Anti-freezing type heating device for greenhouse

Abstract

The application discloses an anti-freezing type heating device for a greenhouse and belongs to the field of greenhouse heating equipment. The anti-freezing type heating device comprises a heating device and a heat pipe heat exchanger. The heating device is heated by circulating hot water. The heat pipe heat exchanger is internally provided with a cavity, and the cavity is filled with phase-change working medium. During installation, the heat pipe heat exchanger is partially embedded in underground soil with a constant temperature of 10 DEG C-20 DEG C and partially attached to the heating device. The heat pipe heat exchanger is used for absorbing heat from the underground soil with a constant temperature of 10 DEG C-20 DEG C and transferring the heat to the heating device, so that frost heaving of the heating device is avoided.

Description

Technical Field

[0001] This invention relates to the field of greenhouse heating equipment, and in particular to a frost-resistant heating device for greenhouses. Background Technology

[0002] A solar greenhouse is used during seasons unsuitable for crop growth to provide a growing period and increase yield. It is primarily used for cultivating or raising seedlings of warm-season vegetables, flowers, and trees during cold seasons. In cold seasons, greenhouse temperatures often drop sharply, sometimes even below the critical survival or growth point for most crops. Heating systems effectively compensate for this heat deficit, regulating the temperature and ensuring it remains stable within the optimal growth range or minimum tolerance range for crops. This prevents chilling injury or frost damage, ensures the normal functioning of key physiological processes, and avoids low-temperature-induced growth stagnation, flower and fruit drop, deformed fruit, tissue necrosis, and even death.

[0003] In cold and arid regions, the application rate of solar greenhouse heating has reached 70-100% in demonstration areas and policy-supported areas, with significant yield increases and temperature improvements: 2-7℃ in low-temperature areas during winter, breaking through the limits of crop growth; off-season vegetable yields exceed 4 tons per mu, doubling income.

[0004] If a greenhouse heating system experiences frost heave, the expansion force of ice far exceeds the tensile strength of metal, causing weld cracks or pipe wall tears. This not only damages equipment and paralyzes the system, but can also lead to crop death or frost damage. Therefore, preventing frost heave in greenhouse heating systems has become an urgent problem to solve. Summary of the Invention

[0005] The purpose of this invention is to provide a frost-resistant heating device for greenhouses, which solves the problem of frost expansion of heating systems in solar greenhouses.

[0006] The technical solution adopted in this invention is as follows:

[0007] This invention provides a frost-resistant heating device for greenhouses, comprising a radiator and a heat pipe heat exchanger; the radiator provides heating through circulating hot water; the heat pipe heat exchanger has an internal cavity filled with a phase change working fluid; during installation, part of the heat pipe heat exchanger is buried in underground soil at a constant temperature of 10℃-20℃, and part is attached to the radiator; the heat pipe heat exchanger is used to extract heat from the underground soil at 10℃-20℃ and transfer the heat to the radiator.

[0008] Furthermore, the saturation temperature of the phase change working fluid is 5℃-15℃.

[0009] Preferably, the saturation temperature of the phase change working fluid is 10°C.

[0010] Preferably, the phase change working fluid is any one of R32, R290, R407c, and R22.

[0011] Furthermore, the minimum filling rate of the phase change working fluid is 20%-30%, and the maximum filling rate is 50%-70%.

[0012] Furthermore, the heat pipe heat exchanger includes a working fluid storage section and several heat pipe components; a liquid pool is provided inside the working fluid storage section for storing the liquid phase change working fluid; several heat pipe components are connected to the top of the working fluid storage section; the internal cavity of the heat pipe components is connected to the liquid pool inside the working fluid storage section; the working fluid storage section at the bottom of the heat pipe heat exchanger and a part of the bottom of the heat pipe components are buried in the underground soil, and the working fluid storage section absorbs heat in the soil at a depth of 300mm-500mm; the contact surface between the heat pipe heat exchanger and the heating element is coated with a heat-conducting material; the above-ground part of the heat pipe heat exchanger and the non-contact surface with the heating element are coated with a heat-insulating material.

[0013] Furthermore, a first filling pipe is provided on each side of the working fluid storage section; a heat pipe is provided between the two first filling pipes; the first filling pipes are connected to the interior of the working fluid storage section; after the heat pipe heat exchanger is installed, the tops of the two first filling pipes are above the ground; one of the two first filling pipes is used to input the working fluid, and the other is used to exhaust the air; a first check valve, a thermometer, a pressure gauge, and a level gauge are provided on the first filling pipe used to input the working fluid, and a second check valve is provided on the first filling pipe used to exhaust the air.

[0014] Furthermore, the first filling pipe for inputting the working fluid is connected to an automatic pressurizing device; the automatic pressurizing device includes a storage tank, which is a pressure tank containing the working fluid, and its internal pressure is greater than a preset value of the internal pressure of the heat pipe heat exchanger; when the internal pressure of the heat pipe heat exchanger is lower than the preset value, the controller controls the first one-way valve to open, and the working fluid in the storage tank is charged into the heat pipe heat exchanger until the internal pressure of the heat pipe heat exchanger is restored to the preset value; then the controller controls the first one-way valve to close.

[0015] Furthermore, the heat pipe heat exchanger is filled with non-condensable gas, and the amount of non-condensable gas does not exceed 5% of the gas phase volume fraction; the heat pipe heat exchanger is also provided with a corrugated pipe displacement structure; the top of all heat pipe components is connected to the corrugated pipe displacement structure; the corrugated pipe displacement structure has a cavity inside, and the inside of the heat pipe components is connected to the inside of the corrugated pipe displacement structure; the volume of the corrugated pipe displacement structure is variable and it is made of elastic material.

[0016] Furthermore, it also includes a heat replenishment device, which adopts a loop oscillating heat pipe. The loop oscillating heat pipe is a closed loop with multiple serpentine bends inside. A second filling pipe is set at the top of the loop oscillating heat pipe. The loop oscillating heat pipe is filled with the same working fluid as the heat pipe heat exchanger. During the day, the heat replenishment device returns the heat in the greenhouse to the ground for the heat pipe heat exchanger to use at night.

[0017] The beneficial effects of this invention are as follows: This invention provides a frost-resistant heating device for greenhouses, including a radiator and a heat pipe heat exchanger; the radiator provides heating through circulating hot water; the heat pipe heat exchanger has an internal cavity filled with a phase change working fluid; during installation, part of the heat pipe heat exchanger is buried in underground soil at a constant temperature of 10℃-20℃, and part is attached to the radiator; the heat pipe heat exchanger is used to extract heat from the underground soil at 10℃-20℃ and transfer the heat to the radiator; thereby preventing the radiator from freezing and expanding. Attached Figure Description

[0018] Figure 1 The image shown is a three-dimensional structural diagram of the antifreeze heating device of this application.

[0019] Figure 2 yes Figure 1 Exploded view.

[0020] Figure 3 This is a diagram showing the installation of the frost-resistant heating device of this application inside a solar greenhouse.

[0021] Figure 4 The figure shown is a three-dimensional structural diagram of a heat pipe heat exchanger according to this application.

[0022] Figure 5 The diagram shown is a structural schematic of the first filling tube on the right side in this application.

[0023] Figure 6 The diagram shown is a structural schematic of the first filling tube on the left side in this application.

[0024] Figure 7 The figure shown is a cross-sectional view of the improved heat pipe fitting of this application.

[0025] Figure 8 The diagram shown is a schematic diagram of the principle of forming a film-like liquid surface inside the heat pipe component of this application.

[0026] Figure 9 The figure shown is a graph showing the relationship between the filling pressure and saturation temperature of R32, R290, and R407c in this application.

[0027] Figure 10 The diagram shown is a schematic diagram of the Tesla valve channel of this application.

[0028] Figure 11 The diagram shown is a structural schematic of the heating device of this application.

[0029] Figure 12 The diagram shown is a schematic diagram of the alternating cross-section channel of this application.

[0030] Figure 13 The diagram shown is a schematic of an ellipsoid placed inside the heating element of this application.

[0031] Figure 14 The figure shown is a preferred dimension diagram of an ellipsoid according to this application.

[0032] Explanation of reference numerals in the attached drawings: 1. Heater; 2. Heat pipe heat exchanger; 201. Working fluid storage section; 202. Heat pipe fitting; 203. First filling pipe; 204. First one-way valve; 205. Thermometer; 206. Pressure gauge; 207. Liquid level gauge; 208. Storage tank; 209. Second one-way valve; 210. Corrugated pipe displacement structure; 211. Tesla valve channel; 212. Wave-shaped channel; 213. Isolation section; 3. Wall; 4. Heat replenishment device; 401. Second filling pipe; 402. Alternating cross-section channel; 5. Ellipsoidal sphere. Detailed Implementation

[0033] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0034] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0035] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0036] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0037] See Figure 1The image shown is a three-dimensional structural diagram of the antifreeze heating device of this application. Figure 2 yes Figure 1 Exploded view. Figure 3 This is a diagram showing the installation of the frost-resistant heating device of this application inside a solar greenhouse.

[0038] This application provides a frost-resistant heating device for greenhouses, comprising a radiator 1 and a heat pipe heat exchanger 2. The radiator 1 uses existing products such as steel radiators, copper-aluminum composite radiators, and aluminum radiators. The radiator 1 shown in the figure is a rectangular radiator. The radiator 1 provides heating through circulating hot water. In extreme cases, the temperature inside the greenhouse may drop below 0°C, causing the water inside the radiator 1 to freeze and expand, damaging the radiator 1 and potentially leading to crop death or frost damage. Therefore, this application includes a heat pipe heat exchanger 2 on the back of the radiator 1. Figure 3 In the usage scenario shown, in the greenhouse, the radiator 1 is installed close to the wall 3. The side of the radiator 1 opposite to the wall 3 is the back of the radiator 1, and the side of the radiator 1 that radiates heat outward is the front.

[0039] In this application, the heat pipe heat exchanger 2 can be made of thermally conductive materials such as steel, copper, aluminum, or copper-aluminum composite. The heat pipe heat exchanger 2 has an internal cavity filled with a phase change working fluid. During installation, part of the heat pipe heat exchanger 2 is buried in underground soil at a constant temperature of 10℃-20℃, and part is attached to the radiator 1. The heat pipe heat exchanger 2 is used to extract heat from the underground soil at 10℃-20℃ and transfer the heat to the radiator 1, thereby preventing the radiator 1 from freezing and expanding.

[0040] The phase change working medium used in this application must meet the following conditions:

[0041] First, temperature is a key factor in determining the selection of the working fluid inside the heat pipe heat exchanger 2 in this application. In this application, the portion of the heat pipe heat exchanger 2 buried underground is located in soil with a temperature of 10℃-20℃. The underground soil temperature remains approximately 10℃-20℃ throughout the year. In this application, the heat pipe heat exchanger 2 operates in a self-driven mode; therefore, the saturation temperature of the phase change working fluid is an important criterion for selection. In this application, a phase change working fluid with a saturation temperature of 5℃-15℃ is selected, and a phase change working fluid with a saturation temperature of approximately 10℃ is further preferred. This saturation temperature is the operating temperature of the heat pipe heat exchanger 2 for self-driven operation. A phase change working fluid at this saturation temperature can smoothly evaporate and condense inside the heat pipe heat exchanger 2, thereby absorbing heat from the soil and transferring it to the heating system 1; simultaneously, the freezing point of the working fluid should be lower than the minimum operating temperature of the heat pipe heat exchanger 2 to prevent solidification.

[0042] Furthermore, the physical properties of the working fluid, such as latent heat of vaporization, thermal conductivity, viscosity, and surface tension, also significantly affect the performance of the heat pipe heat exchanger 2. For example, a high latent heat of vaporization helps reduce liquid evaporation; low viscosity helps improve heat transfer efficiency; and high surface tension facilitates capillary action. Moreover, the working fluid should possess good thermal stability during use to avoid decomposition or the generation of harmful substances. Additionally, the compatibility between the materials of the heat pipe heat exchanger 2 and the working fluid must be considered.

[0043] Considering the above factors, the phase change working fluid in this application can be any one of R32, R290, R407c, and R22. Among them, R22 has a destructive effect on the ozone layer, so R32, R290, and R407c are preferred.

[0044] Secondly, in this application, the factors affecting the self-driven operation of the heat pipe heat exchanger 2 also include the filling rate. The filling rate affects the pressure and saturation temperature of the phase change working fluid, and the three have a one-to-one correspondence. Too low a filling rate leads to insufficient liquid supply, affecting the stable operation of the heat pipe; too high a filling rate leads to an increase in system pressure and saturation temperature, insufficient thermal driving force, and a decrease in heat transfer performance. Considering various factors, this application recommends a minimum filling rate of 20%-30% and a maximum filling rate of 50%-70%. However, since the filling rate is not easy to measure, this application recommends using the filling pressure as the main indicator for the operation of the heat pipe heat exchanger 2. Specifically, as... Figure 9 The diagram shown illustrates the relationship between the charging pressure and saturation temperature of R32, R290, and R407c in this application. The operating temperature range of the heat pipe heat exchanger 2 is 5℃-15℃, preferably 10℃. Figure 9 As shown, the horizontal axis corresponding to the saturation temperature of 5℃-15℃ is the charging pressure, which is the charging pressure of the heat pipe heat exchanger 2 of this application.

[0045] Table 1 below shows the filling pressure corresponding to the saturation temperature of R32, R290, and R407c in this application at 10°C.

[0046] Table 1

[0047] working medium Filling pressure / kPa Saturation temperature / °C R290 637.1 10 R407c 645.1 10 R32 1107.1 10

[0048] In this embodiment, the method for filling the heat pipe heat exchanger 2 with phase change working fluid is as follows: first, a vacuum is drawn, and then the phase change working fluid is filled. The amount of phase change working fluid filled is based on the filling pressure.

[0049] Furthermore, such as Figure 4The diagram shown is a perspective view of a heat pipe heat exchanger 2 according to this application. The heat pipe heat exchanger 2 includes a working fluid storage section 201 and a plurality of heat pipe components 202. The working fluid storage section 201 is cuboid in shape and has a liquid pool inside for storing a liquid phase change working fluid. The top of the working fluid storage section 201 is connected to the plurality of heat pipe components 202. The internal cavity of the heat pipe component 202 is in communication with the liquid pool inside the working fluid storage section 201, and the top of the heat pipe component 202 is closed. Figure 4 In the illustrated embodiment, the heat pipe 202 is a square tube, and its bottom is connected to the top connector of the working fluid storage section 201. This connection can be achieved by welding or by using a sealing connector. Figure 1 As shown, the height of the heat pipe 202 is higher than that of the radiator 1, and a part of the heat pipe 202 is attached to the back of the radiator 1.

[0050] like Figure 3 The diagram shows a schematic of the frost-resistant heating device of this application installed in a solar greenhouse. In this embodiment, the greenhouse is a typical double-layer film solar greenhouse in a cold and arid region. The greenhouse is 70m long from east to west, 8.5m wide from north to south, and 4.75m high at the ridge. The rear wall 3 is a brick-and-earth structure with a height of 3.5m. An air insulation layer of 40-100cm is formed between the outer insulation film and the inner insulation film.

[0051] The antifreeze heating device of this application is installed near the rear wall 3. Specifically, in cold and arid areas, the soil temperature at a depth of 300mm-500mm is generally 10℃-20℃; the soil at this depth is less affected by the air temperature inside the greenhouse; most of the crop roots are within 500mm of the ground surface, and crops are usually not planted below the location where the heating radiator 1 is installed, so it will not affect crop growth. Therefore, in this application, the heating radiator 1 is installed at a certain distance from the ground, for example, 10cm-30cm above the ground; a heat pipe heat exchanger 2 is installed in the space between the heating radiator 1 and the wall 3. The working fluid storage section 201 at the bottom of the heat pipe heat exchanger 2 and a part of the bottom of the heat pipe component 202 are buried in the underground soil, with the working fluid storage section 201 absorbing heat in the soil at a depth of 300mm-500mm. The heating radiator 1 is in contact with the heat pipe component 202.

[0052] Furthermore, the contact surfaces between the heat pipe heat exchanger 2 and the radiator 1 can be coated with a thermally conductive material. This material can be silicone thermally conductive adhesive, epoxy resin thermally conductive adhesive, polyurethane thermally conductive adhesive, acrylic thermally conductive adhesive, etc.

[0053] Furthermore, the above-ground portion of the heat pipe heat exchanger 2 and the non-contact surface with the heating radiator 1 are coated with insulation material. This insulation material can be an aerogel insulation coating, a ceramic coating (alumina, boron nitride, etc.), or a silicate coating (alumina silicate, calcium silicate, etc.). This insulation material prevents heat loss from the heat pipe heat exchanger 2 and improves heat utilization efficiency.

[0054] The working principle of the heat pipe heat exchanger 2 in this application is as follows: After being filled, the liquid phase change working fluid in the heat pipe heat exchanger 2 is stored in the working fluid storage section 201. Part of the phase change working fluid absorbs geothermal heat and becomes gaseous. The gaseous working fluid rises into the heat pipe component 202. When the temperature of the heating radiator 1 is lower than 10°C, the heating radiator 1 absorbs heat from the heat pipe heat exchanger 2. The saturated vapor at 10°C in the heat pipe component 202 condenses into liquid at 10°C. The cooled liquid working fluid falls back into the underground working fluid storage section 201 by gravity. The liquid working fluid is reheated by geothermal heat into gaseous. The gaseous working fluid rises naturally by thermal force to the surface in contact with the heating radiator 1, transferring heat to the heating radiator 1 again. This process is repeated to heat the heating radiator 1. This process is called the working state. When the water temperature in radiator 1 is higher than 10℃, the temperature of the gaseous working fluid inside heat pipe 202 is also higher than 10℃. At this time, the pressure of the working fluid inside heat pipe heat exchanger 2 is higher than its saturation pressure, and the liquid working fluid at the bottom will not turn into a gaseous phase. Both the gaseous and liquid phases in heat pipe heat exchanger 2 are in a relatively stable state. In this state, the high-temperature gaseous working fluid will not naturally fall to the bottom of heat pipe heat exchanger 2. The principle is that after the gaseous phase is heated, its density decreases, generating thermal lift, and it will not fall due to gravity. This state is called the non-working state (i.e., the static state).

[0055] Furthermore, to facilitate the filling of the working fluid, in one specific embodiment of this application, a filling structure is provided on the working fluid storage section 201. For example... Figure 4 As shown, a first filling pipe 203 is provided on each side of the working fluid storage section 201; a heat pipe fitting 202 is provided between the two first filling pipes 203; the first filling pipes 203 are connected to the interior of the working fluid storage section. After the heat pipe heat exchanger 2 is installed, the tops of the two first filling pipes 203 are above the ground. One of the two first filling pipes 203 is used for inputting the working fluid, and the other is used for venting. Figure 4 In the middle, the first filling pipe 203 on the right is used to input the working medium, and the first filling pipe 203 on the left is used to exhaust air during vacuuming.

[0056] like Figure 5 The diagram shown is a structural schematic of the first filling pipe 203 on the right side in this application. In one specific embodiment of this application, a first one-way valve 204, a thermometer 205, a pressure gauge 206, and a level gauge 207 are provided on the first filling pipe 203 on the right side, which are used to monitor the temperature, pressure, and level inside the heat pipe heat exchanger 2, respectively; and to fill the heat pipe heat exchanger 2 with working fluid through the first filling pipe 203 on the right side. Figure 6 The diagram shown is a structural schematic of the left-side first filling pipe 203 in this application. In one specific embodiment of this application, a second one-way valve 209 is provided on the left-side first filling pipe 203 to prevent gas from flowing back into the heat pipe heat exchanger 2.

[0057] Furthermore, the first filling pipe 203 on the right side can be connected to an automatic pressurization device via a pipeline. The automatic pressurization device includes a storage tank 208, which is a pressure tank containing working fluid. Its internal pressure is greater than a preset value for the internal pressure of the heat pipe heat exchanger 2. When the internal pressure of the heat pipe heat exchanger 2 is lower than the preset value, the controller controls the first one-way valve 204 to open, and the working fluid in the storage tank 208 is injected into the heat pipe heat exchanger 2 until the internal pressure of the heat pipe heat exchanger 2 returns to the preset value; then the controller controls the first one-way valve 204 to close. This setting enables automatic pressurization of the heat pipe heat exchanger 2, allowing it to operate normally and continuously.

[0058] The following examples illustrate the pressurization process of different phase change working fluids.

[0059] Taking R290 as an example, its saturation pressure is 637.1 kPa at 10℃; when its pressure drops to 552.1 kPa, its saturation temperature drops to 5℃; when its saturation pressure further decreases, its saturation temperature also decreases accordingly; when its saturation temperature is too low, it will not be able to prevent the heating system from freezing. Therefore, when the working fluid is R290 and the pressure is below 552.1 kPa, automatic filling is activated, and the pressure is restored to 637.1 kPa.

[0060] Taking R407c as an example, when its pressure drops to 547.1 kPa, its saturation temperature drops to 5℃; at this time, the working fluid is started and filled to 645.1 kPa, at which point the saturation temperature recovers to 10℃.

[0061] Taking R32 as an example, when its pressure drops to 942.1 kPa, its saturation temperature drops to 5℃; at this time, the working fluid is started and filled to 1107.1 kPa, at which point the saturation temperature recovers to 10℃.

[0062] Furthermore, in one specific embodiment of this application, the heat pipe heat exchanger 2 may also be filled with a certain amount of non-condensable gas, such as nitrogen or helium. The amount of non-condensable gas filled does not exceed 5% of the gas phase volume fraction; when the volume fraction of non-condensable gas exceeds 5%, the condensation rate of the working fluid vapor will be significantly reduced.

[0063] The function of filling with non-condensable gas in this application is as follows: the non-condensable gas can form a movable gas plug within the heat pipe 202; when the temperature of the heat pipe 202 rises, the non-condensable gas is compressed, thereby increasing the condensation area and improving the heat transfer capacity; when the temperature drops, the non-condensable gas diffuses and occupies the condensation space, weakening the heat transfer intensity. This structure can automatically adjust the heat transfer efficiency at different greenhouse temperatures, adapting to temperature changes in a timely manner without the need for active control equipment.

[0064] Furthermore, in one specific embodiment of this application, a bellows displacement structure 210 may also be provided on the heat pipe heat exchanger 2. For example... Figure 4 As shown, the tops of all heat pipe components 202 are connected to the bellows displacement structure 210. The bellows displacement structure 210 has a cavity inside, and the interior of the heat pipe component 202 communicates with the interior of the bellows displacement structure 210. The bellows displacement structure 210 has a variable volume and is made of an elastic material, such as elastic rubber or elastic metal.

[0065] The function of the bellows displacement structure 210 is as follows: Since it is difficult for the heat pipe heat exchanger 2 to maintain a constant temperature, when the thermal resistance of the heat source is high or the thermal power of the device fluctuates, the temperature of the heat source is difficult to maintain constant, and large temperature fluctuations may occur, which is unacceptable in practical applications. This application adds a mechanical feedback control structure—the bellows displacement structure 210—which links the displacement of the vapor-gas interface with the heat source through the displacement of the bellows, achieving the purpose of feedback control to regulate the temperature of the heat source.

[0066] This application uses a combination of filling with non-condensable gas and a bellows displacement structure 210, which can achieve the effect of temperature fluctuation <3℃ when power fluctuates.

[0067] Furthermore, when the heat pipe 202 has a cuboid or cylindrical cavity inside, its heat exchange area is small and its heat exchange efficiency is limited. Therefore, in one specific embodiment of this application, an improved heat pipe 202 is provided.

[0068] like Figure 7 The figure shows a cross-sectional view of the improved heat pipe fitting 202 of this application. The improved heat pipe fitting 202 has two types of channels internally: a Tesla valve channel 211 at the bottom and multiple parallel wavy channels 212 at the top. In the embodiment shown, two parallel Tesla valve channels 211 are provided at the bottom, and five parallel wavy channels 212 are provided at the top. Adjacent wavy channels 212 are separated by wavy isolation portions 213. The bottom of the Tesla valve channel 211 communicates with the internal cavity of the working fluid storage section 201, and the top of the Tesla valve channel 211 communicates with the bottom of the wavy channels 212. Furthermore, the upper edge of the Tesla valve channel 211 is lower than the contact surface with the heater 1. In a preferred embodiment of this application, the wavy channels 212 are sinusoidal or cosine shaped.

[0069] The improved heat pipe 202 can perform the following functions:

[0070] When the interior of the heat pipe 202 is a cuboid or cylindrical cavity, a film-like liquid surface will form on its surface, such as... Figure 8The diagram illustrates the principle of forming a film-like liquid surface inside the heat pipe fitting 202 of this application. Taking R290 as an example, at 10℃ (saturation pressure 637.1 kPa), its thermal conductivity is 0.100927 W / (m·K), while the thermal conductivity of stainless steel radiator 1 is approximately 15–25 W / (m·K). In this case, forming a film-like liquid surface on the inner surface of the heat pipe fitting 202 will significantly increase the thermal resistance and reduce the heat transfer. Obviously, the larger and thicker the liquid layer separating the vapor from the cold wall, the greater the thermal resistance. In terms of reducing condensation thermal resistance, reducing the thickness of the film-like liquid surface, and even forming bead-like condensation, greatly helps to improve heat transfer.

[0071] The improved heat pipe 202 of this application has a wavy channel 212 set in the vertical direction inside, which can avoid the formation of a continuous film liquid surface on the inner surface of the heat pipe 202; a large amount of wall surface is left open so that it can directly contact the steam for heat exchange; in addition, on the non-flat wall surface, the liquid droplets will grow to a certain size under the action of gravity and move downward along the wall surface. During the movement, on the one hand, the liquid droplets will merge with the liquid droplets they meet to form larger droplets, and on the other hand, the liquid droplets will also sweep away the liquid droplets along the way, avoiding the repeated formation and growth process of liquid droplets.

[0072] Without the corrugated channel 212 structure, a continuous film of liquid always exists on the cold wall surface, with its thickness increasing along the direction of gravity. Therefore, the thermal resistance of film condensation is often more than an order of magnitude greater than that of bead condensation. The heat transfer coefficient of film condensation is on the order of "tens of thousands," while that of bead condensation can reach hundreds of thousands.

[0073] The vertical wave-shaped channel 212 structure design of this application can prevent the formation of a continuous liquid film due to periodic disturbances. At the same time, under the action of gravity, a pressure difference is generated above and below the droplet due to gravity, which drives the liquid to flow downward. This can prevent the formation of laminar flow nearby, reduce turbulence, thin the boundary layer thickness, reduce the diversion and recombination of boundary layer fluid, and thus reduce the resistance of system operation. This is conducive to the self-starting of the heat pipe heat exchanger 2 under a small temperature difference.

[0074] The method for calculating the heat transferred by the heat pipe under different temperature differences in this application is as follows:

[0075] In this application, the different temperature differences refer to the temperature difference between the gaseous working fluid inside the heat pipe 202 and the water temperature inside the heating system 1. The heat generated is calculated according to the following formula:

[0076]

[0077] In formula 1, —Heat exchange, in W; —Heat exchange area, in m² 2 ; —Heat transfer coefficient, in units of W / (m·K); — Thermal conductivity, in units of W / (m·K); — Wall thickness, in meters (m).

[0078] Table 2 below is a summary table of the heat transferred by the heat pipe under different temperature differences in this application.

[0079] Table 2

[0080] Temperature difference heat transfer coefficient Single heat exchange area Rib efficiency Heat exchange ℃ <![CDATA[W / (m 2 ·K)]]> cm2 / W 1 2000 812.2 0.8 130 2 2000 812.2 0.8 260 3 2000 812.2 0.8 390 4 2000 812.2 0.8 520 5 2000 812.2 0.8 650 6 2000 812.2 0.8 780 7 2000 812.2 0.8 910 8 2000 812.2 0.8 1040 9 2000 812.2 0.8 1170 10 2000 812.2 0.8 1300

[0081] In this application, most of the droplets on the inner surface of the heat pipe fitting 202 are carried to the bottom liquid working fluid region; this facilitates the formation of bead-like condensation surfaces, thereby providing a heat transfer coefficient; through the operation of the heat pipe heat exchanger 2, when the water temperature in the heating system 1 is below 10°C, the heat pipe heat exchanger 2 will carry the heat from the ground to the upper part and transfer it to the water in the heating system 1 to increase its temperature and prevent the water in the heating system 1 from freezing.

[0082] In this application, the function of the Tesla valve channel 211 is as follows:

[0083] The Tesla valve channel 211 consists of a series of alternating branching pipe structures. Each pipe branches into two paths, one slightly inclined and the other curved into a semi-loop, returning to the inclined path but with its opening facing backward. Subsequent branches follow the same pattern, and the number of branches can be increased or decreased as needed. This structure allows for virtually unobstructed flow of liquid from top to bottom; however, when flowing upward, liquid exiting from the loop branch collides head-on with liquid in the inclined branch, thus hindering flow. After multiple branches, very little liquid can exit the pipe, and it can even be controlled to prevent liquid from flowing out, thereby preventing liquid entrainment. Figure 10 The diagram shown is a schematic diagram of the Tesla valve channel 211 of this application.

[0084] Furthermore, since the heat pipe heat exchanger 2 extracts heat from the ground for a long time, the soil temperature in the area where the heat pipe heat exchanger 2 is located will decrease, which will lead to a decline in the performance of the heat pipe heat exchanger 2. To address this, in one specific embodiment of this application, a heat replenishment device 4 may also be provided.

[0085] like Figure 11 The diagram shows the structure of the heating device 4 proposed in this application. The heating device 4 uses a loop oscillating heat pipe, as shown in the figure. The loop oscillating heat pipe is a closed loop with multiple serpentine bends inside. A second filling pipe 401 is installed at the top of the loop oscillating heat pipe. The loop oscillating heat pipe is filled with the same working fluid as the heat pipe heat exchanger 2. During the day, the heating device 4 returns heat from the greenhouse to the ground for use by the heat pipe heat exchanger 2 at night.

[0086] Furthermore, in this application, a stable vapor / liquid plug phase distribution can only be formed in the loop oscillating heat pipe when Bo ≤ 2, i.e., the surface tension of the working fluid is greater than gravity. Simultaneously, a smaller pipe diameter leads to a smaller liquid plug amplitude, a higher frequency, a larger heat transfer per unit area, and higher thermal conductivity; however, an excessively small pipe diameter results in higher viscous resistance. Taking all factors into consideration, this application recommends a pipe diameter range of 1.0-5.0 mm for the loop oscillating heat pipe, and recommends copper as the material. Copper has a thermal conductivity as high as 401 W / (m·K), making it one of the most thermally conductive materials among common metals. High thermal conductivity is beneficial for the heat pipe to start up under small temperature differences.

[0087] The working principle of the heating device 4 in this application is as follows: phase change and flow of the working fluid under the action of temperature difference. In the oscillating heat pipe, the working fluid evaporates after being heated in the evaporation section, forming bubbles (gas plugs). At the same time, the liquid column and gas plugs are alternately distributed, forming a dynamic flow state. When the evaporation section is heated, the working fluid evaporates in this area, forming bubbles (gas plugs). The expansion of the bubbles drives the flow of the liquid column and gas column. In the condensation section, the bubbles contract, and the liquid column reforms, thus forming a cyclic flow process.

[0088] This application employs a serpentine pipe design, where the internal working fluid forms dispersed liquid columns and bubbles under the influence of temperature differences. These liquid columns and bubbles oscillate back and forth between the hot and cold ends, achieving heat transfer through this pulsating motion. This loop oscillating pipe does not require the filling of non-condensable gas.

[0089] like Figures 1 to 3 As shown, the heat replenishment device 4 of this application can be installed on the back of the heat pipe heat exchanger 2. Its bottom is buried in the soil at the same depth as the heat pipe heat exchanger 2. The above-ground portion of the heat replenishment device 4 is used for heat absorption.

[0090] Furthermore, a check valve can be installed on the rising section of the loop oscillating heat pipe in this application to prevent the working fluid from accumulating in the lower part and causing the heat pipe to fail to start. The supplementary heating device 4 in this application can also be equipped with an automatic pressurization device, and a one-way valve, thermometer, pressure gauge, and level gauge are installed on the second filling pipe 401. These are used to monitor the amount of working fluid inside the heat pipe and the optimal filling volume (optimal filling rate 40-60%). When the working fluid pressure and temperature are detected to be lower than the saturation temperature at that pressure, the one-way valve opens, and the working fluid is filled from the storage tank into the underground supplementary heating heat pipe. When the working fluid pressure and temperature are higher than the saturation temperature at that pressure, the one-way valve closes.

[0091] Furthermore, proper adjustment of surface tension can optimize the start-up and operating performance of the heat pipe. Alternating cross-section channels 402 can be inserted into the loop oscillating heat pipe to enhance heat transfer. For example... Figure 12The diagram shows a schematic of the alternating cross-section channel 402 of this application, which has multiple sharp corners pointing towards the inner wall of the heat pipe. The presence of these sharp corners enhances the adsorption between the liquid phase and the wall surface, causing the liquid phase to accumulate at the corners, resulting in a thicker average liquid film thickness than in a circular tube, thus improving the heat transfer limit of the heat pipe. The sharp corners also make the liquid film thinner in non-circular cross-sections away from the corners, facilitating evaporation and disturbing the flow of the working fluid within the pipe, thereby enhancing convective heat transfer. The alternating cross-section channel 402 can introduce additional unbalanced capillary driving force, further strengthening the internal working fluid pressure disturbance, which will improve the heat transfer performance of the pulsating heat pipe to some extent. When the alternating cross-section channel 402 is in a static state, it will vibrate due to the oscillating motion of the gas and liquid moving up and down.

[0092] In one specific embodiment of this application, the preferred heat pipe wall thickness is 0.3 mm and the heat pipe inner diameter is 2.2 mm; the alternating cross-section channel 402 is triangular, the channel wavelength is 2.4 mm, and the channel wall thickness is 0.2 mm.

[0093] In one specific embodiment of this application, the saturation temperature of the working fluid inside the loop oscillating heat pipe is 15℃-30℃, preferably 25℃. The automatic filling conditions for the loop oscillating heat pipe in this application are as follows:

[0094] Taking R290 as an example, its saturation pressure is 952.1 kPa at 25℃; when its pressure drops to 732.1 kPa, its saturation temperature is 15℃. As its saturation pressure decreases further, its saturation temperature also decreases. If its saturation temperature is too low, it will not be able to effectively transfer heat from the greenhouse to the ground. Therefore, when the working fluid is R290 and the pressure is below 732.1 kPa, automatic filling is activated, and the pressure is filled to 952.1 kPa.

[0095] Taking R407c as an example, when its pressure is lower than 756.1 kPa (saturation temperature is 15℃), the working fluid is started, and the pressure in the heat pump system is filled to 1020.1 kPa (saturation temperature is 25℃).

[0096] Taking R32 as an example, when its pressure is lower than 1281.1 kPa (saturation temperature is 15℃), the working fluid is started, and the pressure in the heat pump system is charged to 1690.1 kPa (saturation temperature is 25℃).

[0097] Furthermore, an ellipsoidal sphere 5 can be placed inside the heating element 1. The ellipsoidal sphere 5 is hollow inside and made of an elastic, water-resistant material, with a variable volume. Its function is to compress the ellipsoidal sphere 5 when ice forms, reducing the expansion force of ice on the heating element 1. Figure 13 The diagram shown is a schematic of an ellipsoid 5 placed inside the heating element 1 of this application.

[0098] like Figure 14The diagram shows a preferred dimension of an ellipsoid 5 according to this application. The ellipsoid 5 has a wall thickness of 0.2 mm and an inner diameter (L) of 5 mm. The ellipsoids 5 are connected in series by connecting ropes; a single string consists of 55 ellipsoids 5 connected in series, and 24 strings are placed in a single radiator 1. The volume of the hollow part of the ellipsoid 5 accounts for 11.5% of the volume of water in a single radiator 1, which is greater than the volume expansion coefficient of water when it freezes (approximately 9%). Even if the heat pipe heat exchanger 2 fails and the water in the radiator 1 freezes, the ellipsoid 5 will be compressed and cracked, and the radiator 1 will not expand due to freezing.

[0099] The ellipsoid 5 structure in this application has the following advantages:

[0100] (1) Each ellipsoid 5 is a parabolic object of rotation; the ellipsoids 5 in the vertical direction are arranged alternately.

[0101] (2) The flow velocity between the ellipsoids 5 is approximately uniform; even if the ellipsoids 5 are arranged, it will not significantly increase the pressure loss of the fluid.

[0102] (3) The discontinuous arrangement between ellipsoids 5 can enhance the disturbance of the fluid; the fluid boundary layer on the surface of ellipsoid 5 periodically develops from 0, and the thinning of the boundary layer can improve the heat transfer coefficient of the fluid.

[0103] (4) Reducing the amount of liquid filling the heating system 1 can reduce the thermal inertia of the greenhouse and increase the heating rate.

[0104] (5) When the temperature inside the greenhouse is below 0℃ and the heat pump heating 1 fails, ice will form inside the traditional heating 1. The ellipsoid 5 can be compressed to prevent the heating 1 from freezing and expanding.

[0105] It is understood that the present invention has been described through some embodiments, and those skilled in the art will recognize that various changes or equivalent substitutions can be made to these features and embodiments without departing from the spirit and scope of the invention. Furthermore, under the teachings of the present invention, these features and embodiments can be modified to adapt to specific situations and materials without departing from the spirit and scope of the invention. Therefore, the present invention is not limited to the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are within the protection scope of the present invention.

Claims

1. A frost-resistant heating device for greenhouses, characterized in that, The system includes a radiator and a heat pipe heat exchanger. The radiator provides heating via circulating hot water. The heat pipe heat exchanger has an internal cavity filled with a phase change working fluid. During installation, part of the heat pipe heat exchanger is buried in underground soil at a constant temperature of 10℃-20℃, and part is attached to the radiator. The heat pipe heat exchanger extracts heat from the underground soil at 10℃-20℃ and transfers it to the radiator. The heat pipe heat exchanger includes a working fluid storage section and several heat pipe components. The working fluid storage section contains a liquid pool for storing the liquid phase change working fluid. Several heat pipe components are connected to the top of the working fluid storage section. The internal cavities of the heat pipe components are connected to the liquid pool inside the working fluid storage section. The working fluid storage section is located at the bottom of the heat pipe heat exchanger. The bottom portion of the heat pipe is buried in the underground soil, and the working fluid storage section is located in the soil 300mm-500mm underground for heat absorption; the contact surface between the heat pipe heat exchanger and the heating system is coated with a heat-conducting material; the above-ground portion of the heat pipe heat exchanger and the non-contact surface with the heating system are coated with a heat-insulating material; the interior of the heat pipe is a cuboid or cylindrical cavity, and the internal cavity of the heat pipe has two types of channels: a Tesla valve channel at the bottom and multiple parallel wavy channels at the top; adjacent wavy channels are separated by wavy isolation sections; the bottom of the Tesla valve channel is connected to the internal cavity of the working fluid storage section, and the top of the Tesla valve channel is connected to the bottom of the wavy channels; the wavy channels are sinusoidal or cosine shaped.

2. The anti-freezing type heating device for a greenhouse according to claim 1, wherein The saturation temperature of the phase change working fluid is 5℃-15℃.

3. The greenhouse antifreeze heating device according to claim 2, characterized in that, The saturation temperature of the phase change working fluid is 10℃.

4. The greenhouse anti-freeze heating device according to claim 1, characterized in that, The phase change working fluid is any one of R32, R290, R407c, and R22.

5. The greenhouse frost-resistant heating device according to claim 1, characterized in that, The minimum filling rate of the phase change working fluid is 20%-30%, and the maximum filling rate is 50%-70%.

6. The greenhouse antifreeze heating device according to claim 1, characterized in that, A first filling pipe is provided on each side of the working fluid storage section; a heat pipe is provided between the two first filling pipes; the first filling pipes are connected to the interior of the working fluid storage section; after the heat pipe heat exchanger is installed, the tops of the two first filling pipes are above the ground; one of the two first filling pipes is used to input the working fluid, and the other is used to exhaust the air; a first check valve, a thermometer, a pressure gauge, and a level gauge are provided on the first filling pipe used to input the working fluid, and a second check valve is provided on the first filling pipe used to exhaust the air.

7. The greenhouse frost-resistant heating device according to claim 6, characterized in that, The first filling pipe for inputting the working fluid is connected to an automatic pressurizing device; the automatic pressurizing device includes a storage tank, which is a pressure tank containing the working fluid, and its internal pressure is greater than a preset value of the internal pressure of the heat pipe heat exchanger; when the internal pressure of the heat pipe heat exchanger is lower than the preset value, the controller controls the first one-way valve to open, and the working fluid in the storage tank is injected into the heat pipe heat exchanger until the internal pressure of the heat pipe heat exchanger returns to the preset value; then the controller controls the first one-way valve to close.

8. The greenhouse antifreeze heating device according to claim 1, characterized in that, The heat pipe heat exchanger is filled with non-condensable gas, and the amount of non-condensable gas does not exceed 5% of the gas phase volume fraction; the heat pipe heat exchanger is also provided with a corrugated pipe displacement structure; the top of all heat pipe components is connected to the corrugated pipe displacement structure; the corrugated pipe displacement structure has a cavity inside, and the inside of the heat pipe components is connected to the inside of the corrugated pipe displacement structure; the volume of the corrugated pipe displacement structure is variable and it is made of elastic material.

9. The greenhouse frost-resistant heating device according to claim 1, characterized in that, It also includes a heating device, which uses a loop oscillating heat pipe. The loop oscillating heat pipe is a closed loop with multiple serpentine bends inside. A second filling pipe is installed at the top of the loop oscillating heat pipe. The loop oscillating heat pipe is filled with the same working fluid as the heat pipe heat exchanger. During the day, the heating device feeds heat from the greenhouse back to the ground for use by the heat pipe heat exchanger at night.

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