[0001] The invention relates to a refrigerant circuit, where, via a refrigerant, heat is
transferred between a first environment and a second environment, the refrigerant
circuit comprising a compressor for compressing the refrigerant, a first heat exchanger
for transferring heat between the first environment and the refrigerant circuit, a
second heat exchanger for transferring heat between the second environment and the
refrigerant circuit, where the first heat exchanger is configured to operate as a
condenser to cool the refrigerant in a heating mode, and the second heat exchanger
is configured to operate as an evaporator in the heating mode, and with a compressor
driver electrically coupled with the compressor for powering the compressor.
[0002] Air source heat pumps are becoming popular in domestic applications and replace traditional
gas boilers due to improved energy efficiency. Such heat pumps usually comprise a
refrigerant circuit with a refrigerant such as R410a, R290, CO
2, or alike. In general, a compressor is used to increase the pressure and thus separate
a low pressure side of the circuit from a high-pressure side. In such a heat pump,
the refrigerant can be conducted from the high-pressure side of the compressor to
a four way valve, which is used to reverse the refrigerant circuit from heating mode
to cooling mode. In the heating mode, after the four way valve, the refrigerant will
reach the first heat exchanger which may be a plate heat exchanger and works as condenser,
and the refrigerant will change the phase from gas to liquid. This is the condensing
process, where the latent heat of the refrigerant is released to another fluid in
the plate heat on the exchanger, in most cases to water. After the condenser, the
refrigerant will usually flow through one or more valves for pressure reduction. Then
the refrigerant will pass another, second heat exchanger working as evaporator, preferably
with multiple passes. The second heat exchanger may comprise an extended surface for
enhancing heat exchange. In the second heat exchanger, the heat can be transferred
to the refrigerant form another medium such as ambient air, for instance. This process
may be supported by a fan enhancing airflow. As the refrigerant temperature is lower
than the ambient air temperature and the refrigerant is in liquid form, it will evaporate
and absorb heat from the ambient air. After the evaporator, the refrigerant will become
gas again and then flow through the four way valve into the low pressure suction line
of the compressor for the next cycle.
[0003] The main advantage of such air source heat pumps is the high coefficient of performance
(COP). The air source heat pump uses only a small quantity of energy for operating
the compressor and other electrical components to absorb heat from the ambient air
and then release the heat to the carrier medium of a space heating/cooling circuit,
for instance water, in the first heat exchanger. The COP varies from 3 to 5, which
means the heat pump can supply 3 to 5 times the heat corresponding to the total power
consumption of the compressor and other load units, such as electronics, of the heat
pump.
[0004] Usually, heat losses in the heat pump system are not fully used. So, the heat losses
of, for instance the compressor will be dissipated to the ambient even if the temperature
of the (waste) heat source, i.e. the load unit, can be quite high, for instance 80
degree Celsius for electronic components or even 100 degree Celsius for the compressor.
[0005] On the other hand, when the ambient temperature is near 0°C, the humidity in the
air will deposit on thin surfaces of the air side of the evaporator, the second heat
exchanger, and it will form ice, which is called "frosting process". When the frost
becomes significant, it will block the air passage through the evaporator and increase
the thermal resistance of the heat exchanger. This lowers the systems efficiency and
may disrupt the normal operation of the system. Therefore, when such a frosting process
occurs, the heat pump system will reverse the cycle from heating indoor to heating
outdoor by switching said four way valve, for instance. So, the heat pump will start
a defrosting mode, in which it will extract heat from indoors via the first plate
heat exchanger for heating up the second heat exchanger, the evaporator, to a higher
temperature for de-icing the second heat exchanger. This consumes electricity and
further extracts heat from indoors, which causes discomfort.
[0006] To overcome said disadvantages, the
EP 324 4141 A1 discloses a heat pump system including a refrigerant circuit, a compressor driver,
and a heat storage means. The refrigerant circuit includes a compressor for compressing
the refrigerant, a first heat exchanger for transferring heat between the refrigerant
and the interior atmosphere, a throttling device for lowering the pressure of the
refrigerant, and the second heat exchanger for transferring heat between the refrigerant
and the exterior atmosphere. The first heat exchanger operates as a condenser to cool
the refrigerant in the heating mode and operates as an evaporator to vaporize the
refrigerant in the cooling mode. The second heat exchanger operates as an evaporator
in the heating mode and operates as a condenser in the cooling mode. The compressor
driver is electrically connected with the compressor for powering the compressor,
and it generates heat in operation. The heat storage means for storing heat generated
by the compressor driver is in heat transferable contact with the refrigerant in a
defrost mode to transfer stored heat energy to the refrigerant.
[0007] The
US 526 9151 a discloses a passive defrost system that uses a heat exchanger/storage defrost module
containing a thermal storage material such as a phase-change material to capture and
store low-grade waste heat contained in the liquid refrigerant line of a refrigeration
system. The waste heat stored during normal operation. Upon shutdown of the refrigeration
system, the stored heat in the defrost module is released by an automatic device for
defrosting the evaporator.
[0008] The
EP 316 5852 a one discloses another antifrost heat pump which is capable of preventing an evaporator
from frosting during a sub-cooling process by using heat released in the sampling
process in sub-cooling means. The heat pump includes a refrigerant circuit having
an evaporator, a condenser, sub-cooling means arranged to perform a sub-cooling process
of cooling a refrigerant flowing out of the condenser, and heat transfer means arranged
to transfer heat released from the refrigerant in the sub-cooling process from the
sub-cooling means to the evaporator during the sub-cooling process.
[0009] The
US 2009/028 2854 A1 discloses an air conditioning system with a refrigerant circuit in which a compressor,
an indoor radiant panel, a first expansion valve, room air heat exchanger, a second
extension valve, and an outdoor air heat exchanger are connected in this order and
which operates in a refrigeration circuit by reversibly circulating refrigerant therethrough.
During a defrosting operation, the first expansion valve is controlled to reduce the
refrigerant pressure so that in a cooling cycle the refrigerant releases heat in the
outdoor air heat exchanger and the room heat exchanger and evaporates in the indoor
radiant panel. Thus, the air conditioning system concurrently provides the defrosting
of the outdoor air heat exchanger and the room heating of the room air heat exchanger.
[0010] The
US 2011/031 5368 A1 provides another air conditioning apparatus that can effectively utilize heat energy
generated by a control unit. The
US 2008/008 6981 A1 describes a composite, hybrid radiant/forced and natural convection, integrated,
sandwiched, multirole panel optimally integrating heating, cooling, ventilating, air
conditioning, thermoelectric effect, energy recovery, and energy storage function
at very moderate operating temperature such that it can directly utilize renewable
and waste energy resources having very low energy.
[0011] The objective technical problem to be solved by the present invention may therefore
be regarded to improve the efficiency of a heat pump system.
[0012] This problem is solved by the subject-matter of the independent claims. Advantageous
embodiments are disclosed in the dependent claims, the description, and the figures.
[0013] One aspect of the invention relates to a heat pump system with a refrigerant circuit,
where, via a refrigerant, heat is transferred between a first environment, e.g. the
inside of a building, and a second environment, e.g. the outside of the building,
and with a compressor driver. Said environments may also be a local and/or closed
environment, such as a buffer tank or buffer system, filled with, for instance, water.
The heat pump system is operable in a heating mode, where heat is transferred from
the second environment to the first environment. In addition, the heat pump system
may be operable in a cooling mode, where heat is transferred from the first environment
to the second environment.
[0014] The refrigerant circuit comprises a compressor for compressing the refrigerant, a
first heat exchanger for transferring heat between the first environment and the refrigerant
circuit, and a second heat exchanger for transferring heat between the second environment
and the refrigerant circuit. Therein, the first heat exchanger is configured to operate
as a condenser to cool the refrigerant in the heating mode. The first heat exchanger
may be configured to operate as an evaporator to vaporize the refrigerant in the cooling
mode. The second heat exchanger is configured to operate as an evaporator in the heating
mode. The second heat exchanger may be configured to operate as a condenser in the
cooling mode. The first heat exchanger may be a plate heat exchanger. In addition
to the refrigerant as a first working medium, the first heat exchanger uses a second
working medium which may be a liquid such as water. The second heat exchanger may
feature an extended surface for enhancing heat exchanger with ambient air. In addition
to the refrigerant as a first working medium, the second heat exchanger uses a second
working medium which may be a gas such as ambient air. The refrigerant circuit may
comprise a throttling device such as a valve or several valves for lowering the pressure
of the refrigerant in the refrigerant circuit or in a specific section of the refrigerant
circuit. The compressor driver is electrically coupled with the compressor for powering
the compressor.
[0015] In addition to the compressor and said two heat exchangers, the refrigerant circuit
comprises a heat storage means with a heat storage medium different from the refrigerant.
Said heat storage means may also be referred to as distinct heat storage means. The
heat storage means is thermally coupled with the compressor and/or the compressor
driver, and is configured to store heat (which may be referred to as waste heat) generated
by the compressor and/or the compressor driver in a normal operating mode. The normal
operating mode may comprise the heating mode or the cooling mode or the heating and
the cooling mode. The heat storage means is configured to transfer the stored heat
to the refrigerant in a defrost mode of the refrigerant circuit, in particular only
in a defrost mode of the refrigerant circuit.
[0016] So, the heat storage is thermally coupled with the rest of the refrigerant circuit
by the refrigerant running through or along the heat storage when heat is transferred
from the heat storage medium to the refrigerant. As part of the refrigerant circuit,
the heat storage means is coupled to the refrigerant circuit directly, and heat is
transferred from the heat storage medium to the refrigerant directly, that is, preferably
not via another liquid medium or gas medium. In particular, the heat storage means
does not comprise another circuit for another medium, in particular another liquid
and/or gas medium, that may be thermally coupled to the refrigerant circuit. So, the
heat storage means may form an additional heat exchanger in the refrigerant circuit,
with the refrigerant as first working medium and the heat storage medium as second
working medium.
[0017] This gives the advantage that the waste heat generated in the compressor driver or
the compressor is used for defrosting, which saves electricity and renders the extraction
of heat from the first environment, which causes discomfort in the state-of-the-art,
unnecessary. Hence, the overall efficiency of the heat pump system is improved. Here,
the integration of the heat storage means into the refrigerant circuit that allows
a direct transfer from the waste heat to the refrigerant and renders the design particularly
simple and efficient.
[0018] In an advantageous embodiment, the heat storage means is connected to the rest of
the refrigerant circuit parallel to the first heat exchanger, so that the first heat
exchanger can be bypassed by the heat storage means, and the heat storage means can
be bypassed by the heat exchanger.
[0019] This gives the advantage that the heat stored in the heat storage means can either
be contained in the heat storage means or transferred to the refrigerant flowing through
the refrigerant circuit, in particular to the second heat exchanger by, for instance
simply switching one valve of the refrigerant circuit causing of the refrigerant flow
through the heat storage means instead of the first heat exchanger, or through the
first heat exchanger instead of the heat storage means respectively. Hence, said setup
results in a particularly simple and efficient heat pump system.
[0020] In another advantageous embodiment, in addition to the compressor and/or compressor
driver, a control unit and/or at least one additional electrical load is thermally
coupled to the heat storage means.
[0021] This gives the advantage that more wasted heat is stored and used for defrosting,
hence the efficiency of the system is further improved. This is particularly advantageous
in combination with the embodiment described below, where several storage cells are
provided in the heat storage means. Therein, individual characteristics of the different
waste heat sources, the electrical loads or the control unit or the compressor or
the compressor driver, such as different temperature levels of the waste sources,
can be optimally taken advantage of by the different storage cells with different
phase-change temperatures, for instance.
[0022] In a further advantageous embodiment, the compressor and/or compressor driver and/or
the control unit and/or the at least one additional electrical load of the heat pump
system are thermally coupled to the heat storage means by respective heat pipes or
thermosiphons. Each waste heat source may be thermally coupled to the heat storage
means by an individual heat pipe or thermosiphon. Alternatively, several waste heat
sources may be thermally coupled to the heat storage by one respective heat pipe or
thermosiphon.
[0023] This gives the advantage that the thermal coupling of the heat storage means to the
compressor driver, the compressor, the control unit, or another electrical load, shortly,
to the waste heat sources, is realized in a particularly efficient and technically
simple, robust way.
[0024] In another advantageous embodiment, the heat pump system may comprise a casing for
the compressor, the compressor driver, and the heat storage means, as well as, in
particular, the other load units or waste heat sources. In the intended use of the
heat pump system, the heat storage means is preferably arranged above the compressor
and/or the compressor driver and/or the other load that are thermally coupled with
the heat storage means.
[0025] This gives the advantage that gravity supports the heat transfer from the waste heat
sources, the electric load units, to the heat storage means. Consequently the system
is particularly simple, robust, and efficient.
[0026] Therein, storage cells (see below) with lower phase-change temperature may be attached
to the casing in between the casing and the storage cells with higher phase-change
temperature. This gives the advantage of improved thermal efficiency, where excess
heat of the storage cells with higher phase-change temperature is transferred to storage
cells with a lower phase-change temperature, i.e. used to charge storage cells with
a lower phase-change temperature.
[0027] In yet another advantageous embodiment, the heat storage medium comprises or is a
phase-change material. The phase-change material may comprise one or more compositions
of different phase-change materials. This gives the advantage that the heat can be
stored particularly efficiently, and that, by the selection of a phase-change material
with appropriate phase-change temperature, the rate of the heat transfer can be adjusted
optimally to the working conditions of the compressor driver and the other electrical
load units.
[0028] In a further advantageous embodiment, the heat storage means comprises at least two
storage cells with different phase-change materials. Said phase-change materials may
also be different compositions of identical phase-change materials. Each storage cell
has a different phase-change temperature, and each of the cells is thermally coupled
to at least one, i.e. one or several or all, of the following load units: the compressor
and/or the compressor driver and/or the control unit and/or the at least one additional
electrical load. Vice versa, each of the compressor and/or the compressor driver and/or
the control unit and/or the at least one additional electrical load is thermally coupled
to one or several of the storage cells, in particular exactly one of the storage cells.
In particular, the thermal coupling may be realized by respective individual thermosiphons
or heat pipes, so that, for instance, each storage cell is coupled to one or more
load units by respective thermosiphons or heat pipes, or each load unit is coupled
to one or more of the storage cells by respective thermosiphons or heat pipes.
[0029] This gives the advantage that multiple heat losses in different temperature ranges
can be recovered and stored in a latent form in the respective storage cells with
multiple phase-change temperature values. Thus, a particularly efficient heat storage
is achieved. The stored heat can then be used in different ways for improving the
overall efficiency in the flow arrangement, for instance it enables the refrigerant
flow through or along a phase-change material with a low phase-change temperature,
a low temperature phase-change material cell, and afterwards through or along a phase-change
material with a high phase-change temperature, a high temperature phase-change material
cell, as described below.
[0030] Therein, a first storage cell with a lower phase-change temperature than a second
storage cell may be thermally coupled with a first load unit of the load units, which
may for instance be (or comprise) the control unit, where the first load unit has
a lower heat generation, in particular lower average heat generation, and/or a lower
power consumption, in particular lower average power consumption, than a second load
unit of the load units, which may for instance be (or comprise) the compressor driver,
and the second storage cell is thermally coupled with the second load unit. In particular,
the first load unit is not thermally coupled by a heat pipe or thermosiphon to the
second load unit and vice versa. Such a heat storage means may also comprise further
storage cells with other phase-change temperatures, for instance a third storage cell
with a higher phase-change temperature than the second storage cell. The refrigerant
may then flow through a cascade of different storage cells.
[0031] This gives the advantage of a particularly efficient usage of the waste heat, which
allows to adapt the individual storage cells to the characteristics of the different
load units. Furthermore, not only phase-change temperature but also heat storage capacity
of the respective storage cells may be adapted to the load units thermally coupled
with the respective storage cell.
[0032] In another embodiment, the refrigerant circuit, that is, the additional heat exchanger
formed by the heat storage means, is configured to conduct the refrigerant through
or along the storage cells in ascending order of the respective phase-change temperatures
in the defrost mode. So, the refrigerant is receiving heat from a storage cell with
a lower phase-change temperature before receiving heat from storage cell with a higher
phase-change temperature.
[0033] This gives the advantage that the heat transfer from the heat storage means to the
refrigerant is optimized, and the overall efficiency is improved.
[0034] In another advantageous embodiment, one or several first storage cells, in particular
one or several first storage cells with a lower phase-change temperature, are configured
to transfer heat to one or several second storage cells, in particular one or several
second storage cells with a higher phase-change temperature.
[0035] This gives the advantage that the overall amount of stored heat can be optimized
and the working temperature of the load units connected to the respective storage
cells, in particular the first storage cells, can be maintained.
[0036] In a further advantageous embodiment, the heat pump system comprises a temperature
sensor for sensing the temperature of a working medium such as water in a space heating/cooling
circuit, where the space heating/cooling circuit is connected with the first heat
exchanger for heating and/or cooling the first environment. Therein, the heat pump
system is configured to automatically transfer heat from the space heating/cooling
circuit to the refrigerant passing through the first heat exchanger when a temperature
of the working medium decreases to a lower limit value, in particular the lowest phase-change
temperature of the heat storage means, while a temperature of the second heat exchanger
does not reach a predetermined value in the defrost mode.
[0037] This gives the advantage that defrosting is achieved even when the heat stored in
the heat storage means is depleted while the discomfort in the first environment as
well as the usage of electricity for defrosting is minimized.
[0038] In yet another advantageous embodiment, the heat pump system is, in particular in
the heating mode, operable in a partial-load mode. In said partial-load mode, the
refrigerant is used to store heat in the heat storage means in addition to the heat
generated by the compressor and/or the compressor driver, and, when the heat stored
in the heat storage means reaches a preset limit, in particular a maximum heat that
can be stored in the heat storage means, the compressor is switched off and the heat
stored in the heat storage means is transferred to the first environment, in particular
by the refrigerant circuit.
[0039] This gives the advantage that when the heat load is low and the heat pump will, according
to the state-of-the-art, experience frequent on-off cycling behavior, the frequency
of the on-off cycling is decreased. Furthermore, the heat storage means can be charged,
that is heat can be transferred to the heat storage means under a high COP. When the
heat storage means is fully charged, the compressor can stop and the heat storage
means can supply heat to the first environment, for instance the living space, with
a low rate. Consequently, the overall efficiency is improved.
[0040] Therein, in particular, the heat storage means may comprise a connection to the space
heating/cooling circuit, where the space heating/cooling circuit is to be connected
with the first heat exchanger in order to heat or cool the first environment. The
heat storage means is then configured to transfer heat to the working medium of the
space heating/cooling circuit directly, that is, not via another liquid or gas medium,
in particular, not the refrigerant. In particular, the heat storage means may be configured
to transfer the heat to the working medium when the compressor is switched off, preferably
only when the compressor is switched off.
[0041] This gives the advantage that heat, in particular waste heat, can be transferred
to the first environment very efficiently.
[0042] Another aspect of the invention relates to a method for operating a heat pump system
with said refrigerant circuit, where, via a refrigerant, heat is transferred between
a first environment and a second environment, and with said compressor driver. The
refrigerant circuit is operable in a heating mode and may be operable in a cooling
mode.
[0043] As described above, the refrigerant circuit comprises a compressor for compressing
the refrigerant, a first heat exchanger for transferring heat between the first environment
and the refrigerant circuit, and a second heat exchanger for transferring heat between
the second environment and the refrigerant circuit. Therein, the first heat exchanger
is configured to operate as a condenser to cool the refrigerant in the heating mode.
The first heat exchanger may be configured to operate as an evaporator to vaporize
the refrigerant in the cooling mode. The second heat exchanger is configured to operate
as an evaporator in the heating mode. The second heat exchanger may be configured
to operate as a condenser in the cooling mode. The first heat exchanger may be a plate
heat exchanger. In addition to the refrigerant as a first working medium, the first
heat exchanger uses a second working medium which may be a liquid such as water. The
second heat exchanger may feature an extended surface for enhancing heat exchanger
with ambient air. In addition to the refrigerant as a first working medium, the second
heat exchanger uses a second working medium which may be a gas such as ambient air.
The refrigerant circuit may comprise a throttling device such as a valve or several
valves for lowering the pressure of the refrigerant in the refrigerant circuit or
in a specific section of the refrigerant circuit. The compressor driver is electrically
coupled with the compressor for powering the compressor.
[0044] The method is comprises the method step of storing heat generated by the compressor
and/or the compressor driver in a heat storage means of the refrigerant circuit, where
the heat storage means comprises a heat storage medium, via a thermal coupling of
the compressor and/or the compressor driver to the storage means in the heating and/or
cooling mode. Furthermore, the method comprises the method stop of transferring the
stored heat directly from the heat storage medium to the refrigerant in a defrost
mode of the refrigerant circuit.
[0045] Therein, advantages and advantageous embodiments of the described heat pump system
apply to the claimed method.
[0046] The features and combinations of features described above, as well as the features
and combinations of features disclosed in the figure description or the figures alone
may not only be used alone or in the described combination, but also with other features
or without some of the disclosed features without leaving the scope of the invention.
Consequently, embodiments that are not explicitly shown and described by the figures
but that can be generated by separately combining the individual features disclosed
in the figures are also part of the invention. Therefore, embodiments and combinations
of features that do not comprise all features of an originally formulated independent
claim are to be regarded as disclosed. Furthermore, embodiments and combinations of
features that differ from or extend beyond the combinations of features described
by the dependencies of the claims are to be regarded as disclosed.
[0047] Exemplary embodiments are further described in the following by means of schematic
drawings. Therein,
- Fig. 1
- shows an exemplary embodiment of a heat pump system;
- Fig. 2 Fig. 1; and
- shows an exemplary control flow chart of the embodiment of
- Fig. 3 system.
- shows parts of another exemplary embodiment of a heat pump
[0048] In the figures, identical or functionally identical elements have the same reference
signs.
[0049] Figure 1 shows an exemplary embodiment of a heat pump system. The shown heat pump
system 1 comprises a refrigerant circuit 2 and a compressor driver 3. The refrigerant
circuit 2 is operable in a heating mode and, in the present example, also in a cooling
mode, where, via a refrigerant, in the cooling mode heat is transferred from a first
environment 4 to a second environment 5, and in the heating mode heat is transferred
from the second environment 5 to the first environment 4.
[0050] Therein, the refrigerant circuit 2 comprises a compressor 6 for compressing the refrigerant,
a first heat exchanger 7 for transferring heat between the first environment 4 and
the refrigerant circuit 2, a second heat exchanger 8 for transferring heat between
the second environment 5 and the refrigerant circuit 2, as well as a throttling device
9 and a four way valve 10 in the present example. The compressor driver 3 is electrically
coupled with the compressor 6 for powering the compressor 6. The arrows 19 along the
refrigerant circuit 2 indicate the flow direction of the refrigerant in the heating
mode.
[0051] In the shown example, the refrigerant circuit 2 comprises a heat storage means 11
with a heat storage medium. The heat storage means 11 is connected to the rest of
the refrigerant circuit 2 parallel to the first heat exchanger 7. The heat storage
means 11 is thermally coupled with the compressor driver 3 in the present example
by a heat pipe or thermosiphon 12. In the example at hand, the heat storage means
11 is configured to store heat generated by the compressor driver 3 in the heating
and/or cooling mode, and configured to transfer the stored heat to the refrigerant
in the refrigerant circuit 2 in a defrost mode of the refrigerant circuit 2 or the
heat pump system 1, respectively. In order to switch between defrost and heating/cooling
mode, a first valve V1 and a second valve V2 is part of the refrigerant circuit 2.
The first valve V1 enables/disables the flow of the refrigerant through the first
heat exchanger 7, whereas the second valve V2 enables/disables the flow of the refrigerant
through the heat storage means 11.
[0052] In operation of the heat pump system 1, in the heating mode or cooling mode, first
valve V1 is open and second valve V2 closed. The compressor 6 and in particular the
compressor driver 3 generate waste heat that is transferred to the heat storage means
by the heat pipe or thermosiphon 12. As the second valve V2 is disclosed, the stored
heat is not transferred to the refrigerant in a noteworthy extent. When a defrosting
mode is activated and the cycle in the refrigerant circuit 2 is reversed, the first
valve V1 can be closed and the second valve V2 opened. Consequently, heat is transferred
not from the first heat exchanger7 to the second heat exchanger 8, but from the heat
storage means 11 to the second heat exchanger 8 for defrosting the second heat exchanger
8. This is also shown by the control flowchart of figure 2.
[0053] Figure 2 shows an exemplary control flow chart of the embodiment of Fig. 1.Here,
in a first step 20, normal operation of the heat pump system 1 (Fig. 1) is started.
Hence, in a second step 21, heat is transferred to the heat storage means 11 (Fig.
1) and stored therein. In the third step 22, it is decided whether defrosting of the
second heat exchanger 8 (Fig. 1) is necessary or not. If not, the system proceeds
to the final step 29, which is identical to the first step 20 and leads to the desired
normal operating mode as long as the heat pump system 1 is running.
[0054] If defrosting is required, the system proceeds to another step 23, where it is checked
if there is still heat stored in the heat storage means 11. If heat is still stored
and available for transferring in the heat storage means 11, in a subsequent step
24 valve V1 is closed and valve V2 is opened. In a next step 25 following step 24,
the refrigerant circuit is switched to reverse cycle for the defrosting and the system
goes back to step 22.
[0055] If there is no heat stored in the heat storage means 11, that is, heat storage means
11 is depleted, the systems proceeds to another step 26, where the valve V1 is opened
and the valve V2 is closed. Then, it is checked again in step 27 whether defrosting
is required or not for the second heat exchanger 8. If not, the system proceeds to
the final step 29, if yes, the system proceeds to step 28. In step 28, the normal
reverse defrosting cycle is run as known in the state of the art.
[0056] Figure 3 shows parts of another exemplary embodiment of a heat pump system. Therein,
the heat pump system 1 has a casing 13 in which the compressor 6, the thermosiphons
12, 12' as well as the heat storage means 11 and a control unit 14 are enclosed together
with other parts of the refrigerant circuit 2 that are not shown for the sake of simplicity.
[0057] In the shown example, the heat storage means 11 comprises a first storage cell 15
and a second storage cell 16. Therein, each storage cell 15, 16 comprises a phase-change
material with a specific phase-change temperature. The phase-change temperature of
the phase-change material of the first storage cell 15 is lower than the phase-change
temperature of the phase-change material of the second storage cell 16. The compressor
6 is thermally coupled to the second storage cell 16 by the heat pipe or, preferably,
thermosiphon 12. The control unit 14 is thermally coupled to the first storage cell
15 by another heat pipe or, preferably, thermosiphon 12'. This is reasonable as the
compressor 6 (or, alternatively or in addition, the compressor driver 3 (Fig. 1) that
might be thermally coupled to the second storage cell 16) generates more heat at a
higher temperature than the control unit 14 (or, alternatively or in addition, other
load units such as a transformer or diodes dissipating significant heat that might
be thermally coupled to the first storage cell 15).
[0058] The heat storage means 11 also features an inlet 17 as well as an outlet 18 for the
refrigerant of the refrigerant circuit 2. Inlet 17 an outlet 18 are used to conduct
the refrigerant through or along the first storage cell 15 with the lower phase-change
temperature first, and through or along the second storage cell 16 with the higher
phase-change temperature afterwards. Consequently, the heat storage means 11 can be
considered as an additional heat exchanger. As the heat storage means 11 is attached
to the casing 13, the casing 13 functions as the evaporating section of the additional
heat exchanger and the phase-change material of the heat storage means 11 as the condensing
section additional heat exchanger. Advantageously, the first storage cell 15 might
be arranged in between the second storage cell 16 and the casing 13.
[0059] In the present example, the heat storage means 11 is arranged above the compressor
six and the control unit 14 in the x-direction. As said x-direction corresponds to
the direction of the negative gravitational force, simple and robust thermosiphons
12, 12' may be used instead of technologically more advanced heat pipes.
[0060] The integration of the heat storage means 11 in the refrigerant circuit 2, preferably
arranged in the casing 13, enables a sleek design, where the described advantageous
heat pump system 1 with improved defrosting can be installed even without having to
change potentially already existing circuitry. So the heat pump system 1 with casing
13 can be provided as a plug-in module. Hence, the proposed heat pump system is particularly
advantageous.
1. A heat pump system (1) with
a) a refrigerant circuit (2), where, via a refrigerant, heat is transferred between
a first environment (4) and a second environment (5), the refrigerant circuit (2)
comprising:
- a compressor (6) for compressing the refrigerant;
- a first heat exchanger (7) for transferring heat between the first environment (4)
and the refrigerant circuit (2);
- a second heat exchanger (8) for transferring heat between the second environment
(5) and the refrigerant circuit (2);
where the first heat exchanger (7) is configured to operate as a condenser to cool
the refrigerant in a heating mode, and the second heat exchanger (8) is configured
to operate as an evaporator in the heating mode;
b) a compressor driver (3) electrically coupled with the compressor (6) for powering
the compressor (6);
characterized in that
the refrigerant circuit (2) comprises a heat storage means (11) with a heat storage
medium, the heat storage means (11) being thermally coupled with the compressor (6)
or the compressor driver (3) and being configured to store heat generated by the compressor
(6) or the compressor driver (3) in the heating mode and to transfer the stored heat
to the refrigerant in a defrost mode of the refrigerant circuit (2).
2. The heat pump system (1) according to claim 1,
characterized in that
the heat storage means (11) is connected to the rest of the refrigerant circuit (2)
parallel to the first heat exchanger (7).
3. The heat pump system (1) according to any of the preceding claims,
characterized by
a control unit (14) and/or at least one additional electrical load which is thermally
coupled to the heat storage means (11).
4. The heat pump system (1) according to any of the preceding claims,
characterized in that
the compressor (6) and/or the compressor driver (3) and/or the control unit (14) and/or
the at least one additional electrical load of the heat pump system (1) are thermally
coupled to the heat storage means (11) by respective heat pipes or thermosiphons (12,
12').
5. The heat pump system (1) according to any of the preceding claims,
characterized in that
the heat storage medium comprises a phase-change material.
6. The heat pump system (1) according to claims 4 and 5,
characterized in that
the heat storage means (11) comprises at least two storage cells (15, 16) with different
phase-change materials, where each storage cell (15, 16) has a different phase-change
temperature, and each of the storage cells (15, 16) is thermally coupled to at least
one of the following load units: the compressor (6) and/or the compressor driver (3)
and/or the control unit (14) and/or the at least one additional electrical load.
7. The heat pump system (1) according to claim 6,
characterized in that
a first storage cell (15) with a lower phase-change temperature than a second storage
cell (16) is thermally coupled with a first load unit of said load units, where the
first load unit has a lower heat generation than a second load unit of said load units,
and the second storage cell 16) is thermally coupled with the second load unit.
8. The heat pump system (1) according to claim 6 or 7,
characterized in that
the refrigerant circuit (2) is configured to conduct the refrigerant through or along
the storage cells (15, 16) in ascending order of the respective phase-change temperatures
in the defrost mode.
9. The heat pump system (1) according to claim 6 or 7 or 8,
characterized in that
one or several first storage cells (15, 16), in particular one or several first storage
cells (15) with a lower phase-change temperature, are configured to transfer heat
to one or several second storage cells (15, 16), in particular one or several second
storage cells (16) with a higher phase-change temperature.
10. The heat pump system (1) according to any of the preceding claims,
characterized by
a temperature sensor for sensing the temperature of a working medium in a space heating/cooling
circuit connected with the first heat exchanger (7) for heating or cooling the first
environment (4), wherein the heat pump system (1) is configured to transfer heat from
the space heating/cooling circuit to the refrigerant passing through the first heat
exchanger (7) when a temperature of the working medium decreases to a lower limit
value, in particular the lowest phase-change temperature of the heat storage means
(11), while a temperature of the second heat exchanger (8) does not reach a predetermined
value.
11. The heat pump system (1) according to any of the preceding claims,
characterized in that
the heat pump system (1) is operable in a partial-load mode, where the refrigerant
is used to store heat in the heat storage means (11) in addition to the heat generated
by the compressor (6) or the compressor driver (3), and where, when the heat stored
in the heat storage means (11) reaches a preset limit, in particular a maximum heat
that can be stored in the heat storage means (11), the compressor (6) is switched
off and the heat stored in the heat storage means (11) is transferred to the first
environment (4).
12. The heat pump system (1) according to claim 11,
characterized in that
the heat storage means (11) comprises a connection to the space heating/cooling circuit,
where the space heating/cooling circuit is to be connected with the first heat exchanger
(7), and is configured to transfer heat to the working medium of the space heating/cooling
circuit.
13. Method for operating a heat pump system (1) with
a) a refrigerant circuit (2), where, via a refrigerant, heat is transferred between
a first environment (4) and a second environment (5), the refrigerant circuit (2)
comprising:
- a compressor (6) for compressing the refrigerant;
- a first heat exchanger (7) for transferring heat between the first environment (4)
and the refrigerant circuit (2);
- a second heat exchanger (8) for transferring heat between the second environment
(5) and the refrigerant circuit (2);
where the first heat exchanger (7) is configured to operate as a condenser to cool
the refrigerant in a heating mode, and the second heat exchanger (8) is configured
to operate as an evaporator in the heating mode;
b) a compressor driver (3) electrically coupled with the compressor (6) for powering
the compressor (6);
characterized by
- storing heat generated by the compressor (6) or the compressor driver (3) in a heat
storage means (11) of the refrigerant circuit (2) in the heating mode, and
- transferring the stored heat directly to the refrigerant in a defrost mode of the
refrigerant circuit (2).