Four-layer solar heater with optimised heat conservation and improved mechanical resistance

Abstract

The present invention relates to a four-layer solar heater in which the first layer is an internal tank (20) made of surgical stainless steel and having circumferential channels (23), the second layer is a plastic film (30) which is adhered to the outer surface of the internal tank (20), the plastic film (30) consisting of sheets of polyethylene (PE) or polypropylene (PP), the third layer is a thermal insulator (40) made of high-density polyurethane (PU) injected between the two tanks, the thickness of the thermal insulator (40) being between 31 mm and 39 mm, and the fourth layer is an external tank (10) made of linear medium-density polyethylene (LMDPE) with UV stabiliser additives, hexene and azodicarbonamide. The plastic film reduces the expansion and contraction of the internal tank (20), thereby reducing the formation of spaces and cavities between the layer of thermal insulator (40) and the internal tank (20). The layer of plastic film (30) allows better heat conservation in the water located inside the four-layer solar heater (1). In addition to the additives of the layer of the external tank (10) allowing the UV stabilisers to improve the resistance to UV protection, the hexene improves the impact resistance, and the azodicarbonamide acts as an expansion or foaming agent that causes the expansion of the polyethylene (PE) in order to improve the heat conservation in the water located inside the four-layer solar heater (1).

Description

[0001] QUAD-LAYER SOLAR HEATER WITH OPTIMIZED THERMAL CONSERVATION

[0002] AND IMPROVED MECHANICAL RESISTANCE

[0003] Technical field of the invention

[0004] The present invention relates to the field of solar-powered water heaters. In particular, this invention consists of a heater that optimizes the thermal conservation of solar energy through a four-layer arrangement of specifically selected materials to provide novel advantages over prior-art heaters, and also improves mechanical strength through the addition of selected components.

[0005] Background of the invention

[0006] Solar water heaters have been known for many years and currently represent one of the best solutions for heating liquids in an environmentally friendly and economical manner. However, thermal conservation of the liquid in commercially available water heaters has been a constant challenge, seeking to minimize thermal loss. Therefore, the solution proposed in the present invention is a step closer to improved thermal conservation through a four-layer water heater, where the material of each layer has been specifically selected to increase its thermal insulation and / or improve its mechanical strength. It is also important to mention that this selection of layers also addresses technical issues, thus facilitating the water heater's manufacturing. Likewise, these selected materials include additives that can reinforce the water heater's mechanical characteristics.

[0007] There are some patent documents and utility models in the state of the art aimed at providing a combined water heater or water heater that can provide some of the aforementioned advantages.

[0008] In this regard, Chinese utility model CN2550695Y describes a solar water heater having an inner tank made of stainless steel and an outer tank made of plastic material, wherein the plastic material may be a thermosetting polymer or a thermoplastic polymer, the use temperature of which is higher than 70 degrees Celsius. The plastic material may be polyethylene (PE), polypropylene (PP), polycarbonate, polyester, nylon, fluorine plastic or a combination of two or more. Furthermore, both tanks are joined by a metal-plastic adhesive where the adhesive may be a hot melt adhesive, an epoxy resin adhesive, a polyurethane (PU) adhesive, a silicone adhesive or an acrylic resin binder or a combination of two or more. Furthermore, this invention provides one or more plastic layers or multi-layer plastic layers.This invention aims to extend the useful life of the heater by increasing its corrosion resistance and preventing leaks caused by welds in the stainless steel inner tank. The main disadvantage of this heater is that the thickness of the polyurethane (PU) intermediate layer does not allow for optimal thermal insulation. Another disadvantage is that the plastic material of the outer tank will have mechanical properties that depend on the plastic selected, but the document does not specify any of these materials in particular. Finally, it can be seen from the drawing accompanying this document that the inward and outward connections of the inner tank are not optimal for proper distribution of the liquid inside.

[0009] On the other hand, Indian utility model IN201911023425A describes an insulated water storage water heater with a multi-layered tank made of different materials that prevent water quality from deteriorating. The main body of the tank is constructed with a 5 to 10 millimeter thick outer layer of linear low-density polyethylene (PE) material for UV protection, a 45 to 60 millimeter thick middle layer of foam that acts as thermal insulation, and a 0.5 to 1 millimeter thick inner layer of stainless steel that comes into contact with the water. The main disadvantage of this water heater is the technical difficulties faced during manufacturing such a water heater, particularly in managing the application of the foam interlayer. Another disadvantage is that this document does not mention or illustrate whether this water heater can work in conjunction with solar collectors.Finally, it can be seen from the drawing accompanying this document that the connections to and from the water heater for correct distribution of the liquid inside are not described.

[0010] Likewise, international patent applications WO2018226084A1 and W02019112409A1 describe a solar heater or collector with a water storage tank, where the heater heats the water inside it and moves towards the top of the tank due to changes in temperature and density. The tank consists of an outer tank made of polyethylene (PE), an inner tank also made of polyethylene (PE), joined by a polyurethane (PU) layer 40 to 60 mm thick. Both polyethylene (PE) tanks can be manufactured by rotational molding. The water storage tank is intended to prevent heat loss from the water. The main disadvantage of these heaters is that the inner tank made of polyethylene (PE) cannot withstand the high temperatures that the water in the solar collector can reach, so its thermal decomposition can affect the water quality or transmit impurities and plastic waste.Another disadvantage is that, during manufacturing, the reactions of the polyurethane (PU) foam also reach high temperatures that neither the inner nor the outer tank can withstand. This can lead to thermal damage or structural deformations from the manufacturing process, resulting in a defective product. Finally, the accompanying drawings show that the inward and outward connections of the inner tank are not optimal for proper distribution of the liquid inside.

[0011] For its part, the Mexican utility model application MX / u / 2022 / 000360 seeks to protect a solar heater with a hybrid water heater that has been anticipated in documents CN2550695Y and IN201911023425A since it consists of an internal tank made of stainless steel, an intermediate layer of polyurethane (PU) thermal insulation 40 to 60 mm thick and an external tank made of high-density polyethylene (PE) with the intention of providing greater temperature conservation in the water heater, as well as less wear from erosion in its external tank, which corresponds exactly to the same technical problems cited in the documents from China and India. Furthermore, this solar heater has a configuration similar to that of the international applications with publication numbers WO2018226084A1 and W02019112409A1. The main disadvantage of this solar heater is the waste of insulating material due to the high thickness of polyurethane (PU).Another disadvantage is that, during manufacturing, the steel inner tank undergoes significant expansions during foam application due to thermal changes resulting from the chemical reaction of the polyurethane (PU), and subsequently, the inner tank contracts sharply during the cooling of the product. Furthermore, as with other references mentioned above, the accompanying drawings show that the inward and outward connections of the inner tank are not optimal for proper distribution of the liquid inside.

[0012] Finally, the Chinese utility model CN202254420U describes a heater with a hot water tank composed of an inner tank made of 1.2 mm thick stainless steel, the inner wall of which is coated with a modified polypropylene (PP) resin nano-polymer film, an outer tank, and a thermal insulation layer between the two tanks. In addition, the heater has backup electric heating means. The technical problem that this utility model seeks to solve is to provide the inner tank with an anti-corrosion, leak-proof coating that prevents the growth of bacteria. The main disadvantage of this solar / electric heater is the high degree of complexity involved in the material and manufacturing of the modified polypropylene (PP) resin nano-polymer film layer.Likewise, as with other cited background information, it can be seen in the drawings accompanying this document that the connections to and from the inner tank are not optimal for the correct distribution of the liquid inside.

[0013] Based on the above, there is a need in the state of the art for a solar heater that allows for optimal conservation of the heat energy of water in a water heater. There is also a need in the state of the art for a solar heater that facilitates and improves manufacturing, particularly addressing defects caused by expansion / contraction of the inner tank during the thermal reaction of the insulation. Furthermore, there is a need for a solar heater whose storage tank is made of materials that improve the mechanical strength of its various components. Finally, the solar heater must have an optimal configuration of the connections inside and outside the inner tank for water distribution during use.

[0014] Objectives of the invention

[0015] An object of the present invention is to provide a solar heater that allows the heat energy of water to be optimally conserved in a water heater.

[0016] Another objective of the present invention is to facilitate the manufacturing process of the solar heater, addressing defects caused by expansion / contraction of the internal tank during the thermal reaction of the insulation. Likewise, another objective of the present invention is to make the solar heater's water heater tank made of materials that provide greater mechanical strength in its various components.

[0017] Finally, another objective of the present invention is that the solar heater has an internal tank connection configuration for optimal water distribution.

[0018] Brief description of the figures

[0019] To provide a better understanding of the invention, the following drawings are attached:

[0020] Figure 1A refers to a perspective view of the exterior of the quad-layer solar heater of the present invention.

[0021] Figure IB refers to a front view of the quad-layer solar heater of the present invention.

[0022] Figure 1C refers to a top view of the quad-layer solar heater of the present invention.

[0023] Figure ID refers to a bottom view of the quad-layer solar heater of the present invention.

[0024] Figure 1E refers to a side view of the quad-layer solar heater of the present invention.

[0025] Figure 2A shows a perspective view of the inner tank of the four-layer solar heater of the present invention. Figure 2B shows a front view of the inner tank of the four-layer solar heater of the present invention.

[0026] Figure 3A refers to a cross-sectional view of the quad-layer solar heater of the present invention.

[0027] Figure 3B refers to a detailed view of a longitudinal section of the four-layer solar heater of the present invention, during the thermal insulation injection stage.

[0028] Detailed description of the invention

[0029] As can be seen in Figures 1A to 1E, the present invention relates to a four-layer solar heater (1) with optimized thermal conservation, which has an external tank (10), substantially cylindrical, formed by a body (HA) and two covers (11B, 11C) that cover the ends of said body. It should be noted that the substantial shape of the external tank (10) may comprise other types of parallelepipeds or geometric volume shapes.

[0030] The body (HA) of the external tank (10) has on the front face at least one set of slots, preferably circular, where the set of slots (12) where each slot is configured to allow the passage of a collector tube (not illustrated). The collector tubes can be vacuum tubes of various types known in the state of the art, which are part of the solar heater systems acting as solar thermal energy collectors. It is evident to an expert in the field that the number of slots will depend on the number of collector tubes that make up the solar heater system, due to several technical parameters, such as, volume of water, solar incidence, among others. The external tank (10) also has other holes that allow the passage of tubes and connections coming from the interior of the four-layer solar heater (1), which will be explained later.

[0031] Now looking at Figures 2A and 2B, it can be seen that inside the four-layer solar heater (1) there is housed an internal tank (20) that is substantially cylindrical and formed by a body (21A) and two covers (21B, 21C) that cover the ends of the body. It should be noted that the substantial shape of the internal tank (20) may comprise another type of parallelepipeds or geometric shapes of volume, particularly coinciding with the shape of the external tank (10). The body (21A) has on the front face at least one set of slots (22) coinciding with the set of slots (12) of the external tank (10). Each slot of both sets is configured to receive a collector tube (not illustrated) as referred to above. Additionally, the internal tank (20) has circumferential channels (23) distributed evenly along the body (21A) that provide greater mechanical resistance to the internal tank (20).Now, looking at the cross section of the figure.

[0032] 3A, the four layers that make up the four-layer solar heater (1) of the present invention can be observed. From the inside to the outside, the first layer corresponds to the inner tank (20), the second layer corresponds to a plastic film (30) that is adhered to the outer surface of the inner tank (20), the third layer corresponds to a thermal insulator (40) that is injected between both tanks, while the fourth layer corresponds to the outer tank (10).

[0033] Considering the technical problems that are the objective of this invention, the advantages provided by each layer of the quad-layer solar heater (1) are specified below:

[0034] The inner tank (20) is made of surgical grade stainless steel, which favors the sanitary conservation of the water housed inside the tank. Preferably, the thickness of the inner tank (20) is approximately 0.2 mm to 0.6 mm.

[0035] The plastic film layer (30) fulfills two functions, the first is to reduce the direct thermal shock of the chemical reaction produced during the injection of the thermal insulation layer (40), as illustrated in an exemplary manner in the section of figure 3B, since said reaction can reach between 60 ° C to 85 ° C. This change in temperature causes the expansion of the inner tank (20), as well as the corresponding contraction of the inner tank (20) during cooling, thereby reducing the formation of spaces and cavities between the thermal insulation layer (40) and the inner tank (20). The other function of the plastic film layer (30) consists of subtracting from the general thermal conductivity coefficient of the heater to achieve better thermal conservation of the water housed inside the four-layer solar heater (1). The plastic film (30) consists of sheets of polyethylene (PE) or polypropylene (PP).Preferably, the thickness of the plastic film layer (30) is about 0.01 mm to 0.05 mm, which may include 1 to 5 turns of film.

[0036] The thermal insulation layer (40) provides a lower coefficient of thermal conductivity, resulting in greater insulation between the two tanks. The thermal insulation (40) is made of high-density polyurethane (PU). Preferably, the thickness of the thermal insulation (40) is approximately 31 mm to 39 mm.

[0037] Finally, the external tank (10) is made of linear medium density polyethylene (LMDPE), which favors the conservation of the four-layer solar heater (1) against the inclement weather suffered by outdoor heaters and storage tanks, such as corrosion, deterioration by UV rays, among others. Particularly, this type of polyethylene (LMDPE) allows it to be combined with aggregates and additives. Therefore, the external tank (10) is specifically manufactured with the following additives: UV stabilizers to improve resistance to UV protection, hexene to improve the mechanical property of greater impact resistance, and azodicarbonamide which consists of an expansion agent or foaming agent that causes the expansion of the polyethylene (PE) to subtract from the general thermal conductivity coefficient of the heater to achieve better thermal conservation of the water housed inside the four-layer solar heater (1).Preferably, UV stabilizers are added in a range of approximately 0.05% to 5% per kilo of resin, hexene is added in a range of approximately 0.05% to 20% per kilo of resin, and azodicarbonamide in a range of approximately 0.05% to 5% per kilo of resin.

[0038] On the other hand, the four-layer solar heater (1) of the present invention also has an optimal configuration of the connections in and out of the internal tank (20) for the distribution of water during its use. The connections are coincident and pass through the four layers of the four-layer solar heater (1). As mentioned above, inside the internal tank (20) is the water to be heated that flows through the collector tubes, where they receive solar thermal energy. The four-layer solar heater (1) has a drainage tube (2) and a cold water inlet tube (3) in the lower part, an air jug ​​tube (4) in the upper part, an outlet tube (5) in one of the side covers. Additionally, the lower part of the external tank (10) has holes that help in the assembly of the four-layer solar heater.

[0039] (1) •

[0040] Although the specific embodiment of the invention has been described above in detail, the description is merely for purposes of illustration. It should therefore be appreciated that many aspects of the invention were described above by way of example only and are not intended as required or essential elements of the invention unless explicitly stated otherwise. Various modifications of, and equivalent steps corresponding to, the described aspects of the alternative embodiments, in addition to those described above, can be made by one of ordinary skill in the art having the benefit of this disclosure, without departing from the spirit and scope of the invention, as defined in the following claims, which scope is to be given the broadest interpretation to embrace such modifications and equivalent structures.

Claims

Claims 1. A four-layer solar heater characterized in that it comprises: an inner tank (20) made of surgical grade stainless steel, the inner tank (20) has circumferential channels (23) distributed evenly, a plastic film (30) that is adhered to the outer surface of the inner tank (20), the plastic film (30) consists of sheets of polyethylene (PE) or polypropylene (PP), a high-density polyurethane (PU) thermal insulator (40) that is injected between both tanks, the thickness of the thermal insulator (40) is 31 mm to 39 mm, and an outer tank (10) made of linear medium density polyethylene (LMDPE) with UV stabilizing additives, hexene and azodicarbonamide; wherein the plastic film decreases the expansion and contraction of the inner tank (20), thereby decreasing the formation of spaces and cavities between the thermal insulation layer (40) and the inner tank (20).

2. The four-layer solar heater according to claim 1, wherein the thickness of the inner tank (20) is 0.2 mm to 0.6 mm.

3. The four-layer solar heater according to claim 1, wherein the thickness of the plastic film layer (30) is 0.01 mm to 0.05 mm, which may include 1 to 5 turns of film.

4. The quad-layer solar heater according to claim 1, wherein the UV stabilizers are added in an approximate range of 0.05% to 5% per kilo of resin, the hexene is added in an approximate range of 0.05% to 20% per kilo of resin, and the azodicarbonamide in an approximate range of 0.05% to 5% per kilo of resin.

5. The four-layer solar heater according to claim 1, wherein the external tank (10) and the internal tank (20) are substantially cylindrical, formed by a body (HA, 21A) and two covers (HB, 11C, 12B, 12C) that cover the ends of said body.

6. The four-layer solar heater according to claim 5, wherein the shape of the external tank (10) and the internal tank (20) may comprise another type of parallelepipeds or geometric volume shapes.

7. The four-layer solar heater according to claim 5, wherein each body (HA, 21A) has on the front face at least one set of slots (11, 22) coinciding between both tanks.

8. The four-layer solar heater according to claim 7, wherein each slot of both assemblies is configured to receive a collector tube.

9. The quad-layer solar heater according to claim 1, wherein the quad-layer solar heater has matching connections that pass through the four layers of the quad-layer solar heater (1).

10. The four-layer solar heater according to claim 1, wherein the four-layer solar heater has a drainage tube (2) and a cold water inlet tube (3) in the lower part, an air flow tube (4) in the upper part and an outlet tube (5) in one of the side covers.

11. The four-layer solar heater according to claim 1, wherein the four-layer solar heater has holes in the lower part of the external tank (10) that help in the assembly of the four-layer solar heater (1).

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