CN101424491A - Pulsating heat pipe with stable one-way circulation flow - Google Patents

Abstract

The invention discloses a pulsating heat pipe with steady and monodirectional circular flow, which belongs to the range of heat transfer elements. The pulsating heat pipe is formed by connecting a section of increasing coupling between two pipes with different inside diameters, wherein the increasing coupling can reduce symmetry and harmony of a flow passage, match the flowed friction reasonably, and generate the micropump effect due to the action of the liquid-vapor surface tension to guide work substances to move towards the thick pipe, so as to form monodirectional circular flow. The pulsating heat pipe has the advantages that the pulsating heat pipe has a simple structure, good reliability, and multiple realizing patterns; and the new structure adopted can strengthen stability and controllability of operation of the pulsating heat pipe, and improve heat transfer property of the pulsating heat pipe.

Description

Have and stablize the unidirectional pulsating heat pipe that circulates

Technical field

The invention belongs to the heat transfer element scope, can make particularly that two-phase flow has directionality in the pulsating heat pipe, help to realize unidirectional circular flow a kind of have stablize the unidirectional pulsating heat pipe that circulates.

Background technology

Pulsating heat pipe is a kind of high-performance heat transfer components, it is mobile that pulsating heat pipe utilizes phase transformation to produce steam bubble driving working medium, though relatively simple for structure, its internal mechanism is very complicated, relate to stream-liquid two-phase flow system multidisciplinary, multi-parameter, experiment and theoretical research all are scarcely out of swaddling-clothes.

The mobile stream-liquid two-phase flow that belongs in the micro-channel of pulsating heat pipe inside is moving, the pressure of its internal working medium, temperature and speed all present pulsating nature in the running, have many heating power energy imbalances, therefore, its operation characteristic has very big randomness and complexity.From flow direction, flowing of working medium can be divided into pulsation stream and circular flow in the pulsating heat pipe.Unidirectional circulate of working medium in pipe can be improved by evaporator section and be carried to the working medium of condensation segment, strengthens the heat transmission, improves the heat transfer property of pulsating heat pipe.But in the actual motion, stable unidirectional circular flow is difficult to keep, the staggered appearance of fluidised form such as pulse in common and part, stagnation, reverse refluence, and it is very complicated to move phenomenon.Therefore, the controllability of the stability of pulsating heat pipe operation and heat transfer has much room for improvement.

Summary of the invention

The purpose of this invention is to provide a kind of have stablize the unidirectional pulsating heat pipe that circulates, it is characterized in that: this pulsating heat pipe is to connect one section increaser to constitute between the pipe of two sections different inner diameters.

The pipe of described two sections different inner diameters, internal diameter of the pipeline satisfies $D_i<2\sqrt{\mathrm{\&sigma;}/({\mathrm{\&rho;}}_l-{\mathrm{\&rho;}}_g)g},$ In the formula, D ₁Be internal diameter of the pipeline, σ is a surface tension, ρ _i, ρ _gBe working medium liquid phase and vapour phase density.

The pipe of described two sections different inner diameters has reduced the symmetry and the harmony of pulsating heat pipe runner, the mobile of a certain direction is dominant, thereby has improved the possibility that forms unidirectional circular flow.

The pipe of described two sections different inner diameters, extra heavy pipe is lower than the flowing velocity in the tubule, causes flow resistance less thus, therefore can reach the effect of reasonable coupling flow resistance, and guiding working medium forms unidirectional circulating to the motion of extra heavy pipe direction.

In the described pulsating heat pipe, the periodic plug shape steam bubble that produces, because the internal diameter difference of pipeline, the radius of curvature of steam bubble meniscus also can change, and under surface tension effects, will produce the Micropump effect.

The heat conduction of described pulsating heat pipe and flow duct, effect are similar to a check valve.

The invention has the beneficial effects as follows, help to realize that the unidirectional of working medium circulates in the pulsating heat pipe, improve by evaporator section and carry, improve the heat transfer property of pulsating heat pipe, strengthen the stability and the controllability of pulsating heat pipe operation to the working medium of condensation segment.

Description of drawings

Fig. 1 is a principle schematic of the present invention.

Fig. 2 is the modified pulsating heat pipe that adopts new construction.

Fig. 3 is the Micropump effect schematic diagram of new construction.

Fig. 4 is the thermal resistance comparison diagram of common pulsating heat pipe and modified pulsating heat pipe.

Fig. 5 is the flow pattern real scene shooting picture of modified pulsating heat pipe.

1. tubules among the figure, 2. increaser, 3. extra heavy pipe, 4. modified pulsating heat pipe, 5. steam bubble.

The specific embodiment

The invention provides a kind of have stablize the unidirectional pulsating heat pipe that circulates.Illustrated below in conjunction with drawings and Examples.

Embodiment 1:

As shown in Figure 1, this pulsating heat pipe is to connect one section increaser to constitute between the pipe of two sections different inner diameters.Promptly between tubule 1 and extra heavy pipe 3, connect one section flaring pipeline 2 and constitute, form one section complete flow channel.

Embodiment 2:

Be illustrated in figure 2 as the modified pulsating heat pipe.Pipeline is bent to a plurality of elbows, and the liquid in the pipe is heated and cools off, and produces phase transformation, flows by phase transition process and working medium and transmits heat, and pulsating heat pipe can cool off electronic device.At the lower left quarter of pipeline one segment length 100mm, the extra heavy pipe of internal diameter 2mm have been installed; It is 1.6mm that other parts keep internal diameter.This architecture advances has been equivalent in the low order end pipe applications new construction of the present invention.

One section extra heavy pipe installing has destroyed the symmetry and the harmony of pulsating heat pipe runner, and its effect is similar to a check valve, interior the mobile of a certain direction of working medium of pulsating heat pipe is dominant, thereby has improved the possibility that forms unidirectional circular flow.

Fluid flows in pipeline need overcome flow pressure drop.Wherein, friction pressure drop is: $-{\left(\frac{\mathrm{dp}}{\mathrm{dz}}\right)}_f=\frac{{\mathrm{\&tau;}}_{w}P}{A}=\frac{{4\mathrm{\&tau;}}_w}{D},$ (τ when the inside pipe wall surface appearance is identical with the working medium rerum natura _wIdentical) time, extra heavy pipe will diminish than the friction pressure drop in the tubule, and this helps working medium and moves to the extra heavy pipe direction; Gravitational pressure drop is: $-{\left(\frac{\mathrm{dp}}{\mathrm{dz}}\right)}_g=[{\mathrm{\&alpha;\&rho;}}_v+(1-\mathrm{\&alpha;}){\mathrm{\&rho;}}_l]g\sin \mathrm{\&theta;},$ The working medium of equal in quality fluid column in extra heavy pipe is shorter, and gravitational pressure drop is littler, and this also helps working medium and moves to the extra heavy pipe direction.As seen, for the modified pulsating heat pipe, friction pressure drop and gravitational pressure drop in the extra heavy pipe are less, and flow resistance is less, therefore can reach the effect of reasonable coupling flow resistance, and guiding working medium forms unidirectional circulating to the motion of extra heavy pipe direction.

Embodiment 3:

Fig. 3 is a Micropump effect schematic diagram.In flaring pipeline 2, if periodically produce steam bubble 5, because pipe shape is the flaring feature, mandatory variation takes place in the radius of curvature of steam bubble meniscus, under surface tension effects, will produce the Micropump effect.

Surface tension effects makes between the inside and outside liquid of steam bubble and produces pressure reduction,

$p_v-{\mathrm{<figure-callout\; id="1"\; label="p"\; filenames="A200810239934E00081.png"\; state="\{\{state\}\}">p</figure-callout>}}_1=\frac{2\mathrm{\&sigma;}}{{\mathrm{<figure-callout\; id="1"\; label="R"\; filenames="A200810239934E00081.png"\; state="\{\{state\}\}">R</figure-callout>}}_1}$ ? $p_v-{\mathrm{<figure-callout\; id="2"\; label="p"\; filenames="A200810239934E00073.png,A200810239934E00081.png"\; state="\{\{state\}\}">p</figure-callout>}}_2=\frac{2\mathrm{\&sigma;}}{{\mathrm{<figure-callout\; id="2"\; label="R"\; filenames="A200810239934E00073.png,A200810239934E00081.png"\; state="\{\{state\}\}">R</figure-callout>}}_2}$

Therefore have, $p_1-{\mathrm{<figure-callout\; id="2"\; label="p"\; filenames="A200810239934E00073.png,A200810239934E00081.png"\; state="\{\{state\}\}">p</figure-callout>}}_2=-2\mathrm{\&sigma;}(\frac{1}{R_1}-\frac{1}{R_2})<0$

In the formula, p _vBe steam pressure in the steam bubble; p ₁And p ₂Be respectively the fluid pressure of outside tubule of steam bubble and extra heavy pipe one side; R ₁And R ₂Be respectively the radius of curvature of steam bubble, because pipe shape is flaring feature, R at tubule and extra heavy pipe lateral bending lunar surface ₁＜R ₂σ is a surface tension coefficient.

As can be seen, in order to keep pressure balance, steam bubble is surveyed the upstream outward and must be that is to say that than the fluid pressure in tubule road the steam bubble in the capillary flaring pipeline provides a pressure head less than the fluid pressure of downstream than the extra heavy pipe road, produces the Micropump effect.There is capillary flaring pipeline in modified pulsating heat pipe 4 at evaporator section.Steam bubble constantly generates in capillary flaring pipeline, grows up, and leaves, and this has just produced the Micropump effect, drives working medium to thicker pipeline motion.

Fig. 4 has compared the size of thermal resistance when the different heat transfer amount of two kinds of pulsating heat pipes, and working medium is absolute ethyl alcohol, and liquid filled ratio is 50%.Modified pulsating heat pipe 4 helps the formation of circular flow and keeps, and improves by evaporator section and carries to the working medium of condensation segment, strengthens the heat transmission, thereby reduces thermal resistance, improves the heat transfer property of pulsating heat pipe.During Q＜30W, two kinds of pulsating heat pipe thermal resistance sizes are close; At Q〉under the situation of 30W, the thermal resistance of modified pulsating heat pipe 4 is low.

Fig. 5 is when circular flow occurring, the real scene shooting picture of four adjacent channel adiabatic sections of modified type pulsating heat pipe.At this moment, working medium is absolute ethyl alcohol, and liquid filled ratio is 50%, and heating power is 60W.In four pipelines, slug flow and annular flow are interspersed, and tube wall temperature also colds and heat succeed each other thereupon, and the whole one-way flow trend of working medium is obvious.In the A pipe, slug flow down is moved into evaporator section, because heating power is bigger, behind U type pipe, the steam that fluid column is evaporated, is difficult to form fluid column in B pipe adiabatic section to the condensation segment flow at high speed under the impact of steam, and flow pattern flows in the form of a ring; To the steam condensation of condensation segment rear section, vapor (steam) velocity reduces, and is developed into fluid column, forms slug flow in the C pipe.Equally, the slug flow in the C pipe enters U type evaporator section, and high velocity vapor is flowed through, and D is tubular to flow circlewise.

The present invention realizes that pattern is various, can arrange a plurality of new constructions as required in the whole length of pulsating heat pipe.The above embodiment of the present invention only is used for illustrating technical scheme of the present invention, and it should not limit protection scope of the present invention, and the equivalent transformation as if technical scheme in the foregoing description is made all should belong to the scope of protection of the invention.

Claims (6)

1. one kind has and stablizes the unidirectional pulsating heat pipe that circulates, and it is characterized in that, this pulsating heat pipe is to connect one section increaser to constitute between the pipe of two sections different inner diameters.

According to claim 1 described have stablize the unidirectional pulsating heat pipe that circulates, it is characterized in that, the pipe of described two sections different inner diameters, internal diameter of the pipeline satisfies $D_i<2\sqrt{\mathrm{\&sigma;}/({\mathrm{\&rho;}}_l-{\mathrm{\&rho;}}_g)g},$ In the formula, D _iBe internal diameter of the pipeline, σ is a surface tension, ρ _l, ρ _gBe working medium liquid phase and vapour phase density.

According to claim 1 described have stablize the unidirectional pulsating heat pipe that circulates, it is characterized in that the pipe of described two sections different inner diameters has reduced the symmetry and the harmony of pulsating heat pipe runner, the mobile of a certain direction is dominant, thereby improved the possibility that forms unidirectional circular flow.

According to claim 1 described have stablize the unidirectional pulsating heat pipe that circulates, it is characterized in that, the pipe of described two sections different inner diameters, extra heavy pipe is lower than the flowing velocity in the tubule, cause flow resistance less thus, therefore can reach the effect of reasonable coupling flow resistance, guiding working medium forms unidirectional circulating to the motion of extra heavy pipe direction.

According to claim 1 described have stablize the unidirectional pulsating heat pipe that circulates, it is characterized in that, in the described pulsating heat pipe, the periodic plug shape steam bubble that produces, because the internal diameter difference of pipeline, the radius of curvature of steam bubble meniscus also can change, and under surface tension effects, will produce the Micropump effect.

According to claim 1 described have stablize the unidirectional pulsating heat pipe that circulates, it is characterized in that the heat conduction of described pulsating heat pipe and flow duct, effect are similar to a check valve.

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