Note: Descriptions are shown in the official language in which they were submitted.
The present invention relates to a heat exchanger having a main
tube surrounded by water from wllicll heat is to be transferred to a
suitable heat exchanging liquid medium circulating in the main tube,
: By extraction of energy, i.e. heat, :Erom sea water by means of
a heat pump system freezing often occurs of the portion of the system
that extracts the energy from the water. Since the temperature of the
water of seas and other water courses during freezing weather is
quite Low (+1.8 C at the depth of 40 meters approxlmately l meter
~ above the bottom of Lake StorsjQn, Sweden) there is~quite low differ-
; 10` ence in temperature available down to 0 C. This necessitates a cir-
culation of large quantities of the heat exchanging medium in order
to extract a certain energy quantity. Hitherto, any reduction of the
amount of circulating heat exchanging medium has requlred a greater
difference in temperature to accomplish a reduction;of the risk of
freezing of that part of the system which extracts energy.
is therefore a primary object of this~invention to provide
a heat exchanger of the kind where any risk of ~reezing is substan-
tially reduced without utiLizing any increased quantity of heat
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exchangLn~g medium. ~ ~ ~
~ ~ ~Another ob~ect of the present invention is tQ provide a heat
excbanger enabllng the use of inexpenslve tubes, such as plastic
tubes, for instance.~
A Eurther object of the invention is to provide a heat ex-
; changer in the form of a system having an antifreeze llquid~circula-
ting in a closed tube system which can be~placed~directly lnto the
~ sea.
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According to a broad aspect af the present invention, there is
provided a heat exchanger having a tube system containing a circulating heat
exchanging medium having a temperature below the freezing point of water, a
main tube surrounded by water and connected to said tube system, said main
tube including several interior secondary tubes having less diameter than
said main tube and different diameters relative to one another, said secondary
t~bes being arranged substantially concentrically relative to said main tube
and relative to one another to form several annular spaces within said main
tube, means for directing said heat exchanging medium from said tube system
to an innermost one of sai.d secondary tubes and successively through each
of said annular spaces to an outermost one of said annular spaces and back
to said tube system, such that the temperature of said heat exchanging
medium gradually rises to a temperature above the freezing point of water
when flowing through said annular spaces.
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Further objects and advantages of the present invention will
become apparent from the following detailed description of the inven-
tion when taken in conjunction with the accompanying drawing wherein
like reference numerals designate like elements throughout the two
views, and wherein
FIGUR~ 1 is a schematic view of a heat exchanging system,
having one ore more heat exchangers in accordance with the present
invention.
FIGURE 2 is a longitudinal sectional view of a heat exchanger
in accordance with the present invention.
In FIGURR 1 reference numeral 1 denotes a device including a
` circulation pump of known type for circulating a heat exchanging medi-
um under pressure through a tube system 2 disposed on or adjacent the
bottom of a sea. The heat exchanging medium may be an~antifreeze
liquid solution of known type and capable of extracting heat from the
w~ter surrounding the tube system 2. The;device 1 also includes heat
extracting means for extracting heat from the heat exchanging medium.
Such heat extracting means may include tubes which receive the heated
antifreeze liquid and which tubes may be embedded in a paved area
such as a driveway, aircraft runway, and the like~to preclude the
formation of ice thereon. In some cases where the temperature of the
heated antifreeze medium is insufficiently low, the device I may also
include a conventional heat pump for further~ ralsing the temperature
of the antifreeze medlum. Since all components incorporated in the
device are well-known to tllose skilled in the art, and since such
compoDents do not constitute part of the present invention, it is not
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deemecl necessary to show or describe them in detail.
In thc embodiment clescribecl, an exemplary temperature of the
water of the sea may he approximately +2 C, whereas an exemplary-
temperature of the antifreeY.e liquid may be approximately -4 C.
The tube system 2 inc:Ludes two parallel tubes 3 and 4. Connec-
ted between the tubes 3 and 4 is one or several heat exchanging tubes
5, below mentioned as "main tubes". The antifreeze liquied medium is
suppl.ied under pressure through the tube 3 and then through the tubes
5 in the direction of the arrows shown in FIGURE 1. In this way, heat
is extracted by the liquid meclium from the surrounding water such
that the temperature of the liquid medium is raised to appro~imately
~l C when the liquid medium enters the tube 4.
One oE the main tubes shown in FIGURE 1 is illustrated in more
detai.l in FI~RE 2. The main tube 5 has one end sealingly attached to
an annular flange 6 on the wall of the tube 3 and the other end
sealingl.y attached to an an~ular collar flange 7 which is formed
arouDd the edge of a circular opening 8 formed in the wall of the
tube 4.
The:main tube 5 includes four internal secondary tubes 9 to 12,
each disposed substantially concentricall.y withln the tube 5 and sub-
stantially concentrically relative to one another. The wall of the
,
tube 3 is provldecl with a circular opening 13, the edge of which has
a collar flange 14 to which the r.ube 9 is sealingly attached.
The tube 10 is by means of spacing elements~ 15 attached con-
centrically around the tube 9 at some distance from the wall of the
tube 3. The free end of the tube 9 terminates at some distance from
the adjacent end of the tube 10 which end is closed by an end wall 16.
The tube 11 is sealingly secured to an annular flange 17 on the
tube 3. The tube 12 is by means of spacing elements 18 secured concen-
trically around the tube ll at some distance from the wall of the
S tube 3. rrhe end of the tube 12 that faces the tube 4 is closed by an
end wall 19 which is located at some distance from the free end of the
tube 11.
In operation, when tl~e liquid medium enters thé tube 9 through
the opening 13 of the tube 3 it flows through the tube 9 and then in
succession through all of the annular spaces between the tubes 9 to
12 and 5, as is shown by arrows in FIGURE 2. In this way, a control-
led temperature gradient is attained from the contact area between
the water and the heat extracting surface of the heat exchanger to
~; the coldest portion oE the heat extracting medium, thereby effecti-
vely preventing a Ereezing of the outer surface of the wall 5, which
i~s in contact with the water. ~ameLy, when the antifreeze liquid
reaches tlle space between the tubes 5 and 13, its temperature has
; ~ raised to approximately +l C, i.e. to a temperature above the
freezing point of the surrounding sea water.
The tubes 9 to 12 are suitably thin-walled ine~xpensive
plastic tubes. Only the tube 5 has to be diffusion-tight.
By suitably dimensioning the relative values of the zones A
:
and B in FIGURE 2, and suitai)ly dimensioning the tubes and the number
thereof, a desired output temperature of the liquid medium can be
achieved.
While a preferrecl embodiment of the present inventlon has been
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i]lustrated and described, it wi]l be obvious to those skilled in the
art tilat change6 and Illodificatiolls may be made therein without depar-
ting Erom the inven~ic)ll an~ its broader aspects. Various features of
the invention are defined in tile following claim.
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