CA1098510A

CA1098510A - Heat exchanger

Info

Publication number: CA1098510A
Application number: CA327,276A
Authority: CA
Inventors: Erik L. Backlund
Original assignee: Foerenade Fabriksverken AB
Current assignee: Foerenade Fabriksverken AB
Priority date: 1978-05-09
Filing date: 1979-05-09
Publication date: 1981-03-31
Also published as: DK147583C; NO791524L; FI66248B; NO145590C; FI66248C; FI791471A; DK192279A; DK147583B; NO145590B; SE422623B

Abstract

ABSTRACT
Heat exchanger having a main tube surrounded by water from which heat is transferred to a heat exchanging medium flowing through the main tube. The main tube has several interior secondary tubes forming annular spaces through which the heat exchanging medium flows from a innermost one of the secondary tubes through all the annular spaces to an outermost one of the annular spaces, such that the tem-perature of the heat exchanging medium gradually raises in order to avoid freezing of the water contacting the main tube.

Description

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 ~: : : : : : :
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

-3-:' ' 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
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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 , s~

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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Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. 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 dia-meter than said main tube and different diameters relative to one another, said secondary tubes 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 said 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.