U.S. patent application number 14/673349 was filed with the patent office on 2015-10-01 for cooling device for a condenser of a system for a thermodynamic cycle, system for a thermodynamic cycle, arrangement with an internal combustion engine and a system, vehicle, and a method for carrying out a thermodynamic cycle.
The applicant listed for this patent is MTU Friedrichshafen GmbH. Invention is credited to Gerald FAST, Tim HORBACH, Max LORENZ, Mathias MULLER, Jens NIEMEYER, Daniel STECHER, Niklas WAIBEL.
Application Number | 20150276284 14/673349 |
Document ID | / |
Family ID | 52596719 |
Filed Date | 2015-10-01 |
United States Patent
Application |
20150276284 |
Kind Code |
A1 |
WAIBEL; Niklas ; et
al. |
October 1, 2015 |
COOLING DEVICE FOR A CONDENSER OF A SYSTEM FOR A THERMODYNAMIC
CYCLE, SYSTEM FOR A THERMODYNAMIC CYCLE, ARRANGEMENT WITH AN
INTERNAL COMBUSTION ENGINE AND A SYSTEM, VEHICLE, AND A METHOD FOR
CARRYING OUT A THERMODYNAMIC CYCLE
Abstract
A cooling device for a condenser of a system for a thermodynamic
cycle, with a coolant circuit, wherein a conveying device for
conveying a coolant through the coolant circuit is provided, and
wherein the coolant circuit includes a cold branch downstream from
a cooling point for the coolant and a hot branch upstream of the
cooling point. The conveying device has a variable output, and/or
the coolant circuit has a connecting line between the hot branch
and the cold branch. A mixing device is provided, by way of which a
variable portion of coolant can be supplied from the hot branch to
the cold branch via the connecting line, bypassing the cooling
point.
Inventors: |
WAIBEL; Niklas;
(Friedrichshafen, DE) ; STECHER; Daniel;
(Pfulldendorf, DE) ; NIEMEYER; Jens;
(Friedrichshafen, DE) ; LORENZ; Max;
(Friedrichshafen, DE) ; HORBACH; Tim;
(Friedrichshafen, DE) ; FAST; Gerald; (Markdorf,
DE) ; MULLER; Mathias; (Friedrichshafen, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
MTU Friedrichshafen GmbH |
Friedrichshafen |
|
DE |
|
|
Family ID: |
52596719 |
Appl. No.: |
14/673349 |
Filed: |
March 30, 2015 |
Current U.S.
Class: |
165/104.31 |
Current CPC
Class: |
F01K 23/065 20130101;
F25B 39/04 20130101 |
International
Class: |
F25B 39/04 20060101
F25B039/04 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 31, 2014 |
DE |
10 2014 206 026.5 |
Claims
1. A cooling device for a condenser of a system for a thermodynamic
cycle, comprising: a coolant circuit; a conveying device for
conveying a coolant through the coolant circuit, wherein the
coolant circuit comprises a cold branch downstream from a cooling
point for the coolant and a hot branch upstream of the cooling
point, wherein the conveying device has a variable output, and/or
the coolant circuit comprises a connecting line between the hot
branch and the cold branch; and a mixing device provided so that a
variable portion of coolant from the hot branch is sendable to the
cold branch via the connecting line, bypassing the cooling
point.
2. The cooling device according to claim 1, wherein the conveying
device is configured as an automatically controllable conveying
device.
3. The cooling device according to claim 1, and further comprising
a recooling device set up to cool the coolant in the coolant
circuit, wherein the connecting line branches off from the hot
branch upstream of the recooling device, wherein the connecting
line leads to the cold branch downstream from the recooling
device.
4. The cooling device according to claim 1, wherein the connecting
line leads to the cold branch upstream of the conveying device.
5. The cooling device according to claim 1, wherein the mixing
device is a three-way mixer, wherein the cold branch passes through
a first and a second connector of the three-way mixer, and wherein
the connecting line leads to a third connector of the three-way
mixer.
6. The cooling device according to claim 1, further comprising a
control unit operative to produce a presettable absolute or
relative temperature level in the condenser of the system for a
thermodynamic cycle by actuation of the conveying device and/or of
the mixing device.
7. The cooling device according to claim 6, wherein the control
unit is operative to optimize a power yield of the system for a
thermodynamic cycle by actuation of the conveying device and/or by
actuation of the mixing device.
8. A system for a thermodynamic cycle, comprising a cooling device
according to claim 1.
9. The system according to claim 8, wherein the system is
configured to use waste heat of an internal combustion engine.
10. An arrangement, comprising: an internal combustion engine; and
the system according to claim 8.
11. A motor-driven vehicle comprising the arrangement according to
claim 10.
12. The motor-driven vehicle according to claim 11, wherein the
motor-driven vehicle is a water craft.
13. The motor-driven vehicle according to claim 12, wherein the
water craft is a ship.
14. A method for carrying out a thermodynamic cycle, for operating
a system having an evaporator, an expansion device, a condenser,
and a cooling device according to claim 1, the method comprising
the step of adjusting cooling capacity of the condenser by
actuation of a variable-output conveying device of the cooling
device and/or by actuation of a mixing device for supplying a
variable portion of coolant from a hot branch of the cooling device
to a cold branch of the cooling device via a connecting line.
15. The method according to claim 14, including controlling an
output of the conveying device and/or a functional setting of the
mixing device.
16. The method according to claim 14, including controlling cooling
capacity to provide an optimal power yield of the system or to
produce a presettable absolute or relative temperature level in the
condenser.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present application claims priority of DE 10 2014 206
026.5, filed Mar. 31, 2014, the priority of this application is
hereby claimed and this application is incorporated herein by
reference.
BACKGROUND OF THE INVENTION
[0002] The invention pertains to a cooling device for a condenser
of a system for a thermo-dynamic cycle, to a system for a
thermodynamic cycle, to an arrangement consisting of an internal
combustion engine and such a system, to a motor-driven vehicle with
a corresponding arrangement, and to a method for carrying out a
thermodynamic cycle.
[0003] Thermodynamic cycles of the type in question here are known
as such. A working medium is heated, in particular vaporized, in a
vaporizer, and then expanded in an expansion device, wherein heat
of the working medium taken up in the vaporizer is converted to
mechanical energy. The working medium is then cooled, in particular
condensed, in a condenser, and sent back to the vaporizer again.
The organic Rankine cycle, for example, corresponds essentially to
the Clausius-Rankine cycle, except that it is adapted to lower
working temperatures. It is therefore especially adapted to the use
of waste heat of industrial processes, for example, or to that of
internal combustion engines. To cool, in particular to condense,
the working medium in the condenser, a cooling device is provided.
This can be configured as an air cooler, for example, wherein the
cooling capacity of the cooling device is set in this case by the
automatic control of a blower. The disadvantage of this is that the
blower has a very high energy demand. It is also possible for the
cooling device to provide a direct connection between the condenser
and an external heat reservoir in the form of tap water, river
water, or sea water, for example. In this case, the cooling
capacity available for the condenser is determined, so that the
condenser is limited to operation on a certain temperature level
and thus at a certain condensation pressure. This necessarily leads
to a performance yield lower than maximum possible yield at many
operating points of a system for operating thermodynamic cycles.
If, furthermore, the temperature of the working medium at the
outlet from the condenser varies with the operating point of the
system as a result of the fixed cooling capacity, it is possible
that, at certain operating points and especially in high load
ranges of the system, it is impossible to ensure sufficient
supercooling of the working medium below its condensation point in
the condenser, as a result of which there is the danger that
cavitations will occur in the conveying device of the system set up
to convey the working medium through the circuit.
SUMMARY OF THE INVENTION
[0004] The invention is based on the goal of creating a cooling
device by means of which the disadvantages cited above can be
avoided. The invention is also based on the goal of creating a
corresponding system, an arrangement consisting of an internal
combustion engine and a system, a motor-driven vehicle, and a
method for operating a thermodynamic cycle, wherein the cited
disadvantages do not occur.
[0005] The goal is achieved in that a cooling device is set up to
cool a condenser of a system for operating a thermodynamic cycle,
highly preferably an organic Rankine cycle, known by the
abbreviation "ORC", wherein the cooling device comprises a coolant
circuit. A conveying device for conveying a coolant through the
coolant circuit is provided. The coolant circuit comprises a cold
branch upstream of a cooling point for the coolant and a hot branch
downstream from the cooling point. According to a first exemplary
embodiment, the cooling device is characterized in that the
conveying device comprises a variable output. As a result, the
cooling capacity of the cooling device can always be adapted to the
current operating point of the system for the thermodynamic cycle
by variation of the output of the conveying device, so that the
temperature level and thus the condensation pressure in the
condenser can always be set precisely. Alternatively, according to
a second exemplary embodiment, it is provided that the coolant
circuit comprises a connecting line between the hot branch and the
cold branch, wherein a mixing device is provided, by means of which
a variable portion of the coolant can be sent from the hot branch
to the cold branch via the connecting line, thus bypassing the
cooling point. As a result, a temperature level of the coolant
upstream of the condenser is adjustable, as a result of which in
turn the cooling capacity of the cooling device can be adjusted.
This device can therefore always be adapted in this way as well,
exactly and precisely, to an operating point of the system.
[0006] The cooling point refers to an area of the coolant circuit
in which the coolant is cooled, in particular recooled, wherein the
heat taken up by the coolant in the condenser is carried away here.
The cold branch of the coolant circuit connects the cooling point
to the condenser, so that cooled coolant can be supplied to it,
wherein the hot branch connects the condenser to the cooling point,
so that coolant heated in the condenser can be sent to the cooling
point for cooling. The cooling device is to this extent not
configured as an open system with direct connection of the
condenser to the environment or to an external heat reservoir, but
rather as a recooled primary coolant circuit, which is itself
cooled in the area of the cooling point.
[0007] In an exemplary embodiment of the cooling device, the
conveying device is configured as a pump, wherein the output of the
pump is variable, in that it has a variable rotational speed.
[0008] A portion of coolant taken from the hot branch and variable
in the mixing device can be adjusted in particular to achieve a
desired ratio of a volume flow rate of the coolant flowing via the
connecting line to a volume flow rate flowing via the cooling
point. It is obvious that cold coolant thus arriving in the mixing
device from the cooling point can be mixed with hot coolant
arriving from the condenser and branched off upstream of the
cooling point, so that ultimately in this way the temperature of
the coolant supplied to the condenser for cooling is
adjustable.
[0009] In a third exemplary embodiment of the cooling device, both
the conveying device comprises a variable output and the coolant
circuit comprises a connecting line between the hot branch and the
cold branch, wherein a mixing device is provided, by means of which
a variable portion of coolant from the hot branch can be supplied
to the cold branch via the connecting line, thus bypassing the
cooling point. In this way, there are two degrees of freedom
available for automatically controlling the cooling capacity, so
that this capacity can be set very precisely and independently of
the temperature level of the cooling point. Thus the condensation
pressure in the condenser is precisely adjustable and adaptable to
any operating point of the system which may occur. An optimal power
yield can therefore be ensured at all operating points, and the
cooling of the condenser is not limited by a fixed cooling capacity
to a certain temperature level and thus to a certain condensation
pressure. The conveying device, especially when it is configured as
a variable-speed pump, consumes in particular much less power than
the blower of an air-cooled condenser. In addition, the cooling
capacity of the cooling device proposed here can be set more
precisely than is possible with air cooling with ambient air by
means of a blower.
[0010] An exemplary embodiment of the cooling device is
characterized in that the conveying device is configured as an
automatically controllable conveying device. As a result, the flow
rate of the coolant through the coolant circuit, in particular the
volume flow rate of coolant through the condenser, can be set
especially accurately. It is possible for a conveying line of the
conveying device to be automatically controlled to set the volume
flow rate through the condenser. It is especially preferable for
the conveying device to be configured as an automatically
controllable pump. The rotational speed of the pump is preferably
controllable, which represents an especially simple embodiment of
an automatically controllable conveying device.
[0011] An exemplary embodiment of the cooling device is
characterized in that the connecting line branches off from the hot
branch upstream of a recooling device, wherein the recooling device
is set up to cool the coolant in the coolant circuit. The
connecting line leads to the cold branch downstream from the
recooling device. The cooling point of the cooling device in this
exemplary embodiment is realized by the recooling device, wherein
preferably the primary cooling circuit realized by the coolant
circuit is connected for heat transfer to a secondary coolant
circuit. Alternatively, it is possible for the recooling device to
connect the coolant circuit to an external heat reservoir by way of
a thermal connection. The recooling device is preferably configured
to use outside water or air as coolant, in particular tap water,
river water, sea water, or ambient air. Especially in the case of
marine applications of the system, recooling by sea water is
preferred. By means of the recooling device, the coolant can be
cooled very effectively in the area of the cooling point, wherein
its waste heat can be dissipated to the environment easily and at
low cost. Because the connecting line branches off from the hot
branch upstream of the recooling device, as-yet-uncooled coolant
heated in the condenser can be sent through the connecting line.
Because the connecting line leads to the cold branch downstream
from the recooling device, it is possible at this point, at which
preferably the mixing device is also provided, to mix cold coolant
arriving from the recooling device especially efficiently with hot
coolant arriving via the connecting line.
[0012] Another exemplary embodiment of the cooling device is
characterized in that the connecting line leads to the cold branch
upstream of the conveying device. Thus the mixing device is also
preferably arranged upstream of the conveying device, so that it
conveys coolant which has already been mixed and is thus at the
specified temperature reached in the mixing device. In terms of
automatic control technology, this proves to be especially
favorable, and it is easier than if the connecting line were to
lead to the cold branch downstream from the conveying device, which
would mean that the conveying device was merely conveying cold
coolant.
[0013] An exemplary embodiment of the cooling device is
characterized in that the mixing device is configured as a
three-way mixer, wherein the cold branch leads to a first and a
second connector of the three-way mixer, wherein the connecting
line leads to a third connector of the three-way mixer. The part of
the cold branch arriving from the cooling point leads to a first
connector of the three-way mixer, wherein the path of the coolant
continues from a second connector of the three-way mixer to the
condenser. The connecting line is connected to the third connector
of the three-way mixer, so that coolant from the first and third
connectors is mixed in the mixing device and sent to the second
connector. This represents an especially simple and low-cost as
well as easy-to-control embodiment of the mixing device. The mixer
can comprise a first functional setting, in which the first
connector is connected to the second connector, wherein the third
connector is blocked. In this case, the mixing device allows only
cold coolant through, so that, to this extent, a minimum
temperature of the medium is realized. In a second functional
setting, the third connector is connected to the second connector,
wherein the first connector is blocked. In this case, the mixing
device allows only hot coolant through, so that to this extent a
maximum temperature of the medium is realized. Between these two
extreme positions, there are preferably various functional
settings, especially preferably a continuum of functional settings,
that can be realized, so that the temperature of the coolant can be
adjusted by the mixing device to any or to almost any temperature
between the minimum temperature and the maximum temperature of the
medium.
[0014] In another embodiment the cooling device is characterized by
control unit, which is set up to produce a presettable absolute or
relative temperature level in a condenser of a system for operating
a thermodynamic cycle, highly preferably an ORC, by actuating the
conveying device and/or by actuating the mixing device. The control
unit is set up preferably to produce the desired temperature level
by actuation of both the conveying device and the mixing device. By
means of the control unit, it is possible in any case to produce an
absolute or relative temperature level in the condenser in a highly
exact and precise manner, preferably to control it in an open-loop
or closed-loop manner.
[0015] An absolute temperature level is understood to mean an
absolute, previously determined temperature to be reached for the
working medium in the condenser or directly downstream from the
outlet of the working medium from the condenser. A relative
temperature level is understood to mean a previously determined
degree of supercooling of the working medium in the condenser or
directly downstream from the condenser, therefore a previously
determined difference between the working medium temperature and
the condensation point of the working medium in the condenser. By
effectively adjusting the degree of supercooling, it can be ensured
that the working medium does not cavitate in the working medium
pump of the system. By way of the adjustment of the absolute or
relative temperature level in the condenser or directly downstream
from the condenser, furthermore, the power yield of the system can
also be optimized. What is needed for this purpose in particular is
the precise adjustment of the pressure in the condenser, which can
be adjusted very precisely by variation of the working medium
temperature and therefore by variation of the cooling capacity of
the cooling device. This pressure acts as a backpressure at the
expansion device and therefore, together with other operating
parameters of the system, plays a primary role in determining the
power yield of the system. The cooling capacity which the cooling
device must have to adjust the temperature level to a presettable
value varies as a function of the operating point of the system, in
particular as a function of the heat input into the system,
because, depending on the heat input into the vaporizer, a greater
or lesser amount of heat must be carried away from the condenser.
By means of the cooling device proposed here, it is to be prevented
in particular that more heat is carried away than is necessary to
achieve a previously determined supercooling of the working medium.
Otherwise this has a negative effect on the power yield of the
system.
[0016] The control unit is set up to maintain the preset volume
flow rate of the coolant via automatic control of the output of the
conveying device and to maintain the preset coolant temperature at
the inlet into the condenser by actuating or automatically
controlling the mixing device. In this way, the cooling capacity of
the cooling device can be controlled very sensitively by the
control unit in either open-loop or closed-loop fashion, especially
by combining the variation of the output of the conveying device
with the variation of the temperature setting in the mixing
device.
[0017] An exemplary embodiment of the cooling device is
characterized in that the control unit is set up to optimize the
power yield of the system by actuation of the conveying device
and/or of the mixing device. In this case, the control unit
preferably comprises a feedback circuit for at least one parameter
which is a characteristic of the power yield of the system, so that
the power yield can be optimized directly, i.e., automatically
controlled. As a result, the cooling capacity of the cooling device
can always be coordinated optimally with the current operating
point of the system. It is especially preferable for the control
unit to be set up to optimize the power yield of the system by
actuating both the conveying device and the mixing device.
[0018] The goal is also achieved in that a system for operating a
thermodynamic cycle, quite preferably an organic Rankine cycle, is
created, which is characterized by a cooling device according to
one of the previously described exemplary embodiments. The
advantages already described in conjunction with the cooling device
are thus realized for the system. In particular, the system can be
automatically regulated by way of the cooling device to deliver an
optimal power yield at all operating points.
[0019] The system comprises a working medium circuit, around which
a vaporizer, an expansion device, a condenser, and preferably a
working medium pump for conveying working medium through the
circuit are arranged--in that order. The cooling device is
functionally connected to the condenser so that the working medium
can be cooled in the condenser.
[0020] The system also comprises at least one temperature sensor
and/or at least one pressure sensor in the condenser or directly
downstream from the condenser, i.e., downstream with respect to the
direction in which the working medium flows through the circuit,
this sensor being functionally connected to the control unit for
the open-loop or closed-loop control of the cooling device. By the
use of the temperature sensor and/or the pressure sensor, a
thermodynamic state of the working medium in the condenser can be
acquired, and the cooling capacity of the cooling device can be
adjusted on that basis, adjusted in particular in an open-loop or
closed-loop manner.
[0021] An exemplary embodiment of the system is characterized in
that it is set up to use waste heat of an internal combustion
engine. For this purpose in particular, an ORC is preferably
carried out in the system. It is possible in this case to make use
of the waste heat in an exhaust gas stream or in a coolant stream
of the internal combustion engine. Alternatively, it is possible
that the system could be set up to use waste heat or heat from some
other heat source such as industrial waste heat and/or to use
geothermal heat, preferably also by means of an ORC.
[0022] Ethanol is preferably provided as the working medium in the
system. This is especially well adapted to the operating points in
the system which are reached during the use of waste heat from the
exhaust gas of an internal combustion engine and is also well
adapted to an ORC.
[0023] The goal is also achieved in by an arrangement that
comprises an internal combustion engine and a system according to
one of the previously described exemplary embodiments. The system
is functionally connected to the internal combustion engine for use
of the waste heat of the engine. The system can be used to convert
the waste heat into mechanical and/or electrical energy, which is
sent back to the internal combustion engine again, such as to a
crankshaft of the internal combustion engine, especially by means
of an electric motor, which is functionally connected to the
crankshaft. Alternatively or in addition, the energy converted in
the system from the waste heat of the internal combustion engine
can be sent to an external consumer or to a power supply system. It
is possible that the power supply system could be an on-board power
supply system of a motor-driven vehicle which comprises the
arrangement. The system makes it possible to achieve a considerable
increase in the efficiency of the internal combustion engine
through the use of its waste heat. Instead of being uselessly
dissipated into the environment, the waste heat is put to positive
use.
[0024] The internal combustion engine of the arrangement is
preferably configured as a reciprocating piston engine. In a
preferred exemplary embodiment, the internal combustion engine
serves in particular to drive heavy land vehicles such as mining
vehicles and trains or water craft, wherein the internal combustion
engine is used in a locomotive or motor coach or in a ship. The use
of the internal combustion engine to drive a vehicle serving
defensive purposes such as a tank is also possible. In another
exemplary embodiment of the internal combustion engine, it is
stationary and used for stationary power generation to generate
emergency power or to cover continuous-load or peak-load demands,
wherein the internal combustion engine in this case preferably
drives a generator. The stationary use of the internal combustion
engine to drive auxiliary units such as fire-fighting pumps on
offshore drilling rigs is also possible. An application of the
internal combustion engine in the area of the recovery of fossil
materials and especially fossil fuels such as oil and/or gas is
also possible. The internal combustion engine can also be used in
industry or in the construction field for the production of
construction vehicles such as cranes and bulldozers. The internal
combustion engine is preferably configured as a diesel engine; as a
gasoline engine; or as a gas engine for operation with natural gas,
biogas, customized gas, or some other suitable gas. Especially when
the internal combustion engine is configured as a gas engine, it is
suitable for use in block-type thermal power stations for
stationary power generation.
[0025] The goal is also achieved by a motor vehicle that is
characterized by an arrangement according to one of the previously
described exemplary embodiments. With respect to the motor-driven
vehicle, the advantages already explained in conjunction with the
cooling device, the system, and the arrangement are realized. The
energy converted by the system from the waste heat of the internal
combustion engine can be used effectively either to support the
internal combustion engine or for other purposes, such as to supply
an on-board power supply system of the motor-driven vehicle with
electrical energy.
[0026] In an exemplary embodiment the motor-driven vehicle is
configured as a water craft, especially as a ship, preferably as a
ferry. Here the waste heat can be used in a variety of ways to
operate various systems of the ship, especially an on-board power
supply system, i.e., the ship's own power grid, or to support the
internal combustion engine. It in addition, it is also possible to
realize the recooling device in a water craft in an especially
simple and low-cost manner by using sea water or river water for
the recooling. Thus a virtually inexhaustible heat reservoir is
available for recooling, so that, whatever else may happen, the
precise setting of the thermodynamic state of the working medium in
the condenser cannot fail because of a lack of recooling
capacity.
[0027] The goal is also achieved, finally, in that a method for
operating a thermodynamic cycle, quite preferably an organic
Rankine cycle, is created. The method is provided in particular for
the operation of a system according to one of the previously
described exemplary embodiments. In this case the system comprises
an evaporator, an expansion device, and a condenser, arranged in
that order in the direction in which the working medium flows
through the circuit of the system, wherein it also comprises a
cooling device, preferably a cooling device according to one of the
preceding exemplary embodiments. Within the scope of the method,
the desired cooling capacity of the condenser is achieved by
actuation of the variable-output conveying device of the cooling
device and/or by actuation of a mixing device for supplying a
variable portion of coolant from a hot branch of the cooling device
to a cold branch of the cooling device via a connecting line. The
cooling capacity of the condenser is preferably adjusted by
appropriate actuation of both the conveying device and the mixing
device. Thus the advantages which have already been described in
conjunction with the cooling device, the system, the arrangement,
and the motor-driven vehicle are realized.
[0028] Within the scope of the method, a pump, especially a
variable-speed pump, is used as the conveying device, wherein the
output of the pump is adjusted by varying its rotational speed.
[0029] In an embodiment of the method the output of the conveying
device and/or a functional setting of the mixing device is
automatically controlled. This makes possible an especially precise
setting of the cooling capacity of the cooling device and thus
simultaneously of the cooling capacity of the condenser. Preferably
both the output of the conveying device and the functional setting
of the mixing device are automatically controlled.
[0030] Finally, in another embodiment of the method the cooling
capacity of the cooling device is automatically controlled to
achieve the optimal power yield of the system and/or a presettable
absolute or relative temperature level of the working medium in the
condenser or immediately downstream from the condenser. Thus an
optimal power yield can be guaranteed at all operating points of
the system in an especially suitable and exact manner.
[0031] The description of the cooling device and of the system on
the one hand and of the method on the other hand are to be
understood as complementary to each other. In particular, method
steps which have been explained explicitly or implicitly in
conjunction with the cooling device or the system are preferably
steps, individually or in combination, of a preferred embodiment of
the method. In the same way, features of the cooling device or of
the system which have been explained explicitly or implicitly in
conjunction with the method are preferably features, individually
or in combination, of a preferred exemplary embodiment of the
cooling device or of the system. The cooling device or the system
is preferably characterized by at least one feature which is
required by at least one method step of the method. The method is
characterized preferably by at least one method step which is
required by at least one feature of the cooling device or of the
system.
[0032] The various features of novelty which characterize the
invention are pointed out with particularity in the claims annexed
to and forming a part of the disclosure. For a better understanding
of the invention, its operating advantages, specific objects
attained by its use, reference should be had to the drawings and
descriptive matter in which there are illustrated and described
preferred embodiments of the invention.
BRIEF DESCRIPTION OF THE DRAWING
[0033] In the drawing:
[0034] FIG. 1 shows a schematic diagram of an exemplary embodiment
of a motor-driven vehicle with an arrangement consisting of an
internal combustion engine and a system with a cooling device;
[0035] FIG. 2 shows a schematic diagram of an exemplary embodiment
of the cooling device; and
[0036] FIG. 3 shows a schematic diagram of an embodiment of the
method in the form of an automatic control circuit.
DETAILED DESCRIPTION OF THE INVENTION
[0037] FIG. 1 shows a schematic diagram of an exemplary embodiment
of a motor-driven vehicle 1, which comprises an arrangement 3
consisting of an internal combustion engine 5 and a system 7 for
operating a thermodynamic cycle, here in particular an organic
Rankine cycle (ORC). The motor-driven vehicle 1 is preferably
configured as a ship. Alternatively, however, an embodiment of the
motor-driven vehicle 1 as a rail vehicle, as a mining or
construction vehicle, as a defensive vehicle, as a truck, or even
as a passenger vehicle is also possible.
[0038] The use of the arrangement 3 is not limited to motor-driven
vehicles; instead, it can be used in other areas as well, including
stationary uses of the internal combustion engine 5 to operate
pumps on an offshore drilling rig, for example, where the waste
heat of the engine can be put to positive use.
[0039] Finally, the system 7 is not limited to use in an
arrangement with an internal combustion engine 5. On the contrary,
it can be used in other ways to use waste heat such as to use
industrial waste heat or even to use other heat sources such as
geothermal heat.
[0040] The system 7 comprises a working medium circuit 9, along
which an evaporator 11, an expansion device 13, and a condenser 15
are arranged in that order in the flow direction of the working
medium. The working medium is conveyable through the working medium
circuit 9 by a working medium pump 17. The working medium used is
preferably ethanol.
[0041] The expansion device 13 is preferably configured as a
continuous-flow machine or as a displacement machine, especially as
a turbine, as a reciprocating piston expander, as a rotary vane
pump, as a Roots expander, or as a scroll expander. A configuration
of the expansion device 13 as a helical screw expander, however, is
especially preferred. The expansion device 13 is functionally
connected to a generator 19 to convert mechanical energy recovered
in the expansion device 13 into electrical energy.
[0042] The evaporator 11 is functionally connected to the internal
combustion engine 5 preferably in such a way that waste heat
contained in the exhaust gas and/or in the coolant circuit of the
internal combustion engine 5, in particular the waste heat
contained in the exhaust gas of the engine, can be sent to the
working medium of the system 7 in the evaporator 11.
[0043] To cool the working medium in the condenser 15, in
particular to condense it, a cooling device 21 is provided with a
coolant circuit 23. A sensor device 25 for detecting a temperature
and/or a pressure of the working medium in the condenser 15 is
provided preferably directly downstream from the condenser 15 or
even in the condenser 15. The formulation "in the condenser" is
always to be understood not only as a value detected directly
inside the condenser 15 but also as a value detected immediately
downstream from it, because, if these values differ at all from
each other, the difference is irrelevant. The sensor device 25 is
functionally connected to a control unit 27, which for its own part
is functionally connected to the cooling device 21 to adjust its
cooling capacity.
[0044] It has been found that the waste heat supplied to the
evaporator 11 varies as a function of an operating point of the
internal combustion engine 5. Thus an operating point of the system
7 varies at the same time, as well as the cooling capacity of the
cooling device 21 required to achieve an optimal power yield of the
system. The cooling capacity is adjusted precisely by means of the
cooling device 21 and the control unit 27 to achieve the optimal
power yield at every operating point of the system 7.
[0045] FIG. 2 shows a schematic diagram of an exemplary embodiment
of the cooling device 21. Also shown are the condenser 15, a
working medium feed line 29 to the condenser 15, and a working
medium outlet line 31 leading from the condenser 15. The broken
line "L" marks the system boundary between the condenser 15 and the
rest of the system 7.
[0046] The cooling device 21 comprises the coolant circuit 23,
which is configured as a primary coolant circuit. A conveying
device 33, here configured as a pump, is provided to convey coolant
around the coolant circuit 23, where the conveying device 33
comprises a variable output, here a variable rotational speed for
producing the desired volume flow rate of coolant in the coolant
circuit 23. The coolant circuit 23 comprises a cold branch 35
located downstream--with respect to the flow direction of the
coolant--from a cooling point 37, which is configured here as a
recooling device 39, and a hot branch 41, upstream of the cooling
point 37. Between the hot branch 41 and the cold branch 35, a
connecting line 43 is arranged, and a mixing device 45 is provided,
which is configured here as a three-way mixer 47, by means of which
a variable portion of coolant from the hot branch 41 can be sent
via the connecting line 43 to the cold branch 35. The functional
setting of the mixing device 45 is variably adjustable, so that a
variable mixing ratio between the hot coolant arriving through the
connecting line 43 and the cold coolant arriving from the cooling
point 37 can be set.
[0047] The cold branch 35 passes via a first connector 49 to a
second connector 51, wherein the connecting line 43 leads to a
third connector 53 of the three-way mixer 47.
[0048] The arrows P in FIG. 2 indicate the flow direction of the
coolant in the coolant circuit 23, wherein the coolant is
conveyable by the conveying device 33 around the coolant circuit 23
in the indicated flow directions.
[0049] It is obvious here that the connecting line 43 branches off
from the hot branch 41 upstream of the recooling device 39, wherein
it leads to the cold branch downstream from the recooling device
39, wherein it leads in particular into the cold branch at a point
upstream of the conveying device 33.
[0050] The recooling device 39 is configured to recool the coolant
by means of a recooling medium, which is conveyable by a recooling
medium pump 55 around a recooling path 57, which is preferably
configured as a secondary coolant circuit. Sea water is preferably
used here as the recooling medium, especially in the case of an
embodiment of the motor-driven vehicle 1 as a ship. If the ship is
configured as a river boat, however, preferably river water is used
as the recooling medium.
[0051] In other applications of the system 7, it is possible to
provide, as an alternative, that air, especially ambient air, or a
thermal connection with some other external heat reservoir is used
as the recooling medium. Tap water, for example, is another
possible example of a recooling medium.
[0052] The coolant circuit 23 also comprises a compensating
reservoir 59 for the coolant.
[0053] FIG. 2 shows the control unit 27, which is functionally
connected to the sensor device 25 for detecting the thermodynamic
state of the working medium in the condenser 15, especially for
detecting the temperature and/or the pressure of the working
medium.
[0054] The control unit 27 is also functionally connected to the
conveying device 33 for open-loop or closed-loop control of its
output, especially for the open-loop or closed-loop control of the
rotational speed of a conveying device 33 configured as a pump. In
addition, the control unit 27 is functionally connected to the
mixing device 45 for the open-loop or closed-loop control of its
functional setting. By means of appropriate actuation of the mixing
device 45, a temperature of the coolant downstream from the mixing
device 45 and thus in particular a coolant inlet temperature into
the condenser 15 can be automatically controlled, wherein at the
same time, by application actuation of the conveying device 33, a
volume flow rate of the coolant through the coolant circuit 23 and
especially through the condenser 15 can be automatically
controlled. Overall, therefore, the cooling capacity of the cooling
device 21 is automatically controllable preferably as a function of
an operating point of the system 7. It is thus possible to adjust
precisely the state of the working medium downstream from the
condenser 15. This is possible in particular because of the cooling
device 21, even though the temperature of the recooling medium in
the recooling path 57 typically cannot be controlled in open-loop
or closed-loop fashion and instead is determined by external
circumstances. This is obvious when sea water or ambient air is
used as the recooling medium.
[0055] Water is preferably used as the coolant in the cooling
device 21 and especially in the coolant circuit 23.
[0056] FIG. 3 shows a schematic diagram of an embodiment of the
method in the form of an automatic control circuit. A setpoint 61
in the form of a nominal value of a thermodynamic variable of state
of the working medium in the condenser 15, preferably a nominal
temperature or a nominal supercooling of the working medium is
entered into the automatic control circuit. An actual value 63 of
the thermodynamic state variable, which is preferably measured by
the sensor device 25, is sent back to a comparison member 65, and a
control deviation 67 between the setpoint 61 and the actual value
63 is determined.
[0057] The setpoint 61 is preferably taken from a characteristic
diagram, which is based on at least one operating parameter of the
system 7 for characterizing its operating states. As an
alternative, it is also possible to select a constant setpoint 61
for the operation of the system 7. In this case, the cooling
capacity of the cooling device 21 is arrived at in particular as a
function of the heat input into the vaporizer 11.
[0058] The control deviation 67 is sent to the controller 69,
which, on this basis, calculates two values for the actuators,
namely, a first starting value 71 for the output of the conveying
device 33, especially a rotational speed of the conveying device 33
configured as a pump, and a second starting value 73 for the
actuation of the mixing device 45. The two starting values 71, 73
act on a controlled system 75 comprising in particular the mixing
device 45 and the conveying device 33 as well as, finally, the
condenser 15. The output of the conveying device 33 and the
functional setting of the mixing device 45 are preferably adjusted
to match the default values 71, 73, which is not shown here
explicitly. To this extent, what is involved is subsidiary
automatic control.
[0059] In the controlled system 75, a new actual value 63 for the
thermodynamic state variable of the working medium in the condenser
15 is then reached.
[0060] Quite generally, within the scope of the method, therefore,
the cooling capacity of the condenser 15 of the system 7 is
adjusted by actuation of the variable-output conveying device 33,
wherein in addition the mixing device 45 is actuated to supply a
variable portion of coolant from the hot branch 41 to the cold
branch 35 via the connecting line 43.
[0061] If a constant value is selected for the setpoint 61, this
value is preferably determined in such a way that the system 7
delivers the greatest possible power yield at all operating points.
If the setpoint 61 is taken from a characteristic diagram, this
preferably shows the values for the desired setpoint 61 at which
the system 7 supplies its optimal power yield as a function of its
operating point. Accordingly, the cooling capacity of the cooling
device 21 is automatically controlled especially to result in the
optimal power yield of the system. 7.
[0062] Overall it has been found that, by means of the method, it
is possible automatically to control the cooling capacity of the
cooling device 21 in an energy-saving and yet very precise manner,
so that the system 7 can operate with its optimal power yield.
[0063] While specific embodiments of the invention have been shown
and described in detail to illustrate the inventive principles, it
will be understood that the invention may be embodied otherwise
without departing from such principles.
* * * * *