[0001] The present invention relates to a condenser, and in particular to a condenser comprising
part of an automotive airconditioning system.
[0002] It is known for automotive air conditioning system condensers to use heat exchange
tubes of small hydraulic diameter for condensing the system refrigerant. EP0219974
discloses that optimum performance maybe achieved where the hydraulic diameter is
between about 0.4mm and 1mm. Typically the tubes comprise discrete flow channels or
ports between 8 and 20 in number for each tube.
[0003] An improved arrangement has now been devised.
[0004] According to the present invention, there is provided a condenser comprising a first
heat transfer tube arrangement in a relatively upstream portion of the condenser,
and a second heat transfer tube arrangement relatively downstream of the first tube
arrangement, wherein the hydraulic diameter of the first tube arrangement is different
to the hydraulic diameter of the second tube arrangement.
[0005] It is preferred that the hydraulic diameter of the second tube arrangement is greater
than the hydraulic diameter of the first tube arrangement.
[0006] Beneficially, the second tube arrangement is in the sub cooled region of the condenser.
The second tube arrangement is preferably provided in the sub cooled region of the
condenser and also immediately upstream of the sub cooled region of the condenser.
A receiver dryer may be positioned flowise between the sub cooled region of the condenser
and the immediately upstream tube arrangement.
[0007] In certain embodiments, it is preferred that the external depth dimension of tubes
in the first and second tube arrangements is substantially the same. For example in
a so called unified (or combined) condenser and radiator arrangement where banks of
radiator and condenser tubes are arranged side by side, it is beneficial to have the
radiator tubes and condenser tubes in line with one another in order to streamline
airflow through the combined radiator and condenser arrangement.
[0008] In alternative embodiments it may be acceptable to have the external depth dimension
of tubes in the first and second tube arrangements being substantially different,
where the hydraulic diameter ofthe second tube arrangement is greater than the hydraulic
diameter of the first tube arrangement, in such embodiments the external depth dimension
of the second tube arrangement will preferably be substantially greater than that
of the first tube arrangement.
[0009] In certain embodiments it is preferred that the spacing between adjacent tubes in
the first tube arrangement is substantially the same as the spacing between adj acent
tubes in the second tube arrangement.
[0010] In certain embodiments, it is beneficial that the spacing between adjacent tube major
axes in the first tube arrangement is substantially the same as the spacing between
adjacent tube major axes in the second tube arrangement. For example in a so called
unified (or combined) condenser and radiator arrangement where banks of radiator and
condenser tubes are arranged side by side, it is beneficial to have the radiator tubes
and condenser tubes in line with one another in order to streamline airflow through
the combined radiator and condenser arrangement.
[0011] It is preferred that the hydraulic diameter of the tubes of the second tube arrangement
is substantially at or above 1.3 times the hydraulic diameter of the tubes of the
second arrangement. More preferably, the hydraulic diameter of the tubes of the second
tube arrangement is substantially at or above 1.5 times the hydraulic diameter of
the tubes of the second arrangement. More preferably still, the hydraulic diameter
of the tubes of the second tube arrangement is substantially at or above 1.7 times
the hydraulic diameter of the tubes of the second arrangement. In certain embodiments,
the hydraulic diameter of the tubes of the second tube arrangement may be substantially
at or above 2 or even 2.5 times the hydraulic diameter of the tubes of the second
arrangement. For example, suitable performance has been achieved using first tube
arrangement of hydraulic diameter (HD) of 0.71 mm and second tube arrangement of tube
hydraulic diameter (HD) of 2mm giving a ratio for the second tube arrangement of 2.8
times the first tube arrangement hydraulic diameter.
[0012] Advantageously, the hydraulic diameter ofthe tubes ofthe second arrangement is substantially
in the range 0.8mm to 3mm. In some embodiments, it is preferred that the hydraulic
diameter of the tubes of the second arrangement is substantially in the range 1.2mm
to 3mm, more preferably 1.4mm to 3mm, more preferably 1.7mm to 3mm.
[0013] Beneficially, respective tubes of the second arrangement each include a plurality
of channels extending in the longitudinal direction of the tube. In some preferred
embodiments between 2 and 6 channels are provided, more preferably 4 or 5 channels
are provided.
[0014] Preferably respective tubes of the first arrangement each include a plurality of
channels extending in the longitudinal direction ofthe tube. In some preferred embodiments
10 or more channels may be provided.
[0015] It is preferred that in some embodiments the first and second tube arrangements comprise
extruded tubes. Beneficially the first and second tube arrangements comprise aluminium
material tubes.
[0016] The invention will now be further described in specific embodiments, by way of example
only, and with reference to the accompanying drawings in which:
Figure 1 is a schematic side view of an exemplary condenser in accordance with the
invention;
Figure 2 is a schematic side view of an alternative embodiment of a condenser in accordance
with the invention;
Figure 3 is a schematic side view of an alternative embodiment of the invention for
use as the condenser side of a combined (or unified) radiator condenser arrangement;
Figure 4 is a plot of pressure drop against free flow area for a range of tube designs;
and
Figures 5A to 5E are schematic sectional views of exemplary tube geometries in accordance
with the present invention.
[0017] Referring to Figure 1 there is shown schematically an exemplary condenser 1 for use
in an automotive air conditioning system.
[0018] The condenser 1 comprises a pair of spaced headers 2, 3 and interconnecting headers
2, 3, plurality of heat exchange tubes 4 arranged in a bank with air gaps intermediate
respectively tubes 4. An air way matrix of fins (not shown) is typically provided
intermediate adjacent spaced tubes in the bank. The headers 2, 3 contain internal
baffles ensuring that refrigerant flow through the condenser takes place in a number
of discrete passes between headers 2, 3 as shown by the arrows in Figure 1. The refrigerant
enters condenser 1 via inlet 5 in vapour form and is condensed during passage through
the condenser. Prior to exiting the condenser via outlet 6 the refrigerant passes
through a receiver dryer 7 (which includes a desiccant cartridge or the like) ensuring
that all gasses are removed from the refrigerant. The refrigerant leaving receiver
dryer 7 is directed via line 9 into a sub-cool section 10 of the condenser which cools
the refrigerant further to ensure that all refrigerant exiting outlet 6 is in liquid
form.
[0019] An important feature of the present invention is the relationship between the heat
exchange refrigerant tubes 4 present in the sub-cool section 10 and the upstream section
within the condenser. Shown in Figure 1 at reference 4a is a multiported refrigerant
tube 4 which is present in the portion of the condenser upstream of the sub-cool section
10 and receiver dryer 7. Shown at reference 4b in Figure 1 is a refrigerant tube which
is present in the sub-cool section 10 of the condenser 1. Tube 4a has 14 internal
ports or channels extending along the length of tube 4a and a hydraulic diameter which
is typically in the range 0.4 to 1.0 mm. Tube 4b has only four ports and a hydraulic
diameter which is significantly greater than the hydraulic diameter of tube 4a. Typically
the hydraulic diameter will be between 1.3 and 2.5 or more times the hydraulic diameter
of tube 4a. The hydraulic diameter of tubes 4b will typically be varied between 1.2mm
and 2 to 3mm plus. The hydraulic diameter (HD) is defined as four times the cross-sectional
area of the tube (or channel) divided by the wetted perimeter of the tube (or channel).
[0020] It is well understood and accepted within the automotive air conditioning field that
decreasing the port size and hence hydraulic diameter for a condenser tube improves
the efficiency/heat dissipation of the condenser. Although this is the case for a
conventional condenser, there are adverse affects where low hydraulic diameter multi-ported
tubes are used for a sub-cool condenser such as shown in Figure 1. Sub-cooled liquid
refrigerant passing through tubes suffer from reduced flow because of 'choking' effect
in the small hydraulic diameter tube ports. This can result in high pressure drop
across the condenser giving adverse condenser performance. In the embodiment shown
in Figure 1, it should be noted that the depth dimension (h) is greater for tube configuration
4b that tube configuration 4a.
[0021] By ensuring that the free flow area of the ports in tube 4b is significantly larger
than the free flow area of ports in tube figure a (the hydraulic diameter of tube
4b hence being significantly larger than the hydraulic diameter of tube 4a), it is
possible to have greater liquid flow in the tubes 4b in the sub-cool section 10 of
the condenser ameliorating choking effect.
[0022] The arrangement shown in Figure 2 is generally similar to the arrangement shown in
Figure 1, however in this embodiment the tubes 4b are also provided upstream ofthe
sub-cool section 10 in the last pass (from header 2 to header 3) prior to entering
the receiver dryer 7. In this last pass 11, the refrigerant is mostly in liquid phase
and therefore benefits from the increased hydraulic diameter of the tubes 4b present
in this last pass.
[0023] In the arrangement shown in Figure 3 the tubes 4 in the sub-cool section 10 are of
the configuration 4c. These tubes 4c have larger free flow area ports and increased
hydraulic diameter relative to the tubes 4a upstream of the receiver dryer. However
the tube depth h is the same for tubes 4c and 4a. This ensures that, for regularly
spaced tubes in the condenser bank, the spacing between the major axes of adjacent
tubes is identical for the sub-cool section and also the section upstream of the sub-cool
section and receiver dryer. Additionally, the spacing between adjacent tubes in the
sub-cool section 10 and the tube bank section upstream of the sub-cool section and
receiver dryer 7 are also the same. This enables the condenser arrangement to be conveniently
used in so-called unified (or combined) condenser and radiator arrangements.
[0024] By ensuring that maximum liquid refrigerant flow can occur along the sub-cool section,
it is possible to reduce the width dimension w shown in Figure 2a which is a plan
view of the condenser of Figure 2. This minimises the space envelope for the condenser
and hence has weight and other utilisation benefits.
[0025] Figures 5A to 5D show various multi-port configurations of heat exchange tubes 4.
The tubes of Figures 5A, 5D and 5E will be suitable for use in the sub-cool section
of the condenser. Typically the tubes of Figures 5B and 5C will be used in the section
of the condenser upstream of the sub-cool section and receiver dryer 7. The tube of
Figure 5A has 4 ports and a hydraulic diameter (HD) of 1.2mm. The tube of Figure 5B
has 15 ports and a hydraulic diameter (HD) of 0.65mm. The tube of Figure 5C has 14
ports and a hydraulic diameter (HD) of 0.71mm. The tube of Figure 5D has 4 ports and
a hydraulic diameter (HD) of 2mm. The tube of Figure 5C has 3 ports and a hydraulic
diameter (HD) of 3mm.
[0026] Figure 4 shows a plot of pressure drop versus free flow area for condenser tubes.
It can be seen that increasing the tube port size and hydraulic diameter for the sub-cool
phase of a typical sized heat exchanger can reduce the refrigerant pressure losses
dramatically (experimental results show by up to 84 per cent). It should be noted
that while a hydraulic diameter step change has been shown for condenser tubes between
the sub-cool section and condenser bank tubes upstream of the sub-cool section and
receiver dryer, the step change in hydraulic diameter does not need to take place
but could rather be more gradual having adj acent tubes in successive passes having
tube hydraulic diameters slightly increased over the previous pass up to a maximum
hydraulic diameter in the sub-cool section. Therefore whilst condensers have been
shown having only tube configurations of two alternative hydraulic diameters (the
largest hydraulic diameter being in the sub-cool section 10), it is envisaged that
multiple tubes of increasing hydraulic diameter towards the outlet end of the condenser
could be provided.
[0027] Additionally, where tubes of differing depth dimension h are provided through the
condenser then the respective tube plates of condenser headers 2, 3 will require to
be provided with receiving apertures of appropriate receiving dimensions.
1. A condenser comprising a first heat transfer tube arrangement in a relatively upstream
portion of the condenser, and a second heat transfer tube arrangement relatively downstream
of the first tube arrangement, wherein the hydraulic diameter of the first tube arrangement
is different to the hydraulic diameter of the second tube arrangement.
2. A condenser according to claim 1, wherein:
i) the hydraulic diameter of the second tube arrangement is greater than the hydraulic
diameter of the first tube arrangement; and/or
ii) the second tube arrangement is in the sub cooled region of the condenser.
3. A condenser according to claim 1 or claim 2, wherein the second tube arrangement is
in the sub cooled region ofthe condenser and also immediately upstream ofthe sub cooled
region of the condenser, preferably wherein a receiver dryer is positioned flowise
between the sub cooled region of the condenser and the immediately upstream tube arrangement.
4. A condenser according to any preceding claim, wherein:
i) the external depth dimension of tubes in the first and second tube arrangements
is substantially the same; or
ii) the external depth dimension of tubes in the first and second tube arrangements
is substantially different; and/or
iii) the hydraulic diameter of the second tube arrangement is greater than the hydraulic
diameter of the first tube arrangement, and the external depth dimension of the second
tube arrangement is substantially greater than that of the first tube arrangement;
and/or
iv) the spacing between adjacent tubes in the first tube arrangement is substantially
the same as the spacing between adj acent tubes in the second tube arrangement; and/or
v) the spacing between adjacent tube major axes in the first tube arrangement is different
to the spacing between adjacent tube major axes in the second tube arrangement; and/or
vi) the hydraulic diameter of the tubes of the second tube arrangement is substantially
at or above 1.3 times the hydraulic diameter of the tubes of the second arrangement.
5. A condenser according to any preceding claim, wherein:
i) the hydraulic diameter of the tubes of the second tube arrangement is substantially
at or above 1.5 times the hydraulic diameter of the tubes of the first arrangement,
preferably wherein the hydraulic diameter of the tubes of the second tube arrangement
is substantially at or above 1.7 times the hydraulic diameter of the tubes of the
first arrangement, more preferably wherein the hydraulic diameter of the tubes of
the second tube arrangement is substantially at or above 2 times the hydraulic diameter
of the tubes of the first arrangement; and/or
ii) the hydraulic diameter of the tubes of the second arrangement is substantially
in the range 0.8mm to 3mm, preferably substantially in the range 1.2mm to 3mm; more
preferably substantially in the range 1.4mm to 3mm, preferably substantially in the
range 1.7mm to 3mm.
6. A condenser according to any preceding claim, wherein respective tubes of the second
arrangement each include a plurality of channels extending in the longitudinal direction
of the tube.
7. A condenser according to claim 6, wherein between 2 and 6 channels are provided, preferably
wherein 4 or 5 channels are provided.
8. A condenser according to any preceding claim, wherein respective tubes of the first
arrangement each include a plurality of channels extending in the longitudinal direction
of the tube, preferably wherein 10 or more channels are provided.
9. A condenser according to any preceding claim, wherein the first and second tube arrangements
comprise extruded tubes.
10. A condenser according to any preceding claim, wherein the first and second tube arrangements
comprise aluminium material tubes.