CN111076591A - A flat plate heat pipe with multiple evaporating surfaces and a common condensing cavity for battery stack cooling - Google Patents

Abstract

The invention belongs to the technical field of power batteries, and provides a flat heat pipe with multiple evaporation surfaces sharing a condensation cavity for cooling a battery stack. The heat generated by the battery in the working process is taken away by vaporization of the working medium on the evaporation surface, the vaporized working medium is condensed in the condensation cavity, and the heat emitted by condensation is directly taken away by the cooling working medium in the serpentine pipeline, so that the highest temperature of the battery pack and the temperature difference between the battery monomers are effectively controlled. Compare in cooling methods such as traditional forced air cooling, liquid cooling, have following advantage: the phase change of the working medium is utilized to take away the heat generated in the working process of the battery pack, and the heat dissipation efficiency is high; cooling is carried out inside the heat pipe through a serpentine pipeline, so that a heat sink structure is omitted; the phase change points of the working medium in each communicated evaporation cavity are the same, so that the temperature consistency among each battery monomer can be effectively controlled; and multiple evaporation surfaces share one condensation cavity, so that the structure is more compact, and the total volume of the battery pack cooling device is reduced.

Description

Flat heat pipe with multiple evaporation surfaces sharing condensation cavity for cooling cell stack

Technical Field

The invention belongs to the technical field of power batteries, and particularly relates to a flat heat pipe with multiple evaporation surfaces sharing a condensation cavity for cooling a battery stack

Background

Nowadays, new energy automobiles are increasingly the focus of attention, but the development of the new energy automobiles is restricted by the technical level of power batteries. The power battery includes many types, and among them, the lithium ion battery has been widely accepted by society due to its advantages of high energy density, long cycle life, no memory effect, high cell voltage, etc. However, the service life and the working performance of the lithium ion battery are closely related to the temperature, the optimal working temperature range is 15-40 ℃, and when the working temperature of the lithium ion battery exceeds 40 ℃, the cycle life of the lithium ion battery is shortened by two months when the temperature rises by 1 ℃. Meanwhile, in order to fully exert the working performance of each battery unit in the system, the temperature difference of each battery unit is less than 5 ℃. In addition, when the temperature exceeds the upper limit that the lithium ion battery can bear, the internal materials of the lithium ion battery can generate complex chemical reaction due to the overhigh temperature, and generate a large amount of heat, so that the lithium ion battery is promoted to enter a thermal runaway state, dangerous accidents such as fire and explosion are caused, and the life safety of passengers is seriously threatened.

The heat dissipation methods of the power battery are mainly three, namely air cooling type, liquid cooling type and heat dissipation by using phase change materials. In the patent of lithium ion battery thermal management system (patent number: CN201610114215.5) of overseas people and the like, air cooling is utilized to dissipate heat of a battery pack, but for low-temperature-difference heat dissipation of a power battery pack, the convection heat transfer coefficient of air is limited, so that the air-cooled heat dissipation effect is not obvious; in a patent of 'a novel heat management system for vehicle-mounted lithium ion batteries' (patent number: CN201810584328.0), Li wen et al adopt a liquid cooling mode to dissipate heat of a battery pack, and because the heat conductivity coefficient of liquid is greater than that of air, the temperature of a vehicle-mounted power battery can be effectively reduced, but the problem of temperature difference between battery cells is difficult to solve; in the patent of 'a high-power lithium ion battery thermal management system' (patent number: CN201820855714.4), Dynees uses a phase-change material as a cooling working medium, and absorbs heat generated during the operation of a power battery by utilizing the phase-change of latent heat of the phase-change material when the latent heat reaches a phase-change temperature point. At present, paraffin is a main phase-change material, but the thermal conductivity of paraffin is too low, so that the paraffin cannot absorb heat in time when the power battery is discharged at a high rate and generates a large amount of heat.

The flat heat pipe has the advantages of extremely high heat conductivity, excellent isothermal property, larger heat transfer area and the like, so that the requirements of power battery equipment on compactness, high heat dissipation efficiency and the like of a heat dissipation device can be met. Therefore, the invention combines the heat exchange concept of the flat heat pipe with the actual structure of the power battery pack, and provides the flat heat pipe with multiple evaporation surfaces sharing a condensation cavity for cooling a battery stack

Disclosure of Invention

The invention aims to provide a flat heat pipe with multiple evaporation surfaces sharing a condensation cavity for cooling a battery stack, which realizes the control of the highest temperature of a battery pack and the temperature difference between single batteries and simultaneously makes the whole structure more compact.

The technical scheme of the invention is as follows:

a flat heat pipe with multiple evaporation surfaces sharing a condensation chamber for cooling a battery stack comprises ashell 1, aserpentine pipeline 2, aliquid charging pipe 5 and aliquid absorption core 6, wherein:

theshell 1 mainly comprises a horizontal shell and a plurality of vertical shells to form a communicated shell structure; theshell 1 is provided with a hole communicated with the interior of the shell, and theliquid charging pipe 5 is fixedly connected to theshell 1 through the hole; theshell 1 is made of an aluminum-based material, the inner surface of the shell is coated with a nano-thickness super-hydrophilic coating, the main components of the super-hydrophilic coating are nano silicon oxide and nano titanium oxide, and the contact angle is less than 10 degrees;

theserpentine pipeline 2 is arranged in the horizontal shell, and the two ends of the serpentine pipeline are respectively provided with aserpentine pipeline inlet 3 and aserpentine pipeline outlet 4 which are both led out of theshell 1; thesnakelike pipeline 2 is made of an aluminum-based material, the outer surface of the snakelike pipeline is provided with a super-hydrophobic coating, and the super-hydrophobic coating is a Teflon coating with a contact angle larger than 150 degrees;

theliquid absorption core 6 is arranged in the vertical shell, is of a single foamed aluminum structure and has super-hydrophilic characteristics, and the main components of the material for carrying out super-hydrophilic modification on theliquid absorption core 6 are nano silicon oxide and nano titanium oxide.

After aliquid filling pipe 5 is used for filling cooling working media into the flat shell, a certain area of the flat shell is heated, the temperature of the heated area is increased, liquid in the area near the internal evaporation surface corresponding to the area is boiled, the generated gas working media flows upwards due to the pressure difference, the bead condensation is carried out on the outer surface of theserpentine pipeline 2, part of the working media at the evaporation end is converted into a gas state from a liquid state, and the condensed liquid working media continuously flow and supplement to the evaporation end under the driving of the capillary force and the gravity of aliquid absorption core 6. The heat of the heated area is continuously transferred to the cooling working medium in theserpentine pipeline 2 through the gas-liquid phase change and the circular flow of the working medium.

Snakelikepipeline 2 communicates with each other with the external world, and cooling medium gets intosnakelike pipeline 2 throughsnakelike pipeline import 3, flows outsnakelike pipeline 2 throughsnakelike pipeline export 4. The flowing liquid cooling working medium continuously takes away the heat emitted when the steam is condensed, and the reciprocating circulation realizes the effective control of the highest temperature of the battery pack and the temperature difference between the single batteries.

The invention has the beneficial effects that:

1) the phase change of the working medium is utilized to take away the heat generated in the working process of the battery pack, and the heat dissipation efficiency is high;

2) cooling is carried out inside the heat pipe through a serpentine pipeline, so that a heat sink structure is omitted;

3) the serpentine pipeline has the function of supporting the interior of the flat heat pipe while condensing the steam, so that the mechanical strength is improved;

4) multiple evaporation surfaces share one condensation cavity, so that the structure is more compact, and the total volume of the battery pack cooling device is reduced;

5) the phase change points of the working medium in each evaporation cavity are the same, so that the temperature consistency among the single batteries can be effectively controlled;

drawings

FIG. 1 is an oblique view of a housing;

FIG. 2 is a serpentine circuit;

FIG. 3 is an oblique view of a flat heat pipe with multiple evaporation surfaces sharing a condensation chamber (high housing transparency);

FIG. 4 is a top view of a flat heat pipe with multiple evaporation surfaces sharing a condensation chamber (high housing transparency);

FIG. 5 is an oblique view of a flat heat pipe with multiple evaporation surfaces sharing a condensation chamber (housing opaque);

figure 6 is a front view of a shell and wick assembly (high shell transparency);

FIG. 7 is a power cell module model;

fig. 8 is an assembly of a flat heat pipe where the power cell stack and multiple evaporation surfaces share a condensation chamber.

In the figure: 1, a shell; 2, a snake-shaped pipeline; 3, a snakelike pipeline inlet; 4, a serpentine pipeline outlet; 5, filling a liquid pipe; 6 a liquid absorption core; 7 lowest liquid level line.

Detailed Description

The following further describes a specific embodiment of the present invention with reference to the drawings and technical solutions.

To facilitate an understanding of the invention, the invention will now be described more fully with reference to the accompanying drawings. It is to be understood that such description is merely illustrative of the features and advantages of the present invention, and is not intended to limit the scope of the claims.

The invention discloses a power battery heat pipe cooling device which comprises a shell, a liquid absorption core, a serpentine pipeline and a liquid charging pipe.

The shell is made of an aluminum-based material, the inner surface of the shell is coated with a layer of nano-thickness super-hydrophilic coating, the main components of the super-hydrophilic coating are nano silicon oxide and nano titanium oxide, and the contact angle is less than 10 degrees.

The liquid absorption core is of a single foamed aluminum powder structure and has super-hydrophilic characteristics; the main components of the material for super-hydrophilic modification of the imbibing core are nano silicon oxide and nano titanium oxide.

The snakelike pipeline be aluminium base material, its pipeline surface has super hydrophobic coating, super hydrophobic coating is the teflon coating that the contact angle is greater than 150 degrees.

The shell is provided with a hole communicated with the interior of the shell, and the liquid filling pipe is fixedly connected to the shell through the hole;

the space formed by the outer surface of the serpentine pipeline and the inner surface of the shell is sealed, and the shell is sealed in a welding mode.

As shown in fig. 1, which is an oblique view of the housing, the inner surface of the housing has super-hydrophilic characteristics, and since the super-hydrophilic modification technology has been fully developed and applied, there are many ways to modify super-hydrophilic characteristics, and this example selects the coating method. Namely, a layer of super-hydrophilic coating is coated on the inner surface of a flat plate shell, and the main components of the coating are nano silicon oxide and nano titanium oxide. And after the coating is finished, the coating is placed in a vacuum drying oven to be dried for two hours, and the finally obtained surface contact angle is less than 10 degrees. The case is welded from an aluminum plate, and the welding method is not particularly limited, but it is necessary to ensure good sealing. Illustratively, the welding method adopted by the invention is brazing.

As shown in fig. 2, the serpentine pipeline is coated with a teflon coating on its surface, so that the external surface of the pipeline has super-hydrophobic characteristics, and after the surface is dried, the contact angle of the surface is measured to be greater than 150 degrees.

Fig. 3 is an oblique view (high transparency of the casing) of a flat heat pipe with multiple evaporation surfaces sharing a condensation chamber, wherein awick 6 is contained, and the capillary structure of thewick 6 can be sintered aluminum powder, foamed aluminum, a wire mesh and a micro-channel structure. The foam aluminum with larger pore diameter is adopted as theliquid absorption core 2 in the example, and the structure is more stable due to the single capillary structure, so that the mechanical strength of the flat heat pipe is effectively increased. And soaking the sinteredliquid absorption core 6 in a prepared super-hydrophilic solution (the main components of the solution are nano silicon oxide and nano titanium oxide), taking out theliquid absorption core 2 after about 1 hour of soaking, and drying in a vacuum drying oven for 2 hours to finally obtain theliquid absorption core 2 with the super-hydrophilic characteristic.

It can be seen that the outer surface of thewick 6 lies against the inner surface of the housing and can be held in compression. The outer surface of the snake-shaped pipeline is tightly attached to the inner wall of the shell, so that the shell is supported, and the mechanical strength of the device is effectively improved.

Fig. 4 is a top view (high transparency of the shell) of a flat heat pipe with multiple evaporation surfaces sharing a condensation chamber, wherein aserpentine inlet 3 and aserpentine outlet 4 are included. The snakelike pipeline is communicated with the outside, and the cooling working medium enters the snakelike pipeline through the working medium inlet and flows out of the snakelike pipeline through the snakelike pipeline outlet. The flowing liquid cooling working medium continuously takes away the heat emitted when the steam is condensed, and the reciprocating circulation realizes the effective control of the highest temperature of the battery pack and the temperature difference between the single batteries.

Fig. 6 shows a front view of the shell and wick assembly (high transparency of the shell) including the lowestliquid level line 7, i.e., the liquid fill height required to be greater than or equal to the lowestliquid level line 7 during liquid filling, so that the temperature is uniform across the evaporation surface. In this example, taking the lithium ion battery as an example, when the operating temperature of the lithium ion battery exceeds 40 ℃, the cycle life of the lithium ion battery is reduced by two months for every 1 ℃ rise, so that a working medium with a low boiling point is required. Ammonia (25% solution) with a boiling point of 38 ℃ was used in this example.

Fig. 7 shows a battery model used in this example, which is a 1-pack 6-block battery. After the flat heat pipe is assembled, as shown in fig. 8, ammonia water is filled into the flat heat pipe through the liquid filling pipe, a certain area of the flat heat pipe is heated, the temperature of the heated area is increased, liquid in an area near an internal evaporation surface corresponding to the area is boiled, generated gas working medium flows upwards due to air pressure difference, bead-shaped condensation is carried out on the outer surface of the serpentine pipeline, part of working medium at an evaporation end is converted into gas from liquid, and the condensed liquid working medium continuously flows and is supplemented to the evaporation end under the driving of capillary force and gravity of the liquid absorption core. The heat of the heated area is continuously transferred to the cooling working medium in the serpentine pipeline through the gas-liquid phase change and the circular flow of the working medium.

The snakelike pipeline is communicated with the outside, and the cooling working medium enters the snakelike pipeline through the working medium inlet and flows out of the snakelike pipeline through the snakelike pipeline outlet. The flowing liquid cooling working medium continuously takes away the heat emitted when the steam is condensed, and the reciprocating circulation realizes the effective control of the highest temperature of the battery pack and the temperature difference between the single batteries. It is emphasized that the inside of the serpentine circuit is not evacuated,

but the enclosed space between the outer surface of the serpentine and the inner surface of the housing is evacuated.

In summary, the invention discloses a flat heat pipe with multiple evaporation surfaces sharing a condensation cavity for cooling a cell stack, and combines the heat exchange concept of the flat heat pipe with the actual structure of a power battery pack. The improved flat heat pipe has the advantages that the improved flat heat pipe is improved theoretically, a heat sink structure is omitted, steam generated by an evaporation surface can be directly condensed on the outer surface of the serpentine pipeline, and heat emitted by condensation is directly taken away by a cooling working medium in the serpentine pipeline, so that the highest temperature of a battery pack and the temperature difference between battery monomers are effectively controlled.

The technical solutions and advantages of the present disclosure have been described in detail with reference to the specific examples, and it should be understood that the above description is only exemplary of the present disclosure, and is not intended to limit the present disclosure. The sizes and shapes of the various elements in the drawings are not to be considered as reflecting actual sizes and proportions, but are merely representative of the contents of the present example. Any modification, improvement or equivalent replacement made on the principle and spirit of the present disclosure is within the protection scope of the present disclosure.

Claims (5)

1. A flat heat pipe with a multi-evaporation surface shared condensation chamber for cooling a battery stack is characterized by comprising a shell (1), a serpentine pipeline (2), a liquid charging pipe (5) and a liquid absorption core (6), wherein:

the shell (1) mainly comprises a communicating shell structure consisting of a horizontal shell and a plurality of vertical shells; the shell (1) is provided with a hole communicated with the interior of the shell, and the liquid filling pipe (5) is fixedly connected to the shell (1) through the hole;

the snake-shaped pipeline (2) is arranged in the horizontal shell, and the two ends of the snake-shaped pipeline are respectively provided with a snake-shaped pipeline inlet (3) and a snake-shaped pipeline outlet (4) which are both led out of the shell (1);

the liquid absorbing core (6) is arranged in the vertical shell.

2. The flat heat pipe with the multiple evaporation surfaces sharing the condensation cavity for cooling the cell stack as claimed in claim 1, wherein the shell (1) is made of an aluminum-based material, the inner surface of the shell is coated with a layer of nano-thickness super-hydrophilic coating, the super-hydrophilic coating mainly comprises nano-silicon oxide and nano-titanium oxide, and the contact angle is less than 10 degrees.

3. The flat heat pipe with the condensation chamber shared by multiple evaporation surfaces for cooling the cell stack as claimed in claim 1 or 2, wherein the serpentine pipeline (2) is made of an aluminum-based material, and the outer surface of the serpentine pipeline is provided with a super-hydrophobic coating which is a teflon coating with a contact angle of more than 150 degrees.

4. The flat-plate heat pipe with multiple evaporation surfaces sharing a condensation chamber for cooling a battery stack as claimed in claim 1 or 2, wherein the liquid absorption core (6) is a single foamed aluminum structure with super-hydrophilic characteristics, and the main components of the material for super-hydrophilic modification of the liquid absorption core (6) are nano silicon oxide and nano titanium oxide.

5. The flat plate heat pipe with multiple evaporation surfaces sharing a condensation chamber for cooling a battery stack as claimed in claim 3, wherein the liquid absorption core (6) is a single foamed aluminum structure with super-hydrophilic characteristics, and the main components of the material for super-hydrophilic modification of the liquid absorption core (6) are nano silicon oxide and nano titanium oxide.

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