NZ563928A - Heating apparatus - Google Patents

Abstract

A heating apparatus having a boiler connected to a heat exchanger. Liquid exchange between the boiler and the heat exchanger takes place solely as a result of convection. The heat exchanger has flowing through it on the primary side a heat transport medium which is heated by a heat source with a lower temperature than the hot side of the boiler and is evaporated. The heat transport medium is subsequently compressed by a compressor regulated according to rotational speed and is supplied to a primary side of the heat exchanger. In this case, the heat transport medium discharges its entire evaporation heat to the boiler. The condensed heat transport medium subsequently flows back to the heat source. To achieve high efficiency, the compressor is controlled by a regulating device connected to sense the temperature of the heat transport medium and/or the temperature of the hot side of the heat exchanger.

Description

563928 Patent Form No. 5 NEW ZEALAND Patents Act 1953 COMPLETE SPECIFICATION TITLE: HEATING APPARATUS We IFG Solar KG, of Weinbergstrasse 25, D-90607 Ruckersdorf, Germany, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: 4003q INTELLECTUAL PROPERTY" OFFICE OF N.z. 3 - DEC 260/ RECEIVED 563928 1 A HEATING APPARATUS FIELD OF THE INVENTION The invention relates to a heating apparatus. This application claims priority from German Patent Application No. 20 2006 018 320.5 filed on 30 November 2006, the contents of which are to be taken as incorporated herein by this reference.

BACKGROUND OF THE INVENTION A reference herein to a patent document or other matter which is given as prior art is not to be taken as an admission that that document or matter was, in Australia, known or that the information it contains was part of the common 15 general knowledge as at the priority date of any of the claims.

Throughout the description and claims of this specification the word "comprise" and variations of that word, such as "comprises" and "comprising", are not intended to exclude other additives or components or integers.

An apparatus for recovering heat from industrial waste heat, which comprises a boiler and a heat exchanger assigned to the latter, is known from practice. The secondary side of the heat exchanger is in this case connected, on the one hand, to a cold side, and, on the other hand, to a hot side of the boiler, so 25 that a closed circuit is formed between the boiler and the heat exchanger. A heat transport medium which is fed from industrial waste heat flows in this case through the primary side of the heat exchanger. In plants in which industrial waste heat is available to a large extent, this waste heat is easily sufficient not only to heat the water of the boiler, but at the same time to 30 maintain a convection flow between the boiler and the heat exchanger. There is therefore no need in this circuit for a circulating pump which would destroy the desired temperature stratification within the boiler in the event of too high a flow. This known apparatus has proved appropriate in practice and forms the starting point for the present invention.

U:\ECP\NZ\nz15799-07-retyped pages.doc 563928 2 SUMMARY OF THE INVENTION According to the present invention, there is provided a heating apparatus including a boiler which contains a temperature-stratified liquid, a lower cold side and an upper hot side, a heat exchanger having a primary 5 side and a secondary side, the secondary side of the heat exchanger forming a circuit with the boiler driven solely by convection, and the primary side of the heat exchanger having a heat transport medium flowing therethrough which condenses with a discharge of heat and which flows via a line to the heat exchanger and, after discharging heat in the heat exchanger, the heat 10 transport medium flows out of the heat exchanger through an outlet line, the heat transport medium extracting heat from a heat source having a lower temperature than the temperature of the hot side of the boiler and evaporating, the heat source being followed by a compressor which has an outlet and which brings the heat transport medium to a temperature which is greater than 15 the temperature of the hot side of the boiler, the throughflow rate of the compressor being controlled by a regulating device which is connected to a temperature sensor situated at one of the following locations: a) between the outlet of the compressor and the outlet line of the heat exchanger in thermal contact with the heat transport medium, or 20 b) within the circuit driven by convection, in contact with the liquid of the boiler.

The apparatus according to the invention serves for heating. It has at least one boiler which contains a temperature-stratified liquid. As a rule, the boiler is 25 filled with water, any other heat-carrying medium also being suitable. The liquid in the boiler is temperature-stratified, so that there are always in the boiler at least one layer with cold liquid and, lying above it, at least one layer with hot liquid. As a rule, an inflow for the liquid, in particular cold U:\ECP\NZ\nz15799-07-retyped pages.doc 563928 water, is also provided on the cold side of the boiler, while an outflow for heated liquid, in particular hot water, is provided on the hot side. The heated liquid is used, in particular, for heating purposes, while, 5 alternatively or additionally, hot water can also be extracted for domestic purposes. To heat the liquid in the boiler, a heat exchanger is provided, the secondary side of which is connected, on the one hand, to the cold side and, on the other hand, to the hot side of 10 the boiler. The secondary side of the heat exchanger therefore forms with the boiler a circuit which is closed on itself. This circuit is driven solely by the convection of the liquid in the boiler, so that no active circulating pump of any kind is provided. The 15 advantage of this arrangement is that the flow quantity of the liquid in this circuit is coupled directly to the introduction of heat. The situation is therefore ruled out where the liquid is circulated in this circuit, without a sufficiently high introduction of 20 heat taking place. Such circulation would result in the complete destruction of the temperature stratification of the liquid in the boiler, so that the extraction temperature of the boiler would fall correspondingly. On the other hand, the purely convection-bound flow of 25 this circuit presupposes a relatively intensive heating of the liquid, since convection does not come into action if the heating is too low.

To achieve a universal usability of the heating 30 apparatus, it is important also to be able to use heat sources, the temperature of which is lower than the hot side of the boiler. For this purpose, a heat transport medium is employed, which is evaporated by the heat source. Subsequently the heat transport medium is 35 compressed by a compressor which brings the heat transport medium, including the heat contained in it, to a higher temperature. The heat transport medium is subsequently conducted through the primary side of the heat exchanger, where it heats the boiler liquid. At 563928 the same time, the heat transport medium condenses, the evaporation heat for the heat exchanger being discharged to the boiler liquid. The liquid heat transport medium is then returned to the heat source 5 where it can absorb heat anew. Thus, heat is transported from the heat source at a low temperature into the heat exchanger at a higher temperature. It has become clear, however, that the operation of a heat pump of this type, together with a convection-bound 10 heat exchanger, presents serious problems.

In contrast to the utilization of industrial waste heat, in heat pump operation it is important for the system to have high efficiency on account of the energy 15 consumption associated with this. If the introduction of heat from the heat pump into the heat exchanger is too low, convection does not come into action in the boiler circuit. By contrast, if the introduction of heat is too high, the compressor consumes a large 20 amount of energy, without an appreciable heating of the liquid in the boiler occurring.

To solve this problem, a compressor is used, the throughflow rate of which is influenced by a regulating 25 device. This regulating device is in this case influenced by the temperature of the heat transport medium between the outlet of the compressor and the outlet line of the heat exchanger or by the temperature of the liquid of the heat exchanger or boiler. What is 30 achieved by this measure is that the throughput of heat transport medium through the compressor becomes dependent on the heat discharge of the heat transport medium in the heat exchanger. When the apparatus is being run up, therefore, the compressor is utilized 35 with relatively low power, in order to allow time for the convection on the secondary side of the heat exchanger to build up correspondingly. With an increase in convection flow, the power of the compressor is also run-up, since the heat discharge of the heat transport 563928 medium in the heat exchanger then increases correspondingly. This affords an optimal utilization of the heat of the heat source, along with a relatively low energy requirement, so that the overall apparatus 5 has surprisingly high efficiency.

To achieve as low a heat loss as possible, it is advantageous if the heat exchanger is designed as a countercurrent heat exchanger. As a result, the boiler 10 liquid is heated almost to the temperature of the heat transport medium. Heat transmission therefore leads to only a very low temperature loss. If the heat exchanger is provided within a thermal insulation of the boiler, particularly low heat losses occur. Preferably, the 15 heat exchanger is arranged around the boiler, so that heat radiation losses of the boiler are also partially regenerated in the heat exchanger.

In order to maintain as effective a convection as 20 possible, it is beneficial if the heat exchanger has a larger line cross section on the secondary side than on the primary side. This leads on the secondary side to a lower line resistance, so that even a relatively insignificant temperature difference within the heat 25 exchanger leads to an effective convection flow. A large line cross section is not required on the primary side, since the heat transport medium is in any case circulated positively as a result of the action of the compressor.

To achieve sensitive regulation, it is beneficial if the regulating device is influenced by the condensation temperature of the heat transport medium, preferably downstream of the heat exchanger. The condensation 35 temperature is a material-dependent function of the pressure, so that only the pressure of the heat transport medium downstream of the heat exchanger has to be measured in order to determine the condensation temperature in the case of a known heat transport 563928 medium. This measured pressure can then be converted into a condensation temperature, using the vapor pressure curve of the heat transport medium. It is important to know the condensation temperature, since 5 an incomplete condensation of the heat transport medium would result in an incomplete discharge of heat into the heat exchanger and, possibly, in unstable regulation, so that the selected energy consumption of the compressor would be too high. The influence of the 10 condensation temperature on regulation therefore improves the efficiency of the apparatus.

To achieve optimal efficiency, it is beneficial if the regulating device sets the temperature of the heat 15 transport medium, after it flows through the heat exchanger, to a temperature which lies a predetermined temperature span below the condensation temperature of the heat transport medium. The heat transport medium is in this case supercooled, so that the evaporation heat 20 has been discharged completely to the boiler liquid via the heat exchanger. If the heat discharge in the heat exchanger rises, this results in the lowering of the temperature of the heat transport medium at the outlet of the heat exchanger in relation to the condensation 25 temperature. In this case, regulation ensures an increase in the flow through the compressor. The increased heat absorption capacity of the heat exchanger can consequently be utilized directly to increase the power of the apparatus. Moreover, 30 regulation remains stable over the entire operating range.

A range of between IK and 10K has proved appropriate for the temperature span. With a temperature span of 35 below IK, there is the risk that, should faults occur, the condensation of the heat transport medium is no longer complete, so that heat is pumped, unused, in the circuit. Moreover, hunting which is difficult to control may arise as a result. A choice of the 563928 temperature span above 10K is inappropriate, since this would result in restriction of available heat sources. However, depending on the heat source which can be employed, a higher temperature span is possible.

Preferably, the selected temperature span is between 3K and 7K, in order to achieve as sensitive and efficient regulation as possible.

So that the apparatus can be used in a wide power 10 range, it is beneficial if at least one expansion valve is provided between the heat exchanger and the heat source. This expansion valve ensures an expansion of the heat transport medium and consequently keeps the pressure conditions of the heat transport medium in the 15 region of the heat exchanger approximately constant.

In order to ensure that the apparatus achieves optimal efficiency under all conditions, it is advantageous if the expansion valve is operatively connected to a 20 regulating device influenced by the pressure of the heat transport medium. Thus, constant properties of the heat transport medium are implemented over a wide operating range.

Particularly in the case of heat sources having a very low temperature, it is beneficial for the heat exchanger to be followed by at least one container which is in thermal contact with the evaporated heat transport medium. The heat transport medium is 30 consequently additionally cooled in order to improve the heat absorption. Moreover, the final temperature which can be achieved by the compressor rises.

Further advantages and features of the present 35 invention are presented in the following detailed description with reference to the accompanying figure which contains an exemplary embodiment of the present invention. It should be understood, however, that the drawing serves merely for the purpose of illustrating 563928 the invention and does not restrict the scope of protection of the invention.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF DRAWINGS to these and to such other objects that may hereinafter appears, the present invention relates to a heating apparatus as described in detail in the following specification and recited in the annexed 10 claims, taken together with the accompanying drawing in which shows a diagrammatic illustration of a heating apparatus 1.

DETAILED DESCRIPTION OF THE INVENTION The apparatus 1 has a boiler 2 which is filled with water 3. The boiler 2 has an inflow 4 for cold water and an outflow 5 for hot water. Within the boiler 2, a 20 layer boundary 6 is established, where a hot side 7 lies on a cold side 8. Only very slight intermixing occurs between the hot side 7 and the cold side 8, so that the water of the hot side 7 can be extracted at a virtually constant temperature. In particular, the 25 temperature of the water at the outflow 5 does not, in practice, depend on the height of the layer boundary 6.

The boiler 2 is connected via lines 9 to a heat exchanger 10 operated in counter current. The water 3 30 in this case flows through a secondary side 11 of the heat exchanger 10. This secondary side 11 possesses a larger line cross section than a primary side 12 of the heat exchanger 10, so that a free convection flow can be implemented without a circulating pump between the 35 boiler 2 and the heat exchanger 10 via the lines 9. To 563928 _ 9 - achieve as low a heat loss as possible, the heat exchanger 10 is provided within a thermal insulation 13 of the boiler 2. So that the radiant heat of the boiler 2 can also be utilized, the heat exchanger 10 extends 5 around the boiler 2.

In addition, contrary to the illustration, heat sources, for example heat exchangers of fossil fuel heating systems or of high temperature solar heating 10 installations, could also be accommodated in the boiler 2. However, additional heat sources of this type in the boiler 2 have nothing to do with the subject matter of the invention itself and are therefore not illustrated.

Moreover, depending on the application, the heat exchanger 10 could be .thermally decoupled from the boiler 2 by means of an additional thermal insulation layer. Alternatively, depending on the application, it is also conceivable to provide the partition between 20 the heat exchanger 10 and the boiler 2 with orifices or to abandon it entirely, so that improved convection thereby occurs.

A heat transport medium 14 which is circulated in a 25 separate circuit flows through the primary side 12 of the heat exchanger 10. The primary side 12 of the heat exchanger 10 is connected via a line 15 to a container 15a which is designed as an intermediate heat exchanger. In this container 15a, the heat transport 30 medium 14 discharges heat to evaporated heat transport medium 14 which flows through the container 15a in a line 22. This measure improves the heat absorption capacity of the heat transport medium 14.

After leaving the container 15a, the heat transport medium 14 passes into an expansion valve 16 which ensures a reduction in the pressure of the heat transport medium 14. The expansion valve 16 is operatively connected via a regulating device 17 to a 563928 pressure gauge 18 which keeps the pressure of the heat transport medium in the line 15 constant. The regulating device 17 is preceded by a differential amplifier 17b which compares the measured pressure with 5 a desired pressure of a desired-value generator 17a. The comparison result is in this case the controlled variable of the regulating device 17. This ensures that approximately constant pressure conditions of the heat transport medium 14 prevail within the heat exchanger 10 10, so that the heat transport medium 14 has approximately a constant condensation temperature.

The expansion valve 16 is operatively connected via a line 19 to a further heat exchanger 20 which is in 15 contact with a heat source 21. The heat source 21 considered may be, for example, ambient air, but also geothermal heat or a solar heating installation. As a rule, the temperature of the heat source 21 is not sufficient to heat the water 3 in the heat exchanger 10 20 directly. For this purpose, this heat first has to be brought to a higher temperature.

For this purpose, the heat transport medium 14 is selected such that it is liquid within the line 19 and 25 evaporates due to the heat source 21. This vapor is conducted via a further line 22 through the container 15a where it is in heat exchange with the heat transport medium 14 coming from the heat exchanger 10. The heat transport medium 14 is in this case heated 30 approximately to the inflow temperature of the boiler 2 .

After leaving the container 15a, the heat transport medium 14 is supplied to a compressor 23, the 35 throughflow of which can be set via the rotational speed. The compressor 23 compresses the heat transport medium 14, with the result that its temperature level also rises. The heat transport medium 14 returns via a line 24 into the heat exchanger 10 where it discharges 563928 its heat to the secondary-side water 3. In this case, the heat transport medium 14 condenses, so that its entire evaporation heat is discharged to the water.

Moreover, what is achieved by the heat exchanger 10 being designed as a countercurrent heat exchanger is that the water 3, after leaving the heat exchanger 10, has virtually the temperature of the inflowing heat transport medium 14. The temperature loss is very low, 10 since the inflowing heat transport medium 14 initially heats only the uppermost layer of the water 3 which has already virtually reached the temperature of the heat transport medium 14. The heat transport medium 14 flows downward in the heat exchanger and heats even colder 15 water layers, with the result that it cools appreciably. In this case, at a specific point within the heat exchanger 10, the condensation temperature of the heat transport medium 14 is reached, so that, instead of a further cooling of the heat transport 20 medium 14, a condensation of the latter at a constant temperature commences. The condensation of the heat transport medium 14 is in this case complete, so that the entire evaporation heat is discharged. In the lower region of the heat exchanger 10, the now liquid heat 25 transport medium 14 is cooled even further and is subsequently supplied to the expansion valve 16 and the heat source 21. This affords a highly efficient energy utilization of the apparatus 1.

To operate the apparatus 1, a temperature sensor 25 is provided, on the outlet side of the heat exchanger 10, in the region of the line 15. This temperature sensor 25 measures the temperature of the heat transport medium 14 after heat discharge in the heat exchanger 35 10. Moreover, the pressure of the heat transport medium 14 in the line 25 is determined via the pressure gauge 18 already mentioned. Via a computing circuit 26 in which the vapor pressure curve of the heat transport medium 14 is stored, the condensation temperature of 563928 the heat transport medium 14 is calculated from this and is emitted as an electrical signal. The calculated condensation temperature is supplied, together with the signal of the temperature sensor 25 and with a desired 5 value of a desired-value generator 27a, to a differential amplifier 27 which determines from this the supercooling of the heat transport medium 14 in the line 15 to below the condensation temperature and compares it with the desired value.

An output signal 28 from the differential amplifier 27 is supplied to a regulating device 29 which activates the compressor 23 via a frequency converter 30. This ensures that the heat transport medium 14 is always 15 circulated optimally as a function of the convection flow of the water 3. Consequently, on the one hand, the heat source 21 is utilized optimally and, on the other hand, the energy consumption of the compressor 23 is restricted to a minimum. This results, overall, in an 20 optimal efficiency of the apparatus 1.

Since some exemplary embodiments of the present invention are not shown or described, it must be understood that a multiplicity of changes and 25 modifications of this exemplary embodiment described are possible, without departing from the essential idea and scope of protection of the invention defined by the claims. 563928 List of reference symbols 1 Apparatus 2 Boiler 3 Water 4 Inflow Outflow 6 Layer boundary 7 Hot side 8 Cold side 9 Line Heat exchanger 11 Secondary side 12 Primary side 13 Thermal insulation 14 Heat transport medium Line 15a Container 16 Expansion valve 17 Regulating device 17a Desired-value generator 17b Differential amplifier 18 Pressure gauge 19 Line Heat exchanger 21 Heat source 22 Line 23 Compressor 24 Line Temperature sensor 26 Computing circuit 27 Differential amplifier 27a Desired-value generator 28 Output signal 29 Regulating device Frequency converter

Claims (12)

563928 14 THE CLAIMS DEFINMING THE INVENTION ARE AS FOLLOWS:

1. A heating apparatus including a boiler which contains a temperature-stratified liquid, a lower cold side and an upper hot side, a heat exchanger 5 having a primary side and a secondary side, the secondary side of the heat exchanger forming a circuit with the boiler driven solely by convection, and the primary side of the heat exchanger having a heat transport medium flowing therethrough which condenses with a discharge of heat and which flows via a line to the heat exchanger and, after discharging heat in the heat exchanger, 10 the heat transport medium flows out of the heat exchanger through an outlet line, the heat transport medium extracting heat from a heat source having a lower temperature than the temperature of the hot side of the boiler and evaporating, the heat source being followed by a compressor which has an outlet and which brings the heat transport medium to a temperature which is 15 greater than the temperature of the hot side of the boiler, the throughflow rate of the compressor being controlled by a regulating device which is connected to a temperature sensor situated at one of the following locations: a) between the outlet of the compressor and the outlet line of the heat exchanger in thermal contact with the heat transport medium, or 20 b): within the circuit driven by convection, in contact with the liquid of the boiler.

2. The apparatus as claimed in claim 1, wherein the boiler has thermal insulation and the heat exchanger is a countercurrent heat exchanger and is 25 provided within the thermal insulation of the boiler.

3. The apparatus as claimed in claim 1 or 2, wherein the secondary side of the heat exchanger has a larger line cross section than the primary side of the heat exchanger. 30

4. The apparatus as claimed in claim 1, 2 or 3, wherein the heat transport medium has a condensation temperature, and the regulating device is controlled in accordance with the condensation temperature of the heat transport medium. U:\ECP\N2\nz1579£!-07-retyped pages.Goc 563928 15

5. The apparatus as claimed in any preceding claim wherein the regulatory device is controlled in accordance with the condensation temperature of the heat transport medium downstream of the heat exchanger. 5

6. The apparatus as claimed in claim 4 or 5, wherein the regulating device sets the temperature of the heat transport medium, after the heat transport medium flows through the heat exchanger, to a temperature below the condensation temperature of the heat transport medium by a preset amount. 10

7. The apparatus as claimed in claim 6, wherein the preset amount is between 1K and 10K.

8. The apparatus as claimed in claim 6, wherein the preset amount is 15 between 3K and IK.

9. The apparatus as claimed in any preceding claim, further including an expansion valve connected between the heat exchanger and the heat source. 20

10. The apparatus as claimed in claim 9, wherein the expansion valve is operatively connected to a regulating device controlled by the pressure of the heat transport medium.

11. The apparatus as claimed in any preceding claim, wherein the primary 25 side of the heat exchanger is followed by a container which is in thermal contact with the heat transport medium evaporated by the heat source.

12. A treating apparatus substantially as herein described with reference to the accompanying drawings. 30 U:\ECP\NZ\nz15799-07-retyped pages.doc