WO2023017373A1

WO2023017373A1 - Integrated circuit for circulating fluids for gas-absorption heat pumps

Info

Publication number: WO2023017373A1
Application number: PCT/IB2022/057253
Authority: WO
Inventors: Luigi TISCHER; Pietro BREVI; Gianmarco CABRI; Riccardo CAPPADOZZI
Original assignee: Ariston SpA
Current assignee: Ariston SpA
Priority date: 2021-08-09
Filing date: 2022-08-04
Publication date: 2023-02-16
Anticipated expiration: 2024-02-09
Also published as: EP4384768A1; CN118043619A; IT202100021518A1; US20240361053A1

Abstract

A circuit for circulating fluids, in particular for gas-absorption heat pumps, made from a single integrated structure consisting of a compact tube bundle and two connection plates which provide mechanical and fluid connection to the tubes of the tube bundle by virtue of a plurality of internal channels.

Description

INTEGRATED CIRCUIT FOR CIRCULATING FLUIDS FOR GAS-ABSORPTION HEAT PUMPS

FIELD OF THE INVENTION

The present invention relates to the technical field of gas-absorption heat pumps. In further detail, the present invention relates to the technical field of closed circuits for circulating refrigerants, generally water-ammonia or water-lithium bromide, for gas heat pump systems.

BACKGROUND ART

A gas-absorption heat pump is based on an alternating cooling cycle in which the compressor is replaced by a closed circuit travelled by a refrigerant, generally water- ammonia (NH3) or water-lithium bromide (LiBr). The refrigerant takes the liquid or vapor state depending on the temperature and pressure conditions. In the most simplified form thereof, the closed circuit of the absorption heat pump consists of: generator, absorber, condenser, restrictors and evaporator. More frequently, for reasons of increasing thermodynamic efficiency levels, the basic cycle is implemented with a series of internal heat recoveries by further heat exchangers which work between different parts of the circuit. Various embodiments of the prior art include up to 3 or 4 recovery exchangers.

Condenser and evaporator consist of exchangers (often provided as a tube bundle) placed in contact with the service fluids (water or air in the ammonia-absorption gas heat pump) in which the refrigerant flows, which gives heat to the condenser (on the high temperature side) and removes it from the evaporator (on the low temperature side).

The transformations undergone by the refrigerant form the gas-absorption heat pump cycle: by providing energy with a gas burner, the refrigerant, under evaporation, absorbs heat from the external fluid and, by means of the condenser, gives it to the means to be heated.

The presence of refrigerants such as ammonia requires the circuit to be made of steel since the materials containing metals such as aluminum, copper, or zinc cannot be used due to the corrosion to which they would be subjected. Therefore, since the circuit containing the refrigerant needs to be airtight, i.e., hermetically sealed from the environment, the construction thereof requires to provide joints made by welding with different technology and various and more expensive apparatuses as compared to the more common brazing joint which is typical in vapor compression machines utilizing fluorinated gases.

Moreover, the actual closed circuits for circulating refrigerants for gas heat pump systems are manufactured with single heat exchangers, each designed and manufactured individually. The testing of the heat exchangers and the thermal isolation thereof are also performed singularly for each exchanger. Finally, the heat exchangers are connected in the circuit by means of tubular conduits, generally at least four for each heat exchanger (precisely: 2 for each fluid - inlet and outlet - for at least two fluids required to perform the heat exchange), which are welded (by welding) to ensure stability and sealing thereof.

It is apparent that the geometry of the tube-bundle exchanger requires, and is usually obtained by means of, two connections aligned with the tube bundle (for the fluid contained in the tube bundle tubes) and two connections perpendicular to the bundle axis (for the fluid outside the bundle and contained in the so-called shell).

It is also apparent that the procedure described above requires performing several manual welding operations for which it is necessary that the circuit has a certain extension, and that the various components of the circuit - and in particular the various exchangers - are suitably spaced apart from one another in order to allow access to the welding apparatuses.

Therefore, the prior art circumstance in the technical field at hand underlines the need for closed circuits to be employed to circulate refrigerants in gas heat pump systems, which can effectively solve the drawbacks described and other drawbacks present in the prior art.

BRIEF DESCRIPTION OF THE INVENTION

Therefore, the present invention relates to a circuit for circulating ammonia - or other refrigerant - for gas-absorption heat pumps, consisting of a single integrated structure.

The circuit according to the present invention is preferably made of steel (other materials, even plastics, could theoretically be employed), which is completely airtight and substantially comprises three components: a tube bundle comprising a plurality of tubes all substantially having the same height and various diameters, and two connection plates adapted to be connected each, by welding, to a different end of the tube bundle. Said plates comprise a series of fluid connections therein, which suitably connect the various tubes of the tube bundle so as to create the heat exchangers required and the reciprocal connections thereof.

The plates can also be manufactured with one or more layers so as to create various fluid connections placed in parallel and isolated from one another and adapted to obtain circuits and heat exchangers characterized by an even very high degree of complexity.

The present invention allows significantly simplifying the manufacture, testing and maintenance of fluid circuits for circulating ammonia for absorption heat pumps, further allowing the achievement of a level of compactness and minimization of the volumes unknow until today.

With the tube bundle according to the present invention, it is possible to obtain an assembly of heat exchangers which can be different in function and operating conditions or can belong to other components of an absorption heat pump where various fluid circuits run. The suitable configuration of the tube bundle is carried out by virtue of the connection plates which, through a plurality of internal channels, create the required connections and allow increased degrees of integration and optimization of the overall system.

In further detail, the present invention allows manufacturing fluid circuits for circulating ammonia for absorption heat pumps, allowing a very small number of welds as compared to the prior art and allowing the use of automatic and no longer only manual welding techniques, thus allowing the production costs to be decreased and increased production volumes to be obtained. Moreover, the required welds will globally be shorter in length, with immediate benefits in terms of increased quality level and decreased production times and costs. Additionally, the layout of the fluid circuit allowed by the present invention allows conducting tests for testing the airtightness of the individual exchangers and/or the assembly by means of automatic apparatuses, with subsequent improvement in reliability, times and costs of the operations. The simplification of the assembly process of the fluid circuits according to the present invention further allows achieving the isolation of the exchangers in a simpler and more immediate manner.

Finally, the small size of the fluid circuit allowed by the present invention allows using a smaller amount of coolant, with significant benefits in terms of lower costs and better thermodynamic control of the operation of the circuit.

BRIEF DESCRIPTION OF THE DRAWINGS

Further features and advantages of the invention will become apparent from the reading of the following detailed description, given by way of a non-limiting example, with the aid of the figures shown in the accompanying drawings, in which:

Figure 1 shows a view of a preferred embodiment of the circuit for circulating refrigerants for gas-absorption heat pumps, according to the present invention;

Figure 2 shows a detail of an end of the circuit according to the present invention, comprising one of the two connection plates;

Figure 3 shows a detail of the other end of the circuit according to the present invention, comprising one of the two connection plates, and

Figure 4 shows a sectional view of an end of the circuit according to the present invention, comprising one of the two connection plates.

The following description of exemplary embodiments relate to the accompanying drawings. The same reference numerals in the various drawings identify the same elements or similar elements. The following detailed description does not limit the invention. The scope of the invention is defined by the appended claims. DETAILED DESCRIPTION OF THE INVENTION

With reference to accompanying Figure 1 , a preferred embodiment of the integrated circuit for circulating refrigerants for gas-absorption heat pumps according to the present invention comprises a tube bundle 10 adapted to circulate a refrigerant, comprising a plurality of tubes 1 1 having various diameters, and two connection plates 12, 13 adapted to be connected each, by welding, to a different end of the tube bundle 10.

In a preferred embodiment of the invention, the tubes 1 1 of the tube bundle 10 substantially all have the same height. Thereby, the connection plates 12, 13 can have a substantially flat, simpler structure and such as to minimize the volumes. Said tubes 11 of the tube bundle 10 are preferably made of steel, as are the two connection plates 12, 13. Said connection plates 12, 13 comprise a series of holes 14 adapted to engage, on one side, the ends of the tubes 11 of said tube bundle 10 so as to promote the welding thereof to the plate. Therefore, the holes 14 each have shape and size which are compatible with the diameter of the corresponding tube 11 . Moreover, said holes 14 are connectable to at least one internal channel 24 of said plate 12, 13, said at least one channel 24 being adapted to connect fluidly the various tubes 1 1 so as to obtain the complete structure of the tube bundle 10 of a heat exchanger for gas-absorption heat pumps.

These channels 24 can also be made on several layers so as to obtain various fluid connections placed in parallel and isolated from one another and adapted to create circuits and heat exchangers characterized by tube bundles having an even very high degree of complexity. For example, the plates 12, 13 can be obtained by milling from a flat plate while the tubes 1 1 can be obtained, for example, by drawing or bending and welding.

Said holes 14 are also connectable to external connection tubes 15 adapted to connect the tube bundle 10 to the other parts of a circuit for circulating refrigerants for gas-absorption heat pumps.

In a preferred embodiment shown in Figure 2, there are connections 23 between the hole 14 and the tubes 1 1 of the tube bundle 10 or the external connection tubes 15. Said connections 23 can be obtained by means of accessories to be welded to plate 13 or by means of a drawing process of the plate 13 itself.

Further preferred embodiments provide for the plate 12, 13 to have, on the opposite sides, facing holes in various amounts and diameters. Figure 2 shows examples of larger holes 14 arranged on a side of plate 13, facing a plurality of smaller holes 10 on the other side of plate 13.

Moreover, said plate 12, 13 can advantageously comprise supports 22 for performing the welding, thus avoiding or limiting the metal deformations, and thermal break grooves 21 adapted to decrease the conduction heat transfer between different parts of plate 12, 13.

Therefore, the present invention allows manufacturing fluid circuits for circulating ammonia, in particular for absorption heat pumps, allowing a very small number of welds as compared to the prior art and allowing the use of automatic and no longer only manual welding techniques, thus allowing the production costs to be decreased and increased production volumes to be obtained. Moreover, the required welds will globally be shorter in length, with immediate benefits in terms of increased quality level and decreased production times and costs. Additionally, the layout of the fluid circuit allowed by the present invention allows conducting tests for testing the airtightness of the individual exchangers and/or the assembly by means of automatic apparatuses, with subsequent improvement in reliability, times and costs of the operations. Additional advantages associated with the present invention relate to the simplification of the process of assembling the fluid circuit, which allows achieving the isolation of the exchangers in a simpler and less expensive manner.

The small size of the fluid circuit allowed by the present invention further allow using a smaller amount of coolant. A smaller amount of coolant results in significant benefits in terms of better thermodynamic control of the operation of the circuit.

Claims

1. A circuit for circulating fluids for gas-absorption heat pumps, comprising a tube bundle (10) adapted to circulate a plurality of fluids and in turn comprising a plurality of tubes (11 ) and two connection plates (12, 13) adapted to be connected each, by welding, to a different end of the tube bundle (10) and comprising a plurality of internal channels (24), each adapted to connect fluidly at least two tubes (1 1 ) of said plurality of tubes.

2. A circuit according to claim 1 , characterized in that the tubes (1 1 ) of said plurality of tubes have various diameters.

3. A circuit according to one or more of claims 1 to 2, characterized in that the tubes (1 1 ) of the tube bundle (10) all substantially have the same height and the connection plates (12, 13) have a substantially flat structure.

4. A circuit according to one or more of claims 1 to 3, characterized in that said connection plates (12, 13) comprise a series of holes (14) adapted to engage the ends of the tubes (1 1 ) of said tube bundle (10) so as to promote the welding thereof to the plate, said holes (14) each having shape and size which are compatible with the diameter of the corresponding tube (1 1 ).

5. A circuit according to claim 4, characterized in that said holes (14) are connected to at least one internal channel (24) of said plate (12, 13).

6. A circuit according to one or more of claims 1 to 5, characterized in that said holes (14) are further connectable to external connection tubes (15) adapted to connect the tube bundle (10) to the other parts of a circuit for circulating refrigerants for gas-absorption heat pumps.

7. A circuit according to one or more of claims 1 to 6, characterized in that said at least one channel (24) comprises a plurality of channels made on several layers so as to obtain various fluid connections placed in parallel and isolated from one another.

8. A circuit according to one or more of claims 1 to 7, characterized in that said plate (12, 13) comprises at least one connection (23) between the hole (14) and the corresponding tube (1 1 ) of the tube bundle (10) and/or the corresponding external connection tube (15).

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9. A circuit according to one or more of claims 1 to 8, characterized in that said plate (12, 13) comprises, on the opposite sides, facing holes (10, 14) in various amounts and diameters.

10. A circuit according to one or more of claims 1 to 9, characterized in that said plate (12, 13) comprises supports (22) adapted to allow performing the welding while avoiding or limiting metal deformations.

1 1 . A circuit according to one or more of claims 1 to 10, characterized in that said plate (12, 13) comprises thermal break grooves (21 ) adapted to decrease the conduction heat transfer between different parts of the plate (12, 13).

12. A circuit according to one or more of claims 1 to 1 1 , characterized in that it is made of steel.

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