Note: Descriptions are shown in the official language in which they were submitted.
Descriotion
eat Exchan~er
Technical Field
The present in~ention relates to the heating or
cooling of fluids (liquids or gases) efficientl~ and
rapidly and, in particular, to a heat exchanger suit-
- able for various uses, such as heating water or gen- -
erating steam for general use or for space h~ating.
Backqround Art
In most cases i~ which a fluid is being h~ate-d
or cooled i~ is kept physically separa~e frol~ the
mediu~ that is supplying heat to it or receiving he~t
from it by confinement within a vessel or condui~. ?
Like~ise, the msdium supplying heat to or receivin~
heat from the fluid is also usually confined to the
vessel or-conduitO The vessels cr conduits or both
constitute a heat èxchan~er.
M~st heat exchansers use a tube or a sys~em OL
tu~es as the ~arrier between the rluid ~ein~ heats~
or ?~oled ar.d the heating or cooling mediu.~. Ofte.
it is necessaryt in order to maximize the erflcienc~
of the heat transfer, to provide a co~pLica~ed sy~em
of baffles and tu~s and to ~mploY t~.~b~s that a~e
constructed to enhar.ce the rate o~ heat trf1nsfe~, for
example, by inclusicn of rib3, ins, corrugatlons or
the like. For durability falxly cos~.ly metals, .sucn
as copper, are often used~ The comple~it~ o the
structure ~nd t~e high cost CL t~e matQrial~ r~a~e
eFf iciQr.~; long~l~sting heat exchangers very e~Ypensiv
~any d~vices that are in wiâespr~ad use and
emplov h~a~ exchallge~ ha~e reiativel~ io~ ~rficlen-
- cies. ~or example, residential furnaces an~ hot Wat'r
heaters fueled ~y na~ural gas ~r oil have o~erall
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efficiencies of only a~out S0%. ~atural gas and oil
fired equipmeRt could be made con~ider~bly mor~ ef~i-
cient u~ing presently available technology in th~
design of he2t exchanger~, but only by conqid~rably
5 increa~ing the complex~ty and th~ 8iZ~ O~ th~ equlp~
ment and rnaking it much more costly.
There is prov ided, in accordanc~ with the peesenJc
lnventionf a heat exchanger tha~ i5 o ~ry simple
lû con~truction and that can, therefore, be manufactursd
at relatively low cost. I~ ::an also p~ovlde a su~s~can
tial improveA~ent in efficiency withou~ substantially
increasing the cost, particularly when compared ~h
pre~ently known hea'c exchanger~.,
A heat exchanger according to the invention has a
closed vessel defined by thermally conducting external
walls and heat source within the vessel in spaced
relation from the external walls. The vessel. contains
helium gas at an initial filling pressure at ambient
temperature of not less than 200 kPa, the helium gas
being the sole medium for transfer of heat from the
heat source to the thermally conducting external wallsO
In o~ form the vessel of th~ h~at exchang~r i~
tubular in ~hat it has external and int~rnal ~hermalîy
25 conducting walls. Either ~he internal or ~xternal
wall is the heat transf~r mediusl~ between the fluid
belng hea.ed or cooled and the helium gas a~d the
other is a heat, transf~r medium betwe~n th~ ~ourc~ of
heat or cold and the heliu~ gas. For example~ the
30 internal wall may serve as a conduit through which a
flowin~ fluid ~ource o~ heat i~ conducted and by which
heat is tran~ferred to the helium ~n th~ vessel.
~ n another ~orm o~ the presen~ vention the
helium filled vessel is at least partly received
35 withln a container. P~ fluid to or ~rola which hea~ i~
~o be transferred is supplled t!lrough one or ;nor~
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inlets into the container and, having been hea-ted, is
renoved from one or more outlets remote from the inle~
or inlets.
In one embodiment of the present invention the
vessel is tubular and includes an internal wall defin-
in~ a condui~ that is adapted 'o receive a flow of a
hot fluid to be cooledv The external wall of the
vessel is surrounded by a container wall, -thus provid-
ing a passage for flow of a fluid to which heat is tG
be ~ransferred~ In this embodiment both the intern~1
and external walls o~ the ves~el containing the helium
participate in the heat tran~er between the two fluids.
Such a heat exchanger is especially useful in equip~
ment in which it is desirable for safety reasons to
have a double wall barrier bet-~een the two flui~.~s.
hazardous fluid flowing within the intern~3. c~nduit
of the vessel is contained by the outer wall of the
vessel if the i~ner wall should rupture.
- The invention may incorporate one or more of the
~ollowing additional features. T~7here ~he heat ex~han-
ger vessel i5 of the tubular ~orm and is employed to
tran~fer heat bet~een a fluid fiowing wit~ln the inter-
nal wall (or conduit) and a fluid flowins along the
external wall, the two fluids flow in opposite direc-
tions. The conduit of the ~7essel may have flutesextending inwardly and lengthwise to enhance ~he hea~
flux bet~een ~all and the fluid flowlng along ~he
wall. The vessel may have transverse dividers d~fin-
ing a multiplicity of se~arate adjacen~ compartments
to prevent eirculation of the helium along the length
of the heat exchanger and thereb~ pro~o~e a larger
temperature gradient along the iength.
One important advantage of ~he inv2ntion is ~hat
~h~ h~l'um ga~ ln th~ ves~oi providas a coi~paxati~eL~
high rate of heat transfer~ ~elium has, a~ong all
ga~es, a very high coefficient of thermal condu~tivity.
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Accordingly, heat is transferred very rapidly to the
walls OL the vessel and thence through ~he walls ln~o
the fluid medium to which the heat is being transferred.
A hea~ exchanger according to the invention makes
it possible to transfer heat ~rom a very high tempera-
ture source acting over a fairly small area to a la~ge
heat transfer area, namely the external walls OL the
helium containing vessel. The temperature o~ the
vessel walls from which the heat is transferred to
the fluid to be heated is substantially less than tne
temperature o~ the source and, indeed, can be designed
for optimum heat transfer conditions between the Yes-
sel walls and the fluid. For example, effe~tive hea~
~ransfer to liquid is best accomplished under tempera-
lS ture conditions under which film boiling doe~ no~occur. The inherent abili~y of the present inven~ion
to transfer heat from a high tem~erature con~entrated
qource to a relatively lower temperature ~arrier wall
of large area with inexpensive equipment ls an impor- -
tant advantage.
Helium is ~Tery light in weight. Whi~e lt i5
possible with metals and some li~uids to ~rovide a
heat transfer between a concentrated high temperature
area and a large surf~ce a.ea the equi~ment envolved
is heavy and expensive. ~he simple construction and
the Light weight of heat exchang-rs em~odying ~he
present invention facilitate the manufacture and
installation of e~uipmen~ utilizing the inven!cion.
The invention has nu~.erous uses in both consumer
30 products and industrial products, pa.ticularly for
hea~ e~change between fluids at greatly different
temperatures, in applications where two or more
barriers between the two fluids are re~uired or
~eslra~le ~a ~ ere lt is _~slrab'e ~;o .~a~e minimum
storage capacity. A particularly important use of a
heat e~changer emDodying the present i~vention is i~
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water heatin~ or steam generating for general use and
for spac~ heating for individual residences, apartments,
hotels, motels and o~fice and institutional buildings.
~ot water heaters utilizing ~he heat exchanger of the
S invention are economical to make and easy to install
and make possible the use of comparatively small units
located close to the place where the hot water will
be used. Both capital investment and operating costs
can-be saved by locating small water heaters in various
places in a building, ~hereby eliminating expensive
long distribution systems and th~ heat losses that
occur in such systems.
For a better understanding of the inventlon
reference may be mad~ to the following descrlption of
an exemplary embodi~ent ta~en in conjunction s~ith the
figures oE the accompanying drawings.
Brief DescriDtion of ~he Drawings
- Fiq. 1 is a schematic diagram illustrating the
principle of opera~ion of a heat exchan~er embodyin~
the present invention, as applied to a vPry sim~le
electric 'neater;
Fig. 2 is another schematic diagram depictin~ in
a generaiized way a heat exchanger according to ~he
present invention for trans~erring heat from a ho~
fluid to a cold fluid;
Fig. 3 is a side cro s-sectional view of a ver~
simple and inexpensive heat exchanger or pre coo3.ins
a hot re~rigerant in a refriger~tion syste~;
Fig. 4 is a side cross-sectional vie~.~ or an
~ 30 electric ~ater heater embodving a he2t exchanger in
: accordance with the present invention;
Fig, 5 is a side cross~sectional view o~ a qas~
f ired hv~ wa-~er ~lPa~er 4na~ employs a neat e~changer
according to the present inven~ion; and
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Fiq. o ls a fragmentary cross~sectional view of
the internal wall of ~he heat exchanger shown in
- ~ig. 5~
Modes for CarrYinq Out the Invent on
A very simple form of a heat e~changer embodying
the present invention, ~s shown diagramatically in
Fig. 1, is a small electrically energized space heater.
It comprises a closed vessel V that is filled with
helium gas, preferably ai an absolute p~essure of
about 200kPa to about 700kPa t~ilopaScal). Although
the vessel may be of a~y shape, it is desirable tO
make it o~ circular cylindrical shape for ease of
manufacture and uniform heat transfer in all ~irec-
tions radially with respect to the cen~ral axi~.
Thus, the vessel V show~ i~ Fig. 1 comprises a cir-
cular cylindr ica' external wall and top and bottom
walls. One or more elec~rical heating elements H are
- suitably ~ounted within the vessel. The heating ele- .
- ments may be of very simple low cost con~truction~
for exampla, a ceramic support thound witn a hare
resistance wire heating element. T~e ele~trical
leads are connected ~o a source of _~r~ent.
Upon energiza~lon ~he heatin~ elem-~n~. E re2c:~es
a very high temperature Tl~ The heat is conducted by
the helium gas radi~lly outwardly in all dlre~tion~,
as represented by the arrowed line~ within the vessel.
As mentioned above, helium has a relatively hlgh co-
e~ficient of thecmal ~onductivity, as colr.pared to air
and other gases. Accordingly, the hea~ cf the heating
element is trans~erred qulte r.~idI~v to tne waLls ~L
the vessel V~ In the case of a space heater ambient
air from below tne hea~er at a tem~erature T~ is drawn
o_~w~rdly b~ ~he cor-~:ectl~e flow induc~d by the hot
walls of ~he vessel, as represented by the arrowed
Lines designated T~ i~ Fig. 2~ ~s the a~r curren~
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flows over the ex~ernal wall of the vessel, the air
is heated to a temperature T3 and rises in the direc-
tion represented by the arrows T3. The hot w~lls of
the vessel also radiate heat into the space,
The schematic iLlus~ration in Fig. 1 is represen
tative of the basic principle of operation of all
heat exchangers embodying the present invention. The
helium gas contained in the closed vessel Y accepts
heat.~rom any suitable source.located inte~nally of
the vessel, as represented by the electric heating
element H in Fig. 1. The internal source of heat may
be a hot liquid or gas that is conducted -through one
or more pipes within the vessel or passing completely
through an internal conduit in the vessel. Heat i3
transferred from the source within ~he vessel by the
helium gas to the external walls o the ~essel. ~rh~
vessel may be partly or entirely enclosed within an
outer container C, as represented in Fig. 1 by a cir-
cular cy~ indrical shell having one or more inlets and
outlets spaced apart from one another and defining a
passage P for a flow of a gas or liquid that is to be
heated by the hot walls of the vessel. a.ccordingly,
the invention operates by acceptance by the hellum of
hea~ fxom a source at a temperature Tl, the tr~nsfe~
OL that heat by the helium to the w211s of .ha ~essel
and transfer of the heat through the walls o the
vessel to a fluid ~liquid or aas) rlo~ing in contact
with the walls of the vessel, the temperatu.re of the
fluid being raised from T2 to ~3.
~ig. 2 illustrates ~che~.atically some preferred
characteristics of heat exchangers embod~ins th~
present invention, as applied ~o equipment ~r trans-
ferring heat from a higher temperature liquid or gas
~o a iower e~p~ratur~ liquid or gas. I'he h~iu~ ~a~
~ 35 is contained ~ithin a tubular vess~1 ~hichr a3 men-
: tioned above, may b~ of any suitable ~hape but is
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prerera~ly a clrcular c~linder. For purposes of the
present description, it may be assumed tha~ ~ig~ 2
depicts a vessel V having a circular cylindrical
external ~all EW, a circular cylindrical internal
5 wall rw, and annular top and bottom walls TW and BW.
The vessel shown in Fig. 2 is, m~reover, subdivided
into a multiplicity or individual annular chambers by
separator plates S suitably joined to the internal
and external walls. The s~parator plates ~inimize
convective heat trans~er alo~g the length of the
vessel, thus increasing the end-to-end tPmperature
gradientO Accordingly, it is not necessary to ha-Je a
gas tight connection between the ~lates and the walls
of the vessel.
~ hot Eluid at a temperature Tl is introduced
into and passes through the passage defined bi~ the
internal wall IW of the vessel. Heat is transferred
from the hot fluid to the internal wall. Accordingly,
the fluid leaves the passage at a temperature T2 below
the temperature Tl. The heat accepted by the in~ernal
wall o~ the heat exchanger is transferred radially by
conduction through the heliu~ gas to the external
wall, by con-~ection currents o~ the heliu~. gas and ~y
radiation. A fluid to be heated is su?plied at ~he
cold end of the heat exchanger at a temperature T3,
flows along the external ~all EW of the chamber and
exits the heat exchanger at a higher tem~erature T4.
In ~05t cases the flo~ of the fluid ~o be heated is
confined by a con~ainer C that recei~es part or all
of the helium containing ~Jessel and ~hat is repre-
s~nted in Fig ~ diagramatlcally by a cylln~rlcal
shell.
An important advantage of the invention i~ the
ability to ~ransfer heat from a very high ter,lpera~ure
3s sourc~ to an ou~put heat trans~er surace of large
area. The heat exchanger inhere~tly distribu-tes hea~
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_g_
received over a relatively s~all area from a high
temperature source and distributes the heat over the
large area output surface constituted by the external
walls of the vessel. In making such distribution,
the temperature of the output surface is inherently
substantially reduced from the temperature o the
source, assumLng, of course, that heat is transferred
away from the output surfac~ of the heat exchanger.
- The ability of the heat exchanger to distribute heat
over a large surface is of advantage in applications
of the invention where the cool fluid cannot for one
reason or another be subjected to a high t~mperAture,
such as che~ical degradation or unwanted vaporization.
The heat exchanger can be designed so that the cool
liquid is not exposed to a temperature higher than a
predetPrmined safe vaLue.
An example o~ the usefulness of this char~cter-
istic is the space heater described briefly above. A
-space heater can be de~igned to distribute the heat
input over a large enough area thatr given the heat
transfer characteristics between the surface of ~he
extern~l walls of the vessel and the ~ir, the ex~ernal
walls do not reach a temperature 'nigh enough to be
hazardous. Indeed, the outer surface may be kept
well below the temperature t~at would cause severe
discom~ort to someone who touched the heater,
In the case of most liquids, it is desirable to
avoid film boiling of the liquid a~ the external sur-
~ace of the vessel. A heat exchanger embodyin~ the
present invention can be designed to trans~er hea~ at
below the boiling point or within the range of nucleate
boiling at the surface.
Other advantases o~ the invention are evident
f~om the v~.y Sil~pl~ heat exch~nger showll in Fig. 3
3; of the drawings. A length of pipe 50 defines the
intern~l wall of a tubula~ closed vessel 52 and
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10- ~3~ 7
serves as a passage for Elow o~ a hot liquid. For
example, it is desirable in refrigeration systems to
pre-cool the hot compressed refrigerant, such as ~reon.
In order to make efficient use of the heat content of
the refrigerant, the cold side of the heat exchanger
is potable water used in the building The heat
exchanger in this application is used as a hot water
heater to supply part of or all of the requirements
of the building for hot wat~r. 3uilding codes re~uire .
a double barrier between the r2frigerant and the pot-
able water, so that if the refrigerant conduit of the
heat exchanger ruptured and released refrigerant, a
second barrier will prevent the refrigerant Erom enter-
ing the hot water supply. A heat exch~nger embodying
~5 the present invention meets that requirement.
In particular the tubular vessel 52 provides ~he
required double barrier between the ~efrigerant and
the water by means of the external wall 53 and the
conduit 50. The heat exchanger vessel 52 containing
helium under pressure is closed ~t each end by an
annular end pla~e 54 ~elded at the inner and oute~
diameters to ~he internal and external walls. Sur-
roundlng the heaL~ ~ch~nger vessel 52 is a container
de~ined by a cylindrical ~all 5O and annular end pla~es
58 welded at the inner and outer diameters to the
~alls 50 and 53. r~ater to be heated is supplied ~o
the annular passage defined b~ the container and sur-
rounding the heat exchanger ~re55~1 through an inle~
59, flows through the annular passage, as represented
by the arrowed lines, and exit3 through an outle~ 60.
~eat is transferred from the refrigerant flowing
through the conduit 50 to the helium, the helium
transfers the heat to the external wall 53 and the
~ L~ h~ h~ ex~e~n~
Fig. 4 illustrates the ~se of a heat exchanser
accordLng to the present inv2ntion in an electr~c :~
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heater for heating a fluid. It comprises an outer
container 10 having a circular cylindrical side wall
12, a top wall 14 and a bottom wall 16. A closed
vessel 18, which consists o~ a circular cylindrical
side wall 20, a top wall 22 and the bottom wall 16 of
the container, receives any suitable number of elec-
trical resistance heating elements 24. Each heating
element comprises a ceramlc support and 2 helical
wirlding of conven~ional nicrome wire. Preferably,
- 10 the wires of the heating elements 24 are connected in
series by a sys~em of bus-bars ~not shown), and suit-
able electrical connectors 26 conduct ~lectric current
~o the first element and ~rom the last element in the
series. The use of heating elements connected in
series enables heavier gage nicrome wire ~o be used,
thereby ensuring long liEe, but parallel wired elements
and the possibility of having two or more groups of
series wired elements, with the groups wired in paral-
lel is, of course~- entirely feasible. ParalLel wired
electrical heating elements also present the possibil-
ity o~ providing variable heat output by varying the
number of elem~nts that are switched on at any polnt
in time in response to suitable controls.
It is considered preferable for the con~ainer 10
and vessel 1~ ~o be entirely of wPlded construction
fo~ assurance against leakage, and t~i5 iS the case
with the embodiment shown in the drawing. It is,
nonetheless, envisioned that tne he~ting unit (i.e.,
the vessel 18 with electrical heating ~lements ~4)
can be constructed so that it can be remlove~ from the
container 1~. There are va~ious ways that ~ill be
readily apparent to those skilled in the art a~ a
matter of ordinary engineeriny skill of making the
heating unit remo-~2ble. ~or som~ t~p~s o~ serv ce,
notabl~ those in which deposits build up within ~he
container because of the characteristics of 'he fllli2r
. ~
-12~
the abillty to re~ove the heating unit from the con-
~ainer may also be desirable in order ~o provide access
to the container for thorough cleaning frcm time to
time. ~or service with liquids, it will usually be
5 desirable to provide a valved drain outlet (not shown)
in the bottom of the container.
Fluid to be heated is supplied to the container
10 through an inle~ 26 in th~ top adjacent the outer
wall 12.. A manifold distri~ution sy~tem (not.shown)
10 may be interposed be~ween the inlet and the annular
space between the side wall 12 of the container and
the side ~all 20 of the vessel, or multipl~ inlets
can be provided to distribute the incoming fluid
relatively evenly around the upper part o~ the con~
tainer. The annular space between the walls 12 and
~0 is subdivided into an inlet chamber ~0 and an
ou~let chamber 32 by a circular cyclindrical baf,le
28 ~hat extends nearly the entire distan~e from the
top wall 14, to which it is welded, to the bottom
~0 wall 1~ of the c~ntainer. The fluid enter ing the
inlet 26 is compelled by the ba~fl~ ~8 t~ flow do~n
through the inlet chamber to the ~ottom of the cor.-
tainer and then turn and flow up~ardly through the
ou~let chamber to the top of the container. rrhe then
heated fluid flows radially inwardly toward the axis
of the container and enter~ a o~tlet pipe tha~ extends
vertlcally throllgh the vessel 13 and exits through
the bottom wall 16 o~ ~he container to an outle~ 36.
~he vessel 18 contains helium gas at a suitable
pressure, preferably in the range of from about 20~
KPa to about 700 ~Pa. The vesgel 18 may ~e, ~ut need
not be, evacuated before being charged with heliu~.
The helium atm~sp'nere within the vessel provides ~OL
rapid transf~} 9L heat ron~ the electricai resistance
heating elements 2~ in the vessel to the wall~ o the
~essel 18 and the pipe 34.
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~ 3 ~ r~
As ~he ~luid entering the inlet 26 flows down
throug~ ~he inlet chamber 30 betwe~n the baffle 28
and the wall 12 of the container it is gradually
preheated, inasmuch as the fluid flowing up thxough
outlet chamber 3Z ~lows in direct contact with the
hot outer wall 20 of the vessel and transfers some of
the heat it receives from the vessel wall out to the
baf~le which, in turn, trans~ers it to the fluid flo~-
ing through the.inlet chamber. The fluid flowing up
10 along the hot outer wall 20 of the vessel is rapidly
heated in the relatively thin channel defined bet~een
the wall 20 and the baf fle 28 . The wall 20 provides
a very large surface area to which heat is trans-
ferred from a suitable number of heating elements 24
within the vessel very rapidly by the helium atmos-
phere. Thus, ~he heater is ideally suited for 5ub~
stantially instantaneous heating of a fluid. Heat
losses from the heater are kept to a minimum, because
the incoming fluid provides an insulating barrier.
Inasmuch as heat transfer is a function of the dif-
ference in the temperatures on opposite sides o a
barriar, the loss of heat through the outer wall 12
is '~ept low because the incoming ~luid i~ only slightly
heated, as compared to the much higher temperature of
2~ the ~luid flowing through the ou~let cham~er. This
natural barrler of the incoming fluid in the chamber
30 contri~utes to the high efficiency of the unit.
It is pre~erable for the outlet chamber to be
very thin in order to promote turbulant flow of the
fluid, and ihe turbulence ~nd the surface area ~ay ~e
increased by providing a corrugated ou~e.r wall on the
vessel, or ~y providin~ fin~ or other devices for
promoting turbu'ence.
~pon. -2~chin the ~op ~ the out~et cha~er 32,
the fluid flows inwardly across the ~op of the vesselr
~here it receives`additional heat, and ~hen passes
-14~
through the outlet pipe 34, again receiving heat from
the wall of the pipe to which heat is rapidly and
eff2ctively transferred ~y the helium atmosphere within
the ~essel.
The heating elements 24 may be controlled by any
suitable thermostatic control sy~tem, preferably on~
which ~.easures temperature of the incoming fluid near
the inlet by means oE a thermo-couple 38, measuxes
the t~mperature o~ the fluid af~er it has been sub-
stantialLy heated, such as by a thermo-couple 40, and
turns the elements 24 on and off in accordance with
some integrated value that takes into account both
incoming and outgoing temperatures. Many such systems
are known in the art and are shown schematic~lly in
the drawing by means of the block 42 labelled "con-
troller." The abili~y of the helium at~osphere
within the vessel tQ transfer heat rapidly to the
walls along which the fluid passes and by which the
fluid is heated improves the response-rate of the
control system.
~he embodiment lllustrated in the dra~inq i3 an
instantaneous type unit, inasmu~h as it has ~irtually
no storage capacity. It can be controlled to maintain
the temperature of the fluid in the region of the
ther.~o~couplQ 40 somewh2t heated b~t not heat~d to
~he output Se~perature. When fluld is demanded from
the outlet 36, the .hermo~couple 38 detects a dr~p in
temperature and the controller 42 s~itches on the
heating elements 24. In a matter of a ~ew seconds
the helium atmosphere ~1ithin the vessel begins ~rans~
ferring heat from the heating elements to the wall ~0
and the pipe 3~, and the fluid flowing from the outle-t
becomes rapidly ho~ter until it attains a desired
t~nperature. ~he heating element is Snen controLled
primarily by the thermo-couple 40 to cycle the heating
elements on and off and maintain a fairl~ const2nt
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temperatl1re ~f the fluid cominy from the outl~t 36.
When fluid is no longer drawn from the heater, the
thermo-couple 38 will detect an incr~ase in tempera-
ture indicative of the fact that cold fluid is no
longer entering through the inlet 26, and such indica-
tion is processed in the con~roller 42 and shuts off
the heating elements.
The embodiment o Fig. 4 is applicable to storage
. . type liquid heating equipment/ which e~uipment may
incorporate designs known in the prior art insofar as
temperature control, possible recycli~g of fluid from
the container through the heater and similar design
factors. It is also well-suited for heating process
gases, as is a unit having pipes or ducts th~t pass
1~ through the spacQ within the vessel. The side of
wall the vessel mav be corrugated in the longitudinal
direction for greater strength and surface area for a
given overall size and weight.
. Figs. 5 and 6 also illustrate a fluid heater
th~t employs a heat exchanger cons~xuct~d in accor-
dance with the preser.t invention. The he.~ter com-
prises a pul~e-type combustion chamber 101 o~ a type
that is known ,er se. .~ir is injected ~hrough an
inlet 11~ to the cham~e~ 101, and natural gas is
injec~ed through the inlet 11'. An igniter initiates
an explosion of the ruel-gas mixture in the chamber.
The ~orce of the exp~osion drives the hot combustion
products out of the chamber and down through a pas~age
102 defined by the internal wali 120 of a closed ves-
sel 122. The vessel has a circula. cylindrical oute
wall 113 and is s~bdivided into a multiplicity of
annular compartments by plates llO~ The ~-essel can
be assembled by welding the plates 110 to the inner
wall l~ and t~n slidi~lg the outer wall 118 on~o
; 35 the welded inner ~ssembly. If desired, seal~s can be
~ installed between the outer perimeters of the pl~tes
-16- ~ 3 ~
llO and the ou-ter ~all 118, ~hough it i5 probably
unnecessary to do so inasmuch as the purpose of the
plates is only to inhibi~ convective flow o helium
gas within the vessel 122 and thereby increase the
S temperature gradient along the length of the heat
exchanger.
The hot combustion products flow down from the
combustion chamber 101 through the passage 102 in a
state of very high turbulanc~, due to the explosive
force by which they are propelled. To enhance the
heat transfer between the hot combustion produc~s a~d
the internal wall 120, the internal surface oE the
wall 12Q is fluted, as shown in Fig. 6. In addition,
the wa].l l~0 is of fairly large cross~sectional thick-
lS ness so that it acts as a heat sink for heat received
from the hot gases so ~hat heat is stored in the wall
during periods between the combustion pulses. The
ho~ gases of combustion are rapidly cooled as they
~low down through the passage 102 and reach the bottom
at a relati~ely low temperature. Condensate from ~he
combustion process is collected in an exhaust Plen~lm
at the bottom of the hea~er and drains through an
outlet 107, throl~gh a trap (not sho~n) and ther. to a
~aste line~ Exhaust gases e~:it through an ouLle t 105.
2S The vessel 1~2 i~ surrounded on the sides and
top by a container having a cylindrical side wall 113
and an annular top wall 113a. The container defines
with the exterior oE the vessel 122 a thin Passage
114. A fluid to be heated is in.roduced through an
33 inlel lOd to the chamber 114. ~s the fluid flows
upwardly through th~ chamber, it receives hea~ from
the large s~rface area of the hot external ~all 11
of the vessel~ which in turn rapidly receives heat
~rom the ir.ternai wall i20 ~r~nsferred tnrough the
helium to the external wall. Hot fluid is discharged
f rom the hea~er through an outle~ lQ3.
~ 3 ~
A second tubular closed container 115 partly
surrounds the inner container 113. Fluid is delivered
to an inlet 111 to the annular passage within the
container 115 and receives heat by transfer from the
f}uid in the passage 114 ~hrough the wall 113. Thus,
the fluid in the outer container is also heated as it
passes up the annular chamber, and hot fluid is di3-
charged through an outlet 112.
A highly advantageous use for the fluid heater
shown in Figs. 5 and ~ is as a combined furnace and
hot water heater. Hot water produced by the inner
chamber and delivered through the outlet 103 can be
distributed to hot water convectors throughout the
space being served by the furnace, ~his water being
at a relatively high temperature. The water dis-
charged thxough the outlet 112 will be at a somewhat
lower temper~ture, particularly when there is a d~and
for both heating water and hot water for general pur-
pose use in the building. The system~ can ~e opera~ed
2~ simultaneously or separately under the control of
suitable thermostatic controls for the burner. When
there is no demand for heat, water in the lnner con-
tainer does not circulate and functions merely as a
heat transfer medium to tran~fer heat from the vessel
to tne outer con~ainer, so less input heat is needed.
The fluid hea~er shown in Figs~ S and 6 can be
modified t~ employ a pul~e combustion burner unit
located at the bottom. In addition, other types OL
fuel bu~ners can be substituted for the pulse combus-
tion unit. Among the advantages OL this unit is the
simplicity and resulting low c05t oS m~ing i~ and
comparativ~ly high ef-iciency, especially tYith ~
pulse combustion unit -~hich enables substantially all
o~ ~he h~ cont~llt of ~he fuel to ~e transf~i r~ so
that very llttle heat goes out with the exhaust com
bustion sases.
.,
-i8- ~ 3~
The above-descri~ed embodiments of the invention
are intended to be merely exemplary, and numerous
variations and modifications,will be apparent to those
skilled in the art without departing from the spirit
of the 5cope of the invention. All such variations
and modificatiorls are intended to be included within
the scope of the invention, as defined in the appended
claims.
.
'
:' - , - . .
~ 31l~
3 ,1 6-diketo-cholest- 1 ,4-diene-26-oic acid
~6 hydroxycholesterol
34. The use as defined in claim 33 wherein s ud pharmaceutically
acceptable carrier comprises a penetratiGn-enhancing compound.
35. The use as defined in claim 34 wherein said penetration-enhancing
compound is selected from the group of compounds represented by the
structural formula:
o
}~' 11
(C~ N (C~ R
.,
wherein R' is H or a lower allcyl group, m is 3-7, n is 0-17 and R is
-CH3, phenyl or substituted phenyl or
o
--N ~CH2)m
36. The use as defined in claim 3~ wherein when m is 3 and R is -CH3,
then n is not 0-6.
37. The use as del'ined in claim 36 wherein said penetration-enhancing
compnund is 1-n-dodecylazacycloheptan-2-one.
38. ~ The use as defined in clalm 35 wherein sa~d oxygenated cholesterol is
26-hydroxycholesterol.
.
39. The use as defined In claim 35 wherein said oxygenated cholesierol is
cholest- 1 ,4-diene-26-ol-3-one.
3~
~:
