Note: Descriptions are shown in the official language in which they were submitted.
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Method and device for charging a stratified thermal energy
store
TECHNICAL FIELD
The invention relates to a method and a device for charging a
stratified thermal energy store.
BACKGROUND
Stratified thermal energy stores make it possible to uncouple
the time at which energy is generated from that at which it is
used. In particular with fluctuating energy sources such as
regenerative energy types, an uncoupling of the times of this
kind provides security of the supply of energy, in particular
of electrical energy. Stratified thermal energy stores can be
coupled to heat pumps that pump thermal energy (heat) from a
cold to a hot reservoir, the stratified thermal energy store,
taking up electrical energy. By using a stratified thermal
energy store that is coupled to a heat pump, it is thus
possible to uncouple the time of generating thermal energy from
the time of discharging it to a heat consumer, as a result of
which for example peak loads in energy demand can be
compensated, with the result that the security of supply
improves overall.
Typically, a stratified thermal energy store is charged with
heat by means of a heat pump. Here, the heat is transferred to
the stratified thermal energy store through walls of a heat
exchanger. To secure the transport of heat from the heat pump
to the stratified thermal energy store, certain temperature
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differences are required as the driving force for the transport
of heat. At the same time, said temperature differences limit
the temperature of the heat that can be taken from the
stratified store, that is to say its utilizable value.
Furthermore, a constructional space that is not utilizable for
storing thermal energy must be provided for the heat transfer
surfaces of a heat exchanger.
A stratified thermal energy store having a heat exchanger which
has heat transfer surfaces is charged by means of the heat pump
in that a working fluid of the heat pump takes up heat at a low
temperature on the primary side and, within the heat exchanger,
on the secondary side transfers the heat of the working fluid
at a relatively high temperature to a heat carrier of the
stratified thermal energy store (secondary side).
It is known from the prior art, for taking up heat, to conduct
the heat carrier of the stratified thermal energy store through
a condenser on the secondary side, wherein this condenser is
thermally coupled to the heat pump. It is further known from
the prior art to guide the working fluid of the heat pump
through a condenser on the secondary side, wherein this
condenser is located within the stratified thermal energy store
and is in thermal contact with the heat carrier of the
stratified thermal energy store. In other words, the heat from
the heat pump is always transferred to the stratified thermal
energy store through a condenser in which condensation of the
working fluid of the heat pump takes place, wherein the
condenser is located outside the stratified thermal energy
store in the first-mentioned case and within the stratified
thermal energy store in the second-mentioned case and is always
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in thermal contact with the heat carrier of the stratified
thermal energy store.
For efficient transfer of the heat from the working fluid to
the heat carrier, the condensers of the prior art have heat
transfer surfaces occupying a large space, which on .the one
hand require a large constructional space and on the other hand
reduce the economic benefit of the stratified thermal energy
store as a result of high investment costs.
SUMMARY
One embodiment provides a method for charging a stratified
thermal energy store, in which a working fluid of a heat pump
is introduced in a gaseous state into a liquid heat carrier of
the stratified thermal energy store at at least one point of
introduction and is brought into direct material contact with
the heat carrier, wherein the pressure in the stratified
thermal energy store at the point of introduction is greater
than or equal to the condensation pressure of the working
fluid.
In one embodiment, working fluid that is condensed in the
stratified thermal energy store is returned to the heat pump.
In one embodiment, a working fluid is used for which the
density downstream of condensation in the stratified thermal
energy store is greater than or equal to the density of the
heat carrier.
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In one embodiment, the working fluid in the liquid state and
the heat carrier are the same fluid.
In one embodiment, the condensation pressure of the working
fluid at a temperature of 100 C is lower than 1 MPa.
In one embodiment, the working fluid includes at least one of
the substances
1,1,1,2,2,4,5,5,5-nonafluoro-4-
(trifluoromethyl)-3-pentanone, perfluoromethyl
butanone,
1-chloro-3,3,3-trifluoro-1-propene, cis-1,1,1,4,4,4-hexafluoro-
2-butene and/or cyclopentane.
In one embodiment, water is used as the working fluid.
In one embodiment, the working fluid, in the liquid state, is
not miscible with the heat carrier.
In one embodiment, the gaseous working fluid is introduced into
the heat carrier by means of a distribution device, wherein the
distribution device distributes the working fluid homogeneously
in a layer of the heat carrier that is at a constant
temperature.
In one embodiment, a regulated pressure accumulator is used as
the stratified thermal energy store.
In one embodiment, heat from the stratified thermal energy
store is supplied to the working fluid before it is introduced
into a compressor of the heat pump.
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In one embodiment, the heat carrier that has been separated off
from an evaporator of the heat pump by means of a droplet
separator is returned to the stratified thermal energy store.
In one embodiment, the heat carrier is conducted to a heat
consumer for the purpose of utilizing its hea-i, wherein the
heat carrier is conducted through a separator before it is
utilized in the heat consumer.
In one embodiment, a phase change material is used in the
stratified thermal energy store for storing thermal energy.
Another embodiment provides a device including a stratified
thermal energy store with a liquid heat carrier and a heat pump
with a working fluid, wherein the stratified thermal energy
store and the heat pump are constructed and coupled such that
the working fluid is introduced in a gaseous state into the
heat carrier at a point of introduction and is brought into
direct material Contact with the heat carrier, wherein the
pressure of the stratified thermal energy store at the point of
introduction is greater than or equal to the condensation
pressure of the working fluid.
BRIEF DESCRIPTION-OF THE DRAWINGS
Example aspects and embodiments of the invention are described
below with reference to the drawings, in which:
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Figure 1 shows a pressure accumulator that is coupled to a heat
pump, wherein a working fluid of the heat pump is introduced
directly into the heat carrier of the pressure accumulator; and
Figure 2 shows a hydrostatic pressure accumulator that is
coupled to the heat pump, wherein the working fluid of the heat
pump is again introduced directly into the heat carrier of the
pressure accumulator.
DETAILED DESCRIPTION
Embodiments of the present invention may provide improved
charging of a stratified thermal energy store with thermal
energy.
Some embodiments provide a method for charging a stratified
thermal energy store, wherein a working fluid of a heat pump is
introduced in the gaseous state into a liquid heat carrier of
the stratified thermal energy store at at least one point of
introduction and is brought into direct material contact with
the heat carrier, wherein the pressure in the stratified
thermal energy store at the point of introduction is greater
than or equal to the condensation pressure of the working
fluid.
The working fluid of the heat pump is introduced in the gaseous
state directly into the liquid heat carrier of the stratified
thermal energy store, as a result of which there is a direct
material contact between the heat carrier and the working
fluid. The direct material contact results in condensation of
the gaseous working fluid. This is the case because the
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pressure in the stratified thermal energy store at the point of
introduction of the gaseous working fluid, or in a partial
region of the stratified thermal energy store at which the
gaseous working fluid is introduced, is greater than or equal
to the condensation pressure of the working fluid. The
condensation pressure of the working fluid here depends on the
temperature at the point of introduction, and should be
adjusted according to said temperature. The term "condensation
pressure" means the pressure at which the gaseous working fluid
of the heat pump changes from the gaseous to the liquid state,
namely the temperature that is present at the point of
Introduction of the working fluid in the stratified store. In
other words, the condensation point of the gaseous working
fluid is reached at the point of introduction, or in a partial
region of the stratified thermal energy store. As a result of
the direct material contact between the gaseous working fluid
and the liquid heat carrier of the stratified thermal energy
store, and the consequent condensation of the working fluid,
the condensation heat that is released in the process of
condensation of the working fluid is transferred directly to
the heat carrier of the stratified thermal energy store.
Additional condensers, heat exchangers and/or heat transfer
surfaces are thus dispensed with. As a result of the inventive
dispensing with condensers, heat exchangers and/or heat
transfer surfaces, additional losses of thermal energy in
and/or on said components can be avoided, as a result of which
the efficiency of the stratified thermal energy store is
increased.
A further advantage of the direct material contact between the
gaseous working fluid and the liquid heat carrier of the
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stratified thermal energy store is that there is no need for
large temperature differences between the working fluid and the
heat carrier for efficient transfer of heat. If the stratified
thermal energy store is charged by means of a heat pump having
a compressor, an initial pressure at the compressor may
consequently be reduced, as a result of which the consumption
of electrical energy by the heat pump is advantageously
reduced.
The disclosed device for charging a stratified thermal energy
store includes a stratified thermal energy store with a liquid
heat carrier and a heat pump with a working fluid, wherein the
stratified thermal energy store and the heat pump are
constructed and coupled such that the working fluid is
introduced in the gaseous state (as superheated vapor or as
saturated vapor) into the heat carrier at a point of
introduction and is brought into direct material contact with
the heat carrier, wherein the pressure of the stratified
thermal energy store at the point of introduction is greater
than or equal to the condensation pressure of the working
fluid.
The disclosed device enables a direct material contact between
the gaseous and consequently also the condensed (liquid)
working fluid and the liquid heat carrier. This gives like and
equivalent advantages to those of the method according to the
invention that has already been described.
In a further embodiment of the method, the working fluid that
is condensed in the stratified thermal energy store is returned
to the heat pump.
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By returning the condensed and thus liquid working fluid, a
particularly advantageous circulation process for charging the
stratified thermal energy store is made possible. It may be
provided, before it is returned to the working cycle of the
heat pump, for the condensed working fluid to be conducted
through a separator, which separates residues of the heat
carrier that are present in the condensed working fluid, with
the result that no or almost no heat carrier is discharged into
the working cycle of the heat pump. The material separation of
working fluid and heat carrier that is to be performed
downstream of condensation of the working fluid is not
restricted to the use of a separator, and may be performed
using devices that are known from the prior art and/or
equivalents thereof.
According to an embodiment of the method, there is used a
working fluid whereof the density downstream of condensation in
the stratified thermal energy store is greater than or equal to
the density of the heat carrier, wherein a density that is
really greater at all times may be preferred.
The density of the condensed working fluid that is greater than
that of the liquid heat carrier has the advantage that the
working fluid can be introduced or put close to the upper end
of the stratified thermal energy store. As a result of the
action of gravity prevailing at the location of the stratified
thermal energy store, the working fluid, which is denser than
the heat carrier, will fall during and/or after its
condensation, from the point of introduction to a lower end of
the stratified thermal energy store. In this context, the
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relative terms "upper" and "lower", as is known, relate to the
prevailing direction of gravity. Typically, the heat carrier in
the stratified thermal energy store will have the highest
temperature at the upper end thereof.
The advantage of the greater density of the condensed working
fluid and the resulting fall of the working fluid is that the
working fluid is subcooled to the temperature of the stratified
thermal energy store prevailing at the lower end, as a result
of which the heat carrier and consequently the stratified
thermal energy store are charged with additional heat.
It is a further advantage that the condensed working fluid is
almost completely condensed by the fall and the associated
constant material contact with the heat carrier. After the
condensed working fluid has fallen and accumulated at the lower
end of the stratified thermal energy store, for example at the
base, it can be returned from there back to the heat pump.
In an embodiment, one and the same fluid is used for the
working fluid in the liquid state and the liquid heat carrier.
Advantageously, as a result additional separators that separate
the working fluid from the heat carrier, for example before it
is returned to the heat pump or to a heat consumer, can be
dispensed with.
In a further embodiment, there is used a working fluid that, at
a temperature of 100 C (373.15 K), has a condensation pressure
lower than 1 MPa.
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Working fluids that, at a temperature of 100 C, have a
condensation pressure lower than 1 MPa are called low-pressure
fluids here. An advantage of such low-pressure fluids is the
fact that, in combination with known stratified thermal energy
stores, they make it possible to use the disclosed method. This
is the case because stratified thermal energy stores that are
typical in the prior art, in particular stratified stores using
water, are at a pressure lower than 1 MPa and in particular in
the range from 0.3 MPa to 1 MPa. Typical working fluids that
are used in heat pumps, such as the fluids R134a, R400c or
R410a, have a condensation pressure in the range from 2 MPa to
4 MPa at 100 C. The condensation pressure of said working
fluids is thus significantly greater than the pressure that
typically prevails in stratified thermal energy stores, with
the result that when the working fluid is introduced at a
temperature of 100 C no condensation of the working fluid
occurs. Low-pressure fluids, by contrast, have a condensation
pressure that is in the range of pressures that prevail in
stratified stores, with the result that they condense when they
are in contact with the liquid heat carrier of the stratified
thermal energy store.
In some embodiments, the working fluid includes at least one of
the substances
1,1,1,2,2,4,5,5,5-nonafluoro-4-
(trifluoromethyl)-3-pentanone (trade name NovecTM 649),
perfluoromethyl butanone, 1-chloro-3,3,3-trifluoro-l-propene,
cis-1,1,1,4,4,4-hexafluoro-2-butene and/or cyclopentane.
In some embodiments, said substances may be used in combination
with stratified thermal energy stores that are known from the
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prior art. For example, at a temperature of 100 C NovecTM 649
has a condensation pressure of 0.45 MPa, perfluoromethyl
butanone a condensation pressure of 0.89 MPa and cyclopentane a
condensation pressure of 0.42 MPa. At 100 C, therefore, the
condensation pressure of said fluids is significantly below the
condensation pressure of, for example, R134a, which has a
condensation pressure of around 3.97 MPa.
A further advantage of said substances is their ease of
technical handling. They are characterized by good
environmental compatibility and by their properties relating to
safety, such as a lack of flammability and a very low
greenhouse gas potential. In general, the substances NovecTM
649 and perfluoromethyl butanone are allocated to the substance
class of fluoroketones, while cyclopentane is allocated to the
substance class of cycloalkanes.
According to a further embodiment of the method, water is used
as the working fluid.
As a result, advantageously additional separators that are able
to separate the working fluid from the heat carrier can be
dispensed with. In the case of hydrostatic stratified thermal
energy stores, which build up the pressure in the stratified
thermal energy store solely by way of the hydrostatic pressure
of the water column, the height of the point of introduction of
the working fluid into the heat carrier is therefore not
significant. In particular, the stratified store using water
may be charged at its upper end with the introduced gaseous and
subsequently condensed working fluid, as a result of which
advantageously there is only a small time lag between charging
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the stratified store that uses water and reaching the
temperature that is desired at the upper end.
In a further embodiment of the method, there is used a working
fluid that, in the liquid (condensed) state, is not miscible
with the liquid heat carrier.
In other words, the condensed working fluid and the liquid heat
carrier form a two-phase liquid, wherein the one phase is
formed by the condensed working fluid and the other phase by
the liquid heat carrier. It is also possible to provide a
working fluid that has low miscibility with the heat carrier in
the liquid state.
As a result of the mixture of working fluid and heat carrier
being present in two phases, it is possible to perform a
material separation of said fluids in a simple manner, in
particular if the condensed working fluid and the liquid heat
carrier have different densities. For example, the already
mentioned low-pressure fluids NovecTM 649, perfluoromethyl
butanone and cyclopentane are poorly soluble in water, which is
particularly suitable as a heat carrier, and so are only
miscible with water in small quantities. For example, only 20
ppm of water may be dissolved in NovecTM 649.
In a further embodiment, the gaseous working fluid is
introduced into the heat carrier by means of a distribution
device, wherein the distribution device distributes the working
fluid homogeneously in a layer of the heat carrier that is at a
constant temperature.
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Stratified thermal energy stores, such as stratified stores
using water, have a layered construction in respect of the
temperature of their heat carrier, wherein each layer has a
particular temperature and density. As regards the efficiency
of heat transfer from the working fluid of the heat pump to the
heat carrier, it is thus advantageous to distribute the gaseous
working fluid uniformly or homogeneously in a layer of the heat
carrier. The terms "uniform" and "homogeneous", and the
temperature or density of a layer, are in all cases to be
understood as approximate.
Typical stratified stores are oriented vertically - relative to
the gravity prevailing at the stratified store - such that the
individual layers of the stratified store extend horizontally.
As a result of the uniform distribution of the gaseous working
fluid in a layer of the liquid heat carrier, the surface of
material contact (contact surface) between the heat carrier and
the working fluid is increased, as a result of which the
efficiency of the heat transfer from the working fluid to the
heat carrier is improved.
As a result of uniform distribution of the working fluid in a
horizontal layer of the stratified thermal energy store,
furthermore a distribution of the pulses of introduced working
fluid is made possible, with the result that undesired mixing
procedures that could result in the layers becoming completely
mixed can be prevented.
Possible distribution devices are for example horizontal
distributor pipe systems such as are used in stratified stores.
In particular, the distribution devices that are known there
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result In a reduction in the input rate of the working fluid
into the heat carrier (cf. GOppert et al., Chemie Ingenieur
Technik, 2008, 80, No 3). Furthermore, the input rate of the
gaseous working fluid may be regulated by altering the cross-
sectional surface area of input holes in the distribution
device. A further advantage of regulating the cross-sectional
surface areas of the input holes is that a primary bubble size
of the gaseous working fluid can be set.
In one embodiment of the method, a regulated pressure
accumulator is used as the stratified thermal energy store.
Advantageously, with a regulated pressure accumulator the
pressure inside the stratified thermal energy store can be
regulated to a particular pressure range. By regulating the
pressure in the pressure accumulator, the pressure inside the
pressure accumulator can be adjusted to the condensation
pressure of the working fluid, with the result that
condensation of the working fluid occurs regardless of the
temperature that prevails at the point of introduction. For
example, as a result the gaseous working fluid may be
introduced at a point of introduction in the stratified store
that is as high up as possible. In this arrangement, the
temperature of a layer of the stratified store or pressure
accumulator is correlated to the height of the layer, with the
result that a point of introduction that is at the greatest
possible height corresponds to a greatest possible temperature.
According to a further embodiment of the method, heat from the
stratified thermal energy store is supplied to the working
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fluid before it is introduced into a compressor of the heat
pump.
This is particularly advantageous if working fluids whereof the
condensation curve has an overhang are used. The heat that is
required with such working fluids, which serves to superheat
the working fluid before it enters the compressor, can thus be
taken from the stratified thermal energy store.
In a further embodiment, heat carrier that has been separated
off from an evaporator of the heat pump by means of a droplet
separator is returned to the stratified thermal energy store.
As a result of the direct material contact of the working fluid
with the heat carrier of the stratified thermal energy store,
it is in principle not possible to prevent the heat carrier
from being introduced into the working fluid and thus into a
cycle of the working fluid within the heat pump. Thus, liquid
heat carrier that has not (also) evaporated accumulates in
particular in the evaporator of the heat pump. This heat
carrier that accumulates in the evaporator is advantageously
removed from the evaporator by means of a droplet separator and
returned to the stratified thermal energy store.
According to an embodiment, the heat carrier is conducted to a
heat consumer for the purpose of utilizing its heat, wherein
the heat carrier is conducted through a separator before it is
utilized in the heat consumer.
Conducting the heat carrier through a separator is provided in
particular when the heat carrier is removed directly from the
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stratified thermal energy store. When the heat carrier is
removed directly, as a result of the inventive material contact
between the working fluid and the heat carrier, some of the
working fluid is discharged with the heat carrier. In this
arrangement, the working fluid may be discharged in droplet
form (as an emulsion) or indeed as a constituent that is
dissolved in the heat carrier (as a solution).
Advantageously, by means of the separator it is ensured that
the discharged portions of the working fluid do not reach the
heat consumer and where appropriate may be returned to the
stratified thermal energy store and/or the heat pump. Suitable
for the separation are for example active droplet separators
and/or coalescing separators. A further possibility for
preventing working fluid from being discharged is to reduce the
solubility of the working fluid in the heat carrier as a result
of the reduced temperature of the heat consumer. This is the
case for substance mixtures that have a higher solubility at
higher temperature. As a result of the reduced temperature of
the heat consumer, the working fluid is precipitated and can
thus be materially separated from the heat carrier.
In the case of indirect removal of the heat for a heat
consumer, for example by way of a heat exchanger, a separator
of this kind that is on the heat consumer side and separates
the working fluid from the heat carrier may be dispensed with.
According to a further embodiment, a phase change material
(PCM) is used in the stratified thermal energy store for
storing thermal energy.
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The stratified store thus includes two heat carriers, wherein
the further heat carrier takes the form of a phase change
material. Phase change materials or phase change stores may be
preferred, since they can store thermal energy with low losses
and with numerous repeat cycles and over a long period of time.
In particular, a phase change material whereof the melting
point (phase change temperature) is lower than the condensation
point of the working fluid (at condensation pressure) may be
preferred. For example, the condensation point of the working
fluid may be 130 C, so a melting point of 125 C of the phase
change material may be preferred. Thus, a melting point that is
at most 5% lower than the condensation point may be preferred.
The stratified store may include further heat carriers that are
in the solid state. In this arrangement, the porosity of the
solid heat carriers may be adapted to their purpose. For
example, the porosity may be selected such that it becomes
possible to lower the condensed working fluid, which has a
greater density than the liquid heat carrier.
Figure 1 shows, in a schematic illustration, a regulated
pressure accumulator 2 that is coupled to a heat pump 6 such
that the working fluid 4 of the heat pump 6 is distributed
to the heat carrier 10, which is in direct material contact
with the working fluid 12, by way of a distribution device 12
at a height 8 on the pressure accumulator 2.
The heat pump 6 includes a compressor 14, an evaporator 16, an
expansion valve 20, a separator 18, a droplet separator 15 and
a nonreturn valve 22. The working fluid 4 circulates
counterclockwise 36 in the heat pump 6.
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Further visible in Figure 1 is an expansion vessel 24, a pump
28, a further expansion valve 30 and a reservoir 26 for the
heat carrier 10. Said components 24, 26, 28, 30 serve to
regulate the pressure accumulator 2 and/or the heat carrier 10.
In the exemplary embodiment that is shown in Figure 1, water is
used as the heat carrier 10.
The gaseous working fluid 4 is introduced into the heat carrier
downstream of the compressor 14 at the height 8 on the
pressure accumulator 2, by way of the distribution device 12,
and is thus brought into direct material contact with the heat
carrier 10. Here, the temperature of the pressure accumulator 2
at the introduction height 8 is for example 130 C. If for
example NovecTM 649 is used as the working fluid, the pressure
in the pressure accumulator 2 must be at least 0.9 MPa so that
immediate condensation of the gaseous working fluid 4 takes
place.
One advantage of the regulated pressure accumulator 2 is that
the working fluid 4 can be introduced at a point on the
pressure accumulator 2 that is as hot as possible. This is the
case because the condensation pressure of the working fluid 4
at the introduction height 8 can always be exceeded by
adjusting the pressure in the pressure accumulator 2. In
general, the heat from the pressure accumulator 2 is removed
for a heat consumer (which is not shown) at the point of
highest possible temperature. By introducing the working fluid
4 at said point, the pressure accumulator 2 can reach the
temperatures required by the heat consumer efficiently and in
little time with a low thermal load.
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In the exemplary embodiment that is shown in Figure 1, there
may be used as the working fluid 4 NovecTM 649, which has a
density of around 1300 kg/m3. As the heat carrier 10 there is
used water 10, which has a density of 1000 kg/m3, with the
result that the working fluid 4 has a greater density than the
heat carrier 10. The density of the working fluid 4, greater
than that of the heat carrier 10, causes the working fluid 4 to
fall to the base 9 of the pressure accumulator 2 through
gravity 100. As a result of the working fluid 4 falling to the
base 9 of the pressure accumulator 2, the working fluid 4 is
advantageously subcooled until it reaches the temperature of
the pressure accumulator 2 that prevails at the base 9, with
the result that additional heat is removed from the working
fluid 4. Given the low miscibility of NovecTM 649 and water,
there results a phase of the working fluid 4 that is deposited
at the base 9 and can then be removed from the base 9 of the
pressure accumulator 2 and returned to the working cycle 36 of
the heat pump 6 by way of the separator 18. As a result of the
(liquid) separator 18, it is ensured that no heat carrier 10
from the pressure accumulator 2 is introduced into the working
cycle 36 of the heat pump 6.
If a working fluid 4 that has a lower density than water 10 is
used, for example cyclopentane (C5H10), which has a density of
650 kg/m3, the working fluid 4 rises after condensation and
must thus be removed at an upper end of the pressure
accumulator 2.
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The nonreturn valve 22 prevents heat carrier 10 from being
discharged into the compressor 14 and thus into the working
cycle 36 of the heat pump 6.
Figure 2 shows an alternative embodiment of the method
according to the invention, wherein instead of a regulated
pressure accumulator 2 a hydrostatic pressure accumulator 31s
used. In this arrangement, the heat pump 6 includes the
elements that have already been shown and discussed in
Figure 1.
Unlike a pressure accumulator 2, in a hydrostatic pressure
accumulator 3 the pressure inside the store 3 is generated
solely by the hydrostatic pressure of the heat carrier 10, in
this case water 10. In other words, the pressure in the
pressure accumulator 3 is generated solely by way of the liquid
column of water 10. If once again NovecTM 649 is introduced as
the working fluid 4 into the hydrostatic pressure accumulator
at a temperature of 110 C, a pressure of at least 0.6 MPa is
required for the working fluid 4 to condense. The result of
this is that the point of introduction or height 8 at which the
working fluid 4 is introduced into the pressure accumulator 3
must be selected such that at least 50 m of water 10 lies above
the introduction height 8 of the working fluid 4. In general,
the pressure can be selected in accordance with the
introduction height 8 of the working fluid 4.
In order to increase the pressure in the hydrostatic pressure
accumulator 3 further without making the liquid column of the
heat carrier 10 taller or the introduction height 8 lower, a
cold water layer 32 is placed at the upper end of the pressure
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accumulator 3. The cold water layer 32 is separated from the
water 10 of the hydrostatic pressure accumulator 3 by a
separation device 34. Placing the cold water layer 32 at the
upper end of the hydrostatic pressure accumulator 3 ensures
that the pressure at the introduction height 8 exceeds the
condensation pressure of the working fluid 4 as it is
introduced, and condensation of the working fluid 4 occurs. In
this way, the introduction height 8 of the working fluid 4 may
be made higher, as a result of which the temperature at the
introduction height 8 may be increased.
As was already the case in Figure 1, the working fluid 4 falls
to the base 9 of the hydrostatic pressure accumulator 3, as a
result of its density, which is greater than the heat carrier
10, through the effect of gravity 100. From there, it can once
again be supplied to the working cycle 36 of the heat pump 6 by
way of a separator 18. If the heat carrier 10 is denser than
the working fluid 4, removal of the working fluid 4 at an upper
end of the hydrostatic pressure accumulator 3 is provided.
Although the invention has been closely illustrated and
described in detail by way of the preferred exemplary
embodiments, the invention is not restricted by the disclosed
examples, and alternatively other variations may be derived
therefrom by those skilled in the art without departing from
the scope of the invention.
