CN103007792A - Method for mixing micro-channel based on supercutical fluid - Google Patents
Method for mixing micro-channel based on supercutical fluid Download PDFInfo
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- CN103007792A CN103007792A CN2012105573068A CN201210557306A CN103007792A CN 103007792 A CN103007792 A CN 103007792A CN 2012105573068 A CN2012105573068 A CN 2012105573068A CN 201210557306 A CN201210557306 A CN 201210557306A CN 103007792 A CN103007792 A CN 103007792A
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Abstract
The invention discloses a method for mixing a micro-channel based on a supercutical fluid. The method comprises the steps that a near critical fluid and a compound to be mixed are sent into the micro-channel; then the unilateral outer wall surface of the micro-channel is heated or the outer wall surfaces of the two opposite sides are simultaneously heated; and when the fluid in the micro-channel is in a supercutical fluid state, vortex disturbance occurs, and thereby an effective enhanced mixing is achieved. The method has a strong vortex disturbance effect only when the heat is applied outside, external forces or methods of a complicated micro-channel design and the like are not required, the processes of mixing and stirring with good microscales can be achieved, the operation is simple and reliable, and the mixing effect is good; further, impulse type cyclic heating or continuous heating is adopted to generate the strong vortex disturbance in the micro-channel and drive the compound to be mixed to be fully stirred, so that the defect that traditional methods have high costs in terms of designing and manufacturing the complicated channel and loading microscopic scale electromagnetic fields and the like is overcome, and simultaneously the mixing and stirring effects higher than conventional fluid thermal disturbance intensity can be obtained.
Description
Technical field
The invention belongs to field of micro electromechanical technology, relate to a kind of microchannel mixed method based on supercritical fluid.
Background technology
Along with the development of human civilization, biology, machinery, power and other many devices and equipment all present the feature of microminiaturization at present, have brought the advantages such as weight reduces, efficient raising.The microchannel is ubiquitous a kind of device in these micro-systems, often be very important and in the microchannel, reach effective mixing, as the medicine in the biological medicine engineering mix, the mixing etc. of fuel in the micropower system.But because the reducing of size, in microscale channel the convection current of gravity and fluid suppressed, the mixed effect that produces by fluid convection is very small and weak.
Strengthen in the microchannel that at present the method for mixing has that stirrings of micron order motor, small electric disturbance of magnetic field, thermal agitation, mechanical centrifugal rotate, the complex passages structure is mixed naturally etc.Yet these methods all need motion or rotary part, consuming time, the consumption power of making and the installation and operation of the parts of these minute yardsticks, and have the long-time serial shortcomings such as unreliable that allow.And the size of existing mixed method requirement microchannel can not be too little, and less than the microchannel below 1 millimeter, mixed effect is undesirable for hydraulic diameter.
Summary of the invention
For above problems of the prior art, the present invention proposes a kind of microchannel mixed method based on supercritical fluid, adopt the mode of wall heating, utilize near critical fluids changing near near thermophysical property stronger the critical point interval is responsive, apply certain heat in the outside of microchannel, thereby cause the stronger vortex disturbance of supercritical fluid in the microchannel, realize effectively strengthening mixing.
The object of the invention is to propose a kind of microchannel mixed method based on supercritical fluid.
Microchannel mixed method based on supercritical fluid of the present invention may further comprise the steps:
1) near critical fluids and thing to be mixed are sent into the microchannel;
2) wait to flow stable, the outside wall surface of microchannel is heated;
3) elapsed time interval t after the heating, the fluid in the microchannel reaches Supercritical Conditions, and the eddy generation disturbance realizes effectively strengthening mixing.
Wherein, the hydraulic diameter of the minimum of microchannel is 50 microns ~ 1 millimeter.
The material of microchannel can adopt a kind of in copper, stainless steel, aluminium and the alloy.The internal face of microchannel is hydraulically smooth surface, hydraulically rough surface or the wall with certain lines.
Near critical fluids reaches Supercritical Conditions after heating in the microchannel, can be liquid state or gaseous state before entering the microchannel.Near critical fluids is a kind of in water, carbon dioxide, hydrogen and nitrogen, ammonia, freon series, propane and the butane.
The state of thing to be mixed is gaseous state, liquid state or solid-state.
In step 1), control near critical fluids and thing to be mixed are sent into the speed of microchannel, make its Reynolds number below 200.
In step 2) in, the outside wall surface of microchannel adds thermal recovery Resistant heating, electrical bar heating, electric heating piece heating, film heating and heating bath and adds pine for a kind of.The outside wall surface of microchannel is added the one-sided outside wall surface of thermal recovery to be heated or heats simultaneously in relative both sides outside wall surface.The mode of heating of microchannel adopts the heating of pulsed cycle, perhaps continuous heating; The pulsed cycle period interval time of heating is 5 milliseconds ~ 5 seconds; The duration of continuous heating is 5 milliseconds ~ 5 seconds.What of the thing to be mixed of actual size and supercritical fluid flow, minute yardstick are the intensity that applies heat can change with.
In step 3), time interval t satisfies,
Wherein, L is the hydraulic diameter of microchannel, D
TBe thermal diffusion coefficient, γ is the adiabatic coefficent of fluid.
In step 3), the temperature T in the microchannel satisfies, T/T
cValue between 0.8 ~ 1.3, wherein, T
cCritical-temperature for fluid; Pressure P satisfies, P/P
cValue between 0.8 ~ 2, wherein, P
cCritical pressure for fluid.
When the thing to be mixed of near critical fluids and minute yardstick together enter flow steadily in the microchannel after, outside wall surface in the microchannel applies the heating of pulsed cycle or continuous heating, fluid reaches Supercritical Conditions, thermal conduction characteristic changes in the boundary layer of supercritical fluid under this condition, thereby cause stronger thermal agitation effect, this effect further develops with flowing, and produces stronger vortex disturbance, drive thing to be mixed and fully stir, realized that effective enhancing mixes.Method of the present invention only externally applies the stronger vortex disturbance effect of heat generation, and does not need not by the methods such as design of external force or complicated microchannel, can realize the process of mixing and the stirring of good minute yardstick, and operation is simple and reliable, good mixing effect; And the hydraulic diameter of microchannel can reach 50 microns ~ 1 millimeter miniature scale, has also realized good mixing in minute yardstick.
Advantage of the present invention:
The present invention utilizes the characteristic of near critical fluids, adopt the heating of pulsed cycle or continuous heating to produce stronger vortex disturbance in the inside of microchannel, driving thing to be mixed fully stirs, avoid conventional method in the larger cost that manufactures and designs the aspects such as complex passages, loading miniature scale electromagnetic field, can obtain mixing and the mixing effect higher than normal flow body heat strength of turbulence simultaneously.
Description of drawings
Fig. 1 is the structural representation of device of an embodiment of the microchannel mixed method based on supercritical fluid of the present invention;
Fig. 2 is the velocity profile according to the mixing of the microchannel of an embodiment of the microchannel mixed method based on supercritical fluid of the present invention.
The specific embodiment
Below in conjunction with accompanying drawing, the present invention will be further described by example.
As shown in Figure 1, the device based on the microchannel mixed method of supercritical fluid of present embodiment comprises: access road 11, preheater 12, fluid control valve 13, microchannel 14, heating film 15 and exit passageway 16 consist of.In the present embodiment, near critical fluids adopts carbon dioxide; The material of microchannel adopts copper; Mode of heating adopts film heating, and heating film 15 is close on the relative both sides outside wall surface of microchannel 14; Access road 11 and exit passageway 16 adopt stainless steel.
The temperature of nearly critical carbon dioxide fluid should be in 300K ~ 350K scope, and pressure should be in more than the 7.38MPa.
The parameter specific as follows of present embodiment:
Nearly critical carbon dioxide fluid is 304.2K in the temperature of access road, and pressure is 7.5MPa, and the Reynolds number of access road is 26.8;
Adopt continuous heating, the heat flow density of heating is 10000W/m
2, the duration is 5 seconds;
The length of microchannel is 5cm, and the hydraulic diameter in cross section is 333 μ m, and wherein, width is 1mm, highly is 200 μ m.
The microchannel mixed method based on supercritical fluid of present embodiment may further comprise the steps:
1) nearly critical carbon dioxide fluid and thing to be mixed are sent into the microchannel, and coutroi velocity, the Reynolds number of access road are 26.8;
2) treat mobile stablizing, adopt film heating to carry out continuous heating, the both sides outside wall surface relative to the microchannel heats simultaneously, and the duration is 5 seconds;
3) elapsed time interval 0.1s after the heating reaches Supercritical Conditions, and the eddy generation disturbance realizes effectively strengthening mixing.
The device of present embodiment after tested, the temperature of the supercritical fluid of exit passageway is 310K, it is less that pressure changes.Along with the time changes, present stable tendency.Whole mixed process is divided into two stages: resting stage and vortex disturbance phase before the heating.As shown in Figure 2, in the vortex disturbance phase, the inside of microchannel has produced stronger vortex disturbance.Corresponding whirlpool is rounded, extends to till the internal face of microchannel; Whirling motion is take the height 200 μ m of microchannel as diameter, and the cycle occurs on the length direction of microchannel; The eddy current Peak Flow Rate can be reached for more than the 0.1m/s, can realize sufficient mix and blend.
It should be noted that at last, the purpose of publicizing and implementing mode is to help further to understand the present invention, but it will be appreciated by those skilled in the art that: without departing from the spirit and scope of the invention and the appended claims, various substitutions and modifications all are possible.Therefore, the present invention should not be limited to the disclosed content of embodiment, and the scope of protection of present invention is as the criterion with the scope that claims define.
Claims (10)
1. a microchannel mixed method is characterized in that, described mixed method may further comprise the steps:
1) near critical fluids and thing to be mixed are sent into the microchannel;
2) wait to flow stable, the outside wall surface of microchannel is heated;
3) elapsed time interval t after the heating, the fluid in the microchannel reaches Supercritical Conditions, and the eddy generation disturbance realizes effectively strengthening mixing.
2. mixed method as claimed in claim 1 is characterized in that, the material of described microchannel adopts a kind of in copper, stainless steel, aluminium and the alloy; The internal face of described microchannel is hydraulically smooth surface, hydraulically rough surface or the wall with certain lines.
3. mixed method as claimed in claim 1 is characterized in that, described near critical fluids reaches Supercritical Conditions after heating in the microchannel, can be liquid state or gaseous state before entering the microchannel; Near critical fluids is a kind of in water, carbon dioxide, hydrogen and nitrogen, ammonia, freon series, propane and the butane.
4. mixed method as claimed in claim 1 is characterized in that, the state of described thing to be mixed is gaseous state, liquid state or solid-state.
5. mixed method as claimed in claim 1 is characterized in that, in step 1), control near critical fluids and thing to be mixed are sent into the speed of microchannel, make its Reynolds number below 200.
6. mixed method as claimed in claim 1 is characterized in that, in step 2) in, the outside wall surface of microchannel adds thermal recovery Resistant heating, electrical bar heating, electric heating piece heating, film heating and heating bath and adds pine for a kind of.
7. mixed method as claimed in claim 1 is characterized in that, in step 2) in, the outside wall surface of microchannel is added the one-sided outside wall surface of thermal recovery heat or heat simultaneously in relative both sides outside wall surface; The mode of heating of microchannel adopts the heating of pulsed cycle, perhaps continuous heating; The pulsed cycle period interval time of heating is 5 milliseconds ~ 5 seconds; The duration of continuous heating is 5 milliseconds ~ 5 seconds.
8. mixed method as claimed in claim 1 is characterized in that, in step 3), time interval t satisfies,
Wherein, L is the hydraulic diameter of microchannel, D
TBe thermal diffusion coefficient, γ is the adiabatic coefficent of fluid.
9. mixed method as claimed in claim 1 is characterized in that, in step 3), the temperature T in the microchannel satisfies, T/T
cValue between 0.8 ~ 1.3, wherein, T
cCritical-temperature for fluid; Pressure P satisfies, P/P
cValue between 0.8 ~ 2, wherein, P
cCritical pressure for fluid.
10. mixed method as claimed in claim 1 is characterized in that, the hydraulic diameter of the minimum of microchannel is 50 microns ~ 1 millimeter.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110671210A (en) * | 2018-07-02 | 2020-01-10 | 北京动力机械研究所 | Electric heating element for aircraft engine active cooling ground test |
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| CN1537029A (en) * | 2001-05-07 | 2004-10-13 | 环球油品公司 | Apparatus for mixing and reacting at least tow fluids |
| US20080004194A1 (en) * | 2002-09-24 | 2008-01-03 | Air Products And Chemicals, Inc. | Processing of semiconductor components with dense processing fluids |
| US20070214712A1 (en) * | 2006-03-20 | 2007-09-20 | American Beef Processing, Llc | Bio-diesel manufacture with a micro-reactor |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110671210A (en) * | 2018-07-02 | 2020-01-10 | 北京动力机械研究所 | Electric heating element for aircraft engine active cooling ground test |
| CN110671210B (en) * | 2018-07-02 | 2021-02-05 | 北京动力机械研究所 | Electric heating element for aircraft engine active cooling ground test |
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