CN107438349A - A kind of natural heat dissipation device using stack effect - Google Patents

Abstract

A natural heat dissipation device utilizing the chimney effect, the heat dissipation device is composed of a base plate, a set of heat dissipation fins arranged on the base plate, a cover plate and a rear shell arranged on the top of the set of heat dissipation fins; the set of heat dissipation fins adopts Ladder structure; the cover plate is arranged on the top of the heat dissipation fin group, and its lower edge is kept flush with the stepped corners of the heat dissipation fin group, and is perpendicular to the base plate and the two outermost fins of the heat dissipation fin group on the original basis It extends upwards to form a cylinder, which forms a chimney structure. The heat generated by the electronic device is transferred to the aluminum plate through the heat pipe, and the aluminum plate is bonded to the base plate of the heat sink, and finally the heat is dissipated to the environment through the cooling fin group and the cover plate. The self-pumping effect generated by the chimney effect increases the air velocity in the airflow channel, enhances the air convection effect on the surface of the fins, and improves the heat dissipation efficiency, thereby achieving the purpose of prolonging the life of electronic devices and improving the reliability of equipment.

Description

A natural cooling device using the chimney effect

technical field

The invention belongs to the technical field of heat dissipation, and in particular relates to a natural heat dissipation device using the chimney effect, which is suitable for use in solar energy applications, metallurgy, air conditioners, electronic communications and other industries requiring enhanced heat dissipation.

Background technique

At present, the cooling technologies mainly include natural convection cooling, forced air cooling, liquid cooling, heat pipes, microchannel cooling and thermoelectric cooling. Among them, natural convection heat dissipation is the most classic and convenient method. It has the advantages of no energy supply, reliable and stable performance, high safety, no noise and low manufacturing cost. It utilizes the gaps of various components in the equipment and the casing Heat conduction, heat convection and heat radiation to achieve the purpose of heat dissipation. This method is suitable for low-power electronic devices that do not have high temperature control requirements and low heat flux due to device heating. It can also be used in occasions where it is inconvenient to install external power sources such as fans due to narrow space or outdoors. Due to these problems, in some demanding places, natural heat dissipation has become the most suitable heat dissipation method.

For the natural heat dissipation module, analyze its heat dissipation process from the internal heat source (heating element) of the module to the external environment. It can be seen that the heat dissipation thermal resistance on the side of the module shell is much greater than the contact thermal resistance inside the module, as well as the thermal resistance of heat conduction and convection. The heat dissipation on the shell side includes natural convection heat dissipation and radiation heat dissipation. In particular, the natural convection heat resistance is extremely high, which is the key to restricting the improvement of the module's heat dissipation capability. As the power consumption of natural heat dissipation modules continues to increase, how to fully reduce the thermal resistance of the natural heat dissipation module shell side and enhance the heat dissipation capacity of the module is an inevitable requirement to reduce the temperature level of the module and a prerequisite for ensuring the normal and stable operation of the natural heat dissipation module. Considering the limitation of the surface condition of the module and the temperature level, there is limited room for strengthening and optimizing the radiation heat transfer, so the enhanced heat transfer of the natural heat dissipation module is mainly to enhance the natural convection heat dissipation capacity of the shell side, so many scholars at home and abroad have conducted research on this. A large number of experiments and numerical simulation studies have been carried out. At present, the fin structures used in natural convection heat dissipation modules mainly include flat fins, intermittent fins, spore fins, trapezoidal fins, cylindrical fins, honeycomb structure fins and perforated fins. Among them, flat fins are the most commonly used in actual production, which has the advantages of convenient processing, low manufacturing cost, and convenient large-scale production. For vertical flat fins, the airflow channel is from top to bottom, and when the airflow reaches the top of the channel, it has been fully heated, and the temperature is high, resulting in a smaller heat transfer temperature difference between the fluid and the radiator substrate, and its heat dissipation capacity is correspondingly deteriorated . In addition, from the point of view of the field synergy principle (that is, the essence of convective heat transfer enhancement is to reduce the angle between the velocity vector of the flow field and the temperature gradient, when the angle between the velocity vector of the flow field and the temperature gradient is equal to 90°, The convective heat transfer is equal to zero), the angle between the partial air velocity field and the temperature gradient on the vertical flat fins is close to 90°, and the synergy is extremely poor, which leads to poor natural convection heat dissipation and reduces the reliability of the equipment. Compared with ordinary fins, the heat transfer performance of discontinuous fins can usually be increased by about 5% to 18%; the average Nusselt number of butylated fins can be increased by about 68%; It can be increased by about 38%, and the flow resistance can be reduced. Compared with the unfinned substrate, the heat transfer coefficient of cylindrical fins with different distributions is about 1.5 to 2 times; the Nusselt number of aluminum honeycomb fins (left) is 4 times that of bare plates.

The structural size and arrangement of buildings or profiles often form a self-drawing phenomenon, that is, the "chimney effect". The chimney effect is based on the difference in the internal density of the flow channel to generate an internal and external pressure difference, combined with the fluid's own buoyancy to determine the flow of the fluid. Due to the different locations of the heat source, the two effects will ebb and flow. For example, high-rise buildings, internal stairs, elevators, air-conditioning ventilation channels and other parts have strong longitudinal air flow, and there will be a cool feeling without air-conditioning facilities. The chimney effect not only exists in high-rise buildings, as long as the structural design is reasonable, it will have this effect. This effect will greatly increase the heat transfer coefficient of the radiator and improve the heat dissipation performance.

Contents of the invention

Aiming at the above-mentioned technical problems of high airflow temperature on the upper part of the vertical flat fins, low flow velocity and poor coordination of the entire field, the convective heat transfer effect is deteriorated, the present invention provides a natural heat dissipation device using the chimney effect, which can Effectively reduce the temperature of heating elements in heat dissipation equipment under natural heat dissipation conditions, so as to achieve the purpose of prolonging life and improving equipment reliability.

In order to achieve the above-mentioned purpose, the technical solution adopted by the present invention is to include a base plate, a heat dissipation fin group and a cover plate arranged on the base plate to dissipate the heat of the base plate into the environment, and a rear shell arranged at the lower end of the base plate. The heat dissipation fin group adopts a stepped structure; the cover plate is arranged on the top of the heat dissipation fin group, and its lower edge is kept flush with the stepped corners of the heat dissipation fin group. The fins extend vertically upwards to form a cylinder to form a chimney structure.

The height of the chimney and the length of the base plate h/L=0.1˜0.45.

The fin length L ₁ /L ₂ of the upper and lower parts of the stepped heat dissipation fin group is 0.5-2.

The fin heights of the upper and lower parts of the stepped heat dissipation fin group are H ₁ /H ₂ =0.55˜1.8.

The rear shell adopts an aluminum plate.

The heat generated when the electronic device is in operation is transferred to the aluminum plate back shell through the heat pipe, and the aluminum plate back shell is bonded to the radiator substrate, and finally the heat is dissipated to the environment through the cooling fin set and the cover plate. The self-suction effect generated by the chimney effect increases the air flow velocity in the air flow channel, enhances the air convection effect on the surface of the fins, and improves the heat dissipation efficiency.

In the above-mentioned natural heat dissipation device utilizing the chimney effect, compared with the prior art, it has the following advantages:

1) Based on the self-pumping effect of the chimney effect, the natural convection heat dissipation is enhanced. In the present invention, on the basis of the original length of the base plate, the base plate, the two outermost fins of the cooling fin group and the cover plate are vertically extended upwards to form a cylindrical body, that is, a chimney structure. According to the self-pumping effect generated by the chimney effect, the air flow velocity in the airflow channel can be increased, and at the same time, the whole-field synergy between the fluid velocity field and the temperature field has also been significantly improved, thus overcoming the vertical flow often used in production practice. The upper part of the straight flat fin has higher fluid temperature, smaller heat transfer temperature difference, lower flow velocity, and the angle between the fluid velocity field and the temperature gradient is close to 90°, that is, poor synergy and other factors. The convective heat transfer effect is deteriorated , temperature rise and other disadvantages.

2) Change the air intake method. The height of the upper and lower parts of the stepped heat dissipation fin group is different, and the steps of the structure can change the way of air intake. The simultaneous air intake from the bottom and the side can not only reduce the average temperature of the lower part of the substrate, but also introduce more fresh cold air into the upper air flow channel to increase the heat transfer temperature difference, thereby enhancing heat dissipation.

3) The present invention is simple in structure. On the basis of the traditional vertical flat heat dissipation structure, only a simple structure of a "chimney" is extended in the upper space; without adding oblique ribs and arc structures, the vertical flat fins effectively retain their flow resistance and are easy to process. Advantages such as low manufacturing cost.

4) When the power of the electronic device is 100W and the external environment temperature is 35°C, the finned heat sink widely used in the industry can reduce 3°C on the basis of the traditional vertical flat heat sink, while the average temperature of the substrate in the present invention The temperature can drop from 66.38°C of the traditional vertical flat fin radiator to 61.64°C of the new heat sink, which is about 4.7°C lower.

Description of drawings

The following embodiments are described in conjunction with the accompanying drawings to further illustrate the present invention.

Fig. 1 is a structural schematic diagram of the present invention.

Figure 2 is an exploded view of the present invention.

Figure 3 is a front view of the present invention.

Fig. 4 is a comparison diagram of the temperature of the temperature measuring point between the structure of the present invention and the traditional vertical flat fin radiator.

In the figure 1, the radiator base plate, 2, the cooling fin group, 3, the cover plate, 4, the back shell, 5, the chimney.

detailed description

Referring to accompanying drawings 1-3, the heat dissipation device of the present invention includes a substrate 1 and a cooling fin group 2 arranged on the substrate 1, a cover plate 3, and a rear shell 4 made of an aluminum plate arranged at the lower end of the substrate 1; The heat dissipation fin group 2 adopts a stepped structure; the cover plate 3 is arranged on the top of the heat dissipation fin group 2, and its lower edge is kept flush with the stepped corners of the fin group 2, and the cover plate 3 is connected with the base plate 1 and the heat dissipation The two outermost fins of the fins 2 extend vertically upwards on the original basis to form a cylinder to form a chimney 5 structure. Among them, the height of the chimney 5 and the length of the base plate ₁ h/L=0.1～0.45 _; The height of the upper and lower fins is H ₁ /H ₂ =0.55-1.8.

The heat generated by the electronic device is transferred to the aluminum plate through the heat pipe, and then the aluminum plate is bonded to the substrate 1 of the heat sink, and finally the heat is dissipated to the environment through the cooling fin set 2 and the cover plate 3 . The self-suction effect generated by the chimney effect increases the air flow velocity in the air flow channel, enhances the air convection effect on the surface of the fins, and improves the heat dissipation efficiency.

The following is an embodiment of the present invention, including a base plate 1 and a heat dissipation fin group 2 arranged on the base plate 1, and a cover plate 3, and a rear shell 4 made of an aluminum flat plate arranged at the lower end of the base plate 1; The fin group 2 adopts a stepped structure; the cover plate 3 is arranged on the top of the heat dissipation fin group 2, and its lower edge is kept flush with the step corners of the fin group 2, and the cover plate 3 is connected with the substrate 1 and the heat dissipation fin 2 The outermost two fins extend vertically upwards on the original basis to form a cylinder to form the structure of the chimney 5 . Among them, the length L of the substrate 1 is 435mm, the width of the substrate is 210mm, and the thickness of the substrate is 3mm; the heat dissipation fin group 2 of the stepped structure has a fin length of 355mm, a thickness of 1.8mm, and a spacing of 11.2mm. The upper part height H ₁ =55mm, and the lower part height H ₂ = 80mm; the cover plate 3 is located at the top of the heat dissipation fin group 2, the lower edge is flush with the step corner, and the width is 209.8mm, covering all the fins of the upper heat dissipation fin group; on this basis, the outermost two sides of the heat dissipation fin group 2 The root fin extends vertically upwards by 80 mm to form a cylindrical body with the base plate 1 and cover plate 3, that is, the structure of the chimney 5, that is, the length of the two outermost fins of the cooling fin group 2 is 435 mm, and the length of the remaining fins is kept at 355 mm. Five 20W heat sources are evenly arranged on the back side of the substrate, and five temperature measurement points are respectively located at the centers of the five heat sources. Aiming at the structural parameters of this example, numerical calculations were performed on the heat transfer and flow characteristics of the traditional vertical flat fin radiator and the example structure of the present invention, and the temperature distribution on the substrates of the two structures was compared and analyzed. The comparison results of the temperature distribution of the temperature measuring points at the center of the five heat sources of the example structure of the present invention and the traditional vertical flat fin radiator are shown in Fig. 4 . It can be seen from Fig. 4 that, compared with the traditional vertical flat-fin radiator, the average temperature of the substrate can be reduced by about 4.7°C by adopting the structure of the present invention, which significantly enhances the natural heat dissipation capability.

Claims (5)

1. A natural heat dissipation device utilizing the chimney effect, characterized in that: comprise a base plate (1) and a cooling fin group (2) that is arranged on the base plate (1) and dissipates the heat of the base plate (1) into the environment ) and the cover plate (3), and the rear case (4) arranged at the lower end of the substrate (1), the heat dissipation fin group (2) adopts a stepped structure; the cover plate (3) is arranged on the heat dissipation fin group ( 2), the lower edge of which is flush with the stepped corners of the cooling fin group (2), the cover plate (3), the base plate (1), and the two outermost fins of the cooling fin group (2) extend vertically upward Surround into a cylinder to form the structure of the chimney (5). 2. The natural heat dissipation device utilizing the chimney effect according to claim 1, characterized in that: the height of the chimney (5) and the length of the base plate (1) h/L=0.1˜0.45. 3 . The natural heat dissipation device utilizing chimney effect according to claim 1 , characterized in that: the fin length L ₁ /L ₂ of the upper and lower portions of the stepped heat dissipation fin group ( 2 ) = 0.5-2. 4 . 4 . The natural heat dissipation device utilizing the chimney effect according to claim 1 , characterized in that: the fin heights of the upper and lower portions of the stepped heat dissipation fin group ( 2 ) are H ₁ /H ₂ =0.55˜1.8. 5. The natural heat dissipation device utilizing chimney effect according to claim 1, characterized in that: the rear shell (4) is made of aluminum plate.