TECHNICAL FIELD

This specification relates to heat pump-based heating systems comprising boilers serving for initially re ceiving and storing heat produced by the heat pump.

BACKGROUND

In a heating system with a heat pump-based heat produc tion arrangement, heat released by a heat pump may be transferred to a heating fluid such as water and tempo rarily stored in one or more boilers, such as water tanks.

From a boiler, the heat may be further transferred or distributed, for example, by leading heating water from the boiler to a heating circuit such as an underfloor heating circuit or a radiator heating circuit. Thereby, the heat produced by the heat pump may be used for heating the indoor of a building. Alternatively, the heat stored in a boiler may be used to heat domestic hot water of a building.

Due to different temperature ranges typically needed for heating water and the domestic hot water, known heating systems comprise separate heating water boilers and do mestic hot water boilers. When both the heating water boiler and the domestic hot water boiler are to be heated, the heating water boiler may be heated by the condensing heat released at the condenser of the heat pump, and the domestic hot water boiler may be heated by heat released at the hot gas heat exchanger of the heat pump. When there is no need for heating the heating water boiler, e.g. outside the heating season, the heat pump may be used for heating the domestic hot water boiler only, by the condensing heat and possibly addi tionally by heat released at the hot gas heat exchanger also.

The prior art systems are space-consuming and complex. So, there is a need for improved heating systems which are compact.

SUMMARY

This summary is provided to introduce a selection of concepts that are further described below in the De tailed Description. This Summary is not intended to def initely identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.

In one aspect, a heating system is disclosed which may be used for heating a heating fluid and domestic hot water.

The heating system comprises a heat pump with a conden ser and a hot gas heat exchanger, and a boiler with a volume to be filled with the heating fluid.

The boiler is connected to the heat pump by a piping arrangement which is configured to circulate the heating fluid between the heat pump and the boiler to heat the boiler by heat produced by the heat pump.

Advantageously, the boiler comprises an intermediate bottom wall dividing the boiler volume into an upper volume and a lower volume lying, with the boiler in use, below the first volume, and a by-pass flow arrangement connecting the upper and the lower volumes to enable flow of the heating fluid from the upper volume to the lower volume. Further, the piping arrangement advantageously connects the upper volume to the hot gas heat exchanger for heat ing the upper volume by heat released at the hot gas heat exchanger, and is, for connecting the boiler to the condenser, configured to be selectively set to a first connection mode and a second connection mode. In the first connection mode, the lower volume is connected to the condenser of the heat pump for heating the lower volume by condensing heat released at the condenser. In the second connection mode, the upper volume is con nected to the condenser of the heat pump for heating the upper volume by condensing heat released at the conden ser.

The piping arrangement may be configured to supply the water heated by the hot gas of the heat pump to the upper volume of the boiler, preferably to the top part thereof, and take a return flow back to the hot gas heat exchanger from the upper volume of the boiler, prefer ably from the lower part thereof.

In the first connection mode, the piping arrangement may be configured to supply the heating fluid heated at the condenser to the lower volume of the boiler, preferably to the upper part thereof, and take a return flow back to the condenser from the lower volume of the boiler, preferably from the lower part thereof. In the second connection mode, the piping arrangement may be configured to supply the heating fluid heated at the condenser to the upper volume of the boiler, pref erably to the upper part thereof; and to be selectively set to take a return flow back to the condenser from the lower volume of the boiler, preferably from the lower part thereof, or from the upper volume of the boiler, preferably from the lower part thereof. The by-pass flow arrangement may comprise at least one opening formed through the intermediate bottom wall. Then the boiler may comprise a non-return valve assem- bled to the at least one opening to prevent flow of the heating fluid from the lower volume to the upper volume.

Alternatively, the by-pass flow arrangement may comprise a by-pass pipe passing the intermediate bottom wall out- side the boiler volume.

The heating system may comprise a domestic hot water coil arrangement for leading domestic hot water through it, the domestic hot water coil arrangement having an upper part positioned in the upper volume and a lower part positioned in the lower volume of the boiler, the upper and lower parts being connected in series. BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which illustrate various em bodiments, together with the description are intended to explain the principles of various embodiments.

FIGs. 1 and 5 illustrate, as schematic drawings not drawn to scale, heat pump-based heating systems with a boiler and a piping arrangement. FIGs. 2 to 4 illustrate the heating system of FIG. 1 with its piping arrangement set to different connection modes. DETAILED DESCRIPTION

The detailed description provided below is not intended to represent the only forms in which the embodiments may be constructed, implemented, or utilized.

The heating system 100 of FIG. 1 may be used, for exam ple, to heat heating water and domestic hot water. The heating system may utilize as the primary source of heat, for example, condensing heat released at the con denser of a heat pump of a heat extraction arrangement.

Such heat extraction arrangement may be connected, or be a part of, a cooling appliance, such as a domestic or commercial refrigerator, freezer, cold-storage room or cold cabinet, for extracting heat therefrom. In other embodiments, a heat extraction arrangement may be con figured to extract heat from an industrial process, or from any appropriate space or mass to be cooled. Basi- cally, a heat extraction arrangement may be arranged to extract heat from to any appropriate space or material mass as a target to be cooled.

The heating system comprises a heat pump 110 having a condenser 111, a hot gas heat exchanger 112, and a com pressor 113.

The heat pump and the components thereof may be of any appropriate known type. For example, the heat pump may be an inverter type heat pump or an ON/OFF type heat pump. The compressor thereof may be, for example, a scroll compressor or a reciprocating compressor (piston compressor). The heating system further comprises a tank 120 serving as a boiler having an inner volume 121, 122 filled with water 101. In other embodiments, any other appropriate heating fluid may be used instead of water.

Basically, a "boiler" refers to a reservoir or tank of any appropriate type for receiving and storing therein a heating fluid.

"Heating fluid" refers to any appropriate liquid which may be used for receiving and transferring heat. It may be or comprise, for example, water.

The tank 120 comprises an intermediate bottom wall 123, having, in the example of FIG. 1, two openings 124 formed through it. In other embodiments, there may be one or more than two openings. The intermediate bottom wall divides the inner volume of the tank into an upper volume 121 and a lower volume 122 lying, with the tank in its intended, substantially upright use position illus trated in FIG. 1, below the first volume. The openings are parts of a by-pass flow arrangement connecting the upper and the lower volumes to enable flow of the heating fluid from the upper volume to the lower volume.

In the example of FIG. 1, a non-return valve 125, or check valve or one-way valve, is mounted in each of the openings 124. In other embodiments, opening (s) in the intermediate bottom wall may be implemented without any non-return valve therein.

A domestic hot water coil arrangement 140 is positioned within the inner volume of the tank 120 for leading domestic hot water through it. The domestic hot water coil arrangement comprises a water pipe, a part of which is wound to form a coil.

In the example of FIG. 1, the domestic hot water coil arrangement has an upper part 141 positioned in the upper volume 121 and a lower part 142 positioned in the lower volume 122 of the tank. The first and the second parts are connected in series so that domestic hot water may be led first through the lower part and then through the upper part, whereby it can be efficiently heated by heat of the water in the tank. The upper part and the lower part are connected via a connecting part 143 pass ing the intermediate bottom wall 123 outside the tank inner volume.

The lower volume 122 of the tank may be connected to a heating circuit via an inlet and outlet (not illus trated).

The heating system further comprises a piping arrange ment 130 which connects the heat pump 110 and the boiler 120 to each other. The water as a heating fluid is circulated in the piping arrangement between the heat pump and the boiler so that the boiler and the water therein may be heated by heat produced by the heat pump 100.

The piping arrangement 130 comprises a condenser circu lation loop 131 via which the water is circulated be tween the condenser 111 of the heat pump 110 and the tank 120.

The condenser circulation loop 131 comprises a two- branch supply line with a first condenser supply line 132i and a second condenser supply line 132 ₂ . The first condenser supply line is connected to the upper part of the lower volume 122 of the tank 120 to supply the water heated at the condenser 111 of the heat pump 110 therein. The second condenser supply line 132 ₂ is connected to the upper part of the upper volume 121 of the tank 120 to supply the water heated at the condenser 111 of the heat pump 110 therein. In other embodiments, the first and the second condenser supply lines may be connected to different parts of the tank.

A first three-way valve 133 is included in the condenser circulation loop to select which of the first and the second condenser supply lines is in use, i.e. along which of them the water heated at the condenser by the heat released therein is supplied to the tank.

The condenser circulation loop 131 comprises a two- branch return line with a first condenser return line 135i and a second condenser return line 135 ₂ - In other embodiments, it may be possible to have a single con denser return line without two branches. The first con denser return line 135i is connected to the lower part of the lower volume 122 of the tank 120 to take the water out of the tank there. The second condenser return line 135 ₂ is connected to the lower part of the upper volume 121 of the tank 120 to take the water out of the tank there. In the example of FIG. 1, the first and the second condenser return lines join into a common return line before the condenser.

A second three-way valve 139 is included in the conden ser circulation loop to select which of the first and the second condenser return lines is in use, i.e. along which of them the water is returned from the tank to the condenser.

In other embodiments, the first and the second condenser return lines may be connected to different parts of the tank. In yet other embodiments, return lines with a single return line without branches may be implemented. Such single return line may be connected to the tank at any appropriate location thereof. On the other hand, completely separate first and second condenser return lines without any common return line may be implemented. The piping arrangement 130 also comprises a hot gas circulation loop 136 via which the water is circulated between the hot gas heat exchanger 112 of the heat pump 110 and the tank 120.

The hot gas circulation loop 136 comprises a hot gas supply line 137 connected to the top of the tank 120 to supply the water heated at the hot gas heat exchanger 112 of the heat pump 110 therein, i.e. to the top part of the upper volume 121.

The hot gas circulation loop 136 comprises a hot gas return line 138 connected to the lower part of the upper volume 121 of the tank 120 to take the water out of the tank there.

In other embodiments, the hot gas supply and return lines may be connected to different parts of the tank 120 to supply and take the water at different parts of the upper volume 121 thereof.

It is to be noted that the drawing of FIG. 1 is a simplified illustration. The heating system and the parts and arrangements thereof may comprise any appro priate parts, components, elements, and units not il lustrated in the drawing. For example, the piping ar rangement may comprise also further valves, pumps, and/or other actuators in addition to the three-way valves discussed above.

The piping arrangement 130 may be set to different con nection modes illustrated in FIGs. 2 to 4. In the draw ings of FIGs. 2 to 4, the active lines of the piping arrangement, i.e. those lines which are in use, are marked by solid lines whereas those lines not in use are marked by dashed lines. In each of the first connection mode and the first and second alternatives of the second connection modes il lustrated in FIGs. 2, 3, and 4, respectively, the water heated by the hot gas of the heat pump 110 is supplied to the top part of the upper volume 121 of the tank 122 via the hot gas supply line 137. A return flow is then taken from the lower part of the upper volume 121 of the tank 120 and returned back towards the hot gas heat exchanger 112 via the hot gas return line 138. Thereby, the upper volume is connected to the hot gas heat ex changer for heating the upper volume by heat released at the hot gas heat exchanger of the heat pump. In other embodiments, water supply to and return flow from the boiler can be arranged differently to connect the upper volume to the hot gas heat exchanger for heating the upper volume by heat released at the hot gas heat ex changer. In the first connection mode illustrated in FIG. 2, the first three-way valve 133 is set to open the first con denser supply line 132i and close the second condenser supply line 132 ₂ . The second three-way valve 139 is set to open the first condenser return line 135i and close the second condenser return line 135 ₂ - Then, the water heated at the condenser 111 is supplied via the first condenser supply line 132i to the upper part of the lower volume 122 of the tank 120. A return flow back to the condenser is taken from the lower part of the lower volume 122 of the tank 120 via the first condenser return line 135i. Thereby, the lower volume is connected to the condenser of the heat pump for heating the lower volume by condensing heat released at the condenser 111. In other embodiments, water supply to and return flow from the boiler can be arranged differently to connect the lower volume to the condenser for heating the lower volume by heat released at the condenser. The first connection mode may be used, for example, during the heating season when both heating water and hot domestic hot water need is at a relatively high level. The heat pump 100 may operate all or most of the time for heating the heating water contained in the lower volume 122 of the tank 120. Then, the heat re leasable from the hot gas may be sufficient to heat the upper volume to the higher temperature needed for heat- ing the domestic hot water flowing in the domestic hot water coil arrangement 140. Thus, the lower volume 122 may serve as a heating water boiler and the upper volume 121 may serve as a domestic hot water boiler. In the second connection mode illustrated in FIGs. 3 and 4, the first three-way valve 133 is set to close the first condenser supply line 132i and open the second condenser supply line 132 ₂ . Then, the water heated at the condenser 111 is supplied via the second condenser supply line 132i to the upper part of the upper volume

121 of the tank 120.

In the first alternative or variation of the second connection mode illustrated in FIG. 3, a return flow back to the condenser is taken, similarly to the first connection mode, from the lower part of the lower volume

122 of the tank 120 via the first condenser return line 135i. Thereby, the upper volume is connected, in addi tion to the hot gas heat exchanger 112, also to the condenser 111 of the heat pump for heating the lower volume also by condensing heat released at the condenser 111. In other embodiments, water supply to and return flow from the boiler can be arranged differently to connect the upper volume also to the condenser for heat- ing the upper volume by heat released at the condenser. One example is discussed below with reference to FIG. 4. The first alternative of the second connection mode may be used, for example, outside the heating season when only domestic hot water needs to be heated. Then, also the condensing heat released at the condenser may be used to heat the domestic hot water, and the entire inner volume of the tank may serve as a domestic hot water boiler. The second alternative or variation of the second con nection mode illustrated in FIG. 4 differs from the first alternative or variation of FIG. 3 in that the second three-way valve 139 is set to open the second condenser return line 135 ₂ and close the first condenser return line 135i. Then, the return flow to the condenser is taken from the lower part of the upper volume 121 of the tank 120 via the second condenser return line 135 ₂ -

This alternative may be used, for example, during an intermediate season after or before the heating season where still/already some heating energy is needed to heat the heating water. Then, it is possible to switch the supply of the water heated by the condensing heat from the first condenser supply line 132i to the second condenser supply line 132 ₂ for heating the upper volume 121 of the tank serving as a domestic hot water boiler. Thereby, sufficient heating of the domestic hot water may be ensured also when there is not sufficient heat available from the hot gas of the heat pump.

The heating system 200 of FIG. 5 differs from that of FIGs. 1 to 4 in that its by-pass flow arrangement is implemented differently. The by-pass flow arrangement of the heating system 200 of FIG. 5 comprises a by-pass pipe 224 passing the intermediate bottom wall 223 out side the boiler volume. The by-pass pipe may be imple mented, for example, substantially in the form of a horizontal U pipe. There may be (not illustrated) a non return valve, or check valve or one-way valve, included in the by-pass pipe to prevent flow of the heating fluid from the lower volume 221 of the tank 220 to the upper volume 222 thereof.

In the example of FIG. 5, the by-pass flow arrangement comprises one by-pass pipe. In other embodiments, by pass flow arrangements with a plurality of by-pass pipes may be implemented.

In yet other embodiments, by-pass flow arrangements dif ferent from those of FIGs. 1 to 5 may be implemented to connect the upper and the lower volumes to enable flow of the heating fluid from the upper volume to the lower volume of a tank.

The different connection modes described above enable efficient use of the equipment of the heating system. On the other hand, space and cost savings can be achieved in comparison to the prior art solutions with separate tanks or boilers for domestic hot water and heating water. One important advantage is that outside the heat ing season, the entire inner volume of the tank, thus the entire boiler volume, may be used as a domestic hot water heating boiler. The increased volume enables longer operating cycles of the heat pump, which may increase the compressor service interval and lifetime. The heating system may comprise a control unit which may be configured to select, at least partially automati cally, the connection mode of the piping arrangement on the basis of predetermined criteria. That selecting may comprise operating the valve (s) and any other appropri ate actuators of the arrangement.

Such control unit may be basically implemented in ac cordance with the principles as such known in the art. To carry out the selecting and any other appropriate operations a control unit is "configured to" operate, such control unit may comprise one or more processors coupled with at least one memory. The at least one memory may comprise computer-readable program code instruc tions which, when executed by the at least one proces sor, cause the control unit to carry out the opera tion (s) at issue at least partially automatically. Al ternatively, or in addition, at least some of those operations may be carried out, at least partially, by means of some hardware logic elements or components, such as Application-specific Integrated Circuits (ASICs), Application-specific Standard Products (ASSPs), or System-on-a-chip systems (SOCs), without being limited to those examples.

A control unit may be a sub-unit within, or an integral part of, a larger automation unit. In other embodiments, a control unit may be a separate unit appropriately connected to the rest of the arrangement, such as a heat pump.

From another terminology point of view, a control unit being "configured to" perform a specific method opera tion means actually that the control unit comprises or constitutes at least a part of "means for" performing that operation.

"Automatically" performing one or more operations of the method refers to performing the operation (s) at issue partially or completely automatically by means of one or more appropriate data processing units or modules such as control units in accordance with those discussed above with reference to the system or apparatus aspect. Performing an operation completely automatically refers to carrying out the operation according to predetermined rules and procedures, without need for any contribution provided or determination performed by a user of an apparatus or device incorporating such unit or module. In performing an operation partially automatically, some contribution may be provided or determination may be performed by a user of an apparatus or device incorpo rating such unit or module.

The different connection modes of the heating system of FIG. 1 may be considered representing and disclosing also example methods of using the heating system for heating domestic hot water and heating water.

In such methods, the upper volume of the tank is heated by heat released at the hot gas heat exchanger of the heat pump. The condensing heat released at the condenser of the heat pump is alternatively used to heat the lower volume of the tank or the upper volume of the tank, and naturally then also the lower volume as the water may flow through the openings of the intermediate bottom wall. In the first alternative, the upper volume of the tank serves as a domestic hot water boiler and the lower volume serves as a heating water boiler. In the second alternative, the entire inner volume of the tank may serve as a domestic hot water boiler.

The selection between the first and the second alterna tives may be carried out at least partially automati cally, e.g. by means of one or more valve (s) and a control unit, such as those discussed above with refer ence to FIGs. 1 to 4.

It is to be noted that the embodiments of the claims are not limited to those discussed above, but further em bodiments may exist within the scope of the claims. It will be understood that the benefits and advantages described above may relate to one embodiment or may relate to several embodiments. It will further be understood that reference to 'an' item refers to one or more of those items.

The term "comprising" is used in this specification to mean including the feature(s) or act(s) followed there- after, without excluding the presence of one or more additional features or acts.