Note: Descriptions are shown in the official language in which they were submitted.
WV90/10839 ~ LC~ PCT/GB90/00365
.~'',,
A Heat Exchanqer
The present invention relates to a heat exchanger and
particularly, though not exclusively, to a heat exchanger
for use in a power generator plant.
It has been proposed to utilise the temperature
differencPs which can exist~in large bodies of water such as
between the top and bottom of the sea to generate
electricity. Similarly situations where industrial
processes generate large quantities of water of a different
temperature to the surroundings have ~lso been considered as
suitable for thermal po~er generation~ However, the
temperature differences invol~ed are not great and so if the
power generation system relies on expanding a fluid to drive
a turbine for example~, the fluid ~ust have a faixly low
boiling point, e.g. ammonia and the throughput of water
must be high to ensure sufficient energy can be provided to
the system. Such conditions could pose problems in system
- and heat exchanger design.
- The technique known as rollbonding has previously been
used to produce single plate heat exchangers for uses such
as domestic re~rigerators. In rollbonding, a heat exchange
WO90/10839 PCTtGB~0/0036~
~ 9 ~
-- 2
panel is formed by adhering two sheets of material together
at selected places followed by forcing a fluid therebetween
to force the non adhered areas apart to form cavities.
~enceforth the term rrollbonding" will refer to 6uch a
pro~ess. The material used is typically aluminumO
Th~ present invention seeks to utilise rollbonding
technology in the situations described above.
, . . . . ..
In accordance with a first aspect of the present
in~ention there is provided a heat exchanger comprising a
path for fluid flow having a plurality of rollbonded heat
exchange elements connected in parallel provided therein,
each element having a ~urther fluid path defined therein.
The elements are preferably spaced apart so as to
provide low resistance to the flow of fluid through the heat
exchanger. Hence a low pressure is required to force fluid
through the heat exchanger which can consequently be open to
a~mosphere pressure if re~uired. The spacing of the
elements is selected according to the required throughput of
fluid which in turn is dependent u~on the temperature of the
fluid.
The heat exchanger typically comprises a bank of
WO90/10839 ~ PCT/GB90/00365
rollbonded panels having at their edges respective inlet
ports arranged adjacent to each other and respective outlet
ports also arranged adjacent to each other; an inlet
~anifold connected to the inlat ports; and an outlet
manifold connected to the outlet ports. The inlet and/or
outlet ~anifold can comprise a casting or moulding secured
over the inlet and/or outlet ports.
Preferably the heat exchanger comprises banks of heat
exchanging elements, each bank having its own inlet znd
outlet manifoids, the banks being connected in parallel.
The manifolds can also be formed by rollbonding. The banks
are preferably connected in parallel by couplings which
allow each bank to be disconnected without loss of fluid
therefrom.
The heat exchanger is typically arranged such that no
~luid path extends from an inlet chamber, over a first weir,
through the exchanger and thus over surfaces of the heat
exchanging elements, and then over a second weir.
Conveniently, ~eans are provided for distributing flow of
the fluid relatively eYenly between the top and bottom of
the container.
When the heat exchanger comprises banks of heat
: . .,.; , ~, .. . .. ... ..
WO90/10839 PCT/GB90/0036~ -
- 4 -
exchanger elements the inlet chamber typically extends along
one side of the container alongside each bank of elements
and ~eparate first weirs direct the second fluid ~rom the
inlet cha~ber towards respective banks.
The invention also provides a power generation system
comprising: means for pumping relatively cold water from a
large body of water to a first heat exchanger as previously
defined, thereby cooling a working fluid passIng through the
heat exchanger: means for pumpinq relatively warm water from
a large body of which shallow part of the sea to a second
heat exchanger also as previously defined thereby heating
and pressurising the working fluid p~eeviously cooled by the
first mentioned ~eat exchanger; means for using the
pressurised working fluid to derive useful power, and means
~or recirculating the working fluid ~ack to the first
mentioned heat exchanger.
The large bodies of water can be different parts of one
body such as the sea when water is pumped from upper and
lower regions thereof. Alternated separate sources can be
us~d.
The system can also include means for using the
relatively cold water to produce fresh water by condensing
WO`gO/10839 PCT/GB90/00365
water vapour fro~ the air.
A construction as described above is readily adapted to
the re~uirements of different situations since any required
number of identical banks of panels can be placed in a
container of suitable size to provide fox any required heat
transfer rate and any required flow rate.
'
An--advantage of the rollbonding technique is that it
allows relatively co~plex matrix patterns to be formed on
the paralIel plates of the individual heat exchanging
elements thereby providing heat exchanging elements having
complex paths for the fluid selected, to optimise heat
transfer characteristics~ .Further improvement can be
obtained by using different matrix patterns for different
elements with a bank, those near the outside being different
to those near the centre.
The different banks o~ panels will ~ormally be
connected in parallel though it would be possible in
alternative ~onstructions to c~nnect some or all of them in
series.
Where the banks of panels are connected in parallel.
they are preferably connected by special self-sealing
WO 90/10839 .~ s PCI/GB90/003
- 6 -
couplings designed so as to allow any selec:ted bank to be
disconnected without the loss of working fluid from within
it; In cases where connections have to be made ~hrough the
bottom of the tank, a special capping device has been
dssigned to pr~ent spillage of ~a water when changing
, ~
panel ~anks. These features are considered to be of great
significance since they allow any one bank to be removed for
inspection replacement, servicing or cleaning whilst the
rest of the heat exchanger is stilI in operation. These
features could indeed be used in situations where panels
constructed by techni~ues other than rollbonding ~e.g. by
extrusion) are employed.
Potential problems are envisaged with the condensing
heat exchangers in which the working fluid e.g. ammonia is
lead from the botto~ of the heat exc:hanger after condensing.
In a plant of the type described the outlet from the heat
exchanger might be ~eparated from the circulation pump by a
significant distance and it may be required to rou~e the
outlet pipe upwardly over the tank side wall. In such a
case, the working fluid would be subjected to reduced
pressure and as the fluid may be near its boiling point,
problems may occur with re-evaporation and the ~ormation of
gas-locks in the pipeline so preventing proper flow and
affecting the efficiency of the heat exchanger.
WO90/10839 ~ 3 PCTIGB90/0036~
According to a second aspect of the invention there is
provided a condenser comprising: a heat exchange element
formed by rollbonding and defining a path for a working
fluid to be condensed, the element being contained in a
container for a cooling fluid; and means for using condensed
pressurised motive fluid to impel condensed working fluid
from a bottom region of the element upwardly so as to allow
it to be- delivered to a region outside the container for
- recycling.
The use of the invention therefore overcomes the
problem of a gas lock occurring within the condenser outlet
pipe by providing a means for applying a raised pressure to
drive the ~luid from the outlet pipe rather than utilising a
reduced ,pressure to draw the fluid from the pipe. It is
particularIy preferred that the means for using the
pressurised motive fluid is an educator pump or "jet pump"
positioned at the bottom of each heat exchange element. The
motive fluid used is the same as the working fluid in the
heat exchanger but is suppli~d directly to the jet pump ~rom
a high pressure source such as the circulation pump in the
system.
Although the present invention has been described with
WO9Ot10839 PCT/GB90/00365 - ~
3~
a specific reference to a heat exchanger, it is envisaged
that the condenser may be used with other equipment e.g. ;
within the process industry.
.
A further embodi~ent of the second aspect of the
invention provides a condenser comprising a heat exchange
element defining a path for a working fluid to be condensed,
the element being contained in a container for a cooling
fluid; and means to impel condensed working fluid from a
bottom region of the element upwardly so as to allow it to
be delivered to a region outside the container for recycling
wherein the path for a working ~luid and means to impel
condensed working fluid are integrally formed within the
heat exchanger ele~ent.
The invention will now be des,~ribed by way of example,
with reference to the accompanying drawings, in which:-
. ~
Figure 1 is a schematic oYerall view of a systemconstructed in accordance with the invention and having
purpose generating electric power;
,
Figure 2 is a vertical cross section through the line
x-x of Figure l;
~090/10839 ~ 3 PCT/GB90/00365
Figure 3 is a plan view of the heat exchanger of Figure
2;
Figure 4 is a schematic perspective view shown partly
broken away (but not shown to scale) of an inlet manifold
shown at 35 on Figure 2;
Figure 5 is a view showing, partly in cross-section and
partly in elevation,~a releasable coupling also indicated--
generally at 36 on Yigure 2;
:
Figure 6 is a schematic plan view of a manifold layout;
Figure 7 is a diagrammatic view of a system ;
incorporating the record aspect of the invention; and
Figures 8 and 9 are views of alternative forms of heat
exchanger element incorporating the ~econd aspect of the
invention.
''
Re~erring firstly to Figure 1, cold water from near the
sea bottom is pumped by pumps 1 through an inlet 2 to a heat
exchanger 3 (the "condenser"). ~ working fluid, which in
this case is ammonia (though it could alternatively be one
of a range of ~CFC/HFC or other fluids having the right
WO90/1Q839 PCT/GB90/003b~
~ w
-- 10 -- '
characteristics for the application) is cooled and condensed
in the heat exchanger.
It is then pumped by a pump 4 into a second heat
exchanger 5 (the ~evaporator") where it evaporates,
obtaining its latent heat from warm water which is supplied
by pumps 7 from an inlet 8 close to the sea surface. Water
~rom inlet 8 is intermittently treated by a chlorinating
. .
plant ~A so as to prevent accumulation of~fouling organisms
on the plates of the heat exchanger 5O The resulting
a~monia gas under pressure is used to~drive a turbine 9
which is connected to an electricity generator, not shown.
The ammonia gas then passes back into the heat exchanger 3
where it is once again condensed by the cold water from the
sea bed.
Ater passing through the heat exchanger 3 the sea
water, which ~ay still be cold with respect to the air
temperature can be passed, through a conden~er lO which is
used to condense moisture ~ro~ the air to provide a source
of ~resh water. The sea water is then returned ~o the sea
at some suitable distance from the surface water inlet (8)
region.
A sluice l2 can be used to bypass the heat exchanger 3
WO90/10839 PCT/GB90/0036~
3 3
at any time when the flow through the heat exchanger 3 has
to be altered or when complete shut down of t~e power
generation system is required, although such shut-down is
very unlikely when using the techniques of this inve~tion.
The heat exchanger 3 is supported on steel beams 13 and
14 and on square section supports such as indicated by
reference numeral 15. The square section supports a large
tank formed by side walls--16A,-base panels 16~ and end walls
16D. The top of the tank is open at the inlet ~nd outlet
ends, and the centre part (containing the panel banks) are
covered by unsealed lightweig~t decking which ke~ps the
surface of the fl~wing water to the level of the tops of the
panels and supports the weight of maintenance personnel,
allowing clear access for inspection etc. of pan~l banks.
It is intended that thè decking could be held in position
either by its own weight, or by simple quick-release
fastenings~ A feature of the construction of this tank is
that it is made from standard panels which are bolted
together with the inter-position of waterproof seals.
tank of any desired size can thus be erected depending on
the requirements for a particular situation.
Cold water from the pumps 1 passes from a pipe 17 not
an inlet manifold 18 shown on Figure 3. This manifold has
U'090/10839 PCT/GB90/0036
~ 3 - 12 -
eight branches each of which leads to a corresponding hole
in the wall 16A Df the tank, each hole being the~entry point
into one of the tank compartments. The compartment (of
which eight are shown in Figure 3) have two main functions:-
Firstly they divide up the heat exchanger into convenient
modules which may each be isolated from the rest (and
drained if necessary) in the event of working fluid leakage
or other emergency. It is particularly important to have
this~~facility- in the case of toxic/hazardous-wor~ing fluids
(such as ammonia) which might dissolve in the water and
contaminate the mariculture, aside from normal safety
consideration; secondly depending on the level of
maintenance required, they offer a choice of either
uncoupling and changing single panel banks or closing and
draining a whole compartment (e..g. where major tank
cleaning operations are being carried out). They also
impart stiffness to the long walls o:E the tank, so that less
supporting steelwork is needed at the side walls~
After passing through ~ach hole, the water enters a
settling chamber l9 and a riser 20 leadin~ to a weir 21.
~hen there is excessiYe water flow (such as in a temporary
. situation where one of the other sections has to be closed
for maintenance etc.) any excess wa~er passes over an
overflow weir 22 to be expelled at an overflow outlet 23.
,. ; .: .. ., ;, : . ~
WO90/10839 2 ~ PCT/GB90/00365
Normally however all the water passes over the weir 21 and
into a vertical distributor 24A (with barrier plate 16C
mounted above) which is supported on the partition walls and
floor of the tank. The effect of the distribution device
24A is to ensure that the water flow is distributed evenly
between the top and bottom of the tank between the heat
exchanger ele~ents 25. The latter are arranged in banks of
eight as shown best .in Figure 3. After passing the heat
- exchanger elements 25 the water.enters... a. second vertical
distributor 24B which acts in reverse to colle~t the water
flow and pass it towards a second weir 26 where it overflows
into a water outlet manifold 27. This leads to an outlet
pipe 28 and thence to the settling tanks ll as shown on
Figure 1.
The heat exchanger 5 shown in Figure 1 is constructed
on similar principles to the hea1: exchanger 3 though a
different number of banXs of heat exchanger panels of
di~ferent rollbond pattern configuration~ are required.
These manifolds, one per compartment, may be made in
several ways, including rollbonded aluminium. Each manifold
30 inlet is connected to a main manifold (not shown) which
is simply a large pipe suitably situated, running along the
length of the heat exchanger, and having (for this
,
WO90/10839 PCT/GB90/0036~. ~
2 ~ 3 ~;'
- 14 -
particular eight compartment design~ eight branch outlets.
Each ma~ifold 30 has sixteen outlets, each connected to a
panel manifold 34, as shown in Figure 5. Each manifold 34
is shown as an aluminium casting formed with interior
channels arranged to connect with the open inlet part of the
heat exch~nger panels and ~ecured in position with adhesive.
Each heat exchanger panel 25 is formed by two sheets
aluminium (titanium could alternatively be used) connected
together using a rollbonding tech~ique so as to create a
complex matrix pattern of channels within. The different
panels ~f a bank could be provided with different matrix
patterns, those at the outside of a bank, for instance being
di~ferent from layers near the centre so as to optimise heat
transfer characteristics. In ano1:her embodiment of the
invention (not shown) the channels of adjacent panels could
be deliberately arranged so as to be not immediately facing
each other. In this way the raised portions presented by
one panel could be made to face the depressed portions
between the channels of the adjacent panel or panels,
thereby allowing adjacent panels to be more closely spaced
than would otherwise be possible.-
The worXing fluid cools and condenses in its passagethrough the panels and issues via manifold 3S, quick rel~ase
WO90/10839 ~t,,"~ ,~, 3 PCT/GB90/00365
- 15
coupling 36 as shown in Figure 5, flexible pipe 37,
rollbonded manifold 38 and then passes through outlet line
39 to the pump 4. The self sealing, releasable çouplings
are especially designed so that they can be disconnected for
remQval of a bank of panels without the loss of working
fluid. To this end the coupling has a sealing mechanism in
each of two separable halves of it. ~he act of separating
the two halves causes the sealing mechanisms to operate on
- both halves and they do so in such a way as substantially to
avoid any leakage. A suitable self sealing coupling of this
type is made by Heat Transfer Engineers (HTE) Ltd.
It is believed that the princ:iples of the invention as
e~bodied in the illustrated design are likely to achieve
efficient heat transfer without incurring a pressure loss of
more than five or six centimeters,head of water.
The system shown in Figure 7 utilises the second aspect
of the invention and comprises a circulation pump A which
delivers conden~ed fluid via a pipe to an evaporation B in a
tank C containing relatively warm water. The evaporated
fluid is used to drive a turbine D and is subsequently fed
to a condenser E in a tank H of relatively cold water. A
jet pump F i5 provided at the outlet from the condenser E to
drive condensed f luid back to the pump a. A separate feed
WO90/10839 PCT/GB90/003
- 16 -
line G is taXen directly from the outlet of the pump A to
drive the jet pump E. Figur~ ~ shows the condenser E
comprising a heat exchange element lO having a pathway ll
~or workin7 fluid 12 defined therein by rollbonding. A
fluid delivery line 30 connects ~o the element lO at an
upper region thereof at an inlet 31 and the condensed
working fluid leaves the element lO at an outlet 15 provided
t a lower region thereof.
.... ,.~.. -- - -
The ~eed line G provides pressurised, condensed motive
fluid directly to a jet pump 13 which is provided adjacent
the outlet 15, the jet pump 13 ancl the outlet 15 feeding
intojan outlet pipe 18. The jet p~p 13 comprises a nozzle
16 for motive fluid and a cavity 17 defined in the outlet
pipe 18 adjacent the nozzle 16 and outlet 15.
,
Re~erring now to ~igure 9, the condenser shown therein
has essentially the same components as described in relation
to Figure 8 abQve and identified by the same reference
numerals with the suf~ix 'A'. However, In this case the
heat exchange element lOA, jet p~mp 13A and outlet pipe 18A
are ~ormed integrally by rollbonding. In this case the feed
line 14A is at least partially formed in the heat exchanger
lOA by rollbonding, a separate inlet 32A being provided for
connection to the line G.
.. . : , , . , . ,.. ~
W~90/10839 PCT/GB90/00365
- 17 -
In operation, both o~ the embodiments shown in Figures
8 and 9 function in the same mannerO In each case the
condenser forms part of a plant as described in relation to
Figure 7, i.e. condenser 3 in tank 3A or condenser E in
tank H. The workin~ fluid is supplied from the circulation
pump 4, A to the delivery line 30, 30A. The flow of working
fluid 12, 12A is directed into the pathway 11, llA in the
heat exchange element 10, lOA and is condensed in the
pathway 11, l}A and deli~ered to the outlet 15, 15A and into
the outlet pipe 18, 18A. The motive fluid, which is at
higher pressure than the condensing working fluid, is
delivered directly to the jet pump 13, 13A from the
circulation pump 4, A whe~e it is emitted from the nozzle
16, 16A into the cavity 17, 17A. The pressure in the cavity
17, 17A is lower than in the pathway 11, llA so condensed
working fluid 12, 12A will always flow from the outlet 15,
15A. The motive fluid from the jet pump 13, 13A provides
pressure to the fluid in the outlet pipe 18, 18A and serves
to drive the fluid from the condenser to .the circulation
pump. In this manner, the formation of gas bubbles is
reduced and even if bubbles do form, the action of the pump
means that fluid is driven from the condenser E to the
circulation pump A.
'' ~ ', ' ',':: , .':: ' : : ", , ~ "", . :,. ,",: ," ~ " :, ; ".:
WO90/1~839 ~ PCT/C~90~0365 -'
- 18 - ~ .
The jet pump described has the advan~age that it is
easily formed during the production of the condenser and
requires no moving parts and is essentially maintenance
free. However, other types of pUmp5 could still be used to
provide pressurised motive fluid at the outlet from the heat
exchange element.
-- .
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