U.S. patent number 3,782,449 [Application Number 04/879,505] was granted by the patent office on 1974-01-01 for temperature stabilization system.
This patent grant is currently assigned to European Atomic Energy Community (Euratom). Invention is credited to Claus Busse, Karl Schlitt.
United States Patent |
3,782,449 |
Busse , et al. |
January 1, 1974 |
TEMPERATURE STABILIZATION SYSTEM
Abstract
A system for temperature stabilization through the use of a heat
pipe, that zone of the heat pipe which is remote from the heating
zone having an inert gas plug whose volume varies with the vapour
pressure of the heat vehicle. The plug effects variation in the
heat pipe wall area actually radiating heat according to changes in
the volume of the plug, and includes a secondary heat pipe which is
in good thermal connection with that part of the first heat pipe
where the inert gas plug is disposed.
Inventors: |
Busse; Claus (Laveno,
IT), Schlitt; Karl (Ispra, IT) |
Assignee: |
European Atomic Energy Community
(Euratom) (Luxemburg European Center Kirchberg,
LU)
|
Family
ID: |
19725815 |
Appl.
No.: |
04/879,505 |
Filed: |
November 24, 1969 |
Foreign Application Priority Data
Current U.S.
Class: |
165/273;
165/104.14; 165/104.26; 165/274 |
Current CPC
Class: |
F28D
15/06 (20130101); G05D 23/01 (20130101); H01J
45/00 (20130101); F28D 15/0275 (20130101) |
Current International
Class: |
H01J
45/00 (20060101); F28D 15/06 (20060101); G05D
23/01 (20060101); F28d 015/00 () |
Field of
Search: |
;165/32,105 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Davis, Jr.; Albert W.
Attorney, Agent or Firm: Stevens, Davis, Miller &
Mosher
Claims
We claim:
1. A system for temperature stabilization comprising an arrangement
of at least two serially disposed heat pipes, the first heat pipe
having a heating zone coupled to a space where stabilization of
temperature is desired and a cooling zone, said first heat pipe
enclosing a condensable-vaporizable heat vehicle and an inert gas
plug which during operation is displaced in said cooling zone,
there being a boundary region between the heat vehicle and the gas
plug; a second heat pipe having a heating zone and a cooling zone,
the heating zone of said second heat pipe being in good thermal
connection with the cooling zone of the first heat pipe where the
inert gas plug is disposed and a displacement member positioned in
the heat pipe interior to effectively reduce its cross-sectional
area in the boundary region.
2. A system as set forth in claim 1, in which the displacement
member is in good mechanical and thermal connection with the heat
pipe end wall remote from the heating zone.
3. A system as set forth in claim 2, in which the displacement
member is a hollow empty receptacle whose wall thickness is the
minimum necessary to resist the working pressure.
4. The system of claim 1 in which the second heat pipe also
encloses a condensable-vaporizable heat vehicle and an inert gas
plug, there being a boundary region therebetween.
5. The system of claim 4 including a displacement member positioned
in the second heat pipe interior to effectively reduce its
cross-sectional area in the boundary region.
6. The system of claim 4 including a tertiary heat pipe enclosing a
condensable-vaporizable heat vehicle and an inert gas plug, there
being a boundary region therebetween; the heating zone of the
tertiary pipe being in good thermal connection with that point of
the second heat pipe where its inert gas plug is disposed.
7. The system of claim 6 including a displacement member positioned
in the tertiary heat pipe interior to effectively reduce its
cross-sectional area in the boundary region.
Description
The invention relates to temperature stabilization, for example
stabilization of the temperature of the caesium reservoir in a
thermionic converter.
It has already been proposed to stabilize the temperature of a
heated region or surface despite changes in environmental
conditions by means of a heat pipe operable to extract variable
amounts of heat from the region or surface. A heat pipe essentially
comprises a hermetically closed vessel containing a heat carrying
vehicle (e.g., a metal) which circulates by a natural cycle of
evaporation and condensation between a heating zone and a cooling
zone. In some arrangements of heat pipes the circulation of the
vehicle is assisted by capillary action. When a heat pipe is used
for the above purpose the heating zone is arranged to receive heat
from the region or surface to be stabilized and within the vessel
there is a plug of inert gas of which the volume varies with
variations in the vapor pressure of the vehicle. If the temperature
to be stabilized increases so does the temperature of the heating
zone of the heat pipe and the quantity of heat absorbed thereby
increases. This causes an increase in the vapor pressure of the
vehicle, and the inert gas plug, which is disposed in the cooling
zone of the pipe, is compressed. Consequently, since the inert gas
is a much poorer heat conductor than the heat vehicle, the heat
pipe wall area actually radiating heat increases as does the amount
of heat radiated. It has also been proposed to provide a central
displacement member in the boundary region between the heat vehicle
and the inert gas plug, with the aim of improving the control
characteristic by making a given change in vapor pressure produce
an increased change in actual radiating surface.
A disadvantage of heat pipes when used as above described is that
the temperature of the inert gas plug has considerable effect on
the accuracy of control, more particularly because there is only a
small temperature difference between the temperature in the
environment around the heat pipe and the temperature of the plug
and because the pipe walls are good heat conductors. Another
consideration when systems of this kind are used in the range of
radioactivity is the gamma heat evolved in the heat pipe wall.
These disturbances make it difficult to provide accurate
temperature stabilization of the pipe heating zone, since they also
affect the position of the boundary zone between the heat vehicle
vapor and the inert gas plug.
The present invention seeks to reduce or overcome these
disadvantages.
This invention provides a system for temperature stabilization
through the agency of a heat pipe, that zone of the heat pipe which
is remote from the heating zone having an inert gas plug whose
volume varies with the vapor pressure of the heat vehicle, such
plug effecting variation in the heat pipe wall area actually
radiating heat, according to changes in the volume of the plug,
characterised in that that part of the heat pipe where the inert
gas plug is disposed is in good thermal connection with the heating
zone of a secondary heat pipe.
Preferably, the heating zone of the secondary heat pipe is fitted
like a pot or cover over that part of the first heat pipe where the
inert gas plug is disposed. Preferably, an inert gas plug is also
provided in the secondary heat pipe.
To improve stability still further, a displacement member (e.g.,
fixed) may be provided in the primary or secondary heat pipe (or
both). Alternatively or in addition a tertiary heat pipe may be
connected to the secondary heat pipe in just the same way as the
latter is connected to the primary heat pipe. Preferably, the
displacement member is in good mechanical and thermal connection
with the heat pipe end wall remote from the heating zone, since the
temperature of such end wall is more stable than the temperature of
the side walls contiguous with or adjacent to such wall.
Advantageously, to reduce heating of the displacement members by
gamma radiation in cases where they will be subject to such
radiation, the displacement members are empty hollow receptacles
whose wall thickness is exactly suitable for the working pressure
(i.e., the minimum thickness necessary to resist the working
pressure).
The present invention greatly reduces the effect of environmental
factors on the temperature of the inert gas plug in the primary
heat pipe, and so the position of the boundary between heat-vehicle
vapor and the inert gas depends substantially only upon the
quantity of heat taken up from the heating zone of the primary
pipe.
Some examples of the invention will be described in greater detail
hereinafter with reference to the accompanying drawings
wherein:
FIG. 1 is a diagrammatic sectioned view of a first system;
FIG. 2 shows another system comprising a displacement member;
FIG. 3 shows another system, having two displacement members;
FIG. 4 shows a system comprising three heat pipes, and
FIG. 5 is a detailed sectional view showing the suspension of a
displacement member.
The underlying idea of the invention will be described with
reference to FIG. 1. It will be assumed that a surface 1 to be
stabilized (e.g., part of the surface of a caesium reservoir) is
also the heating surface of a first or primary heat pipe 2. Arrows
3 near the heating zone indicate the supply of heat. Heat pipe 2 is
made of a high-temperature-resistant substance covered internally
with longitudinally extending capillary grooves (not shown). The
heat carrying vehicle is a metal; at normal working temperature the
metal is in vapor form in the heating zone and condenses in the
cooling zone remote from the heating zone. Tube 2 has as well as a
metal-vapor chamber 4, an inert gas plug 5 which, since it is
carried along in the heat-vehicle vapor, is disposed at the top of
the tube 2 -- i.e., in the zone remote from the heating zone. A
line 6 denotes the horizontal boundary layer between the heat
vehicle and the plug 5, although in fact the boundary should be
considered as a transitional region. Since the heat pipe wall is a
good conductor of heat, the boundary is particularly fluid at the
pipe wall. Since the inert gas is a much poorer heat conductor than
the metal vapor, the line 6 represents a temperature jump and is a
boundary of that region of the heat pipe which is actually
operative for heat flow and heat radiation.
A second heat pipe 7 is fitted over the pipe 2 near the line 6 and
the external wall surfaces of pipe 7 act as heat radiators. The
heat is radiated in a direction indicated by arrows 8. The second
or secondary pipe 7 therefore acts as a cooler of the primary pipe
2, with the result that at start-up the line 6 first rises rapidly
to the position shown, then remains there substantially stationary
subject substantially only to variation in the vapor pressure of
the metallic heat carrier due to variations in the temperature of
the heating zone. Since the inert gas plug is completely surrounded
by the second heat pipe and scarcely alters its temperature, the
temperature stabilization of surface 1 is likely to be much better
than can be provided by earlier suggestions.
To further improve stabilization, the system shown in FIG. 2 can be
used, like elements having like references. The only difference
from FIG. 1 is that the system shown in FIG. 2 has a displacement
member 9 near the line 6 in the primary heat pipe 2. The
displacement member 9 acts in a known manner to produce an
increased change in effective wall area for a given change in plug
volume.
The temperature stabilization of surface 1 can be further improved
by the system shown in FIG. 3, like references again denoting like
elements. The difference from FIG. 2 is that in FIG. 3 the
secondary pipe 7 also has an inert gas plug 10, and so the
secondary pipe 7 has a boundary line 11 which varies with the heat
flow. Preferably in this case too, a displacement member is used to
act appropriately on the variation characteristic.
Stabilization can be improved still further by further cascaded
arrangements of heat pipes, although the expense is likely to make
any cascade consisting of more than three heat pipes of little
practical value. FIG. 4 shows a three pipe system -- i.e., in this
embodiment substantially all the heat is radiated by the third pipe
13. One way of improving stabilization relatively cheaply is for
the displacement members to be in good mechanical and, more
particularly thermal, connection with that region of the
surrounding heat pipe which has the most stable temperature
pattern. Such region is always the surface 14 remote from the
heating zone. FIG. 5 is a diagrammatic view of how a connection of
this kind can be provided in one heat pipe or in all the heat
pipes. A metal block 15 which is a good heat conductor forms a
bridge between the wall 14 and a displacement member 16. As can
also be gathered from FIG. 5, the displacement member is preferably
hollow and has a wall thickness which just withstands the maximum
working pressure. This ensures that heating of the displacement
member as a result of gamma radiation has very little effect on the
temperature of the inert gas plug 17. Structural bracing or the
like (not shown) can be provided to improve the mechanical
stability of the displacement member.
* * * * *