Water heating system and related manufacturing method

Abstract

The water heating system (100) comprises: a compressor (101); an evaporator (102); a water tank (103); a condenser (104), to transfer heat to the water tank; a fan (105). The compressor (101), the evaporator (102), and the condenser (104) form a refrigeration cycle through which the working fluid circulates. The condenser includes a tube (T) wrapped around the water tank (103) to form a spiral about the longitudinal axis (L) and connected to the water tank (103), wherein at least one segment of the tube (T) in the spiral has, in a cross-section along a radial plane comprising the longitudinal axis (L), a flat wall (T2) in contact with an external surface (1031) of the water tank (103), and a curved wall (T1), joined to the flat wall and radially projecting toward the outside of the water tank (103), so as to form a "D" shape.

Description

[0001] The present invention relates to a water heating system and to a method for manufacturing a water heating system. The present invention also relates to an apparatus for shaping a tube for a condenser of a water heating system.

[0002] Water heating systems can operate with a heat pump.

[0003] A heat pump is a thermal machine capable of extracting and transferring thermal energy using different forms of energy, generally electric energy. Water heating systems consist of a heat pump unit and a tank with domestic hot water to be heated.

[0004] The heat pump unit aims at extracting heat from the air to transfer it to the water contained in the tank.

[0005] The heat pump unit, in turn, comprises: Compressor: aims at pressurizing and recirculating the refrigerant inside the circuit. Evaporator: aims at exchanging heat with the air so as to absorb heat therefrom, causing the refrigerant, circulated by the compressor, to evaporate. Lamination member: aims at ensuring the expansion of the working fluid, lowering the pressure and temperature from the condenser outlet values to the evaporator inlet values. Condenser: aims at exchanging heat with the water tank so as to transfer heat to the latter by condensing the refrigerant circulated by the compressor. Fan: has the task of ensuring the correct stream of air through the evaporator.

[0006] As explained above, the condenser aims at transferring heat to water inside the water tank.

[0007] The heat exchange is carried out by using the latent heat transferred by the refrigerant during the condensation process.

[0008] Note that no direct contact is provided between refrigerant and water inside the tank, and heat must pass through the wall of the condenser and that of the tank before transiting from refrigerant to water.

[0009] Therefore, in order to increase the heat exchange between water and refrigerant, the contact surfaces between the condenser and the water tank need to be increased, and the convective heat exchange coefficients of the refrigerant need to be also increased.

[0010] It is known that the cylindrical tube of the condenser is wrapped around the tank to form a spiral (serpentine), as described, for example, in patent 102022000024204 to the same Applicant.

[0011] The refrigerant used in the refrigeration circuit of known water heating systems, e.g., propane, can be harmful to the environment. In fact, different regulations exist, which determine a maximum value for such refrigerants. Therefore, there is a need to reduce the amount of refrigerant and preserve a good heat exchange between refrigerant and water inside the tank.

[0012] In this context, patent document EP3524914B1 describes a water heating system comprising a tank containing water to be heated, and a condenser wrapped around the tank, where the condenser includes two manifolds, parallel to each other, framing a plurality of mutually parallel strips that are perpendicular to the manifolds, and each strip comprises a plurality of channels for the refrigerant, thus such a solution comprises the use of micro-channel tubes in the serpentine. The solution of patent EP3524914B1 provides for each manifold having, in the cross-section, a general D-shape extending over the entire longitudinal dimension of the manifold.

[0013] Further examples of known heating systems are described in patent documents AU2014268261A1 and EP0336751A2.

[0014] However, the water heating systems with heat pump of the prior art have a number of drawbacks and can be improved. In fact, several needs exist in this field.

[0015] One need is to manufacture a water heating system with reduced complexity and construction costs.

[0016] It is another need to manufacture a safe water heating system which complies with environmental regulations with improved efficiency, robustness, and reliability.

[0017] It is the object of the present invention to provide a water heating system and a method for heating water, which overcome the aforesaid drawbacks of the prior art.

[0018] Said object is fully achieved by the system and method of the present finding, which are characterized by the content of the claims set out below. According to an aspect of the present description, the present finding provides a water heating system.

[0019] The water heating system (the system) comprises a compressor. The compressor is configured to increase the pressure of a working fluid.

[0020] The system comprises an evaporator. The evaporator is configured to receive the working fluid in the liquid state and release the working fluid in the gas state. In an example, the evaporator is configured to receive the working fluid in a two-phase liquid state. The two-phase liquid preferably has a vapor quality within the range of 0 - 0.5. The two-phase liquid preferably has a vapor quality equal to 0.2. In a further example, the two-phase liquid has a vapor quality equal to 0 (completely liquid). In an example, the evaporator is configured to receive the working fluid in a subcooled liquid state.

[0021] In an example, the evaporator is configured to release the working fluid in a superheated gas state.

[0022] Note that the subcooled liquid and superheated gas states shall be understood as states in which the working fluid has a temperature less than and above the lower and higher limit temperature, respectively. The higher and lower limit temperatures are temperatures known to those skilled in the art, once the pressure of the working fluid and the type of working fluid are known.

[0023] The evaporator is configured to receive a stream of outdoor air.

[0024] In an example, the system comprises a lamination member. The lamination member is configured to expand the working fluid. In other words, the lamination member is configured to lower the pressure and temperature so as to bring the working fluid from condenser outlet conditions to evaporator inlet conditions.

[0025] In an example, the lamination member is an expansion valve. Alternatively, the lamination member is a throttling valve or an orifice or a member comprising a constriction.

[0026] The system comprises a water tank. The water tank is configured to contain water. The water tank extends along a longitudinal axis.

[0027] The system comprises a condenser. The condenser is configured to be in contact with an external surface of the water tank. The condenser is configured to receive the working fluid in a gas state. The condenser is preferably configured to receive the working fluid in a superheated gas state. The condenser is configured to release the working fluid in a liquid state. The condenser is preferably configured to release the working fluid in a subcooled liquid state.

[0028] The system comprises a fan. The fan is configured to feed the stream of outdoor air to the evaporator. In an example, the outside air is hot air. Hot air means air having a higher temperature than an operating temperature of the working fluid. In an example, the operating temperature of the working fluid is the evaporation temperature of the working fluid.

[0029] The compressor, the evaporator, and the condenser form a refrigeration cycle through which the working fluid circulates. In an example, the lamination member is also part of the refrigeration cycle.

[0030] The condenser includes a tube. The tube is wrapped around the water tank. The tube forms a spiral about the longitudinal axis. The tube is connected to the water tank. The tube comprises a curved wall. The tube comprises a flat wall. In an example, the tube comprises the curved wall and the flat wall in the spiral, in a cross-section of the tube, along a radial plane comprising the longitudinal axis. At least one segment of the tube has a non-deformed portion. The non-deformed portion of the tube has a circular cross-section with an outer radius and an external diameter. At least one segment of the tube has a deformed portion, according to one or more features of the present description.

[0031] The flat wall is in contact with an external surface of the water tank. The curved wall is joined to the flat wall. In particular, the curved wall is joined to the flat wall so as to delimit an inner volume of the tube. The curved wall radially projects toward the outside of the water tank, so as to form a "D" shape.

[0032] Such a solution allows the refrigeration cycle to operate efficiently. In particular, the D-shaped configuration of the condenser tube allows optimizing the balance between: high heat exchange efficiency, which would require a contact surface between the condenser tube and the water tank which is as wide as possible; reduction of the system volume, due to the limited dimensions and the amount of circulating working fluid which is limited to reduce the environmental impact; high mechanical resistance, since the internal pressure of the working fluid creates internal stress that must not cause the tube itself to deform plastically.

[0033] In an example, the tube has a height measured along a trajectory perpendicular to the longitudinal axis, from a midpoint of said flat wall toward the curved wall. The ratio between the height of the tube and the external diameter of the non-deformed portion can fall within a range of 0.430 - 0.625.

[0034] In an example, the flat wall of the tube has a width measured along the longitudinal axis and between the two ends thereof. A ratio between the value of the width and the value of the height of the tube can fall within a range of 1.920 - 3.140. In an example, the width of the tube and the height of the tube are the same size.

[0035] In an example, a ratio between a thickness of the tube and the height of the tube falls within a range of 0.160 - 0.349.

[0036] In an example, the ratio between the radius of the non-deformed tube portion and an average value of a radius of curvature of the curved wall falls within a range of 0.615 - 0.80.

[0037] Note that the above features relating to the ratios of the geometrical parameters of the aforementioned tube can be present in combination with one another or separately.

[0038] Note that such solutions (in particular, the aforesaid parameters), are related to the "D" shape of the tube and allow optimizing the geometry of the tube, obtaining the best compromise between heat exchange efficiency, volume reduction, and mechanical resistance.

[0039] In an example, the system comprises a high-pressure zone. The high-pressure zone operates at a pressure value of 18-22 bar. The high-pressure zone preferably operates at a pressure value of 20 bar. The system comprises a low-pressure zone. The low-pressure zone operates at a pressure value of 3-7 bar. The low-pressure zone preferably operates at a pressure value of 5 bar.

[0040] In an example, the low-pressure zone can comprise at least a part of the compressor. The low-pressure zone can comprise a part of the lamination member. The low-pressure zone can comprise the evaporator. The high-pressure zone can comprise the condenser. The high-pressure zone can comprise part of the compressor. The high-pressure zone can comprise part of the lamination member.

[0041] Such solutions allow optimizing the operation of the refrigeration circuit.

[0042] In an example, the evaporator is a finned evaporator.

[0043] The evaporator fins allow increasing the heat exchange surface and therefore increasing the heat exchange between the outside air and the working fluid.

[0044] In an example, at least a part of the external surface of the water tank is coated with a layer of thermo-conductive material.

[0045] Such a solution allows reducing the thermal contact resistance between the tank and the condenser.

[0046] In an example, at least a part of the external surface of the condenser is covered with a film. The film is preferably cellophane.

[0047] In an example, the external surface of the water tank and that of the condenser are coated with an insulating material. The insulating material is preferably a polyurethane foam.

[0048] In an example, the heating system can consist of the following elements: a water tank, preferably made of steel; a condenser tube, wrapped in a spiral around the tank; a film, wrapped on top of the condenser, to prevent undesired material from entering the gap between the tube and the water tank, worsening the heat exchange thereof; a frame, arranged around the tank, to create a gap between frame and tank; an insulating material, arranged between frame and water tank, to insulate the water tank. The insulating material is a foam, which is deposited in a liquid state and, when solidified, has properties similar to those of polyurethane. A step of depositing the foam in the gap is referred to as foaming.

[0049] According to an aspect of the present description, the present finding provides a method for heating water.

[0050] The method comprises a step of providing a water heating system.

[0051] The water heating system comprises a compressor, an evaporator, a lamination member, and a condenser, which form a refrigeration cycle through which the working fluid circulates.

[0052] The method comprises a step of feeding outdoor air to the evaporator by means of a fan.

[0053] The method comprises a step of evaporating the working fluid by means of the evaporator. Evaporation occurs by means of heat exchange between the working fluid and the outside air. The heat exchange includes the working fluid being at a lower temperature than the outside air. In particular, in the evaporation step, the energy absorbed by the working fluid serves to compensate for the latent heat which is absorbed for the state change. In a terminal part of the evaporation step, when the working fluid has a unit vapor quality, the absorption of heat by the working fluid leads to an increase in temperature. Therefore, the path for crossing the heat exchanger by the working fluid can be divided into two parts: a first evaporation part and a second superheating part. Furthermore, a parameter, which continuously increases from when the working fluid enters the heat exchanger, is enthalpy. The method comprises a step of compressing the working fluid by means of the compressor. The compression step is such as to increase the pressure of the working fluid. Therefore, the increase in pressure generates an increase in the temperature of the working fluid.

[0054] The method comprises a condensation step by means of the condenser. The condensation step includes the high-temperature working fluid exchanging heat with water in the water tank. The heat exchange is such as to heat water contained in the water tank. The heat exchange is such as to bring the working fluid back to a subcooled liquid state.

[0055] The method comprises an expansion step by means of a lamination member. The expansion step is such as to decrease the pressure of the working fluid, so as to bring it back to optimal conditions for performing a subsequent evaporation step.

[0056] The system comprises a water tank. The water tank contains the water. The water tank extends along a longitudinal axis.

[0057] The method comprises a step of circulating the refrigerant inside a tube.

[0058] The tube is wrapped around the water tank. The tube forms a spiral about the longitudinal axis. The tube is connected to the water tank. The tube comprises a curved wall and a flat wall. In an example, the tube comprises the curved wall and the flat wall in the spiral, in a cross-section of the tube, along a radial plane comprising the longitudinal axis.

[0059] The flat wall is in contact with an external surface of the water tank. The curved wall is joined to the flat wall. The curved wall radially projects toward the outside of the water tank, so as to form a "D" shape.

[0060] In an example, the step of providing a water heating system includes providing a water heating system according to one or more aspects of the present description.

[0061] According to an aspect of the present description, the present finding provides a method of manufacturing a water heating system.

[0062] The method comprises a step of providing a compressor. The compressor increases the pressure of a working fluid.

[0063] The method comprises a step of providing an evaporator. The evaporator is configured to receive the working fluid in a two-phase liquid state. The two-phase liquid preferably has a vapor quality within the range of 0 - 0.5. The two-phase liquid preferably has a vapor quality equal to 0.2. In a further example, the two-phase liquid has a vapor quality equal to 0 (completely liquid). The evaporator receives a stream of outdoor air.

[0064] The method comprises a step of providing a water tank. The water tank extends along a longitudinal axis.

[0065] The method comprises a step of providing a lamination member. The lamination member receives the working fluid in a subcooled liquid state at the outlet of the condenser and lowers the pressure and temperature thereof, bringing it to a two-phase state, with a lower pressure and temperature, ready to enter the evaporator.

[0066] The method comprises a step of providing a condenser. The condenser is in contact with an external surface of the water tank. The condenser receives the working fluid in a gas state. The gas is preferably superheated in the gas state. The condenser releases working fluid in a liquid state. The condenser preferably releases the working fluid in a sub-cooled liquid state. The condenser exchanges heat with the water tank.

[0067] The compressor, the evaporator, and the condenser form a refrigeration cycle through which the working fluid circulates.

[0068] The method comprises a step of providing a fan. The fan feeds the stream of outdoor air to the evaporator.

[0069] The method comprises a step of forming a refrigeration cycle through which the working fluid circulates. The step of forming a refrigeration cycle occurs by means of the compressor, the evaporator, and the condenser.

[0070] The method can comprise a step of shaping a cylindrical tube to flatten at least a part of the tube so as to obtain a shaped tube.

[0071] The method comprises a step of wrapping a shaped tube having at least a flattened part about the longitudinal axis, to form a spiral around the water tank. Therefore, the method can comprise a step of shaping a tube to obtain said shaped tube, or a step of providing a shaped tube that was shaped in advance. Note that the shaped tube is originally a cylinder which is shaped so that it has at least one flattened part. The method comprises a step of connecting the shaped tube to the water tank. The tube is connected to the water tank. The tube is shaped so that, in the spiral, the tube has, in a cross-section along a radial plane comprising the longitudinal axis, a flat wall in contact with the external surface of the water tank, and a curved wall, which is joined to the flat wall and radially projects outside the water tank, so as to form a "D" shape.

[0072] In an example, the tube is gradually shaped, so that an initial part of the cylindrical tube remains unshaped. In the shaping step, the tube is gradually shaped to take a "D" shape.

[0073] In an example, the method comprises a step of placing the water tank on a rotating platform. The method comprises a step of securing an initial part of the tube to the outer wall of the water tank. The method comprises a step of rotating the rotating platform to form the spiral.

[0074] In an example, the initial part of the tube can unshaped.

[0075] In an example, the method includes at least a part of the external surface of the water tank being coated with a layer of thermo-conductive material.

[0076] According to an aspect of the present description, the present finding provides an apparatus for shaping a tube for a condenser of a water heating system. The apparatus for shaping a tube for a condenser of a water heating system (shaping apparatus) comprises an inlet. The inlet is configured to receive a tube. The tube is cylindrical. The shaping apparatus comprises an outlet. The outlet is configured to eject a shaped tube. The shaping apparatus comprises a first bar. The shaping apparatus comprises a second bar. The first bar and the second bar extend longitudinally. The first bar and the second bar are arranged parallel and one on top of the other. The first bar and the second bar are spaced apart from each other.

[0077] The shaping apparatus comprises at least one pair of rollers. The shaping apparatus preferably includes a plurality of pairs of rollers. The pairs of rollers are supported between the first and second bars along the apparatus from the inlet to the outlet. The pairs of rollers are configured to shape the tube transiting therebetween. When there are more than one pair of rollers, the shaping of at least one pair of rollers can be different from that of the rest of the pairs of rollers.

[0078] Such a solution allows housing a virgin tube at the inlet, guiding it and shaping it at the outlet according to the desired "D" shape.

[0079] In an example, the shaping of the pairs of rollers gradually changes from the inlet toward the outlet of the apparatus.

[0080] The gradual shaping of the pairs of rollers is necessary to gradually form the tube and not excessively stress the material of the tube. Excessive variations in the shaping of the rollers between one pair of rollers and the next could cause a greater stress in the tube than the material stress limit. In an example, at least a part of the rollers is configured to rotate freely.

[0081] In an example, the pair of rollers adjacent to the inlet is motorized.

[0082] Note that the pair of motorized rollers is intended for both shaping and advancing the tube during the shaping step. Instead, the pairs of rollers configured to rotate freely are intended only for shaping, and act as a guide for the tube along the path extending from the inlet to the outlet of the shaping apparatus.

[0083] In an example, the shaping apparatus has an open configuration, in which the rollers allow the tube to transit from the inlet to the outlet, therebetween, without shaping the tube. The apparatus has a closed configuration, in which the tube is shaped by the rollers.

[0084] The open configuration is required, in a first step of manufacturing a water heating system, to allow the transition of the tube which will be placed close to the inlet and outlet of the condenser, in the non-spiral part, which maintains the cylindrical shape of the virgin tube.

[0085] According to an aspect of the present description, the present finding provides a method for shaping a tube for a condenser of a water heating system.

[0086] The method comprises a step of providing an apparatus for shaping a tube for a condenser of an incoming water heating system. The method comprises a step of inserting a cylindrical tube into an inlet of the shaping apparatus. The method comprises a step of ejecting a shaped tube from an outlet of the apparatus. The apparatus comprises a first bar and a second bar. The apparatus comprises one or a plurality of pairs of rollers, supported between the first and second bars along the apparatus from the inlet to the outlet, which shape the tube transiting therebetween.

[0087] The method comprises a shaping step, in which the tube is transited between the plurality of pairs of rollers.

[0088] The method includes the shaping of the tube being carried out gradually. In an example, the method includes the shaping of the tube changing gradually from the inlet toward the outlet.

[0089] In an example, the method includes the gradual shaping of the tube being carried out gradually, without excessively stressing the tube material.

[0090] In an example, the method includes at least a part of the rollers rotating freely.

[0091] In an example, the method includes the pair of rollers adjacent to the inlet being motorized.

[0092] In an example, the method includes, in an open configuration of the shaping apparatus, the tube is passed from the inlet to the outlet of the apparatus, between the rollers without being shaped, and in a closed configuration of the apparatus, the tube being shaped by the rollers.

[0093] This and other features will be more apparent from the following description of a preferred embodiment, shown merely by way of a non-limiting example in the accompanying drawings, in which: figure 1 shows a water heating system according to one or more aspects of the present description; figure 2 shows the water heating system without an outer cover case. Figure 3 shows an upper part of the water heating system, containing a compressor, an evaporator, a lamination member, and a fan. Figure 4 shows a cross-section along a radial plane of a tank and a tube of a condenser; figure 5 shows a shaping apparatus according to one or more aspects of the present description; figure 6 shows the shaping apparatus, in which pairs of rollers are highlighted; figure 7 shows a bottom view of the shaping apparatus, in which a pair of motorized rollers is highlighted. Figure 8 diagrammatically shows a refrigeration cycle.

[0094] A water heating system is indicated by reference numeral 100. The water heating system (the system) 100 comprises an outside air inlet mouth 200 and an outside air outlet mouth 300. In an example, the outside air is hot air. Hot air means air having a higher temperature than an operating temperature of the working fluid. In an example, the operating temperature of the working fluid is the evaporation temperature of the working fluid.

[0095] In the transition between the inlet mouth 200 and the outlet mouth 300, the air transfers heat to a working fluid.

[0096] The water heating system is indicated by reference numeral 100.

[0097] The system 100 comprises a compressor 101, an evaporator 102, an expansion valve (106), a water tank 103, a condenser 104, and a fan 105. The compressor 101 includes a compressor inlet point 1011, configured to receive the working fluid. The compressor includes a compressor outlet point 1012, configured to release the working fluid. Between the compressor inlet point 1011 and the compressor outlet point 1012, the compressor 101 is configured to increase the pressure of the working fluid.

[0098] The compressor 101 is oriented according to a vertical position, with an axis thereof parallel to a longitudinal axis of the system.

[0099] The evaporator 102 includes an evaporator inlet point 1021, configured to receive the working fluid in the two-phase state with a vapor quality of about 0.2. The evaporator 102 includes an evaporator outlet point 1022, configured to release the working fluid in the superheated gas state. The evaporator outlet point 1022 is connected to the compressor inlet point 1011, so that during a refrigeration cycle, the working fluid transits from the evaporator to the compressor.

[0100] The expansion valve 106 includes a valve inlet point 1061, configured to receive the subcooled liquid from the condenser. The expansion valve 106 includes a valve outlet point 1062, configured to release the working fluid in the two-phase state. The valve outlet point 1062 is connected to the evaporator inlet point 1021.

[0101] The water tank 103 is configured to contain water. The water tank 103 extends along a longitudinal axis L.

[0102] The water tank comprises an external surface 1031.

[0103] The condenser 104 is configured to be in contact with the external surface 1031 of the water tank 103. The condenser 104 is configured to receive the working fluid in the superheated gas state and release the working fluid in the subcooled liquid state, so that the condenser 104 transfers heat to the water tank 103.

[0104] The condenser 104 includes a tube T. The tube T is wrapped around the water tank 103. The tube T forms a spiral about the longitudinal axis L. The tube T is connected to the water tank 103.

[0105] The tube T comprises a curved wall T1. The tube T comprises a flat wall T2. In an example, the tube T comprises the curved wall T1 and the flat wall T2 in the spiral, in a cross-section of the tube, along a radial plane comprising the longitudinal axis L.

[0106] The flat wall T2 is in contact with the external surface of the water tank 1031. The curved wall T1 is joined to the flat wall T2. The curved wall T1 radially projects toward the outside of the water tank 103, so as to form a "D" shape. In particular, the curved wall T1 is joined to the flat wall T2 to delimit an inner volume of the tube.

[0107] The fan 105 is configured to feed the stream of outdoor air to the evaporator 102. The fan 105 draws the outside air from the inlet mouth 200 and guides it toward the outlet mouth 300.

[0108] The compressor 101, the evaporator 102, and the condenser 104 form the refrigeration cycle in which the working fluid circulates. The refrigeration cycle comprises an evaporation step in which the working fluid enters the evaporator 102 in a two-phase state with a vapor quality of about 0.2. The evaporator 102 is crossed by the stream of air; therefore the air transfers heat to the working fluid, causing it to evaporate. In a compression step, the working fluid in the superheated gas state is sent to compressor 101, which increases the pressure thereof and thus increases the temperature thereof. In a condensation step, the high-pressure and temperature working fluid is sent to the condenser 104. The condenser 104 allows the working fluid to circulate through the tube T and allows the heat exchange between working fluid and water contained in the water tank 103. During the condensation step, the "D" shape of the tube T allows improved heat exchange as compared to a cylindrical tube shape.

[0109] The refrigeration cycle includes an expansion step by means of an expansion valve 106. The expansion step is such as to decrease the pressure of the working fluid, so as to bring it back to optimal conditions for performing the subsequent refrigeration cycle. In particular, the expansion step brings the working fluid back to optimal conditions for performing the subsequent evaporation step.

[0110] In an example, the tube T includes a deformed portion TS and a non-deformed portion TC. The tube includes a transition zone ZT between the deformed portion TS and the non-deformed portion TC.

[0111] In an example, the portion of tube T wrapped in the spiral consists of the deformed tube TS. In an example, at least a part of the tube T wrapped in the spiral is a non-deformed tube TC. In an example, the wrapping has a start wrapping segment and an end wrapping segment. The start wrapping segment includes a non-deformed tube portion TC. The end wrapping segment includes a segment of deformed tube TS. In an example, the tube also includes a segment of deformed tube TS that is not wrapped around the tank. The segment of deformed tube TS not wrapped around the tank is on top of the wrapped turns of tube T.

[0112] In an example, the tube includes a transition zone ZT. In the transition zone ZT, the tube T goes from deformed tube TS to non-deformed tube TC. The transition zone can have a specific length along the segment of tube T, so that the transition from deformed tube TS to non-deformed tube TC takes place gradually.

[0113] In an example, the tube T has a height H measured along a trajectory perpendicular to the longitudinal axis L, from a midpoint of said flat wall T2 toward the curved wall T1. A ratio between the height H of the tube T and an external diameter D1 of the unshaped tube falls within a range of 0.430 - 0.625. In an example, the external diameter is the diameter of an unshaped cylindrical tube TC. Note that external diameter means the measurement of the width of the tube from an outer edge toward the diametrically opposite outer edge. Therefore, the measurement of the external diameter takes the thickness into consideration. Furthermore, note that deformed tube means a tube shaped according to one or more aspects of the present description. In an example, the flat wall T2 of the tube T has a width U measured along the longitudinal axis L and between the two ends thereof. A ratio between the value of the width U and the value of the height H of the tube T falls within a range of 1.920 - 3.140.

[0114] In an example, a ratio between a thickness of the tube S and the height H of the tube T falls within a range of 0.160 - 0.349.

[0115] In an example, a ratio between an outer radius of the non-deformed tube and an average value of a radius of curvature of the curved wall T1 falls within a range of 0.615 - 0.80.

[0116] In other words, the tube has one or more of the following features: Degree of flattening: defined as the ratio between the height H of the deformed (D-shaped) tube TS and the external diameter D1 of tube TC (pre-shaping), which falls within a range of 0.430 - 0.625, and is preferably equal to 0.5; Aspect ratio: width U of the deformed tube TS over the height H of the deformed tube TS, which falls within a range of 1.920 - 3.140, and is preferably equal to 2.55; Thickness ratio: thickness S of the deformed tube TS over the height H of the deformed tube TS, which falls within a range of 0.160 - 0.349, and is equal to 0.25 with possible loss; Arc ratio: outer radius of the unshaped tube over the mean radius of the curved face of the deformed tube TS, which falls within a range of 0.615 - 0.800, and preferably equal to 0.68.

[0117] In an example, the system comprises a high-pressure zone 500. The high-pressure zone 500 operates at a pressure value of 20 bar. The system comprises a low-pressure zone 400. The low-pressure zone 400 operates at a pressure value of 5 bar.

[0118] In an example, the low-pressure zone 400 comprises part of the compressor 101, the evaporator 102, part of the expansion valve 106. The high-pressure zone 500 comprises the condenser 104, part of the compressor, and part of the expansion valve.

[0119] In an example, at least a part of the external surface 1031 of the water tank 103 is coated with a layer of thermo-conductive material.

[0120] In an example, at least a part of the external surface 1031 of the condenser 104 is covered with a film.

[0121] In an example, the external surface 1031 of water tank 103 and condenser 104 are coated with polyurethane foam.

[0122] According to an aspect of the present description, the shaping of a cylindrical tube TC is carried out to flatten at least a part of the tube T so as to obtain a shaped tube TS. The shaped tube TS can be in accordance with one or more aspects of the tube of the present description.

[0123] The shaped tube TS is wrapped about the longitudinal axis L and forms a spiral around the water tank 103.

[0124] In an example, the shaping is carried out gradually, so that an initial part of the cylindrical tube TC remains unshaped. In the shaping step, the tube T is gradually shaped to take a "D" shape.

[0125] In an example, the water tank 103 is placed on a rotating platform. and an initial part of the tube T is secured to the outer wall 1031 of the water tank 103. The rotating platform is rotated to form the spiral around the tank.

[0126] In an example, the initial part of the tube can unshaped.

[0127] In an example, at least a part of the external surface 1031 of the water tank is coated with a layer of thermo-conductive material.

[0128] An apparatus for shaping a tube for a condenser of a water heating system, by means of which the tube T is shaped, is denoted with 1. The heating system can be in accordance with one or more aspects of the present description, or another known heating system.

[0129] The apparatus for shaping a tube for a condenser of a water heating system (the shaping apparatus) 1 comprises an inlet I. The inlet I is configured to receive a cylindrical tube TC. The inlet I comprises an inlet flange I1. The shaping apparatus 1 comprises a support plate 10. The shaping apparatus 1 comprises a transmission box 12. The inlet I comprises an inlet support I2. The inlet support I2 is mounted to the support plate 10. The support flange I1 is mounted to the inlet support I2.

[0130] The shaping apparatus 1 comprises an outlet O. The outlet O is configured to eject a shaped TS tube. In an example, inlet I and outlet O are aligned along the same axis. In an example, inlet I and outlet O are aligned along different axes.

[0131] The shaping apparatus 1 comprises a first bar 2 and a second bar 3. The first bar 2 and the second bar 3 extend longitudinally. The first bar 2 and the second bar 3 are arranged parallel and one on top of the other. The first bar 2 and the second bar 3 are spaced apart from each other.

[0132] The first bar 2 comprises a first upper fin 21 and a second upper fin 22. First upper fin 21 and second upper fin 22 comprise centering holes 210 and 220, respectively. The centering holes 210, 220 are configured to center rollers. The rollers are free to rotate, remaining pivoted at the top in the centering holes 210, 220.

[0133] The second bar 3 comprises a first lower fin 31 and a second lower fin 32. First lower fin 31 and second lower fin 32 comprise centering holes 310 and 320, respectively. The centering holes 310, 320 are configured to center rollers. The rollers are free to rotate, remaining pivoted at the bottom in the centering holes 310, 320.

[0134] The shaping apparatus 1 comprises a plurality of pairs of rollers 4. The pairs of rollers 4 comprise at least one pair of motorized rollers 41. The pair of motorized rollers 41 is adjacent to the inlet I. The pair of motorized rollers 41 is configured to receive motion from a transmission shaft 411. At least one roller, of the pair of motorized rollers 41 receives the motion through the transmission shaft 411. The transmission shaft 411 can be a grooved shaft. In an example, the roller that receives the motion transmits it to the adjacent roller by means of a transmission mechanism 412. In an example, the transmission mechanism 412 can include a plurality of gears.

[0135] The pairs of rollers 4 comprise pairs of idler rollers 42. The pairs of idler rollers 42 are configured to rotate freely while remaining pivoted in the centering holes 210, 220, 310, 320.

[0136] A roller of the pair of rollers 4 is mounted between the first upper fin and the first lower fin. A further roller of the pair of rollers 4 is mounted between the second upper fin and the second lower fin.

[0137] In a different embodiment, the pairs of rollers 4 are idler rollers. In other words, pairs of motorized rollers are not provided.

[0138] The pairs of rollers 4 extend vertically between the first bar 2 and the second bar 3. The pairs of rollers 4 are placed along the apparatus 1 from the inlet

[0139] I to the outlet O. The pairs of rollers 4 are configured to shape the tube T transiting therebetween. The shaping of at least one pair of rollers 4 is different from that of the rest of the pairs of rollers 4.

[0140] In an example, the shaping of the pair of rollers 4 changes gradually from the inlet I toward the outlet O of the shaping apparatus 1.

[0141] In an example, the shaping apparatus 1 has an open configuration, in which the pairs of rollers 4 allow the tube T to transit from the inlet I to the outlet O, without shaping the tube T. The apparatus 1 has a closed configuration in which the pairs of rollers 4 allow the tube T to transit from the inlet I to the outlet O, shaping the tube T.

[0142] The shaping apparatus includes an opening pin 5. The opening pin 5 is hinged to the first and second upper fins 21,22 through a pair of screws 51, 52. The opening pin 5 includes a body 53. The opening pin 5 allows the fins 21 and 22 to rotate along with the fins 31 and 32 in the transition from an open configuration to the closed configuration and vice versa.

[0143] Therefore, when transiting between an open configuration and a closed configuration (and vice versa), the distancing and approaching of the fins results in a distancing and approaching of the rollers, respectively.

[0144] The shaping apparatus includes a closing clamp 6. The closing clamp (the clamp) 6 includes an upper closing lever 61 and a lower closing lever 62. The upper closing lever 61 and the lower closing lever 62 are placed in contact with the first bar 2 and the second bar 3, respectively. The clamp 6 includes a vertical bar 63. The vertical bar 63 is mounted to the clamp 6 in a position perpendicular to the closing levers and perpendicular to the extension direction of the shaping apparatus 1. The clamp 6 includes a thrust plate 65. The clamp 6 includes a thrust pin 64. The thrust pin 64 is integral with the vertical bar 63. The thrust pin 64 is configured to press against the thrust plate 65. In particular, the pressure of the thrust pin 64 can be controlled by automated actuators. Therefore, the actuators can gradually increase the thrust and then the crushing of the tube, while the tube is advancing. Thus, the tube T undergoes a gradual transition from the shaped section, related to the tube TS, to the unshaped or cylindrical one, related to the tube TC.

[0145] In an example, the shaping apparatus can include a plurality of closing clamps 6.

[0146] In the closed configuration of the shaping apparatus 1, the thrust plate 65 is configured to press against a side part of the upper fins 21,22 and the lower fins 31,32.

[0147] According to an aspect of the present description, in a placing step, the water tank 103 is arranged on a rotating platform (not present in the figure). In a securing step, the tube T is secured to the water tank 103. In the securing step, the tube T passes through the shaping apparatus 1 while said apparatus is in an open configuration. In a step of rotating the rotating platform, the tube T is wrapped in a spiral around the water tank 103. During the step of rotating the rotating platform, the shaping apparatus 1 is in the closed configuration, so as to shape the tube in a "D" shape, in contact with the tank 103.

[0148] When tube T is wrapped around the water tank 103, a layer of thermo-conductive material is deposited on the tube T.

Claims

1. A water heating system (100), comprising: - a compressor (101), for increasing the pressure of a working fluid; - an evaporator (102), for receiving the working fluid in a liquid or two-phase state and releasing the working fluid in a gas state, wherein the evaporator (102) receives a stream of outdoor air; - a water tank (103) for containing water, the water tank (103) extending along a longitudinal axis (L); - a condenser (104), in contact with an external surface (1031) of the water tank (103), the condenser (104) being configured to receive the working fluid in a gas state and release the working fluid in a liquid state, so that the condenser transfers heat to the water tank (103); - a fan (105) for feeding the stream of outdoor air to the evaporator (102), wherein the compressor (101), the evaporator (102), and the condenser (104) form a refrigeration cycle through which the working fluid circulates, wherein the condenser (104) includes a tube (T) wrapped around the water tank (103) to form a spiral about the longitudinal axis (L) and connected to the water tank (103), wherein at least one segment of the tube (T) in the spiral has, in a cross-section along a radial plane comprising the longitudinal axis (L), a flat wall (T2) in contact with the external surface (1031) of the water tank (103), and a curved wall (T1), joined to the flat wall (T2) and radially projects toward the outside of the water tank (103), so to form a "D" shape.

2. The water heating system (100) according to claim 1, wherein the flat wall (T2) has a width (U) measured along the longitudinal axis (L) and between the two ends thereof, said at least one segment of the tube (T) having a height (H), measured along a trajectory perpendicular to the longitudinal axis (H), from a midpoint of said flat wall (T2) to the curved wall (T1), wherein the ratio between the value of the width (U) and the value of the height (H) of the tube (T) falls within a range of 1.920 - 3.140.

3. The water heating system (100) according to any one of the preceding claims, wherein said at least one segment of the tube (T) has a height (H), measured along a trajectory perpendicular to the longitudinal axis (L), from a midpoint of said flat wall (T2) to the curved wall (T1), wherein the ratio between a thickness (S) of said at least one segment of the tube (T) and the height (H) of the tube (T) falls within a range of 0.160 - 0.349.

4. The water heating system (100) according to any one of the preceding claims, wherein the tube (T) has a non-deformed portion, having a circular cross-section with an external diameter (D1), and a deformed portion, said at least one segment of the tube (T) belonging to the deformed portion, wherein the cross-section of the tube (T) in the deformed portion has a height (H), measured along a trajectory perpendicular to the longitudinal axis (L), from a midpoint of said flat wall (T2) to the curved wall (T1), and wherein the ratio between the height (H) of the tube (T) and the external diameter (D1) falls within a range of 0.430 - 0.625.

5. The water heating system (100) according to claim 4, wherein the ratio between a radius of the non-deformed portion of the tube (T) and an average value of a radius of curvature of the curved wall (T1) falls within a range of 0.615 - 0.80.

6. The water heating system (100) according to any one of the preceding claims, wherein one or both of the following conditions occur: (i) the evaporator (102) is a finned evaporator; (ii) at least a part of the external surface (1031) of the water tank (103) is coated with a layer of thermo-conductive material;7. The water heating system (100) according to any one of the preceding claims, wherein the external surface of the water tank (103) and that the condenser (104) are coated with a polyurethane foam, wherein at least a part of the external surface of the condenser (104) is covered with a film.

8. A method for manufacturing a water heating system (100), comprising the following steps: - providing a compressor (101), for increasing the pressure of a working fluid; an evaporator (102), for receiving the working fluid in a liquid or two-phase state and releasing the working fluid in a gas state, wherein the evaporator (102) receives a stream of outdoor air; a water tank (103) for containing water, extending along a longitudinal axis (L); a condenser (104), in contact with an external surface (1031) of the water tank (103); the condenser (104) is configured to receive the working fluid in a gas state and release the working fluid in a liquid state, so that the condenser (104) transfers heat to the water tank (103), a fan (105) for feeding the stream of outdoor air to the evaporator (102), wherein the compressor (101), the evaporator (102) and the condenser (104) form a refrigeration cycle through which the working fluid circulates. - shaping a cylindrical tube (TC) to flatten at least a part thereof; - wrapping a shaped tube (TS) having at least one flattened part about the longitudinal axis (L) and connecting it to the water tank (103) to form a spiral around the water tank (103), wherein at least one segment of the tube (T) is shaped so that the tube in the spiral has, in a cross-section along a radial plane comprising the longitudinal axis (L), a flat wall (T2) in contact with an external surface (1031) of the water tank (103), and a curved wall (T1), joined to the flat wall (T2) and radially projecting toward the outside of the water tank (103), so to form a "D" shape.

9. The method according to claim 8, wherein the tube (T) is gradually shaped, so that an initial part of the cylindrical tube (TC) remains unshaped, and the tube (T) is gradually shaped to take the D shape.

10. The method according to any one of claims 8 or 9, comprising the following steps: - placing the water tank (103) on a rotating platform; - securing an initial part of the tube (T) to the external surface of the water tank (103), - rotating the rotating platform to form the spiral.

11. An apparatus (1) for shaping a tube (T) for a condenser (104) of a water heating system (100), the apparatus comprising: - an inlet (I) for receiving a cylindrical tube (TC); - an outlet (O) for ejecting a shaped tube (TS); - a first bar (2) and a second bar (3), extending longitudinally and arranged mutually parallel and one on top of the other, the first bar (2) and the second bar (3) being spaced apart from each other, - a plurality of pair of rollers (4), supported between the first bar (2) and the second bar (3) along the apparatus (1) from the inlet (I) to the outlet (O), and configured to shape the tube (T) transiting therebetween, wherein the shaping of at least one pair of rollers is different from that of the rest of the pairs of rollers.

12. The apparatus (1) according to claim 11, wherein the shaping of the pair of rollers gradually changes from the inlet (I) toward the outlet (O) of the apparatus (1).

13. The apparatus (1) according to any one of claims 11 or 12, wherein at least a part of the rollers (4) is configured to rotate freely.

14. The apparatus (1) according to any one of claims 11 to 13, wherein the apparatus (1) has an open configuration in which the rollers (4) allow the tube (T) to transit from the inlet (I) to the outlet (O), therebetween, without shaping the tube (T), and a closed configuration in which the tube (T) is shaped by the rollers.

15. The apparatus (1) according to any one of the preceding claims from 11 to 14, wherein the pair of rollers adjacent to the inlet (I) is motorized.

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