Solar water heater

Abstract

The invention relates to the field of water heating devices that use solar radiation as an energy source. The present water heating device comprises a heat storage tank and a heat exchange tube. The heat storage tank is filled with a liquid heat transfer fluid and has a dome-like element, the outer surface of which is exposed to solar radiation. The heat exchange tube is disposed inside the heat storage tank such that the outer surface of the heat exchange tube is in contact with the liquid heat transfer fluid, and the interior of the heat exchange tube is isolated from the liquid heat transfer fluid. Water to be used flows through the interior of the heat exchange pipe. The heat exchange pipe contains a valve that is capable of releasing water from the heat exchange pipe into the heat storage tank. The result is a water heating device that has a simplified design and greater operational independence.

Description

SOLAR WATER HEATER Field of technology [1] The invention relates to the field of devices for heating water, in which solar radiation is used as an energy source. Prerequisites for the creation of an invention [2] Using solar radiation to heat water for domestic purposes is a very attractive idea due to the availability and inexhaustibility of this resource. However, the technical implementation of this idea has difficulties associated with the change in the position of the Sun relative to the solar collector during the day, as well as with atmospheric phenomena that can impede the passage of sunlight. Both of these factors reduce the amount of solar flux falling on the solar collector, and therefore negatively affect the efficiency of water heating. [3] Patent publication FR2468077A1, April 30, 1981 discloses a device for heating water, comprising a water-filled dome-shaped reservoir, which is open to solar radiation and which simultaneously functions as a solar collector and a heat accumulator. Since the outer surface of the dome-shaped reservoir has the shape of a hemisphere, at any time of the day on the outer surface of the dome-shaped reservoir there is a section located perpendicular to the sun rays falling on it and receiving the maximum possible amount of solar flux per its specific area. [4] The solar-heated water is supplied to the consumer directly from the dome-shaped tank, and its consumption is compensated by supplying fresh water to the dome-shaped tank so that the water level in the dome-shaped tank remains constant. Due to the large volume of water retained in the dome-shaped tank, it is able to retain heat for a long time, even during periods of cloudy weather or at night. [5] However, this known device, which is an analogue of the invention, has serious drawbacks. Long-term presence of a large volume of ready-to-use water in a heated state promotes the proliferation of pathogenic microorganisms in it, as a result of which the area of ​​safe use of such water is naturally reduced. In addition, salt deposits actively form on the inner surface of the dome-shaped tank in contact with the heated water, which, due to their high thermal conductivity, reduce efficiency of heat transfer from the inner surface of the dome-shaped tank to the heated water, i.e. prevent the water from heating up. [6] The above-mentioned disadvantages are overcome in the water heating device disclosed in patent publication CN203980673U, 03.12.2014, which serves as a prototype of the invention. This known device comprises a water-filled heat-accumulating tank, which, together with a solar collector and a pump, is included in a closed circulation circuit. Water circulating in the closed circulation circuit acts as a liquid heat carrier and receives heat by passing through the solar collector. [7] A coil is placed inside the heat-accumulating tank, which is completely immersed in a liquid heat carrier, and in which water flows, subject to heating for the purpose of further consumption (hereinafter referred to as the consumed water). The prototype of the invention has the advantage that the consumed water is supplied directly from the municipal water supply system and is heated during its flow through the coil, due to which the consumed water is not subjected to long-term storage at an elevated temperature. In addition, since the liquid heat carrier circulates in a closed circulation loop and does not mix with the consumed water, the water used as it can be specially desalinated or replaced with another liquid that does not create deposits. [8] However, the prototype of the invention lacks the favorable features that are inherent in the analog described above. In order to effectively perceive solar radiation, the solar collector of the prototype must be equipped with a tracking system that turns it to follow the Sun. In addition, the prototype must be equipped with a pump that pumps the liquid coolant through a closed circulation loop so that the liquid coolant passes through the solar collector. However, this tracking system, and along with it the closed circulation loop pump, significantly complicate the device and reduce its degree of autonomy. [9] Another disadvantage of the prototype is that the loss of liquid coolant is replenished through a special pipe that connects the heat-accumulating tank to the liquid coolant storage tank. This configuration requires labor-intensive technological operations associated with making an additional hole in the wall of the heat-accumulating tank for the said pipe, as well as with the installation of the pipe, its sealing, etc.

[0010] The technical problem that the invention is aimed at solving is the search for a simplified solution that is capable of autonomously and at any time of the day providing heating of the liquid heat carrier that transfers heat to the consumed water. The essence of the invention

[0011] To solve the said technical problem, a device for heating water (hereinafter also referred to as a solar water heater) is proposed as an invention, comprising a heat-accumulating tank and a heat-exchange tube. The heat-accumulating tank is filled with a liquid heat carrier and contains a dome-shaped element whose outer surface is exposed to solar radiation. The heat exchange tube is located inside the heat-accumulating tank so that the outer surface of the heat exchange tube is in contact with the liquid heat carrier, and the inner volume of the heat exchange tube is isolated from the liquid heat carrier, while water to be consumed flows in the inner volume of the heat exchange tube. The heat exchange tube is equipped with a valve, hereinafter referred to as a "replenishing valve", which is capable of releasing water from the heat exchange tube into the heat-accumulating tank.

[0012] The first technical result of the invention is that the heat-accumulating tank with a liquid heat carrier, which ensures the heating of the consumed water, passing in isolation from the liquid heat carrier, in addition to the function of accumulating thermal energy, also performs the function of a solar collector.

[0013] The cause-and-effect relationship between the features of the invention and the first technical result is that the dome-shaped element of the heat-accumulating reservoir at any time of the day has a section of the outer surface facing the Sun and capable of receiving a solar flux of maximum magnitude per its specific area.

[0014] Thanks to the first technical result, the invention acquires the following advantages in relation to the prototype: (a) there is no need to equip the solar water heater with a closed circulation loop, a solar collector monitoring system and a circulation pump, (b) there is no need to supply electricity to the specified elements. Ultimately, these factors ensure a simplified design of the solar water heater and the autonomy of its operation.

[0015] The second technical result of the invention is the possibility of replenishing the losses of liquid heat carrier directly from the heat exchange tube. Compared to the prototype, where a special branch pipe is used to replenish the losses of liquid heat carrier, separately entering the heat-accumulating tank and connected to the tank for storing the liquid heat carrier, the design of the solar water heater is significantly simplified.

[0016] The third technical result is a reduction in the weight and material consumption of the solar water heater, which is made possible by the absence of a hole in the wall of the heat-accumulating tank for the special pipe used in the prototype, and the resulting increase in the strength of the heat-accumulating tank.

[0017] In the first particular case of the invention, the heat exchange tube contains an element made in the form of a flat spiral, and the outer surface of this element is in contact with the liquid heat carrier. This design allows to increase the length of the path overcome by the consumed water inside the heat-accumulating tank, or in other words, to increase the time of heat exchange between the consumed water and the liquid heat carrier, which without significant The complexity of the design of the solar water heater increases the efficiency of heating the consumed water.

[0018] In the second particular case of the invention, the liquid heat carrier is water taken from the same source as the water to be consumed. This design simplifies the operating conditions of the solar water heater and increases its autonomy.

[0019] In the third particular case of the invention, the replenishing valve is provided with a float, hereinafter referred to as the "control float", which is capable of opening the replenishing valve when moving downwards together with the level of the liquid heat carrier. This design allows for automatically maintaining a specified level of the liquid heat carrier in the heat-accumulating tank without the use of complex sensors, which simplifies the design of the solar water heater. Brief description of the drawings

[0020] The implementation of the invention will be explained by reference to the figures: Fig. 1 - external view of a solar water heater made according to the invention; Fig. 2 - view of a solar water heater made according to the invention, in cross section A-A; Fig. 3 is a three-dimensional image of a solar water heater made according to the invention, with the dome-shaped element of the heat-accumulating tank removed. It should be noted that the shape and dimensions of individual elements shown in the figures may be arbitrary and may be shown in such a way as to most clearly illustrate the relative position of the elements of the solar water heater, as well as their cause-and-effect relationship with the technical result. Implementation of the invention

[0021] The implementation of the invention will be shown in the best examples of its implementation, which do not constitute restrictions on the scope of protected rights.

[0022] Solar water heater 1 (Fig. 1-3) comprises heat-accumulating tank 2, which is formed by upper and lower components 10 and 20, which are hermetically connected to each other and are made of stainless steel. Upper component 10 comprises dome-shaped element 11, the outer surface 12 of which preferably has the shape of a hemisphere, and in a less preferred case, the shape of another closed-at-the-top and open-at-the-bottom figure of rotation. In the embodiment shown in Fig. 1 and 2, dome-shaped element 11 completely coincides with upper component 10, which makes it possible to maximize the solar flux incident on heat-accumulating tank 2. Lower component 20 has the shape of a bowl open at the top and, when connected to upper component 10, forms together with it a closed cavity 3 of heat-accumulating tank 2.

[0023] It should be noted that the upper and lower components 10 and 20 may have a different configuration, for example, the dome-shaped element 11 may occupy only part of the upper component 10, and the lower component 20 may have flat shape. In addition, the heat-accumulating reservoir 2 does not necessarily have to be formed by upper and lower component parts 10 and 20 connected precisely in a horizontal plane, while in the context of the invention, a fundamentally important feature of the heat-accumulating reservoir 2 is the presence of a dome-shaped element 11.

[0024] The heat-accumulating reservoir 2 is positioned during operation so that the outer surface 12 of its dome-shaped element 11 is open to solar radiation. Since the outer surface 12 of the dome-shaped element 11 has the shape of a hemisphere, at any time of the day the dome-shaped element 11 has a section of the outer surface 12 that faces the Sun and is capable of receiving a solar flux of maximum magnitude on its specific area.

[0025] At the surface of the Earth, solar radiation contains a significant infrared component that carries heat, as a result of which the dome-shaped element 11 can be effectively heated by solar heat at any time when solar rays fall on its outer surface 12. To increase the heating efficiency of the dome-shaped element 11, a coating is applied to the outer surface 12 that minimizes reflection and maximizes absorption of solar rays.

[0026] The liquid heat carrier, preferably water, fills essentially the entire closed cavity 3 so that it contacts the inner surface 13 of the dome-shaped element 11 over its entire or almost entire area. Due to the comparatively small wall thickness of the dome-shaped element 11, preferably 1-1.5 mm, essentially all the heat received by the outer surface 12 is transferred to the inner surface 13, and from it to the liquid heat carrier.

[0027] Water has the maximum specific heat capacity among liquids, which is manifested in the high inertia of its temperature increase and decrease during the heat transfer process. Accordingly, the use of water as a liquid heat carrier seems to be appropriate from the point of view of maximizing the time of heat conservation by the liquid heat carrier in the absence of an external heat source, i.e. in cloudy weather or at night. In other words, the use of water as a liquid heat carrier maximizes the heat-accumulating properties of the heat-accumulating reservoir 2. It should also be noted that the invention allows the use of other liquids with high heat capacity as a liquid heat carrier.

[0028] In order to further increase the efficiency of heat conservation in the heat-accumulating reservoir 2, the dome-shaped element 11 is provided with a transparent dome 15, which is made of plexiglass and is installed with a gap to the outer surface 12. In the preferred case, a vacuum is created in the gap between the transparent dome 15 and the dome-shaped element 11, which prevents heat dissipation from the heat-accumulating reservoir 2 due to heat transfer and convection. In addition, the plexiglass prevents the passage of long-wave infrared radiation emitted by the comparatively weakly heated dome-shaped element 11, reflecting it back toward the outer surface 12.

[0029] In addition, in order to retain heat in the heat-accumulating reservoir 2, a heat-insulating layer 24 is fixed to the outer surface 22 of the lower component part 20, which can be made of any material that can be used as insulation.

[0030] Further, on the lower component part 20, an electric heater 30 is installed, which is designed to maintain a given temperature of the liquid heat carrier in cloudy weather or at night. Since the liquid heat carrier has a high heat capacity and is enclosed in a heat-insulated closed cavity 3, it is capable of preserving the accumulated heat for a long time. Due to this, the electric heater 30 is used only in addition to the main source of energy - solar radiation, which, however, significantly increases the convenience of using the solar water heater 1.

[0031] In the closed cavity 3 there is a heat exchange tube 40, which comprises a sequentially arranged inlet pipe 41, an active element 42 and an outlet pipe 43, the outer surface of which is in contact with the liquid heat carrier. Although in the embodiment shown in Figs. 2 and 3, essentially the entire outer surface of the heat exchange tube 40 is in contact with the liquid heat carrier, this is not mandatory, and the heat exchange tube 40 can be in contact with the liquid heat carrier only on a section of its outer surface, for example on the outer surface of the active element 42. Thus, the concept of "the outer surface of the heat exchange tube 40 is in contact with the liquid heat carrier" includes the case when only a section of the outer surface of the heat exchange tube 40 is in contact with the liquid heat carrier.

[0032] The inlet pipe 41 and the outlet pipe 43 are secured to the lower component 20 so that the inlet end of the inlet pipe 41 and the outlet end of the outlet pipe 43, which are respectively the inlet and outlet ends 44 and 45 of the heat exchange tube 40, are led outside the heat-accumulating reservoir 2. Due to this, the internal volume of the heat exchange tube 40 is isolated from the closed cavity 3 and, accordingly, from the liquid heat carrier located in the internal cavity 3.

[0033] The input end 44 is connected to a source of consumed water (not shown), capable of providing pressure in the internal volume of the heat exchange tube 40, as a result of which the consumed water flows through the internal volume of the heat exchange tube 40 and exits from the output end 45, connected to a device for supplying water to the consumer (not shown), such as a mixer or a flow regulator. The source of consumed water can be, for example, a municipal water supply system or a pump supplying consumed water from a well with or without preliminary filtration.

[0034] When in contact with the liquid heat carrier heated by sunlight, the outer surface of the heat exchange tube 40 receives heat from it, which is transferred through the wall of the heat exchange tube 40 to its inner surface, and then to the consumed water in contact with it. Thus, the consumed water flowing in the inner volume of the heat exchange tube 40 is heated by the heat of the liquid heat carrier, remaining isolated from it, and after exiting heat exchange tube 40 the consumed water is immediately supplied to the consumer. Due to this, when using solar water heater 1 the consumed water is not maintained in a heated state for a long time, which eliminates the development of microorganisms in it.

[0035] In addition, since the water used as a liquid heat carrier is not intended for consumption, additives can be introduced into it that slow down or eliminate the occurrence of thermal barrier deposits and corrosion centers on the inner surface 13 of the dome-shaped element 11. As a result, the value of heat transfer between the inner surface 13 and the liquid heat carrier is maintained at an initially high level for a long time, which makes it possible to maintain both the temperature and the heating rate of the liquid heat carrier at a high level.

[0036] However, if the hardness of the consumed water is low, which is achieved, for example, by filtering it on the side of the source of the consumed water, water from the same source as the consumed water can be used as a liquid heat carrier. In terms of the occurrence of deposits, such water is to an acceptable degree equivalent to the specially prepared water described above, but at the same time this design significantly increases the ease of use and the autonomy of the solar water heater 1.

[0037] However, during operation of the solar water heater 1, the liquid heat carrier gradually evaporates, due to which its level in the closed cavity 3 decreases. To replenish the volume of the lost liquid heat carrier, the heat exchange tube 40 is equipped with a replenishing valve 50, which is capable of releasing the consumed water from the heat exchange tube 40 into the closed cavity 3, but preventing the penetration of the liquid heat carrier into the internal volume of the heat exchange tube 40. In addition, as indicated above, the consumed water is in the heat exchange tube 40 under increased pressure, which creates an additional barrier to the penetration of the liquid heat carrier into the internal volume of the heat exchange tube 40.

[0038] In its simplest embodiment, the replenishing valve 50 includes a section of the wall of the heat exchange tube 40, on which a through hole is made, and a valve that is capable of opening and closing this through hole. In addition, the replenishing valve 50 is provided with a control float 51, which is intended for opening and closing the replenishing valve 50, and which is a hollow body capable of being held on the open surface of the liquid heat carrier and moving downwards and upwards together with it.

[0039] The control float 51 engages with the said valve, and when the control float 51 together with the open surface of the liquid heat carrier drops to the lower specified level, the valve opens. After the volume of water is released from the heat exchange tube 40 through the said through hole, ensuring the rise of the control float 51 together with the open surface of the liquid heat carrier to the upper specified level, the control float 51 moves the valve to the closed position, and the solar water heater 1 continues to operate in the normal mode.

[0040] As shown in Fig. 2 and 3, the replenishing valve 50 and the control float 51 are installed on the dead-end section 46 of the inlet pipe 41, which extends vertically upward from the place 47 of connection of the inlet pipe 41 with the active element 42. However, this design does not create a limitation, the replenishing valve 50 and the control float 51 can be installed on any other vertical section of the heat exchange tube 40.

[0041] In addition, the replenishing valve 50 may have a different design, and for example, be controlled by an electric drive based on signals from a level sensor, which is characterized by a different operating principle in relation to the control float 51. In this case, the replenishing valve 50 may be installed on any section of the heat exchange tube 40, without being limited to vertical and dead-end sections.

[0042] It should be noted that due to the tightness of the heat-accumulating tank 2, the losses of the liquid heat carrier caused by evaporation, etc., are insignificant. Even if the liquid heat carrier is specially prepared water, for example, demineralized water, then the comparatively rare introduction of a small amount of consumed water into the volume of the liquid heat carrier is not able to significantly affect the composition and properties of the liquid heat carrier. If the required properties of the liquid heat carrier are ensured by introducing appropriate additives into it, then during the evaporation of the liquid phase, the concentration of these additives increases, and the addition of a certain amount of consumed water into the volume of the liquid heat carrier only ensures the restoration of the concentration of additives to the target level.

[0043] Thus, the use of the replenishing valve 50 and the control float 51 ensures automatic maintenance of a given volume of liquid heat carrier in the heat-accumulating tank 2 while maintaining the properties of the liquid heat carrier for a long time.

[0044] Meanwhile, the replenishment of the liquid heat carrier by means of the replenishing valve 50 installed on the heat exchange tube 40 is achieved without providing the heat-accumulating tank 2 with an additional branch pipe used in the prototype and complicating the design of the prototype. In addition, the solar water heater 1 is made without including in its composition other elements presumably necessary for the implementation of the prototype, namely, an additional tank for storing the liquid heat carrier, an additional pipeline connecting the said additional tank and the additional branch pipe, and an additional pump pumping the liquid heat carrier into the said additional pipeline.

[0045] Furthermore, the use of the control float 51 to control the replenishment valve 50 makes it possible to determine the optimal moments for starting and stopping the supply of liquid heat carrier into the closed cavity 3 without installing complex liquid level sensors that require power supply, etc. Accordingly, due to the use of the replenishment valve 50 and the control float 51 installed on the heat exchange tube 40, the design of the solar water heater 1 is significantly simplified in relation to the prototype, and in addition The ease of use of the solar water heater 1 and the degree of autonomy of its operation are increased.

[0046] In addition, the absence of an additional hole in the wall of the heat-accumulating tank 2, which in the prototype is made for an additional branch pipe, eliminates the occurrence of a stress concentration region in the material of the heat-accumulating tank 2. This circumstance naturally increases the strength of the heat-accumulating tank 2, which means that the wall of the heat-accumulating tank 2 can be made thinner compared to the prototype. As a result, the weight and material consumption of the solar water heater 1 are reduced relative to the prototype.

[0047] The active element 42 is made in the form of a flat spiral, in which each subsequent turn surrounds the previous one, which allows increasing the length of the path overcome by the consumed water inside the heat-accumulating reservoir 2, and therefore increasing the time of heat exchange between the consumed water and the liquid heat carrier through the wall of the active element 42. Thus, due to this very simple solution, the heating temperature of the consumed water coming out of the outlet end 45 of the heat exchange tube 40 can be increased.

[0048] Along with this, it is possible to design when the active element 42 is made in the form of a vertical spiral, in which all the turns have the same diameter and are located side by side with each other. In addition, designs are possible that are a combination of the cases described above, for example, when several flat spirals connected to each other are located one above the other.

[0049] It should be noted that the temperature of the consumed water leaving the outlet end 45 of the heat exchange tube 40 and then entering the device for supplying water to the consumer depends on the temperature of the liquid heat carrier and can sometimes be very high. In order to reduce the temperature of the consumed water to a comfortable value, the device for supplying water to the consumer can be a mixer mixing the heated consumed water leaving the outlet end 45 with the cold consumed water coming directly from the source of the consumed water.

Claims

CLAUSE OF INVENTION 1. A device for heating water, comprising a heat-accumulating tank and a heat-exchange tube, wherein the heat-accumulating tank is filled with a liquid heat carrier and contains a dome-shaped element, the outer surface of which is open to solar radiation, wherein the heat-exchange tube is located inside the heat-accumulating tank such that the outer surface of the heat-exchange tube is in contact with the liquid heat carrier, and the inner volume of the heat-exchange tube is isolated from the liquid heat carrier, wherein water to be consumed flows in the inner volume of the heat-exchange tube, wherein the heat-exchange tube is equipped with a valve that is capable of releasing water from the heat-exchange tube into the heat-accumulating tank.

2. The device according to item 1, in which the heat exchange tube contains an element made in the form of a flat spiral, and the outer surface of this element is in contact with the liquid heat carrier.

3. The device according to claim 1, wherein the liquid heat carrier is water taken from the same source as the water to be consumed.

4. The device according to item 1, in which the valve is provided with a float that is capable of opening the valve when it moves downwards together with the level of the liquid coolant. 10 SUBSTITUTE SHEET (RULE 26)

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