BACKGROUND OF THE INVENTION
(FIELD OF THE INVENTION)
[0001] The present invention relates to a thermal energy recovery device.
(DESCRIPTION OF THE RELATED ART)
[0002] There have conventionally been known thermal energy recovery devices for recovering
power from exhaust heat from various types of equipment such as plants. For example,
JP 2012-97725 discloses a generator system (thermal energy recovery device) including an evaporator,
a closed generator, a condenser, a fluid supply pump, a circulation flow path connecting
the evaporator, the closed generator, the condenser, and the fluid supply pump in
this order, and a cooling tube. The evaporator evaporates working medium. The closed
generator generates electric power from the expansion energy of working medium flowing
out of the evaporator. Specifically, the closed generator has a screw turbine for
expanding working medium, a generator connected to the screw turbine via an output
shaft, and a housing case housing the screw turbine, the output shaft, and the generator
therein. The condenser condenses working medium flowing out of the closed generator.
The fluid supply pump delivers working medium flowing out of the condenser to the
evaporator. The cooling tube connects a site downstream the fluid supply pump in the
circulation flow path and the housing case such that working medium of liquid phase
discharged from the fluid supply pump is partially supplied into the housing case.
[0003] In the thermal energy recovery device, since working medium of liquid phase discharged
from the fluid supply pump during operation is partially supplied into the housing
case through the cooling tube, the generator is cooled effectively during operation
of the device.
[0004] Such a thermal energy recovery device as described in
JP 2012-97725 has a concern that the lubrication of the bearing of the screw turbine may be insufficient
when the device restarts after stopping. Specifically, when the thermal energy recovery
device comes into a stop operation, the rotational speed of the pump starts decreasing.
In this state, if working medium of liquid phase continues to be supplied into the
expander through the cooling tube, working medium of liquid phase that has existed
in the evaporator and heated by heating medium to be evaporated and then flowing into
the expander, for example, may be cooled and thereby condensed by the working medium
of liquid phase supplied through the cooling tube to be reserved within the expander.
When the accumulation of the working medium of liquid phase then causes the bearing
of the screw turbine to be immersed in the working medium of liquid phase, there is
a concern of poor lubrication of the bearing when the device restarts (when the screw
turbine is driven).
[0005] It is hence an object of the present invention to provide a thermal energy recovery
device in which poor lubrication of a bearing can be inhibited when an expander is
driven.
[0006] In order to achieve the foregoing object, the present invention provides a thermal
energy recovery device including an evaporator for evaporating working medium through
heat exchange between heating medium and the working medium, an expander for expanding
working medium flowing out of the evaporator, a power recovery machine connected to
the expander, a condenser for condensing working medium flowing out of the expander,
a pump for delivering working medium flowing out of the condenser to the evaporator,
a circulation flow path connecting the evaporator, the expander, the condenser, and
the pump in this order, a cooling flow path for supplying working medium of liquid
phase flowing out of the pump partially to the power recovery machine, an on-off valve
provided in the cooling flow path, and a control unit, in which the expander has a
rotor to be rotationally driven by the expansion energy of the working medium, a bearing
that bears the rotor such that the rotor is rotatable, and a primary casing housing
the rotor and the bearing therein, and in which the power recovery machine has a power
recovery unit connected to the rotor to rotate together with the rotor and thereby
recover power and a secondary casing housing the power recovery unit therein and having
a shape in communication with the interior of the primary casing, and in which upon
reception of a stop signal for stopping power recovery by the power recovery machine,
the control unit closes the on-off valve.
[0007] In the thermal energy recovery device, upon reception of a stop signal for stopping
power recovery by the power recovery machine (when the power recovery unit is not
required to be cooled), the control unit closes the on-off valve that is provided
in the cooling flow path, whereby working medium of liquid phase is inhibited from
being accumulated within the secondary casing and the primary casing. Accordingly,
the bearing of the expander is inhibited from being immersed in the working medium
of liquid phase and thereby poor lubrication of the bearing is inhibited when the
thermal energy recovery device restarts.
[0008] In the case above, the secondary casing may have an introducing portion connectable
to the cooling flow path and capable of introducing working medium of liquid phase
supplied through the cooling flow path into the secondary casing.
[0009] In the aspect above, the power recovery unit is cooled effectively by the working
medium of liquid phase supplied through the cooling flow path into the secondary casing.
[0010] Alternatively, the power recovery machine may further have a jacket provided in the
secondary casing to form a cooling space that allows working medium of liquid phase
to flow between the jacket and the secondary casing, in which the jacket has an introducing
portion connectable to the cooling flow path and capable of introducing working medium
of liquid phase supplied through the cooling flow path into the cooling space.
[0011] In the aspect above, the power recovery unit is cooled effectively via the secondary
casing by the working medium of liquid phase supplied through the cooling flow path
into the cooling space.
[0012] The present invention also provides a thermal energy recovery device including an
evaporator for evaporating working medium through heat exchange between heating medium
and the working medium, an expander for expanding working medium flowing out of the
evaporator, a power recovery machine connected to the expander, a condenser for condensing
working medium flowing out of the expander, a pump for delivering working medium flowing
out of the condenser to the evaporator, a circulation flow path connecting the evaporator,
the expander, the condenser, and the pump in this order, a cooling flow path for supplying
cooling medium different from the working medium to the power recovery machine to
cool the power recovery machine, an on-off valve provided in the cooling flow path,
and a control unit, in which the expander has a rotor to be rotationally driven by
the expansion energy of the working medium, a bearing that bears the rotor such that
the rotor is rotatable, and a primary casing housing the rotor and the bearing therein,
and in which the power recovery machine has a power recovery unit connected to the
rotor to rotate together with the rotor and thereby recover power and a secondary
casing housing the power recovery unit therein and having a shape in communication
with the interior of the primary casing, and in which upon reception of a stop signal
for stopping power recovery by the power recovery machine, the control unit closes
the on-off valve.
[0013] Also in the thermal energy recovery device above, poor lubrication of the bearing
of the expander is inhibited when the device is driven (starts to operate).
[0014] The thermal energy recovery device preferably further includes a liquid draining
flow path for returning working medium of liquid phase within the primary casing or
the secondary casing to the downstream side of the expander and the upstream side
of the pump.
[0015] With the arrangement above, since the working medium of liquid phase within the primary
casing or the secondary casing is discharged effectively from the primary casing or
the secondary casing through the liquid draining flow path, the bearing is more reliably
inhibited from being immersed in the working medium of liquid phase.
[0016] In the case above, the thermal energy recovery device preferably further includes
a liquid draining valve provided in the liquid draining flow path, a bypass flow path
for bypassing the expander, a bypass valve provided in the bypass flow path, and a
shutoff valve provided at a site of the circulation flow path between a portion where
the circulation flow path and an upstream end portion of the bypass flow path are
connected and the expander, in which upon reception of a stop signal for stopping
power recovery by the power recovery machine, the control unit reduces the rotational
speed of the pump, closes the shutoff valve and opens the bypass valve, and closes
the on-off valve and, after the pump is stopped, opens the liquid draining valve.
[0017] With the arrangement above, the working medium of liquid phase within the primary
casing or the secondary casing is discharged effectively from the casing and, in addition
thereto, the working medium is inhibited from flowing into the primary casing until
the pump is stopped. Specifically, if the liquid draining valve were opened before
the pump is stopped, the working medium discharged from the pump to flow through the
bypass flow path to the downstream side of the expander might counterflow from the
downstream side of the expander through the circulation flow path to flow into the
primary casing of the expander to be liquefied within the primary casing. In contrast,
in the thermal energy recovery device, since the control unit is arranged to open
the liquid draining valve after the pump is stopped, such a trouble as described above
is inhibited.
[0018] As described heretofore, in accordance with the present invention, it is possible
to provide such a thermal energy recovery device in which poor lubrication of a bearing
can be inhibited when an expander is driven.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019]
FIG. 1 is a schematic view showing the configuration of a thermal energy recovery
device according to a first embodiment of the present invention.
FIG. 2 is a flow chart showing control details by a control unit.
FIG. 3 is a schematic view showing the configuration of a thermal energy recovery
device according to a second embodiment of the present invention.
FIG. 4 is a schematic view showing the configuration of a thermal energy recovery
device according to a third embodiment of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0020] Modes for carrying out the present invention will hereinafter be described in detail
with reference to the accompanying drawings.
(First Embodiment)
[0021] FIG. 1 shows the configuration of a thermal energy recovery device according to a
first embodiment of the present invention. The thermal energy recovery device includes
an evaporator 10, an expander 20, a power recovery machine 30, a condenser 40, a pump
50, a circulation flow path 60 connecting the evaporator 10, the expander 20, the
condenser 40, and the pump 50 in this order, a cooling flow path 70, and a control
unit 80.
[0022] The evaporator 10 evaporates working medium through heat exchange between the working
medium and heating medium.
[0023] The expander 20 is provided at a site downstream the evaporator 10 in the circulation
flow path 60. The expander 20 expands working medium of gas phase flowing out of the
evaporator 10. In this embodiment, the expander 20 employs a volumetric screw expander
having a rotor to be rotationally driven by the expansion energy of working medium
of gas phase. Specifically, the expander 20 has a pair of male and female screw rotors
(rotors) 21 to be rotationally driven by the expansion energy of working medium, bearings
22 that bear the screw rotors 21 such that the screw rotors 21 are rotatable, and
a primary casing 23 housing the pair of screw rotors 21 and the bearings 22 collectively.
The primary casing 23 has a suction port 23a for sucking therethrough working medium
flowing out of the evaporator 10 and a discharge port 23b for discharging therethrough
expanded working medium (after the pair of screw rotors 21 are rotationally driven)
to the circulation flow path 60. In this embodiment, the primary casing 23 is installed
in a posture in which the discharge port 23b is arranged horizontally. The bearings
22 are held on the primary casing 23.
[0024] The power recovery machine 30 is connected to the expander 20. Specifically, the
power recovery machine 30 has a power recovery unit 31 and a secondary casing 35.
[0025] The power recovery machine 30 is connected to one of the pair of screw rotors 21
to rotate together with the screw rotor 21 and thereby recover power. In this embodiment,
the power recovery machine 30 employs a generator. That is, the power recovery unit
31 has a rotating shaft 32 connected to one of the pair of screw rotors 21, a rotor
33 fixed on the rotating shaft 32, and a stator 34 arranged around the rotor 33. It
is noted that the power recovery machine 30 may employ a compressor or the like.
[0026] The secondary casing 35 houses the power recovery unit 31 therein. The secondary
casing 35 is fixed to the primary casing 23. The interior of the secondary casing
35 is in communication with the interior of the primary casing 23. This allows working
medium expanded within the primary casing 23 to partially flow into the secondary
casing 35.
[0027] The condenser 40 is provided at a site downstream the expander 20 in the circulation
flow path 60. The condenser 40 condenses working medium flowing out of the expander
20 through heat exchange between the working medium and cooling medium (e.g. cooling
water).
[0028] In this embodiment, a reservoir (receiver) 45 for reserving working medium of liquid
phase is provided at a site downstream the condenser 40 in the circulation flow path
60. It is noted, however, that the reservoir 45 may be formed by a part of the circulation
flow path 60 or may be omitted.
[0029] The pump 50 is provided at a site downstream the condenser 40 (between the condenser
40 and the evaporator 10) in the circulation flow path 60. The pump 50 delivers working
medium of liquid phase flowing out of the condenser 40 to the evaporator 10 at a predetermined
pressure.
[0030] The cooling flow path 70 supplies working medium of liquid phase flowing out of the
pump 50 partially to the power recovery machine 30. In this embodiment, the cooling
flow path 70 connects a site of the circulation flow path 60 between the pump 50 and
the evaporator 10 and the secondary casing 35. Specifically, the secondary casing
35 has an introducing portion 35a capable of introducing working medium of liquid
phase into the secondary casing 35, and a downstream end portion of the cooling flow
path 70 is connected to the introducing portion 35a. Accordingly, working medium of
liquid phase discharged from the pump 50 is partially supplied into the secondary
casing 35 through the cooling flow path 70. This allows the power recovery unit 31
to be cooled effectively.
[0031] The thermal energy recovery device of this embodiment further includes a liquid draining
flow path 71. The liquid draining flow path 71 returns the working medium R of liquid
phase within the primary casing 23 or the secondary casing 35 to the downstream side
of the expander 20 and the upstream side of the pump 50, that is, to a region in which
working medium exists in liquid phase. Specifically, the liquid draining flow path
71 connects a lead-out portion 23c formed in the primary casing 23 and a site of the
circulation flow path 60 between the reservoir 45 and the pump 50. The lead-out portion
23c is provided in a bottom portion 25 positioned lowermost in the primary casing
23. It is noted that a downstream end portion of the liquid draining flow path 71
may be connected to a site of the circulation flow path 60 between the expander 20
and the condenser 40, the interior of the condenser 40, or the reservoir 45.
[0032] The thermal energy recovery device of this embodiment further includes a bypass flow
path 62 for bypassing the expander 20, an on-off valve V1 provided in the cooling
flow path 70, a shutoff valve V2 provided in the circulation flow path 60, a bypass
valve V3 provided in the bypass flow path 62, and a liquid draining valve V4 provided
in the liquid draining flow path 71. The valves V1 to V4 are arranged openable and
closable.
[0033] An upstream end portion of the bypass flow path 62 is connected to a site of the
circulation flow path 60 between the evaporator 10 and the expander 20. A downstream
end portion of the bypass flow path 62 is connected to a site of the circulation flow
path 60 between the expander 20 and the condenser 40.
[0034] The shutoff valve V2 is provided at a site of the circulation flow path 60 between
a portion where the circulation flow path 60 and the upstream end portion of the bypass
flow path 62 are connected and the expander 20.
[0035] During recovery of power (electric power in this embodiment) by the power recovery
machine 30 (when the expander 20, the power recovery machine 30, and the pump 50 are
driven), upon reception of a stop signal for stopping the power recovery by the power
recovery machine 30, the control unit 80 stops cooling the power recovery unit 31,
that is, supplying working medium of liquid phase discharged from the pump 50 partially
to the power recovery machine 30 through the cooling flow path 70. Control details
by the control unit 80 will hereinafter be described with reference to FIG. 2. It
is noted that when the device is being driven, the on-off valve V1 and the shutoff
valve V2 are opened, while the bypass valve V3 and the liquid draining valve V4 are
closed.
[0036] Upon reception of the stop signal, the control unit 80 reduces the rotational speed
of the pump 50, the expander 20, and the power recovery machine 30, closes the shutoff
valve V2, and opens the bypass valve V3 (step S11). This causes working medium of
gas phase flowing out of the evaporator 10 to run through the bypass flow path 62
(bypass the expander 20) to the condenser 40.
[0037] With the reduction in the rotational speed of the expander 20 and the power recovery
machine 30, the power recovery unit 31 is not required to be cooled, and the control
unit 80 therefore closes the on-off valve V1 (step S12). As a result, the supply of
working medium of liquid phase through the cooling flow path 70 into the secondary
casing 35 is stopped. Accordingly, the power recovery unit 31 is inhibited from being
cooled excessively. In other words, accumulation of working medium R of liquid phase
within the secondary casing 35 and the primary casing 23 is inhibited.
[0038] After the pump 50 is stopped, the control unit 80 then opens the liquid draining
valve V4 (step S13). This causes the working medium R of liquid phase within the primary
casing 23 or the secondary casing 35 is discharged effectively from the casing 23
or 35.
[0039] As described heretofore, in the thermal energy recovery device, upon reception of
the stop signal (when the power recovery unit 31 is not required to be cooled), the
control unit 80 stops supplying working medium of liquid phase discharged from the
pump 50 partially to the power recovery machine 30 through the cooling flow path 70.
Specifically, upon reception of the stop signal, the control unit 80 closes the on-off
valve V1 that is provided in the cooling flow path 70. This inhibits accumulation
of working medium of liquid phase within the secondary casing 35 and the primary casing
23. Accordingly, the bearings 22 of the expander 20 is inhibited from being immersed
in the working medium R of liquid phase and thereby poor lubrication of the bearings
22 is inhibited when the thermal energy recovery device restarts.
[0040] In addition, since the control unit 80 opens the liquid draining valve V4 after the
pump 50 is stopped in step S13, the working medium R of liquid phase within the primary
casing 23 or the secondary casing 35 is discharged effectively from the casing 23
or 35 and, in addition thereto, the working medium is inhibited from flowing into
the primary casing 23 until the pump 50 is stopped. Specifically, if the liquid draining
valve V4 were opened before the pump 50 is stopped, the working medium discharged
from the pump 50 to flow through the bypass flow path 62 to the downstream side of
the expander 20 might counterflow from the downstream side of the expander 20 through
the circulation flow path 60 to flow into the primary casing 23 of the expander 20
to be liquefied within the primary casing 23. In contrast, in this embodiment, since
the control unit 80 is arranged to open the liquid draining valve V4 after the pump
50 is stopped, such a trouble as described above is inhibited.
(Second Embodiment)
[0041] Next will be described a thermal energy recovery device according to a second embodiment
of the present invention with reference to FIG. 3. It is noted that in the second
embodiment, only components different from the first embodiment will be described,
and the same structures, operations, and effects as in the first embodiment will not
be described.
[0042] In this embodiment, the power recovery machine 30 has a jacket 36, and the downstream
end portion of the cooling flow path 70 is connected to the jacket 36.
[0043] The jacket 36 provided in the secondary casing 35 to form a cooling space S that
allows working medium of liquid phase to flow between the jacket 36 and the secondary
casing 35. The jacket 36 is arranged on the outside of the outer peripheral surface
of the secondary casing 35. That is, the cooling space S is formed between the outer
peripheral surface of the secondary casing 35 and the inner peripheral surface of
the jacket 36. The jacket 36 has an introducing portion 36a connectable to the downstream
end portion of the cooling flow path 70 and capable of introducing working medium
of liquid phase supplied through the cooling flow path 70 into the cooling space S.
[0044] The cooling medium that has passed through the cooling space S to cool the power
recovery unit 31 via the secondary casing 35 also flows into the circulation flow
path 60 through a discharge flow path 72. An upstream end portion of the discharge
flow path 72 is connected to a discharge portion 36b formed in the jacket 36, and
a downstream end portion of the discharge flow path 72 is connected to a site of the
circulation flow path 60 between the expander 20 and the condenser 40.
[0045] As described heretofore, also in this embodiment, the bearings 22 of the expander
20 is inhibited from being immersed in the working medium R of liquid phase and thereby
poor lubrication of the bearings 22 is inhibited when the thermal energy recovery
device restarts.
(Third Embodiment)
[0046] Next will be described a thermal energy recovery device according to a third embodiment
of the present invention with reference to FIG. 4. It is noted that in the third embodiment,
only components different from the first embodiment will be described, and the same
structures, operations, and effects as in the first embodiment will not be described.
[0047] While this embodiment shares similarity with the second embodiment in that the power
recovery machine 30 has a jacket 36, cooling medium (e.g. cooling water) different
from the working medium is supplied to the cooling space S.
[0048] A cooling flow path 73 branched from a cooling medium supply line L1 for supplying
cooling medium therethrough is connected to the jacket 36. Accordingly, in this embodiment,
cooling medium passing through the cooling space S cools the power recovery unit 31
via the secondary casing 35. Cooling medium that has passed through the cooling space
S is returned through a cooling medium recovery flow path 74 connected to the jacket
36 to a cooling medium discharge line L2 for discharging cooling medium therethrough.
[0049] As described heretofore, this embodiment also exhibits the same effect as the above-described
embodiments.
[0050] It is noted that the above-disclosed embodiment should be construed as illustrative
only and not restrictive in all aspects. The scope of the present invention is defined
not by the above-described embodiment but by the appended claims and further includes
all modifications within the meaning and scope equivalent to the appended claims.
[0051] For example, the secondary casing 35 and the jacket 36, which form the cooling space
S, may be separate members or may be an integrally casted member.
[0052] Provided is a thermal energy recovery device in which poor lubrication of a bearing
can be inhibited when an expander is driven. The thermal energy recovery device includes
an evaporator (10), an expander (20), a power recovery machine (30), a condenser (40),
a pump (50), a circulation flow path (60), a cooling flow path (70) for supplying
working fluid from the pump (50) partially to the power recovery machine (30), an
on-off valve (V1) provided in the cooling flow path (70), and a control unit (80),
in which the expander (20) has a rotor (21), a bearing (22), and a primary casing
(23), and in which the power recovery machine (30) has a power recovery unit (31)
and a secondary casing (35), and in which upon reception of a stop signal for stopping
power recovery by the power recovery machine (30), the control unit (80) closes the
on-off valve (V1).
1. A thermal energy recovery device comprising:
an evaporator for evaporating working medium through heat exchange between heating
medium and the working medium;
an expander for expanding working medium flowing out of the evaporator;
a power recovery machine connected to the expander;
a condenser for condensing working medium flowing out of the expander;
a pump for delivering working medium flowing out of the condenser to the evaporator;
a circulation flow path connecting the evaporator, the expander, the condenser, and
the pump in this order;
a cooling flow path for supplying working medium of liquid phase flowing out of the
pump partially to the power recovery machine;
an on-off valve provided in the cooling flow path; and
a control unit,
wherein the expander has:
a rotor to be rotationally driven by the expansion energy of the working medium;
a bearing that bears the rotor such that the rotor is rotatable; and
a primary casing housing the rotor and the bearing therein,
and wherein the power recovery machine has:
a power recovery unit connected to the rotor to rotate together with the rotor and
thereby recover power; and
a secondary casing housing the power recovery unit therein and having a shape in communication
with the interior of the primary casing,
and wherein upon reception of a stop signal for stopping power recovery by the power
recovery machine, the control unit closes the on-off valve.
2. The thermal energy recovery device according to claim 1,
wherein the secondary casing has an introducing portion connectable to the cooling
flow path and capable of introducing working medium of liquid phase supplied through
the cooling flow path into the secondary casing.
3. The thermal energy recovery device according to claim 1,
wherein the power recovery machine further has a jacket provided in the secondary
casing to form a cooling space that allows working medium of liquid phase to flow
between the jacket and the secondary casing,
and wherein the jacket has an introducing portion connectable to the cooling flow
path and capable of introducing working medium of liquid phase supplied through the
cooling flow path into the cooling space.
4. A thermal energy recovery device comprising:
an evaporator for evaporating working medium through heat exchange between heating
medium and the working medium;
an expander for expanding working medium flowing out of the evaporator;
a power recovery machine connected to the expander;
a condenser for condensing working medium flowing out of the expander;
a pump for delivering working medium flowing out of the condenser to the evaporator;
a circulation flow path connecting the evaporator, the expander, the condenser, and
the pump in this order;
a cooling flow path for supplying cooling medium different from the working medium
to the power recovery machine to cool the power recovery machine;
an on-off valve provided in the cooling flow path; and
a control unit,
wherein the expander has:
a rotor to be rotationally driven by the expansion energy of the working medium;
a bearing that bears the rotor such that the rotor is rotatable; and
a primary casing housing the rotor and the bearing therein,
and wherein the power recovery machine has:
a power recovery unit connected to the rotor to rotate together with the rotor and
thereby recover power; and
a secondary casing housing the power recovery unit therein and having a shape in communication
with the interior of the primary casing,
and wherein upon reception of a stop signal for stopping power recovery by the power
recovery machine, the control unit closes the on-off valve.
5. The thermal energy recovery device according to any one of claims 1 to 4, further
comprising
a liquid draining flow path for returning working medium of liquid phase within the
primary casing or the secondary casing to the downstream side of the expander and
the upstream side of the pump.
6. The thermal energy recovery device according to claim 5, further comprising:
a liquid draining valve provided in the liquid draining flow path;
a bypass flow path for bypassing the expander;
a bypass valve provided in the bypass flow path; and
a shutoff valve provided at a site of the circulation flow path between a portion
where the circulation flow path and an upstream end portion of the bypass flow path
are connected and the expander,
wherein upon reception of a stop signal for stopping power recovery by the power recovery
machine, the control unit reduces the rotational speed of the pump, closes the shutoff
valve and opens the bypass valve, and closes the on-off valve and, after the pump
is stopped, opens the liquid draining valve.