CA1269363A - Spiral corrugated corrosion resistant heat exchanger - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

A heat exchanger is formed of a Pair of concentrically arranged cylindrical shells. closed at each end to define a chamber through which water can pass. A combustion element extends into the inner shell from one end alone the axis thereof and is connected to a source of heat such as a gas/air mixture which ignites in the combustion element causing the radiation of heat outwardly from the combustion element. The inner shell is formed of a corrugated wall which may be formed as a single corrugation comprising a continuous helix alone the length thereof or a plurality of undulations extending along the length of the cylinder.

Description

~t;93~:i3 BACKGROUND OF THE IMVENTION

The Present inventian relates to an radiant heated-water boiler and in Particular to an imProved heat exchan~er therefor.

In Prior. U.S~ 4.442,799. of which the Prsent aPPlicant is a co-inventor. a radiant heated-water boiler is disclosed havin~
a heat exchaneer comPrisin~ a cYlindrical shell- in which a ~35 fired combustion element is concentricallY disPosed. The combustion element is connected to a heat source. such as a ~as/air mixture. which ienites the combustion element. the ienited ~ases Passin~ throu~h the element into the surroundine hollow shell. DisPosed at a clearance Position. about the combustion element is a helicallY coiled tube. throueh which water isPumPedi which water thus absorbs the heat ~rom the combustion element.

~ hile this construction is hiehlY effective and more efficient than those heat exchanee arran~ements PreviouslY known.
several disadvantaees have become known. For examPie, the use of a helicallY coiled tube increases the cost of the heat exchan~er due to its comPlexitY. labor intensiveness. and cost of basic raw material. such as the coPPer needed for the tube~ In addition, the exchanee of heat is based solelY on radiation and convQction imPin~inP on the tube to heat the water in the tube. Further.
onlY a limited throueh-Put of water is Possible. since the water had to Pass seriailY throueh the sPiral tube.

~93~3 It is an obJect of the PresQnt invention to Provide a heat exchanPer for use in a radiant heated-water boiler which i5 simPler in construction than those known heretofnr and which Provides imProved efficiencY in oPeration~

It is a Particular obJect of the Present invention to Provide a heat exchaneer for use in radiant heated-water boilers in which heat transfer is effective bY conduction as well as bY convection.

These obiects as well as other obJects- features and advantaees will be more fullY aPPreciated from the followin~
disclosure of the PresentlY Preferred but nevertheless illustrated embodiments.

SUMMARY OF THE INVENTIûN
. ~ ~

AccordinP to the Present invention- a radiant heated-water boiler is Provided havind a heat exchan~er formed of a Pair of concentricallY arranPed cYlindrical shells- closed at each end to define therebetween a chamber for holdine a fluid. An inlet to the chamber extends throu~h the outer shell at one end and an outlet therefrom at the other end. A combustion element extends into the inner shell from one end alon~ the axis thereof and is connected to a source of heat such as a ~as~air mixture which i~nites in the combustion element causine the radiation of heat outwardlY from the combustion element. The inner shell is formed of a corru~ated wall. PreferablY the wall maY be formed as a sin~le corruPation comPrisind a continuous helix alon~ the len th thereof. havin~ one end of the hetix in communication with the inlet and the other end of the helix in communication with the outl~t. In another form. the corru~ations can be accordion-like.

33~3 w~th the undulations eoine about the PeriPherY of the shell with the ~rooves and rid~es extendine the leneth of the shell.

PreferablY the heat exchaneer is Provided with a ~as cooline or exhaust element in the form of a Plu~ arran~ed alone the central axis ln oPPosition to the combustion element. The exhaust element maY he ceramic. in which case. the inner tiP will elow and further enhance radiation while at the same time rePulatin~ the Passaee of the exhaust ~ases. The Plu~ maY also be made of metai.

Full details of the Present invention are set forth in the followine descriPtion and illustrated in the accomPanYine drawine.

~RIEF DESCRIPTION OF THE DRA~ING

In the Drawine, FIG. 1 is a Partial section throueh the leneth of the heat exchan~er embodYinP the Present invention;

FIG. 2 is a transverse section throueh the heat exchan~er taken alone line 2-2 of FIG. 1;

FIG, 3 is an eniareed Portion of the helical corrueated inner shell; and FIG, 4 is a view similar to that of FIG. 3 showine another form of the invention.

.

1;2~9~3 DESCRIPTION OF THE INVENTION

As seen in FIGS. 1 and 2. the heat exchan~er EenerallY
dePicted bY numberal 10. comPrises an outer cYlindrical shell 12 and an inner cYlindrlcal shell 14, concentricallY sPaced from each other. The uPPer end of the inner shell 14 is flared outwardlY to form a radial ~lan~e 16 adaPted to overlaY a corresPondin~ flaneed end 18 of the outer shell. Secured to the flanee 18 of the)outer shell is a caP 20 which holds the inner shell 14 in a fixed Position. The lower end of the inner shell comPrises a smooth cYlindrical footin~ 22 which is force fit with an O-rin~ seal 24 seated in an annular ~roove 26 formed in a radiallY inwardlY
dlrected flan~e 28 at the lower most end of the outer sheli 12.
In this manner. the inner shell 14 is sealed at its lower end bY
the O-r1ne 24. and at its uPPer end bY the caP 20- so that it extends eoncentricallY within the outer shell 12. definine therewith a closed annular chamber 30 alone its entire lenzth, in which water to be heated maY be located.

An inlet 32 is ProYided for cooled water Passes throu~h the outer shell 12 adJacent its lowær end and an outlet 34 for heated-~ater Passes adjacent its uPper end.

The Present invention differs from the Pr10r device in Providin~ a double shell heat exchaneer. the inner shell bein~

formed of a sinPle metallic cYlinder- which as will be described has a distinctive confi~uration. As seen in the FIGS. 1-3. the inner shell 14 comPrises a sin~le wall 4Z in which a sinZl2 corrueation~ accordion-like alone the lon~itudinai axis- and consistin~ of a continuous helix from one end to the other is form~d. Thus. both the outer and inner surfaces of the wall 42 in lon~itudinal section have continuous undulations; the outer sur~ace helix 44 beine comPletelY in contact with the water in the chamber 30; the inner surface helix 46 bein~ comPletelY oPen for imPineement of the incendiarY ~as and its radiation B~
ConcomitantlYI the outer helix 44 Provides an uPward helicallY
Path F for the water flow. with a ione dwellin time in the chamher. while the inner helix 46 simultaneouslY Provides a helical counter-current downward Path G for the exhaust Pases.

A Porous combustion element 36 is aPProPriatelY mounted in a central clearance Position within the inner shell and communicates throu h a suPPIY duct 38 PasSin~ throu~h the caP 22 with a source of combustible ~as. which is forced under Pressure. arrow A into the combustion element 36 and throueh the PorositY of its wall construction so that it radiates radiallY therefrom as noted bY
the arrows individuallY and collectivelY desi~nated B.

As understood- and as described in detail in the referred-to U.S. Patent No. 4.442.799. the oPeration of the combustion element 36 contemPlates isnitine the combustion ~ases with the result that at- or near. the PeriPherY of the surface of element 36 there is the referred-to combustion reaction that is manifested bY
incandescence. As a result. the radiallY flowin~ exhaust ~ases B
are at an elevated temPerature with which it is hi~hlY desirable to effectuate a heat transfer to a flowin~ heat exchanee fluid, such as water.

To the above end. the heat exchan~er 10 also includes a source of water that is PumPed throuOh a PiPe or conduit ~not shown~ into the inlet 32 such that a continuous stream of water exit-~ throu~h -the outlet 34 after a sufficient Period of dwellin~

~9~3~

time within the chamber 30 such that its temPQrature is si~nificantlY elevated as comPared with the temPeratUre at which lt entered.

.
A Plu~ 40. made of ceramic Porous material is forced. fitted or otherwise mounted tiehtlY within the inner shell at the lower or remote end from the combustion element. so as to Prevent the raPid escaPe of the incendiarY exhaust ases from the inner shell 14.
The Plue 40 on the other`hand reeulates the escaPe of the oas.
while at the same time actin~ to cool the eas Prior to its escaPe.
In cooline the incendiarY ~as. the Plue 4~- itself becomes hot and elOws. at its tlP. addin~ to the heat within the inner ShQ ! I . The ~as is cooled as it Passes around the Plue 40 and exits throuPh the oPen lower end 22 of the inner shell- as seen bY arrow E.

Althouoh the structure described is different from that described in mY earlier mentioned Patent. the basic oPeration of the heat exchanoer is similar so that further details of the combustion element. Plue. and water flow will be aPParent to those skilled in this art.

As has alreadY been noted. the Present invention differs from the Prior device in Providine a double shell heat exchan~er. the inner shell bein~ formed of a sinole metallic cYlinder. which as described has a distinctive confi~uration. As seen in FIGS. 1-3, it will be reco~nized that durin~ oPeratiOn the fluid flow rate is such that the entire chamber 30 formed between the inner and outer shells is filled with the fluidi Passin in contact with the outer surface of the helicallY corruoated inner shell. effectin~ heat conduction. with the entire surface. SimultaneouslY~ the inner surfa~e of the corrueated inner shell Provides an enlare2d area ~ , 3~3 aeainst which the radiant heat maY imPinde. As a result the entire bodY of water in the chanber 30 is subJect to heat transfer at all times.

Amone other nsteworthY advantaPes obtained bY the Present invention are the followine: The construction oF the heat exchan~er has been simPlified bY the use of a relativelY lar~e dlmensioned inner shell rather than the small diameter helical tube; the surface adJacent to the radiant combustion element has been increased si~nificantlY due to the accordion-like corruPated surface and therefore more radiant heat is transferred to the fluid bein~ heated. and similarlY. the surface a~ainst which the water resides is also increased bY the accordion-like structure~
heat transfer occurs due to both convection and conduction and the transfer is more direct because the water surfaces are corresPondin~lY in direct contact with the heatino media; durine oPeration~ there is turbulent helical flow of the radiant and exhaust ~ases which increases heat transfer. as seen in FIG. 2 where it is clear that the water helix sPirals radiallY in one direction while the eas helix sPirals radiallY in the other direction. so that the water and ~as in adJavent axial laYers is in constant movement with resPect to each other; the fluid to be heated takes a helical flow Pattern and is thus turbulent, therebY
reducin~ the effect of the insulatin~ boundarY laYer ~enerallY
caused in smooth helical tubes. and Provides a hi~her heat transfer; and heat transfer is also enhanced bY the fluid flow counter to the radiant heat and exhaust ~ases.

The advanta~es enumerated above are in laree measure obtained because of the increased surface sPace for both water and eas contact, Providin~ an increased dwell time under conditions of heat transfer. while simultaneouslY Providine means for directine the flow of liquid and incendiarY ~as in counterflow direction. Such an advantaee can also be obtained bY constructinP
the inner shell so that the accordion-like corrueations run eenerallY loneitudinal. This form is seen in FIG. 4. whPre similar Parts bear similar reference numerals.

In FIG. 4. the inner shell 50 is Provided with Parallel corrueations circumferential about the entire shell. Each corruPation`has an outwardly oPen-inner directed undulation 529 of narrow trianeular shaPe. and a eenerallY rectaneular undulation 54 which is inwardlY oPen but outwardlY directed. The narrow trianeular undulàtion forms with the outer shell 12'. the water chamher 30~ while the rectan~ular undulation faces the combustion element and forms the wall of the heat chamber. The trian~ular and rectaneular shaPes of the undulations 52 and 54 resPectivelY
have been chosen for convenience. since such shaPes Permit the formation of the corrueations in a flat sheet which can then be bent to form the cYlindrical shell. without distortion. Other forms o~ the undulations can be emPloYed. In addition. a slieht heiical curve can be eivQn the undulations from toP to bottom if desired, so that the li~uid and eas flow somewhat sPirallY about the central axis.

In anY event. the desired increase in surface area for heat exchanPe and directional flow is obtained bY the embodiment shown in FIG. 4.

PreferablY~ the heat exchaneer is comPleted bY enclosine the oute~r shell with a laYer of insulation abuttin thQ outer surface 1~6~363 of the outer shell 12. A surroundin~ decorative housine. not shown. maY be Provided.

A latitude of modification. chan~e and substitution is intended in the forePoinP disclosure. and in so~e instances some features of the invention will be emPloYed without a corresPondin~
use of other features. Accordin~lY. it is aPPnoPriate that the aPPended claims be construed broadlY and in a manner consistent with the sPirit and scoPe of the invention herein.

Claims

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

1. A heat exchanger for a radiant heated water boiler comprising a pair of concentrically arranged cylindrical shells, each formed of a single continuous helix extending from one end thereof to the other and closed at each end to define therebetween a chamber for holding water, an inlet for the supply of water to said chamber extending through the outer shell at one end and an outlet for the discharge of water therefrom at the other end, a combustion element extending into the inner shell from said other end providing a source of heat radiating outwardly therefrom against the inner shell, said inner shell being formed of a corrugated wall, said helix being formed with an angular orientation so that the water in said chamber is caused to flow therein in an upward direction and said radiated source of heat is caused to flow downwardly along the interior surface of said inner shell, and a porous plug arranged in the one end of said inner shell to regulate the exhaust of said heat source therethrough.