U.S. patent number 3,817,322 [Application Number 05/294,652] was granted by the patent office on 1974-06-18 for heating system.
This patent grant is currently assigned to U.S. Philips Corporation. Invention is credited to George Albert Apolonia Asselman, Herman Henricus Maria Van der Aa.
United States Patent |
3,817,322 |
Asselman , et al. |
June 18, 1974 |
**Please see images for:
( Certificate of Correction ) ** |
HEATING SYSTEM
Abstract
A heating system for a machine having a closed thermo-dynamic
cycle, the system comprising a closed space within which several
containers for heat-accumulating material are present as well as a
medium transporting thermal energy by evaporation and condensation.
The containers communicates with a common supply duct for
heat-accumulating material, with spacing members arranged between
the walls of the closed space and the containers as well as between
the containers mutually.
Inventors: |
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: |
19813844 |
Appl.
No.: |
05/294,652 |
Filed: |
October 3, 1972 |
Foreign Application Priority Data
Current U.S.
Class: |
165/104.26;
60/523; 60/517; 60/524 |
Current CPC
Class: |
F01K
9/026 (20130101); F28D 15/04 (20130101); F01K
3/00 (20130101); F02G 1/055 (20130101); F28D
20/02 (20130101); Y02E 60/145 (20130101); Y02E
60/14 (20130101); F02G 2258/10 (20130101) |
Current International
Class: |
F28D
15/04 (20060101); F01K 3/00 (20060101); F01K
9/00 (20060101); F01K 9/02 (20060101); F02G
1/00 (20060101); F02G 1/055 (20060101); F28d
015/00 () |
Field of
Search: |
;165/105,104 ;126/400
;60/517,523,524 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Davis, Jr.; Albert W.
Attorney, Agent or Firm: Trifari; Frank R.
Claims
What is claimed is:
1. In a heating system for supplying thermal energy to a heater of
a hot gas engine, the system being operable with a supply of
meltable, heat-accumulating material, and including: a housing
having walls defining a closed space which encloses said heater and
which has a heat receiving portion, a plurality of containers in
said space, each containing said heat-accumulating material, and
each having at least one heat transmission wall, a heat
transporting medium in said space, which when in liquid receives
thermal energy from said container through said walls and
evaporates into a vapor which flows to said heater to which the
thermal energy is transferred during condensation of said vapor
thereon, a porous mass having a capillary structure on the outside
of said heat transmission walls of said containers, and on the
inside of the housing walls whereby said porous mass transports the
heat transporting medium in the liquid state between the heater,
the heat receiving portion of the housing and the containers, a
common supply duct communicating said supply of heat-accumulating
material through said housing wall to said containers within said
housing, means for controlling flow of said material through said
supply duct, and spacing means in said housing between and
separating said containers, and between said containers and the
housing walls, this spacing means being porous and permitting flow
there through of said heat-transporting medium vapor.
2. A system according to claim 1 wherein said heat-accumulating
material is LiF and said heat transporting medium is Na.
3. A heating system according to claim 1, further comprising a
pressure control device communicating in the said common supply
duct for controlling the pressure in the containers.
4. A heating system according to claim 1, wherein said spacing
means are formed by a porous filling mass, the pores of which have
larger diameters than the pores of said porous mass.
5. A heating system according to claim 4, wherein the porous
filling mass comprises compressed steel wool.
6. A system according to claim 2 wherein said spacing means are
formed by a porous filling mass, the pores of which have larger
diameters than the pores of said porous mass.
7. A system according to claim 2 wherein said porous filling mass
comprises compressed steel wool.
8. A heat pipe system for supplying thermal energy to a heater of a
hot gas engine, the system being operable with a supply of
meltable, heat-accumulating material, and comprising a housing
having walls defining a closed space which encloses said heater and
which has a heat receiving portion, a plurality of containers in
said space, each containing said heat-accumulating material, and
each having at least one heat transmission wall, a heat
transporting medium in said space, which when in liquid receives
thermal energy from said container through said walls and
evaporates into a vapor which flows to said heater to which the
thermal energy is transferred during condensation of said vapor
thereon, a porous mass having a capillary structure on the outside
of said heat transmission walls of said containers and on the
inside of the housing walls whereby said porous mass transports the
heat transporting medium in the liquid state between the heater,
the heat receiving portion of the housing and the containers, a
common supply duct communicating said supply of heat-accumulating
material through said housing wall to said containers within said
housing, means for controlling flow of said material through said
supply duct, and spacing means in said housing between and
separating said containers, and between said containers and the
housing walls, this spacing means being porous and permitting flow
there through of said heat-transporting medium vapor.
Description
BACKGROUND OF THE INVENTION
The invention relates to a heating system for the supply of thermal
energy to a heater of a machine in which a working medium performs
a thermodynamic cycle. The system comprises a closed space within
which several containers for heat-accumulating, meltable material
are arranged. Each container has at least one heat transmission
wall through which heat-accumulating material can exchange thermal
energy with a heat transporting medium which is present in the
closed space and which during operation transports thermal energy
from the containers to the heater by an evaporation-condensation
process. The heater communicates with the heat transmission
container walls via a porous mass having a capillary structure for
the return of heat transporting medium condensate from the heater
to the containers. A heating system of the above-described type is
known from FIG. 2 of the Belgian Patent Specification 758,330.
Examples of machines in which a working medium performs a
thermodynamic cycle and to which working medium thermal energy is
supplied from without through the wall of a heater, are hot-gas
engines and hot-gas turbines.
The heating system in which thermal energy stored in containers is
transported to the heater of a thermodynamic machine by means of an
evaporation-condensation process a heat transporting medium
presents several advantages. First of all, a large quantity of
thermal energy can be transported substantially without temperature
drop, without the use of a pumping device and without further
moving parts. Due to the presence of the porous mass having a
capillary structure, return of heat transporting medium condensed
on the heater to the containers takes place in all circumstances as
a result of capillary action while using the surface tension of the
condensate. Return of condensate thus takes place even against
gravity or without the action of gravity.
The porous mass having a capillary structure may consist, for
example, of a ceramic material, of layers of gauze of wire or
band-shaped material, from arrangements of glass fibres, pipes or
rods, of systems of grooves in the walls, whether or not in
combination with one of the above-mentioned alternatives. Said
porous mass may fully or partly cover the walls of the closed
space, the heat transmitting container walls, as well as the heater
wall. All kinds of materials, for example potassium, sodium,
calcium, lithium, cadmium, cesium, metal mixtures, and so on are to
be considered as heat transporting media. A compact assembly is
obtained by arranging the heater within the closed space.
By using containers which are filled with heat-accumilating
material, the thermal energy stored in the said material can be
used for operating the thermodynamic machine, for example a hot-gas
engine, in places where fuming gases may not be allowed to develop
or in places where no combustion air is available for a normal
burner (mines, submarines, and so on). An example of a
heat-accumulating meltable material to be considered is lithium
fluoride (LiF).
Since the heater is separated from the containers filled with heat
accumulating material, the volume of the containers and hence the
heat capacity thereof is not restricted; this in contrast with
heating systems in which the heater which is normally constructed
from a number of pipes is placed directly in the heat accumulating
material. In the latter case the maximum volume of the container in
question and hence the maximum heat capacity thereof is restricted,
owing to the fact that the heater pipes are restricted to given
maximum length dimensions, in connection with the optimum
thermodynamic cycle of the working medium in the machine which may
be, for example, helium or hydrogen. Moreover, the thermodynamic
machine should then carry the weight of the container filled with
heat accumulating material, which necessitates a heavier machine
construction.
The known heating system exhibits a few drawbacks. The containers
are filed with heat accumulating material one by one, closed, and
arranged inside the closed space separately. The separate filling
and closing of the containers is time-consuming and expensive and
makes the assembly of the heating system less suitable for series
production. Since the containers are arranged separately relatively
movable, the position of the heating system is restricted. This
lack of independence of position means a serious restriction in the
possibilities of application. Independence of position is required,
for example, in aeronautics or on board submarines in which a
hot-gas engine which is equipped with such a heating system may be
present as a power source without exhaust gases.
In order that the evaporation-condensation process of the heat
transporting medium in the closed space can occur smoothly, said
space is normally evacuated. A problem is that in a number of
cases, dependent upon the heat transporting medium chosen, the
vapour pressure of the heat transporting medium in the closed space
lies below the ambient pressure not only at room temperature but
also at the high operating temperature of the heating system. For
example, if sodium is present in the evacuated closed space as a
heat transporting medium, the vapour pressure at 800.degree. K is 8
Torr (1 Torr = 1 mm mercury pressure) and at 1,100.degree. K it is
450 Torr. This means that in particular in heating systems of which
the closed space has flat walls of large dimensions, said walls are
subjected to a considerable mechanical load. Notably at high
operating temperatures of the heating system in which the rigidity
of said walls is considerably lower than at room temperature, this
results in deformation and cracking of the said walls with the
danger of implosion of the closed space.
The porous mass having capillary structure may work loose from the
walls and/or be damaged to such an extent that it is no longer
useful for the return of heat transporting medium condensate from
the heater to the containers. Thicker and hence more rigid walls of
the closed space are usually not possible for reasons of weight,
cost-price and dimensions.
It is the object of the present invention to provide an improved
construction of the heating system of the above-described type in
which the drawbacks described are avoided.
SUMMARY OF THE INVENTION
The heating system according to the invention is characterized in
that the containers communicate with a common supply duct for
heat-accumulating material, and this closable supply duct is passed
through a wall of the closed space to the outside. Spacing members
are present between the walls of the closed space and the
containers as well as between the containers mutually to permit
flow of heat transporting medium vapour.
The filling of the containers with heat accumulating material can
now be carried out in a simple and rapid manner in one single
operation after the complete assembly of the heating system. The
containers may be connected mutually in series or parallel to the
common supply duct. The filling of the containers with liquid heat
accumulating material may be carried out by first evacuating the
containers via the common supply duct and then communicating them
with the storage container for heat accumulating material.
Due to the presence of the spacing members, the heating system has
not only become independent of position, but the closed space is
also protected from implosion since, as a matter of fact, the
spacing members also support the walls of said low pressure space
against the atmospheric pressure ferces exerted theron from
without. The spacing members furthermore ensure that the porous
mass having capillary structure remains in its place so that the
transport of heat transporting medium condensate through said mass
is not disturbed.
In a favourable embodiment of the heating system according to the
invention the containers also communicate with a common outlet
duct, said closable outlet duct being also passed to the outside
through a wall of the closed space. The outlet duct may be arranged
so as to serve as a desaeration duct during filling the containers
and as a suction duct for heat accumulating material after filling,
so as to obtain a certain filling level in the containers. The
outlet duct may also be used in employing the containers provided
with heat accumulating material.
Finally, the common supply and outlet duct may be used collectively
in rinsing the containers with an inert gas, for example, after
filling of containers mutually arranged in series, so as to obtain
equalisation of the filling levels in the various containers. In a
further favourable embodiment of the heating system according to
the invention, a pressure control device is present for controlling
the pressure in the containers.
Transition of heat accumulating material in the containers from the
solid to the liquid phase is associated with a considerable
increase in volume of said material which may result in high
pressure in the containers; This pressure still further increases
when the temperature of the molten heat-accumulating material
increases. By means of the pressure control device it is insured
that the pressure in the containers remains within certain
acceptable limits. Thus it is also possible to use the maximum
filling degree of the containers as a result of which for a given
heat-accumulating power, the dimensions of the heating system and
the heat insulation losses thereof are minimum.
A further favourable embodiment of the heating system according to
the invention is characterized in that the spacing members are
formed by a porous filling mass the pores of which have larger
dimensions than the pores of the porous mass.
Since the pores of the filling mass are larger than those of the
porous mass, the suction effect of the filling mass is negligibly
small as compared with that of the porous mass. This means that
transport of heat transporting medium condensate from the heater to
the containers takes place exclusively through the porous mass
having capillary structure, while on the way no condensate passes
from the porous mass to the filling mass either. Comparatively
large pores of the filling mass are also desirable to keep the flow
losses of heat transporting medium vapour and hence the temperature
gradient between the heat transmission container walls and the
heater small. Thus, vapour transport takes place substantially
unhindered.
According to the invention, compressed steel wool is preferably
used as a filling mass. Steel wool presents the advantage of a low
price, can easily be compressed in all kinds of shapes and can
receive considerable surface pressure in the compressed
condition.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will be described in greater detail with reference to
the drawing.
BRIEF DESCRIPTION OF THE DRAWINGS
FIGS. 1a and 2 show diagrammatically and not to scale embodiments
of heating systems in sectional elevation views. FIG. 1b is a
cross-sectional view taken on the line Ib -- Ib of FIG. 1a.
DESCRIPTION OF THE PREFERRED EMBODIMENT
In FIG. 1, reference numeral 1 denotes a hot-gas engine which
comprises a heater 2 to which thermal energy is to be supplied. The
heater 2 is accommodated inside a closed space 3. Said space
furthermore comprises several containers 4 for heat accumulating
meltable material, for example LiF. Each container 4 comprises at
least one heat transmission wall 5. In this embodiment the
containers are constructed as annular cylinders which are arranged
in a cylindrical compartment 3a of the closed space 3, so that the
annular cylinder axes coincide. A quantity of sodium as a heat
transporting medium is also present in the closed space. The heater
2 communicates with the heat transmission container walls 5 via a
porous mass 6 which has capillary structure.
All the containers 4 communicate with a common supply duct 7 for
heat-accumulating material which is passed to the outside through
the wall of the closed space 3 and there comprises a cock 8. All
the containers also communicate with a common outlet duct 9 which
also debouches outside the closed space 3 and is there provided
with a cock 10. In this embodiment the containers are connected in
series via communication ducts 11.
The pressure inside the containers 4 is maintained within certain
limits throughout the accurring temperature range by means of a
pressure control device 12. The pressure control device 12
comprises a bottle 13 which is filled with an inert gas 14 and
which communicates with a common supply duct 7 via a duct 14 in
which a pressure control valve 15 with exhaust 16 is
incorporated.
In order to maintain the containers 4 inside the cylindrical
compartment 3a of the closed space 3 in their places and hence make
the heating system entirely independent of position, a porous
filling mass 17 of compressed steel wool is present between the
containers mutually and between the walls of the closed space 3
bounding the compartment 3a and the containers. Said filling mass
has pores, the dimensions of which are larger than those of the
pores of the porous mass 6. The heating system finally comprises an
electric heating element 18 which is arranged in the closed space
3.
Making the heating system ready for use may be done as follows.
Thermal energy is supplied to the closed space 3 by means of the
heating element 18. As a result of this, the present in said space
evaporates so that the heating is heated at a high temperature.
Sodium condensed in comparatively cold places is returned through
porous mass 6 on the basis of capillary action to the heating
element 18 to be evaporated there again. The heating element 18 is
for that purpose also lined with a porous mass 6 which locally
communicates with a porous mass 17 on the outer walls of the
containers 4. Since the porous filling mass 17 has pores of
comparatively large dimensions, sodium vapour can flow through it
substantially unhindered.
When the heating system is at the desirable temperature, the
containers 4 are filled with liquid heat-accumulating material, for
example melted LiF, via the common supply duct 7. Common outlet
duct 9 then serves as a desaeration duct.
Filling is carried out in only one batch. The containers are filled
successively via the communication ducts 11. By means of a flow of
inert gas from the gas bottle 13, the containers are then rinsed,
excessive heat-accumulating material being conducted away through
the common outlet duct 9. The level of the heat-accumulating
material then reaches up to the insertion depth of the
communication ducts 11 and of the common outlet duct 9. A certain
inert gas pressure is finally adjusted in the containers. The
pressure control valve 15 ensures that the inert gas pressure
remains within certain limits. Should the pressure increase to
excessively high values, said valve ensures that inert gas is blown
off via outlet 16; in the case of too low a gas pressure, it admits
gas from the bottle 13.
In normal operation, thermal energy is delivered to the sodium by
the heat-accumulating material in the containers 4 via the heat
transmission walls 5, said sodium consequently evaporating and
flowing in the vapour phase to the heater 2 due to the lower vapour
pressure prevailing there as a result of a slightly lower
temperature at that area. Sodium vapour condenses on the heater 2
while giving off thermal energy. Sodium condensate is then returned
through the porous mass 6 to the heat transmission walls 5 of the
container 4 to be evaporated there again. Return of condensate
again takes place by capillary action.
The sodium-containing closed space 3 is otherwise evacuated. In
operation, the sodium vapour pressure is considerably lower than 1
atm. Porous filling mass 17 not only maintains the containers 4 in
their places but also supports the large wall surface of the closed
space 3 against pressure forces excerted thereon from without, as a
result of which the danger of implosion is prevented. The porous
filling mass 17 also maintains the porous mass 6 in its place for
the greater part so that the transport of sodium condensate does
not experience any difficulties. Ib -- Ib of FIG. 1a.
FIG. 2 shows a heating system which in outline is equal to that of
FIG. 1. Therefore, the same reference numerals are used for
corresponding parts. In the present case, the containers 4 are not
connected in series but in parallel, while the pressure control
device 12 consists of an expansion vessel 20 which can be made to
communicate with the common supply duct 7 via a duct 21 in which a
cock 22 is incorporated. The expansion vessel 20 is filled with an
inert gas which serves as a buffer.
When the pressure in the containers increases as a result of an
increase in volume of the heat-accumulating material, for example,
when changing from the solid phase into the liquid phase, the
volume of the inert gas buffer is reduced. When the volume of the
expansion vessel 20 is sufficiently large, the pressure in the
containers remains substantially unvaried. The containers can now
be filled simultaneously in a short period of time with liquid
heat-accumulating material after evacuating the said containers.
The further construction and operation of the present heating
system are identical to those of the system shown in FIG. 1 so that
description may be omitted.
It will be obvious from the above that the invention provides an
interesting heating system which is fully independent of position
and which can be assembled in a rapid and simple manner and be
provided with heat-accumulating material.
* * * * *