Patent Description:
Traditional laundry treating appliances, for example washing machines, washer-driers, tumble driers, typically comprise a cabinet containing a rotatable drum wherein the laundry to be treated (i.e. washed and/or dried) can be loaded.

An operating fluid (e.g., depending on the kind of laundry treating appliance and on the treating process to be applied, water, water mixed with a washing/rinsing additive, air), is circulated through the drum by a circulating system (comprising, for example pumps, valves, fans, etc., depending on the kind of fluid to be circulated).

In some known laundry treating appliances, the operating fluid is heated and/or cooled/dehumidified by a heat pump system, typically comprising a compressor, an expansion valve, two heat exchangers (one operating as a condenser, and the other as an evaporator), and conduits fluidly connecting such elements in a closed circuit.

A heat pump system has an improved energy efficiency with respect to traditional heating systems using an electrical heater as heat source.

Some refrigerant flows through the compressor, the condenser, the expansion valve and the evaporator, and through the conduits connecting these to one another.

The refrigerant releases heat to the operating fluid by means of the condenser, and extracts heat and humidity from the operating fluid by means of the evaporator. The compressor converts electromechanical power to thermal power by compressing the refrigerant in the refrigerant circuit.

A known kind of heat exchanger, widely used in heat pump systems of laundry treating appliances, comprises a metallic pipe, made of copper or aluminum, wherein the refrigerant flows, bent to define a coil structure comprising a plurality of straight sections, parallel one another and connected in twos at one end thereof by a plurality of curved sections; this kind of known heat exchanger comprises a plurality of fins, typically made of aluminum and having a rectangular plane, stacked in spaced and parallel planes and comprising a plurality of through-holes, each housing two straight sections of the metallic pipe.

During the functioning of the heat pump system, the operating fluid flows through the gaps between the fins, exchanging heat with the latter, and therefore with the refrigerant flowing in the metallic pipe, which is thermally connected to the fins. Currently, the refrigerants mainly used in heat pump systems of known laundry treating appliances are hydrofluorocarbon (HFC) refrigerants, in particular the ones known as R134a and R407C. Unfortunately, these refrigerants have a high Global Warming Potential (GWP), so alternative refrigerants start to be more and more used in different industries.

Possible alternative refrigerants used for replacing hydrofluorocarbon (HFC) refrigerants in heat pump systems of laundry treating appliances are hydrocarbons refrigerants, such as propane (R290) and propylene (R1270).

These alternative refrigerants have a negligible impact on GWP and their thermo-physical properties makes them very suitable for the typical working conditions of heat pump systems of laundry treating appliances, in particular tumble driers and washer-driers.

The downside of these alternative refrigerants is that they are flammable, and therefore, for limiting possible risks, regulations (e.g. the IEC <NUM>-<NUM>-<NUM> standard) limit the amount of refrigerant that can be charged in the heat pump system to <NUM> (grams).

Inside the heat pump system, when the compressor is switched ON, most of the refrigerant can be found inside the condenser, since in this heat exchanger the refrigerant is at high pressure and, for a portion thereof, in liquid state, so with a very high density.

The evaporator, on the contrary, works at low pressure, and the refrigerant contained therein is mainly a liquid-vapour mixture and a superheated vapour, so its density is quite low. It has been observed that limiting to <NUM> the refrigerant charge could negatively affect the performances of the heat pump system, in particular its energy efficiency.

There is the need, therefore, to reduce the volume of the components of the heat exchangers wherein the refrigerant flows, so as to limit the refrigerant charge required by the system. On the other hand, it's important not reducing too much the external surface area, so as to keep a good heat exchange performance.

In particular, in order to reduce the overall volume of the single duct of the heat exchanger wherein the refrigerant flows, there could be the possibility to reduce the number of stacked fins, and therefore the overall length of the metallic pipe; unfortunately, reducing the number of fins reduces also the overall thermal exchange surface of the heat exchanger, which reduces the energy efficiency of the heat pump system. <CIT> discloses a household appliance, in particular a laundry treatment appliance, provided with a heat pump comprising a rotary compressor, a condenser, a restrictor, and an evaporator, wherein the condenser is of an expanded tube-and-fin type, with the tubes having an outer diameter of less than <NUM> and wherein the roller has a height-to-radius ratio of <NUM> to <NUM>.

<CIT> discloses a laundry dryer including a heat pump system having a refrigerant circuit in which a refrigerant can flow, said refrigerant circuit including a first heat exchanger where the refrigerant is heated up, a second heat exchanger where the refrigerant is cooled off, a compressor to pressurize and circulate the refrigerant through the refrigerant circuit, and a pressure-lowering device; the first and/or second heat exchanger are apt to perform heat exchange between the refrigerant flowing in the refrigerant circuit and the process air. The refrigerant is a flammable refrigerant. Each of the first and second heat exchanger is a finned tube heat exchanger comprising a tube having multiple sections one above the other and a plurality of fins; it is divided in three portions: a central portion wherein the multiple sections of the tube are in contact with the plurality of fins, and a first and second end portions where the tube is not in contact with the plurality of fins. The value of the ratio between a thickness of the central portion of the second heat exchanger and a thickness of the central portion of the first heat exchanger is lower than <NUM>.

The scientific article by <NPL>, presents a comparable evaluation of R600a (isobutane), R290 (propane), R134a, R22, R410A, and R32 in an optimized finned-tube evaporator, and analyses the impact of evaporator effects on the system coefficient of performance (COP).

The aim of the present invention is therefore obtaining a laundry treating appliance using a heat pump system having a reduced Global Warming Potential (GWP) and an improved efficiency.

Within this aim, a further object of the invention is obtaining a laundry treating appliance fulfilling the safety regulations related to the refrigerants of the heat pump systems, without reducing the overall energy efficiency. Applicant has found that, by selecting, for specific ranges of external diameters of the metallic pipe of a finned heat exchanger which stacked fins have a plurality of through-holes, each housing two mutually parallel straight sections of the metallic pipe, the straight sections being distributed in such a way that, in a cross section whose cutting plane is perpendicular to the straight sections, their centers are aligned along a plurality of mutually parallel straight lines, specific ranges for the distances of the straight lines of adjoining straight lines, and corresponding specific ranges for the distances between the centers of couples of adjoining straight sections aligned along a same straight line, it is possible to reduce the overall internal volume of the metallic pipe of the heat exchanger wherein the refrigerant flows without reducing the length of the metallic pipe nor the number of fins, and therefore without reducing the overall thermal exchange surface.

This inventive solution allows using in the heat pump system of a laundry appliance a flammable refrigerant, like for example propane (R290) or propylene (R1270), which have a very low Global Warming Potential (GWP), but that needs to be used in small quantities, and therefore requires a reduced volume of the metallic pipe of the heat exchanger wherein the refrigerant flows.

In particular, above aim is solved by a laundry treating appliance comprising:.

It is underlined that stating that two straight lines are adjoining (or in other words contiguous, or neighboring, or adjacent) means that there aren't other straight lines positioned between such two straight lines.

It is underlined that stating that two straight sections are adjoining (or in other words contiguous, or neighboring, or adjacent) means that there aren't other straight sections positioned between such two straight sections.

Using the specific inventive ranges of distances between straight lines/straight sections, in combination with the specific inventive ranges of the external diameter of the metallic pipe, allows keeping reduced the internal volume of heat exchanger wherein the flammable refrigerant flows, without significantly affecting the overall dimensions of the stacked fins, and therefore without significantly affecting the heat exchange performances.

In addition, the specific combinations of inventive ranges allow obtaining a uniform heat distribution along the fins, which avoids overheating of some parts of the latter, and also improves the heat exchange.

In an advantageous embodiment, the distance between the centers of two adjoining straight sections aligned along a same straight line among the mutually parallel straight lines is comprised between <NUM> and <NUM>, and the distance between two adjoining straight lines among the mutually parallel straight lines is comprised between <NUM> and <NUM>.

In a further advantageous embodiment, the distance between the centers of two adjoining straight sections aligned along a same straight line among the mutually parallel straight lines is comprised between <NUM> and <NUM>, and the distance between two adjoining straight lines among the mutually parallel straight lines is comprised between <NUM> and <NUM>.

In a preferred embodiment, the distance between two adjoining straight lines among the mutually parallel straight lines is the same for all the couples of adjoining straight lines among the mutually parallel straight lines.

Preferably, the distance between the centers of two adjoining straight sections aligned along a same straight line among the mutually parallel straight lines is the same for all the couples of adjoining straight sections aligned along this same straight line. More preferably, the distance between the centers of two adjoining straight sections aligned along a same straight line among the mutually parallel straight lines is the same for all the mutually parallel straight lines.

In a preferred embodiment, the metallic pipe comprises an inlet portion and an outlet portion protruding both from a same terminal fin of the plurality of stacked fins. Preferably, the flammable refrigerant is or comprises a hydrocarbon. More preferably, the flammable refrigerant is or comprises propane (R290) or propylene (R1270). Advantageously, the plurality of fins is made of, or comprise, aluminum or aluminum alloy, or copper, or copper alloy.

In an advantageous embodiment, the perimeter edges of the stacked fins define as a whole an envelope surface comprising at least a plane portion), and the mutually parallel straight lines are perpendicular to the at least a plane portion. Preferably, fins of the plurality of metallic fins have a width comprised between <NUM> and <NUM>, and a height comprised between <NUM> and <NUM>.

More preferably, fins of the plurality of metallic fins have a width comprised between <NUM> and <NUM>, and a height comprised between <NUM> and <NUM>.

Preferably, the overall length of the stacked fins is comprised between <NUM> and <NUM>.

More preferably, the overall length of the stacked fins is comprised between <NUM> and <NUM>.

Preferably, the metallic pipe is made of, or comprises, aluminum or aluminum alloy, or copper or copper alloy.

In an advantageous embodiment, the laundry treating appliance is a tumble drier or a washer-drier, and the operating fluid is air.

In a further advantageous embodiment, the laundry treating appliance is a laundry washing machine, and the operating fluid is water, or water mixed with a washing/rinsing agent. Other advantages and features of a laundry treating appliance according to the present invention will be clear from the following detailed description, provided only as a not limitative example, in which:.

In the figures, same parts are indicated with the same reference numbers.

Advantageously, the laundry treating appliance <NUM> illustrated in <FIG> is a tumble drier of the "horizontal axis type"; it is however clear that the invention can be applied, without any substantial modification, also to tumble driers of the vertical axis" type, and to washing machines and washer driers, both of the "horizontal axis" and of the "vertical axis" type.

The laundry treating appliance (being it a tumble drier <NUM>, or a washing machine or washer-drier, not illustrated) comprises a cabinet <NUM>, or housing, preferably parallelepiped, configured to be positioned on a horizontal surface <NUM>, for example the floor of a building, preferably by suitable feet <NUM>, one or more of which can have, advantageously, an adjustable height, so as to adapt to a possible not perfect planarity of the horizontal surface <NUM>.

Advantageously, in the frontal wall 20a of the cabinet <NUM> an access opening, not illustrated, is preferably obtained, advantageously selectively closable by a loading/unloading door <NUM>, preferably hinged to the frontal wall 20a.

The laundry treating appliance (being it a tumble drier <NUM>, or a washing machine or washer-drier) comprises a drum <NUM> rotatably housed within the cabinet <NUM>, in which the laundry, not illustrated, can be loaded.

If the laundry treating appliance is a washing machine or a washer-drier, both not illustrated, the cabinet <NUM> also houses a washing tub, not illustrated, preferably suspended to the cabinet through springs and dumpers, also not illustrated, in which the drum <NUM> is rotatably contained.

The laundry treating appliance <NUM> comprises a circulating system <NUM> configured for circulating an operating fluid through the drum <NUM>.

It is underlined that the circulating system <NUM> can define a closed circuit for the operating fluid (i.e. the operating fluid remains within the closed circuit during the laundry treating process, and the same fluid, opportunely treated, passed repeatedly through the drum <NUM>), or it can define an opened circuit for the operating fluid (i.e. the operating fluid is loaded within the laundry treating appliance <NUM> at a certain point of the laundry treating process, and it is drained from the laundry treating appliance <NUM> at another point of the laundry treating process).

In the advantageous embodiment in which the laundry treating appliance <NUM> is a tumble drier, like the advantageous example of <FIG>, or a washer drier, not illustrated, the operating fluid is or comprises air (represented by arrows <NUM>), and the circulating system preferably comprises an air circuit <NUM> and one or more fans <NUM> configured for circulating such air <NUM> through the drum <NUM> and the air circuit <NUM>.

If the laundry treating appliance is a tumble drier <NUM>, it can also advantageously comprise a lint filter <NUM>, arranged in the air circuit <NUM> for trapping lint or fluff released from the laundry.

If the laundry treating appliance is a washing machine or a washer drier, both not illustrated, the operating fluid is or comprises water, or water mixed with a washing/rinsing additive, and the circulating system preferably comprises a water inlet circuit, not illustrated, adapted to feed water into the tub, also not illustrated, and a drain circuit, also not illustrated, adapted for draining washing/rinsing liquid from the machine.

The laundry treating appliance <NUM> advantageously comprises a heat pump system <NUM>, configured for heating the operating fluid, for example, in case of a tumble drier, the air <NUM>. Advantageously, the heat pump system <NUM> can also be configured for cooling and dehumidifying the operating fluid.

Preferably, the heat pump system <NUM> comprises a compressor, not illustrated, an expansion valve, also not illustrated, two heat exchangers 70a, 70b (one operating as a condenser, and the other as an evaporator), and conduits, not illustrated, fluidly connecting such elements in a closed circuit.

A flammable refrigerant flows through the compressor, the condenser 70a, the expansion valve and the evaporator 70b, and through the conduits connecting these to one another.

The flammable refrigerant releases heat to the operating fluid by means of the condenser 70a and extracts heat and humidity from the operating fluid by means of the evaporator 70b. The compressor converts electromechanical power to thermal power by compressing the flammable refrigerant in the refrigerant circuit.

The flammable refrigerant is or comprises a hydrocarbon, preferably propane (R290) or propylene (R1270).

The heat exchangers, for example the condenser 70a and/or the evaporator 70b, comprise a metallic pipe <NUM>, wherein the flammable refrigerant flows, bent to define a coil structure comprising a plurality of straight sections <NUM>, parallel one another and connected in twos at one end thereof by a plurality of curved sections <NUM>.

Advantageously, the metallic pipe <NUM> is made of, or comprise, aluminum or aluminum alloy, or copper or copper alloy.

The straight sections <NUM> are distributed in such a way that, in a cross section which cutting plane Cp (illustrated in <FIG>) is perpendicular to the straight sections <NUM>, their centers Ce are aligned along a plurality of mutually parallel straight lines <NUM>.

The heat exchangers, for example the condenser 70a and/or the evaporator 70b, comprise a plurality of fins <NUM>, stacked spaced and parallel to one another, each provided with a plurality of through-holes <NUM>, each through-hole <NUM> housing two of the straight sections <NUM> of the metallic pipe <NUM>. Advantageously, the fins <NUM> are made of, or comprise, aluminum or aluminum alloy, or copper, or copper alloy. Advantageously, the through-holes <NUM> of any fin <NUM> are respectively aligned with the through-holes <NUM> of the rest of the stacked fins <NUM>.

Advantageously, the straight sections <NUM> are fitted, with their lateral surface into close contact with the border of the respective through-holes <NUM>, so as to obtain an effective heat-exchange between them.

Advantageously, the metallic pipe <NUM> comprises an inlet portion <NUM> and an outlet portion <NUM>, configured for allowing the flammable refrigerant respectively to enter/exit the metallic pipe <NUM>; advantageously, the inlet portion <NUM> and the outlet portion <NUM> are fluidly connected or connectable to the other elements of the heat pump system <NUM>, so as to allow circulation of the flammable refrigerant through the respective heat exchanger 70a or 70b.

Advantageously, like in the examples of attached figures, the inlet portion <NUM> and an outlet portion <NUM> protrude both from a same terminal fin <NUM> of the plurality of stacked fins <NUM>, which simplifies the connection of the single duct <NUM> to the other conduits of the heat pump system <NUM>.

Advantageously, the perimeter edges <NUM> of the stacked fins <NUM> define as a whole an envelope surface, illustrated in <FIG> with a dotted line numbered <NUM>, comprising at least a plane portion <NUM>.

Preferably, the fins <NUM> have a rectangular or square plan, in which case the envelope surface <NUM> comprises four plane portions, corresponding to the four sides of the rectangle or square.

In advantageous embodiments, like for example the ones illustrated in attached figures, in which the fins <NUM> have a rectangular or square plan, and the envelope surface <NUM> comprises four plane portions corresponding to the four sides of the rectangle or square, above defined straight lines <NUM> are advantageously parallel to two sides of such rectangle or square.

Preferably, the width "w" of the fins <NUM> is comprised between <NUM> and <NUM>, more preferably between <NUM> and <NUM>. Preferably, the height "h" of the fins <NUM> is comprised between <NUM> and <NUM>, more preferably between <NUM> and <NUM>. Preferably, the overall length of the stacked fins <NUM> is comprised between <NUM> and <NUM>, more preferably between <NUM> and <NUM>.

According to the invention, the external diameter de of the metallic pipe <NUM>, and in particular of its straight portions <NUM> is comprised between <NUM> and <NUM>, wherein:.

In an advantageous embodiment, if the external diameter de of the plurality of straight sections <NUM> of the metallic pipe <NUM> is comprised between <NUM> and <NUM>, then the distance Tp between the centers Ce of two adjoining straight sections <NUM> aligned along one of the mutually parallel straight lines <NUM> is comprised between <NUM> and <NUM>, and the distance Rp between two adjoining straight lines <NUM> among the mutually parallel straight lines <NUM> is comprised between <NUM> and <NUM>.

In a further advantageous embodiment, if the external diameter de of the plurality of straight sections <NUM> of the metallic pipe <NUM> is comprised between <NUM> and <NUM>, then the distance Tp between the centers Ce of two adjoining straight sections <NUM> aligned along one of the mutually parallel straight lines <NUM> is comprised between <NUM> and <NUM>, and the distance Rp between two adjoining straight lines <NUM> among the mutually parallel straight lines <NUM> is comprised between <NUM> and <NUM>.

In another advantageous embodiment, the distance Rp between two adjoining straight lines <NUM> among the mutually parallel straight lines <NUM> is the same for all the couples of adjoining straight lines <NUM> among the mutually parallel straight lines <NUM>.

Preferably, the distance Tp between the centers Ce of two adjoining straight sections <NUM> aligned along one of the mutually parallel straight lines <NUM> is the same for all the couples of adjoining straight sections <NUM> aligned along a same straight line <NUM>.

More preferably, the distance Tp between the centers Ce of two adjoining straight sections <NUM> aligned along a same straight line <NUM> is the same for all the straight line <NUM>.

Claim 1:
A laundry treating appliance (<NUM>) comprising:
- a cabinet (<NUM>);
- a drum (<NUM>), rotatably housed within said cabinet (<NUM>), in which laundry can be loaded;
- a heat pump system (<NUM>), using one or more flammable refrigerants, configured for exchanging heat with an operating fluid (<NUM>);
- a circulating system (<NUM>) configured for circulating said operating fluid (<NUM>) through said drum (<NUM>);
wherein said heat pump system (<NUM>) comprises a heat exchanger (70a, 70b) comprising:
- a metallic pipe (<NUM>), wherein said flammable refrigerant flows, bent to define a coil structure comprising a plurality of straight sections (<NUM>), parallel one another and connected in twos at one end thereof by a plurality of curved sections (<NUM>), wherein the external diameter (de) of said metallic pipe (<NUM>) is comprised between <NUM> and <NUM>;
- a plurality of fins (<NUM>), stacked, spaced and parallel to one another, each provided with a plurality of through-holes (<NUM>), each through-hole (<NUM>) housing two of said straight sections (<NUM>),
said plurality of straight sections (<NUM>) being distributed in such a way that, in a cross section whose cutting plane (Cp) is perpendicular to said straight sections (<NUM>), their centers (Ce) are aligned along a plurality of mutually parallel straight lines (<NUM>),
characterized in that
- the distance (Tp) between the centers (Ce) of two adjoining straight sections (<NUM>) aligned along a same straight line (<NUM>) among said mutually parallel straight lines (<NUM>) is comprised between <NUM> and <NUM>, and the distance (Rp) between two adjoining straight lines (<NUM>) among said mutually parallel straight lines (<NUM>) is comprised between <NUM> and <NUM>,
or
- the distance (Tp) between the centers (Ce) of two adjoining straight sections (<NUM>) aligned along a same straight line (<NUM>) among said mutually parallel straight lines (<NUM>) is comprised between <NUM> and <NUM>, and the distance (Rp) between two adjoining straight lines (<NUM>) among said mutually parallel straight lines (<NUM>) is comprised between <NUM> and <NUM>.