Note: Descriptions are shown in the official language in which they were submitted.
CA 02894438 2015-06-09
WO 2013/088357
PCT/1B2012/057220
"HIGH PERFORMANCE HEAT PUMP UNIT"
DESCRIPTION
Field of the invention
The present invention relates to the field of heat pumps. In particular, the
invention
relates to a heat pump unit adapted to be used for heating/cooling
environments
and for producing sanitary hot water with high performance in terms of energy
efficiency and use flexibility.
Prior art
Heat pumps are an increasingly widespread technical solution for meeting the
requirements of heating/cooling environments and/or fluids. The reasons for
such
success are mainly to be ascribed to the high energy efficiencies, to the
possibility
of using a single device for both heating and cooling (so-called "reversible"
heat
pumps), to the flexibility in managing thermal users with different
requirements and
to the possibility, in case of use for heating, of considerably reducing the
use of
fossil fuels and thus the outlet of greenhouse gases harmful to the
environment.
In order to make the use of heat pumps increasingly competitive, the focus of
designers and manufacturers is on a constant improvement of the performance
thereof, both in terms of energy efficiency and in terms of use flexibility
(possibility
of use for both heating and cooling, possibility of meeting multiple different
requirements of multiple thermal users, even concurrently, in terms of
heating/cooling power and/or operating temperatures, capability of operating
at
partial loads without energy efficiency degradation, etc.). The optimization
need is
especially felt for heat pump units having a high heating/cooling power (for
example >100kW), typically intended to be used in large buildings with
centralized
thermal users, such as blocks of flats, hotels, hospitals, barracks, sports
centers,
swimming pools, etc.
In the case of gas compression heat pumps intended for heating, a known method
for improving the COP (Coefficient of Performance) consists in performing an
undercooling of the operating fluid after the condensation thereof and in
using the
undercooling heat power thus obtained for preheating the heat carrier fluid
coming
from a heat sink before sending it to the evaporator for determining the
1
CA 02894438 2015-06-09
WO 2013/088357
PCT/1B2012/057220
evaporation of the operating fluid.
Documents DE 3311505 A1 and WO 2011/045752 A1 describe the use of the
above solution in particular in so-called "high temperature" gas compression
heat
pumps. Such heat pumps allow condensation temperatures of 80-85 C to be
achieved ¨ required for the operation of conventional high temperature heating
plants which typically require a delivery temperature of the heat carrier
fluid of at
least 80 C ¨ even when a heat sink is provided the average temperature of
which
does not exceed 7-10 C, as it normally happens with groundwater. Two stage
heat pumps are typically needed in order to operate with so large differences,
which however usually have relatively low COP.
In two stage heat pumps described in the above documents there is provided an
additional heat exchanger connected downstream of the condenser and upstream
of the expansion means in the circuit of each stage. The additional heat
exchangers are further connected to a delivery line of a heat carrier fluid of
a heat
sink, upstream of the evaporator of the lower temperature stage. It is
therefore
possible to preheat the heat carrier fluid coming from the heat sink before
sending
it to the evaporator of the lower temperature heat pump cycle through the heat
power resulting from the undercooling of the operating fluids that perform the
higher and lower temperature heat pump cycles. Thanks to such configuration it
is
possible to obtain COP equal to or higher than 3 even in two stage heat pumps.
Summary of the invention
The technical problem at the basis of the present invention consists in
providing a
heat pump having improved performance compared to the heat pumps having the
same power and type of the prior art. In particular, a heat pump is desired
which is
capable of ensuring a high energy efficiency, with COP in case of heating or
EER
(Energy Efficiency Ratio) in case of cooling equal to or higher than 3, in a
wide
range of operating conditions, also in the presence of thermal users with
different
requirements in terms of heating/cooling power and/or operating temperatures
required.
The Applicants have perceived the possibility of solving such technical
problem
using the heat power resulting from an undercooling subsequent to the
condensation of the operating fluid in a heat pump cycle in an alternative and
more
2
CA 02894438 2015-06-09
WO 2013/088357
PCT/1B2012/057220
effective manner compared to the solution presented in the prior art described
above.
The invention therefore relates to a heat pump unit comprising at least one
main
circuit adapted to perform a main heat pump cycle with a respective operating
fluid, said at least one main circuit comprising:
- a main condenser adapted to perform the condensation of the operating
fluid
of said main heat pump cycle and intended to be connected to an external
circuit of a first thermal user plant in a heating operating mode of said heat
pump unit;
- a first heat exchanger, connected downstream of said main condenser and
upstream of expansion means of said at least one main circuit, adapted to
perform an undercooling of the operating fluid of said main heat pump cycle
after the condensation of the same in said main condenser, and
- a main evaporator adapted to perform the evaporation of the operating
fluid of
said main heat pump cycle and intended to be connected to an external circuit
of a heat sink in a heating operating mode of said heat pump unit,
characterized in that said first heat exchanger is selectively connectable to
the
external circuit of said first thermal user plant so as to be in series with
said main
condenser in said external circuit.
Within the scope of the present description and in the following claims
- the expression "heat pump cycle" is understood to indicate a generic
inverted
thermodynamic cycle, i.e. a thermodynamic cycle adapted to transfer heat
power from a means or system at lower temperature to a means or system at
higher temperature, or in order to increase or keep the temperature of the
means or system at higher temperature high (heating operation), or in order to
decrease or keep the temperature of the means or system at lower
temperature low (cooling operation), and
- the expression "heat sink" is understood to indicate a means or system
capable of yielding or absorbing heat power without considerable variations of
the average temperature thereof.
The heat pump unit of the invention advantageously allows the use of the heat
power resulting from an undercooling of the operating fluid after the
condensation
3
CA 02894438 2015-06-09
WO 2013/088357
PCT/1B2012/057220
thereof for preheating the heat carrier fluid of a thermal user plant before
it
reaches the main condenser.
The Applicants have also found that such use of the undercooling heat power,
substantially different from the use thereof made in the prior art heat pump
units
(preheating of the heat carrier fluid of the heat sink) may have a
considerable
positive effect on the COP of the heat pump unit, especially in specific
operating
conditions.
Such positive effect is related to the undercooling heat power fraction
actually
usable compared to the theoretically available one, which is determined by the
minimum temperature achievable with undercooling, i.e. the evaporation
temperature of the operating fluid of the main heat pump cycle.
Since the undercooling heat power usable is greater as the back temperature of
the heat carrier fluid to be heated is lower, the heat pump unit of the
invention is
particularly advantageous in all those operating conditions wherein a drop of
such
temperature alone or globally of the temperature level in the thermal user
plant is
acceptable with the same heat power transferred thereto. Such situation
occurs,
for example, in high temperature heating plants in autumn and spring.
The heat pump unit of the present invention therefore finds a particularly
advantageous use in combination with high temperature heating plants which
provide for the possibility of changing the backflow temperature of the heat
carrier
fluid in order to optimize the operation of the heating plant.
Another use situation of interest is in combination with high temperature
heating
plants which envision high temperature differences between delivery and
backflow
of the heat carrier fluid.
It has been determined that with a suitable selection of the operating fluid
and of
the operating parameters, in the above operating conditions and/or application
cases, it is advantageously possible to obtain an increase in the COP up to
20%
compared to the values obtainable in conventional heat pumps of the same type
and power.
The heat pump unit of the invention can therefore ensure high energy
efficiency in
a wider range of operating conditions compared to conventional heat pumps of
the
same type and power.
4
CA 02894438 2015-06-09
WO 2013/088357
PCT/1B2012/057220
Moreover, the technical features of the heat pump unit of the invention by
which it
is possible to obtain the advantageous results described above are compatible
and easily integrated with other technical solutions aimed to use the
undercooling
heat power of the operating fluid, such as for example the preheating of the
heat
carrier fluid of the heat sink carried out in the prior art devices.
In a preferred embodiment of the heat pump unit of the invention, said main
circuit
comprises a first sub-circuit adapted to perform a higher temperature main
heat
pump cycle with a respective operating fluid and a second sub-circuit adapted
to
perform a lower temperature main heat pump cycle with a respective operating
fluid, wherein said first and second sub-circuits are in cascading heat
exchange
relationship with each other to perform globally a two-stage main heat pump
cycle,
and wherein said main condenser and said first heat exchanger are connected in
said first sub-circuit and said main evaporator is connected in said second
sub-
circuit.
Such configuration of the main circuit allows a two-stage main heat pump cycle
to
be performed, and thus the operation with thermal gradients significantly
higher
than those obtainable through a single-stage heat pump cycle. Thanks to this
it is
advantageously possible to use the heat pump unit of the invention with
thermal
user plants operating at a high temperature (for example radiator heating
plants
which normally require delivery temperatures around 80 C) also when a heat
sink
is available which consists of water or environmental fluids at low
temperature (for
example groundwater or running water on the surface or in depth, seawater or
lake water, waterworks water, wastewaters, etc., with average temperatures
typically not lower than about 7 C).
In another preferred embodiment, said second sub-circuit comprises a second
heat exchanger connected downstream of a condenser and upstream of
expansion means of said second sub-circuit, said second heat exchanger being
adapted to perform an undercooling of the operating fluid of said lower
temperature main heat pump cycle after the condensation thereof and being
selectively connectable to the external circuit of said heat sink so as to
perform a
preheating of a heat carrier fluid coming from said heat sink by means of heat
power released during said undercooling by the operating fluid of said lower
CA 02894438 2015-06-09
WO 2013/088357
PCT/1B2012/057220
temperature main heat pump cycle.
The recovery of heat power resulting from the undercooling of the operating
fluid
of the lower temperature main heat pump cycle for preheating the heat carrier
fluid
of the heat sink when the heat pump unit of the invention is active in heating
implies a further improvement of the COP.
Preferably, said second heat exchanger is further selectively connectable to
the
external circuit of a second thermal user plant.
In this way, the heat power resulting from the undercooling of the operating
fluid of
the lower temperature main heat pump cycle may be used for serving a further
medium/low temperature thermal user, for example a heating plant with floor or
ceiling radiating panels, fan coils, etc. The possibilities of use and the
overall
energy efficiency of the heat pump unit of the invention therefore are
advantageously increased.
Preferably, moreover, said first sub-circuit comprises a third heat exchanger
connected downstream of said first heat exchanger and upstream of expansion
means of said first sub-circuit, said third heat exchanger being adapted to
perform
an undercooling of the operating fluid of said higher temperature main heat
pump
cycle after the condensation thereof and being selectively connectable to the
external circuit of said heat sink so as to perform, preferably independently
of said
second heat exchanger, a preheating of a heat carrier fluid coming from said
heat
sink by means of heat power released during said undercooling by the operating
fluid of said higher temperature main heat pump cycle.
Preferably, said third heat exchanger is further selectively connectable to
the
external circuit of said second thermal user plant.
These embodiments replicate, in the first sub-circuit for performing the
higher
temperature main heat pump cycle, what described above with reference to the
second sub-circuit for performing the lower temperature main heat pump cycle,
advantageously allowing the increase of the heat power available for
preheating
the heat carrier fluid of the heat sink or a medium/low temperature thermal
user to
be served.
In a preferred embodiment, said first sub-circuit comprises a fourth heat
exchanger
connected downstream of said main condenser and upstream of said third heat
6
CA 02894438 2015-06-09
WO 2013/088357
PCT/1B2012/057220
exchanger, said fourth heat exchanger being adapted to perform an undercooling
of the operating fluid of said higher temperature main heat pump cycle after
the
condensation of the same, and a secondary circuit adapted to perform a
secondary heat pump cycle with a respective operating fluid, said secondary
circuit comprising:
- a
secondary evaporator adapted to perform at least the evaporation of the
operating fluid of said secondary heat pump cycle and in heat exchange
relationship with said fourth heat exchanger to transfer heat power released
by the operating fluid of said main heat pump cycle during said undercooling
to the operating fluid of said secondary heat pump cycle;
- a
secondary condenser adapted to perform the condensation of the operating
fluid of said secondary heat pump cycle and intended to be connected to the
external circuit of said first thermal user plant or to an external circuit of
a
third thermal user plant, different from said first and second thermal user
plants.
Thanks to the arrangement of a fourth heat exchanger and to the performance of
a
secondary heat pump cycle with the features mentioned it is advantageously
possible to bring at least one fraction of the heat power released during the
undercooling of the operating fluid of the main heat pump cycle (i.e. of the
higher
temperature main heat pump cycle in the case of two-stage main heat pump
cycle)
to a higher temperature, in particular substantially equal to the temperature
at
which the condensation heat power is released in the main condenser. The
useful
power that the heat pump unit can provide is therefore increased, since a
fraction
of the undercooling heat power may be used, in addition to the condensation
heat
power released in the main condenser, for serving the first thermal user
plant, or
another thermal user plant operating with similar temperatures, also in
operating
conditions wherein such plants require the maximum temperature levels provided
for their operation.
It has been found that, unlike what happens for example in the case of the
cascading coupling of two heat pump cycles according to the prior art, in this
case
the increase of the above useful heat power leads to an improvement of the
overall COP. This is essentially related to the fact that such increase in the
useful
7
CA 02894438 2015-06-09
WO 2013/088357
PCT/1B2012/057220
heat power may be achieved with a minimum additional use of energy, in
particular electrical energy for compressing the operating fluid in the
secondary
heat pump cycle.
In fact, it should be noted that the undercooling of the operating fluid of
the main
heat pump cycle takes place, due to its nature, with a temperature variation.
The
heat power released during the undercooling of the operating fluid of the main
heat
pump cycle therefore allows not only the evaporation but also a strong
overheating
of the operating fluid of the secondary heat pump cycle, to be obtained.
The overheating, which is stronger as the thermal gradient of the operating
fluid of
the main heat pump cycle is wider during the undercooling, has two important
effects that contribute to a considerable reduction of the electrical
compression
power in the secondary heat pump cycle.
Firstly, there occurs an increase in the enthalpic jump undergone by the
operating
fluid of the secondary heat pump cycle in the heat exchange with the operating
fluid of the main heat pump cycle in the undercooling step. Having established
the
heat power to transfer between the two fluids, such enthalpic jump allows a
corresponding reduction in the mass flow rate of the secondary operating fluid
so
that less compression work is required.
Secondly, the overheating distances the operating fluid of the secondary heat
pump cycle from the saturated steam conditions and therefore allows the use of
compressors with higher isentropic yields, without the risk of intersecting
the
higher limit curve during the compression.
Both aspects mentioned contribute to a reduction in the electrical power used
for
the compression of the operating fluid of the secondary heat pump cycle and
thus,
according to what explained above, to the increase in the overall COP of the
heat
pump unit of the invention.
In a preferred embodiment of the heat pump unit of the invention, both said
main
condenser and said secondary condenser are intended to be connected to the
external circuit of said first thermal user plant and are connected to one
another so
as to be in series in said external circuit of said first thermal user plant.
This embodiment advantageously allows the use of both the condensation heat
power and of at least one fraction of the undercooling heat power of the main
8
CA 02894438 2015-06-09
WO 2013/088357
PCT/1B2012/057220
operating fluid for the same thermal user plant.
Advantageously, moreover, with this embodiment it is possible to obtain a
further
improvement in the overall COP, since it is possible to perform the heating of
the
heat carrier fluid of the user plant in two steps that occur in a sequence in
the
secondary condenser and in the main condenser. Since in this case the
secondary
condenser must only contribute to a part of the heating, the heat power to
transfer
to the thermal user plant being equal, it is possible to decrease the
condensation
temperature in the secondary heat pump cycle, obtaining a simultaneous
decrease
of the compression work required in such cycle and in the practice, an
increase in
the overall COP of the heat pump unit.
A situation of interest for the use of this embodiment therefore is in
combination
with high temperature heating plants which envision high temperature
differences
between delivery and backflow of the respective heat carrier fluid.
Preferably, moreover, the heat pump unit according to the invention comprises
switching means, adapted to allow an exchange of connections of the external
circuits of at least said first thermal user plant and said heat sink
respectively with
at least said main condenser and with said main evaporator.
This allows a reversible heat pump unit to be obtained, capable of operating
both
for heating and for cooling. Advantageously, the choice to perform the cycle
reversal by exchanging the external circuits of the thermal user(s) and of the
heat
sink, respectively, releases the switching between the two operating modes
from
the specific configuration of the heat pump unit (main circuit with one or two
stages, number of heat exchangers connected to a same delivery line of the
thermal user plant(s), etc.).
Preferably, the operating fluid of said main heat pump cycle, or the operating
fluids
of said higher temperature main heat pump cycle and said lower temperature
main
heat pump cycle respectively, and the operating fluid of said secondary heat
pump
cycle are selected from the group consisting of: (E)-2-butene, (Z)-2-butene, 1-
butylene, dimethyl ketone, methylacetylene, methyl alcohol, methylpentane,
methylpropene, n-hexane, R1270, R290, R600, R600a, R601, R601a, RE-170,
tetramethylmethane or RC-270.
The above cooling fluids are characterized by limit curves in diagram h - p
(specific
9
CA 02894438 2015-06-09
WO 2013/088357
PCT/1B2012/057220
enthalpy ¨ pressure) strongly inclined towards the increasing enthalpies, with
increasing inclination as pressure increases. This advantageously allows even
strong undercooling to be performed which, as already explained, allows all
the
advantageous effects on the overall COP that can be obtained by the above
embodiments to be enhanced.
The invention also relates to a system for heating/cooling environments and/or
for
producing sanitary hot water comprising a heat pump unit having the features
described above.
Brief description of the figures
Further features and advantages of the present invention will appear more
clearly
from the following description of some preferred embodiments thereof, made by
way of a non-limiting example with reference to the annexed drawings, wherein:
- Fig. 1 shows a circuit diagram of a first preferred embodiment of the
heat
pump unit of the invention;
- Fig. 2 shows a circuit diagram of a second preferred embodiment of
the heat
pump unit of the invention;
- Fig. 3 shows a circuit diagram of a third preferred embodiment of the
heat
pump unit of the invention;
- Fig. 4 shows a circuit diagram of a fourth preferred embodiment of
the heat
pump unit of the invention;
- Fig. 5 shows a circuit diagram of a fifth preferred embodiment of the
heat
pump unit of the invention;
- Figs. 6A and 6B show circuit diagrams of two operating configurations of
a
sixth preferred embodiment of the heat pump unit of the invention;
- Figs. 7A and 7B show circuit diagrams of two operating configurations of
a
seventh preferred embodiment of the heat pump unit of the invention;
- Figs. 8A and 8B show circuit diagrams of two operating configurations
of an
eighth preferred embodiment of the heat pump unit of the invention;
- Figs. 9A and 9B show circuit diagrams of two operating configurations of
an
ninth preferred embodiment of the heat pump unit of the invention, and
- Fig. 10 shows a circuit diagram of a tenth preferred embodiment of
the heat
pump unit of the invention.
CA 02894438 2015-06-09
WO 2013/088357
PCT/1B2012/057220
Detailed description of preferred embodiments of the invention
In the figures, a heat pump unit according to the invention is globally
indicated with
reference numeral 1.
In such figures, the heat pump unit 1 is shown as a part of a system 100 for
heating/cooling environments and/or for producing sanitary hot water,
comprising
at least one external circuit of a thermal user plant 10 and an external
circuit of a
heat sink 20, which are only schematically shown. A first heat carrier fluid
circulates in the external circuit of the thermal user plant 10, for example
water or
air, whereas a second heat carrier fluid circulates in the external circuit of
the heat
sink 20 which, also in this case, may be water or air.
As indicated above, the expression "heat sink" is understood to indicate a
system
capable of yielding or absorbing heat power without considerable variations of
the
average temperature thereof. Such system may be of the "open" type, such as
for
example a groundwater source, but it may also be of the "closed" type as in
the
case of a user heating/cooling plant. In both cases, anyway, there is provided
an
external circuit for the circulation of the heat carrier fluid resulting from
the system
defining the heat sink.
In situations of use of the heat pump unit 1 wherein both heat production and
cold
production are concurrently required, the heat sink 20 may therefore consist
of a
further thermal user plant capable of using the cooling or heating power
otherwise
disposed of through such heat sink. To this end, the thermal user plant may be
a
unit commonly called "four piped" or an air treatment unit comprising at least
one
heating battery and a post-heating battery.
For the purposes of the present invention, the expression "heat sink"
indicates in
general a system capable of absorbing thermal energy.
Fig. 1 shows a first preferred embodiment of the heat pump unit 1, in
particular for
heating, comprising a main circuit 2 for performing a main heat pump cycle
HPCM
with a respective operating fluid.
The main circuit 2 comprises: a main condenser S4 adapted to perform the
condensation of the operating fluid at a higher pressure of the main heat pump
cycle HPCM and intended to be connected to the external circuit of the thermal
user plant 10 in a heating operating mode of the heat pump unit 1; a main
11
CA 02894438 2015-06-09
WO 2013/088357
PCT/1B2012/057220
evaporator S8 adapted to perform the evaporation of the operating fluid at a
lower
pressure of the main heat pump cycle HPCM and intended to be connected to the
external circuit of the heat sink 20 in a heating operating mode of the heat
pump
unit 1; a compressor C2 adapted to bring the evaporated operating fluid from
the
lower pressure to the higher pressure of the main heat pump cycle HPCM, and
expansion means L2 - for example a lamination valve or other functionally
equivalent known device - adapted to perform the expansion of the operating
fluid
from the higher pressure to the lower pressure of the main heat pump cycle
HPCM.
The main circuit 2 further comprises a heat exchanger S3 connected downstream
of the main condenser S4 and upstream of the expansion means L2, adapted to
perform an undercooling of the operating fluid after the condensation of the
same
in the main condenser S4.
Within the scope of the present description and of the following claims, the
expressions "upstream" and "downstream" are to be understood with reference to
the directions of fluid circulation indicated in the figures by arrows and in
general
determined by the compressors, in the case of circuits for performing heat
pump
cycles, and by the circulation pumps in the case of the external circuits of
the
thermal user plants and of the heat sink, respectively.
The heat exchanger S3, moreover, is selectively connectable in a line FL1
arranged in the heat pump unit 1 for connecting the main condenser S4 to the
external circuit of the thermal user plant 1 so as to be in series with the
main
condenser S4 in said external circuit.
This is preferably obtained by means of a three-way valve V10, preferably a
modulating solenoid valve, arranged in line FL1 so as to selectively allow the
partial or total by-pass of the heat exchanger S3. In particular, valve V10 is
a
"modulating" valve, i.e. such as to allow the dosing of the water intended to
flow
through the heat exchanger S3. That is, such valve V10 allows the flow rate
intended for the heat exchanger S3 to be changed according to the requirements
to allow, for example in heating spring and autumn, the heat carrier fluid
circulating
in the first thermal user plant 10 to receive more heat power even though the
temperature of the same heat carrier fluid in output from exchanger S3 is
always
12
CA 02894438 2015-06-09
WO 2013/088357
PCT/1B2012/057220
lower. In particular, as the winter season becomes colder, through the
modulating
valve V10 it is possible to decrease the percentage of the fluid FL1 flow rate
intended to flow through S3. In this way, the overall temperature of the heat
carrier
fluid flowing through S3 and S4 will advantageously be higher even though the
heat power carried by the same heat carrier fluid will be lower. On the
contrary, as
the winter season becomes less cold, through the modulating valve V10 it is
possible to increase the percentage of the fluid FL1 flow rate intended to
flow
through S3. In this way, the overall flow rate flowing through S3 and S4 can
advantageously receive more heat power even though the temperature of the
same heat carrier fluid will be lower.
The heat exchanger S3 allows the use of the heat power resulting from an
undercooling of the operating fluid of the main heat pump cycle HPCM for
preheating the heat carrier fluid of the first thermal user plant 10 before it
reaches
the main condenser S4. As explained above, this leads to a significant
improvement of the overall COP of the heat pump unit 1 in particular in
operating
conditions wherein a decrease in the temperature level of the thermal user
plant
is acceptable, the heat power transferred thereto being equal, as may happen
for example in a high temperature heating plant in spring and autumn.
Considering the main circuit 2, the heat exchanger S3 therefore is in series
to the
main condenser S4 and both are downstream of compressor C2. It is therefore
clear that the heat exchanger S3 is an undercooler of the operating fluid in
output
from condenser S4. On the other hand, it is noted that the heat exchanger S3
and
the main condenser S4 have both the function of heating the heat carrier fluid
(preferably water) circulating in the external circuit of the thermal user
plant 10.
According to the minimum temperature of the heat sink 20 available, the
embodiment of the heat pump unit 1 shown in Fig. 1 may be used with low/mean
or high temperature thermal user plants. For example, if a heat sink 20 is
available
with a mean temperature of no less than 7 C, as it happens for example in the
case of groundwater or running water on the surface or in depth, seawater or
lake
water, waterworks water, wastewaters, etc., it is possible to serve thermal
user
plants that require temperatures up to 60-65 C, for example heating plants
operating at low/mean temperature, such as plants with floor or ceiling
radiating
13
CA 02894438 2015-06-09
WO 2013/088357
PCT/1B2012/057220
panels, fan coils, etc., or plants for the production of sanitary hot water.
On the other hand, if a heat sink 20 is available with a higher mean
temperature
(at least 30-35 C), for example waste/cooling heat from industrial processes,
hot
spring, etc., it is possible to serve thermal user plants which require
temperatures
even higher than 60-65 C, for example heating plants operating at high
temperature, such as plants with radiators, fan heaters, etc. which typically
require
delivery temperatures of 80 C or higher, or plants for the production of
sanitary
hot water in all those situations where the hot water must be produced at
temperatures considerably higher than 60 to prevent the possible occurrence
of
legionella (hospitals, swimming pools and sports centers, barracks, etc.).
The advantages resulting from the invention are more accentuated in the case
of
use of the heat pump unit 1 for serving thermal user plants operating at a
high
temperature since operating conditions may more frequently occur in such
plants
which allow a decrease of the temperature level whereto they operate at full
load
and which therefore, as already explained, allow the maximum advantage to be
taken from the preheating that may be performed through the heat exchanger S3.
Fig. 2 shows a second preferred embodiment of the heat pump unit 1, which
differs from that of Fig. 1 in the type of main circuit 2. In this case, the
main circuit
2 comprises a first sub-circuit 2a adapted to perform a higher temperature
main
heat pump cycle HPCM_HT with a respective operating fluid and a second sub-
circuit 2b adapted to perform a lower temperature main heat pump cycle
HPCM LT with a respective operating fluid. The first and second sub-circuits
2a,
2b are in cascading heat exchange relationship with each other to perform
globally
a two-stage main heat pump cycle HPCM.
In this case, the first sub-circuit 2a comprises the main condenser S4, the
heat
exchanger S3, the expansion means L2 and compressor C2 described above with
reference to the embodiment of Fig. 1, and an evaporator. The second sub-
circuit
2b comprises the main evaporator S8, already described above as well with
reference to the embodiment of Fig. 1, a compressor C1, a condenser in heat
exchange relationship with the evaporator of the first sub-circuit 2b and the
expansion means L1.
In the preferred embodiments shown herein, the condenser of the second sub-
14
CA 02894438 2015-06-09
WO 2013/088357
PCT/1B2012/057220
circuit 2b and the evaporator of the first sub-circuit 2a are integrated in a
single
heat exchanger device S7 for greater construction compactness and a better
heat
exchange efficiency. In any case, embodiments in which such components are
separate and placed in thermal exchange relationship by an intermediate
circuit for
the circulation of a suitable heat carrier fluid are not excluded.
The embodiment of the heat pump unit 1 with two-stage main heat pump cycle
HPCM finds an advantageous use in all those situations in which it is
necessary to
serve thermal user plants operating at a high temperature but having a low
temperature heat sink available.
Fig. 3 shows a third preferred embodiment of the heat pump unit 1 which
differs
from that of Fig. 2 essentially by the provision, in the second sub-circuit 2b
for
performing the lower temperature main heat pump cycle HPCM_LT, of a further
heat exchanger S6 connected downstream of the heat exchanger device S7 and
upstream of the expansion means L1.
The heat exchanger S6 is adapted to perform an undercooling of the operating
fluid of the lower temperature main heat pump cycle HPCM_LT after the
condensation thereof in the heat exchanger device S7, and is selectively
connectable to the external circuit of the heat sink 20 so as to perform a
preheating of the heat carrier fluid coming from the latter by means of the
heat
power released during said undercooling.
In particular, a first end of the heat exchanger S6 is connected to the second
sub-
circuit 2b as described above and a second end of the heat exchanger S6 is
connected upstream of the main evaporator S8 in a line FL2 arranged in the
heat
pump unit 1 for the connection to the external circuit of the heat sink 20. In
such
line FL2 there is also provided a valve V6, preferably a modulating solenoid
valve,
for adjusting the flow rate of heat carrier fluid of the heat sink 20 which
crosses the
heat exchanger S6, and thus the extent of the undercooling of the operating
fluid
in the higher temperature main heat pump cycle HPCM_LT. Line FL2 preferably
also comprises a first manifold M1 connected upstream of the heat exchanger S6
and a second manifold M2 connected upstream of the main evaporator S8 and
downstream of valve V6. Preferably, manifolds M1 and M2 are also connected by
a bypass line BPL for bypassing the heat exchanger S6, provided with a valve
V5,
CA 02894438 2015-06-09
WO 2013/088357
PCT/1B2012/057220
also preferably a modulating solenoid valve.
This further embodiment of the heat pump 1 therefore allows the heat power
obtained with the undercooling of the operating cycle of the lower temperature
main heat pump cycle HPCM_LT to be used for preheating the heat carrier fluid
of
the heat sink 20. This solution allows an advantageous increase in the COP as
it
advantageously increases the inlet temperature of the heat sink 20 heat
carrier
fluid to evaporator 8, i.e. decreasing the temperature difference between hot
source and cold source.
Preferably, in order to keep a constant flow rate of the heat sink 20 heat
carrier
fluid in the main evaporator S8, a modulation or closure of valve V6 is
compensated through a corresponding modulation or opening of valve V5.
Preferably, in this embodiment and in those described hereinafter, compressors
C1 and C2 are variable flow rate compressors, for example cut-off step or
inverter
compressors. This ensures higher adaptability of the heat pump unit 1 to the
possible unbalances in the thermal power exchange between higher temperature
main heat pump cycle HPCM_HT and lower temperature main heat pump cycle
HPCM_HT which may happen due to the undercooling. Such higher adaptability
has a positive influence on the overall energy efficiency of the heat pump
unit 1, all
the other conditions being equal.
Fig. 4 shows a fourth preferred embodiment of the heat pump unit 1 which
differs
from that of Fig. 3 by the provision, in the first sub-circuit 2a for
performing the
higher temperature main heat pump cycle HPCM_HT, of a further heat exchanger
S5 connected downstream of the heat exchanger S3 and upstream of the
expansion means L2.
Similar to heat exchanger S6, heat exchanger S5 is adapted to perform an
undercooling of the operating fluid of the higher temperature main heat pump
cycle
HPCM_HT after the condensation thereof in the heat exchanger S4, and
optionally
after a first undercooling in heat exchanger S3, and is selectively
connectable to
the external circuit of the heat sink 20 so as to perform a preheating of the
heat
carrier fluid coming from the latter by means of the heat power released
during
said undercooling.
Preferably, heat exchanger S5 and heat exchanger S6 are arranged so as to
16
CA 02894438 2015-06-09
WO 2013/088357
PCT/1B2012/057220
perform the preheating of the heat carrier fluid of the heat sink 20
independently of
one another, i.e. operating in parallel on two separate flows of such heat
carrier
fluid.
In particular, as shown in Fig. 4, heat exchanger S5 is connected in a first
branch
FL2' of line FL2 for the connection to the external circuit of the heat sink
20. In
such first branch FL2' there is also provided a valve V7, preferably a
modulating
solenoid valve, for adjusting the heat carrier fluid flow rate (for example
water) of
the heat sink 20 which crosses the heat exchanger S5. The heat exchanger S6
and valve V6, on the other hand, are connected in a second branch FL2", in
parallel with the first branch FL2', of line FL2. Exchanger S5 therefore
exchanges
heat between the heat carrier fluid of the heat sink (for example water) and
the
operating fluid (cooling fluid) circulating in the first sub-circuit 2a and is
used for
preheating the inlet heat carrier fluid to evaporator S8 if the (cooling)
operating
fluid of the first sub-circuit 2a still has residual heat not transferred
through the
main condenser S4 and the heat exchanger (undercooler S3) previously crossed
by the same operating fluid. Actually, heat exchanger S5 is a further
undercooler
of the cooling fluid in output from heat exchanger S4.
Similar to what mentioned with reference to valve V6, also the modulation or
closing of valve V7 may be compensated through a corresponding intervention on
valve V5 in the bypass line BPL in order to keep a constant flow rate of the
heat
sink 20 heat carrier fluid in the main evaporator S8.
This embodiment of the heat pump 1 allows an undercooling of the operating
fluid
to be performed also in the higher temperature main heat pump cycle HPCM_HT
after the condensation thereof and the use of the heat power thus released for
preheating the heat sink 20 heat carrier fluid. Also this solution therefore
allows an
advantageous increase in the COP, increasing the inlet temperature of the heat
sink 20 heat carrier fluid to evaporator 8, or decreasing the temperature
difference
between hot source and cold source.
Fig. 5 shows a fifth preferred embodiment of the heat pump unit 1 which
differs
from that of Fig. 4 in that the heat exchangers S5 and S6 are further
selectively
connectable to an external circuit of a further thermal user plant 12, in
particular a
thermal user plant operating at mean/low temperature, for example a heating
plant
17
CA 02894438 2015-06-09
WO 2013/088357
PCT/1B2012/057220
with floor or ceiling radiating panels, a plant for the production of sanitary
hot
water, etc.
This is preferably obtained using a three-way valve V8, preferably a solenoid
valve, and two valves V9 and V12, preferably modulating solenoid valves,
arranged in such a way as to allow the connection of the second end of heat
exchangers S5 and S6 alternately to the external circuit of the heat sink 20
or to
the external circuit of the thermal user plant 12.
In particular, when the heat power released at the heat exchangers S5 and S6
must be used for serving the thermal user plant 12, the three-way valve V8 is
diverted towards the external circuit of such plant, valves V6 and V7 are
fully
closed and valves V9 and V12 are fully or partly open. An adjustment of the
opening degree of valves V9 and V12 allows the heat power transferred to the
thermal user plant 12 to be adjusted.
On the contrary, when the heat power released at the heat exchangers S5 and S6
must be used for preheating the heat sink 20 heat carrier fluid, as in the
embodiments described above with reference to Figs. 3 and 4, the three-way
valve
V8 is diverted towards the external circuit of the heat sink 20, valves V9 and
V12
are fully closed and valves V6 and V7 are fully or partly open.
In all the embodiments wherein the pairs of two-way valves V6 + V9 and V7 +
V12
are provided, each of such pairs may be replaced by a three-way valve arranged
so as to perform the functions described above of the corresponding two-way
valves.
Figs. 6A and 6B show a sixth preferred embodiment of the heat pump unit 1
adapted to operate for both heating and cooling, i.e. of the reversible type.
To this end, in this embodiment there are provided switching means adapted to
allow an exchange of connections of the external circuits of the thermal user
plant
and of the heat sink 20 respectively with the main condenser S4 and with the
main evaporator S8. Preferably, such switching means comprise two four-way
valves V1 and V2, preferably solenoid valves, suitably arranged in the lines
for the
connection of the above external circuits to the main condenser S4 and the
main
evaporator S8.
In particular, in the operating configuration shown in Fig. 6A, corresponding
to a
18
CA 02894438 2015-06-09
WO 2013/088357
PCT/1B2012/057220
heating operation (winter or autumn and spring), the external circuit of the
thermal
user plant 10 is connected to the main condenser S4 (and to the heat exchanger
S3), whereas the external circuit of the heat sink 20 is connected to the main
evaporator S8 in a manner totally similar to the embodiments described above.
In the configuration shown in Fig. 6B, corresponding to a cooling operation
(summer), the external circuit of the thermal user plant 10 is connected to
the main
evaporator S8 so as to provide such plant with the required cooling power
whereas the external circuit of the heat sink 20 is connected to the main
condenser S8.
It is noted that in the cooling operation, the use of heat exchangers S5 and
S6 for
the undercooling of the operating fluid respectively in the higher temperature
main
heat pump cycle HPCM_HT and in the lower temperature main heat pump cycle
HPCM_LT allows a substantial increase of the useful cooling power without a
corresponding increase of electrical power used, to the advantage of the
overall
energy efficiency. Numerical simulations carried out have shown that this
embodiment of the heat pump unit 1 when operating for cooling allows EER
values
to be reached that are equal to 3.5 ¨ 4.0, against a value of about 2.2 in the
absence of undercooling.
The undercooling heat power released in this operating configuration at the
heat
exchangers S5 and S6 may advantageously be used for example for the
production of sanitary hot water in a dedicated plant (schematized in Fig. 6B
by
the thermal user plant 12). If it is not possible to use the undercooling heat
power,
this shall be suitably disposed to the external environment.
Moreover, in the cooling operation, the use of heat exchanger S3 is not
generally
needed and the three-way valve V10 is therefore diverted so as to exclude such
heat exchanger from line FL1.
Figs. 7A and 7B show a seventh preferred embodiment of the heat pump unit 1
which differs from that of Figs. 6A and 6B in that it can also serve, in a
dedicated
manner, both in a heating operating configuration (Fig. 7A), and in a cooling
operating configuration (Fig. 7B), a thermal user plant 13 for the production
of
sanitary hot water, in addition to the thermal user plants 10 and 12. In
particular,
this embodiment allows a thermal user plant to be served for the production of
19
CA 02894438 2015-06-09
WO 2013/088357
PCT/1B2012/057220
high temperature (higher than 60 C for preventing the possible occurrence of
legionella) sanitary hot water.
The embodiment shown in Figs. 7A and 7B, by way of an example, envisions that
the heat exchange with the thermal user plant 13 indirectly takes place at a
heat
= accumulator (boiler) 13a, but other solutions known by the man skilled in
the art
are also possible to connect the heat pump unit 1 to the external circuit of
such
thermal user plant.
Compared to the embodiment of Figs. 6A and 6B, connections are further
provided in this case for an external circuit of the thermal user plant 13 and
two
three-way valves V3 and V11, preferably solenoid valves.
The three-way valve V3 is arranged so as to allow, in the heating operating
configuration (Fig. 7A), the connection of line FL1 alternately to the
external circuit
of the thermal user plant 10 or to the external circuit of the thermal user
plant 13.
In this way it is possible to use the heat power released at the main
condenser S4
alternately for heating or production of high temperature sanitary hot water.
The three-way valve V11 is arranged so as to allow, in the cooling operating
configuration (Fig. 7B), the connection of line FL1 alternately to the
external circuit
of the thermal user plant 13. In this way it is possible to use the heat power
released by the main condenser S4 for producing high temperature sanitary hot
water rather than dispersing such power at the heat sink 20.
Figs. 8A and 8B show an eighth preferred embodiment of the heat pump unit 1
which, compared to the embodiment of Figs. 7A and 7B, in addition allows also
low temperature sanitary hot water requirements to be met through the thermal
user plant 13 for the production of sanitary hot water already mentioned. The
embodiment of Figs. 8A and 8B differs from that of Figs. 7A and 7B in
particular by
the presence of a further three-way valve V4, preferably a solenoid valve.
The three-way valve V4 is arranged so as to allow the selective connection of
lines
FL2' and FL2", wherein the heat exchangers S5 and S6 are connected, also to
the
external circuit of the thermal user plant 13 for the production of sanitary
hot water,
so as to create a closed circuit therewith. In this way it is possible to use
the heat
power released at the two heat exchangers S5 and S6 alternately for producing
sanitary hot water both in the heating operating configuration (Fig. 8A) and
in the
CA 02894438 2015-06-09
WO 2013/088357
PCT/1B2012/057220
cooling operating configuration (Fig. 8B), or for preheating the heat sink 20
heat
carrier fluid in the heating operating configuration.
For an optimum operation of this embodiment in the cooling operating
configuration (Fig. 8B) it is suitable to provide, externally to the heat pump
unit 10,
means for bypassing the external circuit of the thermal user plant 10,
intended for
cooling in this operating configuration. Such means preferably comprise a
three-
way valve V13, preferably a solenoid valve, arranged between the external
circuit
of the thermal user plant 10 and the external circuit of the thermal user
plant 13.
The external three-way valve V13, together with the already described three-
way
valve V11 of the heat pump unit 1, allows line FL1 to be connected to the
external
circuit of the thermal user plant 13 bypassing the external circuit of the
thermal
user plant 10.
In particular, in the cooling operating configuration shown in Fig. 8B, the
three-way
valve V11 connects line FL1 to the external circuit of the thermal user plant
13
whereas the external there-way valve V13 allows the external circuit of the
thermal
user plant 10 to be bypassed. In this way it is possible to use the heat power
released by the main condenser S4 for producing high temperature sanitary hot
water rather than dispersing such power at the heat sink 20. This operating
mode
requires circuit FL1 to be a closed circuit.
Figs. 9A and 9B show a ninth preferred embodiment of the heat pump unit 1,
which differs from that of Figs. 8A and 8B mainly in that it comprises a
further heat
exchanger connected in sub-circuit 2a and adapted to perform an undercooling
of
the operating fluid of said higher temperature main heat pump cycle HPCM_HT as
well as a secondary circuit 3 adapted to perform a secondary heat pump cycle
HPCS with a respective operating fluid and in heat exchange relationship with
sub-
circuit 2a at said further heat exchanger.
The further heat exchanger is connected in sub-circuit 2a downstream of the
main
condenser S4 and preferably, of the heat exchanger S3, and upstream of the
heat
exchanger S5.
The secondary circuit 3 for performing a secondary heat pump cycle HPCS
comprises a secondary condenser S1 adapted to perform the condensation of the
operating fluid at a higher pressure of the secondary heat pump cycle HPCS and
21
CA 02894438 2015-06-09
WO 2013/088357
PCT/1B2012/057220
intended to be connected to the external circuit of the thermal user plant 10
or to
the external circuit of a further thermal user plant, separate from the latter
and
from the thermal user plants 12 and 13 mentioned above; a secondary evaporator
adapted to perform at least the evaporation of the operating fluid at a lower
pressure of the secondary heat pump cycle HPCS and in heat exchange
relationship with said further heat exchanger of sub-circuit 2a for
transferring heat
power released by the operating fluid of the main heat pump cycle HPCM during
said undercooling to the operating fluid of the secondary heat pump cycle
HPCS; a
compressor C3 adapted to bring the evaporated operating fluid from the lower
pressure to the higher pressure of the secondary heat pump cycle HPCS, and
expansion means L3 ¨ for example a lamination valve or another functionally
equivalent known device ¨ adapted to allow the expansion of the operating
fluid
from the higher pressure to the lower pressure of the secondary heat pump
cycle
HPCS.
In the embodiment of Figs. 9a and 9b, the further heat exchanger of sub-
circuit 2a
and the secondary evaporator of the secondary circuit 3 are integrated in a
single
heat exchanger device S2 for greater construction compactness and a better
heat
exchange efficiency. In any case, embodiments wherein such components are
separate and placed in thermal exchange relationship by an intermediate
circuit for
the circulation of a suitable heat carrier fluid are not excluded.
Compressor C3 preferably is a variable flow rate compressor, for example a cut-
off
or step or inverter compressor. This allows the extent of the operating fluid
undercooling in the main heat pump cycle HPCM at the heat exchanger device S2
and accordingly, the heat power that can be provided at the secondary
condenser
S1 to be controlled without stressing the compressor with an excessive
repetition
of on-off cycles.
By means of the secondary circuit 3 and the relevant secondary heat pump cycle
HPCS described above it is possible to raise the temperature by at least a
fraction
of the heat power released upon the undercooling of the operating fluid in the
main
heat pump cycle HPCM, bringing it to values equal or close to those of the
heat
power released at the main condenser S4. In this way, the above fraction of
undercooling heat power becomes usable by the thermal user plant 10 or by
22
CA 02894438 2015-06-09
WO 2013/088357
PCT/1B2012/057220
another and separate thermal user plant operating at medium or high
temperature
also in operating conditions wherein such thermal user plants must operate at
the
expected maximum temperatures. Thanks to the fact that such result may be
obtained minimizing the additional energy consumption related to compressor
C3,
as already explained above, the increase in the overall useful heat power
leads to
an increase in the overall COP of the heat pump unit 1.
When both the main condenser S4 and the secondary condenser S1 are intended
to serve the same thermal user plant, as in the embodiment of Figs. 9A and 9B,
they are reciprocally connected in series, with the secondary condenser S1
upstream, in line FL1 for the connection to the external circuit of such
thermal user
plant. In this way it is possible to use the secondary condenser S1 for
performing a
preheating of the heat carrier fluid of the thermal user plant, and the main
condenser S4 for completing the heating up to reaching the required delivery
temperature.
As already explained above, since in this case the secondary condenser S1 must
only contribute to a part of the heating, the heat power to transfer to the
thermal
user plant being equal, it is possible to decrease the condensation
temperature in
the secondary heat pump cycle HPCS, obtaining a simultaneous decrease of the
compression work required in such cycle and thus, a further improvement of the
overall COP of the heat pump unit 1.
Therefore, with reference to the heating operating configuration (Fig. 9A) of
the
ninth embodiment described above, in operating conditions wherein the
temperature level in the thermal user plant 10 must be maximum (for example in
full winter), the three-way valve V10 is preferably diverted so as to connect
the
secondary condenser S1 in line FL1 and exclude the heat exchanger S3.
Advantageously, the heat power provided by the undercooling of the operating
fluid of the higher temperature main heat pump cycle HPCM_HT can thus be
transferred to the thermal user plant 10 at a higher temperature, thanks to
the
secondary heat pump cycle HPCS performed in the secondary circuit 3 (active
compressor C3).
In operating conditions wherein the temperature level in the thermal user
plant 10
may be reduced, the three-way valve V10 is on the contrary preferably diverted
so
23
CA 02894438 2015-06-09
WO 2013/088357
PCT/1B2012/057220
as to connect the heat exchanger S3 in line FL1 and exclude the secondary
condenser S1, and the secondary circuit 3 is deactivated (compressor S3 off).
Advantageously, in this case, the heat power provided by the undercooling of
the
operating fluid of the higher temperature main heat pump cycle HPCM_HT is
transferred to the thermal user plant 10 directly, without heat increase,
through the
heat exchanger S3. The adjustment of the delivery temperature for the thermal
user plant 10 takes place through the modulation of the three-way valve V10. A
further advantage may be obtained by shutting or reducing the number of
revolutions of compressors C1 and C2 in order to reduce the heat power
delivered.
In the heating operating configuration of the ninth embodiment, shown in Fig.
9A,
the use level of the heat exchanger S5, i.e. the fraction of undercooling heat
power
used therein with respect to the total available, depends on the corresponding
use
level of the heat exchanger device S2 and of heat exchanger S3.
In particular, the use level of heat exchanger S5 is maximum when the three-
way
valve V10 is diverted so as to exclude the heat exchanger S3 and the secondary
circuit 3 is not active (compressor C3 off). On the contrary, the use level is
null
when all the undercooling heat power is used in the heat exchanger device S2
(for
example in full winter operating conditions) or in heat exchanger S3 (for
example
in autumn and spring operating conditions). In this case, the heat exchanger
S5 is
excluded from line FL1 by closing valve V7. In intermediate situations, the
use
level of the heat exchanger S5 is partial and valve V7 must modulate
accordingly.
In the cooling operating configuration of the ninth embodiment, shown in Fig.
9B,
the secondary circuit 3 for performing the secondary heat pump cycle HPCS
typically is not active (compressor C3 off). Alternatively, for example in use
situations wherein the production of large amounts of sanitary hot water is
required
even in hot seasons, it is possible to provide also for the transfer of the
power
released at the secondary condenser S1 to a plant for the production of
sanitary
hot water.
In all the embodiments described, the heat pump unit 1 preferably comprises
also
a programmable control unit not shown in the figures. In particular, such
control
unit may be suitably programmed for controlling the opening/closing, the
24
CA 02894438 2015-06-09
WO 2013/088357
PCT/1B2012/057220
modulation or diverting of the valves as well as the switching on/off, the
shutting
degree or the number of revolutions of the compressors present in each
embodiment of the heat pump unit 1.
The operating fluids used in the various heat pump cycles performed in the
heat
pump unit 1 may be equal to or different from, each other.
Operating fluids are preferably selected that allow the following advantageous
features to be combined for the operation of the heat pump unit 1:
- limit curves, and in particular lower limit curve, in diagrams h ¨ p highly
inclined
in the direction of the increasing enthalpies;
- high specific heat of the operating fluid at the liquid state with respect
to the
latent condensation/evaporation heat;
- high specific heat of the operating fluid at the vapor state with respect to
the
latent condensation/evaporation heat.
The first two features mentioned above are particularly important for
embodiments
or operating conditions that use strong undercooling whereas the third one is
particularly important for all the embodiments or operating conditions that
use
strong overheating.
In particular, in order to obtain the best performance of the heat pump unit
1, the
following operating fluids have proven to be particularly advantageous: (E)-2-
butene, (Z)-2-butene, 1-butylene, dimethyl ketone, methylacetylene, methyl
alcohol, methylpentane, methylpropene, n-hexane, R1270, R290, R600, R600a,
R601, R601a, RE-170, tetramethylmethane or RC-270.
Besides having at least one or more of the desired features listed above,
these
operating fluids have the advantage of being so-called "natural" cooling
fluids, i.e.
not harmful for the environment from the viewpoint of negative effects on the
stratospheric ozone, or from the viewpoint of the greenhouse effect.
If the type of operating fluid selected, in particular for its hydrocarbon
nature,
poses safety issues (fire hazard) in the cases in which the heat pump unit 1
must
be installed in underground or basement rooms, the latter is preferably
provided
also with means for the detection and evacuation of gas leaks.
Fig. 10 shows an embodiment of the heat pump unit 1 comprising a system for
the
detection and evacuation of gas leaks. By way of an example, the configuration
of
CA 02894438 2015-06-09
WO 2013/088357
PCT/1B2012/057220
the heat pump unit 1 shown corresponds to the second embodiment described
above with reference to Fig. 2.
The system for the detection and evacuation of gas leaks comprises at least
one
gas detector 31, positioned as close as possible to the bottom of the heat
pump
unit 1 and ventilation means 32, activatable by the gas detector 31 and
arranged
so that the suction thereof is also close to the bottom of the heat pump unit
1,
whereas the delivery thereof is connected to a gas evacuation conduit in
communication with the external environment. Optionally, there may be provided
a
dedicated control device 34 adapted to receive signals from the gas detector
31
and to control the ventilation means 32 accordingly. The control device 34 may
also control sound and/or light warning means 35, if provided, and/or be
configured for sending alarm signals to an optional external
monitoring/supervision
system (not shown). The functions of the control device 34 may also be carried
out
by the programmable control unit of the heat pump unit 1.
Of course, a man skilled in the art may use the technical features of the heat
pump
unit 1 of the invention disclosed with reference to the preferred embodiments
described above also in different combinations in order to meet specific and
contingent application requirements.
26
