CN103245114B - Embedded pressure reduction idle sunning protector for heat collecting element with heat fins and vacuum heat pipe - Google Patents

Abstract

Embedded heat fin vacuum heat pipe heat collector element decompression air drying protector, composed of several controllable heat transfer channels set in the vacuum heat insulation layer, the controllable heat transfer channels are made of heat-sensitive permanent magnet steel, soft iron heat fins Composed of connecting circlips, the feature is that the fixed side of the soft iron heat fin is connected to the end of the inner glass tube or the bottom end of the heat pipe with low thermal resistance, and the movable edge of the soft iron heat fin can be connected between the inner surface of the cover glass tube and the outer surface of the inner glass tube The surface moves; the heat-sensitive permanent magnet steel is set under the movable side of the soft iron heat fin and is covered by the soft iron heat fin; when the heat-sensitive permanent magnet steel is magnetic, the soft iron heat fin is attracted by the heat-sensitive permanent magnet steel The movable side is not connected to the cover glass tube for heat transfer; when the heat-sensitive permanent magnet steel is demagnetized, the soft iron hot fin will be upturned under the action of its own elastic force, and its movable side is connected to the cover glass tube for heat transfer. The invention adopts a low-power air drying protector to ensure that the water vapor pressure inside the heat pipe does not exceed 2 atmospheric pressure all the time, and does not affect the normal operation of the heat collecting element at all.

Description

Embedded heat fin vacuum heat pipe heat collection element decompression air drying protector

technical field

The invention relates to a decompression air-drying protector for heat-collecting elements of embedded heat-fin vacuum heat pipes.

Background technique

The vacuum heat collecting tube is provided with a vacuum heat insulation layer between its cover glass tube and the inner glass tube, which can manufacture a vacuum solar water heater that can also provide domestic hot water in winter. The solar water heater made of heat pipe vacuum heat collecting tube has the advantages of high energy efficiency ratio without water in the tube, conforms to the sanitary drinking water standard, and can work as usual if a single tube is damaged. therefore. The solar vacuum heat pipe water heater without water in the pipe will likely occupy more and more market share.

The use of an integrated glass heat pipe has the advantages of being melted and sealed with the cover glass tube, the surface of the glass heat pipe can be directly made into an absorption film, less heat transfer links, and water with excellent thermophysical properties can be used as the working medium.

However, when drying in air, the internal temperature of the heat pipe of the heat collecting element can reach 230°C, the saturated water vapor pressure corresponding to this temperature is 28.53 atmospheres, and the corresponding ratio of the filling amount of the working medium to the volume of the heat pipe, that is, the volume ratio of the working medium is 1.1%. That is, there are 11 ml of water per 1 liter of volume.

The internal pressure of the heat pipe can be reduced by reducing the filling amount of the working fluid. Take the water working fluid as an example: when the filling amount of the working fluid/the volume ratio of the heat pipe is reduced from 0.5% when it is 5ml/1000ml to 2ml/1000 0.2% in milliliters, correspondingly the highest saturated vapor pressure decreases from about 10 atmospheres at 180°C to about 3.7 atmospheres at 140°C, and the inside of the heat pipe continues to heat up from the highest vapor pressure of about 3.7 atmospheres at 140°C to 180°C When the internal pressure is only about 4 atmospheres. But sometimes the filling amount of working medium cannot be determined only by the internal pressure during air drying. For a heat pipe with a working fluid filling rate/heat pipe volume ratio of 0.2%, an internal volume of 1000 ml, and a length of 2000 mm, if the internal pressure does not exceed 4 atmospheres when the air is exposed to 230 ° C, the working fluid filling volume is about 1.8 ml. The problem is that even if the heat pipe is a light pipe structure, when it works at an inclination of about 45 degrees, the sum of the condensed water at the cold end, the flowing water at the hot end plus 0.353 milliliters of water vapor at 85 ° C will far exceed 1.8 milliliters.

In order to meet the normal operation of the heat pipe and make the working fluid filling amount/heat pipe volume ratio greater than 0.2% or even 0.3%, and to ensure that the glass heat pipe does not explode due to air drying, air drying protection measures must be taken.

Chinese invention patent 2009101951003 anti-drying all-glass vacuum heat pipe heat collecting element discloses an air-drying protected all-glass vacuum heat pipe heat collecting element, by setting a controllable heat transfer channel between the absorber of the vacuum heat collecting element and the cover glass tube The controllable heat transfer channel is composed of a movable heat transfer part and a driving part, and is characterized in that it contains a thermodynamic energy conversion driving part connected with a vacuum heat collecting element absorber with low thermal resistance. Since this patent is not specifically aimed at the heat-collecting elements of gravity heat pipes, it is not very targeted; the bimetal sheet thermal energy conversion drive used in it is originally not consistent with the product, and has the ability to return to its original shape after repeated heat deformation It will be reduced again, and the operating point setting, control variable input, comparison, energy conversion and energy supply and execution functions related to the control system undertaken by it are far from being able to work normally and effectively due to the impact on the accuracy of the possible 20-year design of the heat collecting element. life.

Fig. 3 shows a structural schematic diagram of a light pipe structure gravity heat pipe arranged obliquely.

In Fig. 3, the heat pipe 1 is made of a shell and an internal working fluid. Its working principle is as follows: heat energy is input from the hot end at the bottom, that is, the arrow marked side by side, so that the working fluid at the inner bottom of the heat pipe 1 is heated and vaporized, and the steam travels upward to the cold end of the heat pipe, which is the arrow, under the action of the pressure difference. Side by side, the heat energy is released to the load and condensed into a liquid, which flows back to the cold end below under the action of gravity, and the working medium is heated and vaporized again at the hot end..., thereby continuously circulating to realize the two-phase flow heat exchange cycle. Heat pipes have excellent heat transfer capability, heat flux conversion capability, and isothermal characteristics. If the heat pipe 1 has an input of 100 watts at the hot end, its output at the cold end can reach 97 watts or even higher.

If it is attempted to input heat energy only from below to the heat pipe 1 in FIG. 3 without taking away heat energy, the internal vapor pressure of the heat pipe 1 will rise sharply. If the heat pipe 1 uses water as the working medium and there is enough water, when the temperature of the heat pipe 1 reaches 230° C., the maximum internal pressure can reach 28.53 atmospheres.

If try to heat the heat pipe 1 of Fig. 3 from top to bottom and take out heat energy from a place slightly higher than the bottom of the heat pipe 1 below, for example, a section that accounts for 3% of the length of the whole heat pipe 1 from the bottom, that is, only the bottom is made forward The part accounting for 3% of the total length of the heat pipe 1 is also used as the overlapping cold end, and the vapor pressure inside the heat pipe 1 will drop to the saturated vapor pressure corresponding to the temperature of the cold end below. For example, when using water as the working medium, keep the temperature of the overlapping cold end below the heat pipe 1 at 100°C, even if the other parts above are heated to 230°C, because the liquid working medium inside the heat pipe 1 is all gathered at the overlapping cold end, except for the overlapping cold end. The heat pipe 1 hot end above the end is dry because there is no working medium to supplement the whole, and the two-phase heat transfer mechanism ceases to exist. The steam pressure inside the heat pipe 1 is only about 1 atmosphere.

An example of an overlapping cold end is a heat pipe wall with an absorbing film that absorbs sunlight as heat energy input, while a heat transfer device is used to connect the heat pipe wall with low thermal resistance and transfer heat energy.

This kind of design that the heat pipe 1 is arranged obliquely, the heat energy is input from the top of the heat pipe 1, and only a small section of the bottom is used as the overlapping cold end may not make sense in other occasions, but it is used for air protection of solar heat collecting elements, because only a very small A part of heat dissipation power - this part of heat dissipation power is used to ensure that when air drying occurs, the maximum value of the vapor pressure inside the heat pipe at the beginning of the air drying protection device does not exceed the set value; this part of heat dissipation power is also greater than the overlapping cooling The input power of thermal energy at the end as the hot end—therefore, the cooling device has compact size, reliable performance, small heat dissipation power, less outgassing to the vacuum insulation layer, little influence on the shielding of the absorber, and the tail end of the heat collecting element can be used as heat dissipation Advantages of the interface.

It can be seen that the smaller the area of the overlapping cold ends, the smaller the heat dissipation power required by the air protection device, and the more favorable it is. The actual heat collecting element needs to be installed by devices such as end boxes. The end box will cover the end of the heat collecting element. The part covered by the end box does not belong to the overlapping cold end. The reason why the overlapping cold end is also used is because some heat-collecting element air-drying protection devices are more suitable for installation on the cylindrical section of the vacuum insulation layer or the heat-collecting element cover glass tube has a necked section and is used in the shrinking section. After the neck section is formed, the inner glass tube is assembled, and then the cover glass tube is round-sealed and the tail pipe is referred to as the process of the rear tail pipe. If the round end formed by the back-drawing tailpipe process is not suitable for heat dissipation, it is necessary to use the cover glass tubular section upward from the round end to dissipate heat. The heat pipe or the tail end portion of the inner glass tube corresponding to the cylindrical section belongs to the overlapping cold end.

The overlapping cold end is based on the decompression air-drying protection design based on blocking the two-phase flow heat exchange cycle of the heat pipe. The heat dissipation channels are essentially different.

China 912050845 Utility Model Electric Rice Cooker Automatic Magnetic Temperature Control Switch, introduces a working principle of using thermal magnetic energy conversion element.

Contents of the invention

The object of the present invention is to provide a decompression air drying protector for the heat collecting element of the embedded heat fin vacuum heat pipe.

The technical scheme adopted by the present invention to solve the technical problem: Use several controllable heat transfer channels in the vacuum heat insulation layer at the end of the heat collecting element of the vacuum heat pipe to form a decompression space for the heat collecting element of the embedded heat fin vacuum heat pipe sun protector. The controllable heat transfer channel is composed of heat-sensitive permanent magnet steel, soft iron heat fins and connecting circlips. The controllable heat transfer channel has two stable states: the open heat conduction state when the soft iron heat fin moves upwards and connects the cover glass tube for heat transfer; Adiabatic state. The fixed edge of the soft iron heat fin is connected to the end of the inner glass tube or the bottom end of the heat pipe with low thermal resistance. The thermosensitive permanent magnet steel is arranged under the movable edge of the soft iron hot fin and is covered by the soft iron hot fin. When the heat-sensitive permanent magnet steel is magnetized, the soft iron heat fin is attracted by the heat-sensitive permanent magnet steel and bends down, and its movable edge is not connected to the cover glass tube for heat transfer; when the heat-sensitive permanent magnet steel loses magnetism, the soft iron heat fin It is upturned under the action of its own elastic force, and its movable side is connected with the cover glass tube for heat transfer.

It is also possible to make the inner surface of the tail end of the cover glass tube which is in contact with the movable edge of the soft iron heat fin be affixed with a layer of heat dissipation patch, and the heat dissipation patch is bonded to the tail end of the cover glass tube and connected with low thermal resistance. The heat transfer state between the heat dissipation patch and the movable side of the soft iron heat fin changes according to the change of the state of the heat-sensitive permanent magnet steel.

It is also possible to make the soft iron heat fin exchange heat with the inner glass tube or the hot end of the heat pipe through a heat sink, or make the soft iron heat fin and the heat sink integrally; block the connection.

It is also possible to connect the heat-sensitive permanent magnet steel with the inner glass tube with low thermal resistance through a piece of heat conduction; the soft iron heat fin is integrally made by stamping and flanging on the heat sink; the heat sink and the heat guide are both made with right angles Form connection circlip mounting groove.

A connecting circlip can also be used to connect the heat conduction, heat sink and heat dissipation patch; the heat conduction with low thermal resistance is connected to the heat-sensitive permanent magnet steel; the heat sink and the soft iron heat fin are integrally produced.

Heat sinks and heat guides are used to improve the thermal conductivity of the surface of the glass heat pipe. Heat sink patches are used to improve the heat transfer performance of the cover glass tube.

Beneficial effects of the present invention: The embedded hot-fin vacuum heat pipe heat collecting element decompression air drying protector of the present invention adopts the fixed side of the soft iron heat fin with low thermal resistance to connect the tail end of the inner glass tube or the bottom end of the heat pipe heat end. When the element is in the air-drying state, by opening the controllable heat transfer channel to dissipate heat, the liquid working fluid is collected at the bottom of the heat pipe hot end, and the air-drying protection design that blocks the two-phase flow heat transfer inside the heat pipe can greatly reduce the heat dissipation power. For example: a heat collecting element with an output of 70 watts, the filling volume of working fluid is 3 ml. The technical scheme of uniformly distributing controllable heat transfer channels on the hot end surface of the heat pipe to prevent the heat pipe from exploding. The heat dissipation power of the controllable heat transfer channel is 40 watts, and the maximum internal temperature of the heat pipe is above 150°C. The corresponding water vapor pressure Still up to 4.8 atmospheric pressure exceeds the pressure resistance of the glass tube with an outer diameter of 58 millimeters and a wall thickness of 1.8 millimeters. For the heat collecting element with the same output of 70 watts, only 10 watts of heat dissipation power is needed for the decompression air drying protection heat transfer channel, and the water inside the glass heat pipe can be absorbed at a rate of 0.25 ml/min when air drying occurs. About 6 minutes after the air drying started, although the temperature on the sunny surface of the heat pipe increased by about 30°C, the inside of the hot end of the heat pipe except the bottom was dry, and the vapor pressure was less than 1.5 atmospheres. Saving 30 watts of heat dissipation power has greatly reduced costs, reduced the outgassing of the heat transfer channel to the vacuum insulation layer by 75%, and greatly improved reliability. The key is to effectively solve the problem of large-diameter heat pipes. The invention adopts a low-power air drying protector to ensure that the water vapor pressure inside the heat pipe does not exceed 2 atmospheric pressure all the time, and does not affect the normal operation of the heat collecting element at all.

The heat-sensitive permanent magnet steel drive device has good consistency, good repeatability, high control precision, long service life and satisfactory performance.

Description of drawings

The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

Fig. 1 is a schematic diagram of the composite structure of the vacuum heat-insulating layer provided with an embedded heat-fin vacuum heat pipe heat-collecting element decompression air-drying protector.

Fig. 2 is an expanded view of the integrated soft iron heat fin and heat sink.

Fig. 3 is a structural schematic diagram of a light pipe structure gravity heat pipe arranged obliquely.

In the figure 1. heat pipe; 2. cover glass tube; 3. inner glass tube; 4. heat-sensitive permanent magnet steel; 5. soft iron heat fin; 6. heat sink; 7. movable side; 8. fixed side; 9. Connect the circlip assembly groove; 10. Thermal conduction; 11. Heat dissipation patch. the

Detailed ways

Figures 1 and 2 together illustrate an embodiment of the present invention.

In Fig. 1 and Fig. 2, in the vacuum insulation layer between the end cover glass tube 2 of an all-glass vacuum heat pipe heat collecting element and the inner glass tube 3, that is, the heat pipe 1, two heat-sensitive permanent magnet steels 4 are set. , a controllable heat transfer channel composed of soft iron heat fins 5 and connecting circlips. The soft iron hot fin 5 forms by punching flanging on the heat sink 6, and its movable side 7 is shorter than the fixed side 8. The heat sink 6 is also made with a right-angled connecting clip spring assembly groove 9 to facilitate assembly. The heat sink 6 is rolled into a cylindrical shape with a thin iron plate and wrapped with low thermal resistance and connected to the tail end of the inner glass tube 3, that is, the bottom end of the heat pipe 1 heat end. The thermosensitive permanent magnet steel 4 is arranged under the movable edge 7 of the soft iron heat fin 5 and is covered by the soft iron heat fin 5 . The thermosensitive permanent magnet steel 4 is connected with the inner glass tube 3 with low thermal resistance through a piece of heat guide 10 . The same as the heat sink 6, the heat guide 10 is also made with a right-angled connecting clip spring assembly groove to facilitate assembly. In order to meet the requirement of maintaining high thermal resistance between the heat-sensitive permanent magnet steel 4 and the soft iron heat fin 5 , the heat sink 6 and the heat guide 10 are not in direct contact. The heat sink 6 and the heat guide 10 have a thickness of 0.22mm. A layer of heat dissipation patch 11 is arranged on the inner side of the tail end of the cover glass tube 2 in contact with the soft iron heat fin 5 . The heat dissipation patch 11 has a thickness of 0.22 mm and a width of 40 mm. The heat dissipation patch 11 is bonded to the tail end of the cover glass tube 2 and connected with low thermal resistance.

Materials for heat sink 6 , heat guide 10 and heat dissipation patch 11 include steel plate, aluminum plate and copper plate. The connection clip is a necessary configuration of the all-glass vacuum heat collecting tube, and the related content can refer to the prior art.

The working principle of the embodiment shown in Fig. 1 and Fig. 2: when the heat collecting element is normally inclined and is not in the air drying state, the temperature of the heat-sensitive permanent magnet steel 4 connected to the inner glass tube 3 with low thermal resistance through the heat guide 10 cannot reach the temperature of failure. Magnetic temperature, the soft iron hot fin 5 is attracted by the magnetism of the heat-sensitive permanent magnet steel 4 and the movable edge 7 bends downward without contacting the heat dissipation patch 11 (as shown by the dotted line in Fig. 1 ). The controllable heat transfer channel is in a closed adiabatic state. The heat collecting element collects heat normally.

When the heat-collecting element is in the air drying state, the temperature of the heat-sensitive permanent magnet steel 4 rises and the magnetic force disappears, and the soft iron heat fin 5 rises under the action of its own elastic force and the movable edge 7 is heat-conducted and connected to the heat-dissipating patch 11 (as shown in Fig. 1 ). As shown by the line), the controllable heat transfer channel is in the heat conduction state. The inner glass tube 3, that is, the heat energy at the hot end of the heat pipe 1 is continuously dissipated to the environment through the controllable heat transfer channel. The steam inside the heat pipe 1 flows to the bottom end to condense and gather at the bottom end under the action of the pressure difference, clamping the steam pressure inside the heat pipe 1 to always be at a low level, ensuring that the heat collecting element will not blow up the tube to realize the air drying protection of the heat collecting element.

After the heat collecting element is out of the air drying state, the temperature of the heat-sensitive permanent magnet steel 4 decreases and the magnetic force recovers and attracts the soft iron heat fin 5 to bend down so that the movable side 7 does not conduct heat and connects to the heat dissipation patch 11, and the controllable heat transfer channel is closed and insulated state, the heat collecting element can work normally again.

The embodiment shown in Fig. 1 and Fig. 2 is also applicable to the inserting heat pipe heat collecting element, at this moment, the inner glass tube 3 itself is not a heat pipe, but is connected with an inserting heat pipe in cooperation or with low thermal resistance. The working principle of its air-drying protection is similar, and the state of the controllable heat transfer channel is changed through the temperature rise/decrease and magnetic force disappear/recovery of the heat-sensitive permanent magnet steel 4 during air-drying/non-air-drying, so as to achieve The thermal element is obtained for the purpose of air protection.

Claims (2)

1. Embedded heat-finned vacuum heat-pipe heat-collecting element decompression air drying protector, which is composed of several controllable heat-transfer channels arranged in the vacuum heat-insulating layer at the end of the vacuum heat-pipe heat-collecting element. The controllable heat-transfer channels Composed of heat-sensitive permanent magnet steel, soft iron heat fins and connecting circlips, the controllable heat transfer channel has two stable states: the open heat conduction state when the soft iron heat fins move upward and connect to the cover glass tube; The closed adiabatic state when the movable side of the iron heat fin is bent down without heat transfer and connected to the cover glass tube is characterized by the low thermal resistance of the fixed side of the soft iron heat fin connected to the tail end of the inner glass tube or the bottom end of the heat pipe heat end; heat-sensitive permanent magnet The steel is arranged under the movable side of the soft iron hot fin; when the heat-sensitive permanent magnet steel is magnetic, the soft iron hot fin is attracted by the heat-sensitive permanent magnet steel and bends down, and its movable side is not connected to the cover glass tube for heat transfer; When the sensitive permanent magnet steel is demagnetized, the soft iron hot fins are upturned under the action of their own elastic force, and their movable edges are connected with the cover glass tube for heat transfer. 2. According to claim 1, the embedded hot-fin vacuum heat pipe heat-collecting element decompression and air-drying protector is characterized in that a layer of heat dissipation is pasted on the inner surface of the tail end of the cover glass tube that is in contact with the movable edge of the soft iron hot fin. A patch, the heat dissipation patch is attached to the tail end of the cover glass tube and connected with low thermal resistance; the heat transfer state between the heat dissipation patch and the movable edge of the soft iron heat fin changes according to the state of the heat-sensitive permanent magnet steel. 3. According to claim 1, the embedded hot fin vacuum heat pipe heat collecting element decompression air drying protector is characterized in that the soft iron hot fin exchanges heat with the inner glass tube or the hot end of the heat pipe through a heat sink, or The soft iron heat fins are integrally made with the heat sink; the heat sink is connected with the inner glass tube or the hot end of the heat pipe with low thermal resistance. 4. According to claim 3, the embedded hot-fin vacuum heat pipe heat collecting element decompression and air-drying protector is characterized in that the heat-sensitive permanent magnet steel is connected to the inner glass tube with low thermal resistance through a piece of heat conduction; the soft iron heat fin passes through It is integrally manufactured by punching and flanging on the heat sink; both the heat sink and the heat guide are made with right-angled connecting circlip assembly grooves.