EP0969255B1 - Installation with a heat pump and an accumulator - Google Patents

Abstract

The compressor (22), high temperature heat transmitter (24), expansion device (26) and low temperature heat transmitter (28) are all joined together in a circuit, through which carbon dioxide flows as work medium. The high temperature heat transmitter of the heat pump (18) is arranged in the floor-side area (30) of the temperature-layered accumulator (20). It is a counterflow heat transmitter in a container. A rise pipe (36) connects to the upper side of the container (34) and extends with an outlet (38) to the upper side area (40) of the accumulator. The high temperature heat transmitter is preferably formed as a lamella tube bundle heat transmitter. In the rise pipe is a device for regulating the volume flow of the storage fluid (32) to be heated.

Description

The invention relates to a system with a heat pump, the compressor, a high temperature heat exchanger, an expansion device and one Has low temperature heat exchangers, which are in a circle with each other connected and flowed through by a work equipment, and with one Storage-fluid-containing storage fluid, in its bottom area of the high-temperature heat exchanger of the heat pump is arranged, wherein the high-temperature heat exchanger is a countercurrent heat exchanger is provided in a container on the top In terms of flow, a riser pipe connects, which emerges with a riser pipe outlet extends to the top area of the memory.

From the prospectus of Blomberg - Vertriebsgesellschaft GmbH, 59229 Ahlen: "HOT WATER HEAT PUMPS and HOT WATER STORAGE", 3. Edition, 2/95 a system is known in which the high temperature heat exchanger is designed as a smooth tube heat exchanger. Furthermore is it is known to replace such smooth tubes with finned tubes to the Heat transfer from the high temperature heat exchanger to the storage fluid improve. Said storage fluid is usually Service water or utility water or around heating water.

From CH-PS 524 115 is a water heater for generation and Storage of hot water with one in the lower part of the one Hot water and a cold water container equipped inside of a riser arranged heating unit known. By ordering the Heat exchanger in the lower area of the water heater, and thereby, that the riser pipe opens into the upper area of the container is there ensures that even at low heat output of the heat exchanger hot water is available as early as possible. The heat exchanger will thereby in its lower area on all sides by the water to be heated incident flow.

A water heater of the latter type for generation and Storage of hot water is also known from DE 31 37 146 C2. at this well-known water heater is the one receiving the heating unit Housing part of the riser pipe closed to the inside of the container, the Cold water supply to the container in a manner known per se with a Connection device for a cleaning hose equipped Cold water supply to the tank in the flow direction of the water behind the Cleaning hose connection equipped with a bypass line, which in the Housing for the heating unit opens, a locking device in the Cold water supply between the tank and the connection of the bypass line arranged on the cold water supply line, and on the discharge side of the riser a connection device for connecting a Cleaning hose provided that the inside of the riser pipe against the Detach the interior of the container with the cleaning hose connected. By Such training will make descaling and cleaning easy and quick the heat exchanger, which has, for example, a heating coil, and the riser pipe enabled without much material.

For heat pumps, i.e. Compression heat pumps have so far been used as Work equipment e.g. R134a, R22 or propane for use. Recently tests with carbon dioxide as a working medium have also been carried out or Compression heat pumps with carbon dioxide as a working medium brought. Such is the case with such carbon dioxide compression heat pumps High pressure above the critical pressure of 7.4 Mpa. With such carbon dioxide compression heat pumps there is no longer a condensation process. The Carbon dioxide, which the compressor at high pressure and at high temperature, e.g. with 9 Mpa and 100 ° C, is left without condensing in the high-temperature heat exchanger cooled to a temperature of, for example, 20 ° C.

Apart from the desuperheating and supercooling section, High temperature heat exchanger of a heat pump with conventional Working or refrigerant has a largely constant condensation temperature, which is clearly related to the condensation pressure via the vapor pressure relationship is linked. In the high temperature heat exchanger one Compression heat pump with carbon dioxide as a working medium, however, is one continuous temperature decrease, i.e. a so-called temperature glide, the Carbon dioxide gas.

Heat pumps, especially those with carbon dioxide as the working fluid, can be used after Water heater principle can be used, in which the one to be heated Fluid, especially water, which is warmed up when it is needed. However, it is also possible to store the heated water in a suitable storage temporarily.

Layered memories are known from solar energy technology. This Stratified storage has an internal heat exchanger, which is in one Flow tank with riser pipe is installed. Such a stratified storage is from the prospectus of Solvis Energiesysteme GmbH & Co. KG. 38122 Braunschweig, issue date March 25, 1997: "Stratos Integral: hot water and Heating support in one device ", pages 6 and 7, known. The internal Heat exchanger is used there, the thermal energy from the solar collector deliver upcoming heat transfer fluid to the memory.

A system of the type mentioned is known from DE 29 03 250, in which a riser pipe is arranged in a water reservoir. Items in memory Storage water rises thermosiphonically through the riser pipe and becomes layered in the upper storage area. To the refrigerant are this no state of the art in printed form.

DE 195 42 076 A1 discloses a hot water tank, in particular for Process water, with a closed storage tank with a Cold water inlet in its lower area and a hot water outlet in its upper area, with one arranged upright in the container Flow guide or riser pipe and with one in the lower part of the riser pipe arranged heat exchanger. The heat exchanger can be used as a coil be formed, which is held on a base plate. A heating medium flow and a heating medium return are passed through the base plate and with the Heat exchanger connected. Circulates through the heating medium supply and return liquid heating medium, for example water, through a Solar collector system and / or heated by a conventional boiler is.

From US 4 205 532 a refrigerator or heat pump is known, wherein as work equipment, i.e. is used as a coolant, carbon dioxide or ethane. Carbon dioxide as a coolant for chillers or heat pumps use, is also known from DE 43 15 024 A1.

The invention has for its object a system of the type mentioned to create, which has a high coefficient of performance, the one to be heated Storage fluid the high temperature heat exchanger with the highest possible Usable temperature leaves, the high-temperature heat exchanger compact is trained and has a high heat transfer capacity, and Drive the volume flow of the storage fluid to be heated mechanical Driving means, such as a pump, are unnecessary.

This task is carried out in a plant of the type mentioned solved according to the invention in that the working fluid of the heat pump Is carbon dioxide, and that the compressor by means of a connecting line with the High temperature heat exchanger is connected, which emerges from the riser pipe axially down through the riser.

1) das Kohlendioxid-Gas verlässt den Hochtemperatur-Wärmeübertrager mit einer relativ niedrigen Temperatur, wobei mit abnehmender Temperatur die Leistungsziffer steigt, und

2) das zu erwärmende Speicherfluid verlässt den Hochtemperatur-Wärmeübertrager mit einer relativ hohen Nutztemperatur.

The fact that the high-temperature heat exchanger heats the storage fluid, preferably process water or utility water or heating water, in countercurrent results in the advantage that - in the event that the fluid flow to be heated is optimally designed - the operating point of the high-temperature heat exchanger is two fulfills important requirements, namely

1) the carbon dioxide gas leaves the high-temperature heat exchanger at a relatively low temperature, the coefficient of performance increases as the temperature decreases, and

2) the storage fluid to be heated leaves the high-temperature heat exchanger with a relatively high useful temperature.

The special advantages of carbon dioxide compared to conventional refrigerants lie in the high level of environmental compatibility. In addition, when heating of a fluid to more than 50 ° C higher performance figures than at conventional compression heat pumps. When to be achieved In contrast to carbon dioxide, fluid temperatures of over 65 ° C can conventional refrigerants are no longer used sensibly. Like the specific temperature profiles in the high-temperature heat exchanger clearly is, it is thermodynamically favorable for conventional refrigerants heating fluid with a low temperature glide, because in In this case, the temperature curve of the fluid to be heated better at the largely constant temperature curve of the condensed conventional Adapts refrigerant. Because of the high temperature glide of carbon dioxide correspondingly a high temperature glide of the fluid to be heated thermodynamically favorable.

The fact that in the system according to the invention the compressor Heat pump using a connection line with the high-temperature heat exchanger is connected, which is axially from the riser pipe outlet through the Memory provided riser pipe extends downwards, there is a Improvement or optimization of the thermosiphonic drive and a material-saving increase in countercurrent or Cross-counterflow heat transfer surface between the carbon dioxide Heat pump and the storage fluid to be heated in with the heat pumps connected storage.

It is preferred if the connecting line is coaxial through the Riser pipe extends.

For improved cooling of the carbon dioxide and for material saving Enlargement of the heat transfer area of the high-temperature heat exchanger can this with the expansion device of the heat pump be connected by means of a return line, which pulls in a coil, which in the bottom area of the storage below the high-temperature heat exchanger and is arranged below the container in the memory. The Pipe coil can in this case be arranged in at least one plane leading to Bottom of the memory is provided at least approximately in parallel. The said Pipe coil can also be arranged inside the container.

According to the high-temperature heat exchanger can Cross-countercurrent heat exchanger. The high temperature heat exchanger can be provided in a bell-shaped container which is open on the underside. The said container can also be closed on the underside.

The storage fluid to be heated comes from the lower - i.e. bottom Area of the temperature-stratified storage and the heated storage fluid is in the distant top area of the memory again sandwiched.

By designing the memory with the associated container in the bottom area of the storage and through the top of the container flow-related riser pipe is achieved that the drive of the Volume flow of the storage fluid to be heated takes place thermosiphonically, so that to drive the volume flow of the to be heated Storage fluids no mechanical drive means such as a pump or the like. is required.

It has proven to be advantageous if the High-temperature heat exchanger as a finned tube bundle heat exchanger is trained. Such a finned tube bundle heat exchanger can in advantageously small volume, i.e. be compactly dimensioned or designed, to achieve a correspondingly high heat transfer capacity. The Fins of such a finned tube bundle heat exchanger cause in advantageously only one in the flowing through storage fluid to be heated relatively low pressure drop so that the thermosiphonic drive is not disturbed becomes. On the other hand, it is important that the volume flow of the to be heated Storage fluids do not increase too much, since otherwise the one to be heated up Storage fluid is not heated to the required usable or storage end temperature. On the other hand, the thermosiphonic volume flow of the to be heated Storage fluids must be large enough to hold the heat pump's working fluid cooling carbon dioxide to a sufficient depth.

The riser pipe preferably has such a clear internal cross section and such an axial length dimension that its thermosiphonic Flow pressure drop a volume flow with low high-temperature heat exchanger outlet temperature of the heat pump drive means and with high outlet temperature of the storage fluid to be heated at the riser outlet of the riser pipe. This is a correspondingly high Storage temperature and a high performance figure achieved.

A typical application or operating case of the system according to the invention is drinking water heating, the water in the temperature-stratified Storage of the system in the initial state a homogeneous temperature of e.g. 15 ° C. After switching on the carbon dioxide containing as working medium The heat pump uses the water in the storage tank High temperature heat exchanger heated. Because of this warming it experiences this Water has a thermosiphonic buoyancy and flows through it in the storage tank provided riser pipe in the upper storage area. Here it forms due to the low density compared to the colder storage water warm layer of water. Without any significant mixing of the warm Water with the cold water underneath will gradually become the storage after warmed up until finally the warm water layer also the lower area of the memory reached.

In order to reliably prevent the temperature of the storage fluid at the riser outlet from fluctuating within a certain range depending on the state of charge of the accumulator and / or depending on the operating state of the CO ₂ heat pump in such a system of the type described above, the riser for regulating the Volume flow of the storage fluid to be heated, a control device can be provided. This control device is, for example, a valve with which it is possible to regulate the volume flow in the riser pipe in such a way that, regardless of the state of charge of the accumulator and / or regardless of the operating state of the heat pump at the riser pipe outlet, an at least approximately constant temperature of the accumulator fluid is established , Such a design advantageously ensures an optimal volume flow of the storage fluid without mechanical drive means such as a pump or the like, even at extreme operating points of the system or in modified constructions thereof.

Fig. 1

eine grafische Darstellung des Funktionszusammenhangs im Hochtemperatur-Wärmeübertrager zwischen der Temperatur und der Enthalpie eines konventionellen Wärmepumpen-Arbeitsmittels, von Kohlendioxid als Arbeitsmittel und des zu erwärmenden Fluides im Speicher der Anlage,

Fig. 2

eine Ausbildung des Speichers der Anlage, und

Fig. 3

in einer perspektivischen Ansicht eine Ausbildung des Hochtemperatur-Wärmeübertragers der Anlage gemäß Fig. 2 als Lamellenrohrbündel-Wärmeübertrager.

Further details emerge from the following description of an exemplary embodiment of the system according to the invention which is illustrated in the drawing or essential details thereof. Show it:

Fig. 1

a graphical representation of the functional relationship in the high-temperature heat exchanger between the temperature and the enthalpy of a conventional heat pump working medium, of carbon dioxide as working medium and the fluid to be heated in the storage of the system,

Fig. 2

training the memory of the system, and

Fig. 3

in a perspective view, an embodiment of the high-temperature heat exchanger of the system according to FIG. 2 as a finned tube bundle heat exchanger.

Figure 1 shows the functional relationship between the temperature T and the enthalpy H in the high-temperature heat exchanger of a heat pump with a conventional refrigerant or working fluid, which is illustrated by the line 10, compared to carbon dioxide as a working fluid, which is shown by the dashed line 12 is shown. The reference number 14 in FIG. 1 denotes the functional relationship between the temperature T and the enthalpy H of the fluid to be heated. It can be seen from FIG. 1 that - apart from the heating and supercooling section - there is a largely constant condensation temperature T _K in the high-temperature heat exchanger of a heat pump with a conventional refrigerant or working medium. This condensation temperature T _K is clearly linked to the condensation pressure via the vapor pressure relationship. In contrast, in a high-temperature heat exchanger with the working medium carbon dioxide, as the dashed line 12 shows, there is a continuous decrease in temperature, ie a so-called temperature glide, of the carbon dioxide gas. The temperature of the working or useful fluid to be heated increases linearly proportionally with the enthalpy H, which is illustrated in FIG. 1 by line 14. The special advantages of carbon dioxide compared to conventional refrigerants are their high environmental compatibility. In addition, higher performance figures can be achieved when heating a fluid to over 50 ° C than with conventional compression heat pumps. With fluid temperatures of over 65 ° C to be achieved - in contrast to carbon dioxide - conventional refrigerants can no longer be used sensibly. As can be seen from the special temperature profiles in the high-temperature heat exchanger, it is thermodynamically favorable for conventional refrigerants to heat the fluid to be heated with the low temperature glide, since in this case the temperature profile of the fluid to be heated better matches the largely constant temperature profile of the condensed one conventional refrigerant. Because of the high temperature glide of carbon dioxide, a high temperature glide of the fluid to be heated is thermodynamically favorable, as has already been stated.

Figure 2 shows an embodiment of the memory 20 in a schematic Sectional view. The high temperature heat exchanger 24 is as Lamellar tube bundle heat exchanger 42, as is also shown in FIG a perspective view is drawn. Such finned tube bundle heat exchanger are known per se, so they are not dealt with in more detail are needed.

The high-temperature heat exchanger designed as a finned tube bundle heat exchanger 42 24 is connected to a compressor by means of a connecting line 44 connected to a heat pump. The connecting line 44 extends from one Riser pipe outlet 38 axially, preferably coaxially, through a riser pipe 36 downwards into a container 34 and is there to a high temperature heat exchanger 24 of the heat pump connected. The high temperature heat exchanger 24 is with an expansion device of the heat pump by means of a return line connected, which has a coil 48. The pipe coil 48 is in FIG. 2 in a side view simply as a line and underneath in a top or Bottom view illustrated as a serpentine line. The coil 48 is in bottom area 30 of the storage 20 below the high-temperature heat exchanger 24 and below the bell-shaped, open on the underside Container 34 arranged. The pipe coil 48 can also be in the container 34, for example be provided.

Claims (7)

1. Installation with a heat pump (18), which has a compressor (22), a high-temperature heat exchanger (24), an expansion device (26) and a low-temperature heat exchanger (28), which are connected to one another in a circuit and through which a working medium flows, and with a temperature-stratified accumulator (20) which contains an accumulator fluid (32) and in the bottom-side region (30) of which is arranged the high-temperature heat exchanger (24) of the heat pump (18), the high-temperature heat exchanger (24) being a countercurrent heat exchanger provided in a vessel (34) which has adjoining it fluidically on the top side a riser pipe (26) which extends with a riser-pipe outlet (38) to the top-side region (40) of the accumulator (20), characterized in that the working medium of the heat pump (18) is carbon dioxide, and in that the compressor (22) is connected to the high-temperature heat exchanger (24) by means of a connecting line (44) which extends axially downwards from the riser-pipe outlet (38) through the riser pipe (36).
2. Installation according to Claim 1, characterized in that the connecting line (44) extends coaxially through the riser pipe (36).
3. Installation according to Claim 1, characterized in that the high-temperature heat exchanger (24) is connected to the expansion device (26) by means of a return line (46) which has a pipe coil (48) which is arranged in the bottom-side region (30) of the accumulator (20) below the high-temperature heat exchanger (24) and below the vessel (34).
4. Installation according to Claim 3, characterized in that the pipe coil (48) is arranged in at least one plane which is provided at least approximately parallel to the bottom of the accumulator (20).
5. Installation according to Claim 1, characterized in that the high-temperature heat exchanger (24) is a cross-countercurrent heat exchanger.
6. Installation according to Claim 1, characterized in that the high-temperature heat exchanger (24) is provided in a bell-shaped vessel (34) open on the underside.
7. Installation according to Claim 1, characterized in that the high-temperature heat exchanger (24) is designed as a finned tube bundle heat exchanger (42).

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