Patent Application
20240361053
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.
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.
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 unknown 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.
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:
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.
With reference to accompanying
In a preferred embodiment of the invention, the tubes 11 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 11 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 11 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
Further preferred embodiments provide for the plate 12, 13 to have, on the opposite sides, facing holes in various amounts and diameters.
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.
| Number | Date | Country | Kind |
|---|---|---|---|
| 102021000021518 | Aug 2021 | IT | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/IB2022/057253 | 8/4/2022 | WO |
