AT514877A2 - Exhaust gas heat exchanger for a combined heat and power plant and for operation with a heat pump - Google Patents

Abstract

An exhaust gas heat exchanger for a combined heat and power plant and for combined operation or parallel operation with a heat pump is designed for installation in shafts or chimneys (1). The exhaust gas heat exchanger has a central, one-piece exhaust pipe (2) and at least one along the exhaust pipe (2) arranged and standing with the exhaust pipe in heat-conducting contact passage part (3) for passing a heat-absorbing fluid. Furthermore, one of the exhaust pipe (2) by a high heat insulating insulation (5) separated further passage part (4) for the passage of the fluid along the exhaust pipe (2) is arranged. The passage part (3) and the further passage part (4) surround the exhaust pipe (2) each half-shell-like. Furthermore, a cladding tube (6) for receiving electrical lines, which is separated from the exhaust pipe (2) also by the high heat insulating insulation (5), also along the exhaust pipe (2) may be arranged.

Description

Exhaust gas heat exchanger for a combined heat and power plant and for operation with a heat pump

The invention relates to an exhaust gas heat exchanger for a combined heat and power plant and for combined operation or for parallel operation with a heat pump according to claim 1, wherein the exhaust gas heat exchanger is designed for installation in shafts or chimneys.

In buildings and facilities of various kinds, the energy supply is increasingly ensured with cogeneration units, and these are often, even to meet the seasonal energy needs as efficient and cost to be able to operate more often in the network or in parallel with heat pumps. Heat pumps are basically designed to absorb heat from a suitable medium, such as from the earth, water or air, and deliver it to the consumer in the form of heat energy. However, energy production by means of heat pumps is subject to the known seasonal fluctuations, which is why the mentioned combinations with combined heat and power plants often make sense. If obsolete and inefficient heating systems are replaced by buildings, then a combination of a combined heat and power plant with a heat pump can be considered. In many cases, however, dictate the local conditions, for example, in already heavily overbuilt settlement areas, that only certain types of heat pumps can be meaningful and inexpensive to integrate. The possibility of installing such systems in existing rooms and existing structural conditions is therefore often in the foreground with such renovations. Although chimneys are usually present and they are often used to dissipate the exhaust gases from the cogeneration plant. In general, however, it is the case that the wiring of combined heat and power plants and heat pumps outside the engine room, takes place locally separated.

Technical solutions that allow cost-effective solutions for a combined operation or parallel operation of a combined heat and power plant with a heat pump, especially in conversions and installation in existing buildings and spatial conditions are therefore desirable.

The object is to provide an exhaust gas heat exchanger for a combined heat and power plant, which is designed for installation in shafts or chimneys and allows a parallel operation or in a combined operation with a heat pump meaningful and cost-effective integration and combination of wiring.

Of course, there have long been attempts to use as much of the residual heat energy that is still contained in combustion gases from heating systems and the like and is discharged through chimneys in the ambient air, and recover. An example of such a device is shown in DD-212'288. This document discloses a device for utilizing the chimney heat for hot water treatment by a structurally modified precast element. For this purpose, recesses for receiving water pipes are arranged in the precast elements from which the chimney is constructed. The pipe assembly of the water pipes takes place during the installation of the chimney and the built-in water pipes run along a flue pipe channel element.

Newer solutions for chimney flue gas heat exchangers (KAWT) are also known. Thus, CH-699'393 shows a heat exchanger for the flue gas duct of a furnace inter alia with an embodiment in which in an annular space between an inner tube serving as flue gas channel, and an outer tube, preferably a spiral conduit for a cooling medium such as water the inner tube is arranged around. This Kaminabgaswärmetauscher is essentially built in one piece and extends over a majority of the length of the flue gas duct. This

Chimney flue gas heat exchanger can either be introduced from the top into the chimney or chimney during construction or conversions as a whole.

The solution of the stated object consists in that a suitable for installation in manholes or chimneys exhaust heat exchanger according to the feature combination of claim 1 is designed so that both the flow and the return of the fluid used in a heat pump are guided along the exhaust pipe of the cogeneration plant and that in addition the return of the fluid used in the heat pump can also be used to absorb the residual heat of the duct or the flue gas flowing through the exhaust gas.

One of the main advantages of the inventive exhaust gas heat exchanger is, inter alia, that both the installation of the piping (for cogeneration plant and heat pump) in new buildings as well as the subsequent installation of the piping in existing buildings or parts of buildings can be done much more compact, space-saving and cost-effective. This is achieved in particular by the use of highly heat insulating insulation, which make it possible that lines can now be performed closely spaced parallel, which could not be arranged adjacent for reasons of disturbing heat transfer adjacent.

If a combined heat and power plant is used in combination or in parallel with a heat pump, it is also possible to achieve an additional use of the residual heat of the exhaust gases from the combined heat and power plant that usually rises in the chimney. Although the residual heat in the exhaust gas is already mostly used in cogeneration plants before the discharge into a chimney or a flue pipe in cogeneration plants, but still remains unused residual heat as a rule. This residual heat can be used to improve the efficiency of a heat pump. It is therefore assumed that the heat-absorbing medium of the heat pump used should not only absorb heat from the selected primary heat source (ie from earth, air or water), but also also residual heat from the rising in the chimney flue gases of the combined heat and power plant.

Of course, a great advantage is the particularly simple and compact design of the exhaust gas heat exchanger according to the invention, because all the cables to be pulled up are housed in an integrated component, which is of course particularly the case when the outdoor unit of the heat pump is to be installed on the roof of a house. which has a substantially circular overall cross section. Thus, with the smallest total diameter, the largest cable cross-section sum can be realized and the installability is of course also improved.

By using a highly heat-insulating insulation, for example, one of the high-performance insulation materials known today, a system in which a combined heat and power plant and a heat pump in compound or parallel operation can be operated safely in normal operation. In normal operation, the exhaust temperature of the combined heat and power plant is relatively low (<120 ^). In case of failure of the cogeneration plant-own exhaust gas heat exchanger, the combined heat and power plant is automatically switched off when exceeding a defined exhaust gas temperature in the chimney or a defined maximum brine temperature in the brine circuit. The highly heat-insulating insulation is able to effectively protect both the flow of the heat pump fluid circuit as well as the also close to the exhaust pipe near electrical supply and control lines effectively.

Of course, however - especially with regard to possible incidents - the exhaust gas heat exchanger must be designed so that thermal expansion is always effectively absorbed. Because the exhaust pipe for safety reasons (prevention of the escape of dangerous and harmful gases) must be made in one piece, because of the often extending over several floors total length of the

Exhaust pipe yield large expansion changes. Therefore, the exhaust pipe must also be arranged displaceable relative to the passage part.

Overall, the proposed exhaust gas heat exchanger is particularly well suited for installations with air heat pumps in which the outdoor unit (i.e., the evaporator) is installed on the house roof. In particular, when replacing old furnaces structural changes to the building by conversion of existing fireplaces and chimneys by installing the novel exhaust gas heat exchanger with such integrated management of the heat-absorbing medium of the heat pump can be largely avoided.

It has been shown that in heat pumps of the type described, the heat-absorbing medium is preferably a water / glycol mixture, ie a brine. Brine circuits are particularly suitable for systems where heat from different sources should be taken up alternatively or simultaneously.

In the following, an embodiment of an inventive exhaust gas heat exchanger will be described in more detail with reference to drawings. It shows

Fig. 1 is a schematic longitudinal section through an exhaust gas heat exchanger, and

Fig. 2 is a schematic cross section through the

Exhaust gas heat exchanger according to FIG. 1.

Figures 1 and 2 shows a schematic longitudinal section and a schematic cross section through an inventive exhaust gas heat exchanger. Such an exhaust gas heat exchanger can for a

Combined heat and power plant that is designed for interconnected operation with a heat pump or for parallel operation with a heat pump can be used, and it is designed for installation or for subsequent installation in manholes or chimneys (1). Under composite operation is to be understood as an operating mode in which a block heating in dependence on the heat energy that can provide a heat pump is switched on at a consumer-side demand. Under parallel operation is a mode of operation in which a combined heat and power plant and a heat pump are operated independently.

The exhaust gas heat exchanger consists of a central, one-piece exhaust pipe (2) and at least one along the exhaust pipe (2) arranged and with the exhaust pipe in heat-conducting contact passage part (3) for passing a heat-absorbing fluid. In addition, one of the exhaust pipe (2) by a high heat insulating insulation (5) separated further passage part (4) is present, which also serves for the passage of the fluid along the exhaust pipe (2). In this case, the passage part (3) and the further passage part (4) are formed such that they each enclose the exhaust pipe (2) in the manner of a half shell. Furthermore, a cladding tube (6) for receiving electrical lines, from the exhaust pipe (2) also separated by the high heat insulating insulation (5), the exhaust pipe (2) arranged along.

The total cross section of the inventive exhaust gas heat exchanger is substantially circular. This results in a space-saving way a construction that can be very well introduced into an existing chimney / installed and of course can also be used in new plants.

The mentioned high heat insulating insulation (5) is preferably an airgel-based high performance insulation embedded in flexible high temperature fibers, for example Pyrogel XT or XTF, or a ceramic material.

The exhaust pipe (2) is arranged displaceably with respect to the passage part (3) and with respect to the thermal insulation (5) in order to absorb thermal expansions.

The passage part (3) and the further passage part (4) are designed for the passage of a heat-absorbing fluid of a heat pump, preferably an air heat pump. Preferably, the fluid, so the heat-absorbing medium of the heat pump, a water / glycol mixture, ie a brine.

Function Description:

From a combined heat and power plant (CHP) resulting exhaust gas is passed through an exhaust duct E to the chimney 1. There, the exhaust gas flows through the chimney 1 through the exhaust pipe 2 until it leaves the chimney.

The flow of the brine circuit D of the heat pump (WP) is guided via the further passage part 4 along the exhaust pipe 2 to an outdoor unit A on the roof of a house. The outdoor unit A of the brine circuit is used for heat absorption of the heat pump from the outside air. The return, so the heated brine, is fed via the passage part 3, again along the exhaust pipe 2 to an evaporator of the heat pump. Thus, both flow and return are performed compactly on the exhaust pipe 2 along. The brine circuit feed (that is, the further passage part 4) is protected by the heat insulation 5 from being heated by the exhaust pipe 2. Both in combined operation as well as in parallel operation of the combined heat and power plant with the heat pump, the heat insulation of the flow must be guaranteed compared to the exhaust pipe. The brine circuit return (i.e., the passage part 3), however, is brought into contact with the exhaust pipe 2, whereby an additional heat absorption takes place at the brine circuit return.

Reference number list: 1 Chimney 2 Exhaust pipe 3 Passage section (brine circuit return flow) 4 Further passage section (brine circuit flow) 5 Heat insulation 6 Sheath A Outdoor unit (evaporator in the brine circuit of the heat pump) B Control of the outdoor unit C Power supply of the outdoor unit D Brine circuit of the heat pump E Exhaust duct of the combined heat and power plant

Claims (7)

1. Exhaust gas heat exchanger for a combined heat and power plant and for combined operation or parallel operation with a heat pump, wherein the exhaust gas heat exchanger for installation in wells or chimneys (1) is formed and from a central, one-piece exhaust pipe (2) and at least one along the exhaust pipe (2 ) arranged and with the exhaust pipe in heat-conducting contact passage part (3) for passing a heat-absorbing fluid, characterized in that one of the exhaust pipe (2) by a high heat insulating insulation (5) separate further passage part (4) for the passage of the fluid along the exhaust pipe (2) is arranged, wherein the passage part (3) which is provided for additional heat absorption and the further passage part (4) each half-shell-like embrace the exhaust pipe (2). 2. Exhaust gas heat exchanger according to claim 1, characterized in that further comprises a cladding tube (6) for receiving electrical lines from the exhaust pipe (2) by the high heat insulating insulation (5) separated the exhaust pipe (2) is arranged along. 3. Exhaust gas heat exchanger according to claim 1 and 2, characterized in that the total cross-section is substantially circular. 4. Exhaust gas heat exchanger according to one of the claims 1 to 3, characterized in that the highly heat insulating insulation (5) is a high performance insulation based on airgel or a ceramic material. 5. Exhaust gas heat exchanger according to one of the claims 1 to 4, characterized in that the exhaust pipe (2) relative to the passage part (3) and relative to the thermal insulation (5) is slidably disposed to absorb thermal expansion. 6. Exhaust gas heat exchanger according to one of the claims 1 to 5, characterized in that the passage part (3) and the further passage part (4) are designed for the return and for the flow of the heat-absorbing fluid of an air heat pump. 7. Exhaust gas heat exchanger according to one of the claims 1 to 6, characterized in that the fluid is a brine.