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 exchangers, widely used in heat pump systems of laundry treating appliances, comprises a plurality of fins, typically made of aluminum and having a rectangular plane, stacked in spaced and parallel planes; the fins comprise a plurality of through-holes wherein a plurality straight pipes, made of copper or aluminum, parallel one another and perpendicular to the fins, are fitted, with their lateral surface into close contact with the border of the through-holes, so as to obtain an effective heat-exchange.

The straight pipes are connected in twos, at one end, by a curved pipe, to define as a whole a single duct wherein the refrigerant flows; this single duct has an inlet portion and an outlet portion protruding from the stack of fins, and connectable to the rest of the heat pump system circuit. 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 pipes, which are 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 length of the straight pipes composing the single duct; 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 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>.

<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 heat exchanger, in particular for a heat pump dryer, having at least one tube bent in a meandering shape for the passage of a first medium to be cooled or heated; between the tube there are lamellar layers for the passage of a second medium to be heated or cooled, wherein the layers are connected to one another via layer connecting pieces; recesses are provided, in which partial cross-sections of the respective tube sections of the tube are accommodated.

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 pipes of a finned heat exchanger which stacked fins have a plurality of through-holes distributed to define a plurality of mutually parallel rows of aligned through-holes which centers are aligned to each other along a respective straight line, specific ranges for the distances of the straight lines of adjoining rows, and corresponding specific ranges for the distances between the centers of couples of adjoining through-holes of a same row, it is possible to reduce the overall internal volume of the single duct of the heat exchanger wherein the refrigerant flows without reducing the length of the single pipes composing such a single duct 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 single duct 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 rows are adjoining (or in other words contiguous, or neighboring, or adjacent) means that there aren't other rows positioned between such two rows. It is underlined that stating that two through-holes are adjoining (or in other words contiguous, or neighboring, or adjacent) means that there aren't other through-holes positioned between such two through-holes.

Using the specific inventive ranges of distances between straight lines/through-holes, 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 allows obtaining a uniform heat distribution along the fins, which avoids overheating of some parts of the latter, and also improves the heat exchange.

In another advantageous embodiment, the distance between the centers of two adjoining through-holes of a same row is comprised between <NUM> and <NUM>, and the distance between the straight lines of two adjoining rows is comprised between <NUM> and <NUM>.

In a further advantageous embodiment, the distance between the centers of two adjoining through-holes of a same row is comprised between <NUM> and <NUM>, and the distance between the straight lines of two adjoining rows is comprised between <NUM> and <NUM>.

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

Preferably, the distance between the centers of two adjoining through-holes of a same row is the same for all the couples of adjoining through-holes of a same row.

More preferably, the distance between the centers of two adjoining through-holes of a same row is the same for all the rows.

In an advantageous embodiment, the single duct 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, or is or comprises propane (R290) or propylene (R1270).

Preferably, the plurality of fins and/or the metallic pipes are made of, or comprise, aluminum or aluminum alloy, or copper, or copper alloy.

In an advantageous embodiment, the stacked fins comprise perimeter edges defining as a whole an envelope surface comprising at least a plane portion, and wherein the plurality of mutually parallel rows 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>.

Advantageously, the laundry treating appliance is a tumble drier or a washer-drier, and the operating fluid is air or, 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). Advantageously, the heat exchangers, for example the condenser 70a and/or the evaporator 70b, comprise a plurality of metallic pipes <NUM> (called also simply pipes) wherein the flammable refrigerant flows, and a plurality of fins <NUM> (advantageously metallic), stacked spaced and parallel to one another, each provided with a plurality of through-holes <NUM>) wherein one of the metallic pipes <NUM> is fitted. 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 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.

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>.

Advantageously, the fins <NUM> are made of, or comprise, aluminum or aluminum alloy, or copper, or copper alloy. Advantageously, the metallic pipes <NUM> are made of, or comprise, aluminum or aluminum alloy, or copper or copper alloy.

The metallic pipes <NUM> comprise two or more straight pipes <NUM>, parallel one another and perpendicular to the fins <NUM>, each straight pipe <NUM> being housed in one of the through-holes <NUM> of each stacked fin <NUM>.

Advantageously, the straight pipes <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; this can be obtained by radially expanding such straight pipes <NUM> by suitable tools, not illustrated.

The two or more straight pipes <NUM> are connected in twos, at one end thereof, by a curved pipe <NUM>, to define as a whole a single duct <NUM> wherein the flammable refrigerant flows.

Such a single duct <NUM> advantageously comprises an inlet portion <NUM> and an outlet portion <NUM>, configured for allowing the flammable refrigerant respectively to enter/exit the single duct; 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>.

According to the invention, the through-holes <NUM> are distributed on the respective fins <NUM> to define a plurality of mutually parallel rows <NUM> of aligned through-holes <NUM>, wherein the centers Ce of the through-holes <NUM> of each row <NUM> are aligned to each other along a straight line <NUM>.

In an alternative embodiment, not covered by the subject-matter of the claims, if the external diameter de of the metallic pipes <NUM> is comprised between <NUM> and <NUM>, then:.

Alternatively, not covered by the subject-matter of the claims, if the external diameter de of the metallic pipes <NUM> is comprised between <NUM> and <NUM>, the distance Tp between the centers Ce of two adjoining through-holes <NUM> of a same row <NUM> is comprised between <NUM> and <NUM>, and the distance Rp between the straight lines <NUM> of two adjoining rows <NUM> is comprised between <NUM> and <NUM>.

Alternatively, not covered by the subject-matter of the claims, if the external diameter de of the metallic pipes <NUM> is comprised between <NUM> and <NUM>,
the distance Tp between the centers Ce of two adjoining through-holes <NUM> of a same row <NUM> is comprised between <NUM> and <NUM>, and the distance Rp between the straight lines <NUM> of two adjoining rows <NUM> is comprised between <NUM> and <NUM>.

In an advantageous embodiment, if the external diameter de of the metallic pipes <NUM> is comprised between <NUM> and <NUM>,
the distance Tp between the centers Ce of two adjoining through-holes <NUM> of a same row <NUM> is comprised between <NUM> and <NUM>, and the distance Rp between the straight lines <NUM> of two adjoining rows <NUM> is comprised between <NUM> and <NUM>.

In another advantageous embodiment, if the external diameter de of the metallic pipes <NUM> is comprised between <NUM> and <NUM>, the distance Tp between the centers Ce of two adjoining through-holes <NUM> of a same row <NUM> is comprised between <NUM> and <NUM>, and the distance Rp between the straight lines <NUM> of two adjoining rows <NUM> is comprised between <NUM> and <NUM>. In a preferred embodiment, the distance Rp between the straight lines <NUM> of two adjoining rows <NUM> is the same for all the couples of adjoining rows <NUM>.

In a further preferred embodiment, the distance Tp between the centers Ce of two adjoining through-holes <NUM> of a same row <NUM> is the same for all the couples of adjoining through-holes <NUM> of a same row <NUM>; more preferably, the distance Tp between the centers Ce of two adjoining through-holes <NUM> of a same row <NUM> is the same for all the rows <NUM>.

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, the straight lines <NUM> are parallel to two sides of such rectangle or square.

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 plurality of metallic pipes (<NUM>) wherein said flammable refrigerant flows, wherein the external diameter (de) of said metallic pipes (<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 one of said metallic pipes (<NUM>),
said plurality of through-holes (<NUM>) of said fins (<NUM>) being distributed on the respective fin (<NUM>) to define a plurality of mutually parallel rows (<NUM>) of aligned through-holes (<NUM>), wherein the centers (Ce) of the through-holes (<NUM>) of each row (<NUM>) are aligned to each other along a respective straight line (<NUM>),
wherein said metallic pipes (<NUM>) comprise two or more straight pipes (<NUM>), parallel one another and perpendicular to said fins (<NUM>), each one of said two or more straight pipes (<NUM>) being housed in one of said plurality of through-holes (<NUM>) of each stacked fin (<NUM>), said two or more straight pipes (<NUM>) being connected in twos, at one end, by a curved pipe (<NUM>), to define as a whole a single duct (<NUM>) wherein said flammable refrigerant flows,
characterized in that
- the distance (Tp) between the centers (Ce) of two adjoining through-holes (<NUM>) of a same row (<NUM>) is comprised between <NUM> and <NUM>, and the distance (Rp) between the straight lines (<NUM>) of two adjoining rows (<NUM>) is comprised between <NUM> and <NUM>,
or
- the distance (Tp) between the centers (Ce) of two adjoining through-holes (<NUM>) of a same row (<NUM>) is comprised between <NUM> and <NUM>, and the distance (Rp) between the straight lines (<NUM>) of two adjoining rows (<NUM>) is comprised between <NUM> and <NUM>.