Heat exchanger for an air conditioning or cooling system

Abstract

Heat exchanger (10a, 10b) for an air conditioning system (20a, 20b) provided with at least one circuit (15a, 15b) in which a cooling fluid flows, comprising a plurality of substantially coaxial tubular elements (11, 12, 26) separated by at least one jacket (13, 27), wherein in at least a first tubular element of the plurality of tubular elements (11, 12, 26) there flows a first fluid in liquid or liquid-gaseous form coming, during use, from a condenser (16) of the circuit (15a, 15b) and having a first temperature, and in at least a second tubular element of the circuit (15a, 15b), or in the jacket (13, 27), there flows a second fluid in gaseous or liquid form having a second temperature lower than said first temperature, so as to effect a heat exchange between the first fluid and the second fluid, thereby subcooling, during use, the first fluid exiting the condenser (16).

Description

FIELD OF THE INVENTION

[0001] The present invention concerns a heat exchanger for an air conditioning system, such as for example an air conditioner, a heat pump, a reversible cooling or heating system or suchlike, or for a cooling system, such as a refrigerator or suchlike.

[0002] The present invention also concerns an air conditioning or cooling system and a method for heat exchange in an air conditioning or cooling system.BACKGROUND OF THE INVENTION

[0003] As is known, air conditioning systems are provided with at least one cooling device configured to cool air or a liquid, generally water or glycol water, entering the system. If the cooled fluid is air, there is a ventilation apparatus to convey the air along one or more circulation ducts and a tray, or tub, configured to collect the condensate that forms on the evaporator when the latter cools the air. If the cooled fluid is a liquid, there is also a pumping system to distribute it to the uses, usually in a closed circuit.

[0004] The cooling device consists of a sealed circuit that substantially includes one or more of the following components: a compressor, an evaporator, a condenser and an expansion device, with a cooling liquid circulating inside them. In the case of a reversible system, that is, one that can both cool and heat, there is also a four-way valve that reverses the direction of circulation of the coolant in the system so as to obtain heating instead of cooling.

[0005] The ventilation apparatus comprises a closed casing, inside which a fan is generally disposed, the casing configured to be constrained to a pipe manifold or to make the air circulate directly in the environment to be air-conditioned.

[0006] Assuming that there is only one evaporator, the tray is usually disposed below the evaporator to collect the fall of condensation water coming from the latter and evacuate the air conditioning system in a controlled manner.

[0007] In fact, usually, the tray has a shape able to contain the evaporator in plan, and appears as an open container including at least one condensation water evacuation hole. Generally, the condensation water is simply evacuated without exploiting its cooling potential, except for some air conditioners where it is made to evaporate by making it circulate on the condenser by means of a recirculation pump.

[0008] Known air conditioning systems, whether for cooling only, heating only or reversible, are also improvable from the point of view of thermodynamic cycle efficiency.

[0009] There is therefore the need to perfect a heat exchanger for an air conditioning or cooling system that can overcome at least one of the disadvantages of the state of the art.

[0010] In particular, one purpose of the present invention is to provide a heat exchanger that is capable of increasing the efficiency of the air conditioning or cooling system to which it is applied, whether it is a cooling-only, heating-only, or a reversible system.

[0011] Another purpose of the present invention is to provide a heat exchanger able to subcool the cooling fluid in liquid or liquid-gaseous form exiting the condenser of the air conditioning system thus allowing to increase the system's efficiency.

[0012] Another purpose of the present invention is to provide a heat exchanger usable effectively in a cooling, heating, or dual- or three-fluid reversible air conditioning system.

[0013] Another purpose of the present invention is to provide an effective air conditioning or cooling system provided with a heat exchanger that increases its efficiency.

[0014] Another purpose of the present invention is to provide an efficient method for heat exchange in an air conditioning or cooling system.

[0015] The Applicant has devised, tested and embodied the present invention to overcome the shortcomings of the state of the art and to obtain these and other purposes and advantages.SUMMARY OF THE INVENTION

[0016] The present invention is set forth and characterized in the independent claims. The dependent claims describe other characteristics of the present invention or variants to the main inventive idea.

[0017] In accordance with the above purposes, a heat exchanger according to the present invention for an air conditioning or cooling system provided with at least one heat exchange circuit comprises a plurality of substantially coaxial tubular elements separated by at least one substantially cylindrical jacket. In at least a first tubular element of the plurality of tubular elements, or in the jacket, there flows a first fluid in liquid or liquid-gaseous form coming, during use, from a condenser of the circuit and having a first temperature, and in at least a second tubular element of the circuit, or in the jacket, there flows a second fluid in gaseous or liquid form having a second temperature lower than the first temperature, so as to effect a heat exchange between the first fluid and the second fluid, thereby subcooling the first fluid exiting, during use, the condenser.

[0018] Thanks to this heat exchanger equipped with the tubular elements, it is possible to increase the efficiency of the thermodynamic cycle of the air conditioning or cooling system, therefore of air conditioners or climate control units and / or heat pumps, or reversible machines, or refrigerators, for any type of application whatsoever. In particular, the present heat exchanger allows to subcool the fluid exiting the air conditioning system's condenser, thus allowing for the increase in efficiency.

[0019] According to another aspect of the invention, the heat exchanger comprises two coaxial tubular elements, wherein in a first tubular element there flows the second fluid in the form of a gaseous cooling fluid coming, during use, from an evaporator of the circuit, and in a second tubular element there flows the first fluid in the form of a liquid or liquid-gaseous cooling fluid coming, during use, from the circuit's condenser.

[0020] According to another aspect of the invention, the second tubular element is placed in contact, during use, with the condensation water coming from the evaporator.

[0021] This solution advantageously allows the heat exchange between the condensation water and the hot liquid that flows inside the second tubular element and further increases the cooling of the latter. This exchange can occur as a result of the condensation water dripping onto the second tubular element.

[0022] Advantageously, therefore, the heat exchanger is able to make the cooling liquid exiting the condenser exchange both with the cold cooling gas exiting the evaporator and also with the condensation water collected by the evaporator, thus maximizing its cooling and without the use of electrically driven members.

[0023] According to another aspect of the invention, the present heat exchanger is of the countercurrent type, so that the flow of the first fluid inside the at least one tubular element of the plurality of tubular elements occurs countercurrent with respect to the flow of the second fluid in the second tubular element, or in the jacket.

[0024] According to another aspect of the invention, at least one tubular element of the plurality of tubular elements is provided on the external surface with fins which extend inside the jacket.

[0025] According to another aspect of the invention, the heat exchanger comprises three substantially coaxial tubular elements able to define two jackets between them, the tubular elements being configured to allow, during use, the heat exchange between the first fluid exiting the condenser and the second cooling fluid, during the heating operation of the air conditioning system.

[0026] The invention also concerns an air conditioning, or cooling, system provided with at least one heat exchange circuit comprising at least one compressor, at least one condenser, at least one expansion device and at least one evaporator. The air conditioning system also comprises at least one heat exchanger as defined above.

[0027] According to another aspect of the invention, the heat exchanger is positioned under the evaporator, so that the condensation water produced by the evaporator can fall by gravity onto the heat exchanger.

[0028] According to another aspect of the invention, the air conditioning system comprises a diverter valve (also known as a cycle inversion valve) configured to allow it to switch from a cooling operating mode to a heating operating mode, or vice versa.

[0029] The invention also concerns a heat exchange method for an air conditioning system provided with at least one circuit in which a cooling fluid flows. The method comprises providing a heat exchanger in the circuit having a plurality of substantially coaxial tubular elements separated by at least one jacket, wherein in at least one tubular element of the plurality of tubular elements there flows a first fluid in liquid or liquid-gaseous form coming, during use, from a condenser of the circuit and having a first temperature, and in at least a second tubular element of the circuit, or in the jacket, there flows a second fluid in gaseous or liquid form having a second temperature lower than the first temperature, so as to effect a heat exchange between the first fluid at a higher temperature the and the second fluid at a lower temperature, thus subcooling the first fluid exiting, during use, the condenser.DESCRIPTION OF THE DRAWINGS

[0030] These and other aspects, characteristics and advantages of the present invention will become apparent from the following description of some embodiments, given as a non-restrictive example with reference to the attached drawings wherein: fig. 1 is a schematic view of an air conditioning system according to the present invention for cooling and with dual-fluid operation; fig. 2 is a schematic and larger scale view of a heat exchanger according to the present invention used in the air conditioning system of fig. 1; fig. 3 is a schematic diagram showing the flows of the heat exchanger of the previous drawings; fig. 4 is a schematic view of a reversible air conditioning system according to the present invention, therefore for cooling and heating and with dual-fluid operation; fig. 5 is a schematic diagram showing the flows of the heat exchanger in the air conditioning system of fig. 4 in heating mode; fig. 6 is a schematic view of a heat exchanger according to the present invention with three-fluid operation and in cooling mode, usable in another embodiment of the air conditioning system; fig. 7 is a schematic view of the heat exchanger of fig. 6 in heating mode; fig. 8 is a schematic view of an air conditioning system according to the present invention, with three-fluid operation for cooling or reversible, which uses the heat exchanger operating as in fig. 6; fig. 9 is a schematic view of an air conditioning system according to the present invention, with three-fluid operation for heating or reversible, which uses the heat exchanger operating as in fig. 7; fig. 10 shows the transformations of a thermodynamic cycle of an air conditioning system according to the present invention.

[0031] We must clarify that the phraseology and terminology used in the present description, as well as the figures in the attached drawings also in relation as to how described, have the sole function of better illustrating and explaining the present invention, their purpose being to provide a non-limiting example of the invention itself, since the scope of protection is defined by the claims.

[0032] To facilitate comprehension, the same reference numbers have been used, where possible, to identify identical common elements in the drawings. It is understood that elements and characteristics of one embodiment can be conveniently combined or incorporated into other embodiments without further clarifications.DESCRIPTION OF SOME EMBODIMENTS

[0033] We will now refer in detail to the possible embodiments of the invention, of which one or more examples are shown in the attached drawings, by way of a non-limiting illustration. The phraseology and terminology used here is also for the purposes of providing non-limiting examples.

[0034] With reference to the attached drawings, see for example fig. 1, fig. 2 and fig. 3, a heat exchanger 10a for an air conditioning, or cooling, system 20a comprises at least two substantially coaxial tubular elements 11 and 12 separated by a substantially cylindrical jacket 13. The tubular elements 11 and 12 are therefore disposed one inside the other.

[0035] In a first tubular element 11 there flows a cooling fluid in gaseous form coming, during use, from an evaporator 14 of a circuit 15a of the cooling fluid provided in the air conditioning system 20a. The circuit 15a is in particular a closed circuit.

[0036] In a second tubular element 12 there flows the cooling fluid in liquid or liquid-gaseous form coming, during use, from a condenser 16 of the circuit 15a, so as to effect a heat exchange between the cooling fluid in gaseous form and the cooling fluid in liquid form. The cooling fluid flowing in the second tubular element 12 can be, for example, 95% liquid and 5% gas, or totally in liquid form.

[0037] The cooling fluid flowing in the second tubular element 12 and exiting the condenser 16 represents a first fluid at a higher temperature able to effect a heat exchange with a second fluid at a lower temperature, represented in this case by the gaseous cooling fluid flowing in the first tubular element 11. In this way, the cooling fluid exiting the condenser 16 is subcooled.

[0038] Fig. 1 partly shows the air conditioning system 20a, in particular with dual-fluid operation, where the carrier fluid to be cooled is air, which will be conveyed into a given environment to be air-conditioned. Essentially this shows the cooling fluid's circuit 15a in which the innovative heat exchanger 10a is applied.

[0039] The circuit 15a is completed by a compressor 28 which sends the cooling fluid to the condenser 16, and by an expansion device 29 which sends the cooling fluid to the evaporator 14.

[0040] Advantageously, the tubular elements 11 and 12 are configured to subcool, during use, the liquid or liquid-gaseous cooling fluid exiting the condenser 16 so as to ultimately increase the efficiency of the air conditioning system 20a. The cooling fluid in gaseous form coming from the evaporator 14 is in fact cold, and has a lower temperature than the cooling fluid in liquid form and hot coming from the condenser 16.

[0041] In particular, the cooling fluid in gaseous form flows in the first tubular element 11 which is located inside the second tubular element 12. The cooling fluid in liquid form flows in the jacket 13 defined between the first tubular element 11 and the second tubular element 12. The cooling fluid in gaseous form and the cooling fluid in liquid form flow into, and countercurrent within, the heat exchanger 10a.

[0042] The first tubular element 11 is provided with an inlet 17 and an outlet 18 for the cooling fluid in gaseous form, in cooling mode.

[0043] The second tubular element 12 is provided with an inlet 19 and an outlet 21 for the cooling fluid in liquid form, in cooling mode.

[0044] The tubular elements 11 and 12 are made of metal, in particular copper or cupronickel, or other.

[0045] The tubular elements 11 and 12 can be sealed by welding or by means of any sealing member that guarantees the absence of any cooling fluid leaks and the separation between them.

[0046] The heat exchanger 10a is also positioned under the evaporator 14. The heat exchanger 10a is therefore interposed between the evaporator 14 and a tray 22 for collecting the condensation water D. The condensation water D, in particular in droplet form, flowing from the evaporator 14 toward the tray 22 wets the external surface of the heat exchanger 10a and will further cool the cooling fluid in liquid phase exiting the condenser 16. In particular, the condensation water D falls by gravity onto the surface of the tubular second element 12, into which the cooling fluid in liquid phase flows.

[0047] With sizes being equal, in order to maximize the exchange surface and therefore the effectiveness in subcooling the cooling fluid in liquid phase exiting the condenser 16, the internal tubular element 11 can have a series of fins 23 on its external surface. The fins are shown with a dashed line in fig. 2 and can be obtained by means of a rolling process or through piping with inserted fins, the latter being longitudinal, transverse or helical.

[0048] In order to minimize overall dimensions, the heat exchanger 10a can be bent into a U-shape or wound into a spiral.

[0049] In the event the exchanger is to be applied to a reversible air conditioning system 20a, it is possible to equip it with two non-return valves 24, as shown in fig. 3, which force the cooling fluid, without the use of electrical drives, to pass through the jacket 13 only in the cooling operating mode and allow to bypass it in the heating mode, in which it would have a negative effect.

[0050] When the air conditioning system 10a works in cooling mode, the cold cooling fluid in gaseous phase exiting the evaporator 14 flows in the internal tubular element 11, while the hot cooling fluid in liquid form exiting the condenser 16 flows in the jacket 13, thus being cooled. Finally, the cold condensation water D coming from the evaporator 14 is made to fall onto the external surface, thus further cooling the cooling fluid in liquid form exiting condenser 16.

[0051] Fig. 4 shows a reversible air conditioning system 20b whose circuit 15a is equipped with a diverter valve 25, in particular four-way, which allows to invert the direction of the flow of cooling fluid, so as to switch from the cooling mode shown to a heating mode, or vice versa.

[0052] Fig. 5 schematically shows the heating mode. Please note, in this regard, that the cooling fluid in gaseous form travels through the tubular element 11 of the heat exchanger 10a in an opposite direction to that shown in fig. 4. In particular, in the internal tubular element 11 there flows the hot cooling fluid in gaseous form exiting the compressor 28, while no fluid flows in the jacket 13, that is, in the external tubular element 12.

[0053] A variant of the heat exchanger 10b is shown in fig. 6 and fig. 7. This heat exchanger 10b comprises the two tubular elements 11 and 12 and also an additional tubular element 26, substantially coaxial to the tubular elements 11 and 12. The additional tubular element 26 is located around the second tubular element and a substantially cylindrical jacket 27 is created between them, in which liquid, in particular water, can flow. The additional tubular element 26 comprises an inlet 30 and an outlet 31 for the liquid in the jacket 27. The heat exchanger 10b can be used in a reversible type air conditioning system 20b as in figs. 8 and 9, equipped with a corresponding circuit 15b for the fluid: in fig. 8 the air conditioning system 20b works in cooling mode while in fig. 9 it works in heating mode.

[0054] With reference to fig. 6 and fig. 8, when the air conditioning system 20b works in cooling mode, in the internal tubular element 11 there flows the cold cooling fluid in gaseous form exiting the evaporator 14, in the jacket 13 between the external surface of the internal tubular element 11 and the internal surface of the tubular element 12, which in this case is intermediate, there flows the hot cooling fluid in liquid form exiting the condenser 16, which is therefore cooled.

[0055] With reference to fig. 7 and fig. 9, when the air conditioning system 20b works in heating mode, in the jacket 13 between the external surface of the internal tubular element 11 and the internal surface of the tubular element 12 there flows the hot cooling fluid in liquid form exiting the condenser 16, which is therefore cooled, increasing the efficiency of the thermodynamic cycle, while in the jacket 27 between the outside of the second intermediate tubular element 12 and the inside of the additional external tubular element 26 there flows the cold water, or other liquid, intended for the inlet of the evaporator 14, which will therefore be heated with the double advantage of increasing the temperature of the lower source of the heat pump and of increasing the lower temperature limit of the water itself for the correct operation of the heat pump. The flow of liquids in the jackets 13 and 27 is countercurrent.

[0056] One or more suitably positioned valves 32 allow the air conditioning system 20b to switch from the cooling mode to the heating mode, and vice versa.

[0057] Fig. 10 is an enthalpy H / pressure P diagram which shows the transformations of a thermodynamic cycle of an air conditioning system 20a or 20b that uses a heat exchanger 10a or 10b as described heretofore. The numbers 1, 2, 3 and 4 indicate the traditional points of the cycle, while 1', 2' 3' and 4' indicate the points of the cycle obtainable using the heat exchanger 10a or 10b.

[0058] The increase in efficiency is therefore achieved by further lowering the temperature of the cooling fluid in liquid phase exiting the condenser 16, this gives a double advantage, firstly to enter the evaporator with the cooling gas with a lower vapor content (3' instead of 3) and therefore to be able to exchange a greater amount of heat with the evaporator 14, with its sizes being equal, secondly it allows to adjust the expansion device 29 to a point of lower overheating exiting the evaporator 14, since the exchange with the hot liquid by the liquid exiting the evaporator allows the latter to overheat further (1' instead of 1), protecting the compressor 28 from any returns of liquid.

[0059] A heat exchange method according to the present invention for the air conditioning system 20a, 20b provided with at least the circuit 15a, 15b in which a cooling fluid flows, comprises providing the heat exchanger 10a, 10b in the circuit 15a, 15b, having a plurality of the substantially coaxial tubular elements 11, 12, 26 separated by the jacket 13, 27. In a first tubular element there flows the cooling fluid of the circuit 15a, 15b in gaseous or liquid form and having a first temperature, and in the jacket there flows the cooling fluid in liquid or liquid-gaseous form coming from the condenser 16 of the circuit 15a, 15b and having a second temperature higher than the first temperature, so as to effect a heat exchange between the cooling fluid in gaseous or liquid form at a lower temperature and the cooling fluid in liquid or liquid-gaseous form at a higher temperature.

[0060] It is clear that modifications and / or additions of parts may be made to the heat exchanger for an air conditioning or cooling system as described heretofore, without thereby departing from the field and scope of the present invention, as defined by the claims.

[0061] It is also clear that, although the present invention has been described with reference to some specific examples, a person of skill in the art will be able to achieve other equivalent forms of heat exchanger for an air conditioning or cooling system, having the characteristics as set forth in the claims and hence all coming within the field of protection defined thereby.

[0062] In the following claims, the sole purpose of the references in brackets is to facilitate their reading and they must not be considered as restrictive factors with regard to the field of protection defined by the claims.

Claims

1. Heat exchanger (10a, 10b) for an air conditioning (20a, 20b) or cooling system provided with at least one heat exchange circuit (15a, 15b), characterized in that it comprises a plurality of substantially coaxial tubular elements (11, 12, 26) separated by at least one jacket (13, 27), wherein in at least a first tubular element of said plurality of tubular elements (11, 12, 26), or in said jacket, there flows a first fluid in liquid or liquid-gaseous form coming, during use, from a condenser (16) of said circuit (15a, 15b) and having a first temperature, and in at least a second tubular element of said circuit (15a, 15b), or in said jacket, there flows a second fluid in gaseous or liquid form having a second temperature lower than said first temperature, so as to effect a heat exchange between said first fluid and said second fluid, thereby subcooling said first fluid exiting said condenser (16).

2. Heat exchanger (10a, 10b) as in claim 1, characterized in that it comprises two substantially coaxial tubular elements (11, 12), wherein in a first tubular element (11) there flows said second fluid in the form of a gaseous cooling fluid coming, during use, from an evaporator (14) of said circuit (15a) and in a second tubular element (12) there flows said first fluid in the form of a liquid or liquid-gaseous cooling fluid coming, during use, from said condenser (16) of said circuit (15a).

3. Heat exchanger (10a, 10b) as in claim 2, characterized in that said second tubular element (12) is placed in contact, during use, with the condensation water (D) coming from said evaporator (14).

4. Heat exchanger (10a, 10b) as in any claim hereinbefore, characterized in that it is countercurrent so that the flow of the first fluid inside said at least one tubular element of said plurality of tubular elements (11, 12, 26), or in said jacket, occurs countercurrent with respect to the flow of the second fluid in said second tubular element, or in said jacket.

5. Heat exchanger (10a, 10b) as in any claim hereinbefore, characterized in that at least one tubular element (11) of said plurality of tubular elements (11, 12, 26) is provided on the external surface with fins (23) which extend inside said jacket (13).

6. Heat exchanger (10a, 10b) as in any claim hereinbefore, characterized in that it comprises three substantially coaxial tubular elements (11, 12, 26) able to define two jackets (13, 27) between them, said tubular elements (11, 12, 26) being configured to allow, during use, the heat exchange between said first fluid exiting the condenser (16) and said second cooling fluid, during the heating operation of the air conditioning system (20b).

7. Air conditioning, or cooling, system (20a, 20b) provided with at least one heat exchange circuit (15a, 15b) comprising at least one compressor (28), at least one condenser (16), at least one expansion device (29) and at least one evaporator (14), characterized in that it comprises at least one heat exchanger (10a, 10b) as in any claim hereinbefore.

8. Air conditioning system (20a, 20b) as in claim 7, characterized in that said heat exchanger (10a, 10b) is positioned under said evaporator (14), so that the condensation water (D) produced by said evaporator (14) can fall by gravity onto said heat exchanger (10a, 10b).

9. Air conditioning system (20a, 20b) as in claim 7 or 8, characterized in that it comprises a diverter valve (25) configured to allow its passage from a cooling operating mode to a heating operating mode, or vice versa.

10. Heat exchange method for an air conditioning, or cooling, system (20a, 20b) provided with at least one heat exchange circuit (15a, 15b), characterized in that it comprises providing a heat exchanger (10a, 10b) in said circuit (15a, 15b) having a plurality of substantially coaxial tubular elements (11, 12, 26) separated by at least one jacket (13, 27), wherein in a first tubular element of said plurality of tubular elements (11, 12, 26), or in said jacket, there flows a first fluid in liquid or liquid-gaseous form coming, during use, from a condenser (16) of said circuit (15a, 15b) and having a first temperature, and in at least a second tubular element of said circuit (15a, 15b), or in said jacket, there flows a second fluid in gaseous or liquid form having a second temperature lower than said first temperature, so as to effect a heat exchange between said first fluid and said second fluid, thus subcooling said first fluid exiting said condenser (16).

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