U.S. patent application number 13/157197 was filed with the patent office on 2011-09-29 for temperature control method and apparatus.
Invention is credited to Malcolm Barry JAMES.
Application Number | 20110232856 13/157197 |
Document ID | / |
Family ID | 3808278 |
Filed Date | 2011-09-29 |
United States Patent
Application |
20110232856 |
Kind Code |
A1 |
JAMES; Malcolm Barry |
September 29, 2011 |
TEMPERATURE CONTROL METHOD AND APPARATUS
Abstract
The invention relates to a method of cooling machines.
Typically, the method of cooling is useful in the cooling of dies
used in the moulding of plastics or metals. The method relies upon
taking advantage of the latent heat of vaporisation of a cooling
liquid. A liquid is maintained in a closed chamber in a die such
that the liquid is in contact with the surfaces to be cooled and a
space above the liquid surface is available. The pressure in the
space is adjusted, typically by vacuum equipment, such that the
boiling point of the liquid is adjusted to a level which enables
the principle cooling process to involve latent heat.
Inventors: |
JAMES; Malcolm Barry;
(Campbelltown, AU) |
Family ID: |
3808278 |
Appl. No.: |
13/157197 |
Filed: |
June 9, 2011 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
09719136 |
Dec 7, 2000 |
7964129 |
|
|
PCT/AU99/00448 |
Jun 9, 1999 |
|
|
|
13157197 |
|
|
|
|
Current U.S.
Class: |
164/348 ;
425/404 |
Current CPC
Class: |
F01P 3/22 20130101; B29C
51/428 20130101; B29C 45/73 20130101; B29C 35/007 20130101; B22C
9/065 20130101; B29C 33/04 20130101 |
Class at
Publication: |
164/348 ;
425/404 |
International
Class: |
B22D 27/04 20060101
B22D027/04; B29C 71/02 20060101 B29C071/02 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 11, 1998 |
AU |
PP 4403 |
Claims
1. A temperature control apparatus configured to uniformly cool a
molding surface of a mold or die comprising: a molding surface; at
least one completely closed chamber having air substantially
removed therefrom; a single quantity of liquid in said at least one
completely closed chamber wherein said single quantity of liquid
extends to cover at least one area adjacent to and on an opposite
side of the molding surface of said mold; wherein said molding
surface comprises a separating wall or walls having a uniform
thickness through all of the wall or walls through which cooling is
effected; wherein a level of the liquid is sufficient to cover all
of said at least one area including said separating wall or walls
of the at least one completely closed chamber from which heat is to
be taken and wherein each of said at least one completely closed
chamber is integrated within the mold; a space above the single
quantity of liquid and within the at least one completely closed
chamber in which pressure within the space is caused to be set at a
level which enables the single quantity of liquid to boil into a
vapor at a selected temperature, said selected temperature being at
a level such that the selected temperature is below a temperature
of the at least one area adjacent to the molding surface; and, a
condenser configured to cool the vapor to a selected cooling
temperature, wherein condensation of the vapor returns condensed
vapor to the single quantity of liquid.
2. The apparatus as claimed in claim 1 wherein the single quantity
of liquid is water.
3. The apparatus as claimed in claim 1 further comprising: at least
one heating element located within the at least one completely
closed chamber and within the single quantity of liquid such that
during standby time, temperature of the mold or die is kept within
a selected temperature range.
4. A temperature control apparatus configured to uniformly cool a
molding surface of a mold or die comprising: a molding surface; at
least one completely closed chamber having air substantially
removed therefrom; a single quantity of liquid in said at least one
completely closed chamber wherein said single quantity of liquid
extends to cover at least one area adjacent to and on an opposite
side of the molding surface of said mold; wherein said molding
surface comprises a separating wall or walls having a uniform
thickness through all of the wall or walls through which cooling is
effected; wherein a level of the liquid is sufficient to cover all
of said at least one area including said separating wall or walls
of the at least one completely closed chamber from which heat is to
be taken and wherein each of said at least one completely closed
chamber is integrated within the mold; wherein said at least one
completely closed chamber is configured such that if there is a
temperature differential between any two locations within the at
least one completely closed chamber, the single quantity of fluid
boils at a location with a higher temperature and a resultant vapor
condenses at a location with a lower temperature, in order to
maintain a uniform temperature throughout the at least one
completely closed chamber; and, a space above the single quantity
of liquid and within the at least one completely closed chamber in
which pressure within the space is caused to be set at a level
which enables the single quantity of liquid to boil into the vapor
at a selected temperature, said selected temperature being at a
level such that the selected temperature is below a temperature of
the at least one area adjacent to the molding surface.
5. The apparatus as claimed in claim 4 further comprising: a
condenser configured to cool the vapor to a selected cooling
temperature, wherein condensation of the vapor returns condensed
vapor to the single quantity of liquid.
6. A temperature control apparatus configured to uniformly cool a
molding surface of a mold or die comprising: at least one adjacent
closed chamber adjacent to the molding cavity; a separating wall or
walls between the molding cavity and the at least one adjacent
closed chamber having a uniform thickness through all of the wall
or walls through which cooling is effected; wherein said at least
one adjacent closed chamber comprises a liquid to an extent to
effect substantial exclusion of any other fluid, so that there is
both a liquid portion and a saturated vapor portion of the said
liquid within the at least one adjacent closed chamber and only
this liquid; wherein a level of the liquid is sufficient to cover
all of at least one area including said wall or walls of the
chamber from which heat is to be taken; and, a condenser coupled
with the at least one adjacent closed chamber.
7. The apparatus as claimed in claim 6, wherein the fluid is a
single selected fluid.
8. The apparatus as claimed in claim 6 wherein said mold or die
comprises two molds or dies configured to fit together and hold an
item to be formed.
9. The apparatus as claimed in claim 6, wherein said at least one
adjacent closed chamber adjacent to the molding cavity is within
the mold.
10. The apparatus as claimed in claim 8, wherein said at least one
adjacent closed chamber adjacent to the molding cavity is within
the mold.
11. The apparatus as claimed in claim 8, wherein the level of the
liquid portion is sufficient to cover an area or areas of the said
wall or walls of the chamber from which heat is to be taken, and
within the space above the liquid portion of the fluid, such space
containing substantially only the vapor of the fluid, the pressure
in the space thereby being substantially equal to the vapor
pressure of the fluid which results in, upon there being a
temperature differential between any portion of the surface of the
wall or walls and a cooler portion of the surface of the wall or
walls within the space, some liquid of the fluid boiling at the
said higher temperature location and effecting thereby removal of
heat as latent heat of vaporization from the higher temperature
location through a phase conversion of the fluid to a vapor and
thereafter effecting, by condensation of the vapor which effects
release of its latent heat of vaporization at said lower
temperature location in the space above the said liquid to reduce
said temperature differential and, by condensation of vapor at the
condenser which is cooled from time to time so as to control the
temperature of the fluid to be within a selected range.
12. The apparatus as claimed in claim 10, wherein the level of the
liquid portion is sufficient to cover an area or areas of the said
wall or walls of the chamber from which heat is to be taken, and
within the space above the liquid portion of the fluid, such space
containing substantially only the vapor of the fluid, the pressure
in the space thereby being substantially equal to the vapor
pressure of the fluid which results in, upon there being a
temperature differential between any portion of the surface of the
wall or walls and a cooler portion of the surface of the wall or
walls within the space, some liquid of the fluid boiling at the
said higher temperature location and effecting thereby removal of
heat as latent heat of vaporization from the higher temperature
location through a phase conversion of the fluid to a vapor and
thereafter effecting, by condensation of the vapor which effects
release of its latent heat of vaporization at said lower
temperature location in the space above the said liquid to reduce
said temperature differential and, by condensation of vapor at a
condenser which is cooled from time to time so as to control the
temperature of the fluid to be within a selected range.
13. The apparatus as claimed in claim 6, wherein the level of the
liquid portion is sufficient to cover an area or areas of the said
wall or walls of the chamber from which heat is to be taken, and
within the space above the liquid portion of the fluid, such space
containing substantially only the vapor of the fluid, the pressure
in the space thereby being substantially equal to the vapor
pressure of the fluid which results in, upon there being a
temperature differential between any portion of the surface of the
wall or walls and a cooler portion of the surface of the wall or
walls within the space, some liquid of the fluid boiling at the
said higher temperature location and effecting thereby removal of
heat as latent heat of vaporization from the higher temperature
location through a phase conversion of the fluid to a vapor and
thereafter effecting, by condensation of the vapor which effects
release of its latent heat of vaporization at said lower
temperature location in the space above the said liquid to reduce
said temperature differential and, by condensation of vapor at a
condenser which is cooled from time to time so as to control the
temperature of the fluid to be within a selected range.
14. The apparatus as claimed in claim 13, further comprising an
element configured to control a passage of coolant through the
condenser so as to maintain the temperature of the fluid within a
selected range.
Description
[0001] This application is a continuation of U.S. Pat. No.
7,964,129, filed 7 Dec. 2000, which was the National Stage of
International Application PCT/AU99/00448 filed, 9 Jun. 1999, which
claims the benefit of Australian Patent Application Serial No. PP
4033, filed 11 Jun. 1998, the specifications of which are all
hereby incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] This invention relates to a temperature control method and
apparatus applicable to machines and has particular application to
dies and to moulding of articles using dies in processes such as
injection moulding, thermoforming, vacuum forming metal die casting
and the like.
[0004] 2. Description of the Related Art
[0005] The invention will be described with respect to an
application but it is not intended that the concept should be
constrained simply to that application.
[0006] It is well known that a die can be kept within an acceptable
temperature range by use of water passing through passages in the
die to a separate heat exchange station.
[0007] One of the challenges in the design of dies is to ensure
that the working parts of the die have sufficient access to cooling
water. This can at times be very difficult indeed if, for instance,
there is very little room for appropriate passages for water to be
transported to and from a location in sufficient volume.
[0008] Such a challenge of keeping a die within an acceptable range
of temperatures is no small matter and can involve considerable
costs in the manufacturing and commissioning of a die. One of the
problems experienced is that unless the water is demineralised
which is generally uneconomic because of the volume of replacement
water needed, then scale build up will occur which again can be
costly to treat and can lead to reduced efficiency in cooling over
time.
[0009] A further problem is the corrosion in the cooling passages
caused by their exposure to aerated cooling water.
[0010] Further the efficiency of cooling can be a very significant
factor in the repetition rate of use of a die. If there were a more
efficient way of cooling the die may be able to be used at greater
repetition rates which is significant as far as costs of production
using the die are concerned.
[0011] Further uneven cooling rates between different portions of a
moulding die can cause distortion of the moulded parts for which
rectification or compensation can be costly.
BRIEF SUMMARY OF THE INVENTION
[0012] It is an object of this invention to propose an alternative
way to effect temperature control of a machine which at least
reduces some of the above difficulties.
[0013] In one form of this invention this can be said to reside in
a machine of a type requiring heat to be taken from the machine
from time to time, characterised in that the machine includes at
least one closed chamber having liquid therein which extends to
cover at least one of the areas from which heat is to be taken, and
a space above the liquid and within the closed chamber, wherein
pressure is set at a level which will enable the liquid to boil at
a selected temperature and condensing means to effect, by cooling,
condensation of vapour of the liquid in the space.
[0014] In preference there are more than one chamber and each
chamber is shaped and positioned together with the level of liquid
therein so that the liquid will cover areas in the machine from
which heat is to be taken.
[0015] In preference the liquid is water.
[0016] In preference the machine is a die for moulding of plastics
materials.
[0017] In preference the machine is a die for injection moulding of
plastics materials.
[0018] In preference the machine is a die for moulding by
thermoforming of plastics materials.
[0019] In preference the machine is a die for the die casting of
metals.
[0020] In a further preferred form of this invention this can be
said to reside in a die having an internal cooling arrangement
which includes a closed chamber having therein a liquid with a
volume such that it has an upper level above areas of the die to be
cooled and substantially only the vapour of the liquid within the
chamber above the upper level of the liquid.
[0021] In a further preferred form of this invention this can be
said to reside in a die for injection moulding of plastics
materials having an internal cooling arrangement which is a closed
chamber partially filled with a liquid with an upper level
sufficient that areas of the die within the chamber adjacent to
parts of the die to be cooled are covered by the liquid and, in the
space in the chamber above the liquid, substantially only the
vapour of the liquid. In a further preferred form of this invention
this can be said to reside in a die for injection moulding of
plastics materials having an internal cooling arrangement which is
a closed chamber partially filled with a liquid with an upper level
of sufficient height so that areas of the die within the chamber
adjacent to parts of the die to be cooled are covered by the liquid
and, in the space in the chamber above the liquid, substantially
only the vapour of the liquid, and an arrangement to provide
cooling of any vapour within the space in the chamber above the
liquid level to effect at least some condensation of the vapour
thereby.
[0022] In preference there is at least in addition, a heating means
located within the chamber within the liquid such that during a
standby time, the temperature of the die or mould can be kept
within a selected range of temperatures.
[0023] In preference the cooling means include a tube, a core in
the tube and means to direct cooling water through the tube.
[0024] In a further preferred form of this invention this can be
said to reside in a method of cooling of parts of a machine where
the machine has at least one closed chamber having liquid therein
which extends to cover at least one of the areas from which heat is
to be taken, and a space above the liquid and within the closed
chamber in which the pressure is caused to be at a level at which
the temperature of the boiling point of the liquid will be to at
least a selected extent is below the temperature of the area from
which heat is to be taken and there are condensing means to effect,
by cooling, condensation of vapour of the liquid in the space.
[0025] In a further preferred form of this invention this can be
said to reside in a method of cooling of parts of a machine where
the machine has at least one closed chamber having liquid therein
which extends to cover at least one of the areas from which heat is
to be taken, and a space above the liquid and within the closed
chamber in which the pressure is caused to be at a level at which
the temperature of the boiling point of the liquid will be at least
a selected extent below the temperature of the area from which heat
is to be taken this being by reason of, as a first step, filling of
the closed chamber with the liquid and then extracting a selected
amount of the liquid without allowing air to replace the extracted
liquid, and passing at a selected cooling temperature, liquid
through condensing means to effect, by such cooling, condensation
of vapour of the liquid in the space.
[0026] In use then condensation of the vapour may be effected by
providing a heat exchange either by an independent member within
the space above the liquid level or by having a portion or all of
the wall defining the chamber in an area above the liquid surface
which is at a lesser temperature but in any event, so that there
will be a reasonably effective exchange of heat from the vapour of
the liquid so that this then condenses back into liquid and will
flow back into the body of the liquid within the closed
chamber.
[0027] The portion of the chamber to receive heat will, by reason
of a raised temperature of the immediately adjacent liquid to above
that of the liquid in adjacent areas, effect an exchange of state
of the liquid in this area to vapour which by reason of the latent
heat capacity of the vapour will be a very substantial carrier of
heat. By reason of relative densities then, the vapour thus formed
will rise to the surface of the liquid, continuing to fill the
space above the liquid where continuing condensation is being
effected by a reverse exchange of heat.
[0028] What we have then is a closed chamber with its selected
liquid operating so that it is at a temperature and pressure
governed by its own vapour pressure and by external inputs of
heat.
[0029] A number of variations can be incorporated within the
general concept.
[0030] In a first method, the internal chamber is filled with the
liquid to be used. In preference, such liquid is previously treated
so as to remove dissolved gases and other unnecessary materials so
that in preference, the liquid is a pure liquid without impurities
which may otherwise interfere with the process or the efficiency in
general of the process.
[0031] Once full and sealed, the chamber is then accessed through a
gate valve so that some of the liquid is then extracted with a pump
to a level that is chosen such that the level will be below a
condensation member or means within the upper part of the chamber,
and that there will be liquid in contact with heat source which is
to provide the heat to be dissipated.
[0032] Following these steps, the die is then ready to be used
where there is a heat exchanger in an upper part of the internal
chamber to provide heat exchange where a further liquid is pumped
through the heat exchanger at a preferred mould or die operating
temperature but in preference not a low enough temperature to cause
freezing of the liquid.
[0033] It is expected at this stage that the liquid would normally
be water but it is understood that there are many liquids other
than water that would provide a good effect.
[0034] For each individual circumstance, the degree of heat to be
shifted, the extent of the hot surfaces to be cooled, and the
general temperature that has to be worked on, need to be considered
to take into account the overall dimensions of the chamber, the
fluid to be used, the degree of vapour space above the liquid
level, and the condensing means within the vapour space.
[0035] In experiments so far conducted, such an arrangement
provides very effective and relatively uniform heat transfer. While
reference has been made to a chamber, this does not of itself
exclude the case where there can be separate bodies connected by
sealed conduits.
[0036] A chamber then is to be considered as a concept broad enough
to encompass any closed environment.
BRIEF DESCRIPTION OF THE DRAWINGS
[0037] For a further explanation of the invention this will be
described with reference to a further embodiment which shall be
described with reference to an accompanying drawing wherein:
[0038] FIG. 1 is a schematic cross sectional view of a
thermoforming apparatus in accordance with a first embodiment;
[0039] FIG. 2 is a cross sectional view of the male side of a
plastic injection die;
[0040] FIG. 3 is a cross sectional view along the lines 3-3 in FIG.
2 of the second embodiment;
[0041] FIG. 4 is an exploded perspective view of the plastic
injection die, the male side of which is shown in FIGS. 2 and
3;
[0042] FIG. 5 is an exploded perspective view of the parts forming
the portion of the second embodiment as shown in FIGS. 2 and 3;
and
[0043] FIG. 6 is a section along the lines 6-6 in FIG. 3.
DETAILED DESCRIPTION OF THE INVENTION
[0044] Referring in detail to FIG. 1 there is shown a thermoforming
apparatus 1 with a plug 2 arranged to push plastic sheet into a
shaping cavity 3. The sheet 4 is subject to conventional treatment
including having air at pressure drive the formed sheet 4 into
close conforming shape of the cavity 3.
[0045] The cavity 3 is surrounded by a hollow body 5 which defines
a closed chamber together with conduits 6 and 7 and condensing
container 8. Within the condensing container 8 is a heat exchange
coil 9 which is supplied with appropriate cooling refrigerant.
[0046] Conduit 7 passes beneath plastic sheet holding means 13 and
therefore could cause a liquid blockage to passage of vapour
through to the condensing container 8.
[0047] This effect can be removed by introducing additional heat
through heating coil 11 which will effect a vaporisation of the
liquid at this location.
[0048] Initial startup of this apparatus is achieved by filling the
chamber which includes the hollow body 5, the conduits 6 and 7 and
the container 8 with water. Through the valve 12 water is then
extracted until its level is lowered to a level as shown at 15.
This then leaves an upper evacuated space 16 which will then be
filled implicitly by substantially the vapour of the liquid.
[0049] From here on the arrangement will remain as a closed system
so that heat from the wall of the cavity 3 will be converted into
latent heat of vaporisation with the vapour reaching the condensing
chamber 8 to be returned to liquid. as it gives up the latent heat
of vaporisation to the heat exchange coil 9.
[0050] Now referring to FIGS. 2 through to 5, there is shown
specifically in FIGS. 2,3 and 5 the male side of an injection die
and for ease of description, reference will be made to these parts
and then later to the female side of the die as more generally
shown in FIG. 4.
[0051] Accordingly, the male form 17 is attached through
appropriate bolts which are located at position such as at 18 to a
block 19 which together with a backplate 20 forms a closed chamber
21 which holds a selected quantity of water shown generally at 22.
Male form 17 and block 18 may be formed as a single piece.
[0052] The water 22 does not totally fill the enclosed and closed
space 21 thereby leaving a space 23 above an upper level of the
water 24.
[0053] There is a heat exchanging cooling device at 25 which is
arranged by reason of tube 26 which has a plurality of fins 27 to
effect a cooling of water vapour as it exists within the space
23.
[0054] The temperature of the fins 27 is governed by arranging for
flow of cooling water through an inlet 28 which then proceeds
through the centre of a removable core 29 to an end 30 where the
water then is caused to pass through a spirally shaped gap 31 so
that it will pass fully the length of the hollow core 29 to then
exit through passageway 32.
[0055] An advantage of this arrangement is that the hollow core 29
is held by plug 33 so that from time to time, the core can be
easily removed and any build up of deposits, debris or otherwise
can be then effectively cleaned.
[0056] A gate valve 34 is adapted to effect a closure of aperture
35 and evacuation port 44 and there is a further closable plug at
36.
[0057] In order to charge the die, water is first vigorously boiled
for at least one minute so as to reduce possible dissolve gas from
the water.
[0058] The water is then poured into the chamber 21 through
aperture 36 so that it will fully fill the chamber. The gate valve
34 includes a pair of sealing members 45 thereon which act so that
when open, water can be extracted from the chamber through
evacuation port 44 while maintaining the closure of aperture 35 and
when closed, to prevent air from flowing into the chamber through
the evacuation port 44.
[0059] The amount of water removed is such as to provide a
sufficient space above the selected water level to allow for the
cooling device to operate within the environment generally only of
the water vapour and not the liquid water.
[0060] With the then degassed water partially filling the closed
chamber 21, it will be seen that the water then covers those parts
of the die as shown, for instance, in FIG. 2 which are immediately
adjacent those areas that will be in contact with heated plastics
materials and from which heat is to be extracted.
[0061] By reducing the pressure within the closed chamber 21, the
water adjacent to the hotter parts of the die will be caused to
boil at temperatures somewhat lower than 100 degrees Centigrade
(212 degrees Fahrenheit) and because of the high value of the
latent heat of evaporation of water such effect results in very
efficient extraction of heat from the hotter parts of the die.
[0062] By reason of the orientation of the die, and by reason of
shaping of the internal parts of the die so that vapour when formed
can rise into the uppermost space within the closed chamber 21,
this then will further concentrate water vapour in the space which
in turn will be cooled and therefore be condensed by heat exchange
from the heat exchanger system.
[0063] While different methods of preparing the status of liquid
within the closed chamber 21 can be used, and there has been
described in a general way, such an arrangement, in a further
method, there is firstly provided a funnel with a spout threaded to
fit the inlet or filling port to a capacity greater than the volume
of water to be removed from the filled enclosed chamber 21.
[0064] A reciprocating vacuum pump with a single stroke capacity
equal to the volume of water to be removed is attached to an
evacuation port.
[0065] Once the water has filled the chamber, the vacuum pump can
be used so as to withdraw and then return a number of times so as
to cause water within the system to surge back and forth so as to
assist in removal of any significant air bubbles which may have
been trapped while filling.
[0066] The chamber is then again topped up with water on the basis
that some air has been dislodged and driven to the surface of the
water and the inlet or filling port is then closed.
[0067] The vacuum pump can again be caused to withdraw and return a
number of times so as to cause water in the system to surge back
and forth. With each withdrawal, the pressure inside the chamber
will be considerably reduced and any remaining trapped bubbles of
gas will expand and most will rise to the surface of the water. The
vacuum pump stroke is then returned and the chamber is again topped
up with water and the inlet port is closed.
[0068] With a full stroke of the vacuum pump the required amount of
water will be extracted and the gate valve 34 is then screwed in to
close the evacuation port 44.
[0069] In this process, it is provided that the gate valve 34
allows the water to gravitate easily into the pump. Since air is
excluded substantially, gravity is needed to move the liquid into
the vacuum pump.
[0070] This describes, as has been previously stated, one side of
an injection die where the further portion of the injection die is
shown in exploded detail in FIG. 4. In this case then, there is a
closed chamber 37 which surrounds a female shape 38 into which the
male part 17 is located to form there between a moulding space
served by inlet port 39.
[0071] A back plate 40 has sealed engagement with the die 41 and
there are shown heat exchange means at 42 with a hollow removable
core 43.
[0072] The filling procedure of this side of the die is the same as
with the first male portion of the die.
[0073] One of the advantages of the arrangement described is that
the temperature of the die is automatically evened out because
boiling will occur preferentially at the higher temperature
locations thereby reducing its temperature to that of its
surrounding areas.
[0074] Consequently, with this system, there is a preferential
evening effect of the temperature which means that more
sophisticated techniques for attempting to keep temperatures even
are no longer necessary.
[0075] The mould temperature, for instance, can be controlled very
evenly and effectively by controlling the flow of coolant such as
water, through the heat exchanger. This leads to the further
arrangement including the location of a thermostat so as to respond
to the temperature of the liquid in the closed chamber.
[0076] Accordingly, this can be connected through a servo
controller so as to interrupt flow of coolant liquid through the
heat exchanger whenever the temperature falls below a selected
value and can restore or increase the flow rate of cooling liquid
whenever the temperature of the fluid in the enclosed chamber rises
above another slightly higher selected level.
Experimental Results
[0077] A prototype unit has been made and tested. This unit was
manufactured as the male portion of the injection die which is the
arrangement as shown in FIGS. 2, 3 and 5 with a face area of 250 mm
and of course the disclosed protruding core, 70 mm in diameter and
55 mm long. The enclosed chamber then had a wall thickness at the
die portion of 12 mm.
[0078] The described method of effecting a charging of water which
had been degassed and then having a portion removed to leave only
water vapour in a space was applied.
[0079] The effectiveness of the cooling action described was tested
as follows: 1. Coolant water was supplied to the heat exchanger at
a temperature of 27 degrees Centigrade which was the ambient
temperature at the time of the test.
[0080] 2. Two gas blow torches were directed at the surface of the
core and kept continuously heating on the outer surface of the
protruding die surface.
[0081] The temperature of the coolant, of the core and of water in
the enclosed chamber were monitored using digital pyrometers.
[0082] 3. The flow rate of coolant through the heat exchanger was
adjusted to achieve a flow rate of four litres per minute.
[0083] 4. The output of the blow torches was adjusted until a
temperature rise of 2.7 degrees Centigrade in the coolant was
achieved. This corresponded to a heat extraction rate of 750
watts.
[0084] 5. The temperature of the die was found under these
conditions to reach and be sustained at 48 degrees Centigrade which
is to say 21 degrees
[0085] Centigrade above the coolant temperature.
[0086] 6. The temperature of water in the enclosed chamber was
stabilised and was 35 degrees Centigrade.
[0087] Direct calculation of an expected temperature of the core,
based on its geometry and the test conditions, were also made. The
calculated temperature differential through the walls of the core
is 12 degrees Centigrade and this was found to correspond very well
with the experimental result. The remainder of the temperature
differential (8 degrees Centigrade) is a function of the efficiency
of the heat exchanger.
[0088] It is considered from the above experimental results that
these illustrate a very outstanding effective result which will be
of very significant value in many applications where machines are
to be cooled and where achieving a uniformity of the cooling effect
is of value.
[0089] Further, because the closed chamber keeps the same water
through the full cooling process, it is not expected that there
will be mineral deposit or other significant corrosion (as a result
of the absence of air).
[0090] While in preference only water is used, other liquids or
mixtures of liquids can be used and, in such a case, it is
substantially only the vapours of the liquids that will exist only
in the space above the level of the liquid in the closed
chamber.
* * * * *