WO2018179014A1

WO2018179014A1 - Heat pump apparatus for changing air within domestic spaces and respective mode of operation

Info

Publication number: WO2018179014A1
Application number: PCT/IT2017/000063
Authority: WO
Inventors: Robert Florian
Original assignee: Evolving Living Innovation Center E.L.I.C. S.r.l.
Priority date: 2017-03-28
Filing date: 2017-03-28
Publication date: 2018-10-04

Abstract

The present invention relates to a heat pump apparatus for air renewal inside rooms and, in specific, to a compact heat pump apparatus made by components included in a single housing to be mounted inside a room. Moreover, the invention relates to an operation mode of the mentioned apparatus or conditioning mode of the air inside a room that is able to activate a heat recovery and/or renewed air supply, heating, cooling or dehumidification.

Description

HEAT PUMP APPARATUS FOR CHANGING AIR WITHIN DOMESTIC SPACES AND RESPECTIVE MODE OF OPERATION"

DESCRIPTION TECHNICAL FIELD OF THE INVENTION

[001] The present invention relates to a heat pump apparatus for renewed air supply inside a room and, in particular, to a compact heat pump apparatus made by components included in a single housing to be mounted inside a room. Moreover, the invention relates to an operation mode of the mentioned apparatus or conditioning mode of the air inside a room that is able to activate a heat recovery and/or renewed air supply, heating, cooling or dehumidification.

PRIOR ART

[002] Heat pump apparatus for air conditioning are known and have been widely used for a long time. Effectively, heat pump system is widely used since it provides high efficiency with low energy consumption compared to so-called passive apparatus, which are fitted with a passive heat recovery device that does not involve a thermodynamic work but a simply heat exchange between inlet and outlet air flows.

[003] In general, a heat pump system produces a heat transfer between two fluids: the fluid that flows inside the closed circuit is called primary fluid; the fluid that flows through the system and exchanges thermal energy - in terms of power - with the primary fluid is called secondary fluid. The primary fluid could be synthetic or natural depending on specific needs or preferences; generally, the secondary fluid is air or water. The most elementary assembling system of an apparatus includes traditionally: a compressor that provides energy in the form of compression work to a gas compressing, warming and triggering it. The warm gas reaches a first heat exchanger, called condenser, where the energy is transferred from the primary fluid to the secondary fluid; the gas goes through a phase transformation from gaseous to liquid. The liquid reaches a laminar element inside which it expands and cools down. The cold liquid reaches a second heat exchanger, called evaporator, where the secondary fluid transfers energy to the primary fluid in the form of heat, making it evaporate to return to the gaseous state. After this, the circuit ends with gas returning to the compressor to start the thermodynamic cycle again.

[004] The above described cycle could be applied in apparatuses that provide renewed air supply inside a room. In fact, with the help of an air vent that connects the inside and outside space, stuffy air is ejected and at the same time "new" air is drawn and spread in the room. Renewed air flows through the same heat exchanger that, depending on the outside temperature, will work as a condenser or as an evaporator, heating or cooling down the incoming air, that is the thermodynamic cycle is inverted.

[005] The above described apparatus are structurally bulky because of the need to have of an efficient thermodynamic circuit. In fact, it is known that in order to switch the function summer/winter which means to invert the thermodynamic cycle by means of a conventional four way valve, it is necessary to create a sufficient working pressure in order to slide and maintain the valve's piston in the desired position, particularly after the pilot valve activation that allows the deviation of the working fluid inside the four way valve to slide its piston into the summer working position. In other words, it is necessary to create a pressure differential upstream and downstream the compressor higher than 2.5 bar, that is to say in the suction and discharge of the four way valve. This implicates generally the use of rotary compressors and so compressors with a cooling effect not lower than 0.8 kW. These powers entail big compressor dimensions if compared to domestic spaces.

[006] In addition, also the other components of the thermodynamic circuit have to be adjusted according to the compressor. Therefore, the relative dimensions are important and added up to the ones of the compressor with the result of a decisively bulky apparatus, over-dimensioned and energetically expensive for domestic spaces.

[007] According to what described, it is evident that the known apparatus are not suitable at all to be installed in domestic spaces like kitchens, living rooms, bedrooms, bathrooms.

BRIEF SUMMARY OF THE INVENTION

[008] The purpose of the present invention is thus to supply an heat pump apparatus for renewed air supply with a compact structure, suitable for an internal installation in a domestic space.

[009] This purpose is reached by an heat pump apparatus which includes functional components with small dimensions but steered in order to allow an adequate functionality of the heat pump in every climate condition.

[0010] In consequence, a primary object of the present invention is a heat pump apparatus for renewed air supply inside rooms which has favorable compact dimensions that allow the installation inside the room with a minimum space requirement. [0011] A second object is an highly efficient heat pump for what concerns the overall energy balancing of the space that needs conditioning.

[0012] A third object is an heat pump apparatus with simple and reliable components controlled in order to assure the proper functionality of the thermodynamic cycle according to the space conditioning desired.

[0013] An additional object is an heat pump apparatus especially versatile which is able to heat or cool a space and simultaneously to supply renewed air, to recover heat and/or dehumidify.

[0014] A further object is an operating mode of an heat pump apparatus for the renewed air supply inside domestic spaces.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Other objects and the advantages of the heat pump apparatus of the present invention will be better understood with the following description of an embodiment given as a non-restrictive example with reference to the following figures, and wherein:

- figure 1 is a schematic view illustrating the thermodynamic and aeraulic circuit of the apparatus according to the present invention in a first operating condition;

- figure 2 is a schematic view illustrating the thermodynamic and aeraulic circuit of the apparatus according to the present invention in a second operating condition;

- figure 3 is a schematic view illustrating the thermodynamic and aeraulic circuit of the apparatus according to the present invention in a third operating condition;

- figure 4 is a schematic view illustrating the thermodynamic and aeraulic circuit of the apparatus according to the present invention in a fourth operating condition;

- figure 5 is a schematic view illustrating the thermodynamic and aeraulic circuit of the apparatus according to the present invention in a fifth operating condition.

DETAILED DESCRIPTION OF THE INVENTION

[0016] The idea at the heart of the present invention is to design a heat pump apparatus for renewed air supply with small-dimensioned components that can be included in a single housing to be mounted inside a domestic space where dimensions are precisely important. At the same time, the thermodynamic system must be efficient and must not alter the overall energy balancing of the room that needs conditioning.

[0017] In order to reduce the dimensions, it has been thought that the simplest solution was to reduce the dimensions of the components and, above all, of the compressor. The compressor volume decrease entails a power loss from constructional point of view or, in other words, a loss of the capacity to compress the working fluid. As a consequence, the working pressure of the fluid decreases to a value that is lower than the vale necessary to create the above mentioned differential between suction and discharge in the four way valve, therefore insufficient to move the internal piston that deflects the working fluid flow in one of the two heat exchangers according to the function "summer" or "winter".

[0018] It has been thought to design the thermodynamic circuit in order to avoid this pressure loss in a simple way without being forced to increase the dimensions of the components.

[0019] With reference to the figures, it is illustrated an heat pump apparatus for renewed air supply inside domestic spaces by means of its thermodynamic and aeraulic circuit.

[0020] The apparatus is indicated in general with reference number 1 and includes a compressor 2, a four way valve 3, a first heat exchanger 4 combined to a first fan 5 for air aspiration inside the room, a laminar element 6, a second heat exchanger 7 combined to a second fan 8 for air supply inside the room. All the above mentioned components are included in a box element or housing 9 meant to be fixed on a peripheral wall W internally IN a domestic space.

[0021] The box element 9 is then connected to the external space OUT with a duct 10 provided with a septum 1 1 longitudinal and median that divides the duct itself preferably in two symmetric and distinct portions: the first portion 10A for inside air expulsion which is connected to a first channel 12 of the box element 9 where the first heat exchanger 4 is allocated, a second portion 10B of air insertion from outside that is connected with a second channel 13 where is allocated the second heat exchanger 7. This configuration represents the aeraulic circuit of the apparatus 1 in the present invention.

[0022] The duct 10 is essentially rectilinear along X-X axis perpendicular to the wall W of the room where the apparatus is installed 1. While first 12 and second 13 channels of the box element extend along an common Y-Y axis perpendicular to the mentioned X-X axis of the duct 10.

[0023] It is to be noted that the first channel 12 and the second channel 13 are kept separated and in communication with the respective first portion 10A and second portion 10B of the duct 10 by means of a valve 14. Preferably it is a butterfly valve 14. Therefore, as shown in the figures, it includes a central hinge 14A around which rotate two wings 14B diametrically opposed.

[0024] Advantageously, the apparatus 1 includes a solenoid valve 15 positioned upstream the compressor 2, i.e. on the aspiration side. Solenoid valve 15 has the purpose of closing the working fluid passage to the compressor inlet in order to create a pressure imbalance between suction and discharge side of the compressor. In other words, keeping solenoid valve 15 closed, on the suction side of the compressor occurs an overpressure while on the discharge side occurs a depression. This pressure differential tends to increase and when it reaches a value higher than 2,5 bar, the valve 15 is opened, operating a decompression. In this way, the brusque pressure imbalance causes the push of the four way valve piston, usually controlled by the pilot valve, moving it in the desired position, i.e. in the position in which the working fluid is deflected first on one or on the other heat exchanger, respectively first 4 or second 7.

[0025] The apparatus 1 includes moreover a temperature sensor (not shown) positioned in the second portion 10B of the duct 10 to detect the intake temperature. An additional temperature sensor (not shown) should be positioned nearby the apparatus or in a specific point of the room and connected to the apparatus in order to detect the indoor room temperature.

[0026] Other sensors (not shown) like humidity sensors, intake and outtake flow air sensors, sensors for the working fluid pressure in the thermodynamic circuit, may be positioned as preferred accessories for the apparatus 1.

[0027] All the above mentioned functional components, devices, sensors and valves are operatively connected to a command and control unit (not shown) which is able to receive signals from them concerning their condition. The unit elaborates this signals in values to be compared to preset and selectable values in order to send in turn command signals to modify the operating mode of the apparatus according to this comparison.

[0028] In particular, as shown in figure 1 , the two wings 14B of the butterfly valve 14 are aligned on the same straight line detected by sect 11 , in order to divide the two channels first 12 and second 13 along the shared axis Y-Y and to put them in communication with the respective portions first 10A and second 10B of the duct 10.

[0029] In this position, according to a first working condition, first 5 and second 8 fan are activated in order to draw the indoor room air inside IN the apparatus 1 through the first channel 12 and expel it outdoor OUT and, at the same time, draw the air from outside OUT and spread it indoor IN, as shown by the thick arrows. At this point, if the sensor that detects the intake air inside the room shows a value included in a settled comfort range, then apparatus 1 would be commanded in order to keep the first 5 and second 8 fan activated for an air renewal, without activating the thermodynamic circuit. In other words, the system would work in passive air mode, renewing the air inside the room.

[0030] The settled comfort range may be selected according to specific needs or preferences. Normally, a temperature range considered comfort could be between 15°C and 27°C, considering that the intake air mixes with the indoor air inside the room and thus tends not to modify substantially the inside temperature, being this cooler or warmer compared to the intake air. Preferably, the comfort temperature varies between 18°C and 25°C.

[0031] According to a second operating condition, as shown in figure 2, the aeraulic circuit described before with reference to figure 1 remains unaltered. On the contrary, in the thermodynamic circuit if after the activation of the mentioned first 5 and second 8 fan the sensor positioned along the second portion 10B of the duct 10 should register a temperature lower than the above mentioned comfort range, e.g. 15°C or lower, the command and control unit sends a start signal to the compressor 2. But since the compressor has a low cooling effect, i.e. lower than 0.8 kW, the pressure created inside the four way valve 3 is not sufficient for moving the piston in the position that allows the working fluid flow in the right and established direction. In fact, when the compressor turns on, the internal piston that regulates the functioning is blocked in a casual position, reason why the working fluid can pour out from all three ways, i.e. to the two exchangers and to the compressor. Obviously, the fluid will choose the shortest way that is the return to the compressor, creating therefore a recirculation closed loop involving only the compressor. The solenoid valve 15 included in the invention is closed and blocks therefore the gas suction duct. This condition creates a pressure differential between the discharge and the suction side of the working fluid in correspondence of the compressor 2.

[0032] When the above mentioned pressure differential reaches a preset set point value, e.g. higher than 2.5 bar, first the four way valve 3 activates energizing the spool of its pilot valve (not shown). In this way, the four way valve 3 prearranges in order to let the working fluid flow from the compressor outlet 2 toward the second heat exchanger 7. But being the solenoid or decompression valve 15 closed, the fluid under pressure is not sufficient for effectively moving the piston in the desired position. Therefore, solenoid valve 15 is opened, creating a sudden pressure differential downstream the compressor 2 and upstream the four way valve 3 which allows the piston to move and stop in the predetermined position for the flow of the fluid under pressure. It is to be considered that the blocking of the valve piston in the right position is guaranteed by the persisting pressure differential between suction and discharge of the compressor. It is to be noticed that in conventional conditions the piston could be just in the position for deviating the fluid coming from the compressor to the second exchanger 7, i.e. in the heating position ("winter" position), because the pressure inside the thermodynamic circuit equilibrates and, consequently, pilot valve is by default in a position allowing the piston to maintain said position.

[0033] In this way, the thermodynamic circuit of the heat pump apparatus is fixed in heating mode, i.e in winter mode. Therefore, when the hot working fluid is in the second heat exchanger 7 transfers heat to the air taken from outside OUT by the fan 8 through the second portion 10B of the duct 10 communicating, as explained before, with the second channel 13 where the mentioned second exchanger 7 and second fan 8 are lodged. As a consequence, the fresh, cool air coming from outside is heated and spread inside the room.

[0034] Afterwards, the condensed working fluid passes through the laminar element 6 and then evaporates absorbing heat inside the heat exchanger 4 positioned inside the first channel 12 of the housing 9 of the apparatus 1. Here hot, stuffy air of the room passes through the first exchanger, transferring heat to the working fluid. Stuffy, cooled air is expelled outside through the first portion 10A of the duct 10, while the pre-heated working fluid passes through the four way valve 3 where is led to the compressor inlet; in this way a new thermodynamic cycle for the treatment of incoming external cool air begins.

[0035] According to a third operating mode, as shown in figure 3, the aeraulic circuit described before with reference to figure 2 remains unaltered. On the contrary, the thermodynamic circuit is inverted with reference to the one shown in figure 2. In fact, if after the activation of the first 5 and second 8 fan the sensor positioned in the second portion 10B of the duct 10 detects an incoming temperature higher than the comfort temperature, e.g. 27°C, then the command and control unit activates the compressor 2. As explained before, when the compressor activates, the four way valve 3 deflects the discharge gas to suction the since the internal piston that regulates its functioning is blocked in a random position (or, as previously explained, into the position to draw the fluid towards the second exchanger 7). The electrically unpowered solenoid valve 15 is closed and blocks therefore the gas suction pipe. This condition creates therefore a pressure differential between suction and discharge side of the working fluid in correspondence of the compressor 2. When the above mentioned pressure differential reaches a preset set point value, e.g. higher than 2.5 bar, as before, the solenoid or decompression valve 15 is activated, i.e. it is opened, creating a sudden pressure differential downstream the compressor and upstream the four way valve, which allows the valve piston to move and stop in the predetermined position for the flow of the fluid under pressure. The blocking of the valve piston in the right position is guaranteed by the persisting pressure differential between suction and discharge of the compressor. As above, should the four way valve be in the "winter" position, the pilot valve would be energized to allow the movement of the valve piston to the desired position and, thanks to said pressure effect, it would be maintained in said position.

[0036] In this case, the four way valve 3 moves and blocks in the position for the flow of the fluid under pressure, and therefore heated, directly at the first exchanger 4.

[0037] In this way, the thermodynamic circuit of the apparatus is fixed in cooling mode, i.e. in summer mode. Hence, when the hot working fluid is in the first heat exchanger 4 transfers heat to the air taken from inside IN by the fan 5 through the first channel 12 communicating, as described before, with the first portion 10A of the duct 10 where respectively the mentioned first exchanger 4 and first fan 5 are lodged. As a consequence, stuffy, warm air coming from inside is overheated and expelled from the room.

[0038] Afterwards, the cooled working fluid passes through the laminar element 6 and then evaporates absorbing heat inside the second heat exchanger 7 positioned inside the second channel 13 of the housing 9 of the apparatus 1. Here the hot air from outside enters through the second portion 10B of the duct 10 and then passes through the second channel 13 and goes through the second exchanger 7 transferring heat to the working fluid. At the same time, the pre-heated working fluid passes through the four way valve 3 where it is led to the compressor inlet; in this way a new thermodynamic circuit for the treatment of hot external air begins.

[0039] According to a fourth operating mode, as shown in figure 4, the aeraulic circuit that in the previous conditions remains constant, in this case is modified. In fact, the butterfly valve 14 is rotated to 90° on its axis identified by the hinge 14A, so that each of the two wings 14B closes respectively one of the two portions, first 10A and second 10B, of the duct 10 and, at the same time, they put in direct and straight communication along axis Y-Y the first 12 and second 12 channel of the envelope 9.

[0040] It is evident that with this configuration the apparatus 1 is isolated from outside, while the air drawn from the first channel 12 passes in the second channel 13 that leads the air into the room.

[0041] Moreover, the thermodynamic circuit is activated in order to operate as a dehumidifier of the room internal air. In particular, the first fan 5 is turned on to draw the air from the room. Thanks to the above mentioned configuration, internal air is drawn from the mentioned first fan 5 in the first channel 12 and then passes directly in the second channel 13 of the housing 9 of the apparatus 1. Afterwards, the compressor 2 is turned on and, as referred before to "winter" operating mode, the four way valve 3 is activated after a predetermined time and later also the solenoid valve 15 in order to lead the hot and under pressure working fluid coming from the compressor 2 directly into the second heat exchanger 7. Therefore, incoming air inside the first channel 12 passes through the first heat exchanger 4 where condenses and then passes directly to the second channel 13. In the first channel 12, hot, humid air comes into contact with the first heat exchanger 4 where the cooled working fluid flows, after that it has passed through the second heat exchanger 7 and through the laminar valve 6. As a consequence, the hot, humid air condenses on the first cold heat exchanger 4 transferring humidity and is then spread dehumidified inside the room.

[0042] The above mentioned dehumidification cycle, as known, could cause the frost production on the external surface of the first heat exchanger 4. Therefore, the apparatus 1 is equipped with a defrost system that consists, for instance, in reversing the thermodynamic cycle for a short time until getting the defrosting. Moreover, there is a drip tray that can be removed for emptying or a drain directly to the outside or to other proper space.

[0043] Figure 5 represents a fifth operation mode, wherein the thermodynamic circuit is switched off, as on figure 1 , while the throttle valve 14 is operated so that to close the passage between inside IN and outside OUT of the room. In other words, the two wings 14B rotate with respect to the hinge 14A so that to position respectively one to close the passage between the first portion 10A of the conduct 10 of external communication and the first channel 12 of air intake, and the other to close the passage between the second portion 10B of the conduct 10 and the second channel 13 of air exit.

[0044] Another object of the present invention is an operating mode of an heat pump apparatus for air renewal inside domestic spaces. This mode includes the following steps in succession:

- providing a heat pump thermodynamic circuit equipped with a compressor with cooling capacity lower than 0.8 kW;

- mounting said circuit completely inside a domestic space connecting it to the outside with a duct;

- creating an air flow that passes through two heat exchangers of the thermodynamic circuit;

- switching on the heat pump compressor to force a working fluid in a four way valve while maintaining closed the working fluid passage upstream the compressor until reaching a pressure differential of the working fluid between suction and discharge side of the compressor higher than 2.5 bar;

- suddenly unblocking the passage upstream the compressor once reached the mentioned pressure differential in order to create a thrust sufficient to command the moving and blocking of the four way valve piston in the predetermined position.

[0045] In particular, the blocking of the working fluid before the compressor inlet has the purpose to create a depression in this point so that, when it is unblocked, the fluid is pushed rapidly and with high pressure inside the four way valve. This strong thrust compensates the lower power of the compressor in order to produce a sufficient pressure for moving the four way valve piston in the desired position and to keep it in this position.

[0046] In an operating condition, the air flow creation step to the two heat exchangers includes the air intake from inside to outside through a first portion of the duct communicating with a first channel where the first heat exchanger is lodged, and the air intake from outside to inside through a second portion of the duct in communication with a second channel where a second heat exchanger is positioned.

[0047] The compressor activation phase is followed, before the unblocking step, by a command step of the four way valve in order to deflect the flow of the working fluid to the first heat exchanger where the air flow directed from inside to outside passes through (cooling during summertime). Alternatively, this command phase deflects the air flow to the second heat exchanger where the air flow directed from outside to inside passes through (warming during wintertime).

[0048] According to a variation of the mode, the creation step of the air flow that passes through the first and second heat exchanger occurs along one single path inside the room and the said command step of the four way valve occurs in order to deflect the working fluid flow to the first heat exchanger where the intake air that enters the apparatus passes through.

[0049] Preferably, the operating mode is applied to an apparatus like the one described before.

[0050] As stated before, it is clear that the heat pump apparatus for air renewal inside rooms of the present invention allows advantageously to overcome the drawbacks claimed before referring to the technique known.

[0051] In fact, it is possible to supply an apparatus with especially compact dimensions and with low energy consumption to be mounted in spaces for domestic use, without affecting the proper working mode of the heat pump. This is made possible by the use of compressors with small dimensions and therefore small power, combined with a circulation circuit of the working fluid intercepted by a closing/opening valve like the solenoid valve described before to compensate the small power of the compressor.

[0052] In addition to this, the apparatus is advantageously versatile since it can work both for heating the room during the winter and cooling in summer, as well as dehumidifying. As explained, it can be additionally used to simply renew the stuffy air inside the room.

[0053] Therefore, from the health and comfort point of view, the apparatus enables the setup of the best conditions according to the climate and/or according to specific needs and preferences.

[0054] The apparatus can further be switched off and closed to the outside, simply for preventing the intake of pollutants which could pass through conventional filters.

[0055] Many variations of the apparatus can be applied by the field technician, without however falling outside the scope of protection as defined by the claims attached.

[0056] For instance, the second portion 10B of the communication duct 10 to the outside or the second channel 13 of the housing 9 can be provided with an air filter with the aim of holding potential undesired particles as fine dust and pollen and to avoid insects from entering.

[0057] Each of the two fans, first 5 and second 8, can be controlled by the command and control unit at variable speed in order to adjust itself to the variation of the working conditions of the apparatus, that in turn depend on the ambient/climate conditions.

[0058] Many sensors can be installed in different positions inside and outside the housing 9 and the duct 10 of the apparatus in order to monitor both internal and external conditions of the room, as e.g. temperature, humidity, atmospheric pressure.

[0059] The command and control unit can be connected to all devices, sensors, movable parts of the apparatus in order to receive in real time signal representative of the devices status, elaborate these signals in order to compare them to the parameters preset in its working memory and send control signals coordinated among all mentioned devices and sensors.

[0060] It is also to take into consideration that the use of conventional compressors could be considered when no space restrictions occur. In this situation, obviously, there would not be the desired energy saving above mentioned. However, to obviate to this drawback, the apparatus can be provided with devices such as inverter to compensate the higher energy consumption. Said apparatuses are obviously adapted to large rooms where it would be necessary the use of powerful compressors, but not so powerful to avoid the use of the additional solenoid valve.

Claims

1. Heat pump apparatus (1) for changing air in domestic rooms, comprising a box element (9) to be fixed on a wall (W) or ceiling inside a domestic room, the box element being adapted to contain a compressor (2) for the circulation of a working fluid under pressure, a four-way valve (3) for deviating the flux of said fluid towards a first heat-exchanger (4) combined with a first fan (5) for sucking the inside air, or towards a second heat-exchanger (7) combined to a fan (8) for blowing air into the room, a laminar element (6), and the apparatus further comprising a duct (10) for connecting said box element with the outside, characterized in that an opening/closing valve (15) intercepts the flux of said working fluid upward the compressor (2) and downward the four-way valve (3).

2. Apparatus (1) according to claim 1 , wherein said opening/closing valve (15) is a solenoid valve.

3. Apparatus (1) according to claim 1 or 2, wherein said duct (10) is provided with a longitudinal and middle septum (11) dividing the same duct into two symmetric and distinct portions, a first portion (10A) for expelling the inside air of the room, which first portion communicates with a first channel (12) of the box element (9) wherein the first heat-exchanger (4) is contained, a second portion (10B) for introducing air from the outside of the room, which second portion communicates with a second channel (13) of the box element (9) wherein a second heat-exchanger (7) is contained.

4. Apparatus (1) according to claim 3, further comprising a valve (14) which alternately puts into communication said first portion (10A) of the duct (10) with said first channel (12) of the box element (9) and said second portion (10B) of the duct (10) with said second channel (13) of the box element (9), or it closes the passage between said conduct (10) and said first (12) and second channels (13) instead putting into direct communication said first (12) and second (13) channels.

5. Mode of operation a heat pump apparatus for the change of air of domestic rooms, comprising the following steps in succession:

- providing a thermodynamic heat pump circuit comprising a compressor with a cooling capacity lower than 0.8KW;

- mounting said circuit entirely inside a domestic room, connecting the circuit with outside through a duct;

- creating an air flux crossing two heat-exchangers of the thermodynamic circuit; - switching on the compressor of the heat pump to force a working fluid into a four- way valve while maintaining closed the working fluid passage upward the compressor until a difference of pressure of the working fluid between the suction side and the discharge side of the compressor greater than 2,5 bar is obtained;

- suddenly unblocking the upward passage of the compressor when the above difference of pressure is reached in order to exercise a push sufficient to command the moving and blocking of the piston of the four-way valve in the preselected position.

6. Method according to claim 5, wherein the step of creating the air flux to the two heat-exchangers comprises the suction of air from inside to outside through a first portion of the duct communicating with a first channel wherein a first heat- exchanger is positioned, and comprises the suction of outside air to inside through a second portion of said duct communicating with a second channel wherein a second heat-exchanger is positioned.

7. Method according to claim 5 or 6, wherein the step of switching on the compressor is followed, before the unblocking step, by a command step of the four-way valve in order to deviate the flux of the working fluid toward the first heat-exchanger, which first heat-exchanger is crossed by the air flux directed from inside to outside.

8. Method according to claim 5 or 6, wherein the step of switching on the compressor is followed, before the opening step, by a command step of the four-way valve in order to deviate the flux of the working fluid toward the second heat-exchanger, which second heat-exchanger is crossed by the air flux directed from outside to inside.

9. Method according to claim 8, wherein the step of creating the air flux that crosses the two first and second heat-exchangers is carried out a single pathway inside the room and said command step of the four-way valve is carried out in order to deviate the flux of the working fluid towards the first heat-exchanger which first heat-exchanger is crossed by the air entering the apparatus.