WO2006041388A1

WO2006041388A1 - Heating installation and heating method

Info

Publication number: WO2006041388A1
Application number: PCT/SE2005/001492
Authority: WO
Inventors: Hans-Göran GÖRANSSON
Original assignee: Första Närvärmeverket Ab
Priority date: 2004-10-13
Filing date: 2005-10-10
Publication date: 2006-04-20
Also published as: SE0402477L; SE0402477D0; SE527793C2

Abstract

A heating installation comprising a first circuit (2) containing a first medium, a second circuit (3) containing a second medium, a first heat generating arrangement (4) arranged in the second circuit, a second heat generating arrangement in the form of a heat pump (5), and at least two heat transferring devices (2OA, 20B) arranged in series in the first circuit for transferring heat to the first medium in the first circuit. A first one (20A) of said heat transferring devices arranged in series is arranged to transfer heat from the second medium in the second circuit to the first medium in the first circuit. A second one (20B) of said heat transferring devices arranged in series is arranged in the first circuit upstream of the first heat transferring device (20A) and comprises a heat exchanger (40), which constitutes a subcooler of the heat pump and which is connected between the con¬ denser (5d) and the expansion valve (5f) of the heat pump for transferring heat from the working medium of the heat pump in its condensed state to the first medium in the first circuit.

Description

Applicant: FORSTA NARVARMEVERKET AB

Heating installation and heating method

FIELD OF THE INVENTION AND PRIOR ART

The present invention relates to a heating installation according to the preamble of claim 1 and a method according to the pre¬ amble of claim 13.

A heating installation according to the preamble of claim 1 is previously known from the patent document WO 00/32992 A1. This previously known heating installation comprises two or three heat transferring devices in the form of heat exchangers arranged in a first circuit containing a first medium, for instance in the form of tap hot-water, in order to transfer heat from a sec- ond medium in a second circuit to the first medium in the first circuit. A first heat generating arrangement in the form of a heating boiler and a second heat generating arrangement in the form of a heat pump are arranged in said second circuit in order to generate heat to the second medium in the second circuit. By means of said heat transferring devices, it will be possible to gradually heat the first medium in the first circuit to a desired end temperature. This previously known heating installation makes it possible to use, to a great extent, the heat pump as a primary energy source in the heating installation for heating of tap hot-water as well as radiators, whereas the heating boiler needs to be in operation only at relatively high load in order to satisfy the prevailing heating demands, which will reduce the op¬ erating costs of the heating installation.

OBJECT OF THE INVENTION

The object of the present invention it to achieve a heating in¬ stallation and a method that makes possible an increase of the efficiency of the heat pump in a heating installation of the type indicated by way of introduction.

SUMMARY OF THE INVENTION

According to the invention, said object is achieved by means of a heating installation having the features indicated in claim 1 and a method having the features indicated in claim 13.

The inventive solution implies that a heat exchanger, which con¬ stitutes a subcooler of the heat pump and which is connected between the condenser and the expansion valve of the heat pump, is used in order to transfer heat from the working medium of the heat pump in its condensed state to the first medium in the first circuit, which first medium preferably is water intended to be heated in order to provide tap hot-water. This heat transfer suitably constitutes a first initial heating step in a process for heating tap hot-water to a desired temperature, i.e. a preheating of the tap hot-water. In a subsequent heating step, heat is transferred from the second medium in the second circuit to the first medium in the first circuit via a heat transferring device ar¬ ranged in the first circuit downstream of the heat transferring device that comprises the heat exchanger connected between the condenser and the expansion valve of the heat pump. This subsequent heating step suitably constitutes a final heating step in a process for heating tap hot-water to a desired temperature, i.e. a final heating of the tap hot-water. In the first heating step, surplus heat of the working medium of the heat pump is used in order to give said first medium an initial temperature increase when the heat pump is in operation, whereby the energy re¬ quired in the subsequent heating step or the subsequent heating steps in order to increase the temperature of the first medium to the desired end temperature is reduced correspondingly. By utilizing said surplus heat of the working medium of the heat pump in the heating of the first medium, instead of wasting it, an increase of the efficiency of the heat pump is obtained.

A preferred embodiment of the invention is characterized in - that the heating installation comprises a third circuit containing a third medium, which third circuit is included in the second heat transferring device,

- that the heat exchanger connected between the condenser and the expansion valve of the heat pump constitutes a first heat ex- changer of the second heat transferring device and is arranged in the third circuit, this first heat exchanger being arranged to transfer heat from the working medium of the heat pump to the third medium in the third circuit, and

- that the second heat transferring device comprises a second heat exchanger arranged in the third circuit in series with the first heat exchanger, this second heat exchanger being arranged to transfer heat from the third medium in the third circuit to the first medium in the first circuit.

According to this embodiment, the first medium is consequently not conveyed directly into the heat exchanger connected be¬ tween the condenser and the expansion valve of the heat pump, whereby the risk of damages to the heat pump due to a too high cooling effect from the first medium is reduced.

According to another preferred embodiment of the invention, the second heat transferring device comprises an accumulator ar¬ ranged in the third circuit between the first heat exchanger and the second heat exchanger in order to accumulate the third me¬ dium, which accumulator preferably has its inlet connected to the second heat exchanger and its outlet connected to the first heat exchanger.

According to another preferred embodiment of the invention, the second heat transferring device comprises a third heat ex¬ changer arranged in the third circuit in order to transfer heat from a fourth medium, for instance ambient air, to the third medium in the third circuit. This third heat exchanger may assist the first heat exchanger and give a supplementary heat contri- bution for the initial heating of the first medium and may also be used in order to give the desired heating effect in the initial heating step in those cases when the heat pump is not in opera¬ tion or only used to a limited extent.

According to another preferred embodiment of the invention, the heat pump has its output side connected to the second circuit so that heat exchange between the second medium in the second circuit and the condenser of the heat pump is possible. Hereby, the heat pump may, depending on the prevailing heating de- mands, be used independently or in co-operation with the first heat generating arrangement, for instance in order to achieve the increase of the temperature of the first medium to the de¬ sired end temperature via the first heat transferring device, i.e. in order to achieve a final heating of for instance tap hot-water. The benefit of the heat exchanger connected between the con¬ denser and the expansion valve of the heat pump is at its high¬ est when the heat pump is used for a final heating of the first medium and when the power output of the heat pump conse¬ quently is high, since this heat exchanger then can give a com- paratively large contribution of heat to the preheating of the first medium.

Further preferred embodiments of the inventive heating installa¬ tion and the inventive method will appear from the dependent claims and the subsequent description. BRIEF DESCRIPTION OF THE DRAWINGS

With reference to the enclosed drawings, a more specific de¬ scription of embodiment examples of the invention will follow hereinbelow. It is shown in:

Fig 1 a schematic illustration of a heating installation according to a first embodiment of the present invention,

Fig 2 a schematic illustration of a heating installation according to a second embodiment of the present invention,

Fig 3 a schematic illustration of a heating installation according to a third embodiment of the present invention,

Fig 4 a schematic illustration of a heating installation according to a fourth embodiment of the present invention, and

Fig 5 a schematic illustration of a heating installation according to a fifth embodiment of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The inventive heating installation 1 comprises at least two cir- cuits 2, 3 for two separate media, namely a first circuit 2 con¬ taining a first medium, e.g. tap hot-water, and a second circuit 3 containing a second medium, e.g. water. Different embodiments of a heating installation according to the invention are schemati¬ cally shown in Figs 1 -5. The illustrated heating installations are designed for heating a house or other building and tap hot-water associated therewith. The inventive heating installation may, however, also be designed for satisfying other types of heating demands.

In the embodiments illustrated in Figs 1 -5, a first heat generat¬ ing arrangement 4, for instance a conventional oil-fired and/or wood-fuelled heating boiler, which also may comprise means for heating with a so-called heating cartridge, and a second heat generating arrangement 5 in the form of a heat pump, for in¬ stance for utilizing ground heat and/or solar heat, are arranged in series in the second circuit in order to supply heat to the second medium.

The heat pump 5 comprises an evaporator 5c, a condenser 5d, a compressor 5e and an expansion valve 5f, preferably an electro- mechanical expansion valve. By heat exchange with a medium in a circuit, not shown here, connected to the evaporator 5f, the working medium of the heat pump absorbs heat energy via the evaporator 5c. Work is added via the compressor 5e, whereby the pressure and the temperature of the working medium of the heat pump is increased. In the condenser 5d, heat energy is then emitted to the second medium in the second circuit 3 by heat exchange and the working medium of the heat pump is then returned to the evaporator 5c via expansion valve 5f while being subjected to pressure and temperature decrease. Consequently, the heat pump 5 has its output side connected to the second circuit 3 so that heat exchange between the second medium in the second circuit and the condenser 5d of the heat pump is possible.

By means of a feeding conduit 6, the outlet 4b of the heating boiler 4 is connected to the inlet 7 of one or several heat emit¬ ting devices 8. These devices 8 are used for heating a further medium, in this case the air within the building, and are for in¬ stance constituted by conventional radiators to be operated with hot-water or another medium. The outlet 9 of the heat emitting devices is by means of a return conduit 10 connected to the inlet 5a of the heat pump 5, and the outlet 5b of the heat pump is by means of the return conduit 10 connected to the inlet 4a of the heating boiler.

The return conduit 10 and the feeding conduit 6 are connected to each other via a first connecting conduit 1 1A arranged from a point P1 located at the feeding conduit 6 to a point P2 located between the outlet 5b of the heat pump and the inlet 4a of the heating boiler. The return conduit 10 and the feeding conduit 6 are also connected to each other via a second connecting conduit 1 1 B arranged from a point P3 located between the outlet 5b of the heat pump and the inlet 4a of the heating boiler to a point P4 located at the feeding conduit 6. The heating installa¬ tion further comprises a third connecting conduit 11 C arranged from a point P5 located between the point P4 and the inlet 7 of the radiators to a point P6 located between the outlet 9 of the radiators and the inlet 5a of the heat pump, and a fourth con¬ necting conduit 1 1 D arranged from a point P7 located between the point P4 and the point P5 to a point P8 located between the point P6 and the inlet 5a of the heat pump. At the second con- necting conduit 1 1 B and the feeding conduit 6, a control valve 12 is arranged at the point P4, and a control valve 13 is further arranged at the third connecting conduit 1 1 C and the feeding conduit 6 at the point P5. A nonreturn valve 14 is arranged in the first connecting conduit 1 1A and a nonreturn valve 15 is also arranged in the fourth connecting conduit 1 1 D. Furthermore, a nonreturn valve 16 is arranged in the return conduit 10 at a po¬ sition where the return conduit 10 also constitutes means for bypassing the heat pump 5, i.e. a bypass conduit 17 for the heat pump 5. The last mentioned nonreturn valve 16 is consequently arranged in the part of the return conduit 10 extending between the inlet 5a and the outlet 5b of the heat pump. A circulation pump 18 is arranged in one of the connection conduits between the condenser 5d of the heat pump and the return conduit 10. A circulation pump 19 is also arranged in the feeding conduit 6. The last mentioned circulation pump 19 could alternatively be arranged in the return conduit 10.

In order to transfer heat from the second medium in the second circuit 3 to the first medium in the first circuit 2, i.e. in order to heat tap hot-water in the illustrated embodiments, two or more heat transferring devices 2OA, 2OB, 2OC arranged in series along the first circuit 2 are used in order to gradually heat the first medium. Two heat transferring devices 2OA, 2OB are ar¬ ranged in series in the first circuit 2 in the embodiments illus¬ trated in Figs 1 and 4, and three heat transferring devices 2OA, 2OB, 2OC are arranged in series in the first circuit 2 in the em¬ bodiments illustrated in Figs 2, 3 and 5.

In all of the illustrated embodiments, a first one 2OA of said heat transferring device arranged in series is arranged for final heating of the first medium. In those cases, this first heat transferring device 2OA comprises a heat exchanger 21 ar¬ ranged to transfer heat from the second medium in the second circuit 3 to the first medium in the first circuit 2 by heat ex¬ change between the second medium and the first medium. This heat exchanger 21 is here connected to the feeding conduit 6 via two connection conduits 22, 23. A circulation pump 24 is ar¬ ranged in one of these connection conduits. A nonreturn valve 25 is arranged in the feeding conduit 6 at a position where the feeding conduit 6 constitutes means for bypassing the first heat transferring device 2OA, i.e. a bypass conduit 26 for the first heat transferring device 2OA. The last mentioned nonreturn valve 25 is consequently arranged in the part of the feeding conduit 6 extending between said connection conduits 22, 23. The final-heated tap hot-water is stored in an accumulator 27 arranged in the first circuit 2, which accumulator is connected to the heat exchanger 21 via two connection conduits 28, 29. A cir¬ culation pump 30 is arranged in one of these connection con¬ duits. A return conduit 31 with a circulation pump 32 is arranged between the upper outlet 27b and the lower inlet 27a of the ac- cumulator.

According to the invention, a second one 2OB of said heat transferring devices arranged in series is arranged in the first circuit 2 upstream of the first heat transferring device 2OA. This second heat transferring device 2OB comprises a heat ex¬ changer 40 connected between the condenser 5d and the ex- pansion valve 5f of the heat pump in order to transfer heat from the working medium of the heat pump in its condensed state to the first medium in the first circuit 2. The second heat transfer- ring device 2OB consequently utilizes the condensate of the heat pump 5 for preheating the first medium, for instance in order to achieve, a heating of tap hot-water in a first step. Said heat exchanger 40 constitutes a so-called subcooler of the heat pump 5.

In the embodiment illustrated in Fig 1 , the heating installation 1 comprises a third circuit 41 containing a third medium, for in¬ stance water, which third circuit 41 forms part of the second heat transferring device 2OB. The heat exchanger 40 is arranged in this third circuit 41 and constitutes in this case a first heat ex- changer of the second heat transferring device 2OB. This first heat exchanger 40 is arranged to transfer heat from the working medium of the heat pump in its condensed state to the third me¬ dium in the third circuit 41 by heat exchange between the work¬ ing medium and the third medium. In this case, the second heat transferring device 2OB also comprises a second heat ex¬ changer 42 arranged in the third circuit 41 in series with the first heat exchanger 40, this second heat exchanger 42 being ar¬ ranged to transfer heat from the third medium in the third circuit 41 to the first medium in the first circuit 2 by heat exchange between the third medium and the first medium. Furthermore, a circulation pump 43 is arranged in the third circuit 41. An accu¬ mulator 44 is suitably arranged in the third circuit 41 for accu¬ mulation of the third medium. The accumulator 44 preferably has its inlet 44a connected to the second heat exchanger 42 and its outlet 44b connected to the first heat exchanger 40. The second heat exchanger 42 is here arranged to receive cold-water via a cold-water conduit 80.

The embodiment illustrated in Fig 2 corresponds to the one il- lustrated in Fig 1 , with the exception that a third heat transfer¬ ring device 2OC is arranged in the first circuit 2 in series with and between the first and second heat transferring device 2OA, 2OB. In this case, this third heat transferring device 2OC com¬ prises a heat exchanger 50 arranged to transfer heat from the second medium in the second circuit 3 to the first medium in the first circuit 2 by heat exchange between the second medium and the first medium. This heat exchanger 50 is here connected to the feeding conduit 6 via two connection conduits 51 , 52. A control valve 53 is arranged in the feeding conduit 6 at a posi¬ tion where the feeding conduit 6 constitutes means for bypass- ing the third heat transferring device 2OC, i.e. a bypass conduit 54 for the third heat transferring device 2OC. The control valve 53 is consequently arranged in the part of the feeding conduit 6 extending between said connection conduits 51 , 52.

The embodiment illustrated in Fig 3 corresponds to the one il¬ lustrated in Fig 2, with the exception that the second heat transferring device 2OB also comprises a third heat exchanger 45 arranged in the third circuit 41 in order to transfer heat from a fourth medium to the third medium in the third circuit 41 by heat exchange between the fourth medium and the third me¬ dium. The fourth medium is suitably ambient air, in which case the third heat exchanger 45 is an air heat exchanger. This air heat exchanger 45 is suitably located in the same room as the heat pump 5 in order to utilize the elevated air temperature gen- erated during the operation of the heat pump 5. The third heat exchanger 45 may also be another type of heat exchanger that gives energy for heating the third medium in the third circuit 41 when the heat pump 5 is not used or only used to a low extent, so that a desired preheating effect can be obtained via the sec- ond heat transferring device 2OB also during the operational modes when the heat pump is not generating this preheating effect. In the illustrated case, the third heat exchanger 45 is ar¬ ranged in the third circuit 41 between the outlet 44b of the ac¬ cumulator and the first heat exchanger 40. In the embodiment illustrated in Fig 4, the heat exchanger 40 of the second heat transferring device 2OB, which heat exchanger is connected between the condenser 5d and the expansion valve 5f of the heat pump, is connected to an accumulator 60, which is arranged in the first circuit 2 for accumulating the first medium. This accumulator 60 is here connected to the heat exchanger 40 via two connection conduits 61 , 62. A circulation pump 63 is ar¬ ranged in one of these connection conduits. In this case, the heat exchanger 40 can be arranged to directly receive the first medium, in which case the heat exchanger 40 consequently transfers heat from the working medium of the heat pump to the first medium in the first circuit by heat exchange between the working medium and the first medium. In the embodiment here illustrated, the accumulator 60 is via a conduit 64 connected to the previously mentioned accumulator 27, which is arranged to store the final-heated tap hot-water. The accumulator 60 is ar¬ ranged to receive cold-water via a cold-water conduit 80 and to deliver preheated tap hot-water to the other accumulator 27 via the conduit 64.

The embodiment illustrated in Fig 5 corresponds to the one il¬ lustrated in Fig 4, with the exception that a third heat transfer¬ ring device 2OC is arranged in the first circuit 2 in series with and between the first and second heat transferring device 2OA, 2OB. In this case, this third heat transferring device 2OC com¬ prises a heat exchanger 50 arranged to transfer heat from the second medium in this second circuit 3 to the first medium in the first circuit 2 by heat exchange between the second medium and the first medium. This heat exchanger 50 is here connected to the feeding conduit 6 via two connection conduits 51 , 52. A control valve 53 is arranged in the feeding conduit 6 at a posi¬ tion where the feeding conduit constitutes means for bypassing the third heat transferring device 2OC, i.e. a bypass conduit 54 for the third heat transferring device 2OC. The control valve 53 is consequently arranged in the part of the feeding conduit 6 extending between said connection conduits 51 , 52. In the embodiment illustrated in Fig 5, the heat exchanger 50 of the third heat transferring device 2OC is connected to an accu¬ mulator 55, which is arranged in the first circuit 2 for accumu- lating the first medium. This accumulator 55 is here connected to the heat exchanger 50 via two connection conduits 56, 57. A circulation pump 58 is arranged in one of these connection con¬ duits. The accumulator 55 is here via a conduit 70 connected to the accumulator 60 that is arranged to store the tap hot-water preheated by the second heat transferring device 2OB, and via a conduit 71 connected to the accumulator 27 that is arranged to store the final-heated tap hot-water. The accumulator 55 is con¬ sequently arranged to receive, from the accumulator 60 via the conduit 70, tap hot-water preheated in a first step, and to deliver tap hot-water preheated in a second step to the accumulator 27 via the conduit 71.

Different possible operational modes of a heating installation of the basic configuration illustrated in Figs 1 -5, i.e. different man- ners of operating this heating installation in dependence on pre¬ vailing heating demands, will appear from the above-mentioned patent document WO 00/32992 A1 and will also be apparent to a person skilled in the art.

The invention is of course not in any way limited to the preferred embodiments described above. On the contrary, many possibili¬ ties to modifications thereof will be apparent to a person skilled in the art without departing from the basic idea of the invention as defined in the appended claims. For instance, the heat pump in question does not have to be connected to the above-men¬ tioned second circuit 3 and could instead be arranged to gener¬ ate heat to another circuit than said second circuit 3.

Claims

1. A heating installation comprising a first circuit (2) containing a first medium, a second circuit (3) containing a second medium, a first heat generating arrangement (4), for instance in the form of a heating boiler, arranged in the second circuit (3), a second heat generating arrangement in the form of a heat pump (5), and at least two heat transferring devices (2OA, 20B) arranged in se¬ ries in the first circuit (2) for transferring heat to the first medium in the first circuit (2), a first one (20A) of said heat transferring devices arranged in series being arranged to transfer heat from the second medium in the second circuit (3) to the first medium in the first circuit (2), characterized in that a second one (20B) of said heat transferring devices arranged in series is arranged in the first circuit (2) upstream of the first heat transferring device (20A) and comprises a heat exchanger (40), which constitutes a subcooler of the heat pump (5) and is connected between the condenser (5d) and the expansion valve (5f) of the heat pump for transferring heat from the working medium of the heat pump in its condensed state to the first medium in the first circuit (2).

2. A heating installation according to claim 1 , characterized in:

- that the heating installation comprises a third circuit (41 ) con- taining a third medium, which third circuit (41 ) is included in the second heat transferring device (20B),

- that the heat exchanger (40) connected between the con¬ denser and the expansion valve of the heat pump constitutes a first heat exchanger of the second heat transferring device (20B) and is arranged in the third circuit (41 ), this first heat exchanger (40) being arranged to transfer heat from the working medium of the heat pump to the third medium in the third circuit (41 ), and

- that the second heat transferring device (20B) comprises a second heat exchanger (42) arranged in the third circuit (41 ) in series with the first heat exchanger (40), this second heat ex¬ changer (42) being arranged to transfer heat from the third me- dium in the third circuit (41 ) to the first medium in the first circuit (2).

3. A heating installation according to claim 2, characterized in that the second heat transferring device (20B) comprises an ac¬ cumulator (44) arranged in the third circuit (41 ) between the first heat exchanger (40) and the second heat exchanger (42) for ac¬ cumulating the third medium.

4. A heating installation according to claim 2 or 3, charac¬ terized in that the second heat transferring device (20B) com¬ prises a third heat exchanger (45) arranged in the third circuit (41 ) for transferring heat from a fourth medium, for instance am¬ bient air, to the third medium in the third circuit (41 ).

5. A heating installation according to claim 4 in combination with claim 3, characterized in that the third heat exchanger (45) is arranged in the third circuit (41 ) between the outlet (44b) of the accumulator and the first heat exchanger (40).

6. A heating installation according to claim 1 , characterized in that the heat exchanger (40) of the second heat transferring de¬ vice (20B) is connected to an accumulator (60), which is ar¬ ranged in the first circuit (2) for accumulating the first medium.

7. A heating installation according to claim 1 or 6, charac¬ terized in that the heat exchanger (40) of the second heat transferring device (20B) is connected to the first circuit (2) in such a manner that heat exchange between the working medium of the heat pump and the first medium in the first circuit (2) is possible.

8. A heating installation according to any of the preceding claims, characterized in that the heat exchanger (21 ) of the first heat transferring device (20A) is connected to an accumulator (27), which is arranged in the first circuit (2) for accumulating the first medium.

9. A heating installation according to any of the preceding claims, characterized in that the heating installation also com¬ prises a third heat transferring device (20C) for transferring heat to the first medium in the first circuit (2), this third heat transfer¬ ring device (20C) being arranged in the first circuit (2) in series with said first and second heat transferring devices (2OA, 20B), preferably between these.

10. A heating installation according to claim 9, characterized in that the third heat transferring device (20C) comprises a heat exchanger (50) arranged to transfer heat from the second me- dium in the second circuit (3) to the first medium in the first cir¬ cuit (2).

11. A heating installation according to any of the preceding claims, characterized in that the heat pump (5) has its output side connected to the second circuit (3) so that heat exchange between the second medium in the second circuit and the con¬ denser (5d) of the heat pump is possible.

12. A heating installation according to any of the preceding claims, characterized in that the first heat transferring device

(20A) comprises a heat exchanger (21 ) arranged to transfer heat from the second medium in the second circuit (3) to the first me¬ dium in the first circuit (2).

13. A method for heating a first medium in a first circuit (2), heat generation to a second medium in a second circuit (3) being performable by means of at least a first heat generating ar¬ rangement (4), for instance in the form of a heating boiler, heat transfer from the second medium in the second circuit (3) to the first medium in the first circuit (2) being performed by means of a first heat transferring device (20A) arranged in the first circuit (2), characterized in that heat transfer from a second heat gen¬ erating arrangement in the form of a heat pump (5) to the first medium in the first circuit (2) is performed by means of a second heat transferring device (20B) arranged in the first circuit (2) in series with and upstream of the first heat transferring device (20A) by transferring heat from the working medium of the heat pump in its condensed state to the first medium in the first cir¬ cuit (2) via a heat exchanger (40) included in the second heat transferring device (20B), which heat exchanger is connected between the condenser (5d) and the expansion valve (5f) of the heat pump and constitutes a subcooler of the heat pump (5).