected to
collecting pipes and to distributor pipes, so tha~ after
the liquid has passed through one fin zone it is
arranged to be mixed at least in one collecting pipe
before it is supplied to the distributor pipe of the
next zone, or to the distributor pipes of the following
zones. The second embodiment of the heat exchanger
according to l~he invention is characterized in that the
fin parts are divided into at least two zones in such
a way that there remains between the zones an
intermediate space where the air is arranged to be mixed
before it flows into the next zone. The blending of air
can be made more efficient for example with special
turbulence sheets, air sprays, guide plates or with some
other device known per se.
The primary advantage of the invention is its
flexibility since, if desired, it benefits both the
liquid side and the liquid and air sides, depending on
the requirements of the overall situation. It also
provides production-technical advantages, since it is
possible to select the fin zone according to the
manufacturing technique so that there is no need to use
extended fins. The extended fins tend to cause
additional resistances in the air side and to increase
the gathering of dirt and dust. Additional advantage is
provided by the fact that the heat exchanger according
to the invention can be cleaned in two or more stages
depending on ~he number of spaces remaining between the
fin ~ones. The cleaning method can be for example
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WO 96/24021 PCT/FI9C/OO~G0
vacuuming, a cleaning gun, a combination of a vacuum
cleaner and a cleaning gun, or some other cleaning
method known per se that is either fixed or installed
temporarily for the cleaning stage.
In the following, the invention will be
described in greater detail by means of preferred
embodiments described in the accompanying drawing, in
which
Figure 1 shows the coupling end in the first
embodiment of the heat exchanger according to the
invention,
Figure 2 is a view of the heat exchanger of
Figure 1 taken along arrows II-II of Figure 1,
Figure 3 shows another alternative
implementation of the embodiment of Figure 1 in a
similar m~nne.r as Figure 2,
Figure 4 is a top profile of a second
embodiment of the heat exchanger according to the
invention,
Figure 5 is an end view of the cleanout
arrangement of the embodiment of Figure 1,
Figures 6a and 6b show the different
implementations of a detail in the heat exchanger
according to the invention, and
Figure 7 shows a modification of the embodiment
of Figure 1.
In Figure 1, a bypass manifold for incoming
water is denoted by reference numeral 1, and a
collecting manifold for the water leaving the heat
exchanger by reference numeral 2. A connecting pipe from
the bypass manifold 1 to the network is denoted by
reference numeral 3, and a connecting pipe for the
collecting manifold 2 in turn by reference numeral 4.
A roof element of a possible housing in the heat
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WO 96124021 rCT~ )6Jl)Dl)G~)
exchanger is denoted by reference numeral 12, and a
bottom elemenl- correspondingly by reference numeral 13.
Acco:rding to an essential basic idea of the
inv,ention, th,e fin parts of the heat exchanger are
divided into at least two zones 6, 5 in such a way that
there remains between the zones an intermediate space
7 w]~ere the air is arranged to be mixed before it flows
into the next zone. This is clearly apparent in Figure
l wl~ich shows the direction of the air flow by means Of
an arrow. In the example of the figure, the first fin
zone in the direction of travel of the air is denoted
by reference numeral 6, and the second fin zone
correspondingLy by reference numeral 5. The intermediate
space where l:he air is mixed either mechanically or
thermally is denoted by reference numeral 7, as noted
above.
Figu:re 2 is a top view of the heat exchanger
according to Figure 1. In Figure 2, reference numeral
8 denotes a pipe section, a so-called tube pipe, which
begins ~rom the water distributor pipe 1 and circulates
through the fin zone 5, turning back to the fin zone 5
by means of a bent pipe lO. The fins of the fin zone are
clearly visible in the enlarged partial view of Figure
2. A bent pipe ll transfers the liquid to the next fin
zone 6 past an intermediate space 7 after which a pipe
section 9, a so-called tube pipe, guides the liquid
through the fin zone. The liquid finally arrives at a
collecting manifold 2 for exhaust liquid. It should be
noted that e~ven though the liquid circulation is
described above by means of one pipe section, in reality
there are several pipe sections, i.e. tube pipes. Figure
2 also shows possible end plates of the heat exchanger
by means of reference numerals 14 and 15.
As described above, the invention can be
applied both :in the air and the liquid side. According
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WO96/24021 PCT~196100060
to the basic idea of the invention, the fin parts are
divided into at least two zones 6, 5, and the pipe
sections 8, 9 of the fin zones are connected to
collecting pipes l6 and distributor pipes l8 so that
when the liquid has passed through one fin zone 5, it
is arranged to be mixed at least in one collecting pipe
16 before it is fed into the distributor pipe 18 of the
next zone 6, or into the distributor pipes of the
following zones. This kind of implementation is
described in Figure 3 which shows two separate fin zones
5 and 6, an intermediate space 7, and tube pipes 8 and
9 that pass through the fin zones 5 and 6. Reference
numeral 16 shows a collecting pipe that is situated
after the fin zone 5 and that is joined by a tube pipe,
or in practice tube pipes 8. The liquid that has flowed
through the fin zone 5 is mixed in the collecting pipe
16 before it moves via an interconnector 17 to a
distributor pipe 18 from which tube pipes 9 of the fin
zone 6 divide the liquid further to the fin zone 6.
In the embodiment of Figure 3, the fin zones
5, 6 are separate zones. However, this is not the only
alternative. If the basic idea of the invention is only
applied to the liquid side, the fin zones can also be
implemented as fictitious zones. Figure 4 shows such an
embodiment. The fictitious fin zones are denoted by
reference numerals l9 and 20. The tube pipes of the fin
zone l9 are connected to a collecting pipe 21 from which
the liquid moves after mixing via an interconnector 22
to a distributor pipe 23 where the tube pipes branch
into the fin zone 20.
It should thus be noted that the term used in
the claims covers both separate fin zones and the
fictitious fin zones of Figure 4. The fictitious fin
zones can be produced quite freely without any
intermediate spaces. The basic idea is that the
CA 022120~1 1997-07-31
Wo 96124021 PCT~ G~û~V~ 1)
temperature differences that have occurred in the li~uid
in a fin zone are evened out before the liquid is
supplied into the next fin zone.
Fig~lre 5 in turn shows the cleanout arrangement
of the embodiment of Figure l. Reference numeral 24
shows a cover part by means of which a cleanout is
provided at the intermediate space 7. The heat exchanger
can be advant;ageously cleaned through this cleanout by
means of a suitable cleaning device or cleaning agent.
Figures 6a and 6b show two versions of a li~uid
receiver basin to be attached to the bottom section of
the heat exchanger according to the invention. Reference
numeral 25 shows a basin alternative containing no drain
coImection, and reference numeral 26 shows a basin
al1ernative with a drain connection.
Figure 7 shows a modification of the embodiment
of Figure l. Figure 7, as Figure l, shows the coupling
end of the heat exchanger according to the invention.
Like reference numerals are used in corresponding points
ZO as in Figure l. The bypass manifold for incoming water
is denoted in Figure 7 by reference numeral 27, and the
collecting manifold for the water leaving the heat
exchanger in turn by reference numeral 28. In this
modification, the bypass manifold and the collecting
manifold are provided with connecting pipes 29 and 30
that are parallel with the manifolds. The connecting
pipes 29 and 30 can be oriented in parallel, as in
Figure 7, or in opposite directions.
The above-described embodiments are not
intended to limit the invention in any way, but the
invention can be modified cauite freely within the scope
of the claims. Therefore, it is clear that the heat
exchanger according to the invention, or the details
thereof, do not necessarily have to correspond exactly
to those shown in the figures, but other kinds of
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arrangements are also possible. For example, the
invention is not in any way limited to two fin zones,
even though the examples of the figures show such
embodiments. The invention can also be applied in
connection with two, three or more fin zones. The
invention can also be utilized for both heating and
cooling purposes, as noted above.
