FIELD

The present invention relates to heat pump systems.

BACKGROUND

Air source heat pump systems (ASHP) may transfer heat from outside to inside a building. The heat pump system comprises typically an outdoor unit, which comprises a heat exchanger arranged to transfer heat from outdoor air to a refrigerant. The heat may be subsequently transferred to indoor air by using a compressor and a second heat exchanger. The outdoor unit is typically positioned outside the building, e.g. on a supporting structure attached to the wall of the building.

SUMMARY

An object of the invention is to provide an evaporator unit for a heat pump system. An object of the invention is to provide a heat pump system. An object of the invention is to provide a building, which comprises an evaporator unit. An object of the invention is to provide a method of heating a building. An object of the invention is to provide a method for transporting a building element.

According to an aspect, there is provided an evaporator unit (100) for a heat pump system (500), the evaporator unit (100) comprising:

- a heat exchanger (10),

- a first inlet portion (AP1 ),

- a second inlet portion (AP2),

- a first channel portion (DP1 ) arranged to guide outdoor air (AIR1 ) from the first inlet portion (AP1 ) to the heat exchanger (10), - a second channel portion (DP2) arranged to guide outdoor air (AIR1 ) from the second inlet portion (AP2) to the heat exchanger (10), and

- an axial fan (20) arranged to provide an air jet (JET2) by drawing cooled air (AIR2) from the heat exchanger (10) such that that the distance (di) between the first inlet portion (AP1 ) and the impeller (25) of the fan (20) is smaller than 30% of the initial width (W _JE T2) of the jet (JET2), and the distance (d2) between the second inlet portion (AP2) and the impeller (25) of the fan (20) is smaller than 30% of the initial width (W _JE T2) of the jet (JET2), wherein the fan (20) is located between the first channel portion (DP1 ) and the second channel portion (DP2).

According to an aspect, there is provided a heat pump system, which comprises the evaporator unit. According to an aspect, there is provided a building, which comprises the evaporator unit.

According to an aspect, there is provided a method for heating a building, the method comprising:

- guiding outdoor air (AIR1 ) from a first inlet portion (AP1 ) to a heat exchanger (10) via a first channel portion (DP1 ),

- guiding outdoor air (AIR1 ) from a second inlet portion (AP2) to the heat exchanger (10) via a second channel portion (DP2),

- transferring heat from the outdoor air (AIR1 ) by cooling the outdoor air (AIR1 ) in the heat exchanger (10),

- drawing cooled air (AIR2) from the heat exchanger (10) by an axial fan (20), and

- providing an air jet (JET2) by said axial fan (20) such that that the distance (d1 ) between the first inlet portion (AP1 ) and the impeller (25) of the fan (20) is smaller than 30% of the initial width (wJET2) of the jet (JET2) and the distance (d2) between the second inlet portion (AP2), and the impeller (25) of the fan (20) is smaller than 30% of the initial width (wJET2) of the jet (JET2), wherein the fan (20) is located between the first channel portion (DP1 ) and the second channel portion (DP2). Thanks to the location of the fan between the inlet channel portions, the outer dimensions of the evaporator unit may be reduced or minimized. This in turn may maximize the free usable floor area inside the building and also the free ground area outside the building.

In an embodiment, the evaporator unit may be installed in a portable building. The portable building may be transported e.g. with a trailer. The evaporator unit may be installed such that the evaporator unit may be moved inwards for transportation and outwards for operation. The evaporator unit may be moved inwards in order to avoid damaging the evaporator unit during transportation of the building. After the transportation, the evaporator unit may be moved outwards in order to maximize free floor area inside building during operation of the evaporator unit. In an embodiment, the evaporator unit may comprise an outlet for guiding condensed water into a drain system.

In an embodiment, the evaporator unit may comprise a ventilation air inlet for extracting heat from warm ventilation air.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following examples, several variations will be described in more detail with reference to the appended drawings, in which

Fig. 1 shows, by way of example, in a cross-sectional view, a heat pump apparatus, which comprises an evaporator unit and a compressor unit,

Fig. 2 shows, by way of example, in a cross-sectional view, the evaporator unit, shows, by way of example, in a cross-sectional view, dimensions of the evaporator unit, Fig. 3b shows, by way of example, in a cross-sectional view, dimensions of the evaporator unit, Fig. 4a shows, in a three dimensional view, an opening in the wall of a building,

Fig. 4b shows, in a three dimensional view, the evaporator unit installed in the opening,

Fig. 5a shows, by way of example, in a cross-sectional view, the evaporator unit,

Fig. 5b shows, by way of example, in a three dimensional view, the evaporator unit of Fig. 5a,

Fig. 5c shows, by way of example, in a frontal view, the evaporator unit of Fig. 5a, Fig. 5d shows, by way of example, in a cross-sectional view, the evaporator unit of Fig. 5a,

Fig. 6a shows, by way of example, in a cross-sectional view, the evaporator unit,

Fig. 6b shows, by way of example, in a three dimensional view, the evaporator unit of Fig. 6a,

Fig. 7a shows, by way of example, in a cross-sectional view, an evaporator unit, which comprises auxiliary air inlets,

Fig. 7b shows, by way of example, in a cross-sectional view, the evaporator unit of Fig. 7a in a retracted position, Fig. 8a shows, by way of example, in a three dimensional view, a retractable evaporator unit in an operating position,

Fig. 8b shows, by way of example, in a three dimensional view, the retractable evaporator unit in a transport position,

Fig. 9a shows, by way of example, in a cross-sectional view, an evaporator unit, which comprises a retractable flow guide, Fig. 9b shows, by way of example, in a cross-sectional view, the evaporator unit of Fig. 9a when the flow guide is in an outward position,

Fig. 10a shows, by way of example, in a three dimensional view, an evaporator unit,

Fig. 10b shows, by way of example, in a three dimensional view, an evaporator unit, Fig. 1 1 shows, by way of example, in a frontal view, an evaporator unit,

Fig. 12a shows, by way of example, in a cross-sectional side view, an evaporator unit, which comprises an inlet for ventilation air, Fig. 12b shows, by way of example, in a cross-sectional side view, an evaporator unit, which comprises a heated outlet for condensed water, and

Fig. 12c shows, by way of example, in a cross-sectional side view, an evaporator unit, which comprises a heat transfer element to transfer heat from ventilation air to the water outlet.

All figures are schematic. DETAILED DESCRPTION

Fig. 1 shows a heat pump apparatus 500 installed in a building 900. The heat pump apparatus 500 may be arranged to heat the building 900. The heat pump apparatus 500 may comprise an evaporator unit 100 and a compressor unit 200. The evaporator unit 100 may be installed e.g. in an opening 912 of the wall 910 of the building 900 (see Fig. 4a). The opening 912 of the wall may extend through the wall. The evaporator unit 100 may also be called e.g. as a "wall unit". The evaporator unit 100 may also be called e.g. as an evaporator device. The evaporator unit 100 may also be called e.g. as a heat exchanger device.

The compressor unit 200 may be installed inside the building 900. The heat pump apparatus 500 may comprise conduits CON1 , CON2 for guiding refrigerant R1 from the evaporator unit 100 to a compressor unit 200, and for guiding the refrigerant R1 from the compressor unit 200 back to the evaporator unit 100.

The evaporator unit 100 may comprise two or more air inlet portions AP1 , AP2, a heat exchanger 10, and a fan 20. The evaporator unit 100 may comprise two or more air channel portions DP1 , DP2. A first air channel portion DP1 may be arranged to guide outdoor air AIR1 from a first air inlet portion AP1 to the heat exchanger 10. A second air channel portion DP2 may be arranged to guide outdoor air AIR1 from a second air inlet portion AP2 to the heat exchanger 10. The fan 20 may be arranged to suction air AIR1 through the heat exchanger 10. The fan 20 may be arranged to cause a suction, which draws air through the heat exchanger 10. The fan 20 may be an axial fan. The axial fan 20 may comprise a rotating impeller 25, which may be arranged to suction air guided through the heat exchanger 10. The impeller may comprise a plurality of blades. The fan 20 may comprise an electric motor 27, which may be arranged to rotate the impeller 25. The electric motor 27 may be positioned e.g. in a duct 30 between the heat exchanger 10 and the impeller 25. The electric motor 27 may also be integrated in the impeller 25, in order to minimize the depth of the evaporator unit 100. The air flow may enter the fan 20 after passing through the heat exchanger 10. The heat exchanger 10 may be at the suction side of the fan 20. The heat exchanger 10 also may operate as a filter or grille, which may prevent large particles from impacting on the impeller 25 of the fan 20. Positioning the fan downstream of the heat exchanger may e.g. protect the fan 20 from ice, which may be formed at the input side of the heat exchanger 10. Positioning the fan downstream of the heat exchanger may e.g. protect the fan from debris, which may be carried by the air. Positioning the fan downstream of the heat exchanger may provide a more uniform air flow through the heat exchanger 10. Uniform spatial distribution of velocity of the air entering the heat exchanger may improve efficiency of the evaporator unit, may allow reducing the power of the fan and/or may allow reducing the size of the heat exchanger.

The heat exchanger 10 may provide cooled air AIR2 by transferring heat from the outdoor air AIR1 to the refrigerant R1 . Heat may be transferred from the outdoor air AIR1 to the refrigerant R1 by cooling the outdoor air AIR1 in the heat exchanger 10. The fan 20 may discharge an air jet JET2 from an exit opening OP2 of the evaporator unit 100. The air jet JET2 discharged from the fan 20 may comprise the cooled air AIR2 provided by the heat exchanger 10. The peripheral portions of the jet JET2 may be mixed with outdoor air. The peripheral portions of the jet JET2 may further comprise entrained air AIR1 ' (see Fig. 2).

The jet JET2 may be discharged into a relatively open space outside the building. Consequently, the jet JET2 may be a so-called free jet.

The heat exchanger 10 may transfer heat from the outdoor air AIR1 to the refrigerant R1 . The heat exchanger 10 may comprise one or more channels for guiding the refrigerant R1 from a refrigerant input F1 a to a refrigerant output F1 b. The heat exchanger 10 may comprise one or more heat transfer elements for transferring heat from the outdoor air AIR1 to the refrigerant R1 contained in the channels. The heat exchanger 10 may be e.g. a finned tube heat exchanger, which comprises one or more tubes and an array of plates. The plates may be arranged to conduct heat from the outdoor air AIR1 to a refrigerant R1 contained in the one or more tubes. The heat pump system 500 may be arranged to operate such that the temperature of refrigerant R1 guided to the compressor 220 is as high as possible, in order to improve the efficiency of the heat pump system 500. The heat pump system 500 may be arranged to operate such that the temperature difference between the outdoor air AIR1 and the temperature of the refrigerant R1 guided from the heat exchanger 10 is smaller than a predetermined limit. The refrigerant R1 may be guided from the outlet F1 b evaporator unit 100 to an inlet F2a the compressor unit 200 by a first conduit CON1 . Refrigerant R1 may be guided from an outlet F2b the compressor unit 200 to the inlet F1 b of the evaporator unit 100 by a second conduit CON2. The conduits CON1 , CON2 may be connected to the evaporator unit 100 and/or to the compressor unit 200 e.g. by fittings. The conduits CON1 , CON2 may be e.g. tubes or hoses. In an embodiment, the conduits CON1 , CON2 may be flexible in order to allow moving the evaporator unit 100 without opening the fittings. The compressor unit 200 may comprise a compressor 220, a condenser 210, and an expansion element 250. The expansion element 250 may be e.g. a valve or a constriction. The compressor 220 may receive refrigerant R1 from the evaporator unit 100 via the first conduit CON1 . The compressor 220 may compress the refrigerant R1 such that the refrigerant R1 releases heat in the condenser 210. The expansion element 250 may receive refrigerant R1 from the condenser 210, and the expansion element 250 may provide a flow of expanded refrigerant R1 . The expansion element 250 may cause a pressure drop of the refrigerant R1 . The expanded refrigerant R1 may be guided to the evaporator unit 100 via the conduit CON2. The condenser 210 may transfer heat from the refrigerant R1 to a heat transfer fluid Q1 . The condenser 210 may optionally comprise a second heat exchanger for transferring heat from the refrigerant R1 to the heat transfer fluid Q1 . The condenser 210 may receive heat transfer fluid Q1 , and the condenser 210 may provide heated heat transfer fluid Q2. The heat transfer fluid Q1 may be e.g. water, heat transfer oil, or a second refrigerant. The temperature difference between the input fluid Q1 and the heated fluid Q2 may be e.g. in the range of 2°C to 70°C. The temperature difference between the indoor air and the heated fluid Q2 may be e.g. in the range of 2°C to 70°C. The heating system may be further arranged to transfer heat from the fluid Q2 to indoor air and/or to a structure of the building 900. For example, the fluid Q2 may be circulated in one or more radiators. For example, the fluid Q2 may be arranged to heat a floor of the building 900. The fluid Q2 may be arranged to heat e.g. household water, which may be subsequently used e.g. for washing. The fluid Q2 may be hot household water. The compressor 220 may be operated e.g. by using an electric motor. The electric motor may be integrated in the compressor. The heat pump system may optionally comprise an electric heater to assist in the heating of the fluid Q1 in a situation where the temperature of the outdoor air AIR1 is very low, e.g. when the temperature of the outdoor air AIR1 is lower than -25°C.

The compressor 220 may be located inside the building 900. In particular, the temperature of the environment of the compressor unit 200 may be equal to or higher than the temperature of indoor air inside the building 900. This may improve operating reliability of the compressor. The compressor unit 200 may be e.g. standing on the floor of the building or the compressor unit 200 may be mounted on a wall.

The temperature of the interior of the evaporator unit 100 may be substantially equal to the temperature of the outdoor air AIR1 . The interior of the evaporator unit 100 may be rather cold. The evaporator unit 100 may comprise thermal insulation 120 in order to reduce heat loss through the evaporator unit 100. The evaporator unit 100 may comprise thermal insulation 120 in order to reduce heat loss from the indoor air to the cold outdoor air AIR1 . The heat transfer coefficient ("U-value") of the thermal insulation 120 may be e.g. lower than or equal to 1 .0 W-K ^"1 m ^"2 . The heat transfer coefficient ("U-value") of the back panel of the evaporator unit 100 may be e.g. lower than or equal to 1 .0 W-K ^{' 2} .

The evaporator unit 100 may comprise a housing. The housing may comprise the back panel 102 and side panels 104, 106. The housing may partly define the inlet channel portions DP1 , DP2. The side panels 104, 106 may partly define the inlet channel portions DP1 , DP2. The housing may comprise e.g. metal sheets. The housing may comprise e.g. plastic and/or composite material (e.g. fiberglass-resin-composite). The housing may comprise thermally insulating material. The back panel 102 of the evaporator unit 100 may comprise thermal insulation 120. The side panels 104, 106 of the evaporator unit 100 may comprise thermal insulation 120. A first side panel 104 may partly define the channel portion DP1 , and a second side panel 106 may partly define the channel portion DP2. The panels 102, 104, 106 may comprise thermal insulation 120. The thermally insulated portions of the side panels 104, 106 may at least partly overlap the wall 910 during operation.

The side panels 104, 106 and the back panel 102 of the evaporator unit 100 may be thermally insulated such that the heat transfer coefficient ("U-value") of the back panel of the evaporator unit 100 is lower than or equal to 1 .0 W-K ^"1 m ^"2 .

The thermally insulating material may be e.g. plastic foam or rubber foam. Thermally insulating material may be e.g. polyethylene foam, expanded polystyrene foam, phenolic foam, polyurethane foam, urea foam, urea- formaldehyde foam, and/or polyisocyanurate foam. The thermally insulating material may be e.g. vacuum-insulated panel (VIP), in order to minimize the thickness of the thermal insulation. The vacuum-insulated panel may comprise a rigid porous panel, a membranes to prevent access of air into the panel, and a getter to collect gases leaked through the membrane.

The thermal insulation material may also bear mechanical loads of the structure. The thermal insulation material may also be arranged to operate a flow guiding structure. The thermal insulation may also be arranged to suppress noise generated by the fan 20. The cooled air AIR2 may be guided from the heat exchanger 10 to the fan 20 by a duct 30.

A gap between the evaporator unit 100 and the wall 910 may be optionally sealed with one or more seals S1 . SX, SY and SZ denote orthogonal directions. The direction SZ may be opposite to the direction DIR2 of the air jet JET2. The axis of rotation of the impeller 25 may be substantially parallel to the direction SZ.

The evaporator unit 100 may protrude by a distance b1 with respect to the outer surface of the wall 910 of the building 900.

AIR3 may denote indoor air inside the building 900. The indoor air AIR3 may be guided out of the building 900 as ventilation air.

Fig. 2 illustrates air flows of the evaporator unit 100. The first channel portion DP1 may guide outdoor air AIR1 from a first inlet portion AP1 to the heat exchanger 10. The second channel portion DP2 may guide outdoor air AIR1 from a second inlet portion AP2 to the heat exchanger 10. The heat exchanger 10 and the fan 20 may be located between the first inlet channel portion DP1 and the second inlet channel portion DP2.

Thanks to using the inlet channel portions DP1 , DP2 on both sides of the fan 20, the size of the evaporator unit 100 may be substantially minimized. In particular, the length bioo of the evaporator unit 100 may be reduced or minimized, because using the channel portions DP1 , DP2 on both sides of the unit 100 may allow minimizing the gap between the heat exchanger 10 and the back panel of the unit 100. Reducing the length b ioo may increase the free floor area inside the building 900 and/or reducing the length b ioo may increase the free ground area outside the building 900.

The exit opening OP2 of the fan 20 may be located between the first inlet portion AP1 and the second inlet portion AP2. The fan 20 may be located between the channel portions DP1 , DP2. The impeller 25 of the fan 20 may be located between the channel portions DP1 , DP2. The heat exchanger 10 may be located between the first channel portion DP1 and the second channel portion DP2. The first inlet portion AP1 and a second inlet portion AP2 may be close to the exit opening OP2 of the fan 20. The first inlet portion AP1 , the second inlet portion AP2, and the exit opening OP2 may even be substantially in the same plane PLN1 .

The fan 20 of the evaporator unit 100 may provide the air jet JET2. The jet JET2 may be discharged from the exit opening OP2 of the fan 20. The exit opening OP2 may be optionally protected e.g. with a protective grille (Fig. 1 1 ).

The heat exchanger 10 may provide cooled air AIR2 by transferring heat from the outdoor air AIR1 to the refrigerant R1 . The fan 20 may draw the cooled air AIR2, which has passed through the heat exchanger 10. The fan 20 may cause a partial vacuum, which draws the cooled air AIR2. The fan 20 may provide the jet JET2 by blowing the cooled air drawn through the heat exchanger 10. The fan 20 may suction air through the heat exchanger 10, and the fan 20 may discharge the cooled air AIR2 as the jet JET2. The direction DIR _D pi of air flow in the first channel portion DP1 may be substantially opposite to the direction DIR2 of air flow of the jet JET2. The direction DIR _D p2 of air flow in the second channel portion DP2 may be substantially opposite to the direction DIR2 of air flow of the jet JET2. The direction DIR _D pi of air flow in the first channel portion DP1 may be substantially parallel to the direction DIR _D p2 of air flow in the second channel portion DP2.

The spatially averaged direction of the air stream at the inlet openings AP1 , AP2 may be substantially opposite to the direction DIR2 of air flow of the jet JET2.

The initial width W _{J E} T2 of the air jet JET2 (Fig. 3a) may be determined by the dimension of the exit opening OP2. The initial width W _{J E} T2 may be e.g. in the range of 300 mm to 1000 mm. The jet JET2 may have a central axis AX2. The fan 20 may be an axial fan, and the central axis AX2 of the jet JET2 may be substantially parallel to the rotation axis of the fan 20.

The air jet JET2 may be turbulent. Shear forces between the air jet JET2 and the ambient outdoor air may cause entrainment and mixing of the ambient outdoor air AIR1 ' into the air jet JET2. The turbulent jet JET2 may suck ambient air AIR1 ' towards the JET2. The direction of movement of the outdoor air AIR1 , AIR' near the wall 910 may be substantially parallel to the wall 910 of the building 900.

The heat exchanger extracts heat from the outdoor air AIR1 such that the temperature of the jet JET2 is lower than the temperature of the outdoor air AIR1 . The heat exchanger 10 may provide cooled air AIR2 by extracting heat from the outdoor air AIR1 . The inlet portions AP1 , AP2 may be relatively close to the opening OP2. Circulation of the cold air AIR2 into the inlet portions AP1 , AP2 could decrease the efficiency of the heat pump system 500. However, the jet JET2 may substantially freely discharged into the open space outside the building so that circulation of the cooled air AIR2 of the free jet JET2 into the air inlet portions AP1 , AP2 may be low or negligible. Thus, the first inlet portion AP1 , and the second inlet portion AP2 may be positioned close to the exit opening OP2 so that the size of the evaporator unit 100 may be minimized, without causing circulation of the cooled air AIR2 to the inlet portions AP1 , AP2. The distance l_i between the inlet portion AP1 and the exit opening OP2 may be e.g. smaller than 30% of the width w ₀ p ₂ of the opening OP2. The distance L ₂ between the inlet portion AP2 and the exit opening OP2 may be e.g. smaller than 30% of the width w ₀ p ₂ of the opening OP2. The distances l_i and L ₂ may be e.g. in the range of 10% to 30% of the width w ₀ p ₂ of the opening OP2. The distances l_i and L ₂ may be e.g. in the range of 5% to 15% of the width wioo of the evaporator unit 100.

The position of the fan 20 after the heat exchanger 10 may provide a more confined air jet JET2, which may reduce circulation of the cooled air to the air inlet portions AP1 , AP2. The position of the turbulent jet JET2 between the inlet openings AP1 , AP2 may ensure that the outdoor AIR1 moves towards the jet JET2 in the vicinity of the openings AP1 , AP2. This may effectively prevent circulation of the cooled air AIR2 of the jet JET2 to the inlet openings AP1 , AP2. Positioning the turbulent jet JET2 between the inlet openings AP1 , AP2 may substantially prevent circulation of the cooled air AIR2 of the jet JET2 to the inlet openings AP1 , AP2.

Figs. 3a and 3b show dimensions of the evaporator unit 100. The exit opening OP2 may have a width w ₀ p2- The jet JET2 may have an initial width WJET2- The jet JET2 has the initial width W _{J E} T2 just after it has been discharged from the exit opening OP2, immediately downstream of the exit opening OP2. The initial width W _{J E} T2 of the jet JET2 may be defined by the exit opening OP2. The initial width W _{J E} T2 of the jet JET2 may be substantially equal to the width w ₀ p2- The inlet opening AP1 may have a width w _A pi . Li denotes the distance between the inlet opening AP1 and the exit opening OP2. L ₂ denotes the distance between the inlet opening AP2 and the exit opening OP2. The total length of the bioo of the evaporator unit 100 may be e.g. slightly greater than the thickness s1 of the wall 910. The total length of the bioo of the evaporator unit 100 may be e.g. in the range of 400 mm to 600 mm. The frontal face of evaporator unit 100 may protrude by a length b1 with respect to the outer surface of the wall 910. The back panel of the evaporator unit 100 may protrude by a length b2 with respect to the inner surface of the wall 910.

The wall 910 may comprise thermal insulation. The thickness s1 of the wall 910 may be e.g. in the range of 100 mm to 400 mm. The building 900 may be arranged to operate in arctic conditions, and the thickness of the thermal insulation of the wall 910 may be relatively high. A large part of the evaporator unit 100 may be "hidden" inside the wall . Installing the evaporator unit 100 in the opening of the wall may represent optimum usage of floor area.

Referring to Fig. 3b, the inlet opening AP1 may have a width w _A pi . The inlet opening AP2 may have a width w _A p2- di may denote the distance between the inlet opening AP1 and the impeller 25 of the fan 20. d2 may denote the distance between the inlet opening AP2 and the impeller 25 of the fan 20. The fan 20 may be close to the inlets AP1 , AP2 in order to minimize the size of the evaporator unit 100 and/or in order to minimize flow resistance. The distances di, d ₂ may be e.g. smaller than 30% of the initial width W _{J E} T2 of the jet JET2. The distances di, 02 may be e.g. smaller than 30% of the width w ₀ p2 of the opening OP2. The distances di, 02 may be e.g. smaller than 10% of the width wioo of the evaporator unit 100.

The distances di, 02 may be e.g. smaller than 30% of the initial width W _{J E} T2 of the jet JET2, and the distances l_i and L ₂ may be in the range of 10% to 30% of the initial width w _JET2 .

The fan 20 may be arranged to provide the air jet JET2 by drawing cooled air AIR2 from the heat exchanger 10 such that that the distances di and d ₂ are smaller than 30% of the initial width W _{J E} T2 of the jet JET2. The diameter w ₂ 5 of the impeller 25 may be substantially equal to the width wj _ET 2 of the opening OP2. The distance di may be e.g. smaller than 30% of the diameter w ₂ 5 of the impeller 25. The distance d ₂ may be e.g. smaller than 30% of the diameter w ₂₅ of the impeller 25. The distances di, d ₂ may be e.g. smaller than 30% of the diameter w ₂₅ of the impeller 25. The fan 20 may be arranged to provide the air jet JET2 by drawing cooled air AIR2 guided through the heat exchanger 10 such that that the distances di and d ₂ are smaller than 30% of the diameter w ₂₅ of the impeller 25.

The axial fan 20 may be arranged to provide the air jet JET2 by drawing cooled air AIR2 guided through the heat exchanger 10 such that that the distance di is smaller than 30% of the initial width w _JET2 . The axial fan 20 may be arranged to provide the air jet JET2 by drawing cooled air AIR2 guided through the heat exchanger 10 such that that also the distance d ₂ is smaller than 30% of the initial width w _JET2 . The fan 20 may be located between the first channel portion DP1 and the second channel portion DP2.

Referring to Figs. 4a and 4b, the evaporator unit 100 may be installed in an opening 912 of the wall 910 of a building 900. The building 900 may comprise the evaporator unit 100. The building 900 may comprise a heat pump system 500, which comprises the evaporator unit 100. The floor area of the building may be e.g. greater than 100 m ² , greater than 200 m ² , greater than 500 m ² , greater than 1000 m ² , or even greater than 2000 m ² . The rated thermal power of the heat pump system 500 may be large. Thanks to using the evaporator unit 100, the free floor area inside and/or free ground area outside the building 900 may be increased.

The building 900 has a roof 920. The building 900 may comprise a door 950 and/or a window 960.

Referring to Fig. 5a, the inlet channel portions DP1 , DP2 may be e.g. at both sides of the evaporator unit 100. The fan 20 may be located between the first inlet channel portion DP1 and the second inlet channel portion DP2. The exit opening OP2 of the fan 20 may be located between the first inlet portion AP1 and a second inlet portion AP2. The first inlet portion AP1 may be located e.g. on the left hand side of the fan 20, and the second inlet portion AP2 may be located on the right hand side of the fan 20.

The first inlet portion AP1 and the first channel portion DP1 may also be located e.g. above the fan 20, and the second inlet portion AP2 and the second channel portion DP2 may be located below the fan 20.

The evaporator unit 100 may have a height h ioo, a width wioo, and a length bioo- The height hioo may be measured in the direction SY, the width wioo may be measured in the direction SX, and the length bioo may be measured in the direction SZ. The length bioo may also be called e.g. as the depth. The evaporator unit 100 may be installed in an opening of a wall 910 such that the wall is substantially parallel to the plane defined by the directions SX and SY.

The symbols A-A define a plane for the cross-sectional view of Fig. 5d.

Fig. 5b shows, in a three-dimensional view, the evaporator unit 100 of Fig. 5a. The channel portions DP1 , DP2 may be located on both sides of the fan 20 and the heat exchanger 10. The channel portions DP1 , DP2 may also be portions of an inlet channel, which partly or completely surrounds the heat exchanger 10.

The total cross-sectional open area of the inlet channel portions of the unit 100 may be e.g. in the range of 20% to 100% of the total cross-sectional area of the inlet channel portions of the unit 100. The open area may be selected to be large in order to reduce the effect of flow resistance of the inlet portions. The inlet portions AP1 , AP2 may be e.g. openings of a front panel 50. The front panel 50 of the unit 100 may comprise a plurality of air inlet openings AP1 , AP2. The front panel 50 may comprise e.g. a metal sheet, plastic sheet and/or composite material. The air inlet openings AP1 and/or AP2 may be holes formed in the metal sheet 50. The inlet portions may be optionally protected e.g. by a grille, in order to reduce entrainment of debris into the channel portions. The grille may comprise e.g. metal wires and/or plastic.

The front panel 50 may also provide structural stability to the evaporator unit 100. The total cross-sectional open area of the frontal openings of the unit 100 may also be smaller than 100% of the total cross-sectional area of the inlet channel portions, in order to provide a more rigid front panel and a more stable mechanical structure. A panel 50 having a plurality of holes AP1 , AP2 may be more rigid than e.g. a grille formed of metal wires. The front panel 50 of the unit 100 may comprise a plurality of inlet openings AP1 and/or AP2 so that the total cross-sectional area of the frontal openings of the unit 100 is e.g. in the range of 20% to 80% of the total cross-sectional area of the inlet channel portions of the unit 100.

The total cross-sectional area of the frontal openings may be determined in a plane, which is perpendicular to the direction of the air jet JET2. The total cross-sectional area of the inlet channel portions may be determined in a plane, which is perpendicular to the direction of the air jet JET2. The total cross-sectional area of the openings means the sum of the cross-sectional areas of the individual openings. The total cross-sectional area of the inlet channel portions means the sum of the cross-sectional areas of the channel portions. Fig. 5c shows, in a frontal view, the evaporator unit 100 of Fig. 5a.

Fig. 5d shows, in a cross-sectional view, the inlet channel portions DP1 , DP2 located on both sides of the heat exchanger 10. The view of Fig. 5d represents the cross-section along the plane A-A shown in Fig. 5a.

The cross-sectional area of the first channel portion DP1 may be e.g. greater than 10% of the cross-sectional area of the heat exchanger 10, and the cross-sectional area of the second channel portion DP2 may be e.g. greater than 10% of the cross-sectional area of the heat exchanger 10.

Fig. 6a shows, in a cross-sectional side view, an evaporator unit 100. Fig. 6b shows, in a three-dimensional view, the evaporator unit 100 of Fig. 2a. The channel portions DP1 , DP2 may be portions of an inlet channel, which partly or completely surrounds the heat exchanger 10. The channel portions DP1 , DP2 may be portions of a single inlet channel, which partly or completely surrounds the heat exchanger 10.

The evaporator unit 100 may be implemented such that the unit 100 comprises air inlets AP1 , AP2 only at the frontal plane PLN1 of the unit 100.

The dimensions and structures discussed with reference to Figs. 5a to 6b may apply to the evaporator unit 100 discussed with reference to Fig. 1 and 2.

A front panel 50 of the unit 100 may comprise a plurality of inlet openings AP1 and/or AP2 so that the total cross-sectional area of the frontal openings of the unit 100 is in the range of 20% to 80% of the total cross-sectional area of the inlet channel portions of the unit 100. A front panel 50 of the unit 100 may comprise a plurality of inlet openings AP1 and/or AP2 so that the total cross-sectional area of the frontal openings of the unit 100 is in the range of 20% to 100% of the total cross-sectional area of the inlet channel portions of the unit 100. Referring to Fig. 7a, the evaporator unit 100 may optionally comprise a plurality of auxiliary openings AP1 ', AP2' in order to reduce the effect of flow resistance of frontal air inlet openings AP1 , AP2. The evaporator unit 100 may further comprise one or more auxiliary openings AP1 ', AP2', in addition to the frontal openings AP1 , AP2. The auxiliary opening AP1 ' may be located on a first side of the evaporator unit 100, and the auxiliary opening AP2' may be located on a second side of the evaporator unit 100. Outdoor air AIR1 may be guided to the heat exchanger 100 through the frontal openings AP1 , AP2 and also through the auxiliary openings AP1 ', AP2'. The air flow through the frontal openings AP1 , AP2 may be e.g. greater than or equal to 50% of the total air flow of the heat exchanger 10. The air flow through the frontal openings AP1 , AP2 may be e.g. greater than or equal to 50% of the total air flow guided into the evaporator unit 100. Using the auxiliary openings AP1 ', AP2' in addition to the frontal openings AP1 , AP2 may reduce flow resistance and/or improve efficiency. The outdoor air may be guided through the auxiliary openings AP1 ', AP2' when the wall 910 does not block the openings AP1 ', AP2'. The evaporator unit 100 may be positioned such that the wall 910 does not block the openings AP1 ', AP2'. dr may denote the distance between impeller 25 of the fan 20 and the auxiliary opening AP1 '. 62· may denote the distance between the impeller 25 of the fan 20 and the auxiliary opening AP2'. The distances dr and 62· may be e.g. smaller than 50% of the initial width W _JE T2 of the jet JET2.

The auxiliary openings AP1 ', AP2' may be close to the fan 20 so that outdoor air may be guided via the auxiliary openings AP1 ', AP2' to the heat exchanger 10 also in a situation where the protrusion distance b1 is small. For example, the fan 20 may be located between the auxiliary openings AP1 ', AP2'. The fan 20 may be located between a first auxiliary opening AP1 ' and a second auxiliary opening AP2'. The impeller 25 of the fan 20 may be located between a first auxiliary opening AP1 ' and a second auxiliary opening AP2' of the unit 100.

A front panel 50 of the unit 100 may comprise a plurality of frontal inlet openings AP1 and/or AP2 so that the total cross-sectional open area of the frontal openings of the unit 100 is e.g. in the range of 20% to 100% of the total cross-sectional area of the inlet channel portions of the unit 100. Selecting a large open area may reduce the effect of flow resistance of the openings. A front panel 50 of the unit 100 may comprise a plurality of frontal inlet openings AP1 and/or AP2 so that the total cross-sectional area of the frontal openings of the unit 100 is e.g. in the range of 20% to 80% of the total cross- sectional area of the inlet channel portions of the unit 100, in order to provide a more rigid structure. Using the auxiliary openings AP1 ', AP2' in addition to the frontal openings AP1 , AP2 may reduce flow resistance and/or improve efficiency.

When using the auxiliary openings, the total cross-sectional area of the inlet portions of the unit 100 may even be greater than the total cross-sectional area of the inlet channel portions of the unit 100, in order to reduce the effect of flow resistance of the openings. The total cross-sectional open area of the inlet portions of the unit 100 may be e.g. in the range of 50% to 200% of the total cross-sectional area of the inlet channel portions. The cross-sectional area of an auxiliary opening may be determined in a plane, which is perpendicular to the main direction of air flow in said auxiliary opening.

Referring to Fig. 7b, the evaporator unit 100 of Fig. 7a may be positioned such that the auxiliary openings AP1 ', AP2' are partly or completely blocked by the wall 910. This position may be used e.g. when the evaporator unit 100 is transported together with the building and/or when the protrusion distance b1 should be small. The evaporator unit 100 may be operated such that auxiliary openings AP1 ', AP2' are partly or completely blocked by the wall 910. However, the efficiency may be slightly reduced, when compared with the situation where all openings AP1 , AP2, AP1 ', AP2' are in use.

Referring to Figs. 8a and 8b, the evaporator unit 100 may be installed e.g. in a portable building 900. The evaporator unit 100 may be installed in a portable building element 901 . The evaporator unit 100 may be installed in an opening 912 of the wall 910 of an element 901 of a building 900. The element 901 of the building 900 may comprise the evaporator unit 100. The building 900 may comprise a heat pump system 500, which comprises the evaporator unit 100. The building 900 may be heated by the heat pump system 500.

The portable building may also be called e.g. as a demountable/transportable building. The building 900 may be a part of a larger structure, which may comprise two or more portable buildings. For example, the building 900 may be a part of a larger building complex heated by using the same evaporator unit 100. The building complex may be e.g. a temporary office, school, hospital, or hotel. The floor area of the building complex may be e.g. greater than 100 m ² , greater than 200 m ² , greater than 500 m ² , greater than 1000 m ² , or even greater than 2000 m ² .

The portable building 900 or the element 901 may be transported to the intended location e.g. by a trailer. The building 900 or the element 901 may be lifted to its place e.g. by using a crane. For example, the building 900 may comprise removable or permanent support elements 921 in order to facilitate lifting of the building or the element of the building. The support elements 921 may be e.g. lifting eyes. Fig 8a shows the evaporator unit 100 in an operating position POS1 , and Fig. 8b shows the evaporator unit 100 in a transport position POS2. The length bioo of the evaporator unit 100 may be greater than the thickness of the wall 910. The evaporator unit 100 may be temporarily moved inwards in order to reduce the risk of damaging the unit 100 during transportation. The evaporator unit 100 may be moved outwards in order to maximize the free floor area inside the building 900.

The evaporator unit 100 may be easily damaged during transportation or lifting of the building 900 or the element 901 . The evaporator unit 100 may be temporarily moved inwards such that the evaporator unit 100 does not protrude with respect to the wall 910. The evaporator unit 100 may be connected to the compressor unit 200 by flexible conduits CON1 , CON2 such that the evaporator unit 100 may be moved without opening the fittings of the conduits CON1 , CON2. Opening of the fittings may involve the risk that the refrigerant R1 leaks into the atmosphere. Some refrigerants may have an environmental impact in the atmosphere. Typically only authorized personnel are allowed to open the fittings. Thanks to using the evaporator unit 100 and the flexible conduits CON1 , CON2, the fittings do not need to be opened for transportation.

However, when the evaporator unit 100 is in the transport position, the evaporator unit 100 may cover floor area inside the building 900. After the building has been transported, the evaporator unit 100 may be moved outwards to an operating position POS1 such that the free floor area inside the building may be increased. The evaporator unit 100 may protrude by a distance b1 with respect to the wall 910 in the operating position.

The method may comprise:

- moving the evaporator unit 100 inwards with respect to the wall 910 of the building 900 into a transport position POS2,

- transporting the building 900 and the evaporator unit 100 together, and

- moving the evaporator unit 100 outwards with respect to the wall 910 of the building 900 into an operating position POS1 . For example, the unit 100 of Fig. 1 may be moved from a transport position to an operating position according to the Figs. 8a and 8b.

Referring to Figs. 9a and 9b, the evaporator unit 100 may comprise a retractable flow guide 40 for controlling the air jet JET2. Fig. 9a shows the flow guide 40 in the retracted position, and Fig. 9b shows the flow guide 40 in the extended position. The flow guide 40 may be e.g. a substantially circular short duct, which defines the initial portion of the air jet JET2. The extended duct 40 may help to confine the jet JET2, i.e. the duct may provide a narrower jet.

The flow guide 40 may be moved with respect to the inlet openings AP1 , AP2. e.g. by using a sliding mechanism. The extended flow guide 40 may reduce circulation of air AIR2 to the inlet openings AP1 , AP2. The flow guide 40 may slightly increase the efficiency of the evaporator unit 100 when the flow guide 40 is in the extended position. The extended flow guide 40 may protrude by a distance b3 from the inlet openings AP1 , AP2. The extended flow guide 40 may protrude by a distance b1 ' from the wall 910. The distance b1 ' may be e.g. in the range of 0% to 15% of the width w ₀ p2 of the opening OP2. The distance b1 ' may be e.g. in the range of 5% to 15% of the width w ₀ p2 of the opening OP2.

The duct 40 may slightly increase the total length b ioo of the evaporator unit 100. The evaporator unit 100 may have a length b ioo' when the flow guide 40 is in the extended position.

Figs. 10a and 10b show, in a three dimensional view, an evaporator unit 100, which comprises frontal openings AP1 , AP2, auxiliary openings AP1 ' AP2', and the flow guide 40. Fig. 10a shows the evaporator unit 100 in a situation where a top panel of the unit 100 has been temporarily removed.

Referring to Fig. 1 1 , the evaporator unit 100 may comprise two or more fans 20, in order to increase the thermal power of the evaporator unit 100. A first fan 20 may provide a first air jet JET2, and a second fan may provide a second air jet. The central axis AX2 of the first air jet JET2 may be substantially parallel to the central axis of the second air jet JET2.

The evaporator unit 100 may optionally comprise a grille for protecting the blades of the fans 20 and/or for preventing personal injury caused by the rotating blades.

Referring to Fig. 12a, the evaporator unit 100 may optionally comprise an inlet 80 for guiding ventilation air AIR3 to the heat exchanger 10. The ventilation air may be warm. Heat may be extracted also from the ventilation air AIR3 to the refrigerant R1 , in order to increase the temperature of the refrigerant R1 at the outlet of the evaporator unit 100. This may, in turn, increase the efficiency of the heat pump system 500.

Referring to Fig. 12b, the evaporator unit 100 may optionally comprise a water outlet 70 for guiding condensed water C2 out of the evaporator unit 100. The temperature of the outdoor air AIR1 may be reduced in the heat exchanger 10 such that a part of the water vapor contained in the outdoor air AIR1 may be condensed. The water vapor may be converted into water and/or ice. The ice may be released from the heat exchanger by temporarily increasing the temperature of the heat exchanger 10, in order to melt the ice. The condensed water and/or the ice may fall to the bottom of the evaporator unit 100. The evaporator unit 100 may comprise an inclined portion 72 to collect the water to the outlet 70. The evaporator unit 100 may optionally comprise a heater 75 to heat the inclined portion and/or the water outlet 70. The heater may be arranged to heat the inclined portion and/or the outlet 70 at least temporarily above 0°C in order to melt the ice and/or in order to ensure that the condensed water C2 may be guided out of the evaporator unit 100. The condensed water C2 may be guided e.g. to a drain tube. The heater 75 may be e.g. an electric heater.

Thanks to the water outlet 70, leaking of the condensed water to the outside of the building 900 may be substantially prevented. This may help to reduce the risk of moisture-induced damage to the building. Condensed water on the ground outside of the building may sometimes be converted into ice when the outdoor temperature is below 0°C. The ice on the ground may be slippery and may cause serious personal injury. Thanks to the water outlet 70, this risk may be substantially reduced.

Referring to Fig. 12c, the evaporator unit 100 may be arranged to operate such that the water outlet 70 for the condensed water is at least partly heated by ventilation air AIR3. The evaporator unit 100 may comprise a heat transfer element 74 to transfer heat from the ventilation air AIR3 to the surface of the outlet 70. The heat transfer element may comprise e.g. one or more metallic plates. The plates may extract heat from the ventilation air AIR3 by convection, and the plates may conduct the extracted heat to the water outlet 70.

Using the warm indoor air AIR3 to heat the water outlet 70 may reduce the electric energy needed to operate the heat pump system 500. Using the warm indoor air AIR3 to heat the water outlet 70 may increase the efficiency of the heat pump system 500.

The indoor air AIR3 may be optionally guided to the heat exchanger 10.

The evaporator unit 100 may optionally comprise the retractable flow guide 40, the water outlet 70, the ventilation air inlet 80, and/or the heat transfer element 74. The dimensions and conditions discussed with reference to Figs 3a and 3b may apply to the evaporator unit 100 discussed with reference to Figs. 1 and 2. The evaporator unit 100 discussed with reference to Figs. 1 and 2 may have inlets and channel portions e.g. as shown in Figs. 5a to 6b. The evaporator unit 100 may optionally have auxiliary openings e.g. as shown in Figs. 7a and 7b. However, the evaporator unit 100 may also be implemented without the auxiliary openings. Substantially all outdoor air guided to the heat exchanger may be guided via a plurality of frontal inlets AP1 , AP2. The evaporator unit 100 may be installed in a building 900 as shown in Fig. 4b. The evaporator unit 100 may be moved inwards for transportation and outwards for operation e.g. as shown in Figs. 8a and 8b. The evaporator unit may comprise an extendable flow guide 40 e.g. as shown in Figs. 9a to 1 1 . The evaporator unit 100 may comprise a ventilation air inlet 80 e.g. as shown in Fig. 12a. The evaporator unit 100 may comprise a water outlet 70 e.g. as shown in Fig. 12b. The evaporator unit 100 may comprise a heat transfer element 74 e.g. as shown in Fig. 12c.

The temperature of the outdoor air AIR1 may be e.g. in the range of -25°C to +45°C. The efficiency of the heat pump system may be e.g. greater than 150% in a situation where the temperature difference between the temperature of the outdoor air AIR1 and the temperature of the heated fluid Q2 is equal to 80°C. The efficiency of the heat pump system means the ratio of thermal energy transferred to the fluid Q2 to the electrical energy consumed by the heat pump system 500. The width wioo of the evaporator unit 100 may be e.g. in the range of 500 mm to 1800 mm. The height hioo of the evaporator unit 100 may be e.g. in the range of 500 mm to 1800 mm. The depth bioo of the evaporator unit 100 may be e.g. in the range of 300 mm to 600 mm. The diameter w ₀ p2 of the opening OP2 may be e.g. in the range of 50% to 80 % of the width wioo, preferably in the range of 60% to 70% of the width wioo- The initial width W _{J E} T2 may be e.g. in the range of 50% to 80 % of the width wioo, preferably in the range of 60% to 70% of the width wioo- The diameter of the impeller may be e.g. in the range of 50% to 80 % of the width wioo, preferably in the range of 60% to 70% of the width wioo-

The compressor unit 200 may be remote from the evaporator unit 100. The distance between the compressor 220 and the heat exchanger 10 may be e.g. greater than 0.5 m, greater than 1 .0 m, or even greater than 2.0 m.

The evaporator unit 100 and the compressor unit 200 may be manufactured, transported and/or installed separately. The evaporator unit 100 and the compressor unit 200 may be manufactured in the same factory, or the evaporator unit 100 may be manufactured in a first factory, and the compressor unit 200 may be manufactured in a second different factory.

According to an embodiment, a method for heating a building (900) may comprise:

- guiding outdoor air (AIR1 ) from a first inlet portion (AP1 ) to a heat exchanger (10) via a first inlet portion (AP1 ),

- guiding outdoor air (AIR1 ) from a second inlet portion (AP2) to the heat exchanger (10) via a second inlet portion (AP2),

- transferring heat from the outdoor air (AIR1 ) by cooling the outdoor air (AIR1 ) in the heat exchanger (10),

- drawing cooled air (AIR2) from the heat exchanger (10) by an axial fan (20), and

- providing an air jet (JET2) by said axial fan (20) such that that the distance (di) between the first inlet portion (AP1 ) and the impeller (25) of the fan (20) is smaller than 30% of the initial width (W _{J E} T2) of the jet (JET2) and the distance (d2) between the second inlet portion (AP2), and the impeller (25) of the fan (20) is smaller than 30% of the initial width (w _JE T2) of the jet (JET2), wherein the fan (20) is located between the first channel portion (DP1 ) and the second channel portion (DP2). For the person skilled in the art, it will be clear that modifications and variations of the devices and the methods according to the present invention are perceivable. The figures are schematic. The particular embodiments described above with reference to the accompanying drawings are illustrative only and not meant to limit the scope of the invention, which is defined by the appended claims.