Note: Descriptions are shown in the official language in which they were submitted.
Thc present inventlon relate~ to a ground h~at exchangkr acd~
more particularly, to such an exchang~r adapted to be used in comb~nation
with a heat pump system ~or heatin~ and ¢oolinB o~ enclosed sp3ce~, Juch a~
homes and other bulldings.
The use of the earth as a subatantially constant temperature
heat re~er~oir f~r heat exchange purposes is well kno~n. The use o~ the
earth in heat exchange relstion with a heat pump system including a co~-
pressor, a condenser, an expansion valve and an evQporator, ~ith the
evaporator in the ~or~ o~ a heat exchanger buried in the ground, iJ al~o
~ no~n. Such a h0at pu~p 8yJte~ i~ des¢rlbed, ~or instance~ in ~.S.
Patent 2,513,373 dated July 4, 1950. ~ow~ver, in order to r~ain ~r~i-
oient, a ground hest exchanger, obviously~ ~ust remain in constsnt and rine
contact ~ith the ground ~o that the latter nay act as an orrlcient h~at dnt
or a~ an ~t~icient source of heat. Rowe~er, u8ing the ~a~e heat eschaDger
in ~inter-ti~e to coIlect heat ~ro~ the ground at 8 lo~ tomperature and
a~ a heat dispoGal unit in ~ummer-t~ to di~per~e heat in tho gr wnd,
re~ult~ in considerable variation~ in the operatlng temperature of the heat
e~changer and, consequently, re~ult~ in e~pansion and contraction of the
sa~e. Furthermoro, especially ln Northern cli~ates~ ground, upon rree~ing
snd d~treosing, ~ores appreoiably ~ithin the span o~ ~ust one year.
Thereroro, a groQnd heat eschanger buried in the ground rapidly lo~es lt~
heat esch~nge e~ficiency due to the creation ot ~oid~ or air poc~et~ -
betwoen the heat e~oheng~r surfaeoa and tho adJacent earth. Those heat
02ehang~r~ aro nor~ally ~sdo o~ ate d for low cost ana good heat conoucti~it~.
Howe~or~ ~to d ru~ts quito quio~l~ in the ground. Painti u Or the ate~l
~urraea~, naturally, docreases tho hoat condQcti~it~ at the int~rfae~ Yith
the o~rth.
It i~ thereroro the geDeral obJect of the inrention to pro~de
a eround heat exchslg~r o~ the eharacter described, whlch ~ill obriato the - -
abovo-noted diaadr nt~ges in that it retain~ ita hoat conduct~ng rolatlo~shlp
~ith tho oarth in ~hich it iJ buriod ~or a very long time and despite ropsated
contraction a~d ospan don and alQO ground ~cve~ont.
~nothor ob~oct ot tho invention is to provido a grou~d h~st
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e~ahanger Or the chsracter de~¢ribed having meun~ to auto~aticall~ fill
~ith a heat conducting medium an~ voids or air pocketa dsveloping bet~bon
the ground and he~t exchanger surraces.
Another ob~ect of the inventlon iJ to provlde a ground heat
exchanger of the character de cribed, ha ing meanJ ror the ~l~pl~ rqpl~D-
ishing o~ the heat condlcting ~ediu~.
~ nother ob~ect of the inrention is the pro~is~on Or a h~at
e~changer o~ the character d cribed, in ~hich the ~oid ~illing heat
condlcting ~ediu~ i~ a thermal gres~e wh~ch ooat~ the heat e~ahangor
~ur~ace~ snd pre~enta lts rustln2.
The ~oregoing and other ob~ecta of the in~ention ~ill beco~o
more appsrent durlng the ~ollo~lng disclo~ure and br referring to the
drs~ngs, in ~hlchs
Figure 1 ia a perspocti~e ~le~ Or the s~s~mbly o~ the heat e~ohangsr
unit Or the i~vention;
Figure 2 i8 a partlal cross-Jection, takon along lino 2-2 Or Figure 1
Figuro 3 i~ a partial plan ~ection, tak~n along line 3-3 Or Figure 2
Flgure~ 4, 5, nd 6 re partial cro~-soctlons Or the he~t ox~haDger
plato and coil in accordanco ~ith throe di~rerent ~bodi~e~toJ
snd
Figure ? ~8 8 pl n ~iew Or a prorsrred rr ngo~ent of the nuld
circulating coil ~hich i~ part o~ the heat oxchangcr pl~te ot
tho ~n~ention.
In the dr~lng~, like rereronce ch~racters lndic~to liko el~o~t~
throughout.
Tho ground heat e~chaDger in accordan¢e ~ith the in~entlon i8
generallr indicated at 1 and co~pri~eJ an elongated reotsn~lar ~lat
~et l platb 2 and a pair o~ upright end tube~ 3, oa¢h ha~ing a verti¢ lly
oxtending sllt 4 in the region ot it~ lo~er end portion The sllt 4
ba~ ~ubatantially tho hoight o~ the plate 2 and recei~es the end of the
plato~ ~o that the latter o~tend~ ~ithin the tubo 3, ~9 ~ho~n i~ ~igure 3.
Sllt ~ h J at inter~al~ a plurality o~ in~ard}y o~tending ~ingcrs 5
equally spaced ~long the longth o~ each edge o~ the slit aDd slidsbl~
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3l~3~ f~
engaging tho oppo~lte sur~aces of the plato 2, Slit 4 between the
fingers 5 de~lnes aperture~ 6 on sach side of the plate 2, th~ ~pcrtol~
being in c~mmmication with the inslde of the tube 3. The plate 2 bet~een
tubes 3 carries a fluid circulating coil 7 e~tending over the entire ~r-
face of the nlate and connected at its ends 8, into the circuit o~ a
heat pu~p used as a heating and/or oooling ~y~tem for a house or the like.
3ach tube 3 is filled with a ~lowable heat conauctlng mediu~ 9, whlch i~
maintained under constant pressure within the tube 3 by ~eans o¢ a ~eight
10 freely slidable ~ithin the tube 3 and restinB on top of ~ho ~odiu~ 9.
The pre~sure exorted by the weight 10 ia Ju~lclent to e~trudb
the ~ediu~ 9 through ap~rtures 6 aloDg the plate ~urface~. Plate 2 i~
adapted to be burlod in the ground a in a ver~lcal plane ~ith the upri3ht
tube~ 3 e~teDding above the top ~dge o~ the plato to ter~inato at tho grou~d
Jurrace. ItJ open end i~ normally olosed by a r~o~ablo cap 11 to ~hi¢h
a rope, or ¢able 12, i~ attached and loo~ly e~toDds ~ithin tho tube 3
to be attached at lt~ lower end to the welght 10. ThuJ, the ~eight can
be removed ~rom the tube and the tube rerilled with the tharaal ~ediu~
9, wheDo~er deaired. The bottom ena ar each t~be 3 is closed.
Nediu~ 9 18 prererably a greaso, such a~ lubricating greasa
used in car~, cont d ning a heat-conducting ~otal in powdored for~. Tho
grealo ~ay bo ~ Jilicone grease, su¢h a~ the sillcone greaJo ~snu~actured
b~ Do~ Ch~elcsl~ Iimited, and containing copper o~ide in powdered ~or~
diaper~od tbrou8hout the grease. This is a so-called th~r~al ereaso or
heat-conducting grease~ which ha~ a coefrlcient Or heat conaucti~i~y X ot
.43, a~ co~pared to tbe nor~al oarth conauctivi~y of .oe to 1.4. The X
~actcr ~bo~e ~entionod is de~igned in ter~ Or BT~ trans~itted per ~q~are
foot surface area per inch thickness.
Rerore burying the plate 2, both its surrace~ are entlrely
coated with the ther~al grease and, once buried, the tubes 3 are rilled
with a ther~Ql grease. During use, any air pocket which de~elopJ betw~o~
the plate and the earth i~ quiokly rilled wlth the pressurized ther~al
greaJe being estruded through the apertureJ 6 of the tube~ 3 and the
greaJe noving ~long both ~sces of ths plate to rill the void~ or ~r
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pockets. ~ t~
It has been calculated that an air space of only 1/8 of ar
inch separating the plate surface from the eartl~ wlll reduce the
heat exchange efficiency of the heat exchanger at least five times
For instance, a heat exchanger normally designed to exchange
100,000 BTUs will thus only have 20,000 BTUs per hour.
It has been found that, even after only six months'
operation, such air pockets are formed over substantially the
entire plate surfaces. This is due to ground movement with freezi
and defreezing and with the variation in the operating temperature
of the heat exchanger which is as much as 100F. between winter
snd summer operation. Under this temperature variation, the plate
2 can expand and contract to a total amount of ~" over a length
of about 24', whlch is the length necessary for this plate to have
supposlng a 3' width, to handle the heat exchange load of a
heating pump designed to heat and cool a normal size house. This
contraction and expansion is simply taken care of by the plate
moving out into the end upright tubes 3.
The thermal grease, naturally, also protects the plate
against oxidation and eliminates another heat exchange barrier, th
plate being normally made of copper or an alloy of aluminum and
zinc.
In summer-time, heat dries the earth and, thus, lt may be
necessary, as i8 known, to wet the earth surface in the region Of
the heat exchanger, for instance by means of a perforated water
spinkler tube 1~ connected to a water supply by a pipe 14, in
turn provided with an electro valve 15 automatically controlled
by a humidity responsive transducer 16 buried in the ground.
Whenever the earth is too dry, the pipe 14 will discharge water
to wet the earth around the heat exchanger 1. In winter-time,
the humidlty of the earth migrates towsrds the plate 2 ant no
such watering is neeted.
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The fluid medium circulatlng coil 7, the fluid medium
being for instance Freon, as commonly used in refrigerstlng 8y8t~
can take different forms, as shown in Figures 4, 5, and 6. The
coil 7 may consiRt simply in a pipe 17, of copper, alumlnum or
the like, or steel, directly welded to one side of the plate 2 a~
by weldlng 18.
As an alternative, a pipe 17', formed as a coil, can be
sandwiched between two half plates 2' spot-welded together betwe~
the pipes and bent to form a corrugated cross-section, as shown
in Figure 5.
As another alternative, the pipes could have helicoi!dal
flns lnside the tube, to increase the heat transfer between the
fluit and the plate.
As a further alternatlve, the pipes 17 or 17' are
completely ellmlnated and two half plates 2", of corrugated cros~
sectlon, are ~uxtaposed and spot-welded together, leaving pa~sage
20 for the heat exchange fluid 21.
The coil can have any desired path, for instance a simple
zlgzag path, as shown in Figure l; but it is preferred to design
the coil 90 aR to have the path shown in Pigure 7, including two
sets o~ parallel paths, so connected that substantially equal
fluld flow wlll occur in each set and also in each leg of the set
the system being 80 arranged that substantially the same length :
of flow in each path and, consequently, the same resistance to
flow is encountered in each path.
More speciflcably, there are two sets of parallel tubes 2
and 24 respectlvely, disposed side by side, along the length of
the plate 2. The tubes of both sets are of equal length. The
common inlet tube 25 is bent back at 26 into a U to form a leg 27
which acts as a manifold for the tubes 23 of the first set.
The8e tubes discharge in a common outlet manifold 28, which forms
a branch parallel to the outlet common tube 29 and communicates
therewith at 30.
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1~611r~;~
The arrangem-n~ o~ the ~econd ~et of tube~ 24 1~ rever~ed
namely: the inlet manifold 31 forms a slde branch of the common
inlet tube 25 and i8 parallel to the leg 27 thereof and communlc~
therewith at 32 at one end of the inlet manifold 31, while the
pipes 24 have their outlet in direct communication with the common
outlet tube 29.
The arrangement is such that the path through anyone of t~
tubes 23 and 24 is equal, starting from the common inlet point 32
to the common outlet point 30. Obviously, the diameters of the
tubes 23 and 24 are the same and the diameter of the leg 27,
outlet tube 29, outlet manifold 28 and inlet manifo~d 31 is also
the same.
From the foregoing arrangement, a parallel path system i~
obt8ined for lncreased fluid flow and, at the same time, the ~ :
flow rate in each tube 23 and 24 is substantially the same for ::
uniform heat exchange efficiency over the entire surfaces of the
plate 2.
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