U.S. patent application number 16/757475 was filed with the patent office on 2021-06-24 for apparatus for isochoric gas compression.
This patent application is currently assigned to TURBODEN S. p. A.. The applicant listed for this patent is TURBODEN S. p. A.. Invention is credited to Paolo Belotti, Roberto Bini, Mario Gaia.
Application Number | 20210189912 16/757475 |
Document ID | / |
Family ID | 1000005494188 |
Filed Date | 2021-06-24 |
United States Patent
Application |
20210189912 |
Kind Code |
A1 |
Bini; Roberto ; et
al. |
June 24, 2021 |
APPARATUS FOR ISOCHORIC GAS COMPRESSION
Abstract
An apparatus for gas compression comprising: a container
containing the gas to be compressed; a first heat exchanger
exchanging heat between a high temperature thermal source and the
gas, to introduce heat into the gas; a second heat exchanger
exchanging heat between a low temperature thermal source and the
gas, to extract heat from the gas; supply means of the gas at a
supply pressure and delivery means of the gas at a delivery
pressure greater than the supply pressure); gas permeable means
configured to accumulate and transfer heat to the gas, and gas
permeable or gas impermeable movable means dividing the container
into a first section in thermal communication with the first heat
exchanger and in a second section in thermal communication with the
second heat exchanger and in fluid communication with said supply
means and said gas delivery means.
Inventors: |
Bini; Roberto; (Brescia,
IT) ; Gaia; Mario; (Brescia, IT) ; Belotti;
Paolo; (IT) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
TURBODEN S. p. A. |
Brescia |
|
IT |
|
|
Assignee: |
TURBODEN S. p. A.
Brescia
IT
|
Family ID: |
1000005494188 |
Appl. No.: |
16/757475 |
Filed: |
October 17, 2018 |
PCT Filed: |
October 17, 2018 |
PCT NO: |
PCT/IB2018/058044 |
371 Date: |
April 20, 2020 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F01K 3/262 20130101 |
International
Class: |
F01K 3/26 20060101
F01K003/26 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 20, 2017 |
IT |
102017000119044 |
Claims
1. An apparatus (1) for gas compression comprising: a container (2)
containing the gas to be compressed; a first heat exchanger (3)
exchanging heat between a high temperature thermal source and the
gas, to introduce heat into the gas; a second heat exchanger (4)
exchanging heat between a low temperature thermal source and the
gas to extract heat from the gas; supply means (5) of the gas to a
supply pressure (Pin) and delivery means (6) of the gas at a
delivery pressure (Pout) greater than the supply pressure (Pin);
gas permeable means (7, 7a, 7b, 7c, 7d, 7e, 7e', 7e'') configured
to accumulate and transfer heat to the gas, and gas permeable (7)
or gas impermeable (8) movable means dividing the container (2)
into a first section (2a) in heat communication with the first heat
exchanger (3) and in a second section (2b) in thermal communication
with the second heat exchanger (4) and in fluid communication with
said supply means (5) and said gas delivery means (6); the
apparatus (1) being characterized in that said first heat exchanger
(3) and second heat exchanger (4), said gas permeable means (7, 7a,
7b, 7c, 7d, 7e, 7e', 7e'') and said movable means (7, 8) cooperate
to heat and cool the gas, causing it to cyclically flow between the
first section (2a) and the second section (2b), to obtain the
compression effect of the gas, which is introduced into the
container, from a value equal to the supply pressure (Pin) up to a
value equal to the discharge pressure (Pout).
2. The apparatus according to claim 1, wherein said gas permeable
means (7, 7e, 7e', 7e'') are internal to the container (2).
3. The apparatus according to claim 1, wherein said gas-permeable
means (7a) are external to the container (2) and in fluid-dynamic
communication with both the sections (2a, 2b) of the container.
4. The apparatus according to claim 1, wherein said first heat
exchanger (3) and the second heat exchanger (4) are internal to the
container (2).
5. The apparatus according to one of claim 1 wherein said first
heat exchanger (3) and the second heat exchanger (4) are outside
the container (2).
6. The apparatus according to claim 1, further comprising at least
one fan (9) which moves said movable means (7, 8).
7. The apparatus according to claim 1, further comprising at least
one recirculating duct (R1, R2) provided with a correspondent fan
(9a, 9b, 9c).
8. The apparatus according to claim 1, further comprising an
additional gas permeable means (7b), which is allocated
fluid-dynamically in parallel with respect to the first heat
exchanger (3).
9. The apparatus according to claim 1, further comprising an
additional gas permeable means (7d), which is allocated
fluid-dynamically in parallel with respect to the second heat
exchanger (4).
10. The apparatus according to claim 1, wherein said container (2)
has a shape corresponding to a solid of rotation and said movable
means (8) rotates inside the container (2).
11. The apparatus according to claim 1, wherein said container (2)
contains heat exchange tubes, arranged inside and parallel to its
axis.
12. The apparatus according to claim 1, wherein said first
exchanger (3) extends for a first fraction (x) of the passage
surface crossed by the gases and a second fraction (1-x) comprises
an additional gas permeable means (7e').
13. The apparatus according to claim 1, wherein said second
exchanger (4) extends for a first fraction (y) of the passage
surface crossed by the gases and a second fraction (1-y) comprises
a further gas permeable means (7e''').
14. The apparatus according to claim 10, further comprising at
least two collectors (11, 12) extending through a base flange (FB)
to allow easy removal of the cap of the container (2).
15. The apparatus according to claim 10, further comprising a
double movable means (8, 8') which is impermeable to the gases and
heat exchangers (3, 4) symmetrical to each other and gas permeable
means (7e) symmetrical between them.
16. The apparatus according to claim 1, further comprising a
one-way valve (VNR, 100) which hinders to passage of the gas in the
first heat exchanger (3) during the gas cooling phase, at a greater
degree than during the gas heating phase.
17. The apparatus according to claim 10, in that it comprising an
exchange volume having a front surface, wherein rotating movable
means (8), heat exchangers (3, 4), and gas permeable means (7e),
are helical shaped.
18. The apparatus according to claim 17, wherein said heat
exchangers (3, 4) and the gas permeable means (7e) are fixed to a
base flange or to the cap, while the helical movable means (8) are
fixed to a rotating hub.
19. The apparatus according to claim 1, having an average
peripheral velocity at the farthest point from the axis, between 1
and 7 m/s.
20. The apparatus according to claim 1, wherein said gas permeable
means (7, 7a, 7b, 7c, 7d, 7e, 7e', 7e'') comprise a porous matrix
or a set of wires or strips or even dense metal meshes, said
elements being welded or pressed together and externally crossed by
the gas.
21. The apparatus according to claim 1, wherein said first heat
exchanger (3) is supplied with a carrier fluid having an inlet
temperature between 200.degree. C. and 450.degree. C.
Description
TECHNICAL BACKGROUND OF THE INVENTION
1. Field of the Invention
[0001] The present invention relates to an apparatus for isochoric
gas compression, in particular to a gas for industrial use, which
uses as driving energy the thermal energy deriving from waste
thermal flows preferably from the same industrial plant. The
apparatus according to the invention substantially does not
therefore require the need for mechanical and/or electrical energy
in order to carry out the compression of the gas and consequently
of a thermodynamic cycle which, starting from a thermal source, in
this case waste thermal flows, makes the aforementioned mechanical
and/or electric energy available for carrying out the
compression.
2. Brief Description of the Prior Art
[0002] Many industries in which gas compression plants are used,
have at their disposal large waste thermal flows the thermal energy
of which generally can be exploited for the production of
electrical or mechanical energy. For this purpose, as is known,
recovery organic Rankine cycle (ORC) or Rankine cycle with water
vapor, are used.
[0003] Compression plants need at the same time a driving energy
and a substantial portion of their energy needs is represented by
the compression of air or other gases.
[0004] According to the known art it is therefore possible to
install a recovery cycle (with water vapor, gas or organic fluid),
in order to produce with it electric energy for actuating the
compressors.
[0005] Another known technique is to couple the turbine of the
recovery cycle directly to the compressor by using the mechanical
energy processed in the turbine for the actuation of the
compressor.
[0006] These solutions, although having high yields, require high
installation costs and involve the presence of rotating machines
(turbines and compressors) that require maintenance and can reduce
the reliability of the system.
[0007] The Applicant has therefore recognized the need for
developing an apparatus able to directly use the thermal energy for
compressing a gas, without going through a thermodynamic cycle
which turns the thermal energy into mechanical and/or electric
energy. In this way, an apparatus is obtained which, having a
reasonable efficiency, requires low installation and maintenance
costs, thanks to its simplicity of construction.
SUMMARY OF THE INVENTION
[0008] Purpose of the present invention is to provide an apparatus
for isochoric compressing of gas, in particular of gas for
industrial use, which uses almost exclusively thermal energy as
driving energy deriving from waste thermal flows of the same
industrial plant.
[0009] Traditionally, for compressing a gas using a thermal source,
it is necessary to install a recovery cycle, with which electrical
or mechanical energy can be produced in order to actuate the
compressors, as represented in a simplified way in FIG. 1. In FIG.
1, the heat exchanger 3' uses the high temperature thermal source
for preheating, vaporizing and possibly overheating a working
fluid, for example an organic fluid in an ORC. The vapor is then
expanded into a turbine T, then it is condensed into a 4'
condenser; the liquid in the liquid state is then compressed into a
pump P by closing the cycle. The mechanical energy produced by the
turbine T is used to actuate the electric generator G; the electric
energy thus produced is used for actuating the motor M connected to
the compressor (any difference between the electric energy
generated by G and that absorbed by M is supplied or absorbed by
the network to which G and M are electrically connected). The
compressed gas can optionally be cooled with a 4'' exchanger. In
other configurations, the compressor can be directly coupled to the
generator (the drive rotating train would in this case consist of
turbine, generator and compressor), or directly to the turbine,
instead of the generator.
[0010] Instead, the apparatus according to the present invention,
although having a limited efficiency, does not require the use of
the rotary machines, if not for some auxiliary functions as will be
seen below for some embodiments, and therefore it allows low
installation and maintenance costs, thanks to its simplicity of
construction.
[0011] According to the present invention, it is possible to
compress the gas and return it up to a temperature close to the
suction one, by exploiting a hot thermal source, a cold thermal
source and a gas permeable means, hereinafter also called
regenerator, which is capable of accumulating and giving its heat
to the gas.
[0012] According to the present invention an apparatus is described
for the isochoric compression of gas, the characteristics of which
are set out in the appended independent claim.
[0013] Further embodiments of the aforesaid preferred and/or
particularly advantageous apparatus, are described according to the
characteristics set forth in the attached dependent claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] The invention will now be described with reference to the
accompanying drawings, which illustrate some non-limiting
embodiments thereof, in which:
[0015] FIG. 1 shows the scheme of a compression system with a
recovery cycle according to known art,
[0016] FIG. 2 shows a scheme of an apparatus for the isochoric
compression of gas according to a first embodiment comprising a
container, a heat exchanger which uses the hot source, a heat
exchanger which uses the cold source and a regenerator gas;
[0017] FIG. 3 shows a second embodiment of the invention, described
according to some equivalent variants;
[0018] FIG. 4 shows a third embodiment of the invention, described
according to some equivalent variants;
[0019] FIG. 5 provides details of the operation of the third
embodiment of the invention;
[0020] FIG. 6 shows a fourth embodiment of the invention with a
further regenerator, placed in parallel with the exchanger using
the hot thermal source;
[0021] FIG. 7 shows the gas flows inside the isochoric compressor,
according to the fourth embodiment;
[0022] FIG. 8 and FIG. 9 show a fifth embodiment of the invention
with further regenerators on both hot and cold sides, in parallel
with the corresponding heat exchangers;
[0023] FIGS. 10 A-G show various configurations of a sixth
embodiment of the invention;
[0024] FIG. 11 shows a seventh embodiment of the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0025] Referring now to the aforesaid Figures and in particular to
FIG. 2, the principle of operation of the invention according to a
first embodiment thereof is illustrated.
[0026] The apparatus 1 for isochoric gas compression comprises a
container 2 within which are positioned a first heat exchanger 3,
preferably placed at the top, and a second heat exchanger 4,
preferably placed at the bottom, respectively, in order to
introduce heat into the system and to extract it. By way of
example, the "hot" heat exchanger 3 could be crossed by a
diathermal oil, whereas the "cold" heat exchanger 4 could use water
cooled by a suitable circuit able to exchange heat with the
environment. In the lower section 2b of the container an inlet gas
duct 5 is present, which must be compressed and an outlet duct 6
for the compressed gas, both being equipped with a corresponding
supply valve V1 and the discharge valve V2. The container 2 is
traversed by a gas permeable means, called regenerator 7, movable
between a lower and an upper position and able to accumulate and
transfer heat to the gas (for instance, made with various
overlapping metal mesh layers, which exchange heat with the gas
during the crossing of the same and accumulate it within their
mass). The regenerator 7 divides the container 2 into two sections,
an upper section 2a, at a higher temperature, and a lower section
2b, at a lower temperature. The volumes of the two sections 2a and
2b are obviously variable according to the position of the
regenerator 7. The pressures in the two sections are instead
approximately the same, being the gas permeable septum.
[0027] Referring to the positions of the regenerator 1A to 1E, to
the configurations of the valves V1, V2 (0=closed, 1=open) and to
the corresponding graphs which, according to the aforementioned
positions of the regenerator, respectively represent the
regenerator stroke and the gas pressure, the apparatus) works
according to the following logic: [0028] position 1A: the
regenerator 7, with the thermal storage mass at a temperature close
to T1, is placed in the upper portion of the container, in
correspondence of the first heat exchanger 3 and without the dead
volume occupied by the heat exchanger itself; the pressure in the
entire container 2 is close to the inlet pressure Pin. Almost all
gas present in the apparatus has an inlet temperature T0, except
for which remaining inside the dead volume at the top and a portion
of the gas remaining inside the regenerator matrix, at a
temperature between T1 and T0; [0029] the regenerator 7 moves
downwards due to an actuator (of the known type and not shown in
FIG. 1) which does not perform any mechanical work other than that
necessary to overcome the fluid dynamic and mechanical frictions;
the regenerator when moving downwards, is crossed by a certain flow
of gas and heats the same, due to the previously accumulated heat.
The gas also receives a heat Qin from the "hot" heat exchanger 3.
In this stage, the valves V1, V2 are closed and a gas is heated in
a closed volume, the pressure increases, both in the (hot) portion
at the top of the regenerator and in the one (cold) at the bottom
of the same, which has a fluid connection with the upper one
through the "permeable" matrix of the regenerator; [0030] in
position 1B, the gas has reached the desired pressure, therefore
the valve V2 opens, causing a certain flow of gas to pass to an
environment placed at a pressure Pout.
[0031] It must be considered that in the hypothesis of a perfect
gas, the maximum obtainable pressure is derived from the law of
gases P*V=M*R*T which, once applied to the specific case (To and
T1, V constant, R constant, M constant) permits to obtain
Pout.sub.max=Pin*T1/T0. The valve V2 is actuated at a pressure
lower than this maximum pressure, as by this Pout.sub.max a useful
outlet flow rate would not be associated (in fact, in the applied
gas relation, the volume must be constant). The closer is Pout with
respect to Pin (that is, the lower is the required compression
ratio), the greater the extractable flow rate for each cycle of the
system (at the expense of an obviously moderate Pout/Pin
compression ratio).
[0032] The system delivers a pressurized gas until the regenerator
has reached the lower dead point (position 1C). The supplied gas
has approximately the temperature T0, due to the fact that it
passes through the regenerator before passing through V2 and in the
presence of the "cold" heat exchanger 4 placed in the lower portion
of the container; [0033] in position 1C (regenerator in the lower
position) the valve V2 closes as the system is no longer able to
supply gas at the required pressure; [0034] the regenerator 7 moves
upwards (position 1D) and during this movement cools the gas
passing through it (that is, the regenerator heats up). The
combined effect of the passage through the regenerator and the
transfer of heat towards the "cold" exchanger reduces the pressure,
until opening the valve V1 and thus allowing the reintegration of a
new gas. The gas inlet continues until the regenerator 7 has
reached the upper dead point (position 1E).
[0035] The beginning or the end of some phases may not coincide
with the upper and lower dead points, as the pressure inside the
apparatus, in a certain instant, also depends on the heat input
supplied by the exchangers 3 and 4, and not only on the position of
the regenerator 7.
[0036] In this way it is therefore possible to return the
compressed gas to a temperature close to the suction one, by simply
exploiting a hot thermal source, a cold thermal source and a gas
regenerator, without the need for the addition of other energy as
well as a thermal energy, apart from the small fraction needed to
cyclically actuate the regenerator inside the container.
Preferably, the regenerator 7 performs a complete cycle in a time
ranging from 1 to 10 seconds, for example in relation to a
container volume 2 of about 1000 liters and a height of about 1
m.
[0037] An alternative embodiment of the invention is shown in FIG.
3. This embodiment provides that the regenerator 7a is external to
container 2. In particular, in the configuration 3A, the
regenerator 7a is external to the container 2 and is fixed, whereas
a disc or septum 8 impermeable to gases move within the container;
the movement of this movable means 8 is allowed by an outer
actuator (not shown in the Figure) and causes the gas to move from
the lower section 2b to the upper one 2a or vice versa, by passing
through the regenerator 7a which is in fluid-dynamic connection
with both sections of the container 2.
[0038] The configuration 3B is similar to the previous one, but
instead of moving the disc with a mechanical actuator, the gas is
moved by one or more fans 9 capable of generating a reversible
flow. The disc is made as light as possible and moves accordingly
in order to equalize the pressures between the two sections 2a and
2b of the container.
[0039] In the configuration 3C also the first heat exchanger 3 and
the second heat exchanger 4 are placed outside the container.
Obviously, in FIG. 3 possible combinations are shown between the
various ones.
[0040] A third embodiment of the invention is shown in FIG. 4.
[0041] In particular, in FIG. 4A the heat exchangers 3, 4 and the
regenerator 7 are placed outside the container. Two recirculation
ducts R1, R2 are also present with corresponding fans, in order to
uniform the temperature within the two sections 2a and 2b of the
container. The disc 8 is actuated by suitable not shown
actuators.
[0042] The configuration in FIG. 4 B differs from the previous one
only for the positioning of the heat exchangers 3, 4 which in this
case are housed within the container 2.
[0043] The operating logic of the configuration of FIG. 4A or 4B is
illustrated with reference to the subsequent FIG. 5.
[0044] When the disc 8 moves downwards, that is towards the cold
source (FIG. 5A), the cold gas contained in the lower section 2b
crosses the duct R1 with a flow equal to the sum of the mass flow
m1 corresponding to the movement of the disc 8 within the container
2 (when there is no expulsion or introduction of gas through the
valves V1 and V2) and of the flow rate m2 recycled by the fan. The
"cold" heat exchanger 4 is crossed by a gas flow rate equal to m2,
whereas the regenerator 7a is crossed only by the flow rate m1
corresponding to the movement of the disc 8 within the container
2.
[0045] During the movement downwards of the disc 8, the gas passes
through the regenerator, heating up and then through the fan 9a and
the "hot" heat exchanger 3''. In the heat exchanger 3 passes a flow
rate equal to m1+m3, thanks to the flow rate provided by the fan.
The flow rate m1 which has left the section 2b of the container is
equal to the flow rate that enters the upper section 2a of the
container (subtracted the amounts cumulated in the volumes of the
respective components), whereas the remaining flow rate m3 cannot
but be recycled upstream of the fan for the recirculation duct
R2.
[0046] When the disc moves upwards towards the hot source (FIG.
5B), the regenerator 7a is always crossed by the flow rate m1, but
in the opposite direction. The hot gas contained in the lower
section 2a passes through the recirculation duct R2 with a flow
rate equal to the sum of the flow rate m1 corresponding to the
movement of the disc 8 in the container 2 and of the flow rate m3
recycled by the corresponding fan. The "hot" heat exchanger 3 is
crossed by a gas flow rate equal to m3, whereas the regenerator 7a
is crossed only by the flow rate m1 corresponding to the movement
of the disc 8 in the container 2.
[0047] The gas then passes through the regenerator, cooling down
and then through the fan 9 b and the "cold" heat exchanger 4. In
the heat exchanger 4 passes a flow rate equal to m1+m2, thanks to
the flow rate provided by the fan. The flow rate m1 which has left
the section 2a of the container is equal to the flow rate entering
the lower section 2 b of the container, whereas the remaining flow
rate m2 cannot help but be recycled upstream of the fan for the
recirculation duct R1.
[0048] The flow rates involved are established by the prevalence of
the fan with respect to the load losses of the respective branches.
More in detail, it is sufficient to increase the rotation speed of
the fan 9a of the hot branch with respect to the rotation speed of
the fan 9b of the cold branch, in order to obtain a lowering of the
pressure at the node K with respect to the node H and therefore a
flow from H to K and vice versa. In this way an alternating flow is
obtained without using valves.
[0049] The gas enters or leaves the system through the valves V1
and V2 when, respectively, the pressure in the lower portion of the
exchanger drops below the inlet pressure or rises above the outlet
pressure, with the logic already described for the configuration in
FIG. 2.
[0050] FIG. 6 shows a further possible configuration, in which the
upper "hot" branch has a further gas permeable means, the
regenerator 7b, placed in parallel with the "hot" heat exchanger
3.
[0051] In previous solutions, the regenerator 7, 7a supplies a
great portion of the heat required to bring the gas to a higher
temperature, and the "hot" heat exchanger 3 supplies the remaining
heat portion. Therefore, in the heat exchanger 3, the heat exchange
occurs with the gas being already at high temperature, as the gas
has been already heated by the regenerator. Therefore also the heat
carrier, for example diathermic oil, which flows into the heat
exchanger 3 works with relatively low temperature differences. This
phenomenon may adversely affect the ability to perform an effective
heat recovery from a gaseous effluent as a low temperature
difference of oil affects the ability to effectively cool down the
gaseous source, just because the oil remains at relatively high
temperatures.
[0052] In the configuration of FIG. 5, the central regenerator 7c
which is crossed by the entire gas flow, has a smaller size
compared to those of the previous configurations and therefore its
recovery is lower. This is compensated by the presence of the
second regenerator 7b, in parallel to the heat exchanger 3. In this
way, the gas which moves upwards and outwards of the central
regenerator 7c will exit at the node `X` at a lower temperature
(with respect to the case of a single generator 7c). One portion of
the gas is then heated by the second regenerator 7b and another
portion is parallel heated by the heat exchanger 3 in counter-flow
with the diathermic oil. In this way the introduction of heat from
the diathermic oil takes place at a variable temperature and
starting from a temperature at the lower node `X`, has a greater
effectiveness then regarding the recovery of the gaseous source for
what has been said previously. In the circuit there is present a
non-return valve 100 which allows the gas to cross both the
regenerator 7b and the exchanger 3 when the flow is substantially
directed upwards (that is, when the septum within the container
moves downwards) but permits to cross only the regenerator 7b when
the flow is directed downwards (that is, when the septum within the
container moves upwards).
[0053] In fact, when the flow is directed downwards it would be
counterproductive to let the hot gas flow through the exchanger 3
which has the function of giving heat and not of absorbing it. On
the other hand, the giving of heat from the heat exchanger 3 to the
gas is not continuous, but takes place only for a half-cycle of
operation, or in any case in an uneven manner.
[0054] FIG. 6B shows a similar solution, in which the exchangers 3
and 4 and the regenerator 7b are placed within the container 2, in
order to minimize the dead volumes, that is the spaces occupied by
the compressed gas which the system cannot expel. The exchanger 3
is placed in parallel with the regenerator 7b; for example, and the
exchanger 3 develops on a circular crown inside which there is the
regenerator 7b. The gas flow directed upwards in the heat exchanger
3 is prevented by one or more non-return valves 100, for example of
the clapet type.
[0055] In FIG. 7 the gas flows within the isochoric compression
apparatus are shown, depending on the movement of the disc 8 placed
in the container. If the disc moves downwards, the "cold" heat
exchanger 4 is crossed by a flow rate m1+m2, of which m2 is the
flow rate recycled by the lower fan 9c. The gas then goes up the
central regenerator 7c, heating up with a flow rate m1, generated
by the central fan 9, which can generate a flow in both directions.
Then the gas is divided between the "hot" heat exchanger 3 and the
second regenerator 7b arriving in the upper section 2a of the
container.
[0056] Another possible configuration with regenerators in parallel
with the heat exchangers is shown in FIGS. 8 and 9, in which the
upper "hot" branch has a further gas permeable means (the
regenerator 7b), placed in parallel with the "hot" heat exchanger 3
and the "cold" lower branch has a further gas-permeable means (the
regenerator 7d), placed in parallel to the "cold" heat exchanger 4.
The operating logic corresponds to that already described for FIGS.
5A and 5B, with the addition of two further regenerators 7b and 7d
placed on the recirculation branch and in parallel with the "hot"
and "cold" exchangers.
[0057] FIG. 9 shows a possible arrangement of the regenerators and
the fans according to the diagram of FIG. 8. The fans are
preferably of axial or centrifugal type and receive at their inlet
the outgoing gas from the central regenerator 7c and the second hot
regenerator 7b, arranged around the inlet duct of the fan 9a. The
flow rate expelled by the fan 9a passes the hot exchanger 3 and
arrives inside the container 2. The same arrangement is adopted for
the cold side.
[0058] FIG. 10A shows a further configuration, in which the septum
8 separating the hot and the cold environment within the container
does not translate but rotates around an axis o-o. Its operation is
exactly equal to that described for the configuration of FIG. 2.
When turning the septum clockwise, this causes the gas to move from
the cold to the hot side, by passing through the regenerator 7e.
Preferably the septum will be characterized by a peripheral speed
(at the point furthest from the axis o-o, and therefore with a
greater speed), mediated on a complete working cycle (therefore
with return to the initial position) included in the range between
1 and 7 m/s.
[0059] For the lower values of average peripheral velocity, a law
of motion will be chosen which foresees the length of angular
acceleration and deceleration concentrated towards the beginning
and the end of the displacement (in order to minimize the load
losses).
[0060] For higher average speeds, the motion will preferably be
close to a sinusoidal motion, in order to minimize the forces of
inertia generated by the motion. The hot source is distributed in
the exchange pipes (or is collected by them) through suitable
collectors 11; the cold source is either distributed or collected
by the collectors 12. Duct 5 and duct 6 are respectively the inlet
and outlet ducts of the gas to be compressed.
[0061] The configuration of FIG. 10B is similar, except that the
manifolds supplying the heat exchange tubes are arranged along the
axis of the container 2, so that the manifolds 11, 12 and the pipes
are fixed to one of the bases of the container. In this way the
heat exchangers 3, 4 and 7 and the regenerator can be easily
extracted in the axial direction.
[0062] FIG. 10C shows a further configuration for the system
characterized by a rotating septum around an axis. The
configuration is characterized in that the exchanger with the hot
source 3 extends for a fraction x of the passage surface available
upon crossing the gas pushed by the septum during its rotation
about the axis o-o. The 1-x fraction is instead dedicated to a
further matrix 7e' with characteristics suitable for use as a
regenerator. The fluid within the matrix can be channeled in a
substantially tangential direction, thanks to the presence of
non-permeable or low permeable walls NP. In a completely similar
manner, as shown in FIG. 10D, a portion y of the access surface can
be dedicated to a further regenerator 7e''. Also, in this case, the
non-permeable walls NP can benefit the correct flow orientation.
Moreover, in FIG. 10D the manifolds are arranged within the
container 2. FIG. 10E shows a section of the previous Figure, in
which the manifolds 11-12 are evidenced which protrude through the
base flange FB, so as to allow an easy removal of the dome of
container 2 for maintenance of internal components, in particular
regenerators and heat exchangers, with the hot and cold
sources.
[0063] In FIG. 10F a solution is shown with the heat exchange
elements (heat exchangers with the sources and regenerators) which
are reproduced in a mirror-like manner, and with a double septum 8
and 8'. The advantage of this configuration is to allow a better
balance of the rotating masses, with the consequent possibility of
strongly increasing the oscillation speed of the septum, and
therefore of increasing the production of compressed gas.
[0064] In a further version of the proposed scheme, the mobile
septum 8 is also made by an exchange matrix adapted to constitute a
regenerator. In this case the flow rate passing through the
exchangers 3 and 4 respectively and the matrices of the adjacent
regenerators is pushed through said components as a consequence of
the load loss which is generated during the motion of the septum.
For better clarification, the flow rates are divided between the
rotating septum and the fixed exchange components in relation to
the pressure loss generated by the flow passing through them.
[0065] In FIG. 10G some possible details are added, such as brush
seals SP, between septum and dome. The regenerator can be made with
different compactness, in order to distribute the load losses and
therefore the flow rate in a different way between 7e and 7e'. An
eventually unidirectional valve VNR promotes the motion of the gas
in a certain direction, for example by limiting its passage through
the hot exchanger 3 during the gas cooling phase.
[0066] In a further embodiment of the present invention, as shown
in FIG. 11, a volume is present with a front surface which is
helically increased. The rotating septum and the
exchangers/regenerators are helically shaped. The heat exchange
elements 3, 4, the gas permeable means 7e are fixed either to the
base flange or to the walls of the tank and have non-permeable
walls NP and brush-like seals SP connected to the rotating hub. The
helical septa 8 are fixed to the rotating hub. The elements just
described are clearly visible in the enlargement of FIG. 11: the
volume occupied by the tubes of the hot source is indicated with 3,
the volume occupied by the tubes of the cold source is indicated
with 4 and the regenerator is indicated by 7e.
[0067] This embodiment has peculiar characteristics and consequent
advantages. The helical arrangement releases the frontal area of
the exchangers from the sectional surface of the container. For
example, in the rotating configuration with flat heat
exchangers/regenerators, the section of the latter can only equal
to that of the cylinder. The advantage of the helical arrangement
is to permit to greatly increase the frontal area of the exchange
matrices, substantially by disengaging it from the area of the
axial section of the container.
[0068] Moreover, the conical shape gives the system a certain
elasticity in order to cope with differential thermal expansions
and with the internal pressure.
[0069] This solution makes it possible to vary, during the project,
the passage surface by varying the number of threads (in the
direction of windings) or the angle .alpha..
[0070] Further advantages consist in that the masses are roughly
balanced around the axis and that the cone resists to the pressure
better than a flat surface.
[0071] In all the embodiments of the invention, the regenerator
must be able to accumulate a relatively large portion of the heat
exchanged in the different phases, therefore it must have an
adequate overall mass. In order to limit the overall dimensions and
optimize the heat exchange, the regenerator for example can be
realized as follows: [0072] a porous matrix; [0073] a set of small
diameter wires or tapes which are welded or crushed with each other
and are externally crossed by the gas; [0074] metal wire meshes or
other material suitable for the temperatures of the cycle (that is,
ceramics meshes), which are tightly and overlapping arranged.
[0075] The present invention, in every one of its possible
configurations, can in theory operate with any difference in
temperature between the hot and cold source; obviously, the higher
the temperature of the hot source and the greater the difference in
temperature with the cold source, the better are the performances,
in terms of efficiency and compression ratio. Regarding the cold
source, this could be made of a water-cooled circuit with air
cooler, therefore with water temperatures typically ranging from
10.degree. C. to 50.degree. C. depending on the year season and its
location. The hot source could be made of waste fumes coming from
an industrial process or from the exhaust of an internal combustion
engine or gas turbine, therefore with temperatures typically
ranging between 200.degree. C. and 800.degree. C.; however, as the
gas/gas heat exchangers need large exchange surfaces, it is more
convenient to realize the present apparatus in such a way, that an
intermediate heat exchange circuit is formed between waste fumes
and gas to be compressed (that is, diathermic oil or molten salt).
The Author considers therefore convenient to realize the present
invention so that the "hot" exchanger 3 receives at its inlet a
carrier fluid at a temperature ranging between 200.degree. C. and
450.degree. C., as such temperatures are sufficiently high to
obtain good compression ratios, but, at the same time, remain below
the limits of use of the common diathermic oils present on the
market.
[0076] Within these limits of temperature, the highest compression
ratios attainable (Pout/Pin) are roughly comprised between 1.1 and
2.5. These are maximum values being achieved in a closed system,
that is without entry or exit of gas (therefore with zero
efficiency); the extraction of compressed gas leads to the
achievement of lower pressures with respect to the limits set out
above: the greater the required flow rate, the lower the pressure
reached. According to the Author, a good compromise between
discharge pressure and flow rate is obtained for compression ratios
ranging between 1, 1 and 2.
[0077] The present invention therefore allows to have relatively
low compression ratios, for example close to 1.3.
[0078] It is therefore particularly useful that the inlet pressure
is already high, for example equal to 3 MPa, as with a ratio of
1.3, pressures close to 4 MPa can be achieved.
[0079] It is also evident that higher values of compression ratio
can be achieved by arranging in series a greater number of
apparatuses according to the present invention.
[0080] Due to the fact that the apparatus outputs compressed gas in
a non-continuous way, the energy is related to the speed of
displacement of the separation septum or regenerator (depending on
the configuration considered). The Author believes that the system
can preferably operate with a cycle time of between 1 and 10
seconds, for example in relation to a volume of container 2 of
about 1000 liters and with a height of about 1 m. These time values
consider inertias of the separation septum, thermal energies
reasonably achievable from the exchangers and the regenerator,
energies of fans and therefore load losses.
[0081] In addition to the embodiment of the invention, as described
above, it is to be understood that numerous further variants exist.
It must also be understood that such embodiments are only exemplary
and limit neither the scope of the invention, nor its applications,
nor its possible configurations. On the contrary, although the
above description makes it possible for the skilled technician to
implement the present invention at least according to an exemplary
embodiment thereof, it must be understood that many variations of
the described components are conceivable, without thereby departing
from the scope of the invention, as defined in the attached claims,
which are interpreted literally and/or according to their legal
equivalents.
* * * * *