U.S. patent number 3,702,533 [Application Number 05/093,104] was granted by the patent office on 1972-11-14 for hot-gas machine comprising a heat transfer device.
This patent grant is currently assigned to U.S. Philips Corporation. Invention is credited to George Albert Apolonia Asselman, Adrianus Petrus Dirne, Herman Henricus Maria VAN DER Aa.
United States Patent |
3,702,533 |
Dirne , et al. |
November 14, 1972 |
HOT-GAS MACHINE COMPRISING A HEAT TRANSFER DEVICE
Abstract
A hot-gas machine in which a gaseous medium performs a closed
thermodynamic cycle, includes a heat conveying device which is
capable of conveying heat by means of an evaporation - condensation
process from a heat source to the heater of the machine. This
device comprises at least two closed spaces containing
conveying-medium and arranged one after the other in the direction
of heat conveyance, the distal ends of these spaces being provided
with heat transferring walls across which heat can be conducted
from the heat source to the conveying medium, or the conveying
medium can give off heat to the heater; the proximal ends of these
spaces comprises further heat-transferring walls, between which a
switching element is provided for the establishment of a thermal
and variable contact between these further walls.
Inventors: |
Dirne; Adrianus Petrus
(Emmasingel, Eindhoven, NL), Asselman; George Albert
Apolonia (Emmasingel, Eindhoven, NL), VAN DER Aa;
Herman Henricus Maria (Emmasingel, Eindhoven, NL) |
Assignee: |
U.S. Philips Corporation (New
York, NY)
|
Family
ID: |
19808704 |
Appl.
No.: |
05/093,104 |
Filed: |
November 27, 1970 |
Foreign Application Priority Data
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Dec 24, 1969 [NL] |
|
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6919338 |
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Current U.S.
Class: |
60/524; 165/96;
165/104.26; 60/525; 165/104.14 |
Current CPC
Class: |
F02G
1/055 (20130101); F28D 15/06 (20130101); F02G
1/053 (20130101); F02G 1/047 (20130101); F02G
2258/10 (20130101); F02G 2254/20 (20130101) |
Current International
Class: |
F02G
1/00 (20060101); F02G 1/055 (20060101); F02G
1/053 (20060101); F02G 1/047 (20060101); F28D
15/06 (20060101); F03g 007/06 () |
Field of
Search: |
;60/1,24,25,105,107,108
;165/96,105 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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1,122,970 |
|
1962 |
|
DT |
|
63,822 |
|
1949 |
|
NL |
|
Primary Examiner: Schwadron; Martin P.
Assistant Examiner: Ostrager; A. M.
Claims
What is claimed is:
1. A hot-gas machine such as a hot-gas reciprocating engine or
turbine, in which a gaseous medium performs a closed thermodynamic
cycle, said machine comprising a heat exchanger in which the cyclic
medium receives heat from without from a heat source, such as a
heat accumulator, and a heat transfer device being arranged between
the heat source and the heat exchanger, and containing a
heat-transporting medium which absorbs heat from the heat source
while changing from the liquid to the vapor phase, and gives off
heat to the heat exchanger while changing from the vapor to the
liquid phase, characterized in that the heat transfer device
comprises at least two closed spaces containing heat-transporting
medium and arranged one after the other in the direction of heat
transport, the distal ends of said spaces being provided with
heat-passing walls through which heat from the heat source can be
supplied to the transporting medium and through which the medium
can give off heat to the heat exchanger, whereas the proximal ends
of said spaces comprise further heat-passing walls between which a
switching element is provided for establishing a thermal contact
between said further walls.
2. A machine as claimed in claim 1 characterized in that each space
comprises a porous mass of material which connects the heat-passing
wall with the further heat-passing wall.
3. A machine as claimed in claim 1 characterized in that the
switching element is formed by a reservoir having two heat-passing
walls, each of which is in contact with a further heat-passing wall
or which are formed also by a further heat-passing wall, the
reservoir containing a heat transporting medium, the pressure and
the quantity of which can be controlled.
4. A machine as claimed in claim 3 characterized in that the heat
transporting medium in the reservoir transports heat from a hot
heat-passing wall to a cold heat-passing wall of the reservoir
while changing from the liquid phase to the vapor phase at the
absorption of heat from the hot heat-passing wall of the reservoir
and while changing from the vapor phase to the liquid phase when
giving off heat to the cold heat-passing wall of the reservoir,
there being provided an auxiliary reservoir comprising a portion
operating as a liquid space and a portion operating as a vapor
space, the auxiliary reservoir being in open communication with the
reservoir through a vapor duct connected with the vapor space, the
auxiliary reservoir being capable of absorbing cold from a cold
source for condensing and/or solidifying transporting medium in the
liquid space or of absorbing heat from a heat source for melting
and/or evaporating transporting medium in said liquid space.
5. A machine as claimed in claim 4 characterized in that the
auxiliary reservoir also is in open communication with the
reservoir via a liquid duct connected with the liquid space of the
auxiliary reservoir, through which duct liquid transporting medium
can flow from the auxiliary reservoir to the reservoir, said liquid
duct comprising a liquid trap which can be cooled and in which
liquid transporting medium can solidify for cutting off the liquid
duct.
6. A machine as claimed in claim 5 characterized in that the liquid
trap is formed by at least a portion of the liquid duct in which a
porous filling mass is arranged,
7. A machine as claimed in claim 3, characterized in that the
reservoir comprises a porous mass of material, which interconnects
the heat passing walls of the reservoir.
8. A machine as claimed in claim 3 characterized in that the
reservoir accommodates radiation screens for preventing heat
transfer by radiation between the heat passing walls of the
reservoir.
9. A hot-gas engine in which a gaseous medium performs a closed
thermodynamic cycle, said machine operable with a heat source and
including a heat-exchanger in which said gaseous medium receives
heat from said source, and a heat transfer device which contains a
heat-transporting medium and is disposed between the heat source
and the heat exchanger, this transfer device comprising means
defining at least two closed spaces containing said
heat-transporting medium, these spaces positioned sequentially and
thus having two remote, distal ends and two adjacent proximal ends,
each of said ends comprising a heat-passing wall, whereby heat is
cyclically transmitted through one distal end-wall from the heat
source to said heat-transporting medium in one space, which medium
then changes from liquid to vapor phase, and through the other
distal end wall of said other space from said heat-transporting
medium therein to the heat-exchanger, which medium then changes
from vapor to liquid phase, said device further comprising a
switching element between said proximal end-walls for establishing
a thermal contact therebetween.
10. Apparatus according to claim 9 comprising a porous mass within
said spaces which mass connects each remote wall with a proximal
wall of each space.
11. Apparatus according to claim 9 wherein said switching element
comprises a main reservoir having two heat-passing walls, each of
which is in contact with a proximal heat-passing wall, the
reservoir containing a heat-transporting medium, the pressure and
the quantity of which can be controlled.
12. Apparatus according to claim 11 wherein said heat-transporting
medium in the main reservoir transports heat from a hot
heat-passing wall to a cold heat-passing wall of the main reservoir
while changing from the liquid phase to the vapor phase at the
absorption of heat from the hot heat-passing wall of the main
reservoir and while changing from the vapor phase to the liquid
phase when giving off heat to the cold heat-passing wall of the
main reservoir, the apparatus further comprising an auxiliary
reservoir having a portion operating as a liquid space and a
portion operating as a vapor space, the auxiliary reservoir being
in open communication with the main reservoir through a vapor duct
connected with the vapor space, the auxiliary reservoir being
capable of absorbing cold from a cold source for condensing and/or
solidifying transporting medium in the liquid space or of absorbing
heat from a heat source for melting and/or evaporating transporting
medium in said liquid space.
13. Apparatus according to claim 12 wherein said auxiliary
reservoir also is in open communication with the main reservoir via
a liquid duct connected with the liquid space of the auxiliary
reservoir, through which duct liquid transporting medium can flow
from the auxiliary reservoir to the reservoir, said liquid duct
comprising a liquid trap which can be cooled and in which liquid
transporting medium can solidify for cutting off the liquid
duct.
14. Apparatus according to claim 13 wherein said liquid trap is
formed by at least a portion of the liquid duct in which a porous
filling mass is arranged.
Description
BACKGROUND OF THE INVENTION
The invention relates to a hot-gas machine, for example, a hot-gas
reciprocating engine or a hot-gas turbine, in which a gaseous
medium performs a closed thermodynamic cycle. The machine includes
a heater in which the cyclic medium receives heat from the outside
from a source of heat; particularly a heat accumulator, a heat
transfer device is provided between the heat source and the heater,
said device containing a heat transporting medium which absorbs
heat from the heat source while changing over from the liquid phase
to the vapor phase, and giving off heat to the heater while
changing-over from the vapor phase into the liquid phase. A prior
art machine of this kind is known from Dutch Pat. Specification No.
58,355.
The heat transfer device may serve various purposes. It may be
advantageous for reasons of space to arrange the heat source at a
distance from the heater; for example, in vehicles may be equipped
with a thermodynamic engine, in which the heat is furnished by a
re-chargeable heat accumulator arranged elsewhere in the vehicle.
The nature of the heat source may involve the desirability or
necessity to dispose the machine at a distance from said source,
for example, when the heat is supplied from a nuclear reactor, and
when the machine has to be protected from the dangers of the
radiation released by the nuclear reactions and the like. It may
furthermore be advantageous to use that transfer device for
establishing a thermal contact between the heaters of a number of
thermodynamic machines or the various heaters of a multi-cylinder
thermodynamic engine and one and the same common heat source.
In the above-mentioned cases, practice gives rise to a problem: the
interruption of the heat transfer from the heat source to the
heater. If, for example, a plurality of heaters of one or more
machines communicate through separate heat transfer devices with
the same heat source, and if the heat transport to one of said
heaters has to be interrupted, for examplem because the machine is
stopped or because the power of a multi-cylinder thermodynamic
engine is reduced by putting a cylinder out of operation, the heat
supply from the heat source to the further machines or cylinders
has to be continued. It is then not allowed to arrest the
production of heat by the heat source, if this is possible; nor
neither is it allowed to remove the heat source. The latter
encounters frequent practical difficulties, particularly when the
heat source is a heat accumulator forming an integral part of the
heat transfer device.
The heat transfer device usually forms part of the machine, so that
interruption of the heat transport by removal of the heat transfer
device would require a time-consuming dismounting operation, the
more difficult on account of the high heater temperatures, which
may exceed 700.degree. C in thermodynamic engines. Finally also
turning away and/or displacing of the heat transfer device in
conjunction or not in conjunction with the machine with respect to
the heat source are attended by great practical inconveniences.
THE NEW INVENTION
The present invention has for its object to provide a hot-gas
machine comprising a heat transfer device, in which the heat
transport from the heat source to the heater can be interrupted in
a simple, rapid manner.
The hot-gas machine in accordance with the invention is
characterized in that the heat transfer device comprises at least
two closed spaces containing a heat transporting medium and
arranged one after the other in the direction of heat transport;
the distal ends of these spaces are provided with heat-passing
walls through which heat from the heat source can be conducted to
the transporting medium, or the latter can give off heat to the
heater, the proximal ends of said spaces having further
heat-passing walls between which a switching element is provided
for establishing a thermal contact between said further walls.
In this way a machine is obtained in which the heat transfer from
the heat source to the heater can be interrupted simply by
actuating the switching element.
If the place of condensation of a space is located at a higher
level than the place of evaporation, the return of condensate from
the condensation place to the evaporation place may be performed
under the action of the force of gravity. If this is not the case,
each space of an advantageous embodiment of the machine in
accordance with the invention may comprise a porous mass of
material which connects the heat passing wall with the further
heat-passing wall. By the capillary action of this mass of
material, the reflow of condensate may then also take place without
contribution of the force of gravity and even against the force of
gravity. This means a great independence of position of the machine
comprising a heat transfer device.
In a further advantageous machine embodying the invention the
switching element is formed by a reservoir having two heat-passing
reservoir walls, which are each in contact with a further
heat-passing wall or are also formed by a further heat-passing
wall, the reservoir containing a heat transporting medium of
variable pressure and/or quantity.
The heat transporting medium in the reservoir may be formed by a
liquid which always remains in the same state of aggregation. A
decrease of the quantity of liquid in the reservoir results in a
decrease of the flow of heat between the two heat-passing walls of
the reservoir. The heat transfer is blocked, when the whole
quantity of liquid is removed from the reservoir.
A further advantageous machine embodying the invention is
characterized in that the heat transporting-medium in the reservoir
conducts heat from a hot heat-passing wall to a cold one of the
reservoir while the liquid changes over to the vapor phase when
heat is absorbed from the hot heat-passing wall and the vapor
changes over to the liquid phase when heat is given off to the cold
heat-passing wall; there is provided an auxiliary reservoir having
portions serving as a liquid space and as a vapor space
respectively and being in open communication with the reservoir
through a vapor duct connected with the vapor space; the auxiliary
reservoir is capable of absorbing cold from a cold source for
condensing and/or solidifying the transporting-medium in the liquid
space and of absorbing heat from a heat source for melting and/or
evaporating the transporting-medium in said liquid space. In
operation of the machine, only vaporous transporting-medium can
flow from the reservoir to the auxiliary reservoir or conversely.
Transporting-medium condensed or solidified in the auxiliary
reservoir is retained therein and is therefore no longer available
for the heat transfer between the two heat passing walls of the
reservoir. By storing a greater or smaller quantity of
transporting-medium in the liquid phase and/or solid phase in the
auxiliary reservoir, a smaller or greater heat transfer will occur
from the hot reservoir heat passing wall to the cold heat-passing
wall of the reservoir.
Apart therefrom it is possible by increasing the pressure in the
reservoir, for example, by admitting an inert, compressed gas into
the reservoir, to raise the boiling point of the heat
transporting-medium so that the increased boiling point exceeds the
operational temperature of the hot heat-passing wall of the
reservoir. The transporting-medium is then no longer evaporated and
the heat transfer between the heat-passing walls of the reservoir
is arrested.
According to the invention the aforesaid auxiliary reservoir may be
in open communication with the reservoir also through a liquid duct
connected with the liquid space of the auxiliary reservoir for
passing transporting-medium from the auxiliary reservoir to the
reservoir; this liquid duct includes a liquid trap adapted to be
cooled, in which liquid transporting medium can be solidified for
closing the liquid duct. This provides the advantage that
transporting medium to be conducted back from the auxiliary
reservoir to the reservoir need not be first evaporated, but can
flow back in the liquid phase. By freezing the liquid trap the flow
of liquid can be arrested so that the whole quantity of
transporting medium condensed or solidified in the auxiliary
reservoir is kept therein.
In an advantageous machine embodying the invention the liquid trap
is formed by at least a portion of the liquid duct comprising a
porous filling mass.
A further advantageous machine embodying the invention is
characterized in that the reservoir comprises a porous mass of
material, which interconnects the heat passing walls of the
reservoir. If the heat transport in the reservoir is carried out by
an evaporation-condensation process between the two heat passing
walls of the reservoir, the transporting medium condensed on the
colder wall can readily be conducted back to the hotter wall
without the action of gravity or against gravity by the capillary
action of the suitably chosen porous mass of material. According to
the invention the reservoir may accommodate radiation screens for
preventing heat transfer by radiation between the heat passing
walls of the reservoir.
The invention furthermore relates to a heat transfer device of the
kind set forth. Although the transfer device is particularly
suitable for use in thermodynamic engines, its use is not
restricted thereto. The invention will be described more fully with
reference to the drawing, which shows a few embodiments
schematically not to scale.
DESCRIPTION OF THE DRAWINGS
FIG. 1 shows a hot-gas engine comprising a heat transfer device, in
which the switching element is formed by a liquid layer in a
reservoir between the two spaces.
FIGS. 2 and 3 show hot-gas engines, in which the reservoir serving
as a switching element comprises a medium which transports heat by
means of an evaporation-condensation process, the pressure of said
medium being variable by the supply or outlet of an inert gas in
the reservoir.
FIGS. 4 and 5 show a hot-gas engine in which the reservoir serving
as a switching element comprises a medium transporting heat by
means of an evaporation-condensation process, which medium can be
withdrawn holly or partly from the reservoir and be stored in an
auxiliary reservoir communicating therewith.
FIGS. 6a and 6b each show two hot-gas engines communicating each
via a heat transfer device with a common heat source, each transfer
device comprises as a switching element a reservoir in which a
medium is contained which transports heat by means of an
evaporation-condensation process and which medium can be stored
wholly or partly in an auxiliary reservoir.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to FIG. 1, reference numeral 1 designates the cylinder of
a hot-gas engine in that part in which in operation the cyclic
medium is constantly at a high temperature. The cylinder comprises
a displacer 2 which is capable of displacing hot cyclic medium from
the expansion space 4 towards the cold side of the engine by moving
upwardly and by means of a driving gear (not shown) connected with
the displacer rod 3. The cyclic medium passes through a heater 5, a
regenerator 6 and a cooler 7. Heat can be supplied from without
through the wall of the which is a heat exchanger to the cyclic
medium in the expansion space 4. The wall of the heater 5 forms a
heat passing wall 8 of a closed space 9, which forms part of a heat
transfer device 10. The space 9 has furthermore a further heat
passing wall 11 and is otherwise thermally isolated from the
surroundings.
The heat transfer device 10 comprises furthermore a closed space 12
comprising on the one hand a heat passing wall 13 and on the other
hand a further heat passing wall 14, and being otherwise thermally
isolated from the surroundings. The further heat passing walls 11
and 14 form, in addition, heat passing walls of a reservoir 15,
which is otherwise thermally isolated from the surroundings. The
term "heat passing wall" has to denote a wall having low thermal
resistivity. These are not only walls of material of high thermal
conductivity but also walls of materials of lower thermal
conductivity, provided the thickness of the wall is sufficiently
small.
The further heat passing wall 13 of the space 12 is in thermal
contact with a heat source 16 of high temperature, which may be a
heat accumulator storing latent heat and/or sensible heat. The heat
accumulator may be secured to the heat passing wall 13 or it may be
arranged separately therefrom. As an alternative, the heat
accumulator may be arranged inside the space 12; it has then to be
possible to recharge the heat accumulator after use. The spaces 9
and 12 are both filled partly with a suitably chosen quantity of
liquid transporting medium, which can evaporate at the temperature
level of the heat source.
With a view to the high temperatures (about 700.degree. C) of the
heater of the hot-gas engine, suitable transporting media are, for
example, the metals sodium, potassium, lithium, cadmium, cesium,
metal salts such as the metalogenes, zinc chloride, aluminum
bromide, cadmium iodide, calcium iodide, zinc bromide or mixtures
thereof. Suitable for use are furthermore nitrates, nitrites or
mixtures thereof.
The reservoir 15 contains a liquid which forms a thermal connection
between the further heat passing walls 11 and 14. In the operation
of the hot-gas engine the liquid layer remains in the liquid phase.
It may be chosen in accordance with the choice of the transporting
medium in the spaces 9 and 12 determined by the temperature of the
heater of the heat source.
A liquid inlet 17 and a liquid outlet 18 communicate with the
reservoir 15. The thermal expansion of the small quantity of liquid
in the reservoir 15 may be compensated for by connecting an
expansion vessel with the liquid inlet 17, which is not shown in
the drawing.
The device operates as follows: The heat source 16 supplies heat
through the heat passing wall 13 to the liquid transporting medium
inside the space 12 on said wall. This transporting medium
evaporates and moves to the further heat passing wall 14 owing to
the locally prevailing low vapor pressure as a result of the
comparatively low local temperature. The movement of the vapor is
indicated by broken arrow lines, The vapor then condenses on the
further heat passing wall 14, while giving off evaporation heat to
said wall. Under the action of gravity the condensate flows back to
the heat passing wall 13, where it is again evaporated. The flow of
the condensate is indicated by full arrows. The heat absorbed by
the further heat passing wall 14 passes through the liquid layer in
the reservoir 15 and through the further heat passing wall 11 to
the space 9 and causes evaporation of liquid transporting medium
contained inside said space on the further heat passing wall 11.
The evaporation-condensation process performed inside the space 9
is identical to that in the space 12. The evaporation heat released
by the condensation of transporting medium on the heat passing wall
8 passes through said wall to the cyclic medium in the expansion
space 4 in order to compensate for the caloric energy converted
into mechanical energy during the expansion of the cyclic medium
and also in order to compensate for the normal caloric losses.
If the heat transport from the heat source 16 to the heater 5 has
to be interrupted, for example, for stopping the engine, this can
be carried out in a simple manner by removing the liquid from the
reservoir 15 via the liquid outlet 18 and, if necessary, by further
exhausting the reservoir 15. Even if the heat source 16 continues
supplying heat, for example, if it is a heat accumulator, the
supplied heat cannot attain the heater 5. The sole consequence is
that an evaporation-condensation process is performed only inside
the space 12 until the vapor pressure in the portion of the space
12 adjacent the further heat passing wall 14 is equal to the vapor
pressure at the heat passing wall 13, the latter being determined
by the temperature of the heat source 16. As a matter of course,
the space 12 has to be structurally formed so that its walls can
withstand the potential maximum vapor pressure.
In the device shown in FIG. 1 a small quantity of heat will always
leak from space 12 to space 9 due to thermal radiation from the
further heat passage wall 14 to the further heat passage wall 11.
This may, in general, be prevented by arranging radiation screens
in the reservoir, which screens block the passage of thermal
radiation.
In the device shown in FIG. 2 corresponding parts are designated by
the same reference numerals as in FIG. 1. The reservoir 15
accommodates radiation screens 19, which prevent the radiation heat
from the further heat passing wall 14 from reaching the further
heat passing wall 11. The reservoir 15 is partly filled with liquid
transporting medium.
The operation of this device differs from that of FIG. 1 only to an
extend such that in operation heat supplied by the further heat
passing wall 14 to the reservoir 15 produces evaporation of liquid
transporting medium in said reservoir. The resultant vapor moves
towards the region of low vapor pressure, that is to say, near the
comparatively cold further heat passing wall 11. It condenses on
said wall while giving off the released condensation heat and under
the action of the gravity component it flows along the slope of the
reservoir as a liquid back to the further heat passing wall 14,
where the liquid evaporates again. A duct 20 communicates with the
reservoir and includes a cook 21, which is adapted to establish a
communication between the reservoir 15 and either the gas cylinder
22 containing a compressed inert gas or a pumping device 23.
Between the cock 21 and the gas cylinder 22 a pressure reducing
valve 24 is provided and between the cock 21 and the pumping device
23 a vapor trap 25 is arranged for transporting medium.
If the heat transport from the heat source 16 to the heater 5 has
to be interrupted, inert gas is supplied from the gas cylinder 22
to the reservoir 15. The pressure of the inert gas produces such as
increase in the boiling point of the transporting medium in the
reservoir 15 that the new boiling point exceeds the temperature of
the further heat passing wall 14. The evaporation of liquid
transporting medium in the reservoir is then stopped and hence also
the heat transport from the further heat passing wall 14 to the
further heat passing wall 11.
When the heat transport has to be restored, the reservoir 15 is
communicated with the pumping device 23, which pumps away the inert
gas from the reservoir 15. Any medium vapor carried along with the
inert gas can condensate in the vapor trap 25 by cooling and be
held therein.
Obviously all kinds of shapes and dispositions as, for example,
those of FIG. 1, are possible provided it is ensured that
condensate can flow back to the place of evaporation.
FIG. 3 shows a device which is substantially identical to that of
FIG. 2. Corresponding parts are designated by the same reference
numerals as in FIG. 2. The device shown in FIG. 3 differs
essentially from that of FIG. 2 by the presence of porous masses of
material 26, 27 and 28 on the inner walls of the space 9, the
reservoir 15 and the space 12. These porous masses of material have
such a capillary structure that by utilizing the surface tension of
the liquid transporting medium in the space or the reservoir
respectively, in the given operational state of the space or the
reservoir respectively, they are capable of conducting by capillary
action the condensate formed on the comparatively cold heat passing
wall, on the heat passing wall of the space or on the reservoir
respectively back to the comparatively hot heat passing wall, the
further heat passing wall of the space or the reservoir
respectively.
In this way a flow-back of condensate is possible without using the
force of gravity or in the absence of the gravitational
acceleration, and even against this acceleration. This provides
great freedom in the disposition of the hot-gas engine and in the
disposition or construction of the various parts of the heat
transfer device.
In the assembly of FIG. 3, in which the heat transfer device is
arranged in a horizontal plane, flow-back of condensate is
performed in spite of the horizontal position. This is performed in
space 12 by the absorption of condensate formed at the further heat
passing wall 14 in the porous mass of material 28, which conveys
the condensate by capillary effect to the heat passing wall 13.
In a similar manner condensate in reservoir 15 is conveyed from the
further heat passing wall 11 to the further heat passing wall 14
via the porous mass of material 27 and in space 9 from the heat
passing wall 8 to the further heat passing wall 11 via the porous
mass of material 26.
The operation of the device shown in FIG. 3 is otherwise similar to
that of FIG. 2 so that further description is dispensed with.
The porous mass of material may be formed by ceramic material, by
wire- or tape-shaped material of metal or metal alloys or by an
array of tubes and the like. The choice depends inter alia upon the
chosen heat transporting medium and on the prevailing temperatures
in the operation of the device.
FIG. 4 shows a hot-gas engine comprising a heat transfer device
between the heater and the heat source, the difference from that of
FIG. 3 being that the reservoir 15 in the present case is in open
communication through a vapor duct 29 with an auxiliary reservoir
30, in which a heating coil 31 and a cooling coil 31' are arranged.
If the heat transfer between the heat source 16 and the heater 5
has to be interrupted, this is performed by cooling the auxiliary
reservoir 30. Owing to the low temperature then prevailing in the
auxiliary reservoir transporting medium vapor will flow through the
vapor duct 29 from the reservoir 15 to the auxiliary reservoir, in
which it will condense or even solidify. It is thus possible to
withdraw the whole quantity of medium from the reservoir 15 and to
store it in the auxiliary reservoir 30. In the absence of medium in
the reservoir 15 the heat transfer is blocked. If the heat transfer
has to be restored, heat is conducted to the auxiliary reservoir
30, in this case by means of the heating coil 31, so that medium
evaporates from the auxiliary reservoir 30 and flows back to the
reservoir 15 via the vapor duct 29. In order to maintain the
restored heat transfer, heat, be it a small value, has constantly
to be supplied to the auxiliary reservoir 30 in order to avoid that
the temperature and hence the vapor pressure inside the auxiliary
reservoir 30 drop below those at the further heat passing wall 11.
This might give rise to a flow of medium vapor from the further
heat passing wall 14 to the auxiliary reservoir 30, in which it
would condense instead of travelling on to the further heat passing
wall 11, where it has to condense.
In the device shown in FIG. 4 medium condensed or solidified in the
auxiliary reservoir 30 has first to be evaporated before the return
to the reservoir 15 is possible and in operation the auxiliary
reservoir 30 has to be kept hot.
This is contrary to the device shown in FIG. 5, which coarsely
corresponds with that of FIG. 4, there being provided, however, a
liquid duct 32 joining on the one hand that portion of the
auxiliary reservoir 30 in which liquid or solidified medium can be
stored and on the other hand the reservoir 15. The liquid duct 32
includes a porous filling mass 33, which contributes to the use of
the liquid duct 32 in addition as a liquid trap. The liquid duct 32
can be cooled for this purpose and can be heated with the aid of
the heating coil 31, which surrounds herein not only the auxiliary
reservoir 30 but also the liquid duct 32.
In order to interrupt the heat transport between the heat source 16
and the heater 5 the auxiliary reservoir 30 and the liquid duct 32
are cooled. Then medium vapor is again conveyed from the reservoir
15 through the vapor duct 29 to the auxiliary reservoir 30. This
vapor is condensed and solidified in the auxiliary reservoir. This
operation continues until the reservoir 15 has become dry, so that
the heat transfer in this reservoir is cut off.
By the capillary action of the porous filling mass 33 the liquid
duct 32 is completely filled with liquid. It is thus avoided that
medium vapor from the reservoir 15 penetrates into the liquid duct
32, which would render solidification impossible due to the high
heat content of this vapor.
The porous filling mass 33 performs during the solidification
process also the function of flow resistor, which ensures that
liquid medium can pass only with comparatively low speed through
the liquid duct 32 so that owing to this low speed solidification
of liquid in the liquid duct 32 is additionally facilitated. The
passage is then cut off so that the liquid medium can readily
solidify in the auxiliary reservoir 30.
Even without porous filling mass it is possible to cause
solidification of liquid in the liquid duct 32, for example, by
constructing a portion of the liquid duct in the form of a bend,
which is filled with liquid and cooled.
If the heat transfer has to be restored, the solid medium in the
auxiliary reservoir 30 and the liquid duct 32 is melted with the
aid of the heating coil 31. By the capillary action of the porous
filling mass 33 and in this case also under the action of gravity
liquid medium flows from the auxiliary reservoir 30 via the liquid
duct 32 into the porous mass 27 of reservoir 15 and moves towards
the further heat passing wall 14, where it is evaporated. The
evaporation-condensation process inside the reservoir 15 and hence
the heat transfer are thus restored.
The further operation of this device is identical to that of the
device shown in FIG. 4.
FIGS. 6a and 6b show assemblies in which two hot-gas engines
communicate each via a heat transfer device with a single common
heat source.
Since the construction and the operation of the heat transfer
devices of FIG. 6a are identical to those of the device of FIG. 5,
a further description may be dispensed with. Corresponding parts
are designated by the same reference numerals as in FIG. 5. The
device shown permits in a simple manner of interrupting or
restoring at will the heat transfer from the heat source 16 to the
heater of a hot-gas engine or to the heater of the two hot-gas
engines. This is particularly important when the heat source is
formed by a heat accumulator, which supplies heat continuously to
the spaces 12. By interrupting the heat transfer in a heat transfer
device from the space 12 to the space 9 by means of the reservoir
15, a thermal equilibrium is established between the heat
accumulator 16 and the space 12 concerned.
The device shown in FIG. 6b differs from that shown in FIG. 6a only
to such an extent that the two heat transfer devices have a common
space 12 having a single heat passing wall 13, through which heat
from the heat source 16 can be supplied to the medium inside the
space 12. At the heat passing wall 13 in the space 12 medium
evaporates and flows in two directions towards the two further heat
passing walls 14 of the space 12, where it condenses, while giving
off its condensation heat. The condensate is conducted by the
capillary action of the appropriately chosen porous mass of
material 28 back to the heat passing wall 13, where it evaporates
again.
Interruption or restoration of the heat transfer from the heat
source 16 to one or both heaters 8 are performed in the same manner
as described with reference to FIG. 5.
In the devices of the kind shown in FIGS. 4, 5 and 6 the switching
element may also be a reservoir filled with a liquid forming a
thermally conducting layer between the further heat passing walls
11 and 14. A regulation of the liquid level then results in a
control of the heat passing surface and hence of the heat
transfer.
In the arrangement shown in the drawing the further heat passing
walls of the spaces 9 and 12 also form the heat passing walls of
the reservoir 15. Obviously, the reservoir may have its own heat
passing walls, which are in contact with the further heat passing
walls of the spaces 9 and 12.
* * * * *